JP2006014267A - Directional condenser microphone with improved directivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a directional capacitor microphone with improved directional characteristics so as to enhance the directional characteristics, while reducing the number of parts of the capacitor microphone, minimizing its thickness, and simplifying its assembly process. <P>SOLUTION: There are provided with a support structure 20 to be positioned at an upper step of a fixed electrode 17 and to insulate the fixed electrode 17 and a metal case 11; and a FET to be positioned between the most upper step in the metal case 11 and the support structure 20, to be connected to the metal case 11 and the support structure 20 electrically and to amplify and convert a potential change by the change in the capacitance due to the vibration of a vibrating plate 103 between the vibration plate 103 and the fixed electrode 17 into a electrical signal. A printing circuit substrate 25 punched by a plurality of acoustic wave inflow holes 26 is included, the transfer of the acoustic wave to flow in the acoustic wave inflow holes 26 of the printed-circuit board 25 is delayed, and the fixed electrode 17 is electrically connected to the gate of the FET formed on the printed circuit board 25. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a directional capacitor microphone having improved directivity characteristics, and in particular, insulation between a metal case and a fixed electrode, and electrical connection between the fixed electrode and a field effect transistor (hereinafter referred to as an FET) of a printed circuit board. The thickness of the support is reduced by forming the support, which plays a role of general connection and time delay of sound wave transmission, after being vacuum-deposited on the surface of the support so that it is insulated from the metal case. The present invention relates to a directional condenser microphone with improved directional characteristics that can improve the directional characteristics of a condenser microphone while minimizing the above and simplifying the assembly process.

  In general, a condenser microphone is a microphone that uses the capacitance change of a parallel plate capacitor, and one side is provided with a fixed electrode, and the other side is provided with a conductive diaphragm as an electrode so as to face the fixed electrode. A high DC voltage is applied between these electrodes through a resistance of several tens of KΩ. Thereby, the change in the capacitance between both electrodes due to the change in the electrode interval due to the sound pressure is obtained as an audio signal which is an electrical signal.

  The frequency characteristics of condenser microphones are almost flat up to about 30 kHz, and the output is small. In recent years, including condensers for measurement and broadcasting, they have been widely applied to mobile communication terminals such as mobile phones and PDAs. The operation theory and principle of such a condenser microphone will be explained. The internal components of the condenser microphone are very precise and sensitive to external electric noise. In order to sufficiently protect the substrate, it is laminated and sealed in a metal case in which a sonic inlet is formed.

  When a sound wave is applied to the film metal diaphragm through the sound wave inlet, if the diaphragm vibrates, the distance between the diaphragm and the fixed electrode is changed by the sound wave. The change in capacitance can be grasped by electrically converting.

  Normally, a condenser microphone has a small capacitance and high electrical impedance, so it cannot be used directly connected to a general amplifier. Therefore, in order to match the input impedance required by the amplifier, it is combined with an FET, which is an impedance conversion element. It is common to use.

  Here, the FET is an active element composed of three terminals of a source, a gate, and a drain. However, since the value of a current flowing between the drain and the source changes as the gate potential changes, ECMs (Electrostatic Condenser). The basic operation circuit of the Microphone system is configured to obtain an electrical signal by sound waves.

  Capacitor microphones require a DC external power supply of several hundred volts (V) as the positive voltage, but ECMs are a kind of nonpolar capacitor microphones that deposit metal on polymer films with excellent charge storage characteristics. In this case, the external power supply is omitted by using it as a diaphragm or by adhering a polymer film to a fixed electrode to accumulate charges.

  Capacitor microphones can be used by attaching them to microphones, corded / cordless telephones, video cassette recorders, digital cameras, etc. Generally speaking, there are cases where the sound wave inlet is perforated and acoustic waves located above the case. A filter that prevents dust, moisture, or foreign matter from flowing into the case through the inflow port, and the inside of the case to induce vibration of the sound that is located inside the case and flows through the sound wave inflow port A diaphragm plate for maintaining a space, a vibration plate that is located at the lower stage of the diaphragm plate and vibrates due to the sound that has flowed in through the sound wave inlet, and a vibration plate that is located at the lower stage of the diaphragm and transmits the vibration of the sound A spacer that maintains a constant interval, a support that is located at the lower stage of the spacer, prevents flow of each part, and prevents deformation of the entire shape, and the inside of the support A fixed electrode that detects a capacitance that is changed by vibration of the diaphragm while maintaining a vacuum state while maintaining a certain distance from the diaphragm by the spacer, and is located inside the support and below the fixed electrode. A coupling ring that connects the gate of the matching FET and the fixed electrode, a printed circuit board on which a circuit is wired with a conductive material, and a potential change caused by a change in capacitance by being bonded on the printed circuit board. It comprises FETs that amplify and convert electrical signals.

  1 and 2 are diagrams showing a conventional condenser microphone. The condenser microphone is provided in a metal case 101 with a diaphragm plate 102, a diaphragm 103, a spacer 104, a fixed electrode 105, a filter 106, a support 107, a connecting ring 108, and The printed circuit board 109 and the like are built in. In particular, the condenser microphone shown in FIGS. 1 and 2 has a plurality of sound wave inlets formed in the printed circuit board 109, and a filter 106 is incorporated between the fixed electrode 105 and the printed circuit board 109 so as to flow from the front. It has a directional characteristic that reacts more sensitively to sound waves.

  However, since the condenser microphone described above is provided with a support and a coupling ring to insulate the metal case from the fixed electrode and electrically connect the fixed electrode and the printed circuit board, the number of components increases. Since there is a characteristic as shown in FIG. 3 that delays the sound wave that flows in from the rear through the sound wave inlet of the printed circuit board, it is generated in the rear and then flows forward, that is, through the sound wave inlet of the metal case. Cannot cancel out sound waves more efficiently.

  Typically, a unidirectional condenser microphone is sensitive to sound collection in one particular direction and is relatively insensitive to sound in other directions, although it is a prior art diagram. Referring to FIG. 3 and FIG. 4, there arises a problem that such directivity cannot be maintained due to a change in frequency. More specifically, FIGS. 3 and 4 are graphs showing the characteristics of a directional condenser microphone marketed in Japan and a directional condenser microphone marketed in Korea, respectively. The graph on the upper side shows the volume level measured in decibels (dB) in front of the microphone (0 °) by the change in frequency, and the graph on the lower side shows the rear of the microphone (180 °). The volume of sound measured by the change in frequency is expressed in decibels. As can be seen from the respective graphs, it can be seen that the fluctuation of the volume measured in front of the microphone greatly varies due to the change in frequency. Accordingly, the directivity characteristic in one direction is not good due to the change in frequency.

  In addition, since the sound wave flowing through the sound wave inlet of the printed circuit board is not uniformly filtered for the distance between the printed circuit board and the diaphragm and the entire frequency band, it is uniform for the entire frequency band of the sound wave. Therefore, it is not possible to obtain good directivity characteristics of the condenser microphone from which sound waves generated behind the condenser microphone are completely removed.

  Therefore, the present invention has been made to solve such a conventional problem, and its purpose is to reduce the number of components of the condenser microphone, minimize the thickness, simplify the assembly process, and simplify the assembly process. An object of the present invention is to provide a directional condenser microphone with improved directional characteristics that can be improved.

  Another object of the present invention is to generate a sound wave behind the condenser microphone by delaying the sound wave transmitted to the diaphragm via the sound wave inlet of the printed circuit board with respect to the entire frequency band. An object of the present invention is to provide a directional condenser microphone with improved directivity characteristics that can cancel sound waves transmitted to a diaphragm via a sound wave inlet of a metal case.

  In order to achieve the above object, the directional condenser microphone with improved directivity according to the present invention has a sound wave inlet at the center of the lowermost stage, and the inner end is bent at the end of the uppermost stage. A container-shaped metal case for fixing an element, and a space formed in the metal case so as to be able to induce vibration by a sound wave that is located at the lowermost stage inside the metal case and flows through the sound wave inlet. A diaphragm plate to be moved, and a film-like metal electrode plate which is located on the upper stage of the diaphragm plate and vibrates by a sound wave flowing in through the sound wave inlet and in which electric charges are accumulated. The diaphragm plate It consists of a diaphragm to which the outer shell is fixed, and a metal material that is located above the diaphragm and has a film on which charges are accumulated on the surface facing the diaphragm. A fixed electrode that maintains a gap at a predetermined distance from the diaphragm with a spacer interposed therebetween to support the vibration of the diaphragm, and is positioned above the fixed electrode, A support that insulates the metal case, and is located between the uppermost stage in the metal case and the support, and is electrically connected to the metal case and the support, and is caused by vibration of the diaphragm. And a printed circuit board on which a FET for amplifying and converting a potential change due to a change in capacitance between the diaphragm and the fixed electrode into an electric signal is mounted and a plurality of sound wave inlets are perforated. The transmission of the sound wave flowing into the sound wave inlet of the printed circuit board is delayed, and the fixed electrode is electrically connected to the gate of the FET formed on the printed circuit board.

  According to the present invention, it is possible to reduce the number of components of the condenser microphone, minimize the thickness, and improve the directivity while simplifying the assembly process.

  In addition, the present invention provides a metal case that is generated behind the condenser microphone and forwards by delaying the sound wave transmitted to the diaphragm via the sound wave inlet of the printed circuit board with respect to the entire frequency band. It is possible to effectively cancel the sound waves transmitted to the diaphragm via the sound wave inlet.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  5 and 6 are diagrams showing a directional condenser microphone according to the present invention. The metal case 11 made of a conductive material and having a container shape has a sound wave generated at the front and a sound wave generated at the rear in the center of the lowermost stage. A sonic inlet 12 that can be introduced is perforated. The metal case 11 accommodates a diaphragm plate 14 and a diaphragm 15, which constitute a condenser microphone, a fixed electrode 17, a filter 19, a support 20, and a printed circuit board 25, and is attached to one side of the diaphragm 15. It also serves to electrically connect the plate 14 to the FET of the printed circuit board 25. That is, the upper stage 13 of the metal case 11 is bent inward while the diaphragm plate 14, the diaphragm 15, the fixed electrode 17, the filter 19, the support 20, the printed circuit board 25, and the like are received in the metal case 11. The various components located in the metal case 11 do not move.

  A filter such as a non-woven fabric 10 that blocks the sound wave inlet 12 is attached to the lower surface of the metal case 11 to prevent various foreign matters generated from flowing into the case 11. Has no effect.

  The diaphragm plate 14 and the diaphragm 15 stacked at the lowest level in the metal case 11 maintain a flat state without wrinkles despite the assembly process of the diaphragm 15 and the vibration of the diaphragm 15. In addition, the diaphragm plate 14 and the diaphragm 15 are assembled with the diaphragm 15 attached to the diaphragm plate 14 in order to facilitate the assembly process of the diaphragm plate 14 and the diaphragm 15.

  The diaphragm plate 14 is a plate material processed into a donut shape, and the diaphragm 15 is electrically connected to the metal case 11, and the diaphragm is made of sound waves that are introduced through the sound wave inlet 12 of the metal case 11. A space is formed inside the metal case 11 so that 15 vibrations can be induced. As described above, since the diaphragm 15 is attached to the upper surface of the diaphragm plate 14, the diaphragm plate 14 serves to fix the outline of the diaphragm 15, and the diaphragm 15 is not distorted and is in a flat state. Can be maintained.

  The diaphragm 15 attached to the upper surface of the diaphragm plate 14 is a film-like metal electrode plate in which electric charges are accumulated on the entire surface, and maintains a predetermined separation distance from the fixed electrode 17 with a spacer 16 in between. Then, it vibrates due to the sound wave that flows through the sound wave inlet 12 of the metal case 11. That is, since the distance between the diaphragm 15 and the fixed electrode 17 is changed by the vibration of the diaphragm 15 due to the sound wave that flows through the sound wave inlet 12, the vibration plate 15 and the fixed electrode 17 are changed according to the sound wave. The potential formed between them changes.

  A donut-shaped spacer 16 made of an insulating material is located on the upper stage of the diaphragm 15, and this spacer 16 electrically insulates the diaphragm 15 and the fixed electrode 17, and also connects the diaphragm 15 and the fixed electrode 17. The gap is maintained, and the diaphragm 15 is vibrated by the sound wave that flows through the sound wave inlet 12 of the metal case 11.

  The fixed electrode 17 of another electrode corresponding to the diaphragm 15 which is one electrode is made of a metal material to which a film in which charges are accumulated is attached to the surface facing the diaphragm 15, and this fixed electrode 17 is fixed. The electrode 17 has a plurality of through holes 18 for providing a path through which sound waves and air flow, and maintains a gap at a constant interval from the diaphragm 15 with the spacer 16 interposed therebetween.

  When stacked on the fixed electrode 17, the support 20 stacked with the fixed electrode 17 in the center is a molded product made of an insulating material, and transmits sound waves at a certain distance from the center. A plurality of through-holes 21 are formed, and projecting portions 22a and 22b having a certain height are formed on the outer shell, and nickel 27 is vacuum-deposited on the upper and lower surfaces and the through-holes 21 of the molded product. The upper and lower surfaces of the molded product are electrically connected to each other.

  Of course, the nickel 27 vacuum-deposited on the surface of the support 20 for electrical connection can be treated not only by the vacuum deposition method but also by other methods, and the surface of the support 20 is not only nickel but also electrically Other materials that can be easily connected may be used for processing.

  The support 20 is formed by vacuum-depositing nickel 27 on the entire surface of the molded product that forms the framework of the support 20, and then vacuum-depositing nickel 27 on the side surface 24 of the molded product and the corners 23 a and 23 b of the upper and lower surfaces. It is removed by a cutting method so that the fixed electrode 17 is not electrically connected to the metal case 11 through the nickel 27.

  That is, the nickel 27 vacuum-deposited on the surface of the support 20 forms one loop that electrically connects the fixed electrode 17 and the printed circuit board 25, but the fixed electrode 17 and the metal case 11 are electrically connected. It also serves to prevent connection to the.

  The support 20 is positioned in the upper stage of the spacer 16 in a state where the fixed electrode 17 is incorporated, insulates the fixed electrode 17 and the metal case 11, and enters the sound wave flowing through the sound wave inlet 26 of the printed circuit board 25. The fixed electrode 17 is electrically connected to the gate of the FET formed on the printed circuit board 25.

  In particular, since a filter 19 having a predetermined thickness is built in between the fixed electrode 17 and the support 20, sound waves transmitted to the diaphragm 15 via the sound wave inlet 26 of the printed circuit board 25 are transmitted with a delay. Is done.

  Finally, the printed circuit board 25 stacked on the uppermost layer in the metal case 11 is electrically connected to the metal case 11 and the support 20 by being stacked in the metal case 11. An FET for amplifying and converting a potential change due to a change in capacitance between the diaphragm 15 and the fixed electrode 17 due to vibration of the diaphragm 15 into an electric signal is soldered. The printed circuit board 25 is provided with a plurality of sound wave inlets 26 so that sound waves generated behind the condenser microphone can be transmitted to the diaphragm 15.

  A process in which the condenser microphone configured as described above collects sounds generated in the front while canceling out the sounds generated in the rear will be described with reference to FIG.

  First, sound waves generated in front of the condenser microphone are immediately transmitted to the vibration plate 15 via the sound wave inlet 12 of the metal case 11, and the vibration plate 15 is vibrated by the sound waves generated in front.

  In addition, sound waves generated behind the condenser microphone travel around the outer case of the metal case 11 and are transmitted to the diaphragm 15 via the sound wave inlet 12 of the metal case 11, and sound waves generated behind the capacitor microphone 11 are transmitted to the printed circuit board 25. Is transmitted to the diaphragm 15 through the sonic inlet 26 through the through hole 21 of the support 20, the filter 19, the through hole 18 of the fixed electrode 17 and the like in a time-delayed state.

  That is, the sound wave generated behind the condenser microphone normally flows into the diaphragm 15 via the sound wave inlet 12, but is formed on the support 20 via the sound wave inlet 26 of the printed circuit board 25. The transmission time is delayed by the through hole 21 and the filter 19.

  Therefore, the sound wave that has flowed in through the front sound wave inlet 12 is canceled out by the sound wave that has flowed in through the rear sound wave inlet 26, and the sound wave that is generated behind vibrates the diaphragm 15. Therefore, the diaphragm 15 is vibrated by the sound wave generated in the front.

  In particular, the through-hole 21 of the support 20 and the filter 19 add a time delay to the entire frequency band of the sound wave that flows through the sound wave inlet 26, so that the characteristics for each frequency band as shown in FIG. Can be obtained. Here, the delay time of the sound wave and the frequency band that is time-delayed can be adjusted using the depth, diameter, distance between the components, and the like of the through-hole 21.

  Referring to FIG. 8 in more detail, of the two graphs in the drawing, the upper graph shows the volume level measured in decibels (dB) measured according to the frequency change in front of the microphone (0 °). In the lower graph, the volume measured in response to the change in frequency behind the microphone (180 °) is expressed in decibels. As can be seen from FIG. 8, it can be seen that there is almost no variation in the volume of the sound measured in front of the microphone in accordance with the change in the frequency, and that the sound volume is uniform. Therefore, it can be seen that the directivity characteristic with respect to one direction is better than that of the prior art in accordance with the change in frequency.

  The present invention relates to a microphone that is attached to an audio device used at home, various broadcasting devices and recording devices, a digital camera, a mobile communication terminal, etc., and collects voice and sound, etc. In addition, it is useful for upsizing, thinning, etc., and is useful for making microphones for special purposes.

FIG. 6 is a cutaway perspective view showing a conventional condenser microphone. Sectional drawing which shows the conventional condenser microphone. The figure which shows the directional characteristic of the conventional condenser microphone. The figure which shows the directional characteristic of the conventional condenser microphone. 1 is a cutaway perspective view showing a condenser microphone according to an embodiment of the present invention. The disassembled perspective view which shows the condenser microphone by one Embodiment of this invention. 1 is a cross-sectional view showing a condenser microphone according to an embodiment of the present invention. The figure which shows the directional characteristic of the capacitor | condenser microphone by one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Nonwoven fabric, 11 ... Metal case, 12, 26 ... Sonic inlet, 13 ... Upper stage, 14 ... Diaphragm plate, 15 ... Diaphragm, 16 ... Spacer, 17 ... Fixed electrode, 18, 21 ... Through-hole, 19 ... Filter , 20 ... support, 22a, 22b ... protrusion, 23a, 23b ... corner, 24 ... side, 25 ... printed circuit board, 27 ... nickel.

Claims (5)

A sonic inlet is perforated in the center of the lowermost stage, and a container-like metal case in which the end of the uppermost stage is bent inward to fix the internal components,
A diaphragm plate that is located in the lowermost stage inside the metal case and forms a space in the metal case so that vibrations can be induced by the sound wave that flows in through the sound wave inlet;
It is located at the upper stage of the diaphragm plate, and is composed of a film-like metal electrode plate that is vibrated by sound waves that flow in through the sound wave inlet, and the entire surface of which is accumulated, and its outer shell is fixed by the diaphragm plate. A diaphragm,
In order to support vibration of the diaphragm, which is made of a metal material that is located on the diaphragm and has a film on which charges are accumulated on the surface facing the diaphragm, and a plurality of through holes are perforated. A fixed electrode that maintains a gap between the diaphragm and the diaphragm with a spacer in between,
A support located above the fixed electrode, for insulating the fixed electrode and the metal case;
Located between the uppermost stage in the metal case and the support, and electrically connected to the metal case and the support, between the diaphragm and the fixed electrode due to vibration of the diaphragm An FET for amplifying and converting a potential change due to a change in capacitance into an electrical signal, and a printed circuit board having a plurality of sonic inlets perforated,
A directional condenser microphone characterized in that transmission of sound waves flowing into a sound wave inlet of the printed circuit board is delayed and the fixed electrode is electrically connected to a gate of the FET formed on the printed circuit board. .   The support is a molded product made of an insulating material, and a plurality of through holes for delaying the transmission of sound waves are formed. 2. The directional condenser microphone according to claim 1, wherein nickel is vacuum-deposited on the upper and lower surfaces and the through hole, and the upper and lower surfaces of the molded product are electrically connected to each other.   3. The support according to claim 2, wherein after the nickel is vacuum-deposited on the entire surface of the molded product, the vacuum-deposited nickel is cut on the outer side of the side surface and the upper and lower surfaces of the molded product. The directional condenser microphone described.   A filter for delaying transmission of sound waves transmitted to the diaphragm via the sound wave inlet of the printed circuit board is interposed between the fixed electrode and the support. The directional condenser microphone according to claim 1.   The directional condenser microphone according to claim 1, wherein a non-woven fabric for blocking inflow of foreign substances is attached to a lower part of the lowermost stage of the metal case.

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