The function of the overrunning alternator pulley is to decouple the alternator from the rotational irregularities of the crankshaft in an internal combustion engine, since the alternator has the highest mass moment of inertia in the accessory belt drive. In this way, the alternator is driven using only the acceleration components of the rotational irregularity of the crankshaft.

Advantages

The positive influences on the accessory belt drive result in:

• the damping of belt vibrations
• a reduced load in 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

Decoupling function

The overrunning alternator pulley decouples the alternator from the rotational irregularities of the crankshaft up to an engine speed of approx. 2000 min-1. The decoupling function of the overrunning pulley unit is dependent on the load condition of the engine (amplitude of torsional oscillation), the inertia and the load condition of the alternator. Furthermore the overrunning pulley decouples the alternator inertia during significant decreases in engine speed (gear change).

Design

The overrunning alternator pulley consists of a pulley with the appropriate multiribbed profile on its outside diameter for a multiribbed belt, 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.

A modular concept has been created in order to achieve cost-effective and in due time reaction to corresponding customer enquiries. The overrunning pulley unit and sealing components are thus standard parts for every application.