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JPS5717300

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DESCRIPTION JPS5717300
Description or title of the invention
Vibrating plate of electrodynamic electroacoustic transducer
8. Detailed description of the invention The present invention relates to a diaphragm of an
electrodynamic electroacoustic transducer, and a harmonic by using a fiber reinforced metal
composite material having a large Young's modulus, sound velocity, and heat resistance to a
diaphragm of a speaker. The distortion is suppressed and the bending resonance frequency is
increased fQ'rEndPage: 1 to widen the piston operation range, yet provide a vibration plate which
is also strong against the thermal influence from the voice coil, and in particular, considering the
fiber direction An object of the present invention is to provide a diaphragm that suppresses nonaxisymmetric vibration. In general, what is of fundamental importance to the diaphragm of the
electroacoustic transducer is that the frequency range over which the diaphragm operates as a
rigid piston is as large as possible. For example, it is known that the resonance which regulates
the operating frequency range of the conical shell diaphragm 1 shown in FIG. 1 includes
resonance due to distortion and resonance due to bending, and bending resonance occurs at a
lower frequency. . Therefore, it is preferable to use as the material of the diaphragm 1 the value
of the frequency at which bending resonance occurs as much as possible, and the diaphragm is
regarded as a good rigid piston at frequencies below the bending resonance frequency. Here,
assuming that the bending resonance frequency is / bra, where fbtu subscript h--banding
(bending) (3) r · · · resonance (resonance) ··· resonance order or right side · · · · Order of resonance
h: in FIG. 1, thickness C of the diaphragm 1 longitudinal wave propagation velocity (sound
velocity) where C = Jyp (2) L: in FIG. 1, the diaphragm The radial resonance length of 1) and the
bending resonance frequency of 1 range in which the diaphragm 1 can be used as a rigid body
piston are considered to be the case of n = 1, so this frequency is set to / brl. As the material of
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the diaphragm of the conventional electric sound 1wl converter, various materials have been put
to practical use taking advantage of their respective merits such as paper, metal, metal foam,
plastic, or a combination thereof. Above all, although the diaphragm of paper has a long history
and is a stone with appropriate rigidity and loss, there are problems with the characteristic
variation, the performance variation due to humidity, etc. And the Young's modulus is 2
compared to metal 4) If the vibrational frequency is small because the harmonic distortion is
suppressed and the sound speed C is smaller than in the above equation (21, the resonance
frequency fbr1 is also smaller than the equation (1), and the frequency range in which the
diaphragm 1 operates as a rigid piston is sufficiently wide. Was difficult to say. Also, aluminum
(A1) or nickel (Ni) is used as the diaphragm of the metal, and in this material, the sound velocity
C is as large as about 5-7 seconds (the / brI value of the equation 11 becomes large, which is
convenient. Conversely, because the density が is large, the thickness h (= W / ρ) in the above
equation (1) is smaller than the diaphragm 1 with the same surface density W, ie, the value / br1
is reduced to 1 It also has the opposite effect, and it is also difficult to say that the piston
operating area is sufficiently wide.
Also, as the diaphragm 1 made of plastic, there are styrene, polyester, etc., but the C (sound
velocity) is as small as about 1.8 V second, and the value of / brl is smaller than the formula (1)
and the problem is likewise insufficient. was there. Also, in general, the actual diaphragm has
resonance due to non-axisymmetric vibration in addition to the above-mentioned bending
resonance and elongation resonance, and (5) this resonance is not distributed in sound pressure
frequency characteristics but it appears From oil resonance frequency / brl ll '' 1. It is known that
it originates from a small frequency of stone and greatly impairs the auditory characteristics.
Therefore, it is necessary to increase the frequency at which the resonance due to the nonaxisymmetric vibration starts to occur, and the following method is conventionally used. That is,
in the conventional diaphragm, as shown in FIG. 2, the corrugation 2 having a depth of, for
example, 5 times the thickness of the plate is sculpted in the circumferential direction to increase
the circumferential rigidity. Thus, although the resonance frequency value of the nonaxisymmetric vibration is increased to obtain a good reproduced sound, according to this, there is
a problem that it is more difficult to attach the corrugation while the processing man-hour
increases accordingly. . Therefore, according to the present invention, as a material of the
diaphragm 1, firstly, the Young's modulus is large for harmonic distortion suppression, and the
speed of sound C (= Vρ) and the thickness A (==) for the increase of bending resonance
frequency / br1. A material in which W / ρ) is large, that is, the Young's modulus E is also large,
and the density ρ is small, and a directional rigid material (t) is used to suppress nonaxisymmetric vibration in the packing box 2 EndPage: A material having two properties is
provided to solve the problems of the above-described conventional examples, and each
embodiment will be described below with reference to the drawings. Recently, technology for
producing boron fiber, carbon fiber and silicon carbide fiber has been developed, and in
combination with the remarkable development of surface treatment technology such as wet
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plating, dry plating and thermal spraying, fiber reinforces metal strength. Composite materials, ie,
fiber reinforced metal composites (II'1 barfuinforcadMgtal, abbreviated as FRM), are going to
enter into production phase from research stage, and the present invention is the material of
diaphragm 1 and this fiber reinforced metal composite material Use the call). Until now, FRM has
focused its research on "materials whose strength does not decrease even at high temperatures",
and there is nothing to discuss whether it can be used as a diaphragm of an electrodynamic
electroacoustic transducer. The following table compares the constants of paper, metal, plastic,
and non-practical FRM currently put into practical use as a diaphragm. Regarding sound velocity
data in the table below, the sound velocity of paper, metal and plastic (7) is known because it is
currently used as a diaphragm, but the sound velocity of FRM has not been released yet and was
calculated for the first time It is a thing.
Also, since the density of boron in the FRM in the table has not been published yet, it is estimated
based on the following equation (3) and shown with a tree in the table. That is, the density 88 of
the composite material is 1 + -v1, where ρ. ... Density of metal Af ... Density of boron fiber (=
2.62 x 10 '", 臂) V, ... Fiber volume content. Also, it is necessary to consider the upper limit
frequency / br1 at which the diaphragm made of various materials in the same table acts as a
rigid piston. In this case, / br1 of the diaphragm made of fbrl of various material diaphragms and
aluminum (A1) alone (Af) is compared with each other under the same condition as the following
equation. (8) where Wo: surface density of diaphragm (accumulation per potential area) ρ, C:
density of various materials, speed of sound ρ (A4), '(AJL)' density of aluminum, speed of sound
(9) Comparison Table of Diaphragm Material where B: boron fiber, 0: carbon fiber, 810: silicon
carbide fiber, Af: aluminum, M: magnesium, TI: Titanium, Ml ... (10) EndPage: 3 nickel, vf ... fiber
volume content, headquarters · · · Indicates the inventor's calculated estimated value. The speed
of sound determined from the above table, in the FRMO, is the slowest speed screen 810-A4, 6.2
′ ′ m /: sand, the speed of the highest B-Mg is io 91 m / sec. Single 5. The value of / br1 / fbrl
(Af) in the above-mentioned equation (4) must be at least 1 or more according to the above table,
and according to the above table, boron excluding B-TI is necessary according to the above table
Of the system, 0-AJ! That is, it can be seen that almost all of the FRMs are more effective than the
A1 single material material as the conical shell diaphragm material. In particular, the Young's
modulus of the boron thread FRM is 6 or more times the value of that of A1 alone, and distortion
in harmonics can be extremely effectively suppressed. The diaphragm may be a circular or
rectangular flat plate other than the above-mentioned conical shell shape, and a voice coil may be
attached to this to form a diaphragm of the electrodynamic electroacoustic transducer. It is
known (11) that the same as in the case of conical shell shape, and that it is proportional to c,
that is, C / ρ of the above equation (4). Therefore, it can be understood that the case where the
flat diaphragm is formed of the above-mentioned '[I'RM] is also effective as the conical shell PRM.
Also, it is known that in the FRM, the fibers have directionality, and the Young's modulus is
different between the fiber direction of the FRM and the orthogonal direction, and the Young's
modulus in the fiber direction is about 30 to 60% larger than that in the orthogonal direction. .
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Therefore, it is possible to prevent the resonance of non-axisymmetric vibration in the diaphragm
shown in FIGS. 3 to 5 by utilizing this property as described next. That is, the first vibrating plate
3 of FIG. 5 matches the arrangement direction of the fibers 4 in the circumferential direction of
the conical shell diaphragm 1 to increase the strength in the circumferential direction, whereby
the conventional diaphragm 1 of FIG. To suppress non-axisymmetric vibration in place of the
corrugation 20 function. Further, the rectangular flat diaphragm 5 of FIG. 4 has the arrangement
direction of the fibers 4 aligned with the long side direction to increase the rigidity in the long
side direction, and the elliptically carved flat vibration of FIG. The plate 6 has the arrangement
direction of the fibers i 14 aligned with the major axis direction to increase the rigidity in the
major axis direction (12). That is, each diaphragm 5. As in the case of a diaphragm with different
shapes of longitudinal and transverse lengths, like resonance, resonance always occurs from the
longer side (diameter), so the fiber direction, that is, the one with the higher Young's modulus is
the longer side (diameter) It is possible to increase the frequency at which the above resonance
occurs by matching it with the above. The above six diaphragms 3, 5. As a practical production
method of is, there is a general process of producing a so-called prepreg (prg 118 g; tape
obtained by arranging fibers in a single layer and bonding to metal foil for matrix), laminating
and diffusion bonding to produce FRM It may be stepped on, but if, for example, the fiber
directions of the prepregs are aligned in the same direction and laminated in the middle of the
process, unidirectional reinforced FRM is produced, or the fiber directions of the prepregs are
alternately laminated so that 90 different fiber directions You can freely change the direction like
the method of laminating while shifting the angle by a certain angle. That is, the rigidity of the
diaphragm 6, 5 ° can be selected at an arbitrary aspect ratio by changing the arrangement of
the prepreg and the lamination mode as required. In this respect, it is extremely suitable (15) to
use FFtM for the diaphragm 3.5.6. Also, recently, a diaphragm having a sand-inch structure has
been put into practical use by attaching an aluminum foil or the like to the front and back
surfaces of a plate of a foamed resin, but "1. In addition, since the performance is required that
the Young's modulus and the speed of sound are large, it is extremely effective to use the FRM as
the skin material of the above-mentioned diaphragm of the sand inch structure from the above.
On the other hand, a diaphragm for a speaker has been put into practical use, in which a resin
such as urethane, styrene, or acrylic is foamed in a cone having aluminum molded in a conical
shell shape and filled so that the acoustic radiation surface is flat. It is very effective to use a cone
of FRM instead of a cone of aluminum because the cone is also required to have a lightness, high
Young's modulus, and a high speed of sound.
Also, as can be seen from the fact that the diaphragm made of FRM has originally been
developed as a heat-resistant material, it has high heat resistance and good thermal conductivity,
so the voice coil is heated by a large input and the temperature of the diaphragm is (1A)
EndPage: Even if the temperature rises, the heat of the voice coil can be rapidly transmitted to
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the entire diaphragm without causing deterioration and can be dissipated efficiently. As
described above, according to the diaphragm of the electrokinetic electroacoustic transducer
according to the present invention, a composite material in which the strength of metal is
reinforced by fibers is used, that is, a fiber-reinforced modern composite material (FRM), Due to
the characteristics of 71 M unique to the Young's modulus and sound speed heat resistance, the
harmonic distortion of the diaphragm is suppressed and the bending resonance frequency is
increased to increase the frequency range in which the diaphragm operates as a rigid piston, and
the voice coil The performance of the imaging plate can be improved without deformation or
deterioration due to thermal effects, and (1) when the diaphragm has a conical shape, the fiber
direction is made to coincide with the circumferential direction, and the diaphragm is a flat plate.
In this case, the above fiber direction is made to coincide with the longitudinal direction of the
flat plate to increase the rigidity in the circumferential direction or the flat direction, respectively,
and the resonance frequency value due to nonaxisymmetric vibration is increased. The range of
operation without Hearing characteristics can be improved, and (1) when the above-mentioned
FRM is stuck as a surface material of a foamed resin plate to form a (15) diaphragm of a sandinch structure, and (1) a conical shell shape formed by the above-mentioned FRM The present
invention is also extremely effective in the case of forming a diaphragm formed by foaming and
filling a resin inside a cone, respectively, and has features such as improving the performance of
the diaphragm.
4. Brief description of the drawings FIGS. 1 and 2 are longitudinal sectional views of a general
example and another example of a diaphragm of an electrodynamic electroacoustic transducer,
and FIG. FIG. 4 is a side view of an embodiment of the diaphragm of the sound transducer, and
FIG. 4 and FIG. 5 are front views of other embodiments of the diaphragm. 1.5, 5.6 ... diaphragm,
1a ... conical surface, 2 ... corrugation, 4 ... fiber. (16)CつEndPage: 5
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