Working principle of pneumatic solenoid valve
Solenoid valve is an automatic basic element used to control fluid, which belongs to the actuator; it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. The mechanical devices of the factory are generally controlled by hydraulic steel, so solenoid valves will be used.
The working principle of the solenoid valve, there is a closed cavity in the solenoid valve, there are through holes in different positions, each hole leads to a different oil pipe, the middle of the cavity is the valve, two sides are two electromagnets, which side of the magnet coil Where the energized valve body will be attracted, by controlling the movement of the valve body to block or leak out different oil drain holes, and the oil inlet hole is normally open, hydraulic oil will enter different oil drain pipes and then pass The pressure of the oil pushes the piston of oil, the piston drives the piston rod, and the piston rod drives the mechanical device. In this way, by controlling the current of the electromagnet, the mechanical movement is controlled.
Following the development history of solenoid valves, up to now, solenoid valves at home and abroad are divided into three categories in principle (ie: direct-acting type, step-by-step pilot type), and the difference between the structure and material of the valve disc The difference in principle is divided into six sub-categories (direct-moving diaphragm structure, step-by-step heavy diaphragm structure, pilot membrane structure, direct-moving piston structure, step-by-step direct-moving 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 against the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm.
Distributed 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, after energization, the electromagnetic force directly lifts the pilot small valve and the main valve closing part in sequence and the valve opens. When the inlet and outlet reaches the starting pressure difference, after energization, the electromagnetic force pilot small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber decreases, thereby using the pressure difference to push the main valve upwards; Force or medium pressure pushes the closing piece and moves downward to close the valve.
Features: It can be operated at zero pressure difference or vacuum and high pressure, but the power is large, and it must be installed horizontally.
Pilot solenoid valve:
Principle: When the power is turned on, the pilot hole is opened by electromagnetic force, the pressure in the upper chamber drops rapidly, and a high and low 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 controls the pilot The orifice is closed, and the inlet pressure quickly forms a low, high, and high pressure differential around the valve closing member through the bypass hole. The fluid pressure pushes the closing member downward to close the valve.
Features: The upper limit of the fluid pressure range is higher, and can be installed arbitrarily (need to be customized) but must meet the fluid pressure differential conditions.
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