Abstract:
The invention relates to an airbag module for motor vehicles, comprising a housing for an inflatable airbag and a gas generator, with the gas generator being coupled to the housing without securing means via at least one elastic and/or oscillation damping coupling member.

Description:
TECHNICAL FIELD 
     The invention relates to an airbag module for motor vehicles, comprising a housing for an inflatable airbag and a gas generator. 
     BACKGROUND OF THE INVENTION 
     Airbag modules of this kind serve to accommodate the airbag in the folded together state and to inflate it by means of the gas generator in the event of an accident. The airbag modules are installed in the vehicle as a unit. In this, conflicts can arise with other functional units of the motor vehicle which were previously located at the places where the airbag module is now to be provided in order to offer an ideal protection for the vehicle passenger. For example in drivers&#39; airbags which are to be accommodated in the central region of the steering wheel an ideal capability of functioning both of the airbag system and of the horn system of the vehicle must be ensured if the latter is to be likewise provided in the central region of the steering wheel. Furthermore, problems can arise if oscillations which arise during the operation of the vehicle are transmitted to the airbag module and the airbag module is integrated into the vehicle in such a manner that further tasks are assigned to it in addition to the protective function. Not only the driving comfort, but also additional functions of this kind can be impaired through oscillations of the airbag module. 
     The problem (object) of the invention is to create an airbag module of the initially named kind which is constructed as simply as possible, is not impaired by arising oscillations and can be used in particular as a drivers&#39; airbag which can be integrated into a steering wheel unit. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention only the elastic and/or oscillation damping coupling member is required for coupling the gas generator to the housing. As a result of the coupling without securing means, no separate securing means such as for example screws or the like are required. Through this the attachment of the gas generator at the housing and thus the assembly of the airbag module is particularly simple. 
     The elastic and/or oscillation damping coupling member provides for a decoupling between the gas generator and the housing. Through this it is possible to subdivide the total mass of the airbag module substantially into the mass of the housing and of the airbag on the one hand and into the mass of the gas generator on the other hand. Through this the mass of the gas generator can fulfill an oscillation damping function in an advantageous manner. If the airbag module in accordance with the invention is integrated into a steering wheel unit, disturbing oscillations of the steering wheel can be avoided or reduced through suitable design of the coupling member. The respective masses and the respective type of coupling to the steering wheel system can be intentionally matched to additional functions which are to be transferred to the housing and/or to the gas generator in the installed state. 
     Through the coupling of the gas generator to the housing, the housing with the gas generator which is attached to it and thus the airbag module as a whole can be attached at a motor vehicle, for example at a steering wheel unit. Through the coupling member it is ensured that the gas generator and the housing can move independently of one another; i.e. the gas generator can execute oscillatory movements independently of the housing. 
     In a preferred embodiment of the invention the coupling member has a closed peripheral contour and is formed in particular in the shape of a ring. A coupling member of this kind enables a particularly simple attachment of the gas generator at the housing. 
     To connect the gas generator to the coupling member a particularly preferred embodiment of the invention proposes hanging in the gas generator into the coupling member. 
     In accordance with a particularly preferred embodiment the gas generator is connected to the coupling member in the manner of a bayonet lock. Through this a connection between the gas generator and the coupling member which is simple to manufacture and which is at the same time particularly secure is achieved. 
     The coupling member preferably has at least one in particular groove-like or slit-like recess at an inner side with which a holding section of the gas generator which projects preferably perpendicularly from an outer wall of the gas generator is in engagement. 
     To connect the coupling member to the housing it is provided in accordance with a further preferred exemplary embodiment of the invention that the housing, in particular a base plate, is pushed on onto the coupling member. 
     For this the coupling member preferably has at least one in particular circumferential and preferably groove-like or slit-like recess at an outer side with which a holding section of the housing is in engagement. 
     An edge region of the housing base which bounds a base opening which is provided for the gas generator preferably serves to connect the housing to the coupling member. 
     A particularly secure and nevertheless elastic and/or oscillation damping coupling between the gas generator and the housing is achieved in accordance with a further preferred embodiment of the invention in that sections of the gas generator and of the housing which are in engagement with the coupling member overlap each other in the radial direction. 
     The coupling member can be provided as a separate component or be formed on at the housing or moulded to the housing, in particular vulcanized on the housing, in particular a base plate of the housing. 
     A particularly preferred practical embodiment of the invention proposes providing the coupling member as a sealing between the gas generator and the housing. Through this the coupling member fulfills a plurality of functions at the same time in that it provides not only for an elastic and/or oscillation damping coupling of the gas generator to the housing, but also serves as a sealing. Through this it is possible in an advantageous manner to seal off the interior of the housing containing the inflatable airbag or of the airbag surrounding the gas generator respectively against the surroundings with the coupling member. 
     In accordance with a further preferred exemplary embodiment of the invention the coupling member is clamped in between a diffuser and a base plate of the housing, with the diffuser and the base plate preferably being screwed together. In this way the diffuser provides for a secure fixing of the coupling member and thus of the gas generator at the housing. 
     This fixing is of particular advantage in particular when damages, e.g. fissures, arise at the coupling member during the vehicle operation. The diffuser holds the coupling member and thus the gas generator in position, so that it is ensured that after the triggering of the gas generator the gas which is ejected from the latter reliably enters into the airbag to be inflated even if the coupling member is damaged or is torn in or torn through. 
     It is preferred for the diffuser to be formed as a protection against rotation for the coupling member. 
     In accordance with a further preferred embodiment of the invention it is provided that a diffuser surrounds the gas generator at least region-wise with spacing, with the intermediate space preferably forming a gas inlet chamber which is sealed off by the coupling member. 
     In this way the gas generator can execute oscillations within the diffuser uninfluenced by other components of the airbag module. In particular a contact between the oscillating gas generator and the airbag can be avoided through the diffuser. 
     The coupling by means of the coupling member is preferably designed in such a manner that the gas generator can be moved relative to the housing with a radial component which extends perpendicularly to a propagation direction of the airbag. The gas generator can thereby execute radial oscillations which extend perpendicularly to its longitudinal axis. 
     Further preferred embodiments of the invention are also set forth in the subordinate claims, the description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a an exploded view of an airbag module without airbag in accordance with an embodiment of the invention, 
     FIG. 2 is the airbag module in accordance with the invention in the assembled state in a sectioned side view, and 
     FIG. 3 is the airbag module in accordance with the invention in the assembled state in another sectioned side view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In accordance with FIG. 1 the airbag module comprises a cylindrical gas generator  10 , from the outer wall of which a plurality of lug-like holding sections  11  which are distributedly arranged in the peripheral direction project perpendicularly. The holding lugs  11  are formed in a single piece at the edge of a cap  10   a  which is pushed over the gas generator  10  and which is firmly connected to the gas generator  10 . This will be discussed in more detail elsewhere. 
     A housing of the airbag module comprises a cover  13  and a housing base  12  which is formed by a base plate  12   b  and a pan-like or hat-like diffuser  12   a.    
     The base plate  12   b  is provided with a circumferential, strip-like edge section  26  which extends perpendicularly to the plane of the plate and has a circular opening  28  for the gas generator  10 . An edge region  15  of the base plate  12   b  which bounds the opening  28  is provided with recesses  15   a  for the holding lugs  11  of the gas generator  10 . 
     An annulus-shaped coupling member  18  of a flexible, elastically deformable material, for example of rubber serves for the coupling of the gas generator  10  to the base plate  12   b . The coupling member  18  is formed in a single piece. 
     In the illustrated embodiment the coupling member  18  is a separate component. Alternatively it is also possible to provide the coupling member  18  as an integral constituent of the base plate  12   b  and to form or vulcanize it on respectively at its edge region  15 . 
     At its outer side the coupling member  18  has a circumferential outer groove  20 , into which the edge region  15  of the base plate  12   b  which bounds the opening  28  engages in the assembled state of the airbag module which will be explained in more detail in the following. 
     For each holding lug  11  of the gas generator  10  an inner groove  19  which extends over a limited angular region in the peripheral direction is formed at the inner side of the coupling member  18 . To each inner groove  19  a recess  21  which is open downwardly in FIG.  1  and which is likewise formed at the inner side of the coupling member  18  is associated via which the respective inner groove  19  is accessible. 
     For the coupling of the gas generator  10  at the base plate  12   b  the connection of the coupling member  18  at the base plate  12   b  takes place first. As a result of its flexibility the coupling member  18  can be laid in into the opening  28  of the base plate  12   b  and be pushed on onto its edge region  15  which bounds the opening  28 , and which then engages into the outer groove  20  of the coupling member  18 . 
     For the connection of the gas generator  10  to the coupling member  18  the gas generator  10  is introduced in FIG. 1 from below into the opening  28  of the base plate  12   b  and in this is introduced with the holding lugs  11  through the recesses  15   a  of the edge region  15  and into the recesses  21  at the inner side of the coupling member  18 . Then the gas generator  10  and the coupling member  18  are rotated with respect to one another, so that the holding lugs  11  enter into engagement with the inner grooves  19  of the coupling member  18 . 
     In this way the gas generator  10  and the coupling member  18  are connected to one another in the manner of a bayonet lock. 
     The diffuser  12   a , which can be screwed together with the base plate  12   b  via screw connections  44  and can be pre-fixed by means of bending lugs  48  at openings  46  of the base plate  12   b , comprises a cylinder section  31 , in the side wall of which a plurality of apertures  24  which are uniformly distributed in the peripheral direction are formed, and an annulus-shaped edge section  30 . 
     Connection sections  32  between the edge section  30  and the side wall sections  34  of the cylinder section  31  cooperate in the assembled state with corresponding depressions  23  on the end side of the coupling member  18  facing the diffuser  12   a . In the assembled state of the airbag module the coupling member  18  which is clamped in between the diffuser  12   a  and the base plate  12   b  is fixed together with the gas generator  10  in a manner which is secure against rotation at the base plate  12   b  and thus at the housing  12 ,  13  as a result of the connection sections  32  of the diffuser  12   a  which engage into the depressions  23 . 
     The base plate  12   b  can be inserted together with the coupling member  18 , the gas generator  10  and the diffuser  12   a  into the cover  13  from below in such a manner that the edge section  26  of the base plate  12   b  lies inwardly in contact at a side wall  13   a  of the cover  13 . Securing elements  36  serve for the fixing of the base plate  12   b  to the cover  13 . 
     An insertion element  13   c , which is e.g. provided with an emblem, can be latchingly inserted into a depression  13   c  in the outer side of the cover  13 . 
     FIGS. 2 and 3 show the airbag module in the assembled state. The airbag module is carried via the base plate  12   b  on a component of a steering wheel unit  40 . In this the base plate  12   b  is supported via coil springs  42  at the steering wheel unit  40 . The arrangement for carrying the base plate  12   b  at the steering wheel unit  40 , the concrete design of which will not be discussed in further detail, is also designated as an elastic floating system or floating support respectively, in which the base plate  12   b  and thus the entire airbag module lies so to speak loosely upon the coil springs  42 . The base plate  12   b  and thus the entire airbag module is therefore not rigidly connected to the steering wheel unit  40 , but rather is elastically resiliently supported by means of the floating system, with it being possible for the airbag module to be moved against the restoring force of the coil springs  42  in the direction of the steering wheel unit  40 . 
     The base plate  12   b , which is connected via its edge section  26  to the side wall  13   a  of the cover  13 , engages with its edge region  15  which bounds the opening  28  into the circumferential outer groove  20  of the coupling member  18 . The holding lugs  11  of the gas generator  10  are located in the inner grooves  19  of the coupling member  18  which are formed above the outer groove  20  in FIGS. 2 and 3. In FIGS. 2 and 3 it can be seen that the edge region  15  of the base plate  12   b  and the holding lugs  11  of the gas generator  10  overlap in the radial direction. 
     In addition FIGS. 2 and 3 show that the holding lugs  11  are formed in a single piece with the cap  10   a , which region-wise surrounds the gas generator  10 . The gas generator  10  is firmly connected to the cap  10   a  in such a manner that the gas generator  10  and the cap  10   a  can be moved as a unit. 
     Illustrated in the sectional plane in accordance with FIG. 2 are the connection sections  32  which engage into the depressions  23  (cf. FIG. 1) on the end side of the coupling member  18  facing the diffuser  12   a . The coupling member  18  is clamped in between the connection sections  32  of the diffuser  12   a , which is screwed together with the base plate  12   b  via its edge section  30 , and the edge region  15  of the base plate  12   b.    
     The airbag  14  is clamped in with its edge region  14   a  which bounds the mouthpiece between the edge section  30  of the diffuser  12  and the base plate  12   b . The application of the clamping force takes place through the mentioned screw connections  44 , with which the diffuser  12   a  and the base plate  12   b  are held together. In this way a gas tight anchoring of the airbag  14  takes place at the housing base  12  which is formed by the diffuser  12   a  and the base plate  12   b.    
     The cylinder section  31  of the diffuser  12   a  surrounds the unit consisting of the gas generator  10  and the cap  10   a  with spacing, so that a gas inlet chamber  22  is present between the cylinder section  31  and the gas generator  10 . When the gas generator  10  is triggered the gas which is expelled by the latter first flows into the gas inlet chamber  22  before it enters via the apertures  24  between the side wall sections  34  of the cylinder section  31  of the diffuser  12   a  into the airbag  14 . 
     The gas inlet chamber  22  is sealed off downwardly by the coupling member  18 , which lies sealingly in contact with its inner side at a side wall region of the gas generator  10  which lies outside the cap  10   a  and thus completely fills out the radial intermediate space between the gas generator  10  and the edge region  15  of the base plate  12   b.    
     In FIG. 3 the sectional plane extends through two apertures  24  of the cylinder section  31  of the diffuser  12   a  and through two regions of the end side of the coupling member  18  facing the diffuser  12   a  which separate the depressions  23  (cf. FIG.  1 ). 
     FIG. 3 also shows the bending lugs  48  which protrude through the openings  46  in the base plate  12   b , which are radially bent outwardly and which are formed at the edge section  30  of the diffuser  12   a . The bending lugs  48  permit a pre-fixing of the diffuser  12   a  at the base plate  12   b  before the production of the screw connections  44  (cf. FIGS.  1  and  2 ).