Effect of geometric shape of piston skirt on power loss in piston rod driving type bent-axis-type axial piston pump

Abstract

The bent-axis-type axial piston pump is a type of positive-displacement machinery that is better equipped to solve environmental problems than the swash-plate-type piston pump. For further enhancing this advantage, the power loss due to friction and leakage, and the total power loss have been evaluated based on numerical calculations. The numerical calculations have been carried out for three types of piston skirt shapes, i.e., straight cylindrical and forward/reverse tapers. The power loss in the forward/reverse tapered piston skirts has quantitatively evaluated in comparison to the power loss in the straight cylindrical piston skirt; additionally, the utility of installing the taper on the piston skirt has been investigated in terms of power loss. The results are summarized as follows: (1) Power loss values due to friction and leakage for the reverse tapered piston skirt, as well as the total power loss value, are smaller than those for the straight cylindrical piston skirt. (2) A load ratio considering the taper angle of the piston skirt has been proposed, and the relationship between the load ratio and the reduction rate of the total power loss is clarified. (3) The implementation of the reverse tapered piston skirt is practical under a wide range of conditions; its implementation can be expected to reduce the global environmental load.

Keywords

• oil hydraulics
• bent-axis-type axial piston pump
• piston rod driving type
• piston skirt
• geometric shape
• friction force
• leakage flow
• power loss
• mixed lubrication