Geometry design of a non-pin cycloid drive for in-wheel motor

Cycloid drives are widely used in the in-wheel motor for electric vehicles due to the advantages of large ratio, compact size and light weight. To improve the transmission efficiency and the load capability and reduce the manufacturing cost, a novel cycloid drive with non-pin design for the application in the in-wheel motor is proposed. Firstly, the generation of the gear pair is presented based on the gearing of theory. Secondly, the meshing characteristics, such as the contact zones, curvature difference, contact ratio and sliding coefficients are derived for performance evaluation. Then, the loaded tooth contact analysis (LTCA) is performed by establishing a mathematical model based on the Hertz contact theory to calculate the contact stress and deformation. Finally, based on a numerical example, the two gears are manufactured by using additive manufacturing methodology (3D printing), the meshing characteristics are analyzed and the contact stress and deformation are calculated by using the analytical models and validated by the finite element method (FEM), which shows a good agreement. Meanwhile, a comparison with the conventional cycloid drive is conducted, which demonstrates a salient feature of the proposed cycloid drive. The design and analysis in this study could help designers to design suitable cycloid drives and provide an alternative cycloid drive for the application in the in-wheel motor of electric vehicles.