Abstract:
The invention relates to a gas bag module comprising a gas bag with a gas bag wall, the latter including a front wall which faces an occupant to be restrained and which has a center section, and including a rear wall with an inflation opening to connect up a gas generator. The gas bag module also comprises a fastening which holds the center section in a fully inflated state of the gas bag fastened to the module and, upon inflation of the gas bag, prevents the center section from a free movement towards outside the module, so that a depression is formed by the center section. The gas bag module further comprises a module covering which is opened in a case of restraint for an emergence of the gas bag, the module covering having an annular, predetermined outlet opening which surrounds the fastening. The module covering has a holding section encircled by the outlet opening, and an emblem being provided adjoining the holding section. This emblem is visible from outside, is configured as a separate part and is fastened to the module by an emblem fastening. The emblem fastening also serves for fastening of the center section.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to a gas bag module.  
           [0002]    The invention relates in particular to a driver&#39;s or passenger&#39;s gas bag module with a large-volume bag which protects the head and the upper body in a frontal impact.  
           [0003]    More particularly, the invention relates to gas bags having a depression and a ring section arranged so as to extend around this depression.  
         BACKGROUND OF THE INVENTION  
         [0004]    Gas bags having a depression and an annular chamber formed thereby are distinguished by a small stress on the occupant which occurs when the occupant and the gas bag meet. In particular with an occupant who is “out of position”, e.g. is sitting too close to the steering wheel, the unfolding gas bag can hit the occupant and exert stresses on him. In a conventional gas bag, the gas bag bulges out toward the occupant, so that the latter may undergo a reduced restraining effect by the gas bag when he is “out of position”. In addition, it can not be excluded theoretically that the occupant situated out-of-position slides off the gas bag.  
           [0005]    Among other things, the following disadvantage is intended to be avoided by the invention: the module has a gas bag covering on the outer side of which a heavy emblem of the vehicle manufacturer is fastened. In the case of the sudden swinging up of the module covering, it must be ensured that the emblem is held on the covering, which requires an increased expenditure.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    The invention faces the object of guaranteeing a simple manufacture of a gas bag module having an annular gas bag, in particular of providing for a reliable fastening of the center section.  
           [0007]    This is achieved by a gas bag module which comprises a gas bag with a gas bag wall, the latter including a front wall which faces an occupant to be restrained and which has a center section, and including a rear wall with an inflation opening to connect up a gas generator. The gas bag module also comprises a fastening which holds the center section in a fully inflated state of the gas bag fastened to the module and, upon inflation of the gas bag, prevents the center section from a free movement towards outside of said module, so that a depression is formed by the center section. The gas bag module further comprises a module covering which is opened in a case of restraint for an emergence of the gas bag, the module covering having an annular, predetermined outlet opening which surrounds the fastening. The module covering has a holding section encircled by the outlet opening, and an emblem being provided adjoining the holding section. This emblem is visible from outside, is configured as a separate part and is fastened to the module by an emblem fastening. The emblem fastening serves for fastening of the center section to said module. According to the invention, the fastening of the emblem is configured such that it prevents part of the center section from emerging from the gas bag module.  
           [0008]    In the gas bag module proposed, the additionally provided stable emblem, to be more precise its fastening, has a further function, in that it prevents the center section from an unimpeded movement out of the module, so that a separate fastening for the center section is no longer necessary. In addition, in the gas bag module proposed there is no need for the heavy emblem to fold outwards, so that no danger originates with the emblem, because it is in fact provided on the holding section of the module covering which does not swivel outwards. With this, the fastening of the swivelled open flaps on the rest of the module covering is not to be configured so stable any more, because the flaps have no heavy emblem and they have, as mentioned above, a smaller size than in the prior art.  
           [0009]    The region of the module covering, which lies inwards of the outlet opening, i.e. is surrounded by it, represents a holding section which forms the fastening of the center section. The holding section therefore has a dual function by on the one hand serving for the restraint of the center section and on the other hand for fastening the flaps to the module covering.  
           [0010]    The holding section is preferably fastened to a mounting in the gas bag module, e.g. a cage surrounding the gas generator, which in turn is fastened to the gas generator, to the module housing or for example to a gas generator holding plate, i.e. to a very stable part connected as directly as possible with the vehicle.  
           [0011]    The depression with the center section does not have to be a perfectly circular opening, as seen onto the front wall. An embodiment makes provision that in the fully inflated state, viewed onto the front wall, a slit-shaped opening is produced, i.e. a slit-shaped region is formed as transition from the ring section of the front wall to the depression. This means that the depression closes increasingly, starting from the fastening in the region of the covering toward the ring section. This geometry in the fully inflated state of the gas bag can be achieved by a corresponding shape of the gas bag wall in the region of the depression (also designated as the inner gas bag wall) and a corresponding blank of the adjoining, outer gas bag wall or front wall. Furthermore, it is also possible that the depression in the fully inflated state is closed towards the front wall, by the gas bag wall, which delimits the depression, extending radially inwards until opposite sections of the gas bag wall contact each other. In this case, the depression becomes increasingly narrow, starting from the fastening to the ring section, and is finally closed.  
           [0012]    The manufacture of the gas bag in the region of the deep depression may possibly be a problem. This depression could for example consist of a piece of fabric sewn to form a tube, the problem then consisting here, however, in fastening this piece of fabric to the remainder of the front wall (ring section). An embodiment of the invention provides for a simple manufacture of the gas bag provided in the gas bag module proposed by the depression being delimited by an inner gas bag wall which consists of at least two wall parts, namely a forward and a rearward wall part. The forward wall part, i.e. the wall part closer to the front side, has an annular blank and is connected by its inner edge with the inner edge of the ring section of the front wall, with the inner edges delimiting an opening for the formation of the center section. The rearward wall part, i.e. the wall part closer to the rear wall, is connected with the outer edge of the forward wall part, preferably with its own outer edge. The fastening which prevents the center section from turning outwards, engages in this embodiment on the rearward wall part. In this development, the gas bag looks like two gas bags fitted into each other, in which the inner gas bag is inserted via the opening on the ring section into the outer gas bag. This embodiment is distinguished on the one hand by a simple manufacture, in particular a simple sewing of the wall parts. On the other hand, it has been found surprisingly that this gas bag offers better restraint values than a gas bag in which the center section is formed by a tube.  
           [0013]    To sum up, in the module proposed, the gas bag will remain fastened permanently, in the region of the center section, directly to the module or close to the module, i.e. preferably the module housing. The gas bag is then annular in shape and pushes outwards via an annular flap arrangement. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a cross-sectional view through a first embodiment of the gas bag module according to the invention,  
         [0015]    [0015]FIG. 2 shows a perspective view from above of the gas bag module according to the invention according to FIG. 1,  
         [0016]    [0016]FIG. 3 shows an enlarged sectional view through a left-hand lower half of the gas bag module in the region of the gas generator,  
         [0017]    [0017]FIG. 4 shows a cross-sectional view through a gas bag module according to a second embodiment, with the gas bag partially and fully unfolded,  
         [0018]    [0018]FIG. 5 shows a top view onto the fully unfolded gas bag illustrated in FIG. 4,  
         [0019]    [0019]FIGS. 6 and 7 show two variants for the design of flaps forming a covering,  
         [0020]    [0020]FIG. 8 shows a diagrammatic cross-sectional view through a gas bag module according to a further embodiment with a gas bag not yet fully inflated,  
         [0021]    [0021]FIG. 9 shows the gas bag module according to FIG. 8 with fully inflated gas bag,  
         [0022]    [0022]FIG. 10 shows a top view of the front wall of the fully inflated gas bag in FIG. 9,  
         [0023]    [0023]FIG. 11 shows a perspective view of the inner gas bag wall used in the gas bag module according to FIGS.  9  to  11 ,  
         [0024]    [0024]FIG. 12 shows a side view of a detail of the gas bag module with module covering and casing of the gas generator, including a special variant of the fastening of the module covering to the casing and  
         [0025]    [0025]FIG. 13 shows a cross-sectional view through the covering with the fastening integrated therein, which can be used in a gas bag module according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    In FIG. 1 a gas bag module is shown, housed in the vehicle steering wheel or in the instrument panel on the passenger side and serving to restrain the head and upper body, which module consists of a gas bag  3 , a gas generator  5 , a module housing  7  in which gas bag  3  and gas generator  5  are housed, and a module covering  9 . The gas bag module according to FIG. 1 is in particular a module housed in the steering wheel of a vehicle.  
         [0027]    The gas bag  3  consists of a gas bag wall of fabric material, with a front wall  11  which faces the occupant when the gas bag is inflated, as illustrated in FIG. 1, and which is touched by the occupant. In addition, a rear wall  12  is provided, which may consist of a separate fabric piece which has an inflation opening  21 , via which the gas generator  5  is introduced into the gas bag  3 . The front wall has in addition a so-called center section  13 , which is defined by a deep depression  27  and the deepest region  16  of which is arrested on the covering  9  or a casing (oscillation damper)  33  of the gas generator  5  directly and permanently by a fastening. The fastening is an emblem  15  with a formed-on screw  17 , which is screwed externally on the covering  9  or on the mounting in the form of the casing  33  which is configured like a cage.  
         [0028]    The covering  9  has opening flaps  19  adjoining each other in a ring shape around the center section, which flaps  19  are swung upwards when the gas bag unfolds (see FIG. 3). In the opened state an annular outlet opening  14 , preferably in the form of a circular ring, in the covering  9  is exposed.  
         [0029]    The fastening in the form of the emblem provides for the depression and holds the center section, in particular the region  16  of the center section lying closest to the gas generator  5 , close to the gas bag module. A ring section  23  which surrounds the center section  13  and forms the remaining part of the front wall  11 , has a greater distance from the covering  9 , so that the gas bag has a much greater depth than in the region of the center section  13 , the gas bag in the embodiment shown having no depth at all in the center, because it remains in the part of the center section  13  lying immediately under the emblem  15  in its original position which it also assumed in the folded or inflated state and does not move at all in this region in the direction toward the occupant.  
         [0030]    Inwards of the ring section  23 , the depression  27  in the center of the front wall is produced, which depression, as tests have shown, has a positive influence on the restraining effect. Through the fact that the center section  13  of the gas bag is prevented from emerging from the module, only the ring section  23  can contribute to the opening of the flaps  19 , the force generated on inflation being principally directed radially outwards, so that the gas bag unfolds principally radially at the start of its unfolding process and the movement in the direction toward the occupant is small. In the central region of the center section, no movement at all is possible in the direction to the occupant, so that the stressing of the occupant by the gas bag  3  is reduced. In previous gas bags the center section which moves rapidly outwards is that part of the gas bag wall which represents the greatest stress for the occupant, when the occupant and the gas bag wall hit each other.  
         [0031]    [0031]FIG. 3 shows the clamping of the gas bag  3  in the region of the inflation opening  21 . The gas bag is clamped by the cup-shaped casing  33  of the gas generator on the flange  35  of the gas generator  5 .  37  designates the so-called holding section of the covering  9 , which lies inwards of the annular outlet opening  14  and which together with the emblem  15  forms the fastening of the center section  13 . The opening flaps  19  in the embodiment illustrated are formed on the inner periphery of the annular outlet opening  14 .  
         [0032]    In the embodiment illustrated in FIG. 4, the cage-shaped mounting  33  surrounding the gas generator  5 , and also the fastening of the center section  13  via the emblem  15  on the casing  33  can be seen again. The front wall  11  consists of a ring-shaped fabric section which is connected at its outer edge with the rear wall  12  by means of a seam  41 . On the inner edge of the ring section  23 , which delimits the opening in the ring section  23  and co-defines the center section  13 , the ring section is sewn with the inner edge of a forward wall part  43  having an annular shape. A corresponding peripheral seam is designated by  45 . Adjoining the forward wall part  43  is a rearward wall part  47 , which is connected at its outer edge by means of a peripheral seam  49  with the outer edge of the forward wall part  43 . The rearward wall part  47  is the region which is also fastened to the casing  33  in the region of its center. The wall parts  43 ,  47  form an inner gas bag wall. In the fully unfolded state, which is illustrated by broken lines, the abrupt, deep depression  27  can be readily seen, which is delimited by the forward and rearward wall parts  43 ,  47 .  
         [0033]    By the blanks being cut in the shape of a circle (wall part  47 ) and ring (wall part  43 ), respectively, folds are produced in the fully inflated state in the region of the depression  27  which are symbolized in FIG. 5 by the zigzag line which delimits the depression  27 . However, this irregular folding is probably advantageous as regards the restraining effect, because the gas bag which is thus constructed achieves better restraining effects than a gas bag in which the depression  27  is formed by a cylinder produced from fabric material which does not have any folds in the inflated state, because the folds constrict the cross-section and increase the stability of the inflated airbag.  
         [0034]    In FIGS. 6 and 7 two variants are illustrated for the construction of the opening flaps  19 . According to FIG. 6, all the flaps  19  are formed on the outer periphery of the outlet opening  14 . In the variant shown in FIG. 7, flaps  19  associated with each other are provided on the inner and outer periphery of the outlet opening  14 . The oppositely arranged flaps  19  cover each approximately half the radial extent of the annular outlet opening. This variant has the advantage that the flaps  19  have a shorter overall length as compared with the flaps shown in the FIGS. 3 and 6. On opening, therefore, each individual flap has a comparatively low kinetic energy and in addition does not project so far into the passenger space, so that the risk of injury to the vehicle occupant by the flaps  19  in a possible secondary impact is reduced.  
         [0035]    In the embodiment according to FIG. 8 it can be seen that the depression  27  tapers from the lowest region  16 , i.e. the part of the front wall which does not leave the gas bag module on inflation, to the ring section  23 , and is closed completely or almost completely, so that from outside no opening or only a small opening can be seen, which forms the transition of the ring section to the center section  13  and hence to the depression  27 .  
         [0036]    In FIG. 9 the fully unfolded gas bag is shown, which has an almost closed form toward the vehicle occupant.  
         [0037]    In FIG. 10 it can be seen that the ring section  23  extends around a slit  71  which has a small thickness d. The ring section  23  has an elliptical shape which is formed in that the blank for the ring section  23  is already elliptical and has a region provided with the slit  71 . The slit  71  must be so large that on tearing open of the covering it can slide along the emblem  15  and the part of the covering which lies immediately beneath the emblem  15 , and can move out from the gas bag module.  
         [0038]    The blank of the gas bag wall and of the individual wall parts can also be selected such that with a fully inflated gas bag the slit  71  is closed, which means that opposite sections  73 ,  75  come to lie on each other and close the depression towards the ring section. The thickness d is therefore 0.  
         [0039]    In FIG. 11 the inner gas bag wall, consisting of two wall parts  43 ,  47  in accordance with FIG. 4, can be seen with a fully inflated gas bag, the slit  71  also being shown, which forms the transition from the ring section  23  to the center section  13 .  
         [0040]    The assembly of the gas bag module must take place such that on the one hand the part of the center section  13  held on the covering  9  also in fact is prevented from emerging from the gas bag module. On the other hand, it must be achieved that the entire adjoining part of the gas bag wall can emerge from the gas bag module and from the covering. It must therefore be prevented that apart from the central part of the center section other parts of the gas bag wall are clamped by the fastening of the restrained part of the center section.  
         [0041]    In FIG. 12 it can be seen that the covering  9  has on its inner face a projection  77  in the form of a cylinder, which is formed on and projects to the inside, and which has the same outer diameter as a convexity  79  formed on the upper end wall of the casing  33 . The projection  77  and the convexity  79  lie against each other and clamp between them that part of the center section of the gas bag which is prevented from emerging from the gas bag module. A screw  81 , formed on the emblem  15  and defining an emblem fastening, protrudes through the slit  71  and is fixed on the inside of the casing  33  with a nut  83 . The region of the gas bag wall which forms the edge of the slit  71  runs around the emblem  15  and around the projection  77 . It may also lie radially outside the inner edge  85  of the outlet opening  14 , this also being able to be achieved by a correspondingly large projection  77 . Another possibility consists in that for example the projection  77  in the lower region has the form of the later slit  71  and widens outwards to the emblem  15 , so that the gas bag in the region of the slit  71  widens like a button hole on emerging from the module and then, after emerging, narrows again to the slit  71 . FIG. 12 shows that the emblem fastening together with the holding section serve for securing the lowest end of the center section to the module, more precisely to the casing  33 .  
         [0042]    In FIG. 13 a gas bag holding plate  91 , embedded into the covering  9 , is illustrated with two formed-on threaded pins  93  which form the fastening for the center section  13 , by the threaded pins  93 , in a similar manner to FIG. 12, projecting through the end wall of the casing  33 .  
         [0043]    A further embodiment makes provision that the emblem  15  is constructed as a separate part and is connected with a gas bag holding plate  91 ′ according to FIG. 8, provided outside the covering  9 , or continues in one piece into this.  
         [0044]    Two methods are considered for equipping the gas bag module with the gas bag. The first method makes provision that the covering  9  is constructed as a cup-shaped cap into which the gas bag is folded, it having to be taken into account in this type of folding that, proceeding from FIG. 12, only that part of the gas bag wall is allowed to lie against the end wall of the projection  77  which is to be held back. The remaining part of the center section then lies against the covering surface of the projection  19 . On inserting of the gas bag, a so-called dummy serves as substitute for the casing  33 . After the insertion of the gas bag, the dummy is replaced by the casing  33 , and the nut  83  is screwed on. A further embodiment makes provision that the gas bag module consists of two cup-shaped parts, a cup-shaped cap forming the covering  9  and a cup-shaped receiving part. The casing  33  is placed into the receiving part so that between the peripheral wall of the receiving part and the casing  33  an annular space is formed, into which the gas bag is folded from above. After the insertion of the gas bag, the covering  9  is put in place from above and, for example, is screwed from below.