An Experimental Analysis of Valve Plate Control : a New Approach to Displacement Control for Hydraulic Piston Machines

Abstract

Displacement control of a pump means controlling the amount of fluid that is pumped per rotation. This is used to increase the efficiency or controlling the flow in a system and currently there is almost exclusively one type of displacement control available for piston machines on the market. With this method, the stroke length of the pistons can be varied by changing the angle of the so-called swashplate. There are however drawbacks with this principle that mainly concern in stability or efficiency. In this thesis, an unconventional approach to displacement control has been experimentally evaluated. The principle of this method is to vary the effective use of the stroke length by rotating the valve plate, which is a component that separates the inlet from the outlet. This can be done with an electric motor and the problems concerning efficiency and stability can be avoided. The main drawback with this type of control is however the high noise level caused by pressure ripple in the cylinders. This thesis treats the characteristics of this type of control, both theoretically and experimentally, and describes the analysed prototype. It also deals with new conceptual designs for this type of control. How-ever, in summary it can be said that the prototype behaved as expected but had problems with leakage