JP4533783B2 - Unidirectional condenser microphone unit - Google Patents

Description

  The present invention relates to a unidirectional condenser microphone unit, and more particularly to a technique for preventing noise generation due to electrostatic coupling between an external noise source and a fixed pole.

  In a condenser microphone unit, a diaphragm assembly in which a diaphragm and a fixed pole are combined to face each other via a spacer is housed in a cylindrical cartridge case. A terminal board (circuit board) on which an FET (field effect transistor) as an impedance converter is mounted is disposed in the opening, and the terminal board is fixed by crimping the rear end of the case.

  In unidirectionality, in addition to the front acoustic terminal, there is a rear acoustic terminal that allows sound waves from the sound source to act on the back side of the diaphragm, but the opening that becomes the rear acoustic terminal is pressed on the side of the cartridge case. Since the cost is high when drilling by processing or the like, at present, most of them make the opening of the rear acoustic terminal in the terminal board. A unidirectional condenser microphone unit according to the example will be described with reference to FIG.

  The unidirectional condenser microphone unit includes a cylindrical cartridge case 10 made of an aluminum material or the like having an opening 11 of a front acoustic terminal on one end side and an opening on the other end side. The diaphragm assembly 20 is stored.

  The diaphragm assembly 20 includes a diaphragm 21 stretched on a support ring (diaphragm ring) 22 with a predetermined tension, and a fixed pole 23 supported on an electrically insulating base 24. And the fixed pole 23 are arranged to face each other via a spacer (not shown).

  An electrode lead rod 26 that is electrically connected to the fixed pole 23 is provided at substantially the center of the pedestal 24. In an electret type model, the surface of the fixed pole 23 that faces the diaphragm 21 is polarized by corona discharge or the like. An electret film (not shown) to which is applied is attached.

  In addition, a terminal board (circuit board) 30 on which an FET 31 as an impedance converter is mounted is disposed in the opening on the other end side of the cartridge case 10, and the opening edge 12 of the cartridge case 10 is curled inwardly. Thus, the terminal board 30 is fixed. Due to the pressing force due to the caulking, the constituent elements of the diaphragm assembly 20 are integrally joined together without rattling, and the electrical connection between the electrode extraction rod 26 and the gate electrode of the FET 31 is ensured.

  As shown in the plan view of FIG. 6A and the cross-sectional view of FIG. 6B, the terminal plate 30 is provided with an opening 32 as a rear acoustic terminal, and sound waves entering from the opening 32 are transmitted through the diaphragm 21. Sound passage holes 24a and 23a are formed in the pedestal 24 and the fixed pole 23 so as to reach the back side of the sound source, and between the sound passage holes 24a and 23a in order to obtain predetermined frequency response characteristics. Is provided with an acoustic resistance material 25 such as a felt material.

  The opening 32 of the terminal board 30 is preferably acoustically large. However, when the opening 32 is enlarged, as shown schematically in FIG. 1, the external noise source A (for example, discharge noise of a fluorescent lamp) and the fixed electrode 23 are electrostatically coupled through the opening 32 and noise ( (Hum) may occur.

  One method for preventing this is to open a large number of small holes in the terminal board 30, but this restricts the mounting positions of lead wirings and components formed in the terminal board 30. Particularly in recent years, electronic components such as a capacitor for preventing high-frequency penetration and a Zener diode for preventing FET breakdown due to static electricity are mounted on the terminal board 30 in order to prevent generation of noise due to electromagnetic waves radiated from a mobile phone. Therefore, it is not preferable to make many small holes in the terminal board 30.

  Therefore, an object of the present invention is to provide a terminal plate in a unidirectional condenser microphone unit in which a terminal plate is fixed to the rear end portion of the cartridge case by caulking and an opening of a rear acoustic terminal is formed in the terminal plate. In the mounted electronic component, a large number of substantially small openings of the rear acoustic terminal are formed to prevent noise generation due to electrostatic coupling between the external noise source and the fixed pole.

  In order to solve the above problems, the present invention includes a cylindrical cartridge case having a front acoustic terminal on one end side and an opening on the other end side, and a diaphragm on the front acoustic terminal side in the cartridge case. And a fixed pole are arranged oppositely through a spacer, the other end of the cartridge case is closed by a terminal plate, and the terminal plate has an opening serving as a rear acoustic terminal. In the unidirectional condenser microphone unit that is formed and on which the impedance converter and the chip-type electronic component that protects the impedance converter are mounted on the terminal board, the chip-type electronic component is It arrange | positions on the said opening part so that a part of opening part may be plugged up, It is characterized by the above-mentioned.

  According to a preferred aspect of the present invention, the opening is formed as a long hole, and the chip-type electronic component is disposed on the opening leaving openings at both ends of the long hole.

  The chip-type electronic component includes a capacitor element for preventing high-frequency intrusion and a Zener diode element for preventing electrostatic breakdown, and the capacitor element and the Zener diode element are connected in parallel, and the ground terminal of the audio signal output unit And the signal hot side terminal and between the ground terminal and the signal cold side terminal.

  According to the present invention, by arranging the chip-type electronic component so as to block a part of the opening of the rear acoustic terminal formed on the terminal board, the opening becomes small, and the small opening becomes the chip-type electronic component. Therefore, it is possible to prevent generation of noise due to electrostatic coupling between the external noise source and the fixed pole. Further, restrictions on the arrangement of the chip-type electronic components are eased, and the degree of freedom in designing the terminal board is increased.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 4, but the present invention is not limited to this. FIG. 1 is a sectional view showing the internal structure of a unidirectional condenser microphone unit according to the present invention, FIG. 2 is a plan view showing a state of a terminal board before component mounting, and FIGS. FIG. 4 is a circuit diagram showing a connection state of parts for protecting the FET. Note that the same reference numerals are used for components that may be considered the same as or the same as those of the conventional example of FIG. 5 described above.

  As shown in FIG. 1, this unidirectional condenser microphone unit has a cylindrical cartridge case 10 made of, for example, an aluminum material having an opening 11 of a front acoustic terminal on one end side and an opening on the other end side. The diaphragm assembly 20 is housed in the cartridge case 10.

  The diaphragm assembly 20 includes a diaphragm 21 stretched on a support ring (diaphragm ring) 22 with a predetermined tension, and a fixed pole 23 supported on an electrically insulating base 24. And the fixed pole 23 are arranged to face each other via a spacer (not shown).

  An electrode lead rod 26 that is electrically connected to the fixed pole 23 is provided at substantially the center of the pedestal 24. In an electret type model, the surface of the fixed pole 23 that faces the diaphragm 21 is polarized by corona discharge or the like. An electret film (not shown) to which is applied is attached.

  In addition, a terminal board 30 on which an FET 31 as an impedance converter is mounted is disposed in the opening on the other end side of the cartridge case 10, and the terminal board 30 is formed by a caulking method in which the opening edge 12 of the cartridge case 10 is curled inward. Is fixed. Due to the pressing force due to the caulking, the constituent elements of the diaphragm assembly 20 are integrally joined together without rattling, and the electrical connection between the electrode extraction rod 26 and the gate electrode of the FET 31 is ensured.

  A printed circuit board is used for the terminal board 30. The terminal plate 30 is provided with openings 32 of the rear acoustic terminals. In this example, as shown in FIG. 2, the openings 32 are arranged concentrically at intervals of 90 ° as long holes. In FIG. 2, reference numerals 30 a and 30 b are insertion holes for the source terminal and the drain terminal of the FET 31. Although not shown in FIG. 2, lead wirings are formed on the terminal board 30 in a predetermined pattern.

  In addition to the FET 31, a chip-type electronic component 40 is mounted on the terminal board 30. In the case of the present invention, as shown in FIG. 3, the chip-type electronic component 40 is disposed so as to straddle the opening 32, and the opening is opened. A part of the portion 32 is blocked by the chip-type electronic component 40.

  In the example of FIG. 3, the chip-type electronic component 40 is disposed so as to straddle the opening portion 32 along the short axis direction at the center portion of the long hole-like opening portion 32, whereby a small opening is formed at both ends of the opening portion 32. The portions 32a and 32a are left, and the small opening portions 32a and 32a serve as rear acoustic terminals.

  By arranging the chip-type electronic component 40 in each opening 32 as described above, a total of eight small opening portions 32 a and 32 a are formed in the terminal plate 30, which is small in the terminal plate 30. Since this is substantially equivalent to opening a large number of holes, generation of noise due to electrostatic coupling between an external noise source A (see FIG. 5) such as a fluorescent lamp and the fixed pole 23 is prevented.

  Further, since the chip-type electronic component 40 is arranged on the opening 32, the restrictions on the arrangement of the chip-type electronic component 40 are alleviated as compared with the case where many small holes are formed in the terminal plate 30. The degree of freedom in board design is increased.

  As described above, in order to dispose the chip-type electronic component 40 on the opening portion 32 and make a part of the opening portion 32 a small opening portion 32a, the size of the chip-type electronic component 40 (occupies on the terminal board 30). The size and shape of the opening 32 may be determined in relation to the bottom area.

  In the above example, the opening portion 32 is a long hole, and small opening portions 32a and 32a are formed at both ends. However, as another example, the chip-type electronic component 40 has different lengths and widths. In the case of a rectangular shape, the opening 32 may be formed in a circular shape having an intermediate length between the vertical width and the horizontal width as a diameter. Further, in some cases, the chip-type electronic component 40 may be arranged so that a small opening portion 32a is formed only on one side rather than on both ends of the opening 32.

  With the recent spread of mobile phones, there are increasing opportunities for mobile phones to be used in the vicinity of microphones. Since a very strong electromagnetic wave is emitted from the mobile phone, when the electromagnetic wave enters the cartridge case 10, it may be detected by the FET 31 and noise may be generated. Further, the FET 31 may be destroyed by static electricity.

  In order to prevent these, a capacitor element for preventing high-frequency penetration and a Zener diode element for preventing electrostatic breakdown are used for the chip-type electronic component 40, and each of these elements is as shown in the circuit diagram of FIG. Connected.

  FIG. 4 shows an audio signal output section provided on the terminal board 30. The capacitor element 41 and the Zener diode element 42 are arranged in parallel, and between the ground terminal E and the signal hot side terminal SH of the audio signal output section, and the ground. Each is connected between a terminal E and a signal cold side terminal SC.

Sectional drawing which shows the internal structure of the unidirectional condenser microphone unit by this invention. The top view which shows the state before component mounting of a terminal board. (A) The top view which shows the terminal board after component mounting, (b) The sectional drawing. The circuit diagram which shows the connection state of the components for FET protection. Sectional drawing which shows the internal structure of the conventional unidirectional condenser microphone unit. (A) The top view which shows the terminal board integrated in FIG. 5, (b) The sectional drawing.

Explanation of symbols

10 Cartridge case 11 Opening (front acoustic terminal)
20 Diaphragm assembly 21 Diaphragm 23 Fixed pole 24 Base 30 Terminal plate 31 FET (impedance converter)
32 opening (rear acoustic terminal)
32a Small opening 40 Chip type electronic component

Claims (3)

A cylindrical cartridge case having a front acoustic terminal on one end and an opening on the other end is provided, and a diaphragm and a fixed pole are opposed to the front acoustic terminal in the cartridge case via a spacer. The other end side of the cartridge case is closed by a terminal plate, an opening serving as a rear acoustic terminal is formed in the terminal plate, and on the terminal plate In the unidirectional condenser microphone unit in which the impedance converter and the chip-type electronic component that protects the impedance converter are mounted,
A unidirectional condenser microphone unit, wherein the chip-type electronic component is disposed on the opening so as to block a part of the opening.   2. The unidirectional condenser microphone unit according to claim 1, wherein the opening is formed as a long hole, and the chip-type electronic component is disposed on the opening leaving openings at both ends of the long hole. The chip-type electronic component includes a capacitor element for preventing high-frequency intrusion and a Zener diode element for preventing electrostatic breakdown. The capacitor element and the Zener diode element are connected in parallel, and the ground terminal of the audio signal output unit The unidirectional condenser microphone unit according to claim 1 or 2, wherein the unidirectional condenser microphone unit is connected between a hot side terminal and between a ground terminal and a signal cold side terminal.

Images