Abstract:
An impact beam assembly includes a beam of high-strength steel, and a pair of end brackets constructed of a dissimilar material than the high-strength steel. The brackets are locally deformed onto the beam to thereby surround a portion of the beam. Once deformed, the brackets define a flat section suitable for welding to a vehicle door panel, as well as a section for retaining the beam. The beam can include a surface feature suitable for retaining the beam to the end brackets. A method of reinforcing a vehicle door assembly includes positioning the beam with respect to the end brackets such that the brackets surround a portion of the beam, and then activating a magnetic pulse coil (MPC) to deform an overlapping portion of the brackets onto the beam. The brackets are then attached to a surface of the door assembly to reinforce the door assembly.

Description:
TECHNICAL FIELD 
     The present invention relates generally to an impact beam for reinforcing a portion of a vehicle body, and more particularly to a high-strength mixed metal impact beam for reinforcing a vehicular door assembly or other vehicle body panel. 
     BACKGROUND OF THE INVENTION 
     In order to improve vehicle structural integrity, high-strength impact beams constructed of steel or other suitable impact-resistant material can be integrated into a vehicle body, for example by welding the impact beam into a door assembly. However, there is ordinarily a very limited amount of available space between an outer panel of the door assembly and any window glass and any internal mechanisms of the door assembly when the window glass is in a dropped position. As a result, there are limited options for integrating an impact beam within a vehicle door assembly, as well as a limited number of useful configurations of the impact beam itself. 
     Additionally, in order to achieve ever increasing fuel economy standards, the reduction of weight and mass of modern vehicles is typically an overarching design goal. It is therefore common practice to use aluminum, magnesium, and/or composite materials in constructing vehicle bodies and components. While such light-weight materials are desirable from a vehicle mass reduction standpoint, packaging space limitations as noted above can limit the effectiveness of impact beams constructed from such materials, which often must be enlarged in order to provide strength that is equal to that of an impact beam constructed of a high-strength material such as steel. 
     SUMMARY OF THE INVENTION 
     Accordingly, a method is provided that allows high-strength impact beams to be integrated into a low-mass vehicle body panel, such as but not limited to a door assembly or another closure panel assembly. The low-mass vehicle panel can be constructed of aluminum, magnesium, composite materials, and/or other relatively lightweight or low-mass materials in order to reduce the overall weight and mass of the vehicle. The combination of an impact beam constructed in accordance with the invention with a low-mass vehicular panel assembly provides a low-mass design with optimal structural integrity. Additionally, the formation method utilizes a mechanical deformation or fastening technique to form an mechanical interlock between different components of the impact beam assembly, and as a result provides a relatively low cost solution. 
     In particular, a method of reinforcing a vehicle door assembly or other vehicle panel assembly includes positioning a steel beam with respect to an end bracket such that the end bracket surrounds or circumscribes at least a portion of the steel beam. The steel beam can be fabricated or configured, for example, as a tubular beam having a circular, rectangular, or other suitable cross-sectional shape, an extruded beam with a cross section designed for optimal stiffness, or any other suitable beam design. The method further includes activating a magnetic pulse coil (MPC) to thereby selectively deform an overlapping portion of the end bracket, i.e., a portion of the end bracket that surrounds or circumscribes a portion of the steel beam to thereby overlap a perimeter or circumference thereof, and to thereby form a mechanical joint or interlock in conjunction with the steel beam. The end bracket is then fastened or otherwise attached to an inner surface of the vehicle door assembly for reinforcement of the vehicle door assembly. A substantially similar end bracket is positioned on either end of the steel beam, with each end bracket deformed to the steel beam using an MPC or MPC-based process as noted above, or any other suitable mechanical deformation process producing the desired mechanical interlock as set forth below. 
     Additionally, an impact beam assembly for reinforcing a vehicle panel, such as but not limited to a vehicle door assembly, includes a pair of end brackets, as well as a beam constructed of high-strength steel. The end brackets are each configured for receiving a different end of the beam. To further reduce weight and mass, and to facilitate joining of the brackets to the door assembly, the end brackets can be constructed of a material that is substantially the same as the door construction and dissimilar to that of the high-strength steel, e.g., aluminum, magnesium, and/or other suitable material. The end brackets are locally deformed onto the beam to thereby surround or circumscribe at least a portion of the beam. The end brackets each include a splayed portion defining a flat section suitably adapted for welding or fastening to a surface of the vehicle panel. The end brackets also define a section suitable for retaining the beam. The beam can optionally include a surface feature for further retaining the beam to the end brackets as set forth hereinbelow. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an exemplary reinforced vehicle door assembly in accordance with the invention; 
         FIG. 2  is a schematic illustration of an impact beam assembly usable for reinforcing the vehicle door assembly of  FIG. 1 ; 
         FIG. 3  is a schematic illustration of another embodiment of an impact beam assembly usable for reinforcing the vehicle door assembly of  FIG. 1 ; 
         FIG. 4A  is a schematic illustration of an exemplary alternate steel beam that is usable with the impact beam assembly of  FIGS. 1 and 2 ; 
         FIG. 4B  is a schematic illustration of a second alternate steel beam that is usable with the impact beam assembly of  FIGS. 1 and 2 ; 
         FIG. 4C  is a schematic illustration of a third alternate steel beam that is usable with the impact beam assembly of  FIGS. 1 and 2 ; 
         FIG. 4D  is a schematic illustration of a fourth alternate steel beam that is usable with the impact beam assembly of  FIGS. 1 and 2 ; and 
         FIG. 5  is a graphical flow chart describing a method for forming an impact beam assembly by deformation or crimping using a magnetic pulse coil (MPC). 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, and beginning with  FIG. 1 , a vehicle door assembly  10  includes an inner panel  12  and an outer panel  14 . The inner panel  12  and the outer panel  14  together define an internal space or a cavity  16 . The door assembly  10 , which can be connected to a vehicle body (not shown) and used for entry and egress from a vehicle interior or passenger compartment, further includes window glass  18 . The window glass  18  can be selectively raised to the position shown in  FIG. 1  or lowered into the cavity  16  using an automatic or a manual actuator device (not shown). 
     Within the scope of the invention, the door assembly  10  can be constructed or fabricated of a relatively lightweight or low-mass material such as aluminum, magnesium, a composite material, an alloy, and/or any other suitable lightweight or low-mass material. Such materials are expected to optimize the fuel economy of any vehicle using the door assembly  10 . In order to also optimize the structural integrity of the door assembly  10  without significantly increasing weight and mass, an impact beam assembly  20  is provided therein that is constructed in accordance with the invention as set forth below. That is, the impact beam assembly  20 , which is constructed at least partially of a cylindrical, tubular, or extruded high-strength steel is welded, bolted, and/or otherwise fastened to surfaces of one or both of the inner panel  12  and the outer panel  14 . 
     Referring to  FIG. 2 , the impact beam assembly  20  of  FIG. 1  includes a beam  22  and an end bracket  24 . While only one end bracket  24  is shown in  FIG. 2 , it is understood that an identical or substantially similarly configured end bracket  24  is disposed at the opposite end of the impact beam assembly  20 , as best shown in  FIG. 1 . The beam  22  is constructed of high-strength steel having an exemplary cross-section of a diameter D and a thickness T, and having a length that is dependent on the size and shape of the door assembly  10  of  FIG. 1 . Those of ordinary skill in the art will recognize that the cross-sectional shape and configuration of the beam  22  can vary without departing from the intended scope of the invention. However, if the beam  22  is configured with a cross-sectional shape that is something other than circular as shown, the Magnetic Pulse Device (MPD)  60  described below can be modified to provide the required deformation of the end bracket  24  to the beam  22 . 
     The end bracket  24  can be configured as a section of lightweight/low-mass metallic or other suitable material. In one embodiment, the end bracket  24  is constructed of aluminum, while in another embodiment the end bracket  24  is constructed of magnesium. However, the end bracket  24  can also be constructed of steel and/or other suitable materials, depending on the desired weight/mass goals of the impact beam assembly  20 . Regardless of the materials of construction, in the embodiment of  FIG.2  the end bracket  24  includes an open section  26  and a splayed section  30 , with a slot  28  defined within or by the open section  26  opening to the splayed section  30 . The open section  26  has an end  32  with a diameter that is slightly larger than the diameter D of the beam  22  in order to allow the beam  22  to be inserted with minimal resistance into the end  32 , through the open section  26 , for ultimate positioning adjacent to a flat surface  34  and near an edge  40  of the splayed section  30 . 
     To provide additional structural integrity, the open section  26  can be adapted to include a bonding material  31  (see  FIG. 3 ) such as adhesive material applied at or along an interface between the end bracket  24  and the beam  22  prior to deformation. Such an adhesive material could include glass beads to ensure that the adhesive material is not forced out during deformation. Instead or in addition to adhesive material, abrasive particles or materials could be used at the interface between the end bracket  24  and the beam  22  to promote an optimal mechanical interlock or bond between the end bracket and beam  22  upon deformation of the end bracket  24  as described below. 
     The slot  28  can be cut or formed in or from the open section  26  in such a manner as to facilitate the spreading of opposing portions  36  and  38  into a desired shape or configuration suitable for welding or fastening into the door assembly  10  of  FIG. 1 . That is, while a substantially flat design as shown in  FIG. 2  can facilitate such welding or fastening, while also providing a simplified geometry for placement within the confined space  16  of the door assembly  10  (see  FIG. 1 ), other shapes or configurations can be envisioned for the end bracket  24  without departing from the intended scope of the invention. 
     Still referring to  FIG. 2 , once the beam  22  is inserted into the end bracket  24  as set forth above, the loosely coupled beam  22  and end bracket  24  are moved into a magnetic pulse device (MPD)  60 , as indicated by the arrow A, wherein the beam  22  and end bracket  24  are subjected to a controlled deformation and/or welding process, thus forming a mechanical interlock between the beam  22  and each end bracket  24 . The impact beam assembly  20  thus emerges from the MPD  60 , as indicated generally by the arrow B. 
     Within the scope of the invention, the MPD  60  is configured as a solid-state capacitance-based welding device having a conductive coil  62  surrounding a focal point  64 . Objects being joined, in this instance the beam  22  and the end bracket  24 , are positioned concentrically within the opening of the coil. Upon discharge of the capacitor, a large current pulse passes through the coil. The current pulse rise time is usually less than approximately 100 microseconds. The rapid discharge of energy provides a negligible amount of heating of the materials of construction of the beam  22  and end bracket  24 . 
     Discharged electrical current runs through the conductive coil  62 , which surrounds but does not physically contact the beam  22  or the end bracket  24 . The electrical current in the conductive coil  62  ultimately generates an eddy current within the open section  26  of the end bracket  24 . As will be understood by those of ordinary skill in the art, the electrical current in the conductive coil  62 , as well as the eddy current generated in the end bracket  24 , each produces an opposing magnetic field. The repulsive magnetic force generated between the coil  62  and the end bracket  24  ultimately repels the end bracket  24  away from the coil  62  and toward the beam  22  at a relatively high velocity. The end bracket  24  is thereby deformed around, molded to, or otherwise joined to the beam  22  to form a mechanical interlock therebetween, and the joined impact beam assembly  20  emerges from the MPD  60  as generally indicated by arrow B. 
     After deformation within the MPD  60 , unaffected portions  42  of the end bracket  24  are left in a non-deformed state, while affected portions  44  within the primary coil of the MPD  60  are deformed inward at a high rate of speed, as noted above. The mechanical deformation may cause the components to be joined or coupled into a singular structure having a mechanical joint that is structurally sound, or deformed into an interference fit between the components capable of withstanding the predicted service loads. The flat surface  34  of the end bracket  24  can then be welded or fastened into the door assembly  10  of  FIG. 1 . 
     Referring to  FIG. 3 , another embodiment of the impact beam assembly  20  is shown as the impact beam assembly  20 A. A beam  22 A having a surface feature  46  provides an additional mechanical interlock between a beam  22 A and an end bracket  24 A after the magnetic pulse deformation process. In the exemplary embodiment of  FIG. 3 , the surface feature  46  is a diametric reduction area  47 , i.e., an annular zone having a diameter that is less than the diameter D. Alternate forms of the surface feature  46  can be used without departing from the intended scope of the invention. As noted above, bonding material  31  can be optionally provided at an interface between the end bracket  24 A and the beam  22 A to optimize the mechanical interlock therebetween. While shown only in  FIG. 3  for simplicity, the bonding material  31  can also be used with the embodiment of  FIG. 2 , as will be understood by those of ordinary skill in the art. 
     For example, the surface feature  46  can be alternately embodied as a surface feature  46 A in the form of a set of threads  48  as shown in  FIG. 4A . Alternately, a surface feature  46 B can be provided in the form of a set of axial grooves  52  as shown in  FIG. 4B . As another option, a surface feature  46 C can be a set of adjacent flat zones  54  as shown in  FIG. 4C . As yet another option, a surface feature  46 D can be provided in the form of a diametric expansion area  56 , i.e., a zone or area having a diameter that is greater than the diameter D. 
     Referring again to  FIG. 3 , rather than starting with a modified tubular end bracket  24  as shown in  FIG. 2 , the end bracket  24 A can be alternately formed or configured from a flat piece of sheet metal. The formed sheet metal design allows for relatively larger attachment areas  36 A and  36 B for the impact beam assembly  20 A to weld to or fasten into the door assembly  10  (see  FIG. 1 ). Upended portions  70  and  72  of an open section  26 A of the end bracket  20 A form an alternate slot  28 A for placement of the beam  22 A in preparation for the MPD process. Upended portions  70  and  72  may be brought together and welded to provide a circular open end in a supplementary operation. Thus the bracket can be fabricated from a sheet metal blank rather than from tubing. The circular open end, as opposed to the upstanding flange design, simplifies coil design and the joining process. 
     After welding or deformation, i.e., after the impact beam assembly  20 A emerges from the MPD  60  (see  FIG. 2 ) as generally indicated by arrow C, the upended portions  70  and  72  of the end bracket  20 A are inwardly deformed onto the beam  22 A, thus following the contours of the beam  22 A. The affected portions  44 A and  44 B of the upended portions  70  and  72  conform to the shape of the surface feature  46  to form an interlock between the beam  22 A and the end bracket  24 A. Unaffected portions  42 A and  42 B are not deformed with respect to the beam  22 A, although the unaffected portions  42 A and  42 B can be bent, crimped, folded, or otherwise shaped during processing by the MPD  60 . The beam  22 A and the end bracket  24 A may also be welded into a singular structure in the MPD process in addition to the interlocking engagement. 
     Referring to  FIG. 5 , a method  100  for forming the impact beam assembly  20 ,  20 A begins with step  102 , wherein in one exemplary embodiment the beam  22 ,  22 A can be fabricated or formed into a tubular shape, as best shown in  FIGS. 2 and 3 . In this exemplary embodiment, the beam  22 ,  22 A is formed of high-strength steel, such as low-carbon steel, and with a circular or at least generally circular cross-section. In the embodiment of  FIG. 2 , the beam  22  is formed of a substantially smooth or featureless length of cylindrical tubing, while in the embodiment of  FIG. 3 , the beam  22 A includes one or more surface features  46  as set forth above. 
     Once formed at step  102 , the method  100  includes fabricating or forming the end brackets  24 ,  24 A at step  104 . In an exemplary embodiment, the end brackets  24 ,  24 A are constructed of a reduced mass material, i.e., a dissimilar and lighter weight material than that of the beam  22 ,  22 A. For example, aluminum, magnesium, or a composite material may be used to construct the end brackets  24 ,  24 A. 
     When fabricating the end brackets  24 , as shown in  FIG. 2 , step  104  can include slitting or cutting a length of tubing along at least half of its length L, and then bending, unfolding, and/or shaping the cut end of the tubing to form the flat surface  34 . When fabricating the end brackets  24 A as shown in  FIG. 3 , step  104  can include bending, folding, or shaping a generally rectangular piece of sheet metal to form the slot  28 A in an open section  26 A in the form of a channel. In either embodiment, the diameter of the slot  28 ,  28 A is slightly larger than the diameter (D) of the beam  22 ,  22 A. 
     At step  106 , the beam  22 ,  22 A is loosely coupled with the end brackets  24 ,  24 A. In the embodiment of  FIG. 2 , the beam  22  is inserted into the end  32  of the end bracket  24  until the beam  22  is positioned adjacent to the edge  40  as shown in  FIG. 2 . In the embodiment of  FIG. 3 , the beam  22 A is positioned within the slot  28 A and adjacent the edge  40 . Once positioned in this manner, the method  100  proceeds to step  108 . 
     At step  108 , the loosely coupled beam  22 ,  22 A and end brackets  24 ,  24 A are placed within the MPD  60 , which is discharged as explained above to thereby form the impact beam assembly  20 . If the user of the method  100  is a manufacturer of the impact beam assembly  20 , the method  100  can end with step  108 . However, method  100  can further include step  110 , wherein the impact beam assembly  20  installs the impact beam assembly  20  within the door assembly  10 , i.e., by welding and/or fastening the impact beam assembly  20  to one or both of the inner panel  12  and outer panel  14  of the door assembly  10 . 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.