Title of Invention	A METHOD OF AND A SYSTEM FOR DYNAMICALLY CONTROLLING PRESSURE TO A TORQUE CONVERTER CLUTCH OF A TORQUE CONVERTER
Abstract	A method of dynamically controlling pressure to a torque converter clutch (TCC) of a torque converter coupled to a transmission is provided. The method includes: monitoring throttle position; monitoring engine speed; controlling pressure to the torque converter clutch to increase slip after the throttle position indicates a tip-in has occurred and when engine speed is low; regulating at least one of a transmission steady state pressure to the transmission and pressure to the torque converter to maintain the increased slip; and controlling pressure to the torque converter to reduce slip by engaging the torque converter clutch.

Title of Invention

A METHOD OF AND A SYSTEM FOR DYNAMICALLY CONTROLLING PRESSURE TO A TORQUE CONVERTER CLUTCH OF A TORQUE CONVERTER

Abstract

A method of dynamically controlling pressure to a torque converter clutch (TCC) of a torque converter coupled to a transmission is provided. The method includes: monitoring throttle position; monitoring engine speed; controlling pressure to the torque converter clutch to increase slip after the throttle position indicates a tip-in has occurred and when engine speed is low; regulating at least one of a transmission steady state pressure to the transmission and pressure to the torque converter to maintain the increased slip; and controlling pressure to the torque converter to reduce slip by engaging the torque converter clutch.

Full Text	Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 TORQUE CONVERTER CLUTCH DYNAMIC CONTROL FIELD [0001] The present disclosure relates to methods and systems for controlling a torque converter clutch. BACKGROUND [0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. [0003] Automatic transmissions use a fluid clutch known as a torque converter to transfer engine torque from the engine to the transmission. The torque converter operates through hydraulic force provided by pressurized fluid from the automatic transmission. The torque converter multiplies engine torque and directs it through the transmission. [0004] A conventional torque converter includes a sealed chamber filled with hydraulic fluid. The chamber includes a pump (or impeller) driven by the engine, a turbine connected to an output shaft, and a stator that provides torque multiplication. As the impeller rotates, the centrifugal force pushes the pressurized fluid outward, causing the turbine to rotate. Fluid exiting the turbine strikes the stator. Blades of the stator act to reverse the radial direction of the fluid's motion so that the fluid is moving the same direction as the impeller when it reenters the impeller chambers. This reversal of direction greatly increases the efficiency of the impeller. The force of the fluid striking the stator blades also 1 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 exerts torque on the turbine output shaft, providing additional torque multiplication equivalent to a higher numerical gear ratio. [0005] A torque converter is said to "slip" when the impeller speed and the turbine speed are not equivalent. High slip rates reduce the efficiency of the torque converter and may generate excessive heat. Some converters incorporate a lockup mechanism such as a mechanical clutch that engages at cruising speeds to physically link the impeller with the turbine. The physical link causes the impeller and the turbine to rotate at the same or near the same speed, thereby reducing or eliminating slip. The clutch is applied and released via fluid supplied through a hollow shaft at the center axis of the rotating converter assembly. [0006] Engaging the torque converter clutch is not desirable in all modes of vehicle operation. Lockup conditions prevent the torque converter from providing torque multiplication. Instances may occur, for example, when driving along the highway and the driver steps on the accelerator pedal to pass another vehicle (referred to below as a throttle tip-in). The vehicle is operating in a higher gear with low engine speed (i.e. less than 2000 rpm) and the torque converter clutch is locked. If the current speed is above the requisite speed to initiate a downshift, the engine will remain at the low speed and the lockup will prevent torque transfer that is sufficient to accelerate the vehicle. 2 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 SUMMARY [0007] Accordingly, a method of dynamically controlling pressure to a torque converter clutch (TCC) of a torque converter coupled to a transmission is provided. The method includes: monitoring throttle position; monitoring engine speed; controlling pressure to the torque converter clutch to increase slip after the throttle position indicates a tip-in has occurred and when engine speed is low; regulating at least one of a transmission steady state pressure to the transmission and pressure to the torque converter to maintain the increased slip; and controlling pressure to the torque converter to reduce slip by engaging the torque converter clutch. [0008] In other features, a dynamic torque converter clutch control system, for torque converters coupled to a transmission is provided. The system includes: a dynamic mode module that selects a current mode from an inactive mode, a target determination mode, a pressure regulation mode, and a pressure correction mode; a target determination module that determines target values for engine speed, engine torque and slip error based on the current mode and throttle position; and a torque convert clutch pressure control module that controls pressure to the torque converter clutch based on the current mode and the target values for engine speed, engine torque, and slip error. [0009] 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. 3 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 DRAWINGS [0010] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. [0011] Figure 1 is a functional block diagram of a vehicle including a conventional torque converter system. [0012] Figure 2 is a dataflow diagram illustrating the torque converter clutch (TCC) dynamic control system. [0013] Figure 3 is a graph illustrating modes of the TCC dynamic control system. [0014] Figure 4 is a state transition diagram illustrating the transitions between modes of the TCC dynamic control system. [0015] Figure 5 is a table that lists conditions for each TCC dynamic control transition. DETAILED DESCRIPTION [0016] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 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 executes one 4 Attorney Docket No. 8540P-000381 GM Reference No, GP-307730 or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. [0017] Figure 1 illustrates a vehicle 10 that includes a conventional torque converter system. An engine 12 combusts an air and fuel mixture to produce drive torque. Air is drawn into an intake manifold 14 through a throttle 16. The throttle 16 regulates mass air flow into the intake manifold 14. Air within the intake manifold 14 is distributed into cylinders 18. Although six cylinders 18 are illustrated, it can be appreciated that the engine can have a plurality of cylinders including, but not limited to, 2, 3, 5, 6, 8, 10, 12 and 16 cylinders. [0018] Torque from the engine 12 is supplied to a transmission 20 through a torque converter (TC) 22. The torque converter may be any known lockup converter including a turbine, a stator, and a torque converter clutch (TCC). The transmission includes a hydraulic pump 26 that regulates pressurized fluid within the transmission and controls fluid flow to and from the TC 22 via at least one solenoid-operated valve 30. The engine 12 drives the hydraulic pump 26. A current and/or pulse width modulated signal is commanded by a controller 32 to the solenoid in order to vary the supply of pressurized fluid to the torque converter 22. A slip rate of the TC 22 is varied based on control of the pressurized fluid. [0019] The controller 32 determines the appropriate signal based on inputs received from the TC 22, the engine 12, and the transmission 20. Inputs to the controller 32 may include: an engine speed signal received from an engine speed sensor 34; a turbine speed signal received from a turbine speed sensor 5 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 36; a throttle position signal received from a throttle position sensor 38, and a transmission oil temperature signal received from a transmission oil temperature sensor 40. During normal operating conditions, the controller 32 determines the appropriate pressure to be supplied to the TC 22 based on conventional methods and commands the signal to the solenoid 30 accordingly. During low engine speed conditions (i.e. less than 2000 RPM) after a throttle tip-in occurs, the controller commands the signal to the solenoid 30 according to the TCC dynamic control method of the present disclosure. [0020] Referring to Figure 2, a dataflow diagram illustrates various embodiments of a TCC dynamic control system 44 that implements the TCC dynamic control method. The TCC dynamic control system operates to command hydraulic pressure to the TCC. More specifically, the dynamic control system operates to apply the TCC via the pressurized fluid at low engine speeds (i.e. less than 2000 rpm) and after throttle tip-in operating conditions occur. Various embodiments of TCC dynamic control systems according to the present disclosure may include any number of sub-modules embedded within the controller 32 of Figure 1. [0021] In various embodiments, the TCC dynamic control system 44 of Figure 2 includes a dynamic mode module 46, a target determination module 48, a TCC pressure control module 50, and a steady state (SS) pressure control module 52. The sub-modules shown may be combined and/or further partitioned to provide similar control of hydraulic pressure to the TC 22. After throttle tip-in conditions occur, the modules act collectively to control TCC pressure 56 to 6 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 increase TCC slip, regulate a transmission steady state pressure 54 and TCC pressure 56 to control the higher slip, and then control TCC pressure 56 to reduce slip to meet the TCC on mode requirements. [0022] In order to control slip in this manner, the TCC dynamic control system 44 transitions through a plurality of modes. The dynamic mode module 46 determines a current mode 57 based on inputs such as throttle position 58, engine speed 60, transmission temperature 62, turbine speed 64, and a TCC mode request 66. The current mode 80 can be at least one of an inactive mode, a target determination mode, a maintain mode, a pressure correction mode, and a pressure regulation mode. Based on the current mode, the target determination module 48 determines a target value for engine speed 68, slip error 70, and engine torque 72. Each target valve is determined based on an evaluation of throttle position 58. The target values (68-72) and the current mode 57 are used by the TCC pressure control module 50 and the SS pressure control module 52 to control hydraulic pressure to the torque converter 22 (Figure 1) and the transmission 20 (Figure 1) respectively. [0023] The TCC pressure control module 50, more specifically, calculates a dynamic TCC pressure 56 as a function of target engine torque 72 and target engine speed 68. When in the target determination mode, TCC pressure is set equal to a minimum of the dynamic TCC pressure and the TCC pressure estimated for normal conditions. When in the maintain mode, TCC pressure remains equal to the dynamic TCC pressure calculated at the transition into the maintain mode. When in the pressure correction mode, TCC pressure is 7 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 set equal to the dynamic TCC pressure. When in the TCC pressure regulation mode, TCC pressure is set equal to the dynamic TCC pressure plus a ramp offset. The ramp offset is determined based on the target slip error 70. [0024] The SS pressure control module 52 determines a SS pressure 54 to be supplied to the transmission 20 (Figure 1). When in the target determination mode, the maintain mode, and the pressure correction mode, the SS pressure 54 is set to a maximum of a plurality of determined values. The SS pressure 54 can be set equal to the maximum of a determined steady state pressure, a steady state line pressure at time T-1, a base pressure plus a throttle modifier, and a base pressure plus a TCC throttle modifier. When in the pressure regulation mode, the SS pressure 54 is determined by the following two steps: during time T1 SS pressure 54 equals the SS pressure determined at the transition to the TCC pressure regulation mode; during time T2 SS pressure 54 is decreased according to a determined time ratio. [0025] Referring to Figure 3 in view of Figure 2, a graph illustrates the various modes of the TCC dynamic control system 44 and their sequential execution. The current mode is illustrated along the y-axis at 80. Time is illustrated along the x-axis at 82. TCC dynamic operation begins in the inactive mode 84. While in the inactive mode 84 TCC operation is controlled based on conventional TCC control methods. From the inactive mode 84, TCC dynamic operation transitions to the target determination mode 86 upon which the target determination module 48 determines target values for controlling TCC pressure. 8 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 Based on the target values, the TCC pressure control module 50 commands TCC pressure such that slip is increased. [0026] From the target determination mode 86, TCC dynamic operation transitions to the maintain mode 88. In the maintain mode 88, TCC pressure control module 50 commands the TCC pressure determined in the target determination mode in order to maintain the increased slip. The higher slip will increase torque output. Thus, causing the engine to accelerate according to the throttle tip-in request (high TCC slip leads to low hydraulic torque). From the maintain mode 88, TCC dynamic operation may transition to the pressure correction mode 90 or the pressure regulation mode 92. The pressure correction mode 90 is optional. The pressure correction mode 90 is activated to allow the TCC pressure control module 50 to correct TCC pressure based on a comparison of actual engine torque 94 and target engine torque 72. If the actual engine torque 94 is greater than target engine torque 72, the TCC pressure control module 50 commands TCC pressure such that slip is reduced. While in the pressure regulation mode 92, the TCC pressure control module 50 controls TCC pressure such that slip is reduced over time, until static regulation is reached. This causing a progressive acceleration of the vehicle. [0027] Referring now to Figures 4 and 5, the dynamic mode module 46 of Figure 2 determines when to transition between the five modes. The transitions are governed by a rule set including a plurality of conditions. A first transition occurs between the inactive mode 84 and the target determination mode 86 labeled as A in Figure 4. Control transitions from the inactive mode 84 9 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 to the target determination mode 86 based on throttle position, transmission temperature, and engine speed. Table 1 of Figure 5 lists conditions for transitioning from the inactive mode to the target determination mode. [0028] The filtered throttle gradient listed in Table 1 is determined from the following equation: K1 and K2 are predetermined constants. TG is a throttle gradient calculated based on throttle position at time T (TT) and throttle position at time T-1 (TT-1) and the following equation: TGprev is a previously calculated throttle gradient. [0029] A second transition occurs between the target determination mode 86 and the maintain mode 88 labeled as B in Figure 4. Control transitions from the target determination mode 86 to the maintain mode 88 based on time, throttle position, and engine torque. Table 1 of Figure 5 lists conditions for transitioning from the target determination mode 86 to the maintain mode 88. [0030] A third transition occurs between the maintain mode 88 and the pressure regulation mode 92 labeled as C in Figure 4. Control transitions from the maintain mode 88 to the pressure regulation mode 92 based on time, throttle position, and engine speed. Table 1 of Figure 5 lists exemplary conditions for transitioning from the maintain mode 88 to the pressure regulation mode 92. A fourth transition occurs between the pressure regulation mode 92 and the 10 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 inactive mode 84 labeled as D in Figure 4. Control transitions from the pressure regulation mode 92 back to the inactive mode 84 based on slip error, throttle position, engine speed, turbine speed, and a TCC On mode request. Table 1 of Figure 5 lists conditions for transitioning from the pressure regulation mode 92 to the inactive mode 84. [0031] A fifth optional transition occurs between the maintain mode 88 and the pressure correction mode 90 labeled as E in Figure 4. Control may transition from the maintain mode 88 to the pressure correction mode 90 based on time and engine speed. Table 1 of Figure 5 lists conditions for transitioning from the maintain mode 88 to the pressure correction mode 92. A sixth transition occurs between the pressure correction mode 90 and the pressure regulation mode 92 labeled as F in Figure 4. Control transitions from the pressure correction mode 90 to the pressure regulation mode 92 based on throttle position and engine speed. Table 1 of Figure 5 lists conditions for transitioning from the pressure correction mode 90 to the pressure regulation mode 92. [0032] As can be appreciated, all comparisons made in Tables 1 of Figure 5 can be implemented in various forms depending on the selected values for the minimums, the maximums, the ranges, and the threshold values. For example, a comparison of "greater than" may be implemented as "greater than or equal to" in various embodiments. Similarly, a comparison of "less than" may be implemented as "less than or equal to" in various embodiments. A comparison of "within a range" may be equivalently implemented as a comparison of "less than 11 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 or equal to a maximum threshold" and "greater than or equal to a minimum threshold" in various embodiments. [0033] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, 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, specification, and the following claims. 12 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 CLAIMS What is claimed is: 1. A method of dynamically controlling pressure to a torque converter clutch (TCC) of a torque converter coupled to a transmission, comprising: monitoring throttle position; monitoring engine speed; controlling pressure to the torque converter clutch to increase slip after the throttle position indicates a tip-in has occurred and when engine speed is low; regulating at least one of a transmission steady state pressure to the transmission and pressure to the torque converter to maintain the increased slip; and controlling pressure to the torque converter to reduce slip by engaging the torque converter clutch. 2. The method of claim 1 further comprising: operating in at least one of a an inactive mode, a target determination mode, a maintain mode, a pressure correction mode, and a pressure regulation mode; transitioning between the at least one of the inactive mode, the target determination mode, the maintain mode, the pressure correction mode, and the pressure regulation mode based on at least one of throttle position, 13 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 engine speed, transmission temperature, turbine speed, and a TCC On request; and wherein the controlling and the regulating are based on the one of the inactive mode, the target determination mode, the maintain mode, the pressure correction mode, and the pressure regulation mode. 3. The method of claim 1 further comprising: determining a target engine speed, a target engine torque, and a target slip error based on throttle position; and wherein the controlling and the regulating are based on the target values. 4. The method of claim 2 further comprising: determining a throttle gradient from a first throttle position and a second throttle position; determining a filtered throttle gradient based on a first throttle gradient and a second throttle gradient; and wherein the transitioning is based on the throttle gradient and the filtered throttle gradient. 14 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 5. The method of claim 4 wherein the throttle gradient (TG) is calculated based on a first throttle position at time T (TT), a second throttle position at time T-1 (TT-1), a current execution time (Loop Rate), and from an equation: 6. The method of claim 4 wherein the filtered throttle gradient (TGFilt) is calculated based on constants (K1 and K2), a first throttle gradient (TG), a second throttle gradient that is calculated previous (TGprev) to the first throttle gradient (TG), and from an equation: A dynamic torque converter clutch control system, for torque converters coupled to a transmission, comprising: a dynamic mode module that selects a current mode from an inactive mode, a target determination mode, a pressure regulation mode, and a pressure correction mode; a target determination module that determines target values for engine speed, engine torque, and slip error based on the current mode and throttle position; and a torque convert clutch pressure control module that controls pressure to the torque converter clutch based on the current mode and the target values for engine speed, engine torque, and slip error. 15 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 7. The system of claim 7 further comprising a steady state pressure module that controls a steady state pressure to the transmission based on the mode. 8. The system of claim 7 wherein the dynamic mode module selects the mode based on at least one of throttle position, engine speed, transmission temperature, turbine speed, and a TCC mode request. 9. The system of claim 9 wherein the torque converter clutch pressure control module controls pressure to the torque converter to increase slip when in the target determination mode; to maintain the increased slip when in the maintain mode; and to decrease slip when in the pressure regulation mode. 10. The method of claim 9 wherein the torque converter control pressure control module corrects pressure to the torque converter clutch based on a comparison of actual engine torque and the target value for engine torque when in the pressure correction mode. 16 Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 17 11. The system of claim 8 wherein the steady state pressure module controls a steady state pressure to the transmission based on a maximum of a determined steady state pressure, a steady state line pressure at time T-1, a base pressure plus a throttle modifier, and a base pressure plus a throttle modifier for torque converter clutch. 12. The system of claim 12 wherein the steady state pressure module controls a steady state pressure by decreasing pressure according to a determined time ratio. 13. The system of claim 7 wherein the dynamic mode module determines a current mode based on a throttle gradient and a filtered throttle gradient. 14. The system of claim 14 wherein the dynamic mode module calculates the throttle gradient (TG) based on a first throttle position at time T (TT), a second throttle position at time T-1 (TT-1), a current execution time (Loop Rate), and from an equation: Attorney Docket No. 8540P-000381 GM Reference No. GP-307730 15. The system of claim 14 wherein the dynamic mode module calculates a filtered throttle gradient (TGFilt) based on constants (K1 and K2), a first throttle gradient (TG), a second throttle gradient that calculated previously (TGprev), and from an equation: 16. The system of claim 7 wherein the dynamic mode module governs transitions between at least one of the inactive mode, the target determination mode, the pressure regulation mode, and the pressure correction mode based on the current mode. Dated this 30th day of AUGUST 2007 18 A method of dynamically controlling pressure to a torque converter clutch (TCC) of a torque converter coupled to a transmission is provided. The method includes: monitoring throttle position; monitoring engine speed; controlling pressure to the torque converter clutch to increase slip after the throttle position indicates a tip-in has occurred and when engine speed is low; regulating at least one of a transmission steady state pressure to the transmission and pressure to the torque converter to maintain the increased slip; and controlling pressure to the torque converter to reduce slip by engaging the torque converter clutch.

Full Text

Attorney Docket No. 8540P-000381
GM Reference No. GP-307730
TORQUE CONVERTER CLUTCH DYNAMIC CONTROL
FIELD
[0001] The present disclosure relates to methods and systems for
controlling a torque converter clutch.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0003] Automatic transmissions use a fluid clutch known as a torque
converter to transfer engine torque from the engine to the transmission. The
torque converter operates through hydraulic force provided by pressurized fluid
from the automatic transmission. The torque converter multiplies engine torque
and directs it through the transmission.
[0004] A conventional torque converter includes a sealed chamber
filled with hydraulic fluid. The chamber includes a pump (or impeller) driven by
the engine, a turbine connected to an output shaft, and a stator that provides
torque multiplication. As the impeller rotates, the centrifugal force pushes the
pressurized fluid outward, causing the turbine to rotate. Fluid exiting the turbine
strikes the stator. Blades of the stator act to reverse the radial direction of the
fluid's motion so that the fluid is moving the same direction as the impeller when
it reenters the impeller chambers. This reversal of direction greatly increases the
efficiency of the impeller. The force of the fluid striking the stator blades also
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Attorney Docket No. 8540P-000381
GM Reference No. GP-307730
exerts torque on the turbine output shaft, providing additional torque
multiplication equivalent to a higher numerical gear ratio.
[0005] A torque converter is said to "slip" when the impeller speed and
the turbine speed are not equivalent. High slip rates reduce the efficiency of the
torque converter and may generate excessive heat. Some converters
incorporate a lockup mechanism such as a mechanical clutch that engages at
cruising speeds to physically link the impeller with the turbine. The physical link
causes the impeller and the turbine to rotate at the same or near the same
speed, thereby reducing or eliminating slip. The clutch is applied and released
via fluid supplied through a hollow shaft at the center axis of the rotating
converter assembly.
[0006] Engaging the torque converter clutch is not desirable in all
modes of vehicle operation. Lockup conditions prevent the torque converter from
providing torque multiplication. Instances may occur, for example, when driving
along the highway and the driver steps on the accelerator pedal to pass another
vehicle (referred to below as a throttle tip-in). The vehicle is operating in a higher
gear with low engine speed (i.e. less than 2000 rpm) and the torque converter
clutch is locked. If the current speed is above the requisite speed to initiate a
downshift, the engine will remain at the low speed and the lockup will prevent
torque transfer that is sufficient to accelerate the vehicle.
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Attorney Docket No. 8540P-000381
GM Reference No. GP-307730
SUMMARY
[0007] Accordingly, a method of dynamically controlling pressure to a
torque converter clutch (TCC) of a torque converter coupled to a transmission is
provided. The method includes: monitoring throttle position; monitoring engine
speed; controlling pressure to the torque converter clutch to increase slip after
the throttle position indicates a tip-in has occurred and when engine speed is low;
regulating at least one of a transmission steady state pressure to the
transmission and pressure to the torque converter to maintain the increased slip;
and controlling pressure to the torque converter to reduce slip by engaging the
torque converter clutch.
[0008] In other features, a dynamic torque converter clutch control
system, for torque converters coupled to a transmission is provided. The system
includes: a dynamic mode module that selects a current mode from an inactive
mode, a target determination mode, a pressure regulation mode, and a pressure
correction mode; a target determination module that determines target values for
engine speed, engine torque and slip error based on the current mode and
throttle position; and a torque convert clutch pressure control module that
controls pressure to the torque converter clutch based on the current mode and
the target values for engine speed, engine torque, and slip error.
[0009] 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.
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Attorney Docket No. 8540P-000381
GM Reference No. GP-307730
DRAWINGS
[0010] The drawings described herein are for illustration purposes only
and are not intended to limit the scope of the present disclosure in any way.
[0011] Figure 1 is a functional block diagram of a vehicle including a
conventional torque converter system.
[0012] Figure 2 is a dataflow diagram illustrating the torque converter
clutch (TCC) dynamic control system.
[0013] Figure 3 is a graph illustrating modes of the TCC dynamic
control system.
[0014] Figure 4 is a state transition diagram illustrating the transitions
between modes of the TCC dynamic control system.
[0015] Figure 5 is a table that lists conditions for each TCC dynamic
control transition.
DETAILED DESCRIPTION
[0016] The following description is merely exemplary in nature and is
not intended to limit the present disclosure, application, or uses. It should be
understood that throughout the drawings, corresponding reference numerals
indicate like or corresponding parts and features. 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 executes one
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Attorney Docket No. 8540P-000381
GM Reference No, GP-307730
or more software or firmware programs, a combinational logic circuit, and/or
other suitable components that provide the described functionality.
[0017] Figure 1 illustrates a vehicle 10 that includes a conventional
torque converter system. An engine 12 combusts an air and fuel mixture to
produce drive torque. Air is drawn into an intake manifold 14 through a throttle
16. The throttle 16 regulates mass air flow into the intake manifold 14. Air within
the intake manifold 14 is distributed into cylinders 18. Although six cylinders 18
are illustrated, it can be appreciated that the engine can have a plurality of
cylinders including, but not limited to, 2, 3, 5, 6, 8, 10, 12 and 16 cylinders.
[0018] Torque from the engine 12 is supplied to a transmission 20
through a torque converter (TC) 22. The torque converter may be any known
lockup converter including a turbine, a stator, and a torque converter clutch
(TCC). The transmission includes a hydraulic pump 26 that regulates
pressurized fluid within the transmission and controls fluid flow to and from the
TC 22 via at least one solenoid-operated valve 30. The engine 12 drives the
hydraulic pump 26. A current and/or pulse width modulated signal is
commanded by a controller 32 to the solenoid in order to vary the supply of
pressurized fluid to the torque converter 22. A slip rate of the TC 22 is varied
based on control of the pressurized fluid.
[0019] The controller 32 determines the appropriate signal based on
inputs received from the TC 22, the engine 12, and the transmission 20. Inputs
to the controller 32 may include: an engine speed signal received from an engine
speed sensor 34; a turbine speed signal received from a turbine speed sensor
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Attorney Docket No. 8540P-000381
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36; a throttle position signal received from a throttle position sensor 38, and a
transmission oil temperature signal received from a transmission oil temperature
sensor 40. During normal operating conditions, the controller 32 determines the
appropriate pressure to be supplied to the TC 22 based on conventional methods
and commands the signal to the solenoid 30 accordingly. During low engine
speed conditions (i.e. less than 2000 RPM) after a throttle tip-in occurs, the
controller commands the signal to the solenoid 30 according to the TCC dynamic
control method of the present disclosure.
[0020] Referring to Figure 2, a dataflow diagram illustrates various
embodiments of a TCC dynamic control system 44 that implements the TCC
dynamic control method. The TCC dynamic control system operates to
command hydraulic pressure to the TCC. More specifically, the dynamic control
system operates to apply the TCC via the pressurized fluid at low engine speeds
(i.e. less than 2000 rpm) and after throttle tip-in operating conditions occur.
Various embodiments of TCC dynamic control systems according to the present
disclosure may include any number of sub-modules embedded within the
controller 32 of Figure 1.
[0021] In various embodiments, the TCC dynamic control system 44 of
Figure 2 includes a dynamic mode module 46, a target determination module 48,
a TCC pressure control module 50, and a steady state (SS) pressure control
module 52. The sub-modules shown may be combined and/or further partitioned
to provide similar control of hydraulic pressure to the TC 22. After throttle tip-in
conditions occur, the modules act collectively to control TCC pressure 56 to
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Attorney Docket No. 8540P-000381
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increase TCC slip, regulate a transmission steady state pressure 54 and TCC
pressure 56 to control the higher slip, and then control TCC pressure 56 to
reduce slip to meet the TCC on mode requirements.
[0022] In order to control slip in this manner, the TCC dynamic control
system 44 transitions through a plurality of modes. The dynamic mode module
46 determines a current mode 57 based on inputs such as throttle position 58,
engine speed 60, transmission temperature 62, turbine speed 64, and a TCC
mode request 66. The current mode 80 can be at least one of an inactive mode,
a target determination mode, a maintain mode, a pressure correction mode, and
a pressure regulation mode. Based on the current mode, the target
determination module 48 determines a target value for engine speed 68, slip
error 70, and engine torque 72. Each target valve is determined based on an
evaluation of throttle position 58. The target values (68-72) and the current mode
57 are used by the TCC pressure control module 50 and the SS pressure control
module 52 to control hydraulic pressure to the torque converter 22 (Figure 1) and
the transmission 20 (Figure 1) respectively.
[0023] The TCC pressure control module 50, more specifically,
calculates a dynamic TCC pressure 56 as a function of target engine torque 72
and target engine speed 68. When in the target determination mode, TCC
pressure is set equal to a minimum of the dynamic TCC pressure and the TCC
pressure estimated for normal conditions. When in the maintain mode, TCC
pressure remains equal to the dynamic TCC pressure calculated at the transition
into the maintain mode. When in the pressure correction mode, TCC pressure is
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Attorney Docket No. 8540P-000381
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set equal to the dynamic TCC pressure. When in the TCC pressure regulation
mode, TCC pressure is set equal to the dynamic TCC pressure plus a ramp
offset. The ramp offset is determined based on the target slip error 70.
[0024] The SS pressure control module 52 determines a SS pressure
54 to be supplied to the transmission 20 (Figure 1). When in the target
determination mode, the maintain mode, and the pressure correction mode, the
SS pressure 54 is set to a maximum of a plurality of determined values. The SS
pressure 54 can be set equal to the maximum of a determined steady state
pressure, a steady state line pressure at time T-1, a base pressure plus a throttle
modifier, and a base pressure plus a TCC throttle modifier. When in the
pressure regulation mode, the SS pressure 54 is determined by the following two
steps: during time T1 SS pressure 54 equals the SS pressure determined at the
transition to the TCC pressure regulation mode; during time T2 SS pressure 54 is
decreased according to a determined time ratio.
[0025] Referring to Figure 3 in view of Figure 2, a graph illustrates the
various modes of the TCC dynamic control system 44 and their sequential
execution. The current mode is illustrated along the y-axis at 80. Time is
illustrated along the x-axis at 82. TCC dynamic operation begins in the inactive
mode 84. While in the inactive mode 84 TCC operation is controlled based on
conventional TCC control methods. From the inactive mode 84, TCC dynamic
operation transitions to the target determination mode 86 upon which the target
determination module 48 determines target values for controlling TCC pressure.
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Attorney Docket No. 8540P-000381
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Based on the target values, the TCC pressure control module 50 commands
TCC pressure such that slip is increased.
[0026] From the target determination mode 86, TCC dynamic operation
transitions to the maintain mode 88. In the maintain mode 88, TCC pressure
control module 50 commands the TCC pressure determined in the target
determination mode in order to maintain the increased slip. The higher slip will
increase torque output. Thus, causing the engine to accelerate according to the
throttle tip-in request (high TCC slip leads to low hydraulic torque). From the
maintain mode 88, TCC dynamic operation may transition to the pressure
correction mode 90 or the pressure regulation mode 92. The pressure correction
mode 90 is optional. The pressure correction mode 90 is activated to allow the
TCC pressure control module 50 to correct TCC pressure based on a
comparison of actual engine torque 94 and target engine torque 72. If the actual
engine torque 94 is greater than target engine torque 72, the TCC pressure
control module 50 commands TCC pressure such that slip is reduced. While in
the pressure regulation mode 92, the TCC pressure control module 50 controls
TCC pressure such that slip is reduced over time, until static regulation is
reached. This causing a progressive acceleration of the vehicle.
[0027] Referring now to Figures 4 and 5, the dynamic mode module 46
of Figure 2 determines when to transition between the five modes. The
transitions are governed by a rule set including a plurality of conditions. A first
transition occurs between the inactive mode 84 and the target determination
mode 86 labeled as A in Figure 4. Control transitions from the inactive mode 84
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Attorney Docket No. 8540P-000381
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to the target determination mode 86 based on throttle position, transmission
temperature, and engine speed. Table 1 of Figure 5 lists conditions for
transitioning from the inactive mode to the target determination mode.
[0028] The filtered throttle gradient listed in Table 1 is determined from
the following equation:

K1 and K2 are predetermined constants. TG is a throttle gradient calculated
based on throttle position at time T (TT) and throttle position at time T-1 (TT-1) and
the following equation:

TGprev is a previously calculated throttle gradient.
[0029] A second transition occurs between the target determination
mode 86 and the maintain mode 88 labeled as B in Figure 4. Control transitions
from the target determination mode 86 to the maintain mode 88 based on time,
throttle position, and engine torque. Table 1 of Figure 5 lists conditions for
transitioning from the target determination mode 86 to the maintain mode 88.
[0030] A third transition occurs between the maintain mode 88 and the
pressure regulation mode 92 labeled as C in Figure 4. Control transitions from
the maintain mode 88 to the pressure regulation mode 92 based on time, throttle
position, and engine speed. Table 1 of Figure 5 lists exemplary conditions for
transitioning from the maintain mode 88 to the pressure regulation mode 92. A
fourth transition occurs between the pressure regulation mode 92 and the
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Attorney Docket No. 8540P-000381
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inactive mode 84 labeled as D in Figure 4. Control transitions from the pressure
regulation mode 92 back to the inactive mode 84 based on slip error, throttle
position, engine speed, turbine speed, and a TCC On mode request. Table 1 of
Figure 5 lists conditions for transitioning from the pressure regulation mode 92 to
the inactive mode 84.
[0031] A fifth optional transition occurs between the maintain mode 88
and the pressure correction mode 90 labeled as E in Figure 4. Control may
transition from the maintain mode 88 to the pressure correction mode 90 based
on time and engine speed. Table 1 of Figure 5 lists conditions for transitioning
from the maintain mode 88 to the pressure correction mode 92. A sixth transition
occurs between the pressure correction mode 90 and the pressure regulation
mode 92 labeled as F in Figure 4. Control transitions from the pressure
correction mode 90 to the pressure regulation mode 92 based on throttle position
and engine speed. Table 1 of Figure 5 lists conditions for transitioning from the
pressure correction mode 90 to the pressure regulation mode 92.
[0032] As can be appreciated, all comparisons made in Tables 1 of
Figure 5 can be implemented in various forms depending on the selected values
for the minimums, the maximums, the ranges, and the threshold values. For
example, a comparison of "greater than" may be implemented as "greater than or
equal to" in various embodiments. Similarly, a comparison of "less than" may be
implemented as "less than or equal to" in various embodiments. A comparison of
"within a range" may be equivalently implemented as a comparison of "less than
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Attorney Docket No. 8540P-000381
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or equal to a maximum threshold" and "greater than or equal to a minimum
threshold" in various embodiments.
[0033] Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the present disclosure can be
implemented in a variety of forms. Therefore, while this disclosure has been
described in connection with particular examples thereof, 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, specification,
and the following claims.
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Attorney Docket No. 8540P-000381
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CLAIMS
What is claimed is:
1. A method of dynamically controlling pressure to a torque converter
clutch (TCC) of a torque converter coupled to a transmission, comprising:
monitoring throttle position;
monitoring engine speed;
controlling pressure to the torque converter clutch to increase slip
after the throttle position indicates a tip-in has occurred and when engine speed
is low;
regulating at least one of a transmission steady state pressure to
the transmission and pressure to the torque converter to maintain the increased
slip; and
controlling pressure to the torque converter to reduce slip by
engaging the torque converter clutch.
2. The method of claim 1 further comprising:
operating in at least one of a an inactive mode, a target
determination mode, a maintain mode, a pressure correction mode, and a
pressure regulation mode;
transitioning between the at least one of the inactive mode, the
target determination mode, the maintain mode, the pressure correction mode,
and the pressure regulation mode based on at least one of throttle position,
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Attorney Docket No. 8540P-000381
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engine speed, transmission temperature, turbine speed, and a TCC On request;
and
wherein the controlling and the regulating are based on the one of
the inactive mode, the target determination mode, the maintain mode, the
pressure correction mode, and the pressure regulation mode.
3. The method of claim 1 further comprising:
determining a target engine speed, a target engine torque, and a
target slip error based on throttle position;
and wherein the controlling and the regulating are based on the
target values.
4. The method of claim 2 further comprising:
determining a throttle gradient from a first throttle position and a
second throttle position;
determining a filtered throttle gradient based on a first throttle
gradient and a second throttle gradient; and
wherein the transitioning is based on the throttle gradient and the
filtered throttle gradient.
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Attorney Docket No. 8540P-000381
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5. The method of claim 4 wherein the throttle gradient (TG) is
calculated based on a first throttle position at time T (TT), a second throttle
position at time T-1 (TT-1), a current execution time (Loop Rate), and from an
equation:

6. The method of claim 4 wherein the filtered throttle gradient (TGFilt)
is calculated based on constants (K1 and K2), a first throttle gradient (TG), a
second throttle gradient that is calculated previous (TGprev) to the first throttle
gradient (TG), and from an equation:

A dynamic torque converter clutch control system, for torque converters
coupled to a transmission, comprising:
a dynamic mode module that selects a current mode from an
inactive mode, a target determination mode, a pressure regulation mode, and a
pressure correction mode;
a target determination module that determines target values for
engine speed, engine torque, and slip error based on the current mode and
throttle position; and
a torque convert clutch pressure control module that controls
pressure to the torque converter clutch based on the current mode and the target
values for engine speed, engine torque, and slip error.
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Attorney Docket No. 8540P-000381
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7. The system of claim 7 further comprising a steady state pressure
module that controls a steady state pressure to the transmission based on the
mode.
8. The system of claim 7 wherein the dynamic mode module selects
the mode based on at least one of throttle position, engine speed, transmission
temperature, turbine speed, and a TCC mode request.
9. The system of claim 9 wherein the torque converter clutch pressure
control module controls pressure to the torque converter to increase slip when in
the target determination mode; to maintain the increased slip when in the
maintain mode; and to decrease slip when in the pressure regulation mode.
10. The method of claim 9 wherein the torque converter control
pressure control module corrects pressure to the torque converter clutch based
on a comparison of actual engine torque and the target value for engine torque
when in the pressure correction mode.
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17
11. The system of claim 8 wherein the steady state pressure module
controls a steady state pressure to the transmission based on a maximum of a
determined steady state pressure, a steady state line pressure at time T-1, a
base pressure plus a throttle modifier, and a base pressure plus a throttle
modifier for torque converter clutch.
12. The system of claim 12 wherein the steady state pressure module
controls a steady state pressure by decreasing pressure according to a
determined time ratio.
13. The system of claim 7 wherein the dynamic mode module
determines a current mode based on a throttle gradient and a filtered throttle
gradient.
14. The system of claim 14 wherein the dynamic mode module
calculates the throttle gradient (TG) based on a first throttle position at time T
(TT), a second throttle position at time T-1 (TT-1), a current execution time (Loop
Rate), and from an equation:

Attorney Docket No. 8540P-000381
GM Reference No. GP-307730
15. The system of claim 14 wherein the dynamic mode module
calculates a filtered throttle gradient (TGFilt) based on constants (K1 and K2), a
first throttle gradient (TG), a second throttle gradient that calculated previously
(TGprev), and from an equation:

16. The system of claim 7 wherein the dynamic mode module governs
transitions between at least one of the inactive mode, the target determination
mode, the pressure regulation mode, and the pressure correction mode based on
the current mode.
Dated this 30th day of AUGUST 2007

18

A method of dynamically controlling pressure to a torque converter clutch
(TCC) of a torque converter coupled to a transmission is provided. The method
includes: monitoring throttle position; monitoring engine speed; controlling
pressure to the torque converter clutch to increase slip after the throttle position
indicates a tip-in has occurred and when engine speed is low; regulating at least
one of a transmission steady state pressure to the transmission and pressure to
the torque converter to maintain the increased slip; and controlling pressure to
the torque converter to reduce slip by engaging the torque converter clutch.

A METHOD OF AND A SYSTEM FOR DYNAMICALLY CONTROLLING PRESSURE TO A TORQUE CONVERTER CLUTCH OF A TORQUE CONVERTER

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