The solenoid valve of the automatic transmission (automatic gearbox) of a Subaru car performs the following functions:
* Shift: Control of the solenoid valves allows the transmission control module (TCM) to vary the hydraulic fluid pressure to shift gears.
* Fluid Flow Control: Solenoid valves regulate the flow of hydraulic fluid through various passages and valves within the automatic transmission to control transmission ratios and torque converter lockup.
* Torque Converter Lockup: The torque converter transmits rotation from the engine to the transmission. Some solenoid valves control fluid pressure to lock up the torque converter, improving power transmission efficiency.
* Fluid pressure: Solenoid valves regulate the fluid pressure inside the automatic transmission necessary to engage clutches and other components.
* Torque converter slip ratio: Some solenoid valves control the torque converter slip ratio, which affects vehicle acceleration and smooth shifting.
The operating principle of the automatic transmission solenoid valve is as follows:
* When the TCM sends a signal to the solenoid valve, electric current passes through the coil, creating a magnetic field.
* The magnetic field causes the valve piston to move, opening or closing the flow of hydraulic fluid.
* Valve piston position controls fluid pressure and flow through the various passages of the automatic transmission, allowing the TCM to change gears and other aspects of automatic transmission operation.
Solenoid valves in Subaru automatic transmissions are critical to ensuring smooth and efficient gear changes, controlling gear ratios and controlling fluid flow.