Robust Design of Piston Assemblies in an Axial Piston Pump

Abstract

The piston slipper in an axial piston pump demonstrates most complicated dynamic motions: two rotations (tilting toward to the swash plate and rotating about the pump shaft) and one translation together with the pumping piston. In addition, the slipper is used to lubricate the swash plate surface with hydraulic oil, but prevents high pressure fluid escaping from the piston bores. In hydraulic engineering, improper designs of the piston and slipper assembly cause many instability and unbalance issues while the slipper attempts to lift and tilt off the swash plate. This may cause catastrophic failure and damage to a piston pump. To suppress the undesirable motion is one of most design difficulties that might take a range of different dynamics into consideration and compromise the design parameters of piston assemblies. In this study, the complicated dynamics are simplified and linearized with some assumptions that are able to apply stability conditions. The dynamic response of the assembly as operating needs to follow its desired rotating movement, i.e. the swash plate angular position. The slipper motion is affected by its inputs (including piston bore pressure, hold-down forces, etc.). This paper investigates the dynamic behavior of the piston and slipper assembly by using the parameter perturbation analysis (PPA) method. The results can be used as robust design recommendations for piston assemblies in the piston pump from a novel perspective.