Patent Publication Number: US-2022227326-A1

Title: Side airbag device and method for manufacturing side airbag device

Description:
TECHNICAL FIELD 
     The present invention relates to a side airbag device installed in a vehicle seat and a manufacturing method thereof. 
     BACKGROUND TECHNOLOGY 
     In order to protect passengers in the event of a vehicle collision, it is well known that vehicles are equipped with one or a plurality of airbags. These airbags include, for example, various forms such as: a so-called driver airbag which expands from near the center of the steering wheel of an automobile so as to protect a driver; a curtain airbag which deploys downward along an inner side of a window of an automobile so as to protect passengers during collisions in a lateral direction of the vehicle, as well as when overturning and during rollover accidents; and a side airbag stored in a side port of a seat which is deployed between the passenger and a side panel so as to protect the passenger upon impact in the lateral direction of the vehicle. The present invention relates to a side airbag device. 
     The side airbag device described in Patent Document 1 below is provided with a main airbag which expands and deploys at the front of the vehicle based on gas from an inflator to protect an occupant and an auxiliary airbag which starts inflating prior to the main airbag and moves the occupant towards the inside of the vehicle. The presence of the main airbag and the supplementary airbag is said to ensure the restraint of the occupant in a confined space and to improve the protection performance of the occupant. Note that there are other inventions apart from the invention described in Patent Document 1 of a side airbag device provided with an auxiliary airbag in addition to a main airbag. 
     Herein, the side airbag device is stowed in a side supporting part of a seat. Therefore, there are many restrictions on the shape and size, and thus the airbag device packaging must be compact. Also, ensuring that the airbag is deployed reliably and quickly is an important issue. 
     However, in a side airbag system with a main airbag and an auxiliary airbag, the auxiliary airbag, which starts to deploy first, may disturb the posture of the main airbag and adversely affect the deployment behavior of the main airbag. 
     When the main airbag and the auxiliary airbag are separately folded and stowed, a cover may be used to cover the entire airbag since the two folded bag masses tend to separate, which makes handling as an airbag module inconvenient. However, the provision of a cover as a separate member is inconvenient due to complications in the manufacturing process and an increase in costs. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-023494 
       
    
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     In light of the situation described above, an object of the present invention is to provide a side airbag device capable of improving the deployment speed of an airbag and a manufacturing method thereof. 
     Another object of the present invention is to provide a side airbag device capable of promoting an appropriate deployment behavior of the airbag and a method of manufacturing the same. In particular, the object is to provide a side airbag device capable of securely restraining an occupant with optimal deployment behavior without reducing the deployment speed of the airbag, and a manufacturing method thereof. 
     A further object of the present invention is to provide a side airbag device which is easy to handle, and a manufacturing method thereof. 
     Means for Solving the Problems 
     The present invention is a side airbag device that is housed inside a vehicle seat and protects an occupant seated in the seat, comprising: an airbag that restrains the occupant by expanding and deploying; and an inflator that supplies expansion gas to the airbag. The airbag includes a pre-push chamber with the inflator stowed inside and a main chamber that is connected to the pre-push chamber and deploys toward the front of the vehicle. When the airbag is in the housed state, a first folded part is formed by the main chamber and a second folded part is formed by the pre-push chamber. At the portion where the first folded part and the second folded part overlap, a sewn part is formed that joins the first folded part and at least a portion of the pre-chamber, and the sewn part is configured to break during deployment of the airbag. 
     Another aspect of the present invention is a method of manufacturing a side airbag device that is housed inside a vehicle seat and protects an occupant seated in the seat, comprising the steps: a step of preparing a pre-push chamber that houses an inflator therein and a main chamber that is connected to the pre-push chamber and deploys toward the front of the vehicle; a step of forming a first folded part of the main chamber; a step of forming a second folded part of the pre-push chamber; and a step of forming a sewn part that joins both folded parts at a portion where the first folded part and the second folded part overlap. The sewn part is configured to break during deployment of the airbag. 
     In the present invention as described above, a breakable sewn part is formed at the overlapping portion between the first folded part formed mainly by the main chamber and the second folded part formed mainly by the pre-push chamber so that the first folded part and the second folded part are connected before the airbag operates and so that both folded parts do not come apart and are easy to handle without using a cover or the like that surrounds the entire airbag. 
     In the early stages of airbag deployment, the main chamber will remain connected to the pre-push chamber until the main chamber begins to deploy. As a result, the relative posture (positional relationship) of the chambers and their positional relationship with the bracket and the like can be favorably maintained. For example, in an airbag that utilizes a bracket as a reaction force surface, the position of the airbag relative to the bracket can be properly maintained and the reaction force surface can be effectively utilized. Thus, in the present invention, the deployment speed of the airbag is increased and the deployment shape of the airbag is stabilized, improving occupant restraint performance. 
     A further aspect of the present invention is a side airbag device that is housed inside a vehicle seat and protects an occupant seated in the seat, comprising: an airbag that restrains the occupant by expanding and deploying; and an inflator that supplies expansion gas to the airbag. The airbag includes a pre-push chamber with the inflator stowed inside and a main chamber that is connected to the pre-push chamber and deploys toward the front of the vehicle. When the airbag is in the housed state, a first folded part is formed by the main chamber and a second folded part is formed by the pre-push chamber. A bracket holding the airbag and the inflator and secured to the seat frame of the seat is further provided, the bracket including a first surface facing the direction of travel (forward) of the vehicle. In addition, at least a portion of the second folded part close to the inflator is arranged on the first surface of the bracket. 
     In the above-described form of the present invention, a structure in which the first folded part and the second folded part are connected by a breakable sewn part is not adopted, but at least a portion of the second folded part near the inflator is arranged on the first surface of the bracket, so that in an initial stage of deployment of the airbag, the second folded part corresponding to the pre-push chamber will be deployed first with the front surface of the bracket as a reaction surface. Therefore, until the pre-push chamber is deployed to a certain extent, the main chamber (first folded section) does not expand significantly and remains close to the pre-push chamber. As a result, maintaining a favorable relative posture (positional relationship) between the main chamber and the pre-push chamber and their positional relationship with the bracket becomes possible. 
     The second folded part can be formed in a bellows-folded shape. The first folded part can be formed into a roll shape. 
     The sewn part preferably at least connects the outermost layer of the roll-shaped first folded part with the layer closest to the first folded part of the bellows-folded shape second folded part. 
     The sewn part preferably penetrates the roll-shaped first folded part. The sewn part penetrates the first folded part, thereby enabling the roll-shaped folded part to be reliably retained in the pre-deployed posture thereof. 
     The sewn part preferably penetrates the roll-shaped first folded part in a manner that is offset from the roll center. Having the sewn part penetrate the roll-shaped first folded part avoiding the center of the first folded part enables avoiding a situation that causes a delay in the deployment of the first folded part. 
     The sewn part preferably penetrates near the center of the roll-shaped first folded part if it is possible to avoid the outer sewing for forming the airbag cushion into a bag. Controlling the sewing position appropriately enables maintaining the posture of the folded part before deployment more reliably without causing unnecessary damage to the outer perimeter sewn part, while avoiding a situation in which deployment is delayed. 
     The sewn part preferably penetrates only the rolled part, except for the part folded in a Z-shape which mainly includes the pre-push chamber. This configuration allows the first and second folded parts to be connected to each other with appropriate strength, and avoids a situation of causing a delay in the deployment of the airbag. 
     The airbag and the inflator can be further provided with a bracket that retains the airbag and the inflator. 
     The bracket can include a first surface facing the direction of travel (forward) of the vehicle, and the first folded part and the second folded part can be configured to be arranged on the first surface of the bracket. Being arranged on the first “surface” does not mean being arranged on the “top” in the vertical relationship, but means leaning against, touching, facing, and the like of the surface. 
     The pre-push chamber and the main chamber preferably expand forwardly with the first surface of the bracket as a reaction surface. 
     In the specification and claims of the present application, the direction in which the occupant is facing (the direction of vehicle travel) when the occupant is seated in the seat in a normal posture is referred to as “forward” and the opposite direction is referred to as “rear”, and the axis of the coordinates are referred to as the “front-rear direction”. Moreover, when the passenger is seated in the seat in a regular posture, the right of the passenger is referred to as the “right direction,” the left of the passenger is referred to as the “left direction,” and the direction indicating the coordinate axis is referred to as the “left and right direction.” In the left-right direction, a region on an occupant side from a side frame of the seat shall be referred to as “inside”, and a region opposite from the occupant as viewed from the side frame shall be referred to as “outside”. Similarly, when the passenger is seated in the seat in a regular posture, the head direction of the passenger is referred to as “up,” the waist direction of the passenger is referred to as “down,” and the direction indicating the coordinate axis is referred to as the “vertical direction.” 
     The side airbag apparatus according to the present invention includes a type which is deployed on the door side of (outside) the seat, along with a type which is deployed on the vehicle center side of the seat. A side airbag device of a type which is deployed on the vehicle center side of the seat, for example, is referred to as a far side airbag, front center airbag, rear center airbag, and the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view primarily illustrating an external shape of a vehicle seat according to the present invention, with an illustration of a side airbag device omitted. 
         FIG. 2  is a perspective view illustrating an internal structure (seat frame) functioning as a framework of the vehicle seat illustrated in  FIG. 1 , with an illustration of the side airbag device omitted. 
         FIG. 3  is a schematic side surface view of the vehicle seat according to the present invention, schematically illustrating a condition where the side airbag device is stored therein, observed from the outside in the vehicle width direction. 
         FIG. 4  is a cross sectional view illustrating the structure of the vehicle seat according to the present invention, corresponding to a part of a cross section in an A 1 -A 1  direction of  FIG. 3 . 
         FIG. 5  is a schematic side view of the vehicle seat according to the present invention, illustrating a condition where the airbag is deployed as observed from the outside in the vehicle width direction. 
         FIG. 6  is a side view illustrating an airbag structure that can be employed in the side airbag device according to the present invention, where (A) illustrates a view observed from the outside of the vehicle (opposite the occupant), and (B) illustrates a view observed from the inside of the vehicle (occupant side). 
         FIG. 7(A)  and  FIG. 7(B)  are plan views illustrating a part of the manufacturing steps of the side airbag device according to embodiment 1 of the present invention. 
         FIG. 8(A)  and  FIG. 8(B)  are plan views illustrating a part of the manufacturing steps of the side airbag device according to embodiment 1 of the present invention. 
         FIG. 9(A)  is a plan view illustrating a part of the manufacturing steps of the side airbag device according to embodiment 1 of the present invention.  FIG. 9(B)  is a cross-sectional view in the direction of line A 3 -A 3  in  FIG. 9(A) . 
         FIG. 10(A)  and  FIG. 10(B)  are plan views illustrating a part of the manufacturing steps of the side airbag device according to embodiment 1 of the present invention. 
         FIG. 11(A)  to  FIG. 11(C)  are schematic cross-sectional views illustrating operation of the side airbag device according to embodiment 1 of the present invention, where (C) corresponds to a cross-section in the direction of line A 2 -A 2  in  FIG. 5 . 
         FIG. 12(A)  is a plan view illustrating a part of the manufacturing steps of the side airbag device according to embodiment 2 of the present invention.  FIG. 12(B)  is a cross-sectional view in the direction of line A 4 -A 4  in  FIG. 12  (A). 
         FIG. 13(A)  and  FIG. 13(B)  are plan views illustrating a part of the manufacturing steps of the side airbag device according to embodiment 2 of the present invention. 
         FIG. 14(A)  to  FIG. 14(C)  are schematic cross-sectional views illustrating the operation of the side airbag device according to embodiment 2 of the present invention, where (C) corresponds to a cross-section in the direction of line A 2 -A 2  in  FIG. 5 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     A side airbag device according to embodiments of the present invention will be described below with reference to the accompanying drawings. 
       FIG. 1  is a perspective view primarily illustrating an external shape of a vehicle seat according to the present invention, with an illustration of an airbag device (airbag module)  20  omitted.  FIG. 2  is a perspective view illustrating an internal structure (seat frame) functioning as a framework of the vehicle seat illustrated in  FIG. 1 , with an illustration of the airbag device (airbag module)  20  omitted herein as well.  FIG. 3  is a schematic side surface view of the vehicle seat according to the present invention, illustrating a condition where the airbag device (airbag module)  20  is stowed on a side surface (near side) near a left side seat door as observed from the outside in the vehicle width direction. 
     As illustrated in  FIG. 1  and  FIG. 2 , the vehicle seat in the present embodiment, when viewed as a part, is composed of a seat cushion  2  of a portion in which an occupant is seated; a seat back  1  forming a backrest; and a headrest  3  connected to the upper end of the seat back  1 . 
     As illustrated in  FIG. 2 , a seat back frame  1   f  forming a skeleton of the seat is provided inside the seat back  1 , a pad  16  (refer to  FIG. 4 ) made of a urethane foam material or the like is provided on a surface and periphery thereof, and a surface of the pad  16  is covered with a surface skin  14  such as leather, fabric, or the like. A seating frame  2   f  is provided on a bottom side of the seat cushion  2 . Similar to the seat back  1 , a pad made of a urethane foam material or the like is provided on an upper surface and periphery thereof, and a surface of the pad is covered by the skin  14  ( FIG. 4 ) such as leather, fabric, or the like. The seating frame  2   f  and the seat back frame  1   f  are connected via a reclining mechanism  4 . 
     As illustrated in  FIG. 2 , the seat back frame  1   f  is configured into a frame shape by side frames  10  disposed laterally spaced apart and extending in the vertical direction, an upper frame connecting the upper ends of the side frames  10 , and a lower frame connecting the lower ends thereof. The headrest  3  is configured by providing a cushioned component outside a headrest frame. 
       FIG. 4  is a cross sectional view illustrating the structure of the vehicle seat according to the present invention, corresponding to a part of a cross section in an A 1 -A 1  direction of  FIG. 3 . The side frame  10  can be molded of resin or metal and, as illustrated in  FIG. 4 , can be formed into an L-shaped cross sectional shape or a U-shaped cross sectional shape. An airbag module (side airbag device)  20  is secured to the inside (seat center side) and front side of the side frame  10 . 
     As illustrated in  FIG. 4 , the seat back  1  includes a side supporting part  12  which swells in the vehicle traveling direction (vehicle front) on a side part (end part) in the vehicle width direction. A urethane pad  16  is arranged inside the side supporting part  12 , and the side airbag device  20  is stowed in a gap of the urethane pad  16 . The side airbag device  20  includes: an airbag  33  that restrains an occupant when expanded and deployed; and an inflator  30  that supplies an expansion gas to the airbag  33 . 
     Seams  18 ,  22 ,  24  of the skin  14  of the seat back  1  are interwoven and connected by sewing. Note that the front seam  18  is cleft when the airbag is deployed. 
     The compressed airbag  33  is secured to the side frame  10  via the brackets  52  and  54 . The airbag  33  may be covered by a flexible cover made of fabric. Note that in  FIG. 4 , reference code  25  indicates a door trim. 
     The brackets ( 52  and  54 ) are provided with a first plate  54  that is a flat plate extending in a vertical direction and a second plate  52 , through which two stud bolts  32  that are connected to the inflator  30  are inserted through, such that the second plate  52  is directly secured to the side frame  10 . These types of brackets are generally arranged such that the first plate  54  and second plate  52  are orthogonal when viewed in a cross section perpendicular to the longitudinal direction, and the first plate  54  and the second plate  52  are connected to each other by welding or the like. 
     The first plate  54  of the bracket has a first surface  54   a  that faces the vehicle traveling direction, and the airbag  33  in a stowed state is arranged along the first surface  54   a . Herein, when the long and thin compressed airbag  33  expands and deploys in the vehicle traveling direction, the first surface  54   a  of the first plate  54  is a reaction force surface, and thus the airbag  33  reliably and quickly deploys in a forward direction. 
     On the other hand, the second plate  52  of the bracket has a second surface  52   a  facing the occupant side, and primarily a portion of the pre-push chamber  36  of the airbag  33  is arranged on said second surface  52   a.    
       FIG. 5  is a schematic side view of the vehicle seat according to the present invention, illustrating a condition where the airbag is deployed as observed from the outside in the vehicle width direction.  FIG. 6  is a side view illustrating the structure of the airbag  33 , where (A) illustrates a view observed from the outside of the vehicle (opposite the occupant), and (B) illustrates a view observed from the inside of the vehicle (occupant side). 
     As illustrated in  FIG. 5  and  FIG. 6 , the airbag  33  has a main chamber  34  that deploys toward the front of the side support portion  12 ; and a pre-push chamber  36  that deploys prior to the main chamber  34 . 
     An internal vent hole (not shown) is provided in the partitioning part (boundary portion) between the main chamber  34  and the pre-push chamber  36 , through which expansion gas flows from the pre-push chamber  36  to the main chamber  34 . 
     Exhaust vents V 1  and V 2  are formed at the front end of the main chamber  34  for exhausting gas to the outside. Note that at least one exhaust vent for exhausting the gas to the outside can be formed on a front end part of the pre-push chamber  36 , similar to the main chamber  34 . 
     The main chamber  34  is partitioned into a forward chamber  34 F and a rear chamber  34 R, and expansion gas flows from the rear chamber  34 R to the forward chamber  34 F through a vent hole (not shown). Each chamber  34  ( 34 F,  34 R) and  36  are compartmentally formed by stitches S 1 , S 2 , S 3 . 
     Embodiment 1 
       FIG. 7(A) , (B),  FIG. 8(A) , (B),  FIG. 9(A) , and  FIG. 10(A) , (B) are plan views illustrating a part of a manufacturing process of a side airbag device according to the embodiment 1 of the present invention. In  FIG. 7  to  FIG. 10 , the diagram of the inflator  30  is omitted for convenience of explanation. In the diagram, “front”, “rear”, “top”, and “bottom” indicate the direction in which the airbag device is actually mounted on the seat (when deployed). 
     When folding the airbag  33 , first insert the inflator  30  through the opening  40  of the pre-push chamber  36  and set the inflator  30  so that at least the gas discharge hole (not shown) is completely located inside the pre-push chamber  36 . 
     In the present embodiment, for the airbag  33  set with the inflator  30 , the lower portion of the airbag  33  is first folded upward along the fold line  102  extending generally in the front-back direction, as illustrated in  FIG. 7(A) . 
     Next, as illustrated in  FIG. 7( b ) , the upper portion of the airbag  33  is folded downward along the fold line  104  extending generally in the front-to-back direction. 
     Thereafter, as illustrated in  FIG. 8(A) , the airbag  33  is flipped face down. Next, as illustrated in  FIG. 8(B) , rolling is started from near the forward lower corner of the airbag  33  toward the back diagonally upward, mainly corresponding to the main chamber  34 , to form the initially rolled part  106 . 
     Next, as illustrated in  FIG. 9(A) , the portion mainly corresponding to the main chamber  34  is completely rolled up to form the roll-shaped first folded part  106 X. Furthermore, as also illustrated in  FIG. 9(B) , a sewn part  108  that can be ruptured during expansion and deployment of the airbag is formed so as to penetrate the first folded part  106 X to connect the first folded part  106 X (main chamber  34 ) to the end of the pre-push chamber  36  on the main chamber  34  side. 
     The sewn part  108  is formed by sewing the first folded part  106 X in a slightly collapsed state with a sewing machine, extending parallel to the longitudinal direction of the first folded part  106 X. Here, the sewn part  108  is formed to penetrate a position displaced from the center of the first folded part  106 X. 
     Although the sewing position of the sewn part  108  has a certain degree of freedom, at least the outermost layer of the rolled first folded part  106 X must be connected with the layer of the pre-push chamber  36  (second folded part  110 X) closest to the first folded part  106 X. Here, if the sewing of the sewn part  108  can be made so that, for example, the portion of the sewn part  108  that intrudes into the outer sewn parts of the main chamber and the pre-push chamber is as small as possible (and preferably does not enter the outer sewn parts), then the sewn part may be formed to penetrate at or near the center of the rolled first folded part  106 X. 
     Next, as illustrated in  FIG. 10(A) , the airbag  33  is again flipped face down and the portion mainly corresponding to the pre-push chamber  36  is folded in a bellows shape along the fold line  110  to form the second folded part  110 X. The state in which the airbag  33  is completely folded is illustrated in  FIG. 10(B) . The brackets  52  and  54  are attached to the airbag  33  that has been folded in this manner. Specifically, the stud bolts  32  of the inflator  30  are inserted into the second plate  52 . 
     (Airbag Deployment Behavior) 
       FIG. 11(A)  to  FIG. 11(C)  are schematic cross-sectional views illustrating operation of the side airbag device according to the present invention, and  FIG. 11(C)  corresponds to the cross-section in the A 2 -A 2  direction of  FIG. 5 . First,  FIG. 11(A)  illustrates the state in which the brackets  52  and  54  are set in the airbag device and before the airbag  33  is deployed. 
     In this state, the second folded part  110 X, which is mainly made up of the pre-push chamber  36 , is folded into a bellows shape (Z-fold). At this time, the sewn part  108  is not in this bellows-folded second folded part  110 X, and only reaches the end of the main chamber side of the pre-push chamber  36 , as illustrated in  FIG. 9(B) . When the airbag system is activated, the gas from the inflator  30  causes the pre-push chamber  36 , which initially forms the second folded part  110 X, to begin deployment. When the pre-push chamber  36  deploys, as illustrated in (B), the pre-push chamber  36  deploys with the front surface  54   a  of the bracket  54  as a reaction force surface and is shaped to push the first folded part  106 X forming the main chamber  34  forward. At this time, the sewn part  108  has not yet been ruptured. 
     As the deployment of the airbag  33  further progresses, as illustrated in (C), the sewn part  108  is ruptured and the roll of the first folded part  106 X is unrolled, causing the main chamber  34  to dramatically deploy forwardly. 
     In the present embodiment, the first folded part  106 X formed mainly by the main chamber  34  and the second folded part  110 X formed mainly by the pre-push chamber  36  overlap, preferably at a portion where the first folded part  106 X formed mainly by the main chamber  34  and the breakable sewn part  108  is formed at the portion where the end of the first folded part  106 X of the second folded part  110 X formed by the pre-push chamber  36  overlaps with the end of the first folded part  106 X. In this manner, the sewn part  108  is formed at the overlapping portion of the first folded part  106 X and the second folded part  110 X, so that at the stage (A) before the airbag  33  is activated, the first folded part  106 X and the second folded part  110 X are connected, and the two folded parts  106 X and  110 X can be can be treated as a single unit. In addition, the connection between the first folded part  106 X and the second folded part  110 X is not maintained more than necessary, which avoids a situation in which the deployment speed of the airbag  33  is reduced. 
     The main chamber  34  will remain connected to the pre-push chamber  36  until the point at which the pre-push chamber  36  starts to deploy during the initial stage of deployment of the airbag  33 , or in other words, until the main chamber  34  starts to deploy (B). Therefore, the relative posture (positional relationship) of the chambers  34  and  36  with each other and with the bracket  54  can be favorably maintained. In other words, the position with respect to the bracket  54   a  that is used as a reaction force surface when deployed can be maintained in an appropriate state, and the reaction force surface can be effectively utilized. 
     As described above, the airbag device of the present embodiment stabilizes the deployment shape of the airbag  33  without inhibiting the rapid deployment speed of the airbag  33 , thereby improving the occupant restraint performance. 
     Embodiment 2 
     Next, embodiment 2 of the present invention will be described with reference to  FIG. 9  through  FIG. 12 . Embodiment 1 and embodiment 2 have many parts in common, and the same reference symbols are attached to the same or corresponding components, and duplicate descriptions are omitted. 
     In embodiment 1, the first folded part  106 X and the second folded part  110 X of the airbag  33  are connected by a breakable sewn part ( 108 ), but the sewn part ( 108 ) is not employed in embodiment 2. 
       FIG. 12(A)  and  FIG. 13(A) , (B) are plan views illustrating a part of the manufacturing process of the side airbag device. The manufacturing process (folding process) up to and including  FIG. 12(A)  is the same as in embodiment 1 illustrated in  FIGS. 7(A)  and (B) and  FIGS. 8(A)  and (B). 
     As in embodiment 1, the airbag  33  folded up to the state illustrated in  FIG. 8(B)  is then completely rolled up, mainly the portion corresponding to the main chamber  34 , to form a roll-shaped first folded part  106 X, as illustrated in  FIG. 12(A) . 
     Next, as illustrated in  FIG. 13(A) , the airbag  33  is flipped over and the portion mainly corresponding to the pre-push chamber  36  is folded in a bellows shape along the fold line  110  to form the second folded part  110 X. The state in which the airbag  33  is completely folded is illustrated in  FIG. 13(B) . The brackets  52  and  54  are attached to the airbag  33  that has been folded in this manner. Specifically, the stud bolts  32  of the inflator  30  are inserted into the second plate  52 . 
       FIG. 14(A)  to  FIG. 14(C)  are schematic cross-sectional views illustrating the deployment operation of the side airbag device of embodiment 2, and  FIG. 14(C)  corresponds to the cross-section in the direction of line A 2 -A 2  of  FIG. 5   FIG. 14(A)  illustrates the state in which the brackets  52  and  54  are set in the airbag device and before the airbag  33  is deployed. In this state, the second folded part  110 X, which is mainly made up of the pre-push chamber  36 , is folded into a bellows shape (Z-fold). 
     When the airbag system is activated, the gas from the inflator  30  causes the pre-push chamber  36 , which initially forms the second folded part  110 X, to begin deployment. As illustrated in (B), the pre-push chamber  36  unfolds inwardly (toward the occupant) using the inner surface of the bracket  52  as a reaction force surface, and at the same time, the first folded part  106 X forming the main chamber  34  unfolds forwardly using the front surface  54   a  of the bracket  54  as a reaction force surface. 
     Further, as the deployment of the airbag  33  progresses, the roll of the first folded part  106 X is unrolled and the main chamber  34  is largely deployed forward, as illustrated in  FIG. 14(C) . 
     In the present embodiment, similar to embodiment 1, a structure in which the first folded part  106 X and the second folded part  110 X are connected by a breakable sewn part ( 108 ) as in embodiment 1 is not adopted, but at least a portion of the second folded part  110 X close to the inflator is arranged on the front surface  54   a  of the bracket  54 , so that in the initial stage of deployment of the airbag  33 , the second folded part  110 X corresponding to the pre-push chamber  36  will be deployed ahead of the front surface  54   a  of the bracket  54  as a reaction surface. Therefore, until the pre-push chamber  36  is deployed to a certain extent, the main chamber  34  (first folded part  106 X) does not expand significantly and remains close to the pre-push chamber  34 . As a result, this enables maintaining a favorable relative posture (positional relationship) of the main chamber  34  and the pre-push chamber  36  and their positional relationship with the bracket  54 . 
     Although the present invention has been described with reference to embodiments, the present invention is not limited in any way to these embodiments, and can be changed as appropriate within the scope of the technical idea of the present invention. For example, while a side airbag on the near side has been predominantly mentioned in the embodiments described above, use is also possible with a far side airbag (surface on the far side from a vehicle door of a vehicle seat), in very small vehicles such as a single seat vehicle (irrespective of the presence of a door, a vehicle including parts with only one seat in a single row), and the like.