New Technology to Improve the Performance of Front End Accessory Drive System

The Overrunning Alternator Decoupler (OAD) is a new device for replacing the solid alternator pulley to decouple the alternator rotor inertia from the front-end accessory drive (FEAD) system. The OAD is used primarily to reduce the belt tension fluctuation in the accessory drive system when the alternator inertia, in combination with the engine torsional vibration, creates NVH (noise, vibration and harshness) problems. In this paper, the functional principles of the OAD will be explained and the influence of the decoupled alternator rotor inertia on the performance of a four-components system (CS, AC, Alternator and tensioner) will be reported. The test data and the numerical simulation results show clearly that the amplitude of the belt tension fluctuation, the tension arm movement and the hubload of each component are reduced significantly, when the OAD is used. This study indicates as well that the FEAD system with the decoupled alternator can work with a lower pre-set belt tension.