Abstract:
A front passenger airbag ( 5 ) is described for arrangement in the instrument panel ( 20 ) of a motor vehicle. It has an airbag envelope ( 10 ) having an impact area ( 11 ) and lateral surfaces extending from the impact area ( 11 ). In order to use small gas generators and to reduce the danger for a passenger in a non-standard seating position, the impact area ( 11 ) is nearly exclusively allocated to the front passenger&#39;s (I) head or head and shoulder area, the impact area ( 11 ) having a concave shape when the airbag envelope ( 10 ) is fully expanded and free of external forces, such that a left and right section of the impact area ( 11 ) respectively extend farther into the interior of the motor vehicle than a central section.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. 102009040118.0, filed Sep. 4, 2009, and PCT International Patent Application No. PCT/EP2010/005382, filed Sep. 2, 2010. 
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a front passenger airbag as well as to a motor vehicle with such a front passenger airbag. 
     BACKGROUND OF THE INVENTION 
     So-called front passenger airbags are common in automotive engineering and are used to protect the front passenger, namely in particular to protect his/her head in case of a head-on collision or a laterally displaced head-on collision. Such a front passenger airbag is arranged in the dash panel—mostly in an upper area—and deploys between the instrument panel windscreen and the passengers when a head-on impact is detected. 
     The airbag envelopes of the current front passenger airbags have been designed with a large volume and thus cover the entire upper area of the instrument panel in front of the passenger. As a result, they provide very good protection because the head as well as the chest can be restrained by the front passenger airbag. Besides this advantage provided by a large-volume front passenger airbag, there are, however, also many disadvantages: Owing to the large volume, a correspondingly large and powerful gas generator has to be used, meaning a relatively large weight which is obviously always undesirable. Furthermore, large-volume front passenger airbags have to deploy very quickly in order to attain their full deployment in a timely manner. Consequently, the front passenger gas bag can be dangerous for the passenger if he/she is not in the standard seating position. A great deal of effort is expended to solve this problem, as is apparent from the extensive patent literature published in this regard. 
     SUMMARY OF THE INVENTION 
     Proceeding from the foregoing, the object of the present invention is to further develop a front passenger airbag such that the disadvantages described above are eliminated, or at least reduced. 
     Tests have demonstrated that, in the case of a seat-belted passenger, the part of the airbag envelope of the passenger front airbag which is allocated to the chest area, in many vehicle geometries is much less important for the protection of the passengers than the part of the airbag envelope that is allocated to the head or head and shoulder area. The reason for that is that the pelvic segment of the safety belt usually holds the pelvis in its initial position, so that movement of the upper part of the passenger&#39;s body is basically a tilting movement around the pelvis after the activation of the belt force limiter in case of a head-on impact. The function of restraining the upper part of the body can be achieved by the design of the force limiter. Owing to the fact that the surface of the instrument panel is relatively far from the passenger&#39;s head/chest area the contribution of the restraining effect that is provided by the front passenger airbag for the chest area is frequently not enough, even when applying the belt force limiter. 
     In many countries, in particular in Europe, the rate of seat belt use, also by front passengers, is so high that a belted front passenger has to be assumed when designing the front passenger airbag. 
     According to the present invention, the impact area of the airbag envelope is therefore nearly exclusively allocated to the front passenger&#39;s head or head and shoulder area. The airbag envelope of the front passenger airbag can thus be configured such that it comprises a relatively small volume, preferentially namely a maximum of 50 liters, in particular preferentially 35 to 50 liters. A somewhat larger volume of the airbag of around 60 liters may also be necessary for special applications and requirements. This somewhat larger volume (which, however, is still smaller than that of a standard front passenger airbag) can be necessary in particular in the following cases: On the one hand, if the airbag module is arranged in the uppermost area of the instrument panel close to the windscreen (so-called top mount), and on the other hand, if the front airbag is intended to provide a high degree of lateral protection in case of a laterally displaced head-on collision. In order to provide good protection in case of a laterally displaced head-on collision, the impact area of the airbag envelope of the front passenger airbag has a concave shape when it is fully expanded such that a left and a right section of the impact area respectively extends farther into the interior of the motor vehicle than the central section. 
     As a result of the small volume of the airbag, the weight thereof is considerably reduced and the danger for a passenger who is out of his/her standard seating position is significantly reduced. 
     As has already been mentioned, the front passenger airbag according to the present invention only provides an ideal protection to belted passengers. Owing to the fact that in many countries, for example in Germany, the rate of seat belt use is very high, the advantages provided by the front passenger airbag according to the present invention, in particular with regard to out-of-position situations, can statistically outweigh the disadvantages related to accidents with unbelted passengers. 
     In order to virtually totally exclude accident situations with an unbelted passenger it is preferred that the front passenger airbag only be installed in motor vehicles with a warning system for an unbelted passenger. Such warning systems are known and produce an acoustic signal if a passenger is not belted. 
     Further details of the invention will now be explained in more detail in connection with several illustrative embodiments with reference to  FIGS. 1 to 13 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  shows a base pattern piece according to a first embodiment of the invention; 
         FIG. 2  shows a top pattern piece according to the first embodiment of the invention; 
         FIG. 3  shows a further pattern piece according to the first embodiment of the invention; 
         FIG. 4  shows a airbag envelope composed of the pattern pieces shown in  FIGS. 1 to 3  when it is fully expanded; 
         FIG. 5  shows a top view from the direction A of the airbag envelope from  FIG. 4 ; 
         FIG. 6  shows a schematic cut across a front area of a motor vehicle with a front passenger airbag whose airbag envelope is shown fully expanded; 
         FIG. 7  shows a top view from the direction B of what is shown in  FIG. 6 , but without vehicle seat or safety belt; 
         FIG. 8  shows the same as shown in  FIG. 6  with the passenger plunging into the airbag envelope of the front airbag; 
         FIG. 9  shows the same as shown in  FIG. 8  in an illustration corresponding to  FIG. 4 ; 
         FIG. 9   a  shows the same as shown in  FIG. 9  in case of a laterally displaced head-on collision; 
         FIGS. 10 to 13  show alternative embodiments of the further pattern piece; 
         FIGS. 14   a  to  14   e  show the production process of a second embodiment of an airbag envelope; 
         FIG. 15  shows two pattern pieces for a third embodiment of an airbag envelope; and 
         FIG. 16  shows the expanded airbag envelope assembled from the pattern pieces of  FIG. 15 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1-3  show the pattern pieces for the airbag envelope of a front passenger airbag.  FIG. 1  shows a base cut pattern  12 ,  FIG. 2  a top cut pattern  16  and  FIG. 3  another cut pattern  18 . The base cut pattern  12  and the top cut pattern  16  are congruent, with the exception that the base cut pattern  12  has a gas generator opening  14 . An outflow opening is normally provided which can be designed for example as an opening in the top cut pattern  16  (not shown). The base cut pattern  12  and the top cut pattern  16  have each a first forward protruding section  12   a ,  16   a , and a second forward protruding section  12   b ,  16   b . A concave edge  12   c  and respectively  16   c  extends between both these sections. The other cut pattern  18  is basically lens-shaped, that is, double convex with a lower edge  18   a  and an upper edge  18   b.    
     The just described three pattern pieces are sewn together such that the lower edge  18   a  of the other cut pattern  18  is sewn to the concave edge  12   c  of the base cut pattern  12  and the upper edge  18   b  of the other cut pattern  18  to the concave edge  16   c  of the top cut pattern  16 . The remaining edge sections of the base cut pattern  12  and of the top cut pattern  16  are sewn to one another so that the airbag envelope  10  is closed and encloses a gas chamber. Instead of sewing, other joining methods can obviously also be used, like, in particular, welding or gluing. 
       FIG. 4  shows the airbag envelope  10  of the front passenger airbag  5  in the finished sewn expanded state.  FIG. 5  shows a view from the direction A in  FIG. 4 . It is evident that the other cut pattern  18  is virtually identical to the impact area  11  and that the impact area has a concave shape such that in the mounted state a left section and a right section  11   b ,  11   c  of the impact area  11  extend farther into the interior of the motor vehicle than does a central section  11   a . It is further visible that, owing to the lens-shape of the other cut pattern  18 , the impact area has its maximal height in the center. The top and base pattern pieces  12 ,  16  form the lateral surfaces of the airbag envelope. 
       FIGS. 6 and 7  show an airbag envelope  10 , as has just been described, as a front passenger airbag  5  mounted in a fully expanded state on the instrument panel of a motor vehicle. It is evident that the base cut pattern  12  makes contact with the surface of the instrument panel  20  in sections, and that the airbag envelope  10  extends from there to the interior of the motor vehicle in the direction of the passenger I. The impact area  11  of the expanded airbag envelope is fully positioned above the instrument panel and thus also is exclusively allocated to the head of passenger I. 
     As is apparent from  FIG. 6 , the passenger to be protected is belted, namely by means of a safety belt  30  which has a shoulder section  32  and a pelvic section  34 . The shoulder section  32  and the pelvic section  34  are separated from one another by a seat belt tongue  36 . This seat belt tongue is preferentially configured such that it is blocked when a predetermined traction force is exceeded in the belt strap and thus uncouples the shoulder section and pelvic section of the safety belt from one another. Such a seat belt tongue is for example described in EP 1 983 857 B1 whose disclosure is hereby explicitly incorporated by reference. The length of the pelvic section consequently cannot be increased even upon the activation of the belt force limiter, so that retaining the pelvis in the desired position is improved. 
     In order to ensure that the passenger is belted, a detection system (not shown) is preferentially provided, which detects whether a passenger is sitting on the front passenger seat and produces a warning sound in case a passenger is detected who is not belted. 
       FIGS. 8 and 9  display the same as is shown in  FIGS. 6  and/or  7  when passenger I plunges into the airbag envelope  10 , namely into the impact area  11 . It is evident that the pelvis of passenger I basically does not shift, owing to the pelvic section  34  of the safety belt  30 , so that the upper part of the body of passenger I performs a tilting movement in the forward direction after the activation of the belt force limiter, the head being the foremost part of the upper part of the body and only this part being restrained by the front passenger airbag  5 . 
     Owing to the concave shape of the impact area  11 , the passenger&#39;s head is safely restrained even if it does not exactly meet the center of the impact area, as can be seen in  FIG. 9   a.    
       FIGS. 10 to 13  show different alternative shapes for the other cut pattern  18 . As is apparent in particular from  FIGS. 10 and 11 , the other cut pattern  18  can have lateral areas  18 ,  18 ″ which do not correspond to impact areas but are basically parallel to the longitudinal direction of the vehicle when the airbag envelope is expanded, and thus form a part of the lateral areas of the airbag envelope. 
       FIGS. 12 and 13  show that the other cut pattern can have strong contours, and consequently a particularly good adaptation to the shape of the instrument panel surface is achieved. 
       FIGS. 14   a  to  14   e  show a second embodiment of an airbag envelope which is based on the production process thereof. This airbag envelope also consists of three pattern pieces ( FIG. 14   a ), two pattern pieces  41 ,  42  being congruent, however not the base and top pattern pieces but rather the left and right pattern pieces. Both pattern pieces  41 ,  42  are configured congruent in a kind of horseshoe-shape, and have one indentation each. The third cut pattern  43  is round in the shown exemplary embodiment. 
     Both first pattern pieces  41 ,  42  are first placed next to one another such that the indentations form a circular recess and the first cut pattern  41  overlaps the second cut pattern  42  in sections. Covered lines are shown as dashed lines. Both first pattern pieces are joined to one another in this state by means of the first seams  45 . These first seams shown as dot-dashed lines are shear seams ( FIG. 14   b ). 
     The circular recess is now closed by means of the third cut pattern  43  and sewn by means of the second seam  46 . This seam is likewise a shear seam and is shown as a dot-dashed line. It is, however, also possible to configure this seam as a peel seam ( FIG. 14   c ). 
     The now created work piece is folded along the folding lines (shown as dotted lines)  49  shown in  FIG. 14   c  ( FIG. 14   d ) and closed by means of the third seam  47  (shown in a dot-dot-dash pattern) at the edges ( FIG. 14   e ). The impact area  11  thus obtains the desired concave shape with the left section  11   b , the right section  11   c  and the central section  11   a .  FIG. 14   a  is a top view. 
       FIGS. 15 and 16  show a third embodiment of an airbag envelope. It consists of two pattern pieces, which are designated as fourth and fifth pattern pieces  51 ,  52 , and, as in the first embodiment, are top and base pattern pieces. The pattern pieces are not congruent, but the respective front edge  51   c ,  52   c  is concave in the fourth cut pattern  51  and corrugated in the fifth cut pattern  52 . These pattern pieces also have forward protruding sections  51   a ,  51   b ;  52   a ,  52   b . Both pattern pieces are joined all around, by sewing, for example. A concave impact area  11  results in the expanded state, as indicated in  FIG. 16 . 
     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.