Design optimization and robustness of differential bevel gear for NVH performance improvement 2019-01-1552
With fast pacing development of automobile industry and growing needs for better driving experience, NVH performance has become an important aspect of analysis in new driveline product development especially in hybrid and electric powered vehicles. Differential bevel gear has significant role in the final drive. Unlike parallel axis gears such as spur or helical gear, bevel gear mesh shows more complicated characteristics and its mesh parameters are mostly time-varying which calls for more extensive design and analysis. The purpose of this paper is to conduct optimization and robustness design study of a differential bevel gear for E-drive unit under light torque condition through evaluating its NVH related characteristics. Unloaded tooth contact analysis (TCA) is conducted and compared among several different ease-off design cases to investigate their pattern position and size variation. Loaded TCA that based on semi-analytical and semi-FE method is used to compare other mesh parameters such as mesh point, line-of-action (LOA) and mesh stiffness within one complete mesh cycle. For experimental study, the milled gear pairs are tested at several gear positions to study the robustness of each ease-off design. Both pattern and transmission error(TE) are correlated between simulation and test results. Finally, noise parametric study shows good consistency with gear parametric analysis which proves the effectiveness and accuracy of modeling and supports the design optimization predictions. Results demonstrate that fine pitch and low TE are the two main parameters to improve NVH performance. On the other hand, fine pitch will cause low strength and low TE design is less robust to build variation.