JP2010276351A - Magnetic object detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic object detection device with an extended detection area of a magnetic object attached to an article. <P>SOLUTION: The magnetic object detection device 10 includes an excitation power supply 12, an excitation coil 14, a receiving coil 16, a processing means 18 extracting only a harmonic component of a receiving signal from the receiving coil 16, and a determination means 20 determining the presence of a magnetic object that is not invalid from the extracted harmonic component. A magnetic field generated by the excitation coil 14 includes at least three different magnetic field directions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic object detection device that monitors the movement of an article by a magnetic object attached to the article or placed in the article.

  There is a device that detects a magnetic object when the magnetic object is attached to the article or moved into the article (for example, the following patent document). By detecting the magnetic object, the movement of the article can be monitored. FIG. 9 shows a configuration of a magnetic object detection device 50 conventionally used. The magnetic object detection device 50 includes an excitation unit 55 including an excitation power source 12 and an excitation coil 54, a reception unit 57 including a reception coil 56, a processing unit 18 that extracts only harmonic components of a reception signal from the reception coil 56, Determination means 20 for determining the presence or absence of a magnetic object that has not been revoked from the extracted harmonic components. The term “revocation” as used herein means that a strong magnetic field is applied to a magnetic object using a deactivation device so that a large Barkhausen effect described later is not caused.

  The magnetic object to be detected is formed of an amorphous metal. The magnetization reversal phenomenon of amorphous metal in an alternating magnetic field excited at a predetermined frequency is a phenomenon called the large Barkhausen effect. Large Barkhausen effect means that in a highly permeable metal with low coercive force, when the external magnetic field exceeds a certain threshold value (referred to as coercive force) inherent to the metal, a reverse magnetic domain is suddenly formed in the metal and the domain wall moves. This is a phenomenon in which the magnetization reversal of the metal ends. This magnetization reversal phenomenon does not occur in any direction, but occurs only in the magnetization reversal direction of the amorphous metal. An amorphous metal having high magnetic permeability and low coercivity easily causes a large Barkhausen effect (FIG. 10). The change in the magnetic field accompanying the sudden magnetization reversal due to the large Barkhausen effect is a harmonic component of a specific frequency and is received by the receiving means together with the predetermined frequency component of the alternating magnetic field. The large Barkhausen effect can be prevented from being generated by a defeater.

  The magnetic object has a flexible sheet shape or line shape. If it is a sheet-like magnetic object, it is attached to the article by being pasted or embedded. If it is a linear magnetic object, it is attached to the article by being attached or embedded. The coercive force of the magnetic object against the alternating magnetic field is about several to several tens A / m.

  There are two receiving coils 56, and the receiving coil 56 is provided inside the exciting coil 54 as shown in FIG. The exciting coil 54 generates a magnetic field by the exciting power source 12. An example of the current flowing through the exciting coil 54 by the exciting power source 12 is an alternating current of about 0.5 to 2A. The frequency of the generated alternating magnetic field is 100 to 1000 Hz, preferably 200 to 400 Hz. The number of turns of the exciting coil 54 and the receiving coil 56 is arbitrary. In order to perform differential amplification, which will be described later, the number of turns of the two receiving coils 56 is the same. Both coils 54 and 56 have a rectangular shape. Here, as shown in FIG. 11, the direction in which the magnetic object 22 passes is the x direction, and the direction in which the plate bodies 60 are arranged is the y direction. The plate body 60 is erected in the vertical direction, and the vertical direction is taken as the z direction.

  The exciting coil 54 and the like are provided in the gate 62. The gate 62 generally has two plate bodies 60 opposed to each other with a predetermined interval (FIG. 11B). An excitation coil 54 and the like are provided in each plate body 60. Therefore, the exciting coil 54 and the like face each other at a constant interval. The distance between the gates 62 is, for example, about 900 to 1200 mm, and allows an article to which the magnetic object 22 is attached to pass therethrough. A region surrounded by the exciting coil 54 and the receiving coil 56 facing each other is a detection region of the magnetic object 22.

  The processing means 18 includes a differential amplifier circuit, a band pass filter, an AC amplifier circuit, etc. (not shown). The differential amplifier circuit takes the difference between the potentials of the reception signals from the two reception coils 56 and amplifies them. The band pass filter and the AC amplifier circuit of the processing means 18 are connected in multiple stages. After the differential amplification, a harmonic component of the voltage waveform of the received signal generated due to the magnetization reversal of the magnetic object 22 is extracted by a band pass filter and an AC amplifier circuit. A voltage waveform generated due to the magnetization reversal is a waveform in a specific frequency band of about 3000 to 20000 Hz.

  If there is a revoked magnetic object 22 or if there is no magnetic object 22, the received signal is almost 0V as shown in FIG. 12A, and if there is a non-revoked magnetic object 22, it is large as shown in FIG. A voltage waveform in a specific frequency band accompanying the Barkhausen effect appears.

  The determination means 20 compares the amplitude of the signal derived from the extracted harmonic component with an amplitude threshold value stored in advance in the memory, and determines that the magnetic object 22 that has not expired is present if the signal is larger than the threshold value. To do. Alternatively, a rectangular wave may be generated from the harmonic component, and the presence / absence of the magnetic object 22 that has not expired may be determined from the number of rectangular waves.

  The movement of the article is monitored by determining the presence or absence of a magnetic object 22 that has not expired in the detection area. Monitoring the movement of the article includes monitoring for refusing the movement of the article and monitoring the position of the article by detecting the movement of the article. It also includes monitoring the number of articles moved according to the number of detected magnetic objects 22.

  As described above, in order to reverse the magnetization of the magnetic object 22, it is necessary to apply a magnetic field exceeding the magnetic field strength in the magnetization reversal direction to the magnetic object 22 by the excitation coil 54. The direction of the generated magnetic field is determined by Ampere's law and the shape of the exciting coil 54.

  Here, FIG. 13 shows the distribution of the magnetic fields mx, my, mz formed by the exciting coil 54. The illustrated magnetic fields mx, my, and mz are distributions when the plate body 60 is viewed from the side, and represent the magnetic fields in the x, y, and z directions shown in FIG. The magnetic field is a magnetic field of 24 A / m or more. Magnetic fields mx, my, and mz in the x, y, and z directions are not formed at all positions through which the magnetic object 22 passes. Further, since the magnetic object 22 has a sheet shape or a line shape, magnetization reversal does not occur depending on the direction of the applied magnetic field. For example, as shown in FIG. 14, when the linear magnetic object 22 faces in the z direction, magnetization reversal does not occur in the magnetic fields in the x and y directions, and the magnetic field in the z direction (linear length direction). Magnetization reversal occurs only by. This is because the magnetization reversal directions of the linear magnetic object do not exist in the x and y directions. When the magnetic object 22 has a sheet shape, there is no magnetization reversal direction with respect to the thickness direction.

  Accordingly, magnetization reversal does not occur in the magnetic object 22 depending on the position through which the magnetic object 22 passes and the direction of the magnetic object 22. For example, when the magnetic object 22 moves in the center of the gate 62, there is no magnetic field in the z direction. If the magnetic object 22 is oriented in a direction that causes magnetization reversal only by a magnetic field in the z direction, the magnetic object 22 does not undergo magnetization reversal. There is a possibility that the change of the magnetic field due to the magnetization reversal cannot be detected and the movement of the article cannot be monitored.

JP 2006-268399 A JP 2006-268448 A

  An object of the present invention is to provide a magnetic object detection device having a wide detection area of a magnetic object attached to an article.

  The magnetic object detection device of the present invention detects a magnetic object made of an amorphous metal that is attached to an article that passes through a detection region or is placed in the article. The magnetic object detection device includes an excitation unit that generates an alternating magnetic field whose strength exceeds the coercive force of the magnetic object, a reception unit that detects a magnetic field in the inspection region and generates a reception signal, and a magnetization of the magnetic object from the reception signal. Processing means for extracting a voltage waveform caused by inversion, and determination means for determining the presence or absence of a magnetic object from the voltage waveform extracted by the processing means. And the direction of the alternating magnetic field which an excitation means generate | occur | produces is at least 3 directions, and a magnetic field of at least 3 directions is applied to a magnetic object.

  An AC magnetic field in three directions is generated by the exciting means, and the magnetic field is detected by the receiving means. When receiving, a large Barkhausen effect is produced by the magnetic object. The processing means extracts harmonic components of the voltage waveform caused by magnetization reversal, and the determination means determines the presence or absence of a magnetic object.

  The exciting means includes an exciting coil having a triangular shape or a combination of a plurality of triangular shapes. When the exciting means has a triangular shape, a magnetic field in three directions is generated.

  The receiving means includes a triangular receiving coil, and two receiving coils are provided inside the exciting coil. In order to receive magnetic fields in three directions, the shape of the receiving means is triangular. In order to use differential amplification by the processing means, two receiving means are provided.

  According to the present invention, when the magnetic field has at least three directions, the magnetic object can be applied with a magnetic field in three directions regardless of the passing position of the magnetic object. A magnetic field in the magnetization reversal direction can be applied to the magnetic object from a plurality of directions, and the detection area of the magnetic object can be expanded.

It is a figure which shows the structure of the magnetic object detection apparatus of this invention. It is a figure which shows the shape of the exciting coil and receiving coil which are used for a magnetic object detection apparatus. It is a figure which shows the shape of the exciting coil and receiving coil which are used for a magnetic object detection apparatus. It is a figure which shows the shape of the exciting coil and receiving coil which are used for a magnetic object detection apparatus. It is a figure shown about the gate of a magnetic object detection apparatus, (a) is an exciting coil and a receiving coil in a gate, (b) is a figure which shows arrangement | positioning of a plate. FIGS. 3A and 3B are diagrams illustrating a distribution of a magnetic field generated by the excitation coil of FIG. 2, in which FIG. It is a figure which shows distribution of the magnetic field produced | generated by the exciting coil of FIG. 3, (a) is magnetic field distribution of x direction, (b) is magnetic field distribution of y direction, (c) is magnetic field distribution of z direction. It is a figure which shows distribution of the magnetic field produced | generated by the exciting coil of FIG. 4, (a) is magnetic field distribution of x direction, (b) is magnetic field distribution of y direction, (c) is magnetic field distribution of z direction. It is a figure which shows the structure of the conventional magnetic object detection apparatus. It is a figure which shows the magnetization curve of a normal metal and an amorphous metal. It is a figure shown about the gate of a magnetic object detection apparatus, (a) is an exciting coil and a receiving coil in a gate, (b) is a figure which shows arrangement | positioning of a plate. It is a figure which detects the voltage waveform by a large Barkhausen effect, (a) is a case where there is a magnetic object which has expired or there is no magnetic object, (b) is a figure when there is a magnetic object. It is a figure which shows distribution of the magnetic field produced | generated by the exciting coil of Fig.11 (a), (a) is magnetic field distribution of x direction, (b) is magnetic field distribution of y direction, (c) is magnetic field distribution of z direction. It is. It is a figure which shows the direction of a linear magnetic object, (a) is yz surface in FIG. 11, (b) is xy surface in FIG.

  A magnetic object detection device of the present invention will be described with reference to the drawings. The magnetic object to be detected is made of an amorphous metal as in the conventional case. The magnetic object has a sheet shape or a line shape. The magnetic object is attached to or placed in the object to be monitored for movement.

  The magnetic object detection apparatus 10 shown in FIG. 1 takes out only the harmonic component of the received signal from the receiving coil 16 and the exciting means 15 consisting of the exciting power source 12 and the exciting coil 14, the receiving means 17 consisting of the receiving coil 16. Means 18 and determination means 20 for determining the presence or absence of a magnetic object that has not been revoked from the extracted harmonic components. Since the excitation power source 12, the processing means 18, and the determination means 20 are the same as those described in the prior art, description thereof is omitted.

  The magnetic field generated by the exciting coil 14 is set to have at least three magnetic field directions. For this purpose, as shown in FIG. 2, the exciting coil 14 has a triangular shape. Further, as shown in FIG. 3, the exciting coil 14 may be inclined on the xz plane. Furthermore, as shown in FIG. 4, the exciting coil 14 may have a shape obtained by combining two triangular shapes.

  The receiving coil 16 has a triangular shape in order to detect the magnetic field generated by the exciting coil 14. Two receiving coils 16 are arranged inside one exciting coil 14. The reason why the number of receiving coils 16 is two is that the processing means 18 performs differential amplification. Therefore, the number of turns of the two receiving coils 16 is the same, and the shape is the same.

  As in the prior art, two plates 60 are arranged in parallel to form a gate 62, and one excitation coil and two 14 receiving coils 16 are provided inside one plate 60 (FIG. 5A). (B)). A region surrounded by the opposing exciting coil 14 is a detection region of the magnetic object 22. The width of the detection region is designed so that the magnetic field generated by the exciting coil 14 reaches the magnetic object 22 and the receiving coil 16 can receive the change in the magnetic field. The excitation coil 14 or the like may be built in only one of the plates 60, but the width of the detection region is halved compared to the case where the excitation coil 14 or the like is built in both plates 60.

  As shown in FIG. 5, the direction in which the magnetic object 22 passes is the x direction, and the direction in which the plate bodies 60 are arranged is the y direction. The plate body 60 is erected in the vertical direction, and the vertical direction is taken as the z direction.

  Next, the magnetic field actually generated by the exciting coil 14 will be described. 6 to 8 show magnetic fields mx, my, and mz corresponding to the exciting coil 14 shown in FIGS. The magnetic fields mx, my, and mz are generated according to the shape of the exciting coil 14 and Ampere's law when a current flows through the exciting coil 14. What is shown in the figure is a region where magnetic fields mx, my, and mz that are larger than the magnitude at which magnetization reversal occurs. For example, the magnetic field strength in the magnetization reversal direction is about 24 A / m. The illustrated magnetic fields mx, my, and mz are distributions when the plate body 60 is viewed from the side. The x direction, the y direction, and the z direction are the same as the directions shown in FIG.

  In any exciting coil 14, magnetic fields mx, my, mz in the x direction, the y direction, and the z direction are generated. Further, in any position where the magnetic object 22 passes, the magnetic object 22 is applied with magnetic fields mx, my, and mz in three directions regardless of which position the magnetic object 22 passes. Therefore, the detection accuracy does not change depending on the position and direction of the magnetic object 22. Compared with the prior art, the detection area of the magnetic object 22 becomes wider. The movement of the article can be accurately monitored.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. For example, the shape of the exciting coil 14 is not limited to the shape shown in FIGS. 2 to 4, and may be any shape that can apply a magnetic field in three directions to the magnetic object 22. Furthermore, a magnetic field in three or more directions may be generated at a position where the magnetic object 22 passes. By applying a magnetic field that causes magnetization reversal from multiple directions to the magnetic object 22, the detection area of the magnetic object 22 can be widened.

  In addition, a computer for monitoring the position of the article by detecting the magnetic object 22 is provided as appropriate. For example, by providing a gate 62 between two areas and counting the number of articles that have passed through the gate 62, the number of articles that have moved from one area to another can be determined.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the gist thereof.

10: Magnetic object detection device 12: Excitation power supply 14: Excitation coil 15: Excitation means 16: Reception coil 17: Reception means 18: Processing means 20: Determination means 22: Magnetic object 60: Plate body 62: Gate mx, my, mz :magnetic field

Claims (3)

A magnetic object detection device for detecting a magnetic object made of amorphous metal that passes through a detection region,
Exciting means for generating an alternating magnetic field having a strength exceeding the coercive force of the magnetic object;
Receiving means for detecting a magnetic field in the inspection region and generating a reception signal;
Processing means for extracting a voltage waveform generated due to magnetization reversal of the magnetic object from the received signal;
Determination means for determining the presence or absence of a magnetic object from the voltage waveform extracted by the processing means;
With
A magnetic object detection device in which the direction of the alternating magnetic field at the passing position of the magnetic object is at least three directions. The magnetic object detection device according to claim 1, wherein the excitation means includes an excitation coil having a triangular shape or a combination of a plurality of triangular shapes. The magnetic object detection apparatus according to claim 2, wherein the receiving unit includes a triangular receiving coil, and two receiving coils are provided inside the exciting coil.

Images