Research On Flow Characteristics Of Incline Piston Type Swashplate Variable Displacement Pump

Hydraulic transmission technology has been widely used in construction machinery and other engineering fields. The tansmission efficiency of hydraulilic power system, however, is becoming more and more overhang as the requirements of energy saving and environment protection are higher and higher. As well known, the most effective method to increase efficiency of hydraulilic power system is to use variable displacement pump directly. Because of its techno-dominance such as high supply pressure and easy for variable displacement control, swashplate axial piston variable displacement pumps have been the preferential hydraulic pumps for most hydraulic system with high pressure. To improve flow characteristics of swashplate axial piston variable displacement pump, therefore, is one of the key problems for increasing efficiency of hydraulic transmission system.Taking Incline Piston Type Swashplate Variable Displacement Pump (IPTSVDP) as main researching object, aimed at the flow characteristics such as flow pulsation, control performance of variable displacement machnism and so on, the pump performance are studied systematically by means of combinative methods such as theoretical analysis, numerical simulation and experimental investigation in this dissertation. Aimed at the structure specialty of IPTSVDP, the effects of piston conical angle to IPTSVDP performance are mainly researched. The main study contents of the dissertation are as follows:1. The theoretical model of IPTSVDP is established. According to the law of piston motion in absolute coordinate, transient flow characteristic model of the pump both in ideal liquid state and in actual liquid state are developed respectively by lamped parameter method. Dynamic equitions of friction pairs between piston and its cylinder hole, piton slipper and swash plate are established by rigid-body dynamics. The mathematic model of displacement-force feedback control system for pump delivery variable mechanism are built. Theoretical models above are built based on structucture of specialty IPTSVDP and also the piston axis angle is introduced as variable perameter. The models can be not only used for IPTSVDP performace analysis, but also employed to other type piston pump analysis.2. The research platform for IPTSVDP flow characteristics is created. According to above theoretical model, simulation platform based on the technics of synergism collaborative and virtual prototype and the testing device are built up. The platform could be a fundation for piston pump flow characteristics analysis. The real simulation of actual working state of the pump is carried out by means of data exchange in different modules. Pump pressure, flow rate and angle displacement of swash plate as well as other pump parameters can be measured by sensors in the test device, and the instantaneous discharge flow of piston pump, steady and dynamical performance of variable displacement mechanism are obtained based on the principle of experimentation. The simulation results of collaborative simulation platform can be verified by testing conclusion, besides the collaborative simulation platform is able to accomplish some parameters analyses that is carried out unreachably by experimentation.3. Researches on flow pulsation of IPTSVDP. Piston motion low and the flow pulsation in ideal liquid model of the pump are simulated numerically by Matlab. The flow pulsation varing rule in actual liquid model and its affect factors of the pump are analyzed by means of the collaborative simulation platform. An approximate method for measuring pump flow pulsation is given out, and measurements of pressure ripple and flow pulsation in outlet pipeline of the pump are carried out.4. Researches on variable delivery control characteristics of IPTSVDP. The dynamic performance of the IPTSVDP mechanical component is analyzed by virtual prototyping model, and the friction force affectors of frinction pair between piston and its cylinder hole due to matching clearance and piston dip angle are discussed. The control characteristics and their affecors of the pump variable displacement mechanism in steady state and dynamic state are researched based on collaborative simulation platform. The control characteristics of the pump variable displacement mechanism in steady state and dynamic state are measured by testing device in different operating conditions. The research results show that offsetting spring in displacement-force feedback system is an important factor, which affects the steady state control characteristic of the pump variable displacement mechanism. And there is evident asymmetry in the dynamic control characteristic of the pump variable displacement mechanism based on differential cylinder controlled by a three way valve.The research contents above are the key problems should be solved in design and development of high pressure and large flow rate axial piston variable displacement pump. The research conclusions conduce to comprehending the forming mechanism of flow pulsation and the control principle of variable displacement mechanism. Therefore, these conclusions are the theoretical foundation and data reference for optimizing the flow characteristics of swashplate-type axial variable displacement piston pump.