To supply grease to substantially whole regions of a male spline and a female spline without causing play in the direction of rotation of a meshing face and reduction of rigidity of a meshing part.
A recessed part 5 for storing grease in which a central part is recessed by leaving both end parts in the axial direction is formed on a top land 4a of the male spline 4 so that grease is securely stored over the central part in the axial drection and the vicinity of both end parts in an opposing part of every other tooth tip in the circumferential direction and tooth bottom of the male spline 4 and the female spline 3. The grease stored in the recessed part 5 for storing grease flows into other clearance part between tooth faces smoothly in accordance with minute displacement between the male spline 4 and the female spline 3. Since the recessed part 5 for storing grease is formed by leaving both end parts in the axial direction of the male spline 4, play is prevented by meshing in both end parts in the axial direction of the male spline 4 and the female spline 3.
Hiromichi Kobayashi
Tomioka Kiyoshi