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DESCRIPTION JP2008092370

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DESCRIPTION JP2008092370
A low-cost condenser microphone unit and a condenser microphone capable of improving
frequency response characteristics with a simple configuration. A unit case 1, a front plate 11
integral with the unit case 1, a diaphragm 3 built in the unit case 1, and a built-in component
including a fixed electrode 5 opposed to the diaphragm 3 with a gap. The front plate 11 of the
unit case 1 is formed with a hole that constitutes the front acoustic terminal 12, the peripheral
edge of this hole is a cylinder 18 extending inward, and the length of the cylinder 18 is the front
It is longer than the thickness of the plate 11. The outer periphery of the diaphragm 3 is fixed to
one end face of the ring-shaped diaphragm holder 2, and the diaphragm holder 2 is in contact
with the inner surface of the front plate 11 with the surface opposite to the diaphragm fixed
surface. An acoustic chamber 20 corresponding to the thickness of the diaphragm holder 2 is
formed between the inner surface of the plate and the diaphragm 3, and the cylinder 18 intrudes
into the acoustic chamber 20. [Selected figure] Figure 1
コンデンサーマイクロホンユニットおよびコンデンサーマイクロホン
[0001]
The present invention relates to a condenser microphone unit and a condenser microphone using
the unit, and more particularly to a structure for increasing the acoustic mass in the front
acoustic terminal.
[0002]
In the condenser microphone unit, a film-shaped diaphragm that receives and vibrates sound
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waves, a diaphragm holder that holds the diaphragm by the peripheral edge of the diaphragm
being fixed, and a predetermined gap between the diaphragm and the diaphragm via a spacer A
unit case for housing internal components including fixed electrodes facing each other, these
diaphragms, a diaphragm holder, fixed electrodes, and the like.
The unit case used in a relatively inexpensive condenser microphone unit is formed into a
cylindrical shape with a bottom by using a plastically deformable material such as aluminum, and
after the internal parts are accommodated in this, the open rear end portion The internal
components are integrally fixed in the unit case by caulking inward.
[0003]
FIG. 3 shows a conventional example of a condenser microphone unit. The code | symbol 1
shows a unit case of a bottomed cylindrical shape. The unit case 1 has a portion corresponding to
a bottom plate integrally formed on one end side as the front plate 11 of the microphone unit,
and the center portion of the front plate 11 is pierced by the front plate 11 to obtain the front A
circular hole 12 to be the acoustic terminal 12 is formed. In the unit case 1, the diaphragm
holder 2, the diaphragm 3, the spacer 4, the fixed electrode 5, the insulating seat 6, and the
circuit board 7 are arranged in order from the front plate 11 side. The diaphragm 3 is a film-like
member that vibrates upon receiving a sound wave, and the peripheral edge portion thereof is
fixed to the diaphragm holder 2 to form a diaphragm set. This diaphragm set vibrates with the
front plate 11 of the unit case 1 An acoustic chamber 20 of a thickness corresponding to the
thickness of the diaphragm holder 2 is disposed between the unit case 1 and the plate 3. A fixed
electrode 5 is disposed on the rear surface side of the diaphragm 3 with a spacer 4 interposed
therebetween, and a gap corresponding to the thickness of the spacer 4 is formed between the
diaphragm 3 and the fixed electrode 5. When the diaphragm 3 receives a sound wave and
vibrates, the gap between it and the fixed electrode 5 changes, the capacitance between the
vibration plate 3 and the fixed electrode 5 changes, and the electric signal corresponding to the
sound wave is converted It has become so.
[0004]
A recessed portion is formed in two steps on the front end side of the insulating seat 6, and the
fixed electrode 5 is fitted in the large diameter recessed portion. The position of the outer
periphery of the fixed electrode 5 is restricted by the peripheral wall of the recessed portion, and
the thickness dimension of the fixed electrode 5 is larger than the height of the peripheral wall of
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the recessed portion. It abuts. A hole 51 is formed in the central portion of the fixed electrode 5
so as to penetrate the fixed electrode 5 in the thickness direction, and the hole 51 communicates
with a gap generated between the diaphragm 3 and the fixed electrode 5 and is fixed. It is in
communication with an acoustic chamber 56 formed by the recess on the front end side of the
electrode 5 and the fixed electrode 5. The insulating seat 6 has a plurality of holes 61 for
opening the acoustic chamber 56 at the rear end side, and the rear open end of each hole 61 is
enlarged in diameter, and the enlarged diameter portion is a rear acoustic resistor Eight is fitted.
The circuit board 7 is disposed on the rear end face of the insulating seat 6, and the rear acoustic
resistor 8 is pressed by the circuit board 7. The rear end side of the unit case 1 is an open end,
and the open end edge portion is crimped inward to form a folded portion 14. The circuit board
7 is pressed toward the front side by the folded portion 14, and the insulating seat 6, the fixed
electrode 5, the spacer 4, the diaphragm 3, and the diaphragm holder 2 are sequentially ordered
by the pressing force. The internal components are positioned and integrated in the unit case 1.
[0005]
Holes are formed in the circuit board 7 at positions overlapping the respective rear acoustic
resistors 8, and these holes constitute a rear acoustic terminal 71. A cavity is provided in the
insulating seat 6 near the central axis, and an FET (field effect transistor) 9 as a main component
of an impedance converter is disposed in the cavity. One terminal included in the FET 8 passes
through a hole formed in the circuit board 7 and is soldered to a predetermined circuit pattern
formed on the outer surface of the circuit board 7, whereby the FET 9 is formed on the circuit
board 7. It is fixed in one body substantially. The soldered portion from the outside covers the
hole formed in the circuit board 7 to pass the terminal of the FET 9. The other terminal of the
FET 9 extends toward the fixed electrode 5 and its tip is bent almost at a right angle so that it is
sandwiched between the back surface of the fixed electrode 5 and the front surface of the
insulating seat 6. It is connected.
[0006]
In the above conventional example, the unit case 1 is generally produced by drawing a plate
made of an aluminum material by a press. The plate pressure is about 0.2 to 0.5 mm. The front
acoustic terminal 12 is formed only by a circular hole formed by punching out the front plate 11
of the unit case 1. By so doing, the front acoustic terminal 12 can be formed only by punching
the front plate 11, which is extremely simple.
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[0007]
By the way, the frequency response characteristic of the condenser microphone unit is the
acoustic capacity of the acoustic chamber 20 surrounded by the ring-shaped diaphragm support
2 and formed between the front surface of the diaphragm 3 and the front plate 11 of the unit
case 1 sf and the acoustic mass mf of the front acoustic terminal 12 consisting of a hole formed
by punching out the front plate 11 are greatly influenced. In particular, the frequency response
characteristic from around 10 kHz or more can be improved by the resonance between the
acoustic capacity sf and the acoustic mass mf of the front acoustic terminal 12, and for that
purpose, the volume of the front acoustic terminal 12 is increased. It is better to increase the
acoustic mass mf.
[0008]
However, in the conventional example as shown in FIG. 3, the hole formed by punching out the
front plate 11 of the unit case 1 is only used as the front acoustic terminal 12, so the acoustic
mass of the front acoustic terminal 12 is unit case 1. Limited by the thickness of the plate, and
the acoustic mass can not be increased. Therefore, it is difficult to improve the frequency
response characteristic as a condenser microphone unit.
[0009]
Therefore, as shown in FIG. 4, a ring-shaped member 16 having a relatively large thickness is
fixed in front of the front acoustic terminal 12, and the space surrounded by the inner peripheral
surface of the member 16 is a front acoustic terminal. It is conceivable to enhance the frequency
response characteristic as a condenser microphone unit by communicating with 12 to
substantially expand the volume of the front acoustic terminal and the acoustic mass of the front
acoustic terminal 12. However, preparing the ring-shaped member 16 as a separate member and
fixing it to the front plate 11 of the unit case 1 increases the number of parts and the number of
assembling steps, resulting in an increase in manufacturing cost. It is not desirable because it is a
factor. When the ring-shaped member 16 is fixed to the front surface of the front plate 11 of the
unit case 1, the dimensions of the microphone unit are expanded to the front, so when
assembling the microphone by incorporating the microphone unit into the microphone case, The
bar-like member 16 may be an obstacle to incorporation into the microphone case.
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[0010]
The present applicant has previously filed a patent application for a unidirectional microphone in
which a baffle plate is added as a separate member to the front acoustic terminal of the
microphone unit (see Patent Document 1). The invention described in Patent Document 1 relates,
for example, to a microphone suitable for being incorporated into a personal computer body or a
display, and has a wall diameter larger than the microphone unit and a depth larger than its axial
length. The unit storage portion is formed, and the microphone unit is housed in the unit housing
portion so that the front acoustic terminal is positioned in a plane including the wall surface, and
the above-mentioned microphone unit is disposed on the front acoustic terminal side of the
microphone unit. A baffle plate fitted in the opening surface of the unit storage portion is
attached, and a side acoustic terminal communicating with the rear acoustic terminal is formed
around the baffle plate.
[0011]
According to the invention described in Patent Document 1, the sound wave from the sound
source is captured by the front acoustic terminal and enters from the side acoustic terminal into
the unit storage portion to the rear acoustic terminal, so that a sound pressure gradient occurs
between them. Unique directional characteristics are obtained. However, the invention described
in Patent Document 1 is not the invention focusing on the acoustic mass of the front acoustic
terminal, and the object is also different from the present invention.
[0012]
As an invention related to a microphone focusing on acoustic mass, in order to reduce the
influence of wind noise and proximity effect, a predetermined gap is provided between the outer
peripheral surface of the microphone unit and the inner peripheral surface of the acoustic tube,
and the front of the microphone unit An acoustic resistance material having a predetermined
acoustic resistance to the acoustic mass which acoustically connects the acoustic terminal and
the rear acoustic terminal and exists in the gap between the outer circumferential surface of the
microphone unit and the inner circumferential surface of the acoustic tube There is a narrow
directional microphone which is arranged (see Patent Document 2). The invention described in
Patent Document 2 focuses on the acoustic mass existing in the gap between the outer
circumferential surface of the microphone unit and the inner circumferential surface of the
acoustic tube, and in the invention focusing on the acoustic mass of the front acoustic terminal
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The purpose is also different from the present invention.
[0013]
JP, 2000-32584, A JP, 11-331978, A
[0014]
The present invention solves the problems of the prior art as shown in FIGS. 3 and 4, that is, the
problem that the acoustic mass inside the front acoustic terminal is insufficient and the
frequency response characteristic of 10 kHz or more can not be improved. It is an object of the
present invention to provide, at low cost, a condenser microphone unit and a condenser
microphone capable of improving frequency response characteristics.
Another object of the present invention is to provide a low cost condenser microphone unit and a
condenser microphone capable of improving frequency response characteristics of 10 kHz or
more with a simple configuration.
[0015]
A condenser microphone unit according to the present invention includes a unit case, a front
plate integrated with the unit case, a diaphragm incorporated in the unit case, and a built-in
component including a fixed electrode facing the diaphragm with a gap. A hole forming the front
acoustic terminal is formed in the front plate of the unit case, and a peripheral edge portion of
the hole formed in the front plate is a cylinder extending inward; The main feature is that the
length is longer than the thickness of the front plate. A condenser microphone according to the
present invention is characterized in that the condenser microphone unit according to the
present invention is incorporated in a microphone case.
[0016]
According to the condenser microphone unit of the present invention, since the peripheral
portion of the hole formed on the front plate of the unit case and constituting the front acoustic
terminal is an inwardly extending cylinder, the space surrounded by the cylinder Is the front
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acoustic terminal. And since the length of the above-mentioned tube is longer than the thickness
of the above-mentioned front board, the volume inside is made larger than the front acoustic
terminal which only formed the hole in the front board, and the acoustic mass is increased. Can.
For this reason, there is an advantage that the increased acoustic mass can be effectively
operated as a high frequency resonator, and the frequency response characteristic of the
microphone unit, in particular, the frequency response characteristic of 10 kHz or more can be
improved. In addition, there is also an advantage that a condenser microphone unit exhibiting
such an effect can be provided at low cost without adding components. Since the cylinder
extending from the peripheral edge of the hole constituting the front acoustic terminal is directed
inward, there is no protrusion from the front end face of the unit, and it is difficult to construct a
condenser microphone by incorporating it into the existing microphone case. There is no need to
come. According to the condenser microphone of the present invention, it is possible to obtain a
condenser microphone that exhibits the above effects.
[0017]
Hereinafter, embodiments of a condenser microphone unit and a condenser microphone
according to the present invention will be described with reference to FIGS. 1 and 2. The same
reference numerals as in the prior art shown in FIGS. 3 and 4 denote the same parts.
[0018]
In FIG. 1, the code | symbol 1 shows a unit case of a bottomed cylindrical shape. In the unit case
1, a portion corresponding to the bottom plate integrally formed on one end side is the front
plate 11 of the microphone unit, and a central hole of the front plate 11 pierces the front plate
11 to form a circular hole. The cylinder 18 extending inward from the front plate 11 is integrally
formed by drawing the peripheral portion of the hole. A space surrounded by the tube 18 is a
front acoustic terminal 12. The length L of the tube 18 is longer than the thickness of the front
plate 11.
[0019]
In the unit case 1, the diaphragm holder 2, the diaphragm 3, the spacer 4, the fixed electrode 5,
the insulating seat 6, and the circuit board 7 are arranged in order from the front plate 11 side.
The diaphragm 3 is a film-like circular member that vibrates upon receiving a sound wave, and
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its peripheral edge portion is fixed to the rear end surface (right end surface in FIG. 1) of the
diaphragm holder 2 to form a diaphragm set. This diaphragm set is such that the diaphragm 3
fixed surface of the diaphragm holder 2 is formed so that the acoustic chamber 20 for the
thickness of the diaphragm holder 2 is generated between the front plate 11 of the unit case 1
and the diaphragm 3. The front end face opposite to the above is placed in contact with the inner
side face of the front plate 11 in the unit case 1. A ring-shaped spacer 4 is disposed on the rear
surface side of the diaphragm 3 at a position overlapping with the ring-shaped diaphragm
support 2 in the axial direction, and the fixed electrode 5 is disposed on the spacer 4 under the
interposition. A gap corresponding to the thickness of the spacer 4 is formed between the
diaphragm 3 and the fixed electrode 5. When the diaphragm 3 receives a sound wave and
vibrates, the gap between it and the fixed electrode 5 changes, the capacitance between the
vibration plate 3 and the fixed electrode 5 changes, and the electric signal corresponding to the
sound wave is converted It has become so.
[0020]
As described above, since the length L of the cylinder 18 is longer than the thickness of the front
plate 11, the cylinder 18 intrudes into the acoustic chamber 20. Although the material of unit
case 1 is not specifically limited, For example, it can draw and process the board which consists
of aluminum materials whose board | plate pressure is about 0.2-0.5 mm with a press. Also, the
front plate can be punched out to form a hole, and the peripheral portion of the hole can be
drawn to form the cylinder 18 integrally.
[0021]
A recessed portion is formed in two steps on the front end side of the insulating seat 6, and the
fixed electrode 5 is fitted in the large diameter recessed portion. The position of the outer
periphery of the fixed electrode 5 is restricted by the peripheral wall of the recessed portion, and
the thickness dimension of the fixed electrode 5 is larger than the height of the peripheral wall of
the recessed portion. It abuts. A hole 51 is formed in the central portion of the fixed electrode 5
so as to penetrate the fixed electrode 5 in the thickness direction, and the hole 51 communicates
with a gap generated between the diaphragm 3 and the fixed electrode 5 and is fixed. It is in
communication with an acoustic chamber 56 formed by the recess on the front end side of the
electrode 5 and the fixed electrode 5. The insulating seat 6 has a plurality of holes 61 for
opening the acoustic chamber 56 at the rear end side, and the rear open end of each hole 61 is
enlarged in diameter, and the enlarged diameter portion is a rear acoustic resistor Eight is fitted.
The circuit board 7 is disposed on the rear end face of the insulating seat 6, and the rear acoustic
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resistor 8 is pressed by the circuit board 7. The rear end side of the unit case 1 is an open end,
and the open end edge portion is crimped inward to form a folded portion 14. The circuit board
7 is pressed toward the front side by the folded portion 14, and the insulating seat 6, the fixed
electrode 5, the spacer 4, the diaphragm 3, and the diaphragm holder 2 are sequentially ordered
by the pressing force. The internal components are positioned and integrated in the unit case 1.
[0022]
Holes are formed in the circuit board 7 at positions overlapping the respective rear acoustic
resistors 8, and these holes constitute a rear acoustic terminal 71. The insulating seat 6 is
provided with a cavity near the central axis, and the FET 9 which is the main body of the
impedance converter is disposed in the cavity. One terminal included in the FET 8 passes through
a hole formed in the circuit board 7 and is soldered to a predetermined circuit pattern formed on
the outer surface of the circuit board 7, whereby the FET 9 is formed on the circuit board 7. It is
fixed in one body substantially. The soldered portion from the outside covers the hole formed in
the circuit board 7 to pass the terminal of the FET 9. The other terminal of the FET 9 extends
toward the fixed electrode 5 and its tip is bent almost at a right angle so that it is sandwiched
between the back surface of the fixed electrode 5 and the front surface of the insulating seat 6. It
is connected.
[0023]
FIG. 2 shows the acoustic equivalent circuit of the above embodiment. The acoustic elements of
each part of the above embodiment are defined as follows. P1: sound pressure on the front side
of the unit P2: sound pressure on the rear side of the unit mf: acoustic mass of the front acoustic
terminal sf: stiffness of the air chamber 20 on the front side of the diaphragm m0, s0, r0:
acoustic impedance of the diaphragm ( 2A: m0: acoustic mass of the diaphragm s0: stiffness of
the diaphragm r0: acoustic resistance of the diaphragm s1: stiffness of the air chamber 56
behind the diaphragm 3 r1: acoustic resistance of the rear
[0024]
In the acoustic equivalent circuit of the above embodiment, as shown in FIG. 2, P1, mf, m0, s0, r0,
r1, P2 are connected in series in this order, and the connection point of mf and m0 And s1 is
connected between the connection point of P1 and P2, ie, the ground, and s1 is connected
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between the connection point of r0 and r1 and the connection point of P1 and P2, ie, the ground.
The portion (indicated by symbol B in FIG. 2) formed by the acoustic mass mf of the front
acoustic terminal and the stiffness sf of the air chamber 20 on the front side of the diaphragm 3
constitutes a high-pass resonator, and the larger mf is It can be effectively operated as a high
frequency resonator. In order to increase mf, the volume of the front acoustic terminal 12 needs
to be increased. In the embodiment shown in FIG. 1, the cylinder 18 extending inward is formed
by drawing the peripheral portion of the hole formed in the front plate 11, and the length of the
cylinder 18 is set to the front plate 11. By making the thickness of the front acoustic terminal 12
larger than the thickness of the front acoustic terminal 12, the front acoustic terminal 12 is
designed to operate effectively as a high-frequency resonator. This makes it possible to obtain a
condenser microphone unit having good frequency response characteristics.
[0025]
According to the above embodiment, the cylinder 18 is integrally formed with the unit case 1 by
drawing the peripheral portion of the hole formed in the front plate 11 in order to increase the
volume of the front acoustic terminal 12. Therefore, there is no need to add a separate part for
increasing the volume of the front acoustic terminal 12, the number of parts is small, the number
of assembly steps is small, and a condenser microphone unit having good frequency response
characteristics is provided inexpensively. Can.
[0026]
The condenser microphone unit concerning this invention can comprise a condenser microphone
by incorporating this in a microphone case.
In the condenser microphone unit according to the present invention, in order to increase the
volume of the front acoustic terminal 12, the peripheral portion of the hole formed in the front
plate 11 is made into the cylinder 18 extending in the inward direction, There is an advantage
that the front end side of can be prevented from projecting forward, and it can be built in a
microphone case of a general configuration to constitute a condenser microphone.
[0027]
It is a longitudinal cross-sectional view which shows the Example of the condenser microphone
unit concerning this invention. It is an acoustic equivalent circuit schematic of the said Example.
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It is a longitudinal cross-sectional view which shows the example of the conventional condenser
microphone unit. It is a longitudinal cross-sectional view which shows the example which added
the means to increase the acoustic mass of a front acoustic terminal in the conventional
condenser microphone unit.
Explanation of sign
[0028]
1 unit case 2 diaphragm support 3 diaphragm 4 spacer 5 fixed electrode 6 insulator 7 circuit
board 8 acoustic resistor 12 front acoustic terminal 18 cylinder 20 acoustic chamber 71 rear
acoustic terminal
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