Gas generator free of pyrotechnics

A gas generator, in particular for vehicle passive restraint systems, is constructed without pyrotechnical components for gas production, gas release, or gas heating. The gas generator includes a compressed gas container having an opening that is releasably closed by a closure such as a burst diaphragm, and at least one electrical and/or magnetic device arranged to destroy or release the closure upon triggering. It is also possible to achieve gas heating without the use of pyrotechnical components by coupling electrical and/or magnetic energy from the electrical and/or magnetic device into the gas container and particularly into the gas contained therein.

FIELD OF THE INVENTION 
The invention relates to gas generators, in particular for passive 
restraint systems in motor vehicles, including at least one closed, 
gas-filled, and pressurized gas container. 
BACKGROUND INFORMATION 
There are known restraint systems which are equipped with a gas bag 
(airbag) that is inflated by a gas generated by a gas generator. Two basic 
types are differentiated here: the purely pyrotechnical gas generator and 
the hybrid gas generator. With a purely pyrotechnical gas generator, 
ignition and gas generation are effected by the combustion of suitable 
pyrotechnical propellant agents (generally solid propellants). With a 
hybrid gas generator, only ignition and gas heating are effected by the 
combustion of suitable pyrotechnical propellant agents. Hybrid gas 
generators include a container filled with gas. This gas container is 
pressurized. To prevent premature release of the gas flow, the container 
is sealed by a closure in the form of a burst diaphragm. As this gas does 
not have to be first generated by pyrotechnical means, it is designated as 
cold gas. Furthermore, a hybrid gas generator comprises an igniter 
protruding into a combustion chamber, where the igniter, when triggered, 
will ignite a combustion source in the form of propellant disks, for 
example. This pyrotechnically generated gas, which is also designated as 
hot gas, destroys the closure allowing the cold gas to escape from the 
container. Hot gas and cold gas mix, and then the resulting gas mixture 
escapes to the outside through a discharge aperture and may then be used 
for blowing up an airbag or may be conveyed to another gas-consuming load. 
However, a disadvantage of these arrangements is that the gas flow contains 
pollutants such as pollutant gases and combustion residues which are 
produced by the burning of the pyrotechnical components (propellant 
disks). The substances required for this purpose are highly explosive, 
thus necessitating special precautionary measures to be taken. This may 
cause damage to property and/or personal injury during manufacture and 
assembly. As the pyrotechnical components must maintain their 
functionality over a long period of time, on the one hand, but are also 
extremely sensitive to humidity on the other hand, the combustion chamber 
must be hermetically sealed. Moreover, a further pyrotechnical igniter is 
required for igniting the propellant disks, which also has the 
above-mentioned disadvantages. For disposal and/or recycling, the gas 
generator must either be first ignited or be opened up with great effort; 
and it can be into the recycling process only after it has first been 
cleaned of all contaminants. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a gas generator which does not use 
any pyrotechnical components and thus avoids the above-mentioned 
disadvantages. 
According to the invention, the closure of the cold gas container will be 
removed or broken by means of electric, magnetic or a resulting kinetic or 
thermal energy. Further according to the invention, gas heating is 
achieved by coupling electric and/or magnetic energy into the gas 
generator. 
According to advantageous further developments of the invention, several 
variants are provided for removing or destroying the closure, and/or 
heating up the cold gas. The invention further provides for a complete 
discharge of the vehicle battery caused by this energy consumption. 
The advantages achieved by this invention are in particular that the 
closure of the cold gas container can be opened and/or the gas can be 
heated without pyrotechnical components in a quick and controlled fashion. 
In addition to achieving a simpler generator construction, gas generation 
according to the invention is absolutely free of any pollutants; there 
will be no harmful residues remaining in the gas generator. After use, the 
gas generator can be disposed of or recycled without any problems. A 
combustion chamber will no longer be needed. Pyrotechnical igniters are 
not required. The gas generator structure is reduced in size. Manufacture, 
assembly, and storage are simplified very considerably. Also, the 
discharge of the vehicle battery, if used as an energy source, prevents a 
vehicle fire in the event of an accident.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a cold gas container 1 in which the cold gas 2 is located. The 
cold gas container 1 is closed by a closure 3, e.g. in the form of a burst 
diaphragm, and is pressurized. An ignition chamber housing 7 is mounted on 
the closure end of the cold gas container 1. The ignition chamber housing 
7 is also fitted with outlet apertures 4 through which the gas is fed to 
the consuming device such as a gas bag. Opposite the closure 3, an energy 
source 5 is located in the ignition chamber; in the event of an ignition, 
this energy source 5 will remove or destroy the closure or relevant 
attachments thereof. As described later in relation to FIGS. 3-6, this can 
be done in various ways. The energy source 5 can be supplied with 
electrical power from the vehicle battery. After opening the closure, it 
is also possible to heat up the escaping cold gas 2 by coupling energy 
made available by energy source 5 into the container 1 and specifically 
into the gas 2. The contacts 6 of energy source 5 will be routed to the 
outside through an ignition chamber cover 8 which closes the ignition 
chamber. The gas, which has been heated up by the energy source 5, can 
flow out to the consuming device through the outlet apertures 4, which are 
arranged in a circle around the cylindrical wall of the ignition chamber 
housing 7. 
FIG. 2a also shows a gas container 1 which contains cold gas 2. The gas 
container 1 is closed by a closure 3 and pressurized. However, this time 
the energy source 5--which is used for opening the closure and/or heating 
the gas--is located inside the gas container 1. In this case, closure 3 
may be opened from the inside. Here, in the event of ignition, energy 
source 5 will cause the closure or relevant attachments thereof to be 
removed or destroyed. As described later in connection with FIGS. 3-6, 
this can be effected in various ways. After the closure has been opened, 
the gas 2 can again be heated by coupling energy made available by energy 
source 5 into the gas 2. Opening the closure and heating up the gas by 
coupling energy into the gas may also be effected simultaneously. The 
contacts 6 of energy source 5 are fed either through the wall of cold gas 
container 1 or through closure 3. Advantageously, in the event of closure 
3 being destroyed, a sieve 9 fitted over the opening of the container 1 
prevents ingress of fragments into a gas bag or another consuming device. 
In FIG. 2b, a further variant is illustrated. Here, all contacts 6 are 
attached to gas container 1. Therefore, supply leads may be attached on 
the inside of the container and tapped, via the housing, from outside; 
thus, the container walls need not be pierced. This Figure is also 
intended to illustrate that, e.g., in the event of an attraction force on 
closure 3 coming from energy source 5, it is unnecessary to provide a 
sieve or a similar filter material. Also, the energy source is located 
directly next to or in the gas so that the energy output here can 
contribute directly to the gas heat-up process. By means of various 
particular arrangements which can be implemented using various mechanical, 
magnetic, and electrical technologies, or resulting combinations thereof, 
(see FIGS. 3-6), overall dimensions can be achieved which are only 
dependent on the required size of the gas container. 
FIG. 3a illustrates how the opening mechanism and cold gas heat-up process 
operate if energy source 5 essentially consists of a coil. 
If the energy required is to be taken from a coil 10 through which live 
current flows, then on ignition or triggering a current flow or current 
impulse will be initiated in the coil. This current flow I very quickly 
induces a magnetic field B. Magnetic poles are formed such that attraction 
forces 15 or repulsion forces 16 are exerted on magnetized or 
ferromagnetic materials. If closure 3 consists of ferromagnetic or 
magnetized materials, and if current flow I in coil 10 is sufficiently 
powerful, closure 3 will either be attracted or repulsed by the coil. If 
coil 10 is mounted in a fixed position, this closure 3 will either move 
toward or away from the coil. Cold gas container 1 will be opened. 
It does not matter here whether the coil arrangement 10 is located 
internally, externally, or wound around cold gas container 1. It is also 
possible that cold gas container 1 may consist of a ferromagnetic or 
magnetized material, so that the entire gas container 1 will be 
accelerated and destroyed by deceleration when it impacts with an 
obstruction (e.g. a spike). This variant is not illustrated here. 
Heating of the cold gas by means of a coil 10 can be achieved in various 
ways: 
a) By pulsing coil 10, a suitable gas 2 or an appropriate additive in the 
gas (having atoms or molecules that form a dipole) are caused to vibrate 
and thus heated up. 
b) Coil 10 behaves like a resistor and heats up as a result of the current 
flow; this in turn will heat up the gas when it flows past coil 10. 
c) The gas or additives initiate a chemical reaction during electrical, 
magnetic, and/or mechanical opening, which heats up the gas. To this end, 
e.g., the cold gas container will contain an inert gas and reactive gas 
mixture such as Argon/O.sub.2. On opening the burst diaphragm, metallic 
materials such as Mg, Al or Zr are ignited and thus a combustion of the 
metal (e.g. in the form of a wire) is initiated with O.sub.2 (lightning 
cube principle); this produces a powerful heating effect. In the same way, 
on opening the burst diaphragm, a combustible gas or liquid gas mixture 
consisting of fuels such as H.sub.2 or suitable hydrocarbons and oxidators 
such as O.sub.2 or N.sub.2 O, which mixture is contained in the cold gas 
container together with an inert gas (such as Ar, N.sub.2, CO.sub.2), can 
be ignited. 
d) On opening, the impact of closure 3 and coil 10--for instance--will 
cause a short circuit which produces discharge lightning that heats up gas 
2 either directly or as described at c) above. 
FIG. 3b illustrates another possibility for opening a burst diaphragm 3 by 
means of a coil 10. Here, closure or burst diaphragm 3 is secured by means 
of ferromagnetic or magnetized attachments 11. 
Provided current flow I in coil 10 is sufficiently powerful, these 
attachments 11 will either be attracted or repulsed by the coil when 
magnetic field B is generated. The attachments 11 will be detached, 
closure 3 is pushed toward the outside by the internal pressure of cold 
gas container 1, and gas 2 flows out to the consuming device. In this 
arrangement also, it does not matter whether the coil arrangement 10 is 
located internally, externally, or on cold gas container 1. Also, the 
attachments 11 may be located in any position. To avoid the need of 
providing a collecting sieve for attachments 11, these may be attached to 
the gas generator system by means of a holding device. This prevents the 
attachments 11 from entering into the gas bag or other consuming device. 
The gas is heated up in a fashion identical to the one described in 
connection with FIG. 3a. 
FIG. 3c and FIG. 3d show two further implementation examples for opening 
closure 3 by means of the magnetic field of a coil 10. In FIG. 3c small 
ferromagnetic or magnetized projectiles 12, or in FIG. 3d ferromagnetic or 
magnetized spikes 13, are located within or without the gas container, 
which projectiles or spikes are either attracted or repulsed by coil 10 
due to the application of magnetic field B. The coil can be located 
internally, externally, or wound around the gas container. Here, 
projectiles 12 or spikes 13 will be accelerated by magnetic field B which 
is in turn induced by a current flow or current impulse I. 
The projectiles 12 pierce the burst diaphragm. Depending on how free they 
are in their movement, which may be determined by a suspension or flexible 
mounting device 14, the spikes 13 can pierce the burst diaphragm fully or 
partially, and then, e.g. by reducing, switching off, or pulsing the 
magnetic field, the spikes 13 can be retracted to open or release the 
pierced holes, or only parts thereof; in this way, a controlled flow of 
gas 2 will be achieved. The projectiles can be collected e.g. mechanically 
in a sieve or magnetically by another magnet. The gas is heated up in a 
fashion identical to the one described in connection with FIG. 3a. 
FIG. 4a shows another implementation example in which a capacitor having 
poles 17 and 18 is used as energy source 5. Here, closure 3 arranged in 
the outlet aperture of container 1 itself forms one pole 18 of the 
capacitor. In this implementation example, closure 3 will be negatively 
charged and attracted to the other pole or electrode 17 due to the 
attraction forces of the positively charged other pole the container 17 
located outside the container 1. Charging is effected via leads 6 from an 
electrical power source 5'. By means of the attraction forces 15 of both 
poles, the cold gas container 1 is opened, and the negatively charged 
closure 3 will be discharged at the other positive pole 17. During this 
discharge, energy will be output to the surrounding environment, i.e. the 
gas will be heated. As an alternative, a positively charged electrode in 
the form of a capacitor plate 17a, together with closure 3 and via the 
leads 6a, forms another capacitor as shown in FIG. 4d. Here, the negative 
pole 18 which may be formed by closure 3 is subjected to an attraction 
force 15a in the direction of pole 17a. It is also possible to achieve 
opening by means of the electrical field between the two poles 18 and 17a 
producing spark-overs or discharge lightning, i.e. an electrical 
discharge; in this way, the gas is heated and internal pressure rises. Due 
to the increased pressure differential the closure will be released from 
the container outlet aperture, i.e. the container will be opened. 
Implementation examples where the poles are charged up with the same 
charge, and therefore repulse each other, are also possible but not shown 
here. Also, it is not mandatory that closure 3 must provide a pole. 
Opening can also be achieved by transmitting electrical energy from an 
externally mounted capacitor(not shown), which energy is produced by a 
sudden discharge (e.g. short circuit) taking the form of a current flow or 
spark-over, directly to the diaphragm which is then pierced. 
By means of a capacitor, the cold gas can be heated in various ways: 
a) The gas is conducted in between capacitor plates 17, 18 and heated by 
discharge lightning and sparks between the capacitor plates. 
b) A gas 2, or additives contained therein, are neutralized at the charged 
up capacitor plates. This releases energy, and the gas will heat up. 
c) The gas or additives initiate a chemical reaction during electrical, 
magnetic, and/or mechanical opening, which heats up the gas. To this end, 
e.g., the cold gas container will contain an inert gas and reactive gas 
mixture such as Argon/O.sub.2. On opening the burst diaphragm, metallic 
materials such as Mg, Al or Zr are ignited and thus a combustion of the 
metal (e.g. in the form of a wire) is initiated with O.sub.2 (lightning 
cube principle); this produces a powerful heating effect. In the same way, 
on opening the burst diaphragm, a combustible gas or liquid gas mixture 
consisting of fuels such as H.sub.2 or suitable hydrocarbons and oxidators 
such as O.sub.2 or N.sub.2 0, which mixture is contained in the cold gas 
container together with an inert gas (such as Ar, N.sub.2. CO.sub.2), can 
be ignited. 
d) On opening the burst diaphragm, a short circuit is caused, e.g. by two 
capacitor plates 17 and 18 impacting; and the energy released in this 
process will heat up the gas. 
FIG. 4b, a further implementation of the capacitor solution is presented. 
Here, no separate capacitor or capacitor plate is required but gas 
container 1, together with closure 3, will form the two poles of a 
capacitor. An electric field is produced. The poles will attract or 
repulse each other. This opens closure 3 of gas container 1. By means of 
an appropriate construction design, it is also possible to initiate 
internal discharge events in the form of spark-overs or discharge 
lightning which will cause the gas 2 to heat up, increase internal 
pressure, and thus open the closure. Charging of the capacitor is effected 
via leads 6. The poles are electrically insulated from each other and the 
surrounding environment by an insulating protective layer 21 arranged 
between the container 1 and the closure 3. The gas is heated up in a 
fashion identical to the one described in connection with FIG. 4a. 
FIG. 4c shows a further variant. The container 1 and closure 3 are 
electrically insulated from each other by means of an insulating material 
21 and shielded externally. Even closure 3 is used as an insulator. Two 
poles or electrodes 6A and 6B are arranged in the container 3 adjacent the 
closure 3. Both poles 6A and 6B are charged via leads 6. If the charge 
density on the two poles 6A and 6B is sufficiently large, a discharge 
process 20 will be initiated. Energy is thereby released and used to 
increase the temperature of gas 2. This will cause an over-pressure on the 
inside of container 1 by means of which closure 3 is opened. Using 
suitable housing shapes, opening of the closure can be accelerated and gas 
heat-up optimized. The gas can also be heated in another way as described 
above in connection with FIG. 4a. 
If the energy source 5 comprises a current impulse generator, high voltage 
generator, and/or plasma generator 19 (as shown in FIG. 5), closure 3 will 
be bombarded with ionized particles (electrons, atoms, molecules) or a 
beam of particles 20' produced in the generator, until closure 3 is 
damaged and the holes produced in this way allow the cold gas to escape. 
Also, further variants as already described above in connection with FIGS. 
3a-d and 4a-c can be implemented as such generators essentially comprise 
coils and/or capacitors, thus allowing magnetic forces or electrical 
repulsion and attraction forces to be used for direct opening of a gas 
container closure 3. 
A further option not shown here consists of using a resistor--which, on 
application of a voltage, is heated up very strongly by the current 
flow--to destroy the closure. The resistor may be fitted either on, 
inside, or in the vicinity of the closure. The resistor may take the form 
of a wire or spike. This has the effect that the heat radiation gets 
directly into or upon the closure and destroys it. Here, to increase the 
triggering speed, it may make sense to keep the resistor at a predefined 
temperature by means of continuous operation thereof, so that only a very 
small temperature differential will be required to cause the device to be 
triggered. The heat development at the resistor may also be used to heat 
up the gas and compensate for the cooling loss which occurs during 
outflow. 
All of the above solutions are based on coupling energy produced either 
directly or indirectly by electrical or magnetic means into the container 
and especially into the gas. 
To supply the energy source 5, as shown schematically in FIG. 6a, the car 
battery 5'B provided in the vehicle may be used as the power source 5'; 
its energy contents may be made available completely or partially over the 
time required by means of suitable measures (e.g. short circuit). If the 
device is triggered, this solution provides the advantage of the battery 
being discharged, thus preventing vehicle fires caused by battery arcing 
or the like in the event of an accident. However, it is also possible to 
implement other or additional power sources 5' (e.g. capacitors 5'A as 
shown schematically in FIG. 6b) that will supply the energy source 5 with 
the necessary energy. 
Also, other variants can be implemented such as combinations comprising 
electric and magnetic energy, or combinations comprising electric or 
magnetic energy in conjunction with chemical energy.