JP5249901B2 - Condenser microphone - Google Patents

Description

  The present invention relates to a condenser microphone in which a capacitor portion is formed by a case in which a sound hole is perforated and a diaphragm arranged along the inner surface of the case. Specifically, the microphone having a plurality of diaphragms is improved. About.

  As a condenser microphone configured as described above, Patent Document 1 is different in basic structure from the capacitor unit of the present invention in that a back electrode plate is provided. A configuration comprising a plurality of (two in the embodiment) diaphragms arranged in parallel to the axis, a back electrode plate facing the diaphragm, and transmitting a signal to the amplifier unit via a contactor connected to the back plate. It is shown.

  Patent Document 2 discloses a sound field microphone in which a capsule including a gradient pressure microphone is arranged at a position corresponding to a surface of a polyhedron, although not limited to a condenser microphone.

Japanese Patent Laid-Open No. 2004-40584 Japanese Patent Laid-Open No. 2007-6458

  An omnidirectional microphone may be required to detect sound with high sensitivity regardless of the input direction of acoustic vibration. The microphone is preferably small.

  From such a necessity, it is also conceivable to arrange a plurality of diaphragms disclosed in Patent Document 1 at positions corresponding to the surface of the polyhedron as in Patent Document 2. However, those that require a back electrode plate such as those described in Patent Document 1 hinder downsizing.

  An object of the present invention is to rationally configure a microphone that senses acoustic vibrations from any input direction with high sensitivity.

A feature of the present invention is a condenser microphone in which a capacitor portion is formed by a case in which a sound hole is drilled and a diaphragm arranged along the inner surface of the case.
The case is configured as a metal capsule having a five-sided wall having a shape obtained by removing one side from a hexahedron, and an open portion . the diaphragm is disposed along the inner surface of each form the inner surface of the wall of the respective plurality of said capacitor section by forming an electret layer on at least one of said vibrating plate opposite thereto, An output unit that extracts the change in capacitance of the plurality of capacitor units as an electrical signal is provided .
The wall body includes a base portion that forms the case, and a bulging portion that protrudes outward from the base portion at a portion where the sound hole is formed, and the diaphragm is a diaphragm unit. The capacitor part is configured by making the diaphragm and the bulging part face each other by contacting the frame with the base part.
The output part is composed of a substrate that is fitted and fixed to the open part,
In a state where the diaphragm unit is inserted into the case from the open part, a contact terminal that is electrically connected to the diaphragm of the diaphragm unit is formed at an end of the frame corresponding to the open part,
An input electrode that contacts the contact terminal in a state where the substrate is fitted and fixed in the open portion is formed on the substrate .

  According to this configuration, even in a situation where acoustic vibrations act from any one of three directions orthogonal to each other, it is possible to acquire sound with any diaphragm. In addition, when an acoustic signal is transmitted to the microphone in this way, it is normal that both diaphragms vibrate due to the acoustic vibration acting on each diaphragm. From the vibrations of the plurality of diaphragms, These signals can also be taken out from the output unit as an electric signal. Further, since the electret type capacitor portion is constituted by the wall body and the diaphragm on the inner surface, the back electrode plate is not provided, and the increase in the number of components can be suppressed and the size can be reduced. As a result, the microphone that senses acoustic vibration from any input direction with high sensitivity has been made compact.

In addition , by arranging the diaphragm unit so that the frame of the diaphragm unit is in contact with the base part of the case, a gap can be formed between the diaphragm and the wall body without providing a spacer, thereby realizing further miniaturization. To do.

Furthermore , when the diaphragm unit is inserted into the case and the substrate is fitted and fixed in the open part, the contact terminal at the end of the frame of the diaphragm unit comes into contact with the input electrode of the substrate, so that the vibration of the diaphragm It is possible to transmit the change in the electrostatic capacity due to this to the substrate and to extract it as an electrical signal on this substrate. This makes it possible to assemble the microphone without requiring a special process such as connecting wiring. In addition, it is possible to configure with higher sensitivity by taking in the acoustic vibration from the direction corresponding to the five surfaces of the capsule-like case.

  In the present invention, a separator for isolating the spaces behind the five diaphragms may be provided inside the case.

  According to this, a phenomenon in which the vibration of the diaphragm affects other diaphragms through the air in the case can be suppressed, and high sensitivity can be maintained.

  In the present invention, the output unit may include a single impedance conversion unit that converts a change in capacitance of the plurality of capacitor units into a voltage signal and outputs the voltage signal.

  According to this, the change in the capacitance of the plurality of capacitor portions is converted into a voltage signal by a single impedance conversion means and output, and the structure is simplified by suppressing an increase in the number of components. .

  In the present invention, the output unit may include impedance conversion means as many as the number of capacitor units so that the change in capacitance of the plurality of capacitor units is converted into a voltage signal and output.

  According to this, the conversion of the capacitance of each capacitor unit is converted into a voltage signal by the impedance conversion unit corresponding to each capacitor unit, and for example, the gain of each impedance conversion unit is set to each capacitor. By adjusting according to the portion, it is possible to eliminate variation in the capacitance of each capacitor portion.

It is a general view which shows the whole microphone. It is a disassembled perspective view of a microphone. It is the longitudinal cross-sectional view and enlarged sectional view of a microphone. It is a cross-sectional view of a microphone. It is a perspective view which shows the structure of a diaphragm unit. It is the top view and bottom view of a board | substrate. Perspective view of substrate and diaphragm unit It is an electric circuit diagram of a microphone. It is an electric circuit diagram of different embodiment of a microphone.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1 and FIG. 2, a case A in which a five-sided wall Aw having a shape obtained by removing one side from a hexahedron that is a regular cube is integrally formed, and each wall is formed inside the case A. A polyhedral condenser microphone (hereinafter referred to as a microphone) including five diaphragm units B provided to face Aw, a separator C that divides the internal space of the case A, and an output unit D that closes an open portion of the case A. For short). Although this microphone can be used in any posture, the following description will be made with the upper side of the drawing as the upper side and the lower side of the drawing as the lower side (bottom) according to the posture shown in FIG.

  This microphone is configured as a front electret type in which an electret layer E is formed on the inner surface of the case A, and changes in the capacitance of the capacitor portion caused by the vibrations of the five diaphragms 6 corresponding to the five-walled body Aw. It is converted into an electrical signal (voltage signal) by an output chip 27 (an example of impedance conversion means) such as an FET provided in the output unit D and output.

  In addition, this microphone may be configured as a foil electret type in which an electret layer E is formed on the diaphragm 6, and the acoustic frequency to be acquired includes a low frequency range exceeding the human audible range and an ultrasonic range. It may be a thing.

〔Case〕
As shown in FIGS. 1 to 5, the case A is configured in a capsule shape in which five wall bodies Aw are integrated by drawing a metal material made of a good conductor such as aluminum or copper alloy. Each wall Aw is composed of a flat base portion 1 that determines the shape of the case A, and a bulging portion 3 that protrudes outwardly from a portion where the sound hole 2 is formed, and is formed on the inner surface of each wall Aw. The electret layer E in which the electric polarization state is maintained is formed. The bulging portion 3 is parallel to the base portion 1, and the protruding amounts of the plurality of bulging portions 3 are set equal.

  The electret layer E forms SiO2 (silicon oxide film) on the inner surface of the case A by a technique such as sputtering, vapor deposition, or plasma CVD (Chemical Vapor Deposition), and corona polarization is applied to the SiO2 film. Or formed by a charging process by an electron beam polarization method.

  In addition, the electret layer E can be formed using a polymer film. Specifically, a polymer film such as FEP (Fluoro Ethylene Propylene) is superposed on a plate-like metal material and heat-pressed to form a polymer film. Thereafter, the above-described five-walled body Aw is integrally formed by drawing, and further, the sound hole 2 and the bulging portion 3 are formed. Thereafter, the electret layer E can be formed on the inner surface of the case A by subjecting the polymer film on the inner surface of the case A to electron beam polarization or polarization by corona discharge.

(Diaphragm unit)
The diaphragm unit B has a flat frame 5 formed of an insulating resin material having a size equal to the inner surface size of the wall Aw of the case A, and an opening 5A formed in the frame 5 in a tension state without slack. And a diaphragm 6 made of conductive metal foil. As shown in FIG. 5, each of the five diaphragm units B has a structure in which the frame 5 of another diaphragm unit B is foldably connected to the four sides of the frame 5 of the diaphragm unit B corresponding to the bottom. doing.

  Each frame 5 is formed with a wiring 7 electrically connected to the diaphragm 6 by a printed wiring technique. In the diaphragm unit B around the diaphragm unit B corresponding to the bottom, the wiring 7 is formed in a direction away from the diaphragm unit B at the bottom, and is electrically connected to the contact terminal 8 at the frame end. ing. In addition, the wiring 7 conducting to the diaphragm 6 of the diaphragm unit B corresponding to the bottom is connected to a dedicated contact terminal 8 formed at one frame end of the four diaphragm units B connected to the diaphragm unit B. Connected.

  With such a structure, the four diaphragm units B are bent at right angles with respect to the diaphragm unit B at the bottom, so that the attitudes of the five diaphragm units B correspond to the five wall bodies Aw of the case A. Thus, it can be accommodated in the case A.

  The diaphragm 6 is not necessarily formed of a metal foil. For example, a conductive film such as a metal material may be formed on the surface of a film made of a polymer resin material by a technique such as vacuum deposition.

  Although not shown in the drawings, when the condenser microphone of the present invention is configured in the above-described foil electret type, the electret layer E is formed on the diaphragm 6 by the above-described process such as plasma CVD.

[Separator]
The separator C has a top wall 11 and a bottom wall 12 that are square in a plan view, and has a structure in which a plurality of vertical walls 13 at intermediate positions thereof are integrally formed of an insulating resin. A concave housing space 11A for housing the output chip 27 is formed in the upper wall 11, and a concave back space 12A for securing a space behind the diaphragm 6 of the lower diaphragm unit B is formed in the bottom wall 12. Is formed.

  The separator C has a function of isolating the back space of the five diaphragms 6 so that the vibrations of the five diaphragms 6 do not interfere with each other, and each suppresses transmission of acoustic vibrations. A small-diameter through hole 14 is formed so as to allow air flow.

  The separator C contacts the five diaphragm units B to push the five diaphragm units B in the direction of the corresponding wall body Aw, and the frame 5 of each diaphragm unit B is placed on the base portion 1 of the wall body Aw. It also has the function of contacting the inner surface.

[Output section]
As shown in FIGS. 6 and 7, the output portion D includes an insulating substrate 20 such as glass epoxy, and two output electrodes 21 are formed on the upper surface side (outer surface side). An external ground electrode 22 electrically connected to the ground side is formed on the upper surface side. On the inner surface side (bottom surface side) of the substrate 20, five input electrodes 23 that are in contact with the contact terminals 8 described above, a common electrode 24 that electrically connects these input electrodes 23, and the above-described external ground electrode 22 An internal ground electrode 25 electrically connected through the through hole T, and an output electrode 21 on the power source side (non-ground side) and an intermediate electrode 26 electrically connected through the through hole T are formed.

  The output electrode 21, the external ground electrode 22, the input electrode 23, the common electrode 24, the internal ground electrode 25, and the intermediate electrode 26 are made of a good conductor such as a copper foil. 20 on both sides.

  An output chip 27 (an example of impedance conversion means) is provided on the inner surface side of the substrate 20, and the three terminals of the output chip 27 are electrically connected to the common electrode 24, the internal ground electrode 25, and the intermediate electrode 26 described above using solder or the like. Connected. The substrate 20 is formed with a small-diameter through hole 28 that allows air to flow between the internal space of the case A.

〔assembly〕
In this way, the case A, the diaphragm unit B, the separator C, and the output part D are configured, so that five cases are formed inside the case A from the open part of the case A in which the electret layer E is formed on the inner surface. The diaphragm unit B is inserted, and the separator C is inserted. By this insertion, the frame 5 of the diaphragm unit B is in a positional relationship between the separator C and the wall Aw of the case A, and the frame 5 of the diaphragm unit B is in close contact with the base portion 1 of the wall Aw. A gap is formed between 6 and the bulging portion 3, and the diaphragm 6 and the bulging portion 3 constitute a capacitor portion. Thereafter, the output part D on which the output chip 27 is formed is fitted from the open part of the case A, and the open part of the case A is crimped to complete the assembly of the microphone.

  By crimping the open portion of the case A, the end surface of the open portion of the case A is brought into electrical contact with the external ground electrode 22 of the substrate 20, and the input electrode 23 of the substrate 20 is connected to the contact terminal 8 of the frame 5. Conduction is made by press-contacting. As a result, the electrical system is connected without providing a step of connecting the case A and the external ground electrode 22 or the contact terminal 8 and the input electrode 23 using the wiring.

  The electric circuit of this microphone is shown in FIG. As can be understood from this electric circuit diagram, the change in the capacitance of the parts (capacitor portions) of the five diaphragms 6 can be converted into an electric signal by one output chip 27 and output from the output electrode 21.

  In this microphone, when the acoustic vibration is acquired by the microphone, the acoustic vibration acts on each diaphragm 6 approximately equally, and the capacitance of each capacitor portion changes approximately equally, and the output chip 27 is synthesized. The change in capacitance is converted into a voltage signal. Thereby, the performance which acquires acoustic vibration with very wide directivity and high sensitivity is obtained.

  In particular, as a different embodiment of the microphone of the present invention, instead of the substrate 20 having one output chip 27, the substrate 20 having five output chips 27 corresponding to the five diaphragms 6 may be used. FIG. 9 shows an electric circuit of the microphone having the five output chips 27 for the five diaphragms 6 in this way. In this case, since the five output chips 27 that convert the change in capacitance into voltage signals are provided from the contact terminals 8 electrically connected to the five diaphragms 6, the gain is set to be exceptional in each output chip 27. It is also possible to cope with variations in sensitivity of the five diaphragms 6.

  As described above, the microphone of the present invention accommodates the five diaphragm units B having the five diaphragms 6 inside from the open part of the single case A, and the separator is formed in the space surrounded by the diaphragm units B. C can be accommodated, and furthermore, the output part D can be accommodated in the open part of the case A, and the crimping can be performed in such a manner that the end part of the open part of the case A is bent inward. .

  Further, by forming the bulging portion 3 in the case A, a capacitor portion can be configured by forming a gap between the bulging portion 3 and the diaphragm 6 without providing a spacer or the like. Further, a contact terminal 8 that is electrically connected to the diaphragm 6 via the wiring 7 is formed in the diaphragm unit B, and an input electrode 23 that is connected to the contact terminal 8 is formed on the substrate 20 constituting the output portion D. Thus, when the substrate 20 is fitted into the open portion of the case A and fixed by caulking, the contact terminal 8 and the input electrode 23 reach a conductive state, and assembly is easily realized.

  Acoustic vibration from the outside is transmitted from the sound hole 2 to the inside of the bulging portion 3 of the case A to vibrate the diaphragm 6. In particular, since the five diaphragms 6 are arranged at close positions, when the acoustic vibration is transmitted, the five diaphragms 6 are vibrated substantially equally, and the output part D has five capacitor parts. It is possible to output a combined (combined) change in capacitance as a voltage signal and to function with high sensitivity.

  Further, since the electret layer E is formed on the inner surface of the case A or the diaphragm 6, it is not necessary to provide a back electrode plate, and not only a reduction in the number of components but also a reduction in the size of the entire microphone is realized. .

[Another embodiment]
The present invention may be configured as follows in addition to the embodiment described above.

(A) Different sizes of the plurality of diaphragms.
Thus, by varying the size of the diaphragm, the resonance frequency of each diaphragm is varied, and high sensitivity can be obtained in a wide frequency band.

(B) A microphone is configured without using a separator.
Thus, when a separator is not used, the number of parts can be reduced, and cost reduction and weight reduction are realized.

(C) The case is not a cube like a rectangular parallelepiped but a prism.
By adopting such a structure, for example, a microphone can be provided at the end of a rod-like case.

(D) The number of diaphragms is set to three or four.
That is, the microphone is configured by including a diaphragm corresponding to only three surfaces of a corner of the case such as a rectangular parallelepiped, or including a diaphragm corresponding to only four surfaces surrounding the case among cases such as a rectangular parallelepiped. It becomes possible.

(E) A conductive metal is used for the frame on which the diaphragm is stretched.
In the embodiment, the wiring is formed on the resin frame. However, when there is one output chip as the impedance converting means, the frame is formed of a conductive metal, and a plurality of diaphragms and outputs are formed. The chip can be electrically connected, and no special wiring is required.

  The present invention can be used as a microphone having a wide directivity.

DESCRIPTION OF SYMBOLS 1 Base part 2 Sound hole 3 Swelling part 5 Frame 6 Diaphragm 8 Contact terminal 23 Input electrode 27 Output part and impedance conversion means (output chip)
A Case Aw Wall B Diaphragm unit C Separator D Output part E Electret layer

Claims (4)

A condenser microphone in which a capacitor portion is formed by a case in which a sound hole is drilled and a diaphragm arranged along the inner surface of the case,
The case is configured as a metal capsule having a five-sided wall having a shape obtained by removing one side from a hexahedron, and an open portion . the diaphragm is disposed along the inner surface of each form the inner surface of the wall of the respective plurality of the capacitor portion by forming an electret layer on at least one of said vibrating plate opposite thereto, An output unit that extracts the change in capacitance of the plurality of capacitor units as an electrical signal is provided .
The wall body includes a base portion that forms the case, and a bulging portion that protrudes outward from the base portion at a portion where the sound hole is formed, and the diaphragm is a diaphragm unit. The capacitor part is configured by making the diaphragm and the bulging part face each other by contacting the frame with the base part.
The output part is composed of a substrate that is fitted and fixed to the open part,
In a state where the diaphragm unit is inserted into the case from the open part, a contact terminal that is electrically connected to the diaphragm of the diaphragm unit is formed at an end of the frame corresponding to the open part,
A condenser microphone in which an input electrode that contacts the contact terminal in a state where the substrate is fitted and fixed in the open portion is formed on the substrate . Inside, five condenser microphone according to claim 1, wherein the separator isolates the space between the rear side are provided in the vibration plate of the case. The output unit, the condenser microphone according to claim 1 or 2 comprises a single impedance converting means for converting a change in capacitance of a plurality of the capacitor section to a voltage signal. The output unit, according to claim 1 or 2 and a same number of impedance conversion means of the capacitor portion so as to converts the change in the capacitance of the plurality of the capacitor section to exceptionally voltage signal Condenser microphone.

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