Abstract:
An airbag module having a gas generator ( 14 ), an airbag ( 13 ), a housing ( 10 ), and a retaining part ( 20 ) for fixing the airbag fabric against the housing ( 10 ), whereby the gas generator ( 14 ), which is positionally fixed to the housing ( 10 ), and the retaining part ( 20 ) are arranged inside the airbag ( 13 ). The retaining part ( 20 ) is arranged without a force-absorbing fixation between the gas generator ( 14 ) and the housing ( 10 ) and, during deployment of the airbag ( 13 ), is pressed against the gas generator ( 14 ) by the airbag fabric extending between the retaining part ( 20 ) and the housing ( 10 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an airbag module with a gas generator, airbag, housing, and retaining unit, whereby the gas generator and the retaining unit are located inside of the airbag, and the gas generator is radially and axially attached to the housing. 
   2. Description of the Related Art 
   A related airbag module has been described in EP 0 633 168 B 1. In order for the airbag to receive a gas generator additionally arranged in a gas generator housing, a pocket with two open fabric necks is attached in the area that receives the gas generator on the airbag, which after insertion of the gas generator into the pocket, is folded over, encompassing the gas generator in a labyrinth-like fashion. The gas generator is then firmly connected to the module housing using separate attachment means that penetrate through the fabric layers, especially by means of screw fittings. 
   The known airbag has the initial disadvantage that the manufacture of the airbag with the attached pocket, as well as the assembly of the airbag module as a whole, is complex. The airbag is inserted into the pocket, and the fabric necks of the airbag must be folded over and aligned in such a way that the attachment means of the housing wall of the module housing can be fed through both fabric necks into the gas generator. As the unfolding and inflating of the airbag results in tensile forces applied to the airbag material, at least for a short period of time, the penetration locations of the attachment means through the airbag material are exposed to heavy stresses, which is why additional reinforcement inserts are often worked into the airbag fabric at such critical stress points. 
   The same disadvantage also exists with the airbag module disclosed in DE 298 02 731 U1, in which a pot-shaped gas generator is inserted and attached in an opening contained at the bottom of the module housing. An attachment plate arranged in the interior of the airbag pinches the airbag together with the bottom of the housing, and is connected to the housing by means of screw fittings penetrating through the airbag fabric. 
   A comparable airbag module with the use of a pipe gas generator has been described in DE 298 06 402 U1; however, here an insertion component is arranged in the interior of the airbag and pinched together with the housing. It is also connected to the housing by means of separate screw fittings penetrating through the airbag fabric. 
   The problem to be solved by the invention, therefore, is to provide an airbag module with the general operational characteristics described but with simplified production and assembly. 
   The solution of this problem is shown in the content of the patent claims that follow this description, including advantageous embodiments and further developments of the invention. 
   SUMMARY OF THE INVENTION 
   In its basic idea, the invention provides that the retaining unit is arranged between the gas generator and the housing without any force-receiving attachment, and it is pressed against the gas generator by the airbag fabric extending between the retaining unit and the housing during the unfolding and inflating of the airbag. In more detail, the retaining unit is defined by the gas generator without any force-fit attachment on the airbag, or the gas generator, or the housing on the side opposite of the gas generator between the housing wall of the module housing and the gas generator. The retaining unit absorbs the forces created during the unfolding and inflating of the airbag, and transfers them to the gas generator and its attachment to the module housing. The attachment of the airbag is achieved in a type of floating bearing, because the airbag fabric is led around the retaining unit inserted into the airbag without any special fixation, or attachment. During inflation of the airbag, which generates stresses and forces, the retaining unit supports itself on the gas generator attached in the module housing due to the tensile forces engaging onto the airbag during its unfolding, and thereby transfers these forces. 
   The invention combines the advantage that the airbag fabric supports itself over a planar surface on the retaining unit for the transfer of force, and no puncture stress is present. In this way, the use of reinforcement layers in the production of the airbag can be eliminated. The production and assembly of the airbag module are also simplified because no special measure for the attachment of the retaining unit is necessary; merely a sufficiently large opening for sliding the retaining unit in must be provided. As only the gas generator must be attached to the module housing, and insofar as the retaining unit is firmly placed in a loose arrangement in the module housing, the attachment effort in the assembly of the module is kept to a minimum. 
   Another advantage arises from the close association of the retaining unit and housing wall positioned opposite of the discharge opening. The retaining unit acts to reinforce this area of the module housing so that deformation of the housing wall cannot occur before the airbag is deployed during a brief overpressure in the interior of the module housing caused by activating the gas generator. Therefore, the module housing can be embodied in lighter and more weight-saving designs, and produced from plastic, or die-cast light metal. 
   According to one embodiment example of the invention, the retaining unit has a contour adjusted to the shape of the housing. This ensures the appropriate engagement of the airbag fabric and a good transfer of forces onto the housing due to the alignment of the housing shape and the shape of the retaining unit. 
   According to another embodiment example of the invention, the fixing of the position of the retaining unit within the airbag is facilitated. In this embodiment, the retaining unit has at least one tab that protrudes from the level of the retaining unit and that penetrates through the airbag fabric and the housing wall in an assigned opening. In this way, the retaining unit is purposeflully locally fixed opposite of the housing by means of two tabs. This provides the advantage that the airbag can be properly positioned, or its position can be fixed, respectively, with the retaining unit during assembly. 
   According to another embodiment example of the invention, the retaining unit is deformable. It may transfer stresses on the airbag fabric only after the forces have been absorbed. In this regard it is known from GB 2 343 418 A to improve the pinching in of the airbag fabric between the housing and a flange embodied on the gas generator inserted into the housing in the case of an activation of the gas generator by the fact that the flange is bent by the forces exerted, and the clamping force applied to the airbag fabric is increased. 
   According to an alternative embodiment examples, the retaining unit can consist of plastic, or can be embodied as a retaining plate consisting of metal. In the case of a metal embodiment, especially the tabs penetrating from the level of the retaining unit can be punched out and bent outward. 
   According to one embodiment example, the integration of a retaining unit provides the invention with the possibility of equipping the retaining unit with a diffuser for leading gas into the unfolding airbag; such diffusers are generally known. 
   Since the gas generator is arranged on the inside of the airbag, the retaining unit and the airbag form a closed pressure system, which leads to the fact that the module housing can also be designed as a non-closed system. The forces occurring respectively are transferred from the retaining unit to the gas generator and from it to the faces of the module housing. As the module&#39;s longitudinal sides remain nearly free of forces, openings allowing for the entry of the airbag fabric extending across the bottom may be arranged in the area of the bottom of the module housing that extend parallel to the gas generator. In this way, not only can the module housing be embodied with an optimum weight, but the openings in the bottom of the module housing can also serve to reduce dynamic stresses. In the case of high interior pressure, the airbag expands hemispherically into these openings, and especially the occurring dynamic pressure peaks can thereby be attenuated without the use of any additional means. 
   With regard to the assembly of the airbag module, the airbag has an opening dimensionesufficiently large for inserting the retaining unit, as well as two additional openings for receiving the face ends of the gas generator according to embodiment examples of the invention, whereby the dimensions of the openings in the airbag intended for the attachment of the gas generator on the module housing are adjusted to the respective attachment means provided. 
   With regard to the attachment of the gas generator in the module housing, the gas generator may be attached on the face wall of the module housing with its face end by means of a screw neck, as well as a bore that can be extended through the face wall of the module housing, and by means of an attached nut. Accordingly, the gas generator may be attached to the module housing at its other face end by means of a collar that can be extended from the exterior through the assigned face wall of the module housing, and that receives a face neck of the gas generator within itself. 
   According to an embodiment example of the invention, the module housing is embodied with two sidewalls that are arranged to envelope an obtuse angle between them in a tub-like fashion parallel to the longitudinal axis of the gas generator in conical direction, and two face walls each connecting the two sidewalls. The conical embodiment of the module housing results in an improved unfolding of the airbag from out of the module housing. 
   It can be provided for this purpose that the module housing is embodied asymmetrical to the gas generator with a steeply inclining sidewall, and with a shallow inclining sidewall, whereby the airbag is folded into two folds formed between the gas generator and the two sidewalls in an asymmetrically adjusted fold, and overlaps the gas generator with only one fabric layer. 
   It may be provided in such an embodiment of the module housing that the retaining unit has a contour adjusted to the shape of the sidewalls. 
   Insofar as the embodiment of the airbag module according to the invention opens the possibility of embodying the module housing in a lighter, and weight-saving fashion from a corresponding material, a retaining loop may be attached to the housing wall of the module housing opposite of the discharge opening, which is led into the airbag and wraps around the gas generator, in order to avoid a sagging of the respective housing wall of the module housing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the manner in which the above-recited and other features and advantages of the invention are obtained will be readily inderstood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is a top view of an airbag module. 
       FIG. 2  is a side view of the airbag module of FIG.  1 . 
       FIG. 3  is an exploded illustration of the separate parts of the airbag module of FIG.  1 . 
       FIG. 4  is a sectional top view of the airbag module. 
       FIG. 5  is a different embodiment example of the airbag module in its illustration according to FIG.  1 . 
       FIG. 6  is an additional embodiment example of the airbag module in the illustration according to FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention, as represented in  FIG. 1-6 , is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention. 
   The module housing  10  shown in a simultaneous view of  FIGS. 1 and 2  is comprised of two opposite sidewalls  11 , and face walls  12  that each connect these in a tub-shaped embodiment as a whole, whereby a discharge opening  25  is positioned opposite of the bottom  26  of the module housing  10 , through which an airbag  13  that was folded into the module housing  10  can unfold itself. The upper edge of the module housing  10  is equipped with a surrounding flange  27 , on which, for example, a cover (not illustrated) can be attached. 
   A gas generator  14  is arranged on and attached to the module housing  10  between the face walls  12  at a direction parallel to the side walls  11 , in that one of the face ends of the gas generator  14  is lead through an assigned opening in the associated face wall  12  of the module housing  10  with a screw neck  15 , and a nut  16  is screwed onto the exterior side of the module housing  10  for the attachment of the gas generator  14 . On the opposite side the gas generator  14  has a face neck  17  ending inside of the module housing  10 , onto which a collar  18  is slid on from the exterior side of the module housing  10 . Collar  18  penetrates the assigned face wall  12  through an opening so that the gas generator  14  is fixed above the face neck  17  inside of the collar  18 . A retaining loop  24  is provided for the additional fixation and attachment safety of the gas generator  14 . Retaining loop  24  envelops the collar  18  in a wrap-around fashion and is attached on the bottom  26  of the module housing. Gas discharge openings  19  through which the gas created in the gas generator  14  enters into the airbag  13  are disposed partially around the gas generator. 
   The embodiment shown in  FIG. 1  shows the retaining unit equipped with an optional diffuser schematically shown at  36  for leading gas into the unfolding airbag; such diffusers are generally known. 
   As  FIG. 4  shows in detail, a retaining unit  20  is inserted into the interior of the airbag through an opening  21  contained in the airbag  13 , whereby the airbag  13  additionally has an opening  22  for the penetration of the screw neck  15  of the gas generator  14 , as well as an opening  23  for the penetration of the face neck  17  of the gas generator. The opening  23  is dimensioned in such a way that it can be shifted over the face neck  17  of the gas generator  14  by expanding it. The seal is achieved by inserting the collar  18 . 
   As  FIG. 2  shows in detail, the arrangement is made in such a way that the airbag  13  is inserted with the retaining unit  20 . The retaining unit  20  comprises, for instance, a retaining plate made of metal, that is inserted between the bottom  26  of the module housing  10  and the gas generator  14  in a non-fixed or loose attachment so that the airbag  13  is fixed during its unfolding as indicated in  FIG. 2  by means of the retaining unit  20  retained by the gas generator  14 . If high tensile forces briefly occur with the activation of the gas generator, the retaining unit  20  can deform itself around the gas generator attached in the module housing  10  so that the forces applied to the airbag fabric are deflected via the retaining unit and the gas generator  14  into the module housing  10 . It will be appreciated that the airbag fabric of the airbag  13  envelops the retaining unit  20  in a large surface area, and that the airbag supports itself on the retaining unit without weakening or stressing the airbag fabric, for instance, by means of an opening for attachment means. 
     FIG. 3  shows the basic principle of a simple assembly of the airbag, which consists in a first step of inserting the retaining unit  20  through the opening  21  into the airbag  13 ; in a second step the retaining unit  20  enclosed by the airbag  13  is positioned on the bottom  26  of the module housing  10 ; next, the gas generator  14  is pushed into both the interior of the module housing  12  as into the interior of the airbag  13  through an opening in the face wall  12  of the module housing  10 . The gas generator  14  enters into the interior of the airbag by expanding the opening  23  until the screw neck  15  is extended through the opening  22  of the airbag  13 . The neck  15  is fixed onto in the assigned opening of the face wall  12  of the module housing  10  and screwed on by means of the nut  16 . Subsequently, the collar  18  is inserted into the face wall  12  of the module housing  10  from the insertion side, and attached on the face neck  17  of the gas generator  14  by means of pressing it on to form a seal. 
   In the embodiment examples illustrated in  FIG. 5 , the tub-shaped module housing  10  is embodied asymmetrically to the gas generator  14  with a steeply inclining sidewall  30 , and with a flat inclining sidewall  31 . The airbag  13  is folded into the two folds  32  that are formed between the gas generator  14  and the respective sidewall  30  or  31  in an adjusted asymmetrical fold, whereby the airbag  13  overlaps the gas generator  14  with only one fabric layer. One layer of the airbag  13  extends between the retaining unit  20  inserted into the interior of the airbag and the bottom  26  of the module housing  10  in the same manner. At the same time, the retaining unit  20  has a contour that is adjusted to the shape of the sidewalls  30  and  31 . 
   As  FIG. 6  shows, it may be provided for the proper positioning of the retaining unit during assembly, or for its position fixation, that tabs  35  protrude from the level of the retaining unit  20 , which themselves engage into respectively provided openings in the airbag fabric, and in the housing  10 . 
   The characteristics of the subject of these documents disclosed in the preceding description, the patent claims, the abstract, and the drawing can be utilized individually or in any combination for the creation of the invention in its various embodiments. The present invention may be embodied in other specific forms without departing from its structures, methods, or other characteristics as described herein and claimed hereinafter. The described embodiments are to be considered only as illustrative, and not restrictive.