NuVinci Continuously Variable Planetary Transmission

The transmission is the connection between the speed of the engine and the speed of the vehicle. Conventional transmissions provide a series of gears. Each gear has a fixed ratio between engine speed and vehicle speed. If you wish to go at a given speed and your transmission has for example five gears the engine has to run at one of five speeds. Each engine is most fuel efficient at exactly one specific RPM. If none of the five speeds is at that RPM, your engine will not be able to drive you at your chosen speed as efficiently as possible.

Continuously variable transmissions provide a range of ratios between engine RPM and driveshaft rotation (vehicle speed). This allows the engine to always run at its most fuel efficient RPM. Changing vehicle speed is accomplished by changing the transmission gearing ratio instead of the engine RPM.



There have been many implementations of continuous variable transmissions using a variety of techniques. Good old Wikipedia has a list of automobiles using them. Although automakers have only really been getting serious about their use in the last five years or so. Fallbrook Technologies has recently been developing a new type : the NuVinci. Watch the video above to see how it works. I think it is an ingenious mechanical system. This is a planetary continuously variable transmission. The name comes from Leonardo da Vinci, who first invented continuously variable transmissions 500 years ago. And Detroit has only seen the value about 5 years ago. Oh well, better late then never.