Tracing the development history 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, and pilot-operated), and from the structure and material of the disc The difference and the difference in principle are divided into six sub-categories (direct-acting diaphragm structure, stepped diaphragm structure, pilot diaphragm structure, direct-acting piston structure, stepped piston structure, pilot piston structure).
(1) Direct-acting solenoid valve
Principle: 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: It can work normally under vacuum, negative pressure and zero pressure, but the general diameter does not exceed 25mm.
(2) Step-by-step direct-acting solenoid valve
Principle: It is a combination of direct-acting and pilot-operated principle. When the pressure difference between the inlet and outlet is ≤0.05Mpa, when power is applied, the electromagnetic force directly lifts the pilot small valve and the main valve closing part upwards in turn, and the valve opens. When the pressure difference between the inlet and the outlet>0.05Mpa, when the power is turned on, the electromagnetic force first opens the small pilot valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, thereby using the pressure difference to push the main valve upward; when the power is off, the pilot valve And the main valve uses spring force or medium pressure to push the closing piece and move downward to close the valve.
Features: It can work reliably even under zero pressure difference or under vacuum and high pressure, but the power is large and vertical installation is required.
(3) Pilot solenoid valve
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, forming a high pressure difference around the closing part, pushing the closing part upwards, and the valve opens; when the power is off, the spring force closes the pilot hole , The inlet pressure quickly enters the upper chamber through the bypass hole to form a lower and upper pressure difference around the valve closing member, pushing the closing member downward to close the valve.
Features: The upper limit of the fluid pressure range is very 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 3″, mainly used in agriculture, gardens, golf, industrial dust And fountains and other fields. Commonly used solenoid valves are mostly diaphragm valves, and their working principle is: the valve body is divided into upper and lower chambers, with a diaphragm in the middle. Under the same water pressure, the pressure difference is generated due to the difference between the upper and lower force areas of the diaphragm and reaches the cut-off water flow. Purpose. The open state of the solenoid valve —- when the electric signal is supplied through the remote controller or the solenoid head is manually rotated, the drain channel is opened, the water in the upper diaphragm chamber is discharged, the indoor pressure decreases, the pressure acting on the upper diaphragm becomes smaller, and the upstream pressure acts Push the diaphragm upward to open the pipeline channel. Solenoid valve closed state—-manually turn off or disconnect the electrical signal of the solenoid head to close the drainage channel, and the upper diaphragm chamber is slowly filled with water. Large, make the diaphragm move downwards and close the pipeline channel.
The single electric control has only one solenoid head. After the power is turned on, the solenoid valve changes direction. After the power is lost, the solenoid valve is reset due to the action of the spring. After the power is turned on, the solenoid valve reverses. After the power is lost, 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.