Abstract:
A multi-chambered bumper airbag for deployment from the bumper of a vehicle in the event of a collision with another vehicle is provided. The airbag comprises a main inflatable portion that, when inflated, absorbs the energy from contact with a structural member of the struck vehicle. The airbag also has one or more secondary inflatable portions concentric with the main inflatable portion. Because the secondary inflatable portions have a lower gas pressure than the main inflatable portion, they are used to cushion the occupant of the struck vehicle should the occupants&#39; head and neck be forced out of the window of the struck vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Provisional Patent Application having Ser. No. 60/261,056, filed Jan. 11, 2001, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to motor vehicle safety devices and in particular to a multi-chambered inflatable airbag for use in the bumper area of a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     For years, the automotive industry has tried various methods and products to reduce the damage to passengers and vehicles in collisions. Of prime importance are the various systems of vehicle airbags that are deployed upon the sensing of an actual collision. These airbags are located in and about the passenger compartment of the motor vehicle and are inflated to surround and protect the occupants from serious injury. 
     Other methods of reducing, to some extent, the forces created in a collision from injuring the occupants are various attempts to provide “crush zones” at the front and the rear of the vehicle to absorb some of the collision forces. Still other methods also deal with design of the vehicle frame, engine mounts and other structural members to absorb the forces by means of controlled structural collapsing. 
     Another approach is externally mounted airbags that just prior to the instance of a crash, inflate and form a fluid-filled structure between the striking object or vehicle and the struck object or vehicle. PCT application number WO98/50254 “Collision Protection System for Vehicles” teaches airbags mounted to the front of a vehicle. U.S. Pat. No. 3,656,791 “Vehicle Impact-Cushioning Device” teaches an airbag mounted to deploy from the front end of a vehicle. U.S. Pat. No. 3,708,194 “Vehicle Safety Apparatus” teaches a front-end mounted airbag that includes a fire extinguishing material. 
     Several prior art patents deal with bumper improvements. U.S. Pat. No. 4,518,183 “extendible Safety Impact Bags for Vehicles” teaches mechanisms for extending bumpers outwardly of the vehicle upon the sensing of a potential crash. Air is supplied to airbags to form a somewhat rigid member supporting the bumpers for the duration of the crash and then the airbags are deflated and the bumpers return to their normal position. U.S. Pat. No. 4,930,823 “Vehicle Bumper” teaches front and rear bumpers having airbags that are inflated upon contact of the bumper with an object. U.S. Pat. No. 5,106,137 “Vehicle Bumper with Combination Foam and Airbag Energy Absorber” teaches a bumper having an internal cavity surrounded by compressible energy absorbing plastic. Inside the cavity is an airbag that is inflated upon the onset of a crash to provide more protection to the front or rear end of the vehicle. 
     U.S. Pat. No. 5,651,569 “datable Bumper System” teaches a bumper having an enclosed airbag that is permanently inflated to provide a permanent cushion bumper. U.S. Pat. No. 5,725,265 “Airbag System For Vehicle Bumpers” teaches an airbag concealed inside a bumper that is inflated and extends outwardly of the bumper to reduce the effects of the crash. The bumper has a breakaway panel on the outer surface of the bumper that is removed by the inflation of the airbag. U.S. Pat. No. 6,056,336 “Airbag with Internal Shock Absorber” teaches a bumper airbag having an internal shock absorber. The airbag is deployed in a circular shape. U.S. Pat. No. 6,126,214 “Air Bumper” teaches an air inflatable bumper that responds to a crash to provide an air-supported member to protect the car from damages due to collision. 
     Several prior art patents show a system for the detection of a crash and the deployment of airbags. U.S. Pat. No. 3,822,076 “Fluid Shock Absorbing Buffer,” teaches a front or rear mounted airbag that are inflated when a telescopic rod extending from the vehicle touches a barrier. U.S. Pat. No. 4,176,858 “Energy Absorbing Bumper System” teaches a combination of a pneumatic bumper system supporting an airbag system that deploys in response to increased pressure in the pneumatic system as a result of an impact with an object. 
     U.S. Pat. No. 5,431,463 “Air Cell Bumper Device” teaches a plurality of air cells containing a plurality of small air cells grouped around a much larger air cell that stores inflation fluid. Upon impact, the material of cells is such that the larger cell ruptures and the fluid therein flows to the smaller cells buffering the impact. The invention is particularly useful on the sides of a vehicle. U.S. Pat. No. 5,646,613 “System for Minimizing Automobile Collision Damage” teaches the storage and deployment of various airbags around the vehicle as a result of proximity sensing. The different sides of the vehicle are uniquely controlled. U.S. Pat. No. 5,732,785 “Proactive Exterior Airbag System and Its Deployment Method for a Motor Vehicle” teaches a system having a detection unit, a control unit, and a deployment unit that together will deploy airbags mounted on the vehicle. This system deploys the airbags before the crash and describes the method used to determine distance and speed between the striking and struck vehicles or objects, 
     European Patent Application EP 1,024,063 “Vehicle Bumper and Hood Airbag System” teaches a bumper and hood bag that is inflated prior to the collision of a pedestrian and the vehicle. The airbag is inflated to absorb the collision forces between the areas from the waist down of a pedestrian and the vehicle. JP 6,144,154 “Shock Relaxing Device” teaches an airbag deployed in front of a bumper to reduce the shock of a pedestrian or bike collision with a car. 
     The increased popularity of sports utility vehicles (SUVs), passenger trucks and other retail motor vehicles that stand higher than a standard motor vehicle, such as a sedan or sports car, has created new problems in the area of vehicle collisions. Specifically, when one of these higher standing vehicles broadsides a standard vehicle, because of the difference in height between the two vehicles, the bumper of the high vehicle will contact the side window portion of the struck vehicle instead of the door portion. If the collision happens at high speeds, the head of the occupant sitting adjacent the window portion may move outward past the window and into contact with the bumper of the higher vehicle. 
     Accordingly, there is a need for an airbag that can reduce the severity of such collisions. 
     SUMMARY OF THE INVENTION 
     An advantage of the present invention is that it reduces the energy transmitted when a higher standing vehicle collides with a standard vehicle. 
     Another advantage of the present invention is that it also reduces the energy transmitted to an occupant of the struck vehicle. 
     The present invention is a multi-chambered airbag for use in conjunction with the bumper of a motor vehicle. The airbag is comprised of a main chamber surrounded by one or more concentric secondary chambers. The secondary chambers are separated from adjacent chambers by frangible seams. Just prior to impact the main chamber is inflated to a first internal pressure, (i.e. the hard condition), so as to reduce the amount of momentum transferred to the struck vehicle. Upon contact, the internal pressure increases and the frangible seams sequentially burst allowing the secondary chambers to inflate. With the inflation of the secondary chambers, the pressure in the airbag decreases creating a soft condition making the secondary chambers soft enough to cushion any contact with the occupant of the struck vehicle. Because the airbag has a larger frontal area then a conventional bumper, it also reduces the momentum transfer by spreading it out over a larger area on the struck vehicle. 
     These and other objects, features and advantages of the present invention, are specifically set forth in, or will become apparent from, the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a portion of a vehicle having a bumper airbag as contemplated by the present invention. 
         FIG. 2  is a top view of the vehicle of  FIG. 1 . 
         FIG. 3  is a side view of the vehicle of  FIG. 1 . 
         FIG. 4  is a perspective view of the vehicle of  FIG. 1  showing a closed bumper airbag container. 
         FIG. 5  is a perspective view of the vehicle of  FIG. 1  showing a bumper airbag container with its door open. 
         FIG. 6  is a perspective view of the vehicle of  FIG. 1  showing a bumper airbag container with its door open and the airbag deployed. 
         FIG. 7  is a plan view of the preferred embodiment of the bumper airbag contemplated by the present invention. 
         FIG. 8  is a side view of the un-inflated bumper airbag of  FIG. 7 . 
         FIG. 9  is a partial cross-sectional view taken along line  9 — 9  in  FIG. 7  with the center chamber of the bumper airbag partially inflated. 
         FIG. 10  is a cross-sectional view of the valve body taken along line  10 — 10  in  FIG. 7 . 
         FIG. 11  is a partial cross-sectional view taken along line  11 — 11  in  FIG. 7  with the central chamber of the bumper airbag partially inflated. 
         FIG. 12  is a block diagram control schematic of a control system for a bumper airbag as contemplated by the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1–3 , a bumper airbag as contemplated by the present invention is generally denoted by reference numeral  10 . In these FIGS., the bumper airbag  10  is shown in a partially inflated, deployed state. Though the bumper airbag  10  will be described herein as being mounted to a front bumper of a vehicle, as someone skilled in the art would appreciate, the bumper airbag  10  can also be mounted at other locations around a vehicle such as the vehicle&#39;s rear bumper. 
     With continued reference to  FIGS. 1–3  and reference to  FIGS. 7–9 , the bumper airbag  10  is formed from stitching together two pieces of fabric to define a rear fabric member  24  and a front fabric member  26 . The stitching is sewn along the respective perimeter edges of the two pieces to form, when looking toward the front of the vehicle, atop edge  110 , a bottom edge  112 , a right edge  114  and a left edge  116 . One or more, with two preferred, perimeter stitches  30  are used to couple the fabric members  24 ,  26 . Alternatively, the bumper airbag  10  can be fabricated from a single piece of fabric and then folded over and stitched to define the rear and front members  24 , 26 . The rear member  24  of the airbag  10  abuts against the vehicle when inflated and the front member  26  will contact the stricken vehicle, pedestrian or other object in a collision. 
     The first and second fabric members  24 , 26  are also connected along three frangible seams  14 ,  16 , and  18  to define an inner or main chamber  20  and first, second and third chambers  21 ,  22 , and  23  respectively. Each of the seams  14 ,  16  and  18  extends around the inner chamber  20  with seam  16  spaced radially outward from seam  14  and seam  18  spaced radially outward from seam  16  and radially inward from perimeter seams  30 . Each of the seams  14 , 16 , 18  is fabricated from a frangible nylon thread. The seams can be individual seams or can be a continuous seam wherein the first seam meets with the second seam by means of a threaded crossover. The seams  14 , 16 , 18  are substantially leak-proof, but have frangible threads that will, under the stress of increased pressure, rupture to open up the next chamber. The perimeter seams  30  do not have frangible threads. A folded over reinforcing tape  64  is applied over the entire outer edge of the airbag  10 . The tape  64  in conjunction with the perimeter seams  30  acts to seal the airbag  10 . 
     Referring to  FIGS. 7 and 10 , a first valve assembly  28  is disposed in an aperture  35  through the rear fabric member  24  and places the interior of the airbag  10  in fluid communication with an inflator  27 . The valve assembly  28  includes a reinforcing patch  36  that is applied to the inside of the rear fabric member  24 . In the space between the member  24  and the reinforcing patch  36 , a member  37  having a threaded hole  38  is positioned in line with the aperture  35 . The threaded hole  38  is adapted to receive a corresponding threaded snout  39  that is connected to the inflator  27 . A jam nut  41  secures the inflator snout to the fabric member  24 . The reinforcing patch  36  is secured to the fabric member  24  by means of closely packed stitches made by a strong thread such as a nylon thread. To secure the member  37  an adhesive may be applied to the surfaces that are in contact with the fabric member  24  and/or the reinforcing patch  36 . If two inflators are used, a second valve assembly  29 , identical to valve assembly  28 , may be disposed through the fabric member  24  at a location spaced from the first valve assembly for use with a second inflator. 
     Referring to  FIGS. 4–6 , the bumper airbag  10  is folded into an airbag container  60  with a door  62 . The container  60  is mounted behind the bumper  12  and the door  62  is preferably part of the bumper. Sensors  40 , 42 , which may be proximity sensors, are mounted on opposite sides of the vehicle and sense an imminent collision. Upon sensing a collision, the sensors  40 ,  42  send signals to a control unit  44 , (see  FIG. 12 ), which in turn signals the inflator  27  to ignite. Gas from the inflator passes through the valve assembly  28  and into the inner or main chamber  20  causing it to inflate and blow open door  62  about 10 milliseconds from when a firing signal is received at the inflator. The chamber  20 , when inflated, forms the central portion of the airbag  10  and extends a substantial distance beyond the surface of the bumper and the chambers  21 ,  22 , and  23  when inflated. The first chamber  20  makes contact with door and or window of the struck vehicle absorbing the energy of this contact. This impact causes an increase in pressure in the chamber  20 . Once the pressure reaches a predetermined threshold, the frangible seam  14  ruptures causing the first chamber  21  to inflate. As chamber  21  inflates the gas volume decreases causing a drop of the gas pressure within the airbag  10 . This process continues until all the remaining chambers  22  and  23  have been inflated or the collision as subsided. The pressures in the chambers  21 – 23  will be less than in the main chamber  20 . Thus, the hard main chamber  20  absorbs the energy of the airbag-to-vehicle contact and the softer chambers  21 – 23  absorb the energy of the airbag-to-occupant contact. In one prototype of airbag  10 , the main chamber  20  had a pressure in the range of 10–50 psig (i.e. hard) and the outermost chamber  23 , when inflated had a pressure from 5–10 psig. Importantly, by sizing the different chambers  20 – 23  and selecting the strength of the frangible seams  14 ,  16 ,  18  one can customize the energy attenuation characteristic of the airbag  10  for different collision scenarios including the timing of events in the collision. 
     Further control of the energy attenuation characteristic can be obtained by using one or more vents  32 ,  33 ,  34  as shown in FIGS.  1 , 7 , and  11 . In the preferred embodiment, each of the chambers  21 ,  22 ,  23  has eight vents; four vents through fabric member  24  and four through fabric member  26 . Each vent in fabric member  24  is aligned with a corresponding vent in fabric member  26 . By using these vents one can control the timing of the deflation of the chambers  21 , 22 , 23 . Further control can be accomplished by mounting valves, not shown, in the vents  32 – 34 . 
     The fabric members  24 , 26  are preferably formed of two layers of a woven polyester and/or nylon non-porous material bonded together. The material may be silicone coated on either or both sides to ensure that the bags are nonporous. In some applications the members  24 , 26  may be comprised of a single layer of this nylon material. The outside surfaces of the fabric members  24 , 26  are stalwart puncture and abrasion resistant. Puncture resistance prevents contact with the stricken vehicle from tearing the material and abrasion resistance protects the occupants of the struck vehicle from being injured by the inflated airbag  10 . 
     The inflator  27  is preferably a cold gas inflator. One reason for the cold gas inflator is that the inflation time of the gas in the airbag is longer than the typically hot gas inflator found in most airbags. Either cold gas or hot gas inflators may be used, but if more than one inflator is used, they both must be the same type. 
     Referring to  FIG. 12 , the control unit  44  includes a microprocessor  50  having both a memory section  48  and a deployment algorithm  46  stored therein. The algorithm  46  controls the processing of the sensed electrical signal generated from the sensor or sensors  40 ,  42 . The microprocessor  50  may also receive one or more signals from other sensors on the vehicle that relate to the vehicle&#39;s operating condition. If the algorithm indicates an imminent collision, the microprocessor  50  sends a firing signal to the inflator  27 . If a staged inflation system  54  is used, the firing signal is timed  56  and a second firing signal is generated and supplied to the two-stage inflator  58 . Some systems may want a controlled deflation time to deflate the inflated chambered airbag, in which case another timer  59  is activated from a signal indicating activation to cause one or more vents in the airbag  10  to open. 
     A method for fabricating the bumper airbag  10  comprises the steps of obtaining first and second fabric members  24 , 26  and positioning the two fabric members so their respective perimeters are aligned. Alternatively, the second fabric member  26  can be formed by folding the first fabric member  24  back on itself. A first frangible seam  14  is then sewn radially inward of the perimeters to bind the two fabric members and to define the main chamber  20 . A second frangible seam  16  is sewn radially outward of the first seam  14  to bind the fabric members  24 ,  26  together and to define a second chamber  21  concentric with the main chamber  20 . In a like manner, a third frangible seam  18  radially outward from the second frangible seam  16  is added to define a third chamber  22  concentric with the second chamber  21 . Finally, one or more non-frangible seams  30  are sewn adjacent the perimeters to define a fourth chamber  23  concentric with the third chamber  22  and for sealing the airbag  10 . The frangible seams  14 ,  16 ,  18  are formed from either a continuous length of frangible thread for both seams and wherein at the conclusion of the first complete seam, the thread crosses the second chamber to begin the second seam. If more chambers are being fabricated, the continuous seam will continue across potential new chamber and the seam will continue until the seam is continuous and closed. In the alternative, each seam  14 ,  16 ,  18  may be the length of the frangible thread that completely closes on itself as the chamber  20 – 22  is defined. If separate lengths of frangible threads are used to enclose each successive chamber, the lengths of each seam will increase. Finally, a valve assembly  28  is inserted through one of the fabric members and connected to the inflator  27 . 
     Various modifications and alterations to the above-described preferred embodiment will be apparent to those skilled in the art. Accordingly, this description of the invention should be considered exemplary and not as limiting the scope and spirit of the invention as set forth in the following claims.