The working principle and function of solenoid valve

Solenoid valve is an automation basic component used to control fluid, which belongs to actuator; it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. Factory machinery is generally controlled by hydraulic steel, so solenoid valves are used. Tracing the history of the development of solenoid valves, so far, solenoid valves at home and abroad are divided into three categories in principle (ie: direct-acting, step-by-step direct-acting solenoid valves are automation basic components used to control fluids, which belong to the executive It is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. The mechanical devices of factories are generally controlled by hydraulic steel, so solenoid valves are used. Tracing the development history of solenoid valves, so far, domestic The external solenoid valve is divided into three categories in principle (ie: direct-acting, step-by-step direct-acting, pilot-operated), and the difference in valve structure and material and the difference in principle are divided into six branches Sub-category (direct-acting diaphragm structure, step-diaphragm structure, pilot diaphragm structure, direct-acting piston structure, step-piston structure, pilot piston structure). (1) Principle of direct-acting solenoid valve: when energized, The solenoid generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, and the spring force presses the closing member on the valve seat, and the valve closes. Features: Under vacuum, negative pressure, and zero pressure It can work normally, but the general diameter does not exceed 25mm. (2) The principle of step-by-step direct-acting solenoid valve: it is a principle of combining direct-acting and pilot-operated, when the inlet and outlet pressure difference is less than or equal to 0.05Mpa, energize When the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, the valve opens. When the pressure difference between the inlet and the outlet is >0.05Mpa, when the power is turned on, the electromagnetic force first opens the pilot small valve, and the pressure in the lower cavity of the main valve rises. The pressure in the chamber drops, so that the main valve is pushed up by the pressure difference; when the power is off, the pilot valve and the main valve use the spring force or the medium pressure to push the closing piece, move down, and close the valve. Features: at zero pressure difference or vacuum , It can work under high pressure, but the power is large, and vertical installation is required. (3) Principle of pilot solenoid valve: When energized, electromagnetic force opens the pilot hole, and the pressure in the upper chamber drops rapidly, around the closing part The pressure difference between the upper and lower parts is formed, pushing the closing member to move upward, and the valve opens; when the power is off, the spring force closes the pilot hole, and the inlet pressure quickly enters the upper chamber through the bypass hole, forming a lower, lower and upper chamber around the closing member The pressure difference pushes the closing member to move down to close the valve. Features: The upper limit of the fluid pressure range is high, but the fluid pressure difference condition must be met. At present, the commonly used solenoid valves sold in China are DV (DVF), PGA, PEB (PESB) , BPE series more than a dozen varieties, caliber from 3/4' to 3Divided into two upper and lower chambers, with a diaphragm in the middle. Under the same water pressure, the pressure difference is generated due to the different force areas of the upper and lower diaphragms to cut off the water flow. The solenoid valve is in the open state---when the remote controller is used Power supply signal or manual rotation of the solenoid head, the drain channel is opened, the water in the upper diaphragm room is discharged, the pressure in the room decreases, and the pressure acting on the upper diaphragm becomes smaller. Under the action of the upstream pressure, the diaphragm moves upward to open the pipeline channel. Solenoid valve Closed state-Manually turn off or disconnect the electrical signal of the electromagnetic head, so that the drainage channel is closed, and the upper diaphragm chamber The inside is slowly filled with water. When the upper and lower pressures of the diaphragm are the same, the upper side of the diaphragm will be forced to move downwards and the pipeline channel will be closed due to the larger area of u200bu200bforce on the upper side of the diaphragm. The single solenoid valve has only one solenoid head. After the power is turned on, the solenoid valve changes direction. After the power is off, the solenoid valve is reset due to the action of the spring. The double solenoid valve has 2 solenoid heads, and only one of them can be energized. After the power is turned on, the solenoid valve changes direction. After the power is off, the solenoid valve maintains its position. The solenoid valve on the other side must be energized before the solenoid valve returns to its original position.