Solenoid valves are automated basic components used to control fluids and are actuators; not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. The mechanical mechanisms of the plant are generally controlled by hydraulic steel, so solenoid valves are used. Working principle: There are closed chambers in the solenoid valve. There are through holes in different positions. Each hole leads to different oil pipes. The middle of the cavity is a valve. On both sides are two electromagnets. Which side of the magnet coil is energized? It will be attracted to which side, by controlling the movement of the valve body to block or leak different oil drain holes, and the oil inlet hole is normally open, the hydraulic oil will enter different oil drain pipes, and then pass the oil pressure To push the piston of the oil, the piston drives the piston rod, and the piston cymbal drives the mechanical device. This controls the mechanical motion by controlling the current of the electromagnet. Classification - Direct-acting solenoid valve: Principle: When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, the spring presses the closing member against the valve seat, and the valve closes. . Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm. Distributed direct-acting solenoid valve: Principle: It is a combination of direct-acting and pilot-operated. When there is no pressure difference between the inlet and the outlet, after the power is applied, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upward. The valve opens. When the inlet and outlet reach the starting pressure difference, after the energization, the electromagnetic force leads the small valve, the pressure of the lower chamber of the main valve rises, and the pressure of the upper chamber drops, so that the main valve is pushed upward by the pressure difference; when the power is off, the pilot valve uses the spring The force or medium pressure pushes the closure and moves down to close the valve. Features: It can also be operated at zero differential pressure or vacuum or high pressure, but the power is large and requires horizontal installation.