JP2007286012A - Magnetic detecting element and magnetic identification sensor using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic detecting element and magnetic identification sensor that can freely respond to the detection width of milli order, have a high spacing characteristic, have resistance to a disturbance magnetic field, and can be sufficiently used as an alternative of a magnetic head. <P>SOLUTION: A magnetic thin film 12 is formed as a plurality of parallel patterns interconnected in series on one surface of a non-magnetic substrate 10. The ends of the plurality of parallel patterns are aligned so as to come into contact with or be close to one side of a substrate 10, and a magnetic detection section using the width of the plurality of parallel patterns as a detection width Tw. While, a plane coil 16 is arranged so that the central part thereof crosses the plurality of parallel patterns of the magnetic thin film 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic detection element having a structure in which a magnetic thin film and a planar coil are laminated on a nonmagnetic substrate, and more particularly to a magnetic detection element suitable for detecting local magnetism and a magnetic identification sensor using the same. It is.

  Conventional magnetic reading sensors mainly use magnetic heads. This magnetic reading sensor is used, for example, for bill recognition of vending machines, ticket recognition at automatic ticket gates of railways, magnetic recognition of cash cards at ATMs, or recognition of magnetic characters (MICR characters) such as checks.

  However, even for magnetic heads that have a sufficient track record in practical use, for example, when banknotes, tickets, and the like as described above are transported at a low speed, it is necessary to take measures against the risk of errors accompanying the deterioration of S / N. Further, in order to avoid an error due to dust or the like adhering to the gap portion of the magnetic head, it takes time for maintenance, and there is a potential problem.

  That is, since the magnetic head uses the principle of the induction output that detects the magnetic flux change of the magnetic core with the coil, the sensitivity changes when the conveyance speed changes. Therefore, it is necessary to change the threshold value and gain for each model. Further, since the sensitivity is lowered when the conveyance speed is low, the S / N with respect to the disturbance is reduced, so that it is necessary to strengthen the magnetic shield or use multiple low-pass filters.

  Furthermore, the spacing characteristics with respect to the distance between the magnetic head gap and the medium are weak, and it is necessary to draw external magnetism into the core in a magnetic circuit. And weak. Therefore, it is necessary to frequently clean the gap portion.

  Under such circumstances, there is a demand for a highly sensitive magnetic sensor having a resolution equivalent to that of a magnetic head and having no speed dependency as a sensor replacing the magnetic head. Examples of magnetic sensors with good sensitivity include a magnetoresistive element (MR), a giant magnetoresistive element (GMR), a fluxgate sensor, and the like.

  Among them, the magnetoresistive element includes a ferromagnetic MR such as permalloy and an In—Sb semiconductor MR. Both require a bias magnetic field and are difficult to use to magnetically affect the medium.

  In addition, GMR does not require a bias in the spin valve type, but it is suitable for magnetic detection of micron or less with a very small detection width like a hard disk drive, but it is treated in reverse for the usage that requires detection width of millimeter unit. It ’s hard. Moreover, it is not practical because the cost is extremely high.

On the other hand, in the case of a fluxgate sensor, the orthogonal fluxgate type does not require a bias, and the detection width is suitable for the millimeter order. The inventor of the present application, as a proposal regarding the flack gate sensor, disclosed a magnetic detection element capable of operating an orthogonal flux gate in Japanese Patent Laid-Open No. 2003-163391 and capable of solving the problems of the magnetic head as described above. (Patent Document 1).
JP 2003-163391 A

  In the technique of Patent Document 1, in order to adapt to the use of the magnetic head, further structural ingenuity is required, and it is necessary to solve the following problems. In other words, it was necessary to solve the problem that the detection range of millimeter order can be freely accommodated, the spacing characteristics are good, and the structure is strong against disturbance magnetic fields.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic detection element that can cope with a detection width of the order of millimeters while having a resolution equivalent to that of a magnetic head, has good spacing characteristics, and is strong against a disturbance magnetic field, and a magnetic identification sensor using the same. There is.

  In the present invention, a magnetic thin film is formed as a plurality of parallel patterns connected in series on one surface of a nonmagnetic substrate. In that case, the magnetic detection part which makes the width | variety of a some parallel pattern the detection width is formed by aligning the edge part of a some parallel pattern in contact with one edge | side of a board | substrate, or adjoining. On the other hand, the planar coil has a configuration in which the central portion thereof is arranged so as to cross a plurality of parallel patterns of the magnetic thin film.

  According to the present invention, it is possible to realize a magnetic detection element that is not dependent on speed, has good spacing characteristics, is strong against an external magnetic field, and can freely correspond to a millimeter order detection width. Therefore, it can be sufficiently used as an alternative to the magnetic head. Further, when the magnetic detection element of the present invention is used for a magnetic identification sensor, there is a degree of freedom with respect to the incorporation and detection width of a magnet for magnetizing the medium, and a highly productive sensor can be realized.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of a magnetic detection element according to the present invention. In the figure, reference numeral 10 denotes a rectangular parallelepiped substrate made of a nonmagnetic material such as glass or ceramic. On one surface of the substrate 10, a high permeability magnetic thin film 12 made of permalloy, amorphous, microcrystalline thin film or the like is formed as a plurality of elongated parallel patterns.

  The easy axis of magnetization of the magnetic thin film 12 is preferably attached in a direction in a plane perpendicular to the longitudinal direction of the pattern by film formation in a magnetic field or heat treatment in a magnetic field. Each pattern of the magnetic thin film 12 is connected in series in a zigzag manner, but the end portions may be connected by a conductive magnetic thin film in addition to the magnetic thin film 12 itself as shown in FIG. . At least electrically connected in series.

  An insulating film 14 is formed on the magnetic thin film 12, and a nonmagnetic conductive film such as copper or aluminum is vacuum-deposited on the insulating film 14, followed by dry etching or the like so as to form a predetermined coil pattern. A planar coil 16 is formed.

  The central portion of the planar coil 16 has an elongated shape, but is arranged so that the parallel pattern of the magnetic thin film 12 crosses below. Thereafter, the insulating film 18 is placed on the planar coil 16, and the lead-out line 22 and the electrodes 24a, 24b, 24c, and 24d from the through hole 20 opened at one place to the electrode are formed of a conductive film.

  The lead wire 22 is connected to the electrode 24 a and serves as one terminal of the planar coil 16. The lead wire on the other side of the planar coil 16 is connected to the electrode 24d and serves as a terminal on the other side of the planar coil 16. One end of the magnetic thin film 12 is connected to the electrode 24b, and the other end of the magnetic thin film 12 is connected to the electrode 24c.

  When this magnetic detection element is used like a magnetic head, the surface 10a of the substrate 10 becomes a medium contact surface, and the medium is conveyed in a direction perpendicular to the surface 10b.

  It is preferable in terms of sensitivity distribution that the tips of a plurality of parallel patterns of the magnetic thin film 12 are in contact with or in close proximity to the side in contact with the surface 10a, and the width is a detection width, which is shown in FIG. Tw. The number of magnetic thin film patterns is preferably laid out at an equal pitch in consideration of the required detection width Tw. The detection width Tw can be freely changed, and can be freely coped with a detection width of the millimeter order.

  2 is a cross-sectional view taken along line AB in FIG. In FIG. 2, it is assumed that there is a minute magnet 30 at the tip of the magnetic thin film 12.

  The magnetic flux from the N pole of the minute magnet 30 is sucked into the magnetic thin film 12, leaks out, and returns to the S pole. If this magnetic flux is dominant on the front side of the magnetic film as shown in FIG. 2, the magnetic flux in the magnetic thin film 12 drawn from the magnet 30 by the application of a high-frequency current to the magnetic thin film 12 changes synchronously. Then, it is detected as an induction output by the planar coil 16 and taken out as a sensor output.

  On the other hand, the magnetic thin film 12 on the rear side cancels a magnetic field that is considered uniform by geomagnetism and surrounding magnetism. Therefore, the relationship between the planar coil 16 and the magnetic thin film 12 is opposite in phase between the rear side and the front side, and the induction output on the planar coil 16 is added and canceled.

  In the present invention, the part where the magnetic thin film 12 is drawn out to the side magnetic detection part with the central part of the planar coil 16 as the boundary is the main operation, and the opposite side is the operation for canceling the external magnetic field. Accordingly, the addition is performed in the opposite phase as seen from the planar coil 16, and it is possible to realize a sensor suitable for a local magnetic field that is strong against an external magnetic field by differential operation. Further, since the present invention is a fluxgate sensor, there is no speed dependency in principle.

  Next, a device for increasing the sensitivity of the sensor will be described. FIG. 3 shows an embodiment in that case. In FIG. 3, the same parts as those in FIG.

  As described with reference to FIG. 2, it is preferable that the magnetic flux drawn on the front side does not spread to the rear side. When detecting relatively long NS intervals, the magnetic thin film 12 is divided at the center of the planar coil. More preferably, the front side and the rear side are separated and electrically connected by the conductive film 32. Thus, by magnetically separating the magnetic thin film 12 at the center of the planar coil, a more differential effect can be achieved and sensor sensitivity can be improved.

  In that case, as shown in FIG. 3, the conductive film 34 connecting the parallel patterns of the magnetic thin film 12 in series can be formed in the same process. Further, since the amount of magnetic flux drawn into the magnetic thin film 12 is reduced when the pitch interval of the parallel pattern is increased with respect to the detection width, it is also effective to widen the pattern width so that the cross-sectional area increases toward the tip. Means.

  FIG. 4 shows an example of the tip of the magnetic thin film 12. FIG. 4A shows an example in which the width of the tip is not widened. For example, in addition to 12a simply widened as shown in FIG. 4B, 12b may be formed into a fork by branching the tip as shown in FIG. 4C. Further, in order to balance the sensitivity of the front side and the rear side as much as possible, it is preferable to perform the treatment for widening the tip part also on the rear side.

  Next, an example in which a magnetic detection element was actually manufactured will be described. Here, a magnetic detection element was fabricated with the configuration of FIG. First, 12 ceramics 10 were arranged with a pattern width of 12 μm using a Fe—Ta—C-based thin film (t = 2 μm) as the magnetic thin film 12, and the detection width was set to 1.5 mm.

  The tip of the magnetic thin film 12 was expanded to a width of 36 μm, and the tip was exposed at the medium contact surface (10a) by polishing. The length of the front side and the rear side of the magnetic thin film 12 was 0.76 mm, respectively, and the planar coil 16 laminated thereon was a copper film of 48T.

  The total resistance value of the magnetic thin film 12 was 510Ω, and the resistance of the planar coil 16 was 210Ω. The medium is printed with lines having a line width of 0.1 mm, 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm with magnetic toner, and magnetized by a magnet in the transport direction. The contact surface 10a was applied and scanned to measure the output.

  FIG. 5 shows an example of an evaluation circuit. FIG. 5 shows a sensor circuit that extracts a sensor output using a magnetic detection element. First, a 5 MHz pulse was oscillated by the oscillation circuit 40, and a current was applied to the magnetic thin film 12 by the buffer 42. On the planar coil 16 side, a peak due to the capacitive coupling of the rise and fall of the pulse occurs, and the induction output of the planar coil 16 shifts the peak. Therefore, the detection circuit 42 detects the peak shift amount and amplifies it. The sensor output was taken out by the circuit 44.

  The characteristic evaluation results are shown in FIG. In addition, in FIG. 6, lines with line widths of 0.1 mm, 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm are shown in the form of a bar code, and the output when this is read with this sensor as described above is shown. Show.

  FIG. 6A shows the result when the spacing amount (distance between the surface 10a and the medium) is 0 mm, and FIG. 6B shows the result when the spacing amount is 0.3 mm. As shown in FIGS. 6A and 6B, even when the line width is 0.1 mm, sufficient detection is possible, and it can be seen that the characteristic is strong against spacing.

  FIG. 7 shows the relationship between the amount of spacing and the sensor output value (relative value) in this sensor. The relative value on the vertical axis refers to the output value when the spacing amount is 0 mm. FIG. 7 shows the results for the medium line widths of 0.1 mm, 0.25 mm, 0.5 mm, 0.75 mm, and 1 mm as described above.

  FIG. 7 also shows the characteristics of a conventional magnetic head when the spacing is 0.25 mm. As shown in FIG. 7, for example, when the line width is 0.25 mm and the spacing is 0.1 mm in the magnetic head, the output is 0.1 times, whereas in this sensor, the output is 0.43 times under the same conditions. There is clearly a good spacing performance.

  This is a result of reflecting the distribution of the magnetic field in a straightforward manner without causing a decrease factor due to the magnetic circuit of the core unlike the magnetic head. Moreover, it can be confirmed from the differential effect of the magnetic detection element as described above that the geomagnetism and the magnetic field from the power source are hardly influenced by the influence of the external magnetic field, and it is understood that the magnetic detection element is strong against the external magnetic field.

  Next, a magnetic identification sensor using the magnetic detection element of the present invention will be described. For example, a magnetic identification sensor for banknotes detects a magnetic ink pattern. This sensor needs to be magnetized in advance in order to detect the residual magnetization of the magnetic ink. Although it can be magnetized by a permanent magnet placed in the transport path, it is more convenient to incorporate it in the sensor body 48. In order to do so, a device is required.

  FIG. 8 is a perspective view showing a configuration of an embodiment of a magnetic identification sensor using the magnetic detection element of the present invention. A substrate 10 in FIG. 8 is a nonmagnetic substrate of the magnetic detection element in FIGS. A magnetic thin film 12, a planar coil 16, and the like are formed on the left side surface of the substrate 10, and this magnetic detection element is disposed on the sensor body 48.

  In addition, magnets 50 and 52 are arranged at front and rear positions with respect to the medium conveyance direction of the magnetic detection element. The medium is transported in the transport direction while contacting the sensor sliding surface 10a. At that time, since the magnetic field from the magnet jumps into the magnetic thin film 12 from the magnetic field detection direction, the magnet 50 and the magnet 52 are arranged so as to have opposite polarities in the NS direction as shown in FIG. The application of a magnetic field to the magnetic detection element is canceled. The NS direction of the magnets 50 and 52 is perpendicular to the medium. It is desirable to make the size of both magnets 50 and 52 and the distance between the magnetic detection elements as equal as possible.

  If the magnetic field applied to the magnetic detection element cannot be completely canceled due to variations in the magnet position, it is necessary to surround the magnetic detection element with the shield member 54 as shown in FIG. In addition, the height of the shield member 54 is selected and aligned. At that time, it is important not to break the balance of the differential characteristics of the front side and the rear side with the magnetic thin film 12 of the magnetic detection element.

  There are various detection widths of the magnetic identification sensor. When the detection width exceeds 10 mm, there is a case where the pull-in of the magnetic flux is reduced due to the increase in the pitch of the magnetic detection elements. In addition, the resistance of the magnetic detection element may become too large, and a decrease in sensitivity due to a decrease in drive current may be a problem.

  This can be solved by dividing the magnetic thin film 12 as shown in FIG. 9 and flowing a predetermined current through each magnetic thin film. In terms of circuit, a necessary number of buffer portions 42 of the sensor circuit shown in FIG. 5 may be added and a high-frequency current may be applied from each buffer portion 42 to each magnetic thin film 12.

  In FIG. 9, the same parts as those in FIGS. 1 and 3 are denoted by the same reference numerals. The embodiment of FIG. 9 shows an example in which the magnetic thin film is divided into three. Electrodes 24e, 24f, 24g, 24h, 24i, and 24j in FIG. 9 indicate the magnetic thin film electrodes.

  In this way, the magnets are arranged at positions before and after the magnetic detection element with respect to the conveyance direction of the detection medium, and the NS direction of the magnet is perpendicular to the medium and opposite in polarity to each other. It can be configured as a sensor.

It is a perspective view which shows the structure of one Embodiment of the magnetic detection element which concerns on this invention. It is sectional drawing in the AB line of FIG. It is a top view which shows other embodiment of this invention. It is a figure which shows the example which enlarges a cross-sectional area toward the front-end | tip part in the parallel pattern of a magnetic thin film. It is a circuit diagram which shows an example of the evaluation circuit of a magnetic detection element. It is a figure which shows the evaluation result of the magnetic detection element of this invention. It is a figure which compares and shows the characteristic of the magnetic detection element of this invention, and the conventional magnetic head. It is a perspective view which shows one Embodiment of the magnetic identification sensor using the magnetic detection element of this invention. It is a top view which shows other embodiment of the magnetic detection element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Board | substrate 10a, 10b surface 12 Magnetic thin film 14 Insulating layer 16 Planar coil 18 Insulating layer 20 Through hole 22 Lead wire 24a-24i Electrode 30 Magnet 32, 34 Conductive film 40 Oscillation circuit 42 Buffer 44 Detection circuit 46 Amplification circuit 48 Sensor main body 50 , 52 Magnet 54 Shield member

Claims (5)

In a magnetic sensing element that applies a high-frequency current to a magnetic thin film and extracts a magnetic flux change in the magnetic thin film due to an external magnetic field as an induced output by a planar coil laminated with an insulating layer interposed therebetween, the magnetic thin film is formed on one surface of a nonmagnetic substrate. Formed as a plurality of parallel patterns connected in series, and the ends of the plurality of parallel patterns are aligned in contact with or close to one side of the substrate to detect the width of the plurality of parallel patterns A magnetic detection element, wherein a magnetic detection part having a width is formed, and the planar coil is disposed so that a central part thereof traverses a plurality of parallel patterns of the magnetic thin film. The magnetic detection element according to claim 1, wherein the plurality of parallel patterns of the magnetic thin film are magnetically separated at a central portion of the planar coil and electrically connected by a conductive film. The magnetic detection element according to claim 1, wherein the plurality of parallel patterns of the magnetic thin film are formed so that a cross-sectional area increases toward a tip. 4. The magnetic detection element according to claim 1, wherein the magnetic detection element is disposed such that a medium contact surface is in contact with a medium, and the medium detection direction is the medium detection direction. A magnetic identification sensor, wherein magnets are arranged at positions before and after the magnetic detection element, and the NS directions of the magnets are perpendicular to the medium and have opposite polarities. The magnetic identification sensor according to claim 4, wherein a magnetic shield member having a height corresponding to the length of the parallel pattern of the magnetic thin films is provided around the magnetic detection element.