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Supercharger timing gears have been a source of rattle noise due to torsional vibration from the engine and sometimes have required torsional isolators to reduce the rattle noise significantly. Supercharger gear rattle is studied analytically and experimentally in this paper in order to understand to what extent basic design parameters could impact gear rattle noise to eliminate the need for isolators. A 3 DOF (degree of freedom) discrete model is used to represent a geared rotor system in the supercharger. A mathematical dynamic model is established in Matlab handling the non-linearity due to gear backlash. The fluctuation of input torque is used as source of excitation. A real time simulation technique is used for the analysis. Good correlation has been obtained between the experimental and analytical results. An index for comparing analytical results to gear noise and vibration level has been proposed.

A simulation methodology for dynamic modeling of geared rotor systems such as superchargers was used for determining the housing vibration response. The approach provides an ability to make quick parametric design modifications to the model for evaluation of relative noise response with the assumption that the averaged housing vibration level correlates approximately to the noise radiating from the surface. The housing in some cases was modeled as a lumped mass representation for efficiency, and when higher accuracy of housing modes was needed, a detailed flexible Finite Element Analysis (FEA) representation was used. The interesting features of the methodology were the use of constraint equations to model the gear mesh response per unit Transmission Error (TE) input, along with summarizing the component kinetic and strain energy for each mode and the mesh compliance for fast evaluation of opportunities for noise reduction.