Abstract:
A front airbag comprises a front wall ( 20 ) facing an associated occupant in the inflated state which front wall serves for cushioning the vehicle occupant and is secured to a peripheral wall of the front airbag ( 12 ). The front wall ( 20 ) is composed of at least two cut parts ( 28   a,    28   b ) so that it is curved toward the vehicle occupant and is not adapted to be flatly spread.

Description:
RELATED APPLICATIONS 
       [0001]    This application corresponds to PCT/EP2015/002147, filed Oct. 29, 2015, which claims the benefit of German Application No. 10 2014 016 163.3, filed Nov. 4, 2014, the subject matter of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a front airbag for a vehicle occupant protection system. 
         [0003]    Front airbags are primarily mounted in the instrument panel in the area of the front passenger seat. In a known design the airbag includes a front wall facing the associated occupant in the inflated state which forms a baffle for cushioning the vehicle occupant. Said front wall extends obliquely with respect to the vertical direction so that the vehicle occupant can immerse into the airbag with the upper body part and the head in a relatively optimum manner. 
         [0004]    In the case of a conventional airbag the front wall is connected along its peripheral edge to a bag-shaped peripheral wall which on a backside faced away from the front wall includes an inflation mouth through which the airbag is filled and which also facilitates securing to the instrument panel. Such airbags take a three-dimensional shape already in the non-inflated state, i.e. the non-inflated but completely joined airbag cannot be laid two-dimensionally so that all cut parts of the airbag are at the same time spread flatly, i.e. free from creases. The advantage of said designs resides in the fact that m this way a large filling volume and thus proper cushioning quality for the vehicle occupant can be achieved. 
       SUMMARY OF THE INVENTION 
       [0005]    It is the object of the invention to optimize cushioning of the vehicle occupants by an airbag. 
         [0006]    This is achieved in a front airbag comprising a front wall facing an associated occupant in the inflated state, which front wall serves for cushioning the vehicle occupant and is secured to a peripheral wall of the airbag, wherein the front wall is composed of at least two cut parts so that it is curved toward the vehicle occupant and cannot be spread flatly and thus free from creases. In this way, the shape of the front wall and the volume of the airbag can be specifically influenced in the area of the front wall in a simple manner. According to the invention, the volume of the airbag is increased in the area of the front wall, which permits the vehicle occupant to immerse more softly. In contrast to the conventional airbag shape, the front wall is not designed as an area two-dimensional in the non-inflated state, but already by the connection of the cut parts a three-dimensional shape is imparted to the front wall. 
         [0007]    In a possible embodiment, the front wall is composed of exactly two cut parts, which enables variable adaptation of the shape of the front wall without excessively increasing the manufacturing effort. The composed front wall substantially takes the shape of a lens. 
         [0008]    In another possible embodiment, the front wall is composed of exactly three out parts. Of course, it is also possible to make use of an even larger number of cut parts, which also renders manufacture more complicated, however. 
         [0009]    Each of the individual cut parts consists of one single piece of a suited airbag material, for example a coated fabric. The individual cut parts can be selected as to their shape so that the surface area thereof is not subdivided by notches. Preferably, they do not include any darts, either. 
         [0010]    In order to obtain the increase in volume in a simple manner preferably at least at one cut part an inner edge by which the cut part is attached to an adjacent cut part of the front wall is formed at least in portions so that in the spread not sewn-up state it does not extend in a straight line. 
         [0011]    The inner edge may define, especially in the area of its central portion, a bulge of the associated cut part by which the volume increase of the airbag is achieved in the area of the front wall. The bulge can have, measured in the inflated state, for example a height of approx. 30 to 70 mm, preferably at least 50 mm, so as to create a sufficient additional volume. 
         [0012]    The bulge extends, for example, perpendicularly to a straight line across the intersections of the inner edge of the out part with the peripheral edge of the cut part (which is also part of the peripheral edge of the entire front wall), wherein the maximum distance of the inner edge from the straight line preferably amounts to at least 50 mm. 
         [0013]    The cut parts forming the front wall can be interconnected, according to a variant, when being flatly spread, when the inner edge of two adjacent cut parts extends inversely so that the inner edges of the two cut parts can be flatly superimposed for sewing. 
         [0014]    It is also possible to design the inner edge of two cut parts inversely and to secure each of said two out parts to one or more interposed cut parts the inner edges of which may also have a different contour. 
         [0015]    A central out part of the front wall can have inner edges extending in a straight and especially parallel manner, for example, at which it is connected to other out parts of the front wall in this way, the curvature of the front wall can be easily adjusted to a desired measure. The central cut part e.g. takes the shape of a tape. 
         [0016]    Preferably, the front wall is designed to be mirror-inverted with respect to an imaginary center line which extends from a highest point of the front wall in the mounted and inflated state of the front airbag to a deepest point of the front wall. 
         [0017]    In a possible embodiment, the front wall is subdivided transversely to said imaginary canter line into the individual cut parts, wherein especially each straight line extends across the intersections of the inner edge of the cut part with the peripheral edge of the cut part perpendicularly to the center line (in view of the front wall in the inflated state). The individual cut parts are adjacent to each other along the center line. 
         [0018]    In a different embodiment, the front wall is subdivided along the center line into the individual cut parts, wherein especially a straight line extends across the intersections of the inner edge of the respective cut part with the peripheral edge of the out part in parallel to the center line (equally in view of the front wall in the inflated state). In this case, the individual cut parts are adjacent to each other transversely to the center line. 
         [0019]    Of course, the front wall may also be designed to be not mirror-inverted. Especially, in this case in the individual cut parts the straight lines across the intersections of the inner edge with the peripheral edge can also extend obliquely with respect to the center line. A division which is non-parallel and, resp., perpendicular to the center line may also be favorable to produce specific shapes of the front face. 
         [0020]    The peripheral wall of the airbag connected to the front wall may consist of one or more cut parts. The cut parts of the peripheral wall form no cushioning surface and, where possible, do not get into contact with the vehicle occupant. 
         [0021]    For reducing the waste and for facilitating the connection of the cut parts the peripheral wall may consist of two cut parts which in total connect the front wall to an inflation mouth of the airbag. The entire front airbag may be substantially composed, except for reinforcing layers and the like, of two cut parts forming the peripheral wall as well as of two or three cut parts forming the front wall. 
         [0022]    The peripheral wall may have a bag-shaped geometry when the airbag is inflated. 
         [0023]    The front wall in total has a contour outwardly curved toward the occupant which has no drawing-ins or inward constrictions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention will be described hereinafter in detail by way of several embodiments with reference to the enclosed drawings, wherein: 
           [0025]      FIG. 1  shows a schematic representation of a vehicle occupant protection system comprising a front airbag according to the invention; 
           [0026]      FIG. 2  shows a schematic perspective representation of a front airbag according to the invention; 
           [0027]      FIG. 3  shows a schematic representation of the cut parts of the front wall of a front airbag according to the invention in accordance with a first embodiment; 
           [0028]      FIG. 4  shows a schematic representation of the cut parts of the front wall of a front airbag according to the invention in accordance with a second embodiment; 
           [0029]      FIG. 5  shows a schematic representation of the cut pads of the front wall of a front airbag according to the invention in accordance with a third embodiment; and 
           [0030]      FIG. 6  shows a schematic representation of the cut parts of a front wall of a front airbag according to the invention in accordance with a fourth embodiment. 
       
    
    
     DESCRIPTION 
       [0031]      FIG. 1  illustrates a vehicle occupant protection system  10  in a passenger car not shown in detail. 
         [0032]    A front airbag  12  is arranged on an instrument panel  14  so that it deploys between a windscreen  16  and a vehicle seat  18  so as to offer protection for a passenger. In the schematically shown inflated state a front wall  20  serving as a baffle faces the vehicle occupant. 
         [0033]    The front wall  20  is connected to a peripheral wall  24  of the front airbag  12  along its peripheral edge  22 . The peripheral edge  24  is designed to be approximately bag-shaped and has a rear inflation mouth  26  through which the filling gas can flow into the front airbag  12 . In the area of the inflation mouth  26  the front airbag  12  is fixed to the instrument panel  14 . Prior to its deployment, the front airbag  12  is accommodated in a folded state in a suited space in the instrument panel  14 . 
         [0034]    The front wall  20  of the front airbag  12  is composed in a first embodiment shown in  FIG. 3  of exactly two out parts  28   a,    28   b.  The edge of each of the cut parts  28   a,    28   b  is composed of a segment of the peripheral edge  22  of the later front wall  20  as well as an inner edge  30  by which it is connected to an adjacent cut part of the front wall  20 . 
         [0035]    The connection of the cut parts  28 ,  28   b  of the front airbag  12  to each other may be performed by sewing, gluing, welding or in any other suited way. 
         [0036]    In the embodiment shown in  FIG. 3 , the entire front wall  20  is designed inversely with respect to a center line M. Moreover, each individual one of the cut parts  28   a,    28   b  is designed to be mirror-inverted with respect to the center line M. The center line M extends from a highest point  29  in the mounted and deployed state of the front airbag  12  to a deepest point  31  of the front wall  20 , as indicated in  FIG. 2 . 
         [0037]    Both inner edges  30  of the cut parts  28   a,    28   b  in this case do not extend along a straight line. The inner edge  30  is designed in each case so that it defines a bulge  32  around which a central portion  34  of the inner edge  30  projects vis-à-vis an imaginary straight line G across the intersections  36  of the inner edge  30  with the peripheral edge  22  of the cut part  28   a,    28   b.  In this case, the distance d and thus the height of the bulge between the central portion  34  of the inner edge  30  and the straight line G amounts to about 30 to 70 mm, especially more than 50 mm, however. 
         [0038]    The course of the inner edge  30  is selected so that the latter is composed of three substantially straight portions, wherein the outer portions  37  extend obliquely with respect to the center line M and the central portion  34  extends perpendicularly to the center line M. 
         [0039]    The bulges  32  are designed inversely in both cut parts  28   a,    28   b.  This allows to superimpose the cut parts  28   a,    23   b,  when connecting them, along the bulges  32  up to the intersections  36  and to connect them at the edge, when the cut parts are flatly spread. 
         [0040]    In this way, a front wall  20  is formed having a closed peripheral edge  22  which cannot be flatly spread as the bulges  32  of the two cut parts  28   a,    28   b  result in an outwardly directed curvature which enlarges the volume in the area of the front wall  12 . This is indicated in  FIG. 2 . 
         [0041]    The two cut parts  23   a,    23   b  otherwise are not symmetrically designed. Here the cut part  28   a  forming the upper portion of the front wall is smaller than the cut part  28   b  forming the lower portion of the front wall  20 . In total, the front wall  20  is approximately egg-shaped in a top view, wherein the upper cut part  28   a  in the area of the highest point  29  has a curvature larger than that of the lower cut part  28   b  in the lowest point  31 . Due to the geometry of the cut parts  28   a,    28   b,  the bulge  32  in the finished front wall  20  is closer to the highest point  29  of the front wall  20  than to the lowest point  31 . The highest and lowest points  29 ,  31  relate to the mounted inflated airbag. 
         [0042]    By the shape of the individual cut parts  23   a,    28   b  and the course of the inner edges  30  thereof those skilled in the art can specifically predetermine the shape of the front airbag  12  and the areas having an enlarged volume along the front wall  20  depending on the circumstances. 
         [0043]    The peripheral wall  24  of the front airbag  12  in this case is composed of two cut parts each of which is mirror-inverted with respect to the center line M (not shown in detail). 
         [0044]    For fabricating the front airbag  12 , at first all cut parts are cut out of a suited fabric, for example. The cut parts  28   a,    28   b  of the front wall  20  are interconnected along the inner edges  30 . Subsequently, the front wall  20  is connected to the peripheral wall  24  along the peripheral edge  22 . 
         [0045]      FIG. 4  illustrates a second embodiment in which the front wall  120  of the front airbag  12  is composed of three individual cut parts  128   a,    128   b  and  128   c.    
         [0046]    As to its shape and size, the cut part  128   a  corresponds to the cut part  28   a  and the cut part  128   b  corresponds to the cut part  28   b  of the first embodiment. 
         [0047]    The tape-shaped cut part  123   c  is inserted between the cut parts  128   a  and  128   b,  wherein an inner edge  30  of the central cut part  128   c  is connected to the inner edge  30  of the cut part  28   a  and the other inner edge  30  is connected to the inner edge  30  of the cut part  128   b.  The central cut part  128   c  in this case has straight inner edges  30  extending in parallel to each other. At the central cut part  128   c  no bulge is provided in this case, but each of the inner edges  30  substantially extends along the straight line G between the intersections  36  of the inner edges  30  and the peripheral edge  22  of the cut part  128   c.    
         [0048]    Each of the two peripheral edge portions  22  of the central cut part  128   c  extends in a curve and is composed of three straight portions adjacent to each other in an angular shape, wherein here the central one of the portions extends in parallel to the center line M. The cut part  128   c,  too, is mirror-inverted relative to the center line M. 
         [0049]    The use of a central out part having straight inner edges  30  provides for a flattening of the curvature of the front wall  120  in the area of the central cut part  128   c.    
         [0050]    As already in the first embodiment all peripheral edges  22  of the individual cut parts  128   a,    128   b,    128   c  complement each other to form the complete peripheral edge  22  of the front wall  20 . 
         [0051]    The maximum extension d of the bulge  32  may be equal to the just described embodiment of  FIG. 3 . 
         [0052]      FIG. 5  illustrates a third embodiment of a front wall  220  for the front airbag  12 . In this case, the front wall  220  is composed, as in the just described embodiment, of three separate cut parts  228   a,    228   b  and  228   c,    
         [0053]    The front wall  220  in this case is subdivided along the center line M, however, and not transversely thereto, as in the previous embodiments. The straight lines G across the intersections  36  between the respective inner edge  30  and the peripheral edge or edges  22  of a cut part  228   a,    228   b,    228   c  extend in parallel to the center line M and not, as just described, perpendicularly thereto. Of course, also designs would be imaginable in which the straight lines G are aligned at an angle other than 0 or 90° with respect to the center line M. 
         [0054]    Otherwise, the structure of the front wall  220  is similar to the just described front wall  120 . Each of the two outer cut parts  228   a,    228   b  has an inner edge  30  not extending in a straight line and is inversely shaped. The inner edge  30  forms a bulge  32  vis-à-vis the straight line G of the respective cut part, wherein the maximum extension d of the bulge  32  in its central portion  34  contributes, as in the other embodiments, to e.g. about 30 to 70, especially more than 50 mm, however. 
         [0055]    The inner edges of the central cut parts  228   c  extend straightly and extend in parallel to the center line M in this case. 
         [0056]    Therefore, in the finished front wall  220  the central cut part  228   c  is located along the center of the inflated front airbag  12  as a seamless strip. 
         [0057]    In this embodiment, the bulge  32  along the center line M is placed approximately at half the height of the front airbag  12  between the highest point  29  and the deepest point  31  of the front wall  220 . 
         [0058]    The fourth embodiment shown in  FIG. 6  of a front wall  320  for a front airbag  12  equally includes three separate cut parts  328   a,    328   b,    328   c,  wherein the central cut part  328   c  is located between the two outer cut parts  128   a,    128   b.    
         [0059]    As in the just described embodiment the cut parts  328   a,    328   b,    328   c  are adjacent to each other transversely to the center line M. 
         [0060]    In this example, however, the inner edges  30  of the central cut part  328   c  are not designed to be straight but each has a mirror-image course with respect to the inner edge  30  of the respective adjacent cut part  328   a,    328   b.    
         [0061]    In the variant shown here, the front wall  20  therefore has a continuous seamless and evenly curved central area, while nevertheless comfortable two-dimensional connection of the cut parts  328   a,    323   c  and  328   b,    328   c  of the front wall  320  is given. For this purpose, each of the inner edges  30  of neighboring cut parts  328   a,    328   c  and  328   b,    328   c  are flatly superimposed and are interconnected, which is possible due to the mirror-inverted shape of the cut parts  328   a,    328   b,    328   c  in the area of their inner edges  30 . 
         [0062]    The bulges  32  of the inner edges  30  are offset in the direction of the highest point  29  of the front face  320 . This provides for an increased volume of the front wall  320  in the upper area. 
         [0063]    The peripheral edges  22  of all three cut parts  328   a,    328   b,    328   c  complement each other, as in the other embodiments, to form the entire peripheral edge  22  of the front wall  320 . 
         [0064]    All features of the described embodiments can also be individually realized, can be exchanged for each other or can be freely combined with each other at the discretion of those skilled in the art. 
         [0065]    It is also possible, of course, to arrange three cut parts along the center line M next to each other, as for example in the embodiment shown in  FIG. 4 , and to provide the central cut part  128   c  there equally with inner edges  30  which do not straightly extend and which extend inversely to the inner edges  30  of the respective adjacent cut parte  123   a,    128   b.  It is equally imaginable to compose the front wall of two cut parts which are adjacent to each other transversely to the center line M.