Abstract:
An airbag having an airbag fabric skin ( 10 ) enclosing an interior gas space with a first edge ( 11 ) extending from a first end ( 11   a ) to a second end ( 11   b ), whereby an accommodation area (A) for a gas generator ( 20 ) is located at the first edge outside the gas spaced extending parallel the first edge ( 11 ), which exhibits an area ( 32 ) of a deflector element  930 ) which accommodates the gas generator. In order to ensure that the airbag unit consisting of gas generator and airbag halves in a thrust-neutral manner in case of a fire, deflector element ( 30 ) consists of a tubular, flexible element, whereby the deflector element ( 30 ) exhibits an upper and lower area ( 32, 36 ) whose lower area ( 36 ) is located inside the gas space (G). The deflector element is connected with the airbag skin in an intermediate area ( 34 ) which is located between upper and lower areas.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to DE 10 2005 021 371.5, filed May 4, 2005 and PCT/EP2006/003892, filed Apr. 27, 2006. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an airbag for a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     A side curtain airbag unit has fabric layers forming an inflatable interior with a large surface and a gas generator for filing of the airbag interior. The airbag fabric 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. The airbag must be filled with inflation gas from the gas generator from the upper edge. Two concepts are often used in this connection. 
     In the first concept, the gas generator is located at one of the two ends of the upper edge of the airbag (in most cases at the rear end) and a long, thin metal lance which forms several exit holes extends from the gas generator into the airbag interior and distributes the gas over the length of the airbag. 
     In a second concept, the airbag exhibits an accommodation area for the gas generator in the area of the upper edge between the front and the rear end. The gas generator extends into the airbag interior or is at least connected with the interior. For this purpose, the accommodation area can be L-shaped, for example. 
     Generally, cylindrical gas generators are used which are formed so as to be thrust-neutral for reasons of safety. This means that the gas exit openings are arranged rotation symmetrically on an area of the jacket surface of the gas generator. Thus, if an inflator is activated before it is assembled into an airbag system, the inflator will not behave like a rocket which could cause injury and damage. Without additional measures when the inflator is installed in the airbag, this would lead to the problem that the hot gases would stream directly against the airbag fabric and the airbag fabric would possible be damaged during inflation. Therefore deflectors are use, which protect the airbag fabric against the gas when it streams out. 
     Such a deflector is known from generic patent WO 02/079008 A1, and is in the form of a U-shaped metal sheet. Furthermore, this publication describes a gas guide element of fabric which is sewn into the airbag. 
     A disadvantage of such a deflector element is that when finally assembled, the airbag unit does not behave in a way which is thrust neutral in the case of a fire. If there should be a fire while the airbag assembly is in storage, the airbag skin consisting of plastic fabric burns, while the gas generator and the deflector element connected with the gas generator remain. In order to fulfill its purpose, namely the purpose of protecting the airbag fabric when the gas is streaming out, however, the deflector element must be construed asymmetrically. From this follows, however, that the subassembly consisting of gas generator and deflector does not behave in a thrust neutral manner. If a fire occurs while the airbag is stored, therefore, an additional hazard is presented by gas generator-deflector subassemblies flying around freely. 
     SUMMARY OF THE INVENTION 
     Starting from this it is the task of the invention to improve an airbag of the type generally described above in such a way that the thrust neutrality is also given in the complete airbag unit consisting of airbag and gas generator in case of fire. 
     The deflector element of the airbag unit according to this invention consists of a flexible, tube-shaped element. The thrust neutrality in case of a fire is often already ensured due to the resulting geometry. The flexible, tube-shaped element preferably consists of a material which in the case of relatively long exposure to heat, here relatively long is meant a period of time which is longer than the time it takes for the airbag to expand during a deployment through activating the inflator, and begins to burn or loses its strength. In other words, the deflector element preferably consists of a material which is not highly resistant to heat. This means that in case of fire, the deflector element burns away together with the airbag skin, or loses its strength, so that the gas from the generator which is itself thrust neutral can escape directly to the outside. The deflector element can be formed of a fabric material. 
     The tube-shaped deflector element can be folded from a one-piece or multipiece cutting of fabric, or it can be manufactured without seams, for example it can knitted in a tubular form. For the purposes of this application, fabric is taken to be any flexible basically two-dimensional material which can be cut and which does not consist of metal. The deflector element is arranged in relation to the airbag fabric is such a way that an upper area which is located outside the airbag interior and a lower area, which is located inside the airbag interior. The link with the airbag fabric results via an intermediate area between the upper and lower area. This means that the gas coming from the gas generator only comes into contact with the fabric of airbag skin at a late point, so that damage to the airbag skin is excluded. 
     Preferred forms of the invention can be derived from the subclaims as well as from the embodiments described below in more detail in connection with the drawings. 
    
    
     
       DETAILED DESCRIPTION OF THE INVENTION 
       The drawings are as follows: 
         FIG. 1  is a side view of a curtain airbag according to this invention; 
         FIG. 2  is a section along plane A-A from  FIG. 1 ; 
         FIG. 2   a  is an alternative to that which is shown in  FIG. 2 ; 
         FIG. 3  shows the deflector element from  FIG. 1  with a side view; 
         FIG. 4  shows the curtain airbag from  FIG. 1  with the gas generator inserted; and 
         FIG. 5  is an alternative embodiment of a curtain airbag with inserted base generator in a view corresponding to  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a side view of a curtain airbag. The curtain airbag, referred to in the following text as airbag, exhibits airbag fabric skin  10 , which is closed along circumferential seam  15  and folded edge  16  and thus surrounds the airbag interior gas space G. The first edge  11  extends from the first end  11   a  to the second end  11   b  and forms several fixing tabs  14 . In the case of a curtain airbag, the first edge forms the upper edge  11 . There are several non-inflatable areas  17  formed by seams, which serve for contouring of the airbag when deployed. 
     Above the first edge  11  is located accommodation area A, which serves for the accommodation of a gas generator, which is located outside the gas space G.  FIG. 4  shows the airbag with the gas generator  20 . As accommodation area A is located outside gas space G, the gas streaming radially out of the jacket area of generator  20  must be guided into gas space G. Although accommodation area A communicates for gas flow with the airbag interior gas space G, it is characterized as outside gas space G, since it is separated from the main volume of gas space G, and is outside the perimeter outline of airbag fabric  10 , with a narrow passageway connects accommodation area A with gas space G. Accommodation area A may also be described as separated from the gas space G. The deflector element  30  serves for the purpose of directing gas streaming from gas generator  20  and also for protection of the fabric of the airbag skin. 
     The structure of the deflector element  30  and its fixing to the airbag skin  10  is now described in more detail with reference to  FIGS. 1 ,  2 , and  3 . The deflector element  30  consists of a piece of fabric and is folded to form a tube, whose longitudinal axis is generally parallel to the first edge  11 . The piece of fabric overlaps itself in the upper area  32  of the deflector element  30 , so that in this area of inner section  30   a  and outer section  30   b  are present, as can be seen from  FIG. 2 . Inner section  30   a  and outer section  30   b  are connected with each other by means of an adhesive layer  40 . An increase in the resistance capability in this area is achieved by means of this adhesive layer  40 . An increase in the resistance becomes useful here, as this area is placed under the greatest loading by the gases which stream out when gas generator  20  emits gas. 
     As can be seen in  FIG. 1 , deflector element  30  exhibits three areas, namely the upper area  32 , the intermediate area  34  and the lower area  36 . The upper area  32  is located outside (or separated from) the gas space G and above the upper edge  11 . This upper area  32  accommodates the gas generator  20  directly. The upper area  32  is also surrounded by a further fabric area  50 . Upper area  32  and further fabric area  50  therefore together form the accommodation area A. The further fabric area  50  in this embodiment is formed as a separate fabric element, but can also be made in one piece with the airbag skin. The further fabric area  50  has fixing openings  18 , through which fixing clips  55  are guided, which clamp the further fabric area  50  onto the gas generator  20  (see  FIG. 4 ). Alternatively, the fixing clips  55  can additionally be guided through fixing openings in the deflector element  30 , preferably in the intermediate area  34 . 
     The deflector element  30  extends from the upper area  32  into the gas space G of the airbag. In the lower area  36  gas coming from above is deflected to the left and right and leaves the lower area at the front sides  36   a  and  36   b  ( FIG. 4 ). In the intermediate section  34 , which is located between upper area  32  and lower area  36 , deflector element  30  is connected to the airbag fabric skin  10 . The two drop-shaped seams  62  which extend through all fabric layers serve for this purpose. 
     Furthermore, intermediate area  34  forms semicircular seams  60 , which connect the right and left sides  31   a ,  31   b of  deflector element  30  with one another. By means of this, a narrowed overflow opening  34   a  is formed between upper area  32  and lower area  36 . By means of this arrangement of the several semicircular seams  60 , which only affect deflector element  30  and possibly a reinforcing layer, and which each surround the heads of the drop-shaped seams  62  in a semicircular manner, a very good sealing can be achieved. Furthermore, the all-through drop-shaped seams  62  are protected against the hot gases by the semicircular seams  60 , which do not penetrate the airbag skin. Furthermore, in this embodiment, reinforcing layers  31  are arranged in the area of the semicircular seams (only visible in  FIG. 2 ). Here it is particularly advantageous that when further fabric element  50 , deflector element  30  and airbag skin  10  are sewn together, it is only necessary to apply the two drop-shaped seams  62 . 
     The embodiment of the airbag described here does not exhibit any seams penetrating the airbag skin and which are directly blasted by gas from the gas generator  20 , or which are hit by gases which hare still very hot. This considerably increases the sealing and reliability of the arrangement. 
     Embodiments are also possible which can do without a seam between the deflector element and the airbag skin. In this case it is particularly possible that the deflector element and airbag skin are only held together by the fixing clips already mounted. 
     Deflector element  30  in this embodiment is formed in one piece of cut fabric, however it can be joined together from several cuttings of fabric which can consist of different materials. For example, a more resistant type of material can be selected for inner section  30   a , while outer section  30   b  can consist of a lighter and less costly type of fabric. These two sections can be sewn together at a first edge by means of a connecting seam, while a further connection is carried out by means of the adhesive method already mentioned. The connecting seam is preferably located in the lower area  36  of the deflector element  30 , where the gas has already lost energy when it hits the walls. 
       FIG. 2   a  shows an alternative structure of the deflector element  30 . Here, the deflector element is manufactured of a flexible material in the form of a seamless tube. In particular, it is possible to weave, knit or plait such a tube in a one-piece seamless form. One-piece manufacture of fabric tube is known, for example, from production of fire hoses. If the deflector element exhibits a seamless fabric tube, it can be useful to provide an internal tube made of an elastomer, or a coating in the inside of this fabric tube. It is also possible to extrude the deflector element in a one piece and seamlessly from an elastomer. The embodiment shown in  FIG. 2   a  does not exhibit a reinforcing layer, however it is naturally possible to provide one in an embodiment with a seamless deflector element  30 . The seams are not shown in  FIG. 2   a.    
       FIG. 5  shows an alternative embodiment to the curtain airbag unit shown in  FIG. 4 . Here, gas generator  20  does not extend through accommodation area A, but only into it. A front-facing seam  64  is provided for sealing of the accommodation area A to the outside, which extends through further fabric area  50  and deflector element  30 . 
     The invention was described here in connection of a side curtain airbag, but it can also be used in other airbags, for example side airbags. Depending on the mounting location of such a side airbag, it may be the area of the deflection element described here as “upper area” is not located above the gas space when mounted. Naturally this does not change the construction and mode of functioning of the airbag. 
     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.