JP2017133845A - Magnetic sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor device having a plurality of magnetic sensor elements arranged in one row and generating a bias magnetic field by one long permanent magnet, the magnetic sensor device capable of applying the bias magnetic field generated by the permanent magnet evenly to each magnetic sensor element and also capable of precisely and stably detecting the state of a magnetic substance included in paper sheets.SOLUTION: A plurality of magnetic sensor elements (numeral 1) are arranged in one row. A long permanent magnet (numeral 2) is arranged on the side opposite the conveyance path side of the plurality of magnetic sensor elements (numeral 1). The permanent magnet (numeral 2) extends in parallel to the direction of the array of the plurality of magnetic sensor elements (numeral 1). The plurality of magnetic sensor elements (numeral 1) are arranged at only positions apart by 1/2 or more of the height dimension of the permanent magnet (numeral 2) from both ends in the longitudinal direction of the permanent magnet (numeral 2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic sensor device that detects a magnetic substance contained in a sheet-like object to be detected (hereinafter referred to as a paper sheet) such as banknotes and securities.

  Recently, paper sheets such as forged banknotes and securities have become more and more sophisticated, making it difficult to distinguish between authenticity and authenticity.

  On the other hand, various types of anti-counterfeiting measures have been taken on paper sheets to prevent counterfeiting and authenticate. For example, a fine magnetic material (hereinafter referred to as magnetic printing) having a printed pattern is arranged on a paper sheet, or a plurality of magnetic materials having different magnetic characteristics are arranged.

  The main components of the magnetic sensor device are a magnetic field generator for magnetizing a magnetic material contained in a paper sheet, a magnetoelectric conversion element that converts the magnetic field strength of the magnetized magnetic material into a voltage change or a current change, A detection unit that amplifies and detects a weak output from the magnetoelectric conversion element.

  Here, as a method for generating a magnetic field (hereinafter referred to as a bias magnetic field) for magnetizing a magnetic substance contained in a paper sheet, there are a method using a permanent magnet and a method using an electromagnet. The former is used, which does not require power.

  When a permanent magnet is used, it is necessary to consider the generated magnetic force and magnetic field distribution of the permanent magnet because the bias magnetic field strength (hereinafter referred to as magnetic force) cannot be adjusted by adjusting the coil current like an electromagnet.

  Therefore, as described in the following Patent Document 1 (Japanese Patent Laid-Open No. 2007-085980), when a magnetic printing unit such as a banknote is detected locally, one permanent magnet is arranged for one magnetic sensor element. For example, since the magnetic force received by the magnetic sensor element can be adjusted on a one-to-one basis, there is not much problem with magnetic force variation. However, as in recent years, the magnetic printing part is detected over the entire surface of banknotes, etc., and the accuracy of authenticity discrimination is improved. In this case, as described in the following Patent Document 2 (Japanese Patent Publication No. 2009-524019), a system in which a plurality of magnetic sensor elements are arranged in one row and a bias magnetic field is generated by one long permanent magnet is used. .

  In this case, it is necessary to apply a bias magnetic field with a uniform magnetic force to a plurality of magnetic sensor elements in order to detect the magnetic printing portion over the entire surface of a bill or the like and detect the magnetic printing state accurately and stably. As a characteristic of the rectangular parallelepiped permanent magnet, the magnetic force distribution in the longitudinal direction of the permanent magnet is not uniform, and the magnetic force at both ends of the permanent magnet is increased in a square shape, so that it is difficult to apply the bias magnetic field uniformly.

  Japanese Patent Application Laid-Open No. 2009-524019 below solves this problem by adjusting the electronic circuit for each individual magnetic sensor element, but has a drawback that the electronic circuit becomes complicated.

JP 2007-085980 A Special table 2009-524019

  As described above, in a magnetic sensor device in which a plurality of magnetic sensor elements are arranged in one row and a bias magnetic field is generated by one long permanent magnet, the magnetic force at both ends in the longitudinal direction of the rectangular parallelepiped permanent magnet is extremely high. The bias magnetic field to each magnetic sensor element becomes non-uniform due to the phenomenon that the magnetic sensor element becomes low and squarely high. For this reason, it is difficult to detect the magnetic printing state over the entire surface of a bill or the like and detect the magnetic printing state accurately and stably.

  The present invention has been made in view of the above circumstances, and a permanent magnet is generated in a magnetic field sensor device in which a plurality of magnetic sensor elements are arranged in a row and a bias magnetic field is generated by one long permanent magnet. An object of the present invention is to provide a magnetic sensor device that can uniformly apply a bias magnetic field to each magnetic sensor element and can accurately and stably detect the state of a magnetic substance contained in a paper sheet.

  A magnetic sensor device according to the present invention is a magnetic sensor device that detects a magnetic material contained in a paper sheet conveyed on a conveyance path, and includes a plurality of magnetic sensor elements arranged in a row and a long permanent element. And a magnet. The permanent magnet is disposed on the side opposite to the conveyance path side with respect to the plurality of magnetic sensor elements, and extends in parallel with the arrangement direction of the plurality of magnetic sensor elements. The plurality of magnetic sensor elements are disposed only at positions that are separated from both ends of the permanent magnet in the longitudinal direction by a half or more of the height dimension of the permanent magnet.

  According to such a configuration, a plurality of magnetic sensors are arranged on the inner side of the corner where the magnetic field distribution is increased in a range less than half the height dimension of the permanent magnet from both ends in the longitudinal direction of the permanent magnet. Elements can be placed. Thereby, a non-uniform portion of the magnetic field distribution can be avoided, a uniform magnetic field can be applied to each magnetic sensor element, and the magnetic printing state of the paper sheet can be detected accurately and stably.

  It is preferable that the dimension ratio obtained by dividing the height dimension of the permanent magnet by the width dimension is in the range of 1 to 3.

  According to such a configuration, the permanent magnet can be formed with the most efficient dimension even if the amount of the permanent magnet used is the same. As a result, a permanent magnet having a high magnetic flux density can be formed using as little material as possible, so that the state of magnetic printing on the paper sheet can be accurately detected at a lower cost.

  It is preferable that a dimensional ratio obtained by dividing the longitudinal dimension of the permanent magnet by the height dimension is 3 or more.

  According to such a configuration, when using a permanent magnet having a size that is likely to cause a phenomenon in which the magnetic field distribution is increased in a square shape, a non-uniform portion of the magnetic field distribution is avoided and a uniform magnetic field is applied to each magnetic sensor element. be able to.

  The magnetic sensor element is preferably a hall element.

  According to such a configuration, the magnetic material contained in the paper sheet can be detected not only when the paper sheet is being transported but also when it is stationary, and the operation speed is based on the detection sensitivity. Using a Hall element that hardly affects changes, the state of magnetic printing of paper sheets can be detected more precisely and stably.

  According to the present invention, a bias magnetic field generated by a permanent magnet can be uniformly applied to each magnetic sensor element, and the state of a magnetic body contained in a paper sheet can be detected accurately and stably.

It is the front view which showed the structure of the magnetic sensor apparatus of this invention. It is sectional drawing which showed the structure of the magnetic sensor apparatus of this invention. It is a perspective view explaining the permanent magnet used for this invention. It is the graph which showed the implementation result of this invention. It is the graph which showed the implementation result of this invention. It is the graph which showed the implementation result of this invention.

  1 and 2 are diagrams showing the positional relationship among a magnetic sensor element (reference numeral 1), a permanent magnet (reference numeral 2), and a paper sheet (reference numeral 3), which is a configuration of the magnetic sensor device of the present invention. FIG. 1 shows a front view of the magnetic sensor device, and FIG. 2 shows a cross-sectional view of the magnetic sensor device.

  As shown in the front view of FIG. 1, the magnetic sensor device includes a plurality of magnetic sensor elements (reference numeral 1). The plurality of magnetic sensor elements (symbol 1) are arranged in a row on a base material (symbol 5) provided with electrical wiring. The permanent magnet (reference numeral 2) has an elongated rectangular parallelepiped shape extending in parallel with the arrangement direction of the plurality of magnetic sensor elements (reference numeral 1). In this example, the N pole of the permanent magnet (symbol 2) is located on the magnetic sensor element (symbol 1) side, but not limited to this, the S pole is located on the magnetic sensor element (symbol 1) side. Also good.

  The paper sheet (symbol 3) is transported on a transport path formed on the side opposite to the permanent magnet (symbol 2) side with respect to the plurality of magnetic sensor elements (symbol 1). In this example, the paper sheet (reference numeral 3) is conveyed from the front side to the back side in FIG. 1 or from the back side to the front side. That is, the paper sheet (symbol 3) is transported on the transport path along a direction that intersects, preferably perpendicular to, the arrangement direction of the plurality of magnetic sensor elements (symbol 1). In the cross-sectional view of FIG. 2, the arrows shown on the left and right of the paper sheet (reference numeral 3) indicate the transport direction.

  Further, a thin plate cover (reference numeral 4) made of a nonmagnetic metal is disposed between the plurality of magnetic sensor elements (reference numeral 1) and the paper sheets (reference numeral 3). The cover (reference numeral 4) constitutes a transport path surface of the paper sheet (reference numeral 3) and has a function of protecting the magnetic sensor element (reference numeral 1).

  Although not shown, the magnetic sensor element (reference numeral 1), the permanent magnet (reference numeral 2), and the cover (reference numeral 4) are supported by a nonmagnetic metal or plastic casing so as to have a constant interval. ing. Thus, an integral magnetic sensor device is configured and fixed so that the positional relationship between the magnetic sensor element (reference numeral 1), the permanent magnet (reference numeral 2), and the cover (reference numeral 4) does not change.

  The plurality of magnetic sensor elements (reference numeral 1) are provided in the magnetic field of the permanent magnet (reference numeral 2). When the paper sheet (symbol 3) is transported to the transport path and the magnetic material (magnetic printing unit) included in the paper sheet (symbol 3) passes near the magnetic sensor element (symbol 1), a permanent magnet ( When the magnetic printing unit is magnetized by the magnetic field indicated by reference numeral 2), the magnetic field received by the magnetic sensor element (reference numeral 1) changes. Therefore, the state of magnetic printing can be determined by electrically detecting this change with a plurality of magnetic sensor elements (reference numeral 1).

  The plurality of magnetic sensor elements (symbol 1) are arranged in a range facing the paper sheet (symbol 3) transported through the transport path. Therefore, by detecting the change of the magnetic field by the plurality of magnetic sensor elements (reference numeral 1) while conveying the paper sheet (reference numeral 3) to the conveyance path, the magnetic printing unit is spread over the entire surface of the paper sheet (reference numeral 3). Can be detected.

  As an example of the present invention, a hall element was used as the magnetic sensor element (reference numeral 1). Hall elements mainly include GaAs, InAs, and InSb, but GaAs based on good temperature characteristics was used. In the present invention, the direction in which the magnetic field is applied to the hole element is set at a substantially right angle.

  In addition, as a result of various experiments, the magnetic field magnetic flux density has a good sensitivity output and noise ratio (S / N ratio) if it is 100 to 200 millitesla (hereinafter referred to as mT) at the passing position of the paper sheet (reference numeral 3). In the example, the permanent magnet (reference numeral 2) was selected so that the distance was approximately 150 mT, and the distance between the permanent magnet (reference numeral 2) and the passage position of the paper sheet (reference numeral 3) was 2 mm.

  This distance is not limited to 2 mm, but can be changed depending on the characteristics and shape of the permanent magnet (reference numeral 2) and the shape design of the entire magnetic sensor device.

  In the present invention, in order to determine the state of magnetic printing over the entire area of the paper sheet (reference numeral 3), a plurality of hole elements are arranged in a line. Therefore, in order to accurately and stably detect the magnetic printing state of the paper sheet (reference numeral 3), it is necessary to apply a magnetic field as uniform as possible to each hole element. A rectangular bar-shaped permanent magnet (reference numeral 2) is arranged in parallel to the arrangement direction of the elements (reference numeral 1). Therefore, in order to select the optimum dimension of the permanent magnet (reference numeral 2), as shown in FIG. 3, the material is a resin magnet, and the dimension is a height dimension (reference numeral a), a width dimension (reference numeral b), and a longitudinal dimension (reference numeral). A permanent magnet (reference numeral 2) of a square bar of c) was prepared. Here, N and S in the figure represent magnetic poles. Each dimension of a permanent magnet (reference numeral 2) magnetized on the magnetic pole is prepared, and the Z-axis direction distance (reference numeral d) from the magnet N pole surface is 1 mm away and 2 mm away, respectively. The magnetic flux density was measured with a sensor probe (symbol 6) of a Tesla meter. Specifically, the peak value was measured when the sensor probe (symbol 6) was moved in the Y-axis direction at a substantially central position in the longitudinal direction of the permanent magnet (symbol 2).

As for the dimensions of the produced permanent magnet (reference numeral 2), all the longitudinal dimensions (reference numeral c) were fixed to 50 mm, and the width dimension (reference numeral b) was changed from 4 mm to 16 mm at intervals of 2 mm. The height dimension (symbol a) of the permanent magnet (symbol 2) was changed so that the product of the width dimension (symbol b) and the height dimension (symbol a) was 100 mm ² .

Here, the reason why the product is set to 100 mm ² is to make the usage amount of the permanent magnet (reference numeral 2) constant.

Table 1 below shows the results of the experimental measurement.

  In Table 1, the height dimension / width dimension is shown as a magnet dimension ratio (a / b). FIG. 4 is a graph in which the resulting magnet dimension ratio (height dimension / width dimension) is plotted on the horizontal axis and the magnetic flux density (peak value) is plotted on the vertical axis.

  According to the results of FIG. 4, although slightly different depending on the measurement distance, when the magnet size ratio (height size / width size) is 1 or less, the magnetic flux density tends to increase, and the magnet size ratio (height size / width size). 3 or more indicates that the magnetic flux density is flat or has a downward trend.

  Accordingly, the most efficient permanent magnet (reference numeral 2) with the same amount of material used for the permanent magnet (reference numeral 2) has a magnet size ratio (height dimension / width dimension) of 1 to 3, preferably 2 to 3. By forming the permanent magnet (reference numeral 2) with such dimensions, it is possible to form a permanent magnet (reference numeral 2) having a high magnetic flux density by using as little material as possible. The state of magnetic printing of reference 3) can be accurately detected.

  Next, regarding the longitudinal dimension (symbol c), the height dimension (symbol a) of the permanent magnet (symbol 2) is fixed to 10 mm and the width dimension (symbol b) is fixed to 8 mm in FIG. Was prepared in a stepwise manner from 10 mm to 100 mm. Then, the magnetic flux density in the Z-axis direction at a position where the distance in the Z-axis direction (symbol d) is 1.5 mm away from the magnet N pole surface was measured with a sensor probe (symbol 6) of a Tesla meter. Specifically, the magnetic flux density when the sensor probe (symbol 6) was moved in the X-axis direction at a substantially central position of the width dimension of the permanent magnet (symbol 2) was continuously measured at intervals of 0.2 mm. .

  5 and 6 are graphs of the magnetic field distribution with the measurement distance in the X-axis direction as the horizontal axis and the magnetic flux density at each measurement position as the vertical axis. In these FIG.5 and FIG.6, the result of having experimented by changing the longitudinal dimension (code | symbol c) of a permanent magnet (code | symbol 2) is represented by each magnetic field distribution graph, and the permanent magnet (code | symbol 2) used for each experiment is shown. ) Are shown in a rectangular shape below each graph. FIG. 5 shows the respective magnetic field distribution graphs when the longitudinal dimension (symbol c) of the permanent magnet (symbol 2) is 10 mm, 20 mm, 30 mm, and 40 mm, and FIG. 6 shows the longitudinal direction of the permanent magnet (symbol 2). The magnetic field distribution graphs when the dimension (symbol c) is 50 mm, 70 mm, and 100 mm are shown side by side.

  5 and 6, the vertical line indicated by a broken line inside the permanent magnet (reference numeral 2) is separated from both ends of the permanent magnet (reference numeral 2) by a distance of ½ of the height dimension (reference numeral a). A position and a position separated by a distance of 1/1 are shown. In this example, since the height dimension (symbol a) of the permanent magnet (symbol 2) is 10 mm, the ½ distance is 5 mm and the 1/1 distance is 10 mm.

  According to the experimental results shown in these graphs, the magnetic field distribution becomes flat in a trapezoidal shape as the longitudinal dimension (symbol c) of the permanent magnet (symbol 2) increases. However, the dimension ratio obtained by dividing the longitudinal dimension (symbol c) of the permanent magnet (symbol 2) by the height dimension (symbol a) is 3 or more, that is, the longitudinal dimension (symbol c) of the permanent magnet (symbol 2) is 30 mm or more. Then, the fall of the magnetic field distribution becomes large at both ends of the permanent magnet (reference numeral 2), and the magnetic field distribution increases in a rectangular shape slightly inside the both end parts of the permanent magnet (reference numeral 2). The change in the magnetic flux density is larger than that in the central part. Therefore, the magnetic sensor element (symbol 1) disposed at the end of the permanent magnet (symbol 2) and the magnetic sensor element (symbol 1) disposed at the center of the permanent magnet (symbol 2) have a magnetic field magnetic force. Since the difference occurs, the detection output varies, and the magnetic printing state of the paper sheet (reference numeral 3) cannot be detected accurately and stably.

  Therefore, in the present embodiment, the permanent magnet (reference numeral 2) shown in FIGS. 5 and 6 is located on the inner side of the vertical line position separated from the both ends of the height dimension (reference numeral a) by a distance of 1/2 of the height dimension (reference numeral a). The magnetic sensor element (symbol 1) is arranged in a range on the inner side of the vertical line position separated from both ends of the magnet (symbol 2) by a distance of 1/1 of the height dimension (symbol a). That is, with reference to FIG. 1, the distance e1 from both ends of the long permanent magnet (reference numeral 2) to the magnetic sensor elements (reference numeral 1) located at both ends in the arrangement direction among the plurality of magnetic sensor elements (reference numeral 1). And e2 are set to 1/2 or more, preferably 1/1 or more of the height dimension (reference a) of the permanent magnet (reference 2).

  Thereby, from the both ends of the longitudinal direction of a permanent magnet (code | symbol 2), the position away from 1/2 or more of the height dimension (code | symbol a) of the said permanent magnet (code | symbol 2), Preferably it is only the position away from 1/1 or more. A plurality of magnetic sensor elements (reference numeral 1) are arranged. In this example, the distances e1 and e2 are based on the centers of the magnetic sensor elements (reference numeral 1) arranged at both ends in the arrangement direction of the plurality of magnetic sensor elements (reference numeral 1). The edge of the magnetic sensor element (reference numeral 1) may be used as a reference.

  As described above, in this embodiment, the magnetic field distribution is formed in a square shape that occurs in a range less than ½ of the height dimension (symbol a) of the permanent magnet (symbol 2) from both ends in the longitudinal direction of the permanent magnet (symbol 2). A plurality of magnetic sensor elements (reference numeral 1) can be arranged on the inner side of the portion where the height increases. As a result, a non-uniform portion of the magnetic field distribution can be avoided, a uniform magnetic field can be applied to each magnetic sensor element (reference numeral 1), and the magnetic printing state of the paper sheet (reference numeral 3) can be detected accurately and stably. it can.

  In particular, if the dimensional ratio (a / b) obtained by dividing the height dimension (symbol a) of the permanent magnet (symbol 2) by the width dimension (symbol b) is in the range of 1 to 3, the permanent magnet (symbol 2) Even if the amount of material used is the same, the permanent magnet (reference numeral 2) can be formed with the most efficient dimensions. As a result, a permanent magnet (reference numeral 2) having a high magnetic flux density can be formed using as little material as possible, so that the magnetic printing state of the paper sheet (reference numeral 3) can be accurately detected at a lower cost.

  Further, the magnetic material contained in the paper sheet (reference numeral 3) can be detected not only when the paper sheet (reference numeral 3) is being transported but also when it is stationary, and its operation speed is If a Hall element that hardly affects the change in detection sensitivity is used as the magnetic sensor element (reference numeral 1), the magnetic printing state of the paper sheet (reference numeral 3) can be detected more precisely and stably.

1 Magnetic Sensor Element 2 Permanent Magnet 3 Paper Sheet 4 Cover
5 Substrate 6 Teslamometer sensor probe a Permanent magnet height b Permanent magnet width c Permanent magnet longitudinal dimension d Magnetic field distribution measurement distance e1, e2 Distance from both ends of permanent magnet to magnetic sensor element

Claims (4)

A magnetic sensor device for detecting a magnetic material contained in a paper sheet conveyed through a conveyance path,
A plurality of magnetic sensor elements arranged in a row;
A long permanent magnet disposed on the opposite side of the transport path side with respect to the plurality of magnetic sensor elements, and extending in parallel with the arrangement direction of the plurality of magnetic sensor elements;
The magnetic sensor device is characterized in that the plurality of magnetic sensor elements are arranged only at positions separated from both ends of the permanent magnet in the longitudinal direction by 1/2 or more of the height dimension of the permanent magnet.   2. The magnetic sensor device according to claim 1, wherein a dimensional ratio obtained by dividing the height dimension of the permanent magnet by the width dimension is in a range of 1 to 3.   3. The magnetic sensor device according to claim 1, wherein a dimensional ratio obtained by dividing the longitudinal dimension of the permanent magnet by the height dimension is 3 or more.   The magnetic sensor device according to claim 1, wherein the magnetic sensor element is a hole element.

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