The solenoid valve is composed of the pilot valve and the main valve core to form a channel, and the normally closed type is closed when it is not powered on. When the coil is electrified, the magnetic force causes the moving iron core and the static iron core to absorb, the guide valve port opens, and the medium flows to the outlet. At this time, the pressure on the main valve core decreases, which is lower than the pressure on the inlet side, and the pressure difference is formed to overcome the spring resistance and then move upward, so as to achieve the purpose of opening the main valve port and the flow of the medium. When the coil is out of power, the magnetic force disappears and the moving iron core is reset and closed under the action of spring force. At this time, the medium flows in from the balance hole, the pressure on the upper cavity of the main valve core increases, and moves downward under the action of spring force to close the main port. The normally open principle is just the opposite.

Principle: when electrified, the electromagnetic force opens the pilot hole, the pressure of the upper chamber drops rapidly, forms the lower and higher pressure difference around the open part, the fluid pressure drives the open part to move upward, and the valve opens. When the power is turned off, the spring force opens the pilot hole, and the inlet pressure forms the lower and upper high pressure difference around the closing valve part through the bypass hole, and the fluid pressure drives the open part to move down and open the valve.

Features: with small volume, low power and high upper limit of fluid pressure range, it can be installed at will (need to be customized), but must meet the conditions of fluid pressure difference.