Gas generator

Abstract

To suppress scattering of a case at the time of cleavage when a resin case is used.SOLUTION: A gas generator includes: an igniter; a cylindrical igniter holding part for holding the igniter in a state of surrounding the igniter; an ignition device having a resin fixing part for fixing the igniter to the igniter holding part; and a resin case which stores a gas generator burned by action of the ignition device and has a cylindrical bottom, and has a side wall part whose a base end side is connected to the fixing part and a closing end for closing a tip side. The closing end includes a fragile part opened by a combustion product generated by the gas generator, the periphery of the fragile part has thickness larger than that of the fragile part, and an annular inclination part is formed toward the fragile part from a predetermined position of the side wall part inside the case.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, a gas generator has been proposed that includes an external 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 part of the cover breaks open, releasing the gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2002 / 0062757 Summary of the Invention [Problem to be solved by the invention]

[0004] In a gas generator, when the case that houses the gas generating agent is made of resin, resin generally has 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. [Means for solving the problem]

[0006] In order to solve the above problems, the present disclosure employs the following configuration. 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 closed end includes a weakened portion that is opened by combustion products generated by the gas generating agent; The periphery of the fragile portion is thicker than the fragile portion, An annular inclined portion is formed on the inside of the case from a predetermined position on the side wall portion to the weakened portion. Gas generator.

[0007] In the gas generator, the fragile portion is formed in a radially central portion of the closed end of the case, The weakened portion may be located on an extension of the tip end of the annular inclined portion.

[0008] In the gas generator described above, the weakened portion may be a flat portion formed at a tip end of the annular inclined portion.

[0009] Furthermore, in the gas generator, the weakened portion is formed on the outside of the closed end face of the case. It may also be a recess.

[0010] Furthermore, in the gas generator, in a vertical cross section of the case, the contour of the inner peripheral surface of the case at the boundary between the annular inclined portion and the side wall portion may be curved.

[0011] Furthermore, in the gas generator described above, the case may have a columnar shape and may be fitted into a cylindrical portion to which the gas generator is attached.

[0012] The above-described configurations can be combined or deleted as much as possible without departing from the spirit of the present disclosure. [Effects of the Invention]

[0013] 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. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of a gas generator according to a first embodiment. [Figure 2] FIG. 2 is a schematic axial cross-sectional view showing an example of the gas generator attached to an attachment target according to the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an example of a gas generator according to the second embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a gas generator according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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 to the embodiment, but is limited only by the claims.

[0016] <Embodiment 1> 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 burns the gas generating agent inside 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 an automobile collision. Gas generator 1 also includes an ignition device 2 and a case 3, and contains gas generating agent 4 inside.

[0017] <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 that is interposed between the igniter 21 and the igniter holding portion 22.

[0018] The igniter 21 has, for example, a cup body 211 having a cylindrical shape with one open end and a bottom, an insulating layer 212, a sealing member 213 that closes 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 the outside. In this embodiment, for convenience, the cup body 211 side will be described as the top and the conductive pin 215 side as the bottom. The two conductive pins 215 are connected via a bridge wire (not shown) in the ignition chamber. When the conductive pin 215 receives a current supply from the outside, the bridge wire, which is a resistor, generates heat and burns the ignition charge 214. The ignition charge 214 can be an existing one used in general gas generators. The cup body 211 is, for example, a metal member covered with a resin insulating layer 212. The sealing member 213 is also made of, for example, metal, and is insulated from the two conductive pins 215. The cup body 211 has, for example, radial notches (not shown) on the upper surface, which are cleaved by the combustion products of the ignition charge 214 when the igniter 21 is activated, and combustion products such as flames and combustion gases are released upward.

[0019] 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 into 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.

[0020] 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 has 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 periphery of the side 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.

[0021] <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, which may be the same resin as that of 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.

[0022] 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.

[0023] The closed end 32 has a cross-sectional shape perpendicular to the axial direction of the case 3 that is oval or rounded rectangular. The closed end 32 includes a fragile portion 321 that cleaves, for example, due to an increase in internal pressure in the case 3 or the temperature of combustion products generated by the combustion of the gas generating agent 4, and a thick portion 322 that is thicker than the fragile portion 321. As shown in FIG. 2 , the outer surface of the closed end 32 has a recess of a predetermined shape near its center, and the bottom of the recess is the fragile portion 321. The inner surface of the closed end 32 also has an annular inclined portion 323 whose cross-sectional area gradually decreases toward the tip. The tip of the annular inclined portion 323 converges to a vertex 324 located on the back surface of the fragile portion 321. In other words, the inner space of the case 3 has a conical cavity at its tip. Therefore, when the internal pressure of the case 3 increases, stress is concentrated at the vertex 324. The base end of the annular inclined portion 323 is connected to the inner surface of the side wall portion 31 via a bent portion 325. The bent portion 325 is formed in a circular inclined shape so as to prevent stress from concentrating when the internal pressure of the case 3 increases. The area from the inclined portion 323 to the side wall portion 31 (the boundary between the annular inclined portion 323 and the side wall portion 31) may be formed in a curved shape.

[0024] The outer side of the case 3 is shaped to fit the inside of the tubular part 100 to which it is attached. That is, the side wall 31 is housed in a portion of the tubular part 100 whose inner periphery in cross section is a perfect circle or an almost perfect circle. The closed end 32 is housed in a portion of the tubular part 100 whose inner periphery in cross section is an elongated hole or a rounded rectangle. The side of the case 3 is completely surrounded by the tubular part 100 to which it is attached, and the inner surface of the attachment part is shaped to fit the side of the case 3. Therefore, even if the internal pressure of the case 3 increases, the side of the case 3 is prevented from splitting. The inner diameter of the elongated hole or rounded rectangle portion is smaller in a predetermined direction than the inner diameter of the perfect circle or almost perfect circle portion. Two flat portions are formed opposite closed end 32 of case 3, where the outer diameter of case 3 is smaller at the tip end than at the base end, and tubular 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 case 3 increases. Therefore, when the internal pressure of case 3 increases, or when case 3 melts due to the temperature of combustion products generated by combustion of gas generating agent 4, fragile portion 321 of closed end 32 first cleaves, forming an opening. Furthermore, gas generator 1 is prevented from rotating within tubular portion 100.

[0025] <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 from, for example, 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. However, the gas generating agent 4 is not limited to the above, and a nitrocellulose-based composition may also be used.

[0026] <Operation> When the gas generator 1 is mounted in, for example, a 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 burns 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.

[0027] The side surface 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 or when the case 3 melts due to the temperature of the combustion products generated by the combustion of the gas generating agent 4, only the fragile portion 321 of the closed end 32 splits open, forming an opening. At this time, portions of the case 3 other than the fragile portion 321 are prevented from breaking into small pieces and scattering. Furthermore, the split fragile portion 321 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.

[0028] Furthermore, the combustion gas is discharged from the opening into, for example, the seat belt retractor to which the device is attached. The discharged combustion gas then activates a predetermined mechanism of the seat belt retractor. The seat belt retractor may have an existing structure. For example, the gas generator 1 is connected to one end of a pipe that is part of a seat belt retractor, 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 pretensions the seat belt by using the gear rotation as power to retract the seat belt. At this time, because the gas generator 1 has one weakened portion 321 in the center of the closed end 32, the flow direction of the exhaust gas can be concentrated in the direction in which the pipe extends, and force can be efficiently transmitted to the seat belt retractor.

[0029] <Embodiment 2> 3 is a schematic cross-sectional view showing an example of a gas generator according to the second embodiment. Note that components corresponding to those in the above-described first embodiment are given the same reference numerals and description thereof will be omitted.

[0030] The fragile portion 321A of the case 3 according to this embodiment is formed on an extension of the tip of the annular inclined portion 323 provided on the inside of the case 3, and is similar to the first embodiment in that it is thinner than the surrounding thick portion 322. However, the tip of the internal space of the case 3 is a truncated cone-shaped hollow, and the tip 326 of the annular inclined portion 323 is planar. In addition, the outside of the closed end 32 of the case 3 is flush.

[0031] In the example of Figure 3, the outer periphery of the side surface of case 3 is also flush, but as shown in Figures 1 and 2, the cross section of the tip of case 3 may be an oval or rounded rectangle with a diameter that is small in a predetermined direction.

[0032] In this type of gas generator 1, the side surface of the case 3 is also completely surrounded by the cylindrical portion 100 of the attachment target, and the inner surface of the attachment target has a shape that corresponds to the side surface of the case 3, so that the side surface of the case 3 is prevented from splitting open even 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, only the fragile portion 321A of the closed end 32 splits open, forming an opening. At this time, portions of the case 3 other than the fragile portion 321 are prevented from breaking into small pieces and scattering. Furthermore, the split fragile portion 321A is sufficiently smaller than the cross section of the closed end 32, so that it is burned up by the combustion products of the gas generating agent 4, preventing fragments of the case 3 from entering the interior of the attachment target.

[0033] <Comparative Example> 4 is a schematic cross-sectional view showing an example of a gas generator according to a comparative example. Note that components corresponding to those in the first and second embodiments described above are given the same reference numerals, and description thereof will be omitted.

[0034] In the example shown in FIG. 4, the case 3 does not have the annular inclined portion 323, and the interior space thereof is cylindrical throughout its entire length. A recess is formed in the center of the inside of the closed end 32, and the tip 326 of the recess forms a fragile portion 321B that is thinner than the surrounding thick portion 322. If the case 3 did not have the annular inclined portion 323, stress would be concentrated at the bent portion 325B formed between the side wall portion 31 and the closed end 32. Therefore, not only would the fragile portion 321B tear, but the closed end 32 would also tear radially from the fragile portion 321B, making the closed end 32 more likely to expand outward by approximately 90 degrees around the bent portion 325B. Furthermore, if the closed end 32 were to open outward by approximately 90 degrees, the bent portion 325B would also tear, potentially causing fragments of the closed end 32 to scatter.

[0035] On the other hand, when the internal pressure of the case 3 increases, the annular inclined portion 323 shown in the first and second embodiments receives a force directed toward the side of the case 3 rather than toward the front end of the case 3. However, when the cylindrical portion 100 to be attached, which surrounds the side of the case 3, rotates about the bent portion 325, In addition, the deployment of the closed end 32 is suppressed, so that the closed end 32 can be prevented from breaking into pieces and scattering.

[0036] <Other> Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. For example, in the first embodiment, the tip of annular inclined portion 323 may be an end face as shown in the second embodiment. Furthermore, in the second embodiment, a recess as shown in the first embodiment may also be provided on the outside of closed end 32. Furthermore, in the second embodiment, tip 326 of annular inclined portion 323 may be apex 324 as shown in the first embodiment. Furthermore, in the above embodiments, the outline of annular inclined portion 323 in the vertical cross section of gas generator 1 does not have to be a straight line, and may be somewhat curved as long as thick-walled portion 322 is ensured. [Explanation of symbols]

[0037] 1, 1B: Gas generator 2:Ignition device 21:Igniter 211: Cup body 212: Insulating layer 213: Sealing member 214: Ignition powder 215: Conductive pin 22:Igniter holding part 23: Fixed part 231: 1st fixed part 232:Second fixed part 3: Case 31: Side wall 32: Closed end 321, 321A: Weak part 322:Thick part 323: Circular inclined section 324: Vertex 325: Bend 326: Tip 4: Gas generator 5: Connector 6: Combustion chamber 10: Seat belt retractor 100: Cylindrical part (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 closed end includes a weakened portion that is opened by combustion products generated by the gas generating agent; The periphery of the fragile portion is thicker than the fragile portion, An annular inclined portion is formed on the inside of the case from a predetermined position on the side wall portion to the weakened portion. Gas generator.

2. the weakened portion is formed in a radially central portion of the closed end of the case, The weakened portion is located on an extension of the tip end of the annular inclined portion.

2. The gas generator according to claim 1.

3. The fragile portion is a flat portion formed at a tip end of the annular inclined portion.

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

4. The fragile portion is a recess formed on the outer side of the closed end face of the case. A gas generator according to any one of claims 1 to 3.

5. In a longitudinal cross section of the case, the contour of the inner peripheral surface of the case at the boundary between the annular inclined portion and the side wall portion is curved. A gas generator according to any one of claims 1 to 4.

6. 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 5.

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