U.S. patent application number 16/593451 was filed with the patent office on 2020-09-10 for fluid control device and pump.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Atsuhiko HIRATA, Yukiharu KODAMA.
Application Number | 20200284250 16/593451 |
Document ID | / |
Family ID | 1000005047070 |
Filed Date | 2020-09-10 |
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United States Patent
Application |
20200284250 |
Kind Code |
A9 |
HIRATA; Atsuhiko ; et
al. |
September 10, 2020 |
FLUID CONTROL DEVICE AND PUMP
Abstract
A pump (1) includes a vibrating plate (15) that has a central
part (21), a frame part (22), and connecting parts (23 to 26), a
piezoelectric element (16) that is stacked over the central part
(21) and configured to cause flexural vibrations to occur
concentrically from the central part (21) to the connecting parts
(23 to 26), and an opposed plate (13) that is stacked over the
frame part (22) and positioned facing each of the connecting parts
(23 to 26) with a spacing therebetween. The vibrating plate (15)
has such a resonant mode that an antinode occurs in each of the
central part (21) and the connecting parts (23 to 26). The opposed
plate (13) has, at positions facing the connecting parts (23 to
26), a plurality of channel holes (39 to 43) through which a fluid
flows.
Inventors: |
HIRATA; Atsuhiko; (Kyoto,
JP) ; KODAMA; Yukiharu; (Kyoto, JP) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Kyoto |
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JP |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20200032786 A1 |
January 30, 2020 |
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Family ID: |
1000005047070 |
Appl. No.: |
16/593451 |
Filed: |
October 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15241576 |
Aug 19, 2016 |
10480502 |
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16593451 |
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PCT/JP2015/054531 |
Feb 19, 2015 |
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15241576 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 43/04 20130101;
F04B 45/047 20130101; F04B 43/046 20130101 |
International
Class: |
F04B 45/047 20060101
F04B045/047; F04B 43/04 20060101 F04B043/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2014 |
JP |
2014-031372 |
Sep 4, 2014 |
JP |
2014-180355 |
Claims
1. A fluid control device comprising: an inlet for sucking fluid
from an external space into the fluid control device, an outlet for
discharging the fluid from within the fluid control device to the
external space, a vibrating plate having a circular central part, a
frame part surrounding the central part, and a plurality of
connecting parts connecting between the central part and the frame
part, the connecting parts being located along a circle that is
concentric with the central part; a driver stacked over the central
part, the driver being configured to vibrate the vibrating plate in
a flexural manner from the central part to the plurality of
connecting parts; and an opposed plate stacked over the frame part,
the opposed plate being spaced apart from and opposed to at least
the plurality of connecting parts, wherein the opposed plate has a
plurality of channel holes though which a fluid flows, each of the
channel holes being located at a position opposed to a respective
connecting part of the plurality of connecting parts, and wherein
during operation of the fluid control device, the fluid is sucked
through the inlet, flows through the plurality of channel holes,
and is discharged through the outlet.
2. The fluid control device according to claim 1, wherein the
vibrating plate having a plurality of openings defined by the
plurality of connecting parts, the central part, and the frame
part.
3. The fluid control device according to claim 1, wherein each
connecting part of the plurality of connecting parts includes, at a
position opposed to a respective channel hole of the plurality of
channel holes, a striking part having a width is locally increased
as viewed from the respective channel hole.
4. The fluid control device according to claim 1, wherein each
connecting part of the plurality of connecting parts includes, at a
position opposed to a respective channel hole of the plurality of
channel holes, a projection that projects toward the respective
channel hole.
5. The fluid control device according to claim 1, wherein the
opposed plate includes, around each of the plurality of channel
holes, a projection projecting toward the vibrating plate.
6. The fluid control device according to claim 1, wherein the
opposed plate includes a movable part bendable and provided around
each of the plurality of channel holes, and a restraining part
restraining an area around the movable part.
7. The fluid control device according to claim 6, wherein the
movable part has such a shape in a plan view having a major axis
extending in a direction of producing antinodes uniformly in the
plurality of connecting parts, and a minor axis extending in a
direction orthogonal to the major axis.
8. The fluid control device according to claim 6, further
comprising a channel part stacked over a side of the opposed plate
opposite to the vibrating plate, the channel part having: a
plurality of channels communicating with the plurality of channel
holes of the opposed plate, each channel including an opening and
an extension extended laterally from the opening, the opening being
opposed to a respective channel hole of the plurality of channel
holes and an area around the respective channel hole, and a
plurality of holes opened to the external space each hole
communicating with a respective opening of the channels through the
extension extended laterally from the respective opening.
9. The fluid control device according to claim 8, wherein at least
one of the channel part and the opposed plate has a coefficient of
linear expansion substantially equal to a coefficient of linear
expansion of the vibrating plate.
10. The fluid control device according to claim 1, wherein the
opposed plate is stacked over the vibrating plate by using an
adhesive, and wherein the opposed plate has an opening that extends
along an inner boundary of the frame part of the vibrating
plate.
11. The fluid control device according to claim 1, wherein the
vibrating plate and the opposed plate are each made of an
electrically conductive material, wherein the opposed plate and the
vibrating plate are stacked by using an adhesive containing
electrically conductive particles, and wherein the electrically
conductive particles have a particle diameter equivalent to a
spacing between the opposed plate and the vibrating plate.
12. The fluid control device according to claim 1, further
comprising: an insulating layer stacked over the frame part, the
insulating layer being positioned over a side of the vibrating
plate over which the driver is stacked; and a power feeding plate
stacked over the vibrating plate with the insulating layer
interposed between the power feeding plate and the vibrating plate,
the power feeding plate having an internal connection terminal
formed in a part of the power feeding plate, the internal
connection terminal being connected to the driver.
13. The fluid control device according to claim 12, wherein the
insulating layer includes an insulating coating located between the
vibrating plate and the power feeding plate.
14. The fluid control device according to claim 12, wherein the
insulating layer includes an adhesive mixed with non-electrically
conductive particles.
15. The fluid control device according to claim 12, further
comprising a metal plate stacked over the frame part of the
vibrating plate.
16. The fluid control device according to claim 12, wherein the
frame part of the vibrating plate has a groove located on a side of
the vibrating plate over which the driver is stacked, and wherein
the insulating layer and the power feeding plate are disposed in
the groove.
17. The fluid control device according to claim 1, wherein the
opposed plate has an additional channel hole at a position facing
the central part.
18. The fluid control device according to claim 1, further
comprising a stacking plate further stacked over the vibrating
plate and the driver, wherein the vibrating plate, the driver, and
the stacking plate comprise three layers including an upper layer,
a middle layer, and a lower layer, and a magnitude relationship of
a coefficient of linear expansion of the middle layer with respect
to a coefficient of linear expansion of the upper layer is
identical to a magnitude relationship of a coefficient of linear
expansion of the middle layer with respect to a coefficient of
linear expansion of the lower layer.
19. The fluid control device according to claim 18, wherein among
the three layers including the vibrating plate, the driver, and the
stacking plate, a component corresponding to a layer in contact
with the driver has a coefficient of linear expansion greater than
a coefficient of linear expansion of the driver.
20. The fluid control device according to claim 1, wherein the
opposed plate includes a first opposed plate and a second opposed
plate, the first opposed plate being disposed facing one principal
face of the vibrating plate, the second opposed plate being
disposed facing another principal face of the vibrating plate.
21. The fluid control device according to claim 1, wherein the
driver includes a first driver and a second driver, the first
driver being disposed facing one principal face of the vibrating
plate, the second driver being disposed facing another principal
face of the vibrating plate.
22. A pump comprising: an inlet for sucking fluid from an external
space into the pump, an outlet for discharging the fluid from
within the pump to the external space, a vibrating plate having a
circular central part, a frame part surrounding the central part,
and plurality of connecting parts connecting between the central
part and the frame part, the connecting parts being located along a
circle that is concentric with the central part; a driver stacked
over the central part, the driver being configured to vibrate the
vibrating plate in a flexural manner from the central part to the
plurality of connecting parts; and an opposed plate stacked over
the frame part, the opposed plate being spaced apart from and
opposed to at least the plurality of connecting parts, wherein the
opposed plate has a plurality of channel holes through which the
fluid flows, each of the channel holes being located at a position
opposed to a respective connecting part of the plurality of
connecting parts, wherein the pump further comprises a pump chamber
accommodating the vibrating plate and the driver, wherein the
opposed plate forms a part of an inner wall of the pump chamber,
and, wherein during operation of the pump, the fluid is sucked
through the inlet, flows through the plurality of channel holes,
and is discharged through the outlet.
Description
[0001] This is a Division of U.S. patent application Ser. No.
15/241,576 filed on Aug. 19, 2016 which claims priority from
Japanese Patent Application No. 2014-180355 filed on Sep. 4, 2014,
and claims priority from Japanese Patent Application No 2014-031372
filed on Feb. 21, 2014. The contents of these applications are
incorporated herein by reference in their entireties.
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
[0002] The present disclosure relates to a fluid control device
that controls the flow of fluid by using a driver in which
vibration is produced, and a pump that includes the fluid control
device and sucks and discharges fluid.
Description of the Related Art
[0003] Pumps that utilize vibration of a piezoelectric element are
commonly used (see, for example, Patent Documents 1 and 2). Such
pumps are used for purposes such as directing outside air on a
component that has risen in temperature to cool the component, and
conveying fluid such as oxygen in a fuel cell.
[0004] FIG. 16 schematically illustrates major components of a
conventional pump. A conventional pump 101 illustrated in FIG. 16
includes a housing 102, a vibrating plate 103, an opposed plate
104, and a piezoelectric element 105. The vibrating plate 103, the
opposed plate 104, and the piezoelectric element 105 are
accommodated in the housing 102. The opposed plate 104 defines a
pump chamber 110 inside the housing 102. The vibrating plate 103,
which is provided inside the pump chamber 110, is positioned facing
the opposed plate 104 with a spacing therebetween. The outer
peripheral portion of the vibrating plate 103 is elastically
supported by the housing 102. The piezoelectric element 105 is
stuck on the vibrating plate 103, forming an actuator 111 together
with the vibrating plate 103. The housing 102 has, on its upper
face, a channel hole 112 that provides communication between the
inside and outside of the pump chamber 110. The opposed plate 104
is provided with a channel hole 113 that communicates with the
inside of the pump chamber 110. The housing 102 has, on its lower
face, channel holes 114 that communicate with the pump chamber 110
through the channel hole 113 and also with the outside.
[0005] When voltage is applied to the piezoelectric element 105 of
the pump 101, the vibrating plate 103 undergoes flexural vibration
in the thickness direction as the piezoelectric element 105
attempts to expand or contract in the in-plane direction. This
creates pressure fluctuations in the fluid layer that is sandwiched
between the vibrating plate 103 and the opposed plate 104 inside
the pump chamber 110, producing a fluid flow such that the fluid is
sucked into the pump chamber 110 through the channel holes 114 and
113 and the fluid is discharged to the channel hole 112 from the
pump chamber 110. [0006] Patent Document 1: Japanese Unexamined
Patent Application Publication No. 2013-068215 [0007] Patent
Document 2: Japanese Unexamined Patent Application Publication No.
2013-053611
BRIEF SUMMARY OF THE DISCLOSURE
[0008] There are demands for reduced physical size and improved
driving efficiency of this type of pump. Unfortunately, a reduction
in the physical size of the pump tends to lead to a decrease in
driving efficiency. Thus, with conventional structures, it is
difficult to achieve both reduced physical size and improved
driving efficiency at the same time.
[0009] Accordingly, it is an object of the present disclosure to
provide a fluid control device and a pump having improved driving
efficiency over conventional designs without an increase in
physical size, or reduced physical size over conventional designs
without a decrease in driving efficiency.
[0010] A fluid control device according to the present disclosure
includes a vibrating plate that has a central part, a frame part
surrounding the central part, and a connecting part connecting
between the central part and the frame part, a driver stacked over
the central part, the driver being configured to vibrate the
vibrating plate in a flexural manner from the central part to the
connecting part, and an opposed plate stacked over the frame part,
the opposed plate being positioned facing at least the connecting
part with a spacing between the opposed plate and the connecting
part. The vibrating plate has a resonant mode such that an antinode
occurs in each of the central part and the connecting part. The
opposed plate has a plurality of channel holes though which a fluid
flows, the channel holes being each located at a position facing
the connecting part.
[0011] According to this configuration, channel holes are each
positioned facing the connecting part where an antinode is formed.
As a result, the total amount of parallel fluid flows through the
channel holes can be increased. This allows for an improvement in
driving efficiency, thus enabling a reduction in physical size
while achieving a desired flow rate or pressure.
[0012] The connecting part may include, at a position facing each
of the channel holes, a striking part that is locally increased in
width as viewed from the channel hole. This configuration allows
the amplitude of vibration of the striking part to be increased,
without decreasing the area over which the vibrating plate
(striking part) and the fluid are positioned facing each other in
the vicinity of the channel holes that directly contribute to fluid
control. This makes it possible to reduce unwanted load on the
vibrating plate and the driver, thus improving driving
efficiency.
[0013] The connecting part may include a projection that is
provided at a position facing each of the channel holes and
projects toward the channel hole. Alternatively, the opposed plate
may include, around each of the channel holes, a projection that
projects toward the vibrating plate. As a result of these
configurations, in comparison to the spacing provided between the
vibrating plate and the opposed plate in the vicinity of the
channel holes that directly contribute to fluid control, the
spacing between the vibrating plate and the opposed plate in other
areas can be increased. This makes it possible to reduce unwanted
load on the vibrating plate and the driver to further improve
driving efficiency.
[0014] The opposed plate may include a movable part capable of
flexion provided around each of the channel holes, and a
restraining part that restrains an area around the movable part.
For example, the movable part can be provided by forming the
opposed plate with reduced thickness in the movable part and with
increased thickness in the restraining part.
[0015] Alternatively, for example, the movable part can be formed
by providing the channel plate, which is stacked over the side of
the opposed plate opposite to the vibrating plate, with an opening
that is positioned facing each of the channel holes of the opposed
plate and the area around the channel hole. With this
configuration, vibration of the connecting part also causes the
movable part positioned facing the connecting part to vibrate in
response to this vibration. The vibration of the movable part and
the vibration of the connecting part then couple, allowing fluid to
flow through each channel hole in a fixed direction even without
the presence of a structure that regulates the direction of fluid
flow, such as a check valve. This facilitates fluid flow while
eliminating the need for a component such as a check valve, thus
allowing for improved driving efficiency.
[0016] Preferably, the movable part has such a shape in plan view
that has a major axis extending in a direction in which antinodes
are produced uniformly in the connecting part, and a minor axis
extending in a direction orthogonal to the major axis, for example,
an elliptical shape or an oval shape. This configuration allows the
movable part to be increased in dimension in the major axis
direction while preventing a decrease in the natural frequency of
the movable part. As a result, the amplitude of vibration occurring
near each end portion along the major axis of the movable part can
be increased in comparison to when the movable part has the shape
of a perfect circle. When vibration causes both principal faces of
the connecting part positioned facing the movable part to undergo
expansion or contraction in the minor axis direction, an opposite
contraction or expansion is produced in the major axis direction.
This creates such a vibration in the connecting part that causes
the connecting part to flex as viewed in the minor axis direction.
This vibration has maximum amplitude at each end along the major
axis of the connecting part. Consequently, if vibration produced in
the movable part positioned facing the connecting part has a small
amplitude at each end portion along the major axis of the movable
part, a collision with the connecting part can occur. Accordingly,
the amplitude of vibration produced at each end portion along the
major axis of the movable part is increased as described above,
thus reducing the risk of a collision with the connecting part
positioned facing the movable part. This makes it possible to, for
example, prevent occurrence of abnormal vibration or noise, or
prevent a decrease in pressure caused by such a collision.
[0017] The channel of the channel part includes an opening that is
positioned facing each of the channel holes of the opposed plate
and an area around the channel hole, an extension that is extended
laterally from the opening, and a channel hole that is open to an
external space and communicates with the opening through the
extension. This configuration allows each channel hole of the
opposed plate and the channel hole of the cover plate to be
positioned away from each other in plan view, thus reducing leakage
of vibrating sound generated by vibration of the vibrating
plate.
[0018] Preferably, the components stacked over the frame part of
the vibrating plate each have a coefficient of linear expansion
substantially equal to the coefficient of linear expansion of the
vibrating plate. This makes it possible to further reduce
deformation resulting from a difference in coefficient of linear
expansion.
[0019] The opposed plate may be stacked over the vibrating plate by
using an adhesive containing electrically conductive particles.
Preferably, in this case, the electrically conductive particles
have a diameter equivalent to the spacing between the opposed plate
and the vibrating plate. This configuration ensures a uniform,
desired spacing between the opposed plate and the vibrating plate
even when the opposed plate and the vibrating plate are bonded
together with an adhesive. This makes it possible to reduce
variations in the performance of the fluid control device.
[0020] Preferably, the vibrating plate and the opposed plate are
each made of an electrically conductive material, the opposed plate
is stacked over the vibrating plate by using an adhesive containing
electrically conductive particles, and the electrically conductive
particles have a diameter equivalent to the spacing between the
opposed plate and the vibrating plate. This configuration ensures a
uniform, desired spacing between the opposed plate and the
vibrating plate even when the opposed plate and the vibrating plate
are bonded together with an adhesive. This makes it possible to
reduce variations in the performance of the fluid control device.
Further, power can be fed to the driver through the opposed
plate.
[0021] The fluid control device may include an insulating layer
stacked over the frame part, the insulating layer being positioned
over a side of the vibrating plate over which the driver is
stacked, and a power feeding plate stacked over the vibrating plate
with the insulating layer interposed between the power feeding
plate and the vibrating plate, the power feeding plate having an
internal connection terminal formed in a part of the power feeding
plate, the internal connection terminal being connected to the
driver. With this configuration, the presence of the insulating
layer prevents the power feeding plate and the vibrating plate from
being brought into electrical continuity with each other, thus
allowing power to be fed to the driver through the power feeding
plate.
[0022] In this case, the insulating layer may include an adhesive
mixed with non-electrically conductive particles. With this
configuration, the non-electrically conductive particles reliably
prevent electrical continuity between the power feeding plate and
the vibrating plate.
[0023] The insulating layer may include an insulating coating
provided between the vibrating plate and the power feeding plate.
With this configuration, the insulating coating reliably prevents
electrical continuity between the power feeding plate and the
vibrating plate. The presence of the insulating coating eliminates
the need for the adhesive to contain non-electrically conductive
particles, thus allowing for easy construction of the insulating
layer.
[0024] The fluid control device may further include a metal plate
stacked over the frame part of the vibrating plate. With this
configuration, even when the insulating layer stacked between the
vibrating plate and the power feeding plate is made of a soft
material with a low density and a low Young's modulus, such as
resin, the presence of the metal plate between the vibrating plate
and the insulating layer allows the connecting part of the
vibrating plate to be reliably secured in place, thus preventing
vibration from leaking to other components through the frame part.
This prevents driving efficiency or other performance features of
the fluid control device from decreasing. The insulating layer may
be formed by a coating of insulating film applied on the surface of
the metal plate. In this case as well, stacking the vibrating plate
and the insulating layer with the metal plate interposed
therebetween allows the connecting part of the vibrating plate to
be reliably secured in place.
[0025] The frame part of the vibrating plate may have a groove
located on a side of the vibrating plate over which the driver is
stacked, and the insulating layer and the power feeding plate may
be disposed in the groove. This configuration allows the thickness
of the device to be reduced.
[0026] Preferably, the opposed plate may have a channel hole also
at a position facing the central part. This configuration allows
the number of channel holes to be further increased, thus enabling
a further improvement in features such as flow rate and driving
efficiency.
[0027] Preferably, the fluid control device further includes a
stacking plate further stacked over the vibrating plate and the
driver, the vibrating plate, the driver, and the stacking plate
form three layers including an upper layer, a middle layer, and a
lower layer, and the magnitude relationship of the coefficient of
linear expansion of the middle layer with respect to the
coefficient of linear expansion of the upper layer is identical to
the magnitude relationship of the coefficient of linear expansion
of the middle layer with respect to the coefficient of linear
expansion of the lower layer. This configuration makes it possible
to reduce deformation in components such as the vibrating plate and
the driver resulting from the difference in coefficient of linear
expansion between the vibrating plate and the driver.
[0028] Preferably, among the three layers including the vibrating
plate, the driver, and the stacking plate, a component
corresponding to a layer in contact with the driver has a
coefficient of linear expansion greater than the coefficient of
linear expansion of the driver. This configuration causes
compressive stress to be exerted on the driver, thus reducing
breakage of the driver. If the driver is present in the middle
layer, compressive stress can be uniformly exerted on the driver,
thus reducing breakage of the driver compared to cases such as when
a two-layer construction is employed or when the driver is disposed
in the upper layer or lower layer.
[0029] Preferably, the opposed plate includes a first opposed plate
and a second opposed plate, the first opposed plate being disposed
facing one principal face of the vibrating plate, the second
opposed plate being disposed facing the other principal face of the
vibrating plate. This configuration allows a greater number of
channel holes to be provided in the opposed plate, thus enabling a
further improvement in features such as flow rate and driving
efficiency.
[0030] Desirably, the driver includes a first driver and a second
driver, the first driver being disposed facing one principal face
of the vibrating plate, the second driver being disposed facing the
other principal face of the vibrating plate. This configuration
makes it possible to reduce deformation in the stack of the
vibrating plate and the driver resulting from the difference in
coefficient of linear expansion between the vibrating plate and the
driver, while increasing the amplitude of vibration of the
vibrating plate. This enables a further improvement in features
such as flow rate and driving efficiency.
[0031] Preferably, the pump according to the present disclosure
includes the above-mentioned fluid control device, has a pump
chamber that accommodates the vibrating plate and the driver, and
the opposed plate forms a part of the inner wall of the pump
chamber.
[0032] According to the present disclosure, channel holes are each
positioned facing the connecting part of the vibrating plate,
allowing for an increase in the amount of fluid entering or exiting
through the channel holes. This enables an improvement in driving
efficiency without an increase in physical size, or enables a
reduction in physical size without a decrease in driving
efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0033] FIG. 1 is an external perspective view of a pump according
to a first embodiment of the present disclosure.
[0034] FIG. 2 is an exploded perspective view of the pump according
to the first embodiment of the present disclosure.
[0035] Each of FIG. 3A-3C illustrates a vibrating plate and a
piezoelectric element according to the first embodiment of the
present disclosure.
[0036] FIG. 4 is a cross-sectional view of the pump according to
the first embodiment of the present disclosure.
[0037] Each of FIGS. 5A and 5B schematically illustrates the
operation of a fluid control part according to the first embodiment
of the present disclosure.
[0038] FIG. 6 is an exploded perspective view of a pump according
to a second embodiment of the present disclosure.
[0039] Each of FIG. 7A-7D is a plan view of a vibrating plate, an
opposed plate, a channel plate, and a cover plate according to the
second embodiment of the present disclosure.
[0040] Each of FIGS. 8A and 8B schematically illustrates how the
vibrating plate and the opposed plate vibrate according to the
second embodiment of the present disclosure.
[0041] FIG. 9 is an exploded perspective view of a pump according
to a third embodiment of the present disclosure.
[0042] FIG. 10 is an exploded perspective view of a pump according
to a fourth embodiment of the present disclosure.
[0043] FIG. 11 is an exploded perspective view of a pump according
to a fifth embodiment of the present disclosure.
[0044] Each of FIGS. 12A-12C illustrates a pump according to sixth,
seventh and eighth embodiments of the present disclosure.
[0045] FIGS. 13A-13C illustrates a pump according to ninth, tenth
and eleventh embodiments of the present disclosure.
[0046] FIG. 14 is an exploded perspective view of a pump according
to a twelfth embodiment of the present disclosure.
[0047] FIGS. 15A and 15B are an enlarged perspective view of the
pump according to the twelfth embodiment of the present
disclosure.
[0048] FIG. 16 illustrates major components of a conventional
pump.
DETAILED DESCRIPTION OF THE DISCLOSURE
First Embodiment
[0049] Hereinafter, a pump 1 according to a first embodiment of the
present disclosure will be described with reference to an air pump
that sucks gas as an example.
[0050] FIG. 1 is an external perspective view of the pump 1. As
illustrated in FIG. 1, the pump 1 includes a housing 2, and
external connection terminals 3 and 4. The external connection
terminals 3 and 4 are each connected to an external power source,
and applied with an alternating-current drive signal. The housing
2, which has a principal face (upper principal face) 5 and a
principal face (lower principal face) 6, is a hexahedron with a
small thickness between the principal faces 5 and 6. The housing 2
also has a channel hole 50 provided at the upper principal face 5,
and channel holes 31, 32, 33, and 34 (see FIG. 2) provided at the
lower principal face 6.
[0051] FIG. 2 is an exploded perspective view of the pump 1. As
illustrated in FIG. 2, the pump 1 includes the following components
stacked in the order stated below: a cover plate 11, a channel
plate 12, an opposed plate 13, an adhesion layer 14 (see FIG. 4), a
vibrating plate 15, a piezoelectric element 16, an insulating plate
17, a power feeding plate 18, a spacer plate 19, and a lid plate
20.
[0052] The cover plate 11, which is exposed at the lower principal
face 6 of the housing 2, is stuck on the lower face of the channel
plate 12 by using adhesive (not illustrated) or other materials.
The cover plate 11 has the channel holes 31, 32, 33, and 34
provided at the lower principal face 6 of the housing 2. The
channel holes 31, 32, 33, and 34 have a circular shape. In the
first embodiment, the channel holes 31, 32, 33, and 34 are inlets
for sucking gas from the external space.
[0053] The channel plate 12 is stacked between the cover plate 11
and the opposed plate 13. The channel plate 12 is stuck on the
upper face of the cover plate 11 and the lower face of the opposed
plate 13 by using adhesive (not illustrated) or other materials.
The channel plate 12 has openings 35, 36, 37, and 38 provided at
its upper and lower faces. The openings 35, 36, 37, and 38 have a
circular shape with a diameter larger than the diameter of the
channel holes 31, 32, 33, and 34 of the cover plate 11. The
openings 35, 36, 37, and 38 respectively communicate with the
channel holes 31, 32, 33, and 34 of the cover plate 11.
[0054] The opposed plate 13 is stacked between the channel plate 12
and the vibrating plate 15. The opposed plate 13 is stuck on the
upper face of the channel plate 12 by using adhesive (not
illustrated) or other materials, and is stuck on the lower face of
the vibrating plate 15 by using the adhesion layer 14 (see FIG. 4).
The opposed plate 13 is made of metal, and includes the external
connection terminal 3 that projects outward. The opposed plate 13
also has channel holes 39, 40, 41, and 42 at its upper and lower
faces. The channel holes 39, 40, 41, and 42 have a circular shape
with a diameter smaller that the diameter of the openings 35, 36,
37, and 38 of the channel plate 12. The channel holes 39, 40, 41,
and 42 respectively communicate with the openings 35, 36, 37, and
38 of the channel plate 12, and also communicate with a pump
chamber 51 (see FIG. 4) described later.
[0055] The adhesion layer 14 (see FIG. 4), which is stacked between
the opposed plate 13 and the vibrating plate 15, is bonded to the
upper face of the opposed plate 13 and the lower face of the
vibrating plate 15. The adhesion layer 14 is formed in a frame-like
shape so as to be overlapped with a frame part 22 of the vibrating
plate 15. The space inside the frame-like shape of the adhesion
layer 14 constitutes a part of the pump chamber 51 (see FIG. 4).
The adhesion layer 14 includes a plurality of electrically
conductive particles contained in a thermosetting resin such as an
epoxy resin. The electrically conductive particles are made of, for
example, silica or resin coated with an electrically conductive
metal. Since the adhesion layer 14 contains a plurality of
electrically conductive particles as mentioned above, the thickness
of the adhesion layer 14 around its entire circumference can be
made substantially equal to the particle diameter of the
electrically conductive particles and thus uniform. Accordingly,
the presence of the adhesion layer 14 allows the opposed plate 13
and the vibrating plate 15 to be positioned facing each other with
a uniform spacing between the opposed plate 13 and the vibrating
plate 15. Further, the opposed plate 13 and the vibrating plate 15
can be made electrically continuous by using the electrically
conductive particles present in the adhesion layer 14.
[0056] The vibrating plate 15, which is made of a metal, for
example, SUS430, is stacked between the opposed plate 13 and the
insulating plate 17. The vibrating plate 15 includes a central part
21, the frame part 22, and connecting parts 23, 24, 25, and 26. The
central part 21 has a circular shape in plan view. The frame part
22, which has a rectangular frame-like shape with an opening in
plan view, surrounds the periphery of the vibrating plate 15. Each
of the connecting parts 23, 24, 25, and 26 is in the form of a beam
connecting between the central part 21 and the frame part 22. The
frame part 22 is stuck on the upper face of the opposed plate 13 by
using the adhesion layer 14 (see FIG. 4), and stuck on the lower
face of the insulating plate 17 by using adhesive (not illustrated)
or other materials. The vibrating plate 15 has openings 43, 44, 45,
and 46 surrounded by the central part 21, the frame part 22, and
the connecting parts 23, 24, 25, and 26. The openings 43, 44, 45,
and 46 constitute a part of the pump chamber 51 (see FIG. 4).
[0057] The vibrating plate 15 may be made of a material other than
SUS430, for example, an iron alloy such as SUS301, SUS304, or
SUS631, a copper alloy such as phosphor bronze, beryllium bronze,
or a copper-titanium alloy, an aluminum alloy, a nickel alloy,
carbon, an amorphous metal, or resin.
[0058] The piezoelectric element 16, which has an electrode
provided on each of the upper and lower faces of a sheet made of a
piezoelectric material, corresponds to the "driver" according to
the present disclosure. The piezoelectric element 16 exhibits
piezoelectricity such that the piezoelectric element 16 increases
or decreases in area when subjected to an electric field applied in
the thickness direction. Using the piezoelectric element 16 as a
driver allows the thickness of the driver to be reduced, enabling
miniaturization of a fluid control part 59 and the pump 1 described
later. The piezoelectric element 16, which is disc-shaped, is stuck
on the upper face of the central part 21 of the vibrating plate 15
by using adhesive (not illustrated) or other materials. The
electrode on the lower face of the piezoelectric element 16 is
electrically connected to the external connection terminal 3, via
the vibrating plate 15, the adhesion layer 14, and the opposed
plate 13. The electrode on the lower face of the piezoelectric
element 16 may not be provided but may be substituted for by use of
the vibrating plate 15 that is made of metal.
[0059] The piezoelectric element 16 is made of a piezoelectric
material with a coefficient of linear expansion lower than that of
the vibrating plate 15. The piezoelectric element 16 is bonded to
the central part 21 by using a thermosetting adhesive. Thus, when
thermosetting adhesive is heated and allowed to set, a compressive
stress is allowed to remain in the piezoelectric element 16 under
normal temperature environments. This makes the piezoelectric
element 16 resistant to breakage. Suitable examples of the
piezoelectric material of the piezoelectric element 16 include lead
zirconate titanate (PZT)-based ceramics. PZT-based ceramics have a
coefficient of linear expansion of substantially zero, which is
sufficiently lower than that of the metallic material constituting
the vibrating plate 15, such as SUS430 (which has a coefficient of
linear expansion of approximately
10.4.times.10.sup.-6K.sup.-1).
[0060] The insulating plate 17, which is stacked between the
vibrating plate 15 and the power feeding plate 18, is stuck on the
upper face of the frame part 22 of the vibrating plate 15 and the
lower face of the power feeding plate 18 by using adhesive (not
illustrated) or other materials. The insulating plate 17
corresponds to the insulating layer according to the present
disclosure. Other than using the insulating plate 17, the
insulating layer may be formed by a method such as coating the
surface of the vibrating plate 15 or the power feeding plate 18
with an insulating material, forming an oxide film on the surface
of the vibrating plate 15 or the power feeding plate 18, or
applying a coating of a mixture of an adhesive having insulating
property and non-electrically conductive particles. Alternatively,
a plurality of the above-mentioned components having insulating
property may be combined to form the insulating layer. The
insulating plate 17 has a rectangular frame-like shape with an
opening 47 in plan view. The opening 47 constitutes a part of the
pump chamber 51 (see FIG. 4). The insulating plate 17, which is
made of insulating resin, provides electrical insulation between
the power feeding plate 18 and the vibrating plate 15. The
thickness of the insulating plate 17 is the same as or slightly
larger than the thickness of the piezoelectric element 16.
[0061] The power feeding plate 18, which is stacked between the
insulating plate 17 and the spacer plate 19, is stuck on the upper
face of the insulating plate 17 and the lower face of the spacer
plate 19 by using adhesive (not illustrated) or other materials.
The power feeding plate 18 has a substantially rectangular
frame-like shape with an opening 48 in plan view. The opening 48
constitutes a part of the pump chamber 51 (see FIG. 4). The power
feeding plate 18, which is made of metal, includes an internal
connection terminal 27 that projects into the opening 48, and the
external connection terminal 4 that projects outward. The distal
end of the internal connection terminal 27 is soldered to the
electrode on the upper face of the piezoelectric element 16. The
position of this soldering preferably corresponds to a node of
vibration produced in the piezoelectric element 16. This reduces
leakage of vibration from the piezoelectric element 16 to the
internal connection terminal 27, allowing for improved driving
efficiency. In one particularly preferred arrangement, for a
concentric area corresponding to each node of vibration of the
piezoelectric element 16, the internal connection terminal 27
extends all the way to its distal end portion in a direction
tangential to the concentric area, and the distal end portion of
the internal connection terminal 27 is connected to the
piezoelectric element 16 at the point of tangency on the concentric
area. This configuration further reduces leakage of vibration to
the internal connection terminal 27, allowing for a further
improvement in driving efficiency while preventing the internal
connection terminal 27 from breaking owing to vibration.
[0062] The spacer plate 19, which is stacked between the power
feeding plate 18 and the lid plate 20, is stuck on the upper face
of the power feeding plate 18 and the lower face of the lid plate
20 by using adhesive (not illustrated) or other materials. The
spacer plate 19, which is made of resin, has a substantially
rectangular frame-like shape with an opening 49 in plan view. The
opening 49 constitutes a part of the pump chamber 51 (see FIG. 4).
The spacer plate 19 is provided to prevent the soldered portion of
the internal connection terminal 27 from coming into contact with
the lid plate 20 when vibration occurs. If the upper face of the
piezoelectric element 16 comes too close to the lid plate 20, the
amplitude of vibration decreases owing to air resistance.
Accordingly, the spacer plate 19 preferably has a thickness
substantially equal to or greater than the thickness of the
piezoelectric element 16.
[0063] The lid plate 20 is stacked over the spacer plate 19 such
that the lid plate 20 is exposed at the upper principal face 5 of
the housing 2. The lid plate 20 is stuck on the upper face of the
spacer plate 19 by using adhesive (not illustrated) or other
materials. The lid plate 20 closes the top side of the pump chamber
51 (see FIG. 4), and is positioned facing the vibrating plate 15
with a spacing therebetween. The lid plate 20 has the channel hole
50 at the upper principal face 5 of the housing 2. The channel hole
50 has a circular shape in plan view. The channel hole 50
communicates with the external space, and also communicates with
the opening 49 of the spacer plate 19, that is, the pump chamber
51. In the first embodiment, the channel hole 50 is an outlet for
discharging gas to the external space. Although the channel hole 50
is located at a position away from the center of the lid plate 20
in this example, the channel hole 50 may be provided near the
center of the lid plate 20.
[0064] FIG. 3A is a plan view of the vibrating plate 15 and the
piezoelectric element 16 as seen from the top side. FIG. 3B is a
plan view of the vibrating plate 15 as seen from the bottom side.
FIG. 3C is a side view of the cross-section of the vibrating plate
15 and the piezoelectric element 16 taken along C-C' in FIG.
3A.
[0065] As described above, the vibrating plate 15 includes, in plan
view, the central part 21, the frame part 22, and the connecting
parts 23, 24, 25, and 26, and has the openings 43, 44, 45, and 46.
The piezoelectric element 16 is in the form of a disc slightly
smaller in diameter than the central part 21 of the vibrating plate
15 in plan view. The piezoelectric element 16 is stuck on the upper
face of the central part 21.
[0066] The connecting parts 23, 24, 25, and 26 extend radially from
the central part 21 along the diagonals of the frame part 22 having
a rectangular frame-like shape. The connecting parts 23, 24, 25,
and 26 respectively include striking parts 53, 54, 55, and 56. The
striking parts 53, 54, 55, and 56 are respectively areas in the
connecting parts 23, 24, 25, and 26 that are locally increased in
width near the boundary adjacent to the central part 21. Each of
the striking parts 53, 54, 55, and 56 has a circular shape that is
smaller in diameter than the central part 21 in plan view. The
thickness of the vibrating plate 15 is reduced in areas excluding
the striking parts 53, 54, 55, and 56 and the frame part 22 by
etching performed from the lower face of the vibrating plate 15,
and the striking parts 53, 54, 55, and 56 and the frame part 22 are
thicker than other areas. That is, the striking parts 53, 54, 55,
and 56 and the frame part 22 are formed as projections that project
further toward the bottom side than do other areas of the vibrating
plate 15.
[0067] FIG. 4 is a side view of the cross-section of the pump 1
taken along X-X' in FIG. 3B.
[0068] The pump 1 includes a housing 52 and the fluid control part
59, with the pump chamber 51 provided inside the housing 52. The
housing 52 includes the cover plate 11, the channel plate 12, a
restraining part 58 of the opposed plate 13 that will be described
later, the adhesion layer 14, the frame part 22 of the vibrating
plate 15, the insulating plate 17, the power feeding plate 18, the
spacer plate 19, and the lid plate 20. The fluid control part 59
includes the piezoelectric element 16, the central part 21 and the
connecting parts 23, 24, 25, and 26 of the vibrating plate 15, and
a movable part 57 of the opposed plate 13 that will be described
later. The fluid control part 59, which is provided inside the pump
chamber 51 and vibrates to control fluid, corresponds to the "fluid
control device" according to the present disclosure.
[0069] The opposed plate 13 has the channel holes 39 and 40 that
are open to the pump chamber 51, at positions respectively facing
substantially the center of the striking parts 53 and 54 of the
connecting parts 23 and 24. Although not illustrated in the
cross-sectional view of FIG. 4, the opposed plate 13 has the
channel holes 41 and 42 (see FIG. 2) that are open to the pump
chamber 51, at positions respectively facing substantially the
center of the striking parts 55 and 56 (see FIG. 3) of the
connecting parts 25 and 26. The striking parts 53, 54, 55, and 56
have a diameter larger than the diameter of the channel holes 39,
40, 41, and 42.
[0070] The areas near the channel holes 39 and 40 of the lower face
of the opposed plate 13 are respectively exposed at the openings 35
and 36 of the channel plate 12. Although not illustrated in the
cross-sectional view of FIG. 4, the areas near the channel holes 41
and 42 (see FIG. 2) of the lower face of the opposed plate 13 are
also respectively exposed at the openings 37 and 38 (see FIG. 2) of
the channel plate 12. The lower face of the opposed plate 13 is
secured to the channel plate 12 except in areas near the channel
holes 39, 40, 41, and 42. This configuration allows the areas of
the opposed plate 13 near the channel holes 39, 40, 41, and 42 to
serve as the movable part 57 that is capable of flexion without
being restrained by the channel plate 12. This configuration also
allows the portion of the lower face of the opposed plate 13
secured to the channel plate 12 to serve as the restraining part 58
that is incapable of flexion and restrains the areas around the
movable part 57. The diameter of the movable part 57 and the
diameter of the striking parts 53, 54, 55, and 56 are desirably
relatively similar, but may not necessarily be the same. The
opposed plate 13 and the channel plate 12 may be formed as a single
plate member. In that case, the movable part 57 and the restraining
part 58 may be formed by providing the plate member with a
thin-walled portion of reduced thickness located near the channel
holes 39, 40, 41, and 42, and a thick-walled portion of increased
thickness surrounding the thin portion.
[0071] In the pump 1, application of an alternating-current driving
signal to the external connection terminals 3 and 4 causes an
alternating electric field to be applied in the thickness direction
of the piezoelectric element 16. Then, as the piezoelectric element
16 attempts to expand and contract isotropically in the in-plane
direction, flexural vibrations are generated concentrically in the
thickness direction in the stack of the piezoelectric element 16
and the vibrating plate 15. Accordingly, in the first embodiment,
the alternating-current driving signal applied to the external
connection terminals 3 and 4 is set to a predetermined frequency so
that flexural vibration is produced in the stack of the
piezoelectric element 16 and the vibrating plate 15 in a
higher-order resonant mode.
[0072] FIG. 5A schematically illustrates flexural vibration in a
higher-order resonant mode generated in the stack of the
piezoelectric element 16 and the vibrating plate 15. The following
description will be directed to a third-order resonant mode.
[0073] In the pump 1, the stack of the piezoelectric element 16 and
the vibrating plate 15 has a higher-order (and odd-order) resonant
mode such that the frame part 22 becomes a node, the center of the
central part 21 becomes a first antinode, and the center of each of
the striking parts 53, 54, 55, and 56 becomes a second antinode.
The frequency of the alternating-current driving signal is set so
as to produce such a higher-order resonant mode. For example, in
the third-order resonant mode, the first antinode and the second
antinode differ in their vibration phase by 180 degrees. That is,
when the piezoelectric element 16 expands, the center of the
central part 21 of the vibrating plate 15 bends to become convex
toward the piezoelectric element 16, and the striking parts 53, 54,
55, and 56 are displaced in the direction opposite to the
piezoelectric element 16. When the piezoelectric element 16
contracts, the center of the central part 21 of the vibrating plate
15 bends to become concave toward the piezoelectric element 16, and
the striking parts 53, 54, 55, and 56 are displaced toward the
piezoelectric element 16.
[0074] FIG. 5B schematically illustrates how the areas near the
striking part 53 and the movable part 57 vibrate.
[0075] When vibration occurs in a higher-order resonant mode, this
causes the striking part 53 of the vibrating plate 15 to vibrate in
such a way that the striking part 53 is repeatedly displaced upward
and downward. The areas near the striking parts 54, 55, and 56 (see
FIG. 3) are also subjected to vibration similar to that generated
in the area near the striking part 53. The vibrations produced near
the striking parts 53, 54, 55, and 56 are in synchronous phase with
one another. Then, the striking parts 53, 54, 55, and 56 are
repeatedly struck against a thin fluid layer that is present in the
gap between the opposed plate 13 and the striking parts 53, 54, 55,
and 56 inside the pump chamber 51. This causes repeated pressure
fluctuations to occur in the fluid positioned facing the striking
parts 53, 54, 55, and 56. The repeated pressure fluctuations are
transmitted through the fluid to the movable part 57 positioned
facing the striking parts 53, 54, 55, and 56. The movable part 57,
which has its dimensions such as diameter and thickness designed to
have a predetermined natural frequency, undergoes flexural
vibration in response to the vibration of the striking parts 53,
54, 55, and 56.
[0076] As the vibration of the striking parts 53, 54, 55, and 56
and the vibration of the movable part 57 produced in this way
become coupled, in the gap between the opposed plate 13 and the
vibrating plate 15 inside the pump chamber 51, the fluid flows
toward the outer periphery of the movable part 57 from the vicinity
of the channel holes 39, 40, 41, and 42 located at the center of
the movable part 57. This creates a negative pressure in the
vicinity of the channel holes 39, 40, 41, and 42 inside the pump
chamber 51, causing the fluid to be sucked into the pump chamber 51
from each of the channel holes 39, 40, 41, and 42. Inside the pump
chamber 51, a positive pressure is created in the space located
near the lid plate 20, and this positive pressure is released at
the channel hole 50 provided in the lid plate 20. Consequently, the
fluid sucked into the pump chamber 51 through each of the channel
holes 39, 40, 41, and 42 exits the pump chamber 51 through the
channel hole 50 provided in the lid plate 20.
[0077] In the pump 1 according to the first embodiment, the fluid
is sucked into the pump chamber 51 through each of the four channel
holes 39, 40, 41, and 42 in a parallel fashion. This allows for an
increase in the total amount of fluid entering the pump chamber 51,
thus enabling an improvement in the driving efficiency of the pump
1.
[0078] Further, the striking parts 53, 54, 55, and 56 with an
increased width are provided inside the pump chamber 51, and the
striking parts 53, 54, 55, and 56 are positioned facing the areas
around the channel holes 39, 40, 41, and 42, which directly
contribute to pump action, at a close distance. This configuration
allows the amplitude of vibration of the striking parts 53, 54, 55,
and 56 to be increased without decreasing the area of the fluid
positioned facing the striking parts 53, 54, 55, and 56.
[0079] Further, the striking parts 53, 54, 55, and 56 in the form
of projections are provided inside the pump chamber 51, and the
striking parts 53, 54, 55, and 56 are positioned facing the areas
around the channel holes 39, 40, 41, and 42, which directly
contribute to pump action, at a close distance. This configuration
allows the spacing between the vibrating plate 15 and the opposed
plate 13 to be increased at positions that do not directly
contribute to pump action. These features make it possible to
reduce unwanted load on the piezoelectric element 16 and the
vibrating plate 15, thus enabling improvements in features such as
the pressure or flow rate of the fluid generated by pump action,
and driving efficiency. Although the striking parts 53, 54, 55, and
56 are provided in the form of projections in the first embodiment,
the striking parts 53, 54, 55, and 56 may be provided as flat areas
with the same thickness as the thickness of the surrounding areas.
In that case, the movable part 57 of the opposed plate 13
positioned facing the striking parts 53, 54, 55, and 56 may be
provided so as to project toward the striking parts 53, 54, 55, and
56.
[0080] Preferably, the opposed plate 13, the channel plate 12, and
the cover plate 11 are each made of a material with a coefficient
of linear expansion higher than the coefficient of linear expansion
of the vibrating plate 15, and bonded to the frame part 22 of the
vibrating plate 15 by using a thermosetting adhesive. As a result,
the opposed plate 13 can be bowed to become convex toward the
vibrating plate 15 under normal temperature environments, thus
imparting tension to the movable part 57. This tension makes the
movable part 57 resistant to slacking. This makes it possible to
prevent vibration from being inhibited by deflection or settling of
the movable part 57.
[0081] Preferably, the lid plate 20, the spacer plate 19, the power
feeding plate 18, the insulating plate 17, the vibrating plate 15,
the opposed plate 13, the channel plate 12, and the cover plate 11
all have substantially equal coefficients of linear expansion. In
particular, the lid plate 20, the vibrating plate 15, the opposed
plate 13, the channel plate 12, and the cover plate 11 are
preferably made of identical kinds of metals with equal or similar
coefficients of linear expansion. This reduces variations in the
tension on the movable part 57 resulting from a difference in
coefficient of linear expansion, thus improving the temperature
characteristics of the pump 1.
[0082] Now, a more detailed description will be given of how the
movable part 57 and the striking parts 53, 54, 55, and 56 vibrate.
The movable part 57 is designed to have a natural frequency
corresponding to a frequency slightly lower than the driving
frequency of the striking parts 53, 54, 55, and 56. As a result,
the vibration produced in the movable part 57 in response to the
vibration of the striking parts 53, 54, 55, and 56 has
substantially the same frequency as the driving frequency of the
striking parts 53, 54, 55, and 56, with a slight phase delay.
[0083] Further, the striking parts 53, 54, 55, and 56 have a small
diameter in comparison to the distance from the center of the
vibrating plate 15 to the center of the striking parts 53, 54, 55,
and 56, that is, the distance from the first antinode to the second
antinode. Thus, the striking parts 53, 54, 55, and 56 vibrate so as
to undergo upward and downward displacement while keeping a
relatively flat shape. By contrast, the movable part 57 is
restrained at its outer periphery by the restraining part 58, and
has a diameter substantially equal to the diameter of the striking
parts 53, 54, 55, and 56. Thus, the movable part 57 vibrates so as
to undergo large upward and downward flexion within the area where
the movable part 57 is positioned facing each of the striking parts
53, 54, 55, and 56.
[0084] In this way, a standing-wave vibration that causes upward
and downward displacement is produced in each of the striking parts
53, 54, 55, and 56, and a standing-wave vibration that causes
upward and downward flexion is produced in the movable part 57.
These standing-wave vibrations differ in their wave length and
phase. Consequently, the spacing between the striking parts 53, 54,
55, and 56 and the movable part 57 represented as the difference
between these standing-wave vibrations changes with time like a
travelling wave travelling from the vicinity of the channel holes
39, 40, 41, and 42 toward the outer periphery of the movable part
57, because the two standing-wave vibrations differ in their wave
length and phase. As a result, in the gap between the striking
parts 53, 54, 55, and 56 and the movable part 57, the fluid is
transferred so as to be squeezed out from the vicinity of the
channel holes 39, 40, 41, and 42 toward the outer periphery of the
movable part 57. This allows the direction of fluid flow to be set
even without the presence of a component such as a check valve in
the pump 1, thus facilitating fluid flow. In this respect as well,
unwanted load on the piezoelectric element 16 and the vibrating
plate 15 can be reduced to enable improvements in features such as
the pressure or flow rate of fluid created by pump action, and
driving efficiency.
[0085] As discussed above, the pump 1 according to the first
embodiment allows driving efficiency to be improved without an
increase in its physical size. Alternatively, the pump 1 allows its
physical size to be reduced without a decrease in driving
efficiency.
Second Embodiment
[0086] Next, a pump 1A according to a second embodiment of the
present disclosure will be described with reference to an air pump
that sucks gas as an example.
[0087] FIG. 6 is an exploded perspective view of the pump 1A. The
pump 1A includes the following components stacked in the order
stated below: a cover plate 11A, a channel plate 12A, an opposed
plate 13A, the adhesion layer 14 (not illustrated), the vibrating
plate 15, the piezoelectric element 16, a metal plate 17A, the
insulating plate 17, the power feeding plate 18, the spacer plate
19, and the lid plate 20. The adhesion layer 14 (not illustrated),
the vibrating plate 15, the piezoelectric element 16, the
insulating plate 17, the power feeding plate 18, the spacer plate
19, and the lid plate 20 are of substantially the same
configuration as those in the first embodiment. The side wall
surface of each of the vibrating plate 15, the insulating plate 17,
the power feeding plate 18, and the spacer plate 19 that faces the
pump chamber described later can be made to have any suitable
shape. In this example, the side wall surface has such a shape that
the side wall surface extends along the side wall of each of the
central part 21 and the connecting parts 23, 24, 25, and 26 of the
vibrating plate 15 with a predetermined spacing therebetween.
[0088] In the second embodiment, the metal plate 17A is stacked
between the vibrating plate 15 and the insulating plate 17. The
metal plate 17A is made of a hard metallic material with a density
and a Young's modulus greater than those of the insulating plate
17. Providing the metal plate 17A having such characteristics
allows the vibrating plate 15 to be secured in place with increased
reliability in comparison to when the insulating plate 17 is
directly joined to the vibrating plate 15. In other words,
providing the metal plate 17A makes it possible to reduce leakage
of the vibration of the vibrating plate 15 to other components, in
comparison to when the insulating plate 17 is directly joined to
the vibrating plate 15. This allows the amplitude of vibration of
the vibrating plate 15 to be increased, thus enabling an
improvement in the driving efficiency of the pump 1A.
[0089] In the second embodiment, the cover plate 11A has channel
holes 31A, 32A, 33A, and 34A. The channel plate 12A has channels
35A, 36A, 37A, and 38A. The opposed plate 13A has openings 39A,
40A, 41A, and 42A in addition to the channel holes 39, 40, 41, and
42.
[0090] FIG. 7A is a plan view of the vibrating plate 15. FIG. 7B is
a plan view of the opposed plate 13A. FIG. 7C is a plan view of the
channel plate 12A. FIG. 7D is a plan view of the cover plate
11A.
[0091] The openings 39A, 40A, 41A, and 42A of the opposed plate 13A
illustrated in FIG. 7B are provided to prevent the adhesive of the
adhesion layer 14 (not illustrated) from flowing out toward the
connecting parts 23, 24, 25, and 26 from the frame part 22 of the
vibrating plate 15 illustrated in FIG. 7A. Accordingly, the
openings 39A, 40A, 41A, and 42A are respectively provided so as to
extend along the joints between the frame part 22 and the
connecting parts 23, 24, 25, and 26. In other words, the openings
39A, 40A, 41A, and 42A are provided so as to extend along the outer
periphery of the movable part 57. Providing the openings 39A, 40A,
41A, and 42A in this way makes it possible to prevent the adhesive
of the adhesion layer 14 (not illustrated) from flowing out toward
and becoming firmly fixed on the connecting parts 23, 24, 25, and
26. This prevents problems such as the adhesive of the adhesion
layer 14 (not illustrated) becoming firmly fixed on the connecting
parts 23, 24, 25, and 26 and inhibiting vibration of the connecting
parts 23, 24, 25, and 26. As a result, the vibrating plate 15 is
vibrated in a more stable manner, thus preventing variations in the
performance of the pump 1A. Not only the opposed plate 13A but also
the channel plate 12A may be provided with openings having the same
shape as that of the openings 39A, 40A, 41A, and 42A and used for
preventing outflow of adhesive. Outflow of adhesive toward the
connecting parts 23, 24, 25, and 26 can be also reduced by forming
the vibrating plate 15 thinner in areas other than the striking
parts 53, 54, 55, and 56 and the frame part 22 through etching
performed from the lower face of the vibrating plate 15, and
forming the vibrating plate 15 thicker in the striking parts 53,
54, 55, and 56 and the frame part 22 than in other areas.
[0092] The channels 35A, 36A, 37A, and 38A of the channel plate 12A
respectively have openings 35B, 36B, 37B, and 38B and extensions
35C, 36C, 37C, and 38C.
[0093] The openings 35B, 36B, 37B, and 38B, each of which has an
elliptical shape in plan view, are respectively positioned facing
the channel holes 39, 40, 41, and 42 of the opposed plate 13A and
their surrounding areas. In plan view, the extensions 35C, 36C,
37C, and 38C are extended from the openings 35B, 36B, 37B, and 38B
in the circumferential direction of the central part 21 of the
vibrating plate 15. The extensions 35C, 36C, 37C, and 38C
respectively communicate with the channel holes 31A, 32A, 33A, and
34A of the cover plate 11A described later, in the vicinity of
their end portions distal from the openings 35B, 36B, 37B, and 38B.
Thus, the cover plate 11A and the channel plate 12A each correspond
to the channel part defined in the claims. Providing the extensions
35C, 36C, 37C, and 38C in the channel plate 12A in this way allows
the channel holes 39, 40, 41, and 42 of the opposed plate 13A and
the channel holes 31A, 32A, 33A, and 34A of the cover plate 11A to
be respectively located at positions away from each other in plan
view. This reduces leakage of the vibrating sound generated by
vibration of the vibrating plate 15 from the channel holes 31A,
32A, 33A, and 34A of the cover plate 11A through areas such as the
channel holes 39, 40, 41, and 42 of the opposed plate 13A and the
channels 35A, 36A, 37A, and 38A of the channel plate 12A. This
enables low-noise construction of the pump 1A.
[0094] With respect to the direction of the radius extending toward
the outer side portion from the central part 21 of the vibrating
plate 15, the openings 35B, 36B, 37B, and 38B are substantially the
same or slightly larger in dimension than the striking parts 53,
54, 55, and 56 of the vibrating plate 15. Further, with respect to
the circumferential direction around the central part 21, the
openings 35B, 36B, 37B, and 38B are respectively sufficiently
larger in dimension than the striking parts 53, 54, 55, and 56 of
the vibrating plate 15. That is, the openings 35B, 36B, 37B, and
38B each have a minor axis extending in the radial direction of the
central part 21, and a major axis extending in the circumferential
direction of the central part 21. Since the areas in the opposed
plate 13A positioned facing the openings 35B, 36B, 37B, and 38B
serve as the movable part 57, the movable part 57 of the opposed
plate 13A also has an elliptical shape with a minor axis extending
in the radial direction of the central part 21 and a major axis
extending in the circumferential direction of the central part
21.
[0095] FIG. 8 is a side cross-sectional drawing as viewed in the
direction of the minor axis of the movable part 57, schematically
illustrating how the movable part 57 and the striking part 53
vibrate. The striking parts 54, 55, and 56 of the vibrating plate
15 and the movable part 57 positioned facing the striking parts 54,
55, and 56 also exhibit a similar manner of vibration.
[0096] FIG. 8A illustrates the same configuration as that of the
first embodiment, that is, a configuration in which the movable
part 57 has substantially the same diameter as the diameter of the
striking part 53. FIG. 8B illustrates the same configuration as
that of the second embodiment, that is, a configuration in which
the movable part 57 has a diameter sufficiently larger than the
diameter of the striking part 53 with respect to the major axis
direction.
[0097] As described above with reference to the first embodiment,
the antinodes of flexural vibration are produced concentrically in
plan view in the central part 21 of the vibrating plate 15. Thus,
in the striking part 53, antinodes are produced uniformly in the
circumferential direction of the central part 21 (the major axis
direction of the movable part 57).
[0098] Consequently, the striking part 53 moves up and down as
viewed in cross-section taken in the radial direction of the
central part 21 (the minor axis direction of the movable part 57).
As the striking part 53 moves up and down in this way, at positions
inside the striking part 53 near its both principal faces, the
striking part 53 undergoes expansion in the radial direction of the
central part 21 (the minor axis direction of the movable part 57)
in areas near one principal face, and contraction in the radial
direction of the central part 21 (the minor axis direction of the
movable part 57) in areas near the other principal face. Such
expansion or contraction occurring locally within the striking part
53 produces an opposite contraction or expansion in a direction
orthogonal to this expansion or contraction. That is, expansion
occurring locally within the striking part 53 in a predetermined
direction (the minor axis direction of the movable part 57) creates
contraction in a direction (the major axis direction of the movable
part 57) orthogonal to the direction of the expansion. Further,
contraction occurring locally within the striking part 53 in a
predetermined direction (the minor axis direction of the movable
part 57) creates expansion in a direction (the major axis direction
of the movable part 57) orthogonal to the direction of the
contraction. This causes the striking part 53 to undergo flexural
vibration as viewed in the minor axis direction of the movable part
57.
[0099] This vibration has maximum amplitude in the vicinity of each
end of the striking part 53, as viewed in the cross-section of the
striking part 53 taken in the radial direction of the central part
21 (the minor axis direction of the movable part 57). Thus, if the
amplitude of vibration in the vicinity of each end of the striking
part 53 is increased excessively such as by increasing the driving
voltage applied, as illustrated in FIG. 8A, there is a risk that
the movable part 57 positioned facing the striking part 53, and
each end portion of the striking part 53 may approach and collide
with each other.
[0100] Accordingly, in the second embodiment, the movable part 57
of the opposed plate 13A is formed in an oval shape, thus allowing
the movable part 57 to be increased in dimension in the major axis
direction while minimizing a decrease in the natural frequency of
the movable part 57. This allows the amplitude of vibration of the
movable part 57 to be increased at a position facing each end
portion in the major axis direction of the striking part 53 as
illustrated in FIG. 8B. This makes it possible to reduce the risk
of collision of the movable part 57 with each end portion of the
striking part 53 positioned facing the movable part 57. Therefore,
the pump 1A makes it possible to prevent problems such as
generation of abnormal vibration or noise and reduction of pressure
resulting from collision between the movable part 57 and the
striking part 53.
[0101] As described above, the movable part 57 of the opposed plate
13A desirably have such a shape that its major axis extends in the
circumferential direction of the central part 21 (the direction in
which antinodes are uniformly produced in the striking parts 53,
53, 55, and 56). Suitable examples of the specific planar shape of
the movable part 57 include an oval in addition to an ellipse.
Third Embodiment
[0102] Next, a pump 1B according to a third embodiment of the
present disclosure will be described with reference to an air pump
that sucks gas as an example.
[0103] FIG. 9 is an exploded perspective view of the pump 1B. The
pump 1B includes the cover plate 11, the channel plate 12, the
opposed plate 13, the adhesion layer 14 (not illustrated), the
vibrating plate 15, the piezoelectric element 16, the insulating
plate 17, the power feeding plate 18, the spacer plate 19, the lid
plate 20, and a stacking plate 16B.
[0104] The stacking plate 16B is further stacked for the stack of
the vibrating plate 15 and the piezoelectric element 16. In the
third embodiment, the stacking plate 16B is stacked between the
vibrating plate 15 and the piezoelectric element 16. The stacking
plate 16B has substantially the same disc-like outer shape as that
of the piezoelectric element 16, and has dimensions that are the
same as or slightly larger than those of the piezoelectric element
16 in plan view.
[0105] As in the first embodiment, the piezoelectric element 16 is
made of, for example, PZT-based ceramic with a coefficient of
linear expansion of substantially zero. The vibrating plate 15 is
also made of, for example, SUS430 with a coefficient of linear
expansion of approximately 10.4.times.10.sup.-6K.sup.-1 as in the
first embodiment. The vibrating plate 15 and the piezoelectric
element 16 are thus made of different materials, and differ in
their coefficient of linear expansion.
[0106] This means that in the case of a configuration in which the
vibrating plate 15 and the piezoelectric element 16 are directly
stuck together and stacked as in the first embodiment or second
embodiment, unwanted deformation resulting from temperature
fluctuations occurs in the stack. Generally speaking, the stack of
the vibrating plate 15 and the piezoelectric element 16 undergoes a
deflection such that when subjected to higher temperatures, the
stack becomes more concave in its side near the piezoelectric
element 16 having the lower coefficient of linear expansion, and
when subjected to lower temperatures, the stack becomes more convex
in its side near the piezoelectric element 16 having the lower
coefficient of linear expansion. If such deformation resulting from
the difference in coefficient of linear expansion occurs in the
stack of the vibrating plate 15 and the piezoelectric element 16,
this causes, for example, the spacing and parallelism between the
vibrating plate 15 (the striking parts 53 to 56) and the opposed
plate 13 to change with temperature. Consequently, depending on
conditions such as the setting of the dimensions of various parts
or the design of the materials of various parts, characteristics
such as fluid pressure distribution and fluid pressure fluctuations
in the fluid layer sandwiched between the vibrating plate 15 and
the opposed plate 13 become affected by temperature, causing
excessive fluctuations in the flow rate of the pump due to
temperature.
[0107] Accordingly, in the third embodiment, the stack of the
vibrating plate 15 and the piezoelectric element 16 is further
provided with the stacking plate 16B, thus compensating for thermal
deformation resulting from the difference in coefficient of linear
expansion between the vibrating plate 15 and the piezoelectric
element 16. As the stacking plate 16B, a stacking plate with a
coefficient of linear expansion and a thickness that satisfy a
predetermined relationship with respect to the coefficients of
linear expansion of the vibrating plate 15 and the piezoelectric
element 16 is disposed at a suitable position.
[0108] Specifically, the stacking plate 16B is stacked between the
piezoelectric element 16 and the vibrating plate 15, and the
coefficient of linear expansion of the stacking plate 16B is set to
a value equal to or higher than the coefficient of linear expansion
of each of the piezoelectric element 16 and the vibrating plate 15,
or a value equal to or lower than the coefficient of linear
expansion of each of the piezoelectric element 16 and the vibrating
plate 15. When bonding is performed at high temperatures,
compressive stress is applied to the piezoelectric element 16.
Accordingly, it is desirable to set the coefficient of linear
expansion of the stacking plate 16B equal to or higher than the
coefficient of linear expansion of each of the piezoelectric
element 16 and the vibrating plate 15.
[0109] With the stacking plate 16B set in this way, the deformation
(stress) resulting from the difference in coefficient of linear
expansion between the vibrating plate 15 and the stacking plate
16B, and the deformation (stress) resulting from the difference in
coefficient of linear expansion between the piezoelectric element
16 and the stacking plate 16B can be cancelled out by each other.
As a result, deformation occurring in the stack of the stacking
plate 16B, the piezoelectric element 16, and the vibrating plate 15
due to the difference in coefficient of linear expansion can be
reduced in comparison to when the vibrating plate 15 and the
piezoelectric element 16 are directly stuck together. Therefore,
temperature-induced fluctuations in characteristics such as the
spacing and parallelism between the striking parts 53 to 56
provided in the vibrating plate 15 and the opposed plate 13 can be
reduced, and temperature-induced fluctuations in the flow rate
generated by vibration of the striking parts 53 to 56 can be also
reduced.
[0110] The stacking plate 16B may be made of any suitable material
whose coefficient of linear expansion satisfies the above-mentioned
relationship. Examples of the suitable material that may be used
include materials with coefficients of linear expansion higher than
that of SUS430, and materials with coefficients of linear expansion
lower than that of PZT-based ceramics.
[0111] Even if a material with a coefficient of linear expansion
lower than that of the piezoelectric element 16 is used for the
vibrating plate 15, the coefficient of linear expansion of the
stacking plate 16B is preferably set in the manner as mentioned
above. That is, it is preferable to set the coefficient of linear
expansion of the stacking plate 16B to a value equal to or higher
than the coefficient of linear expansion of each of the
piezoelectric element 16 and the vibrating plate 15, or a value
equal to or lower than the coefficient of linear expansion of each
of the piezoelectric element 16 and the vibrating plate 15. In this
case as well, the deformation (stress) resulting from the
difference in coefficient of linear expansion between the vibrating
plate 15 and the stacking plate 16B, and the deformation (stress)
resulting from the difference in coefficient of linear expansion
between the piezoelectric element 16 and the stacking plate 16B can
be cancelled out by each other. As already described, this makes it
possible to reduce deformation occurring in the stack of the
stacking plate 16B, the piezoelectric element 16, and the vibrating
plate 15 resulting from the difference in coefficient of linear
expansion, in comparison to when the vibrating plate 15 and the
piezoelectric element 16 are directly stuck together.
Fourth Embodiment
[0112] Next, a pump 1C according to a fourth embodiment of the
present disclosure will be described.
[0113] FIG. 10 is an exploded perspective view of the pump 1C
according to the fourth embodiment of the present disclosure.
[0114] The pump 1C, which corresponds to a modification of the
third embodiment mentioned above, includes a stacking plate 16C. As
in the third embodiment mentioned above, the stacking plate 16C is
further stacked for the stack of the vibrating plate 15 and the
piezoelectric element 16. The stacking plate 16C used, which is
disposed at a suitable position, is a stacking plate that has
substantially the same disc-like outer shape as that of the
piezoelectric element 16, has dimensions that are the same as or
slightly larger than those of the piezoelectric element 16 in plan
view, and has a coefficient of linear expansion and a thickness
that satisfy a predetermined relationship with respect to the
vibrating plate 15 and the piezoelectric element 16.
[0115] In the fourth embodiment, the stacking plate 16C is stacked
not between the vibrating plate 15 and the piezoelectric element 16
but over the principal face of the vibrating plate 15 located
opposite to the side where the piezoelectric element 16 is stacked.
Further, the coefficient of linear expansion of the stacking plate
16C is set to a value lower than the coefficient of linear
expansion of the vibrating plate 15 and substantially equal to the
coefficient of linear expansion of the piezoelectric element
16.
[0116] As already mentioned, with the stacking plate 16C set in
this way, the deformation (stress) resulting from the difference in
coefficient of linear expansion between the vibrating plate 15 and
the stacking plate 16C, and the deformation (stress) resulting from
the difference in coefficient of linear expansion between the
vibrating plate 15 and the piezoelectric element 16 can be
cancelled out by each other. As a result, deformation occurring in
the stack of the stacking plate 16C, the piezoelectric element 16,
and the vibrating plate 15 due to the difference in coefficient of
linear expansion can be reduced in comparison to when the vibrating
plate 15 and the piezoelectric element 16 are directly stuck
together. Therefore, temperature-induced fluctuations in
characteristics such as the spacing and parallelism between the
striking parts 53 to 56 provided in the vibrating plate 15 and the
opposed plate 13 can be reduced, and temperature-induced
fluctuations in the flow rate generated by vibration of the
striking parts 53 to 56 can be also reduced.
[0117] The stacking plate 16C may be made of any suitable material
whose coefficient of linear expansion satisfies the above-mentioned
relationship. Examples of the suitable material that may be used
include metallic materials with coefficients of linear expansion
higher than that of SUS430, and resin materials.
[0118] Now, suppose that a material with a coefficient of linear
expansion lower than that of the piezoelectric element 16 is used
for the vibrating plate 15. In this case, the coefficient of linear
expansion of the stacking plate 16C is preferably set in a manner
opposite to that mentioned above. That is, the coefficient of
linear expansion of the stacking plate 16C may be set higher than
the coefficient of linear expansion of the vibrating plate 15. In
this case as well, the deformation (stress) resulting from the
difference in coefficient of linear expansion between the vibrating
plate 15 and the stacking plate 16C, and the deformation (stress)
resulting from the difference in coefficient of linear expansion
between the vibrating plate 15 and the piezoelectric element 16 can
be cancelled out by each other. As already mentioned, this makes it
possible to reduce deformation occurring in the stack of the
stacking plate 16C, the piezoelectric element 16, and the vibrating
plate 15 due to the difference in coefficient of linear expansion,
in comparison to when the vibrating plate 15 and the piezoelectric
element 16 are directly stuck together.
Fifth Embodiment
[0119] Next, the pump 1D according to a fifth embodiment of the
present disclosure will be described.
[0120] FIG. 11 is an exploded perspective view of the pump 1D
according to the fifth embodiment of the present disclosure.
[0121] The pump 1D, which corresponds to a modification of the
third and fourth embodiments mentioned above, includes a stacking
plate 16D. As in the third and fourth embodiments mentioned above,
the stacking plate 16D is further stacked for the stack of the
vibrating plate 15 and the piezoelectric element 16. The stacking
plate 16D used, which is disposed at a suitable position, has
substantially the same disc-like outer shape as that of the
piezoelectric element 16, has dimensions that are the same as or
slightly larger than those of the piezoelectric element 16 in plan
view, and has a coefficient of linear expansion and a thickness
that satisfy a predetermined relationship with respect to the
vibrating plate 15 and the piezoelectric element 16.
[0122] In the fifth embodiment, the stacking plate 16D is stacked
neither between the vibrating plate 15 and the piezoelectric
element 16 nor over the principal face of the vibrating plate 15
located opposite to the side where the piezoelectric element 16 is
stacked. Instead, the stacking plate 16D is stacked over the
principal face of the piezoelectric element 16 opposite to the side
where the vibrating plate 15 is stacked. Further, the coefficient
of linear expansion of the stacking plate 16D is set to a value
higher than the coefficient of linear expansion of the
piezoelectric element 16 and substantially equal to the coefficient
of linear expansion of the vibrating plate 15. The thickness of the
stacking plate 16D is set such that the larger the difference in
coefficient of linear expansion between the piezoelectric element
16 and the vibrating plate 15, the larger the thickness, and
conversely, the smaller the difference in coefficient of linear
expansion between the piezoelectric element 16 and the vibrating
plate 15, the smaller the thickness.
[0123] As already mentioned, with the stacking plate 16D set in
this way, the deformation (stress) resulting from the difference in
coefficient of linear expansion between the vibrating plate 15 and
the piezoelectric element 16, and the deformation (stress)
resulting from the difference in coefficient of linear expansion
between the piezoelectric element 16 and the stacking plate 16D can
be cancelled out by each other. As a result, deformation occurring
in the stack of the stacking plate 16D, the piezoelectric element
16, and the vibrating plate 15 due to the difference in coefficient
of linear expansion can be reduced in comparison to when the
vibrating plate 15 and the piezoelectric element 16 are directly
stuck together.
[0124] Therefore, temperature-induced fluctuations in
characteristics such as the spacing and parallelism between the
striking parts 53 to 56 provided in the vibrating plate 15 and the
opposed plate 13 can be reduced, and temperature-induced
fluctuations in the flow rate generated by vibration of the
striking parts 53 to 56 can be also reduced.
[0125] The stacking plate 16D may be made of any suitable material
whose coefficient of linear expansion satisfies the above-mentioned
relationship. Examples of the suitable material that may be used
include metallic materials with coefficients of linear expansion
higher than that of PZT-based ceramics, and resin materials.
[0126] Now, suppose that a material with a coefficient of linear
expansion lower than that of the piezoelectric element 16 is used
for the vibrating plate 15. In this case, the coefficient of linear
expansion of the stacking plate 16D is preferably set in a manner
opposite to that mentioned above. That is, the coefficient of
linear expansion of the stacking plate 16D may be set lower than
the coefficient of linear expansion of the piezoelectric element
16. In this case as well, the deformation (stress) resulting from
the difference in coefficient of linear expansion between the
vibrating plate 15 and the piezoelectric element 16, and the
deformation (stress) resulting from the difference in coefficient
of linear expansion between the stacking plate 16D and the
piezoelectric element 16 can be cancelled out by each other. As
already mentioned, this makes it possible to reduce deformation
occurring in the stack of the stacking plate 16D, the piezoelectric
element 16, and the vibrating plate 15 due to the difference in
coefficient of linear expansion, in comparison to when the
vibrating plate 15 and the piezoelectric element 16 are directly
stuck together. With this configuration, although the stacking
plate 16D hinders movement of the piezoelectric element 16, the
piezoelectric element 16 is able to move as the piezoelectric
element 16 is located away to one side from the neutral plane of
the three layers made up of the stacking plate 16D, the
piezoelectric element 16, and the vibrating plate 15.
Other Embodiments
[0127] Next, other embodiments of the present disclosure will be
described.
[0128] FIG. 12A is a perspective view of an opposed plate 61
constituting a pump according to a sixth embodiment of the present
disclosure. The opposed plate 61 includes channel-hole gathering
parts 62, 63, 64, and 65 at positions corresponding to the
respective striking parts 53, 54, 55, and 56 of the vibrating plate
15. Each of the channel-hole gathering parts 62, 63, 64, and 65 is
made up of a plurality of channel holes that are integrated
together. Each of the pump and the fluid control part according to
the present disclosure may include the opposed plate 61 configured
as mentioned above.
[0129] FIG. 12B is a cross-sectional view of a pump 71 according to
a seventh embodiment of the present disclosure. In the pump 71, a
striking part 72 in the form of a projection is provided also in
the central part 21 of the vibrating plate 15. Further, a channel
hole 73 of the opposed plate 13, an opening 74 of the channel plate
12, and a channel hole 75 of the cover plate 11 are provided at a
position facing the striking part 72. In the pump and the fluid
control part according to the present disclosure, components such
as a channel hole for sucking fluid from the outside, and a
striking part may be provided in this way also in the area located
facing the central plate. As a result, the number of channel holes
for sucking fluid from the outside can be increased, thus enabling
a further increase in flow rate as well as a further improvement in
driving efficiency.
[0130] FIG. 12C is a cross-sectional view of a pump 81 according to
an eighth embodiment of the present disclosure. The pump 81
includes, in addition to the piezoelectric element 16 stuck on the
upper face of the vibrating plate 15, a piezoelectric element 16'
stuck on the lower face of the vibrating plate 15. That is, in the
pump 81, the piezoelectric element 16, the vibrating plate 15, and
the piezoelectric element 16' are formed as a bimorph structure.
When a stack of piezoelectric element and vibrating plate is formed
as a bimorph structure in this way, the amplitude of vibration of
the resulting stack of piezoelectric element and vibrating plate
can be increased in comparison to the structure (unimorph
structure) of the stack of piezoelectric element and vibrating
plate described above with reference to the first to third
embodiments. Although the manner of feeding power for cases where
two piezoelectric elements are disposed so as to form a bimorph
structure is not particularly limited, a specific example of how
power is fed in such cases will be described later.
[0131] FIG. 13A is a cross-sectional view of a pump 91A according
to a ninth embodiment of the present disclosure. In the pump 91A,
an opposed plate and channel holes of the opposed plate are
disposed on the same side as each principal face of a vibrating
plate. Specifically, the pump 91A includes a vibrating plate 15'
whose upper and lower faces are each projected to form a striking
part 94. Further, the pump 91A has, in addition to the cover plate
11, the channel plate 12, the opposed plate 13, and the adhesion
layer 14 located on the same side as the lower face of the
vibrating plate 15', a cover plate 11', a channel plate 12', an
opposed plate 13', and an adhesion layer 14' disposed on the same
side as the upper face of the vibrating plate 15'. The cover plate
11', the channel plate 12', and the opposed plate 13' are
substantially the same in shape as and arranged in an order
opposite to the cover plate 11, the channel plate 12, and the
opposed plate 13, respectively. That is, the cover plate 11', the
channel plate 12', and the opposed plate 13' include channel holes
39' and 40', openings 35' and 36', and channel holes 31' and 32'
that are located facing the upper face of the striking part 94.
Unlike the cover plate 11, the channel plate 12, and the opposed
plate 13, the cover plate 11', the channel plate 12', and the
opposed plate 13' respectively have openings 91, 92, and 93 at
their central parts. The openings 91, 92, and 93 communicate the
pump chamber with the external space. With this configuration, the
openings 91, 92, and 93 have a function opposite to the channel
holes 31, 32, 31', and 32', that is, function as an outlet for
discharging gas to the outside.
[0132] In the pump and the fluid control part according to the
present disclosure, the channel holes of the opposed plates may be
provided both above and below the vibrating plate as described
above. This allows for a further increase in the number of channel
holes of the opposed plates, thus enabling a further increase in
flow rate as well as a further improvement in driving
efficiency.
[0133] FIG. 13B is a cross-sectional view of a pump 91B according
to a tenth embodiment of the present disclosure. In the pump 91B,
which corresponds to a modification of the pump 91A according to
the ninth embodiment, an opposed plate and channel holes of the
opposed plate are located on the same side as each principal face
of a vibrating plate. In the pump 91B, an opening 95, which has the
function of an outlet opposite to the function of the channel holes
31, 32, 31', and 32', is located not in the cover plate 11', the
channel plate 12', and the opposed plate 13' but at the lateral
side of the vibrating plate 15'.
[0134] In the pump and the fluid control part according to the
present disclosure, an opening that has the function of an outlet
opposite to the function of the channel holes 31, 32, 31', and 32'
may be provided not above or below the vibrating plate but at the
lateral side of the vibrating plate. This configuration allows the
inlet and the outlet to be spaced apart from each other. This
allows for increased freedom in the installation of the device
increases, thus enabling efficient suction and discharge of
gas.
[0135] FIG. 13C is a cross-sectional view of a pump 91C according
to an eleventh embodiment of the present disclosure. The pump 91C
corresponds to a modification of the pumps 91A and 91B according to
the ninth and tenth embodiments. In the pump 91C, the cover plates
11 and 11' are provided with no channel holes, and the channel
plates 12 and 12' are provided with channels 96 that communicate
the openings 35 and 36 and the openings 35' and 36' with each
other, with openings 97 being provided at the lateral sides of the
channel plates 12 and 12' so as to communicate with each other via
the channels 96.
[0136] In the pump and the fluid control part according to the
present disclosure, both the inlet and the outlet may be made to
communicate with the outside not at positions above and below the
vibrating plate but at the lateral sides of the vibrating plate.
This configuration allows gas to be sucked in and discharged even
when components such as an external board and an external housing
are disposed both over and under the pump. Further, each of the
inlet and the outlet areas can be gathered in one space. These
features also lead to increased freedom in the installation of the
device, thus allowing for efficient suction and discharge of
gas.
Twelfth Embodiment
[0137] Next, an example of wiring structure employed when two
piezoelectric elements and two vibrating plates are used to achieve
a bimorph structure will be described with reference to a pump 201
according to a twelfth embodiment of the present disclosure.
[0138] FIG. 14 is an exploded perspective view of the pump 201. The
pump 201 includes cover plates 211 and 211', channel plates 212 and
212', opposed plates 213 and 213', insulating layers 214 and 214',
a vibrating plate 215, piezoelectric elements 216 and 216', and
power feeding plates 217 and 217'. The cover plate 211, the channel
plate 212, the opposed plate 213, the insulating layer 214, the
piezoelectric element 216, and the power feeding plate 217 are
disposed on the same side as the lower face of the vibrating plate
215. The cover plate 211', the channel plate 212', the opposed
plate 213', the insulating layer 214', the piezoelectric element
216', and the power feeding plate 217' are disposed on the same
side as the upper face of the vibrating plate 215.
[0139] The cover plate 211 is exposed at the lower principal face
of the pump 201, and stuck on the lower face of the channel plate
212. The cover plate 211 has a channel hole 231 at the lower
principal face of the pump 201. The channel hole 231 has a circular
shape. In the twelfth embodiment, the channel hole 231 is an inlet
for sucking gas from the external space.
[0140] The channel plate 212 is stacked between the cover plate 211
and the opposed plate 213. The channel plate 212 has openings 232,
233, and 234, and a channel 235 that are provided at its upper and
lower faces. The opening 232, which has a circular shape with
substantially the same diameter as that of the channel hole 231 of
the cover plate 211, communicates with the channel hole 231 of the
cover plate 211. The openings 233, which have a circular shape with
substantially the same diameter as the diameter of striking parts
224 described later, are each provided at a position facing the
corresponding striking part 224. The opening 234, which constitutes
a part of the pump chamber, is provided at a position facing the
piezoelectric element 216 and the power feeding plate 217. The
channel 235, which is sandwiched by the opposed plate 213 and the
cover plate 211 from above and below, extends so as to communicate
the openings 232 and 233 with each other.
[0141] The opposed plate 213 is stacked between the channel plate
212 and the vibrating plate 215. The opposed plate 213 also has
channel holes 236 and 237, and an opening 238 provided at its upper
and lower faces. The channel hole 236, which has a circular shape
with substantially the same diameter as that of the opening 232 of
the channel plate 212, communicates with the opening 232 of the
channel plate 212. The channel holes 237, which are provided at
positions facing the striking parts 224 described later, have a
circular shape that is smaller in diameter than the striking parts
224 and the openings 233 of the channel plate 212. The channel
holes 237 communicate with the pump chamber and the openings 233 of
the channel plate 212. The opening 238, which constitutes a part of
the pump chamber, is provided at a position facing the
piezoelectric element 216 and the power feeding plate 217.
[0142] The vibrating plate 215 is stacked between the opposed plate
213 and the opposed plate 213'. Although not illustrated in FIG.
14, an adhesion layer containing particles is provided at a
predetermined thickness between the vibrating plate 215 and the
opposed plate 213, and between the vibrating plate 215 and the
opposed plate 213'. The particles forming the adhesion layer may be
either electrically conductive or non-electrically conductive.
[0143] The vibrating plate 215 has a central part 221, a frame part
222, and connecting parts 223. The connecting parts 223 are
provided with the striking part 224. The vibrating plate 215 has an
opening 239 surrounded by the central part 221, the frame part 222,
and the connecting parts 223, and a channel hole 240 provided in
the frame part 222. The opening 239 constitutes a part of the pump
chamber. The channel hole 240, which has a circular shape with
substantially the same diameter as that of the channel hole 236 of
the opposed plate 213, communicates with the channel hole 236 of
the opposed plate 213.
[0144] The vibrating plate 215 includes an upper-face lateral
groove 226' provided in the upper face of one side of the frame
part 222, and a lower-face lateral groove 226 provided in the lower
face of one side of the frame part 222 so as to overlap the
upper-face lateral groove 226'. The upper-face lateral groove 226'
and the lower-face lateral groove 226 extend outward from the
opening 239.
[0145] The opposed plate 213' is stacked between the channel plate
212' and the vibrating plate 215. The opposed plate 213 has channel
holes 236' and 237', and an opening 238' that are provided at its
upper and lower faces. The channel hole 236', which has a circular
shape with substantially the same diameter as that of the channel
hole 240 of the vibrating plate 215, communicates with the channel
hole 240 of the vibrating plate 215. The channel holes 237', which
are provided at positions facing the striking parts 224, have a
circular shape with a diameter smaller than the diameter of the
striking parts 224, and communicate with the pump chamber. The
opening 238', which constitutes a part of the pump chamber, is
provided at a position facing the piezoelectric element 216' and
the power feeding plate 217'.
[0146] The channel plate 212' is stacked between the cover plate
211' and the opposed plate 213'. The channel plate 212' has
openings 232', 233', and 234', and a channel 235' that are provided
at its upper and lower faces. The opening 232', which has a
circular shape with substantially the same diameter as that of the
channel hole 236' of the opposed plate 213', communicates with the
channel hole 236' of the opposed plate 213'. The openings 233',
which have a circular shape with substantially the same diameter as
the diameter of the striking parts 224, are each provided at a
position facing the corresponding striking part 224, and
communicate with the channel holes 237' of the opposed plate 213'.
The opening 234', which constitutes a part of the pump chamber, is
provided at a position facing the piezoelectric element 216' and
the power feeding plate 217'. The channel 235', which is sandwiched
by the cover plate 211' and the opposed plate 213' from above and
below, extends so as to communicate the openings 232' and 233' with
each other.
[0147] The cover plate 211' is exposed at the upper principal face
of the pump 201, and stuck on the upper face of the channel plate
212'. The cover plate 211' has a channel hole 231' at the upper
principal face of the pump 201. The channel hole 231' has a
circular shape, and communicates with the opening 234' (pump
chamber) of the channel plate 212'. In the twelfth embodiment, the
channel hole 231' is an outlet for discharging gas to the external
space.
[0148] The piezoelectric element 216, which is disc-shaped, is
stuck onto the lower face of the central part 221 of the vibrating
plate 215. The upper face of the piezoelectric element 216 is
electrically connected to the first external connection terminal
225 through the vibrating plate 215.
[0149] The piezoelectric element 216', which is disc-shaped, is
stuck onto the upper face of the central part 221 of the vibrating
plate 215. The lower face of the piezoelectric element 216' is
electrically connected to the first external connection terminal
225 through the vibrating plate 215.
[0150] In the present example, the power feeding plate 217 is in
the form of a beam that is bent at its distal end. The distal end
of the power feeding plate 217 is joined to the lower face of the
piezoelectric element 216 by a method such as soldering, thus
mechanically and electrically connecting the distal end to the
lower face of the piezoelectric element 216. The proximal end of
the power feeding plate 217 extends to the outside through the
lower-face lateral groove 226 of the vibrating plate 215. In the
present example, the power feeding plate 217' is in the form of a
beam that is bent at its distal end in a direction opposite to the
power feeding plate 217. The distal end of the power feeding plate
217' is joined to the upper face of the piezoelectric element 216'
by a method such as soldering, thus mechanically and electrically
connecting the distal end to the upper face of the piezoelectric
element 216'. The proximal end of the power feeding plate 217'
extends to the outside through the upper-face lateral groove 226'
of the vibrating plate 215.
[0151] The insulating layer 214 is made of an adhesive containing
insulating particles, and secures the power feeding plate 217
inside the lower-face lateral groove 226. The insulating layer 214'
is made of an adhesive containing insulating particles, and secures
the power feeding plate 217' inside the upper-face lateral groove
226'.
[0152] FIG. 15A is a perspective view of a stack made up of the
vibrating plate 215, the piezoelectric elements 216 and 216' (the
piezoelectric element 216 is not illustrated), the power feeding
plates 217 and 217', and the insulating layers 214 and 214'. FIG.
15B is an enlarged perspective view of an area in the vicinity of
the insulating layers 214 and 214'.
[0153] The insides of the upper-face lateral groove 226' and the
lower-face lateral groove 226 of the frame part 222 are
respectively filled with the coatings of the insulating layer 214'
and the insulating layer 214. The power feeding plates 217 and 217'
are respectively positioned so as to pass through the insides of
the insulating layers 214 and 214'. As a result, the power feeding
plates 217 and 217' are led to the outside without being bright
into electrical continuity with the vibrating plate 215 and the
first external connection terminal 225. The proximal end of each of
the power feeding plates 217 and 217' thus functions as a second
external connection terminal.
[0154] The insulating layers 214 and 214' are each made of an
adhesive having insulating property. Non-electrically conductive
particles are mixed in the adhesive. This ensures that the
insulating layers 214 and 214' with a thickness equal to or greater
than the particle diameter of the non-electrically conductive
particles is present between the power feeding plates 217 and 217'
and the vibrating plate 215, respectively.
[0155] The insulating layers 214 and 214' may not contain
non-electrically conductive particles. In that case, it is
desirable to, for example, provide an insulating coating of an
insulating material or an oxide film at locations where the power
feeding plate 217 or 217' or the vibrating plate 215 is exposed
inside the upper-face lateral groove 226' or the lower-face lateral
groove 226. This configuration also reliably prevents electrical
continuity between the power feeding plates 217 and 217', and the
vibrating plate 215 and the first external connection terminal
225.
[0156] In the pump 201 configured as described above, driving the
piezoelectric elements 216 and 216' causes gas to be sucked in from
the outside through the channel hole 231 of the cover plate 211
illustrated in FIG. 14. Then, the gas flows into the pump chamber
from the channel hole 231 of the cover plate 211, through the
opening 232, the channel 235, and the openings 233 of the channel
plate 212, and the channel holes 237 of the opposed plate 213. At
the same time, fluid flows into the pump chamber in a parallel
fashion from the channel hole 231 of the cover plate 211, through
the opening 232 of the channel plate 212, the channel hole 236 of
the opposed plate 213, the channel hole 240 of the vibrating plate,
the channel hole 236' of the opposed plate 213', the opening 232',
the channel 235', and the openings 233' of the channel plate 212',
and the channel holes 237' of the opposed plate 213'. Then, the
fluid is discharged to the outside from the pump chamber through
the channel hole 231' of the cover plate 211'.
[0157] Therefore, in the pump and the fluid control device
according to the twelfth embodiment as well, the channel holes of
the opposed plates can be positioned both above and below the
vibrating plate, thus enabling a further increase in suction flow
rate as well as a further improvement in driving efficiency.
Further, the inlet areas through which gas is sucked in from the
outside and the outlet areas through which gas is discharged to the
outside can be gathered in one space. This increases the freedom in
the installation of the device, thus allowing for efficient suction
and discharge of gas.
[0158] Although the present disclosure can be practiced as in the
embodiments described above, the present disclosure can be also
practiced in other embodiments. For example, although the
above-described embodiments use, as a driver, a piezoelectric
element that undergoes expansion and contraction in the in-plane
direction, the present disclosure is not limited to this. For
example, the vibrating plate may be vibrated in a flexural manner
through electromagnetic drive. Although the piezoelectric element
is made of PZT-based ceramic in the above-described embodiments,
the present disclosure is not limited to this. For example, the
piezoelectric element may be made of a non-lead piezoelectric
ceramic material such as potassium sodium niobate-based ceramic and
alkali niobate-based ceramic.
[0159] In the above-described embodiments, the striking part
provided in each of the connecting parts has such a shape that is
locally increased in width relative to the surrounding areas of the
connecting part and projects toward the bottom side. However, the
present disclosure is not limited to this. For example, the
striking part may be the same in width or thickness as other areas
in the connecting part.
[0160] Although the piezoelectric element and the central part of
the vibrating plate, and the striking parts and the movable part
have diameters similar to each other in the above-described
embodiments, the present disclosure is not limited to this. For
example, the central part of the vibrating plate may be
sufficiently larger than the piezoelectric element. Further, either
the striking parts or the movable part may be sufficiently larger
than the other. Although parts such as the piezoelectric element,
the central part of the vibrating plate, and the striking parts are
circular in shape in the above-described embodiments, the present
disclosure is not limited to this. For example, parts such as the
piezoelectric element, the central part of the vibrating plate, and
the striking parts may be rectangular or polygonal in shape.
[0161] Although the vibrating plate is provided with four
connecting parts and four striking parts, and the opposed plate is
provided with four channel holes and the movable part in the
above-described embodiments, the present disclosure is not limited
to this. Parts such as the piezoelectric element, the central part
of the vibrating plate, and the striking parts may be rectangular
or polygonal in shape. For example, parts such as the connecting
parts, the striking parts, the channel holes of the opposed plate,
and the movable part may be provided in two, three, or five or more
locations.
[0162] Although the frequency of the alternating-current driving
signal is determined so as to vibrate the vibrating plate in a
third-order resonant mode in the above-described embodiments, the
present disclosure is not limited to this. For example, the
frequency of the alternating-current driving signal may be
determined so as to vibrate the fluid control part in other
resonant modes such as a fifth-order resonant mode and a
seventh-order resonant mode.
[0163] Although the above-described embodiments use a gas as an
example of fluid, the present disclosure is not limited to this.
For example, the fluid may be a liquid, a gas-liquid mixture, a
solid-liquid mixture, or a solid-gas mixture. Although fluid is
sucked into the pump chamber through the channel holes provided in
the opposed plate in the above-described embodiments, the present
disclosure is not limited to this. For example, fluid may be
discharged from the pump chamber through the channel holes provided
in the opposed plate. Whether fluid is sucked or discharged through
the channel holes provided in the opposed plate is determined in
accordance with the direction of a travelling wave represented as
the difference in vibration between the striking parts and the
movable part.
[0164] Lastly, the foregoing description of the embodiments is
intended to be illustrative in all respects and not to be construed
as limiting. The scope of the present disclosure is defined not by
the above embodiments but by the appended claims. Further, the
scope of the present disclosure is intended to include all
modifications that fall within the meaning and scope of the claims
and any equivalents thereof. [0165] 1, 1A, 1B, 1C, 1D, 71, 81, 91A,
91B, 91C, 201 pump [0166] 2 housing [0167] 3, 4 external connection
terminal [0168] 5, 6 principal face [0169] 11, 11', 11A, 211, 211'
cover plate [0170] 12, 12', 12A, 212, 212' channel plate [0171] 13,
13', 13A, 61, 213, 213' opposed plate [0172] 14, 14', 214, 214'
adhesion layer [0173] 15, 15', 215 vibrating plate [0174] 16, 16',
216, 216' piezoelectric element [0175] 16B, 16C, 16D, 16D stacking
plate [0176] 17 insulating plate [0177] 17A metal plate [0178] 18,
217, 217' power feeding plate [0179] 19 spacer plate [0180] 20 lid
plate [0181] 21, 221 central part [0182] 22, 222 frame part [0183]
23, 24, 25, 26, 223 connecting part [0184] 27 internal connection g
terminal [0185] 31, 32, 33, 34, 31', 32', 31A, 32A, 33A, 34A, 39,
39', 40, 40', 41, 42, 50, 73, 75, 231, 231', 236, 237, 236', 237',
240 channel hole [0186] 35, 36, 35', 36', 37, 38, 39', 40', 35B,
36B, 37B, 38B, 39A, 40A, 41A, 42A, 43, 44, 45, 46, 47, 48, 49, 74,
91, 92, 93, 94, 97, 232, 233, 234, 232', 233', 234', 238, 238', 239
opening [0187] 35A, 36A, 37A, 38A, 96, 235, 235' channel [0188]
35C, 36C, 37C, 38C extension [0189] 51 pump chamber [0190] 52
housing [0191] 53, 54, 55, 56, 72, 94, 224 striking part [0192] 57
movable part [0193] 58 restraining part [0194] 59 fluid control
part (fluid control device) [0195] 62, 63, 64, 65 channel-hole
gathering part [0196] 225 external connection terminal [0197] 226
lower-face lateral groove [0198] 226' upper-face lateral groove
* * * * *