Nonlinear Responses in Loaded Driveline Rattle

The rattling of lightly loaded or unloaded gears in vehicle power transmission systems is an ongoing issue for automotive manufacturers. Rattle noises influence the customer perception of vehicle quality and may affect the success of a model. The rattle is an unwanted byproduct of clearances in the system and is strongly influenced by design of the torsional isolation system, namely clutch spring rates, hysteresis and flywheel inertia(s). In this paper a generic torsional powertrain model for loaded gear rattle analysis is utilised to examine nonlinear responses of the rattling gears. The rattling of the 1^st gear pair and 5^th gear pair are considered whilst 2^nd gear is engaged and driving. The accelerations of the 5^th gear pair are shown to be more severe under the same excitation conditions and thus found to be a larger contributor to the rattle noise. The system is simulated using a frequency sweep with engine excitation derived from measured data and then peak responses examined and explained. It is shown that a combination of analysis of both the linear and nonlinear characteristics of the system is required to gain a full understanding of the system.