Predicting the Behavior of Slipper Pads in Swashplate-Type Axial Piston Pumps

Abstract

This paper describes a dynamic model for slipper-pads that allows lift and tilt behavior to be predicted, including the effects of possible contact with the swashplate or slipper retaining plate. This model has been incorporated in the Bathfp simulation package and used to examine the dynamic stability of slipper-pads over the pumping cycle, and to compare the behavior over a range of pump speeds. The centripetal tilting moments acting on the slipper-pad increase with speed and as a consequence can lead to contact between the slipper and the swashplate at high speed. This is particularly likely to occur as the piston makes the transition between suction and delivery, where the pressure forces acting on the piston-slipper assembly change abruptly. The predicted nature of the swashplate contacts at high speeds correspond closely with witness marks on a dismantled pump. The model presented may also be used for predicting slipper behavior in other types of pump, for example, wobble-plate type pumps, or in piston motors.