Operating Force of Axial Plunger Pump

Abstract

The use of variable delivery axial plunger pumps is ever increasing in servo-mechanism, stepless variable speed transmission and others. To change the delivery rate, it is necessary to move the positions of some movable parts. The object of this study is to analyse the pump kinematics and to determine the operating force exerted on the movable parts and then to consolidate the design data of flow control mechanism or pessure compensator. Pump kinematics are different each other according to its construction design. This paper describes the pump usually called the Thoma or Janney type whose pistons are con nected to the driving shaft by their connecting rods. A swivel yoke has a tendency to change its tilting angle. This tendency or the moment depends on the construction elements, dimensions of the component parts and applied working conditions. The self-shifting moment is caused by such things as oil hydraulic pressures in the cylinder bores, pressure distribution change and pressure change both due to the overlap of valves, lateral force of the piston rods caused by the three kinds of pressures mentioned above, centri fugal force acting upon the pistons and the piston rods, the force from the universal link which is exerted by the bearing spring, and centrifugal force acting upon the oil inside the cylinder. The effect by each of them can be separately calculated and by summing up them, total shifting moment of the yoke will be obtained. The operating force should be applied against this total moment. The analysis appeared in this paper is verified by experiments. Experimental values nearly coincide with calculated values. Usually, there is an oscillation in the yoke and its causes are explained in the analysis.