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JP2008219692

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DESCRIPTION JP2008219692
An object of the present invention is to provide a speaker in which a portion driven by converting
a digital driving force into an analog is not damaged. A speaker (10) has a bottomed cylindrical
casing (11) having an opening on one side, a super magnetostrictive member (12) disposed in
the casing and displaced according to a variation of a magnetic field, and the super
magnetostrictive member And a magnetic field generation unit 13 for generating a magnetic field
oriented along the displacement direction of the giant magnetostrictive member in response to
supply of a drive current based on a digital signal, and disposed on the opening side of the
housing And at least a diaphragm 14 supported at one end of the giant magnetostrictive
member. In the speaker, the magnetic field generating unit is composed of a plurality of magnetic
field generating coils 13a, 13b, 13c,... Corresponding to respective output bits of the digital
signal. [Selected figure] Figure 1
スピーカ
[0001]
The present invention relates to a speaker that generates and emits a sound wave based on a
digital signal, and more particularly to a speaker that vibrates a diaphragm using a giant
magnetostrictive element to output sound.
[0002]
Many speakers, such as a capacitor type and a dynamic type, are proposed as a speaker which
generates an acoustic wave based on a digital signal and emits sound from a diaphragm (see, for
example, Patent Document 1 and Patent Document 2).
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[0003]
For example, in the case of a capacitor type speaker, the area of the diaphragm or the voltage to
be driven is made to correspond to the size of each quantized bit, and the input digital signal is
synthesized on the diaphragm in an analog manner.
FIG. 5 shows an example of a diaphragm used for a capacitor type speaker driven by a digital
signal, where (a) is a plan view, (b) is a central longitudinal sectional view, and (c) is an electrode
of the speaker It is a schematic diagram which shows an example of the area ratio which divided
¦ segmented the diaphragm radially and set each area (angle) corresponding to the weight of
each bit of a digital signal.
In FIGS. 5A and 5B, the diaphragm 111 is stretched on one surface side of the diaphragm holder
112. Further, in FIG. 5C, the diaphragm 111 has a region corresponding to the weight of each bit
of the digital signal. Here, the case of applying to 8 bits is shown, the area corresponding to the
most significant bit is MSB, the area corresponding to the lower bit is 2 SB, and the area
corresponding to the lower bit is 3 SB, An area corresponding to each lower bit is 4SB, 5SB, 6SB,
7SB, and an area corresponding to the least significant bit is an LSB.
[0004]
However, in such a capacitor type speaker, when the driving force applied to the adjacent bits is
reversed, for example, the boundary portions indicated by symbol A in FIG. 5 try to move in
opposite directions. Therefore, a tensile force is applied to the diaphragm to cause a non-linear
operation at the boundary portion A, which causes distortion in the generated sound. In addition,
if the driving force is increased by a method such as raising the applied voltage in order to
increase the sound pressure, there is also a possibility that the portion A of the boundary of the
diaphragm is plastically deformed and broken.
[0005]
On the other hand, in the case of a dynamic speaker, this can be realized by dividing the portion
of the voice coil which drives the diaphragm into a plurality of parts and making the power for
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driving each voice coil correspond to the size of each bit that each voice coil receives. An
example of a conventional dynamic type speaker can be shown, for example, in FIG. In FIG. 6, the
digital speaker 120 includes a substantially bottomed cylindrical yoke 122 having a center pole
128 at the center, and an annular magnet 126 arranged to surround the base end outer
periphery of the center pole 128. . A magnetic circuit is configured by the magnet 126, the yoke
122, and the center pole 128. Further, the digital speaker 120 includes a coil bobbin 127
surrounding a magnetic circuit with a gap on the outer periphery of the center pole 128, a
plurality of voice coils 123 attached to the coil bobbin 127, and a tip of the voice coil 123. And a
diaphragm 121 attached to the In FIG. 6, the voice coil 123 is constituted by eight coils from the
first coil 123a to the eighth coil 123h. Here, the first coil 123a corresponds to the MSB (most
significant bit), the second coil 123b corresponds to the second lower bit 2SB, and the third coil
123c further corresponds to the next lower bit 3SB. Correspondingly, the fourth coil 123d
corresponds to each 4th bit, the fifth coil 123e to 5SB, the sixth coil 123f to 6SB, and the seventh
coil 123g to 7SB, and so on. It indicates that the coil 123 h corresponds to the LSB (least
significant bit). In the dynamic speaker 120 having such a structure, basically, the voice coil 123
itself moves in proportion to the current flowing through the voice coil 123 when one voice coil
123 coupled to the diaphragm 121 intersects the magnetic field. . Then, the diaphragm 121
coupled to the voice coil 123 vibrates to obtain an audio signal. Therefore, in such a dynamic
speaker, it is necessary to mechanically couple the voice coil corresponding to each bit.
[0006]
However, in the method in which the coils 123a, 123b,... 123h corresponding to the respective
bits are arranged in parallel, there is a problem that the distance from the magnetic pole is large,
a sufficient magnetic flux density can not be obtained, and the function is degraded. Moreover, a
tube which is a non-magnetic material such as paper and which is a non-conductive material is to
be a coil bobbin and which is used to mechanically connect in series each of the coils 123a,
123b,. The reduction of the magnetic flux density as described above can be prevented. However,
if the mechanical strength is insufficient as in a paper tube, for example, if the polarity of the
adjacent bit in the portion indicated by reference symbol B in FIG. 5 is reversed, a compressive or
tensile force is applied to this portion, and the paper tube But it is broken in the axial direction.
Therefore, it is conceivable to increase the mechanical strength of the coil bobbin, but if the
mechanical strength of the coil bobbin is made sufficient, the weight of the tube mechanically
coupling the voice coil increases, and the driving force of the increased weight is Need to
increase. Then, the frequency response is degraded. In addition, when the driving current is
increased to increase the driving force, the heat generated by the current flowing through the
voice coil softens the adhesive that integrates the tube and the voice coil. Therefore, each time a
signal is input, the tube and the voice coil may slip, or the voice coil itself may be burned. In
addition, it is conceivable to use a voice coil in which a plurality of taps are made in the middle of
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the winding and a plurality of adhesives are connected in series without using a coil bobbin.
However, in this case, the adhesive may be softened by the heat generated by the current flowing
through the voice coil, and the connection of each coil may be broken.
[0007]
Such a problem on the diaphragm surface and a problem on the voice coil connection portion are
caused by a lack of mechanical strength of a portion which converts a digital driving force into
an analog to drive.
[0008]
In addition, a speaker using a magnetostrictive element or a giant magnetostrictive element as a
drive unit has been proposed (see, for example, Patent Document 3).
However, the one described in Patent Document 3 relates to an analog type speaker, and does
not correspond to the lack of mechanical strength of a portion that converts digital driving force
into analog. JP 10-51878 JP 10-145887 JP JP 2004-363967
[0009]
The present invention has been made in view of the above circumstances, and an object of the
present invention is to provide a speaker in which a portion driven by converting a digital driving
force into an analog is not damaged.
[0010]
The speaker according to the present invention is a speaker that generates and emits sound
waves based on digital signals, and is provided with a closed-end cylindrical casing having an
opening on the sound emission side, and is disposed in this casing A giant magnetostrictive
member that displaces according to a change, and a space provided around the giant
magnetostrictive member, a magnetic field oriented in a direction along the displacement
direction of the giant magnetostrictive member according to supply of a drive current based on a
digital signal At least a magnetic field generating unit to be generated, and a diaphragm disposed
on the opening side of the housing and supported by one end of the super magnetostrictive
member, the magnetic field generating unit corresponds to each bit of the digital signal. A
plurality of magnetic field generating coils are characterized.
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[0011]
According to the speaker of the present invention, when the drive current based on the digital
signal is supplied to the magnetic field generation unit, the current flows in the respective
magnetic field generation coils corresponding to each bit in the plurality of magnetic field
generation coils included in the magnetic field generation unit. , Generate a magnetic field.
The generated magnetic field is applied to the giant magnetostrictive member, and the giant
magnetostrictive member becomes a portion for converting the digital driving force into an
analog signal and driving it, combining the driving force of the applied magnetic field, and based
on this, it is extended and displaced.
The vibration generated by the extension displacement is transmitted to the diaphragm, and the
diaphragm receives displacement from the giant magnetostrictive member, and is driven to
vibrate based on this displacement. Therefore, it is possible to provide a speaker in which the
portion driven by converting the digital driving power into an analog is not damaged.
[0012]
Hereinafter, an embodiment of a speaker according to the present invention will be described in
detail based on the drawings. FIG. 1 is a longitudinal side view showing an example of a speaker
according to the present invention. As shown in FIG. 1, the speaker 10 is a speaker that generates
and emits a sound wave based on a digital signal, and includes a housing 11, a giant
magnetostrictive member 12, a magnetic field generation unit 13, and a diaphragm 14. At least.
[0013]
The housing 11 is a case for housing the giant magnetostrictive member 12, the magnetic field
generation unit 13, the diaphragm 14 and the like, and can be, for example, a hollow body in a
bottomed cylindrical shape having an opening on the sound output side.
[0014]
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The giant magnetostrictive member 12 is disposed in the housing 11 and is made of a giant
magnetostrictive element that has the property of being displaced (stretched) according to the
fluctuation of the magnetic field.
The giant magnetostrictive member 12 has, for example, a cylindrical shape, supports the
diaphragm 14 at one end, and has the other end fixed to the bottom surface of the housing 11.
The giant magnetostrictive element is, for example, an element made of a single crystal alloy
mainly composed of terbium, dysprosium, iron and the like, and when a magnetic field is applied
from the outside, the Joule effect causes the direction of the external magnetic field. It has the
property of causing a change in the dimension extending along it, and the property of causing a
change in the amount of magnetization due to the billy effect and being compressively deformed
when receiving an external stress. In addition, the giant magnetostrictive element is made of
powder metallurgy and has extremely high mechanical strength such as compressive strength of
600 × 10 <6> (Pa) and tensile strength of 20 × 10 <6> (Pa). In addition, Young's modulus is
also extremely high at 2.0 × 10 <6> (N / m <2>). As described above, since the giant
magnetostrictive member is formed of an element having high mechanical strength, it is not
broken even if the opposite stress is applied to the adjacent bit. Moreover, since the Young's
modulus is high, it is possible to secure the response to high frequency.
[0015]
The magnetic field generation unit 13 is disposed at a distance from the outer circumferential
surface of the giant magnetostrictive member 12, and a magnetic field oriented in the direction
of displacement of the giant magnetostrictive member 12 in response to the supply of a drive
current based on a digital signal. Generate. Further, in the present invention, the magnetic field
generation unit 13 is configured of a plurality of magnetic field generation coils corresponding to
each bit of the digital signal. In FIG. 1, the magnetic field generation unit 13 shows a case where
the number of quantization bits corresponds to 8 bits, and is constituted by eight magnetic field
generation coils from the first coil 13a to the eighth coil 13h. In these magnetic field generating
coils, the first coil 13a corresponds to the MSB (most significant bit), the second coil 13b
corresponds to the second lower bit 2SB, and the third coil 13c further lowers the second one.
The fourth coil 13 d corresponds to the bit 3 SB, and the fourth coil 13 d corresponds to the 4
SB, the fifth coil 13 e to the 5 SB, the sixth coil 13 f to the 6 SB, and the seventh coil 13 g to 7 SB.
The eighth coil 13h corresponds to the LSB (least significant bit). An audio reproducing device or
the like (not shown) is connected to the magnetic field generating coil, and the magnetic field of
the coil is varied based on a digital signal emitted from the audio reproducing device or the like.
More specifically, the signal of the bit handled by each magnetic field generating coil is input to
the magnetic field generating coil corresponding to each bit of the 8-bit digital signal, and the
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magnetic field corresponding to the signal of each bit is input from each magnetic field
generating coil Occurs.
[0016]
In addition, the magnetic field generation unit 13 has a structure in which the plurality of
magnetic field generation coils described above are arranged in series. The speaker provided
with the magnetic field generation unit 13 having such a structure has a small area as viewed
from the front (upper surface in FIG. 1), can be installed in a narrow range, and can contribute to
space saving.
[0017]
In addition, the drive circuit of the speaker according to the above embodiment can be shown, for
example, in FIG. In FIG. 2, the current switch SW is controlled by each bit of the digital signal, and
is turned off when "0" and turned on when "1". The current switches SW each have a current
source of the same value. That is, in order for the super magnetostrictive member 12 to obtain
displacement corresponding to each bit by the magnetic field generation unit 13, it is necessary
to control the magnetic field applied to the super magnetostrictive member 12 corresponding to
each bit. Therefore, the current supplied to the magnetic field generating coil corresponding to
each bit is weighted, and the excess or deficiency of the generated magnetic flux due to the
position of the magnetic field generating coil is adjusted by adjusting the current supplied to
each bit in advance.
[0018]
The diaphragm 14 is a sound source disposed at the opening of the housing 11 and supported by
one end of the giant magnetostrictive member 12, and is a thin plate having a substantially
conical shape (cone shape). The vibration plate 14 has a structure capable of outputting an audio
by transmitting a vibration corresponding to the fluctuation of the giant magnetostrictive
member according to the input signal supplied to the magnetic field generation unit 13.
[0019]
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Therefore, in the loudspeaker according to the present embodiment, the drive current for each
bit is turned on / off in the magnetic field generating coil corresponding to each bit based on the
digital signal. When the drive current of the magnetic field generating coil in each bit is turned
on, the magnetic field generating coil generates a magnetic field oriented along the axial
direction of the giant magnetostrictive member. In addition, the giant magnetostrictive member
vibrates (extends and contracts) in the axial direction when the magnetic field is applied, and the
dimension (length) is displaced. As a result, this displacement is transmitted to the diaphragm,
and the vibration causes the diaphragm to output sound. As described above, by applying a
magnetic field to the giant magnetostrictive member and driving the diaphragm so as to generate
displacement corresponding to each bit, the portion that drives the digital driving force into
analog becomes the giant magnetostrictive member Therefore, the drive unit can be a speaker
without damage.
[0020]
Further, in the present invention, the diaphragm 14 may be supported by one end of the super
magnetostrictive member 12 via the high frequency range damping means 15. The highfrequency range attenuation means 15 reduces harmonic components to act as a low-pass filter
acoustically, and is made of, for example, a rubber-like member having elasticity. Specifically, the
so-called mechanical filter or mechanical filter is used. Therefore, the high-frequency range
attenuation means 15 removes high frequency components of the input signal, and extracts and
outputs an audio signal for driving the speaker. By providing the high frequency range
attenuation means 15 in this manner, unnecessary high frequency components radiated by
synthesizing digital signals can be removed and can not be transmitted to the diaphragm.
[0021]
In the present invention, as shown in FIG. 3, the speaker 20 may further include a radiator 16
near the magnetic field generation unit 13. That is, in the present invention, since the magnetic
field generation unit 13 itself can be fixed to the casing 11 without moving, the radiator 16 for
dissipating the heat generated by driving the magnetic field generation unit 13 is provided. You
can do it. By providing the radiator 16 in this manner, the heat generation of the magnetic field
generation unit 13 due to the drive current can be suppressed, and the possibility of the
magnetic field generation unit 13 being burnt can be reduced.
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[0022]
Further, in the present invention, the magnetic field generation unit is not limited to the speaker
having the above-described series arrangement structure, and may have a structure arranged in
parallel. An example of a speaker having a structure in which magnetic field generating coils are
arranged in parallel can be shown in FIG. Here, differences from the embodiment described
above will be mainly described. Therefore, the same components as those in the above-described
embodiment are denoted by the same reference numerals, and the description thereof is omitted.
Unless otherwise specified, the components are the same.
[0023]
As shown in FIG. 4, the speaker 30 is a speaker that generates and emits a sound wave based on
a digital signal, and includes a housing 21, a giant magnetostrictive member 22, a magnetic field
generation unit 23, and a diaphragm 14. At least. The housing 21 is a case for housing the giant
magnetostrictive member 22, the magnetic field generation unit 23, the diaphragm 14 and the
like, and can be, for example, a hollow body in a bottomed cylindrical shape having an opening
on the sound output side. Therefore, the housing 11 in the above-described embodiment is only
different in size, for example, the length is short (the height is low) and the width (diameter) is
wide.
[0024]
The giant magnetostrictive member 22 is disposed in the housing 21 and is made of a giant
magnetostrictive element having a property of being displaced (stretched) according to the
fluctuation of the magnetic field, and has a cylindrical shape, for example. While the other end is
fixed to the bottom of the housing 21. Therefore, the length (height) of the super
magnetostrictive member 12 in the above-described embodiment is about half, which is different
from this.
[0025]
The magnetic field generation unit 23 is disposed at intervals around the giant magnetostrictive
member 22 and generates a magnetic field oriented along the displacement direction of the giant
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magnetostrictive member 22 in response to the supply of a drive current based on a digital
signal. Further, in the present invention, the magnetic field generation unit 23 is configured of a
plurality of magnetic field generation coils corresponding to each bit of the digital signal. In FIG.
4, the magnetic field generation unit 23 is configured of a first coil 23a disposed inside and a
second coil 23b to an eighth coil 23h disposed outside. That is, the first coil 23a and the second
to eighth coils 23b to 23h are arranged in parallel inside and outside.
[0026]
As described above, the magnetic field generating unit 23 having a structure in which the
magnetic field generating coils are arranged in parallel generates a displacement corresponding
to each bit by applying a magnetic field to the giant magnetostrictive member to drive the
diaphragm to drive it. While being able to be a speaker without damage to the part, it can be
installed at a three-dimensionally low (thin) height, and the depth dimension can be reduced as
compared with the first embodiment.
[0027]
In the third embodiment, the diaphragm 24 may be supported by one end of the giant
magnetostrictive member 22 via the high frequency range damping means 25.
Furthermore, a radiator (not shown) may be further provided in the vicinity of the magnetic field
generation unit 23.
[0028]
FIG. 1 is a longitudinal side view showing a first embodiment of a speaker according to the
present invention. It is a circuit diagram showing an example of a drive circuit of a speaker
concerning the present invention. It is a vertical side view which shows the 2nd Example of the
speaker based on this invention. It is a vertical side view which shows the 3rd Example of the
speaker based on this invention. It is a figure which shows the outline ¦ summary of the
diaphragm used for the conventional capacitor ¦ condenser type ¦ mold speaker, (a) is a top view,
(b) is a longitudinal cross-sectional view, (c) divides a diaphragm radially, Each area (angle) ) Is a
schematic diagram showing an area ratio set corresponding to the weight of each bit of a binarycoded digital signal. It is a vertical side view which shows the example of the conventional
dynamic type ¦ mold speaker.
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Explanation of sign
[0029]
DESCRIPTION OF SYMBOLS 10, 20, 30 Speakers 11, 21 Casing 12, 22 Super magnetostrictive
member (super magnetostrictive element) 13, 23 Magnetic field generation part 14 Diaphragm
15 High-frequency range attenuation means (low-pass filter) 16 Radiator
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