The Impact of Bushing Thickness on the Piston/Cylinder Interface in Axial Piston Pump

A comprehensive multi-domain simulation tool that could predict the lubricating flow between piston and bushing in the cylinder is presented in this paper. The first module simulates the main flow through the piston pump according to a lumped parameter model. The estimation of instantaneous pressure in each displacement chamber is utilized in another module dedicated to the prediction of the lubricating gap flow between piston and bushing. This lubricating gap flow module is a numerical model based on the fluid-structure interaction algorithm in which the fluid film pressure is calculated by the Reynolds equation. The oil film height is determined by the micromotions of the piston and the deformation of both the piston and bushing interface. The micromotions of the piston are obtained from the dynamic force balance of external force and fluid force. Influence method is applied to calculate the deformations of piston and bushing, which is an efficient offline method. With different thicknesses of the bushing, the power loss and the leakage of the piston/cylinder interface are compared. The test rig is built to measure the friction power loss of piston. The results highlight the impact of the bushing on the piston/cylinder lubricating interface. The mathematical model proposed in this paper has the potential to be a theoretical guide for the optimal design of an axial piston pump.