Abstract: In order to study the lubrication characteristics of several key friction pairs in axial piston pump under oil or water medium, the principle of the specialized test system that adopts electrohydraulic units for active and passive control of the lubricating oil film is proposed. The principle and constitution of the simulation test system of the said test system that uses film thickness feedback to control the sealing gap of port plate pair is discussed. The action of micro gap flow on the electrohydraulic control system is simplified to the load on the damper in spring, the physical model of the valve-controlled cylinder of port plate pair in relation to the lubricating film thickness is established, and the precision cylinder displacement control equation is derived. The main control parameters affecting the lubrication performance and their interrelations are analyzed, and the dynamic characteristic of film thickness control is simulated. The preliminary test of planar port plate pair oil film is carried out by using the test system. The results show that the simulation of oil film equilibrium is basically consistent with the test, and oil supply pressure and friction torque have relatively great effect on the formation of lubricating oil film. The feedback control principle of servo proportional valve makes the system’s film thickness dynamic feedback performance tend to keep stable, but when the slope of oil supply pressure varies, the equilibrium value of film thickness has certain variation within the preset range.

Key words: Axial piston pump, Electrohydraulic feedback, Oil film thickness, Herringbone groove bearing, Lubrication, Numerical optimizat, Reynolds equation