Classification of solenoid valves for automatic transmission hydraulic systems

On-off solenoid valve

Controlled by a switch signal output by the computer, the solenoid valve has two states: on and off.

Proportional solenoid valve

The throttle is controlled by a proportional solenoid. The output pressure of the throttle is linearly proportional to the input current of the solenoid.

Duty cycle type solenoid valve

Controlled by the duty signal output by the computer, the spool of the solenoid valve has numerous positions. Switch solenoid valves are mostly used for shift oil circuit control. Early vehicles also used lock-up clutch control. Proportional or duty-type solenoid valves were used for shift oil circuit, main oil pressure, accumulator back pressure, and lock Hydraulic control such as clutch.