What is electromagnetic valve? What is its function?

Solenoid valve controls the position of valve core through an electromagnetic coil to achieve the purpose of changing the flow direction of fluid, or to cut off or connect air source.
The electromagnetic components of the commonly used four-way solenoid valve consist of fixed iron core, moving iron core, coil and other parts. The valve body consists of sliding valve core. Valve body, slide valve sleeve, spring base, etc.
The working principle of four-way solenoid valve is shown in figure 123a. When there is electricity flowing through the coil, excitation will be generated, and the iron core will be fixed to absorb the moving iron core. The moving iron core will drive the sliding valve core and compress the spring, which changes the position of the sliding valve core and thus changes the direction of the fluid. When the coil loses power, the sliding valve core is pushed by the spring's elasticity, and the iron core is pushed back to make the fluid flow in the original direction. This kind of solenoid valve can be used to control the switch of the valve in the switching system.
The working principle of the three-way solenoid valve is shown in figure 123b. It can be used to connect or cut off the air source, so as to switch the pneumatic control film Head air path. It consists of valve body, valve cover, electromagnetic assembly, spring, sealing structure and other parts. The sealing block at the bottom of the movable iron core closes the air inlet of the valve body with the help of the spring pressure. After the electromagnet is electrified, the sealing block with spring on the top of the moving iron core closes the air outlet, and the airflow enters the film head from the air inlet to play a controlling role. When the power is out, the electromagnetic force disappears. The moving iron core leaves the fixed iron core under the action of spring force and moves downward to open the air outlet and block the air inlet. The air flow at the film Head is discharged through the air outlet and the membrane returns to its original position. The three-way solenoid valve can be used in the emergency cut-off of the inlet thin film regulating valve of the turbine expansion machine and the control part of the emergency loading of the braking fan.
The working medium of solenoid valve is filtered clean compressed air, and the working pressure is 0.3 ~ 0.5MPa.