Plunging constant velocity universal joint for propeller shaft

A plunging constant velocity universal joint for a propeller shaft comprising:

• an outer joint member with eight straight guide grooves formed in an axial direction on an inner circumference thereof having a cylindrical shape;
• an inner joint member with eight straight guide grooves formed in the axial direction on an outer circumference thereof having a spherical shape and teeth formed on an inner circumference thereof for the purpose of coupling with a shaft;
• eight balls disposed in ball tracks formed by the guide grooves of the outer joint member and the guide grooves of the inner joint member;
• and
• a cage having an outer circumferential surface, an inner circumferential surface and hollows for encasing the balls, the outer circumferential surface of convex spherical shape guided in contact by the inner circumference of the outer joint member, and the inner circumferential surface of concave spherical shape guided in contact by the outer circumference of the inner joint member, center of curvature of the outer circumference of the cage and center of curvature of the inner circumference of the cage being offset from the center of the hollow in the axial direction to the opposite sides,
• wherein the ratio of width W between the center of curvature of the inner joint member and an end face to a pitch circled diameter Ds of a fitting portion of the inner joint member is set as W/Ds>0.27.