Power roller bearing and a troidal type continuously variable transmission system

A troidal type continuously variable transmission system in which a power roller supported by a power roller bearing is interposed between an input disk and an output disk in a rotatable and incliable manner, said transmission system including said power roller bearing which comprises:

• an inner race with said power roller mounted thereon, said power roller having a traction portion to be contacted with said input and output disks in such a manner the rotation of said input disk is transmitter to said output disk through a rotational movement of said power roller;
• an outer race disposed opposite to said inner race for supporting said power roller rotatably;
• and,
• a rolling element interposed between said inner and outer races in such a manner that it is held between ring-shaped race grooves respectively formed on the mutually opposing surfaces of said inner and outer races,
• wherein each of said race grooves respectively formed on said inner and outer races has a arc-shaped cross section, and the radii of curvatures of the arc-shaped cross sections of said race grooves are set in the range of 52% to 59% of the diameter of said rolling ball body.