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JP2007259008

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DESCRIPTION JP2007259008
PROBLEM TO BE SOLVED: To provide a bone conduction microphone in which a holding and
connecting process of a cantilever type piezoelectric element is simplified while using an
environmentally friendly bonding material. SOLUTION: Piezoelectric elements 1a and 1b and
metal conductive spacers 2 and insulating spacers 4 are overlapped and inserted into rectangular
holes of a good-conductive holding frame fitting 3 having a rectangular cylindrical portion, and
then insulating spacers 4 and piezoelectric elements By press-fitting a wedge-shaped electrode
terminal 5 between the electrode surfaces of the electrodes 1a and 1b, a pressure contact
connection between the electrodes is secured, and a structure in which the piezoelectric elements
1a and 1b are supported in a cantilever manner by the rectangular holes of the holding frame 3
Do. [Selected figure] Figure 3
Bone conduction microphone
[0001]
The present invention relates to a bone conduction microphone that detects bone conduction
vibration using a piezoelectric element and converts it into an electrical signal. In particular, a
bimorph or unimorph piezoelectric element is used to detect bone conduction vibration
transmitted through the human head, The present invention relates to a bone conduction
microphone suitable for converting into a signal and providing for communication.
[0002]
As holding means for supporting a piezoelectric element of a bone conduction microphone using
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a bimorph or unimorph piezoelectric element in a cantilever manner, it is general to hold the end
of the piezoelectric element with an insulating material and connect both electrodes with a
dedicated wire. Among them, as disclosed in Patent Document 1 and Patent Document 2, a
conductive adhesive is used, and a method of supporting on a substrate in a cantilever manner
with a metal spacer interposed, or solder using a conductive adhesive There is something that
replaced.
In this case, it is possible to simplify the wiring as the conducting means of the one-sided
electrode. In addition, in the support method by connection using solder, low melting point
solder, which can work without deteriorating the piezoelectric element, can not be used due to
environmental problems of lead, and instead connection maintenance with a conductive adhesive
is proposed There is a history.
[0003]
The holding method using a conductive adhesive requires highly rigid connection holding in
order to ensure sensitivity and to make the sound frequency band have no resonance point. From
this point of view, it is essential to use a conductive adhesive that cures at around 150 ° C. at
present. In the assembly operation using this adhesive, it is necessary to fix the piezoelectric
element in a necessary position until the adhesive cures, and the adhesive assembly process is
divided into several steps and then fixed with a jig in each process It is necessary to put it in a
high temperature furnace for a certain period of time. For this reason, at the time of mass
production, the number of jigs is also required, and since the process can not be performed in
parallel, there is a drawback that the total operation process time is long. In addition, since the
supporting rigidity depends only on the conductive adhesive, the rigidity and the strength tend to
be insufficient, and the resonance frequency is likely to be lowered. Furthermore, since the liquid
having a large degree of freedom in shape is used, the work variation of the adhesive support
area is likely to occur, and the variation of the sensitivity and the characteristic is also likely to
occur.
[0004]
JP-A-8-330887 JP-A-2005-55305
[0005]
In the above situation, (1) it is not necessary to fix the piezoelectric element with a jig until the
conductive adhesive cures, (2) reduce the number of bonding steps, (3) work variation (4) It is
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important to reduce the form of wiring using a conductive material, which is convenient because
it has a degree of freedom in shape, but is a cause of work variation.
[0006]
Therefore, the object of the present invention is to use a conductive adhesive, without using it as
a main means of holding and electrode connection, without having to install it in a jig and put it
in a high temperature tank, and its working efficiency is good, and required holding rigidity It is
an object of the present invention to provide a structure of a bone conduction microphone which
can obtain a cantilever support and an electrode connection of a unimorph type or bimorph type
piezoelectric element which can secure the reliability of the electrical connection and secure the
electric connection.
In brief, it is an object of the present invention to provide a bone conduction microphone in
which the holding and connecting process of the cantilever type piezoelectric element is
simplified while using an environmentally friendly bonding material.
[0007]
The invention does not merely make the cantilevered support of the piezoelectric element in the
form of a stacked support by soldering with a spacer or conductive adhesive, but the required
electrical connection with the end of the piezoelectric element in the rectangular hole of the
metal frame The above problem is solved collectively by inserting a spacer for securing
insulation and driving a cantilever of the piezoelectric element in such a form that a wedge is
punched into a mutual gap.
[0008]
As described above, according to the present invention, it is also possible to use leaded solder for
the cantilever support of the conventional bimorph-type piezoelectric element and the
connection of its electrodes, and also to use a conductive adhesive in a high temperature bath. It
is possible to provide a bone conduction microphone which can be assembled without being
fixedly inserted into a jig and which can ensure required holding rigidity and reliability of
electrode connection.
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Therefore, environmentally friendly materials can be used to reduce production costs.
[0009]
In the embodiment of the present invention, a rectangular plate-shaped piezoelectric element
portion in which a first electrode surface is formed on one of two main surfaces in a bimorph
type or a unimorph type and a second electrode surface is formed on the other is an external
electrode. A bone conduction microphone provided with a vibration detection means which is
supported in a cantilever manner by a holding frame fitting having a rectangular cylindrical
portion with a rectangular hole is manufactured.
At that time, insert a U-shaped insulating spacer made of an electrically insulating material into
the rectangular hole of the holding frame metal fitting, and (2) fix one end of the first electrode
surface and the side surface of the piezoelectric element portion of the insulating spacer. To
insert into the rectangular hole of the holding frame fitting so that it is surrounded by the inner
circumferential surface of the letter shape, and (3) one end of the second electrode surface of the
piezoelectric element part press-contacts with one face of the rectangular hole of the holding
frame fitting A press-fit spacer having a portion is press-fit between the insulating spacer and
one end of the first electrode surface of the piezoelectric element portion, or between the outer
surface of the insulating spacer and the surface of the rectangular hole of the holding frame
fitting.
[0010]
Further, the first electrode exposed on the outer surface of the piezoelectric element portion is
formed while forming a piezoelectric element portion in which a plurality of rectangular plateshaped piezoelectric elements are stacked and electrically connected in series so as to sandwich a
metal conductive spacer at one end. Insert one end of the surface and the side into the
rectangular hole of the holding frame fitting so that it encloses the U-shaped inner
circumferential surface of the insulating spacer, and the second electrode surface exposed on the
other outer surface of the piezoelectric element part is the rectangular shape of the holding
frame A press-fit spacer having a wedge portion is interposed between the insulating spacer and
the first electrode surface of the piezoelectric element portion, or between the outer surface of
the insulating spacer and the surface of the rectangular hole so as to press against and conduct
to one surface of the hole. Press-fit in between.
[0011]
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The piezoelectric element is juxtaposed in a plane parallel to the main surface inside the Ushaped insulating spacer, and one end of the first electrode surface of the piezoelectric element is
in contact with the inner circumferential surface of the insulating spacer. The spacer and the
piezoelectric element part are inserted into the rectangular hole of the holding frame metal
fitting so that one end of the second electrode surface of the piezoelectric element is in pressure
contact with one surface of the rectangular hole of the holding frame metal fitting and conducts.
It press-fits between the first electrode surfaces or between the outer surface of the insulating
spacer and the surface of the rectangular hole of the holding frame fitting.
[0012]
The press-fit spacer is made of metal, and is press-fit between the first electrode surface of the
piezoelectric element portion and the insulating spacer to form an electrode electrically
connected to the first electrode surface of the piezoelectric element portion.
[0013]
In addition, the holding frame fitting electrically connected to the second electrode surface of the
piezoelectric element portion is used as the electrode on the land side, connected and fixedly held
to the ground pattern of the circuit board constituting the amplifier circuit, and the piezoelectric
element portion is mounted on the circuit board. Support one side.
[0014]
In addition, the holding frame fitting electrically connected to the second electrode surface of the
piezoelectric element portion is used as a land side electrode, and is connected to the ground
pattern of the circuit board constituting the impedance conversion circuit, and the holding frame
fitting is fixed on the circuit board By holding the piezoelectric element portion in a cantilever
manner on the circuit board, the electrode electrically connected to the first electrode surface of
the piezoelectric element portion is directly connected to the signal side pattern of the circuit
board.
[0015]
In addition, most of the back surface of the circuit board on which the piezoelectric element unit
is mounted is on the opposite side of the component mounting side of the piezoelectric element
as the ground pattern, and the case covering the piezoelectric element unit mounted on the
circuit board and the impedance converter is electrically conducted It is formed of a material
having a conductive film on the body or the inner surface, and is electrically connected to the
ground pattern of the circuit board to have an electric shielding effect.
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[0016]
Further, the case is a human body contact portion for picking up the sound vibration of bone
conduction.
[0017]
A preferred embodiment of the present invention is shown in FIGS. 1 to 5 and will be described.
[0018]
(First Embodiment) FIG. 1 is a perspective view of the appearance of a bone conduction
microphone according to a first embodiment, FIG. 2 is a side view thereof, and FIG. 3 is a crosssectional view of the G-G position shown in FIG.
FIG. 4 is an exploded perspective view of the components.
In FIG. 5, in the assembly process, the state excluding case 7 is C, the state excluding circuit
board 6 is D, and the state in which holding frame 3 is removed is E, the state excluding
insulating spacer 4 It is the perspective view which showed to F respectively.
[0019]
Similar to the bimorph piezoelectric element 1a, silver films are applied to the upper and lower
surfaces of the piezoelectric element 1a as electrodes.
The conductive spacer 2 made of copper alloy plays a role of spacing and conducting, and is
disposed between the electrode surfaces of the end portions of the piezoelectric elements 1a and
1b supported in a cantilever manner.
The electrode terminal 5 (a press-fit spacer having a wedge portion) in FIGS. 3 and 4 has a
tapered flat portion whose thickness decreases toward the tip, and the first electrode surface A of
the lower surface side of the piezoelectric element 1b (FIG. 5) ) Is disposed at a position where
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the flat portion is in contact with the
A U-shaped insulating spacer 4 is disposed so as to surround the cantilever supporting ends of
the piezoelectric elements 1a and 1b, the conductive spacer 2, and the placement portion of the
electrode terminal 5, and these are made of metal holding frame fitting having better
conductivity. It has a structure surrounded by three rectangular ring portions.
[0020]
The state shown in D of FIG. 5 is the first collective state of the assembly process.
As an assembly order, first, the insulating spacer 4 is inserted into the rectangular ring hole of
the holding frame 3 (the rectangular hole 35 of the rectangular cylindrical portion), and then the
piezoelectric element 1b, the conductive spacer 2, and the piezoelectric element 1a are in this
order The tapered shape of the electrode terminal 5 is in a space where the inner surface of the
insulating spacer 4 and the first electrode surface A on the lower surface side of the piezoelectric
element 1b face each other after being inserted so as to overlap in the U-shaped inner space of
the spacer 4 Press-fit the flat part of the as a weir.
[0021]
The vertical dimension of the rectangular hole 35 of the holding frame fitting is set smaller than
the total thickness of related parts of the five members (piezoelectric elements 1a and 1b, the
conductive spacer 2, the insulating spacer 4 and the electrode terminal 5) to be inserted. When
the terminals 5 are press-fitted as a wedge, they are pressed against each other and elastically
deformed, and the piezoelectric elements 1a and 1b are cantilevered in parallel with the holding
frame 3 while maintaining an interval of the thickness of the conductive spacer 2 .
The maximum sensitivity direction of vibration detection of the piezoelectric elements 1a and 1b
is the arrow direction 31 shown in FIG.
[0022]
The piezoelectric elements 1a and 1b are not only supported in a cantilever manner, but the
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upper second electrode surface B of the piezoelectric element 1a is the surface inside the
rectangular hole of the holding frame 3 and the lower electrode surface is the surface of the
conductive spacer 2 And electrical conduction is achieved by the upper electrode surface of the
piezoelectric element 1b being in pressure contact with the other surface of the conduction
spacer 2 and the lower first electrode surface A with the surface of the electrode terminal 5, The
piezoelectric elements 1a and 1b are connected in series on the electric circuit using the holding
frame 3 and the electrode terminal 5 as terminals of both electrodes.
[0023]
The reliability of this mutual conduction is achieved by ensuring the cleanliness of each contact
surface, adopting a material that is not easily oxidized, and maintaining an appropriate pressure
contact force by the reaction force of elastic deformation, but the resistance against
environmental conditions In order to ensure the improvement and the stability of the holding, the
flowable insulating adhesive which penetrates the gap of about 10 μm, the gap between the side
surface of the piezoelectric elements 1a and 1b and the insulating spacer 4, and the insulating It
is also possible to apply to the gap between the spacer 4 and the holding frame fitting 3 and the
outer surface of the holding portion.
[0024]
In addition, after the press-fitting operation of the electrode terminal 5, a part of the outer
peripheral part of the contact surface of each connected electrode part is coated with a
conductive adhesive having low mechanical strength but good electrical conductivity as a
support for connection It is also good for improving the reliability of electrical connection.
A V-shaped notch 2a is provided at the end of the conductive spacer 2 in order to expose the
necessary area of the electrode surface to be connected and provide it for connection.
That is, by applying a conductive adhesive for assisting conduction to the V groove portion
formed after combination, reliable conduction can be obtained.
The other connections have exposed portions that are easy to work with, so no particular shape
is provided for them.
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[0025]
In any case, in the work process up to this point, it is not necessary to set the positioning jig, put
it in the high temperature bath, and carry out the curing operation of the conductive adhesive,
and hold the piezoelectric element without directly relying on the adhesive Therefore, its
reliability is good and its rigidity is easy to secure.
[0026]
The block assembled by the above-described process operation is a holding frame metal fitting 3
in which the piezoelectric elements 1a and 1b are connected in series to a circuit board 6 on
which an impedance conversion circuit is formed on one side by FET 8 and capacitor 9 etc. And
the electrode terminal 5 are connected in a required pattern and fixed to each other.
On the back surface side opposite to the component mounting surface of the circuit board 6, a
ground pattern, a solder land, and a signal output solder land are configured (not shown). Note
that an amplification circuit may be configured in which an amplification unit having one or two
stages is provided at the subsequent stage of the FET 8 and the first stage is an impedance
conversion unit.
[0027]
In order to mutually fix the circuit board 6 and the block of the piezoelectric element portion, the
required connection portions of the holding frame 3 and the electrode terminal 5 may be
soldered to the pattern of the circuit board. Here, even if lead-free solder having a high melting
point is used, the temperature can not be increased enough to cause performance damage to the
piezoelectric element by quickly performing the heating operation.
[0028]
In addition, in a situation where quick work of soldering is difficult, instead of using conductive
adhesive and conducting and holding and fixing to the substrate, positioning jig is not necessary
and it is necessary to just align. It can be put in the tank. It is also possible to use a room
temperature curing type conductive adhesive for connection and to use a room temperature
curing type high rigidity adhesive separately for holding, in which case the work process for
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putting in a high temperature tank is not necessary. .
[0029]
After the piezoelectric element block is mounted on the substrate, the case 7 having an electrical
shielding effect and formed of a conductive material or a material having a conductive film on
the inner side is attached so as to cover the circuit portion. By connecting with this, the shielding
effect of the piezoelectric element and the impedance conversion circuit which are high
impedance and weak to external noise is secured. Further, the left and right support protrusions
6a (such as FIG. 4) of the circuit board 6 have a structure for supporting the bone conduction
microphone.
[0030]
The case 7 sandwiches the upper and lower surfaces of the holding frame 3 with the circuit
board 6 to form an exterior of the bone conduction microphone which is an assembled product,
and the holding frame 3 which is a cantilevered support of the piezoelectric elements 1a and 1b
The connection rigidity can be further increased, and when the exterior portion is pressed
against the human body to pick up the sound vibration, it can be transmitted to the piezoelectric
element without damaging the vibration.
[0031]
EXAMPLE 2 FIG. 6 is a perspective view showing the main part of a bone conduction microphone
of Example 2 in which two piezoelectric elements are arranged side by side.
That is, two piezoelectric elements are juxtaposed in a plane parallel to the main surface to form
a piezoelectric element portion. As in the first embodiment described above, the piezoelectric
elements 11a and 11b are held in the rectangular hole of the ring portion 13a having the
rectangular hole of the holding frame fitting 13 in a press-fit state together with the insulating
spacer member, the conductive spacer member, the wedge member and the electrode member.
ing. It is a structure which does not require the hardening operation | work in a high temperature
tank installed in a jig like Example 1. Further, the construction of the impedance conversion
circuit or the amplification circuit on the circuit board 16 is the same as that of the first
embodiment.
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[0032]
(Third Embodiment) FIG. 7 is a perspective view showing the main part of the bone conduction
microphone of the third embodiment. This is obtained by forming a rising portion 23b by press
bending on a substrate member 23 made of a metal plate, which is a structural substrate of the
entire product, and forming a ring portion 23a having a rectangular hole by press drawing. The
ground pattern is mounted on the main plane portion of the substrate member 23, and the
ground pattern is connected to the projection 23c of the substrate member 23 which is one
electrode of the piezoelectric element. Further, an electrode member 25 which is press-fitted
between the piezoelectric element 21b and the insulating sheet member and is another electrode
portion of the piezoelectric element is connected to a signal pattern of the circuit board 26 (not
shown). Also in the third embodiment, the same effect as the first and second embodiments
described above can be obtained.
[0033]
Although the case where two bimorph-type piezoelectric elements are used has been described in
the above embodiments, even in the unimorph-type, the structure in which the first electrode
surface and the second electrode surface are formed on both sides of the plate is a bimorph-type
Since it is the same, it is possible to use a unimorph type piezoelectric element in the present
invention, and the number of piezoelectric elements may be one or three or more.
[0034]
BRIEF DESCRIPTION OF THE DRAWINGS The external appearance perspective view of the bone
conduction microphone of Example 1. FIG.
FIG. 2 is a side view of the bone conduction microphone of Example 1; Sectional drawing of the
GG position shown in FIG. FIG. 2 is an exploded perspective view showing components of the
bone conduction microphone of the first embodiment. The perspective view which shows each
part in an assembly process. FIG. 7 is a perspective view showing the main part of the bone
conduction microphone of Example 2; FIG. 14 is a perspective view showing the main part of the
bone conduction microphone of Example 3;
Explanation of sign
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[0035]
1a, 1b, 11a, 11b, 21a, 21b Piezoelectric element 2 Conducting spacer 2a Notched 3, 13 Holding
frame metal fitting 4 Insulating spacer 5 Electrode terminal 6, 16, 26 Circuit board 6a Support
projection 7 Case 8 FET 9 Capacitor 13a Ring 23 substrate member 23a ring portion 23b rising
portion 23c protrusion 25 electrode member 31 arrow direction 35 rectangular hole A first
electrode surface B second electrode surface
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