JP2016206069A - Magnetic sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor device capable of determining whether a magnetic pattern affixed to a medium is a hard material or a soft material.SOLUTION: A magnetic sensor device 20 has a sensor part 1 for detecting a magnetic pattern M of a medium 3 conveyed along a conveyance surface 2. The sensor part 1 includes: a permanent magnet 5 for applying a bias magnetic field 4; a downstream side yoke 6 arranged on the downstream side of the permanent magnet 5; a first magnetism-sensitive element 11 arranged at a first position A facing the downstream side yoke 6 in an orthogonal direction Z orthogonal to the conveyance surface 2 but not facing the permanent magnet 5; and a second magnetism-sensitive element 12 arranged at a second position B facing the permanent magnet 5 in the orthogonal direction Z. The first magnetism-sensitive element 11 detects a change only of a bias magnetic field 4 due to remnant magnetic flux density of the magnetic pattern M (hard material), and for this reason, it can be determined whether the magnetic pattern M provided for the medium 3 is a hard material or a soft material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic sensor device that detects a magnetic pattern.

  When determining the type or authenticity of a medium such as a banknote to which a magnetic pattern is applied by magnetic ink, a magnetic sensor device including a magnet that generates a bias magnetic field and a magnetosensitive element such as a magnetoresistive element is used. The magnetosensitive element detects a change in the magnetic field when the magnetic pattern passes through the detection position of the magnetic sensor device, and outputs a signal corresponding to the change in its resistance value. Such a magnetic sensor device is described in Patent Document 1.

Japanese Patent No. 3879777

  In the technology described in Patent Document 1, the magnetic pattern is printed with a magnetic ink containing a hard material such as ferrite powder, or a magnetic ink containing a soft material (soft magnetic material) such as soft magnetic stainless steel powder. There is a problem that it is not possible to determine whether or not printing is performed.

  That is, even when a magnetic pattern is formed using any of the above magnetic inks, the magnetic pattern has a magnetic permeability, so that the magnetic sensitive element detects a change in the magnetic field caused by the magnetic permeability. On the other hand, when the magnetic pattern is printed with magnetic ink containing a hard material, the magnetosensitive element detects a change in the magnetic field due to the residual magnetic flux density, but the change in the magnetic field due to the residual magnetic flux density. Is detected by being superimposed on the change in the magnetic field due to the magnetic permeability, so that the signal component derived from the residual magnetic flux density cannot be separated. Therefore, it cannot be determined whether the magnetic pattern is printed with magnetic ink containing hard material or magnetic ink containing soft material.

  In view of the above problems, an object of the present invention is to provide a magnetic sensor device that can determine whether a magnetic pattern applied to a medium is a hard material or a soft material.

  In order to solve the above problems, the present invention provides a magnetic sensor device for detecting a magnetic pattern applied to a medium that moves relative to a moving surface by a magnetosensitive element, a magnet that applies a bias magnetic field to the medium, A downstream yoke disposed on the downstream side of the magnet in the moving direction of the medium, and as the magnetosensitive element, the magnet facing the downstream yoke in an orthogonal direction perpendicular to the moving surface, Comprises a first magnetosensitive element disposed at a first position that does not oppose, and a second magnetosensitive element disposed at a second position that opposes the magnet in the orthogonal direction.

According to the present invention, the second magnetosensitive element is disposed at the second position facing the magnet to which the bias magnetic field is applied. Therefore, when the medium passes through the second position along the moving surface, the change in the magnetic field due to the magnetic permeability of the magnetic pattern can be detected by the second magnetosensitive element. On the other hand, the first magnetosensitive element is disposed at a first position facing a yoke disposed downstream of the magnet to which the bias magnetic field is applied. Here, since the first position is in a region separated from the region facing the magnet, the change in the direction of the magnetic field is small and the magnetic flux density is small when the medium passes through the second position along the moving surface. Therefore, when the medium passes through the second position along the moving surface, the first disposed at the first position.
With respect to the signal component output from the magnetosensitive element, the output of the signal component derived from the magnetic permeability can be made substantially zero. In addition, since the first position is in a region away from the region facing the magnet on the downstream side of the magnet in the moving direction of the medium, the first magnetosensitive element arranged in the first position is caused by the residual magnetic flux density of the magnetic pattern. The change of the magnetic field can be detected. Therefore, based on the signal output from the first magnetosensitive element, it is possible to determine whether the magnetic pattern applied to the medium is a hard material or a soft material.

  In the present invention, the first position and the second position may be in the bias magnetic field from the magnet to the downstream yoke via the moving surface.

  In the present invention, it is desirable that the first magnetosensitive element has a magnetosensitive direction in the moving direction. In this way, the first magnetosensitive element detects the moving direction component of the change in the direction of the magnetic field. Thereby, it becomes easy to make the output of the signal component derived from the magnetic permeability substantially zero for the signal output from the first magnetosensitive element.

  Here, an MR element can be used as the magnetosensitive element.

  In the present invention, it is desirable to have an upstream yoke disposed upstream of the magnet in the moving direction. If it does in this way, it can control that the magnetic field which a magnet generates by downstream Yuku and an upstream yoke spreads more than necessary. Therefore, it is possible to prevent the magnetic sensing element from detecting a change in the magnetic field due to the movement of the magnetic material different from the medium. In this way, it is possible to prevent or suppress the magnetosensitive element from being affected by the magnetic field outside the apparatus.

  In this case, the magnetosensitive element includes a third magnetosensitive element disposed at a third position facing the upstream yoke in a direction orthogonal to the moving surface and not facing the magnet. be able to. In this case, when the relative movement direction is reversed, the change in the magnetic field caused by the residual magnetic flux density of the magnetic pattern (hard material) can be detected by the third magnetosensitive element arranged at the third position. That is, when the relative movement direction of the medium with respect to the apparatus is reversed, the medium passes through the third position after passing through the position facing the magnet along the moving surface. Therefore, when a magnetic pattern made of a hard material is applied to the medium, the hard material is magnetized when the medium passes through the third position. Therefore, a change in the magnetic field due to the residual magnetic flux density of the magnetic pattern (hard material) can be detected by the third magnetosensitive element.

  In this invention, it has a 2nd magnet which applies a 2nd bias magnetic field to the said medium, and the said 2nd magnet shall be located in the downstream of the said downstream yoke in the said moving direction. . In this way, when the relative movement direction of the medium with respect to the apparatus is reversed, the change of the magnetic field caused by the residual magnetic flux density of the magnetic pattern (hard material) is caused by the first magnetosensitive element arranged at the first position. Can be detected. That is, when the relative movement direction of the medium is reversed, the medium passes through the first position after passing through the position facing the second magnet along the moving surface. Therefore, when a magnetic pattern made of a hard material is applied to the medium, the hard material is magnetized when the medium passes through the first position. Therefore, a change in the magnetic field due to the residual magnetic flux density of the magnetic pattern (hard material) can be detected by the first magnetosensitive element.

In the present invention, a plurality of the first magnetosensitive elements and the second magnetosensitive elements are respectively arranged in a direction along the moving surface so as to intersect the moving direction, and the magnet includes a plurality of the second magnetosensitive elements. It is desirable to extend in the arrangement direction of the magnetosensitive elements and to face each second magnetosensitive element. In this way, the magnetic pattern can be detected in a wide range extending in the width direction of the medium. Further, since one long magnet extending in the arrangement direction of the first magnetosensitive elements is used as the magnet, a plurality of magnets corresponding to the first magnetosensitive elements are arranged in the arrangement direction of the first magnetosensitive elements. Compared to the arrangement, it is easy to make the magnetic field of the magnet formed via the transport surface uniform along a predetermined direction. Therefore, it is possible to prevent or suppress the occurrence of a difference in the output from the first magnetosensitive element due to the position of the first magnetosensitive element in the arrangement direction.

  In the present invention, it is preferable that the downstream yoke extends along the magnet and faces each first magnetosensitive element. Since the magnetic field generated by the magnet is guided to the downstream yoke, in this way, the magnetic field of the magnet formed so as to pass through the transport surface is made uniform along the magnetic sensing direction of each magnetic sensing element. be able to. As a result, it is possible to prevent or suppress the occurrence of a difference in the output from the first magnetosensitive element due to the position of the first magnetosensitive element in the arrangement direction.

  In the present invention, it is possible to determine whether the magnetic pattern applied to the medium is a hard material or a soft material based on a signal output from the first magnetosensitive element.

It is explanatory drawing of the magnetic sensor apparatus to which this invention is applied. It is explanatory drawing of the sensor part of the magnetic sensor apparatus of FIG. It is a graph of the resistance value-magnetic flux density characteristic curve of the magnetosensitive element mounted in a sensor part. It is a schematic diagram of a sensor part. It is explanatory drawing of the change of the magnetic flux vector when a magnetic pattern moves. It is explanatory drawing of the change of the magnetic field when the magnetic pattern of a hard material moves. It is a graph of the example of an output from each magnetosensitive element which detected the magnetic pattern. It is explanatory drawing of the sensor part of the modification 1,2.

  Hereinafter, a magnetic sensor device to which the present invention is applied will be described with reference to the drawings.

(overall structure)
FIG. 1 is an explanatory view schematically showing a main part configuration of a magnetic sensor device to which the present invention is applied. The magnetic sensor device 20 of the present invention detects the magnetic pattern M applied to the sheet-like medium 3 such as banknotes conveyed along the conveyance path 21 (conveying surface 2) by the magnetic sensitive elements 11 and 12.

  The magnetic pattern M detected by the magnetic sensor device 20 includes one printed with magnetic ink containing a hard material and one printed with magnetic ink containing a soft material. The hard material is a magnetic material that is easily magnetized when applied with a magnetic field from the outside, such as a magnetic material used in a magnet, having a large hysteresis and a high residual magnetic flux density. The soft material is a magnetic material that has a small hysteresis, a low residual magnetic flux density, and is not easily magnetized, like a core material of a motor or a magnetic head.

  As shown in FIG. 1, the magnetic sensor device 20 includes a sensor unit 1 and a transport mechanism 22 that transports the medium 3 along a transport path 21 that passes through a detection position by the sensor unit 1. The transport mechanism 22 includes a transport roller 23 and a transport motor 24 serving as a drive source for the transport roller 23.

  The sensor unit 1 extends in the width direction Y of the transport path 21 orthogonal to the transport direction X1 of the medium 3. The transport roller 23 is disposed to face the sensor unit 1 and the transport surface 2 in the orthogonal direction Z. The sensor unit 1 is accommodated in a nonmagnetic case 25. In the case 25, the facing surface facing the transport roller 23 defines the detection position of the magnetic pattern M by the magnetic sensor device 20 and constitutes a part of the transport surface 2 in the transport path 21.

The sensor unit 1 includes a plurality of MR substrates 26 on which a first magnetosensitive element 11 and a second magnetosensitive element 12 are formed. The MR substrate 26 is arranged in the width direction Y along the transport surface 2. Therefore, the sensor unit 1 includes a plurality of first magnetosensitive elements 11 arranged in the width direction Y and a plurality of second magnetosensitive elements 12 arranged in the width direction Y. The second magnetosensitive element 12 is disposed upstream of the first magnetosensitive element 11 in the transport direction X1.

  The sensor unit 1 includes a permanent magnet 5, a downstream yoke 6 disposed on the downstream side of the permanent magnet 5 in the conveyance direction X <b> 1 of the medium 3, and an upstream yoke 7 disposed on the upstream side of the permanent magnet 5. Have. The permanent magnet 5 applies a bias magnetic field 4 to the medium 3, the first magnetosensitive element 11 and the second magnetosensitive element 12 conveyed on the conveyance surface 2. The transport surface 2 is disposed on the opposite side (orthogonal direction Z side) of the permanent magnet 5, the downstream yoke 6 and the upstream yoke 7 with the first and second magnetosensitive elements 11 and 12 interposed therebetween. .

  The permanent magnet 5 is long and has a rectangular parallelepiped shape. The permanent magnet 5 extends with a constant width in the width direction Y (the arrangement direction of the plurality of first magnetosensitive elements 11). The permanent magnet 5 faces each second magnetosensitive element 12. The downstream yoke 6 abuts against the downstream end surface of the permanent magnet 5 and extends along the permanent magnet 5 with a constant width in the width direction Y. The downstream yoke 6 faces each first magnetosensitive element 11.

  The upstream yoke 7 contacts the upstream end surface of the permanent magnet 5 and extends along the permanent magnet 5 with a constant width in the width direction Y. The downstream yoke 6 and the upstream yoke 7 are each elongated and have a rectangular parallelepiped shape. The dimensions in the width direction Y of the permanent magnet 5, the downstream yoke 6 and the upstream yoke 7 are the same.

  Here, the first magnetosensitive element 11 and the second magnetosensitive element 12 located at both end portions in the width direction Y are arranged at positions separated from the end portion 5a of the permanent magnet 5 by a predetermined distance T or more. The specified distance T is ½ of the height dimension L in the vertical direction of the permanent magnet 5.

(Sensor part)
FIG. 2 is an explanatory view of the arrangement of the permanent magnet 5 and the magnetic sensitive elements 11 and 12 in the sensor unit 1 of the magnetic sensor device 20 of the present invention. FIG. 3A is a graph of a resistance value-magnetic flux density characteristic curve of the first magnetosensitive element 11, and FIG. 3B is a graph of a resistance value-magnetic flux density characteristic curve of the second magnetosensitive element 12. In FIG. 2, contrary to FIG. 1, the permanent magnet 5 is shown above the magnetic sensing elements 11 and 12 toward the drawing, and the conveying surface 2 is shown below the magnetic sensing elements 11 and 12 toward the drawing.

  The permanent magnet 5 is magnetized in a direction orthogonal to the transport surface 2. In this example, the permanent magnet 5 has the N pole facing the transport surface 2 side. The downstream yoke 6 contacts the permanent magnet 5 from the downstream side, and the upstream yoke 7 contacts the permanent magnet 5 from the upstream side. The end surface of the permanent magnet 5 on the side of the conveyance surface 2 and the end surface of the downstream yoke 6 and the upstream yoke 7 on the side of the conveyance surface 2 are located on the same plane and extend in parallel with the conveyance surface 2.

  The first magnetosensitive element 11 and the second magnetosensitive element 12 are both magnetoresistive elements. More specifically, it is an anisotropic magnetoresistive element (AMR (Anisotropic-Magneto-Resistance)) having a magnetoresistive pattern made of a thin film ferromagnetic metal. When a bias magnetic field 4 is applied from a direction perpendicular to the current direction when a current is passed through the magnetoresistive pattern of the anisotropic magnetoresistive element, the resistance value decreases according to the strength of the magnetic field. The magnetosensitive direction F of the first magnetosensitive element 11 and the second magnetosensitive element 12 is the conveyance direction X1, and the first magnetosensitive element 11 and the second magnetosensitive element 12 detect a change in the magnetic flux vector in the conveyance direction X1. .

The first magnetosensitive element 11 is disposed at a first position A that faces the downstream yoke 6 and does not face the permanent magnet 5 in the orthogonal direction Z perpendicular to the transport surface 2. The second magnetosensitive element 12 is disposed at the second position B facing the permanent magnet 5 in the orthogonal direction Z. The second position B is upstream of the first position A in the transport direction X1. The first position A and the second position B are in the bias magnetic field 4 from the permanent magnet 5 to the downstream yoke 6 via the transport surface 2. The distance between the end surface of the downstream yoke 6 on the transport surface 2 side and the first magnetosensitive element 11 is the same as the distance between the end surface of the permanent magnet 5 on the transport surface 2 side and the second magnetosensitive element 12. is there.

  At the first position A, a bias magnetic field 4 (first magnetic flux vector Ha0) is applied so that the change in resistance value increases with respect to the change in magnetic flux density in the resistance value-magnetic flux density characteristics of the first magnetosensitive element 11. It is a position. In other words, at the first position A, when the first magnetosensitive element 11 is arranged, the resistance value R1 is plotted on the steep curve portion in the resistance value-magnetic flux density characteristic curve of FIG. It is a position. At the second position B, a bias magnetic field 4 (second magnetic flux vector Hb0) is applied such that the change in resistance value increases with respect to the change in magnetic flux density in the resistance value-magnetic flux density characteristics of the second magnetosensitive element 12. It is a position. In other words, at the second position B, when the second magnetosensitive element 12 is arranged, the resistance value R2 is plotted on a curve portion having a steep slope in the resistance value-magnetic flux density characteristic curve of FIG. It is a position.

  As shown in FIG. 2, in this example, the first magnetic flux vector Ha0 at the first position A is inclined in the direction toward the downstream yoke 6 toward the downstream side. The second magnetic flux vector Hb0 at the second position B is inclined in the direction away from the permanent magnet 5 toward the downstream side. The inclination of the first magnetic flux vector Ha0 with respect to the orthogonal direction Z is larger than the inclination of the second magnetic flux vector Hb0 with respect to the orthogonal direction Z.

  As the first magnetosensitive element 11 and the second magnetosensitive element 12, a semiconductor magnetoresistive element, Hall element, MI element (Magneto-Impedance element), fluxgate type magnetic sensor, or the like may be used. Further, the first magnetosensitive element 11 may be disposed on the opposite side of the downstream yoke 6 with the transport surface 2 interposed therebetween. Similarly, the second magnetosensitive element 12 may be disposed on the opposite side of the permanent magnet 5 with the transport surface 2 interposed therebetween. Furthermore, the 1st magnetosensitive element 11 and the 2nd magnetosensitive element 12 may be arrange | positioned on the opposite side on both sides of the conveyance surface 2.

  Further, the second position B can be a position where at least a part of the second magnetosensitive element 12 faces the permanent magnet 5 in the orthogonal direction Z. Further, the distance between the end face of the downstream yoke 6 on the transport surface 2 side and the first magnetosensitive element 11 is the distance between the end face of the permanent magnet 5 on the transport surface 2 side and the second magnetosensitive element 12. It may be different. Further, the upstream yoke 7 may be omitted. The permanent magnet may be arranged with the south pole facing the transport surface 2 side.

(Operating principle)
FIG. 4 is a schematic diagram showing the sensor unit 1 partially enlarged. FIG. 5 is an explanatory diagram of changes in the magnetic flux vectors Ha 0 and Hb 0 when the magnetic pattern M moves on the transport surface 2. FIG. 6 is an explanatory diagram of changes in the magnetic field when the magnetic pattern M including the hard material moves on the transport surface 2. 4 to 6, only the magnetic pattern M applied to the medium 3 is shown without the medium 3 in order to show the change of the magnetic flux vectors Ha0 and Hb0 and the change of the magnetic field in an easily understandable manner.

  First, when the magnetic pattern M applied to the medium 3 passes through the upstream detection position C facing the second position B on the transport surface 2, the bias magnetic field 4 is caused by the magnetic permeability of the magnetic pattern M. The direction of the magnetic flux changes so as to be absorbed by the magnetic pattern M. As a result, the second magnetic flux vector Hb0 passing through the second position B where the second magnetosensitive element 12 is disposed changes its direction before and after the transport direction X.

More specifically, as shown in FIG. 5A, the second magnetic flux vector Hb0 is inclined in the direction approaching the normal line (orthogonal direction Z) toward the magnetic pattern M (magnetic flux vector Hb1). As shown in FIG. 5 (b), it is inclined toward the downstream side of the first magnetic flux vector Hb0 (magnetic flux vector Hb2). Here, as schematically shown in FIG. 4, since the second position B is a position facing the permanent magnet 5 that generates the bias magnetic field 4, the magnetic flux density is large (the magnetic flux vector Hb0 is large). Accordingly, the component Hbf in the magnetic sensing direction F of the magnetic flux vector Hb0 detected by the second magnetic sensing element 12 changes greatly. Thereby, the resistance value of the second magnetosensitive element 12 varies within a relatively large range S2 shown in FIG. 3B, and a signal corresponding to the variation of the resistance value is output from the second magnetosensitive element 12. .

  Here, when the magnetic pattern M passes the upstream detection position C, the direction of the first magnetic flux vector Ha0 passing through the first position A is also changed back and forth. However, since the first position A is farther from the permanent magnet 5 than the second position B, the magnetic flux density of the bias magnetic field 4 passing through the first position A is small (magnetic flux vector Ha0) as schematically shown in FIG. Is small). Moreover, since the inclination of the first magnetic flux vector Ha0 with respect to the orthogonal direction Z is larger than the inclination of the second magnetic flux vector Hb0 with respect to the orthogonal direction Z, for example, the amount of change in the direction of the first magnetic flux vector Ha0 and the second magnetic flux vector Hb0 Even when the amount of change in direction is the same, the component Haf of the first magnetic flux vector Ha0 detected by the first magnetic sensing element 11 in the magnetic sensing direction F is the sensitivity of the first magnetic flux vector Ha0 detected by the second magnetic sensing element 12. It becomes smaller than the component Hbf in the magnetic direction F. As a result, when the magnetic pattern M passes the upstream detection position C, the resistance value of the second magnetosensitive element 12 changes only in a very small range S1 shown in FIG. 3, corresponding to the resistance value fluctuation. Thus, the signal output from the second magnetosensitive element 12 is substantially zero.

  Next, when the magnetic pattern M applied to the medium 3 passes through the downstream detection position D facing the first position A on the transport surface 2, the magnetic pattern M is an area facing the permanent magnet 5 (critical path). Range). Therefore, when the magnetic pattern M is made of a hard material, the magnetic pattern M is magnetized. Therefore, as shown in FIG. 6A, the magnetic pattern M generates a residual magnetic field 8. On the other hand, when the magnetic pattern M is made of a soft material, the magnetic pattern M is not magnetized. Therefore, no residual magnetic field is generated as shown in FIG.

  Here, the downstream side detection position D and the first position A are at positions outside the region (critical path range) facing the permanent magnet 5. Therefore, the first magnetosensitive element 11 detects a change in the magnetic field caused by the residual magnetic flux density of the magnetic pattern M when the magnetic pattern M is magnetized. Thereby, since the resistance value of the first magnetosensitive element 11 varies, a signal corresponding to the variation of the resistance value is output from the first magnetosensitive element 11. On the other hand, when the magnetic pattern M is not magnetized, the first magnetosensitive element 11 does not detect a change in the magnetic field due to the residual magnetic flux density of the magnetic pattern M. Does not output a signal corresponding to a change in resistance value.

  FIG. 7A is a graph showing an output example from the first magnetosensitive element 11 and an output example from the second magnetosensitive element 12 when the sensor unit 1 detects a magnetic pattern M made of a hard material. 7 (b) is a graph showing an output example from the first magnetosensitive element 11 and an output example from the second magnetosensitive element 12 when the sensor unit 1 detects a magnetic pattern M made of a soft material. As shown in FIG. 7A, when the magnetic pattern M is made of a hard material, signals are output from both the second magnetic sensing element 12 and the first magnetic sensing element 11. On the other hand, as shown in FIG. 7B, when the magnetic pattern M is made of a soft material, a signal is output from the second magnetosensitive element 12, but a signal is output from the first magnetosensitive element 11. Not.

  Therefore, the magnetic sensor device 20 can determine whether the magnetic pattern M is formed of a hard material or a soft material based on a signal from the first magnetosensitive element 11. When the magnetic pattern M is made of a hard material, the magnetic information of the magnetic pattern M can be acquired based on the signal from the first magnetosensitive element 11 and the signal from the second magnetosensitive element 12. On the other hand, when the magnetic pattern M is made of a soft material, the magnetic information of the magnetic pattern M can be acquired based on the signal from the second magnetosensitive element 12.

  Further, according to the magnetic sensor device 20, since the plurality of first magnetosensitive elements 11 and the plurality of second magnetosensitive elements 12 arranged in the width direction Y of the conveyance path 21 (conveyance surface 2) are provided, The magnetic pattern M applied to the medium 3 can be detected in a wide range extending in the width direction.

  Here, the first magnetosensitive element 11 detects a component of the magnetic flux vector in the conveyance direction X1 (magnetic sensitivity direction F). Therefore, if the first magnetosensitive element 11 is disposed in a magnetic field portion including a magnetic flux vector directed in the transport direction X1 in the bias magnetic field 4, the first magnetosensitive element 11 can detect a change in the magnetic flux vector. On the other hand, when the first magnetosensitive element 11 is disposed in the magnetic field portion including the magnetic flux vector inclined with respect to the transport direction X1 in the bias magnetic field 4, the first magnetosensitive element 11 is along the transport direction X1 of the magnetic flux vector. Only detected components are detected. Therefore, even when the change amount of the bias magnetic field 4 passing through the first magnetosensitive element 11 is the same, the bias magnetic field 4 (magnetic flux vector) passing through the first magnetosensitive element 11 is directed in the magnetosensitive direction F. Different signals are output from the first magnetosensitive element 11 when the bias magnetic field 4 (magnetic flux vector) passing through the first magnetosensitive element 11 is inclined. Therefore, if the bias magnetic field 4 (magnetic flux vector) is not uniform in the magnetic sensing direction F, there is a problem that the detection accuracy of the magnetic information of the magnetic pattern M is lowered.

  In order to deal with such a problem, in this example, the downstream yoke 6 and the upstream yoke 7 are arranged on both sides of the long permanent magnet 5 between the permanent magnet 5 and the downstream in the transport direction X1. The side yoke 6 and the upstream yoke 7 extend in parallel to a direction orthogonal to the transport direction X1. Accordingly, the bias magnetic field 4 (magnetic flux vector) formed by the permanent magnet 5 so as to pass through the transport surface 2 is guided to the downstream yoke 6 and the upstream yoke 7, and the first magnetosensitive element 11 and the second magnetosensitive element. It becomes uniform in the transport direction X1, which is the magnetic sensing direction F of the element 12. As a result, the bias magnetic field 4 (magnetic flux vector) passing through the first magnetosensitive element 11 is not inclined with respect to the transport direction X1 regardless of the position in the width direction Y. It can be detected.

  In this example, the magnetosensitive elements 11 and 12 arranged at the end in the width direction Y are separated from the end of the permanent magnet 5 by a distance T (1/2 L) or more. Therefore, the bias magnetic field 4 (magnetic flux vector) passing through the magnetosensitive elements 11 and 12 disposed at the end in the width direction Y can also be oriented in the magnetosensitive direction F.

  Further, in the present example, the bias magnetic field 4 generated by the permanent magnet 5 by the downstream side YUK and the upstream side yoke 7 disposed on both sides of the permanent magnet 5 is suppressed from being unnecessarily widened. Accordingly, it is possible to prevent the first magnetic sensing element 11 and the second magnetic sensing element 12 from detecting a change in the magnetic field caused by the movement of a magnetic material different from the magnetic pattern M of the medium 3. Further, by providing the downstream side YUK and the upstream side yoke 7 disposed on both sides of the permanent magnet 5, the first magnetic sensing element 11 and the second magnetic sensing element 12 are affected by the magnetic field outside the sensor unit 1. It can be prevented or suppressed.

(Modification 1 of sensor part)
FIG. 8A is an explanatory diagram of the sensor unit of the first modification, and FIG. 8B is an explanatory diagram of the sensor unit of the second modification. As shown in FIG. 8A, the sensor unit 1A of the first modification includes a first magnetosensitive element 11, a second magnetosensitive element 12, and a third magnetosensitive element 13 as magnetosensitive elements. The third magnetosensitive element 13 is disposed at a third position E facing the upstream yoke 7 in the orthogonal direction Z orthogonal to the transport surface 2 and not facing the permanent magnet 5. The third position E is only in a range where the resistance value of the third magnetosensitive element 13 arranged at the third position E when the medium 3 passes through the second magnetosensitive element 12 along the transport surface 2 is extremely small. It can be set to a position where the signal output from the third magneto-sensitive element 13 becomes substantially zero corresponding to the variation of the resistance value without changing.

According to this example, the reverse conveying direction X2 passing through the downstream yoke 6 and the permanent magnet 5 in this order.
When the medium 3 is conveyed, the third magnetosensitive element 13 detects the residual magnetic flux density of the magnetic pattern M magnetized by the permanent magnet 5. On the other hand, the third magnetosensitive element 13 does not detect a change in the bias magnetic field 4 due to the magnetic permeability of the magnetic pattern M. Accordingly, when the medium 3 is transported in the reverse transport direction X2, whether the magnetic pattern M is formed from a hard material or a soft material based on a signal from the third magnetosensitive element 13 is determined. Can be determined. Further, the magnetic information of the magnetic pattern M made of a hard material can be acquired based on the signal from the second magnetosensitive element 12 and the signal from the third magnetosensitive element 13, and based on the signal from the second magnetosensitive element 12. Magnetic information of the magnetic pattern M made of a soft material can be acquired.

(Modification 2 of sensor part)
As illustrated in FIG. 8B, the sensor unit 1 </ b> B of Modification 2 includes a second permanent magnet 15 on the downstream side of the downstream yoke 6 in the transport direction X <b> 1. The upstream yoke 7 is omitted.

  The second permanent magnet 15 applies a second bias magnetic field 16 to the medium 3. Here, the first position A changes only within a very small range of the resistance value of the first magnetosensitive element 11 disposed at the first position A when the medium 3 passes the position facing the permanent magnet 5. In other words, the signal output corresponding to the variation of the resistance value is substantially zero. In addition, the first position A has a very small resistance value of the first magnetosensitive element 11 disposed at the first position A when the medium 3 passes the position facing the second permanent magnet 15. It can be set to a position where the signal that changes only within a certain range and the signal output corresponding to the change in the resistance value becomes substantially zero.

  According to this example, when the medium 3 is transported in the reverse transport direction X2 passing through the second permanent magnet 15, the downstream yoke 6 and the permanent magnet 5 in this order, the first magnetosensitive element 11 is The residual magnetic flux density of the magnetic pattern M magnetized by the two permanent magnets 15 is detected. On the other hand, the first magnetosensitive element 11 does not detect a change in the bias magnetic field 16 due to the magnetic permeability of the magnetic pattern M. Therefore, when the medium 3 is transported in the reverse transport direction X2, whether the magnetic pattern M is formed of a hard material or a soft material based on a signal from the first magnetosensitive element 11 is determined. Can be determined. Further, the magnetic information of the magnetic pattern M made of a hard material can be acquired based on the signal from the first magnetosensitive element 11 and the signal from the second magnetosensitive element 12, and based on the signal from the second magnetosensitive element 12. Magnetic information of the magnetic pattern M made of a soft material can be acquired.

  Note that the upstream yoke 7 may be provided in the sensor unit 1B. Further, a second downstream yoke may be provided on the downstream side of the second permanent magnet 15 in the transport direction X1. If these yokes are provided, the bias magnetic fields 4 and 16 generated by the permanent magnets 5 and 15 are prevented from spreading more than necessary. Accordingly, it is possible to prevent the first magnetosensitive element 11, the second magnetosensitive element 12, and the third magnetosensitive element from detecting a change in the magnetic field caused by the movement of a magnetic material different from the magnetic pattern M. Moreover, it can prevent or suppress that the 1st magneto-sensitive element 11, the 2nd magneto-sensitive element 12, and the 3rd magneto-sensitive element 13 are influenced from the magnetic field outside the sensor part 1B.

DESCRIPTION OF SYMBOLS 1 ... Sensor part 2 ... Conveyance surface (moving surface)
DESCRIPTION OF SYMBOLS 3 ... Medium 4 ... Bias magnetic field 5 ... Permanent magnet 6 ... Downstream side yoke 7 ... Upstream side yoke 11 ... 1st magnetosensitive element 12 ... 2nd magnetosensitive element 13 ... third magnetic sensing element 15 ... second permanent magnet 16 ... second bias magnetic field 20 ... magnetic sensor device A ... first position B ... second position E ...・ 3rd position F ・ ・ ・ Magnetic sensing direction M ・ ・ ・ Magnetic pattern X1 ・ ・ ・ Moving direction Z ・ ・ ・ Orthogonal direction

Claims (9)

In a magnetic sensor device for detecting a magnetic pattern applied to a medium that moves relatively along a moving surface by a magnetosensitive element,
A magnet for applying a bias magnetic field to the medium;
A downstream yoke disposed on the downstream side of the magnet in the moving direction of the medium,
As the magnetosensitive element, a first magnetosensitive element disposed at a first position facing the downstream yoke in a direction orthogonal to the moving surface and not facing the magnet, and the magnet in the orthogonal direction, A magnetic sensor device comprising: a second magnetosensitive element disposed at a second position facing the magnetic sensor device. In claim 1,
The magnetic sensor device according to claim 1, wherein the first position and the second position are in the bias magnetic field from the magnet to the downstream yoke via the moving surface. In claim 1 or 2,
The magnetic sensor device according to claim 1, wherein the first magnetic sensitive element has a magnetic sensitive direction in the moving direction. In any one of claims 1 to 3,
The magnetic sensor device is characterized in that the magnetosensitive element is an MR element. In any one of claims 1 to 4,
A magnetic sensor device comprising an upstream yoke disposed on the upstream side of the magnet in the moving direction. In claim 5,
A magnetic sensor comprising a third magnetosensitive element disposed at a third position facing the upstream yoke in a direction orthogonal to the moving surface and not facing the magnet as the magnetosensitive element. apparatus. In any one of claims 1 to 4,
A second magnet for applying a second bias magnetic field to the medium;
The magnetic sensor device according to claim 1, wherein the second magnet is positioned downstream of the downstream yoke in the moving direction. In any one of claims 1 to 7,
A plurality of the first magnetosensitive elements and the second magnetosensitive elements are arranged in a direction along the moving surface, intersecting the moving direction, respectively.
The magnetic sensor device according to claim 1, wherein the magnet extends in an arrangement direction of the plurality of second magnetic sensing elements and faces each second magnetic sensing element. In claim 8,
The downstream yoke extends along the magnet and opposes each first magnetosensitive element.