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An object of the present invention is to provide an electromagnetic converter capable of
reproducing a bass range with a flat diaphragm with a smaller depth. SOLUTION: A rod-like
magnet made of a rod-like magnetic material, a rod-like magnet 20 arranged to have the yoke 23
and a predetermined gap 25, and a rod-like member having a conductor pattern 15 formed on
the surface and inserted in the gap 25 The driving member 4, a flat diaphragm 10 fixed to the
driving member 4, and a frame 30 for supporting the diaphragm 10 are provided. [Selected
figure] Figure 2
Electromagnetic converter
The present invention relates to an electromagnetic converter that includes a flat diaphragm that
is driven by a rod-like magnetic circuit to reproduce sound from an audio signal.
With the adoption of flat panel displays (FPDs), the trend toward larger screens and smaller
depths has been progressed, and the installation space has been reduced, enabling wall hanging.
In particular, in a television whose depth has become smaller, the conventional cone type speaker
(hereinafter referred to as an electromagnetic converter) has a large depth and can not be
incorporated into a television cabinet, so the arrangement of the electromagnetic converter is
restricted. Is coming out. A conventional common cone-type electromagnetic transducer
comprises, for example, a vibration system, a magnetic circuit and a frame. The vibration system
is formed by winding a conductor such as a metal wire around the diaphragm, a cap provided at
the center of the diaphragm, an edge supporting the outer periphery of the diaphragm, and a
cylinder, and is coupled to the inner periphery of the diaphragm The voice coil is composed of a
spider that supports the outer peripheral surface of the voice coil. The magnetic circuit is
composed of a magnet, a plate and a pole piece. In addition, the frame supports and fixes the
edge of the vibration system and the outer periphery of the spider, and is fixed to the magnetic
circuit. A terminal for feeding and a lead from the terminal to the voice coil are fixed to the
The operation of the above electromagnetic converter is as follows. When an audio input signal is
applied to the terminal, it is supplied to the voice coil via the lead wire. At the conductor portion
of the voice coil present in the magnetic gap of the magnetic circuit, the driving force is
generated by the signal and vibrates based on the Fleming left-hand rule. That is, the conductor
of the voice coil generates driving force in the vertical direction and vibrates, and a sound wave is
generated from the vibration system coupled to the voice coil.
In the above conventional electromagnetic converter, the vibration system of the cone-shaped
diaphragm having a depth and the cylindrical voice coil coupled to the diaphragm is required to
have a depth. In addition, the magnetic circuit consisting of a magnet, a plate and a pole piece
also needs a depth, and an electromagnetic converter composed of these necessarily has a large
depth. For example, even a small-aperture full-band electromagnetic converter such as that used
in television had a depth of about 5 cm.
Various flat plate type electromagnetic transducers and flat type electromagnetic transducers
have been proposed for electromagnetic transducers having such depth, and some of them have
been commercialized (see Non-Patent Document 1). According to this Non-Patent Document 1, as
a general structure of the flat plate type electromagnetic converter, the diaphragm is composed
of a flat flat diaphragm, a voice coil, and a magnetic circuit similar to the conventional one. On
the other hand, as a flat type electromagnetic converter, a gamouson type electromagnetic
system in which a diaphragm in which a conductor corresponding to a voice coil of a cone type
electromagnetic converter is printed on one thin sheet is driven by the magnetic field of a
magnetic circuit in which rod magnets are arranged There is a converter.
Superintendent Tamon Saeki, "Speaker & Enclosure Encyclopedia", Seibundo Shinkosha, May
1999 issue
However, since the conventional flat electromagnetic transducer described above has the same
structure and magnetic circuit as the conventional electromagnetic transducer in which the voice
coil is required, it has been difficult to reduce the depth.
In addition, although the conventional Gamuzon type electromagnetic converter is flat and small
in depth, it is suitable for a thin television, but there is a problem that the vibration displacement
of the diaphragm can not be increased and it is not suitable for bass reproduction.
The present invention has been made to solve the above-described problems, and it is an object
of the present invention to provide an electromagnetic converter capable of reproducing a low
frequency range with a diaphragm having a simple configuration and having a smaller depth and
a flat surface. Do.
The electromagnetic converter according to the present invention comprises a yoke made of a
rod-like magnetic body, a rod-like magnet arranged to have a predetermined gap with the yoke,
and a rod-like drive having a conductor pattern formed on the surface and inserted in the gap. It
comprises a member, a flat diaphragm fixed to the drive member, and a frame for supporting the
According to the electromagnetic converter of the present invention, the drive member having
the conductor pattern is inserted into the gap between the rod-shaped yoke and the rod-shaped
magnet, thereby reducing the depth with a simple configuration. Flat sound pressure
characteristics can be obtained.
As a result, it is possible to obtain a thinner electromagnetic transducer capable of reproducing
to the low frequency range.
BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic perspective view which shows the
whole electromagnetic converter which concerns on Embodiment 1 of this invention.
It is the AA line (a) longitudinal cross-sectional view of FIG. 1 which shows the structure of the
electromagnetic converter of Embodiment 1, and (b) it is a partially detailed perspective view.
FIG. 5 is a perspective view showing a structure of a drive member of the electromagnetic
converter of the first embodiment. It is a (a), (b) schematic perspective view which shows the
other example of the electromagnetic transducer of Embodiment 1. FIG.
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. Embodiment 1 FIG. 1 is a schematic perspective view showing the entire
electromagnetic transducer of the present embodiment. FIG. 2 is a view showing the
configuration of the electromagnetic converter, and FIG. 2 (a) is a cross-sectional view taken
along the line A-A of FIG. 1, and FIG. 2 (b) is a detailed perspective view showing part of FIG. FIG.
FIG. 3 is a perspective view showing the structure of the drive member.
The electromagnetic converter 1 is roughly divided into a vibration system 2 and a magnetic
circuit 3. The vibration system 2 and the magnetic circuit 3 are supported by a frame 30 as a
support member. As shown in FIG. 1, the electromagnetic converter 1 according to the first
embodiment is provided with a vibration system 2 and a magnetic circuit 3 in which two sets of
rods are arranged in parallel.
The vibration system 2 includes a diaphragm 10, an edge 12 supporting the diaphragm 10, and a
drive member 4. The diaphragm 10 is a rectangular flat plate made of a lightweight material, and
the edge 12 is adhered to the outer periphery thereof. The edge 12 has a semi-rolled cross
section, the inner periphery is adhered to the diaphragm 10, and the outer periphery is It is
adhesively fixed to the frame 30. The driving member 4 is composed of a base 14 and a
conductor pattern 15 formed on the surface of the base 14. The shape of the drive member 4 is a
rod shaped so as to have a U-shaped cross section (hereinafter referred to as a U-shaped cross
section), and one surface of the drive member 4 is adhesively fixed to the back surface of the
diaphragm 10. The detailed structure of the drive member 4 will be described later.
The magnetic circuit 3 is composed of a magnet 20 and a yoke 23. The magnet 20 is a rod-like
permanent magnet having a rectangular cross section, and is magnetized in the width direction
of the cross section. The yoke 23 is made of a rod-like magnetic body having a co-shaped cross
section, induces the magnetic flux of the magnet 20 and efficiently connects magnetic lines It
works to be The magnet 20 is disposed inside the cross-sectional U-shape of the yoke 23, and a
constant gap is formed as a magnetic gap (hereinafter referred to as a gap) 25 between the
magnet 20 and the inner wall of the cross-sectional U-shape of the yoke 23. In the gap 25,
opposing sides of the cross section of the drive member 4 are inserted. In addition, the space |
interval of the gap 25 comprised between the magnet 20 and the yoke 23 is set suitably, The
magnetic flux density in the gap 25 can be enlarged by setting the space | interval small, and a
magnet A strong magnetic path can be formed in the height range of 20.
The magnetic circuit 3 is an elongated rod having a substantially rectangular cross section and a
large length in the length direction, and the driving member 4 opposed to the magnetic circuit 3
also has the same length. The lengths of the magnetic circuit 3 and the drive member 4 are close
to one side of the diaphragm 10.
Here, the structure and manufacturing method of the drive member 4 will be described. As
shown in FIG. 3, the driving member 4 is in the form of a sheet in which the conductor pattern
15 is formed on the base material 14. The conductor pattern 15 is formed in a spiral shape on
both sides or one side of the substrate 14, and terminals 16 are formed on both ends of the
conductor pattern 15 so as to receive an external signal. The base 14 is made of, for example, a
flat sheet of a polymer resin or an engineering plastic, and is formed to have sufficient thickness
and strength to be self-supporting. The conductor pattern 15 is made of, for example, a foil
material such as copper or aluminum, and is bonded onto the surface of the base 14. The foil
material bonded onto the base material 14 is treated so as to leave a predetermined pattern by
etching or the like in the same manner as the FPC (Flexible Printed Circuits) manufacturing
method. The drive member 4 manufactured in this manner is formed into a U-shaped cross
section by thermoforming or the like.
The operation of the electromagnetic converter 1 will be described. In the electromagnetic
converter 1, when a signal is applied to the conductor pattern 15 of the drive member 4 from the
control unit (not shown), a current flows along the conductor pattern 15, and the direction of the
current flow is orthogonal to the magnetic field of the permanent magnet. Therefore, in
accordance with Fleming's left-hand rule, driving force is generated in the vertical direction in the
cross-sectional height direction in the driving member 4, and the diaphragm 10 coupled to the
driving member 4 vibrates up and down to generate sound.
As described above, according to the electromagnetic converter of the first embodiment of the
present invention, a large driving force can be obtained because of the structure utilizing the
high magnetic flux density magnetic field of the narrow magnetic gap 25, and the reproduced
sound pressure level Can realize a highly efficient electromagnetic converter. In addition, since
the plurality of magnetic circuits 3 can be dispersedly arranged to make the driving force
uniform, flat sound pressure frequency characteristics with less fluctuation can be obtained.
Furthermore, as shown in FIG. 1 or 2, since the vibration system 2 having the flat diaphragm 10
as a main member and the bar-like magnetic circuit 3 can be supported by the thin frame 30, the
electromagnetic converter 1 can be configured. While being able to be made very thin, there is
an effect that it is possible to obtain an inexpensive electromagnetic converter with a simple
structure with a small number of parts.
In the description, the edge 12 is described as being adhered and fixed to the frame 30 at its
outer periphery, but the present invention is not limited to this, and the edge 12 may be directly
fixed to the television case as necessary. Good.
Generally, in the diaphragm 10, a divided vibration which is a natural resonance is often
generated in the middle and high range, but this divided vibration is pushed to the high range
and shown in FIG. 1 or FIG. Thus, it is desirable that the number of magnetic circuits 3 be two
(more than three).
That is, by dividing the driving force into a plurality and distributing the driving force evenly to
the diaphragm, the divided vibration is suppressed to realize a wide band.
Moreover, although the electromagnetic transducer of Embodiment 1 showed the structure
which drives with the two sets of magnetic circuits 3 to the rectangular diaphragm 10, this
invention is applicable to the electromagnetic transducer of another form.
As an example thereof, as shown in FIG. 4 (a), the diaphragm 10 having a large aspect ratio is
driven by one magnetic circuit 3, or as shown in FIG. 4 (b) Various combinations are conceivable,
such as the form of driving with the set of magnetic circuits 3.
In addition, although the drive member 4 in the above embodiment has a U-shaped cross section
as described above, in order to suppress the deformation due to the driving force and maintain
the structural strength, the end of the drive member 4 is used as a base. The side surface may be
formed by closing with the material 14 (or the equivalent thereof). That is, the drive member 4
may have a box-like structure.
In addition, since the flat diaphragm 10 is structurally weak, it is preferable to use a three-layer
structure such as a honeycomb structure and a rigid component itself or a thick plate. It is also
possible to use a lightweight material such as a microbubble structure bound with hollow
spheres of
Further, as shown in FIG. 1 or FIG. 2, the flat diaphragm 10 is supported by only the edge 12 and
driven by the drive member 4, but when the vibration system 2 becomes heavy, the edge 12 is
slackened or driven Sometimes rolling can occur.
As a countermeasure for this, a means for supporting the central portion and the peripheral
portion of the diaphragm 10 or a structure in which a spider is joined to and supported by the
drive member 4 as in the conventional electromagnetic transducer spider may be adopted.
Moreover, in FIG. 1, FIG. 4 (a), (b), in order to demonstrate easily, the flame | frame 30 is
abbreviate | omitted and shown.
DESCRIPTION OF SYMBOLS 1 electromagnetic converter, 2 vibration systems, 3 magnetic
circuits, 4 driving members, 10 diaphragms, 12 edges, 14 base materials, 15 conductor patterns,
16 terminals, 20 magnets, 23 yokes, 25 magnetic gaps (gaps), 30 frames .
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