Patent attributes
The contact angle of the ball 15 with each first guide track 21 of an inner joint member 12 is made to become smaller gradually from an opening portion side toward a bottom portion side, and the curvature radius for the first guide track 21 is made to become larger gradually from the opening portion side toward the bottom portion side. If the contact angle only were made to become smaller gradually from the opening portion side toward the bottom portion side, the contact angle would become too small thereby to cause chattering in rotation to be generated. If the curvature radius only were made to become larger gradually from the opening portion side toward the bottom portion side, a contact ellipse M2 defined by the ball 15 and the first guide track 21 would become tool small, which would cause the ball 15 to make dents on the surface of the first guide track 21. However, the aforementioned drawbacks can be obviated by gradually diminishing the contact angle and gradually enlarging the curvature radius from the opening portion side toward the bottom portion side.
