Abstract:
An occupant restraint mechanism is disposed between a rigid member and an instrument panel of an automotive vehicle is provided. The occupant restraint mechanism includes first and second brackets each extending between proximal ends fixedly secured to the rigid member and distal ends coupled to the instrument panel. One of the first and second brackets has at least one notch formed therein. The notch has a predetermined size to allow a predetermined amount of deformation of the first and second brackets during contact of an occupant with the instrument panel during a sudden deceleration of the vehicle.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to an occupant restraint mechanism in an automotive vehicle. More particularly, the invention relates to a pair of brackets that minimizes loading upon and intrusion by an occupant&#39;s legs through an instrument panel during a sudden deceleration of the vehicle.  
         [0003]     2. Description of the Related Art  
         [0004]     It is known to provide a single bracket behind an instrument panel in an automotive vehicle to minimize intrusion of an occupant&#39;s knees through the instrument panel during a sudden deceleration of the vehicle. The same bracket is, however, also expected to minimize loads experienced at the femurs of the occupant. Typically, the bracket deforms to cushion the contact between the occupant&#39;s legs and the instrument panel, thereby minimizing the peak load felt at the femurs. It remains desirable to minimize the peak femur loads when the occupant&#39;s legs contact the instrument panel during a sudden deceleration of the vehicle and, at the same time, minimize intrusion of the occupant&#39;s knees through the instrument panel.  
       SUMMARY OF THE INVENTION  
       [0005]     According to one aspect of the invention, an occupant restraint mechanism disposed between a rigid member and an instrument panel of an automotive vehicle is provided. The occupant restraint mechanism includes first and second brackets each extending between proximal ends fixedly secured to the rigid member and distal ends coupled to the instrument panel. One of the first and second brackets has at least one notch formed therein. The notch has a predetermined size to allow a predetermined amount of deformation of the first and second brackets during contact of an occupant with the instrument panel during a sudden deceleration of the vehicle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0007]      FIG. 1  is a perspective view of an occupant restraint mechanism according to the invention;  
         [0008]      FIG. 2  is a cross sectional view of the occupant restraint mechanism; and  
         [0009]      FIG. 3  is a graph of femur loads versus time elapsed during a deceleration event. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     Referring to  FIGS. 1 and 2 , an occupant restraint mechanism for an automotive vehicle according to the invention is generally indicated at  10 . The occupant restraint mechanism  10  includes a pair of brackets  12 ,  14 , which are preferably formed from stamped steel having a thickness ranging typically between 1.0 mm and 1.2 mm. Each of the pair of brackets  12 ,  14  extends between a proximal end  16 ,  18  and a distal end  20 ,  22 . Preferably, the pair of brackets  12 ,  14  extends longitudinally between the proximal  16 ,  18  and distal  20 ,  22  ends along arcuate paths. Each of the pair of brackets  12 ,  14  includes spaced apart outer  24 ,  26  and inner  28 ,  30  walls. A web  32 ,  34  extends between the outer  24 ,  26  and inner  28 ,  30  walls defining an open, generally U-shaped cross section. Alternatively, a second web spaced apart and generally parallel to the web  32 ,  34  can extend between the outer  24 ,  26  and inner  28 ,  30  walls to define a closed, generally rectangular cross section.  
         [0011]     Each proximal end  16 ,  18  is fixedly secured to a rigid member  36 , which is fixedly supported behind an instrument panel or knee bolster  38  in the vehicle. More specifically, a flange  40 ,  42  is formed at each proximal end  16 ,  18  that allows the pair of brackets  12 ,  14  to be secured to the rigid member  36  by any conventional methods, such as welding, bolting, adhesives or the like. The pair of brackets  12 ,  14  extends generally radially outwardly in a V-shaped manner from the rigid member  36  toward the knee bolster  38 . Each distal end  20 ,  22  is fixedly secured to the knee bolster  38 . More specifically, an end wall  46 ,  48  defines each distal end  20 ,  22  and extends between the outer walls  24 ,  26 , inner walls  28 ,  30  and the web  32 ,  34 . An aperture  49 ,  50  is formed in each end wall  46 ,  48  to receive a bolt or other similar fastener. Preferably, the distal ends  20 ,  22  of the pair of brackets  12 ,  14  are fixedly secured to a common plate  51 . The plate  51 , in turn, is fixedly secured to the knee bolster  38  by any suitable methods, such as by adhesives or molded in-place during formation of the knee bolster  38 .  
         [0012]     A notch  53 ,  54  is formed along an open edge of each of the outer  24  and inner  28  walls of one of the pair of brackets, now referred to as a lower bracket  12 . Each notch  53 ,  54  is generally V-shaped defining a opening length l. The opening length l is the width of each notch  53 ,  54  at its widest point. Additionally, each notch  53 ,  54  extends in a concave manner toward the web  32  defining wall depths d 1  and d 2 . The wall depth d 1  is the distance between the low point of each notch  53 ,  54  and the web  32 . The wall depth d 2  is the distance between the open edge of each of the outer  24  and inner walls  28  and the bottom of the respective notch  53 ,  54 .  
         [0013]     Similarly, a cutout  55 ,  56  is formed along an opend edge of each of the outer  26  and inner  30  walls of the other of the pair of brackets, now referred to as an upper bracket  14 . Each cutout  55 ,  56  is generally U-shaped defining a length L. The length L is the length of the bottom of each cutout  55 ,  56 . Each cutout  55 ,  56  extends in a concave manner toward the web  34  defining wall depths D 1  and D 2 . The wall depth D 1  is the distance between the bottom of the cutout  55 ,  56  and the web  34 . The wall depth D 2  is the distatnce between the open edges of the outer  26  and inner walls  30  and the bottom of the respective cutouts  55 ,  56 .  
         [0014]     In use, each of the pair of brackets  12 ,  14  are oriented longitudinally fore and aft between the rigid member  36  and the knee bolster  38 . The upper bracket  14  is positioned in the vicinity of the knees of the occupant. The lower bracket  12  is positioned below the upper bracket  14 . Both the upper  14  and lower  12  brackets minimize intrusion of the knees through the knee bolster  38  during a sudden deceleration of the vehicle. In general, the chosen size, shape and position of the notches  53 ,  54  and cutouts  55 ,  56  depend on such factors as the particular type of vehicle into which the brackets  12 ,  14  are installed, the specified peak femur load requirements, and type and thickness of material used for the brackets  12 ,  14 . The size and position of the notches  53 ,  54  and cutouts  55 ,  56  along the brackets  12 ,  14  can be modified to affect the amount and direction of deformation of the brackets  12 ,  14  and, thereby, control the amount of femur loading and when the peak loading occurs with respect to the deceleration event.  
         [0015]     In  FIG. 3 , a graph is shown of femur loads versus time elapsed during the deceleration event. Both the lower  12  and upper  14  brackets immediately begin absorbing energy during the deceleration event to minimize intrusion of the knees through the knee bolster  38 . Preferably, the lower  12  and upper  14  brackets yield in a generally successive manner during the deceleration event, in order to reduce the peak femur loading. The solid line in the graph illustrates one such mode. Initially, the femur loads increase as both the lower  12  and upper  14  brackets resist displacement of the instrument panel. Eventually, the lower bracket  12  yields before the upper bracket  14 , resulting in a first peak femur load indicated as P 1 . After the first peak P 1 , the femur loads dip as the lower bracket  12  and the knee bolster  38  are displaced under loading. The upper bracket  14  then begins to resist further displacement, which results in a second increase in femur loads. As the femur loads approach the levels of the first peak P 1 , the upper bracket  14  yields resulting in a second peak femur load P 2 .  
         [0016]     In general, the dimensions of the lower  12  and upper brackets  14  are tuned to maximize energy absorption, while at the same time avoiding excess femur loading. More specifically, the dimensions of the notches  53 ,  54  and cutouts  55 ,  56  are predetermined to control the first P 1  and second P 2  peak levels and when they occur with respect to each other. Increasing or decreasing the length L of the cutouts  55 ,  56 , for example, increases or decreases the time when the second peak P 2  occurs after the first peak P 1 . Further, the first P 1  and second P 2  peak levels can be controlled by making corresponding changes to the wall depths d 2 , D 2  of the lower  12  and upper  14  brackets, respectively.  
         [0017]     A specific example of a lower and upper brackets is now described, wherein the lower and upper brackets are formed from stamped steel having a thickness of 1.2 mm. The dimensions of the notches and the cutouts are summarized in a table below and are based on results from a generic unbelted 25 mph crash test conducted with a 5th percentile female anthropomorphic test specimen.  
                                                                             Reference   Dimension               Numeral   (mm)                                        Notches   1   18.6               d 1     3               d 2     7           Cutouts   L   25.5               D 1     5               D 2     5                      
 
 Lower and upper brackets having notches and cutouts with these dimensions having been shown to achieve the goal of maximizing energy absorption, while at the same time avoiding excess femur loading by allowing the lower and upper brackets to yield sequentially. In this example, the upper bracket yielded 20 ms after the lower bracket, resulting in peak femur loads of 3.5 kN for P 1  and 3.0 kN for P 2 . 
 
         [0018]     The invention has been described in an illustrative manner. It is, therefore, to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Thus, within the scope of the appended claims, the invention may be practiced other than as specifically described.