Spin Mechanism And Oil Film Characteristics Analysis Of Piston-slipper Group

As an important hydraulic power component,the axial piston pump has the advantages of compact structure,small volume,high power density,rated pressure and so on,and is widely used in construction machinery,aerospace and other fields.Meanwhile,the slipper pair,the spherical bearing pair and the piston pair are the three significant friction pairs in the axial piston pump,and their lubrication characteristics of the oil film in the clearance have an important influence on the volumetric efficiency and mechanical efficiency of the axial piston pimp.Therefore,the theoretical research on the oil film characteristics of the three friction pairs can provide reference for the design and optimization of the friction pair,so as to improve the working performance of the axial piston pump.For this reason,this paper conducts research from the following aspects:(1)In this paper,the velocity and acceleration of the piston motion are analyzed from three different viewpoint,and the existence of the slipper and the piston spin motion is proved.In addition,the force analysis of the piston and the slipper assembly is carried out,and the supporting force of the oil film between the bottom of the slipper and the surface of the swashplate on the piston-slipper assembly is derived,and the relevant analytical expressions are obtained.(2)When the slipper exists spin motion around its own axis and the oil between the bottom of the slipper and the surface of the swashplate is squeezed by external load,the oil film pressure distribution,oil film bearing capacity,oil film thickness,oil velocity distribution,leakage flow and power loss are analyzed in the slipper pair,and the analytical expressions of the relevant parameters are obtained.At the same time,according to the characteristics of the oil film bearing capacity in the slipper pair,the pressure-supply bearing capacity and the extrusion bearing capacity are defined;According to the characteristics of the leakage flow in the slipper pair,the inherent leakage flow and the extrusion leakage flow are defined;According to the characteristics of the power loss in the slipper pair,the inherent power loss and the extrusion power loss are defined.In addition,when the inherent power loss is the minimum,the concept of the optimum oil film thickness is proposed.(3)When the ball socket of the slipper and the ball head of the piston have unequal radius,and the center of the slipper ball socket is eccentric to the center of the piston ball head during operation,the oil film pressure distribution,oil velocity distribution,leakage flow and oil film bearing capacity are analyzed in the spherical bearing pair,and the analytical expressions of the relevant parameters are obtained.Meanwhile,the spherical support leakage coefficient and the spherical support bearing coefficient are obtained,which are determined only by the geometric dimensions of the slipper ball socket and the piston ball head and their relative eccentricity.(4)When the damping orifice of piston and the damping orifice of slipper have different structures,the oil film support stiffness are analyzed in the slipper pair and the spherical bearing pair,and the analytical expressions of their stiffness are obtained respectively.Meanwhile,the concept of the optimal oil film thickness is proposed in the slipper pair,according to which the dimensionless discriminant number of the optimal oil film thickness is obtained,which can provide theoretical reference for the design of the slipper pair.(5)When the piston exists processing taper in the axial pump and spin motion around its own axis during operation,the oil film pressure distribution,oil velocity distribution and leakage flow are analyzed in the piston pair,and the analytical expressions of the relevant parameters are obtained.Meanwhile,the concept of the critical radius gap is proposed in the piston pair,the direction of the piston pair leakage flow can be determined in the oil expulsion area,which can provide theoretical reference for the design of the piston pair.(6)When the piston exists spin motion and machining taper,the pressure and friction of oil acting on the piston in the piston pair are solved,and the analytical expressions of the relevant parameters are obtained.Meanwhile,the pressure and friction of oil acting on the piston are dimensionless treated.In addition,the pressure of oil acting on the piston is decomposed into a pose matrix containing only dimensionless number and a feature matrix containing the characteristic parameters of the piston pair,and the product of the pose matrix and the feature matrix is the pressure of oil acting on the piston.