Abstract:
A method for manufacturing an impact absorbing member, starting with a closed or substantially closed hollow section with a mid section and two end sections, wherein at least one the end sections is bent to form a supporting member, whereby at least one imprint is made in the part of the section to be deformed by the bending operation. The invention also relates to an improved impact absorbing member formed by a manufacturing process including bending.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/NO2009/000418, filed Dec. 3, 2009, which designated the United States and has been published as International Publication No. WO 2010/064927 and which claims the priority of Norwegian Patent Application, Serial No. 20085061, filed Dec. 4, 2008, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to an impact absorbing member that includes at last one supporting member. In particular the invention relates to a crash management system including a bumper beam and crash absorbing components in one same and single part. Further, the invention relates to a method for making same. 
     The principle of making an integrated bumper with crash boxes has been disclosed previously, for instance in EP 1154915 B1 and DE 20 2005 016 564 U1. 
     However, it has not been clearly indicated how such systems would behave during common loadcases such as low speed insurance tests and regulation requirements. 
     A key parameter to achieve the performances required is the way the component is formed. 
     SUMMARY OF THE INVENTION 
     The present invention has the advantage of having a geometry which makes that the system has an equivalent stiffness as a traditional crash management system (mechanical assembled between crash boxes and bumper beam) and also fits in a conventional automobile packaging. Further, the invention will represent a cost efficient solution as plural process steps related to assembly of sub-components can be avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the following, the invention shall be further explained by examples and Figures where: 
         FIG. 1  discloses an impact absorbing member in accordance with the present Invention, shown in perspective, with bumper beam and crash absorbing components or crash boxes in one same and single part, 
         FIG. 2  discloses a definition of a vehicles coordinate system, 
         FIG. 3  discloses a cross section view of a member in accordance to the invention in the coordinate system of  FIG. 2 , 
         FIG. 4  discloses an impact absorbing member in accordance with the invention, Design A 1  seen from above divided into areas and indication of corresponding sections, 
         FIG. 5  discloses shape of section after processing in section A-A 
         FIG. 6  discloses shape of section after processing in section B-B 
         FIG. 7  discloses deformation applied simultaneously in two walls to initiate desired shape 
         FIG. 7   a  shows an imprint provided in a rear wall parallel to the bending axis; 
         FIG. 8  discloses a final shape of the component in its bending zone, left side view 
         FIG. 9  discloses section C-C after final forming of the component 
         FIG. 10  discloses one alternative embodiment of the invention, Design B, resulting from different forming processes 
         FIG. 11  discloses from above one right half part, of Design A, 
         FIG. 12  discloses from above one right half part of Design B, 
         FIG. 13  discloses from above one right half part of Design C, 
         FIG. 14  discloses a diagram showing comparison of stiffness between the three designs shown in  FIGS. 11-13 , 
         FIG. 15  discloses an alternative shape of a profile in order to include a towing function, 
         FIG. 16  discloses a section adapted for integration of a pedestrian absorber. 
     
    
    
       FIG. 1  discloses an impact absorbing member  1  in perspective, with a bumper beam  2  and crash absorbing components or crash boxes  3 ,  4  in one same and single part. 
       FIG. 2  discloses a definition of a vehicle&#39;s  5  coordinate system, while  FIG. 3  discloses a cross section view of a section of a beam similar to that shown in  FIG. 2 , however with a rectangular cross section for the sake of clarity. In the figure there is shown an upper wall  14 , rear wall  12 , lower wall  13  and front wall  11 . 
     The impact absorbing member or crash management system is for practical reasons divided in areas as follows which define the following sections A-A/B-B/C-C, see.  FIG. 4 . The crash management system is in this embodiment symmetrical about its mid axis (where cross section A-A is allocated). 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     One embodiment (Design A) of manufacturing the crash management system shall be described in the following:
         1. starting from a rectangular section (which could be for example an extruded profile but which can be in general a hollow section) it is performed an evolutive deformation in one of the walls so that the different sections are as shown in  FIG. 5  which discloses section A-A, and  FIG. 6  which discloses section B-B. As seen from this is that the wall has two crests and one bottom between them. In the  FIGS. 5 ,  6  and  7  reference sign  11  ,  12 ,  13  and  14  relates to front wall, rear wall, lower wall, and upper wall respectively.   2. In a second step, it is applied simultaneously a deformation (e.g.       

     imprints  12 ) in two walls (upper wall  14  and lower wall  13 , see  FIG. 7 ) of the profile by applying a force F, F′ to prepare the deformation of the profile in the bending zone. For example, as shown in  FIG. 7   a , imprint  12  may also be provided in a rear wall parallel to the bending axis. Thereafter a bending of the extremity of the component is performed in such a way that the final form of the component should look as in  FIG. 8 . See section A′. The same is applied to the other end of the profile. 
     The section C-C in the bending zone of this component (see  FIG. 4 ) could look as shown in  FIG. 9 . In the Figure there is shown an upper wall  14 , rear wall  12 , lower wall  13  and front wall  11 . 
     The most important point out of this final form is that in the area called A′, see  FIG. 8 , it is ensured that the transversal section is in contact with the longitudinal section. In that manner, the system is as stiff as any other comparable solution known from prior art. 
     Making imprint(-s) or deformation(-s) before bending has shown to support controllable deformation of the section to be deformed during bending. 
     In a second embodiment (Design B) the shape of the folding could be as shown in  FIG. 10 . To achieve this shape, during step two of the forming in embodiment one, an imprint has to be applied in the rear wall ( 12 ) of the profile (not shown). In a subsequent step, the profile is bent while having a mandrel inside. 
     The most important point out of the final shape is that in the area called A′, it is ensured that the transversal section, along axis X, is in contact with the longitudinal section along axis Y. In that manner, the system can be as stiff as any other similar solution known from prior art. 
     In the bending processes shown in the embodiments above, at least a part of the section that is deformed during bending can be clamped or arrested in a direction perpendicular to the plane of bending. This will influence the folding of said section and also limit the vertical extension of the absorbing member in this area. 
     It is important to emphasize that the way in which the bending process of the system is done will have a very important influence on the stiffness on the system as shown by the The  FIGS. 11 ,  12 ,  13 , correspond to embodiment 1 (Design A), embodiment 2 (Design B) and designs where simple bending is done (Design C) respectively. 
     One important parameter in bumper system design is the stiffness of the system. This can be assessed by applying a displacement in the middle section of the system and calculate the force opposed by the system. The higher the force is, the stiffer the system is. 
     In  FIG. 14 , the stiffness of the three systems is compared. From this result we can see that for example at 100 mm displacement in the middle section, Design A opposes a force of 3.4 kN whereas Design B opposes a force of 4.1 kN, and whereas Design C opposes a force of 2.1 kN. ThCis we show that an increase of 95% can be achieved by applying the forming in accordance with the present invention compared to a simple bending. 
     In a further embodiment, one could think to optimize the shape of the profile in order to improve the integration of a towing function. Such a cross sectional shape is shown in  FIG. 15 . 
     In the Figure there is shown an upper wall  14 ′, rear wall  12 ′, lower wall  13 ′ and front wall  11 ′. 
     In this version, the groove in the profile can be used in order to give better support to a towing function (towing bracket, not shown) since the contact surface is improved. 
     In a still further embodiment, one could think to integrate a pedestrian function taking profit of the shape of the section A-A, see  FIG. 16 . 
     In the Figure there is shown an upper wall  14 , rear wall  12 , lower wall  13  and front wall  11 . 
     Indeed, in this section one can “hide” the material coming from a pedestrian absorber in such a way that, during its deformation, the material from pedestrian absorber does not add an incompressible. 
     Preferably the crash management system is made out of aluminium or an Al-alloy, in particular age hardening alloys of 6xxx, for instance AA6060 or 7xxx alloys such as AA7003. 
     The invention shows the following advantages:
         reduction of components   reduction of assembly operations   function integration