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JPH10149169

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DESCRIPTION JPH10149169
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electromagnetic acoustic transducer used in a sounder or the like for converting an electrical
signal into sound by electromagnetic conversion.
[0002]
2. Description of the Related Art FIGS. 13 and 14 show a conventional electromagnetic acoustic
transducer. In the electromagnetic acoustic transducer, a support ring 102 made of nonmagnetic
metal or the like is fixed to the inside of an outer case 100 made of synthetic resin, and a
resonance plate 104 made of a magnetic material plate is installed on the upper portion thereof.
A magnetic piece 106 is attached to the resonance plate 104. A resonance chamber 108 is
formed by the outer case 100 on the upper surface side of the resonance plate 104, and the
resonance chamber 108 is opened to the outside air by a sound release hole 110 opened in the
outer case 100. A base 112 and a printed circuit board 114 are installed on the back side of the
resonance plate 104, and the back side of the outer case 100 is closed by the base 112 and the
printed board 114. An iron core 116 is attached to the center of the base 112, and a coil 118 is
wound around the core, and a magnet 120 is installed on the circumferential side of the coil 118
with a space. An air gap 122 is formed between the top of the iron core 116 and the resonance
plate 104, and the end of the coil 118 wound around the iron core 116 is connected by soldering
to the base of the terminal pins 124 and 126. There is. Each terminal pin 124, 126 is fixed by
caulking its base to the printed circuit board 114.
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[0003]
By the way, such an electromagnetic acoustic transducer is electrically connected to a printed
circuit board or the like of various electronic devices requiring sound generation by a reflow
soldering process. When it is heated. Then, in order to protect an electroacoustic transducer from
the thermal deterioration by this heat processing, the heat resistance of the component is
improved and the countermeasure which prevents deterioration of acoustic performance is
taken. However, the heat-resistant parts cause an increase in the manufacturing cost of the
electroacoustic transducer.
[0004]
As a measure to improve the heat resistance of the electromagnetic acoustic transducer, the heat
resistance of the magnet 120 and the support ring 102 that most affect the magnetic circuit
characteristics is a problem. In particular, since thermal deformation of the support ring 102
affects the width of the air gap 122 between the resonance plate 104 and the iron core 116, the
heat resistance of the support ring 102 is necessary to keep the air gap 122 constant. It is
essential.
[0005]
The magnet 120 performs reversible demagnetization at about 80 ° C., which is the operating
temperature of the sounder, but does not cause irreversible demagnetization, so that the normal
temperature return of the magnetic force is possible. However, the temperature at the time of the
reflow soldering process is as high as 200 ° C. to 250 ° C. When such heat is received,
irreversible demagnetization occurs and demagnetization of about 5 to 30% occurs after normal
temperature return. It is well known that the degree of the difference varies depending on the
material of which the magnet 120 is made, but generally it is expensive if the demagnetization is
small. In short, the better the heat resistance, the higher the cost.
[0006]
FIG. 15 shows an example of a profile of reflow solder temperature. In this case, the
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measurement temperature is the central temperature on the standard substrate, but as is
apparent from such a profile, the electro-acoustic transducer mounted on the substrate is
subjected to considerable heating, and the magnet 120 is Can not be ignored.
[0007]
When such demagnetization occurs, the magnetic coupling force between the resonance plate
104 and the iron core 116 is reduced, and the acoustic performance of the electromagnetic
acoustic transducer is changed. 16 shows the frequency characteristics (acoustic characteristics)
of the sound pressure before the reflow soldering process, FIG. 17 shows the frequency
characteristics of the sound pressure (acoustic characteristics) after the reflow soldering process,
and FIG. 18 shows the frequency characteristics of the current before the reflow processing. FIG.
19 shows the frequency characteristics of the current after the reflow process. That is, in the
electroacoustic transducer heated by the reflow soldering process, the lowest resonance
frequency Fo of the resonance plate 104 is lowered, the sound pressure level is also lowered, and
the acoustic characteristics are deteriorated.
[0008]
The support ring 102 is formed of nonmagnetic metal, resin or the like. The support ring 102
made of such a material stretches at a temperature of about 80 ° C. according to the linear
expansion coefficient of the material, but shrinks to its original size at normal temperature.
However, at the reflow solder processing temperature, the support ring 102 made of resin
shrinks in size due to the annealing effect or thermal deterioration. The shrinkage factor of LCP
material is shown in FIG. The degree is largely different depending on the material, and in
general, the one having a low thermal contraction rate is expensive.
[0009]
Then, when the support ring 102 contracts due to the heating of the reflow soldering process,
the air gap 122 between the iron core 116 and the resonance plate 104 narrows by that amount,
and the magnetic coupling between the resonance plate 104 and the iron core 116
correspondingly The power will be increased. Table 1 shows the relationship between the
material of the support ring 102 and the air gap change, and FIG. 21 shows the air gap change
associated with the reflow soldering process.
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[0010]
In order to avoid such an adverse effect due to the reflow processing temperature, it has been
practiced to use a magnet having a low irreversible demagnetization rate for the magnet 120 and
a resin or metal having a low contraction rate for the support ring 102. As a result, there is a
problem that the cost of parts of the electroacoustic transducer increases.
[0011]
Then, an object of this invention is to provide the electroacoustic transducer which prevented
deterioration of the acoustic performance by reflow solder processing.
[0012]
[Means for Solving the Problems] In order to achieve the above object, the present invention, as
exemplified in FIGS. 1 to 12, demagnetization by irreversible demagnetization at the reflow
soldering processing temperature possessed by the magnet (10) and The shrinkage due to the
reflow soldering temperature of the support ring 20 causes the reduction of the lowest
resonance frequency Fo of the resonance plate 22 due to the demagnetization of the magnet 10
and the resonance due to the heat shrinkage of the support ring 20. By offsetting the rise of the
lowest resonance frequency Fo of the plate (22), the change of the lowest resonance frequency
Fo of the resonance plate (22) is suppressed to stabilize the acoustic performance.
[0013]
The electromagnetic acoustic transducer according to claim 1 comprises an iron core (16) wound
with a coil (18), a resonance plate (22) vibrating in response to an oscillating magnetic field
generated by the iron core, and the resonance plate A support ring (20) for supporting an air gap
(24) between the core and the core; a magnet (10) provided inside the support ring for applying
a magnetic field to the resonance plate; 18) An electroacoustic transducer that converts an
electric signal applied to the magnetic field into an oscillating magnetic field and causes it to act
on the resonance plate, wherein the magnet is a magnet material that exhibits irreversible
demagnetization at a reflow soldering temperature The support ring is formed of a material that
shrinks at a reflow soldering temperature.
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With this configuration, it is possible to offset the decrease of the lowest resonance frequency Fo
of the resonance plate due to the demagnetization of the magnet and the increase of the lowest
resonance frequency Fo of the resonance plate due to the thermal contraction of the support
ring. It is possible to suppress the change of the resonance frequency Fo and stabilize the
acoustic performance.
[0014]
The electromagnetic acoustic transducer according to claim 2 is characterized in that the magnet
is formed of a samarium cobalt based magnet or a neodymium based magnet.
By using such a magnet material for the magnet, the irreversible demagnetization caused by the
heat due to the reflow soldering processing temperature is balanced with the thermal contraction
of the support ring.
[0015]
The electroacoustic transducer according to claim 3 is characterized in that the support ring is
formed of a synthetic resin. By using such a resin material for the support ring, the thermal
contraction due to the reflow soldering processing temperature is balanced with the
demagnetization of the magnet.
[0016]
And the electromagnetic acoustic converter according to claim 4 is characterized in that the
reflow soldering processing temperature is 200 to 250 ° C. The normal reflow soldering
processing temperature is 200 to 250 ° C, and the minimum resonance frequency of the
resonance plate due to the decrease of the minimum resonance frequency Fo of the resonance
plate due to the demagnetization of the magnet corresponding to the temperature of this degree
and the heat contraction of the support ring The rise of Fo can be offset, and the change of the
lowest resonance frequency Fo of the resonance plate can be suppressed.
[0017]
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DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in
detail below with reference to the embodiments shown in the drawings.
[0018]
1 to 4 show an embodiment of the electroacoustic transducer according to the present invention,
and FIG. 1 is a plan view of the electroacoustic transducer shown partially cut away, and FIG. 2 is
a rear view of the electroacoustic transducer. 3 is a cross-sectional view taken along the line IIIIII in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line IV-IV.
[0019]
The exterior case 2 is configured of two rectangular case pieces 4 and 6, both of which are
molded bodies of synthetic resin, and both are integrally fixed by ultrasonic welding or the like.
The case piece 4 is formed by various molding methods, and for example, is configured as a base
member on a lead frame.
In this embodiment, the case piece 4 is formed as a base member, and the base 8, the magnet 10
and the lead terminals 12 and 14 are insert-molded.
[0020]
The base 8 is a metal plate made of a magnetic material and is flat. A columnar iron core 16 is
integrally erected at the center of the base 8 and a coil 18 is wound around it. An annular
magnet 10 is installed to surround the coil 18. The bottom surface of the magnet 10 is in close
contact with the surface of the base 8. The end of the coil 18 is electrically connected to the lead
terminals 12 and 14 by soldering or the like. When an electrical signal is applied between the
lead terminals 12 and 14, an excitation current flows through the coil 18 according to the
electrical signal, and as a result, an oscillating magnetic field is generated in the iron core 16
according to the frequency of the electrical signal.
[0021]
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The iron core 16 and the magnet 10 are concentric, and the positioning of the magnet 10 is
performed by the support ring 20 formed inside the case piece 4. The support ring 20 may be
configured as a separate member from the case piece 4, but in this embodiment, it is integrally
formed with the case piece 4. Accordingly, the support ring 20 is also made of the same synthetic
resin as the case piece 4. When the support ring 20 is made up of the case piece 4 and a separate
member, it is possible to select a resin material different from that of the case piece 4 and even in
that case, integration with the case piece 4 is possible by insert molding.
[0022]
The resonance plate 22 is installed on the upper portion of the support ring 20. The resonance
plate 22 is a vibrating member and is made of a magnetic material in order to react with the
magnetism from the iron core 16. An air gap 24 is formed between the resonance plate 22 and
the iron core 16, and the width of the air gap 24 is determined by the relative value of the height
of the support ring 20 and the height of the iron core 16. By increasing the height of the air gap
24, an air gap 24 having a desired width is formed.
[0023]
An oscillating magnetic field from the iron core 16 acts on the resonance plate 22 through such
an air gap 24, but a magnetic field from the magnet 10 forming a closed magnetic path with the
resonance plate 22 acts on the resonance plate 22. As a result, resonance The plate 22 vibrates
up and down by the oscillating magnetic field. A magnetic piece 26 is attached to a central
portion of the resonance plate 22 as a means for enhancing the vibration mass.
[0024]
Then, a resonance chamber 28 which is a resonance space is formed on the upper surface side of
the resonance plate 22 with the case piece 6. The resonance chamber 28 is opened to the outside
air by a sound emission hole 30 formed in the case piece 6. The sound generated by the vibration
of the resonance plate 22 resonates with the resonance chamber 28 and is mainly emitted from
the sound emission hole 30 to the outside.
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[0025]
In such an electromagnetic acoustic transducer, the magnet 10 is formed of a magnet material
that exhibits irreversible demagnetization at a reflow soldering processing temperature of about
200 ° C. to 250 ° C. The following is one of the examples. i. Isotropic samarium cobalt
sintered 1-5 series ii. Isotropic samarium cobalt sintered 2-17 system iii. Neodymium bond iv.
Samarium based bond
[0026]
In such an electromagnetic acoustic transducer, the support ring 20 is formed of a synthetic
resin that shrinks at a reflow soldering processing temperature of about 200 ° C. to 250 ° C.
That is, in this embodiment, since it is integral with the case piece 4 which is a base member, the
exterior case 2 itself is formed of this kind of synthetic resin. It will be as follows if an example of
the synthetic resin is listed. a. LCP−1,ベクトラE130ib. LCP−2,ベクトラ
E130ib. ナイロン6T,アーレン230c. PPS,C−100HG
[0027]
The material of the magnet 10 and the support ring 20 formed of such materials can be
arbitrarily combined, but an optimum combination is possible in order to suppress the
fluctuation of the lowest resonance frequency Fo of the resonance plate 22.
[0028]
With such a configuration, when heated by the reflow soldering processing temperature, the
irreversible demagnetization on the magnet 10 side reduces the magnetic coupling force
between the resonance plate 22 and the iron core 16 to change the acoustic characteristics. Do.
In particular, the change of the lowest resonance frequency Fo of the resonance plate 22, in
general, its value decreases, and as a result of the reduction of the sound pressure, the acoustic
characteristics are greatly affected.
[0029]
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Further, when heated by the reflow soldering processing temperature, the support ring 20 is
thermally shrunk, and as a result, the width of the air gap 24 is reduced. When the width of the
air gap 24 is narrowed, the magnetic coupling force between the resonance plate 22 and the iron
core 16 is enhanced, and as a result, the lowest resonance frequency Fo of the resonance plate
22 is increased, that is, the acoustic characteristics are greatly affected. give. This change is
reverse to the demagnetization of the magnet 10.
[0030]
Therefore, the decrease in the minimum resonance frequency Fo due to the demagnetization on
the magnet 10 side and the increase in the minimum resonance frequency Fo due to the heat
contraction on the support ring 20 mutually offset and complement each other, resulting in the
magnet 10 and the support ring 20 By the combination effect of the material relationship of (1),
it is possible to obtain the preferable result that there is no fluctuation of the lowest resonance
frequency Fo as a result of being heated by the reflow soldering processing temperature.
[0031]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the
electromagnetic acoustic transducer shown in FIGS. 1 to 4 will be described.
[0032]
FIG. 5 shows the fluctuation of the lowest resonance frequency Fo of the resonance plate 22
before and after the reflow soldering process when the material of the magnet 10 is changed.
In FIG. 5, M1 is an isotropic samarium cobalt sintered 1-5 type, M2 is an isotropic samarium
cobalt sintered 2-17 type, M3 is a neodymium type bond, and M4 is a samarium type bond.
Shows the characteristics and receives the heat of the reflow soldering processing temperature,
and the fluctuation value of the lowest resonance frequency Fo is 22 Hz for M1, 42 Hz for M2,
94 Hz for M3, and M4 A decrease of 104 Hz is observed.
[0033]
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FIG. 6 also shows the total magnetic flux fluctuation before and after the reflow soldering process
corresponding to the characteristics shown in FIG.
Due to the heat of reflow soldering processing temperature, the fluctuation value of the lowest
resonance frequency Fo is 2.8% in the case of M1, 5.2% in the case of M2, 11.7% in the case of
M3, In the case of M4, a heat demagnetizing factor of 13.5% is generated.
[0034]
Next, FIG. 7 shows the fluctuation of the lowest resonance frequency Fo of the resonance plate
22 due to the fluctuation of the width of the air gap 24 before and after the reflow soldering
process when the material of the support ring 20 is changed. In FIG. 7, C1 uses LCP-1 and
VECTRA E130i and is molded at a molding injection pressure of 40 kg / cm2, C2 uses LCP-2 and
VECTRA E130i and is molded at a molding injection pressure of 60 kg / cm2 and When C6 uses
nylon 6T and Arlen 230, C4 shows each property when PPS and C-100HG are used, and C0
shows when brass is used. In FIG. 7, the fluctuation value of the lowest resonance frequency Fo is
40 Hz for C1, 56 Hz for C2, 80 Hz for C3, and 112 Hz for C4.
[0035]
In addition, as shown in FIG. 8, the variation value of the air gap 24 due to the heat of the reflow
soldering processing temperature is 0μ in the case of C0, -5μ in the case of C1, and -7μ in the
case of C2. , -3μ in case of C3 and -14μ in case of C4, while no change occurs in the case of
brass, the type of the support ring 20 made of resin A significant reduction in the value of the air
gap 24 can be seen.
[0036]
Therefore, by making the total magnetic flux fluctuation by the magnet 10 correspond to the
fluctuation of the air gap 24, the decrease of the lowest resonance frequency Fo due to the
demagnetization of the magnet 10 is due to the increase of the lowest resonance frequency Fo
due to the decrease of the air gap 24. It will be complemented.
The synergetic effects are as shown in FIG. That is, when M1 and C1, M2 and C2, M3 and C3 or
M4 and C4 correspond to each other, the decrease of the lowest resonance frequency Fo due to
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10
the demagnetization of the magnet 10 and the increase of the lowest resonance frequency Fo due
to the decrease of the air gap 24 cancel out. As a result, the variation width ΔF of the lowest
resonance frequency Fo of the resonance plate 22 is corrected to an extremely small value.
[0037]
For example, as shown in FIG. 10, when the material of the support ring 20 is nylon 6T and the
material of the magnet 10 is neodymium bond, a resonance plate due to the demagnetization of
the magnet 10 due to the heat due to the reflow soldering temperature The decrease of the
lowest resonance frequency Fo of 22 is complemented by the increase of the lowest resonance
frequency Fo of the resonance plate 22 due to the fluctuation of the air gap 24. As a result, the
fluctuation width ΔF of the lowest resonance frequency Fo is extremely small. It can be seen that
it becomes smaller than the fluctuation range ΔF of the lowest resonance frequency Fo
possessed by the characteristics of the conventional product shown in FIG.
[0038]
On the other hand, FIG. 11 shows the lowest resonance frequency of the resonance plate 22
when brass is used for the support ring 20 and neodymium bonded magnet is used for the
magnet 10 in the electromagnetic acoustic transducer shown in FIG. 13 and FIG. The fluctuation
characteristic of Fo is shown.
M3 represents the fluctuation of the lowest resonance frequency Fo of the resonance plate 22
due to the demagnetization of the magnet 10 before and after the reflow soldering process, and
C0 represents the fluctuation of the lowest resonance frequency Fo due to the fluctuation of the
air gap 24. In such a configuration, it can be seen that the fluctuation range ΔF of the lowest
resonance frequency Fo is large.
[0039]
FIG. 12 shows the case where brass is used for the support ring 20 and isotropic samarium
cobalt sintered 2-17 magnet is used for the magnet 10 in the electromagnetic acoustic
transducer shown in FIG. 13 and FIG. The fluctuation characteristic of the lowest resonance
frequency Fo of the resonance plate 22 is shown. M1 represents the fluctuation of the lowest
resonance frequency Fo of the resonance plate 22 due to the demagnetization of the magnet 10
before and after the reflow soldering process, and C0 represents the fluctuation of the lowest
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resonance frequency Fo due to the fluctuation of the air gap 24. In such a combination, the
fluctuation range ΔF of the lowest resonance frequency Fo is close to the characteristic of FIG.
10, but there is a problem that the material is expensive.
[0040]
Although the materials of the magnet 10 and the support ring 20 and the combination thereof
have been described in the embodiment, the present invention is not limited to such materials
and the combination thereof, and the minimum resonance frequency Fo by demagnetization of
the magnet 10 Any material and combination may be used as long as the decrease is
compensated by the increase of the lowest resonant frequency Fo due to the contraction of the
support ring 20.
[0041]
As described above, according to the present invention, the following effects can be obtained.
a. The change in magnetic coupling force due to the air gap fluctuation between the resonance
plate and the iron core due to the reflow soldering processing temperature can be correlated
with the demagnetization change of the magnet to complement each other, and the acoustic
performance deterioration due to the reflow soldering processing temperature This can be
prevented, and the acoustic performance can be stabilized. b. Demagnetization, which is the
thermal degradation of the magnet due to the reflow soldering temperature, can be compensated
by the change in the magnetic coupling force caused by the air gap fluctuation between the
resonance plate and the iron core due to the thermal contraction of the support ring. By
corresponding heating, stable and optimum sound pressure characteristics can be obtained. c.
There is no need to suppress fluctuations such as demagnetization of the magnet and thermal
contraction of the support ring due to the reflow soldering processing temperature, inexpensive
materials can be used, and manufacturing costs can be reduced.
[0042]
Brief description of the drawings
[0043]
1 is a plan view with a part cut away showing an embodiment of the electromagnetic acoustic
transducer of the present invention.
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[0044]
2 is a bottom view of the electromagnetic acoustic transducer shown in FIG.
[0045]
3 is a sectional view taken along the line III-III of the electromagnetic acoustic transducer shown
in FIG.
[0046]
4 is a sectional view taken along the line IV-IV of the electromagnetic acoustic transducer shown
in FIG.
[0047]
5 is a diagram showing the fluctuation characteristics of the lowest resonance frequency due to
the total magnetic flux fluctuation before and after the reflow soldering process of the
electromagnetic acoustic transducer according to the present invention.
[0048]
6 is a diagram showing the heat demagnetizing factor before and after the reflow soldering
process in the electromagnetic acoustic transducer of the present invention.
[0049]
<Figure 7> It is the figure which shows the fluctuation characteristic of the lowest resonance
frequency due to the air gap fluctuation before and after the reflow soldering processing in the
electromagnetic acoustic transducer of this invention.
[0050]
8 is a diagram showing the air gap fluctuation characteristics before and after the reflow
soldering process in the electromagnetic acoustic transducer of the present invention.
[0051]
<Figure 9> It is the figure which shows the synergy effect of the fluctuation of the lowest
resonance frequency due to the total flux fluctuation before and after reflow soldering processing
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in the electromagnetic acoustic transducer concerning the present invention and the fluctuation
of the lowest resonance frequency due to the air gap fluctuation.
[0052]
<Figure 10> It is the figure which shows the synergy effect of the fluctuation of the lowest
resonance frequency due to the total flux fluctuation before and after the reflow soldering
processing in the electromagnetic acoustic transducer concerning the present invention and the
fluctuation of the lowest resonance frequency due to the air gap fluctuation.
[0053]
FIG. 11 is a view showing fluctuation characteristics of the lowest resonance frequency due to
total magnetic flux fluctuation before and after reflow soldering processing in the conventional
electromagnetic acoustic transducer and fluctuation characteristics of the lowest resonance
frequency due to air gap fluctuation.
[0054]
12 is a diagram showing the fluctuation characteristic of the lowest resonance frequency due to
the total magnetic flux fluctuation before and after the reflow soldering process in the
conventional electromagnetic acoustic transducer and the fluctuation characteristic of the lowest
resonance frequency due to the air gap fluctuation.
[0055]
13 is a longitudinal sectional view showing a conventional electromagnetic acoustic transducer.
[0056]
14 is a bottom view of the electromagnetic acoustic transducer of FIG.
[0057]
15 is a diagram showing a profile of the reflow soldering processing temperature.
[0058]
16 is a diagram showing the frequency characteristics of the sound pressure before the reflow
soldering process in the conventional electromagnetic acoustic transducer.
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[0059]
<Figure 17> It is the figure which shows the frequency characteristic of the sound pressure after
the reflow soldering processing in the electromagnetic sound transducer of former.
[0060]
18 is a diagram showing the frequency characteristics of the current before the reflow soldering
process in the conventional electromagnetic acoustic transducer.
[0061]
19 is a diagram showing the frequency characteristics of the current after the reflow soldering
process in the conventional electromagnetic acoustic transducer.
[0062]
FIG. 20 is a diagram showing the thermal contraction rate due to the annealing of the support
ring used in the electromagnetic acoustic transducer.
[0063]
21 is a diagram showing the variation of the air gap after the reflow soldering process in the
electromagnetic acoustic transducer.
[0064]
Explanation of sign
[0065]
Reference Signs List 10 magnet 16 iron core 18 coil 20 support ring 22 resonance plate 24 air
gap
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