Design and Development of Wave Spring to Eliminate the Synchronizer Ring Rattle In An Automotive Gearbox

Automotive powertrains are being refined to give good comfort to the occupants. With the refinement of the internal combustion engine, the NVH is improved, and other vehicle noises are surfacing in the vehicle cabin. One such noise is the synchronizer ring rattle noise from the gearbox. The synchronizer rings are assembled freely between the gear and the hub in the gearbox. The manufacturing variations in the gearbox shafts, bearing, and housing bore cause misalignment to the synchronizer ring assembly. This excites the synchronizer rings to rattle. The rattle noise increases when the synchronizer ring is positioned between two different shafts. This rattling reduces the life of the synchronizer. And the rattling noise causes discomfort to the occupants. This research work discusses the different dampening strategies for the synchronizer ring rattle. Higher rattle reduction can be achieved with the wave spring between the input and output shaft. However, the wave spring changes the dynamics of the synchronizer ring. The stiffness of the wave spring is critical to synchronize the speed difference and to achieve good gearshift quality for gear crash avoidance. The new design eliminated the synchronizer ring rattle and improved the life of the synchronizer ring.