Design And Theoretical Investigations Of Water Hydraulic Variable Displacement Piston Pump

Water hydraulic transmission technology is a new technology which uses water, including sea water and fresh water, as working medium and lubrication medium in a hydraulic system. It has advantages of fire resistance, no pollution, small losses for compression, fast response, low temperature rise, small pressure loss and low maintenance cost. Water hydraulic variable displacement pump, the most front topic of current hydraulic pressure transmission engineering research field, is one of the core working cells of hydraulic pressure transmission system. Compared to water hydraulic quantitative pump, water hydraulic variable displacement pump's merit obtains power regulation and energy conservation and can reduce the system's heat loss, lengthen pump's service life.In this thesis, the newest domestic and overseas general researching and application of water hydraulic quantitative pump and oil hydraulic variable displacement pump are summarized. The differences of design theory and methods between them are studied. The key questions of designing water hydraulic variable displacement pump are analyzed and the solutions are discussed. Then the gross structure plan is determined and the primary structure parameters of this pump are calculated. In view of the water medium characteristic, this paper has carried on the design to the constant pressure water hydraulic variable displacement pump's stroking mechanism. A stroking mechanism is composed of the control valve and the variable driving mechanism. This thesis has conducted the research separately to two parts, designs suits take the water as the working medium structure.In this thesis, the volumetric efficiency of the system is analyzed, the percentage of leakage of variable pump is calculated and the leakage control of structural design can give guidance. Water hydraulic variable displacement pump control system is a position control system. The mathematical model of variable displacement pump is set up based on structural design. The constant pressure valve spool displacement, spool radius, spring stiffness ,variable cylinder cavity radius, physical and chemical properties of water to the variable pump in dynamic performance is analyzed.The thesis study on the structure of the variable displacement piston pump and design an innovative variable displacement piston pump. The feasibility of such a design is also discussed which provides theory basis for the research and manufacture of the pump. Conclusion and prospect of the whole project and this dissertation is pointed out. This dissertation believes water hydraulics will have a prospective future with the development of new material, new technology and new process.