Classification and working principle of reversing directional control valve

Classification and working principle of reversing directional control valves

Reversing directional control valves (referred to as reversing directional control valves) Directional valve) changes the direction of gas flow by changing the air flow channel, thereby changing the direction of movement of the pneumatic actuator. It includes air pressure control reversing valve, electromagnetic control reversing valve, mechanical control reversing valve, human control reversing valve and time control reversing valve, etc. 1. Air pressure control reversing valve The air pressure control reversing valve uses gas pressure to move the main valve core to change the flow direction of the gas. According to different control methods, it is divided into three types: pressure control, pressure relief control and differential pressure control. Pressure control means that the added control signal pressure gradually increases. When the air pressure increases to the operating pressure of the valve core, the main valve changes direction;pressure relief control means that the added pneumatic signal pressure is reduced. When it reduces to a certain pressure value, the main valve changes direction;difference Pressure control is to make the main valve core change direction under the action of the pressure difference between the two ends. Pneumatic control valves can be divided into two main forms: cut-off type and slide valve type according to different main valve structures. The structure and working principle of the slide valve type pneumatic reversing valve are basically the same as those of the hydraulic reversing valve. This article mainly introduces the stop-type directional valve. Working principle of stop-type directional valve Figure 1 shows the working principle diagram of a two-position three-way single air-controlled stop-type directional valve. Figure 14-20a shows the state when there is no control signal at the port. Under the action of the spring and the air pressure of the P chamber, the valve core disconnects P and A, connects A and T, and the valve is in the exhaust state. When there is a control signal at port K (see Figure 14-20b), P and A are connected, A and 2 are disconnected, and air enters port A.

Figure 1. Working principle of stop-type reversing valve Figure 2 shows the structural diagram of a two-position three-way single air-controlled stop-type reversing valve. When there is no signal at port K. A and T are connected, and the valve is in the exhaust state;when there is a signal input from the K port, the compressed air enters the positive end of the piston 9, causing the valve stem 5 to move left, and P and A are connected. The valve shown in the figure is a normally-off type valve. If P and T are switched, it becomes a normally-on type.