Principle of pilot solenoid valve

When energized, the pilot hole is opened by electromagnetic force, the pressure in the upper chamber drops rapidly, and a pressure difference is formed around the closing member. The fluid pressure pushes the closing member upward and the valve opens; when the power is turned off, the spring force closes the pilot hole , The inlet pressure quickly forms a low, high, and high pressure difference around the valve closing member through the bypass hole, and the fluid pressure pushes the closing member downward to close the valve.