Research On Operating Characteristics For Conical Spindle Distributing Flow Pair Of Ball Piston Pump

High power density,large displacement of the hydraulic pump is still in an irreplaceable position in the field of vehicle transmission,but the performance requirements of the hydraulic pump is getting higher and higher,and the friction and wear of the contact pair in the hydraulic pump causes the volumetric efficiency and the service life to reduce has not been well solved.Based on this,a new conical flow distribution pair of high power density ball piston hydraulic pump is studied in this paper,consist of theoretical and experimental studies for its working conditions.The conical flow distribution pair(CSP)is a new flow distribution method that has both the advantages of end face distribution and cylindrical shaft distribution.According to its working mechanism,the structure program is the high-pressure port on the opposite,low-pressure port on the left and right to eliminate overturning torque and the distribution shaft is supported with hydraulic static and dynamic pressure.Based on the necessary assumptions,the lubricating model is conducted by combine the fluid continuity equation and N-S equation and its boundary conditions were solved by the method of resistance network.Pressure distribution of flow distribution is obtained by solving Reynolds equation using the finite difference method.Based on this,the influence of structural parameters such as the diameter of short damping hole and half cone angle and operating condition parameters such as working pressure,speed,eccentricity and distribution gap for lubrication characteristics is analyzed.Based on lubricating characteristics,the steady working condition of CSP is studied by conduting the balance equation and solving state parameters.The result shows that the balance point is existing and unique.With this method,the effects of different structural parameters and operating condition parameters for state parameters were analyzed.The results show that the distribution gap and eccentricity get larger when damping hole’s diameter,working pressure and temperature rising and smaller when half cone angle and spindle speed rising.Based on this,the optimized target of CSP is proposed and effectiveness is tested by experiment.According to the ball piston pump usually working in the harsh conditions of the impact load,dynamic characteristics of CSP is necessary.So that the two-degree-of-freedom dynamic model of CSP in axial and radial direction of is established and solved by fourth-order Runge-Kutta method.The results show that,when subjected impact load,the pressure in balance zone experienced three stages consists of rapid rise,overshoot and stable;the distribution gap experiences three stages consists of first decrease,then increase,and finally return to equilibrium state;the eccentricity rate experiences four stages consists of increases first,then increases inversely,then increases again,and finally returns to the steady state.All of these proves that the CSP has adaptive closed loop regulation ability to resist the impact and it is verified by experiment.