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JP2018157347

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DESCRIPTION JP2018157347
Abstract: PROBLEM TO BE SOLVED: To provide a vibration transducer which is less affected by
environmental temperature. A vibration transducer (1) includes a sheet-like piezoelectric element
(2) and a thermal effect element (3) for adjusting the temperature of the piezoelectric element.
Preferably, in the vibration transducer, the thermal effect element faces at least one surface of
the piezoelectric element. The vibration transducer may further comprise a temperature sensor.
The vibration transducer may be a heating element in which the thermal effect element heats the
piezoelectric element without contact. [Selected figure] Figure 1
Vibration transducer
[0001]
The present invention relates to a vibration transducer.
[0002]
For example, vibration transducers, such as speakers and microphones, which convert vibrations
into electrical signals or convert electrical signals into vibrations are widely used.
Among such vibration transducers, one that performs conversion between vibration and an
electric signal using a film-like piezoelectric body is known (see, for example, JP-A-2003304595).
04-05-2019
1
[0003]
The characteristics of the piezoelectric body are not constant depending on the temperature. For
this reason, in the vibration transducer using the piezoelectric body as described in the abovementioned publication, the gain may change depending on the environmental temperature, and
the waveform of the output vibration or electric signal may be distorted. Specifically, when the
microphone using the vibration transducer is used outdoors where the air temperature is at the
freezing point, a disadvantage such as a reduction in the sensitivity of the microphone may occur.
[0004]
Unexamined-Japanese-Patent No. 2003-304595
[0005]
In view of the above problems, the present invention has an object to provide a vibration
transducer that is less affected by environmental temperature.
[0006]
A vibration transducer according to an aspect of the present invention made to solve the above
problems includes a sheet-like piezoelectric element and a thermal effect element that adjusts the
temperature of the piezoelectric element.
[0007]
The vibration transducer is provided with a thermal effect element for adjusting the temperature
of the piezoelectric element, so that the temperature of the piezoelectric element can be
maintained within a certain range regardless of the environmental temperature.
As a result, the vibration transducer is less affected by environmental temperature, has a
substantially constant gain, and provides a relatively linear output.
[0008]
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2
In the vibration transducer, preferably, the thermal effect element faces at least one surface of
the piezoelectric element.
According to this configuration, the temperature of the piezoelectric element can be adjusted
relatively efficiently by the thermal effect element being arranged to be in contact with or to face
the surface of the piezoelectric element.
For this reason, it is possible to effectively suppress the change in output characteristics even in
the case of a sudden change in environmental temperature when, for example, the vibration
transducer is moved from indoor to outdoor.
[0009]
Preferably, the vibration transducer further comprises a temperature sensor. According to this
configuration, the temperature of the piezoelectric element can be accurately grasped, and the
stability of the output characteristic can be further improved.
[0010]
In the vibration transducer, the heat effect element may be a heating element which heats the
piezoelectric element without contact. According to this configuration, since the thermal effect
element does not inhibit signal conversion by the piezoelectric element, a relatively linear high
gain output can be obtained. In addition, since the piezoelectric element can be heated relatively
uniformly by heating the piezoelectric element in a non-contact manner by the heating element,
the linearity of the output can be further improved.
[0011]
As described above, the vibration transducer of the present invention is less affected by the
environmental temperature.
[0012]
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3
It is a typical sectional view showing a vibration transducer of one embodiment of the present
invention.
It is a schematic plan view of the vibration transducer of FIG. It is a typical sectional view
showing a vibration transducer of an embodiment different from Drawing 1 of the present
invention. It is a typical sectional view showing a vibration transducer of an embodiment
different from Drawing 1 and Drawing 3 of the present invention. It is a typical sectional view
showing a vibration transducer of an embodiment different from Drawing 1, Drawing 3, and
Drawing 4 of the present invention.
[0013]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings as appropriate.
[0014]
First Embodiment FIG. 1 and FIG. 2 show a vibration transducer 1 according to a first
embodiment of the present invention.
The vibration transducer 1 has a back surface outer periphery held by an annular support S, and
a microphone for converting sound wave vibration incident on the surface to an electric signal or
a speaker for converting the electric signal to sound wave vibration and emitting it to the surface
side It can be used as The “sound wave vibration” is not limited to the vibration in the audible
area, but may be a low frequency vibration or an ultrasonic vibration in the inaudible area.
[0015]
The vibration transducer 1 includes a sheet-like piezoelectric element 2 and a thermal effect
element 3 for adjusting the temperature of the piezoelectric element 2.
[0016]
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4
In the vibration transducer 1 of the present embodiment, the thermal effect element 3 is
disposed to face the back surface of the piezoelectric element 2.
More specifically, the heat effect element 3 is stacked on the back surface side of the
piezoelectric element 2 via the insulating film 4.
[0017]
<Piezoelectric Element> The piezoelectric element 2 includes a sheet-like or film-like piezoelectric
body 5 and a pair of sheet-like or film-like electrodes 6 and 7 stacked on the front and back of
the piezoelectric body.
[0018]
(Piezoelectric Body) The piezoelectric body 5 can be formed of a piezoelectric material that
converts pressure into voltage.
The piezoelectric material forming the piezoelectric body 5 may be, for example, an inorganic
material such as lead zirconate titanate, but is preferably a polymer piezoelectric material having
flexibility.
[0019]
Examples of the polymeric piezoelectric material include polyvinylidene fluoride (PVDF),
vinylidene fluoride-trifluorinated ethylene copolymer (P (VDF / TrFE)), and vinylidene cyanidevinyl acetate copolymer (P (VDCN /). And the like.
[0020]
Further, as the piezoelectric body 5, a large number of flat pores are formed in, for example,
polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), polyethylene
terephthalate (PET) or the like which does not have piezoelectric characteristics, for example,
corona discharge It is also possible to use one to which a piezoelectric property is imparted by
polarizing and charging the flat pores facing each other.
[0021]
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5
The lower limit of the average thickness of the piezoelectric body 5 is preferably 10 μm, more
preferably 50 μm.
On the other hand, the upper limit of the average thickness of the piezoelectric body 5 is
preferably 500 μm, more preferably 200 μm.
If the average thickness of the piezoelectric body 5 is less than the lower limit, the strength of the
piezoelectric body 5 may be insufficient. On the other hand, when the average thickness of the
piezoelectric body 5 exceeds the upper limit, the deformability of the piezoelectric body 5 is
reduced, and the gain of the vibration transducer 1 may be insufficient.
[0022]
(Electrodes) The electrodes 6 and 7 are stacked on both sides of the piezoelectric body 5 and are
used to detect a potential difference between the front and back of the piezoelectric body 5 or to
apply a potential difference to the front and back of the piezoelectric body 5. Therefore, a wire
(not shown) for outputting or inputting an electric signal is connected to the electrodes 6 and 7.
[0023]
The material of the electrodes 6 and 7 may be any one having conductivity, and examples thereof
include metals such as aluminum, copper and nickel, and carbon.
[0024]
The average thickness of the electrodes 6 and 7 is not particularly limited, and may be, for
example, 0.1 μm or more and 30 μm or less, although it depends on the lamination method.
If the average thickness of the electrodes 6 and 7 is less than the lower limit, the strength of the
electrodes 6 and 7 may be insufficient. Conversely, when the average thickness of the electrodes
6 and 7 exceeds the upper limit, transmission of vibration to the piezoelectric body 5 may be
inhibited.
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6
[0025]
The method of laminating the electrodes 6 and 7 on the piezoelectric body 5 is not particularly
limited, and examples thereof include vapor deposition of metal, printing of a carbon conductive
ink, and coating and drying of silver paste.
[0026]
<Heat Effect Element> A heat generating element is used as the heat effect element 3 in the
present embodiment.
Specifically, the heat effect element 3 may be a heating resistor, and may be a self-control type
heater capable of maintaining the temperature within a certain range by changing the resistance
value according to the temperature.
[0027]
Thus, when using a heat generating element as the heat effect element 3, the temperature of the
piezoelectric element 2 is maintained within the target temperature range by setting the target
temperature range of the piezoelectric element 2 to the upper limit of the assumed
environmental temperature. Can.
[0028]
As a specific example, as shown in FIG. 2, the heat effect element 3 can be a heating resistor
formed in a meandering linear shape.
Such a heating resistor can be, for example, a printing resistor formed by printing carbon paste
or the like.
[0029]
The heat effect element 3 is connected to a wire (not shown) for supplying power to heat the
heat effect element 3.
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7
[0030]
<Insulating Film> The insulating film 4 may be any one as long as it can electrically insulate the
piezoelectric element 2 from the thermal effect element 3. For example, a coverlay for a printed
circuit board, a solder resist or the like can be used.
[0031]
<Advantage> Since the vibration transducer 1 includes the thermal effect element 3 for adjusting
the temperature of the piezoelectric element 2, the temperature of the piezoelectric element 2
can be maintained within a certain range regardless of the environmental temperature.
Thereby, the vibration transducer 1 can obtain a relatively linear output with a substantially
constant gain even if the environmental temperature changes.
[0032]
Second Embodiment FIG. 3 shows a vibration transducer 1a according to a second embodiment
of the present invention.
The vibration transducer 1a has a back surface outer periphery held by an annular support S,
and a microphone that converts sound wave vibration incident on the surface into an electric
signal or a speaker that converts electric signal into sound wave vibration and emits it to the
surface side It can be used as
[0033]
The vibration transducer 1a of the present embodiment includes a sheet-like piezoelectric
element 2 and a thermal effect element 3a for adjusting the temperature of the piezoelectric
element 2. The configuration of the piezoelectric element 2 in the vibration transducer 1a of FIG.
3 can be the same as the configuration of the piezoelectric element 2 in the vibration transducer
1 of FIG. Therefore, in the vibration transducer 1 a of FIG. 3, the same components as those of
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8
the vibration transducer 1 of FIG.
[0034]
<Heat Effect Element> As the heat effect element 3a in the present embodiment, a heating
element stacked in a region near the outer edge of the back surface of the piezoelectric element
2 is used. Specifically, for example, an annular plate-shaped mold heater or the like can be used
as the heat effect element 3a. By using the heat effect element 3 a having an insulating coating
such as a mold heater, the heat effect element 3 a can be stacked directly on the electrode 7 of
the piezoelectric element 2.
[0035]
<Advantage> In the vibration transducer 1a, since the thermal effect element 3a for adjusting the
temperature of the piezoelectric element 2 is stacked only in the region near the outer periphery
of the piezoelectric element 2, the central portion of the piezoelectric element 2 is relatively
freely bent. You can For this reason, the vibration transducer 1a can obtain a relatively linear
output with a substantially constant gain even when the environmental temperature changes,
and can obtain a relatively large gain.
[0036]
Third Embodiment FIG. 4 shows a vibration transducer 1b according to a third embodiment of
the present invention. The vibration transducer 1b can be used as a microphone that converts
sound wave vibration incident on the surface into an electrical signal or a speaker that converts
the electric signal into sound wave vibration and emits the sound wave to the surface side.
[0037]
The vibration transducer 1b according to this embodiment includes a sheet-like piezoelectric
element 2, a thermal effect element 3b for adjusting the temperature of the piezoelectric element
2, a temperature sensor 8 for detecting the temperature of the piezoelectric element 2, and an
output of the temperature sensor 8. And a control circuit 9 for adjusting the output of the
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9
thermal effect element 3b. Further, in the vibration transducer 1b of the present embodiment, the
space between the piezoelectric element 2 and the printed circuit board 10 with the printed
circuit board 10 on which the thermal effect element 3b and the control circuit 9 are mounted,
and the piezoelectric element 2 and the printed circuit board 10 And a spacer 11.
[0038]
The vibration transducer 1b of this embodiment can be used by fixing the printed circuit board
10 to a support (not shown).
[0039]
The configuration of the piezoelectric element 2 in the vibration transducer 1b of FIG. 4 can be
the same as the configuration of the piezoelectric element 2 in the vibration transducer 1 of FIG.
Therefore, for the vibration transducer 1 b of FIG. 4, the same components as those of the
vibration transducer 1 of FIG.
[0040]
<Heat Effect Element> The heat effect element 3 b in the present embodiment is a heating
element that heats the piezoelectric element 2 in a noncontact manner. As such a heating
element, a nichrome wire heater, an incandescent lamp, an infrared light emitting diode, etc. can
be used, for example. The vibration transducer 1 b may have one or more heat effect elements 3
b.
[0041]
As described above, the heat effect element 3b heats the piezoelectric element 2 in a noncontact
manner, thereby maintaining the temperature of the piezoelectric element 2 substantially
constant to suppress the change in the gain of the piezoelectric element 2 due to the temperature
change. The temperature non-uniformity of the element 2 can be suppressed to maintain the
output characteristics of the piezoelectric element 2 relatively linearly.
[0042]
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10
<Temperature Sensor> The temperature sensor 8 may detect the ambient temperature of the
piezoelectric element 2 but is preferably attached to the piezoelectric element 2 so as to detect
the temperature of the piezoelectric element 2.
The temperature sensor 8 is connected to the control circuit 9 by a wire so that an output signal
can be input to the control circuit 9.
[0043]
For example, a thermocouple, a thermistor or the like can be used as the temperature sensor 8.
Further, as the temperature sensor 8, it is preferable to use a minute and lightweight sensor so as
not to inhibit the deformation of the piezoelectric element 2.
[0044]
<Control Circuit> The control circuit 9 controls the current input to the thermal effect element 3b
such that the temperature detected by the temperature sensor 8 falls within a preset range.
[0045]
The control circuit 9 may be configured by an IC, or may be configured by a wiring pattern of the
printed circuit board 10 and a mounting component.
[0046]
The control method by the control circuit 9 includes, for example, proportional control, on / off
control, PID control, etc., but proportional control or on / off control with a relatively simple
configuration is preferably adopted.
[0047]
<Printed substrate> The printed substrate 10 has an insulating base layer and a conductive
pattern formed on the surface of the base layer.
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11
The printed circuit board 10 holds the heat effect element 3b opposite to the piezoelectric
element 2 and provides an electric path for applying a current to the heat effect element 3b.
[0048]
As a material of the base material layer of the printed circuit board 10, a material having a small
heat capacity and thermal conductivity is preferable. Specifically, for example, a resin such as
polyimide, polyamide, polyethylene terephthalate, a composite material such as paper epoxy, etc.
Can.
[0049]
As a material of the conductive pattern of the printed circuit board 10, metals, such as copper,
nickel, aluminum, gold, can be mentioned, for example.
[0050]
<Spacer> The spacer 11 holds the piezoelectric element 2 above the thermal effect element 3 b.
Specifically, the spacer 11 is formed in an annular plate shape or a short cylindrical shape, and
holds an area near the outer edge of the back surface of the piezoelectric element 2.
[0051]
The material of the spacer 11 is preferably one having a relatively small heat capacity and
thermal conductivity, and for example, resins such as polyolefin, polyester and polyamide, for
example, inorganic substances such as ceramics can be used.
Also, the spacer 11 may be formed of a porous material so that the heat capacity and the heat
conductivity can be further reduced.
[0052]
<Advantage> In the vibration transducer 1b, the thermal effect element 3b heats the piezoelectric
04-05-2019
12
element 2 in a noncontact manner, thereby suppressing the change in the gain due to the
temperature change and suppressing the temperature unevenness of the piezoelectric element 2
The output characteristics of can be kept relatively linear.
[0053]
Fourth Embodiment FIG. 5 shows a vibration transducer 1c according to a fourth embodiment of
the present invention.
The vibration transducer 1c can be used as a microphone that converts sound wave vibration
incident on the surface into an electrical signal or a speaker that converts the electric signal into
sound wave vibration and emits it to the surface side.
[0054]
The vibration transducer 1 c according to the present embodiment includes a sheet-like
piezoelectric element 2, a printed circuit board 12 stacked on the back surface of the
piezoelectric element 2, and a first thermal effect element 13 mounted on the back surface of the
printed board 12. A second thermal effect element 14, a temperature sensor 8 and a control
circuit 9 are provided.
The vibration transducer 1 c may have one or more first thermal effect elements 13 and one or
more second thermal effect elements 14, and the plurality of first thermal effect elements 13 and
the plurality of It is preferable that the two heat effect elements 14 and the two heat effect
elements 14 be distributed without deviation.
[0055]
The configurations of the piezoelectric element 2, the temperature sensor 8 and the control
circuit 9 in the vibration transducer 1 c of FIG. 5 can be similar to the configurations of the
piezoelectric element 2, the temperature sensor 8 and the control circuit 9 in the vibration
transducer 1 of FIG.
04-05-2019
13
Therefore, in the vibration transducer 1c of FIG. 5, the same components as those of the
vibration transducer 1 of FIG.
[0056]
<Printed circuit board> The printed circuit board 12 has a base material layer which has
insulation and heat conductivity, and a conductive pattern formed on the back surface of this
base material layer. In addition, by making the heat capacity of the insulating substrate relatively
large, the temperature change of the piezoelectric element 2 can be moderated.
[0057]
In the vibration transducer 1 c of the present embodiment, the temperature of the printed board
12 can be regarded as the temperature of the piezoelectric element 2. In other words, in the
vibration transducer 1 c of the present embodiment, the first thermal effect element 13, the
second thermal effect element 14 and the temperature sensor 8 exchange heat with the
piezoelectric element 2 via the printed circuit board 12.
[0058]
As a base material layer of printed circuit board 12, a thin resin film, a resin sheet containing a
heat conductive filler, a metallic material board, etc. can be used, for example.
[0059]
The base material layer of the printed board 12 may have sufficient flexibility not to inhibit
bending of the piezoelectric element 2 or may have sufficient rigidity to prevent deformation of
the back surface of the piezoelectric element 2 .
When the base material layer of the printed circuit board 12 has flexibility, the piezoelectric
element 2 detects bending strain. On the other hand, when the base material layer of the printed
board 12 has rigidity, the piezoelectric element 2 detects compressive strain in the thickness
direction.
04-05-2019
14
[0060]
Examples of the material of the conductive pattern of the printed board 12 include metals such
as copper, nickel, aluminum, and gold.
[0061]
<First Thermal Effect Element> In the vibration transducer 1c of the present embodiment, the
first thermal effect element 13 is a heating element such as a heating resistor, for example.
The first thermal effect element 13 raises the temperature of the piezoelectric element 2 by
heating the printed circuit board 12.
[0062]
<Second Thermal Effect Element> In the vibration transducer 1c of the present embodiment, the
second thermal effect element 14 is, for example, a heat absorbing element such as a Peltier
element (an element that removes heat on the front side and emits it to the rear side). The second
thermal effect element 14 lowers the temperature of the piezoelectric element 2 by cooling the
printed circuit board 12.
[0063]
As a Peltier element constituting the second thermal effect element 14, blocks of p-type
semiconductor and n-type semiconductor are formed side by side in plan view on the conductive
pattern of the printed board 12, and from the n-type semiconductor to p-type on the printed
board 12 side The semiconductor can be connected so that current flows. The second thermal
effect element 14 may have an array structure in which a large number of blocks of p-type
semiconductor and n-type semiconductor are arranged.
[0064]
04-05-2019
15
<Advantage> The vibration transducer 1c according to the present embodiment includes the first
thermal effect element 13 which is a heating element and the second thermal effect element 14
which is a heat absorbing element. Can be held. Further, the vibration transducer 1 c does not
use the first thermal effect element 13 and the second thermal effect element 14 when the
environmental temperature is in the normal temperature range, and only when the
environmental temperature is particularly low, the first thermal effect Energy consumption can
be suppressed by using the element 13 and using the second thermal effect element 14 only
when the environmental temperature is particularly high.
[0065]
[Other Embodiments] The above embodiments do not limit the configuration of the present
invention. Therefore, the embodiment can omit, substitute, or add the components of each part of
the embodiment based on the description of the present specification and common technical
knowledge, and all of them can be construed as belonging to the scope of the present invention.
It should.
[0066]
In the vibration transducer, a heat effect element or a temperature sensor may be disposed on
the surface side of the piezoelectric element.
[0067]
In the vibration transducer, the planar pattern of the heating element can be in any shape such
as stripe or mesh.
[0068]
The vibration transducer may be used as a vibration sensor that is disposed in contact with the
surface of the object to detect the vibration of the object, or as an excitation device that converts
an electrical signal into vibration to excite the object.
In addition, the vibration transducer may be disposed in close proximity to the surface of the
living body and used for detecting the vibration inside the living body.
04-05-2019
16
For example, it can be disposed closely to the surface of a living body such as a human or an
animal, and can be used to detect vibrations inside the living body. At this time, since the
vibration transducer may be affected by the temperature of the living body, the temperature of
the vibration transducer may be adjusted so that the temperature at which the vibration inside
the living body can be easily detected.
[0069]
The vibration transducer according to the present invention can be particularly suitably used for
a microphone.
[0070]
1, 1a, 1b, 1c Vibration transducer 2 Piezoelectric element 3, 3a, 3b Thermal effect element 4
Insulating film 5 Piezoelectric body 6, 7 Electrode 8 Temperature sensor 9 Control circuit 10, 12
Printed circuit board 11 Spacer 13 First thermal effect element 14 Second heat effect element
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