General principles for structural design of directional valves

1. Determine the number of working edges and paths

The number of working edges and the number of channels should be mainly considered from the three aspects of the type of executing element, performance requirements and manufacturing costs.

Three-way (double-sided) valves can only be used to control differential hydraulic cylinders; Four-way (four-sided) valves can control the hydraulic motor, symmetrical hydraulic cylinder and asymmetric hydraulic cylinder, but the use of symmetrical four-way valves to control the asymmetric hydraulic cylinder   is easy to produce large hydraulic shock, the movement is not smooth. The pressure gain of the four-way valve is twice as high   as that of the three-way valve. The load error of the system controlled by the four-way valve is small and the   response speed of the system is high. Multi-purpose four-way valve with high performance requirements;   Hydraulic servomechanism with small load and low performance requirements, or three-way valves commonly   used in special occasions with external load return trip; Two-way valves are only used where automatic   tracking is required, but there is no performance requirement.

Four-way valves have higher manufacturing costs, followed by three-way valves. Two-way valves are easy to   manufacture.

2.Determine the shape of the valve port

The port shape is determined by the linear requirements of flow size and flow gain. Generally, when the rated flow rate is greater than 30L/min and the dynamic requirements are high, the full opening is used. In order to have sufficient stiffness, the spool of the small flow valve should not be too small, so a local opening is used. Almost all local openings adopt even rectangular Windows, and the distribution of throttling side must be symmetrical. Otherwise, it will increase the friction of the slide valve and thus increase the resolution of the servo valve. Windows are used for electrical discharge or wire cutting.

3.Determination of zero opening type

Zero opening type depends on performance requirements and application. The flow gain of zero opening valve is linear, the pressure gain is high, and it is the most widely used. The flow rate near the zero position of the positive open valve is nonlinear, the pressure gain is linear but the gain is low, and the zero leakage is large, which is generally less used, and is mostly used in the pre-stage, synchronous control system,   high temperature   working environment and constant current system.

4.Determination of the number of shoulders

Shoulder to ensure that the spool has a good support, easy to open the pressure groove, and make the axial size compact for the principle. Four-way valves generally have 3 or 4 shoulders.   Three way valve with 2 or 3   shoulders.The special purpose slide valve, in addition to the control surface at both ends, has an auxiliary control surface, which requires 5 or 6 shoulders.