Fluid film measurements on the spherical valve plate in oil hydraulic axial piston pumps

The fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect or the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate, while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects or the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shaft torque were also investigated in order to clarify the difference between these two types or valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.