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JPH06303695

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DESCRIPTION JPH06303695
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm of a speaker.
[0002]
2. Description of the Related Art In general, a speaker diaphragm is for emitting sound and is
required to have a high elastic modulus to suppress natural resonance, and a conventional
speaker diaphragm is made of, for example, wood pulp. It had a desired elastic modulus by
applying a dumping agent made of a polymer material to a paper diaphragm made of paper or
impregnating it with an oil plasticizer.
[0003]
However, when a dumping agent made of a polymer material is applied to give a high elastic
modulus to a paper diaphragm as described above, the viscosity at the time of application is
large, and it is fine like paper. And the specific elastic modulus decreases, and the dumping agent
is exposed on the surface of the diaphragm, and dust and the like adhere to the surface of the
diaphragm, resulting in an undesirable appearance. .
[0004]
In addition, when the oil-like plasticizer is impregnated, the oil-like plasticizer does not
completely adhere to the diaphragm, so it exudes or diffuses over time, and the specific elastic
modulus of the diaphragm is unstable. There was a problem.
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1
[0005]
The present invention is to provide a speaker diaphragm having a stable specific modulus.
[0006]
According to the present invention, there is provided a speaker diaphragm made of a porous
material having voids inside, such as natural fibers, as a raw material of a gel-like viscoelastic
body whose solution viscosity is adjusted to a low viscosity. A solution is impregnated, and the
gel-like viscoelastic body is contained in the above-mentioned space by heat treatment.
[0007]
The gel-like viscoelastic body is composed of a mixed solution containing a polyolefin polyol and
a polyisocyanate as main components.
[0008]
[Function] Therefore, after a speaker diaphragm made of a porous material having voids inside is
impregnated with a mixed solution containing polyolefin polyol and polyisocyanate as main
components, a mixed solution impregnated at normal temperature or by heating and drying As a
result, the speaker diaphragm in which the gel-like visco-elastic body is contained in the air gap
can be obtained, and a remarkable vibration damping capability can be obtained, and natural
resonance at a specific frequency can be suppressed.
[0009]
An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a side sectional view schematically showing a speaker using a speaker diaphragm
according to an embodiment of the present invention, and FIG. 2 is a frequency characteristic
diagram.
[0010]
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2
As shown in FIG. 1, the loudspeaker according to the present embodiment comprises a magnetic
circuit unit 1 and a vibrating unit 2. Among them, the magnetic circuit unit 1 is disposed at the
center of the circular flat plate portion 3a and the flat plate portion 3a. A support plate 3
comprising a cylindrical center pole 3b provided, an annular magnet 4 concentrically fixed to the
center pole 3b on the side of the center pole 3b of the flat plate portion 3a, and a magnet 4 on
the upper end face of the magnet 4 And an annular top plate 6 provided concentrically.
The air gap formed between the magnet 4 and the upper plate 6 and the center pole 3b is used
as a magnetic gap to guide the magnetic flux from the magnet 4 to a voice coil 5 described later.
[0011]
The vibrating portion 2 has a conical (conical) vibration plate 9, and a voice coil bobbin 5 a of the
voice coil 5 as a vibration source is adhered to a central hole portion corresponding to a cone top
portion of the vibration plate 9. It is fixed by etc.
A flexible annular damper 11 is fixed to the voice coil 5 and the diaphragm 9 by bonding or the
like, and the outer peripheral portion of the damper 11 is conically fixed to the upper end surface
of the upper plate 6. The frame 7 is elastically supported by adhesion or the like.
On the other hand, an edge 8 is adhered to the outer periphery of the cone bottom of the
diaphragm 9, and the edge 8 is fixed to the edge support 7a of the frame 7 by adhesion or the
like.
That is, the frame 7 also supports the diaphragm 9 via the edge 8.
Further, on the voice coil 5 side of the diaphragm 9, a dust cap 10 for preventing dust is
provided.
[0012]
The diaphragm 9 is made of a wood fiber dispersed in water, and is made of a 12 cm-aperture
speaker diaphragm, which has a solution viscosity adjusted to 100 cps, such as polyolefin polyol,
for example, Polyol (registered trademark) HA, and poly After impregnating a mixed solution
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with an isocyanate such as PAPI (registered trademark) 135, heat treatment is performed for one
hour in an atmosphere at 60 ° C. to make the impregnating solution into a gel-like viscoelastic
body, and as a result, a gel-like viscoelastic body in voids. Is included.
[0013]
By the way, the gel-like viscoelastic body formed by the reaction of the polyolefin polyol and the
polyisocyanate has semipermanent viscoelasticity, so that it has a stable specific elastic modulus
and a remarkable vibration damping ability can be obtained.
[0014]
Therefore, the frequency characteristic of a 12 cm diameter speaker using the diaphragm 9 is
shown by the solid line A in FIG.
The broken line B in FIG. 2 indicates the frequency characteristics of the comparative example of
a speaker manufactured on a trial basis without performing any impregnation treatment on a
paper speaker diaphragm manufactured in the same shape as that of this embodiment.
[0015]
Here, it can be seen that in the frequency characteristic shown by the broken line B in FIG. 2,
peak of sound pressure due to natural resonance of the diaphragm and dip due to reverse
resonance occur at around 5 kHz and 7 kHz.
On the other hand, such a peak and a dip are not recognized in the frequency characteristic in
the speaker using the diaphragm by an Example.
That is, the diaphragm 9 impregnated with the mixed solution of the polyolefin polyol and the
polyisocyanate becomes one in which the gel-like visco-elastic body is contained in the voids by
the subsequent heat treatment, and has a stable specific elastic modulus and a remarkable
vibration damping capability. Therefore, flat sound pressure frequency characteristics can be
obtained. Therefore, the natural resonance of the diaphragm 9 is eliminated, and the occurrence
of a significant peak or dip in the frequency characteristic of the speaker can be suppressed.
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[0016]
Therefore, the speaker impregnated with the mixed solution of polyolefin polyol and
polyisocyanate as described above has excellent acoustic characteristics with good frequency
characteristics.
[0017]
Although the solution viscosity of the mixed solution of the polyolefin polyol and the
polyisocyanate is adjusted to 100 cps in this example, it is not limited to this as long as the above
effect can be obtained.
[0018]
As described above, according to the present invention, a vibrating plate formed of a porous
material having voids inside is impregnated with a raw material solution of gel-like viscoelastic
body whose solution viscosity is adjusted to a low viscosity. When the raw material solution
becomes a chemically stable non-flowable gel-like visco-elastic body by the subsequent heat
treatment, the above-mentioned gel-like visco-elastic body contained in the fine internal space of
the diaphragm exudes Since it does not diffuse, it has a stable specific elastic modulus, and a
significant vibration damping capability is obtained, there is no occurrence of a peak due to
natural resonance and a dip due to reverse resonance, so that the speaker has a flat sound
pressure frequency characteristic. You can get
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