Abstract
Under the conditions of the periodic changes in supply pressure and loads, tribological characteristics of spherical bearings for hydraulic piston pumps and motors were examined experimentally using four types of piston assemblies. The apparatus consisted of a piston assembly with the spherical bearing tested, a bushing equipped with eight hydrostatic bearings, an electric motor and the hydraulic circuit. The diameters of the spheres tested were specified by 7.9, 9.5, 12.7 and 15.9 mm. The maximum supply pressure was 4.9 MPa, the maximum frequency of the sinusoidal and rectangular fluctuation was 1 Hz, and the speed of rotation was 10 s^<-1>. Hydraulic oil of ISO VG 32 was used as the test liquid. Frictional torque and leakage flow rate were measured. In conclusion, the frictional torque notably decreased and the squeeze film effect was recognized for the case of the change in the supply pressure and loads being the rectangular wave with high frequency.
