Patent ID: 12235240

DESCRIPTION OF EMBODIMENTS

The present invention provides a magnetic body inspection apparatus including a magnet and a magnetic sensor configured to output an electric signal, and also provides a magnetic body inspection method. When the magnetic sensor acquires at least two electric signals and a difference between the two electric signals thus acquired is outputted, a magnetic body existing in a nonmagnetic body can be detected nondestructively.

The following is a specific description of the present invention with reference to the drawings. However, the prevent invention is not limited to the illustrated examples. It is also possible to implement the invention with appropriate changes to the extent that it can be adapted to the purpose of the preceding and following descriptions. All of these are included in the technical scope of the present invention.

The magnetic body inspection apparatus according to an embodiment of the present invention will be initially described with reference toFIGS.1and2.FIG.1is a schematic view of an exemplary magnetic body inspection apparatus according to the embodiment of the present invention.FIG.2is a schematic view of a magnetic body inspection apparatus according to a modification example of the embodiment of the present invention.

As depicted inFIGS.1and2, the magnetic body inspection apparatus according to the present invention is a magnetic body inspection apparatus1including: a magnet10; a first magnetic sensor21disposed at a predetermined position relative to the magnet10and configured to output an electric signal; and a second magnetic sensor22disposed at a predetermined position relative to the magnet10and configured to output an electric signal. The magnetic body inspection apparatus is configured to output a difference between a first electric signal outputted from the first magnetic sensor21and a second electric signal outputted from the second magnetic sensor22.

The magnet10included in the magnetic body inspection apparatus1has only to be configured to generate a magnetic field, and examples of the magnet include a permanent magnet and an electromagnet. The magnet10is preferably the permanent magnet because the permanent magnet is configured to stably generate a magnetic field from the permanent magnet itself, whereas the electromagnet needs electric power.

The magnet10is not particularly limited in terms of its shape, and can have any one of various shapes including a rectangular parallelepiped shape, a cubic shape, a quadrangular prism shape, a polygonal column shape, and a columnar shape.

The magnet10is not either particularly limited in the number thereof, and the magnetic body inspection apparatus1has only to include at least one magnet. There can be provided two, three, or more magnets10as necessary. A plurality of magnets10is preferably disposed at predetermined positions. Although the above mentions that the magnet10is preferably a permanent magnet, the magnet10may alternatively be an electromagnet, which can generate a stronger magnetic field than that generated by a permanent magnet. Such a stronger magnetic field enables detection of a magnetic body buried at a deeper position. When a plurality of electromagnets is provided, the electromagnets may be exemplarily disposed at predetermined positions. If some of the electromagnets are ON and the others are OFF, there can be formed a plurality of magnetic fields. There can thus be acquired a plurality of electric signals from a magnetic sensor20, for higher specification accuracy of a position or a broken portion of a magnetic body existing in a nonmagnetic body.

The magnetic sensor20has only to be configured to measure magnitude of a magnetic field generated by a magnet. Examples of the magnetic sensor20included in the magnetic body inspection apparatus1include a Hall sensor configured to measure a magnetic field generated by a magnet or a magnetic field generated by current with reference to a Hall effect, and an MR sensor (magnetoresistance effect element) configured to measure magnitude of a magnetic field with reference to a magnetoresistance effect that a magnetic field varies electric resistance of a separate entity. A highly sensitive sensor such as the MR sensor has relatively larger output in comparison to the Hall sensor, so that the output is likely to saturate even when placed in a weak magnetic field. The magnetic sensor20in the magnetic body inspection apparatus1is disposed in a relatively strong magnetic field generated by the magnet10. Accordingly, the magnetic sensor20is preferably a Hall sensor that does not cause saturation even in a relatively high magnetic field, or never generates a saturated magnetic field. Examples of the Hall sensor include a Hall element configured to output Hall voltage when current flows, and a Hall IC including the Hall element provided integrally with an operational amplifier configured to amplify a signal on a circuit. When the Hall element is adopted, which outputs relatively small voltage, the operational amplifier may be provided separately.

The Hall element includes first and second supply electrodes configured to supply current, and first and second measuring electrodes configured to measure voltage. Current flows in a constant direction (an x-axis direction) from the first supply electrode to the second supply electrode. A magnetic field is provided perpendicularly to the current flowing between the two supply electrodes (in a z-axis direction), charge particles carrying the current receive Lorentz force to be distorted in a direction (y-axis direction) perpendicular to a straight line (in the x-axis direction) connecting the two supply electrodes. This causes biased electric charge distribution in the y-axis direction, with a first side being positively electrified and a second side being negatively electrified. The first measuring electrode is disposed on the positively electrified side and the second measuring electrode is disposed on the negatively electrified side, to measure a potential difference between the two measuring electrodes. Measurement of the potential difference enables determination as to whether there is generated any magnetic field, and magnitude of the magnetic field.

Preferably, the magnet10is a permanent magnet and has a first direction from an S pole to an N pole, and the first and second measuring electrodes of the magnetic sensor20face each other in a second direction perpendicular to the first direction. Furthermore, the second direction in which the first and second measuring electrodes of each of the magnetic sensors20face each other is preferably perpendicular to a straight line connecting a gravity center of the first magnetic sensor21and a gravity center of the second magnetic sensor22. Moreover, preferably, the first direction from the S pole to the N pole of the magnet10is perpendicular to the straight line connecting the gravity center of the first magnetic sensor21and the gravity center of the second magnetic sensor22as depicted inFIG.3, or the first direction from the S pole to the N pole of the magnet10is parallel to the straight line connecting the gravity center of the first magnetic sensor21and the gravity center of the second magnetic sensor22as depicted inFIG.1. In such a configuration, the magnetic sensors20are disposed such that a magnetic field12detected by the first magnetic sensor21is substantially equal in magnitude to a magnetic field12detected by the second magnetic sensor22, so as to be suitable for output of the difference by the magnetic body inspection apparatus1.

The magnetic sensor20outputs an electric signal. An electric signal is outputted in accordance with magnitude of a magnetic field detected by the magnetic sensor20. For example, the magnetic field detected by the magnetic sensor20is converted to a signal of voltage, current, or the like according to the magnetic field so as to be outputted.

The magnetic body inspection apparatus1includes at least two magnetic sensors20including the first magnetic sensor21disposed at a predetermined position relative to the magnet10and configured to output an electric signal, and the second magnetic sensor22disposed at a predetermined position relative to the magnet10and configured to output an electric signal. The first magnetic sensor21disposed at a predetermined position relative to the magnet10has only to be positioned to detect the magnetic field12generated by the magnet10. Similarly, the second magnetic sensor22disposed at a predetermined position relative to the magnet10has only to be positioned to detect the magnetic field12generated by the magnet10.

In the magnetic body inspection apparatus1, the magnetic sensors20are preferably disposed such that the magnetic field12detected by the first magnetic sensor21is substantially equal in magnitude to the magnetic field12detected by the second magnetic sensor22. For example, as depicted inFIG.2, a distance between the first magnetic sensor21and the magnet10is preferably equal to a distance between the second magnetic sensor22and the magnet10. Assume that the distance between the first magnetic sensor21and the magnet10is obtained by measuring a distance between a closest portion of the first magnetic sensor21to the magnet10and a closest portion of the magnet10to the first magnetic sensor21. Similarly, assume that the distance between the second magnetic sensor22and the magnet10is obtained by measuring a distance between a closest portion of the second magnetic sensor22to the magnet10and a closest portion of the magnet10to the second magnetic sensor22. If the distance between the magnet10and the first magnetic sensor21is different from the distance between the magnet10and the second magnetic sensor22, the first electric signal acquired from the first magnetic sensor21may be largely different in magnitude from the second electric signal acquired from the second magnetic sensor22. However, the first electric signal is made similar in magnitude to the second electric signal by equalizing the distance between the first magnetic sensor21and the magnet10and the distance between the second magnetic sensor22and the magnet10, for higher inspection accuracy.

Furthermore, as depicted inFIG.2, a line segment L1connecting the first magnetic sensor21and the magnet10is preferably parallel to a line segment L2connecting the second magnetic sensor22and the magnet10. More preferably, the distance between the first magnetic sensor21and the magnet10is equal to the distance between the second magnetic sensor22and the magnet10, and the line segment L1is parallel to the line segment L2. When the distance between the first magnetic sensor21and the magnet10is equal to the distance between the second magnetic sensor22and the magnet10and the line segment L1is parallel to the line segment L2, the first magnetic sensor21and the second magnetic sensor22can detect magnetic fields more similar in magnitude, for higher inspection accuracy. The line segment L1connecting the first magnetic sensor21and the magnet10and the line segment L2connecting the second magnetic sensor22and the magnet10being parallel to each other indicates being positioned substantially within ±5 degrees from such a parallel state.

In the magnetic body inspection apparatus1, the first magnetic sensor21and the second magnetic sensor22are preferably positioned such that magnetic force lines of the magnetic field detected by the first magnetic sensor21are symmetric in shape to magnetic force lines of the magnetic field detected by the second magnetic sensor22. For example, as depicted inFIG.1or2, the first magnetic sensor21and the second magnetic sensor22are preferably positioned symmetrically with respect to the magnet10. The first magnetic sensor21and the second magnetic sensor22being positioned symmetrically with respect to the magnet10indicates being disposed point symmetrically about a gravity center11of the magnet10, or being disposed line symmetrically with respect to a predetermined straight line including the gravity center11of the magnet10. When the first magnetic sensor21and the second magnetic sensor22are positioned as described above, the magnetic force lines of the magnetic field12generated by the magnet10and detected by the first magnetic sensor21are assumed to be identical or symmetric in shape to the magnetic force lines of the magnetic field12generated by the magnet10and detected by the second magnetic sensor22. If the magnetic force lines of the magnetic field12detected by the first magnetic sensor21are not identical or symmetric in shape to the magnetic force lines of the magnetic field12detected by the second magnetic sensor22, there needs calculation for correction in shape. However, when the magnetic force lines of the magnetic field12detected by the first magnetic sensor21are made identical or symmetric in shape to the magnetic force lines of the magnetic field12detected by the second magnetic sensor22, there needs no such calculation for correction upon output of the difference between the first electric signal and the second electric signal. This enables reduction in processing and calculation necessary for output of the difference, for reduction in time necessary for inspection as well as for improvement in inspection accuracy.

The magnetic sensors20do not limitedly include two sensors, namely, the first magnetic sensor21and the second magnetic sensor22. Though not depicted, the magnetic body inspection apparatus1may further include a third magnetic sensor disposed at a predetermined position relative to the magnet10, and a fourth magnetic sensor disposed at a predetermined position relative to the magnet10. In such an exemplary case of providing the third magnetic sensor and the fourth magnetic sensor, the third and fourth magnetic sensors may be positioned to detect magnetic fields12different in magnitude from the magnetic fields12detected by the first magnetic sensor21and the second magnetic sensor22. The magnetic sensors can be disposed such that the magnetic field12detected by the third magnetic sensor is substantially equal in magnitude to the magnetic field12detected by the fourth magnetic sensor. In this case, the magnetic body inspection apparatus can be configured to output a difference between a third electric signal outputted from the third magnetic sensor and a fourth electric signal outputted from the fourth magnetic sensor. Increase in the number of the magnetic sensors20in the magnetic body inspection apparatus1leads to higher inspection accuracy.

The magnetic body inspection apparatus1outputs the difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22.

As the magnetic body inspection apparatus1approaches a magnetic body, the difference between the first electric signal and the second electric signal varies. It can thus be identified that the magnetic body exists ahead of the magnetic body inspection apparatus1being approaching when the difference varies, achieving positional specification of the magnetic body existing in a nonmagnetic body. The magnetic field12of the magnet10concentratedly converges at an end of a magnetic body. A difference outputted at a broken portion of the magnetic body is thus more than a difference outputted at a position where an unbroken magnetic body exists. It is thus possible to identify breakage of the magnetic body at the position where the outputted difference is more than the difference at the position where the unbroken magnetic body exists.

As depicted inFIGS.1and2, the magnetic body inspection apparatus1may include a difference detector30connected to the first magnetic sensor21and the second magnetic sensor22, and the difference may be amplified when the difference detector30receives voltage output of the first electric signal and the second electric signal. As the difference detector30according to an embodiment, the magnetic body inspection apparatus1may further include a differential amplifier circuit31connected to the first magnetic sensor21and the second magnetic sensor22, and the difference may be amplified and outputted simultaneously when the differential amplifier circuit31receives voltage output of the first electric signal and the second electric signal. As the difference detector30according to another embodiment, the magnetic body inspection apparatus1may further include an arithmetic processor32configured to convert an electric signal to a digital signal, and calculate a difference between digital signals, to amplify and output the difference. According to still another embodiment, as depicted inFIG.1, the magnetic body inspection apparatus1may include a memory storing the first electric signal and the second electric signal, and a personal computer40or the like may acquire the first and second electric signals and a central processing unit (CPU) of the personal computer40is configured to calculate the difference between the signals so as to be outputted. The differential amplifier circuit31connected to the first magnetic sensor21and the second magnetic sensor22can be disposed close to the magnetic sensors for achievement of noise reduction. The magnetic body inspection apparatus1is thus preferred to further include the differential amplifier circuit31configured to receive voltage output of the first electric signal and the second electric signal.

As depicted inFIGS.1and2, the magnetic body inspection apparatus1may include a power source unit50configured to adjust externally acquired electric power and supply the electric power thus adjusted into the apparatus. The power source unit50may include a power source switch configured to switch on or off electric power supply.

As depicted inFIG.2, the magnetic body inspection apparatus1may include a display unit60configured to display, to a user, information on the difference between the first electric signal and the second electric signal. Examples of the display unit60can include a monitor configured to visualize magnitude of signals, magnitude of the difference, and the like.

As described above, the magnetic body inspection apparatus1according to the embodiment of the present invention outputs the difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22to specify where a magnetic body exists in a nonmagnetic body, and whether or not the magnetic body is broken.

The magnetic body inspection apparatus1preferably includes the memory storing a database having gathered difference data acquired with use of a reference sample. The reference sample is a magnetic body having a thickness C1. For example, the difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22is measured in a state where the reference sample and each of the magnetic sensors have a distance C2therebetween, and the database has only to store the thickness C1of the reference sample, the distance C2between the reference sample and each of the magnetic sensors, and the difference associated with one another. C1and C2mentioned above are constants more than zero. C1and C2are preferably varied to obtain difference data for creation of the database.

In the magnetic body inspection apparatus1applied to an inspection target, the difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22can be fitted with the difference data stored on the database. The thickness of the reference sample associated with the difference data on the database and the distance between the reference sample and each of the magnetic sensors can be obtained from a result of fitting between the difference obtained from the inspection target and the difference data on the database, so as to identify the thickness of the magnetic body as the inspection target and the distance between the magnetic body as the inspection target and the magnetic sensor. The difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22is fitted with the difference data on the database as described above, so as to identify the thickness of the magnetic body as the inspection target as well as the distance between the magnetic body as the inspection target and each of the magnetic sensors. Fitting according to a different embodiment can be executed in accordance with a method with reference to a model function. There is prepared a model function F1enabling database fitting, and the model function F1is set such that fitting parameters D1and D2of the model function are determined uniquely with respect to C1and C2. Furthermore, modeling is executed by preparing model functions F21and F22such that D1and D2become functions of C1and C2, respectively. The inspection target is measured to obtain a result that is fitted to obtain the parameters D1and D2. The parameters are inversely operated with reference to the model functions F21and F22to determine C1and C2.

Furthermore, the magnetic body inspection apparatus1may be configured to identify a corroded portion in accordance with a difference obtained from the magnetic body as the inspection target, a distance between the magnetic body and a magnetic sensor, and thickness. More specifically, in a case where a reinforcing bar buried in a concrete structure is partially corroded to be radially reduced, the reinforcing bar includes a corroded portion and an uncorroded portion, which are assumed to have different numerical values of an obtained difference, thickness of the reinforcing bar, and a distance between the reinforcing bar and a magnetic sensor. As to the difference obtained from the magnetic body as the inspection target, the thickness, and the distance between the magnetic body and the magnetic sensor, if there is any portion having numerical values different from difference data, thickness of the magnetic body, and a distance between the magnetic body and the magnetic sensor of a peripheral portion, such a portion can be identified as being corroded.

Such fitting may be executed by an arithmetic processor or a controller optionally provided. The above provides the magnetic body inspection apparatus1including the memory storing the database. Alternatively, the database itself can be stored in a memory provided in a different device such as a memory provided to the personal computer or an externally provided memory.

The magnetic body inspection apparatus1is preferably used to inspect a reinforcing bar buried in a concrete structure. In a case where the reinforcing bar exists in the concrete structure, it is possible to specify where the reinforcing bar exists and whether or not the reinforcing bar is broken, without destroying the concrete structure. The concrete structure may have a buried tube or the like in addition to the reinforcing bar or a cavity. Obviously, neither the tube or the like as a nonmagnetic body nor the cavity is detected, so as to stably inspect only the reinforcing bar as the magnetic body. The inspection target of the magnetic body inspection apparatus1according to the embodiment of the present invention is not limited to a reinforcing bar but can be any magnetic body. The magnetic body inspection apparatus1achieves inspection also in a case where a plurality of magnetic bodies is arranged and in a case where magnetic bodies are arranged to form a grid pattern.

A preferred method of using the magnetic body inspection apparatus is specifically described next with reference toFIG.3.FIG.3is a schematic view of the magnetic body inspection apparatus according to the modification example of the embodiment of the present invention and a sectional view of a concrete structure having a buried reinforcing bar serving as an exemplary inspection target.

The magnetic body inspection apparatus1is initially disposed on an inspection target70such that one of the magnetic sensors is positioned closer to the inspection target70than the magnet10, as well as such that another one of the magnetic sensors is positioned farther from the inspection target70than the magnet10. Assume that a distance from a magnetic sensor to the inspection target is obtained by measuring a distance between a closest portion of the magnetic sensor to the inspection target and a farthest portion of the inspection target from the magnetic sensor. Furthermore, assume that a distance from the magnet to the inspection target is obtained by measuring a distance between a closest portion of the magnet to the inspection target and a farthest portion of the inspection target from the magnet. Specifically, the magnetic body inspection apparatus1is disposed on the inspection target70such that the first magnetic sensor21is positioned closer to the inspection target70than the magnet10, as well as such that the second magnetic sensor22is positioned farther from the inspection target70than the magnet10. A surface of the inspection target70is scanned with the positional relation being kept among the magnet10, the magnetic sensors20, and the inspection target70. The magnetic sensors20acquire electric signals while scanning. The magnetic field12of the magnet10is indicated by stable magnetic force lines without change if there is no magnetic body nearby (hereinafter, referred to as “reference magnetic force lines”). However, when there is any magnetic body near the magnet10, the magnetic field12of the magnet10is indicated by magnetic force lines different from the reference magnetic force lines because the magnetic field12of the magnet10has a characteristic of converging at the magnetic body. At the first magnetic sensor21positioned closer to the inspection target70than the magnet10, when the magnetic body exists in the inspection target70, at least part of the magnetic field12converges at the magnetic body and the first magnetic sensor21having detected the magnetic field12outputs an electric signal according to the magnetic field (the first electric signal). In contrast, at the second magnetic sensor22positioned farther from the inspection target70than the magnet10, the magnetic field12keeps lines similar to the reference magnetic force lines and the second magnetic sensor22outputs an electric signal according to the magnetic field12having lines similar to the reference magnetic force lines (the second electric signal). As the magnetic body inspection apparatus1thus configured approaches the magnetic body, the difference between the first electric signal and the second electric signal varies. It can thus be identified that the magnetic body exists ahead of the magnetic body inspection apparatus1being approaching when the difference varies. Accordingly, outputting the difference between the first electric signal and the second electric signal enables identifying where the magnetic body is buried. However, if the first magnetic sensor21and the second magnetic sensor22are not positioned such that the magnetic force lines of the magnetic field detected by the first magnetic sensor21are symmetric in shape to magnetic force lines of the magnetic field detected by the second magnetic sensor22, calculation for correction according to the positions of the magnetic sensors20is needed before output of the difference between the two electric signals. Such calculation can be executed with use of an arithmetic processor or the like.

There has been described the magnetic body inspection apparatus according to the embodiment of the present invention. Described next is a magnetic body inspection method with use of the magnetic body inspection apparatus. The following description does not refer to the configurations having been described in the description of the magnetic body inspection apparatus.

Initially described with reference toFIG.3is a magnetic body inspection method according to a first embodiment.

The magnetic body inspection method according to the first embodiment of the present invention is executed with use of the magnetic body inspection apparatus1including the magnet10, the first magnetic sensor21disposed at a predetermined position relative to the magnet10and configured to output an electric signal, and the second magnetic sensor22disposed at a predetermined position relative to the magnet10and configured to output an electric signal. The magnetic body inspection method includes: acquiring the first electric signal from the first magnetic sensor21(step S1); acquiring the second electric signal from the second magnetic sensor22(step S2); and outputting the difference between the first electric signal and the second electric signal (step S3).

Step S1involves acquiring the first electric signal from the first magnetic sensor21. More specifically, as depicted inFIG.3, the first electric signal is preferably acquired from the first magnetic sensor21in a state where at least part of the magnetic field12of the magnet10converges at the magnetic body.

Step S2involves acquiring the second electric signal from the second magnetic sensor22. More specifically, as depicted inFIG.3, the second electric signal is preferably acquired from the second magnetic sensor22in a state where the magnetic field12of the magnet10does not converge at the magnetic body. In the state where the magnetic field12of the magnet10does not converge at the magnetic body, the magnetic field12has the reference magnetic force lines.

Step S3involves outputting the difference between the first electric signal acquired in step S1and the second electric signal acquired in step S2.

The magnetic body inspection apparatus1used to execute the magnetic body inspection method has only to include two or more magnetic sensors. For example, according to the magnetic body inspection method with use of the magnetic body inspection apparatus1depicted inFIG.3, the first magnetic sensor21measures the magnetic field12generated by the magnet10in a state where a reinforcing bar71exists in the inspection target70in step S1, and the second magnetic sensor22measures the magnetic field12generated by the magnet10in a state where the reinforcing bar71does not exist in the inspection target70in step S2. Subsequently executed is step S3of outputting the difference between the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2. Although step S1may be executed prior to step S2or step2may be executed prior to step1, step S1and step S2are preferably executed simultaneously. Simultaneously executing step S1and step S2shortens time necessary for inspection of the magnetic body.

The magnetic body inspection method preferably includes amplifying the difference between the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2(step S4). For example, step S4of amplifying the difference can be executed prior to step S3. That is, the difference between the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2can be amplified and then outputted. For example in this case, the magnetic body inspection apparatus1can include the arithmetic processor32functioning as the difference detector30, such that the arithmetic processor32converts, to digital signals, the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2, to calculate and amplify the difference between the digital signals. According to a different embodiment, step S4of amplifying the difference can be executed simultaneously with step S3. That is, the difference between the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2can be amplified and outputted simultaneously. This embodiment is preferred in that simultaneously executing step S4and step S3shortens time necessary for inspection. For example in this case, the magnetic body inspection apparatus1can include the differential amplifier circuit31functioning as the difference detector30and connected to the first magnetic sensor21and the second magnetic sensor22, such that the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2are simultaneously transmitted to the differential amplifier circuit31, and the difference between the two electric signals is amplified in accordance with a constant coefficient and outputted simultaneously. The differential amplifier circuit31connected to the first magnetic sensor21and the second magnetic sensor22can be disposed close to the magnetic sensors for achievement of noise reduction. In this manner, the magnetic body inspection method includes amplifying the difference between the first electric signal acquired from the first magnetic sensor21in step S1and the second electric signal acquired from the second magnetic sensor22in step S2(step S4), for higher accuracy in inspection of the magnetic body.

As described above, the magnetic body inspection method according to the first embodiment of the present invention includes outputting the difference between the first electric signal acquired from the first magnetic sensor21and the second electric signal acquired from the second magnetic sensor22, to specify where a magnetic body exists in a nonmagnetic body, and whether or not the magnetic body is broken.

The magnetic body inspection method can include fitting the difference outputted in step S3with the database stored in the memory included in the magnetic body inspection apparatus1(step S5). For example, the difference between the first electric signal outputted from the first magnetic sensor21and the second electric signal outputted from the second magnetic sensor22is measured for the reference sample in the state where the reference sample and each of the magnetic sensors have the distance C2therebetween, and the database stored in the memory has only to store the thickness C1of the reference sample, the distance C2between the reference sample and each of the magnetic sensors, and the difference associated with one another. Step S5involves fitting the difference between the first electric signal and the second electric signal acquired with use of the magnetic body inspection apparatus1actually applied to the inspection target, with the difference data on the database. The thickness of the reference sample and the distance between the reference sample and each of the magnetic sensors associated with the difference data on the database can be obtained from a result of fitting between the difference outputted with the difference data on the database in step5. It is accordingly possible to identify the thickness of the magnetic body as the inspection target and the distance between the magnetic body as the inspection target and each of the magnetic sensors. As described above, the magnetic body inspection apparatus1includes the memory storing the database, and the magnetic body inspection method according to the first embodiment of the present invention includes outputting the difference (step S3) between the first electric signal acquired in step S1and the second electric signal acquired in step S2, and fitting the difference (step S5) outputted in step S3with the data stored on the database, to achieve identification of the thickness of the magnetic body as well as the distance between the magnetic body and each of the magnetic sensors. Fitting according to a different embodiment can be executed in accordance with a method with reference to a model function. There is prepared a model function F1enabling database fitting, and the model function F1is set such that fitting parameters D1and D2of the model function are determined uniquely with respect to C1and C2. Furthermore, modeling is executed by preparing model functions F21and F22such that D1and D2become functions of C1and C2, respectively. The inspection target is measured to obtain a result that is fitted to obtain the parameters D1and D2. The parameters are inversely operated with reference to the model functions F21and F22to determine C1and C2.

The magnetic body inspection method also achieves identification of a corroded portion in accordance with the difference obtained from the magnetic body as the inspection target, the distance between the magnetic body and the magnetic sensor, and the thickness. It is accordingly possible to identify the distance between the magnetic body and the magnetic sensor, the thickness of the magnetic body, a broken portion, as well as the corroded portion. Such fitting may be executed by an arithmetic processor or a controller additionally provided. The above provides the magnetic body inspection method of storing the database in the memory included in the magnetic body inspection apparatus1. Alternatively, the database itself can be stored in a memory provided in a different device such as a memory provided to the personal computer or an externally provided memory.

As described above, the magnetic body inspection method according to the first embodiment of the present invention includes outputting the difference between the first electric signal acquired from the first magnetic sensor21and the second electric signal acquired from the second magnetic sensor22, and fitting the difference with the database, to specify a position and thickness of a magnetic body existing in a nonmagnetic body, a distance between the magnetic body and each of the magnetic sensors, a corroded portion, and whether or not the magnetic body is broken.

Described next with reference toFIGS.3and4is a magnetic body inspection method according to a second embodiment of the present invention.FIG.4is another schematic view of the magnetic body inspection apparatus according to the modification example of the embodiment of the present invention and a sectional view of a concrete structure having a buried reinforcing bar serving as the exemplary inspection target.

The magnetic body inspection method according to the second embodiment of the present invention is executed with use of the magnetic body inspection apparatus1including the magnet10, and the magnetic sensor20configured to output an electric signal. The magnetic body inspection method includes: step T1of acquiring an electric signal from the magnetic sensor20in a state where a magnetic body exists as an inspection target; step T2of acquiring an electric signal from the magnetic sensor20in a state where the magnetic body does not exist; and step T3of outputting a difference between the electric signal acquired in step T1and the electric signal acquired in step T2.

The electric signal acquired in step T1is acquired in the state where the magnetic body exists as the inspection target. More specifically, the electric signal is acquired from the magnetic sensor20in the state where at least part of the magnetic field12of the magnet10converges at the magnetic body.

The electric signal acquired in step T2is acquired in the state where the magnetic body as the inspection target does not exist. More specifically, the electric signal is acquired from the magnetic sensor20in the state where the magnetic field12of the magnet10does not converge at the magnetic body. In the state where the magnetic field12of the magnet10does not converge at the magnetic body, the magnetic field has the reference magnetic force lines.

Step T3involves outputting the difference between the electric signal acquired in step T1and the electric signal acquired in step T2.

The magnetic body inspection apparatus1used to execute the magnetic body inspection method has only to include one or more magnetic sensors. In the case where the magnetic body inspection apparatus1includes two or more magnetic sensors as depicted inFIG.3, step T1of acquiring an electric signal from one of the magnetic sensors20(21) can be executed in the state where the magnetic body exists, and step T2of acquiring an electric signal from another one of the magnetic sensors20(22) can be executed in the state where the magnetic body does not exist. Alternatively, an electric signal may be acquired from one of the magnetic sensors20(21) in the state where the magnetic body exists (step T1), and an electric signal may be acquired from the magnetic sensor20(21) in the state where the magnetic body does not exist (step T2). In the case of executing step T1of acquiring the electric signal from the one of the magnetic sensors20(21) in the state where the magnetic body exists and executing step T2of acquiring the electric signal from the other one of the magnetic sensors20(22) in the state where the magnetic body does not exist, step T1may be executed prior to step T2, step T2may be executed prior to step T1, or step T1and step T2may be executed simultaneously. There can be a method with use of only one of the magnetic sensors even upon adopting the magnetic body inspection apparatus1including the two magnetic sensors as depicted inFIG.3. For example, an electric signal can be acquired from one of the magnetic sensors20(21) in the state where the magnetic body exists, and an electric signal can be acquired from the magnetic sensor20(21) in the state where the magnetic body does not exist. In this case, step T1may be executed prior to step T2, or step T2may be executed prior to step T1. In a case where the magnetic body inspection apparatus1includes only one magnetic sensor20as depicted inFIG.4, an electric signal can be acquired from the single magnetic sensor20in the state where the magnetic body exists (step T1), and an electric signal can also be acquired from the magnetic sensor20in the state where the magnetic body does not exist after the magnetic sensor20is shifted to a place where the magnetic body does not exist (step T2). Alternatively, an electric signal can be acquired from the single magnetic sensor20in the state where the magnetic body does not exist (step T2), and an electric signal can also be acquired from the magnetic sensor20in the state where the magnetic body exists after the magnetic sensor20is shifted to a place where the magnetic body exists (step T2).

The magnetic body inspection method preferably includes step T4of amplifying the difference between the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2. For example, step T4of amplifying the difference can be executed prior to step T3. That is, the difference between the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2can be amplified and then outputted. For example in this case, the magnetic body inspection apparatus1can include the arithmetic processor32functioning as the difference detector30, such that the arithmetic processor32converts, to digital signals, the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2, to calculate and amplify the difference between the digital signals. According to a different embodiment, step T4of amplifying the difference can be executed simultaneously with step T3. That is, the difference between the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2may be amplified and outputted simultaneously. This embodiment is preferred in that simultaneously executing step T4and step T3shortens time necessary for inspection. For example in this case, the magnetic body inspection apparatus1can include the differential amplifier circuit31functioning as the difference detector30, such that the differential amplifier circuit31simultaneously receives the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2, to amplify the difference between the signals in accordance with a constant coefficient and simultaneously output the difference thus amplified. In this manner, the magnetic body inspection method includes step T4of amplifying the difference between the electric signal acquired from the magnetic sensor20in step T1and the electric signal acquired from the magnetic sensor20in step T2, for higher accuracy in inspection of the magnetic body.

As described above, the magnetic body inspection method according to the second embodiment of the present invention includes acquiring the electric signal in the state where the magnetic body exists, acquiring the electric signal in the state where the magnetic body does not exist, and outputting the difference therebetween, to specify where a magnetic body exists in a nonmagnetic body, and whether or not the magnetic body is broken.

The magnetic body inspection method can include step T5of fitting the difference between the electric signal outputted from the magnetic sensor20in the state where the magnetic body exists and the electric signal outputted from the magnetic sensor20in the state where the magnetic body does not exist, with the database stored in the memory included in the magnetic body inspection apparatus1. For example, the difference between the electric signal outputted from the magnetic sensor20in the state where the magnetic body exits and the electric signal outputted from the magnetic sensor20in the state where the magnetic body does not exist is measured when the reference sample and the magnetic sensor have the distance C2therebetween, and the database stored in the memory has only to store the thickness C1of the reference sample, the distance C2between the reference sample and the magnetic sensor, and the difference associated with one another. Step T5involves fitting the difference between the electric signal acquired in step T1and the electric signal acquired in step T2with use of the magnetic body inspection apparatus1actually applied to the inspection target, with the database stored in the memory. The thickness of the reference sample and the distance between the reference sample and the magnetic sensor associated with the difference data on the database can be obtained from a result of fitting between the difference and the database in step T5, so as to identify the thickness of the magnetic body existing in the inspection target and the distance between the magnetic body and the magnetic sensor. Fitting according to a different embodiment can be executed in accordance with a method with reference to a model function. There is prepared a model function F1enabling database fitting, and the model function F1is set such that fitting parameters D1and D2of the model function are determined uniquely with respect to C1and C2. Furthermore, modeling is executed by preparing model functions F21and F22such that D1and D2become functions of C1and C2, respectively. The inspection target is measured to obtain a result that is fitted to obtain the parameters D1and D2. The parameters are inversely operated with reference to the model functions F21and F22to determine C1and C2. Such fitting may be executed by an arithmetic processor or a controller further included in the magnetic body inspection apparatus1.

As described above, the magnetic body inspection method according to the second embodiment of the present invention includes outputting the difference between the electric signal acquired in the state where the magnetic body exists and the electric signal acquired in the state where the magnetic body does not exist, and fitting the difference with the database, to specify a position and thickness of the magnetic body existing in a nonmagnetic body, a distance between the magnetic body and the magnetic sensor, and whether or not the magnetic body is broken.

The magnetic body inspection method also achieves identification of a corroded portion in accordance with the difference obtained from the magnetic body as the inspection target, the distance between the magnetic body and the magnetic sensor, and the thickness. It is accordingly possible to identify the distance between the magnetic body and the magnetic sensor, the thickness of the magnetic body, as well as the corroded portion. The above provides the magnetic body inspection method of storing the database in the memory included in the magnetic body inspection apparatus1. Alternatively, the database itself can be stored in a memory provided in a different device such as a memory provided to the personal computer or an externally provided memory.

A magnetic body inspection method according to a third embodiment of the present invention is executed with use of the magnetic body inspection apparatus1including the magnet10, and the magnetic sensor20configured to output an electric signal. The magnetic body inspection method includes: acquiring an electric signal for a first spot from the magnetic sensor20(step U1); shifting the magnetic sensor20from the first spot to a second spot (step U2); acquiring an electric signal for the second spot from the magnetic sensor20(step U3); and outputting a difference between the electric signal for the first spot and the electric signal for the second spot (step U4).

Step U1involves acquiring an electric signal for the first spot from the magnetic sensor20. The first spot preferably enables acquisition of the electric signal in the state where the magnetic body exists. More specifically, the first spot preferably enables measurement of the state where at least part of the magnetic field12of the magnet10converges at the magnetic body.

Step U2involves shifting the magnetic sensor20from the first spot to the second spot. The second spot has only to be different from the first spot, but preferably enables acquisition of an electric signal in the state where the magnetic body does not exist. More specifically, the second spot preferably enables measurement of the state where the magnetic field12of the magnet10does not converge at the magnetic body. In the state where the magnetic field12of the magnet10does not converge at the magnetic body, the magnetic field has the reference magnetic force lines.

Step U3involves acquiring an electric signal for the second spot from the magnetic sensor20.

Step U4involves outputting the difference between the electric signal for the first spot and the electric signal for the second spot.

According to the above embodiment, the first spot enables measurement of the magnetic field in the state where the magnetic body exists, and the second spot enables measurement of the magnetic field in the state where the magnetic body does not exist. Alternatively, the first spot enables measurement of the magnetic field in the state where the magnetic body does not exist, and the second spot enables measurement of the magnetic field in the state where the magnetic body exits.

The magnetic body inspection method may include disposing the magnetic sensor20at the first spot (step U0) before acquiring the electric signal for the first spot from the magnetic sensor20(step U1).

The magnetic body inspection apparatus used to execute the magnetic body inspection method has only to include one or more magnetic sensors20. For example, the method can include acquiring the electric signal for the first spot with use of the single magnetic sensor20(step U1), shifting the magnetic sensor20from the first spot to the second spot (step U2), and acquiring the electric signal for the second spot (step U3). According to a different embodiment, a plurality of magnetic sensors20may each execute step U1, step U2, and step U3. In the case where the plurality of magnetic sensors20is provided, the magnetic sensors20preferably have the first spots different from each other, and the second spots different from each other. Such a configuration achieves higher inspection accuracy by the magnetic body inspection method.

The magnetic body inspection method preferably includes step U5of amplifying the difference between the electric signal for the first spot and the electric signal for the second spot. For example, step U5of amplifying the difference can be executed prior to step U4. That is, the difference between the electric signal acquired at the first spot and the electric signal acquired at the second spot can be amplified and then outputted. For example in this case, the magnetic body inspection apparatus1can include the arithmetic processor32functioning as the difference detector30, such that the arithmetic processor32coverts, to digital signals, the electric signal for the first spot acquired from the magnetic sensor20in step U1and the electric signal for the second spot acquired from the magnetic sensor20in step U3, to calculate and amplify the difference between the digital signals. According to a different embodiment, step U5of amplifying the difference can be executed simultaneously with step U4. That is, the difference between the electric signal for the first spot acquired from the magnetic sensor20in step U1and the electric signal for the second spot acquired from the magnetic sensor20in step U3can be amplified and outputted simultaneously. This embodiment is preferred in that simultaneously executing step U5and step U4shortens time necessary for inspection. For example in this case, the magnetic body inspection apparatus1can include the differential amplifier circuit31functioning as the difference detector30, such that the differential amplifier circuit31simultaneously receives the electric signal for the first spot acquired from the magnetic sensor20in step U1and the electric signal for the second spot acquired from the magnetic sensor20in step U3, to amplify the difference between the signals in accordance with a constant coefficient and simultaneously output the difference thus amplified. In this manner, the magnetic body inspection method includes step U5of amplifying the difference between the electric signal for the first spot and the electric signal for the second spot, for higher accuracy in inspection of the magnetic body.

As described above, the magnetic body inspection method according to the third embodiment of the present invention includes outputting the difference between the electric signal for the first spot and the electric signal for the second spot to specify where a magnetic body exists in a nonmagnetic body, and whether or not the magnetic body is broken.

The magnetic body inspection method can include step U6of fitting the difference between the electric signal acquired from the magnetic sensor20at the first spot and the electric signal acquired from the magnetic sensor20at the second spot, with the database stored in the memory included in the magnetic body inspection apparatus1. For example, the difference between the electric signal outputted from the magnetic sensor20at the first spot and the electric signal outputted from the magnetic sensor20at the second spot is measured for the reference sample in the state where the reference sample and the magnetic sensor have the distance C2therebetween, and the database stored in the memory has only to store the thickness C1of the reference sample, the distance C2between the reference sample and the magnetic sensor, and the difference associated with one another. Step U6involves fitting the difference between the electric signal acquired in step U1and the electric signal acquired in step U3with use of the magnetic body inspection apparatus1actually applied to the inspection target, with the database stored in the memory. The thickness of the reference sample and the distance between the reference sample and the magnetic sensor associated with the difference data on the database can be obtained from a result of fitting between the difference and the database in step U6, so as to identify the thickness of the magnetic body as the inspection target and the distance between the magnetic body as the inspection target and the magnetic sensor. Fitting according to a different embodiment can be executed in accordance with a method with reference to a model function. There is prepared a model function F1enabling database fitting, and the model function F1is set such that fitting parameters D1and D2of the model function are determined uniquely with respect to C1and C2. Furthermore, modeling is executed by preparing model functions F21and F22such that D1and D2become functions of C1and C2, respectively. The inspection target is measured to obtain a result that is fitted to obtain the parameters D1and D2. The parameters are inversely operated with reference to the model functions F21and F22to determine C1and C2.

Such fitting may be executed by an arithmetic processor or a controller further included in the magnetic body inspection apparatus1. The above provides the magnetic body inspection apparatus1including the memory storing the database. Alternatively, the database itself can be stored in a memory provided in a different device such as a memory provided to the personal computer or an externally provided memory.

As described above, the magnetic body inspection method according to the third embodiment of the present invention includes outputting the difference between the electric signal for the first spot and the electric signal for the second spot, and fitting the difference with the database, to specify a position and thickness of the magnetic body existing in a nonmagnetic body, a distance between the magnetic body and the magnetic sensor, a corroded portion, and whether or not the magnetic body is broken.

The magnetic body inspection method also achieves identification of a corroded portion in accordance with the difference obtained from the magnetic body as the inspection target, the distance between the magnetic body and the magnetic sensor, and the thickness. It is accordingly possible to identify the distance between the magnetic body and the magnetic sensor, the thickness of the magnetic body, a broken portion, as well as the corroded portion.

This application claims the benefit of the priority date of Japanese patent application No. 2020-100072 filed on Jun. 9, 2020. All of the contents of the Japanese patent application No. 2020-100072 filed on Jun. 9, 2020 are incorporated by reference herein.

REFERENCE SIGNS LIST

1: magnetic body inspection apparatus10: magnet11: gravity center12: magnetic field20: magnetic sensor21: first magnetic sensor22: second magnetic sensor30: difference detector31: differential amplifier circuit32: arithmetic processor40: personal computer50: power source unit60: display unit70: inspection target71: reinforcing bar72: concrete structureL1: line segment connecting first magnetic sensor and magnetL2: line segment connecting second magnetic sensor and magnet