Effects of Chevron Micro-Textures on Tribological and Lubricating Performance of Cylinder Block/Valve Plate Interface in Axial Piston Pumps

The cylinder block/valve plate interface is one of the major power loss sources and main failure points in axial piston pumps and motors. Surface micro-texture has been proven to be an effective approach to reduce friction and wear in many tribological applications. In the present paper, the effect of micro-texture on the tribological and lubricating performance of the important cylinder block/valve plate interface is studied experimentally and numerically. The experimental investigation was conducted on a disk-on-disk tribometer with similar geometry, operating speed, material, and working fluid to the cylinder block/valve plate interface in the axial piston pump. The tribological test results confirmed the chevron micro-texture's potential to reduce frictional loss in such lubricating interface. Furthermore, a novel numerical method coupling the dynamic loading, squeeze motion, analytical pressure deformation, mixed friction, and cavitation was proposed to study the lubricating performance of micro-textured valve plate/cylinder block interface. This model was then validated comparing to the tribometer experimental results and was used to study the effect of depths, widths, and distances of chevron micro-textures on the lubrication performance of cylinder block/valve plate interface. The results found that the depth of the chevron micro-textures affected whether the cavitation occurred inside the micro-texture, the width of the chevron micro-texture affected the size of the cavitation area that occurred in the micro-textures, and the chevron micro-texture distance affected the size of the convergence zone where positive pressure generated.