JP2010249764A - Barkhausen noise inspecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Barkhausen noise inspecting device for performing inspection of high precision receiving no effect of residual magnetism without separately providing a demagnetizer. <P>SOLUTION: The Barkhausen noise inspecting device includes an exciting coil 3 for magnetizing an inspection target 30, a detection head 1 having a detection coil 4 for detecting the Barkhausen noise emitted from the magnetized inspection target 30 and a power supply 5 for supplying an AC current, which produces an AC magnetic field for magnetization, to the exciting coil 3. In this constitution, there is provided a demagnetizing means 20, which demagnetizes the residual magnetism of the inspection target 30 by providing a demagnetizing function to the detection head 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a Barkhausen noise inspection apparatus that performs nondestructive inspection using Barkhausen noise.

  Various Barkhausen noise inspection apparatuses using Barkhausen noise have been proposed as inspection apparatuses that perform nondestructive inspections such as grinding burn, residual stress, hardness, and load (for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 02-262958 JP 2001-133441 A JP 2006-266686 A

  Barkhausen noise changes due to the residual magnetism of the inspection object. In a polishing process for manufacturing a mechanical part such as a bearing, a magnet chuck is used, so that magnetism remains in the part. For this reason, when such a machine part is used as an inspection object, the value of Barkhausen noise is affected by the residual magnetism of the machine part, and detection accuracy such as grinding burn is deteriorated. In this case, the inspection object may be demagnetized and then inspected by the Barkhausen noise inspection apparatus. For this purpose, it is necessary to prepare a demagnetizer separately.

  An object of the present invention is to provide a Barkhausen noise inspection apparatus that can perform high-precision inspection without being affected by residual magnetism without separately providing a demagnetizer.

The Barkhausen noise inspection apparatus according to the present invention includes an excitation coil for magnetizing an inspection object, a detection head having a detection coil for detecting Barkhausen noise emitted from the magnetized inspection object, and the excitation coil for magnetization. In a Barkhausen noise inspection apparatus having a power source for supplying an alternating current for generating an alternating magnetic field, a demagnetizing means for demagnetizing residual magnetism of the inspection object by providing a demagnetizing function to the detection head is provided. It is characterized by that.
According to the Barkhausen noise inspection apparatus of this configuration, since the demagnetizing means is provided to demagnetize the residual magnetism of the inspection object by giving the detection head a demagnetization function, without providing a demagnetizer separately, High-precision inspection can be performed without being affected by residual magnetism.

  In the present invention, the demagnetizing means supplies a demagnetizing coil that is provided in the detection head and demagnetizes the object to be inspected, and an alternating current that generates an alternating magnetic field whose amplitude decreases with time. A power supply unit for demagnetization, and the power source may include the power supply unit for demagnetization and an excitation power supply unit that supplies an alternating current that generates an alternating magnetic field for magnetization in the excitation coil. . In this way, demagnetization can be performed effectively by generating an alternating magnetic field whose amplitude decreases with time.

  In the present invention, the exciting coil may be shared by the demagnetizing coil. Thus, if the exciting coil used for detecting Barkhausen noise is shared by the demagnetizing coil of the demagnetizing means, there is no need to separately provide a dedicated demagnetizing coil, and the detection head can be made compact accordingly.

  In this invention, signal processing means for detecting the property of the surface portion of the inspection object from Barkhausen noise detected by the detection head may be provided. The Barkhausen noise inspection apparatus according to the present invention may perform only processing up to detection of Barkhausen noise. However, by providing the signal processing means described above, it is further possible to specify a specific surface portion of the inspection object. It is possible to detect properties. The surface properties to be detected are, for example, surface grinding burn, residual stress, defects, and the like. By comparing the Barkhausen noise value obtained by appropriately processing the detected Barkhausen noise with a threshold value, it is possible to detect the grinding burn, residual stress, defects, and the like.

  In the present invention, the Barkhausen noise inspection device may be used for detecting the property of the surface of the rolling device or the surface of the rolling device component. In this case, the surface property may be detected by bringing the detection head into sliding contact with the surface of the rolling device or the surface of the rolling device component. When the detection head is brought into sliding contact, an air gap does not occur and detection can be performed stably with high sensitivity. The surface property to be detected may be surface grinding burn, residual stress, or a defect.

  The Barkhausen noise inspection apparatus according to the present invention includes an excitation coil that magnetizes an inspection object, a detection head that includes a detection coil that detects Barkhausen noise emitted from the magnetized inspection object, and magnetizes the excitation coil. In a Barkhausen noise inspection apparatus having a power source for supplying an alternating current for generating an alternating magnetic field, a demagnetizing means for demagnetizing residual magnetism of the inspection object by providing a demagnetizing function to the detection head is provided. Therefore, a high-accuracy inspection that is not affected by residual magnetism can be performed without separately providing a demagnetizer.

1 is a schematic configuration diagram of a Barkhausen noise inspection apparatus according to an embodiment of the present invention. It is a wave form diagram of the alternating current magnetic field generated in the demagnetizing coil in the demagnetizing means of the Barkhausen noise inspection apparatus. It is a specific block diagram of the Barkhausen noise inspection apparatus. It is explanatory drawing which shows one usage example of the Barkhausen noise inspection apparatus.

  An embodiment of the present invention will be described with reference to FIGS. The Barkhausen noise inspection apparatus according to this embodiment includes a detection head 1 including an excitation coil 3 and a detection coil 4, and an excitation power supply unit 6 that supplies an alternating current that generates an alternating magnetic field for magnetization to the excitation coil 3. The power supply 5 includes a Barkhausen noise detection circuit 8 that processes the output signal of the detection coil 4 to extract Barkhausen noise, and a demagnetizing unit 20 that demagnetizes the residual magnetism of the detection target 30. The power source 5 and the Barkhausen noise detection circuit 8 are mounted on a circuit board in the inspection apparatus body 2 that is separate from the detection head 1. At the time of inspection, the detection head 1 is pressed against the surface of the inspection object 30. The contact surface of the detection head 1 that is brought into contact with the inspection object 30 may be provided with a friction reducing cover, a cover, or the like (not shown).

  The excitation coil 3 in the detection head 1 is a coil for magnetizing the inspection object 30 and is wound around an iron core 13 serving as a magnetic core. The detection coil 4 in the detection head 1 is a coil for detecting Barkhausen noise generated by the magnetized inspection object 30, and is wound around an iron core 14 serving as a magnetic core. Each of the iron cores 13 and 14 is made of a magnetic oxide such as ferrite or a laminated silicon steel plate. The detection coil 4 may be an air core coil without the iron core 14. The iron cores 13 and 14 are pressed against the surface of the inspection object 30 in a state where the detection head 1 is pressed against the surface of the inspection object 30.

  The demagnetizing means 20 includes a demagnetizing coil that is substituted for the exciting coil 3 and an alternating current that generates an alternating magnetic field whose amplitude is attenuated with time as shown in FIG. And a demagnetizing power supply unit 7 for supplying to the common use. The alternating current supplied by the demagnetization power supply unit 7 is an alternating current that decays with time. The power supply 4 includes the demagnetization power supply unit 7 and the excitation power supply unit 6. The excitation power supply unit 6 supplies an alternating current whose amplitude is not attenuated, but the amplitude, frequency, and waveform of the alternating current can be changed, and a direct current bias current can be superimposed on the alternating current.

  In addition to the excitation coil 3 and the detection coil 4, the detection head 1 is provided with a magnetic field sensor 15 that detects a magnetic flux that excites the inspection object 30. In addition to the excitation power source unit 6 and the demagnetization power source unit 7, the power source 5 controls the alternating current of the excitation power source unit 6 based on the strength of the magnetic flux detected by the magnetic field sensor 15 to set the inspection object 30. A current control unit (not shown) that keeps the magnetic flux to be excited constant is provided. The Barkhausen noise detection circuit 8 includes an amplifier 11 that amplifies the detection signal of the detection coil 4, an extraction filter 12 that extracts Barkhausen noise from the amplified detection signal, and the like.

  FIG. 3 shows a more specific configuration example of the Barkhausen noise inspection apparatus. The detection head 1 is configured by installing an iron core 13 around which an excitation coil 3 is wound and an iron core 14 around which a detection coil 4 is wound in a cylindrical case 16. The exciting coil 3 is wound around the iron core 13 via the winding frame 17, and the detection coil 4 is wound around the iron core 14 via the winding frame 18. The excitation coil 3 and the detection coil 4 are integrated in the case 16 by molding materials 19A and 19B.

  In addition to the power supply 5 and the Barkhausen noise detection circuit 8, the inspection apparatus main body 2 includes a signal processing circuit 9 that performs signal processing on the Barkhausen noise extracted by the detection circuit 8. Specifically, the signal processing circuit 9 measures the effective value, the maximum or average value of the amplitude, the amplitude of the envelope, and the like of the Barkhausen noise signal, and sets this as the Barkhausen noise value. The Barkhausen noise value may be a value obtained by measuring the value of Barkhausen noise for several cycles of the alternating magnetic field and obtaining an average value thereof. The signal processing circuit 9 detects the surface property of the inspection object 30 from the measured Barkhausen noise value. For example, when the Barkhausen noise value exceeds a predetermined threshold value, it is determined that there is an abnormality such as grinding burn on the surface of the inspection object 30. By setting the threshold value to another value, it can be determined that there are defects such as fine cracks and cavities. Further, the signal processing circuit 9 may measure the residual stress of the surface portion of the inspection object 30 from the Barkhausen noise value. The inspection apparatus body 2 is connected to the display unit 10. The display unit 10 displays the measured Barkhausen value, presence / absence of abnormality, and the like.

  In the non-destructive inspection of the inspection object 30 using the Barkhausen noise inspection apparatus having this configuration, the inspection object 30 is demagnetized by the demagnetizing means 20 prior to detection of the Barkhausen noise. In this demagnetization, the iron core 13 and the inspection object 30 constitute a magnetic circuit by pressing the detection head 1 against the inspection object 30 and bringing the iron core 13 into contact with the inspection object 30. In this state, the exciting coil 3 is replaced with a demagnetizing coil, and an alternating current whose amplitude is attenuated with time is supplied to the exciting coil 3 from the demagnetizing power supply unit 7 of the power source 5 of the inspection apparatus body 2. As a result, an alternating magnetic field whose amplitude decays with time is generated in the exciting coil 3 as shown in FIG. 2, and the inspection object 30 is AC demagnetized.

  Thus, after demagnetizing the residual magnetism of the inspection object 30, Barkhausen noise is detected as follows. As in the case of demagnetization, when the detection head 1 is pressed against the inspection object 30, the iron cores 13 and 14 come into contact with the inspection object 30, and the iron core 13 and the inspection object 30 constitute a magnetic closed circuit. . In this state, a constant alternating current whose amplitude is not attenuated is supplied to the excitation coil 3 from the excitation power supply unit 7 of the power supply 5 of the inspection apparatus body 2. As a result, an alternating magnetic field having a constant amplitude is generated in the exciting coil 3 and the inspection object 30 is magnetized. The detection coil 4 detects Barkhausen noise generated by the magnetized inspection object 30. The Barkhausen noise signal detected by the detection coil 4 is amplified by the amplifier 11 in the Barkhausen noise detection circuit 8 of the inspection apparatus body 2, and the Barkhausen noise signal is extracted by the extraction filter 12. The extracted Barkhausen noise signal is processed by a signal processing circuit 9 in the next stage, and a Barkhausen noise value is calculated. From this value, the presence or absence of surface abnormality (such as grinding burn) of the inspection object 30 is determined. .

  If some residual magnetism remains on the inspection object 30 even after the demagnetization process, prior to the detection of Barkhausen noise, for example, the magnetic field sensor 15 (FIG. 1) is used as a residual magnetism detection sensor. When the residual magnetism is detected and the Barkhausen noise value is calculated by the signal processing circuit 9 when the Barkhausen noise is detected, the Barkhausen noise value may be corrected based on the detected value of the residual magnetism.

  As described above, in this Barkhausen noise inspection apparatus, since the demagnetizing means 20 for demagnetizing the residual magnetism of the inspection object 30 is provided, the demagnetizer is not separately provided and the high magnetic force that is not affected by the residual magnetism. Inspection of accuracy can be performed.

  In this embodiment, since the exciting coil 3 used for detecting Barkhausen noise is shared by the demagnetizing coil of the demagnetizing means 20, it is not necessary to separately provide a dedicated demagnetizing coil. Can be configured compactly.

FIG. 4 shows an example of a nondestructive inspection performed using the Barkhausen noise inspection apparatus. Here, it is used as a device for inspecting the quality of the bearing, and specifically, the grinding burn of the rolling surface 21a of the inner ring 21 of the bearing is detected. The detection head 1 of the Barkhausen noise inspection apparatus is supported by a movable support member 22, and detects an abnormal part while sliding on the surface of the rolling surface 21 a of the bearing inner ring 21 by the movement of the support member 22. The bearing inner ring 21 is fitted on the outer diameter surface of the rotating shaft 23. By rotating the rotating shaft 23, the detection head 1 is slid on the entire circumferential surface of the rolling surface 21a of the bearing inner ring 21 and ground. Burns can be inspected.
When the Barkhausen noise inspection apparatus is used on-line in this way, it is possible to inspect all abnormalities such as grinding burn of the rolling surface 21a of the bearing inner ring 21 and improve the quality assurance capability.

  Although FIG. 4 shows an example in which the Barkhausen noise inspection device is used for inspection of grinding burn on the rolling surface 21a of the bearing inner ring 21, surface information to be detected may be residual stress or a defect. Further, the inspection object is not limited to the inner ring 21 that is a bearing component, and may be, for example, one that detects surface information of the bearing itself. Further, the inspection object is not limited to the bearing, and may be another rolling device or rolling device component. In this case, the surface information of the rolling device or rolling device component can be detected with high accuracy. .

1 ... detection head 3 ... excitation coil (also used as demagnetizing coil)
DESCRIPTION OF SYMBOLS 4 ... Detection coil 5 ... Power supply 6 ... Excitation power supply part 7 ... Demagnetization power supply part 20 ... Demagnetizing means 21 ... Bearing inner ring (rolling device components)
30 ... Inspection object

Claims (7)

An excitation coil that magnetizes the inspection object, a detection head having a detection coil that detects Barkhausen noise generated by the magnetized inspection object, and an alternating current that generates an alternating magnetic field for magnetization is supplied to the excitation coil In a Barkhausen noise inspection device equipped with a power supply
A Barkhausen noise inspection apparatus comprising a demagnetizing means for demagnetizing residual magnetism of the inspection object by providing the detection head with a demagnetization function.   2. The demagnetizing unit according to claim 1, wherein the demagnetizing means supplies the demagnetizing coil that is provided in the detection head and demagnetizes the object to be inspected, and an alternating current that generates an alternating magnetic field whose amplitude decreases with time. Barkhausen noise having a power supply unit for demagnetization, and the power supply includes a power supply unit for demagnetization and an excitation power supply unit that supplies an alternating current that generates an alternating magnetic field for magnetization in the excitation coil Inspection device.   3. The Barkhausen noise inspection apparatus according to claim 1, wherein the exciting coil is shared with the demagnetizing coil.   4. The Barkhausen noise inspection apparatus according to claim 1, further comprising a signal processing unit configured to detect a property of a surface portion of the inspection target object from Barkhausen noise detected by the detection head. 5.   The Barkhausen noise inspection apparatus according to any one of claims 1 to 4, wherein the Barkhausen noise inspection apparatus is used for detecting a property of a surface of a rolling device or a surface of a rolling device component.   6. The Barkhausen noise inspection apparatus according to claim 5, wherein the property of the surface is detected by sliding the detection head on the surface of the rolling device or the surface of a rolling device component.   7. The Barkhausen noise inspection device according to claim 4, wherein the surface property to be detected is surface grinding burn, residual stress, or a defect.

Images