Abstract:

A nonlinear torsional model with 4 degrees of freedom for automotive driveline transmission systems at idle is presented and method for calculating dynamic response of the model is proposed. A rattle index is defined for evaluating rattle of a meshed gear pair. For trouble shouting of gear rattle of a car at idle, the influence of nonlinear stiffness and damping of the clutch on rattle index of the car is investigated using the developed model and calculation method. Stiffness and angle limits of the first stage damper of a clutch are improved for reducing gear rattle of a car based on the calculated results of rattle index, meshing force and meshing displacement of the meshed gear pair in the gearbox at idle. Noise at the engine compartment and vibration at one point at the transmission are measured for the baseline clutch and the improved clutches of a car. Comparisons of the measured noise and vibration show that there are corrections between rattle index and the noise at engine compartment and vibration at one point of transmission. It is also concluded that the stiffness and damping can be improved to reduce gear rattle at idle using the modeling and calculating methods presented.

Key words: gear rattle at idle, modeling and experiment, tuning of pre-damper at a clutch, vehicle transmission system