Abstract:
A hybrid inflator includes a gas storage chamber filled with a pressurized gas, a chemical chamber filled with a gas generating chemical, and an initiator attached to the chemical chamber for igniting the chemical to generate a reaction gas. A gas outlet is formed to eject the pressurized gas and the reaction gas from the gas storage chamber, and a sealing plate is disposed in the gas storage chamber for separating the gas outlet from the gas storage chamber. A swirl forming device is disposed between the gas storage chamber and the chemical chamber for swirling the reaction gas from the chemical chamber and guiding the reaction gas into the gas storage chamber.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]     The present invention relates to an inflator, and in particular, to a hybrid inflator constructed to release a gas generated from a gas-generating chemical and a pressurized gas stored in a gas storage chamber. In addition, the present invention relates to an airbag apparatus provided with the inflator.  
         [0002]     A hybrid inflator includes a gas-generating chemical ignited by an initiator and a pressurized gas storage chamber charged with a pressurized gas. When the chemical starts to react by the initiator, a reaction gas flows into the gas storage chamber. Then, the gas ruptures a sealing member separating the gas storage chamber and a gas outlet, and a mixed gas of a gas stored in the gas storage chamber (storage gas) and the reaction gas is released from the gas outlet.  
         [0003]     Japanese Patent Publication (Kokai) No. 2003-226219 discloses an inflator that releases a reaction gas from a hole of a perforated cap and collides the reaction gas against an inner wall of a cylindrical gas storage chamber at one end thereof to stick combustion residues in the reaction gas to a chamber wall. A gas outlet is provided at the other end of the gas storage chamber.  
         [0004]     Patent Document: Japanese Patent Publication (Kokai) No. 2003-226219  
         [0005]     In the inflator disclosed in Japanese Patent Publication (Kokai) No. 2003-226219, the reaction gas generated by the reaction chemicals is not sufficiently mixed with the storage gas in the gas storage chamber. Specifically, when the chemicals start to react and the reaction gas flows into the gas storage chamber, the reaction gas tends to form a bulk portion at one end of the gas storage chamber. Accordingly, the storage gas is pushed and released by the bulk gas, and then the reaction gas is released. When the reaction gas is not sufficiently mixed with the storage gas, a temperature of the released gas becomes high when a gas containing the reaction gas is released. Therefore, an airbag is required to have heat-resistant to maintain strength enough to endure the high temperature gas upon contacting the high temperature gas.  
         [0006]     Japanese Patent Publication (Kokai) No. 2003-226219 also discloses a configuration having no perforated cap. In this case, the gas released from the initiator flows straight into the gas storage chamber and reaches the gas outlet. Thus, the storage gas is not sufficiently mixed with the reaction gas, and the temperature of the released gas becomes high.  
         [0007]     In view of the problems described above, an object of the present invention is to provide an inflator constructed to release a reaction gas generated by chemical after the reaction gas is sufficiently mixed with gas in a storage chamber.  
         [0008]     Further objects ad advantages of the invention will be apparent from the following description of the invention.  
       SUMMARY OF THE INVENTION  
       [0009]     In order to attain the objects described above, according to the present invention, an inflator is a hybrid inflator comprising a gas storage chamber filled with pressurized gas; a chemical chamber filled with a gas-generating chemical; an initiator for igniting the chemical; a gas outlet; and a sealing plate for separating the gas outlet from the gas storage chamber. The chemical reacts to generate gas by the initiator, and the gas flows into the gas storage chamber and ruptures the sealing plate. Accordingly, the gas in the pressurized gas storage chamber and the gas generated from the chemicals are released from the gas outlet. The inflator further comprises a swirl forming device for swirling the gas generated from the chemical and flowing into the gas storage chamber.  
         [0010]     According to the present invention, it is preferable that the swirl forming device is a guide member for guiding the gas to swirl.  
         [0011]     According to the present invention, an airbag apparatus includes the inflator described above and an airbag expanded by the gas from the inflator.  
         [0012]     In the present invention, the gas generated from the reaction of the chemical swirls and flows into the gas storage chamber. Thus, the reaction gas and the storage gas are sufficiently mixed with each other. Therefore, the temperature of the released gas becomes constant. As a result, heat resistance required for the airbag can be decreased.  
         [0013]     The gas guide member with a simple configuration is suitable for the swirl forming device for swirling the gas. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0014]     FIGS.  1 ( a ) to  1 ( e ) are views showing an inflator according to an embodiment of the present invention, wherein  FIG. 1 ( a ) is a longitudinal sectional view,  FIG. 1 ( b ) is an enlarged cross-sectional view of a gas guide member taken along line  1 ( b )- 1 ( b ) in  FIG. 1 ( c ),  FIG. 1 ( c ) is a right side view of the gas guide member viewed from line  1 ( c )- 1 ( c ) in  FIG. 1 ( b ),  FIG. 1 ( d ) is a cross-sectional view taken along line  1 ( d )- 1 ( d ) in  FIG. 1 ( c ), and  FIG. 1 ( e ) is a cross-sectional view taken along line  1 ( e )- 1 ( e ) in  FIG. 1 ( c );  
         [0015]     FIGS.  2 ( a ) to  2 ( c ) are views showing a guide member in an inflator according to another embodiment of the present invention, wherein  FIG. 2 ( a ) is a cross-sectional view of the gas guide member taken along line  2 ( a )- 2 ( a ) in  FIG. 2 ( b ),  FIG. 2 ( b ) is a side view of the gas guide member viewed from line  2 ( b )- 2 ( b ) in  FIG. 2 ( a ), and  FIG. 2 ( c ) is a perspective view of the guide member;  
         [0016]     FIGS.  3 ( a ) and  3 ( b ) are views showing a guide member in an inflator according to a further embodiment of the present invention, wherein  FIG. 3 ( a ) is a front view of the guide member viewed from line  3 ( a )- 3 ( a ) in  FIG. 3 ( b ), and  FIG. 3 ( b ) is a cross-sectional view thereof taken along line  3 ( b )- 3 ( b ) in  FIG. 3 ( a ); and  
         [0017]     FIGS.  4 ( a ) and  4 ( b ) are views showing a guide member in an inflator according to a still further embodiment of the present invention, wherein  FIG. 4 ( a ) is a perspective view of the guide member, and  FIG. 4 ( b ) is a perspective view of semi-elliptic plates. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.  FIG. 1 ( a ) is a longitudinal sectional view thereof;  FIG. 1 ( b ) is an enlarged cross-sectional view of a gas guide member taken along line  1 ( b )- 1 ( b ) in  FIG. 1 ( c );  FIG. 1 ( c ) is a right side view of the gas guide member viewed from line.  1 ( c )- 1 ( c ) in  FIG. 1 ( b );  FIG. 1 ( d ) is a cross-sectional view taken along line  1 ( d )- 1 ( d ) in  FIG. 1 ( c ); and  FIG. 1 ( e ) is a cross-sectional view taken along line  1 ( e )- 1 ( e ) in  FIG. 1 ( c ). FIGS.  2 ( a )- 2 ( c ) to  4 ( a )- 4 ( b ) show configurations of a guide member in an inflator according to embodiments, respectively.  
         [0019]     As shown in  FIG. 1 ( a ), an inflator  1  comprises a substantially cylindrical pressure-proof vessel  2  (vessel); a head block  3  fixed at one end of the vessel  2 ; gas-generating chemicals  4  charged in the head block  3 , an initiator  5  for igniting the chemicals  4 ; a first sealing plate  6  separating the interior of the head block  3  from one end of a gas storage chamber  8 ; a guide member  7  as a swirl forming device; and a second sealing plate  9  separating the other end of the gas storage chamber  8  from a gas outlet  10 .  
         [0020]     The vessel  2  is made of steel and the like, and the gas storage chamber  8  is charged with a gas, for example, nitrogen, argon, or helium at a pressure of 10,000 to 70,000 kPa. The head block  3  made of steel and the like is fixed to one end of the vessel  2  by welding. The head block  3  has a thick cylindrical shape, and an inner hole  3   a  as a chemical chamber is charged with the chemicals  4 . A portion of the inner hole  3   a  at the vessel  2  side is sealed by the first sealing plate  6 .  
         [0021]     The first sealing plate  6  is made of, for example, a stainless sheet, and is fixed to the end surface of the head block  3  at the vessel  2  side by welding. The first sealing plate  6  is provided with a substantially hemispheric bulging portion entering the inner hole  3   a  to endure the pressure of gas from the gas storage chamber  8 . The bulging portion may be provided with a rupture-promoting groove.  
         [0022]     The initiator  5  is disposed to face a portion of the inner hole  3   a  opposite to the vessel  2 . The initiator  5  includes igniting chemicals and an ignition device such as a resistance heating element for igniting the igniting chemicals. In the initiator  5 , when power is applied to the ignition device, the igniting chemicals react to generate a high-temperature gas. The initiator  5  is held in an end sleeve  3   b  of the head block  3  by an initiator holder  11 .  
         [0023]     The other end of the vessel  2  is provided with a guide hole  12 , and the gas outlet  10  is disposed at the end of the guide hole  12 . The second sealing plate  9  is provided so as to seal the inflow end of the guide hole  12 . A hemispheric bulging portion provided at the second sealing plate  9  enters the guide hole  12 . The sealing plate  9  is fixed to the circumferential edge of the inflow end of the guide hole  12 . The gas storage chamber  8  is formed between the sealing plates  6  and  9 . A filter (not shown) may be provided in the guide hole  12  to collect combustion residues of the chemicals  4 .  
         [0024]     Next, a configuration of the guide member  7  will be described with reference to FIGS.  1 ( b ) to  1 ( e ). The guide member  7  is substantially disc-shaped, and a circular recessed part  7   a  is formed in a surface of the guide member  7  facing the first sealing plate  6 . Two nozzles  14  and  15  are provided for communicating a bottom surface  7   b  of the recessed part  7   a  with a rear surface  7   c  of the guide member  7 . The respective nozzles  14  and  15  extend linearly, and their axes have a twisted relationship to each other.  
         [0025]     The nozzle  14  is located at one half with respect to a plane (a plane taken along C-C line in  FIG. 1 ( c )) passing through both the nozzles  14  and  15  and including the axis of the disc-shaped guide member  7 . The nozzle  15  is located at the other half with respect to the plane. With the nozzles  14  and  15  thus arranged, the gas passing through the nozzles  14  and  15  forms a swirl like an arrow G in  FIG. 1 ( a ).  
         [0026]     An operation of the inflator constructed as described above is as follows. When the initiator  5  is supplied with power, the initiator  5  generates a high-temperature gas, and then a large amount of reaction gas is generated by the chemicals  4  contacting the high-temperature gas. The pressure of the high-temperature gas ruptures the first sealing plate  6 , and the reaction gas passes through the nozzles  14  and  15  of the guide member  7  and flows into the gas storage chamber  8  while forming a swirl G. As the gas pressure of the gas storage chamber  8  increases, the second sealing plate  9  is ruptured, and the gas is released from the guide hole  12  via the gas outlet  10 . Then, the gas rapidly expands an airbag.  
         [0027]     In the inflator  1 , the reaction gas of the chemicals  4  forms a swirl G. Accordingly, the reaction gas is sufficiently mixed with the storage gas and released from the gas outlet  10 . Therefore, the temperature of the releasing-gas is almost constant. That is, the hot reaction gas is not localized and released from the gas outlet  10 . Therefore, the airbag expanded by the inflator  1  does not, need to have high heat resistance.  
         [0028]     Other examples of guide members that can be used in the inflator of the present invention will be described with reference to FIGS.  2 ( a )- 2 ( c ) to  4 ( a )- 4  ( b ). A guide member  20  shown in FIGS.  2 ( a )- 2 ( c ) is substantially disc-shaped, and a spiral nozzle  23  is provided to communicate one face  21  of the guide member  20  with the other face  22  thereof. The gas passes through the spiral nozzle  23  disposed in the vessel, thereby forming a swirl G as shown in  FIG. 2 ( c ).  FIG. 2 ( a ) is a cross-sectional view of the guide member  20  taken along an axis thereof and line  2 ( a )- 2 ( a ) in  FIG. 2 ( b ).  FIG. 2 ( b ) is a view seen from line  2 ( b )- 2 ( b ) in  FIG. 2 ( a ), and  FIG. 2 ( c ) is a perspective view of the guide member  20 .  
         [0029]     As shown in FIGS.  3 ( a ) and  3 ( b ), a guide member 30 includes a lot of nozzles  33  (nine nozzles in the figure). Each nozzle  33  communicates a face  31  of the substantially disc-shaped guide member  30  with a face  32  thereof. Every nozzle  33  is inclined in the same direction around the axis of the guide member  30 . The gas passes through the nozzles  33  of the guide member  30  disposed in the vessel  2 , thereby forming a swirl.  FIG. 3 ( a ) is a front view of the guide member  30  viewed from line  3 ( a )- 3 ( a ) in  FIG. 3 ( b ), and  FIG. 3 ( b ) is a cross-sectional view thereof taken along line  3 ( b )- 3 ( b ) in  FIG. 3 ( a ). In order to make the configuration clear, the hatching of the cross-section is omitted in  FIG. 3 ( b ).  
         [0030]     As shown in  FIG. 4 , a guide member  40  includes two pieces of semi-elliptic plates  42  and  43  in a cylindrical casing  41 . The circumferential edges of the semi-elliptic plates  42  and  43  touch the inner circumferential face of the casing  41  and are fixed thereto by welding. Chords  42   a  and  43   a  of the semi-elliptic plates  42  and  43  are connected to each other at their longitudinal intermediate portions. The plate faces of the semi-elliptic plates  42  and  43  intersect each other. The gas passes through the guide member  40  disposed in the vessel  2 , thereby forming a swirl G as shown in  FIG. 4 ( a ).  FIG. 4 ( a ) is a perspective view of the guide member  40 , and  FIG. 4 ( b ) is a perspective view of the semi-elliptic plates  42  and  43 .  
         [0031]     The embodiments described above are just examples of the present invention, and the present invention can be modified from those illustrated in the drawings. For example, the guide member  7  is disposed in the vessel  2  in the embodiment, and a guide bane for forming a swirl may be provided at the inner circumferential edge of the vessel  2 .  
         [0032]     The inflator of the present invention can be applied to various kinds of airbag apparatus such as those for a front passenger, a head-protection, a knee-protection, a driver, and a rear passenger.  
         [0033]     The disclosure of Japanese Patent Application No. 2004-183877, filed on Jun. 22, 2004, is incorporated in the application.  
         [0034]     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.