Abstract:
A gas distribution pipe for balanced inflation and deployment of a side curtain airbag. The pipe has an end gas discharge opening and side gas discharge openings. The side discharge openings are configured to deflect the exiting gas so that at least a portion of the gas flows backwards along the outside of the pipe before entering the adjacent chamber of the airbag. An end cap for the pipe may contain both the end discharge opening and gas diverting and deflecting elements that direct gas to and through the side discharge openings.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of and priority to the following U.S. Provisional Patent Applications: 
        Ser. No. 60/639,324, filed Dec. 28, 2004; and     Ser. No. 60/643,600, filed Jan. 14, 2005.       
 
     
    
     BACKGROUND  
       [0004]     The application relates to a side curtain airbag apparatus for a motor vehicle and, in particular, to an airbag including a gas distribution pipe or tube for delivering inflation gas to the airbag.  
         [0005]     Side curtain airbags typically are housed along the vehicle roof rails and deploy extremely rapidly in an emergency situation to provide side cushioning for the outboard vehicle occupants.  FIG. 1  illustrates a typical known side curtain airbag arrangement. In the example shown, the airbag  1  is divided into a first chamber  3  and a last chamber  4 , which are designed to inflate adjacent the occupant seating positions. Other examples may include intermediate chambers, such as for vehicles having three rows of seats. These chambers have been formed by stitching along sewing lines  2 , which can individually form circular sewing lines  50  at respective inlets of the chambers. The circular sewing lines  50  serve to avoid the concentration of stress when the airbag  1  is inflated.  
         [0006]     Pressurized inflation gas is provided by an inflator mounted in the vehicle A-pillar, in the vehicle C-pillar, in the D-pillar, if so equipped, or in the roof rail between pillars. The inflator is connected to one end of a metallic gas distribution pipe or tube that extends into the airbag. Upon activation, the gas from the inflator flows through the distribution pipe  5 , which is schematically illustrated in dashed lines in  FIG. 1 , into first chamber  3  through gap  54  and into last chamber  4  through channel  52 .  
         [0007]     An exemplary gas distribution pipe is disclosed in U.S. Pat. No. 6,164,688, which is incorporated herein by reference. This type of gas distribution pipe has spaced gas discharge openings along its long body, which are formed by inwardly deformed portions of the tube where incisions have been made, creating indentations that guide gas out of the pipe and into the adjacent airbag chambers. The angle of the indentations is such as to direct the gas obliquely out of the pipe, i.e., at a forward acute angle. Another example, U.S. Pat. No. 6,394,488, which also is incorporated herein by reference, discloses other forms of indentations at the gas discharge openings that direct gas in a similar manner.  
       SUMMARY  
       [0008]     According to an embodiment of the present invention, a safety system, device and/or airbag arrangement is provided so that airbag deployment may be balanced so that all of the airbag chambers fill with inflation gas in substantially the same amount of time. According to an embodiment, the balanced deployment is accomplished by deflecting the gas exiting the side discharge openings of the inflator such that at least a portion of the gas flows generally backwards along the outside of the pipe as it enters the adjacent chamber of the airbag. The deflecting arrangement may take many forms, and effectively creates a flow-directing nozzle that yields a backward gas velocity component.  
         [0009]     Preferably, a portion of the gas is physically divided from the main axial flow in the pipe and is diverted toward the side discharge openings. The flow dividing and diverting arrangement may take many forms, all of which increase the rate of flow through the side discharge openings. Further, instead of discharging gas only along one side of the pipe, gas optionally can be discharged in multiple directions through a plurality of circumferentially spaced side discharge openings located at a particular lengthwise position on the pipe.  
         [0010]     According to another embodiment, a side curtain airbag gas distribution pipe having an end discharge opening and at least one side discharge opening is provided. The side discharge opening may have associated therewith a deflector that directs at least a portion of the gas exiting the side discharge opening generally backwards along the outside of the pipe. The pipe, optionally, may have a plurality of circumferentially spaced side discharge openings at one lengthwise position on the pipe. For example, there may be two diametrically opposed side discharge openings.  
         [0011]     In addition to any of the above arrangements, the gas distribution pipe may also have an internal flow divider associated with the side discharge opening that divides a portion of the gas from the main axial flow and diverts it toward the side discharge opening. In the case of multiple circumferentially spaced side discharge openings at one lengthwise position, the flow divider diverts gas to all of the openings at that lengthwise position.  
         [0012]     The flow divider may be part of an end cap for the pipe. In that case, the end discharge opening is formed in the end cap and the flow divider extends into the pipe up to the lengthwise position of the side discharge opening(s).  
         [0013]     According to another aspect, the invention involves a method of deploying a side curtain airbag by introducing inflation gas into one airbag chamber through a discharge opening at the end of a gas distribution pipe, and introducing inflation gas to an upstream airbag chamber through at least one side discharge opening such that at least a portion of the gas that emerges from the side discharge opening flows generally backwards along the outside of the pipe as it enters the upstream airbag chamber. The gas flow into the upstream airbag chamber preferably occurs through two side discharge openings.  
         [0014]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The aspects, and advantages of the present invention will become apparent from the following detailed description of the exemplary embodiments shown in the drawings, which are not necessarily drawn to scale. The drawing figures are briefly described below.  
         [0016]      FIG. 1  is a side elevational view of a known side curtain airbag.  
         [0017]      FIG. 2  is a bottom plan view of a portion of a gas distribution pipe for a side curtain airbag.  
         [0018]      FIG. 3  is a longitudinal sectional view of the gas distribution pipe of  FIG. 2 , taken along line  3 - 3 .  
         [0019]      FIG. 4  is a plan view of a portion of a gas distribution pipe according to the invention.  
         [0020]      FIG. 5  is a longitudinal sectional view of the gas distribution pipe of  FIG. 4 , taken along line  5 - 5 , showing one embodiment of the invention.  
         [0021]      FIG. 6  is a longitudinal sectional view similar to  FIG. 5 , taken along line  6 - 6 , showing another embodiment of the invention.  
         [0022]      FIG. 6 ( a ) is a cross-sectional view of  FIG. 6 , taken along line  7 - 7 .  
         [0023]      FIG. 7  is a side elevational view of a side curtain airbag with a gas distribution pipe according to the invention that introduces inflation gas at a point intermediate the length of the airbag. 
     
    
     DESCRIPTION  
       [0024]     A gas distribution pipe for an airbag is shown in  FIGS. 2 and 3 , which depict a type of shorter and simpler gas distribution pipe  5 . The distal end of the pipe has an end discharge opening  6  through which gas exits axially (i.e., lengthwise of the pipe, as indicated by arrow  6   a ) toward and into the last chamber  4 . Closely spaced side discharge openings  7  discharge gas into the first chamber  3  in a radial, generally downward direction (as indicated by arrows  7   a ). All discharge openings are in the form of simple holes.  
         [0025]     Gas distribution pipes may be used in arrangements similar to those shown in  FIG. 1 . For example, an alternate arrangement in which a short gas discharge pipe enters a side curtain airbag downwardly at a point intermediate the length of the airbag may be employed. The distal end of the pipe is tapered and blind, with two diametrically opposed holes that discharge inflation gas generally fore and aft. U.S. Pat. No. 6,808,203 discloses a gas distribution pipe and is incorporated by reference herein.  
         [0026]     Preferably, the deployment of a side curtain airbag is balanced such that all protective portions (chambers) of the airbag fill with gas uniformly, i.e., in substantially the same amount of time, so as to afford maximum protection for all outboard vehicle occupants simultaneously. In the past, it has been observed that one chamber of the airbag usually deploys faster than the other chamber. A need therefore exists for a gas distribution pipe for a side curtain airbag that can be relied on to distribute inflation gas in such a way that airbag deployment is balanced.  
         [0027]      FIGS. 4 and 5  depict a gas distribution pipe  10  according to an embodiment of the invention. Pipe  10  has a metallic body  12 , and an end cap  14  at the distal end of the pipe, which is secured to the body by any suitable means that is substantially gas-tight and will withstand the gas pressure within the pipe, such as by welding, brazing, or adhesive. An inflator (not shown), when activated, delivers inflation gas to the pipe, which flows through the pipe towards its distal end in the direction of arrow F.  
         [0028]     The body  12  has two diametrically opposed side gas discharge openings  16 . Each of these openings is formed by a U-shaped cut in the pipe wall. The resulting tab  18  is deformed outwardly to create a generally backward-facing nozzle.  
         [0029]     The end cap  14  has a central bore  20 , which leads to end discharge opening  22 . A reduced-diameter plug portion  24  of the end cap  14  extends into the body  12  up to the position of the side discharge openings  16 . Along the majority of the length of the plug portion  24  there exists a snug fit within the body  12 , but the plug portion  24  tapers inwardly from the root region where tabs  18  are attached to the body  12 , up to the tip  26  of the plug portion  24 .  
         [0030]     With this arrangement, the tip  26  of the plug portion  24  divides the axial flow of gas into a central stream  28  that flows through a central bore  20  and emerges from an end discharge opening  22 , and two side streams  30  that emerge from the side discharge openings  16 . The tapered portion of plug portion  24 , combined with the tabs  18 , serve as flow diverters that redirect the flow of side streams  30  such that each stream has a backward velocity component as it emerges from the side discharge opening  16 . This arrangement causes a portion of each side gas discharge stream to flow backwards along the outside of the pipe as it enters the adjacent chamber of the airbag.  
         [0031]      FIGS. 4 and 6  depict a gas distribution pipe  10  according to another embodiment of the invention. Reference numbers used in connection with the aforementioned embodiment are also used herein, and in  FIG. 6 , to denote substantially identical structure. Thus, a pipe  10  has a body  12  with two side discharge openings  16  formed by tabs  18 , in the same manner as described above. The end cap  32  in this embodiment has a central bore  20 , which leads to an end discharge opening  22 .  FIG. 6  discloses a differently configured plug portion  34  of the end cap.  
         [0032]     The plug portion  34  is reduced substantially in diameter to create an annular space  35  between the plug portion  34  and the body  12 . The plug portion has a wider head portion  37  that lies close to, but does not contact, the root region of tabs  18  (where they are attached to body  12 ) and tapers inwardly up to the tip  36  of the plug portion  34 , where the plug portion  34  terminates in a blunt face  38 .  
         [0033]     The arrangement of  FIG. 6 , like that of  FIG. 5 , divides the axial flow of gas into a central stream  28  that flows through central bore  20  and emerges from the end discharge opening  22 , and side streams, having a backward velocity component, that emerge from side discharge openings  16 . Plug portion  34  actually divides the side flows into two components: streams  30  that emerge directly from side discharge openings  16  after passing head portion  37 ; and streams  40  that first detour through the annular space  35  that surrounds the plug portion  34 .  
         [0034]     Because the head portion  37  does not contact body  12 , gas can flow past the head portion and into the annular space  35 .  FIG. 6 ( a ) shows a cross-section view taken along line  7 - 7  in  FIG. 6 . Gas flow into the annular space  35  occurs in the two semi-annular regions  56  and  57  between the two side discharge openings  16 . This flow is encouraged by the pressure drop in the root regions of the tabs  18  as gas streams  30  emerge directly from the openings  16 , which tends to draw gas from the annular space  35  past the tab root regions (see arrows  40  in  FIG. 6 ). Thus, the detoured flow  40  through the annular space  35  augments the direct flow streams  30 .  
         [0035]     The flow through the annular space  35 , optionally, can be enhanced by enlarging the flow area in the semi-annular regions between the two side discharge openings  16 , such as by notching (not shown) the periphery  58  of the head portion  37 ; or by providing additional flow paths into the annular space  35 , such as by drilling (not shown) through the head portion  37 .  
         [0036]     The gas distribution pipe may be used in several different arrangements, such as the one depicted in  FIG. 1 . The gas distributed pipe of the invention can also be used to inflate a side curtain airbag from a point intermediate the length of the airbag.  FIG. 7  depicts an example of this type of arrangement. In this example the gas distribution pipe  10  (such as, for example, either of the embodiments shown in  FIGS. 5 and 6 ) enters airbag  41  in a downward direction. The arrows show the flow of inflation gas into the airbag chambers  43 ,  44 , which are formed by stitching along sewing lines  2 .  
         [0037]     Given the broad disclosure of the present invention, one versed in the art would appreciate that there are other embodiments and modifications within the scope of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure are to be considered as further embodiments of the present invention.