U.S. patent application number 10/992125 was filed with the patent office on 2005-11-03 for air and fuel supply system for a combustion engine.
Invention is credited to Coleman, Gerald N., Cornell, Sean O., Duffy, Kevin P., Fluga, Eric C., Kilkenny, Jonathan P., Leman, Scott A., Robel, Wade J., Weber, James R..
Application Number | 20050241597 10/992125 |
Document ID | / |
Family ID | 35185806 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241597 |
Kind Code |
A1 |
Weber, James R. ; et
al. |
November 3, 2005 |
Air and fuel supply system for a combustion engine
Abstract
An internal combustion engine has an engine block defining at
least one cylinder, a head, a piston, an air intake valve, and a
valve actuator. The valve actuator has an actuator housing defining
a tank and a bore, and a piston adapted to engages the air intake
valve. The valve actuator further has a control valve disposed
between the tank and the bore in the actuator housing. The control
valve selectively moves between a first position where fluid is
allowed to flow between the tank and the bore and a second position
where the fluid is prevented from flowing to trap fluid in the
bore, thereby preventing the engine valve from returning to a
closed position. The internal combustion engine also has at least
one turbocharger fluidly connected to the air intake port, and a
fuel supply system operable to controllably inject fuel into the
combustion chamber.
Inventors: |
Weber, James R.; (Lacon,
IL) ; Leman, Scott A.; (Eureka, IL) ; Coleman,
Gerald N.; (Corby, GB) ; Duffy, Kevin P.;
(Metamora, IL) ; Fluga, Eric C.; (Dunlap, IL)
; Kilkenny, Jonathan P.; (Peoria, IL) ; Robel,
Wade J.; (Peoria, IL) ; Cornell, Sean O.;
(Gridley, IL) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
35185806 |
Appl. No.: |
10/992125 |
Filed: |
November 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10992125 |
Nov 19, 2004 |
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10933300 |
Sep 3, 2004 |
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10933300 |
Sep 3, 2004 |
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10733570 |
Dec 12, 2003 |
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10733570 |
Dec 12, 2003 |
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10143908 |
May 14, 2002 |
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6688280 |
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10992125 |
Nov 19, 2004 |
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10457351 |
Jun 10, 2003 |
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6941909 |
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Current U.S.
Class: |
123/90.12 ;
123/90.16 |
Current CPC
Class: |
F02D 15/04 20130101;
F02B 2275/14 20130101; F02B 37/013 20130101; F01L 1/08 20130101;
F02M 26/15 20160201; F01L 1/026 20130101; F01L 1/146 20130101; F01L
3/20 20130101; F01L 2820/01 20130101; F01L 2800/10 20130101; F02M
26/19 20160201; F02M 26/21 20160201; Y02T 10/12 20130101; F01L 9/10
20210101; F02B 29/0406 20130101; F02D 13/0226 20130101; F02B 37/004
20130101; F02M 26/23 20160201; F02M 57/023 20130101; F01L 1/16
20130101; F01L 1/267 20130101; F02D 13/0269 20130101; F02M 26/08
20160201 |
Class at
Publication: |
123/090.12 ;
123/090.16 |
International
Class: |
F01L 001/34; F01L
009/02; F01L 001/14 |
Claims
What is claimed is:
1. A method of operating an internal combustion engine including at
least one cylinder and a piston slidable in the cylinder, the
method comprising: supplying pressurized air from an intake
manifold to an air intake port of a combustion chamber in the
cylinder; operating an air intake valve to open the air intake port
to allow pressurized air to flow between the combustion chamber and
the intake manifold substantially during a majority portion of a
compression stroke of the piston; and controlling a hydraulic
actuator to close the air intake port to prohibit pressurized air
from flowing between the combustion chamber and the intake
manifold.
2. The method of claim 1, wherein the controlling is based on at
least one engine condition.
3. The method of claim 1, further including controlling a fuel
supply system to inject fuel into the combustion chamber.
4. The method of claim 3, further including injecting at least a
portion of the fuel during a portion of the compression stroke.
5. The method of claim 4, wherein injecting at least a portion of
the fuel includes supplying a pilot injection at a predetermined
crank angle before a main injection.
6. The method of claim 5, wherein said main injection begins during
the compression stroke.
7. The method of claim 1, further including cooling the pressurized
air prior to supplying the pressurized air to the air intake
port.
8. The method of claim 1, wherein said supplying includes supplying
a mixture of pressurized air and recirculated exhaust gas from the
intake manifold to the air intake port, and wherein said operating
of the air intake valve includes operating the air intake valve to
open the air intake port to allow the pressurized air and exhaust
gas mixture to flow between the combustion chamber and the intake
manifold substantially during a majority portion of the compression
stroke of the piston.
9. The method of claim 8, wherein said supplying a mixture of
pressurized air and recirculated exhaust gas includes providing a
quantity of exhaust gas from an exhaust gas recirculation (EGR)
system.
10. The method of claim 1, further including controlling the
hydraulic actuator to maintain the air intake port open to allow
pressurized air to flow between the combustion chamber and the
intake manifold.
11. The method of claim 1, wherein the controlling includes moving
a piston of the hydraulic actuator between a first position and a
second position.
12. The method of claim 11, further including locking the piston in
the second position.
13. The method of claim 12, wherein the piston engages the air
intake valve in the second position and locking includes: directing
a flow of fluid from a tank disposed within the actuator housing to
a bore in the actuator housing, the bore being associated with the
piston; and selectively preventing the fluid from flowing from the
bore to the tank to trap fluid in the bore and prevent the piston
from moving with respect to the actuator housing, the piston
preventing the air intake valve from returning to the first
position.
14. The method of claim 13, further including selectively allowing
the fluid to flow from the bore to the tank to release the piston
and thereby allow the air intake valve to return to the second
position.
15. The method of claim 14, further including directing a portion
of the flow of fluid between the tank and the bore to an
accumulator.
16. An internal combustion engine, comprising: an engine block
defining at least one cylinder; a head connected with said engine
block, the head including an air intake port, and an exhaust port;
a piston slidable in the cylinder; a combustion chamber being
defined by said head, said piston, and said cylinder; an air intake
valve controllably movable to open and close the air intake port;
an air supply system including at least one turbocharger fluidly
connected to the air intake port; a fuel supply system operable to
inject fuel into the combustion chamber; a cam assembly configured
to move the air intake valve; and a hydraulic actuator configured
to selectively control movement of the air intake valve.
17. The engine of claim 16, wherein the hydraulic actuator is
configured to keep the intake valve open during at least a portion
of a compression stroke of the piston.
18. The engine of claim 17, wherein the hydraulic actuator is
configured to keep the intake valve open for a portion of a second
half of the compression stroke.
19. The engine of claim 16, wherein the hydraulic actuator is
configured to close the intake valve before bottom dead center of
an intake stroke of the piston.
20. The engine of claim 16, wherein the at least one turbocharger
includes a first turbine coupled with a first compressor, the first
turbine being in fluid communication with the exhaust port, the
first compressor being in fluid communication with the air intake
port; and wherein the air supply system further includes a second
compressor being in fluid communication with atmosphere and the
first compressor.
21. The engine of claim 16, wherein the at least one turbocharger
includes a first turbocharger and a second turbocharger, the first
turbocharger including a first turbine coupled with a first
compressor, the first turbine being in fluid communication with the
exhaust port and an exhaust duct, the first compressor being in
fluid communication with the air intake port, the second
turbocharger including a second turbine coupled with a second
compressor, the second turbine being in fluid communication with
the exhaust duct of the first turbocharger and atmosphere, and the
second compressor being in fluid communication with atmosphere and
the first compressor.
22. The engine of claim 16, further including an exhaust gas
recirculation (EGR) system operable to provide a portion of exhaust
gas from the exhaust port to the air supply system.
23. The engine of claim 16, wherein hydraulic actuator includes: an
actuator housing including a tank; a piston slidably disposed in
the actuator housing and configured to engage the air intake valve;
and a control valve disposed between the tank and the piston, the
control valve configured to selectively fluidly communicate the
tank and the piston.
24. The engine of claim 23, wherein the tank includes a
spring-loaded piston.
25. The engine of claim 23, wherein the actuator housing defines a
chamber between the tank and the piston and wherein the chamber
includes a spring-loaded piston.
26. The engine of claim 23, further including a snubbing valve
adapted to slow a movement of the piston.
27. The engine of claim 23, further including a pivotable rocker
arm operably coupling a cam assembly with the air intake valve,
wherein the piston includes an end configured to selectively engage
the rocker arm.
28. A method of operating an internal combustion engine including
at least one cylinder and a piston slidable in the cylinder, the
method comprising: imparting rotational movement to a first turbine
and a first compressor of a first turbocharger with exhaust air
flowing from an exhaust port of the cylinder; imparting rotational
movement to a second turbine and a second compressor of a second
turbocharger with exhaust air flowing from an exhaust duct of the
first turbocharger; compressing air drawn from atmosphere with the
second compressor; compressing air received from the second
compressor with the first compressor; supplying pressurized air
from the first compressor to an air intake port of a combustion
chamber in the cylinder via an intake manifold; operating a fuel
supply system to inject fuel directly into the combustion chamber;
operating a cam assembly to move the air intake valve; and
operating a hydraulic actuator to control movement of the air
intake valve.
29. The method of claim 28, wherein fuel is injected during a
combustion stroke of the piston.
30. The method of claim 29, wherein fuel injection begins during a
compression stroke of the piston.
31. The method of claim 28, wherein said operating a hydraulic
actuator includes operating the hydraulic actuator to keep open the
air intake valve to allow pressurized air to flow between the
combustion chamber and the intake manifold during a portion of a
compression stroke of the piston.
32. The method of claim 31, wherein said operating a hydraulic
actuator includes operating the hydraulic actuator to keep open the
air intake valve for a portion of a second half of a compression
stroke of the piston.
33. The method of claim 28, wherein said operating a hydraulic
actuator includes closing the air intake valve before bottom dead
center of an intake stroke of the piston.
34. The method of claim 28, further including operating the cam to
move the air intake valve and cyclically open and close the air
intake port, wherein said operating the hydraulic actuator includes
interrupting the cyclical opening and closing of the air intake
port.
35. The method of claim 28, wherein operation of the hydraulic
actuator is based on at least one engine condition.
36. The method of claim 28, wherein said first and second
compressors compress a mixture of air and recirculated exhaust gas,
and wherein said supplying includes supplying the compressed
mixture of pressurized air and recirculated exhaust gas to said
intake port via said intake manifold.
37. The method of claim 28, wherein operating a hydraulic actuator
includes extending a piston to engage a rocker arm operably coupled
with the air intake valve.
38. The method of claim 37, further including allowing fluid to
flow from a tank in an actuator housing to a bore in the actuator
housing and trapping the fluid in the bore of the actuator housing
to block retraction of the piston.
39. The method of claim 38, further including selectively allowing
fluid to drain from the bore to the tank to release the piston and
thereby allow the air intake valve to close before bottom dead
center of an intake stroke of the piston.
40. The method of claim 28, further including operating the cam to
move an air intake valve and cyclically open and close the air
intake port, wherein said operating a hydraulic actuator includes
interrupting the cyclical opening and closing of the air intake
port.
41. The method of claim 28, wherein operation of the hydraulic
actuator is based on at least one engine condition.
42. The method of claim 28, wherein said first and second
compressors compress a mixture of air and recirculated exhaust gas,
and wherein said supplying includes supplying the compressed
mixture of pressurized air and recirculated exhaust gas to said
intake port via said intake manifold.
43. A method of controlling an internal combustion engine having a
variable compression ratio, said engine including a block defining
a cylinder, a piston slidable in said cylinder, a head connected
with said block, said piston, said cylinder, and said head defining
a combustion chamber, the method comprising: pressurizing air;
supplying said air to an intake manifold of the engine; maintaining
fluid communication between said combustion chamber and the intake
manifold during a portion of an intake stroke and through a portion
of a compression stroke; injecting fuel directly into the
combustion chamber; and controlling the communication between said
combustion chamber and the intake manifold at least in part by
hydraulic actuator.
44. The method of claim 43, wherein said injecting fuel includes
injecting fuel directly to the combustion chamber during a portion
of a combustion stroke of the piston.
45. The method of claim 43, wherein said injecting fuel includes
injecting fuel directly to the combustion chamber during a portion
of the compression stroke.
46. The method of claim 43, wherein said injecting includes
supplying a pilot injection at a predetermined crank angle before a
main injection.
47. The method of claim 46, wherein said portion of the compression
stroke is at least a majority of the compression stroke.
48. The method of claim 43, wherein said pressurizing includes a
first stage of pressurization and a second stage of
pressurization.
49. The method of claim 48, further including cooling air between
said first stage of pressurization and said second stage of
pressurization.
50. The method of claim 43, further including cooling the
pressurized air.
51. The method of claim 43, wherein the pressurizing includes
pressurizing a mixture of air and recirculated exhaust gas, and
wherein the supplying includes supplying the pressurized air and
exhaust gas mixture to the intake manifold.
52. The method of claim 51, further including cooling the
pressurized air and exhaust gas mixture.
53. The method of claim 43, further including operating the
hydraulic actuator to varying a closing time of an air intake valve
controlling a flow to the combustion chamber.
54. The method of claim 43, further including operating the
hydraulic actuator to move a piston of the hydraulic actuator
between a first position and a second position and selectively
blocking the piston in the second position with fluid from a tank
disposed within the hydraulic actuator.
55. The method of claim 43, further including controlling the
communication between said combustion chamber and the intake
manifold at least in part by a cam assembly.
56. A method of operating an internal combustion engine including
at least one cylinder and a piston slidable in the cylinder, the
method comprising: supplying pressurized air from an intake
manifold to an air intake port of a combustion chamber in the
cylinder; operating an air intake valve to open the air intake port
to allow pressurized air to flow between the combustion chamber and
the intake manifold substantially during a portion of a compression
stroke of the piston; injecting fuel into the combustion chamber
after the intake valve is closed, wherein the injecting includes
supplying a pilot injection of fuel at a crank angle before a main
injection of fuel; and operating a hydraulic actuator to control
movement of the air intake valve.
57. The method of claim 56, wherein at least a portion of the main
injection occurs during a combustion stroke of the piston.
58. The method of claim 56, further including cooling the
pressurized air prior to supplying the pressurized air to the air
intake port.
59. The method of claim 56, wherein said supplying includes
supplying a mixture of pressurized air and recirculated exhaust gas
from the intake manifold to the air intake port, and wherein said
operating the air intake valve includes operating the air intake
valve to open the air intake port to allow the pressurized air and
exhaust gas mixture to flow between the combustion chamber and the
intake manifold substantially during a majority portion of the
compression stroke of the piston.
60. The method of claim 56, wherein said supplying a mixture of
pressurized air and recirculated exhaust gas includes controllably
providing a quantity of exhaust gas from an exhaust gas
recirculation (EGR) system.
61. The method of claim 56, wherein operating a hydraulic actuator
includes moving a piston of the hydraulic actuator between a first
position and a second position, engaging a rocker arm operatively
coupled to the air intake valve, and selectively restricting
movement of the piston when in the second position.
62. The method of claim 61, wherein the moving includes directing a
fluid from a tank within the hydraulic actuator to a bore housing
the piston, and selectively trapping the fluid within the bore.
63. The method of claim 62, wherein the moving further includes
allowing the fluid to drain from the bore to the tank to allow the
piston to move to the first position.
64. The method of claim 61, wherein the moving further includes
moving the piston to slow a closing of the air intake valve.
65. The method of claim 56, further including selectively
mechanically linking a cam to the air intake valve to move the air
intake valve between a first position at which the pressurized air
flows through the air intake port and a second position at which
the air intake valve blocks the flow of pressurized air through the
air intake port; and controlling the hydraulic actuator to decouple
the mechanical link between the cam and the air intake valve.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/933,300, filed Sep. 3, 2004, which is a
continuation-in-part of U.S. patent application Ser. No.
10/733,570, filed Dec. 12, 2003, which is a continuation of U.S.
patent application Ser. No. 10/143,908, filed May 14, 2002, now
U.S. Pat. No. 6,688,280. This application is also a
continuation-in-part of U.S. patent application Ser. No.
10/733,570, filed Dec. 12, 2003, which is a continuation of U.S.
patent application Ser. No. 10/143,908, filed May 14, 2002, now
U.S. Pat. No. 6,688,280. This application is also a
continuation-in-part of U.S. patent application Ser. No.
10/457,351, filed Jun. 10, 2003.
[0002] The entire disclosure of each of the U.S. patent
applications mentioned in the preceding paragraph is incorporated
herein by reference. In addition, the entire disclosure of each of
U.S. Pat. No. 6,651,618 and U.S. Pat. No. 6,688,280 is incorporated
herein by reference.
TECHNICAL FIELD
[0003] The present invention relates to a supply system for an
internal combustion engine and, more particularly, to a fuel and
air supply system for an internal combustion engine.
BACKGROUND
[0004] The operation of an internal combustion engine, such as, for
example, a diesel, gasoline, or gaseous fuel driven engine such as
a natural gas engine, may cause the generation of undesirable
emissions. These emissions, which may include particulates and
nitrous oxide (NOx), are generated when fuel is combusted in a
combustion chamber of the engine. An exhaust stroke of an engine
piston forces exhaust gas, which may include these emissions, from
the engine. If no emission reduction measures are in place, these
undesirable emissions will eventually be exhausted to the
environment.
[0005] Research is currently being directed towards decreasing the
amount of undesirable emissions that are exhausted to the
environment during the operation of an engine and on improving
engine efficiency. One such approach involves adjusting the
actuation timing of the engine valves. For example, the actuation
timing of the intake and exhaust valves may be modified to
implement a variation on the typical diesel or Otto cycle known as
the Miller cycle. In a "late intake" type Miller cycle, the intake
valves of the engine are held open during a portion of the
compression stroke of the piston. By holding the intake valves open
during a portion of the compression stroke of the piston, the
compression ratio of the engine is reduced while maintaining a high
expansion ratio, which results in a temperature reduction of the
fuel/air mixture within the combustion chamber. This improved
thermal efficiency reduces the emission of NOx.
[0006] One system utilized to vary intake valve timing is described
in U.S. Pat. No. 6,237,551 (the '551 patent) issued to Macor et al.
on May 29, 2001. The '551 patent describes a hydraulic actuator
that establishes a hydraulic link between a cam and an intake
valve. When the link is established, the valve will be actuated
according to the shape of the cam. However, when the link is
broken, such as by opening a control valve, the force of a valve
return spring causes the engine valve to close. Thus breaking the
hydraulic link allows the engine valve to close at a different
timing than would be achieved by the shape of the cam.
[0007] Although the valve actuation system of the '551 patent may
provide some flexibility in the opening timing of the intake valve,
it may be problematic. For example, the type of hydraulic actuator
described in the '551 patent typically uses engine lubricating oil
as the operating fluid. Lubricating oil may be supplied to the
hydraulic actuator by a standard engine lubrication system.
However, the lubricating oil may become contaminated with dirt, or
debris, as the lubricating oil is circulated through the engine.
Any such contamination of the lubricating oil may lead to degraded
performance of the hydraulic actuator, which may translate to a
reduction in the overall efficiency of the engine.
[0008] In addition, because the engine of the '551 patent can only
operate by establishing the hydraulic link between the cam and the
intake valve, and because the viscosity of the lubricating oil used
to establish the hydraulic link may depend upon temperature, the
engine of the '551 patent may not operate properly under varying
environmental and operational conditions. For example, when the
lubricating oil is cold, such as when the engine is starting, the
hydraulic actuator may experience slow response times because of
the increased viscosity of the lubricating oil. Under some
environmental conditions, the engine may need to operate for a
period of time to warm the lubricating oil so that the hydraulic
actuator will operate as expected. The engine may experience rough
running conditions or difficulty starting until the lubricating oil
is warmed enough to allow the hydraulic actuator to operate
properly.
[0009] Further reduction in the amount of pollutants emitted to the
atmosphere and improvement in engine efficiency can be realized by
combining a charged air induction system with variable valve
timing. One such system is described in U.S. Pat. No. 6,273,076
(the '076 patent) issued to Beck et al. on Aug. 14, 2001. The '076
patent describes an engine having camless electro-hydraulically
controlled intake valves capable of modulating a supply of air to a
combustion chamber. The engine of the '076 patent also describes a
combined supercharger/turbocharger assembly for directing charged
air to the combustion chamber.
[0010] Although the engine of the '076 patent may reduce the amount
of pollutants emitted from an engine by combining a charged
induction system with variable valve timing, the engine of the '076
patent may also be problematic. In addition to the operational
limitations of the engine of the '076 patent acquired because the
intake valves are hydraulically controlled, the engine of the '076
patent may also be efficiency limited because the air induction
system includes a supercharger. Specifically, the supercharger does
not utilize the energy available in the exhaust flow from the
engine of the '076 patent and requires additional driving energy
from the engine to turn the compressor.
[0011] The disclosed air and fuel supply system is directed to
overcoming one or more of the problems set forth above.
SUMMARY OF THE INVENTION
[0012] In one aspect, the present disclosure is directed to an
internal combustion engine. The internal combustion engine includes
an engine block defining at least one cylinder and a head connected
with said engine block, the head including an air intake port, and
an exhaust port. The internal combustion engine also includes a
piston slidable in the cylinder and a combustion chamber being
defined by said head, said piston, and said cylinder. The internal
combustion engine further includes an air intake valve controllably
movable to open and close the air intake port and a valve actuator.
The valve actuator includes an actuator housing defining a tank
adapted to store a supply of fluid and a bore in fluid
communication with the tank. The valve actuator also includes a
piston slidably disposed in the bore of the actuator housing. The
piston is adapted to move between a first position and a second
position where the piston engages the air intake valve. The valve
actuator further includes a mechanical biasing element acting on
the piston to move the piston towards the second position, and a
control valve disposed between the tank and the bore in the
actuator housing. The control valve selectively moves between a
first position where fluid is allowed to flow between the tank and
the bore, and a second position where the fluid is prevented from
flowing between the bore and the tank to trap fluid in the bore.
The trapped fluid prevents the piston from moving with respect to
the actor housing to thereby prevent the engine valve from
returning to a closed position. The internal combustion engine also
includes an air supply system having at least one turbocharger
fluidly connected to the air intake port, and a fuel supply system
operable to controllably inject fuel into the combustion
chamber.
[0013] In another aspect, the present disclosure is directed to a
method of operating an internal combustion engine having at least
one cylinder and a piston slidable in the cylinder. The method
includes supplying pressurized air from an intake manifold to an
air intake port of a combustion chamber in the cylinder. The method
also includes operating a cam assembly to move an engine valve
between a first position where the engine valve prevents a flow of
the pressurized air between the intake manifold and the combustion
chamber and a second position where the engine valve allows the
flow of pressurized air during a majority portion of a compression
stroke of the piston. The method further includes extending a
piston from an actuator housing to engage the engine valve and
directing a flow of fluid from a tank disposed within the actuator
housing to a bore in the actuator housing, the bore being
associated with the piston. The method additionally includes
selectively preventing fluid from flowing from the bore to the tank
to trap fluid in the bore and prevent the piston from moving with
respect to the actuator housing, the piston engaging the engine
valve to prevent the ending valve from returning to the first
position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagrammatic illustration of an exemplary
disclosed internal combustion engine having an air supply
system;
[0015] FIG. 2 is a cutaway illustration of the internal combustion
engine of FIG. 1;
[0016] FIG. 3 is a cutaway view of a portion of the internal
combustion engine of FIG. 1;
[0017] FIG. 4 is a cross-sectional view illustration of an
exemplary disclosed variable valve closing mechanism;
[0018] FIG. 5 is a cross-sectional view illustration of another
exemplary disclosed variable valve closing mechanism;
[0019] FIG. 6 is a cross-sectional view illustration of another
exemplary disclosed variable valve closing mechanism;
[0020] FIG. 7 is a graph illustrating exemplary disclosed valve
actuations as a function of engine crank angle;
[0021] FIG. 8 is a cross-sectional illustration of an exemplary
disclosed fuel injection assembly for the internal combustion
engine of FIG. 1;
[0022] FIG. 9 is a graph illustrating exemplary disclosed fuel
injections as functions of engine crank angle;
[0023] FIG. 10 is a diagrammatic illustration of another exemplary
disclosed internal combustion engine having an air supply
system;
[0024] FIG. 11 is a diagrammatic illustration of another exemplary
disclosed internal combustion engine having an air supply system;
and
[0025] FIG. 12 is a diagrammatic illustration of another exemplary
disclosed internal combustion engine having exhaust gas
recirculation system.
DETAILED DESCRIPTION
[0026] FIG. 1 illustrates an exemplary power system 10 having
internal combustion engine 12, an air supply system 14, and intake
and exhaust manifolds 16 and 18 fluidly connecting internal
combustion engine 12 and air supply system 14. Internal combustion
engine 12 may include an engine block 20 defining a plurality of
cylinders 22, the number of which depends upon the particular
application. In one example internal combustion engine 12 may
include six cylinders 22, however, it is contemplated that internal
combustion engine 12 may include any number of cylinders 22 and
that cylinders 22 may be disposed in an in-line configuration, a
V-configuration, or any other suitable configuration. It should be
appreciated that internal combustion engine 12 may be any type of
internal combustion engine such as, for example, a diesel engine, a
gasoline engine, a gaseous fuel driven engine such as a natural gas
engine, or any other type of engine known in the art.
[0027] As illustrated in FIG. 2, internal combustion engine 12 may
include numerous additional components and systems that cooperate
to generate a power output. In particular, internal combustion
engine 12 may include a piston 24 slidably disposed within each of
the plurality of cylinders 22, a crankshaft 26, a connecting rod 28
operatively connecting each piston 24 with crankshaft 26, a
cylinder head 30 associated with each of cylinders 22, a series of
valve actuation assemblies 32, and a control system 34.
[0028] Crankshaft 26 may be rotatably disposed within engine block
20 and operably connected to each piston 24. In particular, one
connecting rod 28 may couple each piston 24 to crankshaft 26 so
that a sliding motion of pistons 24 within cylinders 22 results in
a rotation of crankshaft 26. Similarly, a rotation of crankshaft 26
may result in a sliding motion of pistons 24. For example, an
uppermost position of each piston 24 in cylinder 22 may correspond
to a top dead center position of crankshaft 26, and a lowermost
position of each piston 24 in cylinder 22 may correspond to a
bottom dead center position of crankshaft 26.
[0029] Internal combustion engine 12 may be a four-stroke engine,
wherein piston 24 reciprocates between the uppermost position and
the lowermost position during a combustion (or expansion) stroke,
an exhaust stroke, and intake stroke, and a compression stroke. As
piston 24 reciprocates between the upper most and lower most
positions, crankshaft 26 may rotate from the top dead center
position to the bottom dead center position during the combustion
stroke, from the bottom dead center to the top dead center during
the exhaust stroke, from top dead center to bottom dead center
during the intake stroke, and from bottom dead center to top dead
center during the compression stroke. Each stroke of piston 24
correlates to about 180.degree. of crankshaft rotation, or crank
angle. Thus, the combustion stroke may begin at about 0.degree.
crank angle, the exhaust stroke at about 180.degree., the intake
stroke at about 360.degree., and the compression stroke at about
540.degree..
[0030] Each cylinder head 30 may be connected with engine block 20
and associated with one cylinder 22 to form a combustion chamber
36. It is also contemplated that one cylinder head 30 may
alternatively be associated with multiple cylinders 22 to form
multiple combustion chambers 36. Each cylinder head 30 may define
an exhaust port 38 associated with each cylinder 22 that leads from
the respective cylinder 22 to an exhaust passageway 40, and an
intake port 42 that leads from the respective cylinder 22 to an
intake passageway 44. Exhaust passageway 40 may direct exhaust
fluid from exhaust port 38 to exhaust manifold 18 (referring to
FIG. 1), while intake passageway 44 may provide fluid, for example
air or a fuel/air mixture, from intake manifold 16 (referring to
FIG. 1) to intake port 42. It is contemplated that cylinder head 30
may define multiple exhaust ports 38 and/or multiple intake ports
42 for each cylinder 22. Intake manifold 16 and exhaust manifold 18
may be constructed as a single integral parts or, alternatively,
may be constructed as multi-part manifolds, depending upon the
particular application.
[0031] Each valve actuation assembly 32 may be configured to open
and close at least one exhaust port 38 and/or at least one intake
port 42. Specifically, internal combustion engine 12 may include an
exhaust valve 46 disposed within each exhaust port 38. Each exhaust
valve 46 may include a valve stem 48 having a valve head 50, valve
head 50 being sized and arranged to selectively close exhaust port
38. Similarly, internal combustion engine 12 may include an intake
valve 52 with a valve stem 54 and a head 56 at a first end of valve
stem 54, head 56 being sized and arranged to selectively close
intake port 42. As described in greater detail below, each exhaust
valve 46 and intake valve 52 may be actuated to move or "lift"
valve heads 50 and 56 to thereby open the respective exhaust and
intake ports 38 and 42. In a cylinder 22 having a pair of exhaust
valves 46 and a pair of intake valves 52, each of the pairs of
exhaust and intake valves 46, 52 may be actuated by a single valve
actuation assembly 32 or by a pair of valve actuation assemblies
32.
[0032] As illustrated in FIG. 3, each valve actuation assembly 32
may include a rocker arm 58 having a first end 60, a second end 62,
and a pivot point 64. The first end 60 of rocker arm 58 may
operatively engage valve head 56 of intake valve 52 through a
bridge 53 operatively engaged with valve stem 54 of two intake
valves 52. It is contemplated that bridge 53 may be omitted, if
desired, when valve actuation assembly 32 includes only a single
intake valve 52 associated with each cylinder 22. The second end 62
of rocker arm 58 may be operatively associated with a pushrod 66.
Intake valve 52 may be movable between a first position permitting
flow from intake passageway 44 to enter combustion chamber 36 and a
second position substantially blocking flow from intake passageway
44 to combustion chamber 36. It is contemplated that pushrod 66 may
be omitted, if desired.
[0033] Valve actuation assembly 32 may also include a valve spring
68 configured to bias intake valve 52. Specifically, valve spring
68 may act on valve stem 54 to move valve head 56 of intake valve
52 relative to cylinder head 30. In one embodiment, valve spring 68
may bias valve head 56 of intake valve 52 into the first position,
where valve head 56 engages a valve seat 72 within cylinder head 30
to prevent a flow of fluid relative to intake port 42. Valve head
56 of intake valve 52 may be movable against the bias of valve
spring 68 toward a second position where valve head 56 is away from
valve seat 72 to allow a flow of fluid relative to intake port
42.
[0034] Internal combustion engine 12 may also include a camshaft 74
operatively connected to crankshaft 26 and carrying a cam 76 with
one or more lobes 78. Camshaft 74 may be operatively connected with
crankshaft 26 in any manner readily apparent to one skilled in the
art where a rotation of crankshaft 26 may result in a corresponding
rotation of the camshaft 74. For example, camshaft 74 may be
connected to crankshaft 26 through a gear train (not shown) that
reduces the rotational speed of camshaft 74 to approximately one
half of the rotational speed of crankshaft 26.
[0035] Intake valve 52 may be arranged to operate cyclically based
on the configuration of cam 76, lobe 78, and the rotation of
camshaft 74 to achieve a desired predetermined intake valve timing.
As will be explained in greater detail below, the shape of cam lobe
78 on cam 76 may determine, at least in part, the actuation timing
of valve head 56 of intake valve 52. It is contemplated that the
distance between an outer edge of lobe 78 may vary and/or that cam
76 may include a greater number of cam lobes and/or a cam lobe
having a different configuration depending upon the desired intake
valve actuation timing.
[0036] A rotation of cam 76 may cause a cam follower 88 and
associated pushrod 66 to periodically reciprocate between an upper
position and a lower position. The reciprocating movement of
pushrod 66 may cause rocker arm 58 to pivot about pivot point 64.
When pushrod 66 moves in the direction indicated by an arrow 90,
rocker arm 58 may pivot and move bridge 53 in the opposite
direction. The movement of bridge 53 may cause each intake valve 52
to lift from valve seat 72 and open intake port 42. As cam 76
continues to rotate, valve spring 68 may act on bridge 53 to return
each intake valve 52 to the closed position. In one embodiment,
lobe 78 may be configured to operate intake valve 52 in an Otto or
diesel cycle, whereby intake valve 52 moves to the second or closed
position from between about 10.degree. before bottom dead center of
the intake stroke and about 10.degree. after bottom dead center of
the compression stroke. In this manner, the shape and orientation
of cam 76 may control the timing of the actuation of intake valves
52.
[0037] Cam 76 may be configured to coordinate the actuation of the
intake valves 52 with the movement of pistons 24. For example, each
intake valve 52 may be actuated to open intake port 42 when the
associated piston 24 is withdrawing within cylinder 22 to allow air
to flow from intake passageway 44 into the combustion chamber
36.
[0038] Exhaust valve 46 (referring to FIG. 2) may be configured in
a manner similar to intake valve 52 and may be operated by a lobe
(not shown) of cam 76. Alternatively, a second cam (not shown) may
be connected to crankshaft 26 to control the actuation timing of
the exhaust valve 46. Exhaust valve 46 may be actuated to open
exhaust port 38 when piston 24 is advancing within cylinder 22 to
allow exhaust to flow from cylinder 22 into exhaust passageway
40.
[0039] Valve actuation assembly 32 may also include a variable
valve closing mechanism 92 that is structured and arranged to
selectively interrupt cyclical movement of intake valve 52
initiated by cam 76. For example, variable valve closing mechanism
92 may be selectively operated to supply hydraulic fluid, for
example, at a low pressure or a high pressure, in a manner to
resist closing of intake valve 52 by the bias of valve spring 68.
That is, after intake valve 52 is lifted (i.e., opened by cam 76)
and when cam 76 is no longer holding intake valve 52 open, the
hydraulic fluid may hold intake valve 52 open for a desired period.
The desired period may change depending on the desired performance
of internal combustion engine 12 to operate under a conventional
Otto or diesel cycle or under a variable Miller cycle.
[0040] Variable valve closing mechanism 92 may include numerous
components that cooperate to hold intake valve 52 in the open
position. In particular, variable valve closing mechanism 92 may
include a housing 320 that slidably receives a piston 322 having an
end 324. End 324 of piston 322 may be adapted to engage end 60 of
rocker arm 58. One skilled in the art will recognize that end 324
of piston 322 may engage another portion of rocker arm 58 or may be
operatively engaged with intake valves 52 in another way.
[0041] FIG. 4 illustrates housing 320 of variable valve closing
mechanism 92 defining a tank 326, a bore 328, and a fluid
passageway 334 that connects tank 326 and bore 328. Tank 326 may be
adapted to store a supply of fluid. Tank 326 may store any type of
fluid such as, for example, an engine lubricating oil. Bore 328 may
be adapted to slidably receive piston 322. A seal 330 may be
disposed between piston 322 and bore 328 and may be any type of
sealing element such as, for example, an o-ring, that is adapted to
minimize fluid leakage from bore 328 past piston 322. Fluid may
flow within fluid passageway 334 from tank 326 to bore 328 as
spring 332 biases piston 322 away from housing 320 in the direction
of arrow 335.
[0042] Spring 332 may be any mechanical biasing element adapted to
bias piston 322 away from housing 320. The force exerted by spring
332 may be less than the force exerted by springs 68 on bridge 53
(referring to FIG. 3).
[0043] Variable valve closing mechanism 92 may also include a
control valve 336 disposed within fluid passageway 334. Control
valve 336 may be movable between a first position where fluid is
allowed to flow through fluid passageway 334 and a second position
where fluid is prevented from flowing through fluid passageway 334.
Thus, by controlling the position of control valve 336, the rate of
fluid flow between tank 326 and bore 328 may be controlled.
[0044] A snubbing valve 338 may be disposed between bore 328 and
control valve 336. Snubbing valve 338 may be configured to decrease
the rate at which fluid exits bore 328 to thereby slow the rate at
which piston 322 retracts within bore 328. Snubbing valve 338 may
include one or more passageway 340 having openings that connect
bore 328 with the fluid line leading to control valve 336.
[0045] A bleed valve 342 may be disposed in housing 320. Bleed
valve 342 may be adapted to allow air, or any other gas, that finds
its way into tank 326 to be released from tank 326. This will
prevent air from being passed from tank 326 to bore 328. Bleed
valve 342 may also purge air from anywhere within variable valve
closing mechanism 92.
[0046] Variable valve closing mechanism 92 may also include an
accumulator 344 having a piston 346 disposed within a chamber 348,
and spring 350 configured to act on piston 346. Fluid entering
chamber 348 may act to move piston 346 and compress spring 350 if
the force exerted by the fluid on piston 346 is great enough to
overcome the force of spring 350. Spring 350 may act to move piston
346 and force fluid out of chamber 348 when the force of spring 350
is greater than the force exerted by the pressurized fluid on
piston 346.
[0047] A fluid passageway 352 may connect accumulator 344 to fluid
passageway 334 between tank 326 and bore 328. A restrictive orifice
354 may be disposed in an inlet to accumulator 344. As described in
greater detail below, accumulator 344 may act to dampen
oscillations in bore 328 and fluid passageway 334, which could
otherwise cause piston 322 to oscillate relative to housing
320.
[0048] Housing 320 of variable valve closing mechanism 92 may also
include one or more leak passageways 356 and 358. Leak passageways
356 and 358 may be adapted to allow fluid that leaks from either
control valve 336 or accumulator 344 to return to tank 326. As
described in greater detail below, both control valve 336 and
accumulator 344 may be exposed to fluid having a substantial
pressure. Leak passageways 356 and 358 may help prevent any fluid
that leaks through control valve 336 or accumulator 344 from
leaking from variable valve closing mechanism 92.
[0049] Housing 320 of variable valve closing mechanism 92 may be
connected to cylinder head 30. For example, a pair of supports 357
may extend from housing 320 to cylinder head 30. Supports 357 may
be attached to cylinder head 30 by any connecting member readily
apparent to one skilled in the art. For example, bolts 359 may
connected supports 357 to cylinder head 30.
[0050] FIG. 5 illustrates an alternate embodiment of variable valve
closing mechanism 92, wherein a spring loaded piston 360 is
disposed within tank 326. Spring-loaded piston 360 act to exert a
force on fluid contained within tank 326. The force of
spring-loaded piston 360 may increase the pressure of the fluid
within tank 326 to thereby move fluid through fluid passageway 334
to bore 328.
[0051] FIG. 6 illustrates an additional embodiment of variable
valve closing mechanism 92. Variable valve closing mechanism 92 of
FIG. 6 includes a third chamber 362 disposed between tank 326 and
bore 328. Third chamber 362 may include a spring-loaded piston 364
and a check valve 366 disposed within spring-loaded piston 364.
Check valve 366 may be configured to allow fluid to flow from tank
326 towards bore 328. In this manner, check valve 366 may be
adapted to allow for the replacement of fluid that may leak from
variable valve closing mechanism 92.
[0052] Control system 34 may include a controller 104 electrically
connected to variable valve closing mechanism 92 of FIGS. 4-6 via a
communication line 368. Controller 104 may be configured to control
operation of variable valve closing mechanism 92 based on one or
more current engine operating conditions. In particular, controller
104 may be programmed to receive information from one or more
sensors (not shown) operatively connected with internal combustion
engine 12. Each of the sensors may be configured to sense one or
more operational parameters of internal combustion engine 12. For
example, internal combustion engine 12 may be equipped with sensors
configured to sense one or more of the following: a temperature of
an engine coolant, a temperature of internal combustion engine 12,
an ambient air temperature, an engine speed, a load on internal
combustion engine 12, and an intake air pressure. It is
contemplated that controller 104 may also be configured to control
operation of variable valve closing mechanism 92 based on
instructions received from an operator. It should be appreciated
that the functions of controller 104 may be performed by a single
controller or by a plurality of controllers. Controller 104 may
include an electronic control module (not shown) that has a
microprocessor and a memory. As is known to those skilled in the
art, the memory may be connected to the microprocessor and
configured to store an instruction set and variables. Associated
with the microprocessor and part of the electronic control module
may be various other known circuits such as, for example, power
supply circuitry, signal conditioning circuitry, and solenoid
driver circuitry, among others.
[0053] Control system 34 may be further equipped with a sensor
configured to monitor the crank angle of crankshaft 26 to thereby
determine the position of pistons 24 within their respective
cylinders 22. The crank angle of crankshaft 26 may also be related
to actuation timing of intake valves 52 and exhaust valves 46. For
example, exhaust valve actuation may be timed to substantially
coincide with the exhaust stroke of piston 24 and, as indicated in
an exemplary graph 106 of FIG. 7, intake valve actuation 110 may be
timed to substantially coincide with the intake stroke of the
piston 24. FIG. 7 also illustrates valve lift for an exemplary
conventional closing 314 and an exemplary late closing 316 of
intake valve 52.
[0054] Intake valve 52 may begin to open at about 360.degree. crank
angle, that is, when the crankshaft 26 is at or near a top dead
center position of the intake stroke. The closing of intake valve
52 may be selectively extended by the engagement of end 324 of
piston 322 with first end 60 of rocker arm 58 from the cyclical
closing initiated by the rotation of cam 76. That is, after intake
valve 52 is lifted (i.e., opened by cam 76), and when cam 76 is no
longer holding intake valve 52 open, variable valve closing
mechanism 92 may hold intake valve 52 open for a desired period.
The desired period may change depending on the desired performance
of internal combustion engine 12. In one example, the closing of
intake valve 52 may be extended from about 540.degree. crank angle,
that is, when the crank shaft is at or near a bottom dead center
position of the compression stroke, to about 650.degree. crank
angle, that is, about 70.degree. before top center of the
combustion stroke. Thus, intake valve 52 may be held open for a
majority portion of the compression stroke, that is, for the first
half of the compression stroke and a portion of the second half of
the compression stroke. It is contemplated that variable valve
closing mechanism 92 may keep intake valve 52 open at an
intermediate position between fully open and fully closed for a
period of time or may allow continuous movement of intake valve 52
with a delayed and/or slowed closing.
[0055] Although some examples described herein involve late intake
valve closure, it should be understood that certain examples in
accordance with the present invention might involve engine
operation where both late and early intake valve closure is
selectively provided, or engine operation where only early intake
valve closure is selectively provided. For example, in some
exemplary engines cam 76 could have an alternative profile
providing cyclical early intake valve closure and the variable
valve closing mechanism 92 may be controlled to selectively delay
the intake valve closing so that the delayed intake valve closing
occurs before, at, and/or after bottom dead center of the intake
stroke.
[0056] As illustrated in FIG. 8, internal combustion engine 12 may
also include a fuel injector assembly 116 configured to inject fuel
or otherwise spray fuel, for example, diesel fuel, directly into
each combustion chamber 36 via a fuel port 118 within cylinder head
30 in accordance with a desired timing. Fuel injector assembly 116
may embody a mechanically-actuated, electronically-controlled unit
injector, in fluid communication with a common fuel rail (not
shown). Alternatively, fuel injector assembly 116 may be any common
rail type injector and may be actuated and/or operated
hydraulically, mechanically, electrically, piezo-electrically, or
any combination thereof. The common fuel rail may provide fuel to
the fuel injector assembly 116 associated with each combustion
chamber 36. Fuel injector assembly 116 may be associated with an
injector rocker arm 120 and pivotally coupled to a rocker shaft
122. Each fuel injector assembly 116 may include an injector body
124, a solenoid 126, a plunger assembly 128, and an injector tip
assembly 130. A first end 132 of injector rocker arm 120 may be
operatively coupled to plunger assembly 128. Plunger assembly 128
may be biased by a spring 134 toward the first end 132 of injector
rocker arm 120 in the general direction of an arrow 138.
[0057] A second end 140 of injector rocker arm 120 may be
operatively coupled to a camshaft 142. More specifically, camshaft
142 may include a cam lobe 144 having a first bump 146 and a second
bump 148. Camshafts 74, 142 and their respective lobes 78, 144 may
be combined into a single camshaft (not shown) if desired. First
and second bumps 146, 148 may be moved into and out of contact with
the second end 140 of injector rocker arm 120 during rotation of
the camshaft 142. First and second bumps 146, 148 may be structured
and arranged such that second bump 148 may provide a pilot
injection of fuel at a predetermined crank angle before first bump
146 provides a main injection of fuel. It should be appreciated
that cam lobe 144 may have only a first bump 146 that injects all
of the fuel per cycle.
[0058] When one of first and second bumps 146, 148 is rotated into
contact with injector rocker arm 120, the second end 140 of
injector rocker arm 120 may be urged in the general direction of
arrow 138. As the second end 140 is urged in the general direction
of arrow 138, injector rocker arm 120 may pivot about rocker shaft
122 thereby causing the first end 132 to be urged in the general
direction of an arrow 150. The force exerted on the second end 140
by first and second bumps 146, 148 may be greater in magnitude than
the bias generated by spring 134, thereby causing plunger assembly
128 to be likewise urged in the general direction of arrow 150.
When camshaft 142 is rotated beyond the maximum height of first and
second bumps 146, 148, the bias of spring 134 may urge plunger
assembly 128 in the general direction of arrow 138. As plunger
assembly 128 is urged in the general direction of arrow 138, the
first end 132 of injector rocker arm 120 is likewise urged in the
general direction of arrow 138, which causes injector rocker arm
120 to pivot about rocker shaft 122, thereby causing the second end
140 to be urged in the general direction of arrow 150.
[0059] Injector body 124 may define a fuel port 152. Fuel, such as
diesel fuel, may be drawn or otherwise aspirated into fuel port 152
from the fuel rail when plunger assembly 128 is moved in the
general direction of arrow 138. Fuel port 152 may be in fluid
communication with a fuel valve 154 via a first fuel channel 156.
Fuel valve 154 may be, in turn, in fluid communication with a
plunger chamber 158 via a second fuel channel 160.
[0060] Controller 104 may be configured to affect operation of fuel
injector assembly 116. Specifically, solenoid 126 may be
electrically coupled to controller 104 and mechanically coupled to
fuel valve 154. Actuation of solenoid 126 by a signal from
controller 104 may cause fuel valve 154 to be switched from an open
position to a closed position. When fuel valve 154 is in its open
position, fuel may advance from fuel port 152 to plunger chamber
158, and vice versa. However, when fuel valve 154 is in its closed
positioned, fuel port 152 may be isolated from plunger chamber
158.
[0061] Injector tip assembly 130 may include a check valve assembly
162. Fuel may be advanced from plunger chamber 158, through an
inlet orifice 164, a third fuel channel 166, an outlet orifice 168,
and into cylinder 22 of internal combustion engine 12.
[0062] Thus, it should be appreciated that when one of first and
second bumps 146, 148 is not in contact with injector rocker arm
120, plunger assembly 128 may be urged in the general direction of
arrow 138 by spring 134, thereby causing fuel to be drawn into fuel
port 152, which in turn fills plunger chamber 158 with fuel. As
camshaft 142 is further rotated, one of first and second bumps 146,
148 may be moved into contact with injector rocker arm 120, thereby
causing plunger assembly 128 to be urged in the general direction
of arrow 150. If controller 104 is not generating an injection
signal, fuel valve 154 may remain in its open position, thereby
causing the fuel which is in plunger chamber 158 to be displaced by
plunger assembly 128 through fuel port 152. However, if controller
104 is generating an injection signal, fuel valve 154 may be
positioned in its closed position thereby isolating plunger chamber
158 from fuel port 152. As plunger assembly 128 continues to be
urged in the general direction of arrow 150 by camshaft 142, fluid
pressure within fuel injector assembly 116 may increase. At a
predetermined pressure magnitude, for example, at about 5500 psi
(38 MPa), fuel may be injected into combustion chamber 36. Fuel may
continue to be injected into combustion chamber 36 until controller
104 signals solenoid 126 to return fuel valve 154 to its open
position.
[0063] As shown in the exemplary graph of FIG. 9, the pilot
injection of fuel may commence when crankshaft 26 is at about
675.degree. crank angle, that is, about 45.degree. before top dead
center of the compression stroke. The main injection of fuel may
occur when crankshaft 26 is at about 710.degree. crank angle, that
is, about 10.degree. before top dead center of the compression
stroke and about 45.degree. after commencement of the pilot
injection. Generally, the pilot injection may commence when
crankshaft 26 is about 40-50.degree. before top dead center of the
compression stroke and may last for about 10-15.degree. of
crankshaft rotation. The main injection may commence when the
crankshaft 26 is between about 10.degree. before top dead center of
the compression stroke and about 12.degree. after top dead center
of the combustion stroke. The main injection may last for about
20-45.degree. of crankshaft rotation. The pilot injection may use a
desired portion of the total fuel used, for example about 10%.
[0064] As illustrated in FIG. 1, air supply system 14 may include
components that fluidly communicate with intake manifold 16 and the
exhaust manifold 18. In particular, air supply system 14 may
include a first turbocharger 170 and a second turbocharger 172.
First and second turbochargers 170, 172 may be arranged in series
with one another such that second turbocharger 172 provides a first
stage of pressurization and first turbocharger 170 provides a
second stage of pressurization. For example, second turbocharger
172 may be a low pressure turbocharger and first turbocharger 170
may be a high pressure turbocharger. First turbocharger 170 may
include a turbine 174 and a compressor 176. Turbine 174 may be
fluidly connected to exhaust manifold 18 via an exhaust duct 178
and may include a turbine wheel 180 carried by a shaft 182. Shaft
182 may be rotatably carried by a housing 184, for example, a
single-part or multi-part housing. The fluid flow path from exhaust
manifold 18 to turbine 174 may include a variable nozzle (not
shown) or other variable geometry arrangement adapted to control
the velocity of exhaust fluid impinging on turbine wheel 180.
Compressor 176 may be fluidly connected to intake manifold 16 and
may include a compressor wheel 186 carried by shaft 182. Thus,
rotation of shaft 182 by turbine wheel 180 may cause rotation of
compressor wheel 186.
[0065] First turbocharger 170 may include a compressed air duct 188
for receiving compressed air from the second turbocharger 172 and
an air outlet line 190 for receiving compressed air from compressor
176 and supplying the compressed air to intake manifold 16 of the
internal combustion engine 12. First turbocharger 170 may also
include an exhaust duct 192 for receiving exhaust fluid from
turbine 174 and supplying the exhaust fluid to second turbocharger
172.
[0066] Second turbocharger 172 may include a turbine 194 and a
compressor 196. Turbine 194 may be fluidly connected to exhaust
duct 192 and may include a turbine wheel 198 carried by a shaft
200, which in turn may be rotatably carried by housing 184.
Compressor 196 may include a compressor wheel 202 also carried by
shaft 200. Thus, rotation of shaft 200 by the turbine wheel 198 may
in turn cause rotation of compressor wheel 202.
[0067] Second turbocharger 172 may include an air intake line 204
providing fluid communication between the atmosphere and compressor
196. Second turbocharger 172 may also supply compressed air to
first turbocharger 170 via compressed air duct 188. Second
turbocharger 172 may include an exhaust outlet 206 for receiving
exhaust fluid from turbine 194 and providing fluid communication
with the atmosphere. In one embodiment, first turbocharger 170 and
second turbocharger 172 may be sized to provide substantially
similar compression ratios. For example, first turbocharger 170 and
second turbocharger 172 may both provide compression ratios of
between 2:1 and 3:1, resulting in a system compression ratio of at
least 4:1 with respect to atmospheric pressure. Alternatively,
second turbocharger 172 may provide a compression ratio of 3:1 and
first turbocharger 170 may provide a compression ratio of 1.5:1,
resulting in a system compression ratio of 4.5:1 with respect to
atmospheric pressure.
[0068] Air supply system 14 may include an air cooler 208, for
example, an aftercooler, between compressor 176 and the intake
manifold 16. Air cooler 208 may extract heat from the air to lower
the intake manifold temperature and increase the air density.
Optionally, air supply system 14 may include an additional air
cooler 210, for example, an intercooler, between compressor 196 of
second turbocharger 172 and compressor 176 of first turbocharger
170. Intercooling may use techniques such as jacket water, air to
air, and the like. Alternatively, air supply system 14 may
optionally include an additional air cooler (not shown) between air
cooler 208 and intake manifold 16. The optional additional air
cooler may further reduce the intake manifold temperature. A jacket
water pre-cooler (not shown) may be used to protect air cooler
208.
[0069] FIG. 10 illustrates an alternate air supply system 212 for
internal combustion engine 12. Air supply system 212 may include a
turbocharger 214, for example, a high-efficiency turbocharger
capable of producing at least about a 4:1 compression ratio with
respect to atmospheric pressure. Turbocharger 214 may include a
turbine 216 and a compressor 218. Turbine 216 may be fluidly
connected to exhaust manifold 18 via an exhaust duct 220. Turbine
216 may include a turbine wheel 222 carried by a shaft 224, which
in turn may be rotatably carried by a housing 226, for example, a
single-part or multi-part housing. The fluid flow path from exhaust
manifold 18 to the turbine 216 may include a variable nozzle (not
shown), which may control the velocity of exhaust fluid impinging
on the turbine wheel 222.
[0070] Compressor 218 may include a compressor wheel 228 carried by
shaft 224. Thus, rotation of shaft 224 by the turbine wheel 222 in
turn may cause rotation of compressor wheel 228. Turbocharger 214
may include an air inlet 230 providing fluid communication between
the atmosphere and compressor 218 and an air outlet 232 for
supplying compressed air to intake manifold 16 of internal
combustion engine 12. Turbocharger 214 may also include an exhaust
outlet 234 for receiving exhaust fluid from turbine 216 and
providing fluid communication with the atmosphere.
[0071] Air supply system 212 may include an air cooler 236 between
compressor 218 and the intake manifold 16. Optionally, air supply
system 212 may include an additional air cooler (not shown) between
air cooler 236 and intake manifold 16.
[0072] FIG. 11 illustrates another alternate air supply system 238
for internal combustion engine 12. Air supply system 238 may
include a turbocharger 240 having a turbine 242 and first and
second compressors 244, 246. Turbine 242 may be fluidly connected
to exhaust manifold 18 via an inlet duct 248. Turbine 242 may
include a turbine wheel 250 carried by a shaft 252, which in turn
may be rotatably carried by a housing 254, for example, a
single-part or multi-part housing. The fluid flow path from exhaust
manifold 18 to turbine 242 may include a variable nozzle (not
shown), which may control the velocity of exhaust fluid impinging
on the turbine wheel 250.
[0073] First compressor 244 may include a compressor wheel 260
carried by shaft 252, and second compressor 246 may include a
compressor wheel 262 carried by shaft 252. Thus, rotation of shaft
252 by turbine wheel 250 in turn may cause rotation of first and
second compressor wheels 260, 262. First and second compressors
244, 246 may provide first and second stages of pressurization,
respectively.
[0074] Turbocharger 240 may include an air intake line 264
providing fluid communication between the atmosphere and first
compressor 244 and a compressed air duct 266 for receiving
compressed air from first compressor 244 and supplying the
compressed air to second compressor 246. Turbocharger 240 may also
include an air outlet line 268 for supplying compressed air from
second compressor 246 to intake manifold 16 of internal combustion
engine 12. Turbocharger 240 may further include an exhaust outlet
270 for receiving exhaust fluid from turbine 242 and providing
fluid communication with the atmosphere.
[0075] For example, first compressor 244 and second compressor 246
may both provide compression ratios of between 2:1 and 3:1,
resulting in a system compression ratio of at least 4:1 with
respect to atmospheric pressure. Alternatively, second compressor
246 may provide a compression ratio of 3:1 and first compressor 244
may provide a compression ratio of 1.5:1, resulting in a system
compression ratio of 4.5:1 with respect to atmospheric
pressure.
[0076] Air supply system 238 may include an air cooler 272 between
second compressor 246 and intake manifold 16. Optionally, air
supply system 238 may include an additional air cooler 274 between
first compressor 244 and second compressor 246 of turbocharger 240.
Alternatively, air supply system 238 may optionally include an
additional air cooler (not shown) between air cooler 272 and intake
manifold 16.
[0077] FIG. 12 illustrates an exemplary exhaust gas recirculation
(EGR) system 276 associated with an exhaust system 278 of internal
combustion engine 12. In this embodiment, internal combustion
engine 12 includes an air supply system 280 having two-stage
turbocharging similar to air supply system 14 of FIG. 1. Air supply
system 280 may include a first turbocharger 282 having a turbine
284 and a compressor 286. Air supply system 280 may also include
second turbocharger 288 having turbine 290 and compressor 292. The
two-stage turbocharger system operates to increase the pressure of
the air and exhaust gases being delivered to cylinders 22 via
intake manifold 16, and to maintain a desired air to fuel ratio
during extended open durations of intake valves 52 of cylinders 22
(referring to FIG. 2). It is noted that a two-stage turbocharger
system is not required for operation of the present invention.
Other types of turbocharger systems, such as the high pressure
ratio single-stage turbocharger system of FIG. 10, a variable
geometry turbocharger system, and the like, may be used
instead.
[0078] A throttle valve 294, may be located between compressor 286
and intake manifold 16 and used to control the amount of air and
recirculated exhaust gases being delivered to cylinders 22.
Although throttle valve 294 is shown between compressor 286 and an
aftercooler 296, throttle valve 294 may be alternatively positioned
at other locations such as, for example, after aftercooler 296.
[0079] Although EGR system 276 is a low pressure EGR system,
variations of EGR system 276 may be equally used with the present
invention, including both low pressure loop and high pressure loop
EGR systems. Other types of EGR systems, such as for example
by-pass, venturi, piston-pumped, peak clipping, and back pressure,
could be used.
[0080] An oxidation catalyst 298 may receive exhaust gases from
turbine 290 and serve to reduce HC emissions. Oxidation catalyst
298 may also be coupled with a de-NOx, catalyst to further reduce
oxides of nitrogen (NOx) emissions. A particulate matter (PM)
filter 300 may receive exhaust gases from oxidation catalyst 298.
Although oxidation catalyst 298 and PM filter 300 are shown as
separate items, they may alternatively be combined into one
package.
[0081] Some of the exhaust gases may be delivered to the atmosphere
from PM filter 300, while a portion of the exhaust gases may be
routed to intake manifold 16 through an EGR cooler 302, through an
EGR valve 304, and through first and second turbochargers 282, 288.
EGR cooler 302 may be of a type well known in the art, for example
a jacket water or an air to gas heat exchanger type.
[0082] A means 306 for determining pressure within PM filter 300 is
shown. In the preferred embodiment, the means 306 for determining
pressure may include a pressure sensor 308. However, other
alternate means for determining pressure may be employed. For
example, the pressure of the exhaust gases in PM filter 300 may be
estimated from a model based on one or more parameters associated
with internal combustion engine 12. Parameters may include, but are
not limited to, engine load, engine speed, temperature, fuel usage,
and the like.
[0083] A means 310 for determining flow of exhaust gases through PM
filter 300 may be used. Preferably, means 310 for determining flow
of exhaust gases may include a flow sensor 312. Flow sensor 312 may
be used alone to determine pressure in PM filter 300 based on
changes in flow of exhaust gases, or may be used in conjunction
with pressure sensor 308 to provide more accurate pressure change
determinations.
INDUSTRIAL APPLICABILITY
[0084] An air and fuel supply system for an internal combustion
engine in accordance with the exemplary embodiments of the
invention may extract additional work from the engine's exhaust.
The system may achieve fuel efficiency and reduce NOx emissions,
while maintaining work potential and ensuring that the system
reliability meets with operator expectations. The operation of
internal combustion engine 12 will now be explained.
[0085] Internal combustion engine 12 may function in a known manner
using, for example, the diesel principle of operation. Internal
combustion engine 12 may be used with each of the exemplary air
supply systems 14, 212, 238, and 280 of FIGS. 1 and 7-9,
respectively. Compressed air may be supplied from air supply
systems 14, 212, 238, and 280 to combustion chambers 36 via intake
port 42, and exhaust air may exit combustion chambers 36 to air
supply systems 14, 212, 238, and 280 via exhaust port 38. Intake
valve 52 and exhaust valve 46 may be controllably moved to direct
airflow into and exhaust out of combustion chambers 36.
[0086] In a conventional Otto or diesel cycle mode, intake valve 52
may move from the second or closed position to the first or open
position in a cyclical fashion to allow compressed air to enter
combustion chamber 36 of cylinder 22 at or near top dead center of
the intake stroke (about 360.degree. crank angle), as shown in FIG.
7. At or near bottom dead center of the compression stroke (about
540.degree. crank angle), intake valve 52 may move from the first
position to the second position to block additional air from
entering combustion chamber 36. Fuel may then be injected from fuel
injector assembly 116 (referring to FIG. 8) at or near top dead
center of the compression stroke (about 720.degree. crank
angle).
[0087] In accordance with the Miller cycle, the Otto or diesel
cycle may be modified by moving intake valve 52 from the first
position to the second position at either some predetermined time
before bottom dead center of the intake stroke (i.e., before
540.degree. crank angle) or some predetermined time after bottom
dead center of the compression stroke (i.e., after 540.degree.
crank angle). In a late-closing Miller cycle, intake valve 52 may
be moved from the first position to the second position during a
first portion of the first half of the compression stroke.
[0088] Variable valve closing mechanism 92 may enable internal
combustion engine 12 to be operated in an early-closing Miller
cycle, a late-closing Miller cycle, and a conventional Otto or
diesel cycle. Further, injecting a substantial portion of fuel
after top dead center of the combustion stroke, as illustrated in
FIG. 9, may reduce NOx emissions and increase the amount of energy
rejected to exhaust manifold 18 in the form of exhaust fluid. Use
of a high-efficiency turbocharger 214, 240 or series turbochargers
170-172, 282-288 may enable recapture of at least a portion of the
rejected energy from the exhaust. The rejected energy may be
converted into increased air pressures delivered to the intake
manifold 16, which may increase the energy pushing piston 24
against crankshaft 26 to produce useable work. In addition,
delaying movement of intake valve 52 from the open position to the
closed position may reduce the compression temperature in
combustion chamber 36. The reduced compression temperature may
further reduce NOx emissions.
[0089] Controller 104 may operate variable valve closing mechanism
92 to vary the timing of intake valve 52 to achieve desired engine
performance based on one or more engine conditions, for example,
engine speed, engine load, engine temperature, boost, and/or
manifold intake temperature. Variable valve closing mechanism 92
may also allow more precise control of the air/fuel ratio. By
delaying closing of intake valve 52, controller 104 may control the
cylinder pressure during the compression stroke of piston 24. For
example, late closing of intake valve 52 may reduce the compression
work that piston 24 must perform without compromising cylinder
pressure and while maintaining a standard expansion ratio and a
suitable air/fuel ratio.
[0090] The following discussion describes the implementation of a
late intake Miller cycle in a single cylinder 22 of internal
combustion engine 12. One skilled in the art will recognize that
the system of the present invention may be used to selectively
implement a late intake Miller cycle in all cylinders 22 of
internal combustion engine 12 in the same or a similar manner. In
addition, the disclosed system may be used to implement other valve
actuation variations on the conventional diesel cycle, such as, for
example, an exhaust Miller cycle, an early closing Miller cycle,
and other variations known in the art.
[0091] When internal combustion engine 12 is operating under normal
operating conditions, controller 104 may implement a late intake
Miller cycle by controlling the position of control valve 336 in
variable valve closing mechanism 92. The rotation of cam 76 may
cause rocker arm 58 to pivot to thereby actuate intake valves 52
(referring to FIG. 3). The force of spring 332 may cause piston 322
to extend in the direction of arrow 335 (referring to FIG. 4), to
thereby follow the motion of end 60 of rocker arm 58.
[0092] The movement of piston 322 in bore 328 draws fluid into bore
328 from fluid passageway 334 and tank 326. The flow of fluid into
bore 328 may be aided by spring-loaded piston 360, which may be
disposed within tank 326 (referring to FIG. 5) or by spring-loaded
piston 364 disposed within third chamber 360 (referring to FIG. 6).
Spring-loaded pistons 360 and 364 may force fluid through fluid
passageway 334 into bore 328 to ensure that bore 328 is filled with
fluid.
[0093] Controller 104 may send a signal to adjust the position of
control valve 336 to close passageway 334 and thereby trap fluid in
bore 328 when piston 322 is partially or fully extended from
housing 320. For example, controller 104 may close control valve
336 when intake valves 52 are at or near a maximum lift position
such as, for example, at a peak 218 (referring to FIG. 7). Also,
controller 104 may time the closing of control valve 336 to ensure
that bore 328 is filled with fluid before control valve 336 is
moved to the closed position.
[0094] As cam 76 continues to rotate, springs 68 may urge intake
valves 52 towards their closed positions until end 60 of rocker arm
58 engages end 324 of piston 322. The fluid trapped in bore 328 may
prevent piston 322 from moving with respect to housing 320 and
will, therefore, prevent intake valves 52 from closing. As long as
control valve 336 remains in the closed position, the trapped fluid
within bore 328 will prevent springs 68 from returning intake
valves 52 to the closed position. Thus, variable valve closing
mechanism 92 will hold intake valves 52 in position between the
open and closed positions, independently of the actuation of cam
76.
[0095] When rocker arm 58 engages piston 322, the force of springs
68 acting through rocker arm 58 may cause an increase in the
pressure of the fluid within variable valve closing mechanism 92.
In response to the increased pressure, fluid may flow through
restrictive orifice 354 in fluid passageway 352 and into
accumulator 344, which may absorb the pressure spike. In this
manner, accumulator 344 may act to dampen any oscillations that may
result from the engagement of rocker arm 58 and piston 322.
[0096] Controller 104 may close intake valves 52 by sending a
signal to adjust the position of control valve 336 to open
passageway 334. This allows the trapped fluid to flow out of bore
328. The force of springs 68 may overcome the force of spring 332
and force the fluid from bore 328 towards tank 326. The release of
the trapped fluid may allow piston 322 to move within housing 320.
The allows rocker arm 58 to pivot so that intake valves 52 may move
to the closed position.
[0097] Snubbing valve 338 may reduce the rate at which intake valve
52 moves to the closed position. As piston 322 moves within bore
328, fluid may flow through passageways 340. The body of piston 322
will eventually block the openings to passageways 340, thereby
reducing the rate at which fluid may flow from bore 328. This
reduction in fluid flow rate translates to a reduction in velocity
of piston 322 and to a reduction in the closing or seating velocity
of intake valve 52. In this manner, snubbing valve 338 may control
the velocity at which intake valve 52 closes to prevent intake
valve 52 from being damaged.
[0098] It should be appreciated that other alternatives exist for
reducing the closing speed of intake valve 52. For example, an
impact absorber (not shown) may be placed between piston 322 and
rocker arm 58. The impact absorber may include a spring/damper
element, for example, a self-contained hydraulic, pneumatic, or
elastomeric element. As another example, a cam (not shown) may be
used to reduce the closing speed of intake valve 52. Such a cam may
be referred to as a "decelerating" or "handoff" cam because it
reduces the closing speed of intake valve 52 at the handoff or
impact point.
[0099] An exemplary late intake closing of intake valve 52 is
illustrated in FIG. 7. As shown, intake valve 52 may be extended
past a conventional closing 314 into a portion of the compression
stroke of piston 24 during a late closing 316. This allows some of
the air in combustion chamber 36 to escape, thereby changing a
compression ration of internal combustion engine 12. The amount of
air allowed to escape the combustion chamber 36 may determine the
compression ratio of internal combustion engine 12 and may be
controlled by adjusting the crank angle at which control valve 336
is opened. Control valve 336 may be opened at an earlier crank
angle to decrease the amount of escaping air or at a later crank
angle to increase the amount of escaping air.
[0100] The disclosed engine valve actuation system may selectively
alter the timing of the intake and/or exhaust valve actuation of an
internal combustion engine. The actuation of the engine valves may
be based on sensed operating conditions of the engine. For example,
the engine valve actuation system may implement a late intake
Miller cycle when the engine is operating under normal operating
conditions, and the late intake Miller cycle may be disengaged when
the engine is operating under other conditions such as, for example
during starting or otherwise operating under cold conditions. Thus,
the present invention allows for selective disengagement of the
late Miller cycle.
[0101] Controller 104 may disengage the late intake Miller cycle by
leaving control valve 336 in the open position. If control valve
336 is continuously open, no fluid will be trapped within bore 328.
Accordingly, piston 322 will be free to move within housing 320 and
will not prevent intake valves 52 from returning to the closed
position. Thus, the actuation of intake valves 52 will be driven by
the shape of cam 76.
[0102] Thus, when control valve 336 is continuously open, intake
valves 52 will follow a conventional diesel cycle as governed by
cam 76. As illustrated in FIG. 7, intake valve actuation will
follow a conventional closing 314. In the conventional closing 314,
the closing of intake valves 52 may substantially coincide with the
end of the intake stroke of piston 24. When intake valves 52 close
at the end of the intake stroke, no air will be forced from
cylinder 22 during the compression stroke. This results in piston
24 compressing the fuel and air mixture to a higher pressure, which
will facilitate diesel fuel combustion. This is particularly
beneficial when operating in cold conditions.
[0103] As will be apparent from the foregoing description, the
describe system provides an engine valve actuation system that may
selectively alter the timing of the intake and/or exhaust valve
actuation of an internal combustion engine. The actuation of the
engine valves may be based on sensed operating conditions of the
engine. For example, the engine valve actuation system may
implement a late intake Miller cycle when the engine is operating
under normal operating conditions. The late intake Miller cycle may
be disengaged when the engine is operating under adverse operating
conditions, such as when the engine is cold. Thus, the disclosed
system and method provide a flexible engine valve actuation system
that provides for both enhanced cold starting capability and fuel
efficiency gains.
[0104] The disclosed system and method also provides a variable
valve closing mechanism that is self-contained in a single housing.
All essential elements of the variable valve closing mechanism are
contained in the housing, including the fluid supply reservoir. As
the variable valve closing mechanism does not have to share fluid
with another system in the engine, the possibility of operating
fluid contamination is reduced. Also, the variable valve closing
mechanism may use any type of operating fluid, including a fluid
that is not affected by a change in temperature. Thus, the
disclosed variable valve closing mechanism may not experience
performance problems when the operating fluid is cold.
[0105] In addition, the described variable valve closing mechanism
does not rely upon oil from the engine lubrication system.
Accordingly, any contamination of the lubricating oil will not
affect the operation of the variable valve closing mechanism. Also,
as the amount of fluid stored in the variable valve closing
mechanism is substantially less than the amount of oil included in
the engine lubrication system, the fluid in the described variable
valve closing mechanism may reach a normal operating temperature
faster than the oil in the engine lubricating system. Thus, the
described variable valve closing mechanism may provide for reliable
and timely operation, even under undesirable conditions.
[0106] The high pressure air provided by the exemplary air supply
systems 14, 212, 238, and 280 may provide extra boost on the intake
stroke of piston 24 to enable intake valve 52 to be closed even
later than in a conventional Miller cycle engine. In the present
invention, intake valve 52 may remain open until the second half of
the compression stroke of piston 24, for example, as late as about
80.degree. to 70.degree. before top dead center (BTDC). While
intake valve 52 is open, air may flow between combustion chamber 36
and intake manifold 16. Thus, cylinder 22 experiences less of a
temperature rise in combustion chamber 36 during the compression
stroke of piston 24.
[0107] Since the closing of intake valve 52 may be delayed, the
timing of fuel injection may also be retarded. For example,
controller 104 may controllably operate fuel injector assembly 116
to supply fuel to combustion chamber 36 after intake valve 52 is
closed. For example, fuel injector assembly 116 may be controlled
to supply a pilot injection of fuel contemporaneous with or
slightly after intake valve 52 is closed and to supply a main
injection of fuel contemporaneous with or slightly before
combustion temperature is reached within combustion chamber 36. As
a result, a significant amount of exhaust energy may be available
for recirculation by a air supply systems 14, 212, 238, and 280,
which may efficiently extract additional work from the exhaust
energy.
[0108] Referring to the exemplary air supply system 14 of FIG. 1,
exhaust gas from internal combustion engine 12 may be directed from
exhaust manifold 18 through exhaust duct 178 to impinge on and
causes rotation of turbine wheel 180 of first turbocharger 170.
Because turbine wheel 180 is coupled with shaft 182, which in turn
carries compressor wheel 186, the rotational speed of compressor
wheel 186 may correspond to the rotational speed of turbine wheel
180. Second turbocharger 172 may extract otherwise wasted energy
from the exhaust stream of first turbocharger 170 to turn
compressor wheel 202 of second turbocharger 172, which is in series
with compressor wheel 186 of first turbocharger 170. The extra
restriction in the exhaust path resulting from the addition of
second turbocharger 172 may raise the back pressure on piston 24.
However, the energy recovery accomplished through the use of second
turbocharger 172 may offset the work consumed by the higher back
pressure. For example, the additional pressure achieved by the
series turbochargers 170,172 may do work on piston 24 during the
induction stroke of the combustion cycle. Further, the added
pressure on cylinder 22 resulting from second turbocharger 172 may
be controlled and/or relieved by using the late intake valve
closing. Thus, the series turbochargers 170, 172 may provide fuel
efficiency via air supply system 14, and not simply more power.
[0109] It should be appreciated that air coolers 208, 236, 272, and
296 (referring to FIGS. 1 and 7-9) of air supply systems 14, 212,
238, and 280, preceding the intake manifold 16 may extract heat
from the air to lower the inlet manifold temperature, while
maintaining the denseness of the pressurized air. The optional
additional air coolers 210, 274 between compressors 176 and 196,
and 244 and 246 or after air coolers 208, 236, 272, and 296 may
further reduce the inlet manifold temperature, but may lower the
work potential of the pressurized air. The lower inlet manifold
temperature may further reduce NOx emissions.
[0110] Referring to FIG. 12, a change in pressure of exhaust gases
passing through PM filter 300 may result from an accumulation of
particulate matter, thus indicating a need to regenerate PM filter
300 (i.e., burn away the accumulation of particulate matter). For
example, as particulate matter accumulates, pressure in PM filter
300 may increase.
[0111] PM filter 300 may be a catalyzed diesel particulate filter
(CDPF) or an active diesel particulate filter (ADPF). A CDPF allows
soot to burn at much lower temperatures. An ADPF is defined by
raising the PM filter internal energy by means other than internal
combustion engine 12, for example electrical heating, burner, fuel
injection, and the like.
[0112] One method to increase the exhaust temperature and initiate
PM filter regeneration is to use throttle valve 294 to restrict
inlet air, thus increasing exhaust temperature. Other methods to
increase exhaust temperature may include variable geometry
turbochargers, smart wastegates, variable valve actuation, and the
like. Yet another method to increase exhaust temperature and
initiate PM filter regeneration may include the use of a post
injection of fuel ( i.e., a fuel injection timed after delivery of
a main injection).
[0113] Throttle valve 294 may be coupled to EGR valve 304 so that
they are both actuated together. Alternatively, throttle valve 294
and EGR valve 304 may be actuated independently of each other. Both
valves may operate together or independently to modulate the rate
of EGR being delivered to intake manifold 16.
[0114] CDPFs regenerate more effectively when the ratio of NOx, to
particulate matter (i.e., soot) is within a certain range, for
example, from about 20:1 to about 30:1. It has been found, however,
that an EGR system combined with the above described methods of
multiple fuel injections and variable valve timing may result in a
NOx to soot ratio of about 10:1. Thus, it may be desirable to
periodically adjust the levels of emissions to change the NOx, to
soot ratio to a more desired range and then initiate regeneration.
Examples of methods which may be used include adjusting the EGR
rate and adjusting the timing of main fuel injection.
[0115] A venturi (not shown) may be used at the EGR entrance to the
fresh air inlet. The venturi would depress or lower the pressure of
the fresh air at the inlet, thus allowing EGR to flow from the
exhaust to the intake side. The venturi may include a diffuser
portion which would restore the fresh air to near original velocity
and pressure prior to entry into compressor 292. The use of a
venturi and diffuser may increase engine efficiency.
[0116] It will be apparent to those skilled in the art that various
modifications and variations can be made in the disclosed engine
valve actuation system without departing from the scope of the
invention. Other embodiments of the invention will be apparent to
those skilled in the art from consideration of the specification
and practice of the invention disclosed herein. It is intended that
the specification and examples be considered as exemplary only,
with a true scope of the invention being indicated by the following
claims and their equivalents.
* * * * *