JP5545091B2 - Electrostatic speaker - Google Patents

Description

  The present invention relates to an electrostatic speaker.

  The capacitor-type headphones disclosed in Patent Document 1 have a configuration in which a diaphragm is sandwiched between fixed poles. Electrode foils are formed on both surfaces of the fixed electrode, and the front electrode foil and the back electrode foil are non-conductive. The fixed pole is provided with a plurality of holes. In the fixed pole, the electrode foil located on the user's ear side is connected to the ground.

JP 2006-270663 A

  According to the headphone disclosed in Patent Document 1, since the electrode foil located on the ear side of the human body is grounded, there is no risk of electric shock even if the ear is brought close to the electrode foil located on the ear side of the human body. . However, since the fixed pole is provided with a hole, there is a possibility that a liquid such as sweat may enter the headphone through the hole and the insulating property may be lowered.

  The present invention has been made under the background described above, and an object of the present invention is to provide a technique for preventing electric shock and preventing deterioration of insulation in an electrostatic speaker.

  In order to solve the above-described problems, the present invention provides a vibrating body having conductivity, a pair of electrodes that are opposed to each other with the vibrating body interposed therebetween and are spaced apart from the vibrating body, and waterproof and insulating properties. A pair of covers that are opposed to each other with the vibrator and the pair of electrodes interposed therebetween, and the pair of covers and the pair of electrodes. And a pair of spacers that are insulative and through which sound passes, the pair of covers are electrically connected, and a first acoustic signal is applied to one of the pair of electrodes. Provided is an electrostatic speaker connected to the ground of a drive circuit that supplies and supplies a second acoustic signal obtained by inverting the polarity of the first acoustic signal to the other of the pair of electrodes.

In the present invention, edges of the pair of covers may be fixed to each other, and the vibrator and the pair of electrodes may be located in a space between the pair of covers.
In the present invention, the drive circuit includes an amplifier circuit that amplifies an input signal, and the first acoustic signal is amplified in phase by the amplifier circuit when the acoustic signal input to the amplifier circuit is amplified. The second acoustic signal is a signal obtained by amplifying the acoustic signal input to the amplifier circuit with a polarity opposite to that of the acoustic signal in the amplifier circuit, and one terminal on the primary side The other side of the primary side is grounded, one side of the secondary side is connected to the amplifier circuit, and the other side of the secondary side is connected to the ground of the drive circuit It may have a configuration having an insulated transformer.

  ADVANTAGE OF THE INVENTION According to this invention, in an electrostatic speaker, it can prevent an electric shock and can prevent the insulation fall.

1 is an external view of an electrostatic speaker according to an embodiment of the present invention. AA sectional view taken on the line AA of FIG. FIG. 3 is an exploded view of the electrostatic speaker 1. The figure which showed the electrical structure which concerns on the electrostatic speaker. The exploded view of the electrostatic speaker 1 which concerns on a modification. The figure which showed the electrical structure of the drive circuit 100 which concerns on a modification. The figure which showed the electrical structure of the drive circuit 100 which concerns on a modification.

[Embodiment]
FIG. 1 is an external view of an electrostatic speaker 1 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the electrostatic speaker 1 taken along line AA. FIG. 3 is an exploded view of the electrostatic speaker 1, and FIG. 4 is a diagram showing an electrical configuration of the electrostatic speaker 1. In the figure, directions are indicated by orthogonal X-axis, Y-axis, and Z-axis. When the electrostatic speaker 1 is viewed from the front, the left-right direction is the X-axis direction, and the depth direction is the Y-axis direction. The height direction is the Z-axis direction. Also, in the figure, “•” in “◯” means an arrow heading from the back of the drawing to the front. Further, in the figure, “x” in “◯” means an arrow pointing backward from the front of the drawing.

  As shown in the figure, the electrostatic speaker 1 includes a vibrating body 10, electrodes 20U and 20L, elastic members 30U and 30L, spacers 40U and 40L, covers 50U and 50L, and protective members 60U and 60L. In the present embodiment, the configurations of the electrode 20U and the electrode 20L are the same, and the configurations of the elastic member 30U and the elastic member 30L are the same. For this reason, when it is not particularly necessary to distinguish between these members, descriptions of “L” and “U” are omitted. Further, the configuration of the spacer 40U and the spacer 40L is the same, the configuration of the cover 50U and the cover 50L is the same, and the configuration of the protection member 60U and the protection member 60L is the same. For this reason, also in these members, when it is not necessary to distinguish both, description of "L", "U", etc. is abbreviate | omitted. In addition, the dimensions of the constituent elements such as the vibrating body and the electrodes in the drawing are different from the actual dimensions so that the shapes of the constituent elements can be easily understood.

(Configuration of each part of the electrostatic speaker 1)
First, each part constituting the electrostatic speaker 1 will be described. The rectangular vibrating body 10 as viewed from a point on the Z axis is made of a synthetic resin film (insulating layer) having insulating properties and flexibility such as PET (polyethylene terephthalate) or PP (polypropylene). And a sheet-like structure in which a conductive metal is deposited on one surface of the film to form a conductive film (conductive layer). In the present embodiment, the conductive film is formed on one surface of the film, but may be formed on both surfaces of the film.

  The elastic member 30 is a non-woven fabric in the present embodiment, and allows air and sound to pass therethrough without passing electricity, and its shape is rectangular when viewed from a point on the Z-axis. 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. The elastic member 30 may be any member that has insulating properties, allows sound to pass through, and has elasticity. The elastic member 30 is formed by applying heat to a batting and compressing it, a woven cloth, a synthetic resin having insulating properties, and the like. It may be the one that was made. In this embodiment, the length of the elastic member 30 in the X-axis direction is longer than the length of the vibrating body 10 in the X-axis direction, and the length of the elastic member 30 in the Y-axis direction is the length of the vibrating body 10 in the Y-axis direction. It is longer than the length.

  The spacer 40 is a non-woven fabric in the present embodiment, and allows air and sound to pass therethrough without passing electricity, and its shape is rectangular as viewed from a point on the Z axis. The elastic member 30 has elasticity. In the present embodiment, the spacer 40 is made of the same material as the elastic member 30, but may not have elasticity as long as it does not conduct electricity and allows air and sound to pass therethrough. In this embodiment, the spacer 40 has the same length in the X-axis direction and the length in the Y-axis direction as the elastic member 30.

  The electrode 20 is made of an insulating synthetic resin film (insulating layer) such as PET or PP as a base material, and a conductive metal is deposited on one surface of the film to form a conductive film (conductive layer). It has a configuration. The electrode 20 has a rectangular shape when viewed from a point on the Z-axis, and has a plurality of holes penetrating from the front surface to the back surface, so that air and sound can pass therethrough. In addition, illustration of this hole is abbreviate | omitted in drawing. In the present embodiment, the length in the X-axis direction and the length in the Y-axis direction of the electrode 20 are the same as those of the elastic member 30.

The cover 50 is made of a synthetic resin film (insulating layer) having insulation properties such as PET or PP, and a conductive metal (for example, aluminum) is deposited on one entire surface of the insulating layer to form a conductive film (conductive). Layer). In the present embodiment, the length of the cover 50 in the X-axis direction and the length in the Y-axis direction are the same as those of the elastic member 30. The insulating layer of the cover 50 is preferably waterproof and has low moisture permeability and air permeability. In the present embodiment, the conductive film is formed on one surface of the cover 50, but may be formed on both surfaces of the cover 50.
The protection member 60 is an insulating cloth. The protection member 60 has a rectangular shape when viewed from a point on the Z axis, and allows passage of air and sound. In the present embodiment, the length in the X-axis direction and the length in the Y-axis direction of the protection member 60 are the same as those of the elastic member 30.

(Structure of electrostatic speaker 1)
Next, the structure of the electrostatic speaker 1 will be described. In the electrostatic speaker 1, the vibrating body 10 is disposed between the lower surface of the elastic member 30U and the upper surface of the elastic member 30L. In addition, the vibrating body 10 is bonded to the elastic member 30U and the elastic member 30L by applying an adhesive with a width of several millimeters inward from an edge in the left-right direction and an edge in the depth direction, and the portion to which the adhesive is applied The inner side is not fixed to the elastic member 30U and the elastic member 30L.

  The electrode 20U is bonded to the upper surface of the elastic member 30U. The electrode 20L is bonded to the lower surface of the elastic member 30L. The electrode 20U is bonded to the elastic member 30U by applying an adhesive with a width of several millimeters inward from the left and right edges and the depth edge, and the electrode 20L is bonded to the left and right edges and the depth direction. An adhesive is applied with a width of several millimeters from the edge to the inside and is adhered to the elastic member 30L. The electrode 20 is not fixed to the elastic member 30 on the inner side of the portion where the adhesive is applied. The electrode 20U is in contact with the elastic member 30U on the side with the conductive film, and the electrode 20L is in contact with the elastic member 30L on the side with the conductive film.

  The spacer 40U is bonded to the upper surface of the electrode 20U. The spacer 40L is bonded to the lower surface of the electrode 20L. Note that the spacer 40U is adhered to the electrode 20U by applying an adhesive with a width of several millimeters inward from the left and right edges and the depth edge, and the spacer 40L includes the left and right edges and the depth edge. From inside to outside, an adhesive is applied with a width of several millimeters to adhere to the electrode 20L. The spacer 40 is not fixed to the electrode 20 on the inner side of the portion where the adhesive is applied.

  The cover 50U is bonded to the upper surface of the spacer 40U so that the base material of the synthetic resin is in contact with the spacer 40U. The cover 50L is bonded to the lower surface of the spacer 40L so that the base material of the synthetic resin is in contact with the spacer 40L. The cover 50U is coated with an adhesive with a width of several millimeters inward from the left and right edges and the depth edge, and is adhered to the spacer 40U. The cover 50L has a left and right edge and a depth edge. From inside to outside, an adhesive is applied with a width of several millimeters to adhere to the spacer 40L. The cover 50 is not fixed to the spacer 40 on the inner side of the portion where the adhesive is applied. Moreover, it is preferable that the thickness of the cover 50 is around 10 μm. With this thickness, even if the cover 50 is disposed, the sound pressure of the sound generated by the vibrating body 10 does not extremely decrease compared to the case where the cover 50 is not disposed. In this embodiment, the cover 50 is bonded to the spacer 40 so that the synthetic resin film is in contact with the spacer 40. However, the cover 50 is bonded to the spacer 40 so that the conductive film of the cover 50 is in contact with the spacer 40. Also good.

  The protective member 60U is bonded to the upper surface of the cover 50U. The protective member 60L is bonded to the lower surface of the cover 50L. The protective member 60U is adhered to the cover 50U by applying an adhesive with a width of several millimeters inward from the left and right edges and the depth direction edge, and the protective member 60L has the left and right edges and the depth direction. An adhesive is applied to the cover 50L with a width of several mm inward from the edge. The protective member 60 is not fixed to the cover 50 from the inside of the portion where the adhesive is applied.

(Electrical configuration of the electrostatic speaker 1)
Next, an electrical configuration relating to the electrostatic speaker 1 will be described. As shown in FIG. 4, the electrostatic speaker 1 includes an amplifier unit 130 to which an acoustic signal representing sound is input from the outside, a transformer 110, and a bias power source 120 that applies a DC bias to the vibrating body 10. The drive circuit 100 is connected.
The electrode 20U is connected to the terminal T1 on the secondary side of the transformer 110, and the electrode 20L is connected to the other terminal T2 on the secondary side of the transformer 110. In addition, the vibrating body 10 is connected to the bias power source 120 via the resistor R1. The middle point terminal T3 of the transformer 110 is connected to the ground GND, which is the reference potential of the drive circuit 100, via the resistor R2.
An acoustic signal is input to the amplifier unit 130. The amplifier unit 130 amplifies the input acoustic signal and outputs the amplified acoustic signal. The amplifier unit 130 includes terminals TA1 and TA2 that output acoustic signals. The terminal TA1 is connected to the primary terminal T4 of the transformer 110 via the resistor R3, and the terminal TA2 is connected to the resistor R4. Is connected to the other terminal T5 on the primary side of the transformer.
The conductive film of the cover 50U and the conductive film of the cover 50L are electrically connected, and both are connected to the ground GND of the drive circuit 100.

(Operation of electrostatic speaker 1)
Next, the operation of the electrostatic speaker 1 will be described. When an AC acoustic signal is input to the amplifier unit 130, the input acoustic signal is amplified and supplied to the primary side of the transformer 110. When a potential difference is generated between the electrode 20U and the electrode 20L by the supplied voltage, the vibrating body 10 between the electrode 20U and the electrode 20L is attracted to either side of the electrode 20U and the electrode 20L. Such electrostatic force works.

  Specifically, the polarity of the second acoustic signal output from the terminal T2 is opposite to that of the first acoustic signal output from the terminal T1. When a positive acoustic signal is output from the terminal T1 and a negative acoustic signal is output from the terminal T2, a positive voltage is applied to the electrode 20U, and a negative voltage is applied to the electrode 20L. Since a positive voltage is applied to the vibrating body 10 by the bias power source 120, the vibrating body 10 is weakened in electrostatic attraction with the electrode 20U to which the positive voltage is applied, while a negative voltage is applied. Since the electrostatic attractive force between the electrode 20L and the electrode 20L is increased, an attractive force acts on the electrode 20L side according to the difference in electrostatic attractive force applied to the vibrating body 10, and the electrode 20L side (the direction opposite to the Z-axis direction) Displace to

  When a negative first acoustic signal is output from the terminal T1 and a positive second acoustic signal is output from the terminal T2, a negative voltage is applied to the electrode 20U and a positive voltage is applied to the electrode 20L. Is done. Since a positive voltage is applied to the vibrating body 10 by the bias power source 120, the vibrating body 10 is weakened in electrostatic attraction between the electrode 20L to which the positive voltage is applied, while a negative voltage is applied. Since the electrostatic attractive force between the electrode 20U and the electrode 20U is increased, the electrode 20U is displaced toward the electrode 20U (Z-axis direction).

  As described above, the vibrating body 10 is displaced (bends) in the positive direction of the Z axis and the negative direction of the Z axis in accordance with the acoustic signal, and vibration is generated by sequentially changing the displacement direction. Sound waves corresponding to the number, amplitude, and phase are generated from the vibrating body 10. The generated sound wave passes through the elastic member 30 having acoustic transparency, the electrode 20, the spacer 40, the cover 50, and the protective member 60, and is emitted as sound to the outside of the electrostatic speaker 1.

  In addition, since the spacer 40, the cover 50, and the protection member 60 are outside the electrode 20, the human body does not touch the electrode 20, and an electric shock can be prevented. Further, since the conductive film of the cover 50U and the conductive film of the cover 50L are connected to the ground GND of the drive circuit 100 and have the same potential, an electric shock can be prevented. In addition, since the cover 50 is waterproof, there is less possibility that the liquid will reach the electrode 20 or the vibrating body 10 and the insulation performance will be reduced.

[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 addition, you may combine each of embodiment mentioned above and the following modifications.

In the embodiment described above, the electrostatic speaker 1 includes the protection member 60, but the electrostatic speaker 1 may not include the protection member 60.
In the above-described embodiment, each member is bonded to other members by applying an adhesive to the edge portion, but the portion to which the adhesive is applied is not limited to the edge portion of the member. For example, an adhesive may be applied to each member in a lattice shape and bonded to other members. Alternatively, a region where the adhesive is applied in the form of dots may be regularly provided on each member, such as a matrix, to adhere to other members.
Moreover, the method of preventing members from shifting in the electrostatic speaker 1 is not limited to the method of fixing with an adhesive, and for example, the members may be formed with double-sided tape.
In the embodiment described above, the cover 50 has the conductive film formed on the entire surface of the insulating layer, but the conductive film may not be formed on the entire surface of the insulating layer. For example, the conductive film may be formed in a lattice shape on the surface of the insulating layer of the cover 50. Note that the size of the mesh of the lattice is preferably such that a human finger cannot pass through.

  In the above-described embodiment, the electrode 20 has a configuration in which a conductive film is formed on the surface of the film, but the configuration of the electrode 20 is not limited to this configuration. For example, a metal plate having conductivity may be used as the electrode 20. Alternatively, a cloth woven with conductive threads may be formed into a rectangular shape, and the cloth formed into a rectangular shape may be used as the electrode 20. Alternatively, the electrode 20 may be formed by forming a conductive film over a substrate in which an insulating material (for example, glass or phenol resin) is formed in a plate shape.

  In the embodiment described above, the electrode 20 is rectangular when viewed from a point on the Z axis, but the shape of the electrode 20 is not limited to a rectangle. For example, other shapes such as a circle, an ellipse, or a polygon may be used. In addition, the shape of the vibrating body 10 viewed from a point on the Z axis is not limited to a rectangle, and may be another shape such as a circle, an ellipse, or a polygon. Also, the shape of the electrostatic speaker 1 is not limited to a rectangle as viewed from a point on the Z axis, and may be another shape such as a circle, an ellipse, or a polygon. .

  In the embodiment described above, the electrostatic speaker 1 is configured to sandwich the vibrating body 10 between the electrode 20U and the electrode 20L, but the electrostatic speaker 1 is disposed on the front surface (or back surface) side of the vibrating body 10. A single-ended configuration in which only the electrode 20 is disposed may be employed.

In the embodiment described above, the dimensions in the X-axis direction and the Y-axis direction of each member except the vibrating body 10 are the same, but the dimensions may be different for each member. For example, the dimension in the X-axis direction and the dimension in the Y-axis direction of the cover 50 may be longer than other members. In addition, when the dimension in the X-axis direction and the dimension in the Y-axis direction of the cover 50 are longer than those of other members, the edge of the cover 50U and the edge of the cover 50L are bonded to each other so that the cover 50U and the cover 50L You may make it the vibrating body 10, the elastic member 30, and the electrode 20 be located in the sealed space. According to this configuration, the space in which the vibrating body 10, the elastic member 30, and the electrode 20 are sealed is sealed, so that the liquid is prevented from reaching the portion where the current flows from the outside, and the deterioration of the insulating property is prevented. be able to.
The length in the X-axis direction and the length in the Y-axis direction of the electrode 20 are longer than the length in the X-axis direction and the length in the Y-axis direction of the vibrating body 10, and the length in the X-axis direction and the Y-axis direction of the elastic member 30. It may be shorter than the length.

In the above-described embodiment, the elastic member 30 is disposed between the electrode 20 and the vibrating body 10 so that the electrode 20 and the vibrating body 10 do not come into contact with each other. The configuration for preventing contact is not limited to the configuration of the above-described embodiment. For example, a spacer formed of an insulator may be disposed between the electrode 20 and the vibrating body so that the electrode 20 and the vibrating body 10 do not contact each other. FIG. 5 is an exploded view of the electrostatic speaker according to this modification. The spacers 31U and 31L are formed of a rigid synthetic resin insulator, and the shape thereof is a rectangular frame shape as shown in FIG. In the present embodiment, the heights of the spacer 31U and the spacer 31L are the same.
In the electrostatic speaker 1, the electrode 20L is fixed to the lower surface of the spacer 31L, and the electrode 20U is fixed to the upper surface of the spacer 31U. The vibrating body 10 is fixed to the upper surface of the spacer 31L, and the lower surface of the spacer 31U is fixed to the vibrating body 10.
In this modification, the vibrating body 10 is fixed between the frame of the spacer 31U and the spacer 31L in a state where tension is applied so that no slack is generated. According to this configuration, the distance between the electrode 20 and the vibrating body 10 is maintained by the spacers 31U and 31L, and even if the vibrating body 10 vibrates, it does not contact the electrode 20.

In the present invention, the configuration of the drive circuit 100 may be the configuration shown in FIG. In FIG. 6, the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.
In FIG. 6, a transformer 111 is an insulating transformer (insulating transformer), and the primary side and the secondary side are electrically insulated. An acoustic signal is input to one terminal T41 on the primary side of the transformer 111. The other terminal T51 on the primary side of the transformer 111 is grounded to the ground. One terminal T11 on the secondary side of the transformer 111 is connected to the amplifier unit 130, and the other terminal T21 on the secondary side of the transformer 111 is connected to the ground GND and the amplifier unit 130 of the drive circuit 100. It is connected.

An AC (Alternating Current) adapter 200 is a switching type AC adapter, and rectifies an AC voltage obtained from the AC plug 202 and converts it into a DC voltage. The DC voltage obtained by this rectification serves as a power source for the amplifier unit 130. The positive side of the output of the AC adapter 200 is connected to the amplifier unit 130, and the negative side is connected to the ground GND of the drive circuit 100. Also, the negative side of the output of the AC adapter 200 and the grounding side of the AC plug 202 are connected via a capacitor C1. The capacitance of the capacitor C1 is preferably 1000 pF or less, and if it is less than this capacitance, the current flowing through the human body can be suppressed even if the human body contacts the electrode 20.
In the drive circuit 100, the ground GND of the drive circuit 100 may be grounded with high impedance, and the configuration shown in FIG. 7 may be used. In FIG. 7, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted. In the configuration shown in FIG. 7, the acoustic signal is input to the amplifier unit 130 via the resistor R5. The ground of the amplifier unit 130 is grounded via a resistor R6 and connected to the ground GND via a resistor R7. 6 and 7, even if the cover 50 is broken and the human body touches the electrode 20, the current flowing through the human body can be suppressed.

DESCRIPTION OF SYMBOLS 1 ... Electrostatic speaker, 10 ... Vibration body, 20, 20U, 20L ... Electrode, 30, 30U, 30L ... Elastic member, 31U, 31L ... Spacer, 40, 40U, 40L ... Spacer, 50, 50U, 50L ... Cover , 60, 60U, 60L ... protection member, 100 ... drive circuit, 110 ... transformer, 111 ... transformer, 120 ... bias power supply, 130 ... amplifier unit, 200 ... AC adapter, 201 ... capacitor, 202 ... AC plug

Claims (3)

A vibrating body having electrical conductivity;
A pair of electrodes opposed to each other with the vibrator interposed therebetween, and spaced from the vibrator;
A pair of covers having a waterproof and insulating film and a conductive film formed on the entire surface of at least one surface of the film, and facing each other with the vibrator and the pair of electrodes interposed therebetween;
A pair of spacers that are located between the pair of covers and the pair of electrodes, respectively, and have insulating properties through which sound passes;
The pair of covers are electrically connected to each other, supply a first acoustic signal to one of the pair of electrodes, and a second acoustic signal obtained by inverting the polarity of the first acoustic signal to the other of the pair of electrodes. An electrostatic speaker connected to the ground of a drive circuit to be supplied.   The electrostatic speaker according to claim 1, wherein edges of the pair of covers are fixed to each other, and the vibrating body and the pair of electrodes are located in a space between the pair of covers. . The drive circuit includes an amplifier circuit that amplifies an input signal;
The first acoustic signal is a signal obtained by amplifying the acoustic signal input to the amplifier circuit in the same phase in the amplifier circuit, and the second acoustic signal is amplified by the acoustic signal input to the amplifier circuit. In the circuit, the acoustic signal is a signal amplified by reversing the polarity,
The acoustic signal is input to one terminal on the primary side, the other terminal on the primary side is grounded, one terminal on the secondary side is connected to the amplifier circuit, and the other terminal on the secondary side is The electrostatic speaker according to claim 1, further comprising an insulating transformer connected to a ground of the drive circuit.

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