U.S. patent application number 11/023810 was filed with the patent office on 2005-09-01 for method for inflating a gas bag and gas bag module for use in this method.
This patent application is currently assigned to TRW Airbag Systems GmbH. Invention is credited to Reimann, Uwe, Roedig, Karl-Heinz, Schropp, Roland, Zeuner, Siegfried.
Application Number | 20050189054 11/023810 |
Document ID | / |
Family ID | 34585394 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050189054 |
Kind Code |
A1 |
Zeuner, Siegfried ; et
al. |
September 1, 2005 |
Method for inflating a gas bag and gas bag module for use in this
method
Abstract
A method for inflating a gas bag of a safety arrangement in
vehicles provides a gas generator which contains a pyrotechnic
propellant comprising an organic fuel and ammonium perchlorate as
an oxidizing agent. The pyrotechnic propellant, after its
activation, releases a gas which has an amount of hydrochloric
acid. A coating is arranged on the inner surface of the gas bag, on
which the hydrochloric acid is neutralized or absorbed.
Inventors: |
Zeuner, Siegfried;
(Muenchen, DE) ; Reimann, Uwe; (Nuernberg, DE)
; Schropp, Roland; (Tegernheim, DE) ; Roedig,
Karl-Heinz; (Kraiburg, DE) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL & TUMMINO L.L.P.
1111 LEADER BLDG.
526 SUPERIOR AVENUE
CLEVEVLAND
OH
44114-1400
US
|
Assignee: |
TRW Airbag Systems GmbH
|
Family ID: |
34585394 |
Appl. No.: |
11/023810 |
Filed: |
December 28, 2004 |
Current U.S.
Class: |
149/109.6 |
Current CPC
Class: |
C06D 5/06 20130101; B60R
2021/23514 20130101; B60R 21/235 20130101; C06B 23/02 20130101;
C06B 29/22 20130101 |
Class at
Publication: |
149/109.6 |
International
Class: |
C06B 047/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 2004 |
DE |
10 2004 001 625.9 |
Claims
1. A method for inflating a gas bag of a safety arrangement in
vehicles comprising the step of: providing a gas generator and a
gas bag connected to the gas generator, the gas generator
containing a pyrotechnic propellant consisting essentially of one
or more of an organic fuel and ammonium perchlorate and, in
relation to the weight of the fuel and ammonium perchlorate,
between 0 and 10 percent by weight of conventional additives, and
the gas bag having a coating arranged on an inner surface of the
gas bag; activating the pyrotechnic propellant, thereby releasing a
gas which contains an amount of hydrochloric acid, supplying the
gas to the gas bag, and neutralizing or absorbing the hydrochloric
acid on the coating in the gas bag.
2. The method according to claim 1, characterized in that the
coating comprises an amount of chemical substances which are
reacted immediately with the hydrochloric acid to convert the
hydrochloric acid into harmless solid reaction products.
3. The method according to claim 2, characterized in that the
chemical substances are selected from the group consisting of the
oxides, peroxides, hydroxides, carbonates, hydrogen carbonates and
oxalates of alkali metals, alkaline earth metals and transition
metals and mixtures thereof.
4. The method according to claim 2, characterized in that the
chemical substances are selected from the group consisting of
organic amines and polymeric compounds with basic functional
groups.
5. The method according to claim 4, characterized in that the
polymeric compounds are selected from the group of polyamines and
ion exchanger resins.
6. The method according to any of claims 1, characterized in that
the coating comprises surface-active substances capable of
absorbing hydrochloric acid.
7. The method according to claim 6, characterized in that the
surface-active substances are selected from the group consisting of
synthetic silicic acid, aluminium oxide and aluminium hydroxide,
titanium dioxide, activated carbon, soot, nanopowder and mixtures
thereof.
8. A method for inflating a gas bag of a safety arrangement in
vehicles comprising the steps of: providing a gas generator and a
gas bag connected to said gas generator, the gas generator
containing a pyrotechnic propellant consisting essentially of one
or more of an organic fuel and ammonium perchlorate and, in
relation to the weight of fuel and ammonium perchlorate, between
about 0 and 10 percent by weight of conventional additives;
activating the pyrotechnic propellant, thereby releasing a gas,
which contains an amount of hydrochloric acid; and, concurrently
with the activation of the pyrotechnic propellant, releasing and
supplying chemical substances from said gas generator to the gas
bag, which react in the gas bag immediately with the hydrochloric
acid and convert the hydrochloric acid into harmless solid reaction
products.
9. A gas bag module for use in a safety arrangement in vehicles,
comprising a gas bag and a gas generator connected to the gas bag,
the gas generator containing a pyrotechnic propellant which
consists essentially of one or more of an organic fuel and ammonium
perchlorate and, in relation to the weight of the fuel and the
ammonium perchlorate, between about 0 and 10 percent by weight of
conventional additives, and the gas bag having a coating adapted
for the neutralization or absorption of hydrochloric acid released
from the pyrotechnic propellant.
10. The gas bag module according to claim 10, characterized in that
the pyrotechnic propellant consists of the organic fuel and
ammonium perchlorate.
11. The gas bag module according to claim 9, characterized in that
the pyrotechnic propellant has a gas yield, related to mass, of
over 95 percent.
12. The gas bag module according to claim 9, characterized in that
the coating comprises an effective amount of chemical substances
which are adapted for reacting immediately with the hydrochloric
acid.
13. The gas bag module according to claim 12, characterized in that
the chemical substances are selected from the group consisting of
the oxides, peroxides, hydroxides, carbonates, hydrogen carbonates
and oxalates of alkali metals, alkaline earth metals and transition
metals and mixtures thereof.
14. The gas bag module according to claim 12, characterized in that
the chemical substances are selected from the group consisting of
organic amines and polymeric compounds with basic functional
groups.
15. The gas bag module according to claim 14, characterized in that
the polymeric compounds are selected from the group of polyamines
and ion exchanger resins.
16. The gas bag module according to claim 9, characterized in that
the coating comprises surface-active substances with a capability
of absorbing hydrochloric acid.
17. The gas bag module according to claim 16, characterized in that
the surface-active substances are selected from the group
consisting of synthetic silicic acid, aluminium oxide and aluminium
hydroxide, titanium dioxide, activated carbon, soot, nanopowder and
mixtures thereof.
Description
TECHNICAL FIELD
[0001] The invention relates to a method for inflating a gas bag of
a safety arrangement in vehicles and also a gas bag module for use
in this method.
BACKGROUND OF THE INVENTION
[0002] Safety arrangements for vehicles usually contain a gas bag
module which comprises an inflatable gas bag and a gas generator
connected to the gas bag. The gas generator usually contains a
pyrotechnic propellant which is activated as a result of a vehicle
accident and within a very short space of time releases a gas or
gas mixture for inflating the gas bag.
[0003] In the past, in particular mixtures of sodium azide and
inorganic nitrates were used as pyrotechnic propellant. Owing to
the high toxicity of these mixtures, recently, however, propellants
based on organic fuels and inorganic oxidizing agents are being
used. These azide-free propellants are distinguished by high
combustion temperatures which favour the occurrence of liquid or
gaseous by-products. Therefore, large quantities of so-called
slag-forming constituents or cooling agents must be added to these
azide-free propellants, which, however, reduce the gas yield of the
propellant.
[0004] In the motor vehicle industry, on the other hand,
requirements exist for a miniaturizing of all systems, including
the safety arrangements. Therefore, the use of pyrotechnic
propellants with gas yields of over 95 percent would be
advantageous, so that the overall size and the weight of the gas
generators can be further reduced.
[0005] A possibility for the production of pyrotechnic propellants
with a high gas yield would consist in the use of ammonium
perchlorate as oxidizing agent. With the burning of propellants
containing ammonium perchlorate, however, hydrochloric acid is
produced as a by-product, which is not desirable, owing to its
toxicity and corrosivity. Therefore, ammonium perchlorate has been
used as oxidizing agent in pyrotechnic propellants for vehicle
occupant restraint systems hitherto only in small proportions
and/or in a mixture with suitable compounds, such as, for example,
alkali metal nitrates, for the neutralization of the hydrochloric
acid occurring during burning in the propellant. These mixtures,
however, likewise have an insufficient gas yield, owing to the
additives which are then necessary.
[0006] From the U.S. Pat. No. 4,556,236 it is known to arrange a
closed container in the gas bag, which is filled with scented or
aromatic substances, in order to mask unpleasant smells of the gas
used for inflating the gas bag. The container may, for example, be
a plastic bag which is able to be torn open. Neither the type of
substances nor the composition of the gases released from the gas
generator is, however, described in further detail. The described
arrangement of an additional container in the gas bag leads,
moreover, to increased structural space requirements. Also, a
complete distribution of the substances arranged in the container
during the short unfolding phase of the gas bag is not
guaranteed.
[0007] The WO-A 96/13405 relates to a method for reducing the
toxicity of gases which are released in the combustion reaction of
an azide-free fuel and which contain nitrous oxides and carbon
monoxide. For conversion of the nitrous oxides and of the carbon
monoxide, provision is made to coat the inner wall of the gas bag
with a double coating of an alkaline compound and of an oxidation
catalyst. The coating therefore promotes only the adjustment of the
balance of the components present in the gas mixture which,
however, will be dependent on further external parameters such as
pressure and temperature and will only occur to a very incomplete
extent owing to the short reaction time which is available.
[0008] Therefore, the need continues to exist for gas bag modules
with gas generators which owing to the use of pyrotechnic
propellants with a high gas yield are able to be produced so as to
be very small and also light and at a favourable cost, by
dispensing with cumbersome and expensive filter materials.
SUMMARY OF THE INVENTION
[0009] To solve this problem, in accordance with the invention a
method is proposed for inflating a gas bag of a safety arrangement
in vehicles comprising the steps of: providing a gas generator, and
a gas bag connected to the gas generator, the gas generator
containing a pyrotechnic propellant consisting essentially of an
organic fuel and ammonium perchlorate as oxidizing agent and also,
in relation to the weight of said organic fuel and ammonium
perchlorate, between about 0 and 10 percent by weight of
conventional additives, and the gas bag having a coating arranged
on an inner surface of the gas bag; activating the pyrotechnic
propellant, thereby releasing a gas which contains a proportion of
hydrochloric acid; supplying the gas to the gas bag and
neutralizing or absorbing the hydrochloric acid on the coating in
the gas bag.
[0010] The use of ammonium perchlorate as prevailing or even sole
oxidizing agent makes possible the provision of gas-generating
mixtures which are practically totally converted into gas during
combustion. Hereby, a maximum efficiency of the propellant is
achieved. Ammonium perchlorate is, furthermore, compatible with
almost all organic fuels. The gas generators, owing to the use of
pyrotechnic propellants with a high gas yield of over 95 percent,
can be operated with a smaller quantity of propellant than
conventional gas generators. Gas yield is to be understood here as
the mass of the generated gas in relation to the mass of the
propellant which is used. The gas generators can therefore be
produced so as to be smaller and, by dispensing with cumbersome and
expensive filter materials, also lighter and more favourably
priced. The hydrochloric acid occurring from the reaction of the
ammonium perchlorate with the fuel is reliably neutralized inside
the gas bag. Therefore, no toxic or corrosive gas arrives into the
interior of the vehicle. Furthermore, through the evolution of heat
of the neutralization reaction, the service life of the gas bag is
also increased.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] In accordance with the invention, the coating has a
constituent of chemical substances which react directly with the
hydrochloric acid and convert the latter into harmless solid
reaction products. Thereby, the gaseous hydrochloric acid occurring
in the combustion reaction is reliably held back in the gas bag.
The chemical substances can be selected for example from the group
consisting of the oxides, peroxides, hydroxides, carbonates,
hydrogen carbonates and oxalates of alkali metals, alkaline earth
metals and transition metals and also mixtures thereof. These
substances are easily available and favourably priced. Furthermore,
for example, organic amines or polymeric compounds with basic
functional groups are also able to be used. Polymeric compounds of
the group of polyamines and ion exchanger resins are suitable to a
particularly preferable extent. All these compounds are also able
to be used in a mixture with each other.
[0012] Moreover, surface-active substances can also be used for the
coating, on which the gaseous hydrochloric acid can be absorbed.
Particularly suitable as surface-active substances are synthetic
silicic acid, aluminium oxide and aluminium hydroxide, titanium
oxide, activated carbon, soot, nano-powder and mixtures thereof,
which have a high specific surface. The surface-active substances
can be used both in a mixture with each other and also in a mixture
with the previously mentioned chemical substances for the
neutralization of the hydrochloric acid.
[0013] An alternative method in accordance with the invention
provides for a gas generator to be made available which contains a
pyrotechnic propellant with an organic fuel and ammonium
perchlorate as oxidizing agent, the pyrotechnic propellant
releasing a gas after its activation which contains a proportion of
hydrochloric acid, and with the activation of the pyrotechnic
propellant releasing surface-active substances with an absorptive
power for hydrochloric acid or chemical substances and being
supplied to the gas bag preferably in very finely distributed form,
which react in the gas bag directly with the hydrochloric acid and
convert the latter into harmless solid reaction products. As
surface-active substances or chemical substances, the previously
mentioned substances, also in a mixture with each other, can be
used. In this way, the efficiency of the propellant is maintained
in the sense of a high gas yield, whereas the danger of damage to
the gas bag fabric by hot particles is almost ruled out.
[0014] The invention further provides a gas bag module for use in
the method described above, which comprises a gas bag and a gas
generator connected to the gas bag. The gas generator contains a
pyrotechnic propellant which consists essentially of an organic
fuel and ammonium perchlorate as an oxidizing agent, and up to 10
percent by weight of conventional additives for pyrotechnic
propellants, in relation to the weight of fuel and ammonium
perchlorate. Preferably the propellant consists exclusively of the
organic fuel and ammonium perchlorate, whereby the provision of
pyrotechnic propellants with up to 100 percent gas yield is
possible. The gas bag has a coating for neutralizing or absorption
of hydrochloric acid released from the pyrotechnic propellant.
[0015] Compounds of the general total formula
C.sub.xH.sub.yN.sub.vO.sub.w wherein x.gtoreq.1, y.gtoreq.1 and
v.gtoreq.0 and w.gtoreq.0 are suitable as organic fuels. The
usability of organic compounds is almost universal. The only ones
which are ruled out are compounds with characteristics which are
not desirable for the purpose of application in motor vehicles,
such as, for example, high toxicity, carcinogenic characteristics,
mutagenic characteristics or other unacceptable characteristics
related to the environment, such as for example a high danger for
waters or soil. Furthermore, compounds are not desirable which have
a chemical or thermal stability which is too low, or a storage
stability which is too low in test trials at 100 degrees C. over
400 hours. In addition, compounds are to be ruled out which do not
permit a safe processing in the production of the pyrotechnic
propellants, such as sensitive high explosive substances or
mixtures.
[0016] Particularly suitable also are fuels based on polymeric
substances such as, for example, epoxy resins which offer
particular advantages in the production of extruded propellants.
Moreover, organic fuels which already have as high an oxygen
content per molecule as possible are preferred, because hereby the
required proportion of ammonium perchlorate and hence the
proportion of hydrochloric acid which is to be neutralized can be
reduced.
[0017] Tetrazoles, triazoles or guanidine compounds rich in
nitrogen, and also mixtures thereof, are used for example as
organic fuels. Examples of these compounds are 5-aminotetrazole,
1H-tetrazole, bistetrazole, azotetrazole, triazolone,
nitrotriazolone, guanidine carbonate, guanidine nitrate, guanidine
perchlorate, aminoguanidine nitrate, diaminoguanidine nitrate,
triaminoguanidine nitrate, nitroguanidine and also salts,
derivatitves or mixtures thereof.
[0018] The organic fuel can, in addition, be selected from the
group consisting of nitrogenous heterocyclic organic acids and
mixtures thereof. Examples of these nitrogenous heterocyclic
organic acids are cyanuric acid, isocyanuric acid, cyamelide,
urazole, uracile, uramine, urazine, alloxane, alloxanic acid,
alloxantine, xanthine, allantoin, barbituric acid, orotic acid,
dilituric acid, triazolone, violuric acid, succinimide, dialuric
acid, isodialuric acid, hydantoine, pseudohydantoine, imidazolone,
pyrazolone, parabanic acid, furazane, ammeline, creatinine, maleic
acid hydrazide, uric acid, pseudouric acid, guanazine, guanazole,
melamine, and their salts and derivatives or mixtures thereof.
[0019] In addition, a nitrogen-free organic acid can be used as
organic fuel. Fumaric acid, maleic acid, malonic acid, tartaric
acid, tartronic acid, citric acid, ascorbic acid, the salts or
derivatives thereof, or mixtures of the nitrogen-free organic
acids, are preferred in this connection.
[0020] Finally, as organic fuel a polymer compound can be used
which can be selected for example from the group consisting of the
polyalkyl compounds, polyalkylene compounds, polyamides,
polyimides, polyesters, polyethers, polyacetates, polyacrylic
compounds and polyglycols and also their derivatives and copolymers
containing --OH, --CN, --COOH, --NH.sub.2, --N.sub.3, --ONO.sub.2
or --NO.sub.2groups.
[0021] The conventional additives are selected in particular from
the group of combustion moderators, cooling agents and ignition
aids. Also, the addition of a small proportion of further oxidizing
agents can be advantageous to improve the burning temperature or
the burning speed. Examples of these conventional additives are, in
particular, alkali metal nitrates and alkaline earth metal
nitrates, perchlorates and peroxides, transition metal oxides such
as copper oxide or iron oxide, basic metal nitrates such as basic
copper nitrate or soot, graphite, silicon dioxide, aluminium oxide
or molybdenum sulphide. Finally, the conventional additives may
include processing aids, such as for example trickling aids,
compacting aids and/or lubricants.
[0022] The conventional additives are used in a proportion of up to
10 percent by weight, in relation to the total weight of fuel and
ammonium perchlorate. Higher proportions lead to an undesirably low
gas yield of the propellant. If the additives themselves are not at
least partially converted into a gaseous reaction product, their
proportion preferably amounts to a maximum 5 percent by weight,
particularly preferably a maximum 3 percent by weight.
[0023] In burning tests with propellants containing ammonium
perchlorate, it was surprisingly found that even with the use of an
excess of ammonium perchlorate and hence high proportions of
hydrochloric acid in the propellant gas, it was not possible to
detect the gaseous hydrochloric acid by measurement techniques. A
possible explanation for this lies in the high solubility of
gaseous hydrochloric acid in water, so that it can be assumed that
immediately after the burning of the propellant, hydrochloric acid
aerosols are formed from the generated gaseous hydrochloric acid
and water vapour which likewise occurs, which condense during
cooling on the inner wall of the gas bag and are thus removed from
the gas phase. Through the arrangement of a coating neutralizing or
absorbing the hydrochloric acid, this condensation process can be
further substantially accelerated. The amount of the coating is
preferably selected so that the total hydrochloric acid occurring
in the combustion reaction from the propellant is neutralized. The
emission of harmful gaseous hydrochloric acid into the interior of
the vehicle is therefore reliably prevented.
[0024] On the basis of these observations, it is also to be assumed
that the neutralization of the hydrochloric acid in the gas bag
takes place particularly effectively when the fuel which is used
has sufficient proportions of hydrogen residues which are oxidized
to water in the combustion reaction with ammonium perchlorate.
Advantageously, the proportion of hydrogen residues in the fuel is
to be at least so high that for every molecule of hydrochloric
which is formed, at least one molecule of water is produced.
[0025] The method according to the invention and the gas bag module
according to the invention make possible the provision of smaller
and lighter gas generators which can be operated with pyrotechnic
propellants using ammonium perchlorate as oxidizing agent. At the
same time, however, with these gas generators it is ensured that no
harmful gaseous hydrochloric acid arrives from the gas bag module
into the interior of the vehicle.
* * * * *