WO2010103231A1

WO2010103231A1 - Gas generator including a non-pyrotechnic energising device

Info

Publication number: WO2010103231A1
Application number: PCT/FR2010/050403
Authority: WO
Inventors: Paul-Philippe Cord; Céline ZAPATA ÉPOUSE MASSOT
Original assignee: Seva Technologies
Priority date: 2009-03-11
Filing date: 2010-03-10
Publication date: 2010-09-16
Also published as: EP2406577B1; CN102422120A; CN102422120B; FR2943128A1; EP2406577A1

Abstract

The invention relates to a gas generator (1) that includes: a gas generation chamber (10) for storing and decomposing a gas generating compound (11), wherein the product from the permanent-mode decomposition impart to the compound an amount of energy that is not sufficient for sustaining said decomposition; a stabilisation area (8) in communication with the gas generation chamber via at least one discharge opening (14) for discharging the gas generated into the stabilisation area, and with the outside via gas release holes (9); an energy supply device (4) in the form of at least one non-pyrotechnic energy beam such that each beam ensures an energy supply between the gas generating compound and the discharge openings of the stabilisation area in order to increase the energy density of the gases resulting from the decomposition as a complement of the energy released by said decomposition.

Description

GAS GENERATOR COMPRISING AN ENERGIZING DEVICE

NON PYROTECHNIC

The invention relates to a device for generating gas, said gas generator. In particular, the invention applies, in the automotive field, to a gas generator intended to be associated with a safety member, such as an airbag, to form a protection system. (eg in case of shock) of an occupant of a vehicle. The invention extends to other fields of application such as aeronautics (such a gas generator can for example be associated with a safety slide of an aircraft), the space (such a gas generator can for example to be used to modify the trajectory of a satellite), sports (in association, for example, with safety devices such as a buoy or a small inflatable boat in the context of water sports, or such as combination in the context of snow sports, etc.)

The invention applies to a gas generator of the pyrotechnic generator type, which contains an explosive charge in solid form, the combustion or decomposition of which generates gases. The term "explosive charge" means a set of constituents that can produce one or more exothermic chemical reactions during which gases are produced within a very short period of time. The combustion of this explosive charge is initiated by an ignition system integrated into the gas generator. For example, the pyrotechnic gas generators described in WO 01/89885, WO 2004/091981 and FR 05 12745 in the name of the Applicant, whose explosive charge comprises on the one hand a primary pyrotechnic compound (composite propellant, ballistic Lova type) or a pyrotechnic composition, and secondly a secondary compound capable of being decomposed by the products of combustion of the primary compound, the products from the primary and secondary compounds reacting in a redox reaction. The known gas generators have in particular the following disadvantages:

Because their explosive charge includes chemical substances qualified as pyrotechnic, their manufacture must be carried out under strict and binding conditions, essential to guarantee the safety of the people working there. Heavy and costly means must be put in place to obtain all the necessary authorizations and prior to the manufacture, storage, transport, marketing, integration and recycling at the end of life of known gas generators.

In addition, these devices develop, during their operation, very high internal pressures, which leads to the use of thick envelopes, heavy and expensive material, production and recycling.

The pyrotechnic substances especially used in automotive airbag applications have various combustion characteristics and are very sensitive to their environment, and in particular to temperature and hygrometry. Standards have been defined to guarantee the performance of the vehicle. gas generator, depending on the generator's life conditions (environment, required service life ...). These standards sometimes limit the choice of usable pyrotechnic substances and / or oblige to provide the gas generator with specific means of protection of its components.

Energy materials such as gas-generating compounds used in automotive gas generators, in particular airbag systems, must have dynamic gas decomposition characteristics in relation to the duration of their mission, ie such as the combustion time is short, of the order of a few tens of milliseconds. For this purpose, certain properties of propellants such as their ability to burn in parallel layers are used. Their products of combustion (gas) constitute a plasma whose energy density is regulated by the pressure. This plasma emits radiation which transfers to the solid phase of the energetic material an amount of energy sufficient to sustain the combustion thereof and thus maintain gas generation.

In known pyrotechnic gas generators, once initiated by the ignition system, the combustion of the explosive charge can not be stopped and the generator releases the entire volume of gas that it is able to produce. Inadvertent tripping of the ignition system must therefore be avoided.

Thus, in most known gas generators, the volume and the flow rate of the gases generated depend only (under normal conditions of use of the generator) on the amount of explosive charge that the generator contains, the nature of the latter and constructive characteristics of the generator, in particular the nozzle for exhausting the pressurized gas, which determine in particular the combustion conditions of the explosive charge. This volume and this flow rate are thus determined definitively at the time of the design of the gas generator. However, it may be desirable to be able to modulate the generation of the gases according to external circumstances (configuration of the shock suffered by the vehicle or the position of its occupants, in the case of an airbag gas generator) or a modification of the mission for which the gas generator was initially designed (adjustment of the trajectory correction to be applied to a satellite or a missile ...). For this purpose, the manufacturers have developed multi-charge gas generators such as that described in US Pat. No. 5,320,382, comprising three self-igniting combustion chambers, comprising three stages each, and therefore able to offer a certain temporal variation of the volume of gas generated in function of the respective charges of each chamber and the respective instant of ignition of each of them. However, this modulation is very limited by the fact that the charges of the different chambers are predetermined at construction and that the ignition of a chamber causes its complete combustion with its predetermined gas generation profile. In addition, these gas generators have a particularly complex structure (three three-stage combustion chambers, three electric ignition systems ...) which is heavy, bulky and expensive. No. 5,098,123, however, discloses a gas generator for the automobile using the decomposition of an aluminum / water mixture by means of a jet of a plasma obtained by an electric arc to produce a quantity of gas used to inflate a gas. airbag safety. The decomposition of this mixture stops as soon as it is no longer supplied with energy. It should be noted that this technology requires considerable electrical energy to generate a plasma of a temperature and energy capable of activating and sustaining the reaction of these components. However, it turns out that such a quantity of energy is hardly compatible with the automotive environment and requires special means (capacitors and / or high voltage batteries) expensive. As a result, the energy required is rarely available or unavailable for the duration of the generator's mission in the automotive environment, particularly when this gas production is required. In addition, the energy supply being effected in a closed zone, opposite the gas evacuation circuit, they must diffuse through the load. The supply of energy is therefore on the one hand inefficient and can also present a danger if the compound is solid (non-porous) or in case of clogging or obstruction of the gas evacuation circuit by combustion residues. Moreover, the gases formed by this reaction are essentially hydrogen, the flammability hazards of which are known, which render them unfit for the intended application.

The invention aims to overcome these disadvantages by providing a secure and stable gas generator, whose manufacturing operations, transport, integration and recycling at the end of life are facilitated.

The invention also aims to provide a gas generator with reduced risk of nuisance tripping, and for which the possible consequences of such a trigger are benign.

The invention also aims to provide a gas generator whose volume of gas produced and / or the gas release rate can (can) be modulated (s) in operation. The invention further aims to achieve this objective by proposing a gas generator comprising a single generation chamber of gas and a single ignition system.

Another object of the invention is to provide a gas generator of low weight and compactness.

The invention also aims to achieve all these objectives at lower cost, by proposing a gas generator whose cost is lower than that of known generators.

To do this, the invention relates to a gas generator, comprising at least:

a chamber, called a gas generation chamber, for the storage and decomposition of a feedstock comprising at least one solid or liquid compound, said gas generating compound, capable of generating gases by decomposing,

a device, called an energizing device, for supplying energy in the form of at least one non-pyrotechnic energy beam, characterized in that: the gas-generating compound is a compound whose products resulting from the decomposition in a steady state transfer to the compound a quantity of energy insufficient to maintain said decomposition,

at least one zone, called the stabilization zone, communicates in operation at least with the gas generation chamber by at least one opening, called the discharge opening, for evacuation in the stabilization zone of the generated gases, and with the outside of the gas generator by generated gas release holes,

the energizing device is adapted to generate the said energy beam (s) so that: each generated beam produces a suitable energy input to increase the energy density of the gases from the decomposition in addition to the energy released by the decomposition, suitable for maintaining the decomposition of the gas generating compound, each generated beam enters a gas generation chamber so that the energy input is made between the gas generating compound and the discharge openings in the stabilization zone.

The gas generator according to the invention thus has a unique combination of a physical structure comprising a gas generation chamber and a stabilization zone placed in the gas outlet stream, including the discharge orifices and the release holes. are dimensioned to maintain a confinement adapted to maintain a predetermined average pressure, in steady state, in the gas generation chamber; a non-pyrotechnic energizing device placed in a position allowing a supply of energy to the place where it will be most effective and a gas generating compound judiciously chosen to allow an optimal release of the gases in the presence of a moderate amount of energy brought by the energizing device.

Thus, according to the invention, the gas generator comprises one or more gas generation chambers each containing a gas generating compound whose exothermic decomposition produces a quantity of energy, a part of which dissipates, for example with the evacuation of gases. hot gases, and another part is transferred back to the compound to maintain the decomposition reaction. The amount of energy transferred back to the compound therefore depends on the nature of the compound, that is to say a gas-generating compound whose reaction energy released by the exothermic decomposition is less than activation energy of this reaction will not allow to obtain a self-maintained decomposition reaction, but also conditions of use in which this reaction occurs. Indeed, even if the compound has a reaction energy greater than the activation energy, the amount of energy transferred in return depends on the conditions of use, in particular the confinement of the reaction, a reduced or even non-existent confinement favoring the dissipation of the energy produced by the decomposition reaction and reducing the usable energy to maintain the reaction. This decomposition, once initiated, is then not self-maintained or progresses autonomously extremely slowly with regard to the durations of the missions for which the generator can be requested. As a result, the simple ignition of this compound can not lead to its complete and rapid decomposition. This decomposition requires a prolonged supply of energy which according to the invention is provided, not by the combustion products of a propellant, but by an electrically controlled non-pyrotechnic energy source. It should be noted that each gas generating compound according to the invention is preferably a solid compound, stored in a compact form or in the form of divided solids (powder and / or pellets and / or granules and / or strands and / or leaves) . The energizing device which constitutes this source of electrically controlled non-pyrotechnic energy is arranged in such a way that the energy is supplied in the vicinity of the interface between the solid phase of the gas generating compound and its gaseous phase. Thus, the energy density in the zone where the decomposition reaction occurs is a combination of the energy released by this exothermic reaction and that provided by the energy beam. This energy density is then sufficient to maintain and accelerate the decomposition reaction. In addition, the efficiency of the gas generator according to the invention is enhanced because the decomposition zone thus determined is located opposite the stabilization zone, in the vicinity of the discharge openings, so that all the gas generated is at even to evacuate to the stabilization zone and then to use (an airbag for example) without undergoing loss of load due to the crossing of the generating compound.

Advantageously, because of the exothermic decomposition of the gas generating compound, the amount of energy supplied by the energizing device is added to the energy released by this exothermic reaction, and the sum of the two becoming greater than the energy of activation of the reaction, the decomposition of the gas generating compound is maintained or accelerated.

This combination of features has many advantages: The use of a non-pyrotechnic energy source offers the possibility of limiting the explosive charge of the gas generator to the single gas generator compound (s) stored in the gas generation chamber (s). These compounds, whose decomposition is not self-sustaining or is extremely slow in the absence of energy supply, can be formed from particularly stable substances and whose classification as explosive substances is low compared to propellants and other ballistic powders used in known gas generators. It is even possible to use non-pyrotechnic substances (eg ammonium nitrate, basic copper nitrate or guanidine nitrate). The means to be implemented to guarantee the safety of goods and persons involved in the manufacture, integration, etc., of the gas generator are reduced (or even zero in the extreme case where the gas generator is devoid of pyrotechnic substance , its manufacture is not then subject to a binding authorization), and new possibilities of application of the gas generator are offered. Advantageously and according to the invention, the gas generating compound comprises at least one of the components selected from ammonium nitrate, guanidine nitrate and basic copper nitrate. These components, as seen above, are not considered as pyrotechnic substances as such and allow implementation of the gas generating compound with reduced stresses. These components can be used pure or in combination with each other.

In particular, and according to the invention, the gas generating compound comprises ammonium nitrate combined with an additive (or additives) adapted to adjust the oxygen balance of said compound to a value close to zero. This makes it possible to obtain chemically neutral gases and thus to avoid the formation of nitrogen oxides. Advantageously, this additive may be taken from guanidine derivatives (nitro-guanidine, guanidine nitrate, etc.), polyesters, ammonium acetate, oxamide or a derivative thereof, urea or a derivative thereof (nitro-urea for example), hexogen, octogen, aminotetrazole ... Advantageously and according to the invention, the generating compound gas also comprises an additive suitable, in its initial form and / or in its decomposition products, to absorb a portion of the energy of (the) beam (s) energy (s). For example, when the energy supplied by the energizing device is of optical origin, such as a laser beam, the conversion of this energy into thermal energy capable of activating the decomposition of the gas-generating compound is improved by the addition of additives such as carbon, boron or any other additive to improve the energy transfer between the energy beam and the compound and / or its decomposition plasma.

In a first embodiment of the gas generator according to the invention, the gas generating compound is the only explosive charge of the gas generator. The energizing device is then able to generate at least one energy beam whose energy density is sufficient to initiate the decomposition of the gas generating compound. It should be noted that the energy transfer between the energy beam and the gas generating compound can take place directly between said energy beam and the solid particles or possibly the liquid phase of the gas generating compound and / or between the beam and the the gaseous phase resulting from the decomposition products of the gas generating compound.

In a second embodiment, the gas generator according to the invention further comprises an initiator charge adapted to cooperate with the said energy beam (s) of the energizing device to initiate the decomposition of the compound. gas generator. This initiating charge is adapted to be ignited by the energy beam with a lower energy density than that which would be necessary to initiate the reaction of the gas generating compound. This initiating charge can also be ignited by a pyrotechnic device. The initiating charge makes it possible to provide an initial amount of energy greater than the activation energy of the decomposition reaction so that it can be initiated. Depending on the amount of initiator charge, a variable amount of gas generating compound will be decomposed, the remainder of the compound requiring the energy provided by the energy beam to continue its reaction. Advantageously and according to the invention, the energizing device is adapted to modulate the energy input made by said energy beam (s) in response to a command applied to the energy source. for modulating the flow of gas produced by the decomposition of the gas generating compound. By acting on the amount of energy supplied to the decomposition reaction, it acts directly on the amount of gas generating compound solicited and implemented in this reaction and thus on the flow of gas produced. It is thus possible to control the modulation of gas production in both directions, increase and decrease. Such a gas generator, capable of modulating the gas flow produced is particularly attractive, for example for use with an airbag, because it can modulate the deceleration applied to an occupant resting on the cushion to the following a shock.

Advantageously and according to the invention, the energizing device comprises a laser source, for example in the form of a laser diode. The energizing device may also include at least one optical fiber extending between the laser source and a gas generation chamber to guide and focus the laser beam emitted from the laser source to said chamber. In a variant, the laser source is adapted to emit at least one laser beam towards a gas generation chamber. The energizing device then advantageously comprises an optical window capable of transmitting the light (that is to say the laser beam) and producing a hermetic separation partition between the laser source on the one hand, and the gas generation chamber or a stabilization zone communicating with said chamber on the other hand. This optical window can integrate or be replaced by a lens adapted to refocus the laser beam (s) emitted by the laser source in order to reduce the diameter of the beam and / or to increase its energy density. The electromagnetic radiation of the laser is absorbed by the solid phase and / or the gas phase of the gas generating compound and transfers its energy to the decomposition plasma of the compound, increasing the energy density thereof and thus the generation of gas. In a variant, the energizing device comprises a generator of plasma.

Advantageously and according to the invention, the plasma generator comprises two substantially parallel electrodes adapted to generate and maintain a plasma in the path of the gases produced by the decomposition of the gas generating compound. In addition, the electrodes are covered with an insulator adapted to decompose in the combustion zone and in that the plasma is mobile in the vicinity of the surface of the solid phase of the gas generating compound. In this embodiment of the invention, the plasma generated at the end of the electrodes by a priming device moves at the same time that the gas generating compound is consumed and that its solid surface moves. As a result, the energy supply is always effected in the vicinity of the interface between the solid phase and the gaseous phase of the compound.

Advantageously and according to the invention, the plasma generator comprises two coaxial electrodes whose opposite ends are adapted to generate a fixed plasma in the path of the gases produced by the decomposition of the gas generating compound. The two electrodes arranged face to face may be embedded in the gas generating compound.

Advantageously and according to the invention, the plasma is formed of ionized gases at least partially constituted by the gases produced by the decomposition of the gas-generating compound. Thus, during the decomposition of the gas-generating compound, the generated gases that already have a high energy level are subjected to the conditions prevailing in the plasma and in particular to the energy input made by the energizing device. This energy is transferred to the gases whose excitation level, therefore the temperature, increases. These gases are in turn part of said plasma and provide additional energy to increase the amount of decomposed energy material.

Advantageously and according to the invention, the plasma generator comprises a priming device adapted to contribute to the establishment of a high energy plasma between said electrodes during a plasma activation control. In particular, it comprises a priming device such as a explosive wire connected to the electrodes or a pyrotechnic initiator controlled in parallel with the electrodes.

Other sources of energy may also be envisaged, such as sources of ultrasound, microwave sources, inductive sources or any other energy source that can be electrically controlled and provide additional energy. to the decomposition reaction.

The cited energy sources (and in particular the laser and the plasma generator) have the advantage of being able to be activated and develop maximum power instantaneously, ie within 2ms of starting from establishment of an electric current at the input of the source. Likewise, they are able to become inactive instantaneously from the interruption of the electric current at the input of the source. The gas generator according to the invention, which has no transient period, therefore has a better controlled performance than previous generators, which allows, in particular, both to reduce the emission of products whose reaction of Redox is not complete and decreases the amount of gas generating compound to be provided for a given maximum product gas volume.

The invention extends to a gas generation system, comprising on the one hand a gas generator according to the invention, and on the other hand computer and / or electronic control means of its energy source, adapted to control the power supply of said source.

Advantageously and according to the invention, said control means are adapted to control said power supply so as to activate the energy source on receipt of a signal (which may be electrical, or pneumatic, hydraulic, mechanical, optical, electromagnetic. ..) predetermined representative of an event requiring a release of gas.

The control means are more preferably adapted to control the supply of the energy source so as to activate the energy source and keep it active, continuously or sequentially, until a total decomposition of the generating compound is obtained. of gas, on receipt of predetermined signal representative of an event requiring maximum gas release; for example, the control means are adapted to maintain the active energy source for a predetermined duration (from its activation) and which corresponds to that necessary to obtain the total decomposition of the gas generating compound; said duration is for example recorded in a memory of the control means; this duration may be different from one gas generator to another, since it depends on the amount of gas-generating compound that the generator contains, the nature and the power of its energy source ... In a variant or in combination, the control means are adapted to activate the energy source upon receipt of a predetermined signal representative of an event requiring a release of gas, and to maintain said active source, continuously or sequentially, as long as the signal is received, or for a period defined by said signal, or until a signal representative of an event requiring a stopping of the release of gases.

The invention extends to a gas-generating assembly, comprising a gas generator according to the invention and an inflatable chamber, arranged so that the gases released by the gas generator can inflate said enclosure. The invention also extends to a gas-generating assembly, comprising a gas generator according to the invention and a jack, arranged in such a way that the gases released by the gas generator can pressurize said cylinder. These two sets can in particular be integrated into a motor vehicle to ensure the safety of its occupants.

The invention also relates to a gas generator, a gas generation system and a gas-generating assembly, characterized in combination by all or some of the characteristics mentioned above and hereinafter.

Other objects, features and advantages of the invention will appear on reading the following description which refers to the appended figures representing preferred embodiments of the invention given only as non-limiting examples, and in which:

FIG. 1 is a diagrammatic sectional view illustrating a first embodiment of a gas generator according to the invention;

FIG. 2 is a diagrammatic sectional view illustrating a second embodiment of a gas generator according to the invention;

FIG. 3 is a diagrammatic sectional view illustrating a third embodiment of a gas generator according to the invention;

FIG. 4 is a diagrammatic sectional view illustrating a fourth embodiment of a gas generator according to the invention; FIG. 5 is a diagrammatic sectional view illustrating a fifth embodiment of a gas generator according to FIG. 'invention.

The gas generator 1 illustrated in FIG. 1 comprises an elongated, cylindrical, circular section frame formed by a bottom 3 and a tube 2. The tube 2 and the bottom 3 can be assembled together or obtained from a single part, by extrusion or by molding or by stamping, forming .... It comprises, within this tabular frame, an energizing device 4, a stabilization zone 8 and a gas generation chamber 10 which succeed one another (in this order) in the axial direction of the tube 2.

The energizing device 4 comprises a laser diode 5, able to emit a laser beam when it is electrically powered via a connection plug 7, and an optical window 6 integrating or possibly producing a lens 13 adapted to refocus said laser beam, to form an energy beam according to the invention. The diode 5 advantageously has a power greater than 2.5 Watt. The laser diode 5 and the optical window 6 are arranged in close proximity to one another. The optical window has a section substantially corresponding to the internal section of the tube 2; it produces a wall which hermetically separates the laser diode 5 from the stabilization zone 8 and thus prevents any contact between the generated gases and said diode (at least during a maximum duration of mission). The gas generation chamber 10 is delimited by a section of the tube 2, the bottom 3 and a grid 12. It contains a solid gas generating compound 11 based on ammonium nitrate (such as an ammonium nitrate mixed with additives so as to present, in a version preferred, a zero or negative oxygen balance and a good sensitivity to the laser energy beam), the exothermic decomposition of which produces insufficient reaction energy to trigger and maintain the reaction, that is to say whose autonomous and total exothermic decomposition requires under normal operating conditions of the gas generator, a time much greater than the maximum duration of mission of the gas generator or is not self-maintained. The gate 12 has openings 14 for evacuation, in the stabilization zone 8, the gases resulting from the decomposition of the gas generating compound. Among these openings, a central opening allows the entry of the beam emitted by the energizing device 4 into the gas generation chamber 10. The gas generating compound 11 is preferably in the form of a powdered or totally or partially pelletized solid solid. . It is advantageously packaged in a sealed bag (not shown), which is instantly destroyed as soon as the laser diode is activated and the laser energy beam enters the gas generation chamber. In a variant, the gas generating compound is introduced in bulk into the gas generation chamber before the gate is fixed, the openings of which are initially closed by one or more operculas capable of tearing instantaneously as soon as the laser diode is activated. and that the energy beam passes through the seal closing the inlet opening.

The stabilization zone 8 is delimited by a section of the tube 2, the optical window 6 and the gate 12. At this zone, the tube 2 is pierced with holes 9 for releasing the generated gases.

When electrically powered, the laser diode 5 produces a laser beam, centered on the axis of the tube 2 and directed towards the gas generation chamber 10. This laser beam is optionally refocused through the lens 13 of the optical window 6. At the exit of this window, it forms an energy beam according to the invention, which, when it enters the generation chamber gas 10 through the central inlet opening of the grid 12, causes the decomposition of the gas generating compound particles 11 struck by the beam or located in proximity thereto. The focus of the laser beam is such that the focal point is on the surface of the gas generating compound 11 or in the immediate vicinity thereof within the compound. In this way, the energy density per unit area of the beam is maximum and allows, when the laser diode is activated, locally obtain enough energy to trigger the reaction of the gas generating compound on a point surface. As soon as the reaction is initiated, the energy of the laser beam serves only to maintain this reaction. Note that the energy input made by the beam does not necessarily have to be located on the surface of the solid phase gas generating compound, but it can be done in the gas phase, in the vicinity of the decomposition zone. . This energy supply can be modulated by increasing or decreasing the intensity of the current flowing through the laser diode 5. When the energy supply is increased, it is possible to provide the activation energy necessary to make a positive response. large amount of gas generating compound, thereby producing a higher gas flow rate and at the same time a higher amount of reaction energy. Conversely, decreasing the energy supplied reduces the amount of compound mobilized and therefore the flow rate of the generated gases. The decomposition of the particles of the compound is complete (ie without solid residue), and preferably the pressure inside the gas generation chamber does not exceed 250 bar. Indeed, the gas generation is carried out in the gas generation chamber, between the gas generating compound in its solid form and the gate 12 whose evacuation openings 14 allow the gas to evacuate to the zone of stabilization 8 and the holes 9 for releasing gases. The pressure drop is therefore limited and despite a high flow rate of the gases, the pressure is limited. As a result, the tube 2, and possibly the bottom 3, may be made of a material that is not very resistant to pressure and heat, such as aluminum or a polymeric material, and have a thickness less than 5 mm. The gas generator 1 is compact, lightweight and secure. The embodiments illustrated in FIGS. 2 to 5 show similarities with the gas generator 1 of FIG. 1. The elements common to all these embodiments bear the same numerical references and will not be described again. Only the differences between these embodiments and the gas generator 1 are described below.

The gas generator 20, illustrated in FIG. 2, comprises a tabular framework of general shape identical to that of the gas generator 1. This tabular framework comprises, at its axial end opposite the bottom 3, a wall 21 comprising at its center a 24. The energizing device comprises a housing 22 integrating in particular the energy source of the device which is an optical source (such as a laser diode) emitting a primary optical beam, and an optical fiber 23 able to transport the laser beam emitted. , which fiber 23 extends between the housing 22 of the energizing device and the stabilization zone 8, through hermetically through the bore 24, the wall 21 of the frame of the gas generator. This optical fiber 23 may possibly extend so as to cross the stabilization zone 8 and lead into the central discharge opening of the gate 12.

The gas generation chamber 10 comprises, as before, a gas generating compound 11 whose exothermic decomposition is not self-sustaining. In order to allow initiation of the decomposition of the compound, without however involving a large power or, as previously, a particularly high energy density, it is possible to incorporate in the combustion chamber, facing the laser beam, a initiator charge whose combustion is self-maintained, for example a capsule containing a pyrotechnic composition, adapted to cooperate with the energy beam to initiate the decomposition of the gas generating compound.

In this way, a laser beam of energy sufficient to maintain the decomposition of the gas generating compound alone but insufficient to initiate it can start the reaction by igniting the initiating charge 24. Note that the wall 21, the optical fiber 23 and gasket hermetically arranged between said wall and said fiber realize, as well as the optical window 6 of the previous embodiments, an interface between the energy source and the gas generation chamber or the stabilization zone, which interface has the double function to transmit the light (or, more generally, the energy beam emitted by the energy source) and to resist the pressure in the gas generation chamber or the stabilization zone.

The gas generator 30 illustrated in FIG. 3 comprises a tabular frame containing a central stabilization zone 8 and two gas generation chambers 31, 32 on either side of said stabilization zone. The stabilization zone 8 is delimited axially by two grids 39 with openings for evacuation of the generated gases. The gas generation chamber 31 (respectively 32) is delimited axially by one of the grids 39 and one of the end walls of the tubular frame, which wall has a central bore for the passage of an optical fiber 37 (respectively 38). In the example illustrated, the two gas generation chambers have identical volumes and identical gas generating compounds formed from the same charges, but it is also possible to provide separate gas generation chambers and / or containing different gas generating compounds (by the nature and / or quantity of the charges used ...). Like the gas generator 20, the energizing device of the gas generator 30 comprises an optical energy source housed in a housing 22, an upstream optical fiber 23, a bypass 36 and two downstream optical fibers 37 and 38, the optical fiber 37 opening into the gas generation chamber 31, while the optical fiber 38 opens into the gas generation chamber 32. The optical fiber 37 (respectively 38) passes axially through the entire gas generation chamber 31 (32 respectively), so that its end extends, before any activation of the laser source, near the grid 39 defining said chamber. When the laser source is activated, an energy beam according to the invention leaves the optical fiber 37 (or 38) near the stabilization zone 8. Note that the control means associated with the energizing device of the Generator 30 advantageously comprise means for controlling the bypass 36 making it possible to divide the beam transported by the upstream optical fiber 23 in two or to direct said beam into one or the other of the downstream optical fibers 37, 38. In FIG. As illustrated, the grids 39 each support, facing the optical fiber 37 (or 38), a mirror 35 (flat or preferably convex) inserted into the gas generation chamber 31 (respectively 32). The mirrors 35 are adapted to reflect the incident beam exiting the fibers 37 and 38 so that the decomposition of the gas generating compound progresses axially from the stabilization zone 8 to the end wall of the framework.

Upon activation of the energy source, the laser beam generated by the housing 22 is directed by the branch 36 towards one or the other or both fibers 37 and 38. The incident beam emerging from the fibers 37 and or 38 is reflected by the mirror 35 and controls the decomposition of the gas generating compound of the corresponding chamber. Note that the initiation of the decomposition may be triggered by a pyrotechnic initiator (s) (not shown) placed on the surface of the gas-generating compound at the right of the optical fiber and whose triggering is performed simultaneously with the activation of the laser source.

As the charge is consumed, the end of the optical fiber 37 can also be consumed. It should be noted that when a gas phase of the gas generating compound is created, the energy input can be done directly from the end of the optical fiber in this gas phase, the energy density of which increases and allows to increase the amount of decomposed material in the contiguous solid phase. The decomposition of the gas generating compound thus progresses from the stabilization zone to the end wall of the framework delimiting the gas generation chamber. Any risk of clogging the discharge openings of the grid 39 by solid particles is avoided.

The non-pyrotechnic energy source of the energizing device according to the invention is not limited to a source of the laser type. The gas generator 40 illustrated in FIG. 4 comprises the energizing device, the gas generation chamber, the separation grid 12 and the stabilization zone 8 aligned in this order. Alternatively, and equivalently, the stabilization zone 8 could be constituted by a free space in the gas generation chamber 10, between the gas generating compound 11 and the separation grid 12. In this case, the gas discharge openings 14 and the gas release holes 9 are merged.

The stabilization zone 8 is therefore placed opposite the energizing device with respect to the gas generation chamber. The energizing device comprises two electrodes 42, possibly coated with an insulating sheath 43, passing through the gas generating compound inside the gas generation chamber. The electrodes 42 may be parallel to each other and to the axis of the tubular frame or have an angle such that the spacing between the electrodes is maximum near the stabilization zone. The electrodes 42 are connected together, in the vicinity of the surface of the compound and the gate 12 by a priming device 41 adapted to initiate an electric arc and generate a plasma located between the ends of the electrodes. By way of example, the ignition device 41 may be a very thin metal wire which vaporises under the effect of the current flowing through it and generates a metal plasma by explosion, or preferably, a pyrotechnic initiator. The other end of the electrodes is connected to a source of electrical energy capable of generating a voltage sufficient to maintain an electric arc between the electrodes 42. In the example illustrated, the energy source comprises an oscillating circuit 44 excited by a variable oscillator 45. When the energy source is activated, the variable oscillator

45 excites the oscillating circuit 44 in the vicinity of its resonant frequency, which causes an overvoltage across the electrodes 42. The device 41 is then vaporized by the current flowing through it and contributes to establishing an electric arc between the ends of the electrodes 42 The electric arc is maintained as long as the oscillating circuit 44 is energized, and its intensity is regulated according to the frequency excitation voltage applied by the variable oscillator 45, increasing when this frequency approaches the resonant frequency of the oscillating circuit 44 and decreasing when it moves away from it.

The plasma created by the electric arc between the electrodes makes it possible to control the decomposition of the gas generating compound 11 by modulating the additional energy supplied into the gaseous and / or solid phase by the electric arc. The additional energy allowing the modulation of the decomposition is relatively modest compared to the total energy required for the reaction and does not exceed 10 to 20% of this total energy. It should be noted that the gas generated by the decomposition of the gas generating compound is in a very energetic state because of the reaction energy. It participates in the generation of plasma by ionizing very easily due to its high energy level. This phenomenon, in which the gases produced contribute to the formation of the plasma, allows the generation of a highly energetic plasma with an input of measured electrical energy.

As the gas generating compound 11 is consumed, the insulating sheath 43 of the electrodes also burns, and the electric arc follows the surface of the compound not yet consumed. Whatever the position of the electric arc, it brings its energy to the vapor phase of the gas generating compound and maintains its decomposition. Moreover, the material and the size of the electrodes 42 may, if necessary, be chosen so that these electrodes also burn up following the decomposition of the gas generating compound.

The plasma for decomposing the gas generating compound may also be generated by an aligned electrode arc generator as in the gas generator 50 shown in FIG. 5.

The gas generator 50 comprises, like the generators of Figures 1 and 2, a tubular frame, a gas generation chamber, a stabilization zone and an energizing device.

In this embodiment of the gas generator according to the invention, the energizing device comprises two electrodes 51 and 52 placed one facing each other and aligned along the axis of the tabular frame. The opposite ends of the two electrodes are placed in the vicinity of the separation grid 12, in the gas generation chamber. The electrodes are preferably made of tungsten so that the gap between their opposite ends remains substantially constant. The electrodes 51 and 52 are connected to the terminals of an electric generator 56 adapted to initiate and maintain an electric arc between their opposite ends. Of course, as in the case of the gas generator 40, the initiation of the arc can be aided by a similar priming device (not shown). The position of the plasma generated by the electric arc remains fixed at the gap, and the energy provided by this plasma is essentially communicated to the vapor phase during the decomposition of the gas generating compound.

It goes without saying that the invention may be subject to numerous variants with respect to the embodiments described and illustrated, for example by associating the energizing device of any of the generators described with the type of charge used in the chamber. generating gas from another of the described generators.

In addition, the gas generating compound may consist not of a homogeneous mixture but of thin layers of different elements superimposed in parallel planes orthogonal to the axis of the gas generator or rolled into concentric layers along this axis. Such a "composite" compound makes it possible to obtain a decomposition and a redox reaction, in the gas generation chamber, of the elements forming this compound, making it possible to adjust the oxygen balance of the compound to a zero or slightly negative value. to produce chemically neutral gases. In addition, a judicious choice of the elements forming the gas generating compound allows adjustment of the gap between the energy produced by the decomposition reaction and the activation energy necessary for the maintenance of the reaction. Other variations within the reach of the skilled person are possible without departing from the scope of the invention, and in particular, the gas generator may have a framework having a general shape of pancake or puck, it is ie a form of cylinder trunk whose length is less than the diameter. The energizing device of such a gas generator is either arranged outside this frame, or housed in a central zone thereof. The stabilization zone and the gas generation chamber are annular and concentric (the stabilization zone may extend inside the gas generation chamber or at the periphery thereof). The energizing device is adapted to generate a plurality of energy beams in radial directions (for example four beams radially opposite two by two).

Claims

1 / Gas generator (1), comprising at least:

a chamber, said chamber (10) for generating gas, for the storage and decomposition of a charge comprising at least one solid or liquid compound, said compound (11) gas generator, capable of generating gases by decomposing ,

a device, called an energizing device (4), for supplying energy in the form of at least one non-pyrotechnic energy beam, characterized in that: the gas generating compound is a compound whose products resulting from the decomposition in steady state transfer to the compound a quantity of energy insufficient to maintain said decomposition,

- At least one zone, said stabilization zone (8), communicates in operation at least with the gas generation chamber by at least one opening, called the discharge opening (14), for evacuation in the stabilization zone generated gases, and with the outside of the gas generator through holes (9) for releasing the generated gases,

the energizing device is adapted to generate the said energy beam (s) so that: each generated beam produces a suitable energy input to increase the energy density of the gases from the decomposition in addition to the energy released by the decomposition, suitable for maintaining the decomposition of the gas generating compound, each generated beam enters a gas generation chamber so that the energy supply is carried out between the compound gas generator and the discharge openings of the stabilization zone.

2 / gas generator according to claim 1, characterized in that the gas generating compound comprises at least one of the components selected from ammonium nitrate, guanidine nitrate and basic copper nitrate. 3 / gas generator according to claim 1 or 2 characterized in that the gas generating compound comprises ammonium nitrate combined with an additive (s) adapted to adjust the oxygen balance of said compound to a value close to zero.

4 / gas generator according to one of claims 1 to 3, characterized in that the gas generating compound also comprises an additive suitable, in its original form and / or in its decomposition products, to absorb a portion of the energy (of) beam (s) energy (s).

5 / gas generator according to one of claims 1 to 4, characterized in that the gas generating compound is the only explosive charge of the gas generator.

6 / gas generator according to one of claims 1 to 4, characterized in that it further comprises an initiator charge (25) adapted to cooperate with the (s) said (s) beam (s) energy (s) the energizing device for initiating the decomposition of the gas generating compound. 11 gas generator according to one of claims 1 to 6, characterized in that the energizing device is adapted to modulate the energy input effected by the (s) said energy beam (s) in response to a control applied to the power source for modulating the gas flow rate produced by the decomposition of the gas generating compound. 8 / gas generator according to one of claims 1 to 7, characterized in that the energizing device comprises a laser source (5).

9 / gas generator according to claim 8, characterized in that the energizing device comprises at least one optical fiber (23, 37, 38) extending between the laser source and a gas generation chamber. 10 / gas generator according to one of claims 8 or 9, characterized in that the laser source is adapted to emit at least one laser beam towards a gas generation chamber, and in that the energizing device comprises a lens (13) able to refocus this laser beam (s) and to produce a hermetic separation partition between the laser source on the one hand and the gas generation chamber (10) or a stabilization zone ( 8) communicating with said room on the other hand.

11 / gas generator according to one of claims 1 to 7, characterized in that the energizing device comprises a plasma generator.

12 / gas generator according to claim 11, characterized in that the plasma generator comprises two substantially parallel electrodes adapted to generate and maintain a plasma in the path of the gases produced by the decomposition of the gas generating compound.

13 / gas generator according to claim 12, characterized in that the electrodes (42) are covered with an insulator (43) adapted to decompose in the combustion zone and in that the plasma is mobile in the vicinity of the surface of the solid phase of the gas generating compound.

14 / gas generator according to claim 11, characterized in that the plasma generator comprises two electrodes (51, 52) coaxial whose opposite ends are adapted to generate a fixed plasma in the path of the gases produced by the decomposition of the compound gas generator.

15 / gas generator according to one of claims 11 to 14, characterized in that the plasma is formed of ionized gas at least partially constituted by the gases produced by the decomposition of the gas generating compound.

16 / gas generator according to one of claims lia 15, characterized in that the plasma generator comprises a priming device (41) adapted to contribute to the establishment of a high energy plasma between said electrodes when a plasma activation command.

17 / gas generating system comprising firstly a gas generator according to one of claims 1 to 16, and secondly computer and / or electronic control means of its energy source, adapted to control the power supply of said source.

18 / gas generating assembly, comprising a gas generator according to one of claims 1 to 16 and an inflatable chamber, arranged so that the gases released by the gas generator can inflate said enclosure. 19 / gas generating assembly, comprising a gas generator according to one of claims 1 to 16 and a cylinder, arranged so that the gas released by the gas generator can pressurize said cylinder.