Abstract:
An airbag device is formed of an airbag, a holding device for holding the airbag, a gas supply device for supplying gas into the airbag to inflate the same, and an adjusting device connected to the holding device. Upon inflation of the airbag, the adjusting device is actuated to move the holding device for adjusting a location of the airbag. When a vehicle collision speed is less than a predetermined speed, or when a weight of an occupant in the seat is less than a predetermined value, upon inflation of the airbag, the holding device is moved backward. Thus, the distal end position of the airbag is adjusted in accordance with the vehicle collision speed and the weight of the occupant.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to an airbag device for protecting an occupant in a movable subject, such as a vehicle, in case of emergency, such as a collision of the vehicle. 
     An airbag device installed in a vehicle, for example, an automobile, includes a folded airbag, a housing member for accommodating the airbag, and an inflator (gas generator) for inflating the airbag by spouting or ejecting a gas in the event of the collision. 
     In most of the airbag devices for a driver&#39;s seat, the housing member is formed of a retainer and a module cover which can be opened or torn. The airbag and the inflator are attached to the retainer, and the airbag is covered by the module cover. When the inflator is actuated, the module cover is opened or torn, so that the airbag is inflated toward an interior of the vehicle. 
     In most of the airbag devices for a front passenger&#39;s seat, the folded airbag is accommodated in a container in the form of a receptacle, and the container is covered by a lid. When the inflator is actuated, the lid is opened, or starts opening like a door, so that the airbag is inflated in the interior of the vehicle. 
     As one kind of the conventional airbag devices, there is an airbag device wherein a tether belt is disposed inside the airbag. One or front end of the tether belt is sewn to a distal end portion of the airbag, and a rear end thereof is connected to the retainer or container. In case the inflator is actuated, the airbag is inflated until the tether belt is stretched tightly. 
     In the conventional airbag device, however, in case the inflator is being actuated to inflate the airbag, a protruding length of the airbag from the retainer or the container can not be adjusted. 
     Accordingly, an object of the present invention is to provide an airbag device, wherein an airbag user can be protected based on a condition of a vehicle and/or user. 
     Another object of the invention is to provide an airbag device, wherein a protruding length of the airbag from an airbag holding device can be adjusted based on a vehicle speed and user&#39;s weight. 
     A further object of the invention is to provide an airbag device as stated above, wherein the holding condition of the airbag is selected at an optimum value to protect the user. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     To achieve the aforementioned objects, the present invention provides an airbag device which comprises a folded airbag, holding means for holding the airbag, gas supply means for supplying a gas into the airbag to inflate the airbag, and adjusting means for adjusting a location of a distal end of the inflated airbag. 
     In the airbag device structured as described above, adjusting means may be provided with a movable member connected to a rear portion of the airbag, and means for adjusting a position of the movable member. 
     Alternatively, the adjusting means may be provided with a belt having one end connected to the distal end of the airbag, and a supporting device for supporting a rear end of the belt, wherein the supporting device is capable of adjusting a length of the belt extending from the supporting device. 
     According to the airbag device of the present invention, in accordance with a vehicle collision speed, or a position and body size or weight of the occupant, a protruding length of the airbag can be adjusted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a first embodiment of the present invention; 
     FIG. 2 is a explanatory sectional view taken along line  2 — 2  in FIG. 1; 
     FIG. 3 is an explanatory sectional view showing a state that the airbag device shown in FIGS. 1 and 2 is actuated; 
     FIG. 4 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a second embodiment of the invention; 
     FIG. 5 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a third embodiment of the invention, wherein the airbag device is in the actuated state; and 
     FIG. 6 is an explanatory sectional view of an airbag device for a driver&#39;s seat according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereunder, embodiments of the present invention will be explained with reference to the accompanying drawings. 
     FIG. 1 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a first embodiment of the present invention; FIG. 2 is an explanatory sectional view taken along line  2 — 2  in FIG. 1; and FIG. 3 is an explanatory sectional view showing a state that the airbag device shown in FIGS. 1 and 2 is actuated. 
     An airbag device  10  for a front passenger&#39;s seat includes a container  12  in a form of a receptacle with an open front; an airbag  14  folded and stored in the container  12 ; a lid  16  attached to the front of the container  12 ; an inflator  18  disposed in a rear side of the container  12 ; a frame  20  to which a rear end of the airbag  14  is connected; cylinders  22  for advancing and retreating the frame  20 ; piston rods  24  having a distal end connected to the frame  20 ; and inflators  26  for actuating the cylinders in order to provide a gas into the cylinders  22  for retreating the piston rods  24 . The cylinders  22  are respectively disposed at four corners of the container  12 , but a number of the cylinders may be freely decided. 
     The lid  16  is provided with legs  16   a ,  16   b  protruding rearward, and the legs  16   a ,  16   b  are respectively connected to the container  12 . 
     In the event of an emergency, such as vehicle collision, the inflator  18  is actuated to spout the gas. Accordingly, the airbag  14  is inflated, and one of the legs, i.e. leg  16   b , is torn, so that the lid  16  is opened like a door as shown in FIG.  3 . As a result, the airbag  14  is deployed largely inside the vehicle as shown by solid line  14 A in FIG.  3 . Incidentally, instead of the breaking the leg  16   b , it can be structured such that the lid  16  is opened or torn. 
     When a vehicle collision speed is less than a predetermined speed, or when a weight of the occupant in the front passenger&#39;s seat in the vehicle is less than a predetermined value, the inflators  26  for actuating the cylinders are actuated to move the frame backward through the piston rods  24 . Accordingly, a protruding length of the airbag  14  from the container  12  becomes, as shown by two-dotted chain line  14 B, shorter than that in the solid line  14 A. A sensor is attached to the inflators  26  to measure the collision speed and/or weight of the occupant. 
     Incidentally, an amount of generated or spouted gas can be controlled according to the vehicle collision speed or the weight of the occupant in the front passenger&#39;s seat, so as to control the distance of movement of the frame backward. 
     FIG. 4 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a second embodiment of the invention. 
     An airbag device  30  for the front passenger&#39;s seat is provided with guides  32  for guiding a movement of the frame  20  forward and backward. A winder  34  is disposed at a rear part of the container  12 , wherein wires  36  wound around the winder  34  are extended or disposed through wire guides  38 , and ends of the wires  36  are connected to the frame  20 . 
     In this embodiment, in accordance with the vehicle collision speed or weight of the occupant in the front passenger&#39;s seat, the wires  36  are wound up or withdrawn to move the frame  20  forward or backward. Accordingly, the protruding length of the inflated airbag  14  from the container  12  can be adjusted as in the embodiment in FIG.  3 . 
     FIG. 5 is an explanatory sectional view of an airbag device for a front passenger&#39;s seat according to a third embodiment of the invention, wherein the airbag device is in the actuated state. 
     In an airbag device  40 , a rear end portion of the airbag  14  is directly connected and fixed to the container  12 . One end of a tether belt  42  is connected to the distal end of the airbag  14  by sewing or the like. The other end of the tether belt  42  is attached to a winder  44  such that the tether belt  42  is capable of being wound around the winder  44 . When the inflator  18  is actuated in the event of vehicle collision, the airbag  14  is inflated so that the tether belt  42  is stretched tightly. In this case, in accordance with the vehicle collision speed or the weight of the occupant in the front passenger&#39;s seat, a length of winding the tether belt  44  is controlled, so that the protruding length of the airbag  14  from the container  12  can be adjusted as in the embodiment of FIG.  3 . 
     FIG. 6 is an explanatory sectional view of an airbag device for a driver&#39;s seat according to an embodiment of the present invention. 
     An airbag device  50  includes a retainer  52  disposed at a steering wheel; a folded airbag  54 ; a module cover  56  for covering the airbag  54 ; an inflator  58 ; a frame  60  to which a base end of the airbag  54  is connected; rods  62  connected to the frame  60 ; flanges  64  at rear ends of the rods  62 ; and piezoelectric displacement elements  66 . Each piezoelectric displacement element is sandwiched by a main plate portion  52   a  of the retainer  52  and the flange  64 . 
     A distal end side of the inflator  58  passes through a central opening  52   b  of the main plate portion  52   a  of the retainer  52 , and projects forwardly from the retainer main plate portion  52   a . The distal end side of the inflator  58  is provided with gas spouting holes  58   a.    
     A rear end of the airbag  54  is fixed to the frame  60  by holding members  70 , such as nuts. 
     One end of the tether belt  72  is connected to the distal end side of the airbag  54 , and the other end of the tether belt  72  is connected to the frame  60 . 
     When the vehicle collides, the inflator  58  is actuated, and the module cover  56  is opened and torn, so that the airbag  54  is inflated and the tether belt  72  is stretched tightly. 
     At this time, in case the vehicle collision speed is more than a predetermined value, or in case a weight of the occupant in the driver&#39;s seat is more than a predetermined value, voltage is applied to the piezoelectric displacement elements  66  so as to shorten the length of the rod  62  of the piezoelectric displacement elements  66  in the longitudinal direction. Accordingly, the frame  60  is moved in a direction of an arrow S, so that the protruding length of the airbag  54  from the retainer  52  is adjusted. Incidentally, as the collision speed becomes faster, or as the weight of the occupant becomes heavier, the voltage applied to the piezoelectric displacement element  66  may be increased to increase an amount of movement of the frame  60 . Also, the piezoelectric displacement elements  66  may be laminated in layers, and by increasing or decreasing a number of the piezoelectric displacement elements  66 , the amount of movement thereof can be adjusted. 
     As described above, in the airbag device according to the present invention, since the position of the distal end of the inflated airbag can be adjusted, the position of the airbag can be adjusted in accordance with the vehicle collision speed or the weight of the occupant. Thus, the driver or occupant can be protected at a best protection position and holding ability of the airbag as compared with the conventional airbag device. Also, since the driver or occupant is protected at an earlier stage of the vehicle collision, the load that the driver or occupant receives is reduced, so that the energy absorbing amount required by the airbag device is reduced as well. The driver or occupant can be protected more safely. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.