Abstract:
An airbag module has an airbag inflator and a vehicle hood airbag. The vehicle hood airbag is inflated by the airbag inflator and oriented to deploy at an acute angle over a vehicle hood. Following deployment, the vehicle airbag has an airbag length and an airbag width. The airbag length is sized to extend only substantially along the vehicle hood length while the airbag width is sized to extend substantially across a vehicle hood width.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an external airbag module to protect a pedestrian.  
         BACKGROUND OF THE INVENTION  
         [0002]    Airbags are commonly employed to protect a vehicle occupant from injury in a crash. Recently, vehicle manufacturers have considered using airbags to protect individuals outside of the vehicle from injury. Current pedestrian airbag systems focus on preventing injury to a pedestrian who may hit the windshield of the vehicle. Accordingly, these airbags deploy from the rear of the vehicle hood and over the vehicle windshield. In this way, the pedestrian is cushioned from injury resulting from impact with the vehicle windshield.  
           [0003]    While the hood of the vehicle does not pose as significant of a threat to a pedestrian as the vehicle windshield, it has been discovered that there are a significant number of hard points under the hood that a pedestrian may encounter in a front end collision with a vehicle. One known airbag design attempts to cushion these hard points by deploying an external airbag from a vehicle bumper over the vehicle hood. However, the design lacks features that allow the external airbag to deploy quickly onto the vehicle hood.  
           [0004]    Exterior airbag systems are expensive. In an accident involving a pedestrian, the vehicle may receive very insignificant damage. Nevertheless, the airbag will deploy to protect the pedestrian. In light of the minimal damage to the body of the vehicle, it would be desirable to offer an airbag system that may be easily reinstalled after deployment.  
           [0005]    There is a need for an inexpensive exterior airbag system that protects a pedestrian from injury caused by the hard points of the vehicle hood and overcomes the deficiencies of existing external airbag designs.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention comprises an external airbag and an airbag inflator for a vehicle hood. Unlike existing external airbag systems, the inventive airbag module is oriented to deploy at an acute angle to the vehicle hood so that the airbag may deploy quickly over a vehicle hood. The airbag is further sized to cover the entire vehicle hood. In addition, the inventive airbag has elements that allow the airbag to be repacked and reused, thereby reducing the overall cost of the system over the life of the vehicle.  
           [0007]    In addition, the vehicle hood airbag may deploy from a front area of the vehicle rather than near the windshield as some existing airbag systems do. The airbag may deploy from the front area of the vehicle hood to the rear area of the vehicle hood and cover entirely the vehicle hood when deployed. In this way, the pedestrian is protected from injury caused by any hard points that may exist under the vehicle hood.  
           [0008]    In light of the size of the airbag, it is particularly desirable to avoid replacing the airbag. Accordingly, the inventive airbag uses an airbag inflator that will not damage the airbag during deployment. Rather than using a combustion gas generator inflator, the inventive airbag preferably uses a pressurized gas inflator, such as a CO 2  cartridge. Gas from this cartridge is cold and will not burn the vehicle hood airbag. Thus, after deployment, the spent inflation gas cartridge may be replaced and the existing airbag may be repacked.  
           [0009]    The airbag and the airbag inflator may be stored in a storage compartment housing located at the front of the vehicle. The storage compartment housing may have a door that opens during airbag deployment. Following deployment, the airbag may be repacked, the airbag inflator may be replaced, and the door to the storage compartment closed. The door to the storage compartment may be part of the exterior of the vehicle.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment.  
         [0011]    [0011]FIG. 1 is a side view of a vehicle equipped with the inventive airbag module in an undeployed state.  
         [0012]    [0012]FIG. 2 is a side view of the vehicle of FIG. 1 as the airbag deploys.  
         [0013]    [0013]FIG. 3 illustrates the vehicle of FIGS. 1 and 2 with the airbag in a fully deployed state.  
         [0014]    [0014]FIG. 4 is a side view of the vehicle of FIG. 3.  
         [0015]    [0015]FIG. 5 illustrates the replacement of the airbag inflator.  
         [0016]    [0016]FIG. 6 illustrates placing the airbag back into into the vehicle storage compartment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    As used herein and in the claims terms describing a location such as “forward”, “rear”, “front”, “back”, “up” and “down” are understood to relate to such locations relative to a motor vehicle.  
         [0018]    [0018]FIG. 1 is a side view of a vehicle equipped with the inventive airbag module  10 . As shown, airbag module  10  comprises airbag inflator  14  and vehicle hood airbag  18 . The airbag inflator  14  is controlled by an impact detection system  16 . When the impact detection system  16  detects an impact with an object, such as a pedestrian, the airbag inflator  14  is instructed to release a pressurized inflation gas. Preferably, the airbag inflator  14  is a pressurized cartridge containing inflation gas that releases a cold CO 2  gas to inflate the airbag  18  so as to avoid damaging the airbag  14 .  
         [0019]    As shown in FIG. 2, the airbag module  10  is located at the front of vehicle  20  ahead of a vehicle hood  22 . At the front  21  of vehicle  20 , the airbag  18  is positioned to deploy over the vehicle hood  22  at an acute angle relative to the vehicle hood  22  along the direction of arrow A in contrast to deployment at a generally perpendicular angle like existing airbags for a vehicle hood. The deployment of the airbag  18  at such an angle greatly reduces the amount of time for the airbag  18  to reach its resting position over vehicle hood  22  as shown in FIGS. 3 and 4.  
         [0020]    When the impact detection system  16  instructs the airbag inflator  14  to the inflate airbag  18 , the airbag  18  is projected over vehicle hood  22  in the direction of arrow A and starts to pivot in the direction of arrow X. The impact detection system may be of any suitable design including for example a magnetostrictive sensor or pressure sensor. Because the airbag module  10  is located in a forward area  26  of the vehicle hood  22 , movement of the vehicle  20  in the direction of arrow Y as well as gravity will assist pivoting of the airbag  18  in the direction of arrow X as the airbag  18  deploys. Due to the velocity of the vehicle  20  in the direction of arrow Y, wind traveling over the vehicle  20  will also tend to move the airbag  18  in the direction of arrow X over the vehicle hood  22 .  
         [0021]    [0021]FIG. 3 illustrates the airbag  18  in a fully deployed position. As shown, when fully deployed, the airbag  18  has an airbag width A W  and an airbag length A L . The airbag width A W  is about the width of vehicle hood  22  H W , while the airbag length A L  is about the same as the length of the vehicle hood  22 , H L . In this way, the airbag  18  is large enough to cover a substantial portion of the vehicle hood  22  without impairing the vision of the vehicle operator. Preferably, the airbag  18  covers the vehicle hood  22  completely so that many of the hard points underneath the vehicle hood  22  are cushioned.  
         [0022]    [0022]FIG. 4 is a side view of a vehicle with a fully deployed airbag  18  on the vehicle hood  22 . The airbag  18  extends across the vehicle hood  22  and may terminate at a vehicle windshield  25  so as to permit the vehicle driver to see without the obstruction of the airbag  18 .  
         [0023]    The airbag  18  is stored in a vehicle storage compartment  34 , which also houses the airbag inflator  14 . When stored as shown in FIG. 1, the vehicle storage compartment  34  has a hinged door  38 . As shown in FIG. 1, the door  38  forms part of the outer skin of the vehicle  20  and, preferably, shares the same paint color as other exterior portions of the vehicle  20 . When the airbag  18  deploys, as shown in FIG. 2, the door  38  pivots in the direction of arrow C to an open position.  
         [0024]    [0024]FIGS. 5 and 6 illustrate how the airbag module  10  may be serviced for reuse without great additional expense. As already mentioned, the airbag inflator  14  releases a pressurized cold inflation gas into the airbag  18  during deployment. Thus, in contrast to hot inflation gas combustion airbag inflators, the airbag inflator  14  will not burn or damage the airbag  18  during deployment. The airbag  18  may then be repacked and returned to the vehicle storage container  34  as shown in FIG. 6. In addition, the airbag inflator  14  may be replaced in a cartridge-like fashion with another airbag inflator  50 . The door  38  may be closed on its hinge along the direction of arrow B. In this way, the inventive airbag module  10  may be reused without significant additional cost.  
         [0025]    The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.