Abstract:
A side airbag capable of fully absorbing impact directed to a chest region while keeping an arm from being pressed against the chest region due to inflation is provided. A side airbag  30 , an arm facing section  38  which faces an arm H 2  of the occupant H in an inflated state has a dented shape and serves to push up the arm H 2  to a position where the arm H 2  does not overlap a chest H 3  region of the occupant.

Description:
This is a U.S. National Phase application under 35 USC 371 of International Application PCT/JP2011/050379 (not published in English), filed Jan. 12, 2011. 
     TECHNICAL FIELD 
     The present invention relates to a side airbag configured to absorb impact applied laterally to, for example, a vehicle seat. 
     BACKGROUND ART 
     Conventionally, in a vehicle such as an automobile, a front seat, e.g., the driver&#39;s seat or passenger seat, is provided with a side airbag device for protecting an occupant from impact applied laterally relative to the body of the vehicle. The side airbag device comprises an igniter, inflator, side airbag, impact detection sensor, etc., and is secured to, for example, the frame of a seatback. 
     If impact is applied to, for example, a door member (an example of a lateral portion of the vehicle body) that closes a lateral door opening for the passenger seat, the impact detection sensor detects this impact. Then, the igniter is actuated so that gas is emitted from the inflator. The side airbag is inflated by a pressure of the gas emitted from the inflator. 
     The inflated side airbag projects outward from the seatback to be located between the occupant and door member. The side airbag is large enough to cover that region of the occupant which is oriented in the vehicle width direction. The region of the occupant which is oriented outward in the vehicle width direction mainly covers the range from the chest region to the lumbar region. 
     Since the side airbag is thus located between the occupant and the lateral portion of the vehicle body, impact applied laterally relative to the vehicle body can be absorbed by the inflated side airbag. 
     On the other hand, an arm of the occupant in the seat is normally located beside the chest region. In other words, the arm and chest region of the occupant are arranged side by side in the vehicle width direction. If the side airbag is inflated in this state, the arm of the occupant will be located between the inflated side airbag and the chest region of the occupant. 
     While the impact applied to the lateral portion of the vehicle body is absorbed as the side airbag is inflated, the side airbag subjected to the impact moves inward in the vehicle width direction. When this is done, the arm of the occupant is pressed against the chest region. If the arm is pressed against the chest region as the side airbag moves inward in the vehicle width direction, impact applied to the chest region of the occupant may sometimes increase. 
     In order to keep the arm from being pressed against the chest region due to deployment of the side airbag, therefore, a structure has been proposed in which a seam is provided at that part of the side airbag which faces the arm of the occupant, thereby suppressing inflation of that part of the side airbag which faces the arm. As the inflation of that part of the side airbag which faces the arm is suppressed, the arm can be kept from being pressed against the chest region (see Patent Document 1, for example). 
     In order to bind the occupant in a balanced way, a structure has been proposed in which a non-inflation portion is formed at that part of the side airbag which faces the arm of the occupant, and that part of the side airbag which corresponds to the shoulder of the occupant is inflated (see Patent Document 2, for example). 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2008-1187 
         Patent Document 2: Jpn. Pat. Appln. KOKAI Publication No. 2005-119510 
       
    
     DISCLOSURE OF INVENTION 
     Problem to be Solved by the Invention 
     In the techniques disclosed in Patent Documents 1 and 2, the thickness of that part of the side airbag which faces the arm in the vehicle width direction is so small that a space for the absorption of impact applied laterally relative to the vehicle body is small. Consequently, the impact may not be able to be fully absorbed. 
     An object of the present invention is to provide a side airbag capable of fully absorbing impact while keeping an arm from being pressed against the chest region due to inflation. Further, another object of the present invention is to provide a side airbag device comprising the side airbag. 
     Solution to Problem 
     A side airbag according to a first aspect of the present invention is configured to be deployed and inflated between a door of a vehicle and a vehicle occupant in a lateral direction of the vehicle. The side airbag includes an arm facing section. The arm facing section, provided at an upper end of the side air bag, rises upward as the side air bag inflates, and has a dented shape extending in a longitudinal direction of the vehicle and configured to accommodate an arm of a vehicle occupant. A tether extending between the arm facing section and a lower portion of the side air bag is a cord member, one end of which being connected to the arm facing section and an opposite end of which being connected to the lower portion of the side air bag at a position close to a rear of the side air bag in side view of the vehicle with respect to the one end. 
     In a side airbag according to a second aspect of the invention related to the first aspect of the invention, the arm facing section has such a shape as to be dented downward when the side airbag is deployed. 
     In a side airbag according to a third aspect of the invention related to the second aspect of the invention includes a base fabric, which forms the arm facing section, and a cord member pulls the base fabric inward, thereby bringing the base fabric into the dented shape, in the inflated state. 
     In a side airbag according to a fourth aspect of the invention related to the fourth aspect of the invention, the one end of the cord member is secured to the base fabric and the opposite end of the cord member is secured to the inside of an side airbag on a side opposite to the base fabric. 
     In a side airbag according a fifth aspect of to the invention related to one of the fourth aspect of the invention, includes a partition cloth which separates a space inside the airbag into at least an upper compartment, wherein the cord member is secured to the inside of the airbag as the opposite end is secured to the partition cloth. 
     In a side airbag according to an sixth aspect of the invention related to one of the fourth aspect of the invention, the arm facing section is located around a joint which connects two base fabrics, the cord member being secured to the joint. 
     A side airbag according to a seventh aspect of the invention is configured to be deployed and inflated between a door of a vehicle and a vehicle occupant in a lateral direction of the vehicle. The side airbag includes an arm facing section, provided at an upper end of the side air bag, that rises upward as the side air bag inflates. The arm facing section provided at an upper end of the side air bag, that rises upward as the side air bag inflates has a dented shape extending in a longitudinal direction of the vehicle and is configured to accommodate an arm of a vehicle occupant. The arm facing section is located around a joint which connects an occupant-side base fabric located on the occupant side and a vehicle-body-side base fabric located on the side of the lateral portion of the vehicle body. A tether extending between the arm facing section and a lower portion of the side air bag, is a cord member, one end of which being connected to the lower portion of the side air bag at a position close to a rear of the side air bag in side view of the vehicle with respect to the one end. 
     A side airbag according to an eighth aspect of the invention related to the seventh aspect, includes the one end of the cord member is secured to the joint and the opposite end of the cord member is to at least one of the inside of the occupant-side base fabric and the inside of the vehicle-body-side base fabric. 
     Effect of the Invention 
     According to the present invention, a space for the absorption of impact directed to the chest region of an occupant can be secured while keeping an arm from being pressed against the chest region due to deployment of a side airbag. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view showing the interior of an automobile furnished with a side airbag according to a first embodiment of the present invention; 
         FIG. 2  is a sectional view of the automobile taken along line F 2 -F 2  shown in  FIG. 1 ; 
         FIG. 3  is a schematic view of the side airbag of  FIG. 2  in a deployed state taken from the front side of a vehicle body; 
         FIG. 4  is a sectional view of the vehicle body taken along line F 4 -F 4  shown in  FIG. 3 ; 
         FIG. 5  is a sectional view showing the side airbag of  FIG. 4  cross-sectioned along line F 5 -F 5 ; 
         FIG. 6  is a diagram more schematically showing a state where the side airbag is inflated and deployed; 
         FIG. 7  is a sectional view showing a side airbag according to a second embodiment of the present invention in an inflated and deployed state, cross-sectioned in a width direction; 
         FIG. 8  is a side view showing the side airbag of  FIG. 7  in the inflated and deployed state, taken from the outside with respect to the width direction; 
         FIG. 9  is a sectional view showing a side airbag according to at third embodiment of the present invention in an inflated and deployed state, cross-sectioned in the width direction; and 
         FIG. 10  is a sectional view showing a side airbag according to a fourth embodiment of the present invention, cross-sectioned in the same manner as in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A side airbag according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 6 .  FIG. 1  is a side view schematically showing an automobile  10  furnished with a side airbag device  20 . The side airbag device  20  comprises a aide airbag  30  as an example of the present invention. The automobile  10  is an example of a vehicle furnished with the side airbag device  20 . 
       FIG. 1  shows a vehicle interior  11  of the automobile  10 . Front seats  12  and a rear seat  13  are disposed in the vehicle interior  11 . The front seats  12  comprise a driver&#39;s seat (not shown) and passenger seat  14 .  FIG. 1  shows the a passenger seat  14 . 
     The passenger seat  14  comprises a seat cushion  15 , a seatback  16 , and the side airbag device  20 . The seat cushion  15  is supported on a floor panel  18  by a slide mechanism (not shown) for sliding motion in a vehicle-body longitudinal direction A. The seatback  16  is located behind the seat cushion  15 . The seatback  16  comprises a framework member  16   a  (part of which is indicated by a dotted line in  FIG. 1 ) and a cushion material that covers the framework member. The driver&#39;s seat is constructed in substantially the same manner as the passenger seat  14 . 
     The following is a definition of the longitudinal, transverse, and vertical directions of a vehicle body  17 . The direction in which the automobile  10  advances with its accelerator pedal depressed when a steering unit operated by the driver is in its initial position is parallel to the vehicle-body longitudinal direction A when the automobile  10  is placed on a flat surface perpendicular to the direction of the gravitational force and when the reverse gear is not engaged as a traveling gear of the automobile  10 . The direction of the advance is defined as a forward direction along the vehicle-body longitudinal direction, and the opposite direction as a reverse direction along the vehicle-body longitudinal direction. A front-side part of the vehicle body  17  with respect to the vehicle-body longitudinal direction A is defined as a front portion  17   a , and an opposite side of the vehicle body  17  as a rear portion  17   b.    
     A steering wheel is an example of the steering unit. The initial position of the steering unit is a position where the steering unit is not operated by the driver. As for the steering wheel, the steering wheel is not rotating in this position. 
     The vehicle-body longitudinal direction A is perpendicular to a vehicle width direction B. The vehicle-body width direction is the vehicle width direction, and the left-right direction is defined with respect to the longitudinal direction A. A vehicle-body vertical direction C is a direction perpendicular to the vehicle-body longitudinal direction A and vehicle width direction B, and an upper portion  17   c  and lower portion  17   d  are arranged based on the longitudinal and width directions. Further, the vehicle-body vertical direction C is a direction parallel to the direction in which the gravitational force acts when the automobile  10  is placed on a flat surface perpendicular to the direction of the gravitational force. The direction of the gravitational force is defined as a downward direction, and the direction opposite to the direction of the gravitational force as an upward direction. 
     The side airbag device  20  provided at each of the driver seat (not shown) and passenger seat  14 . The side airbag device  20  provided at the driver seat and the side airbag device  20  provided at the passenger seat  14  may be constructed in the same manner. Therefore, the side airbag device  20  provided at the passenger seat  14  will be representatively described below. The passenger seat  14  is an example of a seat according to the present invention. 
     First, the position of the passenger seat  14  in the vehicle interior  11  will be specifically described.  FIG. 2  is a sectional view of the automobile  10  taken along line F 2 -F 2  shown in  FIG. 1   FIG. 2 , in which the vicinity of the front seat  12  of the automobile  10  is cross-sectioned in the vehicle width direction B, shows the vicinity of the passenger seat  14 . As shown in  FIG. 1 , the vehicle body  17  is formed with a door opening  5  outside the passenger seat  14  with respect to the vehicle width direction. The opening  5  is covered with the door member  6  in such a manner that it can be opened and shut. The passenger seat  14  is located inside a door member  6  with respect to the vehicle width direction. A door opening and a door member that closes this opening are disposed in the vicinity of the driver seat, which is constructed in the same manner as the vicinity of the passenger seat  14 . 
     As shown in  FIGS. 1 and 2 , the side airbag device  20  is provided at the seatback  16 . Specifically, the side airbag device  20  is disposed in that part of the framework member  16   a  of the seatback  16  which faces the door member  6 . The side airbag device  20  comprises the side airbag  30 , a case  40 , an inflator  50 , an igniter  60 , an impact detection sensor  70 , etc. 
     The case  40  is secured to the framework member  16   a . The side airbag  30  is accommodated in the case  40 . The side airbag  30  will be described in detail later. The inflator  50  can inject gas into the side airbag  30 . The igniter  60  actuates the inflator  50 . The impact detection sensor  70  detects impact applied to the automobile  10  and actuates the igniter  60  based on the impact. Although the impact detection sensor  70  is shown to be located outside the vehicle body  17  in  FIG. 1 , it is actually disposed somewhere within the vehicle body  17 . 
     If gas is injected by the inflator  50 , the side airbag  30  is inflated and deployed. Therefore, the case  40  is configured to be broken so that the side airbag  30  can be externally deployed when the side airbag  30  is inflated. A notch or the like is formed in that part of the seatback  16  which faces the door member  6  or a region near that part in order to allow the inflated and deployed side airbag  30  to be deployed outside the seat. The deployed side airbag  30  is deployed outside the seat through the notch. 
     The side airbag  30  will be described specifically.  FIG. 3  is a schematic view of the side airbag  30  in a deployed state taken from the front side of the vehicle body.  FIG. 4  is a sectional view of the vehicle body  17  taken along line F 4 -F 4  shown in  FIG. 3 .  FIG. 4  shows the deployed state of the side airbag  30  cross-sectioned in the vehicle-body longitudinal direction A.  FIG. 4  shows the vicinity of the passenger seat  14 .  FIG. 5  shows the deployed side airbag  30  cross-sectioned along line F 5 -F 5  shown in  FIG. 4 .  FIG. 5  illustrates only the side airbag  30  and illustrates neither the passenger seat  14  nor an occupant H seated in the passenger seat  14 . 
     Here are defined a longitudinal direction A 1 , width direction B 1 , and vertical direction C 1  of the side airbag  30 . The various directions of the side airbag  30  are defined based on such an attitude that the side airbag  30  is inflated and deployed laterally relative to the seat. 
     The various directions of the side airbag  30  described above are coincident with directions set for the passenger seat  14  (seat to which the side airbag device  20  is attached). In the present embodiment, a longitudinal direction, width direction, and vertical direction set for the passenger seat  14  are coincident with the vehicle-body longitudinal direction A, vehicle width direction B, and vehicle-body vertical direction C, respectively, defined for the vehicle body  17 . In the present embodiment, therefore, the longitudinal direction A 1 , width direction B 1 , and vertical direction C 1  of the side airbag  30  are coincident with A, B and C, respectively. The directions A 1 , B 1  and C 1  are perpendicular to one another. 
     If the seatback  16  is constructed so that it can be longitudinally reclined relative to the seat cushion  15 , the various directions of the side airbag  30  are set based on a state where the seatback  16  is not reclined. In  FIGS. 2 to 4 , the seatback  16  is not reclined. 
     As shown in  FIG. 5 , the side airbag  30  comprises a first base fabric  31  for use as a vehicle-body-side base fabric, second base fabric  32  as an occupant-side base fabric, third base fabric  33  as a top base fabric, partition cloth  34 , and tether  35 . The first and second base fabrics  31  and  32  are located opposite each other in the width direction B and have substantially the same shape and size. All areas of the first and second base fabrics  31  and  32  except the upper ends of their respective peripheral edges  31   a  and  32   a  are connected to one another. As an example of this connection structure, those areas are sewn together. The first and second base fabrics  31  and  32 , thus sewn together, form a side airbag body  36 . The side airbag body  36  is in the form of an open-top bag. The side airbag body  36  is in the form of an open-top bag. 
     The third base fabric  33  is disposed so as to close the top opening of the side airbag body  36 . The whole area of a peripheral edge  33   a  of the third base fabric  33  is connected to the opening edge of the side airbag body  36 . As an example of this connection structure, those edges are sewn together. In the drawing, reference number  37  denotes a seam (joint) along which the side airbag body  36  and third base fabric  33  are sewn together. As shown in  FIG. 4 , the seam  37  extends a predetermined length in the longitudinal direction A 1 . The predetermined length stated here is a sufficient length to enable an arm facing section  38  (described later) to support an arm H 2 . 
     The partition cloth  34  divides the interior of the side airbag  30  into an upper compartment  45  and a lower compartment  46 . When the side airbag  30  is in the deployed state, the lower compartment  46  faces a lumbar region H 1  of the occupant H. In the vicinity of a region that faces the lumbar region H 1  when the side airbag  30  is in the deployed state, an entire peripheral edge  34   a  of the partition cloth  34  is sewn on the inner surfaces of the first and second base fabrics  31  and  32  throughout the circumference, whereby the interior of the side airbag  30  is divided into the upper and lower compartments  45  and  46 . 
     The tether  35  is in the form of a cord, one end  35   a  of which is secured to the center of the third base fabric  33  with respect to the longitudinal direction A 1  as well as to the width direction B 1 . For this fixing, the one end  35   a  and third base fabric  33  are sewn together, for example. The other end  35   b  of the tether  35  is secured to the center of the partition cloth  34  with respect to the width direction B 1  in a position behind the one end  35   a  with respect to the longitudinal direction A 1 . As an example of this fixing structure, the other end  35   b  and partition cloth  34  are sewn together. The length of the tether  35  is set so that the tether  35  pulls down the center of the third base fabric  33  with respect to its width direction to cause the third base fabric  33  to be dented downward, as shown in  FIG. 5 , when the side airbag  30  is inflated and deployed. As the other end  35   b  of the tether  35  is secured to the partition cloth  34 , moreover, the length of the tether  35  can be reduced so that the arm facing section  38  (described later) can be formed earlier. The tether is an example of a cord member according to the present invention. 
     The following is a more specific description of the position and size of the side airbag  30  and the position of the one end  35   a  of the tether  35 . In the present embodiment, the occupant H is assumed to have the physique of the average Japanese adult, by way of example. 
     The side airbag  30 , which is inflated and deployed, as shown in  FIG. 3 , is located outside the passenger seat  14  with respect to the vehicle width direction. When the occupant H is seated in the passenger seat  14 , the side airbag  30  is disposed just beside the occupant H in a space between the occupant H and door member  6  (vehicle body  11 ). Further, the inflated and deployed side airbag  30  projects outward from that part of the seatback  16  which faces the arm H 2  of the occupant H. When the side airbag  30  is fully deployed, the side airbag  30  pushes up the arm H 2  of the occupant H from below, and the third base fabric  33  that constitutes a top portion faces the arm H 2  from below. A top portion  30   a  of the side airbag  30 , which is formed of the third base fabric  33 , forms the arm facing section  38 . The arm facing section  38  is an example of an arm facing section according to the present invention. The third base fabric  33  is an example of a base fabric that forms the arm facing section according to the present invention. 
     The one end  35   a  of the tether  35  is connected to that part of the third base fabric  33  which faces the center of the arm H 2  with respect to its width direction. The width direction of the arm H 2  is a direction of the arm H 2  parallel to the width direction B 1  of the side airbag device  20 . In the present embodiment, the position of the center of the third base fabric  33  with respect to its width direction faces the center of the arm H 2  with respect to its width direction. Thus, the one end  35   a  of the tether  35  is connected to the center of the third base fabric  33  with respect to the width direction B 1 . 
     As shown in  FIG. 4 , the inflated and deployed side airbag  30  has a size that covers the lumbar region H 1  and the entire area of a chest region H 3  of the occupant H. Further, the inflated and deployed side airbag  30  has such a size that the arm H 2  that is pushed up by the dented arm facing section  38  is parallel or substantially parallel to the longitudinal direction A 1 , as shown in  FIG. 4 . Although the arm H 2  is set to be parallel or substantially parallel to the longitudinal direction in the present embodiment, it is not limited to this. The size of the side airbag  30  should only be such that the arm H 2  is not located between the chest region H 3  and side airbag  30  when the side airbag is inflated and deployed. Thus, the arm H 2  may be pushed up above a position where it is parallel to the longitudinal direction. This is an example of a position where the arm does not overlap a chest region according to the present invention. 
     When the side airbag  30  is inflated and deployed, the seam  37  between the side airbag body  36  and third base fabric  33  is urged to project outward, and the center of the third base fabric  33  is pulled by the tether  35 , so that the arm facing section  38  is dented. The position of the bottom of the hollow is designated by P. In the present embodiment, P is in the center of the third base fabric with respect to the width direction B 1 . In  FIG. 4 , the bottom position P is indicated by a dotted line. The bottom position P extends in the longitudinal direction A 1 . 
     Since the seam  37  and position P extend in the longitudinal direction A 1 , as shown in  FIG. 4 , the dent shape of the arm facing section  38  is kept in the longitudinal direction A 1 . The arm H 2  of the occupant H is accommodated in this dent. The width of the third base fabric  33  is set so that the arm H 2  can be accommodated. Since the other end  35   b  is located behind the one end  35   a , the dent of the arm facing section  38  is formed mainly on the front side. This is because the arm H 2  is located ahead of a shoulder H 4 . In other words, the positions of the ends  35   a  and  35   b  are set so that the dent shape is formed ahead of the Shoulder H 4  of the occupant H at the least. 
     Since the third base fabric  33  is disposed at the top portion  30   a , moreover, the inflated and deployed side airbag  30  has a width W that increases from bottom to top. Specifically, the width of that part of the side airbag  30  which faces the chest region H 3  can be made larger, so that allowance for the absorption of impact applied to the chest region H 3  can be made generous. The width W is set to be larger by virtue of the absence of the arm H 2 . 
     The following is a description of the operation of the side airbag device  20 . If impact is applied laterally to the automobile  10 , the impact detection sensor  70  detects this impact. In the present embodiment, the impact detection sensor  70  is set such that it can detect, for example, impact of a preset magnitude or greater. If the impact detection sensor  70  detects impact, the igniter  60  is actuated. When the igniter  60  is actuated, the inflator  50  discharges gas. Consequently, the side airbag  30  is inflated and deployed. 
     As the side airbag  30  is inflated and deployed, the arm facing section  38  of the side airbag  30  pushes up the arm H 2  of the occupant H. When this is done, the side airbag  30  pushes up the arm H 2  to a position where the arm H 2  does not overlap the chest region H 3  of the occupant H. In  FIG. 4 , the arm H 2  that is not yet pushed up is indicated by a two-dot chain line.  FIG. 6  is a diagram more schematically showing a state where the side airbag  30  is inflated and deployed.  FIG. 6  shows an example in which the passenger seat is viewed from the front. As shown in  FIG. 6 , the inflated and deployed side airbag  30  is located beside the chest region H 3  of the occupant H. Since the side airbag  30  pushes up the arm H 2 , the arm H 2  is not accommodated between the chest region H 3  and side airbag  30 .  FIG. 6  shows a state after the door member  6  is moved so that it strikes the side airbag  30 . 
     If the door member  6  is caused to project inward relative to the vehicle width by lateral impact, as shown in  FIG. 3 , the impact is absorbed by the side airbag  30 . 
     In the side airbag device  20  constructed in this manner, the side airbag  30  pushes up the arm H 2  of the occupant H so that the arm H 2  is not accommodated between the chest region H 3  and side airbag  30 . Consequently, the width W of the side airbag  30 , which is allowance for the absorption of impact, can be fully secured, so that the impact applied to the occupant H can be further reduced. Since the arm H 2  is pushed up, moreover, the arm H 2  cannot be pressed against the chest region H 3 , so that the impact cannot be applied to the chest region H 3  through the arm H 2 . 
     Since the arm facing section  38  is dented, furthermore, the arm H 2  is accommodated into the dent in the process of inflation and deployment, so that the arm H 2  can be smoothly pushed up without being disengaged from the side airbag  30 . 
     In connection with the present embodiment, the side airbag device  20  has been described as being provided at the passenger seat  14 , for example. However, the side airbag device  20  may alternatively be used for the driver seat or rear seat  13 . Also in this case, the same effect as that of the present embodiment can be obtained. 
     A side airbag according to a second embodiment of the present invention will now be described with reference to  FIGS. 7 and 8 . Like reference numbers used in the first embodiment are used to designate configurations having the same functions as those of the first embodiment, and a description thereof is omitted. The present embodiment differs from the first embodiment in the structure of a side airbag  30 . Other structures are the same as those of the first embodiment. The following is a specific description of the different structure. The structures of a side airbag device  20  of the present embodiment other than the side airbag  30  are the same as those of the first embodiment. 
       FIG. 7  is a sectional view showing the side airbag  30  of the present embodiment in an inflated and deployed state, cross-sectioned in the width direction  31 . In the present embodiment, as shown in  FIG. 7 , the side airbag  30  comprises fourth and fifth base fabrics  80  and  81  in place of the first to third base fabrics  31  to  33 . The fourth and fifth base fabrics  80  and  81  are located opposite each other in the width direction  31 , and their respective peripheral edges  80   a  and  81   a  are entirely connected to each other. As an example of the mutual connection structure, those edges are sewn together. The fourth and fifth base fabrics  80  and  81  are an example of two base fabrics according to the present invention. 
     In the present embodiment, a joint that is formed by connecting the peripheral edges  80   a  and  81   a  of the fourth and fifth base fabrics  80  and  81  is located, for example, on an imaginary plane that is defined by the longitudinal direction A 1  and vertical direction C 1 . In other words, a seam that connects the fourth and fifth base fabrics  80  and  81  is located on the imaginary plane defined by the longitudinal direction. A 1  and vertical direction C 1 . 
       FIG. 8  is a side view showing the side airbag  30  of the present embodiment in the inflated and deployed state, taken from the outside with respect to the width direction B 1 . As shown in  FIG. 8 , a seam  82  as a joint along which the respective upper edges of the fourth and fifth base fabrics  80  and  81  are sewn together is designed to extend in the longitudinal direction A 1  and face the center of the arm H 2  when the side airbag  30  is inflated and deployed. The seam  82 , like that of the first embodiment, is long enough to support the arm H 2 . 
     One end  35   a  of a tether  35  is connected to the seam  82 . As an example of the connection structure, the one end  35   a  and seam  82  are sewn together. A partition cloth  34  is connected to those parts of the fourth and fifth base fabrics  80  and  81  near the lumbar region H 1  of the occupant H so as to divide a lower compartment  46  and upper compartment  45  in the inflated and deployed state. The connection structure and position of the partition cloth  34  are the same as those of the first embodiment. The other end  35   b  of the tether  34 , like that of the first embodiment, is connected to the partition cloth  34 . The positional relationship between the one end  35   a  and the other end  35   b  is the same as that of the first embodiment. Specifically, the other end  35   b  is located behind the one end  35   a . Thus, as in the first embodiment, a dent of an arm facing section  38  is formed mainly on the front side. The one end  35   a  and the other end  35   b  are set so that the dent shape of the arm facing section  38  is formed ahead of the shoulder H 4  of the occupant H at the least. 
     When the side airbag  30  is inflated and deployed, as shown in  FIG. 7 , a top portion  83  of the fourth and fifth base fabrics  80  and  81  forms the arm facing section  38 . The length of the tether  35  is set so that the arm facing section  38  is dented. 
     Seams  84  and  85  that extend in the longitudinal direction A 1  are formed near the seam  82  on the top of fourth and fifth base fabrics  80  and  81 . The seams  84  and  85  stated here do not connect different base fabrics but sew threads on them. 
     When the side airbag  30  is inflated and deployed, the seams  84  and  85  face an outer edge  86  of the arm H 2  of the occupant H with respect to the width direction B 1  (B). In other words, the seams  84  and  85  are set so as to face the outer edge  86 . The seams  84  and  85  are an example of bending portions that are formed so that the fourth and fifth base fabrics  80  and  81  are turned back when the side airbag  30  is inflated, and deployed. 
     When the side airbag  30  is inflated and deployed, that part of the seam  82  to which the tether  35  is connected is pulled, and the fourth and fifth base fabrics  80  and  81  are turned back at the seams  84  and  85 , whereby the top portion is dented. Since a bottom position P and the seams  84  and  85  extend in the longitudinal direction A 1 , the dent shape of the arm facing section  38  is maintained in the longitudinal direction A 1 , as in the first embodiment shown in  FIG. 1 . 
     The seams  84  and  85  are an example of the bending portions. Alternatively, they may be formed so that their outside parts are turned back in positions where the fourth and fifth base fabrics  80  and  81  face the outer edge of the arm, or near positions opposite the outer edges of the arm, or near positions opposite the outer edges of the arm. Based on this structure, as in the first embodiment, the arm H 2  can be accommodated at the arm facing section  38 . 
     The size and shape of the inflated and deployed side airbag  30  are the same as those of the side airbag  30  that are constructed using the first to third base fabrics  31  and  33  of the first embodiment. The side airbag device  20  is constructed in the same manner as the first embodiment except for the side airbag  30  described above. The side airbag  30  is deployed in the same manner as in the first embodiment. The deployed side airbag  30  of the present embodiment, like that of the first embodiment, pushes up the arm H 2  of the occupant H to an up position where it does not overlap the chest region H 3  in the width direction B 1 . 
     Also in the present embodiment, the same operation and effect as in the first embodiment can be obtained. 
     A side airbag according to a third embodiment of the present invention will now be described with reference to  FIG. 9 . Like reference numbers used in the first embodiment are used to designate configurations having the same functions as those of the first embodiment, and a description thereof is omitted. The present embodiment differs from the first embodiment in the structure of a side airbag  30 . Other structures are the same as those of the first embodiment. The following is a specific description of the different structure. The structures of a side airbag device  20  of the present embodiment other than the side airbag  30  are the same as those of the first embodiment. 
       FIG. 9  is a sectional view showing the side airbag  30  of the present embodiment in an inflated and deployed state, cross-sectioned in the width direction B 1 . As shown in  FIG. 8 , the side airbag  30  comprises sixth to ninth base fabrics  90 ,  91 ,  92  and  93 , in place of the first to third base fabrics  31  to  33 , and tether  35 . 
     The sixth and seventh base fabrics  90  and  91  are located opposite each other in the width direction B 1 . The respective front and rear edges of the sixth and seventh are connected to one another. As an example of the connection structure, those edges are sewn together. The entire peripheral edge of the eighth base fabric  92  is connected to upper edges  90   a  and  91   a  of the sixth and seventh base fabrics  90  and  91 . As an example of the connection structure, those edges are sewn together. The entire peripheral edge of the ninth base fabric  93  is connected to lower edges  90   b  and  91   b  of the sixth and seventh base fabrics  90  and  91 . As an example of the connection structure, those edges are sewn together. 
     A seam  100  between the sixth and eighth base fabrics  90  and  92  extends in the longitudinal direction A 1 . A seam  101  between the seventh and eighth base fabrics  90  and  92  extends in the longitudinal direction A 1 . The seams  100  and  101  are long enough to support the arm H 2 . 
     The side airbag  30  is formed as a bag as the sixth to ninth base fabrics  90  to  93  are sewn together in the above-described manner. The eighth base fabric  92  forms an arm facing section  38 . One end  35   a  of the tether  35  is connected to that part (e.g., the center with respect to the width direction B 1  of the arm according to the present embodiment) of the eighth base fabric  92  which faces the center of the arm H 2  of the occupant H. The other end  35   b  of the tether  35  is connected to the ninth base fabric  93 . The length of the tether  35  is set so that the arm facing section  38  is dented so as to accommodate the arm H 2  when the side airbag  30  is inflated and deployed. A bottom position P extends in the longitudinal direction A 1 . The eighth base fabric  92  is large enough to accommodate the arm H 2 . 
     When the side airbag  30  is inflated and deployed, it is pulled by the tether  35 , and the seams  100  and  101  between the ninth base fabric  93  and the sixth and seventh base fabrics  90  and  91  project outward, so that the arm facing section  38 , like that of the first embodiment, is dented. The dent shape is maintained in the longitudinal direction A 1 . 
     In the present embodiment, the interior of the side airbag  30  is not divided into upper and lower compartments  45  and  46 . Further, lower edges  90   b  and  91   b  of the sixth and seventh base fabrics  90  and  91  and the ninth base fabric  93  are connected. When the side airbag  30  is inflated and deployed, therefore, a width w of that part of it which faces the lumbar region H 1  of the occupant H can be fully secured. In other words, allowance for the absorption of impact applied to the lumbar region H 1  can be made generous. 
     The side airbag device  20  is constructed in the same manner as the first embodiment except for the side airbag  30  described above. The side airbag  30  is deployed in the same manner as in the first embodiment. The deployed side airbag  30  of the present embodiment, like that of the first embodiment, pushes up the arm H 2  of the occupant H to an up position where it does not overlap the chest region H 3  in the width direction B 1 . 
     Further, the longitudinal positional relationship between the one end  35   a  and the other end  35   b  of the tether  35  is the same as that of the first embodiment. Specifically, the other end  35   b  is located behind the one end  35   a . Thus, as in the first embodiment, a dent of the arm facing section  38  is formed mainly on the front side. The one end  35   a  and the other end  35   b  are set so that the dent shape of the arm facing section  38  is formed ahead of the shoulder H 4  of the occupant H at the least. 
     In the present embodiment, impact applied to the lumbar region H 1  of the occupant H can be further absorbed, in addition to the same effect as that of the first embodiment. 
     A side airbag according to a fourth embodiment of the present invention will now be described with reference to  FIG. 10 . Like reference numbers used in the second embodiment are used to designate configurations having the same functions as those of the second embodiment, and a description thereof is omitted. The present embodiment differs from the second embodiment in the structure of a side airbag  30 . The structures of a side airbag device  20  other than the side airbag  30  are the same as those of the second embodiment. The following is a specific description of the different structure. 
     The side airbag  30  of the present embodiment differs from the side airbag  30  described in connection with the second embodiment in that it does not comprise a partition cloth  34  and in the region to which the other end  35   b  of a tether  35  is secured. The structures of the side airbag  30  of the present embodiment other than the above-described structures are the same as those of the side airbag  30  of the second embodiment. 
       FIG. 10  shows the side airbag  30  of the present embodiment, cross-sectioned in the same manner as in  FIG. 5  showing the first embodiment. As shown in  FIG. 10 , the side airbag  30  of the present embodiment does not comprise the partition cloth  34 . One end  35   a  of the tether  35 , like that of the second embodiment, is connected to a seam  82  along which the respective upper ends of peripheral edges  80   a  and  81  of fourth and fifth base fabrics  80  and  81  are connected to each other. As an example of this connection structure, those edges are sewn together. 
     As shown in  FIG. 10 , the other end  35   b  of the tether  35  is connected to a seam  82   a  along which the respective lower ends of the peripheral edges  80   a  and  81   a  of the fourth and fifth base fabrics  80  and  81  are sewn together at the seam as the joint that connect the peripheral edges  80   a  and  81   a . In other words, the other end  35   b  is connected to both the fourth and fifth base fabrics  80  and  81 . As an example of this connection structure, those edges are sewn together. 
     Also in the present embodiment, the positional relationship between the one end  35   a  and the other end  35   b  in the longitudinal direction A 1  is the same as in the first and second embodiments. Specifically, the other end  35   b  is located behind the one end  35   a . Thus, as in the first embodiment, a dent of an arm facing section  38  is formed mainly on the front side. The one end  35   a  and the other end  35   b  are set so that the dent shape of the arm facing section  38  is formed ahead of the shoulder H 4  of the occupant H at the least. 
     The deployed side airbag  30  of the present embodiment, like that of the first embodiment, pushes up the arm H 2  of the occupant H to an up position where it does not overlap the chest region H 3  in the width direction B 1 . 
     In the present embodiment, moreover, the other end  35   b  of the tether  35  is connected to the seam  82   a  as a joint between the fourth and fifth base fabrics  80  and  81 , whereby it is connected to both the fourth and fifth base fabrics  80  and  81 . However, this is not limitative. The other end  35   b  may be secured to the fourth base fabric  80  only. In this case, the other end  35   b  should only be secured to that part of the fourth base fabric  80  which is located below the one end  35   a . Alternatively, the other end  35   b  may be connected to the fifth base fabric  81  only. In this case, the other end  35   b  should only be secured to that part of the fifth base fabric  81  which is located below the one end  35   a . As in the second embodiment shown in  FIG. 7 , moreover, the other end  35   b  may be connected to both the fourth and fifth base fabrics  80  and  81  by the partition cloth  34 . 
     Thus, the other end  35   b  should only be connected to the fourth base fabric  80 , as an example of the vehicle-body-side base fabric according to the present invention, and/or a fifth base fabric  81 , as an example of the occupant-side base fabric according to the present invention. Even in the case that the other end  35   b  is secured to at least one of the fourth and fifth base fabrics  80  and  81 , the one end  35   a  and the other end  35   b  should preferably be set so that the dent shape of the arm facing section  38  is formed ahead of the shoulder H 4  of the occupant H at the least. 
     In the first to fourth embodiments, the occupant H is assumed to have the physique of the average Japanese adult. The side airbag  30  is formed adaptively to the occupant H. However, the occupant H is not bound to be formed adaptively to the physique of the average Japanese adult. The side airbag  30  may be shaped to fit the body of an occupant of a country where an apparatus (vehicle or automobile) mounted with the side airbag device  20  is used. Also in this case, the deployed side airbag  30  pushes up the arm H 2  of the occupant H to a position where it does not overlap the chest region H 3  in the width direction B 1 . 
     In the first and second embodiments, moreover, the single partition cloth  34  is used to divide the interior of the side airbag  30  into two parts, an upper compartment  45  and lower compartment  46 . However, this is not limitative. The partition cloth should only be able to divide the interior of the side airbag  30  into at least upper and lower compartments. In other words, the partition cloth may be designed to divide the interior of the side airbag into, for example, the upper and lower compartments and one or more additional compartments. In this case, the interior of the side airbag  30  is divided into the upper compartment  45 , lower compartment  46 , and one or more additional compartments. Also in this structure in which the interior of the side airbag  30  is divided into three or more compartments, the other end  35   b  of the tether  35  should only be secured to the partition cloth. Alternatively, a plurality of partition cloths may be used to divide the interior of the side airbag  30  into three or more compartments as described above. In this case, the other end  35   b  of the tether  35  is secured to at least one of the plurality of partition cloths. 
     Also in the above-described structure in which the interior of the side airbag  30  is divided into three or more compartments, the positional relationship between the one end  35   a  and the other end  35  of the tether  35  in the longitudinal direction A 1  is the same as in the first and second embodiments, so that the same effect as those of the first and second embodiments can be obtained. 
     In the first to fourth embodiments, moreover, the side airbag device  20  is provided at the passenger seat, by way of example. However, this is not limitative. The side airbag device  20  may be provided at the vehicle body  17 . For example, the side airbag devices  20  described in connection with the first to fourth embodiments may be provided at the door member  6 . 
     Also in the case that the side airbag device  20  is provided at the vehicle body  17 , the position and attitude of the deployed side airbag  30  relative to the seat are the same as in the first to fourth embodiments. In this case, the longitudinal, vertical, and width directions of the side airbag  30  are coincident with the longitudinal, transverse, and vertical directions, respectively, of the seat that faces the deployed side airbag  30 . 
     In the case that the side airbags  30  described in connection with the first to fourth embodiments are provided at the vehicle body  17 , e.g., the door member  6 , the longitudinal, vertical, and width directions of the side airbag  30  are coincident with the longitudinal, transverse, and vertical directions, respectively, of the passenger seat  14 , that is, the vehicle-body longitudinal direction, vehicle width direction, and vehicle-body vertical direction, respectively. 
     In the first embodiment, moreover, the airbag body  36  and third base fabric  33  form an airbag unit  200 . Thus, in the first embodiment, the side airbag  30  is configured to comprise the airbag unit  200 , tether  35 , and partition cloth  34 . In the fourth embodiment, the side airbag  30  comprises an airbag unit  200  and the tether  35 . 
     In the second and fourth embodiments, the fourth and fifth base fabrics  80  and  81  form an airbag unit  200 . Thus, in the second embodiment, the side airbag  30  comprises the airbag unit  200 , partition cloth  34 , and tether  35 . 
     In the third embodiment, the six, seventh, eighth, and ninth base fabrics  90  to  93  form an airbag unit  200 . Thus, in the third embodiment, the side airbag  30  comprises the airbag unit and tether  35 . 
     The airbag unit  200  described above defines the outline of the side airbag  30 . The side airbag  30  is deployed as gas is injected into the airbag unit  200 . 
     The airbag and the airbag unit are equivalent in the case that the side airbag  30  comprises neither the tether  35  nor the partition cloth  34  and is formed only of a member such as a base fabric that defines the outline of the side airbag  30 . 
     This invention is not limited directly to the embodiments described above, and in carrying out the invention, its constituent elements may be embodied in modified forms without departing from the spirit of the invention. Further, various inventions may be made by suitably combining a plurality of constituent elements disclosed in the foregoing embodiments. For example, some constituent elements may be deleted from all the constituent elements shown in the foregoing embodiments. Furthermore, constituent elements according to different embodiments may be appropriately combined. 
     EXPLANATION OF REFERENCE NUMBERS 
     
         
         
           
               14 : Passenger seat (seat) 
               20 : Side airbag device 
               30 : Side airbag 
               31 : First base fabric (vehicle-body-side base fabric) 
               32 : Second base fabric (occupant-side base fabric) 
               33 : Third base fabric (upper base fabric) 
               34 : Partition cloth 
               33 : Third base fabric (base fabric) 
               35 : Tether (cord member) 
               38 : Arm facing section 
               45 : Upper compartment 
               46 : Lower compartment 
               50 : Inflator 
               60 : Igniter 
               80 : Fourth base fabric (two base fabrics) 
               81 : Fifth base fabric (two base fabrics) 
             H 3 : Chest region