Working of Pulley Based CVT.

The CVT is a continuously variable transmission system. This type of transmission systems are used in vehicle withautomatic transmission. The function of the transmission system is to changethe gear ratio between the engine and rear wheels. A manual transmission will be having many numbers of gears where the CVT will not have gears.

Different type of CVT’s:

1. Pulley based CVT

2. Toroidal CVT

3. Hydrostatic CVT

This topic we will be studying about Pulley based CVT. See the video in this topic for easy understanding.

Pulley based CVT (stage 1)

Pulley based CVT (stage 2)

Main components of a Pulley based CVT:

1. Two sets of pulleys
2. Shafts
3. V-belt
   

Two sets of pulleys: as you can see in the figure there are two sets of pulleys on which the V belt is mounted.

Shaft: One pulley is connected to the driving shaft and the other to the driven shaft.

V belt: a V- grew belt is connecting both the shafts with each other.

Working of pulley based CVT:

As explained in the video the pulley based CVT is capable of changing the gear ratios with out use of gears. One set of pulley is the driving pulley and is connected to the crank shaft (that means the driving pulley is getting its drive from the engine crank shaft). The other pulley is the driven pulley and is connected to the transmission through a shaft as shown. Both these sets of pulleys are capable of moving towards each other and away from each other (see the animation in the video). This helps in varying the pitch radius (pitch radius: the distance from the centre of the shaft of the pulley to the outer of the pulley as shown in the figure) as the pitch radius of the pulleys varies. The radius of the V-belt engaging with the pulleys also varies. This provides infinite number of gear rations.

<<<click here to view Mech/ Automobile Engg vids>>>

Eg 1: if the pitch radius of the driving pulley is smaller and the driven pulley is larger. The driving pulley rotates lower resulting in low gear (see fig).

Eg 2: if the pitch radius of the driven pulley is smaller and the driven pulley is larger. The driving pulley rotates lower, resulting in low gear (see fig).