Functional Testing of Alternator Pulleys in Chassis Dynamometer 2013-36-0124

Alternators usually have a solid pulley to connect it to the Front-End Accessory Drive (FEAD) system. Current stringent emissions regulations and fuel economy push for new alternatives to meet goals such as, for instance, reduced idle speed and engine downsizing. However, achieving these goals could ultimately generate NVH issues, such as belt slip chirp noise, or reduced accessory-drive support bearing life due to the high vibration levels in the FEAD. Furthermore, increased demand for on-board electric/electronics systems are requiring the use of larger alternators, with bigger inertia, becoming an additional source of vibration. To minimize the negative impact on NVH, the alternator solid pulley has been replaced, in some applications, by the Overrunning Alternator Pulley (OAP) or recently by an Overrunning Alternator Decoupler (OAD), with the aim to “detach” the alternator inertia from the FEAD during high speed transients and to reduce the transmission of torsional vibrations from the internal combustion engine to the FEAD, respectively. Experimental test results are an effective way to have a global and detailed evaluation of the performance of each alternator pulley configuration. The dynamometer testing proposed herein was setup using a fully instrumented vehicle and the case study presents the main effects of the different solution principles of alternator pulleys onto the FEAD overall performance in an actual vehicle application. The results of the functional tests aid the decision-makers by providing the basis of a truly quantitative trade-off analysis between increased complexity, cost and FEAD overall performance increase.