Patent ID: 12233812

DESCRIPTION OF EMBODIMENTS

A gas generator according to an embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that the respective configurations and the combinations thereof in the respective embodiments are mere examples, and the configurations can be added, omitted, substituted, and differently modified as appropriate within a scope not departing from the spirit of the present invention. The present disclosure is not limited by the embodiments, but only limited by the claims.

First Embodiment

FIG.1is a longitudinal cross-sectional view of a gas generator100according to a first embodiment. More specifically,FIG.1is a cross-sectional view including a housing center axis denoted by a reference sign A1and an inner tube center axis denoted by a reference sign A5.FIG.1illustrates a state of the gas generator100before activation. The gas generator100is an airbag gas generator used for an airbag, for example.

Overall Configuration

As illustrated inFIG.1, the gas generator100includes a first ignition device4, a first inner tube member5, a transfer charge6, a second ignition device7, a second inner tube member8, a filter9, a first gas generating agent110, a second gas generating agent120, and a housing1that houses these elements. The gas generator100is configured as a so-called dual-type gas generator including two ignition devices. The gas generator100is also configured to activate a first igniter41included in the first ignition device4to burn the first gas generating agent110, activate a second igniter71included in the second ignition device7to burn the second gas generating agent120, and discharge combustion gas, which is a combustion product of these gas generating agents, from gas discharge ports12formed in the housing1. Hereinafter, each configuration of the gas generator100will be described. In the present specification, the activation of the igniter included in the ignition device may be expressed as “activation of the ignition device” for convenience.

Housing

An upper shell2and a lower shell3each formed of metal and formed into a bottomed substantially cylindrical shape are joined in a state where respective open ends face each other. Thus, the housing1is formed in a short cylindrical shape including a tubular peripheral wall portion denoted by a reference sign11and in which both ends of the peripheral wall portion11in an axial direction are closed. The housing center axis A1inFIG.1is a center axis of the peripheral wall portion11. Here, a direction along the housing center axis A1is defined as a vertical direction of the gas generator100, where the side of the upper shell2(i.e., the top side inFIG.1) is defined as a top side of the gas generator100, and the side of the lower shell3(i.e., the bottom side inFIG.1) is defined as a bottom side of the gas generator100.

The upper shell2has an upper peripheral wall portion21in a cylindrical shape and a top plate portion22that closes the upper end of the upper peripheral wall portion21, thereby forming an internal space. An opening portion of the upper shell2is formed by a lower end portion of the upper peripheral wall portion21. A joining portion23extending radially outward is connected to the lower end portion of the upper peripheral wall portion21. The lower shell3has a lower peripheral wall portion31having a cylindrical shape and a bottom plate portion32that closes the lower end of the lower peripheral wall portion31, thereby forming an internal space. A joining portion33extending radially outward is connected to an upper end portion of the lower peripheral wall portion31. A first mounting hole32afor mounting the first ignition device4at the bottom plate portion32and a second mounting hole32bfor mounting the second ignition device7at the bottom plate portion32are formed in the bottom plate portion32.

The joining portion23of the upper shell2and the joining portion33of the lower shell3are overlapped and joined by laser welding or the like to form the housing1having a short cylindrical shape with both axial ends closed. The upper peripheral wall portion21of the upper shell2and the lower peripheral wall portion31of the lower shell3form the peripheral wall portion11that is tubular and connects the top plate portion22and the bottom plate portion32. That is, the housing1includes the peripheral wall portion11that is tubular, the top plate portion22provided at one end of the peripheral wall portion11, and the bottom plate portion32provided at the other end and facing the top plate portion22. The peripheral wall portion11, the top plate portion22, the bottom plate portion32, and the second inner tube member8described below define a first combustion chamber10. The first combustion chamber10is formed as a space in the internal space of the housing1, excluding a second combustion chamber20that is an internal space of the second inner tube member8. The first ignition device4, the first inner tube member5, the transfer charge6, the filter9, and the first gas generating agent110are disposed in the first combustion chamber10. A center axis of the first combustion chamber10coincides with the housing center axis A1.

Here, in the housing1, a plurality of the gas discharge ports12that allow the first combustion chamber10and the external space of the housing1to communicate with each other are formed side by side along the circumferential direction. In more detail, the plurality of gas discharge ports12are formed in the upper peripheral wall portion21of the peripheral wall portion11. The gas discharge ports12are closed by a seal tape13provided on the inner peripheral surface of the peripheral wall portion11in a state before the first ignition device4and the second ignition device7are activated. The seal tape13, which is an example of a closing member, is ruptured by the pressure of the combustion gas, to thereby open the gas discharge ports12. In the present specification, the pressure required to open the gas discharge ports12is referred to as an “opening pressure”. In the case of this example, the opening pressure is a pressure required to rupture the seal tape13.

Ignition Device

As illustrated inFIG.1, the first ignition device4is fixed in the first mounting hole32aformed in the bottom plate portion32of the lower shell3. The first ignition device4includes the first igniter41. The second ignition device7is fixed in the second mounting hole32bformed in the bottom plate portion32of the lower shell3. The second ignition device7includes the second igniter71. Each of the first igniter41and the second igniter71accommodates an ignition charge (not illustrated) therein and is activated by being supplied with an ignition current. Upon activation, the ignition charge burns and a combustion product is discharged to the outside. The first ignition device4and the second ignition device7are activated independently of each other. When activating the second ignition device7, the second ignition device7is activated simultaneously with the activation of the first ignition device4or at a predetermined timing after the activation of the first ignition device4. Compared with a so-called single-type gas generator, the gas generator100can discharge a large amount of combustion gas to the outside with various output profiles by the combustion of the first gas generating agent110combusted by activating the first ignition device4and the combustion of the second gas generating agent120combusted by activating the second ignition device7. The second ignition device7is not always activated. The gas generator100may activate the first ignition device4and the second ignition device7depending on the strength of an impact sensed by a sensor (not illustrated), for example, only activating the first ignition device4without activating the second ignition device7when the impact is weak, or simultaneously activating the first ignition device4and the second ignition device7when the impact is strong.

Inner Tube Member

The first inner tube member5is a tubular member extending from the bottom plate portion32toward the top plate portion22. The first inner tube member5includes a tubular surrounding wall portion51and a lid wall portion52that closes one end portion of the surrounding wall portion51. The first ignition device4is fitted or press-fitted to the other end portion of the surrounding wall portion51, and thus the first inner tube member5is mounted at the bottom plate portion32. An inner tube center axis A5illustrated inFIG.1is a center axis of the surrounding wall portion51. As illustrated inFIG.1, in the gas generator100, the first inner tube member5is disposed such that the inner tube center axis A5is spaced apart from the housing center axis A1of the peripheral wall portion11. Further, the inner tube center axis A5is parallel to the housing center axis A1. As illustrated inFIG.1, the first ignition device4is surrounded by the surrounding wall portion51to form an ignition unit chamber53between the first inner tube member5and the first ignition device4. The transfer charge6that is burned by the activation of the first ignition device4is accommodated in the ignition unit chamber53. The surrounding wall portion51of the first inner tube member5is provided with a plurality of communication holes h1that allow the internal space (i.e., the ignition unit chamber53) and the external space to communicate with each other. The communication holes h1are closed by a seal tape (not illustrated) in a state before the first ignition device4is activated. In addition, instead of using the lid wall portion, for example, the surrounding wall portion51including an open upper end portion may be joined to the top plate portion of the housing by welding or the like. Further, the communication holes h1are disposed at the same height as the gas discharge ports12(height from the bottom plate portion32). However, the heights of the communication holes h1may be different from the heights of the gas discharge ports12.

The second inner tube member8is a tubular member extending from the bottom plate portion32toward the top plate portion22and includes a tubular surrounding wall portion81and a lid wall portion82that closes one end portion of the surrounding wall portion81. The second ignition device7is fitted or press-fitted to the other end portion of the surrounding wall portion81, and thus the second inner tube member8is mounted at the bottom plate portion32. As illustrated inFIG.1, the second combustion chamber20in which the second ignition device7and the second gas generating agent120that is burned by the activation of the second ignition device7are disposed is formed inside the second inner tube member8. The surrounding wall portion81of the second inner tube member8is also provided with a plurality of communication holes h2that allow the internal space (i.e., the second combustion chamber20) and the external space (i.e., the first combustion chamber10) to communicate with each other. The communication holes h2are closed by a seal tape (not illustrated) in a state before the second ignition device7is activated.

Filter

As illustrated inFIG.1, the filter9is formed into a tubular shape and is disposed in the first combustion chamber10such that the filter9surrounds the first gas generating agent110and the gas discharge ports12are located outside the filter9in the radial direction thereof. That is, the filter9is disposed between the first gas generating agent110and the gas discharge ports12and surrounds the first gas generating agent110. Of both end surfaces of the filter9in the axial direction, one end surface (upper end surface) is in contact with and supported by the top plate portion22of the upper shell2, and the other end surface (lower end surface) is in contact with and supported by the bottom plate portion32of the lower shell3. When the combustion gas of the first gas generating agent110and the second gas generating agent120passes through the filter9, the filter9cools the combustion gas by removing heat of the combustion gas. In addition to the cooling function of the combustion gas, the filter9has a function of filtering the combustion gas by collecting combustion residue contained in the combustion gas.

Transfer Charge

In addition to a known black powder, a gas generating agent having good ignition properties and a higher combustion temperature than the first gas generating agent110can be used as the transfer charge6. The combustion temperature of the transfer charge6can be set in a range of 1700 to 3000° C. As the transfer charge6, a known transfer charge containing, for example, nitroguanidine (34 wt %) and strontium nitrate (56 wt %) can be used. In addition, the transfer charge6may have various shapes, such as a granular shape, a pellet shape, a columnar shape, or a disk shape.

Gas Generating Agent

As the first gas generating agent110and the second gas generating agent120, a gas generating agent having a relatively low combustion temperature can be used. The combustion temperature of each of the first gas generating agent110and the second gas generating agent120can be set in the range of 1000 to 1700° C. As the first gas generating agent110and the second gas generating agent120, a known gas generating agent containing, for example, guanidine nitrate (41 wt %), basic copper nitrate (49 wt %), a binder, and an additive can be used. The first gas generating agent110and the second gas generating agent120may also have a variety of shapes, such as a granular shape, a pellet shape, a cylindrical shape, or a disk shape.

Communication Hole

FIG.2is a cross-sectional view taken along line A-A ofFIG.1.FIG.2illustrates a cross-section of a gas generator100before activation, which is orthogonal to the housing center axis A1and the inner tube center axis A5. InFIG.2, the first ignition device4, the second ignition device7, the joining portion23, and the joining portion33are omitted for convenience. As illustrated inFIG.2, an imaginary straight line passing through the housing center axis A1and the inner tube center axis A5as viewed in the axial direction of the surrounding wall portion51is defined as an imaginary center line CL1.

As illustrated inFIG.2, the plurality of communication holes h1are unevenly disposed in the circumferential direction of the surrounding wall portion51. Specifically, communication hole groups each including three communication holes h1close to each other in the circumferential direction of the surrounding wall portion51are formed at two positions of the surrounding wall portion51. The two communication hole groups are formed at line-symmetric positions with the imaginary center line CL1as an axis of symmetry. Thus, the surrounding wall portion51of the first inner tube member5is divided, in the circumferential direction, into combustion product discharge regions R1aand R1bin which the plurality of communication holes h1are collectively disposed and combustion product non-discharge regions R2aand R2bthat are regions of the surrounding wall portion51other than the combustion product discharge regions R1aand R1b. That is, the combustion product discharge regions R1aand R1bare regions where the communication holes h1are disposed, and the combustion product non-discharge regions R2aand R2bare regions where the communication holes h1are not disposed. The combustion product discharge regions R1aand R1bare located line-symmetrically with the imaginary center line CL1as the axis of symmetry. Here, as illustrated inFIG.2, as viewed in the axial direction of the surrounding wall portion51, a straight line extending from the inner tube center axis A5, passing through one end portion of the combustion product discharge region R1ain the circumferential direction and intersecting with the peripheral wall portion11is defined as a first imaginary straight line L1a, and a straight line extending from the inner tube center axis A5, passing through the other end portion of the combustion product discharge region R1ain the circumferential direction, and intersecting with the peripheral wall portion11is defined as a second imaginary straight line L2a. Similarly, as viewed in the axial direction of the surrounding wall portion51, a straight line extending from the inner tube center axis A5, passing through one end portion of the combustion product discharge region R1bin the circumferential direction and intersecting the peripheral wall portion11, is defined as a first imaginary straight line L1b, and a straight line extending from the inner tube center axis A5, passing through the other end portion of the combustion product discharge region R1bin the circumferential direction and intersecting the peripheral wall portion11, is defined as a second imaginary straight line L2b. That is, the surrounding wall portion51is divided by the first imaginary straight line L1a, the second imaginary straight line L2a, the first imaginary straight line L1b, and the second imaginary straight line L2b. More specifically, in the surrounding wall portion51, a region between the first imaginary straight line L1aand the second imaginary straight line L2ais the combustion product discharge region R1a, a region between the first imaginary straight line L1band the second imaginary straight line L2bis the combustion product discharge region R1b, a region between the first imaginary straight line L1aand the first imaginary straight line L1bis the combustion product non-discharge region R2a, and a region between the second imaginary straight line L2aand the second imaginary straight line L2bis the combustion product non-discharge region R2b.

Gas Discharge Port

As illustrated inFIG.2, the peripheral wall portion11of the housing1is divided by the first imaginary straight line L1a, the second imaginary straight line L2a, the first imaginary straight line L1b, and the second imaginary straight line L2binto communication hole-associated regions R10aand R10band communication hole non-associated regions R20aand R20bin the circumferential direction of the peripheral wall portion11. As viewed in the axial direction of the surrounding wall portion51, a range of the communication hole-associated region R10ais defined by the first imaginary straight line L1aand the second imaginary straight line L2a, a range of the communication hole-associated region R10bis defined by the first imaginary straight line L1band the second imaginary straight line L2b, a range of the communication hole non-associated region R20ais defined by the first imaginary straight line L1aand the first imaginary straight line L1b, and a range of the communication hole non-associated region R20bis defined by the second imaginary straight line L2aand the second imaginary straight line L2b. Thus, as illustrated inFIG.2, the combustion product discharge region R1aand the communication hole-associated region R10aface each other, the combustion product discharge region R1band the communication hole-associated region R10bface each other, the combustion product non-discharge region R2aand the communication hole non-associated region R20aface each other, and the combustion product non-discharge region R2band the communication hole non-associated region R20bface each other in the radiation direction with the inner tube center axis A5, which is the center axis of the surrounding wall portion51, as the center. That is, in the gas generator100, the combustion product discharge region R1ais associated with the communication hole-associated region R10a, the combustion product discharge region R1bis associated with the communication hole-associated region R10b, the combustion product non-discharge region R2ais associated with the communication hole non-associated region R20a, and the combustion product non-discharge region R2bis associated with the communication hole non-associated region R20b.

As illustrated inFIG.2, the plurality of gas discharge ports12formed in the peripheral wall portion11of the housing1include first gas discharge ports12aand second gas discharge ports12bhaving different opening pressures. The second gas discharge ports12bare configured to have higher opening pressures than the first gas discharge ports12a. That is, the second gas discharge ports12bare configured to be more difficult to open than the first gas discharge ports12a. Specifically, the cross-sectional area (port diameter) of each second gas discharge port12bis made smaller than the cross-sectional area (port diameter) of each first gas discharge port12a. During the combustion of the first gas generating agent110and the second gas generating agent120, a load acts on the seal tape13due to the pressure of the combustion gas. At this time, since the cross-sectional area of each second gas discharge port12bis smaller than the cross-sectional area of each first gas discharge port12a, the load acting on the part of the seal tape13that closes the second gas discharge ports12bis smaller than the load acting on the part of the seal tape13that closes the first gas discharge ports12a. Accordingly, the second gas discharge ports12bhave higher opening pressures than the first gas discharge ports12aand are more difficult to open.

As illustrated inFIG.2, of the communication hole-associated regions R10aand R10band the communication hole non-associated regions R20aand R20b, the first gas discharge ports12aare formed only in the communication hole-associated regions R10aand R10b, and the second gas discharge ports12bare formed only in the communication hole non-associated regions R20aand R20b. That is, in the communication hole-associated region R10aand the communication hole-associated region R10bfacing the combustion product discharge region R1aand the combustion product discharge region R1bin which the communication holes h1are disposed, the second gas discharge ports12bhaving high opening pressures are not formed, and only the first gas discharge ports12ahaving low opening pressures are formed.

Operation

A basic operation of the gas generator100according to the first embodiment will be described below with reference toFIG.1. In this example, a case in which the second ignition device7is activated following the first ignition device4(that is, after the first ignition device4is activated) will be described.

When a sensor (not illustrated) senses an impact, an ignition current is supplied to the first igniter41of the first ignition device4and the first igniter41is activated. Then, the ignition charge accommodated in the first igniter41is burned, and a flame, high-temperature gas, and the like, which are combustion products of the ignition charge, are discharged to the inside of the ignition unit chamber53. Thus, the transfer charge6accommodated in the ignition unit chamber53is burned, and combustion gas is generated in the ignition unit chamber53. When the seal tape closing the communication holes h1of the surrounding wall portion51is broken by the pressure of the combustion gas of the transfer charge6, the combustion gas is discharged to the outside of the ignition unit chamber53through the communication holes h1. Then, the combustion gas of the transfer charge6comes into contact with the first gas generating agent110disposed around the surrounding wall portion51, and the first gas generating agent110is ignited. When the first gas generating agent110is burned, high-temperature and high-pressure combustion gas is generated in the first combustion chamber10. When this combustion gas passes through the filter9, the combustion gas is cooled, and the combustion residue is filtered. The combustion gas of the first gas generating agent110cooled and filtered by the filter9breaks the seal tape13closing the gas discharge ports12and is discharged from the gas discharge ports12to the outside of the housing1.

Subsequently, when the second igniter71of the second ignition device7is activated, the second gas generating agent120accommodated in the second combustion chamber20is burned, and combustion gas is generated in the second combustion chamber20. When the seal tape closing the communication holes h2of the surrounding wall portion81is broken by the pressure of the combustion gas of the second gas generating agent120, the combustion gas is discharged to the first combustion chamber10through the communication holes h2. After being cooled and filtered by the filter9, the combustion gas of the second gas generating agent120is discharged from the gas discharge ports12to the outside of the housing1.

The combustion gases of the first gas generating agent110and the second gas generating agent120flow into an airbag (not illustrated) after being discharged to the outside of the housing1. This causes the airbag to inflate, forming a cushion between the occupant and the rigid structure and protecting the occupant from the impact.

Correspondence Between Communication Hole and Gas Discharge Port

In general, the combustion performance of the gas generating agent tends to improve as the temperature or pressure around the gas generating agent increases. That is, in a low-temperature and low-pressure environment, the gas generating agent is inactively burned. Thus, to reduce the difference between the output performance of the gas generator during activation at a high temperature (hereinafter referred to as “high-temperature activation”) and the output performance of the gas generator during activation at a low temperature (hereinafter referred to as “low-temperature activation”) and to stabilize the output performance, it is necessary to increase the internal pressure of the housing during the low-temperature activation and improve the combustion performance of the gas generating agent. In the gas generator100, when the communication holes h1, the first gas discharge ports12a, and the second gas discharge ports12bare disposed as described above, the internal pressure of the housing during the low-temperature activation can be increased and the difference between the combustion performance of the gas generating agent during the low-temperature activation and the combustion performance of the gas generating agent during the high-temperature activation can be reduced. This will be described in detail below.

FIG.3is a transverse cross-sectional view illustrating a state of the gas generator100during the low-temperature activation.FIG.4is a transverse cross-sectional view illustrating a state of the gas generator100during the high-temperature activation.FIGS.3and4illustrate cross sections corresponding toFIG.2. As illustrated inFIGS.3and4, the gas generator100is configured such that, of the plurality of gas discharge ports12, only the first gas discharge ports12ahaving low opening pressures are opened during the low-temperature activation, and the second gas discharge ports12bhaving high opening pressures are opened together with the first gas discharge ports12aduring the high-temperature activation. In the gas generator100, since only the first gas discharge ports12aare opened during the low-temperature activation, the combustion gas is more likely to be trapped inside the housing1(the first combustion chamber10) while the combustion gas is also discharged from the first gas discharge ports12athan when all the gas discharge ports12are opened at the same temperature. This increases the internal pressure of the housing1during the low-temperature activation and improves the combustion performance of the gas generating agent. On the other hand, during the high-temperature activation in which the combustion performance of the gas generating agent is expected to be high from the beginning, both the first gas discharge ports12aand the second gas discharge ports12bare opened to discharge the combustion gas, which suppresses an excessive increase in the internal pressure of the housing1. In this way, by improving the combustion performance of the gas generating agent during the low-temperature activation in the gas generator100, the difference between the output performance of the gas generator during the high-temperature activation and the output performance of the gas generator during the low-temperature activation is reduced, which stabilizes the output performance.

Arrows denoted by a reference sign F1inFIGS.3and4indicate the traveling directions of the combustion product discharged from the communication holes h1. As illustrated inFIGS.3and4, the combustion product discharged from the ignition unit chamber53through the communication holes h1by the activation of the first ignition device4is discharged radially with the inner tube center axis A5, which is the center axis of the surrounding wall portion51, as a center. That is, the combustion product is discharged toward the communication hole-associated regions R10aand R10bthat are regions facing the combustion product discharge regions R1aand R1bin the radiation direction with the inner tube center axis A5as a center. Thus, the first gas generating agent110disposed in the first combustion chamber10is sequentially ignited from a part disposed close to the combustion product discharge regions R1aand R1btoward a part disposed close to the communication hole-associated regions R10aand R10b. As a result, most of the combustion gas of the first gas generating agent110flows radially from the combustion product discharge regions R1aand R1band collides with the communication hole-associated regions R10aand R10b.

If the second gas discharge ports12bare formed in the communication hole-associated region R10aand the communication hole-associated region R10b, the second gas discharge ports12bmay be opened due to the pressure of the combustion gas colliding with the communication hole-associated region R10aand the communication hole-associated region R10beven during the low-temperature activation. In this case, since the second gas discharge ports12bare opened in addition to the first gas discharge ports12a, the internal pressure of the housing may not be as high as expected. On the other hand, if the first gas discharge ports12aare formed in the communication hole non-associated region R20aand the communication hole non-associated region R20b, the first gas discharge ports12amay not be opened during the low-temperature activation. In this case, since the number of the first gas discharge ports12athat are opened is insufficient, the internal pressure of the housing may be excessively high. In either case, the combustion performance of the gas generating agent cannot be obtained as expected, and it is difficult to stabilize the output performance.

On the other hand, in the peripheral wall portion11of the gas generator100, the first gas discharge ports12aare formed only in the communication hole-associated regions R10aand R10bfacing the combustion product discharge regions R1aand Rib, and the second gas discharge ports12bare formed only in the communication hole non-associated regions R20aand R20bnot facing the combustion product discharge regions R1aand R1b. Thus, during the low-temperature activation, the first gas discharge ports12aare more easily opened, and the second gas discharge ports12bare less likely to open. Thus, during the low-temperature activation, among the first gas discharge ports12aand the second gas discharge ports12b, it is possible to more reliably open only the first gas discharge ports12a. This can reliably increase the internal pressure of the housing and the combustion performance of the gas generating agent during the low-temperature activation. As a result, the difference between the output performance of the gas generator100during the low-temperature activation and the output performance of the gas generator100during the high-temperature activation can be reduced and the output performance can be stabilized.

Actions and Effects

As described above, in the gas generator100, the plurality of gas discharge ports12include the first gas discharge ports12aand the second gas discharge ports12bhaving higher opening pressures than the first gas discharge ports12a, and the surrounding wall portion51of the first inner tube member5is divided, in the circumferential direction of the surrounding wall portion51, into the combustion product discharge regions R1aand R1bin which the plurality of communication holes h1are collectively disposed and the combustion product non-discharge regions R2aand R2bthat are regions of the surrounding wall portion51other than the combustion product discharge regions R1aand R1b. The peripheral wall portion11of the housing1is divided, in the circumferential direction of the peripheral wall portion11, into the communication hole-associated regions R10aand R10bassociated with the combustion product discharge regions R1aand R1band the communication hole non-associated regions R20aand R20bassociated with the combustion product non-discharge regions R2aand R2b. The first gas discharge ports12aare formed only in the communication hole-associated regions R10aand R10b, and the second gas discharge ports12bare formed only in the communication hole non-associated regions R20aand R20b. With this gas generator100, since the first gas discharge ports12aare formed only in the communication hole-associated regions R10aand R10b, the first gas discharge ports12aare more easily opened, and since the second gas discharge ports12bare formed only in the communication hole non-associated regions R20aand R20b, the second gas discharge ports12bare more difficult to open. This makes it possible to more reliably open only the first gas discharge ports12aduring the low-temperature activation. As a result, as described above, the difference between the output performance during the low-temperature activation and the output performance during the high-temperature activation can be reduced and output performance of the gas generator100can be stabilized.

In addition, in the peripheral wall portion11of the gas generator100, the first gas discharge ports12aand the second gas discharge ports12bare disposed in separate regions (the communication hole-associated regions R10aand R10band the communication hole non-associated regions R20aand R20b). Thus, the second gas discharge ports12bare hardly affected by the combustion gas flowing to the first gas discharge ports12a. This can make it more difficult to open the second gas discharge ports12bduring the low-temperature activation. In the circumferential direction of the peripheral wall portion11, the distance between the first gas discharge port12aand the second gas discharge port12badjacent to each other may be set larger than the distance between the adjacent first gas discharge ports12ain the communication hole-associated regions R10aand R10band the distance between the adjacent second gas discharge ports12bin the communication hole non-associated regions R20aand R20b.

In addition, in the gas generator100, the communication hole-associated regions R10aand R10bare formed as regions of the peripheral wall portion11that face the combustion product discharge regions R1aand R1bin the radiation direction with the inner tube center axis A5as a center. Thus, the communication hole-associated regions R10aand R10bare associated with the combustion product discharge regions R1aand R1b.

Furthermore, in the gas generator100, as viewed in the axial direction of the surrounding wall portion51, ranges of the communication hole-associated regions R10aand R10bare defined by the first imaginary straight lines L1aand L1band the second imaginary straight lines L2aand L2b. Thus, the communication hole-associated regions R10aand R10bare defined as regions facing the combustion product discharge regions R1aand R1bin the radiation direction with the inner tube center axis A5as a center.

Furthermore, in the gas generator100, the inner tube center axis A5, which is the center axis of the surrounding wall portion51, and the housing center axis A1, which is the center axis of the peripheral wall portion11, are spaced apart from each other. That is, the first inner tube member5is disposed eccentrically with respect to the center of the housing1. In addition, the surrounding wall portion51includes the combustion product discharge regions R1aand R1blocated line-symmetrically with the imaginary center line CL1as an axis of symmetry, as viewed in the axial direction. The peripheral wall portion11includes the communication hole-associated region R10aassociated with the combustion product discharge region R1aand the communication hole-associated region R10bassociated with the combustion product discharge region R1b. Further, in the combustion product discharge regions R1aand R1b, the communication holes h1are formed and disposed line-symmetrically with the imaginary center line CL1as an axis of symmetry, and in the communication hole-associated regions R10aand R10b, the first gas discharge ports12aare formed and disposed line-symmetrically with the imaginary center line CL1as an axis of symmetry. That is, in the gas generator100, the communication holes h1and the first gas discharge ports12aare arranged line-symmetrical with the imaginary center line CL1as an axis of symmetry. With this configuration, since the communication hole-associated region R10aand the communication hole-associated region R10bare located line-symmetrically, when only the first gas discharge ports12aare opened during the low-temperature activation, thrust of the combustion gas discharged from the first gas discharge ports12aof the communication hole-associated region R10aand thrust of the combustion gas discharged from the first gas discharge ports12aof the communication hole-associated region R10bcancel out each other. As a result, the balance of the gas generator100during the activation becomes stable.

Furthermore, in the gas generator100, the opening pressures of the first gas discharge ports12aformed in the communication hole-associated region R10aand the opening pressures of the first gas discharge ports12aformed in the communication hole-associated region R10bthat is line-symmetrical to the communication hole-associated region R10aare equal to each other. Since the first gas discharge ports12alocated line-symmetrically to each other have the same opening pressures, the positions of the first gas discharge ports12aopened during the low-temperature activation become symmetrical. As a result, the balance of the gas generator100during the activation becomes more stable. In addition, in the gas generator100, the second gas discharge ports12bformed in the communication hole non-associated regions R20aand R20bare also disposed symmetrically with respect to the imaginary center line CL1, and thus the balance of the gas generator100during the activation becomes more stable.

The combustion product discharge region R1acorresponds to a “first combustion product discharge region” according to the present disclosure, the combustion product discharge region R1bcorresponds to a “second combustion product discharge region” according to the present disclosure, the communication hole-associated region R10acorresponds to a “first communication hole-associated region” according to the present disclosure, and the communication hole-associated region R10bcorresponds to a “second communication hole-associated region” according to the present disclosure.

As illustrated inFIGS.2to4, the second inner tube member8in which the second gas generating agent120is formed is disposed at a position not between the combustion product discharge region R1aand the communication hole-associated region R10aor between the combustion product discharge region R1band the communication hole-associated region R10bin the radiation direction with the inner tube center axis A5as a center. That is, the second inner tube member8is disposed at a position not obstructing flows of the combustion gas of the first gas generating agent110from the combustion product discharge regions R1aand R1btoward the communication hole-associated regions R10aand R10b. This makes it possible to more reliably open the first gas discharge ports12aformed in the communication hole-associated regions R10aand R10b.

In this example, the cross-sectional area (port diameter) of the first gas discharge port12aand the cross-sectional area (port diameter) of the second gas discharge port12bare different from each other, and thus the opening pressures of the first gas discharge port12aand the second gas discharge port12bare different from each other. However, the present disclosure is not limited thereto. For example, the opening pressure of the second gas discharge port may be made higher than the opening pressure of the first gas discharge port by partially adjusting the strength of the closing member that closes the gas discharge ports and making the strength of the part that closes the second gas discharge ports higher than the strength of the part that closes the first gas discharge ports. In addition, the opening pressure may be adjusted by changing both the port diameter of each gas discharge port and the strength of the closing member closing the gas discharge port. Note that examples of the adjustment for strength of the closing member include adjustment of the material of the closing member and adjustment of the thickness of the closing member including pasting the closing member in an overlapping manner.

Further, in this example, the plurality of (three) communication holes h1are disposed in each of the combustion product discharge regions R1aand R1b, but the number of the communication holes disposed in each combustion product discharge region according to the present disclosure is not particularly limited. The combustion product discharge regions may each be provided with only one communication hole instead of the plurality of communication holes. Further, in the present disclosure, the number and arrangement of the communication holes in the surrounding wall portion are not limited to those illustrated inFIG.2and the like. In the above-described example, the communication holes h1may be formed at portions other than the combustion product discharge region R1aor the combustion product discharge region R1b. In addition, the number of the communication holes formed in the surrounding wall portion is not limited to a plurality and may be only one.

In the present example, the transfer charge6is accommodated in the ignition unit chamber53. However, the gas generator of the present disclosure may be configured to ignite the first gas generating agent by increasing the type or amount of the ignition charge of the first igniter41without using the transfer charge6. That is, the gas generator according to the present disclosure is only required to be configured to discharge the combustion product from the ignition unit chamber through the communication holes by the activation of the first ignition device, and the “combustion product” discharged from the communication holes to ignite the first gas generating agent in the present disclosure is not limited to the combustion product of the transfer charge and may be a combustion product of the ignition charge. Further, a component obtained by integrating the transfer charge with the first igniter41may be used as the first ignition device.

Modified Examples of First Embodiment

A gas generator according to a modified example of the first embodiment will be described below. In the description of the modified examples, differences from the gas generator100described with reference toFIGS.1to4will be mainly described, and the same points as those of the gas generator100will be denoted by the same reference signs, and detailed description will be omitted.

First Modified Example of First Embodiment

FIG.5is a transverse cross-sectional view of a gas generator100A according to a first modified example of the first embodiment.FIG.5illustrates a state of the gas generator100A before activation.FIG.6is a perspective view of a first inner tube member5A according to the first modified example of the first embodiment. As illustrated inFIGS.5and6, in the gas generator100A, one communication hole h1A is disposed in each of the combustion product discharge regions R1aand R1b. The communication hole h1A is formed as a single hole extending in the circumferential direction of the surrounding wall portion51over the combustion product discharge region R1aand the combustion product discharge region R1b.

The gas generator100A illustrated inFIG.5can also stabilize the output performance in the same manner as the above-described gas generator100. Further, according to the gas generator100A, since the communication hole h1A is formed in the entire region of the combustion product discharge regions R1aand R1b, the combustion product radially discharged from the ignition unit chamber53through the communication hole h1A is uniformly discharged toward the entire regions of the communication hole-associated regions R10aand R10bfacing the combustion product discharge regions R1aand R1b. This enables the combustion gas of the first gas generating agent110to uniformly collide with the communication hole-associated regions R10aand R10band enables the first gas discharge ports12aformed in the communication hole-associated regions R10aand R10bto be more reliably opened.

Second Modified Example of First Embodiment

FIG.7is a transverse cross-sectional view of a gas generator100B according to a second modified example of the first embodiment.FIG.7illustrates a state of the gas generator100B before activation. As illustrated inFIG.7, the gas generator100B does not include the combustion product discharge region R1band the communication hole-associated region R10bcorresponding to the combustion product discharge region R1b. In this regard, the gas generator100B is different from the gas generator100. That is, in the gas generator100B, the communication holes h1and the gas discharge ports12are disposed asymmetrically with the imaginary center line CL1as an axis of symmetry. As exemplified by the gas generator100B, in the gas generator according to the present disclosure, the communication holes and the gas discharge ports may not be disposed at line-symmetrical positions with an imaginary center line as an axis of symmetry. The gas generator100B illustrated inFIG.7can also stabilize the output performance in the same manner as the above-described gas generator100.

Second Embodiment

Hereinafter, a gas generator according to a second embodiment will be described focusing on differences from the gas generator100, and the same points as those of the gas generator100will be denoted by the same reference signs and a detailed description will be omitted.FIG.8is a longitudinal cross-sectional view of a gas generator200according to the second embodiment.FIG.9is a cross-sectional view taken along line B-B ofFIG.8.FIGS.8and9illustrate a state of the gas generator200before activation.

As illustrated inFIGS.8and9, the gas generator200according to the second embodiment does not include the second ignition device7, the second inner tube member8, the second gas generating agent120, or the second combustion chamber20. In this regard, the gas generator200is different from the gas generator100according to the first embodiment. That is, the gas generator200is configured as a so-called single-type gas generator including only one ignition device located at a position deviated from the housing center axis A1. In the same manner as the gas generator100according to the first embodiment, the gas generator200illustrated inFIGS.8and9can also stabilize the output performance.

First Modified Example of Second Embodiment

FIG.10is a transverse cross-sectional view of a gas generator200A according to a first modified example of the second embodiment.FIG.10illustrates a state of the gas generator200A before activation. As illustrated inFIG.10, in the gas generator200A, the inner tube center axis A5coincides with the housing center axis A1, that is, the gas generator200A is a single-type gas generator in which the first inner tube member5is disposed at the center of the housing1and there is no member accompanying the second combustion chamber. In this regard, the gas generator200A is different from the gas generator200. In the same manner as the gas generator100according to the first embodiment, the gas generator200A illustrated inFIG.10can also stabilize the output performance.

Further, as illustrated inFIG.10, the gas generator200A is formed point-symmetrically as viewed in the axial direction. Specifically, the combustion product discharge region R1aand the combustion product discharge region R1bare located point-symmetrically with the housing center axis A1(the inner tube center axis A5) as a center of symmetry, and the communication hole-associated region R10aand the communication hole-associated region R10bare located point-symmetrically with the housing center axis A1as a center of symmetry. Further, the communication holes h1are formed in the combustion product discharge regions R1aand R1band disposed point-symmetrically with the housing center axis A1as a center of symmetry, and the first gas discharge ports12aare formed in the communication hole-associated regions R10aand R10band disposed point-symmetrically with the housing center axis A1as a center of symmetry. With this configuration, since the communication hole-associated region R10aand the communication hole-associated region R10bare located point-symmetrically, when only the first gas discharge ports12aare opened during the low-temperature activation, thrust of the combustion gas discharged from the first gas discharge ports12aof the communication hole-associated region R10aand thrust of the combustion gas discharged from the first gas discharge ports12aof the communication hole-associated region R10bcancel out each other. As a result, the balance of the gas generator100during the activation becomes stable.

Other

Suitable embodiments according to the present disclosure have been described above, but each embodiment disclosed in the present specification can be combined with each of features disclosed in the present specification.

REFERENCE SIGNS LIST

100,200Gas generator

1Housing

11Peripheral wall portion

12Gas discharge port

12aFirst gas discharge port

12bSecond gas discharge port

4First ignition device

5First inner tube member

51Surrounding wall portion

53Ignition unit chamber

6Transfer charge

7Second ignition device

8Second inner tube member

10First combustion chamber

20Second combustion chamber

110First gas generating agent

120Second gas generating agent

h1Communication hole

A1Housing center axis

A5Inner tube center axis

R1a, R1bCombustion product discharge region

R2a, R2bCombustion product non-discharge region

R10a, R10bCommunication hole-associated region

R20a, R20bCommunication hole non-associated region