Metal detection device

Abstract

To detect magnetic noise while a yoke is correctly pressed against the metal being inspected.SOLUTION: A metal inspection device 10 comprises: an excitation current application unit 51 that applies an excitation current to a yoke 20 that includes a pair of tip parts 26 that are pressed against the metal 80 being inspected; a generated current measurement unit 53 that measures a generated current having been generated by a magnetic field formed to the yoke 20 by application of the excitation current; a generated current determination unit 54 that determines whether the generated current is greater than or equal to a prescribed threshold A; an excitation current adjustment unit 55 that raises the excitation current when the generated current determination unit 54 has determined that the generated current is less than the prescribed threshold A; and a magnetic noise calculation unit 56 that calculates the magnetic noise of the metal 80 being inspected, when the generated current determination unit 54 has determined that the generated current is greater than or equal to the prescribed threshold A.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a metal inspection device.

Background Art

[0002] A metal inspection device using Barkhausen noise is known (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a distortion detection device that includes an electromagnet that applies a magnetic field to a ferromagnetic measurement object, a pickup coil that detects leakage magnetic flux from the measurement object, an integrator that integrates a Barkhausen noise component detected by the pickup coil, and an arithmetic unit that outputs a value of a central magnetic field that is the center of the area of an integration value waveform until the integration value of the output of the integrator saturates, and detects distortion using the value of the magnetic field as an evaluation parameter.

[0004] By the way, in a metal inspection device, it is preferable to detect magnetic noise in a state where the yoke is correctly pressed against the metal to be inspected.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In consideration of the above facts, an object of the present invention is to detect magnetic noise in a state where the yoke is correctly pressed against the metal to be inspected.

Means for Solving the Problems

[0007] A metal inspection apparatus according to a first aspect of the present invention includes an excitation current application unit for applying an excitation current to a yoke having a pair of tip portions that are pressed against a metal to be inspected, a magnetic field measuring unit for measuring the magnitude of the magnetic field formed in the yoke by the application of the excitation current, and a generated current generated by the magnetic field formed in the yoke. The current value is the value of the current generated from the magnetic field correctly formed in the yoke, relative to the excitation current value. The system includes: a current generation determination unit that determines whether the current generation is above a predetermined threshold; an excitation current adjustment unit that increases the excitation current when the current generation determination unit determines that the current generation is below a predetermined threshold; and a magnetic noise calculation unit that calculates the magnetic noise of the metal to be inspected when the current generation determination unit determines that the current generation is above a predetermined threshold.

[0008] A metal inspection apparatus according to a second aspect of the present invention includes an excitation current application unit for applying an excitation current to a yoke having a pair of tip portions that are pressed against a metal to be inspected, a magnetic field measurement unit for measuring the magnitude of the magnetic field formed on the yoke by the application of the excitation current, a magnetic noise calculation unit for calculating the magnetic noise of the metal to be inspected based on the magnetic field formed on the metal to be inspected by the application of the excitation current, and a generated current generated by the magnetic field formed on the yoke. The current value is the value of the current generated from the magnetic field correctly formed in the yoke, relative to the excitation current value. The system includes: a current generation determination unit that determines whether the current generation is above a predetermined threshold; an excitation current adjustment unit that increases the excitation current when the current generation determination unit determines that the current generation is below the predetermined threshold; and a display device that outputs the magnetic noise calculated by the magnetic noise calculation unit when the current generation determination unit determines that the current generation is above a predetermined threshold.

[0009] In a metal inspection apparatus according to a third aspect of the present invention, in a metal inspection apparatus according to a first or second aspect of the present invention, the excitation current raised by the excitation current adjustment unit is regulations The system includes a notification unit that, when a threshold is exceeded, notifies the system to change the way the yoke is pressed against the metal being inspected.

[0010] In a metal inspection apparatus according to a fourth aspect of the present invention, in a metal inspection apparatus according to a first aspect of the present invention, when the generated current determination unit determines that the generated current is above a predetermined threshold, the magnetic noise calculation unit calculates the magnetic noise of the metal to be inspected based on the magnetic field formed by the generated current that the generated current determination unit determined to be above a predetermined threshold. [Effects of the Invention]

[0011] In the metal inspection apparatus according to the first aspect of the present invention, the generated current determination unit determines the generated current This is the generated current value that arises from the magnetic field correctly formed in the yoke, relative to the excitation current value. By including a magnetic noise calculation unit that calculates the magnetic noise of the metal being inspected when it is determined to be above a predetermined threshold, the magnetic noise of the metal being inspected can be detected when the target current flows. Therefore, magnetic noise can be detected when the tip of the yoke is properly pressed against the metal being inspected.

[0012] In a metal inspection apparatus according to a second aspect of the present invention, the generated current determination unit determines the generated current This is the generated current value that arises from the magnetic field correctly formed in the yoke, relative to the excitation current value. By providing a display device that outputs the magnetic noise calculated by the magnetic noise calculation unit when it is determined to be above a predetermined threshold, the detected magnetic noise of the metal being inspected is output to the display device when the target current flows. Therefore, the detected magnetic noise can be displayed on the display device when the tip of the yoke is correctly pressed against the metal being inspected.

[0013] In the metal inspection apparatus of the third aspect of the present invention, the excitation current raised by the excitation current adjustment unit is regulations By including a notification unit that alerts the user to change the way the yoke is pressed against the metal being inspected when a threshold is exceeded, it becomes clear that the tip of the yoke is not being pressed against the metal being inspected in the correct position. Therefore, the user can change the position of the metal being inspected against which the tip of the yoke is pressed, so that the tip of the yoke is properly pressed against the metal being inspected.

[0014] In the metal inspection device according to the fourth aspect of the present invention, the magnetic noise calculation unit calculates the magnetic noise of the metal to be inspected based on the magnetic field formed by the generated current determined by the generated current determination unit to be equal to or greater than a predetermined threshold value, so that the magnetic noise of the metal to be inspected can be detected between the metal to be inspected and the yoke by the exciting current that forms the target magnetic field.

Brief Description of the Drawings

[0015] [Figure 1] It is a perspective view showing an inspection head of a metal inspection device according to the first embodiment. [Figure 2] It is a schematic cross-sectional view showing a metal inspection device according to the first embodiment, showing a cross-section taken along line A-A in FIG. 1. [Figure 3] It is a block diagram showing the functional configuration of a metal inspection device according to the first embodiment. [Figure 4] It is a flowchart showing the control flow of a metal inspection device according to the first embodiment. [Figure 5] It is a flowchart showing the control flow of a metal inspection device according to the second embodiment. [Figure 6] It is a block diagram showing the functional configuration of a metal inspection device according to another embodiment.

Modes for Carrying Out the Invention

[0016] 〔First Embodiment〕 Hereinafter, the metal inspection device according to the first embodiment will be described with reference to the drawings. In the first embodiment, an example will be described in which the metal inspection device is a Barkhausen noise measuring device that measures Barkhausen noise for the purpose of detecting metal polishing burn, residual stress, hardness, etc. In each figure, the arrow UP indicates the upper side of the inspection head, the arrow RH indicates the right side of the inspection head, and the arrow FR indicates the front side of the inspection head.

[0017] [Configuration of the First Embodiment] As shown in FIGS. 1 and 2, the metal inspection device 10 includes an inspection head 12, a control unit 50, and a display device 60 as an announcement unit.

[0018] As shown in FIG. 1, the inspection head 12 includes a yoke (armature) 20, an excitation coil 32, a current detection coil 34, and a magnetic noise detection coil 36 as a noise detection unit.

[0019] (Yoke 20) The yoke 20 is formed of a soft magnetic material. The yoke 20 is formed in a substantially U shape by a pair of leg portions 24 extending in the vertical direction and a connecting portion 22 connecting the proximal ends of the leg portions 24.

[0020] The leg portion 24 is formed in a prismatic shape with a rectangular cross section. The tip portion 26 of the leg portion 24 is adapted to abut against the inspection target metal 80 which is the inspection target. The connecting portion 22 is formed in a prismatic shape with a rectangular cross section.

[0021] (Excitation Coil 32) The excitation coil 32 is wound around the connecting portion 22 via a bobbin (not shown). An excitation current from an AC power source is controlled to a predetermined current value and supplied to the excitation coil 32 by the control unit 50. When the excitation coil 32 is energized, a magnetic field is formed in the yoke 20 and it becomes an electromagnet.

[0022] (Current Detection Coil 34) The current detection coil 34 is wound around one of the leg portions 24 via a bobbin (not shown). An induced current is generated in the current detection coil 34 by the magnetic field formed in the yoke 20.

[0023] (Magnetic Noise Detection Coil 36) The magnetic noise detection coil 36 can be a coil wound around a bobbin (not shown). The magnetic noise detection coil 36 is supported by a housing (not shown) and is provided between the pair of leg portions 24. The magnetic noise detection coil 36 detects the magnetic flux of the inspection target metal 80 which is the inspection target.

[0024] (Display Device 60) The display device 60 can be a monitor for displaying an image.

[0025] [Testing Method] As shown in Figure 2, the tip 26 of the inspection head 12 is brought into contact with the metal 80 to be inspected. At this time, the magnetic noise detection coil 36 may also be brought into contact with the metal 80 to be inspected. This forms a closed magnetic circuit between the yoke 20 and the metal 80 to be inspected. In Figure 2, the magnetic flux M flowing through the closed magnetic circuit between the yoke 20 and the metal 80 to be inspected is schematically shown.

[0026] Next, the control unit 50 supplies an excitation current to the excitation coil 32. This magnetizes the yoke 20 and the metal under inspection 80. Next, the current detection coil 34 generates a current due to the magnetic field formed in the yoke 20. Information on the generated current is input to the control unit 50, and a magnetization curve is calculated. The magnetic noise detection coil 36 detects the magnetic flux of the metal under inspection 80. Information on the magnetic flux detected by the magnetic noise detection coil 36 is input to the control unit 50, and Barkhausen noise is calculated.

[0027] [Functional Configuration of Metal Detection Equipment] As shown in Figure 3, the metal inspection device 10 functions by inputting information on the generated current generated in the current detection coil 34 and information on the magnetic flux detected by the magnetic noise detection coil 36 into the control unit 50, and the information processed by the control unit 50 is displayed on the display device 60, which acts as an output unit. The control unit 50 also outputs an excitation current to the excitation coil 32, which is an excitation current controlled to a predetermined current value from the AC power supply.

[0028] The current detection coil 34 generates a current due to the magnetic field formed in the yoke 20. The current generated in the current detection coil 34 is input to the control unit 50.

[0029] The magnetic noise detection coil 36 detects the magnetic flux of the metal 80 being inspected. The magnetic flux detected by the magnetic noise detection coil 36 is input to the control unit 50.

[0030] The control unit 50 includes an excitation current application unit 51, a magnetization curve calculation unit 52, a generated current measurement unit 53 as a magnetic field measurement unit, a generated current determination unit 54, an excitation current adjustment unit 55, a magnetic noise calculation unit 56, and a notification control unit 57.

[0031] The excitation current application unit 51 controls the current from the AC power supply to a predetermined excitation current value, outputs it to the excitation coil 32, and applies the excitation current to the yoke 20. The excitation current application unit 51 can also output a triangular wave to the excitation coil 32. The excitation current application unit 51 can also output the maximum value of the triangular wave to the excitation coil 32.

[0032] The magnetization curve calculation unit 52 calculates the magnetization curve of the yoke 20 based on the generated current generated by the current detection coil 34.

[0033] The current generation measurement unit 53 measures the value of the generated current generated by the current detection coil 34. In other words, the current generation measurement unit 53 measures the magnitude of the magnetic field formed in the yoke 20 by the application of the excitation current.

[0034] The current generation determination unit 54 determines whether the generated current value is equal to or greater than a predetermined threshold A. The threshold A is the generated current value that is generated from the magnetic field correctly formed on the yoke 20 with respect to the excitation current value.

[0035] The excitation current adjustment unit 55 increases the excitation current value output by the excitation current application unit 51 when the generated current determination unit 54 determines that the generated current value is less than a predetermined threshold A. The excitation current adjustment unit 55 also determines whether the excitation current value is less than a predetermined threshold B. If the excitation current value is greater than or equal to the predetermined threshold B, the excitation current adjustment unit 55 stops increasing the excitation current value output by the excitation current application unit 51. The threshold B is the current value that can flow through the excitation coil 32, and can be, for example, 2A.

[0036] The magnetic noise calculation unit 56 calculates Barkhausen noise as magnetic noise based on the magnetic flux detected by the magnetic noise detection coil 36. In this case, the magnetic noise calculation unit 56 can calculate the Barkhausen noise of the metal under inspection 80 based on the magnetization curve calculated by the magnetization curve calculation unit 52. The calculation results calculated by the magnetic noise calculation unit 56 are output to the display device 60.

[0037] The notification control unit 57 outputs an alert to the display device 60 indicating that the position of the inspection head 12 against the metal to be inspected 80 is inappropriate when the generated current determination unit 54 determines that the generated current value is less than a predetermined threshold A, and the excitation current adjustment unit 55 determines that the excitation current value is equal to or greater than a predetermined threshold B. The alert indicating that the position of the inspection head 12 against the metal to be inspected 80 is inappropriate is intended to prompt a change in how the yoke 20 is pressed against the metal to be inspected 80, and can be, for example, "Please change the position of the inspection head 12."

[0038] [Control flow of metal detection equipment] As shown in Figure 4, when the tip of the yoke 20 of the metal inspection device 10 is pressed against the metal 80 to be inspected, pre-measurement is started, and the excitation current application unit 51 outputs an excitation current to the excitation coil 32, applying an excitation current for pre-measurement to the yoke 20 (step S101). The excitation current for pre-measurement can be the maximum value of a triangular wave.

[0039] Next, the generated current measuring unit 53 measures the generated current generated by the magnetic field formed in the yoke 20 by the application of the excitation current (step S102).

[0040] Next, the generated current determination unit 54 determines whether the generated current value is equal to or greater than a predetermined threshold A (step S103). If it is determined that the generated current value is equal to or greater than the predetermined threshold A (YES in step S103), the process proceeds to step S107. On the other hand, if it is determined that the generated current value is less than the predetermined threshold A (NO in step S103), the excitation current adjustment unit 55 increases the excitation current value output by the excitation current application unit 51 (step S104).

[0041] Next, the excitation current adjustment unit 55 determines whether the excitation current value is less than a predetermined threshold B. If it is determined that the excitation current value is less than the predetermined threshold B (YES in step S105), the process returns to step S101. On the other hand, if it is determined that the excitation current value is greater than or equal to the predetermined threshold B (NO in step S105), the notification control unit 57 outputs a message to the display device 60 indicating that the position in which the inspection head 12 is pressed against the metal 80 to be inspected is inappropriate (step S106), and terminates the process.

[0042] On the other hand, when the process proceeds to step S107, the main measurement is started, and the excitation current application unit 51 outputs an excitation current for the main measurement, which is determined to be equal to or greater than threshold A, to the excitation coil 32, thereby applying an excitation current to the yoke 20 (step S101). The excitation current for the main measurement can be a triangular wave.

[0043] Next, the magnetic noise calculation unit 56 calculates the Barkhausen noise based on the magnetic flux detected by the magnetic noise detection coil 36 (step S108). In other words, the magnetic noise calculation unit 56 calculates the Barkhausen noise of the metal 80 under inspection based on the magnetic field formed by a triangular wave, with the generated current value determined by the generated current determination unit 54 to be above a predetermined threshold A as its maximum value.

[0044] Next, the control unit 50 outputs the calculation result information calculated by the magnetic noise calculation unit 56 to the display device 60 (step S109), and terminates the process.

[0045] [Operation of the First Embodiment] The metal inspection apparatus 10 of the first embodiment includes an excitation current application unit 51 that applies an excitation current to a yoke 20 having a pair of tip portions 26 that are pressed against the metal to be inspected 80; an generated current measurement unit 53 that measures the generated current generated by the magnetic field formed on the yoke 20 by the application of the excitation current; an generated current determination unit 54 that determines whether the generated current is equal to or greater than a predetermined threshold A; an excitation current adjustment unit 55 that increases the excitation current when the generated current determination unit 54 determines that the generated current is less than the predetermined threshold A; and a magnetic noise calculation unit 56 that calculates the magnetic noise of the metal to be inspected 80 when the generated current determination unit 54 determines that the generated current is equal to or greater than a predetermined threshold A.

[0046] The system includes a magnetic noise calculation unit 56 that calculates the magnetic noise of the metal under inspection 80 when the generated current determination unit 54 determines that the generated current is equal to or greater than a predetermined threshold A. This ensures that when the target generated current flows, the magnetic noise of the metal under inspection 80 is detected. When the target generated current flows, the target magnetic flux flows through the yoke 20. In other words, the tip 26 of the yoke 20 is correctly pressed against the metal under inspection 80, and the target magnetic field is formed between the metal under inspection 80 and the yoke 20. Therefore, magnetic noise can be detected when the tip 26 of the yoke 20 is correctly pressed against the metal under inspection 80.

[0047] Furthermore, by providing an excitation current adjustment unit 55 that increases the excitation current when the generation current determination unit 54 determines that the generation current is less than a predetermined threshold A, it is possible to prevent the generation current from falling below the predetermined threshold A due to insufficient excitation current. As a result, it is possible to efficiently confirm whether the tip 26 of the yoke 20 is correctly pressed against the metal 80 to be inspected.

[0048] In the metal inspection apparatus 10 of the first embodiment, a display device 60 is provided to notify that the way the yoke 20 is pressed against the metal 80 to be inspected is changed when the excitation current raised by the excitation current adjustment unit 55 exceeds a predetermined threshold B.

[0049] The system includes a display device 60 that notifies the user to change the way the yoke 20 is pressed against the metal 80 being inspected when the excitation current raised by the excitation current adjustment unit 55 exceeds a predetermined threshold B. This allows the user to see if the tip 26 of the yoke 20 is not being pressed against the metal 80 being inspected in the correct position. Therefore, the user can change the position of the metal 80 being inspected against which the tip 26 of the yoke 20 is pressed, so that the tip 26 of the yoke 20 is properly pressed against the metal 80 being inspected.

[0050] In the metal inspection apparatus 10 of the first embodiment, when the generated current determination unit 54 determines that the generated current is equal to or greater than a predetermined threshold A, the magnetic noise calculation unit 56 calculates the magnetic noise of the metal to be inspected 80 based on the magnetic field formed by the generated current that the generated current determination unit 54 determined to be equal to or greater than the predetermined threshold A.

[0051] The magnetic noise calculation unit 56 calculates the magnetic noise of the metal under inspection 80 based on the magnetic field formed by the generated current that the generated current determination unit 54 has determined to be above a predetermined threshold A. This allows the magnetic noise of the metal under inspection 80 to be detected by an excitation current that forms the target magnetic field between the metal under inspection 80 and the yoke 20.

[0052] [Second Embodiment] The metal inspection apparatus of the second embodiment differs from the metal inspection apparatus of the first embodiment in that the control flow of the metal inspection apparatus is different.

[0053] [Control flow of the metal detection apparatus of the second embodiment] The control flow of the metal inspection apparatus of the second embodiment will be described below. In addition, the same terms or reference numerals will be used to describe parts that are the same as or equivalent to those described in the first embodiment.

[0054] As shown in Figure 5, when the tip of the yoke 20 of the metal inspection device 10 is pressed against the metal to be inspected 80, the excitation current application unit 51 outputs an excitation current to the excitation coil 32, applying the excitation current for this measurement to the yoke 20 (step S201). The excitation current for this measurement can be a triangular wave.

[0055] Next, the generated current measuring unit 53 measures the generated current generated by the magnetic field formed in the yoke 20 by the application of the excitation current (step S202).

[0056] Next, the magnetic noise calculation unit 56 calculates the Barkhausen noise based on the magnetic flux detected by the magnetic noise detection coil 36 (step S203).

[0057] Next, the current generation determination unit 54 determines whether the generated current value at the maximum value of the triangular wave is greater than or equal to a predetermined threshold A (step S204). If it is determined that the generated current value is greater than or equal to the predetermined threshold A (YES in step S204), the process proceeds to step S208. On the other hand, if it is determined that the generated current value is less than the predetermined threshold A (NO in step S204), the excitation current adjustment unit 55 increases the excitation current value output by the excitation current application unit 51 (step S205).

[0058] Next, the excitation current adjustment unit 55 determines whether the excitation current value is less than a predetermined threshold B (step S206). If it is determined that the excitation current value is less than the predetermined threshold B (YES in step S206), the process returns to step S201. On the other hand, if it is determined that the excitation current value is greater than or equal to the predetermined threshold B (NO in step S206), the notification control unit 57 outputs a message to the display device 60 indicating that the position in which the inspection head 12 is pressed against the metal 80 to be inspected is inappropriate (step S106), and terminates the process.

[0059] On the other hand, when the process proceeds to step S208, the control unit 50 outputs the calculation result information calculated by the magnetic noise calculation unit 56 to the display device 60 (step S208), and the process ends.

[0060] [Operation of the second embodiment] The metal inspection apparatus 10 of the second embodiment includes an excitation current application unit 51 that applies an excitation current to a yoke 20 having a pair of tip portions 26 that are pressed against the metal to be inspected 80; an excitation current measurement unit 53 that measures the generated current generated by the magnetic field formed on the yoke 20 by the application of the excitation current; a magnetic noise calculation unit 56 that calculates the magnetic noise of the metal to be inspected 80 based on the magnetic field formed on the metal to be inspected 80 by the application of the excitation current; an excitation current determination unit 54 that determines whether the generated current is at a predetermined threshold A; an excitation current adjustment unit 55 that increases the excitation current when the excitation current determination unit 54 determines that the generated current is less than the predetermined threshold A; and a display device 60 that outputs the magnetic noise calculated by the magnetic noise calculation unit 56 when the excitation current determination unit 54 determines that the generated current is at or above a predetermined threshold.

[0061] The system includes a display device 60 that outputs magnetic noise calculated by a magnetic noise calculation unit 56 when the generated current determination unit 54 determines that the generated current is above a predetermined threshold. This ensures that when the target generated current flows, the detected magnetic noise of the metal under inspection 80 is displayed on the display device 60. When the target generated current flows, the target magnetic flux flows through the yoke 20. This means that the tip 26 of the yoke 20 is correctly pressed against the metal under inspection 80, and the target magnetic field is formed between the metal under inspection 80 and the yoke 20. Therefore, the detected magnetic noise can be output to the display device 60 when the tip 26 of the yoke 20 is correctly pressed against the metal under inspection 80.

[0062] Furthermore, by providing an excitation current adjustment unit 55 that increases the excitation current when the generation current determination unit 54 determines that the generation current is less than a predetermined threshold A, it is possible to prevent the generation current from falling below the predetermined threshold A due to insufficient excitation current. As a result, it is possible to efficiently confirm whether the tip 26 of the yoke 20 is correctly pressed against the metal 80 to be inspected.

[0063] Furthermore, the other configurations and effects are substantially the same as those of the first embodiment described above, so their explanation will be omitted.

[0064] The metal inspection apparatus of the present invention has been described above based on the first and second embodiments. However, the specific configuration is not limited to these embodiments, and changes to the design are permitted as long as they do not deviate from the gist of the invention as described in each claim.

[0065] In the first and second embodiments, an example was shown in which the magnetization curve of the yoke 20 is calculated based on the generated current generated by the current detection coil 34, and whether or not the generated current value is greater than or equal to a predetermined threshold A is determined. However, as shown in Figure 6, a BH detection coil 38 for calculating the magnetization curve of the yoke 20 may be provided separately from the current detection coil 34 that generates the generated current for determining whether or not it is greater than or equal to a predetermined threshold A.

[0066] In the first and second embodiments, the excitation coil 32 is shown to be provided on the connecting portion 22. However, the excitation coil 32 can also be provided on the leg portion 24.

[0067] In the first and second embodiments, examples were shown in which the current detection coil 34 is provided on the leg portion 24 of the yoke 20. However, the location of the current detection coil is not limited to this embodiment, and it can also be provided, for example, on the connecting portion 22 of the yoke 20.

[0068] In the first embodiment, an example was shown in which the measurement is started when it is determined that the generated current value is equal to or greater than a predetermined threshold A (YES in step S103). In this case, the notification control unit 57 may output a notification to the display device 60 indicating that the measurement has started.

[0069] In the first and second embodiments, an example was shown in which the notification unit is a display device 60. However, the notification unit may also be an audio output device that outputs sound.

[0070] In the first and second embodiments, the excitation coil 32, current detection coil 34, and magnetic noise detection coil 36 were shown wound on bobbins. However, the excitation coil, current detection coil, and magnetic noise detection coil may be air-core coils.

[0071] In the first and second embodiments, examples were shown in which the noise detection unit is a magnetic noise detection coil 36. However, a sensor such as a Hall sensor can also be used as the noise detection unit.

[0072] In the second embodiment and the second embodiment, the magnetic field measuring unit is shown as a generated current measuring unit 53 that measures the generated current value of the generated current generated by the current detection coil 34. However, the magnetic field measuring unit may also directly measure the magnetic field formed in the yoke by the application of an excitation current.

[0073] In the first and second embodiments, the yoke 20 was shown to be formed in a substantially U-shape with a rectangular cross-section. However, the shape of the yoke is not limited to this embodiment. [Explanation of Symbols]

[0074] 10... Metal inspection device, 20... Yoke, 26... Tip section, 51... Excitation current application section, 53... Generated current measurement section (example of magnetic field measurement section), 54... Generated current determination section, 55... Excitation current adjustment section, 56... Magnetic noise calculation section, 60... Display device, 80... Metal to be inspected

Claims

1. A yoke having a pair of tips that press against the metal to be inspected, an excitation current application section that applies an excitation current, A magnetic field measuring unit for measuring the magnitude of the magnetic field formed in the yoke by the application of the excitation current, A current generation determination unit that determines whether the generated current generated by the magnetic field formed in the yoke is equal to or greater than a predetermined threshold value which is the generated current value generated from the magnetic field correctly formed in the yoke relative to the excitation current value, When the generated current determination unit determines that the generated current is below a predetermined threshold, the excitation current adjustment unit increases the excitation current. When the generated current determination unit determines that the generated current is above a predetermined threshold, a magnetic noise calculation unit calculates the magnetic noise of the metal to be inspected based on the magnetic field formed by the generated current that the generated current determination unit determined to be above a predetermined threshold, A metal detection device equipped with the following features.

2. A yoke having a pair of tips that press against the metal to be inspected, an excitation current application section that applies an excitation current, A magnetic field measuring unit for measuring the magnitude of the magnetic field formed in the yoke by the application of the excitation current, A magnetic noise calculation unit calculates the magnetic noise of the metal to be inspected based on the magnetic field formed on the metal to be inspected by the application of the excitation current, A current generation determination unit that determines whether the generated current generated by the magnetic field formed in the yoke is equal to or greater than a predetermined threshold value which is the generated current value generated from the magnetic field correctly formed in the yoke relative to the excitation current value, When the generated current determination unit determines that the generated current is below a predetermined threshold, the excitation current adjustment unit increases the excitation current. A notification unit that notifies the user to change the way the yoke is pressed against the metal to be inspected when the excitation current raised by the excitation current adjustment unit exceeds a predetermined threshold, When the generated current determination unit determines that the generated current is above a predetermined threshold, the magnetic noise calculated by the magnetic noise calculation unit is output to the display device, A metal detection device equipped with the following features.

3. A yoke having a pair of tip portions for pressing against a metal to be inspected, and an excitation current application portion for applying an excitation current, A magnetic field measuring unit for measuring the magnitude of the magnetic field formed in the yoke by the application of the excitation current, A current generation determination unit that determines whether the generated current generated by the magnetic field formed in the yoke is equal to or greater than a predetermined threshold value which is the generated current value generated from the magnetic field correctly formed in the yoke relative to the excitation current value, When the generated current determination unit determines that the generated current is below a predetermined threshold, the excitation current adjustment unit increases the excitation current. A notification unit that notifies the user to change the way the yoke is pressed against the metal to be inspected when the excitation current raised by the excitation current adjustment unit exceeds a predetermined threshold, When the generated current determination unit determines that the generated current is above a predetermined threshold, a magnetic noise calculation unit calculates the magnetic noise of the metal to be inspected, A metal detection device equipped with the following features.

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