JP6097906B2 - Inspection device for minute magnetic metal foreign matter - Google Patents

Description

  The present invention relates to an inspection apparatus for minute magnetic metal foreign matter, and in particular, minutely magnetic foreign matter mixed in a liquid such as an active material binder for a lithium battery is magnetically inspected using a high-sensitivity magnetic sensor such as a SQUID magnetic sensor. It is related with the apparatus which performs.

  In the inspection apparatus for the minute magnetic metal foreign matter as described above, in order to measure the residual magnetization of the foreign matter, it is necessary to magnetize the minute magnetic metal foreign matter with a strong magnet before the measurement with the SQUID magnetic sensor. In this device, in order to increase the detection signal, a magnetic field of 0.2 Tesla or more is often applied to magnetize, but if the size of a foreign object to be inspected is reduced to about 10 microns, a larger magnetic field is required. It becomes.

  In general, as shown in FIG. 7, a foreign substance 102 moving in a liquid pipe 101 is magnetized by a cylindrical permanent magnet 103, and the magnetized foreign substance 102 is shielded by a multilayer magnetic shield 104. In many cases, the measurement is performed by the SQUID magnetic sensor 106 disposed in 105 (see Patent Document 1 below). Reference numeral 107 denotes an opening that penetrates the liquid pipe 101 formed in the multilayer magnetic shield 104.

JP 2010-237081 A

  However, in the conventional inspection apparatus as described above, when the foreign matter 102 is small, an action of demagnetizing by the self magnetic field works. Therefore, even when magnetized by the cylindrical permanent magnet 103, the foreign matter is measured when measured by the SQUID magnetic sensor 106. There is a problem that the magnetization of 102 is small, and sufficient measurement is difficult.

  In view of the above situation, an object of the present invention is to provide an inspection apparatus for a minute magnetic metal foreign object that can reliably measure even a minute magnetic metal foreign object.

In order to achieve the above object, the present invention provides
[1] A magnetic field application device is a cylindrical permanent magnet, and a magnetic field application device in which a liquid pipe is disposed through the cylindrical permanent magnet and a magnetic magnetic foreign matter inspection device including a magnetic sensor, ,
(A) are arranged in the moving direction of said micro-magnetic metal foreign object a under the influence of the magnetic field of the magnetic field application device for applying a magnetic field to fine magnetic metal particles that can be moved in the liquid in the pipe, winding a number of turns are the same A differential detection coil in which a pair of coils having opposite directions are connected in series;
(B) is separated from the differential type detection coil by a lead, characterized by having a flux transformer having an input coil for inputting the magnetic flux of the differential type detection coil magnetically coupled to said magnetic sensor And

[ 2 ] The inspection apparatus for a minute magnetic metal foreign matter according to [1], further comprising a differential detection coil pipe, outside the liquid pipe along the moving direction of the minute magnetic metal foreign matter, and The differential detection coil pipe is coaxially arranged, and the differential detection coil is arranged in the differential detection coil pipe.

[ 3 ] The inspection apparatus for minute magnetic metal foreign matter according to [1] or [2] , further including a multilayer magnetic shield and a cryostat, wherein the magnetic sensor is a SQUID magnetic sensor, It arrange | positions in the said cryostat arrange | positioned in this invention, It is characterized by the above-mentioned.

[ 4 ] In the inspection apparatus for minute magnetic metal foreign matter according to [3], the lead wire connected to the differential detection coil is wired through the multilayer magnetic shield in a sealed state. To do.

[ 5 ] The inspection apparatus for minute magnetic metal foreign matter according to [1] or [2] , wherein the magnetic sensor is a fluxgate sensor.

[ 6 ] The inspection apparatus for minute magnetic metal foreign matter according to [1] or [2] , wherein the magnetic sensor is an MI effect element.

  According to the present invention, the following effects can be achieved.

  (1) In the conventional inspection apparatus for minute magnetic metal foreign matter, the multilayer magnetic shield of the SQUID magnetic sensor requires an opening for penetrating the liquid pipe, and the magnetic shield of the SQUID magnetic sensor is not sufficient. Can separate the magnetic field applying unit by the magnet and the signal measuring unit by the magnetic sensor, so that the magnetic field of the magnetic sensor can be sufficiently shielded, noise is reduced, and S / N (signal and Noise ratio) can be improved.

  (2) Since the distance between the magnetic field application unit using the magnet and the signal measurement unit using the magnetic sensor can be increased, a larger magnetic field can be applied to the minute magnetic metal foreign matter, and the measurement signal becomes larger. N can be improved.

  (3) Since the magnetization of the minute magnetic metal foreign object and the measurement by the magnetic sensor are simultaneous, there is no signal attenuation due to demagnetization of the magnetized minute magnetic metal foreign object, so that the measurement signal becomes larger and the S / N is improved. Can do.

  (4) The configuration of the magnetic field application unit and the signal measurement unit using the magnetic sensor is simple. In particular, since the differential detection coil and the input coil are composed of passive circuits, the configuration is simple and adjustment for highly accurate measurement is extremely easy.

It is a schematic diagram which shows the inspection apparatus of the minute magnetic metal foreign material using the magnetic flux transformer which shows the Example of this invention. It is a schematic diagram which shows the magnetic flux transformer of the inspection apparatus of the micro magnetic metal foreign material which shows the Example of this invention. It is a figure which shows the signal waveform by the inspection apparatus of the micro magnetic metal foreign material which shows the Example of this invention. It is a schematic diagram of the inspection apparatus of the minute magnetic metal foreign material as a comparative example. It is a figure which shows the signal waveform by the inspection apparatus of the micro magnetic metal foreign material as a comparative example. It is a schematic diagram which shows the magnetic field application part of the inspection apparatus of the micro magnetic metal foreign material which shows the other Example of this invention. It is a schematic diagram of the inspection apparatus of the conventional minute magnetic metal foreign material.

The inspection apparatus for minute magnetic metal foreign matter according to the present invention is a minute magnetic metal comprising a magnetic field application device in which a magnetic field application device is a cylindrical permanent magnet and a liquid pipe is disposed through the cylindrical permanent magnet and a magnetic sensor. A foreign matter inspection device,
(A) are arranged in the moving direction of said micro-magnetic metal foreign object a under the influence of the magnetic field of the magnetic field application device for applying a magnetic field to fine magnetic metal particles that can be moved in the liquid in the pipe, winding a number of turns are the same A differential detection coil in which a pair of coils having opposite directions are connected in series;
(B) A magnetic flux transformer having an input coil that is separated from the differential detection coil by a lead wire and has an input coil that magnetically couples and inputs the magnetic flux of the differential detection coil to the magnetic sensor.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic diagram showing a minute magnetic metal foreign object inspection apparatus using a magnetic flux transformer according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a magnetic flux transformer of the minute magnetic metal foreign object inspection apparatus.

  In the present invention, in particular, an apparatus for magnetically inspecting a minute magnetic metal foreign matter mixed in a liquid such as an active material binder for a lithium battery using an ultrasensitive SQUID magnetic sensor will be described.

  1 and 2, 1 is a liquid pipe, 2 is a minute magnetic metal foreign material that moves in the liquid pipe 1, 3 is a cylindrical permanent magnet through which the liquid pipe 1 passes, 4 is a magnetic flux transformer, and 5 is a cylindrical permanent magnet. 3 is a differential type detection coil of a magnetic flux transformer 4 arranged in a pair of coils having the same number of turns and the winding direction being reversed, for example, a left-handed coil (or right-handed coil) 5A and a right-handed coil ( Or left-handed coil) 5B. 6 is an input coil of the magnetic flux transformer 4, 7 is a lead wire for connecting the differential detection coil 5 and the input coil 6, 8 is a SQUID magnetic sensor disposed in the input coil 6, and 9 is a liquid of the SQUID magnetic sensor 8. A nitrogen container (cryostat) 10 is a multilayer magnetic shield disposed outside the liquid nitrogen container 9.

  The inspection apparatus for minute magnetic metal foreign matter of the present invention uses a magnetic flux transformer 4. The magnetic flux transformer 4 is coupled to the SQUID magnetic sensor 8 by magnetically coupling the differential detection coil 5 composed of a pair of coils 5A and 5B having the same number of turns and the winding direction being reversed. It comprises an input coil 6. With this configuration, when a uniform static magnetic field or a time-varying magnetic field is applied to the differential detection coil 5, no current flows through the magnetic flux transformer 4 and no signal is generated at the input coil 6. However, when the magnetized minute magnetic metal foreign material 2 passes through the differential detection coil 5 at a certain speed, the balance between the pair of the left-handed coil 5A and the right-handed coil 5B is lost, and a current flows through the magnetic flux transformer 4. The magnitude of the current is proportional to the time variation of the magnetic flux.

  As described above, in the present invention, the magnetic flux transformer 4 including the differential detection coil 5 and the input coil 6 is used, and the differential detection coil 5 is installed in the strong cylindrical permanent magnet 3. The liquid pipe 1 is configured to penetrate through the differential detection coil 5. A signal of the differential detection coil 5 is transmitted by the magnetic flux transformer 4 and is input from the input coil 4 magnetically coupled to the SQUID magnetic sensor 8 installed in the liquid nitrogen container 9 inside the multilayer magnetic shield 10 having a sufficiently high magnetic shielding rate. Communicated. When the minute magnetic metal foreign matter 2 is not mixed, no current flows through the differential detection coil 5 and thus the SQUID magnetic sensor 8 does not detect a signal. However, when the minute magnetic metal foreign matter 2 flows, the minute magnetic metal foreign matter 2 flows. Magnetization by the cylindrical permanent magnet 3 occurs in the foreign material 2, and the magnetic field changes with time due to the movement of the magnetized minute magnetic metal foreign material 2, so that the balance of the differential detection coil 5 is lost. The sensor 8 measures a signal. The lead wire 7 can be sufficiently shielded from the magnetic field of the SQUID magnetic sensor by wiring through the multilayer magnetic shield 10 in a sealed state.

  For example, in the apparatus of the present invention shown in FIG. 1 in which a differential detection coil 5 is arranged in a cylindrical permanent magnet 3, an iron ball having a diameter of 0.6 mm as a minute magnetic metal foreign material 2 is differentially applied while applying a magnetic field. FIG. 3 shows signal waveforms when moved in the mold detection coil 5. In this case, the measurement signal is extremely large and the S / N is 1000 or more, which shows the effectiveness of the present invention in that the magnetic field is applied simultaneously with the signal measurement.

  FIG. 4 is a schematic diagram of an inspection apparatus for minute magnetic metal foreign matter as a comparative example, and FIG. 5 is a diagram showing signal waveforms by the inspection apparatus for minute magnetic metal foreign matter.

  In FIG. 4, 11 is a liquid pipe, 12 is a minute magnetic metal foreign substance that moves in the liquid pipe 11, 13 is a cylindrical permanent magnet that penetrates the liquid pipe 11, and 14 is arranged at a position separated from the cylindrical permanent magnet 13. 15 is a differential detection coil of a magnetic flux transformer 14 disposed around the liquid pipe 11, 16 is an input coil connected to the differential detection coil 15, and 17 is a differential detection coil 15. Lead wire connecting the input coil 16, 18 is a SQUID magnetic sensor disposed in the input coil 16, 19 is a liquid nitrogen container (cryostat) of the SQUID magnetic sensor 18, and 20 is disposed outside the liquid nitrogen container 19. Multi-layer magnetic shield.

  Here, an iron ball having a diameter of 0.6 mm as the minute magnetic metal foreign matter 12 is magnetized in advance by the cylindrical permanent magnet 13, and the magnetized iron ball as the minute magnetic metal foreign matter 12 is differentially detected by the magnetic flux transformer 14. The signal is measured by moving through the coil 15, and the signal waveform is shown in FIG.

  Thus, the differential detection coil 15 was not placed in the cylindrical permanent magnet 13, and no magnetic field was applied to the iron ball as the minute magnetic metal foreign object 12 during signal measurement. In this case, since the self magnetic field of the iron ball as the minute magnetic metal foreign material 12 magnetized in advance is attenuated at the time of measurement, the measurement signal is small and the S / N is about 1. Therefore, by performing the magnetization by the cylindrical permanent magnet and the signal detection by the differential detection coil at the same position as shown in FIG. 1, it is possible to eliminate the attenuation of the self magnetic field and obtain a signal that varies greatly. N can be improved.

  FIG. 6 is a schematic diagram showing a magnetic field application unit of a minute magnetic metal foreign object inspection apparatus according to another embodiment of the present invention.

  In this figure, 21 is a liquid pipe, 22 is a minute magnetic metal foreign substance that moves in the liquid pipe 21, and 23 is a differential in which a differential detection coil 24 that is concentrically disposed outside the liquid pipe 21 is wound. A die detection coil pipe 25 is a cylindrical permanent magnet disposed concentrically outside the differential detection coil pipe 23.

  As described above, since the differential detection coil 24 is arranged in the differential detection coil pipe 23 separate from the liquid pipe 21, direct interference between the liquid pipe 21 and the differential detection coil 24. Can be eliminated. For example, there is an advantage that vibration caused by the liquid pipe 21 does not directly affect the differential detection coil 24.

  In the above embodiment, the measurement by the SQUID magnetic sensor has been described. However, the measurement is not limited to the SQUID magnetic sensor. Instead of the SQUID magnetic sensor, a flux gate sensor, that is, a size and a phase are determined. A detector that produces an electrical output signal proportional to the magnitude and direction of the external magnetic field acting along the axis may be used.

  Further, a magneto-impedance effect element (MI effect element) (for example, see JP-A-7-181239 and JP-A-9-80133) may be used. In other words, the MI effect element can be as small as a Hall element or a magnetoresistive (MR) element, has a magnetic detection sensitivity of 100 times or more that of the Hall element or MR element, and is comparable to a fluxgate sensor. Therefore, it can be used as the magnetic sensor of the present invention.

  According to the present invention, the following effects can be achieved.

  (1) In the conventional inspection apparatus for minute magnetic metal foreign matter, as shown in FIG. 7, the multilayer magnetic shield 104 of the SQUID magnetic sensor 106 requires an opening 107 through which the liquid pipe 101 passes, and the SQUID magnetic sensor 106. However, according to the present invention, the magnetic field applying unit using the magnet and the signal measuring unit using the SQUID magnetic sensor can be separated, so that the magnetic field of the SQUID magnetic sensor can be sufficiently shielded. The noise is reduced and the S / N is improved.

  (2) Since the distance between the magnetic field application unit by the magnet and the signal measurement unit by the SQUID magnetic sensor can be increased, a larger magnetic field can be applied to the minute magnetic metal foreign matter, and the measurement signal becomes larger. / N is improved.

  (3) Since the magnetization to the minute magnetic metal foreign object and the measurement by the SQUID magnetic sensor are simultaneous, there is no signal attenuation due to demagnetization of the magnetized minute magnetic metal foreign object, so the measurement signal becomes larger and the S / N is improved. Is done.

  (4) When a fluxgate sensor or MI effect element is used instead of the SQUID magnetic sensor, the mounting is simpler than the SQUID magnetic sensor, and the cost of the magnetic sensor is greatly reduced. Can do.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The inspection apparatus for minute magnetic metal foreign matter according to the present invention can be used as an inspection apparatus for minute magnetic metal foreign matter that can reliably measure even a minute magnetic metal foreign matter.

1,11,21 Liquid piping 2,12,22 Micro magnetic metallic foreign matter 3,13,25 Cylindrical permanent magnet 4,14 Magnetic flux transformer 5,15,24 Differential detection coil 5A Left-handed coil 5B Right-handed coil 6,16 Input coil 7, 17 Lead wire 8, 18 SQUID magnetic sensor 9, 19 Liquid nitrogen container (cryostat)
10, 20 Multi-layer magnetic shield 23 Differential detection coil piping

Claims (6)

The magnetic field application device is a cylindrical permanent magnet, and a magnetic field application device in which a liquid pipe is disposed through the cylindrical permanent magnet and a magnetic magnetic foreign matter inspection device comprising a magnetic sensor,
(A) are arranged in the moving direction of said micro-magnetic metal foreign object a under the influence of the magnetic field of the magnetic field application device for applying a magnetic field to fine magnetic metal particles that can be moved in the liquid in the pipe, winding a number of turns are the same A differential detection coil in which a pair of coils having opposite directions are connected in series;
(B) A magnetic flux transformer having an input coil separated from the differential detection coil by a lead wire and having an input coil that magnetically couples and inputs the magnetic flux of the differential detection coil to the magnetic sensor. Inspection device for minute magnetic metal foreign matter.   2. The inspection apparatus for a minute magnetic metal foreign object according to claim 1, further comprising a pipe for a differential type detection coil, and along the moving direction of the minute magnetic metal foreign object, on the outside of the liquid pipe and coaxially. An apparatus for inspecting a minute magnetic metal foreign matter, wherein a differential detection coil pipe is arranged, and the differential detection coil is arranged in the differential detection coil pipe. 3. The inspection apparatus for minute magnetic metal foreign matter according to claim 1, further comprising a multilayer magnetic shield and a cryostat, wherein the magnetic sensor is a SQUID magnetic sensor, and the cryostat disposed in the multilayer magnetic shield. An inspection apparatus for minute magnetic metal foreign matter, characterized by being placed inside. 4. The micro magnetic metal foreign matter inspection apparatus according to claim 3, wherein the lead wire connected to the differential detection coil is wired through the multilayer magnetic shield in a sealed state. Foreign matter inspection equipment. 3. The inspection apparatus for minute magnetic metal foreign matter according to claim 1, wherein the magnetic sensor is a fluxgate sensor. 3. The inspection apparatus for minute magnetic metal foreign matter according to claim 1 or 2 , wherein the magnetic sensor is an MI effect element.

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