JP2008185436A - Method and apparatus for measuring electromagnetic characteristics of metal specimen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for measuring the electromagnetic characteristic of a metal analyte capable of reducing the influence of disturbance without damaging the characteristic of a ferromagnetic body core with a U shape. <P>SOLUTION: The electromagnetic characteristic measuring apparatus 1 has a magnetometric sensor 8 formed by winding one exciting coil 4 and four detecting coils 6a-6d about the ferromagnetic body core 2. The ferromagnetic body core 2 has four legs 16a-16d and has a cross section of a substantially H shape. The exciting coil 4 is arranged in the center of or close to the ferromagnetic body core 2. Four detecting coils 6a-6d are formed of coils 6a and 6b for measuring a detecting object characteristic wound about two legs 16a and 16b arranged facedly to the metal analyte 18 and coils 6c and 6d for detecting disturbance wound about two legs 16a and 16b that do not face to the metal analyte 18, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic property measuring method and an electromagnetic property measuring apparatus for a metal object that inspects an electromagnetic property of a metal specimen, such as a steel strip, in a production line or outside a production line by non-contact measurement.

Conventionally, non-contact measurement of electromagnetic properties such as magnetic permeability, iron loss and conductivity of metal materials, or non-contact values correlated with the electromagnetic properties has been used for various purposes as shown below. .
For example, as described in Patent Document 1, a primary coil and a secondary coil for measuring iron loss are arranged in a steel strip production line, a steel plate is passed between them, and an AC magnetic flux is used to make iron A method of measuring loss is used.

Moreover, for example, as described in Patent Document 2, by applying an alternating magnetic flux to a measurement target such as a rolled strip, and measuring a magnetic field generated by the interaction between the applied magnetic flux and the measurement target, A method of measuring a change in a value that changes depending on the temperature of the measurement target, such as conductivity and magnetic permeability, and finally measuring the temperature of the measurement target is used.
As a magnetic sensor used for performing such a measurement, a variety of forms can be considered. As a typical example, a core having a substantially U-shaped cross section as described in Patent Document 3 is used. The thing which has.

FIG. 3 is a diagram showing a basic configuration of a conventional electromagnetic characteristic measuring apparatus.
As shown in FIG. 3, the electromagnetic characteristic measuring apparatus 1 includes a magnetic sensor 8 formed by winding an excitation coil 4 and a detection coil 6 around a ferromagnetic core 2 having a substantially U-shaped cross section. The two legs 16a and 16b of the ferromagnetic core 2 are disposed so as to face a metal object 18 such as a steel strip.

  An AC power source (not shown) is connected to the exciting coil 4, and an AC magnetic flux is generated when an AC current having a predetermined frequency is caused to flow through the ferromagnetic core 2 by the AC power source. The generated AC magnetic flux flows out from one end of the two legs 16a and 16b to the outside of the ferromagnetic core 2, returns to the other of the two legs 16a and 16b, and again returns to the ferromagnetic core 2. And a closed loop is formed that returns to the exciting coil 4.

  The detection coil 6 is disposed in the middle of the above-described closed loop, and has a function of detecting an induced voltage signal generated by the AC magnetic flux. This induced voltage signal is not particularly shown, but is measured as a sensor system through appropriate processing such as processing using a lock-in amplifier and calibration curve processing corresponding to the value to be finally obtained. It will be detected as a value.

  Here, the alternating magnetic flux that flows out of one end of the two legs 16a and 16b to the outside of the ferromagnetic core 2 passes through various paths, but there are the following two typical ones. . One AC magnetic flux passes through the air and reaches the other of the two legs 16a and 16b. The other AC magnetic flux enters the inside of the metal object 18 through a gap formed between the ferromagnetic core 2 and the metal object 18, passes through the surface layer portion thereof, and becomes ferromagnetic again. It reaches the other of the two legs 16a and 16b through a gap formed between the body core 2 and the metal object 18.

  When the AC magnetic flux passes through the inside of the metal object 18 and the surface layer, the amplitude, phase, and waveform of the AC magnetic flux change due to the influence of the electromagnetic characteristics of the metal object 18 due to the eddy current effect and the like. By detecting this change, it is possible to measure the electromagnetic characteristics of the metal specimen 18, and based on this, the crystal grain size, temperature, etc. correlated with the electromagnetic characteristics of the metal specimen 18, Measurement can be performed using a calibration curve or the like.

  The reason why the U-shaped core is generally used as the ferromagnetic core 2 is that, for example, when the U-shaped ferromagnetic core 2 is used, the two legs 16a and 16b are mainly used. Since the AC magnetic flux flows between them, the range in which the AC magnetic flux flows can be limited to a local portion of the metal object 18, and there is a reason that the local electromagnetic characteristics can be measured. Another reason is that, for example, the direction in which the alternating magnetic flux flows can be limited, and the electromagnetic characteristics in a specific direction can be measured for an anisotropic material. .

In the invention described in Patent Document 3, the metal specimen 18 is a steel pipe, and the carburization depth generated on the inner surface of the steel pipe is detected from the detected output by utilizing the change in magnetic properties accompanying carburization of the steel pipe. Looking for.
Japanese Patent No. 2519615 JP-A-53-20986 JP 2004-279055 A

The inventions described in Patent Documents 1 to 3 described above often have good reproducibility and require quantitative measurement even in an environment where the change in the detected signal is weak.
However, in the inventions described in Patent Documents 1 to 3 described above, the installation environment of the magnetic sensor may be a case where a device that can be an electromagnetic noise source such as a high-power motor is disposed in the surroundings, or a high-temperature motor. It is often in a high-temperature production line where the steel strip is conveyed.

In this case, for example, the measurement accuracy decreases due to disturbances such as changes in sensor characteristics caused by temperature changes such as changes in the magnetic permeability of the ferromagnetic core, influences of disturbance magnetic flux, electromagnetic noise, etc. Problems may arise.
The present invention has been made by paying attention to the above-described problems, and is capable of reducing the influence of disturbance without impairing the characteristics of the U-shaped ferromagnetic core. It is an object to provide an electromagnetic characteristic measuring method and an electromagnetic characteristic measuring apparatus.

The present invention has been devised based on the following idea based on the above-described circumstances.
In other words, the present inventors have a measurement system that is not easily affected by disturbances such as those described above, such as changes in sensor characteristics due to temperature changes, such as temperature changes in the magnetic permeability of the ferromagnetic core, disturbance magnetic flux, electromagnetic noise, etc. As a way of thinking, we focused on the difference structure.
Hereinafter, with reference to FIG. 4, the measurement of electromagnetic characteristics of a metal object using a differential structure will be described.
FIG. 4 is a diagram showing a basic configuration of the electromagnetic property measuring apparatus 1 for a metal object using a differential structure.
As shown in FIG. 4, in the electromagnetic characteristic measuring method using the electromagnetic characteristic measuring apparatus 1, two magnetic sensors 8 are used.

  The two magnetic sensors 8 are composed of one magnetic sensor 8 (hereinafter referred to as “magnetic sensor 8a”) and the other magnetic sensor 8 (hereinafter referred to as “magnetic sensor 8b”). Both are provided with two U-shaped ferromagnetic cores 2. In the following description, the U-shaped ferromagnetic core 2 included in the magnetic sensor 8a is referred to as a “detection target characteristic measuring core 2a”, and the U-shaped ferromagnetic core 2 included in the magnetic sensor 8b. Is described as “disturbance detection core 2b”.

The detection target characteristic measurement core 2a is disposed in the vicinity of the metal object 18 with both legs 16a and 16b facing each other, and the disturbance detection core 2b is more than the metal object 18 than the detection target characteristic measurement core 2a. The two leg portions 16c and 16d are arranged facing away from the head.
An excitation coil 4 and a detection coil 6 are wound around the detection target characteristic measurement core 2a and the disturbance detection core 2b. In the following description, the excitation coil 4 wound around the detection target characteristic measurement core 2a is referred to as “excitation coil 4a”, the detection coil 6 as “detection coil 6a”, and wound around the disturbance detection core 2b. The excited excitation coil 4 is referred to as “excitation coil 4b”, and the detection coil 6 is referred to as “detection coil 6b”.

The magnetic field generated by applying the alternating magnetic flux to the metal object 18 by the exciting coil 4a is measured by the detection coil 6a, and the magnetic field generated by applying the alternating magnetic flux to the metal object 18 by the exciting coil 4b is It is measured by the detection coil 6b, and the electromagnetic characteristics of the metal object 18 are measured based on the difference between the outputs of the detection coils 6a and 6b.
Here, the change in the output from the detection coil 6b is the same as the output from the detection coil 6a for the disturbance, and the influence of the metal object 18 is small.

By measuring the electromagnetic characteristics of the metal subject 18 using such a method, the electromagnetic characteristics of the metal subject 18 are measured by the detection coil 6a, and the disturbance is determined by the difference between the outputs of the detection coils 6a and 6b. The influence can be reduced.
For this reason, it is possible to improve the measurement accuracy of the electromagnetic characteristics for the metal object 18.

  However, in the above-described method, it is necessary to dispose the detection target property measuring core 2 a in the vicinity of the metal subject 18 in order to improve the measurement accuracy of the electromagnetic property with respect to the metal subject 18. On the other hand, the disturbance detection core 2b is disposed at a position away from the metal object 18 in order to produce a differential effect and to suppress unnecessary interaction between the cores 2a and 2b. There is a need. Therefore, both the cores 2a and 2b must be arranged at positions separated from each other.

Therefore, when the electromagnetic characteristic measurement apparatus 1 having the above-described configuration is actually used to measure the electromagnetic characteristics of the metal object 18, the following problems may occur.
1. Due to the influence of the ambient temperature and the temperature of the metal object 18 etc., the temperature environment is different, the electromagnetic noise generated from the high power motor etc. installed at the installation location, etc. Problems such as different noise environments received by the cores 2a and 2b.
2. The problem that the arrangement space of both the cores 2a and 2b is required.
3. In order to suppress the error of the differential signal caused by the positional deviation between the two cores 2a and 2b, it is necessary to determine the positional relationship between the two cores 2a and 2b with high accuracy, which makes it difficult to manufacture.
4). Since the exciting coils 4a and 4b are wound separately around the cores 2a and 2b, respectively, a difference with respect to fluctuations related to excitation, for example, influences of fluctuations in the excitation current, mixing of noise into the excitation current, etc. The problem that the reduction effect due to is not exhibited.

In order to solve the above-described problems, the present inventors have attempted to reduce unnecessary interaction between both cores 2a and 2b, and to approximate both the operating environment and noise environment of both cores 2a and 2b. The cores 2a and 2b were brought close to each other and finally integrated. The configuration of the invention is as follows.
That is, the invention described in claim 1 measures a magnetic field generated by applying an alternating magnetic flux to a metal object using a magnetic sensor formed by winding an excitation coil and a detection coil around a ferromagnetic core. An electromagnetic property measurement method for a metal object that measures the electromagnetic property of the metal object based on the measured magnetic field,
The ferromagnetic core has a substantially H-shaped cross section having four legs,
The detection coil is a detection object characteristic measurement coil wound around at least one of the two legs facing the metal object among the four legs, and the coil among the four legs. A disturbance detection coil wound around at least one of the two legs not facing the metal object,
A magnetic field generated by applying an alternating magnetic flux to the metal object by the excitation coil is measured by the detection object characteristic measurement coil and the disturbance detection coil,
The electromagnetic characteristic of the metal object is measured based on the difference between the output of the detection object characteristic measurement coil and the output of the disturbance detection coil.

According to the present invention, the shape of the ferromagnetic core is substantially H-shaped in cross section having four legs, and the detection coil is at least one of the two legs facing the metal object among the four legs. And a disturbance detection coil wound around at least one of the four legs not facing the metal object.
The magnetic field generated by applying an alternating magnetic flux to the metal object by the exciting coil is measured by the detection target characteristic measurement coil and the disturbance detection coil, and the output of the detection target characteristic measurement coil and the disturbance detection coil are output. The electromagnetic characteristics of the metal specimen are measured based on the difference between the two.
As a result, unnecessary interaction between the detection target characteristic measurement coil and the disturbance detection coil can be reduced, and the operating environment and noise environment of the detection target characteristic measurement coil and the disturbance detection coil can be approximated. It becomes possible to make it.

Next, the invention described in claim 2 uses a magnetic sensor formed by winding an excitation coil and a detection coil around a ferromagnetic core to generate a magnetic field generated by applying an alternating magnetic flux to a metal object. An apparatus for measuring an electromagnetic property of a metal object for measuring and measuring an electromagnetic property of the metal object based on the measured magnetic field,
The ferromagnetic core has a substantially H-shaped cross section having four legs,
The detection coil includes a detection object characteristic measurement coil wound around at least one of two legs of the four legs facing the metal object, and the of the four legs. A disturbance detection coil wound around at least one of the two legs not facing the metal object,
Current supply means for supplying an alternating current to the exciting coil;
And an electromagnetic characteristic measuring means for measuring an electromagnetic characteristic of the metal object based on a difference between an output of the detection target characteristic measuring coil and an output of the disturbance detecting coil. .

According to the present invention, the shape of the ferromagnetic core is substantially H-shaped in cross section having four legs, and the detection coil is at least one of the two legs facing the metal object among the four legs. And a disturbance detection coil wound around at least one of the four legs not facing the metal object.
Further, current supply means for supplying an alternating current to the excitation coil, and electromagnetic characteristic measurement means for measuring the electromagnetic characteristics of the metal object based on the difference between the output of the detection target characteristic measurement coil and the output of the disturbance detection coil It has.

As a result, unnecessary interaction between the detection target characteristic measurement coil and the disturbance detection coil can be reduced, and the operating environment and noise environment of the detection target characteristic measurement coil and the disturbance detection coil can be approximated. It becomes possible to make it.
In addition, according to the present invention, since it is not necessary to determine the positional relationship between the detection target characteristic measurement coil and the disturbance detection coil with high accuracy, the magnetic sensor can be easily manufactured, and an electromagnetic characteristic measurement apparatus for a metal object can be provided. A compact configuration can be achieved.

Next, the invention described in claim 3 is the invention described in claim 2, characterized in that the exciting coil is arranged at the center of the ferromagnetic core or in the vicinity thereof.
According to the present invention, since the excitation coil is arranged at or near the center of the ferromagnetic core, it is possible to excite the magnetic field measured by the detection target characteristic measurement coil and the disturbance detection coil in common. Thus, the effect of the difference can be further increased.

According to the present invention, since it becomes possible to reduce the influence of disturbance without impairing the characteristics of the U-shaped ferromagnetic core, it is possible to improve the measurement accuracy of the electromagnetic characteristics for the metal object. It becomes possible.
In addition, according to the present invention, it is possible to easily manufacture the ferromagnetic core, and it is possible to make the configuration of the apparatus compact. Manufacturing cost can be reduced and reliability can be improved.

Next, embodiments of the present invention will be described with reference to the drawings.
First, with reference to FIG. 1, the configuration of an electromagnetic property measuring apparatus (hereinafter referred to as “electromagnetic characteristic measuring apparatus”) for a metal object according to the present invention will be described. In addition, the same code | symbol is attached | subjected and demonstrated about the structure similar to the conventional electromagnetic characteristic measuring apparatus mentioned above.
FIG. 1 is a diagram showing a basic configuration of an electromagnetic characteristic measuring apparatus 1.

As shown in FIG. 1, the electromagnetic characteristic measuring apparatus 1 includes a magnetic sensor 8 formed by winding a single exciting coil 4 and four detecting coils 6a to 6d around a ferromagnetic core 2. Current supply means 10, calculation means 12, and electromagnetic characteristic measurement means 14 are provided.
The ferromagnetic core 2 is formed in a substantially H-shaped cross section having four legs 16a to 16d. In the present embodiment, the material forming the ferromagnetic core 2 has a higher thermal conductivity and Curie point than the commonly used ferrite, and the temperature dependence of the magnetic properties in the normal operating temperature range. A case where steel is used, which has a low property, will be described as an example. Here, by using steel as the material for forming the ferromagnetic core 2, it becomes possible to reduce temperature non-uniformity in the ferromagnetic core 2 compared to the case of using ferrite.

The four leg portions 16 a to 16 d are composed of two leg portions 16 a and 16 b arranged to face the metal subject 18, and two leg portions 16 c and 16 d not facing the metal subject 18. ing. In the present embodiment, the case where the metal object 18 is a steel strip will be described as an example.
The exciting coil 4 is disposed at or near the center of the ferromagnetic core 2 and generates an alternating magnetic flux when an alternating current is supplied by the current supply means 10.

The four detection coils 6a to 6d are each formed of a conducting wire having the same diameter and wound around the ferromagnetic core 2 with the same number of turns.
The four detection coils 6a to 6d are respectively wound around the detection target characteristic measuring coils 6a and 6b wound around the two legs 16a and 16b and around the two legs 16c and 16d, respectively. It comprises disturbance detection coils 6c and 6d.

Similarly to the detection target characteristic measurement coils 6a and 6b, the detection target characteristic measurement coil 6a and the detection target characteristic measurement coil 6b are opposed to each other with the excitation coil 4 interposed therebetween, as viewed from the metal object 18 side. The distance from the exciting coil 4 is the same.
The disturbance detection coil 6c and the disturbance detection coil 6d are arranged at positions facing each other with the excitation coil 4 interposed therebetween, as viewed from the metal object 18 side, and the distance from the excitation coil 4 is the same. It has become.

Further, the detection target characteristic measurement coil 6a and the disturbance detection coil 6c, and the detection target characteristic measurement coil 6b and the disturbance detection coil 6d have the same distance from the excitation coil 4, respectively.
Therefore, the detection target characteristic measurement coil 6a, the detection target characteristic measurement coil 6b, the disturbance detection coil 6c, and the disturbance detection coil 6d are arranged at positions that are symmetric with respect to the excitation coil 4, respectively. .
The current supply means 10 is connected to the exciting coil 4. Further, the current supply means 10 is formed by, for example, an AC power source and has a function of supplying an AC current to the exciting coil 4.

  The calculation means 12 is connected to the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d. Further, when the induced voltage outputs of the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d are input to the calculation means 12, the detection target characteristic measurement coils 6a and the detection target characteristic measurement coils 6b A correction signal corresponding to the difference between the sum of the induced voltage outputs and the sum of the induced voltage outputs of the disturbance detection coil 6c and the disturbance detection coil 6d is calculated, and the calculated correction signal is output to the electromagnetic characteristic measuring means 14. It has a function to do. Specifically, first, the sum of the induced voltage signals output from the detection target characteristic measuring coils 6a and 6b and the sum of the induced voltage signals output from the disturbance detecting coils 6c and 6d are respectively set to, for example, lock Amplification is performed by processing using an in-amplifier. Then, using these amplified signals, the sum of the induced voltage signals output from the disturbance detecting coils 6c and 6d is subtracted from the sum of the induced voltage signals output from the detection target characteristic measuring coils 6a and 6b. Thus, the difference between the two is calculated, a correction signal corresponding to the difference is calculated, and output to the electromagnetic characteristic measuring means 14.

  The electromagnetic characteristic measurement means 14 is connected to the calculation means 12 and functions to measure the electromagnetic characteristics of the metal object 18 based on the correction signal when the correction signal calculated by the calculation means 12 is input. have. Specifically, the correction signal calculated by the calculation means 12 is converted into a numerical value, for example, by adapting it to a calibration curve obtained in advance, and based on this numerical value, an index of the electromagnetic characteristics of the metal object 18 is obtained. taking measurement. The electromagnetic characteristic measuring means 14 has a function of measuring an index of the electromagnetic characteristic of the metal object 18 and outputting the measurement result. In the present embodiment, a case where a display unit (not shown) for displaying a measurement result of electromagnetic characteristics is connected to the electromagnetic characteristic measurement means 14 will be described as an example.

Next, functions and effects of this embodiment will be described.
Hereinafter, a method for measuring the electromagnetic characteristics of the metal object 18 using the above-described electromagnetic characteristics measuring apparatus 1 will be described.
First, the two legs 16a and 16b around which the detection target characteristic measuring coils 6a and 6b are wound are arranged opposite to the metal object 18 with a space therebetween, and the current supply means 10 is connected to the excitation coil 4 by an alternating current. Supply current.
The alternating magnetic flux generated in the exciting coil 4 by supplying the alternating current returns to the exciting coil 4 through various paths (closed loop). In the present embodiment, a method for measuring the electromagnetic characteristics of the metal object 18 using two typical closed loops among various closed loops will be described.

  Of the two closed loops, one of the closed loops (hereinafter referred to as “detection target characteristic loop L1”) is such that the alternating magnetic flux generated by the exciting coil 4 is lower in the ferromagnetic core 2 (in FIG. 1). Branch to the leg portions 16a and 16b), and flows out of the ferromagnetic core 2 from the end of the leg portion 16a facing the metal object 18. After passing through the metal subject 18, the leg 16 b returns to the ferromagnetic core 2 from the end facing the metal subject 18, moves through the ferromagnetic core 2, and returns to the excitation coil 4. . The alternating magnetic flux generated in the exciting coil 4 and branched downward in the ferromagnetic core 2 flows out of the ferromagnetic core 2 from the end portion of the leg portion 16b facing the metal object 18, and the leg portion. It is good also as a structure which returns to the ferromagnetic core 2 from the edge part which opposes the metal object 18 of 16a. In FIG. 1, the detection target characteristic loop L1 is indicated by a broken line for the sake of explanation.

When the detection target characteristic measurement coil 6a and the detection target characteristic measurement coil 6b detect the induced voltage signal by the detection target characteristic loop L1, respectively, the detected induced voltage signal is output to the calculation means 12. The
Here, the induced voltage signals detected by the detection target characteristic measuring coils 6a and 6b reflect the amplitude, phase, time waveform (distortion), and the like of the magnetic flux affected by the electromagnetic characteristics of the metal object 18. Therefore, it is possible to obtain information on the electromagnetic characteristics of the metal object 18 from changes in the induced voltage signal detected by the detection target characteristic measuring coils 6a and 6b.
However, the detection target characteristic measuring coils 6a and 6b are also affected by disturbance factors such as noise caused by the outside of the sensor system, noise due to the sensor itself, fluctuation due to temperature change of the ferromagnetic core 2, and the like. The induced voltage signals detected by the characteristic measuring coils 6a and 6b are changed due to disturbance factors.

  Of the two closed loops, the other closed loop (hereinafter referred to as “difference processing loop L2”) is such that the alternating magnetic flux generated in the exciting coil 4 is first on the upper side in the ferromagnetic core 2 (in FIG. 1). Then, it branches to the leg portions 16c and 16d side, flows out from the end of the leg portion 16c to the outside of the ferromagnetic core 2, passes through the air, and passes from the end of the leg portion 16d to the ferromagnetic core 2. Returning, it moves in the ferromagnetic core 2 and returns to the exciting coil 4. The alternating magnetic flux generated in the exciting coil 4 and branched upward in the ferromagnetic core 2 flows out from the end of the leg 16d to the outside of the ferromagnetic core 2 and from the end of the leg 16c to the ferromagnetic body. It is good also as a structure which returns to the core 2. FIG. Further, in FIG. 1, for the sake of explanation, the difference processing loop L <b> 2 is indicated by a broken line similarly to the detection target characteristic loop L <b> 1.

When the disturbance detection coil 6 c and the disturbance detection coil 6 d detect the induced voltage signal by the difference processing loop L 2, the detected induced voltage signal is output to the computing means 12.
Here, since the induced voltage signals detected by the disturbance detection coils 6c and 6d pass through the air, the electromagnetic wave of the metal subject 18 is electromagnetic like the case where the AC magnetic flux passes through the metal subject 18. It is not directly affected by physical characteristics. Accordingly, since the change in the induced voltage signal detected by the disturbance detection coils 6c and 6d is considered to be due to the disturbance factor, the change in the induced voltage signal detected by the disturbance detection coils 6c and 6d is changed to the disturbance factor. It is possible to measure a change in the induced voltage signal caused by the change.

  The calculating means 12 receives the induced voltage signal from the detection target characteristic loop L1 output from the detection target characteristic measurement coils 6a and 6b and the induced voltage signal from the difference processing loop L2 output from the disturbance detection coils 6c and 6d. When input, based on these signals, the sum of the output of the detection target characteristic measurement coil 6a and the output of the detection target characteristic measurement coil 6b, the output of the disturbance detection coil 6c, and the disturbance detection coil 6d. A correction signal corresponding to a difference from the output sum is calculated. The calculated correction signal is output to the electromagnetic characteristic measuring means 14.

  Here, the change component due to the disturbance factor of the induced voltage signal detected by the detection target characteristic measuring coils 6a and 6b and the change component of the induced voltage signal detected by the disturbance detection coils 6c and 6d are not completely the same. No. However, in the present embodiment, since the shape of the ferromagnetic core 2 is formed in a substantially H-shaped cross section having four legs 16a to 16d, a disturbance factor applied to the detection target characteristic measuring coils 6a and 6b. And the influence of the disturbance factor on the disturbance detection coils 6c and 6d are approximated. For this reason, the difference between the outputs of the detection target characteristic measuring coils 6a and 6b and the outputs of the disturbance detection coils 6c and 6d is calculated, and the correction signal corresponding to the difference is used, whereby the induced voltage signal due to the disturbance factor is calculated. It is possible to reduce the amount of change.

When the correction signal output from the calculation unit 12 is input, the electromagnetic characteristic measurement unit 14 measures the electromagnetic characteristic of the metal object 18 based on the correction signal, and displays the measurement result on the display unit.
Therefore, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the shape of the ferromagnetic core 2 is substantially H-shaped in cross section having the four legs 16a to 16d. In addition, the detection coil 6 is wound around the two legs 16 a and 16 b facing the metal object 18, and the detection target characteristic measurement coils 6 a and 6 b are wound on the detection object 6, and the two legs not facing the metal object 18. It comprises disturbance detection coils 6c and 6d wound around 16c and 16d.

That is, in the ferromagnetic core 2, the portion around which the detection target characteristic measurement coils 6a and 6b are wound and the portion around which the disturbance detection coils 6c and 6d are wound are integrated. , They will be directed in opposite directions.
Further, the magnetic field generated by applying the alternating magnetic flux to the metal object 18 by the exciting coil 4 is measured by the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d, and the detection target characteristic measurement coil 6a. , 6b and the output of the disturbance detection coils 6c, 6d are used to measure the electromagnetic characteristics of the metal object 18.

Therefore, unnecessary interaction between the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d can be reduced, and the detection target characteristic measurement coils 6a and 6b and the disturbance detection coil 6c. , 6d, the operating environment and the noise environment can be approximated.
In addition, the effect of reduction due to the difference can be efficiently exhibited with respect to fluctuations related to excitation, for example, fluctuations in the excitation current and noises in the excitation current.

As a result, it is possible to reduce the influence of the disturbance without impairing the characteristics of the U-shaped ferromagnetic core 2 that can measure local electromagnetic characteristics. It is possible to improve the measurement accuracy of the electromagnetic characteristics for 18.
In the electromagnetic characteristic measuring apparatus 1 according to the present embodiment, the shape of the ferromagnetic core 2 is substantially H-shaped in cross section having the four legs 16a to 16d. Unlike the configuration having two U-shaped cores, it is not necessary to determine the positional relationship between the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d with high accuracy.

For this reason, the magnetic sensor 8 can be easily manufactured and the electromagnetic characteristic measuring apparatus 1 can be made compact.
As a result, it is possible to improve the manufacturing efficiency of the electromagnetic characteristic measuring apparatus 1 and reduce the manufacturing cost of the electromagnetic characteristic measuring apparatus 1. In addition, it is possible to expand the applicable range of the method for measuring the electromagnetic property for the metal object 18 using the electromagnetic property measuring apparatus 1, and to improve the reliability of the electromagnetic property measuring apparatus 1. It becomes possible.

Further, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, since the exciting coil 4 is arranged at the center of the ferromagnetic core 2 or in the vicinity thereof, the detection target characteristic measuring coils 6a and 6b and the disturbance detection The magnetic fields measured by the coils 6c and 6d can be commonly excited.
For this reason, it becomes possible to further increase the effect of the difference by using the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d, and improve the measurement accuracy of the electromagnetic characteristics for the metal object 18. It becomes possible to make it.

In the electromagnetic characteristic measuring apparatus 1 according to the present embodiment, the detection target characteristic measurement coil 6a, the detection target characteristic measurement coil 6b, the disturbance detection coil 6c, and the disturbance detection coil 6d are each a conducting wire having the same diameter. And arranged symmetrically with respect to the exciting coil 4.
For this reason, it becomes possible to further increase the effect of the difference by using the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d, and improve the measurement accuracy of the electromagnetic characteristics for the metal object 18. It becomes possible to make it.

Further, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the calculation means 12 has the sum of the output of the detection target characteristic measurement coil 6a and the output of the detection target characteristic measurement coil 6b and the disturbance detection coil 6c. A correction signal corresponding to the sum and difference between the output and the output of the disturbance detection coil 6d is calculated.
For this reason, it is possible to amplify the signal level of the correction signal, and it is possible to improve the measurement accuracy of the electromagnetic characteristics for the metal object 18.

  In the electromagnetic characteristic measuring apparatus 1 of this embodiment, the sum of the output of the detection target characteristic measurement coil 6a and the output of the detection target characteristic measurement coil 6b, the output of the disturbance detection coil 6c, and the disturbance detection coil 6d. The electromagnetic characteristics of the metal object 18 are measured using a correction signal corresponding to the difference from the sum of the outputs of the above, but the present invention is not limited to this. That is, for example, a correction signal according to the difference between the output of the detection target characteristic measurement coil 6a and the output of the disturbance detection coil 6c may be used. The output of the detection target characteristic measurement coil 6b and the disturbance detection coil 6d may be used. You may use the correction signal according to the difference with this output. Similarly, a correction signal corresponding to the difference between the output of the detection target characteristic measurement coil 6a and the output of the disturbance detection coil 6d may be used, and the output of the detection target characteristic measurement coil 6b and the disturbance detection coil 6c may be used. You may use the correction signal according to the difference with an output. However, like the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the sum of the output of the detection target characteristic measurement coil 6a and the output of the detection target characteristic measurement coil 6b, the output of the disturbance detection coil 6c, and the disturbance detection It is preferable to measure the electromagnetic characteristics of the metal object 18 using a correction signal corresponding to the difference from the sum of the outputs of the coil 6d because the signal level of the correction signal can be amplified. is there.

  In the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the sum of the output of the detection target characteristic measurement coil 6a and the output of the detection target characteristic measurement coil 6b, the output of the disturbance detection coil 6c, and the disturbance detection coil 6d. Although the correction signal according to the difference from the sum of the outputs, that is, the correction signal according to the difference between the outputs of the two detection target characteristic measurement coils 6 and the two disturbance detection coils 6 is used, the present invention is not limited to this. Is not to be done. That is, for example, a correction signal corresponding to the difference between the output of one of the detection target characteristic measurement coils 6a and 6b and the sum of the outputs of the disturbance detection coils 6c and 6d may be used. Similarly, a correction signal corresponding to the difference between the output of the detection target characteristic measurement coils 6a and 6b and the sum of the outputs of one of the disturbance detection coils 6c and 6d may be used. In this case, the coil using only one output has a similar condition to the coil using two outputs, for example, doubling the number of turns.

  Furthermore, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the exciting coil 4 is disposed at or near the center of the ferromagnetic core 2. However, the present invention is not limited to this, and the exciting coil 4 is made of a ferromagnetic material. You may arrange | position in the position away from the center of the core 2, or its vicinity. Of course, like the electromagnetic characteristic measuring apparatus 1 of this embodiment, the exciting coil 4 is arranged at the center of the ferromagnetic core 2 or in the vicinity thereof, the detection target characteristic measuring coils 6a and 6b and the disturbance detecting coil 6c. , 6d can be excited in common, which is preferable.

  Further, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the detection target characteristic measuring coils 6a and 6b and the disturbance detecting coils 6c and 6d are respectively formed by conducting wires having the same diameter, and the exciting coil 4 is centered. However, the configuration is not limited to this. That is, for example, the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d may be formed by conducting wires having different diameters, and are arranged asymmetrically with the excitation coil 4 as the center. It is good also as composition which has. In this case, for example, a configuration may be adopted in which amplification means capable of amplifying the output from each coil is interposed between the detection target characteristic measurement coils 6a and 6b and the disturbance detection coils 6c and 6d and the calculation means 12. .

  Further, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the magnetic sensor 8 is formed by winding one excitation coil 4 and four detection coils 6 a to 6 d around the ferromagnetic core 2. It is not limited. That is, for example, the magnetic sensor 8 may be formed by winding two or more exciting coils 4 around the ferromagnetic core 2. In this case, for example, the detection target characteristic measuring coil 6 is wound around the leg portion 16a, the disturbance detecting coil 6 is wound around the leg portion 16c, and the exciting coil 4 is wound around the leg portions 16b and 16d, respectively. It is good also as the structure currently made.

  Further, in the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the detection target characteristic measuring coils 6a and 6b and the disturbance detecting coils 6c and 6d are independently connected to the computing means 12, respectively. It is not limited to. That is, for example, one end of the detection target characteristic measurement coil 6a and one end of the disturbance detection coil 6c are connected, and the other end of the detection target characteristic measurement coil 6a and the other end of the disturbance detection coil 6c are connected to the calculation means 12. You may connect. Similarly, one end of the detection target characteristic measurement coil 6b and one end of the disturbance detection coil 6d are connected, and the other end of the detection target characteristic measurement coil 6b and the other end of the disturbance detection coil 6d are connected to the calculation means 12. May be.

  Moreover, in the electromagnetic characteristic measuring apparatus 1 of this embodiment, although steel was used as a material which forms the ferromagnetic core 2, it is not limited to this. That is, the material forming the ferromagnetic core 2 may be a metal ferromagnetic material other than steel, such as ferrite, or other ferromagnetic material. In short, the material for forming the ferromagnetic core 2 may be selected appropriately according to the installation environment of the magnetic sensor 8, the measurement conditions, and the like. In this case, for example, there is no need to pay particular attention to the influence on the magnetic sensor 8 due to the ambient temperature or the temperature of the measurement object, and when the excitation frequency is high, a ferromagnetic material is used as a material for forming the ferromagnetic core 2. Ferrite having a small eddy current loss in the core 2 may be used. Thus, as the material for forming the ferromagnetic core 2, it is preferable to select a material that exhibits stable magnetic properties under the temperature conditions to be used.

In the electromagnetic characteristic measuring apparatus 1 of the present embodiment, the metal object 18 is a steel strip. However, the present invention is not limited to this. For example, the metal object 18 may be a metal plate or a steel pipe.
Further, in the electromagnetic characteristic measuring apparatus 1 according to the present embodiment, the leg portions 16a and 16b are arranged to face the metal object 18, and no opposing object is arranged to the leg portions 16c and 16d. Is not to be done. That is, for example, a metal body having physical properties similar to those of the metal object 18 may be disposed at a position facing the leg portions 16c and 16d.
Further, the electromagnetic characteristic measuring apparatus 1 of the present embodiment uses, for example, the relationship between resistivity and temperature in addition to measuring the electromagnetic characteristics of the metal object 18 itself (iron loss, magnetic permeability, resistivity, etc.). It can be applied to various applications such as a thermometer and a particle size utilizing the relationship between electromagnetic characteristics and particle size.

Hereinafter, with reference to FIG. 2, an electromagnetic characteristic measuring apparatus having a configuration similar to that of the present invention is used to apply an AC magnetic flux to a metal object and examine the reaction, thereby determining the difference in electromagnetic characteristics. The experiment results in which the types of materials constituting the metal specimen are distinguished are shown.
Various conditions of this measurement experiment are shown below.
Metal specimen: Three types of materials with different electromagnetic properties (steel, aluminum, hastelloy)
Excitation frequency: 1 [kHz]
Clearance between leg and metal object (lift-off): 5 [mm]
Distance between two legs (center distance between two legs): 35 [mm]
Ferromagnetic core height: 40 [mm]
Ferromagnetic core thickness: 20 [mm]
Ferromagnetic core material: steel

  Under the above-mentioned conditions, the case of using the present invention example and the comparative example, that is, the case of using an electromagnetic property measuring apparatus having two U-shaped ferromagnetic cores as shown in FIG. Among the various disturbance factors, the electromagnetic characteristics of the material constituting the metal specimen were measured under the condition having the disturbance factor due to the temperature change of the ferromagnetic core. In FIG. 2, the vertical axis indicates a value obtained by normalizing the signal change due to the material of the material by the signal change due to the temperature change of the ferromagnetic core. It is possible to suppress the influence.

A specific method for obtaining the value indicated by the vertical axis in the example of the present invention will be described below.
First, when “iron” is used as the material constituting the metal object, the waveform indicating the difference between the detection object characteristic measurement coil and the disturbance detection coil is used, and the material constituting the metal object is “aluminum”. ”Or“ Hastelloy ”, an amplitude value obtained by subtracting a waveform indicating a difference between the detection target characteristic measurement coil and the disturbance detection coil is obtained. That is, from the measured value of the difference when “iron” is used as the material, the change in the measured value of the difference when “aluminum” or “Hastelloy” is used as the material is obtained. The obtained amplitude value is normalized by the change in the amplitude of the differential waveform due to the temperature change of the ferromagnetic core (in this case, the temperature rise from 20 ° to 50 °) when “iron” is used as the material. To do.

Further, in the comparative example, the specific method of obtaining the value indicated by the vertical axis is the same as that of the present embodiment except that the output signal of the detection coil is used instead of the correction signal in the specific method of obtaining the value indicated by the vertical axis. Is being processed.
As shown in the figure, in the case of both the aluminum and hastelloy in the example of the present invention, the signal change due to the material of the material is more dependent on the signal change due to the temperature change of the ferromagnetic core than in the comparative example. The normalized value is about three times larger, and the influence of disturbance is reduced.
Therefore, according to the result of this measurement experiment, according to the electromagnetic characteristic measuring apparatus of the example of the present invention, it is possible to reduce the influence of disturbance without impairing the characteristics of the U-shaped ferromagnetic core. confirmed.

It is a figure which shows the basic composition of the electromagnetic property measuring apparatus of this invention. It is a figure which shows the measurement result in an Example. It is a figure which shows the basic composition of the conventional electromagnetic characteristic measuring apparatus. It is a figure which shows the basic composition of the electromagnetic characteristic measuring apparatus provided with two U-shaped cores.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic characteristic measuring apparatus 2 Ferromagnetic core 4 Excitation coil 6 Detection coil 8 Magnetic sensor 10 Current supply means 12 Calculation means 14 Electromagnetic characteristic measurement means 16 Leg 18 Metal object L1 Detection object characteristic loop L2 Difference processing loop

Claims (3)

Using a magnetic sensor formed by winding an excitation coil and a detection coil around a ferromagnetic core, a magnetic field generated by applying an alternating magnetic flux to a metal object is measured, and the magnetic field is measured based on the measured magnetic field. A method for measuring the electromagnetic characteristics of a metal object for measuring the electromagnetic characteristics of the metal object,
The ferromagnetic core has a substantially H-shaped cross section having four legs,
The detection coil is a detection object characteristic measurement coil wound around at least one of the two legs facing the metal object among the four legs, and the coil among the four legs. A disturbance detection coil wound around at least one of the two legs not facing the metal object,
A magnetic field generated by applying an alternating magnetic flux to the metal object by the excitation coil is measured by the detection object characteristic measurement coil and the disturbance detection coil,
An electromagnetic characteristic measurement method for a metal object, comprising: measuring an electromagnetic characteristic of the metal object based on a difference between an output of the detection object characteristic measurement coil and an output of the disturbance detection coil. Using a magnetic sensor formed by winding an excitation coil and a detection coil around a ferromagnetic core, a magnetic field generated by applying an alternating magnetic flux to a metal object is measured, and the magnetic field is measured based on the measured magnetic field. An apparatus for measuring the electromagnetic characteristics of a metal object for measuring the electromagnetic characteristics of the metal object,
The ferromagnetic core has a substantially H-shaped cross section having four legs,
The detection coil includes a detection object characteristic measurement coil wound around at least one of two legs of the four legs facing the metal object, and the of the four legs. A disturbance detection coil wound around at least one of the two legs not facing the metal object,
Current supply means for supplying an alternating current to the exciting coil;
An electromagnetic characteristic measuring means for measuring an electromagnetic characteristic of the metal object based on a difference between an output of the detection object characteristic measurement coil and an output of the disturbance detection coil; Electromagnetic characteristic measuring device.   3. The apparatus for measuring electromagnetic characteristics of a metal object according to claim 2, wherein the exciting coil is disposed at or near the center of the ferromagnetic core.

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