Abstract:
A fluid formed node is provided to connect structure in an automotive vehicle. Another aspect of the present invention includes a method of forming a structural interconnection including the steps of placing a first member, having an internal cavity in a die pressurizing the internal cavity to form a node integral with and protruding from the first member, disposing the node within an aperture of a second member, and coupling the second member to the node.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention pertains generally to structural members and, more particularly, to a vehicle structure having an integral node.  
           [0002]    In the field of motor vehicle design, it is highly desirable to construct a modular vehicle including a subframe adaptable for use with a variety of aesthetically pleasing outer panels. Additionally, the use of extruded tubular sections within the construct of the subframe greatly enhances the strength and durability of the frame without drastically increasing the weight and cost.  
           [0003]    Unfortunately, many manufacturers have had difficulty reliably interconnecting individual tubular frame components to form a dimensionally correct and structurally robust vehicle frame. Accordingly, some manufacturers have implemented separate connectors, called nodes, to facilitate the joining process. The separate nodes are typically aluminum alloy castings having a plurality of apertures for receipt of tubular frame components. Due to the relative difficulty of welding aluminum alloys, cast nodes are especially prevalent in joints structurally interconnecting stamped or extruded aluminum components. As would be expected, the use of separate nodes is both costly and time consuming. Therefore, a need in the relevant art exists for an apparatus and method for interconnecting structural members.  
           [0004]    Accordingly, it is an object of the present invention to provide an improved vehicle body construction exhibiting the advantages of a tubular construction without the need for separate connectors such as cast nodes.  
           [0005]    It is another object of the present invention to provide a structural component including an integrally hydroformed node for use in a vehicle structure having improved strength and dimensional accuracy.  
           [0006]    In accordance with the present invention, a fluid formed node is provided to connect structure in an automotive vehicle. Another aspect of the present invention includes a method of forming a structural interconnection including the steps of placing a first member, having an internal cavity in a die, pressurizing the internal cavity to form a node integral with and protruding from the first member, disposing the node within an aperture of a second member, and coupling the second member to the node.  
           [0007]    The node of the present invention is advantageous over conventional construction in that the present invention provides an integrally formed attachment location economically created through the use of hydroforming. Additionally, structures incorporating the node of the present invention exhibit superior dimensional stability and structural integrity as compared to the structures previously described. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of an automotive vehicle skeletal structure showing the preferred embodiment of a node of the present invention;  
         [0009]    [0009]FIG. 2 is a fragmentary, exploded perspective view showing the preferred embodiment node;  
         [0010]    [0010]FIG. 3 is a cross-sectional view showing a first embodiment of an extruded tubular member having an integral flange employed with the preferred embodiment node;  
         [0011]    [0011]FIG. 4 is a cross-sectional view showing a second embodiment of an extruded tubular member having two integrally formed flanges employed with the preferred embodiment node;  
         [0012]    [0012]FIG. 5 is a cross-sectional view, taken along line  5 - 5 , showing a third embodiment of an extrusion employed with the preferred embodiment node;  
         [0013]    [0013]FIG. 6 is a cross-sectional view of a pair of hydroforming dies having the extrusion of FIG. 5 disposed within an internal cavity thereof;  
         [0014]    [0014]FIG. 7 is a cross-sectional view of a second pair of hydroforming dies having a partially deformed extrusion disposed within an internal cavity thereof;  
         [0015]    [0015]FIG. 8 is a cross-sectional view, taken along line  8 - 8  of FIG. 2, showing a first member employed with the preferred embodiment node;  
         [0016]    [0016]FIG. 9 is a another fragmentary exploded perspective view showing the preferred embodiment of a structural interconnection;  
         [0017]    [0017]FIG. 10 is a cross-sectional view, taken along line  10 - 10  of FIG. 2, showing a second member employed with the preferred embodiment node; and  
         [0018]    [0018]FIG. 11 is a fragmentary perspective view showing the preferred embodiment structural interconnection. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    The following detailed description of the preferred embodiment is merely exemplary in nature and is no way intended to limit the invention, its application, or uses. For example, the apparatus and techniques disclosed herein may have utility in forming a wide variety of different structures including boats, bicycles, aircraft and railroad structures.  
         [0020]    Referring to FIGS. 1 and 2, an exemplary structural interconnection  10  includes a hydroformed node  12  constructed in accordance with the teachings of the preferred embodiment of the present invention. Hydroformed node  12  is shown operatively associated with an exemplary vehicle frame  14 . It should be appreciated that one or more of the interconnections within vehicle frame  14  may include a hydroformed node such as node  12  and the specific interconnection discussed hereinafter is an example thereof.  
         [0021]    Vehicle frame  14  includes a pair of side rail panel panels  16  extending substantially parallel to a longitudinal or fore-and-aft axis of the vehicle. A header panel  18  transversely spans vehicle frame  14  and interconnects each of the side rail panel panels  16 . Each of the panels  16  and  18  are preferably constructed from an aluminum alloy exhibiting high strength per unit weight.  
         [0022]    With specific reference to FIG. 2, side rail panel  16  is preferably a generally hollow tubular shaped extrusion  20  having a first open end  22 , a second open end  24  with at least one of nodes  12  positioned therebetween. Side rail panel  16  also includes an outer surface  26  and an inner surface  28  defining a wall  30 . The cross sectional shape of the side rail panel  16  may be alternately constructed to suit a variety of different design applications. It is feasible to implement an extrusion having a first wall thickness for an application requiring moderate structural properties while another extrusion, having the same outer surface configuration as the first, may be formed to include a greater wall thickness and correspondingly superior structural properties. In this manner, it is possible to implement the lighter weight extrusion having a thinner wall in an otherwise rigidly framed vehicle such as a coupe while the second stiffer member is more suitable for a convertible automobile application. By maintaining a common outer surface profile, a single hydroforming die can create both coupe and convertible structural components as will be described hereinafter.  
         [0023]    [0023]FIGS. 3 and 4 show two embodiments of pre-hydroformed extrusions. An exemplary first extrusion  31 , not incorporated within vehicle frame  12 , includes an inner surface  32 , an outer surface  33  and a flange  34  integrally formed with and radially protruding from the outer surface  33 . The single flange or first extrusion  31  is contemplated for use as a header panel with the flange  34  providing a mounting surface for a windshield. FIG. 4 shows a second extrusion  35  including a pair of flanges  36  radially extending from an outer surface  38 . The dual flange or second extrusion  35  of FIG. 4 provides mounting locations for other components such as vehicle body panels. It should be appreciated that the outer surface  38  is varied by simply modifying the geometry of the extrusion die (not shown). Accordingly, features such as the mounting flanges  34  and  36  are integrally formed with the tubular member during the extrusion process.  
         [0024]    Referring to FIG. 5, the preferred embodiment of the side rail panel  16  is hydroformed from a third extrusion  40  including a generally constant thickness wall portion  42  and a reinforced thicker portion  44 . The reinforced wall portion  44  intrudes for approximately 30 to 45 degrees of the inner surface  28  of the side rail panel  16  obtaining a maximum thickness of approximately four milimeters. The generally constant thickness wall portion  42  is preferably one milimeter thick. It should be appreciated that the reinforced portion  44  acts as a sump or well of material when forming the node  12  such that a suitable minimum wall thickness is maintained throughout the finished hydroformed node. Because the reinforced portion is structurally necessary only at node locations, it is advantageous to maintain the generally constant wall thickness portion  42  for the majority of the cross section thereby reducing the overall weight of side rail panel  16 . Further weight reduction may be accomplished by selectively removing material located in the reinforced wall portions spaced apart from nodes  12 .  
         [0025]    As mentioned earlier, node  12  of the present invention is integrally formed with side rail panel  16  through the use of internal fluid pressure, preferably by use of a hydroforming process. Hydroforming is essentially the process of deforming a tubular member to a desired complex tubular shape. To this end and with reference to FIG. 6, a tubular member such as extrusion  40  is placed between a first die  46  and a second die  48  having cavities  50  and  52  respectfully, which define the desired resultant shape of the side rail panel  16 . First end  22  and second end  24  of the tubular member are accessible through the dies and a seal (not shown) is connected to the ends of the tubular member. Pressurized fluid  54 , typically water, is then injected into the ends of the extrusion  40  at a pressure of approximately 100,000 PSI, thereby forcing wall  30  to outwardly expand and conform to the internal shape defined by the die cavities. Depending on the material chosen and the depth of draw required, a number of intermediate hydroforming dies may be required to assure uniform deformation of the side rail panel  16  without rupture. For example, and in reference to FIG. 7, a third die  56  and a fourth die  58  comprise a second hydroforming die set  60  for incrementally deforming the partially hydroformed extrusion  40  into the final desired shape. It should also be appreciated that, as mentioned earlier, the side rail panel  16  may be extruded to include other inner and outer contours prior to hydroforming to structurally enhance the side rail panel  16  and/or ease formation of the node  12 .  
         [0026]    With reference to FIGS. 8 and 9, the completed hydroformed node  12  includes an end wall  62  and a side wall  64  extending substantially orthogonally from a longitudinal axis  66  of the side rail panel  16 . Side wall  64  is preferably formed at a small draft angle  68  typically ranging from three to seven degrees to facilitate removal of side rail panel  16  from the dies after hydroforming. Side wall  64  includes a generally convex portion  70 , and a generally concave portion  72  to form an asymmetric shape when viewed from the end wall  62 . The shape of side wall  64  functions to restrain header panel  18  from rotating once interconnected with node  12 . As best shown in FIG. 8, side wall  64  tapers, decreasing in thickness as the side wall approaches the end wall  62  where the section is at a minimum.  
         [0027]    With reference to FIGS. 9 and 10, header panel  18  is also a generally cylindrical hollow extrusion having a first open end  74  and a second open end  76 . In the preferred embodiment each of the ends  74  and  76  are coupled to a node  12  of the present invention. For clarity, only one such interconnection will be described in detail. Specifically, first open end  74  includes an inner surface  77  and an outer surface  78  defining a wall  80 . The wall  80  includes a first recess  82  and a second recess  84  shaped to compliment the outer surface  26  of the side rail panel  16 . In addition, the first open end  74  includes a flared or swaged portion  86  for receipt of the hydroformed node  12 .  
         [0028]    Because the preferred header panel  18  is a tubular member, the flared portion  86  may be created via a hydroforming process as well. In this manner, the flared portion  86  may be accurately formed to provide a slip or interference fit with the hydroformed node  12  as desired. Preferably, the inner surface  77  of the flared portion  86  compliments the draft angle  68  formed by the side wall  64  of the node  12  such that the inner surface  77  is positioned adjacent the side wall  64  at assembly. It should also be appreciated that the tubular header panel  18  is merely exemplary and that a variety of mating components may be utilized including stampings and/or castings. Optimally, the stamping or casting would include a flared portion to compliment the draft angle of the hydroformed node  12 .  
         [0029]    Reference should now be made to FIG. 11 wherein the structural interconnection  10  is completed by engaging node  12  of side rail panel  16  with flared portion  86  of header panel  18 . Header panel  18  is mechanically attached to side rail panel  16  to provide further structural benefit. It is envisioned that a variety of attachment methods may be utilized including welding, mechanical fasteners, including rivets or screws, and adhesives. The preferred embodiment incorporates a plurality of rivets  88  extending through apertures (not shown) formed in the flared portion  86  of the header panel  18  and the side wall  64  of the hydroformed node  12 . The apertures may be created during the hydroforming process or added subsequently by processes such as drilling, stamping or laser cutting.  
         [0030]    Therefore, it should be appreciated that the configuration and operation of the structural interconnection including a hydroformed node provides manufacturing and operational advantages over the prior art. Specifically, the hydroformed node  12  of the present invention provides an integrally formed attachment location economically created through the use of hydroforming.  
         [0031]    The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. While various materials have been disclosed, it should be appreciated that a variety of other materials can be employed. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.