Inner spline member and manufacturing method thereof

Abstract

An interior splined member is a hollow cylinder with an interior cylindrical surface defining a through hole. A major portion of the axial length of the interior cylindrical surface is splined to provide alternating axially extending ribs and troughs disposed between the ribs. A ring-shaped residual portion is an unsplined portion, i.e., a minor portion of the axial length of the interior cylindrical surface and is substantially circular with a diameter that is equal to or smaller than that of a circle on which the distal ends (tips) of the ribs lie. The trough portions are open at one end of the cylindrical member, while closed by the ring-shaped residual portion at the other end of the cylindrical member.

What is claimed is:  
     
         1 . An interior splined member comprising a hollow cylindrical member having an interior cylindrical surface defining a through hole, said interior cylindrical surface including a splined portion providing alternating axially extending ribs and troughs and an unsplined ring-shaped residual portion that is substantially circular with a diameter equal to or smaller than the diameter of a circle defined by the distal ends of said ribs, said troughs opening at an end face at one axial end of said hollow cylindrical member and closed by said ring-shaped residual portion at a second axial end of said hollow cylindrical member.  
     
     
         2 . The interior splined member according to  claim 1 , wherein a cut edge surface is provided at the second axial end of the hollow cylindrical member.  
     
     
         3 . The interior splined member according to  claim 1  wherein said splined portion extends over a major portion of the axial length of said interior cylindrical surface and said unsplined portion extends over a minor portion of the axial length of said interior cylindrical surface.  
     
     
         4 . A method for manufacturing an interior splined member comprising the steps of: 
 providing a cylindrical member having an interior cylindrical surface defining a through hole;    cold forming the interior cylindrical surface to form a splined portion on said interior cylindrical surface, said splined portion providing alternating, axially extending ribs and troughs; and    leaving unsplined a ring-shaped residual portion of said interior cylindrical surface which is substantially circular with a diameter equal to or smaller than the diameter of a circle defined by distal ends of the ribs.    
     
     
         5 . The method for manufacturing an interior splined member according to  claim 4 , further comprising the step of: 
 cutting an end face of the cylindrical member.    
     
     
         6 . The method for manufacturing an interior splined member according to  claim 4 , wherein the cold forging includes: 
 supporting the cylindrical member around an outer peripheral surface using an outer peripheral punch;    inserting an end portion punch into one end of the cylindrical member;    inserting a spline punch into an end of the cylindrical member opposite the one end, the spline punch having a spline-forming portion with a shape corresponding to the spline portion and a column-forming portion with an outer diameter corresponding to an inner diameter of the ring-shaped residual portion;    moving the spline punch relative to the interior cylindrical surface to form the splined portion; and    stopping said moving of the spline punch at a position within the cylindrical member by abutment of at least one portion of the column-forming portion of the spline punch.    
     
     
         7 . The method for manufacturing an interior splined member according to  claim 5 , wherein the cold forging includes: 
 supporting the cylindrical member around an outer peripheral surface using an outer peripheral punch;    inserting an end portion punch into one end of the cylindrical member;    inserting a spline punch into an end of the cylindrical member opposite the one end, the spline punch having a spline-forming portion with a shape corresponding to the spline portion and a column-forming portion with an outer diameter corresponding to an inner diameter of the ring-shaped residual portion;    moving the spline punch relative to the interior cylindrical surface to form the splined portion; and    stopping said moving of the spline punch at a position within the cylindrical member by abutment of at least one portion of the column-forming portion of the spline punch.