U.S. patent application number 09/772753 was filed with the patent office on 2001-06-21 for engine control system for improved driveability.
Invention is credited to Kotwicki, Allan Joseph, Russell, John D..
Application Number | 20010004722 09/772753 |
Document ID | / |
Family ID | 23213180 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004722 |
Kind Code |
A1 |
Kotwicki, Allan Joseph ; et
al. |
June 21, 2001 |
Engine control system for improved driveability
Abstract
A vehicle and engine control system controls engine torque to
maintain positive torque at a transmission input to minimize the
transmission gears from separating. By maintaining a positive
engine torque, operation of the transmission in or through the zero
torque, or lash, zone, is minimized. This minimizes poor vehicle
driveability that would otherwise result from operation in the lash
zone. The control systems uses closed loop control based on a
desired and actual turbine speed ratio, or slip ratio, to provide
positive torque to the transmission.
Inventors: |
Kotwicki, Allan Joseph;
(Williamsburg, MI) ; Russell, John D.; (Farmington
Hills, MI) |
Correspondence
Address: |
John D. Russell
Suite 600 - Parklane Towers East
1 Parklane Boulevard
Dearborn
MI
48126
US
|
Family ID: |
23213180 |
Appl. No.: |
09/772753 |
Filed: |
January 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09772753 |
Jan 30, 2001 |
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09312824 |
May 17, 1999 |
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6199004 |
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Current U.S.
Class: |
701/54 ;
701/101 |
Current CPC
Class: |
B60W 10/11 20130101;
B60W 10/04 20130101; B60W 30/18 20130101; F02D 31/001 20130101;
F02D 41/0087 20130101; B60W 2710/0605 20130101; F02D 2041/001
20130101; B60W 10/06 20130101; F02D 2400/12 20130101; F02D 41/022
20130101; B60W 2710/0644 20130101; F16H 2059/385 20130101; F02D
2250/18 20130101; B60W 2050/0011 20130101; F02D 41/0215 20130101;
B60W 2710/0666 20130101; B60W 30/1819 20130101 |
Class at
Publication: |
701/54 ;
701/101 |
International
Class: |
G06F 007/00 |
Claims
We claim:
1. A vehicle control method for a vehicle having an internal
combustion engine coupled to a torque converter coupled to a
transmission, the method comprising the steps of: providing an
indication when the torque converter is in an unlocked state and
torque converter output speed is greater than torque converter
input speed; and in response to said indication, adjusting an
engine output amount based on said torque converter output speed
and said torque converter input speed.
2. The method recited in claim 1 wherein said engine output amount
is engine torque.
3. The method recited in claim 1 wherein said engine output amount
is airflow inducted into the engine.
4. The method recited in claim 1 wherein said adjusting further
comprises adjusting an engine output amount to maintain said torque
converter input speed greater than said torque converter output
speed.
5. The method recited in claim 1 wherein said adjusting further
comprises creating a desired engine speed to be greater than said
torque converter output speed, and controlling said engine output
amount so that an actual engine speed approaches said desired
engine speed.
6. A vehicle control method for a vehicle having an internal
combustion engine coupled to a torque converter coupled to a
transmission, the method comprising the steps of: providing an
indication when the torque converter is in an unlocked state and
torque converter output speed is greater than torque converter
input speed; and in response to said indication, determining an
engine output amount that will maintain said torque converter input
speed greater than said torque converter output speed; and
controlling and engine operating parameter to provide said
determined engine output amount.
7. The method recited in claim 6 wherein said engine operating
parameter is a throttle position.
8. The method recited in claim 6 wherein said engine operating
parameter is ignition angle.
9. The method recited in claim 6 wherein said engine operating
parameter is fuel injection amount.
10. The method recited in claim 6 wherein said engine operating
parameter is cylinder deactivation.
11. The method recited in claim 6 wherein said engine operating
parameter is cam angle of a variable cam angle system.
12. The method recited in claim 6 wherein said engine output amount
is an engine torque.
13. A vehicle control method for a vehicle having an internal
combustion engine coupled to a torque converter coupled to a
transmission, the method comprising the steps of: providing an
indication when the torque converter is in an unlocked state and
torque converter output speed is greater than torque converter
input speed; and in response to said indication, determining a
speed value related to torque converter output speed; calculating a
desired engine speed that is greater than said speed value; and
controlling and engine operating parameter so that an actual engine
speed approaches said desired engine speed.
14. A vehicle control method for a vehicle having an internal
combustion engine coupled to a torque converter coupled to a
transmission, the method comprising the steps of: indicating when
the torque converter is in an unlocked state; determining torque
converter output speed and torque converter input speed; in
response to said indication, when transitioning through zero engine
brake torque is to be avoided, adjusting an engine control
parameter to maintain said torque converter input speed greater
than said torque converter output speed.
Description
[0001] The present application is a continuation in part of U.S.
Ser. No. 09/312,824 filed May 17, 1999. The present application
incorporates by reference the entire disclosure of U.S. Ser. No.
09/312,824.
FIELD OF THE INVENTION
[0002] The present invention relates to a system and method to
control an internal combustion engine coupled to a torque converter
and in particular to adjusting engine output to control torque
converter slip, or speed ratio.
BACKGROUND OF THE INVENTION
[0003] Internal combustion engines must be controlled in many
different ways to provide acceptable driving comfort during all
operating conditions. Some methods use engine output, or torque
control where the actual engine torque is controlled to a desired
engine torque through an output adjusting device, such as with an
electronic throttle, ignition timing, or various other devices. In
some cases, such as during normal driving conditions, the desired
engine torque is calculated from the amount of depression of an
accelerator pedal. In other conditions, such as idle speed control,
the desired engine torque is calculated based on a speed error
between actual engine speed and a desired engine speed. Some
attempts have been made to use this torque control architecture to
improve driveability during deceleration conditions, such as when a
driver releases their foot to the minimum accelerator pedal
position, known to those skilled in the art as a tip-out. During a
tip-out, the driver is indicating a desire for reduced engine
output.
[0004] One system that attempts to use speed control during
deceleration conditions operates the engine in such a way as to
maintain constant engine speed during slow moving or stopped
conditions. In this system, the engine is controlled to a constant
speed taking into account the loading from the torque converter.
The loading from the torque converter is calculated based on the
engine speed and turbine speed. Engine speed can be controlled to a
constant level during deceleration to adsorb energy from the
vehicle and assists in vehicle braking. Further, as turbine speed
increases, the desired engine speed is reduced to provide even more
engine braking. Such a system is described in D.E. 4321413A1.
[0005] The inventors herein have recognized a disadvantage with the
above invention. In particular, the accelerator pedal is released
and subsequently engaged, the prior art system exhibits poor
driveability due transmission gears lash. For example, when the
engine transitions from exerting a positive torque to exerting a
negative torque (or being driven), the gears in the transmission
separate at the zero torque transition point. Then, after passing
through the zero torque point, the gears again make contact to
transfer torque. This series of events produces an impact, or
clunk, resulting in poor driveability and customer disatisfaction.
In other words, the engine first exerts a positive torque through
the torque converter onto the transmission input gears to drive the
vehicle. Then, when using the prior art approach during
deceleration, the engine is driven by the torque from the
transmission through the torque converter. The transition between
these to modes is the point where the engine is producing exactly
zero engine brake torque. Then, at this transition point, the gears
in the transmission separate because of inevitable transmission
gear lash. When the gears again make contact, they do so
dynamically resulting in an undesirable impact.
[0006] This disadvantage of the prior art is exacerbated when the
operator returns the accelerator pedal to a depressed position,
indicating a desire for increased engine torque. In this situation,
the zero torque transition point must again be traversed. However,
in this situation, the engine is producing a larger amount of
torque than during deceleration because the driver is requesting
acceleration. Thus, another, more severe, impact is experienced due
to the transmission lash during the zero torque transition.
SUMMARY OF THE INVENTION
[0007] Problems of prior approaches overcome, by a vehicle control
method for a vehicle having an internal combustion engine coupled
to a torque converter coupled to a transmission, the method
comprising the steps of: providing an indication when the torque
converter is in an unlocked state and torque converter output speed
is greater than torque converter input speed; and in response to
said indication, adjusting an engine output amount based on said
torque converter output speed and said torque converter input
speed.
[0008] By adjusting engine output in response to an indication that
the torque converter is in an unlocked state and torque converter
output speed is greater than torque converter input speed, it is
possible to provide real-time feedback control and maintain
positive torque in the driveline. In other words, according to the
present invention, it is possible to have an accurate indication of
when the vehicle is near the vehicle lash zone. Further, it is
possible to take control action to minimize the transmission
lash.
[0009] Stated another way, the present invention utilizes the
torque converter characteristics in the following way. Because
these measurements are readily available, a simple controller can
be developed that will provide positive torque application to the
transmission. In the simplest form, according to the present
invention, this amounts to controlling engine torque to keep the
engine speed greater than the torque converter turbine speed. Thus,
during tip-out conditions, driveability problems associated with
traversing the zero torque lash point are avoided. Further, by
using turbine speed to generate the desired engine speed, thus
providing a positive torque, effects from road grade, vehicle mass,
temperature, and other factors are inherently considered without
complexity or addition computation.
[0010] An advantage of the above aspect of the invention is
improved driveability.
[0011] Another advantage of the above aspect of the invention is
improved customer satisfaction.
[0012] Another advantage of the above aspect of the invention is to
minimize or ease transitions through the transmission lash
zone.
[0013] Other objects, features and advantages of the present
invention will be readily appreciated by the reader of this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The object and advantages described herein will be more
fully understood by reading an example of an embodiment in which
the invention is used to advantage, referred to herein as the
Description of the Preferred Embodiment, with reference to the
drawings wherein:
[0015] FIG. 1 is a block diagram of a vehicle illustrating various
components related to the present invention;
[0016] FIG. 2 is a block diagram of an engine in which the
invention is used to advantage;
[0017] FIGS. 3-9 high level flowcharts of various routines for
controlling the engine according to the present invention; and
[0018] FIG. 10 is a figure describing a relationship between engine
speed and torque converter speed ratio used to advantage in the
present invention.
DESCRIPTION OF AN EMBODIMENT
[0019] Referring to FIG. 1, internal combustion engine 10, further
described herein with particular reference to FIG. 2, is shown
coupled to torque converter 11 via crankshaft 13. Torque converter
11 is also coupled to transmission 15 via turbine shaft 17. Torque
converter 11 has a bypass clutch (not shown) which can be engaged,
disengaged, or partially engaged. When the clutch is either
disengaged or partially engaged, the torque converter is said to be
in an unlocked state. Turbine shaft 17 is also known as
transmission input shaft. Transmission 15 comprises an
electronically controlled transmission with a plurality of
selectable discrete gear ratios. Transmission 15 also comprise
various other gears, such as, for example, a final drive ratio (not
shown). Transmission 15 is also coupled to tire 19 via axle 21.
Tire 19 interfaces the vehicle (not shown) to the road 23.
[0020] Internal combustion engine 10 comprising a plurality of
cylinders, one cylinder of which is shown in FIG. 2, is controlled
by electronic engine controller 12. Engine 10 includes combustion
chamber 30 and cylinder walls 32 with piston 36 positioned therein
and connected to crankshaft 13. Combustion chamber 30 communicates
with intake manifold 44 and exhaust manifold 48 via respective
intake valve 52 and exhaust valve 54. Exhaust gas oxygen sensor 16
is coupled to exhaust manifold 48 of engine 10 upstream of
catalytic converter 20.
[0021] Intake manifold 44 communicates with throttle body 64 via
throttle plate 66. Throttle plate 66 is controlled by electric
motor 67, which receives a signal from ETC driver 69. ETC driver 69
receives control signal (DC) from controller 12. Intake manifold 44
is also shown having fuel injector 68 coupled thereto for
delivering fuel in proportion to the pulse width of signal (fpw)
from controller 12. Fuel is delivered to fuel injector 68 by a
conventional fuel system (not shown) including a fuel tank, fuel
pump, and fuel rail (not shown).
[0022] Engine 10 further includes conventional distributorless
ignition system 88 to provide ignition spark to combustion chamber
30 via spark plug 92 in response to controller 12. In the
embodiment described herein, controller 12 is a conventional
microcomputer including: microprocessor unit 102, input/output
ports 104, electronic memory chip 106, which is an electronically
programmable memory in this particular example, random access
memory 108, and a conventional data bus.
[0023] Controller 12 receives various signals from sensors coupled
to engine 10, in addition to those signals previously discussed,
including: measurements of inducted mass air flow (MAF) from mass
air flow sensor 110 coupled to throttle body 64; engine coolant
temperature (ECT) from temperature sensor 112 coupled to cooling
jacket 114; a measurement of throttle position (TP) from throttle
position sensor 117 coupled to throttle plate 66; a measurement of
turbine speed (Wt) from turbine speed sensor 119, where turbine
speed measures the speed of shaft 17, and a profile ignition pickup
signal (PIP) from Hall effect sensor 118 coupled to crankshaft 13
indicating and engine speed (N).
[0024] Continuing with FIG. 2, accelerator pedal 130 is shown
communicating with the driver's foot 132. Accelerator pedal
position (PP) is measured by pedal position sensor 134 and sent to
controller 12.
[0025] In an alternative embodiment, where an electronically
controlled throttle is not used, an air bypass valve (not shown)
can be installed to allow a controlled amount of air to bypass
throttle plate 62. In this alternative embodiment, the air bypass
valve (not shown) receives a control signal (not shown) from
controller 12.
[0026] Referring now to FIG. 3, a routine for detecting
deceleration conditions is described. First, in step 310, driver
actuated pedal position (PP) is compared with calibratable item
(PP_CT), which represents the pedal position at which the pedal is
closed. Alternatively, driver desired wheel torque, which is known
to those skilled in the art to be a function of pedal position and
vehicle speed, can be compared with a minimum desired wheel torque
clip below which deceleration is desired. When the answer to step
310 is YES, then in step 312, both engine speed (N) and turbine
speed (Wt) are read. In step 314, a determination is made as to
whether engine speed is greater than turbine speed. When the answer
to step 314 is YES, then deceleration conditions have been detected
as shown in step 316.
[0027] Referring now to FIG. 4, a routine for calculating a desired
engine speed during deceleration conditions is described. First, in
step 406, a determination is made as to whether deceleration
conditions have been detected. When the answer to step 406 is YES,
a determination is made in step 408 as to whether the torque
converter is in and unlocked state. When the answer to step 408 is
YES, turbine speed is read from turbine speed sensor 119 in step
410. Then, in step 412, a desired speed ratio, SRdes, where
(SR=Wt/N) is calculated based on the turbine speed. In one
embodiment of the present invention, the relationship between
desired speed ratio and measured turbine speed is determined so
that a small positive constant torque is applied to transmission
16. An example of a relationship between speed ratio and turbine
speed that gives a positive constant torque is described later
herein with particular reference to FIG. 10. In another embodiment,
the relationship between desired speed ratio and measured turbine
speed is modified by transmission gear ratio so that a varying
positive torque is applied to transmission 16 to give different
driveability feel at different vehicle speeds. In this type of
system separate relationships are used for each gear when
determining the desired speed ratio as a function of measured
turbine speed.
[0028] According to the present invention, in each embodiment, the
desired speed ratio is always less than unity during deceleration
when the zero torque point is to be avoided and the torque
converter is in an unlocked state. During some conditions engine
braking is required, such as, for example, during speed control
down a hill. In these cases, the routines described in FIGS. 2-9
are circumvented and other actions are taken. Continuing with FIG.
4, in step 414, the desired engine speed is calculated from the
desired speed ratio and the measured turbine speed.
[0029] Referring now to FIG. 5, a routine is described for
controlling actual engine speed to the desired engine speed
calculated in step 414 described previously herein. First, in step
510 actual engine speed (N) is read from sensor 118. Then, in step
512, engine speed error (Werr) is calculated from the desired
engine speed (Ndes) and actual engine speed (N). In step 514, a
determination is made as to whether engine speed error is greater
than zero. When the answer to step 514 is YES, a desired throttle
plate angle (qdes) is calculated as a function (f1) of engine speed
error. Function f1 is a controller known to those skilled in the
art as a PID controller. If the answer to step 514 is NO, then in
step 518 desired throttle plate angle (qdes) is calculated as a
function (f2) of engine speed error. Function f2 is also a
controller known to those skilled in the art as a PID controller.
In a preferred embodiment, the gains of function f2 are tuned to
allow less overshoot or undershoot than function f1, since positive
speed errors are more severe than negative speed errors with
respect to crossings of the zero torque point. Further, function f1
is tuned for producing a smooth transition from driver demand based
engine torque control and deceleration control according to the
present invention. In other words, function f1 is tuned to provide
a smooth transition in engine speed and engine torque that gives
high customer satisfaction and drive comfort. On the other hand,
function f2 is tuned for precise control of engine speed,
minimizing zero torque crossings. In an alternative embodiment, the
controller defined by function f1 could be used when engine speed
is greater than sum of the turbine speed and a calibratable value,
with function f2 used otherwise. This would give precise and fast
control when engine speed is near the desired engine speed or below
the desired engine speed and smooth control when the engine speed
is far away from and above the desired engine speed.
[0030] Referring now to FIG. 6, a routine is described for
controlling throttle position to the desired throttle position
calculated in either step 516 or 518 described previously herein.
First, in step 610 actual throttle position (TP) is read from
sensor 117. Then, in step 612, throttle position error (TPerr) is
calculated from the desired throttle position (qdes) and actual
throttle position (TP). Output signal DC is calculated as a
function (f3) of throttle position error. Function f3 is a
controller known to those skilled in the art as a PID
controller.
[0031] Referring now to FIG. 7, an alternate routine is described
for controlling actual engine speed to the desired engine speed
calculated in step 414 described previously herein. First, in step
710 actual engine speed (N) is read from sensor 118. Then, in step
712, engine speed error (Werr) is calculated from the desired
engine speed (Ndes) and actual engine speed (N). In step 714,
actual engine torque (Te) is calculated using methods known to
those skilled in the art, such as, for example, using engine speed
and turbine speed along with torque converter characteristics.
Alternatively, actual engine torque can be calculated based on
engine operating conditions such as engine speed, engine airflow,
ignition timing, or any other variable known to those skilled in
the art to affect engine torque.
[0032] Continuing with FIG. 7, in step 716 the required change in
engine torque (DTe) to cause actual engine speed to become the
desired engine speed is calculated based on engine speed error,
engine speed, and actual engine torque. This calculation is
completed using characteristic predetermined graphs. Next, in step
718 the required change in throttle position (Dq) is calculated
based on the required change in engine torque. The, in step 720 a
determination is made as to whether engine speed error is greater
than zero. When the answer to step 714 is YES, a desired throttle
plate angle (qdes) is calculated as the sum of function (f4) of
engine speed error, current throttle position TP, and required
change in throttle position. Function f4 is a controller known to
those skilled in the art as a PID controller. If the answer to step
714 is NO, then in step 718 desired throttle plate angle (qdes) is
calculated as the sum of function (f5) of engine speed error,
current throttle position TP, and required change in throttle
position. Function f5 is also a controller known to those skilled
in the art as a PID controller. In a preferred embodiment, the
gains of function f5 are tuned to allow less overshoot or
undershoot than function f4, since positive speed errors are more
severe than negative speed errors with respect to crossings of the
zero torque point.
[0033] Referring now to FIG. 8, another alternate routine is
described for controlling actual engine speed to the desired engine
speed calculated in step 414 described previously herein. First, in
step 810 actual engine speed (N) is read from sensor 118. Then, in
step 812, engine speed error (Werr) is calculated from the desired
engine speed (Ndes) and actual engine speed (N). Then, in step 814,
desired engine torque (Tedes) that would produce an actual engine
speed equal to the desired engine speed is calculated. The desire
torque is calculated taking into account all of the external engine
loading, engine friction, and various other losses known to those
skilled in the art. In addition, the torque converter load is known
from the desired positive torque to be applied to the transmission
input shaft and the current torque ratio across the torque. The
current torque ratio across the torque converter can be determined
based on the actual speed ratio as is known to those skilled in the
art. Then in step 816, the desired engine torque is adjusted based
on the engine speed error. Finally, in step 818, the desired
throttle position is calculated that will proved the adjusted
desired engine torque based on engine operating conditions.
[0034] In alternative embodiments, any other parameters that
affects engine brake (output) torque and is under control of
controller 12, such as, for example, ignition angle, cylinder
deactivation, fuel injection amount, idle air bypass amount, cam
angle of a variable cam angle system, exhaust gas recirculation
amount, or accessory loading from accessories such as, for example,
the alternator or a/c compressor.
[0035] Referring now to FIG. 9, a alternative embodiment of the
present invention is described. FIG. 9 is a routine is described
for controlling actual speed ratio to the desired speed ratio
calculated in step 412 described previously herein. First, in step
910 actual engine speed (N) is read from sensor 118. Then in step
921, actual speed ratio (Sract) is calculated by dividing actual
turbine speed by actual engine speed. Then, in step 914, speed
ratio error (SRerr) is calculated from the desired speed ratio
(SRdes) and actual speed ratio (Sract). In step 916, desired engine
torque (Tedes) is calculated as the sum of the base required engine
torque (Tebase) and function f7 of speed ratio error. Function f7
is also a controller known to those skilled in the art as a PID
controller. Base required engine torque is the base calibration
torque for maintaining the engine speed at the desired engine
speed.
[0036] Continuing with FIG. 9, in step 918 desired throttle
position is calculated based on desired engine torque (Tedes) based
on current engine conditions such as engine speed and temperature
using methods known to those skilled in the art. Then, in step 920,
duty cycle sent to motor 67 is calculated using function f8 of
desired throttle position minus actual throttle position. In a
preferred embodiment, function f8 is a controller known to those
skilled in the art as a PID controller.
[0037] Alternatively, instead of controlling engine torque directly
with throttle position, intermediate values can also be used, such
as, for example, engine airflow. for example, from desired engine
torque, a desire engine airflow can be calculated. Then, throttle
position can then be adjusted so that actual engine airflow as
measured by signal MAF approaches the desired engine airflow.
[0038] Referring now to FIG. 10, a figure showing an example
relationship between turbine speed and speed ratio that provides a
positive constant torque applied to the shaft 18 of transmission
16.
[0039] This concludes the description of the Preferred Embodiment.
The reading of it by those skilled in the art would bring to mind
many alterations and modifications without departing from the
spirit and scope of the invention. For example, if turbine speed is
not measured, vehicle speed and gear ratio can be substituted
without loss of function. Accordingly, it is intended that the
scope of the invention be limited by the following claims.
* * * * *