Tribological optimization of a toroidal-type continuously variable transmission

Continuously variable transmissions (CVTs) 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 a lower mass. Current efforts to reduce the 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 article documents a successfully implemented search algorithm for the dimensional optimization 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 optimization also proved to be a powerful tool that can be used to select the dimensions of the transmission to fulfil any desired characteristics.

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