Relative motion relation in the external return spherical bearing pair of a balanced double

Based on the external compaction return mechanism of a balanced double-row axial piston pump and the vector coordinate transformation principle, a mathematical model of the relative motion relation within the external return spherical bearing pair was built. The influence of slant inclination of the external swash plate and of pump shaft rotating speed and eccentricity on the relative motion trail, movement speed and acceleration was analysed. The relative motion velocity and acceleration between external retainer plate and external spherical hinge, at top and bottom dead centres, were discussed. By increasing the slant inclination of the external swash plate, the relative motion trail increased correspondingly, leading to a larger size of the pump integral structure. The relative speed and acceleration increased with the pump shaft speed and the slant inclination of the external swash plate, leading to a larger fluctuation of the slipper pair oil film. The increase of eccentricity slightly influenced the relative velocity and acceleration along the x-axis, without significantly increasing the fluctuation of the slipper pair oil film. Increasing the pump shaft speed, the external swash plate slant inclination and the eccentricity all caused fluctuations in the relative velocity and acceleration along the y- and z-axes, deepening the grinding crack on the compaction surface of the external retainer plate. In case of eccentricity and a 0° rotation angle of the principal axis, the related acceleration of the radial friction surface of the retainer plate showed the largest fluctuation amplitude, and a scratch could easily occur