Variable Flow Internal Gear Pump
Abstract
Abstract A variable flow internal gear pump is a fixed displacement unit where timing can be varied with respect to the gearing to reduce the net outgoing flow from the delivery volume. Usually, in IC engines lubrication, and at high engine speed, a reduction of the net outgoing flow from the pump is achieved via flow recirculation to inlet through a pressure relief valve. This obviously entails a waste of power. Before thinking of variable displacement units an intermediate step worth of consideration is represented by a variable timing yet constant displacement pump. The management of timing can follow different strategies (either in delay or in advance) and a control philosophy may be implemented whereby timing is varied based on attainment of a constant delivery pressure. The paper, through theoretical analyses, detailed modelling and simulation of the pump unit, of timing and its control, leads to compare possible and feasible alternatives providing solid ground for screening and progressing to the manufacturing of a prototype. These steps as well as test results of the prototype are contrasted with model based predictive simulations.