Gas generator with gas supply for protective device

Abstract

The present invention provides a gas chamber (10) provided with an outlet opening (11); - sealing cap (20), - inflation gas (30) stored in a gas chamber (10); an opening piston (40) movable between an inactive position and an open position; an ignition device configured to move an opening piston (40), The gas generator is at least one retaining element of the opening piston (40) provided to retain the opening piston (40) in a non-operating position before activation of the ignition device; and / or - characterized in that it comprises at least one locking element for the opening piston (40), which is provided for locking the opening piston (40) in a non-operating or operating position after activation of the ignition device.

Description

[Technical Field]

[0001] The present invention relates generally to gas generators, and more particularly to vehicle (car, truck, motorcycle, etc.) integrated or personal protective devices, e.g. Motorcycle helmets (with built-in airbags), Cycling helmets (with built-in airbags), Lumbar support belt (with airbag), This relates to gas generators intended to be fitted to protective jackets for motorcyclists (which incorporate airbags), etc.

[0002] Typically, a gas generator according to the present invention may include a source of gas stored under pressure for rapidly supplying inflation gas to the protective device. [Background technology]

[0003] prior art For example, from US Patent No. 5,653,463 it is known to provide a gas generator with a gas supply sealed by a sealing cap and an opening piston provided to break the sealing cap and ensure that the gas supply can be emptied. However, this system may have drawbacks with regard to the reproducibility of opening and emptying, in particular due to the gas flow cross section after opening, which may depend on the position of the opening piston. Summary of the Invention

[0004] One object of the present invention is to overcome the above-mentioned drawbacks of the prior art, and in particular to first provide a gas generator with a pressurized gas chamber, and in particular to provide a gas generator with a gas chamber that is repeatable in operation with respect to opening the gas chamber and emptying the gas chamber after opening.

[0005] Therefore, for this reason, a first aspect of the present invention relates to a gas generator for a user protection device, the gas generator comprising: a gas chamber provided with an outlet opening; a sealing cap for sealing the discharge opening; an inflation gas stored under pressure in a gas chamber sealed by a sealing cap and provided to deploy the protection device after opening of the sealing cap; an opening piston arranged movably between an inoperative position and an open position, the movement of the opening piston from the inoperative position to the open position causing the opening of the sealing cap; an ignition device configured to move the opening piston from a non-operating position to an opening position; The gas generator is at least one retaining element of the opening piston, provided to retain the opening piston in a non-operating position at least prior to activation of the ignition device; and / or - at least one locking element of the opening piston, which is provided for locking the opening piston in a non-operating position or in an operating position located between the opening position and the non-operating position after activation of the ignition device.

[0006] According to the above embodiment, the gas generator provides a reproducible operation since the position of the opening piston is well controlled before and / or after opening of the sealing cap; - before opening, a retaining element of the opening piston holds, locks, blocks or maintains the opening piston in a non-operating position, and / or After release, the locking element of the release piston holds, locks, blocks or maintains the release piston in a non-operating or operating position (located between the release position and the non-operating position).

[0007] Thus, before opening, the non-operating position of the opening piston is always the same, which ensures that the movement always starts from the same position, regardless of the conditions of use (e.g., new or after a series of drops, shocks or vibrations). Similarly, after opening, the position of the opening piston is always the same (non-operating or operating position), which ensures a reproducible flow cross-section and flow of pressurized gas.

[0008] It should be noted that after opening, the position of the opening piston is not in the open position, but either in the inactive position or in the active position (located between the open and the inactive position), which means that when the sealing cap is opened, the opening piston retracts, leaving a large flow cross section and / or not blocking the discharge opening, thus emptying quickly and not being affected by the cross section and / or dimensions of the opening piston.

[0009] A gas generator can be defined by the following characteristics, either individually or in combination:

[0010] According to one embodiment, the opening piston in the inoperative position can be positioned at a predetermined distance from the sealing cap and / or the discharge opening. In particular, a distance of at least 1 mm, preferably at least 1.5 mm, and preferentially at least 2 mm can be provided between the opening piston in the inoperative position and the sealing cap (and / or the discharge opening). In this way, the opening piston can attain a minimum speed during operation of the gas generator before contacting or colliding with the sealing cap. The opening of the sealing cap is more repeatable and better controlled.

[0011] According to one embodiment, the opening piston in the inoperative position may be separated from the sealing cap by a space that is empty or devoid of other components, in this way the gas flow is not interrupted after opening has taken place.

[0012] According to one embodiment, the release piston may be free or not in contact with any return member, especially in its movement from the inoperative position to the open position. In other words, the gas generator may not include a return member that applies a return force to the release piston after it leaves the inoperative position, except for the inflation gas released from the gas chamber after the gas chamber is opened. In other words, the release piston may be subjected to a force to keep it in place by a solid member only when the release piston is in the inoperative position or the operative position.

[0013] According to one embodiment, the holding and / or locking elements of the opening piston provided for holding and locking the opening piston in a non-operating or operating position, respectively, before and after activating the ignition device, may be provided for ensuring elastic and / or reversible holding and / or locking.

[0014] According to one embodiment, a retaining element and / or a locking element of the opening piston may be provided to retain and lock the opening piston in the inoperative position or in the operative position only, respectively. In other words, the retaining element and / or the locking element of the opening piston may be: as soon as the opening piston leaves its inactive position, and Provision may be made to keep the opening piston free until it returns to the inoperative position or reaches the operative position.

[0015] In particular, a retaining and / or locking element for the release piston may be provided to keep the release piston free when it is in the open position and when it is near the open position (e.g., within a 4 millimeter range of movement before and after the open position).

[0016] According to one embodiment, the retaining element of the opening piston may be a mechanical retaining element and / or the locking element of the opening piston may be a mechanical locking element.

[0017] especially The retaining element of the opening piston may be a reversible, elastic, flexible mechanical retaining element, which is free from plastic deformation, free from shear and remains integral (the retaining element is free from material loss, the retaining element is free from delamination, the retaining element has no separable parts), and / or The locking element of the release piston may be a reversible, elastic, and flexible mechanical locking element that is free from plastic deformation, free from shear, and remains integral (the locking element is free from material loss, the retaining element is free from spalling, and the retaining element has no separable parts). The absence of plastic deformation and / or material spalling ensures that there are no loose particles that could be harmful to the movement of the release piston and / or the integrity of the safety device. In other words, the retaining element and / or locking element can be configured to perform the coupling and / or decoupling operation without plastic deformation and / or without stripping or scraping material from the parts in question. In particular, the movement of the release piston from the inoperative position to the open position during operation can be performed without plastic deformation and / or material spalling. Similarly, the retraction of the release piston from the open position to the operative or inoperative position during operation can be performed without plastic deformation and / or material spalling. This does not exclude the possibility of plastic deformation of the retaining element and / or locking element during the initial assembly of the gas generator (assembly of the release piston in the inoperative position).

[0018] According to one embodiment, the retaining element of the opening piston may be aligned with the locking element of the opening piston, may be identical to the locking element of the opening piston, or may have the same structure as the locking element of the opening piston. According to one embodiment, the retaining element of the opening piston may be the locking element of the opening piston. This makes it possible to limit the number of elements formed on the opening piston, optimizing costs and overall dimensions.

[0019] According to one embodiment, the gas generator may comprise at least one reference part adjacent to the opening piston, such as an igniter support, an igniter overmolded on said support, a containment case, or even a combustion chamber; The opening piston retaining element and / or the opening piston locking element may be at least one male protrusion, such as a rib, arranged on one of the opening piston and the reference piece; and / or at least one female counter feature, such as a groove, arranged on the other of the opening piston and the reference part.

[0020] According to one embodiment, the gas generator comprises: at least one reference part adjacent to the opening piston, such as an igniter support; a first retaining element and / or a first locking element formed by at least one male protrusion, such as a rib, arranged on one of the opening piston and the reference piece; a second retaining element and / or a second locking element formed by at least one female counter shape, such as a groove, arranged on the other of the opening piston and the reference piece. A coupling between the first retaining element of the opening piston and the second retaining element of the opening piston may be provided to hold the opening piston in a non-operating position. A coupling between the first locking element of the opening piston and the second locking element of the opening piston may be provided to lock the opening piston in a non-operating position or in an operating position.

[0021] In particular, when the gas generator is assembled, a resilient coupling, a reversible coupling, a resilient interlock, or a snap fit can be provided between the male protrusion and the female counter shape. In all cases, coupling and / or decoupling between the male protrusion and the female counter shape is possible without plastic deformation and / or material peeling. The absence of plastic deformation and / or material peeling ensures that there are no loose particles that could be harmful to the movement of the release piston and / or the integrity of the safety device. In other words, the male protrusion and the female counter shape can be provided to perform coupling and / or decoupling operations without plastic deformation and / or without peeling or scraping material from the parts. In particular, the movement of the release piston from a non-operating position to an open position during operation can be performed without plastic deformation and / or material peeling. Similarly, the retraction movement of the release piston from an open position to an operating or non-operating position during operation can be performed without plastic deformation and / or material peeling. This does not exclude the possibility of plastic deformation of the opening piston and / or adjacent parts during the initial assembly of the gas generator (assembly of the opening piston in the non-operating position), especially if the male projection and / or female counter shape are made of metal.

[0022] According to one embodiment, at least one of the male protrusion and the female counter shape may comprise a portion for coupling with the other of the male protrusion and the female counter shape, the coupling portion comprising a surface that forms an angle of at least 35°, preferably at least 20°, with respect to the direction of movement of the opening piston. In other words, at least one of the male protrusion and the female counter shape may comprise a chamfer or a beveled portion to facilitate coupling or decoupling.

[0023] According to one embodiment, the male protrusion and / or female counter feature may be: may be asymmetric along the direction of movement of the opening piston; and / or It may be continuous, discontinuous or segmented transversely to the direction of movement of the opening piston.

[0024] According to one embodiment, the opening piston may be provided with lateral guide walls arranged to guide the opening piston within the gas generator as it moves between the inoperative position and the open position, the lateral guide walls having a guide length in the direction of movement of the opening piston between the inoperative position and the open position that is smaller than a characteristic dimension (typically a diameter) of the opening piston in a direction transverse to the direction of movement of the opening piston between the inoperative position and the open position.

[0025] According to one embodiment, the side guide walls have a continuous outer surface, typically a cylindrical surface with a circular base. This ensures operation of the gas generator without a visible flame, in accordance with American Standard SAE-USCAR 24-2 (April 2013), paragraph 3.2.4 "Inflator Flaming." In other words, the side guide walls are devoid of any segments, bosses, or seals.

[0026] According to one embodiment, the opening piston may be cylindrical, for example with a circular cross section.

[0027] According to one embodiment, the opening piston may comprise a central recess and / or an internal bore, and the opening piston retaining element and / or the opening piston locking element may be arranged in the central recess and / or the internal bore, in other words, the opening piston retaining element and / or the opening piston locking element may be separate and / or distinct from the side wall, i.e., the opening piston retaining element and / or the opening piston locking element may be separate and / or distinct from the outer surface of the opening piston.

[0028] According to one embodiment, the guide wall has a radial clearance with the gas generator of less than or equal to 0.075 mm, advantageously less than or equal to 0.05 mm.

[0029] According to one embodiment, the guide wall may be devoid of an opening piston retaining element and / or an opening piston locking element and / or a sealing means, in this way the opening piston retaining element and / or the opening piston locking element have no effect on guiding the opening piston when it moves.

[0030] According to one embodiment, the ignition device may include an electric igniter, and the gas generator may include a containment case disposed at least partially around the electric igniter and / or between the opening piston and the electric igniter. Typically, the containment case is a separate component from the electric igniter, which allows for the use of standardized electric igniters in the gas generator.

[0031] According to one embodiment, the containment case may include a filtering portion disposed at least partially between the opening piston and the electric igniter. The filtering portion may typically be a wall having perforations and / or a screen.

[0032] According to one embodiment, the electric igniter comprises: pyrotechnic materials, a charge case containing a pyrotechnic material and adapted to burst after the pyrotechnic material has been ignited; and an electrically insulating cap, e.g., a plastic cap, covering the charge case. The charge case may be made of metal with a weakened area designed to form a petal shape during operation. Typically, pieces of the charge case and / or the electrically insulating cap may break off. The filtering section can stop this debris and allow for reliable movement of the opening piston (even if it moves back or retracts from the open position), which would otherwise be slowed or impeded by particles generated during operation of the electric igniter.

[0033] A second aspect of the present invention may relate to a protective device integrated into or for a user of a vehicle (such as a car, truck, or motorcycle) that includes at least one gas generator according to the first aspect of the present invention. Some examples include a motorcycle helmet (incorporating an airbag), a cycling helmet (incorporating an airbag), a lap belt (incorporating an airbag), a protective jacket for a motorcycle rider (incorporating an airbag), a safety harness (incorporating an airbag), or a ski vest (incorporating an airbag). In particular, the present invention may relate to a gas generator that does not produce a visible flame during operation (e.g., in accordance with U.S. Standard SAE-USCAR 24-2 April 2013, paragraph 3.2.4 "Inflator Flaming"). In other words, the present invention may relate to a generator in which pyrotechnic combustion generated by an electric igniter remains contained within the generator. [Brief explanation of the drawings]

[0034] Other characteristics and advantages of the present invention will become more apparent on reading the following detailed description of embodiments of the invention, which are given by way of example and not of limitation, and are illustrated by the accompanying drawings, in which: [Figure 1] FIG. 1 shows a cross-sectional view of a gas generator prior to operation. [Figure 2] FIG. 2 shows a detail of the cross section of FIG. [Figure 3] FIG. 3 shows the gas generator of FIG. 1 in operation. [Figure 4] FIG. 4 shows the gas generator of FIG. 1 after operation. DETAILED DESCRIPTION OF THE INVENTION

[0035] FIG. 1 shows a gas generator of a protection device for a user / occupant, the gas generator being a gas chamber 10 provided with an outlet opening 11; a sealing cap 20 sealing the discharge opening 11; inflation gas 30 stored under pressure in a gas chamber 10 sealed by a sealing cap 11 and provided to deploy the protection device after opening of the sealing cap 20; an opening piston 40 arranged in a non-operating position; In this example of FIG. 1, an ignition device is provided, which is an electric ignition igniter 50.

[0036] The gas chamber 10, in this example, is made up of several parts: a chamber body 12; a base 60 welded to the chamber body 12 and having a bottom with an exhaust opening 11; and a plug 14, which is also welded to the chamber body 12. The gas chamber 10 also includes, near the discharge opening 11, a regulating nozzle 13 with an opening having a cross section smaller than the cross section of the discharge opening 11.

[0037] The discharge opening is sealed or blocked by a sealing cap 20 , which may be a thin metal (stainless steel or Inconel) piece welded to the bottom of the base 60 .

[0038] The inflation gas 30 may be stored at a pressure between 20 MPa and 70 MPa and may include inert gases such as argon and helium, although other gases are also contemplated.

[0039] The opening piston 40 is a component movable between a non-operating position (FIG. 1 or 4) and an open position (shown in FIG. 3) and has a tip 41, so that movement of the opening piston 40 from the non-operating position to the open position triggers the opening of the sealing cap 20. For this purpose, the side or outer wall of the opening piston 40 may be provided to form a guide wall within the base 60, and a radial clearance of 0.02 mm to 0.1 mm may be provided (a radial clearance of 0.075 mm, advantageously 0.05 mm or less may also be provided). Such a clearance allows a guide length smaller than the diameter of the opening piston to provide a small axial footprint.

[0040] The opening piston 40 is preferably made from metal, although parts made from plastic or composite material parts can also be used.

[0041] The electric igniter 50 is attached to an igniter support 52 using a sealant 51 and is covered by a containment case 53 having a perforated wall disposed between the electric igniter 50 and the opening piston 40. The containment case 53 may be made generally of metal, although components made of plastic that can withstand the operation of the electric igniter 50 are also contemplated.

[0042] The electric igniter 50 typically includes: a resistive bridge; a pyrotechnic material that can be ignited when an ignition current passes through a resistance bridge; - a containment case made mainly of metal (although plastic parts may also be considered) containing the pyrotechnic material; and an electrically insulating cap covering the charge case. The electric igniter 50 is configured to move the opening piston 40 from the inoperative position to the open position by generating hot combustion gases that push the opening piston toward the right side in FIG. 1 .

[0043] The base 60 has a central bore that opens to the discharge opening and houses the opening piston 40, and an electric igniter 50 attached to an igniter support 52 that is crimped to the base 60. The base 60 is provided with a diffusion hole 61.

[0044] 2 shows detail II of FIG. 1 and shows the retaining element of the release piston 40 in the inoperative position and / or the locking element of the release piston 40 in the open position. As explained above, the release piston 40 occupies the inoperative position before operation of the gas generator. To ensure this inoperative position before operation, the release piston 40 is equipped with a groove 42 and the igniter support 52 is provided with a boss 521.

[0045] Also, please note the following: the opening piston 40 may also comprise an inlet chamfer 44 which forms an angle A1 with respect to the axial direction of the gas generator (or the direction of movement of the opening piston 40), the angle A1 being in the range of values ​​between 5° and 30°, preferably between 15° and 25°; the boss 521 and the groove 42 may be asymmetric; the boss 521 may have an inlet slope 522 that forms an angle A2 with respect to the axial direction of the gas generator (or the direction of movement of the opening piston 40), the angle A2 being in the range of values ​​between 5° and 30°, preferably between 15° and 25°; the groove 42 may have an outlet slope 44 which forms an angle A3 with respect to the axial direction of the gas generator (or the direction of movement of the opening piston 40), the angle A3 being in the range of values ​​between 25° and 45°, preferably between 30° and 45°; The opening piston 40 may be provided with an external constriction 43 which may extend facing or flush with the groove 42 to facilitate positioning and releasing of the piston from the inoperative position.

[0046] In Figure 2, the groove 42 receives the boss 521 when the release piston 40 is in the inoperative position of Figure 1. Because the inlet diameter of the central bore of the release piston 40 is smaller than the diameter of the boss 521, the release piston 40 cannot move freely, and the following may occur: the boss 521 forms a retaining element for the opening piston 40 for retaining the opening piston 40 in the inoperative position, or the groove 42 forms a retaining element for the opening piston 40 for retaining the opening piston 40 in the inoperative position, or To hold the opening piston 40 in the inoperative position, the boss 521 forms a first retaining element 71 of the opening piston 40 and the groove 42 forms a second retaining element 72 of the opening piston 40 .

[0047] However, the inlet diameter of the central bore of the opening piston 40 may be smaller than the diameter of the boss 521 by an interference value of less than 0.1 mm, or even less than 0.05 mm (diameter), so that the opening piston 40 can be released from the inactive position and enter the open position under thrust.

[0048] 3, the electric igniter 50 is ignited to generate combustion gases in the central bore of the opening piston 40, and the opening piston 40 moves to the right in FIG. 3 until it abuts the bottom of the base 60, causing the tip 41 to pierce the sealing cap 20. The adjusting nozzle 13 has a central boss to prevent interference with the tip 41 when the opening piston 40 is in the open position in FIG. 2.

[0049] It should be noted that the electric igniter 50 has thus generated sufficient combustion gases to create a thrust against the opening piston that is greater than the retention force exerted by the engagement of the boss 521 in the groove 42. It should be noted that the decoupling is preferably elastic and / or reversible and / or is performed without plastic deformation or material spalling on the parts, thereby allowing the retention element to be used as a locking element.

[0050] It should also be noted that the containment case 53, through its perforated distal wall, retains any debris that may have come loose from the electric igniter 50 (such as pieces of the plastic insulating cap, pieces of the metal case, or even pieces of pyrotechnic material) and also prevents the expansion of the charge case of the electric igniter 50 during operation from slowing down the movement of the release piston 40, so that the space between the containment case 53 and the release piston 40 or base 60 (particularly the central bore of the release piston 40 and the exposed portion of the inner bore of the base 60) remains relatively clean and / or free of solid particles that may affect the movement of the release piston 40.

[0051] As a result, the opening piston 40 slides by its side wall guide in the base 60, which guide continues to function after operation due to the filtering provided by the storage case, so that the opening piston can be guaranteed to retract after reaching the open position shown in Figure 2. This retraction of the opening piston 40 frees the discharge opening 11, making it possible to guarantee good reproducibility of the surface from one gas generator to the next for the passage of the gas stored in the gas chamber 10.

[0052] As shown in Figure 4, the opening piston 40 can therefore be retracted back to the inoperative position of Figure 1, as in the example shown in Figure 4. However, it may be possible to stop the retraction movement of the opening piston at an operative position located between the inoperative position of Figure 1 and the open position of Figure 3.

[0053] When the release piston returns to its inoperative position, it is locked in this inoperative position by the groove 42 which receives the boss 521. Similar to the situation in Fig. 2 before activation, when the release piston 40 is in the inoperative position in Fig. 4 after activation, the groove 42 receives the boss 521. Because the inlet diameter of the central bore of the release piston 40 is smaller than the diameter of the boss 521, the release piston 40 can no longer move freely and the following may occur: the boss 521 forms a locking element for the opening piston 40 to hold it in the inoperative position, or the groove 42 forms a locking element for the opening piston 40 to hold it in the inoperative position, or To hold the opening piston 40 in the inoperative position, the boss 521 forms a first locking element (identical to the first retaining element 71) of the opening piston 40, and the groove 42 forms a second locking element (identical to the second retaining element 72) of the opening piston 40.

[0054] As a result, the opening piston 40 is securely locked in the inoperative position after activation so that inflation gas can be released in a repeatable manner toward the diffusion holes 61 in the base 60, as shown by the arrows in FIG.

[0055] In general, the following points are worth noting: - Holding the opening piston 40 in a non-operating position before operation ensures that movement towards the opening position always starts from the same position, thus improving reproducibility. It is also worth noting that the filtering or shielding function provided by the containment case 53 ensures repeatable and reliable retraction of the opening piston, and that less debris can be expelled from the gas generator without the need for seals (which would otherwise be detrimental to the free movement of the opening piston 40). The retraction of the opening piston 40 after the opening of the sealing cap provides a repeatable flow of gas from the gas chamber 10 always through the same flow cross section. The control nozzle 13 can be easily adjusted to set the flow rate required for one application or another without changing the opening mechanism. Locking the opening piston 40 in the retracted, activated or non-activated position further contributes to the repeatability of operation by eliminating any risk of bouncing, vibrating or reciprocating movement of the opening piston 40 during complete emptying of the gas chamber 10.

[0056] In the example of FIG. 4, the one or more locking elements are identical to the one or more retaining elements, although separate elements may also be used.

[0057] 2 shows grooves 42 and bosses 521, but flexible tabs, parts adapted to be clamped together, tongues, i.e., any type of resilient, reversible holding and / or locking means, preferably one that does not involve plastic or irreversible deformation, or separation or breakage of parts, especially during operation, may also be provided. Alternatively, the holding and / or locking elements may extend over 360°, or may be segmented or point-based. [Industrial Applicability]

[0058] The gas generator and the manufacture thereof according to the present invention are industrially applicable.

[0059] It will be understood that various modifications and / or improvements apparent to those skilled in the art can be made to the various embodiments of the invention described herein without departing from the scope of the invention.

Claims

1. 1. A gas generator for a user protection device, comprising: a gas chamber (10) provided with an outlet opening (11); - a sealing cap (20) that closes said discharge opening (11); - inflation gas (30) stored under pressure in the gas chamber (10) sealed by the sealing cap (20) and provided to deploy the protection device after opening of the sealing cap (20); an opening piston (40) arranged movably between an inoperative position and an open position, the movement of said opening piston (40) from said inoperative position to said open position causing the opening of said sealing cap (20); an ignition device configured to move said opening piston (40) from said inoperative position to said opening position; Equipped with The gas generator comprises: at least one retaining element of the opening piston (40) provided for retaining the opening piston (40) in the inoperative position at least before activation of the ignition device; and / or at least one locking element of the opening piston (40) provided for locking the opening piston (40) in the inoperative position or in an operative position located between the opening position and the inoperative position after activation of the ignition device; A gas generator comprising:

2. 2. The gas generator according to claim 1, wherein the retaining element for the opening piston (40) is a mechanical retaining element and / or the locking element for the opening piston (40) is a mechanical locking element.

3. at least one reference component, such as an igniter support (52), adjacent to said opening piston (40); The holding element of the opening piston (40) and / or the locking element of the opening piston (40) may be at least one male protrusion, such as a rib, arranged on one of said opening piston (40) and said reference piece, and / or - at least one female counter feature, such as a groove (43), arranged on the other of said opening piston (40) and said reference piece; 3. The gas generator according to claim 1 or 2, comprising:

4. 4. The gas generator according to claim 3, wherein at least one of the male protrusion and the female counter shape comprises a portion for coupling with the other of the male protrusion and the female counter shape, the coupling portion comprising a surface that forms an angle of at least 35°, preferably at least 20°, with respect to the direction of movement of the opening piston (40).

5. The male protrusion and / or the female counter shape may be: - asymmetric along the direction of movement of said opening piston (40), and / or - continuous, discontinuous or segmented in the direction transverse to the direction of movement of the opening piston (40); 5. A gas generator according to claim 3 or 4.

6. 6. The gas generator according to claim 1, wherein the opening piston (40) comprises lateral guide walls arranged to guide the opening piston (40) when it moves between the inoperative position and the open position within the gas generator, the lateral guide walls having a guide length in the direction of movement of the opening piston (40) between the inoperative position and the open position that is smaller than a characteristic dimension of the opening piston (40) in a direction transverse to the direction of movement of the opening piston (40) between the inoperative position and the open position.

7. 7. The gas generator according to claim 6, wherein the guide wall has a radial clearance with the gas generator of less than 0.075 mm, advantageously less than 0.05 mm.

8. 8. Gas generator according to claim 6 or 7, characterized in that the guide wall does not have a retaining element for the opening piston (40) and / or a locking element for the opening piston (40) and / or a sealing means.

9. 9. The gas generator according to claim 1, wherein the ignition device comprises an electric igniter (50), and the gas generator comprises a containment case (53) arranged at least partially around the electric igniter (50) and / or between the opening piston (40) and the electric igniter (50).

10. 10. The gas generator of claim 9, wherein the containment case (53) comprises a filtering portion at least partially disposed between the opening piston (40) and the electric igniter (50).

11. The electric ignition type igniter (50) is - pyrotechnic materials, a charge case containing said pyrotechnic material and adapted to burst after said pyrotechnic material has been ignited; an electrically insulating cap, for example a plastic cap, covering the charge case; 11. The gas generator according to claim 9 or 10, comprising:

12. A user protection device comprising at least one gas generator according to any one of claims 1 to 11.

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