Gas generator

Abstract

To provide a gas generator which permits weight-reduction and reduction of production cost while maintaining preferable gas output characteristics.SOLUTION: A gas generator 1A includes an igniter 40 assembled onto one end part of a housing, a gas generation agent 60 stored on an inner part of the housing and a coil spring 70 which is interposed between the above described one end part of the housing and the gas generation agent 60. The coil spring 70 separates the gas generation agent 60 from the igniter 40, at the same time, energizes the gas generating agent while turning this to the other end part side of the housing and, thereby, fixes the gas generation agent 60 onto the inner part of the housing. The coil spring 70 is arranged onto an axis approximately same with the ignition part 41 so as to surround the ignition part 41 without interposition of another member between the coil spring and the ignition part 41 so that an opening degree of a cup body 41c when the cup body 41c contained in the ignition part 41 of the igniter 40 is opened is regulated by the coil spring 70.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a gas generator to be incorporated in an airbag device as an occupant protection device equipped in an automobile or the like, and in particular to a so-called cylindrical gas generator having an elongated cylindrical outer shape which can be suitably incorporated in a side airbag device or the like. [Background technology]

[0002] Conventionally, airbag devices, which are passenger protection devices, have become widespread from the viewpoint of protecting passengers in automobiles, etc. Airbag devices are installed for the purpose of protecting passengers from impacts that occur when a vehicle or the like crashes, and the airbag instantly inflates and deploys when a vehicle or the like crashes, so that the airbag acts as a cushion to receive the body of the passenger.

[0003] The gas generator is a device incorporated into the airbag device. When a vehicle crashes, an igniter is ignited by electrical current from a control unit. The flame produced in the igniter burns a gas generating agent, instantly generating a large amount of gas, which inflates and deploys the airbag.

[0004] There are gas generators of various configurations based on the specifications of the installation position relative to the vehicle, output, etc. One of them is called a cylinder-type gas generator. The cylinder-type gas generator has a long cylindrical outer shape and is suitably incorporated into a side airbag device, a curtain airbag device, a knee airbag device, a seat cushion airbag device, etc.

[0005] Typically, in a cylinder-type gas generator, an igniter is attached to one axial end of a housing, and a combustion chamber containing a gas generating agent is provided on the one end side, a filter chamber containing a filter is provided on the other axial end side of the housing, and a gas outlet is provided on the peripheral wall of the housing in a part that defines the filter chamber.

[0006] In a cylindrical gas generator configured in this manner, gas generated in the combustion chamber flows into the filter chamber along the axial direction of the housing, passing through the inside of the filter, and the gas after passing through the filter is ejected to the outside via the gas outlet.

[0007] Incidentally, an example of a document disclosing a cylinder-type gas generator having this configuration is JP 2017-193191 A (Patent Document 1).

[0008] Here, in the cylinder-type gas generator disclosed in Patent Document 1, a coil spring is provided between the one end of the housing to which the igniter is assembled and the gas generating agent, for urging the gas generating agent toward the other end of the housing. The coil spring is for fixing the gas generating agent inside the housing while maintaining an appropriate distance from the igniter assembled to the one end of the housing to the gas generating agent.

[0009] In the gas generator disclosed in Patent Document 1, a substantially cylindrical metallic combustion control cover is provided on the one end side of the housing so as to cover the ignition part of the igniter, which is the part that contains the ignition charge. The combustion control cover is for efficiently guiding the thermal particles generated by the igniter during operation to the gas generating agent, and more specifically, for imparting directionality to the traveling direction of the thermal particles generated by the ignition part.

[0010] By using a cylindrical gas generator having such a configuration, it is possible to obtain good gas output characteristics during operation. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2017-193191 A Summary of the Invention [Problem to be solved by the invention]

[0012] However, in the case of a cylindrical gas generator having the above-mentioned configuration, it is necessary to provide a large number of parts at the above-mentioned one end side portion of the housing, which not only increases the number of parts but also complicates the assembly work, resulting in a problem of increased manufacturing costs. Furthermore, if the number of parts can be reduced, the weight of the gas generator as a whole can be reduced accordingly.

[0013] Therefore, the present invention has been made in consideration of the above-mentioned problems, and has an object to provide a gas generator that enables weight reduction and reduction in manufacturing costs while maintaining good gas output characteristics. [Means for solving the problem]

[0014] A gas generator according to the present invention includes a housing, a gas generating agent, an igniter, and a coil spring. The housing is a long cylindrical member having a peripheral wall portion whose one end and the other end in the axial direction are closed. The gas generating agent is accommodated inside the housing. The igniter has an ignition portion in which an ignition charge for burning the gas generating agent is accommodated, and is attached to the one end of the housing so that the ignition portion is positioned to project toward the inside of the housing. The coil spring is interposed between the one end of the housing and the gas generating agent, and fixes the gas generating agent inside the housing by biasing the gas generating agent toward the other end side of the housing while separating the gas generating agent from the ignition portion. The ignition portion includes a cup body that is cleaved by ignition of the ignition charge when the igniter is activated. In the gas generator based on the present invention, the coil spring is arranged approximately coaxially with the ignition portion so as to surround the ignition portion without any other member being interposed between the coil spring and the ignition portion, so that the degree of opening of the cup body when the cup body is ruptured is regulated by the coil spring.

[0015] In the gas generator according to the present invention, the outer shape of the ignition part may be substantially cylindrical, and the coil spring may include a cylindrical part located on the one end side of the housing and having a constant inner diameter, and a diameter-expanded part extending from the end of the cylindrical part on the gas generating agent side toward the gas generating agent side and having an increasing inner diameter as it approaches the gas generating agent. In that case, it is preferable that the coil spring in the part surrounding the igniter is constituted by the cylindrical part.

[0016] In the gas generator according to the present invention, when the inner diameter of the peripheral wall part of the housing in the part where the gas generating agent is accommodated is R1, the outer diameter of the ignition part is R2, the distance along the axial direction of the housing from the part where the ignition charge is accommodated in the ignition part to the gas generating agent is L1, the distance along the axial direction of the housing from the part where the ignition charge is accommodated in the ignition part to the boundary between the cylindrical part and the diameter-expanded part is L2, and the clearance between the ignition part and the cylindrical part is C, it is preferable that the condition of 0 < C ≦ (R1 - R2) × (L2 / L1) / 2 is satisfied.

[0017] In the gas generator according to the present invention, it is preferable that the clearance is 1.0 mm or less.

[0018] In the gas generator according to the present invention, the part of the coil spring surrounding the ignition part may be in contact with the ignition part.

Effect of the Invention

[0019] According to the present invention, it is possible to provide a gas generator capable of achieving weight reduction and reduction of manufacturing cost while maintaining good gas output characteristics.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic view of a cylinder type gas generator according to Embodiment 1. [Diagram 2]2 is an enlarged cross-sectional view of the vicinity of an igniter of the cylinder-shaped gas generator shown in FIG. 1. [Diagram 3] 2 is an enlarged cross-sectional view of the vicinity of a partition member of the cylinder-shaped gas generator shown in FIG. 1. [Figure 4] FIG. 4 is a view for explaining a preferable range of clearance in the cylinder-shaped gas generator according to the first embodiment. [Diagram 5] 11 is an enlarged cross-sectional view of the vicinity of an igniter of a cylinder-shaped gas generator according to a second embodiment. FIG. [Figure 6] 11 is an enlarged cross-sectional view of the vicinity of an igniter of a cylinder-shaped gas generator according to a third embodiment. FIG. [Figure 7] 10 is an enlarged cross-sectional view of the vicinity of an igniter of a cylinder-shaped gas generator according to a fourth embodiment. FIG. [Figure 8] 1 is a table showing test conditions and test results of a verification test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The embodiment shown below illustrates a case where the present invention is applied to a cylinder-type gas generator incorporated in a side airbag device. In the embodiment shown below, the same or common parts are given the same reference numerals in the drawings, and the description thereof will not be repeated.

[0022] (Embodiment 1) Fig. 1 is a schematic diagram of a cylinder-shaped gas generator according to embodiment 1. Figs. 2 and 3 are enlarged sectional views of the vicinity of an igniter and the vicinity of a partition member, respectively, of the cylinder-shaped gas generator shown in Fig. 1. First, with reference to Figs. 1 to 3, the configuration of cylinder-shaped gas generator 1A according to the present embodiment will be described.

[0023] 1, cylinder-shaped gas generator 1A according to this embodiment has a long, cylindrical outer shape and has a long, cylindrical housing with one axial end and the other end closed. The housing includes housing main body 10, holder 20, and closing member 30.

[0024] The housing, which is constituted by the housing main body 10, the holder 20, and the closing member 30, contains internal components such as an igniter 40, a partition member 50, a gas generating agent 60, a coil spring 70, and a filter 80. Also, the housing contains a combustion chamber S1 in which the gas generating agent 60, one of the internal components described above, is mainly disposed, and a filter chamber S2 in which the filter 80 is disposed.

[0025] The housing body 10 constitutes the peripheral wall of the housing and is made of a long cylindrical member with openings formed at both axial ends. The holder 20 is made of a tubular member having a through-hole 21 extending in the same direction as the axial direction of the housing body 10, and has an annular groove 22 for crimping on its outer circumferential surface, which will be described later. The closing member 30 is made of a disk-shaped member having a predetermined thickness, and has an annular groove 31 for crimping on its outer circumferential surface, which will be described later. These annular grooves 22, 31 for crimping are both formed on the outer circumferential surface of the holder 20 and the peripheral surface of the closing member 30 so as to extend in the circumferential direction.

[0026] The housing body 10 may be made of a metal member such as stainless steel, iron steel, aluminum alloy, stainless alloy, etc., or may be made of a press-formed product formed into a cylindrical shape by pressing a rolled steel plate such as SPCE. The housing body 10 may also be made of an electric resistance welded pipe such as STKM.

[0027] In particular, when the housing body 10 is constructed from a press-formed rolled steel plate or an electric resistance welded pipe, the housing body 10 can be formed more cheaply and easily than when metal components such as stainless steel or steel are used, and the weight can be significantly reduced.

[0028] On the other hand, the holder 20 and the blocking member 30 are made of metal members such as stainless steel, iron steel, aluminum alloy, stainless alloy, or the like.

[0029] The holder 20 is fixed to the housing body 10 so as to close one axial open end of the housing body 10. Specifically, with the holder 20 inserted into the one open end of the housing body 10, a portion of the housing body 10 corresponding to an annular groove portion 22 provided on the outer circumferential surface of the holder 20 is reduced in diameter radially inward and engaged with the annular groove portion 22, thereby crimping and fixing the holder 20 to the housing body 10. As a result, one axial end of the housing is constituted by the holder 20.

[0030] The closing member 30 is fixed to the housing body 10 so as to close the other axial opening end of the housing body 10. Specifically, with the closing member 30 inserted into the other opening end of the housing body 10, a portion of the housing body 10 corresponding to annular groove portion 31 provided on the circumferential surface of the closing member 30 is reduced in diameter radially inward and engaged with the annular groove portion 31, thereby crimping and fixing the closing member 30 to the housing body 10. As a result, the other axial end of the housing is constituted by the closing member 30.

[0031] These crimping fixations are called eight-way crimping, which reduces the diameter of the housing body 10 almost uniformly inward in the radial direction. By performing this eight-way crimping, the housing body 10 is provided with crimped portions 12 and 13. As a result, the crimped portions 12 and 13 come into direct contact with the annular grooves 22 and 31, respectively, preventing the occurrence of gaps between them.

[0032] The assembly structure of the holder 20 and the closing member 30 to the housing main body 10 is not limited to the above-mentioned assembly structure, and other assembly structures may be adopted. Also, the housing main body 10 and the closing member 30 may not be separate bodies, but may be configured as one member having a bottomed cylindrical shape.

[0033] 1 and 2, the igniter 40 is mounted to the one end in the axial direction of the housing by being supported by the holder 20. The igniter 40 is for burning the gas generating agent 60, and is installed so as to face the space inside the housing.

[0034] The igniter 40 includes an ignition section 41 and a pair of terminal pins 42. The ignition section 41 includes an ignition charge 41a, a plug 41b, and a cup body 41c, and the ignition charge 41a is accommodated in the ignition section 41 by being disposed in a space defined by the plug 41b and the cup body 41c. A resistor (bridge wire) is attached inside the ignition section 41 so as to connect to the pair of terminal pins 42, and the ignition section 41 is filled with an ignition charge 41a so as to surround the resistor or to be in contact with the resistor. A transfer charge may be loaded into the ignition section 41 as necessary.

[0035] Here, the resistor is generally a nichrome wire or a resistance wire made of an alloy containing platinum and tungsten, and the ignition charge is generally ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), lead tricinate, etc. The transfer charge is generally a composition made of metal powder / oxidizer, such as B / KNO3, B / NaNO3, Sr(NO3)2, etc., a composition made of titanium hydride / potassium perchlorate, or a composition made of B / 5-aminotetrazole / potassium nitrate / molybdenum trioxide. The cup body 41c provided in the ignition unit 41 includes a metal cup.

[0036] When a collision is detected, a predetermined amount of current flows through the resistor via the terminal pin 42. When a predetermined amount of current flows through the resistor, Joule heat is generated in the resistor, and the ignition charge 41a starts to burn. High-temperature heat particles generated by the combustion split open the cup body 41c that contains the ignition charge 41a. The time from when the current flows through the resistor to when the igniter 40 is activated is generally 2 milliseconds or less when a nichrome wire is used for the resistor.

[0037] The igniter 40 is fixed to the holder 20 by a crimping portion 23 provided on the holder 20. More specifically, the holder 20 has the crimping portion 23 for crimping and fixing the igniter 40 at an axial end portion facing the space inside the housing, and the igniter 40 is inserted into the through-hole 21 and abutted against a wall portion of a portion of the holder 20 that defines the through-hole 21, and the above-mentioned crimping portion 23 is crimped in such a state that the igniter 40 is clamped and fixed to the holder 20.

[0038] As a result, the igniter 40 is attached to the holder 20 so that the ignition portion 41 is positioned to protrude toward the inside of the housing. Therefore, when the igniter 40 is activated, the ignition charge 41a is ignited, causing the cup body 41c to split, and the cup body 41c opens along with the split.

[0039] Here, a seal member 25 made of an O-ring or the like is interposed between the holder 20 and the igniter 40, and the gap between the holder 20 and the igniter 40 is filled with the seal member 25 to seal the gap. Therefore, by configuring in this way, it is possible to ensure airtightness in the relevant portion. Note that the method of fixing the igniter 40 is not limited to the fixing method using the crimping portion 23 described above, and other fixing methods may be used.

[0040] A recess 24 is provided at the axial end portion exposed to the outside of the holder 20, which is continuous with the above-mentioned through-hole 21. The recess 24 forms a female connector portion that receives a male connector (not shown) of a harness for connecting the igniter 40 to a control unit (not shown), and a portion of the terminal pin 42 of the igniter 40 near the tip is exposed and positioned within the recess 24. A male connector is inserted into the recess 24 as the female connector portion, thereby achieving electrical continuity between the core wire of the harness and the terminal pin 42.

[0041] 1 and 3, a partition member 50 is disposed at a predetermined position in the space inside the housing. The partition member 50 is a member for dividing the space inside the housing in the axial direction into a combustion chamber S1 and a filter chamber S2.

[0042] The partition member 50 has a generally cylindrical shape with a bottom, and is made of a metal member such as stainless steel, iron or steel, an aluminum alloy, or a stainless alloy. The partition member 50 has a flat partition wall portion 51 arranged perpendicular to the axial direction of the housing body 10, and a cylindrical plate-like annular wall portion 52 standing on the periphery of the partition wall portion 51. The partition member 50 is arranged so that the outer main surface of the partition wall portion 51 abuts against the filter 80, and the outer peripheral surface of the annular wall portion 52 abuts against the inner peripheral surface of the housing body 10.

[0043] A score 51a is provided on the main surface of the partition wall portion 51 that contacts the filter 80. The score 51a is for allowing the partition wall portion 51 to break and form an opening as the internal pressure of the combustion chamber S1 increases due to combustion of the gas generating agent 60, and is composed of, for example, a plurality of grooves provided radially so as to intersect with each other. The score 51a is provided in a portion of the filter 80 that faces the hollow portion 81.

[0044] An annular groove extending in the circumferential direction is provided on the peripheral edge of partition wall portion 51, which is the boundary with annular wall portion 52. An O-ring 53 is housed in this annular groove. With this configuration, O-ring 53 is interposed between partition member 50 and housing body 10, and is in pressure contact with both partition member 50 and housing body 10.

[0045] As a result, the gap between the partition member 50 and the housing body 10 is filled with the O-ring 53. Therefore, the gap is sealed by the O-ring 53, and airtightness in that portion can be ensured.

[0046] The partition member 50 is fixed to the housing body 10 while being inserted into the housing body 10. More specifically, the partition member 50 is press-fitted into the housing body, whereby the annular wall portion 52 of the partition member 50 is in pressure contact with the housing body 10. Therefore, the partition member 50 is fixed to the housing body 10 by the elastic restoring force of the annular wall portion 52.

[0047] As shown in FIGS. 1 to 3, within the space inside the housing, a gas generating agent 60 and a coil spring 70 are disposed in a space sandwiched between the holder 20 and the partition member 50 (that is, the combustion chamber S1).

[0048] The gas generating agent 60 is an agent that generates gas by being ignited and burned by thermal particles generated by the activation of the igniter 40. As the gas generating agent 60, it is preferable to use a non-azide gas generating agent, and the gas generating agent 60 is generally configured as a molded body containing a fuel, an oxidizer, and an additive.

[0049] The fuel may be, for example, a triazole derivative, a tetrazole derivative, a guanidine derivative, an azodicarbonamide derivative, a hydrazine derivative, or a combination of these. Specifically, for example, nitroguanidine, guanidine nitrate, cyanoguanidine, 5-aminotetrazole, or the like is preferably used.

[0050] Examples of the oxidizing agent include basic metal salts such as basic copper nitrate and basic copper carbonate, perchlorates such as ammonium perchlorate and potassium perchlorate, and nitrates containing a cation selected from alkali metals, alkaline earth metals, transition metals, and ammonia. Examples of the nitrates that are preferably used include sodium nitrate and potassium nitrate.

[0051] Examples of additives include binders, slag formers, and combustion control agents. As binders, for example, organic binders such as metal salts of carboxymethylcellulose and stearates, and inorganic binders such as synthetic hydrotalcite and acid clay can be suitably used. As slag formers, silicon nitride, silica, acid clay, etc. can be suitably used. As combustion control agents, metal oxides, ferrosilicon, activated carbon, graphite, etc. can be suitably used.

[0052] The shape of the molded body of the gas generating agent 60 may be granular, pellet-like, cylindrical, or other granular, or disk-like. In addition, for cylindrical molded bodies, perforated molded bodies having through holes inside the molded body (for example, a single-hole cylindrical shape or a multi-hole cylindrical shape) may also be used. These shapes are preferably selected appropriately according to the specifications of the airbag device in which the cylindrical gas generator 1A is incorporated, and it is preferable to select an optimal shape according to the specifications, such as a shape in which the gas generation rate changes over time when the gas generating agent 60 is burned. In addition to the shape of the gas generating agent 60, it is preferable to appropriately select the size and filling amount of the molded body taking into consideration the linear burning rate and pressure exponent of the gas generating agent 60.

[0053] 1 and 2, a coil spring 70 is disposed in a space of the combustion chamber S1 that is located closer to the holder 20 than the gas generating agent 60. The coil spring 70 is formed by bending a metal wire, and includes a cylindrical portion 71, an expanded diameter portion 72, and a pressing portion 73.

[0054] Cylindrical portion 71 is configured by winding a metal wire in a spiral shape so that the inner diameter is constant, and thus has a generally cylindrical shape as a whole. Cylindrical portion 71 is located on the holder 20 side (i.e., the above-mentioned one end side of the housing), and one axial end of the cylindrical portion 71 abuts against holder 20 and / or igniter 40.

[0055] The expanded diameter portion 72 is formed by winding a metal wire in a spiral shape so that the inner diameter increases toward the gas generating agent 60 side, and thus has an overall hollow, generally truncated cone shape. The expanded diameter portion 72 extends from the other axial end (i.e., the end on the gas generating agent 60 side) of the cylindrical portion 71 toward the gas generating agent 60 side. The outer diameter of the end of the expanded diameter portion 72 on the gas generating agent 60 side is configured to be roughly the same as the inner diameter of the housing body 10 or slightly smaller than that.

[0056] The pressing portion 73 is located at the end of the enlarged diameter portion 72 on the gas generating agent 60 side, and is configured to have a generally disk-like shape as a whole, for example, by arranging metal wires substantially in parallel at a predetermined interval, or by arranging metal wires in a spiral shape at a predetermined interval. This pressing portion 73 is in contact with the gas generating agent 60.

[0057] The coil spring 70 is disposed so as to surround the ignition portion 41 of the igniter 40, which has a substantially cylindrical outer shape. That is, the coil spring 70 is disposed substantially coaxially with the ignition portion 41 so as to surround the ignition portion 41 without any other member being interposed between the coil spring 70 and the ignition portion 41. As a result, the side surface of the ignition portion 41 is surrounded by a part of the cylindrical portion 71 of the coil spring 70, and the space located between the ignition portion 41 and the gas generating agent 60 is surrounded by the remaining part of the cylindrical portion 71 of the coil spring 70 and the expanded diameter portion 72.

[0058] Here, the coil spring 70 is in a compressed state by being sandwiched between the holder 20 and / or the igniter 40 and the gas generating agent 60. Therefore, the gas generating agent 60 is elastically biased by the coil spring 70 toward the partition member 50 side (i.e., the above-mentioned other end side of the housing), thereby preventing the gas generating agent 60 from moving inside the housing. Therefore, by configuring in this way, it is possible to prevent the gas generating agent 60 made of a molded body from being crushed by vibration or the like.

[0059] In addition, when the coil spring 70 is assembled, the coil spring 70 is sandwiched and compressed between the holder 20 and / or the igniter 40 and the gas generating agent 60, so that the dimensional variations of the various components housed inside the housing can be absorbed by the coil spring 70.

[0060] Furthermore, by appropriately setting the axial length of the coil spring 70, it is possible to appropriately ensure the distance from the igniter 40 attached to one end of the housing to the gas generating agent 60. Therefore, when the igniter 40 is activated, the cleavage of the cup body 41c of the ignition portion 41 is not hindered by the gas generating agent 60, so that the gas generating agent 60 can be ignited early and reliably.

[0061] In addition, in cylinder-shaped gas generator 1A according to the present embodiment, as described above, ignition portion 41 and the space between ignition portion 41 and gas generating agent 60 are surrounded by coil spring 70, so that when cup body 41c of ignition portion 41 is cleaved open upon activation of igniter 40, the degree to which cup body 41c is opened is regulated by coil spring 70. As a result, it becomes possible to impart directionality to the thermal particles generated in ignition portion 41, the details of which will be described later.

[0062] 1, within the space inside the housing, a filter 80 is disposed in a space sandwiched between the blocking member 30 and the partition member 50 (i.e., filter chamber S2). The filter 80 is made of a cylindrical member having a hollow portion 81 extending in the same direction as the axial direction of the housing body 10, with one axial end face abutting against the blocking member 30 and the other axial end face abutting against the partition member 50.

[0063] The filter 80 functions as a cooling means for cooling the gas by removing the high temperature heat of the gas generated by the combustion of the gas generating agent 60 as the gas passes through the filter 80, and also functions as a removal means for removing slag (residue) and the like contained in the gas. By using the filter 80 made of a cylindrical member as described above, the flow resistance to the gas flowing through the filter chamber S2 during operation is kept low, making it possible to realize an efficient gas flow.

[0064] The filter 80 may be made of an assembly of metal wires or metal mesh materials, preferably made of stainless steel, steel, etc. Specifically, a knitted wire mesh, a plain woven wire mesh, an assembly of crimped woven metal wires, or a combination of these compressed by a press may be used.

[0065] Also, a perforated metal sheet wound around the filter 80 can be used. In this case, the perforated metal sheet can be, for example, an expanded metal sheet made by cutting a metal sheet in a zigzag pattern and expanding the cuts to form holes and process it into a mesh-like shape, or a hook metal sheet made by drilling holes in a metal sheet and flattening the metal sheet by crushing burrs that are generated around the edges of the holes.

[0066] A portion of the housing body 10 that defines the filter chamber S2 is provided with a plurality of gas outlets 11 arranged in the circumferential and axial directions. These gas outlets 11 are for directing the gas that has passed through the filter 80 to the outside of the housing.

[0067] Next, with reference to FIG. 1, an operation during operation of cylinder-shaped gas generator 1A according to the present embodiment will be described.

[0068] Referring to FIG. 1, when a vehicle equipped with a cylinder-shaped gas generator 1A according to this embodiment collides, the collision is detected by a collision detection means provided separately in the vehicle, and based on this, igniter 40 is activated by the passage of electricity from a control unit provided separately in the vehicle.

[0069] When the igniter 40 is activated, the pressure inside the ignition section 41 increases due to the combustion of the ignition charge 41a or, in addition, the transfer charge, causing the cup body 41c of the ignition section 41 to split open, and the thermal particles generated by the combustion of the ignition charge 41a flow out to the outside of the ignition section 41.

[0070] The thermal particles flowing out from the ignition portion 41 are given directionality by the above-mentioned coil spring 70, and thus reach the gas generating agent 60. The thermal particles reaching the gas generating agent 60 combust the gas generating agent 60, thereby generating a large amount of gas in the combustion chamber S1.

[0071] When a large amount of gas is generated in the combustion chamber S1, the pressure and temperature of the combustion chamber S1 rise, and when the internal pressure of the combustion chamber S1 reaches a predetermined pressure, a break occurs in the portion of the partition member 50 where the score 51a is provided. As a result, a communication hole is formed in the partition member 50 in the portion facing the hollow portion 81 of the filter 80, and the combustion chamber S1 and the filter chamber S2 are in communication with each other via the communication hole.

[0072] Accordingly, gas generated in the combustion chamber S1 flows into the filter chamber S2 through the communication holes formed in the partition member 50. The gas that flows into the filter chamber S2 flows in the axial direction through the hollow portion 81 of the filter 80, then turns toward the radial direction and flows through the inside of the filter 80. At that time, the filter 80 removes heat to cool the gas, and the filter 80 removes slag contained in the gas.

[0073] Then, the gas after passing through filter 80 is ejected to the outside of the housing through gas outlet 11. The gas ejected from gas outlet 11 is introduced into the inside of an airbag provided adjacent to cylindrical gas generator 1A, and inflates and deploys the airbag.

[0074] As described above, in cylinder-shaped gas generator 1A according to the present embodiment, coil spring 70 interposed between one axial end of the housing (i.e., holder 20) and gas generating agent 60 is disposed approximately coaxially with ignition portion 41 so as to surround ignition portion 41 of igniter 40 without any other member being interposed between the coil spring 70 and ignition portion 41. Furthermore, coil spring 70 surrounds not only ignition portion 41 of igniter 40, but also the space between ignition portion 41 and gas generating agent 60.

[0075] With this configuration, firstly, since the ignition portion 41 is surrounded by the cylindrical portion 71 of the coil spring 70, when the cup body 41c of the ignition portion 41 is cleaved, it is possible to suppress the side wall portion of the cup body 41c from cleaving or the side wall portion from deforming outward. Therefore, it is possible to make it possible to form an opening mainly at the tip portion, which is the portion of the cup body 41c located on the gas generating agent 60 side.

[0076] Secondly, when the cup body 41c of the ignition part 41 is split open to form an opening at the tip of the cup body 41c, the open part of the cup body 41c comes into contact mainly with the enlarged diameter part 72 of the coil spring 70, and the open part of the cup body 41c is prevented from deforming further outward. Therefore, the enlarged diameter part 72 of the coil spring 70 and the open part of the cup body 41c function as a kind of guide that determines the direction of travel of the thermal particles.

[0077] Therefore, the traveling direction of the thermal particles generated in the ignition portion 41 is narrowed to the axial direction of the housing main body 10, and the thermal particles can be efficiently guided to the gas generating agent 60. Therefore, the coil spring 70 not only functions to fix the gas generating agent 60 inside the housing, but also functions to efficiently guide the thermal particles generated in the igniter 40 during activation to the gas generating agent 60, eliminating the need for a member such as a combustion control cover that was previously required.

[0078] In this way, by using cylinder-shaped gas generator 1A according to the present embodiment, it is possible to reduce the number of parts compared to conventional techniques, which not only simplifies the assembly work but also reduces the weight of the gas generator as a whole. Therefore, it is possible to achieve both weight reduction and reduced manufacturing costs while maintaining good gas output characteristics.

[0079] In order to efficiently guide the thermal particles generated in the ignition portion 41 to the gas generating agent 60, it is necessary to provide the thermal particles with an appropriate degree of directionality, but the degree of directionality provided to the thermal particles is determined in particular by the clearance between the ignition portion 41 and the cylindrical portion 71, which is the portion of the coil spring 70 that surrounds the ignition portion 41. A preferred range of this clearance will be described below with reference to Fig. 4. Fig. 4 is a diagram for explaining a preferred range of clearance in the cylinder-type gas generator according to this embodiment.

[0080] From the viewpoint of preventing cracking or deformation of the side wall portion of cup body 41c, it is preferable that there is no clearance between ignition part 41 and cylindrical part 71. However, it is not necessarily easy to press-fit coil spring 70 made of metal wire into ignition part 41, and from the viewpoint of facilitating the assembly work, it is desirable to provide a small amount of clearance.

[0081] This clearance is preferably at least 1.0 mm or less as confirmed from the results of the verification tests described later, and its upper limit can be determined as follows considering that the enlarged diameter portion 72 and the open portion of the cup body 41c also function as a kind of guide.

[0082] That is, referring to FIG. 4, let the inner diameter of the housing body 10 that defines the space in which the gas generating agent 60 is accommodated be R1, the outer diameter of the ignition part 41 be R2, the distance along the axial direction of the housing body 10 from the portion where the ignition charge 41a in the ignition part 41 is accommodated to the gas generating agent 60 be L1, and the distance along the axial direction of the housing body 10 from the portion where the ignition charge 41a in the ignition part 41 is accommodated to the boundary between the cylindrical part 71 and the enlarged diameter part 72 be L2. In this case, it is preferable that the clearance C between the ignition part 41 and the cylindrical part 71 satisfies the condition of 0 < C ≤ (R1 - R2) × (L2 / L1) / 2 (hereinafter, this is referred to as the "first condition").

[0083] By satisfying the above first condition, when viewed from the ignition part 41, the gas generating agent 60 will be located within the range where the hot particles are guided by the enlarged diameter portion 72 and the open portion of the cup body 41c. Therefore, it is possible to very efficiently guide the hot particles to the gas generating agent 60. Thus, in order to surely obtain the above-described effects, it is preferable that the first condition is satisfied.

[0084] Also, referring to FIG. 4, when the outer diameter of the ignition part 41 is R2 and the inherent elongation rate of the material of the cup body 41c that constitutes the ignition part 41 of the igniter 40 is e, it is preferable that the clearance C between the ignition part 41 and the cylindrical part 71 satisfies the condition of 0 ≤ C ≤ e × R / 2 (hereinafter, this is referred to as the "second condition"). Here, the elongation rate e refers to the ratio of the elongation generated between the gauge marks on the test piece to the gauge mark distance during the tensile test using the said material, expressed as a percentage.

[0085] By satisfying the second condition, when the igniter 40 is activated, the cup body 41c constituting the ignition part 41 is deformed and comes into contact with the cylindrical part 71 before the cup body 41c breaks, thereby suppressing further deformation of the cup body 41c. Therefore, in order to reliably obtain the above-mentioned effect, it is preferable that the second condition is satisfied.

[0086] (Embodiment 2) Fig. 5 is an enlarged cross-sectional view of the vicinity of the igniter of a cylinder-shaped gas generator according to Embodiment 2. Next, with reference to Fig. 5, a cylinder-shaped gas generator 1B according to the present embodiment will be described.

[0087] 5, when cylinder-shaped gas generator 1B according to the present embodiment is compared with cylinder-shaped gas generator 1A according to the first embodiment described above, the inner diameter of cylindrical portion 71 of coil spring 70 is different, whereby cylindrical portion 71 is in contact with ignition portion 41. That is to say, in cylinder-shaped gas generator 1B according to the present embodiment, there is no clearance between ignition portion 41 and cylindrical portion 71.

[0088] Even in this case, the effect similar to that described in the above-mentioned embodiment 1 can be obtained, and it is possible to achieve both weight reduction and reduction in manufacturing costs while maintaining good gas output characteristics. Furthermore, in this case, it is necessary to press-fit the coil spring 70 into the ignition part 41 during assembly, and although the workability is slightly inferior to the case where a clearance is provided, it is possible to obtain the effect of more reliably preventing cracking or deformation in the side wall part of the cup body 41c.

[0089] (Embodiment 3) Fig. 6 is an enlarged cross-sectional view of the vicinity of the igniter of a cylinder-shaped gas generator according to Embodiment 3. Next, with reference to Fig. 6, cylinder-shaped gas generator 1C according to the present embodiment will be described.

[0090] 6, cylinder-shaped gas generator 1C according to the present embodiment differs from cylinder-shaped gas generator 1B according to the above-described embodiment 2 only in the number of turns of metal wire in cylindrical portion 71 of coil spring 70. Specifically, in cylinder-shaped gas generator 1C, the pitch of the metal wire in a portion of cylindrical portion 71 of coil spring 70 that surrounds ignition portion 41 of igniter 40 is configured to be narrower, thereby increasing the number of turns of cylindrical portion 71 in that portion.

[0091] Even in this case, the effect similar to that described in the above-mentioned embodiment 2 can be obtained, and it is possible to achieve both weight reduction and reduction in manufacturing costs while maintaining good gas output characteristics. Furthermore, in this case, the effect of being able to more reliably suppress deformation of the side wall portion of the cup body 41c when the igniter 40 is activated can be obtained by increasing the number of turns of the metal wire in the cylindrical portion 71 of the coil spring 70.

[0092] (Embodiment 4) Fig. 7 is an enlarged cross-sectional view of the vicinity of the igniter of a cylinder-shaped gas generator according to Embodiment 4. Next, with reference to Fig. 7, a cylinder-shaped gas generator 1D according to the present embodiment will be described.

[0093] 7, cylinder-shaped gas generator 1D according to the present embodiment differs from cylinder-shaped gas generator 1C according to the above-described embodiment 3 only in the configurations of cylindrical portion 71 and expanded diameter portion 72 of coil spring 70. Specifically, in cylinder-shaped gas generator 1D, compared to cylinder-shaped gas generator 1C described above, cylindrical portion 71 of coil spring 70 is configured to have a longer axial length, and expanded diameter portion 72 of coil spring 70 is configured to have a shorter axial length.

[0094] That is, in cylinder-shaped gas generator 1D of this embodiment, only the end portion adjacent to pressing portion 73 of coil spring 70 is configured as enlarged diameter portion 72, whereby not only ignition portion 41 of igniter 40 but also most of the space between ignition portion 41 and gas generating agent 60 is surrounded by cylindrical portion 71 of coil spring 70.

[0095] Even when configured in this manner, effects similar to those of the above-mentioned embodiment 3 can be obtained, and it is possible to achieve both weight reduction and reduced manufacturing costs while maintaining good gas output characteristics.

[0096] (Verification test) Verification tests carried out to confirm the effects of the present invention are described below. In the verification tests, cylinder-shaped gas generators according to Verification Examples 1 to 3 based on the above-mentioned embodiment 1 were actually prototyped, and separately, a cylinder-shaped gas generator according to a comparative example not based on the above-mentioned embodiment 1 was prototyped, and the gas output characteristics were measured by actually operating these cylinder-shaped gas generators according to Verification Examples 1 to 3 and the comparative example. Fig. 8 is a table showing the test conditions and test results of the verification test.

[0097] As shown in Fig. 8, the cylinder-shaped gas generators according to verification examples 1 to 3 are provided with the above-mentioned coil spring 70, and are configured so that the degree of opening of cup body 41c of ignition portion 41 is regulated by coil spring 70 (see Fig. 2, etc.). Here, in verification examples 1 to 3, the inner diameters of coil springs 70 used are configured to be different, but the wire diameters, number of turns, etc. are configured to be the same.

[0098] On the other hand, the cylinder-type gas generator according to the comparative example does not have the coil spring 70 described above, and instead, only the pressing portion 73 of the coil spring 70 is fixed to the housing body 10, so that the distance between the ignition portion 41 of the igniter 40 and the gas generating agent 60 is configured to be equivalent to that of the cylinder-type gas generators according to the above-mentioned verification examples 1 to 3.

[0099] Here, the cylinder-shaped gas generators according to verification examples 1 to 3 and the comparative example are configured so that the only differences are the presence or absence of the coil spring described above and the inner diameter of the coil spring, and all other configurations are the same.

[0100] That is, the inner diameter R1 of the housing body 10 is 17.4 mm in all of these cases, and the outer diameter R2 of the ignition portion 41 is 8.05 mm in all of these cases. Also, the distance L1 along the axial direction of the housing body 10 from the portion of the ignition portion 41 containing the ignition charge 41a to the gas generating agent 60 is 10.5 mm in all of these cases, and the distance L2 along the axial direction of the housing body 10 from the portion of the ignition portion 41 containing the ignition charge 41a to the boundary between the cylindrical portion 71 and the expanded diameter portion 72 is 2.3 mm in all of these cases.

[0101] The clearance in the cylinder-shaped gas generators of verification examples 1 to 3 is the above-mentioned clearance C (i.e., the distance between the ignition portion 41 and the cylindrical portion 71), and the clearance in the cylinder-shaped gas generator of the comparative example is the distance between the ignition portion 41 and the housing body 10.

[0102] In the verification test, two samples of each of the cylinder-type gas generators according to Verification Examples 1 to 3 and the Comparative Example were prepared, each of which was placed in a sealed tank and activated, and the change in pressure in the tank over time was measured. Note that the output index in Figure 8 is used when evaluating the gas output characteristics, and indicates the time from the activation of the igniter until a change occurs in the pressure in the tank.

[0103] As shown in Fig. 8, based on the results of the above verification tests, it was confirmed that in the cylinder-shaped gas generators according to Verification Examples 1 to 3 in which clearance C between the ignition portion and the cylindrical portion is 1.0 mm or less, the output index was improved compared to the cylinder-shaped gas generator according to the comparative example in which a coil spring was not provided. That is, it was experimentally confirmed that by configuring coil spring 70 to restrict the degree of opening of cup body 41c of ignition portion 41, gas output can be obtained earlier after activation, and furthermore, it was confirmed that the output index improves more significantly as clearance C is made smaller.

[0104] (Other forms, etc.) In the above-mentioned first to fourth embodiments of the present invention, the coil spring that provides directivity to the heat particles generated in the ignition part of the igniter is configured to include a cylindrical part and an expanded part. However, it is not necessary to use a coil spring with such an external shape. Coil springs of various shapes can be used, such as a coil spring that is tapered or expanded as a whole, a coil spring that has multiple cylindrical parts and expanded parts, or a coil spring that is configured to have the same inner diameter except for the pressing part. In any case, as long as the coil spring is configured to regulate the opening degree of the cup body of the ignition part, a suitable effect can be obtained. In addition, the wire diameter, number of turns, material, etc. of the coil spring can be changed as appropriate.

[0105] Furthermore, in the above-mentioned first to fourth embodiments of the present invention, a cylinder-shaped gas generator not equipped with an auto-ignition agent that automatically ignites without depending on the operation of an igniter has been exemplified and described, but the cylinder-shaped gas generator may be configured to be equipped with this. The auto-ignition agent spontaneously ignites at a temperature lower than that of the gas generating agent, and is intended to prevent abnormal operation from being induced by heating the cylinder-shaped gas generator from the outside in the unlikely event of a fire or the like occurring in a vehicle or the like equipped with an airbag device in which a cylinder-shaped gas generator is incorporated. When this auto-ignition agent is provided in a cylinder-shaped gas generator, for example, the auto-ignition agent may be disposed in the space within the combustion chamber so as to abut against a partition member.

[0106] Furthermore, in the above-mentioned first to fourth embodiments of the present invention, the present invention has been described as being applied to a cylindrical gas generator incorporated in a side airbag device, but the application of the present invention is not limited to this, and the present invention can also be applied to cylindrical gas generators incorporated in curtain airbag devices, knee airbag devices, seat cushion airbag devices, etc., and so-called T-shaped gas generators which have an elongated outer shape like a cylindrical gas generator.

[0107] As such, the above-described embodiments disclosed herein are illustrative in all respects and are not restrictive. The technical scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0108] 1A to 1D cylindrical gas generator, 10 housing body, 11 gas outlet, 12, 13 crimping portion, 20 holder, 21 penetration portion, 22 annular groove portion, 23 crimping portion, 24 recess portion, 25 sealing member, 30 blocking member, 31 annular groove portion, 40 igniter, 41 ignition portion, 41a ignition charge, 41b plug, 41c cup body, 42 terminal pin, 50 partition member, 51 bulkhead portion, 51a score, 52 annular wall portion, 53 O-ring, 60 gas generating agent, 70 coil spring, 71 cylindrical portion, 72 enlarged diameter portion, 73 pressing portion, 80 filter, 81 hollow portion, S1 combustion chamber, S2 filter chamber.

Claims

1. a long cylindrical housing having a peripheral wall portion whose one axial end and the other axial end are closed; a gas generating agent contained within the housing; an igniter having an ignition part containing an ignition charge for burning the gas generating agent, the ignition part being mounted on the one end part of the housing so as to be positioned so as to protrude toward the inside of the housing; a coil spring that is interposed between the one end of the housing and the gas generating agent, and that biases the gas generating agent toward the other end of the housing while separating the gas generating agent from the ignition portion, thereby fixing the gas generating agent inside the housing, The ignition portion includes a cup body that is cleaved by ignition of the ignition charge when the igniter is activated, a coil spring that is disposed approximately coaxially with an ignition portion and surrounds the ignition portion without any other member being interposed between the coil spring and the ignition portion, so that the degree of opening of the cup body when the cup body is torn open is regulated by the coil spring.

2. The outer shape of the ignition part is substantially cylindrical, the coil spring includes a cylindrical portion located on the one end side of the housing and having a constant inner diameter, and an enlarged diameter portion extending from an end of the cylindrical portion on the gas generating agent side toward the gas generating agent side and having an inner diameter increasing as it approaches the gas generating agent, 2. The gas generator according to claim 1, wherein a portion of said coil spring surrounding said igniter is formed by said cylindrical portion.

3. 3. The gas generator according to claim 2, wherein an inner diameter of the peripheral wall portion of the housing at a portion where the gas generating agent is accommodated is R1, an outer diameter of the ignition portion is R2, a distance along the axial direction of the housing from a portion of the ignition portion where the ignition charge is accommodated to the gas generating agent is L1, a distance along the axial direction of the housing from the portion of the ignition portion where the ignition charge is accommodated to a boundary between the cylindrical portion and the enlarged diameter portion is L2, and a clearance between the ignition portion and the cylindrical portion is C, the condition of 0<C≦(R1−R2)×(L2 / L1) / 2 is satisfied.

4. 4. The gas generator according to claim 3, wherein the clearance is 1.0 mm or less.

5. 3. The gas generator according to claim 1, wherein a portion of said coil spring surrounding said ignition portion is in contact with said ignition portion.

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