Vane Pump Theory for Mechanical Efficiency

Abstract

This paper describes the theoretical analysis on the mechanical efficiency of a hydraulic-balanced vane pump and presents a design concept to decide values such as vane thickness and cam lift to improve its mechanical efficiency. In this paper, the friction torque characteristics of the balanced vane pump, especially the friction torque caused by the friction between a cam contour and vane tips are both experimentally and theoretically investigated. Although the friction force increases with vane thickness increase due to increase in the vane force, the mechanical efficiency of the vane pump does not decrease when the cam lift becomes large as the vane thickness is increased. An important parameter ∊ defined as the ratio to be obtained by dividing the cam lift by the vane thickness determines essentially the mechanical efficiency of the vane pump. The pumps with the same ∊ have the same mechanical efficiencies, even if the cam lift or the vane thickness varies. A larger value of ∊ leads the vane pump to obtain a higher mechanical efficiency although the limit of vane strength governs the upper limit for ∊. Additionally, reducing the friction coefficient of the vane tip contributes to improvement of the mechanical efficiency.