JP2013062685A - Electret capacitor type sounding body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electret capacitor type sounding body where the internal structure is simplified and an element itself is miniaturized.SOLUTION: An electret capacitor type sounding body includes: an oscillation film 3; a substrate 5 arranged at a position opposing to the oscillation film 3 via a spacer 4 for keeping a fixed distance from the oscillation film 3; an electret 6 to be arranged on a surface opposing to the oscillation film 3 on the substrate 5 as a back plate; sound holes 8 formed in the substrate 5 and the electret 6 for continuity from an outside; and a metallic and cylindrical capsule 7 for storing the oscillation film 3, the spacer 4, the substrate 5, and the electret 6. An input terminal 9 for applying an electric signal is connected to the electret 6 and also a ground terminal 10 is connected to the oscillation film 3. The oscillation film 3 and the substrate 5 are exposed on the opposite sides of the cylindrical capsule 7.

Description

  The present invention relates to an electret condenser-type sounding body having a vibrating membrane and an electret disposed opposite to one of the surfaces of the vibrating membrane inside a capsule.

  An electret condenser microphone (hereinafter abbreviated as ECM) provided with a vibrating membrane and an electret disposed opposite to one of the surfaces of the vibrating membrane inside a capsule is a mobile phone, PDA, digital camera, etc. Applied to a wide range of electronic devices. Patent Document 1 discloses a structure of a unidirectional ECM. Here, one end surface of the metallic cylindrical capsule is closed by the front plate, and the vibration film attached to the vibration film ring made of a metal material is accommodated in the cylindrical capsule. The diaphragm ring is in electrical and mechanical contact with the front plate. A back electrode plate is disposed on the opposite surface of the vibration film, and an electret derivative film is deposited on the surface of the back electrode plate facing the vibration film. The periphery of the back electrode plate is supported by a back electrode holder made of an insulating material, and a printed circuit board is arranged on the opposite side of the back electrode holder from the back electrode plate. As a result, a back electrode chamber is formed between the back electrode plate and the printed circuit board.

  Such an ECM can be used as a sounding body by applying an electrical signal to the back electrode plate. When an electrical signal is applied to the back electrode plate, the electrostatic attractive force on the diaphragm by the electret changes. As a result, the vibration film vibrates to generate sound.

JP 2000-232700 A

  In the case where the ECM is used as a sounding body, it is preferable that the diaphragm has a large diameter in order to obtain a large sound pressure. Further, when the ECM is used as a sounding body, a back electrode chamber is formed between the back electrode plate and the printed board in the capsule, so that the sounding body becomes thick. For this reason, for example, when an electret condenser type sounding body is incorporated into the earphone, the degree of freedom in designing the earphone housing is limited. In addition, it is conceivable that the air chamber formed by the back electrode chamber formed inside the sounding body and the acoustic air chamber inside the earphone housing cause an interaction and affect the acoustic characteristics.

  An object of the present invention is to provide an electret condenser type sounding body in which the internal structure is simplified and the element itself is miniaturized.

  A first characteristic configuration of the electret condenser-type sounding body of the present invention includes: a vibration film; and a substrate disposed via a spacer that maintains a certain distance between the vibration film at a position facing the vibration film; An electret disposed as a back electrode on a surface of the substrate facing the vibrating membrane; a sound hole formed continuously from the outside on the substrate and the electret; the vibrating membrane, the spacer, the substrate, and A metal cylindrical capsule that accommodates the electret, and an input terminal for applying an electric signal to the electret is connected, a ground terminal is connected to the vibration film, and the vibration film and the substrate are connected to the cylinder. It is in the point exposed to the opposite side of a capsule.

As in this configuration, a substrate disposed via a spacer that maintains a certain distance between the diaphragm and the position facing the diaphragm, and an electret disposed as a back electrode on the surface of the substrate facing the diaphragm Thus, the back electrode plate covered with the electret film and the holder for holding the back electrode plate are not required on the surface facing the vibration film. Thereby, the thickness of the electret condenser type sounding body can be reduced, and the size can be reduced.
Further, when the electret condenser type sounding body is assembled, the substrate having the electret disposed on the surface can be directly assembled in the capsule. For this reason, it is not necessary to push the back electrode plate coated with the electret film subjected to corona discharge into the capsule by the holder, and the assembling work of the electret capacitor type sounding body is simplified.
Furthermore, since the electret is disposed as a back electrode on the surface of the substrate facing the vibration film, no back air chamber is formed between the substrate and the back electrode. For this reason, for example, when an electret condenser type sounding body is incorporated in the housing of the earphone, unnecessary resonance due to the back air chamber hardly occurs. As a result, it is easy to adjust a desired sound pressure characteristic in the earphone.

  According to a second characteristic configuration of the electret condenser-type sounding body of the present invention, a terminal that forms a through-hole communicating with the electret in the substrate and applies an electrical signal to a side of the substrate opposite to the electret in the through-hole. It is in the point which provided.

  With this configuration, the terminal to which the electric signal is applied is electrically connected to the electret via the through hole formed in the substrate, and the electric signal can be reliably applied to the electret.

Cross section of electret condenser type sounding body Disassembled perspective view of electret condenser type sounding body Plan view showing substrate pattern Sectional drawing of electret condenser type sounding body of another embodiment An exploded perspective view of an electret condenser type sounding body of another embodiment

  Hereinafter, embodiments of an electret condenser type sounding body of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 is a cross-sectional view of an electret capacitor-type sounding body 100, and FIG. 2 is an exploded perspective view of the electret capacitor-type sounding body 100.
As shown in FIG. 1, the electret condenser type sounding body 100 is configured by housing various components inside a cylindrical capsule 7 having a cylindrical side surface portion 7a and a top surface portion 7b. Inside the cylindrical capsule 7, the diaphragm 3, the spacer 4, and the substrate 5 are accommodated in this order from the top surface 7b side. And the above-mentioned various components are fixed inside the cylindrical capsule 7 by the edge part of the side part 7a of the cylindrical capsule 7 caulking the board | substrate 5 inside the cylindrical capsule 7. FIG. The cylindrical capsule 7 is formed using a conductive member such as metal.
In the present embodiment, an example in which the cylindrical capsule 7 has a cylindrical shape will be described, but the cylindrical capsule 7 may have a rectangular tube shape.

  The periphery of the vibrating membrane 3 is supported and fixed to the metallic vibrating membrane ring 3a with a constant tension. Inside the cylindrical capsule 7, the vibrating membrane ring 3a is fixed to the inner surface side of the top surface portion 7b. Yes. The vibration film 3 is made of a resin material. For example, a PPS (polyphenylene sulfide) film of about several μm is used, and a metal such as titanium is sputtered and used as a vibration electrode. The spacer 4 is made of resin and is formed in a ring shape, and holds a certain distance between the substrate 5 and the vibration film 3. The thickness of the spacer 4 is appropriately changed in accordance with a desired sound pressure characteristic. The substrate 5 is a ceramic substrate or a printed substrate. An electret 6 is disposed on the surface of the substrate 5 facing the vibration film 3, and this electret 6 serves as a back electrode. The electret 6 is formed by coating the surface of the substrate 5 with a ferroelectric material typified by fluorine resin or ceramic and applying a surface potential by corona discharge. The electret 6, the vibration film 3, and the spacer 4 constitute a capacitor unit C.

  A sound hole 8 for sound removal is formed in the substrate 5 and the electret 6 continuously from the outside to the space where the vibration film 3 is disposed. As shown in FIGS. 2 and 3, the sound holes 8 are provided at a total of five locations, one in the vicinity of the center of the substrate 5 and four in the vicinity of the surrounding four sides.

  A through hole 5 a communicating with the electret 6 is formed in the substrate 5, and an input terminal 9 for applying an electric signal is provided at a position covering the through hole 5 a on the outer surface side of the substrate 5. Similarly, a ground terminal 10 is provided on the outer surface side of the substrate 5. As shown in FIGS. 1 and 3, the ground terminal 10 is electrically connected to the cylindrical capsule 7, and the conductive pattern of the cylindrical capsule 7 and the ground terminal 10 is electrically connected by caulking the cylindrical capsule 7. . Thus, the vibrating membrane 3 is connected to the ground terminal 10 via the cylindrical capsule 7. An input terminal 9 for applying an electric signal is connected to the electret 6, and a ground terminal 10 is connected to the vibrating membrane 3. The vibration film 3 and the substrate 5 are exposed on the opposite sides of the cylindrical capsule 7.

  By configuring the electret capacitor-type sounding body 100 as described above, when an electric signal is applied from the input terminal 9 to the electret 6, the static attractive force to the vibration film 3 changes, and the vibration film 3 vibrates. That is, the electrical signal is converted into sound waves in the electret condenser type sounding body 100.

  Since the electret 6 is disposed as a back electrode on the surface of the substrate 5 facing the vibrating membrane 3, a back electrode plate covered with the electret 6 and a holder for holding the back electrode plate are not necessary on the surface facing the vibrating membrane 3 It becomes. Thereby, the thickness of the electret capacitor type sounding body 100 can be reduced, and the element body can be miniaturized.

  When the electret condenser type sounding body 100 is assembled, the substrate 5 on which the electret 6 is arranged is assembled in the cylindrical capsule 7. For this reason, it is not necessary to push the back electrode plate covered with the electret 6 subjected to the corona discharge into the cylindrical capsule 7 by the holder, and the assembling work of the electret capacitor type sounding body 100 is simplified.

  Moreover, since the electret 6 is arrange | positioned as a back electrode in the surface facing the diaphragm 3 in the board | substrate 5, a back air chamber is not formed between the board | substrate 5 and a back electrode (electret 6). For this reason, for example, when the electret condenser type sounding body 100 is incorporated in the earphone housing, unnecessary resonance due to the back air chamber is unlikely to occur. As a result, it is easy to adjust a desired sound pressure characteristic in the earphone.

[Another embodiment]
In the first embodiment, the example in which the vibrating membrane ring 3a that supports the vibrating membrane 3 is fixed to the cylindrical capsule 7 has been shown. However, as shown in FIGS. 4 and 5, the vibrating membrane 3 is attached to the cylindrical capsule 7. The top surface portion 7b may be directly bonded to the inner surface. By doing so, the diaphragm ring 3a is unnecessary, and the electret condenser type sounding body 100 can be further reduced in height.

  The electret condenser type sounding body of the present invention can be applied to a wide range of devices such as mobile phones, PDAs, digital cameras, headphones, and earphones.

3 Vibration film 3a Vibration film ring 4 Spacer 5 Substrate 5a Through hole 6 Electret 7 Cylindrical capsule 8 Sound hole 9 Input terminal 10 Ground terminal

Claims (2)

A vibrating membrane;
A substrate disposed via a spacer that maintains a certain distance between the vibrating membrane at a position facing the vibrating membrane;
An electret disposed as a back electrode on the surface of the substrate facing the vibrating membrane;
A sound hole formed continuously from the outside in the substrate and the electret;
A metal cylindrical capsule that houses the vibrating membrane, the spacer, the substrate, and the electret;
While connecting an input terminal for applying an electric signal to the electret, a ground terminal is connected to the vibrating membrane,
An electret condenser type sounding body in which the vibrating membrane and the substrate are exposed on opposite sides of the cylindrical capsule.   The electret condenser type sounding body according to claim 1, wherein a through-hole communicating with the electret is formed in the substrate, and a terminal for applying an electric signal is provided on a side of the through-hole opposite to the electret in the substrate.

Images