The pilot valve and the main valve core are connected to form a channel. When the electromagnetic precursor of the normally closed solenoid valve is energized, the generated electromagnetic force makes the pilot valve open, the medium flows to the outlet, and the pressure in the upper chamber of the main valve drops rapidly, forming in the upper and lower chambers of the main valve. The pressure difference overcomes the spring force and moves upward, the main valve opens, the medium flows, and the solenoid valve opens; when the coil is powered off, the electromagnetic force disappears, the moving iron core is reset under the action of the spring force, the pilot valve is closed, and the medium flows from the guide Inflow into the hole, the pressure in the upper chamber of the main spool increases, and moves downward under the action of the spring force, closing the main valve, the medium is cut off, and the solenoid valve is closed. How to use the normally closed solenoid valve Whe