The overrunning alternator pulley is one of the “unsung heroes”. This inconspicuous component reduces vibrations and improves the energy efficiency of modern engines.
The current Schaeffler product range includes more than 400 different overrunning alternator pulleys and more than 140 million of these components have been manufactured in 15 years.
An overrunning alternator pulley manufactured from aircraft-quality aluminum is also used in the Schaeffler DTM Audi.
Overrunning alternator pulley
Head of Communication
Schaeffler Group Automotive
Tel. +49 913282-7557
Fax +49 913282-3584
Manager, Corporate Communications
Schaeffler Japan Co., Ltd.
New Stage Yokohama
1-1-32 Shinurashima-cho, Kanagawa-ku,
Tel. +81 45 274-8250
Fax +81 45 274-8221
2011-11-30 | 000-003-244 DE-EN
SCHAEFFLER AG, TOKYO
The The overrunning alternator pulley is one of the unsung heroes in the field of modern engines. The overrunning alternator pulley is the functional interior of the belt pulley located on the generator. The overrunning alternator pulley decouples the alternator from the rotational irregularities of the crankshaft of an internal combustion engine. It therefore performs a task that must not be underestimated, because the rotational irregularities that occur in modern internal combustion engines are significantly higher than those indicated to the driver by the tachometer needle.
The generator is the component with the greatest mass moment of inertia and the highest speed in the accessory drive. This means that the acceleration and deceleration forces acting on the generator resulting from the rotational irregularity have the greatest effect on the belt transferring these forces. The overrunning alternator pulley ensures that at many operating points only the accelerating proportion of the crankshaft forces that are transferred to the belt drive are used to drive the alternator. The advantages of the alternator pulley with a one-way clutch – which is also called an OAP (overrunning alternator pulley) in the trade – are clear. The reduction in the force level in the belt drive increases the life of individual components while ensuring an increase in the generator speed and a reduction in noise. In addition to increased smoothness, the overrunning alternator pulley makes a contribution to reducing fuel consumption and CO2 emissions.
A reduction in fuel consumption of almost one percent was measured, for example, with Schaeffler’s concept vehicle CO2ncept-10%. Particularly in city traffic – with its high proportion of idling and numerous situations where vehicles are accelerating – a belt drive with an overrunning alternator pulley is subjected to significantly lower loads than a belt drive without an overrunning pulley. Use of the overrunning alternator pulley also enables other components in the overall belt drive system to be designed more cost effectively.
This impressive contribution to improving efficiency also explains why the overrunning alternator pulley has been so successful both in diesel and gasoline engines.
This component, which has now been established for 15 years, was regarded early on as a key component for eliminating the rotational irregularities of the new generation of high-torque, direct-injection diesel engines from the belt drive. The overrunning alternator pulley is now also included in the extensive list of measures for optimizing the fuel consumption of internal combustion engines.
A comprehensive modular system has been developed which offers numerous different customized components with regard to the use of overrunning alternator pulleys in gasoline and diesel engines, passenger cars, commercial vehicles and motorcycles as well as other customer requirements. These include an OAP manufactured partly to aviation specifications which is used in the Schaeffler Audi A4 DTM.
The catalog currently includes more than 400 different belt pulleys with OAP. Over 140 million of these unsung heroes have rolled off the assembly lines in the last 15 years at Schaeffler – and an end to this success story is not in sight.