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TECHNICAL FIELD The present invention relates to a composite diaphragm for a speaker.
BACKGROUND ART AND PROBLEMS As a speaker diaphragm for a speaker, it is necessary to
satisfy the contradictory physical characteristics of being lightweight, having high rigidity, and
having appropriate internal loss. In general, it is not easy to realize such properties with one
material, and it is the fact that the required physical properties are obtained using composite
materials. In recent years, a high rigidity (high Young's modulus) short fiber material (eg, carbon
fiber, alumina fiber, glass fiber, POM whisker, etc.) is contained in a suitable binder (eg,
polyethylene) to form a speaker diaphragm. It is being tried to do. Such a diaphragm has high
rigidity, but tends to have high Q (resonance sharpness) and small internal loss. It is therefore
preferred to use in combination with a suitable damping material. In general, the edge of the
speaker diaphragm is divided into a free edge and a fixed edge. The free edge is a separate edge
attached to the diaphragm base (cone) and is excellent in vibration resistance and durability, but
it is necessary to have the edge forming process and the cone and edge bonding process. It is
expensive. In addition, since the connection between the cone and the edge is a bond of different
substances, there is a problem that a smooth and less distorted vibration characteristic can not
be obtained. On the other hand, the fixed edge is provided with an edge on the outer periphery of
the diaphragm base itself and can be manufactured relatively inexpensively, but the vibration
resistance width and durability are somewhat inferior, and a process of applying a dump material
to suppress resonance. Is required. SUMMARY OF THE INVENTION In view of the problem 1
described above, the present invention combines a diaphragm base containing the abovedescribed short fiber reinforcement and a suitable damping material to obtain a diaphragm
having excellent physical properties and sound quality. The main object is to incorporate the
advantages of both the free edge and the fixed edge, and to obtain a low-cost composite
diaphragm which is excellent in vibration resistance and durability and is easy to manufacture.
SUMMARY OF THE INVENTION A composite diaphragm according to the present invention
comprises laminating a fibrous sheet material and a thermoplastic film on a diaphragm substrate
containing a short fiber reinforcing material, and thermally forming them to form an edge at the
same time. It is With this configuration, sound quality, physical characteristics, and mechanical
characteristics can be improved, and manufacturing can be performed at low cost. EXAMPLES
Examples of the present invention will be described with reference to the drawings. FIG. 2 is a
longitudinal sectional view showing a method of manufacturing a composite diaphragm for a
speaker according to a first embodiment of the present invention, and FIG. 2 is a longitudinal
sectional view of the manufactured diaphragm.
As shown in FIG. 1, a damping material film (2) (for example, a thermoplastic urethane sheet) and
a fibrous sheet +31 (for example, a cotton cloth or silk cloth) are laminated in this order on a
cone-shaped diaphragm substrate (1). The upper and lower molds (4) 151 are subjected to heat
compression molding to form a diaphragm (6) as shown in FIG. As the diaphragm substrate (11,
a highly rigid material containing a short fiber reinforcement such as POM whisker as described
later is used. A mold (41 + 51 has a ring-shaped uneven portion (4a) r5a) for forming an edge
portion of the diaphragm. Then, when the diaphragm substrate (1), the damping material film (2)
and the fibrous sheet (3) are laminated, and these are heat-formed and bonded, the edge portion
(7) is a diaphragm as shown in FIG. It is integrally formed with the part (6). Therefore, while
having a similar structure to the free edge, it can be easily manufactured as in the fixed edge, and
the cost can be reduced. The edge portion (71 is a double structure of the damping material film
(2) and the fibrous sheet 13), which has vibration resistance and durability, and also has
appropriate flexibility. The diaphragm portion (6) has a three-layer structure of a base (1)
containing a short fiber reinforcement, a damping material film (2) and a fibrous sheet (3), and
has a high Young's modulus E and a resonance sharpness Q Show an ideal characteristic with low
internal loss. The diaphragm portion (61 (!: With the edge portion (7) can produce very smooth
vibration, such as the damping material film (2) and the fibrous sheet (the force 1 continuously
connected by the 31 There is little distortion of sound quality or frequency characteristics. A
diaphragm substrate (11 may be used in which a short fiber reinforcement such as carbon fiber
or glass fiber is contained in an appropriate binder, but in this embodiment, as described above,
POM Methylene) single crystal whiskers are used as reinforcement. This diaphragm substrate (1)
can be manufactured, for example, by papermaking. -For example, the POM whiskers and the
polyethylene-based synthetic pulp as a binder are mixed in water at a weight ratio of 1 to 1,
mixed by stirring, mixed, and formed into a cone shape through a network to form a diaphragm
substrate ( You can get eleven. The diaphragm of FIG. 2 is obtained by laminating the damping
material film (2) and the fibrous sheet (3) on the diaphragm base material (11 as shown in FIG. 1)
and heating and compression molding. The heating temperature at the time of compression
molding is a temperature (130 'to 150 ") at which the polyethylene-based synthetic pulp as a
binder melts at a temperature below the softening point (180 DEG to 190 DEG) of whiskers.
In this case, if a material whose melting temperature is approximately equal to the heating
temperature of compression molding is used as the damping material film (2), the diaphragm
substrate (11, damping material film (2) and fibrous sheet L (+ It is pasted together. Although the
fibrous sheet (3) itself does not melt, the molten damping material film (2) penetrates the fiber
layer and both are mechanically bonded. 3 and 4 are longitudinal sectional views similar to FIG. 1
showing an embodiment on the respective side. In FIG. 3, pneumatic molding is used as a heat
compression molding method. As shown in FIG. 6, a cone-shaped diaphragm base (1) using POM
whiskers as a reinforcement is placed on a mold 18), the damping material film (2) and the
fibrous sheet 3) are laminated, By applying and heating, a three-layered diaphragm similar to
that of FIG. 2 is obtained. If the ring-shaped recess (8a) corresponding to the edge portion is
formed in the mold (8), the edge portion (7) can be simultaneously formed as shown in FIG. As
the damping material film (2) and the fibrous sheet 131, the same ones as those in FIG. 1 can be
used, but in this embodiment, an olefile based polypile day pyrene film is used as the damping
material film (2) A non-woven fabric is used as the fibrous sheet (31). The polypropylene film is
modified to have its melting point around 150 ░. The advantage of using a non-woven fabric is
that there is no directionality of the fibers, good vibration characteristics and propagation
characteristics without distortion are obtained over the entire surface of the diaphragm, and the
variation in damping effect at the outer peripheral portion (edge) is small. The embodiment of
FIG. 4 uses the pressure forming method as in FIG. 6, but in this embodiment, the order of
lamination is changed. That is, a non-woven fabric as a fibrous sheet (3) is placed on a diaphragm
substrate containing 11M whiskers (11), and a modified polypropylene film as a damping
material film (2) is placed on top of the l It is molded to obtain a diaphragm similar to that of FIG.
By interposing the non-woven fabric as an intermediate layer, special effects which can not be
obtained in FIGS. 1 and 3 can be obtained. That is, when it is heated and pressed in the laminated
state of FIG. 4, first, a polyethylene-based synthetic pulp (melting point 165 ░) as a binder of 20
M whiskers is melted, and then a polypropylene modified film as a damping material sheet (2) is
melted. Do. And, it penetrates into the non-woven fabric layer which is the outer two layers or the
intermediate layer which is melted, and after cooling, it is pasted as three layers.
When each of the polyethylene synthetic pulp as a binder of 20 M whiskers and the
polypropylene film as a damping material is melted, the 20 M whiskers having a softening point
of 180 ░ to 190 ░ remain without being softened, but the non-woven fabric of the middle layer
Serves as a filter, and the whiskers are effectively prevented from diffusing toward the damping
layer and edge 5 (7). Therefore, since whiskers are not mixed into the damping layer and the
edge portion and the damping ability is not reduced, it is possible to obtain excellent physical
characteristics as a composite diaphragm. The physical properties of the diaphragm
manufactured as described above were measured by the vibration lead method for the
combinations and structures of the materials shown in the example of the m4 figure as follows.
? Resonance sharpness (Q) 13.0 Young's modulus (VnL2) 3 О 10 'Density CWm' 850
Longitudinal wave propagation velocity Cm / S) 1880 In contrast to this, the material of the
common diaphragm is polypropylene based synthesis The characteristics of the diaphragm made
of resin are as follows. ? Resonance sharpness (Q) 16.0 Young's modulus (N / fn2) 1.6 О 10
'density CWm' 900 Longitudinal wave propagation velocity (+ 71 / s) 1330 Furthermore,
polyethylene synthetic pulp is used as a binder and 20 M whiskers are reinforced The
characteristics of the free-edge type vibration plate (the one that has been heat and pressure
molded without being laminated as in the example) contained as a material is as follows. ?
Resonance sharpness (Q) 21 Young's modulus (N, 42)! ??????? Density OW'm ') 850
longitudinal wave propagation velocity (m / S) 2030 Comparing these, G) is slightly inferior
(high) in resonance sharpness Q, but all other points are improved In particular, the Young's
modulus is more than doubled, and a reinforced diaphragm is formed, and the longitudinal wave
propagation velocity (-y 79 '* / If) is also greatly improved. In contrast to these ? ? ?, the
diaphragm according to the present invention, as shown by the characteristics of ?, has a
Young's modulus slightly lower than that of ?, but is much larger than that of ?, and the
resonance sharpness Q is ? ? It has dropped sharply against That is, it shows an ideal
characteristic as a diaphragm having high rigidity and appropriate internal loss. The decrease in
Q is considered to be due to the action of both the polypropylene film as the damping material
film (2) and the non-woven fabric as the fibrous sheet (3). Next, FIG. 5 shows the case where the
laminate type diaphragm 1 of the embodiment shown in FIG. 4 and the conventional diaphragm
(free-edge POM whisker reinforced diaphragm) of the above-mentioned first example are used
for a dynamic speaker of 8 crn aperture. The solid line represents the diaphragm of ? and the
dotted line represents the diaphragm of ?.
As can be seen from FIG. 5, the diaphragm of (1) exhibits substantially uniform frequency
characteristics with less peaks and valleys as compared to (2). Therefore, the sound quality is
also a straight sound with little distortion. In each of the above-described embodiments, at the
time of heat compression molding, the edge portion (7) may be molded and an outer peripheral
ring (such as metal or paper) for fixing the diaphragm may be attached to the outer periphery
thereof. Further, as the damping material sheet to be laminated, thermoplastic resins such as
polypropylene film outer cover, EVA (ethylene vinyl acetate copolymer) and soft vinyl chloride as
described above can be used. Moreover, as a binder for making a diaphragm contain short fiber
reinforcements, such as POM whisker, carbon fiber, and glass fiber, thermoplastic resins, such as
polypropylene, EEA, and EVA, can be used. Effects of the Invention As described above, since the
fibrous sheet material and the damping material film are laminated and bonded to the diaphragm
substrate containing the short fiber reinforcement, the vibration having high rigidity and
appropriate internal loss is obtained. You can get a board. In addition, since the edge portion is
formed when the laminate is heat-formed, the manufacturing process can be simplified and the
cost can be reduced, and the vibration portion and the edge portion are continuously connected
with the same material. In addition to obtaining vibration characteristics with little distortion, an
edge portion excellent in vibration resistance and durability can be obtained.
Brief description of the drawings
FIG. 1 is a longitudinal sectional view showing an example of a method of manufacturing a
composite diaphragm according to the present invention, FIG. 2 is a longitudinal sectional view of
the manufactured diaphragm, and FIGS. 6 and 4 show other embodiments. FIG. 5 is a graph
showing the output sound pressure characteristics of the diaphragm of the present invention and
the conventional diaphragm as in FIG.
In the reference numerals used in the drawings, (1)...... Film (3) иииииииииииииииииииииииииииииииии Diaphragm part
(7) ииииии иииииииииииииииииииииииииииии. Agent Tsutomu Tsukuki Yoshio Tokushi I Sugiura Toshiki
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