Gas generator

Abstract

A gas generator (1) is provided with a housing having a cylindrical section (10), a bolt (2), and a joining section (6). The bolt (2) has a rod-shaped section (3) and is joined to the outer peripheral surface (10a) of the cylindrical section (10). The joining section (6) joins the cylindrical section (10) and the bolt (2) by melting and then solidifying at least one of the outer peripheral surface (10a) and the axial direction end section (4) of the rod-shaped section (3). The rod-shaped part (3) includes a male screw part (3a). The plate thickness of the cylindrical part (10) is less than 1.3 mm. The gas generator (1) satisfies Lgt, where L is the circumference of the outer edge of the boundary between the joining section (6) and the outer peripheral surface (10a), A is the effective cross-sectional area of the male screw section (3a), S1 is the bolt strength of the bolt (2), t is the plate thickness of the cylindrical section (10), S2 is the tensile strength of the cylindrical section (10), and G is the shear coefficient of the cylindrical section (10); (A * S1) / (t * S2 * G).

Description

Technical Field

[0001] This invention relates to a gas generator incorporated into an occupant protection device that protects occupants during a collision in a vehicle or the like, and particularly to a gas generator incorporated into an airbag device equipped in an automobile or the like. Background Technology

[0002] Previously, airbags were widely used as occupant protection devices from the perspective of protecting passengers in vehicles and other similar vehicles. Airbags are devices designed to protect occupants from the impact generated during a collision with a vehicle or other object. They are designed to inflate and deploy instantly upon impact, thus acting as a buffer to support the occupant's body.

[0003] The gas generator is a device that is installed in the airbag device. When a vehicle or other object collides with it, the igniter is ignited by power from the control unit. The flame generated in the igniter ignites the gas generator, which in turn burns the gas generating agent to instantly generate a large amount of gas, thereby causing the airbag to inflate and deploy.

[0004] Gas generators come in various configurations based on their installation location relative to vehicles or other vehicles, as well as their output specifications. One type is the cylinder-type gas generator. Cylinder-type gas generators are long cylindrical in shape and are suitable for use with side airbags, curtain airbags, knee airbags, seat cushion airbags, etc.

[0005] Sometimes, double-ended studs are provided on the outer peripheral surface of the housing of a cylinder-type gas generator for mounting to retaining members of an airbag device, etc. Japanese Patent Application Publication No. 2005-247289 (Patent Document 1) discloses a technique for welding and mounting double-ended studs to the outer peripheral surface of a gas generator housing that has been machined into a flat surface. Furthermore, Japanese Patent Application Publication No. 2005-313752 (Patent Document 2) discloses a technique for welding and mounting the head of a headed bolt with a curved surface to the curved outer peripheral surface of a gas generator.

[0006] Prior art literature Patent documents Patent Document 1: Japanese Patent Application Publication No. 2005-247289; Patent document 2: Japanese Patent Application Publication No. 2005-313752. Summary of the Invention

[0007] The problem that the invention aims to solve In order to ensure the safe operation of the gas generator, even if an unexpected external force is applied to the gas generator or its retaining components, it is essential to prevent deformation or damage at the joint formed by welding the housing to the studded bolts. This issue has become particularly prominent in order to meet the recent demand for lightweight gas generators and reduce the thickness of the housing plate.

[0008] Therefore, the present invention was made to solve the above-mentioned problems, and its object is to provide a gas generator that is lightweight and at the same time is difficult to break at the joint between the housing and the bolt when a certain external force is applied.

[0009] Solution for solving the problem The gas generator based on the present invention ejects gas outward and includes a housing having a cylindrical portion, a bolt, and a connecting portion. The bolt has a rod-shaped portion and engages with the curved outer peripheral surface of the cylindrical portion. The connecting portion engages the cylindrical portion and the bolt by solidifying at least one of the outer peripheral surface of the cylindrical portion and the axial end of the rod-shaped portion on the cylindrical portion side after melting. The rod-shaped portion includes a male threaded portion formed by providing a helical groove on the peripheral surface of the rod-shaped portion. The plate thickness of the cylindrical portion is less than 1.3 mm. In the gas generator based on the present invention, the gas generator satisfies the following formula (1) when the perimeter of the outer edge of the boundary between the connecting portion and the outer peripheral surface of the cylindrical portion is set as L, the effective cross-sectional area of ​​the male threaded portion is set as A, the bolt strength of the bolt is set as S1, the plate thickness of the cylindrical portion is set as t, the tensile strength of the cylindrical portion is set as S2, and the shear coefficient of the cylindrical portion is set as G.

[0010] L>(A×S1) / (t×S2×G)……(1) Invention Effects According to the present invention, a gas generator is provided that is lightweight and is also resistant to damage at the joint between the housing and the bolts when a certain external force is applied. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the cylinder-type gas generator involved in the implementation method.

[0012] Figure 2 yes Figure 1 The diagram shows the state of the bolts before welding, including a perspective view, a side view, and a bottom view.

[0013] Figure 3 It is shown Figure 2 The diagram shows the bolts being installed on the housing.

[0014] Figure 4 yes Figure 1 The side view of the cylinder-type gas generator shown.

[0015] Figure 5 yes Figure 4 Enlarged cross-sectional view of the main part near the joint shown.

[0016] Figure 6 This is a graph showing the measurement results of verification test 1.

[0017] Figure 7 This is a graph showing the measurement results of verification test 2. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments shown below illustrate the application of the present invention to a cylinder-type gas generator installed in a side airbag device. Furthermore, in the embodiments shown below, the same or common parts are labeled with the same reference numerals in the drawings and will not be described again.

[0019] (Implementation Method) Figure 1 This is a schematic diagram of the cylinder-type gas generator involved in the embodiment. First, refer to... Figure 1 The configuration of the cylinder-type gas generator 1 according to this embodiment will be described. Furthermore, Figure 1 Arrows DR1 and DR2 shown indicate the axial directions of the housing body 10 constituting the cylinder-type gas generator 1 and the bolt 2, respectively (described later). Figures 2 to 5 The same applies to China.

[0020] like Figure 1 As shown, the cylinder-type gas generator 1 includes: a housing 90 having a generally elongated cylindrical shape with one end and the other end closed in the axial direction; and two bolts 2, which connect via a joint 6 (see below). Figure 5 (etc.) is joined to the curved outer peripheral surface 10a of the housing body 10, which is a cylindrical part constituting the housing 90.

[0021] Bolt 2 is fitted with a retainer for the airbag device. Bolt 2 is made of a material such as cold-forged carbon steel (SWCH). Furthermore, the number of bolts 2 is not specifically limited to two; it can be one or more.

[0022] The housing 90 includes a housing body 10, a retainer 20, and a blocking member 30. Inside the housing 90, which is composed of the housing body 10 and the like, are housed internal components such as an igniter 40, a partition wall member 50, a chamber setting member 60, a gas generator 70, and a filter 80. The combustion chamber R1, which mainly houses the gas generator 70, and the filter chamber R2, which houses the filter 80, are located inside the housing 90.

[0023] The shell body 10 forms the peripheral wall portion of the shell 90. The shell body 10 is composed of a generally elongated cylindrical component with openings at both ends in its axial direction (refer to arrow DR1). Components constituting the shell body 10 are, for example, structural carbon steel tubing (STK) or mechanical structural carbon steel tubing (STKM). The outer diameter of the shell body 10 is preferably, for example, 15 mm or more and 40 mm or less.

[0024] Furthermore, the thickness of the housing body 10 is preferably less than 1.3 mm, more preferably less than 1.1 mm, and even more preferably less than 0.9 mm. This allows for the lightweighting of the cylinder-type gas generator 1. Additionally, the thickness of the housing body 10 is preferably greater than 0.5 mm.

[0025] The retainer 20 is fixed to the housing body 10 in such a way that it closes one end of the housing 90 in the axial direction. The closing member 30 is fixed to the housing body 10 in such a way that it closes the other end of the housing 90 in the axial direction.

[0026] Igniter 40, used to ignite the gas generator 70, is assembled to one end of housing 90 by means of retainer 20. Thus, igniter 40 is configured to face the interior space of housing 90.

[0027] A partition wall member 50, serving as a dividing section, is disposed at a predetermined position within the internal space of the housing 90. Thus, the internal space of the housing 90 is divided into a combustion chamber R1 and a filter chamber R2 in the axial direction of the housing body 10.

[0028] The space (i.e., combustion chamber R1) between the retainer 20 and the spacer wall component 50 in the internal space of the housing 90 is provided with a chamber setting component 60 and a gas generator 70.

[0029] The chamber setting component 60 is a component that sets up a gas generating agent chamber R1A containing the gas generating agent 70. The chamber setting component 60 is made of relatively fragile parts so that it may break or melt during the combustion of the gas generating agent 70.

[0030] The gas generator 70 is an agent that is ignited and burned by heat particles generated by the operation of the igniter 40, thereby generating gas. As the gas generator 70, a non-azide-based gas generator is preferred, and it is generally formed as a molded body containing fuel, oxidant, and additives.

[0031] A filter 80 is disposed in the space (i.e., filter chamber R2) between the blocking component 30 and the partition wall component 50 in the internal space of the housing 90. The filter 80 functions as a cooling mechanism to cool the gas generated by the combustion of the gas generator 70 by taking away the heat of the high temperature of the gas as it passes through the filter 80, and also functions as a removal mechanism to remove residues (slag) contained in the gas.

[0032] In the housing body 10 of the portion containing the filter chamber R2, a plurality of gas outlets 31 are provided along the circumferential and axial directions of the housing body 10. These plurality of gas outlets 31 are used to exhaust the gas after passing through the filter 80 to the outside of the housing 90.

[0033] Figure 2 (A) Figure 2 (B) and Figure 2 (C) respectively show Figure 1 The diagram shows the state of the bolts before welding, including a perspective view, a side view, and a bottom view. Next, refer to... Figure 2 The configuration of bolt 2 in the state before welding in this embodiment will be explained.

[0034] like Figure 2 (A) Figure 2 (B) and Figure 2 As shown in (C), in its pre-welding state, bolt 2 has: a solid, approximately cylindrical rod-shaped portion 3 extending along the axial direction of bolt 2 (refer to arrow DR2); and a flange portion 4 as the axial end, which is provided at one end of the rod-shaped portion 3 in the axial direction of bolt 2. When viewed along the axial direction of bolt 2, the flange portion 4 has a track shape. Here, the so-called track shape means that its outer edge is a rectangular shape with rounded corners, consisting of two straight sections positioned parallel to each other and two curved sections positioned parallel to each other. Furthermore, the shape of the flange portion 4 is not particularly limited to a track shape, and may also be approximately circular, approximately elliptical, approximately rectangular, etc.

[0035] The rod-shaped portion 3 includes a spiral groove 3a1 provided on its circumferential surface (see below). Figure 5 The male threaded portion 3a is formed by the bolt 2 being welded to the outer peripheral surface 10a of the housing body 10. The flange portion 4 has an opposing surface 8. The opposing surface 8 is the surface that opposes the outer peripheral surface 10a when the bolt 2 is welded to the outer peripheral surface 10a of the housing body 10.

[0036] Figure 3 It is shown Figure 2 The diagram shows the bolts being installed on the housing. Figure 4 From Figure 1 Side view of a cylinder-type gas generator viewed in the direction of arrow IV. Figure 5 yes Figure 4 Enlarged cross-sectional view of the main part near the joint shown. Figure 5 (A) is along Figure 4 Enlarged cross-sectional view of the main portion near the junction of the VA-VA lines shown. Figure 5 (B) is along Figure 4 The enlarged cross-sectional view of the main portion near the junction of the VB-VB lines shown. Next, refer to these... Figures 3 to 5 The method of installing bolt 2 to the housing body 10 in this embodiment and the configuration near the joint 6 in the cylinder-type gas generator 1 according to this embodiment will be described. Furthermore, in Figure 3 The main body 10 of the shell is shown in cross-section. Additionally, for ease of understanding, in... Figure 4 In the middle, add patterns to the joint 6.

[0037] When installing bolt 2 onto the curved outer peripheral surface 10a of the housing body 10, firstly, as... Figure 3 As shown, a voltage is applied to the bolt 2 and the housing body 10, which are positioned opposite each other at a distance. Then, while maintaining the voltage applied to the bolt 2 and the housing body 10, the bolt 2 is moved towards... Figure 3 The bolt 2 moves in the direction of arrow AR1, so that the flange 4 of the bolt 2 is abutted against the outer peripheral surface 10a of the housing body 10.

[0038] At this time, a discharge occurs between the flange portion 4 and the outer peripheral surface 10a, thereby locally heating these portions. Due to this heating, a portion of the flange portion 4 and a portion of the outer peripheral surface 10a of the housing body 10 melt together. Hereinafter, the portion of the flange portion 4 that has melted together with the outer peripheral surface 10a of the housing body 10 is referred to as the molten portion.

[0039] By further pressing the bolt 2 into the housing body 10, the molten portion is clamped between the unmelted portion in the flange portion 4 and the unmelted portion in the outer peripheral surface 10a of the housing body 10. As a result, the molten portion is elongated along the curved outer peripheral surface 10a of the housing body 10.

[0040] Subsequently, the molten portion solidifies, thus as... Figure 4 , Figure 5 (A) and Figure 5As shown in (B), a joint 6 is formed at the position between the bolt 2 and the housing body 10. Thus, the bolt 2 is engaged with the outer peripheral surface 10a of the housing body 10 via the joint 6.

[0041] In this embodiment, the cylinder-type gas generator 1 is configured to prevent damage at the joint 6 between the housing body 10 and the bolt 2 when a certain external force is applied to the gas generator 1, etc., in order to satisfy the formula (1) described later. This point will be explained in detail below.

[0042] During the assembly of a cylinder-type gas generator to its retaining components, or in the event of a collision involving a vehicle equipped with a cylinder-type gas generator, unexpected external forces may be applied to the gas generator. Worryingly, without any countermeasures, these external forces may be applied to the joint between the bolts and the housing body, causing deformation or damage to this joint. If this deformation or damage occurs at the joint, the cylinder-type gas generator may malfunction and fail to perform its intended action during operation.

[0043] Therefore, if the bolt 2 can be broken before excessive external force is applied to the joint 6, any potential damage or deformation at the joint 6 can be prevented. As a result, safe operation of the cylinder-type gas generator 1 can be achieved.

[0044] As for the fracture modes of joint 6, three fracture modes can be considered: fracture in the tensile direction, fracture in the shear direction, and fracture in the torque direction. Among these, fracture in the torque direction is impractical. Furthermore, there is a general tendency for tensile strength to be greater than shear strength. Therefore, if fracture in the tensile direction of joint 6 is suppressed, fracture in the shear direction is also suppressed. Therefore, in the cylinder-type gas generator 1, it is important that fracture in the tensile direction does not occur at joint 6.

[0045] In other words, in the cylinder-type gas generator 1, the weld strength at the joint 6 is required to be greater than the tensile strength of the bolt 2.

[0046] Here, the effective cross-sectional area of ​​the male threaded portion 3a is set as A, the bolt strength of the bolt 2 is set as S1, and the outer edge 6a of the boundary between the joint portion 6 and the outer peripheral surface 10a of the housing body 10 (refer to...) Figure 4 and Figure 5 When the perimeter of the shell body 10 is set as L, the plate thickness of the shell body 10 is set as t, the tensile strength of the shell body 10 is set as S2, and the shear coefficient of the shell body 10 is set as G, the tensile strength T1 of the bolt 2 is expressed by the following formula (11), and the welding strength T2 at the joint 6 is expressed by the following formula (12). In addition, the rationality of formula (11) and formula (12) is confirmed by the verification tests 1 and 2 described later.

[0047] T1=A×S1……(11) T2=L×t×S2×G……(12) The effective cross-sectional area A of the male threaded portion 3a is represented by the following formula (13). Furthermore, d2 refers to the effective diameter of the male threaded portion 3a, and d3 refers to the valley diameter of the male threaded portion 3a. For example... Figure 5 As shown in (A), the effective diameter d2 is the diameter of an imaginary cylinder as follows: when the pitch of the male threaded portion 3a is set to dimension P, the width dimension of the helical groove 3a1 and the width dimension of the thread teeth of the male threaded portion 3a, which is formed in pairs with the helical groove 3a1, are both P / 2. Furthermore, the valley diameter d3 is the diameter of an imaginary cylinder that connects to the valley bottom of the helical groove 3a1.

[0048] A = (π / 4) × ((d² + d³) / 2) 2 ... (13) The cylinder-type gas generator 1 according to this embodiment satisfies the following formula (1): an inequality T2>T1 is established between the tensile strength T1 of the bolt 2 represented by the above formula (11) and the welding strength T2 at the joint 6 represented by the above formula (12), and the inequality is rearranged.

[0049] L>(A×S1) / (t×S2×G)……(1) That is, in the cylinder-type gas generator 1 according to this embodiment, the perimeter L of the outer edge 6a of the boundary between the joint 6 and the outer peripheral surface 10a of the housing body 10 is configured in such a way as to satisfy the above formula (1).

[0050] Thus, by making the perimeter L sufficiently long to satisfy the above formula (1), when a tensile load is applied to the bolt 2 and the joint 6, the bolt 2 will break before an excessive external force is applied to the joint 6. Therefore, any potential damage or deformation to the joint 6 is prevented.

[0051] Therefore, by designing the cylinder-type gas generator 1 according to this embodiment, it is possible to design a gas generator that is lightweight and at the same time makes it difficult to cause damage at the joint between the housing and the bolt when a certain external force is applied.

[0052] Furthermore, in the cylinder-type gas generator 1 according to this embodiment, with the bolt 2 engaged with the outer peripheral surface 10a of the housing body 10, the orientation of the bolt 2 is adjusted so that the length direction of the flange 4 is aligned with the axial direction of the housing body 10.

[0053] More specifically, such as Figure 4As shown, the bolt 2 is engaged with the outer peripheral surface 10a of the housing body 10, such that when viewed along the axial direction of the rod-shaped portion 3, the outer dimensions of the flange portion 4 in the direction parallel to the axial direction of the housing body 10 (refer to arrow DR1) are larger than the outer dimensions of the flange portion 4 in the direction orthogonal to the aforementioned axial direction.

[0054] With this configuration, even if the flange 4 is not specially shaped but rather flat, the gap between the outer peripheral surface 10a of the housing body 10 and the flange 4 can be reduced while ensuring a relatively long perimeter L. Therefore, with this configuration, damage or deformation of the joint 6 can be prevented.

[0055] (Verification Experiment 1) In verification test 1, the rationality of formula (11) was confirmed by comparing the measured value of the tensile strength of the bolt sample prepared for verification test 1 with the theoretical value calculated using formula (11) which represents the tensile strength T1 of the bolt mentioned above.

[0056] In this verification test, ten samples of Sample 1 (bolt with a strength of 667 MPa) and ten samples of Sample 2 (bolt with a strength of 776.25 MPa) were prepared. Both Sample 1 and Sample 2 were made of cold-forged carbon steel (SWCH18A), and both had an effective cross-sectional area of ​​20.1 cm². 2 .

[0057] During verification, each sample was first mounted onto the housing body. The mounting method was the same as that described in the above embodiments. The housing body used here is made of carbon steel tubing for mechanical construction (STKM13C).

[0058] Next, a tensile test was conducted on the sample and the shell body that were joined together by the joint, and the tensile strength of the sample was measured when the sample fractured.

[0059] Figure 6 This is a graph showing the results of verification test 1. The horizontal axis shows the bolt strength (MPa), and the vertical axis shows the bolt tensile strength T1 (kN). Additionally, in... Figure 6 In the figure, the theoretical value calculated using equation (11) is shown by the dashed line. In addition, the standard deviation of the measured values ​​of 10 samples 1 is 0.049 kN, and the standard deviation of the measured values ​​of 10 samples 2 is 0.154 kN.

[0060] from Figure 6 The graphs shown in this verification test confirm that the difference between the theoretical and measured values ​​is quite small. From the above, it is confirmed that equation (11) showing the tensile strength T1 of the bolt is a reasonable equation.

[0061] (Verification Experiment 2) In verification test 2, the rationality of formula (12) was confirmed by comparing the measured value of the weld strength at the joint where the bolts are installed on the main body of the housing with the theoretical value calculated using formula (12) which represents the weld strength T2 at the joint.

[0062] In this verification test, to induce fracture of the joint in the tensile direction, bolts with a strength high enough to prevent fracture before the joint occurred were installed on the housing body. Furthermore, the housing body used here was made of carbon steel tubing for mechanical construction (STKM13C), and the plate thickness was 1.0 mm.

[0063] Next, the perimeter of the joint (more specifically, the perimeter of the outer edge of the boundary between the joint and the outer peripheral surface of the housing body) was measured. Then, a tensile test was performed on the bolts and housing body that were joined together via the joint, and the weld strength at the joint was measured in case of fracture. This verification test was conducted a total of three times, varying the perimeter of the joint.

[0064] Figure 7 This is a graph showing the results of verification test 2. The horizontal axis shows the perimeter of the joint (mm), and the vertical axis shows the weld strength T2 (kN) at the joint.

[0065] from Figure 7 The graphs shown in this verification test confirm that the difference between the theoretical and measured values ​​is quite small. From the above, it is confirmed that equation (12) representing the weld strength T2 at the joint is reasonable.

[0066] (Postscript) If the characteristic configuration of the gas generator disclosed in the above embodiments is summarized, it is as follows.

[0067] [Postscript 1] A gas generator that ejects gas outward, comprising: A shell having a cylindrical portion; A bolt having a rod-shaped portion and engaging the curved outer peripheral surface of the aforementioned cylindrical portion; and The joint, wherein at least one of the outer peripheral surface of the cylindrical portion and the axial end of the cylindrical portion of the rod-shaped portion solidifies after melting, joins the cylindrical portion and the bolt together. The aforementioned rod-shaped portion includes a male threaded portion formed by providing a helical groove on the circumferential surface of the rod-shaped portion. The thickness of the aforementioned cylindrical section is less than 1.3 mm. When the perimeter of the outer edge of the boundary between the joint and the outer peripheral surface of the cylindrical part is set as L, the effective cross-sectional area of ​​the male thread is set as A, the bolt strength of the bolt is set as S1, the tensile strength of the cylindrical part is set as S2, the plate thickness of the cylindrical part is set as t, and the shear coefficient of the cylindrical part is set as G, the following formula (1) is satisfied.

[0068] L>(A×S1) / (t×S2×G)……(1) [Postscript 2] The gas generator described in Appendix 1, when viewed along the axial direction of the rod-shaped portion, has a larger external dimension at the axial end in the direction parallel to the axial direction of the cylindrical portion than at the axial end in the direction orthogonal to the axial direction of the cylindrical portion.

[0069] [Postscript 3] The gas generator described in Appendix 2 has a flange at the axial end.

[0070] [Postscript 4] The gas generator described in Appendix 3, when viewed along the axial direction of the aforementioned rod-shaped portion, has a track-shaped flange portion.

[0071] [Postscript 5] In any of the gas generators described in notes 1 to 4, the thickness of the plate in the cylindrical section is less than 1.1 mm.

[0072] (Other methods, etc.) The shape, structure, size, quantity, material, etc. of the various parts shown in the above embodiments of the present invention can be modified in various ways as long as they do not depart from the spirit of the present invention.

[0073] Furthermore, the characteristic configurations shown in the above embodiments of the present invention can of course be combined with each other without departing from the spirit of the present invention.

[0074] Thus, the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is defined by the claims, and includes all modifications within the meaning and scope equivalent to those stated in the claims.

[0075] Explanation of reference numerals in the attached figures 1. Cylinder-type gas generator; 2. Bolt; 3. Rod-shaped part; 3a. Male threaded part; 3a1. Spiral groove; 4. Flange part; 6. Joint part; 6a. Outer edge; 8. Opposing surface; 10. Housing body; 10a. Outer peripheral surface; 20. Holder; 30. Blocking component; 31. Gas outlet; 40. Igniter; 50. Spacer wall component; 60. Reservoir setting component; 70. Gas generating agent; 80. Filter; 90. Housing; R1. Combustion chamber; R1A. Gas generating agent reservoir; R2. Filter chamber.

Claims

1. A gas generator that ejects gas outward, comprising: A shell having a cylindrical portion; A bolt having a rod-shaped portion and engaging the curved outer peripheral surface of the cylindrical portion; and A joint is formed by solidifying at least one of the outer peripheral surface of the cylindrical portion and the axial end of the cylindrical portion of the rod-shaped portion after melting, thereby joining the cylindrical portion and the bolt together. The rod-shaped portion includes a male threaded portion formed by providing a helical groove on the circumferential surface of the rod-shaped portion. The thickness of the cylindrical section is less than 1.3 mm. When the perimeter of the outer edge of the boundary between the joint and the outer peripheral surface of the cylindrical part is set as L, the effective cross-sectional area of ​​the male threaded part is set as A, the bolt strength of the bolt is set as S1, the tensile strength of the cylindrical part is set as S2, the plate thickness of the cylindrical part is set as t, and the shear coefficient of the cylindrical part is set as G, the following formula (1) is satisfied. L>(A×S1) / (t×S2×G)……(1).

2. The gas generator according to claim 1, wherein, When viewed along the axial direction of the rod-shaped portion, the external dimensions of the axial end in the direction parallel to the axial direction of the cylindrical portion are larger than the external dimensions of the axial end in the direction orthogonal to the axial direction of the cylindrical portion.

3. The gas generator according to claim 2, wherein, The axial end is formed by a flange.

4. The gas generator according to claim 3, wherein, When viewed along the axial direction of the rod-shaped portion, the flange portion has a track shape.

5. The gas generator according to claim 1, wherein, The thickness of the plate in the cylindrical section is less than 1.1 mm.

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