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JPH0619396

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DESCRIPTION JPH0619396
[0001]
FIELD OF THE INVENTION This invention relates to the improvement of speakers.
[0002]
2. Description of the Related Art In an electrodynamic speaker, an increase in temperature of the
voice coil is one of the major causes of speaker breakage. When driving an electrodynamic
speaker, most of it is converted to heat with a few percent being converted into sound. Therefore,
as the output of the voice coil increases, the temperature rise thereof increases. As a result, the
voice coil may be destroyed by heat.
[0003]
Also, the temperature rise causes the resistance of the voice coil to increase. Thus, the substantial
dynamic range of the audio input will be reduced, resulting in a hit reduction of the output
voltage. In order to suppress this temperature rise, conventionally several methods as shown
below have been proposed. One end of a heat pipe is disposed on the center pole, and the other
end is used as a heat radiating portion (Japanese Patent Application Laid-Open No. 59-148499).
A part of the magnetic circuit facing the voice coil is provided with a notch, which is used as a
flow path of air at the time of vibration of the voice coil to cool the voice coil (Japanese Utility
Model Application No. 55-100393).
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[0004]
In the above-described method, since the voice coil is not directly cooled, the cooling effect is
delayed when the input becomes large. Also, in the case of the method described above, since the
vibration of the voice coil is used, it is effective in the case of a large input with a large amplitude
bass, but in the case of a large input with a small amplitude in the middle to high range, Cooling
effect is reduced
[0005]
This invention is made in view of such a subject, Comprising: It aims at providing the speaker
which can control the temperature rise of a voice coil certainly.
[0006]
SUMMARY OF THE INVENTION In the present invention for solving the above-mentioned
problems, a thermoelectric conversion element is disposed in the vicinity of a voice coil, and the
heat generated by the voice coil causes a fan to be generated by an electromotive force generated
in the thermoelectric conversion element. The motor is rotated to generate an air flow, and the
air flow is introduced near the voice coil to cool the voice coil.
[0007]
[Operation] The thermoelectric conversion element is disposed in the vicinity of the voice coil.
As a result, an electromotive force corresponding to the temperature rise of the voice coil can be
obtained promptly.
The electromotive force rotates a motor with a fan and directs the air flow generated by the fan
to a voice coil for cooling. That is, since the voice coil is directly cooled by the air flow, a cooling
effect corresponding to the temperature rise can be obtained in combination with the generation
of the electromotive force corresponding to the temperature rise of the voice coil described
above. Also, the cooling effect can be obtained regardless of the amplitude of the vibration of the
voice coil.
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[0008]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be
described in detail with reference to the drawings. FIG. 1 is a sectional view showing an
embodiment of the present invention. In the figure, 1 is a diaphragm (cone), 2 is an edge, 3 is a
cap, and 4 is a frame. 5はガスケット、6はプレート、7はマグネット、8はヨークである。 9
is a voice coil bobbin, 10 is a voice coil wound around the voice coil bobbin 9, and 11 is a
damper. Reference numeral 12 denotes a hole opened in the damper 11. The lead wire to the
voice coil 10 is omitted in the figure.
[0009]
13 is a thermoelectric conversion element disposed in the vicinity of the voice coil 10, 14 is a
motor, and 15 is a fan. The figure shows an example in which two motors 14 and two fans 15 are
provided. Reference numeral 16 denotes a lead wire led from the thermoelectric conversion
element 13 to the motor 14. The operation of the speaker configured in this way will be
described.
[0010]
When an acoustic signal is input to the voice coil disposed in the static magnetic field, a force
according to Fleming's left-hand rule is applied to the voice coil, and the voice coil 10 vibrates up
and down. As a result, the voice coil bobbin 9 vibrates up and down, and the diaphragm 1
vibrates to generate sound.
[0011]
Here, the thermoelectric conversion element 13 disposed in the vicinity of the voice coil 10
generates an electromotive force as the voice coil 10 generates heat. This electromotive force is
sent to the motor 14 through the lead wire 16. As a result, the motor 14 rotates and the fan
rotates to generate an air flow. This air flow flows as shown by the arrow in the figure, and exits
from the hole 12 opened in the damper 11. That is, the air flow entering from the opening 8 a
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opened in the yoke 8 passes through the gap between the plate 6 and the voice coil 10 and exits
the damper hole 12.
[0012]
At this time, the air flow directly strikes the voice coil 10 to cool the voice coil. According to the
present invention, since the voice coil 10 is directly cooled by the air flow, a cooling effect
corresponding to the temperature rise can be obtained together with the generation of the
electromotive force corresponding to the temperature rise of the voice coil described above. Also,
the cooling effect can be obtained regardless of the amplitude of the vibration of the voice coil
10. According to the present invention, since the external power supply is not required, the
speaker unit can be handled alone.
[0013]
FIG. 2 is a sectional view showing another embodiment of the present invention. The same
components as those in FIG. 1 are denoted by the same reference numerals. The thermoelectric
conversion element 13 is attached to the plate 6 so as to surround the voice coil 10 along the
inner surface of the plate 6. The motor 14 and the fan 15 are disposed inside the voice coil
bobbin 9. Here, the fan 15 is a centrifugal fan, and rotates in a direction for sucking in air. The
lead wire from the thermoelectric conversion element 13 to the motor 14 is omitted.
[0014]
In the speaker thus configured, when an acoustic signal is input to the voice coil disposed in the
static magnetic field, a force according to Fleming's left-hand rule is applied to the voice coil, and
the voice coil 10 vibrates up and down. As a result, the voice coil bobbin 9 vibrates up and down,
and the diaphragm 1 vibrates to generate sound.
[0015]
Here, the thermoelectric conversion element 13 disposed in the vicinity of the voice coil 10
generates an electromotive force as the voice coil 10 generates heat. This electromotive force is
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sent to the motor 14 via a lead (not shown). As a result, the motor 14 rotates and the fan rotates
to generate an air flow. That is, air is sucked from the opening provided in the yoke 8. The drawn
air flow flows in the direction shown by the arrow in the figure and passes through the weave of
the damper 11 to the outside.
[0016]
At this time, the air flow directly strikes the voice coil 10 to cool the voice coil. According to the
present invention, since the voice coil 10 is directly cooled by the air flow, a cooling effect
corresponding to the temperature rise can be obtained together with the generation of the
electromotive force corresponding to the temperature rise of the voice coil described above.
Further, the cooling effect can be obtained regardless of the amplitude of the vibration of the
voice coil 10, as in the embodiment shown in FIG.
[0017]
Next, another example of how to attach the thermoelectric conversion element 13 will be
described. FIG. 3: is a figure which shows an example of how to attach a thermoelectric
conversion element. In this example, the voice coil 10 is disposed on the voice coil bobbin 9 in
proximity to the voice coil 10. FIG. 4 is a view showing an example of another attachment
method of the thermoelectric conversion element. In this embodiment, the voice coil bobbin 9 is
composed of the thermoelectric conversion element itself. The voice coil 10 is wound on a voice
coil bobbin formed of a thermoelectric conversion element.
[0018]
In the above description, the case where the heat generated in the voice coil is cooled by the
cooling fan that constitutes a part of the speaker has been described as an example. In addition, a
temperature sensor such as a thermocouple may be disposed in the vicinity of the voice coil, and
forced cooling may be performed externally by a cooling fan according to the output of the
temperature sensor. In this case, the temperature detected by the temperature sensor can be
controlled to adjust the air volume of the cooling fan.
[0019]
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In addition, this invention is applicable not only to a speaker but to a vibrator etc.
[0020]
As described above in detail, according to the present invention, it is possible to provide a
speaker capable of reliably suppressing the temperature rise of the voice coil.
[0021]
Brief description of the drawings
[0022]
1 is a cross-sectional view showing an embodiment of the present invention.
[0023]
2 is a sectional view showing another embodiment of the present invention.
[0024]
3 is a diagram showing an example of how to attach the thermoelectric conversion element.
[0025]
4 is a diagram showing an example of another mounting method of the thermoelectric
conversion element.
[0026]
Explanation of sign
[0027]
Reference Signs List 1 diaphragm 2 edge 3 cap 4 frame 5 gasket 6 plate 7 magnet 8 yoke 9 voice
coil bobbin 10 voice coil 11 damper 12 hole 13 thermoelectric conversion element 14 motor 15
fan 16 lead wire
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