Study On The Lubrication Characteristics Of The Valve Plate Bearing In Hydraulic Axial Piston Pump

The high pressure-velocity swash-plate type axial piston pμmp is widely use in hydraulic field.However,the technical design level of high-pressure axial piston pμmp does not adapt the development of the national economy.The domestic hydraulic components pressure lever can only reach 31 MPa,and there is a lack of performance index and reliability of speed,resulting in the high pressure-speed hydraulic components can only use the small displacement of the core components of foreign civil 40 MPa grade.The valve plate pair is the friction pair with largest area in axial piston pμmp,which is composed of cylinder balock and valve plate.With the increase of working pressure level,the inclination angle of cylinder block gets big caused the local lubrication deterioration,and in the meanwhile making the leakage increase huge reduced the pμmp volμmetric efficiency.The friction and leakage characteristics of pμmp depend on the couple of cylinder block dynamics and friction feature of valve plate,which brings the challenge to the design of the plunger valve pair.The research object of paper is the plane valve plate for swash plate axial piston pμmp.The in-depth theoretical researches have been carried on about the transient characteristic of micro oil film and the corresponding lubrication characteristics.The paper mainly discusses the pair macro geometrical structure parameters,influencing the working conditions and the surface profile of friction and lubrication characteristics,realize cylinder dynamics,radial surface contour analysis of complex coupled shallow groove fluid effect and friction characteristics,provide method and theoretical basis for the high speed flow side performance analysis and design.The surface radial profile is measured using a profilometer,and the mathematical equation of radial profile is nμmerical fitting.The 12 kinds radial profile dual form models are established considering cylinder block inclined posture.Basing on the analysis of lubricating fluid flow state,the hydrostatic and dynamic coupled lubrication model is built considering the surface radial profile,which is equivalent to the linear superposition model of pure dynamic pressure model and pure hydrostatic lubrication model.A analysis methods to two model relative error is built.The steady lubrication test and static analytical formula are used to respectively validate the pure hydrodynamic and hydrostatic model.The effect of the dual form and flatness to dynamic pressure are researched.The results show that in the experience value of equilibriμm factor B,the result of equivalent superposition model can be acceptable;the concave cylinder and concave valve plate is the most suitable surface radial profile,and increased the ability to generate pressure with the variation of a concave distance decreases nonlinearly,so the design of high pressure valve side should try their best to improve the flatness of the design requirements.The oil pressure model in the piston cylinder is established based on the control unit method.Basing on the analysis of micro motion of the cylinder under constraint,the Euler method is used to building the three degree of freedom dynamics model of cylinder block considering the inertia effect.The asperity contact model is established on the measuring distribution asperity distribution,the average Reynolds equation is used to simulation the support force considering oil film roughness peak effect.According to the mutual conversion of micro motion hypothesis shape parameters and kinetic parameters of realization of oil film,finally built the dynamic model of cylinder block friction dynamics and tribology coupling.The tribo-dynamic model is solved by the Newmark integral method,and the solving process is to convert dynamic least squares norm minimization problem using the L-M method at each time step.The tribo-dynamic model is used to study on the change rule of the micro motion state of cylinder and oil film thickness.The friction and leakage characteristics of cylinder valve pair and the dynamic mechanical properties are studied.The effect of inside and outside belt width on the lubrication properties is analyzed.To verify the rationality of the dynamic model,the dynamic lubrication test is established using the oil film and friction characteristics.Based on the analysis of effect of traditional hydrodynamic bearing pad on lubricating characteristics and the limitations,a new type of shallow groove hydrodynamic bearing pad is proposed,which could expand the scope of working condition.The lubrication model for the shallow groove hydrodynamic bearing pad is built.The lubrication characteristic of shallow groove hydrodynamic bearing pad is studied by the tribo-dynamic model.The result shows that the shallow groove hydrodynamic bearing pad could effectively improve the friction characteristics at low speed and high pressure working conditions without reducing the leakage characteristics at low pressure working conditions.