, Properties and Uses: solenoid valve with solenoid suction to push to transform the direction of fluid flow control valve spool movement, referred to as the solenoid valve. Solenoid valve spool valve and ball valve two structures, commonly referred to as the solenoid valve slide valve structure, known as spherical or conical spool solenoid valve solenoid seat valve, also known as electromagnetic ball valve. Commutation of the role of converting electromagnetic valve the relative operating position of the heart valve in the valve body, the valve ports connected or disconnected, thereby controlling the hydraulic actuators (such as hydraulic rod of the hydraulic motor), or start and stop. The performance requirements of the solenoid valve. Commutation performance under specified operating conditions, the solenoid valve is energized ability to reliably commutation ability to reliably reset after power failure. By the flow, the pressure loss solenoid valve pressure loss flow through the valve port when the solenoid valve flow losses and throttling losses. 3 internal leakage amount of the amount of internal leakage of the electromagnetic directional control valve is in the predetermined operating conditions, in a different operative position, the amount of leakage from the high pressure chamber to the low pressure chamber.