JP2010034779A - Electrostatic speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To narrow a gap between a vibrating body and an electret while preventing reduction in the potential of the electret. <P>SOLUTION: A contact prevention member 80U is arranged between the electret 40U and a cushioning material 45U and a gap is formed between the electret 40U and the contact prevention member 80U. Thereby, the cushioning material 45U, the electret 40U and the contact prevention member 80U are not brought into contact with one another and potential reduction due to discharge in the charge of the electret 40U is prevented. Further, a contact prevention member 80L is arranged between an electret 40L and a cushioning member 45L and a gap is formed between the electret 40L and the contact prevention member 80L. Thereby, the cushioning member 45L is not brought into contact with the electret 40L and potential reduction due to discharge in the charge of the electret 40L can be prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic speaker.

  As an electrostatic speaker using an electret, for example, there is an electrostatic speaker described in Patent Document 1. In this electrostatic speaker, the vibrating body is positioned in a state where tension is applied between two annular spacers, and two electrodes provided with electrets on one side are fixed to the spacer with the electret side facing the vibrating body side. ing.

JP 58-120400 A

  By reducing the gap between the opposing electrode and the vibrating body in the electrostatic speaker, the thickness of the electrostatic speaker can be reduced. However, when the gap between the vibrating body and the electret is narrowed in a configuration in which no member is disposed between the vibrating body and the electret as in the electrostatic speaker disclosed in Patent Document 1, the displacement is caused when the gap between the vibrating body and the electret is narrowed. There is a possibility that the vibrating body contacts the electret and short-circuits.

  In a known electrostatic speaker, a configuration in which a vibrating body is sandwiched between cushioning materials such as ester wool having insulation and elasticity to prevent the vibrating body from being short-circuited has been devised. If it employ | adopts for a structure, a cushion material and an electret will contact, the electric charge of an electret will lose | deviate, the electric potential of an electret will fall, and the force which vibrates a diaphragm will fall.

  The present invention has been made under the above-described background, and an object thereof is to provide a technique for narrowing a gap between a vibrating body and an electret while preventing a decrease in the potential of the electret.

  In order to solve the above-described problem, the present invention has a first electrode having conductivity, a second electrode having conductivity and spaced apart from the first electrode, and has conductivity. A vibrating body disposed between the first electrode and the second electrode so as to be spaced apart from the first electrode and the second electrode; and an insulating body positioned on a surface of the vibrating body on the first electrode side A first cushion material having a property, elasticity and sound permeability, a second cushion material located on the surface of the vibrating body on the second electrode side and having insulation properties, elasticity and sound permeability, and the first A first electret disposed on the surface of the electrode on the vibrating body side, a second electret disposed on the surface of the second electrode on the vibrating body side, and positioned between the first electret and the first cushion material, Holds the first cushion material and has sound permeability A first pressing portion, a second pressing portion that is positioned between the second electret and the second cushion material and presses the second cushion material and has sound permeability, the first pressing portion, and the first pressing portion. Provided is an electrostatic speaker having a first gap forming portion that secures a gap between one electret and a second gap forming portion that secures a gap between the second pressing portion and the second electret. .

  In the present invention, the first pressing part and the second pressing part may be configured as a cloth or a net.

  ADVANTAGE OF THE INVENTION According to this invention, the gap between a vibrating body and an electret can be narrowed, preventing the fall of the electric potential of an electret.

[Embodiment]
FIG. 1 is a diagram schematically showing the external appearance of an electrostatic speaker 1 according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing a cross section and an electrical configuration of the electrostatic speaker 1, and FIG. FIG. 2 is an exploded perspective view of the electrostatic speaker 1.
As shown in the figure, the electrostatic speaker 1 includes a vibrating body 10, electrodes 20U and 20L, spacers 30U and 30L, an electret 40U fixed to the electrode 20U, and an electret 40L fixed to the electrode 20L. Yes. The electrostatic speaker 1 includes contact prevention members 80U and 80L, spacers 31U and 31L, and cushion materials 45U and 45L. In addition, the dimension of each component, such as a vibrating body, an electrode, a spacer, a contact prevention member, an electret, and a cushion material in the drawing, is different from an actual dimension so that the shape of the component can be easily understood. In addition, in the figure, “•” in “◯” means an arrow pointing backward from the front of the drawing.

(Configuration of each part of the electrostatic speaker 1)
First, each component constituting the electrostatic speaker 1 will be described.
The vibrating body 10 is obtained by depositing a conductive metal on a PET (polyethylene terephthalate) film to form a conductive thin film layer on the film surface. In the present embodiment, the thickness of the vibrating body 10 is about several μm to several tens of μm, and the length in the X direction and the Y direction of the vibrating body 10 is the X direction of spacers 30U and 30L, which will be described later. It is shorter than the length in the Y direction.
In the present embodiment, the vibrator 10 may be a film made of a polymer material other than PET, such as PP (polypropylene), and a metal thin film layer having conductivity. Further, in the vibrating body 10, a thin film layer may be formed by applying a conductive paint on the surface of the synthetic resin film.

  The material of the spacers 30U, 30L and the spacers 31U, 31L is an insulator (for example, synthetic resin or ceramics), and the shape thereof is a rectangular frame as shown in FIG. In the present embodiment, the lengths of the spacers 30U, 30L and the spacers 31U, 31L in the X direction and the Y direction are the same as the lengths of the electrodes 20U, 20L in the X direction and the Y direction. Further, the spacers 30U and 30L have the same thickness, and the spacers 31U and 31L have the same thickness.

The electrodes 20U and 20L are formed by forming a conductive metal into a rectangular plate shape.
The electrets 40U and 40L are electrified electrets, and the shape thereof is plate-like and rectangular. The electret 40U is fixed to one surface of the electrode 20U, and the electret 40L is fixed to one surface of the electrode 20L. Has been. Further, the lengths of the electrets 40U, 40L in the X direction and the Y direction are shorter than the lengths of the electrodes 20U, 20L in the X direction and the Y direction, and the areas of the electrets 40U, 40L are smaller than the areas of the electrodes 20U, 20L. ing.
Note that the electret 40U and the electret 40L have the same potential. Further, in the fixed electrode 20U and the electret 40U, and in the fixed electrode 20L and the electret 40L, a plurality of through holes 21 penetrating the electret and the electrode are provided at predetermined intervals in order to ensure sound transmission.

  The cushion materials 45U and 45L are made by compressing cotton by applying heat to allow air to pass therethrough and have a rectangular shape. The cushion members 45U and 45L have sound permeability and elasticity, and are members that are deformed when a force is applied from the outside and return to the original shape when the force applied from the outside is removed. In the electrostatic speaker according to the present invention, the material of the cushion materials 45U and 45L is not limited to cotton, but deforms when a force is applied, and returns to its original shape when the applied force is removed. Other materials such as ester wool may be used as long as they return and have insulating properties and sound transmission properties.

  The contact preventing members 80U and 80L are formed by forming a synthetic resin having insulating properties (for example, PET, PP, acrylic resin, etc.) into a rectangular plate shape, and from one surface to the other to ensure sound transmission. A plurality of through holes 81 penetrating the surface are provided at predetermined intervals. In the present embodiment, the lengths of the contact preventing members 80U and 80L in the X direction and the Y direction are the same as the lengths of the spacers 30U and 30L in the X direction and the Y direction.

(Configuration of electrostatic speaker 1)
In the electrostatic speaker 1, the spacer 30 </ b> U and the spacer 30 </ b> L are fixed to each other with the peripheral portion of the vibrating body 10 interposed therebetween. In the present embodiment, the vibrating body 10 is sandwiched between the spacer 30U and the spacer 30L in a state where no tension is applied.
Further, the contact preventing member 80U is fixed to the opposite side of the vibrating body 10 in the spacer 30U, and the contact preventing member 80L is fixed to the opposite side of the vibrating body 10 in the spacer 30L, and the contact preventing member 80U and the vibrating body 10 are fixed. A cushion material 45U is disposed in the space between them (space inside the spacer 30U), and a cushion material 45L is disposed in the space between the contact prevention member 80L and the vibrating body 10 (space inside the spacer 30L). Yes.

In the contact preventing member 80U, the spacer 31U is fixed to the opposite side of the spacer 30U, and in the contact preventing member 80L, the spacer 31L is fixed to the opposite side of the spacer 30L, and the electret 40U faces the vibrating body 10 and the electrode 20U. Is fixed to the spacer 31U, and the electrode 20L is fixed to the spacer 31L with the electret 40L facing the vibrating body 10 side.
Here, the contact preventing member 80U is located between the electret 40U and the cushion material 45U. A spacer 31U is provided between the contact preventing member 80U and the electrode 20U, and a gap is secured between the electret 40U and the contact preventing member 80U by the spacer 31U. Since the contact prevention member 80U holds the cushion material 45U so as not to contact the electret 40U, the cushion material 45U does not contact the electret 40U and the contact prevention member 80U, and the electric charge of the electret 40U is released and the potential is lowered. There is no.
Further, the contact preventing member 80L is located between the electret 40L and the cushion material 45L. A spacer 31L is provided between the contact preventing member 80L and the electrode 20L, and a gap is secured between the electret 40L and the contact preventing member 80L. Since the contact preventing member 80L presses the cushion material 45L so as not to contact the electret 40L, the cushion material 45L does not come into contact with the electret 40L, and the electric charge of the electret 40L is not released and the potential is not lowered.

  In the present embodiment, the spacers 30U and 30L have the same thickness, the spacers 31U and 31L have the same thickness, and the contact prevention member 80U and the contact prevention member 80L have the same thickness. Therefore, the distance from the vibrating body 10 to the electret 40U is the same as the distance from the vibrating body 10 to the electret 40L, and the distance from the electret 40U to the electret 40L is the same at any position of the electret. Yes.

(Electrical configuration of the electrostatic speaker 1)
Next, the electrical configuration of the electrostatic speaker 1 will be described. As shown in FIG. 2, the electrostatic speaker 1 includes a transformer 50, an input unit 60 to which an acoustic signal is input from the outside, and a bias power source 70 that supplies a DC bias. The input unit 60 is connected to the primary side of the transformer 50. Further, the negative side of the bias power source 70 is connected to the vibrating body 10, the positive side of the bias power source 70 is connected to the middle point (center tap) of the secondary side of the transformer 50, and the electrodes 20U and 20L are respectively transformed. The secondary side of the vessel 50 is connected to one end and the other end.

In this configuration, since the conductive thin film layer on the surface of the vibrating body 10 is connected to the negative side of the bias power source 70, the surface of the vibrating body 10 facing the electrets 40U and 40L is negative.
In a state where no acoustic signal is input to the input unit 60, if the voltage of the bias power supply 70 is E1, and the voltages of the electrets 40U and 40L are E2, the voltage E1 of the bias power supply 70 and the voltage E2 of the electret are added. The obtained voltage (E1 + E2) is a voltage difference between the vibrating body 10 and the electrode 20U (the vibrating body 10 and the electrode 20L). Here, since the voltage difference between the vibrating body 10 and the electrodes 20U and 20L is a voltage (E1 + E2) obtained by adding the voltage E1 and the voltage E2, a higher voltage difference can be obtained than when the electret alone or the bias power source alone. .
Further, when trying to obtain the voltage difference of E1 + E2 only with the bias power supply, it is necessary to cope with a high voltage for the wiring that supplies the bias voltage. However, according to the present embodiment, the voltage supplied from the bias power supply is only E1. And a voltage lower than E1 + E2. Compared with the case where the voltage difference of E1 + E2 is obtained only by the bias power supply, the wiring for supplying the bias voltage does not need to correspond to a higher voltage, and the cost can be suppressed.

(Operation of electrostatic speaker 1)
Next, the operation of the electrostatic speaker 1 will be described.
When an acoustic signal is input to the input unit 60, a voltage corresponding to the input acoustic signal is applied to the electrodes 20U and 20L.
Specifically, when an acoustic signal having positive and negative amplitudes is input to the input unit 60 and the voltage of the portion connected to the electrode 20U on the secondary side of the transformer 50 becomes positive with respect to the center tap, the electrode 20U And the vibrating body 10 is E1 + E2 + E3 obtained by adding the voltage E1 of the bias power source 70, the voltage E2 of the electret 40U, and the voltage E3 obtained by boosting the acoustic signal by the transformer 50.
On the other hand, the potential difference between the electrode 20L and the vibrating body 10 is E1 + E2 obtained by adding the voltage E1 of the bias power source 70 and the voltage E2 of the electret 40L, and a potential difference is generated between the electrode 20U and the electrode 20L. The body 10 is displaced.
In the present embodiment, the voltage value obtained by adding the voltage output from the transformer 50 and the voltage E1 of the bias power supply 70 when the amplitude of the acoustic signal reaches a peak does not exceed a predetermined voltage value. In addition, the voltage E1 of the bias power supply 70 is adjusted.

When an acoustic signal having positive and negative amplitudes is input to the input unit 60 and the voltage at the portion connected to the electrode 20L on the secondary side of the transformer 50 becomes positive with respect to the center tap, the electrode 20L and the vibrating body 10 is E1 + E2 + E3 obtained by adding the voltage E1 of the bias power supply 70, the voltage E2 of the electret 40L, and the voltage E3 obtained by boosting the acoustic signal by the transformer 50.
On the other hand, the potential difference between the electrode 20U and the vibrating body 10 is E1 + E2 obtained by adding the voltage E1 of the bias power source 70 and the voltage E2 of the electret 40U, and a potential difference is generated between the electrode 20U and the electrode 20L. The body 10 is displaced.

  As described above, when an acoustic signal is input to the input unit 60, an electrostatic force is exerted on the vibrating body 10 so as to be drawn toward either the electrode 20 </ b> U or the electrode 20 </ b> L. That is, the vibrating body 10 is displaced (bends) in the Z direction of the figure in accordance with the acoustic signal, and the vibration is generated by sequentially changing the displacement direction, and a sound corresponding to the vibration state (frequency, amplitude, phase) is generated. Generated from the vibrating body 10. The generated sound passes through the cushion materials 45U and 45L, the contact preventing members 80U and 80L, the electrets 40U and 40L, and the electrodes 20U and 20L, and is radiated to the outside of the electrostatic speaker 1.

  When the vibrating body 10 is displaced, the cushion members 45U and 45L receive the force pushed from the vibrating body 10 toward the electrets 40U and 40L. However, since the contact preventing member 80U is positioned between the electret 40U and the vibrating body 10, and the contact preventing member 80L is positioned between the electret 40L and the vibrating body 10, the cushion material is removed from the vibrating body 10. Even if pressed, the cushion materials 45U and 45L do not move and contact the electrets 40U and 40L. In the present embodiment, since the cushion material does not contact the electret as described above, the electric charges of the electrets 40U and 40L are not lost and the potential does not decrease.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. For example, the present invention may be implemented by modifying the above-described embodiment as follows.

  In the embodiment described above, the contact preventing members 80U and 80L are made of synthetic resin in the shape of a rectangular plate. However, the cushioning members 45U and 45L are limited to this configuration as long as they do not contact the electret. Instead, for example, cold protection or insulating cloth may be used as the contact preventing members 80U and 80L, and the contact preventing member may be a net, paper, synthetic resin film, etc. made by knitting an insulating thread. It is good also as 80U and 80L. Even with these members, the cushion material can be pressed so that the cushion material does not contact the electret.

In the present invention, the spacers 31U and 31L are shaped like a lattice like the spacer 31A shown in FIG. 4, and the electrets fixed to the electrodes 20U and 20L are arranged so that the electrets are positioned inside the lattice. You may divide | segment as shown in FIG. According to this structure, it can prevent that a cushion material and an electret contact even if it does not use the contact prevention members 80U and 80L.
Specifically, as shown in FIG. 6, when the spacer 31A is disposed between the spacer 30U and the electrode 20U and between the spacer 30L and the electrode 20L instead of the spacers 31U and 31L and the contact prevention members 80U and 80L, A gap between each electret and the cushion material can be secured by the frame and the lattice portion while pressing the cushion materials 45U and 45L at the lattice portion. Since the portion of the lattice prevents the cushion material and the electret from contacting each other, the contact between the cushion material and the electret can be prevented without using a contact prevention member.

Further, when the spacers 31U and 31L are formed in a lattice shape, the thickness of the lattice portion is made thinner than the thickness of the frame portion of the spacer as in the spacer 31B shown in FIG. You may arrange | position between the spacer 30U and the electrode 20U, and between the spacer 30L and the electrode 20L toward the side.
Also in this configuration, as shown in FIG. 8, when the spacer 31B is arranged between the spacer 30U and the electrode 20U and between the spacer 30L and the electrode 20L, instead of the spacers 31U and 31L and the contact prevention members 80U and 80L. The gap between the electret and the cushion material can be secured at the frame portion while pressing the cushion materials 45U and 45L at the lattice portion. Since the lattice portion prevents the cushion material and the electret from coming into contact with each other, the cushion material and the electret can be prevented from coming into contact without using the contact preventing members 80U and 80L.
Further, as shown in FIG. 8, since the electret is located in the portion where the grid is not provided inside the spacer, it is not necessary to divide the electret and fix it to the electrode as shown in FIGS. It becomes easy to adhere to.

  In the embodiment described above, the contact prevention member and each spacer are separate, but the spacer 31U and the contact prevention member 80U are integrally formed, and the spacer 31L and the contact prevention member 80L are integrally formed. May be.

In the above-described embodiment, the bias power source 70 is connected to the vibrating body 10, but as shown in FIG. 9A, the bias power source 70 is not provided and the two terminals on the secondary side of the transformer 50 are connected. It is also possible to connect two resistors connected in series, and connect the midpoint between one resistor and the other resistor to the vibrating body 10.
Further, as shown in FIG. 9B, the bias power supply 70 may not be provided, and the midpoint of the transformer 50 may be directly connected to the vibrating body 10.
Further, as shown in FIG. 9C, the bias power supply 70 is not provided, and the electret 40U is a negatively charged electret, while the electret 40L is a positively charged electret, and one of the secondary sides of the transformer 50 The electrostatic speaker 1 may be driven by connecting the other terminal to the vibrating body 10 and connecting the other terminal on the secondary side of the transformer 50 to the electrode 20U and the electrode 20L.

1 is an external view of an electrostatic speaker 1 according to an embodiment of the present invention. It is the figure which showed typically the cross section and electrical structure of the electrostatic speaker. 1 is an exploded perspective view of an electrostatic speaker 1. FIG. It is an external view of the spacer 31A which concerns on the modification of this invention. It is an external view of the electret 40L which concerns on the modification of this invention. It is sectional drawing of the electrostatic speaker which concerns on the modification of this invention. It is an external view of the spacer 31B which concerns on the modification of this invention. It is sectional drawing of the electrostatic speaker which concerns on the modification of this invention. It is a schematic diagram of an electrical configuration according to a modification of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrostatic speaker, 10 ... Vibrating body, 20U, 20L ... Electrode, 30U, 30L, 31U, 31L, 31A, 31B ... Spacer, 40U, 40L ... Electret, 45U, 45L ... cushion material, 50 ... transformer, 60 ... input part, 70 ... bias power supply, 80U, 80L ... contact prevention member

Claims (2)

A first electrode having conductivity;
A second electrode having electrical conductivity and spaced apart from the first electrode;
An oscillating body that is electrically conductive and is spaced from the first electrode and the second electrode between the first electrode and the second electrode;
A first cushion material located on the surface of the vibrating body on the first electrode side and having insulating properties, elasticity, and sound transmission properties;
A second cushion material located on the surface of the vibrating body on the second electrode side and having insulating properties, elasticity, and sound transmission properties;
A first electret disposed on the vibrating body side surface of the first electrode;
A second electret disposed on the vibrating body side surface of the second electrode;
A first pressing portion located between the first electret and the first cushion material, and holding the first cushion material and having sound permeability;
A second pressing part located between the second electret and the second cushion material and holding the second cushion material and having sound permeability;
A first gap forming part that secures a gap between the first pressing part and the first electret;
An electrostatic loudspeaker comprising: a second gap forming part that secures a gap between the second pressing part and the second electret.   The electrostatic speaker according to claim 1, wherein the first pressing portion and the second pressing portion are cloth or a net.

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