JP2002112387

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DESCRIPTION JP2002112387
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker for reducing the stiffness of a support system by a magnetic attraction force to expand
the bass reproduction limit and a speaker system equipped with the same.
[0002]
2. Description of the Related Art A conventional speaker comprises a drive means for generating
a vibrational force by electrical input, a movable portion vibrated by the force generated by the
drive means, and a suspension for supporting the movable portion. Speaker system was
configured. For example, in an electrodynamic speaker, a magnetic circuit and a voice coil
inserted in the magnetic gap are driving means, and when an electrical signal is input to the voice
coil, the magnetic flux in the magnetic gap generates a force in the voice coil It is a thing. The
force generated in the voice coil is transmitted to a movable portion constituted by a voice coil
bobbin wound with the voice coil and a diaphragm joined to the tip end thereof. A damper, which
is a suspension for supporting the movable portion, and an edge are respectively joined to the
outer peripheral portion of the voice coil bobbin and the outer peripheral portion of the
diaphragm.
[0003]
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In such a conventional speaker, it is well known that the reproduction limit of the bass is
determined by the vibrating mass including the movable portion and the suspension and the
lowest resonance frequency determined by the stiffness of the suspension. is there. Furthermore,
when mounted in a cabinet, air pressure is applied to the back of the diaphragm and is affected
by the stiffness of the air. If the cabinet has a large enough volume, the lowest resonance
frequency of the speaker will not change significantly, but in most cases the speaker will be
mounted in a small cabinet for miniaturisation, resulting in air stiffness within the cabinet As the
lowest resonance frequency rises, the lack of the bass range reproduced from the speaker
becomes a problem.
[0004]
The present invention solves the above-mentioned problem, and reduces the stiffness value
determined by the speaker suspension or the cabinet volume of the speaker system by the
magnetic attraction force that cancels the stiffness, and reproduces enough bass with a small
cabinet. Purpose.
[0005]
[Means for Solving the Problems] In order to achieve the above object, the present invention
supports a drive means for generating a vibrational force by an electrical input, a movable part in
which a vibration is induced by the drive means, and a support for the movable part. The speaker
is composed of the magnetic pole piece and the two magnetic poles, the suspension, the magnetic
pole piece integrated with the movable portion, and at least two magnetic poles disposed facing
the magnetic pole piece.
Here, a magnetic attraction force is generated between the pole piece joined to the movable
portion and the pole piece disposed opposite to the pole piece. Therefore, the stiffness value of
the suspension supporting the movable part can be reduced by the magnetic attraction force
acting in the direction to cancel it.
[0006]
Further, the driving means is a voice circuit inserted in a magnetic circuit and a magnetic gap of
the magnetic circuit, and the movable portion is connected to a voice coil bobbin joined to the
voice coil and one end of the voice coil bobbin The diaphragm is an electrodynamic speaker.
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[0007]
Furthermore, the magnetic pole piece is joined to the inner peripheral surface of the voice coil
bobbin, and the two magnetic poles disposed opposite to the magnetic pole piece are provided on
the inner peripheral side of the voice coil bobbin, so that The generation unit can be configured
inside the voice coil bobbin, which has conventionally been hollow, and can realize a speaker
capable of reproducing the low frequency range with the same size as the conventional one.
[0008]
Furthermore, by integrating the piezoelectric body and the pole piece by using the driving means
as a piezoelectric body, it is possible to reduce the lowest resonance frequency of the speaker
using the piezoelectric body.
Furthermore, if the pole piece is used as an electrode for supplying electricity to the piezoelectric
body and the electrode is used as a suspension for supporting the piezoelectric body, the
electrode forms a movable part integrally with the piezoelectric body, and further, the pole piece
A magnetic attraction force is generated between the electrode and the magnetic pole disposed
opposite to the pole piece to reduce the stiffness value of the suspension which is also the
electrode, thereby realizing a piezoelectric speaker capable of reproducing the bass region. It is a
thing.
[0009]
Furthermore, when the pole piece is a magnetic body, the two poles are permanent magnets, and
when the pole piece is a permanent magnet, the two poles are magnetic bodies, or the pole piece
and the two poles are permanent. By the combination of the magnets, the value of the magnetic
attraction can be set to an arbitrary value in a wide range, and the magnetic attraction can be
optimized for the speaker to be applied.
[0010]
Furthermore, if the speaker of the above configuration is attached to the cabinet and the
magnetic attraction is set in consideration of the air stiffness in the cabinet, the magnetic
attraction is the stiffness of the speaker suspension and that of the cabinet air. It is possible to
realize a speaker system which can reduce the synthetic value and can reproduce a small and
rich bass.
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In this case, it is desirable that the combined value of the air stiffness of the cabinet and the
stiffness of the speaker suspension be greater than the magnetic attraction force.
This can prevent the pole piece from being attracted to either of the two magnetic poles.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 Hereinafter, an embodiment of
the present invention will be described with reference to the drawings.
[0012]
The speaker in the first embodiment will be described with reference to (a) and (b) of FIG.
However, (a) of FIG. 1 is a plan view of the speaker, and (b) of FIG. 1 is a cross-sectional view of
the speaker of (a) taken along the line A-B. The speaker is configured as follows. A magnet 1 has
a center pole 2 fixed to the upper surface thereof and a wedge-shaped yoke 3 fixed to the lower
surface thereof to form a magnetic circuit. The voice coil 5 wound around the voice coil bobbin 4
is inserted in the magnetic gap formed by the outer peripheral surface of the center pole 2 and
the inner peripheral surface of the cylindrical portion of the wedge-shaped yoke 3. Is fixed. The
edge 7 which is one of the suspensions is joined to the outer peripheral portion of the diaphragm
6, and the damper 8 is joined to the outer peripheral portion of the voice coil bobbin 4. The
central portion of each outer peripheral portion is fixed to the yoke 3. Is joined to the frame 9. A
doughnut-shaped pole piece 10, which is a ferromagnetic material such as an iron material or
permalloy, is joined to the inner periphery of the voice coil bobbin 4, for example. The magnetic
poles 11 and 12 which are magnetized in a donut shape of a magnet material such as
neodymium, ferrite or the like with an N pole on the upper surface and an S pole on the lower
surface, for example, adhere to the upper surface of the center pole 2 It is fixed to the supported
support 13.
[0013]
The operation of the loudspeaker configured as described above will be described. When an
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electrical signal is input to the voice coil 5, a current flows through the voice coil 5 to generate
an oscillating force in the magnetic gap between the voice coil 5, the center pole 2 of the
magnetic circuit, and the yoke 3. The voice coil bobbin 4 and the diaphragm 6 joined thereto
constitute a movable portion, and the movable portion is supported by the edge 7 as a
suspension and the damper 8 so that the vibration force generated in the voice coil 5 is a voice
The diaphragm 6 is vibrated via the coil bobbin 4. The pole piece 10 joined to the inner
peripheral surface of the voice coil bobbin 4 oscillates up and down with the vibration of the
voice coil bobbin 4. Since the magnetic poles 11 and 12 are provided opposite to each other in
the amplitude direction of the pole piece 10, in the case of amplitude on the upper surface, they
approach the magnet pole 11, the pole piece 10 is ferromagnetic, and the pole 11 is a magnet
Therefore, a magnetic attractive force is exerted between the pole piece 10 and the magnetic
pole 11, and when the voice coil bobbin 4 is oscillated on the lower surface, magnetic attraction
is similarly caused between the pole piece 10 and the magnetic pole 12 Power is what works.
The magnetic attraction force between the magnetic poles 11 and 12 accompanying the vertical
amplitude of the pole piece 10 works in the direction of promoting the movement of the movable
portion constituted by the voice coil bobbin 4 and the diaphragm 6. Usually, the lowest
resonance frequency f0 is used as a scale for determining the limit of the bass reproduction
frequency of the speaker. This f0 is obtained as in (Equation 1) by the mass of the vibration
system composed of the movable portion of the speaker and the suspension and the stiffness of
the suspension.
[0015]
However, f01: lowest resonance frequency Sms: suspension stiffness Mms: mass of the vibration
system The spring force of the suspension acts to suppress the movement of the movable portion
as the amplitude increases, whereas the pole piece 10 The magnetic attraction force acting
between the magnetic pole and the magnetic poles 11 and 12 works in the direction to promote
the amplitude of the movable part as the magnetic attraction force increases as the distance
between the pole piece 10 and the magnetic poles 11 and 12 decreases. It is. Therefore, the
stiffness exhibited by the suspension supporting the movable portion is a combined value of the
stiffness of the suspension and the stiffness exhibited by the magnetic attraction force, and the
lowest resonance frequency f02 is
[0017]
However, f02: lowest resonance frequency Smm: stiffness represented by magnetic attraction
Sms: suspension stiffness Mmt: mass of vibration system including pole pieces, composite
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stiffness value is smaller than in the case of equation (1) As a result, it is possible to lower the
lowest resonance frequency f02. In (Equation 2), since the mass of the vibration system also
includes the mass of the pole piece 10, the pole piece 10 also has an action to lower the
minimum resonance frequency f02, but increasing the mass of the vibration system It is
desirable to make it as lightweight as possible to reduce levels.
[0018]
In the first embodiment, the pole piece is a ferromagnetic body and the pole is a magnet, but as
shown in FIG. 2, the pole piece 14 is disposed opposite to a magnet material such as neodymium
or ferrite, etc. The magnetic poles 15 and 16 may be ferromagnetic such as iron or permalloy.
Furthermore, as shown in FIG. 3, the materials of the pole piece 100 and the magnetic poles 101
and 102 may all be magnet materials. In this case, since the magnetic attraction can be further
increased, the stiffness exhibited by the magnetic attraction is increased, and the stiffness of the
suspension can be largely canceled to further reduce the lowest resonance frequency f02 of the
speaker. In the embodiment shown in FIGS. 1, 2 and 3, in the dimensional relationship between
the pole piece and the pole facing it, the inner diameter of the donut-shaped pole piece is larger
than the outer diameter of the donut-shaped pole, ie, the pole piece In the case of large
amplitude, the pole piece collides with the magnetic pole. However, as shown in FIG. 4, the inner
diameter of the pole piece 18 is larger than the outer diameter of the magnetic poles 19 and 20,
and in any case Can be avoided. In this case, since the facing area between the pole piece and the
magnetic pole decreases, the magnetic attraction force is reduced, but the desired magnetic
attraction force can be obtained by adopting a magnet having a larger energy product.
Furthermore, although both of the pole piece 18 and the magnetic poles 19 and 20 are magnet
materials in FIG. 4, either of them may be ferromagnetic. Further, the value of the magnetic
attraction force needs to be set widely depending on the characteristics of the speaker, the
purpose of use, etc. However, the magnetic characteristics of the pole piece or the magnetic pole
is a design problem to be selected arbitrarily. For example, a weak magnetic material such as
stainless steel may be used as long as the magnetic material generates an attractive force.
[0019]
Second Embodiment Next, a speaker according to a second embodiment will be described with
reference to FIGS. 5 (a) and 5 (b). However, Fig.5 (a) is a top view of a speaker, (b) is sectional
drawing of the CD cross section of the speaker of Fig.5 (a). The speaker is configured as follows.
The piezoelectric members 22 and 23 are fixed to both surfaces of an electrode 24 made of a
magnetic material such as permalloy. The outer peripheral portion of the electrode 24 is fixed to
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the upper and lower surfaces by an upper case 25 and a lower case 26 provided with a plurality
of sound holes 27 and 28, and the central portion of the upper case 25 and the lower case 26 is
opposed to the electrode 24 The magnets 29, 30 are disposed. Reference numerals 31 and 32
denote electrical input parts, 31 is connected to the electrode 24, and 32 is connected to the
piezoelectric members 22 and 23.
[0020]
The operation of the speaker configured as described above will be described. When an electrical
signal is input to the electrical input portions 31 and 32, voltages are applied to the upper
surfaces of the electrodes 24 and the piezoelectric body 22 and the lower surface of the
piezoelectric body 22 and the piezoelectric bodies 22 and 23 expand and contract. The movable
part thus configured vibrates. Since the outer peripheral portion of the electrode 24 is fixed to
the upper case 25 and the lower case 26, the electrode 24 also acts as a suspension of the
movable portion. When there is no electrical input, if the distance between the electrode 24 and
the magnet 29 attached to the upper case 25 and the magnet 30 attached to the lower case 26 is
set equal, the magnetic attraction force acting on the electrode which is a magnetic body Are
approximately equally balanced, and no magnetic attraction effects occur. Next, when the
piezoelectric members 22 and 23 expand and contract due to an electrical input and the movable
portion vibrates on the upper surface, the electrode 24 approaches the magnet 29 provided on
the upper case 25 and is attracted by the magnetic force. When the movable portion is oscillated
on the lower surface, the electrode 24 is similarly attracted to the magnet 30 provided on the
lower case 26. As described in the first embodiment, the minimum resonance frequency for
determining the bass reproduction limit frequency of the speaker is determined by the mass of
the vibration system including the movable portion and the suspension and the stiffness of the
suspension also in the present embodiment. However, the magnetic attraction generated between
the electrode 24 and the magnets 29 and 30 acts in the direction to cancel the stiffness of the
suspension, which makes it possible to lower the lowest resonance frequency.
[0021]
Although a magnetic material is used for the electrode in this embodiment, brass or phosphor
bronze having a high electrical conductivity is usually used as the electrode material, and in this
case, a magnetic material or a magnet material is used for the piezoelectric surface. The same
effect can be obtained by forming the pole piece. Further, in the present embodiment, an
application example of the bimorph in which the piezoelectric body is disposed on both sides of
the electrode has been described, but the present invention can also be applied to a monomorph
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piezoelectric loudspeaker in which the piezoelectric body is provided on one side of the
electrode.
[0022]
Furthermore, although the application to the electrodynamic speaker using a voice coil and the
piezoelectric speaker using a piezoelectric body has been described in the above embodiment, a
driving force is generated in a movable portion such as an electrostatic speaker using
electrostatic force. It is applicable to the converter of the various electro-mechanical conversion
system which has a means.
[0023]
Third Embodiment Next, a speaker system according to a third embodiment will be described
with reference to FIG.
However, FIG. 6 is a cross-sectional view of the speaker system. The speaker system is configured
as follows. A speaker 33 according to the first embodiment described with reference to FIG. 1 is
attached to the speaker cabinet 34. Reference numeral 35 denotes a vacant room constituted by
the back of the speaker 33 and the cabinet 34.
[0024]
The operation of the speaker system configured as described above will be described. The
operation when an electrical input is applied to the speaker 33 has already been described, and
thus is omitted to avoid duplication. The difference between the present embodiment and the
first embodiment is that the speaker 33 is attached to the cabinet. As a result, the movable part
of the speaker is affected by the stiffness of the air presented by the cavity 35. The stiffness of
the air is determined by the volume of the cavity 35, but since the speaker system is desired to
be as small as possible, the volume 35 is designed to be small and the lowest resonance
frequency is the speaker 33 alone due to the influence of the air stiffness. It is the conventional
speaker system that is rising more than the one. For example, assuming that the diaphragm
diameter of the speaker is 160 mm, the mass of the vibration system is 10 g, and the lowest
resonance frequency is 50 Hz, the stiffness of the suspension Sms = 987 (N / m) according to
(Equation 1). Assuming that the internal volume of the speaker cabinet is 20 liters, the stiffness
Smb exhibited by the vacant space at the back of the speaker is 2822 (N / m), and the stiffness of
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the speaker system is 3809 (N / m) which is a combined value of Sms and Smb. . As a result, the
lowest resonance frequency of the speaker system is determined by the combined stiffness and
the vibration system mass of the speaker, and the lowest resonance frequency of the speaker
alone rises from 50 Hz to 98 Hz.
[0025]
Next, when the speaker 33 having the configuration described in the first embodiment is
attached to the speaker system of the same volume, the stiffness Smm exhibited by the magnetic
attraction force acting on the diaphragm acts to cancel the stiffness Sms of the suspension.
Therefore, assuming almost complete cancellation, Sms-Smm ≒ 0, and the lowest resonance
frequency of the speaker system can be reduced to 85 Hz, which conventionally increases to 98
Hz. Since the magnitude of the magnetic attraction can be set arbitrarily depending on the
material, shape, etc. of the pole piece and the magnetic pole, the stiffness Smm exhibited by the
magnetic attraction can be set to a value larger than the stiffness Sms exhibited by the speaker
suspension. It is. For example, if the value of the stiffness Smm of the magnetic attraction is set to
2822 (N / m) the same size as the stiffness Smb of the cabinet, the synthetic stiffness as the
speaker system is Sms + Smb-Smm = 987 + 2822-2822 = 987 (N / M), the stiffness exhibited by
the cabinet 34 of the cabinet is canceled out, and 50 Hz which is the lowest resonance frequency
of the single speaker can be realized by the cabinet of 20 liters. Furthermore, if the stiffness
exhibited by the magnetic attraction is made greater than the stiffness exhibited by the cabinet,
the lowest resonance frequency can be further lowered.
[0026]
In addition, it is desirable that the value of the stiffness exhibited by the magnetic attraction force
is smaller than the combined value of the stiffness of the suspension of the speaker and the
stiffness exhibited by the empty space of the cabinet. If it is larger than this, the pole piece joined
to the movable part may be attracted to one pole, and the pole piece can not return to the
position where the pole piece is balanced by the magnetic attraction of the two poles which is the
initial position of vibration. There is.
[0027]
In addition, in order to stabilize the value of the stiffness which the vacant space of a cabinet
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exhibits, it is desirable to set it as the speaker and cabinet structure which raise the airtightness
of the vacant space of a speaker cabinet. Furthermore, in the present embodiment, the speaker is
an electrodynamic speaker driven by a voice coil, but there is no problem even if it is the
piezoelectric speaker or electrostatic speaker described in the second embodiment.
[0028]
As described above, according to the speaker of the present invention, the magnetic pole piece is
integrated with the movable portion, and the magnetic attraction force acts between the
magnetic pole disposed at the position opposed to the magnetic pole piece. Therefore, when the
movable part oscillates, the pole piece approaches the magnetic pole to increase the magnetic
attraction force, thereby canceling the spring force of the suspension supporting the movable
part and reducing the minimum resonance frequency of the speaker to reduce the bass
reproduction limit frequency. It is possible to lower Further, in the speaker system in which the
speaker of the present invention is attached to the cabinet, the stiffness exhibited by the empty
space of the cabinet can be canceled by the magnetic attraction presented to the pole piece, and
the deep bass which can not be reproduced conventionally by the small speaker system A
reproducible speaker system can be realized.
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