U.S. patent application number 10/845221 was filed with the patent office on 2005-02-24 for initiator for a gas generator.
This patent application is currently assigned to TAKATA CORPORATION. Invention is credited to Amano, Junya, Furusawa, Takashi, Sanoki, Hiroyuki, Sugiyama, Tadashi, Yamashitaya, Suguru.
Application Number | 20050039623 10/845221 |
Document ID | / |
Family ID | 34190949 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050039623 |
Kind Code |
A1 |
Furusawa, Takashi ; et
al. |
February 24, 2005 |
Initiator for a gas generator
Abstract
An initiator employs ignition powder which can be manufactured
easily, which can be handled safely, and which is stored in a cup
of the initiator. Pins are inserted into and secured to holes of a
header in the initiator. Distal end surfaces of the pins are flush
with a distal end surface of the header; an insulative membrane is
disposed so as to cover the distal end surface of one of the pins.
When a high-voltage is applied between the pins, the membrane is
destroyed and plasma is created. Further, when a subsequent
low-voltage is applied between the pins, plasma is continuously
generated. The ignition powder initiates its reaction by heat of
the plasma.
Inventors: |
Furusawa, Takashi; (Tokyo,
JP) ; Amano, Junya; (Gotenba-shi, JP) ;
Sugiyama, Tadashi; (Susono-shi, JP) ; Yamashitaya,
Suguru; (Gotenba-shi, JP) ; Sanoki, Hiroyuki;
(Susono-shi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
TAKATA CORPORATION
|
Family ID: |
34190949 |
Appl. No.: |
10/845221 |
Filed: |
May 14, 2004 |
Current U.S.
Class: |
102/202.7 |
Current CPC
Class: |
F42B 3/127 20130101;
B60R 2021/26029 20130101 |
Class at
Publication: |
102/202.7 |
International
Class: |
F42B 003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2003 |
JP |
2003-289737 |
Claims
What is claimed is:
1. An initiator comprising: a casing containing ignition powder; an
electrode; and an insulating layer disposed in the casing, wherein
the insulating layer is in contact with the electrode on one
surface and with the ignition powder on another surface, and
wherein the initiator is configured so that reaction of the
ignition powder is initiated by plasma generated by conducting
electricity through the electrode.
2. The initiator of claim 1, wherein the insulating layer comprises
a synthetic resin or a glass fiber mold of about 10-300 .mu.m in
thickness.
3. The initiator of claim 1, wherein the insulating layer is in the
shape of a sheet and includes holes smaller than the grain diameter
of the ignition powder.
4. The initiator of claim 1, wherein the ignition powder comprises
MgAl alloy powder; KCl0.sub.3 powder; and silicon resin binder.
5. The initiator of claim 2, wherein the ignition powder comprises
MgAl alloy powder; KCl0.sub.3 powder; and silicon resin binder.
6. A method of activating an initiator including a casing
containing ignition powder; an electrode; and an insulating layer
disposed in the casing, wherein the insulating layer is in contact
with the electrode on one surface and with the ignition powder on
another surface, and wherein the initiator is configured so that
reaction of the ignition powder is initiated by plasma generated by
conducting electricity through the electrode, comprising the steps
of: applying a high voltage to the electrode to destroy the
insulating layer; and subsequently applying a low voltage to the
electrode.
7. The method of claim 6, wherein the step of applying the high
voltage includes applying a voltage of at least about 1 kV.
8. The method of claim 7, wherein the high voltage is applied for
between about 0.1 .mu.Sec and about 50 .mu.Sec.
9. The method of claim 6, wherein the step of applying a low
voltage includes applying a voltage of between about 20 V and about
100 V.
10. The method of claim 9, wherein the low voltage is applied for
between about 50 .mu.Sec and about 1 mSec.
11. A gas generator comprising: a gas generating agent; and an
initiator for initiating gas generation reaction of the gas
generating agent, wherein the initiator includes a casing
containing ignition powder, an electrode, and an insulating layer
disposed in the casing, wherein the insulating layer is in contact
with the electrode on one surface and with the ignition powder on
another surface, and wherein the initiator is configured so that
reaction of the ignition powder is initiated by plasma generated by
conducting electricity through the electrode.
12. The gas generator of claim 11, wherein the insulating layer
comprises a synthetic resin or a glass fiber mold of about 10-300
.mu.m in thickness.
13. The gas generator of claim 11, wherein the insulating layer is
in the shape of a sheet and includes holes smaller than the grain
diameter of the ignition powder.
14. The gas generator of claim 11, wherein the ignition powder
comprises MgAl alloy powder; KCl0.sub.3 powder; and silicon resin
binder.
15. The gas generator of claim 12, wherein the ignition powder
comprises MgAl alloy powder; KCl0.sub.3 powder; and a silicon resin
binder.
16. A seatbelt apparatus comprising: a seat belt, a tongue for
connecting to a buckle, and a pretensioner, wherein the
pretensioner includes a gas generator and the gas generator
includes a gas generating agent and an initiator for initiating gas
generation reaction of the gas generating agent, the initiator
including a casing containing ignition powder, an electrode; and an
insulating layer disposed in the casing, wherein the insulating
layer is in contact with the electrode on one surface and with the
ignition powder on another surface, and wherein the initiator is
configured so that reaction of the ignition powder is initiated by
plasma generated by conducting electricity through the
electrode.
17. An airbag apparatus comprising: an airbag and a gas generator;
wherein the gas generator includes a gas generating agent; and an
initiator for initiating gas generation reaction of the gas
generating agent; wherein the initiator includes a casing
containing ignition powder, an electrode; and an insulating layer
disposed in the casing, and wherein the insulating layer is in
contact with the electrode on one surface and with the ignition
powder on another surface, and wherein the initiator is configured
so that reaction of the ignition powder is initiated by plasma
generated by conducting electricity through the electrode.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an initiator suitable for
building in a gas generator for an airbag apparatus or a seat belt
pretensioner, ignition powder therefor, a method of activating the
initiator, and the gas generator having the initiator.
[0002] An airbag apparatus mounted to a high-speed movable body
such as an automotive vehicle is configured to inflate a bag-shaped
airbag quickly with a gas generator so-called "inflator." The gas
generator is provided with a gas generating agent and an initiator
for initiating a gas generating reaction of the gas generating
agent. In the related art, the initiator includes ignition powder
and a filament (bridge wire) as a resistive heat generating member
for initiating the reaction of the ignition powder. (See e.g., U.S.
Pat. No. 5,404,263, incorporated by reference herein in its
entirety).
[0003] Referring now to FIG. 4, an example of the initiator in the
related art will be described. The initiator 10 includes a
substantially cup-shaped casing 12 opening at the rear end (the
lower end in FIG. 4). In the casing 12, ignition powder 14 is
stored. The rear end of the casing 12 is closed by an insulating
material 16 formed of sintered glass or the like. Distal ends of a
pair of electrodes 18, 20 penetrate through the insulating material
16 and are exposed in the interior of the casing 12.
[0004] A filament 22 is bridged between the distal ends of the
electrodes 18, 20. Both ends of the filament 22 are welded to the
distal surfaces of the electrodes 18, 20, respectively. The
filament 22 is in contact with the ignition powder 14 in the casing
12.
[0005] The electrodes 18, 20 and the casing 12 are disposed apart
from each other so as not to be brought into electrical contact
with each other.
[0006] In the initiator 10 thus configured, one electrode 18 is
connected to a positive electrode of a battery 26 of an automotive
vehicle via a control circuit 24 having a voltage-increasing
circuit or the like, and the other electrode 20 is connected
(earthed) to a vehicle body of the automotive vehicle. The negative
electrode of the battery 26 is connected (earthed) to the vehicle
body of the automotive vehicle.
[0007] In case of emergency such as a vehicle collision, a switch
element in the control circuit 24 is turned ON, and a voltage is
applied from the battery 26 to the filament 22 via the respective
electrodes 18, 20. Accordingly, the filament 22 generates heat, and
hence the ignition powder 14 is ignited and initiates a reaction.
By the reaction of the ignition powder 14, high-pressure gas or
heat is generated, whereby the gas generating agent in the gas
generator causes a gas generating reaction.
[0008] The ignition powder employed here includes, for example, a
first ignition powder of mixture of lead styphnate and aluminum
powder so as to surround the filament 22 and a second ignition
powder of BKNO.sub.3 or black powder disposed so as to surround the
first ignition powder. The first ignition powder quickly initiates
an exothermal reaction, and the second ignition powder initiates a
reaction by heat of the first ignition powder to generate a
high-pressure hot gas and fine grains.
[0009] Referring now to FIG. 5, an example of the gas generator
having the initiator 10 will be described. A gas generator 30
includes a container having an outer shell having an upper housing
32 and a lower housing 34, and a cylindrical partition member 36
disposed in the outer shell. An end of the partition member 36
passes through an opening formed on the bottom surface of the lower
housing 34 and projects downward. The inner peripheral surface of
the opening and the outer periphery of the partition member 36 are
welded by laser beam welding or the like. An ignition agent
(booster propellant) 40 is stored in the partition member 36 and a
gas generating agent (main propellant) 42 is stored on the outer
peripheral side of the partition member 36.
[0010] The initiator 10 is disposed on one end of the partition
member 36. When an ignition agent 40 is ignited by the initiator
10, gas is injected from an opening 44 of the partition member 36,
and a large amount of gas is quickly generated, passes through a
filter 46 formed of mesh or the like, and is injected through an
opening 48 out of the gas generator 30, so that the air bag is
inflated. FIG. 5 simply shows an example of the gas generator, and
gas generators of the types other than that shown in the drawings
may be employed.
[0011] In the initiator in the related art shown in FIG. 4
described above, it is required to control the length of the
filament 22 or the conditions of welding precisely to keep the
electric resistance of the filament 22 constant; this precision
makes manufacturing difficult and correspondingly increases the
cost thereof. In addition, the ignition powder 14 needs to be
sensitive so as to be ignited even with a small exothermic energy
of the filament. As a result, the sensitive ignition powder 14
needs to be treated with special care.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide: (a) an
initiator in which the resistance heating element such as the
filament is not used, (b) an ignition powder which can be easily
and safely manufactured, treated, and used, and (c) a method of
initiating the same. It is also an object of the present invention
to provide a gas generator having such initiator.
[0013] According to an embodiment of the present invention, an
initiator is provided. The initiator includes a casing, an ignition
powder disposed in the casing, an electrode, and an insulating
layer disposed in the casing so as to be in contact with the
electrode on one surface and with the ignition powder on the other
surface, wherein a reaction of the ignition powder is initiated by
generating plasma by conducting electricity through the
electrode.
[0014] The insulating layer is preferably formed of synthetic resin
or a glass fiber mold of 10-300 .mu.m in thickness. Preferably, the
insulating layer is formed into a sheet-shape having holes smaller
than the grain diameter of the ignition powder.
[0015] The ignition powder preferably includes MgAl alloy powder,
KCl0.sub.3 powder, and silicon resin binder.
[0016] The method of activating the initiator according to an
embodiment of the present invention includes the steps of applying
a high-voltage to the electrode of the initiator of the present
invention to destruct the insulation, and subsequently, applying a
low-voltage thereon.
[0017] Preferably, the high-voltage is at least 1 kV, and is
applied for 0.1-50 .mu.Sec, and the low-voltage is 20-100 V and is
applied for 50 .mu.Sec to 1 mSec.
[0018] The gas generator according to an embodiment of the present
invention includes a gas generating agent, and the initiator
according to the present invention.
[0019] In the initiator and the gas generator according to an
embodiment of the present invention, when the voltage is applied to
the electrode, plasma of high-temperature is generated in the
casing. The ignition powder initiates reaction by heat of the
plasma, and the gas generating agent in the gas generator is
ignited and activated by high-pressure gas or heat generated by the
reaction. This initiator is easy to manufacture since the
insulating layer is provided instead of filament, and hence
cost-effective manufacture with high process yield and low
dispersions in quality.
[0020] As the energy of plasma is larger than heat-generating
energy of the filament, ignition powder, which can be handled
safely in comparison with the sensitive ignition powder used in the
case where the filament is employed, can be used.
[0021] By disposing the synthetic resin or glass fiber mold of
10-300 .mu.m in thickness so as to come into contact with the end
surface of the electrode, the insulating layer can be formed easily
at low costs.
[0022] When the insulating layer is a sheet-shaped layer having
fine holes, it is susceptible to discharge. By making the diameter
of the holes smaller than the diameter of the grains of the
ignition powder, the ignition powder is prevented from entering the
holes.
[0023] The ignition powder including MgAl alloy powder, KCl0.sub.3
powder, and silicon resin binder can easily be treated and has a
large calorific power.
[0024] By applying a high-voltage when activating the initiator to
at least 1 kV (e.g., for example, to 1-5 kV), occurrence of
insulation destruction is ensured and plasma is generated. The time
period to apply the high-voltage may be as short as 0.1-50 .mu.Sec
(e.g., for example, on the order of 1 .mu.Sec) and the power
consumption is small. When the high-voltage is applied once, a
plasma state may be maintained by only applying low-voltage such as
20-100 V (e.g., for example, on the order of 60 V). A low-voltage
of 50 .mu.Sec-1 mSec (e.g., for example, on the order of 100
.mu.Sec) will be sufficient to maintain the plasma state.
[0025] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only, and are not restrictive of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] These and other features, aspects, and advantages of the
present invention will become apparent from the following
description, appended claims, and the accompanying exemplary
embodiments shown in the drawings, which are briefly described
below.
[0027] FIG. 1 is a cross-sectional view of an initiator according
to an embodiment of the present invention.
[0028] FIG. 2 is a not-to-scale graph showing a pattern of voltage
application of the initiator versus time.
[0029] FIG. 3 is a cross-sectional view of an initiator according
to another embodiment of the present invention.
[0030] FIG. 4 is a cross-sectional view of an initiator in the
related art.
[0031] FIG. 5 is a cross-sectional view of a gas generator
containing the initiator shown in FIG. 4.
[0032] FIG. 6 is a schematic view of an airbag apparatus according
to an embodiment of the present invention.
[0033] FIG. 7 is a schematic view of a seat belt apparatus
including a seat belt pretensioner according to an embodiment of
the present invention.
DETAILED DESCRIPTION
[0034] Referring now to the drawings, embodiments of the present
invention will now be described. FIG. 1 is a cross-sectional view
of an initiator according to an embodiment of the present
invention, and FIG. 2 is a not-to-scale waveform graph showing a
voltage for activating the initiator.
[0035] In an initiator 50 shown in FIG. 1, a casing is formed by a
cup 52, and a header 54 inserted into the entrance of the cup 52,
and an ignition powder 58 is filled in the casing. In this
embodiment, the cup 52 is shaped like a circular container formed
of SUS304 steel or the like. The header 54 is substantially a
disk-shaped or a cylindrical member formed of ceramic, and the cup
52 is fitted on the outer periphery thereof. The cup 52 is secured
to the header 54 by being caulked around the edge thereof.
[0036] Cross-shaped grooves 52a are formed on the outer surface of
the distal end surface of the cup 52, so that the cup 52 cracks
along the grooves 52a when the ignition powder 58 is ignited and
reacted. A ring-shaped gasket 56 is interposed between the cup 52
and the header 54.
[0037] Two bores penetrating through the thickness of the header 54
are formed at the center thereof. Electrode pins 62, 64 are
inserted into the bores, respectively, and these pins 62, 64 are
fixed to the header 54 by fixing material such as glass. The distal
end surfaces of the pins 62, 64 are flush with the distal end
surface of the header 54. A membrane 60 as an insulating layer is
disposed so as to be aligned with the inner end surface of the cup
of the header 54 and cover the distal end of the electrode pin
62.
[0038] The membrane 60 preferably is shaped like a sheet of 10-300
.mu.m in thickness, and has a number of fine holes. The membrane 60
is preferably a synthetic resin sheet, more specifically, a
fluorinated resin sheet having high heat resistance, or a glass
fiber sheet mold.
[0039] The membrane 60 may be attached on the header 54 by an
adhesive agent such as, for example, an acrylic, or
silicon-contained material. The thickness of the adhesive agent is
preferably on the order of 15-100 .mu.m.
[0040] The ignition powder 58 may be only of ignition powder, or
may be a mixture of ignition powder and particles of oxidizing
agent. The ignition powder is not specifically limited, but may be
a single metal such as Mg, Zr, Ti, W, B, Si, C, Be, Li, Al, V,
CaC.sub.2, Ca, Ce, La, and an alloy or a compound thereof. The
oxidizing agent is not specifically limited, but may be KCl0.sub.4,
KCl0.sub.3, Kl0.sub.4, NH.sub.4Cl0.sub.4, NH.sub.4NO.sub.3
KNO.sub.3, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Sr(NO.sub.3).sub.2,
CuO, or NiO. The binder may include, for example, silicon-contained
resin by about 0.5-3 percent by weight. By adding the
silicon-contained binder, static resistance of about 25 kV may be
provided.
[0041] The ignition powder preferably includes MgAl alloy powder,
KCl0.sub.3 powder, and silicon resin binder. The MgAl alloy can
hardly be ignited in comparison with Zr, but it can easily be
handled correspondingly. MgAl alloy exhibits higher heat value than
Zr when ignited.
[0042] According to the initiator 50 thus configured, a
high-voltage of about 3 kV is applied between the pins 62, 64 for
about 1 .mu.Sec to generate plasma, and subsequently, a low-voltage
of about 60 V is applied for about 100 .mu.Sec to maintain
generation of plasma, as shown in FIG. 2. The ignition powder 58
initiates its reaction by heat of the plasma, and gas of
high-pressure and high-temperature including fine grains is
generated. When the ignition powder 58 includes grains of oxidizing
agent, since the metallic particles rapidly start oxidative
reaction by the oxidizing action of the oxidizing agent and
generate heat, the reaction is promoted.
[0043] U.S. patent application Ser. No. 10/681,189 (incorporated
herein by reference) discloses using a plasma to initiate a
reaction.
[0044] According to an embodiment of the present invention, the
filament (wire bridge) is not used, and hence the process steps of
manufacture are significantly reduced.
[0045] During operation of the initiator 50, insulation of
insulating layer (membrane 60) is destroyed by a pulsed
high-voltage initially applied thereto, and the value of resistance
is lowered by such destruction of insulation. Therefore, even with
a low-voltage of about 60 V, electricity flows continuously.
Therefore, it is no longer necessary to apply a high-voltage for a
long time, and energy needed for ignition may be lower to about 1
mJ or below.
[0046] FIG. 3 is a cross-sectional view of the initiator 70
according to another embodiment. In this embodiment, an ignition
powder 78 is filled between a cup 72 and a header 74.
[0047] The outer surface of the cup 72 is covered by a resin cover
75 formed of nylon, polypropylene, or the like. The rear side of
the cup 72 and the rear end surface of the header 74 are covered
with a resin mold 86 formed of nylon, polybutylenetelephtalate, or
the like. The pins 82, 84 penetrate the resin mold 86 and project
outward from the header 74.
[0048] In this embodiment, the header 74 is an annular-shaped
member formed of SUS.sub.30.sub.4 or the like, and the pins 82, 84
are inserted into the header 74 apart from each other so as not to
come into contact with the header 74, and are fixed to the header
74 with an insulative fixing material 76 such as glass, hermetic
seal, or the like. The distal end surfaces of the pins 82, 84 are
flush with the distal end surface of the header 74. A membrane 80
is disposed so as to cover the distal end surface of the pin 82.
The configuration of the membrane 80 is the same as the membrane
60.
[0049] In the initiator 70 thus configured, when a voltage is
applied between the pins 82, 84 in the same pattern as that shown
in FIG. 2, plasma is generated, and the ignition powder 78
initiates its reaction by heat of plasma.
[0050] The embodiments described above are examples of the present
invention, and configurations other than those described above may
also be employed. For example, the insulating layer may be provided
so as to cover both of the pins 62, 64 or 82, 84.
[0051] When the header is formed of conductive material such as
metal, it is also possible to provide only one pin and earth the
header.
[0052] The initiator of the present invention may be applied to
various gas generators. The gas generators may be built in various
airbag apparatuses for a driver's seat, a front passenger's seat, a
rear seat, side protection, head protection, pedestrian protection,
and so on, or in a seat belt tensioner, or even in various
detonators.
[0053] For example, as shown in FIG. 6, the initiator may be
employed in a gas generator 30 positioned in an airbag apparatus
including an inflatable airbag 90. Further by way of example, as
shown in FIG. 7, the initiator may be employed in a gas generator
30 that is positioned in a seat belt retractor 120 for driving a
spool 125 for pretensioning a seat belt 102. U.S. Pat. No.
6,363,722 (incorporated herein by reference) discloses an exemplary
retractor. The seat belt retractor 120 may be part of a seat belt
apparatus 100 which may additionally include a seat belt 102, a
shoulder support 104, a tongue 106, and a buckle 108. The present
invention also includes providing the improved initiator and gas
generator in other known seat belt pretensioners.
[0054] The priority application, Japanese Patent Application No.
2003-289737, filed Aug. 8, 2003 including the specification,
drawings, claims and abstract, is incorporated herein by reference
in its entirety.
[0055] Given the disclosure of the present invention, one versed in
the art would appreciate that there may be other embodiments and
modifications within the scope and spirit of the invention.
Accordingly, all modifications attainable by one versed in the art
from the present disclosure within the scope and spirit of the
present invention are to be included as further embodiments of the
present invention. The scope of the present invention is to be
defined as set forth in the following claims.
* * * * *