Modeling and Simulation of Decoupler Pulley Effects on FEAD Torsional Vibration

In current Internal Combustion Engines (ICE), efforts have been conducted in order to reduce emissions levels and improve fuel efficiency. Some alternatives consistent with this strategy are: engine downsizing and reduction of the idling speed. However, adopting such strategies incur in a trade-off between ICE efficiency and increased torsional vibration levels that could damage Front-End Accessory Drive (FEAD) systems and components. The alternator pulley is another potential source of increased torsional vibration due to being coupled to the largest inertia of the FEAD assembly. Therefore, alternator pulley technologies have evolved aiming to provide vibration attenuation capability. The objectives of this work are to demonstrate the development of an alternator pulley to reduce the torsional vibration in the FEAD, and the development of a virtual model to evaluate the FEAD performance. Development of alternator pulleys to reduce torsional vibration generated by the crankshaft fluctuation can avoid premature failure and durability issues with other components of the system. Usually, these pulleys employ two distinct types of springs: a clutch spring and a torsion spring. Through analytical and numerical models previously developed for each spring, the set of springs of the decoupling pulley under development could be properly designed. Finally, functional prototypes are evaluated in static torque tests, dynamic evaluation in test benches and in-vehicle test. Simulations based on finite element method has demonstrated excellent correlation on vibration attenuation levels of the FEAD, based on a comparison with experimental results.