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JPH08228397

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DESCRIPTION JPH08228397
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker used in various audio equipment.
[0002]
2. Description of the Related Art A conventional loudspeaker will be described below with
reference to the drawings.
[0003]
FIG. 3 is a front sectional view showing the structure of a conventional speaker. In the figure, 1 is
a cylindrical magnet, and a yoke 2 having a concave cross section with a uniform thickness is
connected to the lower surface of the magnet. A magnetic circuit in which a magnetic gap is
formed between the upper surface of the inner peripheral surface of the yoke 2 and the outer
peripheral surface of the plate 3 by connecting the plate 3 having an outer diameter of at least
the outer diameter of the magnet 1 on the upper surface The frame 4 is coupled to the upper
portion of the magnetic circuit, and the diaphragm 4 is coupled to the voice coil 5 fitted in the
magnetic gap, with the voice coil 5 at the center and the outer peripheral portion coupled to the
periphery of the frame 4 Met.
[0004]
However, in the above-mentioned conventional speakers, the weight ratio of the magnetic circuit
to the total weight of the speaker increases as the size of the speaker decreases. As a method,
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1
there is a method of achieving a reduction in size and weight of the magnet 1 by securing the
necessary magnetic flux density of the magnetic gap using the magnet 1 with high magnetic
energy. At the same time, when the speaker is operated, the voice coil 5 may hit the inner bottom
surface of the yoke 2 or the cost of the magnet 1 may be increased.
[0005]
Yet another method is to reduce the material thickness by using a material with a large
saturation magnetic flux such as permendur for the yoke 2 and the plate 3 to secure the
necessary magnetic flux density of the magnetic gap and achieve weight reduction However, in
this method, there are problems such as deterioration in workability of the yoke 2 and cost
increase.
[0006]
The present invention is intended to solve such conventional problems, and to provide a small
and lightweight speaker without using a high energy magnet or changing the material of a yoke
or a plate.
[0007]
SUMMARY OF THE INVENTION In order to solve this problem, the loudspeaker according to the
present invention comprises a yoke lower surface and a plate upper surface of a magnetic circuit
in which a yoke having a concave cross section, a cylindrical magnet and a cylindrical plate are
laminated and coupled. The magnetic circuit has a configuration in which gradients are provided
such that the thickness increases from the center toward the outer periphery.
[0008]
[Function] With this configuration, the magnetic flux flowing out of the magnet increases in cross
section of the magnetic circuit in addition to the increase from the center to the outer periphery
of the magnetic circuit, thereby improving the magnetic flux density without magnetic leakage.
Therefore, unnecessary materials for the lower surface of the yoke and the upper surface of the
plate can be reduced, and weight reduction of the speaker can be realized.
[0009]
Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with
reference to the drawings.
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2
[0010]
FIG. 1 is a front sectional view showing the configuration of the speaker according to the
embodiment, 7 in the figure is a cylindrical magnet, 8 is a yoke with a concave cross section, 9 is
a plate, 10 is a frame, 11 is a voice coil, 12 is a voice coil. The lower surface of the yoke 8 is
provided with a gradient of increasing thickness toward the outer periphery at least the outer
diameter of the magnet 7 from the center, and the upper surface of the plate 9 is also centered.
There is provided a gradient of increasing thickness from the to the outer periphery.
[0011]
The magnetic flux flowing out of the magnet 7 of the speaker of this embodiment thus
constructed flows out in the magnetizing direction, that is, in the vertical direction, and radiates
radially from the center of the magnet 7 in the plate 9 and the yoke 8. Flow in a loop through the
magnetic gap.
[0012]
Therefore, the amount of magnetic flux flowing out from the vicinity of the center of the magnet
7 is small, and increases as it gets closer to the outer periphery. Accordingly, the thickness of the
bottom of the yoke 8 and the thickness of the plate 9 gradually increase from the center toward
the outer periphery By providing a gradient, high magnetic flux density can be exhibited without
leaking magnetic flux, and unnecessary magnetic path thickness can be reduced to make the
magnetic circuit lightweight, and weight reduction of the speaker can be realized easily and at
low cost It is.
[0013]
(Embodiment 2) The second embodiment of the present invention will be described below with
reference to the drawings.
[0014]
FIG. 2 is a front sectional view showing the structure of the speaker according to the
embodiment, and the same reference numerals are given to parts having the same structure as
that of the first embodiment.
[0015]
Here, contents largely different from the first embodiment will be described.
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3
The upper surface and the lower surface of the cylindrical magnet 7A are not parallel planes, but
are each formed into a convex conical shape by providing a gradient in which the thickness
increases from the outer periphery toward the center, and faces the convex conical surface. The
yoke 8A and the plate 9A are formed into a concave conical shape to form a magnetic circuit in
close contact with each other without gaps. By doing this, the volume of the convex conical
portion of the magnet 7A can be increased, Accordingly, the magnetic flux density in the
magnetic gap can be increased.
[0016]
That is, high efficiency can be achieved by increasing the volume as in the case of the magnet 7A
without increasing the weight of the speaker, and thus the size and weight can be easily reduced.
[0017]
As described above, in the loudspeaker according to the present invention, the thickness gradient
is provided to the material thickness of the yoke and the plate with concave cross sections
respectively coupled to the upper and lower surfaces of the cylindrical magnet, so that the
magnet becomes from the center to the outer periphery. It is possible to have a magnetic circuit
cross-sectional area according to the magnetic flux that increases according to the above, it is
possible to reduce unnecessary materials of the yoke and the plate, and to realize the weight
reduction of the speaker easily and at low cost It is.
[0018]
Brief description of the drawings
[0019]
1 is a front sectional view showing the configuration of a speaker according to a first
embodiment of the present invention
[0020]
2 is a front sectional view showing the configuration of the speaker according to the second
embodiment of the present invention
[0021]
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Front sectional view showing the configuration of the conventional speaker
[0022]
Explanation of sign
[0023]
7 magnet 7A magnet 8 yoke 8A yoke 9 plate 9A plate 10 frame 11 voice coil 12 diaphragm
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