Overrunning belt pulleys on alternators
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their work. The information provided on this website is intended for use by suitably qualified personnel only.
During an engine's combustion cycle, the rotary movement of the crankshaft is sped up and slowed down This rotational irregularity is transferred to the accessory drive as a result of the alternator's moment of inertia As a result, extreme forces and high torque fluctuations act on the belt drive.
The overrunning alternator pulley, or alternator freewheel clutch, is mounted directly on the drive shaft of the alternator instead of the rigid pulley and has the task of decoupling the three-phase alternator from the rotational irregularities of the crankshaft. This reduces the influence of the moment of inertia on the alternator and the load on the belt drive.
The overrunning alternator pulley is structured as follows:
By mounting an overrunning alternator pulley, only the driving force of one direction of rotation is transmitted to the alternator, thus reducing friction and wear.
Advantages of an overrunning alternator pulley:
Effects with and without overrunning alternator pulley:
Article numbers: 9XU 358 038-xxx and 9XU 358 039-xxx
We recommend the following procedure:
Refer to the removal and installation instructions from the relevant