Today we have a new type of transmission technology. It’s an automatic but not the familiar old automatic. Its a CVT (continuously variable transmission), similar to an automatic transmission when driving but operates on an entirely different principle.
Conventional automatic transmissions use sets of gears inside that provide different ratios or speeds. A CVT replaces the complex gear sets common in automatic transmissions with two variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt running between them.
The way it works is that during operation the pulleys move in and out such that a drive belt between moves higher on one pulley, lower on the other and this provides a “ continuous” numerical gear reduction. You can picture this roughly as the way a 10-speed bike works, by routing the chain over smaller or larger gears to change the gear ratios.
The controls for a CVT-based car are the same as an automatic-based car: Two pedals (gas and brake) and a P-R-N-D-L-style shift pattern. The CVT’s biggest problem has been user acceptance. Because the CVT allows the engine to rotate at any speed, the noises coming from under the hood can sound odd to ears accustomed to conventional automatic transmissions. The gradual changes in engine note sound like something is “slipping”. Automakers have gone to great lengths to make their CVTs feel more like a conventional transmission.
The future of the CVT remains to be seen. In spite of the obvious efficiencies of CVTs, customers can be fickle and may prefer an older technology. We will likely see how CVT transmissions fare over the next few years or so.
Source: http://www.hzgrandville.com/Continuously-Variable-Transmissions.html