JPS572798

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DESCRIPTION JPS572798
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing one
embodiment of a dynamic speaker according to the present invention, and FIGS. 2A and 2B are
diagrams showing a method of connecting a thermistor of the speaker shown in FIG. 3 shows the
input resistance of the loudspeaker according to the present invention, FIG. 4 shows the input /
output characteristics of the dynamic loudspeaker according to the present invention in
comparison with the conventional example, and FIG. And the relationship between the
temperature of the voice coil and the direct current resistance. Explanation of symbols of main
parts, 1 ························· Voice coil, 3 ········· Center piece, 4 ·······························・・ Thermistor.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynamic
speaker having a voice coil such as a cone speaker and a horn speaker. Loudspeakers used in
audio devices etc. need to have high fidelity when converting the waveform of the input signal to
sound, and in particular the deterioration of the linearity when a large current input signal is
supplied is small Is required. However, since approximately 90 of the power supplied to the voice
coil of the speaker is released as heat, the characteristic deterioration due to the temperature rise
of the voice coil is a problem. For example, due to temperature rise of voice coil 1-7? Because the
resistance of the speaker increases and the decrease in sensitivity of the speaker and the
occurrence of nonlinear distortion can not be avoided, in the case of the conventional speaker,
the heat radiation effect of the magnetic circuit is enhanced and the heat resistance is improved.
Since only measures for improvement are taken, when the resistance of the voice coil is
increased, it is impossible to prevent the deterioration of the characteristics as described above.
The present invention has been made to prevent the above-mentioned drawbacks of the
conventional dynamic speaker, and provides a dynamic speaker capable of preventing the
deterioration of the characteristics even when the temperature of the voice coil rises. The
purpose is The dynamic speaker according to the present invention is characterized in that a
negative temperature characteristic thermistor connected in series or in parallel to the voice coil
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is provided and arranged at a position near the voice coil such as a magnetic circuit. Hereinafter,
embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view showing an example in which the present invention is implemented in a
cone speaker. In the figure, a voice coil 2 is provided at 2- to drive a speaker cone 1 and is
disposed in a gap of a magnetic circuit composed of a center piece 3 and a yoke 4. Assuming that
the temperature of the voice coil 2 is T, the value of T is expressed as a function of the input
power W, and T = WRi α (represented by 1 (1 is a thermal resistance). Although α has a
constant relationship, rapid thermal rise can not be avoided if thermal resistance or saturation
occurs. The relationship between the input power W and the temperature T is shown in FIG. 4 by
a solid line a, and similarly in FIG. 4 the relationship between the temperature T and the
resistance R of the Heuss coil is shown by a broken line. As shown in this figure, the resistance R
of the voice coil 2 is in proportion to the temperature T, but this can not be avoided because the
wire forming the voice coil 2 has a temperature coefficient. The electrical characteristics of the
voice coil 2 are as described above, but referring to FIG. 1 again, the thermistor 5 having a
negative temperature characteristic is disposed on the center piece 3 of the magnetic circuit. Are
thermally coupled.
The thermistor 5 is further electrically connected to the voice coil 2, and the method of
connection thereof is in series or parallel to the voice coil 2 as shown in FIG. 2 (A +, (B). It may be
either. The thermistor 5 is characterized in that its resistance decreases as the temperature rises,
and the combined resistance is kept almost constant against temperature change when
connected to the voice coil 2 either in series or in parallel. It is possible. For example, FIG. 3
shows the relationship between the temperature and the resistance when the voice coil 2 and the
thermistor 5 are connected in series, and the resistance value of the voice coil 2 and the
resistance port of the thermistor 5 have temperature dependency, respectively. It is understood
that the combined resistance value C is maintained at a substantially constant value while the C.
is a dog. In FIG. 4, the solid line a and the broken line 6 respectively indicate the sound output
level with respect to the input voltage of the speaker according to the conventional example and
the present invention. It is clear from this figure that the dynamic speaker according to the
present invention has excellent power linearity and less damping for large inputs. Furthermore,
regardless of the magnitude of the input, a constant dynamic range is obtained, and the variation
of the sound quality is small. Although the thermistor 5 is fixed to the center piece 3 of the
magnetic circuit in the above embodiment, the present invention is not limited to the
embodiment. The thermistor 5 may be disposed on the bobbin of the voice coil 2 or the like. In
this case, in particular, the resistance value of the thermistor 5 immediately changes in response
to the temperature change of the voice coil 2, so that the responsiveness is excellent, and the
dynamic linearity of the speaker can be improved.
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