Title of Invention

A METHOD OF CONTROLLING SLIP IN A TRANSMISSION CONTROL SYSTEM DRIVEN BY A PRIME MOVER

Abstract A method of managing slip in a transmission that is driven by a prime mover includes determining whether a slip condition of the transmission is present based on a slip value and reducing a torque output of the prime mover based on a torque reduction value when the slip condition is present. The method further includes storing the torque reduction value in an array if the slip condition is resolved as a result of the step of reducing and identifying a faulty component within the transmission based on the array.
Full Text GP-307830-PTT-CD
1
TRANSMISSION SLIP CONTROL
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/819,005, filed on July 6, 2006. The disclosure of the above
application is incorporated herein by reference.
FIELD
[0002] The present disclosure relates to a transmission that is
driven by a prime mover, and more particularly to a transmission slip control
for detecting and managing transmission slip.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0004] Traditionally, vehicles include a prime mover, such as an
internal combustion engine, that generates drive torque. The drive torque is
transferred through a powertrain to drive a drivetrain, propelling the vehicle
along a surface. Exemplary powertrain components include a transmission
and a coupling device, through which the drive torque from the engine is
transferred to the transmission. The transmission multiplies the drive torque
by a gear ratio and further transfers the multiplied drive torque to the driveline.
[0005] An exemplary transmission includes an automatic
transmission having a plurality of transmission elements that are hydraulically
engaged to establish a desired gear ratio. Accordingly, each transmission
element includes a corresponding hydraulic circuit having a variable bleed
solenoid (VBS) to regulate the actuation pressure of a corresponding
transmission element.

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[0006] A transmission slip condition can occur when a transmission
element is defective and/or worn or the corresponding hydraulic circuit is
providing insufficient pressure to fully engage the particular transmission
element. The transmission slip condition can damage transmission
components and detrimentally affects the vehicle drivability.
[0007] Accordingly, traditional transmission slip control routines
determine whether a slip condition is present and commands a transmission
shift if the slip condition remains for a predetermined time period. By
executing a shift and monitoring whether a slip condition exists in the next
gear ratio, the traditional transmission slip control can identify which
transmission element and/or hydraulic circuit is the source of the slip
condition. However, if the vehicle operator changes the vehicle operating
conditions (e.g., steps into the accelerator pedal changing the engine torque
request), another transmission shift may be executed. As a result, the
traditional slip control can inaccurately identify a particular transmission
element and/or hydraulic circuit as being defective, which results in increased
warranty costs and customer dissatisfaction.
SUMMARY
[0008] Accordingly, the present invention provides a method of
managing slip in a transmission that is driven by a prime mover. The method
includes determining whether a slip condition of the transmission is present
based on a slip value and reducing a torque output of the prime mover based
on a torque reduction value when the slip condition is present. The method
further includes storing the torque reduction value in an array if the slip
condition is resolved as a result of the step of reducing and identifying a faulty
component within the transmission based on the array.
[0009] In other features, the method further includes incrementing
the torque reduction value if the slip condition is not resolved. A shift of the

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transmission is initiated if the torque reduction value exceeds a maximum
torque reduction value.
[0010] In another feature, the method further includes initiating a
self-correction routine if the slip condition is present.
[0011] In another feature, the slip value is determined based on a
transmission input shaft speed and a transmission output shaft speed.
[0012] In another feature, the torque reduction value is determined
based on the slip value.
[0013] In still another feature, the method further includes setting a
diagnostic trouble code based on the array.
[0014] In yet another feature, the array includes a plurality of torque
reduction values that are associated with a corresponding plurality of clutches
of the transmission.
[0015] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the description and
specific examples are intended for purposes of illustration only and are not
intended to limit the scope of the present disclosure.
DRAWINGS
[0016] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present disclosure in any
way.
[0017] Figure 1 is a functional block diagram of an exemplary
vehicle powertrain that is regulated based on the transmission slip control of
the present invention;
[0018] Figure 2 is a flowchart illustrating exemplary steps executed
by the transmission slip control of the present invention; and
[0019] Figure 3 is a functional block diagram of exemplary modules
that execute the transmission slip control of the present invention.

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DETAILED DESCRIPTION
[0020] The following description of the preferred embodiment is
merely exemplary in nature and is in no way intended to limit the invention, its
application, or uses. For purposes of clarity, the same reference numbers will
be used in the drawings to identify similar elements. 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, or
other suitable components that provide the described functionality.
0021] ferring now to Figure 1, an exemplary powertrain 10 is
illustrated and includes an engine 12 that drives a transmission 14 through a
coupling device 16. More specifically, air is drawn into an intake manifold 18
of the engine 12 through a throttle 20. The air is mixed with fuel and the
air/fuel mixture is combusted within cylinders 22 to reciprocally drive pistons
(not shown) within the cylinders 22. The pistons rotatably drive a crankshaft
(not shown) to provide drive torque. Exhaust generated by the combustion
process is exhausted from the engine through an exhaust manifold 26.
Although 4 cylinders are illustrated, it is appreciated that the present invention
can be implemented in vehicles having any number of cylinders.
[0022] The drive torque drives is transferred through the coupling
device 16 to drive the transmission 14. The transmission 14 multiplies the
drive torque by a desired gear ratio to provide a modified drive torque. The
modified drive torque is transferred to a vehicle driveline (not shown) by a
transmission output shaft 28. The transmission 14 includes an automatic
transmission that provides a plurality of pre-defined, fixed gear ratios, wherein
shifting of the transmission 14 is automatically regulated based on a selected
drive range (e.g., P, R, N, D, L), a vehicle speed (VVEH) and an engine load.
[0023] A control module 30 regulates operation of the powertrain
based on vehicle operating parameters. More specifically, the control module
30 regulates an effective throttle area (AEFF) via a throttle actuator 32. A

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throttle position sensor 34 generates a throttle position signal (TPS) based on
the angular position of the throttle 20. The control module 30 determines a
requested engine torque (TENG) and adjusts the throttle position and other
engine operating parameters to achieve TENG- The other engine operating
parameters include, but are not limited to, a fueling rate, spark timing, a
camshaft phase and/or an intake/exhaust valve lift or timing.
[0024] The control module 30 also regulates operation of the
transmission 14 based on vehicle operating parameters. More specifically, a
crankshaft position sensor 36 generates a crankshaft position signal, which is
used to determine an actual engine speed (RPMENG)- A transmission output
shaft speed (TOSS) sensor 38 generates a TOSS signal, which is used to
determine VVEH, and a transmission input shaft speed (TISS) sensor 39
generates a TISS signal.
[0025] For the purpose of the present description, an exemplary 6-
speed automatic transmission will be briefly described. It is anticipated,
however, that the transmission slip control of the present invention can be
implemented with any type of transmission know in the art. The exemplary 6-
speed automatic transmission includes four clutches C1 - C4 and a brake
element B1, each of which is hydraulically actuated via a corresponding
hydraulic circuit. C1 - C4 and B1 are selectively implemented in pairs to
establish 6 forward gear ratios and a reverse ratio, in accordance with Table
1, below:
1st 2nd 3rd 5tn 6th R
C1 X X X X
C2 X X
C3 X X X
C4 X X X
B1 X X
Table 1

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Accordingly, two transmission elements (i.e., C1 - C4 and B1) are actuated to
establish a desired gear ratio.
[0026] During a gear shift, one of the two transmission elements
remains actuated while the other transmission element gradually disengages
(i.e., is off-going) and a third transmission element gradually engages (i.e., is
on-coming). For example, in 1st gear, C1 and B1 are engaged. During an
upshift to 2nd gear, C1 remains engaged. B1 gradually disengages while C2
gradually engages. Similarly, C1 remains engaged, C2 gradually disengages
and C3 gradually engages during an upshift to 3rd gear.
[0027] The transmission slip control of the present invention
determines whether a transmission slip condition is present based on the
TISS and TOSS signals. More specifically, the transmission slip control
monitors the rotational speed of the transmission input shaft (RPMis) and that
of the transmission output shaft (RPMOs)> and determines a theoretical input
shaft speed (RPMISTHR) by multiplying RPMos by the current gear ratio. If
RPMISTHR is less than RPMis, a slip condition is present. A slip condition
indicates that at least one of the transmission elements for the particular gear
ratio is not fully engages and slip is occurring across the transmission element
(s). The slip condition can result from a defective or worn transmission
element or a low pressure condition of the corresponding hydraulic circuit(s)
(e.g., a fluid blockage), that inhibits the transmission element(s) from fully
engaging.
[0028] In the event that the slip condition is present, the
transmission slip control reduces TENG by a torque reduction value (TRED). It is
also anticipated, however, that a self-correction routine can be executed in an
attempt to clear the associated hydraulic circuits (i.e., corresponding to each
of the two engaged transmission elements) prior to reducing TENG- in general,
the self-correction routine flushes the associated hydraulic circuits with little or
no detriment to the vehicle drivability. That is to say that the hydraulic circuits
can be flushed without the vehicle operator noticing any fluctuation in driving

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performance. If the source of the slip condition is a blockage in the hydraulic
circuit, the self-correction routine could resolve the slip condition without
requiring further action.
[0029] In the event that the slip condition is not resolved, the
transmission slip control reduces TENG based on TRED- TRED can be a
predetermined, fixed value or can be determined based on the slip value (i.e.,
the difference between RPMis and RPMISTHR)- If the slip condition is not
resolved via the initial TENG reduction, TRED can be incremented or otherwise
increased in an effort to further reduce TENG to resolve the slip condition.
However, if the continuous TENG reduction still fails to resolve the slip
condition and TRED has achieved a maximum torque reduction value (TREDMAX)
(e.g., 10 - 15% of the original TENG). a transmission shift is initiated. The
transmission shift preferably includes an upshift, but it is anticipated that a
downshift can be executed (e.g., if the transmission is in 6th gear, for
example). If the slip condition is resolved without TRED achieving TREDMAX, the
transmission continues to operate in the same gear ratio with the reduced
TENG, until a transmission shift is commanded using the normal shift logic (i.e.,
based on VVEH and other operating parameters).
[0030] TRED values associated with each gear ratio are stored in an
array. An exemplary array is provided as provided in Table 2 below:
1st ond 3rd 4m 5tn 6tn R
TRED TREDI TRED2 TRED3 TRED4 TRED5 TRED6 TREDR
Table 2
A faulty transmission element and/or hydraulic circuit can be identified based
on the array values. More specifically, and as discussed in detail above, two
transmission elements are engaged for any particular gear ratio. Accordingly,
if the TRED value is greater than zero for two different gear ratios in which the
same transmission element is engaged, that particular transmission element
and/or the hydraulic circuit associated therewith is defective. For example, if
TREDI and TRED3 are both greater than zero, C1 and/or its associated hydraulic

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circuit are most likely defective, because C1 is the only transmission element
that is engaged in both 1st and 3rd gears.
[0031] The transmission slip control sets a diagnostic trouble code
(DTC) corresponding to a particular transmission element or elements
deemed to be defective. It is anticipated, however, that the DTC may only be
set if the slip condition is particularly sever. For example, if the slip value is
marginal for a particular gear ratio, the transmission slip control may wait for
the slip condition to become more sever before setting the DTC. A technician
can readily identify the defective component by reading the DTCs. In this
manner, the transmission can be easily and effectively repaired, decreasing
warranty and other associated costs.
[0032] Referring now to Figure 2, exemplary steps that are
executed by the transmission slip control of the present invention will be
described in detail. In step 200, control monitors TISS and TOSS. In step
202, control determines whether transmission slip for the particular gear ratio
is present. If transmission slip is not present, control ends. If transmission
slip is present, control initiates the self-correction routine in step 204. In step
206, control determines whether transmission slip is still present. If
transmission slip is not still present, control ends. If transmission slip is still
present, control continues in step 208.
[0033] Control determines TRED based on the slip value in step 208.
In step 210, control reduces TENG by TRED- In step 212, control determines
whether the slip condition is resolved. If the slip condition is resolved, control
stores TRED in the array in step 214. If the slip condition is not resolved,
control determines whether TRED is greater than or equal to TREDMAX in step
216. If TRED is not greater than or equal to TREDMAX, control increments TRED
in step 218 and loops back to step 210. If TRED is greater than or equal to
TREDMAX, control executes a transmission shift in step 220. In step 222,
control identifies a faulty transmission components (e.g., transmission

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element and/or associated hydraulic circuit) based on the array values.
Control sets a corresponding DTC in step 224 and control ends.
[0034] Referring now to Figure 3, exemplary modules that execute
the transmission slip control will be described in detail. The exemplary
modules include a slip determining module 300, a TRED determining module
302, an engine control module 304, a transmission control module 306, a self-
correction module 308 and a DTC module 310. The slip determining module
300 generates a slip value based on the TISS and TOSS signals. The slip
value is output to the TRED determining module 302 and the self-correction
module 308. The TRED determining module 302 determines TRED based on
the slip value and the current gear ratio. The self-correction module 308
selectively generates a self-correction routine signal that is output to the
transmission control module 306.
[0035] The engine control module 304 regulates operation of the
engine (e.g., TENG) based on TRED- Similarly, the transmission control module
306 regulates operation of the transmission based on TRED- The DTC module
310 selectively generates a DTC or DTCs based on the array, which is output
from the TRED determining module 302.
[0036] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the present 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.

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CLAIMS
What is claimed is:
1. A transmission control system for managing slip in a transmission that
is driven by a prime mover, comprising:
a first module that determines whether a slip condition of said
transmission is present based on a slip value;
a second module that reduces a torque output of said prime mover
based on a torque reduction value;
a third module that stores said torque reduction value in an array if said
slip condition is resolved as a result of said step of reducing, and that
identifies a faulty component within said transmission based on said array.
2. The transmission control system of claim 1 wherein said second
module increments said torque reduction value if said slip condition is not
resolved.
3. The transmission control system of claim 2 further comprising a fourth
module that initiates a shift of said transmission if said torque reduction value
exceeds a maximum torque reduction value.
4. The transmission control system of claim 1 further comprising a fourth
module that initiates a self-correction routine if said slip condition is present.
5. The transmission control system of claim 1 wherein said slip value is
determined based on a transmission input shaft speed and a transmission
output shaft speed.
6. The transmission control system of claim 1 wherein said torque
reduction value is determined based on said slip value.

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7. The transmission control system of claim 1 further comprising a fourth
module that sets a diagnostic trouble code based on said array.
8. The transmission control system of claim 1 wherein said array includes
a plurality of torque reduction values that are associated with a corresponding
plurality of clutches of said transmission.
9. A method of managing slip in a transmission that is driven by a prime
mover, comprising:
determining whether a slip condition of said transmission is present
based on a slip value;
reducing a torque output of said prime mover based on a torque
reduction value;
storing said torque reduction value in an array if said slip condition is
resolved as a result of said step of reducing; and
identifying a faulty component within said transmission based on said
array.
10. The method of claim 9 further comprising incrementing said torque
reduction value if said slip condition is not resolved.
11. The method of claim 10 further comprising initiating a shift of said
transmission if said torque reduction value exceeds a maximum torque
reduction value.
12. The method of claim 9 further comprising initiating a self-correction
routine if said slip condition is present.
13. The method of claim 9 wherein said slip value is determined based on
a transmission input shaft speed and a transmission output shaft speed.

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14. The method of claim 9 wherein said torque reduction value is
determined based on said slip value.
15. The method of claim 9 further comprising setting a diagnostic trouble
code based on said array.
16. The method of claim 9 wherein said array includes a plurality of torque
reduction values that are associated with a corresponding plurality of clutches
of said transmission.
17. A method of managing slip in a transmission that is driven by a prime
mover, comprising:
determining whether a slip condition of said transmission is present
based on a slip value;
reducing a torque output of said prime mover based on a torque
reduction value;
storing said torque reduction value in an array if said slip condition is
resolved as a result of said step of reducing;
identifying a faulty component within said transmission based on said
array; and
maintaining normal operation of said transmission during operation
under a reduced torque output condition, wherein a transmission shift is
executed based on a vehicle speed and other operating parameters.
18. The method of claim 17 further comprising incrementing said torque
reduction value if said slip condition is not resolved.
19. The method of claim 18 further comprising initiating a shift of said
transmission if said torque reduction value exceeds a maximum torque
reduction value.

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20. The method of claim 17 further comprising initiating a self-correction
routine if said slip condition is present.
21. The method of claim 17 wherein said slip value is determined based on
a transmission input shaft speed and a transmission output shaft speed.
22. The method of claim 17 wherein said torque reduction value is
determined based on said slip value.
23. The method of claim 17 further comprising setting a diagnostic trouble
code based on said array.
24. The method of claim 17 wherein said array includes a plurality of
torque reduction values that are associated with a corresponding plurality of
clutches of said transmission.

A method of managing slip in a transmission that is driven by a prime mover includes determining whether a slip condition of the transmission is present based on a slip value and reducing a torque output of the prime mover based on a torque reduction value when the slip condition is present. The method further includes storing the torque reduction value in an array if the slip condition is resolved as a result of the step of reducing and identifying a faulty component within the transmission based on the array.

Documents:

00722-kol-2007-abstract.pdf

00722-kol-2007-assignment.pdf

00722-kol-2007-claims.pdf

00722-kol-2007-correspondence others 1.1.pdf

00722-kol-2007-correspondence others 1.2.pdf

00722-kol-2007-correspondence others 1.3.pdf

00722-kol-2007-correspondence others 1.4.pdf

00722-kol-2007-correspondence others.pdf

00722-kol-2007-description complete.pdf

00722-kol-2007-drawings.pdf

00722-kol-2007-form 1.pdf

00722-kol-2007-form 18.pdf

00722-kol-2007-form 2.pdf

00722-kol-2007-form 3.pdf

00722-kol-2007-form 5.pdf

00722-kol-2007-gpa.pdf

00722-kol-2007-priority document.pdf

722-KOL-2007-(06-02-2012)-CORRESPONDENCE.pdf

722-KOL-2007-(12-10-2011)-ABSTRACT.pdf

722-KOL-2007-(12-10-2011)-AMANDED CLAIMS.pdf

722-KOL-2007-(12-10-2011)-DESCRIPTION (COMPLETE).pdf

722-KOL-2007-(12-10-2011)-DRAWINGS.pdf

722-KOL-2007-(12-10-2011)-EXAMINATION REPORT REPLY RECIEVED.pdf

722-KOL-2007-(12-10-2011)-FORM 1.pdf

722-KOL-2007-(12-10-2011)-FORM 2.pdf

722-KOL-2007-(12-10-2011)-FORM 3.pdf

722-KOL-2007-(12-10-2011)-FORM 5.pdf

722-KOL-2007-(12-10-2011)-OTHERS.pdf

722-KOL-2007-(12-10-2011)-PA.pdf

722-KOL-2007-(12-10-2011)-PETION UNDER RULE 137.pdf

722-KOL-2007-ASSIGNMENT.pdf

722-KOL-2007-CORRESPONDENCE 1.1.pdf

722-KOL-2007-CORRESPONDENCE.pdf

722-KOL-2007-EXAMINATION REPORT.pdf

722-KOL-2007-FORM 18.pdf

722-KOL-2007-FORM 3.pdf

722-KOL-2007-FORM 5.pdf

722-KOL-2007-GPA.pdf

722-KOL-2007-GRANTED-ABSTRACT.pdf

722-KOL-2007-GRANTED-CLAIMS.pdf

722-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

722-KOL-2007-GRANTED-DRAWINGS.pdf

722-KOL-2007-GRANTED-FORM 1.pdf

722-KOL-2007-GRANTED-FORM 2.pdf

722-KOL-2007-GRANTED-LETTER PATENT.pdf

722-KOL-2007-GRANTED-SPECIFICATION.pdf

722-KOL-2007-OTHERS.pdf

722-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

722-KOL-2007-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf


Patent Number 253221
Indian Patent Application Number 722/KOL/2007
PG Journal Number 27/2012
Publication Date 06-Jul-2012
Grant Date 04-Jul-2012
Date of Filing 09-May-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 TODD J. THOR 15331 MURRAY BYRON, MICHIGAN 48418
PCT International Classification Number H02K 7/10
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/819,005 2006-07-06 U.S.A.
2 11/739,904 2007-04-25 U.S.A.