Research on the performance of electro-hydraulic proportional flow valve controlled by pilot pump

Abstract

Cartridge flow valves, widely applied in heavy machine and equipment, have the advantages of low leakage, large flow capacity, and simple structure. However, in the existence technologies, in order to reduce the influence of load variety on valve flow, a pressure differential compensator or a cartridge type flow sensor should be added to proportional throttle valve. This method reduces valve flow capacity and increases system throttling loss. In large flow occasion, flow only can be indirectly controlled by changing valve opening area for the limitation of the structure. So a low energy consumption, high controllable electro-hydraulic proportional valve which is structured by a hydraulic transistor (Valvistor) and a small displacement hydraulic pump driven by a servo motor is introduced. Based on the Valvistor valve flow amplification principle, main valve flow is controlled by pilot pump flow which is controlled by changing rotation speed without the influence of load variety. In the research, it's known from the analysis of the new principle valve steady flow characteristics that feedback throttle slot pre-opening will cause the decrease of the main valve flow as pressure drop increases. Soa method of pressure differential-pilot pump rotation speed compensation is put forward and it can obtain ideal flow characteristic. Then the dynamic mathematical model is established and the main valve stability criterion is derived. The influence of the valve parameters on main valve performance is analyzed and simulated. The results provide a new method for the large flow electro-hydraulic proportional control system.