1. Air pressure control directional valve

A pressure controlled directional valve uses gas pressure to move the main valve core and change the direction of gas flow. According to different control methods, it can be divided into three types: pressurization control, depressurization control, and differential pressure control. Pressure control refers to the gradual increase of the control signal pressure applied. When the air pressure reaches the operating pressure of the valve core, the main valve will change direction; Pressure relief control refers to the fact that the pressure of the applied pneumatic control signal decreases, and when it reaches a certain pressure value, the main valve changes direction; Differential pressure control is the process of reversing the main valve core under the pressure difference at both ends.

Pneumatic directional valves can be divided into two main forms: globe type and slide valve type, depending on the main valve structure. The structure and working principle of the slide valve pneumatic directional valve are basically the same as those of the hydraulic directional valve. This mainly introduces the globe directional valve.

2. Pilot operated electromagnetic directional valve

Pilot operated electromagnetic directional valve is controlled by an electromagnet to generate pilot pressure in the air circuit, which then drives the main valve core to change direction. Suitable for situations with larger diameters.

Pilot operated dual electric control two position four way electromagnetic directional valve. It consists of a pilot valve (Dl, D2) and a main valve. The main valve also includes two parts: valve body 1 and piston assembly 2. The diagram shows that both Dl and D2 are in a power-off state. The moving iron cores 5 and 6 of the solenoid valve are in a closed state. When Dl is powered on and D2 is powered off, the moving iron core 5 is sucked up, and compressed air from port P enters the f chamber of the valve through hole a (dashed line). And enter the hole from the lips around the sealing plug 4 (one-way valve) and enter. Wide chamber, push piston assembly 2 down to allow P to pass through A, and B to pass through the center hole h of the valve core to pass through T (exhaust). At the same time as there is compressed air output from port A, a portion of the compressed air flows into hole G. One of the paths enters chamber C through the throttle hole d, causing the sealing plug 4 to move down and seal the exhaust hole b. The other path of compressed air enters chamber f, acting on the upper end of piston assembly 2. At this point, even if Dl is powered off, piston assembly 2 will not be in position, indicating that the valve has a memory function.

When the pilot type dual electric control two position four way electromagnetic directional valve D2 is powered on and Dl is powered off, the moving iron core 6 is sucked up, and the compressed air in the chamber c is discharged through port T1. At this point, compressed air from P to A acts on the large and small pistons, producing an upward force due to the area difference between the large and small pistons, causing piston assembly 2 to move upwards. At the same time, the sealing plug 4 is also moved up and valve port 3 is opened, allowing the compressed air at the upper end of piston assembly 2 to be discharged through hole 6. After piston assembly 2 is moved up, P is connected to B and A is connected to T (exhaust). At this point, even if D2 is powered off, the upward force generated by the difference in the area of the large and small pistons still exists, so the output state will not change, which means it has a memory function. Pneumatic solenoid valves, like hydraulic solenoid directional valves, have many types and their working principles are also similar, and will not be repeated.