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JP2009188516

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DESCRIPTION JP2009188516
The present invention makes it possible to increase the amplitude of a vibrating body while
having sound transparency and rigidity. The electrodes 20U and 20L are formed by processing a
metal porous body having a three-dimensional three-dimensional network structure like a sponge
into a rectangular plate having a predetermined thickness. The metal porous body forming the
electrode 20 has conductivity and air permeability (sound permeability), and the size of the hole
on the back side opposite to the vibrating body 10 is opposite to the vibrating body 10 It is
smaller than the size of the hole on the surface side. Although the electrode 20 has a large
number of holes, the branch of the network structure is thick on the vibrating body 10 side, and
the size of the holes is smaller than the size of the hole on the opposite side to the vibrating body
10 Since the area of the metal portion can be made large, the amplitude of the vibrator 10 does
not become small while having high sound transparency. [Selected figure] Figure 2
Electrostatic speaker
[0001]
The present invention relates to an electrostatic speaker.
[0002]
In the field of loudspeakers, there are loudspeakers called electrostatic loudspeakers.
The electrostatic loudspeaker is composed of two fixed electrodes facing each other at a distance
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and a sheet-like vibrator having conductivity inserted between the two fixed electrodes, and the
predetermined type of the vibrator is as follows. When the bias voltage is applied and the voltage
applied to the fixed electrode is changed, the electrostatic force acting on the vibrating body is
changed, whereby the vibrating body is displaced. If this applied voltage is changed according to
the input acoustic signal, the vibrator repeats displacement (i.e. vibrates) accordingly, and a
reproduction wave corresponding to the sound signal is generated from the vibrator. In such an
electrostatic speaker, as described in Patent Document 1, adopting a punching metal having a
plurality of holes as two fixed electrodes is also performed, and in this configuration, The sound
generated by the vibrator passes through the hole of the punching metal and is radiated to the
outside of the speaker.
[0003]
Unexamined-Japanese-Patent No. 11-178098
[0004]
By the way, when adopting a punching metal as a fixed electrode, if the diameter of the hole of
the punching metal is increased, the area of the metal portion acting as an electrode on the
surface of the punching metal becomes small and the electrostatic force acting on the vibrator
also becomes small. The problem arises that the amplitude of the vibrating body is reduced.
For this reason, in the fixed electrode of punching metal, it is preferable to reduce the diameter of
the hole and widen the area as the electrode while securing sound transmission by providing the
hole. However, since punching metal punches holes in a plate-like metal plate with a metal mold,
it is possible to punch holes with a thin plate thickness easily to make small holes, but if the fixed
electrode is thin, the rigidity of the fixed electrode is It becomes smaller and another problem
arises that it becomes difficult to keep the distance between the fixed electrode and the vibrator
constant.
[0005]
The present invention has been made under the above-described background, and it is an object
of the present invention to provide a technology capable of increasing the amplitude of a
vibrating body while having sound transparency and rigidity.
[0006]
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In order to solve the problems described above, the present invention provides a first electrode
formed of a porous body of a three-dimensional network structure having conductivity and air
permeability, and a three-dimensional network structure having conductivity and air
permeability. A second electrode which is formed of a porous body and is disposed to face the
first electrode, and has conductivity, and the first electrode and the first electrode are disposed
between the first electrode and the second electrode. Provided is an electrostatic speaker having
two electrodes and a vibrator disposed at a distance.
[0007]
In the present invention, in the first electrode and the second electrode, the size of the hole in the
surface facing the vibrator is in the surface opposite to the surface facing the vibrator. It may be
smaller than the size of the hole.
[0008]
According to the present invention, it is possible to increase the amplitude of the vibrating body
while having sound transparency and rigidity.
[0009]
[Mechanical Configuration of Embodiment] FIG. 1 is a view schematically showing the
appearance of an electrostatic speaker 1 according to an embodiment of the present invention,
FIG. 2 is a cross-sectional view of the electrostatic speaker 1, FIG. 1 is an exploded perspective
view of an electrostatic speaker 1. FIG.
As shown in the figure, the electrostatic loudspeaker 1 has a vibrating body 10, an electrode 20U
and an electrode 20L facing each other with the vibrating body 10 interposed therebetween, a
spacer 30U and a spacer 30L.
In the present embodiment, the configurations of the electrodes 20U and 20L are the same, and
the configurations of the spacers 30U and 30L are the same. Therefore, when there is no
particular need to distinguish between the two, the descriptions of "L" and "U" are described.
Omit.
Also, the dimensions of the respective components such as the vibrator and electrodes in the
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drawing are different from the actual dimensions so that the shapes of the components can be
easily understood.
Further, in the drawings, those in which • is described in o means an arrow directed
from the back to the front of the drawing, and those in which x is described in o are the
front of the drawing. It means the arrow from the back to the back.
[0010]
(Structure of Each Part of Electrostatic Loudspeaker 1) The vibrator 10 is obtained by depositing
a metal film or applying a conductive paint to a film such as PET (polyethylene terephthalate,
polyethylene terephthalate) or PP (polypropylene, polypropylene), for example. The thickness is
about several μm to several tens of μm.
[0011]
The spacer 30 is formed of an insulator, and its shape is a square tube as shown in FIG.
In the present embodiment, the lengths in the X direction and the Y direction of the spacer 30
and the lengths in the X direction and the Y direction of the electrode 20 are the same. Further,
the heights of the spacers 30U and the spacers 30L in the Z direction are the same.
[0012]
The electrode 20 is formed by processing a metal porous body having a three-dimensional threedimensional network structure like a sponge into a rectangular plate having a predetermined
thickness. In the present embodiment, the lengths in the X direction and the Y direction of the
electrode 20 and the lengths in the X direction and the Y direction of the vibrating body 10 are
the same. In addition, the metal porous body forming the electrode 20 has conductivity and air
permeability (sound permeability), and the size of the hole on the back surface opposite to the
vibrating body 10 is opposite to the vibrating body 10 It is smaller than the size of the hole on
the surface side.
[0013]
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Here, an example of the manufacturing method of this metal porous body is demonstrated. First,
a metal powder, a binder (bonding agent) and water are kneaded to form a slurry. Next, the
prepared slurry has a three-dimensional three-dimensional network structure, and is
impregnated with a plate-like urethane foam with a predetermined thickness to form a slurry film
on the surface of the branch structure of the urethane foam network structure. Here, by
adjusting the amount of binder and water for the slurry and adjusting the time until the viscosity
and curing, the impregnated slurry is cured while moving from the surface side to the back side
of the urethane foam. The film thickness of the slurry attached to the branch differs between the
front side and the back side. In addition, as a method of changing the film thickness of the slurry
between the surface side and the back side, after the slurry is soaked in the whole urethane foam
and dried, the slurry is again soaked on the back side from the center and the back side from the
center The film thickness of the slurry on the back surface side may be increased by stacking
layers of the slurry.
[0014]
Then, after the slurry is dried, the urethane foam having a film of the slurry is fired to remove the
urethane foam and the binder, and the metal contained in the slurry is sintered in the form of
urethane foam. In the metal porous body produced in this manner, the thickness of the slurry is
thicker on the back side than on the surface side, so the branches forming the network structure
of the metal porous body are thicker from the center side toward the back side It becomes
thinner as it goes from the center side to the surface. And while the branch on the back surface
side is thick, the size of the pores of the porous body is small, while the branch on the front
surface side is thinner than the back surface, the pores of the porous body are larger than the
back surface side.
[0015]
(Overall Configuration of Electrostatic Speaker 1) When assembling the electrostatic speaker 1,
the spacer 30L is fixed to the peripheral portion of the electrode 20L, and the peripheral portion
of the vibrating body 10 is fixed on the spacer 30L. The vibrating body 10 is fixed to the spacer
30L in a state where tension is applied. Then, the spacer 30U is fixed on the peripheral portion of
the vibrating body 10, and the peripheral portion of the electrode 20U is fixed on the spacer
30U. In this configuration, the electrodes 20U and 20L are fixed to the spacers 30U and 30L so
as to face each other across the vibrating body 10, and the vibrating body 10 is perpendicular to
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the electrode 20 in the space between the electrodes 20U and 20L. It is supported so as to be
able to vibrate in the Z direction.
[0016]
Electrical Configuration of Embodiment 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 supply 70 for applying a DC bias to the vibrator 10. The bias power supply 70 is
connected to the vibrating body 10 and the middle point on the output side of the transformer
50, the electrode 20U is connected to the output side terminal of the transformer 50, and the
electrode 20L is on the output side of the transformer 50 Connected to the other terminal of the
In this configuration, when an acoustic signal is input to the input unit 60, voltages
corresponding to the input acoustic signal are applied to the electrode 20 and the vibrating body
10, respectively.
[0017]
When a potential difference is generated between the electrode 20U and the electrode 20L by
the applied voltage, an electrostatic force acts on the vibrating body 10 so as to be drawn to the
side of either electrode 20. That is, the vibrating body 10 is displaced in the Z direction
(deflection) according to the acoustic signal, and the displacement direction is successively
changed to become vibration, and the sound corresponding to the vibration state (frequency,
amplitude, phase) It originates from the vibrating body 10. The generated sound passes through
the electrodes 20U and 20L and is emitted to the outside of the electrostatic speaker 1.
[0018]
In the present embodiment, a metal porous body is adopted as the electrode 20 for vibrating the
vibrating body 10, and the size of the hole securing the acoustic transparency is small on the
electrode surface, and the area as the electrode is wide. There is. Moreover, since the holes are
distributed throughout the electrode 20, the electrode 20 has high air permeability and good
sound transmission. Further, in the electrode 20, the area of the metal portion on the back
surface affects the electrostatic force for driving the vibrating body 10, and the amplitude of the
vibrating body decreases as the size of the hole increases. Although there are a large number of
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holes on the back side, the branches of the network structure are thick and the size of the holes
is smaller than the size of the holes on the front side, and the area of the metal part on the back
side is large. While having transparency, the amplitude of the vibrator 10 does not decrease.
Further, in the present embodiment, in the electrode 20 which is a porous body, the thickness of
the branch forming the porous body on the surface side is thinner than the back side, and the
size of the holes is larger than the back side. As described above, in the present embodiment, the
thickness of the branches on the surface side is thin, and the porous body is formed compared to
the case where the thickness of the branches of the porous body is made the same as a whole
and the size of the pores on the back side is reduced. Since the amount of metal to be used is
reduced, the mass of the electrostatic speaker 1 can be reduced. Further, in the present
embodiment, when forming a small hole in the electrode 20, it is not necessary to reduce the
thickness of the electrode 20 as in the case of punching metal, so the rigidity of the electrode can
be increased. The distance between and can be kept constant.
[0019]
[Modifications] Although the embodiment of the present invention has been described above, the
present invention is not limited to the above-described embodiment, and can be practiced in
various other forms. For example, the above-described embodiment may be modified as follows
to implement the present invention.
[0020]
In the electrode 20 of the embodiment described above, the sizes of the pores of the metal
porous body are different on the back surface side and the surface side, but the sizes of the pores
may be the same on the surface side and the back surface side.
[0021]
When forming the electrode 20, the size of the pores in the surface of the electrode 20, the
thickness in the Z direction, the shape, etc. may be adjusted by pressing the metal porous body in
the X direction, Y direction, Z direction or the like.
Since the electrode 20 is a metal porous body having a three-dimensional three-dimensional
network structure and has a large space, it can be easily pressed as compared with a simple plate
metal. In addition, when processing the shape of the electrode 20, it is not limited to the shape of
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the said embodiment, You may press into various shapes from a viewpoint of a design.
[0022]
In the electrostatic speaker 1, the peripheral portion of the vibrating body 10 is sandwiched and
fixed to the spacer 30, and the amplitude of the vibrating body 10 is larger as the central portion
is farther from the spacer 30 and smaller as it approaches the spacer 30. If the amplitude of the
vibrating body 10 differs between the central portion and the peripheral portion, the radiation
characteristic (directional characteristic) of the sound output from the electrostatic speaker 1 is
affected.
[0023]
In order to control the radiation characteristics of the sound to be output, the distance from the
electrode 20 to the vibrating body 10 is made different between the central portion and the
peripheral portion, and the magnitude of the electrostatic force acting on the vibrating member
10 is the central portion and the peripheral portion There is a method of controlling the radiation
characteristic by controlling the amplitude of the vibrating body 10 differently. When this
method is adopted, the back surface side of the electrode 20 may be processed into a curved
surface by pressing, and the thickness of the electrode 20 may be changed from the central
portion of the electrode 20 toward the periphery. When the electrode 20 of this configuration is
used, the distance from the electrode 20 to the vibrator 10 is different between the central
portion and the peripheral portion. Then, as compared with the case where the thickness of the
electrode 20 is uniform, the magnitude of the electrostatic force acting on the peripheral portion
of the vibrating body 10 and the amplitude of the vibrating body 10 are different, and are output
from the electrostatic speaker 1 The radiation characteristics of the sound are different from
those in the case where the thickness of the electrode 20 is uniform. As the shape of the
electrode 20 of this configuration, there is a shape in which the back surface side is processed
into a convex lens-like curved surface, and the thickness becomes thinner as the central portion
is thicker and the peripheral portion is closer.
[0024]
FIG. 1 is a schematic view of an electrostatic loudspeaker 1 according to an embodiment of the
present invention. FIG. 2 is a view showing a cross section and an electrical configuration of the
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electrostatic speaker 1. FIG. 2 is an exploded perspective view of the electrostatic speaker 1;
Explanation of sign
[0025]
DESCRIPTION OF SYMBOLS 1 ... Electrostatic type speaker, 10 ... Vibrator, 20, 20 U, 20 L ...
Electrode, 30, 30 U, 30 L ... Spacer, 50 ... Transformer, 60 ... Input part, 70 ・ ・ ・ bias power
supply
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