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JP2008252878

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DESCRIPTION JP2008252878
A flexure comprising a vibrator (10) comprising a shim (11) and piezoelectric flexural vibration
elements (12, 13) attached to both front and back surfaces thereof, and a vibrator holding
portion (20) for holding the vibrator Reduce the size and weight of the vibration type actuator,
improve the acoustic characteristics, and improve the excitation efficiency. An elongated platelike base plate (30) which holds a vibrator holding portion (20) and which is disposed below and
spaced apart from the vibrator (10) and extends in the longitudinal direction of the vibrator. And
the high rigidity portion (11a, 11b) of a predetermined length is formed in the shim (11) of a
portion adjacent to the root side end of the vibrator (10), or the root side end of the vibrator (10)
An elastic plate-like body (34) is disposed on the base plate (30) in a portion adjacent to the
portion to fill the gap with the vibrator for a predetermined length. [Selected figure] Figure 1
Flexural vibration type actuator for electronic equipment
[0001]
The present invention relates to a flexural vibration type actuator used for small electronic
devices such as mobile phones, and more particularly to a flexible vibration type actuator for
electronic devices which is small in size, light in weight, excellent in acoustic characteristics and
high in excitation efficiency. is there.
[0002]
Heretofore, small-sized flexural vibration type actuators have been developed for small-sized
electronic devices such as mobile phones.
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1
In this actuator, a bimorph-type vibrator is formed by attaching piezoelectric flexural vibration
elements to both front and back surfaces of a thin plate-like shim. One end of the vibrator or a
central portion in the longitudinal direction is held by a holder, and a bottom plate of an
elongated case supporting the holder is attached to a diaphragm which also serves as a
transparent protective plate on the front surface of the display panel of the electronic device. The
flexural vibration excited by the vibrator is transmitted from the holding portion to the
diaphragm serving as the transparent protective plate on the front surface of the display panel of
the electronic device to which the bottom plate of the case is attached via the bottom plate of the
case supporting the case. Thereby, a speaker of a bending vibration mode (DM) system is formed
(patent documents 1 and 2), JP, 2005-160028, A JP, 2006-116399, A
[0003]
In the above-described conventional flexural vibrator type actuator, mechanical characteristics
such as the cross-sectional shape of the vibrator are uniform along the longitudinal direction. For
this reason, in order to adjust the excitation efficiency and the vibration characteristic to a
predetermined diaphragm, it is necessary to change the length of the vibrator. If the length is
changed, it is necessary to increase the width of the vibrator in order to obtain a constant
vibrational energy. As described above, there has been a problem that it is difficult to optimize
the acoustic characteristic, the excitation characteristic, and the like by the simple design change
and adjustment of the vibrator.
[0004]
In addition, the conventional flexural vibration type actuator is generally housed in an elongated
case. For this reason, there is a problem that the size, weight and manufacturing cost of the case
are increased, making it difficult to reduce the size, weight and cost. Furthermore, if the weight of
the case increases, the fixing mechanism for fixing the case to the diaphragm of the small
electronic device becomes large, heavy and expensive, and the excitation efficiency of the flexural
vibration to the diaphragm decreases. There has been a problem that the manufacturing cost
becomes expensive.
[0005]
Therefore, one object of the present invention is to provide a flexural vibration type actuator
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having good acoustic characteristics and high excitation efficiency.
[0006]
Another object of the present invention is to provide a flexural vibration type actuator which is
small in size, light in weight, inexpensive and has high excitation efficiency of the flexural
diaphragm to the diaphragm which doubles as a protective plate on the front surface of the
display panel of the compact electronic device. .
[0007]
According to a first aspect of the present invention, there is provided a flexural vibration type
actuator which solves the problems of the prior art, a shim comprising an elongated plate-like
body and a vibrator comprising a piezoelectric flexural vibration element attached to both sides
of the shim; And a vibrator holding portion for holding the one end or the central portion in the
longitudinal direction as a root side end, and the flexural vibration excited by the vibrator is
transparent to the front surface of the display panel of the electronic device through the vibrator
holding portion. It is a flexural vibration type actuator that excites flexural vibration on a
diaphragm that doubles as a protective plate.
The actuator includes a base plate of an elongated plate-like member which holds the vibrator
holding portion and is spaced apart below the vibrator and extends in the longitudinal direction
of the vibrator. A high rigidity portion of a predetermined length is formed in the shim adjacent
to the root end.
[0008]
According to the flexural vibration type actuator of the second invention for solving the problems
of the prior art, the vibrator holding portion is held and spaced below the vibrator, and is
extended in the longitudinal direction of the vibrator An elastic plate-like member is disposed on
the base plate of a portion adjacent to the root side end of the vibrator, filling a gap with the
vibrator over a predetermined length.
[0009]
The flexural vibration type actuator according to the first and second aspects of the invention is
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an elongated plate-like body which holds a vibrator holding portion and is spaced apart below
the vibrator and extends in the longitudinal direction of the vibrator. Since the base plate is
provided, the conventional box is not required, and the overall size reduction, weight reduction
and manufacturing cost reduction can be realized.
Moreover, with the weight reduction of this actuator, the attachment mechanism for attaching
this to the diaphragm that doubles as the transparent protective plate on the front surface of the
display panel of the electronic device is simplified, and the excitation characteristics of the
flexural vibration to this diaphragm are also improved. Ru.
[0010]
Further, in the flexural vibration type actuator according to the first aspect of the present
invention, since the high rigidity portion having a predetermined length is formed in the portion
adjacent to the root side end of the vibrator, the length of the vibrator is not adjusted. It is
possible to increase the lowest natural frequency (resonance frequency) from the conventional
bass range to the midrange.
As a result, vibration energy in the midrange increases, and the aural sound pressure level rises.
In addition, since the vibration characteristics in the middle to high range are also flattened, the
sound pressure level versus frequency characteristics are also flattened, and the sound quality is
improved.
[0011]
Further, according to the flexural vibration type actuator according to the second aspect of the
present invention, the elastic plate-like body is disposed on the base plate of the portion adjacent
to the root side end of the vibrator to fill the gap with the vibrator over a predetermined length.
There is. As a result, in the portion adjacent to the root side end, the amplitude of vibration is
suppressed, and substantially the same result as forming the high rigidity portion in the shim,
without adjusting the length of the vibrator The lowest natural frequency can be increased from
the conventional low range to the midrange. As a result, the vibration energy in the midrange
increases, and the aural sound pressure level rises. In addition, since the vibration characteristics
in the middle to high range are also flattened, the sound pressure level versus frequency
characteristics are also flattened, and the sound quality is improved.
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4
[0012]
According to one preferred embodiment of the present invention, a characteristic configuration
of the first invention that a high-rigidity portion of a predetermined length is formed in a portion
adjacent to the root side end portion of the shim, and a vibrator By combining the characteristic
features of the second aspect of the present invention, an elastic plate member is disposed on the
base plate of the portion adjacent to the root side end portion to fill the gap with the vibrator
over a predetermined length. Improvement and improvement of acoustic characteristics.
[0013]
According to another preferred embodiment of the present invention, the base plate is attached
to the diaphragm of the electronic device by an attachment mechanism such as a discretely
disposed double-sided adhesive tape, whereby the protective plate on the front surface of the
display panel from the base plate The vibration transmission characteristics to the diaphragm
which also serves as
[0014]
1 is an exploded perspective view showing the configuration of a flexural vibration type actuator
according to a first embodiment of the present invention, FIG. 2 is a perspective view of the same,
FIG. 3 is a plan view (A) and its BB 'sectional view (B ), Side view (C).
The flexural vibration type actuator includes a vibrator 10, a holding unit 20, and a base plate
30.
[0015]
The vibrator 10 is composed of an elongated thin rectangular shim 11 made of metal, and
piezoelectric flexural vibrating elements 12 and 13 fixed to both surfaces of the shim 11 by
adhesion.
The flexural vibration type actuator further includes a feeding clamp 14 formed by bending a
resilient metal plate such as phosphor bronze for supplying operating power to the piezoelectric
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flexural vibrating elements 12 and 13, and the feeding clamp 14. The piezoelectric bending
vibrators 12 and 13 are provided with an input terminal 15 for supplying an operating power of
an alternating current through the clamp 14.
[0016]
It is desirable to select a material such as stainless steel or aluminum alloy which is hard and
which has low internal friction loss and high Q as a metal constituting the shim 11, both in terms
of acoustic characteristics and excitation efficiency. As the piezoelectric flexural vibration
elements 12 and 13, a structure in which a plurality of thin plates of a piezoelectric ceramic such
as barium titanate is stacked while being sandwiched between electrode layers is preferable. An
L-shaped bent portion 11a and 11b are formed at a root side end of the shim 11 over a
predetermined length, which is a high rigidity portion against bending vibration.
[0017]
The base plate 30 is formed of an elongated thin rectangular metal plate, and on its root side,
locking claws 31 and 32 which are upright from the left and right sides are formed. An opening
33 for vibration suppression is formed in a bent portion which stands upright from the tip of the
base plate 30. In consideration of the convenience of such bending, the base plate 30 is
preferably made of metal such as brass. The vibrator holding portion 20 is formed of a columnar
body made of resin, and as shown in the cross-sectional view of FIG. 3B, a rectangular cross
section in which the root side end of the shim 11 is formed inside the columnar body The
vibrator 10 is held by the vibrator holding portion 20 in a cantilevered state by being pressed
into the inside of the thin slit.
[0018]
A feeding clamp 14 made of a spring metal is inserted along the insertion grooves formed on the
top and bottom of the vibrator holding portion 20, and the tip portion thereof is formed on the
front and back of the vibrator 10. The pressure is applied to the electrodes formed on the
surfaces of the piezoelectric bending vibration elements 12 and 13. Thereby, an electrical
connection with small contact resistance is completed between the feeding clamp 14 and the
piezoelectric flexural vibration elements 12 and 13.
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[0019]
An elastic plate-like body 34 is adhesively fixed to a location adjacent to the root side end of the
base plate 30. A plate-like elastic body 35 is bonded and fixed to a portion adjacent to the tip end
of the base plate 30. After the vibrator holding portion 20 for holding the vibrator 10 in a
cantilevered state is inserted between the locking claws 31 and 32 which are erected from the
left and right of the base end of the base plate 30, the locking claw 31 is , 32 tip part is bent
inward. As a result, the vibrator holding portion 20 is fixed to the upper surface of the root side
end of the base plate 30 by caulking by the locking claws 31 and 32.
[0020]
When the vibrator holding portion 20 is fixed to the base plate 30, the tip end of the shim 11 of
the vibrator 10 is inserted into the vibration suppressing opening 33 formed in the bent portion
which stands upright from the tip of the base plate 30. Referring to the cross-sectional view of
FIG. 3B and the side view of FIG. 3C, the elastic plate-like body 34 disposed at the root end of the
base plate 30 comprises the base plate 30 and the vibrator 10 above it. And adhesively fixed to
the top surface of the base plate 30 and the bottom surface of the vibrator 10 so as to completely
close the gap formed therebetween. The elastic plate-like body 34 is made of an elastic body such
as polyurethane, foamed resin, soft rubber or the like. On the other hand, the plate-like elastic
body 35 disposed at the tip end of the base plate 30 is formed on the upper surface of the base
plate 30 while forming a small gap between the base plate 30 and the vibrator 10 above it. It is
adhesively fixed. The material of the plate-like elastic body 35 is selected to be softer than the
elastic plate-like body 34.
[0021]
The flexural vibration type actuator configured in this way is mounted on the back surface of a
diaphragm that doubles as a transparent protective plate on the front surface of the display panel
of an electronic device (not shown) such as a cellular phone while the base plate 30 Be For the
purpose of enhancing the attachment strength, it is desirable to dispose a double-sided adhesive
tape over the entire bottom surface of the base plate 30. However, in such a configuration, the
structure of the combined beam is formed by the base plate 30 and the diaphragm serving as the
transparent protective plate, the rigidity against the flexural vibration becomes too strong, and
the flexural vibration is excited to the diaphragm serving as the transparent protective plate.
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There is a risk that the efficiency will decline. In order to reduce such a possibility, a
configuration is employed in which the double-sided adhesive tape is used at a distance from the
root side end of the base plate 30 and the tip side end so as to be used less.
[0022]
When power is supplied from the input terminal, alternating current power is supplied to the
piezoelectric flexural vibration elements 12 and 13 formed on the front surface side and the back
surface side of the shim 11 of the vibrator 10 through the feeding clamp 14 and these flexural
vibrations Is started. In the piezoelectric bending vibration elements 12 and 13, polarization in
the thickness direction is formed so as to be opposite to each other. For this reason, the
piezoelectric bending vibration elements 12 and 13 generate bending vibrators which mutually
strengthen each other in opposite phase.
[0023]
The vibration excited by the vibrator 10 is converted to the vibration in the vertical direction of
the vibrator holding portion 20, transmitted to the diaphragm of the small electronic device (not
shown) through the base plate 30, and the bending vibration is excited to this diaphragm Do. As
described above, in order to accommodate the vibrator 10 internally for the purpose of
protecting the vibrator 10, in place of the box used conventionally, a base plate which performs a
function similar to the bottom plate of the conventional box is installed. Ru. For this reason,
downsizing, weight reduction and cost reduction of the manufacturing cost of the entire actuator
can be realized. At the same time, as the weight of the actuator is reduced, the load on the
mechanism for attaching the actuator to the diaphragm of the small electronic device is reduced,
and the application of a simple mechanism such as double-sided adhesive tape becomes possible.
[0024]
Heretofore, the vibrator 10 has been housed inside the box in order to protect the vibrator 10
from excessive shock generated by contact of the user's hand or dropping the electronic device
to the floor or to provide a dustproof function. . However, when attached to a diaphragm that
also serves as a transparent protective plate for small electronic devices such as mobile phones, it
can be housed in a space with a dustproof function on the back side of the diaphragm that also
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serves as this protective plate. As far as destruction and dustproof function by contact is
concerned, it is sufficient to remove only the base plate to perform the vibration mediating
function by removing the box.
[0025]
The piezoelectric fitting vibration elements 12 and 13 constituting the vibrator 10 are formed of
relatively fragile piezoelectric elements such as barium titanate. For this reason, there is a
possibility of breakage due to the occurrence of excessive bending vibration. This excessive
vibration is often generated by an impact when an electronic device such as a mobile phone in
which the actuator is formed falls on a hard floor such as concrete, rather than a signal. In order
to suppress this excessive vibration, a plate-like elastic body 35 and an opening 33 are formed.
[0026]
FIG. 4 is experimental data showing the vibration characteristics of the flexural vibration type
actuator of the first embodiment. The horizontal axis is the frequency of vibration, and the
vertical axis is the driving force (newton) generated at an input voltage of 1 volt. The solid line in
the figure is the vibration characteristic of the actuator of the embodiment described above. The
dotted lines show vibration characteristics obtained for an actuator having a structure different
from the L-shaped bent portions 11a and 11b and not forming the elastic plate-like body 34 in a
portion adjacent to the root side end of the shim 11. It is.
[0027]
The lowest natural frequency (resonance point) of the vibrator is pushed up from near 150 Hz in
the low range to around 800 H in the mid range with bending of the shim and high rigidity by
the insertion of the elastic plate-like body There is. As a result, the vibration level in the middle to
high range of 800 Hz to 5000 Hz, which is high in auditory sensitivity, is increased and the
excitation efficiency is enhanced. At the same time, the vibration characteristics of this middle
and high range approach flat characteristics, and the acoustic characteristics are also improved.
The vibration characteristics can be further finely adjusted by adjusting the length of the folded
portion of the shim in the longitudinal direction, the length of the elastic plate 34 in the
longitudinal direction, or the like.
11-05-2019
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[0028]
In the above, the structure which implement | achieves the highly rigid part with respect to
bending vibration by L-shaped bending was illustrated. However, appropriate changes can be
made, such as further bending the tip of the bent portion above the vibrator.
[0029]
FIG. 5 is an exploded perspective view showing a configuration of a flexural vibration type
actuator for electronic equipment according to a second embodiment of the present invention. In
this figure, the components given the same reference numerals as in FIGS. 1, 2 and 3 are the
same components as those already described with reference to the respective drawings in the
description of the first embodiment. About these, duplicate explanation is omitted.
[0030]
The first point in which the second embodiment differs from the first embodiment is that the
formation of the high-rigidity portions (11a, 11b) by bending of both ends is omitted on the root
side of the shim 11. is there. A second point different from the first embodiment is that the
height of the elastic plate-like body 34 can be adjusted by the thickness of the elastic adhesive
layer 38 which fixes it on the base plate 30.
[0031]
Also in the first embodiment and the second embodiment, the surface of the elastic plate 34 and
the bottom surface of the vibrator 10 are bonded and fixed. In practice, the thickness of the shim
11, the thickness of the lower piezoelectric bending vibrator 13, the manufacturing / assembly
error of the vibrator holder 20, and the like exist. Therefore, a gap is likely to be generated
between the lower surface of the vibrator 10 and the upper surface of the elastic plate-like body
34. If the two are forcedly bonded in a state where a gap is generated, the elastic plate-like body
34 is pulled downward, and the position of the center thereof is shifted downward. Therefore,
there is a problem that the height of the tip end portion of the shim 11 is deviated from the
center position of the opening 33 in the vertical direction. In addition, initial deflection may
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occur in the elastic plate-like body 34 pulled downward, which may deteriorate the acoustic
characteristics.
[0032]
Therefore, in order to solve this problem, in the second embodiment, a structure is adopted in
which the elastic plate-like body 34 is adhered and fixed on the base plate 30 with the thick
elastic adhesive layer 38 interposed. Then, by adjusting the thickness of the thick elastic adhesive
layer 38, the height of the surface of the elastic plate-like body 34 is adjusted, and this does not
form a gap with the bottom surface of the vibrator 10. It makes sure that the bottom surface is in
contact.
[0033]
In assembling the actuator of this embodiment, first, the plate-like elastic body 35 is adhesively
fixed to the front end side of the surface of the base plate 30. Next, on the root side of the base
plate 30, the adhesive film 40 having an adhesive layer formed on the back surface is attached to
the surface of the base plate 30 to fix the adhesive film 40 on the base plate 30. The adhesive
film 40 is made of a polycarbonate (PC) film, a polyethylene terephthalate (PET) film, or the like.
The adhesive film 40 has substantially the same shape as the bottom surface of the elastic
adhesive layer 34 to be stuck thereon. In order to form an elastic adhesive layer 38 on the
surface of the adhesive film 40, a certain amount of elastic adhesive is poured out from the tip of
a nozzle (not shown). The pouring out of the elastic adhesive is preferably performed
automatically using a robot.
[0034]
The elastic adhesive poured out from the tip of the nozzle spreads in the lateral direction because
of the surface tension acting on the surface of the adhesive film 40, even if the elastic adhesive is
spread beyond the periphery of the adhesive film 40. Be suppressed. As a result, the bottom of
the elastic adhesive layer 38 follows the shape of the adhesive film 40. In order to achieve this
purpose, the kinematic viscosity of the elastic adhesive is set to an optimal value. The adhesive
film 40 is manufactured by, for example, die-cutting a single-sided adhesive tape having a large
uniform shape.
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[0035]
Subsequently, on the surface of the adhesive film 40 attached and fixed on the base plate 30, the
elastic plate-like body 34 having the double-sided adhesive tape attached and fixed on the
surface side is placed. Finally, the bottom surface of the vibrator 10 is attached and fixed to the
surface of the elastic plate-like body 34. The thickness of the elastic adhesive layer 38
immediately after injection is set to be a somewhat larger value. This is in order to ensure that
the bottom surface of the vibrator 10 can contact the surface of the elastic plate-like body 34
even if the thickness of the shim 11 and the lower piezoelectric bending vibrator 13 is
insufficient.
[0036]
The contact pressure received from the vibrator 10 causes the elastic plate 34 to slightly
descend. This spreads the elastic adhesive layer 38 before curing slightly laterally and reduces
the thickness slightly. At this time, a preferable state is realized in which the bottom surface of
the vibrator 10 is adhered and fixed while being in slight contact with the surface of the elastic
plate-like body 34. In this state, the tip portion of the shim 11 is adjusted to be at the center of
the opening 33. This series of assembly operations is performed quickly before the elastic
adhesive layer 38 cures.
[0037]
As a material of the elastic adhesive layer 38, a material having a curing shrinkage rate as small
as possible is selected so that the thickness does not change even after curing. Also, a material
such as silicon is selected so that the elastic adhesive layer 38 after curing can exhibit
appropriate elasticity without being too hard. The Shore hardness after curing of this elastic
adhesive is preferably in the range of 50 to 70. As a specific example, Cemedine Super X (siliconbased), Threebond 1530 (silyl group-terminated polymer) and the like are preferable. The area of
the elastic adhesive layer 38 is several tens square mm, and the thickness thereof is preferably in
the range of 0.1 mm to 0.5 mm.
[0038]
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12
The third point of the actuator of the second embodiment shown in FIG. 5 is different from the
actuator of the first embodiment in that a small rectangular plate is formed on the surface of the
tip of the shim 11 and soft such as urethane foam. The impact absorbing piece 39 made of a
material is fixed in advance by adhesion. This absorbs the impact generated when the tip of the
vibrator collides with the inner peripheral portion of the opening 33 due to the impact force
generated when the electronic device falls or the excessive amplitude generated during
operation, thereby avoiding breakage. .
[0039]
The fourth point different from the actuator of the first embodiment is that the feeding clamp 14
is formed with a curved portion that meanders in the horizontal direction. The curved portion
weakens the impact force generated by a drop or the like and transmitted to the fragile and
fragile magnetic piezoelectric bending vibration element 12 or 13 through the power feeding
clamp 14 and protects it from breakage.
[0040]
The structure using the vibrator in the form of a cantilever that holds one end of the vibrator has
been described above. However, a flexural vibration type actuator in which a vibrator in the form
of a cantilever is formed on both sides in the longitudinal direction of the vibrator holding
portion, or a type in which the central portion in the longitudinal direction of the vibrator is fixed
by the vibrator holding portion The present invention can also be applied to a flexural vibration
type actuator.
[0041]
In the first and second embodiments described in detail above, the dimensions of the vibrator 10
are preferably in the range of 20 mm to 50 mm in length, 3 mm to 10 mm in width, and 0.5 mm
to 3 mm in thickness. Below the above-mentioned minimum size, the size is too small and the
manufacture becomes difficult. In addition, when the size is larger than the above-mentioned
maximum size, application to small portable devices such as mobile phones becomes difficult.
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13
[0042]
Further, as the plate-like elastic body 35, a cushioning material having a thickness of 0.3 mm to 1
mm is formed using a urethane foam material having a foaming ratio of 10 to 50 as a material. A
resin molded product is used as the vibrator holding portion 20 in order to realize a complicated
shape.
[0043]
FIG. 1 is an exploded perspective electronic view showing a configuration of a flexural vibration
type actuator for an electronic device according to a first embodiment of the present invention. It
is a perspective electronic view which shows the structure of the bending vibration type actuator
for electronic devices of the said Example. It is a top view (A) which shows the structure of the
bending vibration type | mold actuator for electronic devices of the said Example, B-B 'sectional
drawing (B) of this top view (A), and a side view (C). It is experimental data which shows the
vibration characteristic of the bending vibration type actuator for electronic devices of the said
Example compared with the thing of the conventional bending vibration type actuator for
electronic devices. It is a disassembled perspective electronic view which shows the structure of
the bending vibration type | mold actuator for electronic devices of the 2nd Example of this
invention.
Explanation of sign
[0044]
10 Vibrator 11 Shim 11a, 11b Folded portion of predetermined length 12, 13 Piezoelectric
flexural vibration element 14 Scissors for power supply 15 Input terminal 20 Vibrator holding
portion 30 Base plate 31, 32 Locking claw 33 Opening 34 Elastic plate member 35 Plate shape
Elastic body 36, 37 Double-sided adhesive tape 38 Elastic adhesive layer 39 Impact-absorbing
piece 40 Adhesive film
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14
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