Definition and principle of solenoid valve

Solenoid valve is the basic component of automation used to control flow, which belongs to the actuator; it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. The mechanical devices of power plants are generally controlled by hydraulic steel plates, so solenoid valves are used.
Working principle: The
solenoid valve has a closed cavity with through holes in different positions. Each hole leads to a different tubing. There is a valve in the middle of the cavity. There are two electromagnets on both sides. By controlling the movement of the valve body to block or leak different oil discharge holes, and the oil inlet holes are always open, the hydraulic oil will enter the different oil discharge pipes, and then push the oil to the piston through the oil pressure, and the piston moves the piston rod in turn. Piston rod drive mechanism. Therefore, the mechanical movement is to control the current of the electromagnet.
1. Principle of direct-acting solenoid valve: When the power is turned on, the electromagnetic force of the solenoid coil closes the valve from the valve seat and the valve opens; when the power is turned off, the electromagnetic force disappears, and the spring closes the valve seat on the valve seat and the valve closes. Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is not more than 25mm.
2. Principle of distributed direct acting solenoid valve: It is a combination of direct acting and pilot-operated principle. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly increases to the pilot valve and the closed part of the main valve. turn on. When the inlet and outlet reach the start-up pressure difference, after power on, the electromagnetic force pilots the small valve. The pressure in the lower chamber of the main valve rises and the pressure in the upper chamber drops. The pressure difference pushes the main valve upwards, and the pilot valve uses spring force or medium pressure to push the closing part , Move down to close the valve. Features: When there is zero pressure difference or vacuum, high pressure can also be operated, but the power is large, and it must be installed horizontally.
3. Principle of the pilot solenoid valve: When the pilot hole is opened by current and electromagnetic force, the pressure in the upper chamber drops rapidly, forming a high and low pressure difference around the closure, the fluid pressure pushes the closing movement upwards, and the valve opens; the pilot hole is closed by the spring force, and the inlet pressure Through the bypass hole, a low pressure difference is formed around the closing valve quickly, and the fluid pressure pushes the closing part downward to close the valve. Features: The upper limit of the fluid pressure range is high and can be installed arbitrarily (customization is required), but the fluid pressure difference conditions must be met. Some of its characteristics, such as dielectric properties, ambient temperature, operating frequency, power and other factors should be considered when using it.