Patent Publication Number: US-2022234537-A1

Title: Driver&#39;s seat airbag device

Description:
TECHNICAL FIELD 
     The present invention relates to a driver&#39;s seat airbag device for restraining an occupant in an emergency. 
     BACKGROUND TECHNOLOGY 
     Airbag devices have generally become standard equipment in vehicles in recent years. An airbag device is a safety device that is actuated in the event of an emergency such as a vehicle collision or the like to receive and protect an occupant by expanding and deploying a bag-shaped airbag cushion with gas pressure. In the case of a front row seat, a typical airbag device is primarily installed in the center of a steering wheel for a driver seat and in an instrument panel in front of an occupant for a front passenger seat. 
     For example, Patent Document 1 discloses an airbag device for a front passenger seat. In an airbag device of Patent Document 1, an airbag 1 having a large capacity is provided on a rear portion (occupant side) of an instrument panel, and a flat airbag 2 having a small capacity is provided in an upper portion of the instrument panel. An airbag 2 is expanded between the airbag 1 and a windshield 6 to support the airbag 1 from above on a front side. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: German Patent Invention No. 10021845 
       
    
     SUMMARY OF THE INVENTION 
     The driver seat airbag device is close in distance to the occupant and the steering wheel, and therefore, the airbag cushion must expand and deploy more quickly to prevent the occupant from impacting the steering wheel. At this time, for example, it is difficult for an airbag cushion with a large capacity, such as the airbag 1 of Patent Document 1, to quickly enter the narrow space between the steering wheel and the chest of the occupant. 
     Furthermore, in recent years, new steering wheels that transmit a steering force to the wheels via an electrical signal are being developed, and steering wheel designs are therefore becoming more diverse. In particular, new electrically connected steering wheels do not need to be significantly rotated, unlike conventional steering wheels which physically transmit steering force via a steering shaft. For example, the rim of new steering wheels does not need to be a circular ring because the grip does not need to be rotated more than 180° while being held by the left and right hands like a conventional rim. Therefore, a new steering wheel can adopt a yoke design other than a circular ring shape, such as rims present on only left and right sides with regard to a central hub (hereinafter, a steering wheel with a rim other than a circular ring shape is referred to as a “yoke steering wheel”). 
     In many cases, with the yoke steering wheel described above, a portion of the rim is omitted, which reduces a contact range with the airbag cushion; thus, the airbag cushion may not be supported, causing the posture of the airbag cushion to tilt. In particular, if an upper rim is omitted, the airbag cushion may collapse toward the front of the vehicle due to a load from the head of the occupant and thus may not fully protect the head of the occupant. 
     Problem to be Solved by the Invention 
     In view of the foregoing, an object of the present invention is to provide a driver seat airbag device which can fully restrain the head and chest of an occupant and can be applied to a non-circular steering wheel. 
     Means for Solving the Problems 
     In order to solve the aforementioned problem, a typical configuration of a driver seat airbag device according to the present invention is a driver seat airbag device that restrains an occupant seated in a driver seat of a vehicle, containing: a chest protecting cushion that expands and deploys behind a steering wheel of the vehicle; and a head protecting cushion that expands and deploys adjacent to and above the chest protecting cushion; where the head protecting cushion extends from an upper portion of the chest protecting cushion to an upper surface of an instrument panel when expanded and deployed, and contacts and restrains the head of the occupant from the front. 
     With the aforementioned configuration, the chest and head of the occupant can be fully restrained. In particular, the head protecting cushion is supported by the upper surface of the instrument panel, and therefore, the head protecting cushion can efficiently absorb a load from the head without being dependent on the steering wheel and can restrain the occupant in a stable posture. 
     The volume of the aforementioned head protecting cushion when expanded and deployed may be larger than the volume of the chest protecting cushion when expanded and deployed. With the head protecting cushion of this configuration, the head of the occupant can be fully restrained. 
     A border between the chest protecting cushion and the head protecting cushion described above may be set at a height near an upper end of a hub of the steering wheel. With this configuration, the chest and head of the occupant can be fully restrained even when an upper range of a steering wheel rim is omitted. 
     The height near the upper end of the hub described above may be within a range of ±100 mm relative to the upper end of the hub. If the border between the chest protecting cushion and head protecting cushion is set to this height, the chest and head of the occupant can be fully restrained even when an upper range of a steering wheel rim is omitted. 
     The rim of the steering wheel may be a shape other than circular, a border between the chest protecting cushion and the head protecting cushion may be set at a height near an upper end of the rim of the steering wheel. Even with this configuration, the chest and head of the occupant can be fully restrained. 
     The height near the upper end of the rim of the steering wheel may be within a range of ±100 mm relative to the upper end of the hub at a center of the steering wheel. Even by setting the border between the chest protecting cushion and head protecting cushion to this height, the chest and head of the occupant can be fully restrained even when an upper range of a steering wheel rim is omitted. 
     A rear wall of the head protecting cushion described above may be positioned more toward the front of the vehicle than a rear wall of the chest protecting cushion. With this configuration, the occupant can be restrained in a stable posture by first restraining the chest of the occupant and then restraining the head. 
     A rear end of a rear wall of the head protecting cushion described above may be positioned more toward the front of the vehicle than a rear end of a rear wall of the chest protecting cushion. Even with this configuration, the occupant can be restrained in a stable posture by first restraining the chest of the occupant and then restraining the head. 
     The head protecting cushion described above may complete expansion and deployment later than the chest protecting cushion. With this configuration, by making the completion of the expansion of head protecting cushion later than the chest protecting cushion, the chest of the occupant can be restrained first, thereby reducing the load on the head. 
     The head protecting cushion described above may contact the occupant before the chest protecting cushion. For example, if the occupant leans more forward than a regular seating position, the head is first pushed rearward. Thereby, a space can be secured between the occupant and the steering wheel, and thus the chest protecting cushion can enter between the occupant and the steering wheel. 
     The chest protecting cushion and the head protecting cushion described above may be separated from each other. With this configuration, a configuration that efficiently restrains the occupant can be achieved, such as by varying the timing of expansion and deployment of the chest protecting cushion and the head protecting cushion, or the like. 
     The head protecting cushion described above may be stored in an upper portion of the instrument panel toward the front of the vehicle from the steering wheel. This configuration allows the head protecting cushion to be suitably installed in a vehicle. 
     The chest protecting cushion described above may be stored in the steering wheel. This configuration allows the chest protecting cushion to be suitably installed in a vehicle. 
     The chest protecting cushion may be stored in a lower portion of an instrument panel more toward the front of the vehicle than the steering wheel, and may be capable of protecting a knee of the occupant. This configuration allows the chest protecting cushion to be suitably mounted in a vehicle and to more fully restrain an occupant. 
     The driver seat airbag device may further contain: a chest portion inflator that supplies gas to the chest protecting cushion; a head portion inflator that supplies gas to the head protecting cushion; a camera capable of detecting the position of the occupant; and a control unit that controls the activation start time of the chest portion inflator and the head portion inflator, respectively, based on the position of the occupant detected by the camera. With this configuration, the timing of restraining the head and the chest based on the posture of the occupant can be adjusted to efficiently restrain the occupant. 
     The chest protecting cushion and head protecting cushion described above may be stored in the steering wheel in an integrally connected state. Even with this configuration, an airbag device capable of efficiently restraining the chest and head of an occupant can be achieved. 
     Effect of the Invention 
     The present invention can provide a driver seat airbag device that can fully restrain the head and chest of an occupant and can be applied to a non-circular steering wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating the outline of a driver seat airbag apparatus according to an embodiment of the present invention. 
         FIG. 2  is a diagram illustrating the driver seat airbag device in  FIG. 1( b )  and an occupant seated in a seat. 
         FIG. 3  is a diagram illustrating an outline of a chest protecting cushion in  FIG. 2 . 
         FIG. 4  is a diagram illustrating an outline of a head protecting cushion in  FIG. 2 . 
         FIG. 5  is a diagram illustrating a process of the driver seat airbag device in  FIG. 2  restraining the occupant. 
         FIG. 6  is an enlarged view of the driver seat airbag device in  FIG. 5( c ) . 
         FIG. 7  is a diagram illustrating a first modified example of the driver seat airbag device illustrated in  FIG. 2 . 
         FIG. 8  is a diagram illustrating a process of the driver seat airbag device in  FIG. 7  restraining the occupant. 
         FIG. 9  is a diagram illustrating a first modified example of the chest protecting cushion illustrated in  FIG. 3 . 
         FIG. 10  is a diagram illustrating a second modified example of the chest protecting cushion illustrated in  FIG. 3 . 
         FIG. 11  is a diagram illustrating a third modified example of the chest protecting cushion illustrated in  FIG. 3 . 
         FIG. 12  is a diagram independently illustrating a chest protecting cushion in  FIG. 11 . 
         FIG. 13  is a diagram illustrating a second modified example of the driver seat airbag device illustrated in  FIG. 2 . 
         FIG. 14  is a diagram illustrating an outline of an airbag cushion in  FIG. 13 . 
         FIG. 15  is a diagram illustrating a third modified example of the driver seat airbag device illustrated in  FIG. 2 . 
         FIG. 16  is a diagram illustrating an outline of an airbag cushion in  FIG. 15 . 
         FIG. 17  is a diagram applying an internal tether to each of the airbag cushions in  FIG. 14( a )  and  FIG. 16( a ) . 
         FIG. 18  is a diagram applying an internal panel to the airbag cushion in  FIG. 14( a ) . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments according to the present invention will hereinafter be described in detail with reference to the attached drawings. Dimensions, materials, other specific numerical values, and the like indicated in the embodiments are merely examples for ease of understanding of the invention and do not limit the present invention unless otherwise noted. Note that in the present specification and drawings, elements having essentially identical functions and configurations are labeled with identical symbols in order to omit redundant descriptions along with an illustration of elements not directly related to the present invention. 
       FIG. 1  is a diagram illustrating the outline of a driver seat airbag apparatus  100  according to an embodiment of the present invention.  FIG. 1( a )  is a diagram illustrating a vehicle before activation of the driver&#39;s seat airbag device  100 . Hereinafter, regarding  FIG. 1  and other diagrams, a vehicle front-rear direction is illustrated by the symbols F (Front) and B (Back), a vehicle width direction of the vehicle by the symbols L (Left) and R (Right), and a vehicle up-down direction by the symbols U (Up) and D (Down). 
     The driver&#39;s seat airbag device  100  is applied in the present embodiment as the driver airbag for the driver&#39;s seat for vehicles with a steering wheel on a left side (front row left side seat  102 ). Hereinafter, descriptions are made assuming the front row left side seat  102 , for example, a vehicle outer side in the vehicle width direction (hereinafter, vehicle outer side) refers to a left side of the vehicle, and an inner side in the vehicle width direction (hereinafter, vehicle inner side) refers to a right side of the vehicle. 
     A yoke steering wheel  106  installed in a driver seat in the present embodiment is assumed to be of a configuration in which an operation of the occupant is converted into an electrical signal and transmitted to the wheel. The yoke steering wheel  106  has a rim  114  of a shape other than a circular ring shape, and is different in shape from a conventional steering wheel with a circular rim. The rim  114  accepts an operation of rotating about a central hub  108 , but unlike a conventional circular rim, a rotating operation at a large angle is not necessary, and therefore, there is no need to hold with the left or right hand. Therefore, the rim  114  is shaped to be present only on left, right, and lower sides of the hub  108 , and no structure is present on an upper side of the hub  108 . 
       FIG. 1( b )  is a diagram illustrating an airbag cushion provided with the driver seat airbag device  100  after expansion and deployment. In the present embodiment, two airbag cushions are provided: a lower chest protecting cushion  120  and an upper head protecting cushion  122 . The chest protecting cushion  120  primarily restrains a chest  128  and abdomen  130  of the occupant  124  (see  FIG. 2 ), and the head protecting cushion  122  restrains a head  126  of the occupant  124 . The driver seat airbag device  100  uses these chest protecting cushion  120  and head protecting cushion  122  to restrain the occupant  124  seated in the seat  102  from the front. 
       FIG. 2  is a diagram illustrating the driver seat airbag device  100  in  FIG. 1( b )  and the occupant  124  seated in the seat  102 . In  FIG. 2 , the driver seat airbag device  100  and the occupant  124  are illustrated as viewed from a left side in the vehicle width direction. In the present embodiment, the chest protecting cushion  120  and the head protecting cushion  122  are separated from each other. The chest protecting cushion  120  is configured to expand and deploy from the center of the yoke steering wheel  106 , and the head protecting cushion  122  is configured to expand and deploy from the an upper portion of an instrument panel  104 . 
     The chest protecting cushion  120  has a smaller gas capacity than the head protecting cushion  122  and expands and deploys rearward of the yoke steering wheel  106 . The chest protecting cushion  120  expands and deploys quickly into a narrow space between the yoke steering wheel  106  and the chest  128  of the occupant  124  by reducing a gas capacity thereof, preventing the chest  128  and abdomen  130  of the occupant  124  from contacting the yoke steering wheel  106 . 
     The chest protecting cushion  120  is housed in the central hub  108  (see  FIG. 1( a ) ) of the yoke steering wheel  106  in a configuration folded, wrapped, or the like, along with a chest portion inflator  132 . The chest portion inflator  132  is a device that supplies gas to the chest protecting cushion  120 , and upon receiving the gas, the chest protecting cushion  120  opens a cover  110  of the hub  108  and expands and deploys. 
     The head protecting cushion  122  when expanded and deployed has a larger gas capacity than the chest protecting cushion  120 , in other words, volume when expanded and deployed, and extends from an upper portion of the chest protecting cushion  120  to an upper surface  134  of the instrument panel  104 . The head protecting cushion  122 , in addition to having a large volume, is supported on a front side between the upper surface  134  of the instrument panel  104  and a windshield  136 , so as to suitably restrain the head  126  of the occupant  124  approaching from the rear. 
     The head protecting cushion  122  is stored in the upper portion of the instrument panel  104  toward the front of the vehicle from the yoke steering wheel  106  in a state folded, wrapped, or the like, along with a head portion inflator  138 . The head portion inflator  138  is a device that supplies gas to the head protecting cushion  122 , and upon receiving the gas, the head protecting cushion  122  opens a predetermined cover provided on the upper surface  134  of the instrument panel  104  and expands and deploys. 
     For example, a disc type can be used as the chest portion inflator  132  and the head portion inflator  138 , for example. Each inflator has a portion where a gas discharge port is formed inserted into each cushion, and supplies gas to each cushion due to an impact detection signal sent from the vehicle side. Each inflator is provided with a plurality of stud bolts, which are fastened and secured to predetermined locations inside the yoke steering wheel  106  and on the upper portion of the instrument panel  104 , respectively. 
     In the present embodiment, the chest protecting cushion  120  and the head protecting cushion  122  are configured to be separated, and are provided with the chest portion inflator  132  and head portion inflator  138 , respectively. The chest portion inflator  132  and head portion inflator  138  can have different outputs and activation timings. For example, the chest protecting cushion  120  has a small gas capacity, and therefore, a small and inexpensive inflator with low output can be used for the chest portion inflator  132 , thereby reducing costs. Furthermore, for example, the actuation timing of the chest portion inflator  132  can be accelerated to quickly restrain the chest  128 , while delaying the activation timing of the head portion inflator  138  from that of the chest portion inflator  132  to restrain the head  126  at an appropriate timing. 
     Note that examples of currently prevailing inflators include: types filled with a gas generating agent and that burns the agent to generate a gas; types filled with a compressed gas and supplies the gas without generating heat; hybrid types that utilize both a combustion gas and a compressed gas; and the like. Any type of inflator can be used as the chest portion inflator  132  and head portion inflator  138 . 
       FIG. 3  is a diagram illustrating an outline of the chest protecting cushion  120  in  FIG. 2 .  FIG. 3( a )  is a perspective view of the chest protecting cushion  120  in an expanded and deployed state. The chest protecting cushion  120  is prepared in a shape similar to a flat semicircle by joining a front panel  140  on the occupant  124  (see  FIG. 2 ) side and a rear panel  142  on the yoke steering wheel  106  side. 
       FIG. 3( b )  is a diagram illustrating the front panel  140  of  FIG. 3( a )  spread out on a plane. The front panel  140  has a shape close to a semicircle and functions as a restraining surface that restrains the occupant  124  when the chest protecting cushion  120  is expanded and deployed. 
       FIG. 3( c )  is a diagram illustrating the rear panel  142  of  FIG. 3( a )  spread out on a plane. The rear panel  142  has a shape close to a semicircle with the same dimensions as the front panel  140 , and functions as a reaction force surface that obtains a reaction force from the yoke steering wheel  106  (see  FIG. 1( a ) ) when the chest protecting cushion  120  is expanded and deployed. A securing region  144  is formed on an upper side of the center of the rear panel  142  where the chest portion inflator  132  (see  FIG. 2 ) is inserted and secured inside the yoke steering wheel  106 . 
       FIG. 4  is a diagram illustrating an outline of the head protecting cushion  122  in  FIG. 2 .  FIG. 4( a )  is a perspective view of the head protecting cushion  122  in an expanded and deployed state. The head protecting cushion  122  is prepared in a shape that is long in the vehicle front-rear direction by joining side panels  146   a ,  146   b  in the vehicle width direction and a center panel  148  in the center. 
       FIG. 4( b )  is a diagram illustrating the center panel  148  of  FIG. 4( a )  spread out on a plane. The center panel  148120  has a long rectangular shape and has a securing region  150  formed on an end portion on one side where the head portion inflator  138  (see  FIG. 2 ) is inserted and secured inside the yoke steering wheel  106 . 
       FIG. 4( c )  is a diagram illustrating the side panel  146   a  in  FIG. 4( a ) . The side panels  146   a ,  146   b  have the same configuration. Therefore, the left side panel  146   a  is representatively illustrated, spread out on a plane. The side panel  146   a  is long in the front-rear direction and gradually increases in height from a front side to a rear side. The side panel  146   a  having this shape allows the head protecting cushion  122  to easily enter the upper surface  134  of the instrument panel  104  and the windshield  136  on the front side, which is shorter in height, and to receive the head  126  of the occupant  124  (see  FIG. 2 ) on the rear side, which is taller in height. 
       FIG. 5  is a diagram illustrating a process of the driver seat airbag device  100  in  FIG. 2  restraining the occupant  124 .  FIG. 5( a )  is a diagram illustrating the driver seat airbag device  100  at the start of activation. In the present embodiment, when a predetermined sensor of the vehicle detects or predicts an impact, the chest protecting cushion  120  first starts to expand and deploy. 
       FIG. 5( b )  illustrates a condition when the occupant in  FIG. 5( a )  moves toward the front of the vehicle. The driver seat airbag device  100  quickly restrains the chest  128  of the occupant  124  with the chest protecting cushion  120 . In particular, with regard to the narrow space between the yoke steering wheel  106  and the occupant  124 , early expansion and deployment of the chest protecting cushion  120  with a reduced gas capacity can prevent contact between the chest  128  and abdomen of the occupant  124  and the yoke steering wheel  106 . 
       FIG. 5( c )  illustrates a condition when the occupant  124  in  FIG. 5( b )  moves further toward the front of the vehicle. The head protecting cushion  122  contacts the head  126  of the occupant  124  from the front of the vehicle to restrain the head  126 . The head protecting cushion  122  is supported on the front side by the upper surface  134  of the instrument panel  104  and the windshield  136 , and therefore can efficiently absorb the load of the head  126  of the occupant  124  approaching from the rear. 
     The head protecting cushion  122  is set so as to complete expansion and deployment later than the chest protecting cushion  120 . This is because the chest protecting cushion  120  restrains the chest  128  of the occupant  124  first, followed by the head protecting cushion  122  restraining the head  126  of the occupant  124 . In general, when the head  126  of the occupant  124  is bent forward or rearward when restrained, a load applied on the occupant  124  is likely to increase due to the structure of the human body. With the present embodiment, by receiving the chest  128  of the occupant  124  and then receiving the head  126 , the head  126  can be prevented from bending rearward or the like, and the occupant  124  can be fully restrained while reducing the load applied on the occupant  124 . 
       FIG. 6  is an enlarged view of the driver seat airbag device  100  in  FIG. 5( c ) . In the present embodiment, a rear wall  152 , which is a rear side occupant restraining surface of the head protecting cushion  122 , is set to be positioned more toward the front of the vehicle than a rear wall  154 , which is a rear side occupant restraining surface of the chest protecting cushion  120 . More specifically, at least a rear end (vertical line L 2 ) of the rear wall  152  is positioned more toward the front of the vehicle than a rear end (vertical line L 3 ) of the rear wall  154 , even though the rear wall  152  of the head protecting cushion  122  may be partially positioned more toward the rear of the vehicle than the rear wall  154  of the chest protecting cushion  120 . This configuration allows the chest protecting cushion  120  to contact the chest  128  of the occupant  124  first, and then the head protecting cushion  120  to contact the head  126 . Therefore, the driver seat airbag device  100  is capable of restraining the occupant  124  in a stable posture without causing the head  126  of the occupant  124  to bend backwards or the like. 
     In the present embodiment, a boundary between the chest protecting cushion  120  and the head protecting cushion  122  is set at a height near an upper end P 1  of the hub  108  of the yoke steering wheel  106 . More specifically, the boundary between the chest protecting cushion  120  and the head protecting cushion  122  is set within a range of ±100 mm relative to the height (horizontal line L 1 ) of the upper end P 1  of the hub  108 . An upper end of the rim  114  of the steering wheel  106  is also present within a range of ±100 mm of the height of the upper end P 1  of the hub  108 . In other words, the boundary between the chest protecting cushion  120  and the head protecting cushion  122  is set at a height near the upper end of the rim  114 . 
     In the yoke steering wheel  106 , a range of the rim  114  more on an upper side than the hub  108  may be omitted, such that a structure supporting the airbag cushion on the upper side of the hub  108  is not present. In this case, a conventional airbag cushion may cause the upper side to collapse toward the front of the vehicle when restraining the occupant  124  (see  FIG. 2 ). Therefore, in the present embodiment, the range up to the upper end P 1  of the hub  108  is protected by the chest protecting cushion  120 , and a range thereabove is protected by the head protecting cushion  122 . This configuration allows the driver seat airbag device  100  to fully restrain the chest  128  and head  126  of the occupant  124  without disrupting the posture of the airbag cushion, even when a yoke steering wheel  106  is adopted. 
     Note that the driver seat airbag device  100  of the present embodiment can also be applied to a conventional circular steering wheel. In this case, the head protecting cushion  122  also expands and deploys so as to go over an upper side of the rim of the steering wheel. The aforementioned driver seat airbag device  100  can fully restrain the head  126  and the chest  128  of the occupant  124  without being dependent on the shape of the steering wheel. 
     Modified Example 
     Modified examples of the aforementioned driver seat airbag device  100  and components thereof will be described below. In each of the modified examples illustrated in  FIGS. 7 to 18  below, the same components as those already described are omitted from the description by labeling the components with the same symbol. Furthermore, the same names as the components described above shall have the same functions unless otherwise indicated even when labeled with a different symbol. 
       FIG. 7  is a diagram illustrating a first modified example (driver seat airbag device  200 ) of the driver seat airbag device  100  illustrated in  FIG. 2 . The driver seat airbag device  100  has a different configuration than the driver seat airbag device  100  of  FIG. 2  from the perspective that a camera  202  capable of detecting the position of the occupant  124  and a control unit  204  that controls each inflator based on the position of the occupant detected by the camera  202  are provided. 
     The camera  202  detects the position of the head  126  of the occupant  124  and the like to determine the posture of the occupant  124 . The control unit  204  controls the activation timing, output, and the like of the chest portion inflator  132  and the head portion inflator  138  based on the posture of the occupant  124  determined through the camera  202 . 
       FIG. 8  is a diagram illustrating a process of the driver seat airbag device  200  in  FIG. 7  restraining the occupant  124 .  FIG. 8( a )  is a diagram illustrating the driver seat airbag device  200  at the start of activation. The driver seat airbag device  100  described with reference to  FIG. 5  was configured such that the chest protecting cushion  120  expands and deploys first. On the other hand, in the driver seat airbag device  200 , not only can the chest protecting cushion  120  be expanded and deployed first, but the head protecting cushion  122  can be expanded and deployed first depending on the situation. 
     When a predetermined sensor of the vehicle detects or predicts an impact, the occupant  124  may be in a non-regular seating position (commonly referred to as out-of-position) relative to the seat  102 . For example, if the occupant  124  leans out of the seat  102  and is in close proximity to the yoke steering wheel  106 , the chest protecting cushion  120  may not properly function. In this case, the camera  202  detects the position of the occupant  124  and the control unit  204  activates the head portion inflator  138  first. In some cases, the control unit  204  activates the head portion inflator  138  with a moderately reduced output. Thereby, the head protecting cushion  122  pushes the head  126  of the occupant  124  toward the rear of the vehicle with a non-burdensome force to secure a space between the occupant  124  and the yoke steering wheel  106 . 
       FIG. 8( b )  illustrates a condition where the occupant  124  in  FIG. 8( a )  moves toward the rear of the vehicle. The control unit  204  activates the chest portion inflator  132  at a timing when the head protecting cushion  122  pushes the occupant  124  back to the rear. With this configuration, a space between the yoke steering wheel  106  and the occupant  124  can be secured, and thus the chest protecting cushion  120  can be inserted between the occupant and the steering wheel. 
       FIG. 8( c )  illustrates a condition where expansion and deployment of the chest protecting cushion  120  in  FIG. 8( b )  is completed. Even when the head protecting cushion  122  is expanded and deployed first as in the present embodiment, the chest  128  and head  126  of the occupant  124  can be fully restrained by the head protecting cushion  122  and the chest protecting cushion  120 . In particular, if the occupant  124  is in a non-regular seating position and a prior prediction of an impact is detected, it is possible to prepare for an impact occurring later. 
       FIG. 9  is a diagram illustrating a first modified example (chest protecting cushion  220 ) of the chest protecting cushion  120  illustrated in  FIG. 3 .  FIG. 9( a )  is a perspective view of a chest protecting cushion  220  in an expanded and deployed state. The chest protecting cushion  220  is configured of a front panel  222  and a rear panel  224 , and expands and deploys into a flat rectangular body. 
       FIG. 9( b )  is a diagram illustrating the front panel  222  of  FIG. 9( a )  spread out on a plane. The front panel  222  has a rectangular shape and functions as a restraining surface that restrains the occupant when the chest protecting cushion  220  is expanded and deployed. The front panel  222  is bent at folding lines  222   a ,  222   b  and then joined to the rear panel  224  (see  FIG. 9( c ) ). 
       FIG. 9( c )  is a diagram illustrating the rear panel  142  of  FIG. 9( a )  spread out on a plane. The rear panel  224  is also rectangular, overlaps the front panel  222  ( FIG. 9( b ) ) in an orientation where long sides intersect each other, and is bent at folding lines  224   a ,  224   b  and then joined to the front panel  222 . The rear panel  224  functions as a reaction force surface that obtains reaction force from the yoke steering wheel  106  (see  FIG. 1( a ) ) when the chest protecting cushion  220  is expanded and deployed. The securing region  144  is formed on an upper side of the center of the rear panel  224  where a chest portion inflator  112  (see  FIG. 2 ) is inserted and secured inside the yoke steering wheel  106 . 
     The square chest protecting cushion  220  (see  FIG. 9( a ) ) can suitably restrain the chest  128  of the occupant  124  in the same manner as the chest protecting cushion  120  of  FIG. 2 . Furthermore, the chest protecting cushion  220  has a rectangular front panel  222  and rear panel  224 , which provides a more favorable production ratio (yield) from materials than other complex shapes and is beneficial from the perspective of manufacturing costs. 
       FIG. 10  is a diagram illustrating a second modified example (chest protecting cushion  240 ) of the chest protecting cushion  120  illustrated in  FIG. 3 .  FIG. 10( a )  is a perspective view of a chest protecting cushion  240  in an expanded and deployed state. The chest protecting cushion  240  is configured of a front panel  242  and a rear panel  244 , and expands and deploys into a flat circular shape. 
       FIG. 10( b )  is a diagram illustrating the front panel  242  of  FIG. 10( a )  spread out on a plane. The front panel  242  has a circular shape and functions as a restraining surface that restrains the occupant when the chest protecting cushion  240  is expanded and deployed. 
       FIG. 10( c )  is a diagram illustrating the rear panel  244  of  FIG. 10( a )  spread out on a plane. The rear panel  244  is circular, has the same dimensions as the front panel  242  (see  FIG. 10( b ) ), and is joined to the front panel  242 . The rear panel  244  functions as a reaction force surface that obtains reaction force from the yoke steering wheel  106  (see  FIG. 1( a ) ) when the chest protecting cushion  240  is expanded and deployed. A securing region  140  is formed on the center of the rear panel  244  where a chest portion inflator  112  (see  FIG. 2 ) is inserted and secured inside the yoke steering wheel  106 . 
     The circular chest protecting cushion  240  (see drawings) can suitably restrain the chest  128  of the occupant  124  in the same manner as the chest protecting cushion  120  of  FIG. 2 . Even the circular chest protecting cushion  240  can suitably restrain the occupant  124  without disrupting the posture when expanded, for example, by limiting dimensions to fit within a range overlapping the yoke steering wheel  106 . 
       FIG. 11  is a diagram illustrating a third modified example (chest protecting cushion  260 ) of the chest protecting cushion  120  illustrated in  FIG. 3 .  FIG. 11  illustrates a chest protecting cushion  260 , corresponding to  FIG. 2 . The chest protecting cushion  260  is housed along with a chest portion inflator  262  in a lower portion of the instrument panel  104  more toward the front of the vehicle than the yoke steering wheel  106 , and expands and deploys therefrom to reach behind the yoke steering wheel  106 . 
     The chest protecting cushion  260  is capable of protecting not only the chest  128  of the occupant  124 , but also a knee  131 . This configuration enables the chest protecting cushion  260  to be suitably mounted in the vehicle and also enables the occupant  124  to be more fully protected. 
       FIG. 12  is a diagram independently illustrating the chest protecting cushion in  FIG. 11 .  FIG. 12( a )  is a perspective view of the chest protecting cushion  260  in an expanded and deployed state in  FIG. 11 . The chest protecting cushion  260  is flat and expands and deploys into a curved shape. As illustrated in  FIG. 11 , the chest protecting cushion  260  curves and expands to reach behind the yoke steering wheel  106  and behind the head protecting cushion  122 , similar to the chest protecting cushion  120  in  FIG. 2 . 
       FIG. 12( b )  is a schematic cross-sectional view illustrating an internal structure of the chest protecting cushion  260  of  FIG. 12( a ) . The chest protecting cushion  260  has a plurality of internal tethers  268  as well as a diffuser  266  that streamlines gas from the chest portion inflator  262  (see  FIG. 11 ) inside a main panel  264  configured in a bag shape. The plurality of internal tethers  268  are inserted across various locations on the main panel  264  to limit expansion of each portion of the main panel  264 , causing the main panel  264  to have an overall curved shape when expanded. 
     With the chest protecting cushion  260  of the present embodiment, a portion from the knee  131  to the abdomen  130  and the chest  128  of the occupant  124  can be suitably protected from contact with the instrument panel  104  and the yoke steering wheel  106 . Furthermore, the chest protecting cushion  260  does not need to be stored in the yoke steering wheel  106 , and therefore can be used with various forms of steering wheels from conventional circular steering wheels to next-generation steering wheels that accept electrical operation. 
       FIG. 13  is a diagram illustrating a second modified example (driver seat airbag device  300 ) of the driver seat airbag device  100  illustrated in  FIG. 2 . The driver seat airbag device  300  has a different configuration than the aforementioned embodiments from the perspective that a chest protecting cushion  302  and a head protecting cushion  304  are achieved by a single airbag cushion  306 . 
     The airbag cushion  306  is stored in the yoke steering wheel  106  along with one inflator  301  in a condition where the chest protecting cushion  302  and the head protecting cushion  304  are integrally connected. The chest protecting cushion  302  expands and deploys behind the yoke steering wheel  106  to prevent the chest  128  and abdomen  130  of the occupant  124  from contacting the yoke steering wheel  106 . The head protecting cushion  304  extends from an upper portion of the chest protecting cushion  302  to the upper surface  134  of the instrument panel  104 , and a front side is supported between the upper surface  134  of the instrument panel  104  and the windshield  136  to restrain the head  126  of the occupant  124  approaching from the rear. 
       FIG. 14  is a diagram illustrating an outline of the airbag cushion  306  in  FIG. 13 .  FIG. 14( a )  is a perspective view of the airbag cushion  306  in an expanded and deployed state in  FIG. 13 . The airbag cushion  306  expands in an L-shape, with the chest protecting cushion  302  and the head protecting cushion  304  integrated. The airbag cushion  306  is prepared in the L-shape described above by joining a pair of side panels  308   a ,  308   b  on a side surface in the vehicle width direction and a center panel  310  in the center. 
       FIG. 14( b )  is a diagram illustrating the center panel  310  in  FIG. 14( a )  spread out on a plane. The center panel  310  has a long rectangular shape and has a securing region  312  formed on an end portion on one side where the inflator  301  (see  FIG. 13 ) is inserted and secured inside the yoke steering wheel  106 . 
       FIG. 14( c )  is a diagram illustrating the side panel  308   a  in  FIG. 14( a ) . The side panels  308   a ,  308   b  have the same configuration. Therefore, the left side panel  308   a  is representatively illustrated, spread out on a plane. The side panel  308   a  has an L-shape extending to the chest protecting cushion  302  and the head protecting cushion  304  in  FIG. 13 . 
     As illustrated in  FIG. 13 , the airbag cushion  306  has the inflator  301  inserted into a range of the chest protecting cushion  302 . Therefore, in a similar manner to the driver seat airbag device  100  illustrated in  FIG. 5 , the airbag cushion  306  has a configuration where expansion and deployment thereof starts first with the chest protecting cushion  302 , and expansion and deployment of the head protecting cushion  304  is completed after the chest protecting cushion  302 . Therefore, the airbag cushion  306  is also capable of restraining the chest  128  of the occupant  124  first with the chest protecting cushion  302 , followed by restraining the head  126  of the occupant  124  with the head protecting cushion  304 , and is capable of fully restraining the occupant  124  while preventing the head  126  from bending backward or the like. 
       FIG. 15  is a diagram illustrating a third modified example (driver seat airbag device  320 ) of the driver seat airbag device  100  illustrated in  FIG. 2 . Furthermore, an airbag cushion  322  that the driver seat airbag device  320  has is also similar to the airbag cushion  306  of  FIG. 13 , where the chest protecting cushion  324  and the head protecting cushion  326  are achieved by the single airbag cushion  322 , which is stored in the yoke steering wheel  106 . In particular, in the airbag cushion  322 , a rear wall  328  of the head protecting cushion  326  is set to be positioned more toward the front of the vehicle than a rear wall  330  of the chest protecting cushion  324 . 
     The chest protecting cushion  324  expands and deploys behind the yoke steering wheel  106  to prevent the chest  128  and abdomen  130  of the occupant  124  from contacting the yoke steering wheel  106 . The head protecting cushion  326  extends from an upper portion of the chest protecting cushion  324  to the upper surface  134  of the instrument panel  104 , and a front side is supported between the upper surface  134  of the instrument panel  104  and the windshield  136  to restrain the head  126  of the occupant  124  approaching from the rear. 
       FIG. 16  is a diagram illustrating an outline of the airbag cushion  322  in  FIG. 15 .  FIG. 16( a )  is a perspective view of the airbag cushion  322  in an expanded and deployed state in  FIG. 15 . The airbag cushion  322  is prepared in the L-shape described above by joining a pair of side panels  332   a ,  332   b  on a side surface in the vehicle width direction and a center panel  334  in the center. 
       FIG. 16( b )  is a diagram illustrating the center panel  334  in  FIG. 16( a )  spread out on a plane. The center panel  334  has a long rectangular shape and has a securing region  336  formed on an end portion on one side where an inflator is inserted and secured inside the yoke steering wheel  106 . 
       FIG. 16( c )  is a diagram illustrating the side panel  332   a  in  FIG. 16( a ) . The side panels  332   a ,  332   b  have the same configuration. Therefore, the left side panel  332   a  is representatively illustrated, spread out on a plane. The side panel  332   a  has an L-shape extending to a side surface of the chest protecting cushion  324  and the head protecting cushion  326  in  FIG. 16( a ) . 
     As illustrated in  FIG. 15 , the airbag cushion  322  has the inflator  301  inserted into the chest protecting cushion  324 . Therefore, in a similar manner to the driver seat airbag device  100  illustrated in  FIG. 5 , the airbag cushion  322  has a configuration where expansion and deployment thereof starts first with the chest protecting cushion  324 , and expansion and deployment of the head protecting cushion  326  is completed after the chest protecting cushion  324 . Therefore, the airbag cushion  322  is also capable of restraining the chest  128  of the occupant  124  (see  FIG. 15 ) first with the chest protecting cushion  324 , followed by restraining the head  126  of the occupant  124  with the head protecting cushion  326 , and is capable of fully restraining the occupant  124  while preventing the head  126  from bending backward or the like. 
     As described above, in the airbag cushion  322 , a rear wall  328  of the head protecting cushion  326  is set to be positioned more toward the front of the vehicle than a rear wall  330  of the chest protecting cushion  324 . This configuration allows the airbag cushion  322  to restrain the chest  128  of the occupant  124  first, followed by the head  126 . Therefore, the driver seat airbag device  320  is capable of restraining the occupant  124  in a stable posture without causing the head  126  of the occupant  124  to bend backwards or the like. 
       FIG. 17  is a diagram applying an internal tether to each of the airbag cushions in  FIG. 14( a )  and  FIG. 16( a ) .  FIG. 17( a )  illustrates each panel of the airbag cushion  306  in  FIG. 14( a )  in a transparent manner, and a pair of internal tethers  340   a ,  340   b  provided therein. The internal tethers  340   a ,  340   b  are members that control the shape of the airbag cushion  306  during expansion and deployment. 
     The internal tethers  340   a ,  340   b  are connected to the center panel  310  so as to be inserted across corner portions of the L-shaped airbag cushion  306 . The dimensions of the internal tethers  340   a ,  340   b  are set to dimensions that will tension and pull the center panel  310  together when the airbag cushion  306  is expanded and deployed. The internal tethers  340   a ,  340   b  regulates the expansion of the corner portions of the airbag cushion  306 . With the internal tethers  340   a ,  340   b , the airbag cushion  306  can be efficiently expanded and deployed in an L-shape, such that the chest protecting cushion  302  and the head protecting cushion  304  can function. 
       FIG. 17( b )  illustrates each panel of the airbag cushion  322  in  FIG. 16( a )  in a transparent manner, and a pair of internal tethers  350   a ,  350   b  provided therein. The internal tethers  350   a ,  350   b  are connected to the center panel  334  so as to be inserted across into borders between the chest protecting cushion  324  and the head protecting cushion  326 . The internal tethers  350   a ,  350   b  regulate the expansion of corner portions of the airbag cushion  322  and allow the chest protecting cushion  324  and the head protecting cushion  326  to properly function. 
     Note that the number of each of the internal tethers described above can be further increased. When a plurality of tethers are provided, the tethers are preferably provided at locations not directly contacted by gas from an inflator. 
       FIG. 18  is a diagram applying an internal panel to the airbag cushion  306  in  FIG. 14( a ) .  FIG. 18( a )  illustrates each panel of the airbag cushion  306  in  FIG. 14( a )  in a transparent manner, and an internal panel  360  provided therein. The internal panel  360  is a component that controls the flow of gas inside the airbag cushion  306 . 
     The internal panel  360  is connected to the center panel  310  so as to be inserted across from a bottom portion of the chest protecting cushion  302  to an upper portion of the airbag cushion  306  to divide the inside of the airbag cushion  306  into a lower portion chamber  362  and an upper portion chamber  364 . The inner panel  360  is provided with a gas flow hole  366  to allow gas to pass therethrough. At this time, the securing region  312  into which the inflator  301  (see  FIG. 13 ) is inserted is included in the upper portion chamber  364 . Therefore, the airbag cushion  306  is first supplied with gas in the upper portion chamber  364  followed by gas being supplied in the lower portion chamber  362 . Thus, the airbag cushion  306  can be expanded and deployed first from the head protecting cushion  304 , as in the driver seat airbag device  200  in  FIG. 8 , by the internal panel  360 . 
       FIG. 18( b )  illustrates an internal panel  370  in a different position than the internal panel  360  in  FIG. 18( a ) . The internal panel  370  has gas flow hole  376  and divides the inside of the airbag cushion  306  into a lower portion chamber  372  and an upper portion chamber  374 . At this time, the securing  336  into which the inflator is inserted is included in the lower portion chamber  372 . Therefore, the airbag cushion  322  is first supplied with gas in the lower portion chamber  372 , followed by gas being supplied in the upper portion chamber  374 . Thereby, the airbag cushion  306  can be expanded and deployed first from the chest protecting cushion  302 , as in the driver seat airbag device  100  in  FIG. 5 , by the internal panel  370 . 
     Note that the internal tether in  FIG. 17  and the internal panel in  FIG. 18  can be implemented simultaneously with regard to a single airbag cushion. 
     This configuration enables control of the shape by the internal tether and control of the gas flow by the internal panel to be simultaneously performed. 
     Preferred examples of the present invention were described above while referring to the attached drawings. However, the embodiments described above are preferred examples of the present invention, and other embodiments can be implemented or performed by various methods. In particular, unless described otherwise in the specification of the present application, the invention is not limited to the shape, size, configurational disposition, and the like of parts illustrated in detail in the attached drawings. Furthermore, expressions and terms used in the specification of the present application are used for providing a description, and the invention is not limited thereto, unless specifically described otherwise. 
     Therefore, it is obvious that a person with ordinary skill in the art can conceive various changed examples or modified examples within the scope described in the scope of the claims, which is understood to naturally belong to the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used as an airbag for a driver seat for restraining an occupant during an emergency. 
     Description of Codes 
       100  . . . Driver seat airbag device,  102  . . . Seat,  104  . . . Instrument panel,  106  . . . Yoke steering wheel,  108  . . . Hub,  110  . . . Hub cover,  114  . . . Rim,  120  . . . Chest protecting cushion,  122  . . . Head protecting cushion,  124  . . . Occupant,  126  . . . Head,  128  . . . Chest,  130  . . . Abdomen,  131  . . . Knee,  132  . . . Chest portion inflator,  134  . . . Upper surface,  136  . . . Windshield,  138  . . . Head portion inflator,  140  . . . Front panel,  142  . . . Rear panel,  144  . . . Securing region,  146   a ,  146   b  . . . Side panel,  148  . . . Center panel,  150  . . . Securing region,  152  . . . Rear wall of head protecting cushion,  154  . . . Rear wall of chest protecting cushion,  200  . . . Driver seat airbag device of first modified example,  202  . . . Camera,  204  . . . Control unit,  220  . . . Chest protecting cushion of first modified example,  222  . . . Front panel,  222   a ,  222   b  . . . Folding line of front panel,  224  . . . Rear panel,  224   a ,  224   b  . . . Line of rear panel,  240  . . . Chest protecting cushion of second modified example,  242  . . . Front panel,  244  . . . Rear panel,  260  . . . Chest protecting cushion of third modified example,  262  . . . Chest portion inflator,  264  . . . Main panel,  266  . . . . Diffuser,  268  . . . Internal tether,  300  . . . Driver seat airbag device of second modified example,  301  . . . Inflator,  302  . . . Chest protecting cushion,  304  . . . Head protecting cushion,  306  . . . Airbag cushion,  308   a ,  308   b  . . . Side panel,  310  . . . Center panel,  312  . . . Securing region,  320  . . . Driver seat airbag device of third modified example,  322  . . . Airbag cushion,  324  . . . Chest protecting cushion,  326  . . . Head protecting cushion,  328  . . . Rear wall of head protecting cushion,  330  . . . Rear wall of chest protecting cushion,  332   a ,  332   b  . . . Side panel,  334  . . . Center panel,  336  . . . Securing region,  340   a ,  340   b  . . . Internal tether,  350   a ,  350   b  . . . Internal tether,  360  . . . Internal panel,  362  . . . Lower portion chamber,  364  . . . Upper portion chamber,  366  . . . Gas flow hole,  370  . . . Internal panel,  372  . . . Lower portion chamber,  374  . . . Upper portion chamber,  376  . . . Gas flow hole, P 1  . . . Upper end of hub, L 1  . . . Horizontal line passing through upper end of hub, L 2  . . . Vertical line passing through rear end of rear wall of head protecting cushion, L 3  . . . Vertical line passing through rear end of rear wall of chest protecting cushion