Abstract:
An igniter assembly includes an igniter, a substantially cylindrical collar for holding the igniter, and resin for joining the igniter to the collar. The collar has a cylindrical main body, a collar portion provided inward at the inner circumferential surface of the main body, and a cylindrical surrounding wall portion which extends from one end of the main body in the axial direction of the main body. A groove is formed in a radial surface of the collar portion at the side of the surrounding wall portion. The resin is filled between the igniter and the inner circumferential surface and the radial surface of the internal hole of the collar portion and the inside of the surrounding wall portion so as to fill in the groove. The collar is easily manufactured, and the igniter assembly prevents a gap from being generated due to shrinkage of resin.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]     The present invention relates to an igniter assembly used in an inflator of an airbag device or a seat belt device, an inflator including the igniter assembly, and an airbag device and a seat belt device including the inflator.  
         [0002]     In an igniter assembly assembled in an inflator of an airbag device, if an igniter is energized, high-temperature reaction gas is rapidly generated and a gas generating agent of the inflator starts to react with this reaction gas. Thus, the inflator generates a large amount of gas, and an airbag rapidly expands by this gas.  
         [0003]     A conventional igniter assembly of an inflator will be described with reference to FIGS.  10 ( a )- 10 ( c ).  FIG. 10 ( a ) is a cross-sectional view taken along the axial direction of the igniter assembly,  FIG. 10 ( b ) is a cross-sectional view taken along the axial direction of a collar, and  FIG. 10 ( c ) is an enlarged cross-sectional view of the interface between the collar and a resin.  
         [0004]     The igniter assembly  10 A includes an igniter  20 , a substantially cylindrical collar  30 A for holding the igniter  20 , and the resin  40  for joining the igniter  20  to the collar  30 A. The igniter  20  has a head portion  21  containing a reaction agent and pins  22  and  23  protruded and extended from the head portion  21  as conducting terminals. The collar  30 A has a cylindrical main body  31 , a collar portion  32  provided inward at the inner circumferential surface of the main body  31 , and a cylindrical surrounding wall portion  33  extended from one end of the shaft of the main body  31 . A surface  32   b  of the collar portion  32  at the side of the surrounding wall portion  33  is a radial surface extended in a radiant direction perpendicular to the shaft of the main body  31 .  
         [0005]     The head portion  21  of the igniter  20  is disposed in the surrounding wall portion  33  and the pins  22  and  23  are inserted into the main body  31  through an internal hole of the collar portion  32 .  
         [0006]     The resin  40  is filled between the igniter  20  and the inside of the surrounding wall portion  33  and the inner circumferential surface  32   a  of the internal hole of the collar portion  32  by injection molding or the like.  
         [0007]     The resin  40  is filled between the igniter  20  and the collar  30 A, but then shrinks in the arrow direction A of  FIG. 10 ( c ) during cooling. Accordingly, as shown in  FIG. 10 ( c ), a gap C may be generated between the resin  40  and the inner circumferential surface of the surrounding wall portion  33  and the inner circumferential surface  32   a  of the collar portion  32 . This gap C may function as a passage for leaking gas at the time of operation of the inflator.  
         [0008]     Japanese Unexamined Patent Application Publication No. 2004-293835 discloses a construction in which a cylindrical protrusion is provided on a collar such that a gap extended from the inner circumferential surface of the collar to the outer surface of an igniter is not generated although resin is shrunk. However, in this case, the cost of producing the collar increases by forming the protrusion.  
         [0009]     An object of the present invention therefore is to provide an igniter assembly which can prevent a gap from being generated due to shrinkage of resin, and which has an easily manufactured collar. Another object of the invention is to provide an inflator using the igniter assembly, and an airbag device and a seat belt device including the inflator.  
         [0010]     Further objects and advantages of the invention will be apparent from the following description of the invention and the associated drawings.  
       SUMMARY OF THE INVENTION  
       [0011]     According to an embodiment of the invention, an igniter assembly includes an igniter and a substantially cylindrical collar for holding the igniter, in which the igniter and the collar are integrally joined to each other with resin interposed therebetween. A radial surface which substantially extends in a radial direction is provided in the collar, the resin is attached to the radial surface, and a concave portion is formed in the radial surface.  
         [0012]     According to another aspect of the invention, a groove which extends in a non-radial direction is formed as the concave portion.  
         [0013]     According to another aspect of the invention, the bottom of the groove is rounded.  
         [0014]     According to another embodiment of the invention, an inflator includes the above-described igniter assembly.  
         [0015]     According to still another embodiment of the invention, an airbag device includes the above-described inflator.  
         [0016]     In another embodiment of the invention, a seat belt device includes a seat belt and a pretensioner which applies pretension to the seat belt by gas pressure from the above-described inflator during an emergency.  
         [0017]     In the igniter assembly according to the present invention, the concave portion is provided in the radial surface, shrinkage of the resin is restricted, and a gap is prevented from being generated between the collar and the resin. Furthermore, the concave portion can be more easily formed compared with a protrusion, and the cost of producing the igniter assembly is reduced.  
         [0018]     If the groove which extends in a non-radial direction is provided as the concave portion, shrinkage of the resin can be restricted. In addition, the groove can be easily formed in the collar.  
         [0019]     If the bottom of the groove is rounded, the resin is easily attached to the bottom of the groove.  
         [0020]     The inflator, the airbag device, and the seat belt device including the igniter assembly can prevent gas from leaking through the gap of the igniter assembly upon operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1 ( a ) is a cross-sectional view taken along the axial direction of an igniter assembly according to an embodiment of the invention,  FIG. 1 ( b ) is a cross-sectional view taken along the axial direction of a collar, and  FIG. 1 ( c ) is a partial enlarged cross-sectional view of the collar.  
         [0022]     FIGS.  2 ( a ) and  2 ( b ) are plan views of a collar portion.  
         [0023]      FIG. 3  is a partial enlarged cross-sectional view of the collar portion illustrating a cross-sectional shape of a groove.  
         [0024]      FIG. 4  is a partial enlarged cross-sectional view of the collar portion illustrating another cross-sectional shape of the groove.  
         [0025]      FIG. 5  is a longitudinal cross-sectional view of an inflator for an airbag device including the igniter assembly according to an embodiment of the invention.  
         [0026]      FIG. 6  is a longitudinal cross-sectional view of an airbag device including the inflator shown in  FIG. 5 .  
         [0027]      FIG. 7  is a longitudinal cross-sectional view of an inflator for a seat belt device including the igniter assembly according to an embodiment of the invention.  
         [0028]      FIG. 8  illustrates the entire construction of a seat belt device that includes the inflator shown in  FIG. 7 .  
         [0029]      FIG. 9  is an exploded perspective view of a retractor of the seat belt device shown in  FIG. 8 .  
         [0030]      FIG. 10 ( a ) is a cross-sectional view taken along the axial direction of a conventional igniter assembly,  FIG. 10 ( b ) is a cross-sectional view taken along the axial direction of a collar, and  FIG. 10 ( c ) is an enlarged cross-sectional view of the interface between the collar and a resin. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Hereinafter, embodiments will be described with reference to the attached drawings.  FIG. 1 ( a ) is a cross-sectional view taken along the axial direction of an igniter assembly according to an embodiment,  FIG. 1 ( b ) is a cross-sectional view taken along the axial direction of a collar, and  FIG. 1 ( c ) is a partial enlarged cross-sectional view of the collar. FIGS.  2 ( a ) and  2 ( b ) are plan views of a collar portion.  FIG. 3  is a partial enlarged cross-sectional view of the collar portion illustrating the cross-sectional shape of a groove.  
         [0032]     In the igniter assembly  10  according to the present embodiment, grooves  50  are formed in the upper surface  32   b  of a collar portion  32  of a collar  30  (radial surface at the side of a surrounding wall portion  33 ). These grooves  50  do not extend in a radial direction and are concentrically formed as shown in  FIG. 2 ( a ) in the present embodiment. However, in another possible embodiment, grooves  51  may be formed in a knurling shape, as shown in  FIG. 2 ( b ). The depth of the grooves  50  or  51  is preferably 0.2 to 1.0 mm, and particularly, 0.3 to 0.6 mm. The width of the grooves  50  and  51  along the radial surface  32   b  is preferably 0.3 to 0.8 mm, and particularly, 0.4 to 0.6 mm.  
         [0033]     The bottom of the groove  50  is preferably rounded as shown in  FIG. 3 . The radius of curvature of the rounding is preferably in the order of 0.02 to 0.06 mm. By rounding the bottom of the groove  50 , it is possible to prevent with certainty air from remaining in the bottom of the groove when resin is filled in the groove  50 .  
         [0034]     However, the shape of the groove  50  is not necessarily limited to this. For example, the bottom of the groove  50  may be flat as shown in  FIG. 4 .  
         [0035]     The other constructions of the igniter assembly  10  according to the present embodiment are the same as the igniter assembly  10 A, and like reference numbers denote the like portions.  
         [0036]     In the igniter assembly  10 , in a case where resin  40  is filled between an igniter  20  and the collar  30 , shrinkage of the resin  40  along the radial surface  32   b  is restricted by the grooves  50  formed in the radial surface  32   b  of the collar portion  32 , and a gap C is prevented from being generated between the resin  40  and the collar  30 . Thus, when an inflator including the igniter assembly  10  generates gas, it is possible to prevent the gas from leaking through the gap C.  
         [0037]     Furthermore, since the gap C does not exist, it is possible to prevent moisture from permeating into the inflator.  
         [0038]     The collar may be made of metal such as aluminum, iron, stainless, or zinc or resin such as nylon or polybutyleneterephthalate (PBT). The groove may be formed by cutting the radial surface  32   b  of the collar portion  32 . Alternatively, the groove may be formed by forming a convex protrusion in a mold when manufacturing the collar by casting or injection molding or the like. If the metal collar is forged, the groove may be formed upon forging.  
         [0039]     Next, an inflator including the igniter assembly  10  and an airbag device and a seat belt device including the inflator will be described with reference to  FIGS. 5 through 9 .  
         [0040]      FIG. 5  is a longitudinal cross-sectional view of an inflator for an airbag device according to the embodiment, and  FIG. 6  is a longitudinal cross-sectional view of an airbag device including the inflator.  
         [0041]     The inflator  60  for the airbag device includes an outer covering body composed of an upper housing  61  and a lower housing  62  and a cylindrical partition member  63  disposed in the outer covering body. A gas nozzle  64  is provided in the side surface of the outer covering body. One end of the partition member  63  is protruded downward through an opening formed in the bottom of the lower housing  62 . The outer circumferential surface of the partition member  63  and the inner circumferential surface of the opening are welded by laser beam welding or the like.  
         [0042]     Ignition propellant (booster propellant)  65  is contained in the inside of the partition member  63 , and gas generating propellant (main propellant)  66  is contained in the outside of the partition member  63 . A filter  67  is disposed in the periphery of the gas generating propellant  66  (between the gas generating propellant  66  and the gas nozzle  64 ). The inside and the outside of the partition member  63  are communicated with each other through an opening  68 .  
         [0043]     The igniter assembly  10  is mounted at one end of the partition member  63 . In more detail, the igniter assembly  10  is inserted into the partition member  63  while keeping the igniter  20  in the forefront and a head portion  21  of the igniter  20  contacts or faces the ignition propellant  65  in the partition member  63 . The periphery of one end side of the partition member  63  is caulked to the inside of the partition member  63  to overlap with the rear periphery of the igniter assembly  10  (collar  30 ) such that the igniter assembly  10  is held therein and one end of the partition member  63  is sealed.  
         [0044]     However, the construction for holding the igniter assembly  10  and sealing the partition member  63  is not limited to this.  
         [0045]     In the present embodiment, a flange  69  for mounting the inflator  60  to a retainer  82  is mounted at the side surface of the outer covering body of the inflator  60 . The gas nozzle  64  is disposed in the front of the flange  69 . Furthermore, in the present embodiment, the flange  69  is integrally formed with the lower housing  62  to be laterally protruded from the upper periphery of the lower housing  62 , and the gas nozzle  64  is formed by perforating the side surface of the upper housing  61 . However, the present embodiment is not limited to this. A hole  70  into which a bolt  84   a  is inserted is formed in the flange  69 .  
         [0046]     The airbag device  80  includes the inflator  60 , an airbag  81  which expands by gas emitted from the inflator  60 , and the retainer  82  for holding the inflator  60  and the airbag  81 , and a module cover  83  mounted on the retainer  82  to cover the folded airbag  81 .  
         [0047]     The airbag  81  has a front surface facing a vehicle occupant or the like when the airbag  81  expands and a rear surface opposite to the front surface. An opening (mouth)  81   a  into which the inflator  60  is inserted is provided in the rear surface.  
         [0048]     The retainer  82  includes a main plate portion  82   a  and a leg portion  82   b  bent downward from the periphery of the main plate portion  82   a . An inflator inserting hole  82   c  is formed in the center of the main plate portion  82   a . As shown in  FIG. 6 , the front side of the inflator  60  is inserted from the rear surface of the main plate portion  82   a  into the inflator inserting hole  82   c . The mouth  81   a  of the airbag  81  and the periphery of the inflator inserting hole  82   c  overlap with and are fixed to each other by a mounting ring  84 . The front side of the inflator  60  is disposed in the airbag  81  through the mouth  81   a.    
         [0049]     The bolt (stud bolt)  84   a  is protruded from the mounting ring  84  and is inserted into insertion holes (of which the reference numbers are omitted) of the periphery of the mouth  81   a  and the periphery of the inflator inserting hole  82   c  and an insertion hole  70  of the flange  69  to be protruded from the rear surface of the flange  69 . By tightening a nut  84   b  to the, bolt  84   a , the airbag  81  and the inflator  60  are fixed to the retainer  82 .  
         [0050]     The airbag device  80  is constructed by folding the airbag  81  and mounting the module cover  83  to cover the folded airbag  81 .  
         [0051]     Moreover, in the present embodiment, a leg member  83   a  is standing downward from the rear surface of the module cover  83  and fixed to the leg portion  82   b  of the retainer  82  by a fixing tool  83   b  such as a rivet. The module cover  83  is pushed and cleaved by the airbag  81  when the airbag expands. Reference number  83   c  denotes a tear line for cleavage.  
         [0052]     In the inflator  60  and the airbag device  80  having the aforementioned constructions, when pins  22  and  23  of the igniter assembly  10  are energized, a reaction agent in the igniter  20  reacts and thus the ignition propellant  65  is ignited. Next, the gas generating propellant  66  is ignited by high-temperature gas emitted from the ignition propellant  65  through the opening  68 , thereby generating gas. This gas is emitted from the gas nozzle  64  to the outside of the inflator  60 , that is, the inside of the airbag  81  through the filter  67 . As a result, the airbag  81  expands. The airbag  81  pushes and opens the module cover  83  and expands toward the vehicle occupant or the like, thereby protecting the vehicle occupant or the like.  
         [0053]     In the inflator  60  and the airbag device  80 , the gas is prevented from leaking between the resin  40  and the collar  30  of the igniter assembly  10  upon operation.  
         [0054]      FIG. 7  is a longitudinal cross-sectional view of an inflator for a seat belt device including the igniter assembly  10 ,  FIG. 8  illustrates the entire construction of a seat belt device that includes the inflator, and  FIG. 9  is an exploded perspective view of a retractor (pretensioner) of the seat belt device.  
         [0055]     One end of a seat belt  91  of the seat belt device  90  is retractably connected to the retractor  92  and the other end thereof is fixed to a vehicle body by an anchor  93 . The seat belt  91  penetrates through a shoulder anchor  94  and a tongue  95 . The anchor  93  is disposed at the side surface of the vehicle interior. A buckle device  96  for latching the tongue  95  is provided at the opposite side of the anchor  93  of the seat. The shoulder anchor  94  is disposed on the upper side of the side surface of the vehicle interior.  
         [0056]     In the present embodiment, the retractor  92  includes a pretensioner which applies pretension to the seat belt  91  during an emergency of the vehicle and an impact energy absorbing mechanism (EA mechanism) for absorbing impact energy applied from the seat belt  91  to the vehicle occupant. Hereinafter, the construction of the retractor  92  will be described with reference to  FIG. 9 .  
         [0057]     A spool  98  is received in a base frame  97  of the retractor  92  and one end of the seat belt  91  is wound on the spool  98 . The seat belt  91  is wound on/off by rotating the spool  98 . A torsion bar  99  is mounted at the center of axis of the spool  98  and one end of the torsion bar  99  is supported by a support member  102  through locking components  100  and  101 .  
         [0058]     The torsion bar  99  is a main component of the EA mechanism. If the tension of the seat belt  91  exceeds a predetermined value, the torsion bar  99  is plastic-deformed and thus rotates in an unwinding direction of the seat belt  91  while drag is applied to the spool  98 .  
         [0059]     A gear  103  is mounted at one end (left side of  FIG. 9 ) of the spool  98 . The gear  103  is engaged with a gear (not shown) of a return spring cover  104  shown in lower left side of  FIG. 9 . The spool  98  is biased in a direction of retracting the seat belt  91  by a return spring (not shown) in the return spring cover  104 .  
         [0060]     In  FIG. 9 , a pipe  107  is mounted between a pretensioner cover  105  shown at the right side of the return spring cover  104  and a pretensioner plate  106  shown at the lower right side. An inflator  108  is mounted at one end of the pipe  107 . In the pipe  107 , a spring  109 , a piston  110 , and a plurality of balls  111  are arranged. A notched opening (of which the reference number is omitted) is formed in the vicinity of the other end of the pipe  107 . A guide block  112  is fitted into the other end of the pipe  107 .  
         [0061]     A pin  113  is mounted in the pretensioner cover  105  and holds a ring gear  114  having external teeth and internal teeth. The pipe  107  surrounds the outer circumference of the ring gear  114 . Furthermore, the pipe  107  is arranged such that a direction from one end to the other end thereof becomes a direction of retracting the seat belt of the spool  98 . The opening faces the outer circumferential surface of the ring gear  114  and the front ball  111  exposed through the opening is engaged with the external teeth of the ring gear  114 .  
         [0062]     A pinion  116  engaged with the internal teeth of the ring gear  114  is mounted on a root portion  115  of the gear  103 . When the ring gear  114  is held by the pin  113 , the ring gear  114  is not engaged with the pinion  116 .  
         [0063]     When the inflator  108  emits the gas, the gas is injected into the pipe  107  and the balls  111  moves to the other end of the pipe  107 , that is, in the seat belt retracting direction of the spool  98  by gas pressure. At this time, the front ball  111  presses the ring gear  114  to bend the pin  113 . Thus, a state that the pin  113  holds the ring gear  114  is released and the ring gear  114  is engaged with the pinion  116 .  
         [0064]     As a result, the spool  98  is biased in the seat belt retracting direction by the gas pressure from the inflator  108  through the pinion  116 , the ring gear  114 , and the ball  111 , and the seat belt  91  is wound on the spool  98 . Thus, the pretension is applied to the seat belt  91 .  
         [0065]     In the present embodiment, an inflator  108  includes a substantially cylindrical housing  117  and gas generating propellant  118  is contained in the housing  117 . A gas nozzle  119  is formed in one end of the housing  117 . The gas nozzle  119  is closed by a burst seam  120  upon non-operation of the inflator. When the gas pressure having a predetermined value or more is applied from the inside of the housing  117 , the burst seam  120  bursts and the gas nozzle  119  is opened.  
         [0066]     The igniter assembly  10  is mounted in the other end of the housing  117 . In more detail, the surrounding wall portion  33  of the collar  30  of the igniter assembly  10  is inserted into the housing  117  while keeping the igniter  20  in the forefront and the head portion  21  of the igniter  20  contacts or faces the gas generating propellant  118  in the housing  117 .  
         [0067]     In the present embodiment, a concave portion (of which the reference number is omitted) is formed in a step portion between the surrounding wall portion  33  and the main body  31 , and the other end of the housing  117  is fitted into the concave portion. By caulking the outer periphery of the concave portion in the axial direction of the inflator, the housing  117  and the collar  30  are integrally coupled. In addition, a sealing material (O-shaped ring)  121  for sealing the coupling portion is provided in the concave portion.  
         [0068]     The inflator  108  is inserted into one end of the pipe  107  while keeping the gas nozzle  119  in the forefront and connected with the pipe  107  by a connecting mechanism (not shown).  
         [0069]     In the inflator  108  and the seat belt device  90  having the aforementioned construction, when the pins  22  and  23  of the igniter assembly  10  are energized, the reaction agent in the igniter  20  reacts and the gas generating propellant  118  is ignited, thereby generating gas. Furthermore, the burst seam  120  bursts by the gas pressure, the gas nozzle  119  is opened, and the gas is emitted from the gas nozzle  119  into the pipe  107 . As a result, the pretensioner mechanism of the retractor  92  operates as described above and thus the pretension is applied to the seat belt  91 .  
         [0070]     In the inflator  108  and the seat belt device  90 , it is possible to prevent the gas from leaking between the resin  40  and the collar  30  of the igniter assembly  10  upon operation.  
         [0071]     The aforementioned embodiments are only examples of the present invention, and the present invention may take configurations other than the aforementioned configurations. For example, the collar may be changed to a shape other than the aforementioned shape.  
         [0072]     The igniter assembly according to the present invention may be incorporated in various kinds of inflators. In addition, the inflator may be incorporated in various kinds of airbag devices and seat belt devices.  
         [0073]     The disclosure of Japanese Patent Application No. 2005-079672 filed on Mar. 18, 2005, is incorporated herein.