JP2009296125

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DESCRIPTION JP2009296125
An object of the present invention is to linearly displace a vibrating body while preventing
contact between the vibrating body and an electrode. A raised surface of a cushioning material
40L is in contact with the vibrating body 10, and a raised surface of a cushioning material 40U is
in contact with the vibrating body 10. When the vibrating body 10 is displaced in the direction of
the electrode 20L, the raised layer 41L of the cushioning material 40L is compressed by the
displacement of the vibrating body 10, while the raised layer 41U of the cushioning material 40U
is expanded. The surface of the cushioning material is uniformly brushed, and since the raising
layers 41L and 41U have elasticity, the force to return the portions of the raising layers 41L and
41U to their original shape is in the plane of the cushioning material. There is no variation in the
If the elasticity is uniform in the plane of the cushioning material, no variation in displacement of
the vibrating body 10 occurs when the vibrating body 10 is displaced by electrostatic force, so
that an acoustic signal is correctly reproduced when an acoustic signal is input. It will be.
[Selected figure] Figure 3
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. This
electrostatic speaker has a tensionless structure that does not restrain the peripheral portion of
the vibrating body, and is supported between planar electrodes by sandwiching the vibrating
body with ester wool made of non-woven polyester. 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 type speaker disclosed in Non-Patent Document 1, the ester wool supporting
the vibrator has elasticity, and when the vibrator is displaced due to electrostatic force, it is
compressed and deformed.
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The deformed ester wool tries to return to its original shape by elasticity, but in the sheeted ester
wool, the volume density of the fibers is not necessarily uniform, so the force to return to it, ie,
the force applied to the vibrating body Variation will occur. If the force applied from the ester
wool to the vibrating body varies, the displacement of the vibrating body will vary, and the
acoustic signal is not correctly reproduced when the acoustic signal is input, and the acoustic
signal is not input. Also, since the vibrator can not be held at the center position between the
electrodes, distortion in the acoustic characteristics is increased. In addition, if the thickness of
the ester wool is reduced to narrow the distance between the vibrating body and the flat
electrode to improve the sensitivity of the vibrating body, the force required to displace the
vibrating body by the same amount is greater than when the ester wool is thick. 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 linearly displacing a vibrating body while
preventing contact between the vibrating body and an electrode.
[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 sheet-like fiber assembly having an insulating property, elasticity, and
acoustic transparency, and a vibrator disposed between the first electrode and the second
electrode so as to be separated from the first electrode and the second electrode. A first fiber
assembly disposed between the vibrator and the first electrode and in contact with the vibrator
and the first electrode, and at least one of the sheet-like surfaces being raised; A sheet-like fiber
assembly having elasticity and sound transmission, which is disposed between the vibrator and
the second electrode and in contact with the vibrator and the second electrode, and is a sheet-like
surface An electrostatic speaker having at least one raised second fiber assembly; Subjected to.
[0008]
In the present invention, the first fiber assembly is disposed between the first electrode and the
vibrator with the raised portion compressed and the second fiber assembly is compressed with
the raised portion formed. It may be disposed between the two electrodes and the vibrator.
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Further, in the present invention, both sheet-like surfaces of the first fiber assembly and the
second fiber assembly may be raised.
[0009]
According to the present invention, it is possible to displace the vibrating body linearly while
preventing the contact between the vibrating body and the electrode.
[0010]
FIG. 1 is a view schematically showing the appearance 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.
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]
(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.
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[0012]
The spacer 30 is formed of an insulator, and its shape is a rectangular frame. 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]
The cushioning material 40 is a sheet-like non-woven fabric (fiber aggregate in which fibers are
gathered) having insulation properties in which one surface is raised, and its shape is
rectangular. In the cushion material 40, since air can pass between the fibers constituting the
non-woven fabric, sound transmission is ensured. The cushioning material 40 is compressed in
the Z direction so that the raised fibers are deformed to reduce the thickness, and when the
compression force in the Z direction is removed, the deformed fibers return to the original shape.
That is, the cushioning material 40 has elasticity and deforms in response to an external force.
The nonwoven fabric to be the cushioning material 40 is a long fiber type, preferably having a
basis weight of 50 g or less, a thickness of 0.3 mm or less, and a tensile strength of 50 [N / 50
mm] or more in the longitudinal direction. As a raising method, a method by emery raising is
preferable.
[0015]
(Structure of Electrostatic Speaker 1) Next, the structure of the electrostatic speaker 1 will be
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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. The cushioning material 40L is
disposed inside the frame-shaped spacer 30L so as to be sandwiched between the vibrating body
10 and the electrode 20L, and the raised surface of the cushioning material 40L is in contact
with the vibrating body 10. Further, a cushioning material 40U is disposed inside the frameshaped spacer 30U so as to be sandwiched between the vibrating body 10 and the electrode
20U, and the raised surface of the cushioning material 40U is in contact with the vibrating body
10. Note that the thickness of the cushioning material 40 which is fluffed by raising is thicker
than the thickness of the spacer 30 before being disposed between the vibrating body 10 and the
electrode 20, and the cushioning material 40 includes the vibrating body 10 and the electrode
20. When placed in between, the raised part is in a slightly compressed state.
[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 in the direction opposite to the Z direction
(−Z direction) acts on the vibrator 10.
[0018]
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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, as shown in FIG. 3,
the layer of fiber (blowing layer 41L) which was brushed in the cushioning material 40L is
compressed by the displacement of the vibrating body 10, On the other hand, in the cushioning
material 40U, the layer of raised fibers (the raised layer 41U) swells due to the raising.
The surface of the cushioning material 40 is uniformly brushed, and since the napping layers
41L and 41U have elasticity, the force with which the portions of the napping layers 41L and
41U try to return to their original shape is determined by the cushioning material 40. There is no
variation in the plane and it becomes uniform. Thus, when the elasticity of the cushioning
material 40 is equal within the plane of the cushioning material 40, when the vibrational body 10
is displaced by electrostatic force, the vibrational 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, as shown in FIG. 4,
the napping layer 41U is compressed by the displacement of the vibrating body 10, while the
napping layer 41L is expanded.
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Also in this case, the force for the portions of the raising layers 41L and 41U to return to the
original shape is uniform within the surface of the cushioning material 40 without variation, so
that no variation occurs in the displacement of the vibrating body 10 When the 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 and the thicknesses of the napping layers
41U and 41L are the same, the elasticity of each cushioning material is also the same, and the
napping layers 41L and 41U vibrate. The force pressing the body 10 is the same for all. Then, the
raised portion of the cushioning material 40 uniformly supports the vibrating body 10, and the
displacement of the vibrating body 10 is not dispersed, so that the vibrating body 10 is
accurately supported at an intermediate position between the electrode 20U and the electrode
20L. can do. 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]
Further, since the napping layers 41U and 41L have a smaller elastic force and a larger amount
of expansion and contraction than the non-napped portions, the vibrating body 10 can be
linearly displaced to make the displacement amount large, and the reproduction band of the
speaker can be obtained. Will extend to the low range. In addition, since the thickness of the
napping layers 41U and 41L can be made uniform to a desired thickness by setting the napping
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machine, it is easy to set the thickness of the napping layers 41U and 41L according to the
acoustic characteristics. Desired acoustic characteristics can be obtained. There is also a
proportional relationship between the force required to compress the cushioning 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 state in
which the amount of contraction of the napping layers 41L and 41U is compressed is arranged
between the electrode 20 and the vibrating body 10, the cushioning material 40 vibrates. Since
the force pressing the body 10 is large, the vibrator 10 is less likely to be displaced, and the
sensitivity of the vibrator 10 is lowered. On the other hand, when assembling the electrostatic
speaker 1, if the cushioning material 40 is compressed between the electrode 20 and the
vibrating body 10 in a state in which the contraction amount of the napping layers 41L and 41U
is compressed, the cushioning material 40 is a vibrating body Since the force to hold down 10 is
small, 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]
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 thin, the raised portion is compressed to secure the
displacement amount of the vibrating body 10 And the vibrator 10 is displaced linearly.
[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
various other forms.
For example, the above-described embodiment may be modified as follows to implement the
present invention.
[0027]
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In the embodiment described above, only one side of the sheet non-woven fabric is raised, but
both the front and back surfaces of the sheet non-woven may be raised. In the embodiment
described above, the cushioning material 40 is arranged with the raised surface facing the
vibrating body 10, but the raised surface may be arranged facing the electrode 20.
[0028]
In the present invention, the shapes of the electrode 20, the cushioning material 40 and the
vibrator 10 are not limited to rectangles, and may be other shapes such as polygons, circles, and
ovals. Further, in the present invention, in order to prevent an electric shock or a short circuit,
the whole of the electrostatic speaker 1 may be covered with a non-conductive and soundpermeable cloth.
[0029]
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. Further, in the embodiment described above, the vibrating body 10 is in the tensionless
state, but the four sides of the vibrating body 10 may be restrained to apply tension.
[0030]
In the embodiment described above, the cushioning material 40 is a nonwoven fabric raised, but
it may be a nonwoven fabric rather than a nonwoven fabric as long as the fibers are aggregated.
Moreover, if it is the raw material which a fiber gathers and can raise, it is possible to employ ¦
adopt as the cushioning material 40, for example, it is good also as raising the paper as the
cushioning material 40. FIG.
[0031]
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FIG. 1 is an external view of an electrostatic speaker 1 according to an embodiment of the
present invention. FIG. 2 is a schematic view of a cross section and an electrical configuration of
the electrostatic speaker 1. FIG. 6 is a diagram for explaining the operation of the electrostatic
speaker 1; FIG. 6 is a diagram for explaining the operation of the electrostatic speaker 1;
Explanation of sign
[0032]
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 ... Cushion material, 41 U, 41 L ... Brushed
layer, 50: Transformer, 60: Input part, 70: Bias power supply
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