Abstract:
An airbag device is formed of a retainer having a center opening, an air bag, and at least one inflater fixed to the retainer. The air bag includes an outer bag having an outer bag opening, and an inner bag arranged inside the outer bag and having an inner bag opening. The peripheries of the outer and inner bag openings are directly or indirectly fixed to the retainer so that the inner bag communicates with an outside through the outer bag opening and the center opening. The inflater has a main body containing a gas generating agent therein and faces a space between the outer and inner bags to directly supply gas to the space when the inflater is actuated. When the gas is supplied to the space between the outer and inner bags, air is inspired into the inner bag through the center opening.

Description:
FIELD OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an airbag device installed in a vehicle. More particularly, the present invention relates to an airbag device of a so-called aspiration type, which aspirates air when an airbag is inflated with gas from an inflator. 
     An airbag device for protecting an occupant during a vehicle collision or roll-over is structured so that an airbag thereof is inflated with gas from an inflator. By designing the device to aspirate air into the airbag during its inflation, the inflating speed of the airbag can be increased. An airbag of such a type which aspirates air during the inflation of the airbag is sometimes called as an aspiration-type airbag. 
     Most of the aspiration-type airbags for drivers are structured to aspirate air through vent holes formed in the airbags. Some of the aspiration-type airbags for occupants in front passenger seats or rear seats use such vent holes. As one of the aspiration-type airbag devices for occupants in front passenger seats or rear seats, an airbag device, in which air-through openings are formed in a casing for accommodating an airbag, has been proposed. 
     Because the conventional airbags are designed such that gas from the inflator is supplied therein to fill the entire of the inside volume thereof, an inflator is required to have large capacity of generating gas. 
     OBJECT AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an airbag comprising an outer bag and an inner bag in which gas from an inflator is supplied only to a region between the outer bag and the inner bag. 
     An airbag of the present invention comprises: an outer bag, an inner bag arranged inside said outer bag, and a gas-introduction portion for introducing gas into a space between said outer bag and the inner bag. The inner bag is preferably provided with an opening which allows the ventilation between the inside of the inner bag and the outside of the outer bag. 
     An airbag device of the present invention has an airbag and an inflator for inflating said airbag wherein said airbag is the above explained airbag. 
     In the present invention, gas is supplied from the inflator into a space between the outer bag and the inner bag whereby the outer bag is inflated. While the outer bag is being inflated, air is aspirated into the inner bag through the opening thereof so that the inner bag is substantially inflated only with aspirated air. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a structural view of an airbag according to an embodiment; 
     FIG. 2 is a sectional view taken along a line II—II of FIG. 1; 
     FIG. 3 is a sectional view of an airbag device according to an embodiment; 
     FIG. 4 is a sectional view of the airbag device of FIG. 3 in the process of inflation; 
     FIG. 5 is a sectional view of the airbag device of FIG. 3 in its fully deployed state; 
     FIG. 6 is a plan view of an inflator of the airbag device of FIG. 3; 
     FIG. 7 is a plan view of an inflator used in an airbag device according to another embodiment; 
     FIG. 8 is a sectional view taken along a line VIII—VIII of FIG. 7; 
     FIG. 9 is a sectional view of an airbag device according to another embodiment; 
     FIG. 10 is an enlarged view of a portion X of FIG. 9; 
     FIG. 11 is a perspective view of an inflator used in an airbag device according to another embodiment; 
     FIG. 12 is a sectional view of an airbag device according to further another embodiment; 
     FIG. 13 is an enlarged view of a portion XIII of FIG. 12; 
     FIG. 14 is a perspective view of the portion XIII of FIG. 12; 
     FIG. 15 is a perspective view of a passenger-side airbag according to an embodiment; 
     FIG. 16 is a sectional view taken along a line XVI—XVI of FIG. 15; 
     FIG. 17 is a sectional view of the passenger-side airbag according to the embodiment; and 
     FIG. 18 is a perspective view of the passenger-side airbag according to the embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to attached drawings. FIG. 1 is a perspective view of an airbag according to an embodiment and FIG. 2 is a sectional view taken along line II—II of FIG.  1 . FIGS. 3-5 are sectional views of a driver-side airbag device in which the airbag shown in FIGS. 1 and 2 is employed, FIG. 3 illustrates the state before the inflator is actuate, FIG. 4 illustrates the state where the inflator is in operation, and FIG. 5 illustrates the state where the airbag is completely inflated. FIG. 6 is a plan view of an inflator. 
     An airbag  10  has an outer bag  12  and an inner bag  14 . The outer bag  12  is provided with an opening  16  through which an inflator is inserted. The inner bag  14  is provided with an opening  18  formed therein for introducing (aspirating) air. The opening  18  has a flap  20  made of a fabric or synthetic resin. The outer bag  12  and the inner bag  14  are connected to each other by tethers  22  such as cords or fabric strips. The flap  20  may be disposed to another portion such as a retainer or a casing of the airbag device. 
     In FIGS. 3 and 4, the retainer  30  comprises a flat plate portion  34 , to which an airbag  10  is secured, and a module cover mounting portion composed of a standing piece  36  standing from the edge of the flat plate portion  34  in a direction opposite to an occupant. The airbag  10  is folded and covered by a module cover  38 . The module cover  38  has a leg portion  38   a  in which a proximal portion is laid on the outer surface of the standing piece  36 . Further, a plate  41  is laid on the outer surface of the leg portion  38   a . The leg portion  38   a  is fixed to the retainer  30  by rivets  40  penetrating the plate  41 , the leg portion  38   a , and the standing piece  36 . 
     The inflator  50  is disposed in such a manner that the upper side (front side) thereof enters in the outer bag  12  through an opening  44  formed in the flat plate portion  34  and a flange  53  is fixed to the retainer  30 . The numeral  46  designates an airbag fixing member called as a ring. The periphery around the opening of the outer bag  12  of the airbag  10  is clamped between the ring  46  and the periphery of the opening  44  of the flat plate portion  34 , thereby securing the outer bag  12  to the retainer  30 . Bolts or rivets are inserted through the ring  46 , the outer bag  12 , the flat plate portion  34  of the retainer, and the flange  53 , which will be described later, and are tightened up. 
     The numeral  48  designates a tear line formed in the module cover  38 . 
     The inflator  50  comprises a toroidal main body  52 , flanges  53  projecting from the outer periphery and the inner periphery of the main body  52 , respectively, gas generating agent (propellant)  54  filled in the main body  52 , and an one or a plurality of igniter  55  for igniting the gas generating agent  54 . The igniter  55  may be provided. 
     The main body  52  is provided with a gas outlet  56  formed therein. The gas outlet  56  is composed of a plurality of holes, however, the gas outlet may be composed of a continuous slit extending all around the main body  52 . 
     The flanges  53  have through holes  57  into which fasteners such as bolts or rivets are inserted. Formed inside the inner flange  53  of the main body  52  is an air vent hole  58 . 
     In order to remove particles from gas, a filter is disposed along the gas outlet  56 , but not shown. 
     The periphery of the opening  18  of the inner bag  14  is fixed to the inner flange  53  by a ring  60  and bolts or rivets. Numeral  62  designates through holes for the bolts or rivets which are formed in the outer bag  12  and the inner bag  14 , respectively. 
     When the inflator  50  is actuated to inject gas, substantially the entire volume of gas from the inflator  50  is injected into a space  64  between the outer bag  12  and the inner bag  14 , thereby inflating the outer bag  12 . 
     The inflation of the outer bag  12  is accompanied by the inflation of the inner bag  14 . During this inflation, air is aspirated into the inner bag  14  through the air vent hole  58  and the opening  18  of the inner bag  14 . 
     Therefore, the airbag device of FIGS. 3-5 only requires the inflator  50  to inject such a volume of gas as to fill the space  64  between the outer bag  12  and the inner bag  14 . In the airbag device, an inflator having a small capacity of injecting gas can be employed as the inflator  50 . 
     When the occupant plunges into the inflated airbag  10 , air in the inner bag  14  is discharged through the air vent hole  58 , thereby softening the impact acting on the occupant. 
     Though the inflator  50  is circular in the above embodiments, it may be elliptic, square, rectangular, rhomboid, or polygonal such as hexagon or octagon. Further, though the inflator  50  is annular, the inflator may be composed of plural arcuate inflators as shown in FIGS. 7 and 8. The inflators  50 A shown in FIGS. 7 and 8 are semi-circular and becomes circular like the inflator  50  when combined with each other. Instead of the semi-circular inflators, various arcuate inflators such as quadrant may be employed. Also non-arcuate inflators (for example, L-like, V-like, channel-like, or short bar-like inflators) may be arranged in a circular shape. The other numerals in FIGS. 7 and 8 designate the same and corresponding parts of the inflator  50 . 
     FIGS. 9-11 show an embodiment of an airbag device in which an inflator  70  is incorporated in an airbag  10 , FIG. 9 is a sectional general view, FIG. 10 is an enlarged view of a portion X of FIG. 9, and FIG. 11 is a perspective view of the inflator  70 . 
     As shown in FIG. 11, the inflator  70  comprises a C-like, U-like or semi-circular main body  71 , flanges  72 ,  73  disposed on the outer periphery and the inner periphery of the main body  71 , respectively, propellant  74  within the main body  71 , and an igniter  75 . Numeral  76  designates a gas outlet and  77  designates through holes for bolts or rivets. 
     As shown in FIG. 10, the periphery of the outer bag  12  is clamped between the outer flange  73  and a retainer  30  and fixed by bolts  78 . 
     The periphery of the inner bag  14  is laid on the inner flange  72 , clamped between the inner flange  72  and a ring  79 , and secured to the retainer  30  by rivets  79   a.    
     Also in this case, as the inflator  70  is actuated, gas injected through a gas outlet  76  of the inflator  70  enters into the space  64 , thereby inflating the outer bag  12 . Into the inner bag  14 , air is aspirated through an opening  44  of the retainer  30  and the opening  18  of the inner bag  14 . 
     FIGS. 12-14 show an airbag device in which a plurality of small inflators  80  is arranged. The inflators  80  are inserted through openings or side openings  81  formed in the retainer  30  such that upper portions of the inflators  80  project and are designed to inject gas into the space  64  between the outer bag  12  and the inner bag  14  through gas outlets  82  thereof. Numeral  83  designates a flange of each inflator  80  which is fixed to the retainer  30  by rivets  84 . 
     The periphery of the opening  16  of the outer bag  12  is fixed to the retainer  30  by a ring or outer ring  85  and bolts  86  and the periphery of the opening  18  of the inner bag  14  is fixed to the retainer  30  by a ring or inner ring  87  and bolts  88 . 
     When the inflators  80  are actuated, gas enters into the space  64  through gas outlets  82  so as to inflate the outer bag  12 . Into the inner bag  14 , air is aspirated through an opening  44  of the retainer  30  and the opening  18  of the inner bag  14 . 
     Instead of the inflators  80 , small inflators in various configurations (for example, bar-like inflators) may be secured to the retainer  30 . 
     FIGS. 15 and 16 are a perspective view and a sectional view of an airbag for a front passenger or a rear passenger. FIGS. 17 and 18 are a sectional view and a perspective view of a passenger-side airbag device in which the airbag is employed. 
     An airbag  90  comprises an outer bag  92  and an inner bag  94  which are connected to each other by tethers  96  such as cords or fabric strips. The respective peripheries of openings  92   a ,  94   a  of the outer bag  92  and inner bag  94  are provided with through holes  97  for bolts or rivets. The opening  94   a  of the inner bag  94  has a flap  98  of a fabric piece. One side of the flap  98  is connected to the bag  94  by sewing or adhesion. 
     In this airbag  90 , the outer bag  92  is inflated by supplying gas into a space between the outer bag  92  and the inner bag  94 . During this inflation, the flap  98  opens inwardly and air is aspirated into the inner bag  94  through the opening  94   a.    
     As shown in FIGS. 17 and 18, an passenger-side airbag device  100  comprises a casing  102  called as a container, the aforementioned airbag  90  folded and accommodated within the casing  102 , a lid  104  attached to the front surface of the casing  102 , and inflators  106  arranged in a rear portion of the casing  102 . 
     The back surface of the casing  102  is provided with a vent hole  108 . The periphery of the opening  94   a  of the inner bag  94  of the airbag  90  is secured to the periphery of the vent hole  108  by a frame-like mounting bracket  110  and rivets  112 . The periphery of the opening  92   a  of the outer bag  92  is fixed to sides, the top, and the bottom of the casing  102  by an elongated plate-like mounting brackets  114  and rivets  116 . 
     When the inflators  106  are actuated, gas is injected into the space between the outer bag  92  and the inner bag  94 , thereby inflating the airbag  90  as shown in FIG.  16 . During the inflation of the airbag  90 , the lid  104  opens and the airbag  90  is inflated toward the front of the casing  102  as shown in FIG.  16 . While the outer bag  92  is inflated with gas, air is aspirated into the inner bag  94  through the vent hole  108  and the opening  94   a.    
     Therefore, the airbag  90  can be inflated sufficiently and quickly by the inflators  106  of small capacities. 
     When the occupant plunges into the inflated airbag  90 , air in the inner bag  94  is discharged through the opening  94   a,  thereby softening the impact acting on the occupant. 
     The present invention can be applied to not only a driver airbag device, a front passenger or rear passenger airbag device but also a side airbag device which is disposed on a side of an occupant and an airbag device for protecting the head of the occupant. 
     In the present invention, the inner bag and the outer bag may be connected directly to each other not using the tethers  22 ,  96 . 
     As described above, the airbag of the present invention can be sufficiently and quickly inflated by an inflator of small capacity. The airbag device of the present invention is provided with this airbag, so can employ an inflator of small capacity.