An integrated model of hydrodynamic lubricating for piston/cylinder interface

Due to their compact and simple design, axial piston pumps are widely used in hydraulic systems. The piston/cylinder lubricating interface is one of the most critical design elements in axial piston pumps, which fulfills the bearing and sealing function simultaneously. Also it is the main source of both friction and volumetric powerloss. In order to realize the optimal design of efficient and reliable axial piston pump, an accurate model of the tribological interface in axial piston pump is needed to save the cost and time in the design process. This study is aimed at developing a comprehensive simulation tool to model the lubricating gap flow between the piston and cylinder, which consists of a main flow model according to a lumped parameter approach and a numerical model for piston/cylinder interface. The instantaneous pressure in each displacement chamber is obtained from the main flow model and utilized in the numerical model as an important boundary condition. An adaptive mesh is built for the oil film between piston and cylinder, on which the Reynolds equation is solved to get the pressure field. Also with the force balance check, the micro motion and gap height distribution is obtained. Couette flow, Poiseuille flow and squeeze flow are included in this numerical model. The simulation model proposed in this paper can provides a theoretical guidance for the structural design of axial piston pump.