When electrified, the electromagnetic coil generates electromagnetic force to lift the closing piece from the valve seat and open the valve. When the power is cut off, the electromagnetic force disappears, the spring presses the closing piece on the valve seat, and the valve closes.
There is a closed cavity in the solenoid valve, and there are through holes in different positions. Each hole is connected with a different oil pipe. There is a piston in the middle of the cavity and two electromagnets on both sides. The valve body will be attracted to the side where the electromagnetic coil is energized, and different oil drain holes will be opened or closed by controlling the movement of the valve body.
The oil inlet hole is always open, so the hydraulic oil will enter different oil discharge pipes, and then the piston of the oil cylinder will be driven by the oil pressure, the piston will drive the piston rod, and the piston rod will drive the mechanical device. In this way, the mechanical movement is controlled by controlling the on-off of the electromagnet.
Extended data
Solenoid valves are divided into three categories in principle:
1, direct-acting solenoid valve
Principle: When electrifying, the electromagnetic coil generates electromagnetic force to lift the closing piece from the valve seat and open the valve; When the power is cut off, the electromagnetic force disappears, the spring presses the closing piece on the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and zero pressure, but its diameter is generally less than 25mm.
2. Stepping direct-acting solenoid valve
Principle: It is a combination of direct-acting and pilot-acting. When there is no pressure difference between the inlet and outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing piece in turn, and the valve opens.
When the inlet and outlet reach the starting pressure difference, the electromagnetic force guides the small valve, and the lower chamber pressure of the main valve increases and the upper chamber pressure decreases, so that the main valve is pushed upward by the pressure difference; When power is cut off, the pilot valve uses spring force or medium pressure to push the closing piece to move down and close the valve.
Features: It can operate under zero pressure difference, vacuum and high pressure, but it has high power and must be installed horizontally.
3. Pilot solenoid valve
Principle: When power is on, the electromagnetic force opens the pilot hole, and the pressure in the upper cavity drops rapidly, forming a pressure difference between the upper and lower parts around the closed part. The fluid pressure pushes the closing part to move upwards, and the valve opens.
When power is cut off, the pilot hole is closed under the action of spring force, the inlet pressure quickly forms a low-high pressure difference around the closing valve through the bypass hole, and the fluid pressure pushes the closing piece to move downwards to close the valve.
Features: The upper limit of the fluid pressure range is high, and it can be installed (customized) at will, but the fluid pressure difference condition must be met.
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