gas generator

Abstract

To provide a gas generator high in output and proof pressure and reduced in size and weight.SOLUTION: A gas generator 1 comprises: a cup 40 for storing a gas generating agent; and a holder 10. The holder 10 includes a first recess 12 and an annular groove 16 provided on the end surface of a side facing the surface of the cup 40, a second recess 13 provided on the end surface of the opposite side, and a partition 14 that partitions the first and second recesses 12 and 13. A bottom surface 12a of the first recess 12 includes a first bottom surface 12a1, and a second bottom surface 12a2 positioned inside the first bottom surface and positioned on the second recess 13 side. The gas generator 1 satisfies a condition of A<B<C, in which A denotes a distance from the second bottom surface 12a2 to a bottom surface 13a of the second recess 13, B denotes a distance from the first bottom surface 12a1 to the bottom surface 13a of the second recess 13, and C denotes a distance from the bottom surface 13a of the second recess 13 to the annular groove 16.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gas generator, and particularly to a compact gas generator configured to generate a relatively small amount of gas during operation. Background Art

[0002] Conventionally, from the viewpoint of protecting occupants of automobiles and other vehicles, seat belt devices, which are occupant protection devices, have been widely used. Seat belt devices are equipped for the purpose of protecting occupants from impacts generated during collisions of vehicles and the like, and restrain an occupant to a seat by wrapping a belt around the occupant's body. This prevents the occupant from being thrown out of or into the vehicle during a collision of the vehicle or the like.

[0003] Among seat belt devices, those equipped with a so-called pretensioner incorporate a compact gas generator called a micro gas generator. A pretensioner is a device that instantaneously takes up slack in the seat belt caused by factors such as the thickness of clothing when a collision of a vehicle or the like is detected, and this function is achieved by one end of the seat belt being strongly retracted by the pressure of gas output from the gas generator.

[0004] This compact gas generator has an extremely small total amount of gas generated during operation when compared with a large gas generator called an inflator that is suitably incorporated in airbag devices, and accordingly its structure is also greatly different.

[0005] Examples of gas generators of this type include those disclosed in Japanese Patent Application Laid-Open No. 2008-37389 (Patent Document 1) and those disclosed in Japanese Patent Application Laid-Open No. 2022-36022 (Patent Document 2). The gas generators disclosed in the above Patent Documents 1 and 2 include a substantially cylindrical bottomed cup filled with a gas generating agent that generates gas when burned, an igniter for burning the gas generating agent, and a substantially cylindrical holder that is coaxially assembled to the cup so as to close the open end of the cup and holds the igniter so as to face the gas generating agent. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-37389 [Patent Document 2] Japanese Patent Publication No. 2022-36022 [Overview of the initiative] [Problems that the invention aims to solve]

[0007] Here, as described above, the holder is used to hold the igniter and to assemble the cup; therefore, one axial end face of the holder is provided with a first recess for receiving and holding the igniter and an annular groove for receiving and holding the opening edge of the cup. Furthermore, since a connector for connecting the igniter to the outside needs to be attached to the holder so that it can be inserted and removed, the other axial end face of the holder is provided with a second recess for receiving and holding the connector.

[0008] In pretensioners incorporating the aforementioned gas generator, there is a strong demand for improved mountability in vehicles and other applications. To achieve this improvement, miniaturization and weight reduction of the pretensioner, and consequently the gas generator, are crucial challenges. The holder, made of metal, accounts for a large proportion of the total weight of the gas generator. Therefore, attempts have been made to miniaturize and lighten the gas generator by changing its material, shape, and thickness.

[0009] However, since the holder is a component that is subjected to high pressure when the gas generator is operating, it is necessary to ensure high mechanical strength (i.e., pressure resistance). For example, when the gas generator is activated, the gas generated by the gas generator is introduced into the working space of the pretensioner module incorporated into the seat belt system. At this time, the internal pressure of the working space becomes very high, and this high pressure is applied to the holder. If the holder has insufficient mechanical strength, it will not be able to withstand this high pressure, causing damage to the holder, and as a result, gas will leak from the damaged part.

[0010] Thus, in the gas generators described above, it is essential to achieve stable operation while simultaneously miniaturizing and reducing weight while ensuring high pressure resistance.

[0011] On the other hand, improving the output of the gas generator mentioned above is also an important challenge. In this regard, it is conceivable to increase the amount of gas generating agent that can be filled by increasing the volume inside the cup, but it is not easy to achieve both the improvement in output through this method and the need to ensure the pressure resistance performance and miniaturization and weight reduction mentioned above.

[0012] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide a gas generator that is high-output, high-pressure resistant, and also compact and lightweight. [Means for solving the problem]

[0013] A gas generator according to the present invention comprises: a gas generating agent that generates gas by combustion; an igniter having an ignition unit charged with an ignition charge and a terminal pin connected to the ignition unit; a substantially cylindrical cup with a bottom that accommodates the gas generating agent and has one axial end configured as an open end; and a substantially cylindrical holder that closes the open end by coaxially assembling the cup and holds the igniter such that the ignition unit faces the gas generating agent. The holder includes: a first recess provided on an axial end surface on a side facing the cup, for receiving and holding the igniter; a second recess provided on an axial end surface on a side not facing the cup, where the terminal pin is disposed and for receiving and holding a connector for external connection of the igniter via the terminal pin; a partition part that defines a bottom surface of the first recess and a bottom surface of the second recess to partition the first recess and the second recess; and an annular groove provided on the axial end surface on the side facing the cup, for receiving and holding an opening edge of the cup inserted along the axial direction. Since the bottom surface of the first recess has a stepped shape, when viewed along the axial direction of the holder, the bottom surface of the first recess has an annular first bottom surface located on the outer side, and a second bottom surface located on the inner side of the first bottom surface and closer to the second recess side than the first bottom surface. In the gas generator according to the present invention, when a distance from the second bottom surface to the bottom surface of the second recess is defined as A, a distance from the first bottom surface to the bottom surface of the second recess is defined as B, and a distance from the bottom surface of the second recess to the annular groove is defined as C, the condition A < B < C is satisfied.

Effects of the Invention

[0014] According to the present invention, it is possible to provide a gas generator that has high output, high pressure resistance, and is also reduced in size and weight.

Brief Description of Drawings

[0015] [Figure 1] It is a schematic cross-sectional view of the gas generator according to the embodiment. [Figure 2] It is an enlarged view of region II shown in Fig. 1. [Figure 3]It is a schematic cross-sectional view showing a state where a pretensioner casing is attached to the gas generator shown in FIG. 1. [Figure 4] It is a schematic cross-sectional view showing a method of assembling a shorting clip to the gas generator shown in FIG. 1. [Figure 5] It is a schematic cross-sectional view showing a state where a shorting clip is assembled to the gas generator shown in FIG. 1. [Figure 6] It is a schematic cross-sectional view of a gas generator according to a comparative example. [Figure 7] It is a schematic cross-sectional view showing a state where a pretensioner casing is assembled to a gas generator according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown below exemplify a case where the present invention is applied to a gas generator (a so-called micro gas generator) that is suitably incorporated in a seatbelt device provided with a pretensioner. In the embodiments shown below, the same or common portions are denoted by the same reference numerals in the drawings, and description thereof will not be repeated.

[0017] (Embodiment) FIG. 1 is a schematic cross-sectional view of a gas generator according to an embodiment. FIG. 2 is an enlarged view of region II shown in FIG. 1. FIG. 3(A) is a schematic cross-sectional view showing a state where a pretensioner casing is attached to the gas generator shown in FIG. 1, and FIG. 3(B) is a schematic cross-sectional view showing another embodiment of the pretensioner shown in FIG. 3(A). First, the configuration of a gas generator 1 according to the present embodiment will be described with reference to these FIGS. 1 to 3.

[0018] As shown in FIG. 1, the gas generator 1 in the present embodiment mainly includes a holder 10, an igniter 20, a seal member 30, a cup 40, and a gas generant 50.

[0019] The holder 10 and the cup 40 are combined coaxially to constitute a housing that serves as the outer shell of the gas generator 1. The igniter 20 is held by the holder 10, and the cup 40 is assembled to the holder 10 so as to cover the igniter 20. Further, the gas generant 50 is accommodated in a space defined by the holder 10, the igniter 20, and the cup 40.

[0020] The holder 10 is a member for holding the igniter 20 and the cup 40, and has a substantially columnar shape. Here, in the present embodiment, since the holder 10 is provided with a first recess 12, a second recess 13, and an opening 14a which will be described later, the holder 10 substantially has a substantially cylindrical shape.

[0021] As described above, the holder 10 is also a member constituting a part of the housing, and is formed of a molded product made of a metal material such as aluminum or an aluminum alloy, for example. The holder 10 is formed into the shape shown in the figure, for example, by subjecting a plate-shaped metal member or a rod-shaped metal member as a raw material to forging, punching, cutting or the like one or more times in a predetermined order, respectively.

[0022] The holder 10 has a cylindrical body portion 11 that defines an outer peripheral surface, and the body portion 11 is provided with a first recess 12 and a second recess 13. A partition portion 14 is formed in the body portion 11 at a portion located between the first recess 12 and the second recess 13 so as to partition the first recess 12 and the second recess 13. A locking portion 15 is formed on the portion of the body portion 11 located closer to a bottom wall portion 42 (described later) of the cup 40 than the partition portion 14.

[0023] Further, the body portion 11 includes a cylindrical first body portion 11a provided at an axial end portion on a side facing the cup 40, and a cylindrical second body portion 11b provided at an axial end portion on a side not facing the cup 40.

[0024] The first body portion 11a surrounds the partition portion 14, the end of the first recess 12 on the partition portion 14 side in the axial direction of the holder 10, and the end of the second recess 13 on the partition portion 14 side in the axial direction.

[0025] The second body portion 11b is provided protruding from the axial end of the first body portion 11a on the side not facing the cup 40, and has a smaller radial outer shape than the first body portion 11a. The second body portion 11b also surrounds the end of the second recess 13 of the holder 10 that is opposite to the partition portion 14 in the axial direction.

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

[0027] The bottom surface 12a of the first recess 12 has a stepped shape. As a result, when viewed along the axial direction of the holder 10, the bottom surface 12a of the first recess 12 includes an annular first bottom surface 12a1 located on the outer side of the bottom surface 12a, and a second bottom surface 12a2 located inward from the first bottom surface 12a1 and further towards the second recess 13.

[0028] The second recess 13 is a portion where a pair of terminal pins 23 of the igniter 20, described later, are arranged, and where a connector (not shown) for external connection of the igniter 20 via the pair of terminal pins 23 is provided on the axial end face of the body portion 11 that does not face the cup 40. The bottom surface 13a of the second recess 13 is defined by the partition portion 14, and the inner surface 13b of the second recess 13 is defined by the cylindrical portion of the body portion 11.

[0029] The partition portion 14 is provided with an opening 14a that connects to the first recess 12 and the second recess 13. The opening 14a is the portion through which a pair of terminal pins 23 are inserted (more precisely, the portion into which the pair of terminal pins 23 and the lower end of the base 21 of the igniter 20 that covers them are fitted).

[0030] The locking portion 15 is a part for crimping and fixing the base portion 21 of the igniter 20, and has an annular plate shape. The tip of the locking portion 15 is bent inward, thereby fixing the igniter 20 housed in the first recess 12 to the holder 10 so that it cannot move.

[0031] Here, as shown in Figure 2, an annular groove 16 and an annular flange 17 are provided on the axial end face of the first body portion 11a facing the cup 40, so as to surround the locking portion 15 described above.

[0032] The annular groove 16 is a portion for receiving and holding the flange portion 43 of the cup 40, which will be described later, as it is inserted along the axial direction. Furthermore, the annular groove 16 is provided such that its bottom surface 16a is located closer to the bottom wall portion 42 of the cup 40 than the partition portion 14.

[0033] The annular flange portion 17 is a part for crimping and fixing the flange portion 43 of the cup 40, and has an annular plate shape that protrudes from the first body portion 11a toward the ignition portion 22 so as to define the outer wall surface of the annular groove portion 16. In addition, the tip portion of the annular flange portion 17 is bent inward, thereby fixing the cup 40 to the holder 10 so that it cannot move.

[0034] Here, as shown in Figure 1, in the gas generator 1 according to this embodiment, if the axial length of the second body portion 11b is D, and the sum of the length of the annular flange portion 17 along the axial direction of the first body portion 11a and the axial length of the first body portion 11a in the state after the cup 40 is assembled to the holder 10 is E, then the condition E < 1.8 × D is satisfied. This makes it possible to make the axial length of the second body portion 11b relatively long.

[0035] Furthermore, if the depth of the second recess 13 is F, the condition F < 1.8 × D is satisfied. This also allows for a relatively large axial length of the second body portion 11b.

[0036] The igniter 20 is used to generate a flame and is also called a squib. The igniter 20 has a base 21, an ignition part 22, and a pair of terminal pins 23 (see Figure 4). The base 21 is the part that holds the ignition part 22 and the pair of terminal pins 23, and is also the part that is fixed to the holder 10. The base 21 holds the pair of terminal pins 23 by inserting them through it. Note that in Figure 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.

[0037] The ignition unit 22 contains an igniter that generates a flame when ignited and burned during operation, and a resistor (bridge wire) for igniting the igniter. A pair of terminal pins 23 are connected to the ignition unit 22 to ignite the igniter.

[0038] More specifically, the ignition unit 22 includes a cup-shaped squib cup, the aforementioned resistor is attached to connect the tips of a pair of terminal pins 23 inserted into the squib cup, and an igniter is loaded into the squib cup so as to surround or be close to the resistor.

[0039] Here, nichrome wire is generally used as the resistor, and ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), lead tricinate, etc. are generally used as the igniter. The squib cup mentioned above is generally made of metal or plastic.

[0040] When a collision is detected, a predetermined amount of current flows through the resistor via terminal pin 23. This current generates Joule heat within the resistor, causing the igniter to begin burning. The resulting high-temperature flame ruptures the squib cup containing the igniter. The time from when current flows through the resistor until the igniter 20 activates is generally 2ms or less when a nichrome wire is used for the resistor.

[0041] When assembling the igniter 20 to the holder 10, the igniter 20 is inserted into the first recess 12 from the axial end of the holder 10 on the side where the first recess 12 is provided, such that the pair of terminal pins 23 are inserted into the opening 14a provided in the partition portion 14. As a result, the base portion 21 is housed in the first recess 12 and the opening 14a, and the pair of terminal pins 23 are positioned in the second recess 13. In this state, the tip portion of the locking portion 15 is bent toward the base portion 21, so that the base portion 21 is clamped between the partition portion 14 and the locking portion 15, thereby crimping and fixing the igniter 20 to the holder 10.

[0042] Therefore, the ignition part 22 of the igniter 20 is located on the bottom wall portion 42 of the cup 40, rather than on the axial end face of the holder 10 on the side where the first recess 12 is provided, and the ignition part 22 faces the gas generating agent 50 housed in the housing space 44 of the cup 40, which will be described later.

[0043] Here, a sealing member 30, such as an O-ring, is pre-installed in the first recess 12 of the holder 10, and this sealing member 30 seals the gap between the holder 10 and the igniter 20. More specifically, the sealing member 30 is positioned between the partition portion 14 and the locking portion 15 of the holder 10 and the base portion 21 of the igniter 20, and the sealing member 30 is compressed by the holder 10 and the igniter 20, thereby ensuring a seal between them.

[0044] Furthermore, it is preferable to use a material with sufficient heat resistance and durability as the sealing member 30. For example, an O-ring made of EPDM, a type of ethylene propylene rubber, can be suitably used.

[0045] The cup 40 is a bottomed, substantially cylindrical member with one axial end being an open end 41a, and has a side wall portion 41, a bottom wall portion 42, and a flange portion 43. The gas generating agent 50 is contained in the housing space 44 of the cup 40, which is defined by the side wall portion 41 and the bottom wall portion 42.

[0046] The open end 41a described above is formed at the end of the pair of axial ends of the side wall portion 41 that is opposite to the side where the bottom wall portion 42 is located. The flange portion 43 is positioned to extend outward from this open end 41a. The flange portion 43 is the part for fixing the cup 40 to the holder 10.

[0047] The bottom wall portion 42 of the cup 40 is provided with a score 42a by forming groove-shaped cuts on its surface. This score 42a is provided to create a weaker area at a predetermined position on the bottom wall portion 42 compared to other positions, and by providing this score 42a, the cup 40 can be configured to open starting from that part when the gas generator 1 is in operation.

[0048] The cup 40 is also a component that makes up part of the housing, and is made of a molded product made of a metal material such as aluminum, aluminum alloy, or iron-based material including stainless steel. Generally, press working using a mold is used to form the cup 40.

[0049] As described above, the cup 40 is assembled to the holder 10 by crimping and fixing its flange portion 43 to the annular flange portion 17 provided on the holder 10.

[0050] More specifically, first, the flange portion 43 of the cup 40 is inserted into the annular groove portion 16 provided in the holder 10. As a result, as shown in Figure 2, the first surface 43a of the pair of axially positioned surfaces of the flange portion 43 of the cup 40, which is located on the holder 10 side, comes into contact with the bottom surface 16a of the annular groove portion 16. At the same time, the inner circumferential surface of the side wall portion 41 of the cup 40 comes into contact with the inner wall surface 16c of the annular groove portion 16.

[0051] Next, the tip portion of the annular flange 17 of the holder 10 is bent inward. As a result, the annular flange 17, except for the portion at its base (i.e., the portion connected to the first body 11a), tilts towards the bottom surface 16a of the annular groove 16, and is bent towards the flange portion 43 of the cup 40 as described above.

[0052] As a result, as shown in Figure 2, the tip portion of the annular flange 17 comes into contact with the second surface 43b of the flange portion 43, which is located on the opposite side of the first surface 43a of the pair of surfaces located in the axial direction of the flange portion 43. Therefore, the flange portion 43 is sandwiched between the tip portion of the annular flange 17 and the bottom surface 16a of the annular groove portion 16 in the axial direction of the cup 40. As a result, the open end 41a of the cup 40 is closed by the holder 10 (more precisely, by the igniter 20, etc. in addition to the holder 10).

[0053] The gas generating agent 50 generates a large amount of gas when ignited and burned by the igniter 20. As the gas generating agent 50, molded bodies of smokeless powder (nitrocellulose) or molded bodies of non-azide compositions consisting of organic nitrogen compounds and oxidizing agents are used. Recently, however, there has been growing interest in using non-nitrocellulose gas generating agents as the gas generating agent 50, as these produce extremely low levels of harmful substances such as carbon monoxide.

[0054] As the molded article of the gas generating agent 50, those of various shapes such as granular, pellet, cylindrical, and disk shapes can be used. Further, a porous molded article having through-holes (for example, macaroni shape, lotus root shape, etc.) can also be used as the molded article of the gas generating agent 50. An optimal shape is selected according to the specifications of the pretensioner to which the gas generator 1 is assembled. In addition to the shape, the size and the like of the molded article of the gas generating agent 50 are selected taking into account the linear burning rate, pressure index, and the like. The filling amount of the gas generating agent 50 can be appropriately changed according to the specifications of the pretensioner to which it is assembled, but when smokeless gunpowder is used, it is generally about 0.1 g to 2.0 g.

[0055] As shown in FIG. 2, in the gas generator 1 according to the present embodiment, as described above, the bottom surface 12a of the first recess 12 defined by the partition portion 14 includes a first bottom surface 12a1 and a second bottom surface 12a2, and the second bottom surface 12a2 is located closer to the second recess 13 side than the first bottom surface 12a1. Accordingly, the distance B from the first bottom surface 12a1 of the first recess 12 to the bottom surface 13a of the second recess 13 is configured to be larger than the distance A from the second bottom surface 12a2 of the first recess 12 to the bottom surface 13a of the second recess 13.

[0056] Further, in the gas generator 1, as described above, the annular groove 16 is provided such that the bottom surface 16a thereof is located closer to the bottom wall 42 side of the cup 40 than the partition portion 14. Accordingly, the distance C from the bottom surface 13a of the second recess 13 to the annular groove 16 is configured to be larger than the distance B.

[0057] That is, in the gas generator 1 according to the present embodiment, when the distance from the second bottom surface 12a2 of the first recess 12 to the bottom surface 13a of the second recess 13 is A, the distance from the first bottom surface 12a1 of the first recess 12 to the bottom surface 13a of the second recess 13 is B, and the distance from the bottom surface 13a of the second recess 13 to the annular groove 16 is C, the condition A < B < C is satisfied.

[0058] This configuration makes it possible to create a gas generator that is high-power, high-pressure resistant, and also compact and lightweight, but this point will be explained in detail later.

[0059] As shown in Figure 3(A), when the gas generator 1 is incorporated into the pretensioner 200 of the seat belt device, the substantially cylindrical casing 201 of the pretensioner 200 is assembled to the gas generator 1. More specifically, first, the casing 201 is fitted onto the holder 10 so as to surround the first body portion 11a from the axial end of the holder 10 on the side where the first recess 12 is provided. As a result, the stepped portion provided on the inner circumferential surface of the casing 201 abuts against the axial end surface located on the bottom wall portion 42 side of the cup 40 of the first body portion 11a. In this state, the tip portion of the casing 201 is bent toward the second body portion 11b side, thereby crimping and fixing the casing 201 to the holder 10. In this way, the casing 201 is assembled to the gas generator 1.

[0060] Here, as shown in Figure 3(B), in the pretensioner 200A, which is another form of the pretensioner 200 shown in Figure 3(A), the casing 201A is configured to be thicker than the casing 201 of the pretensioner 200 in order to improve its pressure resistance performance.

[0061] Due to the large thickness of the casing 201A, the tip position of the casing 201A after assembly will move toward the axial end face side of the holder 10 that does not face the cup 40. Therefore, if the axial length of the second body portion 11b (distance D in Figure 1) is relatively short, the tip of the casing 201A will protrude outward from the axial end face of the holder 10, which will cause the problem of difficulty in attaching the connector to the second recess 13.

[0062] In this regard, in the gas generator 1 according to this embodiment, as described above, the axial length of the second body portion 11b (distance D in Figure 1) is made relatively long, so the occurrence of the above problem can be prevented.

[0063] Figure 4 is a schematic cross-sectional view showing the method of assembling the shorting clip to the gas generator shown in Figure 1, and Figure 5 is a schematic cross-sectional view showing the state in which the shorting clip has been assembled to the gas generator shown in Figure 1. Next, the method of assembling the shorting clip 100 to the gas generator 1 in this embodiment will be described with reference to Figures 4 and 5. Note that in Figure 4, only the shorting clip 100 is shown in a side view. Also, in Figure 4, a cross-section perpendicular to the cross-section shown in Figure 1 is shown when the gas generator 1 is viewed from above.

[0064] In the gas generator 1 configured as described above, a shorting clip 100 is used to prevent the gas generator 1 from malfunctioning due to electrostatic discharge or the like, for example, during transport for shipment before being mounted on a vehicle. The shorting clip 100, when attached to the gas generator 1, intentionally short-circuits a pair of terminal pins 23 of the igniter 20.

[0065] As shown in Figure 4, when assembling the shorting clip 100 to the gas generator 1, the shorting clip 100 is inserted into the second recess 13 of the holder 10. At this time, multiple claw portions 101 that protrude outward from the side surface of the shorting clip 100 engage with multiple recesses 13b1 provided on the inner surface 13b of the second recess 13. This engagement fixes the shorting clip 100 in the second recess 13.

[0066] As shown in Figure 5, when the shorting clip 100 is fixed to the second recess 13, the two leaf spring portions 102 provided on the shorting clip 100 are pressed against the pair of terminal pins 23. As a result, the gas generator 1 is maintained in a short-circuited state.

[0067] Next, with reference to Figure 1, the operation of the gas generator 1 in this embodiment will be described.

[0068] Referring to Figure 1, if a vehicle equipped with the gas generator 1 in this embodiment collides, the collision is detected by a collision detection means separately provided on the vehicle, and the igniter 20 is activated based on this. When the igniter 20 is activated, the igniter contained in the ignition unit 22 is ignited and burns, causing the squib cup to rupture.

[0069] The flame generated by the combustion of the igniter is ejected towards the containment space 44 where the gas generating agent 50 is contained, as the squib cup bursts. This flame ignites and burns the gas generating agent 50, generating a large amount of gas in the containment space 44. The combustion of the gas generating agent 50 causes the internal pressure of the containment space 44 to rise rapidly, which causes the bottom wall 42 of the cup 40 to open starting from the score 42a, and the large amount of gas generated is discharged to the outside of the gas generator 1.

[0070] Subsequently, the large amount of gas discharged from the gas generator 1 is guided into the operating space of the pretensioner into which the gas generator 1 is incorporated. This drives the pretensioner, causing one end of the seat belt attached to the seat belt device to be strongly pulled in.

[0071] Here, as described above, when the gas generator 1 is activated and the internal pressure of the containment space 44 increases, the igniter 20 is pressed against the partition 14. As a result, a large external force is applied to the holder 10 of the partition 14 and the portion of it that defines its vicinity.

[0072] At this time, since the igniter 20 and the partition portion 14 located radially inward (that is, the partition portion 14 at the portion defining the second bottom surface 12a2 of the first recess 12) are in surface contact with each other in a state where a relatively large area is secured, large stress is less likely to occur in the partition portion 14 at this portion. On the other hand, since the igniter 20, the partition portion 14 located radially outward (that is, the partition portion 14 at the portion defining the first bottom surface 12a1 of the first recess 12) and the holder 10 at the portion defining the vicinity thereof are in local contact with each other, large stress occurs in the holder 10 at this portion.

[0073] Therefore, the pressure resistance performance of the holder 10 is determined not by the mechanical strength of the partition portion 14 located radially inward as described above, but by the mechanical strength of the partition portion 14 located radially outward and the holder 10 at the portion defining the vicinity thereof.

[0074] In this regard, in the gas generator 1 according to the present embodiment, as described above, the distance B from the first bottom surface 12a1 of the first recess 12 to the bottom surface 13a of the second recess 13 (see FIG. 2) is configured to be larger than the distance A from the second bottom surface 12a2 of the first recess 12 to the bottom surface 13a of the second recess 13 (see FIG. 2). This makes it possible to improve the mechanical strength of the partition portion 14 located between the first bottom surface 12a1 and the bottom surface 13a, which is a portion where large stress occurs when the gas generator 1 is activated as described above.

[0075] Furthermore, by increasing the distance B to such an extent that the mechanical strength of the partition portion 14 at the portion where large stress occurs during the activation is sufficiently secured, the mechanical strength of the entire partition portion 14 can be ensured.

[0076] On the other hand, even when A < B as described above, if the distance C from the bottom surface of the second recess to the annular groove (see FIG. 2) is equal to or less than the distance B, the mechanical strength of the holder at the portion located between the second recess and the annular groove determines the pressure resistance performance of the entire holder.

[0077] In this respect also, in the gas generator 1 according to the present embodiment, as described above, the distance C from the bottom surface 13a of the second recess 13 to the annular groove 16 is configured to be larger than the distance B. As a result, the pressure resistance performance of the holder 10 is determined by the mechanical strength of the partition portion 14 located between the first bottom surface 12a1 and the bottom surface 13a, which is the portion that defines the distance B. Furthermore, since the mechanical strength of the partition portion 14 in this portion is ensured, it is possible to obtain the gas generator 1 having excellent pressure resistance performance as a result.

[0078] In addition, when B < C as described above, the arrangement position of the second recess 13 is retracted in a direction away from the bottom wall 42 of the cup 40, and similarly, the arrangement positions of the first recess 12 and the partition portion 14 are also retracted in a direction away from the bottom wall 42.

[0079] With this configuration, the arrangement positions of the igniter 20 received and held in the first recess 12 and the connector received and held in the second recess 13 are retracted in a direction away from the bottom wall 42. Therefore, the accompanying increase in the volume of the accommodation space 44 of the cup 40 makes it possible to increase the filling amount of the gas generant 50, and as a result, it is possible to achieve higher output of the gas generator 1.

[0080] Furthermore, when B < C as described above, although the axial length of the second body portion 11b (distance D in FIG. 1) is slightly increased, there is no need to make any particular changes to the height of the cup 40 and the axial length of the first body portion 11a, so the gas generator 1 can be reduced in size and weight.

[0081] Therefore, by adopting the gas generator 1 according to the present embodiment described above, it is possible to obtain a gas generator that has high output, high pressure resistance, and is also reduced in size and weight.

[0082] Hereinafter, the effects of employing the gas generator 1 according to the present embodiment described above will be described through comparison with a gas generator according to a comparative example. FIGS. 6(A) and 6(B) are schematic cross-sectional views of gas generators 1X1 and 1X2 according to Comparative Examples 1 and 2, respectively.

[0083] As shown in FIG. 6(A), in the gas generator 1X1 according to Comparative Example 1, a distance A from the second bottom surface of the first recess to the bottom surface of the second recess, a distance B from the first bottom surface of the first recess to the bottom surface of the second recess, and a distance C from the bottom surface of the second recess to the annular groove are configured to satisfy the condition of A<C<B. That is, in the gas generator 1X1 according to Comparative Example 1, since the bottom surface 12a of the first recess 12 has a stepped shape, the mechanical strength of the partition portion 14 located radially outward is improved, while the mechanical strength of the holder 10 located radially outward of the partition portion 14 is configured to be relatively low.

[0084] Here, when C<B as described above, the mechanical strength of the holder portion located between the second recess and the annular groove (that is, the holder portion that defines the distance C) determines the pressure resistance performance of the entire holder. However, in the gas generator 1X1, due to the fact that the distance C is relatively short, and stress concentration is likely to occur at the corner of the second recess and the corner of the annular groove, the mechanical strength of the holder in this portion is relatively low, and as a result, it is difficult to ensure high pressure resistance performance for the entire holder.

[0085] In contrast, in the case of the gas generator 1 according to the present embodiment, since B<C as described above, the mechanical strength of the partition portion 14 located between the first bottom surface 12a1 of the first recess 12 and the bottom surface 13a of the second recess 13 (that is, the partition portion 14 that defines the distance B) determines the pressure resistance performance of the entire holder. Further, the mechanical strength of the partition portion 14 in this portion is ensured. Therefore, by employing the gas generator 1 according to the present embodiment, superior pressure resistance performance can be obtained compared to the gas generator 1X1.

[0086] Further, compared to the gas generator 1X1 in which the distance C is relatively shortened, the gas generator 1 according to the present embodiment has a relatively increased distance C. Therefore, by adopting the gas generator 1 according to the present embodiment, as described above, an increase in the volume of the accommodation space 44 of the cup 40 can be achieved, so that the output can be made higher than that of the gas generator 1X1.

[0087] As shown in Fig. 6(B), the gas generator 1X2 according to Comparative Example 2 is configured to satisfy the condition of A=B<C. That is, in the gas generator 1X2 according to Comparative Example 2, since the bottom surface 12a of the first recess 12 does not have a stepped shape, improvement of the mechanical strength of the partition portion 14 located radially outward is not achieved. On the other hand, the holder 10 at a portion located radially outward of the partition portion 14 is configured to have relatively high mechanical strength, and the volume of the accommodation space 44 of the cup 40 is configured to be large.

[0088] Here, when B<C as described above, the mechanical strength of the partition portion at the portion defining the distance B determines the pressure resistance performance of the entire holder. However, in the gas generator 1X2, since the distance B is relatively shortened due to A=B, the mechanical strength of the partition portion at that portion becomes low, and as a result, it is difficult to ensure high pressure resistance performance of the entire holder.

[0089] In contrast to this, in the case of the gas generator 1 according to the present embodiment, as described above, since the distance B is increased by setting A<B, the mechanical strength of the partition portion 14 at the portion defining the distance B can be ensured. Therefore, by adopting the gas generator 1, excellent pressure resistance performance can be obtained compared to the gas generator 1X2.

[0090] Thus, by comparing it with the gas generators 1X1 and 1X2 according to Comparative Examples 1 and 2, it can be understood that the gas generator 1 according to the above embodiment is a gas generator that is high-output, high-pressure resistant, and also small and lightweight.

[0091] (modified version) Figure 7 is a schematic cross-sectional view showing the gas generator according to the modified example with the pretensioner casing assembled. Hereinafter, the gas generator 1A according to the modified example based on the above-described embodiment will be explained with reference to Figure 7.

[0092] As shown in Figure 7, the modified gas generator 1A differs from the gas generator 1 according to the embodiment described above only in the configuration of the holder 10A.

[0093] More specifically, the holder 10A used in the modified gas generator 1A has a first part 10A1 made of a resin material and a second part 10A2 made of a metal material.

[0094] The first part 10A1 defines the axial end of the holder 10A that does not face the cup 40, including the recessed portion 13b1, and the second part 10A2 defines the remaining portion of the holder 10A. The second part 10A2 also defines the outer circumferential surface of the base side (i.e., the side facing the first body portion 11a) of the second body portion 11b of the holder 10A.

[0095] The first part 10A1 consists of a resin portion formed by injection molding (more specifically, so-called insert molding) and is integrally molded to be fixed to the metal second part 10A2. This first part 10A1 can be formed by using a mold during injection molding to fill a portion of the space defined by the axial end of the second part 10A2 on the side not facing the cup 40, by pouring a fluid resin material into a portion of that space and allowing it to solidify.

[0096] Furthermore, the first part 10A1 is not limited to being integrally molded with the second part 10A2 by insert molding. For example, the first part 10A1 may be molded separately and then assembled to the second part 10A2 by press-fitting or fitting.

[0097] As the raw material for the first part 10A1 formed by injection molding, a resin material with excellent heat resistance, durability, corrosion resistance, etc. after curing is preferably selected and used. In this case, it is not limited to thermosetting resins such as epoxy resin, but it is also possible to use thermoplastic resins such as polybutylene terephthalate resin, polyethylene terephthalate resin, polyamide resin (for example, nylon 6 or nylon 66), polypropylene sulfide resin, and polypropylene oxide resin.

[0098] Even with this configuration, the same effects as those described in the above-mentioned embodiment can be obtained, making it possible to create a gas generator that is high-output, high-pressure resistant, and also compact and lightweight.

[0099] Furthermore, with this configuration, a portion of the holder 10A will be made of resin material, resulting in a gas generator that reduces the manufacturing cost and weight of the holder.

[0100] Furthermore, a large load is applied to the outer circumferential surface at the base of the second body portion 11b of the holder 10A, which is the part that abuts against the tip portion of the casing 201 of the pretensioner 200, during crimping. In the gas generator 1A according to this modified example, this part is made of a second metal portion 10A2. By configuring it in this way, the holder 10A can be made to have mechanical strength that can withstand the above load.

[0101] The characteristic configuration of the gas generator disclosed in the above-described embodiment and its modified form can be summarized as follows.

[0102] [Supplementary Note 1] a gas generant that generates gas by combustion; an igniter having an ignition unit loaded with an ignition charge and a terminal pin connected to the ignition unit; a substantially cylindrical cup with a bottom that accommodates the gas generant, wherein one axial end thereof is configured as an open end; a substantially cylindrical holder that closes the open end by the cup being coaxially assembled thereto, and holds the igniter such that the ignition unit faces the gas generant; the holder includes: a first recess provided on an axial end surface facing the cup and configured to receive and hold the igniter; a second recess provided on an axial end surface not facing the cup, in which the terminal pin is disposed, and configured to receive and hold a connector for external connection of the igniter via the terminal pin; a partition part that defines a bottom surface of the first recess and a bottom surface of the second recess to partition the first recess and the second recess from each other; and an annular groove provided on the axial end surface facing the cup and configured to receive and hold an opening edge of the cup inserted along the axial direction; the bottom surface of the first recess has a stepped shape, such that when viewed along the axial direction of the holder, the bottom surface of the first recess has an annular first bottom surface located on the outer side, and a second bottom surface located more inward than the first bottom surface and closer to the second recess than the first bottom surface; a gas generator satisfying a condition of A < B < C, where A is a distance from the second bottom surface to the bottom surface of the second recess, B is a distance from the first bottom surface to the bottom surface of the second recess, and C is a distance from the bottom surface of the second recess to the annular groove.

[0103] [Supplementary Note 2] the cup has a flange portion extending outward from the open end, an annular flange that defines an outer wall surface of the annular groove is provided on the axial end surface of the holder facing the cup, the flange portion includes a second surface located on a side opposite to a first surface facing the bottom surface of the annular groove, With the flange portion received by the annular groove portion, the annular flange portion is bent inward, causing the tip of the annular flange portion to contact the second surface, thereby sandwiching the flange portion between the tip of the annular flange portion and the bottom surface of the annular groove portion in the axial direction of the cup, and thus the cup is assembled to the holder. The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. The gas generator described in Appendix 1, wherein the axial length of the second body is D, and the sum of the length of the annular flange along the axial direction of the first body and the axial length of the first body in the state after the cup is assembled to the holder is E, and the condition E < 1.8 × D is satisfied.

[0104] [Note 3] The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. A gas generator as described in Appendix 1 or 2, wherein the axial length of the second body is D and the depth of the second recess is F, and the condition F < 1.8 × D is satisfied.

[0105] [Note 4] The gas generator according to any one of the appendices 1 to 3, wherein the inner surface of the second recess is provided with a recess for fixing a shorting clip to the second recess.

[0106] [Note 5] The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. At least the portion of the holder that defines the recess is made of resin. The gas generator as described in Appendix 4, wherein at least the portion of the holder that defines the outer circumferential surface on the base side of the second body is made of metal.

[0107] (Other forms, etc.) The shapes, configurations, sizes, numbers, materials, etc., of each part shown in the embodiments and modifications of the present invention described above can be modified in various ways without departing from the spirit of the present invention.

[0108] Furthermore, the characteristic configurations shown in the embodiments and modifications of the present invention described above can naturally be combined with each other without departing from the spirit of the present invention.

[0109] Thus, the embodiments and their variations disclosed herein are illustrative in all respects and not restrictive. The technical scope of the present invention is defined by the claims and includes all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0110] 1,1A,1X1,1X2 Gas generator, 10,10A Holder, 10A1 First part, 10A2 Second part, 11 Body, 11a First body, 11b Second body, 12 First recess, 12a Bottom surface, 12a1 First bottom surface, 12a2 Second bottom surface, 12b Inner surface, 13 Second recess, 13a Bottom surface, 13b Inner surface, 13b1 Recess, 14 Partition, 14a Opening, 15 Locking part, 16 Annular groove, 16a Bottom surface, 16c Inner wall surface, 17 Annular flange, 20 Ignition device, 21 Base, 22 Ignition part, 23 Terminal pin, 30 Seal member, 40 Cup, 41 Side wall, 41a Open end, 42 Bottom wall, 42a Score, 43 flange section, 43a first surface, 43b second surface, 44 containment space, 50 gas generating agent, 100 shorting clip, 101 claw section, 102 leaf spring section, 200, 200A pretensioner, 201, 201A casing.

Claims

1. A gas generating agent that produces gas when burned, An igniter having an ignition section loaded with ignition powder and terminal pins connected to the ignition section, A bottomed, substantially cylindrical cup containing the gas generating agent, with one end in the axial direction being an open end, The cup is assembled coaxially to close the open end, and the ignition part is held in a substantially cylindrical holder so that it faces the gas generating agent, The holder has a first recess provided on the axial end face facing the cup for receiving and holding the igniter, a second recess provided on the axial end face not facing the cup for receiving and holding a connector for external connection of the igniter via the terminal pins, a partition portion that separates the first recess and the second recess by defining the bottom surface of the first recess and the bottom surface of the second recess, and an annular groove provided on the axial end face facing the cup for receiving and holding the opening edge of the cup inserted along the axial direction. Because the bottom surface of the first recess has a stepped shape, the bottom surface of the first recess has, when viewed along the axial direction of the holder, an annular first bottom surface located on the outside and a second bottom surface located inward from the first bottom surface and on the second recess side from the first bottom surface. A gas generator that satisfies the condition A < B < C, where A is the distance from the second bottom surface to the bottom surface of the second recess, B is the distance from the first bottom surface to the bottom surface of the second recess, and C is the distance from the bottom surface of the second recess to the annular groove.

2. The cup has a flange portion extending outward from the open end, An annular flange is provided on the axial end face of the holder facing the cup, defining the outer wall surface of the annular groove. The flange portion includes a second surface located on the opposite side from the first surface facing the bottom surface of the annular groove portion. With the flange portion received by the annular groove portion, the annular flange portion is bent inward, so that the tip portion of the annular flange portion comes into contact with the second surface, and thereby the flange portion is sandwiched between the tip portion of the annular flange portion and the bottom surface of the annular groove portion in the axial direction of the cup, so that the cup is assembled to the holder. The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. The gas generator according to claim 1, wherein the axial length of the second body is D, and the sum of the length of the annular flange portion along the axial direction of the first body and the axial length of the first body in the state after the cup is assembled to the holder is E, and the condition E < 1.8 × D is satisfied.

3. The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. The gas generator according to claim 1, wherein the axial length of the second body is D and the depth of the second recess is F, and the condition F < 1.8 × D is satisfied.

4. The gas generator according to claim 1, wherein the inner surface of the second recess is provided with a recess for fixing a shorting clip to the second recess.

5. The holder further comprises a cylindrical first body portion that surrounds at least the partition portion, the end of the first recess on the partition portion side in the axial direction of the holder, and the end of the second recess on the partition portion side in the axial direction of the holder, and a cylindrical second body portion that protrudes from the end of the first body portion located on the axial end face side of the holder that does not face the cup, surrounds at least the end of the second recess on the side opposite to the partition portion side in the axial direction of the holder, and has a smaller outer diameter than the first body portion. At least the portion of the holder that defines the recess is made of resin. The gas generator according to claim 4, wherein at least the portion of the holder that defines the outer circumferential surface on the base side of the second body is made of metal.

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