Considering the cost Variable Speed Transmission savings involved with building transmissions with only three shifting parts, you’ll understand why car companies have grown to be very interested in CVTs lately.
All this may sound complicated, but it isn’t. In theory, a CVT is far less complex than a normal automatic transmission. A planetary equipment automatic transmission – offered in the tens of millions this past year – has a huge selection of finely machined shifting parts. It has wearable friction bands and elaborate digital and hydraulic settings. A CVT like the one referred to above has three simple moving parts: the belt and the two pulleys.
There’s another advantage: The lowest and top ratios are also additional apart than they would be in a conventional step-gear transmitting, giving the transmission a greater “ratio spread” This means it is even more flexible.
The engine can always run at the optimum speed for power or for fuel economy, regardless of the wheel speed, which means no revving up or down with each gear change, and just the right rpm for the right speed on a regular basis.
As a result, rather than five or six ratios, you get thousands of ratios between the lowest (smallest-diameter pulley establishing) and highest (largest-diameter pulley setting).
Here’s an example: When you start from a stop, the control computer de-clamps the insight pulley so the belt turns the smallest diameter while the output pulley (which would go to the tires) clamps tighter to make the belt turn its largest diameter. This produces the cheapest gear ratio (say, 3.0-to-1) for the quickest acceleration. As rate builds, the computer varies the pulley diameters, as conditions dictate, to get the best balance of fuel economic climate and power.