JP2022092441A - Inspection device and inspection method - Google Patents

Abstract

To reduce as much as possible the number of a magnetic sensor used for an inspection device for inspecting magnetic characteristics of a test object, for example, presence or absence of foreign substances in the test object.SOLUTION: An inspection device for inspecting magnetic characteristics of a test object includes: a magnetic sensor; a test object table that rotates against the magnetic sensor and on which the test object is placed; and a magnetic shield that surrounds the magnetic sensor and the test object table. A field of view of the magnetic sensor faces a line extending from a center of rotation of the test object table in parallel to the test object table surface and radially.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inspection device using a magnetic sensor such as a SUQUID type and an improvement of the inspection method thereof.

As a kind of non-destructive inspection device, there is one that uses a magnetic sensor.
For example, Patent Document 1 proposes an inspection device using a SUQUID type magnetic sensor. By using such a magnetic sensor, it is possible to detect minute foreign substances in the subject.
In the inspection device disclosed in Patent Document 1, a magnetic sensor is arranged in a magnetic shield, and a linear subject is passed through the magnetic field of view (sensitivity region) of the magnetic sensor, whereby the linear subject is passed. It detects minute foreign substances inside.
Please refer to Patent Document 2 as a prior document related to the present invention.

Patent Document 1 Japanese Patent No. 3152074 Japanese Patent Document 2 Japanese Patent No. 5145552

The subject for which the detection of fine foreign matter is required is not limited to the linear one.
In the example of Patent Document 1, if the linear subject is replaced with a wide one, the width of the field of view of the magnetic sensor is widened according to the width.
Since each magnetic sensor has a narrow field of view, it is necessary to arrange multiple magnetic sensors in a line to obtain a wide field of view (an array of magnetic sensors).
However, since magnetic sensors are expensive, we want to reduce the number of magnetic sensors that make up the array as much as possible.

Also, if the width of the array is widened to widen the field of view, the number of magnetic sensors to be placed there will increase. As a result, it becomes difficult to make the environment of all magnetic sensors the same. Different environments can cause differences in the sensitivity of magnetic sensors. For example, even inside the magnetic shield, the influence of the external magnetic field differs depending on the distance from the wall. As a result, as the number of magnetic sensors constituting the array increases, the sensitivity of each magnetic sensor tends to vary. From this point as well, it is desired to reduce the number of magnetic sensors used in the inspection device as much as possible.

The present invention has been made to solve such a problem.
The first aspect of the present invention is defined as follows. That is,
An inspection device that inspects the magnetic properties of a subject.
With a magnetic sensor
It is provided with a subject table that rotates toward the magnetic sensor and on which the subject is placed, and a magnetic shield that surrounds the magnetic sensor and the subject table.
An inspection device in which the field of view of the magnetic sensor faces a line extending radially from the center of rotation of the subject table, parallel to the surface of the subject table.

According to the inspection device of the first aspect defined in this way, the subject is placed on the subject table and rotated. Here, the field of view of the magnetic sensor is opposed to a line extending radially from the center of rotation of the subject table, parallel to the surface of the subject table. For example, the subject table is made into a circle, and the field of view of the magnetic sensor is opposed to a straight line extending from the center of the circle to the outer circumference. At this time, the length of the magnetic sensor is the length of the radius of the circular table. Even when the subject is equal to the diameter of the circular table, by rotating the subject table, the entire subject can be covered by the magnetic sensor in the field of view that covers the radius of the subject table.
As a result, the number of magnetic sensors can be reduced as much as possible.
The magnetic properties of the subject are inspected by such a magnetic sensor. Here, the magnetic property is a magnetic property that characterizes the subject, and corresponds to, for example, the amount, size, position, and the like of a foreign substance present in the subject. In addition, changes in the composition of the material for forming the subject itself (those that appear as magnetic changes) also fall under this category.

The second aspect of the present invention is defined as follows. That is,
In the inspection device specified in the first aspect, the magnetic sensor is a SQUID type magnetic sensor.
The rotation frequency of the subject table shall be the frequency excluding the commercial frequency and the frequency obtained by an integral multiple thereof.
According to the inspection device of the second aspect defined in this way, by adopting a SUQUID type magnetic sensor, foreign matter existing in the inspection target can be detected with high sensitivity.
By rotating the subject table at a predetermined rotation frequency, foreign matter existing in the subject passes through the field of view of the magnetic sensor at a predetermined frequency. As a result, it can be seen that the signal detected by the magnetic sensor that is repeatedly detected at the frequency corresponds to the foreign matter existing in the subject. When a SUQUID type magnetic sensor is adopted here, it is preferable to keep the rotation frequency of the subject table within the driving frequency (for example, 50 kHz or less). When the rotation frequency is 10 Hz or less, the sensitivity is lowered due to the influence of noise called 1 / f noise. Further, in the usage environment of the inspection device, there is always a magnetic field having a frequency of commercial power (50 Hz, 60 Hz, etc.) and an integral multiple of the frequency due to the harmonics thereof. That is, by rotating the subject table at a frequency excluding the commercial frequency and a frequency that is an integral multiple thereof, the influence of the external magnetic field can be reliably eliminated. Therefore, high sensitivity is ensured for the SUQUID type magnetic sensor.

The third aspect of the present invention is defined as follows. That is, in the inspection device defined in the first or second aspect, a subject feeder for carrying the subject into the subject table and carrying out the subject is further provided.
A passage window through which the subject feeder passes is formed on the side wall of the magnetic shield.
According to the inspection device specified in the third aspect defined in this way, the subject is carried in to the subject table using the subject feeder, and the subject is carried out from the subject table to perform the inspection. Increased throughput.

The fourth aspect of the present invention is defined as follows. That is, in the inspection device specified in the third aspect, one passage window through which the subject feeder passes is formed on one side wall of the magnetic shield.
The subject feeder is passed through the one passage window.
According to the inspection device of the fourth aspect defined in this way, since only one window is formed on the side wall of the magnetic shield, the influence of the external magnetic field is minimized.

The fifth aspect of the present invention is defined as follows. That is, in the inspection device specified in the third or fourth aspect, the magnetic sensor is unevenly distributed on the upper wall side or the bottom wall side of the magnetic shield as compared with the passage window of the magnetic shield.
A table moving device for moving the subject table is further arranged.
The table moving device moves the subject table to the first position and the second position, where the subject is transferred between the subject table and the subject feeder at the first position. It is possible, and at the second position, the subject table faces the magnetic sensor.
According to the inspection device specified in the fifth aspect defined in this way, the magnetic sensor is displaced toward the upper wall side or the bottom wall side as compared with the case where the magnetic sensor is arranged at the same level as the passage window. Therefore, the distance from the passing window to the magnetic sensor becomes long. As a result, the influence of the external magnetic field on the magnetic sensor can be suppressed.

The sixth aspect of the present invention is defined as follows. That is, in the inspection device specified in the first to fifth aspects, the magnetic shield is box-shaped, and the center of rotation of the subject table passes through the center of gravity of the box-shaped magnetic shield and passes through the passage window. The sample feeder and the subject table are arranged on a virtual straight line.
The field of view of the magnetic sensor faces a straight line orthogonal to the virtual straight line.
According to the inspection device of the sixth aspect defined in this way, the influence of the external magnetic field entering through the passing window can be suppressed. That is, the distance from the passing window to each magnetic sensor becomes large.

The seventh aspect of the present invention is defined as follows. That is, it is an inspection method using an inspection device provided with a magnetic sensor, a subject table, and a magnetic shield surrounding the magnetic sensor and the subject table.
The field of view (inspection area) of the magnetic sensor is opposed to a straight line extending radially from the center of rotation of the subject table to the surface of the subject table.
An inspection method in which the subject table on which a subject is placed is rotated so as to face the magnetic sensor.
According to the inspection method specified in the seventh aspect defined in this way, the same operation of the inspection device specified in the first aspect can be obtained.

The eighth aspect of the present invention defines an inspection method using the specified inspection device in the second aspect, and has the same operation as the specified inspection device in the second aspect.
The inspection method of the eighth aspect is defined as follows. That is, in the inspection method specified in the seventh aspect, the magnetic sensor is a SQUID type magnetic sensor.
The rotation frequency of the subject table shall be the frequency excluding the commercial frequency and the frequency obtained by an integral multiple thereof.

The ninth aspect of the present invention defines an inspection method using the specified inspection device in the third aspect, and has the same operation as the specified inspection device in the third aspect.
The inspection method of the ninth aspect is defined as follows. That is, in the inspection method specified in the seventh or eighth aspect, a subject feeder for carrying the subject into the subject table and carrying out the subject is further provided.
A passage window through which the subject feeder passes is formed on the side wall of the magnetic shield.

The tenth aspect of the present invention defines an inspection method using the inspection device specified in the fourth aspect, and has the same operation as the inspection device specified in the fourth aspect.
The inspection method of the tenth aspect is defined as follows. That is, in the inspection method specified in the ninth aspect, one passage window through which the subject feeder passes is formed on one side wall of the magnetic shield.
The subject feeder is passed through the one passage window.

The eleventh aspect of the present invention defines an inspection method using the specified inspection device in the fifth aspect, and has the same operation as the specified inspection device in the fifth aspect.
The inspection method of the eleventh aspect is defined as follows. That is, in the inspection method specified in the ninth or tenth aspect, the magnetic sensor is unevenly distributed on the upper wall side or the bottom wall side of the magnetic shield as compared with the passage window of the magnetic shield.
A table moving device for moving the subject table is further arranged.
The table moving device moves the subject table to the first position and the second position, where the subject is transferred between the subject table and the subject feeder at the first position. The subject table faces the magnetic sensor at the second position.

The twelfth aspect of the present invention defines an inspection method using the specified inspection device in the sixth aspect, and has the same operation as the specified inspection device in the sixth aspect.
The inspection method of the twelfth aspect is defined as follows. That is, in the inspection method specified in any of 7 to 11, the magnetic shield is box-shaped, and the center of rotation of the subject table passes through the center of gravity of the box-shaped magnetic shield and passes through the passage window. The subject feeder and the subject table are arranged on a virtual straight line.
The field of view of the magnetic sensor faces a straight line orthogonal to the virtual straight line.

FIG. 1 is a schematic view showing the structure of the inspection device according to the embodiment of the present invention, FIG. 1A is a plan view, and FIG. 1B is a front view. FIG. 2 is a schematic view (plan view) showing the structure of the inspection device according to another embodiment of the present invention. FIG. 3 is a schematic view (front view) showing the structure of the inspection device according to another embodiment of the present invention. FIG. 4 is a schematic view (front view) showing the structure of the inspection device according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the inspection device 1 of the embodiment includes a magnetic sensor array 10, a subject table 20, a magnetic shield 30, and loading / unloading feeders 41 and 43.
The magnetic sensor array 10 is an array in which a plurality of SQUID type magnetic sensors (elements) are linearly arranged. The array 10 is fixed by a holder (not shown). In this example, the SQUID (superconducting quantum interference element) described in Patent Document 2 proposed by the present inventor is adopted as each magnetic sensor constituting the array 10, but other elements such as a Hall element and a magnetoresistive effect element are used. A general-purpose magnetic sensor can be arbitrarily selected according to the characteristics of the subject, the inspection environment, and the like.
The magnetic sensor array 10 has a wide field of view by sliding the magnetic sensor linearly and setting the detection surface at the same height. The reference line of the array may be a straight line or a curved line. Furthermore, the magnetic sensors can be arranged in a plurality of rows.

The subject table 20 is not particularly limited as long as it can fix and hold the subject when it rotates and does not affect the magnetic field.
In the example of FIG. 1, the resin disk was used as the subject table 20. The subject table 20 is arranged parallel to the arrangement direction of each magnetic sensor constituting the magnetic sensor array 10. In other words, each magnetic sensor is always located at equal distances to the facing surfaces of the subject table 20. Therefore, the influence of magnetism from the subject placed on the subject table is uniformly detected by each magnetic sensor.
By arranging them in a straight line, each magnetic sensor can be placed as close as possible. This makes it possible to make the external environment of each magnetic sensor as uniform as possible, such as the influence of the external magnetic field on each magnetic sensor.
In the subject table 20, each magnetic sensor is arranged so as to extend from the center of rotation to the outer periphery thereof and face a straight line toward the carry-in feeder 41 side, and the magnetic sensor array 10 is configured.

In the above example, the field of view of the magnetic sensor array 10 is set to the same length as the radius of the subject table 20, but the field of view is not limited to this. The field of view can be lengthened or shortened according to the shape and size of the subject. It is also possible to arrange the magnetic sensors in an arc shape to make the field of view arcuate.

The subject table 20 rotates with the rotation of the rotation shaft 23. The frequency of this rotation shall be the frequency excluding the commercial frequency and the frequency obtained by an integral multiple thereof.
The rotation frequency of the subject table 20 is preferably constant, but the rotation frequency can also be changed. In either case, the electronic control circuit 50 picks up a signal corresponding to the rotation frequency from the detection signal of the magnetic sensor array 10.
The electronic control circuit 50 can specify the position of a foreign substance (the cause of the signal) in the subject 3 according to the picked up signal.

The magnetic shield 30 can be arbitrarily designed according to the characteristics of the subject and the external environment. In this example, the magnetic shield 30 is formed of a sheet metal made of a box-shaped high magnetic permeability material (permalloy) having a rectangular flat surface.
A carry-in window 31 and a carry-out window 33 as passage windows are formed in the center of the side walls 34 and 35 facing each other of the magnetic shield 30 shown in FIG. A belt conveyor type carry-in feeder 41 and a carry-out feeder 43 are passed through the windows 31 and 33.
The edges of the carry-in feeder 41 and the carry-out feeder 43 face the subject table 20 and are at the same height.

Next, the operation of the inspection device 1 of FIG. 1 will be described.
First, the rotation frequency of the rotation shaft 23 is determined, and the frequency of, for example, a lock-in amplifier circuit in the electronic control circuit 50 is synchronized and set so that a signal having a frequency corresponding to the rotation frequency is picked up.
The subject 3 is magnetized by a well-known method at a position sufficiently distant from the magnetic shield 30 and placed on the carry-in feeder 41. The subject 3 placed on the carry-in feeder 41 enters the magnetic shield 30 through the carry-in window 31. At the end of the carry-in feeder 41, a pick-and-release device (not shown) receives the subject 3 and places it in the center of the subject table 20.

As in this example, the carry-in feeder 41, the subject table 20, and the carry-out feeder 43 are arranged on the same virtual straight line LH. This facilitates delivery of the subject 3. This virtual straight line LH connects the center axis of the carry-in feeder 41 and the carry-out feeder 43 in the transport direction with the rotation center of the subject table 20. The magnetic sensor array 10 is arranged so as to face the virtual straight line LH.
Further, it is preferable that the rotation center axis of the subject table 20 coincides with the center of gravity of the magnetic shield 20. As a result, the magnetic sensor array 10 associated with the subject table 20 is also arranged near the center of gravity of the magnetic shield. Therefore, the influence of the external magnetic field through the wall portion of the magnetic shield 30 is minimized.

In this example, the disk-shaped subject 3 is adopted. The disk-shaped subject 3 placed in the center of the subject table 20 rotates as the subject table 20 rotates. At this time, the field of view of the magnetic sensor array 10, that is, the arrangement of the magnetic sensors covers one radius of the subject table 20. Therefore, when the subject 3 placed in the center of the subject table 20 is rotated together with the subject table 20, all the regions of the subject 3 are relatively scanned in the field of view of the magnetic sensor array 10. It will be.

As described above, the noise of the external magnetic field can be removed by rotating the subject 3 at a predetermined rotation frequency. That is, the rotation frequency when the SUQUID type magnetic sensor is adopted as the magnetic sensor is set to be within the drive frequency of the SUQUID type magnetic sensor, and the frequency excluding the commercial frequency and the frequency obtained by an integral multiple thereof.
As a result, only the magnetic change caused by the foreign matter is detected. In other words, noise can be removed.
Further, by repeatedly rotating the subject 3, a signal caused by a foreign substance can be repeatedly detected. This makes it possible to increase the sensitivity.

By shifting the timing of picking up the signal, the two-dimensional spread of the foreign matter in the subject 3 can be specified. By combining the data obtained in this way with the image data of the subject 3 on the subject table 20, the absolute position of the foreign substance in the subject 3 can be specified.

When the inspection is completed by the magnetic sensor array 10 and the rotation of the subject table 20 is stopped, the subject 3 on the subject table 20 is moved to the end of the carry-out feeder 43 by the pick and release device. After that, the carry-out feeder 43 is operated, and the subject 3 is carried out from the magnetic shield 30 through the carry-out window 33. Then, it is demagnetized by a well-known method.

FIG. 2 is a schematic view showing the configuration of the inspection device 1A of another embodiment. The same elements as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
In the inspection device 1A of FIG. 2, the magnetic sensor array 10 is arranged so as to be orthogonal to the virtual straight line LH in the transport direction of the subject 3 in a plan view and to face the virtual straight line LV passing through the rotation center of the subject table 20. Orthogonal.
By arranging the magnetic sensor array 10 in this way, the distance between each magnetic sensor constituting the magnetic sensor array and the carry-in window 31 and the carry-out window 33 becomes maximum. Therefore, the influence of the external magnetic field can be suppressed.

FIG. 3 is a schematic diagram showing the configuration of the inspection device 1B of another embodiment. The same elements as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
In this inspection device 1B, a window (carry-in / out window 35) is provided only on one side wall 34 of the magnetic shield 30, and the carry-in / out feeder 45 is passed through the carry-in / out window 35. The subject 3 is carried into the subject table 20 by the carry-in / out feeder 45, and is carried out from the subject table 20.
By limiting the windows provided on the magnetic shield 30 in this way, the influence of the external magnetic field can be suppressed. Therefore, the inspection sensitivity is improved.

FIG. 4 is a schematic diagram showing the configuration of the inspection device 1C of another embodiment. The same elements as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
In this example, the magnetic sensor array 10 is displaced toward the upper wall 37 side of the magnetic shield 30. As a result, the influence of the external magnetic field from the carry-in window 31 and the carry-out window 33 can be suppressed.
The subject table 20 is moved up and down by the lifter 25 as a table moving device. When the subject table 20 is in the lower first position, the subject is transferred between the carry-in feeder 41 and the carry-out feeder 43. When the subject table 20 is in the upper second position, the subject 3 faces the magnetic sensor array 10.
In the example of FIG. 4, the magnetic sensor array 10 is unevenly distributed in the vertical direction as compared with the example of FIG. 1, but from the viewpoint of further separating this from the carry-in window 31 and the carry-out window 33, the magnetic sensor array 10 May be unevenly distributed toward the bottom wall 38 in the vertical direction. Further, the magnetic sensor array in the example of FIG. 1 may be unevenly distributed in the diagonally vertical direction.

The present invention is not limited to the description of the embodiments and examples of the above invention. Various modifications are also included in the present invention to the extent that those skilled in the art can easily conceive without departing from the description of the scope of claims.

1, 1A, 1B, 1C Inspection device 3 Subject 20 Subject table 30 Magnetic shield 31, 33, 35 Window 34, 35 Side wall 37 Upper wall 38 Bottom wall

Claims (12)

An inspection device that inspects the magnetic properties of a subject.
With a magnetic sensor
It is provided with a subject table that rotates toward the magnetic sensor and on which the subject is placed, and a magnetic shield that surrounds the magnetic sensor and the subject table.
An inspection device in which the field of view of the magnetic sensor faces a line extending radially from the center of rotation of the subject table, parallel to the surface of the subject table. The magnetic sensor is a SQUID type magnetic sensor.
The inspection device according to claim 1, wherein the rotation frequency of the subject table is a frequency excluding a commercial frequency and a frequency obtained by an integral multiple thereof. A subject feeder for carrying the subject into the subject table and carrying out the subject is further provided.
The inspection device according to claim 1 or 2, wherein a passage window through which the subject feeder passes is formed on the side wall of the magnetic shield. One passage window through which the subject feeder passes is formed on one side wall of the magnetic shield.
The inspection device according to claim 3, wherein the subject feeder is passed through the one passage window. The magnetic sensor is unevenly distributed on the upper wall side or the bottom wall side of the magnetic shield as compared with the passage window of the magnetic shield.
A table moving device for moving the subject table is further arranged.
The table moving device moves the subject table to the first position and the second position, where the subject is transferred between the subject table and the subject feeder at the first position. The inspection device according to claim 3 or 4, wherein the subject table faces the magnetic sensor at the second position. The magnetic shield is box-shaped, and the center of rotation of the subject table passes through the center of gravity of the box-shaped magnetic shield, and the subject feeder and the subject table that have passed through the passage window are arranged on a virtual straight line. ,
The inspection device according to any one of claims 1 to 5, wherein the field of view of the magnetic sensor faces a straight line orthogonal to the virtual straight line. An inspection method using an inspection device provided with a magnetic sensor, a subject table, and a magnetic shield surrounding the magnetic sensor and the subject table.
The field of view (inspection area) of the magnetic sensor is opposed to a straight line extending radially from the center of rotation of the subject table to the surface of the subject table.
An inspection method in which the subject table on which a subject is placed is rotated so as to face the magnetic sensor. The magnetic sensor is a SQUID type magnetic sensor.
The inspection method according to claim 7, wherein the frequency is a frequency excluding the rotation frequency commercial frequency of the subject table and a frequency obtained by an integral multiple thereof. A subject feeder for carrying the subject into the subject table and carrying out the subject is further provided.
The inspection method according to claim 7 or 8, wherein a passage window through which the subject feeder passes is formed on the side wall of the magnetic shield. One passage window through which the subject feeder passes is formed on one side wall of the magnetic shield.
The inspection method according to claim 9, wherein the subject feeder is passed through the one passage window. The magnetic sensor is unevenly distributed on the upper wall side or the bottom wall side of the magnetic shield as compared with the passage window of the magnetic shield.
A table moving device for moving the subject table is further arranged.
The table moving device moves the subject table to the first position and the second position, and the subject is transferred between the subject table and the subject feeder at the first position. The inspection method according to claim 9 or 10, wherein the subject table faces the magnetic sensor at the second position. The magnetic shield is box-shaped, and the center of rotation of the subject table passes through the center of gravity of the box-shaped magnetic shield, and the subject feeder and the subject table that have passed through the passage window are arranged on a virtual straight line. ,
The inspection method according to any one of claims 7 to 11, wherein the field of view of the magnetic sensor faces a straight line orthogonal to the virtual straight line.

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