Created on:2022-02-17 08:51

Structure and principle of cartridge valve

Structure and principle of cartridge valve

Cartridge valve fork, called logic valve, is a relatively new type of hydraulic element. It is characterized by large flow capacity, good sealing performance, sensitive action and simple structure. Therefore, it is mainly used in systems with large flow or systems with high requirements for sealing performance.

1. Structural principle and symbol of cartridge valve

As shown in Figure 124, it is composed of control cover plate 1, inserting unit (composed of valve sleeve 2, spring 3, valve core 4 and seal), inserting block 5 and pilot element (placed on the control cover plate, not shown in the figure). Because the cartridge unit of this valve mainly plays the role of controlling on and off in the circuit, it is also called two-way cartridge valve. The control cover plate encapsulates the cartridge unit in the cartridge block and communicates the pilot valve and the cartridge unit (also known as the main valve). Through the opening and closing of the main valve core, the on-off of the main oil circuit can be controlled. Using different pilot valves can form pressure control, direction control or flow control, and can form composite control. Several two-way cartridge valves with different control functions are assembled in one or more cartridge blocks to form a hydraulic circuit.

In terms of working principle, the two-way cartridge valve is equivalent to one. A and B are the only two working oil ports of the main oil circuit (called two-way valve), and X is the control oil port. By changing the pressure of the control oil port, the on-off of oil ports a and B can be controlled. When the control port has no hydraulic action, the hydraulic pressure at the lower part of the valve core exceeds the spring force, the valve core is pushed open, and a is connected with B. the direction of liquid flow depends on the pressure at ports a and B. On the contrary, the control port has hydraulic function. When PX ≥ PA and PX ≥ Pb, it can ensure the closure between port a and port B. In this way, it plays the role of "not" gate of logic element, so it is also called logic valve.

Cartridge valves can be divided into two types according to the source of control oil: the first type is externally controlled cartridge valves. The control oil is supplied by a separate power source, and its pressure has nothing to do with the pressure change of ports a and B, which is mostly used for the direction control of oil circuit; The second type is the internal control cartridge valve, which controls the port a or B of the oil white lead valve, and is divided into two types of valve core with damping hole and without damping hole, which are widely used.

2. Directional control cartridge valve

There are two kinds of one-way valve and directional valve.

(1) One way cartridge valve. As shown in Figure 125, connect port x with a or B to become a one-way valve. Different connection methods lead to different conduction directions. When the former PA > Pb, the cone valve is closed and a and B are not connected; When Pb > PA and the opening pressure is reached, the cone valve opens and the oil flows from B to a. The latter can be concluded by similar analysis.

(2) Hydraulic control one-way cartridge valve. If a two position tee is connected to the control cover plate to change the pressure at port x, it becomes a hydraulic control check valve, as shown in Figure 126. If there is no hydraulic action at x, it is in the position shown in the figure. When PA > Pb, a and B are connected and a flows to B; When Pb > PA, a and B are blocked. If there is hydraulic pressure at k ', the two position three-way hydraulic control valve shall be reversed, so that port x is connected to the oil tank and a is connected with B. the flow direction of oil depends on the pressure at points a and B.

125.126

(3) Two position two-way cartridge valve. As shown in Figure 127, in the illustrated state, the cone valve is opened and a is connected with B. If the electromagnetic directional valve is energized and reversed, and PA > Pb, the cone valve is closed and the oil circuits a and B are cut off, which is a two position two-way valve.

(4) Two position three-way cartridge valve. As shown in Figure 128, in the illustrated state, the cone valve on the left is opened and the cone valve on the right is closed, that is, a and o are connected and P and a are not connected. When the solenoid valve is energized, P and a are connected, and a and o are not connected, which is a two position three-way valve.

(5) Two position four-way cartridge valve. As shown in Figure 129, in the illustrated state, the left 1 and right 2 cone valves are opened to realize the connection of a and O and the connection of B and P. When the solenoid valve is energized, the left 2 and right 1 cone valves are opened to realize the connection of a and P and B and O, which is a two position four-way valve.

127.128.129

(6) Three position four-way cartridge valve. As shown in Figure 130, in the illustrated state, all four cone valves are closed, and a, B, P and 0 are not connected. When the left electromagnetic iron is energized, the left 2 and right 1 cone valves are opened to realize the connection of a and P and B and o. When the right solenoid is energized, the left 1 and right 2 cone valves are opened; Realize the connection between a and O, and the connection between B and P, which is a three position four-way valve. If multiple pilot valves are matched with multiple main valves, a two-way cartridge directional valve with complex position through combination can be formed, which is impossible for ordinary directional valves.

130

3. Pressure control cartridge valve

The control port of the cartridge valve is equipped with different pilot pressure valves to obtain various types of pressure control valves. Figure 131 (a) shows the schematic diagram of using the direct acting overflow valve as the pilot valve to control the main valve and use it as the overflow valve. The pressure oil in chamber a enters the control chamber and pilot valve through the damping hole, and connects port B with the oil tank. In this way, the opening pressure of the cone valve can be adjusted by the pilot valve, and its principle is the same as that of the pilot relief valve. If in Figure 131 (a), when chamber B is not connected to the oil tank but connected to the load, it is the sequence valve. In Figure 131 (b), if the two position two-way electromagnetic directional valve is energized, it is used as a unloading valve. Figure 131 (c) shows the schematic diagram of the pressure reducing valve. The main valve core adopts the normally open slide valve core. B is the oil inlet and a is the oil outlet. The pressure of chamber a passes through the damping hole and then passes through the control chamber and the pilot valve. Its working principle is the same as that of the pressure control cartridge valve pressure reducing valve in the ordinary pilot diagram (see Figure 131).

131

In addition, if the proportional relief valve is used as the pilot valve to replace the direct acting relief valve in the figure, a two-way cartridge electro-hydraulic relief valve can be formed.

4. Flow control cartridge valve

 

 

 

 

 

As shown in Figure 132, add a spool stroke regulator on the control cover plate of the cartridge valve to adjust the opening of the spool, and the cone can act as a flow control valve. If a differential pressure reducing valve is connected in series in front of the two-way cartridge throttle valve, a two-way cartridge speed regulating valve can be formed. If the proportional electromagnet is used to replace the manual adjusting device of the throttle valve, a two-way plug-in electro-hydraulic proportional throttle valve can be formed.

Cartridge valve product introduction: domestic products include TJ series, Z series, Rexroth series, etc. except for structural differences, these products have a pressure rating of 31.5Mpa and a diameter range Ф l6~ Ф 160mm。

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