Gas generator containing pressurized propellant

Abstract

A gas generator comprising: - a main gas chamber (10) having a side wall, - gas (20) stored under pressure in the main gas chamber (10), - a pyrotechnic chamber (30) arranged in the main gas chamber (10), - propellant (40) arranged in the pyrotechnic chamber (30) and exposed to the gas (20) stored under pressure, - a pyrotechnic igniter (51) attached to the side wall of the main gas chamber (10) and intended to trigger combustion of the propellant (40), characterized in that the gas generator comprises a sealing element, such as a casing (60), separate from the pyrotechnic igniter (51) and arranged between the pyrotechnic igniter (51) and the gas (20) stored under pressure. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Gas generator comprising pressurized propellant Technical field of the invention

[0001] The present invention relates generally to gas generators used in automotive safety modules. In particular, the invention relates to gas generators comprising a gas reservoir with pressurized propellant. Prior art

[0002] In the prior art of gas generators comprising a gas reservoir with pressurized propellant, it is known to provide an ignition device at one end of the gas generator with a discharge port at the other end, as shown in documents US20120187667A1 or WO2020 / 083773A1. Achieving rapid opening of the pressurized gas reservoir with ignition of the pressurized propellant without damaging the propellant itself is complicated. Rapid opening requires generating a pressure wave that must travel through the entire gas reservoir, but this risks breaking the propellant (block or pellets), which can cause performance variability and high pressure rise rates if the ignition causes propellant breakage with small pieces that burn rapidly. Furthermore, the architecture of these gas generators does not allow for easy control of the discharge of the gases stored in the gas reservoir.This results in a highly aggressive reaction of the gases to the airbag, which must be avoided. It is also known to incorporate an ignition device attached to a side wall of the gas reservoir, as shown in document US7316417B2. However, a cap is designed to cover the ignition device. The cap is designed with several radial orifices, but igniting the propellant is difficult to achieve in conjunction with rapid opening of the cap. Furthermore, the ignition device must be designed to withstand leaks of pressurized gas, which complicates manufacturing. Description of the invention

[0003] One object of the present invention is to address the disadvantages of the prior art mentioned above and in particular, first of all, to propose a gas generator which has improved ignition of the propellant, without however increasing the aggressiveness of the gas from the gas generator on the airbag.

[0004] To this end, a first aspect of the invention relates to a gas generator comprising: - a main gas chamber with a side wall, - gas stored under pressure in the main gas chamber, - a pyrotechnic chamber arranged within the main gas chamber, - propellant arranged within the pyrotechnic chamber and exposed to the gas stored under pressure, - an ignition device, including a pyrotechnic igniter, arranged (or attached directly or indirectly) to the side wall of the main gas chamber and designed to trigger combustion of the propellant, characterized in that the gas generator includes a sealing element, such as a casing, separate from the ignition device and arranged between the ignition device and the pressurized stored gas. The ignition device (the pyrotechnic igniter) attached to the side wall of the main gas chamber allows for rapid ignition of the propellant. Furthermore, the sealing element, separate from the ignition device and arranged between the ignition device and the pressurized stored gas, ensures a good seal without stressing the igniter.It can also be noted that the separate sealing element of the ignition device (of the pyrotechnic igniter) allows the generation of a pressure wave to be adjusted independently of the performance of the ignition device (of the pyrotechnic igniter), thus making it easier to adjust the ignition of the pressurized propellant (rapid ignition, without breakage, or with repeatable propellant breakage).

[0005] According to one embodiment, the main gas chamber may include a main outlet orifice, the gas generator then comprising a secondary nozzle arranged in the main gas chamber between the main outlet orifice and at least a portion of the gas stored under pressure. Such a secondary nozzle (or orifice) arranged in the main gas chamber between the main outlet orifice and at least a portion of the gas stored under pressure allows the discharge rate of the pressurized gas located upstream of this secondary nozzle to be regulated: this provides an additional lever for adjusting the operation and aggressiveness.

[0006] According to one embodiment, the main gas chamber may include a main operculum (or a first operculum) closing the main outlet orifice.

[0007] According to one embodiment, the ignition device may be located on the downstream side of the main gas chamber. In particular, the ignition device may be attached to the main gas chamber at a distance from the main orifice that is less than the distance separating the ignition device from the side of the main gas chamber opposite the side containing the main orifice. In particular, the ignition device may be attached to one half of the main gas chamber containing the main orifice.

[0008] According to one embodiment, the propellant can be arranged between the main outlet orifice and the secondary nozzle. Thus, the main outlet orifice can be configured to control propellant combustion and the secondary nozzle can be configured to control the venting of the majority of the gas stored under pressure. The two orifices can be By defining these parameters independently, the aggressiveness of the initial gas release in the airbag can be reduced. Indeed, the combustion of the propellant is minimally affected by the necessary venting of the pressurized stored gas: operation is better controlled. In prior art generators where the propellant is arranged upstream of most of the pressurized gas (with the igniter positioned opposite the main orifice), the main orifice must be large enough to prevent over-pressurization of the main gas chamber during the release of the propellant-produced gases. A large main orifice results in an initial release of the pressurized stored gases that can be aggressive to the airbag (bag and / or casing), whereas functionally, such an initial gas release is not necessary.

[0009] According to one embodiment, a passage section of the secondary nozzle will be smaller than a passage section of the main nozzle.

[0010] According to one embodiment, the sealing element can be partially arranged within the pyrotechnic chamber. In other words, the sealing element and the pyrotechnic igniter, once the sealing element is opened, lead directly into the pyrotechnic chamber, which ensures rapid ignition of the propellant since the ignition device (the pyrotechnic igniter) is arranged as close as possible to the propellant without being separated from it by a significant volume of gas.

[0011] According to one embodiment, the propellant can be a bulk pyrotechnic charge. A charge of pellets can be considered. However, one or more propellant blocks can also be provided.

[0012] According to one embodiment, the gas generator may include at least one drainage device passing through the bulk pyrotechnic charge.

[0013] According to one embodiment, the drainage element may have at least one portion facing the ignition device, and the portion of the drainage element facing the ignition device may form a screen against gases and / or a pressure wave generated by the ignition device. The portion of the drainage element facing the ignition device that forms a screen ensures that the hot particles and gases from the igniter remain within the pyrotechnic chamber and / or the pyrotechnic charge. Such a screen may also be provided to attenuate a pressure wave generated by the ignition device and its igniter, if necessary. This improves propellant ignition and prevents premature opening of the main seal.

[0014] According to one embodiment, the drainage element may have at least one portion facing the ignition device, and the portion of the drainage element facing the ignition device may be formed with a solid wall. The solid wall ensures that the hot particles and gases from the igniter remain within the pyrotechnic chamber and / or the pyrotechnic charge. Such a solid wall may also be designed to attenuate a pressure wave generated by the ignition device and its igniter, if necessary.

[0015] According to one embodiment, the drainage element may form or include a drainage channel arranged to drain all the combustion gases generated by the propellant. In other words, the drainage element may include at least a portion of piping or passage arranged between the gas reservoir's discharge port and all the propellant. The channel may be in the form of a chimney.

[0016] According to one embodiment, the drainage element may have a drainage direction, and the ignition device may have an axial direction perpendicular to the drainage direction. In particular, the drainage element may be oriented along an axial direction of the gas generator, and the ignition device may be oriented along a radial direction of the gas generator. This simplifies the connection of the ignition device (pyrotechnic igniter) to a firing circuit when the gas generator is placed in a safety module.

[0017] According to one embodiment, the pyrotechnic chamber may be separate from the main gas chamber. In other words, a specific structure forming the pyrotechnic chamber may be installed or provided within the main gas chamber.

[0018] According to one embodiment, the pyrotechnic chamber may comprise: - a lateral tube (like a basket), preferably solid, - a base closing a downstream end of the lateral tube and comprising the drainage channel (an internal chimney) extending up to an upstream end of the lateral tube, - a cap formed by a cup coupled to the upstream end and to the drainage channel (to the internal chimney). In particular, the chimney can form the drainage element.

[0019] According to one embodiment, the main gas chamber may include a chamber bottom (including the main orifice) and a closing wall, for example welded together.

[0020] According to one embodiment, the drainage channel (the internal chimney) may extend beyond the bottom of the chamber. This implementation allows for the standardization of components for several pyrotechnic loading volumes.

[0021] According to one embodiment, the drainage channel (the internal chimney) may extend beyond the lateral tube. This implementation allows for the standardization of components for several pyrotechnic loading volumes.

[0022] According to one embodiment, the cup may include the secondary nozzle. In particular, the chimney and / or the drainage element may be aligned with the secondary nozzle.

[0023] According to one embodiment, the gas generator may comprise: - a second gas chamber, - pressurized gas stored in the second chamber.

[0024] According to one embodiment, the ignition device attached to the side wall of the main gas chamber can be the sole ignition device for the gas generator. Although comprising two separate gas reservoirs, only one ignition device (a single pyrotechnic igniter) is provided. Alternatively, a gas generator can be provided with a single gas chamber (including a pyrotechnic chamber) terminating in a diffuser along the axial direction. A gas generator can even be provided with a single gas chamber filled with gas (including a pyrotechnic chamber), an empty casing, and a diffuser between the gas-filled gas chamber and the empty casing (which could be a buffer volume for the gas exiting the gas-filled gas chamber).

[0025] According to one embodiment, the gas generator may include a gas diffuser common to the main gas chamber and the second gas chamber.

[0026] According to one embodiment, the common gas diffuser can be arranged between the main gas chamber and the second gas chamber.

[0027] According to one embodiment, the gas generator may include a second sealing flap housed in the second gas chamber and supported by a support member arranged to deform and / or break under the effect of gas ejected out of the main gas chamber.

[0028] According to one embodiment, the sealing element separate from the ignition device can be arranged to break under the effect of gas or a pressure wave generated by the ignition device.

[0029] According to one embodiment, the sealing element separate from the ignition device can be arranged to generate a pressure wave when it ruptures due to the activation of the ignition device. The sealing element separate from the ignition device, capable of generating a pressure wave, allows this pressure wave (pressure difference value, direction, type of pressure wave, etc.) to be adjusted independently of the ignition device (pyrotechnic igniter) and its performance (loading, type of casing with radial or axial opening, etc.).

[0030] According to one embodiment, the secondary nozzle may have a passage area smaller than a passage area of ​​the main outlet orifice.

[0031] Another aspect of the disclosure may relate to a gas generator comprising: - a main gas chamber having a side wall and a main outlet orifice, - gas stored under pressure in the main gas chamber, - a pyrotechnic chamber arranged within the main gas chamber, - propellant arranged in the pyrotechnic chamber and exposed to the gas stored under pressure, - an ignition device attached to the side wall of the main gas chamber and intended to trigger combustion of the propellant, characterized in that the gas generator comprises a secondary nozzle arranged in the main gas chamber between the main outlet orifice and at least a portion of the gas stored under pressure and in which the propellant is arranged between the main outlet orifice and the secondary nozzle. Description of the figures

[0032] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of an embodiment of the invention given by way of non-limiting example and illustrated by the accompanying drawings, in which:

[0033] [Fig-1] represents a cross-section of a gas generator according to the invention, according to a plan of a section including a longitudinal axis of the gas generator.

[0034] Detailed description of embodiment(s)

[0035] Figure [1] represents a gas generator comprising: - a main gas chamber 10 having a side wall (here a cylindrical wall, but other shapes can be considered), - gas 20 stored under pressure in the main gas chamber 10, - a pyrotechnic chamber 30 arranged within the main gas chamber 10, - propellant 40 arranged in the main pyrotechnic chamber 10 and exposed to (or immersed in) gas 20 stored under pressure, - an ignition device 50 comprising in particular a pyrotechnic igniter 51 attached to the side wall of the main gas chamber 10 and designed to trigger combustion of the propellant 40, - a sealing element 60 separate from the ignition device 50 and therefore from the pyrotechnic igniter 51 and arranged between the ignition device 50 (the pyrotechnic igniter 51) and the gas 20 stored under pressure - a second gas chamber 70, - gas 80 stored under pressure in the second gas chamber 70, - a diffuser 90 arranged between the main gas chamber 10 and the second gas chamber 70, containing a filter 91 and a support element 92, - fixing studs 15 and 75, respectively welded to the main gas chamber 10 and the second gas chamber 70.

[0036] As regards the main gas chamber 10, it is mainly made up of a chamber bottom 11 and a closing wall 12, welded together. Friction welding is possible, but other types of welding are also possible. The main gas chamber 10 is closed by a closing pin 14, which is welded to the closing wall 12.

[0037] The main gas chamber 10 contains gas 20 stored under pressure. A mixture of inert gases, such as a mixture of argon and helium, can be used, but a so-called "reactive" gas, which could participate in a chemical reaction with the propellant 40, or a gas 80 from the second gas chamber 70, can also be used. A storage pressure at ambient temperature of between 20 MPa and 50 MPa can be used, but these values ​​can be deviated from.

[0038] Finally, the main gas chamber 10 includes a main outlet orifice 16, and a main cover 13 covers the main outlet orifice 16 to ensure the sealing of the main gas chamber 10. The main cover 13 is typically formed by a thin metal disc, welded to the bottom of the chamber 11.

[0039] The main gas chamber 10 also contains propellant 40 stored in the pyrotechnic chamber 30, and immersed in, or exposed to, the gas 20 stored under pressure. The propellant 40, partially shown [Fig. 1], can be a bulk charge, i.e., in pellets. Pellets can have a diameter between 3 mm and 9 mm, and a thickness between 1.5 mm and 5 mm. However, propellant 40 can also be supplied as a monolithic block.

[0040] In the embodiment shown, the pyrotechnic chamber 30 is composed of three distinct parts: a drainage channel, i.e., a chimney 32 which can form the drainage element, a cup 31, and a lateral tube (a basket 33). The basket 33 forms an external wall of the pyrotechnic chamber 30 and contains the propellant 40. The chimney 32 forms an internal tube within the pyrotechnic chamber 30 and has a base that mates with the basket 33 at its end opposite the main outlet orifice 16. The cup 31 mates (here by crimping) with the basket 33 at its end opposite the main outlet orifice 16 to close the basket 33. The structure of the pyrotechnic chamber 30 is shown here in three parts, but other embodiments are possible.

[0041] It can be noted that the chimney 32 has orifices only in its upstream part (at its end opposite the main outlet orifice 16), and that the cup 31 has a secondary nozzle 34, opposite the channel formed by the chimney 32. Finally, the pyrotechnic chamber 30 includes a compensator 35 (a piece of foam or compressible fabric) intended to ensure optimal seating of the propellant 40.

[0042] An ignition device 50 is attached to the side wall of the main gas chamber 10 by a sheath 60, and includes in particular a pyrotechnic igniter 51, an igniter support 53, and a plastic overmolding 51. The pyrotechnic igniter 51 is typically a known electro-pyrotechnic igniter. It should be noted that the pyrotechnic igniter 51 includes, as is known, a metal casing containing a pyrotechnic composition and a heating element. The metal casing of the pyrotechnic igniter 51 is not the casing 60 that forms the sealing element interposed between the ignition device 50 (in particular the pyrotechnic igniter 51) and the gas 20 contained in the main gas chamber 10.

[0043] In particular, the casing 60 is welded to the main gas chamber 10, and the ignition device 50 (including the pyrotechnic igniter 51) is crimped into the casing 60. In this embodiment, the casing 60 is a stamped metal part in the shape of a dome or a closed tube with a rounded end, and a cross-shaped indentation 61 at the end. The cross-shaped indentation 61 allows for adjusting the opening pressure of the casing 60 when the pyrotechnic igniter 51 is ignited. The casing 60 can be formed from low-carbon steel, with a wall thickness of between 1 mm and 3 mm. The cross-shaped indentation 61 can have a depth of between 0.5 mm and 2.5 mm. Other shapes are planned for the 60 case (flat end, lateral weakness zones in addition to or instead of the cruciform 61...).

[0044] It can be noted that the casing 60 forms a sealed barrier between the ignition device 50 (in particular the pyrotechnic igniter 51) and the gas 20 contained in the main gas chamber 10.

[0045] The case 60 and the ignition device 50 give directly into the pyrotechnic chamber 30, but the outlet of the case 60 (the cross-shaped 60) is preferably located opposite the portion of the chimney 32 free of holes.

[0046] As regards the second gas chamber 70, it is, similarly to the main gas chamber 10, primarily composed of a second chamber bottom 71 and a second closing wall 72, welded together. A friction weld may be used, but other types of weld are possible. The second gas chamber 70 is closed by a second closing pin 74, fixed by welding to the closing wall 72.

[0047] The second gas chamber 70 contains gas 80 stored under pressure. A mixture of inert gases, such as a mixture of argon and helium, can be used, but a so-called "reactive" gas can also be used, which could participate in a chemical reaction with the propellant 40, or with the gas 20 from the main gas chamber 10. A storage pressure at ambient temperature of between 20 MPa and 50 MPa can be used, but these values ​​can be deviated from.

[0048] Finally, the second gas chamber 70 includes a second outlet orifice 76, and a second cover 73 covers the second outlet orifice 76 to ensure the sealing of the second gas chamber 70. The second cover 73 is ty a pit formed by a thin metal disc, welded to the second chamber bottom 71. The second outlet orifice 76 may have a passage cross-section less than or equal to a passage cross-section of the secondary nozzle 34. Alternatively, the second outlet orifice 76 may have a passage cross-section between the passage cross-section of the secondary nozzle 34 and a passage cross-section of the main orifice 16.

[0049] A diffuser 90 is provided between the main gas chamber 10 and the second gas chamber 70. This diffuser 90 is welded to the main gas chamber 10 and the second gas chamber 70, and has a plurality of diffusion holes to direct the gases from the main gas chamber 10 and the second gas chamber 70 towards an inflatable cushion.

[0050] The diffuser 90 includes a filter 91 (typically a metal filtering part) and the support member 92 which is in contact with the bottom of the chamber 11 and the second operculum 73 throughout the entire life before the operation of the gas generator to provide reliable support for the second operculum 73.

[0051] The operation of the gas generator is as follows. When the gas generator needs to supply inflation gas to the airbag, the pyrotechnic igniter 51 is triggered. The pressure in the casing 60 increases rapidly, and the cross-shaped opening 61 opens. Thus, hot gases, hot particles, and a pressure wave are propelled into the pyrotechnic chamber 30. However, the outlet of the casing 60 (the cross-shaped opening 60) is located opposite the portion of the chimney 32 without holes, so the hot gases, particles, and pressure wave propelled into the pyrotechnic chamber 30 cannot enter the internal conduit of the chimney 32 without passing through the propellant 40, which generates and causes rapid ignition of the propellant 40.

[0052] Once the propellant 40 is ignited, the pressure in the main gas chamber 10 increases, and the main seal 13 covering the main outlet orifice 16 can rupture. The pressurized stored gas 20 escapes first through the main outlet orifice 16, followed by the combustion gases of the propellant 40. The emptying of the main gas chamber 10 begins.

[0053] In the first moments after the rupture of the main operculum 13, the support member 92 is pushed or broken by the gases exiting the main gas chamber 10 and tilts, so that the second operculum 73 is no longer supported and can open in turn. The emptying of the second gas chamber 70 then begins.

[0054] The gases can pass through the filter 91 and escape from the diffuser 90 to unfold and inflate the airbag not shown.

[0055] During operation, in the main gas chamber 10, the propellant 40 burns and increases the quantity of inflating gas, as well as its temperature. As As seen above, the cup 31 includes a secondary nozzle 34, with a diameter (for example 3mm) smaller than that of the main orifice 16 (for example a diameter of 6mm), so that the combustion gases escape through the latter, and mainly once the combustion of the propellant 40 slows down, the rest of the gas 20 located upstream of the secondary nozzle 34 can drain through the latter and escape from the main gas chamber 10.

[0056] The following points can also be noted: - all the combustion gases of propellant 40 pass into the central drainage channel of chimney 32 because the downstream part of the tube and its base are made of solid sheet metal: the first gases to escape through the main orifice are therefore cold gases initially contained between the propellant and the main orifice, not resulting from the combustion of propellant 40, which helps to limit the aggressiveness on the inflatable cushion during its unfolding / deployment; - a single pyrotechnic igniter is sufficient to open both gas reserves almost simultaneously; - as seen above, the gas 20 stored under pressure and cold present in the central drainage channel of the chimney 32, escapes first from the main gas chamber 10, but the secondary nozzle 34 allows to adjust and regulate the emptying of at least a part (preferably a majority) of the gas 20 stored under pressure in order to lengthen the total emptying time and limit the gas flow at the opening of the main orifice; - the downstream part of the chimney 32 made of solid sheet metal shields the gases, particles and pressure wave initiated by the ignition device and the casing 60, to force them to pass through the propellant 40 and ignite it quickly. Industrial application

[0057] A gas generator according to the present invention, and its manufacture, are capable of industrial application.

[0058] It will be understood that various modifications and / or improvements obvious to a person skilled in the art can be made to the different embodiments of the invention described in this description without departing from the scope of the invention.

Claims

Demands

1. Gas generator comprising: - a main gas chamber (10) having a side wall, - gas (20) stored under pressure in the main gas chamber (10), - a pyrotechnic chamber (30) arranged in the main gas chamber (10), - propellant (40) arranged in the pyrotechnic chamber (30) and exposed to the gas (20) stored under pressure, - an ignition device (50) arranged on the side wall of the main gas chamber (10) and intended to trigger combustion of the propellant (40), characterized in that the gas generator comprises a sealing element, such as a sleeve (60), separate from the ignition device (50) and arranged between the ignition device (50) and the gas (20) stored under pressure.

2. Gas generator according to claim 1, wherein the main gas chamber (10) comprises a main outlet orifice (16), the gas generator comprising a secondary nozzle (34) arranged in the main gas chamber (10) between the main outlet orifice (16) and at least a portion of the gas (20) stored under pressure.

3. Gas generator according to claim 2, wherein the propellant (40) is arranged between the main outlet orifice (16) and the secondary nozzle (34).

4. Gas generator according to any one of claims 1 to 3, wherein the sealing element is partially arranged in the pyrotechnic chamber (30).

5. Gas generator according to any one of claims 1 to 4, wherein the propellant (40) is a bulk pyrotechnic charge.

6. Gas generator according to claim 5, comprising at least one drainage device passing through the bulk pyrotechnic charge.

7. Gas generator according to claim 6, wherein the drainage member has at least one part opposite the ignition device (50), and wherein the part of the drainage member opposite the ignition device (50) forms a screen to gases and / or a pressure wave generated by the ignition device (50).

8. Gas generator according to claim 6, wherein the organ of drainage has at least one part opposite the ignition device (50), and in which the part of the drainage element opposite the ignition device (50) is formed with a solid wall.

9. Gas generator according to any one of claims 6 to 8, wherein the drainage element comprises a drainage channel arranged to drain all of the combustion gases generated by the propellant (40).

10. Gas generator according to any one of claims 6 to 9, wherein the drainage member has a drainage direction, and wherein the ignition device (50) has an axial direction of ignition device perpendicular to the drainage direction.

11. Gas generator according to any one of claims 1 to 10, wherein the pyrotechnic chamber (30) is separate from the main gas chamber (10).

12. Gas generator according to any one of claims 1 to 11, wherein the pyrotechnic chamber (30) comprises: - a lateral tube, preferably solid, - a base closing a downstream end of the lateral tube and comprising the drainage channel rising to an upstream end of the lateral tube, - a cap formed by a cup (31) coupled to the upstream end and to the drainage channel.

13. Gas generator according to any one of claims 1 to 12, comprising: - a second gas chamber (70), - gas (80) stored under pressure in the second chamber.

14. Gas generator according to claim 13, wherein the ignition device (50) attached to the side wall of the main gas chamber (10) is the sole ignition device (50) of the gas generator.

15. Gas generator according to any one of claims 13 or 14, comprising a second sealing cover (73) housed in the second gas chamber (70) and supported by a support member (92) arranged to deform and / or break under the effect of gas ejected out of the main gas chamber (10).

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