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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker diaphragm for use in an acoustic output device or the like.
2. Description of the Related Art In recent years, in the audio-related industry, along with the
digitization of reproduced music sources, the speaker as an audio output device has an output
sound pressure, distortion rate, and flatness which are further superior to those in the past.
There is a demand for high-quality reproduction of reproduced sound, and a speaker diaphragm
that influences the acoustic characteristics is considered more and more important.
In addition, particularly for PA, studio monitor and in-vehicle speakers, the use conditions are
severe, and particularly at the time of large input, a corresponding strength to the diaphragm is
required according to the amount of amplitude of the vibration system.
From the viewpoint of the acoustic characteristics of the speaker, the speaker diaphragm should
ideally move in a piston over the frequency band to be used. However, if the diaphragm is
deformed or split vibration occurs during vibration, the sound pressure-frequency characteristics
The distortion factor, the phase characteristics, etc. deteriorate, which hinders high fidelity
Moreover, when viewed from the viewpoint of input resistance, the speaker diaphragm does not
have sufficient strength against bending stress applied at the time of the amplitude of the
vibration system and peeling force applied to the joint between the diaphragm and other parts In
particular, when the amplitude is large, it will be destroyed.
Problems to be Solved by the Invention In the pulp and paper diaphragm used in the prior art, (1)
E / .rho. (Where E: elastic modulus, .rho .: density) of the material is small, so the high-resonance
frequency is large. Low, the speaker can not play to high frequency.
(2) Since the elastic modulus is low and the strength against bending stress is low, bending
occurs at large input.
(3) The bonding strength between the pulp fibers constituting the material is weak, and the peel
strength in the surface thickness direction is weak, so that peeling failure occurs in layers at the
bonding site.
There was a drawback of that.
SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a
speaker diaphragm having a high high-resonance frequency without deformation of the
diaphragm or occurrence of divided vibration during vibration.
[Means for Solving the Problems] In order to achieve this object, the speaker diaphragm of the
present invention is made by impregnating kraft pulp with polyethylene terephthalate /
oxyethylene copolymer polyester, heating and melting only the surface portion and then cooling
and solidifying it. Also, a material having a shape having a sandwich structure is used as a
According to this configuration, the polymer chains of the impregnated polyester, which is a
copolymerized polyester, crosses with the cellulose which is a constituent unit of the pulp, and
further mutually reinforce each other by the hydrogen bond between them, so that the pulp fiber
In addition, it is possible to improve the bonding strength and the bending rigidity.
In addition, since ethylene chains are introduced into the structure of the above-mentioned
material, a high internal loss can be obtained and peak dip in sound pressure-frequency
characteristics is improved as compared with polyethylene terephthalate resin and paper pulp
alone. Ru.
Further, by heating, melting, cooling and solidifying only the surface layer after impregnation, a
more uniform and dense resin layer can be reformed on the surface, and a material having a
sandwich structure can be easily obtained.
Therefore, after impregnating the above-mentioned resin into paper pulp and using it as a
diaphragm that has been molded to have a predetermined structure, the drawback of
delamination failure of the paper pulp diaphragm is improved, and vibration is improved due to
the improvement of bending rigidity. Of the high frequency resonance frequency and the internal
loss by the suppression of the vibration of the diaphragm and the occurrence of split resonance,
and the increase of the specific elastic modulus E / ρ (where E: elastic modulus, :: density). It is
possible to obtain a speaker having excellent flatness and distortion in pressure-frequency
according to an embodiment of the present invention will be described below.
The speaker diaphragm in the embodiment of the present invention is formed into a
predetermined shape by impregnating kraft pulp with polyethylene terephthalate / oxyethylene
copolymer polyester, heating and melting only the surface layer in a mold, and cooling and
solidifying it. It is.
The speaker diaphragm is fixed to a voice coil bobbin, and a voice coil provided at the tip of the
voice coil bobbin is inserted into the magnetic gap of the magnetic circuit.
The operation of the loudspeaker configured as described above will be described below.
The speaker is composed of a vibration system such as a diaphragm, a voice coil bobbin, and a
voice coil, and a magnetic circuit system including a magnet, a pole, a plate, and a yoke. When a
voice current flows in the voice coil in a uniform magnetic field, a vertical electromagnetic force
is generated in the voice coil and vibrates according to the current. This vibration is correctly
transmitted to the diaphragm and emitted as a sound wave.
Next, a method for producing a diaphragm for a speaker will be described. A polyethylene
terephthalate / oxyethylene copolymer polyester resin synthesized by reacting dimethyl
terephthalate, ethylene glycol and polyoxyethylene glycol in a ratio of 1: 2: 1 is used as a kraft
The pulp was impregnated at a weight ratio of 20% and dried, and then only the surface layer
was heated, melted and cooled in a mold, and solidified into a predetermined shape, to obtain a
As in this example, a speaker using a diaphragm having a sandwich structure in which kraft pulp
is impregnated with a polyethylene terephthalate-oxyethylene copolymer polyester resin, and
only the surface layer is heated and melted and then solidified by cooling is deformation and
division of the diaphragm. No resonance occurred, good acoustic characteristics were obtained,
and the distortion factor could be reduced by 20 dB as compared to a paper cone diaphragm of
the same shape.
Moreover, the high region resonance frequency could be raised from 8 kHz to 11 kHz. Also, due
to the improvement of the internal loss, the peak dip of the output sound pressure could be
reduced by about ± 3 dB as compared to the conventional paper cone diaphragm.
As described above, the speaker diaphragm according to the present invention is made of a
material having a sandwich structure in which kraft pulp is impregnated with polyethylene
terephthalate / oxyethylene copolymer polyester resin and only the surface layer is heated and
melted and then solidified. The diaphragm is used as a diaphragm, so that the forming process is
simple, and at the same time, the distortion rate is small, and the high region resonance
frequency can be increased. Further, a speaker having high input resistance can be obtained, and
a speaker having good acoustic characteristics and sound quality and high reliability can be
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