Solenoid valves at home and abroad are divided into three categories in principle (ie: direct-acting, step-by-step direct-acting, and pilot-operated), and they are divided into six categories based on the difference in valve disc structure and material and the difference in principle. Subcategory (direct acting diaphragm structure, step-by-step heavy film 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 electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is turned off, the electromagnetic force disappears, the spring presses the closing member on the valve seat, and the valve closes.
Features: It can work normally in vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.
• Pilot solenoid valve:
Principle: When energized, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference is formed around the closing member, and the fluid pressure pushes the closing member to move upward, and the valve opens; when the power is turned off, the spring force opens the pilot hole. The hole is closed, the inlet pressure quickly passes through the bypass hole, and the chamber forms a lower pressure difference around the valve closing part, and the fluid pressure pushes the closing part down to close the valve
• Step-by-step direct acting solenoid valve
Principle: It is a combination of direct-acting and pilot-operated principles. When there is no pressure difference between the inlet and outlet, after power is applied, the electromagnetic force directly lifts up the pilot small valve and the closing member of the main valve in sequence, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, the electromagnetic force pilots the small valve, the pressure in the lower cavity of the main valve rises, and the pressure in the upper cavity drops, so that the main valve is pushed upward by the pressure difference; when the power is off, the pilot valve uses a spring Force or medium pressure pushes the closing member, which moves down and closes the valve.
