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JPH08149596

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DESCRIPTION JPH08149596
[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 In recent years, in the speaker market, demands for smaller size,
lighter weight and higher efficiency have been increasing, and these have become mainstream in
technical development.
[0003]
A conventional loudspeaker will be described below with reference to the drawings.
FIG. 4 is a half sectional view showing the structure of a conventional speaker, in which 1 is a
cylindrical center pole, 2 is a disk-shaped lower plate joined to the lower surface of the center
pole 1 at the center portion An annular magnet 3 is joined to the upper surface of the lower plate
2 and magnetized in the thickness direction, 4 is joined to the upper surface of the magnet 3, and
the inner circumferential surface is between the outer circumferential surface of the center pole
1 and An annular top plate which forms a magnetic gap, 5 is a frame joined to the upper surface
of the top plate 4, 6 is a voice coil held in the magnetic gap and vibrates in response to an
electrical input, 7 is this voice coil The cylindrical voice coil bobbin for transmitting the driving
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force generated in 6 to the vibration system, the inner and outer circumferences 8 are
respectively joined to the middle part of the voice coil bobbin 7 and the middle part of the frame
5 to magnetize the voice coil 6 A damper 9 holds the cap and gives the speaker the necessary
stiffness. 9 is a diaphragm having an inner peripheral portion joined to the upper portion of the
voice coil bobbin 7. 10 is an outer peripheral portion of the diaphragm 9 and the frame 5 A rollshaped edge 11 joined to the top of the outer periphery of the edge 10; 12 a voice coil bobbin; It
is a dust cap which covers the upper part of 7 and is joined to the diaphragm 9.
[0004]
As described above, in the conventional speaker, the magnetic circuit is constituted by the center
pole 1, the lower plate 2, the magnet 3 and the upper plate 4.
[0005]
However, in the speaker having the above-described conventional configuration, the area of the
diaphragm 9 is reduced as the speaker is particularly small, and therefore, the voice coil 6 and
the voice are mainly used to realize high efficiency. It is necessary to reduce the weight of the
vibration system composed of the coil bobbin 7, the diaphragm 9, and the dust cap 12 as much
as possible.
In particular, because weight reduction by downsizing of the voice coil 6, the voice coil bobbin 7,
and the dust cap 12 is realistic, it is necessary to use a magnetic circuit having a small diameter
magnetic gap, that is, a small outer diameter of the center pole 1. . Furthermore, to increase the
efficiency, it is necessary to increase the driving force by increasing the magnetic flux density of
the magnetic gap. On the other hand, in order to reduce the weight of the speaker, it is necessary
to miniaturize the magnetic circuit that occupies most of the weight.
[0006]
However, if the center pole 1 has a small diameter, it is likely to be magnetically saturated, and
that the lower part of the voice coil 6 does not collide with the upper surface of the lower plate 2
at the time of large amplitude such as bass reproduction. Since it is necessary to provide a
sufficient height of the center pole 1 corresponding to the distance between the upper surface
and the lower surface of the upper plate 4, a magnetically saturated region of the center pole 1 is
present for a long time, and the magnetic resistance is increased. As a result, the utilization
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efficiency of the magnet 3 is reduced. In order to increase the magnetic flux density in the
magnetic gap, the size of the magnet 3 may be increased, but since the center pole 1 is further
magnetically saturated to increase the magnetic resistance, the utilization efficiency of the
magnet 3 is further reduced. I will. Therefore, in order to obtain the necessary magnetic flux
density in the magnetic gap, a large magnet 3 is used, and as the size of the magnet 3 is
increased, the outer diameters of the upper plate 4 and the lower plate 2 are also increased. And
weight increase.
[0007]
An object of the present invention is to realize a compact magnetic circuit in which a sufficient
magnetic flux density can be obtained in a magnetic gap even if the center pole outer diameter is
small, and to provide a compact and lightweight high efficiency speaker.
[0008]
SUMMARY OF THE INVENTION In order to solve this problem, the speaker according to the
present invention has a space formed by the outer peripheral surface of the center pole, the
upper surface of the lower plate, the inner peripheral surface of the magnet and the lower
surface of the upper plate. An inner plate joined to the upper surface of the lower plate is
provided, and a magnetic circuit in which a submagnetic gap is formed between the inner
peripheral surface of the inner plate and the outer peripheral surface of the center pole is used.
[0009]
With this configuration, the magnetic saturation region of the center pole is reduced, and further
the braking force is applied to the voice coil by the magnetic field in the secondary magnetic gap,
the height of the center pole is shortened and the utilization efficiency of the magnet is improved.
A sufficient flux density can be obtained in the gap.
[0010]
Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with
reference to the drawings.
[0011]
FIG. 1 is a half sectional view showing a loudspeaker according to the embodiment, in which 13
is a center pole, 14 is a lower plate, 15 is a magnet, 16 is an upper plate, 17 is an inner plate, 18
is a frame, 19 is a voice. Reference numeral 20 denotes a voice coil bobbin, 21 denotes a damper,
22 denotes a diaphragm, 23 denotes an edge, 24 denotes a gasket, and 25 denotes a dust cap.
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[0012]
The operation of the loudspeaker of this embodiment configured as described above will be
described.
By providing the inner plate 17 on the upper surface of the lower plate 14, the magnetic path of
the magnetic circuit in the present embodiment is the center pole 13, the lower plate 14, the
magnet 15, the upper plate 16, the outer peripheral surface of the center pole 13 and the upper
plate In addition to the main magnetic gap formed by the inner circumferential surface 16, the
submagnetic gap is formed by the inner plate 17, the outer circumferential surface of the center
pole 13 and the inner circumferential surface of the inner plate 17.
That is, the magnetic flux flowing out of the magnet 15 enters the top plate 16, passes through
the main magnetic gap, enters the center pole 13, and reaches the position of the top surface of
the inner plate 17 inside the center pole 13.
A part passes through the submagnetic gap, passes through the inner plate 17, enters the lower
plate 14, and flows into the magnet 15.
The remainder directly enters the lower plate 14 and flows into the magnet 15.
[0013]
Since the inner plate 17 is provided as described above, all the magnetic flux does not pass
through the bottom of the center pole 13 as compared with the conventional magnetic circuit,
and the area where the center pole 13 is magnetically saturated is reduced. The magnetically
saturated region from the portion near the inner diameter of 15 to the portion near the outer
diameter of the center pole 13 decreases.
Therefore, the magnetic resistance of the magnetic circuit decreases, the utilization efficiency of
the magnet 15 increases, and the amount of magnetic flux supplied to the magnetic circuit
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increases, so the magnetic flux density in the main magnetic gap increases and the efficiency of
the speaker also increases. . In addition, the decrease in the magnetic saturation region of the
center pole 13 and the lower plate 14 and the increase in the utilization efficiency of the magnet
15 mean the reduction in size and weight of the magnetic circuit.
[0014]
Also, the direction of the magnetic field of the auxiliary magnetic gap is opposite to that of the
main magnetic gap. When the voice coil 19 moves downward to reach the submagnetic gap at
the time of large amplitude, the voice coil 19 is driven in the reverse direction, that is, upward,
and the voice coil 19 which is downwardly amplified is immediately damped. Compared to the
prior art, the distance between the bottom of the voice coil 19 and the upper surface of the lower
plate 14 when large amplitude does not collide, ie, the distance from the lower surface of the
upper plate 16 to the upper surface of the lower plate 14 Can be shortened. Therefore, the area
of the magnetically saturated center pole 13 can be further reduced, so that the reluctance
decreases, the magnetic flux density in the main magnetic gap increases, and the efficiency of the
speaker is improved. Makes it possible to reduce the overall height of the magnetic circuit and
realize weight reduction.
[0015]
The inner and outer diameters of the main magnetic gap and the auxiliary magnetic gap are
made equal to minimize the magnetic resistance in the auxiliary magnetic gap, and the distance
between the auxiliary magnetic gaps is set to the lower surface of the upper plate 16 and the
upper end of the inner plate 17 To make the magnetic resistance in the auxiliary magnetic gap
smaller than the magnetic resistance between the lower surface of the upper plate 16 and the
upper end of the inner plate 17, and to magnetically couple the lower surface of the upper plate
16 with the inner plate 17. Magnetic leakage between the top of the
[0016]
(Embodiment 2) The second embodiment of the present invention will be described below with
reference to the drawings.
[0017]
FIG. 2 is a half sectional view showing the loudspeaker according to the embodiment, and the
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reference numerals in the figure are completely the same as those of the first embodiment.
Here, what is largely different from the first embodiment is that the distance between the
auxiliary magnetic gaps is made larger than the distance between the main magnetic gaps.
That is, the inner diameter of the inner plate 17A is made larger than the inner diameter of the
upper plate 16, or the outer diameter of the center pole 13A of the portion forming the
submagnetic gap is larger than the outer diameter of the center pole 13A of the portion forming
the main magnetic gap. It's small.
[0018]
The operation in this embodiment is also the same as that in the first embodiment, but by setting
the gap of the sub magnetic gap larger than the gap of the main magnetic gap, the reluctance of
the sub magnetic gap or the sub magnetic gap is formed. The magnetic resistance that can be
supplied by the magnet 15 is reduced and the magnetic flux density in the magnetic gap is
slightly reduced because the magnetic resistance of the center pole 13A at the target position is
increased, but the support system of the damper 21 and edge 23 is unbalanced when the
amplitude is large. And when the rolling phenomenon occurs due to weight imbalance among the
voice coil 19, the voice coil bobbin 20, the diaphragm 22, and the dust cap 25, the lower end and
the outer peripheral surface of the voice coil 19 and the voice coil bobbin 20 Collision with the
upper surface and the inner peripheral surface, and further, with the inner peripheral surface of
the voice coil bobbin 20 You can avoid collision with the outer peripheral surface of the Poru
13A.
[0019]
(Third Embodiment) The third embodiment of the present invention will be described below with
reference to the drawings.
[0020]
FIG. 3 is a half sectional view showing the loudspeaker according to the embodiment, and the
reference numerals in the figure are completely the same as the previous embodiments.
Here, the major difference from the previous embodiments is that the outer diameter of the inner
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plate 17B is the largest on the lower plate 14 side and the smallest on the upper plate 16 side.
[0021]
The operation in this embodiment is also the same as the first embodiment, but the outer
diameter of the inner plate 17 is maximized on the lower plate 14 side and minimized on the
upper plate 16 side. The magnetic leakage between the lower surface of the upper plate 16 and
the upper surface of the inner plate 17B can be reduced because the area of the upper surface of
the closest inner plate 17B, which is magnetically opposed to the lower surface of the inner plate
17B, is reduced.
Therefore, the reduced magnetic leakage flux passes through the main magnetic gap, the
magnetic flux density in the main magnetic gap increases, and the efficiency of the speaker is
further improved.
[0022]
Incidentally, FIG. 3 showing the present embodiment is drawn for the case where the inner and
outer diameters of the main magnetic gap and the auxiliary magnetic gap are equal as in the first
embodiment, but the second embodiment is shown. Also, as shown in FIG. 2, the present
invention is also applied to the case where the distance between the auxiliary magnetic gaps is
larger than that of the main magnetic gap.
[0023]
Further, although the number of the inner plates 17, 17A and 17B is one and the shape is
substantially cylindrical in the embodiments so far, the auxiliary magnetic gap may be formed
even if it is not cylindrical, for example, the inner plate The same effect can be obtained even if
the segments 17, 17A and 17B are divided radially and partially disposed on the upper surface of
the lower plate 14.
[0024]
As described above, the speaker according to the present invention has a magnetic circuit having
a center pole with a small diameter, but an auxiliary plate is formed between the center plate and
the inner plate by the inner plate provided on the lower plate. Since the magnetic saturation
region of the center pole can be reduced and the voice coil can be damped by this secondary
magnetic gap when the amplitude is large, the center pole can be shortened and the utilization
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efficiency of the magnet can be increased, so that the magnetic circuit can be reduced in size and
weight. A small and highly efficient speaker can be realized.
[0025]
Brief description of the drawings
[0026]
1 is a half sectional view showing a speaker according to a first embodiment of the present
invention
[0027]
2 is a half sectional view showing a speaker according to a second embodiment of the present
invention
[0028]
3 is a half sectional view showing the speaker of the third embodiment of the present invention
[0029]
Fig. 4 Half sectional view showing the conventional speaker
[0030]
Explanation of sign
[0031]
13, 13A, 13B Center pole 14 Lower plate 15 Magnet 16 Upper plate 17, 17A, 17B Inner plate 18
Frame 19 Voice coil 20 Voice coil bobbin 21 Damper 22 Diaphragm 23 Edge 24 Gasket 25 Dust
cap
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