Belt Drive, Basic Function - GF13.21-P-1001A

Engine all (CAR) 

Engine all (4xWD) 

Overview 

This document contains information on:

• General 
• Function 

General 

The belt drive uses the rotational movement of the crankshaft to drive important ancillaries for vehicle operation via a belt.

Function 

Belt drive 

A belt pulley is flange-mounted on the free crankshaft end. Here, the belt pulley is designed as a torsional damper and reduces the speed fluctuations in the series of combustions in the cylinders. The belt pulley drives the ancillaries via a poly-V belt by means of friction. To enable the ancillaries to have different rotational speeds, the different diameters of the driving and driven belt pulleys create a gear ratio. Possible ancillaries which the belt drive drives include:

• Alternator
• Coolant pump
• Refrigerant compressor
• Belt-driven starter alternator

Belt tension 

The crankshaft rotates due to the sequence of the individual combustions in a non-uniform movement. These speed fluctuations are compensated for in the belt drive by a belt tensioner and ensure that the tension in the poly-V-belt is constant. Over the runtime of the engine, the poly-V-belts elongate due to their construction from fiber-reinforced plastic. In order to prevent the poly-V-belt from slipping, the belt tensioner compensates for this elongation.