What is a solenoid valve

There are many kinds of solenoid valves, different solenoid valves play a role in different positions of the control system, the most commonly used one-way valve, safety valve, direction control valve, speed control valve, etc.
Working principle
There is a closed cavity in the solenoid valve. Through holes are opened at different positions. Each hole is connected with different oil pipes. The piston is in the middle of the cavity, and two electromagnets are on both sides. The valve body will be attracted to which side when the magnet coil is energized. Different oil drain holes will be opened or closed by controlling the movement of the valve body. The oil inlet hole is normally open, and the hydraulic oil will enter different oil drain pipes, and then through the The oil pressure pushes the piston of the oil cylinder, the piston drives the piston rod, and the piston rod drives the mechanical device. In this way, the mechanical movement is controlled by controlling the on-off current of the electromagnet.
Main classification
1. Solenoid valves are divided into three categories in principle:
Direct acting solenoid valve
Principle: when energized, the electromagnetic force generated by the electromagnetic coil lifts the closing part from the valve seat and opens the valve; when the power is cut off, the electromagnetic force disappears, and the spring presses the closing part on the valve seat and closes the valve.
Features: it can work normally in vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25 mm.
Step by step direct acting solenoid valve
Principle: it is a combination of direct acting and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force will directly lift the small pilot valve and the main valve closure piece upward one by one, and the valve will open. When the pressure difference between the inlet and the outlet reaches the starting pressure, the small solenoid pilot valve will increase the pressure in the lower chamber of the main valve and decrease the pressure in the upper chamber after being powered on, so as to push the main valve upward by using the pressure difference; when the power is off, the pilot valve will use the spring force or the medium pressure to push the closure piece and move downward to close the valve.
Features: it can also act under zero pressure difference, vacuum or high pressure, but it has high power, so it must be installed horizontally.
Pilot operated solenoid valve
Principle: when the power is on, the electromagnetic force opens the pilot hole, the pressure of the upper chamber drops rapidly, forming a high and low pressure difference around the closing piece, the fluid pressure pushes the closing piece to move upward, and the valve opens; when the power is off, the spring force closes the pilot hole, and the inlet pressure quickly forms a low and high pressure difference around the closing piece through the bypass hole, and the fluid pressure pushes the closing piece downward Move and close the valve.
Features: the upper limit of fluid pressure range is high, which can be installed arbitrarily (customized) but must meet the condition of fluid pressure difference.
2. The solenoid valve is divided into six branches and sub categories according to the difference and principle of valve structure and material: direct acting diaphragm structure, step-by-step direct acting diaphragm structure, pilot diaphragm structure, direct acting piston structure, step-by-step direct acting piston structure and pilot piston structure.
3. Solenoid valves are classified according to their functions: water solenoid valve, steam solenoid valve, refrigeration solenoid valve, low temperature solenoid valve, gas solenoid valve, fire solenoid valve, ammonia solenoid valve, gas solenoid valve, liquid solenoid valve, micro solenoid valve, pulse solenoid valve, hydraulic solenoid valve normally open solenoid valve, oil solenoid valve, DC solenoid valve, high pressure solenoid valve, explosion-proof solenoid valve, etc.