Abstract:
A curtain airbag for a motor vehicle includes an inflatable cushion and a protective sheet having an attachment edge attached to the airbag and a free-length extending from the attachment edge. The cushion formed into a folded condition from which it is deployable in a deployment direction, and the free-length of the sheet is positioned adjacent to the deployment direction of the cushion. The airbag is installed in the vehicle to deploy adjacent to a daylight opening of the vehicle. Deployment of the cushion during inflation causes the protective sheet to be drawn along with the cushion in the deployment direction so that the sheet overlays the outboard-facing side of the cushion (between the cushion and the daylight opening) and thereby provides a degree of protection against damage to the cushion that may be caused by, for example, broken window glass.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to curtain airbag systems used for occupant protection in motor vehicles. 
       BACKGROUND 
       [0002]    Curtain airbags are inflatable devices intended to protect occupants from injury during accidents such as side impacts or rollover events. Curtain airbags are generally located along the sides of the vehicles either above or below the side daylight openings and, when inflated, cover the interior (inboard) surfaces of the side windows, roof support pillars (A-, B-, and/or C-pillars, etc.), and adjacent portions of the vehicle side structure. 
         [0003]    During a accident involving a side impact it is possible for the side window panels to break. During vehicle safety testing that simulates the side of the vehicle striking a pole it has been found that the curtain airbag may be punctured if pieces of the broken window panel are forced against the curtain airbag by the pole during deployment of the curtain. 
         [0004]    It is possible to reduce the likelihood of such damage by constructing the airbag from a more puncture-resistant material. Such a material may, however, be thicker, heavier, and/or stiffer than materials more commonly-used in airbag cushions and thus may take up more space when folded for storage and/or may take longer to deploy. Also, if it is found during testing that only a relatively small portion of the airbag surface is prone to damage, it may be necessary to reinforce only these relatively small areas. 
       SUMMARY 
       [0005]    In a disclosed embodiment, a curtain airbag installed in a motor vehicle, comprises an inflatable cushion folded for deployment in a deployment direction adjacent to a daylight opening of the vehicle, and a protective sheet having an attachment edge secured to the airbag and/or to the vehicle at an outboard side of the folded cushion. A free-length of the sheet extending from the attachment edge is disposed adjacent to the deployment direction of the folded cushion. Deployment of the cushion during inflation causes the protective sheet to be drawn along with the cushion in the deployment direction so that the sheet overlays the outboard-facing side of the cushion to provide a degree of protection against damage to the cushion that may be caused by, for example, broken window glass. 
         [0006]    In a further embodiment, at least one attachment point on the attachment edge is co-located with a zero-length tether connecting an inboard panel and an outboard panel of the cushion. 
         [0007]    In a further embodiment, a distal end of the free-length is folded and positioned adjacent to the deployment direction of the folded cushion. 
         [0008]    In a further embodiment, the free-length is wrapped around the deployment direction of the cushion and positioned on an inboard side of the folded cushion. 
         [0009]    In a further embodiment, a distal end of the free-length is folded and positioned on the inboard side of the folded cushion. 
         [0010]    A method of folding a curtain airbag is also disclosed, the curtain comprising an inflatable cushion and a sheet having an attachment edge attached the airbag and/or to a vehicle. The method comprises folding the cushion into a folded condition from which it is deployable in a deployment direction, and subsequently positioning a free-length of the sheet extending from the attachment edge adjacent to the deployment direction of the cushion. Deployment of the cushion during inflation causes the protective sheet to be drawn along with the cushion in the deployment direction so that the sheet overlays the outboard-facing side of the cushion and thereby provides a degree of protection against damage to the cushion that may be caused by, for example, broken window glass. 
         [0011]    In a further embodiment of the method, the positioning step further comprises wrapping the free-length around the deployment direction of the folded cushion to position a portion of the free-length on a side of the folded cushion opposite from the attachment edge. 
         [0012]    In a further embodiment, the method further comprises folding the portion of the free-length positioned on the side of the folded cushion opposite from the attachment edge. 
         [0013]    In a further embodiment of the method, the positioning step further comprises folding a distal end of the free-length and wrapping an un-folded portion of the free-length around the deployment direction to position the folded distal end adjacent to a side of the stowed cushion opposite from the attachment edge. 
         [0014]    In a further embodiment of the method, the positioning step further comprises folding a portion of the free-length adjacent to the attachment edge and positioning the folded portion adjacent to a side of the folded cushion having the attachment edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Embodiments of the present invention described herein are recited with particularity in the appended claims. However, other features will become more apparent, and the embodiments may be best understood by referring to the following detailed description in conjunction with the accompanying drawings, in which: 
           [0016]      FIG. 1  is a schematic view of a vehicle interior including a multi-row curtain airbag; 
           [0017]      FIG. 2  is a schematic perspective view of a curtain airbag with a protective sheet; 
           [0018]      FIGS. 3A-3E  schematically show a sequence of steps in a method of folding a curtain airbag cushion and protective sheet; 
           [0019]      FIG. 4A  is a schematic cross-sectional view of a curtain airbag in a folded condition; 
           [0020]      FIG. 4B  is the airbag of  FIG. 3A  early in the inflation process; 
           [0021]      FIG. 4C  is the airbag of  FIGS. 4A and 4B  in a fully inflated condition; 
           [0022]      FIG. 5  is a schematic view showing an alternative embodiment of a curtain airbag with a protective sheet folded and stowed on the outboard side of the cushion; 
           [0023]      FIG. 6  is a schematic view showing a second alternative embodiment of a curtain airbag with a protective sheet folded and stowed in a different manner; and 
           [0024]      FIG. 7  is a schematic view showing a protective sheet secured between the airbag and the vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0026]      FIG. 1  schematically and generally shows a typical motor vehicle to include a side body structure  12  comprising front and rear doors  14 . The doors  14  have upper edges or sills  16  which define the lower edges of side daylight openings  18 . A roof rail  20  defines the upper edges of daylight openings  18 . Forward and rear edges are defined by roof support pillars such as A-pillar  22 , B-pillar  24 , and C-pillar  26 . 
         [0027]    Although the present figures depict a sedan-type vehicle having two seating rows (front and rear) and two doors on each side, the invention is also applicable to a vehicle having any number of seating rows and/or doors and/or daylight openings divided by pillars and/or fixed (non-opening) body panels (not shown). Also, while only the left side of the vehicle body structure is shown, but it is to be understood that the right side of the body structure is substantially identical. 
         [0028]    A front-row and a rear-row curtain airbag  30 ,  40  are shown in their fully inflated and deployed positions inside of the vehicle adjacent to side daylight openings  18 . As is well known in the art, curtain airbags are installed in the vehicle in a stowed (deflated and folded) condition (see  FIGS. 4-8 ) along edges of the daylight opening(s). In the depicted embodiment, airbags  30 ,  40  are installed along the upper edge of the daylight openings, adjacent to roof rail  20 . Front-row curtain airbag  30  may extend forward and downward along the A-pillar  22 , and/or rear-row curtain airbag  40  may extend rearward and downward along the C-pillar  26 . 
         [0029]    Front- and rear-row airbags  30 ,  40  are depicted as being separately inflatable, in which case they may be joined to one another by external tethers (not shown) at their adjacent edges, generally along B-pillar  24 . As is well known in the art, a single, multi-row airbag may also be used, without departing from the scope of the present invention. 
         [0030]    In some vehicles, such as those with retractable roofs (convertibles), it is known to install curtain airbags along the door sill  16  such that they deploy upward generally parallel to the daylight opening  18 . The present invention is not limited to a curtain airbag installed above the daylight opening and deploying downward. 
         [0031]      FIG. 2  shows front-row curtain airbag  30  removed from the vehicle and in an unfolded condition. Curtain airbag  30  comprises a cushion  42  having an outboard panel  44  and an inboard panel  46  (not visible in  FIG. 2 ) joined around their common periphery to form at least one inflatable, substantially gas-tight chamber. 
         [0032]    Curtain airbag  30  further comprises an inflator  52  supplying inflation gasses to the cushion  42 . Inflator  52  may comprise a compressed gas cylinder or a pyrotechnic device, as is well known in the art, and is in fluid connection with the cushion via one or more inflation tubes. Inflator  52  may be attached to the cushion  42  so that the airbag  30  may be fabricated as a unitary module that is installed in the vehicle during the vehicle assembly process. 
         [0033]    For purposes of clarity of description, cushion  42  is said to have an inflation edge  42   a  and a distal edge  42   b . The inflation edge  42   a  is defined as that edge at which inflation gasses enter the cushion and from which deployment of the bag propagates. Inflator  52  is located at the inflation edge  42   a  in the depicted embodiment, but this may not necessarily be the case in all vehicle installations. Distal edge  42   b  is defined as the edge generally opposite from inflation edge  42   a.    
         [0034]    The cushion&#39;s inboard and outboard panels  44 ,  46  may be joined by stitching (as generally indicated at  48 ) or any other appropriate technique (adhesive, heat bonding, one-piece woven construction, etc.). Panels  44 ,  46  are made from a flexible, substantially gas-impermeable material, such as a synthetic cloth (nylon or polyester, for example) coated with silicone, polyurethane, or other appropriate material, as is well known in the art. Panels  44 ,  46  may also be connected to one another at one or more locations within the periphery of the cushion by internal tethers  50 , as is well known in the art. Tethers  50  may be located to achieve a desired shape/thickness of the cushion  42  when inflated and/or to provide advantageous flow paths for the inflation gases. One or more of tethers  50  may comprise a “zero-length” tether, where the inboard and outboard panels of the cushion are stitched directly to one another. The stitching used to attach and/or form the tethers  50  is indicated using dashed lines. 
         [0035]    Curtain airbag  30  may further comprise one or more mounting tabs  53  used to secure the airbag to the vehicle structure (such as roof rail  20  and/or pillars  22 ,  24 ,  26 ). The curtain airbag  30  is usually installed behind vehicle interior trim components, which are not shown for clarity of illustration. During installation of the airbag  30 , it is electrically connected to the vehicle electrical system and/or a restraints control module (not shown) which controls activation during a detected crash event, as is well known in the occupant protection art. 
         [0036]    Airbag  30  further comprises a protective sheet  54  secured to the cushion  42  along an attachment edge  54   a  of the sheet. A free-length  54   b  of the sheet extending from the attachment edge is unrestrained relative to the cushion  42 . In the depicted embodiment of a downward-deploying curtain airbag, attachment edge  54   a  is generally adjacent to sheet&#39;s upper edge and the free-length  54   b  drapes downwardly toward a distal edge  54   c  of the sheet. 
         [0037]    Sheet  54  may be made of a fabric material similar to that used for the cushion  42 , but since the sheet does not have to hold gas pressure there is no need for the fabric to be treated with a gas-impermeable coating. Eliminating the coating may be expected to reduce the amount of friction or drag between sheet  54  and cushion  42 , and so result in less resistance to rapid deployment of the cushion. 
         [0038]    In the depicted embodiment, three attachment points  56  define the attachment edge  54   a . Attachment points  56  may, for example, comprise short lengths of stitching. To simplify fabrication of the airbag  30 , it may be advantageous to locate the attachment points  56  on non-inflated portions of the cushion  42 . For example, the depicted embodiment shows attachment points  56  coinciding with the tethers  50 . This placement of attachment points  56  is particularly advantageous in the case of zero-length tethers, since the cushion is not inflated at the zero-length tethers so that the stitching involved will not create any risk of gas leakage from the cushion when inflated. Alternatively or in addition, sheet  54  may be attached to a non-inflated portion of the cushion outside of the peripheral stitching  48 , or to some other portion of the airbag or vehicle, as further described below. 
         [0039]      FIGS. 3A-E  schematically depict a series of steps in folding curtain airbag  30  into a stowed condition for installation in a vehicle. Initially, as seen in  FIG. 3A , the cushion  42  is deflated and flattened and free-length  54   b  of sheet  54  is pulled away from the cushion. In  FIG. 3B , a lower portion of cushion  42  (at least the portion lower than the attachment edge  54   a  of the sheet) is folded using a technique that is commonly referred to in the airbag industry as an “outboard roll”: Beginning at the distal edge  42   b , the cushion is rolled in a spiral fashion toward the side of the curtain airbag  30  that will face the exterior (or outboard side) of the vehicle when the airbag is installed in the vehicle (counter-clockwise as viewed in the present figures). 
         [0040]    In  FIG. 3C , the remaining, unrolled portion of the cushion adjacent to inflation edge  42   a  is folded in an accordion or Z-shaped pattern. The thickness (vertical dimension, as viewed in the figures) of the Z-folded portion is exaggerated for clarity of illustration, as an actual curtain airbag is folded in a manner to be as compact as practical. Folding the curtain airbag  30  in the manner shown establishes a deployment direction D along which the deployment of the cushion  42  propagates during inflation, away from inflation edge  42   a.    
         [0041]    The nature and combination of steps used to fold the cushion  42  is not a limitation on the practice of the present invention, as many other folding techniques are well-known in the art. For example, the cushion  42  may be rolled toward the inboard side or the entire length may be Z-folded. Regardless of the folding steps employed, the folded curtain airbag has a deployment direction D. 
         [0042]    As shown in  FIGS. 3B and 3C , free-length  54   b  of the sheet  54  remains pulled away from the cushion  42  during the folding steps, so that the sheet is not folded along with the cushion. 
         [0043]    In  FIG. 3D , the lower portion of the free-length  54   b  is folded into, for example, a Z-shape indicated at  54   d . As with the folded cushion  42 , the thickness of the Z-folded portion  54   d  is exaggerated for clarity of illustration. The free-length  54   b  is then positioned adjacent to the surface of folded cushion  42  that faces in the deployment direction D, as shown in  FIG. 3E . Airbag  30  may be retained in the folded or stowed configuration shown by one or more temporary straps (not shown for clarity) that break or otherwise release the cushion  42  and sheet  54  during curtain deployment. 
         [0044]      FIG. 3E  also shows airbag  30  mounted to the roof rail  20  of a vehicle adjacent to side daylight opening  18  by, for example, threaded fasteners (not shown) passing through mounting tabs  53  and engaging the roof rail. For clarity of illustration, many well-known components or elements of a typical curtain airbag installation environment are omitted. For example, a headliner (not shown) and/or other interior components (not shown) may cover the airbag  30  so that it is not visible from within the vehicle. 
         [0045]    When installed in a vehicle, the stowed or folded (un-deployed) curtain airbag  30  has an outboard side OB oriented toward daylight opening  18  and an inboard side IB oriented toward the vehicle interior. It should be noted that the outboard OB and inboard IB and sides of the folded airbag  30  do not necessarily coincide with the outboard and inboard panels  44 ,  46  of the cushion. For example, the “outboard roll” folding technique illustrated herein results in the inboard panel  46  of the cushion  42  being exposed on the outside of the spiral roll, and thus being oriented toward both the inboard side IB, the outboard side OB (as well as toward the deployment direction D) of the folded cushion. 
         [0046]      FIG. 4A  schematically depicts an alternative configuration of a stowed curtain airbag  30  differing from that of  FIG. 3E  in that the free-length  54   b  of the sheet is wrapped around the deployment direction so that the Z-fold portion  54   d  is positioned adjacent to the inboard side IB of the folded cushion  42 . In this configuration, a portion of the free-length  54   b  between the attachment edge  54   a  and the Z-fold portion  54   d  is disposed adjacent to the deployment direction D. As with the  FIG. 3E  embodiment, the deployment direction D of the folded airbag is generally parallel to the plane of the daylight opening  18  and/or window pane  28 . The Z-folded portion  54   d  may be positioned anywhere between directly aligned with the deployment direction D (the six-o&#39;clock position relative to the airbag  30 , as in  FIG. 3E ) and extending clockwise around the airbag to a position adjacent to the roof rail  20   
         [0047]    In  FIG. 4B  curtain airbag  30  is shown in a partially inflated state in which the cushion  42  has begun to unfold downwardly in the deployment direction D. The upper, Z-folded portion of cushion  42  is substantially unfolded (inflated), and the spiral-rolled lower portion has just begun to unroll. The free-length  54   b  of sheet  54  is still wrapped around the lower portion of the unrolling cushion  42 , covering the inboard panel  46  that would otherwise be in direct contact with the window pane  28 . Sheet  54  therefore helps protect cushion  42  from being punctured or otherwise damaged during deployment of the cushion airbag by, for example, broken window glass. The sheet  54  causes only a minimal amount of resistance to deployment of cushion  42  and therefore does not significantly slow the deployment. 
         [0048]      FIG. 4C  shows the curtain airbag  30  in the fully deployed position wherein the sheet is  54  is disposed between the inflated cushion  42  and the daylight opening  18 . It may not be necessary for sheet  54  to cover the entire vertical extend of daylight opening  18 , as shown in  FIG. 4C . If testing or real-world experience indicates that only a portion of the length of the cushion  42  is prone to damage during deployment, protective sheet  54  may be sized and positioned accordingly to cover only that particular area. 
         [0049]      FIG. 5  depicts an alternative configuration of a folded curtain airbag  30  in which the lowermost end of free length  54   b  is passed or wrapped around the deployment direction D and a portion of the sheet is folded into a Z-fold  54   e  and packed adjacent to the outboard side OB of the folded cushion  42 . In this configuration, a portion of the free-length  54   b  between the distal edge  54   c  and the Z-folded portion  54   e  is disposed adjacent to the deployment direction D. 
         [0050]      FIG. 6  shows another alternative configuration of a folded curtain airbag  30  in which the distal end of the sheet  54  is rolled in a spiral fashion. The free-length  54   b  is then wrapped around the deployment direction D and the spiral-rolled portion  54   f  is positioned adjacent to the inboard side IB of the folded cushion  42 . In this configuration, a portion of the free-length  54   b  between the attachment edge  54   a  and the rolled portion  54   f  is disposed adjacent to the deployment direction D. The spiral-rolled portion  54   f  may alternatively be positioned adjacent to the deployment direction D, similar to the placement of the Z-fold portion  54   d  shown in  FIG. 3E . 
         [0051]    In all of the embodiments of  FIGS. 3 through 6 , at least a portion of the sheet free-length  54   b  is disposed adjacent to the deployment direction D of cushion  42 . This configuration causes the cushion  42 , as it unfolds during inflation, to draw the sheet  54  along with it in the deployment direction. The sheet  54  thus remains between the cushion  42  and the daylight opening  18  throughout the deployment sequence. 
         [0052]      FIG. 7  shows a further alternative embodiment of a curtain airbag  30  in which sheet  54  (rather than being secured to the cushion  42 ) is secured relative to the airbag  30  and to the vehicle by trapping its uppermost edge between the vehicle and the airbag itself during installation of the airbag into the vehicle. For example, sheet  54  may be trapped between airbag mounting tab(s)  53  and the roof rail  20  as shown. 
         [0053]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.