Automatic transmission torque converter bypass clutch control using engine torque compensation

A method for controlling operation of a torque converter bypass clutch for use in a multiple-gear ratio automatic transmission of a motor vehicle having an engine controlled by a throttle position, comprising the steps of:

• determining a current engine output torque TQ NET;
• developing a bypass clutch schedule at a reference engine output torque BTR BASE, said bypass clutch schedule defining conditions under which the bypass clutch is to be unlocked;
• determining from said bypass clutch schedule a predetermined maximum bypass clutch unlock vehicle speed FN US above which the bypass clutch can unlock;
• determining a bypass clutch vehicle speed adjustment to compensate for a difference between the current engine output torque TQ NET and the reference BTR BASE;
• calculating a bypass clutch unlock engine torque compensation vehicle speed from said bypass clutch vehicle speed adjustment and said predetermined maximum bypass clutch unlock vehicle speed;
• determining a current vehicle speed;
• comparing said current vehicle speed to the bypass clutch unlock engine torque compensation vehicle speed;
• and
• unlocking the bypass clutch when said comparison indicates that said current vehicle speed is less than said bypass clutch unlock engine torque compensation vehicle speed.

A method for controlling, with the aid of a digital computer, operation of a torque converter bypass clutch of a multiple-gear ratio automatic transmission for use in a motor vehicle having an engine controlled by a throttle position, comprising the steps of:

• providing said computer with a data base including at least:
• a bypass clutch schedule at a reference engine output torque BTR BASE, wherein said schedule defining conditions under which the bypass clutch is to be locked and unlocked;
• a bypass clutch vehicle speed adjustment to compensate for a difference between a current engine output torque and the reference BTR BASE;
• repetitively determining in the computer;
• the current engine output torque TQ NET;
• repetitively determining from the bypass clutch schedule a predetermined minimum bypass clutch lock vehicle speed FN LS above which the bypass clutch can lock and a maximum bypass clutch unlock vehicle speed FN US below which the bypass clutch can unlock;
• repetitively determining the bypass clutch vehicle speed adjustment;
• repetitively calculating in the computer a bypass clutch lock engine torque compensation vehicle speed from said bypass clutch vehicle speed adjustment and said predetermined minimum bypass clutch lock vehicle speed, and a bypass clutch unlock engine torque compensation vehicle speed from said bypass clutch vehicle speed adjustment and said predetermined maximum bypass clutch lock vehicle speed;
• supply to the computer a current vehicle speed;
• repetitively comparing in the computer the current vehicle speed to the bypass clutch lock engine torque compensation vehicle speed and the bypass clutch unlock engine torque compensation vehicle speed;
• and
• locking the bypass clutch when said comparison indicates that the current vehicle speed exceeds said bypass clutch lock engine torque compensation vehicle speed and unlocking the bypass clutch when said comparison indicates that the current vehicle speed is less than said bypass clutch unlock engine torque compensation vehicle speed.

A system for controlling operation of a torque converter bypass clutch for use in a multiple-gear ratio automatic transmission of a motor vehicle, comprising:

• an engine having a variable position throttle for controlling the engine;
• memory means containing a bypass clutch schedule developed at reference engine output torque BTR BASE, the schedule defining conditions under which the bypass clutch is to be locked and unlocked, and a schedule from which the current magnitude of engine output torque can be determined;
• means for determining the current commanded gear ratio;
• means for calculating current engine output torque TQ NET;
• means for determining current vehicle speed;
• means for determining bypass vehicle speed adjustment to account for a difference between the current engine output torque and reference BTR BASE;
• means for determining from the bypass clutch schedule a predetermined bypass clutch lock vehicle speed FN LS above which the bypass clutch can lock;
• means for calculating bypass clutch lock engine torque compensation vehicle speed from said bypass clutch vehicle speed adjustment and said predetermined bypass clutch lock vehicle speed;
• means for comparing current vehicle speed to the bypass clutch lock engine torque compensated vehicle speed;
• and
• means for locking the bypass clutch when said comparison indicates current vehicle speed exceeds said bypass clutch lock engine torque compensated vehicle speed.