A Study on Planetary Gear Dynamics With Tooth Profile Modification

Abstract

This study investigates the impact of tooth profile modification on planetary gear dynamic response. Micro-scale geometric deviations from an involute gear tooth profile add an additional excitation source, potentially reducing gear vibration. In order to take account of the excitation, tooth profile modification is included in an analytical planetary gear model. Nonlinearity due to tooth contact loss is considered. Time-varying mesh stiffness and both rotational and translational gear motions are modeled. The accuracy of the proposed model for dynamic analysis is correlated against a benchmark finite element analysis. Perturbation analysis is employed to obtain a closed-form approximation of planetary gear dynamic response with tooth profile modification. Mathematical expressions from the perturbation solution allow one to easily estimate the peak amplitude of resonant response using known parameters. Variation of the peak amplitude with the amount and the length of profile modification illustrates the effect of tooth profile modification on planetary gear dynamic response. For a given external load, the tooth profile modification parameters for minimal response are readily obtained. Static transmission error and dynamic response are minimized at different amounts of profile modification, which contradicts common practical thinking regarding strong correlation between static transmission error and dynamic response. Contrary to the expectation of further reduced vibration, the combination of the optimum sun-planet and ring-planet mesh tooth profile modifications that minimizes response when applied individually increases dynamic response.