Dynamic Analysis of Helical Gear Pair Due to TE and Shuttling Moment Excitations

Helical gears are commonly used instead of spur gears due to their potential higher load carrying capacity, efficiency and lower noise. Transmission Error (TE) is defined as deviation from perfect motion transfer by a gear pair. TE is dominant source of gear whine noise and hence gears pairs are generally analyzed and designed for low TE. In the process of designing helical gears for lower TE, the shuttling moment can become a significant excitation source. Shuttling moment is caused due to shifting of the centroid of tooth normal force back and forth across the lead. The amount of shuttling force or moment is produced by combination of design parameters, misalignment and manufacturing errors. Limited details are available on this excitation and its effect on overall noise radiated from gear box or transmission at its gear mesh frequency and harmonics. In this paper, a detailed methodology is developed to predict the dynamic response of helical gear pair for shuttling moment excitation with the help of Load Distribution Program (LDP) and Finite Element Analysis (FEA). Three helical gears are identified from literature. Gear pairs are selected in such a way that they are designed for low TE at the design torque. The TE and shuttling moment is predicted by using LDP for the selected gear pairs and is verified through published literature. The gear pair assemblies are modelled in FEA and analyzed for response due to TE force and shuttling moment. FEA results show that the TE and shuttling force can excite different structural resonant modes of the system. A methodology is established for understanding the contribution of TE and shuttling force in the vibration of the gear shaft assembly. This methodology helps in identifying the relative contributions of TE and shuttling moment before performing dynamic analysis and design gears for lower excitations.