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JP2002186094

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DESCRIPTION JP2002186094
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer for converting an electrical signal to sound.
[0002]
2. Description of the Related Art An electro-acoustic transducer of this type is known, for
example, as disclosed in JP-A-8-6558. The electro-acoustic transducer disclosed in Japanese
Patent Application Laid-Open No. 8-6558 has a case, and in the case, a pole piece in which a base
and an iron core are integrally fixed is mounted. A coil is disposed on the outer peripheral side of
the iron core. In addition, magnets are disposed on the outer circumferential side of the coil at
intervals. The coil is disposed on the outer peripheral side of the iron core by directly winding a
conducting wire around an iron core or by attaching a winding of a conducting wire in an aircore manner to the iron core.
[0003]
SUMMARY OF THE INVENTION However, it has been found that the electroacoustic transducer
having the above-described configuration has the following problems. When winding a lead
directly to an iron core, there is a risk that the lead (insulation layer) may be damaged by the
metal core. In addition, even in the case of attaching an air-core wound wire to an iron core, the
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wire and the iron core may be rubbed, and the wire (insulating layer) may be scratched. Thus,
when the conducting wire (insulating layer) is damaged, a short circuit occurs due to contact with
the iron core, which causes the reliability and durability of the electroacoustic transducer to be
reduced.
[0004]
In order to solve the problem of the damage etc. of the conducting wire mentioned above, the
structure of providing the bobbin part which winds a conducting wire on the outer side of an iron
core can be considered. However, when the bobbin portion is provided, the volume of the back
space of the electroacoustic transducer is reduced, and the sound pressure characteristics,
particularly the sound pressure characteristics in the low frequency range, are degraded.
[0005]
The present invention has been made in view of the above-mentioned point, and it is possible to
suppress the deterioration of sound pressure characteristics and to prevent the damage of the
lead wire constituting the coil and to suppress the deterioration of reliability and durability. It
aims at providing an acoustic transducer.
[0006]
SUMMARY OF THE INVENTION An electroacoustic transducer according to the present invention
comprises a pole piece having an iron core and a base, a bobbin portion disposed so as to
surround the outer periphery of the iron core, and a conductor wound around the bobbin
portion. And a magnet disposed on the outer peripheral side of the coil, and the bobbin portion is
divided into a plurality of pieces in the circumferential direction of the iron core.
[0007]
In the electro-acoustic transducer according to the present invention, since the coil is configured
by winding the conducting wire around the bobbin portion, it is possible to prevent the
conducting wire (coating layer) from being damaged when winding the conducting wire.
As a result, there is no possibility of contact between the iron core and the damaged lead (coil) to
cause a short circuit.
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As a result, it is possible to suppress deterioration in the reliability and durability of the
electroacoustic transducer.
[0008]
Further, in the electro-acoustic transducer according to the present invention, since the bobbin
portion is divided into a plurality in the circumferential direction of the iron core, the bobbin
portion is intermittently disposed when viewed in the circumferential direction of the iron core.
Volume can be reduced. Thereby, it is possible to suppress the reduction of the sound pressure
characteristic by suppressing the reduction of the volume of the back space of the
electroacoustic transducer as much as possible.
[0009]
In addition, a case including an upper case and a lower case provided with a coil side terminal
portion to which an end of a conducting wire is electrically connected is further provided, and
the bobbin portion is integrally formed on the lower case. Is preferred. As described above, the
case further including the upper case and the lower case provided with the coil side terminal
portion to which the end of the conducting wire is electrically connected is further provided, and
the bobbin portion is integrally formed on the lower case. As a result, since the bobbin portion is
integrally formed with the lower case, there is no need to newly add another component for
winding the conducting wire. As a result, the bobbin portion can be provided without cost
increase due to the new construction of parts and increase in the process, and a configuration
capable of preventing the damage of the lead (covering layer) can be realized simply and at low
cost.
[0010]
Further, the bobbin portion is formed extending from the lower case so as to surround the outer
periphery of the iron core, and it is preferable that the iron core be held by the bobbin portion.
As described above, the bobbin portion is formed to extend from the lower case so as to surround
the outer periphery of the iron core, and by holding the iron core by the bobbin portion, it is
possible to prevent the pole piece from being detached from the lower case.
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[0011]
The base is preferably mounted on the lower case and has a hole through which the bobbin
portion is inserted. Thus, the base can be easily mounted on the lower case without interfering
with the bobbin by having the hole mounted for the insertion of the bobbin on the lower case.
The configuration can be realized extremely simply.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the electroacoustic
transducer according to the present invention will be described in detail below with reference to
the drawings. In the description of the drawings, the same elements will be denoted by the same
reference symbols, and redundant description will be omitted.
[0013]
FIG. 1 is a perspective view showing the entire appearance of an electroacoustic transducer
according to an embodiment of the present invention, FIG. 2 is a cross sectional view showing the
same electroacoustic transducer, and FIG. It is an exploded perspective view showing the
composition of a vessel.
[0014]
The electroacoustic transducer T has a case 1 made of a thermoplastic resin as shown in FIGS. 1
to 3.
The case 1 includes an upper case 11 and a lower case 21. The upper case 11 and the lower case
21 are joined and fixed to each other by using an ultrasonic welding technique. The upper case
11 has a substantially box shape whose lower surface side is open. A sound outlet 12 is formed
in the upper surface portion of the upper case 11, and a sound emitting cylinder 13 is provided
continuously to the sound outlet 12. The upper case 11 is formed with a step 14 for contacting
the ultrasonic welding machine. A pole piece 31, a coil 41, a magnet 51, a resonance plate 61
and the like are accommodated in an internal space defined by the upper case 11 and the lower
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case 21.
[0015]
The pole piece 31 is placed on the lower case 21. The pole piece 31 has a substantially
cylindrical iron core 32 and a base 33 made of a metal material (for example, permalloy or the
like), as shown in FIGS. 4 and 5. The iron core 32 is crimped at the center position of the base 33
and integrally fixed. A notch 34 is formed at a predetermined position of the edge of the base 33.
Further, a plurality of (three in the present embodiment) hole portions 35 for inserting a bobbin
portion 24 described later are formed around the portion of the base 33 to which the iron core
32 is fixed. In the present embodiment, the thickness of the base 33 is set to about 0.6 mm. The
length from the top surface of the base 33 to the top of the iron core 32 (the height of the iron
core 32) is set to about 3.8 mm.
[0016]
As shown in FIGS. 6 and 7, the upper surface of the lower case 21 is engageable with the wall 22
for defining the mounting position of the pole piece 31 and the notch 34 of the base 33. The
protrusion 23 and the bobbin portion 24 for forming the coil 41 are integrally formed. The wall
portion 22 is formed with a protrusion 25 engageable with a protrusion 15 formed on the upper
case 11, and these protrusions 15 and 25 are engaged with each other to lower the upper case
11 and the lower portion. Positioning with the side case 21 is performed. The height of the wall
22 and the projection 23 is set to a value larger than the thickness of the base 33. In the present
embodiment, the height of the wall portion 22 is set to about 1.2 mm, and the height of the
protrusion 23 is set to about 0.8 mm.
[0017]
The bobbin portion 24 is formed extending from the upper surface portion of the lower case 21
toward the internal space of the case 1 so as to surround the outer periphery of the iron core 32,
and a plurality of bobbin portions 24 (in this embodiment, It is divided into 3). The bobbin
portion 24 includes a base portion 26 and an extending portion 27. The height of the base
portion 26 is set to a value larger than the thickness of the base 33 (about 0.85 mm in the
present embodiment). The length of the extension 27 is a value such that the top side of the iron
core 32 protrudes from the end of the extension 27 when the pole piece 31 is placed on the
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lower case 21 (in the present embodiment, 2 It is set to about .95 mm). Further, the inner
diameter of the bobbin portion 24 (base portion 26) is set to a value (about 2.2 mm in the
present embodiment) substantially equal to the outer diameter of the iron core 32.
[0018]
The surface on the core 32 side of the base 26 is curved along the outer periphery of the core
32. The surface of the extension 27 on the side of the iron core 32 and the back surface thereof
(the side on which the wire 42 is wound) are also curved along the outer periphery of the iron
core 32. The cross-sectional area of the base 26 is set to a value larger than that of the extension
27. As a result, the mechanical strength of the bobbin portion 24 can be secured, and the bobbin
portion 24 can be prevented from being detached from the lower case 21.
[0019]
The pole piece 31 (base 33) is inserted in the hole portion 35 of the base 33 through the bobbin
portion 24 (extension portion 27) and the bobbin portion 24 (extension portion 27) is positioned
on the outer periphery of the iron core 32; By being pressed from above the lower case 21, the
lower case 21 is fitted and mounted. At this time, the notch 34 of the base 33 and the projection
23 of the lower case 21 engage with each other to position the pole piece 31 with respect to the
lower case 21. When the pole piece 31 is fitted in the lower case 21, the inner diameter of the
bobbin portion 24 (base 26) is set to a value substantially equal to the outer diameter of the iron
core 32, so the iron core 32 is held by the bobbin portion 24. It will be done. As a result, the pole
piece 31 does not easily come off the lower case 21.
[0020]
The coil 41 is configured by winding the conductive wire 42 around the extension portion 27 of
the bobbin portion 24 and is disposed on the base portion 26 as also shown in FIGS. 8 and 9. In
the present embodiment, a copper wire having a wire diameter of about 60 μm is used as the
conducting wire 42, and an insulating layer is provided on the outer periphery of the copper
wire. The coil height is set to a value equal to or less than the length of the extension 27 (about
2.9 mm in the present embodiment).
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[0021]
Here, since the height of the base portion 26 is set to a value larger than the thickness of the
base 33, the coil 41 and the base 33 (pole piece 31) do not abut each other. Further, since the
bobbin portion 24 (extension portion 27) is divided into a plurality of portions in the
circumferential direction of the iron core 32, the bobbin portion 24 (extension portion 27) is
intermittently arranged as viewed in the circumferential direction of the iron core 32. It will be.
For this reason, when the conducting wire 42 is wound around the bobbin portion 24 (the
extending portion 27), the conducting wire 42 is wound linearly at a position between the
divided extending portions 27.
[0022]
Lead terminals 28 and 29 as coil 41 side terminal portions are provided in the lower case 21 in
an integrated state by a so-called "insert molding method". As shown in FIGS. 8 and 9, the end of
the conductive wire 42 constituting the coil 41 passes through the projection 23 formed on the
lower case 21 and the lead terminal from the notch 30 formed on the wall 22. 28 and 29 are
drawn onto the lands 28a and 29a and soldered to the lands 28a and 29a in this state. In
addition, the notch part 30 formed in the wall part 22 is sealed by a silicone material (not
shown).
[0023]
Refer again to FIGS. 2 and 3. The magnet 51 is an annular plastic magnet, and is disposed on the
outer peripheral side of the coil 41 with a predetermined gap between the magnet 41 and the
coil 41. The magnet 51 is placed in contact with the base 33 of the pole piece 31, and when
placed in contact with the wall 22 of the lower case 21, the placement position of the magnet 51
is regulated.
[0024]
A stepped portion 52 is formed in the magnet 51, and a resonance plate 61 (also referred to as a
diaphragm or an elastic plate) is mounted on the stepped portion 14. In the present embodiment,
the magnet 51 also functions as a support member for supporting the resonance plate 61. At the
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central portion of the resonance plate 61, a magnetic piece 62 as an additional mass is provided.
The resonance plate 61 is attracted by the action of the static magnetic field of the magnet 51,
and is attracted to the magnet 51 side to be in a fixed state. The upward movement of the
resonance plate 61 is restricted by the step 14 of the upper case 11.
[0025]
A back space A is formed on the back side of the resonance plate 61. Further, on the upper
surface side of the resonance plate 61, a resonance space B surrounded by the upper case 11 is
formed. The resonance space B is opened to the outside air through the sound output tube 13
formed in the upper case 11, that is, the sound output port 12.
[0026]
Next, the operation of the electroacoustic transducer T configured as described above will be
described. In the electroacoustic transducer T, the base 33, the iron core 32, the resonance plate
61 and the magnet 51 form a magnetic circuit, the static magnetic field by the magnet 51 acts on
the resonance plate 61, and the magnetized resonance plate 61 is on the iron core 32 side. Are
attracted to The magnet 51 acts on the resonance plate 61 as a bias magnetic field.
[0027]
When an electrical signal such as an alternating current or a pulse is applied between the lead
terminals 28 and 29 with respect to the magnetic field in one direction formed by such a static
magnetic field, the signal current flows through the coil 41 and the iron core 32 responds to the
electrical signal. An oscillating magnetic field is generated. The resonance plate 61 swings away
from the iron core 32 in a section in which the direction of the oscillating magnetic field is
opposite to the static magnetic field of the magnet 51 and is attracted to the iron core 32 in a
section in the same direction as the static magnetic field. Such mechanical up and down motion
depends on the frequency of the electrical signal, and as a result, the resonance plate 61 vibrates
to vibrate air. This vibration is amplified as resonance (resonance) sound in the resonance space
B. This sound is mainly emitted from the sound outlet 12 to the outside.
[0028]
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As described above, in the present embodiment, since the coil 41 is configured by winding the
conducting wire 42 around the bobbin portion 24 (extension portion 27), when the conducting
wire 42 is wound, the conducting wire 42 (covering Layer) can be prevented from being
damaged. As a result, the iron core 32 and the damaged lead 42 (coil 41) do not come in contact
with each other to cause a short circuit. As a result, in the present embodiment, it is possible to
suppress the decrease in the reliability and the durability of the electroacoustic transducer T.
[0029]
Further, since the bobbin portion 24 (the base portion 26 and the extension portion 27) is
divided into a plurality in the circumferential direction of the iron core 32, the bobbin portion 24
(the base portion 26 and the extension portion 27) is intermittent when viewed in the
circumferential direction of the iron core 32. As a result, the volume of the bobbin portion 24 can
be reduced. Thereby, it is possible to suppress the decrease in the sound pressure characteristic
by suppressing the reduction of the volume of the back space A in the electroacoustic transducer
T as much as possible.
[0030]
Further, at the position between the divided bobbin portions 24 (extension portions 27), the
conducting wire 42 is wound in a straight line. Thus, even when any vibration is transmitted to
the coil 41 as in the case of ultrasonic welding of the upper case 11 and the lower case 21, the
coil 41 is restricted from swinging around the bobbin portion 24. As a result, the movement of
the coil 41 in the central axis direction of the iron core 32 is suppressed, and it is possible to
prevent the lead 42 constituting the coil 41 from being scratched or broken.
[0031]
In addition, the case 1 includes an upper case 11 and a lower case 21 provided with lead
terminals 28 and 29, and a bobbin portion 24 (base 26 and extension 27) is integrally formed
with the lower case 21. Therefore, the bobbin portion 24 (the base 26 and the extension 27) and
the lower case 21 (case 1) can be formed at one time, and another component for winding the
conducting wire 42 is newly added. There is nothing to do. As a result, the bobbin portion 24 can
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be provided without cost increase due to the new construction of parts and an increase in the
process, and a configuration capable of preventing the damage of the conducting wire 42
(coating layer) can be realized easily and at low cost.
[0032]
Further, the bobbin portion 24 (the base portion 26 and the extension portion 27) is formed
extending from the lower case 21 so as to surround the outer periphery of the iron core 32, and
the iron core 32 is held by the bobbin portion 24. The pole piece 31 can be prevented from
coming off the lower case 21 with a simple configuration.
[0033]
Further, since the base 33 of the pole piece 31 has the hole 35 for the bobbin portion 24 (the
base 26 and the extension portion 27) to be inserted, the pole piece 31 is inserted into the lower
case 21 and placed. At this time, the bobbin portion 24 (the base portion 26 and the extension
portion 27) and the base 33 do not interfere with each other.
Thus, the configuration in which the pole piece 31 can be easily mounted on the lower case 21
can be realized extremely simply.
[0034]
The present invention is not limited to the above-described embodiment, and the above-described
numerical values, the shapes of the respective components, and the like (for example, the shape
of the bobbin portion 24 and the number of divisions) can be appropriately changed and set.
Further, in the present embodiment, the bobbin portion 24 is configured by the base portion 26
and the extension portion 27. However, without being limited to this, the bobbin portion 24 is
configured only by the portion corresponding to the extension portion 27. May be
[0035]
Moreover, in this embodiment, although the bobbin part 24 is integrally formed with lower side
case 21 (case 1), it is not restricted to this. For example, the bobbin portion 24 may be provided
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separately from the lower case 21 (case 1) and attached and fixed to the lower case 21 by
adhesion or the like.
[0036]
Moreover, in this embodiment, although it comprises so that the pole piece 31 may be engage |
inserted and mounted in lower side case 21, it is not restricted to this. For example, like the lead
terminals 28 and 29, the pole piece 31 may be integrated with the lower case 21 by insert
molding. In this case, the bobbin portion 24 is formed to cover the outer periphery of the iron
core 32 of the pole piece 31.
[0037]
As described above in detail, according to the present invention, it is possible to suppress the
deterioration of sound pressure characteristics and prevent the damage of the conductors
constituting the coil, thereby suppressing the deterioration of reliability and durability. It is
possible to provide an electro-acoustic transducer that can
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