Research on Lubrication Mechanism of Retaining Spherical Pair of Variable Displacement Axial Piston Pump

Retaining spherical pair is widely used in variable displacement axial piston pump with the feature of complex spatial relative motions. According to the kinematic relation and geometric feature of retaining spherical pair, a physical model based on the cylinder feature is proposed to study the process of oil lubrication between ball guide and retaining plate. And the lubricating film within retaining spherical pair is numerically investigated based on the modified Jakobsson-Floberg-Olsson (JFO) cavitation algorithm to consider the influence of shearing velocity. The relations among the distributions of shearing velocity, clearance shape, cavitation index and pressure under the conditions of three different tilting angles of swash plate are discussed. The research results show that the pressure distribution has the characteristics of double peak and double valley, which is depended on the hydrodynamic effect resulted from the clearance shape and the hydrostrictive effect due to shearing velocity. The hydrostrictive effect is positively correlated with the tilting angle of swash plate which plays an important role in eliminating the amount of load support.