Method of attaching a functional element to a sheet metal part

Abstract

The invention relates to a method of attaching a functional element to a sheet metal part. The functional element has a head part having a ring-shaped support surface and a tubular rivet section that is designed as self-piercing and that extends at the side of the support surface of the head part and away from said head part.

1 . A method of attaching a functional element to a sheet metal part of sheet metal material, wherein the functional element has a head part having a ring-shaped support surface and a tubular shaft part that is formed as self-piercing and that extends at the side of the support surface of the head part and away from the head part, wherein the support surface comprises a ring recess, and wherein the sheet metal part is supported on a perforated die that has a bore whose diameter at least substantially corresponds to the outer diameter of the shaft part or is somewhat larger than it, wherein the bore is surrounded at the side of the perforated die facing the sheet metal part by a ring nose that is raised with respect to a support surface of the perforated die and defines a planar circular ring-shaped end surface, wherein the functional element is pressed onto the sheet metal part supported on the perforated die such that a panel slug is punched out of the sheet metal part by means of the shaft part, wherein an undercut is produced at the shaft part on the attachment of the functional element to the sheet metal part, and a portion of the sheet metal material that surrounds the punched hole generated by the punching out of the panel slug is plastically pressed by means of the circular ring-shaped end face of the ring nose into the ring recess while completely filling it, and is pressed in the region of the transition from the head part into the shaft part radially into the shaft part and is further pressed into the undercut formed during the attachment process. 
     
     
         2 . The method in accordance with  claim 1 ,
 wherein the sheet metal part has a thickness of more than 3 mm.   
     
     
         3 . The method in accordance with  claim 1 , wherein features providing security against rotation are provided that are located in the region of the ring recess and/or in the region of the transition of the ring recess into the shaft part and that selectively divide the ring recess into individual fields distributed about the longitudinal axis of the functional element. 
     
     
         4 . The method in accordance with  claim 3 , wherein a portion of the sheet metal material that surrounds the punched hole generated by the punching out of the panel slug is plastically pressed by means of the circular ring-shaped end face of the ring nose into the individual fields. 
     
     
         5 . The method in accordance with  claim 3 , wherein the features providing security against rotation are security against rotation noses. 
     
     
         6 . The method in accordance with  claim 1 , wherein the undercut formed on the attachment of the functional element to the sheet metal part is present in the form of one of a crease and a constriction. 
     
     
         7 . The method in accordance with  claim 1 , wherein the rivet shaft part is free of undercuts prior to the attachment of the functional element to the sheet metal part. 
     
     
         8 . The method in accordance with  claim 1 , wherein the undercut is formed in the region of the transition from the ring recess to the shaft part. 
     
     
         9 . The method in accordance with  claim 1 , wherein, during the punching of the sheet metal part, the ring nose also presses via its circular ring-shaped end surface toward the lower side of the sheet metal part and there forms a recess that extends around the shaft part in the region of its free end, wherein the material displaced by the formation of the recess is pressed into the undercut formed at the shaft part during the attachment process. 
     
     
         10 . The method in accordance with  claim 9 , wherein the material displaced by the formation of the recess enlarges the undercut formed during the attachment of the functional element to the sheet metal part. 
     
     
         11 . The method in accordance with  claim 1 ,
 wherein the functional element is pressed onto the sheet metal part supported on the perforated die such that a portion of the sheet metal material that surrounds the punched hole produced by the punching out of the panel slug starts to flow plastically as a result of contact with the circular ring-shaped end surface of the ring nose and is plastically pressed into the ring recess while completely filling it.   
     
     
         12 . The method in accordance with  claim 1 ,
 wherein the functional element is pressed onto the sheet metal part supported on the perforated die such that a portion of the sheet metal material that surrounds the punched hole produced by the punching out of the panel slug is pressed radially into the shaft part in the region of the transition from the head part into the shaft part.   
     
     
         13 . The method in accordance with  claim 1 ,
 wherein a perforated die is used as the perforated die whose circular ring-shaped end surface of the ring nose has a radial extent that corresponds to approximately half the thickness of the sheet metal part and/or that is smaller than the radial extent of the ring recess, but larger than half the radial extent of the ring recess.   
     
     
         14 . The method in accordance with  claim 1 ,
 wherein a perforated die is used as the perforated die whose ring nose has a volume that substantially corresponds to volume of the ring recess of the functional element.   
     
     
         15 . The method in accordance with  claim 1 , wherein a larger portion of sheet metal material of the sheet metal part is deformed than material of the shaft part of the functional element on attachment of the functional element to the sheet metal part.