Design of port shape for reducing irregularity of oil pump

Internal gerotor pumps has been used commercially in automatic transmissions, fuel pump engines, and compressors. As the automobile industry has required high fuel efficiency and reduction of noise, studies of internal gerotor profiles to obtain high flow rates and low irregularity have been conducted. But flow rate depends on volume of pumping chamber rather than geometric shape, therefore only design of lobe shape influences greatly on flow rate but has the limitation to a significant reduction of irregularity. On the contrary, flow of working oil is stable and smooth by design of port shape, so that it can help reduction of irregularity. In this study, the gerotor (2-ellipse), having a higher flow rate than the existing geroters, was chosen as the optimal design, and a design of the port shape was performed to decrease irregularity greatly through Computational fluid dynamics (CFD) analysis considering ten design parameters. The effect of each geometric parameter on irregularity was investigated through analysis of Signal-to-noise (S-N) ratios. Based on the results, an oil pump assembling the optimal gerotor (2-ellipse) with a new improved port shape was developed and has resulted in a significant reduction of irregularity, maintaining high flow rate.