JP2009302744A - Electrostatic speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To providing a light-weight electrostatic speaker which vibrates a vibrating body with high sensitivity, while improving acoustic transparency. <P>SOLUTION: In conductive clothes 20U, 20L facing each other across the vibrating body 10, a plurality of polyester filaments are arranged on a plurality of polyester filaments arranged in different direction, the cross portion of the filaments is bonded by heating for forming a sheet-like nonwoven fabric, and then one side of the nonwoven fabric is plated with a conductive metal. The conductive clothes 20U, 20L are nonwoven fabrics made of a synthetic resin, so that the weight of an electrostatic speaker 1 is made lighter than when a punching metal is used as an electrode, and radiation sound pressure becomes high since there is a gap between the filaments to improve acoustic transparency. Also, one surface of the conductive fabrics 20U, 20L is plated by metal, thereby vibrating the vibrating body with high sensitivity by increasing an area serving as the electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic speaker.

  The electrostatic loudspeaker disclosed in Patent Document 1 is composed of two parallel flat electrodes facing each other with a gap between them, and a conductive material inserted between the two electrodes and supported at the opposite ends by a housing or the like. If a predetermined bias voltage is applied to the vibrating body and the voltage applied to the electrode is changed, the electrostatic force acting on the vibrating body changes. Due to this, the vibrating body is displaced. If the applied voltage is changed according to the input acoustic signal, the vibrating body repeats displacement (that is, vibrates) accordingly, and an acoustic wave corresponding to the acoustic signal is generated from the vibrating body. Then, the generated acoustic wave passes through the hole formed in the planar electrode and is radiated to the outside.

JP-A-11-178098

  In the electrostatic loudspeaker disclosed in Patent Document 1, punching metal is used as an electrode facing the vibrating body. However, when punching metal is employed as the electrode, there is a problem that when the area of the speaker is increased, the weight increases in proportion to the area and the movement is inconvenient. In addition, a plurality of holes are provided in the punching metal. If the total area of the holes is large, the area acting as an electrode is narrow, the sensitivity of the vibrator is deteriorated, and the radiated sound pressure is lowered. If the area of the hole is narrowed, the sound transmission is deteriorated, and the radiated sound pressure is lowered.

  The present invention has been made under the background described above, and it is an object of the present invention to provide a technique that is lightweight, has good sound permeability, and can vibrate a vibrating body with high sensitivity.

  In order to solve the above-described problems, the present invention provides a sheet-like first electrode, a sheet-like second electrode spaced apart from the first electrode, and a sheet-like conductivity, And 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, wherein the first electrode and the second electrode are arranged in a first direction. At least one of the sheets formed by adhering the plurality of filaments arranged at intervals along the second direction and the plurality of filaments arranged at intervals along the second direction different from the first direction. Provided is an electrostatic speaker that is an electrode having a surface plated with a conductive metal.

  Moreover, in this invention, it is located between the said 1st electrode and the said vibrating body, between the 1st elastic member which has insulation, elasticity, and sound transmittance, and between the said 2nd electrode and the said vibrating body. It is good also as a structure which has the 2nd elastic member which is located and has insulation, elasticity, and sound transmittance.

  According to the present invention, it is lightweight and has good sound permeability, and the vibrating body can be vibrated with high sensitivity.

FIG. 1 is a diagram schematically showing an external appearance of an electrostatic speaker 1 according to an embodiment of the present invention, and FIG. 2 is a diagram schematically showing a cross section and an electrical configuration of the electrostatic speaker 1. is there.
As shown in the figure, the electrostatic loudspeaker 1 includes a vibrating body 10, conductive cloths 20U and 20L, elastic members 30U and 30L, and a thread 40. In the present embodiment, the configurations of the conductive cloth 20U and the conductive cloth 20L are the same, and the configurations of the elastic member 30U and the elastic member 30L are the same. The description of “L” and “U” is omitted. In addition, the dimensions of the constituent elements such as the vibrator and the conductive cloth in the figure are different from the actual dimensions so that the shapes of the constituent elements can be easily understood. Also, in the figure, “•” in “◯” means an arrow heading from the back of the drawing to the front.

(Configuration of each part of the electrostatic speaker 1)
First, the vibrating body 10 is obtained by depositing a metal film or applying a conductive paint on a film such as PET (polyethylene terephthalate) or PP (polypropylene), and has a thickness of several μm. The thickness is about tens of μm.

The elastic member 30 is obtained by compressing batting by applying heat, allowing air to pass therethrough and having sound permeability, and has a rectangular shape. The elastic member 30 has elasticity, and is deformed when a force is applied from the outside, and returns to its original shape when the force applied from the outside is removed. In the present embodiment, the lengths of the elastic member 30 in the X direction and the Y direction are longer than the lengths of the rectangular conductive cloth 20 described later in the X direction and the Y direction, and the X of the vibrating body 10 Longer than the length in the direction and the Y direction. The heights of the elastic member 30U and the elastic member 30L in the Z direction are the same.
Further, in the electrostatic speaker according to the present invention, the elastic member 30 is not limited to the batting, but deforms when a force is applied, returns to its original shape when the applied force is removed, and Other materials may be used as long as they have insulating properties and sound transmission properties.

The conductive cloth 20 has a plurality of polyester filaments aligned in the Y direction on a plurality of polyester filaments aligned in the X direction as shown in FIG. After the crossing portion is bonded by heating to form a sheet-like nonwoven fabric, one side of the nonwoven fabric is plated with a conductive metal. Compared with a nonwoven fabric manufactured by a conventional method such as a spunbond method, the nonwoven fabric having the structure shown in FIG. 3 has a structure in which filaments are aligned, so that the thickness is uniform and the surface is smooth, lightweight and It has the advantages of high strength and excellent dimensional stability. Moreover, since the surface is smooth, it can print easily compared with the conventional nonwoven fabric. In addition, since the filaments are aligned, the thickness can be reduced, the air permeability (sound transmission) is good, and the area acting as an electrode in the conductive cloth 20 by the fringing effect (effective area of the electrode) Can be greatly increased.
In the conductive cloth 20, the gap between the filaments is not blocked by the metal adhered by plating, and allows air to pass therethrough. As the metal plating, it is desirable that aluminum or gold is vapor-deposited to have a surface resistivity of 10 ³ [Ω / sq] or less.

  The thread 40 is a thread for sewing together the conductive cloth 20, the elastic member 30, and the vibrating body 10, and the material thereof is a material that does not have conductivity, such as cotton.

(Assembly method of electrostatic speaker 1)
Next, a method for assembling the electrostatic speaker 1 will be described. When assembling the electrostatic speaker 1, first, the elastic member 30L is placed on the plated surface side of the conductive cloth 20L. When the elastic member 30L is placed on the conductive cloth 20L, the elastic member 30L is placed on the conductive cloth 20L such that each side of the elastic member 30L is positioned outside each side of the conductive cloth 20L. . Next, the vibrating body 10 is placed on the elastic member 30L. When the vibrating body 10 is placed on the elastic member 30L, the vibrating body 10 is placed on the elastic member 30L so that each side of the vibrating body 10 is positioned inside each side of the elastic member 30L.

  Then, the elastic member 30U is placed on the vibrating body 10. When the elastic member 30U is placed on the vibrating body 10, the positions of the four corners of the elastic member 30U and the elastic member 30L overlap with each side of the elastic member 30U positioned outside each side of the vibrating body 10. Thus, the elastic member 30L is placed on the vibrating body 10. Here, since the lengths of the elastic member 30 in the X direction and the Y direction are longer than the lengths of the vibrating body 10 in the X direction and the Y direction, each side of the rectangular vibrating body 10 includes the elastic member 30U and the elastic member 30L. It is located between the elastic members 30U and 30L without protruding from between them.

  Next, the conductive cloth 20U is placed on the elastic member 30U with the plated surface side facing the elastic member 30U. When placing the conductive cloth 20U on the elastic member 30U, the positions of the four corners of the conductive cloth 20U and the conductive cloth 20L are Z while the respective sides of the conductive cloth 20U are positioned on the inner side of the respective sides of the elastic member 30U. The conductive cloth 20U is placed on the elastic member 30U so as to overlap in the direction.

Then, after the conductive cloth 20, the vibrating body 10, and the elastic member 30 are overlaid, the respective members are sewn together with a thread 40 that does not have conductivity. As shown in FIG. 1, the members are sewn and restrained by the thread 40 penetrating the members, so that the conductive cloth 20, the elastic member 30, and the vibrating body 10 do not shift even when deformed.
In addition, the elastic member 30 having insulation has a larger area than the vibrating body 10 and the conductive cloth 20, and each side of the elastic member 30 is positioned outside each side of the vibrating body 10 and the conductive cloth 20. The conductive cloth 20 and the vibrating body 10 do not come into contact with each other and are short-circuited.
In the present embodiment, the conductive cloths 20U and 20L are made of a thin non-woven fabric made of synthetic resin, so that the weight of the electrostatic speaker 1 is lighter than when a punching metal having conductivity is used as an electrode.
In this embodiment, the plated surfaces of the conductive cloths 20U and 20L are directed to the vibrating body 10 side, but may be directed to the opposite side of the vibrating body 10.

(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 applies a DC bias to the vibrating body 10. The bias power source 70 is connected to the vibrating body 10 and the midpoint of the output side of the transformer 50, and the plated portions of the two conductive cloths 20 are respectively connected to one end and the other end of the output side of the transformer 50. It is connected. In this configuration, when an acoustic signal is input to the input unit 60, a voltage corresponding to the input acoustic signal is applied to the conductive cloth 20.
When a potential difference is generated between the conductive cloth 20U and the conductive cloth 20L due to the applied voltage, an electrostatic force that is attracted to either the conductive cloth 20U or the conductive cloth 20L acts on the vibrating body 10.

  For example, when an acoustic signal is input to the input unit 60, a positive voltage is applied to the plated portion of the conductive cloth 20U, and a negative voltage is applied to the plated portion of the conductive cloth 20L, the vibration body 10 is applied. Since a positive voltage is applied by the bias power source 70, a portion of the vibrating body 10 between the conductive cloth 20U and the conductive cloth 20L repels the conductive cloth 20U to which a positive voltage is applied. It is attracted to the conductive cloth 20L to which a negative voltage is applied and displaced toward the conductive cloth 20L.

  Next, when an acoustic signal is input to the input unit 60, a negative voltage is applied to the plated portion of the conductive cloth 20U, and a positive voltage is applied to the plated portion of the conductive cloth 20L, the vibrating body 10 is While repelling the conductive cloth 20L to which a positive voltage is applied, the conductive cloth 20U to which a negative voltage is applied is attracted and displaced toward the conductive cloth 20U.

As described above, the vibrating body 10 is displaced (bends) in the Z direction or -Z direction in the same figure in accordance with the acoustic signal, and vibration is generated by sequentially changing the displacement direction, and the vibration state (frequency, amplitude, phase). A sound corresponding to is generated from the vibrating body 10. The generated sound passes through at least one conductive cloth 20 and is radiated to the outside of the electrostatic speaker 1.
When sound is radiated, the conductive cloths 20U and 20L of the present embodiment have high sound transmission because there is a gap between the filaments as shown in FIG.
Moreover, since one side of the conductive cloth 20 is all plated with a conductive metal, it is possible to widen the area that acts as an electrode while ensuring sound transmission, and to vibrate the vibrating body with high sensitivity. Yes.

[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 conductive cloth 20 according to the present invention, the sound permeability may be adjusted by adjusting the distance between the filaments arranged in the same direction.
In the embodiment described above, the conductive cloth 20 is metal-plated only on one side, but may be metal-plated on both sides.
In the conductive cloth 20 according to the present invention, a larger fringing effect can be obtained if the distance between the filaments arranged in the same direction is less than twice the distance from the vibrating body 10 to the conductive cloth 20. it can.

In the electrostatic speaker according to the present invention, the stitches of the thread 40 are along each side of the electrostatic speaker 1, but may be along a diagonal line.
In the present invention, the shape of the conductive cloth 20, the elastic member 30, and the vibrating body 10 is not limited to a rectangle, and may be other shapes such as a polygon, a circle, and an ellipse.
In the present invention, the entire electrostatic speaker 1 may be covered with a non-conductive and sound-transmitting cloth in order to prevent electric shock and short circuit.

  In the above-described embodiment, the conductive cloths 20U and 20L, the vibrating body 10 and the elastic members 30U and 30L are sewn together with the thread 40. However, an adhesive is applied to a portion near the edge of each member and a plurality of positions corresponding to the thread. The members may be applied and bonded together so that adjacent members do not shift.

In the embodiment described above, the elastic members 30U and 30L are disposed between the vibrating body 10 and the conductive cloths 20U and 20L, but a configuration in which the elastic members 30U and 30L are not disposed may be employed.
Specifically, a rectangular frame-shaped spacer 45U is arranged between the vibrating body 10 and the conductive cloth 20U as in the electrostatic speaker 1A shown in FIG. Also, a rectangular frame-shaped spacer 45L is arranged, and the vibrating body 10 is fixed in a state where tension is applied between the spacer 45U and the spacer 45L. Further, the conductive cloth 20U is fixed in a state where tension is applied to the spacer 45U, and the conductive cloth 20L is fixed in a state where tension is applied to the spacer 45L.
In this configuration, since the tension is applied to the vibrating body 10 and the displacement amount of the vibrating body 10 is limited, there is no possibility that the vibrating body 10 contacts the conductive cloths 20U and 20L.

In the present invention, as shown in FIG. 5, the number of filaments arranged in one direction in the conductive cloth 20 may be made smaller than the number of filaments arranged in the direction intersecting with this filament.
In the above-described embodiment, the conductive cloth 20 is formed of polyester filaments, but is not limited to polyester and may be formed of filaments of other synthetic resins.

1 is an external view of an electrostatic speaker 1 according to an embodiment of the present invention. 1 is a schematic diagram of a cross section and an electrical configuration of an electrostatic speaker 1. FIG. It is an enlarged view of conductive cloth 20U, 20L before plating. It is sectional drawing of the electrostatic speaker 1A which concerns on the modification of this invention. It is an enlarged view of conductive cloth 20U, 20L before plating concerning a modification of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vibrating body 20,20U, 20L ... Conductive cloth, 30, 30U, 30L ... Elastic member, 40 ... Yarn, 45U, 45L ... Spacer, 50 ... Transformer, 60 ... Input unit, 70 ... Bias power supply

Claims (2)

A sheet-like first electrode;
A second electrode in a sheet form and spaced apart from the first electrode;
A sheet-like conductive material, and a vibrating body disposed between the first electrode and the second electrode and spaced apart from the first electrode and the second electrode;
The first electrode and the second electrode include a plurality of filaments arranged at intervals along a first direction and a plurality of filaments arranged at intervals along a second direction different from the first direction. An electrostatic speaker which is an electrode in which at least one surface of a sheet formed by adhering the filament is plated with a conductive metal. A first elastic member located between the first electrode and the vibrating body and having insulating properties, elasticity, and sound transmission;
The electrostatic speaker according to claim 1, further comprising: a second elastic member that is located between the second electrode and the vibrating body and has insulating properties, elasticity, and sound transmission properties.

Images