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JPWO2014024736

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DESCRIPTION JPWO2014024736
Abstract The task is to obtain good sound pressure frequency characteristics. In order to solve
this subject, the sound generator (1) according to the embodiment at least includes a plurality of
piezoelectric elements (excitation devices) (5) and a vibrating body (3a). An electric signal is
input and the plurality of piezoelectric elements (5) vibrate. The plurality of piezoelectric
elements (5) are attached to the vibrator (3a). Further, the plurality of piezoelectric elements (5)
are asymmetrical with respect to all the symmetry axes of the figure drawn by the outline of the
vibrator (3a) in plan view. Is attached to
Acoustic generator, acoustic generator and electronic device
[0001]
Embodiments of the disclosure relate to a sound generator, a sound generator and an electronic
device.
[0002]
Conventionally, a sound generator using an actuator is known (see, for example, Patent
Document 1).
Such a sound generator vibrates the diaphragm by applying a voltage to the actuator attached to
the diaphragm to vibrate, thereby outputting a sound.
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1
[0003]
JP, 2009-130663, A
[0004]
However, since the above-mentioned conventional sound generator actively utilizes the
resonance of the diaphragm, the peak of the frequency characteristic of the sound pressure (the
part where the sound pressure is higher than the surrounding area) and the dip (the sound
pressure is larger than the surrounding area) There is a problem that low parts are likely to occur
and it is difficult to obtain good sound quality.
[0005]
One aspect of the embodiments is made in view of the above, and it is an object of the present
invention to provide an acoustic generator, an acoustic generator and an electronic device
capable of obtaining good frequency characteristics of sound pressure.
[0006]
The sound generator according to one aspect of the embodiment at least includes a plurality of
exciters and a vibrating body.
The plurality of exciters vibrate upon receiving an electrical signal.
The plurality of exciters are attached to the vibrator.
The plurality of exciters are attached to the vibrator so as to be asymmetric with respect to all
symmetry axes of the figure drawn by the outline of the vibrator when viewed in plan.
[0007]
According to one aspect of the embodiment, good sound pressure frequency characteristics can
be obtained.
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[0008]
FIG. 1A is a schematic plan view showing the configuration of the sound generator according to
the first embodiment.
FIG. 1B is a cross-sectional view taken along line A-A 'of FIG. 1A. FIG. 2A is a diagram (part 1)
showing a frequency characteristic of sound pressure. FIG. 2B is a second diagram showing
frequency characteristics of sound pressure. FIG. 3 is a schematic plan view (part 1) showing an
arrangement example of the piezoelectric element. FIG. 4A is a schematic plan view (No. 2)
showing an arrangement example of the piezoelectric element. FIG. 4B is a schematic plan view
(No. 3) showing an example of arrangement of piezoelectric elements. FIG. 5A is a schematic plan
view (No. 4) showing an example of arrangement of piezoelectric elements. FIG. 5B is a schematic
plan view (No. 5) showing an example of arrangement of piezoelectric elements. FIG. 6A is a
schematic plan view (No. 6) showing an example of arrangement of piezoelectric elements. 6B is
a cross-sectional view taken along line B-B 'of FIG. 6A. FIG. 7A is a diagram showing a
configuration of a sound generation device according to a second embodiment. FIG. 7B is a view
showing the configuration of the electronic device according to the third embodiment.
[0009]
Hereinafter, embodiments of a sound generator, a sound generator and an electronic device
disclosed in the present application will be described in detail with reference to the attached
drawings. Note that the present invention is not limited by the embodiments described below.
[0010]
First Embodiment First, the configuration of the sound generator according to the first
embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a schematic plan
view showing the configuration of the sound generator 1 according to the present embodiment,
and FIG. 1B is a cross-sectional view taken along the line A-A ′ of FIG. 1A.
[0011]
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In order to make the explanation easy to understand, FIGS. 1A and 1B show a three-dimensional
orthogonal coordinate system. Moreover, in FIG. 1A, illustration of the resin layer 7 is omitted.
Such an orthogonal coordinate system may also be shown in other drawings used in the
following description.
[0012]
Also, in order to make the description easy to understand, FIG. 1B shows the sound generator 1
greatly exaggerated in the Z-axis direction.
[0013]
As shown to FIG. 1A, the sound generator 1 which concerns on this embodiment is provided with
the frame 2, the diaphragm 3, the several piezoelectric element 5, and the resin layer 7. As
shown in FIG.
[0014]
In addition, as shown to FIG. 1A, in this embodiment, although the case where the sound
generator 1 is equipped with the two piezoelectric elements 5 is mainly illustrated, it should just
be plural, and even if it is three or more, it is sufficient. Good.
Further, in the present embodiment, the description will be given assuming that the two
piezoelectric elements 5 have the same shape unless otherwise specified.
[0015]
The frame 2 is composed of two frame members 2a and 2b having the same rectangular frame
shape, and functions as a support for supporting the diaphragm 3 by sandwiching the peripheral
portion of the diaphragm 3 .
The thickness, material, and the like of the frame 2 are not particularly limited. The frame 2 can
be formed using various materials such as metal and resin. For example, a stainless steel or the
like having a thickness of about 100 to 1000 μm can be suitably used as the frame 2 because of
excellent mechanical strength and corrosion resistance.
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[0016]
The diaphragm 3 has a film-like shape, and its peripheral edge portion is sandwiched and fixed to
the frame 2 in a state where tension is applied. A portion of the diaphragm 3 located inside the
frame 2, that is, a portion of the diaphragm 3 which is not sandwiched by the frame 2 and can
freely vibrate is referred to as a vibrator 3 a. Therefore, the vibrating body 3 a is a substantially
rectangular portion inside the frame 2, and is provided inside the frame 2 so as to be capable of
vibrating.
[0017]
Moreover, the diaphragm 3 can be formed using various materials, such as resin and a metal. For
example, the diaphragm 3 can be made of a resin film of polyethylene, polyimide or the like
having a thickness of about 10 to 200 μm. In addition, when the diaphragm 3 has sufficient
rigidity, it is not necessary to have the frame 2.
[0018]
A plurality of piezoelectric elements 5 are attached to the surface of the vibrating body 3a, and
function as an exciter that excites the vibrating body 3a by vibrating upon receiving an applied
voltage. The piezoelectric element 5 has a plate-like shape whose upper and lower main surfaces
are rectangular. The piezoelectric element 5 includes a laminate 33 formed by alternately
laminating four piezoelectric layers 31 (31a, 31b, 31c, 31d) and three internal electrode layers
32 (32a, 32b, 32c). It includes surface electrode layers 34 and 35 formed on upper and lower
surfaces of the laminate 33, and first to third external electrodes provided at the end of the
laminate 33 in the longitudinal direction (Y-axis direction). .
[0019]
The first external electrode 36 is disposed at the end of the laminate 33 in the -Y direction, and is
connected to the surface electrode layers 34 and 35 and the internal electrode layer 32 b. A
second external electrode 37 and a third external electrode (not shown) are arranged at an end in
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the + Y direction of the stacked body 33 at an interval in the X-axis direction. The second outer
electrode 37 is connected to the inner electrode layer 32a, and the third outer electrode (not
shown) is connected to the inner electrode layer 32c.
[0020]
The upper and lower end portions of the second external electrode 37 are extended to the upper
and lower surfaces of the laminated body 33 to form folded external electrodes 37 a, and these
folded external electrodes 37 a are formed on the surface of the laminated body 33. The surface
electrode layers 34 and 35 are extended at a predetermined distance so as not to be in contact
with the surface electrode layers 34 and 35. Similarly, upper and lower end portions of the third
external electrode (not shown) are extended to the upper and lower surfaces of the laminate 33
to form folded external electrodes (not shown), respectively, and these folded external electrodes
are formed. The surface electrode layers 34 and 35 (not shown) are extended at a predetermined
distance from the surface electrode layers 34 and 35 so as not to contact the surface electrode
layers 34 and 35 formed on the surface of the laminate 33.
[0021]
The piezoelectric layers 31 (31a, 31b, 31c, 31d) are polarized in the direction shown by the
arrows in FIG. 1B, and when the piezoelectric layers 31a, 31b are contracted, the piezoelectric
layers 31c, 31d are extended. When the piezoelectric layers 31a and 31b extend, a voltage is
applied to the first external electrode 36, the second external electrode 37, and the third external
electrode so that the piezoelectric layers 31c and 31d contract. . As described above, the
piezoelectric element 5 is a bimorph type piezoelectric element, and when an electric signal is
input, the piezoelectric element 5 bends and vibrates in the Z-axis direction so that the amplitude
changes in the Y-axis direction. Note that one end of a wiring conductor (not shown) is connected
to the first external electrode 36, the second external electrode 37, and the third external
electrode, and the other end of the wiring conductor (not shown) is a resin layer 7 The electric
signal is input to the first external electrode 36, the second external electrode 37, and the third
external electrode through the wiring conductor.
[0022]
As the piezoelectric layer 31, existing piezoelectric ceramics such as lead-free piezoelectric
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materials such as lead zirconate (PZ), lead zirconate titanate (PZT), Bi layer compounds, tungsten
bronze structure compounds and the like can be used. . The thickness of the piezoelectric layer
31 can be appropriately set in accordance with the desired vibration characteristics, but can be,
for example, 10 to 100 μm from the viewpoint of low voltage driving.
[0023]
The internal electrode layer 32 can be formed using various existing conductor materials, but can
include, for example, a metal component consisting of silver and palladium and a material
component constituting the piezoelectric layer 31. . By causing the internal electrode layer 32 to
contain the ceramic component constituting the piezoelectric layer 31, the stress due to the
thermal expansion difference between the piezoelectric layer 31 and the internal electrode layer
32 can be reduced. The internal electrode layer 32 may not contain a metal component
consisting of silver and palladium, and may not contain a material component constituting the
piezoelectric layer 31.
[0024]
The surface electrode layers 34 and 35 and the first to third external electrodes can be formed
using various existing conductor materials, and for example, they should contain a metal
component and a glass component consisting of silver. Can. Thus, when the surface electrode
layers 34 and 35 and the first to third external electrodes contain a glass component, the surface
electrode layers 34 and 35 and the first to third external electrodes, the piezoelectric layer 31
and Although strong adhesion can be obtained with the internal electrode layer 32, it is not
limited thereto.
[0025]
Further, the main surface on the vibrating body 3 a side of the piezoelectric element 5 and the
vibrating body 3 a are joined by the adhesive layer 26. The thickness of the adhesive layer 26 is
desirably 20 μm or less, and more desirably 10 μm or less. When the thickness of the adhesive
layer 26 is 20 μm or less, the vibration of the laminate 33 can be easily transmitted to the
vibrating body 3 a.
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[0026]
The adhesive for forming the adhesive layer 26 may be a known one such as an epoxy resin, a
silicone resin, or a polyester resin. As a method of curing the resin used for the adhesive, any
method such as heat curing, photo curing or anaerobic curing may be used.
[0027]
Furthermore, in the sound generator 1 of the present embodiment, at least a part of the surface
of the vibrating body 3 a is covered with the covering layer made of the resin layer 7. In detail, in
the sound generator 1 of the present embodiment, the resin is filled inside the frame member 2a
so that the vibrator 3a and the piezoelectric element 5 are embedded, and the resin layer 7 is
formed of the filled resin. It is done.
[0028]
For the resin layer 7, epoxy resin, acrylic resin, silicon resin, rubber or the like can be adopted.
The resin layer 7 preferably covers the piezoelectric element 5 completely from the viewpoint of
suppressing peaks and dips, but the piezoelectric element 5 may not be completely covered.
Furthermore, the resin layer 7 does not necessarily have to cover the whole of the vibrating body
3a, and in some cases, the resin layer 7 may be provided so as to cover a part of the vibrating
body 3a. In addition, although the thickness of the resin layer 7 can be set suitably, it sets, for
example to about 0.1 mm-1 mm. Further, in some cases, the resin layer 7 may not be provided.
[0029]
Thus, by providing the resin layer 7, the resonance of the vibrating body 3a can be appropriately
damped. As a result, the peak or dip in the frequency characteristic of the sound pressure, which
is caused due to the resonance phenomenon, can be suppressed small, and the fluctuation of the
sound pressure due to the frequency can be reduced.
[0030]
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In the sound generator 1 of the present embodiment, when the plurality of exciters (piezoelectric
elements 5) are viewed in a plan view from the direction perpendicular to the main surface of the
vibrating body 3a (the Z-axis direction in the figure), The vibrator 3a is attached to the vibrator
3a so as to be asymmetric with respect to all the symmetry axes of the figure drawn by the
outline of the vibrator 3a (the same as the figure drawn by the outline of the frame 2). When the
sound generator 1 (including the frame 2, the vibrating body 3a, and the piezoelectric element 5)
is viewed in plan, unless otherwise specified, the thickness direction of the vibrating body 3a
(perpendicular to the main surface of the vibrating body 3a) Direction, and viewed in plan from
the Z axis direction of the figure).
[0031]
In the example shown in FIG. 1A, when viewed in plan, the figure drawn by the outline of the
vibrating body 3a is substantially rectangular and has a symmetry axis L parallel to the length
direction (Y-axis direction) and the width direction (X-axis direction) And two symmetry axes
with the symmetry axis W parallel to. Then, one of the two piezoelectric elements 5 is arranged
at a position shifted along the symmetry axis L in the direction shown by the arrow 101 in FIG.
1A from the position shown by the dashed rectangle. Thereby, the plurality of piezoelectric
elements 5 are attached to the vibrating body 3a asymmetrically with respect to the two
symmetry axes (the symmetry axis L and the symmetry axis W) of the vibrating body 3a. In the
present specification, "the symmetry axis of the vibrator 3a" means the symmetry axis of the
figure drawn by the outline of the vibrator 3a in plan view.
[0032]
Thus, by attaching the plurality of exciters (piezoelectric elements 5) to the oscillating body 3a so
as to be asymmetric with respect to the symmetry axis of the oscillating body 3a, the oscillating
body 3a and the plurality of piezoelectric elements oscillate integrally The symmetry of the
composite oscillator constituted by 5 can be reduced. This makes it possible to solve the
degeneration of the resonance mode in the vibration of the composite vibrator and disperse the
resonance peak in the frequency characteristic of the sound pressure. And thereby, while
suppressing the height of the resonance peak in the frequency characteristic of sound pressure,
since the width of a peak can be expanded, the change with a sound pressure is small and it is
high with the frequency characteristic of more flat and excellent sound pressure. A sound
generator 1 capable of generating a high quality sound can be obtained. The extent to which the
position of the piezoelectric element 5 is shifted from the symmetric state with respect to the
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symmetry axis can be appropriately set according to the magnitude of the desired effect. For
example, even when the positions of the piezoelectric elements 5 are different by about 0.5 mm,
corresponding effects can be obtained, but when a certain degree of effect is desired, the
positions of the piezoelectric elements 5 are different by about 5 mm or more. Desirably, when a
large effect is desired, it is desirable to make the positions of the piezoelectric elements 5
different by about 10 mm or more.
[0033]
This point will be described with reference to FIGS. 2A and 2B. 2A and 2B are diagrams showing
frequency characteristics of sound pressure. FIG. 2A shows a sound in a high symmetry state (a
state in which one of the piezoelectric elements 5 is in a position indicated by a broken line
rectangle in FIG. 1A) of the composite vibration body constituted by the vibration body 3a and
the plurality of piezoelectric elements 5. FIG. 2B shows a state in which the symmetry of the
composite vibrator constituted by the vibrator 3a and the plurality of piezoelectric elements 5 is
low (one of the piezoelectric elements 5 is shown by the arrow 101 in FIG. 1A. 7 shows the
frequency characteristics of the sound pressure in the state after being moved in the direction).
[0034]
In a state where the symmetry of the composite vibrator constituted by the vibrator 3a and the
plurality of piezoelectric elements 5 is high, degeneracy of a plurality of vibration modes occurs
in the compound vibrator constituted by the vibrator 3a and the plurality of piezoelectric
elements 5; As shown in FIG. 2A, in the frequency characteristic of sound pressure, a large and
sharp peak or dip is likely to occur.
[0035]
On the other hand, in the state where the symmetry of the composite vibrating body constituted
by the vibrating body 3a including the piezoelectric element 5 and the plurality of piezoelectric
elements 5 is low, the degeneracy of the plurality of vibration modes is released, as shown in FIG.
In addition, the peak and dip in the frequency characteristic of sound pressure become smaller.
In this way, it is possible to obtain good sound pressure frequency characteristics with less
change in sound pressure. Moreover, since the frequency characteristic of the sound pressure of
the midrange range can be brought close to flat especially, it is possible to obtain a good sound
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quality.
[0036]
Next, an example of the manufacturing method of the sound generator 1 of this embodiment is
demonstrated. First, the piezoelectric element 5 is prepared. First, a binder, a dispersant, a
plasticizer, and a solvent are kneaded with powder of a piezoelectric material to prepare a slurry.
As a piezoelectric material, any of lead-based and non-lead-based can be used.
[0037]
Next, the slurry is formed into a sheet to prepare a green sheet. Then, a conductor paste is
printed on this green sheet to form a conductor pattern to be an internal electrode, three green
sheets on which this electrode pattern is formed are stacked, and a green on which no electrode
pattern is printed is formed. The sheets are laminated to produce a laminated molded body. Then,
the laminate molded body is degreased and fired, and cut into a predetermined size to obtain a
laminate 33.
[0038]
Next, the outer peripheral portion of the laminated body 33 is processed as necessary, and the
conductive paste for forming the surface electrode layers 34 and 35 is printed on both principal
surfaces in the laminated direction of the laminated body 33. Conductive paste for forming the
first to third external electrodes is printed on both end surfaces in the longitudinal direction (Yaxis direction) of the above, and the electrodes are baked at a predetermined temperature.
[0039]
Next, in order to impart piezoelectricity to the piezoelectric element 5, DC voltage is applied
through the first to third external electrodes to polarize the piezoelectric layer 31 of the
piezoelectric element 5.
This polarization is performed by applying a DC voltage so as to be in the direction indicated by
the arrow in FIG. 1B. Thus, the piezoelectric element 5 shown in FIGS. 1A and 1B can be
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obtained.
[0040]
Next, the diaphragm 3 is prepared, and the outer peripheral portion of the diaphragm 3 is
sandwiched between the frame members 2 a and 2 b constituting the frame 2, and the
diaphragm 3 is fixed in a tensioned state. Thereafter, an adhesive serving as the adhesive layer
26 is applied to the diaphragm 3, the surface electrode layer 35 of the piezoelectric element 5 is
pressed against the diaphragm 3, and thereafter the adhesive is heated or irradiated with
ultraviolet light. To cure. Then, the resin before curing is poured into the inside of the frame
member 2a, and the resin is cured to form the resin layer 7. Thus, the sound generator 1 of the
present embodiment can be manufactured.
[0041]
Next, another arrangement example of the piezoelectric element 5 in the sound generator 1 of
the present embodiment will be sequentially described with reference to FIGS. 3 to 6B. 3 to 6B,
similarly to FIG. 1A, the members of the sound generator 1 including the piezoelectric element 5
are very simplified and illustrated, and the resin layer 7 is omitted. Also, in FIGS. 3 to 6B, only
different parts from FIG. 1A will be described, and the same components will be assigned the
same reference numerals and overlapping descriptions will be omitted. In FIGS. 3 to 6B, as in FIG.
1A, the figure drawn by the outline of the vibrating body 3a in a plan view is substantially
rectangular and has a symmetry axis parallel to the length direction (Y-axis direction) It has two
symmetry axes of L and a symmetry axis W parallel to the width direction (X-axis direction).
[0042]
FIG. 3 is a schematic plan view (part 1) showing an arrangement example of the piezoelectric
elements 5 in the sound generator 1 of the present embodiment. In the example shown in FIG. 3,
the center of symmetry (point of symmetry) C2 of the two-dimensional figure formed by the two
piezoelectric elements 5 is the center of gravity C1 of the vibrating body 3a (the intersection of
the axis of symmetry L and the axis of symmetry W, They are arranged offset from the symmetry
point of the vibrating body 3a. Thereby, the plurality of piezoelectric elements 5 are arranged so
as to be asymmetrical with respect to the two symmetry axes L and W of the figure drawn by the
outline of the oscillator 3a in plan view of the oscillator 3a and the center of gravity C1. Is
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attached to Even by the arrangement of the piezoelectric element 5 as described above, the
symmetry of the composite vibrating body constituted by the vibrating body 3a and the plurality
of piezoelectric elements 5 is lowered, and good sound pressure frequency characteristics with
small fluctuation of sound pressure are obtained. The sound generator 1 can be obtained.
[0043]
Subsequently, an arrangement example shown in FIGS. 4A and 4B will be described. FIGS. 4A and
4B are schematic plan views (No. 2) and (No. 3) showing an arrangement example of the
piezoelectric element 5.
[0044]
In the example shown in FIG. 4A, one of the two piezoelectric elements 5 is disposed at the center
in the length direction, and the other of the two piezoelectric elements 5 is disposed at a position
different from the center in the length direction. Thereby, the two piezoelectric elements 5 are
attached to the vibrating body 3a so as to be asymmetric with respect to the two symmetry axes
L and W of the figure drawn by the outline of the vibrating body 3a in plan view and the center
of gravity C1. ing. Also by the arrangement of the piezoelectric element 5 as described above, the
symmetry of the composite vibrator constituted by the vibrating body 3 a and the plurality of
piezoelectric elements 5 can be reduced.
[0045]
In the example shown in FIG. 4B, one of the two piezoelectric elements 5 is disposed at the center
in the width direction, and the other of the two piezoelectric elements 5 is disposed at a position
different from the center in the width direction. Thereby, the two piezoelectric elements 5 are
attached to the vibrating body 3a so as to be asymmetric with respect to the two symmetry axes
L and W of the figure drawn by the outline of the vibrating body 3a in plan view and the center
of gravity C1. ing. Also by the arrangement of the piezoelectric element 5 as described above, the
symmetry of the composite vibrator constituted by the vibrating body 3 a and the plurality of
piezoelectric elements 5 can be reduced.
[0046]
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Subsequently, an arrangement example shown in FIGS. 5A and 5B will be described. FIG. 5A and
FIG. 5B are schematic plan views (No. 4) and (No. 5) showing an arrangement example of the
piezoelectric element 5.
[0047]
In the example shown in FIG. 5A, the area of one of the two piezoelectric elements 5 in plan view
is smaller than the area of the other piezoelectric element 5 in plan view. Thereby, the two
piezoelectric elements 5 are attached to the vibrating body 3a so as to be asymmetric with
respect to the two symmetry axes L and W of the figure drawn by the outline of the vibrating
body 3a in plan view and the center of gravity C1. ing. Also by the arrangement of the
piezoelectric element 5 as described above, the symmetry of the composite vibrator constituted
by the vibrating body 3 a and the plurality of piezoelectric elements 5 can be reduced.
[0048]
In the example shown in FIG. 5B, the shape of the one piezoelectric element 5B of the two
piezoelectric elements 5 in plan view is different from the shape of the other piezoelectric
element 5 in plan view. That is, the shape in plan view of at least one of the plurality of exciters
(piezoelectric elements 5) is different from the shape in plan view of the other exciters. Thereby,
the two piezoelectric elements 5 are attached to the vibrating body 3a so as to be asymmetric
with respect to the two symmetry axes L and W of the figure drawn by the outline of the
vibrating body 3a in plan view and the center of gravity C1. ing. Also by the arrangement of the
piezoelectric element 5 as described above, the symmetry of the composite vibrating body
constituted by the vibrating body 3a and the plurality of piezoelectric elements 5 can be reduced,
and good frequency characteristics of sound pressure can be obtained.
[0049]
Moreover, in the example shown to FIG. 5B, the shape when planarly viewing one piezoelectric
element 5B is a trapezoid which is not an equilateral leg, and is a point-symmetrical figure. As
described above, at least one of the plurality of exciters (piezoelectric elements 5) is configured
by the vibrating body 3a and the plurality of piezoelectric elements 5 also by making it have a
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shape that is astigmatically symmetrical in plan view. The symmetry of the complex oscillator can
be reduced to obtain good sound pressure frequency characteristics.
[0050]
Subsequently, an arrangement example shown in FIGS. 6A and 6B will be described. 6A is a
schematic plan view (part 6) showing an arrangement example of the piezoelectric element 5,
and FIG. 6B is a cross-sectional view taken along the line B-B 'of FIG. 6A.
[0051]
In this arrangement example, as shown in FIG. 6B, the thickness h1 of one piezoelectric element
5C and the thickness h2 of the other piezoelectric element 5 are different. Thereby, the mass of
one piezoelectric element 5C and the mass of the other piezoelectric element 5 are different. And
thereby, mass distribution of a plurality of piezoelectric elements 5 and 5C at the time of plane
view is asymmetrical with respect to two symmetry axes L and W. Thus, the mass distribution of
the plurality of exciters (piezoelectric elements 5 and 5C) in plan view is asymmetric with respect
to all symmetry axes of the figure drawn by the outline of the vibrating body 3a in plan view. In
addition, by making the thickness of at least one of the plurality of exciters different from the
thickness of the other exciter, the symmetry of the composite vibrator constituted by the vibrator
3a and the plurality of piezoelectric elements 5 can be obtained. By lowering it, it is possible to
obtain an acoustic generator 1 having good sound pressure frequency characteristics. At this
time, the planar arrangement of the plurality of piezoelectric elements 5 may have symmetry.
[0052]
Thus, “in the case of planar view, a plurality of exciters (piezoelectric elements 5) are vibrators
so as to be asymmetrical with respect to all symmetry axes of the figure drawn by the outline of
the vibrator (the vibrator 3a). "Attached to" means that it corresponds to either of the following
1st case and 2nd case. In the first case, the state in which the plurality of exciters are attached to
the vibrator is asymmetric with respect to all the symmetry axes as a two-dimensional figure
because the planar shape and the arrangement of the plurality of exciters are asymmetric. This is
the case. And, in the second case, the state in which the plurality of exciters are attached to the
vibrator is not asymmetrical with respect to all symmetry axes in a two-dimensional figure, but
the mass of the plurality of exciters is different The two-dimensional mass distribution of a
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plurality of exciters is asymmetrical with respect to all symmetry axes.
[0053]
Second Embodiment Next, the configuration of a sound generating apparatus 70 according to a
second embodiment will be described. FIG. 7A is a view showing an example of the configuration
of a sound generation device 70 configured using the sound generator 1 of the first embodiment
described above. In addition, in FIG. 7A, only the component required for description is shown,
and the description about the detailed structure of the sound generator 1 or a general
component is abbreviate | omitted.
[0054]
The sound generation device 70 of the present embodiment is a so-called speaker-like sound
generation device, and includes, for example, a housing 71 and the sound generator 1 attached
to the housing 71 as shown in FIG. 7A. The housing 71 has a rectangular box-like shape, and has
an opening 71a on one surface. Such a housing 71 can be formed using a known material such
as, for example, plastic, metal, wood or the like. Further, the shape of the housing 71 is not
limited to a rectangular box shape, and can be various shapes such as a cylindrical shape and a
frustum shape, for example.
[0055]
The sound generator 1 is attached to the opening 71 a of the housing 71. The sound generator 1
is the sound generator of the first embodiment described above, and the description of the sound
generator 1 is omitted. Since the sound generator 70 having such a configuration generates
sound using the sound generator 1 that generates sound with high sound quality, sound with
high sound quality can be generated. In addition, since the sound generator 70 can resonate the
sound generated from the sound generator 1 inside the housing 71, for example, the sound
pressure in the low frequency band can be increased. In addition, the place where the sound
generator 1 is attached can be set freely. Also, the sound generator 1 may be attached to the
housing 71 via another object.
[0056]
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Third Embodiment Next, the configuration of an electronic device according to a third
embodiment will be described. FIG. 7B is a diagram showing an example of the configuration of
the electronic device 50 configured using the sound generator 1 of the first embodiment
described above. In addition, in FIG. 7B, only the component required for description is shown,
and the description about the detailed structure of the sound generator 1 or a general
component is abbreviate | omitted.
[0057]
As shown in FIG. 7B, the electronic device 50 includes the electronic circuit 60. The electronic
circuit 60 includes, for example, a controller 50a, a transmitting / receiving unit 50b, a key input
unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound
generator 1 and has a function of outputting an audio signal to the sound generator 1. The sound
generator 1 generates a sound based on an audio signal input from the electronic circuit.
[0058]
The electronic device 50 further includes a display unit 50 e, an antenna 50 f, and the sound
generator 1. In addition, the electronic device 50 includes a housing 40 that accommodates each
of these devices.
[0059]
Although FIG. 7B shows a state in which all the devices including the controller 50a are housed
in one housing 40, the housing form of the devices is not limited. In the present embodiment, at
least the electronic circuit 60 and the sound generator 1 may be accommodated in one housing
40.
[0060]
The controller 50 a is a control unit of the electronic device 50. The transmitting and receiving
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unit 50b transmits and receives data via the antenna 50f based on the control of the controller
50a.
[0061]
The key input unit 50c is an input device of the electronic device 50, and receives a key input
operation by the operator. The microphone input unit 50d is also an input device of the
electronic device 50, and receives a voice input operation and the like by the operator.
[0062]
The display unit 50 e is a display output device of the electronic device 50, and outputs display
information based on the control of the controller 50 a.
[0063]
The sound generator 1 then operates as a sound output device in the electronic device 50.
The sound generator 1 is connected to the controller 50a of the electronic circuit 60, and emits a
sound in response to the application of a voltage controlled by the controller 50a.
[0064]
By the way, although FIG. 7B demonstrated that the electronic device 50 was a portable terminal
device, the electronic device 50 may be various electronic devices which have a function which
emits a sound. The electronic device 50 is, for example, a television or an audio device, as well as
other electric products having a function of generating sound, for example, various electric
products such as a vacuum cleaner, a washing machine, a refrigerator, a microwave oven, etc. It
may be used.
[0065]
(Modifications) The present invention is not limited to the above-described embodiment, and
various modifications and improvements can be made without departing from the scope of the
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present invention.
[0066]
For example, in the embodiment described above, although the case where the figure drawn by
the outline of the vibrating body 3a is rectangular when viewed in plan view is shown, the
present invention is not limited to this.
For example, various shapes having an axis of symmetry, such as an isosceles triangle, a regular
n-gon (n is a positive number of 3 or more), a rhombus, an isosceles trapezoid, a sector, an
ellipse, or a circle may be used.
[0067]
In the embodiment described above, the resin layer 7 is formed to bury the piezoelectric element
5 in the frame 2 as an example. However, the resin layer may not necessarily be formed.
[0068]
Further, in the above-described embodiment, the case in which the support for supporting the
vibrating body 3a is the frame 2 and the peripheral edge of the vibrating body 3a is supported is
described by way of example. It may be supported only at both ends in the longitudinal direction
or the short direction of the body 3a.
[0069]
Moreover, although the case where an exciter was the bimorph-type piezoelectric element 5 was
mentioned as the example and demonstrated in embodiment mentioned above, it is not limited to
this.
For example, the same effect can be obtained by using a unimorph-type piezoelectric element in
which a plate made of metal or the like is attached to one main surface of the piezoelectric
element that vibrates in the plane direction instead of the bimorph-type piezoelectric element.
Can.
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In addition, piezoelectric elements that vibrate in a stretching direction in the plane direction
may be provided on both sides of the diaphragm 3, and unimorph-type or bimorph-type
piezoelectric elements may be provided on both sides of the diaphragm 3.
[0070]
Further, the exciter is not limited to the piezoelectric element, and any exciter may be used as
long as it has a function of receiving an electric signal and vibrating. For example, an
electrodynamic exciter, an electrostatic exciter, or an electromagnetic exciter well known as an
exciter for vibrating a speaker may be used. It is to be noted that the electrodynamic exciter is
such that a current is supplied to the coil disposed between the magnetic poles of the permanent
magnet to vibrate the coil, and the electrostatic exciter is formed of two facing metals The bias
and the electrical signal are supplied to the plate to cause the metal plate to vibrate, and the
electromagnetic exciter is to cause the electrical signal to flow to the coil to cause the thin iron
plate to vibrate.
[0071]
In the embodiment described above, the center of gravity of the figure drawn by the contour of
the vibrating body 3a is asymmetrical with respect to all the symmetry axes of the figure drawn
by the contour of the vibrating body 3a in the plan view. In the case where the plurality of
exciters (piezoelectric elements 5) are attached to the vibrating body 3a so as to be asymmetric
with respect to the above, it is not limited thereto. Even in the case where they are arranged
symmetrically with respect to the center of gravity of the figure drawn by the outline of the
vibrating body 3a in plan view, all the symmetry axes of the figure drawn by the outline of the
vibrator 3a in plan view If it is asymmetric, it can be effective by itself.
[0072]
Further effects and modifications can be easily derived by those skilled in the art. Thus, the
broader aspects of the invention are not limited to the specific details and representative
embodiments represented and described above. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive concept as defined by the
appended claims and their equivalents. It goes without saying that the present invention is also
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applicable to a sound generating device that generates sound having a frequency higher than
that of an audible sound.
[0073]
1: Sound generator 2: Frame 3: Diaphragm 3a: Vibrator 5, 5A, 5B, 5C: Piezoelectric element 7:
Resin layer 40, 71: Case 50: Electronic device 60: Electronic circuit 70: Sound generator C1:
Center of gravity L of the vibrating body, W: Symmetrical axis
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