Patent Publication Number: US-2022227329-A1

Title: Front airbag

Description:
TECHNICAL FIELD 
     The invention relates to a front airbag and to a vehicle comprising a front airbag. 
     BACKGROUND 
     Front airbags in vehicle occupant restraint systems serve for the protection of the occupants seated on the front seats of a vehicle and cushion the occupant in the event of an abrupt vehicle deceleration. Front airbags are known for airbag modules in the steering wheel and on the passenger side, for example in an instrument panel there. 
     A front face of the front airbag is usually configured as a baffle surface which cushions the occupant. The arrangement of the baffle surface is usually optimized for a pure frontal impact without any lateral force component. The front airbag is intended, however, to offer proper protection for the occupant even for others types of a collision, of course. 
     A front airbag having an improved restraining effect is known from DE 10 2016 113 254 A1, for example. This front airbag has an internal tether which is guided starting from the rear wall of the airbag remote from the occupant to the front wall of the airbag. On the rear wall, the tether is fastened relatively centrally in the vicinity of the inflation orifice. Closely to the front wall serving as baffle surface, the tether divides into two sections stitched with the front wall. 
     SUMMARY 
     It is the object of the invention to provide a front airbag that offers an improved restraining effect in particular in the case of a laterally offset frontal impact and has a simple constructional design, in particular can be easily manufactured. 
     This object is achieved by a front airbag comprising the features of claim  1 . The front airbag includes an inflatable chamber which has a baffle surface provided to cushion an occupant to be restrained. There is provided a tether extending inside the inflatable chamber, the tether extending, when the front airbag is mounted on the vehicle and is inflated, obliquely with respect to a vehicle longitudinal direction and being fastened with a first longitudinal end to a single baffle surface-side fastening point on the baffle surface. 
     In the event of an offset or inclined impact, the tether produces a torque which partially counteracts inadvertent rotation of the head of the occupant when the latter impacts on the baffle surface. This results in less angular acceleration and less angular speed of the head. 
     The lateral component of the head movement results in an imbalance of the fabric tensions on both sides of the head. This entails a torque. An additional compensating torque is produced by adding the tether in the impacting area of the head. 
     In the inflated state of the front airbag, the tether forms a small trough in the baffle surface, which results in a more uniform contact of the head of the occupant in the vehicle transverse direction on both sides of the tether. 
     The baffle surface-side fastening point of the tether is preferably located, when the front airbag is mounted on the vehicle and is inflated, in a central area of the baffle surface with respect to a vehicle transverse direction. In this way, a rotation of the occupant&#39;s head can be reduced. 
     Moreover, the baffle surface-side fastening point should be disposed at an upper area of the baffle surface provided for an impact of the occupant&#39;s head. In the ideal case, the fastening point of the tether is located directly at the point where the occupant&#39;s head is cushioned by the baffle surface. 
     In this application, the baffle surface is understood to be a section of a wall of the front airbag. An outer face of the baffle surface faces the occupant, while an oppositely directed inner face points into the inflatable chamber. The tether is fixed, for example sewn with the wall, from the inside. 
     Laterally acting forces can be compensated particularly well when the tether extends as closely as possible to the transverse direction of the vehicle across the chamber of the front airbag. Of preference, the tether therefore encloses, when the front airbag is mounted on the vehicle and is inflated, an angle ranging from 50° to 80°, in particular from 60° to 70°, with the vehicle longitudinal direction. 
     A second longitudinal end of the tether is preferably fastened to a lateral wall of the front airbag to realize an as large angle of the tether as possible with the vehicle longitudinal direction. It has turned out to be sufficient to provide only one single fastening point on the wall of the front airbag for the second longitudinal end of the tether. However, the fastening point of the second longitudinal end of the tether should be away from the baffle surface in an area in which the occupant usually does not come into contact with the front airbag. 
     Thus, in the inflated state of the front airbag, the fastening point of the second longitudinal end of the tether is also preferably located at a distance from an inflation orifice of the front airbag or a housing of an airbag module which accommodates the front airbag in the folded state. 
     It has turned out to be advantageous when the tether extends at least approximately in parallel to a vehicle vertical direction and extends to be inclined in a plane spanned by the longitudinal direction and the transverse direction of the vehicle. In this way, the forces introduced by the impact of the occupant&#39;s head into the front airbag can be absorbed not only punctually but over a larger distance by the tether, thus improving the restraining effect. 
     The fastening point at each of the two longitudinal ends of the tether preferably extends over the entire height of the tether so that both longitudinal ends are tightly connected to the wall of the front airbag over said entire distance. 
     A dimension of the tether along the vehicle vertical direction is larger than 20 cm and is preferably larger than an average height of an occupant&#39;s head, for example, and may range from about 20 cm to 40 cm, for example. 
     The tether is made from the same fabric, for example, that is also used for the wall of the front airbag, and is then flexible but not elastic. 
     As a rule, the tether remains tightly connected to the front airbag during the entire restraining operation at the entire expansion of its fastening points and preferably does not change its length, either. 
     The invention also relates to a vehicle comprising an afore-described front airbag. During normal driving, the front airbag is preferably accommodated, as conventionally known, in a housing of an airbag module. The airbag module is usually disposed in the front area of a passenger compartment and may be mounted in a steering wheel or in an instrument panel, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be described in detail by way of an embodiment with reference to the attached figures, wherein: 
         FIG. 1  shows a schematic sectional view of a front airbag according to the invention in the fully inflated state in a plane spanned by the longitudinal direction and the transverse direction of a vehicle; and 
         FIG. 2  shows a schematic top view of the front airbag from  FIG. 1  in the fully inflated and vehicle-mounted state. 
     
    
    
     DESCRIPTION 
     The Figures illustrate a front airbag  10  which is mounted as passenger or driver airbag in a vehicle  12  schematically indicated in  FIG. 2 . Both Figures illustrate the front airbag  10  in the completely inflated state. In  FIG. 2 , the front airbag  10  is shown in the position mounted on the vehicle  12  which the front airbag  10  adopts in a situation of restraint shortly before or while an occupant  14  immerses into the front airbag  10 . 
     On its side directed to the occupant  14 , the inflated front airbag  10  has a baffle surface  16  provided for contacting the occupant  14 . 
     In the embodiment shown here, the front airbag  10  is made of a single inflatable chamber  18  that is delimited by an airbag wall  20  made from a known flexible airbag fabric. The baffle surface  16  is part of the wall  20 . 
       FIG. 1  illustrates a section across the front airbag  10  along a plane that is spanned by a longitudinal direction L and a transverse direction Q of the vehicle  12 . As is evident from the drawing, the baffle surface  16  extends in the area in which a head  22  of the occupant  14  impacts on the front airbag  10  approximately in parallel to the transverse direction Q. 
     A vehicle vertical direction H is perpendicular to the longitudinal direction L and the transverse direction Q. The baffle surface  16  has such a large expansion along the vehicle vertical direction H that it extends at least from a torso  24  to above the head  22  of the occupant  14 . 
     The baffle surface  16  is approximately opposed to an inflation orifice  26  through which filling gas is introduced to the front airbag  10 , if the latter is to be inflated in a situation of restraint (see  FIG. 1 ). The front airbag  10  is fastened to the inflation orifice  26  in an airbag module (not shown) that is mounted affixed to the vehicle, for example in an instrument panel or a steering wheel of the vehicle  12 . 
     Inside the inflatable chamber  18 , a tether  28  extending from a baffle surface-side fastening point  30  to a wall-side fastening point  32  is disposed. 
     A first longitudinal end  34  of the tether  28  is tightly fastened, such as stitched, to the baffle surface-side fastening point  30  at the inside of the baffle surface  16 . 
     Based on the vehicle transverse direction Q, the baffle surface-side fastening point  30  is located approximately in the middle of the baffle surface  16  here. 
     A second longitudinal end  36  of the tether  28  is tightly fastened, for example also by stitching, to the wall-side fastening point  32  on a lateral wall  37  that is part of the wall  20  of the front airbag  10 . The lateral wall  37  in this case extends from an edge of the baffle surface  16  to the inflation orifice  26 . In this case, the wall-side fastening point  32  is located definitely at a distance from the inflation orifice  26 , however. 
     In the top view along the vehicle vertical direction H, the tether  28  extends obliquely with respect to the longitudinal direction L and the transverse direction Q. An as large angle a as possible with the longitudinal direction L is selected which ranges from 50° to 80° and especially from 50° to 70°, for example. 
     The length of the tether  28  is dimensioned so that the tether  28  is tensioned in the inflated front airbag  10  so strongly that a small trough  38  is formed in the baffle surface  16  at the first fastening point  30 . 
     The tether  28  extends into the image plane of the Figures along the vehicle vertical direction H over a distance of about more than 20 cm to 40 cm and especially over a distance that is larger than the height of the head  22  of the occupant  14 . 
     As a matter of course, the tether  28  could also be inclined by several degrees vis-à-vis the vehicle vertical direction H without its function being impaired. 
     Both the baffle surface-side fastening point  30  and the wall-side fastening point  32  extend over the entire height of the tether  28  along the vehicle vertical direction H. 
     The tether  28  in this case extends along the vehicle vertical direction H mainly in the area where the head  22  of the occupant  14  (standardized to the head of a standard dummy) impacts on the baffle surface  16 . 
     At the first fastening point  30 , the tether  28  exerts a force with a lateral component upon the baffle surface  16 . This results in a lateral force acting on the head  22  when the latter impacts on the baffle surface  16  so that a rotation of the head  22  of the occupant  14  is reduced, if a laterally offset impact which entails a force component in the transverse direction Q upon the vehicle  12  occurs in a situation of restraint. 
     During the entire situation of restraint, the tether  28  always remains tightly connected to the baffle surface  16  and the wall  20  at both fastening points  30 ,  32  and does not change its position.