Abstract:
An inflator includes a bottle for storing a high pressure gas having an opening, a sealing plate attached to the bottle for sealing the opening, a housing having a curved air passage therein and being arranged such that an end faces the sealing plate, an initiator for generating an air blast disposed to communicate with the air passage, and a piston provided inside the housing to communicate with the curved air passage. Upon actuation of the initiator, the piston is urged toward the sealing plate by the air blast to rupture the same to allow the high pressure gas to linearly eject from the bottle.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
         [0001]    The present invention relates to an inflator that generates a gas for inflating an air bag of a vehicle. More specifically, the present invention relates to an inflator having an advantage in that the gas can be ejected and supplied linearly in the axial direction of a bottle.  
           [0002]    Inflators are gas generators that generate a gas for inflating air bags of vehicles. Inflators can be broadly divided into two groups: an inflator that ejects a high pressure gas contained in a container and supply it to an air bag (hybrid type and stored gas type), and an inflator that burns a gas generating agent (propellant) and generates a gas by utilizing a chemical reaction (combustion type).  
           [0003]    An example of a stored gas type inflator is shown in FIG. 6. FIG. 6 is a sectional view schematically showing an inflator disclosed in Japanese Patent Application Publication No. 10-250525 as an example of a conventional stored gas type inflator.  
           [0004]    With reference to the figure, an inflator  100  contains a bottle  101  that is filled with a high pressure gas. One end (the right end in the figure)  102  of the bottle  101  is closed and the other end (the left end in the figure)  103  of the bottle  101  is open. A sleeve  109  is connected to the open end  103  of the bottle  101  via an annular ring  106 . An inner end of the ring  106 , which forms an inside hole  106   a,  protrudes from the interior surface of the bottle  101  and the sleeve  109 .  
           [0005]    A burst disk  107  is attached to the ring  106  at the left side (the side facing the sleeve  109 ) thereof by welding, etc. The burst disk  107  is constructed of a steel plate having a thickness of approximately 0.3 mm. The burst disk  107  receives the filling pressure of the gas contained in the bottle  101  and swells toward the sleeve  109 . In a normal state in which the inflator  100  is not activated, the bottle  101  is sealed by the burst disk  107 .  
           [0006]    A plurality of gas outlets  104 , through which the high pressure gas is expelled when the inflator  100  is activated, is formed in the exterior surface of the sleeve  109 . A housing  110  is attached to the sleeve  109  at the end (the left end in the figure) thereof. The housing  110  includes an initiator fixing member  110   a,  which is fit in the sleeve  109  at the end thereof, and a cylindrical portion  110   b  that protrudes from the initiator fixing member  110   a.  An initiator  112  is fixed inside the initiator fixing member  110   a  of the housing  110 . A tip portion (at the right end)  112   a  of the initiator  112  is inserted beyond the initiator fixing member  110   a  into the cylindrical portion  110   b.  A terminal (at the left end)  112   b  of the initiator  112  is connected to a control unit via electric wires (not shown).  
           [0007]    A piston  115  with a sharply pointed tip  115   a  is disposed inside the cylindrical portion  110   b  of the housing  110 . A hole  115   b  is formed in the piston  115  at the rear end thereof, and the tip portion  112   a  of the initiator  112  is disposed in the hole  115   b.  A tip  110   c  of the cylindrical portion  110   b  of the housing  110  is separated from the burst disk  107  by a predetermined distance as shown in the figure.  
           [0008]    An air bag (not shown) is attached to the inflator  100  in such a manner that the air bag is communicated via the gas outlets  104 . In a normal situation, the gas contained in the bottle  101  is sealed by the burst disk (sealing plate)  107 . When a vehicle collides, a sensor (not shown) is activated and the initiator  112  generates an air blast, so that the piston  115  is pushed to the right in the figure. The tip  115   a  of the piston  115  breaks the burst disk  107  at the midsection thereof, so that the entire body of the burst disk  107  is ruptured and opened widely. Then, the high pressure gas contained in the bottle  101  flows into the sleeve  109 . The gas is ejected through the gas outlets  104  formed in the exterior surface of the sleeve  109  and supplied to the air bag.  
           [0009]    In the above-described conventional inflator  100 , the initiator  112 , the piston  115 , and the burst disk  107  are arranged such that the centers thereof are linearly arranged, and the piston  115  which is pushed by the air blast generated by the initiator  112  moves straight ahead and breaks the burst disk  107 . However, in the above-described construction, the direction in which the gas flows into the sleeve  109  through the open end  103  of the bottle  101  (the horizontal direction in the figure) is approximately perpendicular to the direction in which the gas is ejected through the gas outlets  104  of the sleeve  109  into the air bag (the vertical direction in the figure). Accordingly, there is a problem in that the gas can not flow linearly and smoothly, and an additional component is necessary for changing the flowing direction of the gas.  
           [0010]    In order to solve this problem, in Japanese Patent Application Publication No. 9-58394, a gas generator in which a gas can be ejected in the axial direction of a bottle from the closed end (the end opposite to the end closer to an initiator) toward the other is disclosed. However, in the gas generator of the above-described publication, there is a problem in that the size and the manufacturing cost thereof are increased since an additional large housing which contains the entire apparatus including the bottle is necessary.  
           [0011]    In view of the above-described situation, an object of the present invention is to provide an inflator wherein a gas can be ejected and supplied linearly in the axial direction of a bottle without increasing the size and the manufacturing cost thereof.  
         SUMMARY OF THE INVENTION  
         [0012]    To solve the problems described above, according to one aspect of the present invention, an inflator comprises a bottle with an opening and filled with a high pressure gas; a sealing plate which seals the opening of the bottle; an initiator which generates an air blast for providing driving force to break the sealing plate; a piston which is accelerated by the air blast generated by the initiator, and breaks the sealing plate; and a curved passage which guides the air blast generated by the initiator to the piston.  
           [0013]    According to the present invention, the air blast generated by the initiator moves non-linearly through the curved passage, and then pushes and accelerates the piston. Then, the accelerated piston breaks the sealing plate, and the high pressure gas contained in the bottle is ejected. Since it is not necessary to dispose the initiator in the axial direction of the bottle, design flexibility can be increased. For example, the high pressure gas can be ejected and supplied linearly in the axial direction of the bottle.  
           [0014]    According to another aspect of the present invention, an inflator comprises a bottle with an opening and filled with a high pressure gas; a sealing plate which seals the opening of the bottle; an initiator which generates an air blast for providing a driving force to break the sealing plate; and a piston which is accelerated by the air blast generated by the initiator and breaks the sealing plate. The bottle is a cylindrical shape, and the initiator is disposed in front of the opening of the bottle. A cylindrical diffuser provided with a gas outlet is connected to the bottle in the extending direction thereof. In addition, the initiator is attached to the circumferential surface of the diffuser and the gas outlet is formed in the diffuser at the end opposite to the end closer to the bottle.  
           [0015]    According to the present invention, the initiator is disposed in front of the opening of the bottle and is attached to the circumferential surface of the diffuser. Thus, the initiator is not disposed in the direction in which the high pressure gas is ejected. Accordingly, the high pressure gas can be ejected and supplied linearly in the axial direction of the bottle. The high pressure gas which comes out from inside the bottle flows linearly through the diffuser and is ejected through the gas outlet formed in the diffuser at the end opposite to the end closer to the bottle.  
           [0016]    An inflator of the present invention may further comprise a barrel having an inside hole which guides the piston, and the end surface of the barrel which is closer to the bottle may contact the sealing plate.  
           [0017]    In such a case, the barrel supports a considerable percentage of the filling pressure of the gas contained in the bottle. Thus, even a relatively thin sealing plate can sustain a high pressure. After the sealing plate breaks, the gas flows through the space between the interior surface of the diffuser and the exterior surface of the barrel, and is then ejected through the gas outlet. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a sectional view of an inflator according to an embodiment of the present invention in a state before the inflator is activated;  
         [0019]    [0019]FIG. 2 is a sectional view of the inflator in a state immediately after the inflator is activated;  
         [0020]    [0020]FIG. 3 is a sectional view of the inflator in a state in which the sealing plate breaks;  
         [0021]    [0021]FIG. 4 is an exploded sectional view of the inflator;  
         [0022]    FIGS.  5 (A)- 5 (F) are schematic drawings showing modifications of a piston and a barrel of the inflator according to the present invention, wherein FIGS.  5 (A) and  5 (B) are perspective views showing modifications of the piston, FIGS.  5 (C) and  5 (D) are perspective views showing modifications of the barrel, FIG. 5(E) is a sectional view of the barrel of FIG. 5(D) with the piston before activation, and FIG. 5(F) is a sectional view similar to FIG. 5(E) after activation; and  
         [0023]    [0023]FIG. 6 is a sectional side view schematically showing an inflator disclosed in Japanese Patent Application Publication No. 10-250525 as an example of a conventional stored. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]    The present invention will be further explained with reference to the accompanied drawings.  
         [0025]    In these drawings, an inflator  1  includes a cylindrical steel bottle  3 . The bottle  3  has a hemispherical right end portion  4  and an opening  5  at the left end thereof. A hole  4   a  is formed in the end portion  4  of the bottle  3 , and a gas, such as an inert gas, is injected into an interior  3 C of the bottle  3  through the hole  4   a  at a high pressure. After the interior  3 C of the bottle is filled with the gas, the hole  4   a  is blocked by a steel ball  4   b  to seal the gas.  
         [0026]    A diffuser  12  is connected to the opening  5  of the bottle  3  via an annular ring  6  constructed of a steel plate. The bottle  3 , the ring  6 , and the diffuser  12  all have the same outside diameter and are joined together by welding, etc. As shown in FIGS.  1  to  3 , the inner end of the ring  6 , which forms an inside hole  6   a,  protrudes from the interior surface of the bottle  3  and the diffuser  12 . A sealing plate (burst disk)  9 , which is constructed of a disk-shaped steel plate, is attached to the ring  6  at the right side (the side facing the bottle  3 ) thereof by welding, etc. The inside hole  6   a  of the ring  6  (the opening  5  of the bottle  3 ) is sealed by the sealing plate  9 . The thickness of the sealing plate  9  is typically 0.2 to 0.4 mm.  
         [0027]    The diffuser  12  is a cylindrical member formed of steel and the right end portion (a portion connected to the ring  6 ) thereof has the shape of a straight cylinder. The diffuser  12  is tapered toward the left end thereof, and a gas outlet  15  is formed at the left side of the tapered portion. When the inflator  1  is activated, the high pressure gas contained in the bottle  3  is ejected through the gas outlet  15 . An inner flange  15   a  is formed at the end of the gas outlet  15 , and an external thread  15   b  is formed in the exterior surface thereof. The external thread  15   b  is engaged with a fixing flange  25  (in FIG. 4), which is provided for securing an open end of an air bag (not shown).  
         [0028]    A through hole  12   a  is formed in the circumferential surface (the bottom surface in the figures) of the diffuser  12 , and a housing  17  is inserted through the through hole  12   a.  As shown in FIG. 4, the housing  17  includes an inside part  17 A, which is disposed inside the diffuser  12 , and an outside part  17 B, which is disposed outside the diffuser  12 . The inside and outside parts  17 A and  17 B are joined together by screw joint, welding, press-fitting, etc. The upper surface of the housing  17  (the upper surface of the inside part  17 A) is closed, and the bottom surface thereof (the bottom surface of the outside part  17 B) is open.  
         [0029]    An initiator  11  is retained in the outside part  17 B of the housing  17 , and an end portion of the initiator  11  is inserted in the inside part  17 A. The initiator  11  is connected to a control unit (not shown) via an electric wire. The initiator  11  generates an air blast that provides a driving force for braking the sealing plate  9  when the inflator  1  is activated.  
         [0030]    As is comprehensively shown in FIG. 4, a through hole  17 C is formed in the right surface of the inside part  17 A of the housing  17  at the right side thereof. An internal thread is formed in the inner periphery of the through hole  17 C, and a barrel  21  having a cylindrical shape is screwed into the through hole  17 C. As shown in FIGS.  1  to  3 , in the state in which the housing  17  and the barrel  21  are joined, they are constructed like a reducing elbow having a curved passage therein. One end of the barrel  21  (the right end in FIG. 1) contacts the side surface of the sealing plate  9  at the left side thereof. Accordingly, the barrel  21  supports a considerable percentage of the filling pressure applied to the sealing plate  9  by the gas contained in the bottle  3 . Thus, the sealing plate  9  having a relatively small thickness such as 0.2 to 0.4 mm can sustain a high pressure.  
         [0031]    As shown in FIGS.  1  to  3 , the barrel  21  has an inside hole which includes a large diameter portion  21 A at the side close to the housing  17  and a small diameter portion  21 B at the side close to the sealing plate  9 . A piston  23 , which includes a shaft portion  23   a  and a flange portion  23   b,  is disposed inside the inside hole of the barrel  21  so that the piston  23  can slide in the inside hole. The outside diameter of the shaft portion  23   a  is slightly smaller than the inside diameter of the small diameter portion  21 B, and the outside diameter of the flange portion  23   b  is slightly smaller than the inside diameter of the large diameter portion  21 A. The tip of the piston  23  is sharply pointed.  
         [0032]    Next, the operation of the inflator  1  having the above-described construction will be described below.  
         [0033]    As shown in FIG. 1, in a normal state in which the inflator  1  is not activated, the interior  3 C of the bottle  3  is filled with the gas and is sealed by the sealing plate  9 . The sealing plate  9  serves to prevent the gas from leaking through the opening  5  of the bottle  3 . The piston  23  is retained in the barrel  21  at a predetermined position shown in FIG. 1. In this state, the right end of the barrel  21  is in contact with the sealing plate  9 , and the tip of the piston  23  is separated from the sealing plate  9 .  
         [0034]    When a vehicle receives an impact, the inflator  1  is activated and the high pressure gas contained in the bottle  3  is supplied to the air bag (not shown). In such an emergency situation, the control unit (not shown) sends an electric signal, and the initiator  11  generates an air blast based on the signal. As shown in FIG. 2, the blast air flows inside the inside part  17 A of the housing  17  and the large diameter portion  21 A of the barrel  21  along the curved passage, so that the piston  23  is pushed to the right in the figure.  
         [0035]    Then, as shown in FIG. 3, the tip of the piston  23 , which is pushed by the air blast, breaks the sealing plate  9 . The sealing plate  9  ruptures and the high pressure gas contained in the bottle  3  starts flowing out through between the exterior surface of the barrel  21  and the inside hole  6   a  of the ring  6  into the diffuser  12 . The gas is then ejected and supplied to the air bag (not shown) through the gas outlet  15 . Accordingly, the air bag is inflated. As described above, during the time in which the gas comes out from the bottle  3 , flows inside the diffuser  12 , and is supplied into the air bag, the gas flows linearly. The piston  23  pushed by the air blast generated by the initiator  11  is stopped when the flange portion  23   b  encounters the step portion between the large diameter portion  21 A and the small diameter portion  21 B inside the barrel  21 .  
         [0036]    Next, modifications of the piston and the barrel will be described below.  
         [0037]    FIGS.  5 (A)- 5 (F) are schematic drawings that show modifications of the piston and the barrel. FIGS.  5 (A) and  5 (B) are perspective views showing modifications of the piston of the inflator according to the present invention, and FIGS.  5 (C) and  5 (D) are perspective views showing modifications of the barrel of the inflator according to the present invention. In addition, FIG. 5(E) is a sectional view of the barrel shown in FIG. 5(D) with the piston before activation, and FIG. 5(F) is a sectional view similar to FIG. 5(E) after activation.  
         [0038]    A piston  30  shown in FIG. 5(A) includes a shaft portion  30   a  and a flange portion  30   b.  The tip of the shaft portion  30   a  is sharply pointed. A plurality of grooves  30   c  is formed in the peripheral surface of the flange portion  30   b  along the thickness direction thereof. In the piston  30 , when the initiator is activated, air partially flows through the grooves  30   c  toward the tip of the piston  30 . Thus, the internal pressure of the barrel is reduced, so that the pressure resistance of the barrel can be a relatively low.  
         [0039]    A piston  35  shown in FIG. 5(B) includes a shaft portion  35   a  and a flange portion  35   b.  A hollow portion  35   c  is formed along the shaft center (the center of the shaft portion  35   a  and the flange portion  35   b ) of the piston  35 . In the piston  35 , when the initiator is activated, air flows through the hollow portion  35   c  toward the sealing plate, so that the midsection of the sealing plate ruptures such that a circular hole is formed therein. Accordingly, the sealing plate always breaks in a similar manner.  
         [0040]    A barrel  40  shown in FIG. 5(C) includes a cylindrical main body  41 , and a flange  42  is formed at the end of the main body  41  which is closer to the bottle (the end closer to the sealing plate, or the right end in the figure) . A plurality of holes (orifices)  42   a  is formed in the flange  42 . In the barrel  40 , the flange  42  having a large area contacts the sealing plate. Accordingly, the sealing plate can be more effectively supported. After the piston that slides inside the barrel  40  ruptures the sealing plate, the gas contained inside the bottle flows through the holes  42   a.    
         [0041]    A barrel  45  shown in FIGS.  5 (D),  5 (E), and  5 (F) includes a cylindrical main body  46 , and the diameter of an end portion  47  of the main body  46  at the end closer to the bottle (the end closer to the sealing plate, or the right end in the figure) is gradually reduced. The diameter of an end portion  48  of the main body  46  at the end further from the bottle (the end closer to the housing, or the left end in the figure) is gradually increased. In the barrel  45 , the tip of a piston  50  is inside the barrel  45  before activation, and the tip of the piston  50  protrudes out from the opening formed in the end portion  47  of the barrel  45  after activation. The piston  50  sliding inside the main body  46  is stopped when it engages the end portion  47  which becomes narrower toward the end. Accordingly, the above-described flange portion, which is formed at the rear end of the piston, can be omitted and the shape of the piston can be simpler.  
         [0042]    In addition, the above-described inflator allows, for example, the following modifications:  
         [0043]    (1) the initiator is omitted and the piston is manually moved in order to break the sealing plate. This construction can be applied to such devices as extinguisher, life jacket, etc.  
         [0044]    (2) the piston is disposed inside the bottle.  
         [0045]    (3) the housing is attached to the side surface of the bottle, and the internal pressure of the bottle is increased by solid, liquid, fuel, etc., so as to break the sealing plate. In this case, the piston can be omitted.  
         [0046]    As is apparent from the foregoing explanations, according to the present invention, an inflator in which a gas can be ejected and supplied linearly in the axial direction a bottle without increasing the size and the manufacturing cost thereof can be provided.  
         [0047]    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.