A Study on Reduction of Gear Rattle Noise through Clutch Hysteresis Stabilization

Reducing gear rattle noise within the passenger cabin is a crucial objective in vehicle development due to its direct impact on customer comfort and driving experience. Gear rattle occurs when free gears collide during meshing, primarily driven by high torsional vibrations generated by engine fluctuations. These vibrations are transmitted through the clutch system to the transmission, amplifying noise inside the cabin. To address this issue, this study focuses on optimizing the clutch by stabilizing its hysteresis, which helps in minimizing the torsional vibrations transferred to the transmission input shaft, thereby reducing gear rattle. The investigation centers on a case where significant gear rattle was observed at high vehicle speeds, particularly under high engine torque conditions. A thorough root cause analysis identified that the primary contributor to the noise was a drop in the clutch hysteresis value at elevated engine torques. This drop increased torsional vibrations in the driveline, which in turn amplified gear rattle. By stabilizing the clutch hysteresis across a wide range of engine torque values, the energy transferred through the clutch was better absorbed, reducing the amplitude of driveline vibrations and ultimately mitigating gear rattle noise. The study's results highlight the critical role that clutch hysteresis plays in controlling torsional vibrations. Stabilizing this parameter leads to a significant reduction in noise and improved passenger comfort, especially at high speeds. This paper provides a detailed explanation of the methodology used to optimize the clutch system, offering valuable insights for future vehicle development aimed at improving overall ride quality and noise control.