Optimum Solution for Reduction of Clutch Pedal Vibration and Groan Noise Observed During Clutch Pedal Actuation

In emerging markets like India, manual transmission vehicles are still most preferred & contributes to 85% of passenger vehicle sales due to its cost benefit. However, customer expects good NVH behavior for comfortable driving experience in the vehicle to maneuver effortlessly in the highly congested traffic conditions in India. Clutch & its hydraulic release system in manual transmission of IC engines are the significant components which affects the NVH behavior & maneuverability of the vehicle and the driver comfort significantly. This paper focuses on the clutch pedal vibration & groan noise concern observed during clutch pedal actuation in high power density SUV vehicle developed for Indian market. The vehicle had highly efficient & light weight engine which has high engine axial vibrations. Axial vibrations are caused due to engine firing impulses & crankshaft bending causes flywheel axial movement. This movement in turn leads to vibrations in clutch cover diaphragm fingers which are transmitted to clutch pedal through hydraulic fluid pulsation via clutch release system which comprises of CSC, bleeder, clutch high pressure pipe & CMC. Engine vibrations which are transferred through clutch system to clutch pedal is felt on driver foot and causing discomfort during clutch pedal actuation/modulations while launching, creeping and for shifting of the gears in the vehicle. During pedal actuations at higher rpm for shifting gears, low frequency vibrations becomes high frequency and heard as groan noise inside the passenger cabin which results in uneasiness to driver and passengers. This paper describes the literature available, root cause analysis of the concern, effect of clutch disc, cover assembly, hydraulic release system design variables and the optimum solution which does not affect the other performance of the clutch function while reducing the clutch pedal vibration & groan noise concern through simulation & vehicle measurement results.