U.S. patent application number 12/837667 was filed with the patent office on 2010-11-04 for gas generator and method for manufacturing the same.
This patent application is currently assigned to NIPPON KAYAKU KABUSHIKI KAISHA. Invention is credited to Dairi KUBO, Kazuhisa Tamura.
Application Number | 20100275430 12/837667 |
Document ID | / |
Family ID | 36692333 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100275430 |
Kind Code |
A1 |
KUBO; Dairi ; et
al. |
November 4, 2010 |
GAS GENERATOR AND METHOD FOR MANUFACTURING THE SAME
Abstract
A gas generator that eliminates work for welding-fixing a holder
to a housing and subjecting the holder to an excess processing,
which can be easily manufactured at low cost, and a method for
manufacturing the gas generator. The gas generator includes an
approximately short cylindrical housing including a bottomed member
and a lid member, gas generants arranged in the housing to generate
a high-temperature gas by combustion, a filter arranged in an inner
circumference part of the housing so as to surround the gas
generants in a diameter direction of the housing, an igniter
energized from the outside to ignite, and a holder to which the
igniter is fixed and that is fixed to the bottomed member so that
the igniter is arranged coaxially with the housing. At least one of
the holder and the bottomed member is clamped, and pressed and
deformed in an axial direction of a hole so that the holder is
fixed to the bottomed member.
Inventors: |
KUBO; Dairi; (Himeji-shi,
JP) ; Tamura; Kazuhisa; (Himeji-shi, 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
JP
|
Family ID: |
36692333 |
Appl. No.: |
12/837667 |
Filed: |
July 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11814438 |
Jul 20, 2007 |
|
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PCT/JP2006/300808 |
Jan 20, 2006 |
|
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12837667 |
|
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Current U.S.
Class: |
29/428 |
Current CPC
Class: |
B60R 21/2644 20130101;
Y10T 29/49826 20150115; F42B 3/04 20130101; C06D 5/06 20130101 |
Class at
Publication: |
29/428 |
International
Class: |
B23P 11/00 20060101
B23P011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2005 |
JP |
2005-014433 |
Claims
1. A method for manufacturing a gas generator which has a short
cylindrical external shape, comprising: fitting and fixing a holder
configured to fix an igniter into a housing configured to contain
gas generants therein, the housing including a bottomed member
provided with a hole on the bottom, wherein the step of fitting and
fixing includes a step of clamping and pressurization-deforming at
least one of the holder or the bottomed member in the direction of
a center axis of the hole, thus achieving airtightness in a fixed
contact part between the holder and the bottomed member.
2. The method for manufacturing a gas generator as set forth in
claim 1, wherein the holder includes a first material and the
bottomed member includes a second material, a tensile strength of
the first material is different from a tensile strength of the
second material, and one that includes the material with a lower
tensile strength is deformed.
3. A method for manufacturing a gas generator with a short
cylindrical external shape, comprising: providing a housing
configured to contain gas generants therein, the housing including
a bottomed member provided with a hole; placing a holder configured
to fix an igniter in the hole; and clamping and
pressurization-deforming at least one of the bottomed member or the
holder in a radial direction of the hole with a first metal fitting
and a second metal fitting, the bottomed member, the holder, the
first metal fitting, and the second metal fitting being coaxially
arranged, wherein a contact part between the bottomed member and
the holder is airtight after clamping and pressurization-deforming
at least one of the bottomed member or the holder.
4. The method for manufacturing a gas generator as set forth in
claim 3, wherein the bottomed member is deformed in a diameter
reduction direction.
5. The method for manufacturing a gas generator as set forth in
claim 3, wherein the holder is deformed in a diameter expansion
direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/814,438 filed Jul. 20, 2007, the entire contents of which is
incorporated herein by reference. Application Ser. No. 11/814,438
is a National Stage of PCT/JP06/300808 filed Jan. 20, 2006 and
claims the benefit of priority under 35 U.S.C. .sctn.119 from
Japanese Application No. 2005-014433 filed Jan. 21, 2005.
TECHNICAL FIELD
[0002] The present invention relates to a gas generator for
inflating and deploying an airbag of an automobile, etc., more
particularly, it relates to a gas generator to which an igniter can
be fixed simply and at low cost.
BACKGROUND ART
[0003] A gas generator for immediately deploying an airbag has been
conventionally built in various airbag modules in order to protect
an occupant from an impact caused by an automobile crash. The gas
generator immediately generates a large amount of high-temperature
gas based on a crash detection signal transmitted from a crash
sensor at the time of an automobile crash.
[0004] For the gas generator, an igniter which has a system for
igniting an inner ignition material when receiving the crash
detection signal from the crash sensor and converts an electric
signal to ignition energy, gas generants for receiving the ignition
energy from the igniter to generate a large amount of gas, a
metallic cylindrical housing for housing the igniter and the gas
generants therein, and a holder for fixing the igniter to the
housing are typically cited as minimum components required.
Additionally, a filter may be employed which absorbs a large amount
of heat and combustion particles generated by combustion of the gas
generants as the need arises.
[0005] Moreover, a main part of the igniter generally includes a
plastic material composed of a thermoplastic resin and the like,
and is fixed to the metallic holder by a caulking method.
[0006] As a method for fixing the holder to the metallic housing,
welding and the like are known (see the Patent Document 1).
[0007] Additionally, as a method for fixing a sealing plate of the
gas generator to the housing, caulking is known (see the Patent
Document 2). Particularly, in this method, the sealing plate and
the housing composed of the same kind of steel materials such as a
high-tension plate are subjected to caulking and striking to be
fixed to each other.
[0008] Additionally, a gas generator is known in which a part of an
inner cylindrical member provided in the housing is caulked so that
an igniter assembly (igniter and collar) is fixed to the inner
cylindrical member (see the Patent Document 3).
[0009] Additionally, a gas generator is known in which a part of an
elongated cylindrical housing is diameter-reduction processed in
relation to a lid member with a stage so that the lid member is
fixed to the housing (see the Patent Document 4).
Patent Document 1: Japanese Unexamined Patent Publication No.
2003-112597
[0010] Patent Document 2: U.S. Pat. No. 3,475,392
Patent Document 3: Japanese Unexamined Patent Publication No.
2004-293835
[0011] Patent Document 4: International Publication No.
WO01/074632
DISCLOSURE OF THE INVENTION
Problem(s) to be Solved by the Invention
[0012] In the Patent Document 1, for example, when an iron-based
material widely used at present is used for a housing, it is
preferable that the same kind of iron-based material is necessarily
used for a holder in terms of welding. However, the holder is
required to be cut into a shape suitable for fixing an igniter in a
process such as caulking, and the iron-based material is relatively
expensive to cut.
[0013] In the Patent Document 2, a relatively complicated work is
required that a sealing plate composed of a steel material is fixed
in a pipe body composed of a steel material by caulking, and that a
surface of the sealing plate is subjected to striking so that
struck indentations are left along a circumferential edge of the
sealing plate.
[0014] In the Patent Document 3, a work is required that an igniter
assembly is fixed to the inside of an inner cylindrical member and
the inner cylindrical member is welding-fixed to a closure shell
(housing).
[0015] In the Patent Document 4, a lid member with a stage is
required to be formed thereby increasing cost.
[0016] Thereupon, the present invention aims at providing a gas
generator that eliminates works for welding-fixing a holder to a
housing and subjecting the holder to an excess processing, and can
be easily manufactured at low cost and a method for
manufacturing.
Means for Solving the Problem and Effect
[0017] A gas generator of the present invention includes a holder
which has a short cylindrical external shape for fixing an igniter,
and a housing which has a bottomed member having a hole, into which
the holder is fitted, on the bottom and can contain gas generants
therein. In the gas generator, the holder is fitted in the hole, at
least one of the holder and the bottomed member is deformed in a
diameter direction of the hole, and thus the holder is fixed to the
housing.
[0018] According to the above configuration, a gas generator which
is manufactured without work for welding-fixing the holder to the
bottomed member and subjecting the holder to an excess processing,
and which has a high airtightness in a contact part between the
holder and the bottomed member can be provided.
[0019] In the gas generator of the present invention, the holder
has an approximately columnar external shape, and it is preferable
that the holder is deformed in a diameter expansion direction, or
the bottomed member is deformed in a diameter reduction direction
of the hole.
[0020] According to the above configuration, it is much less
necessary that a projection part, a groove part, or the like is
formed on the bottomed member or the holder of the housing in order
to fix them by caulking or the like. Therefore, the gas generator
can be provided at low cost.
[0021] In the gas generator of the present invention, it is
preferable that at least one of the holder and the bottomed member
is clamped and pressurized in the direction of a center axis of the
hole to be deformed.
[0022] According to the above configuration, a gas generator which
is manufactured by a process easier than the process for directly
deforming the bottomed member or the holder in the diameter
direction, and which has high fixing strength between the holder
and the bottomed member, and has high airtightness in the contact
part between the holder and the bottomed member can be reliably
provided.
[0023] In the gas generator of the present invention, it is
preferable that the holder and the bottomed member are respectively
composed of materials having strengths different from each other,
and that one composed of the material having a lower strength is
deformed.
[0024] According to the above configuration, the material having
the lower strength is easily closely adhered to an interface of the
material having a higher strength with no space therebetween.
Accordingly, a gas generator excellent in strength and airtightness
in a fixed contact part between the holder and the bottomed member
can be provided.
[0025] In the gas generator of the present invention, it is
preferable that the holder has at least two outer diameters
different from each other, and that an inequality, A.ltoreq.an
inner diameter C of the hole provided in the bottomed
member.ltoreq.B, is established wherein A represents a smaller
outer diameter and B represents a larger outer diameter.
[0026] According to the above configuration, the holder can be
constructed so that it hardly comes off the bottomed member, and
the possibility can be lowered that the holder comes off, for
example, in the case where the gas generator operates and an inner
pressure becomes high.
[0027] In the gas generator of the present invention, it is
preferable that the bottomed member is composed of an iron-based
metallic material and the holder is composed of an aluminum-based
material.
[0028] A groove or the like has been conventionally required to be
provided in the holder so that the igniter is fixed to the holder.
However, the cost required in a cutting process in the case where
the holder is composed of the aluminum-based material is lower than
that in the case of being composed of the iron-based material, and
therefore the aluminum-based material is more preferable.
[0029] A method for manufacturing the gas generator of the present
invention includes the step of fitting and fixing the holder for
fixing the igniter into the housing which has the bottomed member
having the hole in the bottom and can contain gas generants
therein, wherein the step of fitting and fixing includes the step
of clamping and pressurization-deforming in the direction of the
center axis of the hole at least one of the holder and the bottomed
member.
[0030] According to the above configuration, the gas generator
which has high airtightness in the contact part between the holder
and the bottomed member can be manufactured, without the work for
welding-fixing the holder to the bottomed member and subjecting the
holder to an excess processing.
[0031] In the method for manufacturing the gas generator of the
present invention, it is preferable that the holder and the
bottomed member are respectively composed of materials having
strengths different from each other, and that one composed of the
material having the lower strength is deformed.
[0032] According to the above configuration, the material having
the lower strength is easily closely adhered to an interface of the
material having the higher strength with no space therebetween.
Accordingly, the gas generator excellent in strength and
airtightness in the fixed contact part between the holder and the
bottomed member can be provided.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] A gas generator according to a first embodiment of the
present invention will be described below with reference to the
accompanying drawings.
[0034] FIG. 1 is a cross sectional view of a gas generator 101
which is an example of the gas generator of the present invention.
In FIG. 1, the gas generator 101, which inflates and deploys, for
example, a driver seat airbag, includes an approximately short
cylindrical housing 3 including a bottomed member 3a and a lid
member 3b, gas generants 4 which are arranged in the housing 3 to
generate a high-temperature gas by combustion, a filter 5 which is
arranged in an inner circumference part of the housing 3 so as to
surround the gas generants 4 in a diameter direction of the housing
3, an igniter 1 which is energized from the outside to ignite, and
a holder 2 to which the igniter 1 is fixed and which is fixed to
the bottomed member 3a so that the igniter 1 is arranged coaxially
with the housing 3.
[0035] The lid member 3b has a cylindrical part having a plurality
of gas discharging holes 7, and a bottom part provided at one end
of the cylindrical part. A diameter of an opening side of the lid
member 3b is expanded so that the opening has a flange shape.
Additionally, the bottomed member 3a similarly has a cylindrical
part and a bottom part, and a hole 3c, into which the holder 2 is
to be fitted and arranged, is provided in the bottom part. An
opening of the bottomed member 3a engages with the vicinity of the
opening of the lid member 3b, and the bottomed member 3a and the
lid member 3b are fixed to each other in a welding part 8 by
welding, etc. Here, as materials of the bottomed member 3a and the
lid member 3b, metallic materials such as iron, stainless-steel,
aluminum and steel are applicable. Additionally, it is preferable
that thicknesses of the bottomed member 3a and the lid member 3b
are in a range of 1.0 to 3.0 mm.
[0036] As described above, the plurality of gas discharging holes 7
for discharging gas generated by combustion of the gas generants 4
are provided in the cylindrical part of the lid member 3b. The
plurality of gas discharging holes 7 enable the high-temperature
gas discharged from the inside of the gas generator 101 to be
stably supplied to a target place such as an inside of the airbag.
The gas discharging holes 7 are manufactured in a cutting process,
a press-molding process, or the like. It is preferable that a shape
of the gas discharging hole 7 is circular having a diameter in a
range of 1.0 to 5.0 mm, in terms of ease in manufacturing.
[0037] Additionally, a band-shaped rupture member 9 is arranged
along the inside of the cylindrical part, in which the gas
discharging holes 7 are positioned, of the lid member 3b, and the
rupture member 9 seals the gas discharging holes 7 so that the
inside of the gas generator 101 is formed into a sealed space. When
the gas generator 101 operates, an inner pressure of the gas
generator 101 is raised by the combustion of the gas generants 4,
the rupture member 9 is ruptured, and the gas is discharged from
the gas discharging holes 7. Here, as a material of the rupture
member 9, steel materials such as iron, stainless-steel and
aluminum and a film made of plastic, etc., are applicable.
Additionally, although the thickness of the rupture member varies
in accordance with the strength of the materials to be used, it is
preferable that it is in a range of 0.01 to 0.5 mm. Additionally,
the strength of the rupture member 9 is set so as to vary in
accordance with the hole diameter of the gas discharging hole 7.
Particularly, it is preferable that the strength of the rupture
member 9 is set so as to be raised as the hole diameter of the gas
discharging hole 7 becomes small. Thus, when the gas generator 101
operates, an initial inner pressure is controlled, and a suitable
combustion property of the gas generants 4 can be obtained.
[0038] The filter 5 is arranged outside a columnar space formed in
the housing 3 and along an inner wall of the housing 3. The filter
5 is fixed so as to be clamped between the bottomed member 3a and
the lid member 3b in an axial direction, and fixed in a manner that
is fitted in an inner circumference part of the bottomed member 3a
in a circumferential direction. Additionally, the filter 5 is
formed by forming an aggregate of stockinet wire netting,
plain-woven wire netting, crimp-woven metal wire or wound metal
wire into a ring having a predetermined thickness. The filter 5 has
the effects of cooling combustion gas of the gas generants 4, and
of collecting metal particles generated by the combustion of the
gas generants 4 to make it difficult for a solid product to come
out of the gas generator 101.
[0039] The inner space surrounded by the filter 5 in the housing 3
is filled with the gas generants 4. Preferably, a non-azide-based
composition, for example, a composition of fuel, oxidizer and
additives (binder, slag forming agent, combustion adjusting agent
and the like) is used as the gas generants 4.
[0040] As a fuel, a nitrogen containing compound is applicable. As
a nitrogen containing compound, for example, one compound or a
mixture of two or more compounds is applicable which is selected
from triazole derivatives, tetrazole derivatives, guanidine
derivatives, azodicarbonamide derivatives, hydradine derivatives,
urea derivatives and ammine complexes. Preferably, among these
nitrogen containing compounds, one compound or a mixture of two or
more compounds selected from the tetrazole derivatives and the
guanidine derivatives is used, and more preferably, nitroguanidine,
guanidine nitrate, cyanoguanidine, 5-aminotetrazole, aminoguanidine
nitrate and guanidine carbonate are used.
[0041] A combination rate of the above nitrogen containing compound
in the gas generants 4 varies depending on the numbers of carbon
atoms, hydrogen atoms and the other atoms to be oxidized in a
molecular formula, and generally, it is preferably in a range of 20
to 70 percent by weight, more preferably, is in a range of 30 to 60
percent by weight. Additionally, an absolute value of the
combination rate of the nitrogen containing compound varies
depending on the kind of oxidizer to be added to the gas generants
4. However, when the absolute value of the combination rate of the
nitrogen containing compound is larger than a perfect oxidation
theoretical amount, a concentration of trace CO in the generated
gas increases. On the other hand, when the absolute value of the
combination rate of the nitrogen containing compound is equal to or
less than the perfect oxidization theoretical amount, a
concentration of trace NOx in the generated gas increases.
Accordingly, most preferably, the absolute value is in a range that
a balance of both the concentrations is kept optimal.
[0042] As the oxidizer, at least one selected from nitrate, nitrite
and perchlorate, which each contains cation, of alkaline metal,
alkaline earth metal, transition metal or ammonium is preferably
used. As the nitrate, for example, sodium nitrate, potassium
nitrate, magnesium nitrate, strontium nitrate, phase-stabilized
ammonium nitrate, basic copper nitrate and the like are applicable,
and preferably, the strontium nitrate, phase-stabilized ammonium
nitrate, basic copper nitrate are used.
[0043] An absolute value of a combination rate of the oxidizer in
the gas generants 4 varies depending on the kind and amount of the
nitrogen containing compound to be used. Preferably, it is in a
range of 30 to 80 percent by weight, and more preferably, is in a
range of 45 to 75 percent by weight in terms of the concentrations
of CO and NOx.
[0044] As the binder which may be contained in the gas generants 4,
organic binders such as methyl cellulose, hydroxypropyl methyl
cellulose, carboxymethyl cellulose, nitrocellulose, cellulose
acetate, polyvinyl alcohol, polyacrylamide, and inorganic binders
such as synthetic hydrotalcite, acid clay, talc, kaolin, silica,
alumina are applicable.
[0045] Additionally, as a concrete example of the slag forming
agent which may be contained in the gas generants 4, silicon
nitride, silicon carbide, acid clay, natural clay, artificial clay,
talc and the like can be cited.
[0046] The gas generants 4 composed as described above are adjusted
into a desired shape by press-molding, extrusion-molding or the
like. As a shape of the gas generants 4, column, cylinder, disc, or
hollow in which both ends are closed can be cited.
[0047] The igniter 1 is fixed to the holder 2 by caulking or the
like via an O-ring 12 composed of rubber and the like. At this
time, the interface of the igniter 1 and the holder 2 has a sealing
property due to the O-ring. The igniter 1 has a role of converting
electric energy energized by the sensor into combustion energy of
powder included therein. The majority of the exterior of the
igniter 1 is covered with a thermoplastic resin and the like by
molding to be electrically insulated.
[0048] The holder 2 has at least two outer diameters different from
each other, and it is preferable that an inequality, A an inner
diameter C of the hole provided in the bottomed member 3a B, is
established wherein A represents the smaller outer diameter and B
represents the larger outer diameter (for example, see the holder 2
shown in FIG. 2 and FIG. 3). As a material of the holder 2, metals
such as iron, stainless-steel, aluminum and steel are applicable.
In the embodiment, it is preferable that the material of the holder
2 is selected to have a strength essentially different from that of
a material used for the bottomed member 3a. For example, a
combination of iron, aluminum, and the like is suitable for the
above material.
[0049] According to the embodiment, the gas generator 101 which is
manufactured without work for welding-fixing the holder 2 to the
bottomed member 3a and subjecting the holder 2 to an excess
processing, and which has high airtightness in a contact part
between the holder 2 and the bottomed member 3a can be
provided.
[0050] Additionally, it is much less necessary that a projection
part, a groove part, or the like is formed on the holder 2 or the
bottomed member 3a of the housing in order to fix them by caulking
or the like. Therefore, the gas generator 101 can be provided at
low cost.
[0051] Further, the gas generator 101 which is manufactured by a
process easier than the process for directly deforming the holder 2
or the bottomed member 3a in the diameter direction, and which has
high fixing strength between the holder 2 and the bottomed member
3a, and has high airtightness in the contact part between the
bottomed member 3a and the holder 2 can be reliably provided.
[0052] Furthermore, since the holder 2 and the bottomed member 3a
are respectively composed of materials having strengths different
from each other, the material having the lower strength is easily
closely adhered to the material having a higher strength, and thus
the gas generator 101 excellent in strength and airtightness in a
fixed contact part between the holder 2 and the bottomed member 3a
can be provided.
[0053] Additionally, since a diameter of a part of the holder 2
inside of the bottomed member 3a is made larger than that of the
hole 3c, the holder 2 can be constructed so that it hardly comes
off the bottomed member 3a. Accordingly, the possibility can be
lowered that the holder 2 comes off, for example, in the case where
the gas generator 101 operates and the inner pressure becomes
high.
[0054] Additionally, a groove or the like has been conventionally
required to be provided in the holder 2 so that the igniter 1 is
fixed to the holder 2. However, the cost for a cutting process in
the case where the holder is composed of the aluminum-based
material is lower than that in the case of being composed of the
iron-based material, and therefore the holder composed of the
aluminum-based material is more preferable.
[0055] Next, a method for fixing the holder 2 to the bottomed
member 3a in the gas generator 101 according to the present
invention will be described with reference to FIG. 2. FIG. 2 shows,
the bottomed member 3a, the holder 2 before the igniter 1 is fixed
thereto, an approximately cylindrical bottomed member pressing down
metal fitting 10a, and an approximately cylindrical bottomed member
pressing up metal fitting 10b. First, the holder 2 is inserted into
the hole 3c provided in the bottomed member 3a. Next, as shown in
FIG. 2, the bottomed member pressing down metal fitting 10a is
pressed from the downside to the upside in the axial direction of
the bottomed member 3a and simultaneously the bottomed member
pressing up metal fitting 10b is pressed from the upside to the
downside in the axial direction of the bottomed member 3a. Thereby,
the metal fittings clamp therebetween an outer circumferential part
of the hole 3c located outside the bottomed member 3a and an outer
circumference of a projection part (whose diameter is represented
as B) of the holder 2 located inside the bottomed member 3a. As a
result, the bottomed member 3a is deformed in a diameter reduction
direction, and consequently a diameter of the hole 3c provided in
the housing 3 is deformed in a diameter reduction direction,
thereby the interface of the holder 2 is adhered and fixed to the
bottomed member 3a. The bottomed member 3a, the holder 2, the
bottomed member pressing down metal fitting 10a and the bottomed
member pressing up metal fitting 10b are coaxially arranged by a
guide not shown.
[0056] Next, a difference between the strengths of the holder 2 and
the bottomed member 3a in the present invention will be described.
In the present invention, it is particularly preferable that there
is a difference between tensile strengths among mechanical
properties of metal. The tensile strength is a value which is
calculated, when a material piece endures a large load exceeding a
break-down point and endurance in the tension test, by dividing the
maximum load at the time by a cross sectional area of the material
piece before a tension test. Additionally, the tensile strength is
closely related to hardness, and an estimation value of the
hardness can be calculated based on the tensile strength with use
of the following expression: Tensile Strength
1(N/mm.sup.2)=3.268871HV.apprxeq.20.593889HS.apprxeq.31.381116HRC
Here, HV represents Vickers hardness, HS represents Shore hardness,
and HRC represents Rockwell hardness. Additionally, the
relationship between the hardnesses including Brinell hardness (HB)
can be checked with use of a hardness conversion chart.
[0057] In an adhering part between the holder 2 and the housing 3,
a material having a low tensile strength adheres to gaps in a
surface of a material having a high tensile strength so that a high
sealing property is kept.
[0058] Generally, in terms of materials, a combination of the
aluminum-based material and the iron-based material is particularly
effective. Here, the aluminum-based material includes an aluminum
alloy containing iron, manganese or the like, in addition to pure
aluminum. Additionally, the iron-based material includes steel
containing carbon, and cast iron, in addition to pure iron
containing no carbon, and further includes a special steel
containing nickel, chrome, molybdenum or the like, and may be
subjected to thermal treatment.
[0059] According to the above method, the gas generator 101 can be
manufactured without work for welding-fixing the holder 2 to the
bottomed member 3a and subjecting the holder 2 to an excess
processing, and which has the high airtightness in the contact part
between the holder 2 and the bottomed member 3a.
[0060] Additionally, in the case where the holder 2 and the
bottomed member 3a are respectively composed of the materials
having the strengths different from each other, and where one
composed of the material having the lower strength is deformed, the
material having the lower strength is easily adhered to the
material having the higher strength with no space therebetween, and
thus a gas generator which is excellent in strength and
airtightness in the fixed contact part between the holder 2 and the
bottomed member 3a can be manufactured.
[0061] Additionally, in the above-described tensile strength,
preferably, a strength difference at a normal temperature (5 to
35.degree. C.) in the present invention, a value of "the tensile
strength of the material having the large strength--the tensile
strength of the material having the small strength" is in a range
of 10 to 800 N/mm.sup.2, more preferably, is in a range of 50 to
400 N/mm.sup.2. When the strength difference is set in such a
range, a gas generator which is excellent in strength and
airtightness can be manufactured.
[0062] Next, a method for fixing the holder 2 to the bottomed
member 3a in the gas generator 101 according to another embodiment
of the present invention will be described with reference to FIG.
3. FIG. 3 shows the bottomed member 3a, the holder 2 before the
igniter 1 is fixed thereto, an approximately cylindrical holder
pressing down metal fitting 11a, and an approximately cylindrical
holder pressing up metal fitting 11b. First, the holder 2 is
inserted into the hole 3c provided in the bottomed member 3a. Next,
as shown in FIG. 3, the holder pressing down metal fitting 11a is
pressed against the holder 2 from the downside to the upside in the
axial direction, the holder pressing up metal fitting 11b is
simultaneously pressed against the holder 2 from the upside to the
downside in the axial direction, and an upper surface of an upper
part of the projection part (the diameter is represented as B) of
the holder 2 and a lower surface of a lower part (the diameter is
represented as A) of the holder 2 are faced and clamped by the
metal fittings. Thus, the holder 2 is deformed in a diameter
expansion direction, and consequently is deformed in the diameter
expansion direction relative to the diameter of the hole 3c
provided in the bottomed member 3a. Thereby, the holder 2 is
adhered and fixed to the bottomed member 3a. The bottomed member
3a, the holder pressing down metal fitting 11a and the holder
pressing up metal fitting 11b are coaxially arranged by a guide not
shown.
[0063] According to the above-described method, an effect can be
obtained that is similar to the effect obtained by the method
described above with reference to FIG. 2.
[0064] Moreover, although not shown, holder pressing metal
fittings, which are combinations of the holder pressing down metal
fitting and the holder pressing up metal fitting shown in FIG. 2
and FIG. 3, may be used so that the holder 2 and the bottomed
member 3a are simultaneously clamped and fixed. Thus, a gas
generator which has higher strength and airtightness can be
manufactured.
[0065] The present invention is not limited to the above
embodiments, and various modifications can be performed without
departing from the scope of the appended claims. For example, like
a gas generator 102 shown in FIG. 4, into which the gas generator
101 according to the first embodiment is modified, the holder 2 of
the first embodiment may be replaced by a holder 14 to which the
igniter 1 and an enhancer holder 13 are caulking-fixed. Moreover,
the enhancer holder 13 is caulking-fixed to the holder 14 in states
where an upper part of the igniter 1 is covered by the enhancer
holder 13 and a space between the igniter 1 and the enhancer holder
13 is filled with powder 15.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] FIG. 1 is a cross sectional view in an axial direction of a
gas generator according to a first embodiment of the present
invention;
[0067] FIG. 2 is a view showing a case where the bottomed member is
deformed when a holder is fixed to the bottomed member in the gas
generator according to the first embodiment of the present
invention;
[0068] FIG. 3 is a view showing a case where the holder is deformed
when the holder is fixed to the bottomed member in the gas
generator according to the first embodiment of the present
invention; and
[0069] FIG. 4 is a cross sectional view in an axial direction of a
gas generator according to a modification of the first embodiment
of the present invention.
DESCRIPTION OF SYMBOLS
[0070] 1 igniter [0071] 2, 14 holder [0072] 3 housing [0073] 3a
bottomed member [0074] 3b lid member [0075] 3c hole [0076] 4 gas
generants [0077] 5 filter [0078] 7 gas discharging hole [0079] 8
welding part [0080] 9 rupture member [0081] 10a bottomed member
pressing down metal fitting [0082] 10b bottomed member pressing up
metal fitting [0083] 11a holder pressing down metal fitting [0084]
11b holder pressing up metal fitting [0085] 12 O-ring [0086] 13
enhancer holder [0087] 15 powder [0088] 101, 102 gas generator
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