Torque converter clutch control

Claim 1

A method of operating a torque converter clutch mechanism so as to avoid the passage of engine-torque perturbations therethrough, in a motor vehicle including a torque converter (12) having an input member (16) adapted to receive engine torque and an output member (26) adapted to supply torque to a vehicle drive train, torque converter clutch mechanism (50) connected between the input and output members (12 and 26) of the torque converter (12), the clutch mechanism (50) being operative when fully engaged to prevent slip between the input and output members (12 and 26) to thereby provide a torque capacity at least as great as the engine torque, and when less than fully engaged to permit slip between the input and output members (12 and 26) to thereby provide torque capacity less than the engine torque, and clutch actuating mechanism for controlling the torque capacity of the clutch mechanism (50) according to the fluid pressure in a control chamber (60) thereof, characterised in that the method comprises the steps of: measuring the torque converter slip; determining the difference between the measured slip and a reference slip amount; and altering the fluid pressure in the clutch actuating mechanism control chamber (60) according to the sense of such difference without regard to the magnitude of such difference, in a manner to increase or decrease the torque capacity of the clutch mechanism (50)at a predetermined rate when the measured slip is respectively greater than and less than the reference slip amount, the predetermined rate defining a predetermined time response characteristic which prevents significant increase or decrease of the clutch mechanism torque capacity in response to the relatively high frequency variations in slip due to engine torque perturbations while permitting increasing and decreasing of the clutch mechanism torque capacity in response to relatively low-frequency variations in slip due to changes in the engine torque and drive train load, such that the engine torque perturbations are absorbed in the torque converter (12) instead of in the drive train and that over a period of vehicle operation the average amount of torque converter slip is maintained at the reference slip amount.

Claim 4

A method according to any one of claims 1 to 3, characterised by the additional steps of: predicting the level of engine torque perturbation as a function of the engine load setting and the torque converter output member speed; and adjusting the reference slip amount in relation to the predicted level of engine torque perturbation such that the torque capacity of the clutch mechanism (50) is controlled at a value less than the lower peak excursion of the engine torque thereby to avoid full engagement of the clutch mechanism (50) and the consequent passage of the engine-torque perturbations therethrough.

Claim 5

A system for controlling the operation of a torque converter clutch mechanism so as to avoid the passage of engine torque perturbations therethrough, in a motor vehicle including a torque converter (12) having . an input member (16) adapted to receive engine torque and an output member (26) adapted to supply torque to a vehicle drive train, and torque converter clutch mechanism (50) connected between the input and output members (16 and 26) of the torque converter (12), the clutch mechanism_(50) being operative when fully engaged to prevent slip between the input and output members (16 and 26) to thereby provide a torque capacity at least as great as the engine torque, and when less than fully engaged to permit slip between the input and output members (16 and 26) to thereby provide a torque capacity less than the engine torque, characterised in that the system comprises slip control means including clutch actuating mechanism for controlling the torque capacity of the torque converter clutch mechanism (50) according to the fluid pressure in a control chamber (60) thereof, electrically operated valve means (122) connected to the control chamber (60) of the clutch actuating mechanism and energizable to produce variable fluid pressure therein for varying the torque capacity of the clutch ` mechanism (50), and slip-responsive means (180) for energizing the valve means (122) in a manner to increase or decrease the torque capacity of the clutch mechanism (50) according to a predetermined time response characteristic when the torque converter slip is respectively greater than or less than a reference slip amount without regard to the magnitude of the difference therebetween, t he predetermined time response characteristic being such that the slip control means is ineffective to significantly adjust the torque capacity of the clutch mechanism (50) in response to the relatively high frequency variations in slip due to engine torque perturbations, whereby the engine torque perturbations are absorbed in the torque converter (12) instead of the drive train and the average amount of torque converter slip over a period of vehicle operation is maintained at the reference slip amount.

Claim 8

A system according to any one of claims 5 to 7, characterised by reference means (202) for adjusting the reference slip amount in relation to a predicted level of engine torque perturbation such that the torque capacity of the clutch mechanism (50) is controlled at a value less than the lower peak excursion of the engine torque thereby to avoid full engagement of the clutch mechanism (50) and the consequent passage of the engine torque perturbation therethrough.

Claim 10

A system for controlling the operation of a torque converter clutch mechanism so as to avoid the passage of engine torque perturbations therethrough, in a motor vehicle including a source (68) of fluid pressure, a torque converter (12) having an input member (16) adapted to receive engine torque and an output member (26) adapted to supply torque to a vehicle drive train, and torque converter clutch mechanism (50) connected between the input and output members (16 and 26) of the torque converter (12), the clutch mechanism (50) being operative when fully engaged to prevent slip between the input and output members (16 and 26) to thereby provide a torque capacity at least as great as the engine torque, and when less than fully engaged to permit slip between the input and output member,3 (16 and 26) to thereby provide a torque capacity less tnan the engine torque, characterised in that the system comprises: clutch actuating means for developin, a clutch mechanism engagement force according to the fluid pressure in an apply chamber (60) thereof and a clutch disengagement force according to the fluid pressure in a release chamber (62) thereof for controlling the torque capacity of the clutch mechanism (50); fluid directing means connected between the fluid source (68) and the clutch actuating means and including first and second electrically actuated valve mechanisms (128 and 168), the first valve mechanism (128) being selectively actuable to a clutch enable state enabling clutch mechanism engagement, for which state the release chamber (62) of the clutch actuating means is exhausted to a low pressure level and the apply chamber (60) of the clutch actuating means is connected to the source (68) of fluid pressure by way of the second valve mechanism (122), and a clutch disable state disabling clutch mechanism engagement, for which state the apply chamber (60) is exhausted to a low pressure level and the release chamber (62) is connected to the source (68) of fluid pressure, and the second valve mechanism (122) being selectively actuable to an apply state for which fluid pressure from the first valve mechanism (128) is directed to the apply chamber (60) and a release state for which fluid pressure from the first valve mechanism (128) is exhausted to a low pressure level; and electronic control means (180) effective when control of the clutch mechanism (50) is desired for actuating the first valve mechanism (128) to its clutch enable state and for alternatively actuating the second valve mechanism (122) between its apply and release states at a duty cycle which increases or decreases the clutch mechanism engagement force according to a predetermined time response characteristic when the torque converter slip is respectively greater than or less than a reference slip amount without regard to the magnitude of the difference therebetween, the said predetermined time response characteristic being such that the slip control means is ineffective to significantly adjust the torque capacity of the clutch mechanism (50) in response to the relatively high frequency variations in slip due to engine torque perturbations, whereby the engine torque perturbations are absorbed in the torque converter (12) instead of the drive train, and the average value of the torque converter slip over a period of vehicle operation is maintained at the reference slip value.