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JP2009290424

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DESCRIPTION JP2009290424
An object of the present invention is to prevent a contact between a vibrating body and an
electrode while vibrating the vibrating body with high sensitivity, and displace the vibrating body
linearly. A cushion member (40U, 40L) is disposed between a vibrator (10) and electrodes (20U,
20L), so that the vibrator (10) and the electrodes (20U, 20L) are not in contact with each other.
Further, the cushioning materials 40U and 40L disposed between the vibrating body 10 and the
electrodes 20U and 20L have elasticity, and the waveforms of the cushioning materials 40U and
40L are regularly arranged, so the waveform is the original one. The force to return to the shape
is uniform and uniform within the surface of the cushioning materials 40U and 40L. As described
above, when the cushion members 40U and 40L have the same elasticity, when the vibrator 10 is
displaced by electrostatic force, the displacement of the vibrator 10 does not vary. Further, even
if the cushion members 40U and 40L are made thin, the waveform is deformed, the displacement
amount of the vibrating body 10 is secured, and the vibrating body 10 is displaced linearly.
[Selected figure] Figure 2
Electrostatic speaker
[0001]
The present invention relates to an electrostatic speaker.
[0002]
The electrostatic speaker is composed of two parallel flat electrodes facing each other at intervals
and a sheet-like vibrating body having conductivity inserted between the two electrodes, and the
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predetermined type of the vibrating body is When the bias voltage is applied and the voltage
applied to the electrodes 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 acoustic signal to be input, the vibrator repeats
displacement (i.e. vibrates) accordingly, and an acoustic wave corresponding to the acoustic
signal is generated from the vibrator. Then, the generated acoustic wave is radiated to the
outside through the hole formed in the flat electrode.
[0003]
By the way, the magnitude of the electrostatic force acting on the vibrating body of such an
electrostatic speaker is related to the distance between the vibrating body and the flat electrode,
and in order to vibrate the vibrating body well, the vibrating body It is sufficient to narrow the
distance between the and the flat electrode. However, when the distance between the vibrating
body and the flat electrode is narrowed, there is a possibility that the vibrating body and the flat
electrode may be in contact with each other. Therefore, there is an electrostatic type speaker
disclosed in Non-Patent Document 1 as an electrostatic type speaker provided with a
configuration for avoiding the contact between the vibrator and the flat electrode. In this
electrostatic speaker, the vibrator has an edgeless structure in which the peripheral portion is not
restrained, and the polyester wool is in the form of a non-woven fabric, and the vibrator is
sandwiched between the flat electrodes. According to this configuration, the vibrator is supported
at a fixed position between the planar electrodes and does not come in contact with the planar
electrodes.
[0004]
M. Okazaki, 4 others, "Condenser speaker with diaphragm that vibrates in all bands and its
application", Proceedings of the 2004 Acoustical Society of Japan Annual Conference on
Acoustics, The Japan Acoustics Society, September 2004, p. 563-564
[0005]
In the electrostatic speaker disclosed in Non-Patent Document 1, the ester wool supported by
sandwiching the vibrator has air inside and has elasticity.
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Therefore, when the vibrator is displaced by electrostatic force, the ester wool is compressed and
deformed. The deformed ester wool tries to return to the original shape by elasticity, but in the
sheeted ester wool, the force to return to the original because the volume density of the fibers is
not necessarily uniform depending on the sheet-like position, That is, variations occur in the
force applied to the vibrator. If the force applied from the ester wool to the vibrating body varies,
the displacement of the vibrating body varies, and the acoustic signal is not correctly reproduced
when the acoustic signal is input. Furthermore, if the elasticity varies in the surface of the ester
wool, the vibrator can not be held at the center position between the electrodes in the state
where the acoustic signal is not input, and distortion in the acoustic characteristics will increase.
If the thickness of the ester wool is reduced to narrow the distance between the vibrator and the
flat electrode to improve the sensitivity of the vibrator, the force required to displace the vibrator
by the same amount is greater than when the ester wool is thick. It becomes large and the
vibrator does not displace linearly.
[0006]
The present invention has been made under the above-described background, and it is an object
of the present invention to provide a technique for displacing a vibrating body linearly by
preventing the contact between the vibrating body and an electrode while vibrating the vibrating
body with high sensitivity. .
[0007]
In order to solve the problems described above, the present invention has a first electrode having
conductivity, a second electrode having conductivity and spaced apart from the first electrode,
and conductivity. A vibrator which is disposed between the first electrode and the second
electrode and spaced apart from the first electrode and the second electrode, and has a wave
shape and elasticity, and between the vibrator and the first electrode And a second cushion
material disposed between the vibrator and the second electrode.
[0008]
In the present invention, the first cushioning material and the second cushioning material are a
plurality of filaments arranged along a first direction, and a plurality of filaments arranged along
a second direction different from the first direction. And may be formed into a corrugated shape
by heating and bonding the bonded nonwoven fabric.
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In the present invention, the number of filaments arranged along the first direction may be
different from the number of filaments arranged along the second direction.
Further, in the present invention, in the first cushion material and the second cushion material,
the direction of the wave of the waveform is the same as the first direction, and the number of
filaments along the first direction is the number of the filaments. It may be less than the number
of filaments along two directions. Further, in the present invention, the first cushion material and
the second cushion material may have a plurality of slits penetrating from the front surface to
the back surface. Further, in the present invention, the direction of the wave of the waveform
may be different between the first cushion material and the second cushion material.
[0009]
According to the present invention, it is possible to vibrate the vibrating body with high
sensitivity while preventing the contact between the vibrating body and the electrode, and to
displace the vibrating body linearly.
[0010]
Example 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, and FIG. FIG. 2 is an exploded perspective view of the speaker 1;
As shown in the figure, this electrostatic speaker 1 has a vibrator 10, electrodes 20U and 20L,
spacers 30U and 30L, and cushioning materials 40U and 40L. In the present embodiment, since
the configurations of the electrodes 20U and 20L are the same, the descriptions of L and
U are omitted unless there is a need to distinguish between the two. Further, since the
configurations of the spacer 30U and the spacer 30L are the same, and the configurations of the
cushioning material 40U and the cushioning material 40L are the same, L and U are not
particularly necessary for these members. The description of "is omitted. Also, the dimensions of
each component such as the vibrator and electrode in the figure are made different from the
actual dimensions so that the shapes of the components can be easily understood, and in What ""
is described means an arrow pointing from the back of the drawing to the front.
[0011]
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(Configuration of Each Part of Electrostatic Speaker 1) First, each part of the electrostatic speaker
1 will be described. The vibrating body 10 is, for example, a film made of PET (polyethylene
terephthalate, polyethylene terephthalate), PP (polypropylene, polypropylene) or the like, with a
metal film deposited or coated with a conductive paint, and the thickness thereof is several μm
to The thickness is about several tens of μm.
[0012]
The spacer 30 is formed of an insulator, and its shape is a rectangular frame 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.
[0013]
The electrode 20 is formed in a rectangular plate shape and has conductivity. Further, in the
electrode 20, in order to ensure sound transmission, a plurality of through holes 21 penetrating
from the front surface to the back surface of the electrode 20 are provided at predetermined
intervals. In the present embodiment, the lengths in the X and Y directions of the electrode 20
and the lengths in the X and Y directions of the vibrating body 10 are the same.
[0014]
As shown in FIG. 4, the cushioning material 40 arranges 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 bonding to form a sheet-like non-woven fabric by heating, the non-woven fabric is
processed into a corrugated shape as shown in FIGS. In the cushioning material 40, the direction
of the corrugated wave (the direction in which the unevenness is repeated) is one direction (X
direction in the cushioning material 40U of FIG. 3 and Y direction in the cushioning material 40L
of FIG. 3) When compressed in the direction, the waveform deforms so as to expand, and when
the compression force in the Z direction is removed, the waveform returns to its original shape.
That is, the cushioning material 40 has elasticity and deforms in response to an external force.
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[0015]
(Structure of Electrostatic Speaker 1) Next, the structure of the electrostatic speaker 1 will be
described. In the electrostatic loudspeaker 1, the peripheral portion of the vibrating body 10 is
sandwiched between the spacer 30U and the spacer 30L in a so-called tensionless state in which
no tension is applied. Further, in the electrostatic speaker 1, the electrode 20U is fixed to the
spacer 30U, and the electrode 20L is fixed to the spacer 30L. And cushion material 40L is
arranged inside frame shaped spacer 30L, and the peak part of the waveform of cushion material
40L is in contact with vibrator 10 and electrode 20L. Further, a cushioning material 40U is
disposed inside the frame-shaped spacer 30U, and the top of the waveform of the cushioning
material 40U is in contact with the vibrating body 10 and the electrode 20U. Here, as shown in
FIG. 3, the cushioning material 40L is disposed such that the direction of the wave of the
waveform is in the Y direction, while the cushioning material 40U is disposed such that the
direction of the wave of the waveform is in the X direction In the cushion material 40U and the
cushion material 40L disposed above and below the vibrating body 10, the direction of the wave
of the waveform is different.
[0016]
(Electrical Configuration of 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 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, and the two electrodes 20 are connected to one end and the other end of the output side of
the transformer 50, respectively. 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]
(Operation of Electrostatic Speaker 1) Next, the operation of the electrostatic speaker 1 will be
described. When an acoustic signal input to the input unit 60 is supplied to the transformer 50
and a voltage difference is generated between the facing electrode 20U and the electrode 20L
due to the voltage applied from the transformer 50, the vibrating body 10 is set to Z in FIG. An
electrostatic force that pulls in the direction side or the direction opposite to the Z direction (−Z
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direction) acts on the vibrator 10.
[0018]
For example, when an acoustic signal is input to the input unit 60, a positive voltage is applied to
the electrode 20U, and a negative voltage is applied to the electrode 20L, a positive voltage is
applied to the vibrating body 10 by the bias power supply 70. Therefore, the portion between the
electrode 20U and the electrode 20L in the vibrator 10 repels the electrode 20U to which the
positive voltage is applied, and is attracted to the electrode 20L to which the negative voltage is
applied. Displace to the 20L side.
[0019]
When the vibrating body 10 is displaced in the direction of the electrode 20L, the cushioning
material 40L is compressed by the vibrating body 10, and the waveform of the cushioning
material 40L spreads in the lateral direction as shown in FIG.
The cushioning material 40L has elasticity, and the corrugations of the cushioning material 40L
are regularly arranged, so that the force to return the corrugation to its original shape is uniform
and uniform within the surface of the cushioning material 40L. . Thus, when the elasticity of the
cushioning material 40L is equal within the plane of the cushioning material 40L, when the
vibration body 10 is displaced by electrostatic force, the vibration body 10 is supported as when
the vibration body 10 is supported by ester wool. As a result, the acoustic signal is correctly
reproduced when the acoustic signal is input.
[0020]
Next, when an acoustic signal is input to the input unit 60, a negative voltage is applied to the
electrode 20U, and a positive voltage is applied to the electrode 20L, the vibrator 10 repels the
electrode 20L to which a positive voltage is applied. While being attracted by the electrode 20U
to which a negative voltage is applied, it is displaced toward the electrode 20U.
[0021]
When the vibrating body 10 is displaced in the direction of the electrode 20U, the cushioning
material 40U is compressed by the vibrating body 10, and the waveform of the cushioning
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material 40U spreads in the lateral direction as shown in FIG.
Since the cushioning material 40U also has elasticity and the corrugations of the cushioning
material 40U are also regularly arranged, the force to return the corrugation to its original shape
is uniform and uniform within the surface of the cushioning material 40U. . As described above,
since the elasticity of the cushioning material 40U is also uniform within the surface of the
cushioning material 40U, when the vibratory body 10 is displaced by electrostatic force, the
vibratory body 10 is supported as when the vibratory body 10 is supported by ester wool. There
is no variation in displacement, and when an acoustic signal is input, the acoustic signal is
correctly reproduced.
[0022]
Thus, the vibrating body 10 is displaced according to the acoustic signal (deflection), and the
displacement direction is sequentially changed to become vibration, and a sound corresponding
to the vibrating state (frequency, amplitude, phase) is transmitted from the vibrating body 10
Occur. The generated sound passes through at least one of the electrode 20U side and the
electrode 20L side and is emitted to the outside of the electrostatic speaker 1.
[0023]
In addition, since the cushion material 40 has elasticity, when the acoustic signal is not supplied
and the electrostatic force does not act on the vibrating body 10, the cushion material 40 tries to
return to the original shape by the elasticity. Here, since the shapes of the cushioning material
40U and the cushioning material 40L are the same, the elasticity of each cushioning material is
the same, and the force with which a plurality of regularly arranged waveforms press the
vibrating body 10 is the same for each cushioning material 40 Become. Then, the portions of the
waveform arranged regularly support the vibrating body 10 evenly, and the displacement of the
vibrating body 10 does not vary. As a result, even in the state where the acoustic signal is not
supplied to the electrostatic speaker 1, no wrinkles or sag occurs in the vibrating body 10.
[0024]
There is also a proportional relationship between the force required to compress the cushioning
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material 40 and the amount of change in thickness of the cushioning material 40 in the Z
direction. For this reason, when assembling the electrostatic speaker 1, if the cushioning material
40 in a compressed state with a large contraction amount is disposed between the electrode 20
and the vibrating body 10, the cushioning material 40 has a force to press the vibrating body 10.
Since the vibration member 10 is large, the displacement of the vibration member 10 becomes
difficult, and the sensitivity of the vibration member 10 becomes low. On the other hand, when
assembling the electrostatic speaker 1, if the cushioning material 40 in a compressed state with a
small amount of contraction is disposed between the electrode 20 and the vibrating body 10, the
cushioning material 40 has a small force to hold the vibrating body 10 down. Therefore, the
vibrating body 10 is easily displaced, and the sensitivity of the vibrating body 10 is improved.
Thus, by adjusting the distance between the vibrating body 10 and the electrode 20 to adjust the
amount of compression of the cushioning material 40, the sensitivity of the vibrating body 10 is
controlled, and the lowest resonance frequency is lowered to reproduce the speaker reproduction
band. Can be extended to the low range.
[0025]
In addition, since the height of the waveform in the cushioning material 40U and the height of
the waveform in the cushioning material 40L are the same, when the vibrating body 10 is
sandwiched between the cushioning material 40U and the cushioning material 40L, the vibrating
body 10 is accurately aligned with the cushioning material 40U It can be supported at an
intermediate position between the cushioning material 40L and the cushioning material 40L.
When the distance between the electrode 20 and the vibrating body 10 is shortened, in the case
of a sheet-like ester wool, the force required to displace the vibrating body by the same amount
increases as compared with the case where the ester wool is thick. Although the displacement
amount of the vibrating body 10 is small, in the present invention, it is possible to make the
cushioning material 40 itself thin, and even if it is thin, the waveform is deformed and the
displacement amount of the vibrating body 10 is secured. The body 10 is displaced linearly. Note
that the size of the waveform may be appropriately set in accordance with the acoustic
characteristics within a range in which the vibrating body is linearly displaced. For example, in
the case of making the electrostatic speaker thin, the waveform of the waveform is The pitch may
be 2 to 4 mm and the height may be 0.3 mm.
[0026]
[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
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various other forms. For example, the above-described embodiment may be modified as follows
to implement the present invention.
[0027]
In the present invention, the cushioning material 40 is slightly compressed in the Z direction so
as not to be separated from the vibrating body 10 when the vibrating body 10 is displaced in the
direction of the electrode 20U or in the direction of the electrode 20L. It is preferable to arrange
between them. If the cushioning material 40 and the vibrating body 10 in the opposite direction
to the displacement direction of the vibrating body 10 are separated when the vibrating body 10
is displaced, the contact state and the non-contact state are repeated when the vibrating body 10
vibrates, Although the acoustic characteristics of the sound to be radiated are deteriorated, if the
vibration member 10 is kept away from the cushioning material 40, it is emitted without
repeating the contact state and the non-contact state when the vibration member 10 vibrates.
Sound characteristics of the sound can be improved.
[0028]
In the electrostatic speaker 1 described above, the direction of the wave of the cushioning
material 40U is different from the direction of the wave of the cushioning material 40L, but as
shown in FIG. 7, the waveform of the cushioning material 40U is And the direction of the
waveform of the cushioning material 40L may be the same.
[0029]
In the electrostatic speaker 1 described above, the wave shape of the cushioning material 40 of
the waveform is a sine wave shape, but may be a triangular wave shape as in the cushioning
material 40A shown in FIG. Moreover, it may be a waveform in which the shape of a semicircle
continues like cushion material 40B shown in Drawing 8 (b).
Further, like a cushioning material 40C shown in FIG. 8C, the shape may be a trapezoidal wave.
[0030]
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In the present invention, when the cushioning material 40 is formed, the number of filaments
extending in the same direction as the direction of the corrugated wave in the cushioning
material 40 is made smaller than the number of filaments aligned in the direction intersecting
the filaments. It is also good. For example, when the wave direction is the X direction as in the
cushioning material 40 shown in FIG. 9, the number of filaments along the X direction is smaller
than the number of filaments along the Y direction. As described above, when the number of
filaments extending in the same direction as the direction of the waves is changed, the elasticity
of the cushioning material 40 is also changed, and thus the sensitivity of the vibrator 10 is also
changed. As a result, the force required to displace the vibrating body 10 can be reduced
compared to the case where the filaments are the same in the longitudinal direction and the
lateral direction, and the minimum resonance frequency can be lowered to extend the
reproduction band of the speaker to the low frequency range. it can.
[0031]
In the present invention, as shown in FIG. 10, a plurality of slits 45 may be provided in the
cushioning material 40, and the filaments forming the cushioning material 40 may be cut to
adjust the elasticity of the cushioning material 40. When the slits 45 are provided in the
cushioning material 40, the length of the slits 45, the width of the slits 45, the number of the slits
45, the interval between the slits, etc. may be appropriately selected according to the required
elasticity. Good. In the present invention, a plurality of holes may be provided instead of the slits
shown in FIG.
[0032]
In the embodiment described above, the four sides of the vibrating body 10 are all sandwiched
between the spacer 30U and the spacer 30L, but only one side may be sandwiched between the
spacer 30U and the spacer 30L. In the present invention, the spacers 30U and 30L may not be
provided.
[0033]
In the embodiment described above, the cushioning material 40 is formed of polyester filaments,
but may be formed of filaments of another synthetic resin without being limited to polyester.
[0034]
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It is a schematic diagram of the external appearance of the electrostatic-type speaker 1 which
concerns on one Embodiment of this invention.
FIG. 2 is a cross-sectional view of the electrostatic speaker 1 and a schematic view of an electrical
configuration. FIG. 2 is an exploded perspective view of the electrostatic speaker 1; It is an
enlarged view of the nonwoven fabric processed into cushion material 40. As shown in FIG. It is a
figure for demonstrating the deformation ¦ transformation of 40 L of cushion materials. It is a
figure for demonstrating the deformation ¦ transformation of cushion material 40U. It is a
disassembled perspective view of the electrostatic-type speaker which concerns on the
modification of this invention. It is the figure which showed the side surface of the cushion
material which concerns on the modification of this invention. It is an enlarged view of a cushion
material concerning a modification of the present invention. It is a schematic diagram of the
external appearance of the cushion material which concerns on the modification of this
invention.
Explanation of sign
[0035]
DESCRIPTION OF SYMBOLS 1 ... Electrostatic type speaker, 10 ... Vibrator, 20, 20 U, 20 L ...
Electrode, 30, 30 U, 30 L ... Spacer, 40, 40 U, 40 L, 40 A-40 C ... Cushion material 50:
Transformer 60: Input part 70: Bias power supply
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