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JP2017183853

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DESCRIPTION JP2017183853
Abstract: In a contact microphone element for pressing a piezoelectric element with a vibrating
element and converting mechanical vibration into an electric signal, even if the piezoelectric
element is pressed by the vibrating element, breakage of the piezoelectric element is prevented.
A piezoelectric vibration plate 3 vibratably supported in an element case 5, and a vibrator 6
accommodated in the element case and disposed above the piezoelectric vibration plate, the
vibrator being a vibrator A spherical portion 6a is in contact with a central portion of the
piezoelectric diaphragm, and an elastic member 7 intervenes in the element case at least between
the piezoelectric diaphragm and the spherical portion of the vibrator. [Selected figure] Figure 1
Contact microphone element and method of manufacturing the same
[0001]
The present invention relates to a contact microphone element and a method of manufacturing
the same, and more particularly, a contact microphone element that uses a piezoelectric element
as a sound receiving element and can prevent breakage of the piezoelectric element when the
vibrator presses the piezoelectric element It relates to the manufacturing method.
[0002]
For example, a piezoelectric element as disclosed in Patent Document 1 is widely used as a
speaker and a piezoelectric buzzer in portable devices and the like that are highly required to be
small and lightweight because of features such as small size, thinness, and low power
consumption.
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1
When the piezoelectric element is used as, for example, a buzzer, as shown schematically in FIG.
4, the thin plate piezoelectric vibration plate 51 can be attached to the metal plate 52 to form the
element 50. When an alternating voltage is applied to the piezoelectric element 50, the
piezoelectric ceramic forming the piezoelectric diaphragm 51 expands and contracts, and
repetitive bending vibration occurs to generate a sound wave.
[0003]
By the way, since the piezoelectric element is a reversible converter having a conversion function
of both an electroacoustic transducer and an acoustoelectric transducer, it is not only used as a
sounding element (electroacoustic transducer) such as a speaker or a piezoelectric buzzer It can
also be used as a sound receiving element (acoustoelectric converter) for detecting and collecting
sound. For example, as microphones that detect vibrations, there are contact microphones that
absorb vibrations of musical instruments and throat microphones that are used for
communication under high noise. In such a microphone, a piezoelectric element having a large
output level is often used to convert mechanical vibration into an electrical signal. As described
above, since many piezoelectric elements are used in speakers and piezoelectric buzzers of small
devices and the like, many types are produced, and there is an advantage that it is inexpensive
and it is possible to select a piezoelectric element suitable for the purpose.
[0004]
Japanese Patent Application Laid-Open No. 48-29420
[0005]
However, when the piezoelectric element is used as a sound pickup element, the thickness of the
diaphragm made of piezoelectric ceramic is thin. Therefore, when attached as it is to a musical
instrument or a human body, the piezoelectric element is partially strong when attached or used
Stress may be applied and the diaphragm may be broken.
[0006]
Specifically, in the case of a piezoelectric buzzer or a speaker using a piezoelectric element as a
sounding element, the displacement when an electrical input is applied with the peripheral edge
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2
of the diaphragm mechanically fixed is that the position of the center of the diaphragm is
maximum. Become.
Similarly, when stress is applied to the piezoelectric element for sound collection, a high output
level can be obtained by maximizing the displacement of the center of the diaphragm.
However, when the piezoelectric element 50 is locally pressed by the vibrator 60 as shown in
FIG. 5 so as to maximize the displacement of the center of the diaphragm, the diaphragm 51
made of piezoelectric ceramic is easily broken.
[0007]
The present invention has been made focusing on the above points, and in a contact microphone
element that presses a piezoelectric element with a vibrating element and converts mechanical
vibration into an electrical signal, the piezoelectric element is pressed by the vibrating element. It
is another object of the present invention to provide a contact microphone element capable of
preventing the breakage of the piezoelectric element and a method of manufacturing the same.
[0008]
In order to solve the problems described above, the contact microphone element according to the
present invention is a contact microphone element that presses a piezoelectric diaphragm with a
vibrator and converts mechanical vibration of the piezoelectric diaphragm into an electrical
signal, The piezoelectric vibration plate supported in a case in a vibratable manner, and the
vibrator housed in the element case and disposed above the piezoelectric vibration plate, the
vibrator comprising the piezoelectric vibration plate It is characterized in that it has a spherical
portion in contact with the central portion, and in the element case, an elastic member is
interposed at least between the piezoelectric diaphragm and the spherical portion of the vibrator.
The elastic member is preferably a solid rubber member. Alternatively, the elastic member may
be a liquid rubber member.
[0009]
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3
According to such a configuration, when the vibrator vibrates in the vertical direction and stress
is applied to the piezoelectric diaphragm, not only the central portion of the piezoelectric
diaphragm with which the spherical portion abuts, but also the piezoelectric diaphragm via the
elastic member. The entire top surface is subjected to distributed stress. Therefore, in the
piezoelectric vibration plate, stress is not partially concentrated, and breakage of the
piezoelectric element can be prevented. Furthermore, since displacement due to stress is applied
to the whole of the piezoelectric diaphragm, a high output level can be obtained.
[0010]
Further, in order to solve the problems described above, a method of manufacturing a contact
microphone element according to the present invention is a contact microphone element which
presses a piezoelectric diaphragm with a vibrator and converts mechanical signals of the
piezoelectric diaphragm into an electrical signal. A manufacturing method, comprising the steps
of: vibratably supporting the piezoelectric diaphragm in an element case; disposing the vibrator
having a spherical portion above the piezoelectric diaphragm in the element case; and And a step
of contacting the center portion of the piezoelectric vibrating plate, and interposing an elastic
member between at least the piezoelectric vibrating plate and the spherical portion of the
vibrator in the element case. Have. In the step of interposing an elastic member between at least
the piezoelectric diaphragm and the spherical portion of the vibrator in the element case, the
element case is filled with a liquid rubber that cures at room temperature, and the liquid is It is
desirable to include the step of curing the rubber at room temperature. Alternatively, in the step
of interposing an elastic member between at least the piezoelectric diaphragm and the spherical
portion of the vibrator in the element case, the element case is filled with a liquid rubber that is
cured by irradiation of ultraviolet light. And curing the upper portion of the liquid rubber filled in
the element case by ultraviolet irradiation.
[0011]
According to such a manufacturing method, the contact microphone element can be obtained,
and the effects described above can be exhibited.
[0012]
A contact microphone element for pressing a piezoelectric element by a vibrating element and
converting mechanical vibration into an electric signal, wherein the piezoelectric element can be
prevented from breaking even if the piezoelectric element is pressed by the vibrating element,
and The manufacturing method can be obtained.
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4
[0013]
FIG. 1 is a cross-sectional view of a contact microphone element according to the present
invention.
FIG. 2 is a diagram showing the dispersion of stress by the vibrator in the contact microphone
element of FIG.
FIGS. 3A to 3D are cross-sectional views for explaining the method of manufacturing the contact
microphone element of FIG. 1 in time series. FIG. 4 is a cross-sectional view showing the
operation of the piezoelectric element used in the piezoelectric buzzer. FIG. 5 is a cross-sectional
view for explaining the problem in the case where the piezoelectric element is used as a sound
collection element.
[0014]
Hereinafter, embodiments of the present invention will be described based on the drawings. FIG.
1 is a cross-sectional view of a contact microphone element according to the present invention.
The contact microphone element 1 shown in FIG. 1 comprises a flat plate-like piezoelectric
element 4 in which a flat plate-like piezoelectric diaphragm 3 made of ceramics is attached to a
flat plate-like metal plate 2 and an element housing 5 opened at the upper side for housing the
piezoelectric element 4. And a vibrator 6 housed in the element housing 5 together with the
piezoelectric element 4 and for pressing the piezoelectric element 4.
[0015]
A convex step portion 5a is formed on the periphery of the bottom portion of the element
housing 5, and the peripheral end of the metal plate 2 is supported on the step portion 5a. Thus,
a space 5 b is formed under the piezoelectric element 4 so that the piezoelectric element 4 can
be bent downward. Further, in the element housing 5, a rubber member 7 (elastic member) is
filled (interposed) in the space between the piezoelectric element 4 and the vibrator 6.
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[0016]
As shown, the lower portion of the vibrator 6 is spherical (spherical portion 6a), and the
lowermost end of the vibrator 6 is in contact with the central portion of the piezoelectric
diaphragm 3. The diameter of the spherical portion 6 a is approximately equal to the diameter of
the piezoelectric diaphragm 3. A rubber member 7 is also filled around the contact points
between the spherical portion 6 a and the piezoelectric diaphragm 3. Therefore, when the
vibrator 6 vibrates up and down and stress F is applied downward from the vibrator 6 as shown
by an arrow in FIG. 2, not only the central portion of the piezoelectric diaphragm 3 with which
the spherical portion 6a abuts, but The entire upper surface of the piezoelectric diaphragm 3
receives the distributed stress via the rubber member 7. Therefore, stress is not partially
concentrated on the piezoelectric vibration plate 3 and breakage of the piezoelectric element 4 is
prevented. Furthermore, since a displacement due to stress is applied to the entire piezoelectric
diaphragm 3, a high output level can be obtained.
[0017]
Subsequently, a method of manufacturing the contact microphone element 1 will be described
based on FIG. FIGS. 3A to 3D are cross-sectional views for explaining the method of
manufacturing the contact microphone element 1 in time series. First, as shown in FIG. 3A, the
element case 5 opened at the upper side is formed of, for example, a resin. At the periphery of
the bottom of the element case 5, a convex step 5a is formed. On the other hand, a thin
piezoelectric diaphragm 3 made of piezoelectric ceramic is attached to the metal plate 2 to form
a piezoelectric element 4. Further, as shown in FIG. 3B, the piezoelectric element 4 is
accommodated in the element case 5, and the peripheral portion of the metal plate 2 of the
piezoelectric element 4 is supported by the stepped portion 5a.
[0018]
Next, the vibrator 6 for pressing the piezoelectric element 4 is formed of, for example, a resin.
Below the vibrator 6, a spherical portion 6a having a diameter substantially the same as the
diameter of the piezoelectric diaphragm 3 is formed. Then, as shown in FIG. 3C, the vibrator 6 is
temporarily held in a state where the lower end of the spherical portion 6a is in contact with the
center of the piezoelectric diaphragm 3 with the spherical portion 6a facing downward. In
addition, the means of temporary holding | maintenance here is not limited, For example, you
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may use a means (for example, pressing with a finger tip etc.) which lightly presses the top |
upper surface of the vibrator | oscillator 6. FIG.
[0019]
Next, in a state where the vibrator 6 is temporarily held in the element case 5 as described above,
as shown in FIG. 3D, the liquid rubber 8 which is cured at room temperature, for example, is
poured into the case. In this operation, it is preferably performed in a vacuum chamber to
remove air bubbles. In the element case 5, the liquid rubber 8 flows into the gap between the
piezoelectric element 4 and the vibrator 6, and the gap in the case is filled with the liquid rubber
8. When left in this state for a predetermined time, the liquid rubber 8 cures at room
temperature to form a rubber member 7 as shown in FIG. 1, and the contact microphone element
according to the present invention is manufactured.
[0020]
As described above, according to the embodiment of the present invention, the spherical portion
6 a of the vibrator 6 formed to have substantially the same diameter as that of the piezoelectric
vibration plate abuts on the center of the piezoelectric vibration plate 3. Then, the rubber
member 7 is also filled (interposed) between the spherical portion 6a and the piezoelectric
diaphragm 3 around the contact point. In this configuration, when stress is applied to the
piezoelectric diaphragm 3 by vertical vibration of the vibrator 6, not only the central portion of
the piezoelectric diaphragm 3 in contact with the spherical portion 6a but also the piezoelectric
diaphragm 3 via the rubber member 7. The entire top surface is subjected to distributed stress.
Therefore, in the piezoelectric vibration plate 3, stress is not partially concentrated, and breakage
of the piezoelectric element 4 can be prevented. Furthermore, since displacement due to stress is
applied to the whole of the piezoelectric diaphragm 3, a high output level can be obtained.
[0021]
In the embodiment described above, the rubber member 7 is formed using liquid rubber that
cures at room temperature, but the present invention is not limited to this form. For example, a
liquid rubber that is cured by irradiating ultraviolet light may be used, and only the periphery of
the vibrator 6 may be irradiated with ultraviolet light to cure only the periphery of the vibrator 6.
In that case, only the periphery of the vibrator 6 (only the upper portion of the liquid rubber) is
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cured, and the liquid rubber 8 intervenes in the gap space between the vibrator 6 and the
piezoelectric element 4 without being cured. The vibration of the piezoelectric diaphragm 3
(piezoelectric element 4) can be made smoother.
[0022]
Further, in the above embodiment, the entire surface excluding the top surface portion of the
vibrator 6 is covered with the rubber member 7. However, in the present invention, the present
invention is not limited to this form. It is sufficient that the rubber member is interposed in the
gap between the piezoelectric diaphragm 3 and the piezoelectric diaphragm 3.
[0023]
Further, in the above embodiment, the elastic member interposed between the vibrator 6 and the
piezoelectric diaphragm 3 is a rubber member, but the present invention is not limited to the
form, and rubber It may be an elastic member other than the member (for example, foamed
urethane foam).
[0024]
1 contact microphone element 2 metal plate 3 piezoelectric diaphragm 4 piezoelectric element 5
element case 6 vibrator 7 rubber member (elastic member) 8 liquid rubber
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