U.S. patent application number 15/298268 was filed with the patent office on 2018-04-26 for method for operating an internal combustion engine employing a dedicated-cylinder egr system.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS LLC. The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Alan W. Hayman, Edward J. Keating.
Application Number | 20180112633 15/298268 |
Document ID | / |
Family ID | 61866551 |
Filed Date | 2018-04-26 |
United States Patent
Application |
20180112633 |
Kind Code |
A1 |
Keating; Edward J. ; et
al. |
April 26, 2018 |
METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE EMPLOYING A
DEDICATED-CYLINDER EGR SYSTEM
Abstract
A multi-cylinder spark-ignition internal combustion engine
includes a plurality of first and second intake valves disposed
between the air intake system and a corresponding plurality of
engine cylinders. The engine also includes a dedicated-cylinder
exhaust gas recirculation (EGR) system including an exhaust runner
fluidly connected between exhaust valve(s) of one of the cylinders
and the air intake system of the engine. A controllable intake
valve activation system is configured to control openings of the
plurality of first and second intake valves. A controller is
operatively connected to the engine and the controllable intake
valve activation system, and includes an instruction set to monitor
operation of the engine, and control openings of the plurality of
first intake valves and control openings of the plurality of second
intake valves to generate in-cylinder mixing of a cylinder charge
that achieves combustion stability for an engine speed/load
operating point.
Inventors: |
Keating; Edward J.;
(Ortonville, MI) ; Hayman; Alan W.; (Romeo,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS
LLC
Detroit
MI
|
Family ID: |
61866551 |
Appl. No.: |
15/298268 |
Filed: |
October 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D 37/02 20130101;
G08B 29/20 20130101; G01R 35/005 20130101; F02D 41/0077 20130101;
F02M 26/43 20160201; Y02T 10/12 20130101; Y02T 10/18 20130101; G01R
31/3191 20130101; G01R 33/0023 20130101; F02D 41/26 20130101; F02D
2200/101 20130101; G01R 27/28 20130101; F02M 26/20 20160201; F02D
13/0257 20130101; F02D 35/023 20130101; F02D 13/0226 20130101 |
International
Class: |
F02M 26/43 20060101
F02M026/43; F02D 41/00 20060101 F02D041/00; F02D 41/26 20060101
F02D041/26; F02D 13/02 20060101 F02D013/02; F02M 26/20 20060101
F02M026/20 |
Claims
1. A multi-cylinder internal combustion engine system, comprising:
an engine subassembly including an engine block defining a
plurality of cylinders and a plurality of first and second intake
valves disposed in a cylinder head between an air intake system and
the cylinders; a dedicated-cylinder exhaust gas recirculation (EGR)
system including an exhaust runner fluidly connected between an
exhaust valve of one of the cylinders and the air intake system of
the engine; a controllable intake valve activation system
configured to control openings of the plurality of first and second
intake valves; a controller operatively connected to the internal
combustion engine and the controllable intake valve activation
system, the controller including an instruction set, the
instruction set executable to: monitor of a parameter associated
with combustion stability in the engine, and operate the
controllable intake valve activation system to control openings of
the first intake valves and control openings of the second intake
valves, wherein the openings of the first and second intake valves
are selected to achieve combustion stability in the engine.
2. The engine system of claim 1, wherein the instruction set is
further executable to: monitor operation of the engine to determine
an engine speed/load operating point, and control the controllable
intake valve activation system to control openings of the first
intake valves and control openings of the second intake valves to
achieve combustion stability at the engine speed/load operating
point.
3. The engine system of claim 2, wherein the instruction set
executable to control the controllable intake valve activation
system to control openings of the first and second intake valves
and control openings of the second intake valves to achieve
combustion stability at the engine speed/load operating point
comprises a calibration that includes preferred openings of the
first and second intake valves based upon the engine speed/load
operating point.
4. The engine system of claim 1, wherein the instruction set
executable to control the controllable intake valve activation
system to control openings of the first intake valves and control
openings of the second intake valves comprises the instruction set
being executable to control the controllable intake valve
activation system to open both the first intake valve and the
second intake valve during each intake stroke of each combustion
cycle.
5. The engine system of claim 1, wherein the instruction set
executable to control the controllable intake valve activation
system to control openings of the first intake valves and control
openings of the second intake valves comprises the instruction set
being executable to control the controllable intake valve
activation system to open only the first intake valve.
6. The engine system of claim 5, further comprising the instruction
set being executable to control the controllable intake valve
activation system to open only the first intake valve during each
intake stroke of each combustion cycle, wherein open time of the
first intake valve is extended to effect valve closing during a
subsequent compression stroke.
7. The engine system of claim 5, further comprising the instruction
set being executable to control the controllable intake valve
activation system to open only the first intake valve during each
intake stroke of each combustion cycle, wherein open time of the
first intake valve is reduced to effect valve closing prior to the
end of the intake stroke.
8. The engine system of claim 1, wherein the instruction set
executable to control the controllable intake valve activation
system to control openings of the first intake valves and control
openings of the second intake valves comprises the instruction set
being executable to control the controllable intake valve
activation system to open only the second intake valve during each
intake stroke of each combustion cycle.
9. The engine system of claim 8, wherein the instruction set is
further executable to control the controllable intake valve
activation system to open only the second intake valve during each
intake stroke of each combustion cycle, wherein open time of the
second intake valve is extended to effect valve closing during a
subsequent compression stroke.
10. The engine system of claim 8, wherein the instruction set is
further executable to control the controllable intake valve
activation system to open only the second intake valve during each
intake stroke of each combustion cycle, wherein open time of the
second intake valve is reduced to effect valve closing prior to the
end of the intake stroke.
11. A method for operating a multi-cylinder internal combustion
engine that includes a variable intake valve activation system and
a dedicated-cylinder exhaust gas recirculation (EGR) system, the
method comprising: monitoring an engine parameter associated with
combustion stability during operation of the dedicated-cylinder EGR
system; and controlling, by a controller, the variable intake valve
activation system to control opening of a first intake valve and
control opening of a second intake valve to achieve combustion
stability.
12. The method of claim 11, further comprising: monitoring
operation of the engine to determine an engine speed/load operating
point, and controlling the controllable intake valve activation
system to control openings of the first intake valves and control
openings of the second intake valves to achieve combustion
stability at the engine speed/load operating point.
13. The method of claim 12, wherein controlling the controllable
intake valve activation system comprises a calibration that
includes preferred openings of the first and second intake valves
based upon the engine speed/load operating point.
14. The method of claim 11, wherein controlling the controllable
intake valve activation system comprises opening both the first
intake valve and the second intake valve during each intake stroke
of each combustion cycle.
15. The method of claim 11, wherein controlling the controllable
intake valve activation system comprises opening only the first
intake valve during each intake stroke of each combustion
cycle.
16. The method of claim 15, further comprising controlling the
controllable intake valve activation system to open only the first
intake valve during each intake stroke of each combustion cycle,
wherein the opening of the first intake valve is extended to end
during a subsequent compression stroke.
17. The method of claim 15, further comprising controlling the
controllable intake valve activation system to open only the first
intake valve during each intake stroke of each combustion cycle,
wherein the opening of the first intake valve is reduced to end
during the intake stroke.
18. The method of claim 11, wherein controlling the controllable
intake valve activation system comprises opening only the second
intake valve during each intake stroke of each combustion
cycle.
19. The method of claim 18, further comprising opening only the
second intake valve during each intake stroke of each combustion
cycle, wherein opening of the second intake valve is extended to
end during a subsequent compression stroke.
20. The method of claim 18, further comprising opening only the
second intake valve during each intake stroke of each combustion
cycle, wherein the opening of the second intake valve is reduced to
end during the intake stroke.
Description
INTRODUCTION
[0001] Internal combustion engines (engines) produce mechanical
power in the form of torque and rotational speed by combusting a
mixture of air and fuel within one or more combustion chambers.
During combustion, various exhaust gases are produced. A portion of
the exhaust gas can be recirculated back into the engine cylinders,
e.g., via an exhaust gas recirculation system. The recirculated
exhaust gas can displace an amount of combustible mixture in the
cylinder resulting in increased engine efficiency and lower
combustion temperatures, which may serve to reduce formation of
certain gaseous byproducts.
SUMMARY
[0002] A multi-cylinder spark-ignition internal combustion engine
system (engine) is described, and includes an engine subassembly
including an engine block defining a plurality of cylinders and a
plurality of first and second intake valves disposed in a cylinder
head between an air intake system and the cylinders. The engine
also includes a dedicated-cylinder exhaust gas recirculation (EGR)
system including an exhaust runner fluidly connected between
exhaust valve(s) of one of the cylinders and the air intake system
of the engine. A controllable intake valve activation system is
configured to control openings of the plurality of first and second
intake valves. A controller is operatively connected to the engine
and the controllable intake valve activation system, and includes
an instruction set that is executable to monitor operation of the
engine, and control openings of the plurality of first intake
valves and control openings of the plurality of second intake
valves to generate in-cylinder mixing of a cylinder charge that
achieves combustion stability for an engine speed/load operating
point.
[0003] One aspect includes monitoring operation of the engine to
determine an engine speed/load operating point and operate the
intake valve activation system to control openings of the first
intake valves and the second intake valves based upon the engine
speed/load operating point.
[0004] One aspect includes operating the intake valve activation
system to open both the first intake valve and the second intake
valve during each intake stroke of each combustion cycle.
[0005] One aspect includes operating the intake valve activation
system to open only the first intake valve or only the second
intake valve during each intake stroke of each combustion
cycle.
[0006] One aspect includes operating the intake valve activation
system to open only the first intake valve or only the second
intake valve during each intake stroke of each combustion cycle,
wherein open time of the first intake valve or the second intake
valve is either increased or reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 schematically shows an internal combustion engine
including an engine subassembly, an air intake system, an exhaust
system, a dedicated-cylinder exhaust gas recirculation (EGR) system
and a turbocharger, in accordance with the disclosure; and
[0008] FIGS. 2-1 through 2-6 graphically show first through sixth
profiles, respectively, that may be employed to control an
embodiment of the internal combustion engine described with
reference to FIG. 1, wherein each of the profiles is in the form of
a valve opening timing chart including timing and lift for first
and second intake valves and exhaust valves in relation to
crankshaft position for a single cylinder over a single four-stroke
engine cycle, in accordance with the disclosure.
DETAILED DESCRIPTION
[0009] The components of the disclosed embodiments, as described
and illustrated herein, may be arranged and designed in a variety
of different configurations. Thus, the following detailed
description is not intended to limit the scope of the disclosure,
as claimed, but is merely representative of possible embodiments
thereof. In addition, while numerous specific details are set forth
in the following description in order to provide a thorough
understanding of the embodiments disclosed herein, some embodiments
can be practiced without some or all of these details. Moreover,
for the purpose of clarity, certain technical material that is
known in the related art has not been described in detail in order
to avoid unnecessarily obscuring the disclosure. Furthermore, the
drawings are in simplified form and are not to precise scale. Any
use of directional terms may not be construed to limit the scope of
the disclosure in any manner. Furthermore, the disclosure, as
illustrated and described herein, may be practiced in the absence
of any element which is not specifically disclosed herein.
Furthermore, the teachings may be described herein in terms of
functional and/or logical block components and/or various
processing steps. It should be realized that such block components
may be composed of any number of hardware, software, and/or
firmware components configured to perform the specified functions.
As employed herein, the term "upstream" and related terms refer to
elements that are towards an origination of a flow stream relative
to an indicated location, and the term "downstream" and related
terms refer to elements that are away from an origination of a flow
stream relative to an indicated location.
[0010] Referring now to the drawings, wherein the depictions are
for the purpose of illustrating certain exemplary embodiments only
and not for the purpose of limiting the same, FIG. 1 schematically
illustrates a four-cycle internal combustion engine assembly
(engine) 10 including an engine subassembly 12, an air intake
system 14, an exhaust system 16 and a dedicated-cylinder exhaust
gas recirculation (EGR) system 60. In one embodiment and as shown,
a turbocharger 18 may be employed. In one embodiment, an
engine-driven or electric motor-driven supercharger may be
employed. The engine 10 may be deployed on a vehicle to provide
propulsion power, wherein the vehicle may include, but not be
limited to a mobile platform in the form of a commercial vehicle,
industrial vehicle, agricultural vehicle, passenger vehicle,
aircraft, watercraft, train, all-terrain vehicle, personal movement
apparatus, robot and the like to accomplish the purposes of this
disclosure.
[0011] The engine 10 is preferably configured as a
high-compression-ratio spark-ignited internal combustion engine,
and may also include another suitable internal combustion engine
that combusts hydrocarbon fuels to generate torque. The engine
subassembly 12 preferably includes an engine block defining a
plurality of cylinders 20 (referenced as cylinders 1-4), a
corresponding plurality of pistons that reciprocate within the
cylinders 20, a rotatable crankshaft that couples to the pistons, a
cylinder head 21, and other engine components such as piston
connecting rods, pins, bearings and the like. Each of the cylinders
20 with corresponding piston and portion of the cylinder head 21
defines a variable-volume combustion chamber 15. Each of the
plurality of cylinders 20 selectively fluidly communicates with the
air intake system 14 via first and second intake valves 23, 24,
respectively, to receive fresh/oxygenated air, and each of the
plurality of cylinders 20 selectively fluidly communicates with the
exhaust system 16 via exhaust valves 25 to expel the byproducts of
combustion. While the illustrated engine 10 depicts an inline
4-cylinder (I4) engine, the present technology is equally
applicable to other engine configurations, including, by way of
non-limiting examples, I2, I3, I5 and I6 engines, or V-2, V-4, V-6,
V-8, V-10, and V-12 engines, among others.
[0012] The cylinder head 21 includes a plurality of intake ports
and associated first and second intake valves 23, 24, respectively,
for each of the cylinders 20, a plurality of exhaust ports and
associated exhaust valves 25 for each of the cylinders 20, and
other ports and associated components including fuel injectors,
spark igniters and combustion sensors. The plurality of first and
second intake valves 23, 24 are disposed between the air intake
system 14 and a corresponding one of the cylinders 20. The
plurality of exhaust valves 25 are disposed between a corresponding
one of the cylinders 20 and the exhaust system 16. The exhaust
system 16 preferably includes a first exhaust manifold 36 and a
second exhaust manifold 62 that are disposed to entrain and direct
exhaust gases that are expelled from the engine 10 via openings of
the exhaust valves 25.
[0013] The first and second intake valves 23, 24 operatively
connect to a variable intake valve activation system 22 that
preferably includes a rotatable camshaft whose rotation is indexed
to rotation of the crankshaft. The exhaust valves 25 operatively
connect to an exhaust valve activation system 26 that preferably
includes a rotatable camshaft whose rotation is indexed to rotation
of the crankshaft. In one embodiment, the exhaust valve activation
system 26 may be variably controlled, as described herein.
[0014] The air intake system 14 can generally include one or more
of, a fresh-air inlet, an exhaust gas recirculation (EGR) mixer 27,
a charge air cooler 28, a throttle 30 and an intake manifold 32.
During operation of the engine 10, fresh air or intake air 34 can
be ingested by the air intake system 14 from the atmosphere through
an associated air-cleaner assembly via the fresh-air inlet. The
throttle 30 can include a controllable baffle that is configured to
regulate the total flow of air through the air intake system 14,
and ultimately into the cylinders 20 via the intake manifold 32.
Airflow from the intake manifold 32 into each of the cylinders 20
is controlled by the first and second intake valves 23, 24, the
activation of which is controlled by the variable intake valve
activation system 22. Exhaust flow out of each of the cylinders 20
to the first and second exhaust manifolds 36, 62 is controlled by
the exhaust valve(s) 25, the activation of which may be controlled
by the exhaust valve activation system 26.
[0015] The term "dedicated-cylinder EGR system" as employed herein
refers to a system in which all exhaust gases generated in one or a
plurality of the cylinders 20 are separated and routed to the air
intake system 14. In one embodiment, the dedicated-cylinder EGR
system 60 includes the second exhaust manifold 62, a controllable
diverter valve 64, and an in-stream EGR heat exchanger 65 that
fluidly connects to the air intake system 14 at an EGR mixer 27
that is located upstream of the charge air cooler 28 and the
throttle 30. The second exhaust manifold 62 entrains exhaust gas
flow from cylinder 4 in this embodiment, and channels such flow to
the air intake system 14 when the diverter valve 64 is controlled
to a first position. The second exhaust manifold 62 entrains and
channels exhaust gas flow from cylinder 4 to the exhaust system 16
via a second conduit 70 when the diverter valve 64 is controlled to
a second position. Other elements preferably include the in-stream
EGR heat exchanger 65 that is configured to reduce or otherwise
manage temperature of the recirculated exhaust gas 41, a first
temperature sensor 61 that is disposed to monitor temperature of
the recirculated exhaust gas 41 upstream of the in-stream EGR heat
exchanger 65 and a second temperature sensor 63 that is disposed to
monitor temperature of the recirculated exhaust gas 41 downstream
of the in-stream EGR heat exchanger 65. Thus, the
dedicated-cylinder EGR system 60 fluidly communicates with the air
intake system 14 to route the recirculated exhaust gas 41 to the
air intake system 14. This recirculated exhaust gas 41 can mix with
the fresh air 34 within the EGR mixer 27 to dilute the oxygen
content of the intake air charge. In one embodiment of the engine
10 employing the dedicated-cylinder EGR system 60, the magnitude of
EGR dilution of the intake air charge is approximately a ratio of
the number of dedicated EGR cylinders to the total number of
cylinders. In FIG. 1, one cylinder, i.e., cylinder 4 supplies
dedicated EGR for engine 12 that has a total of 4 cylinders so EGR
dilution is approximately 25%. The use of the dedicated-cylinder
EGR system 60 can increase fuel efficiency in spark ignition
engines. Furthermore, the dedicated-cylinder EGR system 60 can
reduce the combustion temperature and emission production from the
engine 10. The first exhaust gas 40 is produced by the remaining
three cylinders 20 (i.e., cylinders 1-3) and is expelled from the
engine 10 via the exhaust system 16 through the aftertreatment
device 42.
[0016] The variable intake valve activation system 22 includes
mechanisms and control routines that interact with the intake
camshaft(s) to control the openings and closings of the first and
second intake valves 23, 24, including selectively deactivating one
or both of the first and second intake valves 23, 24. One
mechanization that may be configured to individually selectively
deactivate one or both the first and second intake valves 23, 24
includes stationary hydraulic lash adjusters (SHLA) and roller
finger followers (RFF). Another mechanization that may be
configured to individually selectively deactivate one or both the
first and second intake valves 23, 24 includes an intake camshaft
and related componentry that includes a sliding cam having multiple
cam lobes that may be selectively disposed to interact with and
control openings and closings of one or both of the first and
second intake valves 23, 24. SHLAs, RFFs and sliding cam
mechanizations are known to those skilled in the art.
[0017] Controlling the variable intake valve activation system 22
to control openings and closings of the first and second intake
valves 23, 24 includes opening both the first intake valve 23 and
the second intake valve 24 during the intake stroke of the
combustion cycle for each of the cylinders 20 under certain
operating conditions. This further includes controlling the
variable intake valve activation system 22 to selectively
deactivate one of the first and second intake valves 23, 24 such
that the deactivated valve does not open during the intake stroke
of the combustion cycle for each of the cylinders 20. This may
include controlling the variable intake valve activation system 22
to activate only the first intake valve 23 while deactivating the
second intake valve 24 for each of the cylinders 20 such that the
deactivated second intake valve 24 does not open during the intake
stroke of the combustion cycle for each of the cylinders 20 under
certain operating conditions. This may include controlling the
variable intake valve activation system 22 to deactivate only the
first intake valve 23 while activating the second intake valve 24
for each of the cylinders 20 under certain operating conditions
such that the deactivated first intake valve 23 does not open
during the intake stroke of the combustion cycle for each of the
cylinders 20 under certain operating conditions. Such operations
are described with reference to FIGS. 2-1 through 2-6.
[0018] In one embodiment, the exhaust valve activation system 26
may include a variable camshaft phaser (VCP)/variable lift control
(VLC) device that interacts with the exhaust camshaft(s) to control
the openings and closings of the exhaust valves 25. Controlling the
openings and closings of the first and second intake valves 23, 24
and the exhaust valves 25 can include controlling magnitude of
valve lift and/or controlling phasing, duration or timing of valve
openings and closings. The exhaust valve activation system 26
including the VCP/VLC device is disposed to control interactions
between the exhaust valves 25 and an exhaust camshaft in one
embodiment. Alternatively, the exhaust valves 25 interact directly
or via followers with an exhaust camshaft. The rotations of the
intake and exhaust camshafts are linked to and indexed, variably in
the case of VCP application, to rotation of the engine crankshaft,
thus linking openings and closings of the intake and exhaust valves
23 and 25 to positions of the crankshaft and the pistons housed in
the cylinders 20.
[0019] Reciprocating movement of each of the pistons in its
corresponding cylinder is between a piston bottom-dead-center (BDC)
location and a piston top-dead-center (TDC) location in concert
with rotation of the crankshaft. Engines operating with a
four-stroke engine cycle sequentially execute a repeated pattern of
intake, compression, power and exhaust strokes. During the
compression stroke, a fuel/air charge in the combustion chamber 15
is compressed by rotation of the crankshaft and movement of the
piston in preparation for ignition. The intake valve 23 and the
exhaust valve 25 are closed during at least a portion of the
compression stroke. Closing of the intake valve 23 can be
controlled by controlling the variable intake valve activation
system 22, resulting in controlling an effective compression ratio.
The effective compression ratio is defined as a ratio of a
volumetric displacement of the combustion chamber 15 at closing of
the intake valve 23 and a minimum volumetric displacement of the
combustion chamber 15, e.g., when the piston is at TDC. The
effective compression ratio may differ from a geometric compression
ratio, which is defined as a ratio of a maximum volumetric
displacement of the combustion chamber 15 occurring at BDC and the
minimum volumetric displacement of the combustion chamber 15
occurring at TDC without regard to closing time of the intake valve
23. An early or delayed closing of the intake valve 23 may trap
less air in the combustion chamber 15, thus decreasing pressure and
therefore decreasing temperature in the combustion chamber 15
during combustion. In one embodiment, fuel is metered and injected
into the combustion chamber 15 during the intake stroke. One fuel
injection event may be executed to inject fuel; however, multiple
fuel injection events may be executed. In one embodiment, fuel is
injected early enough in the intake stroke to allow adequate
premixing of the fuel/air charge in the combustion chamber 15.
[0020] Referring again to FIG. 1, the charge air cooler 28 can be
disposed between the EGR mixer 27 and the throttle 30. In general,
the charge air cooler 28 can be a radiator-style heat exchanger
that uses a flow of atmospheric air or liquid coolant to cool an
intake air charge that is a mixture of fresh air and recirculated
exhaust gas. As may be appreciated, the intake air charge can be
warmer than atmospheric temperature due to the pressurization via
the compressor 52, in conjunction with the mixing of the higher
temperature recirculated exhaust gas 41. The charge air cooler 28
can cool the gas mixture to increase its density/volumetric
efficiency, while also reducing the potential for abnormal
combustion such as pre-ignition or knock.
[0021] The exhaust gas passes through an aftertreatment device 42
to catalyze, reduce and/or remove exhaust gas constituents prior to
exiting the exhaust system 16 via a tailpipe 44. The aftertreatment
device 42 can include one or combinations of catalytic devices,
including, e.g., a three-way catalytic device, an oxidation
catalyst, a hydrocarbon trap, a NOx adsorber, or any other suitable
components and accompanying pipes and valves that function to
oxidize, reduce, and otherwise catalyze and/or remove various
exhaust gas constituents prior to exiting the exhaust system
16.
[0022] The air intake system 14 and the exhaust system 16 can be in
mechanical communication through the turbocharger 18. The
turbocharger 18 is in fluid communication with the exhaust system
16 and the turbocharger 18 expels the first exhaust product 40. The
turbocharger 18 can include a turbine 50 in fluid communication
with the exhaust system 16 and a compressor 52 in fluid
communication with the air intake system 14. The turbine 50 and the
compressor 52 can be mechanically coupled via a rotatable shaft 54.
The turbocharger 18 can utilize the energy of the first exhaust
product 40 flowing from the engine 10 to spin the turbine 50 and
the compressor 52. The rotation of the compressor 52 draws fresh
air 34 in from the fresh air inlet and compresses the air 34 into
the remainder of the air intake system 14. The first exhaust
product 40 is expelled through the turbocharger 18. Once the first
exhaust product 40 is expelled from the turbocharger 18, the first
exhaust product 40 flows toward the aftertreatment device 42.
[0023] Operation of the engine 10 can be monitored by a plurality
of sensing devices. By way of non-limiting examples, the sensing
devices may include a combustion sensor 17 that is disposed to
monitor an engine parameter that is associated with combustion in
each cylinder, a first exhaust gas sensor 37 that is disposed in
the first exhaust manifold 36, a second exhaust gas sensor 43 that
is disposed in the exhaust gas feedstream downstream of the
aftertreatment device 42, a temperature sensor 78 that is disposed
to monitor temperature of the aftertreatment device 42, the first
temperature sensor 61 that is disposed to monitor temperature of
recirculated exhaust gas upstream of the in-stream EGR heat
exchanger 65 and the second temperature sensor 63 that is disposed
to monitor temperature of recirculated exhaust gas downstream of
the in-stream EGR heat exchanger 65.
[0024] The combustion sensor 17 may be disposed to monitor an
engine parameter associated with combustion in each cylinder, and
may be in the form of an in-cylinder pressure sensor in one
embodiment. Alternatively, the combustion sensor 17 may be in the
form of a rotational speed sensor that is disposed to monitor
rotational speed and position of the crankshaft, with accompanying
algorithms to evaluate crankshaft speed variations, or another
suitable combustion monitoring sensor. The aforementioned sensors
are provided for purposes of illustration. Any one of or all of the
aforementioned sensors may be replaced by other sensing devices
that monitor a parameter associated with operation of the engine
10, or may instead be replaced by an executable model to derive a
state of an engine operating parameter.
[0025] A controller 72 can be part of an electronic control module
that is in communication with various components of the vehicle.
The controller 72 includes a processor 74 and a memory 76 on which
is recorded instructions for communicating with the diverter valve
64, the variable intake valve activation system 22, the
turbocharger 18, the aftertreatment device 42, etc. The controller
72 is configured to execute the instructions from the memory 76,
via the processor 74. For example, the controller 72 can be a host
machine or distributed system, e.g., a computer such as a digital
computer or microcomputer, acting as a vehicle control module,
and/or as a proportional-integral-derivative (PID) controller
device having a processor, and, as the memory 76, tangible,
non-transitory computer-readable memory such as read-only memory
(ROM) or flash memory. The controller 72 can also have random
access memory (RAM), electrically erasable programmable read only
memory (EEPROM), a high-speed clock, analog-to-digital (A/D) and/or
digital-to-analog (D/A) circuitry, and any required input/output
circuitry and associated devices, as well as any required signal
conditioning and/or signal buffering circuitry. Therefore, the
controller 72 can include all software, hardware, memory 76,
algorithms, calibrations, connections, sensors, etc., necessary to
monitor and control the diverter valve 64, the variable intake
valve activation system 22, the turbocharger 18, the aftertreatment
device 42, etc. As such, a control method can be embodied as
software or firmware associated with the controller 72. It is to be
appreciated that the controller 72 can also include any device
capable of analyzing data from various sensors, comparing data,
making the necessary decisions required to control and monitor the
diverter valve 64, the variable intake valve activation system 22,
the turbocharger 18, the aftertreatment device 42, etc.
[0026] Communication between controllers, and communication between
controllers, actuators and/or sensors may be accomplished using a
direct wired link, a networked communications bus link, a wireless
link or any another suitable communications link. Communication
includes exchanging data signals in any suitable form, including,
for example, electrical signals via a conductive medium,
electromagnetic signals via air, optical signals via optical
waveguides, and the like. The term `model` refers to a
processor-based or processor-executable code and associated
calibration that simulates a physical existence of a device or a
physical process.
[0027] The controller 72 includes the processor 74 and tangible,
non-transitory memory 76 on which is recorded executable
instructions. The controller 72 is configured to control the
variable intake valve activation system 22 and the diverter valve
64 to route the recirculated exhaust gas 41. This includes the
controller 72 configured to actuate the diverter valve 64 in the
first position to route the recirculated exhaust gas 41 toward the
aftertreatment device 42 and bypass the dedicated-cylinder EGR
system 60, and also configured to actuate the diverter valve 64 in
the second position to route the recirculated exhaust gas 41
through the dedicated-cylinder EGR system 60 back to the air intake
system 14.
[0028] The engine subassembly 12, variable intake valve activation
system 22 and dedicated-cylinder EGR system 60 that is described
with reference to FIG. 1 can be advantageously controlled to
achieve combustion stability across the engine speed/load operating
range. The control of the variable intake valve activation system
22 is executed to generate a suitable level of turbulence within
each cylinder during the intake stroke to achieve in-cylinder
mixing and turbulence that results in a flame propagation speed
sufficiently fast to maintain combustion stability at an acceptable
level. The in-cylinder mixing and required turbulence level can be
accomplished and varied by selectively controlling openings and
closings of the first and second intake valves 23, 24, employing
the variable intake valve activation system 22.
[0029] One combustion parameter associated with combustion
stability is a coefficient of variation of indicated mean effective
pressure (CoV-IMEP), which can be determined and monitored
employing a suitable cylinder monitoring scheme, such as by use of
information derived from the combustion sensor 17, an in-cylinder
pressure sensor, or another suitable monitoring device. Devices,
control routines, calibrations and other elements associated with
determining the CoV-IMEP are known to one of ordinary skill in the
art, and thus not described in additional detail. This operation is
intended to improve overall repeatability and robustness of the
entire combustion process, resulting in smooth, consistent engine
operation as measured by such parameters as coefficient of
variation of indicated mean effective pressure (CoV-IMEP). In one
embodiment, the combustion stability may be determined during
on-going engine operation by monitoring inputs from the combustion
sensor 17 and other engine parameters. Alternatively or in
combination, the combustion stability at different speed/load
engine operating points may be predetermined during engine
development.
[0030] The engine controller 72 preferably employs a calibration to
command operation of the variable intake valve activation system 22
to achieve preferred opening and closing times or deactivations for
the first and second intake valves 23, 24 based upon monitored
parameters associated with the engine speed and load. This may be
in the form of a feed-forward control routine. The calibration that
may be employed herein determines the preferred opening and closing
times and/or deactivations for the first and second intake valves
23, 24 that achieve high efficiency with an acceptable level of
combustion stability during operation of the engine 10 described
with reference to FIG. 1, for each speed/load operating point over
a range of engine operation. This may include developing an engine
calibration routine that provides preferred opening and closing
times and/or deactivations for the first and second intake valves
23, 24 for each speed/load operating point over a range of engine
speed/load operating points from idle to a maximum power condition.
Alone, or in combination with the feed-forward control routine, the
engine controller 72 may execute a feedback control routine to
command operation of the variable intake valve activation system 22
to achieve preferred opening and closing times or deactivations for
the first and second intake valves 23, 24 based upon monitored
parameters associated with the engine speed and load and combustion
stability that may be determined during on-going engine operation
by monitoring inputs from the combustion sensor 17 and/or other
engine parameters. The terms "calibration", "calibrate", and
related terms refer to a result or a process that compares an
actual or standard measurement associated with a device with a
perceived or observed measurement or a commanded position. A
calibration as described herein can be reduced to a storable
parametric table, a plurality of executable equations or another
suitable form.
[0031] FIG. 2-1 graphically shows a first profile 210 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1,
wherein the engine 10 is operating in a four-stroke cycle that
includes repetitively occurring exhaust-intake-compression-power
strokes that are associated with the reciprocating movement of the
pistons and rotation of the crankshaft. The graph includes a
magnitude of valve lift on the vertical axis 204 in relation to
engine crankshaft rotation (degrees) on the horizontal axis 205.
Relevant timings of cylinder positions are indicated, including a
first cylinder bottom-dead-center (BDC) point 201 at start of an
exhaust stroke, a cylinder top-dead-center (TDC) point 202 at the
end of the exhaust stroke, and a second BDC point 203 at the end of
the intake stroke. The first profile 210 indicates an exhaust valve
opening 215, which is following by simultaneous and equivalent
openings of the first intake valve 213 and the second intake valve
214. Control of the variable intake valve activation system 22 of
the engine 10 in response to the first profile 210 results in a
nominal magnitude of air flow coupled with a nominal level of
in-cylinder mixing.
[0032] FIG. 2-2 graphically shows a second profile 220 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1. The
second profile 220 indicates the exhaust valve opening 215, which
is following by simultaneous and equivalent openings of the first
intake valve 223 and the second intake valve 224. As shown the open
times of the first intake valve 223 and the second intake valve 224
are extended such that they extend into the beginning of a
subsequent compression stroke, which may be described as a Miller
cycle operation, or an Atkinson cycle operation. An alternate
profile could employ valve open times that terminate prior to the
end of the intake stroke achieving a similar effect. The Miller
cycle may be associated with operation of an internal combustion
engine that employs a turbocharger or a supercharger to boost flow
of the intake air, and includes either a late intake valve closing
event (after BDC) or an early intake valve closing event (before
BDC). The Atkinson cycle may be associated with operation of an
internal combustion engine that is naturally aspirated. The effect
of such operation is to reduce the effective compression ratio. By
way of example, during operation with the second profile 220, the
piston compresses the fuel-air mixture during the compression
stroke only after the intake valves close. During the initial
portion of the compression stroke, the piston pushes part of the
fuel-air mixture through the still-open intake valve, and back into
the intake manifold. When the intake air is cooled by an
intercooler, e.g., the charge air cooler 28, there is a resulting
lower intake charge temperature. The lower intake charge
temperature in combination with the lower compression of the intake
stroke may yield a lower final charge temperature than would be
obtained by simply increasing the compression of the piston. This
allows the ignition timing to be advanced before the onset of
detonation, thus increasing overall efficiency. A lower final
charge temperature may reduce formation of engine emissions.
[0033] FIG. 2-3 graphically shows a third profile 230 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1. The
third profile 230 indicates the exhaust valve opening 215, which is
following by opening of the first intake valve 233, with the second
intake valve 234 deactivated. The effect of such operation is to
increase velocity of the intake air flowing through the one open
valve and increase the in-cylinder mixing and turbulence by an
amount that is greater than the nominal level of in-cylinder mixing
described with reference to FIG. 2-1. Furthermore, the in-cylinder
turbulence is asymmetric, due to the asymmetric locations of the
first and second intake valves 23, 24, which are not arranged in a
manner that is co-axial a longitudinal axis of the respective
combustion chamber 15.
[0034] FIG. 2-4 graphically shows a fourth profile 240 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1. The
fourth profile 240 indicates the exhaust valve opening 215, which
is following by opening of the first intake valve 243, with the
second intake valve 244 deactivated. As shown the open time of the
first intake valve 243 is extended such that its opening extends
into the beginning of a subsequent compression stroke, i.e., a
Miller cycle operation or an Atkinson cycle operation. The effect
of such operation is to increase velocity of the intake air flowing
through the one open valve and increase the in-cylinder mixing and
turbulence by an amount that is greater than the nominal level of
in-cylinder mixing described with reference to FIG. 2-1.
Furthermore, the in-cylinder turbulence is asymmetric, due to the
asymmetric locations of the first and second intake valves 23, 24.
As a result of the operation, the ignition timing may be advanced
before the onset of detonation, thus increasing overall efficiency.
A lower final charge temperature may reduce formation of engine
emissions.
[0035] FIG. 2-5 graphically shows a fifth profile 250 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1. The
fifth profile 250 indicates the exhaust valve opening 215, which is
following by opening of the second intake valve 254, with the first
intake valve 253 deactivated. This operation is analogous to the
third profile 230, and may be selected based upon testing that
indicates the resulting in-cylinder mixing and turbulence maintains
combustion stability at a suitable level for one or more engine
speed/load operating points.
[0036] FIG. 2-6 graphically shows a sixth profile 260 in the form
of a valve opening timing chart that may be employed to control an
embodiment of the engine 10 described with reference to FIG. 1. The
sixth profile 260 indicates the exhaust valve opening 215, which is
following by opening of the second intake valve 264, with the first
intake valve 263 deactivated. The opening of the second intake
valve 264 is extended such that its opening extends into the
beginning of a subsequent compression stroke, i.e., a Miller cycle
operation or an Atkinson cycle operation. The effect of such
operation is to increase velocity of the intake air flowing through
the one open valve and increase the in-cylinder mixing and
turbulence by an amount that is greater than the nominal level of
in-cylinder mixing described with reference to FIG. 2-1. This
operation is analogous to the fourth profile 240, and may be
selected based upon testing that indicates the resulting
in-cylinder mixing and turbulence maintains combustion stability at
a suitable level for one or more engine speed/load operating
points.
[0037] The concepts described herein promote optimum efficiency of
an embodiment of the engine 10 described with regard to FIG. 1
through the use of two intake valve events that are characterized
by valve opening, including a four-cycle event and, by way of a
non-limiting example, a Miller cycle event. Additional efficiency
gains may be achieved at low load conditions by deactivating one of
the intake valves 23, 24 to increase combustion system charge
motion.
[0038] The detailed description and the drawings or figures are
supportive and descriptive of the present teachings, but the scope
of the present teachings is defined solely by the claims. While
some of the best modes and other embodiments for carrying out the
present teachings have been described in detail, various
alternative designs and embodiments exist for practicing the
present teachings defined in the appended claims.
* * * * *