Overigniting protection device, second ignition stage, gas generator and airbag module

Abstract

The invention relates to an overigniting protection device (40) for a multi-stage gas generator (10), comprising a combustion chamber limiting element (34) for limiting a combustion chamber (30) of a second ignition stage (14) of the gas generator (10) as well as an overigniting protection element (38) which is arranged on a side of the combustion chamber limiting element (34) remote from the combustion chamber (30), wherein the overigniting protection element (38) covers the side of the combustion chamber limiting element (34) remote from the combustion chamber (30), wherein the overigniting protection element (38) is tightly connected to the combustion chamber limiting element (34) via a mounting portion (42) and wherein the overigniting protection element (38) is substantially plate-shaped or completely covers the side of the combustion chamber limiting element (34) remote from the combustion chamber (30). Furthermore, the invention relates to a second ignition stage (14) of a multi-stage gas generator, a gas generator (10) and an airbag module comprising a gas generator (10).

Claims

1. An overigniting protection device for a multi-stage gas generator, comprising: a combustion chamber limiting element for limiting a combustion chamber of a second ignition stage of the gas generator, wherein the combustion chamber limiting element comprises one or more openings through which gas flows when the second ignition stage is actuated, wherein the combustion chamber limiting element comprises an annular collar that projects from a surface of the chamber limiting element that is remote from the combustion chamber, the collar having an inward facing inner surface and an outward facing outer surface, wherein the outer surface is spaced inward of an outer peripheral edge of the combustion chamber limiting element; and an overigniting protection element comprising a substantially disk-shaped plate secured to the surface of the combustion chamber limiting element remote from the combustion chamber, wherein the overigniting protection element covers the one or more openings of the combustion chamber limiting element; wherein the collar is configured to receive the overigniting protection element so that an outer edge of the overigniting protection element extends along the inner surface of the collar and the disk-shaped plate surface of the overigniting protection element lies on the surface of the combustion chamber limiting element remote from the combustion chamber, the overigniting protection element being connected to the combustion chamber limiting element via a mounting portion.

2. The overigniting protection device according to claim 1, wherein the combustion chamber limiting element is a combustion chamber disk.

3. The overigniting protection device according to claim 1, wherein the overigniting protection element is materially mounted to the combustion chamber limiting element in an area of the mounting portion.

4. The overigniting protection device according to claim 1, wherein the overigniting protection element comprises a predetermined rupturing point or a predetermined breaking point via which gas can escape from the second ignition stage.

5. The overigniting protection device according to claim 1, wherein the mounting portion comprises a periphery of the overigniting protection element and is connected to the collar.

6. The overigniting protection device according to claim 1, wherein the outer peripheral edge of the combustion chamber limiting is configured to be connected to a wall of the combustion chamber, and wherein the outer surface of the collar is configured to be spaced from the wall of the combustion chamber when the combustion chamber limiting element is connected to the wall of the combustion chamber.

7. The overigniting protection device according to claim 1, wherein the overigniting protection element has a deforming portion which is deformable such that gas can escape from the second ignition stage via the deforming portion.

8. The overigniting protection device according to claim 7, wherein the deforming portion is arranged centrally on the overigniting protection element.

9. The overigniting protection device according to claim 7, wherein the mounting portion is surrounded by the deforming portion.

10. A gas generator comprising a first ignition stage, a second ignition stage and an overigniting protection device the overigniting protection device being configured in accordance with claim 1.

11. The gas generator according to claim 10, wherein at least the second ignition stage is a purely pyrotechnical ignition stage.

12. The gas generator according to claim 10, wherein the first ignition stage is an ignition stage comprising compressed gas so that the gas generator is a hybrid gas generator.

13. An airbag module comprising a gas generator, an airbag inflatable by the gas generator and a mounting unit for attaching the airbag module to a vehicle, wherein the gas generator is configured in accordance with claim 10.

14. The gas generator according to claim 10, wherein between the first ignition stage and the second ignition stage a diffusor including a diffusor chamber is provided.

15. The gas generator according to claim 14, wherein, after a case of release of the gas generator, the overigniting protection element extends at least partly in a direction of the diffusor chamber.

16. A second ignition stage of a multi-stage gas generator, comprising: a combustion chamber; a combustion chamber limiting element for limiting a combustion chamber of the second ignition stage of the gas generator, wherein the combustion chamber limiting element comprises one or more openings through which gas fluid flows when the second ignition stage is actuated, wherein the combustion chamber limiting element comprises an annular collar that projects from a surface of the chamber limiting element that is remote from the combustion chamber, the collar having an inward facing inner surface and an outward facing outer surface, wherein the outer surface is spaced inward of an outer peripheral edge of the combustion chamber limiting element; and an overigniting protection element comprising a substantially disk-shaped plate secured to the surface of the combustion chamber limiting element remote from the combustion chamber, wherein the overigniting protection element covers the one or more openings of the combustion chamber limiting element; wherein the collar is configured to receive the overigniting protection element so that an outer edge of the overigniting protection element extends along the inner surface of the collar and the disk-shaped plate surface of the overigniting protection element lies on the surface of the combustion chamber limiting element remote from the combustion chamber, the overigniting protection element being connected to the combustion chamber limiting element via a mounting portion.

17. The second ignition stage according to claim 16, wherein the overigniting protection element covers openings in the combustion chamber limiting element which are otherwise free from sealing elements.

18. The second ignition stage according to claim 16, wherein the combustion chamber limiting element is a combustion chamber disk.

19. The second ignition stage according to claim 16, wherein the overigniting protection element is welded to the combustion chamber limiting element in an area of the mounting portion.

20. The second ignition stage according to claim 16, wherein the overigniting protection element comprises a predetermined rupturing point or a predetermined breaking point via which gas can escape from the second ignition stage.

21. A gas generator comprising a first ignition stage, a second ignition stage and an overigniting protection device, the second ignition stage being configured in accordance with claim 16.

22. The overigniting protection device according to claim 16, wherein the mounting portion comprises a periphery of the overigniting protection element and is connected to the collar.

23. The overigniting protection device according to claim 16, wherein the outer peripheral edge of the combustion chamber limiting element is configured to be connected to a wall of the combustion chamber, and wherein the outer surface of the collar is configured to be spaced from the wall of the combustion chamber when the combustion chamber limiting element is connected to the wall of the combustion chamber.

24. The second ignition stage according to claim 16, wherein the overigniting protection element has a deforming portion which is deformable such that gas can escape from the second ignition stage via the deforming portion.

25. The second ignition stage according to claim 24, wherein the deforming portion is arranged centrally on the overigniting protection element.

26. The second ignition stage according to claim 24, wherein the mounting portion is surrounded by the deforming portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and characteristics of the invention will be evident from the following description and the drawings which are referred to, and wherein:

(2) FIG. 1 shows a perspective sectional view of a gas generator according to the invention in accordance with a first embodiment in the initial state,

(3) FIG. 2 shows the gas generator from FIG. 1 in the operating case,

(4) FIG. 3 shows a top view onto an overigniting protection element which is used in the gas generator of FIGS. 1 and 2,

(5) FIG. 4 shows a perspective sectional view of a gas generator according to the invention in accordance with a second embodiment in the initial state,

(6) FIG. 5 shows a top view onto an overigniting protection element which is employed in the gas generator according to FIG. 4,

(7) FIG. 6 shows a perspective view of the overigniting protection element according to FIG. 5,

(8) FIG. 7 shows a perspective sectional view of a gas generator according to the invention in accordance with a third embodiment in the initial stage,

(9) FIG. 8 shows a perspective view of an overigniting protection element which is employed in the gas generator according to FIG. 7,

(10) FIG. 9 shows a side view of the overigniting protection element according to FIG. 8,

(11) FIG. 10 shows a sectional view of the overigniting protection element according to FIG. 9 along the line A-A,

(12) FIG. 11 shows a perspective sectional view of a gas generator according to the invention in accordance with a fourth embodiment in the initial state,

(13) FIG. 12 shows the gas generator according to FIG. 11 in the operating case,

(14) FIG. 13 shows a top view onto an overigniting protection element which is employed in the gas generator of FIGS. 11 and 12,

(15) FIG. 14 shows a perspective sectional view of a gas generator according to the invention in accordance with a fifth embodiment in the initial state,

(16) FIG. 15 shows a top view onto an overigniting protection element which is employed in the gas generator according to FIG. 14,

(17) FIG. 16 shows a perspective sectional view of a gas generator according to the invention in accordance with a sixth embodiment in the initial state, and

(18) FIG. 17 shows a top view onto an overigniting protection element which is employed in the gas generator according to FIG. 16.

DESCRIPTION

(19) FIG. 1 illustrates a gas generator 10 comprising a first ignition stage 12 and a second ignition stage 14 each being coupled to a diffusor 16 which includes a diffusor chamber 17. The diffusor 16 is arranged in a longitudinal axial manner, viz. along the longitudinal axis L of the gas generator 10, between the two ignition stages 12, 14.

(20) Each of the two ignition stages 12, 14 comprises an igniter 18, 20 being electrically activatable, wherein they include appropriate contact pins.

(21) In the shown embodiment, the first ignition stage 12 comprises a first combustion chamber 22 in which a compressed gas 24 and a propellant 16 are disposed. The propellant 26 may comprise a bed of individual propellant bodies such as e.g. compressed propellant pellets or extruded bodies, but may as well be present in the form of a monolithic molded body or in the form of lined-up discs or rings.

(22) The first pressure chamber 22 is surrounded by a housing portion of the first ignition stage 12, wherein it is axially closed off by the igniter 18 and additionally via a burst membrane 28 provided in the transition area to the diffusor 16.

(23) The second ignition stage 14 comprises a second combustion chamber 30 in which merely a pyrotechnical propellant 32 is arranged, which means that no prestored compressed gas is accommodated in the second combustion chamber 30 in the idle state or in the non-activated initial state of the gas generator.

(24) In this respect, the second ignition stage 14 is a purely pyrotechnical ignition stage so that the gas generator 10 is in the form of a hybrid gas generator due to the first ignition stage 12 comprising compressed gas.

(25) Alternatively, also the first ignition stage 12 may be a purely pyrotechnical ignition stage so that the entire gas generator 10 is in the form of a purely pyrotechnical gas generator which does not comprise any prestored compressed gas in its idle state or non-activated initial state.

(26) The second combustion chamber 30 is limited toward the diffusor 16 by a combustion chamber limiting element 34, with the combustion chamber limiting element 34 being in the form of a combustion chamber disk.

(27) In the combustion chamber limiting element 34 plural openings 36 are provided which may be closed toward the second combustion chamber 32 via a sealing film or the like attached to the side of the combustion chamber limiting element 34 facing the combustion chamber 32, as is illustrated in FIG. 1.

(28) On the side of the combustion chamber limiting element 34 directed toward the diffusor 16, there is arranged an overigniting protection element 38 which completely covers the combustion chamber limiting element 34, viz. also completely covers the openings 36, and moreover is plate-shaped.

(29) The overigniting protection element 38 is illustrated in more detail in a top view in FIG. 3. It is evident herefrom that the overigniting protection element 38 is equally a disk having substantially the same outer diameter as the combustion chamber disk so that it covers the latter substantially completely.

(30) In addition, the overigniting protection element 38 is configured to be uninterrupted, i.e. without any openings, recesses or the like, so that it is particularly stable.

(31) The openings 36 toward the second combustion chamber 32 also may be open, viz. free from sealing elements, due to the overigniting protection element 32.

(32) If the first ignition stage 12 is activated, the burst disk 28 will rupture or will be opened as intended, resp., so that the compressed gas 24 and a corresponding burn-off gas of the propellant 26 can escape via the diffusor 16 as intended toward an airbag to be inflated (not shown). The overigniting protection element 38 ensures that neither hot particles nor gases may enter from the first ignition stage 12 via the opening 36 into the second combustion chamber 30 so that the propellant 32 of the second ignition stage 14 provided there will not be inadvertently ignited.

(33) In this respect, an efficient overigniting protection device 40 is provided.

(34) Rather, the burn-off gases of the first ignition stage 12 or, resp., an optional compressed gas are not only prevented from flowing into the second combustion chamber 30, but the pressure exerted by the burn-off gases and, resp., the compressed gas on the overigniting protection element 38 additionally improves the overigniting protection device 40, as the overigniting protection element 38 is pressed more strongly onto the combustion chamber limiting element 34 and additionally or even more efficiently seals the openings 36.

(35) FIG. 2 illustrates the gas generator 10 according to the first embodiment in the operating case, viz. upon or after release of the second ignition stage 14.

(36) A comparison of FIGS. 1 and 2 illustrates that the overigniting protection element 38 includes a mounting portion 42 by which the overigniting protection element 38 is tightly connected to the combustion chamber limiting element 34, hence even in the operating case, as is evident from FIG. 2.

(37) For example, the overigniting protection element 38 is welded to the combustion chamber limiting element 34 in the area of the mounting portion 42, thus ensuring that the overigniting protection element 38 will not detach from the combustion chamber limiting element 38 even in the case of activation of the second ignition stage 14.

(38) In the area of the openings 36 of the combustion chamber limiting element 34, the overigniting protection element 38 has a deforming portion 44, on the other hand, which is deformed into the diffusor chamber 17 of the diffusor 16 by activation of the second ignition stage 14 so that the forming inflation gas of the second ignition stage 14 can escape via the deforming portion 44 and the diffusor 16 so as to inflate an airbag not shown here.

(39) In the present case, the deforming portion 44 is a ring, as the overigniting protection element 38 deforms via its radially outer area, if the second ignition stage 14 is activated and gas flows or has flown from the second ignition stage through the openings 36 into the diffusor chamber 17.

(40) In the shown embodiment, the mounting portion 42, which is centrally arranged, consequently is radially surrounded by the deforming portion 44, thus causing the overigniting protection element 38 to extend, in the operating case, into the diffusor chamber 17 at its radially outer edge so as to enable the inflation gas to flow out.

(41) Accordingly, a certain space is formed between the upper side of the combustion chamber limiting element 34, i.e. the side of the combustion chamber limiting element 34 facing the diffusor 16, and the opposite side of the overigniting protection element 38. Said space may also be considered to be an overflow gap for the inflation gas.

(42) FIG. 4 shows a second embodiment of the gas generator 10 which differs from the first embodiment by the configuration of the overigniting protection element 38, as is also evident from FIGS. 5 and 6.

(43) In the shown embodiment, the overigniting protection element 38 includes, in addition to the first embodiment according to FIGS. 1 to 3, a radially outer peripheral edge 46 which is moreover collar-shaped. This results in an appropriately better overigniting protection device 40, if only the first ignition stage 12 has been activated. The collar-shaped edge 46 bears via its axially upright portion radially against the housing of the second ignition stage 14 and, resp., in a transition area of the second ignition stage 14 toward the diffusor 16 such that a larger bearing face or, resp., an optimized sealing bearing face is provided.

(44) In general, the overigniting protection element 38 according to this embodiment completely covers the combustion chamber limiting element 34, wherein it is moreover substantially plate-shaped.

(45) Upon release of the first ignition stage 12, the edge 46 then is pressed even more strongly against the respective housing.

(46) In FIG. 7, a third embodiment of the gas generator 10 according to the invention is shown which is different from the first two embodiments by the design of the overigniting protection element 38.

(47) As is visible from FIGS. 8 to 10, the overigniting protection element 38 includes a central recess 48 which at the same time constitutes the mounting portion 42. Starting from the central recess 48, a respective partially arc-shaped portion is formed radially outwardly so that between the openings 34 and the associated side of the overigniting protection element 38 a cavity 50 will form in which the inflation gas from the second ignition stage 14 can initially accumulate upon activation of the second ignition stage 14. This ensures a different inflation behavior or outflow behavior of the second ignition stage 14.

(48) Consequently, the overigniting protection element 38 according to this embodiment is not plate-shaped. However, it extends over the entire combustion chamber limiting element 34 so that the latter is completely covered, as the radially outer edge bears against the housing of the second ignition stage 14.

(49) The deforming portion 44 again is formed, just as in the second embodiment, by the radially outer area of the overigniting protection element 38 which upon ignition of the second ignition stage 14 deforms into or toward the diffusor chamber 17.

(50) In the embodiment of the gas generator 10 shown in FIG. 11, the overigniting protection device 40 comprises an overigniting protection element 38 that includes a mounting portion 42 arranged radially outside.

(51) In the shown embodiment, the combustion chamber limiting element 34 includes a collar 52 to which the overigniting protection element 38 may be coupled via its mounting portion 42 in the circumferential direction. Accordingly, the overigniting protection element 38 may be tightly connected, especially welded, to the collar 52 at its radially peripheral outer face or outer sidewall and/or may also be appropriately tightly connected, especially welded, to the combustion chamber limiting element 34 to be radially peripheral at a radially peripheral outer area of its end face which is directed to face the combustion chamber limiting element 34.

(52) The overigniting protection element 38 is plate-shaped, wherein at the same time it completely covers the side of the combustion chamber limiting element 34 remote from the second combustion chamber 30 which side is surrounded by the collar 52.

(53) Moreover, the overigniting protection element 38 comprises predetermined rupturing points or predetermined breaking points on its end face directed toward the diffusor space 17 at which points the overigniting protection element 38 ruptures or breaks in the case of release of the second ignition stage 14. This is illustrated in FIG. 12 in which the operating case is shown upon or after activation of the second ignition stage 14.

(54) It is visible therefrom that the area radially inwardly delimited by the predetermined rupturing points or predetermined breaking points 54 still remains coupled to the mounting portion 42, which is why this area can be considered to be a deforming portion 44 which extends into the diffusor chamber 17.

(55) The predetermined rupturing point or predetermined breaking points 54 are in the form of weakened zones having a smaller residual wall thickness rather than in the form of points open for material passage in the overigniting protection element 38. In the shown embodiment, a central area substantially in the form of a pitch circle is configured as a predetermined rupturing point or predetermined breaking point 54 which can also be understood to be a lining-up of plural predetermined rupturing points or predetermined breaking points 54 in the form of a C-shaped curve, as is especially evident from FIG. 13.

(56) The shape of the predetermined rupturing point or predetermined breaking point 54 and the material depth or residual wall thickness thereof helps to adjust the exhaust behavior of the gas from the second ignition stage 14 into the diffusor chamber 17 and, resp., further into the environment of the gas generator 10.

(57) In the embodiment of the gas generator 10 shown in FIG. 14, which substantially corresponds to that of FIG. 11, equally plural predetermined rupturing points or predetermined breaking points 54 spaced apart from each other are provided which define four separated deforming portions 44 extending into the diffusor chamber 17 in the case of release of the second ignition stage 14 so as to release the respective openings 36 in the combustion chamber limiting element 34 so that a fluid communication is present or is provided between the second combustion chamber 30 and the diffusor 16.

(58) As is evident from FIG. 15, the deforming portions are flap-shaped or substantially U-shaped deforming portions 44 of the overigniting protection element 38 which result in an appropriately defined exhaust behavior.

(59) FIG. 16 illustrates another embodiment of the gas generator 10 which is substantially configured just as that of FIGS. 11 and 14.

(60) The overigniting protection device 40 includes predetermined rupturing points or predetermined breaking points 54 arranged centrally in its overigniting protection element 38 which together have a substantially cross-shaped design and result in a substantially cross-shaped deforming portion 44, when the second ignition stage 14 is released.

(61) In the embodiments of FIGS. 11 to 17, the overigniting protection element 38 thus comprises one or more predetermined rupturing points or predetermined breaking points 54 being substantially centrally arranged, with the mounting portion 42 being provided radially outside. For example, the overigniting protection element 38 is tightly connected to the collar 52 of the combustion chamber limiting element 34 via the respective mounting portion 42.

(62) The gas generator 10 may be part of an airbag module which additionally comprises an airbag being inflated by the inflation gas of the gas generator 10.