Gas generator

Abstract

To provide a gas generator in which assembling strength of a holder and a cup along a circumferential direction is highly secured even when the cup is assembled to the holder by caulking fixing.SOLUTION: A gas generator 1 includes: a cup 40 which is stored with a gas generating agent 50 therein and has one end in an axial direction configured as an open end 41a; and a holder 10 which closes the open end 41a and holds an igniter 20 so that an ignition section 22 faces the gas generating agent 50. The cup 40 has a flange section 43 at the open end 41a. The holder 10 has an annular groove section 15 to receive the flange section 43 and an annular flange section 16 which has a tip bent so as to sandwich the flange section 43 between the annular flange section and a bottom face of the annular groove section 15. The cup 40 is harder than the holder 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas generator, and more particularly to a compact gas generator configured to generate a relatively small amount of gas when activated. [Background technology]

[0002] Conventionally, seat belt devices, which are occupant protection devices, have become widespread from the viewpoint of protecting occupants of automobiles, etc. Seat belt devices are equipped with the purpose of protecting occupants from impacts that occur in the event of a vehicle collision, etc., and restrain the occupants in their seats by wrapping a belt around their bodies, thereby preventing the occupants from being thrown into or out of the vehicle in the event of a vehicle collision, etc.

[0003] Among seat belt devices, those equipped with so-called pretensioners incorporate a small gas generator known as a micro gas generator. A pretensioner is a device that instantly retracts a seat belt that has become loose due to factors such as the thickness of clothing when a vehicle collision is detected. This function is achieved by strongly retracting one end of the seat belt using the gas pressure output from the gas generator.

[0004] Furthermore, when compared with large gas generators known as inflators that are preferably incorporated into airbag devices, this small gas generator generates an extremely small amount of gas when activated, and as a result, its structure is also significantly different.

[0005] An example of a document disclosing the specific structure of this type of gas generator is Japanese Patent Application Laid-Open No. 2012-91110 (Patent Document 1). The gas generator disclosed in Patent Document 1 comprises a cup in which a gas generating agent is accommodated, and a holder that holds an igniter and to which the above-mentioned cup is attached, and the cup is attached to the holder by so-called crimping.

[0006] Specifically, in the gas generator disclosed in Patent Document 1, a flange portion extending outward is provided at the open end of the cup, and a crimping flange is provided at the axial end of the holder on the cup side, and the crimping flange is bent inward to engage the flange portion, thereby fixing the cup to the holder.

[0007] The cup and holder are generally made of an aluminum-based material from the viewpoints of facilitating the crimping operation and reducing the weight of the gas generator as a whole. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-91110 Summary of the Invention [Problem to be solved by the invention]

[0009] Here, in this type of gas generator, it is important that the cup is firmly attached to the holder so that the cup will not fall off the holder even when the internal pressure rises during activation, and specifically, it is necessary to ensure sufficient assembly strength between the cup and holder along the axial direction.

[0010] On the other hand, it is necessary to ensure not only the above-mentioned axial assembly strength of the cup and holder but also the circumferential assembly strength of the cup and holder. This is because a so-called screwing method may be used to attach the gas generator to the pretensioner, and if the above-mentioned circumferential assembly strength is not ensured to be sufficiently high, the holder will rotate relative to the cup during the screwing operation, making it impossible to attach the cup to the pretensioner.

[0011] However, when the cup is assembled to the holder by crimping as described above, although the assembly strength of the cup and holder along the axial direction can be secured relatively easily, it becomes difficult to secure high assembly strength of the cup and holder along the circumferential direction.

[0012] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a gas generator in which high assembly strength between the holder and the cup along the circumferential direction is ensured even when the cup is assembled to the holder by caulking. [Means for solving the problem]

[0013] A gas generator according to the present invention comprises a gas generating agent, an igniter, a cup, and a holder. The gas generating agent generates gas by combustion, and the igniter has an ignition portion loaded with an ignition charge and a terminal pin connected to the ignition portion. The cup accommodates the gas generating agent and is a substantially cylindrical member with a bottom and one axial end formed as an open end. The holder is a substantially cylindrical member to which the cup is coaxially assembled, closing the open end and holding the igniter so that the ignition portion faces the gas generating agent. The cup has a flange portion extending outward from the open end, and an axial end face of the holder facing the ignition portion is provided with an annular groove portion that receives the flange portion and an annular flange portion that defines the outer wall surface of the annular groove. The flange portion includes a second surface located opposite to a first surface facing the bottom surface of the annular groove. In the gas generator based on the present invention, the annular collar is bent inward with the flange portion received by the annular groove portion, whereby the tip portion of the annular collar abuts against the second surface, and thereby the flange portion is sandwiched between the tip portion of the annular collar and the bottom surface of the annular groove portion in the axial direction of the cup, and the cup is assembled to the holder. The cup is made of a metal material selected from the group consisting of aluminum, aluminum alloys, and iron-based materials, and the holder is made of a metal material selected from the group consisting of aluminum and aluminum alloys. The cup is harder than the holder.

[0014] In the gas generator according to the present invention, the cup preferably has a Vickers hardness exceeding 130 Hv, and in this case, the holder preferably has a Vickers hardness of 130 Hv or less.

[0015] In the gas generator according to the present invention, the cup preferably has a Vickers hardness of 158 Hv or more, and in this case, the holder preferably has a Vickers hardness of 130 Hv or less.

[0016] In the gas generator according to the present invention, a rotational torque required to rotate the cup and the holder relatively by 5° about the axis may be 5.92 N·m or more. [Effects of the Invention]

[0017] According to the present invention, even when the cup is assembled to the holder by caulking, a gas generator can be provided in which the assembly strength of the holder and the cup along the circumferential direction is high. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view of a gas generator according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of region II shown in FIG. [Figure 3] 2 is a schematic cross-sectional view showing a method of assembling a cup to a holder in the gas generator shown in FIG. 1. FIG. [Figure 4] 1 is a table showing the test conditions and test results of verification tests 1 and 2. [Figure 5] FIG. 1 is a schematic diagram showing measurement points for the Vickers hardness of the cup in Verification Tests 1 and 2. [Figure 6] FIG. 1 is a schematic diagram showing the measurement points of the Vickers hardness of the holder in Verification Tests 1 and 2. [Figure 7] 10 is a table showing the test conditions and test results of Verification Tests 3 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown below exemplify the case where the present invention is applied to a gas generator (so-called micro gas generator) that is suitably incorporated into a seat belt device equipped with a pretensioner. In the embodiments shown below, identical or common parts are designated by the same reference numerals in the drawings, and their description will not be repeated.

[0020] Fig. 1 is a schematic cross-sectional view of a gas generator according to an embodiment. First, with reference to Fig. 1, the configuration of gas generator 1 according to the present embodiment will be described.

[0021] As shown in FIG. 1, gas generator 1 in the present embodiment mainly comprises a holder 10, an igniter 20, a seal member 30, a cup 40, and a gas generating agent 50.

[0022] Holder 10 and cup 40 are combined coaxially to form a housing that serves as the outer shell of gas generator 1. Igniter 20 is held by holder 10, and cup 40 is assembled to holder 10 so as to cover igniter 20. Gas generating agent 50 is contained in a space defined by holder 10, igniter 20, and cup 40.

[0023] Holder 10 is a member for holding igniter 20 and cup 40, and has a substantially cylindrical shape. Here, in the present embodiment, holder 10 is provided with first recess 12, second recess 13, and opening 14a, which will be described later, and therefore holder 10 substantially has a substantially cylindrical shape.

[0024] As described above, the holder 10 is also a component that constitutes part of the housing, and is formed from a molded product made of a metal material such as aluminum or an aluminum alloy. The holder 10 is formed into the shape shown in the drawing by performing processes such as forging, punching, and cutting on a raw metal material, such as a plate-shaped metal material or a rod-shaped metal material, in a predetermined order, one or more times.

[0025] Holder 10 has a body 11 that defines an outer circumferential surface, and body 11 is provided with a first recess 12 and a second recess 13. A partition 14 is formed in a portion of body 11 located between first recess 12 and second recess 13 so as to separate first recess 12 and second recess 13, and a locking portion 15 is formed in a portion of body 11 located closer to a bottom wall 42 (described later) of cup 40 than partition 14.

[0026] First recess 12 is a portion for receiving and holding base 21 (described later) of igniter 20, and is provided on the axial end surface of body 11 facing cup 40. The peripheral surface of first recess 12 is mainly defined by locking portion 15, and the bottom surface of first recess 12 is defined by partition portion 14.

[0027] Second recess 13 is a portion in which a pair of terminal pins 23 (described later) of igniter 20 are disposed, and which receives and holds a connector (not shown) for connecting igniter 20 to the outside via the pair of terminal pins 23, and is provided on the axial end face of body portion 11 on the side that does not face cup 40. The circumferential surface of second recess 13 is defined by the cylindrical portion of body portion 11, and the bottom surface of second recess 13 is defined by partition portion 14.

[0028] Partition portion 14 is provided with opening 14a that communicates with first recess 12 and second recess 13. Opening 14a is a portion through which a pair of terminal pins 23 are inserted (more precisely, a portion into which the pair of terminal pins 23 and the lower end portion of base portion 21 of igniter 20 that covers them are fitted).

[0029] Locking portion 15 is a portion for crimping and fixing base 21 of igniter 20, and has an annular plate shape. Locking portion 15 has a tip bent inward, whereby igniter 20 housed in first recess 12 is fixed to holder 10 so as to be immovable.

[0030] An annular groove portion 16 and an annular flange portion 17 are provided on the axial end face of the body portion 11 facing the ignition portion 22 (i.e., the axial end face located on the bottom wall portion 42 side of the cup 40) so as to surround the above-mentioned locking portion 15.

[0031] Annular groove 16 is a portion for receiving flange 43 (described later) of cup 40, and has bottom surface 16a, outer wall surface 16b, and inner wall surface 16c (see FIG. 2, etc.). Annular flange 17 is a portion for crimping and fixing flange 43 of cup 40, and has an annular plate shape that protrudes from body 11 toward ignition part 22 so as to define outer wall surface 16b of annular groove 16.

[0032] Here, the annular flange portion 17 has its tip portion bent inward, which fixes the cup 40 to the holder 10 so that it cannot move, and details of this will be explained later.

[0033] Igniter 20 is used to generate a flame and is also called a squib. Igniter 20 has a base 21, an ignition unit 22, and a pair of terminal pins 23. Base 21 is a portion that holds ignition unit 22 and the pair of terminal pins 23, and is also a portion that is fixed to holder 10. Base 21 holds the pair of terminal pins 23 by inserting them through it. Note that in FIG. 1, the pair of terminal pins 23 are positioned overlapping in a direction perpendicular to the plane of the paper, so only one of them is visible.

[0034] Ignition unit 22 contains an ignition charge that ignites and burns to generate a flame when activated, and a resistor (bridge wire) for igniting the ignition charge. A pair of terminal pins 23 are connected to ignition unit 22 to ignite the ignition charge.

[0035] More specifically, the ignition section 22 includes a squib cup formed in a cup shape, and the resistor described above is attached so as to connect the tips of a pair of terminal pins 23 inserted into the squib cup, and an ignition charge is loaded into the squib cup so as to surround or be close to the resistor.

[0036] Here, nichrome wire or the like is generally used as the resistor, and ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), lead tricinate, etc. are generally used as the ignition charge. The squib cup mentioned above is generally made of metal or plastic.

[0037] When a collision is detected, a predetermined amount of current flows through the resistor via terminal pin 23. This current flow generates Joule heat in the resistor, causing the ignition charge to begin burning. The high-temperature flame generated by the combustion ruptures the squib cup containing the ignition charge. The time from when the current flows through the resistor to when the igniter 20 is activated is generally 2 ms or less when nichrome wire is used for the resistor.

[0038] When assembling igniter 20 to holder 10, igniter 20 is inserted into first recess 12 of holder 10 from the axial end thereof on the side where first recess 12 is provided, so that pair of terminal pins 23 are inserted into opening 14a provided in partition 14. As a result, base 21 is housed within first recess 12 and opening 14a, and pair of terminal pins 23 are disposed within second recess 13. In this state, the tip side portion of locking portion 15 is bent toward base 21, so that base 21 is sandwiched between partition 14 and locking portion 15, and igniter 20 is thereby fixed to holder 10 by crimping.

[0039] Therefore, the ignition portion 22 of the igniter 20 is located closer to the bottom wall portion 42 of the cup 40 than the axial end face on the side where the first recess 12 of the holder 10 is provided, and the ignition portion 22 faces the gas generating agent 50 contained in the storage space 44 of the cup 40, which will be described later.

[0040] Here, a seal member 30 made of an O-ring or the like is housed in advance within first recess 12 of holder 10, and this seal member 30 seals the gap that occurs between holder 10 and igniter 20. More specifically, seal member 30 is positioned so as to be interposed between partition portion 14 and locking portion 15 of holder 10 and base portion 21 of igniter 20, and seal member 30 is compressed by holder 10 and igniter 20, thereby ensuring the seal between them.

[0041] It is preferable to use a material having sufficient heat resistance and durability as the sealing member 30, and for example, an O-ring made of EPDM, which is a type of ethylene propylene rubber, can be suitably used.

[0042] A substantially cylindrical cover 24 with a bottom is placed in advance over the ignition portion 22 of the igniter 20 and the upper portion of the base 21, and the locking portion 15 of the holder 10 is crimped to fix the igniter 20 together with the cover 24. A fuse hole is provided in the bottom wall of the cover 24 for ejecting a high-temperature flame generated by the combustion of an ignition charge housed in the ignition portion 22 of the igniter 20 toward the gas generating agent 50. The cover 24 is formed as a molded product made of a metal material such as aluminum, an aluminum alloy, or an iron-based material including stainless steel.

[0043] The cover 24 is for efficiently guiding the thermal particles generated in the ignition section 22 to the gas generating agent 50 when the igniter 20 is activated, and more specifically, for providing directionality to the traveling direction of the thermal particles generated in the ignition section 22. This narrows the traveling direction of the thermal particles to the axial direction of the igniter 20, making it possible to output the gas generated in the gas generator 1 to the outside at an early stage.

[0044] The cup 40 is made of a substantially cylindrical member with a bottom, one axial end of which is configured as an open end 41a, and has a side wall portion 41, a bottom wall portion 42, and a flange portion 43. A gas generating agent 50 is accommodated in an accommodation space 44 of the cup 40 defined by the side wall portion 41 and the bottom wall portion 42.

[0045] The open end 41a is one of the pair of axial ends of the side wall 41, and is located opposite the end where the bottom wall 42 is located. The flange 43 extends outward from the open end 41a. The flange 43 is a portion for fixing the cup 40 to the holder 10.

[0046] As described above, cup 40 is fixed to the holder by having its flange portion 43 crimped and fixed by annular flange portion 17 provided on holder 10. Therefore, cup 40 has its open end 41a closed by holder 10 (more strictly, by igniter 20, cover 24, etc. in addition to holder 10).

[0047] Scores 42a are provided in bottom wall portion 42 of cup 40 by forming groove-like cuts in the surface thereof. These scores 42a are provided in order to form weak parts at predetermined positions of bottom wall portion 42 that are weaker than other positions, and by providing these scores 42a, cup 40 can be configured to open from these parts as a starting point when gas generator 1 is activated.

[0048] The cup 40 is also a component that constitutes part of the housing, and is formed from a molded product made of a metal material such as aluminum, an aluminum alloy, or an iron-based material including stainless steel. The cup 40 is generally formed by press working using a mold.

[0049] The gas generant 50 generates a large amount of gas when ignited by the igniter 20 and burns. Examples of gas generants 50 that can be used include molded bodies of smokeless powder (nitrocellulose) and molded bodies of non-azide-based compositions consisting of an organic nitrogen compound and an oxidizer. In recent years, attention has been focused on the use of non-nitrocellulose-based gas generants as gas generants 50, which produce extremely low amounts of harmful substances such as carbon monoxide.

[0050] The molded body of the gas generating agent 50 can be made in various shapes, such as granules, pellets, cylinders, and disks. Also, perforated shapes (such as macaroni or lotus root shapes) having through holes can also be used as the molded body of the gas generating agent 50. The optimum shape is selected depending on the specifications of the pretensioner to which the gas generator 1 is to be assembled. In addition to the shape, the size of the molded body of the gas generating agent 50 is also selected taking into consideration the linear burning velocity, pressure exponent, and the like. The amount of gas generating agent 50 to be filled can be changed as appropriate depending on the specifications of the pretensioner to which it is to be assembled, but is generally about 0.1 g to 2.0 g when smokeless powder is used.

[0051] Next, with reference to FIG. 1, an operation during operation of gas generator 1 in the present embodiment will be described.

[0052] 1, when a vehicle equipped with gas generator 1 in this embodiment collides, the collision is detected by collision detection means separately provided in the vehicle, and based on this, igniter 20 is activated. When igniter 20 is activated, an ignition charge housed in ignition portion 22 is ignited and burns, causing the squib cup to explode.

[0053] The flame generated by the combustion of the ignition charge is ejected toward the accommodation space 44 in which the gas generating agent 50 is accommodated when the squib cup explodes. The gas generating agent 50 is ignited by this flame and burns, generating a large amount of gas in the accommodation space 44. This combustion of the gas generating agent 50 causes a rapid increase in the internal pressure of the accommodation space 44, which causes the bottom wall portion 42 of the cup 40 to open at the score 42a, allowing the large amount of generated gas to be discharged to the outside of the gas generator 1.

[0054] Thereafter, the large amount of gas released from the gas generator 1 is directed to the operating space of the pretensioner in which the gas generator 1 is incorporated, thereby driving the pretensioner and strongly pulling in one end of the seat belt attached to the seat belt device.

[0055] Fig. 2 is an enlarged view of region II shown in Fig. 1. Also, Fig. 3 is a schematic cross-sectional view showing a method of assembling a cup to a holder in the gas generator shown in Fig. 1. Next, with reference to Figs. 2 and 3, the structure for assembling cup 40 to holder 10 in gas generator 1 according to the present embodiment will be described in more detail.

[0056] 2 and 3, in gas generator 1 according to the present embodiment, as described above, cup 40 is assembled to holder 10 by crimping. The crimping is performed by bending annular flange portion 17 provided on holder 10 inward toward flange portion 43 of cup 40.

[0057] 3, first, flange portion 43 of cup 40 is inserted into annular groove 16 provided in holder 10. This insertion of flange portion 43 into annular groove 16 is performed by arranging holder 10 and cup 40 so that they are positioned coaxially, and then relatively moving cup 40 toward holder 10 in the direction of arrow AR1 shown in the figure.

[0058] As a result, of the pair of axially positioned surfaces of flange portion 43 of cup 40, first surface 43a positioned on the holder 10 side comes into contact with bottom surface 16a of annular groove 16. At this time, the inner peripheral surface of side wall portion 41 of cup 40 is abutted against the outer peripheral surface of body portion 11 of the holder 10 at a portion that defines first recess 12 and inner wall surface 16c of annular groove 16.

[0059] Next, the tip end portion of annular flange 17 of holder 10 is bent inward in the direction of arrow AR2 shown in the figure. As a result, the entire annular flange 17, except for its base end portion (i.e., the portion connected to body 11), is tilted toward bottom surface 16a of annular groove 16, and is bent toward flange 43 of cup 40 as described above.

[0060] 2, the tip end portion of outer wall surface 16b of annular flange 17 comes into contact with second surface 43b, which is one of a pair of axial surfaces of flange 43 and is located opposite first surface 43a. Therefore, flange 43 is sandwiched between the tip end portion of annular flange 17 and bottom surface 16a of annular groove 16 in the axial direction of cup 40.

[0061] At this time, the annular collar portion 17 is pressed against the flange portion 43 with a predetermined load. Here, the Vickers hardness of the holder 10 is, for example, 90 Hv or more and 140 Hv or less, and the Vickers hardness of the cup 40 is, for example, 130 Hv or more and 250 Hv or less, and more preferably, 140 Hv or more and 200 Hv or less, provided that the Vickers hardness is greater than the Vickers hardness of the holder 10. Therefore, by setting the load to, for example, 20 kN or more and 30 kN or less, plastic deformation occurs in both the annular collar portion 17 and the flange portion 43. The Vickers hardnesses of the holder 10 and the cup 40 can be measured according to the measurement method described below.

[0062] As a result, flange portion 43 of cup 40 is sandwiched in the axial direction between the tip end portion of annular flange 17 of holder 10 and bottom surface 16a of annular groove 16, thereby assembling cup 40 to holder 10. As described above, annular flange 17 is pressed against flange portion 43 with a predetermined load during crimping, so that flange 43 and the surface of holder 10 in the contacting portion come into pressure contact with each other, and as a result, cup 40 is firmly fixed to holder 10.

[0063] Here, in gas generator 1 according to the present embodiment, cup 40 is harder than holder 10 (that is, the Vickers hardness of cup 40 described above is configured to be greater than the Vickers hardness of holder 10). With this configuration, of annular flange 17 of holder 10 and flange portion 43 of cup 40, which undergo plastic deformation during the above-described crimping fixation, greater plastic deformation occurs in annular flange 17 of holder 10, which is particularly softer.

[0064] Therefore, at the corners on the first surface 43a side of the tip of flange 43 and the portion of annular collar 17 corresponding to these corners, the surface of annular collar 17 is plastically deformed in a curved shape to follow the shape of the corners of cup 40, which is harder, and flange 43 bites into holder 10 at these portions, generating a particularly high contact pressure and achieving a strong fixed state. Hereinafter, this portion will be referred to as the "first contact portion A1."

[0065] Furthermore, at the corners on the second surface 43b side of the tip of flange 43 and the portion of annular collar 17 corresponding to these corners, the surface of annular collar 17 is plastically deformed in a curved shape to follow the shape of the corners of cup 40, which is harder, so that flange 43 bites into holder 10 at these portions, generating a particularly high contact pressure and achieving a strong bond. Hereinafter, this portion will be referred to as the "second contact portion A2."

[0066] In this way, in gas generator 1 according to the present embodiment, a particularly high contact pressure is generated at first abutment portion A1 and second abutment portion A2 described above, resulting in a high frictional force at these portions. Therefore, due to this high frictional force, it is possible to ensure high assembly strength between cup 40 and holder 10 along the circumferential direction, and a configuration can be achieved in which holder 10 does not easily rotate relative to cup 40, even when a relatively high torque is applied between cup 40 and holder 10 along the rotational direction (i.e., the circumferential direction).

[0067] By increasing the frictional resistance between the holder 10 and the cup 40 after they have been crimped and fixed using this configuration, it is possible to greatly simplify the manufacturing process compared to using a method of increasing the frictional resistance by forming unevenness in the annular collar portion 17 and the flange portion 43 in advance by machining or the like, and it is possible to manufacture a gas generator at low cost that can ensure high assembly strength between the cup 40 and the holder 10 along the circumferential direction.

[0068] Therefore, by configuring gas generator 1 as in the present embodiment described above, even when cup 40 is assembled to holder 10 by crimping, it is possible to ensure high assembly strength between holder 10 and cup 40 not only along the axial direction but also along the circumferential direction.

[0069] Fig. 4 is a table showing the test conditions and test results of Verification Tests 1 and 2. Figs. 5 and 6 are schematic diagrams showing the measurement points for the Vickers hardness of the cup and the holder, respectively, in Verification Tests 1 and 2. Details of Verification Tests 1 and 2 conducted by the present inventors and the method for measuring the Vickers hardness of each of the holder 10 and cup 40 described above will be described below with reference to Figs. 4 to 6.

[0070] As shown in Fig. 4, in Verification Test 1, three types of cups, Types I to III, with different specifications (Types I and II were made of aluminum alloy, and Type III was made of steel) were prepared and each was assembled into a Type A holder (made of aluminum alloy) with the same specifications. Comparative Example 1 is a case where a Type I cup was assembled into a Type A holder, Comparative Example 2 is a case where a Type II cup was assembled into a Type A holder, and Example 1 is a case where a Type III cup was assembled into a Type A holder. The sizes (external dimensions) of the Types I to III cups are substantially the same.

[0071] In addition, in Verification Test 2, two types of cups, Type I and III, which have different specifications, were prepared and assembled into Type B holders (made of aluminum alloy) which have the same specifications. Of these, Comparative Example 3 is a case where a Type I cup is assembled into a Type B holder, and Example 2 is a case where a Type III cup is assembled into a Type B holder. The sizes (external dimensions) of the Type A and B holders are substantially the same.

[0072] First, the Vickers hardness was measured for each of the types I to III cups. Specifically, as shown in FIG. 5, a cross section including the axis of the cup 40 was exposed by cutting, and the portion of this exposed cross section corresponding to the flange portion 43 was set as the measurement point, and the Vickers hardness was measured. There were three measurement points, Q1 to Q3 shown in the figure, and the measuring device used was an automatic reading hardness tester HM-220 manufactured by Mitutoyo Corporation. The test force was not particularly limited, but was set to 0.1 kgf to match the hardness of the object to be measured.

[0073] As a result, the average Vickers hardness of the Type I cup was 48 Hv, the average Vickers hardness of the Type II cup was 101 Hv, and the average Vickers hardness of the Type III cup was 195 Hv. The variation in Vickers hardness between measurement points and between samples was negligible.

[0074] Next, the Vickers hardness was measured for each of the Type A and Type B holders. Specifically, as shown in FIG. 6, a cross section including the axis of the holder 10 was exposed by cutting, and the portion of this exposed cross section corresponding to the annular flange portion 17 and the portion defining the bottom surface 16a of the annular groove portion 16 were set as measurement points to measure the Vickers hardness. A total of 14 measurement points were measured, R1 to R6 and S1 to S8, as shown in the figure, and the measuring device used was the Mitutoyo HM-220 automatic reading hardness tester. The test force was not particularly limited, but was set to 0.3 gkgf to match the hardness of the object to be measured.

[0075] As a result, the average Vickers hardness of the Type A holder was 130 Hv, and the average Vickers hardness of the Type B holder was 119 Hv. The variation in Vickers hardness between measurement points and between samples was negligible.

[0076] Next, these cups and holders were assembled by crimping according to the procedure described above with reference to Fig. 3. Note that for each of Comparative Examples 1 to 3 and Examples 1 and 2, a plurality of samples were produced, and three different loads were applied to annular flange portion 17 during crimping: 20 kN, 25 kN, and 30 kN.

[0077] Next, for each of Comparative Examples 1 and 2 and Examples 1 and 2, in order to confirm the assembly strength of the cup and holder along the circumferential direction, a torque was applied between the cup and holder relative to each other along the rotational direction (i.e., the circumferential direction), and the degree of rotation was measured. Specifically, the rotational torque applied to the cup and holder was gradually increased, and the rotational torque required to rotate the cup and holder relatively 5° around the axis (hereinafter referred to as the required rotational torque) was measured. The measurement device used was a bench-top torque tester MODEL-5401VC / 200 manufactured by Aiko Engineering Co., Ltd., and the rotational speed was set to 1 rpm.

[0078] As a result, in Comparative Example 1, the average value of the required rotational torque was 0.93 N·m when the crimping load was 20 kN, 0.86 N·m when the crimping load was 25 kN, and 0.57 N·m when the crimping load was 30 kN. In Comparative Example 2, the average value of the required rotational torque was 4.31 N·m when the crimping load was 20 kN, 4.54 N·m when the crimping load was 25 kN, and 5.77 N·m when the crimping load was 30 kN. In Comparative Example 3, the average value of the required rotational torque was 2.06 N·m when the crimping load was 20 kN, 2.49 N·m when the crimping load was 25 kN, and 2.07 N·m when the crimping load was 30 kN. On the other hand, in Example 1, the average required rotational torque was 6.34 N m when the crimping load was 20 kN, 6.70 N m when the crimping load was 25 kN, and 7.11 N m when the crimping load was 30 kN. In Example 2, the average required rotational torque was 5.92 N m or more when the crimping load was 20 kN, 6.57 N m or more when the crimping load was 25 kN, and 6.81 N m when the crimping load was 30 kN. In Example 2, the average required rotational torque for crimping loads of 20 kN and 25 kN is "5.92 N m or more" and "6.57 N m or more," respectively. This is because, when the rotational torque applied between the cup and holder was gradually increased, damage occurred in areas other than the annular collar and flange, which are the crimped fixing parts between the holder and cup, before the cup and holder were rotated relatively 5° around the axis, making further measurements impossible. Furthermore, for each of Comparative Examples 1 to 3 and Examples 1 and 2, the variation in the required rotational torque for each sample was negligible.

[0079] From the above results, it was confirmed that in Examples 1 and 2, in which the cup is harder than the holder, the required rotational torque is greater than in Comparative Examples 1 to 3, in which the cup is softer than the holder. Therefore, based on the above results, it can be understood that by making cup 40 harder than holder 10, it is possible to ensure high assembly strength between holder 10 and cup 40 along the circumferential direction.

[0080] Furthermore, based on the above results, it can be seen that, in addition to the above conditions, if the Vickers hardness of the cup 40 is 195 Hv or more, it is possible to ensure high assembly strength between the holder 10 and the cup 40 in the circumferential direction, and it can also be seen that, in addition to the above conditions, if the Vickers hardness of the holder 10 is 130 Hv or less, it is possible to ensure high assembly strength between the holder 10 and the cup 40 in the circumferential direction.

[0081] Fig. 7 is a table showing the test conditions and test results of Verification Tests 3 and 4. Details of Verification Tests 3 and 4 conducted by the present inventor will be described below with reference to Fig. 7. Note that Verification Tests 3 and 4 were both conducted in response to the test results of Verification Tests 1 and 2 described above, in order to supplement these Verification Tests 1 and 2.

[0082] More specifically, as shown in Fig. 7, in Verification Test 3, five types of cups (all made of steel) of different specifications, Types IV to VIII, were prepared and each was assembled into the Type A holder (made of aluminum alloy) used in Verification Test 1 described above. Of these, Example 3 is where a Type IV cup is assembled into a Type A holder, Example 4 is where a Type V cup is assembled into a Type A holder, Example 5 is where a Type VI cup is assembled into a Type A holder, Example 6 is where a Type VII cup is assembled into a Type A holder, and Example 7 is where a Type VIII cup is assembled into a Type A holder. The sizes (external dimensions) of the Types IV to VIII cups are substantially the same.

[0083] Furthermore, in Verification Test 4, five types of cups, Types IV to VIII, described above, with different specifications were prepared and each was assembled into the Type B holder (made of aluminum alloy) used in Verification Test 2. Of these, Example 8 was the case where a Type IV cup was assembled into a Type B holder, Example 9 was the case where a Type V cup was assembled into a Type B holder, Example 10 was the case where a Type VI cup was assembled into a Type B holder, Example 11 was the case where a Type VII cup was assembled into a Type B holder, and Example 12 was the case where a Type VIII cup was assembled into a Type B holder.

[0084] First, the Vickers hardness of each of the cups of Types IV to VIII was measured using the same method as in the above-mentioned Verification Tests 1 and 2. As in the above-mentioned Verification Tests 1 and 2, the measuring instrument used was the Mitutoyo HM-220 automatic reading hardness tester, and the test force was set to 0.3 kgf in accordance with the hardness of the object to be measured.

[0085] As a result, the average Vickers hardness of the Type IV cups was 158 Hv, the average Vickers hardness of the Type V cups was 169 Hv, the average Vickers hardness of the Type VI cups was 214 Hv, the average Vickers hardness of the Type VII cups was 170 Hv, and the average Vickers hardness of the Type VIII cups was 239 Hv. The variation in Vickers hardness between measurement points and between samples was negligible.

[0086] Next, these cups and holders were assembled by crimping in accordance with the procedure described above with reference to Fig. 3, as in the above-mentioned Verification Tests 1 and 2. Note that for each of Examples 3 to 12, a plurality of samples were produced, and the load applied to the annular flange portion 17 during crimping was 25 kN in all cases.

[0087] Next, for each of Examples 3 to 12, the required rotational torque (i.e., the rotational torque required to rotate the cup and holder relatively by 5° around the axis) was measured using the same method as in the above-mentioned Verification Tests 1 and 2. As in the above-mentioned Verification Tests 1 and 2, the measuring device used was a bench-top torque tester MODEL-5401VC / 200 manufactured by Aiko Engineering Co., Ltd., and the rotational speed was set to 1 rpm.

[0088] As a result, the average required rotational torque was 7.54 N·m in Example 3, 7.89 N·m in Example 4, 7.72 N·m in Example 5, 6.59 N·m in Example 6, and 6.40 N·m in Example 7. Meanwhile, the average required rotational torque was 7.04 N·m in Example 8, 7.14 N·m in Example 9, 7.56 N·m in Example 10, 6.88 N·m in Example 11, and 9.06 N·m in Example 12. It should be noted that the variation in required rotational torque between samples in each of Examples 3 to 12 was negligible.

[0089] From the above results, it was confirmed that not only in the above-mentioned Examples 1 and 2, but also in Examples 3 to 12 in which the cup is harder than the holder, the required rotational torque is greater than in the above-mentioned Comparative Examples 1 to 3 in which the cup is softer than the holder. Therefore, based on the above results, it can be understood that by making cup 40 harder than holder 10, it is possible to ensure high assembly strength between holder 10 and cup 40 along the circumferential direction.

[0090] Furthermore, based on the above results, it can be seen that, in addition to the above conditions, if the Vickers hardness of the cup 40 is 158 Hv or more, it is possible to ensure high assembly strength between the holder 10 and the cup 40 in the circumferential direction, and it can also be seen that, in addition to the above conditions, if the Vickers hardness of the holder 10 is 130 Hv or less, it is possible to ensure high assembly strength between the holder 10 and the cup 40 in the circumferential direction.

[0091] Here, if we focus on the required rotational torque in Examples 1, 3 to 7 of the above-mentioned Examples 1 to 13, which use the same Type A holder specifications (Vickers hardness: 130 Hv), we can see that as the Vickers hardness of the cup increases to 48 Hv, 101 Hv, and 158 Hv, the required rotational torque also increases proportionally, and once the Vickers hardness of the cup exceeds 158 Hv, it can be confirmed that the required rotational torque generally approaches a constant value.

[0092] An approximate formula was derived that shows the relationship between the Vickers hardness of the cup and the required rotational torque in the range where the required rotational torque increases proportionally as the Vickers hardness of the cup increases, and when 5.92 N m was substituted into the approximate formula as the value of the required rotational torque, the Vickers hardness of the cup in this case was found to be approximately 130 Hv. Here, the required rotational torque value of 5.92 N m is a value that can sufficiently prevent holder 10 from rotating relative to cup 40 when a so-called screw-in method is used to attach the gas generator to the pretensioner (i.e., a value that allows the gas generator to be attached to the pretensioner without any problems).

[0093] Therefore, based on these results, it can be said that it has been experimentally confirmed once again that when the Vickers hardness of the holder is 130 Hv or less, by using a cup with a Vickers hardness exceeding 130 Hv (i.e., by making the cup harder than the holder), it is possible to ensure high assembly strength of the holder 10 and cup 40 along the circumferential direction.

[0094] In the gas generator according to the embodiment described above, the holder is made of aluminum or an aluminum alloy, and the cup is made of aluminum, an aluminum alloy, or an iron-based material including stainless steel. However, the materials of the holder and the cup are not particularly limited to these, and other materials may also be used.

[0095] Furthermore, in the gas generator according to the above-described embodiment, an example has been given in which the flange portion is inserted into the annular groove portion and the annular flange portion is crimped without applying a sealant to the annular groove portion of the holder and the flange portion of the cup in advance, but in order to improve airtightness, a sealant may be applied in advance to at least one of the annular groove portion and the flange portion.

[0096] As such, the above-described embodiments disclosed herein are illustrative in all respects and are not restrictive. The technical scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0097] 1 gas generator, 10 holder, 11 body, 12 first recess, 13 second recess, 14 partition, 14a opening, 15 engaging portion, 16 annular groove, 16a bottom surface, 16b outer wall surface, 16c inner wall surface, 17 annular flange, 20 igniter, 21 base, 22 ignition portion, 23 terminal pin, 24 cover, 30 sealing member, 40 cup, 41 side wall, 41a open end, 42 bottom wall, 42a score, 43 flange, 43a first surface, 43b second surface, 44 storage space, 50 gas generant, A1 first contact portion, A2 second contact portion.

Claims

1. a gas generating agent that generates gas by burning; an igniter having an ignition part loaded with an ignition charge and a terminal pin connected to the ignition part; a substantially cylindrical cup having a bottom and an open end in the axial direction, the cup containing the gas generating agent; a substantially cylindrical holder that closes the open end by coaxially assembling the cup and holds the igniter so that the ignition portion faces the gas generating agent, The cup has a flange portion extending outward from the open end, an annular groove portion for receiving the flange portion and an annular flange portion for defining an outer wall surface of the annular groove portion are provided on an axial end surface of the holder on the side facing the ignition portion; the flange portion includes a second surface located on the opposite side to a first surface facing the bottom surface of the annular groove portion, When the annular flange is bent inward with the flange received in the annular groove, the tip end portion of the annular flange comes into contact with the second surface, and the flange is thereby sandwiched between the tip end portion of the annular flange and the bottom surface of the annular groove in the axial direction of the cup, thereby assembling the cup to the holder; the cup is made of a metal material selected from the group consisting of aluminum, an aluminum alloy, and an iron-based material; the holder is made of a metal material selected from the group consisting of aluminum and aluminum alloys; The gas generator, wherein the cup is harder than the holder.

2. The Vickers hardness of the cup exceeds 130 Hv, 2. The gas generator according to claim 1, wherein the holder has a Vickers hardness of 130 Hv or less.

3. The cup has a Vickers hardness of 158 Hv or more, 2. The gas generator according to claim 1, wherein the holder has a Vickers hardness of 130 Hv or less.

4. 4. The gas generator according to claim 1, wherein a rotational torque required to rotate said cup and said holder relatively by 5 degrees about the axis is 5.92 N·m or more.

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