JP2015080085

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DESCRIPTION JP2015080085
An object of the present invention is to obtain a throat microphone capable of eliminating
variation between resonance acuities of piezoelectric elements supported in a cantilevered
manner. A piezoelectric element (1) is supported in a cantilever shape by fixing one end (11) to a
base (3), and a weight (4) is fixed to the tip of the piezoelectric element (1). A throat microphone
that outputs an audio signal by receiving vibration and vibrating. One end of the piezoelectric
element 1 is fixed to the base 3 so that the vibration direction is parallel to the surface of the
base 3, and a gap is formed between the weight 4 and the base 3. Is intervened. [Selected figure]
Figure 1
Throat microphone
[0001]
The present invention relates to a throat microphone having a piezoelectric element supported in
a cantilever shape as an element for converting throat vibration into an audio signal.
[0002]
A throat microphone that receives throat vibration and converts it into an audio signal has an
advantage of being able to convert human-generated speech into an audio signal without being
affected by ambient noise.
Generally, a piezoelectric element is used as an audio signal conversion element of the throat
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microphone. Among the piezoelectric elements, a piezoelectric bimorph which is compact and
has a large output level with respect to displacement is widely used.
[0003]
An example of a conventional throat microphone using a piezoelectric bimorph is shown in FIG. 3
and FIG. In FIGS. 3 and 4, reference numeral 50 denotes a piezoelectric element formed of a
piezoelectric bimorph. One end 51 of the piezoelectric element 50 is a fixed end, and the one end
51 is fixed to the fixed part 62 which is raised from the base 63, whereby the piezoelectric
element 50 is supported in a cantilever shape. . The piezoelectric element 50 extends parallel to
the surface of the base 63 and is supported in a posture capable of vibrating in the direction
orthogonal to the surface of the base 63.
[0004]
The piezoelectric element 50 formed of a piezoelectric bimorph is a displacement proportional
type, and an output signal of a level corresponding to the amount of displacement can be
obtained. Also, even if the displacement is caused by the external force, when the external force
disappears, the elasticity returns to the original state, and the signal output disappears. That is,
the piezoelectric element 50 is an elastic control type, and a signal output can be obtained by
applying an acceleration. Therefore, as shown in FIGS. 3 and 4, the weight 64 is fixed to the tip
52 of the piezoelectric element 50, and the piezoelectric element 50 is designed to be effectively
accelerated by vibration.
[0005]
Generally, in order to flatten the frequency response of the output signal of the piezoelectric
element 50 to the acceleration applied to the piezoelectric element 50, the resonant frequency is
designed to be the upper limit of the sound collection band. Since the throat microphone by the
piezoelectric element detects acceleration of vibration of the throat, it is designed such that the
resonance frequency of the piezoelectric element 50 is 3 to 4 kHz which is the upper limit of the
voice band. The resonant frequency of the piezoelectric element 50 is determined by the stiffness
of the piezoelectric element 50 and the mass of the weight 64. Since the piezoelectric element 50
is an elastic control type, when the stiffness of the piezoelectric element 50 is constant, as the
mass of the weight 64 is increased, the resonance frequency decreases and the sensitivity to
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acceleration increases. The relationship between the weight 64 and the resonance frequency and
sensitivity is described in Patent Document 1.
[0006]
As described above, by designing the resonance frequency of the piezoelectric element 50 to be
3 to 4 kHz, the clarity of the converted audio signal is enhanced, and the sensitivity to the throat
vibration acceleration in the audio band is increased. Can. However, the frequency response near
the resonance frequency is largely dependent on the resonance sharpness (Q).
[0007]
In the conventional example shown in FIGS. 3 and 4, the vibration system is achieved by
interposing the silicon-based visco-elastic rubber 65, which is a low repulsion material, in the
space generated between the surface of the base 63 and the piezoelectric element 50 Is
configured to brake the As described above, by interposing the visco-elastic rubber 65, the
resonance sharpness (Q) of the piezoelectric element 50 is lowered, and the sensitivity near the
resonance frequency is suppressed, whereby sound can be collected with good sound quality
even under noise. In anticipation of The structure in which the viscous liquid damper is sealed in
a sealed container together with the piezoelectric element as described in Patent Document 2 and
Patent Document 3 is also intended to reduce the resonance acuity of the piezoelectric element
50 as shown in FIG. This is the same as the conventional example shown in FIG.
[0008]
The visco-elastic rubber 65 in the conventional example shown in FIGS. 3 and 4 is likely to have
variations in adhesion between the surface of the base 63 and the surface of the piezoelectric
element 50, that is, the degree of mechanical coupling. Individual differences occur. Therefore, in
the example shown in FIGS. 3 and 4, in order to improve the mechanical coupling between the
base 63 and the piezoelectric element 50, the entire vibration system is covered with a sealing
material 66 made of RTV (Room Temperature Vulcanizing) rubber. However, even if the entire
vibration system is covered with the sealing material 66, it is difficult to improve the individual
difference in the degree of transmission of the vibration to the piezoelectric element 50.
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[0009]
In FIG. 3 and FIG. 4, reference numeral 67 denotes a lead wire connection portion for outputting
an audio signal from the piezoelectric element 50. The code ¦ symbol 68 shows a lead wire.
[0010]
It is also apparent from Patent Document 4 that in the conventional throat microphone, the
vibration direction of the piezoelectric element is perpendicular to the surface of the base.
[0011]
JP, 2012-231204, A JP, 63-49018, A JP, 4-3, 599, JP, 10-7, 999, A
[0012]
The present invention solves the technical problem of the conventional throat microphone, that
is, to provide a throat microphone capable of eliminating variation between resonance sharpness
of cantilever-supported piezoelectric elements. To aim.
[0013]
The present invention includes a piezoelectric element supported in a cantilever shape by fixing
one end to the base, a weight is fixed to the tip of the piezoelectric element, and the piezoelectric
element is subjected to throat vibration. It is a throat microphone that outputs an audio signal by
vibrating, and one end of the piezoelectric element is fixed to the base so that the vibration
direction is parallel to the surface of the base, and between the weight and the base The most
important feature is that a gap is formed in the gap and the vibration absorber is interposed in
the gap.
[0014]
Since the vibration direction of the piezoelectric element is parallel to the base surface, the
vibration surface of the piezoelectric element can be brought close to the base surface, and the
gap between the weight and the base can be reduced.
By interposing the vibration absorber in the gap, it is possible to stabilize the resonance acuity of
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the piezoelectric element and eliminate the variation in the resonance acuity between the
individual.
[0015]
It is a top view which shows the Example of the throat microphone which concerns on this
invention.
It is front sectional drawing of the said Example.
It is a top view which shows the example of the conventional throat microphone.
It is front sectional drawing of the said prior art example.
[0016]
Hereinafter, embodiments of the throat microphone according to the present invention will be
described with reference to the drawings.
[0017]
In FIGS. 1 and 2, reference numeral 1 denotes a piezoelectric element.
The piezoelectric element 1 is formed of a piezoelectric bimorph, that is, a piezoelectric element
having a structure in which two plate-like piezoelectric elements are bonded together, and an
output signal can be obtained by adding the output signals of the two piezoelectric elements. One
end 11 of the piezoelectric element 1 is a fixed end, and the one end 11 is fixed to a fixed
member 2 integral with the base 3. Therefore, the one end 11 of the piezoelectric element 1 is
supported in a cantilever shape by being substantially integrally fixed to the base 3.
[0018]
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The piezoelectric element 1 extends parallel to the surface of the base 3 and at an appropriate
distance from the surface of the base 3. The piezoelectric element 1 has elasticity and can vibrate
with one end 11 as a fulcrum when vibration is applied. One end 11 is fixed to the fixing member
2 so that the vibration direction of the piezoelectric element 1 is parallel to the surface of the
base 3. In other words, the piezoelectric element 1 is fixed such that the surfaces of the two
piezoelectric elements, and hence the bonding surfaces of these piezoelectric elements, are in the
direction orthogonal to the surface of the base 3.
[0019]
The tip 12 of the piezoelectric element 1 is a free end, and a weight 4 is fixed to the tip 12. The
weight 4 has a short cylindrical shape, and a groove is formed in a direction parallel to the
central axis of the weight 4 on a part of the cylindrical peripheral surface, and the tip 12 of the
piezoelectric element 1 is fitted in this groove 4 are fixed to the piezoelectric element 1. The
dimension of the weight 4 in the central axis direction is larger than the dimension in the width
direction of the piezoelectric element 1, that is, the dimension in the vertical direction in FIG. The
circular lower end surface of the weight 4 has a spread surface parallel to the surface of the base
3. The lower end face of the weight 4 is close to the surface of the base 3, and the gap between
the weight 4 and the base 3 is a narrow gap where liquid can enter by capillary action.
[0020]
The vibration absorber 5 intervenes in the gap between the weight 4 and the base 3. The
vibration absorber 5 is a viscous liquid, more specifically silicon oil. The gap between the weight
4 and the base 3 is a slight gap where silicon oil can enter by capillary action, and even in such a
slight gap, it is in the direction parallel to the surface of the base 3 of the piezoelectric element 1
There is no hindrance to the vibration of.
[0021]
In order to make the gap between the weight 4 and the base 3 a slight gap where silicon oil can
enter by capillary phenomenon and to secure this gap with high dimensional accuracy and
without variation, the following manufacturing process is carried out It is good to take. The
piezoelectric element 1 and the weight 4 are fixed by adhesion, and a film is interposed between
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the weight 4 and the base 3 before the weight 4 is adhered to the piezoelectric element 1, and
the distance between the weight 4 and the base 3 is the above film Secure only the thickness of
the In this state, the weight 4 is bonded to the piezoelectric element 1 with an adhesive, and after
the adhesive is cured, the film is removed. By doing this, a gap corresponding to the thickness of
the film is generated between the weight 4 and the base 3, and the gap does not vary. If a viscous
liquid, such as silicone oil, is allowed to enter the gap, the mechanical resistance between the
weight 4 and the base 3 can be set without variation.
[0022]
The mechanical resistance between the weight 4 and the base 3 depends on the size of the gap,
the area of the opposing surface of the weight 4 and the base 3, and the viscosity of the vibration
absorber 5. Since the gap is determined by the thickness of the film, the gap can be determined
by appropriately setting the thickness of the film, and the mechanical resistance can be
appropriately set. The thickness of the film may be suitably selected, for example, in the range of
0.05 to 0.2 mm.
[0023]
When silicone oil as the vibration absorber 5 is injected into the gap, the silicone oil infiltrates
into the gap by a necessary amount by capillary action. The silicone oil as the vibration absorber
5 is interposed between the weight 4 and the base 3 so that the vibration of the piezoelectric
element 1 is damped, the resonance sharpness is reduced, and the sensitivity in the vicinity of the
resonance frequency is suppressed. It is possible to collect sound with good sound quality even
under the bottom. The silicone oil as the vibration absorber 5 is characterized in that the
viscosity is unlikely to change even if the temperature changes.
[0024]
In FIGS. 1 and 2, the vibration system, that is, the piezoelectric element 1, the weight 4 and the
vibration absorber 5 are sealed on the surface of the base 3 by the sealing material 6. The seal
member 6 is made of RTV rubber. By sealing the piezoelectric element 1 made of the
piezoelectric bimorph on the base 3 with the sealing material 6 made of RTV rubber, the
piezoelectric bimorph can be protected from mechanical damage even if an excessive impact
force is applied. In addition, by sealing the vibration absorbing body 5 made of the viscous liquid
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with the sealing material 6, it is possible to prevent the outflow, disappearance, etc. of the
vibration absorbing body 5. The seal member 6 made of RTV rubber does not interfere with the
vibration of the piezoelectric element 1 which has received the vibration of the throat.
[0025]
In FIG. 1 and FIG. 2, reference numeral 7 denotes a lead wire connection portion for outputting
an audio signal from the piezoelectric element 1. The code ¦ symbol 8 shows a lead wire.
[0026]
The components shown in FIGS. 1 and 2 correspond to the so-called microphone unit of the
throat microphone. The microphone unit portion shown in FIG. 1 and FIG. 2 is coupled to or
incorporated into a suitable mounting member such as a mounting belt to constitute a throat
microphone. When the user wears the mounting member together with the microphone unit in a
predetermined mode, the microphone unit is pressed against a predetermined place near the
user's throat, and any vibration of the user can be converted into an audio signal.
[0027]
Reference Signs List 1 piezoelectric element 2 fixing member 3 base 4 weight 5 vibration
absorber 6 sealing material 7 signal output end 8 lead wire 11 one end (fixed end) 12 tip
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