METHOD OF CONTROLLING A DUAL CLUTCH TRANSMISSION

• US 20040166992A1
• Filed: 02/21/2003
• Published: 08/26/2004
• Est. Priority Date: 02/21/2003
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Lemon, Russell, Koenig, Melissa, Buchanan, Mark
• Granted Patent: US 6,790,159 B1
• Time in Patent Office: Days
• US Class Current: 477/181
• CPC Class Codes: B60W 2510/0241 Clutch slip, i.e. difference between input and output speeds
• CPC Class Codes: B60W 2510/0604 Throttle position
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2510/1015 Input shaft speed, e.g. turbine speed
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0644 Engine speed
• CPC Class Codes: B60W 2710/0661 Speed change rate
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: F16D 2500/1026 Hydraulic
• CPC Class Codes: F16D 2500/10412 Transmission line of a vehicle
• CPC Class Codes: F16D 2500/1086 Concentric shafts
• CPC Class Codes: F16D 2500/30426 Speed of the output shaft
• CPC Class Codes: F16D 2500/3061 Engine inlet air flow rate
• CPC Class Codes: F16D 2500/30806 Engaged transmission ratio
• CPC Class Codes: F16D 2500/50224 Drive-off
• CPC Class Codes: F16D 2500/5048 Stall prevention
• CPC Class Codes: F16D 2500/7044 Output shaft torque
• CPC Class Codes: F16D 2500/70454 Engine speed
• CPC Class Codes: F16D 48/06 Control by electric or electronic means, e.g. of fluid pressure
• CPC Class Codes: F16H 2306/52 Applying torque to new gears
• CPC Class Codes: F16H 2312/02 : Driving off
• CPC Class Codes: F16H 3/006 : power being selectively transmitted by either one of the parallel flow paths
• CPC Class Codes: F16H 3/0915 : with coaxial input and output shafts
• CPC Class Codes: F16H 61/0437 : by using electrical signals F16H61/0403 and F16H61/061 take precedence
• CPC Class Codes: F16H 61/688 : with two inputs, e.g. selection of one of two torque-flow paths by clutches

Abstract

A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission to provide predetermined engine acceleration for each gear based on the engine throttle position and subsequent changes of clutch speed that are in response to operatively varying the torque transferred across the engaged clutch as the engine accelerates to a predetermined speed based on the throttle position. The method includes the steps of determining the engine throttle position, determining the currently engaged gear of the transmission, and sensing the speed of the driven member of the engaged clutch. Then, a target engine speed is determined based on the engine throttle position, the currently engaged gear, and the clutch speed. The torque transferred across the engaged clutch is then continuously varied to cause the engine to accelerate toward the target engine speed.

Claims

1. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission to provide a predetermined engine acceleration curve for each gear based on the engine throttle position and subsequent changes of clutch speed as the engine accelerates to a predetermined speed based on the throttle position, said method includes the steps of:

sensing the engine throttle position;

determining the currently engaged gear of the transmission;

sensing the speed of the driven member of the engaged clutch;

determining a target engine speed based on the engine throttle position, the currently engaged gear, and the clutch speed; and

continuously varying the torque transferred across the engaged clutch to cause the engine to accelerate toward the target engine speed.

2. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 1 wherein the step of increasing the torque transferred across the clutch further includes the steps of:

determining a dynamic torque signal that represents the amount of torque that must be transferred across the engaged clutch to cause the engine to track the target engine speed in response to the throttle position;

determining a steady-state torque signal that represents an additional amount of torque that must be transferred across the engaged clutch to compensate for changes in driving conditions;

summing the dynamic torque signal and the steady-state torque signal to provide a target torque signal that represents the total amount of torque that must be transferred across the engaged clutch to cause the engine to track the target engine speed in response to the throttle position and changes in the driving conditions; and

varying the torque transferred across the clutch to cause the engine to track the target torque signal.

3. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 2 wherein the step of determining a dynamic torque signal further includes the steps of:

determining the actual engine speed;

comparing the target engine speed to the actual engine speed and producing a speed error signal; and

proportioning the value of the speed error signal to a relative value within a predetermined range to provide the dynamic torque signal.

4. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 2 wherein the step of determining a steady-state torque signal further includes the steps of:

determining the acceleration of the engine;

determining the acceleration of the engaged clutch;

summing the engine acceleration and the clutch acceleration to determine the clutch slip acceleration;

determining the actual dynamic torque transferred across the clutch from the clutch slip acceleration;

predicting a dynamic torque value that should be transferred across the engaged clutch for the given target torque signal;

determining a dynamic torque error by summing the actual dynamic torque and the predicted dynamic torque value, wherein this sum indicates that changes in driving conditions have occurred that must be compensated for by making a correction to the target torque signal; and

determining the steady-state torque signal by integrating the dynamic torque error, wherein this integration is the corrective value.

5. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 4 wherein the step of determining a steady-state torque signal further includes the steps of:

predicting the value of the steady state torque signal based on inputs from an engine controller when a change in throttle position results in a new engine target speed;

predicting the delay in the engine reaching the new target engine based on known engine response times to changes in the target torque signal; and

summing the predicted delay with the integrated dynamic torque error signal to provide the steady-state torque signal.

6. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 5 wherein the step of predicting a dynamic torque value further includes:

predicting the value of the total torque that should be transferred across the engaged clutch given the target torque signal, based on known transmission responses to the input of the target torque signal;

subtracting a feedback signal of the steady state torque value from the predicted total torque value to provide a predicted dynamic torque value.

7. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 1 wherein said method further includes the steps of:

determining the currently engaged gear of the transmission and sensing the clutch speed when a reduction in the engine throttle position is detected;

decreasing the pressure as applied to the engaged clutch as the engine decelerates thereby controlling the rate of vehicle deceleration;

determining an initial decelerating target engine speed based on the currently engaged gear and the engine throttle position;

varying the torque transferred across the engaged clutch to cause the engine speed to decelerate toward the initial decelerating target engine speed;

incrementally redetermining the target engine speed after the clutch speed reaches a predetermined percentage of the initial target engine speed due to the clutch response to the decreasing engine speed thereby causing the engine speed to track the decreasing target engine speed of said engine deceleration curve; and

continuously varying the torque transferred across the engaged clutch to cause the engine to decelerate along said engine deceleration curve.

8. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission to provide a predetermined engine acceleration curve for each gear based on the engine throttle position and subsequent changes of clutch speed in response to operatively increasing the torque transferred across the engaged clutch as the engine accelerates to a predetermined speed based on the throttle position, said method includes the steps of:

determining the engine throttle position;

determining the currently engaged gear of the transmission;

sensing the speed of the driven member of the engaged clutch;

selecting an engine stall speed for the current gear and engine throttle position at which an increasing transfer of torque across the engaged clutch will stop further engine acceleration and will hold the engine to a constant speed, from a look-up table;

determining a target engine speed based on the engine stall speed;

increasing the torque transferred across the engaged clutch so as to cause the actual engine speed to increase and approach the target engine speed;

continuously redetermining the target engine after the clutch speed reaches a predetermined percentage of the engine stall speed, the clutch speed increasing in response to the increasing engine speed thereby causing the engine speed to track the rising target engine speed of said engine acceleration curve; and

increasing the torque transferred across the engaged clutch so as to operatively lock the clutch and engine together as the clutch speed reaches a predetermined multiple of the engine stall speed.

9. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 8 wherein the step of continually redetermining the target engine speed further includes the steps of:

determining a dynamic torque signal that represents the amount of torque that must be transferred across the engaged clutch to cause the engine to track the target engine speed in response to the throttle position;

determining a steady-state torque signal that represents an additional amount of torque that must be transferred across the engaged clutch to compensate for changes in driving conditions;

summing the dynamic torque signal and the steady-state torque signal to provide a target torque signal that represents the total amount of torque that must be transferred across the engaged clutch to cause the engine to track the target engine speed in response to the throttle position and changes in the driving conditions; and

varying the torque transferred across the clutch to cause the engine to track the target torque signal.

10. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 9 wherein the step of determining a dynamic torque signal further includes the steps of:

determining actual engine speed;

comparing the target engine speed to the actual engine speed and producing a speed error signal; and

proportioning the value of the speed error signal to a relative value within a predetermined range to provide the dynamic torque signal.

11. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 9 wherein the step of determining a steady-state torque signal further includes the steps of:

determining the acceleration of the engine;

determining the acceleration of the engaged clutch;

summing the engine acceleration and the clutch acceleration to determine the clutch slip acceleration;

determining the actual dynamic torque transferred across the clutch from the clutch slip acceleration;

predicting a dynamic torque value that should be transferred across the engaged clutch for the given target torque signal;

determining a dynamic torque error by summing the actual dynamic torque and the predicted dynamic torque value, wherein this sum indicates that changes in driving conditions have occurred that must be compensated for by making a correction to the target torque signal; and

determining the steady-state torque signal by integrating the dynamic torque error, wherein this integration is the corrective value.

12. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 11 wherein the step of determining a steady-state torque signal further includes the steps of:

predicting the value of the steady state torque signal based on inputs from an engine controller when a change in throttle position results in a new engine target speed;

predicting the delay in the engine reaching the new target engine, based on known engine response times to changes in the target torque signal; and

summing the predicted delay with the integrated dynamic torque error signal to provide the steady-state torque signal.

13. A method of controlling the torque transferred across the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 11 wherein the step of predicting a dynamic torque value further includes:

predicting the value of the total torque that should be transferred across the engaged clutch given the target torque signal based on known transmission responses to the input of the target torque signal;

subtracting a feedback signal of the steady state torque value from the predicted total torque value to provide a predicted dynamic torque value.

14. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission to control the torque transferred across the engaged clutch thereby providing a predetermined engine acceleration curve for each gear based on the engine throttle position and subsequent changes of clutch speed in response to operatively varying the pressure on the engaged clutch as the engine accelerates to a predetermined speed based on the throttle position, said method includes the steps of:

determining the engine throttle position;

determining the currently engaged gear of the transmission;

sensing the speed of the driven member of the engaged clutch;

selecting an engine stall speed for the current gear and engine throttle position, at which the increasing pressure applied to the engaged clutch will stop further engine acceleration and will hold the engine to a constant speed, from a look-up table;

increasing the torque transferred across the engaged clutch so as to cause the engine speed to increase and approach the target engine speed thereby increasing the clutch speed and accelerating the vehicle;

reducing the pressure applied to the engaged clutch allowing the engine to continue to accelerate toward the target engine speed when the clutch speed reaches a predetermined percentage of the engine stall speed thereby continuing to increase the clutch speed and accelerating the vehicle;

continuously redetermining a target engine speed based on the engine stall speed and the clutch speed using a target engine speed equation that influences the rate of increase of engine and clutch speed after the clutch speed reaches the predetermined percentage of the engine stall speed, said target engine speed equation defined as;

$T=S+\frac{\{{\left[C+\left[\left(K-2\right)*S\right]\right\}}^2}{4*\left(K-1\right)*S}$

wherein T is the target engine speed, S is the stall speed determined for the current gear and throttle position, C is the clutch speed, and K is a control constant, the clutch speed increasing in response to the increasing engine speed thereby causing the engine speed to track the rising target engine speed; and

increasing the applied pressure on the engaged clutch so as to operatively lock the clutch and engine together as the clutch speed reaches a predetermined multiple of the engine stall speed.

15. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 14 wherein the step of reducing the pressure applied to the engaged clutch when the clutch speed reaches a predetermined percentage of the engine stall speed further includes the defining the predetermined percentage as the relationship ([2−

K]*S), where K is the chosen control constant and S is the stall speed for the given throttle position.

17. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 14 wherein the method further includes the step of increasing the applied pressure on the engaged clutch as the clutch speed reaches a predetermined multiple of the engine stall speed so as to prevent locking of the clutch and engine together but allow a small predetermined amount of slip to occur to provide for a smooth transfer of motive force between the clutch and engine.

18. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 14 further includes a the steps of:

performing a preparatory clutch pressure fill without a transfer of torque to the clutch that will be the engaged clutch for either first gear, or the gear immediately above or below the currently engaged gear, said preparatory clutch pressure fill performed to first gear clutch when the vehicle is stationary and performed to any other gear immediately prior to a shift; and

determining a standby portion of clutch actuation where no engine acceleration has yet occurred but said standby portion is representative of a period prior to the transfer of torque across the clutch that will drive the particular gear.

19. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 14 further includes a the steps of:

performing a predetermined nominal increase to the pressure applied to the clutch that drives first gear after the standby portion for first gear when first gear is engaged, said predetermined nominal pressure increase performed so as to cause a slight forward creep of the vehicle in anticipation of increased torque transfer across the clutch to drive the vehicle forward; and

determining a creep portion for first gear that is representative of said predetermined nominal pressure increase to the clutch, where only slight engine acceleration has occurred and said creep portion is representative of the period immediately prior to the transfer of torque across the clutch that will drive the first gear.

20. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 14 wherein said method further includes the steps of:

determining the currently engaged gear of the transmission and sensing the clutch speed when a reduction in the engine throttle position is detected;

decreasing the pressure as applied to the engaged clutch initially in a linear manner as the engine decelerates thereby controlling the rate of vehicle deceleration;

selecting an engine stall speed for the current gear and engine throttle position at which the increasing pressure applied to the engaged clutch will stop further engine acceleration and will hold the engine to a constant speed;

determining a target engine speed based on the engine stall speed and the clutch speed using a target engine speed equation that influences the rate of decrease of clutch engagement pressure, said target engine speed equation defined as;

$T=S+\frac{\{{\left[C+\left[\left(K-2\right)*S\right]\right\}}^2}{4*\left(K-1\right)*S}$

wherein T is the target engine speed, S is the stall speed determined for the current gear and throttle position, C is the clutch speed, and K is a control constant;

controlling the reduction in the pressure applied to the engaged clutch causing the engine speed to decelerate toward the target engine speed when the clutch speed reaches a predetermined percentage of the engine stall speed thereby continuing to decrease the clutch speed and decelerating the vehicle; and

continuously redetermining the target engine speed to create said engine deceleration curve after the clutch speed reaches the predetermined percentage of the engine stall speed due to the decrease in clutch speed in response to the decreasing engine speed thereby causing the engine speed to track the decreasing target engine speed of said engine deceleration curve.

16. A method of controlling the pressure applied to the engaged clutch of a vehicle having a dual clutch transmission as set forth in claim 16 wherein the step of increasing the applied pressure on the engaged clutch so as to operatively lock the clutch and engine together as the clutch speed reaches a predetermined multiple of the engine stall speed further includes defining the predetermined multiple of the engine stall speed as the relationship (K*S), where K is the chosen control constant and S is the stall speed for the given throttle position.