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; 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; and a reinforcement member which covers at least the closing end and partially has an opening, and has breaking strength larger than that of 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; a reinforcing member that covers at least the closed end and has an opening in a portion thereof, the reinforcing member having a breaking strength greater than that of the case; A gas generator comprising:

[0007] In the above gas generator, the reinforcing member may be a cylindrical cover with a bottom having the opening on its bottom surface.

[0008] In the gas generator described above, the opening may be one opening formed in the center of the bottom surface of the cover.

[0009] Furthermore, in the above-described gas generator, a step may be formed on the outer peripheral surface of the side wall portion of the case, and at least a portion of the peripheral wall portion of the cover may be accommodated in the step, so that at least a portion of the connection portion between the case and the cover is flush.

[0010] Furthermore, in the gas generator described above, the inside of the bottom surface of the cover may be in contact with the outside of the closed end of the case.

[0011] Furthermore, in the gas generator described above, the reinforcing member may be made of metal.

[0012] 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.

[0013] 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]

[0014] 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]

[0015] [Figure 1] FIG. 1 is an exploded perspective view showing an example of a gas generator. [Figure 2] FIG. 2 is a schematic axial cross-sectional view showing an example of an exploded gas generator. [Figure 3] FIG. 3 is a schematic axial cross-sectional view showing an example of a gas generator attached to an attachment object. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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.

[0017] FIG. 1 is an exploded perspective view showing an example of a gas generator. FIG. 2 is a schematic axial cross-sectional view showing an example of an exploded gas generator. FIG. 3 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 a collision of the automobile. Furthermore, gas generator 1 includes an ignition device 2, a case 3, and a cover 4, and contains gas generating agent 5 inside.

[0018] <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.

[0019] The igniter 21 includes, 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 upper side and the conductive pin 215 side as the lower side. 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 may be an existing one used in general gas generators. The cup body 211 is a metal member covered with an insulating layer 212 made of, for example, resin. 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 the upper surface. When the igniter 21 is activated, it is split by the combustion products of the ignition charge 214, and combustion products such as flames and combustion gases are released upward.

[0020] 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.

[0021] 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 6, 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 6 is connected to conductive pin 215.

[0022] <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 7 that accommodates a gas generating agent 5 is formed between the case 3 and the igniter 21. The gas generating agent 5 is ignited by activation of the igniter 21 and burns to generate combustion products such as combustion gas.

[0023] The side wall portion 31 is a cylindrical portion whose inner and outer diameters gradually decrease from the base end toward the tip end. In the example shown in FIGS. 2 and 3 , the side wall portion 31 includes a first side wall portion 311 located at the base end and having the largest diameter, a first reduced diameter portion 312 whose diameter gradually decreases, a second side wall portion 313 whose diameter is smaller than that of the first side wall portion 311, a second reduced diameter portion 314 whose diameter gradually decreases, and a third side wall portion 315 whose diameter is smaller than that of the second side wall portion 313. As shown in FIG. 1 , the third side wall portion 315 has a cross-sectional shape of an oval or rounded rectangle whose diameter decreases in a predetermined direction, and the second reduced diameter portion 314 is formed, together with the third side wall portion 315, on a part of the side circumference of the case 3. In the example shown in FIGS. 1 to 3 , two third side wall portions 315 are formed at opposing positions in the circumferential direction of the side wall portion 31. The base end of the first side wall 311 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 gap between the two members to be welded without any gaps. In the examples of Figures 2 and 3, the parts to be welded by laser welding are indicated by black circles.

[0024] The closed end 32 has a cross section perpendicular to the axial direction of the case 3 that is oval or rectangular with rounded corners. The periphery of the closed end 32 is connected to the tip of the side wall 31. The closed end 32 may be split open at its center, for example, by an increase in the internal pressure of the case 3 or by the temperature of the combustion products generated by the combustion of the gas generating agent 5. As shown in FIG. 1, a radial notch 321 may be provided at the center of the closed end 32. In this case, when the internal pressure of the case 3 increases, , the closed end 32 tears near the center starting from the notch 321. Alternatively, the closed end 32 may have a constant thickness without a notch and may be set to have a lower strength than the side wall 31 so that the entire closed end 32 tears when the cover 4 described below is not present. Therefore, the thickness of the entire closed end 32 can be made thinner than the side wall 31. Alternatively, the thickness of the portion of the closed end 32 corresponding to the opening 421 may be made thinner than the thickness of the remaining portions of the closed end 32.

[0025] <Cover> The cover 4 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 cover the upper part of the case 3. That is, the cover 4 includes a cylindrical side wall portion 41 that extends vertically and a closed end portion 42 that closes the upper end. When the cover 4 is attached to the case 3, the closed end portion 42 of the cover 4 overlaps and contacts the closed end portion 32 of the case 3. The closed end portion 42 of the cover 4 and the closed end portion 32 of the case 3 may be joined with an adhesive, a sealant, or the like. The side wall portion 41 of the cover 4 may also overlap and contact the side wall portion 31 of the case 3. The cover 4 functions as a reinforcing member to prevent the case 3 from tearing open.

[0026] The side wall portion 41 is a cylindrical portion including a portion whose inner diameter and outer diameter gradually decrease from the base end toward the tip end. In the example shown in FIGS. 2 and 3 , the side wall portion 41 includes a first side wall portion 411 located on the base end side and having the largest diameter, a tapered diameter portion 412 whose diameter gradually decreases, and a second side wall portion 413 whose diameter is smaller than that of the first side wall portion 411. As shown in FIG. 1 , the second side wall portion 413 has an oval or rounded rectangular shape whose diameter (width) is small in a predetermined direction, and the tapered diameter portion 412 is formed on a part of the side circumference of the cover 4. That is, the second side wall portion 413 is formed in two locations on the cover at opposing positions in the circumferential direction so as to correspond to the third side wall portion 315. As shown in FIG. 3 , the cover 4 is attached to the case 3 so as to cover the upper part of the case 3 with almost no gap. Furthermore, the outer diameter of the first side wall portion 411 of the cover 4 is the same as or nearly the same as the outer diameter of the first side wall portion 311 of the case 3, and when the cover 4 is attached to the case 3, the first side wall portion 311 of the case 3 and the first side wall portion 411 of the cover 4 are flush with each other.

[0027] The closed end 42 has a cross-sectional shape perpendicular to the axial direction of the cover 4 that is oval or rounded rectangular. The closed end 42 has an opening 421 of a predetermined shape at its center. In the example of FIG. 1 , the opening 421 is circular. The area of ​​the opening 421 may be set to be half or less, preferably one-third or less, of the area of ​​the closed end 42. The shape of the inner surface of the cover 4 corresponds to the shape of the outer surface of the case 3. When the cover 4 is attached to the case 3, the closed end 42 of the cover 4 overlaps the closed end 32 of the case 3 so as to be almost in contact with it. In this case, when the internal pressure of the case 3 increases, the central portion of the closed end 32 of the case 3 that is not covered by the closed end 42 of the cover 4 tears open, while the surrounding portion that is covered by the closed end 42 of the cover 4 does not tear because deformation is suppressed by the cover 4.

[0028] The material of the cover 4 has a higher breaking strength than the case 3. Specifically, for example, metal or ceramic can be used as the material, but metal is particularly preferable from the viewpoints of manufacturing and strength. Specifically, the material of the cover 4 may be metal such as iron, stainless steel, or aluminum. Furthermore, to ensure that the strength of the cover 4 is sufficient so that the cover 4 will not be broken even when the case 3 is torn open, the material and thickness of the closed end 42 can be appropriately determined depending on the expected internal pressure of the combustion gas and the diameter of the case 3. Specifically, the thickness of the closed end 42 may be 0.5 mm to 1.5 mm.

[0029] 3 is attached to case 3, the outer side of gas generator 1 has a shape that fits the inner side of tubular portion 100 to which it is attached. 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, so that even if the internal pressure of case 3 increases, the side surface of case 3 is prevented from splitting open. Furthermore, an elongated hole-shaped or rounded rectangular portion is provided in the upper part of tubular portion 100 along the outer shape of gas generator 1. That is, on the upper side of tubular portion 100, portions (reduced width portions) whose inner diameter (width) is smaller in a predetermined direction than the lower side are formed as flat portions in two locations facing closed end 32 of case 3, and tubular portion 100 also faces these flat portions in a complementary manner, so that if the internal pressure of case 3 increases, case 3 and cover 4 are prevented from being ejected upward. Therefore, if the internal pressure of case 3 increases or if case 3 melts due to the temperature of combustion products generated by combustion of gas generating agent 5, the portion of closed end 32 of case 3 whose upper part is exposed by opening 421 of cover 4 splits open, forming an opening. Furthermore, the gas generator 1 is prevented from rotating within the cylindrical portion 100.

[0030] <Gas generating agent> A predetermined gas generating agent is used as the gas generating agent 5. The combustion temperature of the gas generating agent 5 is, for example, 1000 to 1700°C. The gas generating agent 5 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 5 may be a single-hole cylindrical shape. Note that the gas generating agent 5 is not limited to the above, and a nitrocellulose-based composition may also be used for the gas generating agent 5.

[0031] <Operation> When the gas generator 1 is mounted in, for example, a seat belt retractor 10 of an automobile, the connector 6 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. In addition, the flame and combustion gas, which are combustion products of the ignition charge 214, ignite the gas generating agent 5 filled in the combustion chamber 7. When the gas generating agent 5 burns, it generates combustion gas and the like as combustion products.

[0032] The side surfaces of the case 3 and the cover 4 are completely surrounded by the cylindrical portion 100 to which they are attached, and the inner surface of the attachment target has a shape corresponding to the side surface of the case 3 covered by the cover 4. 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 diameters of the case 3 and the cover 4 include portions where the tip end is smaller than the base end, the entire case 3 and cover 4 are prevented from being ejected upward when the internal pressure of the case 3 increases. In other words, the second reduced diameter portion 314 of the case 3 and the reduced diameter portion 412 of the cover 4 abut against the reduced width portion of the cylindrical portion 100. 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 5, the portion of the closed end 32 of the case 3 exposed by the opening 421 of the cover 4 splits open, forming an opening in the center of the closed end 32 of the case 3. In other words, an opening having substantially the same shape as the opening 421 of the cover 4 is formed in the center of the closed end 32 of the case 3. At this time, the portion of the closed end 32 of the case 3 that is covered by the closed end 42 of the cover 4 is prevented from scattering into small pieces. Furthermore, the portion of the closed end 32 of the case 3 that splits open is sufficiently small compared to the cross section of the closed end 32 and is burned up by the combustion products of the gas generating agent 5, so fragments of the case 3 are prevented from entering the interior of the object to which the case 3 is attached.

[0033] Furthermore, the combustion gas is discharged from the opening into, for example, the seat belt retractor to which the gas generator 1 is attached. The discharged combustion gas then activates a predetermined mechanism of the seat belt retractor. The seat belt retractor can have an existing structure. For example, the gas generator 1 is attached to one end of a pipe that is part of the seat belt retractor. The seatbelt retractor is connected to a pipe, and the pressure of the combustion gas moves steel balls inside the pipe. The moving steel balls rotate a gear, and the rotation of the gear is used as power to retract the seatbelt, thereby pretensioning the seatbelt. At this time, the gas generator 1 discharges combustion gas from a single opening 421 located in the center of the closed end 42 of the cover 4. This allows the gas flow to be concentrated in the direction in which the pipe extends, thereby efficiently transmitting force to the seatbelt retractor. The opening 421 may be formed as a weakened portion of the closed end 42. In other words, the strength of the portion of the closed end 42 corresponding to the opening 421 may be reduced so that it preferentially tears or deforms to open when a load is applied.

[0034] <Other> Each aspect disclosed herein may be combined with any other feature disclosed herein. At least one of the case 3 and the cover 4 does not need to have an oval or rounded rectangular cross-sectional portion at the top. The cover 4 only needs to cover at least the closed end 32 of the case 3. For example, if the cover 4 does not have a sidewall 41, it may consist of only the closed end 42 and be connected to the case 3 or the cylindrical portion 100 to which it is attached with an adhesive or sealant. The closed end 42 may also be fixed by being sandwiched between a protrusion protruding into the cylindrical portion 100 and the case 3 (closed end 32). [Explanation of symbols]

[0035] 1: 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 311: First side wall portion 312: 1st reduced diameter part 313: Second side wall portion 314:Second diameter reduction part 315: Third side wall 32: Closed end 321: Notch 4: Cover 41: Side wall 411: First side wall portion 412: Reduced diameter part 413: Second side wall 42: Closed end 421: Opening 5: Gas generator 6: Connector 7: 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; a cover that covers at least the closed end and has an opening in a portion thereof, the cover having a breaking strength greater than that of the case; Equipped with The cover is in contact with the outside of the closed end of the case.

2. The cover is a cylindrical cover having the opening on its bottom surface.

2. The gas generator according to claim 1.

3. The opening is formed in the center of the bottom surface of the cover.

3. The gas generator according to claim 2.

4. The case has a step formed on the outer peripheral surface of the side wall portion, and at least a part of the peripheral wall portion of the cover is accommodated in the step, so that at least a part of the connecting portion between the case and the cover is flush.

4. The gas generator according to claim 3.

5. The inside of the bottom surface of the cover and the outside of the closed end of the case are in contact with each other. A gas generator according to any one of claims 2 to 4.

6. The cover is made of metal. A gas generator according to any one of claims 1 to 5.

7. 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 6.

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