Design and Performance of an Exponential Roller Gear Continuously Variable Transmission with Band Clutches 2004-40-0018

Many applications will benefit from a higher efficiency continuously variable transmission. This paper presents the design, performance, and measured efficiency of a linear low-slip continuously variable transmission prototype. It discusses the chosen design approach with an emphasis on efficiency and presents improvements on previous designs that make it practical. The ratio variability comes from exponential roller gear and cam gear pairs that function as noncircular gears. The roller/cam pairs are located on three centers of rotation, two fixed and one translating to provide the varying ratio. Two power paths are used and the power from the appropriate path is fed into the output by a band clutch that is synchronized to the output by the exponential gears and tightened by an internal cam. The cam is made up of telescoping segments driven in a nonlinear fashion by the location of the translating axle. Power crosses four gear meshes between the inline input and output shafts. The prototype has a ratio range of 5.85:1. A method of using internal torque to shift the transmission is presented.