U.S. patent application number 09/836356 was filed with the patent office on 2001-11-08 for piezoelectric fluid control valve.
This patent application is currently assigned to SMC Corporation. Invention is credited to Sakurai, Toyonobu.
Application Number | 20010038083 09/836356 |
Document ID | / |
Family ID | 18643032 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038083 |
Kind Code |
A1 |
Sakurai, Toyonobu |
November 8, 2001 |
Piezoelectric fluid control valve
Abstract
The piezoelectric element laminate 20 which expands due to
application of a voltage is disposed between a diaphragm valve 11
applied with elastic force in a valve opening direction and a valve
spring mechanism 25, a distortion amount a of the piezoelectric
element laminate 20 in expansion is set to be larger than an
opening/closing stroke b of the diaphragm valve 11, and a spring
seat 28 separates from a second stopper 30 due to a difference c
between the distortion amount a and the opening/closing stroke b.
As a result, when the piezoelectric element laminate 20 expands to
seat the diaphragm valve 11 on a valve seat 10, the valve spring 29
is compressed and repulsing force of the valve spring 29 acts on
the diaphragm valve 11 through the piezoelectric element laminate
20 and the diaphragm valve 11 is pressed against the valve seat 10
by the repulsing force.
Inventors: |
Sakurai, Toyonobu;
(Tsukuba-gun, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
SMC Corporation
Minato-ku
JP
|
Family ID: |
18643032 |
Appl. No.: |
09/836356 |
Filed: |
April 18, 2001 |
Current U.S.
Class: |
251/129.06 ;
251/331 |
Current CPC
Class: |
F16K 31/007
20130101 |
Class at
Publication: |
251/129.06 ;
251/331 |
International
Class: |
F16K 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2000 |
JP |
2000-134831 |
Claims
What is claimed is:
1. A piezoelectric fluid control valve comprising a valve mechanism
portion for opening and closing a fluid flow path by displacement
of a diaphragm valve and a piezoelectric operating portion for
opening and closing said diaphragm valve, wherein said valve
mechanism portion includes in a first casing said fluid flow paw
path, a valve seat provided at a midpoint of said fluid flow path,
said diaphragm valve for coming in contact with and separating from
said valve seat to open and close said flow path and applied with
elastic force in such a direction as to separate from said valve
seat, and a pressing member in contact with a back face of said
diaphragm valve to be displaced with said diaphragm valve in
opening and closing directions, said piezoelectric operating
portion includes in a second casing connected to said first casing
a piezoelectric element laminate for expanding due to application
of a voltage, a first member disposed on one end side of said
piezoelectric element laminate to transmit expanding force of said
piezoelectric element laminate to said pressing member to seat said
diaphragm valve on said valve seat, a second member disposed for
displacement on the other end side of said piezoelectric element
laminate, a spring seat displaced with said second member in
expansion of said piezoelectric element laminate, and a valve
spring elastically deformed by displacement of said spring seat to
repulse said piezoelectric element laminate, and a distortion
amount of said piezoelectric element laminate in expansion is set
at such a value as to press said pressing member to seat said
diaphragm valve on said valve seat and as to press said spring seat
in a reverse direction to elastically deform said valve spring.
2. A fluid control valve according to claim 1, wherein said first
casing of said valve mechanism portion and said cylindrical second
casing of said piezoelectric operating portion are connected to
each other with an end of said second casing fitted in a valve hole
of said first casing in which said valve seat is provided, an outer
peripheral portion of said diaphragm valve is airtightly sandwiched
and fixed between a tip end portion of said second casing and a
peripheral bottom portion of said valve hole, and said pressing
member is retained for displacement in said second casing.
3. A fluid control valve according to claim 1, wherein said spring
seat is mounted such that a position of said spring seat can be
adjusted by using an adjusting screw and said adjusting screw is
displaced by said second member.
4. A fluid control valve according to claim 1, wherein said second
casing of said piezoelectric operating portion has a first stopper
to which said pressing member is locked to thereby restrict an
opening stroke end of said diaphragm valve when said piezoelectric
element laminate is not energized and a second stopper to which
said spring seat is locked to thereby restrict an expanding end of
said valve spring.
5. A fluid control valve according to claim 1, wherein said
pressing member and said first member are in contact with each
other through a ball fitted in depressions formed at centers of
opposed faces.
6. A fluid control valve according to claim 1, wherein said first
casing has on an end face thereof opposite to a side connected to
said second casing a mounting face to be mounted to a unit
substrate and a plurality of fluid ports communicating with said
fluid flow path are provided to said mounting face.
7. A fluid control valve according to claim 1, wherein said first
casing of said valve mechanism portion and said cylindrical second
casing of said piezoelectric operating portion are connected to
each other with an end of said second casing fitted in a valve hole
of said first casing in which said valve seat is provided, an outer
peripheral portion of said diaphragm valve is airtightly sandwiched
and fixed between a tip end portion of said second casing and a
peripheral bottom portion of said valve hole, and said pressing
member is retained for displacement in said second casing; and said
second casing of said piezoelectric operating portionhas a first
stopper to which said pressing member is locked to thereby restrict
an opening stroke end of said diaphragm valve when said
piezoelectric element laminate is not energized and a second
stopper to which said spring seat is locked to thereby restrict an
expanding end of said valve spring.
8. A fluid control valve according to claim 7, wherein said spring
seat is mounted such that a position of said spring seat can be
adjusted by using an adjusting screw and said adjusting screw is
displaced by said second member.
9. A fluid control valve according to claim 7, wherein said
pressing member and said first member are in contact with each
other through a ball fitted in depressions formed at centers of
opposed faces.
10. A fluid control valve according to claim 7, wherein said first
casing has on an end face thereof opposite to a side connected to
said second casing a mounting face to be mounted to a unit
substrate and a plurality of fluid ports communicating with said
fluid flow path are provided to said mounting face.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a piezoelectric fluid
control valve which is the fluid control valve opened and closed by
piezoelectric elements and more specifically to a normally opened
piezoelectric fluid control valve in which an open state of the
valve is maintained in non-operation.
PRIOR ART
[0002] A piezoelectric fluid control valve which is a fluid control
valve opened and closed by a piezoelectric element laminate formed
by laminating a plurality of piezoelectric elements is known as
disclosed in Japanese Patent Application Laid-open No. 11-173440,
for example. This fluid control valve is of a type in which a valve
member is opened and closed by using expanding and contracting
forces of the piezoelectric element laminate, has an advantage that
large operating force can be obtained, and is generally formed as a
normally closed type. In the normally closed fluid control valve, a
closed state of the valve member is maintained by repulsing force
of a valve spring in non-operation when the piezoelectric element
laminate is not energized and the valve spring is compressed by
expanding force of the piezoelectric element laminate to open the
valve member when the piezoelectric element laminate is
energized.
[0003] However, because a normally opened fluid control valve is
advantageous in some cases depending on use of the fluid control
valve, the fluid control valve having a normally opened structure
is also proposed. In Japanese Patent Application Laid-open No.
11-108227, an example of such a normally opened fluid control valve
is disclosed. This example is of a type in which a valve seat is
opened and closed with a metal diaphragm valve. In non-operation
when a piezoelectric element laminate is not applied with a
voltage, the piezoelectric element laminate is displaced in such a
direction as to separate from the metal diaphragm valve by
repulsing force of a return spring and, as a result, the metal
diaphragm valve opens the valve seat with its own elastic force.
When the piezoelectric element laminate is applied with the
voltage, the piezoelectric element laminate compresses the return
spring with its expanding force to press the metal diaphragm valve
against the valve seat.
[0004] However, because the diaphragm valve is directly pressed
against the valve seat by the large expanding force of the
piezoelectric element laminate in the prior-art normally opened
fluid control valve as described above, the diaphragm valve and the
valve seat are likely to be deformed or damaged and there are
problems with durability and safety.
DISCLOSURE OF THE INVENTION
[0005] It is a technical object of the present invention to provide
a normally opened piezoelectric fluid control valve with a rational
design structure and excellent durability in which valve closing
force can be obtained by repulsing force of a spring by converting
expanding force of a piezoelectric element laminate into the
repulsing force of the spring.
[0006] To achieve the above object, according to the present
invention, there is provided a piezoelectric fluid control valve
comprising a valve mechanism portion for opening and closing a
fluid flow path by displacement of a diaphragm valve and a
piezoelectric operating portion for opening and closing the
diaphragm valve. The valve mechanism portion includes in a first
casing the fluid flow paw path, a valve seat provided in the fluid
flow path, the diaphragm valve for coming in contact with and
separating from the valve seat to open and close the fluid flow
path, and a pressing member in contact with a back face of the
diaphragm valve. The piezoelectric operating portion includes in a
second casing a piezoelectric element laminate for expanding due to
application of a voltage, a first member for transmitting expanding
force of the piezoelectric element laminate to the pressing member
to seat the diaphragm valve on the valve seat, a spring seat
displaced with a second member in expansion of the piezoelectric
element laminate, and a valve spring elastically deformed by
displacement of the spring seat, and a distortion amount of the
piezoelectric element laminate in expansion is set at such a value
as to press the pressing member to seat the diaphragm valve on the
valve seat and as to press the spring seat in a reverse direction
to elastically deform the valve spring.
[0007] In the fluid control valve of the invention having the above
structure, in non-operation, the diaphragm valve separates from the
valve seat due to its own elastic force to maintain an open state
of the valve. If a certain amount of voltage is applied to the
piezoelectric element laminate in this state, the piezoelectric
element laminate expands in an axial direction, pushes the pressing
member to seat the diaphragm valve on the valve seat, and pushes
the spring seat in the reverse direction to elastically deform the
valve spring. As a result, the repulsing force of the valve spring
acts on the diaphragm valve through the piezoelectric element
laminate and the diaphragm valve is pressed against the valve seat
by the repulsing force. In other words, expanding force of the
piezoelectric element laminate is converted into the repulsing
force of the valve spring and the force for seating the diaphragm
valve is obtained by the repulsing force. Therefore, because the
large expanding force of the piezoelectric element laminate does
not directly act on the diaphragm valve and the valve seat, the
diaphragm valve and the valve seat are not deformed or damaged and
durability and safety are improved.
[0008] According to a preferable concrete embodiment of the
invention, the first casing and the second casing are connected to
each other with an end of the second casing fitted in a valve hole
of the first casing, an outer peripheral portion of the diaphragm
valve is airtightly sandwiched and fixed between a tip end portion
of the second casing and a peripheral bottom portion of the valve
hole, and the pressing member is retained for displacement in the
second casing.
[0009] According to another concrete embodiment of the invention,
the spring seat is mounted such that a position of the spring seat
can be adjusted by using an adjusting screw and the adjusting screw
is displaced by the second member.
[0010] It is preferable in the invention that the second casing of
the piezoelectric operating portion has a first stopper to which
the pressing member is locked to thereby restrict an opening stroke
end of the diaphragm valve when the piezoelectric element laminate
is not energized and a second stopper to which the spring seat is
locked to thereby restrict an expanding end of the valve
spring.
[0011] In the invention, it is possible that the pressing member
and the first member are in contact with each other through a ball
fitted in depressions formed at centers of opposed faces.
[0012] According to another concrete embodiment of the invention,
the first casing has on an end face thereof opposite to a side
connected to the second casing a mounting face to be mounted to a
unit substrate and a plurality of fluid ports communicating with
the fluid flow path are provided to the mounting face.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a sectional view of a non-operating state showing
an embodiment of a piezoelectric fluid control valve according to
the present invention.
[0014] FIG. 2 is a sectional view of an operating state of the
fluid control valve shown in FIG. 1.
[0015] FIG. 3 is a diagram showing an operating state of the fluid
control valve of the invention.
DETAILED DESCRIPTION
[0016] FIG. 1 shows a preferable representative embodiment of a
piezoelectric fluid control valve according to the present
invention. This fluid control valve is of a normally opened type in
which an open state of the valve is maintained in non-operation and
is formed by integrally connecting a valve mechanism portion 1 for
controlling a flow of fluid such as process gas and a piezoelectric
operating portion 2 for operating the valve mechanism portion
1.
[0017] The valve mechanism portion 1 has a first casing 5
substantially in a circular-cylindrical shape. An end face of axial
one end of the first casing 5 is formed with a mounting face 6 to
be mounted to a unit substrate 4 of a gas control unit in a
semiconductor wafer producing apparatus or the like and the
mounting face 6 is formed with a plurality of fluid ports 7 and 8.
In the first caging 5, flow paths 7a and 8a for connecting the
ports 7 and 8, a valve hole 9 into which the flow paths 7a and 8a
open, and a valve seat 10 for surrounding an opening portion of the
one flow path 7a in the valve hole 9 are formed. In the valve hole
9, a diaphragm valve 11 for coming in contact with and separating
from the valve seat 10 to open and close the flow path 7a is
provided. The diaphragm valve 11 is made of metal and is fixed in
the valve hole 9 by airtightly sandwiching an outer peripheral
portion of the diaphragm valve 11 between a second casing 15 of the
piezoelectric operating portion 2 and a valve hole peripheral
bottom portion and elastic force in such a direction that the
diaphragm valve 11 separates from the valve seat 10 is applied to
the diaphragm valve 11.
[0018] A pressing member 13 in contact with the diaphragm valve 11
to be displaced with the diaphragm valve 11 in opening and closing
directions of the diaphragm valve 11 is disposed on a back face of
the diaphragm valve 11. The pressing member 13 is housed in a tip
end of the cylindrical second casing 15 and is locked to a first
stopper 14 at the tip end of the second casing 15 in opening of the
diaphragm valve 11 to thereby restrict an opening stroke end of the
diaphragm valve 11.
[0019] On the other hand, the piezoelectric operating portion 2 has
the second casing 15. By screwing a nut member 18 engaged with a
flange portion 15a of an outer periphery over the first casing 5
with a tip end portion of the second casing 15 fitted in the valve
hole 9 of the first casing 5, the second casing 15 is coaxially
connected to the first casing 5.
[0020] In the second casing 15, a piezoelectric element laminate 20
which is formed by laminating a plurality of piezoelectric elements
20a and expands in an axial direction due to application of a
voltage and cap-shaped first and second members 21 and 22 which are
respectively in contact with opposite ends of the piezoelectric
element laminate 20 and are axially displaced as the piezoelectric
element laminate 20 expands and contracts are disposed. The first
member 21 is fitted with a tip end portion of the piezoelectric
element laminate 20 and transmits expanding force of the
piezoelectric element laminate 20 to the pressing member 13 to seat
the diaphragm valve 11 on the valve seat 10. The first member 21
and the pressing member 13 are in contact with each other through a
ball 23 fitted in depressions respectively formed at centers of
opposed faces. On the other hand, the second member 22 is mounted
to a rear end portion of the piezoelectric element laminate 20 and
a spring mechanism 25 is provided between the second member 22 and
a plate 24 fixed to an end portion of the second casing 15.
[0021] The valve spring mechanism 25 includes an adjusting screw 27
in contact with an outer end face of the second member 22 to be
displaced with the second member 22 in an axial direction of the
second casing 15, a spring seat 28 screwed over the adjusting screw
27 such that a position of the spring seat 28 is adjustable, and a
coil-shaped valve spring 29 provided between the spring seat 28 and
the plate 24. The spring seat 28 restricts a maximum expanding
position of the valve spring 29 by being locked to a second stopper
30 provided to a rear end portion of the second casing 15 in
non-operation of the control valve to thereby prevent repulsing
force of the valve spring 29 from acting on the piezoelectric
element laminate 20 and the diaphragm valve 11 and is pushed and
moved by the piezoelectric element laminate 20 through the second
member 22 in such a direction as to separate from the second
stopper 30 to elastically deform the valve spring 29 in operation
of the control valve to thereby cause the repulsing force of the
valve spring 29 to act on the piezoelectric element laminate
20.
[0022] As shown in FIG. 3, a distortion amount (expanding length) a
of the piezoelectric element laminate 20 in expansion is set to be
equal to or greater than the sum of an opening/closing stroke b of
the diaphragm valve 11 and a displacement amount c of the spring
seat 28. As a result, the piezoelectric element laminate 20 seats
the diaphragm valve 11 on the valve seat 10 and, at the same time,
separates the spring seat 28 from the second stopper 30 to
elastically deform the valve spring 29 in expansion of the
piezoelectric element laminate 20.
[0023] A reference numeral 31 in the drawing designates a lead for
feeding the piezoelectric element laminate 20 which is led out of
the second casing 15 through holes formed in the second member 22,
the adjusting screw 27, and the plate 24 and is connected to a
control circuit 32. The control circuit 32 can be provided inside a
cover 33 mounted to the second casing 15 as shown with a chain line
in FIG. 1, for example. In this case, the control circuit 32 is
connected to a controller (not shown) through a connector 34
provided to the cover 33.
[0024] In the fluid control valve having the above structure, in
non-operation, i.e., in a state in which no voltage is applied to
the piezoelectric element laminate 20 or a tiny voltage with which
expansion required to maintain contact between the first member 21
and the pressing member 13 and between the second member 22 and the
adjusting screw 27 is applied to the piezoelectric element laminate
20, the piezoelectric element laminate 20 is not in a required
expanding state as shown in FIG. 1. Therefore, the diaphragm valve
11 separates from the valve seat 10 due to its own elastic force to
maintain an open state of the valve. In this state, the pressing
member 13 is locked to the first stopper 14, the spring seat 28 is
locked to the second stopper 30, and the repulsing force of the
valve spring 29 is not acting on the piezoelectric element laminate
20 and the diaphragm valve 11.
[0025] If a certain amount of voltage is applied to the
piezoelectric element laminate 20 in this state, the piezoelectric
element laminate 20 expands in the axial direction, pushes the
pressing member 13 through the first member 21 to thereby seat the
diaphragm valve 11 on the valve seat 10, and pushes the spring seat
28 in a reverse direction to separate the spring seat 28 from the
second stopper 30 to thereby elastically deform the valve spring 29
as shown in FIG. 2. As a result, the repulsing force of the valve
spring 29 acts on the diaphragm valve 11 through the piezoelectric
element laminate 20 and the diaphragm valve 11 is pressed against
the valve seat 10 by the repulsing force. In other words, expanding
force of the piezoelectric element laminate 20 is converted into
the repulsing force of the valve spring 29 and the force for
seating the diaphragm valve 11 on the valve seat 10 is obtained by
the repulsing force. Therefore, as can be seen from FIG. 3, because
the large expanding force of the piezoelectric element laminate 20
does not directly act on the diaphragm valve 11 and the valve seat
10, the diaphragm valve 11 and the valve seat 10 are not deformed
or damaged and durability and safety are improved.
[0026] Although the coil spring is shown as the valve spring 29 in
the above embodiment, the valve spring 29 may be a leaf spring,
rubber, or other elastic members.
[0027] As described above, according to the invention, it is
possible to obtain a normally opened piezoelectric fluid control
valve which has a rational design structure and excellent
durability and in which the force for closing the valve can be
obtained by the repulsing force of the spring by converting the
expanding force of the piezoelectric element laminate into the
repulsing force of the spring.
* * * * *