Abstract:
An airbag for protecting a vehicle occupant comprising a first and a second material layer each having edge regions, wherein the first and the second layers are sewn together along the edge regions. A fastening section adapted for attaching to a part of the vehicle and connecting to a gas generator configured to inflate the airbag with a gas in response to an accident. A first and a second chamber region disposed opposite a dividing seam, wherein each of the material layers includes a first and a second material section each matched to one of the first or second chamber regions.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The invention relates to an airbag to protect a vehicle occupant according to the preamble of claim  1 . 
         [0002]    Conventional airbags having several chambers are usually manufactured out of two cuttings which are sewn along their edge regions and which demonstrate in darts to separate the chambers. In some airbags, the respective chambers have the task of protecting individual body areas of an occupant. Because of the different masses of the individual body areas, forces of different strength act upon them during an accident. Moreover, the weaker body areas, such as the rib cage, may not be stressed too strongly. This makes it necessary to inflate the chambers at different rates to some extent using different gas pressures. 
       PRIOR ART 
       [0003]    U.S. Pat. No. 6,349,964 suggests a side airbag having an upper chamber assigned to projecting the thorax of the occupant and a lower chamber assigned to protect the pelvis of the occupant, the chambers being separated by a dividing seam. Because of the requirements imposed on the respective chambers in a side impact, it is provided that different gas pressures are used to fill the chambers. Thus in particular, the chamber assigned to the pelvic region is supposed to be filled with a higher pressure than that which fills the chamber assigned to the thoracic region of the occupant. 
         [0004]    One disadvantage of this conventional arrangement of the side airbag consists of the fact that the dividing seam is subjected to high stresses because of the different pressures in the chambers, so that there exists the danger of crack formation or other leakage formation. 
       SUBJECT MATTER OF THE INVENTION 
       [0005]    Proceeding from this prior art, it is the object of the invention to create an airbag in which no crack formation occurs in the region of the dividing seam between the two chamber regions during the inflation process and which is simple to manufacture. 
         [0006]    The object is achieved by an airbag having the features of claim  1 . 
         [0007]    The airbag comprises a first and a second material layer, which are sewn to one another along their edge regions. The airbag demonstrates an opening which can be connected to a gas generator so that the gas generator can inflate the airbag during an accident. The airbag furthermore demonstrates a first and a second chamber region, which are separated from one another by a dividing seam. Each of the two material layers of the airbag comprises at least two material sections, each of which is respectively assigned to the first or second chamber region. The material layers overlap in the region of the dividing seam, which fixes them. 
         [0008]    Because of the overlapping in the region of the dividing seam, the dividing seam extends through four layers of the material sections. In this way, this region of the airbag is reinforced in such a manner that it survives force applied during the inflation process without any leakage formation or crack formation occurring. 
         [0009]    The separate material sections provide the possibility of introducing different fabric layers for the different application regions. Thus, very tear-resistant fabrics can be used for particularly stressed regions whereas light, cost-effective fabrics can be introduced for the remaining regions. In addition, particular material sections can be coated to minimize permeability and to additionally strengthen the fabric. 
         [0010]    Pursuant to the embodiment according to claim  15 , the airbag demonstrates another material layer which is fixed by the dividing seam in the same way and which additionally protects the region around the dividing seam in the event of particularly high stresses from very different gas pressures in the two chamber regions. 
         [0011]    Pursuant to the embodiment according to claim  16 , the airbag is a side airbag to protect the vehicle occupants during a side impact. To this end, the chamber regions are assigned to the pelvic region and thoracic region of the occupant and can be filled with different gas pressures. In general, the chamber assigned to the pelvic region will be filled with a higher gas pressure than the chamber assigned to the thoracic region. To this end, the airbag in the pelvic region is supposed to position itself particularly quickly and fix the center of gravity located in the pelvic region of the occupant in order to prevent the occupant from moving toward the side of the vehicle. 
         [0012]    In order to maintain this high pressure in the airbag for the required time interval, the material sections assigned to the pelvic chamber region demonstrates a particularly heavy fabric and can additionally be coated with a silicone layer or a film, so that the material sections are characterized by high tear resistance in addition to low gas permeability. 
         [0013]    The material sections assigned to the thoracic region are manufactured out of a more permeable fabric. Such a fabric is less expensive and has a lower weight. 
         [0014]    Pursuant to another embodiment according to claim  18 , the airbag is a curtain airbag and demonstrates at least one additional chamber region and an additional dividing seam. In the curtain airbag, the central region below the opening, which can be connected to a gas generator, is particularly stressed by the inflowing high-energy gases. The central chamber region therefore demonstrates material sections made of a very heavy fabric, whereas the two external chamber regions are manufactured out of less-heavy fabric sections. 
         [0015]    Other preferred embodiments result from the further dependent claims and from the explanations to the following figures. The drawing shows: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0016]      FIG. 1  A top view of a side airbag, 
           [0017]      FIG. 1   a  that which is depicted in  FIG. 1  with a mounted gas generator, 
           [0018]      FIG. 2  a longitudinal section along line II-II of  FIG. 1 , 
           [0019]      FIG. 3  assembly of an airbag pursuant to a first embodiment. 
           [0020]      FIG. 4  assembly of an airbag pursuant to a second embodiment, 
           [0021]      FIG. 5  a top view of a curtain airbag. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    The construction of an airbag, which here is configured in the form of a side airbag, will be described in more detail on the basis of  FIGS. 1 and 2 . Side airbags are normally arranged in the backrest of a vehicle seat or in the region of the side door. 
         [0023]    The airbag  1  comprises of two material layers  2 ,  3 , which are manufactured out of fabric. These material layers  2 ,  3  are sewn to one another by a seam  16  along their external contour. The circumferential seam  16  leaves open the fastening region  4  of the side airbag, so that an opening  23  for connecting to a gas generator (not illustrated) is formed, Gas generators frequently demonstrate fastening bolts, which are guided through the fastening holes  21 ,  22  from inside when the gas generator is inserted into the airbag and thereby fasten the airbag to the housing components. 
         [0024]    A dividing seam  7 , which divides the inflatable region into two chamber regions  5 ,  6 , is configured in an approximately central region of the airbag. The dividing seam  7  is configured as a double seam, which extends from the edge region on the front side to the fastening region and is guided back to the front edge region in a curved course. As seen in  FIG. 1 , the end of the dividing seam facing the gas generator  25  (illustrated in  FIG. 1   a ) is disposed approximately at the height of the center of the opening  23  for the gas generator. 
         [0025]    The dividing seam  7  is arranged in such a manner that the gas flowing from the gas generator is guided directly into the two chamber regions  5 ,  6 . To this end, it is possible to introduce a deflector or a gas guide housing, for example, to selectively guide the gas jet. This is illustrated in  FIG. 1   a , from which it is evident that a deflector  27 , which prevents the gases coming from the gas generator from striking directly on the dividing seam, is disposed between the gas generator  25  and dividing seam  7 . The gas generator  25 , deflector  27  and dividing seam  7  are arranged so as to result in a wide separation of the two chamber regions  5 ,  6 . This facilitates the attainment of different pressures in the two chamber regions. 
         [0026]    Following the sewing of the surrounding seam, side airbags are usually turned inside out so that the seam is disposed inside the airbag. The side airbag can thus be tucked through the opening  23  in the fastening region  4  so that the dividing seam  7  can then be added. 
         [0027]    As illustrated particularly clearly in  FIG. 2 , the side airbag comprises four material sections  8 ,  9 ,  10  and  11 , the sections  8  and  10  being assigned to the upper chamber region  5  and sections  9  and  11  being assigned to the lower chamber region  6 . The pairs of material sections  8 ,  10 ;  9 ,  11  respectively assigned to one another 
         [0000]    overlap in the central region and are fixed by the dividing seam  7 . The material sections  8  and  9  of the first material layer  2  are held together by the seam  19  whereas the material sections  10  and  11  of the second material layer  3  are held together by the seam  18 . 
         [0028]    Within the overlapping region of the four material sections  8 ,  9 ,  10 ,  11 , the upper material sections  8  and  10  are disposed inside the lower material sections  9  and  11 . Pursuant to another embodiment (not illustrated), the lower sections  9  and  11  are disposed inside the upper sections  8  and  10 . 
         [0029]    The chamber  6  assigned to the pelvic region of a vehicle occupant comprises a relatively heavy fabric, which is preferably coated. Fabrics in the range of 580 to 700 dtex can be used, for example. 
         [0030]    The chamber  5  assigned to the thoracic region of the occupant comprises a relatively permeable fabric and must not be coated. Fabrics in the range of 235 to 580 dtex can be used here. 
         [0031]      FIG. 3  is a schematic illustration of the individual material sections  8 ,  9 ,  10 ,  11 , The course of the dividing seam  7  is drawn dashed for the sake of clarity, although the dividing seam is added only after the individual material sections have been joined and sewn. 
         [0032]    The two material sections  8  and  10  are formed from a single material layer, which Hi has a butterfly-like shape. The fold axis, around which the material layer is folded, extends along axis of symmetry S. The two remaining material sections  9  and  11  are configured as separate pieces and are sewn onto the associated material sections in each material layer by means of the seams  18 ,  19 . 
         [0033]    Pursuant to the exemplary embodiment according to  FIG. 4 , both the upper material sections  8  and  10  and the lower material sections  9  and  11  are configured as butterfly-like material layers, each of which is folded around its axis of symmetry after the two parts have been joined. In addition, another material layer  12 , which ensures additional reinforcement in the region of overlap of the material sections, is added in this region. 
         [0034]    The invention also includes other embodiments that are not illustrated in the figures. Thus all material sections  8 ,  9 ,  10 ,  11  can consist of separate parts and be fastened to one another. 
         [0035]    To this end, the term “axis of symmetry” should not be understood in a very narrow sense. Slight deviations, caused by manufacture, in the shaping of an airbag and the individual material sections may exist so that the material sections assigned to one another are generally symmetric but can deviate from one another. 
         [0036]      FIG. 5  illustrates a curtain airbag  1 , the upper edge of which are usually fastened to fastening points  4  in the roof frame of the vehicle, where it can be accommodated. 
         [0037]    The curtain airbag demonstrates a first material layer  2  and a second material layer, which are sewn along their external contour. To this end, the seam leaves open the region of the opening  23  so that a gas generator and/or a gas guide element can be inserted into the opening. 
         [0038]    The chamber regions  5 ,  6  and  15  are delimited by dividing seams  7  and  17  so that two external and one central chamber are formed. In accordance with the preceding exemplary embodiment, the material sections  8 ,  10  and  9 ,  11  and  13 ,  14  assigned to one another are connected by seams, of which the seams  18  and  20  are visible here. 
         [0039]    Because of the relatively high stresses when the gas enters, the centrally arranged chamber  6  is provided with a relatively heavy and therefore stable fabric, which can still be coated for extra reinforcement, whereas the external chambers  5  and  15  are manufactured out of plainer fabric to reduce weight and cost. Pursuant to one embodiment, a coated fabric having 700 dtex is chosen for the centrally arranged chamber, whereas an uncoated fabric in the range of 235 to 580 dtex suffices for the external chamber regions. 
         [0040]    The invention described above is can of course also be applied to other types of airbags and should not be restricted to side airbags and curtain airbags. 
       LIST OF REFERENCE CHARACTERS 
       [0000]    
       
           1  airbag 
           2  first material layer 
           3  second material layer 
           4  fastening section 
           5  first chamber region 
           6  second chamber region 
           7  dividing seam 
           8  first material section 
           9  second material section 
           10  third material section 
           11  fourth material section 
           12  reinforcing layer 
           13  fifth material section 
           14  sixth material section 
           15  third chamber region 
           16  circumferential seam 
           17  dividing seam 
           18  fastening seam 
           19  fastening seam 
           20  fastening seam 
           21  fastening opening 
           22  fastening opening 
           23  opening for gas generator 
           25  gas generator 
           27  deflector