Patent ID: 8172689

Claim:
A fixed-type constant velocity universal joint comprising: an outer joint member that is filled with a lubricant and on which a guide groove that extends in an axial direction is formed on a spherical inner circumferential surface; an inner joint member provided on an inner diameter side of the outer joint member and on which a guide groove that extends in the axial direction is formed on a spherical outer circumferential surface; a torque transmitting ball interposed between opposing guide grooves of the outer joint member and the inner joint member so as to roll freely; and a cage that holds the ball, wherein numerous miniscule recesses are randomly formed on a surface of the ball, wherein a maximum coefficient of friction of the ball is 0.07 as measured by a Savan-type friction and wear tester with the lubricant, wherein a minimum surface roughness of the ball on which the numerous miniscule recesses are formed is set to Ra 0.03 μm, a maximum surface roughness is set to Ra 0.6 μm, wherein a maximum parameter SK value of the surface roughness of the ball is set to −1.0, the SK value being defined as follows: SK =∫( x−x 0 ) 3 ·P ( x ) dx/σ 3 wherein x indicates a height of the roughness, x o indicates an average height of the roughness, P(x) indicates a probability density function of the amplitude of the roughness, and σ indicates a mean-squared roughness, and wherein a minimum percentage of a total area of the numerous miniscule recesses to a surface area of the ball is set to 10%, and a maximum percentage of the total area of the numerous miniscule recesses to the surface area of the ball is set to 40%.