How many types of solenoid valves are there?

Vacuum solenoid valves are divided into three categories.
Vacuum solenoid valves are divided into three categories: direct acting, gradual direct acting and dominant.
Now I make a summary at three levels: the preface of the paper, the basic principles and characteristics.

Direct acting vacuum solenoid valve.

Detailed introduction:
There are normally closed test and normally open type. When the normally closed switching power supply is turned off, it is in the off condition. When the electromagnetic coil is powered on, it will cause electromagnetic force, so that the active iron core will get rid of the torsion spring force, immediately open the gate valve containing the static data iron core, and the material will enter the way; when the electromagnetic coil is powered off, the electromagnetic force will subside, and the moving iron will disappear. The core is calibrated under the force of the torsion spring, the valve is closed immediately, and the material is blocked. The structure is simple, the function is reliable, and it works normally under zero pressure difference and micro vacuum pump. On and off are reversed. If the total flow of the vacuum solenoid valve is lower than φ6.
Fundamental:
When the normally closed is plugged in, the magnet coil creates an electromagnetic force, which extends the open member from the valve block and opens the gate valve. When the switching power supply is turned off, the electromagnetic force subsides, and the torsion spring presses the open member against the high-pressure gate valve, thereby opening the gate valve. (reverse on and off)
Features:
It can work normally under vacuum pump, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.

Staged direct-acting vacuum solenoid valve.

Detailed introduction:
The gate valve is connected to one open valve and two open valves. The main valve and pilot valve slowly make the electromagnetic force and pressure difference open the main valve immediately. After the electromagnetic coil is plugged in, it will cause electromagnetic force, suck the movable iron core and the static iron core together, open the port number of the pilot valve, configure the port of the pilot valve on the port number of the main valve, and connect the moving iron core with the main valve core. When the main valve is on, the pressure in the thoracic and abdominal chambers is unloaded according to the pilot valve port number. Under the effect of pressure difference and electromagnetic force, the main valve core moves up, opening the main valve material circulation system. When the solenoid coil is de-energized, the electromagnetic force subsides. At this time, the moving iron core closes the pilot valve hole under the effect of its own total weight and ductility. At this time, the substance enters the thoracic cavity of the main valve core in the equalizing hole, so the thoracic and abdominal cavity pressure increases. At this point, the main valve closes under the effect of the torsion spring calibration and pressure, and the mass is terminated. The structure is reasonable, the function is reliable, and the pressure is zero. Such as ZQDF, ZS, 2W, etc.
Fundamental:
It is a combination of immediate action and engagement. When there is no pressure difference between the channel and the inlet and outlet, the electromagnetic force immediately raises the demonstration point valve and the main valve to the shut-off member, and then opens the gate valve. When the initial pressure difference between the channel and the inlet and outlet is achieved, the electromagnetic force will correctly guide the pressure of the small valve, the main valve and the lower chamber to rise, and the pressure of the upper chamber will decrease to promote the 020-2 to go up; when the switching power supply is turned off, use Torsion spring force or medium pressure urges the pilot valve, moving down to close the gate valve.
Features:
Can also be used with zero differential pressure or vacuum pump or high pressure.
It can be practically operated, but the output power is very large, so it must be installed horizontally.

Indirectly dominate the vacuum solenoid valve.

Detailed introduction:
The vacuum solenoid valve consists of the first pilot valves and main spools that create a safe passage. The normally closed type is turned off when not plugged in. When the electromagnetic coil is powered on, the resulting magnetism attracts the movable iron core and the static iron core together, opens the pilot valve, and the material flows into the inlet and outlet. At this time, the pressure in the upper chamber of the main spool is reduced, which is less than the pressure on the channel side, resulting in a pressure difference. Get rid of the frictional resistance of the torsion spring and move up to open the main valve, the material can circulate the system. When the electromagnetic coil is powered off, the magnetism subsides, the subject active core is calibrated under the force of the torsion spring, and the main port number is turned off. At this time, the material is discharged from the equalizing hole, the pressure of the upper cavity of the main spool is increased, and it moves downward under the action of the torsion spring force. Close the main valve. In turn, the on and off criteria are reversed.
When plugged in, the electromagnetic force opens the guide hole, the pressure in the thoracic and abdominal cavity decreases rapidly, and a pressure difference between the left and right parts is generated around the opening member. The hydraulic pressure pushes the open member up and the gate valve opens. When the switching power supply is turned off, the torsion spring force opens the guide hole. According to the channel pressure of the side buried hole, the low voltage and high pressure difference around the valve part are rapidly generated, and the liquid pressure pushes down the open part to open the gate valve.
Features:
It is small in size, low in output power, and has a high range of hydraulic presses. It can be installed (customized) at will, but it must meet the poor standard of hydraulic presses.