Abstract:
An energy absorbing knee bolster for use in an interior of a vehicle is disclosed. An energy absorbing support structure is configured to support an instrument panel within a vehicle. The energy absorbing structure has a deployable tubular mechanism for absorbing occupant impact energy and an impact plate coupled to said tubular mechanism for absorbing occupant energy. An energy absorbing locking mechanism is disposed between the impact plate and the support structure. The locking mechanism is configured to encourage the collapse of the tubular means for absorbing energy in a telescopic fashion.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an instrument panel reinforcement structure for motor vehicles, and more particularly to a deployable support structure for a knee bolster.  
         BACKGROUND OF THE INVENTION  
         [0002]    The individual components of a restraint system are preferably 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 may 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.  
           [0003]    One integral component in some restraint systems is the lower portion of the instrument panel or knee bolster. In this regard, the knee bolster can function to provide various levels of occupant protection. The interaction of the knee bolster with an occupant as well as the displacement of the knee bolster with respect to the vehicle can help to determine the occupant kinematics.  
           [0004]    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 deployable knee bolster which provides a steady state loading of an occupant&#39;s femurs. It is an object to the present invention to provide an instrument panel a highly tunable deployable knee bolster which provides steady state loading of an occupant&#39;s lower extremities during a crash event.  
         SUMMARY OF THE INVENTION  
         [0005]    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 rapid vehicle deceleration. The knee bolster is formed of a deployable cylinder which is welded to an impact plate on its first end and is slidably positioned within a cylinder which is coupled to a vehicle&#39;s cross-car beam. A gas generator is fluidly coupled to the cylinder and functions to force the impact plate into the occupant compartment. The collapsible cylinder is configured to axially collapse at a predetermined force when impacted by a moving occupant.  
           [0006]    In one preferred embodiment, a knee bolster having a deployable cylinder with a gas generator fluidly coupled to the cylinder is disclosed. An impact plate and locking mechanism are coupled to the cylinder. The deployable cylinder is configured to axially collapse at a predetermined force when impacted by the moving occupant.  
           [0007]    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 deployable tubular member for absorbing occupant impact energy and an impact plate coupled to said tubular member for absorbing occupant energy. An energy absorbing locking mechanism is disposed between the impact plate and the support structure. The energy absorbing locking mechanism is configured to encourage the collapse of the tubular member for absorbing energy in a telescopic fashion.  
           [0008]    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 deployable piston having first and second ends formed within a cylinder. The second end of the deployable piston is coupled to an energy absorbing locking mechanism. An impact plate is coupled to the first end of the deployable piston. The energy absorbing locking mechanism has a plurality of bearing members configured to plastically deform a portion of the cylinder. A collapsible piston is configured to axially collapse at a predetermined force when impacted by a vehicle occupant.  
           [0009]    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  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 represents an interior view of the vehicle utilizing the deployable knee bolster according the present invention;  
         [0012]    [0012]FIG. 2 represents a perspective cross-sectional view of an instrument panel support structure utilizing the deployable knee bolster of the present invention;  
         [0013]    [0013]FIG. 3 represents a cross-sectional view of the deployable knee bolster in an undeployed condition;  
         [0014]    [0014]FIG. 4 represents a locking member according to one embodiment of the present invention;  
         [0015]    [0015]FIG. 5 represents a cross-sectional view of the deployable knee bolster in a deployed condition;  
         [0016]    [0016]FIG. 6 represents a cross-sectional view of the deployable knee bolster in a collapsed condition; and  
         [0017]    [0017]FIG. 7 represents a perspective cross-sectional view of a deployable cylinder according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    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.  
         [0019]    [0019]FIGS. 1-5 represent a deployable knee bolster according to the teachings of the present invention. The deployable knee bolster  10  is formed of four general components, a piston  12  within a fixed exterior tube  14 , an impact plate  16 , and a locking mechanism  18 . Generally, the impact plate  16  is welded to a first end  20  of a tubular member  22  coupled to the piston  12 .  
         [0020]    As best seen in FIGS. 1 and 2, the deployable knee bolster  10  is coupled to a cross-car beam  21  which supports an instrument panel  26  within a vehicle  28 . The instrument panel  26  has a driver and passenger knee bolster  30  and  32 , which are configured to absorb energy from a occupant&#39;s femurs during a vehicle deceleration. It is envisioned that the passenger&#39;s knee bolster  32  can encompass a portion of the vehicle&#39;s glovebox.  
         [0021]    [0021]FIG. 3 represents a cross-sectional view of the deployable knee bolster  10  in an undeployed condition. The fixed exterior tube  14  is formed of a generally cylindrical housing  34 , which is coupled to a outer cylindrical tube  36  to form a piston cavity  38 . The cylindrical housing  34  is coupled to the vehicle cross-car beam  21  using a bracket  24 , which functions to transfer occupant deceleration energy into the cross-car beam  21 .  
         [0022]    Slidably disposed within the cavity  38  is the piston  12 . The piston  12  has a circular surface  40  defined on its proximal end  42  and a cylindrical side surface  44 . Defined within the cylindrical side surface  44  is a locking mechanism  18 , the function of which will be detailed below. The locking mechanism  18  is formed of at least one wedged-shape ramp  48  defining a ramp-shaped cavity and at least one corresponding bearing element  50 . It is envisioned that the bearing element  50  can be spherical or be a wedge-shape. The wedge-shape ramp  48  has a proximal end  52  defined in a first cavity end  54  and a distal end  55  defining a second cavity end  56 . The first cavity end  54  has a depth greater than the diameter of the bearing element  50 , while the second cavity end  56  has a depth less than the diameter of the bearing element  50 , but greater than zero. The depth of the second cavity end  56  can be adjusted along with the thickness and material of the outer cylinder tube  36  to adjust the compression load.  
         [0023]    Disposed at the distal end  58  of the piston  12  is a threaded coupling  60 , which is used to couple the piston  12  to the proximal end  62  of a cylindrical inner tube  64 . The cylinder inner tube  64  is coupled at its distal end  66  via the impact plate  16 . The impact plate  16  is a polymer or metal support positioned beneath a knee bolster fascia  67 .  
         [0024]    Fluidly coupled to the cylindrical housing  34  is a gas generator  68 , which functions to produce gas in response to an electrical signal generated by a controller  70 . Upon a rapid deceleration of the vehicle, the controller  70  produces a signal which causes the release of gas from the gas generator  68 . As the gas travels down a passage  72 , gas pressure imparts against the cylindrical surface  40  of the piston  12 . It is envisioned that the gas generator  68  can be powered by a pyrotechnic propellant, liquid fuel, or a compressed gas.  
         [0025]    The operation of the knee bolster  10  is based on the signal from the controller  70 . Once the controller predicts that a deceleration event is in progress, electronic signals will be sent to the gas generator to extend the knee bolster  10  to a predetermined position. It is envisioned that approximately 0.07 kJ is necessary to deploy a 3 kg knee bolster about 100 mm in 30 msec.  
         [0026]    [0026]FIG. 5 represents the knee bolster  10  in its deployed condition. As can be seen, the piston  12  has been moved from its proximal end  74  of the cylindrical tube  36  to its distal end  76  of the cylindrical tube  36 . Movement of the piston  12  within the cylindrical tube  36  causes the movement of the impact plate  16  a predetermined distance to the vehicle compartment. As can be seen, the bearing elements  50  are positioned of the first cavity end  54  of the locking mechanism  18 .  
         [0027]    [0027]FIG. 6 represents the knee bolster  10  being impacted by an occupant&#39;s leg. As the impact plate  16  is moved toward the front of the vehicle, the bearing element  50  moves from the first cavity end  54  toward the second cavity end  56  along the wedge-shape ramp  48 . When loaded, such as the impact force exerted on the knee bolster surface, the level of the locking force can be designed by selecting a set of parameters, including the size and number of bearing elements  50 , thickness and strength of the outer tube material, slope and angle and gap of the wedge-shape surface  48  and the inner surface of the fixed exterior tube  14 , etc. Two different energy absorption modes can be achieved using the above locking mechanism. One mode will be to allow the inner tube  64  to buckle and be crushed to absorb energy. In this case, the mechanism must be designed to provide a locking force much higher than the tube crushing force. Another mode will allow the bearing elements  50  to plastically deform the inner wall of the outer tube to absorb energy. In this case, the mechanism must be designed to provide a locking force lower than the tube crushing force. It is envisioned that the collapse force would be engineered to help regulate the loads on an occupant&#39;s femurs while managing the occupant&#39;s kinematics during the deceleration events.  
         [0028]    [0028]FIG. 7 represents a knee bolster  10  according to an alternate embodiment of the present invention. Shown is the piston  12  disposed within the cylindrical housing  34 . Defined on the cylindrical side surface  44  of the piston  12  are a plurality of locking mechanisms  18 . As can be seen, the locking mechanisms  18  can have an outer sleeve  78  which define a plurality of bearing raceways  80  which guide the bearing elements  50  along the wedge shaped ramp  48 .  
         [0029]    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.