Study Of Large Flow2D Electro-Hydraulic Proportional Directional Valves

Electro-hydraulic proportional valves are one kind of components which can output proportional pressure and flow rate according to the input current signal by producing displacement of the spool and changing the orifice size. Because of their high rate of quantity and price, and they can meet the technical requirements of ordinary civilian industry, they have become a common part of the hydraulic system. Electro-hydraulic proportional directional valve can not only change the direction of the flow but also the flow rate according to the input signal and it is the important part of electro-hydraulic proportional valves. In this thesis, a two stage proportional directional valve without a seperate pilot valve, large flow2D electro-hydraulic proportional directional valve, has been studied.The2D electro-hydraulic proportional directional valve is composed of2D valve, compression-torsion coupling and electromechanical transducer(proportional electromagnet). The innovative ideas in this thesis is that by the compression-torsion coupling’s function of thrust-torque converter, the thrust of proportional electromagnet has been converted to torque to rotate the spool of2D valve. Thus, the pressures across the spool would change differently. Then, the spool will move by the pressure difference. Therefore, we could realize the target of controlling the direction and flow rate. This valve has both the advantages of direct-acting valves and pilot valves, and can not only work under high pressure and large flow, but also has the advantage of simple structure, and can work under zero pressure or low pressure conditions like direct-acting proportional valves.This thesis firstly summarized and analysed the technical characteristics and development status of the electro-hydraulic proportional control technology, and discussed the advantages and disadvantages of the existing proportional directional valves. Then, make research of2D electro-hydraulic proportional directional valve, the main research contents and results are as follows:(1) Based on the analysis of the servo screw mechanism, for the purpose of reducing the processing costs and meeting the general civil industry, an innovative large flow2D electro-hydraulic proportional directional valve’s structure and principles of it have been carried out.(2) The mathematical model of pilot stage was established, then, the stability analysis and dynamic simulation was carried out by using the Matlab software. Meanwhile, the structure parameters affecting on dynamic characteristics was analysed, providing a theoretical basis for the structural optimization.(3) We have expounded the design about the structure and parameters of the compression-torsion coupling of sliding wedge type, the valve body and the spool.(4) The digital proportional controller which was used in the experiment was described. Then, some experiments which was about the displacement input-output behavior of sliding wedge type compression-torsion coupling and the static flow characteristics have been taken. At the same time, we have researched and analysed those experimental data.