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JPH08102995

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DESCRIPTION JPH08102995
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electromagnetic acoustic transducer suitable for reflow soldering.
[0002]
2. Description of the Related Art Conventionally, an electromagnetic acoustic transducer is
mounted as a notification means in a small electronic device such as a portable telephone, a
pager, a pager, and the like. An electromagnetic acoustic transducer mounted on such an
electronic device is itself small in size, and its component parts are miniaturized, and moreover,
the electrical connection on the electronic device is a reflow process. The soldering method is
taken. The reflow soldering is a method of connecting the solder by passing a portion to be
connected to the heated and melted solder. The reflow temperature is as high as about 300 ° C.,
and the heat is of course applied to the connection portion, but the heat of the portion other than
the connection portion, in particular, the coil of the magnetic drive portion of the electroacoustic
transducer is heat generated by the reflow. It is exposed to
[0003]
By the way, there are a bobbin type and a bobbinless type as the form of the coil installed in the
magnetic drive unit. Among electromagnetic sound transducers that are required to be
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miniaturized, those using bobbinless type coils are the mainstream. This is because the
installation space of the coil occupied in the electromagnetic acoustic transducer is narrowed,
and in order to secure a sufficient number of turns for the coil installed in the narrow space, the
proportion occupied by the coil substantially It is necessary to make the In addition, the fusion
type was used for the wire forming the coil, which also realized the bobbin-less implementation.
[0004]
By the way, when reflow soldering is performed on such an electromagnetic acoustic transducer,
the heat due to the solder reflow deforms the coil, and in particular, increases the coil height, and
the influence is limited to the change in shape. As a result, there is a possibility that the quality of
the final product may be deteriorated, for example, the acoustic characteristics may be
deteriorated, and the generated tone may be changed. Therefore, it may be forced to use a
bobbin type, and it is necessary to take measures such as performing soldering by lowering the
reflow temperature as much as possible.
[0005]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an
electroacoustic transducer which achieves the best characteristics by utilizing heating thereof
without being adversely affected by the heating of reflow soldering.
[0006]
SUMMARY OF THE INVENTION An electromagnetic acoustic transducer according to the present
invention has a coil (24) mounted on a core (22) erected on a base (20), as illustrated in FIGS. 1
and 2. An electromagnetic acoustic transducer including a magnetic drive unit (10) formed by
winding a coil, and the height (L3) of the coil at the time of manufacture is increased by the
thermal expansion at the time of reflow soldering (L2) Only (the coil length L1 is set).
[0007]
Further, as shown in FIGS. 1 and 2, the electromagnetic acoustic transducer according to the
present invention has a magnetic drive in which a coil (24) is wound around a magnetic core (22)
erected on a base (20). An electromagnetic acoustic transducer including a portion (10), in which
the protruding length (H1) of the magnetic core protruding from the coil (24) is increased by the
thermal expansion of the coil (24) during reflow soldering at the time of manufacture (H2) is set
large (H3 is set as a projection length).
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[0008]
In the electromagnetic acoustic transducer of the present invention, the coil heated by reflow
soldering expands to change its height, and as a result, the characteristics of the electromagnetic
acoustic transducer are changed. Deteriorate the characteristics.
In the electromagnetic acoustic transducer of the present invention, the temperature and the
processing time of the reflow soldering are almost constant, and the size (height) of expansion of
the coil in that case can be accurately known in manufacturing. .
Therefore, in the electromagnetic acoustic transducer of the present invention, the height of the
coil at the time of manufacture is set low by the amount of expansion of the coil.
As a result, when heated by reflow soldering, the height of the coil is shifted (optimized) to an
optimum height due to expansion, and the characteristics of the electroacoustic transducer are
determined by the characteristics at the time of manufacturing. Improve. In other words, it can
be said that the electromagnetic acoustic transducer, which is characteristically semi-finished
product at the time of product shipment, is transformed into an optimal final product upon
receiving heating by the reflow process.
[0009]
Even if the electromagnetic acoustic transducer is in an optimal form or state at the time of
manufacture, if it is mounted on an electronic device, the reflow soldering will change the
acoustic characteristics and the desired characteristics can not be obtained. I will meet the
mission as a product. However, in the electromagnetic acoustic transducer according to the
present invention, optimum characteristics can be obtained by heating by reflow soldering, and
the contribution to the final product electronic equipment is more than expected. It is
[0010]
Further, in the electromagnetic acoustic transducer of the present invention, at the time of
manufacture, the projection length of the magnetic core from the coil may be set longer by an
amount corresponding to the length of the coil due to expansion due to the reflow temperature.
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The best characteristics are obtained through the same reflow soldering.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be
described in detail below with reference to the embodiments shown in the drawings.
[0012]
FIG. 1 shows a longitudinal sectional view of the electroacoustic transducer of the present
invention.
In this electromagnetic acoustic transducer, the exterior case 2 is a molded body of synthetic
resin, and the cylindrical main body case 4 and the lid case 6 forming a bowl shape are joined,
and the resonance plate 8 and magnetism are formed therein. The drive unit 10 is built in, and a
resonance chamber 12 is formed on the upper surface side of the resonance plate 8.
Then, in the central portion of the lid case 6, a sound output hole 14 is formed which is a
cylindrical body projecting to the inside. The sound emission hole 14 is opposed to the central
portion of the resonance plate 8, receives the vibration of the resonance plate 8, and emits the
resonance sound to the outside.
[0013]
The resonance plate 8 is a disk made of a magnetic material, and a magnetic piece 16 for
increasing the mass of the resonance plate 8 is fixed at the center thereof. The resonance plate 8
is installed in a step 18 formed in the main body case 4, and an end face on the lid case 6 side is
opposed to the step 18 at a constant interval, as a result, The resonance plate 8 is prevented
from being separated from the step 18.
[0014]
The magnetic drive unit 10 is a drive source that magnetically oscillates the resonance plate 8.
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The magnetic drive unit 10 is provided with a base 20 as a substrate member, and the base 20 is
a disk made of a magnetic material. A cylindrical magnetic core 22 is erected at the central
portion of the base 20, and a coil 24 is installed around the magnetic core 22, and an annular
magnet 26 concentric with the coil 24 is a coil. A space 27 is provided between the outer
circumference of 24 and the space.
[0015]
A constant air gap 28 is formed between the top of the magnetic core 22 and the resonance plate
8. The air gap 28 constitutes a vibration allowance space of the resonance plate 8. A closed
magnetic path is formed by the base 20, the magnetic core 22, the resonance plate 8 and the
annular magnet 26 via the air gap 28. The magnetic force possessed by the annular magnet 26
acts as a bias magnetic field on this closed magnetic path, and the resonance plate 8 is attracted
to the annular magnet 26 side. As a result, the resonance plate 8 is located on the step 18 on the
main body case 4 side. It is fixed to Then, an alternating magnetic field is generated in the coil 24
by the alternating current input applied through the terminals 30, 32, and the resonance plate 8
is vibrated in the front-rear direction of the air gap 28 by the interaction of the alternating
magnetic field and the bias magnetic field. It depends on the frequency which the alternating
current input added to 30, 32 has. As a result of this vibration, a sound is generated in the
resonance chamber 12 and the sound is emitted from the sound emission hole 14.
[0016]
The terminals 30, 32 are rod-like terminals, and are penetrated through a substrate 34 provided
on the back side of the outer case 2 and are erected by caulking and soldering of the end
portions. Although not shown, the ends of the coil 24 are electrically connected to the terminals
30, 32 by means such as soldering. Although not shown, each of the terminals 30 and 32
penetrates the wiring board of the electronic device and is soldered to the conductive pattern and
electrically connected, but reflow soldering is used for the connection.
[0017]
As shown in FIG. 2, a cylindrical magnetic core 22 is erected on the base 20 to form a pole piece
portion. That is, a fixed hole 36 having a diameter smaller than that of the main body of the
magnetic core 22 is formed at the center of the base 20, and the small diameter portion 38
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formed on the magnetic core 22 is press-fitted into the fixed hole 36. And the base 20 are set to
be orthogonal to each other. In this embodiment, the magnetic core 22 is pressed into the base
20, but the base 20 and the magnetic core 22 are not limited to such a fixed form. The base 20
and the magnetic core 22 can be formed by a single member, and for example, the metal plate
forming the base 20 can be formed to project the magnetic core 22. Moreover, even when both
are formed as separate members, it is possible to join by welding. In any case, it is sufficient that
the base 20 and the magnetic core 22 can realize a state in which both are magnetically coupled,
and the form thereof may be any.
[0018]
Further, a coil 24 is fixed to the magnetic core 22. The installation form of the coil 24 may be a
method such as direct winding around the magnetic core 22 or mounting of a coil wound in
advance in a cylindrical shape. Then, the height (the height at the time of manufacture) of the coil
24 is L1. When reflow soldering of an electromagnetic acoustic transducer as a finished product,
the height thermally expanded and increased by heating due to the reflow temperature, that is,
the height of expansion L2, the optimum coil height after expansion (final height Assuming that
L3 is L3, the coil height L1 is a height L1 = L3-L2 obtained by subtracting only the expansion
height L2 from the optimum coil height L3 at the time of mounting on an electronic device.
[0019]
Looking at this relationship on the magnetic core 22 side, the height at which the magnetic core
22 protrudes from the coil 24, ie, the protruding length (the length at the time of manufacture) is
H1, when the coil 24 expands due to heating by the reflow temperature. Assuming that the
expansion height is L2 and the optimum projection length (final length) at the time of mounting
on an electronic device is H3, the projection length H1 of the magnetic core 22 from the end face
of the coil 24 is set to H1 = H2 + H3 at the time of manufacture. That is, between the end faces of
the magnetic core 22 and the coil 24, a protrusion length H1 is set on the magnetic core 22 side
at the time of manufacture, and this protrusion length H1 becomes a step between the end faces
of the core 22 and the coil 24.
[0020]
Next, a method of forming the coil 24 having the coil height L1 will be described. Assuming that
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the height of the conventional coil 24 is L3 for comparison, the first method is a method of
setting the coil height L1 by setting the number of turns smaller than the coil height L3. The
second method is a method of setting the number of turns equal and setting the diameter of the
wire forming the coil 24 small.
[0021]
Next, FIG. 3 shows a wire 40 used for the coil 24. As shown in FIG. As the wire 40, a heat-welding
or solvent-fixing wire such as a fusion magnet wire is used. That is, in the wire 40, an insulation
film 44 made of polyurethane or the like is formed around a conductor 42 made of copper or the
like having a circular cross section, and a fusion film 46 made of polyamide or other
thermoplastic resin is formed on the surface thereof. It is formed.
[0022]
Referring now to FIG. 4, an embodiment of the coil 24 is shown. The coil 24 of this embodiment
is multi-wound. Since the fusion film 46 is formed on the surface of the wire 40, the heat-welding
wire can be melted and cured by heating while winding, and the solvent-fixing wire can be
wound while winding and a solvent such as alcohol Can be melted and cured. Then, the wound
coil is shaped as a coil 24. Therefore, after winding on the magnetic core 22, the coil 24 which
has been hardened or wound separately and hardened may be mounted and fixed to the
magnetic core 22.
[0023]
The electroacoustic transducer thus constructed is shipped as a product and mounted on an
electronic device such as a portable telephone, and the electrical connection is made by reflow
soldering. In that case, the built-in coil 24 is heated by the reflow temperature to cause thermal
expansion.
[0024]
As a result of this thermal expansion, as shown in FIG. 5, the coil 24 of the magnetic drive unit
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10 axially extends, and as shown in FIG. 6, the height L1 of the coil 24 is equal to the expansion
height L2 In addition, it shifts to the optimal height L3. As a result, the protrusion length H1 of
the magnetic core 22 is reduced by the expansion height H2 as a result of the thermal expansion
of the coil 24, and is changed to the optimum protrusion length H3.
[0025]
The experimental results of this electromagnetic acoustic transducer are as follows.
[0026]
【0026】a.
Reduction of the number of turns of the coil 24 The number of turns of the wire 40 is reduced by
the amount by which the coil 24 expands due to thermal expansion, and the electromagnetic
acoustic transducer is formed using the coil 24 whose height L1 is set. For example, the coil
length L1 was changed from 1.4 mm to 1.25 mm, and the expansion height was reduced by 0.15
mm. When the number of turns of the coil 24 is thus reduced to reduce the coil length L1, the
magnetomotive force (ampere turn) on the coil 24 side is reduced accordingly. However, by
increasing the volume of the resonance chamber 12, the resonance effect can be enhanced, and
in this case, the reduction of the magnetomotive force can be compensated.
[0027]
【0027】b. The coil length L1 is shortened by using the wire 40 having the same
conductor diameter and having the same thickness as the insulating film 44 and the fusion film
46 and thus the outer diameter is reduced. When such a wire 40 is used, the number of turns is
reduced. Without the coil length L1 can be set. As the method, by using the wire 40, the number
of layers in the height direction of the coil 24 is reduced by about one layer, and the number of
layers is increased in the outer peripheral direction of the coil 24 by one layer. In this case, the
outer diameter of the coil 24 does not change. According to the experiment, the coil height L1
could be changed from 1.4 mm to 1.3 mm and reduced by about 0.1 mm. In this case, as in the
case a, there is no change in the magnetomotive force generated by the coil 24, and adjustment
of the resonance chamber 12 is unnecessary, and sound pressure characteristics equivalent to
those of the conventional electroacoustic transducer are obtained. It was done.
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[0028]
【0028】c. In the case of the sound pressure characteristics a and b before and after the
reflow, there is no problem in the sound pressure characteristics, and when heating is performed
at a temperature equal to the reflow temperature, no defective product occurs due to the shape
change of the coil 24. The expansion height L2 of the coil 24 using a hot air fixed type
polyurethane copper wire for the wire 40 is 10 to 15%. For example, in the case of the coil 24
having a coil length L1 = 1.4 mm, the expansion height thereof The length L2 was 140 to 210
μm, and almost no change in the outer diameter side of the coil 24 was observed.
[0029]
As described above, according to the present invention, the following effects can be obtained.
a. The coil height can be optimized by the heat treatment by the reflow temperature, so the
product at the time of shipment usually exhibits characteristics, but when it is mounted in an
electronic device, it is an electroacoustic sounding having the best characteristics by heating by
reflow soldering. It can be transformed into a converter, and after being mounted on an
electronic device, can exhibit its best characteristics. b. Conventionally, when an
electroacoustic transducer exhibiting the best characteristics in a product at the time of shipment
is mounted on an electronic device, it is possible to reliably prevent the characteristic change and
the product deterioration caused by the heating of the reflow soldering. c. It is not necessary
to use a wire having a small thermal deformation as the wire forming the coil, and it is only
necessary to control the deformation, and a coil using a wire that is a general-purpose product
can be used. The cost can be reduced, and the quality control of the wire can be facilitated in
manufacturing. d. When a wire with small thermal deformation is used for the coil, the coil can
be miniaturized in anticipation of thermal expansion, and the yield can be enhanced.
[0030]
Brief description of the drawings
[0031]
1 is a longitudinal sectional view showing an embodiment of the electromagnetic acoustic
transducer of the present invention.
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[0032]
2 is an enlarged sectional view showing the structure of the pole piece portion.
[0033]
3 is a cross-sectional view showing a wire used for the coil.
[0034]
4 is an enlarged sectional view showing a winding mode of the coil.
[0035]
5 is a longitudinal sectional view showing an embodiment of the electromagnetic acoustic
transducer of the present invention.
[0036]
6 is an enlarged sectional view showing the structure of the pole piece portion.
[0037]
Explanation of sign
[0038]
DESCRIPTION OF SYMBOLS 10 magnetic drive part 20 base 22 core 24 coil L1 coil height
(setting height at the time of manufacture) L2 expansion height L3 coil height (final length) H1
protrusion length (setting length at the time of manufacture) H2 expansion length H3 protrusion
length (Final leader)
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