There are many types of solenoid valves, and different solenoid valves play a role in different positions of the control system. The most commonly used ones are one-way valves, safety valves, directional control valves, speed regulating valves, etc.
Working principle
The solenoid valve has a sealed chamber with through holes at different positions, each connected to a different oil pipe. The middle of the chamber is a piston, and there are two electromagnets on both sides. The valve body will be attracted to which side when the magnet coil on the other side is energized. By controlling the movement of the valve body, different oil discharge holes can be opened or closed. The oil inlet hole is normally open, and hydraulic oil will enter different oil discharge pipes. Then, the pressure of the oil will push the piston of the oil cylinder, which in turn drives the piston rod, which drives the mechanical device. In this way, the mechanical motion is controlled by controlling the current on and off of the electromagnet.
Main classification
1. Electromagnetic valves can be classified into three main categories based on their principles:
Direct acting solenoid valve
Principle: When powered on, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; When the power is cut off, the electromagnetic force disappears, and the spring presses the closing member against the valve seat, causing the valve to close.
Characteristics: It can work normally under vacuum, negative pressure, and zero pressure, but the diameter generally does not exceed 25mm.
Step by step direct acting solenoid valve
Principle: It is a combination of direct action and pilot operated principle. When there is no pressure difference between the inlet and outlet, after being energized, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upward in sequence, and the valve opens. When the inlet and outlet reach the starting pressure difference, after being energized, the electromagnetic force pilot small valve, the lower chamber pressure of the main valve rises, and the upper chamber pressure drops, thereby using the pressure difference to push the main valve upwards; When the power is cut off, the pilot valve uses spring force or medium pressure to push the closing member downwards, causing the valve to close.
Features: It can also operate under zero pressure difference, vacuum, and high pressure, but with high power, it must be installed horizontally.
Pilot operated solenoid valve
Principle: When powered on, the electromagnetic force opens the pilot hole, causing the pressure in the upper chamber to rapidly decrease, creating a pressure difference of high and low around the closing element. The fluid pressure pushes the closing element to move upward, and the valve opens; When the power is cut off, the spring force closes the pilot hole, and the inlet pressure quickly forms a lower and higher pressure difference around the closing valve through the bypass hole. The fluid pressure pushes the closing valve to move downward and close the valve.
Features: The upper limit of the fluid pressure range is relatively high, and it can be installed freely (customized), but it must meet the fluid pressure difference conditions.
2. Electromagnetic valves are divided into six sub categories based on differences in valve structure, materials, and principles: 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. Electromagnetic valves are classified according to their functions: water solenoid valves, steam solenoid valves, refrigeration solenoid valves, low-temperature solenoid valves, gas solenoid valves, fire solenoid valves, ammonia solenoid valves, gas solenoid valves, liquid solenoid valves, miniature solenoid valves, pulse solenoid valves, hydraulic solenoid valves, normally open solenoid valves, oil solenoid valves, DC solenoid valves, high-voltage solenoid valves, explosion-proof solenoid valves, etc.
