What is the working principle of solenoid valve?

     There are many kinds of solenoid valves. Different solenoid valves play a role in different positions of the control system. The common ones are one-way valve, direction control valve, speed control valve, etc.
First of all, let's talk about the working principle of the solenoid valve
There are closed cavities in the solenoid valve. There are through holes in different positions. Each hole is connected with different oil pipes. The piston is in the middle of the cavity, and two electromagnets are on both sides. The valve body will be attracted to which side when the magnet coil is energized. Different oil drain holes can be opened or closed by controlling the movement of the valve body. The oil inlet hole is normally open, and the hydraulic oil will enter into different oil drainage pipes and pass through The oil pressure pushes the piston of the oil cylinder, which in turn drives the piston rod, which drives the mechanical device. In this way, the mechanical movement is controlled by controlling the current of electromagnet.
The working principle of solenoid valve can be divided into three categories
1. Direct acting solenoid valve
When electrified, the electromagnetic coil produces electromagnetic force to lift the closing part from the valve seat and open the valve; when the power is off, the electromagnetic force disappears and the spring presses the closing part on the valve seat, and the valve is closed.
2. Step by step direct acting solenoid valve
When there is no pressure difference between the inlet and the outlet, the electromagnetic force will directly lift the small pilot valve and the closing part of the main valve in turn, and the valve will be opened. When the inlet and outlet reach the start-up pressure difference, after power on, the electromagnetic force pilot small valve, the pressure of the lower chamber of the main valve rises, and the pressure of the upper chamber decreases, so as to push the main valve upward by using the pressure difference; when the power is off, the pilot valve uses the spring force or medium pressure to push the closing part and move downward to close the valve.
3. Pilot operated solenoid valve
When electrified, the electromagnetic force opens the pilot hole, and the pressure of upper chamber drops rapidly When the power is cut off, the spring force will close the pilot hole, and the inlet pressure will quickly form a low pressure difference around the valve closing piece, and the fluid pressure will push the closing piece to move downward to close the valve. There are many kinds of solenoid valves. Different solenoid valves play a role in different positions of the control system. The common ones are one-way valve, direction control valve, speed control valve, etc.