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Solenoid Valve Working Principle

Solenoid valves are industrial equipment controlled by electromagnetics. They are the basic components of automation used to control fluids. They belong to actuators; they are not limited to hydraulics and pneumatics. It is widely used in our daily life. First of all, we have a preliminary understanding of solenoid valves. Solenoid valves are composed of solenoid coils and magnetic cores, and are valve bodies containing one or more holes. When the coil is energized or de-energized, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off to achieve the purpose of changing the direction of the fluid.
The working principle of the solenoid valve: There is a closed cavity in the solenoid valve with through holes at different positions. Each hole leads to a different tubing. In the middle of the cavity is the valve. There are two electromagnets on both sides. Which side of the magnet coil is energized The valve body will be attracted to which side, by controlling the movement of the valve body to block or leak the different oil discharge holes, and the oil inlet hole is normally open, the hydraulic oil will enter the different oil discharge pipes and then pass the oil The pressure to push the piston of the cylinder, the piston drives the piston rod, and the piston rod drives the mechanical device to move. In this way, the mechanical movement is controlled by controlling the current of the electromagnet.
According to the principle, solenoid valves are divided into three categories: direct-acting, distributed direct-acting, and pilot-operated; according to their structure, they are divided into two types: diaphragm solenoid valves and piston solenoid valves.
Working principle of direct-acting solenoid valve:
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, and the spring presses the closing member on the valve seat, and the valve closes.
Working principle of distributed direct-acting solenoid valve:
It is a combination of direct-acting and pilot-acting principles. Normally closed type—when there is no pressure difference between the inlet and the outlet, the electromagnetic force directly opens the pilot hole to connect to the main valve after energization, and the piston is lifted upward in turn, and the valve opens; when the inlet and outlet reach the starting pressure difference, the electromagnetic force first When the pilot hole is opened, the pressure in the upper cavity of the main valve piston drops, so that the main piston is pulled by the pressure difference and electromagnetic force, and the valve port opens; when the power is off, the pilot hole is closed by the spring reset, the upper cavity of the main piston is pressurized, and the main piston is pushed down Move, the valve closes. Normally open is the opposite of normally closed.
The working principle of the pilot solenoid valve:
Normally closed type—when energized, the electromagnetic force attracts the pilot hole spool, the pilot hole opens, the pressure in the upper cavity of the main valve piston drops, and the upper and lower chambers of the main piston form high pressures, so that the lower cavity pressure pushes The main piston opens the valve; when the power is off, the spring force resets to close the pilot hole, the upper chamber of the main piston is pressurized, and the upper and lower chambers of the main piston form high and low pressures. The medium pressure and spring force push the main piston and the valve closes. . Normally open is the opposite of normally closed.
Working principle of diaphragm solenoid valve:
When energized, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, forming a high pressure difference around the closing member, the fluid pressure pushes the closing member to move upward, and the valve opens; when the power is off, the spring force closes the pilot hole , The inlet pressure passes through the bypass hole and the chamber quickly forms a low and high pressure difference around the valve closing member, and the fluid pressure pushes the closing member to move downward to close the valve.
Working principle of piston solenoid valve:
After the coil is energized, the movable iron core moves down due to the suction force, the auxiliary valve plug is pressed down, the auxiliary valve is closed, the pressure in the main valve cup rises, when the pressure rises to a certain value, the upper and lower pressure difference of the main valve cup is the same , Due to the electromagnetic force, the moving iron core loses the main valve under the cup, and the main valve seat is pressed and the valve is closed. When the coil is de-energized, the electromagnetic suction force is zero, the auxiliary valve plug and the supporting iron core are lifted up due to the action of the spring, the auxiliary valve opens, and the fluid on the main valve cup flows away through the auxiliary valve, reducing the effect on the main valve cup When the pressure on the main valve cup is reduced to a certain value, the main valve cup is pushed up by the pressure difference, the main valve opens, and the medium flows.


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