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DESCRIPTION JP2004363967
The present invention provides a magnetostrictive speaker device capable of reproducing a wide
band by combining a magnetostrictive element or a super magnetostrictive element and a
magnetic circuit. In a magnetostrictive speaker device, a magnetostrictive element, a magnetic
field generating coil generating a magnetic field in the expansion and contraction direction of the
magnetostrictive element, a support member movably supporting both ends of the
magnetostrictive element, and both ends of the magnetostrictive element And a diaphragm fixed
to one end of the magnetostrictive element. When a high frequency voice current (AC) flows
through the magnetic field generating coil, a magnetic field is generated, and the
magnetostrictive element expands and contracts (oscillates) in the direction of the magnetic field.
The vibration of the magnetostrictive element is transmitted to the diaphragm, and high
frequency sound is reproduced from the diaphragm. On the other hand, when a low frequency
sound current flows in the magnetic field generating coil, the polarity of the magnetostrictive
element, which is a magnetic substance, changes. Since the magnetostrictive element is disposed
in the direct current magnetic field formed by the magnetic circuit, the magnetostrictive element
vibrates in accordance with the polarity of the direct current magnetic field generated by the
magnetic circuit and the polarity of the magnetostrictive element, and low frequency sound is
reproduced. [Selected figure] Figure 1
Magnetostrictive speaker device
TECHNICAL FIELD [0001] The present invention relates to a speaker device using a
magnetostrictive element or a giant magnetostrictive element. [0002] A magnetostrictive element
is known to exhibit a magnetostriction phenomenon in which the element size changes in
response to an external magnetic field. In particular, an RFe2 Laves type intermetallic compound
such as TbFe2 system is called a super magnetostrictive element because the amount of
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magnetostriction is extremely large. When a coil is wound around the magnetostrictive element
and a current is supplied to the coil, a magnetic field proportional to the magnitude of the
current and the number of turns of the coil is generated, and the magnetostrictive element
expands and contracts in accordance with the magnitude of the magnetic field. Various speakers
have been proposed which utilize such properties of the magnetostrictive element. For example,
a magnetostrictive speaker (see, for example, Patent Document 1) has been proposed in which a
speaker diaphragm is driven using a magnetostrictive element to make the entire speaker thin.
Further, one end of the giant magnetostrictive rod is fixed to the disk-like yoke, and the other end
is fixed to the diaphragm, and the giant magnetostrictive rod is expanded and contracted without
sliding on the housing etc. to prevent noise and the like. Such a giant magnetostrictive actuator
and a giant magnetostrictive speaker using the same (for example, see Patent Document 2) have
been proposed. However, the magnetostrictive element has a change in magnetic field due to a
high frequency current. In general, a speaker using a magnetostrictive element has difficulty in
reproducing the low frequency region because the vibration velocity is high and the vibration
velocity is low depending on the change in the magnetic field due to the low frequency current.
As problems to be solved by the present invention, the above-mentioned ones can be mentioned
as an example. An object of the present invention is to provide a magnetostrictive speaker device
capable of reproducing a wide band from a low band to a high band. According to a first aspect
of the present invention, there is provided a magnetostrictive speaker device comprising: a
magnetostrictive element; a magnetic field generating coil for generating a magnetic field in the
expansion and contraction direction of the magnetostrictive element; and the magnetostrictive
element And a magnetic circuit for applying DC magnetic fields of different polarities to both
ends of the magnetostrictive element, and a diaphragm fixed to one end of the magnetostrictive
element. . According to a third aspect of the present invention, in the magnetostrictive speaker
device, a magnetostrictive element, a magnetic field generating coil generating a magnetic field in
the expansion and contraction direction of the magnetostrictive element, and one end of the
magnetostrictive element are fixed. A magnetic circuit having an air gap on the other end side of
the magnetostrictive element and applying a DC magnetic field of different polarity to both ends
of the magnetostrictive element, a support member movably supporting the other end of the
magnetostrictive element, and Providing the coil bobbin, the movable coil wound around the coil
bobbin, the low-frequency diaphragm fixed to the coil bobbin, and the high-frequency diaphragm
fixed to the other end of the magnetostrictive element It features.
BEST MODE FOR CARRYING OUT THE INVENTION The present invention comprises a
magnetostrictive device (hereinafter, "a super magnetostrictive device" is included) having a low
vibration velocity in the low region, and a magnetic circuit comprising a yoke and a bias
magnetic field generating magnet. By using in combination, a speaker device is provided that
enables sound reproduction over a wide band from low to high frequencies. In one aspect of the
present invention, a magnetostrictive speaker device includes a magnetostrictive element, a
magnetic field generating coil that generates a magnetic field in the expansion and contraction
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direction of the magnetostrictive element, and a support member that movably supports both
ends of the magnetostrictive element. And a magnetic circuit for applying DC magnetic fields of
different polarities to both ends of the magnetostrictive element, and a diaphragm fixed to one
end of the magnetostrictive element. According to the above magnetostrictive speaker device,
when a high frequency audio current (AC) flows in the magnetic field generating coil, a magnetic
field is generated, and the magnetostrictive element expands and contracts (oscillates) in the
direction of the magnetic field. The vibration of the magnetostrictive element is transmitted to
the diaphragm, and high frequency sound is reproduced from the diaphragm. On the other hand,
when a low frequency sound current flows in the magnetic field generating coil, the polarity of
the magnetostrictive element, which is a magnetic substance, changes. Since the magnetostrictive
element is disposed in the direct current magnetic field formed by the magnetic circuit, the
repulsive / attracting force acts on the magnetostrictive element in accordance with the polarity
of the direct current magnetic field generated by the magnetic circuit and the polarity of the
magnetostrictive element. The magnetostrictive element vibrates due to the repulsion / suction
force, and the vibration is transmitted to the diaphragm to reproduce low-pass sound. Thus, the
use of the magnetostrictive element enables audio reproduction from low to high frequencies. In
one aspect of the above magnetostrictive speaker, a nonmagnetic material is provided at both
ends of the magnetostrictive device, and the magnetostrictive device is supported by the support
member via the nonmagnetic material, and one of the nonmagnetic materials is The diaphragm
can be fixed to the According to another aspect of the present invention, a magnetostrictive
speaker device includes a magnetostrictive element, a magnetic field generating coil generating a
magnetic field in the expansion and contraction direction of the magnetostrictive element, and
one end of the magnetostrictive element fixed thereto. A magnetic circuit having an air gap on
the other end side and applying DC magnetic fields of different polarities to both ends of the
magnetostrictive element, a support member movably supporting the other end of the
magnetostrictive element, and the magnetic circuit disposed in the air gap A coil bobbin, a
movable coil wound around the coil bobbin, a low-range diaphragm fixed to the coil bobbin, and
a high-range diaphragm fixed to the other end of the magnetostrictive element. According to the
above magnetostrictive speaker device, when a high frequency audio current (AC) flows in the
magnetic field generating coil, a magnetic field is generated, and the magnetostrictive element
expands and contracts (oscillates) in the direction of the magnetic field.
The vibration of the magnetostrictive element is transmitted to the diaphragm, and high
frequency sound is reproduced from the diaphragm. On the other hand, when a low frequency
sound current flows through the movable coil disposed in the air gap of the magnetic circuit, an
electromagnetic force acts on the coil bobbin around which the movable coil is wound, causing
vibration. This vibration is transmitted to the diaphragm to reproduce low-pass sound. Thus, the
use of the magnetostrictive element enables audio reproduction from low to high frequencies. In
one aspect of the magnetostrictive speaker, the magnetic field generating coil and the movable
coil can be the same coil. In another aspect of the above magnetostrictive speaker, the
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magnetostrictive speaker further includes an input circuit formed by connecting the magnetic
field generating coil and the movable coil in parallel, and the input circuit is configured to
generate a high frequency component of an input audio signal as the magnetic field. A high pass
filter that supplies a generation coil, and a low pass filter that supplies a low pass component of
the input audio signal to the movable coil. In this aspect, the high frequency component is
filtered from the input voice signal, the high frequency component is supplied to the magnetic
field generating coil, and the low frequency component is supplied to the movable coil. Thus, the
low band and the high band can be reproduced respectively. Another aspect of the above
magnetostrictive speaker includes an input circuit in which the magnetic field generating coil and
the movable coil are connected in parallel, and the input sound signal is parallel to the magnetic
field generating coil and the movable coil. Is input to In still another aspect, the magnetic
recording apparatus further includes an input circuit in which the magnetic field generating coil
and the movable coil are connected in series, and the input sound signal is serially input to the
magnetic field generating coil and the movable coil. Since the magnetostrictive element basically
has a property of generating a large vibration velocity only for high frequency band signals, the
input sound signal may be supplied to the magnetic field generating coil and the movable coil
without band limitation. In another aspect of the above magnetostrictive speaker device, the
magnetic field generating coil is fixed to the magnetic circuit without contacting the
magnetostrictive element. According to this aspect, the magnetic field generating coil is fixed by
being wound around the magnetic circuit, for example, the inner wall of the cylindrical yoke
without contacting the magnetostrictive element. Therefore, the expansion and contraction
(vibration) of the magnetostrictive element is transmitted to the diaphragm without being
inhibited. In another aspect of the above magnetostrictive speaker device, the magnetostrictive
element includes a super magnetostrictive element. Thereby, the amount of magnetostrictive
deformation can be increased according to the characteristics of the speaker device. In another
aspect of the above magnetostrictive speaker device, the support member movably supports the
magnetostrictive element in the expansion and contraction direction of the magnetostrictive
element.
Thereby, expansion and contraction (vibration) by the magnetostrictive element is faithfully
transmitted to the diaphragm without being inhibited by the support member. In another aspect
of the above magnetostrictive speaker device, the magnetic circuit includes a magnetic field
generating means, and a yoke magnetized in accordance with the magnetic field generated from
the magnetic field generating means. According to this aspect, the magnetic energy generated by
the magnetic field generating means can be efficiently transmitted to the yoke, and the magnetic
energy can be applied to the air gap. In another aspect of the above magnetostrictive speaker, the
magnetic field generating means may be a coil in which a magnet and / or a wire is wound. For
example, a magnetic field having a magnitude corresponding to the former or the latter can be
generated by passing an audio current by means of a permanent magnet or a wire wound around
an exciting coil. Also, depending on the characteristics of the speaker device, both the permanent
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magnet and the excitation coil can be adopted. Preferred embodiments of the present invention
will now be described with reference to the drawings. First Embodiment FIG. 1 shows a crosssectional view along the axial direction of the speaker device 100 according to the first
embodiment. The speaker device 100 mainly includes, as shown in FIG. 1, a rod-shaped
magnetostrictive element 1, disk-shaped dampers 2a and 2b, nonmagnetic members 3a and 3b, a
cylindrical yoke 4, and a bias. A magnetic field generating magnet 5, a magnetic field generating
coil 6, a conical frame 7, and a conical diaphragm 8 are provided. The magnetostrictive element
1 is disposed substantially at the center of the speaker device 100, with the element dimensions
being displaced (expanded) according to the magnitude from the external magnetic field. The
dampers 2a and 2b have a plurality of concentrically formed wave shapes, are provided at
positions closing the opening of the yoke 4, and movably support the magnetostrictive element 1.
The nonmagnetic members 3a and 3b are fixed to the end portions 1a and 1b of the
magnetostrictive element 1, respectively, and are supported so as to penetrate substantially the
center portions of the dampers 2a and 2b. The yoke 4 accommodates the magnetostrictive
element 1 and the nonmagnetic members 3a and 3b in the cylinder and is fixed to the peripheral
portions of the dampers 2a and 2b, respectively. The bias magnetic field generating magnet 5 is
ring-shaped, and is provided substantially at the center of the yoke 4 so as to cover the outer wall
of the yoke 4. The magnetic field generating coil 6 is wound along the inner wall of the bias
magnetic field generating magnet 5 without being in contact with the magnetostrictive element
1, and the conical frame 7 is formed along the circumferential direction on the outer wall on one
end side of the yoke 4 It is fixed by covering. The diaphragm 8 has one end fixed to one end of
the nonmagnetic member 3 b not fixed to the magnetostrictive element 1, and the peripheral
portion in the vicinity of the edge portion 8 a fixed to the peripheral portion of the frame 7.
The reproduction of the sound in the low band or the high band of the speaker device 100 in
such a configuration is performed by the method described below. First, the principle of
reproduction of low-pass audio signals will be described. In the low frequency range, sound is
reproduced by an operation similar to that of the movable iron type speaker, and the
magnetostriction phenomenon of the magnetostrictive element does not contribute to the
reproduction. Specifically, when a low frequency audio current (AC current) flows through the
magnetic field generating coil 6, the polarity of the magnetostrictive element 1 becomes N pole
or S pole according to the change of the polarity (+ or −) of the audio current. Change. On the
other hand, the polarities in the air gaps 9a and 9b formed by the yoke 4 and the bias magnetic
field generating magnet 5 are determined by the bias magnetic field generating magnet 5 (in this
example, the air gap 9a is an S pole and the air gap 9b is an N pole). Therefore, depending on the
relationship between the polarity of each of the air gaps 9a and 9b and the polarity of the
magnetostrictive element 1, a repulsive force or an attractive force acts on the magnetostrictive
element 1, and the magnetostrictive element 1 is displaced in the axial direction X in FIG. This
displacement is transmitted to the diaphragm 8 via the nonmagnetic material 3b, and a lowrange sound wave is emitted from the diaphragm 8. By selecting the resonance frequency
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generated by the equivalent mass of the vibration system and the compliance of the dampers 2a
and 2b to a predetermined value, it is possible to vibrate the magnetostrictive element 1 in a
desired low band. Next, the principle of reproduction of the high frequency range audio signal
will be described. The high frequency range audio signal is reproduced by the magnetostriction
phenomenon of the magnetostrictive element. When a high frequency sound current flows in the
magnetic field generating coil 6, a change in the magnetic field occurs in the axial direction X of
the magnetostrictive element 1. Then, in response to the change of the magnetic field, the
magnetostrictive element 1 expands and contracts in the axial direction X to generate vibration.
This vibration by the magnetostrictive element 1 is transmitted to the diaphragm 8 through the
nonmagnetic material 3 b, and a high-range sound wave is emitted from the diaphragm 8. As
described above, the speaker device 100 according to the first embodiment reproduces a low
frequency signal by the repulsion / suction action of the DC magnetic field formed by the
magnetic field generating coil 6 and the yoke 4 and the magnetism of the magnetostrictive
element 1 The high frequency signal is reproduced by the magnetostriction phenomenon of the
element 1. Therefore, the audio signal can be reproduced over a wide band from the low band to
the high band. In the speaker device 100 according to the first embodiment, the magnetostrictive
element 1 is supported by supporting the nonmagnetic members 3a and 3b with the dampers 2a
and 2b without fixing the end 1a of the magnetostrictive element 1 to the yoke 4. It is
displaceable in the axial direction X. For this reason, in the magnetostrictive element 1, the
vibration in the high region is reduced while the vibration in the low region is increased. The
reason for this will be described in detail with reference to FIGS. 1 and 2.
FIG. 2 shows an enlarged view of the magnetostrictive element 1 of the speaker device 100
shown in FIG. 2 (a) shows the case where the end of the magnetostrictive element 1 is not fixed,
and FIG. 2 (b) shows the case where the left end of the magnetostrictive element 1 is fixed. The
lengths of the magnetostrictive element 1 shown in FIGS. 2A and 2B are the same length L.
Further, in the present example, for convenience of explanation, it is assumed that the length
when the magnetostrictive element 1 is extended and the length when it is contracted are both
equal. Moreover, in FIG. 2 (a) and (b), the length of L2 is twice the length of L1. As shown in FIG.
2A, when an audio current flows through the magnetic field generating coil 6, the
magnetostrictive element 1 expands and contracts in the axial direction X by the length L1 of
each end 1a and 1b. Therefore, when the right end portion 1b of the magnetostrictive element 1
is fixed to the diaphragm via the nonmagnetic material in FIG. 2A, the amplitude at which the
diaphragm vibrates is L1. On the other hand, as shown in FIG. 2 (b), when the same audio current
flows while the left end of the magnetostrictive element 1 is fixed, the right end 1b of the
magnetostrictive element 1 is axially oriented by the length L2 (= 2 × L1). Displace to X
Therefore, when the left end portion 1a is fixed to the diaphragm via the nonmagnetic material,
the amplitude at which the diaphragm vibrates is L2, which is twice that in the case where the
end of the magnetostrictive element 1 is not fixed. In the first embodiment, since the end of the
magnetostrictive element 1 is not fixed, the amount of vibration of the magnetostrictive element,
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that is, the amplitude of the reproduction high-frequency signal is half that in the case where the
magnetostrictive element is not fixed. However, the magnetostrictive element has the property
that the vibration velocity is larger than that of the high frequency band signal. Therefore, in the
present embodiment, the amplitude of the high band signal is suppressed as the magnetostrictive
element is not fixed, and the low band signal which can not be reproduced by the expansion and
contraction of the magnetostrictive element is increased according to the above principle. It is
possible to obtain various frequency characteristics. As described above, in the speaker device
100 according to the first embodiment, the magnetostrictive element 1 having a low vibration
velocity in the low band is used in combination with the magnetic circuit including the yoke 4
and the bias magnetic field magnet 5. The low band is similar to the principle of the movable iron
type speaker, and the high band is reproduced by the vibration principle of the magnetostrictive
element 1. As a result, it becomes possible to reproduce wideband sound from low to high
frequencies, and it is possible to provide a tweeter with extended low frequencies. Second
Embodiment In the second embodiment, in addition to the high-frequency diaphragm that
radiates a sound wave by the vibration from the magnetostrictive element 11, the vibration from
a magnetic circuit similar to an electrokinetic type such as the yoke 14 Thus, the speaker device
200 capable of reproducing sound over a wide band from the low band to the high band is
provided by providing the diaphragm for the low band that radiates the sound wave.
A cross-sectional view along the axial direction of the speaker device 200 is shown in FIG. 3 (a).
FIG. 3 (b) shows a cross-sectional view of a portion of the magnetic circuit of the speaker device
200 shown in FIG. 3 (a). Further, in the magnetic circuit shown in FIG. 3 (b), a magnetic path is
formed along the direction shown by the code s30. In the magnetic circuit shown in FIG. 3B, for
convenience of explanation, components other than the yoke 14, the bias magnetic field
generating magnet 15, and the magnetostrictive element 11 are omitted. As shown in FIG. 3A,
the speaker device 200 mainly includes a rod-shaped magnetostrictive element 11, a disk-shaped
damper 12, a cylindrical yoke 14 with a bottom, and a ring-shaped bias magnetic field
generation. A magnet 15, a magnetic field generating coil 16, a cylindrical voice coil bobbin 21, a
movable coil 20, a conical frame 17, a diaphragm 18 (woofer) for low range reproduction, and a
diaphragm for high range reproduction 22 (tweeter) and. The magnetostrictive element 11 is
disposed at substantially the center of the speaker device 200, with the element dimensions
displaced in accordance with the magnitude from the external magnetic field. The damper 12 has
a plurality of concentrically formed waves and is provided at a position closing the opening of
the yoke 14 and supports the magnetostrictive element 11 movably. The yoke 14 accommodates
the magnetostrictive element 11 in the cylinder and fixes one end 11 a of the magnetostrictive
element 11. The bias magnetic field generating magnet 15 is provided substantially at the center
of the yoke 14 so as to cover the outer wall of the yoke 14. The first magnetic field generating
coil 16 is wound along the inner inner wall of the yoke 14 without being in contact with the
magnetostrictive element 11. The voice coil bobbin 21 is interposed between one end 11 b of the
magnetostrictive element 11 and the opening of the yoke 14 and penetrates the approximate
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center of the damper 12. The movable coil 20 is wound around the outer wall of the voice coil
bobbin 21 disposed in the air gap 19 on the opening side of the yoke 14. The conical frame 17 is
fixed so as to cover the outer wall on one end side of the yoke 14 along the circumferential
direction. The diaphragm 18 for low frequency reproduction is fixed so as to cover the outer wall
on one end side of the voice coil bobbin 21 along the circumferential direction, and the
peripheral portion near the edge portion 18a is fixed to the peripheral portion of the frame 17 It
has a conical shape. The diaphragm 22 for high frequency reproduction has a conical shape fixed
to the end 11 b of the magnetostrictive element 11. The reproduction of the sound in the low
band or high band in such a configuration is performed by the method described below.
First, a method for reproducing low-range sound will be described. As shown in FIGS. 3 (a) and 3
(b), a magnetic field is formed by the yoke 14 at the position of the movable coil 20 (see the code
s30 in the magnetic circuit shown in FIG. 3 (b)). When a voice current flows through the coil 20,
an electromagnetic force acts on the voice coil bobbin 21 to vibrate the voice coil bobbin 21 in
the left-right direction toward the paper surface. The vibration of the voice coil bobbin 21 is
transmitted to the diaphragm 18 for low-range reproduction, and a low-range sound wave is
emitted from the diaphragm 18. That is, this is the same method of reproducing sound as the
electrodynamic speaker. Next, a method for reproducing high-range sound will be described,
which is substantially the same as the method described in the first embodiment. That is, when a
high frequency sound current flows in the magnetic field generating coil 16, a change of the
magnetic field occurs in the axial direction of the magnetostrictive element 11, and the
magnetostrictive element 11 expands and contracts (oscillates) in the axial direction X. This
vibration by the magnetostrictive element 11 is transmitted to the diaphragm 22 for high
frequency range reproduction, and a high frequency sound wave is emitted from the vibration
plate 22. However, the speaker device 200 according to the second embodiment is different from
the speaker device 100 according to the first embodiment in that one end 11a of the
magnetostrictive element 11 is fixed to the yoke 14. Therefore, the first embodiment The
amplitude of the vibration of the magnetostrictive element 11 is approximately doubled as
compared with the speaker device 100 according to the above. Thus, the speaker device 200
according to the second embodiment can reproduce higher frequency sounds. As described
above, the speaker device 200 according to the second embodiment applies the principle of the
electrodynamic speaker to the speaker device using the magnetostrictive element suitable for
high frequency band reproduction and reproduces the low frequency band. Thus, the audio
signal can be reproduced over a wide band from the low band to the high band. Thus, it is
possible to provide an extended tweeter in the low range. Next, various examples of the
electronic circuit applicable to the speaker device 200 according to the second embodiment are
shown in FIGS. 4 (a) to 4 (c). First, in FIG. 4A, a closed circuit C2 for driving the diaphragm 22
(tweeter) for high-frequency reproduction and a closed circuit C3 for driving the diaphragm 18
(woofer) for low-frequency reproduction Are connected in parallel. In the closed circuit C2 shown
in FIG. 4A, a closed circuit is configured by connecting in series a magnetic field generating coil
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16 for driving the diaphragm 22 for high frequency range reproduction and a high pass filter Hf.
Therefore, when an audio current is applied to the input terminal S1, in the closed circuit C2, the
high pass filter Hf cuts the audio current of the low frequency component and supplies the audio
current of a constant high frequency component to the magnetic field generating coil 16 side. .
Then, when an audio current of a constant high frequency flows in the magnetic field generating
coil 16, the magnetostrictive element 11 expands and contracts (oscillates) in the axial direction
of the speaker device 200 and vibrates the diaphragm 22 for high frequency band reproduction.
Therefore, the closed circuit C2 reproduces the high frequency sound through the high
frequency reproduction diaphragm 22. On the other hand, in the closed circuit C3 shown in FIG.
4A, the closed circuit is configured by serially connecting the movable coil 20 for driving the
diaphragm 18 for low-range reproduction and the low pass filter Lf. . Therefore, when the audio
current is applied to the input terminal S1, the low pass filter Lf cuts the audio current of the
high frequency component in the closed circuit C3 and supplies the audio current of a constant
low frequency component to the movable coil 20. Then, when a constant low frequency sound
current flows through the movable coil 20, the voice coil bobbin 21 is displaced, and the
diaphragm 18 for low frequency reproduction is vibrated. Thus, the closed circuit C3 reproduces
the low frequency sound through the low frequency reproduction diaphragm 18. As described
above, by applying the electronic circuit C100 shown in FIG. 4A to the speaker device 200, it is
possible to reproduce voices in a wide band from the low band to the high band. Next, in FIG. 4B,
an electron in which a closed circuit C5 for driving the diaphragm 22 for high-frequency
reproduction and a closed circuit C6 for driving the diaphragm 18 for low-frequency
reproduction are connected in parallel. Circuit C 200 is shown. In the closed circuit C5 shown in
FIG. 4 (b), unlike the above-described closed circuit C2 shown in FIG. 4 (a), the high pass filter Hf
is not provided. Therefore, in the closed circuit C5, when an audio current containing a low
frequency component and a high frequency component is applied to the input terminal S1, the
audio current flows in the magnetic field generating coil 16. However, since the magnetostrictive
element 11 has a property that the vibration velocity is small depending on the change of the
magnetic field corresponding to the audio current of the low frequency component, it vibrates at
a large vibration velocity only by the change of the magnetic field corresponding to the audio
current of the high frequency component become. Therefore, by the closed circuit C5, only the
audio signal of the high frequency band is reproduced through the diaphragm 22 for high
frequency band reproduction. Further, in the closed circuit C6 shown in FIG. 4B, unlike the
above-described closed circuit C3 shown in FIG. 4A, the low pass filter Lf is not provided.
However, in the closed circuit C6, by applying an audio current of a low frequency component to
the input terminal S1, the audio current flows through the movable coil 20 and vibrates the voice
coil bobbin 21 in the axial direction of the speaker device 200.
As a result, the diaphragm 18 for low range reproduction is vibrated. Therefore, the closed circuit
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C6 reproduces the low-range audio signal through the low-range reproduction diaphragm 18. As
described above, when the electronic circuit C200 shown in FIG. 4B is applied to the speaker
device 200, the voice over the wide band from the low band to the high band without providing
the high pass filter Hf or the low pass filter Lf. Regeneration of the signal takes place. In FIG. 4C,
an electronic circuit C300 in which a magnetic field generating coil 16 for driving the diaphragm
22 for high-frequency reproduction and a movable coil 20 for driving the diaphragm 18 for lowfrequency reproduction are connected in series. Is shown. In the electronic circuit C300 shown in
FIG. 4C, when an audio current containing a low frequency component and a high frequency
component is applied to the input terminal S1, the audio current flows to the magnetic field
generating coil 16 and the movable coil 20. . Thereby, the magnetostrictive element 11 vibrates
at a large vibration velocity only by the change of the magnetic field corresponding to the audio
current of the high frequency component, and reproduces the high frequency sound through the
diaphragm 22 for high frequency reproduction. On the other hand, when a low frequency
component audio current flows through the movable coil 20, the voice coil bobbin 21 is vibrated
in the axial direction of the speaker device 200. Thus, the low frequency sound is reproduced
through the low frequency reproduction diaphragm 18. Therefore, when the electronic circuit
C300 shown in FIG. 4C is applied to the speaker device 200, the high pass filter Hf and the low
pass filter Lf are not provided as in the electronic circuit C200 shown in FIG. 4B. The sound can
be reproduced over a wide band from low to high. Third Embodiment A speaker device 300
according to a third embodiment is one in which the magnetic field generating coil 16 and the
movable coil 20 in the speaker device 200 according to the second embodiment described above
are constituted by one coil. . A sectional view along the axial direction of the speaker device 300
is shown in FIG. The configuration of the speaker device 300 is almost the same as the
configuration of the speaker device 200 according to the second embodiment described above.
Therefore, only parts of the configuration different from the speaker device 200 according to the
second embodiment will be described. In the illustrated speaker apparatus 300, the same
components as those of the speaker apparatus 200 according to the second embodiment are
designated by the same reference numerals. The speaker device 300 of this embodiment uses a
long voice coil bobbin 121 extending from the vicinity of the damper 12 to the vicinity of one
end 11 a of the magnetostrictive element 11 as shown in FIG. I'm turning.
The coil 120 has the functions of both the magnetic field generating coil 16 and the movable coil
20 in the second embodiment. In the speaker device 300 having such a configuration, when an
audio current of a low frequency component flows in the coil 120, the voice coil bobbin 121
vibrates in the axial direction X of the speaker device 300 according to the principle of
electromagnetic action. Then, this vibration is transmitted to the diaphragm 18 for low range
reproduction, and a sound wave in the low range is emitted from the diaphragm 18. At this time,
although the change of the magnetic field occurs in the magnetostrictive element 11, the
vibration speed is small due to the change of the magnetic field corresponding to the audio
current of the low frequency component. On the other hand, when a voice current of a high
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frequency component flows through the magnetic field generating coil 120, a change of the
magnetic field occurs in the axial direction X of the magnetostrictive element 11, and the
magnetostrictive element 11 expands and contracts (oscillates) in the axial direction X. Then, the
vibration due to the magnetostrictive element 11 is transmitted to the diaphragm 22 for high
frequency range reproduction, and a high frequency sound wave is emitted from the vibration
plate 22. As described above, the speaker device 300 according to the third embodiment can
reproduce sound over a wide band from low to high frequencies by using one coil.
[Modifications] In the first to third embodiments, the bias magnetic field generating magnets 5
and 15 are provided to generate a magnetic field in the speaker devices 100, 200 and 300, but
instead of this or in addition to this, Alternatively, a coil wound with a conducting wire may be
provided, and a magnetic field may be generated by supplying a current to the conducting wire.
Further, an audio current may be superimposed on the current on this coil. BRIEF DESCRIPTION
OF THE DRAWINGS FIG. 1 shows an axial sectional view of a speaker device according to a first
embodiment of the present invention. FIG. 2 shows displacement states of the magnetostrictive
element when one end of the magnetostrictive element is fixed and when both ends are not fixed.
FIG. 3 shows an axial sectional view of a speaker device according to a second embodiment of the
present invention and a sectional view of a magnetic circuit portion. FIG. 4 shows various
examples of an electronic circuit applicable to the speaker device according to the second
embodiment of the present invention. FIG. 5 is a cross-sectional view along the axial direction of
a speaker device according to a third embodiment of the present invention. [Explanation of the
code] 1, 11 Magnetostrictive element 4, 14 Yoke 5, 15 Bias magnetic field generating magnet 6,
16 Magnetic field generating coil 7, 17 Frame 8, 18, 22 Diaphragm 9, 19 Air gap 20 Movable
coil 21, 121 Voice coil bobbin 100, 200, 300 speaker devices
04-05-2019
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