JP2011237181A - Fine metal detection device provided with high performance magnetic shield and ultra sensitive magnetic sensor - Google Patents

Abstract

A fine metal detection device capable of detecting a metal foreign object of a fine magnetic material mixed in an object to be inspected.
A fine metal detection device (1) has a magnetizing means for magnetizing a metal foreign object in a direction coinciding with a magnetism detection direction by a fluxgate sensor (50) with an object to be inspected facing each other, and after passing the magnetizing means. Support means 3 capable of supporting the object to be inspected 2 and keeping the distance between the object to be inspected 2 and the fluxgate sensor 50 at a predetermined size, and a fluxgate sensor capable of detecting magnetism of 50 pT / √ (Hz) or less The magnetic detection unit 5 includes 50, a PC permalloy shield 6b for magnetic shielding that covers the magnetic detection unit 5, and an aluminum shield 6a for high-frequency shielding.
[Selection] Figure 7

Description

  The present invention provides a high-performance magnetic shield and an ultrahigh-sensitivity magnetic sensor that magnetizes fine metallic foreign matter mixed in an object to be inspected and detects the presence of the metallic foreign matter by detecting enhanced magnetism of the metallic foreign matter. The present invention relates to a fine metal detection apparatus including

  In recent years, secondary batteries have been actively developed in the spotlight of hybrid vehicles and electric vehicles. In addition, secondary batteries are beginning to spread in various fields in response to environmental considerations and social demands for energy conservation.

  On the other hand, incidents such as smoke or ignition from secondary batteries are sometimes taken up by mass communication, and the safety of secondary batteries is strongly demanded.

  With such a background, there is a strong demand from manufacturers of secondary batteries and manufacturers of final products such as electric vehicles incorporating the secondary batteries to detect and remove foreign substances contained in the secondary batteries.

  The secondary battery includes a film-like anode substrate made of aluminum, a film-like cathode substrate made of copper, and a film-like separator that is placed between the anode and the cathode and made of a synthetic resin or the like. It consists of. Some secondary batteries are manufactured using an active material-containing paste. This paste may contain foreign metal foreign matter such as iron, nickel, cobalt, etc. If this foreign metal is larger than a certain size, secondary battery ignition or premature deterioration. There is a problem of generating a bug. Considering that iron, nickel, cobalt, etc. are magnetic materials, while aluminum, copper, and synthetic resin are non-magnetic materials, among the foreign materials contained in the secondary battery, the magnetic metal materials are magnetized. It is conceivable to detect by magnetizing with.

  2. Description of the Related Art Conventionally, in a manufacturing process for beverages and the like, a device for detecting a metallic foreign object of a magnetic substance contained in the beverage is known.

For example, Patent Document 1 discloses an apparatus described below. This apparatus uses a non-magnetic fluid as an object to be inspected, and detects a metallic foreign object contained in the fluid.
This device includes a non-magnetic transfer pipe for flowing a fluid therein, a magnetizing device arranged to surround the transfer pipe and magnetizing the magnetic material contained in the fluid, and a transfer pipe downstream of the magnetizing device. And a detector configured to be disposed so as to be surrounded by an MI sensor (Magneto-Impedance Sensor).

JP 2006-98117 A

  Even if a very fine metallic foreign object can be strengthened by a magnetizing device, the magnetic field itself is extremely fine, so a sensor that can detect weak magnetism is used. Without it, it is impossible to detect the contamination of metallic foreign matter.

  However, the resolution of the MI sensor disclosed in Patent Document 1 is about 1 nT / √ (Hz), and the size of the metal foreign object that can be detected even if the separation distance between the MI sensor and the inspection object is as short as possible. The detection limit is approximately 150 Φ μm to 200 Φ μm. Therefore, there is a problem that metal foreign objects having a size smaller than this cannot be detected.

  In view of this, the present invention has an object to provide a fine metal detection device including a high-performance magnetic shield and an ultra-sensitive magnetic sensor that can detect fine metallic foreign matter mixed in an object to be inspected. I have to.

  In order to solve the above-mentioned problems, the present invention is intended to magnetize fine metallic foreign matter mixed in an object to be inspected and detect the presence of metallic foreign matter by detecting residual magnetism from the metallic foreign matter. This is a fine metal detection device equipped with a performance magnetic shield and an ultra-sensitive magnetic sensor.

  In such a fine metal detecting device, the present invention is characterized in that magnetizing means for magnetizing a metallic foreign object in a direction coinciding with the direction of detection of residual magnetism by an ultrasensitive magnetic sensor opposed to an object to be inspected, and magnetizing means Support means capable of supporting the object to be inspected after passing and maintaining the distance between the object to be inspected and the ultrasensitive magnetic sensor at a predetermined size, and 50 pT / √ (Hz) or less as an ultrasensitive magnetic sensor A magnetic detection unit including a fluxgate sensor capable of detecting the magnetism of the magnet, a PC permalloy shield for magnetic shielding that covers the magnetic detection unit as a high-performance magnetic shield, and an aluminum shield for high-frequency shielding. .

  In one of the preferred embodiments of the present invention, the fine metal detection device includes a machine direction in which the object to be inspected travels, a magnetic detection direction orthogonal to the machine direction, and a cross direction orthogonal to the machine direction and the detection direction. The magnetizing means and the magnetic detection unit are arranged from the upstream to the downstream in the machine direction, and the support means causes the inspection object to travel in the machine direction.

  In another preferred embodiment of the present invention, as a circuit for amplifying a magnetic signal detected by the magnetic detection unit immediately after the magnetic detection unit, unnecessary noise due to stray capacitance or induction is routed to the magnetic detection unit. And a signal in a frequency band corresponding to the traveling speed of the object to be inspected by the support means out of the magnetic signal, and an amplification circuit that can obtain a good signal-to-noise ratio (S / N). An electronic circuit having a low-pass filter that cuts off a frequency equal to or higher than a predetermined first frequency and a high-pass filter that cuts a frequency equal to or lower than a predetermined second frequency smaller than the first frequency, Also covers the amplifier circuit and the electronic circuit.

  In another preferred embodiment of the present invention, the magnetic detection unit has a plurality of fluxgate sensors in the machine direction, and the upstream fluxgate sensor in the machine direction and the downstream flux adjacent thereto. With respect to the flux gate sensor on the upstream side, the upstream flux gate sensor and the downstream flux gate sensor do not coincide with each other when viewed from the upstream side. The downstream fluxgate sensor is biased in the crossing direction.

  In another embodiment of the present invention, each of the fluxgate sensors for detecting residual magnetism is provided with a test coil for detecting an abnormality of the fluxgate sensor, and each of the test coils is connected in series. By connecting and forming a circuit in which the same current flows in each of the test coils, and applying a predetermined test voltage to the circuit, each of the flux gate sensors can detect the same level of magnetism generated by each of the test coils, With the waveform judgment device for the magnetism detected by each fluxgate sensor, the presence or absence of the same level of magnetism is judged, and it is judged that there is an abnormality in the fluxgate sensor when the same level of magnetism is not detected It is possible to provide the test coil.

  In another embodiment of the present invention, a power source that gives a constant waveform for the same test to all of the test coils, and a control unit that controls the power source are provided. In the process of continuously detecting the residual magnetism, a test current that can be judged to be abnormal in the fluxgate sensor is intermittently passed through the test coil for a certain period of time, and the same level characteristic of the test current The magnetic sensor that is detecting the residual magnetism is automatically detected to detect the presence of an abnormality in the fluxgate sensor.

  In another preferred embodiment of the present invention, annular first to sixth active shield circuits provided along ridge lines in three sets of mutually parallel virtual planes forming a virtual parallelepiped, and virtual A three-directional magnetic sensor that detects the magnitude of magnetism in a direction perpendicular to each of the virtual planes inside the parallelepiped, a power source that applies a voltage to the first to sixth active shield circuits, and a three-directional magnetic sensor And a control unit that applies a voltage to the first to sixth active shield circuits in order to cause the first to sixth active shield circuits to generate a reverse magnetic field that cancels the detected magnetism based on the detection result of An active shield space is formed inside the hexahedron, and a magnetic detector, a PC permalloy shield, and aluminum are formed inside the active shield space. While arranging the Rudo, it is arranged magnetized means any external and internal active shield space.

  In another preferred embodiment of the present invention, each of an inlet and an outlet for entering an inspection object formed in the PC permalloy shield and traveling in the machine direction, and an inlet and an outlet in the PC permalloy shield, respectively. An entrance coil and an exit coil provided in the vicinity of the periphery and forming an annular active shield circuit; a power source for applying a voltage to the entrance coil and the exit coil; and a space surrounded by the annular active shield circuit. A reverse magnetic field that is provided inside and detects the magnetism that enters the detection space from the entrance and the magnet that enters the detection space from the exit by the magnetic sensor, and cancels the detected magnetism based on the detection result of the magnetic sensor. Shield the external magnetism by passing current through the inlet coil and outlet coil to generate in the inlet coil and outlet coil And a that controller.

  In another preferred embodiment of the present invention, the aluminum shield is an assembly made of at least one material of a plurality of aluminum steel plates and a machined product from the aluminum steel plates, and the materials are fitted and It is assembled by at least one assembly means of fastening with screws used so as not to penetrate the material.

  The fine metal detection device according to the present invention includes a magnetizing means for magnetizing a metal foreign object in a direction that coincides with the direction of detection of magnetism by the ultrasensitive magnetic sensor with the object to be inspected, and a target after passing the magnetizing means. Support means capable of supporting the inspection object and keeping the distance between the object to be inspected and the ultra-sensitive magnetic sensor at a predetermined size, and capable of detecting magnetism of 50 pT / √ (Hz) or less as the ultra-sensitive magnetic sensor Because it has a magnetic detection unit including a fluxgate sensor, and a PC permalloy shield and aluminum shield that cover the magnetic detection unit as a high-performance magnetic shield, it detects metal foreign objects of fine magnetic materials mixed in the inspection object. can do.

The block diagram which shows the control system of a fine metal detection apparatus. The front view of a fine metal detection apparatus. Sectional drawing in the III-III line of FIG. Sectional drawing in the IV-IV line of FIG. FIG. 5 is a detailed view of a main part in FIG. 4. The perspective view which shows an active shield. Sectional drawing in the VII-VII line of FIG. Sectional drawing in the VIII-VIII line of FIG. Sectional drawing in the IX-IX line of FIG. The partial diagram of the control system in one mode of a fine metal detecting device.

  The details of a fine metal detection device including a high-performance magnetic shield and an ultra-sensitive magnetic sensor according to the present invention will be described with reference to the accompanying drawings as follows.

  FIG. 1 is a configuration diagram showing a control system of a fine metal detection device according to the present invention, and FIG. 2 is a front view showing an internal structure when the device is viewed from the upstream side in the machine direction MD described later, 3 is a sectional view taken along line III-III in FIG. 2, and FIG. 4 is a sectional view taken along line IV-IV in FIG. 2 to 4, MD is a machine direction, VD is a vertical direction perpendicular to the machine direction MD, and CD is a machine direction MD and a cross direction perpendicular to the vertical direction VD (Cross direction). Each is shown. In the present invention, the machine direction MD and the opposite direction may be referred to as the length direction, and the direction from the upper side to the lower side in the vertical direction may be referred to as the magnetic detection direction.

  The fine metal detection apparatus 1 illustrated in FIGS. 1 to 4 detects a metallic foreign object such as iron, nickel, cobalt, and stainless steel contained in the inspection object 2 at room temperature. The inspection object 2 is, for example, a sheet-like aluminum continuum used as an anode of a secondary battery such as a lithium ion battery, a sheet-like copper continuum used as a cathode, or a sheet-like used as a separator. Non-magnetic sheet-like continuum such as a synthetic resin continuum or a composite continuum in which an active material-containing paste is applied to the sheet-like continuum. However, what is subject to metal detection by the fine metal detector 1 is not limited to a continuous body such as the inspected object 2. Even a fluid or a solid placed in an individual container such as a glass bottle can be an object to be inspected in the present invention.

  The fine metal detection device 1 includes a frame 10, a support means 3, a magnetism means 4, a magnetic detection unit 5, an aluminum shield 6 a, a PC permalloy shield 6 b, an active shield 7, and a test coil 17. The power supply 18 and the CPU (control unit) 80 are provided, and the magnetizing means 4 and the magnetic detection unit 5 are arranged in the machine direction MD.

  The frame 10 includes a lower frame 11 and an upper frame 12. As shown in FIGS. 2 and 4, the lower frame 11 extends in a cross direction CD and a first frame member 11a extending in the machine direction MD. The second frame member 11b is attached to both ends of the first frame member 11a, and the top plate 13 is attached to the upper end of the second frame member 11b. Yes.

As shown in FIG. 4, the support means 3 includes a rotating roller 30 constituted by a plurality of rotating rollers 30a, 30b, 30c, 30d, 30e, 30f, 30g, and 30h that cause the inspection object 2 to travel in the machine direction MD. The object 2 to be inspected is fed from a feed roller (not shown) located upstream of the support means 3 and taken up by a take-up roller (not shown) located downstream of the support means 3. . The inspection object 2 is given a required tension between the feeding roller and the take-up roller. A tension roller may be provided between the feeding roller and the take-up roller as necessary.
The rotating rollers 30a to 30h are attached to the top plate 13 via spacers 32b as shown in the drawing, and are rotatable about a rotating shaft 30x (see FIGS. 5 and 9). Each of the rotating rollers 30b, 30d, 30e, and 30g includes a unique height position adjusting unit 32, and the height position adjusting unit 32 can adjust the position in the vertical direction VD. The fine metal detection device 1 also changes the vertical position VD of the rotating rollers 30b, 30c, 30d, and 30e by rotating the dial 32 that is the height position adjusting means, and thereby the tension of the inspection object 2 is increased. Can be adjusted. The dial 32 can be operated manually, or can be automatically operated using a dial drive source 33a connected to a motor or the like for rotating the dial 32. The rotation rollers 30d and 30e of the support means 3 are located upstream and downstream of the magnetic detection unit 5 and keep the distance between the object to be inspected 2 and the flux gate sensor 50 described later at a predetermined size. (See FIG. 5). Specifically, if the inspection object 2 is positioned above the vertical direction VD with the dial 32, the inspection object 2 is held at a detection position in which the distance from the flux gate sensor 50 is maintained at a predetermined dimension. If the inspection object 2 is positioned below the inspection position, the inspection object 2 is placed in a non-detection position where the fluxgate sensor 50 is not affected by the magnetic field of the metal foreign matter. As an example, the support means 3 can run the inspection object 2 at a speed of 30 to 80 m / min.

  The magnetized means 4 includes a support base 40, a first permanent magnet 41 attached to the support base 40, and a second permanent magnet 42 attached to the support base 40 above the first permanent magnet 41. Yes. As an example of the magnetizing means 4, the first permanent magnet 41 is arranged so that its upper end is an N pole, while the second permanent magnet 42 is arranged so that its lower end is an S pole. It always forms a magnetic field from the bottom to the top. When the inspected object 2 enters the magnetizing means 4 and the metallic foreign material of the magnetic material comes between the first permanent magnet 41 and the second permanent magnet 42, the magnetic material of the metallic foreign material is below the vertical direction VD. It is magnetized in the direction of heading and has a remanent magnetism on the downstream side of the magnetizing means 4.

  The magnetic detection part 5 is provided inside the aluminum shield 6a, and details thereof are as described based on FIGS. 5 and 7 to 9 described later. A PC permalloy shield 6b is provided outside the aluminum shield 6a. As an example, a flux gate sensor 50 capable of detecting magnetism of 50 pT / √ (Hz) or less is used in the magnetic detection unit 5.

As shown in FIGS. 1 and 7 to 9, the magnetic detection unit 5 includes individual amplification circuits 51, electronic circuits 52, sensor circuit boards 53, and amplification electronic circuit boards 54 corresponding to the individual fluxgate sensors 50. It has. The sensor circuit board 53 is attached to the upper end portion of the flux gate sensor 50, and is attached to the amplification electronic circuit board 54 via a spacer 53a that adjusts the interval in the machine direction MD. 51, an electronic circuit 52, a sensor circuit board 53, and an amplification electronic circuit board 54 are integrated.
The amplifier circuit 51 amplifies the magnetic signal detected by the fluxgate sensor 50 inside the aluminum shield 6a. The amplification circuit 51 in the illustrated example amplifies the magnetic signal detected by the fluxgate sensor 50 by 5,000 times.
The electronic circuit 52 includes a low pass filter and a high pass filter.
The low-pass filter cuts a frequency equal to or higher than a predetermined first frequency among the magnetic signals detected by the fluxgate sensor 50. In an example of the illustrated electronic circuit 52, the low-pass filter cuts a frequency of 60 Hz or more.
The high-pass filter cuts a frequency that is lower than a predetermined second frequency smaller than the first frequency in the magnetic signal. In an example of the electronic circuit 52 in the illustrated example, the high-pass filter cuts a frequency of 0.1 Hz or less.
As described above, the electronic circuit 52 can extract a signal in a frequency band corresponding to the traveling speed of the inspection object 2 by the support unit 3 from the magnetic signal detected by the magnetic detection unit 5 by the low-pass filter and the high-pass filter. In the illustrated example, a signal between 0.1 Hz and 60 Hz can be extracted. Therefore, if the frequency band of noise is known in advance, the noise can be cut by the electronic circuit 52.
The sensor circuit board 53 is a board on which a sensor circuit 56 for the fluxgate sensor 50 is formed. The amplification electronic circuit board 54 is a board on which the amplification circuit 51 and the electronic circuit 52 are formed.

  The amplification electronic circuit board 54 is attached to the plate member 55 via a spacer 54a. The plate member 55 is attached to the attachment member 16 so that the position of the cross direction CD can be adjusted. In order to adjust the position of the cross direction CD, for example, the mounting member 16 is provided with a slide rail, and the plate member 55 is provided with a protrusion slidably fitted to the slide rail. Due to the movement of the plate member 55 in the cross direction CD, the flux gate sensor 50 can be moved in the cross direction CD. The magnetic detection unit 5 includes a mechanism (not shown) that can move the fluxgate sensor 50 in the vertical direction VD. In the device 1 illustrated in FIG. 7, the sensor mounting members 16 are arranged at a pitch L4 in the machine direction MD. The fluxgate sensors 50 are arranged at a pitch L2 in the machine direction MD. As shown in FIG. 8, the flux gate sensor 50 includes a flux gate sensor 50 located on the upstream side in the machine direction MD and a flux gate sensor 50 adjacent to the flux gate sensor 50 on the downstream side. When viewed from the upstream side in the direction MD, they are arranged at the pitch L3 in the cross direction CD. Further, in FIG. 9, two fluxgate sensors 50 are arranged in the cross direction CD on the most upstream side of the detection unit 5, and the center interval in the cross direction CD of these fluxgate sensors 50 is L1. If the fluxgate sensor 50 is arranged as illustrated in FIGS. 7 and 8, it is possible to detect the residual magnetism due to the metal foreign matter with respect to the entire width of the inspection object 2. Further, when the fluxgate sensor 50 arranged in this way is viewed from the upstream side in the machine direction MD, the upstream fluxgate sensor 50 and the downstream fluxgate sensor 50 partially overlap with each other. 2 can be inspected without gaps in the cross direction CD. When the flux gate sensors 50 are arranged in a line in the cross direction CD, adjacent sensor circuit boards 53 may come into contact with each other and a gap may be formed between the flux gate sensors 50. Residual magnetism of metallic foreign objects cannot be detected.

The inside of the aluminum shield 6a is as shown in FIGS. 7 to 9, wherein FIG. 7 is a view taken along the line VII-VII in FIG. 3, and FIG. 8 is a view taken along the line VIII-VIII in FIG. 9 is a view taken along line IX-IX in FIG.
The aluminum shield 6a is a hollow hexahedron, and has a peripheral wall 6b having four surfaces, an upstream end wall 6c, and a downstream end wall 6d. Such an aluminum shield 6a is an assembly of a plurality of aluminum steel plates 69. A shield space 60a is formed inside the assembly, and the magnetic detector 5 is housed in the space 60a. The plurality of aluminum steel plates 69 are assembled using screws 69a, aluminum square members 69b, and aluminum block members 69c (see FIG. 7). More specifically, the aluminum steel plate 69 is attached to the square member 69b by a screw 69a, and the square member 69b is fixed to each other via a block member 60c. In the aluminum shield 6a assembled in this way, it is possible to efficiently prevent electromagnetic waves that become noise when detecting a metallic foreign object from entering between the steel plates 69 and 69. Instead of such an assembly method, it is possible to assemble the aluminum shield 6a by welding the steel plates 69 and 69 while closing the gap between the steel plates 69, but the welded portion has a porous structure. Therefore, it is not preferable to employ welding instead of screwing. However, local welding of the steel plates 69 and 69 for the purpose of reinforcing the structure of the aluminum shield 6a can be used in combination with screwing. Further, the steel plate 69 can be assembled by fitting it into an aluminum sash instead of screwing it or using it together with screwing. A machined product from an aluminum steel plate can also be used for the aluminum shield 6a. The aluminum shield 6a can prevent radio waves emitted from a mobile phone or the like from entering the shield space 60a.

2 to 5 again, the PC permalloy shield 6b includes a first shield 61 and a second shield 62 formed of a high-permeability PC permalloy steel plate. The first and second shields 61 and 62 form a magnetic shielding space 60 b inside the first shield 61 by double shielding the magnetism. An aluminum shield 6a is disposed in the magnetic shield space 60b, and a flux gate sensor 50, a sensor circuit board 53, an amplification circuit board 54, and the like are disposed inside the aluminum shield 6a.
The first shield 61 is formed with an inlet 63 and an outlet 64 for the inspection object 2 traveling in the machine direction MD. The second shield 62 is formed with an inlet 65 and an outlet 66 for the inspection object 2 traveling in the machine direction MD.

  In the present invention, a high performance magnetic shield in the fine metal detecting device 1 is formed by the PC permalloy shield 6b and the aluminum shield 6a disposed inside thereof.

Further, in FIGS. 2 to 4, the active shield 7 forms an edge of a virtual parallelepiped 72 (see FIG. 6) defined by three sets of mutually parallel virtual planes 101 to 106 (see FIG. 6). Four pipes 74a, 74b, 74c, 74d extending in the machine direction MD, four pipes 74e, 74f, 74g, 74h extending in the cross direction CD, and four pipes 74i, 74j, 74k extending in the vertical direction VD , 74l, and first to sixth active shield circuits 70a to 70f extending into the pipes 74a to 74l, and a three-direction magnetic sensor 71. The pipes 74a to 74l are made of a nonmagnetic material such as copper, aluminum, or plastic.
6 is a perspective view showing an assembled state of the pipes 74a to 74l in the active shield 7. FIG. In FIG. 6, pipes 74e, 74i, 74h, and 74j to which end portions are connected are on the same plane to define a first virtual plane 101, and an annular first active shield circuit 70a is formed inside these pipes. The first coil C1 to be formed is arranged.
Pipes 74f, 74l, 74g, and 74k to which ends are connected define a second virtual plane 102 that is on the same plane and parallel to the first virtual plane 101, and is located inside these pipes 74f, 74l, 74g, and 74k. The second coil C2 forming the annular second active shield circuit 70b is arranged.
The pipes 74a, 74l, 74b, and 74i to which the end portions are connected define the second virtual plane 103 that is on the same plane and orthogonal to the first and second virtual planes 101 and 102, and these pipes 74a, 74l, and 74b. , 74i is provided with a third coil C3 forming an annular third active shield circuit 70c.
Pipes 74d, 74k, 74c, and 74j whose ends are connected to each other define a fourth virtual plane 104 that is on the same plane and parallel to the fourth virtual plane 103, and the inside of these pipes 74d, 74k, 74c, and 74j. Is arranged with a fourth coil C4 forming an annular fourth active shield circuit 70d.
Pipes 74e, 74d, 74f, and 74a whose ends are connected to each other define a fifth virtual plane 105 that is on the same plane and orthogonal to the first to fourth virtual planes 101 to 104, and these pipes 74e, 74d, A fifth coil C5 that forms an annular fifth active shield circuit 70e is disposed inside 74f and 74a.
Furthermore, pipes 74h, 74c, 74g, 74b whose ends are connected to each other define a sixth virtual plane 106 that is on the same plane and parallel to the fifth virtual plane 105, and these pipes 74h, 74c, 74g, 74b. Is arranged with a sixth coil C6 which forms an annular sixth active shield 70f.
A partial enlarged view of the pipe 74j in FIG. 4 shows a part of two conductive wires forming the first coil C1 and the fourth coil C4 arranged inside the pipe 74j. As shown in this partially enlarged view, each of the pipes 74a to 74l accommodates two conductors that form two coils.
2 to 4 again, the three-direction magnetic sensor 71 is disposed inside the virtual parallelepiped 72 and detects the magnitude of magnetism in the direction orthogonal to each of the first to sixth virtual planes 101 to 106. Is. In FIG. 2, the three-direction magnetic sensor 71 is attached to the top of the support bar 71a. In the active shield 7, the CPU 80 causes the first to sixth active shield circuits 70 a, 70 b, 70 c, 70 d, 70 e, and 70 f to generate reverse magnetic fields that cancel the magnetism detected by the three-direction magnetic sensor 71. A voltage is applied to the sixth active shield circuits 70 a, 70 b, 70 c, 70 d, 70 e, and 70 f to form an active shield space 75 inside the virtual parallelepiped 72. As apparent from FIGS. 2 and 3, the magnetic detection unit 5, the aluminum shield 6 a, and the PC permalloy shield 6 b are arranged in the active shield space 75, and the magnetic means is disposed outside the active shield space 75. 4 is arranged. However, the magnetism means 4 can be arranged in the active shield space 75 to implement the present invention.

  As shown in FIG. 1, the test coil 17 is provided at the tip of each fluxgate sensor 50 and is electrically connected to the power source 18. When a test voltage is applied from the power source 18, the test coil 17 causes the flux gate sensor 50 to generate a magnetic field in the magnetic detection direction. Note that the test coils 17 provided in each fluxgate sensor 50 are connected in series, and a circuit (not shown) in which the same current flows is formed in each of the test coils 17.

  The power source 18 is a dial drive that can set the inspection object 2 in the magnetic detection unit 5 to either the inspection position or the non-inspection position by a drive source 31 such as a motor that drives the inspection object 2 and the dial 32. It is electrically connected to the source 33a, the first to sixth active shield circuits 70a, 70b, 70c, 70d, 70e, 70f, and the test coil 17, and a voltage is applied to them based on a command from the CPU 80 To do. The power source 18 is built in the control device 8 in FIG.

In addition to the power supply 18, the control device 8 includes a CPU 80, a memory 81, a display unit 82, an operation unit 83, and an alarm unit 84.
The CPU 80 controls the fine metal detection device 1 in an integrated manner, and the operation thereof is as described later.
The memory 81 is a storage unit, and stores a program for operating the fine metal detection device 1 and a waveform of a signal obtained in the process of detecting the presence of a metal foreign object in the inspection object 2.
The display unit 82 displays a waveform of a signal obtained in the process of detecting the presence of the metal foreign object based on a command from the CPU 80.
The operation unit 83 is a man-machine interface and inputs, for example, a threshold value for issuing an alarm by the alarm unit 84.
In the alarm unit 84, when the magnitude of the signal obtained in the process of detecting the presence of the metal foreign object exceeds the threshold set in the operation unit 83, the alarm lamp is turned on or an alarm sound is generated. .

In the fine metal detector 1 thus formed, the detection of the residual magnetism of the magnetic metal and the detection of the presence of the metal foreign object in the inspection object 2 are performed as follows.
Detection of residual magnetism in the inspection object 2 is as follows. First, the inspected object 2 is caused to travel continuously or intermittently in the machine direction MD by starting the driving source 31 via the CPU 80 or starting a driving source by a power source different from the CPU 80. The magnetic metal foreign matter mixed in the inspection object 2 is magnetized, and the magnetism detecting unit 5 detects the residual magnetism due to the magnetic metal foreign matter, thereby detecting the presence of the metal foreign matter. In the magnetic detection unit 5, the active shield 7, the aluminum shield 6 a, and the PC permalloy shield 6 b are more preferably arranged inside the magnetic shield space 60 a formed inside the aluminum shield 6 a and the PC permalloy shield 6 b. The residual magnetism is detected using the fluxgate sensor 50 capable of detecting a magnetism of 50 pT / √ (Hz) or less inside the magnetic shielding space 60a formed inside the magnetic shield space 60a. As a circuit for amplifying the signal, an amplifier circuit 51 for obtaining a good signal-to-noise ratio (S / N) by preventing unwanted noise from entering through the path between the magnetic detection unit 5 due to stray capacitance and induction. use. The magnetic signal amplified by the amplifier circuit 51 is subjected to signal processing in which only a magnetic signal in a predetermined frequency band is extracted by the electronic circuit 52, and the magnetic signal after the signal processing is stored in the memory 81 by the CPU 80. When the magnetic signal stored in the memory 81 includes a magnetic signal larger than a preset threshold value, the CPU 80 determines that a metal foreign object has been mixed in the inspection object 2, and the alarm unit 84. Will alert you.

The action of the active shield 7 in the process of detecting the weak magnetism due to the metal foreign object is as follows. In the process of detecting the residual magnetism from the metal foreign object, the CPU 80 detects the magnitude of magnetism in the direction orthogonal to each of the first to sixth virtual planes 101 to 106 via the three-direction magnetic sensor 71.
When magnetism is detected in any of the first to sixth virtual planes 101 to 106, the CPU 80 reverses the magnetic field with respect to the active shield circuits 70a to 70f constituting the virtual planes 101 to 106. In order to generate the voltage, a voltage is applied from the power source 18. By such a reverse magnetic field, it is possible to prevent a large external magnetism that causes noise for the detection of a metal foreign object from entering the active shield space 75.

  The test coil 17 and the test voltage for each fluxgate sensor 50 are used as follows. In the process of continuously detecting the residual magnetism from the metal foreign object, a test voltage is applied to the test coil 17 at a predetermined time interval for a fixed time, that is, intermittently for a short time. For example, the test voltage is applied only for 50 to 200 μsec so that a weak test current having a constant waveform is generated in the test coil 17 once every 0.5 to 1 hour. In the test coil 17 to which the test voltage is applied, magnetism characteristic of the weak current is generated in the magnetic detection direction of the fluxgate sensor 50. At this time, if the fluxgate sensor 50 operates normally, the characteristic magnetism can be detected. If the fluxgate sensor 50 cannot detect the characteristic magnetism, a waveform determination device (not shown) in the CPU 80 automatically determines that there is an abnormality in the fluxgate sensor 50 and detects the abnormality. Can be displayed by an electric display means, or an alarm can be issued by the alarm unit 84 to prompt the inspection or replacement of the fluxgate sensor 50. Note that the weak current in the test coil 17 is for causing the test coil 17 to generate a magnetism weaker than the residual magnetism due to the magnetic metal foreign matter. In the present invention, in order to clarify whether or not magnetism due to the test voltage is detected, when the test voltage is applied, the traveling of the inspection object 2 is temporarily stopped or the dial drive source 33a is driven. Accordingly, it is possible to adopt means for moving the inspection object 2 at the detection position to the non-detection position or temporarily separating the inspection object 2 from the fluxgate sensor 50. It is preferably employed when the production speed of the product 2 is not a problem.

According to the fine metal detection device 1 according to the present invention, since the magnetic detection unit 5 including the flux gate sensor 50 capable of detecting magnetism of 50 pT / √ (Hz) or less is provided, the fine metal mixed in the inspection object 2 is provided. It is possible to detect metallic foreign matter of a magnetic material.
In addition, a flux gate sensor 50, an amplifier circuit 51, an electronic circuit 52, and a sensor circuit 56 are provided inside the space 60a with a PC permalloy shield 6b and an aluminum shield 6a that cover the magnetic detection unit 5, and immediately after the magnetism is detected. Since the magnetic signal is amplified, before the magnetic signal is amplified and processed, it is possible to prevent noise from entering and reliably detect the presence of the metal foreign matter.
The magnetic detection unit 5 can reliably detect the presence of the metal foreign object by shielding with the overall active shield 7 for the fine metal detection device 1.

  The present invention is not limited to the embodiment described above. For example, a plurality of flux gate sensors 50 can be provided so as to form a row in the cross direction CD. At that time, the flux gate sensors 50 are to be inspected 2 passing through a gap generated between adjacent flux gate sensors 50. Can be inspected by a fluxgate sensor 50 provided on the downstream side of the row. The high-performance magnetic shield formed by the aluminum shield 6a and the PC permalloy shield 6b and the active shield 7 are preferably used in combination, but the present invention is implemented using only the high-performance magnetic shield. You can also

FIG. 10 is a diagram for explaining an aspect of the fine metal detection device 1, and shows a partial active shield 9 used for a part of the fine metal detection device 1 and a one-position magnetic sensor 99. ing. The active shield 9 can be used in combination with the active shield 7 or in place of the active shield 7. In FIG. 5, an entrance coil 91 and an exit coil 92 for forming the active shield 9 are imaginary lines. It is shown by.
The inlet coil 91 and the outlet coil 92 are provided annularly at either the peripheral edge of the inlet 65 and the outlet 66 in the second shield 62 of the PC permalloy shield 6b or in the vicinity of the peripheral edge. An active shield 9 is formed. A power source 18 for applying a voltage to the coils 91 and 92 is connected to the inlet coil 91 and the outlet coil 92.
The one-position magnetic sensor 99 is provided inside each of the active shield spaces 60b surrounded by the entrance coil 91 and the exit coil 92, respectively. The one-position magnetic sensor 99 is provided for an entrance that detects magnetism that enters the space 60b from the entrance 65, and for an exit that detects magnetism that enters the space 60b from the exit.
In this case, the CPU 80 of the fine metal detection device 1 applies a voltage to the inlet coil 91 and the outlet coil 92 in order to generate a reverse magnetic field that cancels the magnetism detected by the one-position magnetic sensor 99 in the inlet coil 91 and the outlet coil 92. .
According to the fine metal detection device 1 using the active shield 9, the first to sixth active shield circuits 70a to 70f may be unnecessary, and at that time, avoid the complicated configuration of the device 1. Can do. In addition, if the partial active shield 9 and the overall active shield 7 are used in combination, intrusion of magnetic noise can be reliably prevented.
In the illustrated example, the inlet coil 91 and the outlet coil 92 are provided on the periphery of the inlet 65 and the outlet 66 in the second shield 62 of the PC permalloy shield 6b. However, the present invention is not limited to this. A support (not shown) separate from the permalloy shield 6 b may be provided, and the support may be provided with the inlet coil 91 and the outlet coil 92, and may be provided near the periphery of the inlet 65 and the outlet 66.

DESCRIPTION OF SYMBOLS 1 Fine metal detection apparatus 2 Inspected object 3 Support means 4 Magnetization means 5 Magnetic detection part 6a Aluminum shield 6b PC permalloy shield 7 Active shield 9 Active shield 17 Test coil 18 Power supply 50 Flux gate sensor 50 (Ultra high sensitivity magnetic sensor )
51 Amplifier Circuit 52 Electronic Circuit 63 First Entrance (Inlet)
64 First exit (exit)
70a, 70b, 70c, 70d, 70e, 70f First to sixth active shield circuits 71 Three-directional magnetic sensor 72 Virtual parallelepiped 73a, 73b, 73c, 73d, 73e, 73f Virtual plane 80 CPU (control unit)
91 Inlet coil 92 Outlet coil 99 One-position magnetic sensor MD Machine direction CD Crossing direction VD Vertical direction

Claims (9)

Fine metal detection provided with a high-performance magnetic shield and an ultra-sensitive magnetic sensor that magnetizes fine metal foreign matter mixed in the inspection object and detects the presence of the metal foreign matter by detecting residual magnetism of the metal foreign matter In the device
Magnetizing means for magnetizing the metal foreign object in a direction coinciding with the direction of detection of the residual magnetism by the ultrasensitive magnetic sensor opposed to the inspection object;
Support means capable of supporting the object to be inspected after passing through the magnetizing means and maintaining a predetermined distance between the object to be inspected and the ultra-sensitive magnetic sensor;
A magnetic detection unit including a fluxgate sensor capable of detecting magnetism of 50 pT / √ (Hz) or less as the ultra-sensitive magnetic sensor;
PC permalloy shield for magnetic shielding and aluminum shield for high frequency shielding covering the magnetic detection unit as the high performance magnetic shield,
The fine metal detection device comprising:   The fine metal detecting device has a machine direction in which the inspection object travels, a magnetic detection direction orthogonal to the machine direction, and a cross direction orthogonal to the machine direction and the detection direction. 2. The fine metal detection device according to claim 1, wherein the magnetism means and the magnetic detection unit are arranged from upstream to downstream in the direction, and the support means causes the inspection object to travel in the machine direction. As a circuit for amplifying the magnetic signal detected by the magnetic detection unit immediately after the magnetic detection unit, it is possible to prevent unnecessary noise from entering in the path between the magnetic detection unit due to stray capacitance and induction, and good An amplifier circuit capable of obtaining a high signal-to-noise ratio (S / N),
In order to extract a signal in a frequency band corresponding to the traveling speed of the object to be inspected by the support means from the magnetic signal, a low-pass filter that cuts a frequency equal to or higher than a predetermined first frequency, and a predetermined smaller than the first frequency An electronic circuit having a high-pass filter that cuts frequencies below the second frequency of
The fine metal detection device according to claim 1, wherein the high-performance shield also covers the amplification circuit and the electronic circuit.   The magnetic detection unit includes a plurality of the flux gate sensors in the machine direction, and the upstream of the flux gate sensor on the upstream side in the machine direction and the downstream flux gate sensor adjacent to the flux gate sensor. When viewed from the side, the downstream side fluxgate sensor is positioned so that the upstream side fluxgate sensor does not coincide with the downstream side fluxgate sensor so that the upstream side fluxgate sensor does not coincide with the upstream side fluxgate sensor. The fine metal detection device according to claim 1, wherein a fluxgate sensor is biased in the crossing direction.   Each of the fluxgate sensors for detecting the residual magnetism is provided with a test coil for detecting an abnormality of the fluxgate sensor, and each of the test coils is connected in series to each of the test coils. Forming a circuit through which the same current flows, and applying a predetermined test voltage to the circuit, each of the flux gate sensors can detect the same level of magnetism generated by each of the test coils. In the waveform determination device for each detected magnetism, it is determined whether or not the same level of magnetism is detected, and it is determined that there is an abnormality in the fluxgate sensor when the same level of magnetism is not detected. The fine metal detection according to any one of claims 1 to 4, further comprising the test coil capable of being deformed. Location. A power supply that provides a constant waveform for the same test to all of the test coils;
A control unit for controlling the power source,
In the process of continuously detecting the residual magnetism from the metal foreign matter, the control unit intermittently applies the test current that can be determined that the abnormality exists in the fluxgate sensor for a certain period of time. The flux gate sensor is caused to flow only through the test coil to generate the same level of magnetism characteristic of the test current, and to cause the magnetic sensor that is detecting the residual magnetism to detect the same level of magnetism. The fine metal detection device according to claim 5, wherein the presence of the abnormality is automatically determined. Annular first to sixth active shield circuits provided along ridge lines in three sets of mutually parallel virtual planes forming a virtual parallelepiped;
A three-directional magnetic sensor for detecting the magnitude of magnetism in a direction perpendicular to each of the virtual planes inside the virtual parallelepiped;
A power supply for applying a voltage to the first to sixth active shield circuits;
Based on the detection result of the three-direction magnetic sensor, a voltage is applied to the first to sixth active shield circuits in order to cause the first to sixth active shield circuits to generate a reverse magnetic field that cancels the detected magnetism. A control unit;
An active shield space is formed inside the virtual parallelepiped by
The magnetic detection unit, the PC permalloy shield, and the aluminum shield are disposed inside the active shield space, and the magnetizing means is disposed either outside or inside the active shield space. The fine metal detection apparatus in any one of 1-6. An inlet and an outlet for entering and exiting the inspection object formed in the PC permalloy shield and traveling in the machine direction;
An inlet coil and an outlet coil that are provided at either the peripheral edge of the inlet and the outlet of the PC permalloy shield or in the vicinity of the peripheral edge to form an annular active shield circuit;
A power source for applying a voltage to the inlet coil and the outlet coil;
A one-position magnetic sensor that is provided inside a space surrounded by each of the annular active shield circuits and detects a magnet that enters the space from the entrance and a magnet that enters the space from the exit;
A control unit for applying a voltage to the inlet coil and the outlet coil in order to cause the inlet coil and the outlet coil to generate a reverse magnetic field that cancels the detected magnetism based on a detection result of the one-position magnetic sensor;
The fine metal detection device according to any one of claims 2 to 7.   The aluminum shield is an assembly made of at least one of a plurality of aluminum steel plates and a machined product from the aluminum steel plate, and is used so that the material does not fit and penetrate the material. The fine metal detection device according to any one of claims 1 to 8, wherein the fine metal detection device is assembled by at least one assembling means of fastening by screws.

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