Abstract:
A tubular gas guide element for a side curtain airbag for guiding gas coming from a gas generator comprising at least two layers of fabric. With the use of such a gas guide, thrust of the gas inflowing into an airbag can be balanced.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Patent Application PCT/EP2006/001584 filed Feb. 22, 2006 and DE Patent Applications 10 2005 009 433.3 and 10 2005 009 432.5 which were both filed on Mar. 2, 2005. 
     
    
     FIELD OF THE INVENTION   
       [0002]    The invention relates generally to an airbag system for a motor vehicle and more specifically to a curtain airbag system including several of its elements. 
       BACKGROUND OF THE INVENTION  
       [0003]    So-called side curtain airbags are known in vehicle technology. These airbags are located in the area of the side roof rail of a motor vehicle and expand in front of the side windows and possibly the B-pillar of a motor vehicle in case of need. Such a curtain airbag by its nature exhibits a relatively large basic area. This large area results in the problem of evenly discharging the gas emerging form a single gas generator into the airbag. 
         [0004]    A curtain airbag unit exhibits a large-surface airbag skin and a gas generator for filling of the airbag skin. The airbag skin typically has an upper edge, which is fixed in the area of the roof rail of the motor vehicle, so that the longitudinal direction of the airbag extends along the longitudinal axis of the vehicle. Filing preferably occurs from the upper edge. Two concepts are currently used for this result. 
         [0005]    In the first concept, the gas generator is located on one of the two ends of the upper edge (generally the rear end), and a long, thin metal lance forming several outlet openings extends from the gas generator into the inside of the airbag skin, said metal lance distributes the gas over the length of the airbag skin. 
         [0006]    In a second concept, the airbag skin exhibits an accommodation area for the gas generator in the area of the upper edge between the front and the rear end, which extends into the inside of the airbag skin or which is at least connected with the inside. For this purpose the accommodation area can be L-shaped, for example. 
         [0007]    If, according to the first concept, gas guide elements in the form of metal tubes are used, at least two disadvantages result: on the one hand such tubes are relatively thin in relation to their length, which makes them very susceptible to damage and therefore there are considerable transport costs involved during transport from the manufacturer to the site of final assembly. Furthermore, the assembly unit of gas generator and gas guide element is not thrust neutral and therefore constitutes a risk. 
         [0008]    Therefore, the suggestion has already been made to manufacture gas guide elements of fabric. A gas guide element made of fabric is described, for example in JP 2002-187519 A. 
         [0009]    One problem in the use of tubular gas guide elements made of fabric is that if cylindrical gas generators which are thrust neutral are used, the hot gas first strikes directly against the inner walls of the fabric tube. This can lead to failure of the material and therefore to faulty function of the airbag. 
         [0010]    In the second concept, the following problem occurs: generally, cylindrical gas generators are used which are formed so as to be thrust neutral for reasons of safety. This means that the gas outlet openings are arranged so as to be rotationally symmetrical on a part of the jacket surface of the gas generator. Without additional measures there would be the problem that airbag fabric would be directly subjected to the stream of the hot gases and would possibly be damaged. Therefore deflectors are used which protect the airbag fabric against the outflowing gas. 
         [0011]    Such a deflector, implemented in the form of a U-shaped metal sheet, is known from patent WO 02/079008 A1. Furthermore, a gas guide element made of fabric which is sewn into the airbag skin is known from this publication. 
         [0012]    A disadvantage of such a deflector element is that the airbag unit, when finally assembled and complete, does not behave in a manner which is thrust neutral. Namely, if the airbag becomes overheated due to a thrust imbalance, the airbag skin consisting of plastic fabric material may become burned. 
       SUMMARY OF THE INVENTION  
       [0013]    The present invention seeks improving a tubular gas guide element, a gas generation and feed unit consisting of such a tubular gas guide element and a gas generator, and a side curtain airbag unit in such a way that both a high degree of functional safety and also thrust neutrality are ensured. 
         [0014]    In at least one embodiment of the present invention, a gas first streams from a gas generator into a gas guide element or deflector element completely consisting of fabric. This is formed of at least two layers, whereby the inner layer protects the outer layer and in particular covers joining lines such as seams, bonding or welding lines which reach into the surroundings outside the gas chamber of the airbag. 
         [0015]    In one aspect of the invention, the tubular gas guide element comprises at least two fabric cuttings where a first fabric cutting forms a tubular outer skin. Inside the tube formed of the first fabric cutting, a second fabric cutting is located, which at least covers the area in which the two longitudinal edges of the first fabric cutting are connected with each other. Namely, it has been discovered that the critical area of a gas element made of fabric is the area in which gas strikes radially against a seam. 
         [0016]    Advantageously, the two fabric cuttings are rectangles, which are first joined to form an “L”. Then the gas generator is wound into the second cutting which lies uppermost; finally the two longitudinal edges of the first fabric cutting are joined together, preferably sewn. This means that the second cutting which preferably completely surrounds the gas generator, does not exhibit a seam at least in the area of the outflow opening of the gas generator, so that direct flow of gas onto a seam in the area of the outflow openings is avoided. 
         [0017]    In at least one other embodiment of the present invention, the deflector element of an airbag element also is made, preferably completely, of fabric and therefore burns up together with the airbag skin in case of fire, or deterioration of strength, so that the gas can escape from the thrust-neutral gas generator directly into the environment. Like the gas generator, the deflector element is formed as a cylinder, such as for example, by being folded to a cylinder from a flat fabric cutting and held together by a first connecting line, which is mostly in the form of a connecting seam. The deflector element is connected with the airbag skin by means of a fixing seam. In order to guarantee sufficient resistance capacity over the period when the gas is flowing out, the deflector element is formed in two layers, with an inner and outer layer. Here, the inner layer covers the first connecting line. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]    Advantageous embodiments result from the subclaims and from the embodiments explained below in relation to the drawings. The drawings are as follows: 
           [0019]      FIG. 1  is a first and a second fabric cutting, which are connected together to form an L; 
           [0020]      FIG. 2  is a gas guide element with a gas generator accommodated in it; 
           [0021]      FIG. 3  is a section along Line A-A from  FIG. 2 ; 
           [0022]      FIG. 4  is a schematic representation of a gas generator; 
           [0023]      FIG. 5  is a schematic representation of a curtain airbag unit; 
           [0024]      FIG. 6  is a longitudinal section through a curtain airbag unit according to a first example; 
           [0025]      FIG. 7  is fabric cuttings for an inner layer and an outer layer of the deflector element used in the first example; 
           [0026]      FIG. 8  is two layers of the deflector element connected by means of a second connection seam; 
           [0027]      FIG. 9  is a section through the finished sewn deflector element including its first connecting seam; 
           [0028]      FIG. 10  is the deflector element from  FIG. 4  in a perspective view; 
           [0029]      FIG. 11  is fabric cuttings for an inner and an outer layer of a deflector element according to a second example; 
           [0030]      FIG. 12  is the two fabric cutting from  FIG. 6 , which are connected with one another by means of a connecting seam; 
           [0031]      FIG. 13  is a section through the deflector element according to a second embodiment; and 
           [0032]      FIG. 14  is a deflector element and an airbag skin according to a second embodiment in a perspective view. 
       
    
    
     DETAILED DESCRIPTION  
       [0033]    In at least one embodiment of the present invention, a tubular gas guide element basically extends over the entire length of the curtain airbag and the gas generator is located proximate one end of the curtain airbag and preferably outside of the airbag. 
         [0034]      FIG. 5  illustrates a side curtain airbag unit. This consists of a curtain airbag  50 , the gas generator  40  and the tubular guide element  5 , in whose first end  5   a  gas generator  40  is accommodated. If gas generator  40  is actuated, gas streams into tubular gas guide element  5  and streams out of its second end  5   b  and through holes  14  out of tubular gas guide element  5  and into the inside of curtain airbag  50 . 
         [0035]    Tubular gas guide element  5  may be made of fabric. In one aspect, it may be manufactured of two fabric cuttings  10 , 20 , as illustrated in  FIGS. 1 ,  2  and  3 . Both fabric cuttings  10 , 20  are rectangles with first edges  11   a,b,  second edges  12   a,b,  third edges  21   a,b,  and fourth edges  22   a,b.  First edges  11   a,b  of first fabric cuttings  10  are the longitudinal edges of this fabric cutting. They are generally considerably longer than second edges  12   a,b.  In addition, through holes  14  are inside the first fabric cutting  10 . 
         [0036]    In a first assembly step, the second fabric cutting  20  is fastened to the first cutting  10 . This can be done, for example, by means of the assembly seam  30 . As can be seen, the first third edge  21   a  of the second fabric cutting  20  is co-linear in relation to first first edge  11   a  of the first fabric cutting  10 . In the same way, first fourth edge  22   a  is in some sections co-linear to first second edge  12   a  of the first fabric cutting  10 . The two fabric cuttings connected together therefore form an “L”. 
         [0037]    In the second assembly step, a gas generator  40 , as shown in schematic form in  FIG. 4 , is wound into the second fabric cutting  20 . As third edges  21   a,b  of second fabric cutting  20  are longer than second edges  12   a,b  of first fabric cutting  10 , the jacket surface of the section of gas generator  40  which projects into guide element  5  is completely surrounded by second fabric cutting  20 , so that there is no contact between gas generator  40  and first fabric cutting  10 . 
         [0038]    Finally, first fabric cutting  10  is laid together so as to form a tube and first edges  11   a,b  are connected to each other by means of connecting seam  32 . This is done in a way that first fabric cutting  10  is turned over or folded such that through sewing by means of connecting seam  32 , the first surface  15  of first fabric cutting  10  in some sections comes into contact with itself. In the area of the first end  5   a  of tubular gas guide element  5 , first third edge  21   a  of second fabric cutting  20  is accommodated between the two first edges  11   a,b  of the first fabric cutting  10 . Alternatively, the second fabric cutting can be fixed to the first fabric cutting by means of the assembly seam. 
         [0039]    The items illustrated in  FIGS. 2 and 3  result from this assembly process where  FIG. 3  is a section along plane A-A from  FIG. 2 . As can be seen from  FIG. 3 , the connecting area between first edges  111   a  formed by connecting seam  32  is, in the area of the gas generator, completely covered by the second fabric cutting  20 . The second third edge  21   b  of second fabric cutting  20  may be located without a seam inside the tubular gas guide element  5 , so that the gas coming radially from the outflow openings  44  of gas generator  40  does not strike a seam. 
         [0040]    As an alternative to the assembly process described above, it can be advantageous first to connect the first and second fabric parts  10 , 20  with one another in the manner described, and then to connect gas generator  40  with first end  5   a  of the gas guide element. This makes it possible to avoid a sewing process with the gas generator inserted. 
         [0041]    The invention was described here in relation to a curtain airbag; however it is clear that a tubular gas guide element according to the invention can also be used with another type of airbag, for example a side airbag. 
         [0042]    In at least one other embodiment of the present invention, a gas generator is basically located proximate the middle of the upper edge of a curtain airbag. With this arrangement, at least the outflow area of the gas generator is surrounded by a deflector element which consists of at least two layers made of fabric. 
         [0043]      FIG. 6  illustrates in a longitudinal section, a first embodiment of the gas generator located proximate the middle of the upper edge of the curtain airbag. The curtain airbag unit exhibits an airbag skin  110  with an upper edge  111 , on which are located fixing tabs  114  for fixing of the airbag skin in a vehicle structure. The airbag skin  110  may be manufactured of a one-piece fabric cutting, which is folded at lower edge  116  and which is stitched to itself by means of circumferential seam  115 . Airbag skin  110  provides non-inflatable areas  117 , which are separated from the gas chamber by means of separating seams. 
         [0044]    Upper edge  111  extends from rear end  111   a  to front end  111   b.  In the area of the upper edge  111  between rear end  111   a  and front end  111   b,  proximate the middle, the accommodation area A for gas generator  120  (shown here in non-assembled state) is provided. In accommodation area A there is: also the fixing opening  118 , through which a hose clamp can be guided, by means of which gas generator  120  is clamped to airbag skin  110 . 
         [0045]    Deflector element  130 , preferably made of fabric, is located in the accommodation area and is sewn to the airbag skin by means of fixing seam  136 . In this area, fixing seam  136  may be congruent with circumferential seam  115 . Deflector element  130  is of tubular form with two open end sides and, at least when the cylindrical gas generator is mounted, forms a cylindrical body. The gas streams in an axial gas stream and a radial gas stream into the gas chamber of the airbag skin through front end side  131  and radial through holes  135 . The deflector element  130  therefore also fulfils the further task of a gas guide element. 
         [0046]    In the sewn state, but not yet mounted in the vehicle, the positioning axis of the cylindrical deflector element, which in this embodiment extends inside airbag skin  110  and underneath upper edge  111 , is inclined in relation to upper edge  11  of airbag skin  110 . On the one hand, this has the advantage that the fabric cutting for the airbag skin can exhibit a simple geometry. In addition, advantages can accrue from this with regard to force transmission when the gas generator is activated. 
         [0047]    The structure of deflector element  130  is now explained in more detail in relation to  FIGS. 7 to 10 : 
         [0048]      FIG. 7  shows the two cuttings Z 1  and Z 2 . The inner layer of deflector element  130  hereby results from first cutting Z 1 , and outer layer  134  results from second cutting Z 2 . As can be seen, first cutting Z 1  defines side recesses  133   a , which in finally a mounted position are part of the radial opening  133 . Cutting Z 2  defines holes  135   a , which in a sewn condition form radial through-holes  135 . 
         [0049]    In a first work step shown in  FIG. 8 , the two cuttings Z 1  and Z 2  are sewn together by means of second connecting seam  138 . Within this process, first cutting Z 1  is sewn onto second cutting Z 2  in such a way that the recesses  133   a  of the one longitudinal edge  32   a  are congruent with holes  135   a . Following this, first s cutting Z 1  is rolled in and both longitudinal edges  134   a  of the outer layer are laid on one another and secured with the first connecting seam  137 . Deflector element  130  is then sewn together with airbag skin  110  with fixing seam  136 , which in this area can also be the circumferential seam  115 . In order to be able to achieve this, second edge  134   b  of second cutting Z 2  has to be longer than second edge  132   b  of first cutting Z 1 . Instead of forming first connecting seam  137  and fixing seam  136  separately, these can also be in the form of one single seam. 
         [0050]    Referring to  FIGS. 9 and 10 ,  FIG. 9  depicts a birds-eye view of  FIG. 10  from Direction R. The longitudinal edges  132   a  of inner layer  132  (illustrated in  FIG. 7 ) are not sewn together with one another, so that a continuous radial slit S results, which forms the radial opening together with recesses  133   a  (illustrated in  FIG. 7 ). 
         [0051]    The second connecting seam  138  may be directly affected by the gas stream in some places, but separation of this seam in some places is not harmful, as even in this case, since substantially no gas is lost. The inner and outer layers remain connected to one another and first connecting seam  137  remains covered by inner layer  132 . 
         [0052]      FIGS. 11 to 14  illustrate a second embodiment proximate the middle of the upper edge of the curtain airbag. 
         [0053]    As in the first embodiment, inner layer  132  and outer layer  134  of deflector element  130  are each manufactured of a cutting Z 1 ,Z 2 . The second cutting Z 2 , however, does not exhibit a through hole, whereas an oval hole L is located in first cutting Z 1  (see  FIG. 11 ). 
         [0054]    As can be seen from  FIG. 12 , first cutting Z 1  and second cutting Z 2  are sewn together by means of a second connecting seam  138  as in the first embodiment. First cutting Z 1  is rolled in and second cutting Z 2  is sewn to itself at outer sections AA of its longitudinal edges  134   a  by means of first connecting seam  137 . In the area of upper edge  111  of airbag skin  110 , deflector element  130  is sewn to the airbag skin. Fixing seams  136  serve for this purpose. This is shown in  FIGS. 13 and 14 , whereby  FIG. 13  is a section through  FIG. 14  along Line IV-IV. 
         [0055]    In the areas of outer sections AA, a fixing opening  118  is also provided for a hose clamp. The gas generator is held by means of hose clamps and by pressing the two fabric layers  132 ,  134  onto the jacket surface of the gas generator. Gas is sealed off in axial direction. 
         [0056]    In contrast to the first embodiment, deflector element  130  formed of inner layer Is  132  and outer layer  134 , is located above upper edge  111 , in other words completely outside airbag skin  110 . Gas generator  120 , not shown, extends completely through deflector element  130 . When the gas generator is activated, gas streams through oval hole L, which forms the radial opening  133  of inner layer  132 , through the opening area between outer layer  134  and airbag skin  110  into the gas chamber of the airbag skin. Alternatively, an additional fabric pocket can be connected with upper edge  111  of airbag skin  110 , which encloses the deflector element at least in part in order to avoid any leakage losses into the surrounding environment. 
         [0057]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.