Solenoid valve is an automation basic component used to control fluid, which belongs to actuator; it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. Factory machinery is generally controlled by hydraulic steel, so solenoid valves are used.
The working principle of the solenoid valve, the solenoid valve has a closed cavity with through holes at different positions, and each hole leads to a different tubing. In the middle of the cavity is the valve. On both sides are two electromagnets. Which side is the magnet coil The energized valve body will be attracted to which side, by controlling the movement of the valve body to block or leak out the different drain holes, and the oil inlet hole is normally open, the hydraulic oil will enter the different drain pipes and then pass The oil pressure pushes the oily piston, 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.
Tracing the development history of solenoid valves, so far, solenoid valves at home and abroad are divided into three categories in principle (ie: direct-acting, step-by-step pilot-operated), and the differences in valve structure and materials are The difference in principle is divided into six sub-categories (direct-acting diaphragm structure, step-by-step structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure).
Direct-acting solenoid valve:
Principle: When energized, the solenoid 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.
Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.
Distributed direct-acting solenoid valve:
Principle: It is a combination of direct action and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the start-up pressure difference, after energization, 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, so that the pressure difference pushes the main valve upward; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing piece and moves downward to close the valve.
Features: It can also be operated under zero pressure difference or vacuum and high pressure, but the power is large, and it must be installed horizontally.
Pilot solenoid valve:
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a high pressure difference is formed around the closing part. The fluid pressure pushes the closing part to move upward and the valve opens; when the power is off, the spring force controls the pilot The hole is closed, and 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.
Features: The upper limit of the fluid pressure range is high, and it can be installed arbitrarily (customization is required) but the fluid pressure difference condition must be met.
