Mixed lubrication analysis for sliding part between rotor and spherical valve plate of swash plate type piston pump

Abstract

A mathematical model of rotor motion and an analysis model on mixed lubrication between the rotor and the spherical valve plate for a swash plate type piston pump have been presented in order to evaluate lubrication characteristics in the sliding part. The analysis on the mixed lubrication consists of Average-Flow-Model by Patir-Cheng and the contact theory by Greenwood-Tripp. The numerical calculations have been carried out under operating conditions and specifications of the spherical surface. It is found that (1) the torque efficiency in the sliding part can estimate with using nR_SVC_S/P_D under each radius and radial clearance of the spherical surface, (2) the reduction rate of the torque efficiency with large spherical radius and radial clearance is smaller than that in other conditions, so that it is possible to obtain the torque efficiency substantially constant under a wide range of conditions, (3) asperity contact force and the friction torque decrease due to squeeze film effect for high pressure of the pump, and (4) the minimum film thickness and the torque efficiency decrease when the rotor motion is stabilized with increasing the rotation of the pump.