Hybrid gas generator, method for operating a hybrid gas generator, airbag module and vehicle safety system

Abstract

The invention relates to a hybrid gas generator (10) which comprises a compressed gas chamber (20) and an igniting unit (30), wherein the compressed gas chamber (20) is closed by a first igniter-side bursting membrane (21) and a second bursting membrane (22). According to the invention, a first, rapidly burning-off pyrotechnic agent (51) and a second pyrotechnic agent (52) burning off slowly in comparison to the first pyrotechnic agent (51) are located in the hybrid gas generator (10), wherein the second bursting membrane (22) is openable by positive pressure which can be generated in the compressed gas chamber (20) and the first pyrotechnic agent (51) is separated from the second pyrotechnic agent (52) in such a manner that the positive pressure in the compressed gas chamber (20) for opening the second bursting membrane (22) can be generated by the first pyrotechnic agent (51).

Claims

1. A hybrid gas generator comprising: a compressed gas chamber closed off by a first bursting membrane and a second bursting membrane; an igniting unit comprising an igniter; a first pyrotechnic agent configured to be ignited by the igniter; and a second pyrotechnic agent configured to be ignited by burning off of the first pyrotechnic agent, the second pyrotechnic agent being configured to burn off slowly as compared to the first pyrotechnic agent; wherein the second pyrotechnic agent is disposed in the compressed gas chamber and the first pyrotechnic agent is contained within a holder of the igniting unit outside the compressed gas chamber, the first bursting membrane being secured to the holder and separating the first pyrotechnic agent in the holder from the second pyrotechnic agent in the compressed gas chamber; wherein the separation of the first and second pyrotechnic agents is configured so that the second bursting membrane opens due to a pressure rise in the compressed gas chamber resulting from the burning off of the first pyrotechnic agent, wherein the second pyrotechnic agent is disposed in a combustion chamber within the compressed gas chamber, the combustion chamber being axially separated from a pyrotechnic chamber in the holder where the first pyrotechnic agent is contained, and wherein the combustion chamber is spaced apart from the pyrotechnic chamber by a resilient element.

2. The hybrid gas generator recited in claim 1, wherein the holder is configured to support the first bursting membrane, the holder defining a chamber within the compressed gas chamber that contains the first pyrotechnic agent, wherein the holder and the first bursting membrane isolate the first pyrotechnic agent from the second pyrotechnic agent prior to activation of the inflator.

3. The hybrid gas generator recited in claim 2, wherein the igniter is configured to ignite the first pyrotechnic agent and rupture the first bursting membrane, which opens the holder and releases burn-off gases of the first pyrotechnic agent into the compressed gas chamber, which creates the pressure rise in the compressed gas chamber that opens the second bursting membrane.

4. The hybrid gas generator recited in claim 1, wherein the gas generator is configured so that the pressure rise in the compressed gas chamber opens the second bursting membrane without influence from a shockwave and with the hybrid gas generator being free from projectiles for puncturing the second bursting membrane.

5. The hybrid gas generator according to claim 1, wherein the burning off of the first pyrotechnic agent forms positive pressure in the compressed gas chamber that directly opens the second bursting membrane.

6. An airbag module configured for installation in a vehicle, comprising the hybrid gas generator according to claim 1 and an airbag inflatable by the hybrid gas generator.

7. A vehicle safety system for protecting a person, comprising a hybrid gas generator, an airbag inflatable by the gas generator as part of an airbag module, and an electronic control unit configured to activate the hybrid gas generator when a release situation is given, wherein the hybrid gas generator is configured according to claim 1.

8. A method for operating the hybrid gas generator according to claim 1, comprising steps of: a) activating the igniting unit of the hybrid gas generator; b) igniting the first pyrotechnic agent, which ruptures the first bursting membrane and releases burn-off gases into the combustion chamber; c) building up, via the burn-off gases released into the compressed gas chamber, positive pressure in the compressed gas chamber; d) igniting the second pyrotechnic agent and partially generating propelling gas; e) opening the second bursting element due to the built-up positive pressure in the compressed gas chamber; f) generating further propelling gas by the second pyrotechnic agent; and g) discharging the further propelling gas through the opened second bursting element.

9. The method for operating the hybrid gas generator according to claim 8, wherein the first pyrotechnic agent acts as ignition booster for the second pyrotechnic agent and as positive pressure generator, wherein the positive pressure required for opening the second bursting element is generated prior to reaching a maximum gas generation rate of the second pyrotechnic agent.

10. The method according to claim 8, wherein the maximum gas generation rate of the second pyrotechnic agent is reached subsequent to the method step e), and/or wherein bursting of the first bursting element is carried out subsequent to the step a) or the step b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereinafter, the invention will be illustrated in detail by way of example embodiments with reference to the attached schematic drawings, wherein:

(2) FIG. 1 shows a hybrid gas generator according to the invention in accordance with a first example embodiment:

(3) FIG. 2 shows a hybrid gas generator according to the invention in accordance with a second example embodiment; and

(4) FIG. 3 shows a hybrid gas generator according to the invention in accordance with a third example embodiment.

DESCRIPTION

(5) In the following, like reference numerals will be used for like and equally acting parts.

(6) The hybrid gas generator 10 shown in FIG. 1 comprises an elongate tubular outer housing in the form of a compressed gas chamber housing 11. The hybrid gas generator 10 especially serves for inflating a gas bag, especially an airbag (not shown), wherein it may also comprise an actuator element, especially a hood prop, a belt tensioner or a safety bar element in a vehicle. The hybrid gas generator 10 comprises a central elongate cylindrical compressed gas chamber 20 as well as an igniting unit 30 which includes an igniter 33. The compressed gas chamber 20 is closed by a first igniter-side bursting membrane 21 and a second bursting membrane 22. The second bursting membrane is positioned on the airbag side or on the diffuser side, i.e. it is attached to an area of the hybrid gas generator 10 in the environment of which an airbag (not shown) or a diffuser 70 is located.

(7) In the idle state of the hybrid gas generator 10, i.e. prior to activation thereof, the compressed gas chamber 20 is filled with a compressed gas of helium, a helium/argon mixture or a helium/argon/oxygen mixture at a pressure of from 240 to 1500 bars. The igniting unit 30 comprises a base 31 serving as a support of the igniter 33.

(8) A first bursting element holder 23 which serves for fastening the first bursting element 21 is attached to the igniting unit 30. The second bursting element 22, too, is fastened by means of a second bursting element holder 25 in the housing of the compressed gas chamber 20.

(9) In the compressed gas chamber 20 a first rapidly burning-off pyrotechnic agent 51 and a second pyrotechnic agent 52 burning off slowly as compared to the first pyrotechnic agent 51 are located. The second bursting membrane 22 can be opened by positive pressure generated in the compressed gas chamber 20 upon activation of the hybrid gas generator 10 and, resp., the igniting unit 30. The first pyrotechnic agent 51 is separated from the second pyrotechnic agent 52 in such a way that the positive pressure in the compressed gas chamber 20 for opening the second bursting membrane 22 can be generated by the first pyrotechnic agent 51, concretely speaking by burn-off of the first pyrotechnic agent 51 with appropriate generation of pressure.

(10) In the compressed gas chamber 20 a guide tube 40 is formed. The guide tube 40 takes a cylindrical shape. The guide tube 40 has such length, wherein the length of the guide tube 40 is understood to be the extension in the direction of the longitudinal axis L of the hybrid gas generator 10, which corresponds to approximately 90% of the total length of the compressed gas chamber 20 of the hybrid gas generator 10. The guide tube 40 substantially extends from the first bursting element 21 to about the second bursting element 22. Especially, the guide tube 40 extends to an area of the compressed gas chamber 20 which merges into an end-side tapering 24. That is to say that the guide tube 40 in the shown example does not reach completely, when viewed in the axial length, to the second bursting element 22. The guide tube 40 rests on an inner portion of the tapering 24.

(11) The first pyrotechnic agent 51 may be in the form of granules and/or of compressed pellets, annular bodies and/or of extruded bodies with at least one, especially axial, through-passage and/or of extruded bodies without an axial through-passage. The first pyrotechnic agent 51 is located in a first portion 41 of the guide tube 40 close to the igniter.

(12) The first portion 41 is delimited in the axial direction, i.e. in the direction of the longitudinal axis L of the hybrid gas generator 10, by a disk element 42. The disk element 42 includes a central axial gas outlet 43. In addition, in the first portion 41 of the guide tube 40 at least two radial discharge openings 44 are formed. That is to say that the first pyrotechnic agent 51 provided in the first portion 41 of the guide tube 40 is surrounded by compressed gas of the compressed gas chamber 20.

(13) The second pyrotechnic agent 52, on the other hand, is located in an intermediate chamber 60. The intermediate chamber 60 is delimited by a packing 61 at its first igniter-side end. The packing 61 is configured to be permeable to gas and, resp., to fluid. The second diffuser-side end of the intermediate chamber 60 is formed by a limiting disk 62. The limiting disk 62 includes plural axial through-openings in the form of intermediate chamber outlets 64, with a tamping 63 being applied to the side of the limiting disk 62 facing the intermediate chamber 60 which tamping is made, for example, from an adhesive gas-impermeable metallic foil, e.g. from copper, steel or aluminum. Accordingly, the intermediate chamber outlets 64 may be closed in the non-activated state of the hybrid gas generator 10.

(14) In the non-activated state of the hybrid gas generator 10, the limiting disk 62 prevents the second pyrotechnic agent 52 from leaving the intermediate chamber 60. The limiting disk 62 rests especially on a bead 12 formed circumferentially within the compressed gas chamber housing 11. The intermediate chamber 60 is formed especially between the inner face 13 of the compressed gas chamber housing 11 and the central guide tube 40. In the present case, the compressed gas chamber housing 11 corresponds to an outer housing of the hybrid gas generator 10.

(15) In the shown example, the second pyrotechnic agent 52 is provided in the form of compressed pellets. It is also possible for the second pyrotechnic agent 52 to be provided in different geometric forms such as in the form of stacked rings or as stacked propellant rings, wherein also propellant segments, especially as sections of a ring, may be present to be stringed together so that in total they take a ring shape. Moreover, the second pyrotechnic agent 52 may be provided in common forms such as granules and/or extruded bodies with one or more through-passages and/or extruded bodies without a through-passage.

(16) In the shown example, the intermediate chamber 60 is arranged axially downstream of the first portion 41 of the guide tube 40. It is also possible that the intermediate chamber 60 filled with the second pyrotechnic agent 52 surrounds the first portion 41 of the guide tube 40.

(17) The radial discharge openings 44 in the guide tube 40 form a fluid connection from the first portion 41 of the guide tube 40 to the intermediate chamber 60. Due to the area ratio of the discharge openings 44 to the gas outlet 43 of the disk element 42, the flow behavior of the gas ignited by the first pyrotechnic agent 51 can be determined.

(18) The hot gas and the particles forming during burn-off of the first pyrotechnic agent 51 are thus subdivided. A first part, viz. the major part, escapes through the gas outlet 43 in a flow direction S1 extending substantially in the direction of the longitudinal axis L of the hybrid gas generator 10 into the interior of the guide tube 40. With the aid of the first pyrotechnic agent, thus positive pressure is generated in the interior of the guide tube 40 as well as in the compressed gas chamber 20 so that the second bursting membrane 22 is opened.

(19) Another portion of the gas and of the particles forming during burn-off of the first pyrotechnic agent 51 flow along a flow path and, resp., along a flow direction S2 via the radial discharge openings 44 of the guide tube 40 in the direction of the second pyrotechnic agent 52, wherein they flow through the packing 61 permeable to gas and particles so as to ignite the second pyrotechnic agent. Accordingly, the further portion of the gas and of the particles leaves the interior of the guide tube 40 initially in the radial direction via the discharge openings 44 in order to then continue flowing in an axial direction to the second pyrotechnic agent 52. The first pyrotechnic agent 51 thus acts both as an ignition booster for the second pyrotechnic agent 52 and as positive pressure generator for opening the second bursting membrane 22, as already described before.

(20) The positive pressure required for opening the second bursting element 22 is generated prior to reaching the maximum gas generation rate of the second pyrotechnic agent 52. Accordingly, the compressed gas chamber 20 and, resp., the second bursting element 22 are opened so rapidly that the second pyrotechnic agent 52 is not yet ignited completely and the maximum gas generation rate thereof has not yet been reached. As a consequence, the maximum operating pressures within the hybrid gas generator 10, especially within the compressed gas chamber 20, are lower than in standard hybrid gas generators which work on the principle of positive pressure opening without a portion of shockwaves. The hybrid gas generator according to the invention thus constitutes an improvement for hybrid gas generators that work with a relatively slow positive pressure opening without requiring a supporting and relatively rapid propagation of a shockwave for opening the second bursting element 22. Due to the two pyrotechnic agents 51 and 52, also a hybrid gas generator 10 having a two-stage pyrotechnic charge is provided. Gas generation is prolonged and, resp., is kept steady over a quite long period of time due to the subsequent reaching of the maximum gas generation rate of the second pyrotechnic agent 52. Thus, quasi controlled resupply of propelling gas is made available, wherein airbag service lives, for example, can be increased.

(21) In the operating case of the hybrid gas generator 10, in the intermediate chamber 60 the said propelling gas is generated due to the ignited second pyrotechnic agent 52. After opening the tamping 63, by positive pressure the propelling gas flows through the intermediate chamber outlets 64 of the limiting disk 62 in the direction of radial inlet openings 49 of the guide tube 40. The radial inlet openings 49 serve for the fluid connection of the intermediate chamber 60 to the interior of the guide tube 40. After that, the propelling gas flows through the opened second bursting element 22 into the diffuser 70. Through openings of the diffuser 70, the generated propelling gas and the stored compressed gas flow out of the hybrid gas generator 10.

(22) FIG. 2 illustrates a second embodiment of a hybrid gas generator 10 according to the invention which acts according to the same basic principle as the hybrid gas generator 10 of FIG. 1. That is to say that in the hybrid gas generator 10, too, a compressed gas chamber 20 is formed in which a first rapidly burning-off pyrotechnic agent 51 and a second pyrotechnic agent 52 burning off slowly are located. The second bursting membrane 22 of the compressed gas chamber 20 is opened by positive pressure which can be generated in the compressed gas chamber 20, said positive pressure being primarily generated by the first pyrotechnic agent 51.

(23) The first pyrotechnic agent 51 is located in a pyrotechnic chamber 45 close to the igniter. The second pyrotechnic agent 52 is axially separated from the first pyrotechnic agent 51. The second pyrotechnic agent 52 is located in a portion of the compressed gas chamber 20 in the form of a combustion chamber 55. The combustion chamber 55 is delimited, on the igniter side, by a packing 61 through which gas or particles may flow in the axial direction. On the diffuser side, the combustion chamber 55 corresponding to the intermediate chamber 60 of FIG. 1 is delimited by a limiting disk 62. The limiting disk 62 includes combustion chamber outlets 65. In addition, on the side of the limiting disk 62 facing the combustion chamber 55 a tamping 63 is formed.

(24) The housing 46 of the pyrotechnic chamber 45 has a step-like element 47. Axial chamber discharge openings 48 are equally formed.

(25) In the example embodiment of FIG. 2, too, in the idle state of the hybrid gas generator 10 both the first pyrotechnic agent 51 and the second pyrotechnic agent 52 are surrounded by the stored compressed gas of the compressed gas chamber 20.

(26) Moreover, it is evident that the combustion chamber 55, especially the packing 61, is spaced apart from the pyrotechnic chamber 45 by a spring 80. The spring 80 rests on the step-like element 47 of the housing 46.

(27) In the example embodiment of FIG. 2, upon activation of the hybrid gas generator 10 and, resp., of the igniting unit 30 by generating pressure, energy and/or hot particles by the igniter 33 the first bursting element 51 and thus also the compressed gas chamber 20 are opened from outside. Immediately afterwards, the first pyrotechnic agent 51 is ignited and burnt off, thus causing hot burn-off gases and, resp., particles to leave the pyrotechnic chamber 45 through the chamber discharge openings 48 and to flow through the packing 61 and the spring 80 primarily in the axial direction or, resp., to flow past said components so as to reach the combustion chamber 55. The burn-off gas of the first pyrotechnic agent 51 and the positive pressure forming in this way propagates directly through the combustion chamber 55, while opening the tamping 63 and flowing through the combustion chamber outlets 65, to the second bursting element 22 which is then opened.

(28) In addition, the hot burn-off gases and, resp., particles of the first pyrotechnic agent 51 also ignite the second pyrotechnic agent 52 when entering into the combustion chamber 55, preferably immediately before the second bursting element 22 is opened. In this way, analogously the advantages as described already concerning FIG. 1 are resulting. For example, gas generation is prolonged and, resp., kept steady over a longer period of time due to the subsequent reaching of a maximum gas generation rate of the second pyrotechnic agent 52.

(29) FIG. 3 illustrates a third embodiment of a hybrid gas generator 10 according to the invention which works on the same basic principle as the hybrid gas generator 10 of FIGS. 1 and 2. That is to say that also in FIG. 3 a first rapidly burning off pyrotechnic agent 51 and a second pyrotechnic agent 52 burning off slowly are located in the hybrid gas generator 10. The second bursting membrane 22 of the compressed gas chamber 20 is opened by positive pressure which can be generated in the compressed gas chamber 20, said positive pressure being primarily generated by the first pyrotechnic agent 51.

(30) Said third embodiment is structured similarly to the second embodiment of FIG. 2, but it shows several differences, wherein the most important ones shall be discussed in the following.

(31) As is illustrated in FIG. 3, in the third embodiment the first pyrotechnic agent 51 is accommodated outside the compressed gas chamber 20 in a chamber 45. Hence the chamber 45 in the non-activated state of the hybrid gas generator 10 is merely under atmospheric ambient pressure of the hybrid gas generator 10. The chamber 45 is surrounded and, resp., partially confined by a housing 46 which at the same time serves and, resp., is configured as a first bursting membrane holder 23. Thus, the chamber 45 is delimited in the axial direction by the first bursting element 21. The chamber 45 and, resp., the first bursting membrane holder 23 are surrounded by a packing 61 including a spring 80 and an axial end in the form of a plate 90 through which gas and particles can flow and which is preferably tightly connected to the spring. The plate 90 may be a perforated plate which, when being biased by the spring 80, presses axially against the second pyrotechnic agent 52 to form volume compensation with respect to the fill level for the second pyrotechnic agent 52 during manufacture of the hybrid gas generator 10 and in the non-activated state thereof.

(32) The specific operating case for the third example embodiment resembles that of FIG. 2. However, in this case after activating the hybrid gas generator 10 and the igniting unit 30, in addition the first pyrotechnic agent 51 is also ignited, outside the compressed gas chamber 20, before the first bursting element 21 and thus also the compressed gas chamber 20 can be opened from outside by burn-off gases and, resp., particles of the igniting unit 30 and of the first pyrotechnic agent 51.

(33) After the burn-off gases and, resp., particles flow into the compressed gas chamber 20 and, resp., the combustion chamber 55 through the opened first bursting element 21, the positive pressure forming in this way propagates directly through the combustion chamber 55, while opening the tamping 63 and flowing through the combustion chamber outlets 65, to the second bursting element 22 which is then opened.

LIST OF REFERENCE NUMERALS

(34) 10 hybrid gas generator 11 compressed gas chamber housing 12 bead 13 inner face 20 compressed gas chamber 21 first bursting element 22 second bursting element 23 first bursting element holder 24 tapering 25 second bursting element holder 30 igniting unit 31 base 33 igniter 35 guide tube 41 first portion 42 disk element 43 gas outlet 44 radial discharge opening 45 pyrotechnic chamber 46 housing 47 step-like element 48 chamber discharge opening 49 inlet opening guide tube 51 first pyrotechnic agent 52 second pyrotechnic agent 55 combustion chamber 60 intermediate chamber 61 packing 62 limiting disk 22 63 tamping 64 intermediate chamber outlet 65 combustion chamber outlet 70 diffuser 80 spring 90 plate L direction of the longitudinal axis of hybrid gas generator S1 flow direction S2 flow direction