Abstract: A technique for controlling the rate of engagement of a friction element in response to a commanded change in operating range of an automatic transmission. Hydraulic pressure at a blip magnitude fills the hydraulic cylinder of a friction element. The pressure magnitude at the base of a pressure ramp and a magnitude at the top of the ramp are calibrated over a range of transmission oil temperature for each type of range change required by the vehicle operator. The calibrations minimize the length of engagement and produce a smooth engagement. Execution of an algorithm produces a high level of pressure magnitude on the basis of these calibrated values, a step down at the base of a ramp, a rate of increase during the period of engagement, and a maximum pressure at the top of the ramp.

Abstract: A system and method for controlling the bypass clutch of an automatic transmission includes an electronic microprocessor, an electronic memory accessible to the microprocessor, solenoid-operated bypass valve, pressure actuated bypass clutche, a variable force solenoid-operated bypass valve, a torque converter bypass friction clutch, and control algorithms that produce output signals to control the state of the solenoid-operated valve. The vehicle speed at which the bypass clutch engages and disengages, according to a reference schedule, is compensated for loss of engine torque at conditions that differ from the conditions at which the reference schedule is defined. Vehicle speed is compensated for torque variation with reference to the ratio of current calculated engine torque divided by current engine output torque.

Abstract: A system and method for controlling gear ratio changes in an automatic transmission includes an electronic microprocessor, an electronic memory accessible to the microprocessor, solenoid-operated shift valves, pressure actuated friction clutches and brakes, a variable force solenoid-operated valve, a torque converter bypass friction clutch, and control algorithms that produce output signals to control the state of the solenoid-operated valves. The vehicle speed and engine speed at which upshifts and downshifts occur, according to a standard gear shift schedule, is compensated for loss of engine torque at conditions that differ from the conditions at which a reference shift schedule is defined. Vehicle speed is compensated for torque variation with reference to the ratio of current calculated engine torque divided by current engine output torque.