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JP2011082931

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DESCRIPTION JP2011082931
A speaker using a piezoelectric member that can be applied to various applications and can be
manufactured more easily. A piezoelectric sheet (1) is formed on upper and lower surfaces of the
piezoelectric sheet (1), and the piezoelectric sheet (1) is expanded or contracted in an in-plane
direction orthogonal to the application direction of the electric field when the electric field is
applied. And a pair of electrode films 2 and 3 for applying an electric field. Then, the
piezoelectric sheet 1 on which the pair of electrode films 2 and 3 is formed is cylindrically
wound, and one end of the piezoelectric sheet 1 and the other end opposite to the one end are
directly connected. Or indirectly connected. [Selected figure] Figure 1
スピーカ
[0001]
The present invention relates to a speaker, and more particularly to a speaker using a
piezoelectric element.
[0002]
Heretofore, various sound sources (speakers) using piezoelectric elements such as piezoelectric
buzzers have been developed.
In a speaker using such a piezoelectric element, for example, a voltage (electric field) is applied in
the thickness direction of a plate-like piezoelectric element formed of piezoelectric ceramic or the
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like to expand and contract the piezoelectric element in the thickness direction. As a result, the
air around the piezoelectric element is vibrated to generate sound (sound wave). In a speaker
using such a piezoelectric element, the amount of expansion and contraction of the piezoelectric
element is small, so the generated sound is a high-pitched sound.
[0003]
Moreover, conventionally, a speaker using a cylindrical piezoelectric element has also been
proposed (see, for example, Patent Document 1). Patent Document 1 proposes a nondirectional
speaker constituted of, for example, a cylindrical vibrating body formed of piezoelectric ceramic
or the like, and electrodes formed respectively on the inner and outer surfaces thereof. In the
nondirectional speaker proposed in Patent Document 1, by making the vibrating body cylindrical,
sound is generated over 360 degrees in the horizontal direction.
[0004]
JP-A-9-327092
[0005]
One of the conventionally developed audio speakers is, for example, a 2-way speaker consisting
of a woofer that generates sounds in the low range and a tweeter that generates sounds in the
high range.
However, although the two-way speaker tweeter that has been conventionally developed is
configured using a voice coil, generally there is a problem that the directivity of the sound is
strong and the listening position is limited.
[0006]
As a method for solving this problem, for example, it is conceivable to use an omnidirectional
speaker using a piezoelectric element as proposed in Patent Document 1 as a tweeter. However,
in the omnidirectional speaker proposed in Patent Document 1, the vibrator is formed into a
cylindrical shape by, for example, a method such as sintering, and electrodes are formed on the
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inner wall surface and the outer wall surface. Therefore, in the nondirectional speaker of Patent
Document 1, for example, there remain manufacturing and cost problems such as difficulty in
forming an electrode on the inner wall surface and relatively high cost.
[0007]
The present invention has been made to solve the above problems. An object of the present
invention is to provide a speaker capable of generating sound in all directions and easily
manufactured at low cost.
[0008]
In order to solve the above problems, the speaker of the present invention is formed on a
piezoelectric sheet that expands or contracts mainly in an in-plane direction orthogonal to the
application direction of the electric field when an electric field is applied, and on the upper and
lower surfaces of the piezoelectric sheet And a pair of electrode films for applying an electric
field to the piezoelectric sheet. Then, the piezoelectric sheet on which the pair of electrode films
are formed is cylindrically wound, and one end of the piezoelectric sheet is directly or indirectly
connected to the other end opposite to the one end. The configuration is as follows.
[0009]
In the speaker of the present invention, when a voltage is applied between the pair of electrode
films, the piezoelectric sheet expands and contracts in the in-plane direction of the sheet. At this
time, since the piezoelectric sheet is wound in a cylindrical shape, the entire piezoelectric sheet
vibrates in the radial direction with respect to the central axis of the cylindrical piezoelectric
sheet. As a result, air around the cylindrical speaker vibrates, and sound waves propagate in all
directions with respect to the central axis of the speaker.
[0010]
As described above, in the speaker of the present invention, since the piezoelectric sheet on
which the pair of electrode films are formed is cylindrically wound, by applying a voltage
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between the pair of electrodes, the center of the cylindrical piezoelectric sheet is obtained. Sound
waves can be propagated in all directions with respect to the axis. Furthermore, the speaker
according to the present invention has a configuration in which the piezoelectric sheet having the
electrode film formed on both sides is wound in a cylindrical shape and the opposing side
portions of the piezoelectric sheet are connected to each other. Speakers can be manufactured.
[0011]
Fig.1 (a) is a schematic perspective view of the speaker based on the 1st Embodiment of this
invention, FIG.1 (b) is a schematic top view of a speaker. FIG. 2 is a disassembled perspective
view of the speaker of the first embodiment. FIG. 3 is a diagram for explaining the operation
principle of the speaker according to the first embodiment. FIG. 4A is a schematic perspective
view of the speaker of the first modification, and FIG. 4B is a schematic cross-sectional view of
the speaker of the first modification in the direction along the center axis CX. FIG. 5 is a
schematic perspective view of the support member in the speaker of the first modification. FIG. 6
is a diagram showing an example of the frequency characteristic of sound pressure in the
speaker of the first embodiment. FIG. 7 is a schematic perspective view of a loudspeaker
according to a second embodiment of the present invention. FIG. 8 is an example of the
frequency characteristic of sound pressure in the speaker of the second embodiment. FIG. 9 is a
schematic perspective view of a loudspeaker according to a second modification. FIG. 10 is a
schematic perspective view of the support member in the speaker of the second modification.
FIG. 11 is a schematic perspective view of a loudspeaker according to a third modification. FIG.
12 is an example of the frequency characteristic of the sound pressure in the speaker of the
fourth modification. FIG. 13 is a schematic perspective view of a loudspeaker according to a fifth
modification.
[0012]
Below, the example of composition of the speaker concerning the embodiment of the present
invention is explained in the following order, referring to drawings. The present invention is not
limited to the following examples. 1. First Embodiment Example of Basic Configuration of
Cylindrical Speaker Second Embodiment: Configuration Example of Spiral Cylindrical
Loudspeaker
[0013]
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<1. First Embodiment> [Configuration of Speaker] FIGS. 1A and 1B show a schematic
configuration of a speaker according to a first embodiment of the present invention. FIG. 1A is a
schematic perspective view of the speaker of the present embodiment, and FIG. 1B is a schematic
top view of the speaker of the present embodiment. The speaker 10 according to the present
embodiment mainly includes the piezoelectric sheet 1, the outer electrode 2 (electrode film)
formed on one surface of the piezoelectric sheet 1, and the inner side formed on the other
surface of the piezoelectric sheet 1. And the electrode 3 (electrode film).
[0014]
The speaker 10 is formed by cylindrically winding a sheet-like member including the
piezoelectric sheet 1, the outer electrode 2, and the inner electrode 3 and connecting a pair of
opposing side portions of the sheet-like member. The portion indicated by arrow 5 in FIG. 1 is the
connecting portion. Therefore, the appearance of the entire speaker 10 of the present
embodiment is cylindrical, and the through hole 6 is defined in the inside of the speaker 10.
[0015]
The outer diameter of the speaker 10 can be, for example, about 50 mm and the height can be
about 20 cm. However, the dimensions of the entire speaker 10 are not limited to this example,
and can be appropriately set according to, for example, the application, the frequency
characteristic of the required sound, and the like.
[0016]
Further, the outer electrode 2 of the speaker 10 is connected to one output terminal of the
external drive power supply 100, and the inner electrode 3 is connected to the other output
terminal of the drive power supply 100. Note that an alternating current power supply can be
used as the drive power supply 100. Further, the drive power supply 100 may be configured by a
DC power supply and a switch, and the switch may be turned on / off to apply a pulse-like
periodic voltage between the outer electrode 2 and the inner electrode 3.
[0017]
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The mode at the time of disassembling the speaker 10 of this embodiment is shown in FIG. That
is, FIG. 2 is a schematic configuration view of a sheet-like member before the sheet-like member
including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is cylindrically
wound.
[0018]
The sheet-like member 11 before being cylindrically wound is a sheet member whose surface is
rectangular. In addition, the surface of a sheet-like member is not limited to a rectangular shape,
It can comprise by arbitrary shapes. For example, the surface shape of the sheet-like member
may be square or polygonal. The thickness of the piezoelectric sheet 1 can be, for example, about
several tens to 100 μm. In addition, the shape and dimension of the piezoelectric sheet 1 are not
limited to this example, For example, it can set suitably according to a use, the frequency
characteristic of the sound required, etc.
[0019]
Also, when a voltage (electric field) is applied in the thickness direction, the piezoelectric sheet 1
mainly has dimensions (shapes) in the direction orthogonal to the voltage application direction,
that is, in the in-plane direction of the piezoelectric sheet 1. Is formed of a piezoelectric material
that shrinks or expands. Conventionally, as a deformation mode when a voltage is applied in the
thickness direction of a piezoelectric sheet, a mode called d33 mode in which the dimension
changes in the application direction of the voltage (sheet thickness direction) is orthogonal to the
voltage application direction A mode called d31 mode in which the dimension changes in the
direction is known. A conventional piezoelectric buzzer or the like utilizes the d33 mode, but in
the present embodiment, a sound is generated using the d31 mode.
[0020]
As a forming material of such a piezoelectric sheet 1, a polymeric piezoelectric film can be used,
and for example, a ferroelectric material such as vinylidene fluoride resin (PVDF: Polyvinylidene
Difluoride) or the like can be used. For example, when PVDF is used as a forming material of the
piezoelectric sheet 1, the piezoelectric sheet 1 in which the main deformation mode is the d31
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mode can be manufactured by performing predetermined polarization processing on the
uniaxially stretched film of PVDF. it can.
[0021]
The outer electrode 2 is formed of a metal film having a rectangular surface, and is formed over
substantially the entire surface of one surface of the piezoelectric sheet 1. Thereby, when the
sheet-like member 11 is cylindrically wound and the speaker 10 is comprised, the substantially
whole area of the outer wall surface of the speaker 10 will be in the state covered with the outer
side electrode 2. In the present embodiment, the dimension (length and width) of the surface of
the outer electrode 2 is set to be slightly smaller than that of the piezoelectric sheet 1. However,
the present invention is not limited to this, and the surface dimension of the outer electrode 2
may be the same as that of the piezoelectric sheet 1.
[0022]
On the other hand, the inner electrode 3 is formed of a metal film having a rectangular surface,
and is formed over substantially the entire surface of the other surface of the piezoelectric sheet
1. Thereby, when the sheet-like member 11 is cylindrically wound and the speaker 10 is
comprised, the substantially inner region of the inner wall surface of the speaker 10 is covered
with the inner electrode 3. In the present embodiment, the configuration (for example, the shape,
dimensions, etc.) of the inner electrode 3 is the same as that of the outer electrode 2.
[0023]
Moreover, as a forming material of the outer electrode 2 and the inner electrode 3, metal
materials, such as silver (Ag), can be used, for example. However, the present invention is not
limited to this, and any conductive material can be used as a forming material of each electrode,
and it is appropriately selected according to, for example, the application and the use
environment. Moreover, since the speaker 10 in the present embodiment is configured by
cylindrically winding the sheet-like member 11 including the piezoelectric sheet 1, the outer
electrode 2 and the inner electrode 3, the material for forming the outer electrode 2 and the
inner electrode 3 is It is preferable to use a flexible conductive material.
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[0024]
In addition, the structure (for example, a shape, a dimension, a formation material etc.) of the
outer side electrode 2 and the inner side electrode 3 is not limited to the structure of this
embodiment. For example, one of the outer electrode 2 and the inner electrode 3 may be
configured by a plurality of electrodes, and the substantially entire area of one surface of the
piezoelectric sheet 1 may be covered by the plurality of electrodes.
[0025]
Here, the production procedure of the speaker 10 of the present embodiment will be briefly
described. First, for example, a uniaxially stretched film such as PVDF is prepared, and the
uniaxially stretched film is subjected to polarization treatment so that the main deformation
mode of the film becomes the d31 mode, and the piezoelectric sheet 1 is manufactured.
[0026]
Next, the outer electrode 2 and the inner electrode 3 are formed on one side and the other side
of the piezoelectric sheet 1 by, for example, a method such as a sputtering method or a vapor
deposition method. Thereby, the sheet-like member 11 (FIG. 2) which consists of the piezoelectric
sheet 1, the outer electrode 2, and the inner electrode 3 is produced.
[0027]
Then, the manufactured sheet-like member 11 is cylindrically wound, and the pair of opposing
short sides of the sheet-like member 11 are connected, for example, via an adhesive or the like.
However, in this embodiment, at this time, the entire facing surfaces of the short side portions to
be connected are connected so as to overlap each other. In this embodiment, the cylindrical
speaker 10 is manufactured in this manner.
[0028]
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8
As described above, the speaker 10 according to the present embodiment can be manufactured
by cylindrically winding the sheet-like member 11 including the piezoelectric sheet 1, the outer
electrode 2, and the inner electrode 3. That is, in the present embodiment, as in the
nondirectional speaker proposed in Patent Document 1, for example, it is not necessary to form
the vibrator in a cylindrical shape by sintering or the like, and the formation of the inner
electrode 3 is easy. . Therefore, according to the present embodiment, the speaker 10 can be
manufactured more easily and at low cost.
[0029]
[Principle of Operation of Speaker] Next, the principle of operation of the speaker 10 of the
present embodiment will be described with reference to FIG. FIG. 3 is a top view of the speaker
10.
[0030]
When a voltage is applied from the drive power supply 100 connected to the outer electrode 2
and the inner electrode 3, as described above, the piezoelectric sheet 1 contracts or expands in
the in-plane direction. At this time, since the piezoelectric sheet 1 is cylindrically wound, the
piezoelectric sheet contracts or expands in the direction of circling with respect to the central
axis CX of the through hole 6 of the speaker 10 (thick solid line arrow A1 in FIG. 3). ). As a result,
the overall diameter of the cylindrical speaker 10 becomes smaller or larger. Next, when the
applied voltage is turned off (the voltage is set to 0 V), the diameter of the speaker 10 returns to
the original size.
[0031]
Thus, when ON and OFF of the voltage applied to the outer electrode 2 and the inner electrode 3
are repeated, the diameter of the cylindrical speaker 10 fluctuates accordingly. That is, the outer
and inner walls of the speaker 10 vibrate in the radial direction (radial direction) with respect to
the central axis CX of the speaker 10 (broken line arrow A2 in FIG. 3).
[0032]
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Due to the radial vibration A2 of the speaker 10, ambient air vibrates to generate a sound wave.
At this time, since the speaker 10 of the present embodiment vibrates 360 degrees all around
(entire azimuth) with respect to the central axis CX, the generated sound wave also propagates in
all azimuths. Further, at this time, since the entire speaker 10 simultaneously expands and
contracts in all directions with respect to the central axis CX, the generated sound wave becomes
a plane wave which linearly propagates in all directions and has less attenuation. Therefore,
according to the present embodiment, the user can hear the sound at any position relative to the
speaker 10.
[0033]
When an AC power supply is used as the drive power supply 100, the outer wall and the inner
wall of the speaker 10 vibrate in all directions simultaneously with the central axis CX in
synchronization with the cycle.
[0034]
As described above, in the present embodiment, it is possible to provide the speaker 10 capable
of generating sound waves in all directions and easily manufactured at low cost.
Furthermore, in the present embodiment, the following effects can be obtained.
[0035]
When the present inventors examined the frequency characteristics of the sound generated from
the speaker 10 of the present embodiment, it was confirmed that high sound with a frequency of
several kHz or more was generated. An example will be described later. Further, in the present
embodiment, the lower limit frequency of the generated sound can be changed according to the
material, thickness and the like of the piezoelectric sheet 1. Therefore, the speaker 10 of this
embodiment can be applied to various applications.
[0036]
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10
For example, in the speaker 10 of the present embodiment, for example, when the piezoelectric
sheet 1 is formed of PVDF and the thickness thereof is about 100 μm, the lower limit frequency
of the sound generated from the speaker 10 is about 1 to 2 kHz. In this case, the speaker 10 of
this embodiment can be used as a tweeter for a two-way audio speaker.
[0037]
When the speaker 10 of the present embodiment is applied as a tweeter, the following effects
can be obtained. In a conventional voice coil tweeter, a cone is provided around the vibrating
surface of the voice coil. Therefore, when sound is generated by the voice coil in the conventional
tweeter, the cone is also bent, and a vibration called division vibration due to the bending of the
cone is generated to cause a problem that the sound quality is deteriorated. However, in the
speaker 10 of the present embodiment, as in the prior art, it is not necessary to provide a cone at
the sound generation source, so the above-described divided vibration does not cause
deterioration in sound quality, and higher sound quality can be provided. .
[0038]
Further, in a tweeter using a conventional voice coil, the upper limit frequency of sound is about
20 kHz. On the other hand, according to the verification experiment of the present inventors, in
the speaker 10 of the present embodiment, high sound up to about 100 kHz can be generated,
and sound with higher sound quality can be provided. Furthermore, in the speaker 10 of the
present embodiment, no current flows in the speaker 10, so the power consumption is lower
than that of the tweeter using a conventional voice coil.
[0039]
[Modification 1] FIGS. 4A and 4B show a schematic configuration of a speaker of Modification 1.
FIG. 4 (a) is an external perspective view of the speaker 20 of the first modification, and FIG. 4 (b)
is a schematic cross-sectional view in a direction along the central axis CX of the speaker 20. As
shown in FIG. In FIG. 4A, the same components as those of the speaker 10 (FIG. 1A) of the first
embodiment are indicated by the same reference numerals.
[0040]
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The speaker 20 according to the first modification mainly includes the piezoelectric sheet 1, an
outer electrode 2 formed on one surface of the piezoelectric sheet 1, and an inner electrode 3
formed on the other surface of the piezoelectric sheet 1. A support member 15 is provided in a
cylindrical through hole defined by the inner electrode 3. The speaker 20 of this example has the
same configuration as the speaker 10 (FIG. 1A) of the first embodiment except that the support
member 15 is provided. Therefore, only the configuration of the support member 15 will be
described here, and the description of the other components will be omitted.
[0041]
FIG. 5 shows an external perspective view of the support member 15. The support member 15
includes a disc-shaped first support plate 15a, a disc-shaped second support plate 15b, and a
columnar support rod 15c connecting the first support plate 15a and the second support plate
15b. Be done. The centers of the first support plate 15a, the second support plate 15b, and the
support bar 15c are coaxially disposed on the central axis CX of the speaker 20. The support
member 15 can be made of, for example, plastic or the like.
[0042]
In the speaker 20 of this example, when the sheet-like member including the piezoelectric sheet
1, the outer electrode 2 and the inner electrode 3 is cylindrically wound, the first support plate is
near the long side end of the sheet-like member on the inner electrode 3 side. It winds around
the side of 15a and the 2nd support plate 15b. At this time, long-side end portions of the sheetlike member on the side of the inner electrode 3 are adhered and fixed to the side surfaces of the
first support plate 15a and the second support plate 15b by adhesion means such as an adhesive.
The pair of opposing short sides may be connected indirectly.
[0043]
As described above, in the speaker 20 of this example, as in the first embodiment, the sheet-like
member including the piezoelectric sheet 1, the outer electrode 2, and the inner electrode 3 is
cylindrically wound. Therefore, in the speaker 20 of this example, sound waves are generated in
all directions in the same principle as the first embodiment, and the same effect as the first
03-05-2019
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embodiment can be obtained.
[0044]
In addition, by providing the support member 15 inside the cylindrical sheet-like member as in
this example, the outer shape of the speaker 20 can be stably maintained, and the strength of the
entire speaker 20 can also be improved. . Furthermore, when the speaker 20 of this example is
placed, for example, on a table with one support plate down, the stability of the speaker 20 on
the table can be further improved.
[0045]
The configuration of the support member 15 is not limited to the example shown in FIG. 5, but
may be configured so as to stably maintain the shape of the sheet-like member consisting of the
piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 in a cylindrical shape. For
example, any configuration can be made.
[0046]
<2.
Second Embodiment> Next, although the configuration of a speaker according to a second
embodiment of the present invention will be described, before that, the frequency characteristic
of the sound obtained by the speaker 10 of the first embodiment is simplified. Explain to.
[0047]
FIG. 6 shows an example of the frequency characteristic of the sound generated from the speaker
10 of the first embodiment. The horizontal axis in FIG. 6 is frequency, and the vertical axis is
sound pressure level. As apparent from FIG. 6, according to the speaker 10 of the first
embodiment, it is understood that high sound of several kHz or more can be generated.
[0048]
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13
However, since the shape of the speaker 10 of the first embodiment is cylindrical, the sound
waves generated by the expansion and contraction of the entire speaker 10 propagate radially
outward from the central axis CX of the speaker 10, but the center Sound waves also propagate
toward the axis CX. In this case, since the sound waves propagating toward the central axis CX
are reflected by the opposite inner wall surfaces and return, the sound waves interfere with each
other in the through hole 6 of the speaker 10 to cause resonance of the sound waves. When the
resonance of the sound wave occurs in the through hole 6 of the speaker 10, the sound pressure
level corresponding to the resonance frequency decreases. In the example shown in FIG. 6, for
example, the region surrounded by circles 25 to 27 in the frequency characteristic is a region in
which the sound pressure level is lowered due to the resonance phenomenon inside the speaker
10.
[0049]
The frequency of the sound pressure level and the amount of reduction thereof which are
lowered by the resonance phenomenon inside the speaker 10 as described above change
depending on the diameter (configuration) of the speaker 10. Therefore, depending on the
configuration of the speaker 10, the influence of the resonance phenomenon may not be ignored.
Therefore, in the second embodiment, a configuration of a speaker capable of reducing the
influence of the resonance phenomenon in the above-described speaker 10 will be described.
[0050]
[Configuration of Speaker] FIG. 7 shows a schematic perspective view of the speaker of the
present embodiment. In addition, in FIG. 7, the same code | symbol is attached | subjected and
shown to the structure similar to the speaker 10 (FIG. 1 (a)) of the said 1st Embodiment. As in the
first embodiment, the speaker 30 according to this embodiment includes the piezoelectric sheet
1, the outer electrode 2 (electrode film) formed on one surface of the piezoelectric sheet 1, and
the other surface of the piezoelectric sheet 1. And an inner electrode 3 (electrode film) formed on
the upper side. The outer electrode 2 of the speaker 30 is connected to one output terminal of
the external drive power supply 100, and the inner electrode 3 is connected to the other output
terminal of the drive power supply 100.
[0051]
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However, in the present embodiment, when the sheet-like member including the piezoelectric
sheet 1, the outer electrode 2 and the inner electrode 3 is cylindrically wound to produce the
speaker 30, a part of the opposing surface on the short side of the sheet-like member The facing
surfaces are shifted in the extending direction of the short side and connected so that the two
may overlap.
[0052]
As a result, as shown in FIG. 7, the extending direction of the sheet-like member including the
piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is a helical direction with
respect to the central axis CX of the speaker 30.
That is, the speaker 30 of this example is manufactured by winding a sheet-like member
including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 in a spiral
cylindrical shape.
[0053]
In addition, when overlapping a part of opposing surfaces on the short side of the sheet-like
member, the short sides such that the area of the opposing surface to be overlapped is not more
than half the total area of the opposing surfaces on the short side It is preferable to connect a
part of the opposing surfaces on the part side. According to the verification experiment of the
present inventors, if the area of the facing surface on the short side portion side to which the
sheet-like member is overlapped is about half or less of the total area of the facing surface on the
short side portion side, For example, it has been confirmed that dips in the area surrounded by
circles 25 to 27 can be sufficiently suppressed.
[0054]
[Principle of Operation of Speaker] The shape of the speaker 30 according to the present
embodiment is also cylindrical, so that a sound wave is generated according to the same principle
as the first embodiment, and the central axis CX of the speaker 30 is generated. The sound wave
propagates in all directions. Therefore, in this embodiment, the same effect as that of the first
embodiment can be obtained.
03-05-2019
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[0055]
Moreover, the speaker 30 of this embodiment has a helical cylindrical shape with respect to the
central axis CX, as described above. In this configuration, as shown in FIG. 7, the area of the inner
wall surface of the speaker 30 facing each other across the central axis CX is made smaller than
that of the speaker 10 (FIG. 1A) of the first embodiment. Can. Therefore, among the sound waves
directed to the central axis CX of the speaker 30, the sound waves reflected and returned by the
opposing inner wall surface are reduced, and the resonance phenomenon in the speaker 30 can
be suppressed. As a result, in the present embodiment, it is possible to suppress a dip (a decrease
in sound pressure level) in the frequency characteristic caused by the resonance phenomenon.
[0056]
An example of the frequency characteristic of the sound obtained by the speaker 30 of this
embodiment is shown in FIG. The speaker 30 having the characteristics shown in FIG. 8 has the
characteristics shown in FIG. 6 except that the sheet-like member consisting of the piezoelectric
sheet 1, the outer electrode 2 and the inner electrode 3 is wound in a spiral cylindrical shape. It
was set as the same composition as speaker 10 obtained.
[0057]
As is apparent from the comparison of the frequency characteristics in FIGS. 6 and 8, in the
frequency characteristics of the speaker 30 in the present embodiment (FIG. 8), for example, as
shown in the boxed area in the characteristics, It can be seen that the dip that appeared in is
sufficiently suppressed. Also from this, it is understood that the resonance phenomenon of the
sound wave in the speaker 30 of the present embodiment is sufficiently suppressed.
[0058]
As described above, in the speaker 30 of the present embodiment, the same effect as that of the
first embodiment can be obtained, and sound with better sound quality can be provided.
[0059]
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16
[Modification 2] In the speaker 30 of the second embodiment, the sheet-like member including
the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is wound in a spiral
cylindrical shape, so for example It is difficult to place on stable.
So, in the modification 2, the example of composition of the speaker which can hold the speaker
30 of the above-mentioned 2nd embodiment more stably is explained.
[0060]
FIG. 9 is an external perspective view of the speaker of the second modification. In FIG. 9, the
same components as those in the second embodiment (FIG. 7) are denoted by the same reference
numerals.
[0061]
The speaker 40 according to the second modification mainly includes the piezoelectric sheet 1,
the outer electrode 2 formed on one surface of the piezoelectric sheet 1, and the inner electrode
3 formed on the other surface of the piezoelectric sheet 1. And a support member 45 provided in
a cylindrical through hole defined by the inner electrode 3. The speaker 40 of this example has
the same configuration as the speaker 30 (FIG. 7) of the second embodiment except that the
support member 45 is provided. Therefore, only the configuration of the support member 45 will
be described here, and the description of the other components will be omitted.
[0062]
An external perspective view of the support member 45 is shown in FIG. The support member 45
includes three disk-shaped first to third support plates 45a to 45c, a columnar first support rod
45d connecting the first support plate 45a and the second support plate 45b, and a second
support rod 45d. A cylindrical second support rod 45e is provided to connect between the
support plate 45b and the third support plate 45c. The centers of the first support plate 45a to
the third support plate 45c, the first support bar 45d, and the second support bar 45e are
coaxially disposed on the central axis CX of the speaker 30.
03-05-2019
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[0063]
In the speaker 30 of this example, when the sheet-like member including the piezoelectric sheet
1, the outer electrode 2 and the inner electrode 3 is wound in a spiral cylindrical shape, the inner
electrode 3 of the sheet-like member is a first support plate 45 a and a second support plate
Wrap around the side of 45b. At this time, the inner electrode 3 of the sheet-like member is
adhered and fixed to the side surface of the first support plate 45a and the second support plate
45b by an adhesion means such as an adhesive, and the pair of opposing short sides of the sheetlike member The parts may be connected indirectly.
[0064]
As described above, in the speaker 40 of this example, as in the second embodiment, the sheetlike member including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is
wound in a spiral cylindrical shape. The same effect as that of the second embodiment can be
obtained.
[0065]
In addition, by providing the support member 45 inside the spiral cylindrical sheet-like member
as in this example, the outer shape of the speaker 40 can be stably maintained, and the strength
of the entire speaker 40 can be improved. it can.
Furthermore, for example, when the speaker 40 is placed on the table via the third support plate
45 c, the stability of the speaker 40 on the table can be further improved.
[0066]
The configuration of the support member 45 is not limited to the example shown in FIG. 10, and
the configuration can stably maintain the shape of the sheet-like member including the
piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 in a spiral cylindrical shape.
If there is, it can be configured arbitrarily.
[0067]
03-05-2019
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[Modification 3] In the second embodiment and the modification 2, when the sheet-like member
including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is wound in a
spiral cylindrical shape, the short sides of the sheet-like members are Although the connection
example has been described, the present invention is not limited thereto.
For example, the long sides of the sheet-like member may be connected. FIG. 11 shows an
example (Modification 3).
[0068]
FIG. 11 is a schematic perspective view of the speaker 50 of the third modification. In addition, in
FIG. 11, the same code | symbol is attached | subjected and shown to the structure similar to the
speaker 30 (FIG. 7) of the said 2nd Embodiment.
[0069]
In this example, when the sheet-like member including the piezoelectric sheet 1, the outer
electrode 2 and the inner electrode 3 is wound in a spiral cylindrical shape to produce the
speaker 50, parts of opposing surfaces of the long side portion of the sheet-like member are The
opposing surfaces are shifted in the extending direction of the long side and connected so as to
overlap. Even in such a configuration, the extending direction of the sheet-like member including
the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is a helical direction
with respect to the central axis CX of the speaker 50 as shown in FIG. .
[0070]
Also in the configuration of this example, the area of the inner wall surface of the speaker 50
facing each other across the central axis CX is smaller than that of the speaker 10 (FIG. 1A) of the
first embodiment. Therefore, also in this example, the resonance phenomenon inside the speaker
50 can be suppressed, and the same effect as that of the second embodiment can be obtained.
03-05-2019
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[0071]
[Modification 4] Although an example in which the inside of the speaker 30 is hollow has been
described in the second embodiment and the modifications 2 and 3, the present invention is not
limited to this. For example, a sound absorbing member may be provided in the through hole in
the speaker 30.
[0072]
That is, a cylindrical sound absorbing member may be prepared, and a sheet-like member
including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 may be wound
in a spiral cylindrical shape on the side surface of the sound absorbing member. At this time, the
inner electrode 3 of the sheet-like member is adhered and fixed to the side of the soundabsorbing member by an adhesion means such as an adhesive, and a pair of opposing short sides
of the sheet-like member are indirectly connected. It is also good.
[0073]
In addition, as a formation material of a sound absorption member, sponge, glass wool, a
urethane foam, a polyethylene foam etc. can be used, for example.
[0074]
An example of the frequency characteristic of the sound obtained by the speaker (modification 4)
which provided the sound absorption member in the through-hole of the speaker 30 of the said
2nd Embodiment in FIG. 12 is shown.
As apparent from the comparison of the frequency characteristics in FIGS. 8 and 12, it can be
seen that the dip in the frequency characteristics (reduction of the sound pressure level) is
further suppressed in the loudspeaker of this example.
[0075]
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20
[Modification 5] In the second embodiment and the modifications 2 and 3, the rectangular sheetlike member including the piezoelectric sheet 1, the outer electrode 2 and the inner electrode 3 is
wound in a spiral cylindrical shape to Although the example of suppressing the resonance
phenomenon has been described, the present invention is not limited thereto. The configuration
can be any configuration as long as the region of the inner wall facing each other across the
central axis CX of the speaker can be reduced.
[0076]
In the fifth modification, another configuration example will be described in which the area of the
inner wall facing each other across the central axis CX of the speaker can be reduced. FIG. 13
shows a schematic configuration of the loudspeaker of the fifth modification. In FIG. 13, the same
components as those of the speaker 10 (FIG. 1A) of the first embodiment are indicated by the
same reference numerals.
[0077]
In this example, first, a sheet-like member including the piezoelectric sheet 1, the outer electrode
2 and the inner electrode 3 is cylindrically wound in the same manner as in the first embodiment.
Then, both open ends of the cylindrical member are cut in an oblique direction with respect to
the central axis CX. In the example shown in FIG. 13, both open ends of the cylindrical member
are cut such that the cut surfaces 60a and 60b of both open ends are parallel to each other.
[0078]
With such a configuration, it is possible to reduce the area of the inner wall facing each other
across the central axis CX of the speaker 60. Therefore, also in the speaker 60 of this example, as
in the second embodiment and the second and third modifications, the resonance phenomenon
inside the speaker 60 can be suppressed, and the same effect as the second embodiment. Is
obtained.
[0079]
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21
Although the example shown in FIG. 13 shows a configuration in which the cut surfaces 60a and
60b of both open ends of the cylindrical member are parallel, the present invention is not limited
to this. The shape of the cut surface of the open end of the cylindrical member can be arbitrarily
set as long as the area of the inner wall facing each other across the central axis CX of the
speaker can be reduced. For example, both open ends of the cylindrical member may be cut at
different angles, or only one open end of the cylindrical member may be cut. Furthermore, the
support member described in the second modification and / or the sound absorbing member
described in the fourth modification may be applied to the speaker 60 of this example.
[0080]
In the first and second embodiments and the third and fifth modifications, the end face of the
opposing end (short side or long side) of the sheet-like member including the piezoelectric sheet
1, the outer electrode 2 and the inner electrode 3. Although the example which directly connects
is demonstrated, this invention is not limited to this. For example, a joining member may be
provided at the opposing end of the sheet-like member, and the opposing ends of the sheet-like
member may be indirectly connected via the joining member. In this case, the facing ends of the
sheet-like members may be connected in contact with each other, or a slight gap may be
provided between the facing ends of the sheet-like members.
[0081]
In the first and second embodiments and the first to fifth modifications, an example (see FIG. 2)
in which a sheet-like member including the piezoelectric sheet 1, the outer electrode 2 and the
inner electrode 3 is formed as a flat sheet Although described, the present invention is not
limited thereto. For example, as the sheet-like member, a sheet-like member which meanders
along the extending direction and whose variation direction of the meander is a thickness
direction may be used. When such a sheet-like member is cylindrically wound to constitute a
speaker, the outer wall surface becomes an uneven surface.
[0082]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric sheet, 2 ... outer electrode, 3 ... inner electrode, 10,
30 ... speaker, 11 ... piezoelectric member, 15 ... support member, 100 ... starting power supply
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