Automotive Traction Drive CVTs - An Overview

On the Feasibility of Independently Controllable Transmissions

“…CVTs primarily differ in the type of variator used: commonly the belt type [1][2][3][4][5][6][7][8][9][10], but also hydrostatic [11][12][13], traction [14][15][16], and electric (e-CVT) [17][18][19] ones, based on the ability of variable speed electric machines to continuously change their shaft speed from zero to an arbitrary required speed. Infinitely variable transmissions [20][21][22][23] have been successfully applied as vehicle transmission.…”

Design and analysis of a modified power-split continuously variable transmission

“…The definition of a friction type CVT is a transmission device that uses friction as a medium for power transmission. This friction is of the "static" type in that the design is intended to transmit power from one element to the other with no relative displacement between the two elements (Hewko, 1986). An example of this phenomenon is the variable diameter pulley and belt system, where the belt slides axially or radially, but frictional force prevents tangential belt slip (Kluger and Fussner, 1997).…”

“…Motors also performed extensive research and development work on the CVT in this time period, but its work was halted at the testing stage of development (Hewko, 1986). This work was resumed in the 1960's by Perbury Gear, which produced an automotive transmission with a higher power capacity.…”

“…While technical development has brought the CVT back into the realm of automotive design, it still suffers from such problems as poor launch feel or reduced high speed fuel economy because of limited ratio coverage and torque capacity (Vahabzadeh, 1990), and the CVT has shorter transmission life at high power densities when compared to conventional transmissions (Hewko, 1986). These problems can be overcome by combining the CVT with one or more epicyclic gears to create a power-split transmission (Beccari and Cammalleri, 2001).…”

“…It is recognized that the power capacities of CVTs still fall far short of the power output of large-displacement engines used in larger automobiles. These power capacities can be extended when the CVT is combined with an epicyclic gear set (Beccari and Cammalleri, 2001), and the life of the CVT can be extended if its transmitted power is kept to a minimum (Hewko, 1986) 1.1 Problem Statement and Thesis Objectives…”