Control system for controlling the pressure of the oncoming servo hydraulic pressure based on a predicted time to sync from output shaft acceleration in automatic transmission

摘要

A control system is provided for servo hydraulic pressure in an automatic transmission. Upon downshifting, one of first and second frictional engagement devices is released while the other is engaged. A directional control valve is provided to feed or drain servo hydraulic pressure to selectively engage or release the first and second devices. The hydraulic pressure is regulated by a pressure regulator under the control of an electronic control unit. Detectors are also provided to determine input rotation and torque, respectively. The regulator is interposed between the directional control valve and the engaged device. The regulator is controlled to maintain the servo hydraulic pressure at a predetermined value under the control of the electronic control unit until predetermined input rotation is detected and then to gradually raise the servo hydraulic pressure under the control of the electronic control on the basis of the value of input torque.