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JPH0440799

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DESCRIPTION JPH0440799
[0001]
FIELD OF THE INVENTION This invention relates to a method of manufacturing a speaker
diaphragm. [Prior Art] Conventionally, as a diaphragm for a speaker, it is desirable that the
specific elastic modulus E / ρ (E: Young's modulus, ρ: density) is large, that is, it is desirable in
terms of acoustic characteristics that the rigidity is large and light. For this purpose, various
materials, shapes and manufacturing methods of the speaker diaphragm have been studied.
Recently, ceramics having a relatively large E / ρ value as compared with metals such as
aluminum and titanium have come to be applied to the speaker diaphragm. FIG. 5 is a schematic
view for explaining steps of a method of manufacturing a speaker diaphragm to which the
conventional ceramic is applied. In the figure, (A) is a plasma spraying step, (B) is a releasing step
(D) is a firing step. In each of these steps (A), (B) and (D), 1 is a thermal spray gun, 2 is a powder
supply nozzle, 3 is a powder for thermal spraying, 4 is a plasma flame, and 5 is a mold having a
desired shape such as a dome shape. 6 is a film to be a diaphragm, 7 is a container such as an
electric furnace, 8 is a heater such as a resistance wire, 9 is an outlet with a valve, and 10 is an
inlet with a valve for introducing an inert gas. Next, a method of manufacturing the abovedescribed conventional speaker diaphragm will be described. First, in the plasma spraying step
(A), a high temperature, high speed plasma flame generated by radiating a mixed gas of argon
(Ar) and hydrogen (H) or nitrogen (N) and hydrogen (H) from the spraying gun 1 The powder 3
of ceramic such as boron carbide (BaC) is loaded onto the carrier argon or nitrogen from the
powder supply nozzle 2 at the center of the above. Then, the sprayed powder 3 for melting is
melted, and the melted powder 3 for thermal spraying is deposited on the surface of the mold 5
having a desired shape such as a dome shape installed in front of the plasma flame 4 and
vibrated. A film 6 to be a plate is formed. Subsequently, in the mold release step (B), the skin M6
is separated from the mold 5 to form a film 6 consisting of a single ceramic. Subsequently, in the
firing step (D), the film 6 is placed in a container 7 such as an electric furnace, and firing is
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performed at about 2 ooo ° C. by a heater 8 in vacuum or in an inert gas. Thereby, a diaphragm
having a high E / ρ value is obtained. [Problems to be Solved by the Invention] The abovementioned conventional vibration for a speaker is created by the above manufacturing method,
and for that purpose, a diaphragm made of metal such as titanium aluminum (TI-A1) and the like
In comparison, a diaphragm having a significantly higher E / ρ value was obtained.
However, even after the diaphragm 6 made by the above-mentioned conventional manufacturing
method is fired in the film 6 to be the diaphragm in the baking step (D), the diaphragm made is
about 17% to about There is a void in the This fact is substantiated by the experimental results of
a test study by the applicant of the present invention. Therefore, in the conventional method of
manufacturing a diaphragm for a speaker, as described above, a diaphragm having a gap of
about 17% is created in the diaphragm including the skin 116, and the gap is small. And there is
a problem that it is extremely difficult to create a diaphragm having a still higher E / E value. The
present invention has been made to solve the above-mentioned problems, and has a very high E /
ρ value, and is capable of producing a diaphragm suitable for a speaker with even higher
performance. The purpose is to obtain a manufacturing method. [Means for Solving the
Problems] In the method of manufacturing a diaphragm for a speaker according to the present
invention, a coating such as ceramics is formed on a mold of a desired shape by plasma spraying,
and after this coating is released from the mold To fill the ceramic or metal in the voids present
in the film, or in the voids present in the film after firing the film in vacuum or in an inert gas, to
form a diaphragm by the CVD method The [Method of manufacturing a diaphragm for a speaker
according to the invention includes a first step of forming a coating such as ceramics deposited
on a mold by plasma spraying, and a coating formed by the first step. In the second step of
releasing the mold from the mold and in the third step of firing the film formed in the second
step or in the voids present in the film formed in the second step Since the diaphragm is made by
the fourth step of filling the ceramic or metal by the CVD method in the void existing in the film
after the formation, the diaphragm having an extremely high E / .rho. Value is manufactured.
Can. FIG. 1 is a schematic view for explaining steps of a method of manufacturing a speaker
diaphragm which is an embodiment of the present invention. In the figure, (A) is a plasma spray
process, (B) is a mold release process, (C) is a CVD (chemical vapor deposition) process, and (D) is
a firing process. In each of these steps (A), (B), (C) and (D), 1 is a spray gun, 2 is a powder supply
nozzle, 3 is a powder for thermal spraying, 4 is a plasma flame, and 5 is a dome shape etc. A
mold 6 has a film to be a diaphragm, 7 is a container such as an electric furnace, 8 is a heater
such as a resistance wire, 9 is an outlet with a valve, 10 is an inlet with a valve for introducing an
inert gas, 11 Is a CVD (chemical vapor deposition) apparatus container, 12 is a carbon serving as
a susceptor, 13 is a high frequency coil for induction heating, 14 is a CVD source gas, 15 is a gas
inlet for the CVD source gas 14 and 16 is a gas of the CVD source gas 14 It is an exhaust port.
Next, a method of manufacturing the speaker diaphragm according to the embodiment of the
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present invention will be described. As in the conventional manufacturing method shown in FIG.
5, first, in the plasma spraying step (A), a high temperature (~2000 °) generated by radiating a
mixed gas of argon and hydrogen or nitrogen and hydrogen from the spraying gun 1 C) At the
center of the high speed plasma flame 4, the powder 3 for thermal spraying of ceramics such as
boron carbide having an average particle diameter of 20 μm is loaded from argon or nitrogen
for transportation from the powder supply nozzle 2. Then, the introduced thermal spraying
powder 3 is melted or semi-melted in the plasma flame 4 and is deposited at high speed on the
surface of the mold 5 having a desired shape such as a dome shape installed in front of the
plasma flame 4 The film 6 is cooled and assimilated to form a diaphragm 6. Subsequently, in the
mold release step (B), the surface of the mold 5 is smoothed in advance, and the film 6 formed as
described above can be separated from the mold 5 by appropriately selecting the material
thereof, Thus, a film 6 made of a single ceramic such as boron carbide is formed. The film 6 thus
formed has a configuration in which most of the particles of boron carbide are mechanically
deposited, so that the bonding of each particle is relatively weak and about 17% or so Because of
the presence of air gaps, the E / ρ value is relatively small. Therefore, in the present invention, in
the subsequent CVD step (C), the above-mentioned voids present in the film 6 are filled with the
ceramic by the CVD method. Here, a method of filling, for example, boron carbide in the void of
the film 6 will be described. First, the film 6 is placed in a CVD apparatus container 11 and
evacuated to about 10- 'or less by a vacuum pump, and then the carbon 12 and the film 6 are
heated at about 800.degree. C. to 1300.degree. Heat to Next, gasified BCl 3, co and H are
adjusted with a mass flow meter and sprayed onto the film 6 as the CVD source gas 14 for the
skin M 6 thus heated. The sprayed CVD source gas 14 adheres to particles on the surface of the
film 6 and also penetrates and deposits in the voids of the film 6 and can gradually fill the voids
(voids). Here, the evacuation in the CVD apparatus container 11 is continued during the CVD
process. Further, the structure of the coating 6 before the CVD treatment is crushed as a feature
of the thermal sprayed coating in the vicinity of the portion in contact with the mold 5 and the
voids are reduced. Therefore, it is more efficient to spray the CVD source gas 14 onto the film 6
in the direction in which the CVD source gas 14 has more voids in the film 6, ie, the direction
shown in FIG. be able to.
On the contrary, when CVD source gas 14 is sprayed to the film 6 from the direction of the
portion in contact with the mold 5, the voids of the film 6 are quickly clogged and it is very
difficult to fill the voids of the entire film 6 become. In this example, about 70% of the voids
present in the coating 6 could be filled with boron carbide (BaC). Next, after boron carbide is
filled in the voids of the film 6, the film 6 is further fired in the firing step (D). In this firing, the
film 6 is placed in a container 7 such as an electric furnace, and the temperature of the film 6 is
raised in vacuum evacuating the container 7 or in an atmosphere containing an inert gas such as
argon or nitrogen after evacuation. Do the baking. The degree of sintering of the film 6 in this
case varies with the firing temperature, and the E / ρ value gradually increases from about 1000
° C. to a peak value at about 2100 ° C. 2 and 3 are schematic diagrams for explaining steps of
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a method of manufacturing a speaker diaphragm according to another embodiment of the
present invention, and the same reference numerals as in FIG. 1 denote the same or
corresponding parts. The detailed description is omitted. In the manufacturing method according
to another embodiment of the present invention shown in FIG. 2, the plasma spraying step (A)
and the 51 type step (B) are the same steps as the manufacturing method shown in FIG. In the
case of the example, the firing step (D) is performed after releasing from the mold 5 in the
release step (B). That is, while the film 6 is placed in the container 7, the film 6 is baked at high
temperature in vacuum or in an inert gas such as argon or nitrogen in the baking step (D) to
obtain boron carbide (B4C) of the film 6 Increase the cohesion of particles. In the film 6 after
such treatment, the bonding between particles is increased as compared with the film 6 before
firing, and a few open pores can be formed. However, there are still many open pores in the film
6. Then, boron carbide (BaC) is filled in the voids of the film 6 by the CVD process (C) as
described above. As a result, about 60% of the voids in the film 6 are filled with boron carbide
(84C), and the E / ρ value can also be improved by about 10% or more as compared with the
one just fired in the firing step (D). Further, in the manufacturing method according to the other
embodiment of the present invention shown in FIG. 3, after the processes according to the
respective steps (A), (B), (D) and (C) of the embodiment shown in FIG. And a baking process (D).
FIG. 4 is a view comparing E / ρ values of films in the method of manufacturing the speaker
diaphragm according to the conventional example and each embodiment of the present
invention.
Here, the firing of the film 6 in the firing step (D) shows the case of firing at a firing temperature
of about 2000 ° C. in an atmosphere of argon. In the above example, although the case where
boron carbide (84C) is filled in the voids of the film 6 by the CVD method is shown, the substance
to be filled is preferably a substance having a high E / ρ value, and SiC is a ceramic. S 13 Na, T i
C, C, etc. are suitable, and as metals, Be, Ti, etc. are suitable. The substrate temperature is
preferably about 1000 ° C. to 1500 ° C., using S i c 1m + c 3 H 6 as the raw material by the 5i
COCVD method. In addition, BCl 3 + H 2 is used as a raw material of the B CVD method, and the
temperature of the substrate is preferably about 500 ° C. to 1500 ° C. [Effects of the
Invention] As described above, according to the method of manufacturing a diaphragm for a
speaker of the present invention, a coating of ceramic is formed on a mold having a desired
shape by plasma spraying, and this coating is separated from the mold After molding, the
diaphragm is filled with ceramics or metal by the CVD method in the voids present in the film, or
in the voids present in the film after firing the film in vacuum or in an inert gas. Since it is made
to produce, it has an excellent effect that an E / 奏 value is extremely high, and a diaphragm
optimum for a speaker with higher performance can be created.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a schematic diagram for explaining steps of a method of manufacturing a speaker
diaphragm which is an embodiment of the present invention, and FIGS. 2 and 3 are diagrams of a
speaker diaphragm which is another embodiment of the present invention. FIG. 4 is a schematic
view for explaining the steps of the manufacturing method, and FIG. 4 is a view showing a
comparison of E / 皮膜 values of films in the method for manufacturing the speaker diaphragm
according to the conventional example and each embodiment of the present invention; The
drawing is a schematic diagram for explaining steps of a method of manufacturing a speaker
diaphragm to which the conventional ceramic is applied.
In the figure, 1 ... thermal spray gun, 2 ... powder supply nozzle, 3 ... thermal spray powder, 4 ...
plasma flame, 5 ... mold, 6 ... coating, 7 ... Container 8 8 heater 9 exhaust port 10 O inlet 11 CVD
(chemical vapor deposition) apparatus container 12 carbon 13 high frequency coil 14. · CVD
source gas, 15 · · · gas inlet, 16 · · · gas exhaust port, (A) · · · · plasma spraying process, (B) · · ·
demolding process, (C) · · · · CVD (chemical Vapor deposition step, (D) ... firing step. In the figures,
the same reference numerals indicate the same or corresponding parts.
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