Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-06-28
2002-10-15
English, Peter C. (Department: 3616)
Land vehicles
Wheeled
Attachment
C029S516000, C029S522100
Reexamination Certificate
active
06464254
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an inflator for generating gas for inflating and deploying an airbag and a method of manufacturing the same. More particularly, the present invention relates to an airbag inflator and a method of manufacturing the same having advantages such as reduced manufacturing cost.
Airbag inflators are gas generators for deployment of airbags. Some inflators have a plurality of gas combustion chambers. By adjusting the ignition selectively or ignition timing of the gas generants in the combustion chambers, the gas generation for deploying an airbag can be adapted to the severity of accident and the situation of an occupant, thereby achieving a preferable airbag deployment.
For instance, an inflator of this kind is disclosed in Japanese Patent Publication (KOKAI) H10-329638.
FIG. 5
is a sectional view showing the internal constitution of an airbag module. The airbag module shown in
FIG. 5
comprises a gas generator (inflator)
104
, and an airbag
102
which is deployed with a gas discharged from the gas generator
104
. The inflator
104
is accommodated in a module casing
103
. In
FIG. 5
, the airbag
102
is in a folded state. Defined between the inner surface of the module casing
103
and the outer surface of the gas generator
104
is a space S
1
as a gas passage for airbag deployment.
The gas generator
104
comprises a cylindrical outer shell
121
. Both ends of the outer shell
121
are closed by lid members
129
A (left side) and
129
B (right side). A disc-like partition
122
is fixed to a middle portion of the outer shell
121
. The partition
122
comprises a central disc portion
122
a
and a flange
122
b
radially extending from the central disc portion
122
a
. The partition
122
is crimped at a drawn portion (crimped portion)
131
of the outer shell
121
. The inside of the outer shell
121
is divided into a first combustion chamber GI with a small capacity and a second combustion chamber G
2
with a large capacity. The id outer shell
121
is provided with a plurality of gas outlets
128
a
corresponding to the combustion chambers G
1
, G
2
. The gas outlets
128
a
are normally closed by burst plates
133
.
Arranged in the combustion chambers G
1
, G
2
of the outer shell
121
are filter cylinders
115
A,
115
B, respectively. Each filter cylinder
115
A,
115
B is composed of an inner shell
125
and a filter
124
attached to the inner surface of the inner shell
125
. There is a space S
2
as a gas passage defined between the inner surface of the outer shell
121
and the outer surface of the filter cylinder
115
A or
115
B. The inner spaces of the filter cylinders
115
A,
115
B are filled with gas generants
123
. The inner shell
125
is provided with a plurality of gas holes
125
a for allowing the communication between the filter
124
and the space S
2
. The left end of the filter cylinder
115
A in
FIG. 5
is fitted to a convexity
129
a
formed on the inner face of the lid member
129
A. On the other hand, the right end of the filter cylinder
115
B in
FIG. 5
is fitted to a convexity
129
b
formed on the inner face of the lid member
129
B. The flange
122
b
of the partition
122
is sandwiched between the filter cylinders
115
A and
115
B.
Annular seals
132
are interposed between the filter cylinders
115
A,
115
B and the flange
122
b
of the partition
122
, respectively. The annular seals
132
isolate the gas flow and heat transfer between the filter cylinders
115
A and
115
B.
Cushion members
134
are attached to both surfaces of the central disc portion
122
a
, respectively. The cushion members
134
prevent the gas generants
123
to become powder and also isolate the heat transfer between the combustion chambers G
1
and G
2
. The annular seals
132
and the cushion members
134
are made of a material having heat insulation property.
The lid members
129
A,
129
B at both sides of the outer shell
121
include initiators
126
A,
126
B. Each initiator
126
A or
126
B includes a booster propellant
135
and an igniter
136
. The booster propellant
135
is accommodated in a cap
137
fitted to the convexity
129
a
(
129
b
) of the lid member
129
A (
129
B). As the igniter
136
is triggered, the booster propellant
135
is fired so that fire spouts out into the combustion chamber through holes (not shown) of the cap
137
. The fire spreads to ignite the gas generant
123
so that the gas generant
123
burns to generate gas with high temperature and high pressure. The gas flows into the filter
124
where the slag contained in the gas is removed and the gas is cooled. Then, the gas flows into the space S
2
through the gas holes
125
a
of the inner shell
125
. As the inner pressure of the combustion chamber reaches a predetermined value, the burst plates
133
are torn, so that the gas spouts out into the space S
1
through the gas outlets
128
a
. Then, the gas flows into the airbag
102
, thereby inflating and developing the airbag.
Because of the two chambers G
1
, G
2
of the gas generator
104
, the deployment of the airbag
102
can be controlled as explained below.
In the highly severe collision, both initiators
126
A and
126
B are triggered simultaneously. Therefore, the gas generants
123
in the first and second combustion chambers G
1
and G
2
are fired simultaneously to discharge a large amount of gas, thereby inflating and deploying the airbag
102
immediately.
In the medium collision, the initiator
126
B for the second combustion chamber G
2
having a larger capacity for generating a larger amount of gas is triggered first. After a very short time, the initiator
126
A for the first combustion chamber G
1
having a smaller capacity for generating a smaller amount of gas is In triggered. Therefore, the airbag
102
is inflated and developed slowly by the gas generated in the second combustion chamber G
2
in the initial stage. From the middle stage, the airbag
102
is developed rapidly by the total of the gases generated in both combustion chambers G
1
and G
2
, respectively.
In the relatively light collision, only the initiator
126
B for the second combustion chamber G
2
is triggered. Alternatively, the initiator
126
A of the first combustion chamber G
1
is also triggered after a large time delay following the beginning of the initiator
126
B. In this case, the airbag
102
is slowly inflated and developed for a relatively long period of time.
By the way, the conventional gas generator
104
mentioned above has the following drawbacks. When the gas generant
123
in one of the combustion chambers G
1
, G
2
is fired, a large pressure difference is applied to the partition
122
. Since the partition
122
is just crimped at the crimp portion of the outer shell
121
, the sealing property between the chambers G
1
and G
2
is poor, though the thickness of the partition
122
is large.
To improve the sealing property between the chambers, as shown in FIGS.
6
(A)-
6
(C), other crimping methods are also known in which sealing members, such as O rings and gaskets, are interposed between the outer periphery of the partition and the inner surface of the outer shell.
FIGS.
6
(A)-
6
(C) are sectional views for explaining the examples of the fixing and sealing structure between the partition and the outer shell in the conventional gas generator.
Referring to FIG.
6
(A), a gasket
155
is interposed between the outer periphery of the partition
152
and the inner surface of the outer shell
151
, so that the partition
152
is crimped at a middle portion
152
x
in the thick direction of the partition.
Referring to FIG.
6
(B), the partition
162
is provided with an O-ring groove
162
x
formed in a middle portion in the thick direction of the partition
162
. An O-ring
165
is fitted in the O-ring groove
162
x
. The partition
162
is crimped at the portion where the O-ring
165
is fitted.
Referring to FIG.
6
(C), this example is similar to the example shown in FIG.
6
(B) using an O-ring
165
for sealing the p
Chikaraishi Tsuneo
Doi Makoto
English Peter C.
Kanesaka & Takeuchi
Takata Corporation
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