Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/04—Blasting cartridges, i.e. case and explosive for producing gas under pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
  • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
  • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
  • B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
  • B60R21/264—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic
  • B60R21/2644—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic using only solid reacting substances, e.g. pellets, powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
  • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
  • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
  • B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
  • B60R21/264—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic
  • B60R21/2644—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic using only solid reacting substances, e.g. pellets, powder
  • B60R2021/2648—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic using only solid reacting substances, e.g. pellets, powder comprising a plurality of combustion chambers or sub-chambers

Definitions

• the invention relates to a pyrotechnic process for generating gas at two consecutive operating regimes for rapidly pressurizing a structure and then maintaining, in said structure, the pressure for a long time (said long time is generally 40 milliseconds to 1 minute) .
• the invention also relates to a pyrotechnic gas generator suitable for implementing said method.
• the field of application of the invention relates more particularly to the airbag side protection, also called “curtain airbags", used in automotive safety. It also includes devices useful for emptying a fluid reservoir or moving a piston.
• airbags used in automotive safety. It also includes devices useful for emptying a fluid reservoir or moving a piston.
• These air bags are generally deployed by means of hot gases delivered by a pyrotechnic gas generator.
• the cushion should deploy quickly and remain inflated in the moment of shock.
• the pyrotechnic gas generators are, in these cases, designed to operate in a short period of time: of the order of a few tens of milliseconds.
• curtain airbags must deploy quickly (a few milliseconds) at the time of impact and then remain inflated for a period of time of about ten seconds.
• the bag After deployment, the bag, to remain inflated, must be supplied with gas in order to compensate, on the one hand, gas leaks (bag porosity.) And, on the other hand, the cooling of the hot gases from the generator pyrotechnic.
• the fast gas generators conventionally used for front or side airbags are therefore not more suitable since, after the inflation phase, it is necessary to continue generating for ten seconds of the lower flow rate gases to maintain the inflated bag.
• the gas generator adapted to this type of device must first, in short, generate a high flow, to deploy and inflate the bag and, in a second step, longer, generate a lower gas flow to maintain the pressure in the bag. It is therefore a generator with two operating modes: the first being qualified as a high-speed regime and the second low-speed regime.
• This type of generator is also suitable for pressurizing a cavity with variable volume. The targeted applications can then be the emptying of a fluid reservoir or the displacement of a piston.
• US Pat. No. 5,967,550 describes a generator containing two pyrotechnic charges of different compositions, arranged in a single combustion chamber.
• the application WO 01/34516 describes a generator containing two pyrotechnic charges of different compositions, each arranged in the two compartments of a single combustion chamber.
• the intervention of two loadings obviously presents a disadvantage on the industrial level since it is necessary to qualify, to manufacture and to handle two pyrotechnic compositions.
• the device described in the application US 2006/0086408 comprises a first chamber provided with an igniter and connected by orifices to the outside environment. After activation of the generator, the second combustion chamber is connected to the first, its charging is ignited by the hot gases from the first chamber. This second chamber debits to the outside via the first chamber. In this case, the effect is to generate a low flow in the first moments to dislodge the airbag from its receptacle and then produce a larger flow to inflate the bag.
• the application FR 2 877 428 has a device internally divided by two partitions which define three chambers, namely two combustion chambers each containing a pyrotechnic charge, disposed on either side of a plenum chamber open to the outside environment.
• the partitions are traversed by an orifice which allows the controlled passage of the gases generated by the combustion in the combustion chambers to the plenum.
• This device is provided with only one igniter so that the gases generated by the pyrotechnic charge of one of the two combustion chambers pass through the plenum chamber and enter the second combustion chamber devoid of igniter where they cause the combustion of the charge which is present there.
• the patent application FR 2 863 986 describes a pyrotechnic gas generator for an airbag.
• Said generator comprises, in a cylindrical housing provided with a gas discharge opening and a closed end, an inner cylindrical member housing a gas producing agent, a filter and ignition means.
• said generator comprises two combustion chambers, a first combustion chamber which discharges into a second combustion chamber, itself discharging towards the outside via the discharge opening. No indication is provided on the operating pressure of said two chambers.
• the gas production agents involved in said two chambers differ from each other (by at least one of their characteristics: quantity, composition, composition ratio, size, shape). It is this difference which makes it possible to adjust the flow of gas, to obtain a bi-regime effect: strong then weak or weak then strong.
• the gas generator according to said application FR 2 863 986 does not generate a strong and low flow using two identical gas production agents.
• Pyrotechnic devices with gas flow regulation using moving members are also described, for example, in patent application EP 149 332. They are also well known in the field of throttle thrust gas throttling. These systems have the main disadvantage of implementing moving members subjected to hot gas flows, increasing their cost, complexity and probability of failure.
• hybrid generators coupling a pressurized gas supply to a pyrotechnic gas generator (FR 2 831 122, FR 2 829 570, US 6 786 507).
• These hybrid systems have, on the one hand, the disadvantage of using a reserve gas under pressure may leak during the lifetime and, secondly, a complex architecture of connecting the two chambers: one pyrotechnic and the other comprising a gas under pressure.
• the pyrotechnic charge consists of bulk propellant grains placed inside the channel of a cylindrical propellant block. The two loadings of different geometries therefore coexist in the same combustion chamber. Deployment of the bag is provided by the pressurized gas reserve heated by the operation of the gas generator whose initial flow is essentially delivered by the loading of bulk grains. The combustion of the channel block ensures the supply of gas for the inflated maintenance of the bag.
• the method of the invention - pyrotechnic process for generating gas at two successive rates, a first rate then a second rate, said first rate being greater than said second rate - comprises;
• said first combustion chamber operates at high pressure and said second combustion chamber operates at low pressure.
• the notions of "high pressure” and “low pressure” are here relative notions.
• the high pressure is usually at least 3 times higher than the low pressure.
• the low pressure is generally between 0.1 and 10 MPa, advantageously equal to or close to the atmospheric pressure (0.1 MPa), while the high pressure is generally between 0.3 and 30 MPa, is advantageously about 10 MPa.
• two combustion chambers operating at different pressures are used.
• the first flow rate which can be described as a high flow rate, corresponds to the sum of the gas flow rates, initially generated by the combustion of the two pyrotechnic charges and then the second flow, which is may qualify as low flow rate, corresponds to the delivery gas flow, for a longer time, during the continuation of the combustion of the second combustion chamber load.
• the high-pressure combustion generates gases which, via at least one nozzle, are discharged, generally directly or almost directly (it is obvious that one thus seeks to avoid any cooling of said gases) in the second combustion chamber called lower chamber pressure.
• Said gases initiate the combustion of the second pyrotechnic charge in said second combustion chamber.
• Said second combustion chamber is equipped with at least one outwardly venting vent. It works at low pressure.
• the vents of the low pressure chamber are sized so that the flow of gas generated in the chamber operating at high pressure called high pressure chamber is, in the first moments of the combustion of the first pyrotechnic charge, sufficient to pressurize the lower chamber. pressure.
• An initial pressurization is favorable for, on the one hand, to obtain a good initiation of the combustion of the charge of the low pressure chamber and, on the other hand, to generate a high gas flow rate in the first phase of operation.
• the loading of the high pressure chamber ends burning before the loading of the low pressure chamber.
• the end of the combustion of the loading of the high pressure chamber induces a pressure drop in the low pressure chamber: the combustion rate of the charging of the low pressure chamber decreases accordingly.
• the burning speed of the propellant is all the more important as the pressure in the combustion chamber is high. It is therefore understood that the high pressure chamber contributes mainly to the flow of the gas generator during the first phase at high flow.
• the second phase of low flow operation is thus ensured by the only combustion of the low pressure chamber charge.
• Said low pressure chamber is equipped with at least one vent.
• the opening diameter of said at least one vent is sufficient to drop the pressurization of the chamber to a value close to that of the external environment, when the loading of the high pressure chamber has finished burning. It may be wise to multiply the number of vents, to decrease the opening of each. This allows, on the one hand, to better distribute the gases produced, for example, in the device to be inflated and, on the other hand, to trap, within the second combustion chamber, the skeletons (residues) of combustion of the pyrotechnic charge, skeletons that can not escape to the outside via small openings.
• the first and second pyrotechnic charges may each be associated with an independent ignition device.
• the method of the invention is initiated by the single ignition of the first charge in the first combustion chamber.
• a single pyrotechnic igniter intervenes thus, mounted on the high pressure chamber.
• the loading of said high pressure chamber is thus ignited by said igniter.
• the hot gases delivered enter the low pressure chamber via said at least one nozzle ("inter-chamber orifice"). Said hot gases initiate the charging of the low pressure chamber.
• the loading of said low pressure chamber then advantageously adds its gas flow rate to that of the loading of the high pressure chamber, for the production of a high flow rate, useful, for example, in the context of a deployment and inflation phase. 'a structure.
• the first and second pyrotechnic charges used have the same composition.
• the clamping coefficient total combustion area / total area of the chamber orifices.
• the clamping coefficient total combustion surface / total area of the orifices of the chamber
• the clamping coefficient of the first combustion chamber is advantageously greater than that of the second combustion chamber (operating at low pressure).
• first and second pyrotechnic charges have or not the same dimensions and / or geometries.
• the first and second pyrotechnic charges may have the same composition, the same dimensions and the same geometry or may differ from one another by at least one of said parameters. .
• the difference in operation (regime) high pressure / low pressure between the two chambers is controlled solely by the diameters of the orifices of the two chambers.
• the diameter of the at least one orifice of the high pressure chamber must be smaller than that of the at least one orifice of the low pressure chamber.
• the pyrotechnic process of the invention is efficient, in its simplest implementation version, with: a single propellant composition
• the propellant blocks often used for airbag applications are most often pellets obtained by compressing granules of energetic materials.
• pellets of the same composition by varying the diameter and thickness of the pellets of each load, it is possible to accentuate the difference in flow rate and duration of combustion between the two chambers.
• the first pyrotechnic charge may have a thickness to be burned lower than that of said second charge (second charge which is intended to be burned as long as possible);
• the propellant element (the propellant elements) constituting the second pyrotechnic charge may have at least one of its (their) combustion surfaces inhibited. It is thus intended to prolong the burning time of said second load.
• the arrangement of the block or blocks in the low pressure combustion chamber is such that the flame front propagates only on one side of the block or blocks.
• the block or blocks may be partially inhibited to obtain a frontal combustion (so-called cigarette).
• the first pyrotechnic charge consists of a single propellant element or of several propellant elements arranged in bulk or arranged, advantageously arranged in bulk and, independently, the second pyrotechnic charge consists of a single element of propellant. propellant or propellant, arranged in bulk or arranged.
• the pyrotechnic charge of the high pressure chamber is thus advantageously composed of one or more propellant elements (pellets, strands, etc.) in bulk, of small dimensions such as, for example, those usually used for airbag applications.
• This type of loading conventionally makes it possible to generate a large amount of gas for a short period of time so as to ensure the deployment and inflation of the bag.
• the high pressure in the chamber is provided both by the large combustion surface of this type of loading and by the small diameter of said at least one nozzle separating the two chambers. The high operating pressure leads to a high combustion rate favorable to obtaining a large flow of gas.
• the pyrotechnic charge of the low pressure chamber is advantageously in the form of at least one propellant block operating at low pressure.
• Said load has a greater burning thickness than the loading of the high pressure chamber.
• the combustion time of said load operating at low pressure is longer than that of the advantageously bulk load operating at high pressure.
• the load is composed of several monolithic blocks, the latter are advantageously stacked on top of one another. The blocks then light up as the combustion front advances. This makes it possible to maintain the gas flow for a longer time than that generated by the bulk loading.
• the loading of the low pressure chamber thus continues to burn after the end of combustion of the charging of the high pressure chamber. This allows in particular to maintain the pressure in an inflatable structure after deployment.
• the length of the blocks used can in particular vary between 5 and 10 mm, in the case of composition without binder used in the field of automotive safety.
• the composition of the pyrotechnic charges of the invention advantageously comprises basic copper nitrate, as an oxidizing charge and guanidine nitrate, as a reducing charge. It very advantageously comprises basic copper nitrate, as sole oxidizing charge and guanidine nitrate, as the only reducing charge.
• Such a combination of basic nitrate of copper / guanidine nitrate is in fact known to present, in the field of automotive safety (driver type airbags), a combustion rate, already rather low compared to those of other compositions used in this field.
• said composition generally comprises: from 45 to 55% by weight of guanidine nitrate;
• the method of the invention is also advantageously implemented so that the gases generated in the first combustion chamber are removed from the second combustion chamber, via said at least one vent (opening on the outside), without flow through the second pyrotechnic charge.
• the gases produced by the combustion of the second pyrotechnic charge are cooled within the second combustion chamber.
• the present invention relates to a new type of pyrotechnic gas generator with two combustion chambers, suitable for implementing the method described above.
• said two combustion chambers communicate via at least one nozzle
• the other which opens out via at least one vent, is able to operate at low pressure.
• the geometry of such a generator is advantageously cylindrical.
• the combustion chamber adapted to (designed to) operate at high pressure can be integrated into the combustion chamber suitable for
• the two chambers are contiguous, so that the two pyrotechnic charges are expected to be vis-à-vis.
• the clamping coefficient of the chamber capable of operating at high pressure is advantageously greater than the clamping coefficient of the chamber capable of operating at low pressure.
• said at least one vent formed on the body of said chamber capable of operating at low pressure is advantageously at a level such that it allows the evacuation of the gases generated.
• the pyrotechnic charge of the chamber capable of operating at low pressure can thus be a full block, inhibited, with frontal combustion, of diameter equivalent to that of said chamber.
• the vent (the vents) of the low pressure chamber is (are) advantageously arranged on the body of said chamber, between the inter-chamber separation orifice (s) (nozzle (s)) and the loading of said chamber.
• said second combustion chamber (able to operate at low pressure) therefore comprises means for cooling the gases generated within it.
• Such means contain a cooling agent, such as water or, advantageously, any other liquid or solid having a high calorific value and capable of vaporizing at high temperature (in contact with the combustion gases).
• the coolant remains in the liquid phase at a lower temperature than that of water. It may especially consist of the Novec 1230® agent marketed by the company 3M.
• Such means advantageously consist of at least one capsule, capable of releasing the agent that it contains as and when the combustion of the pressure maintaining charge (second pyrotechnic charge).
• Figure 1 is a generator diagram of the invention, loaded, suitable for implementing the method of the invention.
• Figure 2 schematically illustrates the presence of a coolant in the low pressure combustion chamber of said generator.
• Figure 3 shows a particular embodiment of generator of the invention (loaded), suitable for implementing the method of the invention.
• Figure 4 is a generator diagram of the invention, loaded, suitable for the implementation of the method of the invention in its simplest version (with two identical loadings).
• the generator 100 comprises the two combustion chambers
• the combustion chamber 1 is that which operates at high pressure HP,
• the combustion chamber 2 is the one that operates at low pressure BP.
• Said two chambers 1 (HP) and 2 (BP) communicate via the nozzle 3.
• the gases generated from the chamber 1 and the chamber 2 are discharged to the outside via the vents 21.
• 1 consists of n pellets 10 'of propellant.
• 2 consists of 20 m propellant blocks.
• cooling means 22 have been shown for the combustion gases generated in chamber 2 (LP). Said means 22 are in the form of toric capsules.
• FIG. 3 shows at 12 a pyrotechnic ignition relay charge and at 13 a holding spring of said pyrotechnic ignition relay charge 12 and of the charge 10 of the chamber 1.
• FIGS. 1 and 3 FIG. it is clearly seen that the two loadings 10 and 20 are arranged facing each other, the vents 21 of the chamber 2 being disposed on the body of said chamber 2 between the nozzle 3 and the loading 20 of said chamber 2 (advantageous variant ).
• FIG. 4 (very diagrammatic), there is a generator 100 of the invention, of the same type as that of FIGS.
• a generator of the type of the invention was designed to quickly pressurize (inflate) a structure by rapidly delivering a large flow of gas and then maintain for a long time t (10 milliseconds ⁇ t ⁇ 1 min) the pressure within said structure, while delivering a lower gas flow.
• the length of the entire generator is 220 mm for an internal diameter of 17 mm.
• the length of the chamber operating at low pressure is 123 mm, this length is adjusted according to the dimensions of the pressure maintaining load.
• Said generator is as shown in FIG. 3.
• the ignition relay charge typically has a mass of 0.4 g.
• the generator of the invention was tested with pellets and blocks having the same weight composition, known composition of the prior art (see in particular WO 2006/047085) and consisting of a mixture of basic copper nitrate, guanidine nitrate and alumina (additive).
• the pyrotechnic charge of the high-pressure chamber is composed of 4 g of pellets 6 mm in diameter and a thickness of 1.8 mm. Said pellets intervene in bulk.
• the orifice separating the two chambers has a diameter of 3 mm.
• a maximum value of the pressure in the high pressure chamber is 20 MPa, during the operation of the load, for an operating time of 40 milliseconds.
• the pyrotechnic charge of the low pressure chamber consists of 3 to 10 g of stacked cylindrical blocks each measuring 17 mm in diameter and 9 mm in thickness.
• the body of said low pressure chamber is provided with three vents 3 mm in diameter.
• the pressure in the low pressure chamber during the combustion phase of the pyrotechnic charge of the other chamber is about 2 MPa. After the end of the combustion of said charging of the high pressure chamber, said pressure in said low pressure chamber is (almost) identical to that of the outside of the generator ( ⁇ close to the ambient pressure). This characteristic directs the choice of the pyrotechnic composition which must have stable combustion at low pressure.
• the burning time of the low pressure chamber charge is 60 s to 2 s depending on the configuration of the stack loading.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Air Bags (AREA)

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• 2007
  • 2007-10-08 EP EP07858521A patent/EP2076410A2/de not_active Withdrawn
  • 2007-10-08 WO PCT/FR2007/052090 patent/WO2008043946A2/fr active Application Filing
  • 2007-10-08 US US12/444,632 patent/US8453575B2/en not_active Expired - Fee Related

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