Gas generator

Abstract

[Problem] To provide a gas generator that makes it possible for electricity to be easily conducted between a metal holder and a metal part of a bottom part of a retainer without imposing costs. [Solution] A gas generator according to the present invention has a long, substantially cylindrical outer shape and includes: a housing 10; a connector connection part 20, a holder 25, and a directional member 53 that are installed near one open end of the housing 10; an igniter 50 that is held by the holder 25 and ignites a gas generation agent 31; a sealing member that is installed at another end of the housing 10 to seal another open end of the housing 10; and a filter. Electricity is conducted via a conductive resin 40 between the holder 25 and a metal part that is provided to a bottom part of a retainer 40 that is fitted into the connector connection part 20.

Description

Gas generator

[0001] The present invention relates to a gas generator to be incorporated in an airbag device as an occupant protection device mounted on an automobile or the like.

[0002] In conventional gas generators, various measures have been taken to remove static electricity, such as using a holder molded from a conductive resin (see, for example, Patent Document 1 listed below). Furthermore, for example, in a stage (such as during transportation) prior to assembly into an airbag module or the like, a component called a retainer used to short-circuit the igniter may be attached to the gas generator at a location where an external connector is connected when the gas generator is assembled into an airbag module or the like. Among retainers, there are retainers that also have the function of removing static electricity accumulated in the gas generator via a metal holder.

[0003] JP 2017-61185 A

[0004] When using this retainer, it is possible to use a metal holder and discharge static electricity from the side of the retainer, but metal is relatively difficult to process, which increases costs. Furthermore, metal tends to be heavy. Therefore, the holder can be made from resin to reduce weight, but in this case, metal grounding parts must be provided on the side and bottom of the holder. However, gaps tend to form between the metal bottom part and the metal holder, making it difficult to maintain contact.

[0005] Therefore, an object of the present invention is to provide a gas generator that can easily fill the gap that occurs between the metal part at the bottom and the metal holder without incurring additional costs, and can maintain electrical continuity between the metal part at the bottom of the retainer and the metal holder.

[0006] (1) A gas generator of the present invention comprises: a housing loaded with a gas generating agent that generates gas when burned, containing a filter through which the gas passes, and having a gas outlet formed at a position corresponding to the filter for ejecting the gas; an igniter capable of igniting and burning the gas generating agent; a resin tubular portion disposed at one axial end of the housing, into which an external connector can be fitted at the one end for applying electricity to the igniter when the housing is assembled to an external device, and into which a retainer having metal portions on at least portions of its side and bottom surfaces can be fitted; and a metal or alloy tubular holder fixed to the housing so as to face the tubular portion and holding a portion of the igniter, wherein when the retainer is fitted to the tubular portion, at least a portion of the portion of the holder facing the retainer and the metal portion of the retainer are electrically connected via conductive resin or conductive grease.

[0007] (2) In the gas generator of (1) above, it is preferable that the conductive resin or the conductive grease is applied to at least a portion of the holder that faces the metal portion.

[0008] (3) In the gas generator of (2) above, it is preferable that an annular surface is formed on the cylindrical portion side of the holder, and that the conductive resin or the conductive grease is attached all around the annular surface.

[0009] (4) In the gas generator of (1) above, it is preferable that the portion facing the holder is in contact with the metal portion provided on at least a part of the bottom surface of the retainer.

[0010] According to the present invention, it is possible to provide a gas generator in which the gap that occurs between the metal part at the bottom and the metal holder can be easily filled without incurring any cost, and in which the metal part at the bottom of the retainer and the metal holder can be kept electrically conductive.

[0011] Fig. 2 is a schematic diagram (partially omitted) showing the internal structure of a gas generator according to an embodiment of the present invention, shown partially in cross section. Fig. 3 is a diagram showing the vicinity of one end of the gas generator of Fig. 1. Fig. 4 is an enlarged view of region A of Fig. 2. Fig. 5 is a perspective view showing a state of a holder before being assembled to the gas generator of Fig. 1.

[0012] Hereinafter, the internal structure of a cylinder-type gas generator according to an embodiment of the present invention will be described with reference to FIGS.

[0013] (Configuration of gas generator 100) Gas generator 100 has a long, approximately cylindrical outer shape, and includes housing 10, connector connection portion 20 (cylindrical portion) attached near one open end of housing 10, holder 25, directional member 53, and closing member 12 attached to the other end of housing 10 so as to close the other open end of housing 10.

[0014] Housing 10 has peripheral walls 10a, 10c, 10d, and 10e and is made of a long, cylindrical member having openings at both axial ends. Gas outlets 11 are provided in the peripheral wall near the end of housing 10 on the side where closing member 12 is attached. Gas outlets 11 are holes for ejecting gas generated inside gas generator 100 to the outside, and a plurality of gas outlets 11 are provided along the circumferential and axial directions of housing 10.

[0015] The blocking member 12 is made of metal such as stainless steel, iron steel, aluminum alloy, or stainless alloy. As shown in Fig. 1, inside the other end portion of the housing 10, the blocking member 12 is in contact with the other end of the filter 41 and inserted into the housing 10. Then, a portion of the peripheral wall 10a of the housing 10 corresponding to a part of the blocking member 12 is contracted radially inward (crimped), thereby crimping and fixing the blocking member 12 to the housing 10.

[0016] The connector connection portion 20 is a generally cylindrical member made of resin. On the side opposite the holding position of the igniter 50, the connector connection portion 20 includes a fitting portion 21 into which an external connector (not shown) for energizing the igniter 50 can be fitted and into which a retainer 30 can be fitted. The fitting portion 21 also includes an annular groove 22 formed on the outer peripheral surface and extending in the circumferential direction, and a flange portion 26 formed at the end of the annular groove 22 on the holder 25 side. The flange portion 26 has an outer diameter smaller than the outer diameter of the annular portion 27 of the holder 25. The annular portion 27 has a portion (contact portion) on its outer periphery that contacts the inner wall of the housing. The peripheral wall 10e of the housing 10, corresponding to the flange portion 26 on the outer peripheral surface of the connector connection portion 20, is reduced in diameter (crimped) radially inward to engage with the flange portion 26, thereby crimping and fixing the connector connection portion 20 to the housing 10. The end of the holder 25 on the connector connection portion 20 side is inserted into the interior of the connector connection portion 20. As a result, when the peripheral wall 10e of the housing 10 is reduced inward in the radial direction, the flange portion 26 is sandwiched between the end of the holder 25 on the connector connection portion 20 side and the inner wall of the peripheral wall 10e of the housing 10, thereby more firmly fixing the connector connection portion 20 to the housing 10. In other words, sealing between the housing 10 and the holder can be ensured. Here, as a modified example, instead of the flange portion 26, a simple end portion (without a flange protruding in the radial direction) continuing from the surface of the annular groove portion 22 may be used, and this end portion may be sandwiched between the end of the holder 25 on the connector connection portion 20 side and the inner wall of the peripheral wall 10e of the housing 10.

[0017] Here, a resin material that exhibits excellent heat resistance, durability, and corrosion resistance after curing is preferably selected and used as the raw material for the connector connection portion 20. In this case, the raw material is not limited to thermosetting resins such as epoxy resin, but thermoplastic resins such as polybutylene terephthalate resin, polyethylene terephthalate resin, polyamide resin (e.g., nylon 6 or nylon 66), polypropylene sulfide resin, polypropylene oxide resin, and polyacetal resin can also be used. When using such a thermoplastic resin as the raw material, it is preferable to incorporate glass fiber or the like as a filler into the resin material to ensure the mechanical strength of the connector connection portion 20 after molding. However, if sufficient mechanical strength can be ensured with the thermoplastic resin alone, the addition of a filler as described above is not necessary. The directional member 53 can also be formed from the same raw material as the connector connection portion 20.

[0018] As described above, a female connector is formed at fitting portion 21 of connector connection portion 20. This female connector is a site to which an external connector of a harness that transmits a signal from collision detection means that is provided separately from gas generator 100 is connected. Note that, prior to assembly into an external device such as an airbag module, retainer 30 having a metal portion (not shown) for removing static electricity is attached to at least a portion of the side surface and the bottom surface on the igniter side (the surface facing holder 25) of the female connector. This retainer 30 is attached to prevent malfunction of cylindrical gas generator 100 due to electrostatic discharge or the like during transportation of gas generator 100, and at the stage of assembly into an airbag device, the male connector of the harness is inserted into the female connector to release contact with terminal pin 52.

[0019] Holder 25 is a generally cylindrical member made of a metal such as stainless steel or steel, an aluminum alloy, or a stainless alloy, with an annular surface 28 formed on the connector connection portion 20 side, and the portion that comes into contact with the inner wall of housing 10 has a larger outer diameter than flange portion 26 of connector connection portion 20. Holder 25 has a tapered fitting portion 23 into which a portion of igniter 50 (mainly the main body portion) is inserted, and a portion of its exterior is fitted into connector connection portion 20. As shown in FIG. 3 , at least a portion of the portion of holder 25 facing retainer 30 and a metal portion provided on the bottom of retainer 30 are electrically connected via conductive resin 40.

[0020] The conductive resin 40 is preferably a conductive paste containing a conductive material such as gold, silver, copper, nickel, palladium, or carbon black. Furthermore, as shown in FIG. 4 , by applying (adhering) the conductive resin 40 to the entire surface 28 of the holder 25 in advance, the holder 25 can be electrically connected to the metal portions (e.g., four equally spaced metal portions facing the surface 28 of the holder 25) on the bottom of the retainer 30 even when assembled without considering their relative positions. The conductive resin 40 is preferably a conductive adhesive that hardens over a predetermined period of time by heat curing or at room temperature. The hardening of the conductive resin 40 adheres the conductive resin 40 to the holder 25, forming a layer (protrusion) of the conductive resin 40 that is not easily removed from the holder 25. This ensures reliable contact between the metal portions of the retainer 30 and the layer (protrusion) of the conductive resin 40. Furthermore, when applying (attaching) the conductive resin 40, it is preferable to use a resin with relatively low or no fluidity (high viscosity). By using a resin with low fluidity, even if the shape of the retainer 30 is complex, the holder 25 and the metal part can be electrically connected via the conductive resin 40. In this case, the conductive resin 40 may be hardened after the holder 25 and the retainer 30 are assembled to the housing 10. Furthermore, instead of the conductive resin 40, a conductive grease that is conductive and has relatively low or no fluidity (high viscosity) may be used.

[0021] Igniter 50 is fixed to holder 25 by crimping with crimping portion 24 provided at the open end, with O-ring 60 disposed inside holder 25. Furthermore, with holder 25 sandwiched between connector connection portion 20 and directional member 53, peripheral wall 10d (described below) and peripheral wall 10e (described above) are formed, thereby fixing holder 25 to housing 10.

[0022] The directional member 53 is a resin, substantially cylindrical member with a bottom, and includes an annular groove portion 54 (small diameter portion) formed in the outer peripheral surface so as to extend circumferentially for crimping fixation, and a bottom surface 55 having a hole 55a and a hole 55b having a diameter smaller than that of hole 55a. The directional member 53 is fixed to the housing 10 by performing a diameter reduction process (such as crimping) from the outer periphery of the housing 10 to the interior at a position corresponding to the annular groove portion 54 to form a peripheral wall 10d. A portion of the igniter 50 (mainly the squib cup 51) and the crimped portion 24 are inserted into the directional member 53. The directional member 53 also serves to direct the direction of the flame generated in the igniter 50 toward the gas generating agent 31 by means of holes 55a and 55b. Here, as a modified example, the annular groove portion 54 does not necessarily have to be groove-shaped, but may be formed so as to include at least a portion whose diameter is smaller than the diameter of the end (portion near the surface 55) of the directional member 53 on the side opposite to the holder 25 side (the gas generating agent 31 side), to an extent that it can be used for fixing by diameter reduction processing.

[0023] 1, an igniter 50 is disposed at one axial end of the housing 10 as means for igniting the gas generating agent 31. The igniter 50, a holder 25 for fixing the igniter 50, a directional member 53, and a connector connection portion 20 function as ignition means for generating a flame for burning the granular gas generating agent 31, which will be described later.

[0024] As shown in Figure 1, the igniter 50 is inserted into the fitting portion 23 of the holder 25 and held together with a directional member 53 (described later). More specifically, the igniter 50 includes a base frame through which a pair of terminal pins 52 are inserted and which holds the pair, and a squib cup 51 (cup-shaped member) attached to the base frame. A resistor (bridge wire) is attached so as to connect the tips of the terminal pins 52 inserted into the squib cup 51, and an ignition charge is filled in the squib cup 51 so as to surround or be in contact with the resistor. A nichrome wire or the like is generally used as the resistor, and ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), lead tricinate, or the like is generally used as the ignition charge. In addition to the ignition charge, a transfer charge may also be filled into the squib cup 51. Examples of transfer charges that can be placed together with the ignition charge include a composition consisting of a metal / oxidizer, such as boron / potassium nitrate, a composition consisting of titanium hydride / potassium perchlorate, or a composition consisting of boron / 5-aminotetrazole / potassium nitrate / molybdenum trioxide.

[0025] When a collision is detected, a predetermined amount of current flows through the resistor via the terminal pin 52. When a predetermined amount of current flows through the resistor, Joule heat is generated in the resistor, and this heat causes the ignition charge to start burning. The high-temperature flame generated by the combustion ruptures the squib cup 51 containing the ignition charge. If nichrome wire is used for the resistor, the time from when the current flows through the resistor to when the igniter 50 is activated is 2 milliseconds or less.

[0026] The squib cup 51 is generally made of metal or resin. The peripheral wall of the squib cup 51, except for the vicinity of the tip, is fixed to the holder 25 together with the igniter 50 by crimping with the crimping portion 24.

[0027] In the space between the igniter 50 and the filter 41 within the housing 10, a gas generating agent 31, an AI agent 32, a coil spring 35, and a bypass prevention member 36 are disposed.

[0028] The gas generating agent 31 is an integrally molded product that is ignited by a flame generated by ignition by the igniter 50 and burns to generate gas. The gas generating agent 31 is generally formed as a molded product containing a fuel, an oxidizer, and an additive. Examples of fuels that can be used include triazole derivatives, tetrazole derivatives, guanidine derivatives, azodicarbonamide derivatives, hydrazine derivatives, and combinations thereof. Specifically, nitroguanidine, guanidine nitrate, cyanoguanidine, and 5-aminotetrazole are preferably used. Examples of oxidizers that can be used include basic metal nitrates such as basic copper nitrate, basic metal carbonates such as basic copper carbonate, perchlorates such as ammonium perchlorate and potassium perchlorate, and nitrates containing cations selected from alkali metals, alkaline earth metals, transition metals, and ammonia. Examples of nitrates that can be used include sodium nitrate and potassium nitrate. Examples of additives that can be used include binders, slag-forming agents, and combustion adjusters. Suitable binders include organic binders such as cellulose derivatives (e.g., hydroxypropylene methyl cellulose), metal salts of carboxymethyl cellulose, and stearates, as well as inorganic binders (e.g., synthetic hydroxytalcite and acid clay). Suitable slag-forming agents include silicon nitride, silica, and acid clay. Suitable combustion-adjusting agents include metal oxides, ferrosilicon, activated carbon, and graphite.

[0029] The bypass prevention member 36 has a bottom surface portion 36a with a weakened portion in the center and an outer peripheral wall portion 36b, and is welded and fixed to the housing 10 via the outer peripheral wall 10c, which is also a welded portion. The bypass prevention member 36 also serves as a member that separates the housing 10 into the filter 41 and the combustion chamber of the gas generating agent 31. Upon activation, the weakened portion of the bottom surface portion 36a breaks due to the pressure of the generated gas. The bypass prevention member 36 is also disposed so that the bottom surface portion 36a abuts against the end of the filter 41 and the outer peripheral wall portion 36b abuts against the inner wall of the housing 10. This prevents the generated gas from bypassing between the inner wall of the housing 10 and the outer peripheral portion of the filter 41 and leaking out to the gas outlet 11. In other words, the bypass prevention member 36 allows the generated gas to flow into the filter 41 side through the ruptured center portion upon activation.

[0030] The coil spring 35 is disposed so that one end thereof abuts against the AI ​​agent 32. The coil spring 35 is formed in a spiral shape so that the diameter thereof decreases from one end to a midpoint and then increases from the midpoint to the other end, and the one end thereof presses the gas generating agent 31 toward the igniter 50.

[0031] The AI ​​agent 32 is provided in approximately the center of the igniter 50 side of the bottom surface portion 36a of the bypass prevention member 36, and has an auto-ignition (AI) function that automatically ignites without the operation of the igniter 50. Explaining in more detail, the AI ​​agent 32 automatically ignites at a lower temperature than the gas generating agent 31, and therefore, in the unlikely event of a fire or the like occurring in a vehicle or the like equipped with an airbag device or the like in which the gas generator 100 is incorporated, it is possible to prevent the induction of abnormal operation of the gas generator 100 due to external heating.

[0032] The filter 41 is a cylindrical member having a generally cylindrical hollow portion 41a at its center. The use of the filter 41 made of the cylindrical member reduces the flow resistance of the working gas during operation, allowing for efficient gas flow. The filter 41 may be made of wire material made of metal such as stainless steel or steel, or a wound or pressed mesh material. Specifically, a knitted wire mesh, a plain weave wire mesh, or an assembly of crimped metal wire materials may be used. The filter 41 functions as a cooling means for cooling the gas generated in the housing 10 by removing the high-temperature heat of the gas as it passes through the filter 41, and also functions as a removal means for removing slag and other contaminants contained in the gas. As a variation of the filter 41, a filter having a labyrinth-shaped flow path formed by combining generally cylindrical or cone-shaped metal components may be used. This allows the working gas to be redirected in various directions, thereby cooling the gas and removing slag.

[0033] Furthermore, in the above-described embodiment of the present invention, a filter made of so-called knitted wire mesh is used as an example, but instead, a filter made by winding punched metal or expanded metal can also be used. Here, punched metal refers to a metal plate in which only openings are provided (i.e., no protrusions are provided around the edges of the openings), and expanded metal refers to a metal plate in which openings are provided in the plate metal member by, for example, making staggered cuts and then expanding the cuts to form a mesh-like structure. Even when such punched metal or expanded metal is used instead of the knitted wire mesh, the same effects as those described in the above-described embodiment of the present invention can be obtained.

[0034] Furthermore, in the above-described perforated metal and expanded metal, the filter is formed as a laminate by winding a single metal plate-like member, but the configuration of the filter is not limited to this. That is, the filter may be formed as a laminate by combining different metal plate-like members each having different layers, or the filter may be formed as a laminate by combining a plurality of layers in which some layers are formed as a single metal plate-like member and the remaining layers are formed as a different single metal plate-like member.

[0035] Next, an operation during activation of gas generator 100 described above will be described. When a vehicle equipped with an airbag device incorporating gas generator 100 in the present embodiment collides, the collision is detected by collision detection means separately provided in the vehicle, and igniter 50 is activated based on this detection. When igniter 50 is activated, the pressure inside igniter 50 increases due to combustion of the ignition charge, causing the tip of squib cup 51 of igniter 50 to rupture, and a flame flows from the tip of squib cup 51 of igniter 50 to the side of gas generating agent 31 inside housing 10.

[0036] The flame that has flowed in in this manner ignites and burns the gas generating agent 31 within the housing 10, generating a large amount of gas. This combustion of the gas generating agent 31 increases the pressure within the housing 10, and the generated gas ruptures the weak portion of the bottom surface portion 36a of the bypass prevention member 36 and flows into the hollow portion 41a and the internal space 12a. The generated gas then passes through the filter 41 and is ejected from the gas outlet 11 to the outside of the gas generator 100, but since it passes through the filter 41, the generated gas is cooled to a predetermined temperature. The gas ejected from the gas outlet 11 is then guided into the interior of the airbag, inflating and deploying the airbag.

[0037] (Major features of gas generator 100) According to the present embodiment, gas generator 100 can be provided that can easily, without additional cost, fill the gap that occurs between the metal portion at the bottom of retainer 30 and metal holder 25, thereby maintaining electrical continuity between the metal portion at the bottom of retainer 30 and metal holder 25.

[0038] Furthermore, according to this embodiment, the conductive resin 40 is applied (adhered) in advance to the entire surface 28 of the holder 25, so that the holder 25 and the metal portion provided at the bottom of the retainer 30 can be electrically connected even when the holder 25 is assembled without considering the positional relationship between the two.

[0039] Furthermore, if a conductive adhesive that hardens over a predetermined period of time under heat or room temperature conditions is used to form the conductive resin 40 in this embodiment, a layer (protrusion) of conductive resin 40 that is not easily detached from holder 25 can be formed.

[0040] Furthermore, according to the present embodiment, connector connection portion 20 and directional member 53 are made of resin, and holder 25 is made of metal or an alloy, making it easier to mold the holder than conventionally and enabling a reduction in weight compared to when the entire holder is made of metal or an alloy. In other words, according to the present embodiment, it is possible to provide gas generator 100 that is easier to manufacture, lighter in weight than conventional gas generators, and that can further reliably keep costs down.

[0041] Furthermore, according to the present embodiment, by dividing the connector connection portion 20, holder 25, and directional member 53, it is not necessary to form a complex shape all at once, and therefore it is possible to provide a gas generator 100 that is easier to manufacture than conventional gas generators.

[0042] Furthermore, according to this embodiment, the directional member 53 can be used as a protective member for the crimped portion 24 of the holder 25 .

[0043] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration should not be considered to be limited to these embodiments. The scope of the present invention is defined by the claims, rather than by the description of the above-described embodiments, and further includes all modifications within the meaning and scope of the claims. For example, the present invention is applicable to a disk-type gas generator in which a retainer similar to the above-described retainer 30 can be fitted to a connector joint of a metal holder that holds an igniter. Here, the disk-type gas generator has a cylindrical upper shell with a bottom and a cylindrical lower shell with a bottom, which are assembled and joined so that their open surfaces face each other to form a housing, a holder that holds an igniter is formed in the approximate center of the lower shell, and a gas generating agent is filled inside the housing.

[0044] In the above embodiment, the method for reducing the diameter of the housing is explained by taking caulking as an example, but any processing method that can reduce the diameter of the housing may be used.

[0045] REFERENCE SIGNS LIST 10 Housing 10a, 10c, 10d, 10e Peripheral wall 11 Gas outlet 12 Closure member 12a Internal space 20 Connector connection portion 21, 23 Fitting portion 22, 54 Annular groove portion 24 Crimping portion 25 Holder 26 Flange portion 27 Annular portion 28 Surface 30 Retainer 31 Gas generating agent 32 AI agent 35 Helical spring 36 Bypass prevention member 36a Bottom surface portion 36b Outer circumferential wall portion 40 Conductive resin 41 Filter 41a Hollow portion 50 Igniter 51 Squib cup 52 Terminal pin 53 Directional member 55 Bottom surface 55a, 55b Hole 60 O-ring 100 Gas generator

Claims

1. A gas generator comprising: a housing loaded with a gas generating agent that generates gas when burned, containing a filter through which the gas passes, and having a gas outlet formed at a position corresponding to the filter for ejecting the gas; an igniter capable of igniting and burning the gas generating agent; a resin tubular portion disposed at one axial end of the housing, into which an external connector can be fitted at the one end for energizing the igniter when the housing is assembled to an external device, and into which a retainer having metal portions on at least portions of its side and bottom surfaces can be fitted; and a metal or alloy tubular holder fixed to the housing so as to face the tubular portion, and for holding a portion of the igniter; wherein when the retainer is fitted to the tubular portion, at least a portion of the portion of the holder facing the retainer and the metal portions of the retainer are electrically connected via conductive resin or conductive grease.

2. A gas generator according to claim 1, wherein the conductive resin or the conductive grease is applied to at least the portion of the holder that faces the metal portion.

3. A gas generator according to claim 2, characterized in that an annular surface is formed on the cylindrical portion side of the holder, and the conductive resin or the conductive grease is attached all around the annular surface.

4. A gas generator according to claim 1, characterized in that the conductive resin is in contact with the metal portion provided on at least a part of the bottom surface of the retainer, the metal portion facing the holder.

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