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Recently the automotive marked is showing a trend towards increased adoption of hybrid vehicles to reduce emissions and increase vehicle efficiency. Fleet average targets for CO2 are compelling car manufacturers to reach very challenging fuel economy targets. The development of mild-hybrid vehicles has gained traction in this scenario. Another key driver has been the rapid evolution of electrical systems in new vehicles, ranging from advanced safety systems, driver assistance, and infotainment. This greater demand on electrical load has also contributed to the adoption of mild hybrid powertrains that work alongside traditional combustion engines and existing 12-volt systems. Many leading OEMs and suppliers are developing 48-volt architecture on the basis that it can achieve large efficiency gains at lower costs in the medium term than full electrification.

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.

In current Internal Combustion Engines (ICE), efforts have been employed in reducing emissions and fuel consumption. One of the alternatives is the reduction of the idling speed of the engines. However, such strategy involves great challenges from the aspect of torsional vibrations in the Front-End Accessory Drive (FEAD) system. Because it is coupled to the largest inertia of the FEAD assembly, the alternator pulley should provide a good vibration attenuation capability. The objective of this work is to demonstrate the development of an automotive component that employs two distinct types of springs: a clutch spring and a torsion spring. These elements are required in alternator pulleys to reduce torsional vibration generated by the crankshaft fluctuation and to avoid damage or durability issue with other components of the FEAD system.

Among the alternatives for solving NVH (Noise, Vibration and Harshness) problems in automobiles, the alternator pulley has become one of the most promising alternatives in the Frond-End Accessory Drive (FEAD) of modern engines. The rigid pulley has evolved from a simple device whose only function is torque transmission to a system with much more complex functions. At this higher level of complexity, many innovative designs have been created, such as pulleys with overrunning function and pulleys with both One-Way Clutch (OWC) and vibration dampening functions, which are devices that require a high level of study in order to guarantee an adequate design of the system for each new application. This paper presents the steps taken in dimensioning two distinct types of springs: a clutch spring and a torsion spring, to be applied in alternator pulleys with OWC and vibration dampening systems.