Noise, vibration and harshness during dry clutch engagement oscillations

Abstract

Determining the root causes of various noise, vibration and harshness phenomena in modern automotive drivetrains is a critical task for industry, since noise, vibration and harshness issues often result in worsened driving experience. The aim of the current research is to investigate the dynamics during dry clutch engagement and the associated – often problematic – oscillations. This paper reports the development and partial validation of numerical models to study dry clutch behaviour. The models are used to investigate the influence of clutch and throttle actuation on the occurrence of unwanted clutch oscillations. The dynamic coefficient of friction between the clutch interacting surfaces was measured using a pin-on-disc rig under different slip speeds and contact pressure conditions, which are representative of a typical clutch engagement manoeuvre. The paper highlights the occurrence of instability issues in clutch dynamics (disc radial mode) as potential generators of aggressive noise, vibration and harshness, particularly during two different clutch pedal actuations. Such analysis has not hitherto been reported in the open literature.

Automotive dry clutch fully coupled transient tribodynamics

“…Minas et al [29] drafted a two dimensional, six dof analytical model to examine the oscillatory behaviour of the various clutch components during various pull away manoeuvres. The model used engagement data (friction torque, coefficient of friction) taken from a three-dof torsional model, simulating the engagement process.…”

“…This eccentricity and the relative radial velocities of the discs change the direction of the resultant friction force vector. However, the friction in radial direction is negligible compared to the friction generated due to the relative rotation of the components and consequently in this study only the latter is considered [29,35].…”

“…The dynamic friction coefficient l kin is determined from experimental measurements described in the next section. The dynamic coefficient of friction ðl kin Þ which couples the tilting, radial, bending and axial motions of the clutch components with the torsional degrees of freedom can be calculated as [9,10,29,44].…”

“…The force from the straps is negligible compared to the force applied from the diaphragm and cushion springs and is therefore neglected in the current analysis [29]. The simulation of the clutch engagement manoeuvre uses an exponential profile for the cushion spring force, as well as for the diaphragm spring force.…”

“…4 Schematic representation of the loads applied in the dry clutch system Fig. 5 and are described by the following equations [29]:…”