Abstract
Comfort requirements have significantly increased in recent years. Car manufacturers have therefore turned their attention to reducing engine noise and vibration reduction. As consequence, the other phenomena have become more audible and even lightly shift lever vibrations have become significant. This article presents a new test methodology developed to find out the shift lever root cause deriving from the dynamic behaviour of the gearbox´s internal components. The analysis was carried out on an innovative NVH Transmission test rig (1). The test rig allows to reproduce the main gearbox vibrations and acoustic emissions exactly as occurs on a car, with the great advantage of decoupling the gearbox noises from all the other engine and vehicle noises (2). The investigations was conducted using a new equipment specifically designed for this activity. It has permitted to measure the dynamic vibrations of all the internal shifter mechanism, starting from the gear and the sleeve, through the shift fork and its selector rail, the selection and engagement mechanism, up to the external knob shift lever. The dynamic behaviour of the whole system has been displayed via a running mode analysis and the phenomena frequency content has been determinated. At the end, the specific root cause for the analysed case was found. Further investigations are suggested in order to explore a wider range of possible root causes.
Keywords: nvh, gearbox, comfort, shift lever vibrations.