We are constantly searching for ways to perform the tasks essential to our lifestyle in ways that have a smaller impact on the environment. In the United States cars are exceedingly common, nearly twenty percent of American households own three or more vehicles (U.S. Department of Energy Web). These vehicles are also one of the largest contributors to our impact on the environment. The majority of cars use automatic transmissions, although not very efficient, they offer convenience of not shifting gears. The continuously variable transmissions (CVT) can now satisfy societies goal of reducing our effect on the environment with the convenience of the automatic transmission.
To make the most fuel efficient vehicle, every aspect of the vehicle needs to be efficiently designed to the max. While the internal combustion engine is nearing perfection for efficiency, manufacturers are focusing transmission designs. Automatic transmissions are the most commonly used in the vehicles of today. These automatic transmissions are not very energy efficient when compared to other forms of transmissions. Manual transmissions are much more fuel efficient in comparison. A third type of transmission is a continuously variable transmission. It brings the convenience of an automatic transmission and the fuel efficiency of a manual transmission together.
Manual transmissions ideally offer the best fuel efficiency when compared to automatic transmissions. Manual transmissions are transmissions that require the driver to shift gears. Many drivers of manual cars will burn gas by accelerating too fast or driving in a gear that provides the incorrect ratio for maximizing efficiency. The efficiencies of both the manual transmission and automatic transmission are limited by their fixed ratio design and the number of mechanical gears installed. A continuously variable transmission has an infinite amount of gear ratios to allow the engine to run in its maximum efficiency range.
How the Continuously Variable Transmission works
To get an idea of how a continuously variable transmission operates, consider the drivetrain of a bicycle. Most bicycles have two sets of sprockets, one on the back wheel and the other on the pedal axle. The rear set usually has five or six sprockets of different diameters. When changing the gears on a bicycle, a lever pushes the chain from one sprocket to the next. If we replaced the rear set of sprockets with a cone-shaped piece of metal, this would produce a continuously variable range of gear ratios. By using the cone, there are now a set of infinite diameters between the large base of the cone, up to the tiny tip of the cone, instead of six different sized sprockets.
A Continuously Variable Transmission is very simple in design, making many wonder why it is not in every car on the road today. This concept works with at least two sheaves (also known as pulleys). Each sheave consists of a pair of cones that can close together or move...