Overrunning alternator pulley

During normal operation alternator pulleys can rotate at up to 18,000rpm and coupled with rapid acceleration and deceleration can lead to premature alternator, pulley and drive belt failure. To prevent this Overrunning Alternator Pulleys (OAPs) were developed that are designed to decouple the alternator from the rotational irregularities of the crankshaft in an internal combustion engine, as the alternator has the highest mass moment of inertia in the accessory belt drive. As a result of this decoupling the alternator is only driven using the acceleration components of the rotational irregularity of the crankshaft.

The overrunning alternator pulley consists of a pulley, an overrunning clutch unit with a double bearing support, a drawn inner ring and outer ring and two sealing rings. For protection against heavy water impacts and other dirt contamination, a cover snap is fitted on the front side^[1].

Advantages of an overrunning alternator pulley ^[2]

· Damping of belt vibrations^[3]

· Reduced load on the belt drive

· Reduced tensioner movement

· Increased belt life

· Improved noise behaviour of the belt drive

· Increased alternator speed in the idling speed range

· Reduced belt slip and noise on the alternator drive wheel during gear changes

· Increased fuel economy^[4]

References

1. ^ "Overrunning alternator pulleys", Schaeffler Group
2. ^ "Advantages of an overrunning alternator pulley", OAP Advantages - Schaeffler Group
3. ^ "Video showing damping of belt vibrations", '
4. ^ "Advantages of an overrunning alternator pulley", Fuel economy improvements using overrunning alternator pulleys - Litens