U.S. patent application number 09/817870 was filed with the patent office on 2002-09-26 for regenerative deceleration for a hybrid drive system.
This patent application is currently assigned to Visteon Global Technologies, Inc.. Invention is credited to Kahlon, Gurinder S., Klocinski, James J., Swales, Shawn H..
Application Number | 20020138182 09/817870 |
Document ID | / |
Family ID | 25224060 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020138182 |
Kind Code |
A1 |
Swales, Shawn H. ; et
al. |
September 26, 2002 |
REGENERATIVE DECELERATION FOR A HYBRID DRIVE SYSTEM
Abstract
A control system is provided for the drive system of automotive
vehicles. A control determines a combination of torque to be
applied from an integrated starter-generator and compression torque
to be applied from an engine. The combination of the integrated
starter-generator torque and engine compression torque results in a
desired deceleration torque. The control preferentially applies
torque from the integrated starter-generator over the compression
torque, thus maximizing regeneration.
Inventors: |
Swales, Shawn H.; (Canton,
MI) ; Kahlon, Gurinder S.; (Canton, MI) ;
Klocinski, James J.; (Saline, MI) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Visteon Global Technologies,
Inc.
|
Family ID: |
25224060 |
Appl. No.: |
09/817870 |
Filed: |
March 26, 2001 |
Current U.S.
Class: |
701/22 ;
180/65.26; 180/65.28; 180/65.285; 903/947 |
Current CPC
Class: |
B60W 2510/244 20130101;
B60W 2520/10 20130101; Y02E 60/10 20130101; Y10S 903/947 20130101;
B60W 2510/087 20130101; B60L 7/26 20130101; B60W 2540/12 20130101;
B60W 2710/083 20130101; H01M 16/006 20130101; B60W 10/18 20130101;
B60W 2510/081 20130101; B60W 20/13 20160101; B60W 2510/0638
20130101; B60W 20/00 20130101; F02D 13/0253 20130101; F02D 41/12
20130101; F02D 13/0269 20130101; Y02T 10/7072 20130101; B60W
2510/246 20130101; B60K 6/485 20130101; B60L 2240/423 20130101;
B60L 2240/425 20130101; Y02T 10/64 20130101; B60W 2510/084
20130101; Y02E 60/50 20130101; F02N 11/04 20130101; Y02T 10/70
20130101; B60L 58/24 20190201; F02D 2041/001 20130101; F02D 2250/18
20130101; B60W 2510/0604 20130101; Y02T 10/62 20130101; Y02T 10/12
20130101; B60W 10/08 20130101; B60W 10/26 20130101; F02D 2200/503
20130101; B60L 2240/421 20130101; B60L 2240/441 20130101; B60L
50/16 20190201; B60W 10/06 20130101; F02D 13/0215 20130101 |
Class at
Publication: |
701/22 ;
180/65.3 |
International
Class: |
B60L 011/00 |
Claims
1. A control system for regenerative braking, the control system
comprising: a control receiving sources of input data, said input
data comprising a desired deceleration torque, an integrated
starter-generator ("ISG") torque capacity, and an internal
combustion engine compression torque capability; said control using
said sources of input data to determine an ISG torque to be applied
and an engine compression torque to be applied to achieve said
desired deceleration torque, said determination preferentially
applying said ISG torque; and said control transmitting signals
based on said determination to said ISG and said engine thereby
changing a torque applied by said ISG and changing a compression
torque applied by said engine.
2. The control system according to claim 1, wherein said control
continuously receives said sources of input data and continuously
changes said ISG torque and said engine compression torque.
3. The control system according to claim 1, wherein said desired
deceleration torque is predetermined.
4. The control system according to claim 1, wherein said desired
deceleration torque comprises a deceleration map programmed in a
storage medium, said deceleration map producing said desired
deceleration torque based on deceleration sensors monitoring
vehicle characteristics.
5. The control system according to claim 4, wherein said
deceleration sensors comprise a sensor measuring engine speed, a
sensor measuring vehicle speed, a sensor measuring throttle
position, and a sensor measuring brake position.
6. The control system according to claim 1, wherein said ISG torque
capacity is calculated as a function of ISG speed, ISG temperature,
battery state of charge, battery temperature, and electricity draw
of vehicle electrical components.
7. The control system according to claim 1, wherein said internal
engine compression torque capability is calculated as a function of
engine speed and an operating range of a variable valve timing
system ("VVT").
8. The control system according to claim 1, wherein said internal
combustion engine comprises a piston engine; and further comprising
a variable valve timing system ("VVT").
9. The control system according to claim 1, wherein the ISG torque
to be applied is the lesser of said ISG torque capacity and a
difference between said desired deceleration torque and a minimum
engine compression torque, said engine compression torque to be
applied being equal to a difference between said desired
deceleration torque and said ISG torque to be applied.
10. The control system according to claim 9, wherein said internal
combustion engine comprises a piston engine; further comprising a
variable valve timing system ("VVT"), said VVT operable to change a
compression ratio of said engine thereby changing said engine
compression torque; wherein said desired deceleration torque
comprises a deceleration map programmed in a storage medium, said
deceleration map producing said desired deceleration torque as a
function of deceleration sensors monitoring vehicle
characteristics; wherein said ISG torque capacity is calculated as
a function of ISG speed, ISG temperature, battery state of charge,
battery temperature, and electricity draw of vehicle electrical
components; and wherein said internal engine compression torque
capability is calculated as a function of engine speed and an
operating range of said VVT.
11. The control system according to claim 10, wherein said control
continuously receives said sources of input data and continuously
changes said ISG torque and said engine compression torque; wherein
said desired deceleration torque is predetermined; and wherein said
deceleration sensors comprise a sensor measuring engine speed, a
sensor measuring vehicle speed, a sensor measuring throttle
position, and a sensor measuring brake position.
12. A hybrid drive system for an automotive vehicle, the hybrid
drive system comprising: an internal combustion engine; a variable
valve timing system ("VVT") connected with said engine; an
integrated starter-generator ("ISG") electrically connected to a
battery and an electrical system; and a control changing both a
setting of said VVT and a setting of said ISG.
13. The hybrid drive system according to claim 12, wherein said
control changes said VVT setting and said ISG setting during a
regenerative deceleration mode in which deceleration power is
converted to electrical power, said control preferentially setting
the ISG to apply more torque and setting the VVT to apply less
engine compression torque.
14. The hybrid drive system according to claim 12, wherein said
control determines a combination of said ISG torque and said engine
compression torque substantially equal to a desired deceleration
torque.
15. The hybrid drive system according to claim 14, wherein said
desired deceleration torque simulates coasting behavior of the
vehicle, said coasting behavior not including braking deceleration
performed by an autonomous braking system.
16. The hybrid drive system according to claim 14, wherein said ISG
torque is the lesser of an ISG torque capacity and a difference
between said desired deceleration torque and a minimum engine drag
torque, said engine compression torque being a difference between
said desired deceleration torque and said ISG torque.
17. The hybrid drive system according to claim 12, wherein said
control changes said VVT setting and said ISG setting in response
to sources of input data, said input data comprising a desired
deceleration torque, an ISG torque capacity, and an engine
compression torque capability, wherein said desired deceleration
torque is produced from a deceleration map in response to sensors
monitoring at least engine speed, vehicle speed, throttle position,
and brake position, wherein said ISG torque capacity is responsive
to sensors monitoring at least ISG speed, ISG temperature, battery
state of charge, battery temperature, and electricity draw of
vehicle electrical components, and wherein said engine compression
torque capability is responsive to at least a sensor monitoring
engine speed and an operating range of said VVT.
18. The hybrid drive system according to claim 12, wherein said VVT
is an electrical VVT with solenoids actuating cylinder valves.
18.5. The hybrid drive system according to claim 12, wherein said
VVT is an electro hydraulic VVT with hydraulic actuators
controlling cylinder valves.
19. The hybrid drive system according to claim 12, wherein said ISG
is mounted to said engine and to a transmission, said ISG
comprising a stationary stator and a rotating rotor, said rotor
being connected to a crankshaft of said engine and connected to an
input shaft of said transmission.
20. The hybrid drive system according to claim 12, wherein said
hybrid drive system is a low storage hybrid drive system whereby
said internal combustion engine is the dominant power source and
said ISG is a supplemental power source.
21. The hybrid drive system according to claim 20, wherein said
control changes said VVT setting and said ISG setting during a
regenerative deceleration mode in which deceleration torque is
converted to electricity; wherein said control determines a
combination of said ISG torque and said engine compression torque
as a function of a desired deceleration torque, wherein said
desired deceleration torque simulates coasting behavior of the
vehicle; and wherein said ISG torque is the lesser of an ISG torque
capacity and a difference between said desired deceleration torque
and a minimum engine drag torque, said engine compression torque
being a difference between said desired deceleration torque and
said ISG torque.
22. The hybrid drive system according to claim 21, wherein said
control changes said VVT setting and said ISG setting in response
to sources of input data, said input data comprising a desired
deceleration torque, an ISG torque capacity, and an engine
compression torque capability, wherein said desired deceleration
torque is produced from a deceleration map in response to sensors
monitoring at least engine speed, vehicle speed, throttle position,
and brake position, wherein said ISG torque capacity is responsive
to sensors monitoring at least ISG speed, ISG temperature, battery
state of charge, battery temperature, and electricity draw of
vehicle electrical components, and wherein said engine compression
torque capability is responsive at least a sensor monitoring engine
speed and an operating range of said VVT; wherein said VVT is an
electrical VVT with solenoids actuating cylinder valves; and
wherein said ISG is mounted to said engine and to a transmission,
said ISG comprising a stationary stator and a rotating rotor, said
rotor being connected to a crankshaft of said engine and connected
to an input shaft of said transmission.
23. A method of controlling a hybrid drive system in an automotive
vehicle, the method comprising: monitoring a torque applied by an
integrated starter-generator ("ISG"); and changing a compression
torque of an internal combustion engine in response to said ISG
applied torque.
24. The method according to claim 23, wherein a combination of said
ISG applied torque and said engine compression torque decelerates
said vehicle at a predetermined desired torque.
25. The method of claim 23, wherein said combination of torques
comprises a maximum torque capacity of said ISG and an additional
engine compression torque providing said desired deceleration
torque, said ISG applied torque being reduced from said maximum
torque capacity to a difference between said desired deceleration
torque and a minimum engine torque when said ISG torque capacity
exceeds said difference.
26. The method of claim 23, wherein said desired deceleration
torque simulates coasting behavior of the vehicle.
27. The method of claim 23, further comprising transferring torque
with said ISG comprising a stationary stator and a rotating rotor,
said rotor being connected to a crankshaft of said engine and
connected to an input shaft of said transmission.
28. The method of claim 23, wherein said changing of said engine
compression torque comprises changing a setting of a variable valve
timing system ("VVT"), said VVT being an electrical VVT.
29. The method of claim 23, further comprising changing said ISG
applied torque in response to at least ISG speed, ISG temperature,
battery state of charge, battery temperature, and electricity draw
of vehicle electrical components.
30. The method of claim 29, wherein said combination of torques
comprises a maximum torque capacity of said ISG and an additional
engine compression torque providing said desired deceleration
torque, said ISG applied torque being reduced from said maximum
torque capacity to a difference between said desired deceleration
torque and a minimum engine torque when said ISG torque capacity
exceeds said difference.
31. The method of claim 30, wherein said desired deceleration
torque simulates coasting behavior of the vehicle; and wherein said
hybrid drive system is a low storage hybrid drive system whereby
said internal combustion engine is the dominant power source and
said ISG is a supplemental power source.
32. The method of claim 31, further comprising transferring torque
with said ISG comprising a stationary stator and a rotating rotor,
said rotor being connected to a crankshaft of said engine and
connected to an input shaft of a transmission.
Description
BACKGROUND
[0001] Due to a growing market demand for automotive vehicles that
are fuel efficient and environmentally friendly, automotive vehicle
manufacturers increasingly are devoting a substantial portion of
their research resources on fundamentally new technologies. Much of
this research has focused on the internal combustion engine, which
is used in the vast majority of automotive vehicles currently
produced.
[0002] Although the internal combustion engine is inexpensive,
reliable, easy to refuel and provides the desired performance, it
is desirable to reduce the consumption of fossil fuels and
emissions of these engines. To further address these concerns,
manufacturers are also focusing their research on other areas of
the automotive vehicles, such as braking systems and other
drivetrain components.
[0003] As a result of this research emphasis, the automotive
industry has developed a number of alternative drive systems for
powering automotive vehicles. Generally speaking, a range of
different concepts have been developed for automotive drive
systems. At one end of this spectrum of available drive systems is
the conventional drive system which uses an internal combustion
engine that directly drives a standard automatic or manual
transmission. At the other end of the spectrum is the electrical
vehicle concept. Electrical vehicles operate completely on
electrical energy stored on board, but generated elsewhere from
fossil fuel or other sources. Typically, the drive system of an
electrical vehicle uses a large electrical drive motor for torque
generation and large capacity batteries for electricity storage.
Some critics of conventional internal combustion engine drive
systems prefer the concept of electrical vehicles because the
electrical drive motor emits no polluting exhausts. Electrical
automotive vehicles have generally been unsuccessful in the
marketplace, however, because they can only travel short distances
before the batteries must be recharged. In addition, the recharging
process usually lasts several hours.
[0004] In response to the disadvantages of electrical vehicles,
manufacturers of automotive vehicles have developed the concept of
hybrid drive systems. This drive system typically includes both an
internal combustion engine powered by fossil fuel and an electrical
motor powered by electricity. The goal of hybrid drive systems is
to combine the advantages of conventional internal combustion
engine drive systems with the advantages of electrical drive
systems. Thus, the optimal hybrid drive system desirably is capable
of traveling long distances with good drive performance while
requiring only a short amount of time to refill with fuel or
recharge the batteries. Additionally, the drive system may be fuel
efficient and environmentally friendly.
[0005] The concepts of hybrid drive systems are generally defined
by two categories. In one category, referred to as high storage
hybrids, the electrical drive system acts as the dominant system
and the internal combustion engine provides supplemental power when
needed. These systems typically include a large electrical motor
and large capacity batteries similar to an electrical vehicle but
also include a small internal combustion engine. The internal
combustion engine provides additional power when extra acceleration
is desired and can be used to generate electricity for longer
distance travel. In the other hybrid category, referred to as low
storage hybrids, this combination of drive systems is reversed. The
internal combustion engine acts as the dominant system and the
electrical drive system provides supplemental power. In this type
of system fuel efficiency is increased by using a smaller internal
combustion engine than is typically used in conventional automotive
vehicles. However, drive performance remains similar to
conventional drive systems since the electrical drive system
provides assist power when needed. The electrical drive system can
also be used in a regeneration mode to divert torque from the
drivetrain to generate electricity for recharging the batteries.
Low storage hybrid drive systems may be more readily acceptable to
consumers as an alternative to conventional drive systems. One
reason for this acceptance is that consumers typically demand drive
performance and vehicle behavior equal to or similar to what they
have experienced with current automotive vehicles.
[0006] Typically, an integrated starter-generator ("ISG") is used
for the electrical drive system in low storage hybrid drive
systems. Several different versions of ISGs are available; but
generally speaking, the ISG is connected to the drivetrain of the
automotive vehicle between the internal combustion engine and the
wheels. Accordingly, the ISG is usually capable of functioning like
a motor to generate drive torque from electricity stored in the
batteries. Alternatively, the ISG is able to generate electricity
from drive system torque. Thus, at least four different modes of
operation of the ISG are possible. In the first mode, the ISG
supplies torque to the engine to turn the crankshaft during
starting of the engine. The ISG acts like a conventional starter in
this mode; therefore the need for a standalone starter is
eliminated. In the second mode, the ISG diverts some of the torque
produced by the engine during normal operation in order to generate
electricity. The electricity is then used to recharge the batteries
and for powering the various electrical components used throughout
the automotive vehicle. In this mode the ISG acts similarly to a
conventional alternator, thus eliminating the need for a standalone
alternator. In the third mode, the ISG draws electricity from the
batteries to supply torque to the drivetrain during heavy loading.
This mode enhances drive performance of the automotive vehicle by
improving acceleration or allowing the engine to operate at lower
average speed and higher average load for improved thermal
efficiency. In the fourth mode, the ISG generates electricity from
torque supplied by the drivetrain. This mode is sometimes referred
to as regenerative braking or regenerative deceleration. In effect,
this mode allows the automotive vehicle to recapture energy that is
normally lost by conventional drive systems during deceleration, or
slowing, of the vehicle.
[0007] Several problems are commonly encountered with the
regenerative deceleration mode in currently available low storage
drive systems. For example, the ISG causes the automotive vehicle
to decelerate at an inconsistent rate between different
deceleration events of the vehicle. This problem occurs because the
torque applied by the ISG changes depending on the amount of
electricity stored in the batteries and the electricity being used
by the vehicle's electrical components. When the batteries are very
low and capable of receiving a lot of electricity, the ISG applies
more torque to generate more electricity. When the batteries are
fully charged, the ISG applies very little torque, if any, for
electricity generation. This variance in torque is undesirable
because the driver can not predict the rate at which the vehicle
will slow down.
[0008] Another problem is that the ISG typically produces an
unfamiliar deceleration behavior. In conventional drive systems,
deceleration of the vehicle is provided by either wheel brakes or
from compression braking when the drivetrain rotates faster than
the equilibrium speed of the engine. Compression braking commonly
occurs when the driver lets off of the gas pedal or when the
vehicle is coasting down a hill. In these situations, compression
is produced in the engine cylinders of the internal combustion
engine by the rotating pistons, thereby resulting in a consistent
and predictable slowing of the automotive vehicle.
[0009] Hybrid drive systems employing regenerative braking are
currently unable to produce a deceleration behavior that is similar
to conventional drive systems. The deceleration torque experienced
by the driver no longer varies predictably depending on vehicle
speed, engine speed and transmission setting as inherently happens
in conventional drive systems. Like the inconsistent deceleration
behavior that results from varying electricity demands, consumers
can find this difference between hybrid and conventional drive
systems inconvenient and disconcerting. The deceleration behavior
of hybrid drive systems is also complicated further by the fact
that the internal combustion engine, which continues to be used as
the dominant power source, also produces deceleration due to
conventional compression braking in addition to the deceleration
produced by the ISG.
BRIEF SUMMARY OF THE INVENTION
[0010] Accordingly, a control system is provided for decelerating a
vehicle at a predictable rate while optimizing regeneration of the
deceleration torque. The control system receives input data,
including a desired deceleration torque, an integrated
starter-generator ("ISG") torque capacity, and a compression torque
capability of an internal combustion engine. The control then
changes a setting of the ISG and a setting of a variable valve
timing system ("VVT") to achieve the desired deceleration torque.
The torque applied by the ISG is maximized and the compression
torque of the engine is minimized to increase efficiency of the
regenerative deceleration mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention, including its construction and method of
operation, is illustrated more or less diagrammatically in the
drawings, in which:
[0012] FIG. 1 is a schematic view of one embodiment of an
automotive vehicle with a low storage hybrid drive system;
[0013] FIG. 2 is a cross-section schematic view of one embodiment
of an integrated starter-generator;
[0014] FIG. 3 is a flow chart of one embodiment of operation of a
control system; and
[0015] FIG. 4 is a chart showing torques used in one embodiment of
the hybrid drive system during different stages.
DETAILED DESCRIPTION
[0016] Referring now to the drawings, and particularly to FIGS. 1
and 2, a control system is provided for automotive hybrid drive
systems. The control system uses a number of sensors to constantly
monitor characteristics of the automotive vehicle 10 during
deceleration of the vehicle 10. A control then calculates
adjustments for an integrated starter-generator ("ISG") 28 and a
variable valve timing system ("VVT") 24 to achieve a deceleration
behavior that is both efficient and acceptable to the driver. The
control system is described herein in relation to low storage
hybrid drive systems. However, the principles of this control
system may be beneficial in other drive systems, such as high
storage hybrid drive systems or non-hybrid electrical systems.
[0017] FIG. 1 shows an automotive vehicle 10 with a low storage
hybrid drive system. The hybrid drive system uses a conventional
internal combustion engine 22 as the dominant source of drive
torque for moving the vehicle 10. An ISG 28 supplements the power
of the engine 22 and converts torque into electricity.
[0018] A typical example of a conventional automotive vehicle has a
six cylinder engine with 4.0 liters of cylinder capacity. The
electrical system in this vehicle usually is set to run at 14
volts, and the load rating of the battery is 40-50 amp-hr. A
starter is required to start the engine in this vehicle, and a 1.0
kW alternator is typically used to provide electricity. A
comparable example of a low storage hybrid vehicle 10 uses a
smaller six cylinder engine 22 with a capacity of about 3.2 to 3.5
liters. The smaller engine 22 results in improved efficiency, while
driving performance remains similar to the conventional vehicle due
to power assist by the ISG 28. Usually, the electrical system
voltage is increased to 42 volts or higher because of the increased
use of electricity throughout the vehicle 10. The capacity of the
battery 32 is also increased by about four times for greater
electricity storage. Thus, although the load rating of the battery
32 remains at about 40-50 amp-hr, the voltage supply of the battery
32 is now 42 volts or higher instead of 14 volts. Because the ISG
28 produces electricity to power the electrical system similar to
an alternator, the alternator is eliminated in the hybrid vehicle
10. Additionally, the ISG 28 can perform the same starting function
of a conventional starter, thus the starter is also eliminated from
the hybrid vehicle 10.
[0019] Internal combustion engines 22 use a number of pistons that
reciprocate inside of cylinders in the engine 22, thereby rotating
and driving a crankshaft 23. The engine 22 is powered by fossil
fuel and air mixed together and ignited in the cylinders. Normally,
a fuel tank 26 is provided for storing the fossil fuel, with fuel
lines 25 supplying the fuel to the engine 22. The flow of fuel and
air into the cylinders is controlled by valves that reciprocally
open and close to feed and exhaust the cylinders and seal the
cylinders during ignition. Therefore, the valves control the amount
of compression that forms in the cylinders by sealing the cylinder
during a portion of the cycle.
[0020] The engine 22 is also provided with the VVT 24. A variety of
VVTs 24 are known to those skilled in the art, and any type of VVT
24 that can control compression is contemplated to work with the
present invention. The VVT 24 allows the timing of the
reciprocating valves to be varied during operation of the vehicle
10. A number of technologies have been used to accomplish variable
timing of the valves, including mechanical systems, hydraulic
systems, electrical systems and various combinations thereof. In
one embodiment, an electrically powered VVT 24 is provided. In the
electrical VVT 24, each valve is actuated by a separate electrical
solenoid. The solenoids are then controlled by a control system
that controls the timing of the valves.
[0021] As is understood by those in the art, the VVT 24 varies the
compression produced in the cylinders during operation of the
vehicle 10. This ability allows automotive vehicle manufactures to
improve both performance and efficiency of the vehicle 10 in a
number of ways. Generally speaking, internal combustion engines 22
operate most efficiently with a high compression ratio. Thus, for
example, a compression ratio of 10:1 is often used in automotive
vehicles 10. However, the optimum compression ratio for a
particular vehicle 10 varies depending on several factors, such as
the temperature of the engine 22, the atmosphere and the level of
load on the engine 22. The compression ratio also causes a braking
effect of the vehicle 10 when the drivetrain is rotating faster
than the coasting equilibrium point of the engine 22. In this
situation, a high compression ratio produces a large drag torque
that will tend to decelerate the vehicle 10. The deceleration is
generally consistent and predictable. On the other hand,
compression braking is an inefficient process for decelerating the
vehicle 10 because the energy used to slow the vehicle 10 is turned
into unusable heat in the engine 22. The heat is then dissipated
and discarded.
[0022] Those skilled in the art will recognize that certain changes
to engine operating parameters, such as spark timing, fuel injector
timing, and throttle position may be required to achieve the
benefits of this system, and further may improve the overall
effectiveness of the system. The fact that these changes may be
made does not limit the scope of the present invention.
[0023] In one embodiment, the crankshaft 23 of the engine 22 is
connected directly to the ISG 28. In other embodiments, the ISG 28
is indirectly connected to the crankshaft 23 by locating the ISG 28
elsewhere in the drivetrain of the vehicle 10 and rotating the ISG
28 with a belt, chain or gear drive. Moreover, a variety of ISG 28
types that are capable of converting drive torque to electricity
and electricity to drive torque may be used.
[0024] One type of ISG 28 is shown in FIG. 2. This ISG 28 has a
rotor 29 directly connected to the engine crankshaft 23. The rotor
29 is also directly connected to a transmission input shaft 35.
Accordingly, the rotor 29 rotates within a stationary stator 27 at
the same rotational speed of the crankshaft 23 and transmission
shaft 35.
[0025] The ISG 28 operates in four different modes. In the first
mode, the ISG 28 rotates the crankshaft 23 during startup of the
vehicle 10 until the engine 22 begins to operate self-sufficiently.
In this mode, the ISG 28 draws stored electricity from the
batteries 32 through connecting cables 33. In the second mode, the
ISG 28 applies a torque load to the rotor 29 that is less than the
engine torque provided by the crankshaft 23. The ISG 28 then
converts this applied torque to electricity that is used to
recharge the batteries 32 and to power various electrical
components throughout the vehicle 10. The remaining engine torque
that is not used by the ISG 28 drives the transmission shaft 35. In
the third mode, electricity is drawn from the batteries 32 and is
converted by the ISG 28 into a torque at the rotor 29. In this
mode, the torque supplied by the ISG 28 assists the engine torque.
Thus, the torque received by the transmission shaft 35 is the sum
of both the engine torque and the ISG torque. In the fourth mode,
the ISG 28 applies a torque to the transmission shaft 35 to
decelerate the vehicle 10. This mode is often referred to as
regenerative deceleration because a large portion of the energy
used to slow the vehicle 10 is recaptured by the ISG 28. The ISG 28
converts the deceleration torque into electricity, which can then
be stored in the batteries 32 or used by the electrical system. In
alternative embodiments, fewer, additional or different modes are
provided.
[0026] A control 30 determines when to convert torque into
electricity and when to convert electricity into torque.
Accordingly, the control 30 switches the ISG 28 between each of the
various operating modes at the appropriate times depending on
whether more torque or more electricity is needed.
[0027] The control 30 also varies the amount of torque or
electricity that is produced at any particular moment. For example,
in the torque assist mode, the amount of torque produced by the ISG
28, and consequently the amount of electricity drawn from the
batteries 32, may be variable based on the capacity of the ISG 28
to provide torque and the driver's desire for power. As another
example, in the regenerative deceleration mode, the amount of
electricity produced, and consequently the torque load applied to
the transmission shaft 35, also varies depending on the capacity of
the ISG 28.
[0028] When the batteries 32 become fully charged, the electrical
system of the vehicle 10 may no longer accept additional
electricity from the ISG 28. The control 30 then reduces the amount
of torque load applied to the rotor 29. A number of signals are
routed to the control 30 to determine when electricity generation
can be increased or should be decreased. For example, one signal
indicates the charge in the batteries 32 to ensure that the
batteries 32 are not overcharged. Another sensor measures the
battery 32 temperature. Another sensor measures the voltage of the
vehicle's electrical system to regulate the ISG 28 voltage in the
desired range. A sensor also monitors the temperature of the ISG 28
to ensure that the ISG 28 does not overheat and damage, and another
sensor measures the speed of the ISG 28.
[0029] The transmission input shaft 35 rotates the internal
components of the transmission 34, thereby converting the rotating
speed of the input shaft 35 to the desired output speed used by the
wheels 12. The transmission 34 comprises any known or later
developed transmissions, such as an automatic transmission, a
manual or automated manual transmission or a continuously variable
transmission. The output torque of the transmission 34 is
distributed to the wheels 12 through drive shafts 18 and axle
shafts 16, thereby rotating the wheels 12 and propelling the
vehicle 10. Brakes 14 are also provided at each of the wheels 12
for slowing the vehicle 10.
[0030] FIG. 3 is a flow chart representing the operation of the
control system. Three primary sources of input data 36, 38, 40 are
provided for the control 30. The first source of data 36 is the
desired deceleration torque 36. The desired deceleration torque 36
is a map, look up table or profile. The map is determined by the
automotive vehicle manufacturer and is programmed into the control
30 or other storage medium. The driver may change the deceleration
map based on individual preference in some embodiments. The output
of the deceleration map may depend on one or more characteristics,
such as engine speed, vehicle speed and the positions of the
throttle and brake controls. Sensors are provided to monitor each
of these characteristics, with the data being continuously,
periodically or intermittently routed to the control 30.
[0031] The deceleration map represents the actual deceleration of
the vehicle 10 that the driver experiences. In one embodiment, the
deceleration map simulates the coasting behavior of the vehicle 10.
In this embodiment, the wheel brakes 14 operate independently of
the ISG 28 as an autonomous system. In alternative embodiments, the
deceleration of the vehicle 10 due to actuation of the brake pedal
is also incorporated into the function of the ISG 28. The
deceleration map may be designed to produce a variety of
deceleration behaviors. For example, in many low storage hybrid
vehicles 10, consumers may prefer a deceleration map that mirrors
the deceleration behavior of conventional vehicles. However, a more
aggressive deceleration behavior may also be desirable to increase
the amount of regenerative braking, thereby further improving
efficiency. Alternatively, less aggressive deceleration may be
used.
[0032] The second source of data 38 is the torque capacity 38 of
the ISG 28. As previously described, the amount of torque 38 that
the ISG 28 applies is nonconstant and varies based on a number of
factors. Accordingly, the ISG torque capacity 38 is a function of a
number of characteristics, including the speed and temperature of
the ISG 28, the state of charge and temperature of the batteries
32, and the electrical load of the vehicle's electrical components.
Signals for each, or a subset of, these characteristics are
provided, and the data is continuously provided to the control 30.
The control 30 then uses the data from these signals to calculate
the maximum torque 38 that the ISG 28 can provide to decelerate the
vehicle 10.
[0033] The third source of data 40 is the compression torque
capability 40 of the engine 22. As described above, the compression
ratio of the engine 22 can be varied by the VVT 24. Accordingly,
the compression torque capability 40 of the internal combustion
engine 22 is a function of engine speed and the operating range of
the VVT 24. Electrical VVTs 24 have an extended range of operation
that allows the compression ratio to be reduced to zero compression
and increased up to a maximum compression possible in the engine
22. Even at a setting of zero compression, a small amount of engine
drag 46 may exist. Other VVTs 24, such as mechanical VVTs, may have
a more restricted range and commonly are able to provide a range of
compression ratios between 5:1 to 10:1.
[0034] The control 30 continuously monitors each of these data
sources 36, 38, 40 and calculates the ISG torque to be applied and
the setting of the VVT 24. The combination of the deceleration
torque applied by the ISG 28 and the compression braking applied by
the engine 22 equals the desired deceleration torque 36. For
example, the ISG torque is set equal to the lesser of the ISG
torque capacity 38 and the desired deceleration torque 36 minus the
minimum engine drag torque 46. The VVT setting is then determined
so that the compression torque applied by the internal combustion
engine 22 is equal to the difference between the desired
deceleration torque 36 and the applied ISG torque 38, 44. Next, the
control 30 transmits signals to the ISG 28 and the VVT 24 to change
the regenerative torque applied by the ISG 28 and the compression
torque applied by the internal combustion engine 42. The control 30
continuously or periodically determines the correct ISG torque and
VVT settings so that the ISG 28 and VVT 24 can be changed as
needed. Thus, the driver experiences the predetermined deceleration
behavior stored in the deceleration map regardless of the torque
capacity 38 of the ISG 28.
[0035] FIG. 4 graphically shows a combination of the ISG torque
capacity 38 and internal combustion engine applied compression
torque 42 to achieve the desired deceleration torque 36. The
desired deceleration torque 36 is shown as a fixed value for
simplicity. However, the desired deceleration torque 36 may vary
depending on the status of several characteristics as previously
described. The chart shows three stages 48, 50, 52 for explanatory
purposes. In stage 1 (48), the ISG torque capacity 38 is shown to
be relatively low compared to the desired deceleration torque 36.
This type of situation may occur when the batteries 32 are almost
fully charged. A low ISG torque capacity 38 is also possible when
the electrical components in the vehicle 10 are drawing a minimal
amount of electricity. Cold temperatures also contribute to a low
ISG torque capacity 38 due to poor charge acceptance of chemical
batteries at lower temps 32. In some cases, the ISG torque capacity
38 may approach zero if the batteries 32 are fully charged. As seen
in the chart, the VVT 24 sets the compression ratio of the engine
10 relatively high in this stage 48 to provide a high amount of
engine compression torque 42. Thus, the sum of the ISG torque
capacity 38 and the engine compression torque 42 equals the desired
deceleration torque 36.
[0036] In stage 2 (50), the ISG 28 has a higher torque capacity 38.
This situation occurs when the batteries 32 are low and capable of
receiving a high rate of electrical charge and when the vehicle's
electrical components are drawing more electricity. The ISG torque
capacity 38 can exceed the desired deceleration torque 36 in some
cases. As a result, the engine compression torque 46 is reduced.
Thus, the sum of the ISG torque 44 and engine compression torque 46
remains equal to the desired deceleration torque 36. As previously
described, when the ISG torque capacity 38 exceeds the difference
44 between the desired deceleration torque 36 and the minimum
engine drag torque 46, the applied ISG torque 44 is reduced to this
difference 44. In this situation, the VVT 24 sets the compression
ratio of the engine 10 to the lowest value possible, thus
maximizing regeneration of the deceleration energy. Other
combination functions using the minimum or maximum ISG or engine
torque may be used.
[0037] In stage 3 (52), the ISG torque capacity 38 is relatively
high like stage 2(50) but is less than the difference 44 between
the desired deceleration torque 36 and the minimum engine drag
torque 46. This situation represents a case when the batteries 32
and the electrical system are capable of receiving a relatively
high level of electrical charge but not enough to absorb all the
energy needed to decelerate the vehicle 10. Thus, as in the other
stages 48, 50, the compression ratio of the engine 10 is adjusted
so that the engine compression torque 42 contributes the additional
torque needed to achieve the desired deceleration torque 36.
[0038] A consistent and predictable deceleration behavior is
provided while also improving the efficiency of the regenerative
deceleration mode. Accordingly, the vehicle 10 decelerates at a
predetermine desired deceleration torque 36 regardless of the
status of the batteries 32 or the electrical system. The control 30
then preferentially applies torque 38, 44 from the ISG 28 to
maximize recovery of the energy used to decelerate the vehicle 10.
The control 30 also adjusts the setting of the VVT 24 to change the
compression ratio of the engine 10 so that the sum of the torque
38, 44 from the ISG 28 and the compression torque 42, 46 from the
engine 10 equals the desired deceleration torque 36. Thus, the
compression ratio of the engine 10 is minimized during deceleration
to reduce unrecoverable energy losses that occur during compression
braking.
[0039] While preferred embodiments of the invention have been
described, it should be understood that the invention is not so
limited, and modifications may be made without departing from the
invention. The scope of the invention is defined by the appended
claims, and all devices that come within the meaning of the claims,
either literally or by equivalence, are intended to be embraced
therein.
* * * * *