A design and performance prediction method for axial piston pumps with integral controls

Abstract

The thesis presents the findings of a programme of research into the design and performance of variable displacement axial piston pumps of the swashplate type with integral controls. The work is principally concerned with developing a systematic design and performance prediction method for use at the design stage. The method developed outlines stage by stage the problems which arise and give guidance on the decisions which have to be made during the design process. Existing theory and technological data is integrated in the method and is augmented by the author's own contributions in the area of force analysis and contact stresses in the cylinder bores. Graphical optimisation methods are employed and the effects of manufacturing tolerances and .pump working ranges are investigated. The effectiveness of the method is demonstrated by designing a pump to the same specification as that of an existing industrial pump and by making a critical comparison of the two designs. Various regions of power loss are identified and equations derived for estimating these losses. The equations are developed and integrated into a performance prediction method which is novel in that unlike any known method, pump performance can be predicted without the need to test a similar pump. Using data readily available at the design stage the method is used to compare the performance of the existing pump with predicted values. Close agreement is claimed as an indication of the reliability of the method. The thesis gives an account of the historical development of the axial piston pump, a survey of published work on design and performance and a description of axial piston pumps and hydrostatic transmissions. Also included is an analytical treatment for the frequency response of servo controlled pumps by manual and electrohydraulic control.