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In the present invention, a synthetic resin film is used as a diaphragm substrate, and a diaphragm
having a spiral conductor formed on at least one surface of the substrate is disposed in a
magnetic field between the front plate and the center pole, and sound waves are emitted directly
from the diaphragm. The present invention relates to an improvement of a diaphragm used for
so-called whole surface 1 drive dynamic speaker. As shown in FIG. 1, the full-field drive
electrodynamic speaker has a magnetic circuit comprising a center pole 1, a freon 1-flat 2, a back
play 1 and 3 and a magnet 4 and a synthetic resin film as a base 5a. The diaphragm 5 is
configured such that a part or all of the spiral conductor 5b formed on at least one side of the
above is disposed in the magnetic field between the center pole 1 and the front plate 2 of the
magnetic circuit. Then, an audio signal is flowed to the spiral conductor 51) to vibrate the
diaphragm 5, and a sound wave proportional to the audio signal is emitted to the atmosphere. As
the diaphragm base material of such an electrodynamic speaker, it is necessary not to thermally
deform due to the Joule heat generated by the resistance U of the spiral conductor 5b. An
aromatic polyimide resin film having a high deformation temperature has been widely used. On
the other hand, with the recent increase in power, it is necessary to improve the surface J input
characteristics to the speaker, but as described above, problems such as burning of the conductor
5b due to Joule heat generated in the conductor 51) and thermal deformation of the base 5a
There is also a limit to the improvement of input resistance characteristics. That is, a part of the
Joule heat is radiated from the surface of the conductor 51) as radiant heat, the other part is
conducted to the center pole 1 and the front plate 2 through the base 521, and is dissipated in
the part. Furthermore, as a means for radiating Joule heat of the conductor 5b, a configuration is
also conceivable in which a cotton-like metal fine wire is disposed between the magnet 4 and the
center ball 1 to promote the radiation. The cotton-like metal fine wire has a heat absorbing effect
as well as a heat releasing effect. However, since the aromatic polyimide resin which is the
substrate 5a has extremely low thermal conductivity, most of the heat radiation is radiation heat
directly radiated from the conductor 5b, so the temperature rise of the conductor 51) is large and
the resistance characteristic of the input is improved. "There was a limit to two. Therefore, in the
present invention, the heat dissipation of the conductor 5b by heat conduction is promoted by
including an aromatic polyimide resin to which a boron nitride powder having a thermal
conductivity larger than that of a conventional aromatic polyimide resin is added as the
substrate. Therefore, the input resistance characteristic is "directed", which will be described in
detail below.
The thermal conductivity of an aromatic polyimide resin to which 3 wt% of boron nitride powder
to be a diaphragm substrate used in the present invention is added is compared with that of a
conventional aromatic polyimide resin. As apparent from the above table, the substrate of the
diaphragm of the present invention has a thermal conductivity about twice that of the prior art.
Next, FIG. 2 shows the temperature-E rise characteristics 21.22 of each of the conductors 51] of
the same-type speaker using the full-field drive electrodynamic speaker based on the aromatic
polyimide resin and the diaphragm base of the present invention. . FIG. 2 shows an input signal
of 2000 l-Iz male support plate signal, and an input changed from IW to 5 W, and a thermal
parity temperature of C conductor tip 5 b is determined 611. As is clear from the figure, the
conductor temperature of the conventional example 21 reaches about C. at 4 W
large input, and the conductor and the base are thermally separated and fractured, whereas the
invention 22 stays up to about C. There is no unusual condition up to about 4,8 W
human power. In other words, according to the present invention, the input load resistance can
be improved by about 20%. This is because the diaphragm substrate of the present invention has
better thermal conductivity than that of the conventional example, so the amount of heat
radiated from the center pole 1 or the front plate 2 through the substrate of zinc heat generated
in the conductor 5b Is increased. As described above, the present invention is a diaphragm of a
full drive electrodynamic speaker having an aromatic polyimide resin film to which boron nitride
is added as a base, and a spiral conductor formed on at least one side of the base The extremely
large thermal conductivity of the plate substrate can promote the heat dissipation in the center
ball and plate due to the thermal conduction of Joule heat generated from the conductor, and has
a large effect of suppressing the temperature rise of the conductor, which makes the speaker
resistant It has the advantage of being able to "tune" the input characteristics.
Brief description of the drawings
FIG. 1 is a cross-sectional view of a full drive electrodynamic speaker, and FIG. 2 is a temperature
rise characteristic diagram of a conductor of the full drive electrodynamic speaker using the
diaphragm of the present invention and the conventional diaphragm.