Gas generator

Abstract

The invention relates to a gas generator comprising at least: - a gas chamber (10, 40); - inflation gas (G1, G2), stored under pressure in the gas chamber (10, 40); - a pyrotechnic opening device (20); - a distribution chamber (50), arranged to receive the inflation gas (G1, G2) opened by the pyrotechnic opening device (20) and comprising distribution holes (52); - a ventilation device, with an internal plug (35) that is arranged in the distribution chamber (50) and is movable between: • a first position, defining a first passage area; and • a second position, defining a second passage area, characterised in that the gas generator comprises a non-return device arranged to keep the internal plug (35) in the second position.

Description

DESCRIPTION TITLE: Gas Generator Technical field of the invention

[0001] The present invention relates generally to gas generators intended for inflating airbags in a motor vehicle. In particular, the present invention relates to gas generators comprising a pressurized gas reservoir or chamber, a diffusion chamber with diffusion holes for diffusing the inflation gases to the outside and a mechanism inside the diffusion chamber for acting on the flow and / or path of the inflation gases between the gas chamber and the diffusion holes. State of the art

[0002] In the prior art of gas generators, document EP 2 928 731 B1 is known, which discloses a gas generator comprising two reserves or pressurized gas chambers, a diffusion chamber arranged between the two gas chambers and with diffusion holes for diffusing outwardly the inflation gases received from the gas chambers, and a mechanism inside the diffusion chamber. On the other hand, this system may have disadvantages related to the reproducibility of operation, in particular if variations in flow, flow rate or trajectories are observed inside the mechanism, which may lead to variabilities in deployment of the airbag. Statement of the invention

[0003] An aim of the present invention is to address the drawbacks of the prior art mentioned above and in particular, first of all, to propose a gas generator whose operating reproducibility is improved and which therefore allows more robust inflation and / or deployment of a safety cushion.

[0004] For this, a first aspect of the invention concerns a gas generator comprising at least: - a gas chamber, with a gas outlet, - a cover, closing the gas outlet, - inflation gas, stored under pressure in the gas chamber with the gas outlet closed by the cover, - a pyrotechnic opening device, arranged to open the gas outlet, - a diffusion chamber, arranged to receive the inflation gas once the gas outlet is opened by the pyrotechnic opening device and comprising diffusion holes for diffusing the inflation gas towards the outside of the gas generator, - a ventilation device, with an internal shutter arranged in the diffusion chamber and movable between: • a first position, in which the internal shutter defines a first passage surface between the gas outlet of the gas chamber and the diffusion holes, and • a second position, in which the internal shutter defines a second passage surface between the gas outlet of the gas chamber and the diffusion holes and greater than the first passage surface, characterized in that the gas generator comprises a non-return device arranged to retain the internal shutter in the second position, comprising a deformable portion, preferably formed on the internal shutter, arranged to deform, preferably irreversibly, when the internal shutter passes from the first position to the second position, and to maintain the internal shutter in position in the second position.

[0005] According to the above implementation, the internal shutter is held in place in the second position. In other words, the gas generator includes a non-return device to ensure that the internal shutter remains in the second position once it has arrived there. Thus, once the internal shutter in the second position, the internal shutter remains in the second position and the flow rate, flux or trajectory of the inflation gas in the diffusion chamber is repeatable because there is no physical change of configuration in the diffusion chamber. Furthermore, it can be noted that the actuation of the opening device and the ventilation device are independent, so that the flow rate of gas passing through the diffusion holes can be controlled independently of the opening of the gas chamber, which makes it possible to adapt to the desired retention.

[0006] The gas generator can be defined by the following characteristics, taken individually or in combination.

[0007] According to one implementation, the internal shutter in the second position may be free from tearing or breaking, relative to the internal shutter in the first position. In other words, the transition of the internal shutter from the first position to the second position may be carried out without tearing, breaking or detaching part of the internal shutter: the latter may remain intact, but may be deformed elastically or preferably plastically. According to one implementation, the internal shutter in the second position may slide or translate from the first position to the second position.

[0008] According to one implementation, the internal shutter may perform a single movement during operation: from the first position to the second position. In particular, the internal shutter may perform only a single movement during operation: from the first position to the second position. In other words, the internal shutter may not perform multiple round trips or movements between the first position and the second position.

[0009] According to one implementation, the ventilation device, and in particular the internal shutter, the non-return device and the opening device may be distinct from one another. In particular, the ventilation device, and in particular the internal shutter, may be distinct from the opening device. In other words, the ventilation device, and in particular the internal shutter, may not participate in the opening of the gas chamber. The ventilation device, and in particular the internal shutter, may be free of any supporting part or perforation of the seal.

[0010] According to one implementation, the internal shutter can occupy the first position once the opening device is activated, and / or once the seal is open, and / or once the first inflation gases have left the diffusion chamber. In other words, the internal shutter can remain in the first position at least at the start of the diffusion of the inflation gases out of the diffusion chamber.

[0011] According to one implementation, the gas generator may comprise at least one blocking portion, arranged to engage with said at least one deformable portion after deformation and block a movement of the internal shutter from the second position to the first position. The deformable portion, after deformation, may abut or brace against the blocking portion, which provides a robust non-return device.

[0012] According to one implementation, said at least one deformable portion may comprise at least one actuating surface, arranged to be located in a gas path traveled by the inflation gas going from the gas chamber to the diffusion holes, when the internal shutter is in the second position, so as to cause the deformation of the deformable portion. Thus, the deformation (preferably plastic) of the deformable portion is caused, at least partially, by the inflation gases which escape from the gas chamber.

[0013] According to one implementation, the diffusion chamber may comprise at least one diffusion hole arranged to impose the gas path opposite or to bypass said at least one actuating surface of the internal shutter in the second position. In other words, the deformable portion, when the internal shutter is in the second position, is located on a path of the inflation gas going from the gas chamber to the diffusion holes.

[0014] According to one implementation, the internal shutter may comprise a zone of weakness arranged to concentrate or cause or facilitate the deformation of the deformable part.

[0015] According to one implementation, the actuating surface of the internal shutter in the second position may be arranged in a cantilever manner relative to the weak zone. In particular, the deformation may be a bending which is supported by or articulated around the blocking portion. The weak zone (with the internal shutter in the second position) may be opposite the blocking portion.

[0016] According to one implementation, the ventilation device may comprise: - a pyrotechnic ventilation actuator arranged to move the internal shutter from the first position to the second position, - a control piston, arranged between the pyrotechnic ventilation actuator and the internal shutter. In other words, the transition of the internal shutter from the first position to the second position can be controlled by a pyrotechnic ventilation actuator and can be independent of the gas chamber opening command. According to a preferred embodiment, the triggering of the pyrotechnic ventilation actuator can be offset in time relative to the triggering of the pyrotechnic opening actuator. The triggering of the pyrotechnic ventilation actuator can be offset relative to the triggering of the pyrotechnic opening actuator by a few milliseconds, for example 2 ms, 3 ms, 4 ms, 5 ms, 6 ms, 7 ms, 8 ms, 9 ms, 10 ms, 15 ms.

[0017] According to one implementation, when the internal shutter is in the second position, the control piston may be movable relative to the internal shutter and may release an internal passage to allow inflation gas to pass from the gas chamber to the diffusion holes. The piston The control unit can, in turn, return backwards to open or leave free an internal passage. The inflation gas can cause this backward movement.

[0018] According to one implementation, the ventilation device may comprise an internal diffuser, arranged in the diffusion chamber and supporting the internal shutter, at least in the first position. The internal diffuser may be a supporting structure arranged in the diffusion chamber.

[0019] According to one implementation, the internal shutter may comprise at least one anchoring portion, arranged to retain, preferably elastically, the internal shutter in the first position. A flexible tab may be provided. More generally, the gas generator may comprise a position-holding device arranged to maintain the internal shutter in the first position, with an obstacle to be overcome so that the internal shutter leaves the first position. The obstacle to be overcome may be a portion to be deformed elastically, plastically or to break.

[0020] According to one implementation, the pyrotechnic opening device may comprise at least: - a pyrotechnic opening actuator, - a movable support, arranged to be moved by the pyrotechnic opening actuator from a first position, in which the movable support supports the cover closing the gas outlet, to a second position, in which the movable support does not provide support for the cover.

[0021] According to one implementation, the internal diffuser: - can provide guidance to the mobile support, preferably in translation, - may include the blocking portion, - can be connected to the gas outlet, - can be arranged to collect the inflation gas at the gas outlet of the gas chamber, - can be arranged to distribute / guide inflation gas to the holes of diffusion, - can be arranged to force the deformation of said at least one deformable portion when the internal shutter moves from the first position to the second position, - may include an intermediate diffusion hole between the two deformable portions, and / or between the two ends of the U or the rider.

[0022] According to one implementation, the internal shutter: - in the first position, can close a first gas passage orifice and preferably a second gas passage orifice in the internal diffuser, - in the second position, can release in the internal diffuser the first gas passage orifice and preferably the second gas passage orifice, - can be formed by a stamped part, - may include two deformable portions, - may have a U or rider shape, and the two deformable portions are arranged symmetrically on the U or the rider, - may comprise a proximal portion and a distal portion, and the deformable portion is on the distal portion, and the proximal portion is arranged near the pyrotechnic ventilation actuator or the control piston, - can be designed to deform irreversibly in bending, - may comprise at least one protrusion forming a beam with a free end intended to deform irreversibly, preferably in bending.

[0023] According to one implementation, the internal shutter in the second position may be exposed to a gas flow, and in particular, the internal shutter, in the second position (or just before fully arriving there) and before deformation, may comprise a portion arranged to at least partially block (or restrict or be exposed to) a gas flow, for generate an internal force in the internal shutter sufficient to cause irreversible deformation. As a result, the internal shutter, in the second position and after deformation, allows the gas flow free and can no longer return to the first position.

[0024] According to one implementation, the internal shutter may have a U or rider shape, and the two deformable portions are arranged symmetrically on the U or the rider to open the legs of the U or the rider outwards.

[0025] According to one implementation, the internal shutter may comprise a cantilevered portion intended to deform irreversibly upon arrival of the internal shutter in the second position. More particularly, the cantilevered portion may have a free end to receive a deformation force and force the internal shutter to deform irreversibly. In particular, the deformation force may be applied to the cantilevered portion by a gas flow (for example an internal gas flow present during operation of the gas generator), and / or by contact with another component of the gas generator (for example a wall of the gas generator forming an obstacle on the path of the internal shutter towards the second position and requiring irreversible deformation).

[0026] According to one implementation, the internal shutter may deform irreversibly just before arriving in the second position. For example, the internal shutter may travel from the first position to the second position, and the irreversible deformation may occur only after 10%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90% of the travel from the first position to the second position. In any event, provision may be made to irreversibly deform the internal shutter as soon as it has left the first position. Thus, returning to the first position is impossible. According to one implementation, the travel from the first position to the second position may be a translation of the internal shutter body (i.e., the parts that do not deform irreversibly have a translational movement).

[0027] According to one implementation, the control piston: - can be secured or attached to the pyrotechnic ventilation actuator when the internal shutter is in the first position, - may be integral or attached to the internal shutter when the internal shutter is in the first position, - can be uncoupled or detached or released from the pyrotechnic ventilation actuator when the internal shutter is in the second position, - can be uncoupled or detached or released from the internal shutter when the internal shutter is in the second position, - may include a shoulder (or a stop portion) to come into contact with the internal diffuser when the internal shutter reaches the second position, - can be free to leave the stop on the internal diffuser once the internal shutter has reached the second position, - can release one of the first gas passage orifice and the second gas passage orifice by leaving the stop on the internal diffuser once the internal shutter has arrived in the second position.

[0028] According to one implementation, the gas generator may comprise a deformation guide surface, arranged for example on the internal diffuser or the diffusion chamber, and arranged to force the deformation of the deformable portion during its passage from the first to the second position.

[0029] According to one implementation, the diffusion chamber may be free of diffusion holes between the two deformable portions, and / or between the two ends of the U or the rider. Description of figures

[0030] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of embodiment(s) of the invention given as non-limiting example(s) and illustrated by the appended drawings, in which:

[0031] [fig. 1] represents a gas generator comprising two gas chambers and a diffusion chamber arranged between the two gas chambers;

[0032] [fig. 2] represents a section along a longitudinal plane of the gas generator of figure 1, to show a part of the gas chambers still closed, the interior of the diffusion chamber, including in particular an opening device, an internal diffuser and an internal shutter;

[0033] [fig. 3] represents a section of the gas generator of figure 1 along a plane parallel to the section plane of figure 2, to show in perspective the interior of the diffusion chamber;

[0034] [fig. 4] represents a perspective view of the internal shutter mounted in the diffusion chamber of the gas generator of figure 1;

[0035] [fig. 5] represents two sectional views of the gas generator of figure 1 according to a sectional plane perpendicular to a longitudinal axis of the gas generator, to show the internal shutter before and after operation of the gas generator.

[0036] Detailed description of embodiment(s)

[0037] Figure 1 shows a gas generator intended to inflate a safety cushion installed in a motor vehicle, comprising at least: - a first gas chamber 10, comprising inflation gas and having an elongated shape, - a second gas chamber 40, comprising inflation gas and having an elongated shape, and aligned with the first gas chamber 10, - a pyrotechnic opening device 20, arranged to open the first gas chamber 10 and the second gas chamber 40, and a connection interface of which projects upwards relative to a generally cylindrical casing of the gas generator, - a diffusion chamber 50, arranged between the first gas chamber 10 and the second gas chamber 40 to receive the inflation gas once the first gas chamber 10 and the second gas chamber 40 are opened by the pyrotechnic opening device 20 and comprising diffusion holes 52 to diffuse the inflation gas towards the outside of the gas generator, - a ventilation device 30, with an internal shutter not visible in figure 1 and arranged in the diffusion chamber 50, and of which a connection interface projects upwards relative to the generally cylindrical casing of the gas generator, and adjacent to the connection interface of the opening device 20.

[0038] As shown in Figure 1: - the gas generator has an elongated shape in an axial direction, - the first gas chamber 10 and the second gas chamber 40 each have one end attached (by a weld for example) to the diffusion chamber 50 and another rounded end (hemispherical for example) comprising a filling hole closed by a plug (welded for example), - the diffusion chamber 50 is arranged substantially in the middle of the gas generator and supports the connection interfaces of the opening device 20 and the ventilation device 30, - fixing studs are fixed (here welded) on each of the gas chambers.

[0039] Figure 2 represents a section along a longitudinal plane of the gas generator of Figure 1, to show a part of the first gas chamber 10 and the second gas chamber 40 still closed, the interior of the diffusion chamber 50, comprising in particular the ventilation device 30 with an internal diffuser 34 and the internal shutter 35.

[0040] In detail, the first gas chamber 10 includes: - a first body 11 welded to the diffusion chamber 50, - a first gas outlet 14, - a first cover 12, closing the first gas outlet 14 and welded onto the first body 11, - a first support portion 13, supporting the first cover 12, - inflation gas G1, which may include an inert gas (argon, helium, etc.) and / or a reactive gas (oxygen, hydrogen, etc.) and stored under a pressure ranging from 10 MPa to 60 MPa.

[0041] In a comparable manner, the second gas chamber 40 comprises: - a second body 41 welded to the diffusion chamber 50, - a second gas outlet 44, - a second cover 42, closing the second gas outlet 44 and welded onto the second body 41, - a second support portion 43, supporting the second cover 42, - inflation gas G2, which may include an inert gas (argon, helium, etc.) and / or a reactive gas (oxygen, hydrogen, etc.) and stored under a pressure ranging from 10 MPa to 60 MPa.

[0042] The pyrotechnic opening device 20 comprises: - a first igniter 21, - a first igniter support 22, housing the first igniter 21 and fixed (here crimped but could be welded) on the diffusion chamber 50, - a first gas concentrator 23, covering a case of the first igniter 21 and also housed in the first igniter support 22, - a mobile support 24, formed by a cut-out plate arranged in the diffusion chamber 50, with a receiving face arranged directly in facing the first gas concentrator 23, a first support leg 241 arranged directly facing the first support portion 13, and a second support leg 242 arranged directly facing the second support portion 43.

[0043] The ventilation device 30 comprises: - a second igniter 31, - a second igniter support 32, housing the second igniter 31 and fixed (here crimped but could be welded) on the diffusion chamber 50, - a second gas concentrator 33, covering a case of the second igniter 31 and also housed in the second igniter support 32, - a control piston 34, attached to a frangible portion of the second gas concentrator 33, - the internal shutter 35, arranged in the diffusion chamber 50 and directly opposite the control piston 34, - an internal diffuser 36, fixed in the diffusion chamber 50 and supporting, according to a sliding connection, the internal shutter 35 and the movable support 24.

[0044] In particular, the internal diffuser 36: - forms a structure housed in the diffusion chamber 50, - provides a first sliding connection with the mobile support 24, with two guide tabs of the mobile support 24 housed in guide holes of the internal diffuser 36 visible in figure 2, - provides a second sliding connection with the internal shutter 35, - has a generally elongated shape, for example a cylinder shape with a square or rectangular section, - has a first end resting on the first gas chamber 10, and which surrounds the first gas outlet 14, so that inflation gases G1 leaving the first gas outlet 14 will be received first in the internal diffuser 36 before passing into the rest of the diffusion chamber 50, - has a second end resting on the second gas chamber 40, and which surrounds the second gas outlet 44, so that inflation gases G2 exiting the second gas outlet 44 will be received first in the internal diffuser 36 before passing into the rest of the diffusion chamber 50, - comprises at least one permanent gas passage 363 allowing inflation gases to pass from the interior space of the internal diffuser 36 to the intermediate space of the diffusion chamber included or defined between the internal diffuser 36 and a wall 51 of the diffusion chamber 50.

[0045] The diffusion chamber 50 therefore comprises the diffusion wall 51, formed with diffusion holes 52. The diffusion wall 51 is of generally cylindrical shape and receives the first gas chamber 10 at one of its ends and the second gas chamber 40 at the other of its ends.

[0046] Figure 3 represents a section of the gas generator of Figure 1 along a plane parallel to the section plane of Figure 2, to show in perspective the interior of the diffusion chamber 50.

[0047] We find figure 3: - the pyrotechnic opening device 20 with the mobile support 24 arranged under the first igniter support 22, - the ventilation device 30 with the second igniter support, the control piston and the internal shutter 35 supported by the internal diffuser 36, - the diffusion chamber 50 whose diffusion wall 51 contains in particular the internal diffuser 36, and whose diffusion holes 52 are arranged only on a lateral part, and not on the upper or lower part of the diffusion wall 51.

[0048] It can be noted in Figure 3 that the internal shutter 35 has a rider or U shape which surrounds the second support leg 242 of the movable support, and whose lateral legs are housed in holes 361 of the internal diffuser 36 to provide the second sliding connection. Thus, the movable support 24 can be moved without moving the internal shutter 35 in the case where the pyrotechnic opening device 20 is activated before the ventilation device 30.

[0049] Figure 4 shows a perspective view of the internal shutter 35 mounted in the diffusion chamber 50 of the gas generator of Figure 1. The internal shutter 35 therefore has a general jumper or U-shape, and comprises: - a bowl 351 which receives one end of the control piston 34, - two side legs 352, thinned in their lower part, - two holes 353 each passing through a side tab 352, - two curved parts 354, each arranged at a free end of a lateral tab 532, and curved towards the inside of the U.

[0050] Figure 5 shows two sectional views of the gas generator of Figure 1 along a sectional plane perpendicular to a longitudinal axis of the gas generator, to show the internal shutter before and after operation of the gas generator. In particular, the sectional plane passes through the axis of the second igniter support 32, to clearly show the ventilation device 30.

[0051] The left-hand sectional view of Figure 5 shows the gas generator before operation. The movable support 24 is in a first support position, as in Figures 2 and 3, and supports the first support portion 13 and the second support portion 43. The internal shutter 35 is in a retracted position, housed in the internal diffuser 36. It can be noted that the two curved parts 354 of the internal shutter 35 are supported on the internal diffuser 36 and prevent the internal shutter 35 from descending (the free ends of the internal shutter 35 are in abutment to ensure that it is held in the first position). Thus, the internal shutter 35 is held in the internal diffuser 36 without the possibility of movement, since on the upper side, the control piston 34 and the bowl 351 prevent any upward movement.

[0052] The right-hand sectional view of Figure 5 shows the gas generator after operation. The movable support 24 is in a second release position, in which the first support portion 13 and the second support portion 43 are no longer supported. As a result, the first seal 12 and the second seal 42 are broken and the inflation gas G1 and G2 respectively contained in the first gas chamber 10 and in the second gas chamber 40 can escape into the internal diffuser 36 then into the diffusion chamber 50, then into the safety cushion via the diffusion holes 52.

[0053] The internal shutter 35 is in a deployed position, partially housed in the internal diffuser 36. It can be noted that the second igniter 31 has been triggered, so that the second gas concentrator 33 has broken, the control piston 34 has been projected downwards to come into abutment on the internal diffuser 36, thus pushing the internal shutter 35 into the deployed position shown. It can be noted that: - an internal passage 362 is no longer obstructed by the bowl 351 of the internal shutter 35 which increases the passage section allowing the inflation gases (G1, G2) to pass from the gas chamber (10, 40) to the diffusion holes (52). In fact, the control piston 34 is not held in position and can be moved by the pressure of the gases, - the two curved parts 354 of the internal shutter 35 have passed through the holes 361 of the internal diffuser 36 under the impulse given by the control piston 34, despite the initial support visible in the left view of figure 5 (it can be provided that the passage through the holes 361 is done by elastically deforming the lateral tabs 352 of the U and / or the two curved parts 354. However, it can be provided that the passage through the holes 361 is done by plastically deforming the lateral tabs 352 of the U to move them outwards, so that the return of the internal shutter 35 to the first position is impossible as soon as the two curved parts 354 have passed through the holes 361), - the lower parts of the lateral legs 352 are bent outwards at the holes 353, under the action of the gas flow passing through the holes 361 of the internal diffuser and going towards the diffusion holes 52 (indeed, as can be seen in the right-hand view of Figure 5, the lower parts of the lateral legs 352 form an obstacle to the gas flow going towards the diffusion holes 52, and the deformation is facilitated by the holes 353).

[0054] The deformation of the lower parts of the lateral legs 352 outwards is preferably an irreversible plastic deformation, and it can be noted that this deformation provides the internal shutter 35 with a non-return function towards the retracted position of the left view. Indeed, the deformed parts of the lateral legs 352 would come into contact with or interfere with the side walls of the internal diffuser 36. Thus, the deployed position of the internal shutter 35 is indeed guaranteed, once it is reached since the internal shutter 35 can no longer rise to obstruct the internal passage 362 (it can be noted in Figure 5 the arrows showing the passage of gas through the internal passage 362).

[0055] In the operating sequence of the gas generator, the following steps can be foreseen: - the pyrotechnic opening device 20 is triggered alone, thus the first seal 12 and the second seal 42 are broken, the inflation gas G1 and G2 respectively contained in the first gas chamber 10 and in the second gas chamber 40 can escape into the internal diffuser 36 then into the diffusion chamber 50, then into the safety cushion via the diffusion holes 52, with a first flow rate, regulated by the available openings of the internal diffuser 36 when the internal shutter 35 is still in the retracted position, - the first flow of gas allows the airbag to begin to inflate and unfold, - once the safety cushion is unfolded or partially unfolded under the effect of the first moderate gas flow, the ventilation device 30 is then triggered, thus the internal shutter 35 passes (typically by translation) into the deployed position, releasing the holes 361 of the internal diffuser 36 as well as the internal passage 362, which makes it possible to increase the inflation gas flow, the lateral tabs 352 are deformed by this increased gas flow to block the internal shutter 35 in the deployed position, to obtain a second gas flow from the internal diffuser 36 to the diffusion chamber 50 and the diffusion holes 52, - the second gas flow (higher than the first gas flow) allows the airbag to be deployed and pressurized more quickly. In any case, the internal shutter 35 does not tear, does not lose any part and remains in one piece throughout operation (no lost debris). Industrial application

[0056] A gas generator according to the present invention, and its manufacture, are capable of industrial application.

[0057] It will be understood that various modifications and / or improvements obvious to those skilled in the art may be made to the various embodiments of the invention described in the present description without departing from the scope of the invention.

[0058] In particular, it can be noted that the holes 353 can be replaced by notches or thinned areas, the whole being to provide a zone of weakness which facilitates the deformation of the lateral legs 352.

Claims

CLAIMS

1. Gas generator comprising at least: - a gas chamber (10, 40), with a gas outlet (14, 44), - a cover (12, 42), closing the gas outlet (14, 44), - inflation gas (G1, G2), stored under pressure in the gas chamber (10, 40) with the gas outlet (14, 44) closed by the cover (12, 42), - a pyrotechnic opening device (20), arranged to open the gas outlet (14, 44), - a diffusion chamber (50), arranged to receive the inflation gas (G1, G2) once the gas outlet (14, 44) is opened by the pyrotechnic opening device (20) and comprising diffusion holes (52) for diffusing the inflation gas (G1, G2) towards the outside of the gas generator, - a ventilation device (30), with an internal shutter (35) arranged in the diffusion chamber (50) and movable between: • a first position, in which the internal shutter (35) defines a first passage surface between the gas outlet (14, 44) of the gas chamber (10, 40) and the diffusion holes (52), and • a second position, in which the internal shutter (35) defines a second passage surface between the gas outlet (14, 44) of the gas chamber (10, 40) and the diffusion holes (52) and greater than the first passage surface, characterized in that the gas generator comprises a non-return device arranged to retain the internal shutter (35) in the second position, comprising a deformable portion, preferably formed on the internal shutter (35), arranged to deform, preferably irreversibly, when the internal shutter (35) passes from the first position to the second position, and to maintain the internal shutter (35) in position in the second position.

2. A gas generator according to claim 1, comprising at least one locking portion, arranged to engage with said at least one locking portion. at least one deformable portion after deformation and blocking a movement of the internal shutter (35) from the second position to the first position.

3. Gas generator according to one of claims 1 to 2, wherein said at least one deformable portion comprises at least one actuating surface, arranged to be located in a gas path traveled by the inflation gas (G1, G2) going from the gas chamber (10, 40) towards the diffusion holes (52), when the internal shutter (35) is in the second position, so as to cause the deformation of the deformable part.

4. A gas generator according to claim 3, wherein the diffusion chamber (50) comprises at least one diffusion hole (52) arranged to impose the gas path opposite or to bypass said at least one actuating surface of the internal shutter (35) in the second position.

5. A gas generator according to any one of claims 1 to 4, wherein the internal shutter (35) comprises a zone of weakness arranged to concentrate or cause deformation of the deformable portion.

6. A gas generator according to claim 5 as dependent on claim 3 or 4, wherein the actuating surface of the internal shutter (35) in the second position is arranged cantilevered relative to the weak zone.

7. Gas generator according to one of claims 1 to 6, in which the ventilation device comprises: - a pyrotechnic ventilation actuator (31) arranged to move the internal shutter (35) from the first position to the second position, - a control piston (34), arranged between the pyrotechnic ventilation actuator and the internal shutter (35).

8. A gas generator according to claim 7, wherein when the internal shutter (35) is in the second position, the control piston (34) is movable relative to the internal shutter (35) and can release an internal passage (362) to allow inflation gas (G1, G2) to pass from the gas chamber (10, 40) to the diffusion holes (52).

9. Gas generator according to one of claims 1 to 8, wherein the ventilation device comprises an internal diffuser (36), arranged in the diffusion chamber (50) and supporting the internal shutter (35), at least in the first position.

10. Gas generator according to one of claims 1 to 9, wherein the internal shutter (35) comprises at least one anchoring portion, arranged to retain, preferably elastically, the internal shutter (35) in the first position.

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