JPH07184294

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DESCRIPTION JPH07184294
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer using a diaphragm.
[0002]
2. Description of the Related Art For example, in an electrodynamic speaker generally used in
conventional audio equipment etc., many materials have been developed as a material of the
diaphragm thereof. For example, wood pulp Typical physical properties of the diaphragm made
of the material are 0.485 in density, 1.17 × 10 10 dyn / cm 2 in Young's modulus, and 0.0714
in internal loss.
[0003]
Generally, the diaphragm of such a speaker has ideal conditions such as (1) low density, (2) high
rigidity, and (3) high internal loss. Conventionally, a diaphragm material incorporating a highly
rigid substance such as carbon fiber or aramid fiber, or a diaphragm material having a large
internal loss such as polypropylene has been developed.
[0004]
By the way, when attempting to increase the rigidity of the diaphragm, the internal loss may
decrease or the density may increase, and if it is attempted to obtain a large internal loss, the
rigidity may increase. It tends to be lower and the density is higher.
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[0005]
Therefore, it is important to make the diaphragm (corn paper) of the speaker to balance the
elements (1) to (3) in high dimensions.
[0006]
For example, in the case of aluminum, the density is 2.7, the Young's modulus is 62 × 10 10 dyn
/ cm 2, the internal loss is 0.002, and in the case of polypropylene, the density is 0.91, the
Young's modulus is 1.08 × 10 10 dyn / cm2, internal loss is 0.07.
[0007]
In the case of a diaphragm made of wood pulp, the internal loss is moderately large and the
density is also small, but there is a problem that the frequency band is narrow due to the lack of
rigidity. In order to obtain wood pulp, deforestation is required. In order to restore the forest to
the place after harvesting, it requires a large amount of money and a long time, and there is a
problem that it is difficult to obtain high quality pulp as it is.
[0008]
Furthermore, when making a diaphragm with wood pulp, the wood pulp is subjected to beating
over a long time (tapping the wood pulp into water) in order to make the fibers of the wood pulp
easy to catch and obtain a high quality diaphragm. It must be done (if it is beaten, the vascular
bundle is loosened, the fiber becomes a proper length, the fiber swells and tears longitudinally,
and the fiber becomes entangled easily), and there has been a problem that the production is
very time-consuming.
[0009]
The present invention can balance the characteristics of the density, internal loss, and Young's
modulus of the diaphragm at a high level, and can improve the productivity of the diaphragm in
the production process, and further from the viewpoint of forest protection. Another object of the
present invention is to provide an electroacoustic transducer with high practical effect.
[0010]
SUMMARY OF THE INVENTION The present invention uses a diaphragm obtained by pulping
fibers taken out of kenaf stems and fibers taken out of juvenile silkworms.
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[0011]
In addition, a diaphragm is used in which fibers taken out from the stem of kenaf and fibers
taken out from the juvenile silkworm are mixed with wood pulp.
[0012]
[Function] Therefore, the fibers taken out from the stem of kenaf and the fibers taken out from
the juvenile silkworm are pulped up, and the fibers taken out from the stem of kenaf and the
fibers taken out from the silkworm juvenile are wood pulp The rigidity and internal loss can be
improved without increasing the density as a diaphragm for the electroacoustic transducer by
forming the diaphragm by mixing it into a sheet, thereby restricting the use of wood pulp. Can.
[0013]
Embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a side sectional view showing an embodiment of an electrodynamic speaker using the
diaphragm of the present invention, FIG. 2 is a frequency characteristic diagram of the
electrodynamic speaker using the diaphragm of the first embodiment, FIG. It is a frequency
characteristic figure of an electrodynamic-type speaker using a diaphragm of a 2nd example.
[0015]
In FIG. 1, reference numeral A denotes a support plate in which a center pole I is provided at the
center of the upper surface so as to protrude. A magnet B and an upper plate C are sequentially
fixed on the support plate A.
G is a voice coil loosely fitted to the top of the center pole I and supported by the frame D via the
damper H.
At the top of the voice coil G, the peripheral edge of the diaphragm E and the peripheral edge of
the frame D are connected by an edge F formed on a ring.
[0016]
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The diaphragm E is formed mainly of fibers taken out from the stem of kenaf, and as other
materials to be mixed with this main material, fibers taken out from the juvenile silkworm and
fibers taken out from the wood are used. It was
[0017]
Here, the kenaf that is the material of the diaphragm E and the juvenile cocoons will be
described.
Kenaf is an annual herb of the mallow family, and it must be grown every year after harvesting,
but it can grow to about 4 m in 4 to 5 months, and an average harvest of 20 t per hectare is
possible.
If this is converted to wood pulp, it corresponds to the pulp of 60 trees with a diameter of 20 cm
and a height of 15 m. If it takes 15 years on average to grow into such trees, 900 trees can be
grown by kenaf that can be grown in 1 hectare It will save trees.
In addition, juvenile juveniles are a method of harvesting only young stems (juvenile juveniles)
and have no effect on relatives, and can be harvested at the same place every year.
Therefore, it can be useful for forest protection by using kenaf and juvenile chicks.
[0018]
In addition, although the fiber of silkworm is short, the growing juvenile has a thin fiber wall, and
the fibers in the vascular bundle are accumulated on the bundle, so-called fiber bundle acts like a
long fiber. Therefore, it is possible to obtain a diaphragm having a property that there is no
increase in density while enabling improvement in rigidity and internal loss, and a highdimensional and balanced diaphragm can be realized, and kenaf, and Since the high-strength
paper can be obtained without crushing it, the productivity of the diaphragm can be improved.
[0019]
Next, an example in which the above-mentioned diaphragm E is formed using fibers taken out of
the stem of kenaf will be described in the first embodiment and the second embodiment.
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[0020]
[First Embodiment] In the first embodiment, the diaphragm E is formed by mixing 50% of the
fibers taken out of the stem of kenaf and 50% of the fibers taken out of the juveniles of the Kuril
Islands. The physical properties of the diaphragm E are: density is 0.64, Young's modulus is 3.50
× 10 10 dyne / cm 2, and internal loss is 0.035.
[0021]
Therefore, a frequency characteristic diagram of a speaker using such a diaphragm E is shown by
a solid line in FIG.
The broken lines in FIG. 2 indicate the frequency characteristics of a comparative example of a
speaker using a diaphragm made of wood pulp and having the same shape as that of the first
embodiment.
[0022]
Here, in FIG. 2, it can be seen that the frequency characteristic of the speaker using the
diaphragm according to the comparative example shown by the broken line starts to attenuate at
about 16000 Hz.
On the other hand, such attenuation is not recognized in the frequency characteristics of the
speaker using the diaphragm according to the embodiment shown by the solid line.
That is, according to the diaphragm E formed by mixing together 50% of the fibers taken out of
the stem of kenaf and 50% of the fibers taken out of the juveniles of the Kuril Islands, the rigidity
of the diaphragm E is improved by the improvement of the Young's modulus. In particular, the
high frequency band characteristics are improved, and a wider frequency band and better
frequency characteristics than the conventional diaphragm can be obtained.
[0023]
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In this example, the juvenile silkworm was used as the juvenile silkworm, but the type of the
silkworm is not limited to this, and fibers taken from the stem of kenaf and the juvenile silkworm
are used. The mixing ratio with the fibers taken out is not limited to the examples.
[0024]
Second Embodiment In the second embodiment, the diaphragm E is mixed with 50% of the fibers
taken from the stem of kenaf, 40% of the fibers taken from juveniles of the Kuril Islands, and 10%
of the pulp of wood. The diaphragm E has a density of 0.66, a Young's modulus of 3.30 × 10 10
dyne / cm 2, and an internal loss of 0.034.
[0025]
Therefore, a frequency characteristic diagram of a speaker using such a diaphragm E is shown by
a solid line in FIG.
The broken lines in FIG. 3 indicate the frequency characteristics of a comparative example of a
loudspeaker using a diaphragm formed in the same shape as that of the second embodiment
using wood pulp.
[0026]
Here, in FIG. 3, it can be seen that the frequency characteristic of the speaker using the
diaphragm according to the comparative example shown by the broken line starts to attenuate at
about 16000 Hz.
On the other hand, such attenuation is not recognized in the frequency characteristics of the
speaker using the diaphragm according to the embodiment shown by the solid line.
That is, according to the diaphragm E formed by mixing 50% of fibers taken out of the stem of
kenaf, 40% of fibers taken out of juveniles of the Kuril Islands, and 10% of pulp of wood, the
Young's modulus is improved. The rigidity of the diaphragm E is enhanced, and in particular, the
high-band characteristics are improved, and a wider frequency band and better frequency
characteristics than the conventional diaphragm can be obtained.
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[0027]
In this example, the juvenile silkworm was used as the juvenile silkworm, but the type of the
silkworm is not limited to this, and fibers taken from the stem of kenaf and the juvenile silkworm
are used. The mixing ratio of the taken-out fiber to the wood pulp is not limited to the examples.
[0028]
As described above, according to the present invention, the characteristics of density, internal
loss, and Young's modulus of the diaphragm used in the electroacoustic transducer can be
balanced in a high degree, The frequency characteristics of the electroacoustic transducer can be
improved, especially for the high band, and good frequency characteristics can be obtained in a
wide band.
[0029]
Moreover, since it is not necessary to beat wood pulp for a long time in the production process of
the diaphragm, the productivity of the diaphragm can be improved, and furthermore, the use of
the wood pulp can be limited, so from the viewpoint of forest protection. It can be highly
practical.
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