Non-undercutting region and property evaluation of epitrochoidal gerotor geometry

The gerotor pump is widely used for industrial applications. In this paper, the inner rotor profile is an equidistant epitrochoidal curve, and the outer rotor is generated by the inner rotor profile. This paper discusses an undercutting analysis of the rotor profile, in which the undercutting equations are derived by the theory of gearing. The non-undercutting region is determined by the undercutting curves of the inner and the outer rotors. Numerical examples show that the non-undercutting region on the gerotor profiles only needs to consider the lower part of the undercutting curve of the inner rotor. Besides, the curvature equations of the outer and inner rotors are derived for evaluating the rotor profile properties such as assessing the sealing property and the Hertz stress forecast. The theoretical stress and software simulations proved the stress forecast. The results obtained are important for using the gerotor profile in optimum design.