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"Guid" ·, 21 inventors, -5,-,-Name (6699) Patent Attorney Shino Kuwano [Phase] Japan Patent
Office 0 JP-A 52-374190 Published Japanese Patent 52. (1977), 3.23 internal reference number
1ttlf-掠 specification t title of the invention
Fully driven electrodynamic speaker
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement
of a flat-plate full-drive electrodynamic speaker. A conventional flat-plate full-drive
electrodynamic speaker has been configured as shown in FIG. That is, in FIG. 1,% (1), (11 is a
permanent magnet magnetized in the thickness direction (direction of arrow A-A in FIG. 1) and
adjacent adjacent permanent magnets of different polarity, (2) is a thin film vibration A plate, (3)
is a meandering thin foil-like conductor bonded to a diaphragm and squeezing an audio signal,
(4)-(41 ') is a plate of a magnetic material having a permanent magnet and forming a magnetic
circuit, (The opening (5) is provided in the space between the permanent magnets for $ 1 '.
Permanent magnet (1) attached to plate (41, (4) ') of magnetic material. (1) A magnetic field line
is passed between each magnetic pole, and four bodies (5) arranged so that the diaphragm (2)
vibrates in the same direction according to Fleming's law are placed in this magnetic field line
and the diaphragm (2) was driven and voice was obtained from the opening (5) of the magnetic
plate (4) 1. However, the flat speaker device of the conventional type uses an expensive highpermanence permanent magnet to obtain the required performance because the magnetic flux
density change of the air gap is small for one ordinary permanent magnet because of the size of
the air gap. If there is no end point: 1 The present invention has been made to solve the abovementioned drawbacks, and the magnetic flux density in the gap between the magnetic poles can
be made higher than that of a conventional permanent magnet. The present invention will be
described in detail according to an embodiment shown in the drawings. 2 (6) (... permanent
magnet magnetized in the width direction (BB direction in FIG. 2), (7) is magnetized in the width
direction 1 / r and is between permanent magnets (6). A pole piece having a convex cross section
in which a protrusion (7a) is embedded. (8) is a plate made of a nonmagnetic material for
securing the permanent magnet (6) on the side opposite to the diaphragm and preventing a
magnetic short circuit. There is. (11'f21 (31 (4) 'are respectively a permanent magnet, a
diaphragm, a conductor, a plate of a magnetic material, and these are the same as conventional
ones. (1) '(41' constitutes a second magnetic circuit, and an opening (5) is provided here. In the
flat speaker device according to the present invention thus configured, the end (7b) (b) of the
wide portion of the magnetic pole piece (7) having a convex cross section embedded in the back
of the adjacent permanent magnets (6) having the same polarity. The concentrated magnetic flux
passes between 7C), and almost no leakage magnetic flux is generated. From this end face (7b)
(7c), a uniform magnetic flux of high magnetic flux density runs to the end face of the adjacent
pole piece (7) through the conductor (3) bonded to the diaphragm (2).
The other permanent magnet (1) sandwiching the diaphragm (2) has a thickness direction so that
the lines of magnetic force sweat in the same direction as the direction of the lines of magnetic
force formed by the permanent magnet (6) and the pole piece (7) 2) Magnetize in the direction of
AA, as a result, a force acts on the conductor (3), and the diaphragm (2) is uniformly driven over
the entire surface, and the magnetic plate (4 of the second magnetic circuit) Sound is emitted
from the opening (5) provided in 1). FIG. 3 is a cross-sectional view 1 showing the relationship
between the permanent magnet (1) T and the opening (5) provided in the magnetic material (4) I.
As described above, according to the present invention, the permanent magnet of one of the
magnetic circuits of the two magnetic circuits holding the diaphragm is magnetized in the width
direction, and the projection of the convex pole piece is embedded in the gap between the
permanent magnets. The magnetic flux density in the vicinity of the conductor on the diaphragm
sandwiched by the two magnetic circuits is increased by opposing the adjacent pole pieces and
the permanent stone of the magnetic circuit magnetized in the other thickness direction. It is
possible to obtain a high magnetic flux density in the air gap without using a high performance
permanent magnet. The present invention can be applied to headphones and the like as well.
4. Brief description of the drawings. FIG. 1 is a longitudinal sectional view of a main part of a flatplate full-surface drive electrodynamic speaker according to a conventional method, and FIG. 2 is
a longitudinal sectional view of a main part showing one embodiment of the present invention.
The figure is a cross-sectional view for showing the relation between the magnetic plate (4) l and
the permanent magnet (1) I. In the drawings, the same reference numerals indicate the same or
corresponding parts, (1) '-(6+ permanent magnet, (2) sliding plate, (3) a conductor, (4) a magnetic
plate, (5) Is an aperture, c71 is a pole piece, and (8) is a nonmagnetic plate. Agent Patent
Attorney Noboru Ogino-EndPage: 2 ◆ ◆ ◆ ◆ 6. Inventors other than the above (1) Inventor
address? ! Nayamaishi-1 stone do not, gommi, stop + 2 ffE; No. 14 40 Mitsubishi Electric
Corporation Product Research Institute Address EndPage: 3