U.S. patent application number 15/181075 was filed with the patent office on 2017-12-14 for engine stop position control system and method.
The applicant listed for this patent is GM Global Technology Operations LLC. Invention is credited to Brian P. Hannon, JR., Eric B. Schutt, Gregory J. York, James R. Yurgil.
Application Number | 20170356376 15/181075 |
Document ID | / |
Family ID | 60419985 |
Filed Date | 2017-12-14 |
United States Patent
Application |
20170356376 |
Kind Code |
A1 |
Yurgil; James R. ; et
al. |
December 14, 2017 |
ENGINE STOP POSITION CONTROL SYSTEM AND METHOD
Abstract
An engine control system for an auto-stop/start vehicle includes
an auto-stop/start module that generates an auto-stop command for
shutting down an engine while an ignition is ON and subsequently
generates an auto-start command for re-starting the engine. The
system includes an actuator control module that disables an engine
load, parks exhaust and intake cam phasers, disables fuel, sets a
first throttle opening, monitors a crankshaft rotational position,
speed, and deceleration, sets a second throttle opening for a
predetermined duration if a piston simultaneously crosses a target
position below a target engine speed and below a target degrees of
rotation remaining, sets a third throttle opening, and determines
if an engine speed is below a threshold speed before setting a
fourth throttle opening when the engine speed is below the
threshold speed, and causes the piston to rest in a predetermined
position range.
Inventors: |
Yurgil; James R.; (Livonia,
MI) ; York; Gregory J.; (Fenton, MI) ; Schutt;
Eric B.; (Oxford, MI) ; Hannon, JR.; Brian P.;
(White Hall, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM Global Technology Operations LLC |
Detroit |
MI |
US |
|
|
Family ID: |
60419985 |
Appl. No.: |
15/181075 |
Filed: |
June 13, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D 2200/703 20130101;
F02D 41/0002 20130101; F02D 41/009 20130101; F02N 19/005 20130101;
F02N 2200/121 20130101; F02D 41/062 20130101; Y02T 10/42 20130101;
Y02T 10/40 20130101; F02D 41/042 20130101 |
International
Class: |
F02D 41/06 20060101
F02D041/06; F02D 41/04 20060101 F02D041/04 |
Claims
1. An engine control system for controlling the a resting position
of at least one piston within a cylinder of an engine of an
auto-stop/start vehicle, the system comprising: an auto-stop/start
module that selectively generates an auto-stop command for shutting
down an engine while an ignition is in an ON state and that
selectively generates an auto-start command for re-starting the
engine after the generation of the auto-stop command; and an
actuator control module that, in response to the generation of the
auto-stop command and before the generation of the auto-start
command: disables a load on the engine; parks exhaust cam phasers
and intake cam phasers; disables fuel to the engine; sets a
throttle valve opening to a first predetermined throttle opening
level; monitors a crankshaft rotational position; determines if a
position of a piston is entering a predetermined position based on
the crankshaft rotational position; monitors an engine speed;
monitors a barometric pressure; determines an engine speed
threshold as a function of the barometric pressure; estimates
degrees of engine rotation before the engine stops rotating based
on the engine speed, an engine deceleration and the barometric
pressure; determines if the engine speed is less than the engine
speed threshold; sets a throttle valve opening to a second
predetermined throttle opening level; sets a throttle valve opening
to a third predetermined throttle opening level after a
predetermined time has elapsed from the setting of the second
predetermined throttle opening level; determines if the engine
speed is less than a second predetermined engine speed; sets a
throttle valve opening to a fourth predetermined throttle opening
level when the engine speed is less than the second predetermined
speed; and whereby the resting position of the piston is in a
predefined piston position range.
2. The engine control system of claim 1 wherein the actuator
control module estimates a remaining degrees of engine rotation
when the piston is entering the predetermined position, wherein the
remaining degrees of engine rotation estimation is based on the
engine speed and the barometric pressure.
3. The engine control system of claim 1 wherein the actuator
control module maintains the throttle valve at a first
predetermined throttle opening level to further reduce pressure in
the intake manifold.
4. The engine control system of claim 3 wherein the actuator
control module maintains the throttle valve at a second
predetermined throttle opening level to rapidly increase the
pressure in the intake manifold.
5. The engine control system of claim 1 wherein the actuator
control module maintains the throttle valve at a third
predetermined throttle opening level to return the opening position
to a position at or slightly above the position associated with an
unpowered throttle actuator.
6. The engine control system of claim 1 wherein the actuator
control module further comprises sets a predetermined fuel rail
pressure.
7.-8. (canceled)
9. The engine control system of claim 1 wherein the predetermined
position is one of a predefined crankshaft rotational position.
10. The engine control system of claim 9 wherein the second
predetermined throttle opening level is configured to raise the air
pressure in at least one cylinder to approximately ambient
barometric pressure.
11. The engine control system of claim 1 wherein the actuator
control module further comprises sets a throttle valve opening to a
fourth predetermined throttle opening level when the engine speed
is about zero.
12. An engine control method for controlling the a resting position
of at least one piston within a cylinder of an engine of an
auto-stop/start vehicle, the method comprising: generating an
auto-stop command for shutting down an engine while an ignition is
in an ON state; generating an auto-start command for re-starting
the engine after the generation of the auto-stop command; disabling
a load on the engine in response to the generation of the auto-stop
command and before the generation of the auto-start command;
parking exhaust cam phasers and intake cam phasers in response to
the generation of the auto-stop command and before the generation
of the auto-start command; disabling fuel to the engine in response
to the generation of the auto-stop command and before the
generation of the auto-start command; setting a throttle valve
opening to a first predetermined throttle opening level; monitoring
a crankshaft rotational position; determining if a position of a
piston is entering a predetermined position based on the crankshaft
rotational position; monitoring an engine speed monitoring a
barometric pressure in response to the generation of the auto-stop
command and before the generation of the auto-start command;
determining an engine speed threshold as a function of the
barometric pressure; estimating degrees of engine rotation before
the engine stops rotating based on the engine speed, an engine
deceleration and the barometric pressure; determining if the engine
speed is less than the engine speed threshold; setting a throttle
valve opening to a second predetermined throttle opening level;
setting a throttle valve opening to a third predetermined throttle
opening level after a predetermined time has elapsed from the
setting of the second predetermined throttle opening level;
determining if an engine speed is less than a second predetermined
speed; setting a throttle valve opening to a fourth predetermined
throttle opening level when the engine speed is less than the
second predetermined speed; and whereby the resting position of the
piston is in a predefined piston position range.
13. The engine control method of claim 12 wherein controlling the
resting position of at least one piston further comprises
estimating a remaining degrees of engine rotation when the piston
is entering the predetermined position, wherein the remaining
degrees of engine rotation estimation is based on the engine speed
and the barometric pressure.
14. The engine control method of claim 12 wherein maintaining the
throttle valve at the first predetermined throttle opening level
further comprises maintaining the throttle valve at an opening
level to further reduce pressure in the intake manifold.
15. The engine control method of claim 14 wherein maintaining the
throttle valve at the second predetermined throttle opening level
further comprises maintaining the throttle valve at an opening
level to rapidly increase the pressure in the intake manifold.
16. The engine control method of claim 12 wherein maintaining the
throttle valve at the third predetermined throttle opening level
further comprises maintaining the throttle valve at an opening
level to return the opening position to a position at or slightly
above the position associated with an unpowered throttle
actuator.
17. The engine control method of claim 12 further comprising
setting a predetermined fuel rail pressure in response to the
generation of the auto-stop command and before the generation of
the auto-start command.
18.-19. (canceled)
20. The engine control method of claim 12 wherein the predetermined
position is one of a predefined crankshaft rotational position.
21. The engine control method of claim 20 wherein the predetermined
position for the piston is entering an intake stroke.
22. The engine control method of claim 20 wherein the second
predetermined throttle opening level is configured to raise the air
pressure in at least one cylinder to approximately ambient
barometric pressure.
23. The engine control method of claim 12 further comprising
setting a throttle valve opening to a fourth predetermined throttle
opening level when the engine speed is approximately zero.
Description
FIELD
[0001] The present invention relates to stop-start control systems
for automobile powertrains, and more particularly to systems and
methods for managing the engine stop position during a stop-start
sequence to improve the overall efficiency of the powertrain.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may or may not
constitute prior art.
[0003] Air is drawn into an engine through an intake manifold. A
throttle valve controls airflow into the engine. More specifically,
the throttle valve adjusts throttle area, which increases or
decreases airflow into the engine. As the throttle area increases,
the air flow into the engine increases. A fuel control system
adjusts the rate that fuel is injected into the engine cylinders to
provide a desired air/fuel mixture to the cylinders and/or to
achieve a desired torque output. Increasing the amount of air and
fuel provided to the cylinders increases the torque output of the
engine.
[0004] The air/fuel mixture is combusted within one or more
cylinders of the engine. In spark-ignition engines, spark initiates
combustion of the air/fuel mixture provided to the cylinders. In
compression-ignition engines, compression of the air/fuel mixture
in the cylinders combusts the air/fuel mixture. Spark timing and
airflow are the primary mechanisms for adjusting the torque output
of spark-ignition engines, while fuel flow is the primary mechanism
for adjusting the torque output of compression-ignition engines.
Incomplete, or partial combustion of the air/fuel mixture during
engine start may cause the engine to vibrate.
[0005] During engine shutdown, a rotation direction of a crankshaft
in the engine may be reversed before the crankshaft stops. In turn,
a piston coupled to the crankshaft may stop near top dead center
(TDC) before movement of the piston is reversed. This reversal of
piston movement during engine shutdown is referred to as rock back.
As the piston rocks back, the piston draws exhaust gas into the
cylinder in which the piston is disposed. Exhaust gas is also be
drawn into an intake manifold of the engine due to a pressure
difference between the intake manifold and the cylinders. When the
engine is restarted, exhaust gas flows from the intake manifold to
the cylinder, and exhaust gas present within the cylinder may cause
the cylinder to misfire which in turn may cause the engine and the
passenger compartment to vibrate.
[0006] An engine control module (ECM) controls the torque output of
the engine. Under some circumstances, the ECM shuts down the engine
between vehicle startup (e.g., key ON) and vehicle shutdown (e.g.,
key OFF). The ECM selectively shuts down the engine, for example,
to increase fuel efficiency (i.e., reduce fuel consumption). The
ECM starts the engine at a later time.
[0007] While traditional stop-start systems for internal combustion
engines are effective, there is room in the art for an improved
stop-start system and method that ensures the appropriate amount of
air and fuel are supplied to the cylinders for low-vibration engine
start. Especially desirable, would be a stop-start system that
performs under a wide variety of ambient conditions while reducing
engine start vibration.
SUMMARY
[0008] In one embodiment of the present invention, an engine
control system for controlling the resting position of at least one
piston within a cylinder of an engine of an auto-stop/start vehicle
includes an auto-stop/start module that selectively generates an
auto-stop command for shutting down an engine while an ignition is
in an ON state and that selectively generates an auto-start command
for re-starting the engine after the generation of the auto-stop
command. The engine control system also includes an actuator
control module that, in response to the generation of the auto-stop
command and before the generation of the auto-start command:
disables a load on the engine, parks exhaust cam phasers and intake
cam phasers, disables fuel to the engine, sets a throttle valve
opening to a first predetermined throttle opening level, monitors a
crankshaft rotational position, determines if a position of a
piston is entering a predetermined position based on the crankshaft
rotational position, monitors an engine speed, determines if the
engine speed is less than a first predetermined engine speed,
monitors a barometric pressure, sets a throttle valve opening to a
second predetermined throttle opening level, sets a throttle valve
opening to a third predetermined throttle opening level after a
predetermined time has elapsed from the setting of the second
predetermined throttle opening level, determines if an engine speed
is less than a second predetermined speed, sets a throttle valve
opening to a fourth predetermined throttle opening level when the
engine speed is less than the second predetermined speed, and the
resting position of the piston is in a predefined piston position
range.
[0009] In another embodiment of the present invention, the actuator
control module estimates a remaining degrees of engine rotation
when the piston is entering the predetermined position, and the
remaining degrees of engine rotation estimation is based on the
first predetermined engine speed and the barometric pressure.
[0010] In another embodiment of the present invention, the actuator
control module maintains the throttle valve at first predetermined
throttle opening level to further reduce pressure in the intake
manifold.
[0011] In yet another embodiment of the present invention, the
actuator control module maintains the throttle valve at a second
predetermined throttle opening level to rapidly increase the
pressure in the intake manifold.
[0012] In yet another embodiment of the present invention, the
actuator control module maintains the throttle valve at a third
predetermined throttle opening level to return the opening position
to a position at or slightly above the position associated with an
unpowered throttle actuator.
[0013] In yet another embodiment of the present invention, the
actuator control module further comprises sets a predetermined fuel
rail pressure.
[0014] In yet another embodiment of the present invention, the
actuator control module further comprises monitors a barometric
pressure.
[0015] In yet another embodiment of the present invention, the
actuator control module further comprises estimates degrees of
engine rotation before the engine stops rotating based on a speed
of the engine, an engine deceleration and the barometric
pressure.
[0016] In yet another embodiment of the present invention, the
predetermined position is one of a predefined crankshaft rotational
position.
[0017] In yet another embodiment of the present invention, the
second predetermined throttle opening level is configured to raise
the air pressure in at least one cylinder to approximately ambient
barometric pressure.
[0018] In yet another embodiment of the present invention, the
actuator control module further comprises sets a throttle valve
opening to a fourth predetermined throttle opening level when the
engine speed is about zero.
[0019] In a further embodiment of the present invention, an engine
control method for controlling the resting position of at least one
piston within a cylinder of an engine of an auto-stop/start vehicle
includes, generating an auto-stop command for shutting down an
engine while an ignition is in an ON state. The method also
includes generating an auto-start command for re-starting the
engine after the generation of the auto-stop command. The method
also includes, disabling a load on the engine in response to the
generation of the auto-stop command and before the generation of
the auto-start command. The method also includes, parking exhaust
cam phasers and intake cam phasers in response to the generation of
the auto-stop command and before the generation of the auto-start
command. The method also includes disabling fuel to the engine in
response to the generation of the auto-stop command and before the
generation of the auto-start command: setting a throttle valve
opening to a first predetermined throttle opening level, monitoring
a crankshaft rotational position, determining if a position of a
piston is entering a predetermined position, monitoring a
barometric pressure, setting a throttle valve opening to a second
predetermined throttle opening level, setting a throttle valve
opening to a third predetermined throttle opening level after a
predetermined time has elapsed from the setting of the second
predetermined throttle opening level, determining if an engine
speed is less than a second predetermined speed, setting a throttle
valve opening to a fourth predetermined throttle opening level when
the engine speed is less than the second predetermined speed, and
achieving a resting position of the piston that is in a predefined
piston position range.
[0020] In a further embodiment of the present invention, the method
includes estimating a remaining degrees of engine rotation when the
piston is entering the predetermined position, and the remaining
degrees of engine rotation estimation is based on the first
predetermined engine speed and the barometric pressure.
[0021] In a further embodiment of the present invention, the method
includes maintaining the throttle valve at the first predetermined
throttle opening level further comprises maintaining the throttle
valve at an opening level to further reduce pressure in the intake
manifold.
[0022] In a further embodiment of the present invention, the method
includes maintaining the throttle valve at the second predetermined
throttle opening level further comprises maintaining the throttle
valve at an opening level to rapidly increase the pressure in the
intake manifold.
[0023] In a further embodiment of the present invention, the method
includes maintaining the throttle valve at the third predetermined
throttle opening level further comprises maintaining the throttle
valve at an opening level to return the opening position to a
position at or slightly above the position associated with an
unpowered throttle actuator.
[0024] In a further embodiment of the present invention, the method
includes setting a predetermined fuel rail pressure in response to
the generation of the auto-stop command and before the generation
of the auto-start command.
[0025] In a further embodiment of the present invention, the method
includes monitoring a barometric pressure in response to the
generation of the auto-stop command and before the generation of
the auto-start command.
[0026] In a further embodiment of the present invention, the method
includes estimating degrees of engine rotation before the engine
stops rotating based on a speed of the engine, an engine
deceleration and the barometric pressure.
[0027] In a further embodiment of the present invention, the method
includes wherein the predetermined position is one of a predefined
crankshaft rotational position.
[0028] In a further embodiment of the present invention, the method
includes the predetermined position for the piston is entering an
intake stroke.
[0029] In a further embodiment of the present invention, the method
includes the second predetermined throttle opening level is
configured to raise the air pressure in at least one cylinder to
approximately ambient barometric pressure.
[0030] In a further embodiment of the present invention, the method
includes setting a throttle valve opening to a fourth predetermined
throttle opening level when the engine speed is approximately
zero.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way. The components in the figures are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like reference numerals designate corresponding parts
throughout the views. In the drawings:
[0032] FIG. 1 is a functional block diagram of an exemplary engine
system according to the principles of the present disclosure;
[0033] FIG. 2 is a functional block diagram of an exemplary engine
control system according to the principles of the present
disclosure;
[0034] FIG. 3 is a graph of a plurality of engine data traces
plotted as functions of time according to the principles of the
present disclosure;
[0035] FIG. 4 is an exemplary crankshaft rotation diagram according
to the principles of the present disclosure; and
[0036] FIG. 5 is a flowchart depicting an exemplary method of
controlling the MAP according to the principles of the present
disclosure.
DETAILED DESCRIPTION
[0037] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses. As used herein, the term module refers to an Application
Specific Integrated Circuit (ASIC), an electronic circuit, a
processor (shared, dedicated, or group) and memory that execute one
or more software or firmware programs, a combinational logic
circuit, and/or other suitable components that provide the
described functionality.
[0038] Referring now to FIG. 1, a functional block diagram of an
exemplary engine system 100 is presented. Engine system 100
includes an engine 102 and an engine control system 101. The engine
102 generates drive torque for the vehicle. While the engine 102 is
shown and will be discussed as a spark-combustion internal
combustion engine (ICE), the engine 102 may include another
suitable type of engine 102, such as a compression-combustion ICE.
One or more electric motors (or motor-generators) may additionally
generate drive torque. The engine control system 101 includes an
engine control module (ECM) 118 that automatically shuts down the
engine 102 when the engine 102 is idling to reduce fuel consumption
and emissions and automatically shuts down the engine 102 when a
driver depresses a brake pedal and the vehicle speed is zero. The
engine control system 101 automatically restarts the engine 102
when the driver releases the brake pedal after the engine 102 is
automatically shut down.
[0039] The engine 102 includes a throttle valve 104, an intake
manifold 106, a cylinder 108, a fuel injector 110, a crankshaft
112, a spark plug 114, and a flywheel. Air, designated by arrow
"A", is drawn into the engine 102 through the throttle valve 104 to
the intake manifold 106. Airflow into the engine 102 is varied
using the throttle valve 104. One or more fuel injectors, such as
fuel injector 110, mix fuel with the air to form an air/fuel
mixture. The air/fuel mixture is combusted within cylinders of the
engine 102, such as cylinder 108. Although the engine 102 is
depicted as including one cylinder 108, the engine 102 may include
more than one cylinder 108.
[0040] The cylinder 108 includes a piston (not shown) that is
mechanically linked to the crankshaft 112. One combustion cycle
within the cylinder 108 includes four phases: an intake phase, a
compression phase, a combustion (or expansion) phase, and an
exhaust phase. During the intake phase, the piston moves toward a
bottommost position and draws air into the cylinder 108. During the
compression phase, the piston moves toward a topmost position and
compresses the air or air/fuel mixture within the cylinder 108.
[0041] During the combustion phase, spark from the spark plug 114
ignites the air/fuel mixture. The combustion of the air/fuel
mixture drives the piston toward the bottommost position, and the
piston drives rotation of the crankshaft 112. Resulting exhaust gas
is expelled from the cylinder 108 to complete the exhaust phase and
the combustion event. The flywheel 116 is attached to and rotates
with the crankshaft 112, and the engine 102 outputs torque to a
transmission (not shown) via the crankshaft 112.
[0042] The ECM 118 receives data from and controls a plurality of
components of engine system 101. The plurality of components of
engine system 101 includes the throttle valve 104, the fuel
injector 110, the spark plug 114, a throttle actuator module 120, a
fuel actuator module 122, a spark actuator module 124, a crankshaft
position sensor 126, a manifold absolute pressure (MAP) 132 sensor,
an accelerator pedal position (APP) sensor 136, a brake pedal
position (BPP) sensor 140, a transmission control module (TCM) 146,
and an ignition system 148.
[0043] The ECM 118 controls the throttle valve 104 via the throttle
actuator module 120, the ECM 118 controls the fuel injector 110 via
a fuel actuator module 122, and the ECM controls the spark plug 114
via a spark actuator module 124. More specifically, the ECM 118
controls an opening area and opening duration of the throttle valve
104, a fuel injection amount and timing, and spark timing. While
not shown, the ECM 118 may also control other engine actuators,
such as one or more camshaft phasers, an exhaust gas recirculation
(EGR) valve, a boost device (e.g., a turbocharger or a
supercharger), and/or other suitable engine actuators.
[0044] The crankshaft position sensor 126 monitors rotation of the
crankshaft 112 and outputs a crankshaft position signal 128 to the
ECM 118 based on rotation of the crankshaft 112. The crankshaft
position sensor 126 also measures direction of rotation of the
crankshaft 112, and outputs a direction signal indicating the
direction of rotation of the crankshaft 112, or the crankshaft
position sensor 126 indicates the direction of rotation via the
crankshaft position signal 128. The crankshaft position signal 128
is used, for example, to determine rotational speed of the
crankshaft 112 (e.g., in revolutions per minute or RPM). The
rotational speed of the crankshaft 112 is referred to as engine
speed 130. The MAP 132 sensor measures pressure within the intake
manifold 106 and generates a MAP signal 134 based on the pressure
within the intake manifold 106.
[0045] The ECM 118 controls the torque output of the engine 102
based on one or more driver inputs, such as the accelerator pedal
position, brake pedal position, and/or other suitable driver
inputs. The APP sensor 136 measures position of an accelerator
pedal (not shown) and generates an APP signal 138 based on the
position of the accelerator pedal. The BPP sensor 140 measures
position of a brake pedal (not shown) and generates a BPP signal
142 based on the position of the brake pedal.
[0046] The engine system 100 also includes one or more other
sensors 144 (collectively illustrated as other sensors), such as a
mass air flowrate (MAF) sensor, an intake air temperature (IAT)
sensor, an engine coolant temperature sensor, an engine oil
temperature sensor, and/or other suitable sensors. The ECM 118 also
communicates with one or more other modules, such as the TCM
146.
[0047] A user inputs vehicle startup and vehicle shutdown commands
to the ECM 118 via the ignition system 148 (collectively
illustrated as ignition). In one aspect, the user inputs vehicle
startup and vehicle shutdown commands by turning a key, pressing a
button, or in another suitable manner. When the user has input a
vehicle startup command and before a vehicle shutdown command has
been received, the ignition system 148 is in an ON state. The
ignition system 148 is in an OFF state when a vehicle shutdown
command is input. A key cycle refers to a period between a first
time when the user commands vehicle startup and a second time when
the user commands vehicle shutdown. The ECM 118 selectively shuts
down the engine 102 during a key cycle, (i.e., before a vehicle
shutdown command is received) under some circumstances. An
auto-stop event refers to shutting down the engine 102 during a key
cycle. In one aspect, the ECM 118 selectively performs an auto-stop
event during a key cycle when a user applies pressure to the brake
pedal and/or when one or more other suitable conditions are
satisfied. Shutting down the engine 102 under such conditions may
decrease fuel consumption.
[0048] The ECM 118 selectively terminates the auto-stop event and
restarts the engine 102. An auto-start event refers to starting the
engine 102 after an auto-stop event during a key cycle. In one
aspect, the ECM 118 performs an auto-start event when the user
releases the pressure from the brake pedal, when the user applies
pressure to the accelerator pedal, and/or when one or more other
suitable conditions are satisfied.
[0049] Referring now to FIGS. 2, 3, and 4, an exemplary engine
control system 101 is presented. The engine control system 101
includes an ECM 118 and a plurality of sensors and modules. The ECM
118 includes an engine speed determination module 202, a target
engine speed module 204, an actuator control module 206, an engine
load estimation module 208, a throttle controller 210, and an
auto-stop/start module 212. The ECM 118 also includes a spark
timing adjustment module 124 that selectively adjusts spark timing
to alter engine 102 torque outputs.
[0050] The engine speed determination module 202 determines the
engine speed 130 based on the crankshaft position signal 128. In
one aspect, the crankshaft position sensor 126 generates a high
amplitude reading and a low amplitude reading. The crankshaft
position sensor 126 produces a low amplitude reading until a
specific condition is met. For example, the low amplitude reading
of the crankshaft position sensor 126 is interrupted by the high
amplitude reading when a tooth of an N-toothed wheel (e.g., the
flywheel 116) passes the crankshaft position sensor 126. For a
further example, a target angle crossing pulse 317 is generated as
the crankshaft 112 rotates past a predetermined position (for
example, TDC 414) for a cylinder 108 of the engine 102. The engine
speed determination module 202 determines the engine speed 130
based on a period between two or more teeth of the N-toothed wheel.
The engine speed determination module 202 also determines the
engine rate of deceleration based on a time interval between two or
more of the target angle crossing pulses 317.
[0051] To determine the engine rate of deceleration, the ECM 118
relies upon derivation of angular rotational speed and acceleration
of the crankshaft 112 using equations of angular motion for a
system undergoing constant angular acceleration. A summary of the
relevant equations follows.
.omega..sub.f.sup.2=.omega..sub.0.sup.2+2.alpha..DELTA..theta.
(600)
[0052] In equation (600), .omega.x=angular speed of the crankshaft
112 in radians/second at a particular point in time x, .alpha. is
the angular acceleration in radians/second.sup.2 of the crankshaft
112, and .DELTA..theta. is angular displacement of the crankshaft
112 in radians during a time interval between a first time t.sub.0
and a second time t.sub.f. When crankshaft 112 ceases to rotate and
the engine speed 130 drops to zero, .omega..sub.f=0 radians/second
and equation 600 becomes:
0=.omega..sub.0.sup.2+2.alpha..DELTA..theta. (602).
[0053] Rearranging, equation 602 becomes:
.DELTA..theta. = .omega. 0 2 ( 2 .alpha. ) . ( 604 )
##EQU00001##
[0054] That is, .DELTA..theta. represents the estimated change in
rotational position (angular position) of the crankshaft 112
between the current pulse 317 and when the engine speed 130 becomes
zero. The .omega. represents the angular speed of the crankshaft
112 at a particular point in time, and |.alpha.| represents the
absolute value of the angular acceleration of the crankshaft 112.
In an exemplary case in which the ECM 118 has initiated an
auto-stop, because the engine 102 is decelerating, the angular
acceleration of the crankshaft 112 has a negative value. To convert
the equation 604 into degrees, rather than radians, a series of
substitutions may be made.
.omega. ( rad sec ) = rpm ( 2 .pi. 60 ) ( 606 ) .DELTA..theta. (
rad ) = .DELTA. Deg ( 2 .pi. 360 ) ( 608 ) .alpha. ( rad sec 2 ) =
.DELTA.rpm sec ( 2 .pi. 60 ) ( 610 ) ##EQU00002##
[0055] In one aspect, the ECM 118 uses the time intervals between
pulses 317 to form the foundation of an event-based approach to
update the angular displacement estimate. That is, the ECM 118
updates .omega. on an event basis. For instance, the event may
occur at each crossing of a predetermined crankshaft 112 angle
.theta. relative to a predetermined crankshaft 112 rotational
position such as TDC 414 for a particular cylinder 108.
[0056] The angular acceleration .alpha. is calculated as the change
in the event-based angular speed of the crankshaft 112 over the
time between the prior event sample (n-1) and the current event
sample (n), where n represents the current update event value(s)
and n-1 represents the prior update event value(s).
.alpha. [ n ] = { .omega. [ n ] - .omega. [ n - 1 ] } { t [ n ] - t
[ n - 1 ] } ( 612 ) ##EQU00003##
[0057] The ECM 118 uses the target engine speed 216 to determine
when to instruct the throttle controller 210 to command specific
throttle valve 104 areas during an engine 102 auto-stop. The target
engine speed module 204 determines the target engine speed 216
based on barometric pressure. In one aspect, because engine 102
pumping losses decrease with decreased barometric pressure, the
target engine speed module 204 will set a target engine speed 216
at ten thousand feet of altitude that is a lower target engine
speed 216 than the target engine speed module 204 would set at sea
level. In the ten thousand foot example above, because the engine
102 pumping losses are decreased relative to the pumping losses in
an engine 102 at sea level, the number of crankshaft 112
revolutions before the engine 102 stops will be greater than the
number of crankshaft 112 revolutions before engine stop of the same
engine 102 at sea level. Therefore, to reliably predict engine stop
position, the target engine speed module 204 alters the target
engine speed 216 based in part on barometric pressure.
[0058] With continued reference to FIG. 3, exemplary graphs of
alternator load, fuel pressure, intake and exhaust cam phasers, MAP
132, throttle area, and engine position as functions of time are
presented. Exemplary trace 302 tracks auto-stop pre-conditioning
and fuel shut-off. Exemplary trace 304 tracks the engine alternator
load. Exemplary trace 306 tracks the fuel pressure. Exemplary trace
308 tracks the exhaust cam phaser position. Exemplary trace 310
tracks the intake cam phaser position. Exemplary trace 130 tracks
the engine speed. Exemplary trace 312 tracks engine position.
Exemplary trace 128 tracks the target angle crossing pulse 317
events. Exemplary trace 132 tracks the MAP. Exemplary trace 316
tracks the actual throttle area. Exemplary trace 314 tracks the
desired throttle area.
[0059] With reference to FIG. 5, and with additional reference to
FIGS. 2, 3 and 4, in one aspect, the engine control system 101 has
an exemplary auto-stop sequence 500 that begins at block 502 and
proceeds to block 504 where the ECM 118 determines whether an
auto-stop event has been commanded during a key cycle. If the auto
stop event has not been commanded, the method returns to block 502.
However, if an auto-stop has been commanded, the method proceeds to
block 504, where the method enters a pre-conditioning period
P.sub.1 from time T.sub.1 to time T.sub.2. During the
pre-conditioning period P.sub.1, the ECM 118 first commands the
actuator control module 206 to reduce a load on the engine 102 at
block 506 by disabling the alternator to reduce an alternator load
304 and disabling the A/C clutch to reduce an A/C load (not shown).
Decreasing the load on the engine 102 improves the accuracy of load
estimations generated by the engine load estimation module 208. The
method then proceeds to block 508, where the ECM 118 parks the
exhaust cam phaser 308 at a predetermined timing position and the
ECM parks the intake cam phaser 310 at a predetermined timing
position in preparation for the engine 102 to shut down. At block
510, the ECM 118 increases a fuel rail pressure 306 to a
predetermined target fuel pressure 318, at which point the ECM 118
disables the engine fuel supply at time T.sub.2 at block 512. Once
the engine fuel supply has been disabled, the auto-stop sequence
enters the shut-down period P.sub.2.
[0060] During the shut-down period P.sub.2, from time T.sub.2 to
time T.sub.4, the engine 102 shuts off. In the shut-down period
P.sub.2 from T.sub.2 to T.sub.4, the fuel rail pressure 306
continues to increase to the predetermined target fuel pressure
318. At block 514, the ECM 118 sets the desired throttle area 314
of the throttle valve 104 to a first predetermined throttle opening
320. The first predetermined throttle opening 320 reduces the MAP
132 and thus, reduces the trapped pressure in the cylinder 108 or
cylinders 108 entering the intake phase. In one aspect, the first
predetermined throttle opening 320 includes a predetermined idle
throttle opening or another suitable throttle opening. Setting
desired throttle area 314 to the first predetermined throttle
opening 320 chokes the engine 102 and minimizes shudder. Shudder
refers to vibration experienced within the passenger cabin as the
engine speed approaches zero.
[0061] During the auto-stop sequence, and during the shut-down
phase after time T.sub.2 in particular, the ECM 118 monitors a
plurality of conditions. The plurality of conditions that the ECM
118 monitors includes crankshaft position 128 data at block 516,
engine speed 130 data at block 518, barometric pressure at block
520, engine deceleration data at block 522, and at block 524 the
ECM 118 estimates the remaining degrees of engine rotation prior to
a predetermined engine stop position 332. In one aspect, the
predetermined engine stop position 332 for an exemplary piston 400
is within a target auto-stop range 420.
[0062] With further reference to FIG. 4, a rotational diagram of a
combustion cycle for a first cylinder 400 in an exemplary
four-stroke four-cylinder engine in terms of crankshaft 112
position is presented. The cylinders 108 of the exemplary
four-stroke four-cylinder engine have the firing order 1-3-4-2,
repeating. For the purposes of the following explanation, the first
cylinder 400 refers to cylinder #1 in the exemplary four-stroke
four-cylinder engine. However, the cylinder 400 may be any of the
four cylinders in the exemplary four-stroke four-cylinder
engine.
[0063] The crankshaft 112 rotates in a clockwise direction as
indicated by reference number 402. A portion of the combustion
cycle of the first cylinder 400 includes an intake valve opening
event 404, an intake valve duration 406, an exhaust valve closing
event 408, an exhaust valve duration 410, a valve overlap duration
412, TDC 414, a bottom dead center (BDC) position 416, an intake
valve closing event 418, and a target auto-stop range 420.
[0064] For the first cylinder 400 of the exemplary four-stroke
four-cylinder engine to complete a full combustion cycle, and
return to the same point in the combustion cycle, two full
revolutions of the crankshaft 112 are required. An exemplary
combustion cycle for the first cylinder 400 begins with the intake
phase in which there is an intake valve opening event at 404. The
period during which the intake valve is open is referred to as the
intake valve duration 406. As the intake valve opening event occurs
at 404, an exhaust valve closing event 408 has not yet occurred.
The period during which the exhaust valve is open is referred to as
the exhaust valve duration 410. Thus the intake valve duration 406
and the exhaust valve duration 410 may overlap within a portion of
the combustion cycle. The portion of the combustion cycle in which
both the intake valve and exhaust valve are open is referred to as
the valve overlap duration 412 of the first cylinder 400. The valve
overlap duration 412 occurs near TDC 414. The intake valve overlap
duration 406 can vary substantially depending on intake cam phaser
310 timing setting and the exhaust cam phaser 308 timing setting.
The valve overlap duration 412 can also vary substantially between
engines 102. Fresh air "A" is drawn into the engine 102 during the
intake phase. In one aspect, the intake valve remains open for a
duration 406 that extends to an intake valve closing event 418 that
is beyond bottom dead center (BDC) 416. Because of the previously
mentioned 1-3-4-2 firing order, when the exemplary first cylinder
400 is in the intake phase and is next in sequence to enter the
compression phase, an exemplary third cylinder (cylinder #3, not
shown) is in the exhaust phase and is next in sequence to begin the
intake phase. Likewise an exemplary second cylinder (cylinder #2,
not shown) is in the compression phase and is next in sequence to
enter the expansion phase, and an exemplary fourth cylinder
(cylinder #4, not shown) is in the expansion phase and is next in
sequence to enter the exhaust phase. During the exhaust phase of
the first cylinder 400, the third cylinder is in the expansion
phase. Thus, the first cylinder 400 and third cylinder of the
exemplary four-stroke four-cylinder engine are always 180.degree.
rotationally offset from one another. Likewise, the second cylinder
and fourth cylinder of the exemplary four-stroke four-cylinder
engine are always 180.degree. rotationally offset from one
another.
[0065] Referring once again to the first cylinder 400, after
completing the intake phase, the first cylinder 400 then enters the
compression phase. During the compression phase, the intake valve
closing event 418 occurs, and the pressure of the trapped air
mixture rises as first cylinder 400 approaches TDC 414. As the
compression phase of the first cylinder 400 is completed, the first
cylinder 400 transitions to the expansion phase with both the
intake and exhaust valves remaining closed. While the first
cylinder 400 is engaged in the compression phase, the third
cylinder is engaged in the intake phase. After the first cylinder
400 completes the expansion phase, an exhaust valve opening event
422 occurs, and the exhaust valve remains open for the exhaust
valve duration 410. The first cylinder 400 then re-enters the
intake phase in which the intake valve opening event 404 and
overlap 412 occur.
[0066] With continued reference to FIG. 4, and with further
reference to FIGS. 2, 3, and 5, after time T.sub.2, because the
engine fuel supply and spark have been disabled, and because the
first predetermined throttle opening 320 reduces the MAP 132 and
chokes the engine 102 by reducing the airflow "A" to the intake
manifold 104, the engine speed 130 decreases toward zero as no
torque is being produced by the engine 102. At block 526 the ECM
determines whether the engine speed determination module 202 data
indicates that the engine speed 130 has decreased to a first
predetermined engine speed threshold 322. Furthermore, at block
526, the crankshaft position sensor 128 generates the target angle
crossing pulse 317 as each cylinder 108 crosses a predetermined
engine position (e.g., TDC 414) relative to the intake phase. From
the pulse 317, the ECM 118 determines whether the engine 102 has
reached a predetermined threshold engine position crossing
threshold 326 that indicates the engine 102 will stop with a
cylinder 108 within the target engine stop range 420. If each of
the engine speed threshold 322, remaining rotation threshold (not
shown), and engine position crossing threshold 326 have been met,
the method proceeds to block 528. If the predetermined engine speed
threshold 322, remaining rotation threshold (not shown), and engine
position crossing threshold 326 have not been met, the method
reverts to block 516, and begins monitoring the crankshaft
position, engine speed 130, barometric pressure, engine rate of
deceleration, and the ECM 118 estimates remaining degrees of engine
rotation again.
[0067] At block 528, if the engine 102 in an auto-stop sequence has
reached the shut-down phase, and target angle crossing pulse 317 is
generated, the ECM 118 commands the second predetermined throttle
opening if the engine speed 130, and crankshaft position signal 128
allow the ECM 118 to determine that the remaining degrees of
rotation will put a cylinder 108 into the target auto-stop position
range 420.
[0068] To determine the second predetermined throttle opening 328
and predetermined period P.sub.3, the ECM 118 uses the crankshaft
position signal 128, engine speed 130, and barometric pressure. In
one aspect of the present invention, the ECM 118 also uses an
estimate of the number of degrees of rotation remaining before the
engine 102 stops to predict the engine stop position 332. The
estimate of degrees of rotation remaining is accomplished by using
the engine speed 130 to calculate a rate of angular deceleration
(using equation 612 above) at each target angle crossing pulse 317.
Using the unit conversions and simplifying the equations previously
discussed, the engine stop position 332 may be predicted by the
following remaining degrees of rotation equation 614.
.DELTA. Deg [ n ] = 3 ( rpm [ n ] rpm [ n ] ) ( t [ n ] - t [ n - 1
] ) ( rpm [ n - 1 ] - rpm [ n ] ) ( 614 ) ##EQU00004##
[0069] In an aspect of the present invention, the second
predetermined throttle position 328 is applied once the engine
crankshaft position 128 has crossed a predetermined threshold
crankshaft position 330, and the engine speed 130 is below the
engine speed threshold 322 for a particular ambient barometric
pressure as determined from a lookup table. The engine speed
threshold 322 in the lookup table is a function of barometric
pressure, and correlates to a target auto-stop range 420 that
reduces the level of auto-stop and auto-start vibration. Therefore,
when the ECM 118 uses the barometric pressure at sea-level to
calculate the engine speed threshold 322, the reliability of the
engine speed threshold 322 to stop the engine 102 in the target
auto-stop range 420 decreases as the difference between the
barometric pressure at sea-level and the actual barometric pressure
increases.
[0070] Referring once more to the previous example of a four-stroke
four-cylinder engine with the first piston 400, in FIG. 3, as the
auto-stop period P.sub.2 progresses past time T.sub.3, the ECM 118
selects a specific cylinder (in this example, the first cylinder
400) for which each of the shutdown threshold criteria:
predetermined threshold crankshaft position 330, engine speed
threshold 322, and/or estimated remaining degrees of rotation
threshold have been achieved. The ECM 118 then uses the first
cylinder 400 for triggering the second predetermined throttle
opening 328 that will control an engine stop position 332, and more
specifically, that will control a stop position of the first
cylinder 400. If at time T.sub.3, when shutdown threshold criteria
have been achieved for the first cylinder 400, and the ECM 118
instead uses a different cylinder 108, such as the
previously-described second, third, or fourth cylinder, to initiate
the second predetermined throttle opening 328, the target auto-stop
range 420 may not be achieved. For a further example, in the case
where the ECM 118 targets the second cylinder, which in the
exemplary engine precedes the first cylinder 400 in the firing
order, the engine speed 130 is higher than the engine speed
threshold 322 for the first cylinder 400 for which all of the
threshold criteria have been met. In the example, when the engine
speed 130 is higher than the engine speed threshold 322 for the
first cylinder 400, the engine 102 will exceed the target auto-stop
range 420 and engine position 332. When the target auto-stop range
420 is not achieved, undesirable noise, vibration, and harshness
result during auto-stop and auto-start events.
[0071] Using equation 614, the ECM 118 commands the second
predetermined throttle opening 328, where the second predetermined
throttle opening 328 is greater than the first predetermined
throttle opening 320 and includes any single opening or plurality
of suitable openings that allow the MAP 132 to rapidly increase
toward barometric pressure while also reducing throttle valve 104
audible noise. By rapidly increasing the MAP 132, pressure in the
intake manifold 106 and in one or more cylinders 108 that are in
sequence to enter the intake phase is also increased.
[0072] In the example above, because the exhaust cam phaser and
intake cam phaser 308, 310 are parked prior to the ECM 118
commanding the second predetermined throttle opening 332, the
intake valve and the exhaust valve of the cylinder in the
compression stroke and the cylinder in the expansion stroke (e.g.,
the first cylinder 400 and the second cylinder respectively) are
closed as the engine 102 slows to a momentary stop 334, and the
first cylinder 400 reaches the target auto-stop range 420.
Furthermore, because the second predetermined throttle opening 328
rapidly increases air pressure within the intake manifold 106 and
the first cylinder 400 in the intake phase, as the first cylinder
400 completes the intake phase and undergoes the compression phase,
the first cylinder 400 stops momentarily at or near TDC 414. When
the first cylinder 108 stops at or near TDC 414, movement of the
crankshaft 112 is momentarily reversed due to trapped pressure in
the cylinders. This reversal of crankshaft 112 movement during
engine 102 shutdown is referred to as rock back. As the crankshaft
112 rocks back, air pressure within the next cylinder 108 in the
firing order (e.g., the third cylinder, relative to the exemplary
first cylinder 400) tends to approach barometric pressure and comes
to rest on the compression stroke in the target auto-stop range
420. When the MAP 132 and the exemplary third cylinder pressures
approach barometric pressure, less exhaust gas is present in the
intake manifold 106 and the third cylinder, and the potential for a
misfire is reduced when the engine 102 is restarted. Engine
vibration may be prevented when the engine 102 is restarted by
preventing misfires.
[0073] Referring once more to FIG. 5, and with continuing reference
to FIGS. 1, 2, 3, and 4, at block 530, the ECM 118 determines
whether the predetermined time period P.sub.3, has been met. At
T.sub.4, the ECM 118 sets a third predetermined throttle opening
336 at block 532 that is equal to or slightly above or slightly
below the first throttle predetermined opening 320. In part,
because there is a lag between the desired throttle area 314 and
the actual throttle area 316, in one aspect, the second
predetermined throttle opening 328 holding period P.sub.3 may
extend beyond T.sub.4. Additionally, because the first
predetermined throttle opening 320 chokes the engine 102 and
because the second predetermined throttle opening 328 pressurizes
the intake manifold 106 and at least one cylinder 108, the desired
and actual throttle areas 314, 316 further cause the engine speed
130 to decrease and eventually arrest rotation of the engine
102.
[0074] The throttle controller 210 also provides throttle valve 104
position commands to the actuator control module 206 under a
variety of conditions. In one aspect, during the holding period
P.sub.3 of the second predetermined throttle opening 328, the
throttle controller 210 starts a timer in a timer module 218. The
timer in the timer module 218 tracks the duration of the holding
period P.sub.3 since the second predetermined throttle opening 328
was set. During the holding period P.sub.3, the throttle controller
210 selectively varies the desired throttle area 314 to follow a
predetermined throttle opening profile, when the timer is less than
the predetermined holding period P.sub.3. In one aspect, the
throttle controller 210 transitions the desired throttle area 314
to the third predetermined throttle opening 336 when the
auto-stop/start module 212 generates an auto-start command. When
the auto-start command is generated, the actuator control module
206 commands a starter actuator module 150 to activate the ignition
148 and thereby start the engine 102. In this manner, if the engine
102 should be auto-started when the second predetermined throttle
opening 328 has been set for less than the full extent of the
holding period P.sub.3, the engine 102 is started without the
throttle valve 104 at or near a desired throttle opening.
[0075] At block 534, the ECM 118 determines whether the engine 102
has stopped rotating. If the engine speed determination module 202
has determined that the engine speed 130 is approximately zero, the
ECM 118 commands a fourth predetermined throttle opening 338
starting at time T.sub.5 at block 536. The fourth predetermined
throttle opening 338 is for example, at a level that is higher
than, the same as, or lower than the third throttle opening. At
block 538, the auto-stop method ends.
[0076] While the principles of the present disclosure are discussed
as relating to adjusting spark-ignition engines, the principles of
the present disclosure are also applicable to adjusting fuel
injection timing in compression-combustion engines. In one aspect,
the fuel injection timing is adjusted based on an injection timing
correction that is determined based on the difference between the
target engine speed 216 and the engine speed in
compression-combustion engine systems. The broad teachings of the
disclosure can be implemented in a variety of forms. Therefore,
while this disclosure includes particular examples, the true scope
of the disclosure 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.
* * * * *