Abstract:
An airbag module including an inflatable airbag and an inflator configured to provide gas for inflating the airbag. The airbag includes a vent opening in a surface of the airbag to allow inflation gas to escape the airbag. A tether is aligned against the surface of the airbag adjacent the opening. The tether includes a first tether opening and wherein the tether is configured so that the first tether opening and the vent opening are aligned prior to the full deployment of the airbag. During deployment of the airbag the position of the tether changes so that the first tether opening and vent opening are no longer aligned.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/506,885 filed Jul. 12, 2011. The foregoing provisional patent application is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present application relates generally to the field of airbag systems. More specifically, the application relates to an airbag system including variable passive venting. 
     SUMMARY 
     According to an exemplary embodiment disclosed herein an airbag module includes an inflatable airbag and an inflator configured to provide gas for inflating the airbag. The airbag includes a vent opening in a surface of the airbag to allow inflation gas to escape the airbag. A tether is aligned against the surface of the airbag adjacent the opening. The tether a first tether opening and is configured so that the first tether opening and the vent opening are aligned prior to the full deployment of the airbag. During deployment of the airbag the position of the tether changes so that the first tether opening and vent opening are no longer aligned. 
     The tether may include a second tether opening that is aligned with the vent opening when the airbag is fully deployed. The second tether opening may be a different size than the first tether opening. The module may further include a tether guide layer positioned on the opposite side of the tether from the airbag opening to maintain the position of the tether against the surface of the airbag. The guide layer may include a third opening aligned with the vent opening. The size of the third opening is substantially the same as the size of the vent opening. 
     The tether includes first and second ends and, prior to deployment of the airbag, both the first and second ends may be connected to the airbag. During deployment of the airbag the first end may be configured to separate from the airbag. The tether may include a frangible portion that severs when the airbag deploys so that after the frangible portion severs, a portion of the tether containing the first tether opening has a free end not connected to the airbag. The tether may include a second opening that is aligned with the vent opening when the airbag is fully deployed. The second opening may be a different size than the first opening. The airbag may include a side panel extending substantially in a plane parallel to a direction of deployment of the airbag, and wherein the tether is connected to the side panel. The tether may be oriented in a direction transverse or parallel to the direction of deployment of the airbag. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below. 
         FIG. 1  is a perspective view of a passenger compartment of an exemplary motor vehicle. 
         FIG. 2  is a cross-car partial section view of a passenger-side airbag shown in a deployed or unfolded position supporting an occupant. 
         FIG. 3  is a side view of the passenger-side airbag of  FIG. 2  in a partially inflated state, according to an exemplary embodiment. 
         FIG. 4  is a side view of the passenger-side airbag of  FIG. 2  in a fully inflated state, according to an exemplary embodiment. 
         FIG. 5  is a plan view of several components of the passenger-side airbag of  FIG. 2 , according to an exemplary embodiment. 
         FIG. 6  is a side and front perspective view of an exemplary embodiment of a passenger-side airbag. 
     
    
    
     DESCRIPTION 
     The same or like reference numbers have been used throughout the drawings to refer to the same or like parts. Although the specification refers primarily to a front passenger-side airbag assembly, it should be understood that the subject matter herein is applicable to an airbag assembly in general. 
     For purposes of this disclosure, the term “coupled” means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components or the two components and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 
       FIG. 1-5  illustrate an airbag assembly  20 , for example a passenger-side airbag assembly  20 , for use within a motor vehicle  10 . As shown in  FIG. 1 , the vehicle  10  may be a typical sedan. Other types of passenger vehicles (e.g. truck, van, cross-over vehicle, etc.), as well as other moving vehicles that offer occupant protection to seated passengers in the form of frontal airbags (such as passenger-side airbags included in passenger-side airbag assemblies) may also be used. The passenger-side airbag assembly  20  may be used within the vehicle  10  to provide an occupant  12  with frontal protection during a vehicle dynamic event that triggers deployment of the airbag assembly  20 . 
     Referring to  FIG. 2 , the airbag assembly or module  20  may include an airbag  22  or airbag cushion  22 , an inflator  24  configured to provide gas to the airbag  22 , and a housing  26  configured to retain the inflator  24  and the airbag  22  in position. 
     Typically, deployment of the airbag  22  included in the passenger-side airbag assembly  20  is triggered by a dynamic impact of the vehicle  10 , whereby impact sensors communicate to a vehicle module or other device which communicates to the inflator  24  of the airbag assembly  20 . The inflator  24  generates inflation gas, which is then forced into the airbag cushion  22  of the passenger-side airbag assembly  20 . As the amount of inflation gas forced into the airbag cushion  22  of the passenger-side airbag assembly  20  increases, the internal chamber pressure of the airbag cushion  22  increases, allowing the airbag cushion  22  to breach the dashboard  14  (or other stored position), whereby the airbag cushion  22  deploys substantially outward (i.e., substantially perpendicular to the longitudinal or fore-aft axis of the vehicle) and rearward toward the occupant  12 . The airbag cushion  22  is formed of a suitable fabric, such as nylon. 
     The airbag  22  of the passenger-side airbag assembly  20  improves occupant safety by providing protection to the occupant  12  by limiting further passenger-side displacement of and by decelerating the occupant  12 . The airbag cushion  22  of the airbag assembly  20  also absorbs energy, such as kinetic energy, and the forces exerted by the occupant  12  when the vehicle accelerates or decelerates. The airbag cushion  22  absorbs energy from the occupant  12  that would otherwise be transferred to the occupant  12  through an impact to the dashboard  14  or other relatively rigid bodies within in the vehicle  10  interior. 
     As shown in  FIGS. 3-4 , the airbag cushion includes one or more vents  30  through which inflation gas is allowed to escape. The escape of the inflation gas allows the airbag cushion to deflate, facilitating the dissipation of the kinetic energy of the occupant  12  impacting the airbag cushion  22 . Airbags, such as airbag assembly  20 , are configured to be most effective when the occupant  12  is restrained in the vehicle by a safety device such as a safety belt  16  (e.g., an “in-position” situation). In an in-position situation, the airbag cushion  22  is allowed to fully inflate before the occupant  12  impacts the cushion  22 . The airbag cushion includes a boundary layer that retains the inflation gas. The boundary layer may be formed by one or more material panels. The panels may be formed by fabric. For example, in one disclosed embodiment the boundary layer may be formed by a pair of side panels and a main panel located therebetween. 
     However, in some scenarios, an occupant  12  may not be restrained and may be closer to the vehicle dash  14  or other structure during the vehicle crash (e.g., an “out-of-position” situation). In other scenarios, the vehicle  10  may be occupied by a child in a child safety seat. In either situation, the occupant  12  may impact the airbag cushion  22  as the cushion  22  is still inflating. In out of positions situations, it is desirable to limit the force of the airbag cushion deployment. Thus, in these situations it may be desirable to deploy the airbag cushion with a vent or vent openings open to allow inflation gas to escape the airbag and reduce the deployment force of the airbag. 
     According to an exemplary embodiment, the vent opening  30  includes a tether guide  32  and a tether  40  with at least two openings  42  and  44 . The vent  30  for airbag cushion  22  is configured to be a variable vent that allows a conventional rate of deflation if an occupant  12  impacts the airbag cushion  22  in an “in-position” situation and allows inflation gas to more easily escape the interior of the airbag cushion  22  to allow an increased rate of deflation if an occupant  12  impacts the airbag cushion  22  in an “out-of-position” situation. 
     The tether guide  32  is coupled along at least two sides  34  to a side panel  28  (see  FIG. 5 ) of the airbag cushion  22  to provide a passage (e.g., sleeve, slot, etc.) for the tether  40 . The tether guide  32  includes an opening  36 . The tether guide  32  is coupled to the side panel  28  such that the opening  36  is aligned with an opening  29  in the side panel  28 . According to an exemplary embodiment, tether guide  32  may be formed from a fabric similar to the fabric of the airbag cushion  22 . 
     The tether  40  is formed from a strip or panel of fabric and has a first end  45  and a second  46 . The first end  45  and the second end  46  are each coupled to the side panel  28  of the airbag cushion  22 . According to an exemplary embodiment, the first end  45  is coupled to side panel  28  by one or more frangible portions  48  (e.g., tear tabs, breakaways, etc.). 
     At least a portion of the tether  40  is provided between the tether guide  32  and the side panel  28  to restrain or control the position and movement of the tether  40 . According to an exemplary embodiment, the first end  45  is coupled to the side panel  28  under the tether guide  32  while the second end  46  extends beyond the tether guide  32 . In other exemplary embodiments, the first end  45  may extend beyond the tether guide  32  on a side opposite of the second end  46 . 
     The tether  40  includes at least two openings  42  and  44 . At various points in the inflation and deflation process for the airbag system  20 , the openings  42  and  44  are aligned with the opening  36  in the tether guide  32  and the opening  29  in the side panel  28  to provide an outlet passage for inflation gasses to escape the interior chamber of the airbag cushion  22 . The openings  42  and  44  are differently sized and/or shaped to provide varied areas for the outlet passage and therefore control the internal pressure, deflation rate and deployment force of the airbag cushion  22 . According to an exemplary embodiment, the first opening  42  has a diameter that is approximately equal to the diameters of the of the opening in the side panel  29  and the opening in the vent guide  36  and the second opening  44  has a diameter that is less than the diameters of the opening in the side panel  29  and the opening in the vent guide  36 . According to a particular exemplary embodiment, the first opening  42  has a diameter of approximately 65 mm. and the second opening  44  has a diameter of approximately 45 mm. In a preferred embodiment, the cross sectional area of the second opening  44  is about 60-75 percent of the cross-sectional area of the first opening  42 . 
     As shown in  FIG. 3 , with the cushion  22  in a partially inflated state, the tether  40  is not yet fully extended and the vent  30  is in a first configuration. In the partially inflated state shown in  FIG. 3 , the first opening  42  is aligned with the opening  36  in the tether guide  32  and the opening  29  in the side panel  28 . If the inflation of the cushion  22  is impeded (e.g., by the airbag cushion  22  striking an out-of-position occupant or a child seat, etc.), the relatively large outlet passage of the vent  30  allows the inflation gas to more easily escape the airbag cushion  22 . This reduces the internal pressure of the cushion  22  and reduces the force applied to an occupant striking the cushion  22  as it is inflating. 
     As shown in  FIG. 4 , as the cushion  22  continues to inflate, the second end  46  is pulled away from the first end  45 , until the first end  45  is decoupled from the side panel  28  by the tearing of the frangible portions  48 . With the first end  45  no longer coupled to the side panel  28 , the tether  40  can be pulled between the tether guide  32  and the side panel  28 . When the airbag cushion  22  is fully inflated, the smaller second opening  44  is aligned with the opening  36  in the tether guide  32  and the opening  29  in the side panel  28 . In this configuration, the second opening  44  decreases the size of the outlet passage of the vent  30  such that the cushion  22  has a relatively high internal pressure. The internal pressure of the cushion  22  with the vent  30  in the second configuration is high enough to reduce the likelihood that an in-position occupant  12  will be able collapsing the cushion  22  prematurely and impacting a rigid structure such as the dashboard  14 . 
     The variable nature of the vent  30  provides several advantages. The internal pressure of the cushion  22  at various points during deployment may be varied by changing the diameters of the openings  29 ,  36 ,  42 , and  44  or by providing more openings of various sizes and locations in the tether  40 . The vent  30  is a passive mechanism that does not require additional active components such as squibs. By decreasing the size of the outlet passage of the vent  30  later in the deployment process, the output of the inflator  24  may be reduced without increasing the likelihood of the occupant collapsing the airbag cushion  22  prematurely and impacting the dashboard  14 . 
     While only one variable vent  30  is described, the airbag cushion  22  may include more than one variable vent  30 . For instance, a vent  30  as described above may be provide for each of the side panels of the airbag cushion  22 . 
     In another exemplary embodiments, a variable vent similar to the vent  30  described may be used that initially provides a small outlet passage and later provides a larger outlet passage. The vent may be utilized to control the flow of gasses between the interior of the cushion  22  and the exterior or between sub-chambers in the cushion  22 . 
     As shown in  FIG. 6 , the tether  40  and tether guide  32  may be oriented in the direction of deployment of the airbag. The first end  45  of the tether may be connected to the side panel  28  or at a location adjacent the airbag inflator and vehicle mounting location for the airbag module. The tether guide  32  may be coupled along at least two sides  34  to the side panel  28 . The second end  46  of the tether may be coupled near the edge of the side panel  28  toward the occupant or directly to the main panel  26 . In such a configuration as shown in  FIG. 6 , the location of the occupant (e.g., an out of position occupant) may limit deployment of the airbag and tether and thereby control the position of the tether and the alignment of the openings, and thereby the venting of the airbag. 
     It is important to note that the construction and arrangement of the airbag as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosure herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments.