抄録
The development of hydraulic equipment has shown a tendency to increase the power density (power/weight). To increase the power density of swashplate type axial piston motors (hereinafter referred to as motors), high pressure with a speedy operation are necessary. As for the high pressure state, approximately 40 MPa and over, not only countering the increase in leakage but also the high stiffness of the motors should be achived. Therefore, presently, it is not possible to assume the motors to be rigid at a state of high pressure.
This study has been made to clarify 1) the distortion and stress distribution in the piston balls and hydrostatic slipper bearings (hereinafter referred to as slippers) and 2) oil film thickness and flow rate between slipper seal land and swashplate in motors at a high pressure state. The piston balls and slippers mostly affect volumetric mechanical efficiency of the motors. A number of investigations of these part have been made, but these parts were assumed to be rigid, because the studies were conducted in the low and middle pressure region. This simplified approach ignores the importance of the distortion in these parts. We carried out a structural analysis of these parts by means of the axisymmetric finite element method (hereinafter referred to as FEM), with a swashplate angle of zero and the slipper floating on a film of oil, that is the piston thrust load is equal to the slipper load carrying capacity. The load condition of the FEM analysis, the pressure on sliding part between the slipper and the swashplate were obtained from the Reynolds equation.
In addition, distortion, stress distribution, oil film thickness and flow rate characteristics with change in slipper pad thickness were discussed. The results obtained in the structural analysis have provided the basic technical data to enable the motors to operate at a high pressure state.
