A Solution For An Electronically-Controlled Variable Delivery External Gear Pump

This paper describes an innovative design concept to enable electronic control of the flow delivered by external spur gear pumps. The basic principle used to obtain flow variation relies on a variable timing concept previously demonstrated by the author's research team. This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. Previous work proved the applicability of the proposed concept in a pressure compensated design of an external gear pump for high pressure applications. This concept took advantage of the pressure differential acting on the "slider", which is an internal element performing the flow regulation.In this paper, a solution that permits to achieve balance of the pressure forces acting on the slider is proposed. This solution reduces the actuation forces, thus enabling direct flow control actuation through an electronic control system. The proposed solution is cost effective, it consists of a limited number of parts, and it is suitable for pumps without pressure compensation, i.e. for low or intermediate pressures.The paper details the aspects of the pump design, which was performed by using a multi-objective algorithm that maximizes the flow operating range and at the same time the pump. The optimum design could achieve a flow variation of about 32% in simulation and this was also demonstrated in actual experiments on a prototype realized at the author's Research Center.he proposed design can impact several of the current applications of external gear pumps, introducing the additional "flow on demand" capability.