PYROTECHNIC GAS GENERATOR

Abstract

The present disclosure relates to a gas generator comprising a housing, an igniter and a pyrotechnic charge via which gas for filling a gasbag can be provided, wherein the gas generator is free from stored pressurized gas in the idle state, characterized in that each possible diffusion path out of the internal chamber of the housing is sealed relative to the environment of the gas generator by means of a weld seam. The present disclosure also relates to a method for leak testing a pyrotechnic gas generator of this type, wherein, before the gas generator is welded against diffusion, a test amount of helium is introduced into the housing and, in a subsequent leak testing step, a measurement is carried out to determine whether helium is passing out of the housing.

Claims

1. A gas generator comprising: a housing, an igniter and a pyrotechnic charge via which gas for filling an airbag can be provided, wherein the gas generator is free from stored pressurized gas in its idle state, and wherein each possible diffusion path out of the interior of the housing is sealed relative to the environment of the gas generator by means of a weld seam.

2. The gas generator according to claim 1, wherein the housing of the gas generator is hermetically closed by being formed exclusively from components of metal welded to one another.

3. The gas generator according to claim 2, wherein the igniter is fastened outside the hermetically closed housing.

4. The gas generator according to claim 1 wherein the housing includes a tube and the igniter is mounted on an igniter carrier, the igniter carrier being welded to the tube, especially in a front-side opening of the tube.

5. The gas generator according to claim 4, wherein the housing includes a bottom plate in addition to the tube, and in that the bottom plate is welded to the tube.

6. The gas generator according to claim 1 wherein the housing has at least one discharge opening which is closed by a tamping, and in that the tamping is welded to the housing.

7. The gas generator according to claim 6, wherein the discharge opening is provided in the/a bottom plate of the housing.

8. The gas generator according to claim 6, wherein the/a bottom plate separates a combustion chamber of the gas generator from a filter chamber, and in that the tamping is welded, especially to the bottom plate, on the combustion chamber side or on the filter chamber side.

9. The gas generator according to claim 8, wherein the igniter is accommodated in the/an igniter carrier and a metallic tamping, especially in the form of a cap, is welded to the igniter carrier by the/a radially circumferential weld seam so as to hermetically seal the housing against the igniter.

10. The gas generator according to claim 9 wherein the housing is tubular and an opening acting as a discharge opening is provided in a wall of the tubular housing, wherein a/the tamping is welded to the tubular housing and closes the opening.

11. The gas generator according to claim 1, wherein the housing comprises a lower shell and an upper shell which are radially circumferentially connected to each other by the weld seam, wherein the igniter is mounted in an igniter carrier and the igniter carrier is received in an opening within the lower shell and is fastened there by means of the weld seam.

12. The gas generator according to claim 11 wherein the internal volume of the housing contains a test amount of helium.

13. The gas generator according to claim 1 wherein the housing includes a lower shell and an upper shell which are connected by a/the weld seam, the housing including at least one discharge opening which is closed by a tamping, wherein the tamping is welded to the housing at least in an area between the discharge opening and the weld seam.

14. The gas generator according to claim 13, wherein the tamping is radially circumferentially fastened on the housing, preferably on the upper shell of the housing, especially substantially in parallel to the weld seam.

15. The gas generator according to claim 13, wherein the tamping is welded to the housing annularly around the at least one discharge opening.

16. A method for leak testing a pyrotechnic gas generator according to claim 15, wherein, before the gas generator is welded against diffusion, a test amount of helium is introduced into the housing and, in a subsequent leak testing step, a measurement is carried out to determine whether helium escapes from the housing.

17. A method for manufacturing a housing assembly of a pyrotechnic gas generator comprising the steps of: a) Providing a lower shell and an upper shell having at least one discharge opening for a housing, especially an outer housing, of the gas generator, and providing a tamping; b) Welding the tamping to the upper shell, especially to the inner face thereof, in such a way that the tamping closes the at least one discharge opening; c) Welding the upper shell to the lower shell, especially by a radially circumferential weld seam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Hereinafter the present disclosure shall be described by way of different embodiments illustrated in the attached drawings, wherein:

[0033] FIG. 1 shows a schematic section of a gas generator according to a first embodiment of the present disclosure;

[0034] FIG. 2 shows a schematic section of a gas generator according to a second embodiment of the present disclosure;

[0035] FIG. 3 shows a configuration variant of the gas generator shown in FIG. 2;

[0036] FIG. 4 shows another configuration variant of the gas generator shown in FIG. 2;

[0037] FIG. 5a illustrates the gas generator with the pyrotechnic charge;

[0038] FIG. 5b illustrates the gas generator, igniter carrier, and the weld seam; and

[0039] FIG. 5c illustrates the gas generator, the vacuum chamber and the helium sensor.

DETAILED DESCRIPTION

[0040] FIG. 1 illustrates a pyrotechnic gas generator according to a first embodiment of the present disclosure which in this case has a toroidal structure. It includes a lower shell 10 which is connected in a diffusion-tight manner to an upper shell 14 by means of a circumferential weld seam 12, the lower shell 10 and the upper shell 14 forming at least a subarea of a housing (10, 14), especially an outer housing, of the gas generator. The weld seam 12 has been used per se already in the gas generators known from prior art, because it is required with respect to a sufficiently robust connection between the lower shell 10 and the upper shell 14.

[0041] In the lower shell 10 an igniter carrier 16 in which an igniter 18 is accommodated as a prefabricated part is inserted. An O-ring 19 is disposed between the igniter carrier 16 and the igniter 18.

[0042] An ignition sleeve 20 is attached to, especially slipped or pressed onto, the igniter carrier 16, the ignition sleeve surrounding a booster compartment 22 in which a pyrotechnic ignition mixture 24 (booster propellant) is accommodated.

[0043] The ignition sleeve 20 is provided with plural overflow outlets 26 through which a burn-off gas forming upon activation of the gas generator by igniting or by burning off the ignition mixture 24 in the booster compartment 22 can flow into a combustion chamber 28 of the gas generator in which a pyrotechnic charge 30 is accommodated.

[0044] The combustion chamber 28 in turn includes plural discharge openings 32 which in this case are provided in the outer wall of the upper shell 14. Through said discharge openings a burn-off gas forming upon burning off the pyrotechnic charge 30 flows out of the combustion chamber 28. The pyrotechnic charge 30 is a pyrotechnic propellant that may consist of a filling of individual propellant bodies, such as e.g. compressed propellant pellets or extruded bodies, but may also be in the form of a monolithic molded body or in the form of stringed disks or rings.

[0045] The entire gas generator is free from pre-stored pressurized gas in its idle state, viz. prior to activation. The interior of the gas generator merely has a pressure level that is prevailing in the form of an ambient pressure during manufacture of the gas generator. Consequently, the gas generator of the present disclosure is a purely pyrotechnic gas generator rather than a known hybrid gas generator which already in the idle state comprises pre-stored pressurized gas, usually at a pressure of several hundred bars.

[0046] In order to reliably seal both the ignition mixture 24 and the pyrotechnic charge 30 relative to the environment of the gas generator, several diffusion-tight weld seams are provided.

[0047] First of all, the igniter carrier 16 which is at least partly made from metal is welded to the lower shell 10 via a circumferential weld seam 34.

[0048] The interface between the igniter carrier 16 and the igniter 18 is sealed against the booster compartment 22 by means of a metallic tamping 38 which is hermetically connected to the igniter carrier 16 via a circumferential weld seam 40. The tamping 38 is in the form of a cap and thus has a closed cap bottom which merges directly into a radially circumferential cap sidewall ending with a cap opening opposed to the cap bottom. When mounting the gas generator 5, at first the O-ring 19 is inserted into the igniter carrier 16, then the igniter 18 is pressed onto the O-ring 19 and is retained in the same by means of a beaded extension of the igniter carrier 16. From FIG. 1 already said mounted state is evident with the beaded extension of the igniter carrier 16 which is pressed and, resp., beaded onto a trapezoidal area of the igniter 18. The cap-shaped tamping 38 is attached, after afore-described assembly, with its cap opening above or onto the pre-assembled igniter 18 in such way that the cap opening contacts the periphery of the igniter carrier 16 and can be connected there to the igniter carrier 16 by means of the circumferential weld seam 40. The cap bottom of the tamping 38 may contact, as illustrated in FIG. 1, the igniter 18, especially the front-side cap end thereof, or else may be at a certain distance therefrom. What is crucial is the fact that, in the afore-described connection of the tamping 38 to the igniter carrier 16 in accordance with the present disclosure, said two parts, i.e. the igniter carrier 16 and the tamping 38, are understood to be parts of the housing of the gas generator. Thus, the tamping 38 constitutes, as a component of the housing of the gas generator according to the present disclosure, also a hermetic seal and a delimitation of the gas generator from the environment thereof. As is evident from FIG. 1, the igniter 18 is thus positioned and, resp., fastened outside the housing of the gas generator.

[0049] Each of the overflow outlets 26 in the ignition sleeve 20 is closed by means of a tamping 42, e.g. a metal foil, which is glued radially circumferentially onto the inner sidewall of the ignition sleeve 20.

[0050] Finally, each of the discharge openings 32 is closed by means of a tamping 46 that is hermetically connected to the housing of the gas generator, concretely speaking here the upper shell 14, via a circumferential weld seam 48.

[0051] Each of the tampings 38, 46 is a metal foil, especially made from aluminum, copper or steel, which has a sufficient wall thickness, especially in a respective welding zone, to allow welding to the underlying carrier. The tamping 38 may also be in the form of an inherently stable metal cap.

[0052] FIG. 2 illustrates a second embodiment of a gas generator according to the present disclosure. For the component parts known from the first embodiment the same reference numerals are used and insofar the foregoing explanations are referred to.

[0053] The most essential difference between the first embodiment and the second embodiment consists in the fact that the gas generator of the second embodiment is a tubular gas generator. Accordingly, the housing 11 of the gas generator, especially a subarea of the outer housing of the gas generator, is a tube.

[0054] In the second embodiment, too, the igniter carrier 16 is inserted in the housing 11, especially in a front-side opening of the tubular housing 11, and is welded against diffusion via a circumferential weld seam 34.

[0055] Also, the tamping 38 is welded against diffusion to the igniter carrier 16 via a circumferential weld seam 40. In this case, the tamping 38 is equally in the form of an inherently stable cap, wherein, in contrast to FIG. 1, the cap bottom of the tamping 38 exhibits a clear distance from the front-side cap end of the igniter 18. Above the tamping 38 and partly surrounding the latter, an ignition sleeve (not shown) may further be positioned, similarly to FIG. 1, wherein, analogously to FIG. 1, a booster compartment 22 filled with a pyrotechnic ignition mixture (booster propellant) may form in a space between such ignition sleeve and the tamping 38. Such booster compartment comprising booster propellant is not mandatory, however, as the igniter 18, as shown in FIG. 2, can open (break or locally destroy) the tamping 38 after being activated to directly ignite the pyrotechnic charge 30.

[0056] In contrast to the first embodiment, in the second embodiment the discharge opening 32 does not lead out of the housing of the gas generator directly to the environment of the gas generator but is provided in a bottom plate or a combustion chamber bottom 50 which delimits the combustion chamber 28 comprising the pyrotechnic charge 30 toward a filter chamber 52. From the filter chamber 52 the gas or, resp., inflation gas that can be formed upon activation of the gas generator by burning off the pyrotechnic charge 30 then can flow through openings 54 into an airbag to be deployed (not shown). In the filter chamber 52 there may be located a filter (not shown), e.g. a body made from a metal reel or knitted metal fabric, which cools the gas or, resp., inflation gas and, resp., deposits slag therefrom.

[0057] The combustion chamber bottom 50 is welded against diffusion to the housing 11 by means of a circumferential weld seam 56. The tamping 46 is welded to the circumferential weld seam 48 on the combustion chamber bottom 50, namely on the inner face of the combustion chamber 28 in which the pyrotechnic charge 30 is disposed.

[0058] FIG. 3 illustrates a configuration variant which differs from the embodiment shown in FIG. 2 by the fact that the tamping 46 is welded to the combustion chamber bottom 50 on the outer face of the combustion chamber 28, i.e. on the side of the filter chamber 52.

[0059] FIG. 4 illustrates another configuration variant which differs from the embodiment shown in FIG. 2 and from the configuration variant shown in FIG. 3 by the fact that the tamping 46 closes the openings 54 on the inside, i.e. on the side of the filter chamber 52, in a diffusion-tight manner. For this purpose, the tamping 46 is connected to the housing 11 by means of the circumferential welding seams 48 and 49.

[0060] By way of FIGS. 5a, 5b, and 5c, the method according to the present disclosure shall be described hereinafter.

[0061] In FIG. 5a, the gas generator 5 is visible which is provided already with the pyrotechnic charge 30. Just before the last production step in manufacturing the gas generator 5 by which the interior of the gas generator 5 is sealed in a diffusion-tight manner relative to the environment of the gas generator 5, a test volume of helium is introduced into the interior of the gas generator 5. Subsequently, the housing of the gas generator 5 is hermetically sealed, indicated here by the welding of the igniter carrier 16 to the housing of the gas generator 5 via the weld seam 34. (see FIG. 5b) The igniter carrier 16 is indicated only schematically here and, when viewed per se, forms a hermetically tight unit and, thus, can especially include already the igniter 18 and especially the tamping 38 with an appropriate weld seam 40.

[0062] In a subsequent testing step, the gas generator 5 is introduced into a vacuum chamber 60 in which a helium sensor 62 senses whether helium escapes from the gas generator 5. (see FIG. 5c) Unless this is the case, it is safeguarded that the interior of the gas generator and consequently also the pyrotechnic charge located in the same as well as also the igniter are sealed in a diffusion-tight manner relative to the environment of the gas generator 5.