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JP2000341794

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2000341794
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sealed box type direct radiation flat loudspeaker in which the magnetostrictive element of a
magnetostrictive speaker driver is vibrated to produce a direct sound to improve the sound
pressure and reduce the thickness of the entire speaker.
[0002]
2. Description of the Related Art FIG. 7 is a longitudinal sectional view showing an example of a
conventional closed box type planar speaker. The closed box type planar speaker 1 shown in the
same figure drives a flat diaphragm 2 from the back side by a voice coil type speaker driver 3.
The speaker driver 3 comprises a voice coil 5 one end of which is bonded to the center of the
back surface of the diaphragm 2 via the piston plate 4 and a columnar magnet 6 coaxially
disposed on the other end side of the voice coil 5. Be done. The columnar magnet 6 is
accommodated in a flanged bottomed cylindrical yoke 7, and a ring-shaped gasket is mounted on
the frame 9 assembled to the peripheral portion of the plate-like back plate 8 holding the
cylindrical portion of the yoke 7. The peripheral portion of the diaphragm 2 is fixed via 9a. The
voice coil 5 is connected to the ridge of the yoke 7 by a damper 10 whose one end is connected
to the side surface thereof. In the conventional speaker driver 3, when a voice current is supplied
to the voice coil 5 in the magnetic field formed by the columnar magnet 6 to excite the voice
current, the force of the framing generated in the voice coil 5 causes the piston plate 4 to move
forward and backward. In order to drive, the diaphragm 2 vibrates to generate a sound pressure.
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[0003]
However, since the diaphragm drive capability of the speaker driver 3 is proportional to the
number of turns of the voice coil 5, the sound pressure required for practical use is sufficient for
the above-mentioned conventional closed box type planar speaker 1 In order to ensure the
above, the voice coil 5 or the columnar magnet 6 also needs to have a shaft length of a certain
extent or more, and therefore, there is a problem that there is a certain limit to thinning in the
vibration direction. . Further, in the closed box type direct emission flat speaker 1, when it is
miniaturized, the air compliance between the back plate 8 and the diaphragm 2 is reduced as the
volume in the speaker is reduced, and therefore low. The area limit reproduction frequency has
risen, and as the reproduction band is narrowed, there is a problem such that the sound
reproduction with high quality can not be expected.
[0004]
On the other hand, it has been a long time since the appearance of speakers of electrostatic type
or the like which drives the diaphragm without using the voice coil 5 or the like, and speaker
drivers using various materials have been put to practical use. For example, an electrostrictive
material that deforms upon application of a voltage such as barium titanate porcelain generally
functions as a "piezoelectric substance" because it apparently functions in the same way as a
piezoelectric substance (PZT) such as Rochelle salt. However, it is known that such a piezoelectric
substance changes its piezoelectric effect depending on the direction of the applied electric field.
In addition, while Rochelle salt exhibits the piezoelectric transverse effect that deforms most in
the direction perpendicular to the direction of the electric field, quartz and barium titanate
exhibit the piezoelectric longitudinal effect that deforms most in the same direction as the
direction of the electric field. . However, for example, an electrostrictive speaker driver using
barium titanate ceramic formed by sintering powdered barium titanate is used exclusively as a
high-pitched speaker (tweeter) because the resonance frequency of the vibrator is relatively high.
The current situation is that it can not be expected to be used as a low frequency transducer.
[0005]
On the other hand, some ferromagnetic materials such as single metals such as Ni and Co, Fe-Al
alloys or ferrites exhibit a magnetostriction phenomenon in which the dimensions of the element
change in response to an external magnetic field. It is known that the magnetic (magnetization)
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characteristics of the element change due to twisting and torsional stress (torque) when the
characteristics change or when orthogonal magnetic fields are simultaneously applied. Since a
magnetostrictive element obtained by processing this type of magnetostrictive material into a
specific shape can be used for a speaker driver, development of an element having a large stress
or stress distortion generated in response to an applied magnetic field is urgently required. In
fact, magnetic materials having a Laves-type crystal structure consisting of rare earth-transition
metals exhibit 50 to 100 times the displacement of conventional ferromagnetic materials, and
even 2 to 2 times the size of piezoelectric materials (PZT). It has been found that three times the
generated stress can be obtained. Among magnetostrictive devices represented by (Tb0.3Dy0.7)
Fe2 which is one of such magnetic materials, a device exhibiting a magnetostrictive deformation
whose displacement amount exceeds 1000 ppm has been discovered, and in order to distinguish
it from a normal magnetostrictive device, It may be called a magnetostrictive element or the like.
However, even with such a giant magnetostrictive element, there are hardly any ones that can
obtain practical sound pressure at present, and practical use of a speaker incorporating a
magnetostrictive speaker driver has been considered as a future issue.
[0006]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems,
and it is an object of the present invention to vibrate a magnetostrictive element of a
magnetostrictive speaker driver for direct sound generation to improve the sound pressure and
to thin the entire speaker.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
according to claim 1 is a square box-shaped speaker casing having a front opening, and the side
edge not being restrained and the side edge being terminated. Flat plate-like magnetostrictive
element which is fixed to the speaker housing and disposed in the front opening of the speaker
housing, receives an external magnetic field, and is magnetostrictively deformed in a direction
substantially orthogonal to the magnetic field application direction. And an exciting coil wound
around the outer periphery of the magnetostrictive element, energized and excited to cause
magnetostrictive deformation of the magnetostrictive element to vibrate, and a gap between the
magnetostrictive element on which the exciting coil is wound and the speaker housing And a
damper for closing the speaker housing.
[0008]
The present invention according to claim 2 is a square tubular speaker housing having an open
front and a rear, and both ends which end the side edge without being restricted by the side edge
fixed to the speaker housing. They are arranged in the front opening of the speaker housing so as
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to face each other in the front-rear direction, receive an external magnetic field, and undergo
magnetostrictive deformation in a direction substantially orthogonal to the magnetic field
application direction. A pair of front and rear plate-like magnetostrictive elements that radiate, an
excitation coil that is wound around the outer periphery of each of the magnetostrictive
elements, energized and excited to cause magnetostrictive deformation of the magnetostrictive
elements to vibrate, and the excitation coil is wound around It is characterized by comprising a
pair of front and rear dampers which close the gaps between the magnetostrictive elements and
the speaker housing to seal the speaker housing from the front and rear.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present
invention will be described with reference to FIGS.
FIG. 1 is an exploded perspective view showing a first embodiment of the sealed box type direct
emission flat loudspeaker according to the present invention, and FIGS. 2A and 2B are each an
enclosed box direct emission flat loudspeaker shown in FIG. FIG. 3 is a front view and a
longitudinal sectional view of the magnetostrictive speaker driver shown in FIG. 1, and FIG. 4 is a
magnetostrictive characteristic of the magnetostrictive element shown in FIG. FIG. 5 is an
exploded perspective view showing a second embodiment of the sealed box direct emission flat
loudspeaker according to the present invention, and FIGS. 6 (A) and 6 (B) are each a sealed box
direct emission shown in FIG. It is a partially cutaway front view and a longitudinal crosssectional view of a flat speaker.
[0010]
1 and 2 (A) and 2 (B), a closed box type direct emission flat speaker 11 is constructed by
assembling a pair of magnetostrictive speaker drivers 13 in two rows into a square box-like
speaker housing 12 whose front face is open. The magnetostrictive speaker driver 13 itself emits
a direct sound.
As shown in FIGS. 3A and 3B, each magnetostrictive speaker driver 13 is not restrained at the
side edge but fixed at both ends terminating the side edge to the speaker housing 12 so that the
front opening of the speaker housing 12 is opened. The magnetostrictive element 14 disposed in
the portion, and the exciting coil 15 which is wound around the outer periphery of the
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magnetostrictive element 14 and is energized and excited to cause magnetostrictive deformation
of the magnetostrictive element 14 to vibrate.
The magnetostrictive element 14 is formed by forming a magnetostrictive material exhibiting a
magnetostrictive lateral effect that expands and contracts in a direction substantially orthogonal
to the application direction of the magnetic field into a rectangular thin plate shape, and holds
the fixing portion 16 holding both ends in the speaker housing 12 It is done. The exciting coil 15
is configured by connecting in series a series of coil pairs 15a, 15b, 15c wound around the
circumference of the magnetostrictive element 14 divided into three equal parts. Whether the
coil is wound directly around the circumference of the magnetostrictive element 14 Alternatively,
a spacer (not shown) made of butyl rubber or a vinyl sheet or the like which allows relative
displacement of the exciting coil 15 between the magnetostrictive element 14 is tightly inserted
and wound, and when the spacer is used, the magnetostrictive element 14 is The binding of the
excitation coil 15 to magnetostrictive deformation is reduced. In addition, the gap between the
side edge of the magnetostrictive element 14 and the inner edge of the speaker housing 12 and
the gap between the side edges of the pair of magnetostrictive elements 14 are made of sheet
rubber etc. And the speaker housing 12 is closed by the damper 17.
[0011]
By the way, the magnetostrictive element 14 having the following characteristics is used for the
sample having 20 coils per 1 cm, and the magnetostrictive element 14 used in the present
embodiment shows (Tb0.3Dy0.7) Fe2 exhibiting magnetostrictive deformation exceeding 1000
ppm as described above. It can be said to be a super giant magnetostrictive element because it
exhibits a magnetostrictive deformation which is ten times greater than the giant
magnetostrictive element represented by. Electric resistance: (20 to 30) × 10 -8 Ω m Relative
permeability: 100 to 300 Holding power: 1 to 2 Oe Young's modulus: (15 to 20) × 10 10 n / m
2 Tensile strength (10 to 40) x 107 Pa · thermal expansion coefficient; (10 to 12) ppm / ° C
[0012]
Note that, for example, a powder metallurgy method in which a plurality of raw material alloys
are crushed, formed in a magnetic field, processed and coated after sintering, or low pressure
casting of a raw material alloy is performed. It can be manufactured by the Bridgman method in
which crystal growth is followed by annealing treatment, processing and coating, or a method of
improving them or a method completely different from this. However, the magnetostriction
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characteristics of such an ultra-magnetostrictive element 14 are easily influenced by the
component ratio of the raw material alloy and the way of blending, and it is necessary to repeat
various trial and error for manufacturing from the laboratory stage to the practical stage.
However, it is confirmed from, for example, the test results shown in FIG. 4 that the element has
a large generation stress with a magnetostrictive deformation capability which is more than ten
times that of a conventional element called a giant magnetostrictive element. The figure plots the
displacement of the other end with respect to the magnetic field when the magnetic field is
applied by fixing one end of the 28 cm-long magnetostrictive element 14. It is clear from this test
result that when the magnetic field of 40 oersteds (Oe) is applied to the magnetostrictive element
14, the magnetostrictive lateral effect close to 8 mm at maximum is exhibited, but both ends of
the magnetostrictive element 14 are fixed and the magnetic field is Even when applied, it has
been confirmed that the displacement of the two equidistant points of the magnetostrictive
element 14 is close to 6 mm when the magnetic field of 40 oersted (Oe) is applied.
[0013]
In the closed box type direct emission flat speaker 11 configured as described above, when the
three series wound coil pairs 15a, 15b, 15c are energized and excited, the magnetostrictive
element 14 is displaced in the front-rear direction. That is, since the exciting coil 15 is excited by
being supplied with a voice current, a magnetic field corresponding to the magnitude of the voice
current is generated. That is, since the series coil pairs 15a, 15b and 15c are connected in series
with each other, a magnetic field of the same polarity proportional to the magnitude of the
current and the number of coil turns is generated, and the magnetostrictive element 14 is
magnetostrictive according to the magnitude of the magnetic field. Deform. Since the
magnetostrictive element 14 is displaced in the front-rear direction by the magnetostrictive
lateral effect, the piston 17 vibrates in the front-rear direction while bending the damper 17 to
generate a sound pressure. The stress generated by the magnetostrictive element 14 has a very
large value that is appropriate to be called an extra-magnetostrictive element, and therefore, even
if the sealed box type direct emission flat loudspeaker 11 is miniaturized, the volume of the
speaker is reduced, which has conventionally been a problem. Sufficient low-range regeneration
ability can be exhibited regardless of the accompanying decrease in compliance.
[0014]
As described above, in the sealed box type direct emission flat speaker 11, the magnetostrictive
element 14 itself that exhibits the magnetostrictive lateral effect that expands and contracts in
the direction substantially orthogonal to the application direction of the magnetic field directly
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generates sound. The thickness of the speaker measured in the vibration direction can be made
sufficiently small, and the structure can be made extremely thin. Moreover, since both ends of
the magnetostrictive element 14 are fixed, the magnetostrictive element 14 can be driven in the
front-rear direction with strong driving force from both sides sandwiching the driving point
corresponding to two points dividing the magnetostrictive element 14 into three. The vibration of
the magnetostrictive element 14 can be converted into sound pressure without waste.
Furthermore, by using, as the magnetostrictive element 14, an extra-magnetostrictive element
exhibiting magnetostrictive deformation that is several tens of times greater than that of the
extra-magnetostrictive element, a sufficient sound pressure not comparable to existing
magnetostrictive speaker drivers can be obtained. Thus, the diaphragm can be piston-driven over
a wide band from the low band to the high band, and good sound reproduction is possible.
[0015]
In addition, since the exciting coil 15 is composed of a plurality of series wound coil pairs 15a,
15b, 15c wound around the magnetostrictive element 14 at a predetermined distance from each
other, the exciting coil 15 is subjected to magnetostrictive deformation of the magnetostrictive
element 14. Magnetostrictive speaker driver using a collectively wound excitation coil having the
entire length of the connection of the series-wound coil pairs 15a, 15b, 15c in which the seriespaired coil pairs 15a, 15b, 15c share the required deformation. As described above, excessive
stress is not generated over the entire length of the exciting coil, and it is possible to prevent
inconvenience such as plastic deformation of the exciting coil 15 or premature failure due to
repeated magnetostrictive deformation. Further, since the plurality of series wound coil pairs
15a, 15b and 15c are connected in series with each other, the voltage applied to both ends of the
exciting coil 15 corresponds to the number of turns of each series wound coil pair 15a, 15b and
15c. A magnetic field can be generated.
[0016]
In the above embodiment, the front drive type closed box type direct emission flat loudspeaker
11 for driving the magnetostrictive element 14 facing forward is taken as an example, but it is
shown in FIG. 5 and FIGS. 6A and 6B. Like a closed box type direct emission flat speaker 21, it
may be configured as a double side drive type. The sealed box type direct radiation flat surface
speaker 21 is configured by arranging a front surface magnetostrictive speaker driver 13 f and a
rear surface magnetostrictive speaker driver 13 r in two rows on a square cylindrical speaker
housing 22 having an open front surface and a rear surface. In a word, the closed box direct
emission flat speaker 21 has a structure in which the closed box direct emission flat speaker 11
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described above is closely connected to the back and the barrier of the connecting portion is
removed. A space between the front opening of the speaker housing 22 and the magnetostrictive
element 14 of the front magnetostrictive speaker driver 13f is closed by the front damper 17f,
and the rear opening of the speaker housing 22 and the magnetostrictive element 14 of the rear
magnetostrictive speaker driver 13r The space between them is closed by a rear damper 17r.
[0017]
Since the closed box type direct radiation flat loudspeaker 21 drives the magnetostrictive
speaker drivers 13f and 13r of the front and back two rows in phase, the sound pressure
radiated to the front and the sound pressure radiated to the rear become the same phase. . For
this reason, the sound pressure of the antiphase which went around from the back to the front of
the speaker housing 22 does not cancel the sound pressure emitted forward, and the sound
pressure of the same phase goes from the back to the front of the speaker housing 22 As a result
of increasing the sound pressure radiated forward, a very high sound pressure can be obtained.
[0018]
In each of the above embodiments, the configuration using two magnetostrictive elements 13 as
a diaphragm is taken as an example, but the diaphragm may be configured by one
magnetostrictive element, or three or more magnetostrictive elements may be arranged in
parallel. It can also be provided as a diaphragm.
[0019]
As described above, according to the present invention as set forth in claim 1, the rectangular
box-shaped speaker housing having an open front is subjected to an external magnetic field and
magnetostrictive deformation in a direction substantially orthogonal to the magnetic field
application direction. Side edge does not restrain the flat magnetostrictive element in the shape
of a flat, and the both ends which terminate the side edge are fixed, the gap between the
magnetostrictive element which wound the excitation coil around the periphery and the speaker
housing is closed by damper Since the case is sealed and the excitation coil is energized and
excited to magnetostrictively deform the magnetostrictive element to vibrate so that the
magnetostrictive element radiates the sound directly, the magnetostrictive element itself can
function as a diaphragm, so that the magnetostriction can be generated. Since it is not necessary
to provide a diaphragm separately from the element, the thickness of the speaker measured in
the vibration direction of the magnetostrictive element can be made sufficiently small, and an
extremely thin structure can be obtained. By using a magnetostrictive speaker driver consisting
of a super magnetostrictive element exhibiting a shape, it is possible to obtain a sufficient sound
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pressure which can not be compared with the existing magnetostrictive speaker driver.
Therefore, even when the speaker is miniaturized, Therefore, the diaphragm can be piston-driven
over a wide band from low to high, regardless of the reduction in compliance with the decrease
in the speaker internal volume. There are excellent effects such as good sound reproduction
being possible.
[0020]
According to the second aspect of the present invention, a pair of flat plate-like front and back
pairs that receive an external magnetic field and magnetostrictively deform in a direction
substantially orthogonal to the magnetic field application direction to the square tubular speaker
housing having an open front and back. Fix the magnetostrictive element at both ends without
constraining the side edge and fix the ends that terminate the side edge, and close the gap
between the magnetostrictive element and the speaker housing by winding the excitation coil
around the outer circumference with a damper to seal the speaker housing At the same time, the
exciting coil is energized and excited to magnetostrictively deform the magnetostrictive element
to vibrate, and the pair of magnetostrictive elements vibrates the sound directly in the back and
forth direction, so that the magnetostrictive element itself can function as a diaphragm. Since it is
not necessary to provide a diaphragm separately from the magnetostrictive element, the
thickness of the speaker measured in the vibration direction of the magnetostrictive element can
be made sufficiently small, and an extremely thin structure can be obtained. By using a
magnetostrictive speaker driver composed of a super magnetostrictive element exhibiting
magnetostrictive deformation, a sufficient sound pressure can not be obtained as compared with
the existing magnetostrictive speaker driver, and a pair of magnetostrictive elements in front and
rear is driven in phase Because the sound pressure radiated to the front and the sound pressure
radiated to the rear are in phase with each other, the sound pressure of the opposite phase that
has come around from the rear of the speaker chassis forward cancels the sound pressure
radiated to the front It is possible to obtain a very high sound pressure by enhancing the sound
pressure emitted forward by the in-phase sound pressure that has come around from the rear of
the speaker housing to the front, thereby miniaturizing the speaker Even in this case, sufficient
low-frequency reproduction capability can be exhibited regardless of the reduction in compliance
caused by the decrease in the volume in the speaker, which has been considered to be a problem
in the past, and this allows a wide band from low to high Across the diaphragm to the piston
drive, an excellent effect of equal are possible good sound reproduction.
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