Classification and working principle of solenoid valve
Looking at solenoid valves at home and abroad, up to now, they can be divided into three categories in terms of action: direct-acting, stepwise direct-acting, and pilot-operated.
From the difference in valve structure and material, and the difference in principle, the step-by-step direct-acting type can be divided into: step-by-step direct-acting diaphragm solenoid valve, step-by-step direct-acting piston solenoid valve; pilot type can be divided into : Pilot diaphragm solenoid valve, pilot piston solenoid valve.
From the valve seat and sealing material, it can be divided into: soft sealing solenoid valve, rigid sealing solenoid valve, semi-rigid sealing solenoid valve.
1. Direct-acting solenoid valve
Principle: When the normally-closed direct-acting solenoid valve is energized, the solenoid coil generates electromagnetic suction to lift the valve core, so that the seal on the valve core leaves the valve seat port and the valve opens; when the power is off, the electromagnetic force disappears and the valve is held by the spring force The seal on the core presses on the valve seat port and the valve is closed. (The normally open type is the opposite of this) Features: It can work normally under vacuum, negative pressure and zero pressure difference. The larger the valve diameter, the larger the volume and power of the solenoid head. For example, the direct-acting solenoid valve produced by our company with the introduction of HERION technology can be used for 1.33×10-4 Mpa vacuum.
2. Step-by-step direct-acting solenoid valve (recoil type)
Principle: Combination of direct action and pilot. When energized, the solenoid valve opens the auxiliary valve first. The pressure in the lower chamber of the main valve is greater than the pressure in the upper chamber, and the pressure difference and electromagnetic force are used to open the valve; when the power is off, the auxiliary valve is used The spring force or medium pressure pushes the seal to close and moves downward to close the valve port.
Features: It can work reliably under zero pressure difference or about a certain pressure. Generally, the working pressure difference does not exceed 0.6 MPa, but the power and volume of the electromagnetic head are relatively large, requiring vertical installation.
Three, pilot solenoid valve
Principle: When energized, the pilot valve is driven by electromagnetic force to open the pilot valve, the pressure in the upper cavity of the main valve drops rapidly, and a pressure difference is formed in the upper and lower cavities of the main valve. Depending on the medium pressure, the main valve closing part is pushed up and the valve opens; when the power is off, The spring force closes the pilot valve, and the inlet medium pressure quickly enters the upper cavity of the main valve through the orifice, forming a pressure difference in the upper cavity, thereby closing the main valve.
Features: Small size, low power, but the medium pressure difference range is limited, and the pressure difference condition (0.01MPa) must be met.