U.S. patent application number 11/734705 was filed with the patent office on 2007-10-18 for actuator.
This patent application is currently assigned to Daicel Chemical Industries, Ltd.. Invention is credited to Masato Hirooka, Nobuyuki Katsuda, Kenji Numoto.
Application Number | 20070240417 11/734705 |
Document ID | / |
Family ID | 38603525 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070240417 |
Kind Code |
A1 |
Hirooka; Masato ; et
al. |
October 18, 2007 |
ACTUATOR
Abstract
The present invention provides an actuator including: a housing
having an igniter housing and a cylinder, an igniter accommodated
inside the igniter housing and a piston provided inside the
cylinder to be slidable, the piston having a rod and an enlarged
surface portion formed on one end surface or an outer peripheral
surface of the rod, and part of the piston, which includes the
other end of the rod, protruding outside the housing before
activation, the igniter disposed such that the central axis
direction of the igniter and the central axis direction of the rod
of the piston are different from each other, wherein, during the
activation of the igniter, the piston slides inside the cylinder by
pushing the enlarged surface portion by a combustion product
generated due to activation of the igniter, and the protruding
portion of the piston is retracted inside the housing due to the
sliding of the piston.
Inventors: |
Hirooka; Masato;
(Tatsuno-Shi, JP) ; Katsuda; Nobuyuki;
(Tatsuno-Shi, JP) ; Numoto; Kenji; (Tatsuno-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Daicel Chemical Industries,
Ltd.
Sakai-shi
JP
|
Family ID: |
38603525 |
Appl. No.: |
11/734705 |
Filed: |
April 12, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60792625 |
Apr 18, 2006 |
|
|
|
Current U.S.
Class: |
60/635 |
Current CPC
Class: |
F15B 15/19 20130101;
F42B 3/006 20130101 |
Class at
Publication: |
060/635 |
International
Class: |
F01B 29/08 20060101
F01B029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 2007 |
JP |
2007-28154 |
Apr 13, 2006 |
JP |
2006-110760 |
Claims
1. An actuator comprising: a housing having an igniter housing and
a cylinder, an igniter accommodated inside the igniter housing and
a piston provided inside the cylinder to be slidable, the piston
having a rod and an enlarged surface portion formed on one end
surface or an outer peripheral surface of the rod, and part of the
piston, which includes the other end of the rod, protruding outside
the housing before activation, the igniter disposed such that the
central axis direction of the igniter and the central axis
direction of the rod of the piston are different from each other,
wherein, during the activation of the igniter, the piston slides
inside the cylinder by pushing the enlarged surface portion by a
combustion product generated due to activation of the igniter, and
the protruding portion of the piston is retracted inside the
housing due to the sliding of the piston.
2. The actuator according to claim 1, wherein the combustion
product generated when the igniter is activated changes direction
by impinging on a collision surface portion provided in the
housing, and then pushes the enlarged surface portion.
3. The actuator according to claim 2, wherein the collision surface
portion is a wall surface separating the igniter housing from the
cylinder.
4. The actuator according to claim 2, wherein the collision surface
portion is a wall surface separating the igniter housing from the
cylinder, and the wall surface form part of a wall surface of the
cylinder.
5. The actuator according to claim 2, wherein the collision surface
portion is a cap member disposed to surround an activation portion
of the igniter, which is capable of ejecting the combustion
products in a direction of the enlarged surface portion.
6. The actuator according to any one of claims 1 to 5, wherein the
collision surface portion forms a closed space including the
igniter together with other members including the enlarged surface
portion.
7. The actuator according to any of claims 1 to 5, wherein the
enlarged surface portion of the piston is a portion which extends
from the one end surface of the rod or an axial central portion of
the rod either unidirectionally outward in a radial direction of
the rod or in flange form.
8. The actuator according to claims 6, wherein the enlarged surface
portion of the piston is a portion which extends from the one end
surface of the rod or an axial central portion of the rod either
unidirectionally outward in a radial direction of the rod or in
flange form.
Description
[0001] This nonprovisional application claims priority under 35
U.S.C. .sctn. 119(a) on Patent Application No. 2006-110760 filed in
Japan on 13 Apr. 2006 and Patent Application No. 2007-028154 filed
in Japan on 7 Feb. 2007, and 35 U.S.C. .sctn. 119(e) U.S.
Provisional Application No. 60/792,625 filed on 18 Apr. 2006, which
are incorporated by reference.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to an actuator that can be
used in a human body restraining device of an automotive vehicle
such as a steering retractor or an engine hood lifting device.
[0004] 2. Description of Related Art
[0005] In addition to air bag type restraining devices used in
passenger restraining devices and pedestrian protection devices for
vehicles, devices for lifting the hood of a vehicle during a
collision to protect pedestrians and devices for retracting the
steering wheel (toward the front of the vehicle), for example, also
exist.
[0006] In these devices, a pyrotechnic actuator is used, and known
actuators include a type that ejects a pin upon activation and a
type (known as a pin puller) that retracts a protruding pin inward
upon activation. A pin puller is structured such that prior to
activation, a tip end portion of the pin protrudes from a cylinder
(housing), and upon activation, the pin is retracted into the
interior of the cylinder (housing), and includes an igniter for
moving the pin. The igniter is disposed parallel or at a right
angle to the movement direction of the pin.
[0007] U.S. Pat. No. 4,412,420 discloses a pin puller type
actuator. In an actuator shown in FIG. 1, a bore 14 accommodating a
piston P is formed in a housing H serving as a cylinder, and the
piston P is provided to slide within the bore 14. A cartridge C is
screwed into a screw portion formed in the housing H and disposed
at a right angle to the axis of the piston P.
[0008] With the actuator structure shown in FIG. 1, an annular
space 27 is formed around the piston P, and gas generated from the
cartridge C is charged into the annular space 27, thereby raising
the pressure in the interior of the annular space 27 such that the
piston P moves in a leftward direction of FIG. 1. As a result, a
right end portion of the piston P is retracted into the interior of
the housing H.
SUMMARY OF INVENTION
[0009] The present invention provides an actuator including:
[0010] a housing having an igniter housing and a cylinder,
[0011] an igniter accommodated inside the igniter housing and a
piston provided inside the cylinder to be slidable,
[0012] the piston having a rod and an enlarged surface portion
formed on one end surface or an outer peripheral surface of the
rod, and part of the piston, which includes the other end of the
rod, protruding outside the housing before activation,
[0013] the igniter disposed such that the central axis direction of
the igniter and the central axis direction of the rod of the piston
are different from each other,
[0014] wherein, during the activation of the igniter, the piston
slides inside the cylinder by pushing the enlarged surface portion
by a combustion product generated due to activation of the igniter,
and the protruding portion of the piston is retracted inside the
housing due to the sliding of the piston.
BRIEF DESCRIPTION OF DRAWINGS
[0015] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention and wherein:
[0016] FIG. 1 shows a longitudinal sectional view of an
actuator;
[0017] FIG. 2 shows a longitudinal sectional view of an actuator
according to another embodiment;
[0018] FIG. 3 shows a longitudinal sectional view of an actuator
according to another embodiment; and
[0019] FIG. 4 shows a longitudinal sectional view of an actuator
according to another embodiment.
DETAILED DESCRIPTION OF INVENTION
[0020] The present invention provides a pin puller type actuator
which retracts a piston, which is capable of retracting the piston
reliably without damaging the piston.
[0021] In the actuator according to the present invention, upon
activation of the igniter, combustion products (a flame,
high-temperature gas, a shock wave, and so on) generated when the
igniter is activated collide with and push the enlarged surface
portion of the piston, but do not collide with the rod. The
enlarged surface portion is disposed in the flow direction of the
combustion products generated by the igniter.
[0022] In the actuator of the present invention, the igniter is
disposed such that the central axis direction of the igniter and
the central axis direction of the piston rod are different
(preferably orthogonal) to each other, and therefore, as described
above, the combustion products can be caused to collide with the
enlarged surface portion of the piston by guiding the combustion
products generated upon activation of the igniter to the enlarged
surface portion of the piston. A method of forming a combustion
product guidance passage in the housing or a method of providing an
opening portion, in the direction of the enlarged surface portion,
in the igniter housing accommodating the igniter, for example, may
be applied to guide the combustion products to the enlarged surface
portion of the piston.
[0023] In so doing, the shock wave is prevented from colliding
directly with the rod, as occurs in the invention of U.S. Pat. No.
4,412,420, and instead the combustion products collide with the
enlarged surface portion. Hence, the entire piston is retracted
into the housing reliably without damaging the rod. Moreover, in
comparison with a case in which the igniter and piston are disposed
such that respective central axis directions thereof are parallel
to each other, the entire actuator can be reduced in size. Note
that the entire piston does not have to be retracted into the
housing, and only a part thereof need be retracted.
[0024] The enlarged surface portion of the piston is formed
integrally with the rod end surface, and there are no particular
limitations on the shape and size thereof. However, a plane or
curved surface having a surface area that is equal to or greater
than at least the cross-section or end surface of the rod is
preferably employed.
[0025] The igniter may employ a well-known electric igniter used
widely in air bag gas generators and the like (using an ignition
charge including zirconium and potassium perchlorate), and where
necessary, an auxiliary charge may also be used.
[0026] The present invention further provides an actuator being the
above shown invention actuator, wherein the combustion product
generated when the igniter is activated changes direction by
impinging on a collision surface portion provided in the housing,
and then pushes the enlarged surface portion.
[0027] The collision surface portion is disposed in a position
facing (preferably directly facing) the ejecting direction of the
combustion products generated from an activation portion upon
activation of the igniter, and therefore the combustion products
collide with the collision surface portion, change direction, and
then collide with the enlarged surface portion. Thus, the
combustion products are caused to collide with the enlarged surface
portion reliably such that the protruding part of the piston can be
retracted.
[0028] The collision surface portion may be a wall surface
separating the igniter housing from the cylinder. When the
collision surface portion is a wall surface separating the igniter
housing from the cylinder, the wall surface may form part of a wall
surface of the cylinder. Further, the collision surface portion may
be a cap member disposed to surround the activation portion of the
igniter, which is capable of ejecting the combustion products in
the direction of the enlarged surface portion.
[0029] Furthermore, by having the collision surface portion form a
closed space including the igniter together with other members (for
example, the igniter housing, the cylinder, and so on) including
the enlarged surface portion, all of the combustion products
generated upon activation of the igniter can be used to push the
enlarged surface portion, which is preferable in terms of
efficiency.
[0030] Here, the term "closed space" may signify a sealed space
formed by press-contacting separate members with each other, or a
state in which separate members abuts against each other or are
disposed with a slight gap therebetween. In other words, any closed
space capable of ensuring by its existence that the combustion
products generated upon activation of the igniter can be caused to
collide with the enlarged surface portion reliably without escaping
(without entering a gap between the piston and cylinder, for
example) may be used.
[0031] Note that when the cap member is used as the collision
surface portion, a cap member having an opening or a fragile
portion in the ejecting direction of the combustion products may be
used. The fragile portion is a part that is formed thinly or has a
notch inserted therein so that it ruptures and opens easily upon
reception of the pressure of the combustion products.
[0032] The present invention further provides the actuator being
the above shown invention actuator, wherein the enlarged surface
portion of the piston is a portion which extends from the one end
surface of the rod or an axial central portion of the rod either
unidirectionally outward in the radial direction of the rod or in
flange form.
[0033] The shape and size of the enlarged surface portion may be
set appropriately in accordance with the structure of the actuator.
For example, when the actuator is to be made as small as possible,
an enlarged surface portion that extends unidirectionally outward
in the radial direction of the rod from the one end surface or the
central portion (including the central portion and its vicinity) of
the rod may be used, and when the piston is large (having large
mass), an enlarged surface portion that extends in flange form
around the periphery of the one end surface or the central portion
(including the central portion and its vicinity) of the rod may be
used, whereby the enlarged surface portion is increased in size and
the piston is retracted with greater force.
[0034] With the actuator of the present invention, the combustion
products including a shock wave that are generated upon activation
of the igniter collide with the enlarged surface portion rather
than colliding directly with the piston rod, and therefore the
piston can be retracted into the cylinder reliably without damaging
the piston rod.
[0035] The invention actuator can be used in a human body
restraining device of an automotive vehicle, such as a steering
retractor or an engine hood lifting device.
Embodiment of Invention
(1) Actuator of FIG. 1
[0036] FIG. 1 is a cross-sectional view of an actuator.
[0037] An outer shell of an actuator 10 is formed by a housing 11
by combining an igniter housing 11a and a cylinder 11b. The igniter
housing 11a and cylinder 11b share a part of the outer shell
member. The housing 11 (igniter housing 11a and cylinder 11b) is
made of metal, and the overall shape and size thereof are
determined according to the attachment subject and attachment
position of the actuator 10.
[0038] An igniter accommodating space 12 is formed in the interior
of the igniter housing 11a. The igniter accommodating space 12 is
formed, in advance, with an interior shape that corresponds to the
exterior shape of an electric igniter 14 serving as an attachment
subject. The electric igniter 14 is fitted into the igniter
accommodating space 12 through a first opening portion 21 of the
housing and then fixed by crimping a first opening peripheral edge
portion 21a.
[0039] An activation portion 14a of the igniter is positioned
within a closed space 12a remaining after the igniter 14 is fitted,
and does not contact an inner wall surface of the housing 11. The
closed space 12a serves as a passage for combustion products
generated by activation of the igniter 14. 19 is an O-ring for
maintaining airtightness.
[0040] A metal piston 15 having an L-shaped axial cross-section is
accommodated slidably in a cylinder sliding space 13 inside the
cylinder 11b. The piston 15 has a rod 16 and an enlarged surface
portion 17 formed on an one end surface 16a of the rod 16, and a
part thereof including the other end surface 16b of the rod
protrudes to the outside of the housing 11 (cylinder 11b). The
protruding portion including the other end surface 16b is retracted
into the cylinder 11b upon activation of the actuator 10, and a
length (L.sub.1) thereof is determined in accordance with the
operating performance required by the attachment subject.
[0041] The enlarged surface portion 17 is a surface enlarged
unidirectionally from the one end surface 16a of the rod 16 in a
perpendicular direction to the axial direction of the rod 16 (i.e.
in a radial direction), and has a surface area that is equal to or
greater than the surface area of the one end surface 16a or the
other end surface 16b of the rod 16. Annular grooves are formed in
the circumferential direction in the rod 16 and the enlarged
surface portion 17 respectively, and O-rings 18a, 18b for
maintaining airtightness are fitted into the respective annular
grooves.
[0042] A part of a surface of the enlarged surface portion 17 on
the closed space 12a side abuts against a stepped surface 26 of the
cylinder 11b, and therefore the other end surface 16b of the rod
does not protrude any further to the outside of the housing 11
(cylinder 11b).
[0043] The piston 15 is fitted into the cylinder sliding space 13
through a second opening portion 22 in the housing. A partition
wall 23 is fitted into an annular stepped surface in the vicinity
of the second opening portion 22 and fixed by crimping the a second
opening edge portion 22a to seal the second opening portion. The
partition wall 23 may be formed by any member capable of keeping
piston movement within a predetermined range upon activation, and
need not seal the second opening portion 22 completely.
[0044] A movement space 25 allowing the piston 15 to slide is
defined, between the enlarged surface portion 17 and the partition
wall 23, by the enlarged surface portion 17, the partition wall 23,
and the housing 11. A gap L.sub.2 between the enlarged surface
portion 17 and partition wall 23 is equal to the length L.sub.1 of
the protruding portion. By adjusting the lengths of L.sub.1 and
L.sub.2, the length by which the piston 15 is retracted into the
cylinder 11b can be adjusted.
[0045] The igniter housing 11a and the cylinder 11b are partitioned
by a collision surface portion 20 serving as a common outer wall
surface forming both the igniter housing 11a and cylinder 11b. The
collision surface portion 20 forms a part of a cylindrical wall
surface, and is the surface with which the combustion products
generated upon activation of the igniter 14 collide.
[0046] The igniter 14 and piston 15 are disposed such that a
central axis direction of the igniter 14 and a central axis
direction of the piston rod 16 are orthogonal to each other. Thus,
the activation portion 14a of the igniter 14 directly faces the
collision surface portion 20.
[0047] The closed space 12a is surrounded by the igniter 14
(activation portion 14a), the collision surface portion 20, the
igniter housing 11a, and the enlarged surface portion 17 (a
pressure receiving surface 17a). A slight gap (of approximately 1
mm or less, for example) may be formed between a tip end surface
20a of the collision surface portion 20 and the pressure receiving
surface 17a of the enlarged surface portion 17 within a range that
does not impede normal operations, or the tip end surface 20a and
pressure receiving surface 17a may be abutted against each other or
pressed against each other. When a gap exists between the tip end
surface 20a of the collision surface portion 20 and the pressure
receiving surface 17a of the enlarged surface portion 17, the
dimensional precision of the components can be managed easily.
[0048] Next, an operation of the actuator 10 shown in FIG. 1 will
be described. Upon activation of the igniter 14, combustion
products (a flame, high-temperature gas, a shock wave, and so on)
are generated from the activation portion 14a. The generated
combustion products collide with the collision surface portion 20,
which is positioned inside the closed space 12a to face the
activation portion 14a directly, and then change direction.
[0049] The outer peripheral surface of the rod 16 is isolated from
the closed space 12a by the collision surface portion 20 and the
enlarged surface portion 17, and therefore the combustion products,
having changed direction, collide with the pressure receiving
surface 17a of the enlarged surface portion 17 rather than the rod
16, thereby pushing the pressure receiving surface 17a. The
pressure receiving surface 17a is also pushed by an increase in the
internal pressure of the closed space 12a (change in the flow of
the combustion products is illustrated by an arrow in FIG. 1). At
this time, the combustion products collide with the collision
surface portion 20 and the enlarged surface portion 17 (pressure
receiving surface 17a), causing the rod 16 to move axially at the
moment of collision, and airtightness is maintained by the O-rings
18a, 18b. Therefore, normal operations are not affected even when a
slight gap exists between the tip end surface 20a and the pressure
receiving surface 17a, and the operation progresses in a similar
manner to a case in which the tip end surface 20a and pressure
receiving surface 17a are abutted against each other or pressed
against each other.
[0050] The enlarged surface portion 17 pushed by the combustion
products moves through the movement space 25 towards the partition
wall 23, and hence the piston rod 16 slides through the cylinder
11b towards the partition wall 23 such that the protruding portion
of the piston rod 16 is retracted into the cylinder 11b (housing
11). As described above, L.sub.1=L.sub.2, and therefore the piston
15 is retracted completely into the cylinder 11b (housing 11).
(2) Actuator of FIG. 2
[0051] FIG. 2 is a longitudinal sectional view of an actuator
according to another embodiment. An actuator 100 shown in FIG. 2 is
identical in its basic structure to the actuator 10 shown in FIG.
1, and therefore only different parts will be described. Note that
identical reference numerals to those used in FIG. 1 denote
identical components.
[0052] A cap member 30 made of stainless steel or the like, which
corresponds to the collision surface portion 20 shown in FIG. 1, is
fitted onto the activation portion 14a of the igniter. When the
thin cap member 30 is used in place of the collision surface
portion 20 shown in FIG. 1, the axial dimension of the actuator 100
becomes smaller than the axial dimension of the actuator 10 shown
in FIG. 1, and therefore the actuator 100 is reduced in size.
[0053] The cap member 30 is fixed such that a flange portion 31
thereof is sandwiched between the igniter housing 11a and the
igniter 14. The cap member 30 has a single or a plurality of
ejection ports 32 in a part of a side surface thereof for ejecting
the combustion products. The ejection port 32 faces the enlarged
surface portion 17 of the piston directly.
[0054] When the igniter 14 is activated, the combustion products
generated by the activation portion 14a are ejected through the
ejection port 32 alone due to the action of the closed space 12a
defined by the activation portion 14a and cap member 30. The
combustion products ejected through the ejection port 32 collide
with and push the pressure receiving surface 17a of the enlarged
surface portion 17, which directly faces the ejection port 32
(change in the flow of the combustion products is illustrated by an
arrow in FIG. 2), and as a result, the piston 15 is retracted into
the cylinder 11b.
(3) Actuator of FIG. 3
[0055] FIG. 3 is a longitudinal sectional view of an actuator
according to another embodiment. An actuator 200 shown in FIG. 3 is
identical in its basic structure to the actuator 10 shown in FIG.
1, and therefore only different parts will be described. Note that
identical reference numerals to those used in FIG. 1 denote
identical components.
[0056] The piston 15 accommodated in the cylinder 11b has a
T-shaped axial cross-section, and has the piston rod 16 and an
annular enlarged surface portion 27 extending in flange form from
the one end surface 16a of the piston rod 16.
[0057] The closed space 12a remaining after the igniter 14 is
fitted into the igniter accommodating space 12 is a substantially
cylindrical space, and substantially the entirety of a pressure
receiving surface 27a of the enlarged surface portion 27 faces the
closed space 12a.
[0058] The collision surface portion 20 takes a substantially
cylindrical form, similarly to the substantially cylindrical closed
space 12a, and when the igniter 14 is activated, the combustion
products generated from the activation portion 14 collide with a
surface thereof directly facing the activation portion 14a.
[0059] Upon activation of the igniter 14, the combustion products
generated from the activation portion 14a change direction due to
the action of the collision surface portion 20, and fill the
entirety of the substantially cylindrical closed space 12a, thus
raising the internal pressure thereof. The outer peripheral surface
of the rod 16 is isolated from the closed space 12a defined by the
collision surface portion 20, the cylinder 11b, and the annular
enlarged surface portion 27, and therefore the combustion products,
having changed direction, collide with the pressure receiving
surface 27a of the enlarged surface portion 27 rather than the rod
16, thereby pushing the pressure receiving surface 27a (change in
the flow of the combustion products is illustrated by an arrow in
FIG. 3). The pressure receiving surface 27a is also pushed by the
increase in the internal pressure of the substantially cylindrical
closed space 12a. As a result, the piston 15 is retracted into the
cylinder 11b.
[0060] In the actuator 200, the enlarged surface portion 27 is
larger than the enlarged surface portion 17 shown in FIGS. 1 and 2,
and therefore the actuator 200 becomes larger than the actuators
shown in FIGS. 1 and 2. However, the entire surface of the annular
enlarged surface portion 27 is pushed evenly, and therefore the
operation to retract the piston 15 becomes easier.
(4) Actuator of FIG. 4
[0061] FIG. 4 is a longitudinal sectional view of an actuator
according to another embodiment.
[0062] An outer shell of an actuator 300 is formed by joining
together an igniter collar 320 and a cylinder 330, which are
provided as separate members. The igniter collar 320 includes a
main body portion 321 contacting an igniter 323, and a first
cylindrical joint portion 322 extending therefrom. The cylinder 330
includes a cylindrical piston accommodating portion (cylinder main
body) 331, and a second cylindrical joint portion 332 protruding
from a peripheral surface thereof. The igniter 323 is sandwiched
between a tip end of the second cylindrical joint portion 332 and
the igniter collar 320, and connected to the cylinder 330.
[0063] The igniter collar 320 and cylinder 330 are connected by
fitting the first cylindrical joint portion 322 onto a step (a
groove 332a) formed on an outer surface of the second cylindrical
joint portion 332 and performing crimping from the outside of the
first cylindrical joint portion 332.
[0064] The cylinder 330 has a first opening portion 333 and a
second opening portion 334 on the respective end sides thereof, and
has a communication hole 336 communicating with an igniter
accommodating space 325 on a side surface thereof.
[0065] A disk-shaped enlarged surface portion 351 is formed at a
desired position, in a length direction, of a piston 350 that is
accommodated inside the cylindrical 330. The enlarged surface
portion 351 has a pressure receiving surface 352 on the second
opening portion 334 side, and abuts against a first stepped portion
337 formed in the interior of the cylinder main body 331.
[0066] The piston 350 has a first rod 358 existing on the first
opening portion 333 side of the enlarged surface portion 351, and a
second rod 359 existing on the second opening portion 334 side of
the enlarged surface portion 351. The interior space of the
cylinder 330 is divided into a first space 341 and a second space
342 by the enlarged surface portion 351. The second space 342 forms
a single space (closed space) integrally with the communication
hole 336 and the igniter accommodating space 325.
[0067] A cylindrical collision surface portion 360 is formed in the
second space 342 in the cylinder 330 so as to cover an outer
peripheral surface of the second rod 359. The cylindrical collision
surface portion 360 is formed integrally with a wall surface of the
cylinder 330 on the second opening portion 334 side, and a tip end
surface 360a thereof abuts against the pressure receiving surface
352 of the enlarged surface portion 351. Note that upon activation,
the combustion products generated from the activation portion 324
collide with a part of the surface of the cylindrical collision
surface portion 360 directly facing the activation portion 324, and
then change direction, rather than colliding with the entire
collision surface portion.
[0068] A sealing member 345 and a thin annular stopper 347 are
disposed in a laminated fashion at the end portion of the first rod
358. The sealing member 345 has an opening portion 346 having an
inner diameter that is slightly larger than the outer diameter of
the first rod 358, while the inner diameter of the annular stopper
347 is slightly smaller than the outer diameter of the first rod
358. The sealing member 345 and annular stopper 347 are fitted into
a second stepped portion 338 formed in the cylinder main body 331,
and fixed by crimping a side end portion 330a of a first opening
portion in the cylinder main body 331. The thin annular stopper 347
prevents movement of the piston 350 prior to activation.
[0069] Next, an operation of the actuator shown in FIG. 4 will be
described. When combustion products are generated from the ignition
portion 324 upon activation of the igniter 323, the combustion
products pass through the igniter accommodating space 325 and the
communication hole 336 and flow into the second space 342. The
igniter accommodating space 325, communication hole 336, and second
space 342 together form a closed space, and therefore the
disk-shaped pressure receiving surface 352 is pushed by the
combustion products. The pressure receiving surface 352 is also
pushed by an increase in the internal pressure of the second space
342, and as a result, a driving force acts on the piston 350.
[0070] At this time, the cylindrical collision surface portion 360
covers the outer peripheral surface of the second rod 359, and the
tip end 360a thereof abuts against the pressure receiving surface
352. Therefore, the combustion products flowing into the second
space 342 are unlikely to enter the gap between the collision
surface portion 360 and the second rod 359, and the entire amount
of the generated combustion products is used to drive the
piston.
[0071] Then, from a state in which movement is blocked by the
stopper 347 at the end portion of the first rod 358, the stopper
347 is ruptured and the piston 350 moves axially.
[0072] Note that in the embodiment shown in FIG. 4, the clearance
between the outer peripheral surface of the enlarged surface
portion 351 and the inner peripheral surface of the cylinder main
body 331 and the clearance between the second opening portion 334
and the second rod 359 are managed strictly, and therefore the
O-rings used in FIGS. 1 to 3 are not required.
[0073] The structures described above illustrate specific examples
of the present invention, but the present invention is not limited
to these structures. The sectional form of the piston, the shape of
the collision surface portion, the formation method of the housing
and cylinder, and so on may be modified arbitrarily to the extent
that the effects of the present invention are exhibited.
[0074] The invention thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *