Tribological optimization of a toroidal-type continuously variable transmission

Continuously variable transmissions (CVT) are mechanical devices that allow a continuous variation of the output velocity by adjusting its internal geometrical configuration. Through the use of an epicyclic gear set, a CVT can deliver an infinite number of transmission ratios, allowing the vehicle's engine to operate within a higher efficiency envelope for longer periods of time. This offers several advantages over traditional transmissions such as better fuel efficiency, quieter operation, and lower mass. Current efforts to reduce vehicles' fuel consumption in order to protect the environment and save fuel have seen a recent revival in CVT research, especially in the automotive industry. This paper documents a successfully implemented search algorithm for the dimensional optimisation of a novel CVT design in order to determine the maximum theoretical efficiency of the device. In addition to showing an economical and simple method of calculating contact losses, this method of optimisation also proved to be a powerful tool which can be used to select dimensions of the transmission to fulfil any desired characteristics.