The Impact of Using a Secondary Swash-Plate Angle Within an Axial Piston Pump

In this paper, the control and containment forces acting on the swash plate of an axial-piston pump are examined. The most novel aspect of this research is that it includes the analysis of a secondary swash-plate angle that is occasionally used in aerospace pump applications. From a practical standpoint, swash-plate control and containment devices take on many different designs; however, they must all resist the same essential moments and forces that attempt to dislocate the swash plate from its proper position. By considering the basic machine design without its control and containment mechanisms, this work generally derives the needed forces and moments for insuring proper swash plate motion and thereby gives the designer of these machines a useful tool for designing control and containment devices of any type. In this research, the dynamic characteristics of the control and containment forces are studied by deriving instantaneous and average equations of motion for the swash plate. Results from this analysis are generated by holding the pump speed and discharge pressure constant, and by prescribing a typical second-order response for the primary swash plate angle. In conclusion, it is shown that the primary advantage of implementing a secondary swash-plate angle is that it can be used to reduce the overall control effort of the pump. Disadvantages of using the secondary swash-plate angle are associated with additional containment requirements for the swash plate.