A novel design concept for variable delivery flow external gear pumps and motors

Abstract

This paper presents an original concept for variable delivery external spur gear machines, which combines the well-known advantages of these units (such as low cost, good reliability, acceptable efficiency) – traditionally fixed displacement – in a solution capable of varying the amount of flow displaced at each shaft revolution. The proposed design concept realizes a variable timing for the connections of each tooth space volume with the inlet and outlet ports, through a movable element (“slider”) placed at the gears lateral side. The position of the slider determines the amount of flow displaced by the unit per revolution. In order to extend the range of flow variation achievable by the unit, an asymmetric involute tooth profile for the gears was proposed. A multi-objective genetic algorithm was used to optimize the design of the gears along with the design of the timing grooves in the slider. This algorithm is based on the HYGESIM (HYdraulic GEar machines Simulator) tool developed by the authors’ resea...