Loose part vibration in vehicle transmissions - Gear rattle


Abstract: Minimising noise is becoming an increasingly important factor in motor vehicle development. The importance of this development goal is increasing with rising customer expectations and increasingly stringent legal restrictions on noise emissions. The cause of rattling and clattering noise is torsional vibration of transmission components that are not under load, that move backwards and forwards within their functional clearances. This noise is perceived as distinct from other sources of noise, and is intrusive because of its undesirable character. The transmission parameters backlash, axial clearance and main centre distance were varied by experimental analyses in test stand trials, showing the effect on propensity to rattle and clatter. By optimising these parameters, it was possible to minimise the rattling and clattering noise. Measures internal to the transmission to reduce loose part vibration in vehicle transmissions were also considered. The calculated noise level with the EKM-Simulation program correlates with the measured noise level. Parameter studies with the EKM-Simulation program, which contains all relevant parameters for the excitation of rattling noise caused by idle gears, shows the significant parameters for the investigated transmissions.

Keywords: Transmission noise minimising, Gear rattle, Torsional vibration, Backlash, Axial clearance

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