Analysis of friction-induced vibration leading to "EEK" noise in a dry friction clutch

Abstract

This study deals with a severe noise problem (Eek) that arises during the engagement of a dry friction clutch in a vehicle with manual transmission. Measurements have shown that near the full engagement the pressure plate suddenly starts vibrating (rigid body wobbling mode) with a frequency close to the first natural frequency of the rotational sub-system. This self-excited vibration problem exhibits typical signs of a dynamic instability associated with a constant friction coefficient. The transient event results in the generation of high transient noise levels and often consumers will change clutches prematurely in an effort to eliminate this noise. Our work focuses on developing a linearized lumped-parameter model of the clutch. The effect of key parameters on the system stability is examined by calculating complex eigensolutions. Results of this analytical study are in agreement with experimental observations. It is seen that the instability of the rigid body wobbling mode is controlled by the friction forces. This mode may, however, be also affected by the first bending mode of the pressure plate. Therefore, a stiffer plate could lead to a design with a reduced tendency to Eek.