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JP2011024092

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DESCRIPTION JP2011024092
An object of the present invention is to solve electro-acoustic conversion by a plate-like metal in
which springback after pressure forming is eliminated, the thickness of each part in the radial
direction of the diaphragm becomes uniform, and an oxide film for corrosion prevention is
formed on the surface simultaneously with forming. Providing a dexterous diaphragm and its
manufacturing method. SOLUTION: A shallow concave is formed in a plate-like metal, pure water
is placed only in the lower part, and sealed in a female mold space heated to the boiling point or
more of pure water for a predetermined time, and heat pressure forming is performed with
generated steam pressure. Take a method. The springback is eliminated due to heating, and the
concave lower portion is heated and pressurized later than the upper portion because of pure
water existing in the initial stage, the thickness in each radial direction becomes uniform, and the
surface exposed to water vapor pressure is oxidized The membrane will be the simultaneously
generated diaphragm. [Selected figure] Figure 1
Diaphragm for electro-acoustic transducer by steam pressure molding and method of
manufacturing the same
[0001]
The present invention relates to a diaphragm for an electroacoustic transducer by water vapor
pressure molding, particularly to a diaphragm made of metal, and a method of manufacturing the
same.
[0002]
Conventionally, in order to manufacture a diaphragm for an electroacoustic transducer with a
plate-like metal, pressure forming using air pressure, gas forming using gas pressure, oil pressure
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1
forming using oil pressure, vacuum forming using vacuum pressure, A variety of manufacturing
processes have been used, such as upper and lower mold forming with a mold.
[0003]
In the manufacture of metal cones for speakers by these various pressure forming processes for
plate-like metals, generally, the amount of springback of the processed product is large as a
result of normal temperature processing, and mold correction and forming are necessary to
obtain prescribed forming. It is necessary to repeat the
In order to improve this point, the springback amount of the metal cone molded article is
reduced, and pressure forming is performed at a temperature (150 to 250 ° C.) near the
recrystallization temperature of the workpiece so as to satisfy sufficient strength. A method and
apparatus have been proposed (see Patent Document 1).
[0004]
However, in any pressure forming, the following problems remain in common.
In the case of (1), in the case of a cone-shaped molded product, uniform thickness can not be
obtained at each portion in the radial direction, and the neck portion (inner peripheral portion) is
always the thinnest and gradually thickens from the middle portion to the outer peripheral
portion Therefore, it causes partial strength reduction and intense axisymmetric occurrence in
vibration mode. (2) The molded product must be subjected to surface treatment in a separate
step to prevent surface corrosion after molding.
[0005]
Japanese Patent Application Laid-Open No. 52-25617
[0006]
The problem to be solved by the present invention is that diaphragm production by conventional
pressure forming of sheet metal requires correction of mold and repeated forming in order to
reduce the amount of springback at the time of cold pressure forming. Because the thickness
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2
after molding becomes uneven overall, the strength of the diaphragm is partially reduced, and an
axisymmetric rapid mode is generated even in the vibration mode, and further, it is different for
preventing corrosion after the forming processing. It is necessary to carry out surface treatment
in the process.
[0007]
The present invention, therefore, does not generate a springback in the plate-like metal material
despite the pressure forming, and the thickness after forming is uniform at each portion in the
radial direction, resulting in a partial strength reduction or a partial shaft. It is an object of the
present invention to provide a diaphragm for an electroacoustic transducer using a plate-like
metal, which can prevent the occurrence of a symmetrical vibration mode and can also perform
surface treatment for corrosion prevention simultaneously with pressing and its manufacturing
method. Do.
[0008]
According to the present invention, the diaphragm for an electroacoustic transducer with a platelike metal according to claim 1 is formed into a desired diaphragm shape by heating a plate-like
metal having a concave surface together with pure water containing the concave bottom. It is
sealed in a mold inner space for a predetermined time, and is formed into a desired shape by
steam pressure vaporized in a heating sealed space, so that it is formed on the inner peripheral
part, middle part, outer peripheral part, and molding side surface made uniform thickness. And
an oxidized film.
Further, according to the present invention, in the method of manufacturing a diaphragm for an
electroacoustic transducer using a plate-like metal according to the second aspect of the present
invention, a process of providing a concave on a metal plate-like material, and A step of injecting
pure water in an amount corresponding to the dimensions of the plate-like material, a step of
heating the formed female die having the desired diaphragm-shaped recess to a predetermined
temperature above the boiling point of pure water, and Positioning the upper part of the space in
the heated molding female mold together with the pure water in the concave bottom, and
lowering the molding upper mold having the on-off valve in the closed state to deionize the
molding female inner space including the plate material And pressure-forming the plate material
in a heated state by steam pressure generated in the molding female internal space by closing for
a predetermined time according to the amount of After the pressure in the mold is reduced, the
upper mold is raised, and the formed plate material is taken out. The features.
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The method for manufacturing a diaphragm according to claim 3 is characterized in that the
concave surface provided on the plate-like material is formed by making substantially the entire
area of the portion to be molded a shallow spherical surface.
[0009]
According to the present invention, since the metal plate material is first pressure-formed in a
heated state, the amount of spring back is reduced, and pure water is put in the bottom or lower
part of the concave provided on the plate material. By heating and pressurizing, the concave
bottom or lower part touching pure water is heated and pressurized later than the concave upper
part exposed from pure water, and finally all pure water is vaporized Therefore, it is not thinner
than the upper portion or the outer peripheral portion, and is molded with a uniform thickness in
the entire radial direction.
Furthermore, since a metal oxide film is formed on the surface of a molded article made of a
metal plate material by water vapor generated during molding, surface treatment for preventing
corrosion is applied simultaneously with molding.
[0010]
FIG. 1 is a cross-sectional view showing a step of positioning a diaphragm plate material in the
upper part of a heated molding female internal space together with pure water placed on the
concave surface in an embodiment of a method of manufacturing a diaphragm according to the
present invention. It is. FIG. 2 is a cross-sectional view showing a state in which pressing with
water vapor is started by lowering the upper molding die onto the female die in the embodiment
of FIG. FIG. 3 is a cross-sectional view showing a state in which pressure molding has been
almost completed, shifting from the state of FIG. FIG. 4 is a cross-sectional view of the vibrating
plate material after pressure forming according to the present invention, showing that the
thicknesses of the inner circumferential portion, the outer circumferential portion and the middle
portion are equal. FIG. 5 is a frequency characteristic diagram comparing acceleration frequency
characteristics of the diaphragm according to the present invention and the conventional product
pressure-molded under the same conditions as the present invention. FIG. 6 shows respective
vibration modes of the conventional product and the product of the present invention, wherein
(a) is the conventional product and (b) is the vibration mode of the product of the present
invention. FIG. 7 is an infrared absorptiometry diagram on the molding surface side of the
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conventional product and the product of the present invention, where (a) shows an analysis of
the conventional product and (b) shows an analysis of the product of the present invention. FIG.
8 is a 5000 × magnified cross-sectional photograph of the molding side surface of the
diaphragm of the present invention, showing the formation of an oxide film on the surface.
[0011]
An embodiment of a method of manufacturing a diaphragm for an electroacoustic transducer by
water vapor pressure forming of a metal plate material for achieving the object of the present
invention will be described with reference to FIGS. 1 to 3.
[0012]
If a method of manufacturing a cone-type loudspeaker diaphragm of 10 cm in diameter
according to the present invention using an aluminum foil with a thickness of 100 μm as an
example is shown in FIG. A shallow spherical concave 2 having a diameter of 10 cm or less is
formed in advance, and 5 cc of pure water 3 is introduced into the bottom or lower part of the
concave 2.
The amount of pure water 3 is determined to a value sufficient for the application of water vapor
pressure forming of the plate material 1 used while exposing the upper part of the concave
surface 2.
[0013]
On the other hand, the molding female die 4 which is the lower mold of the pressure molding die
and has the desired diaphragm shape concave portion 5 is heated in advance to 200 ° C. which
allows the aluminum foil to be molded by exceeding the boiling point of pure water. First, as
shown in FIG. 1, the concave portion of the plate-like material 1 is placed on top of the space in
the concave portion 5 of the molding female die 4 together with the pure water.
[0014]
Next, as shown in FIG. 2, the flat-plate-like upper die 6 of the pressure-molding die is lowered to
seal the inner space of the recess 5 of the molding female die 4.
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Although the upper mold 6 has an on-off valve 7 which communicates the space in the recess
with the external space, it is of course closed at this time. The sealing time under heating at 200
° C. is set to 30 seconds. During this time, a load of 5 t is applied to the upper mold 6, and the
water vapor pressure generated by boiling pure water present on the surface side of the concave
surface 2 of the plate 1 acts accordingly on the surface side of the plate 1 Do. However, at the
initial stage of the sealing time, the lower part or the bottom part of the concave surface 2 of the
plate material 1 does not have a temperature higher than the boiling point of pure water because
the pure water exists, and the upper part of the concave surface 2 exposed from pure water That
is, the portion corresponding to the outer peripheral portion of the cone-shaped diaphragm first
reaches high temperature, and the forming progresses from the outer peripheral portion first.
[0015]
In the final stage, as shown in FIG. 3, all the pure water 3 becomes water vapor 3 ', and the
concave bottom, that is, the portion corresponding to the inner peripheral portion of the
diaphragm is also exposed and reaches high temperature and is subjected to water vapor
pressure forming. As described above, the portion corresponding to the inner peripheral portion
of the diaphragm is heated behind the concave upper portion corresponding to the outer
peripheral portion and pressurized, and as a result, both portions have a uniform thickness and
the female concave portion 5 has a uniform thickness. It is shaped into a shape. After the sealing
time of 30 seconds has elapsed, the on-off valve 7 is opened to evacuate the water vapor in the
mold, the upper mold 6 is lifted, and the diaphragm 10 made of the formed plate material 1 is
removed from the mold.
[0016]
FIG. 4 is a cross-sectional view of the cone-shaped diaphragm 10 manufactured from the
aluminum plate 1 by the above-described steam pressure forming according to the present
invention, and three different positions A in the radial direction The inner peripheral part), B
(middle part) and C (outer peripheral part) are shown. Using 1000 pieces of aluminum plate
material under the same conditions as the test sample and performing water vapor pressure
molding under the same conditions, 1000 diaphragms 10 obtained were created, and the
average value of the measurement for all these samples was obtained. The same thickness of
0.083 mm was measured at A, B and C.
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[0017]
For comparison, using the aluminum plate material under the same conditions as above, 1000
diaphragms of the same size as above are made by pressure forming using air pressure as an
example of the prior art, and the same three positions A to C as FIG. The thickness was measured
for each of the above, and the average value was taken. A remarkable non-uniformity of 0.075
mm at position A, 0.083 mm at position B, and 0.090 mm at position C was observed.
[0018]
FIG. 5 is a characteristic curve diagram showing the comparison between the above-mentioned
conventional product and the product of the present invention with respect to diaphragm
acceleration frequency characteristics.
In the figure, the curve by the thick line shows the frequency characteristic of the product of the
present invention, the curve by the thin line shows the frequency characteristic of the
conventional product, and the peak dip due to resonance becomes large in the conventional
product at around 10 kHz and above. In the product of the present invention, the peak dip is
suppressed to a small value, which clearly demonstrates that the uniform thickness of the
diaphragm prevents partial strength reduction.
[0019]
FIG. 6 shows vibration mode analysis diagrams of the conventional product and the product of
the present invention at frequencies around 12.8 kHz, where (a) is the conventional product, (b)
is the product of the present invention, and (a) is the shaft Symmetrical intense vibration modes
appear, apparently due to a partial loss of strength due to the non-uniform thickness of the
diaphragm, but in (b) with thickness uniformity A non-axisymmetric stable vibration mode can be
confirmed.
[0020]
Finally, the presence or absence of the composition change of the pressure molding side surface
of the conventional product and the product of the present invention is observed.
FIG. 7 is an infrared absorption analysis chart, (a) is a conventional product, (b) is a product of
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the present invention, and FIG. 8 is an enlarged cross-sectional photograph of the product of the
present invention on the water vapor pressure molding side. As apparent from comparison
between (a) and (b) in FIG. 7, it is confirmed that the surface of the product of the present
invention has 43.2% of the number of atoms indicating oxide O which is not present in the
conventional product. Ru. Also in the cross-sectional picture of FIG. 8, a layer different from the
aluminum base material is formed on the molding side surface of the product of the present
invention, and it is apparent from FIG. 7 (b) that this surface layer is an oxide film. It is.
[0021]
Although aluminum is shown as an example of the metal used in the above embodiment, the
present invention is not limited to aluminum, and is commonly used as a diaphragm for an
electroacoustic transducer, and includes titanium, permalloy, and magnesium alloys. The same
applies to metals and various alloys, and the amount of pure water, the heating temperature and
the sealing time are determined according to the size and properties of the selected material. In
addition, pure water can also be substituted with water of high purity as long as it does not
contain undesirable impurities.
[0022]
Reference Signs List 1 plate material 2 concave surface 3 pure water 4 molded female mold 5
concave portion 6 upper mold 7 on-off valve 10 diaphragm
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