U.S. patent application number 14/266979 was filed with the patent office on 2014-08-21 for piezoelectric power generating device and manufacturing method thereof.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. The applicant listed for this patent is MURATA MANUFACTURING CO., LTD.. Invention is credited to Katsumi Fujimoto.
Application Number | 20140230209 14/266979 |
Document ID | / |
Family ID | 46171604 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140230209 |
Kind Code |
A1 |
Fujimoto; Katsumi |
August 21, 2014 |
PIEZOELECTRIC POWER GENERATING DEVICE AND MANUFACTURING METHOD
THEREOF
Abstract
A piezoelectric power generating device is provided which is
capable of extracting a large amount of power without an increase
in device size, even when applied with vibration of low frequency
or weak external force, and which is easy to manufacture. The
piezoelectric power generating device includes a piezoelectric
power generating plate including a piezoelectric plate having a
polarized regions that are different in polarization direction, and
a support member attached to the piezoelectric power generating
plate. Further, the piezoelectric power generating plate includes a
fixed portion fixed to the support member, a free end displaced
relative to the fixed portion when an external forced, such as a
vibration forced, is applied, and a cutout located between the
fixed portion and the free end.
Inventors: |
Fujimoto; Katsumi;
(Nagaokakyo-Shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MURATA MANUFACTURING CO., LTD. |
Nagaokakyo-Shi |
|
JP |
|
|
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
Nagaokakyo-Shi
JP
|
Family ID: |
46171604 |
Appl. No.: |
14/266979 |
Filed: |
May 1, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13894711 |
May 15, 2013 |
8749121 |
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14266979 |
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PCT/JP2011/075635 |
Nov 7, 2011 |
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13894711 |
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Current U.S.
Class: |
29/25.35 |
Current CPC
Class: |
H01L 41/113 20130101;
H02N 2/188 20130101; Y10T 29/42 20150115; H01L 41/1136 20130101;
H01L 41/25 20130101; H01L 41/33 20130101 |
Class at
Publication: |
29/25.35 |
International
Class: |
H01L 41/33 20060101
H01L041/33; H01L 41/25 20060101 H01L041/25 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2010 |
JP |
2010-268771 |
Claims
1. A manufacturing method of the piezoelectric power generating
device comprising: preparing a piezoelectric power generating plate
having a fixed portion and a free end displaced relative to the
fixed portion, forming a cutout in the piezoelectric power
generating plate between the fixed portion and the free end; and
attaching a support member to the fixed portion of the
piezoelectric power generating plate, wherein the piezoelectric
power generating plate includes a first piezoelectric power
generating plate portion disposed between the fixed portion and the
free end, and a second piezoelectric power generating plate portion
disposed between the cutout and the free end.
2. The manufacturing method of the piezoelectric power generating
device described in claim 1, wherein, in response to the external
force, the first piezoelectric power generating plate portion and
the second piezoelectric power generating plate portion are
displaced in different directions.
3. The manufacturing method of the piezoelectric power generating
device described in claim 1, wherein the piezoelectric power
generating plate is a unimorph type comprising a metal plate and a
piezoelectric plate on the metal plate, wherein, the step of
forming the cutout in the piezoelectric power generating plate
comprises forming the cutout in the piezoelectric plate, and
wherein the step of preparing the piezoelectric power generating
plate comprises attaching the piezoelectric plate having the cutout
to the metal plate and forming a corresponding cutout in the metal
plate by a sandblasting process performed from the side of the
piezoelectric plate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional application of U.S.
application Ser. No. 13/894,711, filed on May 15, 2013, which is a
continuation of International Application No. PCT/JP2011/075635,
filed Nov. 7, 2011, which claims priority to Japanese Patent
Application No. 2010-268771, filed Dec. 1, 2010, the entire
contents of each of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a piezoelectric power
generating device which is displaced when applied with vibration or
external force and generates power through the piezoelectric effect
and a manufacturing method of the device, more specifically a
piezoelectric power generating device using a plate-shaped
piezoelectric power generating member and a manufacturing method of
the device.
BACKGROUND OF THE INVENTION
[0003] In the past, a variety of piezoelectric power generating
devices using the piezoelectric effect have been proposed. For
example, the following Patent Document 1 discloses a piezoelectric
power generating device 1001 illustrated in FIG. 13.
[0004] The piezoelectric power generating device 1001 includes a
metal plate 1002 bent in a U-shape. At least one piezoelectric
element 1003 is fixed to the metal plate 1002. One end of the metal
plate 1002 is fixed to a fixing member 1004. The metal plate 1002
bent in a U-shape includes a first arm portion 1002a fixed to the
fixing member 1004. The metal plate 1002 is bent at an end portion
of the first arm portion 1002a opposite to an end portion of the
first arm portion 1002a fixed to the fixing member 1004. Further, a
second arm portion 1002c is connected to the first arm portion
1002a via a bent intermediate portion 1002b. The leading end of the
second arm portion 1002c forms a free end.
[0005] The piezoelectric power generating device 1001 uses the
metal plate 1002 bent in a U-shape as described above. When
vibration or external force is applied from outside, therefore, the
free end is substantially displaced, and is capable of generating a
relatively large amount of power.
[0006] Further, the following Patent Document 2 discloses a
piezoelectric power generating device using a piezoelectric power
generating plate folded multiple times into an accordion shape. The
piezoelectric power generating plate is a plate-shaped
piezoelectric power generating element. Also in this case, with the
use of the piezoelectric power generating plate folded into an
accordion shape, the piezoelectric element is increased in area,
and is capable of generating a large amount of power when vibration
or external force is applied from outside.
CITATION LIST
Patent Documents
[0007] Patent Document 1: Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2010-517285 [0008]
Patent Document 2: Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2005-507627
[0009] In some fields using piezoelectric power generating devices,
there are cases in which the vibration applied to a piezoelectric
power generating device has a relatively low frequency. For
example, in a piezoelectric power generating device attached to a
motor vehicle or a piezoelectric power generating device which
generates power by using vibration caused by human walking, the
piezoelectric power generating device is required to generate power
from vibration of relatively low frequency. To cause the
piezoelectric power generating device to generate power from
vibration of low frequency, it is necessary to reduce the resonant
frequency of the piezoelectric power generating element.
[0010] In a case using a plate-shaped piezoelectric power
generating element, therefore, it is necessary to increase the
length of the plate-shaped piezoelectric power generating element
or reduce the thickness thereof so as to reduce the resonant
frequency of the piezoelectric power generating element. However,
if the length of the plate-shaped piezoelectric power generating
element is increased by folding the piezoelectric power generating
element in a U-shape or by using a piezoelectric power generating
element folded multiple times into an accordion shape, as described
in Patent Document 1 or Patent Document 2, the height dimension is
inevitably increased. Further, if the thickness of the plate-shaped
piezoelectric power generating element is reduced, the strength of
a folded portion is reduced, and plastic deformation or brittle
fracture occurs. It is therefore difficult to reduce the thickness
of the plate-shaped piezoelectric power generating element.
Further, in the piezoelectric power generating device 1001
described in Patent Document 1, the piezoelectric element 1003 is
attached only to a portion of the metal plate 1002. Therefore, the
occupancy rate of the piezoelectric member in the piezoelectric
power generating element is small, and thus the power generation
amount is prevented from being sufficiently increased.
[0011] Further, in the piezoelectric power generating device
described in Patent Document 2, the piezoelectric power generating
plate having an accordion shape needs to be processed into a
three-dimensional shape, and the processing is substantially
complicated. Furthermore, an operation of performing a partial
poling treatment on such a complicatedly shaped piezoelectric power
generating plate in different directions is also complicated.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide a
piezoelectric power generating device involving no increase in
device size, easy to manufacture, and capable of extracting a large
amount of power even when applied with vibration of low frequency,
and a manufacturing method of the device.
[0013] A piezoelectric power generating device according to the
present invention includes a piezoelectric power generating plate
including a piezoelectric plate having a plurality of polarized
regions different in polarization direction, and a support member
configured to fix and support the piezoelectric power generating
plate. The piezoelectric power generating plate includes a fixed
portion fixed and supported by the support member, a free end of
the piezoelectric power generating plate displaced relative to the
fixed portion when applied with external force, and a cutout
located between the fixed portion and the free end. The cutout is
formed such that, when the external force is applied, a first
piezoelectric power generating plate portion located between the
cutout and an end portion on the side of the fixed portion and a
second piezoelectric power generating plate portion located between
the cutout and an end portion on the side of the free end are
displaced in different directions.
[0014] In a specific aspect of the piezoelectric power generating
device according to the present invention, the cutout has a frame
shape with a portion thereof removed. The piezoelectric power
generating plate includes the second piezoelectric power generating
plate portion corresponding to a portion surrounded by the cutout,
the fixed portion, the first piezoelectric power generating plate
portion corresponding to a portion other than the second
piezoelectric power generating plate portion, and a connecting
portion connecting the first piezoelectric power generating plate
portion and the second piezoelectric power generating plate
portion. Further, the second piezoelectric power generating plate
portion includes, in an end portion opposite to the connecting
portion, a first free end which is displaced when applied with the
external force. In this case, the piezoelectric power generating
plate portion inside the cutout is easily displaced differently
from the piezoelectric power generating plate portion outside the
cutout.
[0015] In another specific aspect of the piezoelectric power
generating device according to the present invention, the cutout
having the frame shape with a portion thereof removed is provided
in plurality such that a relatively outer cutout surrounds a
relatively inner cutout, and an end portion of a piezoelectric
power generating plate portion surrounded by a cutout located
innermost in the piezoelectric plate forms a second free end. In
this case, when the external force is applied, the piezoelectric
power generating plate is displaced in a meandering shape, as
viewed along a planar direction of the piezoelectric power
generating plate. Even if vibration of low frequency is applied,
therefore, it is possible to generate a larger amount of power.
[0016] In still another specific aspect of the piezoelectric power
generating device according to the present invention, the cutout is
provided such that the first piezoelectric power generating plate
portion and the second piezoelectric power generating plate portion
located outside the first piezoelectric power generating plate
portion in a planar direction are connected on one end side of the
cutout. An end portion of the second piezoelectric power generating
plate portion located opposite to a connecting portion connecting
the first piezoelectric power generating plate portion and the
second piezoelectric power generating plate portion forms a free
end. In this case, the first piezoelectric power generating plate
portion and the second piezoelectric power generating plate portion
are differently displaced via the connecting portion. Even if
vibration of low frequency or weak external force is applied,
therefore, it is possible to generate a larger amount of power.
[0017] In still another specific aspect of the piezoelectric power
generating device according to the present invention, the support
member is fixed on one end side of the piezoelectric power
generating plate, and an end portion opposite to an end portion
fixed with the support member forms a free end. In this case, the
piezoelectric power generating plate is fixed on the one end side
thereof, and the opposite end portion forms a free end. When
external force is applied, therefore, it is possible to generate a
large amount of power by using the entire dimension in the length
direction of the piezoelectric power generating plate connecting
the above-described one end and the opposite end portion.
[0018] In still another specific aspect of the piezoelectric power
generating device according to the present invention, the cutout is
provided in plurality between the fixed portion and the free end,
and when a direction connecting the fixed portion and the free end
is defined as a first direction, adjacent cutouts of the plurality
of cutouts are alternately formed on opposite end edges in a second
direction perpendicular to the first direction. In this case, the
plurality of cutouts are provided, and thus three or more
piezoelectric power generating plate portions different in
displacement direction are provided between the fixed portion and
the free end. Accordingly, it is possible to generate a larger
amount of power.
[0019] In still another specific aspect of the piezoelectric power
generating device according to the present invention, the fixed
portion is located in a central region between one end and another
end of the piezoelectric power generating plate. The one end and
the other end of the piezoelectric power generating plate form free
ends, and the cutout is provided between the fixed portion and each
of the free ends. The fixed portion is thus located in the central
region between the one end and the other end of the piezoelectric
power generating plate. Accordingly, it is possible to stably
support the piezoelectric power generating device.
[0020] In the piezoelectric power generating device according to
the present invention, the piezoelectric power generating plate may
be a unimorph type including a metal plate and a piezoelectric
plate laminated on the metal plate, or may be a bimorph type.
[0021] A manufacturing method of a piezoelectric power generating
device according to the present invention is a manufacturing method
of a piezoelectric power generating device configured in accordance
with the present invention, and includes a step of preparing a
piezoelectric power generating plate, a step of forming a cutout in
the piezoelectric power generating plate, and a step of joining a
support member to the piezoelectric power generating plate.
[0022] In another specific aspect of the manufacturing method of a
piezoelectric power generating device according to the present
invention, the piezoelectric power generating plate is a unimorph
type including a metal plate and a piezoelectric plate laminated on
the metal plate. In the step of preparing the piezoelectric power
generating plate, the piezoelectric plate provided with a cutout is
attached to one surface of the metal plate, and a cutout according
to the shape of the cutout is formed in the metal plate by a
sandblasting process performed from the side of the piezoelectric
plate, to thereby obtain the piezoelectric power generating plate
including the cutout. In this case, it is possible to easily obtain
a piezoelectric power generating plate including a cutout only by
attaching a ceramic plate provided with a cutout to one surface of
a metal plate and performing a flattening process, such as a
sandblasting process.
[0023] In the piezoelectric power generating device according to
the present invention, the cutout is formed at a position between
the fixed portion and the free end of the piezoelectric power
generating plate displaced relative to the fixed portion when
applied with the external force. The cutout is formed such that,
when the external force is applied, the first piezoelectric power
generating plate portion located between the cutout and the end
portion on the side of the fixed portion and the second
piezoelectric power generating plate portion located between the
cutout and the end portion on the side of the free end are
displaced in different directions. It is therefore possible to
reduce the resonant frequency of the piezoelectric power generating
plate, and increase the displacement amount. Accordingly, it is
possible to generate a large amount of power, even when vibration
of low frequency or weak external force is applied.
[0024] In addition, it is possible to increase the power to be
generated only by forming the cutout in the piezoelectric power
generating plate. It is therefore possible to obtain a large amount
of power without increasing the dimension along the thickness
direction of the piezoelectric power generating plate.
[0025] Further, the manufacturing method of a piezoelectric power
generating device according to the present invention is capable of
easily manufacturing a piezoelectric power generating device
according to the present invention only by forming a cutout in a
piezoelectric power generating plate and thereafter joining thereto
a support member.
BRIEF DESCRIPTION OF DRAWINGS
[0026] In FIG. 1, (a) and (b) are a plan view for describing a
piezoelectric power generating device according to a first
embodiment of the present invention, and a cross-sectional view
illustrating a portion along a B-B line in (a) of FIG. 1,
respectively.
[0027] In FIG. 2, (a) and (b) are a schematic perspective view and
a schematic front view, respectively, for describing a displacement
state of the piezoelectric power generating device according to the
first embodiment of the present invention.
[0028] FIG. 3 is a schematic plan view for describing a plurality
of polarized regions of a piezoelectric power generating plate in
the piezoelectric power generating device according to the first
embodiment of the present invention.
[0029] In FIG. 4, (a) and (b) are diagrams for describing a method
of manufacturing the piezoelectric power generating device
according to the first embodiment of the present invention, (a) of
FIG. 4 being a plan view illustrating a laminate in which a
piezoelectric plate provided with a cutout is attached to a metal
plate, and (b) of FIG. 4 being a front cross-sectional view along a
C-C line in (a) of FIG. 4.
[0030] FIG. 5 is a schematic perspective view of a piezoelectric
power generating device according to a second embodiment of the
present invention.
[0031] FIG. 6 is a schematic perspective view of a piezoelectric
power generating device according to a third embodiment of the
present invention.
[0032] FIG. 7 is a schematic perspective view of a piezoelectric
power generating device according to a fourth embodiment of the
present invention.
[0033] FIG. 8 is a schematic plan view for describing a plurality
of polarized regions of a piezoelectric power generating plate in
the piezoelectric power generating device according to the fourth
embodiment of the present invention.
[0034] In FIG. 9, (a) to (d) are schematic plan views for
describing piezoelectric power generating devices in a comparative
example and first to third experimental examples.
[0035] In FIG. 10, (a) and (b) are a plan view for describing a
piezoelectric power generating device according to a fifth
embodiment of the present invention, and a cross-sectional view
illustrating a portion along a D-D line in (a) of FIG. 10,
respectively.
[0036] FIG. 11 is a plan view of a piezoelectric power generating
device according to a sixth embodiment of the present
invention.
[0037] FIG. 12 is a plan view of a piezoelectric power generating
device according to a seventh embodiment of the present
invention.
[0038] FIG. 13 is a perspective view for describing an example of a
conventional piezoelectric power generating device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0039] With reference to the drawings, specific embodiments of the
present invention will be described below to thereby reveal the
present invention.
[0040] FIG. 1 illustrates a piezoelectric power generating device 1
according to a first embodiment of the present invention. In FIG.
1, (a) is a plan view of the piezoelectric power generating device
1 according to the first embodiment of the present invention, and
(b) is a cross-sectional view illustrating a portion along a B-B
line in (a) of FIG. 1.
[0041] The piezoelectric power generating device 1 includes a
piezoelectric power generating plate 2 and a support member 3. The
piezoelectric power generating plate 2 has a rectangular plate
shape with a length direction, and includes mutually facing short
sides 2b and 2c and mutually facing long sides 2d and 2e in a plan
view. The support member 3 fixes and supports a portion on the side
of the short side 2b corresponding to one end of the piezoelectric
power generating plate 2. A portion of the piezoelectric power
generating plate 2 fixed by the support member 3 is a fixed
portion.
[0042] The support member 3 is provided to support and fix the
piezoelectric power generating device 1 to an external object. In
other words, the support member 3 is a member for fixing the
piezoelectric power generating plate 2 to a part to which the
piezoelectric power generating device 1 is attached. Such a support
member 3 may be made of an appropriate material, such as metal,
resin, or ceramics.
[0043] The piezoelectric power generating plate 2 includes a metal
plate 4 and a piezoelectric plate 5 attached to one surface of the
metal plate 4. That is, the piezoelectric power generating plate 2
is a unimorph type. The piezoelectric plate 5 is polarized in a
thickness direction. In the present embodiment, the above-described
support member 3 is fixed to the lower surface of the piezoelectric
plate 5, and the metal plate 4 is attached to the upper surface of
the piezoelectric plate 5, as illustrated in (b) of FIG. 1. With
the support member 3 fixed to the lower surface of the
piezoelectric plate 5, compressive stress constantly acts on the
piezoelectric plate 5. The support member 3, however, may be fixed
to the upper surface of the piezoelectric power generating plate
2.
[0044] The metal plate 4 is made of an appropriate metal material,
such as metal like iron or aluminum, or alloy containing iron or
aluminum, such as stainless steel, for example. The piezoelectric
plate 5 is made of an appropriate piezoelectric material, such as
PZT-based ceramics or non-lead-based piezoelectric ceramics
including alkali niobate-based ceramics, such as potassium sodium
niobate.
[0045] An electrode 6 is formed on the lower surface of the
piezoelectric plate 5, and an electrode 7 is formed on the upper
surface of the piezoelectric plate 5. The electrodes 6 and 7 are
respectively formed on the entire area of the lower surface and the
entire area of the upper surface of the piezoelectric plate 5
excluding a later-described cutout.
[0046] The electrodes 6 and 7 are made of an appropriate conductive
material. Further, since the metal plate 4 is conductive, the
electrode 7 formed on the surface of the piezoelectric plate 5
attached with the metal plate 4 may be omitted.
[0047] FIG. 3 illustrates a schematic plan view of the
piezoelectric power generating plate 2 in the piezoelectric power
generating device 1 according to the first embodiment of the
present invention. In FIG. 3, the metal plate 4 is omitted.
Although the piezoelectric plate 5 is subjected to a poling
treatment in the thickness direction, a hatched polarized region P1
and a polarized region P2 corresponding to the remaining portion
are polarized in mutually opposite directions in the thickness
direction, as illustrated in FIG. 3. That is, the piezoelectric
plate 5 includes the plurality of polarized regions P1 and P2
different in polarization direction. If the piezoelectric power
generating plate 2 is displaced when applied with vibration or
external force from outside, a first region of the piezoelectric
power generating plate 2, in which compressive strain or tensile
strain occurs in a surface of the piezoelectric plate 5 and
compressive stress or tensile stress is generated, and a second
region of the piezoelectric power generating plate 2, in which the
strain direction is reversed and tensile stress or compressive
stress opposite to the stress in the first region is generated, are
separately formed in these plurality of polarized regions P1 and
P2. With the polarized regions P1 and P2 having the opposite
polarization directions, therefore, positive and negative charges
generated in the polarized regions P1 and P2 by the piezoelectric
effect are not offset, even if a common electrode is formed in the
polarized regions P1 and P2 in the piezoelectric power generating
plate 2, and it is possible to efficiently extract power based on
the generated charges.
[0048] These polarized regions P1 and P2 and the state of
displacement and strain of the piezoelectric power generating plate
2 will be described in more detail later.
[0049] A feature of the piezoelectric power generating device 1 of
the present embodiment lies in that a cutout 2a is formed in the
piezoelectric power generating plate 2. The cutout 2a has a closed
frame shape with a portion thereof removed. More specifically, as
illustrated in (a) of FIG. 1, the piezoelectric power generating
plate 2 has a rectangular plate shape with a length direction, in
which a portion of the piezoelectric power generating plate 2 on
the side of the short side 2b includes a fixed portion fixed with
the above-described support member 3, and the cutout 2a includes a
pair of cutout components 2al and 2a2 extending from the side of
the short side 2c toward the side of the short side 2b
corresponding to the fixed portion side. The cutout components 2a1
and 2a2 are provided such that the distance therebetween is reduced
from the side of the short side 2c toward the side of the short
side 2b. Further, respective end portions of the cutout components
2a1 and 2a2 on the side of the short side 2b are connected to a
cutout component 2a3 extending parallel to the short side 2b,
thereby forming a cutout in which the cutout components 2a1, 2a2,
and 2a3 are continuously connected. Meanwhile, respective end
portions of the cutout components 2al and 2a2 on the side of the
short side 2c do not form a continuous cutout. Therefore, the
cutout 2a formed by the cutout components 2a1, 2a2, and 2a3 has a
trapezoidal shape with the lower base thereof removed, i.e., a
closed frame shape with a portion thereof removed, as illustrated
in (a) of FIG. 1. This cutout 2a is formed in an inner region of
the piezoelectric power generating plate 2 excluding the
rectangular outer circumference thereof.
[0050] The piezoelectric power generating plate 2 includes a first
piezoelectric power generating plate portion 2u and a second
piezoelectric power generating plate portion 2f. The second
piezoelectric power generating plate portion 2f corresponds to the
portion surrounded by the cutout 2a. The first piezoelectric power
generating plate portion 2u corresponds to the portion not
surrounded by the cutout 2a, i.e., the portion other than the
second piezoelectric power generating plate portion 2f. The cutout
2a has the above-described shape. When vibration or external force
is applied from outside, therefore, the second piezoelectric power
generating plate portion 2f is capable of being displaced in a
different direction from that of the first piezoelectric power
generating plate portion 2u. A leading end 2f1 of this second
piezoelectric power generating plate portion 2f forms a first free
end.
[0051] In FIG. 2, (a) is a schematic perspective view for
describing a displacement state of the piezoelectric power
generating device 1 according to the first embodiment of the
present invention, and (b) is a schematic front view thereof. That
is, if the piezoelectric power generating plate 2 is applied with
vibration or external force from outside, e.g., if the
piezoelectric power generating plate 2 is applied with external
force including a component directed from the upper side of the
piezoelectric power generating plate 2 toward the lower side
thereof, the piezoelectric power generating plate 2 is displaced,
as illustrated in (a) and (b) of FIG. 2. In this case, relative to
the fixed portion supported by the support member 3, the first
piezoelectric power generating plate portion 2u corresponding to
the portion outside the cutout 2a of the piezoelectric power
generating plate 2 is displaced in a bending mode, with the fixed
portion acting as a fulcrum. Further, the second piezoelectric
power generating plate portion 2f corresponding to the portion
surrounded by the cutout 2a is displaced in a different direction
from that of the first piezoelectric power generating plate portion
2u in the bending mode, with a connecting portion connecting the
second piezoelectric power generating plate portion 2f and the
first piezoelectric power generating plate portion 2u acting as a
fulcrum. Accordingly, the leading end 2f1 forming the first free
end is displaced as indicated by an arrow in (b) of FIG. 2.
[0052] In the rectangular piezoelectric power generating plate 2,
with the cutout 2a provided as described above, the second
piezoelectric power generating plate portion 2f corresponding to
the portion surrounded by the cutout 2a and the first piezoelectric
power generating plate portion 2u corresponding to the remaining
portion are displaced in different directions to have respective
displacement fulcrums in the bending mode at mutually different
positions within the continuous flat plate of the piezoelectric
power generating plate 2. In such displacement, a region having
compressive strain and a region having tensile strain are
separately generated in the piezoelectric power generating plate 2.
The regions reversed to each other in strain direction to have
compressive strain or tensile strain are identifiable by analysis
according to the finite element method or the like.
[0053] The polarized regions P1 and P2 in FIG. 3 thus correspond to
the region in which, when the piezoelectric power generating plate
2 provided with the cutout 2a is displaced, the strain direction of
the piezoelectric power generating plate 2 corresponds to tensile
strain, and the region in which, when the piezoelectric power
generating plate 2 provided with the cutout 2a is displaced, the
strain direction of the piezoelectric power generating plate 2
corresponds to compressive strain, respectively. As previously
described, therefore, the polarized regions P1 and P2 have mutually
opposite polarization directions of the piezoelectric plate 5 in
the thickness direction. Even with a simple planar structure in
which a common electrode is formed in the polarized regions P1 and
P2, therefore, the charges generated in the polarized regions P1
and P2 are not offset. Accordingly, even if vibration of low
frequency or weak external force is applied from outside, and even
with a simple structure, it is possible to reliably obtain a large
amount of power without an increase in height dimension
perpendicular to a main surface of the piezoelectric power
generating plate 2.
[0054] Particularly, as compared with a piezoelectric power
generating plate having the same outer dimension as that of the
piezoelectric plate 5 but not including a cutout, the
above-described piezoelectric power generating plate 2 in the
present embodiment is formed with the cutout 2a, and thus is
capable of extracting a large amount of power. This is because,
when vibration or external force is applied from outside, the
second piezoelectric power generating plate portion 2f
corresponding to the portion surrounded by the cutout 2a and the
first piezoelectric power generating plate portion 2u corresponding
to the remaining portion are displaced in different directions, as
described above. That is, it is because, even if vibration of low
frequency or weak external force is applied from outside, the
piezoelectric power generating plate 2 as a whole is capable of
obtaining a larger displacement amount, and therefore is capable of
increasing the total amount of charges to be generated.
[0055] Accordingly, the piezoelectric power generating device 1 of
the present embodiment is capable of obtaining a large power
generation amount without increasing the dimension of the
piezoelectric power generating plate 2.
[0056] In addition, as described later, with a change in shape of
the cutout 2a, it is also possible to easily control the resonant
frequency of the piezoelectric power generating plate 2, when the
piezoelectric power generating plate 2 is applied with vibration or
external force.
[0057] Further, since the above-described piezoelectric power
generating plate 2 only requires the cutout 2a to be formed
therein, the manufacturing process is simple. Furthermore, since
the piezoelectric plate 5 having a flat plate shape only requires
the polarized regions P1 and P2 to be formed therein, the poling
treatment is also simple.
[0058] Description will be given of an example of a manufacturing
method of the above-described piezoelectric power generating device
1. In FIG. 4, (a) and (b) are diagrams for describing a method of
manufacturing the piezoelectric power generating device 1 according
to the first embodiment of the present invention. In FIG. 4, (a) is
a plan view illustrating a laminate 8 in which the piezoelectric
plate 5 provided with a cutout 2a' is attached to the metal plate
4, and (b) is a front cross-sectional view along a C-C line in (a)
of FIG. 4. The piezoelectric plate 5 is first prepared which
includes the cutout 2a' forming the cutout 2a. This process may be
performed by obtaining a rectangular piezoelectric ceramic plate
and thereafter forming the cutout 2a' by laser processing,
mechanical processing, or the like. Alternatively, the
above-described piezoelectric plate 5 may be obtained by molding an
unbaked piezoelectric plate to have the cutout 2a' and thereafter
baking the piezoelectric plate.
[0059] Then, the piezoelectric plate 5 is polarized. After the
piezoelectric plate 5 including the cutout 2a' is first prepared, a
portion of the upper surface of the piezoelectric plate 5
corresponding to the polarized region P1 and a portion of the upper
surface of the piezoelectric plate 5 corresponding to the polarized
region P2 are formed with respective polarizing electrodes such
that the polarizing electrodes are not in contact with each other.
The entire lower surface of the piezoelectric plate 5 is formed
with an electrode. Then, a poling treatment may be performed by
applying a voltage between the electrodes on the upper and lower
surfaces such that the direction of the applied voltage is opposite
between the polarized region P1 and the polarized region P2.
[0060] After the above-described poling treatment, the polarizing
electrodes may be removed from the upper surface of the
piezoelectric plate 5, and thereafter the electrode 7 may be formed
on the entire surface. Alternatively, the electrode 7 may be formed
by forming a conductive film to cover the entire upper surface of
the piezoelectric plate 5, with the polarizing electrodes left
unremoved. The polarizing electrode formed on the entire lower
surface of the piezoelectric plate 5 may be used as the electrode
6.
[0061] The electrodes 7 and 6 are thus formed on the upper and
lower surfaces of the piezoelectric plate 5. Thereafter, the
piezoelectric plate 5 is attached to the metal plate 4 not
including a cutout, to thereby obtain the laminate 8 illustrated in
(a) and (b) of FIG. 4. After the laminate 8 is obtained, a
sandblasting process is performed from the side of the cutout 2a'
of the piezoelectric plate 5. Thereby, a cutout is formed in the
metal plate 4 under the cutout 2a' of the piezoelectric plate 5.
The piezoelectric power generating plate 2 illustrated in FIG. 1 is
obtainable in such a manner. The piezoelectric power generating
device 1 is obtainable by fixing the support member 3 to the
piezoelectric power generating plate 2.
[0062] The process of forming a cutout in the metal plate 4 is not
limited to the sandblasting method, and may employ another grinding
method, a processing method using a laser, or the like.
[0063] According to the above-described manufacturing method, it is
possible to easily obtain the shape of the piezoelectric power
generating plate 2 only by performing a process leaving just a
two-dimensional processing path, such as the sandblasting process,
after the laminate 8 is obtained.
[0064] To attach the piezoelectric plate 5 to the metal plate 4, an
appropriate adhesive, such as a conductive adhesive or an
insulating adhesive, may be used. Also in a case in which the
electrode 7 is omitted, the piezoelectric plate 5 may be attached
to the metal plate 4 by a conductive adhesive or an insulating
adhesive. Even with the use of an insulating adhesive, if the
insulating adhesive is substantially thin, the piezoelectric plate
5 and the metal plate 4 having surfaces with fine irregularities
locally come into contact with each other to be electrically
connected to each other. Alternatively, with the piezoelectric
plate 5, the metal plate 4, and the insulating adhesive functioning
as a capacitor, it is possible to transmit alternating-current
power.
[0065] FIG. 5 is a schematic perspective view illustrating a
piezoelectric power generating device 21 according to a second
embodiment of the present invention. In the piezoelectric power
generating device 21 of the second embodiment, the piezoelectric
power generating plate 2 is similar to that of the first
embodiment, except for the shape of the cutout. Therefore,
identical portions are assigned with identical reference numerals,
to thereby incorporate the description of the first embodiment. In
the first embodiment, the cutout 2a has the cutout components 2a1
and 2a2 provided such that the distance therebetween is reduced
from the side of the short side 2c toward the side of the short
side 2b. Meanwhile, in the piezoelectric power generating device 21
illustrated in FIG. 5, the cutout components 2a1 and 2a2 are
provided to extend parallel to the long sides 2d an 2e. Therefore,
the second piezoelectric power generating plate portion 2f
corresponding to the portion surrounded by the cutout 2a has a
rectangular shape. The shape of the second piezoelectric power
generating plate portion 2f surrounded by the cutout 2a may thus be
changed as appropriate. With a change in planar shape of the second
piezoelectric power generating plate portion 2f corresponding to
the portion surrounded by the cutout 2a, it is possible to easily
adjust the resonant frequency of the piezoelectric power generating
plate 2 when applied with vibration or external force from outside.
In FIG. 5, the support member 3 and the electrodes 6 and 7 are
omitted.
[0066] FIG. 6 is a schematic perspective view illustrating a
piezoelectric power generating device 31 according to a third
embodiment of the present invention. In the piezoelectric power
generating device 31 of the third embodiment, the piezoelectric
power generating plate 2 is similar to that of the first
embodiment, except for the shape of the cutout. Therefore,
identical portions are assigned with identical reference numerals,
to thereby incorporate the description of the first embodiment. In
the piezoelectric power generating device 31, a cutout 2g is
further formed in addition to the cutout 2a illustrated in FIG. 5.
The cutout 2g has the shape of the cutout 2a reversed in the
portion surrounded by the cutout 2a. That is, the plurality of
cutouts 2a and 2g are provided such that the cutout 2a located
relatively outside surrounds the cutout 2g located relatively
inside. The cutout 2g includes a pair of cutout components 2g1 and
2g2 extending parallel to the long sides 2d and 2e from the side of
the short side 2b toward the side of the short side 2c, and
respective end portions of the cutout components 2g1 and 2g2 on the
side of the short side 2c are connected by a cutout component 2g3
extending parallel to the short side 2c. In FIG. 6, the support
member 3 and the electrodes 6 and 7 are omitted.
[0067] Since the cutout 2g is formed in addition to the cutout 2a,
a leading end 2h1 of a third piezoelectric power generating plate
portion 2h corresponding to the portion surrounded by the cutout 2g
forms a second free end.
[0068] Since the cutouts 2a and 2g are formed, in the piezoelectric
power generating device 31, the third piezoelectric power
generating plate portion 2h corresponding to the portion surrounded
by the cutout 2g is further displaced in a different direction from
that of the second piezoelectric power generating plate portion 2f
corresponding to the portion surrounded by the cutout 2a, when
vibration or external force is applied from outside. In this case,
in a front view of the piezoelectric power generating plate 2,
i.e., when the piezoelectric power generating plate 2 is viewed
from the side of the long side 2e, the piezoelectric power
generating plate 2 has the second piezoelectric power generating
plate portion 2f displaced at a different angle to a peripheral
portion including the fixed portion, and has the third
piezoelectric power generating plate portion 2h further displaced
in a different direction from that of the second piezoelectric
power generating plate portion 2f. That is, the piezoelectric power
generating plate 2 is displaced in a substantially meandering
shape. Since each of the second piezoelectric power generating
plate portion 2f and the third piezoelectric power generating plate
portion 2h is thus displaced in a different direction from that of
a portion including the fixed portion and the first piezoelectric
power generating plate portion 2u, it is possible to extract a
larger amount of power.
[0069] In the present embodiment, the third piezoelectric power
generating plate portion 2h corresponding to the portion surrounded
by the above-described cutout 2g is provided inside the second
piezoelectric power generating plate portion 2f corresponding to
the portion surrounded by the above-described cutout 2a. A portion
connecting this second piezoelectric power generating plate portion
2f and the third piezoelectric power generating plate portion 2h
corresponds to the aforementioned first free end. Further, the
third piezoelectric power generating plate portion 2h extends from
the first free end, and the leading end 2h1 of the third
piezoelectric power generating plate portion 2h corresponds to the
second free end of the present invention.
[0070] Also in the present embodiment, therefore, the first
piezoelectric power generating plate portion 2u located on the
fixed portion side and the cutouts 2a and 2g located between the
fixed portion and the leading end 2h1 forming the second free end
of the present invention are present. The cutouts 2a and 2g are
formed such that the first piezoelectric power generating plate
portion 2u, the second piezoelectric power generating plate portion
2f, and the third piezoelectric power generating plate portion 2h
are displaced in different directions.
[0071] Although the first and second cutouts 2a and 2g are provided
in FIG. 6, a larger number of cutouts may be provided.
[0072] FIG. 7 is a schematic perspective view of a piezoelectric
power generating device 41 according to a fourth embodiment of the
present invention. In the piezoelectric power generating device 41
of the fourth embodiment, the piezoelectric power generating plate
2 is similar to that of the first embodiment, except for the shape
of the cutout. Therefore, identical portions are assigned with
identical reference numerals, to thereby incorporate the
description of the first embodiment.
[0073] In the piezoelectric power generating device 41, cutouts 2i
and 2j are formed in the piezoelectric power generating plate 2.
The cutouts 2i and 2j include cutout components 2i1 and 2i2 and
cutout components 2j1 and 2j2, respectively. The cutout component
2i1 extends from the long side 2d toward the long side 2e of the
piezoelectric power generating plate 2, and a leading end portion
thereof is connected to the cutout component 2i2. The cutout
component 2i2 extends from the side of the short side 2b toward the
side of the short side 2c of the piezoelectric power generating
plate 2. The cutout component 2j1 extends from the long side 2e
toward the long side 2d of the piezoelectric power generating plate
2, and a leading end portion thereof is connected to the cutout
component 2j2. The cutout component 2j2 extends from the side of
the short side 2b toward the side of the short side 2c of the
piezoelectric power generating plate 2.
[0074] The cutout components 2i2 and 2j2 extend from respective end
portions thereof connected to the cutout components 2i1 and 2j1
toward the short side 2c, and are provided such that the distance
therebetween is reduced toward the short side 2c. Further, the
cutout components 2i2 and 2j2 are provided not to reach the short
side 2c. A region on the side of the long side 2e and a region on
the side of the long side 2d both on the side of the short side 2b
of the piezoelectric power generating plate 2 are joined with a
common weight 10.
[0075] In the piezoelectric power generating device 41 of the
present embodiment, the cutouts 2i and 2j are formed as described
above. When vibration or external force is applied from outside,
therefore, piezoelectric power generating plate portions 2k1 and
2k2 outside the cutouts 2i and 2j are displaced in a different
direction from that of the fixed portion fixed with the support
member 3 and corresponding to the portion surrounded by the cutouts
2i and 2j. Herein, the respective leading ends of the piezoelectric
power generating plate portions 2k1 and 2k2 form free ends. That
is, respective portions of the piezoelectric power generating plate
portions 2k1 and 2k2 reaching the cutout components 2i1 and 2j1
form free ends.
[0076] Also in the present embodiment, therefore, the cutouts 2i
and 2j are formed between the fixed portion and the free ends.
[0077] Further, with the above-described cutouts 2i and 2j formed
also in the present embodiment, a piezoelectric power generating
plate portion on the fixed portion side from the cutouts 2i and 2j
and a piezoelectric power generating plate portion on the free end
side from the cutouts 2i and 2j are displaced in different
directions between the fixed end and the free ends. It is therefore
possible to reduce the resonant frequency of the piezoelectric
power generating device 41, and obtain a large displacement amount.
Accordingly, it is possible to obtain a large power generation
amount, when vibration or external force is applied from
outside.
[0078] Moreover, the free ends corresponding to the respective
leading ends of the piezoelectric power generating plate portions
2k1 and 2k2 outside the cutouts 2i and 2j are both joined with the
weight 10. When vibration or external force is applied from
outside, therefore, torsional deformation and the phase difference
in flexion deformity between the free ends are suppressed, and it
is possible to suppress a reduction in power generation amount of
the piezoelectric power generating device 41.
[0079] The above-described piezoelectric power generating device 41
includes a portion in which stress is reversed when vibration or
external force is applied from outside. Therefore, the portion in
which stress is reversed and the remaining portion may be subjected
to a poling treatment in opposite directions in the thickness
direction. FIG. 8 illustrates a schematic plan view of the
piezoelectric power generating plate 2 in the piezoelectric power
generating device 41. The hatched polarized region P1 corresponds
to a portion in which, when vibration or eternal force is applied
from outside, strain is generated in the opposite direction to that
of strain generated in the polarized region P2 corresponding to the
remaining portion. The piezoelectric plate 5 is therefore subjected
to the poling treatment in the thickness direction similarly as in
the first embodiment, and the polarized region P1 and the remaining
polarized region P2 may be subjected to the poling treatment in
opposite directions in the thickness direction.
[0080] As described previously, it is possible in the present
invention to easily change the shapes of a plurality of differently
displaced portions of the piezoelectric power generating plate 2 by
devising the shape of the above-described cutout. Accordingly, it
is possible to control the resonant frequency of the piezoelectric
power generating plate 2. This will be described with reference to
(a) to (d) of FIG. 9. A plurality of piezoelectric power generating
devices were prepared each having a piezoelectric power generating
plate including a metal plate having a thickness of 0.1 mm and a
piezoelectric plate joined thereto. In FIG. 9, (a) is a schematic
plan view of a piezoelectric power generating device in a
comparative example including a piezoelectric power generating
plate 111. The piezoelectric power generating plate 111 is a
rectangular piezoelectric power generating plate including a
rectangular metal plate having a length (L1) of 30 mm, a width of
20 mm, and a thickness of 0.1 mm joined to a piezoelectric plate
having the same outer dimension and the same thickness. As
illustrated in (a) of FIG. 9, when the piezoelectric power
generating plate 111 was fixed in a fixed portion 9 corresponding
to a region of the piezoelectric power generating plate 111
surrounded by a broken line, specifically a region of the
piezoelectric power generating plate 111 extending by 5.0 mm from
one end thereof in the length direction, and vibration or external
force was applied from outside to cause cantilever vibration, the
resonant frequency of the piezoelectric power generating plate 111
in the piezoelectric power generating device of the comparative
example was 220.1 Hz. Herein, when the length from the one end of
the piezoelectric power generating plate 111 in the length
direction to an end portion of the fixed portion 9 is represented
as L2, L2 is 5.0 mm in the comparative example.
[0081] In FIG. 9, (b) is a schematic plan view of a piezoelectric
power generating device in a first experimental example including a
piezoelectric power generating plate 112. In FIG. 9, (c) is a
schematic plan view of a piezoelectric power generating device in a
second experimental example including a piezoelectric power
generating plate 113. The piezoelectric power generating plates 112
and 113 are each a piezoelectric power generating plate including a
metal plate having a substantially trapezoidal shape in a plan view
and a thickness of 0.1 mm joined with a piezoelectric plate having
the same outer dimension and the same thickness. In the
piezoelectric power generating plate 112, L1 is 30 mm, and L2 is
5.0 mm, similarly as in the piezoelectric power generating plate
111. In the piezoelectric power generating plate 113, L2 is 5.0 mm,
similarly as in the piezoelectric power generating plates 111 and
112. The piezoelectric power generating plate 113, however,
includes a portion extending from an end portion of the
piezoelectric power generating plate 112 by a length L3 of 6.0 mm.
That is, the length of the piezoelectric power generating plate 113
is L1+L3, which is 36.0 mm. In each of the piezoelectric power
generating plates 112 and 113, a length (W) of the other end in the
length direction opposite to the one end in the length direction of
the piezoelectric power generating plate is 4.0 mm. As illustrated
in (b) and (c) of FIG. 9, when the piezoelectric power generating
plates 112 and 113 were fixed in the fixed portion 9 corresponding
to a region of the piezoelectric power generating plates 112 and
113 surrounded by a broken line, and vibration or external force
was applied from outside to cause cantilever vibration, the
resonant frequency of the piezoelectric power generating plate 112
in the piezoelectric power generating device of the first
experimental example was 312.1 Hz, and the resonant frequency of
the piezoelectric power generating plate 113 in the piezoelectric
power generating device of the second experimental example was
224.7 Hz.
[0082] In FIG. 9, (d) is a schematic plan view of a piezoelectric
power generating device in a third experimental example including a
piezoelectric power generating plate 42. The piezoelectric power
generating plate 42 has a similar shape to that of the
piezoelectric power generating device 41 of the above-described
fourth embodiment, and has L1 of 30 mm, L2 of 5.0 mm, and W of 4.0
mm. As illustrated in (d) of FIG. 9, when the piezoelectric power
generating plate 42 was fixed in the fixed portion 9 corresponding
to a region of the piezoelectric power generating plate 42
surrounded by a broken line, and vibration or external force was
applied from outside to cause cantilever vibration, the resonant
frequency of the piezoelectric power generating plate 42 in the
piezoelectric power generating device of the third experimental
example was 184.1 Hz. That is, it is understood that the
piezoelectric power generating device 41 of the above-described
embodiment is capable of substantially reducing the resonant
frequency of the piezoelectric power generating plate 42, as
compared with the rectangular piezoelectric power generating plate
111 illustrated in (a) of FIG. 9 having the same outer dimension.
It is also understood from comparison of (a) to (d) of FIG. 9 that,
with a change in shape of the cutouts and the portion surrounded by
the cutouts, it is possible to easily adjust the resonant frequency
of the piezoelectric power generating plate to a low frequency,
while suppressing a reduction in area of the piezoelectric power
generating plate. Accordingly, it is understood that it is possible
to form a piezoelectric power generating device to obtain a larger
power generation amount by changing the shape of the portion
surrounded by the cutouts or the shape of the cutouts in accordance
with the purpose, i.e., in accordance with the frequency of the
vibration applied from outside.
[0083] FIG. 10 illustrates a piezoelectric power generating device
51 according to a fifth embodiment of the present invention. In
FIG. 10, (a) is a plan view of the piezoelectric power generating
device 51 according to the fifth embodiment of the present
invention, and (b) is a cross-sectional view illustrating a portion
along a D-D line in (a) of FIG. 10.
[0084] In the piezoelectric power generating device 51 of the fifth
embodiment, the rectangular piezoelectric power generating plate 2
is fixed with the support member 3 at an end portion thereof on the
side of short side 2b, i.e., on one end side thereof. That is, the
fixed portion is located on the side of the short side 2b. Further,
the piezoelectric power generating plate 2 is supported by the
support member 3 in a cantilever fashion. Accordingly, an end
portion on the side of the short side 2c, i.e., on the side
opposite to the fixed portion forms a free end.
[0085] In the piezoelectric power generating device 51 of the
present embodiment, a plurality of cutouts 2m and 2n are formed
between the fixed portion and the free end described above. The
cutout 2m extends from one long side 2d toward the other long side
2e. The cutout 2n extends from the long side 2e toward the other
long side 2d. That is, the plurality of cutouts 2m and 2n extend in
a direction perpendicular to a direction connecting the fixed
portion and the free end, and are alternately provided on opposite
end edges of the piezoelectric power generating plate in the
direction connecting the fixed portion and the free end.
[0086] In the present embodiment, when vibration or external force
is applied from outside, a first piezoelectric power generating
plate portion between the cutout 2n and the fixed portion, a second
piezoelectric power generating plate portion sandwiched between the
cutouts 2m and 2n, and a third piezoelectric power generating plate
portion between the cutout 2m and the free end are displaced in
different directions. Similarly as in the first embodiment,
therefore, the piezoelectric plate 5 may be subjected to the poling
treatment in different polarization directions in the thickness
direction in accordance with the region in which stress is reversed
when the displacement occurs in these different directions.
Accordingly, it is possible to extract power from charges generated
when the piezoelectric plate 5 is displaced.
[0087] Also in the present embodiment, the cutouts 2m and 2n are
formed. It is therefore possible to reduce the resonant frequency
of the piezoelectric power generating plate, and generate a large
amount of charges even when vibration of low frequency or weak
external force is applied from outside, to thereby extract a large
amount of power. As described above, the cutout of the present
invention may be provided between the fixed portion and the free
end, and may be formed into an appropriate shape in which the
piezoelectric power generating plate portion on the fixed portion
side from the cutout and the piezoelectric power generating plate
portion on the free end side from the cutout are differently
displaced.
[0088] FIG. 11 is a plan view of a piezoelectric power generating
device 61 according to a sixth embodiment of the present invention.
The piezoelectric power generating device 61 of the present
embodiment corresponds to a structure integrating two piezoelectric
power generating devices 21 of the second embodiment. That is, the
piezoelectric power generating plate 2 is formed with a cutout 2o.
The cutout 20 has a structure in which the cutouts 2a of the second
embodiment are integrated to share the cutout component 2a3. In the
piezoelectric power generating device 61, therefore, a pair of
piezoelectric power generating plate portions 2p1 and 2p2
surrounded by the cutout 20 are provided, and the respective
leading ends of these piezoelectric power generating plate portions
2p1 and 2p2 form free ends. Also in this case, when vibration or
external force is applied from outside, the piezoelectric power
generating plate portions 2p1 and 2p2 surrounded by the cutout 20
and the remaining piezoelectric power generating plate portion are
displaced in different directions. Accordingly, it is possible to
extract a large amount of power similarly as in the second
embodiment.
[0089] Further, in the present embodiment, the support members 3
are fixed to respective central portions in the length direction of
the long sides 2d and 2e of the above-described piezoelectric power
generating plate 2. That is, the fixed portion is located at the
center in the length direction of the piezoelectric power
generating plate 2. Thus, the fixed portion of the piezoelectric
power generating device of the present invention is not limited to
one end side of the piezoelectric power generating plate.
[0090] FIG. 12 is a plan view of a piezoelectric power generating
device 71 according to a seventh embodiment of the present
invention. In the piezoelectric power generating device 71 of the
present embodiment, the piezoelectric power generating plate 2 is
formed with a plurality of cutouts 2q, 2r, 2s, and 2t similarly as
in the fifth embodiment. Herein, the support member 3 is fixed at
the center in the length direction of the rectangular piezoelectric
power generating plate 2. Therefore, a piezoelectric power
generating plate portion between the support member 3 and an end
portion on one side of the piezoelectric power generating plate 2
and a piezoelectric power generating plate portion between the
support member 3 and an end portion on the other side of the
piezoelectric power generating plate 2 are displaced with the fixed
portion acting as a fulcrum. Each of the piezoelectric power
generating plate portion on the one side and the piezoelectric
power generating plate portion on the other side functions
similarly to the piezoelectric power generating device 51 of the
fifth embodiment. Accordingly, even in a case in which the
piezoelectric power generating device 71 is supported with the
fixed portion disposed at the center in the length direction of the
piezoelectric power generating plate 2, it is possible to extract a
large amount of power similarly as in the fifth embodiment.
[0091] Further, the fixed portion is provided at the center of the
piezoelectric power generating plate, as in the sixth and seventh
embodiments. Thus, the position of the fixed portion is not limited
to an end portion of the piezoelectric power generating plate.
Accordingly, it is possible to increase the degree of design
freedom of the portion for fixing the support member to an external
object.
REFERENCE SIGNS LIST
[0092] piezoelectric power generating device [0093] 2, 42
piezoelectric power generating plate [0094] 2a, 2g, 2i, 2j, 2m, 2n,
2o, 2q, 2r, 2s, 2t cutout [0095] 2a1, 2a2, 2a3, 2g1, 2g2, 2g3, 2i1,
2i2, 2j1, 2j2 cutout component [0096] 2b, 2c short side [0097] 2d,
2e long side [0098] 2f second piezoelectric power generating plate
portion [0099] 2h third piezoelectric power generating plate
portion [0100] 2f1, 2h1 free end [0101] 2k1, 2k2 piezoelectric
power generating plate portion [0102] 2p1, 2p2 piezoelectric power
generating plate portion [0103] 2u first piezoelectric power
generating plate portion [0104] support member [0105] metal plate
[0106] piezoelectric plate [0107] 6, 7 electrode [0108] 8 laminate
[0109] 9 fixed portion [0110] 10 weight [0111] 21, 31, 41, 51, 61,
71 piezoelectric power generating device
* * * * *