What is the working principle of solenoid valve

The working principle of solenoid valve:

There is a closed cavity in the solenoid valve with through holes at different positions. Each hole leads to a different oil pipe. In the middle of the cavity is the valve. On both sides are two electromagnets. Where it is attracted, 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 push the oil through the oil pressure The rigid 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 difference in valve structure and material and the difference in principle are divided into six There are three sub-categories (direct-acting diaphragm structure, step-by-step double-piece 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.