Patent Publication Number: US-2004046373-A1

Title: Dual stage airbag inflator

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an airbag inflator and, more particularly, to a dual stage airbag inflator for use in an automobile for deploying the airbag of the automobile with an inflation gas.  
       [0003] 2. Description of Related Art  
       [0004] Regular motor vehicle airbags are commonly of one-stage inflation design, i.e., when the actuating signal produced, the exclusive igniter ignites all gas generant material to produce gas. The pressure-time curve obtained from this method has a particular mode that is not variable to fit different application requirements when deployed with the inflation gas, the airbag may cause damage to the driver or passengers having a poor sitting posture. In order to eliminate this problem, dual stage airbag inflators or the so-called “Intelligent airbag inflators” are developed.  
       [0005] U.S. Pat. No. 6,032,979 discloses a dual stage airbag inflator, which can supply airbag inflation gas in an adaptive output. The inflator includes two discrete isolated chambers of gas generant materials and permits to adjust the pressure curve of deploying by controlling the time of igniting of the igniters. However, because the exhaust holes of the second chamber is directly connected to the first chamber, the gas pressure or heat energy produced from the combustion of the gas generant material in the first chamber may enter into the second chamber to ignite the gas generant material in the second chamber accidentally. Therefore, it will be no meaning of using dual stage airbag inflator.  
       [0006] Therefore, it is desirable to provide a dual stage airbag inflator that eliminates the aforesaid drawbacks.  
       SUMMARY OF THE INVENTION  
       [0007] It is the main object of the present invention to provide a dual stage airbag inflator, which prevents interference between different inflation gases that are produced at different times, assuring the desired dual stage inflation effect respectively.  
       [0008] It is another object of the present invention to provide a dual stage airbag inflator, which reduces the dynamic energy of combustion particles of the generated inflation gases, improving the filtering performance of the gas filter.  
       [0009] To achieve these and other objects and according to one aspect of the present invention, the dual stage airbag inflator is comprised of a housing, a first igniter, and a second igniter. The housing comprises a plurality of exhaust holes arranged around the periphery thereof, a first chemical chamber mounted inside the housing and comprises a plurality of first gas outlets arranged around the periphery thereof and disposed in communication with an exhaust chamber formed outside the first chemical chamber by the remaining space of the housing and the exhaust chamber and disposed in communication with the exhaust holes, a first inflation gas generant material puts in the first chemical chamber, a second chemical chamber mounted inside the first chemical chamber and comprising at least one second gas outlet disposed in communication with the exhaust chamber, and a second inflation gas generant material puts in the second chemical chamber. A first igniter mounted in the first chemical chamber and adapted for igniting the first inflation gas generant material for producing a first inflation gas for enabling the first inflation gas to pass through the first gas outlets, the exhaust chamber and the exhaust holes to the outside of the housing. A second igniter mounted in the second chemical chamber and adapted for igniting the second inflation gas generant material for producing a second inflation gas for enabling the second inflation gas to pass through the at least one second gas outlet, the exhaust chamber and the exhaust holes to the outside of the housing.  
       [0010] Because the at least one second gas outlet is singly disposed in communication with the exhaust chamber and exhaust holes, therefore the first inflation gas could itself pass through the first gas outlets, the exhaust chamber and the exhaust holes to the outside of the housing directly. It could prevent interference between different inflation gases that are produced at different times and assure the desired dual stage inflation effect respectively.  
       [0011] According to another aspect of the present invention, each second gas outlet is respectively mounted with a normal-close one-way valve flap adapted for isolating the first inflation gas and for enabling only the second inflation gas can pass out of the second chemical chamber through the second gas outlet to the exhaust chamber, exhaust holes and the outside of the housing.  
       [0012] According to still another aspect of the present invention, the housing is comprised of an upper casing and a lower casing, and the exhaust holes are formed in the periphery of either of the upper casing and the lower casing. The upper casing and the lower casing can be fastened together by a screw joint. Alternatively the upper casing and the lower casing can be fastened together by welding, soldering, or any of a variety of conventional fastening means.  
       [0013] According to still another aspect of the present invention, the dual stage airbag inflator further comprises at least one annular flow guide, at least one gas filter and a gasket layer. The at least one annular flow guide mounted in the exhaust chamber to radially separate the exhaust chamber into two or more gas passages that are eccentrically arranged one inside the other and in communication with each other to reduce the dynamic energy of the combustion particles of generated inflation gases and to improve the filtering performance of the gas filter. The at least one gas filter mounted in the exhaust chamber and adapted for filtering solid matter such as combustion particles from the first inflation gas and the second inflation gas. The gasket layer mounted in the exhaust chamber adjacent to an inside wall thereof and adapted for masking the exhaust holes.  
       [0014] Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is an exploded view of a dual stage airbag inflator according to the present invention.  
     [0016]FIG. 2 is a sectional view of the present invention, showing the first stage gas deploying action of the dual stage airbag inflator.  
     [0017]FIG. 3 is a sectional view of the present invention, showing the second stage gas deploying action of the dual stage airbag inflator.  
     [0018]FIG. 4 is a pressure-time curve obtained from typical tests in a 60 liters discharge tank according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0019] With reference to FIGS. 1 and 2, a dual stage airbag inflator in accordance with the present invention is shown comprising a housing formed of an upper casing  1  and a lower casing  2 . The upper casing  1  and the lower casing  2  are fastened together by, for example, a screw joint. The upper casing  1  has a plurality of exhaust holes  11  around the periphery. When the upper casing  1  and the lower casing  2  fastened together, a receiving space  3  is defined within the upper casing  1  and the lower casing  2 . A first chemical chamber  31  is disposed inside the receiving space  3 . The remaining space outside the chemical chamber  31  within the receiving space  3  forms an exhaust chamber  32 , which is in communication with the exhaust holes  11  of the upper casing  1 . The top side of the first chemical chamber  31  is sealed with a top cover  310 . The first chemical chamber  31  has a plurality of first gas outlets  311  around the periphery in communication with the exhaust chamber  32 . A first inflation gas generant material  312  puts in the first chemical chamber  31 . A first igniter  21  is installed in the first chemical chamber  31  and adapted for igniting the enhanced material of the enhanced material chamber  35  to combuse the first inflation gas generant material  312  speedily. When ignited, the first inflation gas generant material  312  burns and produces a first inflation gas  313 , enabling the produced first inflation gas  313  to pass out of the first gas outlets  311  of the first chemical chamber  31 , the exhaust chamber  32  and the exhaust holes  11  into the airbag (not shown) to inflate the airbag instantly.  
     [0020] Referring to FIG. 3 and FIG. 1 again, a second chemical chamber  34  is mounted inside the first chemical chamber  31  and sealed with the top cover  310 . A second gas outlet  341  is disposed singly on the top cover  310  and in communication with the second chemical chamber  34 . Four spacers  314  are protruded from the top sidewall of the top cover  310  to contact with the inside wall of the upper casing  1  to define a gas passage  315  in communication between the second gas outlet  341  and the exhaust chamber  32 . A normal-close one-way valve flap  344  is installed in the second gas outlet  341 . A second inflation gas generant material  342  puts in the second chemical chamber  34 . A second igniter  22  is installed in the second chemical chamber  34  and adapted for igniting the second inflation gas generant material  342 . When ignited, the second inflation gas generant material  342  burns and produces a second inflation gas  343 , and the normal-close one-way valve flap  344  is opened from the second gas outlet  341  by gas pressure, enabling the produced second inflation gas  343  to pass out of the second chemical chamber  34  through the second gas outlet  341  to the gas passage  315 , the exhaust chamber  32 , and the exhaust holes  11  to the outside of the housing.  
     [0021] In actual practice, the first igniter  21  is ignited at the first stage to burn the first inflation gas generant material  312  in the first chemical chamber  31 , enabling the produced first inflation gas  313  itself to pass through the first gas outlets  311  and the exhaust chamber  32  to the outside of the housing via the exhaust holes  11 . Because the second gas outlet  341  is in communication with the exhaust chamber  32  and the exhaust holes  11  independently, the first inflation gas  313  does not pass through the second gas outlet  341  to auto-ignite the second inflation gas generant material  342  in the second chemical chamber  34  accidentally. Furthermore, because the normal-close one-way valve flap  344  normally closes the second gas outlet  341 , it prevents the first inflation gas  313  from auto-igniting the second inflation gas generant material  342  accidentally.  
     [0022] A predetermined time delay (for example, 20 ms) after ignition of the first inflation gas generant material  312  enters into the second stage, i.e., the second igniter  22  is started to ignite the second inflation gas generant material  342  in the second chemical chamber  34 , thereby causing the second inflation gas generant material  342  to burn and to produce a second inflation gas  343 , enabling the produced second inflation gas  343  to pass out of the second chemical chamber  34  through the valve flap  344  of the second gas outlet  341  to the gas passage  315 , the exhaust chamber  32 , and the exhaust holes  11  to the outside of the housing. The second inflation gas  343  will be mixed with the first inflation gas  313  in the exhaust chamber  32  in this stage.  
     [0023]FIG. 4 is a pressure-time curve obtained from typical tests in a 60 liters discharge tank. Curve A is a gas pressure curve obtained from the test where only the first inflation gas generant material is ignited in the first chemical chamber. Curve B is a gas pressure curve obtained from the test where the first inflation gas generant material and the second inflation gas generant material are respectively ignited in the first chemical chamber and the second chemical chamber at the same time (the time delay is zero). Curve C is a gas pressure curve obtained from the test where the first inflation gas generant material and the second inflation gas generant material are respectively ignited in the first chemical chamber and the second chemical chamber at different times (for example, the second inflation gas generant material is ignited at 20 ms after the ignition of the first inflation gas generant material). By controlling the delay time of dual stage of igniting the gas generant materials in different chemical chambers flexibly, it could protect the driver or passengers having a poor sitting posture and assure the desired dual stage inflation effect.  
     [0024] Referring to FIG. 3, an annular flow guide  12  is mounted in the exhaust chamber  32  to radially separate the exhaust chamber into two gas passages  121  that are eccentrically arranged one inside the other and in communication with each other. The gas passages  121  form a maze of flow path. When the first inflation gas  313  and the second inflation gas  343  produced, the flow guide  12  guides the flow of gas to go by a detour, thereby causing the dynamic energy of combustion particles of the gases  313 , 343  to be reduced. A gas filter  4  is mounted in the exhaust chamber  32 , and adapted for filtering solid matter such as combustion particles from the first inflation gas  313  and the second inflation gas  343 . Reducing the dynamic energy of combustion particles of the gases passing through the gas filter  4  relatively increase the filtering performance of the gas filter  4 . There is also provided an annular gasket layer  13  mounted in the exhaust chamber  32  adjacent the housing&#39;s inside wall  33  and adapted for making the exhaust holes  11  to isolate outside moisture from passing to the chemical chambers  31 , 34 .  
     [0025] According to this embodiment, the annular gasket layer  13  is made of aluminum foil. Other equivalent sealing material may be used for making the annular gasket layer  13  to isolate outside moisture from passing to the chemical chambers  31 , 34 .  
     [0026] The aforesaid members may be welded or soldered together, or sealed with On-rings or other sealing materials. The mechanical mounting and airtight sealing arrangement can easily be achieved by conventional techniques.  
     [0027] Although the present invention has been explained in relation to its preferred embodiments, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.