NONLINEAR COUPLED VIBRATION RESPONSE OF SERPENTINE BELT DRIVE SYSTEMS

This theoretical and experimental study identifies a key nonlinear mec hanism that promotes strongly coupled dynamics of serpentine belt driv e systems. Attention is focused on a prototypical three-pulley system that contains the essential features of automotive serpentine drives h aving automatic( spring-loaded) tensioners. A theoretical model is pre sented that describes pulley and tensioner arm rotations, and longitud inal and transverse belt vibration response. A recent investigation de monstrates that infinitesimal belt stretching creates a linear mechani sm that couples transverse belt vibration to tensioner arm rotation. H ere, it is further demonstrated that finite belt stretching creates a nonlinear mechanism that may lead to strong coupling between pulley/te nsioner arm rotation and transverse belt vibration, in the presence of an internal resonance. Theoretical and experimental results confirm t he existence of this nonlinear coupling mechanism. In particular, it i s shown that very large transverse belt vibrations can result from sma ll resonant torque pulses applied to the crankshaft or accessory pulle ys. These large amplitude transverse vibrations are particularly sensi tive to seemingly small changes in the rotational mode characteristics .