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JP2014127749

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DESCRIPTION JP2014127749
Abstract: To obtain good sound pressure frequency characteristics. A sound generator according
to an embodiment includes at least an exciter, a flat vibrator, a support on which the vibrator is
stretched, and a damping material. The exciter vibrates when an electrical signal is input. The flat
vibrator is attached with the exciter, and vibrates with the exciter due to the vibration of the
exciter. The support body stretches the vibrating body and vibrates together with the vibrating
body by the vibration of the exciter. The outer peripheral shape of the vibrating body is elliptical.
[Selected figure] Figure 3
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]
An acoustic generator according to one aspect of the embodiment includes an exciter that
receives an electric signal and vibrates, and a flat vibrator that is attached with the exciter and
that vibrates with the exciter due to the vibration of the exciter. An acoustic generator
comprising at least a vibrator and a support that vibrates together with the exciter and the
vibrator due to the vibration of the exciter, wherein an outer peripheral shape of the vibrator is
an elliptical shape.
[0007]
According to one aspect of the embodiment, good sound pressure frequency characteristics can
be obtained.
[0008]
(A) is a typical top view which shows schematic structure of a basic sound generator, (B) is an AA 'line sectional view of Drawing 1A.
It is a figure which shows an example of the frequency characteristic of sound pressure.
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(A) is a typical top view which shows the structure of the sound generator which concerns on
embodiment, (B) is a B-B 'line schematic cross section of FIG. 3A.
(A) is a schematic plan view (part 1) showing a specific arrangement example of the vibrator, (B)
is a schematic plan view (part 2) showing a concrete arrangement example of the vibrator is
there.
(A) is a schematic plan view (No. 3) showing a specific arrangement example of the damping
material, (B) is a schematic plan view (No. 4) showing a concrete arrangement example of the
damping material (C) ) Is a schematic plan view (No. 5) showing a specific arrangement example
of the damping material.
(A) is a figure which shows the structure of the sound generation apparatus which concerns on
embodiment, (B) is a figure which shows the structure of the electronic device which concerns on
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, prior to the description of the sound generator 1 according to the embodiment, a schematic
configuration of a basic sound generator 1 'will be described using FIGS. 1A and 1B. FIG. 1A is a
schematic plan view showing a schematic configuration of the sound generator 1 ′, 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 description easy to understand, FIGS. 1A and 1B illustrate a threedimensional orthogonal coordinate system including a Z axis in which the vertically upward
direction is a positive direction and the vertically downward direction is a negative direction.
Such an orthogonal coordinate system may also be shown in other drawings used in the
following description. Moreover, in FIG. 1A, illustration of the resin layer 7 is omitted.
[0012]
Also, in order to make the description easy to understand, FIG. 1B shows the sound generator 1
′ in a greatly exaggerated manner in the thickness direction (Z-axis direction).
[0013]
As shown in FIG. 1A, the sound generator 1 ′ includes a frame 2, a diaphragm 3 and a
piezoelectric element 5.
As shown in FIG. 1A, the following description exemplifies the case where one piezoelectric
element 5 is provided unless otherwise specified. However, the number of piezoelectric elements
5 is not limited.
[0014]
The frame 2 is formed of two frame members having the same rectangular frame shape and
functions as a support for holding the peripheral portion of the diaphragm 3 and supporting the
diaphragm 3. The diaphragm 3 has a plate-like or film-like shape, and its peripheral edge portion
is sandwiched and fixed to the frame 2. That is, the diaphragm 3 is supported in a stretched state
within the frame 2. 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 portion having a substantially rectangular
shape in the frame of the frame 2.
[0015]
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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.
[0016]
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. Note that FIG. 1A shows an example in
which the shape of the inner region is a substantially rectangular shape that can be seen well in
the related art.
[0017]
The piezoelectric element 5 is provided by being attached to the surface of the vibrating body 3a
or the like, and is an exciter that excites the vibrating body 3a by vibrating upon receiving an
applied voltage.
[0018]
As shown in FIG. 1B, the piezoelectric element 5 is, for example, a laminated body in which
piezoelectric layers 5a, 5b, 5c, and 5d made of four layers of ceramics and three layers of
internal electrode layers 5e are alternately stacked; The laminate includes surface electrode
layers 5f and 5g formed on the upper and lower surfaces of the laminate, and external electrodes
5h and 5j formed on the exposed side surfaces of the internal electrode layer 5e.
Further, lead terminals 6a and 6b are connected to the external electrodes 5h and 5j.
[0019]
The piezoelectric element 5 has a plate shape, and the main surfaces on the upper surface side
and the lower surface side have a polygonal shape such as a rectangular shape or a square shape.
The piezoelectric layers 5a, 5b, 5c and 5d are polarized as shown by arrows in FIG. 1B. That is,
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the direction of polarization with respect to the direction of the electric field applied at a certain
moment is polarized such that one side and the other side in the thickness direction (Z-axis
direction in the figure) are reversed.
[0020]
Then, when a voltage is applied to the piezoelectric element 5 through the lead terminals 6a, 6b,
for example, at a certain moment, the piezoelectric layers 5c, 5d on the side adhered to the
vibrating body 3a shrink and the upper surface of the piezoelectric element 5 The piezoelectric
layers 5a and 5b on the side deform so as to extend. Therefore, by giving an alternating current
signal to the piezoelectric element, the piezoelectric element 5 can be bent and vibrated, and the
bent vibration can be applied to the vibrating body 3a.
[0021]
Further, the main surface of the piezoelectric element 5 is bonded to the main surface of the
vibrating body 3a by an adhesive such as an epoxy resin.
[0022]
As materials for forming the piezoelectric layers 5a, 5b, 5c and 5d, lead-free piezoelectric
materials such as lead zirconate titanate (PZT), Bi layer compounds, tungsten bronze structure
compounds, etc. are conventionally used. Piezoelectric ceramics can be used.
[0023]
Moreover, various metal materials can be used as a material of the internal electrode layer 5e.
For example, in the case of containing a metal component consisting of silver and palladium, and
a ceramic component forming the piezoelectric layer 5a, 5b, 5c, 5d, the piezoelectric layer 5a, 5b,
5c, 5d and the internal electrode layer 5e Since the stress due to the thermal expansion
difference can be reduced, it is possible to obtain the piezoelectric element 5 having no stacking
fault.
Also, the lead terminals 6a, 6b can be formed using various metal materials. For example, when
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the lead terminals 6a and 6b are formed using a flexible wiring in which a metal foil such as
copper or aluminum is sandwiched by resin films, the height of the piezoelectric element 5 can
be reduced.
[0024]
Further, as shown in FIG. 1B, the acoustic generator 1 ′ is disposed so as to cover the surfaces
of the piezoelectric element 5 and the vibrating body 3a in the frame of the frame 2, and is
integrated with the vibrating body 3a and the piezoelectric element 5. The resin layer 7 is further
provided.
[0025]
The resin layer 7 is preferably formed, for example, using an acrylic resin so that the Young's
modulus is in the range of about 1 MPa to 1 GPa.
In addition, since the appropriate damping effect can be induced by embedding the piezoelectric
element 5 by the resin layer 7, the resonance phenomenon can be suppressed, and the peak and
dip in the frequency characteristic of the sound pressure can be suppressed small. .
[0026]
Further, FIG. 1B shows a state in which the resin layer 7 is formed to have the same height as the
frame 2, but it is sufficient if the piezoelectric element 5 is embedded, for example, the resin
layer 7 is a frame It may be formed to be higher than the height of the body 2.
[0027]
Moreover, in FIG. 1B, although the bimorph-type laminated piezoelectric element was mentioned
as an example as the piezoelectric element 5, it is not restricted to this.
For example, it may be a unimorph type in which a piezoelectric element that expands and
contracts is attached to the vibrating body 3a.
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[0028]
By the way, as shown in FIG. 1A and FIG. 1B, in the acoustic generator of this example, the
piezoelectric element 5 is attached to the vibrating body 3a and covered with the resin layer 7,
thereby the vibrating body 3a, the piezoelectric element 5 and the resin layer 7 are integrated,
and the vibrator 3a, the piezoelectric element 5 and the resin layer 7 vibrate integrally.
[0029]
In the case where the composite vibrator constituted by the vibrator 3a, the piezoelectric element
5 and the resin layer 7 as described above has symmetry as a whole, the peaks are concentrated
at a specific frequency and steep peaks and dips are generated. Is likely to occur.
This point is illustrated in FIG.
[0030]
As an example, attention is focused on a portion enclosed by a dashed closed curve PD in FIG.
When such a peak occurs, the sound pressure varies depending on the frequency, which makes it
difficult to obtain good sound quality.
[0031]
In such a case, it is effective to take measures to lower the height of the peak P (see arrow 201 in
the figure) and widen the peak width (see arrow 202 in the figure) to reduce the peak and dip.
[0032]
Therefore, in the present embodiment, first, the outer peripheral shape of the vibrating body 3a
is an elliptical shape.
In addition, the elliptical shape means not only a mathematically defined elliptical shape but also
a general shape in which the outer periphery is a curve convex outward.
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[0033]
Since the resonance frequency is dispersed into various frequencies as compared with the
vibrating body 3a whose outer peripheral shape is substantially rectangular by making the
vibrating body 3a whose outer peripheral shape is an elliptical shape in this way, the peak of
sound pressure at a specific frequency And dips are less likely to occur, and the flatness of the
frequency-sound pressure characteristics can be improved.
[0034]
Further, in the sound generator of the present embodiment, when the outer peripheral shape of
the frame 2 is a rectangular shape having symmetry, a peak or dip of sound pressure is easily
generated at a specific frequency. The effect of making the outer peripheral shape elliptical is
great.
[0035]
Furthermore, it is preferable that the major axis direction and the minor axis direction of the
vibrating body 3a and the diagonal direction, the long side direction and the short side direction
of the frame 2 do not overlap.
The resonance and anti-resonance frequency of the vibrating body 3a and the frame by making
the long axis direction and the short axis direction of the vibrating body 3a not overlap with the
diagonal direction, the long side direction and the short side direction of the support 2 It
becomes possible to prevent the frequency of the resonance and antiresonance of 2 from
overlapping, and it becomes possible to make the flatness of the frequency-sound pressure
characteristic better.
[0036]
Moreover, it is preferable that the gravity center of the frame 2 and the gravity center of the
vibrating body 3a do not overlap.
When the center of gravity of the frame 2 and the center of gravity of the vibrating body 3a do
not overlap, it is possible to further improve the flatness of the frequency-sound pressure
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characteristic.
[0037]
Hereinafter, it demonstrates concretely using FIG. 3A-FIG. 4B. FIG. 3A is a schematic plan view
showing the configuration of the sound generator 1 according to the embodiment, and FIG. 3B is
a schematic cross-sectional view taken along the line B-B 'shown in FIG. 3A. 4A to 4C are layout
explanatory views (part 1) to (part 2) of the vibrator 3a in which the diaphragm 3 is viewed in
plan.
[0038]
As shown to FIG. 3A, the outer periphery shape of the vibrating body 3a becomes elliptical shape
with respect to the sound generator 1 'shown to FIG. 1A and FIG. 1B. The outer peripheral shape
of the vibrating body 3a means not only the elliptical shape defined by mathematics as described
above, but also the entire shape in which the outer periphery is a curve convex outward. The
lengths of the major and minor axes are the lengths of the long side and the short side of the
frame 2 and the longitudinal and lateral lengths of the piezoelectric element 5 in accordance with
the frequency-sound pressure characteristics required of the sound generator 1. It is decided
appropriately along with etc. Further, the frame 2 has a function of holding the diaphragm 3 and
fixing the sound generator 1 to a sound generator to be described later. From such a viewpoint,
the narrowest portion of the width of the frame Is about 1 to 10 mm, preferably 2 to 8 mm.
[0039]
Moreover, as shown to FIG. 4A, it is preferable to set it as the structure which the major axis
direction and minor-axis direction of the vibrating body 3a do not overlap with the diagonal
direction of the frame 2, a long side direction, and a short side direction. By making the
configuration in which the major axis direction and the minor axis direction of the vibrating body
3a do not overlap with the diagonal direction, the long side direction and the short side direction
of the frame 2, the flatness of the frequency-sound pressure characteristic is better It becomes
possible to
[0040]
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Furthermore, as shown to FIG. 4B, it is preferable to set it as the structure which the gravity
center of the frame 2 and the gravity center of the vibrating body 3a do not overlap. With the
configuration in which the center of gravity of the frame 2 and the center of gravity of the
vibrating body 3a do not overlap, it is possible to further improve the flatness of the frequencysound pressure characteristics.
[0041]
Moreover, as shown to FIG. 5A-5C, it is preferable to arrange ¦ position the damping material 8 in
the upper part of at least one of the frame 2, the vibrating body 3a, the piezoelectric element 5,
and the resin layer 7. FIG. By arranging the damping material 8 on the upper part of at least one
of the frame body 2, the vibrating body 3a, the piezoelectric element 5 and the resin layer 7, it is
possible to damp the vibration peak directly by the damping material 8. Thus, by adopting the
configuration in which the outer peripheral shape of the vibrating body 3a is an elliptical shape,
it is possible to further improve the flatness of the frequency-sound pressure characteristic.
[0042]
5A to 5C, when one rectangular damping material 8 is disposed in the upper part of the
piezoelectric element 5, it is disposed in the upper part across the piezoelectric element 5 and
the vibrator 3a. Although the case where the piezoelectric element 5, the vibrating body 3 a and
the frame 2 are disposed at the upper part is illustrated, the shape, the number, and the
arrangement area are not limited. It may be disposed on the top of at least one of the vibrating
body 3 a, the piezoelectric element 5 and the resin layer 7.
[0043]
The damping member 8 may be any member having mechanical loss, but it is desirable that the
damping member 8 be a member having a high mechanical loss coefficient, in other words, a low
mechanical quality coefficient (so-called mechanical Q).
[0044]
Such a damping material 8 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.
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[0045]
In particular, porous rubber materials such as urethane foam can be suitably used.
The damping material 8 is attached to the surface of the resin layer 7 shown in FIG. 1B and
integrated with the vibrating body 3 a, the piezoelectric element 5 and the resin layer 7.
[0046]
Further, by providing the damping material 8 in this manner, the region where the damping
material 8 is disposed receives the vibration loss due to the damping material 8 via the resin
layer 7, thereby suppressing the resonance phenomenon.
[0047]
The outer peripheral shape of the damping member 8 may be an oval shape, a quadrangular
shape, a triangular shape, a semicircular shape, a crescent shape, a star shape, a polygonal shape
such as a pentagonal shape or a hexagonal shape, or a circular shape.
[0048]
Next, a sound generating device and an electronic device equipped with the sound generator 1
according to the embodiment described above will be described with reference to FIGS. 6A and
6B.
FIG. 6A is a view showing the configuration of the sound generation device 20 according to the
embodiment, and FIG. 6B is a view showing the configuration of the electronic device 50
according to the embodiment.
In both figures, only the components necessary for the description are shown, and the
description of general components is omitted.
[0049]
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The sound generation device 20 is a sound generation device such as a so-called speaker, and as
shown in FIG. 6A, for example, includes a sound generator 1 and a housing 30 that houses the
sound generator 1.
The housing 30 resonates the sound emitted by the sound generator 1 internally, and radiates
the sound to the outside from an opening (not shown) formed in the housing 30.
By having such a housing 30, for example, the sound pressure in the low frequency band can be
increased.
[0050]
Also, the sound generator 1 can be mounted on various electronic devices 50. For example, in
FIG. 6B shown below, it is assumed that the electronic device 50 is a mobile terminal device such
as a mobile phone or a tablet terminal.
[0051]
As shown in FIG. 6B, 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. The sound
generator generates a sound based on an audio signal input from the electronic circuit.
[0052]
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.
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[0053]
Although FIG. 6B shows a state in which all the devices including the controller 50a are housed
in one housing 40, the housing form of each device 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.
[0054]
The controller 50 a is a control unit of the electronic device 50. The transmitting and receiving
unit 50b transmits and receives data via the antenna 50f based on the control of the controller
50a.
[0055]
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.
[0056]
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.
[0057]
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.
[0058]
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By the way, although the electronic device 50 was described as what is a portable terminal device
in FIG. 6B, it does not ask the type of the electronic device 50, and may be applied to various
consumer devices having a function of emitting sound. . For example, flat-screen TVs and car
audio devices may be used for various products such as vacuum cleaners, washing machines,
refrigerators, microwave ovens, etc. .
[0059]
In the embodiment described above, the explanation has been made mainly by exemplifying the
case where the piezoelectric element 5 is provided on one main surface of the vibrating body 3a,
but the present invention is not limited to this. The piezoelectric element 5 may be provided.
[0060]
In the embodiment described above, the case where the resin layer 7 is formed so as to cover the
piezoelectric element 5 and the vibrating body 3a in the frame of the frame 2 is taken as an
example, but such a resin layer is not necessarily formed It is good.
[0061]
Further, in the embodiment described above, the diaphragm is made of a thin film such as a resin
film. However, the present invention is not limited to this. For example, the diaphragm may be
made of a plate-like member.
[0062]
In the above-described embodiment, although the case where the exciter is the piezoelectric
element 5 has been described as an example, the exciter is not limited to the piezoelectric
element, and a function of vibrating when an electric signal is input What is necessary is to have.
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
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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.
[0063]
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.
[0064]
1, 1 'Sound generator 2 Frame 3 Vibrator 3a Vibrator 5 Piezoelectric element 5a, 5b, 5c, 5d
Piezoelectric layer 5e Internal electrode layer 5f, 5g Surface electrode layer 5h, 5j External
electrode 6a, 6b Lead terminal 7 Resin layer 8 Damping material 20 Sound generation device 30,
40 Case 50 Electronic device 50a Controller 50b Transmitter and receiver unit 50c Key input
unit 50d Microphone input unit 50e Display unit 50f Antenna 60 Electronic circuit P Peak
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