Worm gear hub

Abstract

A method of making a worm gear. The method includes forming a gear blank having a plurality of individual lugs formed about an outer circumferential edge of said blank to facilitate a uniform flow of a material around said plurality of individual lugs. The method also includes molding said material around said plurality of individual lugs to form a ring.

What is claimed is: 
     
         1 . An electric power steering system comprising:
 a steering shaft connected to a handwheel at one end and a rack and pinion steering mechanism at an opposite end;   a steering assist unit comprising an electric motor operated by a controller and driving a worm and a worm gear interposed between said worm and said steering shaft, said worm having worm teeth and said worm gear fitted on said steering shaft;   said worm gear further comprising:
 a disk having a first face axially disposed opposite a second face; 
 a first plurality of individual lugs formed on said first face circumferentially adjacent an outer circumferential edge of said disk, wherein each lug of said first plurality of individual lugs having a first inner circumferential edge formed on said first face along a first retaining diameter, said first retaining diameter generally less than a disk diameter, circumferentially adjacent lugs of said first plurality of individual lugs having a first circumferential spacing therebetween; 
 a ring overlaying a portion of said disk including said first plurality of individual lugs, said ring having an outer diameter, said outer diameter generally greater than said disk diameter; and 
 a plurality of gear teeth on an outer edge surface of said ring for meshing with said worm teeth. 
   
     
     
         2 . The electric power steering system of  claim 1 , further comprising:
 a second plurality of individual lugs formed on said second face circumferentially adjacent said outer circumferential edge of said disk and opposite and offset the first plurality of individual lugs, wherein each lug of said second plurality of individual lugs having a second inner circumferential edge formed on said second face along a second retaining diameter, said second retaining diameter generally less than said disk diameter, circumferentially adjacent lugs of said second plurality of individual lugs having a second circumferential spacing therebetween.   
     
     
         3 . The electric power steering system of  claim 1 , wherein each lug of said first plurality of individual lugs having a radially extending first lateral edge and a radially extending second lateral edge formed on said first face. 
     
     
         4 . The electric power steering system of  claim 1 , wherein said disk includes a concentric opening therethrough. 
     
     
         5 . The electric power steering system of  claim 4 , wherein a hub portion adjacent to said concentric opening is thicker than said first and second face. 
     
     
         6 . The electric power steering system of  claim 1 , wherein said worm gear is formed by at least one process of a group consisting of: stamping, hot forging, cold forging, spin forming, flow forming, machining, and pressing powdered metal. 
     
     
         7 . The electric power steering system of  claim 1 , wherein said ring is polymeric. 
     
     
         8 . A method of making a worm gear comprising:
 forming a gear blank having a plurality of individual lugs formed about an outer circumferential edge of said blank to facilitate a uniform flow of a material around said plurality of individual lugs; and   molding said material around said plurality of individual lugs to form a ring.   
     
     
         9 . The method of  claim 8 , further comprising:
 pressing said gear blank on a shaft; and   hobbing gear teeth onto an outer surface of said ring.   
     
     
         10 . The method of  claim 8 , the gear blank having a disk having a first face axially disposed opposite a second face, and said plurality of individual lugs comprising:
 a first plurality of individual lugs formed on said first face circumferentially adjacent an outer circumferential edge of said disk, wherein each lug of said first plurality of individual lugs having a first inner circumferential edge formed on said first face along a first retaining diameter, said first retaining diameter generally less than a disk diameter, circumferentially adjacent lugs of said first plurality of individual lugs having a first circumferential spacing therebetween.   
     
     
         11 . The method of  claim 10 , said plurality of individual lugs further comprising:
 a second plurality of individual lugs formed on said second face circumferentially adjacent said outer circumferential edge of said disk and opposite and offset the first plurality of individual lugs, wherein each lug of said second plurality of individual lugs having a second inner circumferential edge formed on said second face along a second retaining diameter, said second retaining diameter generally less than said disk diameter, circumferentially adjacent lugs of said second plurality of individual lugs having a second circumferential spacing therebetween.   
     
     
         12 . The method of  claim 8 , wherein said ring is overlaying a portion of said gear blank including said plurality of individual lugs, said ring having an outer diameter, said outer diameter generally greater than a gear blank diameter.