Continuously variable transmissions

Manual, automated or conventional automatic gearboxes combine one or two of the following features:

• torque break at every gear change ;

• discrete-ratio" transmissions, in other words, with a limited number of ratios.

These two aspects have consequences in terms of comfort (jerks due to torque breakdown), fuel consumption and pollutant emissions (engine operating point management).

The CVT (Continuously Variable Transmission) does not have these disadvantages; shifts are insensitive and engine operating point management is much more flexible. It should be noted, however, that the CVT still lags behind in terms of intrinsic efficiency, despite significant progress in recent years.

A CVT can be defined as a transmission with...