JP2000341792

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DESCRIPTION JP2000341792
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
multipoint drive type planar speaker in which the sound pressure is improved by driving the
diaphragm at multiple points using a magnetostrictive speaker driver and at the same time the
entire speaker is thinned.
[0002]
2. Description of the Related Art FIGS. 7A and 7B are longitudinal sectional views showing
various operation modes of an example of a conventional multipoint drive type flat loudspeaker.
In the multipoint drive type flat speaker 1 shown in the figure, four drive points of the flat platelike diaphragm 2 are driven from the back side by the voice coil type speaker driver 3
respectively. The four speaker drivers 3 all have the same configuration, and the voice coil 5 has
one end bonded to the center of the back surface of the diaphragm 2 via the piston plate 4 and
the other end side of the voice coil 5 coaxially It comprises the columnar magnet 6 and the like
disposed. 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 platelike 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 is driven in
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phase at four drive points to generate sound pressure.
[0003]
However, since the above-described conventional multi-point drive type flat speaker 1 has four
speaker drivers 3 assembled to the back surface of one flat diaphragm 2, individual speakers can
not be used. For example, as shown in FIG. 7A, only the voice coil 5 of a specific speaker driver 3
is deviated from the center of the magnetic path of the columnar magnet 6 or a diaphragm due
to the variation in the dimensions of the driver 3. As shown in FIG. 7 (B), the axis of the voice coil
5 is not orthogonal to the diaphragm 2 due to the warpage etc. of 2 and the inclined voice coil 5
butts against the yoke 7 And other issues. Furthermore, in the conventional multi-point drive
type flat speaker 1, the diaphragm drive capacity of each speaker driver 3 is proportional to the
number of coil turns of the voice coil 5. The voice coil 5 or the columnar magnet 6 needs to have
a certain axial length or more, which causes a problem that there is a certain limit to thinning in
the vibration direction. In addition, when the multi-point drive type flat speaker 1 is miniaturized,
the air compliance between the back plate 8 and the diaphragm 2 becomes smaller as the
internal volume of the speaker is smaller, so the low frequency range can be reduced. The limit
reproduction frequency has risen, and as the reproduction band is narrowed, it has a problem
such that the reproduction of a good sound 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.
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[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)
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 drive a diaphragm at multiple points using a
magnetostrictive speaker driver, to improve the sound pressure and to make the entire speaker
thinner.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
according to claim 1 is a flat diaphragm having a peripheral portion fixed to a speaker frame, and
an external magnetic field to which a magnetic field application direction is substantially applied.
A plurality of series wound coils are wound around the thin magnetostrictive element which is
magnetostrictively deformed in a direction perpendicular to each other at a predetermined
interval, and both ends of the magnetostrictive element are fixed to the speaker frame, and And a
magnetostrictive speaker driver in which the magnetostrictive elements between the series-
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wound coils are coupled to a plurality of driving points separately provided.
Further, the magnetostrictive speaker drivers are arranged in a plurality of rows on the back
surface of the diaphragm.
[0008]
The present invention according to claim 3 excites the outer periphery of a flat plate-like
diaphragm having its peripheral portion fixed to the speaker frame, and a thin plate-like
magnetostrictive element magnetostrictively deformed in a direction substantially orthogonal to
the magnetic field application direction. A plurality of magnetostrictive speakers in which a coil is
wound, one end of the magnetostrictive element is fixed to the speaker frame, and the other end
of the magnetostrictive element is connected corresponding to a plurality of driving points
provided on the diaphragm. And a driver. Further, the excitation coil is characterized in that it
comprises a plurality of series wound coils wound around the magnetostrictive element at
predetermined intervals.
[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 an embodiment of the multipoint drive type flat speaker of the present invention, and
FIGS. 2A and 2B are partial cut-away views of the multipoint drive type flat speaker shown in FIG.
3 is a view showing the magnetostriction characteristics of the magnetostrictive element shown
in FIG. 1, FIG. 4 is an exploded perspective view showing another embodiment of the multipoint
drive type flat speaker of the present invention, 5 (A) and 5 (B) are respectively a front view and
a longitudinal sectional view of a partially cutaway plan view of the multipoint drive type flat
speaker shown in FIG. 4, and FIGS. 6 (A) and 6 (B) are respectively shown in FIG. It is a partially
cutaway front view and a cross-sectional view showing a modification of the multipoint drive
type flat speaker shown.
[0010]
The multipoint drive type flat speaker 11 shown in FIG. 1 and FIGS. 2 (A) and 2 (B) is to drive the
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four back faces of the rectangular thin plate shaped diaphragm 12 to produce sound and to
generate sound. A configuration is employed in which two rows of magnetostrictive speaker
drivers 13 drive two drive points in each row, respectively, to achieve thinning of the entire
speaker and widening of the reproduction band. The magnetostrictive speaker driver 13 forms 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, fixes both ends, and divides the three equidistant points into two
diaphragms. A magnetostrictive element 14 corresponding to 12 drive points, and an exciting
coil 15 in which a series-wound coil pair 15a, 15b, 15c wound around each periphery of the
magnetostrictive element 14 divided into three equal parts are connected in series . The exciting
coil 15 may be wound directly on the outer periphery of the magnetostrictive element 14 or a
spacer (not shown) such as butyl rubber or a vinyl sheet which allows relative displacement of
the exciting coil 15 in close contact with the magnetostrictive element 14. When wound and
using a spacer, the restriction of the exciting coil 15 on the magnetostrictive deformation of the
magnetostrictive element 14 is reduced.
[0011]
The diaphragm 12 has four driving points connected to two equidistant points of the
magnetostrictive element 14 through the connecting pieces 16 in the shape of thumb. Further,
the peripheral portion of the diaphragm 12 is fixed to the speaker frame 18 holding the fixing
plate 17 holding the both ends of the magnetostrictive element 14 through the gasket 19. That
is, the magnetostrictive speaker driver 13 winds a plurality of series wound coil pairs 15a, 15b
and 15c at predetermined intervals on the outer periphery of the magnetostrictive element 14
and fixes both ends of the magnetostrictive element 14 to the speaker frame 18.
Magnetostrictive elements 14 between series wound coil pairs 15a and 15b and between 15b
and 15c are connected to correspond to four driving points provided on the diaphragm 12,
respectively.
[0012]
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
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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
[0013]
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
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 has been confirmed, for example, from the test results shown in FIG. 3 and the like
that it is a large element of generated stress having a magnetostrictive deformation ability which
is more than a dozen times larger than the element called a conventional 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.
[0014]
In the flat speaker 11 configured as described above, each drive point of the diaphragm 12 is
displaced in the front-rear direction when the three pairs of direct-wound coil pairs 15a, 15b,
15c disposed across the drive point are energized and excited. 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 magnetostrictively deformed magnetostrictive element 14 is displaced in the back and forth
direction by the magnetostrictive lateral effect, the diaphragm 12 in which the four drive points
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are respectively connected to the magnetostrictive element 14 through the connection pieces 16
is arranged longitudinally from four back sides It is driven in phase in the direction to generate
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 when the
multipoint drive type flat speaker 11 is miniaturized, it is accompanied by the reduction of the
volume inside the speaker which has been a problem in the prior art Sufficient low-range
regeneration ability can be exhibited regardless of the reduction in compliance.
[0015]
As described above, in the multipoint flat speaker 11 described above, the diaphragm 12 is
coupled with the magnetostrictive element 14 exhibiting the magnetostrictive lateral effect that
expands and contracts in the direction substantially orthogonal to the application direction of the
magnetic field. The magnetostrictive element 14 can be configured so as to face the back side of
the back face 12, and the thickness of the speaker measured in the vibration direction of the
diaphragm 12 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 diaphragm 12 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 diaphragm 12 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.
[0016]
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
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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. Furthermore, since the magnetostrictive speaker drivers
13 are arranged in two rows on the back of the diaphragm 12, the number n (= 2) of drive points
for each magnetostrictive speaker driver 13 and the number m (= 2) of magnetostrictive speaker
drivers 13 Based on this, four driving points dispersed in a matrix of n × m (= 2 × 2) can be
uniformly piston-driven, and the design correspondence according to the plane area of
diaphragm 12 or the required sound pressure is It is easy.
[0017]
In each of the above embodiments, the two points that divide the magnetostrictive element 14
into three equal parts correspond to the driving points, but the multipoint drive type plane
shown in FIG. 4 and FIGS. 5A and 5B. Like the speaker 21, four magnetostrictive speaker drivers
23 are provided corresponding to four driving points, one end of the magnetostrictive element
24 is fixed for each magnetostrictive speaker driver 23, and the other end is a driving point. You
can also In the magnetostrictive speaker driver 23 shown in the present embodiment, a pair of
series wound coils 25a and 25b are wound around the outer periphery of the magnetostrictive
element 24 as the exciting coil 25, but the magnetostrictive element 24 itself is half or less of the
magnetostrictive element 14 described above. It is a size. Therefore, unlike the multi-point drive
type flat speaker 21 described above, the magnetostrictive element 24 exists only on the upper
side or the lower side of the drive point, and the back side of the diaphragm 22 is further
compacted. Can be provided.
[0018]
In addition, since the exciting coil 25 is composed of two series wound coil pairs 25 a and 25 b
wound around the magnetostrictive element 24 at a predetermined distance from each other, the
exciting coil 25 is moved to the exciting coil 25 along with the magnetostrictive deformation of
the magnetostrictive element 24. Like the magnetostrictive speaker driver using a batch wound
excitation coil, the required deformation is shared by the individual series wound coils 25a and
25b, and thus the combined length of the series wound coils 25a and 25b, the entire length of
the excitation coil Therefore, excessive stress is not generated, and it is possible to prevent the
problem that the exciting coil 25 is plastically deformed or broken at an early stage due to
repeated magnetostrictive deformation. Further, since the plurality of series wound coils 25a and
25b are connected in series with each other, it is possible to generate a magnetic field
corresponding to the number of turns in each series wound coil 25a and 25b simply by applying
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a voltage to both ends of the exciting coil 25. it can.
[0019]
Further, in the multipoint drive type flat speaker 21 shown in the above embodiment, the
magnetostrictive speaker driver 23 is disposed on the row extending in the longitudinal direction
with respect to the diaphragm 22, but it is shown in FIGS. 6 (A) and 6 (B). Like the multipoint
drive type flat speaker 31, the magnetostrictive speaker driver 33 can be disposed on a row
extending in the lateral direction with respect to the diaphragm 32. Although the
magnetostrictive speaker driver 33 is composed of a single magnetostrictive element 34 and a
single excitation coil 35, the operation principle of the magnetostrictive speaker driver 33 itself
is the same as that of the magnetostrictive speaker driver 23. Further, the change in arrangement
regarding the magnetostrictive speaker driver is similarly possible for the magnetostrictive
speaker driver 13 of the multipoint drive type flat speaker 11 described above.
[0020]
As described above, according to the present invention as set forth in claim 1, the
magnetostrictive speaker driver for driving the flat diaphragm having its peripheral portion fixed
to the speaker frame at multiple points receives an external magnetic field. A plurality of series
wound coils are wound around the thin-plate shaped magnetostrictive element
magnetostrictively deformed in a direction substantially orthogonal to the magnetic field
application direction, and both ends of the magnetostrictive element are fixed to the speaker
frame. Since the magnetostrictive element between the series-wound coils is connected to
correspond to a plurality of drive points provided on the diaphragm, the magnetostrictive
transverse effect expands and contracts in a direction substantially orthogonal to the application
direction of the magnetic field. By connecting the magnetostrictive element and the diaphragm at
the driving point, the magnetostrictive element can be made to face each other in the vicinity of
the back side of the diaphragm to form a speaker, and the thickness of the speaker measured in
the vibration direction of the diaphragm Do Since the magnetostrictive element is fixed at both
ends, the diaphragm can be driven back and forth with strong driving force from both sides of
the drive point between the magnetostrictive elements. Can convert the vibration of the
diaphragm into sound pressure without waste, and also can not compare with existing
magnetostrictive speaker drivers by using a super magnetostrictive element that exhibits
magnetostrictive deformation that is more than ten times that of a giant magnetostrictive
element An adequate sound pressure can be obtained, and thereby the diaphragm can be pistondriven over a wide band from the low band to the high band, and an excellent effect such as good
sound reproduction can be obtained.
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[0021]
Further, since the magnetostrictive speaker drivers are arranged in multiple rows on the back
surface of the diaphragm, the dispersion is performed in a matrix of n × m based on the number
n of driving points for each magnetostrictive speaker driver and the number m of
magnetostrictive speaker drivers. The individual drive points can be uniformly piston-driven, and
the design corresponding to the plane area of the diaphragm or the required sound pressure can
be easily achieved.
[0022]
Further, according to the present invention, the plurality of magnetostrictive speaker drivers for
driving the flat plate-like diaphragm whose peripheral portion is fixed to the speaker frame at
multiple points is subjected to the external magnetic field in a direction substantially orthogonal
to the magnetic field application direction. An excitation coil is wound around the outer
periphery of a thin plate-like magnetostrictive element that undergoes magnetostrictive
deformation, one end of the magnetostrictive element is fixed to the speaker frame, and the
magnetostriction is made to correspond individually to a plurality of drive points provided on the
diaphragm. Since the other end of the element is connected, the magnetostrictive element can
exist only on one side of the drive point, not on both sides of the drive point as in the method
using the equidistant point of the magnetostrictive element as the drive point. Therefore, each
magnetostrictive speaker driver can be made to be 1/2 or less the size of the diaphragm, and by
making the back side of the diaphragm more compact, a thin and small speaker can be provided.
At Excellent effects such as that.
[0023]
Further, since the exciting coil is composed of a plurality of series wound coils wound around the
magnetostrictive element at predetermined intervals, the required deformation of the exciting
coil along with the magnetostrictive deformation of the magnetostrictive element can be
individual direct Like a magnetostrictive speaker driver using a batch wound excitation coil
having a total length equal to the total length of the wound coils that are shared by the wound
coils, excessive stress is not generated over the entire length of the excitation coil, It is possible to
prevent the problem that the exciting coil is plastically deformed or broken at an early stage due
to repeated magnetostrictive deformation, and since a plurality of series wound coils are
connected in series with each other, a voltage is applied to both ends of the exciting coil The
effect of being able to generate a magnetic field according to the number of turns in each series
wound coil can be achieved simply by the above.
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