Abstract:
A curtain airbag includes an inflatable cell below a non-inflatable portion that resists being bent when the curtain airbag is inflated. The curtain airbag has a non-inflatable portion and a plurality of inflatable cells that are disposed in front of, behind, above, and below the non-inflatable portion. The lower-side inflatable cell is formed in a convex shape that projects downwardly. When the curtain airbag is inflated, a tensile force acting to pull up the lower-side inflatable cell is generated in the non-inflatable portion. However, as the inflatable cell is formed in a convex shape that projects downwardly, the inflatable cell resists being pulled up and is, therefore, prevented from being bent.

Description:
BACKGROUND 
   The present invention relates to a curtain airbag device that includes a curtain-shaped airbag (“curtain airbag”) to be deployed along an inner side surface of a vehicle cabin. 
   In an automobile provided with a curtain airbag device, a curtain airbag of the curtain airbag device is inflated downwardly along an inner side surface (for example, doors and pillars) of the vehicle cabin in the event that the automobile undergoes a lateral collision or rollover, thereby protecting the head of an occupant and restraining the occupant inside the cabin. 
   Japanese Patent Unexamined Publication No. 2003-104162 discloses an example of such a curtain airbag  60 , as shown in  FIGS. 2A-2B . In the curtain airbag  60 , numeral  60   a  designates a seam for forming and defining inflatable cells, later described in detail. In addition, tabs  60   b  are provided for fixing the curtain airbag  60  to the vehicle body and a gas introduction port  60   c  is provided to receive gas from a gas generator (not shown). 
   In the curtain airbag  60 , horizontally long inflatable cells  68 ,  69  are arranged above and below a non-inflatable portion  72  and vertically long inflatable cells  61 - 67  are arranged in front of and behind the non-inflatable portion. Specifically, the curtain airbag  60  includes, in order from the front to the rear, a non-inflatable portion  71 , vertically inflatable cells  61 ,  62 ,  63 , and  64 , a non-inflatable portion  72 , and vertically inflatable cells  65 ,  66 , and  67 . A horizontally inflatable cell  68 , which is disposed above the non-inflatable portion  72 , communicates with upper portions of the inflatable cells  64  and  65 . In addition, a horizontally inflatable cell  69 , which is disposed below the non-inflatable portion  72 , communicates with lower portions of the inflatable cells  64  and  67 . 
   During the inflation and deployment of the conventional curtain airbag  60 , as shown in  FIG. 2B , tensile forces F 1 , F 2  in the vehicle longitudinal direction are exerted on the non-inflatable portion  72  by the inflatable cells  64 ,  65  in front of and behind the non-inflatable portion  72 . As a result, the non-inflatable portion  72  is tensioned so as to restrain the occupant from moving toward the outside of the vehicle. However, because of the outward function of tensile forces F 1  and F 2 , a tensile force F 3  is exerted upward on horizontally inflatable cell  69 , below the non-inflatable portion  72 . As a result of this vertical force F 3 , the inflatable cell  69  may be constricted upward, i.e., bent into substantially inverted V shape, as shown in  FIG. 2B . In turn, the surface area of the airbag  60  that is available to protect a vehicle occupant is reduced. 
   Accordingly, the present invention has been made in light of the aforementioned problems. More specifically, an object of the present invention is to provide a curtain airbag device capable of preventing (or at least greatly inhibiting) a bending of a horizontally inflatable cell that is below a non-inflatable portion. 
   SUMMARY 
   According to an embodiment of the present invention, a curtain airbag configured to be deployed downwardly along an inner side surface of a vehicle cabin is provided. The curtain airbag includes, among other possible things: (a) a non-inflatable portion; and (b) inflatable cells disposed along a front side and a rear side of the non-inflatable portion. A lower-side inflatable cell is disposed below the non-inflatable portion. The lower-side inflatable cell has a middle portion in a longitudinal direction of the lower-side inflatable cell that is formed in a convex shape projecting downwardly. 
   According to a further embodiment of this curtain airbag, a center line of the lower-side inflatable cell may have its lowermost point at a middle portion. Further, the center line may gradually rise from the middle portion toward the front side and the rear side. 
   According to another further embodiment of this curtain airbag, when the curtain airbag is not inflated, the lowermost point may be positioned from 10 to 150 mm lower than a segment of a line that connects points on the center line of the lower-inflatable cell that are 250 mm before and 250 mm behind the lowermost point. 
   According to an embodiment of the present invention, a curtain airbag device is provided. The curtain airbag device includes, among other possible things: (a) a curtain airbag configured to be deployed downwardly along an inner side surface of a vehicle cabin; and (b) a gas generator for supplying gas into the curtain airbag to inflate the curtain airbag. A portion of the curtain airbag is non-inflatable. Inflatable cells are disposed along a front side and a rear side of the non-inflatable portion. A lower-side inflatable cell is disposed below the non-inflatable portion. The lower-side inflatable cell has a middle portion in a longitudinal direction of the lower-side inflatable cell that is formed in a convex shape projecting downwardly. 
   According to a further embodiment of the curtain airbag device, a center line of the lower-side inflatable cell may have its lowermost point at a middle portion. Further, the center line may gradually rise from the middle portion toward the front side and the rear side. 
   According to another further embodiment of the curtain airbag device, when the curtain airbag is not inflated, the lowermost point may be positioned from 10 to 150 mm lower then a segment of a line that connects points on the center line of the lower-inflatable cell that are 250 mm before and 250 mm behind the lowermost point. 
   Another embodiment of the present invention addresses a vehicle that includes, among other possible things: (a) a curtain airbag configured to be deployed downwardly along an inner side surface of a vehicle cabin, the curtain airbag including, among other possible things: (i) a non-inflatable portion; and (ii) inflatable cells disposed along a front side and a rear side of the non-inflatable portion; and (b) a gas generator configured to supply gas to the curtain airbag in the event of collision or roller by the vehicle. A lower-side inflatable cell is disposed below the non-inflatable portion. The lower-side inflatable cell has a middle portion in a longitudinal direction of the lower-side inflatable cell that is formed in a convex shape projecting downwardly. 
   According to a further embodiment of this vehicle, a center line of the lower-side inflatable cell may have its lowermost point at a middle portion. Further, the center line may gradually rise from the middle portion toward the front side and the rear side. 
   According to another further embodiment of this vehicle, when the curtain airbag is not inflated, the lowermost point may be positioned from 10 to 150 mm lower than a segment of line that connects points on the center line of the lower-inflatable cell that are 250 mm before and 250 mm behind the lowermost point. 
   In the curtain airbag device according to the present invention, the inflatable cell below the non-inflatable portion is formed in a downwardly projecting shape when the curtain airbag is inflated and deployed. Therefore, even if tensile force F 3  as shown in  FIG. 2B  is exerted at the early stage of inflation and deployment of the airbag, the inflatable cell is prevented (or at least greatly inhibited) from being bent upwardly. Specifically, the center line of the lower-side inflatable cell has its lowermost point at a middle portion and has a line shape gradually rising from the middle portion toward the front side and the rear side. This line shape improves the effect of preventing the inflatable cell below the non-inflatable portion from being bent. In particular, when the curtain airbag is un-inflated, the lowermost point is positioned from 10 to 150 mm lower than a segment of a line connecting points on the center line of the lower-inflatable cell that are 250 mm before and 250 mm behind the lowermost point. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 

   
     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 as follows: 
       FIGS. 1A-1E  show a curtain airbag device according to an embodiment of the present invention, in which  FIG. 1A  is a side view of the curtain airbag when inflated and deployed;  FIG. 1B  is a sectional view taken along a line B-B in  FIG. 1A ;  FIG. 1C  is a sectional view taken along a line C-C of  FIG. 1A ;  FIG. 1D  is an explanatory drawing showing tensile forces at a rear portion of the curtain airbag; and  FIG. 1E  is an explanatory drawing of the configuration of an inflatable cell below the non-inflatable portion; and 
       FIGS. 2A and 2B  are side views of a conventional curtain airbag. 
   

   DETAILED DESCRIPTION 
   The present invention will now be described with reference to the  FIGS. 1A-1E . In this embodiment, a curtain airbag  1  is disposed along a roof-side portion (boundary portion between the ceiling and the inner side surface of the vehicle cabin) of an automobile in a folded state in a longitudinally elongate shape. A roof-side garnish (not shown) is arranged at the roof-side portion such that the curtain airbag  1  is covered by the roof-side garnish. 
   The curtain airbag  1  is provided on the upper edge with tabs  1   a  that are fixed to the roof-side portion. The curtain airbag  1  is folded in zigzag fashion along folding lines extending in the longitudinal direction of the vehicle body and the tabs  1   a  are fixed to the roof-side rail. 
   A projection  1   b  is provided at the middle in the longitudinal direction of the upper edge. A gas introduction port  1   c  is formed in the projection  1   b.  The tip of the inflator is inserted into the gas introduction port  1   c  and is fixed by a band (not shown). The curtain airbag  1  starts to be inflated with gas from an inflator (i.e., gas generator) when the automobile undergoes a lateral collision or rollover. The airbag  1  is inflated and deployed downwardly along the inner side surface of the vehicle cabin such as doors and pillars. 
   The curtain airbag  1  is formed of two opposing sheets  11 ,  11  of the same configuration, one of which faces the side wall of the vehicle cabin and the other of which faces the interior of the vehicle cabin. The sheets  11 ,  11  are superposed on each other and are connected by line-shaped connected portions  12 - 19  (i.e., seams) and circular connected portions  21 - 28 . The line-shaped connected portions  12 - 19  and the circular connected portions  21 - 28  form inflatable cells  31 - 43  and non-inflatable portions  51 ,  52 , as hereafter discussed in detail. 
   The line-shaped connected portions  12 - 19  and the circular connected portions  21 - 28  are obtained by robust connecting means, e.g., sewing with high-strength yarns, bonding with high-adhesion adhesives, welding, or other suitable means. Moreover, the line-shaped connected portions  12 - 19  and the circular connected portions  21 - 28  are capable of gas-tightly connecting the sheets  11 ,  11  to prevent the sheets  11 ,  11  from being separated from each other, even when the internal pressure of the curtain airbag  1  rises to the upper design limit. 
   A line-shaped connected portion  12  extends substantially around the periphery of the curtain airbag  1 . However, at the front end side  1 F, the line-shaped connected portion  12  extends downwardly from the upper edge of the front end side  1 F into a U-like shape, thereby for the non-inflatable portion  51  (along the upper edge of the front end side  1 F) and the envelope-like inflatable cell  31 . The line-shaped connected portion  12  also extends along the edges of the projection  1   b  of the curtain airbag  1  and discontinues across the rear edge of the projection  1   b,  thereby forming the gas introduction port  1   c.    
   A vertically inflatable cell  32  is defined between the line-shaped connected portion  13  and a curved portion of the line-shaped connected portion  12  at the front side of the curtain airbag. The upper portion of the vertically inflatable cell  32  communicates with the gas introduction port  1   c  and the lower portion of the vertically inflatable cell  32  communicates with vertically inflatable cell  31  and horizontally inflatable cell  40 . 
   A line-shaped connected portion  17 , which is disposed slightly behind the center of the curtain airbag  1 , extends around into a substantially square shape. The upper side and the lower side of the line-shaped connected portion  17  are spaced apart from the line-shaped connected portion  12  at the upper edge and the lower edge of the curtain airbag. As a result, the line-shaped connected portion  12  and the line-shaped connected portion  17  form an upper horizontally inflatable cell  41  and a lower horizontally inflatable cell  42  at the upper edge and the lower edge of the curtain airbag  1 , respectively. The interior of the line-shaped connected portion  17  is isolated from the gas introduction port  1   c.  As a result, the interior of the line-shaped connected portion  17  defines the non-inflatable portion  52 , which preferably extends 300-500 mm in the longitudinal direction of the vehicle. 
   Vertically inflatable cells  33 ,  34 ,  35 ,  36 , which communicate with horizontally inflatable cells  40  and  41 , are formed between the line-shaped connected portions  13 ,  14 ,  15 ,  16 ,  17 , respectively. The vertically inflatable cells  33 - 35  open only at their upper side so as to communicate with the gas introduction port  1   c . The vertically inflatable cell  36  opens only at its lower side so as to communicate with horizontally inflatable cells  40 ,  42 . 
   At the rear side  1 R of the curtain airbag  1 , vertically inflatable cells  37 ,  38 ,  39  are formed by line-shaped connected portions  18 ,  18   b , and  19 , which are substantially U-shaped. The vertically inflatable cell  37  is disposed adjacent to the rear side of the non-inflatable cell  52  and communicates with the horizontally inflatable cells  41 ,  42  at its upper side and the lower side, respectively. The vertically inflatable cells  38 ,  39  open only at their upper side so as to communicate with the gas introduction port  1   c.    
   A horizontally inflatable cell  43  is formed between a lower portion  18   b  of the line-shaped connected portion  18  and the line-shaped connected portion  12  along the lower edge of the curtain airbag. The horizontally inflatable cell  43  opens only at its front edge side so as to communicate with the horizontally inflatable cell  42 . 
   The inflatable cell  42  at the lower side of the non-inflatable portion  52  is formed to have a center line C of a convex shape project downwardly, as shown in  FIG. 1D . Specifically, the center line C has its lowermost position in a central portion of the horizontally inflatable cell  42 . As a result, the center line C gradually rises upward from the central portion of the horizontally inflatable cell  42  toward both the front and rear ends of the horizontally inflatable cell  42 . 
   As shown in  FIG. 1E , a portion C′ of the center line C is formed by plotting middle points in the vertical direction of the inflatable cell  42 . A point Q is the lowermost point of the center line C′. A point P is a point on the center line C′ 250 mm before the point Q and a point R is a point on the center line C′ 250 mm behind the point Q. Further, the point Q is from about 10 to about 150 mm below a line a that connects points Q and R. 
   When an automobile with the curtain airbag device having the aforementioned structure undergoes a lateral collision or rollover, the inflator generates gas to start the inflation of the curtain airbag  1 . The curtain airbag  1  pushes and opens the roof-side garnish and is deployed downwardly. As the curtain airbag  1  is inflated and deployed, as shown in  FIG. 1D , tensile forces F 1 , F 2  are generated to act on the non-inflatable portion  52  in the longitudinal direction. Correspondingly, tensile force F 3  is generated in a vertical direction, thereby pulling up the lower-side inflatable cell  42 . However, as the lower-side inflatable cell  42  is formed in a convex shape projecting downwardly, the inflatable cell  42  is prevented (or at least is greatly inhibited) from being constricted or bent upward into an inverted V-shape such as that suffered by the conventional airbag  60  shown in  FIG. 2B . As a result, the non-inflatable portion  52  can be kept in a widely deployed state. 
   The aforementioned embodiment is an example of the present invention and the present invention may take other configurations. For example, the number and the arrangement of inflatable cells may be different from those of the illustrated embodiment. Moreover, the center line C′ of the lower-side inflatable cell  42  may have a lowermost portion extending a predetermined length in the longitudinal direction of the vehicle. 
   The priority application, Japanese Application 2003-423082, which was filed Dec. 19, 2003, is incorporated herein by reference in its entirety. 
   Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. Moreover, the technical scope of the present invention is not limited to the embodiments described herein. Rather, modifications are permissible within the scope and spirit of the present invention. The scope of the present invention is to be defined as set forth in the following claims.