Laser-hardened fillet-rolled crankshaft

Abstract

An automotive shaft fillet treating method including laser hardening a green machined fillet surface to a uniform depth d to induce compressive stresses into the surface, the surface extending the entire length l between outer edges of two undercut regions of the fillet, and applying additional compressive stress to the laser hardened surface via fillet rolling such that the uniform depth d is maintained along the entire length l during a subsequent grinding operation.

What is claimed is: 
     
         1 . An automotive shaft fillet treating method comprising:
 laser hardening a green machined fillet surface to a uniform depth d to induce compressive stresses into the surface, the surface extending the entire length l between outer edges of two undercut regions of the fillet; and   applying additional compressive stress to the laser hardened surface via fillet rolling such that the uniform depth d is maintained along the entire length l during a subsequent grinding operation.   
     
     
         2 . The method of  claim 1 , wherein the surface includes the undercuts, crests, end regions, and a central region of the fillet. 
     
     
         3 . The method of  claim 1 , wherein a hardened depth d of the surface is about 1.0 mm. 
     
     
         4 . The method of  claim 1 , wherein the surface includes about 80 to 100% fillet contact area. 
     
     
         5 . The method of  claim 1 , wherein the shaft is a crankshaft or a camshaft. 
     
     
         6 . The method of  claim 1 , wherein the fillet rolling is performed at about 5 to 15 kN. 
     
     
         7 . The method of  claim 1 , wherein the fillet is a main journal, a pin journal, or a post. 
     
     
         8 . The method of  claim 7 , wherein the subsequent grinding operation includes remanufacturing. 
     
     
         9 . A method of treating a fillet, the method comprising:
 laser hardening an undercut-to-undercut surface of a green fillet to a uniform depth d to induce compressive stresses uniformly into the surface; and   applying additional compressive stress to the laser hardened surface via fillet rolling such that the uniform depth d is maintained along the entire surface.   
     
     
         10 . The method of  claim 9 , wherein the surface includes the undercuts, crests, end regions, and a central region of the fillet. 
     
     
         11 . The method of  claim 9 , wherein the uniform depth d of the surface is about 1.0 mm. 
     
     
         12 . The method of  claim 9 , wherein the surface includes about 80 to 100% of fillet contact area. 
     
     
         13 . The method of  claim 9 , wherein the shaft is a crankshaft or a camshaft. 
     
     
         14 . The method of  claim 9 , wherein the fillet rolling is performed at about 5 to 15 kN. 
     
     
         15 . The method of  claim 9 , wherein the fillet is a main journal, a pin journal, or a post. 
     
     
         16 . The method of  claim 9 , wherein the uniform depth d is maintained along the entire surface during subsequent operation(s). 
     
     
         17 . A shaft fillet comprising:
 an undercut-to-undercut surface area defined by and between outer edges of two undercut regions of the fillet, an entirety of the surface area being laser hardened to a uniform depth d to form a layer containing hardened portions configured to receive additional compressive stress via fillet rolling without fracture.   
     
     
         18 . The fillet of  claim 17 , wherein the depth d is about 1.0 mm. 
     
     
         19 . The fillet of  claim 17 , wherein the fillet is a main journal, a pin journal, or a post. 
     
     
         20 . The fillet of  claim 17 , wherein the surface area includes the undercuts, crests, end regions, and a central region of the fillet.