CONTROL METHOD OF SERVO HYDRAULIC PRESSURE IN AUTOMATIC TRANSMISSION

摘要

A method is provided for the control of servo hydraulic pressure in an automatic transmission. Servo hydraulic pressure is adapted to engage or release first and second frictional engagement elements arranged in such a relationship that upon shifting from a particular speed stage to another, one of the first and second frictional engagement elements is released while the other is engaged. The servo hydraulic pressure is linearly lowered in a torque phase during a shift so that the servo hydraulic pressure on a side of the frictional engagement element to be released by using as an input the servo hydraulic pressure on a side of the frictional engagement element to be engaged is maintained in conformity with an inversely proportional relationship between engaging pressure and drain pressure.