Abstract:
An airbag assembly for a motor vehicle includes an inflator and a curtain airbag securable to a body structure of the motor vehicle. The airbag includes two or more deployment tubes and two or more inflatable chambers. Vents connect the deployment chambers with the inflatable chambers. Gasses from the inflator pass first into the deployment tubes to rapidly inflate them to vertically extending positions and draw the airbag over a window opening. The gasses then pass through the vents into the inflatable chambers to complete the deployment of the curtain airbag. The rapid inflation and deployment of the deployment chambers provides cushioning for an occupant&#39;s head early in a crash event, followed by the inflation of the inflatable chambers to provide additional head protection and increasing the resistance of the curtain airbag to ejection through the underlying window apertures.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to GB 1020629.0 filed Dec. 6, 2010 and to GB 1110582.2 filed Jun. 22, 2011, which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     This invention relates to curtain airbag assemblies used for occupant protection in motor vehicles. 
     BACKGROUND 
     It is well known to provide a motor vehicle with a curtain airbag to protect an occupant of the motor vehicle from injury during an accident. 
     To achieve rapid inflation of such curtain airbags, a very large inflator may be required. Such large inflators are difficult to package on a vehicle and are so undesirable. Furthermore the curtain airbag is easily distorted during inflation and so it is possible for it to be pushed out through the window aperture if impacted against before full operating pressure is reached within the airbag. 
     SUMMARY 
     According to a first disclosed embodiment, a curtain airbag for occupant protection in a motor vehicle has an upper edge securable to a body structure of the motor vehicle and comprises at least one deployment tube receiving gasses from an inflator; at least one inflatable chamber; and a vent opening connecting the deployment tube(s) with the inflatable chamber(s) and through which the gasses flow from the deployment tube(s) into the inflatable chamber(s) during deployment of the curtain airbag. 
     Each deployment tube may extend substantially vertically down from the upper edge of the curtain airbag when the curtain airbag is fully deployed. 
     Each deployment tube may extend from the upper edge of the curtain airbag towards a lower edge of the curtain airbag for substantially the entire length of the curtain airbag. 
     The total volume of the deployment tubes may be relatively small compared to the combined total volume of the deployment tubes and the inflatable chambers, thereby reducing the time required to deploy the curtain airbag. 
     At least one deployment tube may include one or more vents for supplying gas to at least one inflatable chamber. 
     The one or more vents may supply gas to a bottom end of the at least one inflatable chamber. 
     Each inflator may be connected to the curtain airbag via a manifold having a separate output for each deployment tube. 
     According to an embodiment, an airbag assembly for a motor vehicle comprises an inflator and a curtain airbag. The curtain airbag has an upper edge securable to a body structure of the motor vehicle, at least one deployment tube receiving gasses from the inflator, at least one inflatable chamber, and vents connecting the deployment chambers with the inflatable chambers. The gasses from the inflator pass first into the deployment tubes to inflate them to their vertically extending positions, then pass through the vents into the inflatable chambers to complete the deployment of the curtain airbag. 
     According to an embodiment, the curtain airbag may have two inflatable chambers and each of the chambers may be bounded on both sides by a respective deployment tube, an inflator has a manifold with a first outlet for supplying gas to a first deployment tube located at one end of the airbag, a second outlet for supplying gas to a second deployment tube located at an opposite end of the airbag, a third outlet for supplying gas to a third deployment tube located between the two inflatable chambers, a fourth outlet tube for supplying gas to one of the two inflatable chambers and a fifth outlet for supplying gas to the other of the two inflatable chambers. 
     According to an embodiment the assembly may have a first inflator for providing gas to first and second deployment tubes, a second inflator for supplying gas to third, fourth and fifth deployment tubes and each of the deployment tubes may be partially surrounded by a respective inflatable chamber. 
     In an embodiment, each inflatable chamber may be shaped so as to form a number of fingers that interleave with the fingers on the adjacent inflatable chamber when the inflatable chambers are inflated. 
     Each of the deployment tubes may be shaped so as to provide a large head protection area and a small inflation volume. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying drawing of which:— 
         FIG. 1  is a partial side view of a right hand side of a motor vehicle having a curtain airbag assembly according to a first embodiment of the invention showing the airbag assembly in a stowed state prior to deployment; 
         FIG. 2  is a view similar to  FIG. 1  but showing an airbag forming part of the airbag assembly in a deployed state; 
         FIG. 3  is an enlarged view of an inflator and manifold forming part of the airbag assembly; 
         FIG. 4  is a scrap cross-section along the line  4 - 4  on  FIG. 2  through a deployment tube forming part of the airbag showing the deployment tube in a fully inflated condition; 
         FIG. 5  is a scrap side view of the high pressure deployment tube shown in  FIG. 4  at the commencement of inflation; and 
         FIG. 6  is a side view of a curtain airbag assembly according to a second embodiment of the invention showing the airbag curtain in a deployed state. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     With reference to  FIG. 1  there is shown part of the right hand side of a motor vehicle  5  as viewed from a passenger compartment of the motor vehicle  5 . The motor vehicle  5  has a body structure  6  including a side wall  6 W having three structural members in the form of an A-post  8 A, a B-post  8 B and a C-post  8 C. The side wall  6 W has two window apertures  7 A and  7 B formed therein. A storage compartment  9  for a curtain airbag  30  is disposed at the top of the side wall  6 W for stowing the curtain airbag  30  prior to deployment. 
     Referring now to  FIGS. 2 to 5  a curtain airbag assembly  50  includes the curtain airbag  30 . The curtain airbag  30  has an upper edge  36 , a lower edge  37 , a front edge  38  and a rear edge  39 . When deployed the curtain airbag  30  has a width “W” and a length “L” (as shown on  FIG. 2 ). 
     The curtain airbag  30  includes first and second inflatable chambers  31 ,  32  and first, second and third deployment tubes  33 ,  34  and  35 . The deployment tubes  33 ,  34 ,  35  are formed as an integral part of the curtain airbag  30  and are defined by columns of stitching  52  that sealingly separate the deployment tubes  33 ,  34 ,  35  from the inflatable chambers  31 ,  32 .  FIG. 4  shows two columns of stitching  52  defining the third deployment tube  35 . 
     Each of the inflatable deployment tubes  33 ,  34 ,  35  is of a small internal volume compared to the two inflatable chambers  31 ,  32 . In one example, the volume of each of the deployment tubes  33 ,  34 ,  35  was 2% of the volume of the inflatable chamber  31  and the inflatable chamber  32  was of substantially the same volume as the inflatable chamber  31 . 
     It will however be appreciated that in other embodiments the two inflatable chambers  31 ,  32  could be of differing volume or there could be more or less than two inflatable chambers. However, in all cases, the volume of each deployment tube  33 ,  34 ,  35  is considerably smaller than any of the inflatable chambers of the curtain airbag thereby permitting it to be rapidly inflated during deployment of the curtain airbag  30 . 
     Each of the deployment tubes  33 ,  34 ,  35  extends for substantially the entire vertical length of the curtain airbag  30 . Each of the deployment tubes  33 ,  34 ,  35  extends when the curtain airbag  30  is deployed substantially vertically from a position close to the upper edge  36  of the curtain airbag  30  to a position close to the lower edge  37  of the curtain airbag  30 . 
     An inflator  21  is provided as part of the airbag assembly  50  to inflate the curtain airbag  30  so as to deploy it. The inflator  21  is controlled by an electronic controller (not shown) in accordance with parameters stored in the controller and inputs received by the controller from sensors (not shown) located on the motor vehicle  5  as is well known in the art. 
     The inflator  21  is connected to a manifold  22  having a number of small cross-sectional area outlets  23 ,  24 ,  25 ,  26  and  27 . Because of the very high pressure developed in the inflator  21 , the flow rate from the outlets  23 ,  24 ,  25 ,  26  and  27  is sufficient to produce the desired inflation, yet when the curtain airbag  30  is collapsing following the exhaustion of the inflator  21  the small cross-section area provides a significant resistance to flow of the relatively low pressure gas of (approx 1.0 Bar) from the inflatable chambers  31 ,  32 . The provision of the small cross-sectional area outlets therefore acts as a virtual two-way valve allowing flow into the chambers during inflation yet restricting flow out of the chambers during deflation. The outlets  23 ,  24 ,  25 ,  26  and  27  are connected to the two inflatable chambers  31 ,  32  and to the three deployment tubes  33 ,  34 ,  35  in the following manner. 
     The outlet  23  is connected to the first deployment tube  33  located near to the front edge  38  of the curtain airbag  30  and is arranged to provide a gas flow “A” (see  FIG. 3 ) to the respective deployment tube  33  when the curtain airbag  30  is being deployed. 
     The outlet  24  is connected to the second deployment tube  34  located near to the rear edge  39  of the curtain airbag  30  and is arranged to provide a gas flow “D” to the respective deployment tube  33  when the curtain airbag  30  is being deployed. 
     The outlet  25  is connected to the third deployment tube  35  located between the two inflatable chambers  31 ,  32  and is arranged to provide a gas flow “F” to the respective deployment tube  35  when the curtain airbag  30  is being deployed. 
     The outlet  26  is connected to the first inflatable chamber  31  located towards the front of the curtain airbag  30  and is arranged to provide a gas flow “B” to the first chamber  31  when the curtain airbag  30  is being deployed. 
     The outlet  27  is connected to the second inflatable chamber  32  located towards the rear of the curtain airbag  30  and is arranged to provide a gas flow “C” to the second inflatable chamber  32  when the curtain airbag  30  is being deployed. 
     The cross-sectional area of the outlets  23  to  27  could be identical or they could of differing cross-sectional area so as to provide differing flow rates “A” to “F”. 
     In  FIG. 5  the curtain airbag  30  is showed in a rolled up stowed state just after inflation has commenced and the third deployment tube  35  is beginning to inflate. It will be appreciate that the curtain airbag  30  could be folded rather than being rolled up in its stowed state. 
     Operation of the airbag assembly is as follows: When the inflator  21  receives a command to inflate the curtain airbag  30  it begins to produce gas that flows into the manifold  22  and then out via the outlets  26 ,  27 ;  23 ,  24 ,  25  to the inflatable chambers  31 ,  32  and to the deployment tubes  33 ,  34 ,  35  respectively. Because the deployment tubes  33 ,  34 ,  35  are of a relatively small volume the initial gas flow will rapidly inflate them, causing them to straighten from their stowed positions thereby pulling the rest of the curtain airbag  30  into position before the inflation of the inflatable chambers  31 ,  32  has completed. The gas continues to flow thereby inflating the inflatable chambers  31 ,  32  which have been correctly pre-positioned by the deployment tubes  33 ,  34 ,  35  to overlie the window apertures  7 A,  7 B. 
     Therefore, unlike a conventional curtain airbag, the time taken to locate the curtain airbag  30  in position is not determined by the time taken to fill the relatively large volume inflatable chambers  31 ,  32 , but rather is dictated by the time taken to inflate the deployment tubes  33 ,  34 ,  35  which assist the deployment of the curtain airbag  30  by rapidly pulling it into position as they unfold. 
     One advantage of the invention is that a smaller inflator can be used compared to a conventional curtain airbag because the filling time of the two inflatable chambers  31 ,  32  does not determine the time taken to position the curtain airbag  30  unlike a conventional curtain airbag. 
     A further advantage can be obtained if the pressure in the deployment tubes  33 ,  34 , is arranged to remain high during the time period that the curtain airbag  30  is deployed. In such a case, the deployment tubes  33 ,  34 ,  35  act as stiffening members that can prevent undue distortion of the curtain airbag  30  and reduce the possibility of part of the curtain airbag being extruded out through one of the window apertures  7 A,  7 B. The deployment tubes  33 ,  34 ,  35  therefore are able to stabilize the curtain airbag  30  and help to maintain it in position. 
     Another advantageous arrangement is to provide one or more vents in one or more of the deployment tubes  33 ,  34 ,  35 . The vent or vents (not shown) are located near to the lower edge  37  of the curtain airbag  30 . As the deployment tubes  33 ,  34 ,  35  approach their fully deployed positions the unfolding or unrolling of the material forming the deployment tubes  33 ,  34 ,  35  reveals or uncovers the vent or vents thereby allowing gas to flow from the respective deployment tube  33 ,  34 ,  35  into an adjacent inflatable chamber  31 ,  32 . This has the effect of increasing the speed of filling of the inflatable chambers  31 ,  32  after the curtain airbag  30  has been positioned by the initial filling of the deployment tubes  33 ,  34 ,  35 . Such an arrangement allows the inflatable chambers  31 ,  32  to be filled from the top via the manifold  22  and the outlets  26 ,  27  and from the bottom via one or more vents in one or more of the deployment tubes  33 ,  34 ,  35 . This is advantageous in that it is normally difficult to produce rapid inflation of the bottom of a curtain airbag and yet, in some cases, this is where initial contact of an occupant may occur. 
     Although as described above the curtain airbag has two inflatable chambers it will be appreciated that it can be advantageously applied to curtain airbags having a different number of inflatable chambers. 
     Referring now to  FIG. 6  there is shown a second embodiment of a curtain airbag assembly  150  comprising a curtain airbag  151  and two inflators  120 A,  120 B. 
     The curtain airbag  151  has an upper edge  136 , a lower edge  137 , a front edge  138  and a rear edge  139 . When deployed the curtain airbag  151  has a width “W” and a length “L” (as indicated on  FIG. 6 ). 
     The curtain airbag  151  includes first, second, third, fourth and fifth inflatable chambers  140 ,  142 ,  143 ,  145  and  147  respectively and first, second, third, fourth and fifth deployment tubes  130 ,  132 ,  131 ,  133  and  135  respectively. 
     The deployment tubes  130 ,  132 ,  131 ,  133  and  135  are formed as an integral part of the curtain airbag  151  and are defined by stitching that sealingly separate the deployment tubes  130 ,  132 ,  131 ,  133 , and  135  from the inflatable chambers  140 ,  142 ,  143 ,  145  and  147 . 
     Each of the inflatable deployment tubes  130 ,  132 ,  131 ,  133  and  135  is of a relatively small internal volume so as to permit them to be rapidly inflated. 
     Each of the deployment tubes  130 ,  132 ,  131 ,  133  and  135  extends from a position close to the upper edge  136  of the curtain airbag  151  towards the lower edge  137  of the curtain airbag  151  in a lengthwise direction of the curtain airbag  151  and extends substantially vertically when the curtain airbag  151  is inflated. 
     The two separate inflators  120 A and  120 B are provided to inflate the curtain airbag  151  so as to deploy it. The inflators  120 A,  120 B are controlled by an electronic controller (not shown) in accordance with parameters stored in the controller and inputs received by the controller from sensors (not shown) located on the motor vehicle to which the curtain airbag  151  is fitted as is well known in the art. 
     The first inflator  120 A is connected via a manifold (not shown) to two outlets (indicated by arrows on  FIG. 6 ). 
     The first of these outlets provides gas to the first deployment tube  130  and the other outlet provides gas to the second deployment tube  132 . Each of the deployment tubes  130 ,  132  include one or more vents formed by weakened stitching. In the example shown in  FIG. 6  the first deployment tube has two vents v 1  and v 2  and the second deployment tube  132  also has two vents v 3  and v 4  but it will be appreciated that there could be a different number of vents. The vents v 1 , v 2 ; v 3 , v 4  are located at a lower end of the respective deployment tube  130 ,  132  and are formed by the localized failure of the stitching forming the respective deployment tube  130 ,  132  when the pressure in the respective deployment tube  130 ,  132  reaches a certain predefined level. After the vents v 1 , v 2 ; v 3 , v 4  are formed gas can flow from the two deployment tubes  130 ,  132  into the two respective inflatable chambers  140 ,  142 . That is to say, the first chamber  140  is filled by the gas flowing from the first deployment tube  130  via the vents v 1  and v 2  and the second chamber  142  is filled by the gas flowing from the second deployment tube  132  via the vents v 3  and v 4 . 
     Each of the chambers  140 ,  142  is substantially U-shaped and partially envelopes the deployment tube  130 ,  132  from which it is filled. Each of the deployment tubes  130 ,  132  is shaped so as to provide a good area of head protection with minimum volume. In the example shown, the deployment tubes  130 ,  132  are wider near to the lower edge  137  of the curtain airbag  151  than they are near to the upper edge  136 , as may be an appropriate design in the case where it is expected that the head of a passenger is more likely to contact the lower edge  137  than the upper edge  136  when the curtain airbag  151  is deployed. 
     As an alternative to the arrangement described above, one or more of the vents v 1 , v 2 ; v 3 , v 4  may be permanently open, but of a small area so as to form a choke or restriction to flow. In either case, the vents v 1 , v 2 , v 3  and v 4  ensure that the deployment tubes  130 ,  132  are rapidly deployed first to provide head protection and subsequently the first and second chambers  140 ,  142  fill to provide roll-over ejection protection. 
     The second inflator  120 B is connected via a manifold (not shown) to three outlets (indicated by arrows on  FIG. 6 ). 
     The first of these outlets provides gas to the third deployment tube  131 , the second of these outlets provides gas to the fourth deployment tube  133  and the third outlet provides gas to the fifth deployment tube  135 . Each of the deployment tubes  131 ,  133  and  135  includes one or more vents that may be formed by weakened stitching. In the example shown in  FIG. 6 , the third deployment tube  131  has two vents v 5  and v 6 , the fourth deployment tube  133  has two vents v 7 , v 8  and the fifth deployment tube  135  also has two vents v 9  and v 10 , but it will be appreciated that there may be a different number of vents. The vents v 5 , v 6 ; v 7 , v 8  and v 9 , v 10  are all located at a lower end of the respective deployment tube  131 ,  133 ,  135  and may be formed by the localized failure of the stitching forming the respective deployment tube  131 ,  133 ,  135  when the pressure in the respective deployment tube  131 ,  133 ,  135  reaches a certain predefined level. 
     After the vents v 5 , v 6 ; v 7 , v 8  and v 9 , v 10  are formed, gas can flow from the deployment tubes  131 ,  133  and  135  into the respective enveloping chambers  143 ,  145  and  147 . That is to say, the third chamber  143  is filled by the gas flowing from the third deployment tube  131  via the vents v 5  and v 6 , the fourth chamber  145  is filled by the gas flowing from the fourth deployment tube  133  via the vents v 7  and v 8  and the fifth chamber  147  is filled by the gas flowing from the fifth deployment tube  135  via the vents v 9  and v 10 . 
     One of more of the chambers  143 ,  145 ,  147  may be substantially U-shaped and partially envelope the deployment tube  131 ,  133 ,  135  from which it is filled. Each of the deployment tubes  131 ,  133 ,  135  is shaped so as to provide a good area of head protection with minimum volume. In the example shown, the deployment tubes  131 ,  135  are therefore wider near to the lower edge  137  of the curtain airbag  151  than they are near to the upper edge  136 , as may be an appropriate design in the case where it is expected that the head of a passenger is more likely to contact the lower edge  137  than the upper edge  136  when the curtain airbag  151  is deployed. 
     As an alternative to the arrangement described above, one or more of the vents v 5 , v 6 ; v 7 , v 8  and v 9 , v 10  may be permanently open, but of a small area so as to form a choke or restriction to flow. In either case, the vents v 5 , v 6 ; v 7 , v 8  and v 9 , v 10  ensure that the deployment tubes  131 ,  133 ,  135  are rapidly deployed to provide head protection and then the third, fourth and fifth inflatable chambers  143 ,  145  and  147  fill to provide roll-over ejection protection. 
     It will be noted that the vertical edges of the respective chamber  140 ,  142 ,  143 ,  145  and  147  where they interact have a finger-like shape so that when the inflatable chambers  140 ,  142 ,  143 ,  145  and  147  are inflated the fingers are interleaved with one another. This arrangement may be advantageously used when the fingers are located so as to overlie the vertical structure of the motor vehicle (A, B, C, D etc. posts). In addition, the finger-like structure so formed locally stiffen the curtain airbag  151  and may provide increased resistance to localized ejection of the airbag curtain  151  through the underlying window aperture while reducing the volume of gas needed to provide this functionality. 
     The deployment tubes  130 ,  132 ,  131 ,  133 , and  135  have the primary function of deploying the airbag curtain  151  rapidly so as to provide rapid head protection. For example, head cushioning can be provided in as little as 30 ms after initiation of the inflators  120 A,  120 B. This is achieved by using a relatively small gas volume for each of the deployment tubes  130 ,  132 ,  131 ,  133 , and  135 . Each of the deployment tubes  130 ,  132 ,  131 ,  133 , and  135  is shaped so as to provide a large head protection area and a small inflation volume. 
     Then, after providing the initial deployment and head protection functions, the deployment tubes  130 ,  132 ,  131 ,  133 , and  135  are used to fill the inflatable chambers  140 ,  142 ,  143 ,  145  and  147  whose primary function is to provide increased resistance to ejection of the curtain airbag  151  along with further head impact protection coverage. 
     It will be appreciated that if the size of the deployment tubes  130 ,  132 ,  131 ,  133  and  135  was increased to cover all of the area covered by the combination of the deployment tubes  130 ,  132 ,  131 ,  133  and  135  and the inflatable chambers  140 ,  142 ,  143 ,  145  and  147  then the time taken to fill such a large volume would be much longer if the same size inflators are used. Slower filling is undesirable because less head impact protection is provided early in a crash event. 
     Operation of the airbag assembly  150  is as follows. 
     When a crash event required deployment of the curtain airbag  151  is detected, the two inflators  120 A,  120 B are energized and begin to produce gas which very rapidly inflates the five deployment tubes  130 ,  132 ,  131 ,  133  and  135  thereby deploying the curtain airbag  151  to a fully deployed state overlying the underlying window apertures and body structure so as to provide head protection early in the crash event. The pressure in deployment tubes  130 ,  132 ,  131 ,  133  and  135  then continues to rise until the predefined pressure at which the vents v 1 , v 2 , v 3 , v 4 , v 5 , v 6 , v 7 , v 8 , v 9  and v 10  open is reached at which point all of the vents v 1 , v 2 , v 3 , v 4 , v 5 , v 6 , v 7 , v 8 , v 9  and v 10  open so as to allow gas to flow into the surrounding inflatable chambers  140 ,  142 ,  143 ,  145  and  147  thereby providing additional head protection and increasing the resistance of the curtain airbag  151  to ejection through one or more of the underlying window apertures (not shown). 
     It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention as set out in the appended claims. 
     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.