Crash box and method for producing the same

Abstract

A crash box has excellent axial crushing performance and in which, even if the sheet thickness of a tubular body constituting the crash box is smaller than 1.4 mm, good welding can be performed with the tubular body butted against a set plate. The crash box (1) having a metallic longer-length tubular body and a method for producing the crash box are provided. The tubular body has a basic cross-sectional shape that is a flat polygon surrounded by a plurality of ridges (2-1 to 2-4) extending in a longitudinal direction and a plurality of side wall portions (4), includes one or more groove portions (3-1 and 3-2) on side wall portions (4) on long sides substantially parallel to the major axis direction of the cross section that extend in longitudinal direction, and includes outward flanges (5-1 to 5-4) in an end portion in the longitudinal direction.

1 - 17 . (canceled) 
     
     
         18 . A method of producing crash box comprising a longer-length metallic tubular body and a set plate including locking sections,
 the locking sections are individually formed as a part of the set plate,   the tubular body having a basic cross-sectional shape that is a polygon surrounded by a plurality of ridges extending in a first direction and a plurality of side wall portions, the tubular body including one or more groove portions in side wall portions on long sides that are substantially parallel to a major axis direction of the cross section, the groove portions extending in the first direction, and the tubular body including a curved portion molded integrally with the tubular body and outward flanges continuing to the curved portion at an end portion of the tubular body in the first direction,   the set plate being welded to an end of the tubular body having the outward flanges, and the locking sections section being integral with the set plate and projecting upwardly from a surface of a portion of the set plate positioned within the tubular body,   wherein the locking sections section of the set plate are is butted against the curved portion of the tubular body, wherein   the method comprising following First Step, Second Step, and Third Step;   First Step: a step of, using a pressing device including: a punch that includes a groove portion that extends in a second direction and a side wall provided in an end portion in the second direction; a die that is disposed facing the punch; and a pad that includes a protrusion extending in the second direction, to depress a developed blank of the tubular body into the groove portion of the punch by a protrusion of the pad and bend the developed blank using the die and the punch, so as to produce two press molded bodies with an open cross-section, the press molded bodies each having a basic cross-sectional shape that is a polygon surrounded by a plurality of ridges extending in the second direction and a plurality of side wall portions, the press molded bodies each including one or more groove portions in side wall portions on long sides substantially parallel a major axis direction of the cross section, the groove portions extending in the second direction, and the press molded bodies each including outward flanges in an end portion in the second direction, the outward flanges being continuous in a part of region along a cross-section circumferential direction; and   Second Step: a step of overlapping and welding the two press molded bodies produced through the first step, at plane portions that are each formed at both ends in a cross-section circumferential direction of each of the two press molded bodies, so as to produce the tubular body.   Third Step: a step of overlapping the tubular body obtained through the second step and the set plate with the outward flanges interposed therebetween, and attaching the tubular body to the set plate by spot welding, fillet arc welding, or laser welding.   
     
     
         19 . The method for producing a crash box according to  claim 18 , wherein the polygon is a flat polygon. 
     
     
         20 . The method for producing a crash box according to  claim 18 , wherein the outward flanges are provided in all the ridges excluding at least regions of the end portion corresponding to a groove portion. 
     
     
         21 . The method for producing a crash box according to  claim 18 , wherein the outward flanges are molded integrally with the tubular body. 
     
     
         22 . The method for producing a crash box according to  claim 18 , wherein the tubular body is a press molded body of the metal sheet. 
     
     
         23 . The method for producing a crash box according to  claim 18 , wherein the metal sheet has a sheet thickness of 1.2 mm or smaller. 
     
     
         24 . The method for producing a crash box according to  claim 18 , wherein the metal sheet has a sheet thickness of 1.0 mm or smaller. 
     
     
         25 . The method for producing a crash box according to  claim 18 , wherein the metal sheet is a steel sheet having a tensile strength of 440 MPa or higher. 
     
     
         26 . The method for producing a crash box according to  claim 18 , wherein the metal sheet is a steel sheet having a tensile strength of 590 MPa or higher. 
     
     
         27 . The method for producing a crash box according to  claim 18 , wherein the polygon is a substantial quadrilateral. 
     
     
         28 . The method for producing a crash box according to  claim 18 , wherein the pad includes restraining portions that restrain portions in the developed blank to be molded into ridges in a vicinity of outward flanges, the portions in the developed blank to be molded into the ridge in the vicinity of the outward flanges are retained by the restraining portions. 
     
     
         29 . The method for producing a crash box according to  claim 28 , wherein the set plate includes a locking section that is provided projecting from a surface of the plate and is butted against an inner surface of an end portion in a longitudinal direction of the tubular body.