Torsion bar for a steering system assembly

Abstract

A torsion bar for a steering system includes a main body. Also included is an end region having a cylindrical outer surface extending from an axial end surface. Further included is a serrated portion disposed proximate the end region and axially offset from the axial end surface.

Having thus described the invention, what is claimed is: 
     
         1 . A torsion bar for a steering system comprising:
 a main body;   an end region having a cylindrical outer surface extending from an axial end surface; and   a serrated portion disposed proximate the end region and axially offset from the axial end surface.   
     
     
         2 . The torsion bar of  claim 1 , wherein the serrated portion comprises a plurality of serrations circumferentially spaced from each other, each of the serrations having a leading edge to be press fit into a steering shaft, the leading edges oriented symmetrically about a central axis of the main body to avoid twisting during press fitting into the steering shaft. 
     
     
         3 . The torsion bar of  claim 2 , wherein the leading edges are partially conical in an axial direction. 
     
     
         4 . The torsion bar of  claim 2 , wherein the leading edges are partially conical in a radial direction. 
     
     
         5 . The torsion bar of  claim 2 , wherein the leading edges have a common geometry. 
     
     
         6 . A torsion bar for a steering system comprising:
 a main body; and   an end region having a plurality of serrations circumferentially spaced from each other, each of the serrations having a leading edge to be press fit into a steering shaft, the leading edges oriented symmetrically about a central axis of the main body to avoid twisting during press fitting into the steering shaft.   
     
     
         7 . The torsion bar of  claim 6 , wherein the end region comprises a cylindrical outer surface extending from an axial end surface of the torsion bar, the leading edges of the plurality of serrations axially offset from the axial end surface. 
     
     
         8 . The torsion bar of  claim 6 , wherein the leading edges are partially conical in an axial direction. 
     
     
         9 . The torsion bar of  claim 6 , wherein the leading edges are partially conical in a radial direction. 
     
     
         10 . The torsion bar of  claim 6 , wherein the leading edges have a common geometry. 
     
     
         11 . A method of manufacturing a torsion bar for a steering system comprising:
 supporting a torsion bar blank on a cold forming machine with a plurality of dies at a first end region of the torsion bar blank and a second end region of the torsion bar blank; and   rolling the torsion bar blank to form an end region having a cylindrical outer surface extending from an axial end surface and a serrated portion disposed proximate the end region and axially offset from the axial end surface.   
     
     
         12 . The method of  claim 11 , wherein the plurality of dies comprises a first pair of dies driven by a first spindle and a second pair of dies driven by a second spindle, wherein each of the first pair of dies includes a toothed portion to form the serrated portion and a smooth portion to form the end region, wherein each of the second pair of dies only includes a toothed portion. 
     
     
         13 . The method of  claim 11 , wherein forming the serrated portion comprises forming a plurality of leading edges oriented symmetrically about a central axis of the torsion bar to avoid twisting during press fitting of the torsion bar into a steering shaft. 
     
     
         14 . The method of  claim 11 , wherein forming the serrated portion comprises forming a plurality of leading edges that are partially conical.