Design of Gerotor Oil Pump with 2-Expanded Cardioids Lobe Shape for Noise Reduction

Gerotor pump technology is being increasingly employed in innovative application fields, such as engines and as the hydraulic source of automatic transmissions. The most important issues in the automobile industry in recent years are improvement of fuel efficiency and noise reduction, so the existing studies relating to design of the gerotor profiles and the port in gerotor oil pumps have been conducted to ensure high flow rates and low irregularity. This study proposes a new gerotor lobe shape with 2-expanded cardioids to reduce the noise of the oil pump used in the automatic transmissions of automobiles. Theoretical equations to generate the tooth profile with 2-expanded cardioids was established, and then the gerotor profile to reduce noise was proposed using an automatic program. A design method for generation of a port shape suitable for the proposed gerotor was introduced, and performance tests (2000 rpm~3000 rpm) of the new oil pump with the suggested gerotor and port shape were implemented. The test results showed that the flow rate was improved by 7.3%~1.5% and the noise was reduced by 2.8 dB~4.8dB compared to those of the existing oil pump, so it was demonstrated that the design methods for the gerotor with 2-expanded cardioids and the port shape were validated. It is expected that the new lobe shape with 2-expanded cardioids and the port shape design method could be adopted in various fields, and will contribute to improving the performance of oil pumps.