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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
movable magnet type speaker, and in particular, by using a magnet having a high maximum
magnetic energy product and a low density and a low inertia, it is uniform over a wide frequency
range. The present invention relates to a highly efficient movable magnet type speaker capable of
reproduction. [Prior Art] A speaker which is an electroacoustic transducer is classified into a
movable ring type speaker and a movable magnet type speaker from the configuration thereof.
And in the past, most of the former was for reducing inertia as much as possible to improve
fidelity. Therefore, the latter speaker has also been technically studied from old times. For
example, in Japanese Utility Model Publication No. 10-288, the upper and lower portions of the
conduit are loosely fitted to the magnetic pole end of the magnet, and the vibration magnet is
provided in the central portion. The speaker is described. Also known is a movable magnet type
speaker supported so that pole pieces including magnets and pole pieces having different
polarities are movable as releasably offset centering on the equilibrium position of the stator
core. The purpose is to obtain a powerful voice output with a simple configuration (see Japanese
Patent Publication No. 40-20121). Furthermore, there is also known a movable magnet type
speaker disposed so as to be able to vibrate around the core and having magnetic poles of
different poles at the axial end (see Japanese Patent Publication No. 59-2239). In order to
achieve high output, the number of coil turns is increased by making bankruptcy of Also, based
on the same technical idea, one having three magnetic poles in the axial direction is known (see
Japanese Patent Publication No. 59-2240). This is also intended to compensate for the lack of
driving force of the magnet by increasing the number of coil turns. Although the movable magnet
is described as being integrally provided with the cone in these two inventions, it is not
specifically disclosed, and it can be understood as bonding by a known adhesive. [The problem to
be solved by the invention] The above-mentioned movable magnet type speaker is limited to the
rare earth / cobalt magnet even if the magnet is the strongest, and the mass is limited due to the
restriction of inertia reduction, so that the driving force is insufficient. In order to compensate for
this, it has been devised to increase the number of turns of the coil. As a result, the inductance
increases, and particularly at high frequencies, as a result of the significant increase, the
attenuation is particularly remarkable for the high frequency component of the audio current,
and the fidelity and linearity are inferior. In addition, the magnet itself can not be downsized in
order to secure the driving force, and the inertial force is large and it is difficult to faithfully
reproduce the voice. Furthermore, the magnet and the diaphragm are manufactured separately
and bonded by an adhesive, but require a relatively difficult bonding process of quality control
and automation, and their connection parts are driven together with the cone In this case, the
constant vibration of the cone sometimes leads to distortion of the cone and further to breakage
This is because the material of the cone is usually paper. Therefore, an object of the present
invention is to provide a highly efficient movable magnet type speaker capable of faithfully
reproducing sound in a wide frequency range without increasing the number of windings. Means
for Solving the C Problem] The present invention comprises a coil for passing an audio current, a
yoke serving as a path of magnetic flux generated by the coil, and a movable magnet to which a
diaphragm is coupled, and is generated by the audio current. In the movable magnet type
speaker which vibrates the diaphragm and converts it into sound by repulsive attraction between
the magnetic flux and the movable magnet, the movable magnet is an R-Fe-B based permanent
magnet (wherein R is a rare earth element including Y) Or a combination of Fe, Fe, Fe, Fe, and Fe,
and a part thereof may be replaced with a transition metal other than Fe or another metallic or
nonmetallic element, and B is boron) It is a magnet type speaker. In the present invention, the
movable magnet is an R-Fe-B system, preferably having a thickness of 21) or less and a density of
7.4 g / cc or less, and the maximum magnetic energy product (BH) max of 7 MGOeO It is
suitable. The reason is that when the thickness exceeds 2 dragons, the magnetic driving force is
insufficient for the increase in mass. This is because as the thickness becomes thicker (the
relative proportion of portions contributing to the magnetization decreases. In addition, the air
resistance at the time of driving also increases. A more preferable thickness is 1 + n or less, but
the R-Fe-B based magnet according to the present invention can not do this because of excellent
(BH) max and good processability. When the density exceeds 7.4 g / cc, the voice fidelity is
deteriorated because the inertia force is large and the responsiveness of the movable magnet is
deteriorated. A more preferred density is 6.5 g / cc or less. Maximum magnetic energy product
(Bll) max is the maximum product of the magnetic flux density (Bd) on the demagnetization curve
of the magnet and the strength of the demagnetizing factor (Hd), and can be effectively used
externally It is the magnetic energy per unit volume of the magnet and is an indicator of the
performance of the permanent magnet. Therefore, the larger the (BH) wax, the larger the
magnetic flux density (Φ) of the air gap when the speaker magnetic circuit is assembled, and as a
result, the efficiency as a speaker is improved in proportion to Φ2. For the relationship between
Φ and the speaker efficiency, refer to Tricraps Technical Document No. 58, pp. 9.5 to 9.9 °
published by Trikraps Inc., for example. In the present invention, in the case of using a so-called
bonded magnet, (BH) max can be used from about 7 MGOe because tffi is light.
On the other hand, when using a so-called sintered magnet, the density is high and the mass
inevitably increases, so 25 MGOe or more is required, and preferably 30 MGOe or more. The RFe-B based magnet is an excellent magnet that can meet this requirement. The method for
producing a movable magnet according to the present invention comprises a method of
obtaining a sintered body by powder metallurgy, a method of solidifying flakes, powder and the
like obtained by melt polymerization with a nonmagnetic binder material [abbreviated below as
rRQIJ . ). A method (hereinafter referred to as rRQIIJ) of densifying and solidifying flakes,
powders, etc. obtained by the melt quenching method using a hot press (hereinafter referred to
as rRQIIJ), flakes obtained in the melt quenching method, powders, etc. A method of imparting
magnetic anisotropy by high temperature processing after solidification [hereinafter referred to
as (RQ *)]. Further, after solidifying RQI [[, the magnetic anisotropic magnetic powder is obtained
by regrinding, and then it becomes a so-called pound magnet by compression or injection
molding together with a binder in a radial anisotropy, (multi) pole, anisotropic magnetic field
Method [hereinafter referred to as rRQnBJ. Etc.) can be according to various manufacturing
methods. In particular, RQI [[B is suitable for the production of thin-walled cylindrical (ring)
magnets and fully meets the requirements of the present invention. The shape of the movable
magnet according to the present invention may be any shape such as a ring (cylindrical), a
polygon, a flat plate, a block, etc., and the magnetization pattern thereof is a radial (radial)
anisotropy, a polar difference It is possible to select according to the application, such as
anisotropy (multipolar magnetization anisotropy), through bipolar, axial anisotropy, and the like.
Moreover, it is not necessary to be anisotropic, and it is also possible to use an isotropic magnet
in a small speaker. In addition, it is essential that the ring-shaped movable magnet according to
the present invention be coupled to the diaphragm in the function as a speaker. Therefore,
although it is possible to bond conventionally with an adhesive such as epoxy resin, in the
present invention, especially in the case of RQI or RQI [IB in the case of IB, it can be
simultaneously compression-molded and injection-molded. By utilizing the technology, it is also
possible to integrally bond with an adhesive or the like, and thereby it is possible to expect
effects such as process reduction and reliability improvement. That is, as the adhesive control
conditions are well known, care must be taken, and particularly in the case of a two-component
adhesive, adhesion failure may occur due to a defect in the compounding ratio or the like, leading
to a peeling accident during use There was also. In addition, due to the streaks and the like at the
time of bonding, distortion is added to the diaphragm of the speaker, which hinders faithful
reproduction of sound.
The diaphragm in the present invention may be any of a cone, a horn and a flat plate. Although
the material is usually plain paper, it has a high specific modulus A1. BN or the like can also be
used, and LCP which is an engineering plastic whose elastic modulus is improved as the
thickness becomes thinner can also be used. In particular, Af, BN and the like, and LCP and the
like having good heat resistance are suitable for integral molding in RQI and RQIIIB of the
present invention. The material of the movable magnet is preferably R-Fe-B. This is because it is
possible to meet the requirements of a wall thickness of 鰭 or less and a density of 6 g / cc or
less. Here, R is at least one of rare earth elements including Y (at least one may be a combination
of two or more. R preferably contains 8 to 30 atomic percent. If the content is less than 8
atomic%, the crystal structure has much cubic structure identical to that of α-iron, so that the
magnetic properties, particularly the coercivity, can not be obtained. On the other hand, if it
exceeds 30 atomic%, the R-rich (enriched, concentrated) nonmagnetic phase increases and the
residual magnetic flux density (Br) also decreases, and a permanent magnet obtained can not be
obtained. The boron (B) is preferably in the range of 2 to 28 atomic percent. If it is less than 2
atomic%, it becomes a rhombohedral structure and high coercivity can not be obtained. If it
exceeds 28 atomic%, B-rich nonmagnetic phase increases and residual magnetic flux density (Br)
decreases. It is because it can not be obtained. The content of Fe is preferably 42 to 90 at%. If it
is less than 42 atomic%, Br is lowered, and if it exceeds 90 atomic%, high coercivity can not be
obtained. In addition, various additive elements Co in the R-Fe-8 basic system. By adding AI, Nb,
W, Ge, Cr, Mo + Zr, Hf, etc., the coercivity can be further improved. Hereinafter, a movable
magnet type loudspeaker according to the present invention will be described in detail by way of
examples. EXAMPLES Example 1 Production of Movable Magnet Assembly An Nd 1s F 8 t J 7 Ga
1 alloy was prepared by arc melting, and a molten metal was prepared in the form of flakes by
the single roll method in an Ar atmosphere. The roll obtained at a roll peripheral speed of 30 m /
see was amorphous with a thickness of about 30 μm. The flakes were roughly pulverized to a
size of 32 mesh or less and molded into a molded body by molding. The molding pressure was 6
ton / cal, and no magnetic field was applied. The density of the molded body was 5.8 g / cc. The
resulting compact was hot pressed at The temperature of the hot press is 700 ° C.
and the pressure is 2 ton / aJ. The density obtained by the hot press is 7.30 g / cc. The bulk body
thus densified was further processed at 700 ° C.
The height of the sample was adjusted so that the compression ratio was 3 before and after the
swaging process (h0 / h = 3, where h is the height before swaging and h is the height after
swaging). The swaged sample was heated to 750 ° C. in an Ar atmosphere and held for 60
minutes, and then water-cooled (cooling rate: 7 ° C./5 ec). This heat treatment initially improved
the llc to 4.8 koe to 13.0 kOe. The heat-treated sample was roughly crushed and adjusted to a
particle size range of 250 to 500 μm to obtain magnetic powder. This magnetic powder is mixed
with an epoxy resin of 16% and 01% in a dry state, and molded in a magnetic field with an outer
diameter of φ20, an inner diameter of φ19, a height of 7 (unit capacity) and a magnetic field
applied in the radial direction. At this time, a diaphragm made of LCP, which is a heat-resistant
engineering plastic and recently noted as a speaker diaphragm, is integrated by insert molding.
Thereafter, a thermosetting treatment was carried out at 120 ° C. for 3 hours to obtain a
movable magnet assembly (one in which the magnet and the diaphragm are integrated). Example
2 The movable magnet assembly obtained in Example 1 was incorporated into the speaker
shown in FIG. The aperture of the speaker is 160 cranes. The voice current flows through the coil
to make the yoke a magnetic flux path, and the repulsive absorption of the magnetic flux in the
air gap and the ring-like movable magnet causes the movable magnet to move, thereby vibrating
the diaphragm and converting it into voice. (Comparative Example 1) is a rare earth cobalt
magnet having a composition in which Cn is 26.5%, CO is 59.5%, Sa + is 8.0%, Fe is 5.0%, Zr is 0%
by weight, A magnet having the same size as the magnet of Example 1) was produced. Here, it
was difficult to directly obtain one having a thickness of 0.5 H, so one having an outer diameter
of φ22 and an inner diameter of φ19 was prepared in advance, and the outer diameter was
made to be φ20 by outer periphery grinding. At this time, the yield was 43% because grinding
was difficult. Furthermore, in this case, the process is laborious because it is necessary to bond
the diaphragm with a two-component epoxy resin. The sample obtained as described above was
incorporated into the magnetic circuit shown in FIG. Compared to the conventional
electrodynamic type speaker, it became about 1/3 size. That is, the size of the diaphragm is made
the same as in Example 1 and the power necessary to drive it is calculated, and an
electrodynamic speaker produced by a well-known design means is taken as FIG. 3 (comparative
example 2) Shown in. Next, the present invention will be described in detail. When an audio
current is not applied to the coil 1, no magnetic flux is generated in the gap of the core 2, and the
movable magnet 3 is not moved since the movable magnet is supported by the damper (not
shown). There is no displacement at all.
Now, when a voice current is applied to the coil 1 to excite it, an AC magnetic flux corresponding
to it is generated in the gap, and the movable magnet 3 is laterally displaced due to repulsive
attraction. As displacement of the movable magnet is caused, sound waves are emitted from the
diaphragm because the diaphragms coupled together are also vibrated integrally. Next, the
acoustic characteristics of the speakers produced in (Example 2) and (Comparative Examples 1
and 2) were measured. FIG. 4 shows the output sound pressure frequency characteristics.
According to the present invention, it can be seen that the effective frequency band is
significantly broadened, and the improvement particularly in the high range is remarkable.
Figure 5 shows the frequency characteristics of the harmonic distortion rate. According to the
invention it can be seen that the improvement is particularly pronounced in the upper range. FIG.
6 shows the frequency characteristics of the electrical impedance. According to the present
invention, it is understood that the bass resonance frequency is also significantly improved to the
low temperature side. (Third Embodiment) FIG. 7 shows another embodiment of the present
invention. A solenoidal coil 1 faces the ring-shaped movable magnet 3 via a gap. In addition, the
modification which provides a solenoid inside a ring-shaped magnet is also considered. FIG. 8
shows another embodiment of the present invention. This is a modification in the case of FIG. 7,
in which a center ball is provided on the yoke 2 to increase the driving force of the movable
magnet. FIG. 9 shows a flat movable magnet. The coil 1 may be an ordinary Ii electric wire or a
disk-shaped coil. Moreover, it is also possible to change flat form into a block form. According to
the present invention, since sufficient driving force is provided by the thin-walled magnet, it is
not necessary to increase the number of windings as in the prior art, and as a result, the acoustic
characteristic as a speaker is significantly improved without increasing the inductance. It is
possible to obtain a speaker with excellent fidelity and linearity over a wide frequency range.
Brief description of the drawings
FIG. 1 is a cross-sectional view showing an embodiment of a loudspeaker according to the
present invention, FIG. 2 is a diagram showing an embodiment of a movable magnet assembly,
and FIG. 3 is a cross-sectional view of a conventional electrodynamic loudspeaker. Are graphs
showing the output sound pressure frequency characteristics of the present invention and the
comparative example, FIG. 5 is a graph showing the frequency characteristics of the harmonic
distortion rate, and FIG. 6 are the same (a graph showing the frequency characteristics of
electrical impedance, FIG. 7 9 to show another embodiment of the present invention.
Fig.1 Fig.2 Fig.3 Fig.5 Frequency (Hz) Fig.6 Fig.7 jIs Fig.9 Fig.9 Procedure 正) 1 doo
(spontaneous) Showa q β, 10 over
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