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FIELD OF THE INVENTION The present invention relates to a diaphragm for a speaker. [Prior Art]
Conventionally, for example, a diaphragm for a so-called hard dome-shaped speaker has a single
plate of aluminum (?1), titanium (Ti), magnesium (Mg), beryllium (Be) or the like formed in a
dome shape There are many things. And, in order to improve the acoustic effect, the diaphragm
formed of a single plate such as a coin is designed to reduce its thickness and weight. [Problems
to be solved by the invention] However, if the thickness of the diaphragm is made thin and
lightened, the rigidity is reduced, and distortion due to non-axisymmetric vibration of the
diaphragm occurs in a low frequency region, Distortion due to the axisymmetric split resonance
increases, resulting in a large peak dip in frequency characteristics. And, it is known that the
primary resonance of the dome-shaped diaphragm occurs at a relatively low frequency at a
portion slightly inside the peripheral portion of the dome-shaped diaphragm. And since the wide
area reproduction limit frequency of the speaker is limited by this resonance, it is necessary to
make the rigidity of the diaphragm as high as possible to prevent the resonance. If the rigidity is
simply increased, the thickness of the diaphragm may be increased, but on the other hand, the
weight is increased to lower the efficiency of the speaker. Therefore, it is necessary to increase
the rigidity and to reduce the weight. As a technology to satisfy such requirements, a diaphragm
with a laminated structure in which several lightweight members are stacked can be considered.
In fact, a planar diaphragm using a honeycomb core material is put to practical use It is done.
However, it is extremely difficult in terms of formability and adhesion to form a dome shape with
a small radius of curvature in a honeycomb structure. A dome-shaped diaphragm having a
laminated structure using a honeycomb structure has not been put to practical use yet. Generally,
the rigidity (D) of the diaphragm is expressed by the following equation:% E: Young's modulus of
the diaphragm (dyne / cm) t ... thickness of the diaphragm cm) ? ... Poisson of the diaphragm
The ratio and Poisson's ratio in this equation are small and squared, and may be omitted.
Equation (1) is transformed as follows. D = Et ? ? / 12 (2) However, the material is assumed to
be uniform. As seen from this equation (2), the thickness 1) is proportional to the stiffness (D)
and is raised to the third power, so the stiffness (D) of the diaphragm is greatly increased by a
slight increase of the value. It turns out that it becomes high. Now, assuming that the surface
density (?) of the diaphragm is constant, the density (?) has a relationship of ???t
ииииииииииииииииииииииииииииии (3) Substituting the equation (3) into the equation, D = (E / 12) x (? / ?) 3- (?3
/ 12) О (E / D3) (4) From this equation, DCy!
E / D 3 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (5). ????????????
Therefore, the density (?) is small, the Young's modulus (E) is large, the rigidity (D) is high, and
the speed of sound (r?;-) is large, and the vibration is appropriately performed over a wide
frequency. Efficiency, low distortion, wide-area reproduction limit increased, flat and wide
frequency characteristics. Also, in order to prevent resonance and reduce distortion, it is
desirable that the internal loss (tan ?) is also large. The present invention has been made under
such a background, and is for a speaker having a laminated structure which is lightweight, high
in rigidity, low in distortion, excellent in frequency characteristics, and easily formed into a cone
shape or a flat shape as well as a dome shape. It is an object of the present invention to provide a
diaphragm. [Means for Solving the Problems] In order to solve the above-mentioned problems,
the diaphragm of the present invention has a carbon fiber layer superimposed on one surface of
a substrate formed of a foamable hard resin, and a light metal on the other surface of the
substrate. Layers are stacked to form a stacked structure. [Operation] The diaphragm of the
present invention is made of foamable hard resin, carbon fiber and light metal, so it is lightweight
and can be formed into various shapes, and these materials themselves have small density, high
Young's modulus, and Since the Young's modulus is increased by laminating them, the rigidity is
enhanced and both the light weight and the high rigidity are provided. Embodiment An
embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG.
The diaphragm of this embodiment has a laminated structure of three layers in which a carbon
fiber layer 2 is laminated on one surface of a substrate 1 formed in a dome shape with a
foamable hard resin and a light metal layer 3 is laminated on the other surface of the substrate 1
It is The substrate 1 is made of an acrylic resin foamed 15 to 30 times as a material capable of
being subjected to heat molding and adhesion, and the thickness thereof is formed to be 5 mm to
3 mm. The carbon fiber layer 2 is formed of a so-called prepreg-type carbon fiber woven fabric 4
impregnated with an epoxy resin, and the carbon fiber woven fabric 4 is attached to the convex
side of the substrate 1 . The light metal layer 3 is formed of an aluminum foil 5 having a
thickness of 10 ?m to 50 ?m, and the aluminum foil 5 is attached to the concave side of the
substrate 1. Next, a method of manufacturing the speaker diaphragm of this embodiment will be
described. In the manufacture of the speaker diaphragm of this embodiment, a mold 11 is used
as shown in FIG. 2 and FIG. The mold 11 includes a dome-shaped recessed female mold 12 and a
dome-shaped projecting male mold 13 corresponding to the female mold 12, each of which has a
heater 14.
Then, first, the carbon fiber woven fabric 4 is placed on the female die 12, and the flat diskshaped substrate 1 which is not dome-shaped yet is overlaid thereon. Next, the mold 11 is heated
to about 130 ░ C. to 140 ░ C. by the heater 14, and the male die 13 is gradually lowered and
pressurized to make the substrate 1 and the woven cloth 4 of carbon fiber into a dome shape. At
this time, since the woven fabric 4 of carbon fiber is impregnated with the epoxy resin, the epoxy
resin is melted by the heat of the mold 11 and the woven fabric 4 of carbon fiber is attached to
the substrate 1 1, thus, A two-layered diaphragm of 1 and a carbon fiber layer 2 is formed as
shown in FIG. 3, but even with this alone, considerable rigidity (D) can be obtained. Then, after
pulling up the male mold 13, the aluminum foil 5 previously formed into a dome shape by
vacuum molding is placed on the concave side of the dome-shaped substrate 1 through a
polyamide non-woven adhesive 15. The male die 13 is lowered again, and the adhesive 15 in the
form of a polyamide non-woven fabric is melted by heat pressing, and the aluminum foil 5 is
attached to the substrate 1. Thus, since the so-called prepreg type carbon fiber woven fabric 4
impregnated with an epoxy resin and the polyamide non-woven fabric adhesive 15 are used, the
carbon fiber woven fabric 4 to the substrate 1 and the aluminum foil 5 are Easy to paste. Thus, a
diaphragm having a three-layer structure is formed, and as shown in FIG. 5, a damper 21 and the
like are attached to the periphery and incorporated as a speaker 22. By the way, the acrylic resin
foam forming the substrate 1 has a small density (.rho.) And is very light and very thick in order
to enhance the rigidity (D). Therefore, high rigidity and weight reduction can be realized together.
Also, carbon fiber is glass! ! The density 1 (?) is smaller and the Young's modulus (E) is larger
than strings. Therefore, high rigidity, lightening can be achieved, and the speed of sound (! ) Is
large. Furthermore, aluminum (8 l) contributes to weight reduction because it can easily form a
thin foil although its ratio (E) is smaller than that of carbon Il fiber. Then, since the light shielding
layer 3 of the inter-ill-carbon layer and the aluminum foil 5 is stacked on the substrate 1 to form
three layers, the whole Young's modulus (E) becomes larger than the individual Young's modulus
(E) of each layer by the synergistic effect. Moreover, the weight is not so heavy. And since the
frequency characteristic of the diaphragm formed in this way is high rigidity and light weight, it
is called an aluminum single plate (hereinafter referred to as A1 single plate) as shown in FIG.
Elongated in the high region is better than the dome-shaped diaphragm formed in 2.), and the
second harmonic distortion is less. Although the diaphragm of the embodiment is formed in a
dome shape, the present invention is not limited to this shape, and may be a cone shape or a
planar shape.
In this respect, since the substrate 1 is formed of a hard synthetic resin having a heat generating
property, it can be formed into any shape. Furthermore, the thickness 1) of the substrate 1 may
not be constant, and U1 may be uneven if necessary. Further, the substrate 1 is not limited to
acrylic, and may be a foam such as vinyl chloride. Further, although the carbon fiber layer 2 is
formed of carbon fiber woven fabric 4 in the above embodiment, the woven fabric 4 may be
woven by plain weave, twill weave, satin weave, braid, or any other weave, In addition, the oneside aligned UD (unidirectional) or the one-side aligned UD may be an orthogonal double layer. In
particular, UD has high rigidity (D) in the aligned direction and exhibits excellent characteristics.
Therefore, in the case where one aligned straight UD is formed by stacking two orthogonal
layers, the rigidity in the four directions (D> is high, which greatly contributes to the
improvement of the characteristics. The light metal layer 3 in the embodiment is formed of the
aluminum foil 5, but other light metals such as Ti, Mg, Be, or alloys thereof may be used, and the
aluminum foil 5 is anodically oxidized to form an oxide film ( Eight j! zo 3) may be formed to
improve physical property values such as Young's modulus (E>). Furthermore, in the
embodiment, the aluminum foil 5 is attached with the non-woven fabric adhesive 15 of
polyamide type and the light metal layer 3 is superposed on the concave side of the substrate 1,
but the light metal layer 3 is deposited by vapor deposition of aluminum (A1) or the like. May be
formed directly on the surface of the substrate 1. The physical properties of the diaphragm
formed of A1 single plate and the physical properties of the diaphragm of various three-layer
structure according to the present invention are as shown in Table 1 below. Table 1A type: A
carbon woven fabric of satin weave and an interlayer of 5 times foamed acrylic and a 20 ?m
thick aluminum foil. Type B: plain weave carbon lIH layer + 25 times foam acrylic substrate +
20? thick aluminum foil. Type C: Carbon fiber layer + 25 times foamed acrylic substrate + 20 ?
thick aluminum foil with unidirectional double alignment UD in two orthogonal layers. ?
ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии Sound velocity of sound (Cm) X 105 tan ? ..... Internal loss. D
ииииииииииии stiffness (dVne / cm) X 107C ииииииииииии A1 surface density of the vibration plate of the
comparison 3-layer structure of a single-plate stiffness ( The rigidity (D) of an Al single plate
having a thickness 1) with the same surface density (?) as the stem of the ?) is derived, and the
rigidity of the three-layer diaphragm to the rigidity (D) of the Al single plate The ratio of (D) was
1 ........... As apparent from thick fence cm) Table 1 of the diaphragm, three layers ivi granulation
of the diaphragm than its Young instep (E) is A, the Q veneer Because the density is low, but the
density (??) is small, the speed of sound (F- ?] 7. o is equal to or higher than that of the plane
density (?). It is also back and forth, which greatly contributes to the improvement of frequency
characteristics. In addition, since the internal loss (tan ?) is three or more times as large as that
of the A1 single plate, it is difficult for resonance to occur so that the so-called noise of the
diaphragm can be stopped. As described above, the reason why the internal loss (tan ?) is large
is based on the difference in the material itself and the three-layer structure. [Effects of the
Invention] According to the present invention, since it is formed using a material with low
density, weight reduction can be achieved, moreover, rigidity becomes large, and furthermore, a
carbon IM interlaminar layer substrate having a large Young's modulus The three-layer structure
is obtained by overlapping the m-carbon layer on one surface of the substrate and additionally
forming the light metal layer on the other surface of the substrate, so that the rigidity is further
enhanced. Due to the properties of the material and the three-layer structure, a large vibration
damping effect, ie internal loss, results. Therefore, the frequency characteristic is improved,
distortion is reduced, and good sound quality can be obtained. In addition, since the shape can
also be freely, it is possible to easily manufacture one having an optimum shape in terms of
acoustic characteristics.
Brief description of the drawings
FIG. 1 is a longitudinal sectional view showing an embodiment of the diaphragm of the present
invention, FIGS. 2 to 4 are diagrams showing the manufacturing process thereof, and FIG. 5 is a
longitudinal cross section of a speaker using the diaphragm of the present invention FIG. 6 is a
comparison diagram of the frequency characteristics of the present invention and the prior art.
1 и и Substrate, 2 и и Carbon! f + fiber layer и и light metal layer.
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