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JPH10276497

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DESCRIPTION JPH10276497
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
loudspeaker using a flat plate as a diaphragm, and more particularly to a loudspeaker suitable for
obtaining a wide band and good sound quality.
[0002]
2. Description of the Related Art In general, a speaker is an electroacoustic transducer that
converts electrical signals into sound waves which are vibrations of air, and cone dynamic
speakers, electrostatic speakers and the like are known.
[0003]
For example, as shown in FIG. 6, the cone-type dynamic speaker 10 uses, as a diaphragm, conical
cone paper 12 in terms of material characteristics such as mechanical strength and sound
pressure characteristics.
In the magnetic field generated between the center pole 16 and the yoke 18 by the permanent
magnet 14, there is a voice coil 20 attached to the inward end of the cone paper 12, and the
current flowing through the voice coil 20 is Cone 12 vibrates according to Fleming's left-hand
rule.
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[0004]
As described above, the cone type dynamic speaker 10 as described above uses the cone paper
12 as the diaphragm in terms of sound pressure characteristics and material characteristics, but
as shown in FIG. An acoustic distortion λ occurs in the inner central portion of The distortion λ
is considered to occur due to interference because the vector of the sound wave w2 generated
from the other side opposite to the sound wave w1 generated from one side of the cone paper 12
is not parallel.
[0005]
This acoustic distortion λ causes a phenomenon of losing the sharpness of the sound emitted
from the speaker 10 or blurring the localization of the sound image.
[0006]
Therefore, a speaker using a flat diaphragm capable of solving various problems of the cone type
dynamic speaker 10 has been studied, and is put to practical use in the electrostatic type
speaker.
[0007]
In the speaker using this flat diaphragm, since the driving force is applied to the entire surface of
the diaphragm, it is difficult to cause divided vibration, and there is no advantage of acoustic
distortion generated in the cone type dynamic speaker 10. Have.
[0008]
By the way, there are many known examples of the speaker using the above-mentioned flat
diaphragm, for example, Japanese Patent Application Laid-Open No. 61-7797 discloses a flat
ceramic. A loudspeaker using a face plate is disclosed.
[0009]
In this known example, a flat diaphragm is certainly used, but as shown in the drawing (FIG. 1), a
voice coil as a drive source is a voice provided perpendicularly to the diaphragm. The diaphragm
is wound around a coil bobbin. In this case, the diaphragm is required to have a sufficient
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strength to support the voice coil bobbin and the voice coil portion including the voice coil, and
the diaphragm itself can not be extremely thin.
Therefore, a corresponding force is required to drive the diaphragm, and even delicate sounds
may not be faithfully reproduced.
[0010]
In addition, as a method of driving a planar diaphragm, there is a driving method such as an
electrostatic speaker.
For example, as shown in FIG. 7 and FIG. 8, the electrostatic type speaker is superimposed by
interposing the ring-shaped spacer member 36 between the flat diaphragm 32 and the fixed
plate 34 also serving as a flat electrode. By arranging the electrode 38 formed on one plate
surface of the diaphragm 32 and the fixed plate 34 so as to face each other, one capacitor is
configured.
[0011]
Then, by applying a voltage between the electrode 38 and the fixed plate 34, an electrostatic
force acts between the diaphragm 32 and the fixed plate 34, and the diaphragm 32 is vibrated by
this electrostatic force. In order to produce an acoustic output proportional to the signal voltage,
a bias voltage E is superimposed on the signal voltage e and applied between the electrode 38
and the fixed plate 34.
[0012]
That is, in the conventional electrostatic speaker, a dedicated power supply such as a bias power
supply is required, which is not very common.
[0013]
The present invention has been made in consideration of such problems, and it is possible to
drive a flat diaphragm which is thin and easy to vibrate, while making use of the advantages of
the conventional magnet type, and faithfully to delicate sounds. It aims at providing the speaker
which can be reproduced.
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[0014]
A speaker according to the present invention as set forth in claim 1 is configured by forming a
coil in a planar shape on a diaphragm having a thickness of 1 μm or more and 30 μm or less.
[0015]
That is, a flat coil is formed directly on the diaphragm, and the diaphragm is driven by the
magnetic field generated from the coil.
As a result, since it is not necessary to support the voice coil which is the conventional magnetic
field generation source, the diaphragm can be made thin.
Specifically, a diaphragm having a thickness of 1 μm to 30 μm can be obtained.
[0016]
Incidentally, the thickness of the diaphragm (membrane) of the speaker with the conventional
conical cone is, for example, about 40 to 50 μm as described in JP-B-56-53920, but in the
present invention, As described above, the thickness can be further reduced, and the followability
to audio signals, as well as the reproducibility of various sounds can be improved.
[0017]
Further, in the above configuration, the diaphragm may be formed of at least one layer of
ceramic (the invention according to claim 2), or the diaphragm is formed of metal foil, and the
diaphragm is formed on the metal foil. The coil may be formed via an insulating layer (the
invention according to claim 3).
Furthermore, the diaphragm may be made of a plastic film coated with a ceramic (the invention
according to claim 4).
[0018]
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In this case, since the diaphragm made of ceramic or metal foil is not hygroscopic, the sound
quality is not impaired even if the speaker is used in a high humidity environment.
The plastic film coated with the ceramic is also excellent in a high humidity environment because
it has much lower hygroscopicity than the plastic alone.
In addition, since the diaphragm is a flat diaphragm, the interference of sound does not occur as
in a cone type dynamic speaker using a conical cone paper, and the sound quality can be further
improved.
[0019]
Further, in the above configuration, a fixing plate may be provided at a position facing the
diaphragm, and a coil may be formed on the surface of the fixing plate facing the diaphragm.
By supplying a direct current to the coil formed on the fixed plate, the coil becomes an
electromagnet, and hence the diaphragm is made to attract and repel the magnetic field
corresponding to the AC signal generated on the coil formed on the diaphragm. Vibrates.
[0020]
Further, in the above configuration, a fixing plate may be provided at a position facing the
diaphragm, and a layer including a permanent magnet may be formed on the surface of the fixing
plate facing the diaphragm. invention).
In this case, since the permanent magnet performs the same function as the direct current
electromagnet, the connection of the direct current power source can be eliminated.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, several embodiments of a
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loudspeaker according to the present invention will be described with reference to FIGS.
[0022]
First, as shown in FIG. 1, a loudspeaker 50A according to the first embodiment has, for example,
a flat polygonal shape (including a circular shape), and a diaphragm 54 in which a coil 52 of a
conductor is formed on one main surface. And a fixed plate 56 having a planar polygonal shape
(including a circular shape) in a similar manner, for example, with a ring-shaped spacer member
58 interposed therebetween.
[0023]
The diaphragm 54 is made of a ceramic flat plate having a thickness of 1 μm or more and 30
μm or less.
Since the ceramic flat plate has no hygroscopicity, the sound quality is not impaired even if the
speaker 50A according to the first embodiment is used in a high humidity environment.
Moreover, the ceramic flat plate has a high specific elastic modulus and can improve the sound
quality. Moreover, since the diaphragm 54 is flat, interference of sound does not occur as in a
cone-type dynamic speaker using cone-shaped cone paper, and the sound quality can be further
improved.
[0024]
By the way, if the thickness of the ceramic flat plate which comprises the diaphragm 54 exceeds
30 micrometers, the diaphragm 54 will not fully vibrate, and a big sound can not be obtained.
Therefore, the thickness of the ceramic flat plate is preferably 20 μm or less. In this case, the
drive amplitude of the diaphragm 54 can be further increased, which is advantageous in sound
quality and volume.
[0025]
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It is preferable to use zirconia as the ceramic flat plate that constitutes the diaphragm 54.
Zirconia is used as a sintered body, but its elastic modulus is as high as 200 GPa and its density
is 5.9 g / cm 3, so its specific elastic modulus is 3.4 × 10 11 cm 2 / sec 2, which is a
conventional plastic Compared with, for example, the elastic modulus 2 GPa, density 1.38 g / cm
3, and specific elastic modulus 0.14 × 10 11 cm 2 / sec 2 of the material of the diaphragm, for
example, polyester, it is advantageous as sound quality improvement.
[0026]
In particular, zirconia having yttria added in an amount of 2 to 4 mol%, which is mainly
tetragonal, or mainly tetragonal or cubic, has a bending strength as high as about 400 to 1000
MPa, and the diameter of crystal particles constituting the sintered body is also 0.1 Since it is as
small as about 0.5 μm, it is extremely convenient for processing as a thin flat plate.
[0027]
Besides the above-mentioned zirconia, for example, ceramics such as silicon nitride, silicon
carbide, and alumina are preferably used as the material of the diaphragm 54 of the electrostatic
speaker 50A because they are easily processed as a thin flat plate having a high elastic modulus.
can do.
[0028]
On the other hand, as shown in FIG. 2, the coil 52 has a conductor with a line width of about
several μm to 1 mm, for example, spirally and planarly toward the outer periphery of the
diaphragm 54 starting from the central portion of the diaphragm 54. It is configured by forming.
The gap between the conductors is about several μm to several hundred μm.
As the conductor, a metal such as copper or aluminum or an oxide conductor such as ITO can be
formed as a thin film by vapor deposition, sputtering or the like, or a thick film by a printing
method or the like. Note that the outer peripheral side end of the diaphragm 54 in the coil 52 is
referred to as the end for convenience.
[0029]
Further, in the speaker 50A according to the first embodiment, as shown in FIG. 1, the source of
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the audio signal e (audio signal e between the start and end of the coil 52 formed on the surface
of the diaphragm 54) Signal source 60 is connected.
[0030]
The fixing of the diaphragm 54 and the spacer member 58 and the fixing of the fixing plate 56
and the spacer member 58 are performed using, for example, an adhesive.
The spacer member 58 uses an insulator such as plastic, thermosetting phenolic resin, acrylic
resin or the like.
[0031]
The fixing plate 56 is formed of an insulator such as ceramic, and a coil 62 of a conductor is
formed on one main surface (a surface facing the diaphragm 54) of the fixing plate 56. Similarly
to the coil 52 formed on the diaphragm 54, the coil 62 also has a conductor with a line width of
about several μm to 1 mm, for example, spirals toward the outer periphery of the fixed plate 56
starting from the central portion of the fixed plate 56. And by being formed in a planar shape.
The gap between the conductors is about several μm to several hundred μm.
[0032]
One DC power supply 64 (voltage E) having the positive end of the end of the coil 62 is
connected between the beginning and the end of the coil 62 formed on the surface of the fixed
plate 56.
[0033]
In the speaker 50A according to the first embodiment, since the audio signal (current signal) e is
supplied to the coil 52 formed on the diaphragm 54 through the audio signal source 60, the
current to the coil 52 is generated. The diaphragm 54 vibrates following the sound signal e by
the magnetic field generated by the supply.
[0034]
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As described above, in the speaker 50A according to the first embodiment, since the diaphragm
54 can be driven by the magnetic field generated from the coil 52 formed on the diaphragm 54,
it is a conventional magnetic field generation source. There is no need to support the voice coil,
and the diaphragm 54 can be made thinner.
Specifically, the diaphragm 54 with a thickness of 1 μm to 30 μm can be obtained.
As a result, it is possible to improve the followability to the audio signal e as well as the
reproducibility of various sounds.
[0035]
Further, in the speaker 50A according to the first embodiment, the coil 62 functions as a direct
current electromagnet by supplying a direct current to the coil 62 formed on the fixed plate 56
through the direct current power supply 64. The diaphragm 54 vibrates due to the attraction and
repulsion acting between the magnetic field generated thereby and the magnetic field
corresponding to the AC signal generated on the coil 52 on the diaphragm 54.
[0036]
Next, a modified example of the speaker 50A according to the first embodiment will be described
with reference to FIG.
[0037]
A speaker 50Aa according to this modification has substantially the same configuration as the
speaker 50A according to the first embodiment, as shown in FIG. 3, but includes a ring-shaped
permanent magnet on one main surface of a fixing plate 56. The difference is that the layer 66 is
formed.
The magnetic layer is formed such that, for example, the ring-shaped layer 66 has an S pole on
the inner side and an N pole on the outer side, and a plurality of concentric layers are arranged
with a slight gap. The magnetic field exits through the gap and interacts with the magnetic field
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generated by the coil 52 on the diaphragm 54.
[0038]
In this case, since the ring-shaped layer 66 performs the same function as the DC electromagnet,
the connection of the DC power supply 64 can be omitted, and the miniaturization and weight
reduction of the speaker 50Aa can be further promoted. . The fixing plate 56 may be a
permanent magnet, and the ring-shaped layer 66 may be omitted.
[0039]
Next, a loudspeaker 50B according to a second embodiment will be described with reference to
FIG. The same reference numerals are given to components corresponding to those in FIG.
[0040]
The speaker according to the second embodiment has substantially the same configuration as the
speaker 50A according to the first embodiment, as shown in FIG. The difference is that a metal
foil 70 of 0.5 μm or more and 30 μm or less is used. Then, an insulating film 72 made of SiO2,
SiN, plastic or the like is formed on one main surface (surface facing the fixing plate 56) of the
metal foil 70, and the coil 52 of a conductor is formed on the surface of the insulating film 72.
ing.
[0041]
Since the metal foil 70 has no hygroscopicity, the sound quality is not impaired even if the
speaker 50B according to the second embodiment is used in a high humidity environment. The
metal foil 70 also has a high specific modulus, for example, 2.81 × 10 11 cm 2 / sec 2 for
aluminum, 2.44 × 10 11 cm 2 / sec 2 for stainless steel, 2.39 × 10 11 cm 2 / sec 2 for
titanium, 2.30 × 10 11 cm 2 for nickel It is 1.54 × 10 11 cm 2 / sec 2 for / sec 2 and beryllium
copper, and the sound quality can be improved. Moreover, since the diaphragm 54 is flat,
interference of sound does not occur as in the conventional cone-type dynamic speaker 10 using
cone-shaped cone paper, and the sound quality can be further improved.
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[0042]
If the thickness of the metal foil 70 constituting the diaphragm 54 exceeds 30 μm, the
diaphragm 54 does not vibrate sufficiently, and a loud sound can not be obtained. Therefore, the
thickness of the metal foil 70 is preferably 20 μm or less. In this case, the drive amplitude of the
diaphragm 54 can be further increased, which is advantageous in sound quality and volume.
[0043]
Alternatively, the metal foil 70 may be coated with a ceramic to increase the elastic modulus. In
this case, SiC, SiN, ZrO2, Al2O3, diamond or the like can be used as the ceramic.
[0044]
Then, in the speaker 50B according to the second embodiment, as with the speaker 50A
according to the first embodiment, an audio signal is transmitted to the coil 52 formed on the
diaphragm 54 through the audio signal source 60 ( Since the current signal e) is supplied, the
diaphragm 54 vibrates following the sound signal e by the magnetic field generated by the
current supply to the coil 52.
[0045]
Thus, also in the speaker 50B according to the second embodiment, the diaphragm 54 can be
thinned similarly to the speaker 50A according to the first embodiment, and the followability to
the audio signal e, and Reproducibility of various sounds can be improved.
[0046]
Next, a modification of the speaker 50B according to the second embodiment will be described
with reference to FIG.
[0047]
The speaker 50Ba according to this modification has substantially the same configuration as the
speaker 50B according to the second embodiment, as shown in FIG. 5, but includes a ring-shaped
permanent magnet on one main surface of the fixing plate 56. The difference is that the layer 66
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is formed.
[0048]
In this case, since the ring-shaped layer 66 performs the same function as the DC electromagnet,
the connection of the DC power supply 64 can be unnecessary, and the miniaturization and
weight reduction of the speaker 50Ba can be further promoted. .
[0049]
Although the example which used the ceramic plane board and metal foil as the diaphragm 54
was shown in the speaker (also including each modification) concerning the 1st and 2nd
embodiment, the plastic film which coated ceramics in addition to this The diaphragm 54 can
also be configured using
[0050]
In this case, polyethylene, polyester, polystyrene or the like is preferable as the plastic, and those
coated with SiO, SiO2, Al2O3 or the like by a method such as CVD or PVD can be applied.
[0051]
These films have improved hygroscopicity compared to films without a coating, can ensure longterm reliability, and can be used as the diaphragm 54 of a speaker.
[0052]
The speaker according to the present invention is, of course, not limited to the above-described
embodiment, and various configurations can be adopted without departing from the scope of the
present invention.
[0053]
As described above, according to the speaker of the present invention, the coil is formed in a
planar shape on the diaphragm having a thickness of 1 μm or more and 30 μm or less.
[0054]
For this reason, it is possible to drive a thin, easily vibrating, flat diaphragm while taking
advantage of the conventional magnet type, and it is possible to achieve an effect of being able to
faithfully reproduce even delicate sounds.
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[0055]
Brief description of the drawings
[0056]
1 is a block diagram showing a speaker according to the first embodiment.
[0057]
2 is a front view of the diaphragm of the speaker according to the first embodiment viewed from
one direction.
[0058]
FIG. 3A is a configuration view showing a modification of the loudspeaker according to the first
embodiment, and FIG. 3B is an enlarged view showing a portion of FIG. 3A in which a layer
including a permanent magnet is formed. Ru.
[0059]
4 is a configuration diagram showing a speaker according to a second embodiment.
[0060]
FIG. 5A is a configuration view showing a modification of the loudspeaker according to the
second embodiment, and FIG. 5B is an enlarged view showing a portion of FIG. 5A where a layer
including a permanent magnet is formed. Ru.
[0061]
6 is an explanatory view showing the configuration and acoustic distortion of a typical cone-type
dynamic speaker.
[0062]
7 is a front view of a general electrostatic speaker.
[0063]
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8 is a configuration diagram showing an electrostatic speaker.
[0064]
Explanation of sign
[0065]
50A, 50Aa, 50B, 50Ba: Speaker 52: coil 54: diaphragm 56: fixed plate 58: spacer member 60:
audio signal source 62: coil 64: DC power source 66: layer (permanent magnet material) 70:
metal foil 72: Insulating film
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