Evaluation of noise behaviour on a multi stage gearbox for e-mobility

Reduction of noise behaviour is one major goal in the early design stage of gearboxes. In literature, design approaches for the calculation of noise behaviour mainly focus on a single gear mesh. Measurement results from multistage gearboxes show influences from all meshes. To obtain a sound basis for the optimization of noise behaviour, a thorough evaluation of these effects has to be considered. This is demonstrated by means of numerical and experimental investigations on a multistage gearbox. In the practice, quasi-static approaches have demonstrated good accuracy in the estimation of gear noise behaviour without extensive computational time. Therefore, they are favourable i.e. in the optimization of gear stages. For instance, quasi-static loaded transmission error is determined as fluctuation of the deformation of gear mesh under a static load condition. This is widely used for designing gear micro geometries. Furthermore, tooth force excitation can be derived from a similar approach with a result in form of fluctuation of force. For multi stage gearboxes, the tooth excitations of adjacent stages can be summed up vectorially into the so-called bearing force according to Sattelberger. The bearing force level can then be derived from this measurement as a compact scalar value, which facilitates the comparability of noise behaviour between different gear variations. In this paper, the correlation between the computational results and the real measurements by means of structure-borne noise will be shown. Influences of each gear mesh will be investigated from both approaches. Additionally, in order to advance the formulation of the theoretical bearing force according to Sattelberger, the precision of gear noise estimation with the bearing force can be enhanced by means of the frequency response functions. Under consideration of speed influences, this extended quasi-dynamic approach ensures a good estimation of gear noise behaviour at different speeds without jeopardizing the calculation time.