JP2009164818A - Electrostatic loudspeaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic loudspeaker that is freely bendable, and also that maintains a distance between electrodes to the predetermined value or less. <P>SOLUTION: The electrostatic loudspeaker 1 is formed by sequentially laminating the members of a conductive cloth 20L, an elastic member 30L, a vibrating material 10, an elastic member 30U, and a conductive cloth 20U. The conductive cloth 20U is woven with a ferromagnetic thread and the conductive cloth 20L, with a thread having a magnetic force, so that the conductive cloth 20U is attracted toward the conductive cloth 20L with a magnetic force of the conductive cloth 20L and thereby each member of the cloth is restricted. Accordingly, each member is never displaced in the X direction and Y direction and distance between the conductive cloth 20U and conductive cloth 20L is maintained to a constant value with the elastic member 30, so that the uniformity of the distance between the conductive cloth 20U and the conductive cloth 20L is never broken even when the electrostatic loudspeaker 1 is deformed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic speaker.

In the field of speakers, there are speakers called electrostatic speakers. This electrostatic speaker is composed of two electrodes facing each other at an interval and a conductive sheet-like vibrating body inserted between the two electrodes. When a bias voltage is applied and the voltage applied to the electrode is changed, the electrostatic force acting on the vibrating body is changed, and thereby the vibrating body is displaced. If this applied voltage is changed according to the input acoustic signal, the vibrating body repeats displacement (that is, vibrates) accordingly, and a reproduction wave corresponding to the acoustic signal is generated from the vibrating body.
In such an electrostatic speaker, as described in Non-Patent Document 1, two electrodes and a vibrating body are made of a soft material and can be deformed into various shapes. An electrostatic speaker has also been devised.

Adult Takeoka, 5 others, “1-bit wavefront recording and playback system using condenser microphone / speaker”, IEICE technical report. EA, Applied Acoustics, The Institute of Electronics, Information and Communication Engineers, June 2005, pp. 25-30

Now, the flexible electrostatic speaker described in Non-Patent Document 1 is edge-free, and the vibrating body is not constrained with respect to the electrodes. Because it is not constrained, it can be bent freely and can be deformed into various shapes. On the other hand, because it is not constrained, the electrode and the vibrator are easily displaced, and because it is not constrained, it can be deformed. The distance between the electrodes increases and becomes non-uniform.
When the distance between the electrodes is non-uniform, the magnitude of the electrostatic force acting on the vibrating body is different where the distance between the electrodes is short and long, and the sensitivity of the vibrating body 10 to react to the electrostatic force is the vibrating body. There is a problem that the entire surface of 10 is not uniform and sensitivity is lowered.

  The present invention has been made under the background described above, and is a technique that can be freely bent in an electrostatic speaker, and that the distance between electrodes when bent is not more than a predetermined distance. The purpose is to provide.

  In order to solve the above-described problems, the present invention provides a cloth-like first electrode having ferromagnetism and conductivity, and a cloth-like second electrode having conductivity and spaced apart from the first electrode. An electrode, a vibrating body having conductivity and positioned between the first electrode and the second electrode, and positioned between the vibrating body and the first electrode, and having insulating properties, elasticity, and sound transmission A first elastic member having a property, and a second elastic member positioned between the vibrating body and the second electrode, and having insulating properties, elasticity, and sound transmission properties. An electrostatic loudspeaker drawn toward the second electrode is provided.

In the present invention, the second electrode may be formed by weaving a conductive thread and a magnetic thread.
In the present invention, the first electrode may be formed by weaving a conductive thread and a ferromagnetic thread.
In the present invention, the first electrode and the second electrode may be woven in a stretchable manner.
In the present invention, peripheral edges of the first electrode, the first elastic member, the vibrating body, the second elastic member, and the second electrode may be sewn together by a non-conductive thread.
In the present invention, the first electrode and the second electrode may be sewn in an expanded state.
In the present invention, a magnet may be disposed on the surface of the second electrode opposite to the surface facing the first electrode.

  According to the present invention, an electrostatic speaker can be bent freely, and the distance between electrodes of the electrostatic speaker can be kept below a predetermined distance when bent.

[First Embodiment]
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 speaker 1 includes a vibrating body 10, conductive cloths 20U and 20L, elastic members 30U and 30L (first elastic member and second elastic member), and a thread 40. Yes. In the present embodiment, the configurations of the elastic members 30U and 30L are the same, and therefore, the description of “L” and “U” is omitted unless it is particularly necessary to distinguish between them.
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, and “×” in “○” is the front of the drawing. It means an arrow pointing from the back to the back.

(Configuration of each part of the electrostatic speaker 1)
First, each part constituting the electrostatic speaker 1 will be described. The vibrating body 10 is formed by depositing aluminum on a film such as PET (polyethylene terephthalate) or PP (polypropylene), and has a thickness of about several μm to several tens of μm. It has become.

  The elastic member 30 having elasticity is, for example, one obtained by compressing batting and applying heat so that air can pass therethrough, and the shape thereof is rectangular. The elastic member 30 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 rectangular conductive cloths 20U and 20L described later in the X direction and the Y direction, and the vibrating body 10 It is longer than the length in the X direction and Y direction. The heights of the elastic member 30U and the elastic member 30L in the Z direction are the same.

As shown in FIG. 3, the conductive cloth 20 </ b> U (first electrode) is a cloth obtained by plain weaving conductive warp 21 and ferromagnetic weft 22.
As shown in FIG. 4, the weft 22 includes a core layer 22A having a circular cross-section that serves as a core, and a protective layer 22B that covers the outer periphery of the core layer 22A. The core layer 22A is a layer in which polyamide, polyester, polyvinyl polymer, polyolefin, polyether, polyurethane, polycarbonate, and the like are mixed with particles mainly composed of a ferromagnetic substance such as iron, cobalt, nickel, The protective layer 22B is a layer formed of a fiber-forming polymer such as polyamide, polyester, polyolefin, or polyether.
The conductive cloth 20U has a rectangular shape and is plain woven so that air can pass therethrough, so that sound transmission is ensured. In addition, as long as the warp yarn 21 has conductivity, various yarns can be used, such as those obtained by subjecting a synthetic fiber to copper-nickel plating, and those obtained by adding carbon to a synthetic fiber.

As shown in FIG. 5, the conductive cloth 20 </ b> L (first electrode) is a cloth obtained by plain weaving warp 21 having conductivity and weft 23 having magnetic force.
As shown in FIG. 6, the weft 23 is composed of a core layer 23A having a circular cross section as a core and a protective layer 23B covering the outer periphery of the core layer 23A. The core layer 23A is a layer obtained by mixing a powder of a magnet of a ferrite magnet, a samarium magnet, or a neodymium magnet with polyamide, polyester, polyvinyl polymer, polyolefin, polyether, polyurethane, polycarbonate, or the like, and a protective layer 23B. Is a layer formed of the same fiber-forming polymer as the protective layer 22B.
The conductive cloth 20L has a rectangular shape and is plain woven so that air can pass therethrough, so that sound transmission is ensured.

  The thread 40 is, for example, a thread for sewing together the conductive cloths 20U and 20L, the elastic member 30, and the vibrating body 10, and the material thereof is a non-conductive (non-conductive) material such as cotton.

(Assembly method of electrostatic speaker 1)
Next, a method for assembling the electrostatic speaker 1 will be described. When the electrostatic speaker 1 is assembled, first, the elastic member 30L is placed on the conductive cloth 20L. When placing the elastic member 30L 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. 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 cloths 20U and 20L, the vibrating body 10 and the elastic member 30 are overlaid, the peripheral portions of the respective members are sewn together with the thread 40. Since the peripheral portion of each member is sewn and restrained by the thread 40 penetrating each member, even if the electrostatic speaker 1 is deformed, the conductive cloths 20U and 20L, the elastic member 30 and the vibrating body 10 may be displaced. Absent.
Further, since the conductive cloth 20L is woven using the weft 23 having magnetic force, and the conductive cloth 20U facing the conductive cloth 20L is woven using the ferromagnetic weft 22, the conductive cloth 20U is magnetic. Is attracted to the conductive cloth 20L.
Although all the surfaces of the conductive cloth 20U facing the conductive cloth 20L are drawn toward the conductive cloth 20L, the distance between them is kept constant by the elastic member 30, so that even if the electrostatic speaker 1 is deformed. The distance between the conductive cloth 20U and the conductive cloth 20L does not become uneven.
In addition, the insulating elastic member 30 has a larger area than the vibrating body 10 and the conductive cloths 20U and 20L, and each side of the elastic member 30 is outside the respective sides of the vibrating body 10 and the conductive cloth 20U and 20L. Therefore, the conductive cloths 20U and 20L and the vibrating body 10 do not contact and short-circuit.

(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 a midpoint on the output side of the transformer 50, and the two conductive cloths 20U and 20L are connected to one end and the other end on the output side of the transformer 50, respectively. Yes. 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 cloths 20U and 20L.
When a voltage is applied from the transformer 50 to the conductive cloths 20U and 20L and a potential difference is generated between the conductive cloth 20U and the conductive cloth 20L, the vibrating body 10 has either side of the conductive cloth 20U or the conductive cloth 20L. An electrostatic force that can be attracted by 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 at least one of the conductive cloth 20U and the conductive cloth 20L and is radiated to the outside of the electrostatic speaker 1.

In the present embodiment, the conductive cloth 20U is attracted to the conductive cloth 20L by magnetic force, and even if the electrostatic speaker 1 is deformed, the distance between the conductive cloth 20U and the conductive cloth 20L may be non-uniform. Therefore, the electrostatic force acting on the vibrating body 10 is the same everywhere on the vibrating body 10, and as a result, the sensitivity of the vibrating body 10 to react to the electrostatic force is the same everywhere on the vibrating body 10. Further, even when the vibrating body 10 is deformed, the distance between the conductive cloths is maintained, so that the sensitivity when the vibrating body 10 reacts to the electrostatic force does not decrease.
Moreover, in this embodiment, since the vibrating body 10, the conductive cloths 20U and 20L, and the elastic member 30 are flexible, they can be deformed into an arc shape or deformed along a curved surface. It can be attached to clothes.
Moreover, since each member is flexible, there is no possibility of damaging the human body even if the human body collides. For this reason, if it is attached to the headrest or placed inside a full-face helmet, it can be pronounced at the ear without damaging the human body.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. As shown in FIG. 7, the electrostatic speaker 1A according to the second embodiment includes a conductive cloth 25U and a conductive cloth 25L. The other elastic members 30, the vibrator 10, the yarn 40, the transformer 50, the input unit 60, and the bias power source 70 have the same configuration as in the first embodiment.

The conductive cloth 25U (first electrode) is not a plain weave but a cloth knitted as shown in FIG. 8A, and is woven using a conductive thread 26 and a ferromagnetic thread 27. Yes. The yarn 26 has the same configuration as the warp yarn 21 in the first embodiment, and the yarn 27 has the same configuration as the weft yarn 22 in the first embodiment.
The conductive cloth 25L (second electrode) is also a cloth knitted instead of plain weave, and is a cloth obtained by replacing the thread 27 in FIG. 8A with a thread 28 having magnetic force. The yarn 28 has the same configuration as the weft yarn 23 in the first embodiment.

Since the conductive cloths 25U and 25L are knitted, they have elasticity. The conductive cloths 25U and 25L are not limited to knitted weaves as long as they have stretchability. For example, the conductive cloths 25U and 25L may be rubber knitted as shown in FIG. 8 (b), and FIG. 8 (c). Pearl knitting may be used as shown.
In the case of rubber knitting or pearl knitting, two types of yarns 26 and 27 are used in the conductive cloth 25U, and two types of yarns 26 and 28 are used in the conductive cloth 25L.

  In the same manner as in the first embodiment, the members are stacked in the order of the conductive cloth 25L, the elastic member 30L, the vibrating body 10, the elastic member 30U, and the conductive cloth 25U, and the stacked members are stitched together with the thread 40. In this embodiment, when the members are sewn together, the conductive cloths 25U and 25L are sewn in a state where they are slightly stretched in the X direction and the Y direction.

For example, when the conductive cloths 25U and 25L having a plain weave are sewn without stretching as in the first embodiment, if the electrostatic speaker 1 is deformed into an arc shape, the plain weave has less stretchability than the knitted weave. For this reason, as shown in FIG. 9A, a portion not sewn with a thread on the inner peripheral side may sag, and the distance between the conductive cloths may not be constant.
However, according to the present embodiment, when the conductive cloths 25U and 25L are stitched together, the conductive cloths 25U and 25L are stretched and stitched together. Thus, the conductive cloth on the inner circumference side does not sag because the stretched conductive cloth shrinks on the inner circumference side, and the conductive cloth is stretched and pinched on the outer circumference side because it is knitted weave. Therefore, the distance between the conductive cloths does not change greatly.

  Moreover, in this embodiment, since the thread | yarn which comprises the conductive cloth 25U and 25L is provided with a clearance gap between a thread | yarn so that it may have a stretching property, compared with the case where a plain-woven conductive cloth is used. Air permeability is good and sound permeability is good.

[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 first embodiment described above, the conductive cloth 20U may be formed by performing copper-nickel plating on the surface of the yarn having the configuration of the weft yarn 22, and plain weaving the plated yarn as warp and weft. .
Alternatively, the conductive cloth 20L may be formed by performing copper nickel plating on the surface of the yarn having the configuration of the weft 23 and plain weaving the plated yarn as warp and weft.
Also in the second embodiment, copper nickel plating is applied to the surface of the yarn having the configuration of the weft yarn 22, and a knitted weave (or rubber weaving or pearl knitting) is used only for the plated yarn to conduct the conductive cloth 25U. The surface of the yarn having the structure of the weft 23 is plated with copper nickel, and only the plated yarn is knitted (or rubber woven, pearl knitted) to form the conductive cloth 25L. May be.

In the first embodiment described above, the conductive cloth 20L may be formed by plain weaving a yarn having the same configuration as the warp yarn 21. In this case, like the electrostatic speaker 1B shown in FIG. 10, the sheet-like permanent magnet 100 is adhered and disposed on the surface of the conductive cloth 20L. In this configuration, since the permanent magnet 100 attracts the conductive cloth 20U, the distance between the conductive cloth 20U and the conductive cloth 20L may be non-uniform even if the electrostatic speaker 1 is deformed as in the first embodiment. Absent.
When the permanent magnets are arranged on the surface of the conductive cloth 20L, a plurality of permanent magnets 100 may be bonded to the conductive cloth 20L as in the electrostatic speaker 1C shown in FIG. Also in this configuration, since the permanent magnet 100 attracts the conductive cloth 20U, even if the electrostatic speaker 1 is deformed, the conductive cloth 20U and the conductive cloth 20L do not shift.

In addition, in the structure which arrange | positions a magnet, you may make it not sew together the peripheral part of each member with the thread | yarn 40. FIG. The conductive cloth 20U is attracted toward the conductive cloth 20L by the magnetic force of the magnet, and each member is restrained if the magnetic force of the magnet is sufficient, so that each member does not shift in the X direction or the Y direction.
In the first embodiment and the second embodiment that do not use a magnet, the thread 40 may not be sewn together.
In the first embodiment, the conductive cloth 20U is attracted to the conductive cloth 20L side by the magnetic force of the conductive cloth 20L, and each member is restrained if the magnetic force of the conductive cloth 20L is sufficient. There is no deviation in the direction.
Also in the second embodiment, the conductive cloth 25L is attracted to the conductive cloth 25L side by the magnetic force of the conductive cloth 25L, and each member is restrained if the magnetic force of the conductive cloth 25L is sufficient. And no shift in the Y direction.

  In the above-described embodiment, the conductive cloth 20L is woven using a thread having magnetic force. However, the conductive cloth 20L is magnetized to a conductive cloth woven using a conductive thread and a ferromagnetic thread. A conductive cloth to which a magnetic force is applied may be used as the electrode of the electrostatic speaker.

1 is a schematic diagram 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. The figure which showed typically the weaving method of the conductive cloth 20U. The figure which showed the structure of the weft 22 typically. The figure which showed typically the weaving method of the conductive cloth 20L. The figure which showed the structure of the weft 23 typically. It is a schematic diagram of the electrostatic speaker 1A which concerns on 2nd Embodiment of this invention. It is the figure which showed the modification of the weave of a conductive cloth. It is a figure showing the section when changing the electrostatic speaker concerning the present invention. It is a schematic diagram of the electrostatic speaker which concerns on the modification of this invention. It is a schematic diagram of the electrostatic speaker which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Electrostatic speaker, 10 ... Vibrating body, 20U, 20L ... Conductive cloth, 21 ... Warp, 22, 23 ... Weft, 25U, 25L ... Conductive Cloth, 26, 27, 28 ... thread, 30U, 30L ... elastic member, 40 ... thread, 50 ... transformer, 60 ... input section, 70 ... bias power supply, 100 ··magnet

Claims (7)

A cloth-like first electrode having ferromagnetism and conductivity;
A cloth-like second electrode having electrical conductivity and spaced apart from the first electrode;
A vibrating body having electrical conductivity and positioned between the first electrode and the second electrode;
A first elastic member located between the vibrating body and the first electrode and having insulating properties, elasticity, and sound transmission;
A second elastic member positioned between the vibrating body and the second electrode and having insulating properties, elasticity, and sound transmission properties;
An electrostatic speaker in which the first electrode is attracted toward the second electrode by a magnetic force.   The electrostatic speaker according to claim 1, wherein the second electrode is formed by weaving a conductive thread and a magnetic thread.   The electrostatic speaker according to claim 1, wherein the first electrode is formed by weaving conductive yarn and ferromagnetic yarn.   The electrostatic speaker according to claim 1, wherein the first electrode and the second electrode are woven in a stretchable manner.   The peripheral edges of the first electrode, the first elastic member, the vibrating body, the second elastic member, and the second electrode are sewn together by a non-conductive thread. Electrostatic speaker.   The electrostatic speaker according to claim 5, wherein the first electrode and the second electrode are stitched together in an expanded state.   The electrostatic speaker according to claim 1, wherein a magnet is disposed on a surface of the second electrode opposite to the surface facing the first electrode.

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