A Study on Lubrication Characteristics between Piston Ring and Cylinder Bore of Bent-Axis Type Piston Pump

The bent-axis type piston pump which is driven by the piston rod works on the way that the piston rod drives the cylinder block, so the taper angle of the piston rod and the swivel angle between the cylinder block and the shaft are very important design factors. If the above factors can not satisfy the conditions for optimum design, the friction loss between the cylinder bore and the piston increases, and the pump could fail to work under conditions of severe friction and wear. Since the piston reciprocates in the cylinder bore with high velocity, and at the same time it rotates on its own axis and revolves on the center of the cylinder block, there is a decrease of the volume efficiency generated on account of the leakage between the cylinder bore and the piston. Therefore, to prevent this case, the piston ring is designed at the end of the piston, and the friction characteristics between the piston ring and the cylinder bore are in need of research due to its great influence on the performance of piston pump. Thus, in this paper, the elastohydrodynamic lubrication(EHL) analysis of the film thickness, the pressure distribution and the friction force, have been studied between the piston ring and the cylinder bore in the bent-axis type piston pump. The analyzed results show that friction force is influenced by rotating speed and discharge pressure.