U.S. patent application number 10/617520 was filed with the patent office on 2005-01-13 for cylinder bank work output balancing based on exhaust gas a/f ratio.
Invention is credited to Herrin, Ronald J..
Application Number | 20050005923 10/617520 |
Document ID | / |
Family ID | 33541418 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050005923 |
Kind Code |
A1 |
Herrin, Ronald J. |
January 13, 2005 |
CYLINDER BANK WORK OUTPUT BALANCING BASED ON EXHAUST GAS A/F
RATIO
Abstract
A system for balancing first and second work outputs between
first and second cylinder banks of an engine includes a first
intake camshaft associated the first cylinder bank and a first fuel
injector associated with the first cylinder bank. A controller
trims a pulse-width of the first fuel injector until first and
second A/F ratios of respective exhaust of the first and second
cylinder banks are equivalent. The controller adjusts timing of the
first intake camshaft to effect air flow into the first cylinder
bank and trims the pulse-width to maintain equivalency of the first
and second A/F ratios.
Inventors: |
Herrin, Ronald J.; (Troy,
MI) |
Correspondence
Address: |
CHRISTOPHER DEVRIES
General Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
33541418 |
Appl. No.: |
10/617520 |
Filed: |
July 11, 2003 |
Current U.S.
Class: |
123/684 ;
123/692 |
Current CPC
Class: |
F02D 41/1443 20130101;
F02D 41/0082 20130101; Y02T 10/40 20130101; F02D 41/0085 20130101;
F02D 41/0002 20130101; Y02T 10/42 20130101; Y02T 10/44 20130101;
F02D 2041/001 20130101; F02D 41/401 20130101 |
Class at
Publication: |
123/684 ;
123/692 |
International
Class: |
F02D 041/14 |
Claims
1. A system for balancing first and second work outputs between
first and second cylinder banks of an engine, comprising: a first
intake camshaft associated with said first cylinder bank; a first
fuel injector associated with said first cylinder bank; and a
controller that trims a pulse-width of said first fuel injector
until first and second A/F ratios of respective exhaust of said
first and second cylinder banks are equivalent, adjusts timing of
said first intake camshaft to effect air flow into said first
cylinder bank and trims said pulse-width to maintain equivalency of
said first and second A/F ratios.
2. The system of claim 1, further comprising a first cam phaser
that is interconnected with said first intake camshaft and that
adjusts said timing of said first intake camshaft.
3. The system of claim 1, further comprising first and second
exhaust oxygen sensors located in respective exhaust flow paths of
said first and second cylinder banks, wherein said controller
determines said first and second A/F ratios of said first and
second cylinder banks based on signals from said first and second
oxygen sensors.
4. The system of claim 1, further comprising: a second intake
camshaft associated with said second cylinder bank; and a second
fuel injector associated with said second cylinder bank, wherein
said controller trims a pulse-width of said first and second fuel
injectors until said fuel injectors achieve a target pulse-width,
adjusts timing of said first and second intake camshafts to effect
respective air flows into said first and second cylinder banks and
maintains equivalency of said first and second A/F ratios.
5. The system of claim 4, wherein said controller determines said
target pulse-width based on engine speed and manifold absolute
pressure.
6. The system of claim 4, further comprising a second cam phaser
that is interconnected with said second intake camshaft and that
adjusts said timing of said second intake camshaft.
7. A method of balancing first and second work outputs between
first; and second cylinder banks of an engine, comprising; trimming
a fuel injector pulse-width of one of said first and second
cylinder banks until first and second A/F ratios of said first and
second cylinder banks are equivalent; adjusting timing of a
camshaft of one of said first and second cylinder banks to effect
air flow into one of said first and second cylinder banks; and
trimming said fuel injector pulse-width to maintain equivalency of
said first and second A/F ratios.
8. The method of claim 7, further comprising: determining said
first and second A/F ratios of said first and second cylinder
banks; and comparing said first and second A/F ratios, wherein said
step of trimming said fuel injector pulse-width occurs if said
first and second A/F ratios are not equal.
9. The method of claim 8, wherein said first and second A/F ratios
ace determined as an average A/F ratio of respective cylinders of
said first and second cylinder banks.
10. The method of claim 7, further comprising comparing said fuel
injector pulse-widths of said first and second cylinder banks,
wherein said step of adjusting timing of said camshaft occurs if
said first and second fuel injector pulse-widths are not equal.
11. The method of claim 7, further comprising determining a
particular camshaft to adjust based on a current position of said
camshafts.
12. The method of claim 7, further comprising: determining a
pulse-width target; and trimming said fuel injector pulse-widths
until said fuel injector pulse-widths are equal to said pulse-width
target.
13. The method of claim 12, wherein said pulse-width target is
based on engine speed and manifold absolute pressure.
14. A method of balancing first and second work outputs between
first and second cylinder banks of an engine, comprising:
determining whether first and second A/F ratios of said first and
second cylinder banks are unequal; trimming a fuel injector
pulse-width of one of said first and second cylinder banks until
said first and second A/F ratios are equivalent; comparing
respective pulse-widths of said first and second cylinder banks;
adjusting timing of a camshaft of one of said first and second
cylinder banks to effect air flow into one of said first and second
cylinder banks if said respective fuel injector pulse-widths are
unequal; and trimming said fuel injector pulse-width to maintain
equivalency of said first and second A/F ratios.
15. The method of claim 14, further comprising measuring an oxygen
content of respective exhaust streams from said first and second
cylinder banks to determine: said first and second A/F ratios.
16. The method of claim 14, wherein said first and second A/F
ratios are determined as an average A/F ratio of respective
cylinders of said first and second cylinder banks.
17. The method of claim 14, further comprising determining a
particular camshaft to adjust based on a current position of said
camshafts.
18. The method of claim 14, further comprising: determining a
pulse-width target; and trimming said fuel injector pulse-widths
until said fuel injector pulse-widths are equal to said pulse-width
target.
19. The method of claim 18, wherein said pulse-width target is
based on engine speed and manifold absolute pressure.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to engine control, and more
particularly to balancing work output of cylinder banks of the
engine based on an exhaust gas air-to-fuel (A/F) ratio.
BACKGROUND OF THE INVENTION
[0002] Conventional internal combustion engines having a V-, W-or
flat (i.e., horizontally opposed) shaped configurations include
multiple cylinder banks. The cylinder banks include pistons that
are reciprocally driven through cylinders by a combustion process
to produce driving force. An air and fuel mixture is provided and
is ignited within the cylinders during the combustion process. The
air and fuel quantity within a cylinder defines the work output of
the cylinder. The air rates of the cylinders are controlled by the
phase angle or timing of a camshaft with respect to a driven
crankshaft. The fuel rate is controlled by the pulse-width of a
fuel injector.
[0003] The timing of intake valve closing with respect to piston
position within the cylinder influences the volume of air that is
drawn into the cylinder. When intake valve closing occurs near a
bottom-dead-center (BDC) piston position, cylinder volume is
changing slowly and variations in intake valve timing have only a
minor effect. If an engine having variable cam timing implements an
early or late intake valve closing strategy to improve engine
efficiency, intake valve closing can occur when the piston velocity
is higher and air volume into the cylinder is changing rapidly.
Differences in the intake valve closing timing (i.e., cam position
of the camshafts) can significantly influence the volume of air
drawn into the cylinder.
[0004] Conventional control algorithms attempt to balance the
bank-to-bank cam positions of the camshafts. This is achieved by
measuring the radial position of mechanical targets installed on
each camshaft or cam phasers associated with each camshaft.
Balancing of the bank-to-bank cam positions, however, does not
insure bank-to-bank balancing of intake air flow. This is a result
of manufacturing and assembly variations that create ambiguity
between sensed cam positions and actual timing of intake
valves.
[0005] Imbalance of intake air flow results in an A/F ratio
imbalance across the cylinder banks that effects engine smoothness
and engine efficiency. Traditionally, the fuel rate is trimmed to
compensate for air flow variation across the cylinder banks.
However, this compensation strategy fails to correct the
fundamental problem of air flow imbalance. Another method of
alleviating this imbalance is to provide tighter manufacturing and
assembly tolerances. This, however, results in increased
manufacturing and assembly costs.
SUMMARY OF THE INVENTION
[0006] Accordingly, the present invention provides a system for
balancing first and second work outputs between first and second
cylinder banks of an engine. The system includes a first intake
camshaft associated with the first cylinder bank and a first fuel
injector associated with the first cylinder bank. A controller
trims pulse-width of the first fuel injector until first and second
A/F ratios of respective exhaust of the first and second cylinder
banks are equivalent. The controller adjusts timing of the first
intake camshaft to effect air flow into the first cylinder bank and
trims the pulse-width to maintain equivalency of the first and
second A/F ratios.
[0007] In one feature, the system further includes a first cam
phaser that is interconnected with the first intake camshaft and
that adjusts the timing of the first intake camshaft.
[0008] In another feature, the system further includes first and
second exhaust oxygen sensors located in respective exhaust flow
paths of the first and second cylinder banks. The controller
determines the first and second A/F ratios of the first and second
cylinder banks based on signals from the first and second oxygen
sensors.
[0009] In another feature, the system further includes a second
intake camshaft associated with the second cylinder bank and a
second fuel injector associated with the second cylinder bank. The
controller trims a pulse-width of the first and second fuel
injectors until the fuel injectors achieve a target pulse-width.
The controller adjusts timing of the first and second intake
camshafts to effect respective air flows into the first and second
cylinder banks and maintains equivalency of the first and second
A/F ratios.
[0010] In still another feature, the controller determines the
target pulse-width ratio based on engine speed and manifold
absolute pressure.
[0011] In yet another feature, the system further includes a second
cam phaser that is interconnected with the second intake camshaft
and that adjusts the timing of the second intake camshaft.
[0012] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0014] FIG. 1 is a functional block diagram of a vehicle including
an engine;
[0015] FIG. 2 illustrates a cylinder bank of the engine;
[0016] FIG. 3 is a perspective view of a portion of the engine,
illustrating an intake camshaft and an exhaust camshaft associated
with a cylinder bank, a crankshaft and cam phasers; and
[0017] FIG. 4 is a flowchart illustrating steps for balancing a
cylinder bank according to the principles of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The following description of the preferred embodiments is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0019] Referring now to FIG. 1, a vehicle 10 is shown and includes
an engine 12 having cylinder banks 14,16, an intake manifold 18,
exhaust manifolds 20,22 and cam phasers 24,26. Air is drawn into
the intake manifold 18 through a throttle 28 and is distributed to
the cylinder banks 14,16. Exhaust gas from the cylinder banks 14,16
flows through the respective exhaust manifolds 20,22 to an exhaust
system. Oxygen (O.sub.2) sensors 30,32 are associated with each
exhaust manifold 20,22. The O.sub.2 sensors 30,32 measure the
amount of 02 in exhaust gas exiting the respective exhaust
manifolds 20,22.
[0020] A controller 34 balances the cylinder banks 14,16 of the
engine 12. The controller 34 communicates with the throttle 28, the
cylinder banks 14,16, the cam phasers 24,26 and the O.sub.2 sensors
30,32. As discussed in further detail below, the controller 34
receives signals from the O.sub.2 sensors 30,32 to determine A/F
ratios of the exhaust gas through the respective exhaust manifolds
20,22. The controller 34 controls operation of the cylinder banks
14,16 to adjust fuel injection and the cam phasers 24,26 to adjust
fuel flow and air flow into cylinders of the cylinder banks 14,16,
as will be described more fully below.
[0021] Referring now to FIG. 2, an exemplary cylinder bank 14,16 is
shown. The cylinder bank 14,16 includes at least one cylinder 36.
Additional cylinders are shown by dotted lines. Although the
exemplary cylinder bank 14,16 illustrates three cylinders 36 (e.g.,
for a 6 cylinder V-type engine), the cylinder bank 14,16 can
include any number of cylinders 36 based upon the particular design
of the engine 12. Each cylinder 36 includes one or more inlet
valves 38, one or more exhaust valves 40 and one or more fuel
injectors 42 associated therewith.
[0022] The inlet valves 38 regulate opening and closing of inlet
ports (not shown) to control air intake into the cylinder 36. The
exhaust valves 40 regulate opening and closing of exhaust ports
(not shown) to control exhaust of combustion gas from the cylinder
36. The fuel injector 42 can be configured in two manners. The fuel
injector 42 can inject fuel directly into the cylinder 36 to mix
with the air therein for combustion. Alternatively, the fuel
injector 42 can be disposed upstream of the inlet valves 38 to
inject fuel into the intake air prior to the intake air passing by
the open inlet ports into the cylinder 36. The fuel injector 42 is
pulse-width modulated to control the fuel rate into the cylinder
36.
[0023] The controller 34 adjusts the pulse-widths of the fuel
injectors 42 to regulate the A/F ratios of the cylinder banks
14,16. The fuel injector pulse-widths are individually and
independently trimmed as between the cylinder banks 14,16. More
particularly, the controller 34 determines a nominal pulse-width
for the cylinder banks 14,16 based on the current operating
condition (i.e., engine speed and load). If the nominal pulse-width
is commanded by the controller 34 and the cylinder banks 14,16 are
not at the desired A/F ratio, then the pulse-widths are trimmed by
the controller 34 to bring the cylinder banks 14,16 to the desired
A/F ratio. The trim values are learned for each cylinder bank
14,16. As described in further detail below, the controller 34
compares the learned trim values of the fuel injector pulse-widths
to determine air intake imbalance across the cylinder banks
14,16.
[0024] Referring now to FIG. 3, a perspective view of a portion of
the engine 12 is shown. The engine 12 includes a cylinder head 44
that supports an intake camshaft 46 and an exhaust camshaft 48 and
a cylinder block 50 that supports a crankshaft 52. Each cylinder
bank 14,16 includes an intake camshaft 46 and an exhaust camshaft
48. Accordingly, the illustration of FIG. 3 represents the
camshafts 46,48 associated with one cylinder bank 14,16. The
camshaft phasers 24,26 are interconnected with the intake camshafts
46 to adjust the phase angle or timing of the intake camshaft 46.
The crankshaft 52 is interconnected to pistons (not shown) by
connecting rods (not shown). The pistons are driven by the
combustion process to provide the driving force that rotates the
crankshaft 52. A sprocket 54 is fixed for rotation with the
crankshaft 52 and is interconnected to a sprocket 56 by a belt or
chain. The sprocket 56 drives the intake camshaft 46.
[0025] The intake camshaft 46 includes intake cam pairs 58
associated with each cylinder 36. Each intake cam 58 interfaces
with a respective rocker arm (not shown) to control movement of the
intake valves 38 for regulating opening and closing of the intake
ports. Similarly, the exhaust camshaft includes exhaust cam pairs
60 associated with each cylinder 36. Each exhaust cam 60 interfaces
with a respective rocker arm (not shown) to control movement of the
exhaust valves 40 for regulating opening and closing of the exhaust
ports.
[0026] The camshaft phasers 24,26 either advance or retard the
intake valve timing. The ability of the camshaft phasers 24,26 to
adjust the timing is limited in either direction. That is to say,
the camshaft timing can only be adjusted so far until a home or
parked position is achieved. Once the camshaft phaser 24,26 has
sufficiently adjusted the camshaft timing in one direction to
achieve the parked position, the camshaft phasers 24,26 can no
longer adjust the camshaft timing in that direction. In other
words, in the parked position the camshaft timing adjustment has
reached its maximum.
[0027] The cylinder bank balancing control of the present invention
enables balancing of air rates, A/F ratios, fuel rates and work
output across the cylinder banks 14,16. As explained in further
detail below, the cylinder bank balancing control uses differences
in the fueling rate across the cylinder banks 14,16 as an indicator
of bank-to-bank variation in intake cam timing. Exhaust gas A/F
ratios are determined for each cylinder bank 14,16 using the
O.sub.2 sensors 30,32. The fuel rate is adjusted by trimming the
injector pulse-width to balance the A/F ratios across the cylinder
banks 14,16. As a result, the bank-to-bank pulse-widths trim values
vary. The difference between the injector pulse-width trim values
across the cylinder banks 14,16 is used to adjust the intake cam
timing using the cam phasers 24,26 until the fuel rates are
balanced.
[0028] Referring now to FIG. 4, the cylinder bank balancing control
will be described in detail. In step 100, control determines the
A/F ratios of the cylinders banks 14,16 based on signals from the
O.sub.2 sensors 30,32. In step 102, control determines whether the
A/F ratios are equivalent. If not, control continues in step 104.
If so, the A/F ratios across the cylinder banks 14,16 are balanced
and control continues in step 106.
[0029] In step 104, control trims the fuel injector pulse-widths of
the cylinder banks 14,16 until the A/F ratios balance. Once the A/F
ratios are balanced, control determines whether the fuel injector
pulse-widths across the cylinder banks 14,16 are balanced in step
106. If the pulse-widths are balanced, control ends. Otherwise,
control continues in step 108 to determine whether any intake
camshaft 46 is in the parked position. If not control continues in
step 110. If so, control continues in step 112.
[0030] In step 110, control determines the nominal pulse-width or
pulse-width target of the fuel injectors 42 from a look-up table.
The pulse-width target is based on the current vehicle operating
conditions such as throttle position, engine speed (RPM), manifold
absolute pressure (MAP) and the like. In step 114, control selects
the intake camshaft 46 on the cylinder bank 14,16 that has the
largest pulse-width deviation from the pulse-width target. Control
increments the intake camshaft position in step 116 in the
direction needed to converge the pulse-widths of the cylinder banks
14,16.
[0031] In step 112, control selects the intake camshaft 46 that is
adjustable in the direction required to balance the air flow. More
specifically, if, in step 108, it is determined that one of the
intake camshafts 46 is in the parked position adjustment of the
particular intake camshaft 46 is limited to a single direction
(i.e., advance or retard). Therefore, the intake camshaft 46 that
is able to be adjusted in the desired direction is selected. In
step 116, control increments the intake camshaft position in the
direction needed to converge the pulse-widths of the cylinder banks
14,16.
[0032] As the intake camshaft timing is incremented, control trims
the fuel injector pulse-width of the corresponding cylinder bank
14,16 in step 118. In this manner, the A/F ratio of the cylinder
bank 14,16 is maintained and the pulse-width converges with the
pulse-width of the other cylinder bank 14,16. In step 120, control
determines whether the fuel injector pulse-widths across the
cylinder banks 14,16 are balanced. If not, control loops back to
step 116 to increment the intake camshaft position. If so, control
stores the intake camshaft trim value for the current operating
conditions in step 122 and control ends.
[0033] Alternatively, it is anticipated that the cylinder bank
balancing control can trim the intake camshaft positions until both
cylinder bank pulse widths achieve the pulse-width target. To
achieve this, control increments the camshaft positions of both
intake camshafts 46 of the cylinder banks 14,16. Concurrently,
control trims the fuel injector pulse-widths until they converge on
the pulse-width target. In this manner, the cylinder bank balancing
control can maintain the desired A/F ratio balance across the
cylinder banks 14,16 and achieve the pulse-width target for both
cylinder banks 14,16.
[0034] Although the A/F ratio sensing described above is for the
cylinder bank 14,16, it is anticipated that the A/F ratio for
individual cylinders within each cylinder bank can be determined.
Further, it is anticipated that pulse-width control of individual
fuel injectors 42 in each cylinder bank 14,16 is achievable. In
such a case, the cylinder bank balancing control of the present
invention determines an average pulse-width value for the fuel
injectors 42 of each cylinder bank 14,16. The average pulse-width
values of the cylinder banks 14,16 are compared to determine
imbalance across the cylinder banks 14,16 or achievement of the
pulse-width target.
[0035] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the current
invention can be implemented in a variety of forms. Therefore,
while this invention has been described in connection with
particular examples thereof, the true scope of the invention should
not be so limited since other modifications will become apparent to
the skilled practitioner upon a study of the drawings, the
specification and the following claims.
* * * * *