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JPH06141396

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH06141396
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electrodynamic speaker which energizes a voice coil to obtain an electromagnetic driving force.
[0002]
BACKGROUND OF THE INVENTION FIG. 7 is a cross-sectional view of a typical prior art
loudspeaker 61. As shown in FIG. The magnetic circuit of the speaker 61 is an external magnet
type in which an annular permanent magnet 65 is held between a bottom yoke 63 and a top
plate 64, and a frame 66 is attached to the top plate 64. A bobbin 68 is disposed in the magnetic
air gap formed between the bottom yoke 63 and the top plate 64. The voice coil 67 is wound
around the bobbin 68, and the frame 66 and the cone 69 are supported by the damper 62. The
proximal end of the cone 69 is bonded to the tip of the bobbin 68 by an adhesive. The outer
peripheral edge of the cone 69 is connected to the radially inward portion of the edge 70, and
the radially outer portion of the edge 70 is sandwiched and joined by the frame 66 and the
gasket 71. The gasket 71 is provided with a plurality of insertion holes, and a lower part of the
insertion hole is provided with a mounting hole, and a screw or the like is used to fix the
mounting hole to this portion. A dust cap 72 is attached to the end of the bobbin 68. The damper
62 is formed, for example, by impregnating a cloth with a resin such as phenol, and the like. In
addition, a corrugation is formed concentrically with the bobbin 68 in the damper 62, and thus
the braking effect of the cone 69 is obtained.
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[0003]
In the speaker 61, when the drive power is supplied, an axial drive force is induced based on the
magnetic action between the magnetic gap and the voice coil 67. This force is transmitted to the
cone 69 which is a diaphragm via the bobbin 68. The cone 69 vibrates back and forth under the
action of this driving force to radiate sound waves toward the space on the front.
[0004]
[Problems to be Solved by the Invention] In order to reproduce the sense of presence, which is an
important factor in playing music, it is important to increase the maximum sound pressure level
as much as possible in order to increase the so-called dynamic range. It becomes. In order to
increase the maximum sound pressure level to realize reproduction at a large volume, the driving
current to be sent is increased to increase the axial driving force based on the electromagnetic
action between the magnetic gap and the voice coil 67. It will be necessary. However, most of the
drive current is more easily converted to heat energy than the acoustic energy which is the drive
force, heat is generated in the voice coil 67, and the temperature in the vicinity of the voice coil
67 rises with the lapse of reproduction time. As a result, the resin such as varnish bonding the
voice coil 67 becomes soft, causing a problem that distortion increases when transmitting the
driving force, and frequency characteristics deteriorate. In addition, the heat generated by the
voice coil 67 may cause the paper bobbin 68 to burn.
[0005]
Therefore, if the diameter of the winding of the voice coil 67 is increased in order to suppress the
heat generation of the voice coil 67, a large magnetic circuit is required, and a new problem that
the entire speaker 61 is increased in size occurs. However, if the temperature of the heat
generated in the voice coil 67 exceeds a certain temperature, the normal operation as a speaker
is lost. As described above, since the heat-resistant temperature is one factor that determines the
range of the allowable input, it is possible to reproduce the speaker 61 with higher fidelity by
suppressing the heat generation.
[0006]
Therefore, an object of the present invention is to provide a speaker capable of improving input
resistance and frequency characteristics by suppressing the temperature rise of the voice coil.
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2
[0007]
SUMMARY OF THE INVENTION The present invention relates to a speaker in which a speaker
frame is attached to a magnetic circuit, in which a groove communicating from an inner diameter
side to an outer diameter side is formed in an attachment surface of the speaker frame to the
magnetic circuit. It is a speaker to be characterized.
[0008]
Further, according to the present invention, in a speaker in which a voice coil is inserted into a
magnetic gap formed in a magnetic circuit and electromagnetically driven, the speaker is formed
of a shape memory material in the vicinity of the magnetic circuit and is closed at normal
operating temperature. It is a speaker characterized by providing an opening-and-closing
member opened at more than fixed temperature.
[0009]
According to the present invention, the speaker frame is attached to the magnetic circuit in
which the annular magnet is held between the bottom yoke and the top plate, and the mounting
surface of the speaker frame to the magnetic circuit has an outer diameter from the inner
diameter side. A groove communicating with the side is provided to constitute a speaker.
Normally, the vicinity of the magnetic circuit is sealed by a dust cap or a damper, and there is no
air flow from the outside.
When the voice coil is driven, the air inside flows, so that the heat generated from the voice coil
can be dissipated through the groove, and cold air from the outside can be taken inside to
suppress the temperature rise.
[0010]
Further, according to the present invention, the voice coil is inserted into the magnetic gap
formed in the magnetic circuit, and the speaker is electromagnetically driven.
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An open / close member formed of a shape memory material is provided in the vicinity of the
magnetic circuit of the speaker, and is closed at a normal operating temperature. When the
temperature in the vicinity of the magnetic circuit rises due to the heat generated from the voice
coil and reaches a predetermined temperature or more, the open / close member is opened to
cause the flow of internal and external air, thereby suppressing the temperature rise.
[0011]
1 is a cross-sectional view showing the structure of a speaker 1 according to a first embodiment
of the present invention, FIG. 2 is a front view of the speaker 1 excluding a vibration system, and
FIG. It is sectional drawing of the speaker 1 seen from cutting plane line III-III. The magnetic
circuit of the speaker 1 is an external magnet type in which an annular permanent magnet 5 is
held between a bottom yoke 3 made of a soft steel such as SPCD and a top plate 4. A frame 6
made of iron or aluminum die-cast is fixed to the top plate 4 by screwing or caulking. In the case
where the frame 6 is a cast-formed product such as aluminum die-casting, drawing is performed
in the forming step, or in the case of iron in the pressing step, the surface 6 contacts the top
plate 4, for example As shown in FIG. 2, grooves 13 a, 13 b, 13 c, 13 d (hereinafter sometimes
collectively referred to as “13”) are formed orthogonally to each other with the center of
bottom yoke 3 as an intersection point. I try to escape the heat that The magnetic flux generated
from the permanent magnet 5 is concentrated in the magnetic gap 8g between the bottom yoke
3 and the top plate 4, and the bobbin 8 is disposed. A voice coil 7 is wound around a heatresistant paper bobbin 8 and a frame 6 and a cone 9 are supported by a damper. The proximal
end of the cone 9 is bonded to the distal end of the bobbin 8 by an adhesive. The outer
peripheral edge of the cone 9 is connected to the radially inward portion of the edge 10, and the
radially outward portion of the edge 10 is sandwiched and joined by the frame 6 and the gasket
11. The edge 10 may be formed of a material other than the cone 9, for example, a foamed
urethane resin, and may be bonded to the cone 9.
[0012]
The gasket 11 is provided with a plurality of insertion holes, and a mounting hole is provided in
the lower portion of the insertion hole, and a cabinet or the like is fixed to this portion using a
screw or the like. A dust cap 12 made of paper, rubber, metal or the like is attached to the end of
the bobbin 8 to prevent the intrusion of dust and the like. The damper 2 is formed, for example,
by impregnating a cloth with a resin such as phenol, and the like by heat molding. A corrugation
is formed concentrically with the bobbin 8 in the damper 2 and holds the bobbin 8 so as to be
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4
displaceable in the axial direction. The damper 2 and the edge 10 have a moderate internal loss
and obtain the braking effect of the cone 9. FIG. 1 is a cross-sectional view taken along the line I-I
of FIG.
[0013]
When driving power is supplied to the speaker 1, an axial driving force is induced based on the
electromagnetic interaction between the magnetic flux generated in the magnetic gap 8g and the
current flowing through the voice coil 7. This force is transmitted to the cone 9 which is a
diaphragm via the bobbin 8. The vibration system such as the cone 9 and the dust cap 12
vibrates back and forth in the axial direction under the action of this driving force, and radiates a
sound wave toward the front space.
[0014]
In this embodiment, when the bobbin 8 vibrates back and forth by the driving force in the axial
direction, heat accumulated in the magnetic circuit portion is dissipated through the groove 13
and outside air is taken in the magnetic circuit to suppress temperature rise. . Therefore, the
input resistance characteristic can be improved, the deterioration of the frequency characteristic
and the distortion characteristic can be prevented, and sound reproduction with higher fidelity
can be realized. When the frame 6 is made of iron and the groove 13 is formed by drawing, the
strength of the frame 6 can be improved by forming the groove-like rib, and the resonance can
be reduced. Further, since the contact surface with the top plate 4 is reduced by the formation of
the groove 13, the vibration of the magnetic circuit portion and the leakage flux from the frame 6
can be reduced.
[0015]
FIG. 4 is a cross-sectional view showing the structure of the speaker 21 of the second
embodiment of the present invention. The same reference numerals as those in the first
embodiment are given except for the characteristic parts of this embodiment. In the present
embodiment, a double cone is used, and a sub cone 34 is provided in addition to a normal cone 9.
A single cone makes it difficult to signal both the low and high range to the cone 9, so a low
frequency signal will be received and vibrated by the normal cone 9 and a high frequency signal
will be received by the sub cone 34. Vibrate. Further, the dust cap 32 for preventing the intrusion
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of dust and the like is made of a shape memory alloy made of, for example, a Ti-Ni alloy and
attached.
[0016]
FIG. 5 is an enlarged front view of the dust cap 32 of the present embodiment. As shown in FIG. 5
(1), a slit 32 a is formed at the center of the dust cap 32. When the speaker 21 is driven with
high power for a long time or excessive input is performed, heat is generated from the voice coil
7 or the magnetic circuit, and the temperature in the vicinity of the magnetic circuit rises. When
this temperature exceeds a predetermined temperature, as shown in FIG. 5 (2), the shape in the
vicinity of the slit 32 a changes and the slit 32 a is flipped up to form the insertion hole 32 b to
release the internal heat and the outside air is inside Break into Thus, when the temperature
drops below the predetermined temperature, the insertion hole 32b is closed again by returning
to the original shape as shown in FIG. 5 (1). Therefore, the same effect as that of the first
embodiment is produced also in the present embodiment.
[0017]
However, when the shape of the dust cap 32 changes and the insertion hole 32b is formed, the
sound quality changes, so that in this state, faithful sound quality reproduction can not be
performed. Therefore, taking measures such as stopping the driving with high power and the
excessive input as one alarm that this sound quality has changed is taken.
[0018]
In addition, although the double cone type speaker 21 is used in the present embodiment, the
same effect can be obtained in the case of a normal single cone.
[0019]
FIG. 6 is a cross-sectional view showing the structure of the speaker 41 of the third embodiment
of the present invention.
Similar to the second embodiment, the same reference numerals as those of the first embodiment
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are given except for the parts characterizing the present embodiment. In the present
embodiment, the communication hole 55 is provided inside the bottom yoke 43 portion. At the
both ends of the communication hole 55, lids 55a and 55b of shape memory alloy made of, for
example, a Ti-Ni alloy are formed so as to close the communication hole 55. Each cover 55a, 55b
opens and closes from the central portion to the left and right to allow the communication hole
55 to be inserted or closed.
[0020]
When the speaker 41 is driven with high power for a long time or excessive input is performed,
heat is generated in the voice coil 7 and the temperature in the vicinity of the magnetic circuit
rises. When the temperature exceeds a predetermined temperature, the shapes of the lids 55a
and 55b change, and the central portions of the lids 55a and 55b open to the left and right, both
ends of the bottom yoke 43 are inserted, and the inside and outside air are exchanged. The heat
near the voice coil 7 is removed. Thus, when the temperature drops below a predetermined
temperature, the lids 55a and 55b at both ends of the bottom yoke 43 return to the original
shape, and the communication hole 55 is closed. Therefore, the same effects as in the first and
second embodiments can be produced also in this embodiment.
[0021]
As described above, according to the present invention, the speaker is formed by forming a
groove communicating from the inner diameter side to the outer diameter side by a method such
as casting or drawing processing on the mounting surface of the speaker frame to the magnetic
circuit. The heat in the magnetic circuit generated by the drive of is driven to the outside, and the
air cooled from the outside is taken in to suppress the temperature rise in the magnetic circuit.
Therefore, the input resistance characteristic is improved, the deterioration of the frequency
characteristic and the distortion characteristic can be prevented, and more faithful sound
reproduction can be performed. Further, when the groove is formed on the iron speaker frame by
drawing, the strength of the speaker frame is improved, the reverberation due to the resonance is
reduced, and the clear sound can be reproduced. Furthermore, since the contact area with the
magnetic circuit is reduced, the leakage flux can be reduced.
[0022]
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Further, according to the present invention, the temperature in the vicinity of the magnetic
circuit is provided by providing an open / close member formed of a shape memory material in
the vicinity of the magnetic circuit, which is normally closed and opens when the temperature in
the magnetic circuit is higher When the pressure rises, the opening and closing member opens to
release the heat in the magnetic circuit to the outside, and the air cooled from the outside is
taken in to suppress the temperature rise in the magnetic circuit. Therefore, the input resistance
characteristic is improved, the deterioration of the frequency characteristic and the distortion
characteristic can be prevented, and more faithful sound reproduction can be performed.
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