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DESCRIPTION JPH062895

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DESCRIPTION JPH062895
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker magnetic circuit in which the symmetry of the magnetic flux density distribution of the
magnetic gap in the vertical direction is improved centering on the upper plate in an external
magnet type speaker magnetic circuit.
[0002]
2. Description of the Related Art The most typical structure of the conventional external magnet
type speaker magnetic circuit is, for example, as shown in FIG. 3, on a lower plate 14 having a
center pole 12 protruding at the center. A ring-shaped magnet 13 is mounted, a ring-shaped
upper plate 11 is mounted on the magnet 13, and magnetic lines of force are radially formed by
the side surfaces of the center pole 12 and the inner surface of the central hole of the upper
plate 11. A ring-shaped magnetic air gap 16 is formed to flow therethrough.
[0003]
In the conventional magnetic circuit having such a structure, as shown in FIG. 3, the expansion of
the space outside the top plate of the magnetic gap and the space in the inward direction of the
magnetic circuit. In the spread of the magnetic circuit, it is not symmetrical due to the
arrangement of the components that make up the magnetic circuit, and the leakage permeance is
small outside the magnetic circuit as the magnetic flux distribution near the air gap is
schematically shown in While the density drops sharply as it leaves the air gap, the leakage
permeance is larger at the inner side of the magnetic circuit than at the outer part, so the
decrease in magnetic flux density is more gradual than the outer part, and As shown by the
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dotted line in FIG. 2 showing the distribution, the decrease in magnetic flux density is not
symmetrical, and when used for a speaker, the driving force generated in the voice coil is also
asymmetrical. Result non-linear distortion degradation of the resulting reproduced sound is a
problem to be solved that is inevitable.
[0004]
Therefore, the present invention aims to provide a magnetic circuit for a speaker, which solves
the disadvantages of the above-mentioned prior art and improves the asymmetry of the magnetic
flux distribution of the magnetic circuit with a simple structure.
[0005]
[Means for Solving the Problems] The speaker magnetic circuit according to the present
invention for achieving the above object will be described with reference to FIGS. 1 and 2
showing an embodiment. A speaker magnetic circuit is characterized in that the auxiliary magnet
5 is fixed on the upper surface of the upper plate 1 of the magnetic circuit in alignment with the
magnetic pole side different from the magnetic pole of the upper plate 1.
[0006]
In the magnetic circuit having such a configuration, the polarities of the upper surface of the
auxiliary magnet 5 and the center pole 2 are opposite to each other, and the magnetic flux
emitted from the upper surface of the auxiliary magnet 5 is attracted to the center pole. Thus, the
magnetic flux density is high at the upper end of the air gap, and the symmetry of the magnetic
flux distribution is improved as shown by the solid line in FIG.
[0007]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 showing the
central longitudinal cross section of the magnetic circuit, the embodiment of the present
invention will be described in detail. A ring is formed on a lower plate 4 having a center pole 2
projecting from the center. The magnet 3 is placed, the ring-shaped upper plate 1 is placed on
the magnet 3, and magnetic flux lines flow in the radial direction between the side surface of the
center pole 2 and the inner surface of the center hole of the upper plate 1 A ring-shaped
magnetic air gap 6 is formed to constitute an external magnetic circuit of a known structure.
In this embodiment, the magnet 3 is magnetized such that the lower side is an S pole and the
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upper surface is an N pole, so that the center pole 2 is an S pole, the upper plate 1 is an N pole,
and the magnetic flux is released from the upper plate 1 Enter Center Pole 2.
[0008]
A thin auxiliary magnet 5 is attached to the upper surface of the upper plate 1 with the lower
surface magnetized to the S pole and the upper surface magnetized to the N pole to constitute
the magnetic circuit of the present invention.
In the magnetic circuit having such a configuration, the magnetic flux emitted from the upper
surface of the auxiliary magnet 5 is drawn to the center pole 2 serving as the S pole, as if the
upper surface of the auxiliary magnet 5 became the upper end of the magnetic gap. The
magnetic flux density on the upper surface of the center pole 2 is higher than that in the case
without the auxiliary magnet 5, and the magnetic flux density distribution is vertically paired
with the magnetic gap.
[0009]
In the above embodiment, the magnetizing direction of the magnet 3 may be such that the lower
side is the N pole and the upper surface is the S pole in the opposite direction to the above. In
this case, the auxiliary magnet 5 has the lower surface The top surface is magnetized to the S
pole at the N pole.
[0010]
According to the experimental results, the magnetomotive force of the auxiliary magnet 5 is
generally about 1/20 to 1/10 times the magnetomotive force of the magnet 3 regardless of the
material of the magnet, the permeance of the magnetic gap, etc. Is effective.
[0011]
Although the speaker magnetic circuit according to the present invention has been described in
detail based on the embodiment considered to be representative, the embodiment of the
magnetic circuit according to the present invention is not limited to the structure of the above
embodiment. Rather, it can be appropriately modified and implemented as long as it has the
configuration requirements described in the above-mentioned utility model registration request,
exhibits the action according to the present invention, and has the effects described below.
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[0012]
The speaker magnetic circuit according to the present invention has the following effects.
[0013]
The polarities of the upper surface of the auxiliary magnet and the center pole are opposite to
each other, and the magnetic flux emitted from the upper surface of the auxiliary magnet is
attracted to the center pole, and the magnetic flux density becomes high at the upper end of the
air gap. The vertical symmetry of the magnetic flux distribution is improved as indicated by.
Therefore, when used in a speaker, the linearity of the driving force generated in the voice coil is
improved, and as a result, there is no factor that degrades the reproduced sound such as
nonlinear distortion.
[0014]
With the above advantages, it has the effect that the characteristics of the loudspeaker can be
improved by a simple structure.
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