The hydraulic automatic control system usually consists of oil supply, manual gear selection, parameter adjustment, shift timing control, and shift quality control.
The oil supply part adjusts the oil pressure of the oil pump output to a prescribed value according to the change of the throttle opening degree and the position of the selector lever to form a stable working hydraulic pressure.
In the hydraulically controlled hydraulic automatic transmission, the parameter adjustment part mainly includes a throttle pressure regulating valve (referred to as a throttle valve) and a quick control pressure regulating valve (also called a governor). The throttle pressure regulating valve allows the output hydraulic pressure to reflect the throttle opening; the quick-control pressure regulating valve allows the output hydraulic pressure to reflect the speed of the vehicle.
The shift timing control portion is for switching an oil passage leading to each shift actuator (clutch and brake), thereby implementing shift control. The lock signal valve is controlled by the solenoid valve to properly engage and disengage the lockup clutch in the torque converter. The shift quality control section is used to make the shifting process smoother and softer.