Abstract: This paper addresses the problem of severe impact noise induced in the powertrain of a manual-equipped coach during transient clutch disengagement in reverse gear. A comprehensive dynamic model of the powertrain is developed using AMESim, which integrates the engine, transmission, drive shaft, rear axle and the lumped inertia of the entire vehicle. Combined with vehicle-level noise, vibration, harshness (NVH) test data, the underlying mechanism of the impact noise is revealed. The abnormal noise is primarily caused by the alternating switching between driving and driven conditions on the meshing interfaces of gears and splines along the power transmission path. Moreover, the impact response occurs earlier in the rear components of the powertrain than in the front components. Using the speed difference of the reverse idler gear as an evaluation index, simulation analyses are conducted to investigate the effects of clutch disengagement rate and internal clearances in the transmission on impact noise characteristics. Both simulation and experimental results demonstrate that lowering the clutch disengagement rate can significantly attenuate the powertrain impact noise. Gears located on the non-powertransmission paths of the transmission exert no influence on the impact noise. Merely reducing the backlash of transmission gears and splines provides only a limited improvement in suppressing the powertrain impact noise.

Key words: coach; powertrain; impact noise; clutch; reverse gear; AMESim

摘要： 文章针对某手动挡客车倒车过程离合器瞬态断开工况下，传动系出现明显冲击异响的 问题，基于 AMESim 构建了涵盖发动机、变速器、传动轴、后桥以及整车惯量的传动系动力 学模型，结合整车噪声、振动、声振粗糙度（NVH）测试结果，揭示了异响主要由动力传递 路径上齿轮、花键啮合面的主被动转换诱发，以及传动系后端部件冲击时序先于前端的机理。 以倒挡介轮转速差为评价参数，仿真分析了离合器踩断速率、变速器内部间隙对冲击噪声的 影响规律。仿真与整车试验验证表明，降低离合器断开速率能够明显改善冲击噪声，变速器 非动力传递路径上齿轮对冲击异响无影响，仅减小变速器齿轮及花键侧隙对传动系冲击异响 改善效果有限。

关键词: 客车；传动系；冲击异响；离合器；倒挡；AMESim