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JP2004343527

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complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2004343527
The present invention provides an electroacoustic transducer which can be made thin and which
can vibrate a diaphragm reliably in response to an audio signal. An electroacoustic transducer
according to the present invention includes a flat diaphragm 5 and an upper plate 1 and a lower
plate 2 disposed above and below the diaphragm 5 with a predetermined gap. A ring-shaped
magnet 6 having a circular space 6a at the center and a flat portion 6b parallel to the upper plate
1 and the lower plate 2 is disposed at a predetermined position of the diaphragm 5, and the flat
portion 6b of the magnet 6 is disposed. The first coil 7 wound in a spiral shape in a direction
parallel to the flat portion 6 b of the magnet 6 is disposed on the upper plate 1 at a position
opposite to the first coil 7 at a position facing the first coil 7 with the magnet 6 interposed
therebetween. The lower plate 2 is provided with a second coil 8 wound in the same shape as the
first coil 7. [Selected figure] Figure 1
Electro-acoustic transducer
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electro-acoustic transducer, and more particularly to a thin electro-acoustic transducer having a
flat and small depth dimension. [0002] Conventionally, a thin electroacoustic transducer has
been adopted as a speaker or a microphone used for various electronic devices such as a laptop
personal computer, a thin television, or a portable telephone. . Such a conventional
electroacoustic transducer will be described based on FIG. 3. A ring-shaped magnet 21 consisting
of a permanent magnet such as a ferrite magnet has a circular space 22 at its central portion and
has a ring-shaped outer shape. The S pole is formed at the inner edge and the N pole is formed at
the outer edge. In addition, a thin film diaphragm 23 is disposed above the ring magnet 21 with a
predetermined gap, and a coil 24 is spirally wound in a range corresponding to the shape of the
ring magnet 21 on one surface of the diaphragm 23. It is wound and fixed to the diaphragm 23
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by an adhesive 25. The diaphragm 23 is stretched inside the housing 26 without slack, and the
coil 24 is adhered to the diaphragm 23 on the upper side facing the flat surface of the ringshaped magnet 21. There is. Further, the ring-shaped magnet 21 is fixed to the bottom plate 26 a
of the housing 26 with an adhesive or the like through a soft iron yoke 27 having a
predetermined thickness. When the conventional electroacoustic transducer is a speaker, a
magnetic field is generated by flowing an audio current through the coil 24 by the magnetic flux
generated at the S pole at the inner edge and the N pole at the outer edge of the ring magnet 21.
Thus, a repulsive force or a suction force is generated between the coil 24 and the ring-shaped
magnet 21. As a result, the diaphragm 23 vibrates to reproduce sound. However, in the
conventional electro-acoustic transducer as described above, the coil 24 wound in a spiral shape
is used. Since the adhesive 25 adheres to the diaphragm 23, the diaphragm 23 may be slackened
downward due to the weight of the coil 24 and the adhesive 25. If slack occurs in the diaphragm
23, the diaphragm 23 can not be vibrated properly, which may make it impossible to reproduce
sound normally. In addition, the gap between the diaphragm 23 and the ring magnet 21 should
be increased so that the diaphragm 23 does not contact the ring magnet 21 even if the
diaphragm 23 is slackened by the weight of the coil 24 and the adhesive 25. Thinning was
difficult because it was not good.
Further, since the ring-shaped magnet 21 is formed of a permanent magnet such as a ferrite
magnet having a predetermined thickness dimension and is attached to the bottom plate 26a via
the yoke 27 having a predetermined thickness, the diaphragm 23 and the bottom plate 26a
There is a problem that the thickness of the conventional electro-acoustic transducer becomes as
thick as about 2 mm. The present invention has been made in view of the problems as described
above, and it is an object of the present invention to provide an electroacoustic transducing
device which can be thinned and which can vibrate the diaphragm reliably in response to an
audio signal. To aim. SUMMARY OF THE INVENTION As a first means for solving the abovementioned problems, an electroacoustic transducer according to the present invention comprises:
a flat diaphragm; and predetermined ones up and down across the diaphragm. An upper plate
and a lower plate disposed opposite to each other with a gap between them, and at a
predetermined position of the diaphragm, there is a circular space at the central portion and a
flat portion parallel to the upper and lower plates A ring-shaped magnet is disposed, and a first
coil spirally wound in a direction parallel to the flat portion of the magnet is disposed on the
upper plate at a position facing the flat portion of the magnet. A second coil wound in the same
shape as the first coil is disposed on the lower plate at a position facing the first coil with a
magnet interposed therebetween. Further, as a second means for solving the above-mentioned
problems, the magnet is characterized in that a magnetic paste, into which magnetic powder is
kneaded, is printed on the surface of the diaphragm. Further, as a third solution for solving the
above-mentioned problems, the magnet is characterized in that the inner peripheral edge and the
outer peripheral edge are magnetized in the radial direction in which the magnetic poles are
different from each other. Further, as a fourth solution for solving the above-mentioned
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problems, in the first coil or / and the second coil, yokes are disposed on the spiral inner and
outer peripheral sides. It is characterized by Further, as a fifth solution for solving the abovementioned problems, the ring-like width dimension of the second coil including the yokes on the
inner and outer circumferential sides is magnetized in the radial direction. It is characterized in
that it is formed to have the same size as the width dimension of the magnet. BEST MODE FOR
CARRYING OUT THE INVENTION An embodiment of an electroacoustic transducer according to
the present invention will be described below based on FIGS. 1 and 2. FIG. FIG. 1 is a crosssectional view of an essential part for explaining an embodiment according to the present
invention, and FIG. 2 is a plan view for explaining a magnet according to the present invention.
First, as shown in FIG. 1, in the electro-acoustic transducer according to one embodiment of the
present invention, the upper plate 1 made of a stainless steel plate or the like having a circular
outer shape and a thickness of about 0.1 mm is disposed. . Further, the lower plate 2 is disposed
to face the lower plate 2 with a predetermined gap at the upper and lower sides of a diaphragm 5
described later. The lower plate 2 is formed of the same material as the upper plate 1 and has the
same outer shape, and a plurality of holes 2a are formed at predetermined positions. Further,
annular first and second spacers 3 and 4 are disposed between the upper plate 1 and the lower
plate 2, and the first and second spacers 3 and 4 are provided with the upper plate 1 and the
lower plate 2. The outer peripheral portion is supported, and the inside sandwiched between the
upper plate 1 and the lower plate 2 is hollow. A diaphragm 5 made of a polymer material such as
a PET film and having a thickness of about 10 μm is interposed between the first and second
spacers 3 and 4. Since the diaphragm 5 is supported while being held in pressure contact with
the first and second spacers 3 and 4 in a state where tension is uniformly applied to the outer
peripheral end of the circular shape, slack is produced at any position. It is not supposed to.
Further, on the upper surface of the diaphragm 5, a ring-shaped magnet 6 having a circular
space 6a at the center portion is formed. The magnet 6 is formed by printing a magnetic paste,
which is prepared by kneading magnetic powder made of SmFeN or the like into a binder such as
polyester resin, in a ring shape on the diaphragm 5. And the upper surface of the magnet 6
which opposes the upper plate 1 is formed in planar shape, and it has become the plane part 6b.
In addition, the magnet 6 is formed to be thin as approximately 0.1 mm in thickness by printing a
magnetic paste, and the weight can be made very light at approximately 0.02 g. Therefore, no
slack occurs in the diaphragm 5 due to the weight of the magnet 6. Further, as shown in FIG. 2,
the magnet 6 is magnetized in different radial directions on the inner and outer circumferential
sides thereof, and for example, the inner circumferential side is an S pole and the outer
circumferential side is an N pole. Further, on the upper plate 1 at a position facing the magnet 6,
a first coil 7 in which a plurality of turns are spirally wound in the radial direction same as the
magnetization direction of the magnet 6 with an adhesive or the like It is fixed and disposed.
Further, on the lower plate 2 at a position facing the first coil 7 with the magnet 6 interposed
therebetween, a second coil 8 wound in the same shape as the first coil 7 is fixedly disposed by
an adhesive or the like. . Further, the gaps between the first and second coils 7 and 8 and the
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magnet 6 are set to approximately 0.2 mm so as not to contact even when the diaphragm 5
vibrates to the maximum. The thickness of the second spacers 3 and 4 is set.
Further, by reducing the gap between the first and second coils 7 and 8 and the magnet 6 to
about 0.2 mm, leakage of the magnetic field between the magnet 6 and the first and second coils
7 and 8 can be reduced. It is supposed to be. Further, in the second coil 8, an inner yoke 9 is
disposed on the inner circumferential side and an outer yoke 10 is disposed in close contact on
the outer circumferential side. The ring-like width dimension of the second coil 8 including the
inner yoke 9 and the outer yoke 10 is formed to be substantially the same as the width
dimension of the magnet 6 magnetized in the radial direction. The inner yoke 9 and the outer
yoke 10 are formed of a magnetic material such as soft iron and are in close contact with the
second coil 8, and therefore, the inner yoke 9 and the outer yoke 10 and the space between the
second coil 8 Magnetic field leakage can be reduced. Therefore, when the electro-acoustic
transducer of the present invention is a speaker, a large magnetic flux density can be obtained
even if the current supplied to the second coil 8 is small, and the diaphragm 5 can be vibrated
efficiently. . When such an electroacoustic transducer according to the present invention is a
speaker, when an alternating current is applied to the first and second coils 7 and 8 using a
sound signal as an electric signal, the first, The magnetic field generated in the second coils 7 and
8 and the magnetic field of the magnet 6 act to attract the magnet 6 to the first coil 7 and repel
to the second coil 8 or repel to the first coil 7 By being attracted by the second coil 8, the
diaphragm 5 vibrates in the vertical direction in the figure at a predetermined frequency. The
vibration of the diaphragm 5 reproduces a sound in a predetermined sound range and outputs
the reproduced sound to the outside. When the electro-acoustic transducer of the present
invention is a microphone, when the diaphragm 5 vibrates due to the sound from the outside, the
magnet 6 vibrates in synchronization with the vibration of the diaphragm 5. Then, an induced
electromotive force is generated in the first and second coils 7 and 8, and an electric signal of a
current generated by the induced electromotive force can be input as a sound signal. A method of
manufacturing the magnet 6 used in the electro-acoustic transducer of the present invention will
be described. First, the magnetic paste for printing on the diaphragm 5 is made of SmFeN or the
like in a binder such as polyester resin. The magnetic powder comprising the above is mixed at a
predetermined mixing ratio, and manufactured with a predetermined viscosity. The magnetic
powder made of SmFeN or the like has a particle diameter of approximately 0.1 mm. Then, a
wide base material (not shown) of the diaphragm 5 is annealed at a predetermined temperature
and time, and a metal is formed on the base material of the diaphragm 5 in which a plurality of
print patterns of the ring-shaped magnet 6 are formed. The mask plate (not shown) is positioned,
and the magnetic paste is printed on the surface of the diaphragm 5.
Thereafter, by drying the magnetic paste at a predetermined temperature and time, a plurality of
ring-shaped magnets 6 having a thickness as thin as 0.1 mm or less are formed on the base
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material of the diaphragm 5. Next, the base material of the wide diaphragm 5 on which the
plurality of magnets 6 are formed by printing is cut into a circular shape as shown in FIG. 2 and
separated, and a radial by a magnetizing machine (not shown) The magnet 6 is formed by
magnetizing in the direction and magnetized. As described above, the magnet 6 is magnetized in
the radial direction, so that the demagnetizing field can be reduced and the permeance (magnetic
conductivity) can be increased. Therefore, even if the thickness is as thin as 0.1 mm or less, the
magnet 6 is strong Magnetic force can be obtained. Therefore, the thickness of the magnet 6 can
be reduced to 0.1 mm or less. The thickness of the magnet 6 printed and formed on the vibrating
plate 5 can be determined according to the particle size of the magnetic powder, and in the
present embodiment, the particle size of the magnetic powder is 0. 0. Although the magnet 6 was
described to be formed to a thickness of 0.1 mm using a large size of 1 mm, the thickness of the
magnet 6 can be changed by changing the particle size of the magnetic powder as necessary.
There is. In addition, when it is not necessary to make the electroacoustic device thin, the
thickness of the magnet can be increased by making the thickness of the magnet thicker by
repeatedly performing multilayer printing of the magnetic paste on the magnet 6 formed by
printing the magnetic paste. It is also possible to obtain a magnetic force. In the embodiment of
the present invention, although the magnet 6 magnetized in the radial direction such that the
magnetic poles are different on the inner circumferential side and the outer circumferential side
has been described, the magnet magnetized in the thickness direction It is good. Further, the
inner yoke 9 and the outer yoke 10 formed in the second coil 8 may be formed in the first coil 7
or in both of them. Alternatively, the inner yoke 9 and the outer yoke 10 may not be formed on
either of the first and second coils 7 and 8. That is, it is sufficient that the first coil 7 and / or the
second coil 8 have the yokes 9 and 10 disposed on the inner peripheral side and the outer
peripheral side which are spirally wound. Alternatively, the inner yoke 9 and the outer yoke 10
may not be formed on either of the first and second coils 7 and 8. Further, although the first and
second coils 7 and 8 in the present invention are described as being composed of conducting
wires wound in a spiral shape, conductive patterns printed and formed in a spiral shape on the
upper plate 1 and the lower plate 2 It may be made of As described above, on the upper plate at
a position facing the magnet, the first coil spirally wound in the direction parallel to the flat
portion of the magnet is disposed to sandwich the magnet. In the lower plate facing the first coil,
the second coil wound in the same shape as the first coil is disposed. Therefore, when the electroacoustic transducer of the present invention is a speaker, By energizing the second coil with an
alternating current using a sound signal as an electric signal, the diaphragm can be reliably and
efficiently vibrated corresponding to the sound signal.
Then, by reliably vibrating the diaphragm efficiently, it is possible to provide a high-performance
electro-acoustic transducer capable of faithfully reproducing sound and outputting it to the
outside. In addition, since the magnet is formed by printing the magnetic paste on which the
magnetic powder is kneaded on the surface of the diaphragm, it is possible to form a thin magnet
by changing the particle size of the magnetic component. The electro-acoustic transducer of the
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present invention can be made thin. Further, since the magnet is magnetized in the radial
direction in which the magnetic poles are mutually different at the inner peripheral edge and the
outer peripheral edge, a strong magnetic force can be obtained even with a thin magnet. In
addition, since the first coil and / or the second coil has the yokes disposed on the spiral inner
and outer peripheral sides, a large magnetic flux density can be obtained even if the current
supplied to the coil is small. You can get it. In addition, since the ring-like width dimensions of
the second coil including the yokes on the inner circumferential side and the outer
circumferential side are formed to be the same dimensions as the width dimension of the magnet
magnetized in the radial direction, The magnetic flux generated in the two coils can be efficiently
applied to the magnet, and the diaphragm can be reliably vibrated in response to the sound
signal. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an essential
part for explaining an embodiment according to the present invention. FIG. 2 is a plan view
illustrating a magnet according to the present invention. FIG. 3 is a cross-sectional view of an
essential part for explaining a conventional electroacoustic transducer. [Explanation of the code]
1 upper plate 2 lower plate 3 first spacer 4 second spacer 5 diaphragm 6 magnet 6a circular
space 6b flat portion 7 first coil 8 second coil 9 inner yoke 10 outer yoke
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