How much do you know about directional control valves?

The directional control valve is referred to as the directional valve, which is mainly used to switch the oil circuit or switch the direction of the oil flow to meet the requirements for the start, stop and movement direction of the actuator. According to its use, it can be divided into two categories: one-way valve and reversing valve.

(1) Check valve

The one-way valve is also called the check valve, its function is to make the oil flow only in one direction. According to the different spool structure, one-way valve can be divided into two types: ball valve type and poppet valve type. Figure 5-1 shows the structure of two check valves and the symbols of check valves. The ball valve spool has a simple structure, but it is easy to cause poor sealing due to friction, and is only used in low pressure applications. The poppet valve type is used more and has better sealing performance. According to the channel in the valve, it can be divided into straight-through type and right-angle type. The straight-through liquid flow resistance is small, and the replacement of the spring is also more convenient. Generally, a tubular connection is used; while the right-angle type can be used for a tubular connection. Plate connection or flange connection can also be used.

The main function of the spring in the one-way valve is to help the valve to close quickly when there is no oil flow through or the oil flows back. But it also increases the resistance when the valve opens and becomes the main part of the pressure loss when the oil flows through the one-way valve. The spring should be made softer without affecting the sensitivity and reliability of the valve. 'Generally, the opening pressure of the one-way valve is 0.035-0.05MPa, and the pressure loss when the whole flow passes through is about 0.1-0.3MPa.

(2) Reversing valve

The function of the reversing valve is to use the relative movement of the spool and the valve body to connect or close the oil circuit or change the flow direction of the oil to the actuator, so that the actuator can start, stop or change the direction of movement.

(1) Classification of reversing valves

According to the structure, the reversing valve can be divided into rotary valve type and slide valve type; according to the number of working positions of the valve core, there are two-position, three-position and multi-position, etc.; according to the number of inlet and outlet channels, there are two-way, three-way, four-way and five-way According to the operation and control methods, there are manual, motorized, electric, hydraulic and electro-hydraulic, etc.; according to the installation method, there are tubular, plate and flange types.

①Rotary valve

It changes the flow direction of the oil by using the rotation of the valve core relative to the valve body. This valve has three working positions, four ports, and is manually operated, so it is called a three-position four-way rotary valve type manual reversing valve. The rotary valve has poor sealing performance and unbalanced radial force, and is generally used in low-pressure, small-flow systems.

②Slide valve

It changes the flow direction of the oil by using the axial displacement of the valve core relative to the valve body. The reversing valve changes the left and right positions, that is, the actuator changes the direction of movement. This valve has two working positions, four ports, and the valve core is moved by the thrust of the electromagnet, so it is called a two-position four-way spool type electromagnetic directional valve.