Piston surface design to improve the lubrication performance of a swash plate pump

Abstract

Abstract Mechanical power loss in hydraulic piston pumps comes from the friction between parts in relative motion, and wear is among the top pump failure mechanisms. Reducing friction and preventing wear require lubrication enhancement, which may be accomplished by proper surface texture design. Cylinder length is an important factor affecting the lubrication performance of the piston-cylinder system in a swash-plate pump. Our previous analyses revealed that under the same load, increasing the cylinder length could decrease the maximum pressure and increase the minimum film thickness, favorable for the pump operation with reduced wear; however, friction would become higher. The work reported in this paper intends to lower friction by textures in the piston surface while increasing, or at least maintaining, the load capacity of the piston system. Several textures are designed and their lubrication performances investigated, aiming at reducing the piston friction and improving the load-carrying ability of the system in a wide range of operation conditions. The effects of texture type, application location, and texture shape are studied, and their relationships with the friction and film thickness characteristics of the piston-cylinder interface are explored. Two optimal surface-texture designs are suggested, which are named the Step-Multiple-Grooves design and the Combine design.