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FIELD OF THE INVENTION
The present invention relates to an inflator for an inflatable device, such
as an air bag in a vehicle, and particularly relates to an auto-ignition
device for such an inflator.
BACKGROUND OF THE INVENTION
An air bag system for restraining a vehicle occupant commonly includes an
inflator containing gas generating material which, when ignited, rapidly
produces a large volume of gas for inflating the air bag. Such a system
also includes a collision sensor. The collision sensor senses the
occurrence of a predetermined amount of vehicle deceleration indicative of
a collision, and completes a circuit to provide an electrical signal upon
sensing such vehicle deceleration. The gas generating material in the
inflator is ignited in response to the electrical signal. The gas
generating material is thus ignited to produce the gas for inflating the
air bag upon the occurrence of a vehicle collision.
The inflator may become subjected to abnormally high ambient temperatures
if, for example, the vehicle is involved in a fire. The gas generating
material could then become heated to a temperature at which it is ignited
by the heat of the fire. It is known to include an auto-ignition material
in the inflator to prevent the gas generating material from being ignited
at a time when the ambient temperature of the vehicle has reached an
excessively high level. The auto-ignition material will ignite at a
temperature that is lower than the temperature at which the gas generating
material will ignite. When the ambient temperature of the vehicle reaches
the ignition temperature of the auto-ignition material, the auto-ignition
material ignites automatically. The auto-ignition material then produces
products of combustion that ignite the gas generating material. The gas
generating material is thus ignited before the ambient temperature of the
vehicle reaches an excessively high level.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus for inflating an
inflatable vehicle occupant restraint, such as an air bag, comprises an
inflator means and a collision sensor means. The inflator means includes a
source of inflation fluid for inflating the vehicle occupant restraint,
and supplies inflation fluid from the source when the inflator means is
actuated. The collision sensor means senses a predetermined amount of
vehicle deceleration indicative of a collision, and provides a collision
signal upon sensing the predetermined amount of deceleration. The
apparatus further includes a first actuator means and a second actuator
means. The first actuator means actuates the inflator means in response to
the collision signal. The second actuator means actuates the inflator
means when the ambient temperature of the inflator means reaches a
predetermined elevated level.
The second actuator means includes an actuator member which is deflectable
under the influence of heat. The actuator member deflects into a
predetermined condition when the ambient temperature of the inflator means
reaches the predetermined elevated level. The second actuator means
actuates the inflator in response to deflection of the actuator member
into the predetermined condition.
In a first preferred embodiment of the present invention, the source of
inflation fluid comprises an ignitable gas generating material which, when
ignited, generates gas for inflating the vehicle occupant restraint. The
predetermined elevated temperature at which the actuator member deflects
into the predetermined condition is lower than the elevated temperature at
which the gas generating material would ignite automatically. The second
actuator means ignites the gas generating material in response to
deflection of the actuator member into the predetermined condition, and
thus ignites the gas generating material before the ambient temperature of
the inflator means increases to the greater elevated level at which the
gas generating material would ignite automatically.
In a second preferred embodiment of the present invention, the inflator
means includes a container means for defining a sealed chamber which
contains gas for inflating the vehicle occupant restraint. The container
means includes a container wall which is rupturable to release the gas
from the sealed chamber when the inflator means is actuated. The
predetermined elevated temperature at which the actuator member deflects
into the predetermined condition is lower than an elevated temperature at
which it would become undesirable to maintain the gas under pressure in
the chamber. The second actuator means ruptures the rupturable container
wall to release the gas from the chamber in response to deflection of the
actuator member into the predetermined condition. The second actuator
means thus releases the gas from the chamber before the ambient
temperature of the chamber reaches the greater elevated level at which it
would be undesirable to maintain the gas under pressure in the chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features of the present invention will become
apparent to those skilled in the art to which the present invention
relates upon reading the following description with reference to the
accompanying drawings, in which:
FIG. 1 is a schematic view of a vehicle occupant restraint system which is
a first embodiment of the present invention;
FIG. 2 is a sectional view of parts of the system of FIG. 1;
FIG. 3 is view of the parts of FIG. 2 in different positions;
FIG. 4 is a schematic view of a vehicle occupant restraint system which is
a second embodiment of the present invention;
FIG. 5 is an enlarged sectional view of parts of the system of FIG. 4; and
FIG. 6 is a view of the parts of FIG. 5 in different positions.
DESCRIPTION OF PREFERRED EMBODIMENTS
A first embodiment of the present invention is shown in FIGS. 1-3. As shown
schematically in FIG. 1, a vehicle occupant restraint system 10
constructed in accordance with the present invention includes an
inflatable vehicle occupant restraint 12, commonly referred to as an air
bag, and an inflator 14. The system 10 further includes a base plate 16
which supports the air bag 12 and the inflator 14 on a vehicle steering
wheel (not shown) in a known manner. The air bag 12 has a folded
condition, as indicated partially in solid lines in FIG. 1, and has an
inflated condition, as indicated partially in dashed lines in FIG. 1. The
system 10 is actuated upon the occurrence of a vehicle collision. The
inflator 14 then directs a rapid flow of inflation fluid, specifically an
inert gas, into the air bag 12 to inflate the air bag 12 from the folded
condition to the inflated condition. When the air bag 12 is in the
inflated condition, it extends rearwardly from the steering wheel toward
the driver of the vehicle and restrains movement of the driver.
The inflator 14 has a cylindrical housing 20 with a circular lower end wall
22, a circular upper end wall 24, and a cylindrical outer wall 26. The
lower end wall 22 has an inner edge surface 27 defining an opening
extending through the lower end wall 22. The outer wall 26 has a plurality
of inner edge surfaces 28 which define gas flow openings 30 extending
through the outer wall 26.
The housing 20 also has a cylindrical inner wall 32. The inner wall 32 has
a plurality of inner edge surfaces 34 which define gas flow openings 36
extending through the inner wall 32. The housing 20 thus defines a
combustion chamber 40 radially inward of the inner wall 32, and further
defines a gas flow chamber 42 between the inner wall 32 and the outer wall
26. A sheet 44 of rupturable pressure controlling material extends around
the inner surface of the inner wall 32 and over the gas flow openings 36.
The sheet 44 of rupturable pressure controlling material blocks the flow
of gas radially outward through the gas flow openings 36 from the
combustion chamber 40 to the gas flow chamber 42.
An annular filter assembly 50 is contained within the housing 20 in the gas
flow chamber 42. A source of inflation fluid in the form of combustible
gas generating material 60 and an auto-ignition device 62 are contained
within the housing 20 in the combustion chamber 40. An igniter 64 extends
into the combustion chamber 40 through the opening defined by the inner
edge surface 27 of the lower end wall 22.
The gas generating material 60 includes a plurality of annular disks 70 of
gas generating material. The disks 70 of gas generating material are
stacked in the combustion chamber 40 in a cylindrical shape, as shown in
FIG. 1. The disks 70 are formed of a known material which, when ignited,
rapidly produces a large volume of gas. Although many types of gas
generating material could be used in the inflator 14, especially suitable
gas generating materials are disclosed in U.S. Pat. No. 3,895,098. An
annular cushion 76 holds the disks 70 in place in the combustion chamber
40.
The igniter 64 is of known construction, and includes a casing 80
containing a pyrotechnic charge. The pyrotechnic charge can be formed of
any suitable pyrotechnic material known in the art. The igniter 64 is
actuated upon the passage of electric current through the igniter 64
between a pair of lead wires 82.
The restraint system 10 further includes an electrical circuit 90. The
electrical circuit 90 includes a power source 92, which is preferably the
vehicle battery, and a normally open switch 94. The switch 94 is
preferably part of a deceleration sensor 96. The deceleration sensor 96
senses the occurrence of a predetermined amount of vehicle deceleration
indicative of a collision, and closes the switch 94 upon sensing the
occurrence such deceleration. Electric current then passes between the
lead wires 82 in the igniter 64 to actuate the igniter 64.
When the igniter 64 is actuated, the pyrotechnic charge in the igniter 64
ignites and produces products of combustion which rupture the casing 80
and emerge from the igniter 64 in the combustion chamber 40. The products
of combustion emerging from the igniter 64 move against the ignitable gas
generating material 60 and ignite the gas generating material 60. Each of
the disks 70 of gas generating material then burns in the combustion
chamber 40 and produces products of combustion including heat, hot
particles and a large volume of gas.
The gas generated in the combustion chamber 40 is at first confined within
the combustion chamber 40 by the sheet 44 of rupturable pressure
controlling material which extends over the gas flow openings 36. When the
pressure of the gas in the combustion chamber 40 reaches a predetermined
elevated level, the gas ruptures the sheet 44 of rupturable pressure
controlling material and emerges from the combustion chamber 40 through
the gas flow openings 36. The gas then flows radially outward through the
filter member 50, which cools the gas and removes hot particles from the
gas, and emerges from the inflator 14 through the gas exit openings 30 to
inflate the air bag 12. The air bag 12 is thus inflated from the folded
condition to the inflated condition upon the occurrence of a vehicle
collision.
The auto-ignition device 62 is shown in detail in FIGS. 2 and 3. As shown
in FIG. 2, the auto-ignition device 62 includes a housing 100 with a
rupturable end portion 102. The housing 100 is fixed to the upper end wall
24 of the inflator housing 20 by any suitable means, such as by an
adhesive. The rupturable end portion 102 of the housing 100 contains a
pyrotechnic charge 104 which, like the pyrotechnic charge in the igniter
64, is formed of a suitable pyrotechnic material known in the art. A
support member 106 in the housing 100 supports a primer 108 in a position
adjacent to the pyrotechnic charge 104. The primer 108 can be a percussion
primer or a stab primer, as known in the art, and emits products of
combustion when actuated. The support member 106 has a cylindrical inner
surface 110 which defines a flash hole 111 for directing the products of
combustion from the primer 108 to the pyrotechnic charge 104.
The support member 106 also supports an actuator member 112 in the housing
100. The actuator member 112 is a disk having first and second metal
layers 114 and 116. The first metal layer 114 has a first coefficient of
thermal expansion, and the second metal layer 116 has a second coefficient
of thermal expansion different from the first coefficient of thermal
expansion. The actuator member 112 is thus constructed as a bi-metal snap
action disk which deflects under the influence of heat as a result of the
difference between the first and second coefficients of thermal expansion.
More specifically, the actuator member 112 has an initial condition, as
shown in FIG. 2, in which the shape of the actuator member 112 is concave
relative to the primer 108. A firing pin member 120 on the actuator member
112 is then spaced from the primer 108. As the ambient temperature
increases, the actuator member 112 deflects from the condition shown in
FIG. 2 toward a flat condition, and thus moves the firing pin member 120
toward the primer 108.
The actuator member 112 is designed with reference to a predetermined
elevated temperature. The predetermined elevated temperature is lower than
the elevated temperature at which the gas generating material 60 would
ignite automatically. When the ambient temperature increases to the
predetermined elevated temperature, the actuator member 112 deflects
beyond the flat condition toward a condition in which its shape is convex
relative to the primer 108. The actuator member 112 then snaps quickly
into the condition shown in FIG. 3, and thus moves the firing pin member
120 forcibly against the primer 108. The primer 108 is thereby actuated by
the firing pin member 120, and emits products of combustion through the
flash hole 111 to ignite the pyrotechnic charge 104. The ignited
pyrotechnic charge 104 emits products of combustion which rupture the
rupturable end portion 102 of the housing 100. The products of combustion
of the pyrotechnic charge 104 emerge from the housing 100 in the
combustion chamber 40 (FIG. 1) and ignite the gas generating material 60
in the combustion chamber 40. The gas generating material 60 is thus
ignited by the auto-ignition device 62 at a predetermined elevated
temperature which is lower than the temperature at which the gas
generating material 60 would ignite.
A second embodiment of the present invention is shown schematically in
FIGS. 4-6. As shown in FIG. 4, a vehicle occupant restraint system 200
constructed in accordance with the present invention includes an air bag
202 and an inflator assembly 204. The inflator assembly 204 inflates the
air bag 202 from a folded condition, as indicated partially in solid lines
in FIG. 4, to an inflated condition, as indicated partially in dashed
lines in FIG. 4, upon the occurrence of a vehicle collision.
The inflator assembly 204 includes a pressure vessel 210 with a rupturable
closure wall 212. The pressure vessel 210 defines a chamber 214, and has a
neck portion 216 with an opening 218. The rupturable closure wall 212 is
welded to the neck portion 216 over the opening 218, and seals the chamber
214. A quantity of gas under pressure is stored in the sealed chamber 214.
A closure cap 220 is received over the neck portion 216 of the pressure
vessel 210, as shown in FIG. 4. The closure cap 220 has a plurality of
cylindrical inner surfaces defining a central chamber 222 and a plurality
of gas flow passages 224. The gas flow passages 224 extend radially from
the central chamber 222 and communicate the central chamber 222 with the
exterior of the closure cap 220.
An igniter 230 is located in the central chamber 222 in the closure cap
220. The igniter 230 includes a cylindrical casing 232 containing a
pyrotechnic charge 234. The pyrotechnic charge 234 can be formed of any
suitable pyrotechnic material known in the art.
A squib 240 is supported by the closure cap 220 in a position adjoining the
igniter 230. The squib 240 contains a pyrotechnic charge which also can be
formed of any suitable material known in the art. The squib 240 has a pair
of lead wires 242 which are connected in an electrical circuit 250. The
electrical circuit 250, like the electrical circuit 90 described above,
includes a power source 252 which is preferably the vehicle battery, and
further includes a normally open switch 254 which is preferably a part of
a vehicle deceleration sensor 256.
When the vehicle experiences a collision, the vehicle deceleration sensor
256 closes the switch 254 to complete the circuit 250 and actuate the
squib 240. The pyrotechnic charge in the squib 240 is then ignited and
emits products of combustion which ignite the pyrotechnic charge 234 in
the igniter 230. The ignited pyrotechnic charge 234 emits products of
combustion including heat and a pressure wave which rupture the casing 232
and the rupturable closure wall 212. The products of combustion of the
pyrotechnic charge 234 thus open the sealed chamber 214 and release the
gas in the chamber 214 to flow outward through the opening 218. The
products of combustion of the pyrotechnic charge 234 also enter the
chamber 214 to heat and pressurize the gas in the chamber 214, either
directly or through ignition of additional combustible material in the
chamber 214. As the gas emerges from the gas flow passages 224 in the
closure cap 220, a diffuser 260 directs the gas outward through gas flow
openings 262 and into the air bag 202 to inflate the air bag 202. The air
bag 202 is thus inflated from the folded condition to the inflated
condition upon the occurrence of a vehicle collision.
As shown in FIG. 4, the vehicle occupant restraint system 200 further
includes an auto-release device 270. As shown in detail in FIGS. 5 and 6,
the auto-release device 270 includes a support member 272, a second
rupturable closure wall 274, and an actuator member 276.
The support member 272 has a peripheral surface 278, and is closely
received within an opening defined by an inner edge surface 280 of the
pressure vessel 210. The support member 272 is preferably welded to the
pressure vessel 210 around the peripheral surface 278 to block the gas in
the chamber 214 from flowing outward between the surfaces 278 and 280. A
cylindrical inner surface 282 of the support member 272 defines a passage
284 extending through the center of the support member 272. The second
rupturable closure wall 274 is welded to the support member 272 in a
position extending across the passage 284, and blocks the gas in the
chamber 214 from flowing outward through the passage 284.
The actuator member 276 is supported in the passage 284 outward of the
second rupturable closure wall 274. The actuator member 276 is a disk
having first and second metal layers 286 and 288. The first metal layer
286 has a first coefficient of thermal expansion, and the second metal
layer 288 has a second coefficient of thermal expansion which differs from
the first coefficient of thermal expansion. The actuator member 276 is
thus constructed as a bi-metal snap action disk which deflects under the
influence of heat as a result of the difference between the first and
second coefficients of thermal expansion.
The actuator member 276 has an initial condition, as shown in FIG. 5, in
which the shape of the actuator member 276 is concave relative to the
second rupturable closure wall 274. A punch member 290 on the actuator
member 276 is then spaced from the second rupturable closure wall 274. As
the ambient temperature increases, the actuator member 276 deflects from
the condition shown in FIG. 5 toward a flat condition, and thus moves the
punch member 290 toward the second rupturable closure wall 274. When the
ambient temperature increases to a predetermined elevated level, the
actuator member 276 deflects beyond a flat condition toward a condition in
which its shape is convex relative to the second rupturable closure wall
274. The actuator member 276 then snaps quickly into the condition shown
in FIG. 6, and thus moves the punch member 290 forcefully against the
second rupturable closure wall 274 to rupture the second rupturable
closure wall 274. The gas in the chamber 214 then flows outward through
the passage 284 past the second rupturable closure wall 274 and around the
actuator member 276. The auto-release device 270 thus operates to release
the gas from the chamber 214 before the ambient temperature reaches an
excessively high level at which it would be undesirable to contain the gas
under pressure in the chamber 214.
From the above description of the invention, those skilled in the art will
perceive improvements, changes and modifications. Such improvements,
changes and modifications within the skill of the art are intended to be
covered by the appended claims.
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