Characteristics of Fluid Films Between a Valve Plate and a Cylinder Block of Axial Piston Pumps and Motors

Characteristics of a fluid film between a valve plate and a cylinder block of axial piston pumps and motors are investigated. The effects of hydrostatic, wedge film and squeeze film are obtained separately by solving Reynolds equation numerically. Main specific points of interest are as follows; (1) Since the seal part of a valve plate in most of the piston pumps and motors does not have compensating mechanism as a hydro-static bearing, magnitude of fluid film coefficient of a valve plate depends on the pad part. Even the fluid film coefficients of a valve plate with fairly large pad part are smaller than those of usual bearings such as journal bearings, and performance of a valve plate as a hydro-dynamic bearings is inferior to usual bearings. (2) Main factors for power loss between a valve plate and a cylinder block are clarified and data for valve plate design are presented.