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JP2015046946

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DESCRIPTION JP2015046946
PROBLEM TO BE SOLVED: To provide an acoustic generator having small peaks and dips in
frequency characteristics of sound pressure, and an acoustic generator using the same.
SOLUTION: At least a diaphragm and a plurality of piezoelectric elements attached to the
diaphragm at a distance from each other for vibrating the diaphragm, the plurality of
piezoelectric elements have at least two kinds of different thicknesses. An acoustic generator
having piezoelectric elements 1 and 2 and in which piezoelectric elements 1 and 2 having
different thicknesses are arranged in each of two mutually intersecting directions on the main
surface of a diaphragm, and sound using the same It is a generator. It is possible to obtain an
acoustic generator and an acoustic generator having a small peak or dip in the frequency
characteristic of sound pressure. [Selected figure] Figure 1
Sound generator and sound generator using the same
[0001]
The present invention relates to a sound generator and a sound generator using the same.
[0002]
Conventionally, an acoustic generator in which a piezoelectric element is attached to a
diaphragm is known (see, for example, Patent Document 1).
[0003]
Unexamined-Japanese-Patent No. 2004-23436
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1
[0004]
However, the above-described conventional sound generator has a problem that a resonance
phenomenon occurs at a specific frequency, and a large peak or dip easily occurs in the
frequency characteristic of sound pressure.
[0005]
The present invention has been made in view of the problems in the prior art as described above,
and its object is to provide an acoustic generator having small peaks and dips in frequency
characteristics of acoustic pressure and an acoustic generator using the acoustic generator. It is
to provide.
[0006]
The sound generator according to the present invention comprises at least a diaphragm and a
plurality of piezoelectric elements attached to the diaphragm at a distance from each other for
vibrating the diaphragm, the plurality of piezoelectric elements comprising It has at least two
kinds of the piezoelectric elements different in thickness, has two or more of at least one kind of
the at least two kinds of the piezoelectric elements, and crosses each other on the main surface of
the diaphragm. The piezoelectric elements having different thicknesses are arranged in each of
the directions.
[0007]
The sound generation device of the present invention at least includes at least one high-pitched
speaker, at least one low-pitched speaker, and a support for supporting the high-pitched speaker
and the low-pitched speaker, the high-pitched speaker And at least one of the bass speakers is
the sound generator.
[0008]
According to the sound generator and the sound generator of the present invention, it is possible
to reduce the peak and dip in the frequency characteristic of sound pressure.
[0009]
It is a top view which shows typically the sound generator of the 1st example of embodiment of
this invention.
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2
It is the A-A 'line sectional view in FIG.
It is a top view which shows typically the sound generator of the 2nd example of embodiment of
this invention.
It is a top view which shows typically the sound generator of the 3rd example of embodiment of
this invention.
It is a top view which shows typically the sound generator of the 4th example of embodiment of
this invention.
It is a perspective view which shows typically the sound generation apparatus of the 5th example
of embodiment of this invention.
It is a graph which shows the frequency characteristic of the sound pressure of the sound
generator of the 1st example of embodiment of this invention.
It is a graph which shows the frequency characteristic of the sound pressure of the sound
generator of a 1st comparative example.
It is a top view which shows the sound generator of a 2nd comparative example typically.
[0010]
Hereinafter, the sound generator of the present invention will be described in detail with
reference to the attached drawings. The sound generator has a function of converting an
electrical signal into a sound signal, and the sound is not only in the audible frequency range but
also in vibrations of frequencies beyond the audible frequency range such as ultrasonic waves.
Shall be included.
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3
[0011]
First Example of Embodiment FIG. 1 is a plan view schematically showing an acoustic generator
according to a first example of the embodiment of the present invention. FIG. 2 is a crosssectional view taken along the line A-A 'in FIG. In order to facilitate understanding of the
structure, illustration of the resin layer 20 is omitted in FIG. 1, and in FIG. 2, the resin layer 20 is
shown enlarged in the thickness direction of the acoustic generator (z-axis direction in the
figure). There is.
[0012]
As shown in FIGS. 1 and 2, the sound generator of this example includes a plurality of
piezoelectric elements 1, a plurality of piezoelectric elements 2, a film 3, frame members 5 a and
5 b, a resin layer 20, and a conducting wire 22 a. , 22b, 22c, 22d.
[0013]
The film 3 is held in a tensioned state with its peripheral edge held between the frame members
5a and 5b and fixed. The film 3 is vibratably supported by the frame members 5a and 5b and
functions as a diaphragm.
[0014]
The piezoelectric elements 1 and 2 stretch and vibrate in a direction parallel to the main surface
of the film 3 by the addition of the electric signal.
The plurality of piezoelectric elements 1 are in pairs, and the two piezoelectric elements 1
constituting the pair are arranged on both sides of the film 3 so as to sandwich the film 3.
Further, the two piezoelectric elements 1 forming the pair are arranged such that the directions
of the stretching vibration substantially coincide with each other. When one of the piezoelectric
elements 1 constituting the pair is contracted, the other piezoelectric element 1 is expanded. The
plurality of piezoelectric elements 2 are also in pairs, and the two piezoelectric elements 2
constituting the pair are arranged on both sides of the film 3 so as to sandwich the film 3.
Further, the two piezoelectric elements 2 constituting the pair are arranged such that the
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directions of the stretching vibration substantially coincide with each other. When one of the
piezoelectric elements 2 constituting the pair is contracted, the other piezoelectric element 2 is
expanded.
[0015]
In addition, eight piezoelectric elements 1 are attached to the film 3, four on each side of the film
3, and four piezoelectric elements 2 on each side of the film 3, eight in total. Is attached to That
is, the number of piezoelectric elements 1 attached to the film 3 and the number of piezoelectric
elements 2 are equal. The plurality of piezoelectric elements 1 and 2 are attached to the film 3 so
as to be spaced apart from each other on each of both sides of the film 3.
[0016]
Furthermore, the thickness of the piezoelectric element 1 and the thickness of the piezoelectric
element 2 are different from each other, and two directions intersecting each other on the main
surface of the film 3 (two directions in the x-axis direction and the y-axis direction orthogonal to
each other). In each of the above, the vibrators (piezoelectric elements 1 and 2) having respective
thicknesses are arranged in order. That is, the piezoelectric element 1 and the piezoelectric
element 2 are alternately arranged in each of the x-axis direction and the y-axis direction in the
figure which are two directions (two directions orthogonal to each other) intersecting each other
on the main surface of the film 3 There is.
[0017]
The distance between the piezoelectric elements 1 and the distance between the piezoelectric
elements 2 and the adjacent piezoelectric elements 1 and 2 in one of two mutually crossing
directions (x-axis direction in the drawing) on the main surface of the film 3 And intervals are all
made equal. Further, the intervals between the piezoelectric element 1 and the piezoelectric
element 2 adjacent to each other in the other two directions (y-axis direction in the drawing)
intersecting each other on the main surface of the film 3 are all equal.
[0018]
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The piezoelectric elements 1 and 2 have a laminate 13 formed by alternately laminating a
piezoelectric layer 7 made of ceramic and an internal electrode layer 9, and surface electrode
layers 15 a and 15 b formed on the upper and lower surfaces of the laminate 13. A pair of
external electrodes 17 and 19 are provided at both ends of the laminate 13 in the longitudinal
direction (y-axis direction in the drawing). The piezoelectric element 1 has four layers of
piezoelectric layers 7 and three layers of internal electrode layers 9, and the piezoelectric
element 2 has two layers of piezoelectric layers 7 and one layer of internal electrode layers 9.
have. Therefore, the thickness of the piezoelectric element 1 is about twice the thickness of the
piezoelectric element 2.
[0019]
In the piezoelectric element 1, the external electrode 17 is connected to the surface electrode
layers 15 a and 15 b and the one internal electrode layer 9, and the external electrode 19 is
connected to the two internal electrode layers 9. In the piezoelectric element 2, the external
electrode 17 is connected to the surface electrode layers 15 a and 15 b, and the external
electrode 19 is connected to one internal electrode layer 9. The piezoelectric layers 7 are
alternately polarized in the thickness direction of the piezoelectric layer 7 as shown by the
arrows in FIG. 2, and the piezoelectric layers 7 of the piezoelectric elements 1 and 2 disposed on
the upper surface of the film 3 shrink. In order to extend the piezoelectric layers 7 of the
piezoelectric elements 1 and 2 disposed on the lower surface of the film 3, a voltage is applied to
the external electrodes 17 and 19.
[0020]
The upper and lower end portions of the external electrode 19 are extended to the upper and
lower surfaces of the laminate 13 to form extended portions 19a, and these extended portions
19a are surface electrode layers 15a formed on the surface of the laminate 13, It is disposed at a
predetermined distance from the surface electrode layers 15a and 15b so as not to be in contact
with the surface 15b.
[0021]
In the surface of the laminate 13 opposite to the film 3, the extension portions 19a of the
piezoelectric elements 1 and 2 adjacent to each other in the longitudinal direction (the x-axis
direction in the drawing) of the sound generator are connected by the conducting wire 22a.
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Furthermore, one end of the conducting wire 22b is connected to the extension 19a of the
vibrator located at one end, and the other end of the conducting wire 22b is drawn out.
Further, the front surface electrode layers 15b connected to the external electrodes 17 in the
vibrator adjacent in the lengthwise direction (the x-axis direction of the figure) of the sound
generator are connected by the conducting wire 22d and further located at one end One end of
the conducting wire 22c is connected to the front surface electrode layer 15b in the vibrating
body, and the other end of the conducting wire 22c is drawn to the outside.
[0022]
Therefore, the plurality of piezoelectric elements 1 and 2 arranged in the longitudinal direction
of the sound generator (the x-axis direction in the figure) are connected in parallel to each other,
and the same voltage is applied through the conductive wires 22b and 22c. It will be.
[0023]
The piezoelectric elements 1 and 2 are plate-shaped, the upper and lower main surfaces are
rectangular, and the internal electrode layers 9 are alternately drawn in the longitudinal direction
of the main surface of the laminate 13 (the y-axis direction in the figure). It has a pair of side
surfaces.
[0024]
In the piezoelectric elements 1 and 2, the main surface on the film 3 side and the film 3 are
bonded by the adhesive layer 21.
The thickness of the adhesive layer 21 between the piezoelectric elements 1 and 2 and the film 3
is set to 20 μm or less.
In particular, the thickness of the adhesive layer 21 is preferably 10 μm or less. As described
above, when the thickness of the adhesive layer 21 is 20 μm or less, the vibration of the
laminate 13 is easily transmitted to the film 3.
[0025]
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7
As an adhesive for forming the adhesive layer 21, known materials such as epoxy resin, silicon
resin, polyester resin and the like can be used.
[0026]
The piezoelectric characteristics of the piezoelectric elements 1 and 2 are desirably such that the
piezoelectric d31 constant has a characteristic of 180 pm / V or more in order to induce a large
bending deflection vibration and to increase the sound pressure.
When the piezoelectric d31 constant is 180 pm / V or more, the average sound pressure at 60
KHz to 130 KHz can be 65 dB or more.
[0027]
And in the sound generator of this example, resin is filled inside the frame members 5a and 5b so
that the piezoelectric elements 1 and 2 are embedded, and the resin layer 20 is formed. The
conducting wire 22 a and a part of the conducting wire 22 b are also embedded in the resin layer
20. The resin layer 20 may be made of, for example, an acrylic resin, a silicone resin, or rubber,
and preferably has a Young's modulus in the range of 1 MPa to 1 GPa, and more preferably 1
MPa to 850 MPa. Moreover, as for the thickness of the resin layer 20, it is desirable to apply |
coat in the state which covers the piezoelectric elements 1 and 2 completely from the point of
suppressing a spurious. Furthermore, since the film 3 functioning as a diaphragm also vibrates
integrally with the piezoelectric elements 1 and 2, the region of the film 3 not covered by the
piezoelectric elements 1 and 2 is also covered with the resin layer 20.
[0028]
In the sound generator according to this embodiment, the film 3, the two piezoelectric elements
1 and 2 respectively provided on the upper and lower surfaces of the film 3, and the frame
member so as to embed the piezoelectric elements 1 and 2. By including the resin layer 20
formed on the inner side of 5a and 5b, it becomes possible for the multilayer piezoelectric 1 to
induce bending and bending vibration of a wavelength corresponding to high frequency sound,
and for the super high frequency component of 100 KHz or more. It becomes possible to play the
sound.
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[0029]
Furthermore, the peaks and dips associated with the resonance phenomenon of the piezoelectric
elements 1 and 2 induce appropriate damping effects by embedding the piezoelectric elements 1
and 2 in the resin layer 20, and the peaks and dips are reduced along with the suppression of the
resonance phenomenon. While being able to suppress, it becomes possible to make frequency
dependency of sound pressure small.
[0030]
In addition, by attaching the plurality of piezoelectric elements 1 and 2 to one film and applying
the same voltage, strong vibration is suppressed by mutual interference of the vibrations
generated by the respective piezoelectric elements 1 and 2, and the vibration is dispersed Bring
about the effect of reducing peaks and dips.
The sound pressure can be increased even at ultra-high frequencies above 100 KHz.
[0031]
As the piezoelectric layer 7, other piezoelectrics conventionally used, such as lead-free
piezoelectric materials such as lead zirconate (PZ), lead zirconate titanate (PZT), Bi layer
compounds, tungsten bronze structure compounds, etc. Ceramics can be used.
The thickness of one layer of the piezoelectric layer 7 is preferably 10 to 100 μm from the
viewpoint of low voltage driving.
[0032]
It is desirable that the internal electrode layer 9 contain a metal component composed of silver
and palladium and a material component constituting the piezoelectric layer 7. By containing the
ceramic component constituting the piezoelectric layer 7 in the internal electrode layer 9, it is
possible to reduce the stress due to the thermal expansion difference between the piezoelectric
layer 7 and the internal electrode layer 9, and the piezoelectric element 1 having no stacking
fault , 2 can be obtained. The internal electrode layer 9 is not particularly limited to the metal
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9
component consisting of silver and palladium, and is not limited to the material component
constituting the piezoelectric layer 7 as the ceramic component, and other ceramics It may be an
ingredient.
[0033]
The surface electrode layers 15a and 15b and the external electrodes 17 and 19 desirably
contain a glass component in the metal component made of silver. By containing the glass
component, a strong adhesion can be obtained between the piezoelectric layer 7 or the internal
electrode layer 9 and the surface electrode layers 15 a, b or the external electrodes 17, 19.
[0034]
Moreover, as an external shape when the piezoelectric elements 1 and 2 are seen from the
lamination direction, what made polygons, such as a square and a rectangle, is good.
[0035]
The frame members 5a and 5b are rectangular as shown in FIG.
The outer peripheral portion of the film 3 is sandwiched between the frame members 5a and 5b,
and the film 3 is fixed in a tensioned state. The frame members 5a and 5b can be made of, for
example, stainless steel having a thickness of 100 to 1000 μm. The material of the frame
members 5a and 5b is not limited to stainless steel, and may be any material that is less
deformable than the resin layer 20. For example, hard resin, plastic, engineering plastic,
ceramics, etc. can be used. The thickness and the like are not particularly limited. Furthermore,
the shape of the frame members 5a and 5b is not limited to the rectangular shape, and may be
circular or rhombic.
[0036]
The film 3 is fixed to the frame members 5a and 5b in a state in which the film 3 is tensioned in
the surface direction by sandwiching the outer peripheral portion of the film 3 between the
frame members 5a and 5b, and the film 3 is a diaphragm. Play a role. The thickness of the film 3
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10
is, for example, 10 to 200 μm. The film 3 can be made of, for example, a resin such as
polyethylene, polyimide, polypropylene, polystyrene, or ten, or a paper made of pulp, fibers or
the like. Peaks and dips can be suppressed by using these materials.
[0037]
Next, the manufacturing method of the sound generator of this invention is demonstrated.
[0038]
First, the piezoelectric elements 1 and 2 are prepared.
The piezoelectric elements 1 and 2 add a binder, a dispersing agent, a plasticizer, and a solvent to
the powder of the piezoelectric material and stir them to prepare a slurry. As a piezoelectric
material, any of lead-based and non-lead-based can be used.
[0039]
Next, the obtained slurry is formed into a sheet to prepare a green sheet. A conductor paste is
printed on the green sheet to form an internal electrode pattern, and the green sheet on which
the internal electrode pattern is formed is laminated to produce a laminate molded body.
[0040]
Next, the laminate molded body is degreased and fired, and cut into a predetermined size,
whereby the laminate 13 can be obtained. The outer peripheral part of the laminated body 13 is
processed as needed. Next, a conductor paste for forming the surface electrode layers 15a and
15b is printed on the main surface in the stacking direction of the stacked body 13, and on both
side surfaces of the stacked body 13 in the longitudinal direction (y axis direction in the drawing)
The conductor paste for forming the electrodes 17 and 19 is printed. By baking the electrodes at
a predetermined temperature, the piezoelectric elements 1 and 2 shown in FIGS. 1 and 2 can be
obtained.
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[0041]
Next, in order to impart piezoelectricity to the piezoelectric elements 1 and 2, a direct current
voltage is applied through the surface electrode layer 15 b or the external electrodes 17 and 19
to polarize the piezoelectric layer 7 of the piezoelectric elements 1 and 2. At this time, a DC
voltage is applied such that the polarization direction is the direction indicated by the arrow in
FIG.
[0042]
Next, a film 3 to be a diaphragm is prepared, and the outer peripheral portion of the film 3 is
sandwiched between the frame members 5a and 5b, and the film 3 is fixed in a tensioned state.
Specifically, an adhesive is applied to both sides of the film 3, the piezoelectric elements 1 and 2
are pressed against both sides of the film 3 so as to sandwich the film 3, and the adhesive is
cured by irradiating heat or ultraviolet light. Then, after the resin is poured inside the frame
members 5a and 5b and the piezoelectric elements 1 and 2 are completely embedded in the
resin, the resin is cured to obtain the acoustic generator of this example.
[0043]
The sound generator of the present example configured as described above has a simple
structure, which can achieve downsizing and thinning, and maintains a high sound pressure up to
an ultra high frequency. In addition, since the piezoelectric elements 1 and 2 are embedded in
the resin layer 20, the piezoelectric elements 1 and 2 are not easily affected by water or the like,
and the reliability can be improved.
[0044]
Further, the sound generator of the present example has at least a film 3 which is a diaphragm,
and a plurality of piezoelectric elements which are attached to the film 3 at a distance from each
other and which vibrate the film 3. The plurality of piezoelectric elements have at least two types
of piezoelectric elements (piezoelectric elements 1 and 2) having different thicknesses. That is,
the plurality of piezoelectric elements include at least two types of piezoelectric elements
(piezoelectric elements 1 and 2) having different thicknesses. Then, piezoelectric elements 1 and
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12
2 having different thicknesses are disposed in each of two mutually crossing directions (x-axis
direction and y-axis direction in the figure which are two directions orthogonal to each other) on
the main surface of film 3 There is. Thereby, the peak and dip in the frequency characteristic of
sound pressure can be made small. The reason why this effect is obtained is that the resonance
frequency of the bending vibration of the piezoelectric elements having different thicknesses is
different, so the vibration generated by arranging the piezoelectric elements 1 and 2 having
different thicknesses in both directions crossing each other It can be inferred that the number of
modes can be increased, thereby allowing energy to be dispersed to multiple vibration modes to
reduce the energy possessed by one vibration mode. In addition, as for the two directions to
mutually cross | intersect, it is desirable that it is a direction orthogonal to the edge which frame
member 5a, 5b opposes, respectively. Thus, by lowering the symmetry in the structure of the
sound generator, it is possible to reduce the level of the peak generated on the frequency
characteristic of the sound pressure.
[0045]
Further, in the sound generator of the present example, adjacent piezoelectric elements 1 and 2
in each of two mutually crossing directions (the x-axis direction and the y-axis direction in the
drawing which are directions orthogonal to each other) on the main surface of the film 3 The
thickness of 2 is different. Thereby, the frequency characteristic of sound pressure can be further
improved. It is speculated that this may be due to the distribution of the vibration generated by
the piezoelectric elements 1 and 2 and the distribution of the mass on the film 3 being made
uniform, the structural symmetry becoming low, etc. it can.
[0046]
Further, the sound generator of this example has two types of different thicknesses in each of
two mutually crossing directions (the x-axis direction and the y-axis direction in the figure which
are directions orthogonal to each other) on the main surface of the film 3 Piezoelectric elements
(piezoelectric elements 1 and 2) are alternately arranged. Thereby, the frequency characteristic
of sound pressure can be further improved. It is speculated that this may be due to the
distribution of the vibration generated by the piezoelectric elements 1 and 2 and the distribution
of the mass on the film 3 being made uniform, the structural symmetry becoming low, etc. it can.
[0047]
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13
Further, in the sound generator of this example, the number of piezoelectric elements of each
thickness is all equal. That is, the number of piezoelectric elements 1 and 2 is equal. Thereby, the
frequency characteristic of sound pressure can be further improved. It is speculated that this may
be due to the distribution of the vibration generated by the piezoelectric elements 1 and 2 and
the distribution of the mass on the film 3 being made uniform, the structural symmetry becoming
low, etc. it can.
[0048]
Second Example of Embodiment FIG. 3 is a plan view schematically showing an acoustic
generator according to a second example of the embodiment of the present invention. In FIG. 3,
the resin layer 20 and the conductors 22a, 22b, 22c and 22d are not shown, and the detailed
structures of the piezoelectric elements 1 and 2 are not shown, in order to make the structure
easy to understand. There is. Further, in the present example, only the points different from the
first example of the embodiment described above will be described, and the same components
will be denoted by the same reference numerals and redundant description will be omitted.
[0049]
In the sound generator of this example, eight piezoelectric elements 1 and 2 are arranged on
both main surfaces of the film 3 respectively. That is, 32 piezoelectric elements in total, 16 pieces
each, are arranged on both main surfaces of the film 3. As in the first example of the abovedescribed embodiment, each of the piezoelectric elements 1 and 2 is in pairs, and the two
piezoelectric elements constituting the pair sandwich the film 3. Are disposed at the same
position on both main surfaces of the film 3.
[0050]
The acoustic generator of this example is a piezoelectric device having two types of piezoelectric
elements having different thicknesses in two mutually crossing directions (x-axis direction and yaxis direction in the figure which are orthogonal to each other) on the main surface of the film 3
(Piezoelectric elements 1 and 2) are alternately arranged. Thereby, the frequency characteristic
of sound pressure can be improved. It is speculated that this may be due to the distribution of the
vibration generated by the piezoelectric elements 1 and 2 and the distribution of the mass on the
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film 3 being made uniform, the structural symmetry becoming low, etc. it can.
[0051]
Further, in the sound generator of this example, more piezoelectric elements 1 and 2 are
arranged on the film 3 than the sound generator of the first example of the embodiment
described above, so Peak and dip levels can be further reduced. It can be inferred that this is
because the number of vibration modes generated on the film 3 further increases.
[0052]
In addition, the acoustic generator of this example is a piezoelectric element of each thickness in
each of two mutually crossing directions (x-axis direction and y-axis direction in the figure which
are directions orthogonal to each other) on the main surface of the film 3 The (piezoelectric
elements 1 and 2) are arranged at equal intervals. Thereby, the frequency characteristic of sound
pressure can be further improved. It is speculated that this may be due to the distribution of the
vibration generated by the piezoelectric elements 1 and 2 and the distribution of the mass on the
film 3 being made uniform, the structural symmetry becoming low, etc. it can.
[0053]
In addition, the acoustic generator of this example is a piezoelectric element of each thickness in
each of two mutually crossing directions (x-axis direction and y-axis direction in the figure which
are directions orthogonal to each other) on the main surface of the film 3 The intervals between
(piezoelectric elements 1 and 2) are all equal. That is, the distance between the piezoelectric
elements 1 and the distance between the piezoelectric elements 2 are equal. Thereby, the
frequency characteristic of sound pressure can be further improved. It is speculated that this may
be due to the distribution of the vibration generated by the piezoelectric elements 1 and 2 and
the distribution of the mass on the film 3 being made uniform, the structural symmetry becoming
low, etc. it can.
[0054]
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Third Example of Embodiment FIG. 4 is a plan view schematically showing an acoustic generator
according to a second example of the embodiment of the present invention. In FIG. 4, the resin
layer 20 and the conductors 22a, 22b, 22c and 22d are not shown, and the detailed structures of
the piezoelectric elements 1, 2 and 4 are not shown, in order to make the structure easy to
understand. doing. Further, in the present example, only the points different from the second
example of the embodiment described above will be described, and the same reference numerals
will be given to the same components and redundant description will be omitted.
[0055]
In the sound generator of this example, five piezoelectric elements 1, six piezoelectric elements 2
and five piezoelectric elements 4 are disposed on both main surfaces of the film 3. That is, 32
piezoelectric elements in total, 16 pieces each, are arranged on both main surfaces of the film 3.
The piezoelectric element 4 has a structure similar to that of the piezoelectric elements 1 and 2
but includes six piezoelectric layers 7 and five internal electrode layers 9. It has about twice the
thickness.
[0056]
The acoustic generator of this example is a piezoelectric element of each thickness in each of two
mutually crossing directions (x-axis direction and y-axis direction in the figure which are two
directions orthogonal to each other) on the main surface of the film 33 (Piezoelectric elements 1,
2, 4) are arranged in order. Thereby, the frequency characteristic of sound pressure can be
improved. It is speculated that this may be due to the distribution of the vibration generated by
the piezoelectric elements 1 and 2 and the distribution of the mass on the film 3 being made
uniform, the structural symmetry becoming low, etc. it can.
[0057]
Fourth Example of Embodiment FIG. 5 is a plan view schematically showing an acoustic
generator according to a second example of the embodiment of the present invention. In FIG. 5,
the resin layer 20 and the conductors 22a, 22b, 22c and 22d are not shown, and the detailed
structures of the piezoelectric elements 1 and 2 are not shown, in order to facilitate
understanding of the structure. There is. Further, in the present example, only the points
different from the second example of the embodiment described above will be described, and the
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same reference numerals will be given to the same components and redundant description will
be omitted.
[0058]
In the sound generator of this example, two piezoelectric elements 1 and two piezoelectric
elements 2 are disposed on one main surface of the film 3 (the main surface on which the frame
member 5a is located). That is, four piezoelectric elements are disposed on one main surface of
film 3 (the main surface on the side where frame member 5a is located), and the other main
surface of film 3 (the main surface on the side where frame member 5b is located) The
piezoelectric element is not disposed in The resin 20 is also disposed only on the one main
surface side of the film 3 and is not disposed on the other main surface side of the film 3.
Moreover, the piezoelectric elements 1 and 2 in the sound generator of this example are bimorph
piezoelectric elements, respectively. That is, the piezoelectric elements 1 and 2 in the sound
generator of this example have a relationship between the direction of polarization at a certain
moment and the direction of the electric field in the thickness direction (z-axis direction
perpendicular to both x-axis and y-axis in the figure). It is a piezoelectric element which is
designed to be reversed on one side and the other side, and can bend and vibrate alone when an
electric signal is inputted.
[0059]
The acoustic generator of this example having such a configuration also has a thickness in each
of two mutually crossing directions (the x-axis direction and the y-axis direction in the figure
which are mutually orthogonal directions) on the main surface of the film 3 Since two different
types of piezoelectric elements (piezoelectric elements 1 and 2) are disposed, it is possible to
reduce the level of the peak generated in the frequency characteristic of the sound pressure.
Furthermore, piezoelectric elements 1 and 2 having different thicknesses are alternately
arranged in each of two mutually crossing directions (x-axis direction and y-axis direction in the
drawing which are directions orthogonal to each other) on the main surface of film 3 Because of
this, it is possible to further reduce the level of the peak generated in the frequency characteristic
of sound pressure.
[0060]
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(Fifth Example of Embodiment) FIG. 18 is a perspective view schematically showing a sound
generation apparatus of a fifth example of the embodiment of the present invention. As shown in
FIG. 6, the sound generating apparatus of this embodiment includes a high-pitched speaker 31, a
low-pitched speaker 32 and a support 33.
[0061]
The treble speaker 31 is the sound generator of the first example of the embodiment, and is a
speaker mainly for outputting treble. For example, it is used to output a sound having a
frequency of about 20 KHz or more.
[0062]
The bass speaker 32 is a speaker mainly for outputting a low temperature. For example, it is used
to output sound at a frequency of about 20 KHz or less. From the viewpoint of facilitating the
output of low frequency sound, for example, in the case of a rectangular shape or an elliptical
shape, the bass speaker 32 has the longest side longer than the treble speaker 31, and the others
are the treble speaker 31. The one having the same configuration as that of the above can be
used.
[0063]
The support 33 is formed of, for example, a metal plate, and the high sound speaker 31 and the
low sound speaker 32 are respectively accommodated and fixed in the two openings.
[0064]
The sound generator of this example having such a configuration uses the sound generator of the
first example of the embodiment as the high-tone speaker 31, so that the high-pitched sound
with a small peak or dip in the frequency characteristic of the sound pressure Can be output.
[0065]
As described above, the sound generation device of the present example at least includes at least
one high sound speaker 31, at least one low sound speaker 32, and a support 33 for supporting
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high sound speaker 31 and low sound speaker 32. And at least one of the high-pitched speaker
31 and the low-pitched speaker 32 is the above-described sound generator of the present
invention.
As a result, it is possible to obtain a high-performance sound generator capable of outputting a
sound having a small peak or dip in the frequency characteristic of sound pressure.
[0066]
(Modification) The present invention is not limited to the examples of the embodiments described
above, and various changes and improvements can be made without departing from the scope of
the present invention.
[0067]
For example, the number of piezoelectric elements attached to the film 3 is not limited to the
example of the embodiment described above.
In addition, four or more types of thickness of the vibrator may be used.
[0068]
Further, in the first example of the embodiment described above, although an example in which
the film 3 is used as the diaphragm is shown, the present invention is not limited to this.
For example, a plate-shaped diaphragm made of metal or resin may be used.
[0069]
Moreover, in the example of embodiment mentioned above, although the example which formed
the resin layer 20 which coat | covers the surface of the film 3 and a piezoelectric element was
shown, it is not limited to this. The resin layer 20 may not be provided.
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[0070]
(First Embodiment) A concrete example of the sound generator of the present invention will be
described. The acoustic generator of the first example of the embodiment of the present
invention shown in FIGS. 1 and 2 was manufactured, and its electrical characteristics were
measured.
[0071]
First, a piezoelectric powder containing lead zirconate titanate (PZT) in which a part of Zr is
replaced with Sb, a binder, a dispersant, a plasticizer, and a solvent are kneaded by ball milling
for 24 hours to obtain a slurry. Made. And the green sheet was produced by the doctor blade
method using the obtained slurry. A conductor paste containing Ag and Pd as an electrode
material was applied to the green sheet in a predetermined shape by screen printing. Then, the
green sheet to which the conductor paste was applied and the green sheet to which the
conductor paste was not applied were laminated and pressed to produce a laminate molded
body. Then, the laminate was degreased in the air at 500 ° C. for 1 hour, and then fired in the
air at 1100 ° C. for 3 hours to obtain a laminate.
[0072]
Next, both end surface portions in the longitudinal direction (y-axis direction in the drawing) of
the obtained laminate were cut by dicing to expose the tip of the internal electrode layer 9 on the
side surface of the laminate. Then, in order to form surface electrode layers 15a and 15b on both
main surfaces of the laminate, a conductive paste containing Ag and glass was applied by screen
printing on one side of the main surface of the piezoelectric body. Thereafter, a conductive paste
containing Ag and glass as a material of the external electrodes 17 and 19 is applied to both side
surfaces in the longitudinal direction (y-axis direction in the figure) by dip method, and in air at
700 ° C. for 10 minutes. I burned it. Thus, a laminate 13 as shown in FIG. 2 was produced. The
dimensions of the main surface of the produced laminate were 6 mm in width and 7 mm in
length. The thickness of the laminate 13 was 100 μm for the piezoelectric element 1 and 50
μm for the piezoelectric element 2.
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20
[0073]
Next, a voltage of 100 V was applied for 2 minutes between the internal electrode layers 9 and
between the internal electrode layer 9 and the surface electrode layers 15a and 15b through the
external electrodes 17 and 19 for polarization, to obtain a unimorph-type laminated piezoelectric
element. .
[0074]
Next, a film 3 made of a polyimide resin having a thickness of 25 μm was prepared, and the film
3 was fixed to the frame members 5a and 5b in a state where the film 3 was given tension.
Then, an adhesive made of an acrylic resin is applied to both main surfaces of the fixed film 3
and the piezoelectric elements 1 and 2 are pressed from both sides so as to sandwich the film 3
against the portion of the film 3 coated with the adhesive. The adhesive was cured in air for 1
hour at ° C. to form a 5 μm thick adhesive layer 21. The dimensions of the film 3 in the frame
members 5a and 5b were 48 mm in length and 18 mm in width. The distance between the
piezoelectric element 1 and the piezoelectric element 2 adjacent to each other is 6 mm in the
longitudinal direction (x-axis direction in the drawing) of the acoustic generator, and the interval
in the width direction (y-axis direction in the drawing) of the acoustic generator It was 1 mm.
Thereafter, conducting wires 2a, 2b, 2c and 2d were joined to the piezoelectric elements 1 and 2
for wiring.
[0075]
Then, an acrylic resin having a Young's modulus after solidification of 17 MPa is poured into the
inside of the frame members 5a and 5b, and the acrylic resin is filled and solidified to have the
same height as the height of the frame members 5a and 5b. , And the resin layer 20 was formed.
Thus, an acoustic generator as shown in FIGS. 1 and 2 was produced.
[0076]
And about the frequency characteristic of the sound pressure of the produced sound generator, it
evaluated according to JEITA (Electronic Information Technology Industries Association
standard) EIJA RC-8124A. For evaluation, a sine wave signal with an effective value of 2.8 V was
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21
input between the conductors 22b and 22c of the sound generator, and a microphone was placed
at a point 1 m above the reference axis of the sound generator to evaluate the sound pressure.
The evaluation result is shown in FIG. Moreover, the sound generator of the first comparative
example in which the thicknesses of the piezoelectric elements 1 and 2 were all equal was
manufactured, and the frequency characteristics of the sound pressure were evaluated. The
evaluation result of the sound generator of the first comparative example is shown in FIG. In the
graphs of FIG. 7 and FIG. 8, the horizontal axis indicates frequency, and the vertical axis indicates
sound pressure.
[0077]
According to the graph shown in FIG. 7, it can be seen that a high sound pressure exceeding 70
dB is obtained at most frequencies in a wide frequency wave up to about 20 to 180 kHz. Further,
as compared with the frequency characteristic of the sound pressure of the sound generator of
the first comparative example shown in FIG. 8, it can be seen that the peak and the dip are
reduced, and an almost flat excellent sound pressure characteristic is obtained. This confirms the
effectiveness of the present invention.
[0078]
Second Example The sound pressure characteristics of the sound generator of the fourth example
of the embodiment shown in FIG. 5 and the sound generator of the second comparative example
shown in FIG. 9 are affected. The number of eigenvalues of vibration (the number of vibration
modes) was calculated by simulation. The difference between the sound generator of the fourth
example of the embodiment shown in FIG. 5 and the sound generator of the second comparative
example shown in FIG. 9 is only in the method of arranging the piezoelectric elements 1 and 2. .
That is, the sound generators of the fourth example of the embodiment shown in FIG. 5 have
different thicknesses in each of two directions (the x-axis direction and the y-axis direction in the
figure which are directions orthogonal to each other) intersecting each other. Two types of
piezoelectric elements (piezoelectric elements 1 and 2) are disposed. On the other hand, in the
sound generator of the second comparative example shown in FIG. 9, although two types of
piezoelectric elements (piezoelectric elements 1 and 2) having different thicknesses in the x-axis
direction in the drawing are arranged, Only piezoelectric elements having the same thickness are
arranged in the y-axis direction in the figure. That is, the sound generator of the second
comparative example shown in FIG. 9 has a line symmetrical structure with respect to a line
parallel to the x-axis located at the center in the y-axis direction of the drawing.
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22
[0079]
In this simulation, the frame members 5a and 5b have a frame shape with a length of 60 mm on
the outside and a width of 50 mm, and a length of 50 mm on the inside with a width of 40 mm
and a thickness of 1 mm. The thickness of the film 3 was 0.03 mm. The piezoelectric element 1
was a square plate having a side of 10 mm and a thickness of 0.1 mm. The piezoelectric element
2 was a square plate having a side of 10 mm and a thickness of 0.05 mm. The distance between
adjacent piezoelectric elements was 15 mm.
[0080]
As a result of simulation, the number of characteristic values of vibration affecting the sound
pressure characteristic in the frequency range of 1 kHz to 10 kHz is 38 in the second
comparative example shown in FIG. 9 and shown in FIG. The number of sound generators in the
fourth example of the embodiment was 73. That is, the sound generator of the fourth example of
the embodiment shown in FIG. 5 generates about twice as many vibration modes as the sound
generator of the second comparative example shown in FIG. It turned out to be done. Thereby, in
the sound generator according to the present invention, the number of generated vibration
modes increases and the peaks generated in the frequency characteristic of sound pressure are
dispersed, thereby reducing the level of the peak generated in the frequency characteristic of
sound pressure. It is possible to obtain one support for prediction that flatter sound pressure
characteristics can not be obtained.
[0081]
1, 2, 4: Piezoelectric element 3: Film 31: High-pitch speaker 32: Bass speaker 33: Support
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