It is made easy to design so that the sliding resistance, when subjected to an
impact in the axial direction, is kept within a prescribed value. A constant velocity
universal joint is provided, which has track grooves extending in the axial direction
on the outer circumference surface of the inner ring, and formed in an intersecting
arrangement, and which also embeds balls in these track grooves. In this constant
velocity universal joint, the cross-sectional shape of the track groove of the
inner ring is constituted by a Gothic arch portion which is a Gothic arch shape
up to a location that exceeds a contact point where the groove angular contacts
with the ball, and a straight-line portion which is formed continuously with the
Gothic arch portion, between the location exceeding the contact point and a shoulder
portion of the track groove, and which extends in the direction of the tangent
line at the location that exceeds the contact point.
