A shift gearbox is a commonly used element in automotive transmissions, which is needed for two reasons. Firstly, it transmits the driving torque of the motor. Secondly, because a combustion engine works best at its nominal speed, it changes the gears. Experimental data reveal that undesired vibrations can arise during the clutch engagement process. The aim of this research is to explain the emergence of such vibrations in order to understand how to successfully prevent them.
Depending on the manifestation of the vibrations, several model approaches are thinkeable to explain the effect. A basic idea is to investigate the stability of the stationary behaviour and the origination of friction-induced vibrations, because the vibrations only occur while the disc contact is sliding. The physical modelling of the system is a flexible multibody system approach. Components taken into account are the clutch disc, gears, shafts and the actuation.
Well-known reasons for friction induced vibrations are clutch judder at low frequencies and the wobbling disc instability. They both cause vibrations perceiveable by customers, and which can be measured e.g. acoustically.
Another instability at medium frequencies arises because of the gear coupling, where the amplification of clutch friction forces induces an instability. In this case, strong translational vibrations of shafts occur with opening contacts in clutch and gears and stick-slip-transitions. Because of the translational movement, such vibrations can be measured in the actuation signal of the clutch.
Yet further instabilities can arise because of the interaction of elastic disc modes with rigid-body modes. The frequency of such instable behaviour is higher than the previous ones. Here too, translational vibrations occur in combination with elastic plate oscillations.
Contact: Prof. A. Fidlin, G. Jehle