Abstract:
An airbag apparatus with adaptive inflation characteristics vents inflation gas prior to full airbag deployment to afford proper protection for an out-of-position occupant. A vent opening in the casing is controlled by a movable control section of the airbag itself. The control section has a control opening that is registered with the vent opening when the airbag is uninflated, or when it is partially inflated, such as when the airbag encounters an out-of-position occupant. For a properly positioned occupant, the control section moves to cover the vent opening as the airbag becomes fully inflated to block the escape of gas from the casing.

Description:
BACKGROUND  
       [0001]     The present invention relates to an airbag device for protection of a vehicle occupant and, more particularly, to an airbag that is inflatable in front of a vehicle occupant.  
         [0002]     Airbags are employed in various locations in vehicles as secondary restraint mechanisms to operate in conjunction with seat belts in order to provide enhanced protection for vehicle occupants during an impact event. A front impact airbag typically is designed to inflate over a 15-40 millisecond time frame, and to deflate in a controlled manner as the occupant moves forwardly against the inflated airbag to absorb kinetic energy.  
         [0003]     Some front airbags are designed to inflate partially in the case of an out-of-position occupant, such as an occupant who at the time of the impact event is leaning forwardly, or in other situations where the occupant is too close to the airbag module for proper airbag deployment. Such arrangements are intended to reduce the inflation force so that the closely positioned occupant is not injured by the expanding airbag. Examples of such devices are mentioned briefly below.  
         [0004]     U.S. Pat. Nos. 5,709,405, 6,161,866, 6,199,895 and 6,746,044 disclose airbag devices in which an electronic control system operates a mechanical vent valve. Valve actuation is governed by an occupant position sensor. When an out-of-position occupant condition is detected, a portion of the inflation gas is vented from the casing of the device to moderate the degree of airbag inflation.  
         [0005]     U.S. Pat. No. 5,280,953 discloses an airbag having side vents that are progressively closed by a tether-actuated sliding flap as the airbag inflates. The degree of vent closure depends on the displacement of the airbag toward the fully deployed position.  
         [0006]     US patent publication No. US 2004/0188990 A1 discloses various tether-actuated valve arrangements that close a gas vent channel in the airbag module casing as the airbag approaches the fully deployed position.  
       SUMMARY  
       [0007]     The present invention provides a front airbag apparatus of simplified construction that provides for venting of inflation gas prior to full airbag deployment to afford proper protection for an occupant who is out of position, or otherwise is too close to the apparatus.  
         [0008]     An airbag apparatus of the present invention comprises a casing having walls defining a chamber, the chamber having an inner end and an opposite airbag deployment end. An airbag is folded within and is attached to the casing. The airbag has a front face adapted to contact and cushion a vehicle occupant and a control section. A gas generator provides gas to the chamber to inflate the airbag. One wall of the casing has at least one vent opening through which a portion of the gas can escape from the chamber. A first portion of the control section extends along the one wall and has a control opening registered with the vent opening when the airbag is uninflated or partially inflated such that gas can escape from the casing through the registered openings. The first portion of the control section moves over the one wall as the airbag becomes fully inflated to move the control opening out of registry with the vent opening so that the control section covers the vent opening to substantially block the escape of gas therethrough.  
         [0009]     In a preferred embodiment the vent opening is in a side wall of the casing; and the control section of the airbag has a second portion that is folded when the airbag is uninflated or partially inflated, and unfolds as the airbag becomes fully inflated to allow the first portion to move over the side wall. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.  
         [0011]      FIGS. 1-3  sequentially illustrate the operation of an airbag apparatus according to the invention to cushion an out-of-position occupant.  
         [0012]      FIG. 1  is a schematic longitudinal cross-sectional view of the airbag apparatus prior to an impact event that triggers the release of inflation gas.  
         [0013]      FIG. 2  is a view similar to  FIG. 1 , showing the airbag partially inflated and just making contact with an out-of-position occupant.  
         [0014]      FIG. 3  is a view similar to  FIG. 2 , showing the airbag further inflated.  
         [0015]      FIGS. 4-6  sequentially illustrate the operation of an airbag apparatus according to the invention to cushion a properly positioned occupant.  
         [0016]      FIG. 4  is identical to  FIG. 1 .  
         [0017]      FIG. 5  is a view similar to  FIG. 4 , showing the airbag partially inflated.  
         [0018]      FIG. 6  is a view similar to  FIG. 5 , showing the airbag fully inflated.  
         [0019]      FIG. 7  is a schematic perspective view of a folded portion of the control section of the airbag according to the invention, retained by a strap.  
         [0020]      FIG. 8  is a view similar to  FIG. 7 , showing the folded portion, retained by a strap and/or  0 -rings.  
         [0021]      FIG. 9  is a view similar to  FIG. 7 , showing the folded portion, retained by a strap and/or tacking. 
     
    
     DETAILED DESCRIPTION  
       [0022]      FIG. 1  illustrates the basic components of one example of an airbag apparatus according to the invention. This example is tailored for installation in the vehicle instrument panel. However, those skilled in the art will appreciate that the apparatus can be adapted for use in front of any seating position in the vehicle.  
         [0023]     Casing  10  defines a chamber  20  that houses a gas generator  30  and a folded airbag  40 . Casing  10  has side walls  12 ,  14 , an end wall  16  at the inner end of the chamber, and an opening  18  at the opposite deployment end of the chamber. Opening  18  is closed by a conventional cover (not shown) that opens to permit the airbag to deploy as it inflates. Side wall  12  has at least one vent opening  15 , the purpose of which is described below.  
         [0024]     Gas generator  30  may be of any known type that generates inflation gas when triggered by an impact event, such as a frontal collision of the vehicle. The gas generator has at least one gas outlet  32  through which inflation gas is delivered to chamber  20 . Although gas generator  30  is shown disposed within the chamber, it could be located outside chamber  20  and deliver inflation gas to the chamber through a conduit.  
         [0025]     Airbag  40  can be made of any fabric that is conventionally used for airbags, and is folded near the deployment end of chamber  20  so that it can freely expand into the passenger compartment of the vehicle when filled with inflation gas. The airbag is attached to the casing, preferably at the inner end of the casing by any suitable means, such as a retaining strap  44  (see  FIG. 7 ) with bolts or rivets (not shown) that pass through holes  46  and are anchored to the casing. The airbag may also wrap around the gas generator  30 , as shown in  FIG. 1 . The airbag has a front face  42  adapted to contact and cushion a vehicle occupant P (see  FIG. 2 ) when the airbag is inflated. The airbag also has deflation vents of any known type (not shown) that allow the escape of gas after inflation to effect controlled dissipation of impact energy.  
         [0026]     Airbag  40  has a control section  50 , preferably made of the same fabric as the rest of the airbag, and/or made of stiff material (metal or plastic) to retain the folded airbag that extends along side wall  12 . A first portion  52  of control section  50  has a control opening  55  that is initially registered with vent opening  15  in side wall  12 , i.e., when the airbag is uninflated ( FIGS. 1, 4 ) or partially inflated ( FIGS. 2, 3 ,  5 ). A second portion  54  of control section  50  is folded on itself near the inner end of the chamber. A retainer ( FIG. 7 , described below) is designed to keep the second portion  54  in folded condition when the airbag is uninflated ( FIGS. 1, 4 ) or partially inflated ( FIGS. 2, 3 ,  5 ), but release the fold as the airbag becomes fully inflated ( FIG. 6 ).  
         [0027]     Referring to  FIGS. 1-3 , the operation of the airbag apparatus according to the invention will first be described with reference to an out-of-position occupant P.  FIG. 1  shows the condition of the apparatus at the moment (0 ms) an impact event triggers the release of inflation gas from gas generator  30 . A portion of the gas escapes through the registered vent and control openings  15 ,  55 , but the airbag  40  will begin to inflate as it fills with gas.  FIG. 2  shows the condition at approximately 13 ms after the impact event, when the front face  42  of the airbag contacts the occupant P, who is located as close as about 6 inches from the deployment end of the casing. The airbag will continue to deploy, but the obstacle presented by the occupant prevents it from inflating fully. See  FIG. 3 , which shows the condition at approximately 18 ms after the impact event, when the inflation gas source ( 30 ) is spent. Here, the airbag has begun to envelop the occupant, but there is insufficient force on the control section  50  of the airbag to cause the second portion  54  to unfold. As a result, the vent and control openings  15 ,  55  remain in registry, allowing gas to continue to escape from the chamber. The effect is a less forceful inflation of the airbag, which lessens the chance of inflation-related injury for the out-of-position occupant.  
         [0028]     The situation with a properly positioned occupant is described with reference to  FIGS. 4-6 .  FIG. 4 , like  FIG. 1 , shows the condition of the apparatus at the moment (0 ms) an impact event triggers the release of inflation gas from gas generator  30 . A portion of the gas escapes through the registered vent and control openings  15 ,  55 , but the airbag  40  will begin to inflate as it fills with gas.  FIG. 5  shows the condition at approximately 13 ms after the impact event. This is similar to the condition shown in  FIG. 2 , but the occupant (not shown), being properly positioned, does not present an obstacle to the expanding airbag. Accordingly, the airbag will continue to expand towards its fully inflated condition (18 ms,  FIG. 6 ). As it does so the force on the airbag pulls control section  50  so that the second portion  54  unfolds. This allows the first portion  52  to move over side wall  12 , and move control opening  55  out of registry with vent opening  15 . The imperforate portion of the control section thus covers the vent opening  15  and is pressed against the side wall  12  by gas pressure to substantially block the escape of gas from the chamber through vent opening  15 . In this condition the fully inflated airbag affords maximum protection for the properly positioned occupant as deflation occurs through the normal airbag deflation vents (not shown).  
         [0029]      FIGS. 7-9  show examples of how the second portion  54  of the control section  50  is releasably retained in a folded condition (the sides of the airbag have been omitted for the sake of clarity). Other examples will be apparent to those skilled in the art. These figures also show that a plurality of control openings  55  may be provided for registry with a like plurality of vent openings (not shown) in side wall  12 . In the example shown, there are three collinear control openings  55 .  
         [0030]     Referring to  FIG. 7 , the retaining strap  44  that attaches the airbag to the casing may also be used to cinch the second portion  54  in its folded condition. The retaining strap maintains the folded condition until the inflation force overcomes the frictional force between the strap  44  and the airbag material, whereupon the second portion will unfold and pay out to close the vent opening(s)  15 .  
         [0031]     Referring to  FIG. 8 , the retaining strap may be supplemented or replaced by frangible O-rings  60  at the sides of the airbag that maintain the fold, but are designed to break when the inflation force on the airbag fabric exceeds a predetermined threshold value.  
         [0032]     Referring to  FIG. 9 , the retaining strap may be supplemented or replaced by releasable stitching (tacking)  70  that is placed at the sides of the airbag, or extends partly or completely across the width of the airbag. This tacking maintains the fold but yields when the inflation force on the airbag fabric exceeds a predetermined threshold value.  
         [0033]     The invention thus provides a simple, economical and reliable arrangement for automatically adjusting airbag inflation depending on the position of the occupant, without the need for position sensors, mechanical valves and actuators, and electronic controls.  
         [0034]     Given the disclosure of the present invention, one versed in the art would appreciate that there are other embodiments and modifications within the scope of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure are within the scope of the present invention and are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.