JP5421082B2 - Magnetic detection device - Google Patents

Description

  The present invention relates to a magnetic substance detection apparatus, and more particularly to a magnetic substance detection apparatus using a magnetic sensor, particularly a magnetic impedance (MI) sensor.

2. Description of the Related Art A magnetic (metal) detection device using an MI sensor is known. The MI sensor is a magnetic sensor that uses the magneto-impedance effect. The magnetic field strength H of the magnetic material is represented by H = m / 2πr ³ where m is the magnetic quantity of the magnetic material and r is the distance between the MI sensor and the magnetic material. Therefore, the MI sensor can detect a relatively large magnetic material (that is, a relatively large amount of magnetic material) more easily than a relatively small magnetic material (which has a relatively small amount of magnetic material), and is relatively close to the MI sensor. It is easier to detect a magnetic material than a relatively remote magnetic material. In addition, the magnetic field strength H is proportional to the magnetic quantity m, but inversely proportional to the cube of the distance r. Therefore, the MI sensor is less affected by the size of the magnetic body than the MI sensor. Susceptible to the distance between.

  It is desirable that a magnetic body detection apparatus using an MI sensor operates so as to generate a detection signal when a magnetic body having a size to be detected (hereinafter referred to as “target magnetic body”) is detected. That is, it is desirable that the magnetic body detection device operates so as not to generate a detection signal in response to magnetism such as the surrounding environment, and a magnetic body smaller than the size to be detected (hereinafter referred to as “micro magnetic body”). It is desirable to operate so as not to generate a detection signal.

  However, the magnetic body detection device may generate a detection signal in response to magnetism such as the surrounding environment. For example, in the case of a magnetic body detection device that generates a detection signal based on the signal level of the MI sensor, when the MI sensor generates a signal of a predetermined level or more due to magnetism (noise) in the surrounding environment, The magnetic body detection device may generate a detection signal even though there is no magnetic body having a size to be detected.

  The magnetic body detection apparatus for preventing the detection signal from being generated includes a first MI sensor for detecting both a magnetic body having a size to be detected and noise, and a second MI sensor for detecting only noise. Are prepared, a signal obtained by subtracting the signal level of the second MI sensor from the signal level of the first MI sensor is generated, and a detection signal is generated based on this signal (for example, Patent Documents 1 and 2). reference).

JP 2006-71347 A JP 2006-98117 A

  Further, in a magnetic body detection device that generates a detection signal based on a signal level of a magnetic sensor, particularly an MI sensor, the magnetic body detection device may not perform a desired operation depending on the distance between the MI sensor and the magnetic body. .

  First, the magnetic body detection device may generate a detection signal for a minute magnetic body that should not generate a detection signal. Specifically, when the minute magnetic body passes in the immediate vicinity of the MI sensor, the magnetic amount of the minute magnetic body is small but the distance between the minute magnetic body and the MI sensor is small, so that the magnetic field reaching the MI sensor from the minute magnetic body is small. Is relatively large, and the signal level of the MI sensor is increased. In response to the signal level, the magnetic body detection device may generate a detection signal even though the target magnetic body is not present.

  Second, the magnetic body detection device may not generate a detection signal for a target magnetic body that should generate a detection signal. Specifically, when the target magnetic body passes through a location far from the MI sensor, the strength of the magnetic field reaching the MI sensor becomes small, the strength of the magnetic field reaching the MI sensor becomes relatively small, and the signal level of the MI sensor Becomes smaller. In response to the signal level, the magnetic body ejector may not generate a detection signal despite the presence of the target magnetic body.

  When a minute magnetic body that should not generate a detection signal passes through a place far from the MI sensor, the signal level of the MI sensor is small and the magnetic body detection device does not generate a detection signal. Further, when the target magnetic body for generating the detection signal passes near the MI sensor, the signal level of the MI sensor is large, and the magnetic body detection device generates the detection signal.

  Accordingly, the present invention provides a magnetic sensor that uses a magnetic sensor, particularly an MI sensor, that does not generate a detection signal for a minute magnetic body and operates to generate a detection signal for a target magnetic body. Is to provide.

In order to achieve the above object, a magnetic body detection device according to the present invention is a magnetic body detection device that detects a magnetic body that moves in a moving direction, and is a first magnetic sensor that is arranged at intervals in the moving direction. And a second magnetic sensor, and a controller connected to the first magnetic sensor and the second magnetic sensor, and the smallest of the magnetic bodies having a size to be detected is the first magnetic sensor. When the second magnetic sensor comes in front of the sensor, the second magnetic sensor generates a signal larger than a certain level, and the largest of the magnetic bodies smaller than the magnitude to be detected is in front of the first magnetic sensor. The second magnetic sensor is arranged with respect to the first magnetic sensor so that the second magnetic sensor does not generate a signal larger than the predetermined level when the second magnetic sensor comes. Both two magnetic sensors When that caused the larger signal than the predetermined level at the same time, it is characterized by generating the magnetic body detection signal.

  In the magnetic body detection apparatus configured as described above, when the magnetic body (target magnetic body) having a size to be detected comes before the first magnetic sensor, the second magnetic sensor and the target magnetic body Both first magnetic sensors having a distance between and a second magnetic sensor that are shorter than the second magnetic sensor simultaneously generate a signal that is greater than a certain level. In response to this, the controller generates a magnetic substance detection signal. On the other hand, when a magnetic body (small magnetic body) smaller than the size to be detected comes before the first magnetic sensor, the second magnetic sensor is not related to the level of the signal generated by the first magnetic sensor. , A signal larger than the certain level is not generated. In this case, the controller does not generate a magnetic substance detection signal. Thus, the magnetic body detection device operates so as not to generate a detection signal for the minute magnetic body and to generate a detection signal for the target magnetic body.

  In the embodiment of the magnetic body detection apparatus according to the present invention, preferably, the magnetic body detection apparatus further includes a conveyor belt for moving the magnetic body. The first magnetic sensor and the second magnetic sensor may be disposed immediately below the conveyor belt, may be disposed above the conveyor belt, or may be disposed on both.

In order to achieve the above object, a magnetic body detection device according to the present invention is a magnetic body detection device that detects a magnetic body that moves in a moving direction, and is arranged in a line at equal intervals in a direction crossing the moving direction. A plurality of magnetic sensors and a controller connected to the plurality of magnetic sensors, and n pieces of the smallest magnetic material having a size to be detected cross the plurality of magnetic sensors. When the above magnetic sensor generates a signal greater than a certain level and the largest of the magnetic bodies smaller than the size to be detected crosses the plurality of magnetic sensors, there are fewer than n magnetic sensors. The certain level is determined so as not to generate a signal larger than the certain level, and the controller has n or more magnetic sensors that generate a signal larger than the certain level. To come, it is characterized by generating the magnetic body detection signal.

  In the magnetic body detection apparatus configured as described above, when a magnetic body (target magnetic body) having a size to be detected crosses a plurality of magnetic sensors, n or more magnetic sensors output signals larger than a certain level. generate. In this case, the controller generates a magnetic substance detection signal. On the other hand, when a magnetic material (small magnetic material) smaller than the size to be detected crosses a plurality of magnetic sensors, only less than n magnetic sensors generate a signal greater than the certain level. In this case, the controller does not generate a magnetic substance detection signal. Thus, the magnetic body detection device operates so as not to generate a detection signal for the minute magnetic body and to generate a detection signal for the target magnetic body.

  In the embodiment of the magnetic body detection apparatus according to the present invention, preferably, the magnetic body detection apparatus further includes a conveyor belt for moving the magnetic body. The plurality of magnetic sensors may be disposed immediately below the conveyor belt, may be disposed above the conveyor belt, or may be disposed on both.

  As described above, the magnetic body detection device according to the present invention using a magnetic sensor, particularly an MI sensor, can be operated to detect a target magnetic body without detecting a minute magnetic body.

1 is a schematic front view of a magnetic body detection device according to the present invention. 1 is a schematic plan view of a magnetic body detection device according to the present invention. It is a figure which shows the signal level of MI sensor when a micro magnetic body or a target magnetic body passes in front of one MI sensor. It is a figure similar to FIG. 3 which added the 2nd MI sensor. It is a figure which shows the signal level of a some sensor when a target magnetic body crosses a some sensor. It is a figure which shows the signal level of a some sensor when a micro magnetic body crosses a some sensor.

  Hereinafter, an example of an embodiment of a magnetic substance detection device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic front view of a magnetic body detection device according to the present invention. FIG. 2 is a schematic plan view of the magnetic body detection device of FIG.

  As shown in FIGS. 1 and 2, the magnetic substance detection device 1 is in the form of a conveyor, and has a conveyor belt 6 wound around an entrance end roller 2 and an exit end roller 4. The conveyor belt 6 has a flat conveyance section 6a and is driven in the direction A by a motor, a speed reducer, a transmission device or the like (not shown). The material of the conveyor belt 6 is preferably a material that does not contain a magnetic material.

  The magnetic body detection device 1 has an upstream MI sensor 10 and a downstream MI sensor 12 below the transport section 6 a of the conveyor belt 6. In FIG. 1, one upstream side MI sensor 10 and one downstream side MI sensor 12 are shown. In addition, the magnetic body detection device 1 includes an upstream MI sensor 14 and a downstream MI sensor 16 above the transport unit 6 a of the conveyor belt 6. In FIG. 1, only one upstream MI sensor 14 and one downstream MI sensor 16 are shown, but a plurality of downstream MI sensors 16 may be provided as shown in FIG. 2. These sensors 10, 12, 14, and 16 are attached to the frame (not shown) of the magnetic body detection device 1 through, for example, a support bracket (not shown).

  The MI sensors 10, 12, 14, and 16 are preferably the same type of MI sensor, and the detection range thereof is, for example, 0 to 25 mm. The MI sensors 10 and 12 arranged on the lower side of the conveyor belt 6 are preferably arranged as close to the conveyor belt 6 as possible in order to widen the detection range above the conveyor 6a of the conveyor belt 6 as much as possible. . When the detection range of the MI sensors 10 and 12 is 0 to 25 mm, an alternate long and short dash line B in FIG. 1 indicates a position 25 mm from the detection surfaces 10 a and 12 a of the MI sensors 10 and 12. Moreover, it is preferable that MI sensor 14 and 16 arrange | positioned above the conveyor belt 6 arrange | positions the detection surfaces 14a and 16a in the place of 25 mm upwards from the place of the dashed-dotted line B. FIG. By arranging in this way, it is possible to detect the target magnetic body ML contained in the detection object P up to a height of 25 mm.

  The plurality of downstream side MI sensors 16 are preferably arranged such that their detection surfaces 16a are as close as possible in the direction crossing the moving direction A. The plurality of MI sensors 16 are preferably arranged in a line at equal intervals. The pitch of the MI sensors 16 is 11 mm, for example. In the present embodiment, the plurality of MI sensors 16 are arranged obliquely with respect to the movement direction A, but may be arranged perpendicular to the movement direction A.

  The target magnetic material to generate the detection signal is, for example, a metal scrubber or a thin piece of a blade, for example, a piece of iron having a dimension of 0.8 mm or more, preferably 0.5 mm or more. The fine magnetic material that should not generate the detection signal is, for example, soil, sand, iron ore, etc. that are magnetized in nature, and is, for example, a dust-like material having a size smaller than 0.3 mm.

  The magnetic body detection device 1 further includes a controller 20 to which MI sensors 10, 12, 14, and 16 are connected. The controller 20 preferably has a signal processing device and an arithmetic device. Further, an alarm and display device 22 is connected to the controller 20.

  Next, the characteristics of the MI sensor focused on by the inventors of the present invention will be described. FIG. 3 is a diagram illustrating a signal level of the MI sensor when a minute magnetic body or a target magnetic body passes in front of one MI sensor. In FIG. 3, the horizontal axis is time, and the position where the MI sensor 10 is described is when the minute magnetic body or target magnetic body passes in front of (upper) the MI sensor 10. The horizontal axis can also be considered as the distance from the MI sensor 10 when the minute magnetic body or the target magnetic body passes in front of (above) the MI sensor 10, and in the present invention, it should be considered as such. Further, a line 3a shows a case where the minute magnetic body passes through a place close to the MI sensor, and a line 3b shows a case where the target magnetic body passes a place far from the MI sensor.

  When the threshold value of the signal level of the MI sensor is 3s1 as in the conventional operation method, the magnetic body detection device 1 generates detection signals for both the target magnetic body and the minute magnetic body. When the threshold value is increased and set to 3 s 2, a detection signal is not generated for the target magnetic body, but a detection signal is generated for the minute magnetic body. These operations are not desirable operations of the magnetic substance detection device 1.

  The inventor of the present application indicates that the signal level indicated by the line 3a is large only near the MI sensor 10 and rapidly decreases as the distance from the MI sensor decreases, whereas the signal level indicated by the line 3b is not only near the MI sensor 10. Attention was paid to the fact that a certain size was maintained even at a certain distance from the MI sensor 10. That is, it was noted that the magnetic field reached by the magnetic material differs between the case where the minute magnetic material passes just near the MI sensor and the case where the target magnetic material passes far from the MI sensor. The present invention is an invention that can be made by utilizing this fact.

  Next, a first operation example of the magnetic body detection device 1 according to the present invention will be described. FIG. 4 is a view similar to FIG. 3 in which a second MI sensor is added. The horizontal axis in FIG. 4 is the distance from the MI sensor 10 when the minute magnetic body or the target magnetic body passes in front of the MI sensor 10. A line 4a shows a case where the minute magnetic body passes through a position close to the MI sensor, and a line 4b shows a case where the target magnetic body passes a place far from the MI sensor.

  The second MI sensor 12 is arranged at a certain distance L from the first MI sensor 10. Specifically, the second MI sensor 12 generates a signal larger than a certain level 4 s when the target magnetic body comes in front of (above) the first MI sensor 10, and the minute magnetic body is the first magnetic body. So that the second MI sensor 12 does not generate a signal larger than a certain level 4 s when the second MI sensor 12 comes before (above) the second MI sensor 10. Be placed.

  In addition, the controller 20 is configured to generate a magnetic body detection signal when both the first MI sensor 10 and the second MI sensor 12 simultaneously generate a signal that is greater than a certain level 4 s.

  The detection object P or the minute magnetic body MS including the target magnetic body ML is moved in the direction A.

  When the target magnetic body ML passes far from the inspection surface 10a of the upstream (first) MI sensor 10 (for example, 25 mm), the target magnetic body ML is in front of the upstream MI sensor 10 (upper ), The signal level of the upstream MI sensor 10 and the signal level of the downstream (second) MI sensor 12 are both greater than the threshold value 4s (see line 4b). In this case, the controller 20 generates a magnetic substance detection signal.

  Further, when the target magnetic body ML passes close to the inspection surface 10a of the upstream MI sensor 10 (for example, 1 mm), the target magnetic body ML comes to the front (upper) of the upstream MI sensor 10. When this occurs, the signal level of the upstream MI sensor 10 and the signal level of the downstream MI sensor 12 are both greater than in the above case, and thus greater than the threshold value 4s. In this case, the controller 20 generates a magnetic substance detection signal.

  On the other hand, when the minute magnetic body MS passes near (for example, 1 mm) from the inspection surface 10a of the upstream MI sensor 10, the minute magnetic body MS comes to the front (upper) of the upstream MI sensor 10. In this case, the signal level of the upstream MI sensor 10 is higher than the threshold value 4s, but the signal level of the downstream MI sensor 12 is lower than the threshold value 4s (see line 4a). In this case, the controller 20 does not generate a magnetic body detection signal.

  Further, when the minute magnetic body MS passes through a location far from the inspection surface of the upstream MI sensor 10 (for example, 25 mm), when the minute magnetic body MS comes before the upstream MI sensor 10, The signal level of the MI sensor 10 on the side and the signal level of the MI sensor 12 on the downstream side are smaller than the above case, and the signal level of the MI sensor 12 on the downstream side is smaller than the threshold value 4s. In this case, the controller 20 does not generate a magnetic body detection signal.

  Thus, the magnetic body detection apparatus 1 operates so as to generate a detection signal for the target magnetic body ML without generating a detection signal for the minute magnetic body MS. The alarm and display device 22 may issue an alarm or display an alarm based on a detection signal generated by the controller 20.

  In the first operation example, by changing the distance between the first MI sensor 10 and the second MI sensor 12, it is possible to easily change the size for distributing the target magnetic body and the minute magnetic body.

  Next, a second operation example of the magnetic body detection device according to the present invention will be described. 5 and 6 are diagrams showing signal levels of the plurality of sensors when the target magnetic body and the minute magnetic body cross the plurality of sensors, respectively. The horizontal axis in FIGS. 5 and 6 is time. The positions where the MI sensors 16a, 16b, 16c, and 16d are described are when the minute magnetic body or the target magnetic body passes in front of (below) the MI sensors 16a, 16b, 16c, and 16d, respectively. Further, lines 5a, 5b, 5c, and 5d in FIG. 5 indicate cases where the target magnetic body ML passes far away from the MI sensors 16a, 16b, 16c, and 16d, respectively. Further, lines 6a, 6b, 6c, and 6d in FIG. 6 respectively show the cases where the minute magnetic material passes through the immediate vicinity of the MI sensors 16a, 16b, 16c, and 16d.

  When the target magnetic body crosses the plurality of MI sensors 16, n (for example, three) or more MI sensors 16 generate a signal larger than a certain level 5s, and the micro magnetic body crosses the plurality of MI sensors. Sometimes, a constant level 5s is determined such that fewer than n (eg, 3) MI sensors generate a signal greater than the constant level 5s.

  The controller 20 is configured to generate a magnetic substance detection signal when there are n (for example, three) or more MI sensors 16 that generate a signal greater than a certain level 5 s.

  The detection object P or the minute magnetic body MS including the target magnetic body ML is moved in the direction A.

  When the target magnetic body ML passes far from the inspection surface 16a of the plurality of MI sensors 16 (for example, 25 mm), the signal levels of the MI sensors 16a, 16b, and 16c become higher than the threshold value 5s (FIG. 5). In this case, since n is 3 or more, the controller 20 generates a magnetic body detection signal. The timing at which the signal level of each MI sensor 16 becomes larger than the threshold value 5s may be simultaneous or different.

  Further, when the target magnetic body ML passes close to (for example, 1 mm) from the inspection surfaces 16a of the plurality of MI sensors 16, the MI sensor 16 whose signal level is larger than the threshold value 5s is as described above. More than. Also in this case, the controller 20 generates a magnetic body detection signal.

  On the other hand, when the minute magnetic body MS passes close to the inspection surface 16a of the plurality of MI sensors 16 (for example, 1 mm), only the signal level of the MI sensor 16a becomes larger than the threshold value 5s (FIG. 6). reference). In this case, since n is smaller than 3, the controller 20 does not generate a magnetic body detection signal.

  Further, when the minute magnetic bodies MS pass through a location far from the inspection surfaces 16a of the plurality of MI sensors 16 (for example, 25 mm), when the plurality of minute magnetic bodies MS come in front of the upstream MI sensor 10. The MI sensor 16 whose signal level is higher than the threshold value 5s is smaller than in the above case. Also in this case, the controller 20 does not generate a magnetic substance detection signal.

  Thus, the magnetic body detection device operates to generate a detection signal for the target magnetic body without generating a detection signal for the minute magnetic body. The alarm and display device may issue an alarm or display an alarm according to a detection signal generated by the controller 20.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims. Needless to say, these are also included within the scope of the present invention.

  In the first operation example, the first MI sensor is the lower upstream MI sensor 10 of the conveyor belt 6, and the second MI sensor is the lower downstream MI sensor 12 of the conveyor belt 6. Although described, on the contrary, the first MI sensor may be the downstream MI sensor 12 and the second MI sensor may be the upstream MI sensor 10. Further, the first MI sensor and the second MI sensor may be the MI sensors 14 and 16 on the upper side of the conveyor belt 6.

  In the first operation example, two MI sensors are used, but three or more MI sensors are spaced apart in the movement direction A, and the controller 20 has all these MI sensors simultaneously greater than a certain level. When the signal is generated, a magnetic substance detection signal may be generated.

  In the second operation example, the plurality of MI sensors are described as the downstream MI sensor 16 on the conveyor belt 6, but a plurality of other MI sensors 10, 12, and 14 are provided, and the plurality of MI sensors are arranged. It may be configured.

  Moreover, in the said embodiment, although MI sensor 10, 12, 14, 16 was arrange | positioned above or the downward direction of the conveyor belt 6, you may arrange | position to a side.

DESCRIPTION OF SYMBOLS 1 Magnetic body detection apparatus 6 Conveyor belt 10 Upstream side MI sensor (1st MI sensor)
12 Downstream MI sensor (second MI sensor)
14 Upstream MI sensor (first MI sensor)
16 Downstream MI sensor (second MI sensor, multiple MI sensors)
20 Controller A Movement direction ML Target magnetic body (magnetic body having a size to be detected)
MS Magnetic material smaller than size to be detected 4s Constant level 5s Constant level

Claims (9)

A magnetic body detection device for detecting a magnetic body moving in a moving direction,
A first magnetic sensor and a second magnetic sensor arranged at intervals in the moving direction;
A controller connected to the first magnetic sensor and the second magnetic sensor,
The second magnetic sensor generates a signal larger than a certain level when the smallest of the magnetic bodies having the magnitude to be detected comes before the first magnetic sensor, and the magnitude to be detected So that the second magnetic sensor does not generate a signal greater than the certain level when the largest of the smaller magnetic bodies comes before the first magnetic sensor. One magnetic sensor,
The controller generates a magnetic substance detection signal when both the first magnetic sensor and the second magnetic sensor simultaneously generate a signal larger than the predetermined level.   The magnetic body detection device according to claim 1, further comprising a conveyor belt for moving the magnetic body.   The magnetic body detection device according to claim 2, wherein the first magnetic sensor and the second magnetic sensor are disposed immediately below the conveyor belt.   4. The magnetic body detection device according to claim 2, wherein the first magnetic sensor and the second magnetic sensor are disposed above the conveyor belt. 5. A magnetic body detection device for detecting a magnetic body moving in a moving direction,
A plurality of magnetic sensors arranged in a line at equal intervals in a direction crossing the moving direction;
A controller connected to the plurality of magnetic sensors;
When the smallest of the magnetic bodies having a size to be detected crosses a plurality of magnetic sensors, n or more magnetic sensors generate a signal that is greater than a certain level, and are larger than the size to be detected. The constant level is determined such that when the largest of the small magnetic bodies crosses the plurality of magnetic sensors, fewer than n magnetic sensors generate a signal greater than the constant level;
The controller generates a magnetic substance detection signal when there are n or more magnetic sensors that generate a signal larger than the predetermined level.   The magnetic body detection device according to claim 5, further comprising a conveyor belt for moving the magnetic body.   The magnetic body detection device according to claim 6, wherein the plurality of magnetic sensors are arranged immediately below the conveyor belt.   The magnetic substance detection device according to claim 6, wherein the plurality of magnetic sensors are disposed above the conveyor belt.   The magnetic body detection device according to claim 1, wherein the magnetic sensor is an MI sensor.

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