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JPH0720799

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DESCRIPTION JPH0720799
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker employing a magnetic repulsion circuit.
[0002]
2. Description of the Related Art A magnetic circuit employed in a conventional speaker generally
has a magnet mounted and fixed on a yoke on which a center pole is erected, and a plate
mounted and fixed on the magnet and the center pole The magnetic gap between them is a
magnetic gap, and by energizing the voice coil placed in this magnetic gap and driving it, the
diaphragm made of cone paper etc. vibrates. . However, since the magnetic circuit having such a
structure uses a yoke which is made of an iron material and is heavy, there is a problem that the
weight reduction of the speaker is inhibited.
[0003]
In recent years, therefore, a speaker has been proposed which has been made lighter by adopting
a magnetic repulsion circuit. As shown in the cross-sectional view of FIG. 4, this ring has a pair of
annular magnets 2 fixed across the plate 1 with their N poles facing each other, and a ring 3
made of ferromagnetic material and A magnetic gap G for disposing the voice coil 4 is formed
between the plate 1 and the plate 1. Therefore, as shown in the magnetic field line distribution
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diagram of FIG. 5, the magnetic field lines coming out of the N pole of each magnet 2 and
returning to the S pole can be aligned substantially in parallel in the magnetic gap G, and
homogenization of the magnetic flux distribution can be achieved. The magnetic circuit suitable
for driving the voice coil 4 can be configured. Such a magnetic circuit is referred to as a magnetic
repulsion circuit, and has the advantage that the weight reduction of the speaker can be
promoted since it is not necessary to incorporate a heavy yoke, and the magnetic flux
distribution in the magnetic gap G is uniform. There is also an advantage that the sound quality
can be improved by
[0004]
Incidentally, reference numeral 5 in FIG. 4 denotes a bobbin on which the voice coil 4 is wound,
6 denotes a diaphragm made of cone paper or the like and the above-mentioned bobbin 5 is
attached to the inner periphery, 7 denotes a center cap, 8 Is a frame made of a cone edge, 9 is a
damper, and 10 is a metal plate, and the frame 10 holds the magnetic repulsion circuit and
supports the diaphragm 6 via the cone edge 8 and the damper 9 When the voice coil 4 is driven
by electromagnetic interaction, the diaphragm 6 vibrates.
[0005]
By the way, as shown in FIG. 5, the magnetic repulsion circuit suitable for reducing the weight of
the speaker has arched magnetic force lines distributed on the generatrix of the outer peripheral
surface 2a of each magnet 2 as shown in FIG. Although the ratio of the magnetic lines of force
returning to the S pole without passing through the magnetic gap G among the magnetic lines of
force coming out of the N pole of each magnet 2 is high, the conventional speaker employing
such a magnetic repulsion circuit However, since this kind of leakage flux does not act on the
voice coil 4 or generates a reverse magnetic field and only causes current magnetostriction, there
is a problem that the driving efficiency is extremely low anyway.
[0006]
Therefore, an object of the present invention is to solve the problems of the prior art described
above, and to provide a speaker having an improved driving efficiency while adopting a magnetic
repulsion circuit.
[0007]
SUMMARY OF THE INVENTION The above object of the present invention is to provide a
magnetic repulsion circuit in which a magnetic gap is formed around the plate by making the
same poles of a pair of magnets face each other via the plate, and In a speaker including a voice
coil disposed in a magnetic gap and a diaphragm that vibrates by driving the voice coil, a wire
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common to the voice coil is wound in the opposite direction to the voice coil. This is achieved by
providing a reverse wound coil portion and arranging the reverse wound coil portion in a region
out of the magnetic gap along the driving direction of the voice coil.
[0008]
Because a reverse magnetic field in which the direction of the magnetic field is reverse to that in
the magnetic gap is generated in a region which is deviated from the magnetic gap by a
predetermined distance along the driving direction of the voice coil. If the reverse winding coil
portion is disposed in the magnetic field region, the electromagnetic force acting on the reverse
winding coil portion has the same direction as the electromagnetic force acting on the voice coil,
and the reverse winding coil is driven to drive the voice coil. Since the driving force of the unit is
added, the driving force is improved accordingly.
In addition, unlike a voice coil whose number of turns is restricted because it is placed in a
narrow magnetic gap, the reverse wound coil portion with few restrictions on space can be
wound with many layers thick, so that a reverse magnetic field with a small magnetic flux density
Even in the region, a relatively large electromagnetic force can be applied to the reverse winding
coil portion.
[0009]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a loudspeaker according to an embodiment of the present
invention, FIG. 2 is an enlarged view of a main part of the loudspeaker shown in FIG. 1, and FIG.
3 is a schematic view of a voice coil and a reverse winding coil portion shown in FIGS. The
portions corresponding to FIGS. 4 and 5 used in the description of the prior art are given the
same reference numerals.
[0010]
The loudspeakers shown in FIGS. 1 to 3 employ a magnetic repulsion circuit as in the prior art to
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reduce weight, and a pair of annular magnets 2 fixed on both sides of a plate 1 The magnetic gap
G is formed between the ring 3 and the plate 1 made of ferromagnetic material, and the voice coil
4 wound around the bobbin 5 is formed in the magnetic gap G. However, unlike the prior art, this
speaker is provided with a reverse winding coil portion 11 wound on a bobbin 5 in the opposite
direction to the voice coil 4 on the upper and lower sides of the voice coil 4 in the figure. Thus,
each of the reversely wound coil sections 11 is disposed in a reverse magnetic field region in
which the direction of the magnetic field is reversed to that in the magnetic gap G.
That is, the magnetic lines of force that exit from the N pole of each magnet 2 and return to the S
pole generate a radially outward magnetic field in the magnetic gap G, but from the magnetic gap
G along the driving direction of the voice coil 4 Since a radially inward reverse magnetic field is
generated in a region out of the predetermined distance (see FIG. 5), the reverse coil portion 11
for arranging in the reverse magnetic field is a voice coil as shown in the schematic view of FIG.
A conductor 12 common to 4 is processed and formed on one end side and the other end side of
the voice coil 4 so that each reverse wound coil portion 11 receives an electromagnetic force
from a reverse magnetic field when energized.
[0011]
Incidentally, reference numeral 6 in FIG. 1 is a diaphragm made of cone paper or the like and
having the above-mentioned bobbin 5 attached to the inner periphery, 7 is a center cap, 8 is a
cone edge, 9 is a damper, 10 is a metal plate or The frame 10 is made of a plastic, and the frame
10 holds the magnetic repulsion circuit and supports the diaphragm 6 via the cone edge 8 and
the damper 9.
[0012]
As described above, in this embodiment, the voice coil 4 and the reverse wound coil portion 11
wound in the opposite direction from the common conducting wire 12 are formed in parallel, and
these voice coil 4 and the reverse wound coil portion 11 are formed. The direction of the flowing
current is reversed as shown in FIG. 2, but the direction of the magnetic field is opposite to that
in the magnetic gap G in the region where each reverse wound coil portion 11 is disposed, so the
electromagnetic force acting on the voice coil 4 The electromagnetic force acting on the reverse
wound coil portion 11 changes in synchronization with each other while always matching the
direction of the force.
That is, when a current flows through the conducting wire 12, the force for driving the respective
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reverse wound coil portions 11 is added to the force for driving the voice coil 4, so that a large
driving force can be obtained.
Also, although the voice coil 4 can be wound only about two layers because it is limited by the
space limitation of being disposed in the narrow magnetic gap G, the reverse wound coil portion
11 can be wound with many layers with less space limitations. Therefore, even in the reverse
magnetic field region where the magnetic flux density is small, a relatively large electromagnetic
force can be applied to the reverse winding coil portion 11. Therefore, as shown in FIG. 2, if
several layers are wound with each reverse wound coil portion 11 thick, the driving efficiency
can be greatly improved, and a power saving type lightweight speaker can be realized
inexpensively.
[0013]
As described above, in the present invention, the reverse-wound coil portion formed by winding
the common wire with the voice coil in the direction opposite to the voice coil is disposed in the
reverse magnetic field region of the magnetic repulsion circuit. According to the invention, the
power for driving the voice coil is added to the power for driving the voice coil at the time of
energization, so there is an excellent effect that the driving efficiency is enhanced while adopting
the magnetic repulsion circuit, and space constraints Since the reverse-wound coil portion having
a small amount of winding can be wound thickly and in many layers, it is also possible to
inexpensively provide a power saving type lightweight speaker whose driving efficiency is greatly
enhanced.
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