Abstract:
Disclosed is a passenger protection device provided with a side curtain airbag which expands in the form of a curtain, along the inner surface of a side portion of a vehicle. A side curtain airbag ( 31 ) is comprised of a gas introduction chamber ( 40 ) which introduces gas; and lower expansion portions ( 51, 52 ) which are expanded in the lower portion of the gas introduction chamber by the gas introduced from the gas introduction chamber. The gas introduction chamber has a plurality of large upper expansion portions ( 42, 43, 44 ) which are arranged in the longitudinal direction of a vehicle, so as to be respectively positioned in a plurality of pillars ( 15, 16, 17 ). The large upper expansion portions expand more widely than small expansion portions ( 45, 46 ), i.e., other portions of the gas introduction chamber, in the width direction of a vehicle.

Description:
TECHNICAL FIELD 
     The present invention relates generally to vehicle occupant protection apparatus which are constructed to deploy, in a passenger compartment, a side curtain airbag in a curtain-like shape along a window (side window) of the vehicle. 
     BACKGROUND ART 
     In recent years, there have been developed techniques for enhancing performance for protecting a vehicle occupant, particularly the head of the vehicle occupant, when impact force has been applied to a side section of the vehicle. For such a type of vehicle occupant protection apparatus, a technique has been developed, according to which a side curtain airbag is stored in a folded configuration or position along a side corner of a roof (roof rail) of a vehicle body so that the side curtain airbag can be deployed in a curtain shape along a vehicle window when the vehicle has been subjected to impact force greater than a predetermined intensity. Such vehicle occupant protection apparatus are disclosed, for example, in patent literature 1 and patent literature 2. 
     In the vehicle occupant protection apparatus disclosed in patent literature 1 and patent literature 2, the side curtain airbag has an upper communication passage for introducing gas from an inflator, and a plurality of cells (inflation portions) that inflate by gas flowing thereinto via the upper communication passage. The upper communication passage extends in a front-rear direction of the vehicle body, and the plurality of cells are arranged in the front-rear direction of the vehicle body under the upper communication passage. The cells are arranged in such a manner that their upper ends differ in height alternately. Because the upper ends of the cells are located non-uniformly in a vertical or up-down direction, the gas flows from the upper communication passage into the cells with time differences. 
     However, deployment of the side curtain airbag disclosed in patent literature 1 and patent literature 2, where only the upper communication passage is provided along the roof rail, cannot sufficiently protect vehicle occupants when the vehicle occupants are brought into secondary collisions against upper portions of a front pillar, center pillar and rear pillar and neighborhoods thereof. 
     Emergency where impact force is applied to a side portion of the vehicle is encountered in various occasions, such as a lateral collision, rollover, etc. of the vehicle. Thus, there has been a demand for the side curtain airbag to achieve an enhanced vehicle protection performance in such an emergency. 
     Prior Art Literature 
     Patent Literature 1: Japanese Patent No. 3626701 
     Patent Literature 1: Japanese Patent No. 3999475 
     SUMMARY OF INVENTION 
     Technical Problem 
     It is therefore an object to provide an improved technique which can enhance a vehicle occupant protection effect or performance of a vehicle occupant protection effect apparatus provided with a side curtain airbag. 
     Solution to Problem 
     According to an aspect of the present invention, there us provided a vehicle occupant protection apparatus, which comprises: a side curtain airbag stored folded along a side portion of a roof of a vehicle body; and an inflator for supplying gas to the side curtain airbag so that the side curtain airbag is inflated and deployed in a curtain shape along an inner surface of a vehicle window, the side curtain airbag including: a gas introduction chamber extending in a front-rear direction of the vehicle body along the side portion of the roof, the gas introduction chamber introducing thereinto the gas in the front-rear direction of the vehicle body; and a lower inflation portion inflatable under the gas introduction chamber by the gas flowing from the gas introduction chamber into the lower inflation portion, the gas introduction chamber including a plurality of upper large inflation portions disposed adjacent to respective ones of a plurality of pillars of the vehicle body and arranged in the front-rear direction of the vehicle body, each of the plurality of upper large inflation portions being inflatable in a vehicle width direction by a greater amount than a small inflation portion that is another inflation portion than the upper large inflation portions in the gas introduction chamber. 
     Preferably, the plurality of upper large inflation portions include a front-pillar large inflation portion that, as the side curtain airbag is deployed, inflates to a region rearward of the front pillar along a rear upper portion of the front pillar of the plurality of pillars. 
     Preferably, the plurality of upper large inflation portions include a rear-pillar large inflation portion that, as the side curtain airbag is deployed, inflates to a region forward of the rear pillar along a front upper portion of the rear pillar of the plurality of pillars. 
     Preferably, the side curtain airbag includes a distortion restraint portion for restraining the lower inflation portion from being distorted in the front-rear direction of the vehicle body when the side curtain airbag has been deployed, and the distortion restraint portion is formed on the lower inflation portion so as to positionally correspond to at least an intermediate position of the plurality of upper large inflation portions. 
     Preferably, the lower inflation portion includes a sub inflation portion that is located near a front edge of the vehicle window when the side curtain airbag is in a deployed position. 
     Advantageous Effects of Invention 
     In the present invention, the gas introduction chamber of the side curtain airbag extends along the side portion of the roof (i.e., along the upper edge of the vehicle window). The gas introduction chamber includes the plurality of upper large inflation portions arranged in the front-rear direction of the vehicle body, and these upper large inflation portions are disposed in correspondence with respective positions of the plurality of pillars of the vehicle body. Once the gas is introduced from the inflator into the gas introduction chamber in the event of an emergency (first or primary collision), such as a lateral collision or rollover of the vehicle, the side curtain airbag is deployed in a curtain shape along the inner side surface of the vehicle. By the gas flowing from the gas introduction chamber to the lower inflation portion, the lower inflation portion inflates to protect the vehicle occupant. During that time, the plurality of upper large inflation portions inflate in the vehicle width direction by a greater amount than the lower inflation portion disposed between and in communication with the upper large inflation portions. Namely, the upper large inflation portions inflate greatly in the neighborhood of the plurality of pillars and in the neighborhood of the vehicle window. 
     Namely, according to the present invention, as the side curtain airbag is deployed in a curtain shape, the lower inflation portion disposed under the gas introduction chamber inflates, and the plurality of upper large inflation portions greatly inflate in the vehicle width direction. The thus-inflated upper large inflation portions separate between upper portions of the plurality of pillars and neighborhoods thereof and one or more vehicle occupants. As a result, the present invention can enhance the vehicle occupant protection effect or performance when the vehicle occupants are brought into collisions against the inner surface of the vehicle body, i.e. at the time of a so-called second or secondary collision, following occurrence of the first or primary collision of the vehicle. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle, the present invention can sufficiently protect the vehicle occupants in the neighborhoods of the plurality of pillars and in the neighborhoods of the upper edges of the vehicle windows. 
     Further, as the side curtain airbag is deployed in a curtain shape, the front-pillar upper large inflation portion inflates to a region rearward of the front pillar along a rear upper portion of the front pillar. The thus-inflated front-pillar upper large inflation portion separates between an upper portion of the front pillar and neighborhood thereof and the vehicle occupant. As a result, the present invention can enhance the vehicle occupant protection effect when the vehicle occupants are brought into a collision against the inner surface of the vehicle body, i.e. at the time of a so-called secondary collision, following occurrence of the primary collision of the vehicle. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle, the present invention can sufficiently protect the vehicle occupant in the neighborhood of the front pillar and in the neighborhood of the upper edge of the vehicle window. 
     Furthermore, as the side curtain airbag is deployed in a curtain shape, the rear-pillar upper large inflation portion inflates to a region forward of the rear pillar along a front upper portion of the rear pillar. The thus-inflated rear-pillar upper large inflation portion separates between an upper portion of the rear pillar and neighborhood thereof and the vehicle occupant. As a result, the present invention can enhance the vehicle occupant protection effect when the vehicle occupant is brought into a collision against the inner surface of the vehicle body, i.e. at the time of a so-called secondary collision, following occurrence of the primary collision of the vehicle. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle, the present invention can sufficiently protect the vehicle occupant in the neighborhood of the rear pillar and in the neighborhood of the upper edge of the vehicle window. 
     Furthermore, the side curtain airbag of the present invention includes a distortion restraint portion for restraining the lower inflation portion from being distorted in the front-rear direction of the vehicle body when the side curtain airbag has been deployed. As the plurality of upper large inflation portions inflate, the lower inflation portion disposed under the gas introduction chamber can be distorted due to the influence of the inflation of the upper large inflation portions. If distortion of the lower inflation portion can be restrained, then the entire side curtain airbag would be much less likely to be distorted in the vehicle width direction. Thus, the present invention can restrain distortion of the entire side curtain airbag, as a result of which the present invention can even further enhance the vehicle occupant protection effect by the side curtain airbag. 
     Furthermore, in the present invention, the sub inflation portion is located near the front edge of the vehicle window when the side curtain airbag is in the deployed position. Thus, the present invention can even further enhance the vehicle occupant protection effect when the vehicle occupant has been brought to a secondary collision against the neighborhood of the front edge of the window. Further, when the vehicle occupant has hit the lower inflation portion, e.g. when the vehicle occupant has been brought into a secondary collision against the neighborhood of the front edge of the window, the present invention can cause the inner pressure of the lower inflation portion to escape to the sub inflation portion. Thus, the present invention can restrain increase of the inner pressure of the lower inflation portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a vehicle having a side curtain airbag, constituting a first embodiment of a vehicle occupant protection apparatus of the present invention, stored in a folded position; 
         FIG. 2  is a side view showing the vehicle with the first embodiment of the side curtain airbag in a deployed position; 
         FIG. 3  is a view showing the side curtain airbag of  FIG. 2  in the deployed position; 
         FIG. 4  is an enlarged sectional view taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is an enlarged sectional view taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a side view showing a vehicle with a side curtain airbag, constituting a second embodiment of the vehicle occupant protection apparatus of the present invention, in a deployed position; 
         FIG. 7  is a view showing the side curtain airbag of  FIG. 6  in a deployed position; 
         FIG. 8  is a side view showing a vehicle with a side curtain airbag, constituting a third embodiment of the vehicle occupant protection apparatus of the present invention, in a deployed position; and 
         FIG. 9  is a view showing the side curtain airbag of  FIG. 8  in the deployed position. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     As shown in  FIG. 1 , a vehicle  10  includes a vehicle body  11  of a monocoque construction, which includes two, i.e. front and rear, seats  13  and  14  provided in a passenger compartment  12 . A vehicle occupant Mf, such as a human driver, is seated in the front seat  13 , and another vehicle occupant Mr is seated in the rear seat  14 . 
     The vehicle body  11  includes a front pillar  15 , a center pillar  16 , a rear pillar  17 , and a roof side rail  18  fixedly connected to the respective upper ends of the pillar  15 ,  16  and  17 . The roof side rail  18  is an elongated member extending in a front-rear direction of the vehicle body  11  and supports a roof  19 . The roof side rail  18  is disposed along a side edge (side portion or side portion corner)  19   a  of the roof  19 . 
     The vehicle body  11  includes a front side door  21  provided between the front pillar  15  and the center pillar  16 , and a rear side door  22  provided between the center pillar  16  and the rear pillar  17 . The front side door  21  is disposed adjacent to the front seat  13  and has a vehicle window (front window  23 ) in its upper half portion. The rear side door  22  is disposed adjacent to the rear seat  14  and has a vehicle window (rear window  24 ) in its upper half portion. 
     A first embodiment of a vehicle occupant protection apparatus  30  is provided on the roof side rail  18 . More specifically, the vehicle occupant protection apparatus  30  includes a side curtain airbag  31  mounted in a stored (folded or wound) state on the roof side rail  18  along the side edge  19   a  of the roof  19 , i.e. along the upper edges  23   a  and  24   a  of the windows  23  and  24  of the vehicle body  11 . The side curtain airbag  31  will hereinafter be referred to simply as “airbag  31 ”. 
     In the vehicle occupant protection apparatus  30 , gas is produced from an inflator  32  once impact force greater than a predetermined intensity is applied to a side section of the vehicle  10 , and the thus-produced gas is supplied to the airbag  31  so that the airbag  31  is deployed toward the interior of the passenger compartment  12  along the windows  23  and  24 . Such a vehicle occupant protection apparatus  30  is also called “side curtain airbag apparatus”. 
     As shown in  FIG. 2 , the airbag  31  deployed within the passenger compartment  12  protects the vehicle occupants Mf and Mr, seated in the respective seats  13  and  14 , by not only covering the windows  23  and  24  but also absorbing impact that acts on the vehicle occupants Mf and Mr. The inflator  32  (gas supply source  32 ) is not only mounted on the rear pillar  17  but also connected to a gas inlet port  41  of the airbag  31 . 
     Next, with reference to (a) and (b) of  FIG. 3 , the airbag  31  will be described in detail.  FIG. 3  shows the airbag  31  deployed within the passenger compartment. The airbag  31  is formed, for example, of a pair of outer and inner flexible sheets, such as fabrics having airtightness. The airbag  31  includes a gas introduction chamber  40  and a deployment section  50 . 
     The gas produced from the inflator  32  flows in the front-rear direction of the vehicle body into the gas introduction chamber. This gas introduction chamber  40  is formed in a substantially cylindrical shape extending in the front-rear direction of the vehicle body along the side edge  19   a  of the roof  19 . The gas inlet port  41  for introducing the gas from the inflator  32  is provided at the rear end of the gas introduction chamber  40 . 
     As shown in (a) of  FIG. 3 , the gas introduction chamber  40  has a plurality of upper large inflation portions  42 ,  43  and  44  arranged in the vehicle body front-rear direction in such a manner that the upper large inflation portions  42 ,  43  and  44  are located in correspondence with the respective positions of the positions of the pillars  15 ,  16  and  17 . These upper large inflation portions  42 ,  43  and  44  are in communication with one another via a plurality of small inflation portions  45  and  46 , and they inflate greatly in a vehicle width direction (i.e., in a direction toward and away from a reader of  FIG. 3 ) in such a manner that they take on a greater thickness than the small inflation portions  45  and  46  inflated at the time of deployment of the airbag  31 . More specifically, the plurality of upper large inflation portions  42 ,  43  and  44  are three upper large inflation portions, i.e. a front-pillar large inflation portion  42 , a center-pillar large inflation portion  43  and a rear-pillar large inflation portion  44 . 
     As the airbag  31  is deployed, the front-pillar large inflation portion  42  inflate to the front pillar  15  and to a region rearward of the front pillar  15  along a rear upper edge portion of the front pillar  15 . As shown in  FIGS. 3 to 5 , as the gas flows into the gas introduction chamber  40 , the front-pillar large inflation portion  42  inflates to a thickness greater than the small inflation portion  45  inflated. It is preferable that each of the upper large inflation portions  42 ,  43  and  44  in the inflated position have a greater thickness (in the vehicle width direction) than each of lower inflation portions  51  and  52 . 
     As the airbag  31  is deployed, the center-pillar large inflation portion  43  inflates to an upper portion of the center pillar  16  and regions in front of and behind the center pillar  16 . 
     As the airbag  31  is deployed, the rear-pillar large inflation portion  44  inflates to the rear pillar  17  and a region in front of the rear pillar  17  along a front upper edge portion of the rear pillar  17 . 
     The deployment section  50  is a sheet-shaped member that is deployable in a curtain shape along the inner surface of each of the windows  23  and  24  and thereby protects the vehicle occupants Mf and Mr ( FIG. 1 ). The deployment section  50  includes a plurality of, e.g., a pair of front and rear, lower inflation portions  51  and  52 , that inflate with pressure of the gas as the deployment section  50  is deployed. These lower inflation portions  51  and  52  inflate greatly, in the vehicle width direction, under the gas introduction chamber  40 , by the gas flowing from the gas introduction chamber  40  into the lower inflation portions  51  and  52 . The first lower inflation portion  51  is located in a front half region of the deployment section  50 , while the second lower inflation portion  52  is located in a rear half of region the deployment section  50 . 
     The first lower inflation portion  51  inflates at a position corresponding to the vehicle occupant seated in the front seat  13  ( FIG. 1 ). The first lower inflation portion  51  further includes a sub inflation portion (first sub inflation portion)  53  located near the front edge of the front window  23  when the airbag  31  is in the deployed position. This first sub inflation portion  53  is designed to adjust the inner pressure of the first lower inflation portion  51 , and it is located adjacent to the front end of the first lower inflation portion  51  and in communication with the first lower inflation portion  51  via a lower communication passage  54 . The lower communication passage  54  is designed to provide a narrowed gas passage to limit a flow rate of the gas when the first lower inflation portion  51  is in the inflated position. The first sub inflation portion  53  is located in front of the vehicle occupant Mf (particularly an upper half portion of the vehicle occupant&#39;s body) seated in the front seat  13 . Thus, the first sub inflation portion  53  is located at a considerable distance from the front seat  13  and inflatable in the vehicle width direction. 
     The second lower inflation portion  52  inflates at a position corresponding to the vehicle occupant seated in the rear seat  14  ( FIG. 1 ). The second lower inflation portion  52  further includes a sub inflation portion (second sub inflation portion)  55  located near the front edge of the rear window  24  when the airbag  31  is in the deployed position. This second sub inflation portion  55  is designed to adjust the inner pressure of the second lower inflation portion  52 , and it is located adjacent to the front end of the second lower inflation portion  52  and in communication with the second lower inflation portion  52  via a lower communication passage  56 . The lower communication passage  56  is designed to provide a narrowed gas passage to limit the flow rate of the gas when the second lower inflation portion  52  is in the inflated position. The second sub inflation portion  55  is located in front of the vehicle occupant Mr (particularly an upper half portion of the vehicle occupant&#39;s body) seated in the rear seat  14 . Thus, the second sub inflation portion  55  is located at a considerable distance from the rear seat  14  and inflatable in the vehicle width direction. 
     Namely, when the airbag  31  is in the deployed position, the first and second sub inflation portions  53  and  55  are located near the front edges of the windows  23  and  24 . Thus, the instant embodiment can enhance the vehicle occupant protection effect or performance for protecting the vehicle occupants, particularly the vehicle occupants&#39; heads, when the vehicle occupants Mf and Mr have been brought into secondary collisions against the neighborhoods of the front edges of the windows  23  and  24 . Further, when the vehicle occupants Mf and Mr have hit the first and second lower inflation portions  51  and  52 , the inner pressure of the first and second lower inflation portions  51  and  52  can be caused to escape to the first and second sub inflation portions  53  and  55 . In this way, it is possible to prevent increase of the inner pressure of the first and second lower inflation portions  51  and  52 . 
     The airbag  31  further includes a plurality of distortion restraint portions  57  for restraining the first and second lower inflation portions  51  and  52  from being distorted in the vehicle body front-rear direction when the airbag  31  has been deployed. The distortion restraint portions  57  are formed on the first and second lower inflation portions  51  and  52  in such a manner as to positionally correspond to at least intermediate positions of the upper large inflation portions  42 ,  43  and  44  arranged in the vehicle body front-rear direction. More specifically, the distortion restraint portions  57  extend straightly upward by predetermined lengths from the bottoms of the first and second lower inflation portions  51  and  52  and sub inflation portion  55 . The distortion restraint portions  57  are formed, for example, by the two, i.e. outer and inner, flexible sheets, constituting the airbag  31 , being sewn together, and the distortion restraint portions  57  function as reinforcing ribs. 
     When the plurality of upper large inflation portions  42 ,  43  and  44  have inflated, the first and second lower inflation portions  51  and  52 , disposed under the gas introduction chamber  40 , can be distorted (deformed) in the vehicle body front-rear direction due to the influence of the inflation of the inflation portions  42 ,  43  and  44 . 
     Thus, the first embodiment is constructed in such a manner that the distortion restraint portions  57  can restrain the first and second lower inflation portions  51  and  52  from being distorted (deformed) in the vehicle body front-rear direction when the airbag  31  has been deployed in a curtain shape. Because distortion of the first and second lower inflation portions  51  and  52  can be restrained in the aforementioned manner, the airbag  31  would be much less likely to be distorted in its entirety in the vehicle body front-rear direction. Thus, even when the plurality of upper large inflation portions  42 ,  43  and  44 , disposed over the first and second lower inflation portions  51  and  52 , inflate, the airbag  31  would be much less likely to be distorted in its entirety. As a consequence, the instant embodiment can even further enhance the vehicle occupant protecting performance. 
     Further, the airbag  31  includes a plurality of upper mounting portions  61 , a front mounting portion  62  and a rear mounting portion  63 . The plurality of upper mounting portions  61  are in the form of mounting pieces extending upward from an upper end portion of the deployed airbag  31  and arranged along the roof side rail  18 . The upper mounting portions  61  are each fixed to the roof side rail  18 . The front mounting portion  62  is in the form of a mounting piece extending forward from a lower front end portion of the deployed airbag  31  and fixed to the front pillar  15 . The rear mounting portion  63  is in the form of a mounting piece extending rearward from a lower rear end portion of the deployed airbag  31  and fixed to the rear pillar  17 . 
     The following summarize the first embodiment, with reference to  FIGS. 2 and 3 . 
     The gas introduction chamber  40  extends in the vehicle body front-rear direction along the side portion  19   a  of the roof  19  (i.e., along the upper edges of the windows  23  and  24 ), and it includes the plurality of upper large inflation portions  42 ,  43  and  44  arranged in the vehicle body front-rear direction. The upper large inflation portions  42 ,  43  and  44  are disposed in correspondence with the respective positions of the pillars  15 ,  16  and  17 . 
     Once the gas is introduced from the inflator  32  into the gas introduction chamber  40  in the event of an emergency (primary collision), such as a lateral collision or rollover of the vehicle  10 , the airbag  31  is deployed downward in a curtain shape along the windows  23  and  24 . As the gas flows from the gas introduction chamber  40  into the front and rear lower inflation portions  51  and  52 , the front and rear lower inflation portions  51  and  52  inflate to protect the vehicle occupants Mf and Mr. At that time, the upper large inflation portions  42 ,  43  and  44  inflate in the vehicle width direction by a greater amount than the small inflation portions  45  and  46 . Namely, the upper large inflation portions  42 ,  43  and  44  inflate greatly in the neighborhoods of the pillars  15 ,  16  and  17  and in the neighborhoods of the upper edges  23   a  and  24   a  of the windows  23  and  24 . 
     Namely, according to the first embodiment, as the airbag  31  is deployed in a curtain shape, not only the front and rear lower inflation portions  51  and  52 , disposed under the gas introduction chamber  40 , inflate, but also the upper large inflation portions  42 ,  43  and  44  in the gas introduction chamber  40  inflate greatly in the vehicle width direction. The thus-inflated upper large inflation portions  42 ,  43  and  44  separate between upper portions of the pillars  15 ,  16  and  17  and neighborhoods thereof and the vehicle occupants Mf and Mr. Thus, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupants Mf and Mr are brought into collisions against the inner surface of the side section of the vehicle body  11 , i.e. at the time of a so-called secondary collision, following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the first embodiment can sufficiently protect the vehicle occupants Mf and Mr in the neighborhoods of the pillars  15 ,  16  and  17  and in the neighborhoods of the upper edges  23   a  and  24   a  of the windows  23  and  24 . 
     Further, as noted above, the inflated upper large inflation portions  42 ,  43  and  44  abut against the plurality of pillars  15 ,  16  and  17 . Thus, the entire airbag  31  is supported close to the vehicle occupants Mf and Mr by means of the pillars  15 ,  16  and  17 . Further, when the vehicle occupants Mf and Mr are brought into secondary collisions against the pillars  15 ,  16  and  17 , the first embodiment can restrain the entire airbag  31  from freely swinging in the vehicle width direction. Therefore, the first embodiment can advance the timing at which the vehicle occupants Mf and Mr should start to be restrained by the airbag  31 . 
     Similarly, when the vehicle occupants Mf and Mr are just about to be brought into secondary collisions with the windows  23  and  23 , the upper large inflation portions  42 ,  43  and  44 , having high resistance against deformation, have already inflated between the pillars  15 ,  16  and  17  and windows  23  and  24  and the vehicle occupants Mf and Mr. Deformation amounts (stroke amounts) by which the upper large inflation portions  42 ,  43  and  44  are deformable in the vehicle width direction are great as compared to the small inflation portions  45  and  46 . Thus, the instant embodiment can secure greater stroke amounts for the upper large inflation portions  42 ,  43  and  44  than for the small inflation portions  45  and  46 , but also secure necessary gas flows into the lower inflation portions  51  and  52 . 
     Further, as the airbag  31  is deployed in a curtain shape, the front-pillar large inflation portion  42  inflates to a region rearward of the front pillar  15  along the upper rear edge of the front pillar  15 . The thus-inflated front-pillar large inflation portion  42  sufficiently separates between an upper portion of the pillar  15  and neighborhood thereof and the vehicle occupant Mf. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mf is brought into a collision against the inner side surface of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the first embodiment can sufficiently protect the vehicle occupant Mf in the neighborhoods of the front pillar  15  and upper edge  23   a  of the window  23 . 
     Further, as the airbag  31  is deployed in a curtain shape, the rear-pillar large inflation portion  44  inflates to a region forward of the rear pillar  17  along the upper front edge of the rear pillar  17 . The thus-inflated rear-pillar large inflation portion  44  sufficiently separates between an upper portion of the pillar  17  and neighborhood thereof and the vehicle occupant Mr. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mf is brought into a collision against the inner surface of the side section of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the first embodiment can sufficiently protect the vehicle occupant Mr in the neighborhoods of the front pillar  15  and upper edge  24   a  of the window  24 . 
     Embodiment 2 
     Now, with reference to  FIGS. 6 and 7 , a description will be given about a second embodiment of the vehicle occupant protection apparatus  130 , where the same members and elements as in the first embodiment shown in  FIGS. 1 to 5  are indicated by the same reference numerals and characters and will not be described hereinbelow to avoid unnecessary duplication. (a) of  FIG. 7  shows an airbag  131  deployed within the passenger compartment  12 , and (b) of  FIG. 7  shows the airbag  131  in the deployed position. 
     As shown in  FIGS. 6 and 7 , the second embodiment of the vehicle occupant protection apparatus  130  includes the airbag  131  that includes a gas introduction chamber  140  and a deployment section  150 . 
     The gas introduction chamber  140  has a plurality of upper large inflation portions  142 ,  143  and  144  arranged in the vehicle body front-rear direction in such a manner that there are located in correspondence with the respective positions of the pillars  15 ,  16  and  17 . The upper large inflation portions  142 ,  143  and  144  inflate in the vehicle width direction by a greater amount than small inflation portions  145  and  146  that are other inflation portions within the gas introduction chamber  140 . The gas introduction chamber  140  has a gas inlet port  41  for introducing the gas. 
     The plurality of upper large inflation portions  142 ,  143  and  144  are a front-pillar large inflation portion  142 , a center-pillar large inflation portion  143  and a rear-pillar large inflation portion  144 . 
     The deployment section  150  is a sheet-shaped member that is deployable in a curtain shape along each of the windows  23  and  24  and thereby protects the vehicle occupants Mf and Mr. The deployment section  150  includes a plurality of lower inflation portions  151  that inflate with pressure of the gas as the deployment section  150  is deployed. These lower inflation portions  151  inflate greatly, in the vehicle width direction, under the gas introduction chamber  140 , by the gas flowing from the gas introduction chamber  140  into the lower inflation portions  151 . The lower inflation portions  151  are arranged in the vehicle body front-rear direction, and the lower inflation portions  151  are open at their upper ends  153  (including upper ends  153 A to  153 C) in such a manner that the gas flows branch downward from the gas introduction chamber  140 , and the lower inflation portions  151  are closed at their lower ends. 
     Adjoining ones of the lower inflation portions  151  are partitioned off from each other by partition walls  152  (including partition walls  152 A to  152 C). The partition walls  152  are each a member provided in the deployment section  150  and extending straightly upward from near the bottom of the deployment section  150  to near the introduction chamber  140 , and the partition walls  152  are each formed, for example, by the two, i.e. outer and inner, flexible sheets, constituting the airbag  131 , being sewn together. 
     The partition walls  152  function also as the above-mentioned distortion restraint portions  57  provided in the first embodiment. Namely, the partition walls  152  restrain the lower inflation portions  151  from being distorted in the vehicle body front-rear direction when the airbag  131  has been deployed. For that purpose, the partition walls  152  are provided in the lower inflation portions  151  in such a manner so to positionally correspond to at least intermediate positions of the upper large inflation portions  142 ,  143  and  144  arranged in the vehicle body front-rear direction. 
     When the airbag  131  has been deployed, the partition walls  152  restrain the lower inflation portions  151  from being distorted in the vehicle body front-rear direction. Because distortion of each of the lower inflation portions  151  can be restrained like this, the entire airbag  131  would be much less likely to be distorted. Thus, even when the upper large inflation portions  142 ,  143  and  144 , disposed over the lower inflation portions  151 , have inflated, distortion of the entire airbag can be restrained. As a consequence, the second embodiment can even further enhance the vehicle occupant protection effect or performance by the airbag  131 . 
     Of the plurality of partition walls  152 , the partition walls  152 A to  152 C disposed immediately under the corresponding upper large inflation portions  142 ,  143  and  144  have their respective upper ends  153 A to  153 C located lower than upper ends  153  of the other partition walls. More specifically, when the airbag  131  is in the deployed position, the upper ends  153  of the partition walls  152  are located on a reference line Ls. 
     The upper end  153 A of the partition wall  152 A disposed immediately under the front-pillar large inflation portion  142  is located lower than the reference line Ls by a distance X 1 , so that a relatively large first space portion  142  is formed in a front region, in a longitudinal direction, of the gas introduction chamber  140 . The first space portion  142  constitutes the front-pillar large inflation portion  142 . 
     The upper end  153 B of the partition wall  152 B disposed immediately under the center-pillar large inflation portion  143  is located lower than the reference line Ls by a distance X 2 , so that a relatively large second space portion  143  is formed in a middle region, in the longitudinal direction, of the gas introduction chamber  140 . The second space portion  143  constitutes the center-pillar large inflation portion  143 . 
     The upper end  153 C of the partition wall  152 C disposed immediately under the rear-pillar large inflation portion  144  is located lower than the reference line Ls by a distance X 3 , so that a relatively large third space portion  144  is formed in a rear region, in the longitudinal direction, of the gas introduction chamber  140 . The third space portion  144  constitutes the rear-pillar large inflation portion  144 . 
     In the deployment section  150 , the frontmost lower inflation portion  151  includes a sub inflation portion  155  that is located near the front edge of the front window  23  when the airbag  131  is in the deployed position. The sub inflation portion  155  is designed to adjust the inner pressure of the first lower inflation portions  151 , and it is located adjacent to the front end of the foremost lower inflation portions  151  and in communication with the lower inflation portion  151  via a communication passage  156 . The communication passage  156  provides a narrowed gas passage to limit the flow rate of the gas. 
     Namely, when the airbag  131  is in the deployed position, the sub inflation portion  155  is located near the front edge of the front window  23 . Thus, the instant embodiment can even further enhance the vehicle occupant protection effect when the vehicle occupants Mf and Mr (see  FIG. 1 ) have been brought into secondary collisions against the neighborhoods of the front edges of the windows  23  and  24 . Further, when the vehicle occupants Mf and Mr have hit the lower inflation portions  151 , e.g. when the vehicle occupants Mf and Mr have been brought into secondary collisions against the neighborhoods of the front edges of the windows  23  and  24 , the inner pressure of the lower inflation portions  151  can be caused to escape to the sub inflation portion  155 . In this way, it is possible to prevent increase of the inner pressure of the lower inflation portions  151 . 
     The second embodiment can accomplish the same behavior and advantageous benefits as the first embodiment. Namely, the upper large inflation portions  142 ,  143  and  144  having inflated can separate between upper portions of the pillars  15 ,  16  and  17  and neighborhoods thereof and the vehicle occupants Mf and Mr. Thus, the instant embodiment can even further enhance the vehicle occupant protection effect when the vehicle occupants Mf and Mr are brought into collisions against the inner surface of the side section of the vehicle body  11 , i.e. at the time of a so-called secondary collision, following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the second embodiment can sufficiently protect the vehicle occupants Mf and Mr in the neighborhoods of the pillars  15 ,  16  and  17  and in the neighborhoods of the upper edges of the windows  23  and  24 . 
     Further, the inflated front-pillar large inflation portion  142  separates between an upper portion of the front pillar  15  and neighborhood thereof and the vehicle occupant Mf. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mf is brought into a collision against the inner side surface of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the second embodiment can sufficiently protect the vehicle occupant Mf in the neighborhoods of the front pillar  15  and upper edge of the window  23 . 
     The inflated rear-pillar large inflation portion  144  separates between an upper portion of the rear pillar  17  and neighborhood thereof and the vehicle occupant Mr. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mr is brought into a collision against the inner side surface of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the second embodiment can sufficiently protect the vehicle occupant Mr in the neighborhoods of the rear pillar  17  and upper edge of the rear window  24 . 
     Embodiment 3 
     Now, with reference to  FIGS. 8 and 9 , a description will be given about a third embodiment of the vehicle occupant protection apparatus, where the same members and elements as in the first embodiment shown in  FIGS. 1 to 5  are indicated by the same reference numerals and characters and will not be described hereinbelow to avoid unnecessary duplication. (a) of  FIG. 9  shows an airbag  231  deployed within the passenger compartment  12 , and (b) of  FIG. 9  shows the airbag  231  in the deployed position. 
     As shown in  FIGS. 8 and 9 , the third embodiment of the vehicle occupant protection apparatus  230  includes the airbag  231  that includes a gas introduction chamber  240  and a deployment section  250 . 
     The gas introduction chamber  240  has a plurality of upper large inflation portions  242 ,  243  and  244  arranged in the vehicle body front-rear direction in such a manner that they are located in correspondence with respective positions of the pillars  15 ,  16  and  17 . The upper large inflation portions  242 ,  243  and  244  inflate in the vehicle width direction by a greater amount than small inflation portions  245  and  246  that are other inflation portions within the gas introduction chamber  240 . The gas introduction chamber  240  has a gas inlet port  241  for introducing the gas. 
     The plurality of upper large inflation portions  242 ,  243  and  244  are three upper large inflation portions, i.e. a front-pillar large inflation portion  242 , a center-pillar large inflation portion  243  and a rear-pillar large inflation portion  244 . The front-pillar large inflation portion  242  corresponds to the front-pillar large inflation portion  42  provided in the first embodiment, the center-pillar large inflation portion  243  corresponds to the center-pillar large inflation portion  43  provided in the first embodiment, and the rear-pillar large inflation portion  244  corresponds to the rear-pillar large inflation portion  44  provided in the first embodiment. 
     The deployment section  250  is a sheet-shaped member that is deployable in a curtain shape along each of the windows  23  and  24  and thereby protects the vehicle occupants Mf and Mr ( FIG. 1 ). The deployment section  250  includes a plurality of lower inflation portions (main inflation portions)  251  and  252 , e.g., two front lower inflation portions  251  and two rear front lower inflation portions  252 , that inflate with pressure of the gas as the deployment section  250  is deployed. These lower inflation portions  251  and  252  inflate greatly, in the vehicle width direction, under the gas introduction chamber  240 , by the gas flowing from the gas introduction chamber  240  into the lower inflation portions  251  and  252 . The first lower inflation portions  251  are located in a front half region of the deployment section  250 , while the second lower inflation portions  252  are located in a rear half region of the deployment section  250 . 
     The first lower inflation portions  251  inflate at positions beside the front seat  13  ( FIG. 1 ). The first lower inflation portions  251  includes a sub inflation portion (first sub inflation portion)  253  located near the front edge of the front window  23  when the airbag  231  is in the deployed position. This first sub inflation portion  253  is designed to adjust the inner pressure of the first lower inflation portions  251 , and it is located adjacent to the front end of one of the first lower inflation portions  251  and in communication with the first lower inflation portions  251  via a communication passage  254  (narrowed portion  254 ). The communication passage  254  provides a narrowed gas passage to limit the flow rate of the gas. More specifically, the first sub inflation portion  253  is located in front of the vehicle occupant Mf (particularly the head of the vehicle occupant) seated in the front seat  13 . Thus, the first sub inflation portion  253  is inflatable in the vehicle width direction at a position considerably distant from the front seat  13 . 
     The second lower inflation portions  252  inflate at positions beside the rear seat  14  ( FIG. 1 ). The second lower inflation portions  252  include a sub inflation portion (second sub inflation portion)  255  located near the front edge of the rear window  24  when the airbag  231  is in the deployed position. This second sub inflation portion  255  is designed to adjust the inner pressure of the second lower inflation portions  252 , and it is located adjacent to the front end of one of the second lower inflation portions  252  and in communication with the second lower inflation portions  252  via a communication passage  256 . The communication passage  256  provides a narrowed gas passage to limit the flow rate of the gas. More specifically, the second sub inflation portion  255  is located in front of the vehicle occupant Mr (particularly the head of the vehicle occupant) seated in the rear seat  14 . Thus, the second sub inflation portion  255  is inflatable in the vehicle width direction at a position considerably distant from the rear seat  14 . 
     Namely, when the airbag  231  is in the deployed position, the first and second sub inflation portions  253  and  255  are located near the front edges of the windows  23  and  24 . Thus, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupants Mf and Mr have been brought into secondary collisions against the neighborhoods of the front edges of the windows  23  and  24 . Further, when the vehicle occupants Mf and Mr have hit the first and second lower inflation portions  251  and  252 , e.g. when the vehicle occupants Mf and Mr have been brought into secondary collisions against the neighborhoods of the front edges of the windows  23  and  24 , the inner pressure of the first and second lower inflation portions  251  and  252  can be caused to escape to the first and second sub inflation portions  253  and  255 . In this way, it is possible to prevent increase of the inner pressure of the first and second lower inflation portions  251  and  252 . 
     The airbag  231  further includes a plurality of distortion restraint portions  257  for restraining the first and second lower inflation portions  251  and  252  from being distorted in the vehicle body front-rear direction. The distortion restraint portions  257  are formed on the first and second lower inflation portions  251  and  252  and second sub inflation portion  255  in such a manner as to positionally correspond to at least intermediate positions of the upper large inflation portions  242 ,  243  and  244  arranged in the vehicle body front-rear direction. More specifically, the distortion restraint portions  257  are portions extending straightly upward by predetermined lengths from the bottom of the first and second lower inflation portions  251  and  252  and sub inflation portion  255 . The distortion restraint portions  257  are formed, for example, by the two, i.e. outer and inner, flexible sheets, constituting the airbag  231 , being sewn together. 
     The distortion restraint portions  257  restrain the first and second lower inflation portions  251  and  252  from being distorted in the vehicle body front-rear direction when the airbag  231  has deployed in a curtain shape. Because distortion of the first and second lower inflation portions  251  and  252  is restrained like this, the entire airbag  231  would be much less likely to be distorted in the vehicle body front-rear direction. Thus, even when the upper large inflation portions  242 ,  243  and  244 , disposed over the first and second lower inflation portions  251  and  252 , have inflated, the instant embodiment can restrain distortion of the entire airbag  231 . As a result, the instant embodiment can even further enhance the vehicle occupant protection effect by the airbag  231 . 
     The third embodiment can accomplish the same behavior and advantageous benefits as the first embodiment. Namely, the upper large inflation portions  242 ,  243  and  244  having inflated can separate between upper portions of the pillars  15 ,  16  and  17  and neighborhoods thereof and the vehicle occupants Mf and Mr. Thus, the instant embodiment can even further enhance the vehicle occupant protection effect when the vehicle occupants Mf and Mr are brought into collisions against the inner side surface the vehicle body  11 , i.e. at the time of a so-called secondary collision, following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the third embodiment can sufficiently protect the vehicle occupants Mf and Mr in the neighborhoods of the pillars  15 ,  16  and  17  and in the neighborhoods of the upper edges of the windows  23  and  24 . 
     Further, the inflated front-pillar large inflation portion  242  separates between an upper portion of the pillar  15  and neighborhood thereof and the vehicle occupant Mf. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mf is brought into a collision against the inner side surface of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the third embodiment can sufficiently protect the vehicle occupant Mf in the neighborhoods of the front pillar  15  and upper edge of the window  23 . 
     The inflated rear-pillar large inflation portion  244  separates between an upper portion of the rear pillar  17  and neighborhood thereof and the vehicle occupant Mr. As a result, the instant embodiment can enhance the vehicle occupant protection effect when the vehicle occupant Mr is brought into a collision against the inner side surface of the vehicle body  11 , following occurrence of a primary collision. Thus, in the event of an emergency, such as a lateral collision or rollover of the vehicle  10 , the third embodiment can sufficiently protect the vehicle occupant Mr in the neighborhoods of the rear pillar  17  and upper edge of the rear window  24 . 
     INDUSTRIAL APPLICABILITY 
     The vehicle occupant protection apparatus  30 ,  130  and  230  of the present invention are well suited for application to side curtain airbags of passenger vehicles, such as wagons and sedans. 
     LEGEND 
     
         
         
           
               10  vehicle 
               11  vehicle body 
               12  passenger compartment 
               15  front pillar 
               16  center pillar 
               17  rear pillar 
               19  roof 
               19   a  side portion 
               23 ,  24  window 
               30 ,  130 ,  230  vehicle occupant protection apparatus 
               31 ,  131 ,  231  side curtain airbag 
               32  inflator 
               40 ,  140 ,  240  gas introduction chamber 
               42 ,  142 ,  242  front-pillar large inflation portion 
               44 ,  144 ,  244  rear-pillar large inflation portion 
               45 ,  46 ,  145 ,  146 ,  245 ,  246  small inflation portion 
               51 ,  52 ,  151 ,  251 ,  252  lower inflation portion 
               53 ,  55 ,  155 ,  253 ,  255  sub inflation portion 
               57 ,  152 ,  257  distortion restraint portion 
             Mf, Mr vehicle occupant