Automotive Transmission Rattle:Root Causes to Innovative Solutions

近年来，车辆操纵和发动机降噪方面的显著改进，以及动力传动系统部件中越来越多地使用更轻的材料，导致出现了过多的噪声、振动和声振粗糙度（NVH）问题，将其确立为直接影响销售的车辆质量指标（J. D. Power & Associates Reviews）。满足客户的NVH期望的行业成本为数千万磅，而保修索赔可能进一步增加总成本。随着发动机气缸压缩比的不断提高，变速器齿轮的振动被制造商和客户视为NVH改善的首要目标。变速器齿轮振动是在各种负载或空载条件下，在啮合齿轮齿存在齿隙的情况下，润滑表面之间反复碰撞的结果。由于燃烧和惯性力引起的发动机扭矩波动以及整个系统的动态响应导致齿轮箱中的轻负载部件（例如惰轮、同步器环和滑动套筒）的振动。振动从齿轮轴通过轴承传递到齿轮箱壳体是主要的机制，将噪声辐射到环境中。目前的汽车设计趋向于更轻的飞轮和更低的怠速，这使得齿轮敲击声成为主要的噪声源。由于对传动系统及其组成部件之间复杂的相互作用缺乏了解，以及行业对及时解决方案的需求，导致了昂贵的缓解方法。在设计过程的后期，所有这些快速修复的共同特点是它们的应用特定性。因此，这些方法不遵循根本原因，可持续系统的方法。拟议的研究介绍了一个整体的，广泛的和基本的数值和实验研究的传动系统，侧重于齿轮敲击的根本原因识别，强调润滑齿轮啮合表面的影响。虚拟原型的开发，模拟系统行为将导致可持续的解决方案，以减少嘎嘎声，帮助汽车制造商实现其减少上市时间的主要目标。这里提出的方法旨在通过采取预防性方法来实现显着的成本节约，从而为英国汽车行业及其供应商基础带来强大的竞争优势。

In recent years, significant improvements in vehicle handling and engine noise reduction, together with the growing use of lighter materials in powertrain components have led to the emergence of a plethora of Noise, Vibration and Harshness (NVH) concerns, establishing them as indicators of vehicle quality with direct impact on sales (J. D. Power & Associates Reviews). The cost to industry of meeting customers' NVH expectations is in the order of tens of millions of Pound, whilst warranty claims may further increase the total cost. Transmission gear rattle is now recognised by manufacturers and customers as the number one target for NVH improvement, following the continuous development of engines with higher cylinder compression ratios.Transmission rattle is the result of repetitive impacts between lubricated surfaces in the presence of backlash at the meshing gear teeth, under various loaded or unloaded conditions. Engine torque fluctuations due to combustion and the inertial forces, together with the dynamic response of the complete system result in vibration of the lightly loaded components in the gearbox, such as the idler gears, synchronizer rings and sliding sleeves. Transmission of vibration from the gear shafts through bearings to the gearbox housing is the principal mechanism, radiating noise to the environment. Current vehicle design trends towards lighter flywheels and lower idling speeds increase the prominence of gear rattle as a major noise source.Lack of understanding of the complex interactions between the drivetrain system and its constituent components and industry's need for timely solutions have resulted in costly palliative methods. The common characteristic of all these quick fixes , late in the design process, has been their application-specific nature. Therefore, these approaches do not follow a root-cause, sustainable system method.The proposed research introduces a holistic, wide-ranging and fundamental numerical and experimental study of the drivetrain system, focusing on the gear rattle root cause identification, with emphasis on the effect of lubricated gear meshing surfaces. The development of virtual prototypes, simulating system behaviour will result in sustainable solutions for attenuation of rattle, assisting car manufacturers in their primary target of reducing time to market. The approach proposed here aims to bring a powerful competitive advantage to the UK automotive industry and its supplier base by following a preventive approach to achieve significant cost-savings.