Toroidal-type continuously variable transmission

A toroidal-type continuously variable transmission, comprising:

• an input disk and an output disk disposed coaxially so as to be opposed to each other;
• and
• a pair of power roller bearings, each power roller bearing including an inner race, an outer race and a plurality of rolling elements disposed so as to roll on the toroidal surfaces of said input and output disks,
• wherein at least one of said input disk, said output disk, said inner race and said outer race is made of medium-carbon steel containing carbon in an amount ranging from 0.3 wt % to 0.5 wt %, and
• further wherein assumed maximum non-metallic inclusion diameters of said medium-carbon steel in an area of 3000000 mm2 are at 40 μm or less, wherein said assumed maximum inclusion diameters are determined by an extreme statistical method which is carried out by checking 30 pieces of its samples while using a microscope, measuring the maximum inclusions in an area of 100 mm2 in each samples, and finding the assumed inclusion diameters in an area of 3000000 mm2 through the measurement of a total area of 3000 mm2.