In-Vehicle Experimental Tests to Evaluate the Performance of Alternator Pulleys

Vehicle alternator pulleys with one-way-clutch and vibration attenuation mechanisms have recently been adopted in modern vehicles in order to reduce or mitigate undesirable side effects of torsional vibrations generated by Internal Combustion Engines (ICE) during its normal operation. It is noticeable how excessive vibration can be particularly detrimental to the components of the Front-End Accessory Drive (FEAD) system. Increase of inertia forces due to the use of larger alternators along with the increase in torsional vibration amplitudes of downsized engines added up with lower idling speeds to reduce emissions have set a challenge for proper FEAD functioning and validation. In order to validate potential design solutions, in-vehicle experimental tests are an important approach. How to define an adequate test plan, execute test cycles and post-process bulk experimental data to assure proper assessment of alternator pulley alternatives is a key factor of success. Proper parameter selection and measurement procedure during operating conditions of the vehicle should be carefully stablished. An experimental procedure to evaluate potential vibration attenuation of each alternator pulley technology by checking transverse displacement of the drive belt and transmission error and other FEAD performance based on post-processing of rotational speed data is proposed herein. In addition, selection and development of custom fitted sensors for FEAD evaluation have also been an outcome of the research, due to packaging space constraints and sample rate required to capture the dynamic events during vehicle operation. The results obtained allow a comprehensive functional analysis of different types of alternator pulleys and its impact in overall system performance, defining an in-vehicle experimental method that can be applied to confirm design alternatives during FEAD development and validation phases.