Abstract:
A vehicle structural frame member incorporates an internal lightweight brace member spanning between the opposing flanges of the co-joined hat-shaped members forming the structural frame member. The internal brace is formed of thin material, such as steel, to help the frame member retain its geometric shape when placed under a load. The internal brace can be formed into a ladder-like configuration with longitudinally spaced members that span between the opposing flanges to keep the geometric shape from collapsing. A substantial improvement in load carrying capability before collapse is obtained with a small increment in additional weight in the structural frame member.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to an automotive frame member and, more particularly, to a stability device for maintaining a geometric profile during crush loading. 
       BACKGROUND OF THE INVENTION 
       [0002]    Federal safety requirements require vehicles to withstand loads on the vehicle roof area for occupant safety and protection. These load requirements, expressed as a percentage of vehicle weight, increase as newer Federal requirements are established. The roof load requirements are intended to simulate loads on the vehicle encountered during a vehicle rollover event. Other frame members, such as upper and lower frame rails that extend generally longitudinally on the automotive frame, also experience crushing loads from crashes that result in the collapse of the frame member. The newer, more demanding Federal requirements force countermeasures, i.e. changes to the structure of vehicle body and frame, which can ultimately add significant cost and weight to the vehicle. 
         [0003]    It is essential to minimize the weight of the vehicle, and thus the countermeasures adopted to meet the newer Federal safety requirements, as added weight to the vehicle frame translates into increased load requirements, as the requirements are expressed in terms of a percentage of the total vehicle weight. Increasing frame size is, therefore, a “Catch 22” type of situation in that the addition of structure to meet the load requirements of the newer regulations results in increased load requirements that must be resisted by the frame structure to satisfy the Federal requirements. Thus, conventional solutions required to meet the Federal safety requirements, by adding large, heavy steel reinforcements are counterproductive. The utilization of lighter weight materials and composites can offer equivalent vehicle frame structure that will withstand the required roof loads; however, these lightweight materials are typically substantially more expensive than conventional steel components, which make the cost of the vehicle frame prohibitively expensive and would render the vehicle commercially uncompetitive. 
         [0004]    When the vehicle frame components are loaded through the roof, the vehicle body pillars and rail cross-sections achieve a peak loading and then proceed to collapse. In the process of collapsing, the frame cross-section changes geometric shape into a less stable cross-sectional profile. The progressing geometric shape change continues until the load carrying capability of the structural frame member is reduced below the buckling threshold, where collapse occurs. 
         [0005]    The conventional approach to increasing the load carrying capacity of a vehicle structural frame member can be seen in U.S. Pat. No. 6,328,376, issued to Baik-Lark Son on Dec. 11, 2001, in which a reinforcing member that cooperates with a stepped portion of the reinforcing panel in a manner to delimit the closed space and increase the overall rigidity of the center pillar. Similarly, a reinforcing panel is added to the vehicle structural frame member formed from two hat-shaped components to increase the weight and the section of the structural member in U.S. Pat. No. 6,397,553, granted to Tooru Horikawa, et al on Jun. 4, 2002. 
         [0006]    A reinforcement for a vehicle roof rail and center pillar is placed between the inner and outer panels of the structural member as taught in U.S. Pat. No. 6,705,668, issued on Mar. 16, 2004, to Masashi Makita, et al by welding flanges of the reinforcement member and inner and outer panels to each other, thus increasing vehicle rigidity. In U.S. Pat. No. 6,917,654, granted on Nov. 16, 2004, to Yuichi Kitagawa, et al, a pillar reinforcement panel has flanges that are pinched and welded between corresponding flange parts of inner and outer pillar pieces to increase pillar rigidity. 
         [0007]    U.S. Pat. No. 6,988,763, issued on Jan. 24, 2006, to Hidetsugu Saeki, et al discloses a U-shaped energy absorbing section welded to the outside of a center roof pillar to provide structural integrity such that other members are deformed only after the energy absorbing section has completely deformed due to impact loading. The U-shaped reinforcement member can be welded to the inside surface of the outer pillar panel to provide an impact absorbing member. In U. S. Patent Application Publication No. 2005/0212326, by Thomas Marion, dated Sep. 29, 2005, a reinforcement member has three pivotable walls positioned within the vehicle structure defining a cavity, such as a roof assembly or a roof pillar in a vehicle. 
         [0008]    It would be desirable to provide a stability device in a vehicle structural frame member that is operable to retain the geometric cross-sectional shape of the frame member while undergoing crash loading. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing a stability device in a vehicle structural frame member so that the frame member will retain geometric shape during loading. 
         [0010]    It is another object of this invention to provide an interior brace across the structural beam that prevents the profile from changing into a less stable configuration under load. 
         [0011]    It is a feature of this invention to provide an interior brace spanning across the cross-sectional configuration of a vehicle structural beam. 
         [0012]    It is an advantage of this invention that the interior brace helps the structural beam to maintain geometric shape while under load. 
         [0013]    It is another advantage of this invention that the vehicle frame member is capable of sustaining increased loads before collapsing. 
         [0014]    It is still another advantage of this invention that the increase in load capacity is obtained without a significant increase in weight for the vehicle structural frame member. 
         [0015]    It is another feature of this invention that the structural frame member is formed from hat-shaped components welded together at opposing flanges. 
         [0016]    It is still another feature of this invention that the opposing flanges are interconnected by a flat internal brace. 
         [0017]    It is still another advantage of this invention that the flat internal brace is formed from relatively thin material to hold the spacing of the opposing flanges. 
         [0018]    It is yet another advantage of this invention that the internal brace can be inserted into the structural frame member without increasing the overall dimensions of the frame member. 
         [0019]    It is yet another feature of this invention that the internal brace can be formed into a ladder-like configuration with longitudinally spaced members spanning between opposing flanges on the structural frame member. 
         [0020]    It is a further feature of this invention that the longitudinally spaced members of the internal brace can be located where collapse of the frame member is most likely to occur. 
         [0021]    It is a further advantage of this invention that the internal brace functions to help the structural frame member to resist collapse. 
         [0022]    It is a further object of this invention to provide a stability device for a vehicle structural frame member that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
         [0023]    These and other objects, features and advantages are accomplished according to the instant invention by providing a vehicle structural frame member that incorporates an internal lightweight brace member spanning between the opposing flanges of the co-joined hat-shaped members forming the structural frame member. The internal brace is formed of thin material, such as steel, to help the frame member retain its geometric shape when placed under a load. The internal brace can be formed into a ladder-like configuration with longitudinally spaced members that span between the opposing flanges to keep the geometric shape from collapsing. A substantial improvement in load carrying capability before collapse is obtained with a small increment in additional weight in the structural frame member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
           [0025]      FIG. 1  is a perspective view of an automotive structural frame member, such as, but not limited to, a B-pillar, incorporating the principles of the instant invention; 
           [0026]      FIG. 2  is a cross-sectional view taken through the structural frame member in  FIG. 1  corresponding to lines  2 - 2 , the upper hat-shaped member being shown in to complete the structural frame member; 
           [0027]      FIG. 3  is an exploded schematic perspective view of a first embodiment of the instant invention; 
           [0028]      FIG. 4  is a perspective view of the first embodiment of the instant invention; 
           [0029]      FIG. 5  is a cross-sectional view of a structural frame member, similar to that of  FIG. 2 , but depicting a second embodiment of the instant invention; 
           [0030]      FIG. 6  is an elevational view of the structural frame member depicted in  FIG. 5 ; 
           [0031]      FIG. 7  is a plan view of the internal brace member utilized in  FIGS. 5 and 6 ; 
           [0032]      FIG. 8  is a cross-sectional view of a structural frame member, similar to that of  FIG. 5 , but depicting a third embodiment of the instant invention; 
           [0033]      FIG. 9  is an elevational view of the structural frame member depicted in  FIG. 8 ; 
           [0034]      FIG. 10  is a plan view of the internal brace member utilized in  FIGS. 8 and 9 ; 
           [0035]      FIG. 11  is an enlarged partial elevational view of the structural frame member shown in  FIG. 9 ; and 
           [0036]      FIG. 12  is a graph depicting the load capability of a structural frame member having a stability device placed internally thereof compared to the load capability of a structural frame member not have the stability device incorporating the principles of the instant invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0037]    Referring to  FIGS. 1-4 , a structural frame member for use in an automotive vehicle and having a first embodiment of an internal brace incorporating the principles of the instant invention can best be seen. The structural frame member  10  is preferably placed in an automobile in a place that requires resistance to collapse due to the placement of loads thereon. Examples of such structural frame members  10  are roof pillars for the automobile, the roof rails, or the lower frame rails where impact or rollover loads can cause collapse of the structural frame member. Other examples of automotive structural frame members that can benefit from an adoption of the principles of the instant invention include: front and rear roof headers, roof bows, A-pillars, front hinge pillars, B-pillars, rockers, roof rails, front and rear longitudinal railsfloor cross members, front upper rails, door beams, frame rails, C-pillars and D-pillars. Federal safety requirements for the frame of an automotive vehicle mandate that the roof be capable of resisting substantial loads, which are typically expressed as a percentage of the overall vehicle weight. Accordingly, the pillars and the roof rails must be capable of withstanding a specified load before collapsing under the loading imposed on the frame member. 
         [0038]    When the structural frame member is placed under loading, the geometric shape, best seen in a cross-section, such as is depicted in  FIG. 2 , undergoes a progressing change in shape or configuration, placing the frame member in a less stable configurations until the frame member collapses. This progressing change in geometric shape typically results in the opposing flanges  15  of the co-joined inner and outer hat-shaped members  12 ,  13 , spreading apart to cause a reduction in the depth of the frame member&#39;s cross-section, and thereby lessening the ability in the frame member to carry a load. Conventional practice to increase the structural frame member&#39;s load carrying capacity is to add structural reinforcements, such as the reinforcement  14  placed into the outer hat-shaped member  13 , as seen in  FIGS. 1-4 . These reinforcements  14  are welded to the outer hat-shaped member  13  to be operable as an integral part thereof 
         [0039]    While the addition of the reinforcement  14  adds more mass and weight to the frame member  10 , and thereby increasing the difficulty for the geometric cross-section to change shape, sufficient loading will ultimately cause the shape to change and the load carrying capacity to decrease until collapse occurs. According to the principles of the instant invention, the structural frame member  10  can be formed with an internal brace  20  that spans across the center of the frame member to tie into the opposing flanges  15  to maintain the cross-sectional shape and configuration of the frame member  10 . 
         [0040]    A first embodiment of the invention is depicted in  FIGS. 1-4  wherein the brace member  20  is in the form of a C-shaped member, similar to that of the reinforcement member  14 , but turned oppositely of the reinforcement member  14  so that a central span  22  of the brace member  20  is substantially aligned with the center of the frame member  10  and extends from one transverse side of the frame member  10  to the other. In this first embodiment, the C-shaped brace member  20  has a pair of transversely opposed mounting legs  23  oriented generally perpendicularly to the central span  22  and positioned to be welded against the corresponding legs of the reinforcement member  14 . In this first embodiment, the internal brace  20  interconnects the opposing sides of the frame member  10  next to the flanges  15  by welding the legs  23  to the reinforcement member  14 , which in turn is welded to the outer hat-shaped member  13 . 
         [0041]    Accordingly, the brace member  20  keeps the frame member  10  from spreading transversely. With the legs  23  turned toward the outer hat-shaped member  13  to be welded to the reinforcement member  14 , the brace member  20  does not increase the vertical spacing, i.e. the thickness dimension, at the flanges  15  of the frame member  10 . Yet, the internal brace  20  will still serve to prevent the opposing flanges  15  from spreading apart while under load. As is noted in  FIGS. 3 and 4 , the internal brace member  20  is preferably formed in a ladder-like configuration with the central span  22  being formed as transversely extending rungs  24  interspersed by openings in the brace member  20  to keep the brace member  20  as light in weight as possible. The rungs  24  serve to maintain transverse spacing between the opposing flanges  15  without adding substantial weight to the frame member  10 . 
         [0042]    In  FIGS. 5-7 , a second embodiment of the internal brace member  20  is depicted. The second embodiment of the brace member  20  is similar in shape to the first embodiment in that the brace member  20  is formed in a ladder-like configuration with a pair of transversely spaced side portions  26  interconnected by a series of rungs  24  forming the central span  22  of the brace member  20 . Instead of the side portions  26  forming legs that bend toward one of the hat-shaped members  12 ,  13  to be welded internally, the brace member  20  is generally planar and the side portions  26  are welded between the flanges  15  of the inner and outer members  12 ,  13 . While  FIG. 7  depicts the brace member  20  as being regularly formed with evenly spaced rungs  24 , the rungs  24  could be positioned across the frame member  10  at irregularly spaced positions to be placed at the positions deemed to be the most likely locations in the frame member  10  to experience deformation under loading conditions. 
         [0043]    A third embodiment of the brace member  20  is shown in  FIGS. 8-11 . In this structural frame member, such as a roof rail in which the flanges are formed with raised portions  17  to increase rigidity and provide a preferred mounting surface for chassis members (not shown) to be attached. Rather than the rungs  24  extending between opposing side members  26 , as depicted in the first two embodiments shown in  FIGS. 1-7 , the rungs  24  project outwardly in a cantilevered manner from a center longitudinally extending support member  29  with opposing rung projections defining a rung  24  that extends between opposing flanges  15 . The rung projections  24  are oriented and sized to fit within a corresponding raised portion  17  in the flange  15 . As noted previously, the longitudinal spacing of the rungs  24  on the internal brace  20  do not need to be a regular spacing. Clearly, the preferred embodiment is to design the rung spacing to correspond to the raised portion spacing within which the rungs are to be welded. Since the internal brace member  20  needs only to be a thin stability device that is operable to prevent the opposing flanges  15  from spreading apart under load, the thin rungs  24  can fit within the gap beneath the inner member  12  at the formed raised portion  17 , as is best seen in  FIG. 11 . Thus, the incorporation of the internal brace member  20  into the frame member  10  does not increase the thickness dimension of the flanges  15  of the frame member  10 . 
         [0044]    In all three embodiments, but particularly with respect to the planar configurations shown in  FIGS. 5-11 , the internal brace member  20  is a thin, preferably sheet metal, member that is welded to the opposing flanges  15 . The purpose of the thin brace member  20  is not to reinforce, as the brace member  20  does not have sufficient mass to provide conventional reinforcement functions, but to stabilize the cross-sectional shape of the frame member  10  and prevent the flanges  15  from moving apart and causing the frame member to lose load carrying capability. Preferably, the thickness of the internal brace member  20  will be in the range of 0.7 mm to 1.2 mm, but could be as thin as 0.5 mm. 
         [0045]    Clearly, the internal brace member  20  is strongest in tension, which is how the brace member  20  would be stressed if the flanges  15  try to spread apart. With the rungs  24  welded to the opposing flanges  15 , the opposing flanges can&#39;t spread apart and reconfigure the cross-section into a less capable shape. In  FIG. 12 , a graph depicts the increased load carrying capability of a representative structural frame member  10  with and without the internal brace member  20 . As can be seen in this graph, the utilization of the thin internal brace member  20  spanning between the opposing flanges  15  more than doubles the load carrying capability of the frame member  10 , increasing the maximum load from about 3000 pounds to about 8500 pounds. The load at collapse increases from about 2000 pounds to about 6000 pounds. Accordingly, one skilled in the art will readily recognize the benefits of incorporating a structure stability device, such as the internal brace member  20  extending between the flanges  15  of the frame member  10 . 
         [0046]    It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. 
         [0047]    In the way of examples, the principles of the instant invention can be utilized in any type of thin shell structural span member found anywhere on an automotive vehicle body or frame. The internal brace member  20  can be as simple as a single thin span of metal placed appropriately across the center of a structural frame member to force the structural frame member to maintain its cross-sectional shape while under load. The internal brace member  20  can be used with conventional reinforcing members, such as is depicted in the aforementioned prior art documents, to achieve optimal performance results as required. One skilled in the art will understand that the principles of the instant invention are not limited to crush loads in the roof, as many other structural frame members are subjected to other crushing loads, such as impact loads, that will cause the structural frame member to change its geometric shape. Lastly, the principles of the instant invention are not limited to use on automotive structural frame member, and can be used on substantially any structural frame member subjected to a crushing load that will tend to deform the cross-sectional geometric shape of the frame member.