Geometric Design for a Gerotor Pump With High Area Efficiency

This paper proposes a gerotor profile design based on the theory of gearing. Presented first is the curve of the outer rotor, whose conjugate profile is the inner rotor. Next, the analysis assesses the feasibility of three different design curves: an epitrochoid curve, a hypotrochoidal curve, and a curve made by continuously connecting the epicycloid and hypocycloid. The undercutting equation derived from the mathematical model—which is presented in parametric form—facilitates identification of the design parameter limits, while the sealing property and nonundercutting on the profile are estimated using curvature analyses. Finally, the offset concept is applied to the gerotor design. First, two conjugate curves are obtained, whose offset curves are then found. Pump performance—including area efficiency and sealing—is also compared for these designs, which include both offset and nonoffset rotor profiles.