Influence Study Of The Clutch On The Judder During Vehicle’s Starting

A low-frequency vibration that arises during the clutch engagement in the longitudinal direction of the vehicle is defined as clutch judder, which is caused by frictional vibration in a slipping clutch. Clutch judder has a great effect on the vehicles riding comfort. In this article, theoretical analysis and experimental research have been carried on clutch judder.Firstly, a classical belt-friction model is developed for the mechanism research of judder. The friction characteristic of friction surface and the changes of pressing force on the body both are considered in calculation. Results show that the negative gradient of friction coefficient would lead to self-excited vibration and the body would occur resonance when the frequency of pressing force is close to the resonance frequency. Thus, the self-excited vibration by negative gradient of friction coefficient and the resonance by the change of pressing force are the main causes of clutch judder.Secondly, the model for dynamic analysis of driveline system including friction clutch is established. In the model, Karnopp and hyperbolic tangent friction formulas for calculating friction torque generated by a friction clutch during stick and slip are developed. Having a calculation on the dynamic model using the two different friction formulas, and the two results are compared. What’s more, the influence of the torsional stiffness, the inertia, the damping, friction characteristic and the axial stiffness of wave cushion on the starting judder of a vehicle are analyzed.Finally, as for two vehicles existing clutch judder, adjusting the driven disc torsional stiffness for one car and changing the waveform cushion stiffness for another to improve the judder based on theoretical analysis. The result of experiment shows the judders of two vehicles are reduced greatly after the clutch parameters adjusted, which validate the proposed model and analytical method.