Compressor Pulley: Description and Operation

Component Identification:

Purpose
The pulley drives the A/C compressor. Moreover, the pulley serves as a torque damper and torque limiter.

Design
The hub (1) is rigidly connected to the A/C compressor shaft and to the pulley (3) by the rubber elements (2).






Function during normal operation
During normal operation the rubber element (2) is resistant to deformation. The rubber element (2) therefore transfers the torque from the pulley (3) to the hub (1) simultaneously to the A/C compressor shaft, whereby the hub (1) and pulley (3) turn in the direction indicated by the arrow.
In this operating state the following torque relationship exists

A/C compressor torque < rubber element torque limit
In this operation state the rubber element (2) operates as a damping element by preventing resonance with other engine components over the pulley.







Function when A/C compressor locks up
When the A/c compressor locks up the torque required to drive the A/C compressor is greater than the torque present at the pulley (3). This causes slip between the pulley (3) and hub (1) resulting from the change in shape and wear to the rubber element (2). The pulley (3) continues to turn even though the A/C compressor is locked up. In this operating state the following torque relationship exists.

A/C compressor torque > rubber element torque limit
In this operation state the rubber element (2) acts as a belt protection device.