Clutch-to-clutch power-on downshifting in a motor vehicle automatic transmission

摘要

A clutch-to-clutch power-on downshift in a motor vehicle automatic transmission (l4) is effected by reducing the torque capacity of the off-going clutching device (28,30,32) to permit the transmission input speed to increase towards a target speed which it will finally attain subsequent to the shift; increasing the torque capacity of the off-going clutching device and preparing the on-coming clutching device when the input speed approaches its target speed, so that the input speed is held near the target speed by the time the on-coming clutching device is prepared to transmit torque; and concurrently applying and releasing the on-coming and off-going clutching devices to complete the shift.;Since the input speed is substantially at its target value when the interchange of the clutching devices occurs, a high-quality shift with minimal driveline torque disruption can be obtained.