U.S. patent application number 10/204623 was filed with the patent office on 2003-01-30 for gas generator with automatic firing function.
Invention is credited to Takahori, Takeshi, Wu, Jianzhou, Yamato, Yo.
Application Number | 20030019387 10/204623 |
Document ID | / |
Family ID | 18590113 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030019387 |
Kind Code |
A1 |
Yamato, Yo ; et al. |
January 30, 2003 |
Gas generator with automatic firing function
Abstract
A gas generator for an air bag which includes a gas generating
agent having an automatic igniting function is provided. Since a
gas generating agent 9b stored in a second combustion chamber 5b
has an automatic igniting function, the gas generating agent 9b
automatically ignites in case of a vehicle fire, which is
accompanied by the combustion of the gas generating agent 9a and
the transfer charge 16a and 16b.
Inventors: |
Yamato, Yo; (Hyogo, JP)
; Wu, Jianzhou; (Hyogo, JP) ; Takahori,
Takeshi; (Hyogo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
18590113 |
Appl. No.: |
10/204623 |
Filed: |
August 22, 2002 |
PCT Filed: |
March 13, 2001 |
PCT NO: |
PCT/JP01/01944 |
Current U.S.
Class: |
102/530 |
Current CPC
Class: |
B60R 2021/26064
20130101; C06C 9/00 20130101; B60R 2021/2648 20130101; C06D 5/06
20130101; B60R 21/2644 20130101; B60R 2021/2633 20130101 |
Class at
Publication: |
102/530 |
International
Class: |
C06D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2000 |
JP |
2000-071538 |
Claims
1. A gas generator wherein a gas generating agent having an
automatic igniting function is used.
2. A gas generator according to claim 1, wherein the gas generating
agent maintains the automatic igniting function even after a long
period of time elapses.
3. A gas generator according to claim 1 or 2, wherein the gas
generating agent maintains the automatic igniting function even
after the gas generating agent has been kept at 105.degree. C. for
400 hours.
4. A gas generator according to any one of claims 1 to 3, wherein
the gas generating agent has a low ignition temperature.
5. A gas generator according to any one of claims 1 to 4, wherein
the gas generating agent has an ignition temperature of 200.degree.
C. or lower.
6. A gas generator according to any one of claims 1 to 5, wherein
an enhancer agent which does not have an automatic igniting
function is further used.
7. A gas generator having an automatic igniting function.
8. A gas generator according to claim 7, wherein the gas generator
maintains the automatic igniting function even after a long period
of time elapses.
9. A gas generator according to claim 7 or 8, wherein a gas
generating agent having a low ignition temperature is used.
10. A gas generator according to any one of claims 7 to 9, wherein
a gas generating agent having an ignition temperature of
200.degree. C. or lower is used.
11. A gas generator according to any one of claims 7 to 10, wherein
an enhancer agent which does not have an automatic igniting
function is further used.
12. A gas generator wherein a gas generating agent having a low
ignition temperature is used.
13. A gas generator according to claim 12, wherein the gas
generator has an automatic igniting function.
14. A gas generator according to claim 12 or 13, wherein the gas
generator maintains an automatic igniting means even after a long
period of time elapses.
15. A gas generator according to any one of claims 12 to 14,
wherein the gas generator maintains the automatic igniting function
even after the gas generator has been kept at 105.degree. C. for
400 hours.
16. A gas generator according to any one of claims 12 to 15,
wherein a gas generating agent having an ignition temperature of
200.degree. C. or lower is used.
17. A gas generator according to any one of claims 12 to 16,
wherein an enhancer agent which does not have an automatic igniting
function is further used.
18. A gas generating agent, which is used in a gas generator
according to any one of claims 1 to 17.
19. A gas generating agent, which has an automatic igniting
function.
20. A gas generating agent according to claim 19, wherein the gas
generating agent has a low ignition temperature.
21. A gas generating agent according to claim 19 or 20, wherein the
ignition temperature is 200.degree. C. or lower.
22. A gas generating agent according to any one of claims 19 to 21,
wherein the gas generating agent maintains the automatic igniting
function even after a long period of time elapses.
23. A gas generating agent according to any one of claims 19 to 22,
wherein the gas generating agent maintains the automatic igniting
function even after the gas generating agent has been kept at
105.degree. C. for 400 hours.
24. A gas generating agent, which maintains an automatic igniting
function even after a long period of time elapses.
25. A gas generating agent according to claim 24, wherein the gas
generating agent maintains the automatic igniting function even
after the gas generating agent has been kept at 105.degree. C. for
400 hours.
26. A gas generating agent according to claim 24 or 25, wherein the
gas generating agent has a low ignition temperature.
27. A gas generating agent according to any one of claims 24 to 26,
wherein the gas generating agent has an ignition temperature of
200.degree. C. or lower.
28. An automatic igniting material comprising a gas generating
agent having a low ignition temperature.
29. An automatic igniting material according to claim 28, wherein
the ignition temperature is 200.degree. C. or lower.
30. An automatic igniting material according to claim 28 or 29,
wherein the automatic igniting material maintains the automatic
igniting function even after a long period of time elapses.
31. An automatic igniting material according to any one of claims
28 to 30, wherein the automatic igniting material maintains the
automatic igniting function even after the automatic igniting
material has been kept at 105.degree. C. for 400 hours.
32. An enhancer agent, which does not have an automatic igniting
function.
Description
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
[0001] The present invention relates to a gas generator for an air
bag in which a gas generating agent has an automatic igniting
function so that it is unnecessary to use a material having an
automatic igniting function separately.
PRIOR ART
[0002] An air bag system which is mounted on various kinds of
vehicles and the like including automobiles, aims to hold a
passenger by means of an air bag (a bag body) rapidly inflated by a
gas when the vehicle collides at a high speed so as to prevent the
passenger from crashing into a hard portion inside the vehicle such
as a steering wheel, a windshield due to an inertia and from
getting injured. Such an air bag system generally comprises a gas
generator which is actuated due to a collision of the vehicle to
burn a gas generating agent and discharge a gas, and an air bag in
which the gas is introduced to be inflated. The gas generating
agent in this gas generator is burnt directly or through combustion
of an enhancer agent (a transfer charge) by activation of a
mechanical or electrical igniting means due to actuation of the
system based upon an instruction of a sensor detecting the impact
at a time of collision.
[0003] In this manner, since the gas generator is actuated due to a
collision of a vehicle, it is not actuated when such an emergency
situation as a vehicle fire which is not caused by a vehicle
collision. Therefore, in case that the ambient temperature of the
gas generator rises to a temperature equal to or more than an
ignition temperature of the gas generating agent, there is a risk
such that the gas generating agent ignites and burns (explodes). At
this time, in case that a thermal stability of an outer shell
container of the gas generator is low and the ignition temperature
of the gas generating agent is high, the strength of the outer
shell container is reduced by deformation of the container due to
rising of the ambient temperature or the like. Thereafter, when the
gas generating agent explodes, there is a risk such that the outer
shell container is broken and scattered by an explosive pressure so
that a human body may be injured.
[0004] In order to avoid such an event and secure a safety,
conventionally, a material having an automatic igniting function
(an automatic igniting material), which automatically ignites
according to rising of the ambient temperature without association
of a mechanical or electrical igniting means, i.e., without
actuation of the gas generator is arranged in the transfer charge.
For example, nitrocellulose (ignition temperature: 170.degree. C.)
is conventionally used as the automatic igniting material, and, in
a case of a vehicle fire or the like, nitrocellulose automatically
ignites at a temperature lower than a temperature at which the
strength of the outer shell container of the gas generator is
lowered, and it burns the transfer charge and simultaneously burns
the gas generating agent.
[0005] However, since nitrocellulose has a poor thermal stability,
there is a possibility that it is decomposed and degraded while a
long term elapses (indicating the life of a vehicle which will be
normally between several years to ten and some years), so that the
automatic igniting function does not develop. Also, in case that
the automatic igniting material is used, since increase in weight
of the gas generator or increase in manufacturing cost occurs due
to such a use of the material, there is a room for improvement in
view of such a point.
DISCLOSURE OF THE INVENTION
[0006] An object of the present invention is to provide a gas
generator for an air bag which can secure a safety in such an
emergency situation as a vehicle fire while maintaining an
automatic igniting function even after a long term elapsed and in
which a weight is reduced and a manufacturing cost isi restricted
can be achieved.
[0007] The present invention has solved the above problem by
imparting an automatic igniting function to a gas generating agent
itself instead of arranging an automatic igniting material such as
nitrocellulose separately in a conventional manner. That is, the
present invention is to provide a gas generator for an air bag
using a gas generating agent having an automatic igniting function
in which a mechanical or electrical igniting means does not
participate.
[0008] The expression "an automatic igniting function in which a
mechanical or electrical igniting means does not participate" in
the present invention means a function of natural igniting due to
rising of an ambient temperature. Here, the expression "an firing
ambient temperature (i.e., corresponding to an igniting temperature
of a gas generating agent)" means a temperature at which the above
problem can be solved in relation to a gas generator for an air
bag, particularly, an outer shell container (a housing),
specifically, it means such a temperature at which the strength of
the outer shell container of the gas generator for an air bag is
not lowered. Incidentally, when "an automatic igniting function" is
expressed in the following description, it means "an automatic
igniting function in which a mechanical or electrical igniting
means does not participate".
[0009] In case that a gas generator is of pyrotechnic type in which
a gas supplying source is only a gas generating agent, "a gas
generator for an air bag" according to the present invention can be
applied not only to a gas generator for an air bag for a driver
side air bag of various vehicles, a gas generator for an air bag
for a passenger side next to the driver, a gas generator for a side
collision air bag but also to a gas generator for an inflatable
curtain air bag, a gas generator for a knee-bolster air bag, a gas
generator for an inflatable seat belt, a gas generator for a
tubular system and a gas generator for a pretensioner.
[0010] A desirable gas generating agent used in the present
invention is one such that, after it held at 110.degree. C. for 400
hours, a weight reduction ratio is 2.0 weight % or less,
preferably, 1.0 weight % or less, more preferably 0.5 weight % or
less, and that an automatic igniting function is maintained after
the gas generating agent is held under the above condition.
[0011] As the gas generating agent used in this invention, it is
desirable to use one having an ignition temperature of preferably
200.degree. C. or less, more preferably, 200 to 175.degree. C.
[0012] As the gas generating agent used in this invention, it is
desirable that one includes a guanidine derivatives and a basic
metal nitrate, or it includes a guanidine derivatives, a basic
metal nitrate and an additive.
[0013] The gas generator for an air bag of the present invention
can be enhanced in safety and reliability because the gas
generating agent has the automatic igniting function and the
function is not deteriorated for a long term.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a vertical cross sectional view of one embodiment
of a gas generator for an air bag of the present invention.
[0015] FIG. 2 is a vertical cross sectional view of another
embodiment of a gas generator for an air bag of the present
invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0016] First, one embodiment of the present invention will be
explained with reference to FIG. 1. FIG. 1 is a vertical cross
sectional view of a gas generator for an air bag of the present
invention, and particularly it has a structure suitable to be
arranged on a driver side.
[0017] The gas generator comprises a housing 3 which is formed by
joining a diffuser shell 1 having a gas discharge port(s) and a
closure shell 2 forming an inner accommodating space with the
diffuser shell, a substantially cylindrical inner cylindrical
member 4 arranged inside the housing and a first combustion chamber
5a formed in the outer side of the inner cylindrical member 4.
[0018] Further, a stepped notch portion 6 is provided inside the
inner cylindrical member 4, a partition wall 7 in shape of a
substantially flat disk is arranged in the stepped notch portion 6,
and the partition wall further partitions the inside of an inner
cylindrical member 4 into two chambers to form a second combustion
chamber 5b in the diffuser shell side and an ignition means
accommodating chamber 8 in the closure shell side,
respectively.
[0019] As a result, in the gas generator, the first combustion
chamber 5a and the second combustion chamber 5b are concentrically
provided in the housing 3, being adjacent to each other in the
radial direction of the housing. Gas generating agents 9a, 9b which
is to be burnt by a ignition means activated upon the impact for
generating a combustion gas are stored in the first and second
combustion chambers, respectively, and the ignition means to be
actuated upon the impact is stored in the ignition means
accommodating chamber 8.
[0020] A through-hole 10 is provided in the inner cylindrical
member 4 which defines the first combustion chamber 5a and the
second combustion chamber 5b, and the through-hole is closed by a
seal tape 11. The seal tape 11 is ruptured when the gas generating
agent is burnt, and thereby, both the combustion chambers can
communicate with each other through the through-hole 10. It is
necessary to adjust a material and a thickness of the seal tape 11
such that the seal tape 11 is not ruptured by the combustion of the
gas generating agent 9a in the first combustion chamber 5a but it
is ruptured by the combustion of the gas generating agent 9b in the
second combustion chamber 5b. In the present embodiment, a
stainless steel seal tape having a thickness of 40 .mu.m is used.
Further, an opening area of the through-hole 10 is larger than that
of a gas discharge port 26, and the through-hole 10 does not have a
function for controlling an internal pressure of the combustion
chamber 5b.
[0021] In the present invention, the ignition means accommodating
chamber 8 is made of a space between an initiator collar 13 and the
partition wall 7, and a substantially cylindrical separating
cylinder 14 is arranged to surround one igniter 12b (hereinafter,
referred to as "a second igniter"), a first transfer-charge
accommodating chamber 15a is defined in the outer side thereof and
a second transfer-charge accommodating chamber 15b is defined in
the inner side thereof, respectively, and the igniters 12a and 12b,
and the transfer charges 16a and 16b which constitute the ignition
means together with the igniters are stored in the respective
accommodating chambers. In this embodiment, there is no space
inside the ignition means accommodating chamber 8 except for the
respective transfer charge accommodating chambers. As a result, the
ignition means accommodating chamber 8 is partitioned into two
chambers which are the first transfer charge accommodating chamber
15a and the second transfer charge accommodating chamber 15b. And
the transfer charges 16a and 16b which constitute the ignition
means together with the igniters are securely separated and
allocated to the respective igniters 12a and 12b.
[0022] When the transfer charge 16a in the first transfer charge
accommodating chamber 15a is burnt, the seal tape 18 closing the
flame-transferring hole 17 formed in the inner cylindrical member 4
is ruptured, so that the first transfer charge accommodating
chamber 15a communicates with the first combustion chamber 5a to
ignite and burn the porous gas generating agent 9a. When the
transfer charge 16b in the second transfer charge accommodating
chamber 15b is burnt, the seal tape 20 closing the
flame-transferring hole 19 formed in the partition wall 7 is
ruptured, so that the second transfer charge accommodating chamber
15b communicates with the second combustion chamber 5b to ignite
and burn the single perforated gas generating agent 9b. A
combustion gas generated in the second combustion chamber 9b flows
into the first combustion chamber 5a through the through-hole 10
provided in the diffuser shell 1 side of the inner cylindrical
member 4. Accordingly, in this gas generator, at activation, a
flame, which is generated due to ignition and combustion of the
first igniter 12a, ignites and burns the transfer charge 16a in the
accommodating chamber 15a and then, the flame thereof passes
through the flame-transferring hole 17 formed in the inner
cylindrical member 4 to ignite and burn a gas generating agent 9a
with seven holes stored in the first combustion chamber 5a
positioned in the radial direction of the chamber 15a.
[0023] Particularly, in the gas generator shown in FIG. 1, the
second igniter 12b and the first igniter 12a can be simultaneously
ignited in order to stabilize an operation performance, however,
the former 12b is never ignited earlier than the latter 12a. That
is, the gas generating agent 9b stored in the second combustion
chamber 5b burns simultaneously with or with a delay from the gas
generating agent 9a stored in the first combustion chamber 5a. When
the gas generating agent 9a in the first combustion chamber 5a
burns earlier than the second gas generating agent 9b does, the
seal tape 11 is not broken by combustion of the first gas
generating agent 9a but it is broken only by combustion of the
second gas generating agent 9b.
[0024] Also, in the gas generator shown in FIG. 1, a separating
cylinder 14 disposed between the initiator collar 13 and the
partition wall 7 is arranged in such a manner that a hole portions
corresponding to an outer shape of the separating cylinder 14 are
provided on the lower surface of the partition wall 7 and the upper
surface of the initiator collar 13, respectively, and the upper end
and the lower end of the separating cylinder 14 are fitted into the
respective hole portions. By arranging the separating cylinder 14
in this manner, a flame of the transfer charge generated in either
of the transfer charge combustion chambers never burns directly the
transfer charge in the other transfer charge accommodating chamber,
and the gas generating agents stored in two combustion chambers are
respectively ignited and burnt by flames generated by the
combustions of the transfer charges in the different sections.
Namely, in general, when the transfer charge burns in the
separating cylinder 14 (that is, in the second transfer charge
accommodating chamber), a pressure of a gas generated by the
combustion expands the separating cylinder 14 in the radial
direction. Nonetheless, because the separating cylinder 14 is
disposed to be supported firmly at the upper and lower end portions
by a curcumferential walls of the respective hole portions into
which the end portions are fitted, a leakage of a combustion gas
and a flame can be blocked more securely compared with a case such
that the separate cylinder 14 is simply held between the partition
wall 7 and the initiator collar 13.
[0025] The ignition means includes two electric ignition type
igniters (12a and 12b) to be activated by the activating signal
outputted on the basis of detection of the impact by the sensor,
and the igniters are provided in parallel to each other in one
initiator collar 13, having head portions thereof protruded. As
mentioned above, by fixing two igniters to one initiator collar 13,
two igniters fixed to the initiator collar become a single member,
thereby facilitating an assembly to the gas generator. In
particular, in the gas generator shown in this drawing, the
initiator collar 13 is made in a size capable of being inserted
into the inner cylindrical member 4, and thereby, the igniters are
easily and securely fixed by crimping the lower end of the inner
cylindrical member 4 to fix the initiator collar 13 after inserting
the initiator collar 13 provided with two igniters (12a and 12b)
into the inner cylindrical member 4. Further, when arranging two
igniters (12a and 12b) in the initiator collar 13, a direction of
each igniter can be easily controlled.
[0026] Further, a coolant/filter 22 for purifying and cooling the
combustion gas generated by the combustion of the gas generating
agents (9a and 9b) is disposed in the housing 3, an inner
peripheral surface in the diffuser shell 1 side thereof is covered
with a short-pass preventing member 23 so that a combustion gas
does not pass between an end surface of the coolant/filter 22 and
an inner surface of a ceiling portion in the diffuser shell 1.
[0027] An outer layer 24 for preventing the coolant/filter 22 from
expanding outwardly due to passing of a combustion gas or the like
is arranged on the outer side of the coolant/filter 22. The outer
layer 24 is, for example, formed by using a layered wire mesh body,
and in addition, may be formed by using a porous cylindrical member
having a plurality of through-holes on a peripheral wall surface or
a belt-like suppressing layer obtained by forming a belt-like
member with a predetermined width into an annular shape.
[0028] A gap 25 is further formed on the outer side of the outer
layer 24 so that a combustion gas can pass through the entire
surface of the filter 22. The gas discharge port 26 formed in the
diffuser shell 1 is closed by a seal tape 27 for blocking outer air
from entering. This seal tape 27 is ruptured when discharging a
gas. The seal tape 27 aims to protect the gas generating agent from
outside moisture, and it does not influence performance adjustments
such as an internal combustion pressure at all.
[0029] In this embodiment, as the gas generating agents 9a and 9b,
one including (a) guanidine derivatives and (b) basic metal
nitrates, or one including (a) guanidine derivatives, (b) basic
metal nitrates and (c) additives is used. Incidentally, in this
embodiment, since the seal tape 11 is ruptured only by the
combustion of the gas generating agent 9b, the gas generating agent
9b must be a gas generating agent having the above-described
automatic igniting function, but the gas generating agent 9a may or
may not have the automatic igniting function.
[0030] As the guanidine derivatives of the component (a), at least
one selected from the group consisting of guanidine, mono-, di-,
and tri-aminoguanidine nitrates, guanidine nitrate, guanidine
carbonate, nitroguanidine (NQ), dicyandiamide (DCDA), and
nitroaminoguanidine nitrite can be proposed. Among them,
nitroguanidine and dicyandiamide are preferable.
[0031] The basic metal nitrates of the compound (b) are a series of
compounds generally expressed by the following formula. Also, some
compounds further contain hydrates, too. In the formula, M
indicates a metal, x' indicates the number of metals, y and y' each
indicates the number of NO.sub.3 ions, z' indicates the number of
OH ions, and n indicates a ratio of an M(OH).sub.2 moiety to an
M(NO.sub.3).sub.y moiety.
M(NO.sub.3).sub.y.nM(OH).sub.z or
M.sub.x'(NO.sub.3).sub.y(OH).sub.z'
[0032] Examples of the compounds corresponding to the above formula
include those containing, as a metal M, copper, cobalt, zinc,
mnganese, iron, molybdenum, bismuth and cerium, such as
Cu.sub.2(NO.sub.3)(OH).sub.- 3,
Cu.sub.3(NO.sub.3)(OH).sub.5.2H.sub.2O,
Co.sub.2(NO.sub.3)(OH).sub.3, Zn.sub.2(NO.sub.3)(OH).sub.3,
Mn(NO.sub.3)(OH).sub.2, Fe.sub.4(NO.sub.3)(OH).sub.11.2H.sub.2O,
Bi(NO.sub.3)(OH).sub.2, and Ce(NO.sub.3).sub.3(OH).3H.sub.2O.
[0033] As the basic metal nitride of the component (b), at least
one selected from the group consisting of a basic copper nitrate
(BCN), a basic cobalt nitrate, a basic zinc nitrate, a basic
manganese nitrate, a basic iron nitrate, a basic molybdenum
nitrate, a basic bismuth nitrate and a basic cerium nitrate is
proposed. Among them, a basic copper nitrate is preferable.
[0034] In case that the gas generating agent includes the (a) and
(b) components, the content of the component (a) is preferably 5 to
60 weight %, more preferably, 15 to 55 weight %. The content of the
component (b) is preferably 40 to 95 weight %, more preferably, 45
to 85 weight %.
[0035] One preferable embodiment when the gas generating agent
includes the components (a) and (b) can include (a) nitroguanidine
and (b) basic copper nitrate. In this case, preferably, the
contents are (a) nitoguanidine of 30 to 70 weight % and (b) basic
copper nitrate of 30 to 70 weight %.
[0036] As the additives of the component (c), at least one selected
from the group consisting of carboxymethyl cellulose (CMC),
carboxymethyl cellulose sodium salt (CMCNa), carboxymethyl
cellulose potassium salt, carboxymethyl cellulose ammonium salt,
cellulose acetate, cellulose acetate butyrate (CAB), methyl
cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC),
ethyl hydroethyl cellulose (EHEC), hydroxypropyl cellulose (HPC),
carboxymethylethyl cellulose (CMEC), microcrystalline cellulose,
polyacrylamide, aminated polyacrylamide, polyacrylic hydrazine,
acrylamideacrylic acid metal salt copolymer, copolymer of
polyacrylamide and polyacrylate ester compound, polyvinyl alcohol,
acrylic rubber, guar gum, starch, silicone, molybdenum disulfide,
Japanese acid clay, talc, bentonite, diatomaceous earth, kaolin,
calcium stearate, silica, alumina, sodium silicate, silicon
nitride, silicon carbide, hydrotalsite, mica, metal oxide, metal
hydroxide, metal carbonate, basic metal carbonate, and molybdate is
proposed.
[0037] As the metal oxide of the compound (c), at least one
selected from the group consisting of copper oxide, iron oxide,
zinc oxide, cobalt oxide, manganese oxide, nickel oxide, and
bismuth oxide can be proposed. As the metal hydroxide, at least one
selected from the group consisting of cobalt hydroxide and aluminum
hydroxide can be proposed, and as the metal carbonate and basic
metal carbonate, at least one selected from the group consisting of
calcium carbonate, cobalt carbonate, basic zinc carbonate, basic
copper carbonate, basic cobalt carbonate, basic iron carbonate,
basic bismuth carbonate, and basic magnesium carbonate can be
proposed. As the molybdate, at least one selected from the group
consisting of cobalt molybdate and ammonium molybdate. The
compounds of these components (c) can serve as a slag-forming agent
and/or a binder.
[0038] In case that the ignition performance of the gas generating
agent is increased, carboxymethyl cellulose sodium salt and
carboxymethyl cellulose potassium salt are preferable, and among
them the sodium salt is more preferable.
[0039] One embodiment of a case such that the gas generating agent
includes the components (a), (b) and (c) can include components
containing (a) nitroguanidine, (b) basic copper nitrate, and (c)
carboxymethyl cellulose sodium salt. In this case, preferably, the
contents are (a) nitroguanidine of 15 to 55 weight %, (b) basic
copper nitrate of 45 to 70 weight %, and (c) carboxymethyl
cellulose sodium salt of 0.1 to 15 weight %.
[0040] Another preferable embodiment of a case such that the gas
generating agent includes the (a), (b) and (c) components can
include one containing (a) nitroguanidine, (b) basic copper
nitrate, and (c) guar gum. In this case, it is preferable that the
contents are (a) nitroguanidine of 20 to 60 weight %, (b) basic
copper nitrate of 35 to 75 weight %, and (c) guar gum of 0.1 to 10
weight %.
[0041] The gas generating agent can be formed in a desired shape,
and it is formed in a single-perforated cylindrical, a porous
cylindrical or a pellet-shaped molded material. These molded
materials an be produced by a method comprising steps of adding and
mixing water or organic solvent into a gas generating agent and
extrusion-molding (the single hole cylindrical and porous
cylindrical molds) or a method comprising steps of performing
compression-molding using a pelletizer or the like (the
pellet-shaped molded material).
[0042] In the gas generator of the present embodiment, the transfer
charges (enhancer agents) 16a and 16b and the gas generating agents
9a and 9b are burnt to generate a gas in a normal actuation time,
as described below.
[0043] In the gas generator of the present embodiment, the first
igniter 12a disposed inside the ignition means accommodating
chamber 8 but outside the separating cylinder 14 is activated, the
transfer charge 16a stored in the first transfer charge
accommodating chamber 15a is ignite/burnt, and its flame passes
through the flame-transferring hole 17 of the inner cylindrical
member 4 to burn the porous cylindrical first gas generating agent
9a having seven holes stored in the first combustion chamber
5a.
[0044] Also, when the second igniter 12b surrounded by the
separating cylinder 14 is activated simultaneously with or with
delay from the first igniter 12a, the transfer charge 16b stored in
the second transfer charge accommodating chamber 15b is
ignited/burnt, and its flame ignites/burns the single-perforated
cylindrical second gas generating agent 9b stored in the second
combustion chamber 5b.
[0045] As a result, the output form (operation performance) of the
gas generator can arbitrarily be adjusted by adjusting the ignition
timing of two igniters (12a and 12b), in other words, by making the
second igniter activated after activation of the first igniter or
by making the first igniter and the second igniter activated
simultaneously. And further, in various situations such as a speed
of a vehicle at a time of collision and an environment temperature,
the development of an air bag can be made most optimal when an air
bag apparatus described later is formed.
[0046] Particularly in the gas generator shown in this drawing, the
gas generating agents (9a and 9b) with different shapes are used
for the respective combustion chambers (5a and 5b), in which the
porous cylindrical first gas generating agent 9a and the
single-perforated cylindrical second gas generating agent 9b are
respectively stored in the first combustion chamber 5a and the
second combustion chamber 5b. Also, the amounts of the gas
generating agents stored in the respective combustion chambers (5a
and 5b) are different from each other, in which the gas generating
agents (9a and 9b) of 35 g and 6 g are respectively stored in the
first combustion chamber 5a and the second combustion chamber 5b.
As a result, in this gas generator, it is possible to adjust the
output form more accurately.
[0047] Further, in the gas generator of the embodiment, the
transfer charges (the enhancer agents) 16a and 16b and the gas
generating agents 9a and 9b are burnt to secure a safety in an
emergency situation such as a vehicle fire or the like.
[0048] When the ambient temperature of the gas generator rises due
to a vehicle fire or the like, and when the ambient temperature
reaches the ignition temperature (for example, about 200.degree.
C.) of the gas generating agent 9b, the gas generating agent 9b
ignites and burns. According thereto, the seal tapes 11 and 20 are
ruptured to burn the gas generating agent 9a and the transfer
charge 16b, and further, according to the combustion of the gas
generating agent 9a, the seal tape 18 is ruptured to burn the
transfer charge 16a. This is a case when only the gas generating
agent 9b has the automatic igniting function. When the gas
generating agent 9a also has the automatic igniting function, the
gas generating agents 9a and 9b are automatically ignited together
to burn the transfer charges 16a and 16b. Accordingly, even when a
material having a low melting point such as aluminum (about
660.degree. C.) is used as a housing material, since the gas
generating agents and the transfer charges burns before the
strength of the housing is lowered, the housing itself is prevented
from being ruptured and scattering due to the combustion of the gas
generating agent, due to that the gas generating agent reaches its
ignition temperature at last after the strength of the housing has
been lowered due to a high temperature.
[0049] Next, another embodiment of the present invention will be
explained with reference to FIG. 2. FIG. 2 is a vertical sectional
view of a gas generator for an air bag of the present invention,
showing a structure which is particularly suitable for being
arranged in a driver side. This embodiment is a gas generator
including one combustion chamber.
[0050] This gas generator comprises, in a housing 3 which is formed
by joining a diffuser shell 1 having gas discharge ports and a
closure shell 2 forming an inner accommodating space with the
diffuser shell, an inner cylindrical member 113 formed in a
substantially cylindrical shape, a combustion chamber 122 defined
in the outer side of the inner cylindrical member and an ignition
means accommodating chamber 155 defined in the inner side thereof.
As a result, in this gas generator, the combustion chamber 122 and
the ignition means accommodating chamber 155 are concentrically
provided in the housing 3, and arranged adjacent to each other in
the radial direction of the housing. A gas generating agent 106
which is to be burnt by an ignition means activated upon the impact
for generating a combustion gas is stored in the combustion
chamber, and the ignition means to be actuated upon the impact is
stored in the ignition means accommodating chamber 155. An igniter
104 is disposed in the ignition means accommodating chamber 155 via
an initiator collar 114, a transfer charge 105 is stored in a
transfer means accommodating chamber 123, and the remaining space
160 exists in the ignition means accommodating chamber 155. In FIG.
2, numeral 107 denotes a coolant/filter, 109 denotes a clearance,
111 denotes a gas discharge hole, 125 denotes a seal tape, 126
denotes a communication hole, and 150 denotes a short pass
preventing member.
[0051] In the present embodiment, a gas generating agent having an
automatic igniting function as described above is used as the gas
generating agent 106. Accordingly, in an emergency situation such
as a vehicle fire, the gas generating agent 106 automatically
ignites due to rising of the ambient temperature. Since the
combustion temperature of the gas generating agent is as high as
about 2000.degree. C., the enhancer agent or the igniting agent
ignites/burns due to the combustion heat with a delay from the
combustion of the gas generating agent.
EXAMPLE
[0052] The present invention will be further explained below in
detail according to examples, but it is not limited by these
examples.
[0053] (1) Weight Loss Ratio
[0054] 40 g of the gas generating agent (incidentally, only a fuel)
was put into a container made of an aluminum, and the total weight
was measured, so that (the total weight--the weight of the aluminum
container) was set as a sample weight before test. After the
aluminum container containing the sample was put into an SUS thick
container (the content volume: 118.8 ml) and a lid was applied to
the container, this container was put into a thermostat bath of
110.degree. C. At this time, the container was sealed by using a
rubber packing and a clamp. After a predetermined period elapsed,
the SUS thick container was taken out from the thermostat bath, the
lid was opened after the temperature of the SUS thick container
returned back to the room temperature, and the aluminum container
was taken out therefrom. The total weight including the aluminum
container was measured and the sample weight after the test was
obtained from (the total weight--the weight of the aluminum-made
container). Then, a thermal stability was evaluated by comparing
the weight changes of the sample before and after test to obtain a
weight reduction ratio. The weight loss ratio was obtained from
[(the weight of the gas generating agent before test--the weight of
the gas generating agent after test)/the weight of the gas
generating agent before test].times.100.
Example 1
[0055] A gas generating agent with a composition comprising
nitroguanidine/basic copper nitrate/guar gum=44.2/52.8/3.0 (weight
%) was produced, and its ignition temperature and weight loss ratio
were measured. The ignition temperature was measured by a Krupp
type ignition temperature tester and the measured value was
indicated by a 60 seconds ignition temperature. As a result, the
ignition temperatures were 193.degree. C. in case of a gas
generating agent put in a crushed state (a crushed agent) and
201.degree. C. in case of the gas generating agent put in an
extrusion-molded state (an extruded agent), and the weight loss
ratios were 0.27% when 214 hours passed at 110.degree. C. and 0.45%
when 408 hours passed at 110.degree. C.
[0056] As apparent from this result, since the ignition temperature
of the gas generating agent used in the gas generator of the
present invention is low, it is clear that the gas generating agent
automatically ignites before the housing is degraded due to heat in
case of a vehicle fire. Further, as apparent from the fact that the
weight loss ratio is small, the thermal stability is not lowered
even after a long term elapsed so that the automatic igniting
function is not lost.
* * * * *