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JP2000032587

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2000032587
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates mainly
to an electroacoustic transducer which is a full drive flat speaker.
[0002]
2. Description of the Related Art FIG. 4 (a) is a front view of a conventional electroacoustic
transducer, FIG. 4 (b) is a cross-sectional view thereof, and FIG. 5 is a perspective view of
magnetic circuit components such as yokes and magnets, 6 (a) is a plan view of the magnetic
circuit structure, and FIG. 6 (b) is a cross-sectional view taken along the line B-B of FIG. 6 (a).
[0003]
In FIG. 4 to FIG. 6, the frame 30 is a rectangular frame, in which a substantially flat diaphragm
31 is disposed.
A rectangular frame shaped edge 32 is bonded to the entire outer peripheral edge of the
diaphragm 31, and the entire outer peripheral edge of the edge 32 is fixed to the frame 30. The
diaphragm 31 is vibratably supported in the frame 30 via the edge portion 32. The diaphragm
31 is provided with a plurality of main vibrating portions 31a that project to the front side and
extend in a fixed direction (vertical direction in the drawing) at fixed intervals. A voiced coil 33
(shown in FIG. 4B), which is a coated wire, is wound around each of the main vibration portions
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31a, and a drive current can be supplied to the voiced coil 33. The diaphragm 31 is made of a
polyimide (PI) film which resists the heat generation of the voice coil 33 and is excellent in
mechanical characteristics as the diaphragm 31.
[0004]
A flat yoke 34 is fixed to the back side of the frame 30, and the yoke 34 is made of a metal plate
such as iron. Magnets 35 are fixed on the diaphragm side of the yoke 34 and at corresponding
positions of the main vibrating portions 31a, and pole pieces 36 are fixed on the top surfaces of
the magnets 35, respectively. The pole piece 36 is made of iron or the like to concentrate the
magnetic flux of the magnet 35. That is, a magnetic circuit is configured by the yoke 34, the
magnet 35, the voice coil 33, and the like.
[0005]
At the four corners of the inner periphery of the frame 30, dampers 37 are disposed on the
surface side of the edge portion 32, and each of the dampers 37 includes a frame mounting
portion 37a and a diaphragm support portion 37b on the inner peripheral side. It is comprised
from the leaf | plate spring part 37c which connects these. The frame attachment portion 37 a is
fixed to the frame 30, and the diaphragm support portion 37 b is in contact with the upper and
lower end portions of the main vibration portion 31 a located at the left and right ends of the
diaphragm 31.
[0006]
That is, although the damper 37 supports the diaphragm 31 by the diaphragm support portion
37b, the vibration itself of the diaphragm 31 is permitted by the spring force of the plate spring
portion 37c. The damper 37 is made of a thermoplastic resin such as polycarbonate, which is a
substance having high spring resistance and high impact resistance and heat resistance.
[0007]
In the above configuration, when the magnet 35 generates a magnetic field around the boil coil
33 and a drive current flows through the boil coil 33, an electromagnetic force corresponding to
the drive current acts on the boil coil 33. The diaphragm 31 vibrates with the vibrating portion
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31a as a main component.
[0008]
However, in the configuration of the prior art, since the maximum magnetic flux density between
the magnets 35 is not constant, the driving force (electromagnetic force) of the diaphragm 31 is
not uniform. There was a problem of becoming
[0009]
Therefore, the present invention has been made to solve the above-mentioned problems, and
provides an electroacoustic transducer in which the driving force of the diaphragm is made
substantially uniform by making the magnetic flux density between a plurality of magnets
approximately the same. The purpose is to
[0010]
According to the first aspect of the present invention, a substantially flat diaphragm is vibratably
supported in a frame, and a flat yoke is fixed in the frame. A plurality of magnets are disposed on
the diaphragm side of the yoke, a boil coil is wound on the portion of the diaphragm
corresponding to each of the magnets, and the diaphragm is vibrated by a drive current supplied
to the boil coil. In the electro-acoustic transducer, the yoke is provided with magnetic flux density
adjusting means for adjusting the maximum magnetic flux density between the magnets
substantially uniformly.
[0011]
According to a second aspect of the present invention, in the electro-acoustic transducer
according to the first aspect, the magnetic flux density adjusting means is constituted by a hole
which also serves for air removal.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present
invention will be described based on the drawings.
[0013]
FIG. 1 (a) is a perspective view of a magnetic circuit component such as a yoke and a magnet of
an electroacoustic transducer according to an embodiment of the present invention, and FIG. 1
(b) is a cross section of the main part of the electroacoustic transducer. FIG. 2A is a plan view of
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the magnetic circuit component of FIG. 2A, and FIG. 2B is a cross-sectional view taken along the
line A-A of FIG.
[0014]
In FIGS. 1 (a) to 2 (b), in the electro-acoustic transducer of this embodiment, the same
components as those of the prior art are denoted by the same reference numerals in the
drawings, and the description thereof is omitted. Only the components will be described.
[0015]
That is, in this embodiment, in order to make the maximum magnetic flux density among the five
magnets 35a to 35e substantially uniform, a hole 1 which is a magnetic flux density adjusting
means is provided in the yoke 34.
Specifically, the holes 1 are provided at two places between the leftmost magnet 35a and the
adjacent magnet 35b, and between the rightmost magnet 35e and the adjacent magnet 35d, and
the holes 1 are formed of the magnets 35a to 35e. It is configured as a hole longer than the
longitudinal direction.
Each hole 1 penetrates the upper and lower surfaces of the yoke 34 and doubles as an air vent
hole through which the air on the back side of the diaphragm 31 flows out and enters.
Therefore, it is not necessary to separately provide the yoke 34 with an air vent hole.
[0016]
FIG. 3 is a characteristic diagram showing magnetic flux density at each position in FIG. 2 (b) and
FIG. 6 (b) by numerical analysis in the case of the present embodiment and in the case of the
conventional example.
As shown in FIG. 3, in the conventional example, the magnetic flux density is higher at the a
position and the d position than at the other positions, but in the present embodiment, the hole 1
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is provided at that position and there is a magnetic flux leakage at the a position and the d
position. As the interference between the position and the c position is reduced, the magnetic flux
density is almost the same at each point.
[0017]
Further, the position of the yoke 34 and the size of the hole 1 can be easily determined by
measuring the actual magnetic flux density or theoretically calculating the magnetic flux density.
be able to.
[0018]
In the above configuration, a magnetic field is generated around the boil coil 33 by the five
magnets 35a to 35e, and when a drive current flows through the boil coil 33, an electromagnetic
force corresponding to the drive current acts on the boil coil 33. The diaphragm 31 vibrates by
force mainly on the main vibrating portion 31a.
[0019]
Here, as shown by the solid line in FIG. 3, since the maximum magnetic flux density among the
respective magnets 35a to 35e is substantially uniform, the driving forces (electromagnetic
forces) in the respective main vibrating portions 31a are substantially the same. .
That is, the distribution of the driving force acting on the diaphragm 31 becomes substantially
uniform, and an ideal vibration state of the diaphragm 31 can be obtained.
[0020]
In this embodiment, the magnetic flux density adjusting means is configured as the through hole
1. However, any means that can substantially equalize the magnetic flux density among the
magnets 35a to 35e may be used. You may comprise by the member etc. from which magnetic
permeability differs.
However, in this case, it is necessary to separately provide an air vent hole.
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[0021]
It is also conceivable to make the maximum magnetic flux density nearly uniform by varying the
distance between the magnets 35a to 35e, but according to the present invention, the distance
between the magnets 35a to 35e is maintained constant. Since the maximum magnetic flux
density among the magnets 35a to 35e can be made substantially uniform in the state, there is
also an advantage that the driving force distribution of the diaphragm 31 can be made
symmetrical in the left-right direction.
[0022]
As described above, according to the first aspect of the invention, the yoke is provided with the
magnetic flux density adjusting means for adjusting the magnetic flux density between the
magnets substantially uniformly. The distribution of driving forces becomes almost uniform, and
an ideal vibration state of the diaphragm can be obtained.
[0023]
According to the second aspect of the present invention, in the electroacoustic transducer
according to the first aspect, the magnetic flux density adjusting means is constituted by a hole
which also serves for air removal. Therefore, in addition to the effects of the first aspect of the
invention. Since it is not necessary to provide a separate air vent and basically it is the same as
the conventional configuration, it can be realized at low cost.
[0024]
Brief description of the drawings
[0025]
FIG. 1A is a perspective view of a magnetic circuit component such as a yoke or a magnet of an
electroacoustic transducer according to an embodiment of the present invention, and FIG. 1B is a
cross-sectional view of a main part of the electroacoustic transducer.
[0026]
Fig.2 (a) is a top view of the magnetic circuit structure based on one Embodiment of this
invention, (b) is sectional drawing in alignment with the AA of Fig.2 (a).
[0027]
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3 is a characteristic diagram showing the magnetic flux density at each position by numerical
analysis in the case of the embodiment of the present invention and in the case of the
conventional example.
[0028]
FIG. 4A is a front view of the conventional electroacoustic transducer, and FIG. 4B is a crosssectional view thereof.
[0029]
5 is a perspective view of a magnetic circuit component such as a yoke, a magnet and the like of
the conventional electro-acoustic transducer.
[0030]
6 (a) is a plan view of a magnetic circuit structure according to a conventional example, and FIG.
6 (b) is a cross-sectional view taken along the line B-B in FIG. 6 (a).
[0031]
Explanation of sign
[0032]
1 hole (magnetic flux density adjusting means) 31 diaphragm 33 boil coil 34 yoke 35a to 35e
magnet
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