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JP2000201397

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DESCRIPTION JP2000201397
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer which is mounted on a portable terminal such as a portable telephone
and a pager and is used to reproduce an alarm sound upon an incoming call.
[0002]
2. Description of the Related Art A plan view of a conventional electromagnetic electroacoustic
transducer is shown in FIG. 9 (a) and a cross-sectional view is shown in FIG. 9 (b). The
conventional electromagnetic type electroacoustic transducer has a cylindrical casing 107 and a
disk-like yoke 106 disposed so as to cover the bottom of the casing 107. A center pole 103
integrally formed with the yoke is provided. A coil 104 is wound around the center pole 103. An
annular magnet 105 is provided on the outer periphery of the coil 104, and an appropriate
distance is provided between the coil 104 and the inner peripheral surface of the magnet 105
over the entire periphery. The outer peripheral surface of the magnet 105 abuts on the inner
peripheral surface of the housing 107. A disc-shaped non-magnetic first diaphragm 100 is
supported at the upper end of the housing 107, and between the first diaphragm 100 and the
magnet 105, the coil 104, and the center pole 103. There are appropriate intervals. At the
central portion of the first diaphragm 100, a second diaphragm 101, which is a disk-shaped
magnetic body, is provided concentrically with the first diaphragm 100.
[0003]
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1
The operation and effects of the electromagnetic electroacoustic transducer configured as
described above will be described. In the initial state in which no current flows in the coil 104, a
magnetic path is formed by the magnet 105, the second diaphragm 101, the center pole 103,
and the yoke 106, and the second diaphragm 101 is on the magnet 105 and center pole 103
side. And is displaced to the point where it is equal to the elastic force of the first diaphragm 100.
When an alternating current flows through the coil 104 in such an initial state, an alternating
magnetic field is generated in the magnetic path, and an alternating current driving force is
generated on the second diaphragm 101. When such an alternating current driving force is
generated in the second diaphragm 101, the second diaphragm 101, together with the first
diaphragm 100 fixed by the interaction with the static attractive force generated by the magnet
105. It vibrates from the initial state. The vibration is emitted as sound. However, in the above
configuration, the distance between the magnet 105 and the second diaphragm 101 is large, and
the magnetic flux can not be effectively applied to the second diaphragm 101.
[0004]
FIG. 10 is a magnetic flux vector diagram of the conventional electromagnetic electroacoustic
transducer shown in FIG. In this magnetic flux vector diagram, only one half with respect to the
central axis is displayed, and the first diaphragm 100 and the housing 107 are not displayed
because they are nonmagnetic materials. In the conventional electromagnetic electroacoustic
transducer, a magnetic path is formed in the second diaphragm 101 from the magnet 105 via a
large magnetic gap. Therefore, it is difficult to supply a sufficient magnetic flux to the second
diaphragm 101 from the magnetic path from the central portion of the magnet 105 because the
air layer acting as the magnetic resistance is large.
[0005]
There is also a means of using a magnetic material as the material of the first diaphragm 100 and
utilizing it as a magnetic path. However, also in this case, it is difficult to provide the first
diaphragm with a thickness that can be used without magnetic saturation as the magnetic path if
the resonance frequency is designed to match the frequency to be reproduced as the alarm
sound.
[0006]
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2
SUMMARY OF THE INVENTION It is an object of the present invention to solve the above
problems, and by arranging a magnetic thin plate between the magnet and the first diaphragm,
the space between the magnet and the second diaphragm can be obtained. The electromagnetic
path is reinforced, and static attraction force and AC drive force are efficiently generated on the
second diaphragm, so that highly efficient electromagnetic waves can be generated without
changing the size of the magnet and the second diaphragm. Type electro-acoustic transducer.
[0007]
SUMMARY OF THE INVENTION The electromagnetic electroacoustic transducer according to the
present invention comprises a first diaphragm disposed vibratable and a magnetic material
provided at a central portion of the first diaphragm. A first diaphragm, a yoke provided opposite
to the first diaphragm, a center pole provided on the surface of the yoke facing the first
diaphragm, and a coil disposed to surround the center pole A magnet disposed so as to surround
the coil, and a magnetic thin plate provided between the magnet and the first diaphragm and
having an inner peripheral edge overlapping the outer peripheral edge of the second diaphragm;
Achieves the above object.
[0008]
The first diaphragm, the magnet and the yoke may form a sealed space.
[0009]
At least one of the first diaphragm, the magnet and the yoke may be provided with at least one
air hole communicating the sealed space with the outside of the sealed space.
[0010]
The apparatus may further include a housing, and the first diaphragm may be disposed in the
housing.
[0011]
The first diaphragm and the housing may form a sealed space.
[0012]
At least one air hole may be provided in at least one of the first diaphragm and the housing for
communicating the sealed space with the outside of the sealed space.
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[0013]
The first diaphragm, the housing, and the yoke may form a sealed space.
[0014]
At least one of the first diaphragm, the housing, and the yoke may be provided with at least one
air hole communicating the sealed space with the outside of the sealed space.
[0015]
At least one air hole may be provided at the position of the yoke where the diameter of the yoke
is equal to or greater than the outer peripheral edge of the magnet.
[0016]
The radial length of the magnetic thin plate overlapping the outer diameter of the second
diaphragm may be 4% to 15% of the outer diameter of the second diaphragm.
[0017]
The inner diameter of the magnetic thin plate may be equal to or less than the inner diameter of
the magnet.
[0018]
The magnet may have a recess on the inner peripheral side of the surface facing the first
diaphragm, and the magnetic thin plate may be fitted into the recess.
[0019]
The outer peripheral edge of the magnetic thin plate may be substantially coincident with the
neutral point at which the direction of the magnetic flux vector generated on the magnet surface
switches in the radial direction to the central direction and the outer peripheral direction.
[0020]
The second diaphragm may be provided with a plurality of radially projecting portions in the
circumferential direction.
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[0021]
The specific gravity of the material forming the first diaphragm may be equal to or less than the
specific gravity of the material forming the second diaphragm.
[0022]
The electromagnetic electroacoustic transducer of the present invention may be incorporated in
a portable terminal device.
[0023]
According to the present invention, it is possible to realize a portable terminal device capable of
reproducing a high sound pressure alarm sound without changing the capacity of a portable
telephone incorporating an electromagnetic electroacoustic transducer.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0025]
Embodiment 1 An electromagnetic electroacoustic transducer according to Embodiment 1 of the
present invention will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a cross-sectional view of an electromagnetic electroacoustic transducer according to
Embodiment 1 of the present invention.
The electromagnetic electroacoustic transducer according to Embodiment 1 of the present
invention includes a cylindrical casing 7 and a disk-shaped yoke 6 disposed so as to cover the
bottom surface of the casing 7. A center pole 3 integrally formed with the yoke is provided at the
center of the yoke 6.
A coil 4 is wound around the center pole 3.
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5
An annular magnet 5 is provided on the outer periphery of the coil 4, and an appropriate
distance is provided between the coil 4 and the inner peripheral surface of the magnet 5 over the
entire periphery.
The outer peripheral surface of the magnet 5 abuts on the inner peripheral surface of the
housing 7.
An annular magnetic thin plate 9 is provided on the upper surface of the magnet 5 so as to cover
the entire upper surface of the magnet 5, and the tip of the center pole 3 is located in the inner
peripheral portion of the magnetic thin plate 9.
The inner diameter of the magnetic thin plate 9 is equal to or less than the inner diameter of the
magnet 5, and the inner peripheral edge of the magnetic thin plate 9 extends inwardly from the
inner peripheral surface of the magnet 5.
A nonmagnetic disk-shaped first diaphragm 1 is vibratably supported at the upper end portion of
the housing 7, and the first diaphragm 1, the magnetic thin plate 9, the coil 4, and the center
pole An appropriate distance is provided between them and 3.
A disc-shaped second diaphragm 2 made of, for example, permalloy, which is a magnetic
substance, is provided concentrically with the first diaphragm 1 at the center of the first
diaphragm 1.
The inner diameter of the magnetic thin plate 9 is smaller than the outer diameter of the second
diaphragm 2, so that the inner peripheral edge of the magnetic thin plate 9 overlaps the outer
peripheral edge of the second diaphragm 2.
The yoke 6 has a plurality of air holes 8 communicating the space between the coil 4 and the
inner circumferential surface of the magnet 5 with the outside of the space between the first
diaphragm 1 and the yoke 6 in the circumferential direction. It is provided at appropriate
intervals.
Each air hole 8 discharges the air between the coil 4 and the inner circumferential surface of the
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magnet 5 to the outside to reduce the acoustic load applied to the first diaphragm 1.
[0026]
The operation and effects of the electromagnetic electroacoustic transducer configured as
described above will be described.
In the initial state in which no current flows through the coil 4, a magnetic path is formed by the
magnet 5, the magnetic thin plate 9, the second diaphragm 2, the center pole 3, and the yoke 6,
and the second diaphragm 2 is a magnet 5. And is attracted to the side of the center pole 3 and
displaced to the point where it is equal to the elastic force of the first diaphragm 1.
When an alternating current flows through the coil 4 in such an initial state, an alternating
magnetic field is generated in the magnetic path, and an alternating current driving force is
generated on the second diaphragm 2.
When such an alternating current driving force is generated in the second diaphragm 2, the
second diaphragm 2 together with the first diaphragm 1 fixed by the interaction with the static
attraction generated by the magnet 5 It vibrates from the initial state.
The vibration is emitted as sound.
[0027]
In the first embodiment of the present invention, since the magnetic thin plate 9 is provided
between the magnet 5 and the second diaphragm 2, the magnetic resistance is suppressed, and
the magnetic flux density in the magnetic path is large. It has become.
As a result, the AC driving force applied to the second diaphragm 2 becomes large, and the first
diaphragm 1 and the second diaphragm 2 vibrate with a larger amplitude, so that the
reproduction sound pressure becomes larger.
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When the magnetic thin plate 9 is provided, the static attraction force is about 71%, and the AC
driving force is about 43% larger than when the magnetic thin plate 9 is not provided.
[0028]
FIG. 2 is a graph showing the relationship between the overlapping ratio of the inner peripheral
edge of the magnetic thin plate 9 and the outer peripheral edge of the second diaphragm 2 and
the AC driving force.
Here, the overlapping rate refers to the ratio of the overlapping length of the inner diameter of
the magnetic thin plate 9 and the outer diameter of the second diaphragm 2 and the length of
the outer diameter of the second diaphragm 2. In the graph of FIG. 2, the horizontal axis
represents the overlapping rate, and the vertical axis represents the alternating current driving
force. When the overlapping rate is about 9%, the alternating current driving force is maximized.
Also, when the overlapping rate is 5%, the static attraction force is applied to the case where the
inner diameter of the magnetic thin plate 9 and the outer diameter of the second diaphragm 2
coincide and the overlapping rate is 0% that does not overlap each other. It is 21%, 10% larger in
AC drive power. From the graph of FIG. 2, in order to increase the AC driving force, it is
preferable to set the overlapping rate to about 4% to 15%.
[0029]
In the electromagnetic electroacoustic transducer according to the first embodiment of the
present invention shown in FIG. 1, the inner diameter of the magnetic thin plate 9 is smaller than
the inner diameter of the magnet 5, but the inner diameter of the magnetic thin plate 9 is second
The inner diameter of the magnetic thin plate 9 may be the same as or larger than the inner
diameter of the magnet 5 as long as it is smaller than the outer diameter of the diaphragm 2.
Further, if the thin magnetic plate 9 is disposed between the magnet 5 and the first diaphragm 1,
it is not necessary to be in contact with the magnet 5. The magnetic thin plate 9 preferably has a
thickness that does not cause magnetic saturation in order to suppress the magnetic resistance
and increase the magnetic flux density in the magnetic path.
[0030]
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8
Second Embodiment FIG. 3 is a cross-sectional view of an electromagnetic type electroacoustic
transducer according to a second embodiment of the present invention. In the electromagnetic
type electroacoustic transducer shown in FIG. 3, a recess into which the magnetic thin plate 19 is
inserted is provided on the inner peripheral side portion of the upper surface of the magnet 15,
the magnetic thin plate 19 is inserted into the recess, and the magnet It is integrally fixed with
15. The inner peripheral edge of the thin magnetic plate 19 protrudes from the inner peripheral
edge of the magnet 15. The other configuration is the same as that of the electromagnetic
electroacoustic transducer according to the first embodiment of the present invention shown in
FIG.
[0031]
In the electromagnetic type electroacoustic transducer configured as described above, by
inserting the magnetic thin plate 19 into the magnet 15, the static attraction force generated by
the magnet 15 and the AC driving force applied to the second diaphragm 2 can be almost
obtained. The overall height of the electromagnetic electroacoustic transducer can be reduced
without reduction.
[0032]
FIG. 4 is a magnetic flux vector diagram of the electromagnetic electroacoustic transducer shown
in FIG.
In this magnetic flux vector diagram, only the magnetic flux vector of one side half with respect
to the central axis is displayed, and since the first diaphragm 1 and the housing 7 are
nonmagnetic materials, they are not shown in FIG. Also, the holes 8 are not shown in FIG. 4 in
order to display the magnetic path more properly. As shown in FIG. 4, the direction of the
magnetic flux vector generated on the magnet 15 is switched between the central direction and
the outer peripheral direction at the neutral point in the radial direction of the magnet 15. In this
case, since the magnet 15 is provided with the magnetic thin plate 19, the magnetic flux from the
central portion of the magnet 15 toward the center can also be concentrated near the inner
peripheral edge of the magnet 15 by the magnetic thin plate 19. Further, the magnetic layer is
efficiently supplied to the second diaphragm 2 because the air layer in the magnetic path
between the central portion of the magnet 15 and the second diaphragm 2 becomes smaller and
the magnetic resistance is reduced. Is possible.
03-05-2019
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[0033]
The direction of the magnetic flux vector generated on the magnet 15 is switched between the
central direction and the outer peripheral direction with the radial neutral point, so the outer
diameter of the magnetic thin plate 19 is adjusted to the maximum diameter at which the
magnetic flux vector is generated toward the central direction. Thus, the magnetic thin plate 19
concentrates the magnetic flux directed toward the center of the magnet 15 most effectively to
the second diaphragm 2 by making the outer peripheral edge of the magnetic thin plate 19
substantially coincide with the neutral point. be able to.
[0034]
FIG. 5 is a graph showing the relationship between the outer diameter of the magnetic thin plate
19 and the static attraction force and the alternating current driving force applied to the second
diaphragm 2.
In this graph, the horizontal axis represents the outer diameter of the magnetic thin plate 19 and
the vertical axis represents the static attraction force and the alternating current driving force
applied to the second diaphragm 2, and it is static near the neutral point shown in FIG. It can be
seen that the suction power is at a maximum.
[0035]
Third Embodiment FIG. 6 is a cross-sectional view of an electromagnetic type electroacoustic
transducer according to a third embodiment of the present invention. In the electromagnetic
electroacoustic transducer shown in FIG. 6, the magnet 15 is disposed such that a space is
formed between the outer peripheral surface of the magnet 15 and the inner peripheral surface
of the housing 7, and the space and the first A plurality of air holes 28 communicating the
outside of the space between the diaphragm 1 and the yoke 26 are provided in the yoke 26 at
appropriate intervals in the circumferential direction. The other configuration is the same as that
of the electromagnetic electroacoustic transducer of the second embodiment of the present
invention shown in FIG.
[0036]
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10
In the electromagnetic electroacoustic transducer configured as described above, air between the
outer peripheral surface of the magnet 15 and the inner peripheral surface of the housing 7 is
discharged to the outside through the air holes 28. By providing the air hole 28 on the outer
peripheral side portion of the yoke 26, the magnet 15 can be provided on the center side of the
yoke 26. In addition, since the air hole 28 is outside the magnet 15 and the magnetic thin plate
19 does not block the passage of air between the first diaphragm 1 and the air hole 28, the inner
peripheral edge portion of the magnetic thin plate 19 The inner diameter of the thin magnetic
plate 19 can be reduced so that the coil 4 overlaps the coil 4. As a result, the outer diameter of
the second diaphragm 2 whose outer peripheral edge is overlapped with the inner peripheral
edge of the magnetic thin plate 19 can also be reduced. When the outer diameter of the second
diaphragm 2 is reduced, the elastic support portion of the first diaphragm 1 other than the
portion supporting the second diaphragm 2 becomes wider, and the second diaphragm 2
vibrates. The reproduction sound pressure can be increased because the amplitude of the signal
can be increased.
[0037]
(Fourth Embodiment) FIG. 7 (a) is a plan view of an electromagnetic type electroacoustic
transducer according to a fourth embodiment of the present invention, and FIG. 7 (b) is a
sectional view taken along the line I-I of FIG. 7 (a). It is. In the electromagnetic type
electroacoustic transducer shown in FIG. 7, the second diaphragm 32 fixed to the central portion
of the first diaphragm 1 cuts out a plurality of locations of the peripheral portion in the disk
shape, and the diameter A plurality of projecting portions projecting in the direction are formed
in a shape provided at equal intervals in the circumferential direction. Each protrusion has a side
edge along a quadratic curve so that the sum of the cross-sectional areas is constant at any
position in the radial direction. The thickness of the second diaphragm 32 is preferably thicker
than that of the first diaphragm 1. The other configuration is the same as that of the
electromagnetic electroacoustic transducer according to the third embodiment of the present
invention shown in FIG.
[0038]
In the second diaphragm 2 in the first to third embodiments of the present invention, since its
shape is a disk, the cross-sectional area over the entire circumference in the circumferential
direction at a predetermined position in the radial direction becomes larger toward the outer
periphery. The cross-sectional area over the entire circumference in the circumferential direction
is uneven in the radial direction. Since the magnetic flux density in the magnetic body is inversely
03-05-2019
11
proportional to the cross-sectional area through which the magnetic flux passes, the magnetic
flux density inside the second diaphragm 2 becomes uneven in the radial direction. However, the
second diaphragm 32 in the fourth embodiment of the present invention has a cross-sectional
area of each projection at any position in the radial direction at the outer peripheral portion
where the projection of the second diaphragm 32 is provided. Each protrusion is formed such
that the sum of the two is constant. Accordingly, the magnetic flux density is made uniform at the
outer peripheral portion where the projecting portion of the second diaphragm 32 is provided.
[0039]
In addition, by cutting out the peripheral portion of the second diaphragm 32 to such an extent
that magnetic saturation does not occur, the amount of magnetic flux passing through the second
diaphragm 32 is equal to that of the magnetic flux passing through the disk-shaped second
diaphragm 2. The AC driving force acting on the second diaphragm 32 can be made substantially
the same as that of the second diaphragm 2 without much difference from the amount. As a
result, due to the vibration of the second diaphragm 32 having a uniform magnetic flux density, a
sound is emitted without causing the characteristic deterioration.
[0040]
In the electromagnetic electroacoustic transducer shown in FIG. 7, since the second diaphragm
32 thicker than the first diaphragm 1 is formed by cutting out the peripheral portion, the first
diaphragm 1 and the second diaphragm 32 are not required. The entire mass of the diaphragm
32 is reduced in weight as compared with the case where the notch is not provided like the
second diaphragm 2, and as a result, the reproduction sound pressure level can be increased. The
projecting portion of the second diaphragm 32 is preferably provided on the outer peripheral
side of the portion of the second diaphragm 32 facing the center pole 3.
[0041]
In the electromagnetic type electroacoustic transducer shown in FIG. 7, the second diaphragm 32
is formed by cutting out a disc to reduce the overall weight of the diaphragm, but the material of
the first diaphragm may be used. The same effect can be obtained even if the weight is reduced
by using a material having a small specific gravity. For example, the same effect can be obtained
by changing from permalloy, which is also used as the first diaphragm material, to titanium
03-05-2019
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having a small specific gravity.
[0042]
In the electromagnetic electroacoustic transducers according to the second to fourth
embodiments of the present invention shown in FIGS. 3, 6 and 7, the inner diameter of the
magnetic thin plate 19 is smaller than the inner diameter of the magnet 15. If the inner diameter
of the thin body plate 19 is smaller than the outer diameter of the second diaphragm 2 or the
second diaphragm 32, the inner diameter of the magnetic thin plate 19 may be the same as or
larger than the inner diameter of the magnet 15. Further, in order to suppress the magnetic
resistance and increase the magnetic flux density in the magnetic path, the magnetic thin plate
19 preferably has a thickness that does not cause magnetic saturation.
[0043]
FIG. 8 is a partially cutaway perspective view of a portable telephone as an example of a portable
terminal equipped with the electromagnetic electroacoustic transducer of the present invention.
The electromagnetic electroacoustic transducer used in this mobile phone is the same as that
shown in the first to fourth embodiments of the present invention.
[0044]
The portable telephone 61 has a housing 62, and a sound hole 63 is provided on one side of the
housing 62. In the housing 62, the electromagnetic electroacoustic transducer 10 of the present
invention is provided so that the first diaphragm 1 faces the sound hole 63. The portable
telephone 61 incorporates a signal processing circuit (not shown) for converting a call signal for
receiving a signal and inputting it to the electromagnetic type electroacoustic transducer 10.
When the signal processing circuit of the portable telephone 61 receives a signal indicating an
incoming call, the signal is inputted to the electromagnetic type electroacoustic transducer 10
and a ringing tone is reproduced. As a result, the user can know the incoming call.
[0045]
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13
In the mobile phone 61 in which the electromagnetic electroacoustic transducer 10 of the
present invention is used, the reproduction sound pressure of the ringing tone can be increased
without taking measures such as increasing the size of the second diaphragm and the magnet. it
can. Therefore, it is possible to provide a high-sounding ringing tone without increasing the
capacity of the portable telephone 61 itself which incorporates the electromagnetic type
electroacoustic transducer 10.
[0046]
In the mobile phone 61, the electromagnetic electroacoustic transducer 10 is directly attached to
the housing 62, but may be attached on a substrate built in the mobile phone 61. Also, an
acoustic port may be added to further increase the sound pressure of the ringing tone.
[0047]
Further, although a mobile phone is shown as an example of the mobile terminal in FIG. 8, the
present invention is not limited to this.
[0048]
In the embodiment of the present invention, although the case where the shape of the magnetic
thin plate is annular is disclosed, the shape of the magnetic thin plate is not limited to annular,
and even if the annular magnetic thin plate has a notch portion Alternatively, the magnetic thin
plate may be configured by intermittently arranging a plurality of magnetic bodies in the
circumferential direction of the top surface of the magnet.
[0049]
Further, in the embodiment of the present invention, the component that vibratably supports or
fixes the first diaphragm is not limited to the housing.
Any component may be used as long as it can vibratably support or fix the first diaphragm.
[0050]
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14
Further, in the embodiment of the present invention, a sealed space is formed by the first
diaphragm, the housing, and the yoke, but the sealed space is formed by the first diaphragm, the
magnet, and the yoke. In this case, the first diaphragm is supported by the magnet.
Also, the sealed space may be formed by the first diaphragm and the housing. Moreover, the air
hole which connects said sealed space and the exterior of sealed space may be provided in any
component which comprises the electromagnetic type electroacoustic transducer of this
invention.
[0051]
According to the electromagnetic type electroacoustic transducer of the present invention, since
the magnetic thin plate having the inner diameter smaller than the outer diameter of the second
diaphragm is disposed on the upper surface of the magnet, the magnet and the second vibration
are produced. The reluctance can be reduced without increasing the size of the plate, and thus
the static attraction and the ac drive can be increased. As a result, since the second diaphragm
can be made smaller, the mass of the entire diaphragm can be reduced, and the reproduction
sound pressure can be increased. Furthermore, the overall height of the electromagnetic
electroacoustic transducer can be reduced by providing a recess on the inner peripheral side of
the top surface of the magnet and inserting a magnetic thin plate therein. Further, by providing a
notch in the second diaphragm or using a material having a small specific gravity as the material
of the first diaphragm, the weight of the entire diaphragm can be reduced and the reproduction
sound pressure level can be improved. Can. Further, an air hole for removing air between the
first diaphragm and the yoke is disposed on the outer peripheral side of the yoke to reduce the
inner diameter of the magnetic thin plate and to reduce the outer diameter of the second
diaphragm as well. The elastic support portion of the first diaphragm can be made wide and the
amplitude can be made large.
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