U.S. patent application number 12/159877 was filed with the patent office on 2009-10-29 for ignition device, gas generator for air bag and gas generator for seat belt pretensioner.
This patent application is currently assigned to NIPPONKAYAKU KABUSHIKIKAISHA. Invention is credited to Dairi Kubo, Shigeru Maeda, Hirotaka Mukonoki.
Application Number | 20090266265 12/159877 |
Document ID | / |
Family ID | 38228336 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266265 |
Kind Code |
A1 |
Maeda; Shigeru ; et
al. |
October 29, 2009 |
Ignition Device, Gas Generator for Air Bag and Gas Generator for
Seat Belt Pretensioner
Abstract
The invention provides an ignition device having a high
shielding-performance from electro-magnetic wave noise and the
like, while being compact in size and enabling electric current
securely to flow through electric circuits built in the ignition
device. The ignition device includes a metal cup and a metal header
for holding a plurality of electrode pins respectively insulated
and closing the opening of the cup to integrate the header in the
cup, and further includes, in the cup, ignition charge, an ASIC, a
capacitor, and a heating element. The ASIC is electrically
connected to the electrode pins, the capacitor and the heating
element, respectively, and the heating element abuts against the
ignition charge. The header is provided on its outer periphery with
a metal flange for fixing the header to an installation body of the
ignition device.
Inventors: |
Maeda; Shigeru; (Himeji-shi,
JP) ; Mukonoki; Hirotaka; (Himeji-shi, JP) ;
Kubo; Dairi; (Himeji-shi, JP) |
Correspondence
Address: |
PETERS VERNY , L.L.P.
425 SHERMAN AVENUE, SUITE 230
PALO ALTO
CA
94306
US
|
Assignee: |
NIPPONKAYAKU
KABUSHIKIKAISHA
Tokyo
JP
|
Family ID: |
38228336 |
Appl. No.: |
12/159877 |
Filed: |
January 5, 2007 |
PCT Filed: |
January 5, 2007 |
PCT NO: |
PCT/JP2007/050039 |
371 Date: |
July 2, 2008 |
Current U.S.
Class: |
102/530 ;
102/202.7; 102/202.9 |
Current CPC
Class: |
B60R 2021/26029
20130101; F42B 3/122 20130101 |
Class at
Publication: |
102/530 ;
102/202.9; 102/202.7 |
International
Class: |
C06D 5/00 20060101
C06D005/00; F42B 3/12 20060101 F42B003/12; F42B 3/13 20060101
F42B003/13 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 6, 2006 |
JP |
2006/001548 |
Claims
1. An ignition device including a metal cup and a metal header for
holding a plurality of electrode pins respectively insulated and
closing the opening of said cup to integrate the header in said
cup, and further including, in said cup, ignition charge, an ASIC,
a capacitor, and a heating element, said ASIC being electrically
connected to said electrode pins, said capacitor and said heating
element, respectively, and said heating element abutting against
said ignition charge, characterized in that said header comprises
on its outer periphery a metal flange for fixing the header to an
installation body of the ignition device.
2. The ignition device as claimed in claim 1, characterized
comprising an ASIC component including said ASIC and said capacitor
both mounted on a substrate molded with a resin to form a resin
mold, said resin mold having at its top the heating element
connected to said ASIC and at the bottom communication electrodes
for connecting said ASIC to said electrode pins.
3. The ignition device as claimed in claim 2, characterized in that
said electrode pins and said communication electrodes are jointed
to each other under pressure.
4. The ignition device in claim 1, characterized in that said
heating element and said ignition charge are in contact with each
other under pressure.
5. The ignition device in claim 1, characterized in that the upper
surface of said heating element is coated with an ignition charge
composition.
6. The ignition device in claim 1, characterized in that said
heating element comprises a semiconductor bridge chip.
7. The ignition device in claim 6, characterized in that said
semiconductor bridge chip includes a bridge formed by laminating a
metal and an insulator.
8. A gas generator for an air bag, characterized in that said
flange provided on the ignition device as claimed in claim 1 is
electrically connected and fixed to a metal section of the
installation body of the ignition device provided in said gas
generator by means of caulking or welding.
9. A gas generator for a seat belt pretensioner, characterized in
that said flange provided on the ignition device as claimed in
claim 1 is electrically connected and fixed to a metal section of
the installation body of the ignition device provided in said gas
generator by means of caulking or welding.
10. The ignition device in claim 2, characterized in that said
heating element and said ignition charge are in contact with each
other under pressure.
11. The ignition device in claim 2, characterized in that the upper
surface of said heating element is coated with an ignition charge
composition.
12. The ignition device in claim 2, characterized in that said
heating element comprises a semiconductor bridge chip.
13. A gas generator for an air bag, characterized in that said
flange provided on the ignition device as claimed in claim 2 is
electrically connected and fixed to a metal section of the
installation body of the ignition device provided in said gas
generator by means of caulking or welding.
14. A gas generator for a pretensioner, characterized in that said
flange provided on the ignition device as claimed in claim 2 is
electrically connected and fixed to a metal section of the
installation body of the ignition device provided in said gas
generator by means of caulking or welding.
15. The ignition device in claim 3, characterized in that said
heating element and said ignition charge are in contact with each
other under pressure.
16. The ignition device in claim 3, characterized in that said
heating element comprises a semiconductor bridge chip.
17. A gas generator for an air bag characterized in that said
flange provided on the ignition device as claimed in claim 3 is
electrically connected and fixed to a metal section of the
installation body of the ignition device provided in said gas
generator by means of caulking or welding.
18. A gas generator for a pretensioner, characterized in that said
flange provided on the ignition device as claimed in claim 3 is
electrically connected and fixed to a metal section of the
installation body of the ignition device provided in said gas
generator by means of caulking or welding.
19. The ignition device in claim 4, characterized in that the upper
surface of said heating element is coated with an ignition charge
composition.
20. The ignition device in claim 2, characterized in that said
heating element comprises a semiconductor bridge chip.
Description
TECHNICAL FIELD
[0001] This invention relates to an ignition device to be installed
in a gas generator or the like used in a safety device for a car
such as an air bag and the like, and more particularly to a gas
generator with such an ignition device installed therein for an air
bag and a gas generator with the ignition device for a seat belt
pretensioner.
BACKGROUND ART
[0002] A variety of electric ignition devices have been developed
as ignition devices for gas generators for inflating air bags
equipped in cars. Such an ignition device usually has metal pins
for electrically connecting to the external, and a heating element
at the other ends of the metal pins for igniting an explosive.
[0003] As examples of such a heating element, heating elements
incorporated in a printed sub-circuit have been known as disclosed
in a patent document 1 and a patent document 2 corresponding to the
patent document 1.
[0004] On the other hand, moreover, it has been envisioned that an
air bag system is linked to a local area network (LAN) so that
ignition of an ignition device is controlled by communication.
[0005] In this case, it is necessary to locate electric circuits in
the ignition device for the communication and ignition as described
in a patent document 3.
[0006] With the ignition device constructed as described above,
therefore, it is required to provide means for causing electric
current to flow through the electric circuits built in the ignition
device.
[0007] In a patent document 4, for example, disclosed is a
structure of an electric circuit substrate fixed to electrode pins
of a header by means of soldering or the like.
[0008] Patent document 1: Specification of French Patent
Application Opened No. 2,704,944
[0009] Patent document 2: Specification of U.S. Pat. No.
5,544,585
[0010] Patent document 3: Official Gazette of Japanese Patent No.
3,294,582
[0011] Patent document 4: Specification of European Patent
Application Opened No. 1,256,775
DISCLOSURE OF THE INVENTION
Task to be Solved by the Invention
[0012] In order to prevent any erroneous ignition, an ignition
device incorporating electric circuits therein for communication
and ignition need only be able to shield the internal electric
circuits from external electro-magnetic noise and electro-magnetic
induction.
[0013] In the case of the ignition device of the prior art
incorporating therein electric circuits, after the circuits have
been previously constructed on a substrate and connected to
electrode pins of a header, the circuits and the substrate must be
molded with a resin as described in the patent document 4.
[0014] However, particularly the resin molding under a condition
already connected to a header is seriously lower in productivity as
compared with the molding of parts such as a usual IC fixed to a
lead frame.
[0015] In the case that connection between the electrode pins and
the electric circuits is firmly fixed by soldering, moreover, there
would be a risk of solder cracks due to residual stresses.
[0016] Furthermore, in order to obtain a strong connection between
the electrode pins and the electric circuits, connection lengths
are required to some extent. If such a construction of longer
connection lengths is employed in an ignition device originally
having a small volume, the ignition device becomes unavoidably
bigger causing a problem that a gas generator having the ignition
device built therein would also become bigger.
[0017] The invention has been developed in view of the
circumstances described above and has an object to provide an
ignition device having the construction incorporating electric
circuits therein, which is able to effectively shield the internal
electric circuits from the electro-magnetic noise and the like.
[0018] Moreover, the invention has another object to provide an
ignition device ensuring passage of electric current into the
electric circuits built in the ignition device without lowering the
productivity in manufacturing the resin mold and without increasing
the size of the ignition device.
[0019] Furthermore, the invention has a further object to provide a
gas generator for an air bag including the ignition device
described above installed therein which is compact and has a high
shielding performance from electro-magnetic noise and the like
described above.
Solution for the Task
[0020] By the way, first, the inventors of the present application
have investigated means for cutting off the electro-magnetic noise
and the like in order to prevent electric circuits incorporated in
the ignition device from malfunctioning.
[0021] As a result, they have had a knowledge that the interior of
an ignition device is effectively shielded and the ignition device
itself can be electrically grounded through a gas generator by
covering the environment of internal electric circuits with a metal
cup which is integrated with a metal header provided on its
periphery with a flange which is connected to a housing of an
installation body (for example, an inflator) of the ignition
device.
[0022] Moreover, the inventors have had another knowledge that by
connecting the flange to the housing by caulking, the flange can be
rigidly fixed to the installation body, and the fixation can
sufficiently withstand the pressure upon operation of the gas
generator.
[0023] Further, the inventors have earnestly investigated a
connecting method between electrode pins and electric circuits and
have gotten the following recognitions.
a) By molding only the circuits of an ASIC and the like except for
the electrode pins of the header, the manufacture of the resin mold
can be performed with a high productivity. b) The connection
between the electrode pins and the electric circuits in the resin
mold is effected by contact therebetween through communication
electrodes provided in the resin mold. With this arrangement, the
connection between the electrode pins and the electric circuits
becomes easy, and in addition the volume of the ignition device is
kept to the minimum.
[0024] However, it has become apparent that in the event that the
electrode pins of the header are pushed to the communication
electrodes provided in a resin mold by a force to an extent in
slight contact with each other, the connection between the
communication electrodes and the electrode pins would be often
broken down upon the ignition device being shocked.
[0025] With that, the inventors have continued the investigation
and found the following facts.
c) In the case that the cup and the header of the ignition device
are jointed together to form an integrated unit by welding, if the
welding is performed in a state that the header has been forced
into the cup of the ignition device at a pressure higher than a
certain constant pressure, the communication electrodes and the
electrode pins are jointed to each other under pressure owing to
elastic reaction force of the cup and the resin mold enclosing the
electric circuits. With such a joint formed under pressure, even if
the ignition device is subjected to a considerable impact, the
connection between the communication electrodes and the electrode
pins is never disconnected. d) With such a joint under pressure,
further, since the elastic reaction force of the resin mold and the
cup also acts between ignition charge and the heating element, the
heating element provided at the other end of the resin mold and the
ignition charge are jointed under pressure, thereby achieving a
reliable ignition and shortening of the ignition time.
[0026] The invention is based on the recognition and knowledge
described above.
[0027] Therefore, the aspects of the invention are as follows.
[0028] (1) The ignition device including a metal cup and a metal
header for holding a plurality of electrode pins respectively
insulated and closing the opening of said cup to integrate the
header in said cup, and further including, in said cup, ignition
charge, an ASIC, a capacitor, and a heating element, said ASIC
being electrically connected to said electrode pins, said capacitor
and said heating element, respectively, and said heating element
abutting against said ignition charge, characterized in that said
header comprises on its outer periphery a metal flange for fixing
the header to an installation body of the ignition device.
[0029] (2) The ignition device as in the above (1), characterized
comprising an ASIC component including said ASIC and said capacitor
both mounted on a substrate molded with a resin to form a resin
mold, said resin mold having at its top the heating element
connected to said ASIC and at the bottom communication electrodes
for connecting said ASIC to said electrode pins.
[0030] (3) The ignition device as in the above (2), characterized
in that said electrode pins and said communication electrodes are
jointed to each other under pressure.
[0031] (4) The ignition device in any one of the above (1) to (3),
characterized in that said heating element and said ignition charge
are in contact with each other under pressure.
[0032] (5) The ignition device in any one of the above (1) to (4),
characterized in that the upper surface of said heating element is
coated with an ignition charge composition.
[0033] (6) The ignition device in any one of the above (1) to (5),
characterized in that said heating element comprises a
semiconductor bridge chip.
[0034] (7) The ignition device in the above (6), characterized in
that said semiconductor bridge chip includes a bridge formed by
laminating a metal and an insulator.
[0035] (8) The gas generator for an air bag, characterized in that
said flange provided on the ignition device in any one of the above
(1) to (7) is electrically connected and fixed to a metal section
of the installation body of the ignition device provided in said
gas generator by means of caulking or welding.
[0036] (9) The gas generator for a seat belt pretensioner,
characterized in that said flange provided on the ignition device
in any one of above (1) to (7) is electrically connected and fixed
to a metal section of the installation body of the ignition device
provided in said gas generator by means of caulking or welding.
EFFECT OF THE INVENTION
[0037] The effects of the invention can be enumerated as
follows.
[0038] (1) The electric circuits in the ignition device can be
effectively shielded from external electro-magnetic noise and
electro-magnetic induction so that any malfunctioning of the
internal electric circuits and hence erroneous ignition can be
prevented.
[0039] (2) The ignition device can be firmly fixed to an
installation body and can sufficiently withstand the pressure when
the gas generator is operated.
[0040] (3) As a resin is not used for fixed portions, even if the
installation body is exposed to high temperatures, there will be
little, if any, softening by heat so that no burst occurs and
degree of safety becomes higher.
[0041] (4) Since the molding with a resin is limited to the
electric circuits such as the ASIC and the like, the productivity
of resin mold is improved.
[0042] (5) One step in the production process of the ignition
device can be omitted because external molding of the ignition
device is not required, whereby the ignition device can be
inexpensively manufactured.
[0043] Further, the following effects can be obtained by the
preferable aspects according to the invention.
[0044] (6) The joint of the electric circuits and the electrode
pins is carried out by jointing the communication electrodes
provided at the bottom of the resin mold and the electrode pins
under pressure so that the ignition device itself becomes compact
and its assembling is simplified.
[0045] (7) Since the communication electrodes and the electrode
pins are jointed under pressure, even if the ignition device is
subjected to a considerable impact, the connection between the
communication electrodes and the electrode pins is never
disconnected.
[0046] (8) Owing to the jointing under pressure described above,
the heating element and the ignition charge are jointed under
pressure, thereby achieving a reliable ignition and shortening of
the ignition time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a sectional view of a preferable ignition device
according to the invention;
[0048] FIG. 2 is an explanatory view of an ignition charge of a
two-layer structure;
[0049] FIG. 3 is an explanatory view of the case of a heating
element the upper surface of which is coated with an ignition
charge composition;
[0050] FIG. 4 is a view illustrating how to mount the ignition
device onto an inflator;
[0051] FIG. 5 is a conceptual view of a gas generator for an air
bag;
[0052] FIG. 6 is a conceptual view of a gas generator for a seat
belt pretensioner; and
[0053] FIG. 7 is an explanatory view of a central control unit.
DESCRIPTION OF THE REFERENCE NUMERALS
[0054] 1 Cup [0055] 2 Ignition charge [0056] 2' Booster charge
[0057] 2'' Ignition charge composition [0058] 3 ASIC component
[0059] 4 ASIC [0060] 5 Capacitor [0061] 6 Heating element [0062] 7
Communication electrode [0063] 8 Header [0064] 9 Electrode pin
[0065] 10 Glass to metal sealing [0066] 11 Flange [0067] 12
Ignition electrode [0068] 13 Housing [0069] 21 Gas generator for
air bag [0070] 22 Ignition device [0071] 23 Enhancer [0072] 24 Gas
generant [0073] 25 Filter [0074] 26 Outer vessel [0075] 27 Hole
[0076] 31 Gas generator for seat belt pretensioner (micro
gas-generator) [0077] 32 Ignition device [0078] 33 Gas generant
[0079] 34 Base (holder) [0080] 35 Cup [0081] 110 Central control
unit [0082] 111a to 111d Air bag modules [0083] 114, 115 Electrode
pins
BEST MODE FOR CARRYING OUT THE INVENTION
[0084] The invention will then be specifically explained.
[0085] FIG. 1 illustrates in section the ignition device according
to the invention. In the drawing, reference numeral 1 shows a metal
cup, and reference numeral 2 denotes ignition charge. Reference
numeral 3 denotes an ASIC component which is formed by molding with
a resin a substrate having elements required for electric circuits
such as an ASIC, a capacitor and the like mounted thereon.
Reference numeral 4 denotes the ASIC, and numeral 5 shows the
capacitor. In this place, the ASIC (application specific integrated
circuit) 4 is an integrated circuit for a particular use, which
functions as intercommunication switching means in the present
invention for igniting the ignition device based on coded
information obtained by intercommunicating with the external.
Moreover, the capacitor 5 serves as electric energy-accumulating
means.
[0086] Further, reference numeral 6 denotes a heating element
arranged on the top of the ASIC component 3, and reference numeral
7 denotes communication electrodes arranged at the bottom of the
ASIC component 3. As the substrate for the ASIC component 3,
moreover, a lead frame may be used.
[0087] Reference numeral 8 shows a metal header to which electrode
pins 9 are fixed by means of glass to metal sealing 10 for
electrically connecting the electric circuits to the external. The
electrode pins are fixed by the glass to metal sealing in this
manner to ensure electric insulation while maintaining high air
tightness. Furthermore, the metal cup and the metal portion of the
header are welded to each other to seal the interior of the cup in
high air tightness. A metal flange 11 is provided on the outer
periphery of the header 8. Preferable examples of metals for the
flange include iron families, for example, stainless steel,
nickel-iron, nickel-plated SPC and the like.
[0088] And now, first, the ignition charge 2 is arranged at the
innermost portion in the cup 1 according to the invention. As shown
in FIG. 1, the ignition charge 2 may be of one kind of explosive
arranged in a single layer, but as shown in FIG. 2, it is more
beneficial to arrange booster charge 2' of stronger in inflammation
on the outside of the ignition charge 2 so as to form a two-layer
structure.
[0089] As the booster charge 2', here, it is preferable to contain
zirconium in its composition. Other than this, those containing
titanium hydride, boron or lead trinitroresorcinate are also
advantageously suitable.
[0090] Moreover, as usable ignition charges 2 other than those
described above, there are, for example, those disclosed in the
specification of Japanese Patent Application No. 2001-140,468 and
the official gazette of Japanese Patent Application Opened No.
2002-362,992. Ignition charges are not particularly limited for
this purpose.
[0091] The heating element 6 is arranged so as to be in contact
with the ignition charge 2.
[0092] On this occasion, the upper surface of the heating element 6
is preferably coated with an ignition charge composition 2'' as
shown in FIG. 3 which is beneficial for more stabilizing the
contact between the heating element and the ignition charge.
[0093] A so-called SCB chip as such a heating element 6 is
favorably suitable, which makes it possible to ignite the powder
with low energy. Moreover, it is more advantageous to make such an
SCB chip into the form of a bridge structure by laminating metals
and insulators because large sparks occur with low energy. In this
place, the "SCB" means a semiconductor bridge which is a heating
element produced by the use of the manufacturing process for usual
semiconductor integrated circuits.
[0094] As the bridge structure described above, it is also possible
to apply a structure formed by alternately laminating one or more
compositions selected from a group consisting of titanium, a nickel
chrome alloy, nickel, aluminum, magnesium and zirconium, and one or
more compositions selected from a group consisting of calcium,
manganese, silicon dioxide and silicone.
[0095] A structure formed by alternately laminating titanium and
SiO.sub.2 (or boron) on a silicone substrate is advantageously
suitable as a preferable bridge structure. Thicknesses of the
respective layers are preferably of the order of 0.05 to 10 .mu.m,
and more preferably of 0.1 to 4 .mu.m.
[0096] Furthermore, an electrical connection of the heating element
6 is effected through ignition electrodes 12 provided on the upper
surface of the ASIC component 3.
[0097] Built in the ASIC component 3 according to the invention are
the ASIC 4 as means for the intercommunication and triggering
particular electric pulse strings, and the capacitor 5 as means for
accumulating the electric energy. Moreover, the ASIC component 3 is
integrated through the two electrode pins 9 into an air bag system
later described which is linked to a local area network (LAN) and
communicating with a central control unit.
[0098] Furthermore, it is necessary for the ASIC component 3 to be
smoothly inserted into the cup 1 by forming the ASIC component 3 as
a cylindrical shape of a size matching with the inner diameter of
the cylindrical cup 1. For this purpose, the outer diameter of the
ASIC component 3 is preferably of the order of 85% to 99% of the
inner diameter of the cup.
[0099] The diameter of the communication electrodes 7 arranged at
the bottom of the ASIC component 3 is preferably somewhat smaller
than the diameter of the electrode pins 9 so that even if contact
positions of the communication electrodes 7 and the electrode pins
9 are somewhat shifted to each other owing to assembling errors or
the like, these electrodes 7 and the pins 9 can be always
maintained in jointed or connected states, thereby enabling the
electrical connections between them to be maintained.
[0100] It is moreover beneficial that the contact portions of the
communication electrodes 7 and the electrode pins 9 are flat to
ensure stable contact between them when they are strongly pushed to
each other.
[0101] According to the invention, after the cup 1 is packed with
the ignition charge 2 at the innermost portion of the cup, the ASIC
component 3 is inserted into the cup such that the heating element
6 arranged at the top of the ASIC component 3 abuts against the
ignition charge 2. Then, after the header 8 is inserted into the
cup 1 such that the electrode pins 9 provided in the header 8 abut
against the communication electrodes 7 arranged at the bottom of
the ASIC component 3, the cup 1 and the header 8 are integrated
with each other by welding.
[0102] In this manner, the interior of the ignition device
including the ASIC is covered with the electrically conductive
metal body and fixed in a gas generator through the flange, thereby
enabling effective shielding of the device from electro-magnetic
noise and the like.
[0103] Moreover, the cup 1 and the header 8 are integrated with
each other by means of welding so that the air tightness in the cup
can be securely held.
[0104] Furthermore, as the whole ignition device is covered with
the metal body, even if the gas generator is exposed to high
temperatures upon encountering a fire or the like during its
transportation, safety is ensured without burst.
[0105] In contrast therewith, with the ignition devices of the
prior art, since the insulation is kept by a plastic material, upon
encountering a fire the plastic portions are unavoidably softened
so that when a gas generant acts, there is a possibility that parts
will be blown away in all directions by the inner pressure. With
such prior art devices, in order to preclude this, particular
measures have been needed.
[0106] In welding the cup 1 and the header 8 to be integrated, it
is preferable to carry out the welding under the state that the
header 8 has been press-fitted in the cup 1.
[0107] Namely, when the welding is effected in the state that the
enheader 8 has been forced into the cup 1 at a pressure higher than
a certain constant pressure, the communication electrodes 7 and the
electrode pins 9 are jointed together under pressure by the elastic
reaction force caused by the ASIC component 3 molded with the resin
and the cup 1. As a result, even when the ignition device is
subjected to an impact with a substantial force, any disconnection
between the communication electrodes 7 and the electrode pins 9 can
be effectively prevented.
[0108] In the case that the communication electrodes 7 and the
electrode pins 9 are jointed together under the pressure as
described above, the elastic reaction force of the ASIC component 3
and the cup 1 acts also in the opposite direction so that the
heating element 6 provided on the opposite side of the ASIC
component 3 is jointed to the ignition charge 2 under pressure,
that is, to increase the density of the ignition charge 2, thereby
achieving reliable ignition and effective shortening of the
ignition time.
[0109] In comparison with the structure whose connection portions
are fixed by soldering or welding, moreover, the jointing under
pressure as described above has advantages that the operation for
jointing is simple and easy, and a volume for jointing is hardly
required.
[0110] In this place, the force for press-fitting the header 8 into
the cup 1 is preferably of the order of 1 to 250 MPa. If the force
is less than 1 MPa, a pushing force sufficient to joint the
communication electrodes 7 and the electrode pins 9 is not
obtained, while if the force is more than 250 MPa, the stress
applied to the ASIC component becomes too large so that there is a
risk of breakage of the ASIC component. The more preferable force
for press-fitting is 2 to 130 MPa.
[0111] As shown in FIG. 3, according to the invention the upper
surface of the heating element 6 may be previously coated with the
ignition charge composition 2''. In other words, the ignition
charge in a slurry state is dispensed or applied to the upper
surface of the heating element 6 and then dried. As compared with
the case that the ignition charge in a powder state is merely
packed, the dried ignition charge composition 2'' is more stable in
the contact with the heating element to effectively contribute to
the reliable ignition and shortening of the ignition time.
[0112] In the case that the ignition device according to the
invention is arranged in an installation body, for example, in an
inflator, it is desirable to joint the flange 11 directly to a
housing 13 of the inflator by the use of caulking as shown in FIG.
4. In addition, welding is also advantageously used for the
jointing other than the caulking described above.
[0113] The reasons for employing the jointing method described
above lie in the fact that the interior of the ignition device is
effectively shielded and the ignition device itself can be
electrically grounded through the inflator.
[0114] With the ignition device according to the invention, the
ASIC component 3 can be arranged in the header 8 and the cup 1
which are held in an airtight state, and further the electrical
connection between the communication electrodes 7 and the electrode
pins 9 can be kept by the contact between them, so that although
the ASIC component 3 is loaded in the device, the overall size of
the ignition device 1 can be kept nearly to the sizes of prior art
ignition devices.
[0115] Moreover, the ignition device according to the invention can
communicate with the exterior (for example, a central control unit)
by the use of the ASIC 4 as intercommunication switching means and
the capacitor 5 as electric energy-accumulating means both built in
the ASIC component 3.
[0116] Accordingly, if such an ignition device described above is
used in each of air bag modules, for example, incorporated in a car
and connected to a central control unit through an air bag system
linked to a local area network (LAN), it becomes possible for the
central control unit to ignite only a required air bag module upon
collision, while particular electric energy for igniting such an
ignition device need no longer be transmitted.
[0117] These functions and effects are achieved especially by
providing the capacitor 5 in each of ignition devices for
accumulating faint energy contained in voltage signals generated
from the central control unit, using the SCB chip as the heating
element 6 which causes ignition charge to be ignited with lower
energy than those with the prior art, and providing the ASIC 4 as
intercommunication and switching means which detects coded
information transmitted from the central control unit and in turn
transmits command for sending the state of the ignition device.
[0118] In the invention, moreover, the term "coded information"
used in the intercommunication with the central control unit is
intended to mean both the information including a command for
igniting each of the ignition devices and the information
concerning states of electronic elements included in each of the
ignition devices to be transmitted to the central control unit.
[0119] A gas generator for an air bag using the ignition device
according to the invention will then be explained.
[0120] FIG. 5 is a conceptual view of a gas generator for an air
bag. As shown in FIG. 5, the gas generator 21 for the air bag
comprises therein an ignition device 22, an enhancer 23, gas
generant 24, and filters 25, and outside the generator an outer
vessel 26 withstanding the pressure when the gas generant 24 is
burned. The outer vessel 26 is formed with holes 27 for discharging
the generated gas into the air bag.
[0121] When the ignition device 22 is actuated, the enhancer 23
burns by heat energy produced from the ignition device 22 to
generate a hot gas by means of which the gas generant 24 is burned
to generate a gas for inflating the air bag. The generated gas is
discharged out of the outer vessel 26 through the holes formed in
the outer vessel 26. At this time, the gas passes through the
filters 25 so that residues of the burned gas generant are
collected at the filters and the gas itself is cooled
simultaneously.
[0122] Although the ignition device according to the invention
includes the communication circuit comprising the ASIC, the
ignition device is similar in size to the prior art ignition
devices as described above. Therefore, the gas generator for an air
bag using the ignition device according to the invention is
effectively compact and has a size almost similar to sizes of prior
art gas generators. Moreover, since the SCB is used as a heating
element, ignition occurs in a short period of time so that delay in
ignition due to the communication can be prevented.
[0123] Moreover, a gas generator for a seat belt pretensioner using
the ignition device according to the invention will be
explained.
[0124] FIG. 6 is a conceptual view illustrating the gas generator
(micro gas-generator) for a seat belt pretensioner. As shown in
FIG. 6, the micro gas-generator 31 comprises therein an ignition
device 32 and a gas generant 33. The ignition device 32 is fixed to
a metal base 34 called a holder. Further, a cup 32 for storing a
gas generant 33 therein is also fixed to the holder by means of,
for example, caulking. When the ignition device 32 is actuated, the
gas generant 33 in the cup 35 is burned by the heat coming from the
ignition device 32 to generate a gas.
[0125] The ignition device according to the invention is compact,
although it has the communication circuit comprising the ASIC as
described above. Therefore, by using the ignition device, it is
also possible to provide the micro gas-generator which is compact
and has a size almost similar to sizes of the prior art gas
generators. Similarly, by using the SCB as a heating element,
ignition occurs in a short period of time so that delay in ignition
due to the communication can be prevented.
[0126] The igniting operation of the ignition device according to
the invention will then be explained.
[0127] Under a normal condition, that is, for example, when a car
does not encounter any accident requiring the development or
expansion of an air bag having the ignition device 1 incorporated
therein, the capacitor as electric energy-accumulating means is
under a condition accumulating the energy according to
communication signals sent from the central control unit.
[0128] Here, when the ignition device 1 is requested to operate by
impact caused by an accident or the like, the central control unit
transmits an ignition command in the form of a particular electric
pulse string to the ASIC component 3 in the ignition device. In the
ASIC component, at this moment the accumulated electric energy is
discharged from the capacitor 5 to the heating element 6 by means
of the electronic switch. The heating element 6 causes the ignition
charge 2 to start its ignition with the aid of the electric energy
from the capacitor 5.
[0129] The control procedure by the central control unit will then
be explained. FIG. 7 illustrates an example of the air bag system
linked to a local area network (LAN) and integrated with the
central control unit 110 and four air bag systems 111a, 111b, 111c
and 111d. The two airbag modules 111b and 111c each may have a gas
generator for inflating, for example, a front air bag, while the
other two air bag modules 111a and 111d each may have a gas
generator for inflating, for example, a side air bag.
[0130] The ignition device is put in the gas generator included in
each of these modules. Each of the ignition devices has two
electrode pins 114 and 115, the former electrode pins 114 being
connected to a first electric-supply conductor 112 connected to the
central control unit 110, and the latter electrode pins 115 being
connected to a second electric-supply conductor 113 connected to
the central control unit 110.
[0131] Under a normal condition, that is, when a car does not
encounter a particular accident requiring activation of one or more
air bag modules 111a, 111b, 111c and 111d, the central control unit
110 periodically gives the electric-supply conductors 112 and 113
low electric current which is fed through the electrode pins 114
and 115 to the electric energy storing means (capacitors) of the
ignition devices included in the four air bag modules 111a, 111b,
111c and 111d, respectively.
[0132] In the event that for example, upon impact, the activation
of the air bag module 111c is desired, the central control unit 110
feeds a particular electric pulse string constituting an ignition
command for the ignition device of the air bag module 111c to the
first electric-supply conductor 112. Although the particular
electric pulse string is fed to each of the ignition devices
through the electrode pins 114 and 115, only the intercommunication
means included in the ignition device of the air bag module 111c
responds to the command to activate the electric
energy-accumulating means associated with the ignition switching
means, thereby activating the ignition charge in the manner
described above.
[0133] Following the impact, if it is desired to activate some air
bag modules, for example, the air bag modules 111a and 111b, the
central control unit 110 gives the first electric-supply conductor
112 a particular electric pulse string for each of the ignition
devices included in the air bag modules 111a and 111b,
respectively. The two ignition devices operate in the same manner
as described above.
* * * * *