Hydraulic control directional valve, referred to as directional valve, is mainly used to turn on and off the oil circuit or switch the direction of oil flow to meet the requirements for the start, stop and movement direction of the actuator. According to their use, it can be divided into two categories: check valves and directional valves.
Check valves, also known as check valves, have the function of making oil flow only in one direction. According to the different spool structure, check valves can be divided into two types: ball valve type and poppet valve type. The ball valve type spool has a simple structure, but it is easy to deteriorate the sealing due to friction, and is only used in low-pressure occasions. The poppet valve type is more used and has good sealing. According to the channel situation in the valve, it can be divided into straight type and right angle type. The straight-through fluid flow resistance is small, and it is more convenient to replace the spring, generally using a tube connection, while the right angle type can be connected by a tube connection, and can be connected by a plate or a flange.
The main function of the spring in a check valve is to help the valve close quickly when no oil flows through or the oil back flows, but it also increases the resistance when the valve is opened and becomes the main part of the pressure loss when the oil flows through the check valve. While not affecting the sensitivity and reliability of the valve, the spring should be made softer. Generally, the opening pressure of the check valve is 0.035~0.05MPa, and the pressure loss when the total flow passes is about 0.1~0.3MPa.
The function of the directional valve is to use the relative movement of the spool and the valve body to turn on, close the oil circuit or change the flow direction of the oil to the actuator, so that the actuator starts, stops or changes the direction of movement.
The directional valve is divided into rotary valve type and spool valve type according to the structure; According to the number of valve core working positions, there are two, three and multiple positions; According to the number of import and export channels, there are two, three, four and five links; According to the operation and control mode, it is divided into manual, motorized, electric, hydraulic and electric hydraulic; According to the installation method, it is divided into tube type, plate type and flange type.
The rotary valve changes the flow direction of the oil by using the rotation of the spool relative to the valve body. This valve has three working positions, four ports, and is manually operated, so it is called a three-way four-way rotary valve manual directional valve. The sealing performance of the rotary valve is poor, and the radial force is unbalanced, which is generally used in low-pressure, small-flow systems.
The spool valve changes the flow direction of the oil by using the axial displacement of the spool relative to the valve body. The directional valve changes the left and right positions, even if the actuator changes the direction of movement. This valve is called a two-position four-way spool type solenoid directional valve because it has two working positions and four ports, and the spool moves by the thrust of the solenoid.
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