Gas generator and manufacturing method of the same

Abstract

To provide a gas generator which achieves stable output performance.SOLUTION: In a gas generator, multiple gas discharge holes include at least one first gas discharge hole and at least one second gas discharge hole which have different cleavage pressures for cleaving a closing member. A minimum passage cross sectional area of a gas passage formed by the first gas discharge hole is equivalent to a minimum passage cross sectional area of a gas passage formed by the second gas discharge hole. The first gas discharge hole and the second gas discharge hole are different from each other in at least one of a shape and a circumference of an opening at the inner surface side of a housing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a gas generator and a method for manufacturing a gas generator. [Background technology]

[0002] Conventionally, a gas generator has been widely used in which an igniter and a gas generating agent are disposed within a housing, the gas generating agent is burned by activating the igniter, and the combustion gas is discharged to the outside from a plurality of gas exhaust holes formed in the housing.

[0003] The gas generator is configured such that the inside of the housing is kept airtight before activation by blocking a plurality of gas exhaust ports with a blocking member such as a sealing tape, and when activated, the blocking member is torn open by the pressure of the combustion gas to open the gas exhaust hole. In relation to this, in order to reliably break the blocking member when the gas generator is activated and stabilize the output performance, a technique is known in which the gas exhaust hole is perforated so that a protrusion (burr) is formed around the inner wall surface side of the housing at the gas exhaust hole, and the area including the gas exhaust hole and the protrusion is covered with a sealing tape (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-241102 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the output performance of a gas generator is determined by parameters such as the amount of combustion gas discharged and the discharge time, and in order to obtain stable (highly reproducible) output performance, it is important to stably burn the gas generating agent.

[0006] The technique of the present disclosure has an object to provide a gas generator with stable output performance. [Means for solving the problem]

[0007] In order to solve the above problems, the technology of the present disclosure employs the following configuration. That is, the technology of the present disclosure is a gas generator. The gas generator according to the present disclosure includes an igniter, a gas generating agent that generates a combustion gas by burning when the igniter is activated, a housing that accommodates the igniter and the gas generating agent inside, a plurality of gas discharge holes that penetrate the inside and outside of the housing, and a blocking member that is attached to an inner surface of the housing, covers openings of the plurality of gas discharge holes on the inner surface side of the housing before the igniter is activated, thereby blocking the plurality of gas discharge holes, and cleaves under pressure of the combustion gas generated by the activation of the igniter to open the plurality of gas discharge holes. The multiple gas discharge holes include at least one first gas discharge hole and one second gas discharge hole having different rupture pressures for the blocking member, the minimum flow path cross-sectional area of ​​the gas flow path formed by the first gas discharge hole is equal to the minimum flow path cross-sectional area of ​​the gas flow path formed by the second gas discharge hole, and the first gas discharge hole and the second gas discharge hole are different from each other in at least one of the shape and perimeter of their openings on the inner surface side of the housing.

[0008] According to the gas generator according to the present disclosure, by making the minimum flow path cross-sectional area for controlling the gas discharge amount equal between the first gas discharge hole and the second gas discharge hole, the gas discharge amount per unit time from the first gas discharge hole and the gas discharge amount per unit time from the second gas discharge hole can be made equal. Furthermore, by making at least one of the shape and perimeter of the opening on the inner surface side of the housing different between the first gas discharge hole and the second gas discharge hole, the rupture pressure of the first gas discharge hole and the rupture pressure of the second gas discharge hole can be made different from each other. In other words, two types of gas discharge holes that have the same internal pressure control function of the housing but different ease of opening can be intentionally set. This makes it possible to make the opening timing of the first gas discharge hole and the second gas discharge hole different, thereby suppressing a sudden drop in internal pressure of the housing when the igniter is activated. As a result, the combustion performance of the gas generating agent can be maintained and the output performance of the gas generator can be stabilized.

[0009] Moreover, in the gas generator according to the present disclosure, the first gas discharge hole and the second gas discharge hole may be closed by the closing member having the same specifications.

[0010] Moreover, in the gas generator according to the present disclosure, the first gas discharge hole and the second gas discharge hole may be holes having a circular cross section, and the first gas discharge hole and the second gas discharge hole may have different hole diameters at their openings on the inner surface side of the housing.

[0011] Furthermore, in the gas generator according to the present disclosure, the first gas discharge hole and the second gas discharge hole may include a straight portion having a constant cross section in a thickness direction of the housing, and a tapered portion that is connected to the straight portion and has a cross-sectional area that increases away from the straight portion in the thickness direction, and one of the first gas discharge hole and the second gas discharge hole has the tapered portion opening on an inner surface side of the housing and the straight portion opening on an outer surface side of the housing, and the other of the first gas discharge hole and the second gas discharge hole has the straight portion opening on the inner surface side of the housing and the tapered portion opening on the outer surface side of the housing.

[0012] Moreover, in the gas generator according to the present disclosure, the straight portion may be formed by a sheared surface, and the tapered portion may be formed by a fractured surface.

[0013] In the gas generator according to the present disclosure, when the thickness of the housing is t1 and the length of the straight portion in the thickness direction of the housing is t2, <t2 / t1<0.7であってもよい。

[0014] Furthermore, in the gas generator according to the present disclosure, a protrusion protruding into the inside of the housing may be formed on at least a portion of the periphery of the opening on the inner surface side of the housing of only one of the first gas exhaust hole and the second gas exhaust hole, and the blocking member may be attached to the inner surface of the housing so as to cover the protrusion.

[0015] Moreover, in the gas generator according to the present disclosure, a periphery of an opening of only one of the first gas discharge hole and the second gas discharge hole on the inner surface side of the housing may be chamfered.

[0016] The technology according to the present disclosure can also be specified as a manufacturing method for a gas generator. That is, the technology according to the present disclosure is a manufacturing method for a gas generator including an igniter, a gas generating agent that generates a combustion gas by burning when the igniter is activated, a housing that accommodates the igniter and the gas generating agent inside, a plurality of gas discharge holes penetrating the inside and outside of the housing, and a blocking member that blocks the plurality of gas discharge holes, the manufacturing method including forming a plurality of gas discharge holes including at least one first gas discharge hole and at least one second gas discharge hole in the housing such that the rupture pressure of the blocking member differs between the first gas discharge hole and the second gas discharge hole, and attaching the blocking member to an inner surface of the housing so as to cover openings of the plurality of gas discharge holes on the inner surface side of the housing, and in forming the plurality of gas discharge holes in the housing, The method for manufacturing a gas generator may include making the minimum flow path cross-sectional areas of the gas flow paths formed by the second gas discharge holes equivalent to each other, and making at least one of the shape and the perimeter of the openings on the inner surface side of the housing different between the first gas discharge hole and the second gas discharge hole.

[0017] Furthermore, in the manufacturing method of a gas generator according to the present disclosure, when forming the multiple gas exhaust holes in the housing, one of the first gas exhaust hole and the second gas exhaust hole may be formed by punching from the outer surface side of the housing, and the other of the first gas exhaust hole and the second gas exhaust hole may be formed by punching from the inner surface side of the housing.

[0018] Furthermore, in the manufacturing method of a gas generator according to the present disclosure, when forming the plurality of gas exhaust holes in the housing, chamfering may be performed on an opening on the inner surface side of the housing of only one of the first gas exhaust hole and the second gas exhaust hole.

[0019] Furthermore, in the manufacturing method of a gas generator according to the present disclosure, when attaching a closing member to the inner surface of the housing, the first gas discharge hole and the second gas discharge hole may be closed by the closing member of the same specifications. Effect of the Invention

[0020] According to the technique of the present disclosure, it is possible to provide a gas generator with stable output performance. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a vertical sectional view showing the gas generator according to the first embodiment in a state before activation. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 3 is an enlarged cross-sectional view illustrating the shape of a first small hole according to the first embodiment. [Figure 4] 5 is a diagram showing the shape of an opening of a first small hole on the inner surface side of a housing according to the first embodiment. FIG. [Diagram 5] 4 is an enlarged cross-sectional view illustrating the shape of a second small hole according to the first embodiment. FIG. [Figure 6] 6 is a diagram showing the shape of an opening of a second small hole on the inner surface side of a housing in the first embodiment. FIG. [Figure 7] 4 is a flowchart of a method for manufacturing the gas generator according to the first embodiment. [Figure 8] 5A to 5C are cross-sectional views illustrating a method for forming a first small hole according to the first embodiment. [Figure 9] 5A to 5C are cross-sectional views illustrating a method for forming second small holes according to the first embodiment. [Figure 10] 10 is an enlarged cross-sectional view illustrating the shape of a second small hole according to Modification 1 of Embodiment 1. FIG. [Figure 11] 13 is an enlarged cross-sectional view illustrating the shape of a first small hole according to Modification 2 of Embodiment 1. FIG. [Figure 12] 13 is an enlarged cross-sectional view illustrating the shape of a second small hole according to Modification 2 of Embodiment 1. FIG. [Figure 13] FIG. 11 is an enlarged cross-sectional view illustrating the shape of a first small hole according to the second embodiment. [Figure 14] FIG. 11 is an enlarged cross-sectional view illustrating the shape of a second small hole according to the second embodiment. [Figure 15] 11A and 11B are diagrams showing examples of shapes of an opening of a small hole on the inner surface side of a housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A gas generator according to an embodiment of the present disclosure will be described below with reference to the drawings. In the embodiment described below, a mode in which the technology according to the present disclosure is applied to a gas generator (inflator) for an airbag will be described. However, the use of the technology according to the present disclosure is not limited thereto, and it may be applied to a gas generator for a seat belt retractor, for example. Each configuration and combination thereof in each embodiment is merely an example, and any suitable configuration may be used within the scope of the gist of the present invention. The present disclosure is not limited to the embodiments, but is limited only by the claims.

[0023] <Embodiment 1> Hereinafter, a description will be given of embodiment 1. Embodiment 1 corresponds to an embodiment in which the circumferential length of the opening of the first gas exhaust hole on the inner surface side of the housing and the circumferential length of the opening of the second gas exhaust hole on the inner surface side of the housing are different from each other, among the embodiments that the technology according to the present disclosure can adopt.

[0024] Fig. 1 is a vertical cross-sectional view showing a state before activation of gas generator 100 according to embodiment 1. Fig. 1 shows a cross section along the central axis of housing 1 indicated by reference symbol CA1. Gas generator 100 according to embodiment 1 is configured as a so-called dual-type gas generator having two igniters. However, the technology according to the present disclosure is not limited thereto. In other words, the gas generator according to the present disclosure may be a so-called single-type gas generator having only one igniter, or may be a gas generator having three or more igniters.

[0025] [Overall configuration] 1, the gas generator 100 includes a first ignition device 4, a first inner cylinder member 5, an enhancer charge 6, a second ignition device 7, a second inner cylinder member 8, a filter 9, a first gas generating agent 110, a second gas generating agent 120, a housing 1 accommodating these, a plurality of gas discharge holes H1 penetrating the inside and outside of the housing 1, and a seal tape S1 closing the plurality of gas discharge holes H1. The gas generator 100 is configured to combust the first gas generating agent 110 by activating a first igniter 41 included in the first ignition device 4, combust the second gas generating agent 120 by activating a second igniter 71 included in the second ignition device 7, and release the combustion gas, which is a combustion product thereof, from the plurality of gas discharge holes H1 formed in the housing 1. Here, the direction along the central axis CA1 of the housing 1 is defined as the up-down direction of the gas generator 100, the upper shell side indicated by reference numeral 2 (i.e., the upper side in FIG. 1) is the upper side of the gas generator 100, and the lower shell side indicated by reference numeral 3 (i.e., the lower side in FIG. 1) is the lower side of the gas generator 100. Each component of the gas generator 100 will be described below. Note that in this specification, the operation of an igniter included in an ignition device may be expressed as "the ignition device operates" or "the gas generator operates" for convenience.

[0026] [housing] The housing 1 is formed into a short cylinder shape including a cylindrical peripheral wall portion indicated by reference numeral 11, with both axial ends of the peripheral wall portion 11 closed, by joining an upper shell 2 and a lower shell 3, each of which is made of metal and formed into a substantially cylindrical shape with a bottom, with their open ends facing each other. The central axis CA1 in FIG. 1 is the central axis of the peripheral wall portion 11.

[0027] The upper shell 2 has a cylindrical upper peripheral wall portion 21 and a top plate portion 22 closing the upper end of the upper peripheral wall portion 21. A joint portion 23 extending radially outward is connected to the lower end of the upper peripheral wall portion 21. The lower shell 3 has a cylindrical lower peripheral wall portion 31 and a bottom plate portion 32 closing the lower end of the lower peripheral wall portion 31. A joint portion 33 extending radially outward is connected to the upper end of the lower peripheral wall portion 31. A first mounting hole 32a for mounting the first ignition device 4 to the bottom plate portion 32 and a second mounting hole 32b for mounting the second ignition device 7 to the bottom plate portion 32 are formed in the bottom plate portion 32.

[0028] The joint portion 23 of the upper shell 2 and the joint portion 33 of the lower shell 3 are overlapped and joined by laser welding or the like to form the housing 1 in the shape of a short cylinder with both axial ends closed. The upper peripheral wall portion 21 of the upper shell 2 and the lower peripheral wall portion 31 of the lower shell 3 form a cylindrical peripheral wall portion 11 that connects the top plate portion 22 and the bottom plate portion 32. In other words, the housing 1 is made up of the cylindrical peripheral wall portion 11 and the top plate portion 22 provided on one end side of the peripheral wall portion 11. and a bottom plate portion 32 provided at the other end side so as to face the top plate portion 22. A first combustion chamber 10 is defined by the peripheral wall portion 11, the top plate portion 22, the bottom plate portion 32, and a second inner cylinder member 8 described below. In the first combustion chamber 10, a first ignition device 4, a first inner cylinder member 5, an enhancer charge 6, a filter 9, and a first gas generating agent 110 are arranged.

[0029] [Ignition device] As shown in FIG. 1, the first ignition device 4 is fixed to a first mounting hole 32a formed in the bottom plate portion 32 of the lower shell 3. The first ignition device 4 includes a first igniter 41. The second ignition device 7 is fixed to a second mounting hole 32b formed in the bottom plate portion 32 of the lower shell 3. The second ignition device 7 includes a second igniter 71. The first igniter 41 and the second igniter 71 each contain an ignition charge (not shown) therein, and are actuated by the supply of an ignition current to burn the ignition charge and release the combustion product to the outside. The first igniter 41 and the second igniter 71 are examples of the "igniter" according to the present disclosure. The first ignition device 4 and the second ignition device 7 operate independently of each other. When the second ignition device 7 is activated, the second ignition device 7 is activated simultaneously with the activation of the first ignition device 4 or at a predetermined timing after the activation of the first ignition device 4. The gas generator 100 can emit a large amount of combustion gas to the outside with various output profiles by the combustion of the first gas generating agent 110 by the activation of the first ignition device 4 and the combustion of the second gas generating agent 120 by the activation of the second ignition device 7, as compared with a so-called single-type gas generator. Note that the second ignition device 7 does not always operate. For example, the gas generator 100 can operate only the first ignition device 4 without activating the second ignition device 7 when the impact is weak, or can simultaneously activate the first ignition device 4 and the second ignition device 7 when the impact is strong, depending on the impact detected by a sensor (not shown).

[0030] [Inner cylinder material] The first inner cylinder member 5 is a bottomed cylindrical member extending from the bottom plate portion 32 toward the top plate portion 22, and includes a cylindrical surrounding wall portion 51 and a cover wall portion 52 closing one end of the surrounding wall portion 51. The first ignition device 4 is fitted or pressed into the other end of the surrounding wall portion 51, so that the first inner cylinder member 5 is attached to the bottom plate portion 32. As shown in FIG. 1, the first ignition device 4 is surrounded by the surrounding wall portion 51, so that a transfer chamber 53 is formed between the first inner cylinder member 5 and the first ignition device 4. The transfer chamber 53 contains a transfer charge 6 that is burned by the operation of the first ignition device 4. In addition, the surrounding wall portion 51 of the first inner cylinder member 5 has a plurality of communication holes h1 that communicate between its internal space (i.e., the transfer chamber 53) and the external space. Before the first ignition device 4 is activated, the communication hole h1 is closed by a sealing tape (not shown).

[0031] The second inner cylinder member 8 is a bottomed cylindrical member extending from the bottom plate portion 32 toward the top plate portion 22, and includes a cylindrical surrounding wall portion 81 and a cover wall portion 82 closing one end of the surrounding wall portion 81. The second ignition device 7 is fitted or pressed into the other end of the surrounding wall portion 81, so that the second inner cylinder member 8 is attached to the bottom plate portion 32. As shown in FIG. 1, the second combustion chamber 20 is formed inside the second inner cylinder member 8, in which the second ignition device 7 and the second gas generating agent 120 that is burned by the operation of the second ignition device 7 are disposed. In addition, the surrounding wall portion 81 of the second inner cylinder member 8 is formed with a plurality of communication holes h2 that communicate the internal space (i.e., the second combustion chamber 20) with the external space (i.e., the first combustion chamber 10). The communication holes h2 are closed by a seal tape (not shown) before the second ignition device 7 is activated.

[0032] [filter] 1, the filter 9 is formed in a cylindrical shape, and is disposed in the first combustion chamber 10 so as to surround the first gas generating agent 110 and have the gas discharge holes H1 located outside thereof in the radial direction. In other words, the filter 9 is disposed between the first gas generating agent 110 and the plurality of gas discharge holes H1 so as to surround the first gas generating agent 110. The filter 9 has an upper end surface that abuts against and is supported by the top plate portion 22 of the upper shell 2, and a lower end surface that abuts against and is supported by the bottom plate portion 22 of the lower shell 3. The filter 9 is supported in contact with the portion 32. When the combustion gas of the first gas generating agent 110 or the second gas generating agent 120 passes through the filter 9, the filter 9 removes heat from the combustion gas to cool the combustion gas. In addition to the function of cooling the combustion gas, the filter 9 also has a function of filtering the combustion gas by collecting combustion residue contained in the combustion gas.

[0033] [Explosive powder] As the enhancer charge 6, in addition to known black powder, a gas generating agent having good ignition properties and a higher combustion temperature than the first gas generating agent 110 can be used. The combustion temperature of the enhancer charge 6 can be set in the range of 1700 to 3000°C. As such an enhancer charge 6, for example, a known material containing nitroguanidine (34% by weight) or strontium nitrate (56% by weight) can be used. In addition, the enhancer charge 6 can be in various shapes, such as granular, pellet, cylindrical, or disk-like.

[0034] [Gas generator] The first gas generating agent 110 generates a combustion gas by burning in response to the activation of the first igniter 41. The second gas generating agent 120 generates a combustion gas by burning in response to the activation of the second igniter 71. A gas generating agent having a relatively low combustion temperature can be used for the first gas generating agent 110 and the second gas generating agent 120. The combustion temperature of the first gas generating agent 110 and the second gas generating agent 120 can be set in the range of 1000 to 1700°C. As such a first gas generating agent 110 and the second gas generating agent 120, for example, a known agent containing guanidine nitrate (41% by weight), basic copper nitrate (49% by weight), a binder, and an additive can be used. In addition, the first gas generating agent 110 and the second gas generating agent 120 can be in various shapes, such as granular, pellet, cylindrical, and disk shapes.

[0035] [Gas exhaust hole] As shown in Fig. 1, a plurality of gas exhaust holes H1 are formed in the peripheral wall portion 11 of the housing 1, aligned in the circumferential direction, penetrating the inside and outside of the housing 1. The gas exhaust holes H1 penetrate from the inner surface 11a (the inner peripheral surface of the peripheral wall portion 11) of the housing 1 to the outer surface 11b (the outer peripheral surface of the peripheral wall portion 11). The internal space of the housing 1 (the first combustion chamber 10) and the external space of the housing 1 are connected via the gas exhaust holes H1. As a result, the gas exhaust holes H1 form a flow path for discharging combustion gas from the inside of the housing 1 to the outside.

[0036] Here, in this specification, the cross-sectional area of ​​the gas flow path formed by the gas exhaust hole H1 is defined as the cross-sectional area perpendicular to the flow direction of the combustion gas. In the first embodiment, the direction in which the gas exhaust hole H1 penetrates the housing 1, that is, the thickness direction of the housing 1, is the flow direction of the combustion gas. The minimum cross-sectional area in the gas flow path is defined as the minimum cross-sectional area. In the gas exhaust hole H1, the point with the minimum cross-sectional area is the rate-limiting (restricting) point for gas exhaust. In other words, the amount of gas exhausted per unit time from the gas exhaust hole H1 is determined according to the minimum cross-sectional area. The internal pressure of the housing 1 can be controlled by adjusting the number of opened gas exhaust holes and the amount of gas exhausted per unit time from the gas exhaust holes.

[0037] As shown in Fig. 1, the multiple gas discharge holes H1 are configured to include multiple large holes 12 and multiple small holes 13 having different minimum flow path cross-sectional areas. In gas generator 100 according to embodiment 1, large holes 12 have a larger minimum flow path cross-sectional area than small holes 13. Therefore, large holes 12 have a larger gas discharge amount per unit time than small holes 13. As shown in Fig. 1, in peripheral wall portion 11, multiple large holes 12 are arranged side by side in the circumferential direction, and multiple small holes 13 are arranged side by side in the circumferential direction at positions lower than the multiple large holes 12. However, the arrangement of large holes 12 and small holes 13 is not limited to this.

[0038] [Sealing tape] As shown in FIG. 1, a sealing tape S1 is attached to the inner surface 11a of the housing 1. The sealing tape S1 is an example of a "blocking member" according to the present disclosure. The sealing tape S1 is a strip-shaped member having an adhesive layer formed on one side of a base layer made of, for example, a metal, and is attached to the inner surface 11a of the housing 1 by adhering the adhesive layer to the inner surface 11a. The base layer is preferably made of aluminum, but may also be made of stainless steel or copper. The adhesive layer may be a layer made of a known synthetic resin adhesive. As the adhesive, a silicone-based, rubber-based, or epoxy-based adhesive is preferable in terms of heat resistance and adhesiveness. However, the material of the sealing tape S1 is not limited to the above.

[0039] 1, the sealing tape S1 is attached to the inner surface 11a while covering the opening of the gas discharge hole H1 on the inner surface 11a side of the housing 1, thereby closing the multiple gas discharge holes H1. Before the first igniter 41 is activated, the gas discharge hole H1 is closed by the sealing tape S1, thereby preventing outside air (moisture) from entering the inside of the housing 1 through the gas discharge hole H1, and the inside of the housing 1 is maintained airtight.

[0040] 1, in the first embodiment, the large holes 12 and the small holes 13 are closed with separate sealing tapes S1. All of the large holes 12 are closed collectively with one sealing tape S1, and all of the small holes 13 are closed collectively with another sealing tape S1. Note that each of the multiple gas discharge holes H1 may be closed with a separate sealing tape, or all of the gas discharge holes H1 may be closed collectively with one sealing tape.

[0041] When the first igniter 41 is activated, the sealing tape S1 is ruptured by the pressure of the generated gas to open the multiple gas discharge holes H1. Here, in this specification, the pressure required to rupture the blocking member (the sealing tape S1 in this example) at each gas discharge hole to open the gas discharge hole is defined as the "rupture pressure". When the blocking member is ruptured, the blocking member, which receives the pressure of the combustion gas, is pressed against the periphery of the opening of the gas discharge hole on the inner surface side of the housing, and is sheared along the periphery. Therefore, the rupture pressure of the blocking member at each gas discharge hole is determined according to the specifications of the blocking member and the properties of the opening of the gas discharge hole. The specifications of the blocking member are specifically the tensile strength and thickness of the blocking member. The lower the tensile strength of the blocking member is, or the thinner the blocking member is, the lower the rupture pressure is. Also, the properties of the opening of the gas discharge hole are specifically the shape and periphery (length of periphery) of the opening of the gas discharge hole on the inner surface side of the housing. The shape of the opening includes the planar shape of the periphery of the opening, as well as protrusions and chamfers formed on the periphery of the opening. If a protrusion is formed on the periphery of the opening, the rupture pressure is lower, and if the periphery of the opening is chamfered, the rupture pressure is higher. Also, the longer the periphery of the opening, the lower the rupture pressure.

[0042] In gas generator 100 according to embodiment 1, the rupture pressure of seal tape S1 at large hole 12 is set to be lower than the rupture pressure of seal tape S1 at small hole 13. In setting the rupture pressures of large hole 12 and small hole 13, for example, the circumferential length of the opening of large hole 12 on the inner surface 11a side of housing 1 may be longer than the circumferential length of the opening of small hole 13 on the inner surface 11a side may be made longer, or the seal tape S1 closing large hole 12 may be made thinner than the seal tape S1 closing small hole 13.

[0043] [First and second small holes] Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 2 shows a cross section perpendicular to the central axis CA1 of gas generator 100 before activation. For convenience, the first ignition device 4, the second ignition device 7, and joints 23, 33 are omitted from Fig. 2.

[0044] 2, the plurality of small holes 13 includes a plurality of first small holes 13a and a plurality of second small holes 13b. The first small holes 13a are an example of a "first gas exhaust hole" according to the present disclosure. The second small hole 13b is an example of a "second gas discharge hole" according to the present disclosure. In the peripheral wall portion 11 of the housing 1, the first small holes 13a and the second small holes 13b are arranged alternately at equal intervals in the circumferential direction.

[0045] In gas generator 100 according to embodiment 1, the first small hole 13a and the second small hole 13b have the same gas discharge amount per unit time, but the rupture pressure of seal tape S1 at first small hole 13a and the rupture pressure of seal tape S1 at second small hole 13b are subtly different. Details will be described later, but in gas generator 100 according to embodiment 1, the properties of the opening on the inner surface 11a side of small hole 13 are set so that the rupture pressure of seal tape S1 at first small hole 13a is lower than the rupture pressure of seal tape S1 at second small hole 13b. However, this does not limit the magnitude relationship between the rupture pressure of the first gas discharge hole (first small hole) and the rupture pressure of the second gas discharge hole (second small hole) in the technology according to the present disclosure. Furthermore, in the technology according to the present disclosure, it is not essential that there are a plurality of first gas exhaust holes and a plurality of second gas exhaust holes, and it is sufficient that the plurality of gas exhaust holes include at least one first gas exhaust hole and one second gas exhaust hole having different rupture pressures of the blocking member. Furthermore, the arrangement of the first gas exhaust holes and the second gas exhaust holes in the technology according to the present disclosure is not limited to the above, and for example, a plurality of first gas exhaust holes and a plurality of second gas exhaust holes may be unevenly distributed.

[0046] Fig. 3 is an enlarged cross-sectional view for explaining the shape of the first small hole 13a according to the first embodiment. Fig. 3 shows the cross section BB of Fig. 2. In Fig. 3, reference numeral 13a1 indicates an opening of the first small hole 13a on the inner surface 11a side of the housing 1, and reference numeral 13a2 indicates an opening of the first small hole 13a on the outer surface 11b side of the housing 1. The first small hole 13a according to the first embodiment is formed as a hole having a circular (perfect circle) cross section perpendicular to the thickness direction (gas flow direction) of the housing 1. The opening 13a1 of the first small hole 13a is covered by a seal tape S1.

[0047] As shown in FIG. 3, the first small hole 13a includes a straight portion 131 and a tapered portion 132. The straight portion 131 is formed so that its cross section (cross-sectional shape and cross-sectional area) is constant in the thickness direction of the housing 1. An inner wall surface 131a forming the straight portion 131 has a cylindrical shape with a constant diameter in the thickness direction of the housing 1. The tapered portion 132 is formed so that it is continuous with the straight portion 131 and has a cross-sectional area that increases as it moves away from the straight portion 131 in the thickness direction of the housing 1. The inner wall surface 132a forming the tapered portion 132 has a cylindrical shape with a diameter that increases as it moves away from the straight portion 131 in the thickness direction of the housing 1. In the first small hole 13a according to the first embodiment, the tapered portion 132 opens on the inner surface 11a side of the housing 1, and the straight portion 131 opens on the outer surface 11b side of the housing 1. The tapered portion 132 of the first small hole 13a opens on the inner surface 11a to form an opening 13a1. The straight portion 131 of the first small hole 13a opens to the outer surface 11b to form an opening 13a2. Although details will be described later, the first small hole 13a according to the first embodiment is formed by perforating the housing 1 from the outer surface 11b side by punching. The inner wall surface 131a of the straight portion 131 is formed as a sheared surface by punching. The inner wall surface 132a of the tapered portion 132 is formed as a fractured surface by punching. The sheared surface is formed as a relatively smooth surface having a metallic luster, and the fractured surface is formed as a relatively rough surface without a metallic luster.

[0048] As shown in Fig. 3, the cross-sectional area of ​​the gas flow path formed by the first small hole 13a is smallest at the straight portion 131. That is, in the first small hole 13a, the straight portion 131 becomes a throttle for gas discharge. The minimum flow path cross-sectional area of ​​the first small hole 13a is defined as A1. A cross-sectional view C1 in Fig. 3 shows a cross section perpendicular to the thickness direction of the housing 1 at the straight portion 131. As shown in the cross-sectional view C1, in the first small hole 13a according to the first embodiment, the cross-sectional area of ​​the straight portion 131 is the minimum flow path cross-sectional area A1.

[0049] Fig. 4 is a diagram showing the shape of the opening 13a1 of the first small hole 13a on the inner surface 11a side of the housing 1 according to the first embodiment. As shown in Fig. 4, the periphery of the opening 13a1 of the first small hole 13a has a circular planar shape. The diameter of the opening 13a1 is D1, and the periphery of the opening 13a1 (the length of the periphery of the opening 13a1) is P1.

[0050] Fig. 5 is an enlarged cross-sectional view for explaining the shape of the second small hole 13b according to the first embodiment. Fig. 5 shows the CC cross section of Fig. 2. Reference numeral 13b1 in Fig. 5 indicates an opening of the second small hole 13b on the inner surface 11a side of the housing 1, and reference numeral 13b2 indicates an opening of the second small hole 13b on the outer surface 11b side of the housing 1. The second small hole 13b according to the first embodiment is formed as a hole having a circular cross section perpendicular to the thickness direction (gas flow direction) of the housing 1, similar to the first small hole 13a. The opening 13b1 of the second small hole 13b is covered by a seal tape S1.

[0051] The second small hole 13b includes a straight portion 131 formed by a sheared surface and a tapered portion 132 formed by a broken surface, similar to the first small hole 13a. The diameter of the straight portion 131 of the second small hole 13b is equal to the diameter of the straight portion 131 of the first small hole 13a. In the second small hole 13b according to the first embodiment, the straight portion 131 opens on the inner surface 11a side of the housing 1, and the tapered portion 132 opens on the outer surface 11b side of the housing 1, unlike the first small hole 13a. The straight portion 131 of the second small hole 13b opens on the inner surface 11a to form an opening 13b1. The tapered portion 132 of the second small hole 13b opens on the outer surface 11b to form an opening 13b2. Although details will be described later, the second small holes 13b according to the first embodiment are formed by perforating the housing 1 from the inner surface 11a side by punching, unlike the first small holes 13a.

[0052] As shown in Fig. 5, the cross-sectional area of ​​the gas flow passage formed by the second small hole 13b is smallest at the straight portion 131, as in the first small hole 13a. That is, in the second small hole 13b as well, the straight portion 131 acts as a throttle for gas discharge. The minimum flow passage cross-sectional area of ​​the second small hole 13b is defined as A2. Cross-sectional view C2 in Fig. 5 shows a cross section perpendicular to the thickness direction of the housing 1 at the straight portion 131. As shown in cross-sectional view C2, in the second small hole 13b according to embodiment 1, the cross-sectional area of ​​the straight portion 131 is the minimum flow passage cross-sectional area A2.

[0053] Fig. 6 is a diagram showing the shape of the opening 13b1 of the second small hole 13b on the inner surface 11a side of the housing 1 according to the first embodiment. As shown in Fig. 4, the planar shape of the periphery of the opening 13b1 of the second small hole 13b is circular, similar to the opening 13a1 of the first small hole 13a. The diameter of the opening 13b1 is D2, and the periphery of the opening 13b1 (the length of the periphery of the opening 13b1) is P2.

[0054] Here, the first small hole 13a and the second small hole 13b are compared in terms of the minimum flow passage cross-sectional area and the properties of the opening on the inner surface 11a side of the housing 1. As described above, the first small hole 13a and the second small hole 13b have the minimum flow passage cross-sectional area in the straight portion 131 having the same diameter. Therefore, the minimum flow passage cross-sectional area A1 of the first small hole 13a and the minimum flow passage cross-sectional area A2 of the second small hole 13b are equivalent. In other words, A1=A2. Therefore, the first small hole 13a and the second small hole 13b have the same gas discharge amount per unit time. Also, as shown in FIG. 4 and FIG. 6, the opening 13a1 of the first small hole 13a and the opening 13b1 of the second small hole 13b are both circular and the same shape. Here, because the opening 13a1 of the first small hole 13a is formed by a tapered portion 132, while the opening 13b1 of the second small hole 13b is formed by a straight portion 131, the opening 13a1 of the first small hole 13a and the opening 13b1 of the second small hole 13b have different hole diameters. Specifically, the diameter D1 of the opening 13a1 is larger than the diameter D2 of the opening 13b1. Since D1>D2, the perimeter P1 of the opening 13a1 of the first small hole 13a is longer than the diameter D2 of the opening 13b1. The perimeter P1 is longer than the perimeter P2 of the opening 13b1 of the second small hole 13b. In other words, P1>P2. Therefore, the tearing pressure of the seal tape S1 at the first small hole 13a is lower than the tearing pressure of the seal tape S1 at the second small hole 13b. As a result, the first small hole 13a is easier to open than the second small hole 13b.

[0055] [Gas generator manufacturing method] Next, a method of assembling the gas generator according to the first embodiment will be described. However, the method of manufacturing a gas generator according to the present disclosure is not limited to the following method. Fig. 7 is a flowchart of the method of manufacturing a gas generator according to the first embodiment. As shown in Fig. 7, the method of assembling the gas generator according to the first embodiment includes a preparation step of step S101, a forming step of a gas discharge hole in step S102, an attachment step of a blocking member in step S103, and an assembly step of step S104.

[0056] First, in the preparation process of step S101, the first ignition device 4, the first inner cylinder member 5, the transfer charge 6, the second ignition device 7, the second inner cylinder member 8, the filter 9, the upper shell 2, the lower shell 3, the first gas generating agent 110, the second gas generating agent 120, and the sealing tape S1 are prepared.

[0057] Next, in the gas exhaust hole forming process of step S102, a plurality of gas exhaust holes H1 are formed in the housing 1 so that the rupture pressure of the sealing tape S1 is different between the first small hole 13a and the second small hole 13b. Specifically, the upper peripheral wall portion 21 of the upper shell 2 is punched to form a plurality of large holes 12 and a plurality of small holes 13. The large holes 12 are punched using a punch with a larger diameter than the punch used to punch the small holes 13. This makes the minimum flow path cross-sectional area of ​​the large holes 12 larger than the minimum flow path cross-sectional area of ​​the small holes 13. As a result, the large holes 12 emit more gas per unit time than the small holes 13.

[0058] In addition, in forming the plurality of small holes 13, punching is performed so that the rupture pressure of the seal tape S1 at the first small hole 13a and the rupture pressure of the seal tape S1 at the second small hole 13b are different from each other. FIG. 8 is a cross-sectional view for explaining a method for forming the first small hole 13a according to the first embodiment. FIG. 9 is a cross-sectional view for explaining a method for forming the second small hole 13b according to the first embodiment. The first small hole 13a and the second small hole 13b are formed by punching using a punch of the same diameter. Reference numeral 200 in FIG. 8 and FIG. 9 indicates a punch used for processing. As shown in FIG. 8, the first small hole 13a is formed by perforating from the outer surface 11b side of the housing 1 by punching. As a result, in the first small hole 13a, a straight portion 131 is formed by a shear surface on the outer surface 11b side of the housing 1, and a tapered portion 132 is formed by a fracture surface on the inner surface 11a side of the housing 1. 9, the second small hole 13b is formed by punching from the inner surface 11a side of the housing 1. As a result, in the second small hole 13b, a straight portion 131 is formed on the inner surface 11a side of the housing 1, and a tapered portion 132 is formed on the outer surface 11b side of the housing 1.

[0059] In the gas discharge hole forming process, the punch 200 having the same diameter is used for the first small hole 13a and the second small hole 13b, so that the straight portion 131 having the same diameter is formed in each of the first small hole 13a and the second small hole 13b. As a result, the minimum flow passage cross-sectional area A1 of the first small hole 13a and the minimum flow passage cross-sectional area A2 of the second small hole 13b become equal. In addition, in the gas discharge hole forming process, the punching direction is opposite for the first small hole 13a and the second small hole 13b, so that the positional relationship between the straight portion 131 and the tapered portion 132 is reversed between the first small hole 13a and the second small hole 13b. As a result, the circumferential length is different between the opening 13a1 of the first small hole 13a and the opening 13b1 of the second small hole 13b. In this example, the perimeter P1 of the opening 13a1 of the first small hole 13a is longer than the perimeter P2 of the opening 13b1 of the second small hole 13b.

[0060] Next, in the process of attaching the blocking member in step S103, the sealing tape S1 is attached to the inner surface 11a of the housing 1 so as to cover the openings of the multiple gas discharge holes H1 on the inner surface 11a side of the housing 1. This blocks the multiple gas discharge holes H1. In this example, all of the large holes 12 are blocked collectively with one sealing tape S1, and all of the small holes 13 are blocked collectively with another sealing tape S1. Therefore, the first small hole 13a and the second small hole 13b are blocked by the sealing tape S1 of the same specifications.

[0061] Next, in the assembly process of step S104, the first ignition device 4 and the second ignition device 7 are attached to the lower shell 3, the first inner cylinder member 5 filled with the transfer charge 6 is fixed to the first ignition device 4, and the second inner cylinder member 8 filled with the second gas generating agent 120 is fixed to the second ignition device 7. Thereafter, a filter 9 is placed in the lower shell 3, and the inside of the filter 9 is filled with the first gas generating agent 110. Finally, the upper shell 2 is placed over the lower shell 3, and the joint portion 23 of the upper shell 2 and the joint portion 33 of the lower shell 3 are overlapped and joined by laser welding or the like to form the housing 1. In this manner, the gas generator 100 is assembled.

[0062] [Operation] Hereinafter, a basic operation of the gas generator 100 according to the first embodiment will be described with reference to Fig. 1. In this example, a case will be described in which the second ignition device 7 is activated with a delay from the first ignition device 4 (i.e., after the first ignition device 4 is activated).

[0063] When a sensor (not shown) detects an impact, an ignition current is supplied to the first igniter 41 of the first ignition device 4, and the first igniter 41 is activated. Then, the ignition charge housed in the first igniter 41 burns, and the combustion products such as flame and high-temperature gas are released into the transfer chamber 53. As a result, the transfer charge 6 housed in the transfer chamber 53 burns, and combustion gas is generated in the transfer chamber 53. When the seal tape blocking the communication hole h1 of the surrounding wall portion 51 of the first inner cylinder member 5 is torn by the pressure of the combustion gas of the transfer charge 6, the combustion gas is discharged to the outside of the transfer chamber 53 through the communication hole h1. Then, the combustion gas of the transfer charge 6 comes into contact with the first gas generating agent 110 arranged around the surrounding wall portion 51, and the first gas generating agent 110 is ignited. When the first gas generating agent 110 burns, high-temperature and high-pressure combustion gas is generated in the first combustion chamber 10. The sealing tape S1 is ruptured by the pressure of the combustion gas, thereby opening a plurality of gas exhaust holes H1. The combustion gas passes through the filter 9, whereby the combustion gas is cooled and combustion residue is collected. The combustion gas of the first gas generating agent 110, which has been cooled and filtered by the filter 9, is exhausted to the outside of the housing 1 through the plurality of gas exhaust holes H1.

[0064] Next, when the second igniter 71 of the second ignition device 7 is activated, the second gas generating agent 120 accommodated in the second combustion chamber 20 is combusted, generating combustion gas within the second combustion chamber 20. When the sealing tape blocking the communication hole h2 of the surrounding wall portion 81 of the second inner cylindrical member 8 is ruptured by the pressure of the combustion gas of the second gas generating agent 120, the combustion gas is discharged through the communication hole h2 to the first combustion chamber 10. The combustion gas of the second gas generating agent 120 is cooled and filtered by the filter 9, and then discharged to the outside of the housing 1 through the multiple gas discharge holes H1.

[0065] The combustion gas of the first gas generating agent 110 and the second gas generating agent 120 flows into an airbag (not shown) after being discharged to the outside of the housing 1. When the airbag inflates, a cushion is formed between the occupant and a hard structure, protecting the occupant from an impact.

[0066] [Opening timing] Generally, the combustion performance of a gas generating agent tends to improve as the temperature or pressure around the gas generating agent increases. In other words, in a low temperature and low pressure environment, the combustion of the gas generating agent becomes sluggish. Therefore, for example, when operating at a high temperature (high temperature operation) and when operating at a low temperature (low pressure operation), In order to reduce the difference in output performance of the gas generator between low and high temperature operation and to stabilize the output performance, it is necessary to maintain the internal pressure of the housing during low temperature operation, especially in the initial stage when the gas generating agent begins to burn.

[0067] As described above, in the gas generator 100 according to the first embodiment, the rupture pressure of the seal tape S1 at the large hole 12 is set to be lower than the rupture pressure of the seal tape S1 at the small hole 13. For example, assume that the first igniter 41 and the second igniter 71 are simultaneously activated during low-temperature operation, and the first gas generating agent 110 and the second gas generating agent 120 are all combusted. In this case, in the initial stage, only the large hole 12 of the multiple gas discharge holes H1 opens as the internal pressure of the housing 1 increases. As a result, a portion of the combustion gas is discharged and the internal pressure of the housing 1 decreases, but since the small hole 13 is closed, the combustion performance of the gas generating agent is maintained. Then, when the internal pressure of the housing 1 further increases as the gas generating agent burns, the small hole 13 opens after the large hole 12. However, if all the small holes 13 (all the first small holes 13a and all the second small holes 13b) are opened at once, the internal pressure of the housing 1 drops suddenly, and there is a concern that the combustion performance of the gas generating agent may be reduced. In contrast, in the gas generator 100 according to the first embodiment, the rupture pressure of the seal tape S1 is slightly different between the first small holes 13a and the second small holes 13b, so that the ease of opening is different between the first small holes 13a and the second small holes 13b. Therefore, the first small holes 13a, which have a relatively low rupture pressure, open relatively early, and the second small holes 13b, which have a relatively high rupture pressure, open relatively late. By differentiating the opening timing between the first small holes 13a and the second small holes 13b so that all the small holes 13 are not opened at once, a sudden drop in the internal pressure of the housing 1 is suppressed, and the combustion performance of the gas generating agent is maintained.

[0068] [Actions and Effects] As described above, the gas generator 100 according to the first embodiment includes the housing 1 that accommodates the first igniter 41 and the first gas generating agent 110 therein, a plurality of gas discharge holes H1 penetrating the inside and outside of the housing 1, and the seal tape S1 attached to the inner surface 11a of the housing 1. Before the operation of the gas generator 100, the seal tape S1 covers the openings of the plurality of gas discharge holes H1 on the inner surface 11a side of the housing 1 to block the plurality of gas discharge holes H1, and opens the plurality of gas discharge holes H1 by rupturing under the pressure of the combustion gas generated in the housing 1 by the operation of the gas generator 100. The plurality of gas discharge holes H1 include at least one each of the first small hole 13a and the second small hole 13b that differ in rupture pressure of the seal tape S1. The minimum flow path cross-sectional area A1 of the gas flow path formed by the first small hole 13a is equal to the minimum flow path cross-sectional area A2 of the gas flow path formed by the second small hole 13b, and the first small hole 13a and the second small hole 13b have different circumferential lengths of their openings on the inner surface 11a of the housing 1 so that their rupture pressures are different from each other.

[0069] According to the gas generator 100 configured as above, by making the minimum flow passage cross-sectional area for controlling the gas discharge amount equal between the first small hole 13a and the second small hole 13b, the gas discharge amount per unit time of the first small hole 13a and the gas discharge amount per unit time of the second small hole 13b can be made equal. Furthermore, by making the circumferential length of the opening on the inner surface 11a side of the housing 1 different between the first small hole 13a and the second small hole 13b, the rupture pressure of the first small hole 13a and the rupture pressure of the second small hole 13b can be made different from each other. In other words, it is possible to intentionally set two types of gas discharge holes that have the same internal pressure control function of the housing 1 but different ease of opening. According to this, the timing of opening is made different between the first small hole 13a and the second small hole 13b, and a sudden drop in the internal pressure of the housing 1 at the beginning of operation of the gas generator 100 can be suppressed. As a result, the combustion performance of the gas generating agent can be maintained, and the output performance of the gas generator 100 can be stabilized.

[0070] In gas generator 100 according to embodiment 1, first small hole 13a and second small hole 13b are closed with sealing tape S1 of the same specifications. Instead, the difference in rupture pressure is caused by the difference in the properties (perimeter) between the opening 13a1 of the first small hole 13a and the opening 13b1 of the second small hole 13b. This eliminates the need to use different specifications for the seal tape S1 for the first small hole 13a and the second small hole 13b, making it possible to block all the small holes 13 with a common (single) seal tape S1. However, in the technology disclosed herein, the specifications of the blocking member for the first gas exhaust hole and the second gas exhaust hole may be different from each other.

[0071] In addition, in gas generator 100 according to embodiment 1, the rupture pressure of first small hole 13a is configured to be lower than the rupture pressure of second small hole 13b, but in the technology according to the present disclosure, the magnitude relationship between the rupture pressure of the first gas discharge hole and the rupture pressure of the second gas discharge hole is not limited to the above. The rupture pressure of the first gas discharge hole may be higher than the rupture pressure of the second gas discharge hole. In addition, in gas generator 100 according to embodiment 1, large hole 12 and small hole 13 having different minimum flow path cross-sectional areas are included in the multiple gas discharge holes H1, but in the technology according to the present disclosure, it is not essential that multiple types of gas discharge holes having different minimum flow path cross-sectional areas exist.

[0072] Furthermore, in the technology according to the present disclosure, the multiple gas discharge holes may include, in addition to the first gas discharge hole and the second gas discharge hole, a gas discharge hole having an equivalent minimum flow path cross-sectional area and a blocking member rupture pressure different from the first gas discharge hole and the second gas discharge hole. In other words, there may be three or more types of gas discharge holes having the equivalent minimum flow path cross-sectional area and a blocking member rupture pressure different from the first gas discharge hole and the second gas discharge hole.

[0073] In gas generator 100 according to embodiment 1, first small hole 13a and second small hole 13b are formed as holes having a circular cross section, and first small hole 13a and second small hole 13b have openings (13a1, 13b1) on the inner surface 11a side of housing 1 with different hole diameters (D1, D2). This makes it possible to make the perimeters (P1, P2) of the openings on the inner surface 11a side of housing 1 different between first small hole 13a and second small hole 13b. Note that in the technology according to the present disclosure, the cross-sectional shape of the first gas discharge hole and second gas discharge hole and the shape of the openings of the first gas discharge hole and second gas discharge hole are not limited to a circle, and various shapes such as an ellipse, an oval, or a polygon can be adopted as described later.

[0074] Moreover, the first small hole 13a and the second small hole 13b according to the first embodiment include a straight portion 131 having a constant cross section in the thickness direction of the housing 1, and a tapered portion 132 that is continuous with the straight portion 131 and has an increasing cross-sectional area as it moves away from the straight portion 131 in the thickness direction. In one of the first small hole 13a and the second small hole 13b (the first small hole 13a), the tapered portion 132 opens on the inner surface 11a side of the housing 1, and the straight portion 131 opens on the outer surface 11b side of the housing 1. In the other (the second small hole 13b), the straight portion 131 opens on the inner surface 11a side of the housing 1, and the tapered portion 132 opens on the outer surface 11b side of the housing 1. In this manner, by configuring the positional relationship between the straight portion 131 and the tapered portion 132 to be reversed between the first small hole 13a and the second small hole 13b, it is possible to make the rupture pressure of the sealing tape S1 different from each other while making the minimum flow path cross-sectional area of ​​the first small hole 13a and the second small hole 13b equal. Note that in the technology disclosed herein, the second gas discharge hole (second small hole 13b) may have a tapered portion opening on the inner surface side of the housing and a straight portion opening on the outer surface side of the housing, and the first gas discharge hole (first small hole 13a) may have a straight portion opening on the inner surface side of the housing and a tapered portion opening on the outer surface side of the housing.

[0075] In addition, in the gas generator 100 according to Embodiment 1, the straight portion 131 is formed by a shearing cross section, and the tapered portion 132 is formed by a fracture cross section. The gas discharge hole H1 having such a straight portion 131 and tapered portion 132 can be preferably formed by punching. However, in the technology according to the present disclosure, the method of forming the first gas discharge hole and the second gas discharge hole in the housing is not limited to punching. For example, the first gas discharge hole and the second gas discharge hole may be drilled by drilling.

[0076] Here, as shown in FIGS. 3 and 5, let the thickness of the housing 1 be t1, and the length of the straight portion 131 of the small hole 13 in the thickness direction of the housing 1 be t2. At this time, it is also possible to set 0.3 < t2 / t1 < 0.7. Such a gas discharge hole H1 can be preferably formed by punching. However, in the technology according to the present disclosure, the relationship between the thickness of the housing and the length of the straight portion is not limited to the above.

[0077] In addition, the manufacturing method of the gas generator 100 according to Embodiment 1 includes a step of forming a plurality of gas discharge holes H1 including at least one of the first small hole 13a and the second small hole 13b in the housing 1, and a step of attaching a sealing tape S1 to the inner surface 11a of the housing 1 so as to cover the opening on the inner surface 11a side of the housing 1 in the plurality of gas discharge holes H1. In the step of forming a plurality of gas discharge holes H1 in the housing 1, the minimum flow path cross-sectional area A1 of the gas flow path formed by the first small hole 13a and the minimum flow path cross-sectional area A2 of the gas flow path formed by the second small hole 13b are made equal, and the first small hole 13a and the second small hole 13b are used to make the circumferences of the openings on the inner surface 11a side of the housing 1 different from each other. Thus, in the manufacturing method of the gas generator 100, a plurality of gas discharge holes H1 are formed in the housing 1 so that the cracking pressure of the sealing tape S1 is different between the first small hole 13a and the second small hole 13b. By such a manufacturing method, the opening timings are made different between the first small hole 13a and the second small hole 13b, and a rapid internal pressure drop of the housing 1 can be suppressed. That is, a gas generator 100 with stable output performance can be manufactured.

[0078] Furthermore, in the manufacturing method of gas generator 100 according to embodiment 1, in the step of forming a plurality of gas discharge holes H1 in housing 1, first small hole 13a is formed by perforating from outer surface 11b side of housing 1 by punching, and second small hole 13b is formed by perforating from inner surface 11a side of housing 1 by punching. That is, first small hole 13a and second small hole 13b are punched in opposite directions. This allows first small hole 13a and second small hole 13b to have different circumferential lengths of openings on inner surface 11a side of housing 1. Note that such a difference in circumferential length of the openings of the gas discharge holes on inner surface 11a side of housing 1 may be applied to large hole 12 in addition to first small hole 13a and second small hole 13b.

[0079] [Modification of the first embodiment] The following describes a gas generator 100 according to a modification of embodiment 1. In describing the modification, differences from the aspect described in Figs. 1 to 9 will be mainly described, and a detailed description of similarities will be omitted.

[0080] [Modification 1 of the first embodiment] Fig. 10 is an enlarged cross-sectional view for explaining the shape of the second small hole 13b according to Modification 1 of Embodiment 1. Fig. 10 shows a cross section corresponding to Fig. 5. Moreover, cross-sectional view C3 in Fig. 10 shows a cross section perpendicular to the thickness direction of the housing 1 at the second small hole 13b.

[0081] The second small hole 13b according to the first modification is formed as a hole having a circular cross section. The second small hole 13b according to the first modification is different from the second small hole 13b shown in FIG. 5 in that the cross section is constant from the opening 13b1 on the inner surface 11a side of the housing 1 to the opening 13b2 on the outer surface 11b side. In other words, the second small hole 13b according to the first modification does not have the tapered portion 132 as shown in FIG. 5. Therefore, the cross-sectional area of ​​the gas flow passage formed by the second small hole 13b according to the first modification is constant at the minimum flow passage cross-sectional area A2 in the thickness direction of the housing 1.

[0082] In the first modification, the first small hole 13a shown in FIG. 3 and the second small hole 13b shown in FIG. 10 are combined so that the minimum flow passage cross-sectional areas (A1, A2) are equivalent. Diameter D1 of opening 13a1 on the inner surface 11a side of small hole 13a is larger than diameter D2 of opening 13b1 on the inner surface 11a side of second small hole 13b. As a result, circumferential length P1 of opening 13a1 of first small hole 13a is longer than circumferential length P2 of opening 13b1 of second small hole 13b, and therefore the rupture pressure of first small hole 13a is lower than the rupture pressure of second small hole 13b. As described above, in gas generator 100 according to modification 1 as well, first small hole 13a and second small hole 13b have the same minimum flow path cross-sectional area and the rupture pressures of the blocking members are different from each other.

[0083] [Modification 2 of the first embodiment] FIG. 11 is an enlarged cross-sectional view for explaining the shape of the first small hole 13a according to the second modification of the first embodiment. In FIG. 11, a cross section corresponding to FIG. 3 is illustrated. Also, the end view E1 of FIG. 11 shows the opening 13a2 on the outer surface 11b side of the housing 1 in the first small hole 13a. FIG. 12 is an enlarged cross-sectional view for explaining the shape of the second small hole 13b according to the second modification of the first embodiment. In FIG. 12, a cross-section corresponding to FIG. 5 is illustrated. Also, the end view E2 of FIG. 12 shows the opening 13b1 on the inner surface 11a side of the second small hole 13b. The first small hole 13a and the second small hole 13b according to the second modification are formed as holes having a circular cross section. The first small hole 13a according to the second modification is formed so that the cross-sectional area increases from the opening 13a2 on the outer surface 11b side of the housing 1 to the opening 13a1 on the inner surface 11a side. On the other hand, the second small hole 13b according to the modified example 2 is formed so that the cross-sectional area increases from the opening 13b1 on the inner surface 11a side of the housing 1 to the opening 13b2 on the outer surface 11b side. In other words, the first small hole 13a and the second small hole 13b according to the modified example 2 do not have the straight portion 131 as shown in Fig. 3 and Fig. 5, and the taper directions are opposite to each other.

[0084] 11, the first small hole 13a according to the second modification has a minimum flow passage cross-sectional area at an opening 13a2 on the outer surface 11b side of the housing 1. Also, as shown in FIG. 12, the second small hole 13b according to the second modification has a minimum flow passage cross-sectional area at an opening 13b1 on the inner surface 11a side of the housing 1.

[0085] In the second modification, the minimum flow passage cross-sectional area A1 of the first small hole 13a and the minimum flow passage cross-sectional area A2 of the second small hole 13b are equivalent. Therefore, the diameter D1 of the opening 13a1 on the inner surface 11a side of the first small hole 13a is larger than the diameter D2 of the opening 13b1 on the inner surface 11a side of the second small hole 13b. As a result, the perimeter P1 of the opening 13a1 of the first small hole 13a is longer than the perimeter P2 of the opening 13b1 of the second small hole 13b, so that the rupture pressure of the first small hole 13a can be made lower than the rupture pressure of the second small hole 13b. As described above, in the gas generator 100 according to the second modification, the minimum flow passage cross-sectional areas of the first small hole 13a and the second small hole 13b are equivalent and the rupture pressures of the blocking members are different. 10 to 12 may also be applied to the large holes 12, and two types of large holes 12 may be provided that have the same minimum flow passage cross-sectional area but slightly different burst pressures.

[0086] <Embodiment 2> Hereinafter, a gas generator 100 according to embodiment 2 will be described. Of the possible aspects of the technology according to the present disclosure, embodiment 2 corresponds to an aspect in which the shape of the opening of the first gas discharge hole on the inner surface side of the housing and the shape of the opening of the second gas discharge hole on the inner surface side of the housing are different from each other. In the description of embodiment 2, differences from the aspect of embodiment 1 described in Figs. 1 to 12 will be mainly described, and detailed description of similarities will be omitted.

[0087] Fig. 13 is an enlarged cross-sectional view for explaining the shape of the first small hole 13a according to the second embodiment. Fig. 13 shows a cross section corresponding to Fig. 3. Also, cross-sectional view C4 of Fig. 13 shows a cross section perpendicular to the thickness direction of the housing 1 at the first small hole 13a. Fig. 14 is an enlarged cross-sectional view for explaining the shape of the second small hole 13b according to the second modification of the first embodiment. Fig. 12 shows a cross section corresponding to Fig. 5. Also, cross-sectional view C5 of Fig. 14 shows the cross section of the second small hole 13b. 1 shows a cross section at small hole 13b perpendicular to the thickness direction of housing 1. First small hole 13a and second small hole 13b according to embodiment 2 are formed as holes with circular cross sections, and the cross sections are constant from the opening on the inner surface 11a side to the opening on the outer surface 11b side of housing 1. In embodiment 2, the minimum flow path cross-sectional area A1 of first small hole 13a and the minimum flow path cross-sectional area A2 of second small hole 13b are equivalent.

[0088] As shown in FIG. 12, a protrusion 133 that protrudes toward the inside of the housing 1 is formed on the periphery of the opening 13a1 on the inner surface 11a side of the housing 1 in the first small hole 13a according to the second embodiment. The protrusion 133 is, for example, a burr generated during processing of the first small hole 13a. For example, in the process of forming a plurality of gas discharge holes H1 in the housing 1, the first small hole 13a is perforated from the outer surface 11b side of the housing 1 by punching or drilling, and the burr generated at the opening 13a1 on the inner surface 11a side of the housing 1 is left without being removed, thereby forming the protrusion 133. As shown in FIG. 13, the seal tape S1 is attached to the inner surface 11a of the housing 1 so as to cover the protrusion 133. When the gas generating agents 110, 120 are burned during the operation of the gas generator 100, the seal tape S1 is pressed against the periphery of the opening 13a1 of the first small hole 13a by the pressure of the combustion gas. At this time, the protrusions 133 press the seal tape S1 so as to pierce the seal tape S1, so that the seal tape S1 is more likely to tear than when the protrusions 133 are not formed. In other words, the formation of the protrusions 133 reduces the tear pressure of the seal tape S1 at the first small hole 13a.

[0089] As shown in FIG. 14, a chamfered portion 134 is formed by C-chamfering on the periphery of the opening 13b1 on the inner surface 11a side of the housing 1 in the second small hole 13b according to the second embodiment. For example, in the process of forming a plurality of gas exhaust holes H1 in the housing 1, the second small hole 13b is perforated from the outer surface 11b side of the housing 1 by punching or drilling, and the opening 13b1 on the inner surface 11a side of the housing 1 is chamfered to form the chamfered portion 134. The chamfered portion 134 is not limited to C-chamfering, and may have other shapes such as R-chamfering. As shown in FIG. 13, the sealing tape S1 is attached to the inner surface 11a of the housing 1 so as to cover the chamfered portion 134. When the gas generating agents 110, 120 burn, the sealing tape S1 is pressed against the periphery of the opening 13b1 of the second small hole 13b by the pressure of the combustion gas, but because the corners of the periphery are rounded off by the chamfered portion 134, a shear force is less likely to act on the sealing tape S1 compared to a case in which the chamfered portion 134 is not formed, making the sealing tape S1 less likely to tear. In other words, by forming the chamfered portion 134, the tearing pressure of the sealing tape S1 at the second small hole 13b is increased.

[0090] As described above, in gas generator 100 according to embodiment 2, in the step of forming a plurality of gas discharge holes H1 in housing 1, first small hole 13a and second small hole 13b have openings with different shapes on the side of inner surface 11a of housing 1. Therefore, also in gas generator 100 according to embodiment 2, first small hole 13a and second small hole 13b have the same minimum flow path cross-sectional area and different rupture pressures of seal tape S1. This makes it possible to stabilize the output performance of gas generator 100.

[0091] In the second embodiment, the protrusion 133 is formed on the first small hole 13a and the chamfered portion 134 is formed on the second small hole 13b, but the technology according to the present disclosure is not limited to this. By forming a protrusion on at least a part of the periphery of the opening on the inner surface side of the housing in only one of the first gas exhaust hole (first small hole 13a) and the second gas exhaust hole (second small hole 13b), it is possible to make the first gas exhaust hole and the second gas exhaust hole have different rupture pressures. For example, one of the first gas exhaust hole and the second gas exhaust hole is perforated by punching or drilling from the outer surface side of the housing and the other is perforated by punching from the inner surface side of the housing, so that at least a part of the opening on the inner surface side of the housing in only the one of the first gas exhaust hole and the second gas exhaust hole is perforated by punching or drilling. A protrusion can be formed on the opening of the first gas exhaust hole or the second gas exhaust hole on the inner surface side of the housing. Also, by chamfering the periphery of the opening of only one of the first gas exhaust hole or the second gas exhaust hole on the inner surface side of the housing, the burst pressure of the first gas exhaust hole and the second gas exhaust hole can be made different from each other. Furthermore, the shape shown in Fig. 13 or 14 may also be applied to the large hole 12, and two types of large holes 12 having the same minimum flow passage cross-sectional area but slightly different burst pressures may be provided.

[0092] [Modification of the second embodiment] In the second embodiment, the planar shape of the periphery of the opening on the inner surface 11a side of the housing 1 may be different between the first small hole 13a and the second small hole 13b. FIG. 15 is a diagram showing an example of the shape of the opening of the small hole 13 on the inner surface 11a side of the housing 1. FIG. 15(A) shows a case where the opening is circular, FIG. 15(B) shows a case where the opening is elliptical, FIG. 15(C) shows a case where the opening is rectangular, and FIG. 15(D) shows a case where the opening is square. Note that the shapes shown in FIG. 15 are merely examples. In addition to the shapes shown in FIG. 15, various shapes such as oval and polygons other than square can be adopted as the shape of the opening.

[0093] For example, the opening 13a1 of the first small hole 13a and the opening 13b1 of the second small hole 13b may each be selected from the shapes shown in Figs. 15(A) to (D). In this way, the tearing pressure of the seal tape S1 can be made different between the first small hole 13a and the second small hole 13b. For example, the first small hole 13a may be an elliptical hole with a constant cross section, and the second small hole 13b may be a circular hole with a constant cross section and a flow path cross-sectional area equivalent to that of the first small hole 13a. When compared with the same area, the ellipse has a longer perimeter than the circle. Also, for example, the first small hole 13a may be a rectangular hole with a constant cross section, and the second small hole 13b may be a square hole with a constant cross section and a flow path cross-sectional area equivalent to that of the first small hole 13a. When compared with the same area, the rectangle has a longer perimeter than the square. In both of the above examples, the perimeter P1 of the opening 13a1 of the first small hole 13a is longer than the perimeter P2 of the opening 13b1 of the second small hole 13b. In other words, the first small hole 13a and the second small hole 13b can be made different not only in the shape of the opening on the inner surface 11a side of the housing 1 but also in the perimeter of the opening, and the bursting pressure can be suitably made different. Note that such a difference in shape may also be applied to the large hole 12, and two types of large holes 12 having the same minimum flow passage cross-sectional area but slightly different burst pressures may be provided.

[0094] <Other> Although the preferred embodiment of the present disclosure has been described above, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In the first embodiment, the first gas exhaust hole and the second gas exhaust hole have different circumferential lengths of the openings on the inner surface side of the housing, and in the second embodiment, the openings have different shapes. However, both the shape and circumferential length of the openings may be different between the first gas exhaust hole and the second gas exhaust hole. In other words, the technology according to the present disclosure only requires that at least one of the shape and circumferential length of the openings on the inner surface side of the housing is different between the first gas exhaust hole and the second gas exhaust hole. Even if there are multiple gas exhaust holes with different shapes and circumferential lengths of the openings on the inner surface side of the housing, those in which the difference in shape and circumferential length is recognized to be within the range of the processing tolerance of the gas exhaust holes are excluded from the technology according to the present disclosure. In the above-described embodiment, a so-called dual-type gas generator having two igniters is exemplified, but even when the technology according to the present disclosure is applied to a so-called single-type gas generator having only one igniter as shown in FIG. 1 of JP 2019-156107 A, for example, the same effect as that of the above-described embodiment can be obtained. For example, in a single-type gas generator, a case is assumed in which at least two types of gas exhaust holes (first gas exhaust hole and second gas exhaust hole) having the same gas exhaust amount per unit time (internal pressure control function of the housing) and different rupture pressures (ease of opening) of the blocking member are provided. Even in this case, since the opening timing of the first gas exhaust hole and the opening timing of the second gas exhaust hole differ during operation of the gas generator, that is, the gas exhaust hole opens in multiple stages, for example, a sudden drop in internal pressure during low-temperature operation is suppressed, and the gas generator can be normally operated. It is possible to realize combustion performance similar to that at warm or high temperatures. Note that the technology according to the present disclosure is intended to control the internal pressure of the housing when the gas generator is in operation, and is not limited to application only to cases where the environmental temperatures during operation are different as in the above-described embodiment, so long as the usage can adjust the timing at which the first gas discharge hole and the second gas discharge hole open. [Explanation of symbols]

[0095] 100 Gas Generator 1. Housing 41 First igniter (an example of an igniter) 110 First gas generating agent (an example of a gas generating agent) H1 Gas exhaust hole 13a First small hole (an example of a first gas exhaust hole) 13b Second small hole (an example of a second gas exhaust hole) S1 Sealing tape (an example of a blocking material)

Claims

1. An igniter, A gas generating agent that generates a combustion gas by burning in response to activation of the igniter; a housing that accommodates the igniter and the gas generating agent therein; A plurality of gas exhaust holes passing through the housing from the inside to the outside; a blocking member attached to an inner surface of the housing, which covers openings of the plurality of gas exhaust holes on the inner surface side of the housing before activation of the igniter to block the plurality of gas exhaust holes, and which breaks under the pressure of the combustion gas generated by activation of the igniter to open the plurality of gas exhaust holes, the plurality of gas exhaust holes include at least one first gas exhaust hole and one second gas exhaust hole, the blocking member having a different rupture pressure; a minimum flow path cross-sectional area of ​​a gas flow path formed by the first gas discharge hole is equal to a minimum flow path cross-sectional area of ​​a gas flow path formed by the second gas discharge hole, The first gas discharge hole and the second gas discharge hole are different from each other in at least one of a shape and a circumferential length of an opening on an inner surface side of the housing. Gas generator.

2. the first gas exhaust hole and the second gas exhaust hole are blocked by the blocking member having the same specifications; 2. The gas generator according to claim 1.

3. the first gas exhaust hole and the second gas exhaust hole are holes having a circular cross section, the first gas exhaust hole and the second gas exhaust hole have openings on the inner surface side of the housing with different hole diameters; 3. A gas generator according to claim 1 or 2.

4. the first gas discharge hole and the second gas discharge hole include a straight portion having a constant cross section in a thickness direction of the housing, and a tapered portion that is connected to the straight portion and has a cross-sectional area that increases with distance from the straight portion in the thickness direction, one of the first gas discharge hole and the second gas discharge hole has a tapered portion that opens to an inner surface side of the housing and a straight portion that opens to an outer surface side of the housing, the other of the first gas discharge hole and the second gas discharge hole has a straight portion that opens to an inner surface side of the housing and a tapered portion that opens to an outer surface side of the housing.

3. A gas generator according to claim 1 or 2.

5. The straight portion is formed by a shear surface, The tapered portion is formed by a fractured surface.

5. The gas generator according to claim 4.

6. If the thickness of the housing is t1 and the length of the straight portion in the thickness direction of the housing is t2, 0.3<t2 / t1<0.7; 5. The gas generator according to claim 4.

7. a protrusion protruding toward the inside of the housing is formed on at least a part of a periphery of an opening of only one of the first gas discharge hole and the second gas discharge hole on the inner surface side of the housing, The blocking member is attached to the inner surface of the housing so as to cover the protrusion.

3. A gas generator according to claim 1 or 2.

8. a periphery of an opening of only one of the first gas discharge hole and the second gas discharge hole on the inner surface side of the housing is chamfered; 3. A gas generator according to claim 1 or 2.

9. A method for manufacturing a gas generator comprising: an igniter; a gas generating agent that generates a combustion gas by burning in response to activation of the igniter; a housing that accommodates the igniter and the gas generating agent therein; a plurality of gas discharge holes that penetrate the housing from inside to outside; and a blocking member that blocks the plurality of gas discharge holes, forming a plurality of gas exhaust holes including at least one first gas exhaust hole and at least one second gas exhaust hole in the housing such that the first gas exhaust hole and the second gas exhaust hole have different rupture pressures for the blocking member; and attaching the blocking member to the inner surface of the housing so as to cover openings of the plurality of gas exhaust holes on the inner surface side of the housing, In forming the plurality of gas discharge holes in the housing, a minimum flow path cross-sectional area of ​​a gas flow path formed by the first gas discharge hole and a minimum flow path cross-sectional area of ​​a gas flow path formed by the second gas discharge hole are made equivalent, and at least one of a shape and a circumferential length of an opening on an inner surface side of the housing is made different between the first gas discharge hole and the second gas discharge hole. A method for manufacturing a gas generator.

10. In forming the plurality of gas exhaust holes in the housing, forming one of a first gas discharge hole and a second gas discharge hole by punching an outer surface side of the housing; forming the other of the first gas discharge hole and the second gas discharge hole by punching from an inner surface side of the housing; A method for manufacturing the gas generator according to claim 9.

11. In forming the plurality of gas exhaust holes in the housing, chamfering an opening of only one of the first gas discharge hole and the second gas discharge hole on the inner surface side of the housing; A method for manufacturing the gas generator according to claim 9.

12. In attaching a closing member to the inner surface of the housing, the first gas discharge hole and the second gas discharge hole are closed by the closing member having the same specifications. A method for manufacturing the gas generator according to any one of claims 9 to 11.

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