DE102019118065A1 - PYROTECHNIK-FREE COLD GAS GENERATOR AND SAFETY DEVICE FOR A VEHICLE WITH A PYROTECHNIK-FREE COLD GAS GENERATOR - Google Patents

Abstract

A pyrotechnic-free cold gas generator (10), in particular for a safety device in a vehicle, comprises a pressurized gas container (12) in which a gas with an oxygen content is enclosed under pressure. The pyrotechnic-free cold gas generator (10) further comprises an activation device (16) for opening the compressed gas container (12) and a gas heating device (18) for heating the gas that can flow out of the compressed gas container (12). The gas heating device (18) is set up to generate ozone from the oxygen content.

Description

The invention relates to a pyrotechnic-free cold gas generator, in particular for a safety device in a vehicle. The invention also relates to a safety device for a vehicle with such a gas generator.

Gas generators are an indispensable part of today's, especially s, safety technology in vehicles. If necessary, they deliver gas that z. B. is used to fill a gas bag or to drive a seat belt tensioner. For the sake of simplicity, the filling of a gas bag is primarily considered below, the invention not being restricted to this application.

Various types of gas generators are known. Pyrotechnic gas generators have a solid propellant with pyrotechnics, usually in tablet form, which, when the gas generator is activated, is ignited with the aid of an ignition unit and then burns down. A hot gas produced by this burn-off of the pyrotechnics flows from the gas generator into the gas bag in order to fill it with gas.

In the case of hybrid or cold gas generators, the gas required to fill the gas bag is largely generated from a pressurized cold gas stored in a pressure chamber of the gas generator in its non-activated state. When the gas generator is activated, the pressure chamber is usually opened by a pyrotechnic igniter igniting a pyrotechnic propellant that heats the gas and destroys a membrane that closes the pressure chamber to the outside when the gas generator is not activated so that the heated gas can flow out. Known gas generators use, for example, a helium-argon mixture as compressed gas, which is stored in the pressure chamber at a pressure of up to 800 bar.

Time-consuming and costly qualifications are required for the use of pyrotechnic substances in safety equipment, even if only small quantities are used. In addition, in view of the increasing number of airbag systems in modern vehicles and the constantly increasing life expectancy of vehicles, the safety requirements for propellants and ignition devices are becoming ever more stringent. Therefore, gas generators that are completely freed from pyrotechnics are fundamentally advantageous.

The DE 195 24 094 A1 already proposes a gas generator for restraint systems that should do without pyrotechnic components. The gas generator has a pressurized gas cylinder, the closure of which is to be opened by an operation whose energy comes from an electrical and / or magnetic energy source, e.g. B. in the form of a spark discharge from a capacitor. The gas is also to be heated without pyrotechnics by coupling in electrical and / or magnetic energy.

The object of the invention is to create a pyrotechnic-free cold gas generator with effective gas heating.

This object is achieved by a pyrotechnic-free cold gas generator with the features of claim 1. Advantageous and expedient configurations of the pyrotechnic-free cold gas generator according to the invention are specified in the dependent claims.

The pyrotechnic-free cold gas generator according to the invention is provided in particular for a safety device in a vehicle and comprises a pressurized gas container in which a gas with an oxygen content is enclosed under pressure. The pyrotechnic-free cold gas generator further comprises an activation device for opening the compressed gas container and a gas heating device for heating the gas flowing out of the compressed gas container. According to the invention, the gas heating device is set up to generate ozone from the oxygen content.

The invention is based on the knowledge that when ozone is generated from oxygen and, above all, during the subsequent recombination, a great deal of heat is generated, which can be used to heat a cold gas stored in a pressurized gas container and thereby expand its volume so much that a safety device in a vehicle, such as an airbag restraint device or a belt tensioner, can be operated. The advantage here is that no pyrotechnics are required to generate the ozone. It is true that a large amount of energy is required to set the reaction in motion and, if necessary, to maintain it over a certain period of time. The necessary energy can, however, e.g. B. be provided as electrical energy from a power source. In the case of electric vehicles in particular, such a high-voltage source is available in the form of at least one accumulator, which is primarily intended to drive the vehicle.

A first possibility to set the ozone production in motion is to cause an electrical discharge on a capacitor through a voltage breakdown (visible as a sparkover). Some of the free electrons produced during the discharge are so energetic that they Can split oxygen molecules (O ₂ ). The oxygen atoms (O) created in this way then combine with other oxygen molecules to form ozone (O ₃ ), which by recombination exothermically decays back to molecular oxygen.

According to a first embodiment of the pyrotechnic-free cold gas generator, the gas heating device therefore has a capacitor provided for connection to a high-voltage source, on which a voltage breakdown can be brought about.

The condenser should either be arranged inside the pressurized gas container or, if this is not possible or technically too complex, in the immediate vicinity of a closure of the pressurized gas container, which can be opened by the activation device of the gas generator. “In the immediate vicinity” is to be understood as meaning that the condenser is located in the flow path of the gas flowing out of the pressurized gas container after the closure has been opened.

A second possibility of starting the production of ozone is to split oxygen molecules by means of high-energy radiation, in particular UV radiation. This process is known as photodissociation or photolysis. The individual oxygen atoms then combine with other oxygen molecules to form ozone, which by recombination exothermically disintegrates again into molecular oxygen.

According to a second embodiment of the pyrotechnic-free cold gas generator, the gas heating device therefore has a radiation source, in particular for providing UV radiation, in order to thereby generate ozone from the oxygen content of the stored cold gas.

It is sometimes desirable that the main heat generation should not take place directly in or on the gas generator, but z. B. in a diffuser connected downstream of the pressurized gas container or in a gas bag even further away. To this end, the invention provides means for influencing the temperature and / or the pressure and / or the ozone concentration during ozone generation. These parameters determine the time frame for the recombination of the ozone molecules with the oxygen atoms to form molecular oxygen, which is responsible for the main heat development.

In a further development of the invention, it is provided that an energy supply to the gas heating device can be set automatically. By automatically setting the energy input, it is basically possible to adapt the ozone generation and the recombination process to varying external conditions, such as the ambient temperature. In addition, different power levels of the gas generator can be defined.

The gas heating device for generating ozone can be arranged completely outside of the pressurized gas container, which is the technically simpler solution, since no parts have to be integrated into the pressurized gas container.

The gas heating device can, however, also be arranged at least partially within the pressurized gas container. Accordingly, in this embodiment, the ozone generation takes place directly in the pressurized gas container. This creates the possibility of using the initial heating inside the pressurized gas container also to open the pressurized gas container, so that in this case no separate activation device is required, but the activation device and the gas heating device are implemented as a common device.

In addition, a pressure sensor for monitoring the pressure in the pressurized gas container can be provided in order to be able to check the operational suitability of the gas generator according to the invention at any time.

The invention also provides a safety device with a pyrotechnic-free cold gas generator as described above. The safety device according to the invention also comprises a gas bag or a belt tensioner, the pyrotechnic-free cold gas generator being provided for filling the gas bag or for driving the belt tensioner.

The present invention is primarily aimed at electric vehicles. Therefore, according to this preferred application, the safety device according to the invention comprises an accumulator provided primarily for driving an electric vehicle. The accumulator is electrically connected to the capacitor of the gas heating device in order to charge it and to generate a voltage breakdown.

Particularly in the event that after an impact the ozone generation and the gas heating caused by it do not take place sufficiently quickly enough for the operation of a normal safety device, for example when using a radiation source, it is advisable to use the gas generator according to the invention in a safety device that provides a pre-crash -Sensor technology. Namely, with such a system the need becomes Recognized before the actual impact, which is why more time is available for gas heating.

• - 1 eine schematische Darstellung eines erfindungsgemäßen pyrotechnikfreien Kaltgasgenerators nach einer ersten Ausführungsform; und
• - 2 eine schematische Darstellung eines erfindungsgemäßen pyrotechnikfreien Kaltgasgenerators nach einer zweiten Ausführungsform.

Further features and advantages of the invention emerge from the following description and from the attached figures, to which reference is made. In the figures show:

• - 1 a schematic representation of a pyrotechnic-free cold gas generator according to the invention according to a first embodiment; and
• - 2 a schematic representation of a pyrotechnic-free cold gas generator according to the invention according to a second embodiment.

In 1 is a gas generator 10 with a pressurized gas container 12th shown by a clasp 14th , e.g. B. in the form of a bursting membrane is closed. In the pressurized gas container 12th is cold gas under high pressure, for example 550 bar at room temperature, included. The cold gas is a mixture of several gases, e.g. B. argon and / or helium, with a certain proportion of oxygen.

To open the shutter 14th of the pressurized gas container 12th is an activation device (shown here only symbolically) 16 provided, which is connected to a controller. On the mechanism of the activation device 16 will not be discussed in detail here. Various measures are known to those skilled in the art to open the closure of a pressurized gas container quickly enough to meet the requirements for a safety device.

A gas heating device also connected to the control 18th ensures that after activation of the gas generator 10 and thus opening of the pressurized gas container 12th that from the pressurized gas container 12th Gas flowing into the airbag is heated to a sufficient extent and its volume is thereby expanded so that the airbag fully unfolds in the time allotted for this.

The in 1 The embodiment shown is the gas heating device 18th the pressurized gas container 12th downstream. In principle, however, there is also an arrangement of the gas heating device 18th , or essential components thereof, within the pressurized gas container 12th possible.

The gas heating device 18th is set up to generate ozone from the oxygen content of the stored gas by electrical spark discharge.

According to a first embodiment, a capacitor is used for this 20th provided just behind the breech 14th arranged and connected to a power source 22nd connected. One or both electrodes of the capacitor 20th can also through one or different sections of the pressurized gas container 12th or other parts of the gas generator 10 be educated. As a power source 22nd In particular, an accumulator can be used in an electric car.

After or already during the opening of the closure 14th by the activation device 16 comes with the power source 22nd the capacitor 20th electrically charged until it comes to a discharge through a voltage breakdown. The voltage required for this depends on the type of gas mixture as well as its humidity and pressure. If enough current is supplied to the spark discharge, an arc discharge or an arc is created. The following explains how the voltage breakdown is used to generate ozone and, in connection with this, to heat the cold gas.

Some of the free electrons that are created during discharges have high speeds. Such high-energy electrons can transfer their energy to the oxygen molecules through inelastic collisions, which leads to their dissociation: $$O_2+e\to O+O+e$$

wobei M ein sogenannter „dritter Stoßpartner“ ist, d. h. ein Gasmolekül, welches die überschüssige Energie der Reaktion aufnimmt.The oxygen atoms created in this way tend to react quickly with oxygen molecules and form ozone: $$O+O_2+\mathrm{M.}\to O_3+\mathrm{M.}+\mathrm{W.}Ärme$$

where M is a so-called “third collision partner”, ie a gas molecule that absorbs the excess energy of the reaction.

The resulting ozone can then be destroyed again by recombination: $$O+O_3\to 2O_2+\mathrm{W.}Ärme$$

The energy released as heat during the formation and destruction of the ozone thus heats the gas when the gas bag is filled.

With regard to the extent of the heating, it should be noted that the electron energy and density, which are determined by the reduced field strength or discharge power, significantly influence the concentration of oxygen atoms and thus the heat development.

If one looks at the time sequence of the above-mentioned reactions, it can be seen that the dissociations of the oxygen molecules occur after about 0.2 ns due to a discharge pulse. The subsequent ozone production by reaction of oxygen atoms with oxygen molecules also takes place very quickly. Overall, ozone formation through a discharge pulse is a very fast process.

The temperature rise of the gas due to the formation of ozone is around 300 K. At temperatures in the range of 600 K, ozone decomposes exothermically within 1 to 2 ms. The energy released when the ozone breaks down also quickly contributes to the heating of the gas.

Another, somewhat slower alternative for ozone generation is ozone synthesis through radiation. A corresponding structure for this is in 2 shown. The gas heating device 18th shows a radiation source here 24 with the gas still in the pressurized gas container 12th and / or when flowing out of the pressurized gas container 12th is exposed to UV radiation.

$$O+O_2+M\to O_3+M+W\ddot{a}rme$$

$$O_3+h\cdot v_2\to O+O_2$$

$$O+O_3\to 2O_2+W\ddot{a}rme$$

wobei h die Planck-Konstante, v₁ bzw. v₂ die Wellenlänge der einfallenden Strahlung und M ein beliebiges Gasmolekül ist, das für die Energiebilanz der Reaktion erforderlich ist.Typical gases that are enclosed in a compressed gas container of a gas generator are not photochemically active, which is why it is not possible to heat them significantly by radiation. Thanks to the pressurized gas tank 12th However, based on the so-called "Chapman cycle" (ozone-oxygen cycle), the gas temperature can be increased significantly overall. The following reactions take place continuously as long as UV radiation is available: $$O_2+H\cdot v_1\to 2O$$

$$O+O_2+\mathrm{M.}\to O_3+\mathrm{M.}+\mathrm{W.}\ddot{a}rme$$

$$O_3+H\cdot v_2\to O+O_2$$

$$O+O_3\to 2O_2+\mathrm{W.}\ddot{a}rme$$

where h is the Planck constant, v ₁ or v _{2 is} the wavelength of the incident radiation and M is any gas molecule that is required for the energy balance of the reaction.

For the dissociation of molecular oxygen, v ₁ must be between about 190 and 240 nm, and for the dissociation of ozone, v ₂ must be between about 200 and 300 nm. The radiation source 24 is set up accordingly to provide UV radiation in these wavelength ranges.

The energy released can also be used to heat the gas in the case of ozone formation brought about by UV radiation and the subsequent decomposition through recombination.

Although ozone synthesis by radiation is somewhat slower compared to the previously described ozone synthesis by voltage breakdown, it can be useful to use this technology in safety systems with pre-crash sensors, since in such systems the need is recognized before the actual impact and therefore more time is available for gas heating. There is also the possibility of accelerating the radiation-induced ozone formation using catalysts.

Regardless of the type of ozone generation, it is basically possible to influence the point in time of the recombination of the oxygen atoms and ozone molecules and the resulting heat by means of suitable measures. The length of time in which ozone and molecular oxygen can coexist depends on the temperature, the pressure and the ozone concentration. If, depending on the temperature and pressure, the ozone concentration falls below such critical levels that could lead to detonations, moderate deflagration can be brought about. The deflagration speed can, for example, be set so that only in one of the pressurized gas containers 12th downstream diffuser or even only in the gas bag the recombination takes place and accordingly the thermal energy is only made available there.

It is also possible in principle to automatically adjust the energy input (voltage breakdown or UV radiation) to obtain an adaptive mechanism that z. B. allows a compensation of the ambient temperature or the gas pressure or even a power control for the representation of certain load cases.

When the gas heater 18th , or essential components thereof, as indicated above, within the pressurized gas container 12th is arranged, the pressure increase brought about by the gas heating in the interior of the pressurized gas container 12th to open the shutter 14th be used. In this case the activation device 16 and the gas heater 18th sensibly realized as a common facility.

Using a pressure sensor 26th in the pressurized gas container 12th the usability of the gas generator 10 always check.

List of reference symbols

10

Gas generator

12

Pressurized gas container

14th

Clasp

16

Activation device

18th

Gas heating device

20th

capacitor

22nd

Power source

24

Radiation source

26th

Pressure sensor

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19524094 A1 [0006]

Claims (13)

Pyrotechnic-free cold gas generator (10), in particular for a safety device in a vehicle, with a pressurized gas container (12) in which a gas with an oxygen content is enclosed under pressure, an activation device (16) for opening the compressed gas container (12), and a gas heating device (18) for heating the gas that can flow out of the pressurized gas container (12), wherein the gas heating device (18) is set up to generate ozone from the oxygen content. Pyrotechnic-free cold gas generator (10) according to Claim 1 , characterized in that the gas heating device (18) has a capacitor (20) provided for connection to a high-voltage source (22). Pyrotechnic-free cold gas generator (10) according to Claim 2 , characterized in that the condenser (20) is arranged in the immediate vicinity of a closure (14) of the pressurized gas container (12) which can be opened by the activation device (16). Pyrotechnic-free cold gas generator (10) according to Claim 1 , characterized in that the gas heating device (18) has a radiation source (24), in particular for providing UV radiation. Pyrotechnic-free cold gas generator (10) according to one of the preceding claims, characterized by means for influencing the temperature and / or the pressure and / or the ozone concentration during ozone generation. Pyrotechnic-free cold gas generator (10) according to one of the preceding claims, characterized in that an energy supply to the gas heating device (18) can be set automatically. Pyrotechnic-free cold gas generator (10) according to one of the preceding claims, characterized in that the gas heating device (18) is arranged completely outside of the pressurized gas container (12). Pyrotechnic-free cold gas generator (10) according to one of the Claims 1 to 6th , characterized in that the gas heating device (18) is arranged at least partially within the pressurized gas container (12). Pyrotechnic-free cold gas generator (10) according to Claim 8 , characterized in that the activation device (16) and the gas heating device (18) are implemented as a common device. Pyrotechnic-free cold gas generator (10) according to one of the preceding claims, characterized by a pressure sensor (26) for monitoring the pressure in the pressurized gas container (12). Safety device for a vehicle, characterized by a pyrotechnic-free cold gas generator (10) according to one of the preceding claims and with a gas bag or a belt tensioner, the pyrotechnic-free cold gas generator (10) being provided for filling the gas bag or for driving the belt tensioner. Safety device according to Claim 11 for an electric vehicle, with an accumulator provided primarily for driving the electric vehicle and a pyrotechnic-free cold gas generator (10) Claim 2 , wherein the accumulator is electrically connected to the capacitor in order to charge it and generate a voltage breakdown. Safety device according to Claim 11 or 12th , characterized in that the safety device has a pre-crash sensor system.

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