DE19541797A1 - Variable performance gas generator for airbags - Google Patents

Abstract

Gas generator for inflating a driver's airbag having an auxiliary heater to control the temperature of the gas. Also claimed is the process under which this gas generator operates. The generated gas is heated by elements (10) whose action is varied by a controller influenced by (a) ambient temperature, (b) driver's weight and (c) driver's position, especially that of the driver's head.

Description

The invention relates to a gas generator of an impact protection system for Vehicle occupants who are under pressure of the propellant gas to inflate of the airbag of an airbag system.

Such a gas generator is known for example from DE 29 15 202 C3 or US 4,878,690.

In the event of a vehicle crash, so-called airbag gas generators generate Gas for filling an airbag, which the occupants in front of the vehicle Impact on hard vehicle interior parts like the steering wheel protects. Physically seen nothing else happens than that by the vehicle crash accelerated occupant braked by the relatively soft airbag or is caught. This collection occurs in that gas mass through ventilation openings (so-called ventholes) from the airbag flows. Accordingly, the airbag has the task of reducing the kinetic energy of the Dismantle occupants as "softly" as possible.

Airbag concepts today mostly use pyrotechnic gas generators Kind, as for example from DE 40 05 871 C2, DE 40 12 893 A1 or DE 41 35 299 A1 are known. Pyrotechnic gas generators work generally such that a current pulse from one Sensor technology recognizing vehicle crashes an igniter in the gas generator is ignited. This kind of ignition is caused by a kind of ignition charge that generates hot particles. Hit these hot particles then on the surface of what is usually in tablet form Fuel, which then ignites itself and in the so-called combustion chamber  developing high pressure and temperature burns. This creates the gas to fill the airbag. Besides pure gas also liquid or solid components during combustion arise, the gas flow through appropriate filters in one Filter chamber cleaned before exiting the gas generator. At the When flowing through the filter, the gas flow is additionally cooled.

It is important that there is always a complete burn, and therefore always the same amount of gas is generated when the propellant burning has been started once. Furthermore, the Temperature of the gas generated essentially only by the Ignition of the gas generator prevailing ambient temperature flows. Because the filters remain unchanged and therefore cool the gas flow always in the same way. This means nothing else than that Catching effect of the airbag system essentially through the reverse exercise temperature is affected.

There are also airbag concepts that use it to fill the airbag required propellant gas in a so-called compressed gas container Hybrid gas generator is stored. So is from DE 44 05 997 C1 such gas generator is known in which pyrotechnically by means of it resulting hot gases opened the sealing disc of the pressure gas container becomes. The outflowing cold gas mixes with the hot gas in one Filter chamber and is then placed in the filter Airbag headed.

With such a hybrid gas generator, the temperature of the in the airbag flowing gas only from the ambient temperature determined and thus essentially the catch effect of the Airbag.

The dependence on the ambient temperature leads to the mentioned Gas generators over a temperature range from -35 ° C to + 85 ° C to different pressures in the airbag. This can do that cause that at low temperatures the airbag too weak and at high temperatures is inflated too much.  

In addition, the occupant's kinetic energy depends on both with pyrotechnic gas generators as well as with hybrid gas generators of completely different parameters, such as crash speed, weight of the Occupants, size of occupants, seating position, seat belt fastened yes / no, etc.

Therefore, in terms of optimal occupant protection, performance should of the airbag system and consequently the mass and / or the temperature of the gas generated by the gas generator on the kinetic to be collected Energy. If you consider this in a first approximation ideal gas law

p * V = m * R * T

With
p = pressure in the airbag
V = volume in the airbag
m = mass of gas in the airbag
R = gas constant
T = temperature of the gas

and if we first assume that V, m and R in the case under consideration as can be viewed largely constant, then the essential Influencing factor for the pressure in the airbag is the gas temperature.

As already mentioned, the pyrotechnically generated gas stream is in the gas generator cooled and cleaned by built-in filters. It depends The cooling effect depends, among other things, on the temperature of the filter internals. Because if theoretically the temperature of the filter internals is equal to Is gas temperature, then no cooling of the gas flow through the Filters are installed. Therefore, the cooling effect depends on the tempera difference between the built-in filter and the gas flow temperature. A The ambient temperature is not taken into account.

From the article "Increasing occupant safety through airbag and belt strammer "by Luigi Brambilla in ATZ Automobiltechnische Zeitschrift 84 (1982) 2, pages 77 to 81 is known that by multi-layer metal filter  a favorable gas cooling and gas purification is achieved, so that a relatively clean and tempered gas gets into the airbag. The above described dependence of the airbag system's impact on the However, ambient temperature is also not taken into account.

Finally, also in DE 44 05 997 C1 cited above known hybrid gas generator does not take the ambient temperature into account inspects

In contrast, the object of the present invention is a gas generator to introduce gate with the features described above, in which in The performance of the airbag system with regard to optimum occupant protection depending on the ambient temperature on the kinetic to be collected Energy of the vehicle occupants currently to be protected are matched can, the structure compared to known gas generators without Influencing temperature is not much more complicated and time-consuming and the outer dimensions of the gas generator essentially correspond to those of known systems.

According to the invention, this complex task is just as effective how surprisingly simple way solved that on the way of the propellant gas to the airbag a heater for tempering the propellant gas flowing past is provided; or that at least one with a pressurized gas container filled with flammable liquid gas is provided in a heater is provided inside.

In the first-mentioned gas generator according to the invention, therefore for the pressure in the airbag essential propellant temperature variable be th and by appropriate control of the heater vary within wide limits. In the second invention According to the gas generator that is stored in the compressed gas tank combustible liquid gas by means of the heater on a certain Temperature maintained so that after ignition of the liquefied gas as burning product that exits the airbag at the desired temperature having.

In this way, different degrees of filling of the air cushion can be generated and thus the catch effect optimally on the actual kinetic  Energy of the respective occupant can be matched. The clear influence the ambient temperature on the performance of the airbag system can be decisively reduced by the principle according to the invention. The The heater itself can be designed so small in volume that it does not stand out in relation to the total volume of the gas generator. It is also possible to use existing gas generators according to the invention with the heater for tempering the propellant gas on simple and inexpensive way to retrofit.

An embodiment of the invention is particularly preferred Gas generator in the heating device, a control device is assigned, which is dependent on signals from one or more External sensors cause the heater to flow past Propellant at a correspondingly higher or lower To temper temperature level. It is a particularly good and auto automatic adjustment of the system to the current requirements the individual parameters of the vehicle occupant to be protected possible.

In an advantageous development of this embodiment, a Temperature sensor connected to the control device, which in Dependence on the ambient temperature of the airbag system electrical or outputs mechanical signals to the control device. To this In particular, the ambient temperature can be more important Include parameters in the control of the inflation behavior of the airbag system be drawn.

One is particularly simple, inexpensive and inexpensive to manufacture Development in which the temperature sensor comprises a bimetal element.

A further development is also preferred, in which a weight sensor with the Control device is connected, depending on the respective Weight of the vehicle occupant sitting behind the impact protection system Outputs signals to the control device.

A further development in which a position sensor is also advantageous the control device is connected, which is dependent on the respective seating position, especially depending on the position of the  Head of the vehicle occupant sitting behind the impact protection system Outputs signals to the control device.

By using both a weight and a position feed Sors can advantageously the precise kinetic energy of the occupant be determined when hitting the air cushion, so that an optimal setting of the airbag system's impact is made possible.

An embodiment of the invention is particularly preferred Gas generator, in which the heating device electrically heated Heizele includes. By using electrical energy to Heating the propellant gas can lead to particularly short reaction times full development of the heating effect can be achieved. This results in a relatively large range for setting the gas temperature.

In special world formations, the electrical heating elements can or more heating plates and / or one or more heating wires include. The respective heating element can either be directly in the Propellant flow protrude, or indirectly others, with the propellant flow heat up directly connected components.

The heating device according to the invention can preferably be used at pyrotech African gas generators are used, the heater either inside the combustion chamber in front of its gas outlet opening is arranged or between the combustion chamber and the airbag.

In the latter case, the heating device is preferably in the Filter chamber of a gas generator or outside in front of the gas flow openings of the gas generator arranged.

Furthermore, the heating device according to the invention can also advantageously be used Hybrid gas generators are used. Here is the heater on the way of the gas flowing out of the compressed gas container arranged.

In a particularly preferred, extremely easy to implement Embodiment is in the propellant gas flow to the airbag at least one (per se known) filter device arranged according to the invention with the  Heater is connected and thus tempered by this can. Since the propellant gas flows through the filter device in any case must and can be cooled by this, as already mentioned above described by controlling the temperature difference between hot Propellant gas cooler filter device relative to it the cooling effect on the propellant gas and thus the fuel gas temperature can be controlled.

In an advantageous development of this embodiment is pre- see that the filter device electrically conductive parts such. B. a comprises metallic sieve and / or a metallic housing, which as electri shear resistance act, and that at least one of the electrically conductive Parts controllably connected to an electrical energy source. In all The simplest case only needs an electrical lead to the corresponding metallic parts of the filter device are provided be at the other end, for example with the positive pole of the Battery of the vehicle can be connected, the metallic parts the filter device electrically at the ground potential of the vehicle are connected. Variables are further improved embodiments, where the supplied current or voltage and thus the electrical heating energy varies by means of a control device can be.

Methods for operating a gas also fall within the scope of the invention generator of an impact protection system for vehicle occupants, in which either a pressurized propellant to inflate the airbag an airbag system is generated, and the propellant gas on its way into the Airbag is tempered by means of a heater, or in one Pressurized gas tank stored propellant gas by means of a heating device is tempered.

In an advantageous variant of the method according to the invention provided that the propellant gas depending on the ambient temperature Airbag system and / or the weight of the behind the Impact protection system seated vehicle occupants and / or by his Sitting position and / or the expected impact and / or the Impact energy of his head is tempered. So that the Aufblasver keep the airbag system optimal to the current conditions can be set.  

In a further advantageous method variant, the Tempering of the propellant gas simply by electrically heating one or more heating elements.

Further advantages of the invention result from the description and the Drawing. Likewise, the above and the others Features listed according to the invention individually for themselves or to several can be used in any combination. The shown and described embodiments are not intended to be final To understand enumeration, but rather have exemplary character for the description of the invention.

In the following, the invention is to be illustrated using exemplary embodiments of Devices for gas flow temperature control by controlling the Filter temperature explained in connection with drawings and to be discribed. Show it:

Figure 1 is a schematic representation of a pyrotechnic gas generator with heating devices arranged in its filter chamber.

Fig. 2 is a schematic representation of a further pyrotech African gas generator with in the combustion chamber angeord designated heaters;

Figure 3 is a schematic representation of another pyrotech African gas generator with heaters arranged outside the filter chamber.

Fig. 4 is a schematic representation of a further pyrotech African gas generator with both in its filter chamber and arranged outside the same heaters;

Figure 5 is a schematic representation of a tubular pyrotech African gas generator with a temperature-controlled filter arranged in its filter chamber.

Figure 6 is a schematic representation of a hybrid gas generator with a filter chamber arranged in its temperature-filter.

Fig. 7 is a schematic representation of a liquid gas generator, in the compressed gas container, a heating device is housed; and

Fig. 8 is a schematic representation of another liquid gas generator, in which a heating device is arranged outside the compressed gas container.

In the example shown in the Fig. 1 embodiment, a schematic vertical section is seen by a cylindrical gas generator 1 is ignited in which a central ignition chamber 2, if necessary, an ignition charge by an igniter 11, enter the hot gases via connecting openings 3 in a combustor 4 , where solid firing tablets 17 are stored, which are ignited by the hot ignition gases and in turn generate a hot propellant when burned, which is fed through outlet openings 5 into a filter chamber 6 and through a filter 7 through outlet openings 8 to the airbag of an airbag system. The gas generator 1 shown has a rotationally symmetrical design, but for the sake of simplicity only the side shown in the figure on the left has been described.

According to the invention, in the gas generator 1 shown, power lines 9 lead from the filter 7 to an electrical energy source, which is also not shown in the drawing. As a result, the filter 7 can be heated by means of a heating device 10 which, in addition to the function of filtering out solid and liquid constituents from the propellant gas stream, can now also take on the task of uniform temperature control of the propellant gas. The essential for the pressure of the airbag Treibgastem temperature is thus variable and can be varied in a simple manner by heating the filter 7 accordingly. As a result, different degrees of filling of the air cushion can be generated and the catch effect on the actual kinetic energy of a vehicle occupant can be optimally coordinated.

By using electrical energy to heat the filter 7 by means of the heating device 10 , extremely short reaction times are achieved until the end temperature is reached. This results in a relatively large range for the optimal setting of the propellant temperature. The significant influence of the ambient temperature on the performance of the airbag system can be significantly reduced by this principle.

The drawing does not show sensors with which the electrical power supplied to the heating device 10 and thus the final temperature of the propellant gas flow to be tempered can be taken into account on the basis of external parameters, such as the ambient temperature, weight and seat position of the vehicle occupant, etc.

However, the principle according to the invention can also be shown in FIG Embodiments can be realized in which instead of the filter or in addition, the propellant gas stream is heated at other points. This can, for example, by heating plates, heating wires or other types of heatable heating elements happen either directly with a protrude hot surface in the propellant gas stream, or indirectly through this Temper heating of boundary surfaces of the propellant gas flow.

The following exemplary embodiments show examples of further arrangements Possibilities for different gas generator types.

2 also shows as Fig. A matching with the structure of the gas generator of FIG. 1 embodiment, however, is being arranged in the combustion chamber 4, in contrast to that a heating device 10 in front of the outflow opening. 5 This heating device 10 can also be embedded in a filter (not shown).

FIGS. 3 and 4 also show a gas generator which corresponds to the structure of the gas generators described above . The gas generator 1 according to FIG. 3 has a filter 7 a which can be temperature-controlled with a heating device 10 and which is outside the filter chamber 6 in front of its outflow openings 8 is arranged, while the filter chamber 6 contains a conventional filter 7 . In contrast, the gas generator 1 according to FIG. 4 contains two temperature-controlled filters 7 and 7 a, which are arranged in combination with the exemplary embodiments according to FIGS. 1 and 3 with a heating device 10 in the filter chamber 6 and with a heating device 10 a outside the filter chamber 6 . This further heating device 10 a is supplied with electrical energy via power lines 9 a.

The tubular pyrotechnic gas generator 1 according to FIG. 5 has a combustion chamber tube 15 for forming a combustion chamber 4 , which receives an ignition unit 11 for igniting the fuel tablets 17 which generate the propellant gas. The space between the combustion chamber tube 15 and a filter tube 16 surrounding it forms a filter chamber 6 of this gas generator 1 .

Combustion chamber outflow openings 5 are arranged at the end of the combustion chamber 15 opposite the ignition unit 11 , whereas filter chamber outflow openings 8 are provided at the opposite end of the filter tube 16 . The filter chamber 6 comprises a hollow cylindrical filter 7 having a heatable this filter 7 in the region of 8 Filterkammerabströmöffnungen heater 10, the electric current through services 9 is energized.

The hybrid gas generator 1 according to FIG. 6 consists of a compressed gas container 12 which has a gas outlet opening 18 which is closed by a bursting membrane 13 . In the area of this gas outlet opening 18 , a filter tube 19 is flanged, which has a combustion chamber 20 having an ignition unit 11 . This combustion chamber 20 takes fuel in the form of pellets 17 , which generates a gas flowing through a combustion chamber outflow opening 21 when the ignition unit 11 is ignited. Since this combustion chamber outflow opening 21 is arranged in the combustion chamber 20 with respect to the bursting membrane 13 , this is welded on by the propellant gas, so that the cold gas emerging therefrom from the compressed gas container 12 deals with the hot propellant gas in through the filter tube 19 , the pressurized gas container 12 and the combustion chamber 20 formed filter chamber 22 mixes.

The filter chamber 22 in the area between the filter tube 19 and the combustion chamber 20 has a hollow cylindrical filter 7 which can be heated by means of a heating device 10 . The propellant gas passes through this filter 7 and the filter openings 8 arranged in its area in the filter tube 19 into an airbag (not shown).

The last exemplary embodiments according to FIGS. 7 and 8 each show a liquid gas generator which is constructed with a compressed gas container 12 containing a combustible gas mixture. This pressure vessel 12 contains a gas outlet opening 18 which is closed by a bursting membrane 13 . If the liquid gas is ignited by means of an ignition unit 11 , a pressure ruptures the bursting membrane 13 due to the combustion gases generated, so that the combustion gases formed as combustion products emerge from the container and can inflate the airbag (not shown) of an airbag system as a propellant gas.

In the liquefied gas generator according to Fig. 7 in the compressed gas container 12, a heater 10 is disposed in order to heat the stored liquefied gas to a certain temperature, so that after an ignition flowing into the airbag has the desired temperature at the inner wall.

In the liquid gas generator according to FIG. 8, a heating device 10 is not arranged inside but outside of the pressure gas container 12 in a housing 19 forming a diffuser, which is flanged to the pressure gas container 12 in the area of the bursting membrane 13 .

The heating device 10 can be provided there alone or together with a filter 7 , whereby it should be noted that the outflowing gas is guided past this heating device 10 or is passed through the filter 7 in order to subsequently pass through gas outlet openings 8 provided in the housing 19 to enter an airbag (not shown).

The heating devices 10 in the exemplary embodiments of FIGS. 6 to 8, as in the previously described exemplary embodiments, are supplied with the electrical energy via power lines 9 .

Claims (21)

1. Gas generator ( 1 ) of an impact protection system for vehicle occupants, which generates a pressurized propellant for inflating the airbag of an airbag system, characterized in that a heating device ( 10 ) is provided on the path of the propellant gas to the airbag for temperature control of the propellant gas flowing past. 2. Gas generator of an impact protection system that generates a pressurized propellant for inflating the airbag of an airbag system, characterized in that at least one pressurized gas container ( 12 ) filled with a combustible liquid gas is provided and that a heating device ( 10 ) is arranged in this pressurized gas container . 3. Gas generator according to claim 1 or 2, characterized in that the heating device ( 10 ) is assigned a control device which, depending on signals from one or more external sensors, causes the heating device ( 10 ), the propellant gas flowing past to a correspondingly higher or lower To temper the temperature level. 4. Gas generator according to claim 3, characterized in that a tempe Temperature sensor is connected to the control device, which is dependent speed of the ambient temperature of the airbag system electrical or outputs mechanical signals to the control device. 5. Gas generator according to claim 4, characterized in that the tempe rature sensor comprises a bimetallic element.   6. Gas generator according to one of claims 3 to 5, characterized in net that a weight sensor is connected to the control device, the depending on the respective weight of the behind the impact protection system seated vehicle occupants signals to the control device delivers. 7. Gas generator according to one of claims 3 to 6, characterized in net that a position sensor is connected to the control device, which depends on the respective seating position, especially in Dependence on the position of the head of the behind the impact protection system seated vehicle occupant signals to the control device. 8. Gas generator according to one of the preceding claims, characterized in that the heating device ( 10 ) comprises electrically heatable heating elements. 9. Gas generator according to claim 8, characterized in that the Heating elements one or more heating plates and / or one or more Include heating wires. 10. Gas generator according to one of claims 1 or 3 to 9, characterized in that the gas generator ( 1 ) has at least one combustion chamber ( 4 ) in which due to electrical signals of an acceleration sensor provided in the vehicle by an exothermic chemical reaction of one or more fuels the pressurized propellant gas for inflating the airbag of the airbag system is generated, and that the heating device ( 10 ) in the combustion chamber ( 4 ) is arranged in front of its outlet opening ( 5 ). 11. Gas generator according to one of claims 1 or 3 to 9, characterized in that the gas generator ( 1 ) has at least one combustion chamber ( 4 ) in which due to electrical signals of an acceleration sensor provided in the vehicle by an exothermic chemical reaction of one or more fuels the pressurized propellant gas for inflating the airbag of the airbag system is generated, and that the heating device ( 10 ) is arranged between the combustion chamber ( 4 ) and the airbag. 12. Gas generator according to claim 11, characterized in that a filter chamber ( 6 ) connects to the combustion chamber ( 4 ) and that the Heizvor direction ( 10 ) is arranged in the filter chamber ( 6 ). 13. Gas generator according to claim 11, characterized in that a filter chamber ( 6 ) connects to the combustion chamber ( 4 ) and that the heating device ( 10 a) is arranged in the propellant gas flow between the filter chamber ( 6 ) and the airbag. 14. Gas generator according to claim 12, characterized in that a further heating device ( 10 a) is arranged in the propellant gas flow between the filter chamber ( 6 ) and the airbag. 15. Gas generator according to one of claims 1 or 3 to 9, characterized in that at least one of an inert gas or gas mixture or a combustible liquid gas store the compressed gas container ( 12 ) is provided, which is opened on the basis of electrical signals of an acceleration sensor provided in the vehicle and that the heating device ( 10 ) is arranged on the path of the gas flowing out of the compressed gas container ( 12 ). 16. Gas generator according to one of claims 1 or 3 to 15, characterized in that at least one filter device ( 7 ) is arranged in the propellant gas flow to the airbag, and that the heating device is connected to the filter device ( 7 ) and can temper it. 17. Gas generator according to claim 16, characterized in that the filter device ( 79 comprises electrically conductive parts ( 109 such as a metallic sieve and / or a metallic housing, which act as an electrical resistor and that at least one of the electrically conductive parts is controllably connected to an electrical energy source. 18. A method for operating a gas generator ( 1 ) of an impact protection system for vehicle occupants, in which a pressurized propellant gas is generated for inflating the airbag of an airbag system, characterized in that the propellant gas is tempered by a heating device on its way into the airbag. 19. A method for operating a gas generator ( 1 ) of an impact system for vehicle occupants, in which a pressurized propellant gas is generated for inflating the airbag of an airbag system, characterized in that the propellant gas stored in a pressurized gas container is heated by means of a heating device. 20. The method according to claim 18 or 19, characterized in that the Propellant gas depending on the ambient temperature of the airbag system and / or the weight of the person sitting behind the impact protection system Vehicle occupants and / or from their seating position and / or from ahead visible impact and / or the impact energy of his head tempe is riert. 21. The method according to claims 18 to 20, characterized in that temperature control by electrically heating one or more heaters elements done.