JP2014203396A - Magnetic quality discrimination apparatus, and magnetic quality discrimination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate a plurality of sorts of magnetic substances having respectively different coercive forces.SOLUTION: A magnetic quality discrimination apparatus for detecting and discriminating magnetic quality of a magnetic substance contained in a paper sheet conveyed on a conveying path, comprises: a magnetism detection unit for generating a bias magnetic field defining a direction forming a predetermined angle with a conveying surface of the paper sheet as a magnetic field direction on the conveying path and detecting a magnetic quantity of the magnetic substance by a change in the bias magnetic field; and a magnetization unit arranged on the upstream side in the conveying direction as compared with the magnetism detection unit and capable of magnetizing the magnetic substance by generating a magnetization-magnetic field defining a direction different from the magnetic field direction of the bias magnetic field as a magnetic field direction on the conveying path. On a magnetism detection position by the magnetism detection unit, a low coersive force magnetic substance whose coersive force is smaller than a predetermined coersive force and another magnetic substance whose coersive force is larger than the predetermined coersive force are magnetized in respectively different magnetization directions by the magnetization-magnetic field and the bias magnetic field.

Description

  The present invention relates to a magnetic quality discriminating apparatus and a magnetic quality discriminating method for detecting the magnetism of a paper sheet, and more particularly to a magnetic quality discriminating apparatus and a magnetic quality discriminating method capable of discriminating a plurality of types of magnetic bodies having different coercive forces. .

  Conventionally, from the viewpoint of preventing forgery, magnetic ink containing a magnetic material is used for printing paper sheets such as checks and gift certificates. Security technology using magnetism is becoming more sophisticated year by year, and in recent paper sheets, a plurality of types of magnetic materials having different magnetic characteristics may be included in one paper sheet. In order to perform such authenticity determination of paper sheets, it is necessary to determine each magnetic body contained in the paper sheets.

  As an apparatus for discriminating a plurality of types of magnetic bodies contained in paper sheets, for example, Patent Document 1 discloses an apparatus for discriminating magnetic bodies having different coercive forces. In this apparatus, a magnetic material having a high coercive force and a magnetic material having a low coercive force are magnetized in the same magnetization direction by a first magnet having a high magnetic force, and then a detection signal based on the magnetism of both magnetic materials is obtained by a first sensor. Thereafter, the magnetization direction of the low coercivity magnetic material is changed by the low magnetism second magnet, and then a detection signal based only on the magnetism of the high coercivity magnetic material is obtained by the second sensor. The difference between the detection signal from the first sensor obtained from the high coercivity magnetic material and the low coercivity magnetic material and the detection signal from the second sensor obtained from the high coercivity magnetic material is the difference between the low coercivity magnetism. A detection signal obtained only from the body is obtained.

US Patent Application Publication No. 2010/0327062

  However, according to the above-described prior art, two magnets with high magnetic force and low magnetic force and two magnetic sensors are required, so that there is a problem that the number of parts increases and the manufacturing cost increases. There is also a problem that the structure is complicated and the size of the magnetic quality discrimination device is increased.

  The present invention has been made to solve the above-described problems caused by the prior art, and can realize a magnetic quality discrimination device capable of discriminating a plurality of types of magnetic bodies having different coercive forces while realizing downsizing of the device. An object is to provide a magnetic quality discrimination method.

  In order to solve the above-described problems and achieve the object, the present invention is a magnetic quality discrimination device that detects and discriminates the magnetic quality of a magnetic material contained in a paper sheet conveyed on a conveyance path, A magnetic detection unit that detects a magnetic quantity of the magnetic body by generating a bias magnetic field on the transport path, the direction of which forms a predetermined angle with the transport surface of the paper sheet, on the transport path and detecting a change in the bias magnetic field And magnetizing the magnetic body by generating a magnetizing magnetic field on the transport path that is disposed upstream of the magnetic detection unit in the transport direction and having a magnetic field direction different from the magnetic field direction of the bias magnetic field. A low coercivity magnetic body having a coercive force smaller than a predetermined coercive force and a coercive force greater than the predetermined coercive force at the magnetic detection position by the magnetic detection unit. Characterized by magnetizing heard another a magnetic body in a different magnetization directions.

  Further, the present invention is the above invention, wherein the magnetic field strength of the magnetizing magnetic field is set to a magnetic field strength that magnetizes a magnetic material having the largest coercive force among the magnetic materials to be discriminated in a saturated magnetization state, The magnetic field strength of the bias magnetic field is set to a magnetic field strength that magnetizes the low coercivity magnetic material to be discriminated into a saturated magnetization state and a magnetic field strength that does not magnetize the other magnetic material into a saturated magnetization state. To do.

  Further, the present invention is the above invention, wherein the magnetic field strength of the bias magnetic field is set to 1.5 times or more of the coercive force of the magnetic material having the largest coercive force among the objects to be discriminated in the above invention. Is set to be not more than twice the coercivity of the magnetic body having the minimum coercivity among the high coercivity magnetic bodies to be discriminated.

  In the present invention, the magnetic material transport direction is set to 0 degree, the magnetic field direction of the bias magnetic field is set to 30 to 60 degrees or 120 to 150 degrees, and the magnetic field direction of the magnetizing magnetic field is set to 80 degrees. It is set to an angle range excluding -100 degrees, or the magnetic field direction of the bias magnetic field is set to -30 to -60 degrees or -120 to -150 degrees, and the magnetic field direction of the magnetizing magnetic field is 80 to 100 degrees. It is characterized in that it is set in an angle range excluding.

  The present invention is characterized in that, in the above-described invention, the magnetic detection unit determines a coercive force of the magnetic body based on a waveform shape of a detection signal obtained by detecting the magnetic body.

  According to the present invention, in the above invention, when the detection signal for detecting the magnetic body shows a waveform that is substantially symmetrical with respect to the peak position, the magnetic body is determined to be a low coercivity magnetic body. Features.

  The present invention is also a magnetic quality discrimination method for detecting and discriminating the magnetic quality of a magnetic material contained in a paper sheet transported on a transport path, wherein the direction forms a predetermined angle with the transport surface of the paper sheet A magnetic field detection step for detecting a magnetic amount of the magnetic body by detecting a change in the bias magnetic field by generating a bias magnetic field having a magnetic field direction on the transport path and detecting the magnetic amount in the magnetic amount detection step A magnetizing step of magnetizing the magnetic body by generating a magnetizing magnetic field on the transport path with a direction different from the magnetic field direction of the bias magnetic field on the upstream side in the transport direction from the position to be When detecting the amount of magnetism in the magnetism detection step, a low coercivity magnetic body having a coercive force smaller than a predetermined coercive force and other magnets having a coercive force larger than the predetermined coercive force by the magnetizing magnetic field and the bias magnetic field. Different magnetization direction from the body And characterized in that the magnetization.

  According to the present invention, a magnetic quantity detection type that generates a bias magnetic field in a magnetic field direction that forms a predetermined angle with a transport surface on which a paper sheet including a magnetic material is transported and detects magnetism based on a change in the bias magnetic field. When the magnetic detection unit detects a magnetic field in a direction different from the magnetic field direction of the bias magnetic field on the upstream side in the conveyance direction, the magnetization direction of the magnetic material varies depending on the coercive force when the magnetic detection unit detects the magnetic field. Therefore, each magnetic body can be distinguished by obtaining different detection waveforms according to the coercive force of the magnetic body.

FIG. 1 is a diagram for explaining a magnetic quality discrimination method performed by the magnetic quality discrimination apparatus according to the present embodiment. FIG. 2 is a diagram for explaining the magnetic field strengths of the magnetizing magnetic field and the bias magnetic field. FIG. 3 is a diagram for explaining the magnetization state at the time of magnetic detection of the magnetic material. FIG. 4 is a diagram for explaining the relationship between the magnetization state and the detection signal from the magnetic sensor. FIG. 5 is a diagram for explaining the detection signal of the magnetic material obtained by the magnetic quality discrimination device. FIG. 6 is a diagram for explaining a magnetic quality discriminating apparatus in which the magnetic field direction of the magnetizing magnetic field is different from the magnetic field direction of the bias magnetic field. FIG. 7 is a diagram for explaining the magnetic field direction of the magnetizing magnetic field when the magnetic material to be discriminated by the magnetic quality discriminating apparatus shown in FIG. 6 is different. FIG. 8 is a diagram for explaining a magnetic quality discrimination method performed by a magnetic material discrimination device for reverse conveyance. FIG. 9 is a diagram for explaining a magnetic detection signal obtained by the magnetic quality discrimination device for reverse conveyance.

  Exemplary embodiments of a magnetic quality discrimination device and a magnetic quality discrimination method according to the present invention will be explained below in detail with reference to the accompanying drawings. The magnetic quality discriminating apparatus according to the present embodiment has a function of discriminating the type of magnetic material by detecting magnetism caused by various magnetic materials used in paper sheets such as checks, gift certificates, and securities. The magnetic quality determination device is used, for example, in a paper sheet processing apparatus to determine the type of a magnetic material contained in a paper sheet and determine whether it is a true paper sheet.

  The magnetic quality determination apparatus according to the present embodiment can determine whether the magnetic body is a high coercivity magnetic body, a medium coercivity magnetic body, or a low coercivity magnetic body from a signal detected from the magnetic body. The magnetic bodies to be discriminated are a high coercivity magnetic body, a medium coercivity magnetic body, and a low coercivity magnetic body in descending order of coercivity. The high coercivity magnetic body, the medium coercivity magnetic body, and the low coercivity magnetic body are the ratio of the coercivity between the high coercivity magnetic body and the medium coercivity magnetic body, and the coercivity magnetic body and the low coercivity magnetic body. The magnetic force ratio is 2 times or more, but the coercive force ratio is preferably 10 times or more. Specifically, for example, the magnetic quality discriminating apparatus 1 discriminates a 50 Oe magnetic body as a low coercivity magnetic body, a 300 Oe magnetic body as a medium coercivity magnetic body, and a 3000 Oe magnetic body as a high coercivity magnetic body. Hereinafter, each magnetic body is described as a low coercivity magnetic body, a medium coercivity magnetic body, and a high coercivity magnetic body.

  FIG. 1 is a schematic diagram for explaining a magnetic quality discrimination method by the magnetic quality discrimination apparatus 1 according to the present embodiment. FIG. 1B shows an outline of the magnetic quality discriminating apparatus 1, and FIG. 1A shows the magnetization states of three kinds of magnetic bodies having different coercive forces.

  As shown in FIG. 1B, the magnetic quality determination device 1 is included in a magnetizing unit 3 for magnetizing a magnetic material included in a paper sheet 100 conveyed above the device, and the paper sheet 100. And a magnetic detection unit 2 for detecting the magnetism of the magnetic body.

  The paper sheet 100 is transported in the direction of the arrow 400 shown in FIG. 1B by a transport mechanism (not shown). The magnetic quality discriminating apparatus 1 is installed below the transport path. In the magnetic quality discriminating apparatus 1, the magnetizing unit 3 is arranged upstream of the magnetic detection unit 2 in the transport direction. The magnetic material included in the paper sheet 100 is magnetized when passing over the magnetizing unit 3. Then, after that, the paper sheet 100 is further conveyed, a signal for detecting the magnetic material is acquired when passing over the magnetic detection unit 2, and the type of the magnetic material is determined from the obtained detection signal.

  The magnetizing unit 3 includes a magnetizing magnet 20 and generates a magnetizing magnetic field so that the direction of the magnetic field is the direction indicated by the broken line arrow in FIG. The magnetizing magnetic field has a magnetic field strength that magnetizes all of the magnetic materials to be discriminated in a saturated magnetization state. Specifically, in order to magnetize the high coercivity magnetic body having the maximum coercive force among the magnetic bodies to be discriminated into the saturation magnetization state, the magnetic field strength of the magnetization magnetic field is set to 1 of the coercivity of the high coercivity magnetic body. .5 times or more. However, the magnetic field strength of the magnetizing magnetic field is preferably at least three times the coercivity of the high coercivity magnetic body.

  If the magnetization direction of each magnetic body having a different coercive force can be made different when detecting the magnetic body, it is not necessary to magnetize the high coercivity magnetic body in a completely saturated magnetization state, and a state close to the saturation magnetization state. What is necessary is just to magnetize. Details will be described later.

  The magnetic detection unit 2 includes a bias magnet 30 for generating a bias magnetic field, and a magnetic sensor 10 that detects a magnetic material passing through the bias magnetic field and outputs a signal. The bias magnet 30 generates a bias magnetic field around it as shown by a broken line arrow in FIG. The magnetic detection unit 2 is characterized in that the magnetic sensor 10 is disposed in an inclined state so as to form an angle with a conveyance surface (XY plane) on which the paper sheet 100 is conveyed. With this configuration, the magnetic sensor 10 outputs a detection signal corresponding to the amount of magnetism of the magnetic material. In the present embodiment, the magnetic sensor 10 includes one magnetic detection element. However, the magnetic sensor 10 may include two magnetic detection elements. The magnetic sensor 10 is installed so as to detect the amount of change in the bias magnetic field that fluctuates in the vertical direction in FIG. For example, a magnetoresistive element is used as the magnetic detection element, a change in resistance value of the magnetoresistive element is output as a change in voltage value, and this voltage value is used as a detection signal for the magnetic material. Since the configuration, function, and operation of such a magnetic quantity detection type magnetic detection unit 2 are disclosed in, for example, Japanese Patent No. 4894040, detailed description thereof is omitted.

  The magnetic field strength of the bias magnetic field generated by the magnetic detection unit 2 is also set according to the coercive force of the magnetic material to be determined, similarly to the magnetic field strength of the magnetizing magnetic field. FIG. 2 schematically shows saturation magnetization curves (BH curves) of three types of magnetic materials, ie, a low coercive force magnetic material, a medium coercive force magnetic material, and a high coercive force magnetic material, which are to be determined by the magnetic quality determination device 1. It is shown. The magnetic field strength of the bias magnetic field is between the coercive force 602 of the medium coercive force magnetic material and the coercive force 603 of the high coercive force magnetic material, while the low coercive force magnetic material is magnetized in a saturated magnetization state. It is set so as not to be magnetized in the saturation magnetization state. For example, it is set to be 1.5 times the coercive force 602 of the medium coercive force magnetic body. The magnetic field strength of the magnetizing magnetic field by the magnetizing unit 3 described above corresponds to the point 601 in FIG.

  Next, a method for discriminating each of the high coercive force magnetic material, the medium coercive force magnetic material, and the low coercive force magnetic material by the magnetic quality determination device 1 shown in FIG. 1B will be described. Hereinafter, the direction of the magnetic field will be described with reference to arrows and angles in the drawing. As for the angle, as shown in the right diagram of FIG. 1A, the positive Y-axis direction that coincides with the transport direction 400 is 0 degree, the positive Z-axis direction above the transport path is 90 degrees, and the reverse direction of the transport direction 400 The Y-axis negative direction is expressed as 180 degrees. Similarly, the positive Y-axis direction is 0 degree, the negative Z-axis direction below the transport path is -90 degrees, and the negative Y-axis direction is -180 degrees.

  The magnetic field strength of the magnetizing magnetic field by the magnetizing unit 3 is, for example, a high coercive force magnetic body at a position P1 on the transport path corresponding to the S pole side and transport direction side edge of the magnetized magnet 20 shown in FIG. The coercive force (3000 Oe) is 1.5 times as strong (4500 G). Further, for example, the magnetic field intensity of the bias magnetic field in the magnetic detection unit 2 is 1.5 at the coercivity (300 Oe) of the medium coercivity magnetic body at the position P4 on the conveyance path where the magnetic sensor 10 detects the magnetism of each magnetic body. It is assumed that it is double (450G).

  At the position P4 where the magnetic sensor 10 detects the magnetism of the magnetic material, the magnetic field direction 302 of the bias magnetic field is set between 30 and 60 degrees. The magnetic field direction 201 of the magnetizing magnetic field at the position P1 is set based on the coercive force of the magnetic body to be discriminated. For example, when the high coercive magnetic body is to be discriminated, the range is from −100 to −170 degrees. It is set to be inside. In the following description, it is assumed that the magnetic field direction at the position P1 is −160 degrees.

  When the magnetic material included in the paper sheet 100 is a high coercive force magnetic material (3000 Oe), the magnetic field strength (4500 G) of the magnetizing magnetic field is strong when the magnetic material is conveyed in the conveying direction 400 above the magnetizing unit 3. Therefore, when passing through the position P1 shown in FIG. 1B, it is magnetized to a saturation magnetization state or a state close to the saturation magnetization state. At this time, as shown in FIG. 1A, the magnetization direction 501a of the high coercive force magnetic body is the same direction (−160 degrees) as the magnetic field direction 201 of the magnetization magnetic field at the position P1. The high coercive force magnetic body is in a saturation magnetization state when the magnetization direction is between −150 and −170 degrees.

  The paper sheet 100 passes through the position P1 shown in FIG. 1B and is further transported in the transport direction 400. However, since the magnetic field strength of the magnetizing magnetic field gradually weakens, the paper sheet 100 is not affected by this. For this reason, the magnetization state of the high coercive force magnetic body does not change, and the magnetization direction 502a of the high coercivity magnetic body when passing through the position P2 is a direction in which the magnetization direction 501a at the magnetization position P1 is maintained.

  Even if the paper sheet 100 is further conveyed and enters the bias magnetic field, the magnetic field strength (450G) of the bias magnetic field is affected by weakness of 1/6 or less of the coercive force (3000 Oe) of the high coercive magnetic body. Absent. For this reason, the magnetization direction 503a when passing through the position P3 and the magnetization direction 504a when passing through the position P4 are also directions in which the same magnetization direction 501a (−160 degrees) as that during magnetization is maintained.

  When the magnetic material included in the paper sheet 100 is a medium coercive force magnetic material, as shown in FIG. 1B, when the magnetic material is conveyed in the conveying direction 400 above the magnetizing unit 3, the high coercive force magnetic property is obtained. As in the case of the body, it is magnetized to the saturation magnetization state at the position P1. At this time, the magnetization direction 501b of the medium coercivity magnetic body is the same as the magnetic field direction 201 of the magnetization magnetic field at the position P1, as in the case of the high coercivity magnetic body. However, since the coercive force of the medium coercive magnetic material is smaller than that of the high coercive force magnetic material, it is continuously influenced by the magnetizing magnetic field while being transported in the transporting direction 400, and the magnetization direction is in the direction of the magnetizing magnetic field. Will change accordingly. When passing through the position P2, the magnetization direction 502b of the medium coercive force magnetic body is the same direction (around 180 degrees) as the magnetic field direction 202 of the magnetization magnetic field. Further, when the magnetic field is conveyed, the magnetic field strength is attenuated while the magnetic field direction of the magnetizing magnetic field is changed from 180 degrees to 170 degrees, and there is no effect on the magnetization of the medium coercive force magnetic body.

  When the paper sheet 100 is further conveyed and enters the bias magnetic field, it is also affected by the bias magnetic field. At the position P3, the magnetization direction 503b is slightly rotated from the magnetization direction 502b at the position P2 in a direction coinciding with the magnetic field direction 301 of the bias magnetic field at the position P3. The position P4 also becomes a direction 504b slightly rotated from the magnetization direction 503b at the position P3 toward the direction coincident with the direction 302 of the bias magnetic field at the position. However, since the magnetic field strength (450 G) of the bias magnetic field is smaller than the strength to make the coercive force (300 Oe) of the medium coercive force magnetic body in the saturation magnetization state, the final magnetization direction of the medium coercive force magnetic body is magnetized. This is a direction 504b between the magnetization direction 502b (around 180 degrees) when exiting the magnetic field and the magnetic field direction 302 (30 to 60 degrees) of the bias magnetic field at the position P4. For example, the magnetization direction 504b of the medium coercive force magnetic body at the position P4 is about 120 degrees.

  When the magnetic material included in the paper sheet 100 is a low coercive force magnetic material, as shown in FIG. As in the case of the body, it is magnetized to the saturation magnetization state at the position P1. At this time, the magnetization direction 501c of the low coercive force magnetic body is the same as the magnetic field direction 201 of the magnetizing magnetic field at the position P1, as with the other magnetic bodies. However, since the low coercive force magnetic body has a small coercive force, it continues to be influenced by the magnetizing magnetic field while being conveyed in the conveying direction 400, and the magnetization direction changes according to the direction of the magnetizing magnetic field. For this reason, similarly to the medium coercive force magnetic body, the magnetization direction 502c when passing through the position P2 is the same direction (around 180 degrees) as the magnetic field direction 202 of the magnetizing magnetic field.

  When the paper sheet 100 is further conveyed and enters the bias magnetic field, it is also affected by the bias magnetic field. At the position P3, the magnetization direction 502c of the low coercive force magnetic body is the same magnetization direction 503c as the magnetic field direction 301 of the bias magnetic field at the position, and at the position P4, the magnetization direction 504c is the same as the bias magnetic field direction 302. Since the magnetic field strength (450G) of the bias magnetic field is sufficiently larger than the coercive force (50 Oe) of the low coercive force magnetic material, the low coercive force magnetic material is in a saturated magnetization state at each position. The magnetization direction of the body coincides with the direction of the bias magnetic field at each position.

  In order to bring a magnetic material into a saturation magnetization state, a magnetic field strength that is three times the coercive force is required. For this reason, in the magnetic quality discriminating apparatus 1, the magnetic field intensity of the bias magnetic field at the position P4 where the magnetism is detected by the magnetic sensor 10 is more than three times the coercivity of the low coercivity magnetic material to be discriminated and the medium coercivity magnetism. The coercive force of the body is 2 times or less. However, the vicinity of the magnetic field corresponding to the coercive force of the medium magnetic material is excluded. This is because the output of the magnetic material having a medium coercive force becomes zero in this bias magnetic field. For example, the magnetic field strength is set to 450 Oe so that the low coercive force magnetic material having a coercive force of 50 Oe is in a saturation magnetization state and the medium coercivity magnetic material having a coercive force of 300 Oe is not magnetized in the saturation magnetization state. Thereby, the magnetization direction 504c of the low coercive force magnetic body at the position P4 can be set to the same direction as the bias magnetic field direction 302 at the position P4. On the other hand, the magnetization direction of the medium coercive force magnetic body changes within the bias magnetic field, but the magnetization magnetic field is set so as to be in a direction that does not coincide with the magnetization direction 302 of the bias magnetic field even after the change. For this reason, the magnetization direction 504b of the medium coercivity magnetic body at the position P4 and the magnetization direction 504c of the low coercivity magnetic body can be made different directions.

  Further, in the high coercive force magnetic body, the same magnetization direction 501a as the magnetic field direction 201 of the magnetizing magnetic field is maintained without being affected by the bias magnetic field, but the magnetic field direction 201 of the magnetizing magnetic field is the medium coercive force magnetism at the position P4. The magnetization direction 504b of the high coercivity magnetic body at the position P4 is set to be different from the magnetization direction 504b of the body and the magnetization direction 504b of the low coercivity magnetic body. And 504c. If the magnetization direction 504a of the high coercivity magnetic body can be different from the magnetization directions 504b and 504c of the medium coercivity magnetic body and the low coercivity magnetic body, the high coercivity magnetic body is attached to the saturation magnetization magnetization state. There is no need to magnetize, and a mode of magnetizing in a state close to the saturation magnetization state may be used.

  As described above, in the magnetic quality discriminating apparatus 1, the magnetization direction 504a of the high coercivity magnetic body, the magnetization direction 504b of the medium coercivity magnetic body, and the low coercivity magnetism at the position P4 on the transport path where the magnetism detection unit 2 detects magnetism. One feature is that the magnetization directions 504c of the body are all different directions.

  In the magnetic quality discriminating apparatus 1 shown in FIG. 1, the magnetic field strength of the magnetizing magnetic field by the magnetizing unit 3 is set to a magnetic field strength that can magnetize the high coercive force magnetic body in the saturated magnetization state, and the magnetic field strength of the bias magnetic field is set to the high coercive force magnetism. The magnetic field strength does not affect the magnetization state of the body. Further, the magnetic field direction 201 of the magnetizing magnetic field at the position P1 at which the high coercive force magnetic body is magnetized to the saturation magnetization state and the magnetic field direction 302 of the bias magnetic field at the position P4 at which the magnetic body is detected are used as the origin. On the other hand, it is set to be in the opposite quadrant. Further, the magnetic field intensity of the bias magnetic field at the position P4 is set to an intensity for magnetizing the low coercivity magnetic body in the saturation magnetization state and an intensity for not magnetizing the medium coercivity magnetic body in the saturation magnetization state. By setting as described above, at the position P4, the magnetization direction 504a of the high coercivity magnetic body is the same as the magnetic field direction 201 of the magnetization magnetic field, and the magnetization direction 504c of the low coercivity magnetic body is the magnetic field direction 302 of the bias magnetic field. The magnetization direction 504b of the medium coercivity magnetic body can be set to a direction between the magnetization direction 504a of the high coercivity magnetic body and the magnetization direction 504c of the low coercivity magnetic body. Note that the type, number, shape, and the like of the magnet 20 included in the magnetizing unit 3 are not particularly limited as long as the above-described magnetic field direction and magnetic field strength of the magnetizing magnetic field can be realized.

  Next, a detection signal obtained when the magnetic sensor 10 of the magnetic detection unit 2 detects the high coercivity magnetic body, the medium coercivity magnetic body, and the low coercivity magnetic body magnetized in different magnetization directions in this way. Will be described.

  FIG. 3 shows the magnetic field distribution in the Z-axis direction in the vicinity immediately below (about 0.5 mm position) of the magnetic material magnetized in the magnetization directions 507 to 510. When the magnetization direction is upward 507, the magnetic field distribution in the Z-axis direction is as shown in FIG. 3A. When the magnetization direction is leftward 508, the magnetic field distribution in the Z-axis direction is as shown in FIG. 3 are oblique directions 509 and 510 as shown in FIGS. 3 (c) and 3 (d). When the magnetized magnetic material passes through the bias magnetic field generated by the bias magnet 30 as shown in FIG. 3, the direction and density of the bias magnetic field change. The magnetic sensor 10 outputs the change in the bias magnetic field as a detection signal. 3 corresponds to the 180 degree direction in FIG. 1, and the upper direction in FIG. 3 corresponds to the 90 degree direction in FIG.

  FIG. 4 is a diagram for explaining the relationship between the change in the bias magnetic field and the detection signal from the magnetic sensor 10. In FIG. 4, the magnetization direction of the passing magnetic material is shown in the upper part, and the change in the magnetic field lines of the bias magnetic field is shown in the lower part. As shown in FIG. 4A, when the magnetic body in the magnetization direction 505 passes through the position P4 where the magnetic sensor 10 detects the magnetic body, the magnetic field lines change upward from the initial state indicated by the broken line as indicated by the solid line. To do. At this time, the magnetic sensor 10 is set so as to obtain a positive output detection signal corresponding to the change in the magnetic field direction of the bias magnetic field and the change in the magnetic flux density. On the other hand, as shown in FIG. 4B, when the magnetic body in the magnetization direction 506 passes through the position P4 where the magnetic sensor 10 detects the magnetic body, the lines of magnetic force are shown as solid lines from the initial state shown by the broken lines. To change downward. At this time, the magnetic sensor 10 is set so that a negative output detection signal corresponding to a change in the magnetic field direction of the bias magnetic field and a change in the magnetic flux density can be obtained.

  FIG. 5 shows a magnetic quality discriminating apparatus 1 shown in FIG. 1B, in which a high coercivity magnetic body 101, a medium coercivity magnetic body 102, a low coercivity magnetic body 103, and laminated magnetic bodies 104 and 105 are combined with the magnetic detection unit 2. The waveform of the detection signal at the time of detection is shown. The vertical axis indicates the output from the magnetic sensor 10, and the horizontal axis indicates time. FIG. 5 shows detection signals output from the magnetic sensor 10 when the paper sheet 100 including each magnetic material passes the position P4. It becomes a waveform. In FIG. 5, each magnetic body 101-105 corresponding to each detection signal is shown in the upper part of each figure.

  In the low coercivity magnetic body 103 shown in FIG. 5C, a positive output is shown in almost the entire region, and the waveform is substantially symmetrical with respect to the peak position. Since the low coercive magnetic body 103 is saturated and magnetized by the bias magnetic field, the waveform of the detection signal from the magnetic sensor 10 does not depend on the magnetic field generated by the low coercive magnetic body. Since the low coercivity magnetic body has a high magnetic permeability and acts to collect magnetic lines of force, the amplitude of the detection signal output from the magnetic sensor 10 increases as the low coercivity magnetic body approaches the position P4. For this reason, the detection signal obtained by detecting the low coercive force magnetic body shows a maximum value when passing through the vicinity of the position P4, and shows a substantially symmetrical waveform before and after that.

  FIG. 5B shows a detection signal of the medium coercive force magnetic body 102. At position P4 of the magnetic quality determination device 1 shown in FIG. 1B, the magnetization direction of the medium coercive force magnetic body is directed obliquely upward to the left. At this time, the magnetic field distribution in the Z-axis direction in the vicinity immediately below the medium coercive force magnetic body is as shown in FIG. 3D, and a magnetic signal is detected so that the shape of this magnetic field distribution is traced from the right. As a result, as shown in FIG. 5B, a detection signal indicating a negative output after a positive output is obtained. As with the low coercivity magnetic body 103, a positive output is obtained in almost the entire region, but the waveform of the positive output is asymmetrical with respect to the peak position. It can be distinguished from the detection signal of the magnetic magnetic body 103.

  FIG. 5A shows a detection signal of the high coercivity magnetic body 101. At position P4 of the magnetic quality determination device 1 shown in FIG. 1B, the magnetization direction of the high coercive force magnetic body is directed diagonally downward to the left. The magnetic field distribution in the Z-axis direction in the vicinity immediately below the high coercive force magnetic body at this time is as shown in FIG. 3C, and a magnetic signal is detected so as to follow the shape of this magnetic field distribution from the right. As a result, as shown in FIG. 5A, a detection signal indicating a negative output after a positive output is obtained. Like the middle coercive force magnetic body 102, a positive output and a left-right asymmetric waveform are shown. However, the detection signal of the high coercivity magnetic body 101 shows a negative output in most of the detection signals. The detection signal can be distinguished from the detection signals of the low coercivity magnetic body 103 and the medium coercivity magnetic body 102.

  In the laminated magnetic body 104 composed of the high coercivity magnetic body 101 and the medium coercivity magnetic body 102 shown in FIG. 5D, a positive output is shown and then a negative output is shown. The laminated magnetic body 104 has a waveform obtained by adding the detection signal of the high coercivity magnetic body 101 and the detection signal of the medium coercivity magnetic body 102. The detection signal of the laminated magnetic body 104 shows an output that swings in both positive and negative directions, like the high coercivity magnetic body 101 shown in FIG. However, unlike the detection signal of the high coercivity magnetic body 101 in the detection signal of the laminated magnetic body 104, the positive and negative amplitudes are substantially the same. Therefore, the detection signal of the laminated magnetic body 104 and the detection signal of the high coercivity magnetic body 101 are Can be distinguished. When there is only one type of laminated magnetic body included in the discrimination target and the laminated magnetic body 104 is composed of the high coercive force magnetic body 101 and the medium coercive force magnetic body 102, the laminated magnetic body 104 is made of paper by this discrimination method. It can be recognized that it is present at a predetermined location on 100.

  The laminated magnetic body 105 composed of the high coercivity magnetic body 101 and the low coercivity magnetic body 103 shown in FIG. 5E shows a negative output after showing a positive output. The laminated magnetic body 105 has a waveform obtained by adding the detection signal of the high coercivity magnetic body 101 and the detection signal of the low coercivity magnetic body 103. The detection signal of the laminated magnetic body 105 shows an output that swings in both positive and negative directions, similarly to the high coercivity magnetic body 101 shown in FIG. However, unlike the detection signal of the high coercivity magnetic body 101 in the detection signal of the laminated magnetic body 105, the positive and negative amplitudes are substantially the same. Therefore, the detection signal of the laminated magnetic body 105 and the detection signal of the high coercivity magnetic body 101 are Can be distinguished. When there is only one type of laminated magnetic body included in the discrimination target and the laminated magnetic body 105 is composed of the high coercivity magnetic body 101 and the low coercivity magnetic body 103, the laminated magnetic body 105 is made of paper by this discrimination method. It can be recognized that it is present at a predetermined location on 100.

  In this laminated magnetic body discrimination method, the laminated magnetic body to be discriminated is a combination of the high coercivity magnetic body 101 and the medium coercivity magnetic body 102 or the combination of the high coercivity magnetic body 101 and the low coercivity magnetic body 103. Of these, except for the case where both combinations coexist, the detected signal of the laminated magnetic material is the laminated magnetic material 104 in which the laminated magnetic material is composed of the high coercive force magnetic material 101 and the medium coercive force magnetic material 102, or the high coercive force magnetic material 101. It can be determined that the laminated magnetic body 105 is composed of the low coercivity magnetic body 103.

  In the description of the detection signal of the laminated magnetic body in FIGS. 5D and 5E, the case where the high coercivity magnetic body 101 is in the upper layer has been described. The detection signals of the magnetic materials are also the same, and are not affected by the positional relationship of the layers.

  As shown in FIG. 5, in order to obtain a detection signal having a waveform distinguishable among the high coercivity magnetic body 101, the medium coercivity magnetic body 102, the low coercivity magnetic body 103, and the laminated magnetic body (104 or 105). For example, as shown in FIG. 1, the direction 201 of the magnetic field at the edge portion of the magnetized magnet 20 is set to about −160 degrees, and the direction 302 of the bias magnetic field at the position P4 corresponding to the magnetic sensor 10 is set to 30˜. 60 degrees.

  However, the relationship between the magnetization magnetic field direction 201 at the magnetization position P1, the bias magnetic field direction 302 and the transport direction 400 at the detection position P4 for detecting magnetism is not limited to the relationship shown in FIG. FIG. 6 is a diagram illustrating the magnetic quality determination device 1 in which the magnetic field direction of the magnetization magnetic field, the magnetic field direction of the bias magnetic field, and the transport direction are different. 6A and 6C show the relationship when the paper sheet 100 is conveyed in the forward direction, and FIGS. 6B and 6D show the relationship when the paper sheet 100 is conveyed in the reverse direction. Yes. Here, forward conveyance refers to a case where the angle between the conveyance direction 400 and the magnetic field direction 301 of the bias magnetic field is 90 degrees or less, and reverse conveyance refers to the conveyance direction 400 and the magnetic field direction 303 of the bias magnetic field. The case where the angle between them is 90 degrees or more.

  The forward conveyance shown in FIG. 6A corresponds to FIG. 1, and is a case where the conveyance direction 400 is 0 degree and the bias magnetic field direction 301 at the detection position P4 is 30 to 60 degrees. In the forward conveyance, as shown in the left diagram of FIG. 6A, the magnetizing magnetic field direction 201 is set between −100 and −170 degrees.

  The magnetic detection unit 2 for reverse conveyance shown in FIG. 6B is in a state where the magnetic detection unit 2 for forward conveyance shown in FIG. In the case of reverse conveyance shown in FIG. 6B, the magnetic field direction 303 of the bias magnetic field at the detection position P4 is a direction obtained by reversing the magnetic field direction 301 with respect to the Z axis in the case of forward conveyance, that is, 120 to 150. The direction of the degree. Similarly, the magnetic field direction 203 of the magnetizing magnetic field at the magnetizing position P1 is a direction obtained by reversing the magnetic field direction 201 with respect to the Z axis in the case of forward conveyance, that is, −10 to −80 degrees. In order to realize such a magnetic field direction 203 of the magnetizing magnetic field, the magnetizing magnet 20 included in the magnetizing unit 3 is installed above the conveyance path.

  In the forward direction magnetic detection unit 2 shown in FIG. 6C, the magnetic field direction 201 of the magnetization magnetic field is the same direction (−100 to −170 degrees) as that of the magnetic detection unit 2 shown in FIG. The magnetic field direction 305 of the bias magnetic field is a direction obtained by inverting the magnetic field direction 301 of the bias magnetic field of the magnetic detection unit 2 shown in FIG. 6D, the magnetic field direction 203 of the magnetizing magnetic field is the same direction (−10 to −80 degrees) as that of the magnetic detection unit 2 shown in FIG. 6B. However, the magnetic field direction 306 of the bias magnetic field is a direction obtained by reversing the magnetic field direction 303 of the bias magnetic field of the magnetic detection unit 2 shown in FIG. .

  Thus, the conveyance direction 400 is 0 degree, and the combinations of the magnetic field direction of the bias magnetic field and the magnetic field direction of the magnetizing magnetic field are 30 to 60 degrees and -100 to -170 degrees shown in FIG. b) 120 to 150 degrees and −10 to −80 degrees, (c) −30 to −60 degrees and −100 to −170 degrees, or −120 to −150 illustrated in FIG. When the angle is set to −10 to −80 degrees, as shown in FIG. 5, the high coercivity magnetic body 101, the medium coercivity magnetic body 102, the low coercivity magnetic body 103, and the laminated magnetic body (104 or 105). A detection signal having a distinguishable waveform can be obtained.

  FIG. 6 shows the case where the high coercivity magnetic body 101, the medium coercivity magnetic body 102, and the low coercivity magnetic body 103 are discriminated. For example, the low coercivity magnetic body 103 and other magnetic bodies Can be discriminated, the angle range that can be set as the magnetic field direction of the magnetizing magnetic field is relaxed. FIG. 7 shows the magnetic quality discriminating apparatus 1 shown in FIG. 6 that discriminates the low coercivity magnetic body 103 and other magnetic bodies, that is, the high coercivity magnetic body 101, the medium coercivity magnetic body 102, and the laminated magnetic body 104. It is a figure explaining the relationship between the magnetic field direction of a magnetization magnetic field, and the magnetic field direction of a bias magnetic field in the case. FIGS. 7A to 7D correspond to FIGS. 6A to 6D, respectively.

  Specifically, in the case of discriminating the low-coercivity magnetic body 103 from other magnetic bodies with the forward-conveyance magnetic quality discrimination apparatus 1 shown in FIG. 6A, as shown in FIG. 7A. In addition, the magnetic field direction of the magnetizing magnetic field may be set to a direction other than 80 to 100 degrees. Similarly, in the magnetic quality discriminating apparatus 1 shown in FIGS. 6B to 6D, when discriminating between the low coercive force magnetic body 103 and other magnetic bodies, the processes shown in FIGS. 7B to 7D are performed. As shown, the magnetic field direction of the magnetizing magnetic field may be set to a direction other than 80 to 100 degrees. By setting in this way, as shown in FIG. 5, the low coercive force magnetic body 103 shows only a positive output, and the other magnetic bodies have a part or all of a negative output. It becomes possible.

  That is, the conveyance direction 400 is set to 0 degree, the magnetic field direction of the bias magnetic field is set to 30 to 60 degrees or 120 to 150 degrees, and the magnetic field direction of the magnetization magnetic field is set to an angle range excluding 80 to 100 degrees, Alternatively, if the magnetic field direction of the bias magnetic field is set to −30 to −60 degrees or −120 to −150 degrees, and the magnetic field direction of the magnetizing magnetic field is set to an angle range excluding 80 to 100 degrees, the low coercive force magnetic body 103. And other magnetic materials can be discriminated.

  FIG. 8 is a schematic diagram for explaining a magnetic quality determination method in the case of reverse conveyance shown in FIG. FIG. 8B shows an outline of the magnetic quality discriminating apparatus 1, and FIG. 8A shows the magnetization states of three types of magnetic bodies having different coercive forces. As a device configuration, the magnetizing unit 3 including the magnetizing magnet 20 is disposed above the conveyance path, and the magnetism detecting unit 2 including the magnetic sensor 10 and the bias magnet 30 is inverted around the Z axis. This is different from the magnetic quality discriminating apparatus 1 shown in FIG. In the magnetic quality discriminating apparatus 1 shown in FIG. 8B, the magnetic field direction 203 of the magnetization magnetic field and the magnetic field direction 303 of the bias magnetic field are directions in which the directions 201 and 302 shown in FIG. It becomes.

  When the magnetic material included in the paper sheet 100 is a high coercive force magnetic material, the magnetic field strength (4500G) of the magnetic field is strong when the magnetic material is conveyed below the magnetization unit 3 in the conveyance direction 400. When passing the position P1 shown in FIG. 8B, the magnetized state is magnetized to a saturation magnetization state or a magnetization state close to the saturation magnetization state. At this time, as shown in FIG. 8A, the magnetization direction 511a of the high coercive force magnetic body is the same direction (−20 degrees) as the magnetization field direction 203 at the position P1. Even after the paper sheet 100 is transported in the transport direction 400, since there is no magnetic field enough to change the magnetization state of the high coercivity magnetic body, the subsequent magnetization directions 512a, 513a, and 514a The magnetization direction 511a, that is, the same direction as the magnetic field direction 203 of the magnetizing magnetic field remains.

  When the magnetic body contained in the paper sheet 100 is a medium coercive force magnetic body, it is magnetized to a saturation magnetization state at the position P1. However, since the coercive force is smaller than that of the high coercive force magnetic body, it is continuously influenced by the magnetizing magnetic field and the bias magnetic field while being transported in the transporting direction 400, and at the magnetization direction 512b and the position P3 at the position P2. Changes the magnetization direction 513b. The final magnetization direction 514b is a direction between the magnetic field direction 204 at the position P2 when exiting the magnetizing magnetic field and the magnetic field direction 303 of the bias magnetic field at the position P4.

  When the magnetic material included in the paper sheet 100 is a low coercive force magnetic material, since the coercive force is small, it is continuously influenced by the magnetizing magnetic field and the bias magnetic field while being conveyed in the conveying direction 400. The magnetization directions 511c to 514c at the positions P1 to P4 are the same as the magnetic field directions 203, 204, 304, and 303 at the positions.

  Thus, also in the case of the reverse conveyance, as in the case of the forward conveyance shown in FIG. 1, the magnetization direction 514a of the high coercivity magnetic body and the magnetization of the medium coercivity magnetic body at the detection position P4 for detecting the magnetic substance. The direction 514b and the magnetization direction 514c of the low coercive force magnetic body can all be different directions. As a result, similar to the detection signal for forward conveyance shown in FIG. 5, the high coercivity magnetic body 101, the medium coercivity magnetic body 102, the low coercivity magnetic body 103, and the laminated magnetic body (104 or 105) have different waveforms. A detection signal can be obtained.

  FIG. 9 shows the magnetic material discrimination device 1 of the reverse conveyance shown in FIG. 8B. The high coercivity magnetic body 101, the medium coercivity magnetic body 102, the low coercivity magnetic body 103, and the laminated magnetic bodies 104 and 105 are magnetized. The waveform of the detection signal at the time of detecting with the detection unit 2 is shown. The vertical axis indicates the output of the magnetic sensor 10, and the horizontal axis indicates time. The detection signal output from the magnetic sensor 10 when the paper sheet 100 including each magnetic material passes the position P4 is a waveform shown in FIG. It becomes. 9 also shows the magnetic bodies 101 to 105 corresponding to the detection signals at the top of each figure, as in FIG.

  The waveform of the detection signal of the low coercive force magnetic body 103 shown in FIG. 9C shows a positive output in almost the entire region, even in the case of reverse direction conveyance, and the waveform is at the peak position. On the other hand, the waveform is substantially symmetrical.

  In the detection signal of the medium coercive force magnetic body 102 shown in FIG. 9B, a positive output is shown in almost the entire region. Although this detection signal shows a positive output like the low coercive force magnetic body 103, it has a waveform that is asymmetrical with respect to the peak position, so that it can be distinguished from the detection signal of the low coercivity magnetic body 103. .

  The detection signal of the high coercive force magnetic body 101 shown in FIG. 9A shows a negative output and then a positive output. Since this detection signal shows a negative output in most of the detection signals, it can be distinguished from the detection signals of the low coercivity magnetic body 103 and the medium coercivity magnetic body 102.

  In the laminated magnetic bodies 104 and 105 shown in FIGS. 9D and 9E, a negative output is shown and then a positive output is shown. In the laminated magnetic body 104 of FIG. 4D, a waveform obtained by adding the output of the high coercive magnetic body 101 and the waveform of the medium coercive magnetic body 102 is obtained. In the laminated magnetic body 105 of FIG. 101 and the low coercive force magnetic body 103 are added. Similar to the high coercivity magnetic body 101 shown in FIG. 9A, the detection signals of the laminated magnetic bodies 104 and 105 show both positive and negative outputs. However, unlike the detection signal of the high coercivity magnetic body 101, the positive and negative amplitudes of the detection signals of the laminated magnetic bodies 104 and 105 are substantially the same. Therefore, the detection signal of the laminated magnetic bodies 104 and 105 and the high coercivity magnetic body 101 A detection signal can be distinguished.

  In the forward conveyance, the position P4 where the magnetism is detected immediately after entering the bias magnetic field is reached, but in the reverse conveyance, the influence of the bias magnetic field on the medium coercive force magnetic body 102 is large before reaching the position P4. Become. Specifically, the amount of magnetization of the medium coercive force magnetic body 102 decreases due to the influence of the bias magnetic field, and as can be seen from the comparison of the detection signals in FIG. 5B and FIG. The detection signal has a waveform with a smaller amplitude than that of the forward conveyance detection signal. The high coercivity magnetic body 101 is not affected by the bias magnetic field because the magnetic field strength of the bias magnetic field is smaller than the coercive force.

  As described above, the detection signal waveform of the magnetic material is different between the forward conveyance and the reverse conveyance. In any case, the high coercivity magnetic material 101, the medium coercivity magnetic material 102, the low coercivity magnetic material 103, and the laminated magnetic material. Since different detection signals are indicated by the body (104 or 105), each of the magnetic bodies 101 to 103 and 104 or 105 can be determined based on the detection signal.

  Each of the high coercivity magnetic body 101, the medium coercivity magnetic body 102, the low coercivity magnetic body 103, and the laminated magnetic body (104 or 105) based on the detection signal is determined by the signal waveform with respect to the amplitude and peak position of the detection signal. Judgment based on symmetry. For example, if the amplitude of the negative peak position is greater than a predetermined value, if the majority of the detection signal is a negative output from the ratio of the time when the negative output is obtained and the time when the positive output is obtained, It is determined as the high coercive force magnetic body 101, otherwise, it is determined as the laminated magnetic body 104. Further, when the amplitude of the negative peak position is smaller than a predetermined value, if the positive waveform is substantially symmetrical with respect to the peak position, it is determined as the low coercivity magnetic body 103, and if it is an asymmetric waveform. The medium coercive force magnetic body 102 is determined. The method of determining the symmetry of the signal waveform is not particularly limited. For example, the symmetry is determined by comparing the distance in the horizontal axis direction from the peak position to the position where the amplitude is 0 (zero) in both directions. Alternatively, the symmetry may be determined from the correlation between the original waveform and the waveform reversed left and right around the peak position.

  According to the magnetic quality determination device 1 according to the present embodiment, a high coercivity magnetic body, a medium coercivity magnetic body, a low coercivity magnetic body, and a laminated magnetic body can be determined. Even if the bodies are different, it is possible to determine the authenticity of the paper sheet 100 by determining the type of the magnetic material included in each paper sheet 100. In addition, even when a pattern is drawn on the paper sheet 100 with each magnetic material, this can be recognized. Further, even when a code is formed by a combination of magnetic materials, the code can be recognized by accurately identifying each magnetic material.

  As described above, according to the present embodiment, the magnetic field strength and magnetic field direction of the magnetic field generated by the magnetic unit 3 and the magnetic field strength and magnetic field direction of the bias magnetic field generated by the magnetic detection unit 2 are set appropriately. Since the magnetization direction of each magnetic body can be set to a different direction at the position where the magnetic detection unit 2 detects magnetism, each magnetic body can be determined from the characteristics of the detection signal that has detected the magnetism.

  For example, the magnetic field strength of the magnetizing magnetic field is set as the magnetic field strength that brings the high coercive force magnetic material into the saturation magnetization state, the magnetic field strength of the bias magnetic field is set as the low coercivity magnetic material in the saturation magnetization state, and the medium coercive force magnetic material is saturated in magnetization. Detection is performed by setting the magnetic field intensity so as not to be magnetized to the state and setting the direction of the bias magnetic field at the position where the magnetic substance is detected by the magnetic detection unit 2 to be different from the direction of the magnetic field magnetizing each magnetic substance. A high coercivity magnetic body, a medium coercivity magnetic body, a low coercivity magnetic body, and a laminated magnetic body can be distinguished from the amplitude and waveform of the signal.

  Further, for example, the above-described magnetizing magnetic field can be realized by only one magnetizing magnet 20, and each magnetic body can be discriminated by obtaining a detection signal by one magnetic sensor 10. A small and inexpensive device can be obtained.

  As described above, the present invention is a useful technique for detecting and discriminating a plurality of magnetic bodies having different coercive forces with a small magnetic quality discrimination device.

DESCRIPTION OF SYMBOLS 1 Magnetic quality discrimination apparatus 2 Magnetic detection unit 3 Magnetization unit 10 Magnetic sensor 20 Magnetization magnet 30 Bias magnet 100 Paper sheets

Claims (7)

A magnetic quality discriminating device for detecting and discriminating the magnetic quality of a magnetic material contained in a paper sheet conveyed through a conveyance path,
Magnetic detection for detecting a magnetic quantity of the magnetic material by generating a bias magnetic field on the transport path having a direction that forms a predetermined angle with the transport surface of the paper sheet as a magnetic field direction and detecting a change in the bias magnetic field Unit,
A magnetizing unit that is disposed upstream of the magnetic detection unit in the transport direction and generates a magnetizing magnetic field on the transport path that has a magnetic field direction different from the magnetic field direction of the bias magnetic field to magnetize the magnetic body; With
At a magnetic detection position by the magnetic detection unit, a low coercivity magnetic body having a coercive force smaller than a predetermined coercive force is different from another magnetic body having a coercive force larger than the predetermined coercive force by the magnetization magnetic field and the bias magnetic field. Magnetic quality discriminating apparatus characterized by being magnetized in the magnetization direction. The magnetic field strength of the magnetizing magnetic field is set to a magnetic field strength that magnetizes a magnetic material having the maximum coercive force among magnetic materials to be discriminated into a saturated magnetization state,
The magnetic field strength of the bias magnetic field is set to a magnetic field strength that magnetizes the low coercivity magnetic material to be discriminated into a saturated magnetization state and a magnetic field strength that does not magnetize the other magnetic material into a saturated magnetization state. The magnetic quality discrimination device according to claim 1. The magnetic field strength of the magnetizing magnetic field is set to 1.5 times or more of the coercive force of the magnetic body having the largest coercive force among the discrimination targets,
3. The magnetic quality discriminating apparatus according to claim 2, wherein the magnetic field strength of the bias magnetic field is set to not more than twice the coercive force of the magnetic material having the minimum coercive force among the high coercive force magnetic materials to be discriminated. . The conveyance direction of the magnetic material is 0 degree,
The magnetic field direction of the bias magnetic field is set to 30 to 60 degrees or 120 to 150 degrees, and the magnetic field direction of the magnetization magnetic field is set to an angle range excluding 80 to 100 degrees, or the magnetic field direction of the bias magnetic field is set 4. The magnetic field direction of the magnetizing magnetic field is set to an angle range excluding 80 to 100 degrees by setting to -30 to -60 degrees or -120 to -150 degrees. The magnetic quality discrimination device described.   5. The magnetic quality determination according to claim 1, wherein the magnetic detection unit determines a coercive force of the magnetic body based on a waveform shape of a detection signal detected from the magnetic body. apparatus.   6. The magnetism according to claim 5, wherein the magnetic body is determined to be a low coercivity magnetic body when a detection signal for detecting the magnetic body shows a waveform that is substantially symmetrical with respect to a peak position. Quality discrimination device. A magnetic quality discrimination method for detecting and discriminating the magnetic quality of a magnetic material contained in a paper sheet conveyed through a conveyance path,
Magnetic quantity detection for detecting a magnetic quantity of the magnetic body by detecting a change in the bias magnetic field by generating a bias magnetic field on the conveyance path that has a magnetic field direction as a direction that forms a predetermined angle with the conveyance surface of the paper sheet. Process,
A magnetizing magnetic field having a magnetic field direction different from the magnetic field direction of the bias magnetic field is generated on the transport path upstream of the position where the magnetic quantity is detected in the magnetic quantity detection step. Including a magnetizing step of magnetizing,
When detecting the magnetic quantity in the magnetic quantity detection step, a low coercivity magnetic body having a coercive force smaller than a predetermined coercive force and a coercive force larger than the predetermined coercive force by the magnetization magnetic field and the bias magnetic field. A magnetic quality discrimination method comprising magnetizing a magnetic substance in a different magnetization direction.

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