Abstract:
An energy absorbing knee bolster for use in an interior of a vehicle is disclosed. The knee bolster is configured to absorb energy from the vehicle&#39;s occupants during a crash. The knee bolster is formed of a collapsible cylinder which is welded to an impact plate on its first end and to a vehicle&#39;s cross-car beam at its second end. A coupling flange is disposed between the impact plate and a medial portion of the collapsible cylinder. The collapsible cylinder is configured to axially collapse at a predetermined force when impacted by a moving occupant.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an instrument panel reinforcement structure for motor vehicles, and more particularly to a tubular support structure for a knee bolster.  
         BACKGROUND OF THE INVENTION  
         [0002]    Critical to the fundamental development of a restraint system are the concepts of occupant energy management and occupant kinematics. In this regard, Federal Motor Vehicle regulations provide load limitations for various anatomical features of a seated occupant in a forward crash. These load limitations generally have been set to reduce the overall percentage chance of an injury for a given anatomical feature caused by a vehicle crash at a specific vehicle crash speed.  
           [0003]    The individual components of a restraint system must be designed with the view of the other components in the restraint system, as well as the specific vehicle geometry. For example, the stiffness of an airbag cushion must be designed with view of the stiffness of a vehicle&#39;s steering column, windshield slope, and instrument panel stiffness. As such, it is very desirable during the development of a restraint system to have components which have easily modifiable engineering properties.  
           [0004]    One integral component in any restraint system is the lower portion of the instrument panel or knee bolster. In this regard, the knee bolster functions to absorb a significant amount of an occupant&#39;s impact energy during a crash event. Further, the knee bolster is critical in a regulation of an occupant&#39;s kinematics. Specifically, the knee bolster regulates the angle an occupant rotates about its hip to encounter a deploying airbag. The regulation of the occupant&#39;s kinematics is a function of the load the knee bolster imparts onto an occupant&#39;s knees as well as the displacement of the knee bolster with respect to the vehicle. The travel of an occupant&#39;s hips within the vehicle is closely related to the translation of the knee bolster. It is known by those skilled in the art that the adjustment of the stiffness of the knee bolster can be used to reduce the likelihood an occupant will hit a windshield for an unbelted occupant during a crash event, by reducing the amount of rotation of an occupant&#39;s torso.  
           [0005]    As such, it would be desirable to have a knee bolster for use in a restraint system which has engineering properties that can be easily tuned based upon vehicle geometry, occupant loading, and occupant displacement. It also would be desirable to provide a knee bolster which provides a steady state loading of an occupant&#39;s femurs so as to absorb as much energy during a crash event without exceeding government and industry set safety standards.  
           [0006]    It is an object to the present invention to provide an instrument panel which overcomes the disadvantages of present knee bolster systems. Specifically, it is an object of the present invention to provide a highly tunable knee bolster which provides steady state loading of an occupant&#39;s lower extremities during a crash event.  
         SUMMARY OF THE INVENTION  
         [0007]    In accordance with the teachings of the present invention, an energy absorbing knee bolster for use in an interior of a vehicle is disclosed. The knee bolster is configured to absorb energy from the vehicle&#39;s occupants during a crash. The knee bolster is formed of a collapsible cylinder which is welded to an impact plate on its first end and to a vehicle&#39;s cross-car beam at its second end. A coupling flange is disposed between the impact plate and a medial portion of the collapsible cylinder. The collapsible cylinder is configured to axially collapse at a predetermined force when impacted by a moving occupant.  
           [0008]    In one preferred embodiment, a knee bolster having a collapsible cylinder with a first end and a medial portion is disclosed. An impact plate is coupled to the first end, while a coupling flange is coupled to the impact plate and to the medial portion of the collapsible cylinder. The collapsible cylinder is configured to axially collapse at a predetermined force when impacted by the moving occupant.  
           [0009]    In another embodiment of the invention, an energy absorbing support structure configured to support an instrument panel within a vehicle is disclosed. The energy absorbing structure has a tubular means for absorbing occupant impact energy and an impact plate coupled to said tubular means for absorbing occupant energy. A coupling bracket is disposed between the impact plate and the tubular means for absorbing impact energy. The coupling bracket is configured to encourage the collapse of the tubular means for absorbing energy in a telescopic fashion.  
           [0010]    In yet another embodiment of the invention, a cross-car beam is disclosed. The cross car beam is formed by a first member, which is disposed between two points with a vehicle compartment and a collapsible cylinder having first and second ends. The second end of the collapsible cylinder is coupled to the first member. An impact plate is coupled to the first end of the collapsible cylinder. A coupling flange coupled to the impact plate and to the collapsible cylinder. The collapsible cylinder is configured to axially collapse any predetermined force when impacted by a vehicle occupant.  
           [0011]    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 the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 represents a perspective view of a knee bolster bracket according to the teachings of the present invention;  
         [0014]    [0014]FIG. 2 depicts a perspective view of the knee bolster bracket according to the teachings of the present invention in an automobile environment;  
         [0015]    [0015]FIG. 3 depicts a top view of the knee bolster bracket according the teachings of the present invention;  
         [0016]    [0016]FIGS. 4 and 5 represent side views of the knee bolster bracket according to the present invention;  
         [0017]    [0017]FIGS. 6 and 7 depict collapsed knee bolster brackets according to the teachings of the present invention;  
         [0018]    [0018]FIG. 8 represents an alternate embodiment of the present invention; and  
         [0019]    [0019]FIGS. 9 and 10 represent load versus displacement curves for the knee bolster according to the teachings of the first embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0021]    FIGS.  1 - 5  represent the knee bolster support bracket  10  according to the teachings of the present invention. The bracket  10  is formed of three general components, a cylindrical or tubular member  12 , a first impact plate  14 , and a coupling bracket  16 . Generally, the impact plate  14  is welded to a first end  18  of the tubular member  12 . As best seen in FIG. 2, the tubular member  12  is welded at its second end  20  to a cross-car beam  22  of a vehicle instrument panel  24 . The tubular member  12  is formed of a single steel tube which is plastically deformed to form first and second tubular members  26  and  28 . Generally, the diameter of the second tubular member  28  is set so the first tubular member  26  can be forced into the second tubular member  28  by deformation of the transition portion  30 . While the tubular member  12  is shown having a circular cross section, it is envisioned the tubular member  12  can have other closed cross sections such as an oval, square, or rectangle.  
         [0022]    The tubular member  12  is preferably formed of 1008 or 1010 mild steel. The first tubular member  26  preferably has a diameter from about 1.25 to 1.75 and most preferably 1.5 inches, while the second tubular member  28  preferably has a diameter of from about 1.75 to 2.25 and most preferably 2 inches. The tube wall preferably has a thickness from about 0.5 to about 2 millimeters. The outer diameter of the first tubular member  26  is smaller than the outer diameter of the second tubular member  28 , and most preferably smaller than an inner diameter of the second tubular member  28 .  
         [0023]    As best seen in FIG. 2, the impact plates  14  generally conform to the shape of a knee bolster facia  36  and has a thickness between about 1.5 to about 2.5 mm, and preferably about 2.0 mm. With respect to the driver side  38  of the vehicle, a plate  40  is disposed between a pair of knee bolster brackets  10 . This plate  40  is preferably made of sheet steel which is welded using spot welding techniques or mechanically fastened to the impact plate  14 . Disposed between the brackets  10  on the driver&#39;s side is a steering column  42 . It is envisioned that the brackets  10  would be positioned adjacent the steering column  42  so as to reduce the likelihood an occupant&#39;s knee will interact with the steering column  42  member.  
         [0024]    Disposed between the tubular sections  26  and  28  is a transition portion  30  having generally concave and convex sections  32  and  34 . The forces needed to collapse the tubular member  12  are a function of the stiffness, thickness, and the geometry of the transition portion  30 . Specifically, they are a function of the diameter of the tubular members  26  and  28 .  
         [0025]    [0025]FIG. 2 additionally shows the coupling of the knee bolster brackets  10  to the vehicle cross-member  22  in the passenger side  44  of the vehicle. In this regard, the brackets  10  will be positioned so that the impact plates  14  are positioned adjacent to or will form a portion of the glove box door frame  46 . The forces from a passenger&#39;s knees into the glove box door is transferred through the frame  46  to the brackets  10 .  
         [0026]    As it is best seen in FIGS. 4 and 5, the impact plate  14  is welded generally perpendicular to the first end  18  of the tubular member  12 . The generally perpendicular placement of the impact plate  14  with respect to the first tubular member  26  allows for the proper axially linear transfer of energy from the impact plate  14  to the tubular member  12 .  
         [0027]    The coupling bracket  16  is welded to a medial portion  58  of the tube  12  and specifically to the second tube member  28  at a coupling member first end  48 . Additionally, the coupling bracket  16  is welded at its second end  50  to the impact plate  14 . The first end  48  of the coupling bracket  16  has a defined notch  52  which forms a pair of forked members  54 . These forked members  54  are bent to be generally parallel to an exterior surface  56  of the second tube portion  28  and are coupled to the tubular member  12  using general welding techniques.  
         [0028]    As best seen in FIGS. 4 and 5, the coupling brackets  16  define a generally concave shape with respect to the impact plate  14 . In this regard, the coupling bracket  16  regulates the off-axis collapsing of tubular member  12  to provide relatively steady-state reaction forces to the occupant&#39;s femurs. As best seen in FIGS. 6 and 7, when the impact plate  14  is loaded, the transition portion  30  plastically deforms. The first tubular member  26  of tubular member  12  telescopes into the second tubular member  28  of the tubular member  12 . In this regard, the outer diameter of the first tubular member  26  must be configured along with the transition portion  30  to allow the collapse of the first tubular member  26  into the second tubular member  28  when the tube is axially loaded. A coupling bracket  16  functions to regulate the collapse of the tubular member  12  and prevent the first tubular member  26  from folding at the transition portion  30 . In this way, the coupling bracket  16  allows for the telescopic collapse of the tubular member  12 .  
         [0029]    [0029]FIG. 8 represents an alternate embodiment of the present invention; specifically, a knee bolster bracket  60  having a tubular member  62 , an impact plate  64 , a first optional coupling bracket  67  and a second optional coupling bracket  68 . Tubular portion  62  is defined having first, second and third tubular portions  66 ,  69 , and  70 . Disposed between the tubular portions  66 ,  69 , and  70  are transition portions  72  and  74 . While the knee bolster bracket  60  is shown having two coupling brackets  67  and  68 , it is envisioned that only one coupling bracket  67  or  68  may be used. The knee bolster bracket  60 , according to the second embodiment, functions in a manner similar to the functioning of the first knee bolster bracket  10 . Specifically, the tube  62  is designed to collapse one or both the transition portions  74  and  72  while the coupling brackets  66  and  68  function to regulate the collapse of the tubular portion  62  so that it telescopically collapses under axial loading.  
         [0030]    The first tubular portion  66  will be allowed to telescope into the second tubular portion  69  and/or the second tubular portion  69  will be allowed to telescopically collapse into the third tubular portion  70 . In having knee bolster bracket structures that can collapse at two different locations, it is possible to tune the collapse so that the first tubular portion  66  collapses into the second tubular portion  69  at a first impact load while the second coupling mechanism collapses at a second impact load. This presents the option of designing the first impact region to collapse for a specific occupant type while the second collapsible region will collapse for a second occupant type. This allows the restraint engineer to design the displacement of the knee bolster for a given occupant.  
         [0031]    [0031]FIGS. 9 and 10 represent load versus displacement curves for brackets according to the teachings of the first embodiment of the invention. FIG. 9 depicts the axial loading of the collapsible tubular members  12  without having the associated coupling brackets. FIG. 10 depicts the collapsing of the bracket  10  according to the first embodiment of the invention. It should be noted that the first dip  76  within the load versus displacement curves  78  and  80  represent the initiation of plastic deformation of the transition portion  30  between the first and second tubular portions  26  and  28  of tubular member  12 . As can be seen, as the first member  26  of tubular member  12  telescopes into the second tubular member  28 , the load versus displacement curve represents a generally flat load without large spikes, which may indicate unacceptable loading on an occupant&#39;s femurs.  
         [0032]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.