Burst membrane for a gas generator with a through-hole

Abstract

Burst membrane (14) for a gas generator (10) for a vehicle safety system with at least one predetermined breaking contour (24) which is destructive upon activation of the gas generator (10), wherein a shock wave can be generated, characterized in that the predetermined breaking contour (24) has a through-opening (25) at all endpoints (27) and the predetermined breaking contour (24) is designed in a double-C or H-shape.

Description

[0001] The invention relates to a bursting membrane for a gas generator for a vehicle safety system, comprising at least one predetermined breaking contour that can be destroyed upon activation of the gas generator, wherein a shock wave can be generated and the predetermined breaking contour has a through-opening at at least one end point. The invention also relates to a gas generator, a gas bag module, and a vehicle safety system.

[0002] Gas generators, for example, supply gas for filling an airbag or powering a seatbelt tensioner. In both cases, it is important that the generated gas is available quickly. According to a known technique, this gas is generated at least partially from a pressurized gas stored in the gas generator's housing. A membrane seals the housing, in which the pressurized gas is stored, in a fluid-tight manner. The housing is opened by a pyrotechnic igniter that destroys the membrane upon / after activation of the gas generator, allowing the gas to escape.

[0003] Such a gas generator is known, for example, from published patent application US 2005 / 0206145 A1. This gas generator has a combustion chamber containing an igniter that can be activated under pressure. Furthermore, a storage chamber filled with compressed gas is provided, which, when the gas generator is not activated, is pressure-tightly sealed from the combustion chamber by a rupturable membrane. The rupturable membrane has a weakened zone that can be destroyed upon activation of the gas generator, in order to establish a fluid connection between the combustion chamber and the compressed gas-filled storage chamber upon / after activation of the gas generator.

[0004] DE 10 2011 009 309 A1 discloses a bursting membrane for a gas generator for a vehicle safety system, comprising at least one predetermined breaking contour that can be destroyed upon activation of the gas generator, generating a shock wave. An overflow opening is created by channels between the bursting membrane and a housing wall.

[0005] The document DE 39 01 586 A1 discloses a bursting disc of a safety pressure relief device, wherein the bursting membrane has overflow openings and can be designed particularly easily with regard to a desired bursting pressure.

[0006] From the document US 6 382 668 B1 a bursting membrane for a gas generator for a vehicle safety system is known, comprising at least one predetermined breaking contour which can be destroyed upon activation of the gas generator, wherein a shock wave can be generated, and the predetermined breaking contour has a through opening at at least one end point.

[0007] The object of the present invention is to further develop such a membrane. Furthermore, the invention also aims to provide a gas generator, a gas bag module, and a vehicle safety system with such a membrane.

[0008] According to the invention, this object is achieved with regard to the further developed bursting membrane by the subject matter of patent claim 1.

[0009] The invention is therefore based on the idea of ​​specifying a bursting membrane for a gas generator, a vehicle safety system, with at least one predetermined breaking contour which can be destroyed upon activation of the gas generator, whereby a shock wave can be generated, whereby the predetermined breaking contour has a through opening at all end points and the predetermined breaking contour is double-C-shaped or H-shaped.

[0010] A predetermined rupture contour has at least two end points, whereby the end points describe the end regions of linear or curved geometries. The predetermined rupture contour has a through opening at all end points. The advantage of the bursting membrane according to the invention is that, thanks to the through opening(s) in the bursting disc, a pressure-tight design of the bursting disc is unnecessary. This means that the bursting disc does not have to be laboriously attached to the housing of the gas generator in a pressure-tight manner, since it does not represent a pressure-tight closure for a pressurized gas within the gas generator. In addition, the through opening(s) offer

[0011] Through-openings in the bursting membrane make it possible to store a larger quantity of pressurised gas in a gas generator, since in addition to a pure pressure storage chamber located on one side of the bursting membrane, further space can be used for additional storage of pressurised gas on the other (opposite) side of the bursting membrane, for example in a combustion chamber containing pyrotechnic propellant.

[0012] The predetermined breaking contour is destroyed upon activation of the gas generator, or the bursting membrane ruptures along the predetermined breaking contour, generating a shock wave, as described in more detail below. To enable uniform destruction and generation of a shock wave, the predetermined breaking contour is designed in a double C-shape or H-shape.

[0013] The bursting membrane can have a cap-shaped or semicircular outer contour. The outer contour of the bursting membrane is the contour of the outer surface of the bursting membrane. In other words, the bursting membrane can have the shape of a cap with a hemispherical lid and an adjoining truncated cone-shaped or cylindrical peripheral wall. It is also possible for the bursting membrane to have a truncated cone-shaped or cylindrical peripheral wall, with the lid merely having a flat curvature. A flat lid is also possible.

[0014] The through-opening of the predetermined breaking contour can be circular. The through-opening has at least one opening width, in particular with a diameter, of 0.5 - 3.00 mm, in particular of 1.0 - 2.5 mm, in particular of 1.2 - 2.0 mm, in particular of 1.4 mm. If the through-opening is circular, the opening width can be referred to as the diameter.

[0015] Preferably, the outer surface of the bursting membrane has a uniform material thickness. In other words, the outer surface of the bursting membrane can have the same material thickness throughout or across the entire outer surface.

[0016] The predetermined breaking contour of the bursting membrane is preferably incorporated into the cover, which can be hemispherical, curved, or flat, of the outer surface of the bursting membrane. The predetermined breaking contour can be formed by embossing, milling, notching, or laser ablation. The predetermined breaking contour forms a weakening zone of the bursting membrane, so that the types of possible predetermined breaking contour designs outlined above represent good methods for easily and precisely adjusting a well-reproducible opening force and thus the bursting pressure, for example, by adjusting the number and depth of the various areas of embossing, milling, notching, or laser ablation.

[0017] The embossings or millings or notches or laser ablations preferably have a smaller material thickness than that of the lateral surface and do not penetrate this lateral surface.

[0018] With regard to a gas generator, the problem is solved by the features of patent claim 6.

[0019] Such a gas generator according to the invention has a bursting membrane according to the invention. The gas generator preferably comprises at least one combustion chamber filled with propellant and gas and having an outflow end. Furthermore, the gas generator comprises at least one igniter unit by which the propellant can be ignited. The igniter unit can be in the form of a pyrotechnic igniter, for example. The bursting membrane is preferably connected to an outer housing of the gas generator in a material-to-material or form-fitting manner. A material-to-material connection of the bursting membrane to the outer housing of the gas generator can be achieved, for example, by gluing and / or welding. A form-fitting connection of the bursting membrane to the outer housing of the gas generator is achieved, for example, by clamping or a corresponding clamp connection.

[0020] In the inactivated or non-activated state of the gas generator, i.e., in an unignited state, the bursting membrane separates the combustion chamber from a gas storage chamber. At least one through-opening of the predetermined rupture contour is designed as a fluid connection or flow connection between the combustion chamber and the gas storage chamber.

[0021] In summary, it can be stated that the gas generator comprises at least one combustion chamber in which a propellant, in particular solid propellant, which burns with the evolution of gas is accommodated. Furthermore, the gas generator comprises a storage chamber filled with gas, in particular compressed gas, and an igniter and a bursting membrane arranged between the combustion chamber and the storage chamber. There is at least one flow or fluid connection between the storage chamber and the combustion chamber. The bursting membrane has an additional predetermined breaking contour which can be destroyed when the gas generator is activated, whereby a shock wave can be generated. In detail, this means that the combustion of the propellant in the combustion chamber builds up a higher pressure than that prevailing in the gas-filled storage chamber. If the bursting pressure of the bursting membrane is reached or exceeded.exceeded, it opens, i.e. tears it open along the predetermined breaking contour, in order to enable an abrupt, relatively large-area pressure equalization between the pressure built up in the combustion chamber and the gas pressure in the pre-filled storage chamber. The opening of the bursting membrane or this abrupt pressure equalization creates a shock wave which travels at high speed along the longitudinal axis of the gas generator through the storage chamber in order to open a closure means, preferably a bursting disc, at one end of the storage chamber by means of local pressure increase. Inflation gas, in particular a mixture of the gas generated by the combustion of the propellant and the gas which is stored under pre-tension in the storage chamber, can then leave the gas generator via a diffuser in order to flow, for example, into an inflatable airbag.Due to the bursting of the bursting membrane when the gas generator is activated, an enlarged outlet opening can be created, allowing gas generated by the combustion of the propellant to flow more quickly into the storage chamber and through it out of the gas generator. Due to the generation of the shock wave, the closure device or bursting disc of the storage chamber can be opened more quickly than with gas generators that do not generate a shock wave when in use.

[0022] It is also possible to arrange a combustion chamber screen, preferably in line with the predetermined breaking contour of the bursting membrane and the bursting membrane. A combustion chamber screen can retain any burn-up particles that may be generated by the combustion of the propellant, especially the solid propellant.

[0023] Furthermore, it is advantageous to arrange the igniter, the bursting membrane, the combustion chamber screen, the predetermined breaking contour of the bursting membrane, and / or the bursting disc along the gas generator's longitudinal axis. Such an arrangement achieves optimal ignition of the propellant, particularly the solid propellant, and / or the compressed gas, as well as effective formation and propagation of the shock wave, thus destroying the bursting membrane and / or bursting disc. This ultimately ensures safe and rapid operation of the gas generator. For example, molded bodies pressed into tablet form can be used as solid propellants.

[0024] The through-opening has at least an opening width, in particular a diameter, of 0.5 - 3.00 mm, in particular of 1.4 mm. The through-opening has at least an opening width such that, for the production of the gas generator, when the generator is filled with gas, pressure equalization between the gas storage chamber and the combustion chamber takes place in less than 15 seconds, in particular in less than 10 seconds, in particular in less than 8 seconds, in particular in less than 5 seconds. In other words, the opening width or the diameter of the through-opening is at least large enough that, during the production of the gas generator, after the construction of the combustion chamber, rapid pressure equalization from the gas storage chamber to the combustion chamber is achieved, wherein the cycle time is in particular 5 seconds.

[0025] Furthermore, the through-opening, in particular the opening width, can be designed such that, upon activation of the gas generator, a pressure increase occurs in the combustion chamber to cause the bursting membrane to open. In other words, the opening width or diameter of a through-opening must not be too large, so that the formation of the shock wave or the functional opening of the bursting membrane is not impaired. Despite the presence of the through-opening, a significant pressure increase must be possible in the combustion chamber so that the bursting membrane can be destroyed or opened as required.

[0026] In summary, the opening width or diameter of a through-hole must be designed between two opposing parameters: the necessary pressure increase in the combustion chamber and the pressure equalization between the gas storage chamber and the combustion chamber.

[0027] Furthermore, it is possible for an additional propellant to be stored within the gas storage chamber of the gas generator for the subsequent supply of hot gas. In other words, in addition to the propellant located in the combustion chamber of the gas generator, an additional propellant can be stored in the gas storage chamber. This propellant is ignitable after the bursting membrane opens and / or after the shock wave is formed, and can thus serve as an additional source of hot gas for supporting or subsequent filling of an inflatable airbag.

[0028] The additional fuel in the gas storage chamber may be present in loose and / or packed form, whereby the chemical composition and / or geometric shape of the additional fuel may differ from the fuel in the combustion chamber.

[0029] In particular, the additional fuel may be a fluid, in particular a gaseous, flammable fuel.

[0030] With regard to a gas bag module, the object is achieved by the features of claim 12. Accordingly, a gas bag module has a gas generator according to the invention.

[0031] With regard to a vehicle safety system, the object is achieved by the features of claim 13, according to which the vehicle safety system comprises an airbag module according to the invention. The vehicle safety system can be a vehicle occupant restraint system, for example, an airbag and / or a seat belt.

[0032] Further advantages of the invention will become apparent from the following description with reference to the accompanying drawings, in which: Fig. 1: a schematic cross-section through a gas generator according to the invention; Fig. 2: a perspective view of a bursting membrane with a predetermined breaking contour not designed according to the invention; Fig. 3: View of a predetermined breaking contour not designed according to the invention and Fig. 4 - 5: Views of predetermined breaking contours designed according to the invention.

[0033] Fig. 1 shows a gas generator 10 with an elongated, cylindrical housing 11, which forms the outer casing of the gas generator 10. An igniter 12 is provided at the first axial end of the housing 11, and a diffuser 13 is provided at the second axial end of the housing 11. The diffuser 13 is provided with outlet openings and adjoins the housing 11 in the axial direction, directing the escaping gas to a location of use, for example, to an inflatable gas bag (not shown).

[0034] A bursting membrane 14 divides the housing 11 into a combustion chamber 15 and a gas storage chamber 16. In the direction of the gas generator's longitudinal axis L, the combustion chamber 15 adjoins the igniter 12 in the housing 11. A predetermined amount of propellant (not shown) is located in the combustion chamber 15. This propellant can be in tablet form, for example.

[0035] In the direction of the gas generator's longitudinal axis L, the combustion chamber 15 is adjoined by the storage chamber 16. The storage chamber 16 is filled with gas, in particular cold gas (for example argon, helium or a suitable gas mixture). The bursting membrane 14 does not seal the gas storage chamber 16 off from the combustion chamber 15 in a pressure-tight manner, so that a flow connection exists between the two chambers 15 and 16. Due to this, during manufacture of the gas generator 10, when the gas storage chamber 16 is filled with gas, in particular cold gas, this gas also flows into the combustion chamber 15 via through openings in the bursting membrane 14 until pressure equalization between the two chambers 15 and 16 is achieved. Pressure equalization is preferably achieved in approximately 5 seconds. Before the gas generator 10 is activated, compressed gas is therefore present in both the gas storage chamber 16 and the combustion chamber 15, in reciprocal flow connection.

[0036] In the variant of the gas generator according to the invention shown here, the bursting membrane 14 according to the invention is pressed or clamped into the housing 11. However, the bursting membrane 14 can also be integrally connected to the housing 11.

[0037] The housing 11 has an annular circumferential notch 17 in the area where the bursting membrane 14 is secured in the housing 11. The outer surface of the bursting membrane 14 rests against the inside of the notch 17, so that the bursting membrane 14 is supported in the area of ​​the notch 17 and the bursting membrane 14 is thus additionally secured. In the event that the bursting membrane 14 is integrally bonded to the housing 11, the annular circumferential notch 17 can be omitted, whereby the housing can also have a continuous cylindrical shape in this area.

[0038] For example, in order to retain combustion particles, a combustion chamber sieve 18 can be inserted in front of the bursting membrane 14 in the combustion chamber 15.

[0039] Upon activation of the gas generator 10, the igniter 12 receives an electrical signal to activate it or to ignite the fuel. The ignition of the fuel, particularly solid fuel, in the combustion chamber 15 leads to a sudden increase in pressure in the combustion chamber 15, so that the Fig. 1, the predetermined breaking contour of the bursting membrane 14 (not shown) is destroyed or opened, so that a large opening in relation to the diameter of the housing 11 suddenly appears in the bursting membrane 14. This abrupt opening generates a shock wave that enters the gas storage chamber 16 and passes through it to the bursting disc 19, as already described above.

[0040] In the illustrated embodiment of a gas generator 10 according to the invention, the igniter 12, the combustion chamber screen 18, and the bursting membrane 14 are located on the gas generator's longitudinal axis L. This ensures optimal ignition of the propellant in the combustion chamber 15, thus ensuring effective formation and propagation of the shock wave. The gas generator shown here can be used, for example, to inflate a gas bag, in particular an airbag, and / or in a belt tensioner system.

[0041] Furthermore, it is possible for an additional fuel (not shown) to be accommodated in the gas generator (10) within the gas storage chamber (16) for the subsequent supply of hot gas.

[0042] In Fig. Figure 2 shows a possible embodiment of a bursting membrane 14. The bursting membrane 14 essentially has the shape of a cap with a flat lid 23. The outer contour 26 of the bursting membrane 14 is initially formed by a cylindrical peripheral wall 20 and a bevel 21. Adjoining the bevel 21 is another partial segment of the outer contour, or rather, the lateral surface, or the entire peripheral wall. This is the frustoconical peripheral wall 22, to which the flat lid 23 is connected.

[0043] As in Fig. As shown in Figure 1, the combustion chamber screen 18 lies completely within the bursting membrane 14, with the combustion chamber screen 18 resting against the inside of the bevel 21. The curvatures of the bursting membrane 14 and the combustion chamber screen 18 are formed in opposite directions to each other.

[0044] A predetermined breaking contour 24 is incorporated in the cover 23 of the bursting membrane 14. The predetermined breaking contour 24 is designed according to the Fig. 2 C-shaped in the form of a predetermined breaking contour 24 not according to the invention. Furthermore, two through-openings 25 are provided there, wherein the through-openings are formed at the end points 27 of the predetermined breaking contour 24. The end points 27 refer to the regions of a geometric shape, line, or arcuate contour. The through-openings 25 prevent bursting membrane parts from separating when the bursting membrane 14 opens or tears open. In other words, the through-openings 25 have a hinge or tear-stopping function. As already mentioned, the through-openings 25 allow the passage of cold gas when filling the gas storage chamber 16 during the manufacture of a gas generator. In the present case, the through openings 25 are circular and have a diameter of 0.5 - 3.0 mm, in particular of 1.0 - 2.5 mm, in particular of 1.2 - 2.0 mm, in particular of 1.4 mm.

[0045] The cross section of the through-opening 25 is small enough to allow, in the case of operation, i.e. when the gas generator is activated, a pressure increase in the combustion chamber 15 until the bursting membrane 14 bursts as intended.

[0046] The predetermined breaking contour is preferably formed by embossing, milling, notching, or laser ablation, whereby the residual wall thickness in the area of ​​the embossing, for example, has a lower material thickness than the outer surface or outer contour 26, and whereby the embossing does not break through in the inactivated state of the gas generator. The bursting pressure of the predetermined breaking contour 24 can be adjusted very precisely and with high reproducibility by adjusting the number, length, and depth of the embossing.

[0047] When the gas generator 10 is activated, the predetermined breaking contour 24 tears open, so that a relatively large opening is created, which preferably extends over more than half the total diameter of the housing 11

[0048] In Fig. 3 shows only the cover 23 of a bursting membrane 14, or rather a top view thereof. The predetermined breaking contour 24 incorporated into the cover 23 is, in the present case, cross-shaped in the form of a predetermined breaking contour 24 not according to the invention. The cross-shaped predetermined breaking contour 24 is formed by two mutually perpendicular lines or predetermined breaking lines 28. The two predetermined breaking lines 28 each have the same length and intersect in the middle. Through-openings 25 are formed at the end points 27 of the two predetermined breaking lines 28.

[0049] The diameters or cross-sections of the through-openings 25 are identical. In other words, all through-openings 25 of the bursting membrane 14 have the same opening width. When the four formed through-openings 25 are connected, a square is formed. In other words, the through-openings 25 are the corner regions or corners of an imaginary square. Upon activation of the gas generator and the associated destruction or opening of the predetermined breaking contour 24, the predetermined breaking lines 28 tear open, so that triangular cover segments 29 fold outwards and thus form an opening in the cover 23. By folding over the cover segments 29, a square or approximately square opening is formed, from which the shock wave is formed or introduced into the gas storage chamber 16 (not shown).

[0050] Also in Fig. 4 shows the cover 23 of a bursting membrane 14, or rather a top view thereof. A predetermined breaking contour 24 is incorporated into the cover 23. In the example shown, the predetermined breaking contour 24 is formed from three predetermined breaking lines arranged in an H-shape. At the end points 27 of the predetermined breaking lines 28 arranged parallel to one another, through openings 25 are formed. In this case, too, the through openings 25 are arranged in such a way that they form the corners of an imaginary square. By tearing or breaking open the predetermined breaking lines 28, two rectangular cover segments 29 are curved outwards, so that these in turn form an opening in the cover 23 of the bursting membrane 14.

[0051] The predetermined breaking contour 24 formed in the cover 23 according to the embodiment of the Fig. 5 is formed by two predetermined breaking curves 30. The predetermined breaking contour is therefore double-C-shaped. The predetermined breaking curves 30 are, in particular, semicircular. At the end points 27 of both predetermined breaking curves 30, through-openings 25 are formed, which in turn form the corners of an imaginary square. Upon activation of the gas generator 10 or upon rupture of the predetermined breaking contour 24, two semicircular cover segments 29 bulge outward, forming an enlarged opening in the bursting membrane 14.

[0052] The gas generators, gas bag modules and vehicle safety systems according to the invention are provided with bursting membranes 14 according to the invention in accordance with the Fig. 4 - 5 illustrated embodiments. List of reference symbols 10 Gas generator 11 housings 12 lighters 13 Diffuser 14 Bursting membrane 15 Combustion chamber 16 Gas storage chamber 17 Notch 18 Combustion chamber sieve 19 Rupture disc 20 cylindrical peripheral wall 21 Bevel 22 frustoconical peripheral wall 23 lids 24 Predetermined breaking contour 25 passage opening 26 Outer contour 27 Endpoint 28 Predetermined breaking line 29 Lid segment 30 predetermined breaking arches L Gas generator longitudinal axis

Claims

[1] Bursting membrane (14) for a gas generator (10) for a vehicle safety system with at least one predetermined breaking contour (24) which can be destroyed upon activation of the gas generator (10), wherein a shock wave can be generated, characterized by that the predetermined breaking contour (24) has a through opening (25) at all end points (27) and the predetermined breaking contour (24) is double C-shaped or H-shaped. [2] Bursting membrane (14) according to claim 1, characterized by that the bursting membrane (14) has an outer contour (26) which is cap-shaped or semicircular. [3] Bursting membrane (14) according to one of the preceding claims, characterized by that the through opening (25) is circular. [4] Bursting membrane (14) according to one of the preceding claims, characterized by that the through opening (25) has at least an opening width of 0.5 - 3.0 mm. [5] Bursting membrane (14) according to one of the preceding claims, characterized by that the predetermined breaking contour (24) is formed by embossing or milling or notching or laser ablation. [6] Gas generator (10) with a bursting membrane (14) according to one of the preceding claims. [7] Gas generator (10) with at least one combustion chamber (15) which is filled with fuel and gas and has an outflow end, with at least one igniter unit by which the fuel can be ignited, and with at least one bursting membrane (14) according to one of claims 1 to 5, wherein the bursting membrane (14) is connected to an outer housing (11) of the gas generator (10) in a materially or positively locking manner. [8] Gas generator (10) according to claim 7, characterized by in that the bursting membrane (14) separates the combustion chamber (15) from a gas storage chamber (16) in the inactivated state of the gas generator (10), wherein the through opening (25) is designed as a fluid connection between the combustion chamber (15) and the gas storage chamber (16). [9] Gas generator (10) according to claim 8, characterized by that the through opening (25) has at least an opening width such that, in order to produce the gas generator (10), when the gas generator (10) is filled with gas, a pressure equalization between the gas storage chamber (16) and the combustion chamber (15) takes place in less than 15 seconds. [10] Gas generator (10) according to one of claims 7 to 9, characterized by that the through opening (25) is designed such that upon activation of the gas generator (10) a pressure increase in the combustion chamber (15) takes place in order to cause the bursting membrane (14) to open. [11] Gas generator (10) according to one of claims 8 to 10, characterized by that an additional fuel is accommodated within the gas storage chamber (16) for the subsequent supply of hot gas. [12] Gas bag module with a gas generator (10) according to one of the preceding claims 6 to 11. [13] Vehicle safety system with an airbag module according to claim 12.

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