Gas generator

Abstract

[Problem] To provide a gas generator capable of easily attaching a partition member to a cup-shaped member while ensuring sealability between a cylindrical part of the cup-shaped member and an inner wall of a housing by welding. [Solution] This gas generator 100 includes a housing 10, a holder 20 attached to one opening end of the housing 10, and a closing member 12 attached to the other end of the housing 10 so as to close the other opening end of the housing 10. An AI agent 33 is held by the cup-shaped member 32 and a partition member 34 so as not to contact a gas generating agent 31. The cup-shaped member 32 includes a first cylindrical part 32a having a bottom part 32b at one end, a second cylindrical part 32d welded and fixed to the housing 10 on the other end side of the first cylindrical part 32a and having a diameter greater than that of the first cylindrical part 32a, and an annular connection part 32d connecting the first cylindrical part 32a and the second cylindrical part 32d. The cup-shaped member holds the AI agent 33 together with the partition member 34 disposed in the first cylindrical part 32a.

Description

Gas generator

[0001] The present invention relates to a gas generator incorporated in an airbag device as an occupant protection device mounted on an automobile or the like, and more particularly to a so-called cylinder-type gas generator having an elongated cylindrical shape.

[0002] In a cylinder-type gas generator, the elongated cylindrical housing is generally configured such that one end is closed by a closing member and the other end is closed by a holder having an ignition part (see, for example, Patent Document 1 below). The gas generator of Patent Document 1 below includes a housing having a gas ejection port, a gas generating agent loaded in the housing, and an auto-ignition agent (AI agent) provided in the vicinity of the gas generating agent via a partition member in the housing. Further, in the housing of the gas generator represented by the following patent documents, in order to prevent moisture from flowing into the space (combustion chamber) where the gas generating agent is disposed from the gas ejection port side, a cup-shaped member having a cylindrical part is provided between the combustion chamber and the gas ejection port, and the cylindrical part of the cup-shaped member and the housing may be sealed by penetration welding. The cup-shaped member can also be used to hold the AI agent together with the partition member. Further, in the case of penetration welding, the cylindrical part of the cup-shaped member needs to have a thickness equal to or less than a predetermined thickness suitable for penetration welding.

[0003] Japanese Unexamined Patent Application Publication No. 2022-102514

[0004] However, when the cylindrical part of the cup-shaped member and the housing are penetration-welded, since it is necessary to make the cylindrical part of the cup-shaped member to be welded have a thickness equal to or less than a predetermined thickness (thin-walled), a bead may occur on the inner wall of the cylindrical part of the cup-shaped member. If the bead portion exists on the inner wall of the cylindrical part of the cup-shaped member, when the partition member is inserted into the cup-shaped member to hold the AI agent with the partition member and the cup-shaped member, the bead becomes an obstacle. In particular, when the partition member is to be press-fitted into the cup-shaped member, the presence of the bead may cause a poor press-fit.

[0005] Furthermore, when welding the cylindrical portion of the cup-shaped member to the housing through, it is preferable to provide a gap between the cylindrical portion of the cup-shaped member and the inner wall of the housing in order to suppress the occurrence of blowholes. However, if such a gap is provided, when the partition member is press-fitted into the cup-shaped member, the cylindrical portion of the cup-shaped member to be welded must be made to a thickness of less than a predetermined thickness (thin-walled) in order to perform through welding. As a result, the cylindrical portion of the cup-shaped member is prone to expanding in diameter and deforming during press-fitting, and the partition member may come off during vibration, causing the automatic ignition function of the AI ​​agent to be lost.

[0006] Therefore, the present invention aims to provide a gas generator that ensures a seal between the cylindrical portion of the cup-shaped member and the inner wall of the housing by welding, while also making it easy to attach the partition member to the cup-shaped member, and preventing the partition member from easily coming off the cup-shaped member when it is press-fitted into the cup-shaped member.

[0007] (1) The gas generator of the present invention is characterized by comprising: a long cylindrical housing loaded with a gas generating agent that generates gas by combustion and having a gas outlet formed therein for ejecting the gas; an igniter capable of igniting and burning the gas generating agent; a holder that holds a part of the igniter and is fixed to one end of the housing in the axial direction; a blocking member fixed to the other end of the housing in the axial direction; an auto-igniter provided inside the housing that ignites at a lower temperature than the gas generating agent; a partition member provided inside the housing that separates the gas generating agent and the auto-igniter; a first cylindrical portion provided inside the housing and having a bottom at one end; a second cylindrical portion that is welded and fixed to the housing at the other end of the first cylindrical portion and has a larger diameter than the first cylindrical portion; and a bottomed cylindrical member having an annular connecting portion that connects the first cylindrical portion and the second cylindrical portion, and holding the auto-igniter disposed at the bottom together with the partition member disposed inside the first cylindrical portion.

[0008] (2) In the gas generator described in (1) above, it is preferable that the partition member is press-fitted against the inner wall of the first cylindrical portion.

[0009] (3) From another perspective, in the gas generator described in (1) above, the partition member is a member having a bottom portion and a cylindrical portion, the bottom portion of the partition member is in contact with the auto-ignition agent, and the cylindrical portion of the partition member may be press-fitted against the inner wall of the first cylindrical portion.

[0010] (4) In the gas generator described in (3) above, it is preferable that the wall thickness of the first cylindrical portion is greater than the wall thickness of the cylindrical portion of the partition member.

[0011] According to the present invention, it is possible to provide a gas generator that ensures a seal between the cylindrical portion of the cup-shaped member and the inner wall of the housing by welding, while also making it easy to attach the partition member to the cup-shaped member, and preventing the partition member from easily coming off the cup-shaped member when it is press-fitted into the cup-shaped member.

[0012] This is a schematic diagram (partially omitted) showing the internal structure of a gas generator according to an embodiment of the present invention, with a portion shown in cross-section. This is a schematic diagram showing an enlarged view of the area around the partition member in Figure 1.

[0013] A cylinder-type gas generator according to an embodiment of the present invention will be described below with reference to Figures 1 and 2.

[0014] (Configuration of gas generator 100) The gas generator 100 has an elongated, roughly cylindrical outer shape and includes a housing 10, a holder 20 attached to one open end of the housing 10, and a closing member 12 attached to the other end of the housing 10 so as to close the other open end of the housing 10.

[0015] The housing 10 consists of a long, cylindrical member having a peripheral wall and openings at both ends in the axial direction.

[0016] The sealing member 12 consists of a disc-shaped member having a predetermined thickness. In addition, a gas outlet 11 is provided on the peripheral wall near the end of the housing 10 on the side to which the sealing member 12 is attached. This gas outlet 11 is a hole for ejecting gas generated inside the gas generator 100 to the outside, and multiple outlets are provided along the circumferential and axial directions of the housing 10.

[0017] Furthermore, the closing member 12 is made of metal such as stainless steel, iron or steel, aluminum alloy, or stainless steel alloy. As shown in Figure 1, with a portion of the closing member 12 inserted into one open end of the housing 10, the closing member 12 is fixed to the housing 10 by forming an annular welded portion 13 by laser welding or the like.

[0018] The holder 20 is made of a metal such as stainless steel, iron or steel, aluminum alloy, or stainless alloy, and has a tapered fitting portion 23 into which the igniter 50 is fitted, an annular welded portion 22 formed by laser welding or the like, and a fitting portion 21 on the opposite side of the holding position of the igniter 50 into which a female connector (not shown) for supplying power to the igniter 50 can be fitted.

[0019] As mentioned above, a female connector is formed on the mating portion 21 of the holder 20. This female connector is the part to which the male connector of a harness that transmits signals from a collision detection means, which is provided separately from the gas generator 100, is connected. A retainer 60 is attached to the female connector. This retainer 60 is attached to prevent the cylinder-type gas generator 100 from malfunctioning due to electrostatic discharge or the like during transport of the gas generator 100, and when the male connector of the harness is inserted into the female connector during the assembly stage to the airbag system, contact with its terminal pins (not shown) is released.

[0020] As shown in Figure 1, an igniter 50, which serves as an ignition means for the gas generating agent 31, is positioned at one end of the housing 10 in the axial direction (i.e., the part closer to the holder 20). The igniter 50 and the holder 20 that fixes the igniter 50 function as ignition means that generate a flame for burning the granular gas generating agent 31, which will be described later.

[0021] As shown in Figure 1, the igniter 50 is held in the holder 20 by being inserted into the fitting portion 23 of the holder 20. More specifically, the igniter 50 comprises a base frame through which a pair of terminal pins (not shown) are inserted and held, and a squib cup 51 (cup-shaped member) mounted on the base frame. A resistor (bridge wire) is attached to connect the tips of the terminal pins (not shown) inserted into the squib cup 51, and an igniter is filled into the squib cup 51 so as to surround the resistor or in contact with the resistor. Generally, nichrome wire is used as the resistor, and generally, ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), lead tricinate, etc. are used as the igniter. In addition to the ignition agent, a propeller agent may also be filled into the squib cup 51. Examples of propeller agents that can be placed simultaneously with the ignition agent include compositions consisting of a metal / oxidizing agent 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.

[0022] When a collision is detected, a predetermined amount of current flows through the resistor via terminal pins (not shown). This current generates Joule heat within the resistor, and this heat causes the igniter to begin burning. The resulting high-temperature flame ruptures the squib cup 51 containing the igniter. The time from when current flows through the resistor until the igniter 50 activates is less than 2 milliseconds when a nichrome wire is used for the resistor.

[0023] Furthermore, the squib cup 51 is generally made of metal or resin. A substantially cylindrical member (not shown) that covers the peripheral wall of the squib cup 51 except for the area near the tip may be crimped and fixed to the holder 20 together with the igniter 50 by a crimping portion 24. Here, the substantially cylindrical member is a directional member that directs the flame generated in the igniter 50 when in operation toward the cup-shaped member 32 (bottomed cylindrical member).

[0024] As shown in Figure 1, the internal space of the housing 10 contains a sealed space 10A containing a gas generating agent 31 and a filter 41, which are arranged in parallel in the axial direction of the housing 10.

[0025] The gas generating agent 31 is a composition that generates gas by being ignited by a flame produced by an igniter 50 and then combusted. The gas generating agent 31 is generally formed as a molded body containing a fuel, an oxidizer, and additives. As fuels, for example, triazole derivatives, tetrazole derivatives, guanidine derivatives, azodicarbonamide derivatives, hydrazine derivatives, etc., or combinations thereof can be used. Specifically, for example, nitroguanidine, guanidine nitrate, cyanoguanidine, 5-aminotetrazole, etc., are preferably used. As oxidizers, for example, basic metal nitrates such as basic copper nitrate and basic copper carbonate, perchlorates such as ammonium perchlorate or potassium perchlorate, nitrates containing cations selected from alkali metals, alkaline earth metals, transition metals, and ammonia, etc. As nitrates, for example, sodium nitrate and potassium nitrate, etc., are preferably used. As additives, examples include binders, slag-forming agents, or combustion modifiers. Suitable binders include, for example, cellulose derivatives such as hydroxypropylene methylcellulose, metal salts of carboxymethylcellulose, organic binders such as stearate, and inorganic binders such as synthetic hydroxytalcite and acid clay. Suitable slag-forming agents include silicon nitride, silica, and acid clay. Suitable combustion modifiers include metal oxides, ferrosilicon, activated carbon, and graphite.

[0026] Furthermore, within the housing 10, the space where the gas generating agent 31 is loaded and the space where the AI ​​agent (auto-ignition agent) 33 is provided are separated by a partition member 34.

[0027] Since the AI ​​agent 33 automatically ignites at a lower temperature than the gas generating agent 31, in the event of a fire or other incident in a vehicle equipped with an airbag system or the like that incorporates the gas generator 100, it is possible to prevent the gas generator 100 from malfunctioning due to external heating. Furthermore, the AI ​​agent 33 is held inside the bottom 32b of the cup-shaped member 32 by being sandwiched between the partition member 34 and the cup-shaped member 32. In this way, since the AI ​​agent 33 is held by the cup-shaped member 32 and the partition member 34, no special parts are required to hold the AI ​​agent 33. In addition, the partition member 34 prevents the AI ​​agent 33 from coming into contact with the gas generating agent 31.

[0028] The partition member 34 is a bottomed cylindrical member shorter than the cup-shaped member 32, comprising a cylindrical portion 34a having an opening at the end on the gas generating agent 31 side, and a bottom portion 34b provided to close the end of the cylindrical portion on the filter 41 side. The partition member 34 is press-fitted and fixed to the first cylindrical portion 32a of the cup-shaped member 32. As one modification, the partition member 34 may be inserted into the first cylindrical portion 32a of the cup-shaped member 32 and fixed to the first cylindrical portion 32a by adhesive. Alternatively, the partition member 34 may be a plate member (with an outer circumference shape that follows the shape of the inner wall of the housing 10).

[0029] Furthermore, the partition member 34 is provided with one or more holes (not shown). The size of each hole is predetermined (for example, set by diameter) in order to adjust the amount of flame when the AI ​​agent 33 ignites.

[0030] The coil spring 37 is formed by winding a spiral so that its overall appearance resembles a cylindrical shape. One end of the coil spring 37 surrounds the squib cup 51 and abuts against the crimping portion 24, while the other end, which is formed in a spiral shape, abuts against the gas generating agent 31, thereby biasing the gas generating agent 31 with elastic force. Due to this biasing force, the gas generating agent 31 is fixed within the housing 10 by being sandwiched between the coil spring 37 and the partition member 34. Furthermore, since the coil spring 37 as a whole has a cylindrical shape that follows the shape of the squib cup 51 from the igniter 50 side to the gas generating agent 31 side, it is possible to easily direct the direction of the flame emitted from the igniter 50 towards the gas generating agent 31.

[0031] The cup-shaped member 32 is a short, bottomed cylindrical member that closes the end of the filter 41 on the gas generating agent 31 side, and comprises a first cylindrical portion 32a, a bottom portion 32b that closes the end of the first cylindrical portion 32a on the filter 41 side, a second cylindrical portion 32c with a larger diameter than the first cylindrical portion 32a, and an annular connecting portion 32d that connects the first cylindrical portion 32a and the second cylindrical portion 32c. The first cylindrical portion 32a, the connecting portion 32d, and the second cylindrical portion 32c form a stepped shape in cross-section. The bottom portion 32b is melted or damaged by the gas generated during operation. The cup-shaped member 32 is made of, for example, a metal such as stainless steel or iron, or an alloy such as an aluminum alloy or stainless steel alloy. Furthermore, the cup-shaped member 32 is fixed to the housing 10 by forming an annular welded portion 35 from the outside of the housing 10 by laser welding (through welding) or the like, so that the filter 41 can be positioned at a predetermined position (for example, a position facing the gas nozzle 11 as shown in Figure 1). Here, the first cylindrical portion 32a may be relatively thick (for example, thicker than the cylindrical portion 34a). This prevents deformation of the first cylindrical portion 32a even when the partition member 34 is press-fitted into the first cylindrical portion 32a.

[0032] As described above, by welding and fixing the cup-shaped member 32 to the housing 10, the generated gas can be bypassed between the inner wall of the housing 10 and the outer circumference of the filter 41 and prevented from leaking out to the gas outlet 11, while also ensuring a seal. In other words, the cup-shaped member 32 allows the gas generated on the igniter 50 side inside the housing 10 to flow into the filter 41 side through a portion that has been opened by melting or damage at the bottom 32b (a portion corresponding to one end of the hollow portion 41a).

[0033] The filter 41 consists of a cylindrical member having a columnar (for example, roughly cylindrical, roughly rectangular, etc.) hollow portion 41a in the center. By using a filter 41 made of a cylindrical member, the flow resistance of the working gas flowing during operation is kept low, enabling efficient gas flow. The filter 41 can be made of, for example, wire made of metal such as stainless steel or iron, or a mesh material that has been wound or compressed by pressing. Specifically, knitted wire mesh, plain woven wire mesh, or an assembly of crimped metal wire can be used. The filter 41 functions as a cooling means to cool the gas by removing the high temperature heat from the gas as it passes through the filter 41, which is generated in the housing 10, and also functions as a removal means to remove slag and other substances contained in the gas. As one modification of the filter 41, a filter having a labyrinthine flow path formed by combining roughly cylindrical or mortar-shaped parts made of metal may be used. This allows the path of the working gas to be changed in various directions, making it possible to cool the gas and remove slag.

[0034] Furthermore, in the embodiments of the present invention described above, an example was given in which a filter made of so-called knitted wire mesh was used. However, it is also possible to use a filter made by winding perforated metal or expanded metal instead. Here, perforated metal refers to a metal plate in which only openings are provided (i.e., no protrusions are provided around the periphery of the openings), and expanded metal refers to a metal plate in which openings are provided in a mesh-like structure by, for example, making cuts in a staggered pattern on a metal plate and then expanding it. Even when such perforated metal or expanded metal is used in place of the knitted wire mesh described above, the same effects as those described in the embodiments of the present invention described above can be obtained.

[0035] Furthermore, in the perforated metal and expanded metal described above, a filter consisting of a laminate is constructed by winding a single metal plate-shaped member, but the structure of the filter is not limited to this structure. That is, each layer may be made of a separate metal plate-shaped member and these may be combined to form a laminate filter, or some of the layers may be formed by winding a single metal plate-shaped member, and the remaining layers may be formed by winding another single metal plate-shaped member, and these may be combined to form a laminate filter.

[0036] Next, the operation of the gas generator 100 during normal operation, as described above, will be explained. When a vehicle equipped with an airbag system incorporating the gas generator 100 in this embodiment is involved in a collision, the collision is detected by a collision detection means separately provided in the vehicle, and the igniter 50 is activated based on this. When the igniter 50 is activated, the pressure inside the igniter 50 increases due to the combustion of the igniter, causing the tip of the squib cup 51 of the igniter 50 to rupture, and the flame flows out from the tip of the squib cup 51 of the igniter 50 towards the cup-shaped member 32 inside the housing 10.

[0037] The flames that flow in in this way ignite and burn the gas generating agent 31 inside the housing 10, generating a large amount of gas. The combustion of this gas generating agent 31 increases the pressure inside the space 10A in the housing 10, and the generated gas passes through the holes provided in the partition member 34, melting or damaging the portion of the cup-shaped member 32 corresponding to the hollow portion 41a at the bottom 32b, causing it to rupture and flow into the hollow portion 41a. The generated gas is then ejected from the gas outlet 11 to the outside of the gas generator 100 via the filter 41, but because 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 airbag, causing it to inflate and deploy.

[0038] Next, the operation of the gas generator 100 during emergency activation, as described above, will be explained. In the event of a fire or other incident in a vehicle equipped with an airbag system incorporating the gas generator 100 in this embodiment, and the inside of the gas generator 100 reaches a predetermined high temperature, the AI ​​agent 33 ignites, igniting and burning the gas generating agent 31 to generate gas. Due to the gas pressure inside the housing 10, the generated gas melts or damages the portion of the cup-shaped member 32 corresponding to the hollow portion 41a at the bottom 32b, causing it to rupture and flow into the hollow portion 41a. Subsequently, the generated gas is ejected to the outside of the gas generator 100 from the gas outlet 11 via the filter 41. As 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 airbag, causing it to inflate and deploy.

[0039] (Main features of the gas generator 100) According to this embodiment, the gas generator 100 can be made in which the sealing performance between the first cylindrical portion 32a of the cup-shaped member 32 and the inner wall of the housing 10 is ensured by welding. In addition, since excess material is less likely to be created by welding, the partition member 34 is easier to press-fit into the cup-shaped member 32, and the partition member 34 is easier to attach and fix to the cup-shaped member 32. Furthermore, when the partition member 34 is press-fitted into the first cylindrical portion 32a of the cup-shaped member 32, the gas generator 100 can be made in which the partition member 34 is less likely to come off the cup-shaped member 32.

[0040] Furthermore, when the partition member 34 is press-fitted into the first cylindrical portion 32a of the cup-shaped member 32, the press-fitting load of the partition member 34 remains stable regardless of the welding condition, thus preventing cracking (damage) of the AI ​​agent 33 due to excessive load on the AI ​​agent 33.

[0041] Furthermore, since there is no need to use specially shaped and highly rigid parts to avoid deformation of the partition member 34 and excess weld during through-welding, the parts can be made of simpler shapes, resulting in improved assembly efficiency and lower parts costs compared to conventional methods.

[0042] Furthermore, when the partition member 34 is press-fitted into the first cylindrical portion 32a of the cup-shaped member 32, making the first cylindrical portion 32a relatively thick (for example, thicker than the cylindrical portion 34a of the partition member 34) can suppress deformation of the cup-shaped member 32 during press-fitting, and even if there is vibration, it is possible to better prevent the partition member 34 from coming off the cup-shaped member 32, thereby better retaining the AI ​​agent 33.

[0043] Although embodiments of the present invention have been described above with reference to the drawings, it should be understood that the specific configuration is not limited to these embodiments. The scope of the present invention is indicated by the claims rather than the above description of embodiments, and further includes all modifications within the meaning and scope equivalent to the claims.

[0044] For example, the coil spring 37 in the above embodiment does not necessarily have to be provided. Also, the coil spring may be any elastic body. For example, a leaf spring may be used, or a rubber member with relatively high heat resistance may be used.

[0045] Also, the filter 41 in the above embodiment does not necessarily have to be provided and may be provided as needed.

[0046] 10 Housing 10A Space 11 Gas jet outlet 12 Blocking member 13, 22, 35 Welded part 20 Holder 21, 23 Fitting part 24 Caulked part 31 Gas generating agent 32 Cup-shaped member 32a First cylindrical part 32b, 34b Bottom part 32c Second cylindrical part 32d Connection part 33 AI agent 34 Partition member 34a Cylindrical part 37 Coil spring 41 Filter 41a Hollow part 50 Igniter 51 Squib cup 60 Retainer 100 Gas generator

Claims

1. A long cylindrical housing containing a gas generating agent that generates gas when burned, and having a gas outlet formed therein for ejecting the gas; an igniter capable of igniting and burning the gas generating agent; a holder that holds a part of the igniter and is fixed to one end of the housing in the axial direction; a closing member fixed to the other end of the housing in the axial direction; an auto-igniter provided inside the housing that ignites at a lower temperature than the gas generating agent; a partition member provided inside the housing that separates the gas generating agent from the auto-igniter; a bottomed cylindrical member provided inside the housing, having a first cylindrical portion with a bottom at one end; a second cylindrical portion with a larger diameter than the first cylindrical portion and welded and fixed to the housing at the other end of the first cylindrical portion; and an annular connecting portion connecting the first cylindrical portion and the second cylindrical portion, and holding the auto-igniter disposed at the bottom together with the partition member disposed inside the first cylindrical portion. A gas generator characterized by having the following features.

2. The gas generator according to claim 1, characterized in that the partition member is press-fitted against the inner wall of the first cylindrical portion.

3. The gas generator according to claim 1, wherein the partition member is a member having a bottom portion and a cylindrical portion, the bottom portion of the partition member is in contact with the auto-ignition agent, and the cylindrical portion of the partition member is press-fitted against the inner wall of the first cylindrical portion.

4. The gas generator according to claim 3, characterized in that the wall thickness of the first cylindrical portion is greater than the wall thickness of the cylindrical portion of the partition member.

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