Abstract:
An apparatus for the damping of vibrations in a steering column in a motor vehicle, having a mounting ( 10 ) and an accommodation device ( 11 ) elastically supported in the mounting ( 10 ) to which a gas generator ( 20 ) is secured, a separate supplemental weight ( 30 ) is secured to the gas generator ( 20 ) or to the accommodation device ( 11 ) to provide desired vibration damping characteristics of the steering column assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 10 2011 017 350.1, filed Apr. 18, 2011 and PCT/EP2012/001360, filed Mar. 28, 2012. 
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for the damping of vibrations, in particular in a steering column of a motor vehicle, with a mounting and an accommodation device elastically supported in the mounting to which a gas generator is secured. 
     BACKGROUND 
     From DE 199 08 915 B4 a vibration eliminator for a steering wheel with an airbag is known, in which the inertial mass of the vibration eliminator is formed by the gas generator of the airbag. The gas generator is connected via a spring element to the airbag housing; said spring element engages the outer wall of the gas generator and consists of reinforced, gas-impermeable, elastomeric material. The spring element has the shape of a blunt cone which essentially features a constant wall thickness. 
     In a motor vehicle, the steering column and the steering wheel with the driver airbag form a vibrating system. In order to eliminate, or at least to reduce, harmful or unpleasant vibrations in a vibrating system, the coordination and arrangement of a mass with a particular weight is helpful. By a change in the inertial mass, the vibration behavior can be changed so that the elimination of vibrations will ideally result. 
     In the prior art, the inertial mass is provided by the gas generator; the gas generator is connected via a connecting plate to the spring element. The object of the present invention is to create an apparatus for the damping of vibration by means of which an adaptation to different frequencies of a steering column or to a different, vibration system is possible in order to suppress undesirable vibrations. 
     According to the invention, this object is attained by an apparatus with the features described herein. Advantageous embodiments and refinements of the invention are presented, in the description and in the figures. 
     SUMMARY 
     In accordance with this invention, the apparatus for the damping of vibrations, in particular in a steering column in a motor vehicle with a mounting and an accommodation device elastically supported in the mounting, to which a gas generator is secured, provides for a separate supplemental weight which can be secured to the gas generator and/or to the accommodation device. In order to attach a gas generator to the steering column or to the steering wheel, a mounting is provided in which an accommodation device is elastically mounted for the airbag and/or for the gas generator. Thus, the gas generator acts as a vibration damper for the driver unit comprised of the steering column, steering wheel and airbag. Depending on the configuration of the driver unit and on the eigen-frequency (resonant frequency) of the steering column or vibration system, different masses can be required as vibration dampers, which cannot be achieved by one single gas generator. More recent generations of gas generators can be so light-weight, for example, that they do not reach the required inertial mass for purposes of vibration damping. As a result of the supplemental weight, a balanced inertial mass can be provided which is adapted to the vibration properties of the steering column, of the steering wheel and of the airbag attached thereon. In particular, with very light-weight gas generators and light-weight materials it is possible to increase and adapt the inertial mass by means of the supplemental weight and to secure it to the accommodation device and/or to the gas generator so that the supplemental weight is elastically secured to the mounting via the gas generator and the accommodation device. 
     Attachment elements to secure the supplemental weight can be arranged on or configured on the accommodation device and/or on the gas generator. These attachment elements can be configured as plastically deformable tabs, elastic snap elements, positive locking elements in general, as hooks, clips or the like in order to allow an attachment of the supplemental weight to the gas generator, to the accommodation device or to both components. For this purpose, corresponding positive-locking elements are advantageously arranged or configured on the supplemental weight for the attachment elements provided on the accommodation device, so that the supplemental weight can be optionally mounted before or after the attachment of the gas generator to the accommodation device. 
     The supplemental weight can be reversibly secured to the gas generator and/or to the accommodation device, so that it can be replaced for maintenance or repair, for example, within the scope of any adaptation or modification. It is also possible first to supply a basic variant of the device consisting of mounting, gas generator and supplemental weight, and only adapt it to the particular requirements of the vehicle at the mounting place. In this regard it may be useful to be able to remove the supplemental weight from the gas generator or from the accommodation device. 
     The supplemental weight can be glued, crimped, compressed, screwed, clipped and/or riveted to the gas generator and/or to the accommodation device, so that it can also be irreversibly (permanently) attached to the particular components. 
     The gas generator in a driver airbag is typically configured as a cylindrical or approximately cylindrical element, so that the supplemental weight is configured ring-shaped or dish-shaped for a space-saving assembly and a tightest possible fit to the gas generator, so that the mass is uniformly distributed around the gas generator. Likewise, due to the ring-shaped or dish-shaped configuration of the supplemental weight with a corresponding contouring relative to the gas generator, an arrangement with a minimum installation volume is possible. 
     At least one opening can be provided in the supplemental weight for the passage of lines, wires, and/or attachment elements. The opening can likewise be used for the passage of contacts of the gas generator through the bottom of the supplemental weight. Other components, such as plugs, can also protrude through the at least one opening. 
     One embodiment of the invention provides that the supplemental weight features a recess along its perimeter which acts as a circumferential positive-locking element for locking to the gas generator or to the accommodation device. The supplemental weight can have a circumferential ring located in a plane, which is preferentially configured closed and acts as an anchoring element for the attachment elements. The ring is preferentially arranged on the outside of the supplemental weight and can form the recess which extends radially outward as an undercut or positive-locking element for the attachment elements. 
     The mounting can be configured as a vibration eliminator for an airbag, so that the apparatus together with the airbag can be configured as an airbag module, in which the gas generator and possibly the supplemental weight are elastically supported. Due to the mass of the mounting, together with the mass of the gas generator, of the airbag and potentially of the supplemental weight, the vibrations of the steering wheel can be effectively eliminated. 
     Predefined break lines can be configured in the supplemental weight which surround regions with defined weights, so that, proceeding from a base supplemental weight, by removal of defined weights, the desired supplemental weight can be adjusted. For this purpose, the material within the predefined break lines is removed which corresponds to the removed weight. 
     The invention also relates to a fully assembled module as an apparatus for the damping of vibrations consisting of a mounting with an elastically supported accommodation device to which the gas generator and the separate supplemental weight are attached, the attachment also being possible by fixing the supplemental weight to the gas generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments will be explained hereafter in greater detail with reference to the included figures. 
         FIG. 1  is an exploded view of the apparatus; 
         FIG. 2  shows a variant of  FIG. 1 ; and 
         FIG. 3  illustrates a fully assembled apparatus consisting of mounting, gas generator and supplemental weight. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exploded view of an apparatus for vibration damping on a steering column of a motor vehicle, with a mounting  10  which is configured as a retaining ring, with a flange which has recesses  15  for attachment to the steering column or steering wheel, for example. The recesses (or holes)  15  are used to allow for the insertion of screws or other attachment elements, for example. A collar  17  extends from the flange essentially perpendicularly upward on whose inside there is an accommodation device  11 . The collar  17  as such can be configured as an elastic element; it is likewise possible to configure the collar  17  as a shaped metal element to which an elastic component is attached for securing the accommodation device  11 . Such an elastic element is preferentially arranged on the inside of the collar  17 ; it is preferred that the accommodation device  11  be in general elastically supported relative to the flange of the mounting  10  which is attached to the steering column or to the steering wheel. 
     Tabs  18  are arranged on the accommodation device  11 , which protrude radially inward. In the shown embodiment, the accommodation device  11  has a circular shape, but different geometries are possible. 
     Attachment elements  12 ,  13  configured as tabs or tongues are provided on the accommodation device  11  and extend parallel to the collar  17 ; the function of said tabs will be explained below. Likewise, a plug insert  14  is provided, for example for grounding of the accommodation device  11 , which is essentially configured as a single-piece sheet metal part. A multi-part configuration of the accommodation device  11  is likewise possible, as is an accommodation device  11  with an open cross section. In the shown embodiment, the accommodation device  11  is elastically joined to the flange of the mounting  10  via an elastomeric element  16 . The elastomeric element  16  is attached to the outside of the accommodation device  11 , for example by adhesion or vulcanizing. A similar attachment is also possible on the mounting  10 . 
     Beneath the mounting  10  there is a gas generator  20  shown in an essentially cylindrical configuration. Outlet openings  22  are configured in the jacket of the cylindrical section of the gas generator  20  to guide deployment gas to the outside into an airbag (not shown). Beneath the outlet openings  22  there is a circumferential protrusion  21 , on whose underside there is a recess  25 . On the underside of the gas generator  20  there are electrical connections  23  for contacting with an electric signal and control circuit. In the assembled state, the circumferential protrusion  21  rests against the tabs  18  of the accommodation device  11  and thereby defines the installation position of the gas generator  20  relative to the accommodation device  11  and thus to the mounting  10 . In the assembled state, the attachment elements  12 ,  13  have the shape of tabs bent inward or as inward directed springs in order to firmly secure the gas generator  20  in the accommodation device. The attachment elements  12  are thereby configured so that they resiliently rest against the outer perimeter of the protrusion  21 ; the longer attachment elements  13  are configured such that they are inclined radially inward, so that they engage behind the recess  25  and cause a positive-locking, permanent locking of the gas generator  20  in the accommodation device  11 . 
     Underneath the gas generator  20  there is a supplemental weight  30  shown in a dish-like configuration. On the underside there is an opening  33  to allow for an access to the electrical contacts  23  of the gas generator  20 . Through the opening  33  it is also possible to adjust the weight of the supplemental weight  30 , the greater the size of the opening  33 , the smaller is the weight of the supplemental weight  30  with otherwise constant dimensions. 
     A second opening  34  is configured in a lateral region at the upper edge of the supplemental weight  30 . Due to this second opening  34  an individual adaptation to the desired, supplemental weight is possible; likewise, the second opening  34  is used to pass a connection contact  14  at the accommodation device  11 . 
     The dish-like configuration of the supplemental weight  30  has a rim  35  on the upper, circumferential edge  31  extending up to the interruption resulting from the opening  34 . The rim  35  forms a positive-locking element, so that one or a plurality of attachment elements  13  can engage behind the rim  35 , so that a positive locking engagement takes place. The attachment elements  12 ,  13  can be configured inward in a resilient radial manner, so that due to the resilient restoring force in connection with the radially inward bent tab of the elongated attachment element  13 , a secure locking of the supplemental weight  30  both to the gas generator  20  and to the accommodation device  11  will take place. The inside of the supplemental weight  30  can advantageously be configured such that the underside of the gas generator  20  can be accommodated therein, preferentially of a perfectly fitting shape of the underside of the dish-like supplemental weight  30  matching the outside contour of the underside of the gas generator  20 , so that a compact design is obtained. The supplemental weight  30  will then rest with the entire surface against the underside of the gas generator  20 . 
     A variant of the invention is shown in  FIG. 2  in which the mounting  10  and the gas generator  20  correspond to the embodiment according to  FIG. 1 . A different configuration of the supplemental weight  30  is provided, in which the edge  31  is configured as a circumferential ring  36  located in a plane which is circumferentially uninterrupted, the ring also extending along the top side of the opening  34 , so that the opening  34  is configured as a window surrounded on all sides by the material of the supplemental weight  30 . Several such openings  34  in the form of a window can be distributed around the perimeter along the supplemental weight  30 . Likewise, in  FIG. 2  predefined break lines  37  are configured inside the supplemental weight  30  so that material can be more easily removed from the supplemental weight  30 . Preferentially the predefined break lines  37  advantageously define a material region which has a fixed weight, so that, starting from an initial total weight, an adaptation to the desired total weight is possible more easily by removing the respective region. For example, the regions inside the predefined break line  37  have a weight of 10 g or 20 g, so that a stepped reduction of the weight is possible by removing the proportionate amount of material. 
       FIG. 3  shows the assembled state of the apparatus for the damping of vibrations on a steering column or on a steering wheel. The mounting  10  with the four attachment openings  15  and the accommodation device  11  mounted on the elastomer element  16  is shown as seen from the underside. The gas generator  20  is inserted into the cavity of the ring-shaped accommodation device  11 . The attachment elements  12  rest against the outer perimeter of the gas generator  20 . The supplemental weight  30  rests upon the gas generator  20 ; this weight is defined by the tab-like attachment elements  13  which engage behind the outer edge  31  at the rim  35 . The attachment elements  13  can be configured either plastically deformable or elastically resilient in a radial inward direction. The opening  33  in the bottom region of the supplemental weight  30  allows for an access to the electrical contacts  23  of the gas generator  20 . There are two openings  34  positioned symmetrically opposite each other which are used for adapting the weight of the supplemental weight  30 . In the shown embodiment, the plug contact  14  is located outside of the supplemental weight  30 , that is, at the outer edge outside of the perimeter of the supplemental weight  30 . 
     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.