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TECHNICAL FIELD The present invention relates to an imaging plate for a speaker, which is made
of a fiber reinforced plastic (FRP) using a triaxial woven fabric as a so-called reinforcing material.
2. Description of the Related Art An imaging plate for a speaker made of FRP is well known. For
example, Japanese Patent Publication No. 59-47520 discloses cone vibration made by
reinforcing a resin with a so-called biaxial fabric, which is very common as a woven fabric, using
two pairs of mutually orthogonal carbon fiber yarns as a woven yarn. The board is described.
However, since this conventional diaphragm uses a biaxial fabric, the arrangement of the yarn is
not symmetrical with respect to the axis of the cone, and the yarn has two directions of
generatrix and circumferential direction of the cone. Since the portions extending in the direction
and the portions extending at ± 45 ° offset from each other exist alternately, the change in
elastic modulus in the circumferential direction of the cone is large, and in general, it is bellshaped There is a problem that a resonant vibration mode called vibration tends to appear and
distortion of sound is large. On the other hand, Japanese Patent Application Laid-Open No. 6149592 discloses an FRP cone-shaped diaphragm in which a resin is reinforced with a spiral
weave made of carbon fiber yarn. Thus, in the case of the spiral weave, the yarns extend in two
directions, circumferential and radial, and the arrangement of the yarns is symmetrical with
respect to the axis of the cone. Does not happen. However, on the other hand, there are problems
as described below. That is, since the yarn in the radial direction is radial as described above, the
yarn density is so dense on the inside (neck side) of the diaphragm and coarse on the outside
(edge side). Therefore, the difference in elastic modulus in the generatrix direction of the cone is
very large. For example, in the case of a diaphragm having an inner diameter of 3 cm and an
outer diameter of 15 cm, the outer portion is approximately 50% by volume, which is a very
common value for FRP, in terms of volume fraction of carbon fiber In this case, the volume is
about 10% by volume, and the elastic modulus is reduced in proportion thereto. On the other
hand, if the outer portion is about 50% by volume, adjacent yarns in the inner portion become so
dense that they overlap with each other, and even forming becomes difficult. Even if it can be
molded, the thickness is increased at the inner portion, and the weight of the diaphragm is
increased to lower the efficiency. Such a problem naturally becomes noticeable as the difference
between the inner diameter and the outer diameter increases as the diameter increases.
SUMMARY OF THE INVENTION The object of the present invention is to solve the abovementioned problems of the conventional diaphragm, and it has excellent non-uniform
distribution of yarn, and hence less variation of elastic modulus, less distortion of sound, and
excellent acoustic characteristics. To provide a diaphragm for a speaker.
Means for Solving the Problems In order to achieve the above-mentioned object, the present
invention reinforces a resin with 3 #A fabric in which three sets of reinforcing fiber yarns
crossing each other form one weave yarn and have no seam. It features a speaker diaphragm
made of fiber-reinforced plastic. The diaphragm of the present invention may be marketed in
various shapes such as a cone shape and a dome shape. More specifically, according to the
present invention, as a so-called reinforcing material of a resin, a triaxial woven fabric in which
three sets of intersecting reinforcing fiber yarns are used as yarns and which has no seam
[triaxial fabric] (Also called (Doweave)) is used. The reinforcing fiber yarn is composed of
multifilaments of high strength and high elastic modulus fibers such as carbon fibers, crow
fibers, polyaramid fibers, and alumina fibers. Although depending on the kind of m fiber, the
single yarn diameter is about 4 to 40 #m, preferably about 4 to 20 μm, and the number of
single yarns is about 500 to 6000, preferably about 500 to 3000. Usually, the same fineness and
the same thickness are used for three sets of yarns. However, reinforcing fiber yarns have
advantages such as facilitating balance between elastic modulus and internal loss when different
reinforcing fibers such as carbon fibers and polyaramid fibers are used in combination. A triaxial
woven fabric having such a reinforcing fiber yarn as a yarn is, as shown by reference numeral 4
in FIG. 2, three pairs (three) of yarns 1 (long), 2 (weft), 3 (long) Are such that they are organized
plainly while crossing each other at an angle of 60 '. Of course, the crossing angle of the yarn
does not necessarily have to be 60 '. That is, although it is preferable to be 60 ° in the case of a
cone-like or dome-like imaging plate, it is different as 50 ′, 50 ′, 80 ′ in the case of an
elliptical cone shape or a semielliptical sphere. Is preferred. In that case, the portion 80 'is used
in the minor axis direction. 3! The third woven fabric 4 also has, as shown in FIG. 3, yarns
(warp> 18.1b, yarns (weft> 28.2b, and yarns (warp)) 3a, 3b extending in the same direction. And
may be organized as a pair. The three-axis woven fabric as shown in FIGS. 2 and 3 and the
method for producing the same are described, for example, in "Overseas Textile Technology
Literature Bundle", Vol. 23, No. 11 (November 1973, Japan 7 Textile Machinery Society) And in
U.S. Pat. No. 3.446.251. The above-mentioned triaxial woven fabric may have a crimp rate of 10%
or less, preferably 5% or less.
Here, the chestnut] / the customer C (%) is a formula, C-[(L-Lo) / Lo] x 100, where L; the length of
the woven yarn which is straightened and measured without crimp o: Given the length of the
woven yarn measured in the crimped state, if the crimp rate is 10% or less, the stress
concentration in the bent portion of the woven yarn will be small, and the decrease in elastic
modulus will be small Become. The resin forming the so-called matrix of the diaphragm is
thermosetting resin such as epoxy resin, unsaturated polyester resin, polyimide resin, phenol
resin, polyamide resin, polybutylene terephthalate resin, polyether ether ketone resin,
polypropylene And thermoplastic resins such as poly-4-methylpentene-1 resin. The use of the
thermosetting resin mixed with 10 to 20% by weight of a flexibility imparting agent such as
polyethylene glycol, polypropylene glycol, polysulfide or the like improves the vibration damping
property. In addition, when 20 to 200% by weight of polyisobutylene resin is mixed in poly-4methylpentene-1 resin, not only the vibration damping property but also the specific elastic
modulus of the diaphragm is improved. The diaphragm of this invention usually has only one 3f
111! If materials are used, but two or more triaxial woven fabrics are used in such a manner that
the directions of the yarns of adjacent triaxial woven fabrics are slightly deviated, quasi-isotropy
is further improved. Moreover, it is also possible to superimpose and use the three-axis fabric
mentioned above, and a normal biaxial fabric, a mat, etc. The diaphragm of the present invention
can be molded using a known molding method or the like. That is, for example, the 3eX
described above! A: A prepreg made of a fabric impregnated with a thermosetting resin is placed
on a female mold having a desired cone shape, a male mold is placed on the surface of the
prepreg, and molding is performed by pressing and heating to cure the resin. Can. Also, instead
of using a prepreg, so-called raw 3 not impregnated with a thermosetting resin! The Tl 1 l fabric
may be placed on a female mold and prepregged by applying a thermosetting resin containing a
curing agent. When the resin is a thermoplastic resin, the prepreg can be stamped and formed
into a diaphragm. The same is true for other shapes such as a dome shape. The embodiment
shows a cone-shaped diaphragm, which is made of FRP formed by reinforcing the resin 5 with
the triaxial fabric 4 shown in FIG. The diaphragm of this embodiment has a cross angle of 60 'for
each of the three sets of yarns of the 3EIIl fabric used, so that a rotation of 60 DEG around the
cone axis gives the same yarn arrangement.
That is, it has 60 'rotational symmetry. By the way, since only the 90 'rotational symmetry can be
obtained with a conventional diaphragm using a two-ply woven fabric, the diaphragm of this
embodiment i is improved in pseudoisotropy, and the difference in elastic modulus in height in
the circumferential direction The lower it becomes, the less likely it is to produce a bell-shaped
vibration. In addition, even if it occurs, the characteristic frequency increases by that much
because it becomes from 60 degrees of 4 rotation symmetry to 60 degrees of 6 rotation
symmetry, and it becomes less of a problem in terms of characteristics as a shooting plate for
speakers . According to the present invention, since the noise plate uses three sets of intersecting
reinforcing fiber yarns as yarns as a so-called reinforcing material of resin, and a 3 @ lI fabric
having no seam, As compared with the conventional two-axis woven fabric, the unevenness of the
yarn distribution in the circumferential direction such as a cone and the like, the unevenness of
the elastic modulus becomes very small, and the bell-shaped vibration hardly occurs to reduce
the distortion of the sound. Since the unevenness of the yarn distribution is reduced, the shape
distortion is also reduced. It also makes it possible to prevent the loss of efficiency due to the
increase in weight, which is a drawback of using helical fabrics.
Brief description of the drawings
FIG. 1 is a schematic plan view showing an imaging plate for a speaker according to one
embodiment of the invention, and FIGS. 2 and 3 are schematic planes showing three-axis woven
fabrics of different modes used in the invention. FIG.
1.1a, 1b: woven yarn 2.2a, 2b: woven yarn 3.3a, 3b: woven yarn 4: triaxial woven fabric 5: resin
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