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JP2017161454

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DESCRIPTION JP2017161454
PROBLEM TO BE SOLVED: To improve the magnetic flux density and to improve the signal
strength of transmission and reception by devising the arrangement of magnets in an
electromagnetic ultrasonic sensor. An electromagnetic ultrasonic sensor 1 according to the
present invention includes a coil 2 for generating an eddy current inside an inspection object W,
and an electromagnetic ultrasonic sensor 1 disposed on the opposite side of the inspection object
W with the coil 2 interposed therebetween. An electromagnetic ultrasonic sensor 1 comprising a
main magnet 3 for forming a static magnetic field in a direction to penetrate the object W, and
generating an ultrasonic wave inside the inspection object W by an interaction between an eddy
current and the static magnetic field, The auxiliary magnet 4 for increasing the magnetic flux
density of the main magnet 3 is provided on the side of the main magnet 3, and the auxiliary
magnet 4 is orthogonal to the direction of the magnetic pole connecting the N pole and the S
pole of the main magnet 3. It is characterized in that the magnetic pole of the auxiliary magnet 4
is oriented in the same direction. [Selected figure] Figure 1
Electromagnetic ultrasonic sensor
[0001]
The present invention relates to an electromagnetic ultrasonic sensor used for ultrasonic flaw
detection on an object to be inspected such as metal.
[0002]
Ultrasonic flaw detection is performed as one of the methods of inspecting the flaws present
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1
inside the object to be inspected such as metal and measuring the thickness of the object to be
inspected.
In ultrasonic flaw detection using a conventional piezoelectric element, ultrasonic flaws
generated in a probe (sensor) are transmitted to an object to be inspected via a contact medium,
whereas ultrasonic flaw detection using electromagnetic ultrasound is used. In this case, a probe
(EMAT: Electro Magnetic Acoustic Transducer) for transmitting an ultrasonic wave directly to an
inspection object by an electromagnetic action is used.
[0003]
FIG. 17 is a schematic view of a sensor that generates a transverse wave in ultrasonic flaw
detection using electromagnetic ultrasonic waves. The generation principle of the EMAT
described above is based on the static magnetic field generated inside the inspection object by
the main magnet arranged to face the inspection object, and the pulse to the coil disposed
between the main magnet and the inspection object The Lorentz force is generated inside the
inspection object to generate an ultrasonic wave by the interaction with the eddy current
generated inside the inspection object by passing the current.
[0004]
By the way, in ultrasonic flaw detection using EMAT, although an ultrasonic wave can be
transmitted without contact with the inspected object, there is a problem that the receiving
sensitivity is lower by two digits than ultrasonic flaw detection using a piezoelectric element.
Therefore, in the electromagnetic ultrasonic sensor of Patent Document 1, the surface shape of
the main magnet facing the object to be inspected is made a complicated shape (an arch-shaped
curved surface in which the central portion is recessed) to focus the magnetic flux and increase
the reception sensitivity. Therefore, the sensitivity is lower than that of the piezoelectric element.
[0005]
JP, 2006-005508, A
[0006]
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2
By the way, in the electromagnetic ultrasonic sensor of Patent Document 1, although the
reception sensitivity can be increased, it is not practical to make the shape of the magnet
complicated in terms of processing.
If such a complex shaped magnet is used, it takes time and labor to process the magnet and the
price of the electromagnetic ultrasonic sensor becomes high, which is not preferable. The present
invention has been made in view of the above-mentioned problems, and can provide an
electromagnetic ultrasonic sensor capable of enhancing the magnetic flux density in the inside of
the inspection object by a simpler mechanism and improving the detection sensitivity. The
purpose is to
[0007]
In other words, an object of the present invention is to provide an electromagnetic ultrasonic
sensor capable of improving the magnetic flux density and improving the signal strength of
transmission and reception by devising the arrangement of magnets.
[0008]
In order to solve the above-mentioned subject, the electromagnetic ultrasonic sensor of the
present invention takes the following technical measures.
That is, the electromagnetic ultrasonic sensor according to the present invention includes a coil
for generating an eddy current inside the inspection object, and a direction in which the coil is
disposed on the opposite side of the inspection object with the coil interposed therebetween and
penetrates the inspection object An electromagnetic ultrasonic sensor that generates an
ultrasonic wave by the interaction of an eddy current and a static magnetic field inside the
inspection object, and is provided on the side of the main magnet An auxiliary magnet for
increasing the magnetic flux density of the main magnet is provided, and the auxiliary magnet
has a magnetic pole of the auxiliary magnet in a direction perpendicular to the direction of the
magnetic pole connecting the N pole and the S pole of the main magnet. It is characterized in that
it is deployed towards.
[0009]
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Preferably, the main magnet is disposed at a position corresponding to a coil that generates the
eddy current. Preferably, in the coil, a first conductor group in which current flows in one
direction along the surface of the inspection object, and a second conductor in which the current
direction is opposite to that of the first conductor group. And the main magnet includes a first
main magnet corresponding to the first wire group and a second main magnet corresponding to
the second wire group. Good.
[0010]
Preferably, the auxiliary magnet includes a central auxiliary magnet between the first main
magnet and the second main magnet, and the central auxiliary magnet is the first main magnet or
the second main magnet. It is preferable that the width of the main magnet is smaller than that of
the main magnet. Preferably, a magnet having a coercive force higher than that of the first main
magnet and the second main magnet is preferably used for the central auxiliary magnet.
[0011]
Preferably, the auxiliary magnet has a side auxiliary magnet on the outer side of the first main
magnet or the second main magnet. Preferably, a yoke connecting the main magnet and the
auxiliary magnet is provided.
[0012]
According to the electromagnetic ultrasonic sensor of the present invention, the magnetic flux
density can be improved by devising the arrangement of the magnets, and the signal strength of
transmission and reception can be improved.
[0013]
It is the figure which showed the structure of the electromagnetic ultrasonic sensor of 1st
Embodiment.
It is the figure which showed the structure of the electromagnetic ultrasonic sensor of the prior
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art example. It is sectional drawing at the time of cut | disconnecting the electromagnetic
ultrasonic sensor of FIG. 1 by XX. It is the figure which showed the BH curve of the magnet
which can be utilized for the magnet of the electromagnetic ultrasonic sensor of 1st Embodiment.
It is the figure which showed the magnetic force line which generate | occur | produces from the
magnet arrangement | positioning provided with the auxiliary magnet. It is the figure which
showed the magnetic force line which generate | occur | produces from the magnet arrangement
| positioning which is not equipped with the auxiliary magnet. It is the figure which compared
the magnetic flux density formed in the inside of a to-be-inspected object by an electromagnetic
ultrasonic sensor by the prior art example and 1st Embodiment. It is the figure which showed the
signal strength at the time of reception at the time of carrying out ultrasonic flaw detection with
respect to the to-be-inspected object of aluminum using the electromagnetic ultrasonic sensor of
1st Embodiment. It is the figure which showed the signal strength at the time of reception at the
time of carrying out ultrasonic flaw detection with respect to the to-be-inspected object of
aluminum using the electromagnetic ultrasonic sensor of a prior art example. It is the figure
which showed the structure of the electromagnetic ultrasonic sensor of 2nd Embodiment. It is
the figure which compared the magnetic flux density formed in the inside of a to-be-tested |
inspected object by an electromagnetic ultrasonic sensor in the prior art example, 1st
Embodiment, and 2nd Embodiment. It is the figure which showed the structure about the
electromagnetic ultrasonic sensor of 3rd Embodiment. It is the figure which showed the structure
about the electromagnetic ultrasonic sensor of the modification of 3rd Embodiment. It is the
figure which showed the structure of the electromagnetic ultrasonic sensor of the prior art
example using a circular type coil. It is the figure which showed the structure about the
electromagnetic ultrasonic sensor for longitudinal waves of a prior art example. It is the figure
which showed the magnet arrangement | sequence of the electromagnetic ultrasonic sensor of
4th Embodiment which used three magnets. It is a figure showing magnet arrangement of an
electromagnetic ultrasonic sensor of a 4th embodiment which used five magnets. It is the figure
which compared the magnetic flux density formed in the inside of a to-be-inspected object by an
electromagnetic ultrasonic sensor by the prior art example and 4th Embodiment. It is the figure
which showed the structure about the electromagnetic ultrasonic sensor of 5th Embodiment. It is
the figure which compared the magnetic flux density formed in the inside of a to-be-inspected
object by the electromagnetic ultrasonic sensor by the number of objects of a magnet. It is the
figure which showed the structure about the electromagnetic ultrasonic sensor of the prior art
example.
[0014]
First Embodiment An embodiment of an electromagnetic ultrasonic wave sensor 1 according to
the present invention will be described in detail with reference to the drawings. FIG. 1
schematically shows the electromagnetic ultrasonic sensor 1 according to the first embodiment.
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As shown in FIG. 1, the electromagnetic ultrasonic sensor 1 according to the first embodiment is
used for ultrasonic flaw detection for inspecting a flaw existing in an object to be inspected W
such as metal and measuring the thickness of the object to be inspected W Sensor attached to the
probe. That is, this probe is an electromagnetic ultrasonic flaw detector (EMAT: Electro Magnetic
Acoustic Transducer) that transmits ultrasonic waves directly to the inspection object W by
electromagnetic action.
[0015]
Specifically, the electromagnetic ultrasonic sensor 1 of the first embodiment is disposed on the
opposite side of the inspection object W with the coil 2 generating the eddy current inside the
inspection object W and the coil 2. The main magnet 3 which forms a static magnetic field in the
direction which penetrates the to-be-tested object W is provided. For example, when a pulse
current is supplied to the coil 2 described above, an eddy current is generated inside the
inspection object W. On the other hand, a static magnetic field is also generated inside the
inspection object W by the main magnet 3. Therefore, when the generated eddy current and the
static magnetic field interact with each other, a Lorentz force is generated inside the inspection
object W. Ultrasonic waves are generated inside the object W by the Lorentz force generated in
this manner.
[0016]
The main magnet and the coil as described above are also provided in the electromagnetic
ultrasonic sensor 101 of the conventional example shown in FIG. 2, and even in the
electromagnetic ultrasonic sensor 101 of the conventional example, the static magnetic field by
the main magnet 103 and the eddy current by the coil 102 The interaction with it generates
ultrasound as well. By the way, in the electromagnetic ultrasonic sensor 101 of the conventional
example described above, ultrasonic waves can be transmitted without contact with the
inspection object W (without contact), while ultrasonic sensors using piezoelectric elements, etc.
There is a problem that the receiving sensitivity is reduced by two digits as compared with that.
That is, in order to increase the sensitivity of flaw detection or the like in the electromagnetic
ultrasonic sensor 101 of the conventional example, it is necessary to increase the signal intensity
output from the probe or the signal intensity received by the probe. It is necessary to increase
the magnetic flux density inside the inspection object W in order to improve the For example,
although it is theoretically possible to increase the magnetic flux density by using a magnet
having a strong magnetic force as the main magnet 103, in reality it is often difficult to further
increase the magnetic force of the main magnet 103.
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[0017]
Therefore, in the electromagnetic ultrasonic sensor 1 of the present embodiment, the auxiliary
magnet 4 is provided to improve the magnetic flux density of the main magnet 3 by devising the
magnet arrangement, more specifically, to the side of the main magnet 3. By increasing the
magnetic flux density of the main magnet 3 by this, the magnetic flux density inside the
inspection object W is increased. Specifically, the auxiliary magnet 4 of the electromagnetic
ultrasonic sensor 1 of the present embodiment has its own magnetic pole (auxiliary magnet 4) in
the direction orthogonal to the direction of the magnetic pole connecting the N pole and the S
pole of the main magnet 3. Of the magnetic pole) is deployed. As described above, if the auxiliary
magnet 4 is disposed to the side of the main magnet 3, the magnetic lines of force radiated from
the main magnet 3 to the inside of the inspection object W can be distorted, and the magnetic
flux density inside the inspection object W can be increased. It becomes.
[0018]
In the electromagnetic ultrasonic sensor 1 of the present invention, various embodiments can be
considered depending on the number of magnets used and the arrangement of the magnets. In
the following first embodiment, the electromagnetic ultrasonic sensor 1 according to the first
embodiment is exemplified by taking the electromagnetic ultrasonic sensor 1 for transverse
waves using five magnets according to the main magnet 3 and the auxiliary magnet 4 as an
example. The main magnet 3, the coil 2, and the auxiliary magnet 4 to be configured will be
described in detail.
[0019]
As shown in FIG. 3, the coil 2 provided in the electromagnetic ultrasonic sensor 1 according to
the first embodiment is a flat coil formed by winding the conducting wire 5 so as to go around
the flat surface a plurality of times. (Lace track type coil). The coil 2 is formed by being wound
from the inside to the outside or from the outside to the inside so that the conducting wire 5 has
an oval or rectangular trajectory when viewed from above. That is, when the coil 2 is cut at a cut
surface extending in the vertical direction through the winding center of the conducting wire 5,
that is, the center of the coil 2, a plurality of first wire groups 6 are formed in the coil 2 on the
left side of the winding center. The conductors 5 are disposed, and on the right side of the coil 2,
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a plurality of conductors 5 constituting a second conductor group 7 are disposed.
[0020]
Each of the first wire group 6 and the second wire group 7 is composed of a plurality of wires 5
arranged in parallel with each other at substantially equal intervals. The direction of the current
is the same in all the plurality of wires 5 belonging to the first wire group 6, and the direction of
the current is also the same in the plurality of wires 5 belonging to the second wire group 7. The
direction of the current in the lead group 6 and the direction of the current in the second lead
group 7 are opposite to each other. The first main magnet 8 described above corresponding to
the first wire group 6 is disposed on the first wire group 6 of the coil 2, and the first main
magnet 8 is disposed on the second wire group 7. A second main magnet 9 is provided
corresponding to the two-wire group 7.
[0021]
In the case of the electromagnetic ultrasonic sensor 1 according to the first embodiment, in the
case of the above-described electromagnetic ultrasonic sensor 1 for transverse waves, the
magnetic flux in the vertical direction is required immediately below the coil 2, so the first
conductor group 6 and the second conductor group 7 In correspondence with the above, the
main magnet 3 is disposed above each of the wire groups 5 respectively. That is, in the case of
the electromagnetic ultrasonic sensor 1 according to the first embodiment, the phrase “deploy
the main magnet 3 at the position corresponding to the coil 2 generating the eddy current”
means the wire group of the coil 2 generating the eddy current. It is nothing but to arrange the
main magnet 3 above.
[0022]
As described above, in the coil 2 of the electromagnetic ultrasonic sensor 1 according to the first
embodiment, the first lead wire group 6 in which the current flows in one direction along the
surface of the inspection object W and the first lead wire group 6 And the second lead group 7 of
the opposite direction. A first main magnet 8 is provided corresponding to the first wire group 6,
and a second main magnet 9 is provided corresponding to the second wire group 7. The main
magnet of the first embodiment Reference numeral 3 is composed of two magnets of the first
main magnet 8 and the second main magnet 9.
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[0023]
The first main magnet 8 and the second main magnet 9 described above each have a vector
connecting an N pole and an S pole in the magnet (hereinafter referred to as “magnetic pole”
in the present embodiment) as the inspection object W It is deployed in the direction to penetrate
the In the case of the present embodiment, the first main magnet 8 is disposed with the N pole
facing downward, and the second main magnet 9 is disposed with the S pole facing downward.
That is, the magnetic poles of the first main magnet 8 and the second main magnet 9 face in the
vertical direction.
[0024]
Further, the width of the first main magnet 8 and the second main magnet 9 in the left-right
direction is the width of the first lead group 6 in the left-right direction and the width of the
second lead group 7 in the left-right direction. It is approximately equal to the width along.
Furthermore, the first main magnet 8 and the second main magnet 9 are required to increase the
magnetic flux density as the electromagnetic ultrasonic sensor 1 (EMAT sensor), so that the
coercivity as shown by the solid line in FIG. Instead of a large magnet, a magnet of a material
having a large magnetic flux density as shown by a dotted line in FIG. 4 is preferably used.
[0025]
The auxiliary magnet 4 of the first embodiment includes one central auxiliary magnet 10
provided between the first main magnet 8 and the second main magnet 9, and the first main
magnet 8 or the second main magnet. A total of two side auxiliary magnets 11 are provided, one
each provided on the outer side of 9. These auxiliary magnets 4 are provided on the side of the
main magnet 3 and have the function of increasing the magnetic flux density of the main magnet
3, and each of them has its own magnetic field in the direction orthogonal to the direction of the
magnetic pole of the main magnet 3. It is arranged in such a manner that the pole (the magnetic
pole of the auxiliary magnet 4 itself) is directed.
[0026]
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9
Specifically, among the auxiliary magnets 4 described above, the central auxiliary magnet 10 is a
magnet disposed between the first main magnet 8 and the second main magnet 9. The direction
of the magnetic pole of the central auxiliary magnet 10 is horizontal, and is orthogonal to the
direction (vertical direction) of the magnetic pole of the main magnet 3. Specifically, the central
auxiliary magnet 10 of the first embodiment is attached with the N pole facing the first left side
(the main magnet 3 side), and the S pole the right side (the second main magnet 9 side) It is
attached towards).
[0027]
Further, the width dimension in the left-right direction of the central auxiliary magnet 10
described above is narrower than the first main magnet 8 or the second main magnet 9. In
addition, as the central auxiliary magnet 10, a magnet having a coercive force higher than that of
the first main magnet 8 and the second main magnet 9 is used. The reason why the central
auxiliary magnet 10 uses a magnet narrower in the lateral direction than the main magnet 3 and
having a high coercivity is to reduce the influence of the demagnetization of the central auxiliary
magnet 10 itself, not the demagnetization of the main magnet 3. is there. That is, in a magnet
having a large thickness in the magnetization direction (a magnet such as the main magnet 3), it
is not necessary to consider demagnetization due to an external magnetic field. However, in the
case of a magnet having a small thickness in the magnetization direction (a magnet such as the
central auxiliary magnet 10 of the present embodiment), the influence of the demagnetization
due to the external magnetic field is significantly likely to occur.
[0028]
More specifically, as the electromagnetic ultrasonic sensor 1 is required to have a large magnetic
flux density inside the inspection object W, as described above, a magnet having a large residual
magnetic flux density is adopted for the main magnet 3 . On the other hand, although it is
desirable to use a material having a large residual magnetic flux density for the central auxiliary
magnet 10, the magnetic flux density and the coercivity are in a trade-off relationship, and the
coercivity of the magnet having a large residual magnetic flux density is small. In particular,
when the shape in the direction of the magnetic pole is small (the thickness in the magnetization
direction is small) as in the central auxiliary magnet 10, irreversible demagnetization due to the
external magnetic field is likely to occur. When demagnetization due to such an external
magnetic field occurs, the sensitivity (reception sensitivity) as the electromagnetic ultrasonic
sensor 1 also decreases.
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10
[0029]
Therefore, if the central auxiliary magnet 10 is not a magnet with a large residual magnetic flux
density but a magnet with a large coercive force, the influence of demagnetization can be
reduced, and the sensitivity (reception sensitivity) of the electromagnetic ultrasonic sensor 1 is
improved. It is possible to That is, the electromagnetic ultrasonic sensor 1 according to the first
embodiment can be viewed as a whole sensor by using a magnet having a large coercive force or
a narrow magnet even at the sacrifice of the residual magnetic flux density to the central
auxiliary magnet 10. The influence of the demagnetization is reduced, the magnetic flux density
inside the inspection object W is improved, and the reception sensitivity is improved.
[0030]
Specifically, when selecting the material of the magnet of the central auxiliary magnet 10,
focusing on the material of a certain magnet, the BH curve and the JH curve are uniquely
determined, and when the shape of the magnet is determined, the operation of the magnet is
determined from the dimensional ratio The point is decided. Furthermore, since it is determined
whether the demagnetization is reversible or irreversible and the amount of demagnetization
from the magnitude of the external magnetic field, it is sufficiently possible to select the material
of the magnet of the central auxiliary magnet 10. That is, since the one having a large magnetic
flux density has a trade-off relationship that the coercivity is small, the material of the coercivity
having a high remanent magnetic flux density and high reversibility and small demagnetization
amount from the shape of the magnet and the size of the external magnetic field. It is important
to select
[0031]
Further, among the auxiliary magnets 4 described above, the side auxiliary magnet 11 is a
further outside of the first main magnet 8, that is, a left side auxiliary magnet 11L disposed on
the left side of the first main magnet 8, and The right side auxiliary magnet 11 R disposed on the
further outside of the two main magnets 9, that is, the right side of the second main magnet 9.
Further, the left side auxiliary magnet 11L is disposed such that the N pole of the left side
auxiliary magnet 11L faces the N pole of the central auxiliary magnet 10 (with the N pole
directed to the right). Furthermore, the right side auxiliary magnet 11R is disposed such that the
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11
south pole of the right side auxiliary magnet 11R faces the south pole of the central auxiliary
magnet 10 (with the south pole facing to the left).
[0032]
In the first embodiment, an example in which one left side auxiliary magnet 11L and one right
side auxiliary magnet 11R are used as the side auxiliary magnet 11 has been described, but the
left side auxiliary magnet 11L is described. The number of the right side auxiliary magnets 11R
may be two or more. For example, in the case where two magnets are used for the left side
auxiliary magnet 11L, the direction of the magnetic pole is opposite to that of the first main
magnet 8 on the left side of the left side auxiliary magnet 11L of the first embodiment (180 If
different magnets may be used, and two magnets are used for the right side auxiliary magnet
11R, the second main magnet 9 is a magnetic element on the right side of the right side auxiliary
magnet 11R in the first embodiment. Magnets with opposite pole orientations (different 180 °)
may be used.
[0033]
In addition, the electromagnetic ultrasonic sensor 1 according to the first embodiment includes
the yoke 12 connecting the main magnet 3 and the auxiliary magnet 4 described above. In the
case of this embodiment, the yoke 12 passes from the top of the left side auxiliary magnet 11 to
the top of the first main magnet 8, the central auxiliary magnet 10, and the second main magnet
9 to form the right side auxiliary magnet. It is provided in the range which reaches the upper
part of 11, and is arranged so that all of five magnets may be straddled.
[0034]
For example, as shown in FIG. 5A, in the case of an electromagnetic ultrasonic sensor provided
with an auxiliary magnet or in the case of an electromagnetic ultrasonic sensor not provided with
an auxiliary magnet as shown in FIG. In order to generate an ultrasonic wave by interacting with
the eddy current generated by the sensor, the higher the density of magnetic lines of force
extending from the main magnet to the inspection object W side, in other words, the larger the
magnetic flux density, the higher the sensitivity as a sensor. Become.
[0035]
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12
In this respect, as shown in FIG. 5A, in the magnet arrangement provided with the auxiliary
magnet, the density of magnetic lines of force confirmed on the inspected object W side is the
test object W side in the magnet arrangement not provided with the auxiliary magnet shown in
FIG. Clearly denser than the magnetic field lines identified.
Actually, as shown in FIG. 6, when the magnetic flux density of the electromagnetic ultrasonic
sensor 101 of the first embodiment and the conventional example is calculated by simulation, the
electromagnetic ultrasonic sensor (dotted line) of the first embodiment It can be seen that the
magnetic flux density in the vertical direction (vertical direction) required for driving the
ultrasonic wave is larger than that of the sound wave sensor (solid line).
[0036]
However, even if it is possible to increase the magnetic flux density by adopting the auxiliary
magnet 4, if the external magnetic field by the auxiliary magnet 4 acts on the main magnet 3, the
main magnet 3 is demagnetized and the magnetic flux density is sufficiently improved It may not
be possible. Therefore, in the first embodiment described above, the dimensional shape and the
coercivity (residual magnetic flux density) of the auxiliary magnet 4 are preferably defined to
reduce the influence of demagnetization when viewed as a whole of the sensor to be inspected.
The magnetic flux density inside W is greatly improved.
[0037]
By adopting the auxiliary magnet 4 whose size and shape and coercive force are optimized as
described above, the sensitivity of the electromagnetic ultrasonic sensor 1 according to the first
embodiment can be actually enhanced as shown in FIG. That is, the results of FIGS. 7A and 7B
show that, for the aluminum plate of 100 mm in thickness, the electromagnetic ultrasonic sensor
101 of the conventional magnet arrangement is used on the receiving side and the magnets of
the first embodiment and the conventional example on the transmitting side. The reception signal
is measured using the array of electromagnetic ultrasonic sensors 1 and 101. The result of the
magnetic flux density of the first embodiment shown in FIG. 7A is that the signal strength is
about 1.5 times higher than the reception signal of the conventional example shown in FIG. 7B,
and the electromagnetic ultrasonic sensor 1 of the first embodiment However, the sensitivity is
higher than that of the conventional example. Further, FIG. 7A shows the result of only reception,
but it is possible to improve the efficiency of transmission and reception up to about 2.25 which
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is a square of 1.5 times by combining both transmission and reception. Second Embodiment
Next, an electromagnetic ultrasonic sensor 1 according to a second embodiment of the present
invention will be described.
[0038]
As shown in FIG. 8, in the electromagnetic ultrasonic sensor 1 of the second embodiment, the
side auxiliary magnet 11 is removed from the auxiliary magnets 4 provided in the
electromagnetic ultrasonic sensor 1 of the first embodiment, and one central electric magnet is
detected. Only the auxiliary magnet 10 is used. That is, the electromagnetic ultrasonic sensor 1
according to the second embodiment is configured by aligning the main magnet 3 and the
auxiliary magnet 4 and arranging three magnets.
[0039]
As shown in FIG. 9, even in the case of the electromagnetic ultrasonic sensor 1 of the second
embodiment, although the magnetic flux density generated by the electromagnetic ultrasonic
sensor 1 of the first embodiment (in the case of the five magnet array) is low. The magnetic flux
density (magnetic flux density in the vertical direction) confirmed on the inspection object W side
is high, and it can be seen that the magnetic flux density is improved. Although the second
embodiment described above is an example in which the number of the side auxiliary magnets
11 is reduced from the first embodiment while leaving the central auxiliary magnet 10, the
second auxiliary motor 10 does not It is also conceivable to increase the number of side auxiliary
magnets 11 from one embodiment. However, even if the number of side auxiliary magnets 11 is
increased to two or more, the effect of the improvement of the magnetic flux density does not
change much compared to the case of the first embodiment, and the effect of the improvement of
the magnetic flux density is that the number of magnets is five. Saturation occurs in the state,
and the magnetic flux density does not increase even if the number of magnets is further
increased. Therefore, although the description about the example which provided two or more
side auxiliary magnets 11 is abbreviate | omitted in this specification, the magnet arrangement |
sequence which provided two or more side auxiliary magnets 11 is naturally included in this
invention. Third Embodiment Next, an electromagnetic ultrasonic sensor 1 according to a third
embodiment of the present invention will be described.
[0040]
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As shown in FIGS. 10A and 10B, the electromagnetic ultrasonic sensor 1 according to the third
embodiment is an electromagnetic ultrasonic sensor 1 similar to the first embodiment and the
second embodiment. The shapes of the magnet 3 and the auxiliary magnet 4 are different. That
is, as shown in FIGS. 10A and 10B, the coil 2 provided in the electromagnetic ultrasonic sensor 1
according to the third embodiment is formed in a circular plate shape, and the conductor 5 is
wound in a spiral state. There is. Further, the main magnet 3 (center main magnet 3) provided in
the electromagnetic ultrasonic sensor 1 of the third embodiment is formed in a cylindrical shape
whose axis is directed in the vertical direction, and the auxiliary magnet 4 is the center main
magnet It is in the form of a coaxial cylinder disposed around 3. Furthermore, FIG. 10A shows a
case where one cylindrical auxiliary magnet 4 is coaxially disposed around one cylindrical central
main magnet 3 (in the case of two magnets), but it is shown in FIG. 10B. The electromagnetic
ultrasonic sensor 1 (the electromagnetic ultrasonic sensor 1 with three magnets) in which the
cylindrical side auxiliary magnet 11 having a larger diameter is coaxially disposed around one
cylindrical auxiliary magnet 4 The magnetic flux density for the inspection object W is improved
compared to the conventional example shown in FIG. 11 (the electromagnetic ultrasonic sensor
101 using one circular coil 102 and one cylindrical magnet 103). be able to. Fourth Embodiment
Next, an electromagnetic ultrasonic sensor 1 according to a fourth embodiment of the present
invention will be described.
[0041]
The electromagnetic ultrasonic sensor 1 according to the fourth embodiment generates
longitudinal ultrasonic waves with respect to the inspection object W in comparison with the first
to third embodiments, in which longitudinal waves with respect to the inspection object W are
generated. It is configured to generate ultrasonic waves. In the electromagnetic ultrasonic sensor
1 that generates ultrasonic waves of such longitudinal waves, unlike the ones that generate
transverse waves, the inside of the inspection object W located directly below the coil 2 is
laterally (horizontally) It is necessary to create a magnetic field.
[0042]
For example, FIG. 12 exemplifies an electromagnetic ultrasonic sensor 101 for longitudinal
waves according to a conventional example. As shown in FIG. 12, in the electromagnetic
ultrasonic sensor 101 for longitudinal waves, a flat coil 102 disposed along the horizontal
direction along the surface of the inspection object W and the coil 102 are surrounded. And a
main magnet 103 provided at a distance above the coil 102. That is, the main magnet 103
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provided in the electromagnetic ultrasonic sensor 101 for longitudinal waves has a first main
magnet 108 and a second main magnet 109 which are disposed with a distance in the horizontal
direction, and these two The coil 102 described above is disposed below the space (air gap)
formed between the two main magnets 108 and 109.
[0043]
Compared with the conventional electromagnetic ultrasonic sensor 101 for longitudinal waves
provided with such a coil 102 and the main magnets 108 and 109, the electromagnetic
ultrasonic sensor 101 for longitudinal waves of the fourth embodiment is shown in FIG. 13A and
FIG. The configuration is as shown in FIG. 13B. That is, in the electromagnetic ultrasonic sensor 1
according to the fourth embodiment shown in FIG. 13A, the central auxiliary magnet 10 as the
auxiliary magnet 4 is disposed between the first main magnet 8 and the second main magnet 9;
In other words, it has a configuration including three magnets. Further, the electromagnetic
ultrasonic sensor 1 of the modification of the fourth embodiment shown in FIG. 13B only
includes the central auxiliary magnet 10 as the auxiliary magnet 4 between the first main magnet
8 and the second main magnet 9. Instead of the first main magnet 8 and the second main magnet
9, the side auxiliary magnet 11 is disposed outside, that is, five magnets are provided.
[0044]
Also in the electromagnetic ultrasonic sensor 1 of the fourth embodiment, as shown in FIG. 14,
the magnetic flux density formed on the side of the inspection object W uses the conventional
example (the electromagnetic ultrasonic sensor 101 of FIG. 12). It is judged that the transmission
and reception efficiency of the electromagnetic ultrasonic sensor 1 can be enhanced, which is
dramatically improved from the case. Fifth Embodiment Next, an electromagnetic ultrasonic
sensor 1 according to a fifth embodiment of the present invention will be described.
[0045]
As shown in FIG. 15, the electromagnetic ultrasonic sensor 1 according to the fifth embodiment
has a central portion except for the side auxiliary magnet 11 among the auxiliary magnets 4 as
compared with the electromagnetic ultrasonic sensor 1 according to the first embodiment. Only
the auxiliary magnet 10 is removed. That is, the electromagnetic ultrasonic sensor 1 according to
the fifth embodiment does not use the central auxiliary magnet 10 but uses only the side
04-05-2019
16
auxiliary magnet 11 as the auxiliary magnet 4 (the main magnet 3 and the side auxiliary magnet
11 are It is the one using individual magnets).
[0046]
Even when the electromagnetic ultrasonic sensor 1 according to the fifth embodiment is used, as
shown in FIG. 16, the magnetic flux density (in the case of the gray solid line in the figure)
formed on the inspection object W side is It can be seen that the transmission and reception
efficiency of the electromagnetic ultrasonic sensor 1 can be enhanced, as compared with the case
of using the conventional example (in the case of the solid line in the figure). In addition, from
the results of FIG. 16, the larger the number of magnets (the number of magnets used in the
electromagnetic ultrasonic sensor 1) of the combination of the main magnet 3 and the auxiliary
magnet 4 is 5 than in the case of three magnets. It can be seen that the transmission and
reception efficiency of the electromagnetic ultrasonic sensor 1 can be improved by the individual
case.
[0047]
It should be understood that the embodiments disclosed herein are illustrative and nonrestrictive in every respect. In particular, in the embodiment disclosed this time, matters not
explicitly disclosed, such as operating conditions and conditions, various parameters, dimensions
of components, weights, volumes, etc., deviate from the range normally practiced by those skilled
in the art. It is not necessary for the person skilled in the art to use values that can easily be
assumed.
[0048]
DESCRIPTION OF SYMBOLS 1 electromagnetic ultrasonic sensor 2 coil 3 main magnet 4 auxiliary
magnet 5 conducting wire 6 1st conductive wire group 7 2nd conductive wire group 8 1st main
magnet 9 2nd main magnet 10 central auxiliary magnet 11 side auxiliary magnet 11 L left side
Auxiliary magnet 11R Right side auxiliary magnet 12 Yoke 108 1st main magnet 109 2nd main
magnet 101 electromagnetic ultrasonic sensor 102 of conventional example Coil 103 of
conventional example Main magnet W of conventional example
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17
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