Abstract:
An inflator assembly for an airbag includes a container with a plurality of exhaust ports positioned about a perimeter. A rupturable, non-combustible material covers the perimeter of the container to cover the exhaust ports. A plurality of perforated and rupturable walls define a plurality of chambers concentrically disposed within the container. Within each of the plurality of chambers is a detonator to trigger a gas-producing chemical to inflate an airbag cushion. The detonators disposed in each of the individual chambers can be detonated separately from other detonators in other chambers.

Description:
This application is a 371 of PCT/IO01/01723 Sep. 19, 2001 which claims benefit of provisional 60/233,743 Sep. 19, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an airbag assembly for a motor vehicle and specifically to an airbag inflator assembly with multiple chambers and detonators. Typically, an airbag assembly includes an airbag cushion and an inflator assembly. Conventional inflator assemblies include a detonator to trigger a gas-producing chemical. Triggering the gas-producing chemical produces a large quantity of rapidly expanding gas that inflates the airbag cushion. The inflator is typically triggered electrically by way of an electronic control module positioned within a motor vehicle. The rapidly expanding gas that inflates the airbag cushion exerts a large force in a relatively short duration of time. This large force is a product of the speed in which an airbag must fully inflate in order to provide impact prevention to occupants of the vehicle during a collision. 
     The force of inflation is set at a level such that an occupant of normal size and weight will not be injured. The force of inflation of an airbag cushion required varies depending on the specific size and weight of the occupant. Injury to smaller occupants, such as children is a design consideration taken into account when determining the magnitude of airbag inflation. As appreciated, the large forces exerted by an inflating airbag can cause injury to the occupants they are designed to protect. 
     For this reason, warnings and devices are currently in uses that simply turn the air bag off upon the sensing of specific conditions. In some instances a simply switch is installed to turn off the airbag. Other devices sense the size or weight of the occupant and activate the airbag only under a predefined set of conditions. It is well proven that airbag cushions provide an additional level of safety to an occupant during a collision. Devices that disable the airbag remove this level of safety to the detriment of smaller occupants. 
     For this reason, it is desirable to develop an airbag assembly that can inflate at various force levels such that the safety benefits of an airbag cushion can be used for occupants of all sizes. 
     SUMMARY OF THE INVENTION 
     An embodiment disclosed in this application is an airbag inflator assembly including multiple chambers each containing separate individually triggerable detonators to control inflation of an airbag cushion. 
     The inflator assembly includes a container with a plurality of exhaust ports disposed about a perimeter and covered by a rupturable, non-combustible material. The container is cylindrically shaped and includes a plurality of chambers disposed about a common axis. Each chamber is defined and separated from the other chambers by a wall. Surrounding each chamber are modular walls that comprise a structural layer having a plurality of perforations and a non-combustible layer covering the perforations to contain a gas-producing chemical. Each of the chambers includes a detonator for triggering the gas-producing chemical. Each detonator can be triggered separate from any of the others such that the amount of gas discharged to inflate the airbag cushion can be varied and controlled. All detonators can be triggered at once, individually, sequentially or in any other predetermined manner to initiate gas production from specific chambers. 
     The disclosed airbag inflator assembly includes multiple chambers, each including an individually triggerable detonator that provides control over the inflation of the airbag cushion to vary the magnitude of force exerted by the airbag cushion during inflation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a cross-sectional view of the air bag inflator; 
         FIG. 2  is a cross-sectional view of one chamber of the airbag inflator; and 
         FIG. 2A  is an enlarged view of construction of a modular wall. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an inflator assembly for an airbag system is generally indicated at  10  in FIG.  1 . The inflator assembly  10  includes a cylindrical container  12  extending between first and second axial ends  14 , 16 . First and second end caps  18  disposed at each of the axial ends  14 , 16  seal the cylindrical container  12 . The container includes inflator chambers  30 , 32 , and  34  disposed along the axis  42  and defined by divider walls  33 . The divider walls  33  are not rupturable and isolate the inflator chambers  30 , 32  and  34  from each other. 
     Referring to  FIG. 2 , a cross-section of one chamber is shown and includes a plurality of exhaust ports  20  disposed within an outer wall  22 . The exhaust ports are disposed about a perimeter  24  of the cylinder  12  to allow flow of inflating gas emanating from the multiple chambers  30 , 32  and  34 . The total area of all exhaust ports  20  comprises at least a minimum flow area for proper gas exhaustion. Further, the number of exhaust ports  20  disposed about the perimeter  24  of the container  12  is of sufficient number to properly vent gas. A worker knowledgeable in the art would understand that the size and number of exhaust ports  20  are dependent on the specific application. 
     Referring to  FIG. 2A , a cross-sectional view of a modular wall structure  54  is shown. The outer wall  22  along with other walls described hereafter within the inflator assembly  10  are constructed with according to the modular wall structure indicated at  54 . The modular wall structure indicated at  54  includes a a rupturable, non-combustible material  46  supported by a structural layer  44 . The structural layer  44  includes the exhaust ports  20 . The structure of the modular wall indicated at  54  is used for various walls of this inventive inflator assembly  10 . The rupturable, non-combustible material  46  contains a gas-producing chemical within the container  12  until activation. During activation of the gas-producing chemical, the rupturable, non-combustible material  46  blows out to allow gas to flow from the container  12  outwardly to inflate an airbag cushion (not shown). 
     Referring back to  FIG. 1 , within the container  12  the divider-walls  33  defining the chambers  30 , 32 , and  34 . Each of the chambers  30 , 32 , and  34  contains a quantity of gas producing chemical  36  and a detonator  28 . 
     The detonator  28  in each chamber  30 , 32 , and  34  is preferably triggered by an electric signal initiated from the motor vehicle. Because each chamber  30 , 32 , and  34  includes a detonator  28 , each chamber  30 , 32 , and  34  can detonate independent of any of the other chambers  30 , 32 , and  34 . In this manner, inflation of the airbag cushion (not shown) can be initiated by triggering the chambers  30 , 32 , and  34  simultaneously, sequentially or individually to control inflation of the airbag cushion. 
     Referring to  FIG. 2A , the modular wall structure  54  comprises the structural layer  44  supporting the rupturable non-combustible layer  46 . The rupturable, non-combustible layer  46  is substantially heat resistance to withstand any heat generated from triggering of the gas-producing chemical. 
     Referring again to  FIG. 2 , each chamber includes a centrally located detonation chamber  26 . A detonator  28  is disposed within each of the detonation chambers  26 . A detonation chamber wall  40  defines the detonation chamber  26  and is a modularly constructed wall including the structural layer  44  and the rupturable layer  46  described and best shown in FIG.  2 A. Disposed about the detonation chamber  26  is a chemical chamber  38  filled with the gas producing chemical  26 . Disposed about the chemical chamber  38  is a layer of coarse wire gauze  50 . The wire gauze layer  50  is disposed on an inner surface of gas chamber wall  48 . The gas chamber wall  48  defines the chemical chamber  38  and is of modular construction including the structural layer  44  and rupturable layer  46 . The specific configuration of the wire gauze layer  50  is known by those knowledgeable in the art. 
     To the outside of the gas chamber wall  48  is a concentric space  52  that does not contain gas producing chemical  36 . Disposed about the concentric space is an intermediate wall  64  constructed according to the modular constructed wall. The intermediate wall  64  includes the structural layer  44  and the non-combustible material  46 . To the outside of the intermediate wall  64  is a layer of insulation  56 . The intermediate wall  64  is covered with a layer of course wire gauze  58 . A fine wire gauze  60  covers the course wire gauze  58 . And the outer wall  22  is disposed about the fine wire gauze  60 . A substantially square shaped bracket  60  surrounds the container  12  to facilitate mounting of the inflator  10  within an airbag assembly. 
     In operation, the inflator assembly  10  responds to a controller (not shown) that is in communication with each of the detonators  28 . Upon detection of a condition requiring air bag inflation, the controller signals for the detonation of at least one of the detonators  28 . Because each of the detonators  28  are isolated within separate chambers  30 ,  32 , and  34 , activation of one detonator  28  does not cause detonation of the other detonators. Each chamber  30 ,  32 , and  34  may be actuated separately, sequentially or concurrently. The flexibility of separate detonator  28  actuation provides for the control of air bag inflation force by actuating only the specific amount of gas producing chemical desired according to a specific application of condition. 
     The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. 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 are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.