Solenoid valve is used to control the fluid of the basic components of automation, are actuators; is not limited to hydraulic, pneumatic. Solenoid valve used to control the direction of hydraulic flow, the factory's mechanical devices are generally controlled by the hydraulic steel, it will use the solenoid valve. Solenoid valve works, the solenoid valve has a closed cavity, opened in different positions through-hole, each hole leads to a different tubing, the middle of the valve chamber, on both sides of the two electromagnets, which side of the magnet coil Energized valve body will be attracted to which side by moving the valve to control the body to live or leak different oil drain hole, and the inlet hole is normally open, the hydraulic oil will enter the different oil drain pipe, and then through The pressure of oil to promote the oil just piston, the piston and piston rod, piston rod driven mechanical device. This controls the mechanical movement by controlling the electromagnet current.