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JP2014116795

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DESCRIPTION JP2014116795
Abstract: To obtain good sound pressure frequency characteristics. An acoustic generator
according to an embodiment includes a vibrator, an exciter, and a damping material. The exciter
is provided on the vibrator. The damping material is attached to be integral with the vibrating
body. When the vibrator is viewed in plan, the side of the damping material facing the exciter is
shorter than the side of the exciter facing the damping material. [Selected figure] Figure 1A
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, an acoustic generator using an actuator is known.
For example, Patent Document 1 describes an acoustic generator that vibrates a diaphragm to
output sound by applying a voltage to the piezoelectric element attached to the diaphragm to
vibrate the piezoelectric element.
[0003]
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1
Unexamined-Japanese-Patent No. 2004-23436
[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 includes a vibrator, an exciter,
and a damping material.
The exciter is provided on the vibrator.
The damping material is attached to be integral with the vibrating body.
Further, when the vibrator is viewed in plan, the side of the damping material opposed to the
exciter is shorter than the side opposed to the exciter damping material.
[0007]
According to one aspect of the embodiment, good sound pressure frequency characteristics can
be obtained.
[0008]
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Drawing 1A is an explanatory view by plane view of a sound generator concerning a 1st
embodiment.
FIG. 1B is a cross-sectional view taken along line A-A 'of FIG. 1A. FIG. 2 is a block diagram of the
sound generator. FIG. 3 is a block diagram of the electronic device. FIG. 4: is explanatory drawing
by planar view of the sound generator which concerns on the modification in 1st Embodiment.
FIG. 5: is explanatory drawing by planar view of the sound generator which concerns on 2nd
Embodiment. FIG. 6A is an explanatory view in plan view of a sound generator according to a
first modified example of the second embodiment. FIG. 6B is an explanatory view in plan view of
the sound generator according to the second modified example of the second embodiment. FIG.
6C is an explanatory view in plan view of a sound generator according to a third modification of
the second embodiment. FIG. 7A is an explanatory view of a cross section of the sound generator
according to the third embodiment. FIG. 7B is an enlarged view of a portion H shown in FIG. 7A.
FIG. 8 is an explanatory view of a cross section of the sound generator according to the fourth
embodiment.
[0009]
Hereinafter, with reference to the accompanying drawings, embodiments of the sound generator,
the sound generator and the electronic device disclosed in the present application will be
described. Note that the present invention is not limited by the embodiments described below.
[0010]
First Embodiment A configuration of a sound generator according to a first embodiment will be
described using FIGS. 1A and 1B.
[0011]
The sound generator 1 according to the first embodiment is a so-called piezoelectric speaker, and
has a configuration for generating sound pressure using a resonance phenomenon of a vibrating
body.
Specifically, as shown in FIGS. 1A and 1B, the sound generator 1 includes a frame 10, a vibrating
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body 20 stretched over the frame 10, and a piezoelectric element provided on the vibrating body
20. The vibration element 30 and the damping members 50a to 50d are provided.
[0012]
1A is an explanatory view in plan view of the sound generator 1 according to the first
embodiment as viewed from a direction perpendicular to the main surface of the vibrating body
20, and FIG. 1B is an AA 'of FIG. 1A. FIG. In FIG. 1B, the sound generator 1 is shown expanded
and deformed in the vertical direction to facilitate understanding.
[0013]
The vibrating body 20 can be formed using various materials such as resin, metal, and paper. For
example, the thin plate-like vibrating body 20 can be made of a resin film of polyethylene,
polyimide, polypropylene or the like having a thickness of about 10 to 200 μm. Since the resin
film is a material having a lower elastic modulus and mechanical Q value than a metal plate or
the like, by forming the vibrating body 20 with a resin film, the vibrating body 20 is bent and
vibrated with a large amplitude to obtain sound pressure The width and height of the resonance
peak in the frequency characteristic can be increased to reduce the difference between the
resonance peak and the dip. A composite of metal and resin may be used as the vibrator 20.
[0014]
The frame 10 has a role of holding the vibrating body 20 to form a fixed end of vibration. For
example, as shown to FIG. 1B, the rectangular upper frame member 11 and the lower frame
member 12 are joined up and down, and the frame 10 is comprised. And the outer peripheral
part of the vibrating body 20 which consists of resin films is pinched | interposed between the
upper frame member 11 and the lower frame member 12, and it is fixing in the state to which
predetermined | prescribed tension | tensile_strength was provided. Therefore, it becomes the
sound generator 1 provided with the vibrating body 20 with few deformations, such as bending,
even if used for a long time.
[0015]
The thickness and the material of the frame 10 are not particularly limited, but in the first
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embodiment, for example, a stainless steel material having a thickness of 100 to 1000 μm
because of excellent mechanical strength and corrosion resistance. Is used.
[0016]
The piezoelectric vibrating element 30 includes the laminate 33, the surface electrode layers 34
and 35 formed on the upper and lower surfaces of the laminate 33, and the outside formed on
the side surface where the end face of the internal electrode layer 32 of the laminate 33 is
exposed. Electrodes 36 and 37 are provided.
The lead terminals 38 and 39 are connected to the external electrodes 36 and 37, respectively.
[0017]
The laminate 33 is formed by alternately laminating four piezoelectric layers 31a, 31b, 31c, and
31d made of ceramics and three internal electrode layers 32. In the piezoelectric vibrating
element 30, the main surfaces on the upper surface side and the lower surface side are
rectangular, and the piezoelectric layers 31a and 31b and the piezoelectric layers 31c and 31d
are polarized in different directions in the thickness direction, The piezoelectric layers 31b and
31c are polarized in the same direction.
[0018]
Therefore, when a voltage is applied to the piezoelectric vibrating element 30 through the lead
terminals 38 and 39, for example, the lower surface side of the piezoelectric vibrating element
30, that is, the piezoelectric layers 31c and 31d on the vibrating body 20 side shrinks, The
piezoelectric layers 31a and 31b on the side deform so as to extend. As described above, the
piezoelectric layers 31a and 31b on the upper surface side of the piezoelectric vibrating element
30 and the piezoelectric layers 31c and 31d on the lower surface exhibit opposite stretching
behavior, and as a result, the piezoelectric vibrating element 30 has a bimorph-type bending. By
vibrating, the vibrating body 20 can be given a constant vibration to generate a sound.
[0019]
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As described above, since the piezoelectric vibration element 30 is a bimorph-type laminated
piezoelectric vibration element and the piezoelectric vibration element 30 itself bends and
vibrates alone, it is, for example, a soft vibration body 20 regardless of the material of the
vibration body 20. However, strong vibration can be generated, and a sufficient sound pressure
can be obtained by the small number of piezoelectric vibrating elements 30.
[0020]
Here, as materials for forming the piezoelectric layers 31a, 31b, 31c, and 31d, conventionally,
lead-free piezoelectric materials such as lead zirconate titanate (PZT), Bi layer compounds, and
tungsten bronze structure compounds are used. The piezoelectric ceramic used can be used.
[0021]
Further, the material of the internal electrode layer 32 contains metal, for example, silver and
palladium as main components.
The internal electrode layer 32 may contain ceramic components constituting the piezoelectric
layers 31a, 31b, 31c, 31d, whereby the piezoelectric layers 31a, 31b, 31c, 31d and the internal
electrode layers 32, 32 can be obtained. , 32 can reduce the stress due to the thermal expansion
difference.
[0022]
In addition, the surface electrode layers 34 and 35 and the external electrodes 36 and 37 contain
a metal, such as silver, as a main component.
Moreover, you may contain a glass component. By containing the glass component, strong
adhesion can be obtained between the piezoelectric layers 31a, 31b, 31c, 31d or the internal
electrode layer 32 and the surface electrode layers 34, 35 or the external electrodes 36, 37. . The
content of the glass component may be, for example, 20% by volume or less.
[0023]
In addition, as the wiring connected to the lead terminals 38 and 39, in order to reduce the
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height of the piezoelectric vibrating element 30, it is preferable to use a flexible wiring in which a
metal foil such as copper or aluminum is sandwiched by resin films.
[0024]
Further, as shown in FIG. 1B, the acoustic generator 1 according to the first embodiment is
provided with a resin-made covering layer 40 filled in the frame 10 so as to embed the
piezoelectric vibrating element 30.
As described above, by embedding the piezoelectric vibration element 30 with the covering layer
40 made of resin, it is possible to induce an appropriate damping effect, to suppress the
resonance phenomenon and to further reduce the difference between the resonance peak and
the dip. be able to. Furthermore, the piezoelectric vibration element 30 can also be protected
from the external environment.
[0025]
In the first embodiment, the entire surface of the vibrating body 20 is covered by the covering
layer 40, but it is not necessary to cover the entire surface. That is, in the sound generator 1, the
piezoelectric vibrating element 30 and at least a part of the surface of the vibrating body 20 on
the side where the piezoelectric vibrating element 30 is disposed may be covered by the covering
layer 40.
[0026]
Although the difference between the resonance peak and the dip in the frequency characteristic
of the sound pressure is reduced by the above-described covering layer 40, in the first
embodiment, the damping members 50a to 50d are disposed on the surface side of the covering
layer 40, The mechanical vibration loss due to the damping members 50a to 50d is applied to
the vibrating body 20 to further reduce the difference between the resonance peak and the dip.
[0027]
The damping members 50a to 50d are formed in, for example, a substantially rectangular
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parallelepiped shape.
In the first embodiment, each of the damping members 50a to 50d has the same shape, and is
attached to the surface of the covering layer 40 through the adhesive 60, as shown in FIG. 1B. ,
And the piezoelectric vibration element 30 and the covering layer 40.
[0028]
In addition, the coating layer 40 and the adhesive agent 60 are examples of the intermediate |
middle layer provided between the vibrating body 20 and each damping material 50a-50d. The
cover layer 40 and the adhesive 60 are formed of a member having a thermal conductivity lower
than that of the vibrator 20. As a result, heat is less likely to be transmitted from the damping
members 50a to 50d to the vibrating body 20, so that local temperature change of the vibrating
body 20 can be reduced. Therefore, it is possible to suppress the fluctuation of the sound quality
due to the local temperature change of the vibrating body 20.
[0029]
In the first embodiment, as shown in FIG. 1A, each of the damping members 50a to 50d is viewed
in plan from the direction perpendicular to the vibrating surface (that is, the Z-axis direction in
the figure). The piezoelectric vibrating elements 30 are disposed so as to face each side.
Specifically, when the vibrating body 20 is viewed in plan, each of the damping members 50a to
50d is the left side (side in the Y-axis negative direction) and right side (side in the Y-axis positive
direction) of the piezoelectric vibration element 30. And the upper side (the side in the negative
direction of the X-axis) and the lower side (the side in the positive direction of the X-axis).
[0030]
And in the sound generator 1 which concerns on 1st Embodiment, the edge which opposes the
piezoelectric vibration element 30 of each damping material 50a-50d is shorter than the edge
which opposes each damping material 50a-50d of the piezoelectric vibration element 30 It is
formed.
[0031]
For example, as shown in FIG. 1A, the right side (the side in the positive Y-axis direction) of the
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damping material 50a is shorter than the left side (the side in the negative Y-axis direction) of the
opposing piezoelectric vibrating element 30, and The lower side (the side in the positive direction
of the X axis) is shorter than the upper side (the side in the negative direction of the X axis) of
the facing piezoelectric vibrating element 30.
[0032]
Thus, in the sound generator 1 according to the first embodiment, the side of the damping
members 50a to 50d facing the piezoelectric vibrating element 30 is shorter than the side facing
the damping members 50a to 50d of the piezoelectric vibrating element 30. doing.
Thereby, in the vibration surface of the vibrating body 20, a region (for example, the region 3a
shown in FIG. 1A) where the damping members 50a to 50d and the piezoelectric vibration
element 30 face each other and a region shown for example in FIG. 3b), the vibration of the
vibrating body 20 can be made different.
Therefore, the sound pressure peak can be dispersed, the sound pressure frequency
characteristic can be flattened, and a good sound pressure frequency characteristic can be
obtained.
[0033]
Each of the damping members 50 a to 50 d is disposed at an interval from the vibrating body 20
when the vibrating body 20 is viewed in plan. As a result, each damping material 50a to 50d is
less susceptible to the vibration of the piezoelectric vibrating element 30 itself as compared to
the case where each damping material 50a to 50d is disposed at a position in contact with the
vibrating body 20 in plan view. Sound pressure frequency characteristics can be further
flattened. Moreover, degradation of each damping material 50a-50d can also be suppressed.
[0034]
The damping members 50a to 50d may be those having mechanical loss, but it is desirable that
the damping members 50a to 50d be members having a high mechanical loss coefficient, in
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other words, a low mechanical quality coefficient (so-called mechanical Q). Such a damping
material 50 can be formed, for example, using various elastic bodies, but since it is desirable that
it is soft and easily deformed, it can be suitably formed using a rubber material such as urethane
rubber. In particular, porous rubber materials such as urethane foam can be suitably used.
[0035]
Next, a sound generating apparatus equipped with the sound generator 1 according to the
present embodiment will be described with reference to FIG. FIG. 2 is a block diagram of the
sound generator.
[0036]
As shown in FIG. 2, the acoustic generator 1 can be configured by housing the acoustic generator
1 having the above-described configuration in the resonance box 400. The resonance box 400 is
a housing that houses the sound generator 1, resonates the sound emitted by the sound
generator 1, and emits the sound from the housing surface as a sound wave. The sound
generation device 4 can be used alone as a speaker, or can be suitably incorporated into, for
example, various electronic devices 2.
[0037]
As described above, since it is possible to reduce the difference between the resonance peak and
the dip in the frequency characteristic of the sound pressure which is disadvantageous in the
piezoelectric speaker, the sound generator 1 according to the present embodiment is a mobile
phone or a thin television Or, it is possible to be preferably incorporated into an electronic device
2 such as a tablet terminal.
[0038]
The electronic device 2 to which the sound generator 1 can be incorporated is not limited to the
above-described mobile phone, flat-screen TV, tablet terminal, etc., but, for example, a
refrigerator, a microwave, a vacuum cleaner, a washing machine, etc. Also included are home
appliances that were not previously considered important for sound quality.
[0039]
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10
Here, an electronic device including the above-described sound generator 1 will be briefly
described with reference to FIG.
FIG. 3 is a block diagram of the electronic device 2.
The electronic device 2 includes the sound generator 1 described above, an electronic circuit
connected to the sound generator 1, and a housing 200 for housing the sound generator 1 and
the electronic circuit.
[0040]
Specifically, as shown in FIG. 3, the electronic device 2 includes an acoustic circuit 1, an
electronic circuit including a control circuit 21, a signal processing circuit 22 and a wireless
circuit 23 as an input device, an antenna 24, and the like. And a housing 200 for housing the
Although the wireless input device is illustrated in FIG. 3, it can naturally be provided as a signal
input by normal electrical wiring.
[0041]
In addition, description is abbreviate | omitted about the other electronic member (For example,
devices and circuits, such as a display, a microphone, a speaker, etc.) with which the electronic
device 2 is equipped, here. Moreover, although one sound generator 1 was illustrated in FIG. 3,
two or more sound generators 1 and other oscillators can also be provided.
[0042]
The control circuit 21 controls the entire electronic device 2 including the wireless circuit 23
through the signal processing circuit 22. An output signal to the sound generator 1 is input from
the signal processing circuit 22. Then, the control circuit 21 controls the signal processing circuit
22 to generate an audio signal S by controlling the signal processing circuit 22, and outputs the
audio signal S to the sound generator 1.
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[0043]
Thus, the electronic device 2 shown in FIG. 3 reduces the difference between the resonance peak
and the dip to suppress the frequency fluctuation as much as possible while incorporating the
small and thin acoustic generator 1. The sound quality can be generally improved even in the
high-pitched area, including the low-pitched sound area.
[0044]
Although FIG. 3 exemplifies the electronic device 2 on which the sound generator 1 is directly
mounted as the sound output device, for example, the sound generator 4 in which the sound
generator 1 is housed in a housing is mounted as the sound output device. The configuration
may be different.
[0045]
The arrangement of the damping members 50a to 50d is not limited to the example shown in
FIG. 1A.
So, below, the other example of arrangement | positioning of damping material 50a-50d is
demonstrated using FIG.
FIG. 4: is explanatory drawing by planar view of the sound generator 1-1 which concerns on the
modification in 1st Embodiment.
[0046]
FIG. 1A shows an example in which each of the damping members 50a to 50d is disposed at
equal intervals from the piezoelectric vibrating element 30, but the spacing between each of the
damping members 50a to 50d and the piezoelectric vibrating element 30 is The damping
members 50a to 50d may be different.
[0047]
For example, as shown in FIG. 4, in the sound generator 1-1, the damping material 50 a is
disposed away from the piezoelectric vibrating element 30 by the distance L 1, and the damping
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material 50 b is shorter than the distance L 1 from the piezoelectric vibrating element 30. Placed
just apart.
[0048]
Thus, in the vibration surface of the vibrating body 20, the vibrating body 20 is a region on the
left side (the Y-axis negative direction side) of the piezoelectric vibrating element 30 and a region
on the right side (the Y-axis positive direction side) of the piezoelectric vibrating element 30. Can
be made different.
Therefore, the frequency characteristic of the sound pressure can be further flattened, and the
sound quality can be further improved.
[0049]
Further, two damping materials opposed to each other with the piezoelectric vibration element
30 interposed therebetween may be arranged to be relatively shifted.
For example, in the sound generator 1-1, the damping material 50d is disposed at a position
shifted with respect to the damping material 50c. Thereby, the vibration of the vibrating body 20
can be made different between the region on the upper side (X-axis negative direction side) of
the piezoelectric vibration element 30 and the region on the lower side (X-axis positive direction
side) of the piezoelectric vibration element 30 . Therefore, the frequency characteristic of the
sound pressure can be further flattened, and the sound quality can be further improved.
[0050]
In the first embodiment, although the case where the sound generators 1 and 1-1 include four
damping members 50 a to 50 d is illustrated, the number of damping members is not limited to
four, 1 to 3 or 5 or more may be sufficient.
[0051]
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Second Embodiment Next, the configuration of a sound generator according to a second
embodiment will be described with reference to FIG.
FIG. 5: is explanatory drawing by planar view of the sound generator which concerns on 2nd
Embodiment.
[0052]
As shown in FIG. 5, an acoustic generator 1A according to the second embodiment includes a
damping material 50e instead of the damping material 50a included in the acoustic generator 1
according to the first embodiment. The damping member 50e has a large area when the
vibrating body 20 is viewed in plan as compared to the other damping members 50b to 50d.
[0053]
Thus, in the vibration surface of the vibrating body 20, the damping material 50b is formed in
the region on the left side (Y-axis negative direction side) of the piezoelectric vibration element
30 and in the region on the right side (Y-axis positive direction side) of the piezoelectric vibration
element 30. , 50e can be made different. That is, since the vibration of the vibrating body 20 in
both regions can be made different, the frequency characteristic of the sound pressure can be
further flattened.
[0054]
As described above, the acoustic generator 1A according to the second embodiment includes the
damping member 50e having an area different from those of the other damping members 50b to
50d, whereby the vibrating body 20, the piezoelectric vibrating element 30, the covering layer
40, and the like. The symmetry of the composite vibrator configured by the damping material
(here, the damping materials 50b to 50e) can be lowered. Therefore, the frequency characteristic
of sound pressure can be further flattened, and the sound quality can be further improved.
[0055]
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Moreover, in the sound generator 1A which concerns on 2nd Embodiment, the damping material
50e and the damping material 50b from which an area differs mutually are arrange | positioned
in the position which opposes on both sides of the piezoelectric vibration element 30. FIG. As
described above, by making the areas of the damping materials (here, the damping material 50e
and the damping material 50b) facing each other across the piezoelectric vibration element 30
different, the complex vibration is compared to the case where the areas of the adjacent damping
materials are different. The symmetry of the body can be further reduced.
[0056]
Furthermore, as shown in FIG. 5, by arranging the damping members 50b and 50e having
different areas in the longitudinal direction of the vibrating body 20, the symmetry of the
composite vibrating body can be further improved as compared to the case where the damping
members 50b and 50e are arranged in the lateral direction It can be effectively lowered.
[0057]
Here, in the sound generator 1A, the damping material 50e is a damping material having a larger
area than the other damping materials 50b to 50d, but the damping material 50e is a damping
having a smaller area than the other damping materials 50b to 50d. It is good also as material.
[0058]
Next, a modification of the sound generator 1A according to the second embodiment will be
described with reference to FIGS. 6A to 6C.
6A to 6C are explanatory views in plan view of the sound generator according to the first to third
modifications of the second embodiment.
[0059]
As shown in FIG. 6A, in the sound generator 1A-1 according to the first modification, when the
vibrating body 20 is viewed in plan, the upper side (the negative direction of the X axis) and the
lower side of the piezoelectric vibrating element 30 (the Two dumping materials are arranged
side by side on the X axis positive direction side).
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Specifically, the damping material 50f and the damping material 50g are arranged side by side
on the upper side of the piezoelectric vibrating element 30, and the damping material 50h and
the damping material 50i are arranged sideways on the lower side of the piezoelectric vibrating
element 30.
[0060]
As shown in FIG. 6A, the damping members 50f and 50g have different areas in plan view of the
vibrating body 20, and the damping members 50h and 50i have different areas in planar view of
the vibrating body 20. .
[0061]
By arranging the damping members 50 f to 50 i having different areas in this way on one side of
the piezoelectric vibrating element 30 as compared with the case where the damping members
having the same area are arranged on one side of the piezoelectric vibrating element 30. Thus,
the symmetry of the complex oscillator can be lowered.
[0062]
Moreover, as shown to FIG. 6B, sound generator 1A-2 which concerns on a 2nd modification is
equipped with damping material 50j-50m.
The damping members 50j to 50m are all different in area in plan view, and the damping
members 50j, 50k, 50l, and 50m are larger in this order.
Thus, the symmetry of the composite vibrator can be further lowered by making the areas of all
the damping members 50j to 50m different.
[0063]
Moreover, as shown to FIG. 6C, sound generator 1A-3 which concerns on a 3rd modification is
provided with damping material 50n-50q. The shapes of these damping members 50n to 50q in
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plan view are all different. Thus, the symmetry of the composite vibrator can be further lowered
by making the damping members 50n to 50q different in shape.
[0064]
In addition, although the example in case all the shapes of damping material 50n-50q differ was
shown here, the shape of at least one of several damping material should just be different from
another shape.
[0065]
Third Embodiment Next, an acoustic generator according to a third embodiment will be described
with reference to FIGS. 7A and 7B.
FIG. 7A is an explanatory view of a cross section of the sound generator according to the third
embodiment. FIG. 7B is an enlarged view of a portion H shown in FIG. 7A.
[0066]
As shown to FIG. 7A, sound generator 1B which concerns on 3rd Embodiment is replaced with
the coating layer 40 with which the sound generator 1 which concerns on 1st Embodiment is
equipped, and is provided with coating layer 40 '. The covering layer 40 'contains pores 41, socalled voids, inside. The pores 41 are preferably spherical in order to facilitate absorption of
stress and resonance energy from all directions in the covering layer 40 '.
[0067]
As described above, by providing the pores 41 in the covering layer 40 ′, the regions having
different Young's modulus are scattered in the covering layer 40 ′, so that the resonance
frequency is not partially aligned, and the sound pressure at the resonance frequency The peak
shape of is smooth. As a result, the difference between the resonance peak and the dip in the
frequency characteristic of the sound pressure can be suppressed, and the frequency
characteristic can be flattened.
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[0068]
Moreover, it replaces with the adhesive agent 60 with which the sound generator 1 which
concerns on 3rd Embodiment is equipped with the sound generator 1 which concerns on 1st
Embodiment, and is provided with adhesive agent 60 '. As shown in FIG. 7B, such an adhesive 60
'also includes pores 61 inside as well as the covering layer 40'. The pores 61 are also preferably
spherical.
[0069]
In this manner, by providing the pores 61 in the adhesive 60 ', as in the above, regions with
different Young's modulus are scattered in the adhesive 60', so that the resonance frequencies
become partially nonuniform. The peak shape of the sound pressure at the resonance frequency
becomes smooth. As a result, the difference between the resonance peak and the dip in the
frequency characteristic of the sound pressure can be suppressed, and the frequency
characteristic can be flattened. Here, although the pores are provided in both the coating layer
40 ′ and the adhesive 60 ′, the pores may be provided in only one of the coating layer 40 ′
or the adhesive 60 ′. Even in such a case, it is possible to make the peak shape of the sound
pressure at the resonance frequency smooth.
[0070]
Fourth Embodiment Next, a sound generator according to a fourth embodiment will be described
with reference to FIG. FIG. 8 is an explanatory view of a cross section of the sound generator
according to the fourth embodiment.
[0071]
In each embodiment mentioned above, although an example in case a damping material was
attached to a surface of covering layer 40, 40 'was explained, a mounting position of damping
material is not limited to this. For example, as shown in FIG. 8, an acoustic generator 1 </ b> C
according to the fourth embodiment includes a damping material 50 r inside the covering layer
40. In addition, the sound generator 1 </ b> C includes a damping material 50 s on the surface of
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the vibrating body 20 opposite to the surface to which the piezoelectric vibrating element 30 is
attached. The damping members 50 r and 50 s are attached to the surface of the vibrating body
20 via the adhesive 60.
[0072]
As described above, the damping material is not limited to the surface of the covering layer 40,
and may be provided on the surface of the covering layer 40 or on the opposite side of the
surface of the vibrating body 20 to which the piezoelectric vibrating element 30 is attached.
[0073]
In the above-described sound generator, one piezoelectric vibrating element 30 is disposed on
the vibrating body 20, but two or more piezoelectric vibrating elements 30 may be disposed on
the vibrating body 20. I do not care.
Moreover, although the piezoelectric vibration element 30 is made into rectangular shape by
planar view, it may be square.
[0074]
In each of the above-described embodiments, an example is shown in which the damping
material and the piezoelectric vibration element 30 are spaced apart from each other when the
vibrating body 20 is viewed in plan, but the damping material is in contact with the piezoelectric
vibration element 30 It may be arranged in a state of
[0075]
Moreover, although the so-called bimorph-type laminated type is illustrated as the piezoelectric
vibration element 30, a unimorph-type piezoelectric vibration element can also be used.
[0076]
Moreover, although the case where a piezoelectric vibration element was used as an example was
mentioned as an example and demonstrated in each embodiment mentioned above, an exciter is
not limited to a piezoelectric vibration element, An electric signal is input and What is necessary
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is just to have a function to vibrate.
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.
[0077]
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.
[0078]
DESCRIPTION OF SYMBOLS 1 sound generator 2 electronic device 4 sound generator 10 frame
body 20 vibrator 30 piezoelectric vibration element 40 coating layer 50a-50s damping material
60 adhesive
11-05-2019
20
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