In principle, there are three types of irrigation solenoid valves: direct-acting, stepwise direct-acting, and pilot operation. According to the different structures, materials, and principles of the valve disc, it is divided into six subcategories: direct-acting diaphragm structure, direct-acting diaphragm structure, pilot diaphragm structure, direct-acting piston structure, direct-acting piston structure, pilot piston structure.
1. Indirect irrigation solenoid valve
The solenoid valve is connected by the pilot valve and the spool to form a combined channel. The type that is usually closed is closed when it is not open. When the coil is energized, the magnetic force generated causes the moving iron core and the static iron core to close, the pilot valve port is opened, and the medium flows to the outlet. At this time, the pressure of the upper cavity of the spool decreases, which is lower than the pressure on the inlet side, forming a pressure difference, overcoming the resistance of the spring to move upward, thereby opening the port of the spool and making the medium flow. When the coil is de-energized, the magnetic force disappears, the iron core resets, and the conduction port closes under the action of the spring force. At this time, the medium flows out of the balance hole, the pressure in the upper cavity of the spool increases, and it moves down under the action of the spring force, and the spooling port is closed. The principle of normal openness is quite the opposite.
Principle: When opening, the electromagnetic force opens the pilot hole, the pressure of the upper cavity drops rapidly, a high and low-pressure difference is formed around the opening part, the fluid pressure pushes the opening part up, and the valve opens; When the power is cut off, the spring force opens the pilot hole, the inlet pressure quickly passes through the bypass hole, and the valve chamber forms an upper and lower pressure difference around the closed part. The fluid pressure pushes down the opening section and opens the valve.
Features: small size, low power, high upper limit range of fluid pressure, can be installed arbitrarily (customized), but must meet the fluid pressure differential conditions.
2. Step-type direct-acting solenoid valve
The valve is connected to the primary and secondary opening valves. Step by step, the main valve, and pilot valve allow the electromagnetic force and differential pressure to open directly to the port of the main valve. When the coil is energized, the electromagnetic force is generated to make the moving iron core and the static iron core close, open the pilot valve port, the pilot valve port is set on the main valve port, and the moving iron core is connected to the main valve core. At this point, the pressure from the chamber on the main valve is discharged through the port of the pilot valve, and the main valve moves upward under the action of differential pressure and electromagnetic force, thus opening the flowing medium of the main valve. When the coil is turned off, the electromagnetic force disappears. At this time, the moving iron core closes the pilot valve bore under the action of its own weight and spring force. At this time, the medium enters the upper cavity of the spool through the balance hole, increasing the pressure in the upper cavity. At this time, the main valve is closed under the action of the return spring and pressure, and the medium is cut off. Reasonable structure, reliable action, reliable operation with zero pressure difference.
Principle: It is a combination of direct action and leading action. When there is no pressure difference between the inlet and outlet, after the power is applied, the electromagnetic force directly opens and closes the small pilot valve and the main valve in turn, and the valve opens. When the starting pressure difference is reached at the inlet and outlet, the small electromagnetic pilot valve can increase the pressure in the lower cavity of the main valve and reduce the pressure in the upper cavity, so that the main valve is pushed upward by the differential pressure, and the pilot valve uses spring force or medium pressure to push the seal down and close when the power fails.
3. Direct-acting solenoid valve
There are two types: normally closed type and normally open type. The normally closed type is closed when the power is off, and the electromagnetic force is generated when the coil is energized so that the moving iron core overcomes the spring force and the static iron core closes the valve directly, and the medium is in a path; When the coil is de-energized, the electromagnetic force disappears, and the moving iron core is reset under the action of the spring force, and the valve port is directly closed, and the medium is not through. Simple structure, reliable action, normal operation under zero pressure difference, and micro vacuum. The normally open type is the opposite.
Principle: When the normally closed type is energized, the electromagnetic coil generates electromagnetic force to lift the open part from the valve seat, and the valve opens; When the power is cut off, the electromagnetic force disappears, the spring presses the open part on the valve seat, and the valve is open. (normally open type is the opposite) characteristics: it can work normally under vacuum, negative pressure, and zero pressure, but the diameter is generally not more than 25mm.
