Structure and working principle of Superposition valve
Structure and working principle of Superposition valve
Superposition valve is a new type of hydraulic component developed on the basis of plate valve integration, but its preparation form is very different from plate valve and cartridge valve. The Superposition valve is an integrated control circuit composed of relevant pressure, flow and one-way control valves, which is installed between the plate reversing valve and the base plate. Each stack valve not only has the function of hydraulic valve, but also acts as an oil passage. Therefore, the hydraulic system composed of superimposed valves does not need another connector between valves, but takes the superimposed valve body as the connector, which is directly superimposed and combined with bolts. Superposition valve is named for its structural shape. The size, position and quantity of oil ports and screw holes of various superposition valves with the same diameter are the same as those of the matching plate directional valve. Therefore, as long as the superposition valves of the same diameter are superimposed for a certain number of times, together with the electromagnetic control directional valve, various typical hydraulic systems can be formed. Usually, the hydraulic circuit of a group of superposition valves controls only one actuator. If several installation bottom plates (also with interconnected channels) are stacked horizontally, a hydraulic system for controlling several actuators can be formed.
Figure 118 is an example of a superimposed valve block and its hydraulic circuit diagram controlling two actuators (hydraulic cylinder and).
The working principle of Superposition valve is basically the same as that of plate valve, but it has its own characteristics in structure and connection mode, so it forms its own system. For example, there are only two main oil inlets and outlets P and t on the bottom of the plate relief valve; In addition to the standardized top port and bottom port of the 4400 type oil valve, the standard top port and outlet port of the 770 type oil valve are overlapped with each other, so that the standard top port and outlet port of the 4400 type oil valve are more interchangeable.
According to different functions, the Superposition valve is usually divided into two types: single function valve and composite function valve.
1. Structure and working principle of single function superposition
Like ordinary hydraulic valves, single function superposition valves also have pressure control valves (including overflow valve, pressure reducing valve, sequence valve, etc.), flow valves (such as throttle valve, one-way throttle valve, speed regulating valve, etc.) and directional valves (such as directional valve, one-way valve, hydraulic control one-way valve, etc.). In order to facilitate the connection and form a system, each valve body has more than 4 through channels such as P, t, a and B. the oil ports in the valve are respectively connected with their own corresponding channels according to the function of the valve. In order to facilitate superposition, the positions of the above channels are the same on the joint surface of the valve body. Due to the limitation of structure, most of these channels are special-shaped holes formed by precision casting.
The control principle and internal structure of the single function Superposition valve are similar to those of ordinary plate hydraulic valves of the same type. In order to avoid repetition, only Y1 overflow valve is taken as an example to illustrate the structural characteristics of the Superposition valve.
Figure 119 (a) shows the structure of the pilot superimposed relief valve. In the figure, the pilot valve is a conical valve, and the main valve core is a cylinder with a conical surface at the front end. The pressure oil enters the right end E cavity of the main valve core from the valve port P and acts on the right end of the main valve core; At the same time, it enters the left chamber B of the main valve core through the small hole D, and then acts on the conical valve core 3 through the small hole a. When the pressure at the oil inlet is less than the adjustment pressure of the valve, the conical valve core is closed and the main valve core has no overflow. When the pressure at the oil inlet increases and reaches the adjustment pressure of the valve, the conical valve core opens, then reaches through holes D and a, the oil outlet T, and then passes through damping hole D, resulting in a pressure drop, resulting in a pressure difference between the two ends of the main valve core. This pressure difference overcomes the spring force and moves the main valve core 6 to the left, The main valve core begins to overflow. Adjust the push rod 1 to compress the spring 2, so as to adjust the set pressure of the valve. Figure 119 (b) shows the type spectrum symbol of the superimposed relief valve.
2. Structure and working principle of composite function Superposition valve
Composite function Superposition valve is also called multi-function Superposition valve. It is a superposition valve that realizes more than two control functions in one control valve core unit. Taking the sequential back pressure valve as an example, this paper introduces the structural characteristics of the composite Superposition valve.
Figure 120 shows the sequential back pressure valve, which is used to ensure the smooth return oil of the hydraulic cylinder when the actuator moves rapidly in the differential system; When the actuator enters the working process, the sequence valve closes automatically and the back pressure valve works to establish the required back pressure in the oil return chamber of the oil cylinder. The working principle of the valve is as follows: when the actuator is fast forward, the pressure at port a is lower than the set pressure of the sequence valve, the main valve core 1 is at the right end under the action of the pressure regulating spring 2, the fluid flow at port B is unblocked, and the sequence valve is in a normally open state. After the actuator enters work, the pressure of the system rises due to the action of the flow valve. When the pressure at the oil inlet a exceeds the pressure setting value of the sequence valve, the control plunger 3 pushes the main valve core to move to the right, the oil circuit B is cut off, and the sequence valve is closed. At this time, the oil return resistance of chamber B increases, and the pressure oil acts on the left end of the step with axial triangular groove on the main valve core, generating a right thrust on the valve core. Under the action of the oil pressure of chambers a and B, the main valve core 1 continues to move to the right to open the throttle valve port, and the oil in chamber B returns through the throttle port to maintain the oil return of chamber B and maintain a certain pressure value.