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INDUSTRIAL APPLICABILITY The present invention relates to a vibration system material of, for
example, an electrodynamic speaker as an electroacoustic transducer, in particular, a diaphragm
having a cone shape or a dome shape, a voice coil bobbin, and a voice coil bobbin in a flat
speaker using a joint drive system. And a connecting cone for connecting the inside of a cylinder
generated at the first resonant frequency of a flat diaphragm, and a vibration for an
electroacoustic transducer for which a high elastic modulus is required such as a surface material
of a diaphragm having a side stitch structure. It relates to a system material. Conventional
structure and its problems Generally, mica has excellent electrical insulation and heat resistance.
With its rigidity, flexibility, water resistance, etc. and relatively low cost, it occupies an important
position as an insulating material for electrical equipment. In addition, a laminated mica product
obtained by pulverizing mica into flakes and forming it into a sheet has been widely used. On the
other hand, mica has the characteristics desired as a vibration system material for speakers, such
as relatively light weight, high elastic modulus, high heat resistance and high water resistance,
etc. It is put to practical use as a diaphragm. However, in the conventional laminated mica note,
scale pieces having a size difference of about 0.1 to 3-9 and a thickness of about 0.1 to 10 μm
are large at random (the lamination density is uneven, and the surface is uneven. The smoothness
of the speaker was bad, and the speaker characteristics were prone to variations. In addition, in
laminated mica, scale pieces are adhered in close contact, and the van der Waals force acts so
that the larger the contact area, the more the laminated structure tends to be dense and the
closer to the state of the raw stone (the higher the physical properties (elasticity Rate) is
obtained. Here, for example, when scale pieces having a small particle size and a small aspect
ratio are stacked between two large-size mica flakes, a gap is generated between the flakes, and
the bonding force is weakened. Conventional laminated mica does not have an ideal laminated
structure because flakes of various particle sizes and aspect ratios are assembled, and the elastic
modulus also shows a low value. By the way, the elastic modulus is 1.85 × 10 dyn / cnf, the
density is 2.9. The elastic modulus of the laminated mica sheet (fired mica) obtained by
impregnating and curing 20% of the epoxy resin to natural mica with a sound velocity of 7987 m
/ sec is 8.05 × 10 ′ ′ dyn / cnf density 1.9. The speed of sound is 6509 m / pass. Next, the
conventional example in the case of using the laminated mica as a coupling cone for a flat
speaker will be described. In a flat speaker, in order to faithfully transmit the driving force
generated in the voice coil to the diaphragm, the coupling cone must have a sufficient elastic
modulus and be lightweight, that is, one having a high sound velocity of the material is desired.
As described above, mica has been studied for practical use because it has a physical property
considerably higher than that of aluminum (elastic modulus 7 × 10 dyn / cm, density 2.7 sound
velocity 5092 m / 5 ec). However, the variation in thickness is large, and the problem of variation
in characteristics or thickness is left. The construction of the prior art will be described according
to FIGS. 1 and 2. FIG. FIG. 1 shows the shape of the core material by cutting out the appearance
of the plane diaphragm and part of the surface roughness. In FIG. 1, reference numeral 1 denotes
an axisymmetric core made of aluminum foil of 20 μm, whose both sides [40 I 1 m aluminum
foil 2 are bonded together] 19.1 cm in diameter and 6 mm in height for playing bass It is a
stationary plate. Fig. 2 (shows the entire structure of the speaker. In FIG. 2, reference numeral 11
denotes the diaphragm shown in FIG. 1, which is adhesively held on the frame 13 through the
edge 12. A magnetic circuit 14 has a bobbin 116 having a voice coil in a cap supported for piston
movement. The reference numeral 16 denotes a combined cone, which in the prior art uses a
laminated mica with a thickness of 100 pm. The combined cone 16 is formed into a sheet of
scaly mica which is sized to about 5 to 400 mesh (300 to 40 μm) and impregnated with 20 to
30% (by weight) of an epoxy resin, and then cured by heating and pressing. It was molded into a
sheet-la-coat form. The cone shape has an open end diameter of φ 13 Q and a voice coil bobbin
joint diameter of φ 46. The height is 4 cm. The weight of the molded article is 2. There was a
variation of ± 12 with a median of 3.05g between esg and 3.42g. The surface roughness of the
laminated mica still according to the above-mentioned method is shown in FIG. A Tokyo SeimitsuSurfcom E-RC-DA type was used for measurement. As can be seen from FIG. 3 asperities of about
10 μm were also responsible for the variations given to the characteristics. SUMMARY OF THE
INVENTION An object of the present invention is to provide a vibration system material for an
electroacoustic exchanger which can improve physical properties such as high elastic modulus,
low density and high sound velocity by obtaining laminated mica close to an ideal laminated
structure. It is to do. Structure of the Invention The vibration-based material for the
electroacoustic transducer of the present invention is obtained by selecting and selecting the size
and thickness of mica flakes, and impregnating and curing this resin. Because it is difficult to size
the specific size and thickness of mica and flakes, it is necessary to pass the meshy to define the
upper limit of the size, and the flakes that have passed are now different in descending speed in
water To define the upper limit of thickness.
In this way, the upper limit of the size and thickness is changed and the collected flakes are
formed into a sheet, and the thermosetting resin is impregnated and cured. The elastic modulus
of the obtained sheet is measured by the vibration reed method, and the speed of sound is
determined. The thinner the thickness of the mica flakes and the larger the aspect ratio, the
faster the speed of sound. 2. Description of the Example The raw material mica '1760t: from
which impurities have been removed is fired for about 60 minutes, treated with an alkali, treated
with an acid, and then ground with a pulper mixer to form scaly mica. Next, the mixture was
sieved with an opening diameter of 0.17.1 m to 2711 m to obtain several types of mica having
different upper limits of size. The mica having a specified upper limit of size is introduced into
water, the mica having a high sedimentation speed, ie, the mica having a large thickness, is
removed by difference in sedimentation speed, and only mica having a desired thickness or less
is collected. Size in the above way. The formed mica group can be easily obtained by forming
each mica having the upper limit of thickness in a cone shape, a dome shape, a sheet shape or
the like. By impregnating the laminated mica base with about 20% (% by weight) of epoxy / resin
and heat-pressing and curing, a surface material of a bonded cornla diaphragm and a sand-inch
diaphragm is obtained. Fig. 4 Mica before papermaking, thickness of flakes total 10μm or less,
5μm or less, 1μm or less, 0.5μm or less, and further size of each flake is divided into 200 or
more, 500 or more, 750 or more in aspect ratio The measured sound speed of each of the
prepared mica groups is shown. It can be seen from FIG. 4 that the smaller the thickness of the
scale and the larger the aspect ratio, the faster the speed of sound. In particular, the thickness is
1 μm or less. A remarkable effect is obtained when the aspect ratio is 500 or more. When the
maximum thickness is 1.0 .mu.m aspect ratio or 600 or more, the elastic modulus is 9,
55.times.10 dyn 101, the density is 2.0 sound velocity 6910 m / se C, and much higher values
than the conventional one can be obtained. The same shape as that of the combined cone shown
in the conventional example was manufactured with mica having a maximum thickness i and an
o μm aspect ratio of 500 or more. The surface roughness of the combined cone is measured by
the method described in the prior art, and is shown in FIG. In contrast to the prior art having
irregularities of about 10 μm, it was improved to about 2 to 3 μm. In addition, since the sound
velocity is improved by 6.2 as compared with the conventional example, it can be configured
with a thinner foil to obtain the same characteristics. Therefore, the vibration system can be
reduced in weight and the efficiency of the speaker can be improved. For example, the same
characteristic is obtained at 90 μm. Further, according to the present invention, the variation in
the property of reducing the variation in the lamination density of mica is suppressed.
For example, the weight of the combined cone of the example was 2.166 to 2.949 with a
variation of ± 5 around 2.89, which was a practically sufficient value. Although the above has
described the embodiment of the flat diaphragm as a connecting cone, the vibration system
material of the present invention can be used similarly as a normal cone-like, dome-like
diaphragm or a sandwich skin material. An effect can be obtained, and a high-performance and
high-quality speaker can be provided. Effects of the Invention As described above, according to
the present invention, a thermosetting resin is impregnated into a laminated mica sheet formed
by forming a sintered mica containing 1.0 μm or less in thickness and a flake Q 90 or more
having an aspect ratio of 500 or more. Because it is hardened, it is possible to obtain a laminated
mica close to the ideal laminated structure, and the high modulus required for the vibration
system material. Physical properties such as low density and high sound velocity can be
improved. Therefore, it is possible to realize a high efficiency, wide surface light band high state
speaker entirely, and to obtain a speaker with little variation in efficiency and sound pressure
frequency characteristics.
Brief description of the drawings
FIG. 1 is an external view showing the shape of a core material by cutting out a part of the
surface material of a flat diaphragm, FIG. 2 is a cross-sectional view of a flat speaker, and FIGS.
3a and 3b show a conventional example and an embodiment of the present invention FIG. 4 is a
view showing the surface roughness of the vibration-based material, and FIG. 4 is a view showing
the relationship between the size of the mica flakes before papermaking and the speed of sound
when it is used as the mica composite.
Name of agent Attorney Nakao Toshio One other person Fig. 1 @ 2 Fig. 3 (亙 ♂-/ θ 霜 (θ) (b)
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description, jps5970099
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