Patent Publication Number: US-2022227323-A1

Title: Driver airbag module and steering device comprising such a driver airbag module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of International Application No. PCT/EP2020/067647, filed Jun. 24, 2020, the disclosure of which is incorporated herein by reference in its entirety, and which claimed priority to German Patent Application No. 202019103552.8, filed Jun. 27, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a driver airbag module for installing on a steering device which can be rotated about a steering axis, comprising an inflatable airbag and a module housing with a housing axis which is substantially parallel to the steering axis which defines a receiving chamber for the folded airbag, the receiving chamber being delimited by a housing front wall which faces a vehicle occupant when the driver airbag module is installed, an opposing housing rear wall which is axially spaced therefrom as well as a housing lateral wall which extends between the housing front wall and the housing rear wall, the housing lateral wall having an opening section via which the airbag is unfolded when the driver airbag module is activated. Moreover, the disclosure also relates to a steering device, in particular a vehicle steering wheel, comprising such a driver airbag module. 
     BACKGROUND 
     Currently, driver-side front airbag modules for restraining occupants are usually accommodated in a steering wheel hub, wherein the airbag usually exits the module housing through a housing front wall facing the occupant and deploys toward the occupant when the module is activated. The hub region of the steering wheel located centrally in a field of view of a driver has been largely unused so far for ensuring an easy breaking of the housing front wall and a desired airbag deployment. 
     In the meantime, there have been intentions, however, to utilize a central hub region of the steering wheel for display and/or input devices, for example, such as a touchscreen. In DE 10 2017 120 770 A1, therefore already a generic driver airbag module is disclosed in which, in the event of module activation, the airbag exits the module housing through an outer face different from the front face, rather than through the front face facing the occupant. Consequently, in this case, a display and/or input device may be disposed on the front face of the airbag module. 
     New challenges are involved with a lateral exit of the airbag from the module housing, however, to safeguard a desired deployment of the airbag and, thus, a particularly efficient occupant protection. 
     Therefore, there is a need to provide a driver airbag module that allows for an airbag laterally exiting the module housing, but with the airbag showing a desired and hence a quick predefined and reliably reproducible deployment behavior. 
     SUMMARY 
     In accordance with the disclosure, a driver airbag module of the above-mentioned type is provided in which the housing front wall is inclined relative to the housing rear wall. In one exemplary arrangement, each of the housing front wall and/or the housing rear wall is configured to be substantially flat at least on the side facing the folded airbag package. When the driver airbag module is activated, in a receiving chamber of the module housing an increasing gas pressure is formed. The resulting deployment force of the airbag can be directed by inclination of the housing front wall relative to the housing rear wall with low effort specifically in a desired direction, and in one exemplary arrangement, in a direction to the opening section of the housing lateral wall, and can be intensified. This results in the airbag exiting the opening section of the airbag housing at an early stage and, consequently, in the airbag deploying particularly quickly. 
     In one exemplary arrangement, the receiving chamber for the folded airbag has its largest axial dimension in the area of the opening section of the housing lateral wall and has its smallest axial dimension at the housing lateral wall opposed to the opening section. When the airbag module is activated, the deployment force of the airbag is thus directed particularly efficiently toward the opening section. 
     According to one exemplary arrangement of the driver airbag module, the housing front wall is inclined relative to the housing rear wall by at least 10°, and in one exemplary arrangement by about 15° to 20°, with the housing rear wall extending substantially perpendicularly to the housing axis. An important direction of the airbag deployment force and, thus, a noticeable effect on the airbag deployment only starts at inclination angles from about 10°. Large inclination angles, on the other hand, result in an undesirably large space required, in particular in the axial direction, which is why the inclination angles are selected to be less than 40°, and in one exemplary arrangement, less than 30°. 
     On a side of the housing front wall remote from the folded airbag, a spacer for fastening a module cover or a display and/or input device is disposed. In one exemplary arrangement, the spacer is wedge-shaped to compensate, for example, for the inclination of the housing front wall and to achieve an optimum position for the display and/or input device and, resp., the module cover. In several configuration variants, the wedge angle of the spacer can be variably adjusted by the occupant to individually adapt the position of the display and/or input device. Further, a cavity for receiving electric components for the display and/or input device may be provided in the wedge-shaped spacer. 
     According to one exemplary arrangement of the driver airbag module, the opening section of the housing lateral wall is in the form of a pivoting door, and in one particular exemplary arrangement, wherein the door is pivoted on the housing rear wall side and is radially movable between a closing position and an open position on the housing front wall side. Such a door helps direct the airbag during deployment thereof in a desired main deployment direction, for example between a steering wheel hub and a steering wheel rim to the occupant. 
     In one exemplary arrangement, a housing front wall side door edge abuts on a door-side housing edge of the housing front wall, the door edge and/or the housing edge being rounded, in particular a rounding radius of the door or housing edge being at least 2 mm. In one exemplary arrangement, the rounding radius of the door is about 5 mm. With respect to the receiving chamber, the edges are rounded especially outwardly, i.e., away from the receiving chamber. In this way, the airbag is reliably prevented, with low effort, from being damaged when it exits the receiving chamber. 
     Further, the module housing may include a limit stop for the door of the housing lateral wall, the limit stop defining a maximum pivot angle of the door in its open position. Based on a closing position of the door, in one exemplary arrangement, the maximum pivot angle ranges from 30° to 60°. 
     For the rest, the disclosure also relates to a steering device, for example, a vehicle steering wheel, comprising a grip portion for manually operating the steering device which grip portion can be rotated about a steering axle, a hub portion which is disposed radially inwardly from the grip portion, and a spoke portion which interconnects the grip portion and the hub portion, wherein an afore-described driver airbag module is mounted on the hub portion of the steering device. 
     The hub portion may include, adjacent to the housing lateral wall of the driver airbag module, a steering device wall in which linear weakening zones extending especially along lateral edges of the door opposed in the circumferential direction are formed. In one exemplary arrangement, the steering device wall especially made from foamed plastic material extends, just as the housing lateral wall, substantially in the axial direction so that also the linear weakening zones are substantially axially aligned. 
     In one exemplary arrangement, the pivoting door is further adopts a maximum pivot angle in its open position and the grip portion is configured as_a peripheral steering wheel rim, wherein the lateral edges of the door opposed in the circumferential direction extend along a straight line and the maximum pivot angle is selected such that the two straight lines extend through the peripheral steering wheel rim. In one exemplary arrangement, each of the two straight lines can be tangent to the steering wheel rim in a contact point. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Further features and advantages of the disclosure will be evident from the following description of an exemplary arrangement with reference to the drawings, wherein: 
         FIG. 1  shows a section across a driver airbag module according to the disclosure in its closing position; 
         FIG. 2  shows a section across the driver airbag module according to  FIG. 1  in its open position; 
         FIG. 3  shows another section across the driver airbag module according to  FIG. 1  in its open position; 
         FIG. 4  shows a top view onto a steering device according to the disclosure comprising a driver airbag module according to the disclosure in its closing position; 
         FIG. 5  shows a section V-V across the steering device according to  FIG. 4 ; 
         FIG. 6  shows a section VI-VI across a hub region of the steering device according to  FIG. 5 ; 
         FIG. 7  shows a lateral view S of the steering device according to  FIG. 5 ; 
         FIG. 8  shows a top view onto the steering device according to  FIG. 4  comprising a driver airbag module according to the disclosure in its open position; and 
         FIG. 9  shows a section IX-IX across the steering device according to  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  illustrate a driver airbag module  10  for installing on a steering device  12  which can be rotated about a steering axis A (see, e.g.,  FIG. 5 ). The driver airbag module  10  comprises an inflatable airbag  14  and a module housing  16  having a housing axis B substantially parallel to the steering axis A which defines a receiving chamber  18  for the folded airbag  14 , wherein the receiving chamber  18  is delimited by a housing front wall  20  which faces a vehicle occupant when the driver airbag module  10  is installed, an opposing housing rear wall  22  which is axially spaced therefrom, and a peripheral housing lateral wall  24  which extends between the housing front wall  20  and the housing rear wall  22 , the housing lateral wall  24  including an opening section  26  via which the airbag  14  deploys when the driver airbag module  10  is activated. 
     The opening section  26  of the housing lateral wall  24  in the shown exemplary arrangement is configured as a pivoting door  28 , the door  28  being pivoted to the module housing  16  on the housing rear wall side and being radially movable, on the housing front wall side, between a closing position according to  FIG. 1  and an open position according to  FIGS. 2 and 3 . 
     Furthermore, the driver airbag module  10  comprises a gas generator  30  which is accommodated at least partially in the module housing  16  and inflates the folded airbag  14  when the driver airbag module  10  is activated. The door  28  is moved from its closing position to its open position by the gas pressure increasing when the generator is triggered and by the resulting increasing deployment force of the airbag  14  in the receiving chamber  18  so that the airbag  14  can exit the receiving chamber  18  via the opening section  26  and can deploy in the direction of an occupant. 
     In order to intensify the deployment force of the airbag  14  acting on the door  28  and thus to accelerate the opening of the door and the deployment of the airbag, the housing front wall  20  is inclined relative to the housing rear wall  22  so that the receiving chamber  18  for the folded airbag  14  in the area of the door  28  has its maximum axial dimension h max  and opposed to the door  28  has its minimum axial dimension h min . 
     In one exemplary arrangement, an inclination angle a between the substantially flat housing front wall  20  and the substantially flat housing rear wall  22  is at least 10°. In one exemplary arrangement, the inclination angle α is: 10°≤α≤30°. 
     A housing front wall side door edge  32  abuts, in the closing position of the door  28 , on a door-side housing edge  34  of the housing front wall  20 , wherein the edges may form a gap or may be in contact with each other. According to  FIG. 1 , both the door edge  32  and the housing edge  34  are rounded respectively outwardly, i.e., away from the receiving chamber  18 . A rounding radius amounts to at least 2 mm, and in one exemplary arrangement, about 5 mm. 
       FIG. 3  illustrates by way of example and schematically a door design of the driver airbag module  10 , the module housing  16  having a limit stop  36  for the door  28  of the housing lateral wall  24 . Based on the closing position of the door  28 , a maximum door pivot angle β is reached in the open position of the door  28  defined by the limit stop  36  and in one exemplary arrangement, ranges from 30° to 60°. 
       FIGS. 4 to 7  illustrate a steering device  12  for a vehicle comprising an afore-described driver airbag module  10  in its closing position. 
     The steering device  12  is concretely configured as a vehicle steering wheel and comprises a grip portion  38  for manually operating the steering device  12  which grip portion can be rotated about the steering axis A, a hub portion  40  which is disposed radially inwardly from the grip portion  38 , and a spoke portion  42  which interconnects the grip portion  38  and the hub portion  40 , the driver airbag module  10  being installed on the hub portion  40  of the steering device  12  in such a way that the housing rear wall  22  of the module housing  16  abuts on the hub portion  40 . 
     On a side of the housing front wall  20  remote from the folded airbag  14 , according to  FIG. 5  a wedge-shaped spacer  44  is disposed on which a display and/or input device  46  in the form of a touch screen is fastened in the shown exemplary arrangement. 
     The wedge-shaped spacer  44  in the present case compensates for the inclination of the housing front wall  20  so that the display and/or input device  46  extends substantially perpendicularly to the housing axis B, wherein generally any desired positioning of the display and/or input device  46  can be realized by the geometry of the spacer  44 . According to a specific exemplary arrangement of the driver airbag module  10 , the spacer is formed especially integrally with the housing front wall  20  of the module housing  16 . 
     The spacer  44  is configured to be sufficiently stable to prevent or at least minimize bending of the housing front wall  20  due to the gas pressure increasing in the receiving chamber  18  when the module is activated. Further, in the spacer  44  a cavity may be provided, for example for receiving electric components of the display and/or input device  46 . 
     In the shown exemplary arrangement, at least the spacer  44 , optionally also the display and/or input device  46 , is preassembled on the module housing  16  and is then fastened, together with the driver airbag module  10 , to the hub portion  40  of the steering device  12 . 
     Alternatively, it is also imaginable, as a matter of course, that the spacer  44  as well as the display and/or input device  46  are installed, only after fastening the driver airbag module  10  to the hub portion  40  of the steering device  12 , as separate components or as a group of components either on the module housing  16  or on the steering device  12 . 
       FIG. 6  shows a partial section VI-VI across the steering device  12  and illustrates that, adjacent to the housing lateral wall  24  of the driver airbag module  10 , the hub portion  40  includes a steering device wall  48  in which linear weakening zones  50  extending along lateral edges  52  of the door  28  opposed in the peripheral direction are formed. The housing lateral wall  24  of the driver airbag module  10  peripheral in the circumferential direction with respect to the housing axis B in this case has a rectangular cross-section with four substantially flat side wall portions, one of the side wall portions being configured as a pivoting door  28  and defining the opening section  26  of the module housing  16 . 
     In the shown exemplary arrangement, the steering device  12  includes a metal skeleton which is foam-wrapped, inter alia in the area of the grip portion  38 , with plastic material. Accordingly, also the steering device wall  48  may be a foamed wall made of the foamed plastic material and is directly formed integrally with the hub portion  40  of the steering device  12  during foam-wrapping of the metal skeleton. 
       FIGS. 8 and 9  show the steering device  12  according to  FIGS. 4 to 7  with the driver airbag module  10  in its open position. 
     The driver airbag module  10  installed on the hub portion  40  of the steering device  12  is positioned in a circumferential direction in such a way that the door  28  and, resp., the opening section  26  defined in this way in a neutral position of the steering device  12  for straight-ahead travel shown in  FIG. 8  is approximately in a “12 o&#39;clock position” (viz. at the top according to  FIG. 8 ). In the area about the  12  o′clock position, no spoke portions  42  are provided so that, when the module is activated, the airbag  14  can deploy unhindered between the hub portion  40  and the grip portion  38  in the direction of an occupant. 
     According to the present exemplary arrangement of the steering device  12 , the grip portion  38  is in the form of a peripheral steering wheel rim. In its open position according to  FIGS. 8 and 9 , the pivoting door  28  adopts the maximum pivot angle β, wherein each of the opposed lateral edges  52  of the door  28  extends along a straight line  54  and the maximum pivot angle β is selected such that the two straight lines  54  extend through the peripheral steering wheel rim and are tangent to the steering wheel rim especially in a contact point P. In this way, the inclined housing front wall  20  and the maximally pivoted door  28  help predefine a type of deployment channel for the airbag  14  which enables the airbag to deploy especially quickly and unhindered between the hub portion  40  and the grip portion  38  of the steering device  12  in the direction of the occupant. The module cover and, resp., the display and/or input device  46  remain fixed stationarily on the hub portion  40  of the steering device  12  when the module is activated and are covered by the airbag  14  when the airbag is completely deployed so as to prevent any contact with the occupant.