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The present invention relates to a manufacturing method for inexpensively manufacturing an
acoustic diaphragm made of a material which can not be obtained by ordinary machining.
Generally, a material having a large Young's modulus and a small mass is preferable as a
diaphragm for a speaker or the like, but such a material is generally poor in brittleness, and it is
very difficult to form an accurate shape by machining. Difficult to For this reason, a method of
forming a thin plate by spraying and depositing, at a high speed, on a template formed in the
shape of a diaphragm, a microparticle of a material suitable as a diaphragm to form a thin plate,
and manufacturing the diaphragm by separating this thin plate from the template. Have been
proposed (see Japanese Patent Application Laid-Open No. 56-115097). However, according to
such a method, although a diaphragm excellent in both material 1 dimensional accuracy can be
obtained, the separation of the thin plate and the template becomes very troublesome. That is, in
order to separate the formed thin plate from the template, a method utilizing the difference in
thermal contraction of the material of the thin plate and the material of the template, and the
template made of a material which can easily be dissolved in a copper tube In the former, the
difference in thermal expansion coefficient between the two materials needs to be sufficiently
large while the method of melting the template is used, and the materials that can be used for the
template are limited. Actually, it is difficult to obtain a sufficient difference in thermal expansion
coefficient required for separation, and even if it is obtained, it is very expensive. Further, in the
latter case, the work of dissolving the template is complicated, and furthermore, the template
becomes a consumable product, so that there is a drawback that the manufacturing cost becomes
high. This invention was made in view of the above-mentioned point, and the place made into the
purpose is providing the manufacturing method of the acoustic diaphragm which can
manufacture the diaphragm which consists of a material excellent in acoustic characteristics at
low cost. It is in. In order to achieve such an object, the present invention is to spray a gold alloy,
a ceramic, or a mixture thereof onto a paper base material to form a film, and then burn off only
the base material. It is Hereinafter, the present invention will be described in more detail by way
of examples. FIG. 1 is a cross-sectional view showing a state in which a sheet to be a base
material is formed. In the figure, the paper 1 is made of pulp or the like, and is in the form of a
long band and is wound around the core 2 in a roll. The mold comprises a cylindrical first lower
mold 3, a cylindrical second lower mold 4 slidably inserted in the first lower mold 3, and a
cylindrical upper mold 5. The upper surface of the second lower IJ, 4 is formed in a convex
spherical shape, and the lower surface central portion of the upper die 5 is formed in a concave
spherical shape concentric with the convex spherical surface. Further, on the outer peripheral
surface of the upper die 5, a punching can 6 having a blade portion at its lower end is slidably
The paper 1 is inserted between the first lower mold 3 and the upper mold 5 of such a mold and
the second lower mold 4 is raised to form the paper 1 into a spherical surface, and then the first
lower mold 3 and the upper mold 5 is put together to form the flange portion of the spherical
outer periphery. After that, the punching cutter 6 is lowered to cut the paper 1 around the mold.
When the upper and lower molds are separated and the molded paper is taken out, a base
material 10 having a shape as shown in FIG. 2 is obtained. The base material 10 has substantially
the same shape as the diaphragm 'to be manufactured. Next, a powder of a metal suitable for a
diaphragm material such as B, Be, Ti, Mg, etc., is plasma sprayed and deposited on the base
material 10. FIG. 3 is a block diagram of a plasma spraying apparatus, and FIG. 4 is a crosssectional view of a spraying gun. The plasma spraying apparatus includes a power supply unit
11, a cooling water tank 12, a working gas cylinder 13, an electric input from these, and a
control device 14 for sending a working water of cooling water 9 as a control output, a powder
feeding gas bomb 15, a powder feeding It comprises a powder feeding device 16 for inputting a
gas and delivering metal powder at a predetermined pressure, a thermal spray gun 17 and the
like. Reference numeral 18 denotes a line for supplying the electric power and the coolant 9
working gas to the thermal spray gun 17, 19 denotes a line for supplying the metal powder to
the thermal spray gun 17, and 20 denotes a plasma jet. A cathode 21 made of Triqum tungsten
alloy and an anode 22 made of copper are formed concentrically in the nozzle portion of the
thermal spray gun 17 outside the cathode 21 to form a gas passage 23. A powder passage 24 is
formed near the opening. Then, a high DC voltage is applied between the cathode 21 and the
anode 22 to generate the arc 25, causing the working gas fed from the gas passage 23 to make a
vigorous swirling motion to flow toward the outlet, and the arc 25 to the central axis of the
nozzle Stabilize to narrow down. As a result, the working gas is heated by the arc 25 and ejected
from the nozzle outlet as a high velocity plasma jet 20. The metal powder is carried by the
powder delivery gas and blown into the dent from the powder passage 24. The metal powder is
in a molten state while moving on the jett, and given a large thermal energy and kinetic energy, it
becomes a molten particle 26 and is hit and bonded to the surface of the base material 10, as
shown in FIG. Thus, a coating 28 made of a metal material suitable for the diaphragm is formed
on the surface of the base material 1 ° according to the shape. At this time, the temperature of
the base material 10 is about 200 ° C. or less p. The base material 10 is not damaged at this
temperature. Next, the base material 1o on which the film 28 is formed is burned away.
FIG. 6 shows a cross-sectional view of a heating furnace. In the figure, an inner container 31
made of stainless steel or the like is provided inside an outer container 30 made of a large object,
and a heater 32 is wound around the outer peripheral surface of the inner container 31.
Furthermore, a partition plate 33 having a large number of pores is provided inside the inner
container 31, and the base material 1 o on which the film 28 is formed is placed on the partition
plate 33. In addition, 34 is a landing plate. When the base material 10 is placed in the heating
furnace as described above, the heater 32 is energized to heat the inside of the furnace to 400 °
C. or more, the base material 10 made of paper is burned off and only the coating 28 remains.
Thus, as shown in FIG. 7, a diaphragm made of the coating 28 having the same shape as the base
material 10 is obtained. Since this diaphragm has advanced material characteristics, it has
frequency characteristics when it is incorporated into a speaker or the like. Excellent products
such as transient characteristics and damping characteristics can be obtained. In addition, since
the diaphragm is formed of a base material of paper which is easy to form any shape, it can be
easily formed into a desired shape. In the above embodiments, the thermal spraying apparatus
has been described using a plasma, but in addition to that, a gas thermal spraying apparatus
using combustion flames such as an oxygen-acetylene flame and an oxygen-propane flame as
heat sources, and arc heat due to arc discharge Electric arc thermal spray equipment used as a
heat source, explosion thermal spray equipment using a high temperature high speed flame
generated at the time of explosion of mixed gas such as oxygen-acetylene as a heat source [.theta.
I detonation spray equipment etc. can be used. Further, as the material of the thermal spray
material, that is, the material of the vibration plate, besides the metals described above, it is also
possible to use cermet which is a mixture of metal such as alloy, ceramic, boron nitride and the
like and ceramic. In particular, ceramic and cermet are suitable for this method because they are
difficult to form in the desired shape. In addition, sintered crystals such as ceramics and cermets
can be sintered at the time of burning out of the base material or in the subsequent firing step. In
addition, the material shown to the following table as a ceramic is suitable. As described above,
according to the method of manufacturing an acoustic diaphragm according to the present
invention, the work of removing the base material from the film is extremely simple in order to
burn out and remove the base material of the paper on which the film is formed. The monthly
paper can easily form the desired shape of the diaphragm, and the cost can be reduced, and the
diaphragm made of a material having excellent acoustic characteristics can be manufactured
Brief description of the drawings
1 is a cross-sectional view showing the forming of the base material, FIG. 2 is a front view of the
formed base material, FIG. 3 is a block diagram of the plasma spraying apparatus, and FIG. 4 is a
cross-sectional view of the spraying gun, FIG. 6 is a cross-sectional view of the base material in a
state where a thermally sprayed coating is formed on the surface, FIG. 6 is a cross-sectional view
of a heating furnace, and FIG. 7 is a front view of the coating serving as a diaphragm. 1 ... Paper,
3 ... first lower mold, 4 ... second lower mold, 5 ... upper mold, Kang-out 6 ... punching, 10 ... Base
material 17, spray gun 20, plasma spray device 21, cathode 22, anode 23, gas passage 24,
powder passage 24 2B: Coating, 30, 30: Outer container 31, 31: Inner container 32, 32: Heater
33: Partition plate. Patent Assignee Nippon Musical Instruments Manufacturing Co., Ltd. Agent
Masaki Yamakawa (1 other person) Fig. 1 Fig. 2 n Fig. 3 Fig. 4 7 Seventh Plan q