U.S. patent application number 09/758502 was filed with the patent office on 2001-05-31 for method of operating a vehicle.
Invention is credited to Schechter, Michael M..
Application Number | 20010002379 09/758502 |
Document ID | / |
Family ID | 22266236 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002379 |
Kind Code |
A1 |
Schechter, Michael M. |
May 31, 2001 |
Method of operating a vehicle
Abstract
A method and a system for converting kinetic energy of a vehicle
and part of energy supplied by its engine into energy of compressed
air and using it to assist in vehicle propulsion later. A novel
system of valves employing variable valve timing and valve
deactivation is used to implement and control a two-way flow of
compressed air between the engine and an air-reservoir where
air-temperature control is maintained. During operation with
compressed-air assist the engine operates both as an air-motor and
as an internal combustion engine during each cycle in each
cylinder. The engine can selectively and interchangeably operate
either as a four-stroke or as a two-stroke internal combustion
engine.
Inventors: |
Schechter, Michael M.;
(Farmington Hills, MI) |
Correspondence
Address: |
Michael M. Schechter
31110 Country Ridge Circle
Farmington Hills
MI
48331
US
|
Family ID: |
22266236 |
Appl. No.: |
09/758502 |
Filed: |
January 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09758502 |
Jan 12, 2001 |
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09098010 |
Jun 15, 1998 |
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Current U.S.
Class: |
477/115 ;
477/118 |
Current CPC
Class: |
F01L 9/10 20210101; F02B
2075/025 20130101; B60T 17/02 20130101; F01L 13/0005 20130101; F01B
17/02 20130101; F02N 9/04 20130101; F02B 21/00 20130101; B60K 3/00
20130101; F01L 13/065 20130101; B60K 6/12 20130101; F01L 9/18
20210101; F02D 13/04 20130101; F01L 2013/0094 20130101; Y02T 10/62
20130101; F02B 2075/027 20130101; F02B 75/02 20130101 |
Class at
Publication: |
477/115 ;
477/118 |
International
Class: |
B60K 041/04 |
Claims
I claim:
1. A method of operating a wheeled vehicle, said method comprising
the steps of: (a) providing an engine mounted in said vehicle and
coupled to at least one vehicle wheel for its propulsion and
braking, said engine including: (1) at least one cylinder, (2) a
cylinder chamber within said at least one cylinder, (3) a head
mounted to said at least one cylinder, and (4) a piston operatively
engaging said at least one cylinder, with the piston to head and
cylinder relationship being such that the volume of said cylinder
chamber shrinks during a volume decreasing stroke, when said piston
moves towards said head, and expands during a volume increasing
stroke, when said piston moves away from said head, (b) providing
an air-reservoir means mounted in said vehicle for receiving,
storage, and discharge of compressed air, (c) providing a control
means for controlling the operation of said engine and said vehicle
in response to driver's demands and in accordance with a control
program incorporated in said control means, (d) providing a gas
exchange controlling means for selectively, variably, and
alternatively connecting said cylinder chamber to outside
atmosphere and to said air-reservoir means, in timed relation to
said engine operation, (e) providing a fuel delivery means for
selectively and variably adding fuel to the air intended for
participation in combustion in said engine in timed relation to
said engine operation, (f) providing a means for allowing a vehicle
driver to perform vehicle control functions including: (1)
selectively demanding a vehicle braking force, (2) selectively
demanding a vehicle propulsion force, (3) selectively demanding a
change in magnitude of said vehicle braking force, and (4)
selectively demanding a change in magnitude of said vehicle
propulsion force, (g) operating said engine in a compressor mode
driven by a vehicle momentum in response to a demand for a vehicle
braking force, when said vehicle is in motion and said engine is
coupled to said at least one vehicle wheel, by repeatedly
performing a two-stroke compressor cycle in said at least one
cylinder, said two-stroke compressor cycle including the steps of:
(1) receiving air from said outside atmosphere into said cylinder
chamber during a second part of said volume increasing stroke, (2)
compressing air in said cylinder chamber during a first part of
said volume decreasing stroke, (3) displacing a fraction of
compressed air from said cylinder chamber into said air-reservoir
means during a second part of said volume decreasing stroke for
storage therein, and (4) expanding the fraction of compressed air
left in said cylinder chamber during a first part of said volume
increasing stroke, whereby work of air compression and displacement
performed during said volume decreasing stroke contributes to
braking said vehicle, whereby compressed air stored in said
air-reservoir means is available to perform useful work, and
whereby work of air expansion performed during said volume
increasing stroke returns to said piston at least a fraction of
energy contained in said fraction of compressed air left in said
cylinder chamber, and (h) operating said engine in a prime mover
mode propelling said vehicle in response to a demand for a vehicle
propulsion force when there is no concurrent demand for said
vehicle braking force, said prime mover mode including: (I)
operating said engine in a mode selected from a set of propulsion
modes comprising: (1) an air-motor mode including repeated
performance of a two-stroke air-motor cycle in said at least one
cylinder, said two-stroke air-motor cycle including the steps of:
(A) receiving compressed air from said air-reservoir means into
said cylinder chamber and displacing said piston during a first
part of said volume increasing stroke, (B) expanding said
compressed air in said cylinder chamber and displacing said piston
during a second part of said volume increasing stroke, and (C)
expelling a substantial fraction of air contained in said cylinder
chamber into said outside atmosphere during said volume decreasing
stroke, whereby a substantial fraction of energy contained in said
compressed air is transferred to said piston, and whereby said
vehicle is propelled without any fuel being consumed, and (2) a
fuel propulsion mode including operating said engine in a
conventional internal combustion mode receiving air from said
outside atmosphere, and (II) changing said engine operation from
one propulsion mode to another one selected from said set of
propulsion modes.
2. The method of claim 1 wherein the step of providing said gas
exchange controlling means comprises the steps of: (a) providing at
least one normally-closed intake valve for selectively and variably
connecting said cylinder chamber to said outside atmosphere, (b)
providing at least one normally-closed exhaust valve for
selectively and variably connecting said cylinder chamber to said
outside atmosphere, and (c) providing at least one normally-closed
charging valve for selectively and variably connecting said
cylinder chamber to said air-reservoir means.
3. The method of claim 2 wherein the operation of said engine in
said compressor mode comprises, during each two-stroke cycle, the
steps of: (a) deactivating said fuel delivery means, (b)
deactivating said at least one exhaust valve, (c) expanding the
residual compressed air during a first part of said volume
increasing stroke, (d) variably opening said at least one intake
valve, (e) receiving air from said outside atmosphere into said
cylinder chamber during a second part of said volume increasing
stroke, (f) variably closing said at least one intake valve, (g)
compressing said air in said cylinder chamber during a first part
of said volume decreasing stroke, (h) variably opening said at
least one charging valve, (i) substantially displacing the
compressed air from said cylinder chamber into said air-reservoir
means during a second part of said volume decreasing stroke, and
(j) variably closing said at least one charging valve.
4. The method of claim 2 wherein the operation of said engine in
said air-motor mode comprises, during each two-stroke cycle, the
steps of: (a) deactivating said fuel delivery means, (b)
deactivating said at least one intake valve, (c) variably opening
said at least one charging valve, (d) receiving compressed air into
said cylinder chamber from said air-reservoir means during a first
part of said volume increasing stroke, (e) variably closing said at
least one charging valve, (f) expanding said compressed air in said
cylinder chamber during a second part of said volume increasing
stroke, (g) variably opening said at least one exhaust valve, (h)
substantially expelling the air from said cylinder chamber during
said volume decreasing stroke, and (i) variably closing said at
least one exhaust valve.
5. The method of claim 2 further comprising the step of responding
to a demand for a change in magnitude of said vehicle braking or
propulsion force by making changes in at least one parameter
selected from a set of parameters controlling the operation of said
gas exchange controlling means, said set of parameters including:
(a) timing of opening of said at least one intake valve, (b) timing
of closing of said at least one intake valve, (c) timing of opening
of said at least one exhaust valve, (d) timing of closing of said
at least one exhaust valve, (e) timing of opening of said at least
one charging valve, and (f) timing of closing of said at least one
charging valve, and changing the quantity of fuel added to the air
intended for participation in combustion, when operating in said
conventional internal combustion mode, whereby the net negative
work-per-cycle performed in said at least one engine cylinder is
changed.
6. The method of claim 1 further comprising the steps of providing
a transmission means for selectively coupling said engine to said
at least one vehicle wheel with a variable transmission ratio, and
responding to a demand for a change in magnitude of said vehicle
braking or propulsion force by selectively changing said
transmission ratio.
7. The method of claim 1 wherein the step of providing said gas
exchange controlling means comprises the steps of: (a) providing an
intake manifold means for accomodating gas flow into or out of said
cylinder chamber, (b) providing at least one normally-closed intake
valve for selectively and variably connecting said cylinder chamber
to said intake manifold means, (c) providing an exhaust manifold
means for accomodating gas flow out of or into said cylinder
chamber, (d) providing at least one normally-closed exhaust valve
for selectively and variably connecting said cylinder chamber to
said exhaust manifold means, and (e) providing a switching means
for setting the arrangement of said gas exchange controlling means
into a configuration selected from a variety of configurations, and
switching said arrangement from one configuration to another in
accordance with said program incorporated in said control means,
said variety of configurations including: (1) a first switching
configuration wherein said intake manifold means is connected to
outside atmosphere and disconnected from said air-reservoir means,
and said exhaust manifold means is connected to said air-reservoir
means and disconnected from outside atmosphere, (2) a second
switching configuration wherein said intake manifold means is
connected to said air-reservoir means and disconnected from outside
atmosphere, and said exhaust manifold means is connected to outside
atmosphere and disconnected from said air-reservoir means, and (3)
a third switching configuration wherein said intake manifold means
and said exhaust manifold means are both connected to outside
atmosphere and disconnected from said air-reservoir means.
8. The method of claim 7 wherein the operation of said engine in
said compressor mode comprises the step of operating said gas
exchange controlling means in said first switching configuration,
and the operation of said engine in said prime mover mode comprises
the steps of: (a) operating said gas exchange controlling means in
said second switching configuration if said engine operates in said
air-motor mode, and (b) operating said gas exchange controlling
means in said third switching configuration if said engine operates
in said conventional internal combustion mode.
9. The method of claim 8 wherein the operation of said engine in
said compressor mode comprises, during each two-stroke cycle, the
steps of: (a) deactivating said fuel delivery means, (b) expanding
the residual compressed air remaining in said cylinder chamber
during a first part of said volume increasing stroke, (c) variably
opening said at least one intake valve, (d) receiving air from said
outside atmosphere into said cylinder chamber during a second part
of said volume increasing stroke, (e) variably closing said at
least one intake valve, (f) compressing said air in said cylinder
chamber during a first part of said volume decreasing stroke, (g)
variably opening said at least one exhaust valve, (h) substantially
displacing the compressed air from said cylinder chamber into said
air-reservoir means during a second part of said volume decreasing
stroke, and (i) variably closing said at least one exhaust
valve.
10. The method of claim 8 wherein the operation of said engine in
said air-motor mode comprises, during each two-stroke cycle, the
steps of: (a) deactivating said fuel delivery means, (b) variably
opening said at least one intake valve, (c) receiving compressed
air into said cylinder chamber from said air-reservoir means during
a first part of said volume increasing stroke, (d) variably closing
said at least one intake valve, (e) expanding said compressed air
in said cylinder chamber during a second part of said volume
increasing stroke, (f) variably opening said at least one exhaust
valve, (g) substantially expelling the air from said cylinder
chamber during said volume decreasing stroke, and (h) variably
closing said at least one exhaust valve.
11. A method of braking a wheeled vehicle, said method comprising
the steps of: (a) providing an engine mounted in said vehicle and
coupled to at least one vehicle wheel for its propulsion and
braking, said engine including: (1) at least one cylinder, (2) a
cylinder chamber within said at least one cylinder, (3) a head
mounted to said at least one cylinder, and (4) a piston operatively
engaging said at least one cylinder, with the piston to head and
cylinder relationship being such that the volume of said cylinder
chamber shrinks during a volume decreasing stroke, when said piston
moves towards said head, and expands during a volume increasing
stroke, when said piston moves away from said head, (b) providing
an air-reservoir means mounted in said vehicle for receiving,
storage, and discharge of compressed air, (c) providing a control
means for controlling the operation of said engine and said vehicle
in response to driver's demands and in accordance with a control
program incorporated in said control means, (d) providing a gas
exchange controlling means for selectively, variably, and
alternatively connecting said cylinder chamber to outside
atmosphere and to said air-reservoir, in timed relation to said
engine operation, (e) providing a means for allowing a vehicle
driver to perform vehicle control functions including: (1)
selectively demanding a vehicle braking force, and (2) selectively
demanding a change in magnitude of said vehicle braking force, (f)
operating said engine in a compressor mode driven by a vehicle
momentum in response to a demand for a vehicle braking force, when
said vehicle is in motion and said engine is coupled to said at
least one vehicle wheel, by repeatedly performing a two-stroke
compressor cycle in said at least one cylinder, said two-stroke
compressor cycle including the steps of: (1) receiving air from
said outside atmosphere into said cylinder chamber during a second
part of said volume increasing stroke, (2) compressing air in said
cylinder chamber during a first part of said volume decreasing
stroke, (3) displacing a fraction of compressed air from said
cylinder chamber into said air-reservoir means during a second part
of said volume decreasing stroke for storage therein, and (4)
expanding the fraction of compressed air left in said cylinder
chamber during a first pair of said volume increasing stroke,
whereby work of air compression and displacement performed during
said volume decreasing stroke contributes to braking said vehicle,
whereby compressed air stored in said air-reservoir means is
available to perform useful work, and whereby work of air expansion
performed during said volume increasing stroke returns to said
piston at least a fraction of energy contained in said fraction of
compressed air left in said cylinder chamber.
12. The method of claim 11 wherein the step of providing said gas
exchange controlling means comprises the steps of: (a) providing at
least one normally-closed first valve for selectively and variably
connecting said cylinder chamber to said outside atmosphere, and
(b) providing at least one normally-closed second valve for
selectively and variably connecting said cylinder chamber to said
air-reservoir means.
13. The method of claim 12 wherein the operation of said engine in
said compressor mode comprises, during each two-stroke cycle, the
steps of: (a) expanding the residual compressed air during a first
part of said volume increasing stroke, (b) variably opening said at
least one first valve, (c) receiving air from said outside
atmosphere into said cylinder chamber during a second part of said
volume increasing stroke, (d) variably closing said at least one
first valve, (e) compressing said air in said cylinder chamber
during a first part of said volume decreasing stroke, (f) variably
opening said at least one second valve, (g) substantially
displacing the compressed air from said cylinder chamber into said
air-reservoir means during a second part of said volume decreasing
stroke, and (h) variably closing said at least one second
valve.
14. The method of claim 13 wherein the step of expanding the
residual compressed air during a first part of said volume
increasing stroke continues until the pressure in said cylinder
chamber becomes substantially equal to the pressure in said outside
atmosphere.
15. The method of claim 13 wherein the step of compressing said air
in said cylinder chamber during a first part of said volume
decreasing stroke continues until the pressure in said cylinder
chamber becomes substantially equal to the pressure in said
air-reservoir means.
16. The method of claim 13 wherein the step of variably opening
said at least one second valve takes place before the pressure in
said cylinder chamber becomes equal to the pressure in said
reservoir means, whereby the air displacement work performed during
said second part of said volume decreasing stroke increases, and
whereby a substantially greater braking force can be achieved.
17. The method of claim 12 further comprising the step of
responding to a demand for a change in magnitude of said vehicle
braking force by making changes in at least one parameter selected
from a set of parameters controlling the operation of said gas
exchange controlling means, said set of parameters including: (a)
timing of opening of said at least one first valve, (b) timing of
closing of said at least one first valve, (c) timing of opening of
said at least one second valve, and (d) timing of closing of said
at least one second valve, whereby the net negative work-per-cycle
performed in said at least one engine cylinder is changed.
18. The method of claim 11 further comprising the steps of
providing a transmission means for selectively coupling said engine
to said at least one vehicle wheel with a variable transmission
ratio, and responding to a demand for a change in magnitude of said
vehicle braking force by selectively changing said transmission
ratio.
19. A method of propelling a wheeled vehicle, said method
comprising the steps of: (a) providing an engine mounted in said
vehicle and coupled to at least one vehicle wheel for its
propulsion and braking, said engine including: (1) at least one
cylinder, (2) a cylinder chamber within said at least one cylinder,
(3) a head mounted to said at least one cylinder, and (4) a piston
operatively engaging said at least one cylinder, with the piston to
head and cylinder relationship being such that the volume of said
cylinder chamber shrinks during a volume decreasing stroke, when
said piston moves towards said head, and expands during a volume
increasing stroke, when said piston moves away from said head, (b)
providing an air-reservoir means mounted in said vehicle for
receiving, storage, and discharge of compressed air, (c) providing
a control means for controlling the operation of said engine and
said vehicle in response to driver's demands and in accordance with
a control program incorporated in said control means, (d) providing
a gas exchange controlling means for selectively, variably, and
alternatively connecting said cylinder chamber to outside
atmosphere and to said air-reservoir, in timed relation to said
engine operation, (e) providing a fuel delivery means for
selectively and variably adding fuel to the air intended for
participation in combustion in said engine in timed relation to
said engine operation, (f) providing a means for allowing a vehicle
driver to perform vehicle control functions including: (1)
selectively demanding a vehicle propulsion force, and (2)
selectively demanding a change in magnitude of said vehicle
propulsion force, and (g) operating said engine in a mode selected
from a set of propulsion modes in response to a demand for a
vehicle propulsion force, said set of propulsion modes comprising:
a four-stroke air-power-assist mode including repeated performance
of a hybrid four-stroke cycle in said at least one cylinder, said
hybrid four-stroke cycle comprising two power strokes: (1) a first
power stroke including expansion of a compressed-air charge,
received from said air-reservoir means, in said cylinder chamber
during a first volume increasing stroke, and (2) a second power
stroke including expansion of combustion gas produced as a result
of fuel combustion in said cylinder chamber during a second volume
increasing stroke, whereby work performed during said first power
stroke is added to work performed during said second power stroke,
and a two-stroke air-power-assist mode including repeated
performance of a hybrid two-stroke internal combustion cycle in
said at least one cylinder during which a compressed-air charge is
received into said cylinder chamber from said air-reservoir means
and used for combustion during the same cycle, whereby energy of
said compressed-air charge supplements the energy released in
combustion.
20. The method of claim 19 wherein the step of providing said gas
exchange controlling means comprises the steps of: (a) providing at
least one normally-closed first valve for selectively and variably
connecting said cylinder chamber to said air-reservoir means, and
(b) providing at least one normally-closed second valve for
selectively and variably connecting said cylinder chamber to said
outside atmosphere.
21. The method of claim 20 wherein the operation of said engine in
said four-stroke air-power-assist mode comprises, during each
four-stroke cycle, the steps of: (b) variably opening said at least
one first valve, (c) receiving compressed air into said cylinder
chamber from said air-reservoir means during a first part of a
first volume increasing stroke, (d) variably closing said at least
one first valve, (e) expanding said compressed air in said cylinder
chamber during a second part of said first volume increasing
stroke, (f) compressing the air in said cylinder chamber during a
first volume decreasing stroke, (g) adding fuel to said air in said
cylinder chamber, (h) initiating combustion of said fuel in said
cylinder chamber, whereby said fuel and said air are converted into
a combustion gas, (i) expanding said combustion gas in said
cylinder chamber during a second volume increasing stroke, (j)
variably opening said at least one second valve, (k) substantially
expelling said combustion gas from said cylinder chamber during a
first part of a second volume decreasing stroke, (l) variably
closing said at least one second valve, and (m) trapping the
residual combustion gas remaining in said cylinder chamber during a
second part of said second volume decreasing stroke, whereby work
performed by said combustion gas during said second volume
increasing stroke is supplemented by work performed by said
compressed air during said first volume increasing stroke, and
whereby trapping said residual combustion gas in said cylinder
chamber during said second part of said second volume decreasing
stroke contributes to reduction in harmful nitrogen oxide
emission.
22. The method of claim 19 wherein the operation of said engine in
said two-stroke air-power-assist mode comprises, during each
two-stroke cycle, the steps of: (a) variably opening said at least
one first valve, (b) receiving compressed air into said cylinder
chamber from said air-reservoir means during a second part of said
volume decreasing stroke, (c) variably closing said at least one
first valve, (d) compressing the air and the residual combustion
gas in said cylinder chamber during a third part of said volume
decreasing stroke, (e) adding fuel to the mixture of said air and
said residual combustion gas in said cylinder chamber, (f)
initiating combustion of said fuel in said cylinder chamber,
whereby said fuel and said air are converted into a combustion gas,
(g) expanding said combustion gas in said cylinder chamber during
said volume increasing stroke, (h) variably opening said at least
one second valve, (i) substantially expelling said combustion gas
from said cylinder chamber during a first part of said volume
decreasing stroke, and (j) variably closing said at least one
second valve, whereby receiving of said compressed air into said
cylinder chamber from said air-reservoir means reduces the amount
of compression work required, and whereby the peak torque and the
power of said engine increase.
23. The method of claim 20 further comprising the step of
responding to a demand for a change in magnitude of said vehicle
propulsion force by selectively making changes in at least one
parameter selected from a set of parameters controlling operation
of said gas exchange controlling means, said set of parameters
including: (a) timing of opening of said at least one first valve,
(b) timing of closing of said at least one first valve, (c) timing
of opening of said at least one second valve, and (d) timing of
closing of said at least one second valve, and changing the
quantity of fuel added to the air intended for participation in
combustion, whereby the net positive work-per-cycle performed in
said at least one engine cylinder is changed.
Description
[0001] This is a division of Ser. No. 09/098,010 filed Jun. 15,
1998.
FIELD OF THE INVENTION
[0002] The present invention relates to vehicle systems capable to
accumulate energy derived from vehicle motion during its
deceleration or obtained from operation of the vehicle engine, and
use the accumulated energy to assist in vehicle acceleration and
propulsion at a later time.
BACKGROUND OF THE INVENTION
[0003] Most automotive vehicles are propelled by internal
combustion engines consuming hydrocarbon fuels. Burning these fuels
produces exhaust gas containing harmful air-pollutants, such as
carbon monoxide, nitrogen oxides, and unburned hydrocarbons. It
also contains substantial amount of carbon dioxide which, if
produced in large quantities worldwide over long period of time,
can contribute to an undesirable increase in average global
temperature. Concern for clean air and a desire to prevent adverse
consequences of man-made global warming dictate a need to
substantially improve fuel efficiency of automotive vehicles.
[0004] By itself, the internal combustion engine is a reasonably
efficient machine. Unfortunately, the driving pattern of most
automotive vehicles is such, that a substantial fraction of energy
produced by their engines is wasted. Typically, the driving pattern
involves frequent accelerations, each followed by a deceleration.
Each acceleration involves a significant increase in fuel
consumption needed to produce the additional energy necessary to
increase the vehicle speed. Then, during a subsequent deceleration,
this added energy is absorbed by vehicle brakes and dissipated as
heat.
[0005] Attempts to overcome such waste of energy led to development
of systems in which the energy of vehicle motion is not dissipated
during braking, but converted into a form in which it can be
temporarily stored and, then, used again to accelerate the vehicle
at a later time. Typically, such system includes an internal
combustion engine, an energy storage, and a second machine
absorbing the energy of vehicle motion and placing it into the
storage during braking. During subsequent acceleration, the second
machine receives energy from the energy storage and uses it to
supplement the work of the internal combustion engine. Such systems
are known as hybrid vehicle systems. An electric hybrid includes an
electric generator/motor as a second machine, and an electric
battery for energy storage. A fluid-power hybrid includes a
pump/motor and a pressurized-fluid accumulator. A flywheel hybrid
includes a variable-ratio transmission and a flywheel.
[0006] A disadvantage, common to all of the above mentioned
hybrids, is added cost and complexity associated with the need for
the second machine and associated mechanisms needed to connect it
to vehicle wheels in-parallel to or in-line with the internal
combustion engine. Added complexity also increases probability of
failures, thus contributing to a reduction in overall system
reliability.
[0007] Another significant disadvantage is a substantial increase
in vehicle weight, which is especially pronounced in hybrids using
electric batteries for energy storage. Electric batteries are
excellent energy storage devices, but the weight of their
electrode-plates and electrolyte often adds so much to the mass of
the vehicle that it requires a larger engine to drive it. In
addition, a heavier vehicle is likely to cause more damage in
traffic accidents.
[0008] Another deficiency of hybrids using a second machine is that
the process they use for energy conversion is often inefficient.
For example, one-way energy conversion efficiency of many
conventional electric generators and motors does not exceed 50%,
and therefore, at best, only a quarter of braking energy can be
reclaimed for acceleration. More advanced generators and motors
have higher efficiency, but their cost is often prohibitive.
[0009] A very significant drawback of electric batteries is a
relatively slow rate at which they can be efficiently charged. This
limits their ability to absorb the vehicle braking energy during a
strong deceleration.
[0010] In view of the above, it is clear that it is highly
desirable to have a vehicle system which does not suffer from the
above disadvantages, while retaining all the fuel economy
advantages of other hybrid systems. A properly conceived hybrid
system using compressed-air for energy storage can meet these
requirements. Such a system is the subject of the present
invention.
BACKGROUND ART
[0011] The concept of saving kinetic energy of a vehicle during
braking, storing it as compressed-air, and later using it for
vehicle acceleration has been proposed before. A U.S. Pat. No.
5,529,549 to Moyer describes one such concept. A review of the
differences between the present invention and its advantages over
the above patent is given below.
[0012] (1) The above patent is limited to a case of saving the
energy of braking and using it for later acceleration. The present
invention, in addition to saving the braking energy, includes
charging the air-reservoir with compressed-air during periods other
than vehicle braking, whenever the pressure in the air-reservoir
drops below a predetermined level. This is accomplished by
operating the engine partly as a compressor charging the
air-reservoir and, at the same time, partly as an internal
combustion engine propelling the vehicle and driving the
compressor. Preventing a complete discharge of the air-reservoir is
a significant advantage, since it assures availability of
compressed-air whenever it is needed for acceleration or for assist
in constant speed operation.
[0013] (2) Moyer's patent describes an internal combustion
operation limited to a four-stroke cycle. The present invention, on
the other hand, describes an engine which can selectively operate
as a four-stroke, or as a two-stroke internal combustion engine,
quickly switching from one cycle to another whenever needed.
Ability to switch from the four-stroke to the two-stroke internal
combustion operation permits a substantial increase in engine
torque. It is especially useful during acceleration from low engine
speed, when torque produced by a four-stroke engine is often
inadequate.
[0014] (3) The present invention includes, in its preferred
embodiment, a third type of a valve in each engine cylinder. This
valve, the charging valve, is dedicated to connecting the cylinder
to the air-reservoir, whenever needed. Thanks to the charging
valves, the engine can receive air partly from the air-reservoir
through the charging valves, and partly from an intake manifold
through intake valves. This permits the engine to receive fuel into
its cylinders via injection into the intake ports rather than via
direct injection into the compressed air in the cylinders. Port
fuel injection is much less expensive than direct fuel injection.
Currently, most automobiles use port fuel injection. In addition,
the charging valves permit recharging the air-reservoir with
compressed-air during normal internal combustion operation. This is
accomplished by selectively opening the charging valve during each
compression stroke. The charging valve also eliminate the need for
distribution valves. The above patent does not provide for the
charging valves and therefore does not offer the above described
advantages of the present invention.
[0015] (4) Moyer proposes to control the flow of air from the
cylinder to the pressure tank and back by flowing the air through a
variable restriction. As it is well known, throttling an air-flow
in a restriction inevitably leads to a substantial loss of energy.
The present invention avoids this type of energy loss. It envisions
flowing the air through unrestricted passages and controlling the
magnitude of the braking force by varying the volume of the
air-charge received into the engine cylinder, as well as varying
the volume and the degree of compression of the air discharged from
the cylinder into the air-reservoir. This is accomplished by
varying the timings of the valves openings and closings.
[0016] (5) The above patent includes a supercharged engine
function. Supercharging an internal combustion engine involves
filling its cylinders with pressurized air so that, at the
beginning of the compression stroke, the cylinder pressure is
higher than atmospheric pressure. This permits an increase in
engine power. In contrast to this, the present invention is not
limited to supercharging. It provides for a compressed-air assist
at all levels of engine power, from light-load to full-load. This
is accomplished by metering a variable volume of compressed-air
into the cylinder, first without changing the pressure of the
air-charge and then subjecting it to an orderly variable expansion
during which its energy is transmitted to the piston. At the
beginning of the compression stroke the pressure in the cylinder
may be less than, equal to, or higher than atmospheric pressure,
depending on the required level of engine power. During a
four-stroke cycle mode of operation, each engine cylinder has two
power strokes, one with compressed-air and one with combustion-gas,
during each cycle. During a two-stroke cycle mode of operation, the
compressed-air charge eliminates or reduces the amount of required
compression work. Moyer's patent does not include these modes of
engine operation.
[0017] (6) The present invention provides for a compressed-air
reservoir with a heating jacket through which a variable and
controllable flow of exhaust gas can be maintained. This prevents
heat loss through external walls of the air-reservoir and maintains
optimum air-temperature level for best engine operation. The above
patent does not include any such measures. Without them,
substantial energy losses, associated with cooling of compressed
air during its storage, will result.
[0018] (7) The present invention includes a method for controlling
the magnitude of the braking force by varying the transmission
ratio during compression braking. The above patent does not
anticipate such method of control.
[0019] (8) The present invention includes controlling the braking
force by omitting some of the engine cycles during compression
braking. This is not included in Moyer's patent.
[0020] (9) The present invention includes a method of preserving
the energy of the residual compressed-air trapped in the clearance
volume between the piston and the cylinder head at the end of the
compression stroke during compression braking, when the engine
operates as a compressor. It involves postponing opening the intake
valve until the residual compressed-air expands to atmospheric
pressure during the volume increasing stroke of the piston. During
expansion, energy of the residual compressed-air is transmitted to
the piston. Moyer's patent does not include such method of energy
saving.
[0021] (10) The present invention includes a method for controlling
the quantity of residual exhaust gas retained in the cylinder for
nitrogen oxide control during operation with compressed-air assist.
The method involves a variable early exhaust valve closing. This
replaces exhaust gas recirculation which is not feasible when the
engine receives its intake air from the air-reservoir. The above
patent does not include such method.
[0022] (11) Moyer's patent includes a cylinder disabling function
(listed in No 1 and No 6 independent claims). The present invention
does not preclude, but does not require cylinder disabling. A
better method of operation is to operate some of the cylinders as
an internal combustion engine, and some as a compressor recharging
the air-reservoir, as described in the present invention.
[0023] (12) The present invention includes a concept of using
compressed-air to operate the vehicle electric generator only when
needed, rather than continuously. This eliminates needless
generator operation and saves fuel. The above patent does not
include this.
[0024] (13) The present invention includes a concept of using a
compressed-air hybrid system in combination with an electric
hybrid. The above patent does not include this.
[0025] A U.S. Pat. No. 5,695,430 to Moyer is a continuation of U.S.
Pat. No. 5,529,549. It includes the following:
[0026] (1) Flow of air into and out of the cylinder is controlled
by varying the amplitude of the engine valve lift from zero to
100%. This type of flow control involves throttling the flow, which
inevitably leads to a substantial energy loss. Controlling the
quantity of air received into and discharged from the engine
cylinder without throttling by varying the volume of the air-charge
via variable valve timing, as proposed in the present invention, is
not included in the above patent.
[0027] (2) The above patent also describes utilization of waste
heat from the coolant and exhaust while returning the stored
compressed-air to the cylinders for air-motor operation. It is
dubious that much heat transfer can take place during the short
duration of each intake stroke, and, besides, this does not prevent
loss of heat energy from the compressed-air during its storage. In
contrast to this, the present invention includes a concept of an
air-reservoir with a controllable heating jacket which prevents
heat loss and maintains proper temperature of stored air on a
continuous basis.
SUMMARY OF THE INVENTION
[0028] In its embodiments, the present invention contemplates a
system for and a method of operating a vehicle on wheels. The
system includes an air-reservoir capable to receive, store, and
discharge compressed-air. It also includes a reciprocating-piston
engine capable to selectively operate as an internal combustion
engine, or as a compressor, or as an air-motor. The engine can also
operate concurrently as an internal combustion engine and a
compressor, or concurrently as an internal combustion engine and an
air-motor. During the internal combustion operation, the engine can
selectively operate either as a four-stroke, or as a two-stroke
internal combustion engine.
[0029] The engine has a gas exchange controlling system comprising
a set of deactivatable and variably controllable valves which can
selectively connect engine cylinders either to outside atmosphere,
or to the air-reservoir. There is also a deactivatable fuel
delivery system. The overall system also includes a control system,
which is an on-board computer capable to monitor the vehicle
driver's demands and respond to them by controlling the operation
of the engine and other vehicle components according to a program
contained in its software.
[0030] During vehicle braking the fuel delivery system is
deactivated, and the engine valves activity is such, that the
engine operates as a two-stroke compressor driven by a torque
coming from the vehicle wheels, thus slowing down the vehicle
motion. In each engine cylinder, during each volume-increasing
stroke, a charge of atmospheric air is received into the cylinder
chamber, and, during a subsequent volume-decreasing stroke, this
air-charge is compressed and displaced into the air-reservoir. In
this way, kinetic energy of vehicle motion is transformed into
potential energy of compressed-air stored in the air-reservoir.
Varying the timings of the valves openings and closings varies the
intensity of braking.
[0031] During subsequent vehicle acceleration fuel delivery is
reactivated, and the engine valves activity is such, that the
engine operates as an internal combustion engine receiving air,
needed for its operation, from the air-reservoir. Each
compressed-air charge, received into each engine cylinder from the
air-reservoir, brings-in its energy which supplements the energy
released in combustion. This reduces the fuel consumption necessary
to produce the required engine torque. In this way, a significant
fraction of the braking energy is reclaimed during acceleration.
Changing the schedule of the engine valves operation and doubling
the frequency of fuel delivery can switch the engine operational
cycle from a four-stroke to a two-stroke cycle, or vice versa. The
engine can also operate as a conventional internal combustion
engine receiving air from outside atmosphere.
[0032] To save fuel, the engine operation can be completely
deactivated during vehicle coasting, when the driver depresses
neither the acceleration pedal, nor the brake pedal. The same can
be done whenever the vehicle stops. To restart the engine after a
brief stop, it can be brought up to speed by operating it as a
two-stroke air-motor receiving compressed-air from the
air-reservoir.
[0033] Charging the air-reservoir with compressed-air can also be
accomplished concurrently with internal combustion operation at
part-load. For this, the schedule of the engine valves operation is
modified, so that a fraction of the air-charge compressed in each
cylinder by the cylinder piston during each volume-decreasing
stroke is diverted into the air-reservoir. In another alternative,
some of the engine cylinders operate as a compressor, while other
cylinders operate as an internal combustion engine. If so desired,
air-reservoir charging can also be performed during vehicle
coasting and during short stops.
[0034] Accordingly, it is an object of the present invention to
reduce the cost and complexity of a hybrid vehicle system by
eliminating the need for a second machine complementing the
internal combustion engine. Instead, a single engine is provided,
capable to operate both as an internal combustion engine and as a
compressor/air-motor.
[0035] Another object of the present invention is to improve the
reliability of a hybrid vehicle system by eliminating a large
number of components and subsystems needed for proper operation of
the above second machine.
[0036] A further object of the present invention is to reduce the
weight penalty associated with hybrid systems by using
compressed-air as a medium for energy storage. Air, even when
compressed to high pressure, is very light, and therefore the added
weight is, essentially, limited to the weight of the reservoir.
Elimination of the above second machine and associated components
also contributes to weight reduction.
[0037] Yet another object of the present invention is to improve
efficiency of a hybrid vehicle system by eliminating the energy
losses and inefficiences associated with operation of the above
second machine and related components. In addition, compressing air
in a cylinder and, then, reversing this event by expanding the air
in the same cylinder of a fast operating engine is a very efficient
process.
[0038] A further object of the present invention is to increase the
peak torque and power of the engine by supercharging it with
compressed-air from the air-reservoir, and by switching its
internal combustion operation from a four-stroke to a two-stroke
cycle. Supercharging increases the mass of air received by the
engine cylinders and permits burning of an increased amount of fuel
during each cycle at full-load operation. Switching from the
four-stroke to the two-stroke cycle doubles the number of
combustion events and leads to a significant step-up in engine
torque and power.
[0039] Another object of the present invention is to reduce the
fuel consumption during part-load operation by reducing the size of
the engine. A reduction in engine size is possible thanks to the
above increase in its torque and power. It is a significant
advantage, since a smaller engine consumes less fuel at part-load.
An additional reduction in fuel consumption is achieved by
deactivating the combustion during vehicle coasting and during
short stops.
[0040] A further object of the present invention is to reduce or
eliminate the need for electric starter by starting the engine with
compressed-air received from the air-reservoir. This is another
cost reduction.
[0041] Another object of the present invention is to eliminate the
external exhaust gas recirculation system. Exhaust gas
recirculation is used in most engines to reduce nitrogen oxide
emission. The variable valve systems employed by the embodiments of
the present invention can trap sufficient amount of residual gas in
each cylinder at the end of each exhaust stroke to control the
amount of nitrogen oxide produced in the next cycle without the
need for an external exhaust recirculation. Elimination of the
exhaust gas recirculation system leads to a substantial cost
reduction.
[0042] Another object of the present invention is to use stored
energy of compressed-air to drive an on-board electric power
generator independently of the engine operation. Generating
electric power by selectively operating an on-board electric
generator with an approximately constant speed, and only when its
operation is needed, is a substantial improvement over conventional
systems, in which the generators are continuously driven with
variable speed, regardless of need. Selective generation of
electric power in quantities matching the vehicle needs eliminates
waste and thus improves the overall vehicle fuel economy. In
addition, eliminating the need for the vehicle engine to drive the
electric generator increases the peak engine torque and power
available for vehicle propulsion
[0043] A further object of the present invention is to reduce wear
and increase durability of the vehicle friction brakes by using
compression braking instead of friction braking.
[0044] Finally, it is a key object of the present invention to
achieve a significant reduction in fuel consumption by saving and
storing the energy of vehicle motion during its deceleration, and
reusing it later during its subsequent acceleration and
propulsion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a schematic, cross-sectional side-view of an
engine cylinder and head arrangement and its connection to a
compressed-air reservoir, in accordance with a preferred embodiment
of the present invention.
[0046] FIG. 2 is a schematic diagram illustrating a system of
sensors sending input signals to a vehicle control system which
sends out output signals to actuators controlling operation of
various components of the system, in accordance with a preferred
embodiment of the present invention.
[0047] FIG. 3A is a schematic diagram illustrating a single
electrohydraulically actuated engine valve, which is an example of
an engine valve useable with the present invention.
[0048] FIG. 3B is an enlarged view taken from encircled area 2 in
FIG. 3A.
[0049] FIG. 4 is a schematic diagram illustrating automatic
air-temperature control in a compressed-air reservoir useable with
the present invention.
[0050] FIG. 5 is a schematic, cross-sectional side-view of an
engine cylinder and head arrangement and its connection to a
compressed-air reservoir, in accordance with an alternative
embodiment of the present invention.
[0051] FIGS. 6A to 6D are schematic diagrams providing step-by-step
illustrations of the vehicle engine cycle, when it operates as a
compressor, in accordance with the present invention.
[0052] FIGS. 7A, 7B, and 7C are pressure-volume diagrams of the
vehicle engine cycle illustrating its operation as a compressor, as
shown in FIGS. 6A to 6D.
[0053] FIGS. 8A to 8F are schematic diagrams providing step-by-step
illustrations of the vehicle engine cycle, when it operates as a
compressed-air-assisted four-stroke internal combustion engine, in
accordance with the present invention.
[0054] FIG. 9 is a pressure-volume diagram of the vehicle engine
cycle illustrating its operation as a four-stroke internal
combustion engine, as shown in FIGS. 8A to 8F.
[0055] FIGS. 10A to 10D are schematic diagrams providing
step-by-step illustrations of the vehicle engine cycle, when it
operates as a compressed-air-assisted two-stroke internal
combustion engine, in accordance with the present invention.
[0056] FIG. 11 is a pressure-volume diagram of the vehicle engine
cycle illustrating its operation as a two-stroke internal
combustion engine, as shown in FIGS. 10A to 10D.
[0057] FIGS. 12A to 12C are schematic diagrams providing
step-by-step illustrations of the vehicle engine cycle, when it
operates as an air-motor, in accordance with the present
invention.
[0058] FIG. 13 is a pressure-volume diagram of the vehicle engine
cycle illustrating its operation as an air-motor, as shown in FIGS.
12A to 12C.
[0059] FIG. 14 is a pressure-volume diagram of the vehicle engine
cycle illustrating its operation as a compressed-air-assisted
four-stroke internal combustion engine receiving air partly from
the compressed-air reservoir and partly from outside atmosphere, in
accordance with the present invention.
[0060] FIG. 15 is a pressure-volume diagram of the vehicle engine
cycle illustrating its operation as a conventional four-stroke
internal combustion engine propelling the vehicle and recharging
the compressed-air reservoir at the same time, in accordance with
the present invention.
[0061] FIGS. 16A to 16C are schematic diagrams illustrating three
different engine valves operating configurations serving various
engine operating modes, in accordance with an alternative
embodiment of the present invention.
[0062] FIG. 17 is a schematic diagram illustrating an example of a
system using stored energy of compressed-air to operate an on-board
electric power generator.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0063] A preferred embodiment of the present invention is
illustrated in FIGS. 1 to 4. FIG. 1 is a schematic, cross-sectional
side-view of an engine cylinder and head arrangement and its
connection to a compressed-air reservoir. An engine 10 has at least
one cylinder 12 containing a piston 14. Piston 14 is mounted upon a
connecting rod 13 by a wrist pin 15 and can reciprocate in cylinder
12, thus varying the volume of a cylinder chamber 16 enclosed
between piston 14 and a cylinder head 18 attached to the top of
cylinder 12.
[0064] Three types of normally-closed valves: an intake valve 20,
an exhaust valve 22, and a charging valve 24, are installed in
cylinder head 18. Valves 20, 22, and 24 are slideably mounted in
guides 30, 32, and 34, respectively, which are arranged in cylinder
head 18. Depending on the needs of the engine, there may be more
than one valve of each type in each engine cylinder. A conventional
spark plug 26 and a fuel injector 28 are also mounted within
cylinder head 18 and protrude into cylinder chamber 16. If engine
10 is a diesel, there is no need for spark ignition and spark plug
26 is omitted.
[0065] Intake valve 20 is shown in its closed position in which it
separates cylinder chamber 16 from an intake port 36 which opens
into an intake passage 38. Intake passage 38 connects to an intake
manifold 40 to which all intake ports and all intake passages from
all engine cylinders are connected. Intake manifold 40 is connected
to outside atmosphere, usually through a system of intake pipes, an
air-filter, etc.
[0066] Exhaust valve 22 is shown in its closed position in which it
separates cylinder chamber 16 from an exhaust port 42 which opens
into an exhaust passage 44. Exhaust passage 44 connects to an
exhaust manifold 46 to which all exhaust ports and all exhaust
passages from all engine cylinders are connected. Exhaust manifold
46 is connected to outside atmosphere, usually through a system of
exhaust pipes, a muffler, a catalyst, etc.
[0067] Charging valve 24 is shown in its closed position in which
it separates cylinder chamber 16 from a charging port 48 which
opens into a charging passage 50. Charging passage 50 connects to a
charging manifold 52 to which all charging ports and all charging
passages from all engine cylinders are connected. Charging manifold
52 is connected via a duct 54 to an air-reservoir 56. Air-reservoir
56 is made of a material capable to contain and withstand the
pressure of compressed-air inside the reservoir. It can be located
anywhere in the vehicle. If so desired, the vehicle may have
several air-reservoirs, all connected to charging manifold 52.
[0068] Fuel injector 28 is of the kind in which timing of fuel
injection and quantity of fuel injected during each engine cycle is
determined by timing and duration, respectively, of injector
opening. It is connected via a passage 58 to a fuel manifold 60 to
which all fuel injectors from all engine cylinders are connected.
Fuel manifold 60 is filled with fuel pressurized to a predetermined
constant pressure and delivered to fuel manifold 60 from a vehicle
fuel supply system 64 via a fuel line 62.
[0069] FIG. 2 is a schematic diagram illustrating a system of
sensors sending input signals to a vehicle control system which
sends out output signals to actuators controlling operation of
various components of the system. The signals generated by the
sensors inform the control system about vehicle driver's demands
for a specific vehicle propulsion or braking force, as the case may
be. Propulsion force is a force acting on the vehicle in a
direction of its motion. Braking force is a force acting on the
vehicle in a direction opposite to its motion. The input signals
also carry information on physical and operational conditions in
various parts and components of the engine and the vehicle. The
control system evaluates the received information and, in
accordance with its internal logic, controls operation of the
engine and other vehicle components, so as to satisfy the driver's
demands while maintaining optimum fuel consumption efficiency.
[0070] As shown in FIG. 2, a pressure sensor 72 and a temperature
sensor 74 are mounted in air-reservoir 56. They measure pressure
and temperature of air inside air-reservoir 56 and transmit these
data to a control system 70 via electric lines 122 and 124,
respectively.
[0071] Two sensors, 78 and 80, monitor piston 14 position in
cylinder 12 (FIG. 1). They are installed in proximity to a
crankshaft 66 and actually measure rotational position of a crank
68 but, since motion of piston 14 is a well defined function of
crank 68 rotation, this also defines piston 14 position. Sensor 78
sends a single electric pulse via an electric line 128 to control
system 70 every time crank 68 puts piston 14 in a top dead center
position. The top dead center is a piston position in which the
direction of the piston motion is reversed and the volume of the
cylinder chamber is at its minimum. Conversely, a bottom dead
center is a piston position in which the direction of the piston
motion is reversed and the volume of the cylinder chamber is at its
maximum. Sensor 80 sends a continuous series of electric pulses via
an electric line 130 to control system 70 during each crank 68
revolution. These pulses are separated from each other by equal
angles of crank 68 rotation, each such angle being a fraction of
crank 68 revolution. The two signals coming from sensors 78 and 80
supply control system 70 with frequently updated information on
crank 68 and piston 14 positions relative to the top dead center in
cylinder 12. This also supplies information on positions of cranks
and pistons in all other engine cylinders, since positions of other
cranks relative to crank 68 are known. In addition, time intervals
between arrivals of individual pulses generated by sensor 80
provide control system 70 with information on the speed of
crankshaft 66 rotation.
[0072] Two sensors, 82 and 92, are intended to inform control
system 70 about the driver's demands for the vehicle braking or
propulsion force, as the case may be. Sensor 82 is installed on a
pivot-shaft 84 to which a brake pedal 86 is rigidly attached. In
its free position, a spring 90 keeps brake pedal 86 pressed against
a stop 88. In this position, sensor 82 generates no signal.
Whenever brake pedal 86 is depressed, sensor 82 generates an
electric signal the magnitude of which increases with an increase
in brake pedal 86 travel away from stop 88. An increase or a
decrease in the magnitude of this signal is a demand for an
increase or a decrease, respectively, in the magnitude of the
braking force.
[0073] Installation and operation of sensor 92 is similar to that
of sensor 82. Sensor 92 is installed on a pivot-shaft 94 to which
an acceleration pedal 96 is rigidly attached. In its free position,
a spring 100 keeps acceleration pedal 96 pressed against a stop 98.
In this position, sensor 92 generates no signal. Whenever
acceleration pedal 96 is depressed, sensor 92 generates an electric
signal the magnitude of which increases with an increase in
acceleration pedal 96 travel away from stop 98. An increase or a
decrease in the magnitude of this signal is a demand for an
increase or a decrease, respectively, in the magnitude of the
propulsion force.
[0074] The signals generated by sensors 82 and 92 are transmitted
to control system 70 via electric lines 132 and 134, respectively.
Absence of signals from sensor 82, or from sensor 92, is
interpreted by control system 70 as an absence of a demand for a
braking force, or an absence of a demand for a propulsion force,
respectively. Absence of signals from both sensors, 82 and 92, is
interpreted as an absence of a demand for either of the two
forces.
[0075] A clutch sensor 102 is installed on a pivot-shaft 104 to
which a clutch pedal 106 is rigidly attached. In its free position,
a spring 110 keeps clutch pedal 106 pressed against a stop 108. In
this position sensor 102 generates an electric signal which is
transmitted to control system 70 via an electric line 136. This
informs control system 70 that the vehicle clutch is engaged.
Whenever clutch pedal 106 is depressed and moves away from stop
108, sensor 102 generates no signal. This informs control system 70
that the vehicle clutch is disengaged and the engine is not coupled
to the vehicle wheels. In vehicles without a clutch, sensor 102 and
line 136 are omitted.
[0076] A transmission ratio sensor 112 is mounted in a transmission
ratio change mechanism 114 which is part of a transmission 116.
Transmission 116 couples engine 10 (FIG. 1) to at least one of the
vehicle wheels with a variable transmission ratio, except when it
is in a neutral position, or when the vehicle clutch is disengaged.
The transmission ratio is a ratio of the speed of a transmission
input shaft 119 to the speed of a transmission output shaft 120.
The neutral position is a temporary transmission components
arrangement providing no mechanical coupling between transmission
input shaft 119 and transmission output shaft 120. When
transmission 116 is in neutral position, engine 10 is not coupled
to the vehicle wheels. Transmission ratio sensor 112 sends a
variable electric signal carrying information on the transmission
ratio to control system 70 via an electric line 138. Whenever
transmission 116 is in neutral position, transmission ratio sensor
112 generates no signal.
[0077] A vehicle motion sensor 118 is installed in proximity to
transmission output shaft 120. Alternatively, sensor 118 may be
installed in proximity to the vehicle driveshaft or any other
component which rotates when the vehicle is in motion. Sensor 118
detects vehicle motion, measures its speed, and sends this
information to control system 70 via an electric line 140.
[0078] Control system 70 is an on-board computer programmed to
control operation of various components of the engine and the
vehicle in accordance with a strategy program incorporated into its
software. The software contains algorithms and data which permit
the control system to evaluate the stream of input signals and
determine the magnitude and the timing of each output signal. The
output signals controlling operation of the engine and other
vehicle components are updated at least once every engine
cycle.
[0079] Control system 70 controls operation of spark plug 26 and
fuel injector 28 by sending control signals to a spark plug
actuator 148 and to a fuel injector actuator 149 via electric lines
156 and 158, respectively. It also controls spark plugs and fuel
injectors in all other engine cylinders. Spark plug actuator 148 is
an ignition coil installed directly on top of spark plug 26.
Alternatively, an ignition coil can be remotely installed and
electrically connected to the spark plug.
[0080] Fuel injector actuator 149 is a solenoid which opens and
closes fuel injector 28, thus initiating and terminating,
respectively, fuel injection into cylinder chamber 16. The timing
and the duration of the control signal sent to fuel injector
actuator 149 determine the timing of the fuel injection and the
quantity of fuel injected, respectively. While this type of
arrangement is the preferred embodiment of fuel injection and its
control in the present invention, other types of fuel injection
systems, possibly including solenoid-controlled plunger-type pumps
and other types of fuel injection pumps, and other types of fuel
injectors , may be used in accordance with the present
invention.
[0081] If transmission 116 is of the type which operates under
electronic control, transmission ratio change mechanism 114
incorporates a transmission ratio change actuator 113 capable to
change the transmission ratio on a signal received from control
system 70 via an electric line 139. In systems without electronic
transmission control, actuator 113 and line 139 are omitted.
[0082] Control system 70 can also activate a conventional friction
brake system 29. Whenever necessary, a control signal sent from
control system 70 to friction brake system 29 via electric line 159
activates electrohydraulic, electromechanical, or electropneumatic
actuators which bring into rubbing contact friction brake
components, such as, for example, brake shoes and brake drums, with
force that increases with an increase in the magnitude of the
control signal coming from control system 70.
[0083] Control system 70 also controls operation of intake valve
20, exhaust valve 22, and charging valve 24 by sending control
signals to valve actuators 142, 144, and 146, respectively, which
effectuate opening and closing of their respective valves. It also
controls all valves in all other engine cylinders. Each valve
actuator receives two separate control signals, one for valve
opening and one for valve closing. Actuator 142 receives signals
for valve opening and closing via lines 150 and 151, respectively.
These two lines are shown as a single line labeled 150/151 in FIG.
2. Actuator 144 receives signals for valve opening and closing via
lines 152 and 153, respectively. Actuator 146 receives signals for
valve opening and closing via lines 154 and 155, respectively.
Timing of each valve opening and closing is determined by timing of
respective control signals received by its actuator. Valve lift can
be varied by varying duration of the signals.
[0084] FIG. 3A is a schematic diagram illustrating a single
electrohydraulically actuated engine valve, which is an example of
an engine valve useable with the present invention. It shows
actuator 146 controlling charging valve 24, but similar actuators
can be used to control other engine valves. While this example is
the preferred embodiment of the valve actuator, other hydraulic,
pneumatic, electrical, and mechanical systems can also be used to
variably control engine valves, in accordance with the present
invention. This includes an actuator disclosed in U.S. Pat. No.
5,255,641 to Schechter, which is incorporated herein by
reference.
[0085] As shown in FIG. 3A, a valve piston 210, attached to the top
of charging valve 24, is slideable within the limits of a first
hydraulic chamber 214. Valve piston 210 divides first hydraulic
chamber 214 into two volumes, a variable first upper volume 216 and
a variable first lower volume 212. The piston pressure area in
first upper volume 216 is larger than that in first lower volume
212. An amplifier piston 218 is slideable within the limits of a
second hydraulic chamber 220, separated from first hydraulic
chamber 214 by a partition 222. A push-rod 224, integral with or
otherwise coupled to amplifier piston 218, slideably protrudes
through an opening in partition 222 into first upper volume 216.
Amplifier piston 218 divides second hydraulic chamber 220 into two
volumes, a variable second upper volume 226 and a variable second
lower volume 228.
[0086] Actuator 146 also includes two normally closed solenoid
valves, a high pressure solenoid valve 230 and a low pressure
solenoid valve 232, and two check-valves, 234 and 236.
High-pressure fluid is supplied from a high-pressure fluid source
238 through a high-pressure passage 240 to a high-pressure port 242
and, from there, is distributed to high-pressure solenoid valve
230, to check-valve 234, and to first lower volume 212 through
passages 244, 246, and 248, respectively. Passages 262 and 264
connect solenoid valve 230 and check valve 234 to upper volumes 216
and 226, respectively. Low-pressure fluid is supplied from a
low-pressure fluid source 250 through a low-pressure passage 252 to
a low-pressure port 254 and, from there, is distributed to
low-pressure solenoid valve 232, to check-valve 236, and to second
lower volume 228 through passages 256, 258, and 260, respectively.
Passages 266 and 268 connect solenoid valve 232 and check valve 236
to upper volumes 216 and 226, respectively. The installation of the
two check-valves is such, that check-valve 234 permits flow only in
the direction leading back into high-pressure fluid source 238, and
check-valve 236 permits flow only in the direction leading out of
low-pressure fluid source 250.
[0087] High-pressure solenoid valve 230 and low-pressure solenoid
valve 232 receive control signals from control system 70 via
electric lines 154 and 155, respectively. Each control signal
causes opening of the respective solenoid valve for the duration of
the signal.
[0088] Opening of charging valve 24 is initiated by opening of
high-pressure solenoid valve 230. This supplies high-pressure fluid
to upper volumes 216 and 226 through passages 262 and 264,
respectively. Because of a difference between valve piston 210
upper and lower pressure areas, a net hydraulic force acting on it
is directed downward, toward charging valve 24 opening. High
pressure in second upper volume 226 also generates a hydraulic
force pushing amplifier piston 218 downward, and this additional
force is transmitted to valve piston 210 by push-rod 224. A
combined force of the two pistons is sufficient to crack-open
charging valve 24 against pressure in cylinder chamber 16. This
drops the pressure in cylinder chamber 16 and eliminates the need
for a high hydraulic force during further opening travel of
charging valve 24. Because of that, downward travel of amplifier
piston 218 is limited to a short distance 4 sufficient to
crack-open charging valve 24 enough to drop the pressure in
cylinder chamber 16. After that, only the net hydraulic force
acting on valve piston 210 accelerates charging valve 24 downward.
Thanks to assist from amplifier piston 218, lower level of pressure
can be maintained in high-pressure fluid source 238, which leads to
lower energy consumption for engine valves operation.
[0089] When high-pressure solenoid valve 230 closes, pressure in
upper chambers 216 and 226 drops, the net hydraulic force acting on
valve piston 210 reverses its direction, and valve piston 210
decelerates, pumping fluid from first lower volume 212 back into
high-pressure fluid source 238. This recovers some of the energy
that was used to accelerate charging valve 24 downward.
Concurrently, low-pressure fluid flowing through check-valve 236
fills upper volume 216. When charging valve 24 exhausts its
momentum and its motion stops, check-valve 236 closes, and charging
valve 24 remains locked in its open position.
[0090] Closing of charging valve 24 is initiated by opening
low-pressure solenoid valve 232. This drops the pressure in and
permits fluid to escape from upper volumes 216 and 226 through
passages 266 and 268, respectively. As a result, the net hydraulic
force acting on valve piston 210 accelerates charging valve 24
upward, towards its closing. When low-pressure solenoid valve 232
closes, pressure in first upper volume 216 rises, the net hydraulic
force acting on valve piston 210 reverses its direction, and valve
piston 210 decelerates, pumping fluid from first upper volume 216
through check-valve 234 back into high-pressure fluid source 238.
This recovers some of the energy that was used to accelerate
charging valve 24 upward.
[0091] When charging valve 24 approaches its closed position, valve
piston 210 contacts push-rod 224, and added resistance of amplifier
piston 218 pumping fluid from second upper volume 226 through
passage 264 and check-valve 234 back to high-pressure fluid source
238 absorbs the remaining momentum of charging valve 24. When
charging valve 24 closes, valve piston 210 becomes mechanically
latched in its uppermost position by at least one latch 270 located
in upper part of first upper volume 216. This eliminates the need
for a high hydraulic pressure to keep charging valve closed against
high air-pressure in charging port 48 when pressure in cylinder
chamber 16 is low.
[0092] FIG. 3B is an enlarged view taken from encircled area 2 in
FIG. 3A. It illustrates latch 270 and its engagement with valve
piston 210. Several such latches may be installed along the
circumference of upper volume 216.
[0093] A latch pin 272 is slideably installed in a tightly fitting
guide 273. A spring 274, located in a latch chamber 275, exerts a
force on latch pin 272 pushing it left, towards the center of first
upper volume 216. A passage 276 leads to low-pressure fluid source
250 (FIG. 3A).
[0094] A dome 277, integral with valve piston 210, has an annular
grove 278 with a trapezoidal cross-section. When valve piston 210
is in its uppermost position, a conical tip 279 of latch pin 272
engages annular grove 278, as shown in FIG. 3B, thus latching valve
piston 210. When high pressure is applied to first upper volume
216, pressure differential between first upper volume 216 and latch
chamber 275 forces latch pin 272 to retract from first upper volume
216, thus permitting downward motion of valve piston 210. When
valve piston 210 returns to its uppermost position again, and the
pressure in first upper volume 216 drops, spring 274 pushes latch
pin 272 back into grove 278, thus latching valve piston 210 again.
It then remains latched until high pressure from high-pressure
fluid source 238 (FIG. 3A) is again applied to first upper volume
216.
[0095] Actions of amplifier piston 218 and latch 270 reduce the
required level of pressure in high-pressure fluid source 238.
Without them, much higher fluid pressure, or much larger valve
piston 210 would be needed to crack-open charging valve 24 against
high gas-pressure in cylinder chamber 16, and to keep it closed
against high air-pressure in charging port 48. In either case, this
would lead to an increase in energy consumption. Thus, application
of amplifier piston 218 and latch 270 permits substantial reduction
in energy needed for engine valves operation. In addition,
amplifier piston 218 with push-rod 224 serve as a shock absorber
insuring soft and quiet landing of charging valve 24 on its seat.
Additional energy savings are realized thanks to fluid being pumped
back into high-pressure fluid source 238 during charging valve 24
decelerations.
[0096] For good engine operation, it is desirable to control the
temperature of compressed-air in the air-reservoir. FIG. 4 is a
schematic diagram illustrating automatic air-temperature control in
a compressed-air reservoir useable with the present invention. The
air-temperature control has two objectives. The first one is to
insure that relationship between the temperature and the pressure
of compressed-air in the air-reservoir is within limits determined
by an algorithm contained in the control system software. This is
to insure that the engine gets air which is neither too cold, nor
too hot for proper engine operation. If the air entering the engine
cylinders is too cold, this may adversely affect the combustion
process. If the air is too hot, this may lead to engine knock.
[0097] As shown in FIG. 4, outer surface of air-reservoir 56 has a
double wall forming a heating jacket 280 through which hot
exhaust-gas can be circulated during engine operation. A
plate-valve 282 is rotatably installed on a pivot 284 inside an
exhaust pipe 286. Depending on its position, plate-valve 282 can
divert a variable fraction of total exhaust-gas flow into an inlet
duct 288 leading into heating jacket 280. After circulating through
heating jacket 280, the exhaust gas returns through an outlet duct
290 back into exhaust pipe 286. Arrows in the drawing illustrate
the flow of exhaust gas.
[0098] An actuator 292, which, typically, is a stepper-motor, can
vary the position of plate-valve 282, thus varying the exhaust-gas
flow through heating jacket 280. Actuator 292 is controlled by a
variable signal from control system 70 via an electric line 294.
Control system 70 receives information on pressure and temperature
of air inside air-reservoir 56 from pressure sensor 72 and
temperature sensor 74, respectively, via electric lines 122 and
124, respectively. On the basis of this information, it controls
the exhaust-gas flow through heating jacket 280 to insure that the
temperature of the air inside air-reservoir 56 is a proper function
of its pressure, as dictated by the algorithm contained in the
control system software. Increasing or decreasing the exhaust-gas
flow through heating jacket 280 increases or decreases,
respectively, the temperature of compressed-air in air-reservoir
56.
[0099] Availability of compressed-air stored in the air-reservoir
creates an opportunity to use it to drive an on-board electric
power generator. Most automotive vehicle systems include electric
generators which produce electricity to satisfy various vehicle
needs. Usually, such generator is mechanically driven by the
vehicle engine and, therefore, operates continuously, regardless of
need, which leads to waste of energy. A more efficient energy
utilization can be achieved if the electric generator is driven
only when its operation is needed.
[0100] FIG. 17 is a schematic diagram illustrating an example of an
alternative system for operating an on-board electric power
generator. A normally closed solenoid valve 1112 is installed on
air-reservoir 56 and is connected via an air-duct 1114 to an
air-motor 1116. Various types of air-motors such as, for example,
vane-type or piston-type motors can be used. In other alternatives,
an air-turbine or other type of a prime mover, using compressed-air
as a source of energy, can be used. A shaft 1118 couples air-motor
1116 to an electric generator 1120, which is electrically connected
to an electric battery 1122 via an electric line 1124, a regulator
1126, and an electric line 1128. Regulator 1126 may include a
voltage regulator and, if needed, an AC to DC current converter. A
battery charge sensor 1138 and an electric line 1130 connect
electric battery 1122 to control system 70, which permits the
latter to monitor the battery charge. Control system 70 can control
operation of solenoid valve 1112 by sending a control signal via an
electric line 1132. Varying the intensity of the control signal can
vary solenoid valve 1112 opening. A speed sensor 1134 is installed
in the vicinity of shaft 1118. It sends a speed signal via an
electric line 1136 to control system 70 which monitors the
rotational speed of electric generator 1120.
[0101] Control system 70 continuously monitors the state of charge
in electric battery 1122 and, whenever the charge drops below a
first predetermined level, opens solenoid valve 1112. This sends
compressed-air through air-duct 1114 to air-motor 1116, which
starts its operation. Air-motor 1116 rotates shaft 1118, which
drives electric generator 1120. Operation of electric generator
1120 supplies electric power through electric line 1124, regulator
1126, and electric line 1128 to electric battery 1122. This
recharges the battery. When the state of charge of electric battery
1122 exceeds a second predetermined level, which is higher than the
first predetermined level, control system 70 closes solenoid valve
1112, thus terminating the operation of air-motor 1116 and electric
generator 1120. The values of the first and the second
predetermined levels of battery charges are contained in control
system 70 memory. Control system 70 can be programmed to maintain
the rotational speed of electric generator 1120 within
predetermined limits by controlling the flow of compressed-air to
air-motor 1116. This can be accomplished by varying the opening of
solenoid valve 1112.
[0102] Generating electric power by selectively operating an
on-board electric generator with an approximately constant speed,
and only when its operation is needed, is a substantial improvement
over conventional systems, in which the generators are continuously
driven with variable speed, regardless of need. Selective
generation of electric power in quantities matching the vehicle
needs eliminates waste and thus improves the overall vehicle fuel
economy. In addition, eliminating the need for the vehicle engine
to drive the electric generator increases the peak engine torque
and power available for vehicle propulsion.
[0103] The system of the present invention can also be arranged in
combination with an electric hybrid system. For this, the system
also includes an electric generator which can be selectively
coupled either to the engine crankshaft or to the vehicle wheels,
an electric motor which can be selectively coupled to the vehicle
wheels, and an electric battery which is electrically connected to
both the generator and the motor and can, selectively, either power
the motor or be charged by the generator. The generator and the
motor may be combined into a single generator-motor unit. When the
electric hybrid system is activated, the generator converts energy
derived either from vehicle motion during its deceleration or from
operation of its engine into electric energy which is transferred
to the electric battery for storage therein. Later, electric energy
is transferred from the battery to the electric motor where it is
converted into mechanical energy assisting in vehicle acceleration
and propulsion. Such an electric hybrid system can serve as a
back-up for the compressed-air-based hybrid system, and, in general
the two systems complement each other's operation. The control
system is programmed to determine how to combine the operation of
the two systems.
[0104] Those skilled in art will appreciate in view of this
disclosure that other engine valves arrangements, other
arrangements for supplying the control system with necessary
information, and other methods of actuation of the key components
of the system, possibly including other types of sensors and
actuators, and other means of signal transmission, may be used
according to the present invention. An example of an alternative
embodiment of the present invention comprising an alternative valve
arrangement is described below.
Description of an Alternative Embodiment
[0105] FIG. 5 is a schematic, cross-sectional side-view of an
engine cylinder and head arrangement and its connection to a
compressed-air reservoir, in accordance with an alternative
embodiment of the present invention. In contrast to the above
described preferred embodiment, the below described alternative
embodiment features only two types of valves, an intake valve and
an exhaust valve, in each engine cylinder. There are also switching
arrangements which can selectively change the nature of functions
performed by the intake and exhaust valves.
[0106] As shown in FIG. 5, an engine 310 has two types of
normally-closed valves, an intake valve 312 and an exhaust valve
314, installed in a cylinder head 316 above an engine cylinder 318.
Identical valve arrangements exist for all engine cylinders. Valves
312 and 314 are slideably mounted in guides 320 and 322,
respectively. Depending on the needs of the engine, there may be
more than one valve of each type in each engine cylinder
[0107] Intake valve 312 is shown in its closed position in which it
separates a cylinder chamber 324 from an intake port 326 which
opens into an intake passage 328. Intake passage 328 connects to an
intake manifold 330 to which all intake ports and all intake
passages from all engine cylinders are connected.
[0108] Exhaust valve 314 is shown in its closed position in which
it separates cylinder chamber 324 from an exhaust port 332 which
opens into an exhaust passage 334. Exhaust passage 334 connects to
an exhaust manifold 336 to which all exhaust ports and all exhaust
passages from all engine cylinders are connected.
[0109] An intake switching arrangement 338 includes a switching
chamber 340, attached to intake manifold 330, and two valves, a
first intake switching valve 342 and a second intake switching
valve 344. Intake switching chamber 340 can be connected to an
opening 346 in the side of intake manifold 330, as shown in FIG. 5,
with no opening at either of the two ends of the intake manifold.
Alternatively, an intake switching chamber can be connected to an
opening at one of the intake manifold two ends, with no opening at
the other end. Valves 342 and 344 are slideably mounted in guides
348 and 350, respectively, which are arranged in switching chamber
340 First intake switching valve 342 is shown in its closed
position, in which it separates intake manifold 330 from outside
atmosphere. Second intake switching valve 344 is shown in its
closed position, in which it separates intake manifold 330 from a
port 352 connected via a duct 354 to an air-reservoir 358.
[0110] An exhaust switching arrangement 359 includes a switching
chamber 360, attached to exhaust manifold 336, and two valves, a
first exhaust switching valve 362 and a second exhaust switching
valve 364. Exhaust switching chamber 360 can be connected to an
opening 366 in the side of exhaust manifold 336, as shown in FIG.
5, with no opening at either of the two ends of the exhaust
manifold. Alternatively, an exhaust switching chamber can be
connected to an opening at one of the exhaust manifold two ends,
with no opening at the other end. Valves 362 and 364 are slideably
mounted in guides 368 and 370, respectively, which are arranged in
switching chamber 360 First exhaust switching valve 362 is shown in
its closed position, in which it separates exhaust manifold 336
from outside atmosphere. Second exhaust switching valve 364 is
shown in its closed position, in which it separates exhaust
manifold 336 from a port 372 connected via a duct 374 to
air-reservoir 358.
[0111] A control system 376 controls operation of intake valve 312,
first intake switching valve 342, and second intake switching valve
344 by sending control signals to actuators 378, 380, and 382,
respectively, via cables 384,386, and 388, respectively. Each cable
may contain two lines, one for valve opening and one for closing.
Control system 376 also controls operation of exhaust valve 314,
first exhaust switching valve 362, and second exhaust switching
valve 364 by sending control signals to actuators 390, 392, and
394, respectively, via cables 396,398, and 399, respectively. Each
cable may contain two lines, one for valve opening and one for
closing.
[0112] In the above described example of the alternative embodiment
there is only one intake manifold and one exhaust manifold. In
other cases, however, the engine may have more than one intake
manifold, each with its own intake switching arrangement, and more
than one exhaust manifold, each with its own exhaust switching
arrangement. In such a case, intake ports from a selective group of
cylinders are connected to one of the intake manifolds, and exhaust
ports from the same group of cylinders are connected to one of the
exhaust manifolds. Intake and exhaust ports from other groups of
cylinders are connected to other pairs of intake and exhaust
manifolds. For example, in an eight-cylinder engine with two intake
manifolds and two exhaust manifolds intake ports from a selective
group of four cylinders can be connected to one of the two intake
manifolds, while exhaust ports from the same group of cylinders are
connected to one of the two exhaust manifolds. Similarly, intake
and exhaust ports from a second group of four cylinders are
connected to the second intake manifold and to the second exhaust
manifold, respectively. Such an arrangement is useful when, as
described below, some of the cylinders are assigned to operate as
an internal combustion engine, while other cylinders operate as a
compressor.
[0113] In all other respects, the above described alternative
embodiment is identical to the previously described preferred
embodiment. Those skilled in art will appreciate in view of this
disclosure that other valve switching arrangements and other types
of switching valves, possibly including rotary valves, may be used
to effectuate connection of cylinder chambers in all engine
cylinders through respective intake valves, selectively, either to
outside atmosphere or to the air-reservoir, and through respective
exhaust valves ,selectively, either to outside atmosphere or to the
air-reservoir, according to the present invention.
Description of Operation of the Preferred Embodiment
[0114] The system described in the Description of Preferred
Embodiment can operate in a variety of braking and propulsion modes
which are described below.
[0115] BRAKING--Vehicle braking is performed whenever the vehicle
driver signals a demand for a braking force by pressing on the
brake pedal. It can be used to slow down the motion of the vehicle
or to restrict its speed in a downhill drive. Compression braking
is a preferred type of braking and is used whenever possible.
Friction brakes are used only when needed to supplement compression
braking, or when compression braking can not be used. Compression
braking can be used only when the engine is coupled to the vehicle
wheels and the vehicle is in motion.
[0116] In a moving vehicle with the engine coupled to the vehicle
wheels, control system 70 (FIG. 2) responds to the driver's demand
for a vehicle braking force by operating the engine in the
compression braking mode. If the vehicle is not in motion, or if
the engine is not coupled to the wheels, control system 70 responds
to the driver's demand for a vehicle braking force by activating
friction brake system 29 (FIG. 2).
[0117] During compression braking, no fuel is injected into the
engine cylinders, and the engine operates as a reciprocating-piston
two-stroke compressor driven from the vehicle wheels by vehicle
motion. Air is received from outside atmosphere into the engine
cylinders, compressed there, and displaced into air-reservoir 56
(FIG. 1). Work performed by the engine pistons absorbs the kinetic
energy of the vehicle and slows it down or restricts its motion. In
this way the energy of the vehicle motion is transformed into
energy of compressed-air stored in air-reservoir 56.
[0118] FIGS. 6A to 6D illustrate a typical compression braking
process employed by the preferred embodiment of the present
invention. It is described as applied to cylinder 12 (FIG. 1), but,
with proper shift in timing, it takes place in all engine
cylinders. Arrows in the diagrams show the directions of crankshaft
rotation and piston motion, as well as the motion of air into and
out of the cylinder chamber. Each downstroke of the piston is a
volume increasing stroke, and each upstroke is a volume decreasing
stroke. The process can be considered consisting of four steps:
intake, compression, air-reservoir charging, and residual-air
expansion. Each four-step process is completed within a single
engine revolution.
[0119] FIG. 6A is a diagram illustrating the step of intake. Intake
valve 20 is open while the other valves remain closed, and a
downward motion of piston 14 draws in atmospheric air through
intake port 36 into cylinder chamber 16. The air comes to intake
port 36 from intake manifold 40 (FIG. 1) through intake passage 38
(FIG. 1). The intake ends when intake valve 20 closes. Timing of
intake valve 20 closure determines the volume of the air-charge
received into cylinder chamber
[0120] FIG. 6B illustrates the next step, the compression. All
valves in cylinder 12 are closed, and an upward motion of piston 14
compresses the air-charge trapped in cylinder chamber 16. The
compression ends when charging valve 24 opens. Timing of charging
valve 24 opening determines how much the air-charge is
compressed.
[0121] FIG. 6C illustrates the third step, the air-reservoir
charging. Charging valve 24 is open while the other valves remain
closed. Piston 14 continues its upward motion, displacing air from
cylinder chamber 16 into charging port 48. From there, the
displaced air flows (see FIG. 1) through charging passage 50,
charging manifold 52, and duct 54 into air-reservoir 56. The
air-reservoir charging ends when charging valve 24 closes, which,
in a typical case, takes place when piston 14 reaches its
top-dead-center position. Opening charging valve 24 before or after
the top-dead-center reduces the amount of compressed-air displaced
into air-reservoir 56.
[0122] FIG. 6D illustrates the last step, the residual-air
expansion. All valves in cylinder 12 are closed, and a downward
motion of piston 14 expands the remnants of the air-charge left in
cylinder chamber 16 after the closure of charging valve 24. This
step ends when intake valve 20 opens, preferably when the pressure
in cylinder chamber 16 drops to the level of atmospheric pressure.
If intake valve 20 opens before the residual-air expands to
atmospheric pressure, some of the air will be discharged back into
intake port 36. This will reduce the expansion work performed on
the piston by the residual-air. In an extreme case, intake valve 20
opens at top-dead-center, and there is no expansion of
residual-air.
[0123] Control system 70 (FIG. 2) is programmed to control the
process of compression braking in a manner which assures that the
process generates a braking force of required magnitude, as
determined by the magnitude of the signal generated by sensor 82
(FIG. 2). The magnitude of the braking force produced by
compression braking increases or decreases with an increase or a
decrease, respectively, in the rate at which the engine uses energy
when it operates as a compressor. Therefore the braking force
increases or decreases with an increase or a decrease,
respectively, in the net negative work-per-cycle performed by the
piston in each of the engine cylinders participating in the
compression braking process. It also increases or decreases with an
icnrease or a decrease, respectively, in frequency of the cycles
repetition, and therefore it increases or decreases with an
increase or a decrease, respectively, in the transmission ratio.
Thus the braking force produced by compression braking can be
varied by varying the work-per-cycle, or by varying the
transmission ratio, or by varying both.
[0124] Thanks to operational flexibility offered by ability to
quickly activate and deactivate the engine valves, the frequency of
the cycles repetition can also be reduced, whenever needed, by
selectively omitting some of the cycles. For example, the cycle can
be performed once every other engine revolution, while during the
in-between-cycle revolutions the valves are deactivated. This
reduces the compression braking force in half, without any change
in the work-per-cycle and the transmission ratio. Omission of some
of the cycles is an additional method which the control system can
use to control the magnitude of the braking force.
[0125] Compression braking is a preferable method for the braking
force generation and control. However, if the compression braking
can not produce the required braking force even at the maximum
work-per-cycle and at the highest transmission ratio, control
system 70 (FIG. 2) activates friction brake system 29 (FIG. 2),
which then works in-parallel with compression braking.
[0126] The work-per-cycle in each cylinder is a function of the
timings of the engine valves openings and closings. These timings
control various parameters contributing to the amount of
work-per-cycle performed, such as the quantity of air received into
the cylinder chamber, the ratio of air compression, the quantity of
air displaced into the air-reservoir, and the ratio of residual-air
expansion. Changing the timing of intake valve 20 closing varies
the quantity of air received. Changing the timing of charging valve
24 opening varies the air compression ratio. Changing the timing of
charging valve 24 closing varies the quantity of compressed-air
displaced into the air-reservoir. Changing the timing of intake
valve 20 opening varies the residual-air expansion ratio. Control
system 70 (FIG. 2) controls and varies the braking force produced
by compression braking by varying any, some, or all of the above
valve timings and the transmission ratio according to a program
contained in the control system software.
[0127] A more detailed insight into the above described compression
braking process and its control can be acquired by examining a
pressure-volume diagram of its cycle. Pressure-volume diagrams are
frequently used to illustrate operation of reciprocating-piston
machinery. Each diagram is a plot of pressure inside a cylinder as
a function of the cylinder chamber volume, which varies with change
in piston position. FIGS. 7A and 7B show pressure-volume diagrams,
each illustrating a single cycle of compression braking in one of
the engine cylinders. In each diagram, the cylinder chamber volume
and the pressure are plotted along the horizontal and vertical
axes, respectively. The pressure and volume axes in each diagram
are labeled by letters P and V, respectively. The minimum volume at
the top-dead-center and the maximum volume at the
bottom-dead-center are marked on the horizontal axes by labels TDC
and BDC, respectively. Each is an idealized diagram which assumes
instantaneous valves opening and closing, and instantaneous air
filling into and discharge from the cylinder chamber.
[0128] A typical pressure-volume diagram of compression braking
during an early stage of the process is shown in FIG. 7A. Intake
valve 20 (FIG. 6A) opens at a variable point 410 and later closes
at a variable point 412. During this period, atmospheric air is
received into cylinder chamber 16 (FIG. 6A) at constant pressure.
This period, which takes place during a second part of the volume
increasing stroke, corresponds to what is shown in FIG. 6A.
[0129] From point 412 to a variable point 414 all valves are
closed, and the air-charge is compressed. This takes place during a
first part of the volume decreasing stroke and corresponds to FIG.
6B.
[0130] At point 414 charging valve 24 (FIG. 6C) opens and remains
open until its closure at a variable point 418. With opening of
charging valve 24 at point 414, pressure in cylinder chamber 16
drops to the level of pressure in air-reservoir 56 (FIG. 1), which
is illustrated by a point 416. From point 416 to point 418, air is
displaced from cylinder chamber 16 into air-reservoir 56 at nearly
constant pressure. There is only a relatively small increase in
pressure associated with compression of air in air-reservoir 56.
This takes place during a second part of the volume decreasing
stroke and corresponds to FIG. 6C.
[0131] From point 418 to point 410 all valves are closed, and the
fraction of the initial air-charge, still left in cylinder chamber
16, expands, preferably until its pressure drops to atmospheric
pressure at point 410. This period takes place during a first part
of the volume increasing stroke and corresponds to FIG. 6D.
[0132] In this description, work-per-cycle is referred to as net
negative work, if it produces a braking force. If, on the other
hand, it produces a propulsion force, it is referred to as net
positive force. Net negative work performed during the above
described cycle is equal to compression work performed from point
412 to point 414, plus displacement work performed from point 416
to point 418, and minus expansion work performed from point 418 to
point 410.
[0133] A preferred method of controlling the work-per-cycle, during
this stage of compression braking, is by controlling the
compression work. Control system 70 (FIG. 2) can vary the
compression work by varying the timing of intake valve 20 closure
(point 412), or the timing of charging valve 24 opening (point
414), or the timing of both. Varying the timing of point 412 varies
the quantity of air received into the cylinder. Varying the timing
of point 414 varies the maximum pressure to which the air-charge is
compressed.
[0134] Pressure in air-reservoir 56 (FIG. 1) increases with every
compression braking cycle. Eventually, during a later stage of the
process, pressure inside air-reservoir 56 may rise to the level of
pressure in the engine cylinder at the end of compression. To
continue pumping air into air-reservoir 56, each air-charge must be
compressed, preferably, to a pressure at least equal to the
pressure in the air-reservoir. Accordingly, control system 70 (FIG.
2) adjusts the required level of compression for every cycle.
[0135] FIG. 7B shows a typical pressure-volume diagram of
compression braking during a later stage of the process. Intake
valve 20 (FIG. 6A) opens at a variable point 510 and later closes
at a variable point 512 after bottom-dead-center (in other cases
point 512 may be timed before or at the bottom-dead-center). During
this period, atmospheric air is received into cylinder chamber 16
(FIG. 6A) at constant pressure. This period takes place during a
second part of the volume increasing stroke and corresponds to what
is shown in FIG. 6A.
[0136] From point 512 to a variable point 514 all valves are
closed, and the air-charge is compressed until its pressure becomes
equal to pressure in air-reservoir 56. This takes place during a
first part of the volume decreasing stroke and corresponds to FIG.
6B.
[0137] At point 514 charging valve 24 (FIG. 6C) opens and remains
open until its closure at a variable point 518. From point 514 to
point 518, air is displaced from cylinder chamber 16 into
air-reservoir 56 at nearly constant pressure. There is only a
relatively small increase in pressure associated with compression
of air in air-reservoir 56. This period takes place during a second
part of the volume decreasing stroke and corresponds to FIG.
6C.
[0138] From point 518 to point 510 all valves are closed, and the
fraction of the initial air-charge, still left in cylinder chamber
16, expands, preferably until its pressure drops to atmospheric
pressure at point 510. This period takes place during a first part
of the volume increasing stroke and corresponds to FIG. 6D.
[0139] For each new cycle, control system 70 (FIG. 2) rises the
pressure at the end of compression, at point 514, to match the
pressure in air-reservoir 56. This is accomplished by retarding the
timing of point 514. To maintain the required value of
work-per-cycle, the volume of the air-charge is adjusted for each
new cycle to compensate for the increase in pressure. This is
performed by varying the timing of point 512.
[0140] Opening intake valve 20 before the pressure in cylinder
chamber 16 drops to atmospheric pressure increases the
work-per-cycle, since it results in a reduction in expansion work.
This, however, is a less desirable method of work-per-cycle
control, since it involves dumping of compressed-air into the
atmosphere and, consequently, leads to a loss of energy.
[0141] An alternative method of implementing compression braking
involves opening the charging valve before the pressure in the
cylinder chamber reaches the level of pressure in the
air-reservoir. This may be useful when a substantial increase in
work-per-cycle is needed. Such process is illustrated in a
pressure-volume diagram shown in FIG. 7C.
[0142] Intake valve 20 (FIG. 6A) opens at a variable point 1210 and
later closes at a variable point 1212. During this period,
atmospheric air is received into cylinder chamber 16 (FIG. 6A) at
constant pressure. This period, which takes place during a second
part of the volume increasing stroke, corresponds to what is shown
in FIG. 6A.
[0143] From point 1212 to a variable point 1214 all valves are
closed, and the air-charge is compressed. This takes place during a
first part of the volume decreasing stroke and corresponds to FIG.
6B.
[0144] At point 1214 charging valve 24 (FIG. 6C) opens and remains
open until its closure at a variable point 1218. With the opening
of charging valve 24 at point 1214, pressure in cylinder chamber 16
increases to the level of pressure in air-reservoir 56 (FIG. 1),
which is illustrated by a point 1216. From point 1216 to point
1218, air is displaced from cylinder chamber 16 into air-reservoir
56 at nearly constant pressure. There is only a relatively small
increase in pressure associated with compression of air in
air-reservoir 56. This takes place during a second part of the
volume decreasing stroke and corresponds to FIG. 6C.
[0145] From point 1218 to point 1210 all valves are closed, and the
fraction of the initial air-charge, still left in cylinder chamber
16, expands, preferably until its pressure drops to atmospheric
pressure at point 1210. This period takes place during a first part
of the volume increasing stroke and corresponds to FIG. 6D
[0146] The above described process of compression braking, coupled
with transfer of the compressed air into an air-reservoir, is a
substantial improvement over a conventional braking involving
friction brakes, which absorb the kinetic energy of the vehicle and
dissipate it as heat. It is also an improvement over other types of
compression braking, in which the compressed air is exhausted into
the outside atmosphere. Instead, the energy of the vehicle motion
is transformed into energy of compressed-air and stored in the
air-reservoir. Later, the stored energy can be used to assist in
vehicle propulsion and acceleration.
[0147] Using the vehicle engine as both an internal combustion
engine and a compressor eliminates the need for additional
machines, such as electric generators, hydraulic pumps, etc., which
are employed by other hybrid vehicle systems. This simplifies the
system and reduces its cost and weight.
[0148] Using air as a medium for energy storage has a distinct
advantage over using other media, since air, even when compressed
to a high pressure, is very light. This reduces the weight of the
hybrid system. In addition, compressing air in a cylinder and,
then, reversing this event by expanding the air in the same
cylinder of a fast operating engine is a very efficient
process.
[0149] Another advantage of the above described method of vehicle
braking is reduced usage of friction brakes. This improves their
reliability and extends their life, thus reducing the costs
associated with their repair and replacement.
[0150] FIRST PROPULSION MODE--Control system 70 (FIG. 2) operates
engine 10 (FIG. 1) as a prime mover selectively propelling the
vehicle in one of several propulsion modes whenever the vehicle
driver signals a demand for a propulsion force by pressing on
accelerator pedal 96 (FIG. 2) and not pressing on brake pedal 86
(FIG. 2). The choice of the propulsion mode is determined by a
control strategy incorporated in control system 70 software.
[0151] The first propulsion mode involves performance of a
four-stroke hybrid cycle, during which the engine operates both as
an air-motor and as an internal combustion engine. In this mode of
operation the intake valves are deactivated and air is received
into the engine cylinders from a compressed-air reservoir rather
than from the outside atmosphere. The compressed-air charge expands
in each cylinder and performs work displacing the piston during a
first volume increasing stroke. Then the same air-charge is used in
an internal combustion process, and expanding combustion gas
performs additional work on the piston during a second volume
increasing stroke. Thus each four-stroke cycle includes two power
strokes, one with compressed-air and another one with combustion
gas.
[0152] FIGS. 8A to 8F illustrate a typical first propulsion mode
cycle. It is described as applied to cylinder 12 (FIG. 1), but,
with proper shift in timing, it takes place in all the engine
cylinders. Arrows in the diagrams show the directions of crankshaft
rotation and piston motion, as well as motion of air into and
exhaust gas out of the cylinder. Each downstroke of the piston is a
volume increasing stroke, and each upstroke is a volume decreasing
stroke. The process can be considered consisting of six steps:
cylinder charging, air expansion, compression and ignition, gas
expansion, exhaust, and residual gas retention. Each six-step cycle
is completed within two engine revolutions.
[0153] FIG. 8A is a diagram illustrating the first step--the
cylinder charging. Charging valve 24 is open while the other valves
remain closed. Piston 14 moves downward, and cylinder 12 is charged
with compressed-air flowing through charging port 48 and open
charging valve 24 into an expanding volume of cylinder chamber 16.
The air comes to charging port 48 from air-reservoir 56 (FIG. 1)
through duct 54 (FIG. 1), charging manifold 52 (FIG. 1), and
charging passage 50 (FIG. 1). Cylinder charging ends when charging
valve 24 closes. Timing of charging valve 24 closure determines the
volume of the compressed-air charge received into the cylinder.
[0154] FIG. 8B illustrates the next step--the air expansion. All
valves in cylinder 12 are closed, and a downward motion of piston
14 expands the air-charge trapped in cylinder chamber 16. The
expansion ends when piston 14 reaches its bottom-dead-center
position.
[0155] FIG. 8C illustrates the third step--compression and
ignition. All valves in cylinder 12 remain closed, and an upward
motion of piston 14 compresses the air-charge in cylinder chamber
16. Fuel is injected into cylinder chamber 16 and is ignited,
preferably, before piston 14 reaches the top-dead-center. In
spark-ignition engines fuel can be injected even before the
bottom-dead-center.
[0156] FIG. 8D illustrates the fourth step--the gas expansion. All
valves in cylinder 12 remain closed. The air-fuel mixture burns in
cylinder chamber 16, and the gaseous products of combustion expand,
performing useful work on the downward moving piston 14. Expansion
continues until exhaust valve 22 opens.
[0157] FIG. 8E illustrates the next step--the exhaust. Exhaust
valve 22 is open while the other valves remain closed, and an
upward motion of piston 14 expels the products of combustion, the
combustion gas, from cylinder chamber 16 through the opened exhaust
valve 22 and exhaust port 42. The exhaust ends when exhaust valve
22 closes.
[0158] FIG. 8F illustrates the last step--the residual-gas
retention. Exhaust valve 22 has closed before piston 14 reached the
top-dead-center, and a certain quantity of combustion-gas, the
residual-gas, remains trapped in cylinder chamber 16. This gas is
needed to restrict production of harmful nitrogen oxide in the next
cycle. Timing of exhaust valve 22 closure determines the volume of
residual-gas retained in the cylinder. This step ends when charging
valve 24 opens, and then the same cycle is repeated again during
the next two engine revolutions.
[0159] Control system 70 (FIG. 2) is programmed to control the
first propulsion mode in a manner which assures that the process
generates a propulsion force of required magnitude, as determined
by the magnitude of the signal generated by sensor 92 (FIG. 2). The
magnitude of the propulsion force increases or decreases with an
increase or a decrease, respectively, in the net positive
work-per-cycle performed on the piston in each of the engine
cylinders. It also depends on frequency with which the cycles are
repeated, and therefore it increases or decreases with an increase
or a decrease, respectively, in the transmission ratio. Thus, the
propulsion force can be varied by varying the work-per-cycle, or by
varying the transmission ratio, or by varying both.
[0160] Two key contributors to the work-per-cycle are: work
performed by compressed-air and work performed by combustion-gas.
Work performed by compressed-air is a function of the timings of
charging valve 24 opening and closing, which determine the quantity
of air received from air-reservoir 56 (FIG. 1). Work performed by
combustion-gas depends on the quantity of fuel added to the air in
the cylinder. Thus, the work-per-cycle can be varied by varying
three parameters: timings of charging valve 24 opening and closing,
and the quantity of fuel added to the air-charge. Control system 70
(FIG. 2) controls the propulsion force by varying any, some, or all
of the above parameters, and by varying the transmission ratio
according to a program contained in the control system software. In
vehicles with manual transmission control, it is the vehicle driver
who varies the transmission ratio.
[0161] A typical idealized pressure-volume diagram of the first
propulsion cycle is shown in FIG. 9. Charging valve 24 (FIG. 8A)
opens at a point 610, and the pressure in the cylinder increases to
the level of pressure in air-reservoir 56 (FIG. 1), which
corresponds to a point 612. A preferred timing of charging valve 24
opening is at the top-dead-center. From point 612 to a point 614
piston 14 (FIG. 8A) is displaced by a nearly constant air-pressure
in cylinder chamber 16 (FIG. 8A). There is only a relatively small
drop in pressure associated with expansion of air in air-reservoir
56. This period takes place during a first part of a first volume
increasing stroke and corresponds to what is shown in FIG. 8A.
[0162] At point 614 charging valve 24 closes, and from point 614 to
a point 616, which is at the bottom-dead-center, the air-charge in
cylinder chamber 16 expands. This takes place during a second part
of the first volume increasing stroke and corresponds to FIG.
8B.
[0163] From point 616 to a point 618 the cylinder charge is
compressed, and from point 618 to a point 620 heal generated by
combustion increases its pressure at nearly constant volume. This
period takes place during a first volume decreasing stroke and
corresponds to FIG. 8C.
[0164] From point 620 to a point 622 combustion is completed, and
the expanding combustion-gas displaces piston 14 until it reaches
its bottom-dead-center at point 622. This takes place during a
second volume increasing stroke and corresponds to FIG. 8D.
[0165] Exhaust valve 22 (FIG. 8E) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to a
nearly atmospheric pressure, as shown at a point 624 (it coincides
with point 616 in the diagram). From point 624 to a point 626
combustion-gas is expelled from cylinder chamber 16 through the
open exhaust valve 22. This period takes place during a first part
of a second volume decreasing stroke and corresponds to FIG.
8E.
[0166] At point 626 exhaust valve 22 closes, and from point 626 to
point 610 all valves are closed, and residual-gas compression takes
place. This takes place during a second part of the second volume
decreasing stroke and corresponds to FIG. 8F.
[0167] Net positive work performed during the above described cycle
is equal to displacement work performed from point 612 to point
614, plus expansion work performed from point 614 to point 616,
minus compression work performed from point 616 to point 618, plus
expansion work performed from point 620 to point 622, and minus
compression work performed from point 626 to point 610. It is
assumed here that exhaust work from point 624 to point 626 is
negligibly small.
[0168] The above described four-stroke cycle is just a typical
example of operation in the first propulsion mode. Those skilled in
art will appreciate that other variants of that cycle, with other
sequences of events can be used for such operation. For example,
instead of closing charging valve 24 at point 614 (FIG. 9) during
the downstroke of piston 14, closure of the charging valve can be
delayed until the piston returns to the same position during its
upstroke. The volume of air received into the engine cylinder is
determined by the position of the piston in the cylinder at the
time of the charging valve closure, regardless of whether this
position was reached during the downstroke or during the upstroke
of the piston.
[0169] The fact that the above described first propulsion mode
cycle includes two power strokes, one with compressed-air and
another with combustion-gas, is a significant advantage over a
conventional four-stroke internal combustion cycle including only
one power stroke. Work performed by compressed-air during one power
stroke is added to work performed by combustion-gas during a second
power stroke. This reduces the work which the combustion-gas must
perform and, thus, reduces the quantity of fuel required. Since the
work performed by compressed-air represents energy which was
previously saved, a substantial reduction in fuel consumption is
achieved.
[0170] The additional work performed by compressed-air increases
the magnitude of the peak torque that can be produced by the
engine. A further increase in the peak torque and peak power of the
engine can be achieved by supercharging the engine with
compressed-air from the air-reservoir. Charging the engine
cylinders with quantities of air in excess of what a conventional
naturally aspirated engine can receive increases the maximum
quantity of fuel that can be burned in each cylinder during each
cycle. An increase in the peak engine torque and power, without an
increase in engine displacement, creates an opportunity for a
reduction in engine size (smaller engine displacement). This is a
significant advantage, since a smaller engine consumes less fuel
during part-load operation.
[0171] An additional advantage of the above described cycle is its
ability to trap a variable and controllable quantity of
residual-gas in each engine cylinder at the end of the second
volume decreasing stroke. Retention of residual-gas contributes to
a reduction in harmful nitrogen oxide emission and eliminates the
need for exhaust-gas recirculation systems used for the same
purpose in conventional internal combustion engines. This leads to
a substantial reduction in costs.
[0172] SECOND PROPULSION MODE--The second propulsion mode involves
performance of a two-stroke hybrid cycle, during which the engine
operates as a two-stroke internal combustion engine with a
compressed-air assist. An entire cycle in each engine cylinder is
completed during a single engine revolution. The intake valves are
deactivated, and air is received into the engine cylinders from the
compressed-air reservoir only.
[0173] In a typical second propulsion mode cycle, compressed-air
from air-reservoir 56 (FIG. 1) is received into each engine
cylinder and subjected to additional compression during a part of
the piston volume decreasing stroke. Fuel is injected into the
air-charge, and the air-fuel mixture is ignited, preferably before
the piston reaches the top-dead-center. Combustion and
combustion-gas expansion takes place during a volume increasing
stroke of the piston, followed by exhaust during an early part of
the volume decreasing stroke of the piston preceding the
compressed-air intake.
[0174] FIGS. 10A to 10D illustrate a typical second propulsion mode
cycle. It is described as applied to cylinder 12 (FIG. 1), but,
with or without a shift in timing, it takes place in all the engine
cylinders. Arrows in the diagrams show the directions of crankshaft
rotation and piston motion, as well as motion of air into and
exhaust gas out of the cylinder. Each downstroke of the piston is a
volume increasing stroke, and each upstroke is a volume decreasing
stroke. The process can be considered consisting of four steps:
cylinder charging, compression and ignition, gas expansion, and
exhaust. Each four-step cycle is completed within one engine
revolution.
[0175] FIG. 10A is a diagram illustrating the first step--the
cylinder charging. Charging valve 24 is open while the other valves
remain closed. Piston 14 moves upward, and cylinder 12 is charged
with compressed-air flowing through charging port 48 and open
charging valve 24 into a shrinking volume of cylinder chamber 16.
The air comes to charging port 48 from air-reservoir 56 (FIG. 1)
through duct 54 (FIG. 1), charging manifold 52 (FIG. 1), and
charging passage 50 (FIG. 1). Inside cylinder chamber 16, the air
is mixed with residual exhaust-gas. Cylinder charging ends when
charging valve 24 closes.
[0176] FIG. 10B illustrates the next step--compression and
ignition. All valves in cylinder 12 are closed, and an upward
motion of piston 14 compresses the mixture of air and residual gas.
Fuel is injected into cylinder chamber 16 and is ignited,
preferably, before piston 14 reaches the top-dead-center.
[0177] FIG. 10C illustrates the third step--the gas expansion. All
valves in cylinder 12 remain closed. The air-fuel mixture in
cylinder chamber 16 burns, and the gaseous products of combustion
expand, performing useful work on the downward moving piston 14.
Expansion continues until exhaust valve 22 opens.
[0178] FIG. 10D illustrates the last step--the exhaust. Exhaust
valve 22 is open while the other valves remain closed, and an
upward motion of piston 14 expels the products of combustion from
cylinder chamber 16 through the open exhaust valve 22 and exhaust
port 42. This step precedes the first step of the next cycle, which
takes place during the same piston stroke. The exhaust ends when
exhaust valve 22 closes.
[0179] Control system 70 (FIG. 2) controls the second propulsion
mode in the same way as the first propulsion mode. The factors
affecting the magnitude of the propulsion force are the same as in
the case of the first propulsion mode. The propulsion force
increases or decreases with an increase or a decrease,
respectively, in the net positive work-per-cycle, and with an
increase or a decrease, respectively, in the transmission ratio. As
in the first propulsion mode, the work-per-cycle can be varied by
varying three parameters: timings of charging valve 24 opening and
closing, and the quantity of fuel added to the air-charge. Control
system 70 (FIG. 2) controls the propulsion force by varying any,
some, or all of the above parameters, and by varying the
transmission ratio according to a program contained in the control
system software. In vehicles with manual transmission control it is
the vehicle driver who varies the transmission ratio.
[0180] A typical idealized pressure-volume diagram of the second
propulsion mode cycle is shown in FIG. 11. Charging valve 24 (FIG.
10A) opens at a point 710, and the pressure in the cylinder
increases to the level of pressure in air-reservoir 56 (FIG. 1)
during an upstroke of piston 14 (FIG. 10A), which corresponds to a
point 712. From point 712 to a point 714 piston 14 moves against
nearly constant pressure in cylinder chamber 16 (FIG. 10A). There
is only a relatively small increase in pressure associated with
compression of air in air-reservoir 56. This takes place during a
second part of the volume decreasing stroke and corresponds to FIG.
10A.
[0181] At point 714 charging valve 24 closes, from point 714 to a
point 716 the cylinder charge is compressed, and from point 716 to
a point 718 heat from combustion increases its pressure at nearly
constant volume. This takes place during a third part of the volume
decreasing stroke and corresponds to FIG. 10B.
[0182] From point 718 to a point 720 combustion is completed, and
the expanding combustion-gas displaces piston 14 until it reaches
its bottom-dead-center at point 720. This takes place during the
volume increasing stroke and corresponds to FIG. 10C.
[0183] Exhaust valve 22 (FIG. 10D) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to
nearly atmospheric pressure, as shown at a point 722. After point
722, upward motion of piston 14 (FIG. 10D) expels combustion-gas
from cylinder chamber 16 (FIG. 10D) through the open exhaust valve
22 until the exhaust valve closes. This takes place during a first
part of the volume decreasing stroke and corresponds to FIG. 10D.
Timing of exhaust valve 22 closure determines the quantity of
residual-gas retained in the cylinder. A preferred timing of
exhaust valve 22 closing coincides with the timing of charging
valve 24 (FIG. 10D) opening at point 710. From then on, the same
cycle is repeated again during the next engine revolution.
[0184] The net positive work performed during the above described
cycle is equal to expansion work performed from point 718 to point
720, minus displacement work performed from point 712 to point 714,
and minus compression work performed from point 714 to point 716.
It is assumed here that the exhaust work from point 722 to point
710 is negligibly small.
[0185] Charging each engine cylinder with compressed-air during
each volume decreasing stroke reduces the amount of compression
work required. This reduces the work which the combustion-gas must
perform and, thus, reduces the quantity of fuel required. Since the
work performed by compressed-air represents energy which was
previously saved, a substantial reduction in fuel consumption is
achieved.
[0186] Engine operation can be switched from a four-stroke cycle
(first propulsion mode) to a two-stroke cycle (second propulsion
mode), or vice versa simply by changing the sequence and frequency
of operation of the engine valves, injectors, and spark plugs (when
applicable). Such a change can be accomplished in one engine cycle.
Ability to selectively switch the engine operation from a
four-stroke cycle to a two-stroke cycle and back is an important
advantage over conventional internal combustion engines, which,
depending on their design, can operate only either as four-stroke,
or as two-stroke engines. A switch from the four-stroke to the
two-stroke cycle doubles the number of combustion events at a given
engine speed, which leads to a significant step-up in engine torque
and power. This is especially useful during acceleration from a low
vehicle speed, when a sudden increase in torque is very
desirable.
[0187] THIRD PROPULSION MODE--In the third propulsion mode the
engine operates as a two-stroke air-motor receiving compressed-air
from a compressed-air reservoir. An entire cycle in each engine
cylinder is completed during a single engine revolution. In a
typical third propulsion mode cycle, fuel injectors are
deactivated, and compressed-air from air-reservoir 56 (FIG. 1) is
received into each engine cylinder and expands there displacing the
piston during its volume increasing stroke. Then, during a volume
decreasing stroke, the expanded air is exhausted from the cylinder
into the outside atmosphere.
[0188] FIGS. 12A to 12C illustrate a typical third propulsion mode
cycle. It is described as applied to cylinder 12 (FIG. 1), but,
with proper shift in timing, it takes place in all the engine
cylinders. Arrows in the diagrams show the directions of crankshaft
rotation and piston motion, as well as motion of air into and out
of the cylinder. Each downstroke of the piston is a volume
increasing stroke, and each upstroke is a volume decreasing stroke.
The process can be considered consisting of three steps: cylinder
charging, air expansion, and exhaust. Each three-step cycle is
completed within one engine revolution.
[0189] FIG. 12A is a diagram illustrating the first step--the
cylinder charging. Charging valve 24 is open while the other valves
remain closed. Piston 14 moves downward, and cylinder 12 is charged
with compressed-air flowing through charging port 48 and open
charging valve 24 into an expanding volume of cylinder chamber 16.
The air comes to charging port 48 from air-reservoir 56 (FIG. 1)
through duct 54 (FIG. 1), charging manifold 52 (FIG. 1), and
charging passage 50 (FIG. 1). Cylinder charging ends when charging
valve 24 closes. Timing of charging valve 24 closure determines the
volume of the compressed-air charge received into the cylinder.
[0190] FIG. 12B illustrates the next step--the air expansion. All
valves in cylinder 12 are closed, and a downward motion of piston
14 expands the air-charge trapped in cylinder chamber 16. The
expansion ends when piston 14 reaches its bottom-dead-center
position.
[0191] FIG. 12C illustrates the last step--the exhaust. Intake
valve 20 is open while the other valves remain closed, and an
upward motion of piston 14 expels the air from cylinder chamber 16
through open intake valve 20 and intake port 36. This step ends
when intake valve 20 closes and charging valve 24 opens, and then
the same cycle is repeated again during the next engine
revolution.
[0192] In the above described cycle the exhaust valves are
deactivated. Expelling the air from the cylinder through the intake
valve, rather than through the exhaust valve, is preferable, since
it prevents undesirable cooling of a catalyst which is part of the
engine exhaust system. Nevertheless, in another variant of the
above cycle, the intake valves can be deactivated and the air
exhausted through the exhaust valves.
[0193] Control system 70 (FIG. 2) controls the magnitude of the
propulsion force by controlling the net positive work-per-cycle and
the transmission ratio. The work-per-cycle is controlled by varying
the timings of the charging valve opening and closing, which
determine the quantity of air received into the cylinder from
air-reservoir 56 (FIG. 1). The propulsion force increases or
decreases with an increase or a decrease, respectively, in the net
positive work-per-cycle, and with an increase or a decrease,
respectively in the transmission ratio. In vehicles with manual
transmission control, it is the vehicle driver who varies the
transmission ratio.
[0194] A typical pressure-volume diagram of the third propulsion
mode cycle is shown in FIG. 13. Charging valve 24 (FIG. 12A) opens
at a point 810, which is preferably at the top-dead-center, and the
pressure in cylinder chamber 16 (FIG. 12A) rises to the level of
pressure in air-reservoir 56 (FIG. 1), which is illustrated by a
point 812. From point 812 to a point 814 cylinder chamber 16 is
charged with compressed-air from air-reservoir 56. This takes place
during a first part of the volume increasing stroke and corresponds
to FIG. 12A.
[0195] At point 814 charging valve 24 (FIG. 12A) closes, and from
point 814 to a point 816 the air-charge expands, preferably to
atmospheric pressure. This takes place during a second part of the
volume increasing stroke and corresponds to FIG. 12B.
[0196] At a point 816, which is, preferably, at the
bottom-dead-center, intake valve 20 (FIG. 12C) opens, and from
point 816 to point 810 air is expelled from cylinder chamber 16
(FIG. 12C). This takes place during the volume decreasing stroke
and corresponds to FIG. 12C. Closing of intake valve 20
approximately coincides with opening of charging valve 24 at point
810, and then the same cycle is repeated again.
[0197] The net work performed during the above described cycle is
equal to displacement work performed from point 812 to point 814,
plus expansion work performed from point 814 to point 816. It is
assumed here that the exhaust work from point 816 to point 810 is
negligibly small.
[0198] No fuel is consumed by the engine during periods of
operation in the third propulsion mode. The vehicle is propelled by
compressed-air, and, since the work performed by compressed-air
represents energy previously saved, periodic operation in the third
propulsion mode contributes to a reduction in average fuel
consumption.
[0199] Operation in the third propulsion mode is especially useful
for engine starting, since it permits starting the engine motion
from rest and bringing it to a required speed without resorting to
an electric starter. This reduces, and in some cases eliminates,
the need for an electric starter, which contributes to a cost
reduction.
[0200] FOURTH PROPULSION MODE--The fourth propulsion mode involves
repeated performance of a four-stroke cycle, during which the
engine operates as a conventional four-stroke internal combustion
engine. The charging valves are deactivated, and air is received
into the engine cylinders from the outside atmosphere. Each
cylinder receives its air-charge through an open intake valve
during a first volume increasing stroke. Then, during a first
volume decreasing stroke, the air-charge is compressed, fuel is
added to it, and the air-fuel mixture is ignited. During a second
volume increasing stroke the expanding combustion-gas performs
positive work on the piston, and during a second volume decreasing
stroke the gas is expelled from the cylinder through an open
exhaust valve. As in other four-stroke internal combustion engines,
work-per-cycle is a function of the quantity of fuel burned in each
cylinder during the cycle. Control system 70 (FIG. 2) controls the
magnitude of the propulsion force by controlling the quantity of
fuel added to each air-charge and by varying the transmission
ratio. In vehicles with manual transmission control, it is the
vehicle driver who varies the transmission ratio.
[0201] Control system 70 (FIG. 2) controls the quantity of air
received into each cylinder during each cycle by controlling the
timings of the intake valves opening and closing. Ability to vary
the quantity of air received by varying the timings of the intake
valve events is an important advantage over most other conventional
four-stroke engines, since it eliminates the need for throttling
the intake air flow. Elimination of throttling reduces the pumping
loss and thus contributes to better fuel economy.
[0202] Control system 70 also controls the quantity of residual-gas
remaining in the cylinder after the end of each cycle by
controlling the timing of the exhaust valve closure. Such ability
to control the quantity of residual gas is another important
advantage, since it eliminates the need for an external exhaust-gas
recirculation system needed, in most engines, to restrict nitrogen
oxide emission. Elimination of the external exhaust-gas
recirculation system leads to a reduction in costs.
[0203] OPERATION WITH PORT-INJECTION--The previously described
first propulsion mode requires direct fuel injection into the
engine cylinders. However, many internal combustion engines operate
with port fuel injection involving injection of fuel into each
engine intake port in advance of the air-intake event. The system
described in this invention can also be adopted to operate in a
vehicle propulsion mode with port fuel injection. For this, each
engine cylinder receives a fraction of its air-charge from the
air-reservoir, and the rest of the air-charge comes from the
outside atmosphere. Fuel is added to the atmospheric air while it
is still in the intake port, before it enters the cylinder
chamber.
[0204] FIG. 14 shows a typical pressure-volume diagram illustrating
a modified first propulsion mode cycle operating with port fuel
injection. Charging valve 24 (FIG. 1) opens at a point 910, and the
pressure in the cylinder increases to the level of pressure in
air-reservoir 56 (FIG. 1), which corresponds to a point 912. A
preferred timing of charging valve 24 opening is at the
top-dead-center. From point 912 to a point 914 piston 14 (FIG. 1)
is displaced by a nearly constant air-pressure in cylinder chamber
16 (FIG. 1). There is only a relatively small drop in pressure
associated with expansion of air in air-reservoir 56. This is the
first part of the first volume increasing stroke.
[0205] At point 914 charging valve 24 closes, and from point 914 to
a point 915 the air-charge in cylinder chamber 16 expands,
preferably until the pressure in the cylinder drops to the level of
pressure in intake manifold 40 (FIG. 1). This is a second part of
the first volume increasing stroke.
[0206] Fuel is injected into intake port 36 (FIG. 1) in advance of
intake valve 20 (FIG. 1) opening. At point 915 intake valve 20
opens, and from point 915 to a point 916 air mixed with fuel enters
cylinder chamber 16 (FIG. 1) from intake port 36 (FIG. 1), through
the open intake valve 20. This air-fuel mixture is further mixed
with the air previously received into cylinder chamber 16 from
air-reservoir 56. This takes place during a third part of the first
volume increasing stroke. The intake of the air-fuel mixture ends
when intake valve 20 closes at point 916.
[0207] From point 916 to a point 918 the cylinder charge is
compressed and ignited, and from point 918 to a point 920 heat
generated by combustion increases its pressure at nearly constant
volume. This takes place during a first volume decreasing
stroke.
[0208] From point 920 to a point 922 combustion is completed, and
the expanding combustion-gas displaces piston 14 until it reaches
its bottom-dead-center at point 922. This takes place during a
second volume increasing stroke.
[0209] Exhaust valve 22 (FIG. 1) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to a
nearly-atmospheric pressure, as shown at a point 924 (it coincides
with point 916 in the diagram). From point 924 to a point 926
combustion-gas is expelled from cylinder chamber 16 through the
open exhaust valve 22. This takes place during a first part of a
second volume decreasing stroke.
[0210] At point 926 exhaust valve 22 closes, and from point 926 to
point 910 all valves are closed, and residual-gas compression takes
place. This takes place during a second part of the second volume
decreasing stroke. Then the same cycle is repeated again.
[0211] Control system 70 (FIG. 2) controls this propulsion mode in
the same way as the previously described first propulsion mode
using direct fuel injection. The factors affecting the magnitude of
the propulsion force are the same as in the case of the first
propulsion mode. The propulsion force increases or decreases with
an increase or a decrease, respectively, in the net positive
work-per-cycle, and with an increase or a decrease, respectively,
in the transmission ratio. As in the first propulsion mode, the
work-per-cycle can be varied by varying three parameters: timings
of charging valve 24 opening and closing, and the quantity of fuel
added to the air-charge. Control system 70 (FIG. 2) controls the
propulsion force by varying any, some, or all of the above
parameters, and by varying the transmission ratio according to a
program contained in the control system software. In vehicles with
manual transmission control, it is the vehicle driver who varies
the transmission ratio.
[0212] In all the above described propulsion modes the frequency of
cycles repetition can be reduced by selectively omitting some of
the cycles, as it was previously described for the case of
compression braking. To omit a cycle in a cylinder, all its valves
and the fuel injector are deactivated. Then they are reactivated
again for the next active cycle. Often this can be accomplished
without changing the engine firing order. For example, in a
three-cylinder engine every other cycle can be omitted without a
change in the firing order. In a four-cylinder engine the firing
order can remain unchanged if two out of every three cycles are
omitted. Omission of some of the cycles can be beneficial during
light-load engine operation, since, at a given engine load, it
increases the work performed during each active cycle. At higher
level of work-per-cycle mechanical efficiency of the engine is
higher, and this reduces the fuel consumption.
[0213] ENGINE DEACTIVATION--To improve fuel economy, the engine is
deactivated whenever its operation would serve no useful purpose.
Typical, in this respect, is vehicle coasting. Vehicle coasting
takes place whenever neither accelerator pedal 96 (FIG. 2), nor
brake pedal 86 (FIG. 2) are depressed while the vehicle is in
motion. For best fuel economy, a preferred control strategy during
coasting involves deactivation of all fuel injectors and all
valves, preferably keeping the valves closed. This eliminates
unproductive fuel consumption and air pumping. The vehicle is
coasting down-the-road with its speed being slowly reduced by
internal friction.
[0214] For best fuel economy, the engine is also deactivated
whenever the vehicle stops. A typical pattern of driving an
automotive vehicle often involves numerous short stops. This is
especially typical for driving in urban environment. In most
vehicles, internal combustion of the engine continues during short
vehicle stops. In contrast to this, the system described in this
invention stops the engine by deactivating all fuel injectors and
all valves whenever the vehicle comes to a complete stop and the
driver does not press on accelerator pedal 96 (FIG. 2). When
crankshaft 66 (FIG. 2) stops, information on piston 14 (FIG. 1)
position and direction of its motion is transmitted to control
system 70 (FIG. 2) and retained in its memory. Later this
information is used to restart the engine. When the driver presses
on accelerator pedal 96 again, control system 70 restarts the
engine by operating it as an air-motor in the previously described
third propulsion mode. During this period, which can be as short as
a fraction of a second, the engine crankshaft is disconnected from
the vehicle wheels. This can be done either automatically by the
control system, or manually by the driver. When the engine is
brought to a speed at which efficient combustion can take place,
control system 70 switches the engine to internal combustion
operation, and the connection between the crankshaft and the wheels
is restored.
[0215] Elimination of unproductive fuel consumption during vehicle
stops and during coasting is an important advantage over most other
vehicle operating systems using conventional internal combustion
engines, since it contributes to a substantial improvement in
average vehicle fuel consumption.
[0216] OTHER METHODS OF CHARGING THE AIR-RESERVOIR--In addition to
compression braking, charging the air-reservoir with compressed-air
can also be performed by using other methods during other modes of
operation. This increases availability of compressed-air for
operation in the above described first, second, and third
propulsion modes. Availability of compressed-air-assist, whenever
needed, is a significant advantage, since it permits to achieve the
required peak power and torque with a smaller engine size. Smaller
engines are more economical in terms of fuel consumption. Control
system 70 (FIG. 2) monitors the pressure in air-reservoir 56 (FIG.
1) and, whenever this pressure drops below a first predetermined
level, initiates charging of the air-reservoir with compressed-air
by using at least one of the below described methods. Charging is
discontinued when the pressure in the air-reservoir 56 exceeds a
second predetermined level, which is higher than the first
predetermined level. The values of the first and the second
predetermined levels of pressure are contained in the control
system memory.
[0217] Air-reservoir 56 can be charged with compressed-air during
vehicle coasting. To accomplish this, the engine must remain
coupled to the vehicle wheels and, in contrast to the above
described case of engine deactivation, operates as a two-stroke
compressor receiving air from outside atmosphere into each engine
cylinder during each volume increasing stroke, and compressing it
and substantially displacing it into the air-reservoir during each
volume decreasing stroke. This process is the same as in the case
of compression braking, except that the vehicle driver does not
press on the brake pedal. Control system 70 controls the negative
work-per-cycle to insure that a predetermined rate of vehicle
deceleration, preferably smaller than any produced when the driver
presses on the brake pedal, is maintained. The vehicle slowly
decelerates, and its kinetic energy is transformed into energy of
compressed-air stored in the air-reservoir.
[0218] Charging the air-reservoir can also be performed while the
vehicle is propelled by the engine in response to a demand for a
propulsion force. To accomplish this, the engine operates both as
an internal combustion engine and as a compressor during each cycle
in each engine cylinder. FIG. 15 is a pressure-volume diagram
illustrating a hybrid four-stroke cycle during which the engine
works as an internal combustion engine propelling the vehicle, and
as a compressor charging the air-reservoir.
[0219] Intake valve 20 (FIG. 1) opens at a point 1010 (FIG. 15),
and from point 1010 to a point 1012 atmospheric air is received
into cylinder chamber 16 (FIG. 1) through the open intake valve 20.
This takes place during a first volume increasing stroke.
[0220] At point 1012 intake valve 20 closes, and from point 1012 to
a point 1014 all valves are closed, and the air-charge is
compressed, preferably to a pressure at least equal to pressure in
air-reservoir 56 (FIG. 1). This takes place during a first part of
a first volume decreasing stroke.
[0221] At point 1014 charging valve 24 (FIG. 1) opens, and from
point 1014 to a point 1016 a fraction of the air-charge is
displaced from cylinder chamber 16 (FIG. 1) through the open
charging valve 24, charging port 48 (FIG. 1), charging passage 50
(FIG. 1), charging manifold 52 (FIG. 1), and duct 54 (FIG. 1) into
air-reservoir 56 (FIG. 1). This is a second part of the first
volume decreasing stroke.
[0222] At point 1016 charging valve 24 closes. From point 1016 to a
point 1018 the cylinder charge is further compressed, fuel is
injected, and the air-fuel mixture is ignited, and from point 1018
to a point 1020 heat generated by combustion increases the cylinder
pressure at nearly constant volume. This takes place during a third
part of the first volume decreasing stroke.
[0223] From point 1020 to a point 1022 combustion is completed, and
the expanding combustion-gas displaces piston 14 (FIG. 1) until it
reaches its bottom-dead-center at point 1022. This takes place
during a second volume increasing stroke.
[0224] Exhaust valve 22 (FIG. 1) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to a
nearly atmospheric pressure, as shown at a point 1024 (it coincides
with point 1012 in the diagram). From point 1024 to point 1010
combustion-gas is substantially expelled from cylinder chamber 16
(FIG. 1) through the open exhaust valve 22. This period takes place
during a second volume decreasing stroke. Exhaust valve 22 closes
at or shortly after the top-dead-center, and then the same cycle is
repeated again.
[0225] In the above described cycle the engine operates both as a
prime mover propelling the vehicle and as a compressor pumping
compressed-air into the air-reservoir. Part of the energy released
in combustion is used to propel the vehicle, and another part of
that energy is transformed into energy of compressed-air stored in
the air-reservoir.
[0226] A process very similar to the one described above can be
used to charge the air-reservoir when the vehicle is not in motion.
To accomplish this, the engine is decoupled from the vehicle wheels
and, in contrast to the previously described case of engine
deactivation, operates as both an internal combustion engine and as
a compressor, as described above and illustrated in FIG. 15. In
this case, a substantial part of the energy released in combustion
is transformed into energy of compressed-air stored in the
air-reservoir.
[0227] Another method of air-reservoir charging involves operating
some of the engine cylinders as an internal combustion engine and
operating the rest of the cylinders as a compressor pumping
compressed-air into the air-reservoir. For example, four cylinders
of an eight-cylinder engine can operate as a four-stroke internal
combustion engine, while the other four operate as a two-stroke
compressor. Whenever a significant increase in torque is required,
control system 70 (FIG. 2) switches the operation to internal
combustion in all cylinders. When the vehicle is not in motion, the
engine is decoupled from the vehicle wheels, and the cylinders
operating as an internal combustion engine drive the cylinders
operating as a compressor. When the vehicle is in motion, the
engine is coupled to the vehicle wheels, and the cylinders
operating as an internal combustion engine drive the cylinders
operating as a compressor and propel the vehicle at the same
time.
[0228] In any multi-cylinder internal combustion engine harshness
of its operation decreases with an increase in the number of
operating cylinders. This is due to a greater overlap of firing
cycles and increased frequency of engine firings. The above
described method of charging the air-reservoir involves a reduction
in the number of cylinders operating as an internal combustion
engine. This leads to increased harshness in engine operation. To
alleviate this, a second propulsion mode can be used in the
cylinders operating as an internal combustion engine. Operating
these cylinders as a two-stroke internal combustion engine doubles
the frequency of firings, relative to a four stroke operation, and
eliminates the excessive harshness. For example, four cylinders of
an eight-cylinder engine can operate as a two-stroke internal
combustion engine in the second propulsion mode, while the other
four operate as a two-stroke compressor. The frequency of firings
remains the same as when all eight cylinders operate as a
four-stroke internal combustion engine. A fraction of the
compressed-air pumped by the cylinders operating as a compressor is
used by the cylinders operating as a two-stroke internal combustion
engine, and the balance goes into the air-reservoir. In some cases,
the quantity of compressed-air produced can be adjusted to match
the quantity consumed by the cylinders operating as a two-stroke
internal combustion engine. In such a case, the balance of
compressed-air going into the air-reservoir is zero. This permits
prolonged operation of some cylinders in the second propulsion mode
without changing the quantity of compressed-air in the
air-reservoir.
Description of Operation of The Alternative Embodiment
[0229] The alternative embodiment of the present invention,
illustrated in FIG. 5, can operate in a variety of alternative
modes of operation, including compression braking and first,
second, third, and fourth propulsion modes. Its ability to operate
in each mode depends on a specific configuration of switching
valves opening and closing in the intake and exhaust switching
arrangements. FIGS. 16A to 16C illustrate three different switching
configurations.
[0230] FIG. 16A shows a first switching configuration, in which
first intake switching valve 342 and second exhaust switching valve
364 remain continuously open, while second intake switching valve
344 and first exhaust switching valve 362 remain continuously
closed. In this configuration, intake manifold 330 and intake
switching chamber 340 are connected through the open first intake
switching valve 342 to outside atmosphere, while exhaust manifold
336 and exhaust switching chamber 360 are connected through the
open second exhaust switching valve 364, port 372, and duct 374 to
air-reservoir 358 (FIG. 5).
[0231] FIG. 16B shows a second switching configuration, in which
second intake switching valve 344 and first exhaust switching valve
362 remain continuously open, while first intake switching valve
342 and second exhaust switching valve 364 remain continuously
closed. In this configuration, exhaust manifold 336 and exhaust
switching chamber 360 are connected through the open first exhaust
switching valve 362 to outside atmosphere, while intake manifold
330 and intake switching chamber 340 are connected through the open
second intake switching valve 344, port 352, and duct 354 to
air-reservoir 358 (FIG. 5).
[0232] FIG. 16C shows a third switching configuration, in which
first intake switching valve 342 and first exhaust switching valve
362 remain continuously open, while second intake switching valve
344 and second exhaust switching valve 364 remain continuously
closed. In this configuration, intake manifold 330 and intake
switching chamber 340 are connected through the open first intake
switching valve 342 to outside atmosphere, while exhaust manifold
336 and exhaust switching chamber 360 are connected to outside
atmosphere through the open first exhaust switching valve 362.
[0233] COMPRESSION BRAKING--Compression braking requires the system
to be in the first switching configuration, as illustrated in FIG.
16A. The engine operates as a two-stroke compressor, and its cycle
is similar to that in the previously described preferred embodiment
and can be illustrated by either FIG. 7A, or 7B, or 7C. A
description given below refers to the pressure-volume diagram shown
in FIG. 7B.
[0234] Intake valve 312 (FIG. 16A) opens at a variable point 510
and later closes at a variable point 512 after bottom-dead-center
(in other cases point 512 may be timed before or at the
bottom-dead-center). During this period, atmospheric air is
received into cylinder chamber 324 (FIG. 16A) at constant pressure.
This period takes place during a second part of the volume
increasing stroke.
[0235] From point 512 to a variable point 514 all valves in the
cylinder are closed, and the air-charge is compressed until its
pressure becomes equal to pressure in air-reservoir 358 (FIG. 5).
This takes place during a first part of the volume decreasing
stroke.
[0236] At point 514 exhaust valve 314 (FIG. 16A) opens and remains
open until its closure at a variable point 518. From point 514 to
point 518, air is displaced from cylinder chamber 324 into
air-reservoir 358 (FIG. 5) at nearly constant pressure. There is
only a relatively small increase in pressure associated with
compression of air in air-reservoir 358. This period takes place
during a second part of the volume decreasing stroke.
[0237] From point 518 to point 510 all valves in the cylinder are
closed, and the fraction of the initial air-charge, still left in
cylinder chamber 324, expands, preferably until its pressure drops
to atmospheric pressure at point 510. This period takes place
during a first part of the volume increasing stroke.
[0238] FIRST PROPULSION MODE--Operation in the first propulsion
mode requires the system to be in the second switching
configuration, as illustrated in FIG. 16B. The engine operates as a
four-stroke internal combustion engine with compressed-air assist.
Its cycle is similar to that in the previously described preferred
embodiment and can be illustrated by the pressure-volume diagram
shown in FIG. 9.
[0239] As shown in FIG. 9, intake valve 312 (FIG. 16B) opens at a
point 610, and the pressure in the cylinder increases to the level
of pressure in air-reservoir 358 (FIG. 5), which corresponds to a
point 612. A preferred timing of intake valve 312 opening is at the
top-dead-center. From point 612 to a point 614 piston 315 (FIG.
16B) is displaced by a nearly constant air-pressure in cylinder
chamber 324 (FIG. 16B). There is only a relatively small drop in
pressure associated with expansion of air in air-reservoir 358
(FIG. 5). This period takes place during a first part of a first
volume increasing stroke.
[0240] At point 614 intake valve 312 closes, and from point 614 to
a point 616, which is at the bottom-dead-center, the air-charge in
cylinder chamber 324 expands. This takes place during a second part
of the first volume increasing stroke.
[0241] From point 616 to a point 618 the cylinder charge is
compressed, and from point 618 to a point 620 heat generated by
combustion increases its pressure at nearly constant volume. This
period takes place during a first volume decreasing stroke.
[0242] From point 620 to a point 622 combustion is completed, and
the expanding combustion-gas displaces piston 315 (FIG. 16B) until
it reaches its bottom-dead-center at point 622. This takes place
during a second volume increasing stroke.
[0243] Exhaust valve 314 (FIG. 16B) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to a
nearly atmospheric pressure, as shown at a point 624 (it coincides
with point 616 in the diagram). From point 624 to a point 626
combustion-gas is expelled from cylinder chamber 324 through the
open exhaust valve 314. This takes place during a first part of a
second volume decreasing stroke.
[0244] At point 626 exhaust valve 314 closes, and from point 626 to
point 610 all valves in the cylinder are closed, and residual-gas
compression takes place. This takes place during a second part of
the second volume decreasing stroke.
[0245] SECOND PROPULSION MODE--The second switching configuration
(FIG. 16B) also permits operation in the second propulsion mode.
The engine operates as a two-stroke internal combustion engine with
compressed-air assist. Its cycle is similar to that in the
previously described preferred embodiment and can be illustrated by
the pressure-volume diagram shown in FIG. 11.
[0246] As shown in FIG. 11, intake valve 312 (FIG. 16B) opens at a
point 710, and the pressure in the cylinder increases to the level
of pressure in air-reservoir 358 (FIG. 5) during an upstroke of
piston 315 (FIG. 16B), which corresponds to a point 712. From point
712 to a point 714 piston 315 moves against nearly constant
pressure in cylinder chamber 324 (FIG. 16B). There is only a
relatively small increase in pressure associated with compression
of air in air-reservoir 358. This takes place during a second part
of the volume decreasing stroke.
[0247] At point 714 intake valve 312 closes, from point 714 to a
point 716 the cylinder charge is compressed, and from point 716 to
a point 718 heat from combustion increases its pressure at nearly
constant volume. This takes place during a third part of the volume
decreasing stroke.
[0248] From point 718 to a point 720 combustion is completed, and
the expanding combustion-gas displaces piston 315 (FIG. 16B) until
it reaches its bottom-dead-center at point 720. This takes place
during the volume increasing stroke.
[0249] Exhaust valve 314 (FIG. 16B) opens at or shortly before the
bottom-dead-center, and the pressure in the cylinder drops to
nearly atmospheric pressure, as shown at a point 722. After point
722, upward motion of piston 315 (FIG. 16B) expels combustion-gas
from cylinder chamber 324 (FIG. 16B) through the open exhaust valve
314 until the exhaust valve closes. This takes place during a first
part of the volume decreasing stroke. Timing of exhaust valve 314
closure determines the quantity of residual-gas retained in the
cylinder. A preferred timing of exhaust valve 314 closing coincides
with the timing of intake valve 312 (FIG. 16B) opening. From then
on, the same cycle is repeated again during the next engine
revolution.
[0250] THIRD PROPULSION MODE--The second switching configuration
(FIG. 16B) can also be used for operation in the third propulsion
mode. The engine operates as a two-stroke air-motor. Its cycle is
similar to that in the previously described preferred embodiment
and can be illustrated by the pressure-volume diagram shown in FIG.
13.
[0251] As shown in FIG. 13, intake valve 312 (FIG. 16B) opens at a
point 810, which is preferably at the top-dead-center, and the
pressure in cylinder chamber 324 (FIG. 16B) rises to the level of
pressure in air-reservoir 358 (FIG. 5), which is illustrated by a
point 812. From point 812 to a point 814 cylinder chamber 324 is
charged with compressed-air from air-reservoir 358. This takes
place during a first part of the volume increasing stroke.
[0252] At point 814 intake valve 312 (FIG. 16B) closes, and from
point 814 to a point 816 the air-charge expands, preferably to
atmospheric pressure. This takes place during a second part of the
volume increasing stroke.
[0253] At a point 816, which is, preferably, at the
bottom-dead-center, exhaust valve 314 (FIG. 16B) opens, and from
point 816 to point 810 air is expelled from cylinder chamber 324
(FIG. 16B). This takes place during the volume decreasing stroke.
Closing of exhaust valve 314 approximately coincides with opening
of intake valve 312, and then the same cycle is repeated again.
[0254] Operation in the third propulsion mode can also be performed
when the system is in the first switching configuration. The
process is, essentially, the same as in the above described case of
operation in the second switching configuration, except that the
roles of the intake and exhaust valves are interchanged.
Compressed-air enters from air-reservoir 358 into cylinder chamber
324 through exhaust valve 314 and, after expansion, exits through
intake valve 312. Exhausting the air through the intake system,
rather than through the exhaust, avoids excessive cooling of the
vehicle catalyst.
[0255] FOURTH PROPULSION MODE--Operation in the fourth propulsion
mode requires the system to be in the third switching
configuration, as illustrated in FIG. 16C. The engine operates as a
conventional four- stroke internal combustion engine receiving no
air from air-reservoir 358.
[0256] OTHER MODES--Whenever the vehicle stops, the engine can be
deactivated by deactivating all valves and all fuel injectors in
all engine cylinders. During vehicle coasting, the engine can be
deactivated, or, alternatively, it can operate as a two-stroke
compressor driven by the vehicle momentum and pumping
compressed-air into the air-reservoir.
[0257] As in the case of the preferred embodiment, charging of the
air-reservoir with compressed-air can also be performed by
operating some of the engine cylinders as an internal combustion
engine and operating the rest of the cylinders as a compressor
pumping compressed-air into the air-reservoir. For example, four
cylinders of an eight-cylinder engine can operate as a four-stroke
internal combustion engine, while the other four operate as a
two-stroke compressor. For this, the engine must have at least two
intake manifolds and two exhaust manifolds, each with its own
switching arrangement. The intake and exhaust manifolds serving the
cylinders operating as an internal combustion engine have their
respective switching valves arranged into the third switching
configuration (FIG. 16C), while the intake and exhaust manifolds
serving the cylinders operating as a compressor have their
respective switching valves arranged into the first switching
configuration (FIG. 16A). Whenever a significant increase in torque
is required, control system 376 (FIG. 5) switches the operation to
internal combustion in all cylinders. When the vehicle is not in
motion, the engine is decoupled from the vehicle wheels, and the
cylinders operating as an internal combustion engine drive the
cylinders operating as a compressor. When the vehicle is in motion,
the engine is coupled to the vehicle wheels, and the cylinders
operating as an internal combustion engine drive the cylinders
operating as a compressor and propel the vehicle at the same
time.
[0258] As in the case of the preferred embodiment, the cylinders
operating as an internal combustion engine can be operated using a
two-stroke cycle in the second propulsion mode. In such a case, the
intake and exhaust manifolds serving the cylinders operating as a
two-stroke internal combustion engine have their respective
switching valves arranged into the second switching configuration
(FIG. 16B). A fraction of the compressed-air pumped by the
cylinders operating as a compressor is used by the cylinders
operating as a two-stroke internal combustion engine, and the
balance goes into the air-reservoir.
Operational Strategy
[0259] A preferred operational strategy for the system of the
present invention is intended to minimize fuel consumption,
whenever possible, and maximize the engine torque and power,
whenever needed. To achieve good fuel economy, energy derived from
the vehicle motion is accumulated in the air-reservoir during
vehicle deceleration and then used to assist in subsequent vehicle
acceleration. Additional fuel saving can be realized by eliminating
unproductive fuel consumption during vehicle stops and when the
vehicle is coasting.
[0260] When the vehicle is cruising with a substantially constant
speed, the engine, usually, operates as a conventional internal
combustion engine in the fourth propulsion mode. During braking,
the vehicle is decelerated by compression braking, and the engine
operates as a two-stroke compressor driven by the vehicle momentum
and pumping compressed-air into the air-reservoir. During
subsequent vehicle acceleration, the engine operates either in the
first, or in the second propulsion mode, thus utilizing the energy
previously accumulated during vehicle deceleration. Operation in
the second propulsion mode is, preferably, used only when the
magnitude of the required engine torque exceeds a certain
predetermined level, specified in the control system software.
During vehicle stops and during coasting all engine valves and all
fuel delivery means in all cylinders are deactivated. To restart
the engine after a full stop, a third propulsion mode is used.
[0261] During braking the engine operates as a compressor, while
during acceleration it operates as both an air-motor and an
internal combustion engine. Therefore the energy accumulated in the
air-reservoir during vehicle deceleration may not be fully used up
during acceleration. This often permits the engine to operate in
the first and second propulsion modes even during constant speed
driving, at least part of the time.
[0262] To improve availability of compressed-air, the control
system can be programmed to prevent a complete discharge of the
air-reservoir. Whenever the pressure in the air-reservoir drops
below a first predetermined level, the control system initiates
operation in an auxiliary charging mode which includes selective
charging of the air-reservoir by operating the engine partly as a
compressor pumping compressed-air into the air-reservoir, and
partly as an internal combustion engine driving the compressor.
Several variants of this type of a hybrid engine operation were
described above. Recharging the air-reservoir, during operation in
the auxiliary charging mode, can also be performed by operating the
engine as a compressor driven from the vehicle wheels by vehicle
momentum when the vehicle is coasting. When, as a result of the
recharging, the pressure in the air-reservoir exceeds a second
predetermined level, higher than the first predetermined level, the
above operation in the auxiliary charging mode is terminated.
Deactivation of all engine valves and all fuel delivery means in
all engine cylinders during vehicle stops and during coasting is
still practiced, but only when the engine is not operating in the
above auxiliary charging mode.
[0263] While certain embodiments of the present invention have been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing this invention as defined by the
following claims.
* * * * *