Gas generator

Abstract

The present invention suppresses, when a resin case is used, scattering of the case when the case is cleaved. Provided is a gas generator comprising an ignition device including an igniter, a tubular igniter retaining part which holds the igniter in a state in which the igniter retaining part surrounds the igniter, and a resinous fixing part which fixes the igniter to the igniter retaining part, and a resinous, bottomed tubular case which accommodates a gas generation agent to be combusted through activation of the ignition device and which includes a side wall part having a base end side connected to the fixing part and a closing end part which closes a distal end side. The case includes a tilted surface which is located on the distal end side and extends obliquely with respect to the axial direction of the case and a fragile part which is formed in the edge part of the tilted surface excluding at least the base end part of the tilted surface.

Description

Gas generator

[0001] The present invention relates to a gas generator.

[0002] Conventionally, a gas generator has been proposed that includes an outer housing having a cup-shaped receiving portion and a cover that closes the receiving portion (for example, Patent Document 1). In this technology, the receiving portion and the cover are made of resin, forming an airtight housing that is protected from the intrusion of moisture. When the gas generator of this technology is activated, the gas generating agent inside the cover burns, causing the pressure inside the cover to increase, and a part of the cover breaks open to release the gas.

[0003] U.S. Patent Application Publication No. 2002 / 0062757

[0004] In a gas generator, when the case that houses the gas generating agent is made of resin, resin generally has a lower breaking strength than metal, so there is a high possibility that fragments will fly when the case is ruptured. The above-mentioned Patent Document 1 does not disclose any configuration for suppressing scattering of fragments when the case is ruptured.

[0005] An object of the present disclosure is to provide a technique for preventing a resin case from scattering when the case is broken open.

[0006] In order to solve the above problems, the present disclosure employs the following configuration: A gas generator comprising: an ignition device having an igniter, a cylindrical igniter holding portion that surrounds and holds the igniter, and a resin fixing portion that fixes the igniter to the igniter holding portion, and a bottomed cylindrical case that contains a gas generating agent that burns when the ignition device is activated, the case being made of resin and having a side wall portion whose base end is connected to the fixing portion and a closed end portion that closes the tip end side, wherein the case has: an inclined surface on the tip end side that extends obliquely with respect to the axial direction of the case; and a fragile portion formed on at least an edge portion of the inclined surface excluding the base end portion.

[0007] In the gas generator, the top of the inclined surface may be a tip of the closed end.

[0008] In the above gas generator, the case may be deformed such that the tip of the closed end splits open when the gas generating agent burns, and the inclined surface opens outward with the base end side of the inclined surface as a fulcrum.

[0009] In the above gas generator, the case may have a limiting portion formed to surround the inclined surface and limiting the amount of deformation of the inclined surface when the inclined surface opens outward.

[0010] In the above gas generator, the inclined surface may have a thickness greater at the base end portion of the inclined surface that is connected to the side wall portion than at other portions.

[0011] In the gas generator, the inclined surface may be connected to the side wall portion at the base end portion, and the base end portion may be formed into a curved surface.

[0012] In the above gas generator, the inclined surface may be arranged such that flat surfaces of a pair of isosceles trapezoids whose short sides are located on the tip side and flat surfaces of a pair of isosceles triangles whose vertices are located on the tip side are arranged opposite each other, and the apex of the inclined surface may be formed by the short sides of the isosceles trapezoids and the vertex of the isosceles triangles with the flat surfaces of the isosceles trapezoids and the isosceles triangles inclined toward the inside of the case.

[0013] In the gas generator, the weakened portion may be formed linearly at a contact portion between an apex of the inclined surface and the adjacent isosceles trapezoid and the adjacent isosceles triangle.

[0014] In the above gas generator, the inclined surface may be formed by a combination of a plurality of isosceles trapezoids each having a short side and a long side opposite to the short side, and the closed end may include a flat portion connected to the short side of each of the plurality of isosceles trapezoids.

[0015] In the above gas generator, the case may have a columnar shape and may be fitted into a cylindrical portion to which the gas generator is attached.

[0016] The above-described configurations can be combined or deleted as much as possible without departing from the spirit of the present disclosure.

[0017] According to the present disclosure, when a resin case is used, it is possible to provide a technique for preventing the case from scattering when it is broken open.

[0018] FIG. 1 is a perspective view showing an example of a gas generator according to a first embodiment. FIG. 2 is a schematic axial cross-sectional view showing an example of a gas generator according to the first embodiment attached to an attachment target. FIG. 3 is a perspective view showing an example of a gas generator according to a modified example of the first embodiment. FIG. 4 is a schematic cross-sectional view showing an example of a gas generator according to a second embodiment. FIG. 5( a) is a perspective view showing an example of a gas generator according to a third embodiment, and FIG. 5( b) is a plan view of the gas generator according to the third embodiment as viewed from above. The figure is a perspective view showing the state of a closed end when the gas generator according to the third embodiment is activated. FIG. 7 is a schematic cross-sectional view showing an example of a gas generator according to a comparative example.

[0019] Hereinafter, a gas generator according to an embodiment of the present disclosure will be described with reference to the drawings. Note that each configuration and combination thereof in the embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited by the embodiment, but is limited only by the scope of the claims.

[0020] <First embodiment> Fig. 1 is a perspective view showing an example of a gas generator. Fig. 2 is a schematic axial cross-sectional view showing an example of a gas generator attached to an attachment target. When activated, gas generator 1 combusts an internal gas generating agent and releases the generated combustion gas to the outside. As shown in Fig. 2, gas generator 1 is incorporated into, for example, a seat belt retractor (pretensioner) 10 of an automobile, and is used to retract the seat belt in the event of a collision of the automobile. Furthermore, gas generator 1 includes an ignition device 2 and a case 3, and accommodates gas generating agent 4 therein.

[0021] <Ignition Device> The ignition device 2 includes an igniter 21 that is ignited by an ignition current, an igniter holding portion 22 that supports the igniter 21, and a fixing portion 23 interposed between the igniter 21 and the igniter holding portion 22.

[0022] The igniter 21 includes, for example, a cylindrical cup body 211 having an open end and a closed end, an insulating layer 212, a sealing member 213 closing the opening of the cup body 211, an ignition charge 214 housed in an ignition chamber formed by the cup body 211 and the sealing member 213, and two conductive pins 215 for receiving a current supply from an external source. In this embodiment, for convenience, the cup body 211 side is referred to as the upper side and the conductive pin 215 side as the lower side. The two conductive pins 215 are connected within the ignition chamber via a bridge wire (not shown). When the conductive pin 215 receives a current supply from an external source, the bridge wire, which is a resistor, generates heat and burns the ignition charge 214. The ignition charge 214 may be an existing one used in general gas generators. The cup body 211 is a metal member covered with, for example, a resin insulating layer 212. The sealing member 213 is also made of, for example, metal, and the two conductive pins 215 are insulated from each other. The cup body 211 has, for example, a radial notch (not shown) on its upper surface, and when the igniter 21 is activated, the notch is split open by the combustion products of the ignition charge 214, releasing combustion products such as flames and combustion gases upward.

[0023] Igniter holding portion 22 is, for example, a metal collar that supports the side of igniter 21. That is, igniter holding portion 22 is a metal member formed in a cylindrical shape, and holds igniter 21 inside thereof. Note that, in order to suppress circumferential rotation of fixing portion 23 relative to igniter holding portion 22, the inner peripheral surface of igniter holding portion 22 that comes into contact with fixing portion 23 may be provided with irregularities. Igniter holding portion 22 is fixed by crimping to cylindrical portion 100, which is an attachment target, for example, the seat belt retractor main body. Cylindrical portion 100 is a cylindrical member into which case 3 of gas generator 1 can be inserted.

[0024] The fixing portion 23 is a resin connecting portion interposed between the igniter 21 and the igniter holding portion 22 by injection molding and fixes the igniter 21 to the igniter holding portion 22. A resin material that exhibits excellent heat resistance, durability, corrosion resistance, and the like after hardening can be suitably used as the material for the fixing portion 23. In the example of FIG. 2 , the fixing portion 23 includes a first fixing portion 231 located on the upper side and fixing the cup body 211 of the igniter 21, and a second fixing portion 232 located on the lower side and mainly surrounding the conductive pin 215. The fixing portion 23 covers the lateral periphery of the igniter 21 so that, for example, a portion of the cup body 211 or the insulating layer 212 is exposed from the fixing portion 23. Note that the entire cup body 211 or the insulating layer 212 may be overmolded by the fixing portion 23. Furthermore, fixing portion 23 engages with the inside of igniter holding portion 22, thereby fixing igniter 21 to igniter holding portion 22. Second fixing portion 232 may fix connector 5, for supplying power from an external power source to conductive pin 215, to the inside of igniter holding portion 22 in a state where connector 5 is connected to conductive pin 215.

[0025] <Case> The case 3 is a cylindrical member with a bottom that extends from the base end (the ignition device 2 side) to the tip end (upper side) so as to surround the upper part of the ignition device 2. The case 3 is made of a resin, and may be made of the same resin as the fixing part 23, for example. The case 3 includes a cylindrical side wall part 31 that extends vertically, and a closed end part 32 that closes the upper end. A combustion chamber 6 that accommodates a gas generating agent 4 is formed between the case 3 and the igniter 21. The gas generating agent 4 is ignited by activation of the igniter 21 and burns to generate combustion products such as combustion gas.

[0026] The side wall portion 31 is a cylindrical portion whose inner and outer diameters are constant or nearly constant. The base end of the side wall portion 31 is connected to the fixed portion 23 by, for example, full-circumference welding. Full-circumference welding is a continuous, annular weld in the circumferential direction, which seals the two members to be welded together without any gaps. In the example of Figure 2, the portions to be welded by laser welding are indicated by black circles.

[0027] The closed end 32 has an oval cross section (track-shaped, rounded rectangular) in a direction perpendicular to the axial direction of the case 3. The closed end 32 has an inclined surface 321 extending obliquely with respect to the axial direction of the case 3 on the tip side, and a weakened portion 323 formed on the edge of the inclined surface 321 excluding the base end. As shown in FIG. 1 , the inclined surface 321 is composed of four flat surfaces, including two isosceles trapezoidal flat surfaces and two isosceles triangular flat surfaces. When the gas generator 1 is viewed from above, the isosceles trapezoidal flat surfaces and the isosceles triangular flat surfaces are arranged to face each other. Furthermore, the upper sides of the two isosceles trapezoidal flat surfaces are short sides, and the upper sides of the two isosceles triangular flat surfaces are arranged to be vertices. In the present embodiment, the inclined surface 321 is inclined toward the inside of the case 3, and an apex 322 of the inclined surface 321 is formed by the short side of the isosceles trapezoid and the apex of the isosceles triangle. This apex 322 constitutes the tip of the closed end 32.

[0028] Furthermore, the inside of the top portion 322 of the case 3 forms a fragile portion 323. When the internal pressure of the case 3 increases, stress concentrates at the fragile portion 323 inside the top portion 322. The fragile portion 323 is cleaved due to the increase in internal pressure of the case 3 or the temperature of the combustion products generated by the combustion of the gas generating agent 4. As a result, when the gas generating agent burns, the tip of the closed end of the case 3 is cleaved, and each flat surface of the inclined surface 321 is deformed so as to open outward with the base end 324 side of the inclined surface 321 as a fulcrum. In this way, the base end 324 of the inclined surface 321 serves as a hinge portion when the inclined surface 321 opens. Furthermore, the base end 324 is connected to the inner surface of the side wall portion 31. The base end 324 is formed in a curved shape on the boundary side of the side wall portion 31 so that stress does not concentrate when the internal pressure of the case 3 increases. Furthermore, inclined surface 321, base end 324 that connects to side wall portion 31 of case 3 is thicker than other portions. This makes it possible for gas generator 1 to prevent inclined surface 321 from tearing off from base end 324 when inclined surface 321 opens outward with base end 324 as a hinge portion.

[0029] Furthermore, case 3 has limiting portion 325 formed to surround inclined surface 321. Limiting portion 325 limits the amount of deformation of inclined surface 321 when it opens outward. Limiting portion 325 extends along the axial direction of case 3. This allows limiting portion 325 to limit the amount of outward deformation of inclined surface 321 to the axial direction of case 3. Furthermore, when gas generator 1 is viewed from the top to bottom, the tip of limiting portion 325 and top 322 of the inclined surface are at the same height. Note that in the present embodiment, limiting portion 325 is formed to continuously surround inclined surface 321, but limiting portion 325 may also be formed to discontinuously surround inclined surface 321.

[0030] Furthermore, the outer side of the side surface of case 3 is shaped to fit the inside of tubular portion 100 to which it is attached. That is, side wall portion 31 is housed in a portion of tubular portion 100 whose inner periphery in cross section is a perfect circle or approximately a perfect circle. Furthermore, closed end portion 32 is housed in a portion of tubular portion 100 whose inner periphery in cross section is an oval. This allows case 3 to fit into tubular portion 100 to which gas generator 1 is attached. The side surface of case 3 is surrounded all around by tubular portion 100 to which it is attached, and the inner surface of the attachment target has a shape that corresponds to the side surface of case 3. Therefore, even if the internal pressure of case 3 increases, the side surface (side wall portion 31) of case 3 is prevented from cracking. Furthermore, the inner diameter of the oval-shaped portion is smaller in a predetermined direction than the inner diameter of the circular or approximately circular portion. Two flat portions are formed opposite the closed end 32 of the case 3, where the outer diameter of the case 3 is smaller at the tip end than at the base end, and the cylindrical portion 100 also faces these flat portions in a complementary manner, so that the entire case 3 is prevented from being ejected upward when the internal pressure of the case 3 increases. Therefore, when the internal pressure of the case 3 increases, or when the case 3 melts due to the temperature of the combustion products generated by the combustion of the gas generating agent 4, the fragile portion 323 of the closed end 32 first cleaves, forming an opening. Furthermore, rotation of the gas generator 1 within the cylindrical portion 100 is also prevented.

[0031] <Gas Generating Agent> A predetermined gas generating agent is used as the gas generating agent 4. The combustion temperature of the gas generating agent 4 is, for example, 1000 to 1700°C. The gas generating agent 4 is formed, for example, from guanidine nitrate (41% by weight), basic copper nitrate (49% by weight), a binder, and an additive. The shape of each gas generating agent 4 may be a single-hole cylindrical shape. Note that the gas generating agent 4 is not limited to the above, and a nitrocellulose-based composition may also be used for the gas generating agent 4.

[0032] <Operation> When the gas generator 1 is mounted in, for example, the seat belt retractor 10 of an automobile, the connector 5 is connected to the two conductive pins 215, enabling power to be supplied to the igniter 21. In this state, when a sensor (not shown) mounted on the automobile or the like detects an impact, an ignition current is supplied to the conductive pin 215, and the igniter 21 is activated. The igniter 21 combusts the ignition charge 214 in the cup body 211 and releases the combustion products to the outside of the cup body 211. Furthermore, the flame and combustion gas, which are combustion products of the ignition charge 214, ignite the gas generating agent 4 filled in the combustion chamber 6. When the gas generating agent 4 burns, it generates combustion gas and the like as combustion products.

[0033] The side surface (side wall portion 31) of the case 3 is completely surrounded by the cylindrical portion 100 of the attachment target, and the inner surface of the attachment target has a shape corresponding to the side surface of the case 3. Therefore, even if the internal pressure of the case 3 increases, the side surface of the case 3 is prevented from splitting open. Furthermore, because the outer diameter of the case 3 includes a portion where the tip end is smaller than the base end, the entire case 3 is prevented from being ejected upward when the internal pressure of the case 3 increases. Therefore, when the internal pressure of the case 3 increases, the fragile portion 323 of the closed end 32 splits open, forming an opening. Furthermore, even if the case 3 melts due to the temperature of the combustion products, the melted portion is limited to the inclined surface 321 or a portion thereof. Therefore, portions of the case 3 other than the fragile portion 323 are prevented from breaking into small pieces and scattering. Furthermore, the split fragile portion 323 is sufficiently small compared to the cross section of the closed end 32, and even if fragments are generated, they are burned up by the combustion products of the gas generating agent 4, preventing the fragments of the case 3 from penetrating into the interior of the attachment target.

[0034] Furthermore, combustion gas is discharged from the opening into, for example, the seat belt retractor 10 to which the gas generator 1 is attached. The discharged combustion gas then activates a predetermined mechanism of the seat belt retractor 10. The seat belt retractor 10 may have an existing configuration. For example, the gas generator 1 is connected to one end of a pipe that is part of the seat belt retractor 10, and the pressure of the combustion gas moves steel balls inside the pipe. The moving steel balls rotate a gear, and the seat belt retractor 10 pretensions the seat belt by using the rotation of the gear as power to retract the seat belt. At this time, because the gas generator 1 has one weakened portion 323 in the center of the closed end 32, the flow direction of the discharged gas can be concentrated in the direction in which the pipe extends, and force can be efficiently transmitted to the seat belt retractor 10.

[0035] Furthermore, after the fragile portion 323 is cleaved, the case 3 deforms so that the inclined surface 321 opens outward with the base end 324 side as a fulcrum. As a result, the diameter of the opening of the case 3 in the gas generator 1 increases, making it easier to discharge the combustion gas into the seat belt retractor 10. Since the closed end 32 has the inclined surface 321 extending obliquely with respect to the axial direction of the case 3, the amount of movement of the inclined surface 321 at the time of activation is smaller than that of a closed end surface extending in a direction perpendicular to the axial direction (see FIG. 7 described later), and the amount of outward deformation of the inclined surface 321 is limited by the limiting portion 325. Therefore, the gas generator 1 prevents the inclined surface 321 from deforming more than necessary, thereby preventing the inclined surface 321 from being destroyed. By preventing the destruction of the inclined surface 321, the gas generator 1 suppresses the generation of fragments thereof and thereby suppresses the intrusion of fragments of the inclined surface 321 into the seat belt retractor 10. An example of destruction of inclined surface 321 is when inclined surface 321 is torn off at base end 324. In this way, according to gas generator 1 according to the present embodiment, when a resin case 3 is used, scattering of case 3 when it is ruptured can be suppressed.

[0036] <Modification> Fig. 3 is a perspective view showing an example of a gas generator according to a modification of the first embodiment. In this modification, the fragile portion 323 is formed linearly not only at the portion where the short sides of the isosceles trapezoids abut, but also at the portion where adjacent isosceles trapezoids and isosceles triangles abut. The fragile portion 323 is formed on the inside of the case 3 as shown in Fig. 2, and Fig. 3 indicates the range in which the fragile portion 323 is formed when the case 3 is viewed from the outside. Note that "linear" in this case includes a state in which the fragile portion 323 is formed continuously or discontinuously in the extension direction. Furthermore, the fragile portion 323 may be formed on the outside of the closed end portion 32 (toward the apex 322).

[0037] 4 is a schematic cross-sectional view showing an example of a gas generator according to a second embodiment. Note that components corresponding to those in the first embodiment described above are given the same reference numerals, and descriptions thereof will be omitted.

[0038] In gas generator 1 according to the present embodiment, inclined surface 321 is formed in an annular shape except for one straight line portion of the oval shape of closed end 32, and is connected to this one straight line portion. The outside of this connected portion is apex 322 of inclined surface 321, and the inside thereof is weakened portion 323.

[0039] In this gas generator 1 as well, when the internal pressure of the case 3 increases, stress concentrates at the weakened portion 323 on the inside of the top portion 322. The weakened portion 323 is cleaved open by the increase in internal pressure of the case 3. Furthermore, even if the case 3 melts due to the temperature of the combustion products, the melted portion is limited to the inclined surface 321 or a part thereof. As a result, when the gas generating agent 4 burns, the tip of the closed end of the case 3 is cleaved open, and the annular inclined surface 321 deforms so as to open outward with the base end 324 side of the inclined surface 321 as a fulcrum.

[0040] When the internal pressure of case 3 rises, or when case 3 melts due to the temperature of combustion products generated by combustion of gas generating agent 4, only fragile portion 323 ruptures, forming an opening. At this time, portions of case 3 other than fragile portion 323 are prevented from scattering into small pieces. Furthermore, inclined surface 321 deforms outward, but the amount of deformation of inclined surface 321 is limited by limiting portion 325. As with the first embodiment described above, when a resin case 3 is used, gas generator 1 according to this embodiment can also prevent case 3 from scattering when it is ruptured.

[0041] <Third embodiment> Fig. 5(a) is a perspective view showing an example of a gas generator according to a third embodiment, and Fig. 5(b) is a view of the gas generator according to the third embodiment as viewed from above. Note that components corresponding to those in the first embodiment described above are given the same reference numerals, and descriptions thereof will be omitted. Furthermore, illustration of the limiting portion 325 in the first embodiment is omitted in Figs. 5(a) and (b) and Fig. 6 described below.

[0042] 5( a) and 5(b) , inclined surface 321 forming closed end 32 is formed by combining a plurality of isosceles trapezoids having a short side disposed on the upper side and a long side disposed opposite the short side. The short sides of the isosceles trapezoids are disposed relatively on the upper side of gas generator 1, and the long sides of the isosceles trapezoids are disposed relatively on the lower side of gas generator 1, with the orientations of the respective short sides and the respective long sides (up-down arrangement direction) being aligned. Specifically, inclined surface 321 is formed by two types of isosceles trapezoids: two first trapezoids 321a and two second trapezoids 321b. First trapezoids 321a have a larger area than second trapezoids 321b. Two first trapezoids 321a are arranged opposite each other, and two second trapezoids 321b are also arranged opposite each other, so that first trapezoids 321a and second trapezoids 321b are arranged alternately when gas generator 1 is viewed in the circumferential direction. Furthermore, first trapezoids 321a have longer short and long sides than second trapezoids 321b, and the cross-sectional shape of case 3 on the closed end 32 side is an ellipse including two parallel straight lines, with the long side of first trapezoid 321a located on the straight side of the ellipse and the long side of second trapezoid 321b located on the curved side of the ellipse. Furthermore, closed end 32 has a rectangular flat surface portion 330 that forms the tip of case 3. Flat surface portion 330 abuts against the short sides of first trapezoid 321a and second trapezoid 321b, and the length of each side of flat surface portion 330 is equal to the length of each short side. The closed end portion 32 has a quadrangular pyramid shape formed by the first trapezoid 321 a , the second trapezoid 321 b , and the flat portion 330 .

[0043] The fragile portions 323 formed on the inside of the closed end portion 32 are linearly formed at abutment portions 335 between the adjacent first trapezoid 321a and second trapezoid 321b, at abutment portions 336 between the short sides of the first trapezoid 321a and the flat portion 330, and at abutment portions 337 between the short sides of the second trapezoid 321b and the flat portion 330. In FIG. 5B , the areas where the fragile portions 323 are formed are indicated by bold lines. In this embodiment, there are two abutment portions 336 between the short sides of the first trapezoid 321a and the flat portion 330, but the fragile portions 323 are formed only in one of the two abutment portions 336. The fragile portions 323 may also be formed on the outside of the closed end portion 32.

[0044] Furthermore, the flat portion 330 is formed with the same thickness as the first trapezoid 321a and the second trapezoid 321b except for the fragile portion 323, but it is also possible to make the entire area surrounded by the abutting portions 336, 337 thinner, for example. In this case, the fragile portion 323 is formed at the abutting portion 335 between the first trapezoid 321a and the second trapezoid 321b. Note that, as in the first and second embodiments, the strength is increased by increasing the thickness of the base end portion 324 (see FIGS. 2 and 3) of the first trapezoid 321a or the second trapezoid 321b that connects to the side wall portion 31.

[0045] Fig. 6 is a perspective view showing the state of closed end 32 when gas generator 1 according to the present embodiment is activated. Fig. 6 shows only closed end 32 and the side wall portion 31 in the vicinity thereof. In gas generator 1, the pressure inside case 3 increases due to combustion of gas generating agent 4 shown in Figs. 2 and 3 , and when this pressure increase preferentially causes fragile portion 323 to rupture, first trapezoid 321a and second trapezoid 321b open outward, forming opening 350. That is, inclined surface 321 ruptures at abutment portion 335 between first trapezoid 321a and second trapezoid 321b (see Figs. 4(a) and 4(b)). Furthermore, flat portion 330 ruptures at fragile portions 323 formed at two abutment portions 337 with two second trapezoids 321b. Furthermore, one of the two first trapezoids 321a has weakened portion 323 formed at abutment portion 336 with flat portion 330, and therefore splits at weakened portion 323, but the other abutment portion 336 does not have weakened portion 323 formed therein, and therefore flat portion 330 opens while connected to one of first trapezoids 321a, as shown in Fig. 6. Furthermore, when inclined surface 321 opens, base end portion 324 (see Figs. 2 and 3) functions as a hinge, and therefore first trapezoid 321a and second trapezoid 321b open radially outward about each base end portion 324, and form opening 350 in closed end 32. If flat portion 330 were thinner than other portions (e.g., inclined surface 321) forming case 3, flat portion 330 would be more likely to melt when gas generator 1 is activated, and therefore fragments of flat portion 330 would be less likely to be generated. For this reason, the area of ​​flat surface portion 330 can preferably be made narrower than first trapezoid 321 a, and may further be equal to or narrower than second trapezoid 321 b. As with the above-described first embodiment, gas generator 1 according to this embodiment can also suppress scattering of case 3 when case 3 made of resin is used when it is ruptured.

[0046] When gas generator 1 according to the third embodiment is attached to tubular portion 100 (see FIGS. 2 and 3 ) to which it is to be attached, side wall portion 31 of case 3 is arranged along the inside of tubular portion 100. At this time, second trapezoid 321b may be formed at closed end 32 so that second trapezoid 321b is also arranged along the inside of tubular portion 100. In this case, when gas generator 1 is activated, only first trapezoid 321a ruptures from fragile portion 323 and deploys, while second trapezoid 321b is held inside tubular portion 100 and does not deploy. As described above, flat portion 330 may deploy while remaining connected to one of first trapezoids 321a.

[0047] In gas generator 1 according to the third embodiment, first trapezoid 321a and second trapezoid 321b may be formed to have the same shape and size, and flat portion 330 may be formed to be square. Alternatively, three or five or more first trapezoids 321a or second trapezoids 321b of the same shape may be formed, and the shape of flat portion 330 may also be a polygon that follows the short side of first trapezoid 321a or second trapezoid 321b.

[0048] 7 is a schematic cross-sectional view showing one example of a gas generator 1B according to a comparative example. Note that components corresponding to those in the first or second embodiment described above are given the same reference numerals, and description thereof will be omitted.

[0049] In the example of FIG. 7 , gas generator 1B does not have inclined surface 321, and the internal space of case 3 is cylindrical over the entire length. Furthermore, a recess is formed at the center of the inside of closed end 32, and tip 326 of the recess forms fragile portion 323B that is thinner than surrounding thick portion 327. If gas generator 1B does not have inclined surface 321, stress will also concentrate on base end 324B formed between side wall portion 31 and closed end 32. Thus, not only will fragile portion 323B tear open, but closed end 32 will also tear radially from fragile portion 323B, making it easier for closed end 32 to expand outward by approximately 90 degrees with base end 324B as the center. Furthermore, if closed end 32 opens outward by approximately 90 degrees, base end 324B will also tear, and fragments of closed end 32 may fly off.

[0050] On the other hand, in the case of gas generator 1 according to the first embodiment or the second embodiment, by forming inclined surface 321 on case 3, only fragile portion 323 can be cleaved. This enables gas generator 1 to inhibit fragments of case 3 from entering the interior of the object to which it is attached. Furthermore, inclined surface 321 deforms outward after fragile portion 323 is cleaved. Gas generator 1 prevents inclined surface 321 from deforming more than necessary by providing limiting portion 325, thereby preventing inclined surface 321 from being destroyed. According to gas generator 1, when a resin case 3 is used, scattering of case 3 when cleaved can be inhibited.

[0051] <Others> Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. For example, the inclined surface 321 of the case 3 may be configured with a combination of a flat surface and an annular surface. Also, the inclined surface 321 of the case 3 may be configured with three or more flat surfaces (e.g., triangular flat surfaces).

[0052] DESCRIPTION OF SYMBOLS 1, 1B: Gas generator 2: Igniter 21: Igniter 211: Cup body 212: Insulating layer 213: Sealing member 214: Igniter charge 215: Conductive pin 22: Igniter holding portion 23: Fixing portion 231: First fixing portion 232: Second fixing portion 3: Case 31: Side wall portion 31: Cylindrical portion 32: Closed end portion 321: Inclined surface 321a: First trapezoid 321b: Second trapezoid 322: Top portion 323, 323B: Weak portion 324, 324B: Base end portion 325: Limiting portion 326: Tip portion 327: Thick portion 335, 336, 337: Contact portion 4: Gas generating agent 5: Connector 6: Combustion chamber 10: Seat belt retractor 100: Cylindrical portion (mounting object)

Claims

1. an ignition device including an igniter, a cylindrical igniter holding portion that surrounds and holds the igniter, and a resin fixing portion that fixes the igniter to the igniter holding portion; a cylindrical case with a bottom that accommodates a gas generating agent that burns when the ignition device is activated, the case being made of resin and having a side wall portion whose base end side is connected to the fixing portion and a closed end portion that closes the tip end side; Equipped with The case is an inclined surface extending obliquely with respect to the axial direction of the case on the tip side; a weakened portion formed at least on an edge portion of the inclined surface excluding a base end portion thereof; having Gas generator.

2. The apex of the inclined surface is the tip of the closed end.

2. The gas generator according to claim 1.

3. When the gas generating agent is burned, the tip of the closed end of the case is torn open, and the inclined surface is deformed so as to open outward with the base end side of the inclined surface as a fulcrum.

3. The gas generator according to claim 2.

4. the case has a limiting portion formed to surround the inclined surface and limiting the amount of deformation of the inclined surface when the inclined surface opens outward.

4. The gas generator according to claim 3.

5. The thickness of the base end portion of the inclined surface, which is connected to the side wall portion, is thicker than that of other portions. The gas generator according to any one of claims 1 to 3.

6. the inclined surface is connected at the base end portion that connects to the side wall portion, The base end portion is formed into a curved surface. The gas generator according to any one of claims 1 to 3.

7. The inclined surface is a pair of isosceles trapezoidal flat surfaces whose short sides are located on the tip side, and a pair of isosceles triangular flat surfaces whose vertices are located on the tip side are arranged opposite to each other, a top of the inclined surface is formed by the short side of the isosceles trapezoid and the vertex of the isosceles triangle in a state where each plane of the isosceles trapezoid and the isosceles triangle is inclined toward the inside of the case; The gas generator according to any one of claims 1 to 3.

8. The weakened portion is formed linearly at the apex of the inclined surface and at the contact portion between the isosceles trapezoidal shape and the isosceles triangular shape, which are adjacent to each other.

8. The gas generator according to claim 7.

9. the inclined surface is formed by a combination of a plurality of isosceles trapezoids each having a short side and a long side opposite to the short side, the closed end portion includes a planar portion connected to the short side of each of the plurality of isosceles trapezoids, 2. The gas generator according to claim 1.

10. the case has a columnar shape and is fitted into a cylindrical portion to which the gas generator is attached. A gas generator according to any one of claims 1 to 3.