Testing System Design For Investigating The Properties Of Oil-Film Between Piston And Cylinder In Axial Piston Pump

The development trend of positive displacement hydraulic transmission towards high speed, high pressure and high flow demands higher performance of piston pump. As one of the most important friction pairs in axial piston pump, piston pair has great influence on volumetric efficiency, mechanical efficiency, temperature rise, wear, the reliability and working life of axial piston pump, it also plays a decisive role in whether piston pump can achieve the maximum working pressure, the largest displacement and maximum speed.Traditional studies on piston pair mainly focused on theoretic analysis, while experimental studies are very little, and most of them just use single-piston pump to simulate the piston pair's function. Due to the complexity of dynamics and kinematics of the piston pair, theoretical studies and earlier tests have much simplification on them, thus they can not reflect the real working condition well. In view of this, this paper designed a set of test rig based on the real piston pump for investigating the properties of oil-film between piston and cylinder in axial piston pump, such as film temperature distribution, film pressure distribution, film thickness and the friction between piston and cylinder, etc.This paper includes six chapters and the summary of each chapter is as follows:In chapter 1, the axial piston pump and its key friction pairs were simply introduced, and then the piston pair and its important role in piston pump were analyzed. The methods for investigating oil-film properties and the research status quo of piston pair were introduced; the main contents and research meaning of the thesis are given out finally.In chapter 2, the testing method for investigating oil-film pressure distribution was given out and the main structures of model pump were designed. Then the methods to install, seal, fix sensors and cables were analyzed and corresponding structures were designed. At last, the influence of the pressure pipeline effect on measurement result and the sensor hole on the oil-film pressure distribution were discussed.In chapter 3, the scheme design and main structure design of the model pump used for investigating oil-film temperature distribution and oil-film thickness were given out. The methods to install, seal, fix sensors and cables were analyzed and the influence of the sensor hole on the oil-film pressure distribution was discussed.In chapter 4, a method using hydrostatic bearing to measurement the friction between piston and cylinder was proposed. Then the structure design and parameters calculation of hydrostatic bearing and restrictor were given out. The main structures of model pump were also designed in this chapter. At last, the friction transfer process and the working parameters were analyzed.In chapter 5, the hydraulic principle of the model pump test rig was given out, and the hardware of measurement and control system was selected based on the system parameters calculation. Four data acquisition and control procedure interface were given out based on the Labview software and debugged successfully.In chapter 6, the summary of the whole work and the prospect in the future are proposed.