U.S. patent application number 12/299187 was filed with the patent office on 2009-10-22 for gas generant composition for gas actuator for activating safety device and gas generator for gas actuator using the same.
This patent application is currently assigned to Nippon Kayaku Kabushiki Kaisha. Invention is credited to Nanao Horiishi, Ryoi Kodama.
Application Number | 20090260730 12/299187 |
Document ID | / |
Family ID | 38667720 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090260730 |
Kind Code |
A1 |
Kodama; Ryoi ; et
al. |
October 22, 2009 |
GAS GENERANT COMPOSITION FOR GAS ACTUATOR FOR ACTIVATING SAFETY
DEVICE AND GAS GENERATOR FOR GAS ACTUATOR USING THE SAME
Abstract
Disclosed is a gas generant composition for a gas actuator used
for activating a safety device, which contains (A) a
nitrogen-containing organic compound, (B) a metal nitrate and/or a
perchlorate, (C) a water-soluble polymer binder, and (D) a magnetic
material. When compared with the conventional gas generant
compositions, this gas generant composition is excellent in
combustibility under low pressure conditions and reduced in CO gas
generation during combustion. In this gas generant composition, (D)
the magnetic material is preferably composed of a magnetic iron
oxide. It is also preferable that (A) the nitrogen-containing
organic compound is composed of one or more substances selected
from nitroguanidine, guanidine nitrate, bitetrazole,
azobistetrazole and 5-aminotetrazole; (B) the metal nitrate is
composed of a metal salt selected from alkali metals and alkaline
earth metals, while the perchlorate is composed of ammonium
perchlorate or potassium perchlorate; (C) the water-soluble polymer
binder is composed of a mixture of hydroxypropyl methylcellulose
(HPMC) and a polyacrylamide; and (D) the magnetic iron oxide has a
spinel crystal structure.
Inventors: |
Kodama; Ryoi; (Hyogo,
JP) ; Horiishi; Nanao; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Nippon Kayaku Kabushiki
Kaisha
Chiyoda-ku, Tokyo
JP
Toda Kogyo Corp.
Hiroshima-shi, Hiroshima
JP
|
Family ID: |
38667720 |
Appl. No.: |
12/299187 |
Filed: |
April 27, 2007 |
PCT Filed: |
April 27, 2007 |
PCT NO: |
PCT/JP07/59196 |
371 Date: |
October 31, 2008 |
Current U.S.
Class: |
149/62 ; 149/45;
149/75; 149/76; 149/78 |
Current CPC
Class: |
C06D 5/06 20130101; C06B
23/007 20130101; F42B 3/04 20130101; B60R 2021/26029 20130101; B60R
21/2644 20130101 |
Class at
Publication: |
149/62 ; 149/45;
149/75; 149/78; 149/76 |
International
Class: |
C06B 31/12 20060101
C06B031/12; C06B 31/00 20060101 C06B031/00; C06B 29/00 20060101
C06B029/00; C06B 29/16 20060101 C06B029/16; C06B 29/22 20060101
C06B029/22 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2006 |
JP |
2006-128539 |
Claims
1. A gas generant composition for a gas actuator for activating a
safety device, containing the following components (A) to (D): (A)
a nitrogen-containing organic compound, (B) metal nitrate and/or
perchlorate, (C) a water-soluble polymer binder, and (D) a magnetic
material.
2. The gas generant composition according to claim 1, wherein (D)
the magnetic material is (D) magnetic iron oxide.
3. The gas generant composition according to claim 2, wherein (A)
the nitrogen-containing organic compound is at least one substance
selected from nitroguanidine, guanidine nitrate, bitetrazole,
azobistetrazole and 5-aminotetrazole, (B) the metal nitrate is a
metal salt selected from alkali metals and alkaline earth metals
while the perchlorate is ammonium perchlorate or potassium
perchlorate, and (C) the water-soluble polymer binder is a mixture
of hydroxypropyl methylcellulose and polyacrylamide.
4. The gas generant composition according to claim 2, wherein (D)
the magnetic iron oxide is magnetic iron oxide having a spinel
crystal structure.
5. The gas generant composition according to claim 2, wherein (D)
the magnetic iron oxide is powder having a specific surface area of
2.5 to 80 m.sup.2/g.
6. The gas generant composition according to claim 2, further
containing (E) a metal oxide other than the magnetic iron
oxide.
7. The gas generant composition according to claim 6, wherein (E)
the metal oxide other than the magnetic iron oxide is at least one
substance selected from CuO, Cu.sub.2O, ZnO,
(.alpha.-Fe.sub.2O.sub.3, Mn.sub.2O.sub.3 and Mn.sub.3O.sub.4.
8. The gas generant composition according to claim 6, wherein the
content of (A) the nitrogen-containing organic compound is 25 to 55
weight %, the content of (B) the metal nitrate and/or the
perchlorate is 40 to 70 weight %, the content of (C) the
water-soluble polymer binder is 2 to 10 weight %, the content of
(D) the magnetic iron oxide is 1 to 5 weight %, and the content of
(E) the metal oxide other than the magnetic iron oxide is 1 to 5
weight %.
9. A compact of the gas generant composition according to claim
1.
10. The compact according to claim 9, having magnetism.
11. A small gas generator for a gas actuator for activating a
safety device, using the gas generant composition according to
claim 1 or the compact of the gas generant composition according to
claim 9.
Description
TECHNICAL FIELD
[0001] The present invention relates to a gas generant composition
for generating working gas and a gas generator for a gas actuator
using the same in a gas generator for a gas actuator loaded on an
automobile or an aircraft and employed for human body
protection.
BACKGROUND ART
[0002] In general, a seat belt device and an air bag device are
widespread in view of protection of the passenger of an automobile.
In these, the seat belt device is equipped for the purpose of
preventing the passenger from being thrown out into the automobile
or from the automobile due to a shock caused upon vehicle
collision, and restricts/fixes the passenger to the seat by winding
the belt on the body of the passenger.
[0003] In recent years, a seat belt device comprising a
pretensioner function for improving the passenger protection
function has rapidly come into wide use. Also as to the
pretensioner device, the number of use thereof tends to increase
not only on the driving seat but also on the passenger seat and the
back seat, due to the recent improvement of safety consciousness.
This pretensioner function immediately tensions the seat belt
loosened due to the thickness of clothes or the like upon collision
or immediately before the collision, and improves the effect of
restricting the passenger. This pretensioner function is
implemented by instantaneously moving a piston in a cylinder, for
example, by combustion gas of a gas generant output from a small
gas generator for a gas actuator referred to as a micro gas
generator and strongly drawing the seat belt by power supplied to
the pretensioner in association with this piston. In addition, a
device such as a hood lifter for reducing the degree of harm on a
pedestrian is also currently being loaded on a vehicle in order to
absorb a shock on the pedestrian upon collision between the vehicle
and the pedestrian in view of pedestrian protection, and a small
gas generator is employed for activating this device.
[0004] As a gas generant employed for such a pretensioner device, a
propellant gas generant based on nitrocellulose is known in general
(refer to Japanese Patent Laying-Open No. 49-50619 (Patent Document
1), for example). This gas generant based on nitrocellulose has
high gas generation efficiency, and is excellent in moisture
absorption resistance.
[0005] Japanese Patent Laying-Open No. 2001-2488 (Patent Document
2) discloses a non-propellant gas generant for a pretensioner
device. In addition, Japanese Patent Laying-Open No. 2002-12492
(Patent Document 3) also discloses a non-propellant gas generant
for a pretensioner device, containing nitrocellulose.
Patent Document 1: Japanese Patent Laying-Open No. 49-50619
Patent Document 2: Japanese Patent Laying-Open No. 2001-2488
Patent Document 3: Japanese Patent Laying-Open No. 2002-12492
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] In the gas generant based on nitrocellulose described in
Patent Document 1, however, slight contamination with CO gas is
unavoidable in the generated gas, and hence a gas generant
generating a slighter amount of CO gas is demanded. This also
applies to the gas generant disclosed in Patent Document 3.
[0007] The gas generant according to Patent Document 2 has a slow
combustion speed due to employment of a binder containing a large
number of carbon atoms, the content of an inorganic oxidizer for
completely combusting the binder increases, there is a possibility
that the amount of generated gas decreases as compared with the
propellant based on nitrocellulose as a result, and the quantity of
the gas generant must be increased in order to exert equivalent
performance. Further, this gas generant uses a sodium salt such as
sodium nitrate as a chlorine neutralizer, and hence such a
possibility is sufficiently conceivable in a test for evaluating
moisture absorption resistance (test of exposing a small gas
generator under environment of a temperature of 85.degree.
C..times.humidity of 85% for 1000 hours) that the gas generator
absorbs moisture after the test.
[0008] The present invention has been proposed in order to solve
the aforementioned problems, and an object thereof is to provide a
gas generant composition for a gas actuator for activating a safety
device, superior in combustibility under a low pressure as compared
with the conventional art and capable of reducing the amount of CO
gas generated in combustion.
Means for Solving the Problems
[0009] The gas generant composition according to the present
invention is employed for a gas actuator for activating a safety
device. The gas actuator is a device converting the pressure of gas
to power, and a device employed for activating a pretensioner or a
hood lifter which is an automobile safety device can be listed, for
example.
[0010] The gas generant composition for a gas actuator for
activating a safety device according to the present invention
contains the respective components of (A) a nitrogen-containing
organic compound, (B) metal nitrate and/or perchlorate, (C) a
water-soluble polymer binder, and (D) a magnetic material.
[0011] Preferably, (A) the nitrogen-containing organic compound is
at least one substance selected from nitroguanidine, guanidine
nitrate, bitetrazole, azobistetrazole and 5-aminotetrazole, (B) the
metal nitrate is a metal salt selected from alkali metals and
alkaline earth metals while the perchlorate is ammonium perchlorate
or potassium perchlorate, and (C) the water-soluble polymer binder
is a mixture of hydroxypropyl methylcellulose (HPMC) and
polyacrylamide.
[0012] (D) The magnetic material in the gas generant composition
according to the present invention has a property attracted to a
magnet, and is preferably magnetic iron oxide, particularly
preferably magnetic iron oxide (Fe.sub.xO.Fe.sub.2O.sub.3: where
0.ltoreq.x.ltoreq.1) having a spinel crystal structure. The
magnetic iron oxide mentioned herein has magnetism and a redox
catalytic function, dissimilarly to iron oxide (Fe.sub.2O.sub.3)
generally employed as a catalyst.
[0013] Preferably, the gas generant composition according to the
present invention further contains (E) a metal oxide other than the
magnetic iron oxide, and more preferably, (E) the metal oxide other
than the magnetic iron oxide is at least one substance selected
from CuO, Cu.sub.2O, ZnO, .alpha.-Fe.sub.2O.sub.3, Mn.sub.2O.sub.3
and Mn.sub.3O.sub.4.
[0014] Preferably in the gas generant composition according to the
present invention, the content of (A) the nitrogen-containing
organic compound is 25 to 55 weight %, the content of (B) the metal
nitrate and/or the perchlorate is 40 to 70 weight %, the content of
(C) the water-soluble polymer binder is 2 to 10 weight %, the
content of (D) the magnetic iron oxide is 1 to 5 weight %, and the
content of (E) the metal oxide other than the magnetic iron oxide
is 1 to 5 weight %.
[0015] Preferably, (D) the magnetic iron oxide in the gas generant
composition according to the present invention is a composition
expressed in Fe.sub.xO.Fe.sub.2O.sub.3 (0.ltoreq.x.ltoreq.1), and
is powder having a specific surface area of 2.5 to 80
m.sup.2/g.
[0016] Preferably, the gas generant composition according to the
present invention is worked into a compact. This compact has a
property attracted to a magnet.
[0017] Preferably, the gas generant composition according to the
present invention is employed for a pretensioner or a hood
lifter.
[0018] The present invention also provides a small gas generator
for a gas actuator for activating a safety device employing the
aforementioned gas generant composition according to the present
invention. Preferably, this small gas generator is employed for a
pretensioner or a hood lifter.
EFFECTS OF THE INVENTION
[0019] The gas generant composition having magnetism according to
the present invention contains the magnetic iron oxide, and hence
has a catalytic effect of accelerating combustion under a low
pressure, oxidizing CO gas generated in combustion to CO.sub.2 and
reducing the CO gas concentration due to combustion catalytic
performance of this magnetic iron oxide powder. When the gas
generant composition having magnetism as the compact is charged
into the gas generator, the same can be charged to fill up the
internal space due to magnetic force, whereby such particular
effects are attained that both of the combustion accelerating
effect under a low pressure and the effect of reducing the
concentration of the CO gas generated in combustion are further
increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a sectional view schematically showing a gas
generator 1 of a pretensioner device in a case of employing a gas
generant composition according to the present invention.
[0021] FIG. 2 illustrates sectional views schematically showing a
process of assembling gas generator 1 shown in FIG. 1.
[0022] FIG. 3 is a sectional view schematically showing a gas
generator for a pretensioner or a hood lifter.
DESCRIPTION OF THE REFERENCE SIGNS
[0023] 1 gas generator, 10 igniter, 20 holder, 30 combustion
control cover, 40 AC cup, 50 gas generant, 150 dedicated filling
jig.
BEST MODES FOR CARRYING OUT THE INVENTION
[0024] The present invention provides a gas generant composition,
containing respective components of (A) a nitrogen-containing
organic compound, (B) metal nitrate and/or perchlorate, (C) a
water-soluble polymer binder, and (D) a magnetic material. The
respective components (A) to (D) contained in the gas generant
composition according to the present invention are now described in
detail.
[0025] (A) Nitrogen-Containing Organic Compound
[0026] The nitrogen-containing organic compound contained in the
gas generant composition according to the present invention can be
widely employed for the present invention without particular
limitation, so far as the same is an organic compound, other than
nitric ester, containing nitrogen having been employed as a fuel
for gas generation in this field. The nitrogen-containing organic
compound has a structure basically suppressing generation of CO due
to a high proportion of nitrogen atoms and a low proportion of
carbon atoms in the molecular structure, and is easy in handling
properties including thermal stability.
[0027] As a preferable example of the nitrogen-containing organic
compound other than nitric ester, at least one substance selected
from a triazole derivative, a tetrazole derivative, a guanidine
derivative, an azodicarbonamide derivative and a hydrazine
derivative can be listed, for example. More specifically,
5-oxo-1,2,4-triazole, tetrazole, 5-aminotetrazole, aminotetrazole
nitrate, nitroaminotetrazole, bitetrazole (5,5'-bi-1H-tetrazole),
5,5'-bi-1H-tetrazole diammonium salt, azobistetrazole,
5,5'-azotetrazole diguanidium salt, guanidine, nitroguanidine,
cyanoguanidine, triaminoguanidine nitrate, guanidine nitrate,
aminoguanidine nitrate, biuret, azodicarbonamide, carbohydrazide,
carbohydrazide nitrate complex, oxalic acid hydrazide, hydrazine
nitrate complex, amine complex and the like can be listed. Among
these nitrogen-containing organic compounds, at least one substance
selected from the tetrazole derivative and the guanidine derivative
is preferable, and at least one substance selected from
nitroguanidine, guanidine nitrate, bitetrazole, azobistetrazole and
5-aminotetrazole is particularly preferable, since the same is at a
low cost, excellent in reactivity and relatively easy to
handle.
[0028] The content (compounding ratio) of the nitrogen-containing
organic compound in the gas generant composition according to the
present invention is preferably 25 to 55 weight %, more preferably
30 to 50 weight %. If the content (compounding ratio) of the
nitrogen-containing organic compound is less than 25 weight %, the
number of moles of the generated gas per 100 g of the gas generant
composition is reduced, and generation of NO.sub.x tends to
increase due to excess oxygen. If the content (compounding ratio)
of the nitrogen-containing organic compound exceeds 55 weight %,
the true specific density of the gas generant composition decreases
due to increase in the quantity of organic matter, the loading
weight per volume decreases, and CO gas tends to generate in a
large amount due to insufficiency of an oxidizer component.
[0029] (B) Metal Nitrate and/or Perchlorate
[0030] The gas generant composition according to the present
invention contains at least either metal nitrate or perchlorate as
an oxidizer, and preferably contains both of metal nitrate and
perchlorate.
[0031] While a metal salt selected from alkali metals, alkaline
earth metals, iron, copper, magnesium, cobalt, nickel, zinc and the
like, for example, can be listed as the metal nitrate employed in
the present invention, a metal salt selected from alkali metals and
alkaline earth metals is preferable, in view of reactivity and
handleability. More specifically, at least one substance selected
from sodium nitrate, potassium nitrate, magnesium nitrate, barium
nitrate, strontium nitrate and the like is illustrated as such
metal nitrate. In particular, potassium nitrate or strontium
nitrate is preferable.
[0032] While at least one substance selected from ammonium
perchlorate, potassium perchlorate, sodium perchlorate and the
like, for example, can be listed as the perchlorate employed in the
present invention, the perchlorate is not restricted to these.
Among the above, ammonium perchlorate or potassium perchlorate
generating a large amount of gas and having high reactivity is
particularly preferable.
[0033] The content (compounding ratio) of metal nitrate and/or
perchlorate in the gas generant composition according to the
present invention is preferably 40 to 70 weight %, more preferably
45 to 65 weight %. This is because CO gas tends to generate in a
large amount due to insufficient oxygen if the content (compounding
ratio) of metal nitrate and/or perchlorate is less than 40 weight %
while generation of NO.sub.x tends to increase due to excess oxygen
if the content (compounding ratio) of metal nitrate and/or
perchlorate exceeds 70 weight %. If the gas generant composition
according to the present invention contains both of metal nitrate
and perchlorate as the (B) component, the aforementioned content
denotes the ratio at which the total quantity thereof occupies the
gas generant composition.
[0034] (C) Water-Soluble Polymer Binder
[0035] The gas generant composition according to the present
invention contains a water-soluble polymer binder, in view of
improving breaking strength and other mechanical properties (wear
resistance, thermal form stability etc.). While a mixture of
hydroxypropyl methylcellulose (HPMC) and polyacrylamide, cellulose
acetate, sodium carboxylmethylcellulose, hydroxyethyl cellulose,
hydroxypropyl methylcellulose, carboxymethylcellulose, guagum,
polyvinyl alcohol, polyvinyl pyrolidone and the like, for example,
can be listed as such water-soluble polymer binders, the
water-soluble polymer binder is not restricted to these. In
particular, the water-soluble polymer binder is preferably the
mixture of HPMC and polyacrylamide, for the reason of extrudability
and environmental resistance. While the mixing ratio of this
mixture is not particularly limited, preferably
HPMC:polyacrylamide=8:1 to 2:1, more preferably
HPMC:polyacrylamide=5:1 to 3:1, due to excellent handleability in a
kneaded state or an extruded state.
[0036] The content (compounding ratio) of the water-soluble polymer
binder in the gas generant composition according to the present
invention is preferably 2 to 10 weight %, more preferably 2 to 8
weight %. This is because the strength of a compact of the gas
generant composition tends to lower if the content (compounding
ratio) of the water-soluble polymer binder is less than 2 weight %
while CO gas tends to generate in a large amount due to
insufficient oxygen if the content (compounding ratio) of the
water-soluble polymer binder exceeds 10 weight %.
[0037] (D) Magnetic Material
[0038] While the magnetic material contained in the gas generant
composition according to the present invention is not particularly
limited, magnetic iron oxide is preferable, and magnetic iron oxide
having a spinel crystal structure is particularly preferable.
Magnetite (Fe.sub.3O.sub.4), maghemite (.gamma.-Fe.sub.2O.sub.3),
bertholide (Fe.sub.xO.Fe.sub.2O.sub.3) (0.ltoreq.x.ltoreq.1),
ferrite (MO. Fe.sub.2O.sub.3) (M: bivalent metal) and the like, for
example, can be listed as such magnetic iron oxide, and magnetite
(Fe.sub.3O.sub.4) containing a large quantity of bivalent iron
having a redox function is preferable in particular. It is possible
to confirm that magnetite is contained in the gas generant
composition by approximating a magnet and observing presence or
absence of attraction, for example.
[0039] It is also preferable to employ bertholide which is an
intermediate oxide expressed in Fe.sub.xO.Fe.sub.2O.sub.3
(0.ltoreq.x.ltoreq.1) as the magnetic iron oxide in the gas
generant composition according to the present invention. This is
because such an effect is attained that the redox action can be
controlled by employing bertholide expressed in
Fe.sub.xO.Fe.sub.2O.sub.3 (0.ltoreq.x.ltoreq.1).
[0040] When employing the magnetic iron oxide expressed in
Fe.sub.xO.Fe.sub.2O.sub.3 (0.ltoreq.x.ltoreq.1), this magnetic iron
oxide is preferably powder having a specific surface area 2.5 to 80
m.sup.2/g. It is unpreferable since chemical activity is low and
both of the combustion effect and the CO gas concentration reducing
effect are small if the specific surface area of the said magnetic
iron oxide is less than 2.5 m.sup.2/g, while chemical activity is
so excessively high that there is an apprehension that the magnetic
iron oxide becomes unstable in the atmosphere and hard to handle if
the specific surface area exceeds 80 m.sup.2/g. The said specific
surface area is more preferably in the range of 10 to 60 m.sup.2/g,
particularly preferably 20 to 50 m.sup.2/g. The specific surface
area of the aforementioned magnetic iron oxide denotes a value
measured by a BET method through nitrogen adsorption, for
example.
[0041] The content (compounding ratio) of the magnetic iron oxide
in the gas generant composition according to the present invention
is preferably 1 to 5 weight %, more preferably 2 to 4 weight %.
This is because the redox catalytic effect tends to lower if the
content (compounding ratio) of the magnetic iron oxide is less than
1 weight % while the ratio of the gas generant component so lowers
that the gas generation efficiency tends to lower if the content
(compounding ratio) of the magnetic iron oxide exceeds 5 weight
%.
[0042] The gas generant composition having magnetism according to
the present invention containing the aforementioned components (A)
to (D) preferably contains the magnetic iron oxide as the
composition, whereby the same is excellent in combustibility under
a low pressure, and can reduce the amount of CO gas generated in
combustion. The gas generant composition according to the present
invention having such effects can be preferably employed for a
pretensioner or a hood lifter.
[0043] More specifically, the wording "excellent in combustibility
under a low pressure" indicates that, while a combustion speed
(5%-30%) dP/dt which is a parameter indicating ignitability and
combustibility under a low pressure (5 to 30 MPa) has been 0.1 to
0.3 in a conventional gas generant composition (specific example:
nitroguanidine/strontium nitrate/ammonium perchlorate/binder), the
combustion speed (5%-30%) dP/dt under the same pressure is 1.8 to
5.9 in the gas generant composition according to the present
invention. (5%-30%) dP/dt mentioned herein denotes 5% pressure (P5)
at a time of setting the maximum ultimate pressure in a bomb to
100%, and assuming that t5 represents a time from energization up
to P5 and t30 similarly represents a time up to 30% pressure (P30),
the combustion speed (5%-30%) dP/dt is expressed in
(P30-P5)/(t30-t5) (combusting 1250 mg of the gas generant
composition in a bomb of 27 cc with a hole of 3 mm in diameter and
measuring the current internal pressure of the bomb with a pressure
sensor).
[0044] Further, the wording "can reduce the amount of CO gas
generated in combustion" more specifically indicates that, while
the amount of CO gas generated by a conventional gas generant
composition (specific example: smokeless powder mainly composed of
nitrocellulose) in combustion has been 4000 to 5000 ppm, the amount
of CO gas generated by the gas generant composition according to
the present invention in combustion is 200 to 300 ppm (measuring
gas generated by combusting 1000 mg of the gas generant composition
in a bomb of 10 cc with a hole of 1 mm in diameter in a tank of 60
L with a gas detecting tube).
[0045] The gas generant composition according to the present
invention is worked into a compact containing magnetic iron oxide
to have magnetism, whereby such a particular effect is attained
that chargeability can be improved by magnetic force when employed
as a gas generant for a small gas generator used for a pretensioner
or a hood lifter. This point is now described.
[0046] FIG. 1 is a sectional view schematically showing a small gas
generator 1 for a pretensioner or a hood lifter in a case of
employing the gas generant composition according to the present
invention, and FIG. 2 illustrates sectional views schematically
showing a process of assembling gas generator 1 shown in FIG. 1.
FIG. 1 shows a case of employing gas generator 1 of a lateral
blowing type, for example, as the small gas generator for a
pretensioner or a hood lifter. As shown in FIG. 1, gas generator 1
mainly comprises an igniter 10, a holder 20 as a base substrate
holding igniter 10, an actuating charge cup (AC cup) 40 as a cup
member forming a gas generant storage chamber storing a gas
generant (compact of a gas generant composition) 50 between the
same and holder 20 holding igniter 10, and a combustion control
cover 30 arranged in the aforementioned gas generant storage
chamber and so provided as to cover holder 20 and igniter 10.
[0047] Combustion control cover 30 is formed by a hollow and
substantially cylindrical member, and has a large-diametral portion
31 covering the upper portion of holder 20, a small-diametral
portion 32 covering a squib cup 12 of igniter 10 and a tapered
portion 33 coupling large-diametral portion 31 and small-diametral
portion 32 with each other. Combustion control cover 30 performs a
function of protecting squib cup 12 in non-operation, a function of
preventing fragments resulting from rupture of squib cup 12 in
operation from outward scattering and a function of supplying
directivity to a flame formed in igniter 10 and laterally guiding
the flame toward the gas generant storage chamber storing gas
generant 50.
[0048] In the process of assembling gas generator 1, combustion
control cover 30 is mounted on the inner part of AC cup 40 molded
into a desired shape, and gas generant 50 is thereafter charged
into a space formed between combustion control cover 30 and AC cup
40 with a dedicated filling jig 150 in general, as shown at (a) in
FIG. 2. At this time, gas generant 50 is charged into the
aforementioned space as densely as possible by vibrating AC cup 40
or the like. Then, dedicated filling jig 150 is detached from AC
cup 40 by pulling up dedicated filling jig 150 toward a direction
of arrow G in the drawing, as shown at (b) in FIG. 2. Thereafter
holder 20 to which igniter 10 is caulked/fixed through an O-ring 61
is inserted into large-diametral portion 31 of combustion control
cover 30 assembled into AC cup 40 charged with gas generant 50, and
these are set on a stage (not shown) having a receiving surface on
a lower portion. Then, the caulked portion of holder 20 is bent and
plastic-deformed to roll in a flange portion 43 of AC cup 40,
thereby caulking/fixing AC cup 40 to holder 20. Gas generator 1
having the structure shown in FIG. 1 is manufactured through this
process.
[0049] However, such an assembling process has such restriction in
manufacturing that positioning portions for dedicated filling jig
150 and combustion control cover 30 must be provided on the AC cup,
and cannot be applied to that having no positioning portions on AC
cup 40 as in the example shown in FIG. 1, for example. Further,
there is a possibility that gas generant 50 charged into the gas
generant storage chamber formed by igniter 10, holder 20 and AC cup
40 is unevenly distributed. If the gas generant is unevenly
distributed in the aforementioned gas generant storage chamber,
there is an apprehension that a uniform gas output cannot be
obtained toward all directions of a working space, and there is
also an apprehension that such an inconvenience takes place that a
desired gas output cannot be obtained as the case may be. In a
recent gas generator, not only a request for downsizing the device
but also a requirement for increasing the gas output increases. In
order to satisfy these conflicting requests, it is necessary to
charge the gas generant into the gas generant storage chamber in
high density. However, a gas generant molded by extrusion molding
or the like is prepared in various shapes such as granular,
pelletlike, columnar and discoidal shapes, and hence it is
extremely difficult to densely charge the gas generant having such
complicated shapes into the gas generant storage chamber.
[0050] According to the inventive gas generant composition, this
composition is worked into a compact and contains magnetic iron
oxide as the component (D), whereby dedicated filling jig 150 and
combustion control cover 30 may not be employed when charging the
aforementioned gas generant. In other words, the gas generator is
manufactured by simply charging a constant quantity of the gas
generant compact into AC cup 40, then applying a magnet from
outside AC cup 40 thereby magnetizing the gas generant to the wall
surface of AC cup 40 by magnetic force and providing a space in the
central portion of AC cup 40 and thereafter inserting holder 20
having igniter 10 (igniter 10 inserted into large-diametral portion
31 of combustion control cover 30 if necessary) into the space.
Thus, the steps from charging of the gas generant up to assembling
of the gas generator can be simply carried out. Therefore, the gas
generant can be charged up to a portion around an opening of AC cup
40 in high density as a result, and chargeability is improved as
compared with a case of employing a gas generant composition
containing no magnetic iron oxide. Consequently, it has been
possible to further increase both of combustion efficiency and the
CO gas reducing effect.
[0051] The gas generant composition according to the present
invention preferably further contains a metal oxide other than
magnetic iron oxide as the component (E), in view of further
improving combustibility. While at least one substance selected
from CuO, Cu.sub.2O, ZnO, .alpha.-Fe.sub.2O.sub.3, Mn.sub.2O.sub.3,
Mn.sub.3O.sub.4 and the like, for example, can be listed as this
metal oxide other than magnetic iron oxide, the metal oxide is not
restricted to these. In particular, the metal oxide is preferably
at least one substance selected from CuO, Cu.sub.2O and
.alpha.-Fe.sub.2O.sub.3, due to an excellent combustion catalytic
function.
[0052] When containing the aforementioned component (E), the
content (compounding ratio) of this metal oxide other than magnetic
iron oxide in the gas generant composition according to the present
invention is preferably 1 to 5 weight %, more preferably 1 to 3
weight %. This is because the combustion catalytic effect tends to
lower if the content (compounding ratio) of the aforementioned
metal oxide is less than 1 weight % while the ratio of the gas
generant component so lowers that the gas generation efficiency
tends to lower if the content (compounding ratio) of the
aforementioned metal oxide exceeds 5 weight %.
[0053] The gas generant composition according to the present
invention may contain various additives (RDX (trimethylene
trinitroamine), HMX (tetramethylene tetranitroamine), PETN
(pentaerythritol tetranitrate), TAGN (triaminoguanidine nitrate),
HN (hydrazine nitrate) etc.) in a range not hampering the effects
of the present invention, as a matter of course.
[0054] The gas generant composition according to the present
invention can be molded into a proper shape and provided as a gas
generant. The shape of the compact is not particularly limited but
a pelletlike, discoidal, spherical, barlike, hollow cylindrical,
confeito-like or tetrapodic shape can be listed, and the compact
may be imperforate or perforated. Further, the pelletlike or
discoidal compact may be provided with about one to several
protrusions on a single surface or both surfaces. The shape of the
protrusions is not particularly limited, but a columnar, conical or
multi-pyramidal shape, for example, can be listed.
[0055] The present invention also provides a small gas generator
for a gas actuator for activating a safety device employing the
aforementioned gas generant composition according to the present
invention. The small gas generator according to the present
invention, not particularly limited so far as the same employs the
gas generant composition according to the present invention, can be
preferably implemented by that comprising pretensioner gas
generator 1 shown in FIG. 1, or a small gas generator for a
pretensioner or a hood lifter shown in FIG. 3, for example.
[0056] While the present invention is now described in more detail
with reference to Examples and comparative examples, the present
invention is not restricted to these.
[0057] Examples 1 to 4 and comparative examples 1 to 4 are shown
below.
Example 1
[0058] 27.2 weight % of ammonium perchlorate, 27.2 weight % of
strontium nitrate, 2.9 weight % of magnetic iron oxide (magnetite:
Fe.sub.3O.sub.4) having an average particle diameter of 0.2 .mu.m
and a specific surface area of 20 m.sup.2/g, 4.6 weight % of
hydroxypropyl methylcellulose and 1.2 weight % of polyacrylamide
were mixed in a rocking mixer, and homogeneously kneaded in a
kneader while adding 36.9 weight % of nitroguanidine and
ion-exchanged water having an outer percentage of 14 weight %.
Then, the said mixture was extruded in an extruder through a die of
1.5 mm in diameter with application of a prescribed pressure, to be
extruded into a prescribed shape. The extruded compact of the gas
generant composition was cut to a length of 2.0 mm, and dried to
obtain a columnar gas generant composition.
[0059] A combustion speed (5%-30%) dP/dt and CO concentration which
are parameters showing ignitability and combustibility of the
obtained gas generant composition were measured. As the method of
measuring the combustion speed (5% -30%) dP/dt, 1250 mg of the gas
generant composition was combusted in a bomb of 27 cc with a hole
of 3 mm in diameter for measuring the current internal pressure of
the bomb with a pressure sensor and obtaining the relation between
the combustion time and the combustion pressure. As to the CO
concentration measurement, 1000 mg of the gas generant composition
was combusted in a bomb of 10 cc with a hole of 1 mm in diameter in
a tank of 60 L, and generated gas in 60 L was collected after 5
minutes from energization. The collected gas was measured with a
Kitagawa gas detecting tube. As to the magnetism of the gas
generant composition, a permanent magnet (coercive force Hc: 2.5
kOe to 4.0 kOe) was approximated, so that a denotes a case
attracted to the magnet and b denotes a case not attracted thereto.
Thus, presence or absence of improvement in chargeability by
magnetic force can be determined.
[0060] Table 1 shows results as to Example 1.
TABLE-US-00001 TABLE 1 (5%-30%) dP/dt CO concentration in
combustion speed gas generated in attraction to composition of gas
generant weight % (MPa/ms) tank of 60 L (ppm) magnet nitroguanidine
36.9 2.1 300 a ammonium perchlorate 27.2 strontium nitrate 27.2
magnetic iron oxide (Fe.sub.3O.sub.4) 2.9 (specific surface area:
20 m.sup.2/g) hydroxypropyl methylcellulose 4.6 polyacrylamide
1.2
Examples 2 to 4 and Comparative Examples 1 to 4
[0061] Also in Examples 2 to 4 and comparative examples 1 to 3, gas
generant compositions were manufactured by a method similar to that
in Example 1, and the respective characteristics were evaluated by
the same methods as Example 1. As to comparative example 4,
commercially available smokeless powder was used and the
characteristics were evaluated by the same methods as Example
1.
[0062] Table 2, Table 3 and Table 4 show results as to Example 2,
Example 3 and Example 4 respectively. Further, Table 5, Table 6,
Table 7 and Table 8 show results as to comparative example 1,
comparative example 2, comparative example 3 and comparative
example 4 respectively.
TABLE-US-00002 TABLE 2 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 36.9
0.8 400 a ammonium perchlorate 27.2 Strontium nitrate 27.2 magnetic
iron oxide (Fe.sub.3O.sub.4) 2.9 (specific surface area: 4
m.sup.2/g) hydroxypropyl methylcellulose 4.6 polyacrylamide 1.2
TABLE-US-00003 TABLE 3 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 36.2
5.9 300 a ammonium perchlorate 26.7 strontium nitrate 26.7 magnetic
iron oxide (Fe.sub.3O.sub.4) 2.8 (specific surface area: 40
m.sup.2/g) copper oxide (CuO) 1.9 hydroxypropyl methylcellulose 4.6
polyacrylam 1.1
TABLE-US-00004 TABLE 4 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 36.2
4.7 300 a ammonium perchlorate 26.7 strontium nitrate 26.7 magnetic
iron oxide (Fe.sub.3O.sub.4) 2.8 (specific surface area: 20
m.sup.2/g) copper oxide (CuO) 1.9 hydroxypropyl methylcellulose 4.6
polyacrylamide 1.1
TABLE-US-00005 TABLE 5 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 38.0
0.2 600 b ammonium perchlorate 28.0 strontium nitrate 28.0
hydroxypropyl methylcellulose 4.8 polyacrylamide 1.2
TABLE-US-00006 TABLE 6 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 36.9
0.4 500 b ammonium perchlorate 27.2 strontium nitrate 27.2 Iron
oxide (.alpha.-Fe.sub.2O.sub.3) 2.9 hydroxypropyl methylcellulose
4.6 polyacrylamide 1.2
TABLE-US-00007 TABLE 7 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet nitroguanidine 36.9
3.8 550 b ammonium perchlorate 27.2 strontium nitrate 27.2 copper
oxide (CuO) 2.9 hydroxypropyl methylcellulose 4.6 polyacrylamide
1.2
TABLE-US-00008 TABLE 8 (5%-30%) dP/dt CO concentration combustion
speed in gas generated in attraction composition of gas generant
weight % (MPa/ms) tank of 60 L (ppm) to magnet smokeless powder 100
6.5 4500 b
[0063] Examples 1 and 2 can be compared with comparative examples 1
and 2, and show that the combustion speed (5%-30%) dP/dt can be
increased and the amount of CO gas can be reduced by containing
magnetic iron oxide. Examples 3 and 4 can be compared with
comparative example 3, and show that copper oxide which is a metal
oxide can increase the combustion speed (5%-30%) dP/dt while CO gas
exhibits a slightly high value of 550 ppm, and the combustion speed
(5%-30%) dP/dt can be further increased and the amount of CO gas
can be reduced by further adding magnetic iron oxide. While
comparative example 4, smokeless powder which is the conventional
art, shows that a large amount of CO gas is generated although the
combustion speed (5%-30%) dP/dt is high. Examples 1 to 4 containing
at least 1 weight % of magnetic iron oxide exhibited
characteristics attracted to magnets as compared with comparative
examples.
[0064] The embodiment, Examples and comparative examples disclosed
this time must be considered as illustrative in all points and not
restrictive. The range of the present invention is shown not by the
above description but by the scope of claims for patent, and it is
intended that all modifications within the meaning and range
equivalent to the scope of claims for patent are included.
* * * * *