To enhance the fatigue strength of a male spline part by mitigating the stress concentration of both tensile stresses and shear stresses at the male spline part of a stem part of an outer joint member.
A male spline part Sm is formed on an outer circumference of a stem part of an outer joint member. An expansion part 21b with its outside diameter dimension being gradually increased toward a counter shaft end side is provided on a part on the counter shaft end side out of a valley part 21 of the male spline part Sm. Round parts 21b1 of an arc-shaped section are formed on both sides of the circumferential direction of the expanded part 21b, and the radius of curvature of the round parts 21b1 is gradually increased toward the counter shaft end side.
YOSHIDA KAZUHIKO
MATSUBARA YUKIO
Yoshiyuki Shiraishi
Kunihiko Shiromura
Tsuyoshi Kumano