JP4633030B2 - Condenser microphone unit and condenser microphone - Google Patents

Description

  The present invention relates to a condenser microphone unit and a condenser microphone using this unit, and more particularly to a structure for increasing the acoustic mass in a front acoustic terminal.

  The condenser microphone unit includes a film-like diaphragm that vibrates in response to sound waves, a diaphragm holder that holds the diaphragm with the periphery of the diaphragm fixed, and a predetermined gap between the diaphragm and the diaphragm. And a unit case for housing internal parts including the diaphragm, the diaphragm holder, the stationary electrode, and the like. The unit case used in a relatively inexpensive condenser microphone unit is molded into a bottomed cylinder using a plastically deformable material such as aluminum, and the internal parts are housed in this, and the rear end is open. The internal parts are fixed integrally in the unit case by caulking inward.

  FIG. 3 shows a conventional example of a condenser microphone unit. Reference numeral 1 denotes a bottomed cylindrical unit case. In the unit case 1, a portion corresponding to a bottom plate integrally formed on one end side is a front plate 11 of the microphone unit, and the front plate 11 is punched through the front plate 11 at the center of the front plate 11. A circular hole 12 to be the acoustic terminal 12 is formed. In the unit case 1, a diaphragm holder 2, a diaphragm 3, a spacer 4, a fixed electrode 5, an insulating seat 6, and a circuit board 7 are arranged in this order from the front plate 11 side. The diaphragm 3 is a film-like member that vibrates in response to sound waves. The diaphragm is fixed to the diaphragm holder 2 to form a diaphragm set. The diaphragm set is configured to vibrate with the front plate 11 of the unit case 1. It is arrange | positioned in the unit case 1 so that the acoustic chamber 20 for the thickness of the diaphragm holder 2 may arise between the board 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 the fixed electrode 5 changes and the capacitance between the diaphragm 3 and the fixed electrode 5 changes and is converted into an electric signal corresponding to the sound wave. It has become so.

  A recessed portion is formed in two stages 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 regulated by the peripheral wall of the recessed part, and the thickness of the fixed electrode 5 is larger than the height of the peripheral wall of the recessed part, so that the outer peripheral edge of the front surface of the fixed electrode 5 becomes the spacer 4. It is in contact. A hole 51 is formed in the central portion of the fixed electrode 5 so as to pass through the fixed electrode 5 in the thickness direction. The hole 51 communicates with a gap formed between the diaphragm 3 and the fixed electrode 5 and is fixed. The acoustic chamber 56 is formed by the recessed portion 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 on the rear end side, and the diameter of the rear open end of each hole 61 is increased. 8 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 caulked inward to form a folded portion 14. The circuit board 7 is pressed toward the front side by the folded portion 14, and by this pressing force, the insulating seat 6, the fixed electrode 5, the spacer 4, the diaphragm 3, and the diaphragm holder 2 are sequentially placed on the front plate 11 of the unit case 1. These built-in components are positioned and integrated in the unit case 1.

  Holes are formed in the circuit board 7 at positions overlapping the respective rear acoustic resistors 8, and these holes constitute rear acoustic terminals 71. The insulating seat 6 is provided with a cavity near the central axis, and an FET (field effect transistor) 9 that forms the main body of the impedance converter is disposed in the cavity. One terminal of 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 so that the FET 9 is connected to the circuit board 7. It is fixed substantially integrally. The soldering portion closes a hole formed in the circuit board 7 from the outside so as to allow the terminal of the FET 9 to pass therethrough. The other terminal of the FET 9 extends toward the fixed electrode 5, and the tip is bent at a substantially right angle, and is sandwiched between the back surface of the fixed electrode 5 and the front surface of the insulating seat 6. It is connected.

  In the above conventional example, the unit case 1 is generally produced by drawing a plate made of an aluminum material with 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 the front plate 11 of the unit case 1. This is because the front acoustic terminal 12 can be formed only by punching the front plate 11 and is extremely simple.

  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 holder 2 and formed between the front surface of the diaphragm 3 and the front plate 11 of the unit case 1. It is greatly influenced by sf and the acoustic mass mf of the front acoustic terminal 12 made of a hole formed by punching the front plate 11. In particular, the frequency response characteristics from about 10 kHz or more can be improved by 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. Thus, the acoustic mass mf may be increased.

  However, in the conventional example as shown in FIG. 3, since the hole formed by punching the front plate 11 of the unit case 1 is merely the front acoustic terminal 12, the acoustic mass of the front acoustic terminal 12 is the unit case 1. It is limited by the thickness of the plate, and the acoustic mass cannot be increased. Therefore, it is difficult to improve the frequency response characteristics as a condenser microphone unit.

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 defined as the front acoustic terminal. It is conceivable that the frequency response characteristics of the condenser microphone unit can be improved by communicating with 12 and substantially expanding the volume of the front acoustic terminal and expanding the acoustic mass of the front acoustic terminal 12.
However, preparing the ring-shaped member 16 as a separate member and fixing the ring-shaped member 16 to the front plate 11 of the unit case 1 increases the number of parts and the number of assembling steps, which increases the manufacturing cost. It is not desirable because it becomes 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 side. Therefore, when the microphone unit is assembled in the microphone case and the microphone is assembled, the ring The member 16 may be a hindrance to the microphone case.

  The present applicant has previously filed a patent application regarding 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, for example, relates to a microphone suitable for incorporation into a personal computer body or a display. The wall surface into which the microphone is incorporated has a larger diameter than the microphone unit and a depth greater than the axial length thereof. Forming a unit housing portion, housing the microphone unit in the unit housing portion so that the front acoustic terminal is located in a plane including the wall surface, and placing the microphone unit on the front acoustic terminal side of the microphone unit. A baffle plate to be fitted in the opening surface of the unit housing portion is attached, and a side acoustic terminal communicating with the rear acoustic terminal is formed around the baffle plate.

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 the unit storage portion from the side acoustic terminal to the rear acoustic terminal, so that a sound pressure gradient is generated between them. Unidirectional characteristics can be obtained.
However, the invention described in Patent Document 1 is not an invention that focuses on the acoustic mass of the front acoustic terminal, and the object is also different from the present invention.

  As an invention related to a microphone that focuses on acoustic mass, in order to reduce the effects of wind noise and proximity effects, a predetermined gap is provided between the outer peripheral surface of the microphone unit and the inner peripheral surface of the acoustic tube. An acoustic resistance material having a predetermined acoustic resistance with respect to the acoustic mass existing in the gap between the outer peripheral surface of the microphone unit and the inner peripheral surface of the acoustic tube is acoustically connected to the acoustic terminal and the rear acoustic terminal. There is a narrow directional microphone arranged (see Patent Document 2). The invention described in Patent Document 2 focuses on the acoustic mass that exists in the gap between the outer peripheral surface of the microphone unit and the inner peripheral surface of the acoustic tube, and is an invention that focuses on the acoustic mass of the front acoustic terminal. The object is also different from the present invention.

JP 2000-32584 A JP-A-11-331978

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 characteristics of 10 kHz or more cannot be improved. An object of the present invention is to provide a condenser microphone unit and a condenser microphone that can improve frequency response characteristics at a low cost.
Another object of the present invention is to provide a low-cost condenser microphone unit and condenser microphone that can improve frequency response characteristics of 10 kHz or more with a simple configuration.

A condenser microphone unit according to the present invention includes a unit case, a front plate integrated with the unit case, a diaphragm built in the unit case, a built-in component including a fixed electrode facing the diaphragm with a gap therebetween, A hole is formed in the front plate of the unit case, and a peripheral edge of the hole formed in the front plate extends inward. The main feature is that the length is longer than the thickness of the front plate.
The condenser microphone according to the present invention is characterized in that the condenser microphone unit according to the present invention is built in a microphone case.

According to the condenser microphone unit of the present invention, since the peripheral portion of the hole that forms the front acoustic terminal is formed in the front plate of the unit case and extends inwardly, the space surrounded by the cylinder Becomes the front acoustic terminal. And since the length of the cylinder is longer than the thickness of the front plate, the internal volume becomes larger than the front acoustic terminal simply having a hole formed in the front plate, and the acoustic mass is increased. Can do. 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, particularly the frequency response characteristic of 10 kHz or more can be improved. Further, there is an advantage that the condenser microphone unit having such an effect can be provided at a low cost without adding parts.
Since the cylinder extending from the peripheral edge of the hole that constitutes the front acoustic terminal faces inward, there is no protrusion from the front end surface of the unit, which hinders the construction of a condenser microphone built in an existing microphone case. Never come.
According to the condenser microphone of the present invention, it is possible to obtain a condenser microphone having the above effects.

  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 components as those of the conventional example shown in FIGS. 3 and 4 are denoted by common reference numerals.

  In FIG. 1, reference numeral 1 denotes a bottomed cylindrical unit case. In the unit case 1, a portion corresponding to a bottom plate integrally formed on one end side is a front plate 11 of the microphone unit, and a circular hole is punched through the front plate 11 in the center of the front plate 11. And a cylinder 18 extending inward from the front plate 11 is integrally formed by drawing the peripheral edge of the hole. A space surrounded by the cylinder 18 is the front acoustic terminal 12. The length L of the cylinder 18 is longer than the thickness of the front plate 11.

  In the unit case 1, a diaphragm holder 2, a diaphragm 3, a spacer 4, a fixed electrode 5, an insulating seat 6, and a circuit board 7 are arranged in this order from the front plate 11 side. The diaphragm 3 is a film-like circular member that vibrates in response to sound waves, and its peripheral edge is fixed to the rear end face (right end face in FIG. 1) of the diaphragm holder 2 to form a diaphragm set. In this diaphragm set, the diaphragm 3 fixing surface of the diaphragm holder 2 is formed so that the acoustic chamber 20 corresponding to the thickness of the diaphragm holder 2 is generated between the front plate 11 and the diaphragm 3 of the unit case 1. The front end surface on the opposite side of the front plate 11 is in contact with the inner surface of the front plate 11 and is disposed in the unit case 1. On the rear surface side of the diaphragm 3, a ring-shaped spacer 4 is disposed at a position overlapping with the ring-shaped diaphragm holding body 2 in the axial direction, and a fixed electrode 5 is disposed with the spacer 4 interposed. 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 the fixed electrode 5 changes and the capacitance between the diaphragm 3 and the fixed electrode 5 changes and is converted into an electric signal corresponding to the sound wave. It has become so.

  As described above, since the length L of the cylinder 18 is longer than the thickness of the front plate 11, the cylinder 18 enters the acoustic chamber 20. The material of the unit case 1 is not particularly limited. For example, the unit case 1 can be formed by drawing a plate made of an aluminum material having a plate pressure of about 0.2 to 0.5 mm with a press. Further, the front plate can be punched to form a hole, and the peripheral portion of the hole can be drawn to form the cylinder 18 integrally.

  A recessed portion is formed in two stages 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 regulated by the peripheral wall of the recessed part, and the thickness of the fixed electrode 5 is larger than the height of the peripheral wall of the recessed part, so that the outer peripheral edge of the front surface of the fixed electrode 5 becomes the spacer 4. It is in contact. A hole 51 is formed in the central portion of the fixed electrode 5 so as to pass through the fixed electrode 5 in the thickness direction. The hole 51 communicates with a gap formed between the diaphragm 3 and the fixed electrode 5 and is fixed. The acoustic chamber 56 is formed by the recessed portion 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 on the rear end side, and the diameter of the rear open end of each hole 61 is increased. 8 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 caulked inward to form a folded portion 14. The circuit board 7 is pressed toward the front side by the folded portion 14, and by this pressing force, the insulating seat 6, the fixed electrode 5, the spacer 4, the diaphragm 3, and the diaphragm holder 2 are sequentially placed on the front plate 11 of the unit case 1. These built-in components are positioned and integrated in the unit case 1.

  Holes are formed in the circuit board 7 at positions overlapping the respective rear acoustic resistors 8, and these holes constitute rear acoustic terminals 71. The insulating seat 6 is provided with a cavity near the central axis, and an FET 9 that forms the main body of the impedance converter is disposed in the cavity. One terminal of 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 so that the FET 9 is connected to the circuit board 7. It is fixed substantially integrally. The soldering portion closes a hole formed in the circuit board 7 from the outside so as to allow the terminal of the FET 9 to pass therethrough. The other terminal of the FET 9 extends toward the fixed electrode 5, and the tip is bent at a substantially right angle, and is sandwiched between the back surface of the fixed electrode 5 and the front surface of the insulating seat 6. It is connected.

FIG. 2 shows an acoustic equivalent circuit of the above embodiment. The acoustic element of each part of the above embodiment is 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 ( (Indicated by A in FIG. 2)
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 part

  As shown in FIG. 2, the acoustic equivalent circuit of the above embodiment is such that P1, mf, m0, s0, r0, r1, P2 are connected in series in this order, and the connection point between mf and m0. And sf is connected between the connection point of P1 and P2, that is, ground, and s1 is connected between the connection point of r0 and r1, and the connection point of P1 and P2, that is, ground. A portion (a portion indicated by a symbol B in FIG. 2) composed of 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-frequency resonator, and the larger mf is It can be effectively operated as a high-frequency resonator. In order to increase mf, it is necessary to increase the volume of the front acoustic terminal 12. In the embodiment shown in FIG. 1, a cylinder 18 extending inward is formed by drawing a peripheral portion of a hole formed in the front plate 11, and the length of the cylinder 18 is set to the front plate 11. The volume of the front acoustic terminal 12 is increased by making it longer than the thickness of the first acoustic terminal 12 so that the front acoustic terminal 12 operates effectively as a high-frequency resonator. As a result, a condenser microphone unit having good frequency response characteristics can be obtained.

  According to the above embodiment, the cylinder 18 is formed integrally with the unit case 1 by drawing the peripheral edge of the hole formed in the front plate 11 in order to increase the volume of the front acoustic terminal 12. Therefore, it is not necessary to add another part for increasing the volume of the front acoustic terminal 12, and the condenser microphone unit having a small number of parts, a small number of assembly steps, and a good frequency response characteristic can be provided at low cost. Can do.

  The condenser microphone unit according to the present invention can constitute a condenser microphone by incorporating it into 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 edge portion of the hole formed in the front plate 11 is formed into a cylinder 18 extending inwardly. It is possible to avoid the front end side from protruding forward, and there is an advantage that a condenser microphone can be configured by being built in a microphone case having a general configuration.

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 diagram of the embodiment. 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 symbols

DESCRIPTION OF SYMBOLS 1 Unit case 2 Diaphragm holder 3 Diaphragm 4 Spacer 5 Fixed electrode 6 Insulation seat 7 Circuit board 8 Acoustic resistor 12 Front acoustic terminal 18 Cylinder 20 Acoustic chamber 71 Rear acoustic terminal

Claims (4)

A unit case, a front plate integrated with the unit case, a diaphragm built in the unit case, and a built-in component including a fixed electrode facing the diaphragm with a gap therebetween, and the front plate of the unit case A condenser microphone unit in which a hole constituting the front acoustic terminal is formed,
The peripheral edge of the hole formed in the front plate is a cylinder extending inward,
A condenser microphone unit characterized in that the length of the tube is longer than the thickness of the front plate.   2. The capacitor according to claim 1, wherein the unit case is formed by pressing a plate-like material so that the front plate is integrally formed, and a cylinder extending inward from the front plate is integrally formed by drawing. Microphone unit.   The outer peripheral edge of the diaphragm is fixed to one end surface of the ring-shaped diaphragm holder, and the surface of the diaphragm holder opposite to the diaphragm fixing surface is in contact with the inner surface of the front plate of the unit case. 2. The condenser microphone unit according to claim 1, wherein an acoustic chamber corresponding to the thickness of the diaphragm holder is formed between the inner surface of the plate and the diaphragm, and a cylinder extending from the front plate enters the acoustic chamber. A condenser microphone comprising a condenser microphone unit built in a microphone case, wherein the condenser microphone unit is a condenser microphone unit according to any one of claims 1 to 3.

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