JP2013217768A - Magnetic sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic sensor device capable of detecting a magnetic pattern of an object to be detected stably with high sensitivity in a non-contact state in which an object to be detected having a magnetic pattern is separated from a magnetoresistance effect element by a minute distance.SOLUTION: There is provided a magnetic sensor device which comprises: a magnet which faces one surface of an object to be detected and has alternately different magnetic poles along the conveying direction of the object to be detected; a magnetic body which faces the other surface of the object to be detected, is disposed facing the magnet along the conveying direction and generates a cross magnetic field which is formed between the magnet and crosses the object to be detected; and a plurality of magnetoresistance effect elements which are mounted on a surface facing the object to be detected of the magnetic body in an array shape, have an output terminal, and have a magnetic sensitive action in the conveying direction for outputting a change in the conveying direction component of the magnetic field by the magnetic component conveyed in the cross magnetic field as a change in a resistance value.

Description

  The present invention relates to a magnetic sensor device that detects a minute magnetic pattern formed on a paper sheet medium such as a banknote.

  The magnetic sensor device is a sensor device using a plurality of magnetoresistive effect elements having a characteristic that the resistance value changes with respect to the magnetic field intensity. In a line-type magnetic sensor device that simultaneously detects multi-channel magnetic patterns contained in paper-like media such as banknotes, the amount of magnetization of these magnetic patterns is very small. Using an anisotropic magnetoresistive effect element having higher sensitivity than the magnetoresistive effect element, and providing a plurality of anisotropic magnetoresistive effect elements in a magnetic field strength environment in which all of the magnetoresistive effect elements are not magnetically saturated and the sensitivity is increased. For example, a paper-like medium needs to pass through a strong magnetic field environment.

  However, in a magnetic sensor device using an anisotropic magnetoresistive effect element, since the anisotropic magnetoresistive effect element is saturated at a magnetic field strength of about 10 mT, a plurality of anisotropic magnetoresistive effect elements are not saturated. There is a problem that it is difficult to arrange in an environment with a high magnetic field strength.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. 2008-145379 (see Patent Document 1) discloses a ferromagnetic thin film magnetoresistive element (an anisotropic magnetoresistive effect element) to which a magnetic field for detection by a permanent magnet is simultaneously applied. The magnetic sensor is disclosed in which the position of the permanent magnet is adjusted so that the bias magnetic field intensity in the magnetic sensing direction becomes a magnetic flux amount equal to or less than the saturation magnetic field.

JP 2008-145379 A

  However, the magnetic sensor described in Patent Document 1 discloses a permanent magnet arrangement method in which the bias magnetic field strength in the magnetically sensitive direction of a specific ferromagnetic thin film magnetoresistive element is a magnetic flux amount equal to or less than a saturation magnetic field. Absent. Further, in order to output in multiple channels, it is necessary to make the bias magnetic field strength in the magnetic sensitive direction applied to the plurality of ferromagnetic thin film magnetoresistive elements uniform, but this method is not disclosed.

In order to improve the detection sensitivity of an object to be detected in a non-contact type magnetic sensor, the object to be detected is conveyed while increasing the magnetic force of the bias magnet and applying an appropriate bias magnetic field to the anisotropic magnetoresistive element. It is necessary to increase the magnetic field strength of the transport path to be detected, but the detected object passes farther than the bias magnet than the anisotropic magnetoresistive element, so the change in the magnetic field strength due to the detected object is small and individual anisotropic. There is a problem that the output signal of the magnetoresistive element becomes small.

  The present invention has been made to solve the above-described problems. In a non-contact state in which an object to be detected having a magnetic pattern is separated from a magnetoresistive element by a small distance, the multi-channel is stable and has high sensitivity. A magnetic sensor device for detecting a magnetic pattern of an object to be detected is obtained.

A magnetic sensor device according to the present invention faces one surface of the detected object, and has magnets having different magnetic poles alternately along the transport direction of the detected object,
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. And a magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value.

Further, the magnetic sensor device according to the present invention has a magnet that faces one surface of the detected object and has a magnetic pole having a predetermined length along the conveying direction of the detected object.
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. And a magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value.

  According to the present invention, variations in the bias magnetic field strength in the magnetosensitive direction applied to the plurality of anisotropic magnetoresistive elements are reduced, and the magnetic pattern of the object to be detected can be stably detected with high sensitivity across the plurality of channels. Detected.

It is sectional drawing seen from the conveyance direction of the to-be-detected body of the magnetic sensor apparatus in Embodiment 1 of this invention. It is sectional drawing seen from the insertion / extraction direction of the to-be-detected body of the magnetic sensor apparatus in Embodiment 1 of this invention. It is an enlarged view which shows the mounting state of the board | substrate and AMR element to the magnetic body carrier in FIG. It is a top view which shows the mounting state of the AMR element which looked at the board | substrate side from the hollow part in FIG. It is a connection diagram which shows the connection state of the AMR element of the line type magnetic sensor apparatus in Embodiment 1 of this invention, and an external circuit. It is a figure which shows the magnetic field distribution produced | generated from the magnet in the line type magnetic sensor apparatus shown in FIG. 1, a yoke, and a magnetic body carrier. It is a magnetic force line vector diagram explaining the detection principle of the magnetic sensor in Embodiment 1 of this invention. It is a figure which shows the form which calculated in order to demonstrate the detection principle of the magnetic sensor in Embodiment 1 of this invention. It is a figure which shows the intensity | strength change in the conveyance direction (X-axis direction) of the magnetic field of the conveyance direction (X-axis direction) in FIG. It is a figure which shows the intensity | strength change in the conveyance direction (X-axis direction) of the magnetic field of the space | interval direction (Z-axis direction) in FIG. It is a figure which shows the applied magnetic field and resistance change rate of an AMR element. It is a top view of the AMR element which has a meander-shaped resistance pattern in Embodiment 1 of this invention. It is a top view which shows the mounting state at the time of changing the structure method of the magnetoresistive pattern in FIG. 4 to a T-shaped structure. FIG. 14 is a top view of an AMR element having a meander-shaped resistance pattern in FIG. 13. It is sectional drawing seen from the conveyance direction of the to-be-detected body of the magnetic sensor apparatus in Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view as seen from the conveying direction of a detected object (detected object) of the line type magnetic sensor device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the magnetic sensor device according to Embodiment 1 of the present invention as seen from the insertion / ejection direction of the detected object. 1 and 2, the housing 1 has a hollow portion 2 inside, and the first width is provided on one side surface (side wall) of the housing 1 over a reading width (a direction perpendicular to the conveyance direction of the detected object). The second slit portion 4 is provided in parallel to the first slit portion 3 on the other side surface (side wall), and the first slit portion 3 and the second slit portion are provided via the hollow portion 2. 4, for example, a bill 5 including a magnetic pattern, which is a detected object, is inserted from the first slit portion 3, transported using the hollow portion 2 as a transport path, and from the second slit portion 4. Discharged.

  A magnet 6 having S poles and N poles along the transport direction in which a pair of magnet yokes 7 for improving magnetic field uniformity is arranged on one side surface in the transport direction in the hollow portion 2 on both side surfaces in the transport direction. The body 1 is placed away from the banknote 5, and the magnetic carrier 8 is placed on the housing 1 away from the banknote 5 on the opposite surface.

  A substrate 9 made of a resin such as glass epoxy is provided on the conveyance path side surface of the magnetic carrier 8 so as to be separated from the bill 5, and an anisotropic magnetoresistive element (AMR element) 10 is provided on the magnetic carrier 8. Is mounted and mounted. The AMR element 10 includes a resistor on the surface of a substrate such as silicon or glass, and has a characteristic that the resistance value changes in response to a change in magnetic field orthogonal to the direction of current flowing through the resistor. The magnetic carrier 8 is a soft magnetic material such as iron.

  FIG. 3 is an enlarged view showing a mounting state of the substrate 9 and the AMR element 10 on the magnetic carrier 8 in FIG. FIG. 4 is a top view showing a mounted state of the AMR element 10 when the substrate 9 side is viewed from the hollow portion 2 in FIG. 3 and 4, the substrate 9 is fixed to the magnetic substance carrier 8. The substrate 9 has a hole 9a, and may be formed of a multilayer substrate when the circuit scale is large.

  The AMR element 10 is fixed to the surface of the magnetic carrier 8 exposed at 9 a with an adhesive so as to be surrounded by the substrate 9. The electrodes 101 a to 101 c of the AMR element 10 are respectively connected to the electrodes 111 a to 111 c provided on the substrate 9 by metal wires 12, and the electrodes 111 a to 111 c are external pads provided on the back surface outside the substrate 9 through the transmission line 11. 112a to 112c are connected. External circuits such as an amplifier circuit, a signal processing circuit, and a bias voltage are connected to the external pads 112a to 112c. The hole 9a of the substrate may be sealed with a resin or the like in order to protect the AMR element 10 and the metal wire 12.

  In FIG. 4, the resistor patterns 102a and 102b of the AMR element 10 are arranged in parallel so that the long side of the rectangular shape extends in the reading width direction (Y-axis direction), and the adjacent resistor patterns 102a and 102b are The series connection is connected to the electrode 101b of the AMR element 10, the other of the resistor pattern 102a is connected to the electrode 101a, and the other of the resistor pattern 102b is connected to the electrode 101c.

  FIG. 5 is a connection diagram showing a connection state between the AMR element 10 and the external circuit of the line type magnetic sensor device according to the first embodiment of the present invention. 4 and 5, the electrode 101a is connected to the electrode 111a by the metal wire 12 (electrical connection means), and is connected to the DC power supply voltage Vcc via the external pad 112a. The electrode 101b is connected to the electrode 111b by a metal wire 12, and is connected to a processing circuit 15 that processes a signal via an external pad 112b. The electrode 101c is connected to the electrode 111c by a metal wire 12, and is DC grounded (GND) via an external pad 112c.

  FIG. 6 is a diagram showing a magnetic field distribution generated from the magnet 6, the magnet yoke 7 and the magnetic carrier 8 in the line type magnetic sensor device shown in FIG. In FIG. 6, components necessary for explaining the magnetic field distribution are described from the components in FIG. 1, and others are omitted.

  As shown in FIG. 6, the magnetic field (Bx) in the X-axis direction is very small near the surface of the magnetic carrier 8 due to the characteristic that the magnetic field lines are perpendicular to the magnetic pole surface of the magnetic material (Bz direction). A magnetic field (Bz) in the (Z-axis direction) is the main component. The AMR element 10 is provided on the surface of the magnetic carrier 8 where the Bx is very small and the magnetic field (Bz) in the interval direction (Z-axis direction) has a strong magnetic field strength, and the bill 5 has a strong magnetic field (Bz) in the interval direction. It passes through the position having the magnetic field strength so as to cross the magnetic field in the interval direction.

  In FIG. 6, the magnetic field lines 17 are magnetized from the N pole of the magnet 6, which is a crossing magnetic field that intersects the transport path, in the vicinity of where the resistor patterns 102 a and 102 b of the anisotropic magnetoresistive element (AMR element) 10 are arranged. Although the component toward the body carrier 8 is the main component, as shown in FIG. 7A, this is slightly inclined in the transport direction (X-axis direction) from the interval direction (Z-axis direction). A component in the magnetic field conveyance direction (X-axis direction) acts as a bias magnetic field of the AMR element 10.

When the detected object (banknote) 5 approaches, as shown in FIG. 7B, the magnetic field lines 17 tilt toward the detected object (banknote) 5 side, so that the magnetic field (Bx) in the transport direction (X-axis direction) is increased. When the detected object (banknote) 5 becomes smaller and moves away, as shown in FIG. 7C, the magnetic force lines 17 are inclined toward the detected object (banknote) 5 side, so that the magnetic field (X-axis direction) ( As Bx) increases, the resistance value of the anisotropic magnetoresistive element (AMR element) 10 that senses the X-direction component changes, and the object (banknote) 5 can be detected.

  FIG. 8 is a diagram showing a form in which calculation is performed to explain the detection principle of the magnetic sensor according to Embodiment 1 of the present invention. In FIG. 8, constituent elements necessary for explaining the magnetic field distribution are described from the constituent elements in FIG. 1, and others are omitted.

  FIG. 9 shows the result of calculating the strength change in the conveyance direction (X-axis direction) of the bill 5 of the magnetic field strength (Bx) in the X-axis direction as a parameter in FIG. The interval direction (Z-axis direction) between the facing magnet 6 and the magnetic carrier 8 is changed from Z = 0 mm to 0.6 mm. The origin in the X-axis direction is the center of the magnet 6, and the origin in the Z-axis direction is the surface of the magnetic carrier 8.

  FIG. 10 is a result of calculating a change in strength in the conveyance direction (X-axis direction) of the bill 5 of the magnetic field strength (Bz) in the Z-axis direction in FIG. 8, and as a parameter between the magnet 6 and the magnetic carrier 8 facing each other. The interval direction (Z-axis direction) is changed from Z = 0 mm to 2 mm. The origin in the X-axis direction is the center of the magnet 6, and the origin in the Z-axis direction is the surface of the magnetic carrier 8.

  When the AMR element having a saturation magnetic field strength of 10 mT shown in FIG. 11 is used as the AMR element 10, appropriate sensitivity is obtained around Bx = −2 to −6 mT (bias magnetic field range A) and +2 to 6 mT (bias magnetic field range B). Therefore, it is necessary to arrange the AMR elements 10 with high accuracy so that Bx applied to the resistor patterns 102a and 102b of each AMR element 10 falls within the bias magnetic field range A or the bias magnetic field range B.

  According to FIG. 9, for example, when the thickness of the AMR element 10 is 0.3 mm (Z = 0.3 mm), in order to keep Bx applied to the resistor patterns 102a and 102b in the bias magnetic field range A, the AMR element 10 X = 3.7 mm to 4.8 mm, and it is possible to fit the AMR element in the bias magnetic field range with a very loose assembly position accuracy of Δ1 mm or more. Variations in the bias magnetic field strength in the magnetic sensing direction of the AMR element 10 are reduced, which is very effective in suppressing variations between channels. By this effect, not only the AMR element 10 but also the assembly accuracy of the magnet 6 and the magnetic carrier 8 can be relaxed.

  Further, the magnetic field change when the banknote 5 is applied to the resistor patterns 102 a and 102 b is proportional to the magnetic field around the banknote 5 (the magnetic field applied to the banknote 5), and the AMR element 10 detects the magnetic field change. In order to increase the output, it is necessary to apply a larger magnetic field to the banknote 5, but in Embodiment 1 of the present invention, the magnetic field applied to the banknote 5 is Bz = about 180 mT from FIG. Even if the bills 5 are separated, the magnetic pattern of the bills 5 is detected with high sensitivity.

  According to this configuration, even if the magnetic field strength of the magnet 6 is increased for high output, Bx applied to the resistance patterns 102a and 102b of the AMR element 10 is small, so that the assembly accuracy is not greatly deteriorated. A stable output can be obtained in the magnetic sensor device of the type.

  Further, as the thickness of the AMR element 10 is reduced, Bx applied to the resistance patterns 102a and 102b is reduced, so that the AMR element 10 having higher sensitivity (the steeper slope in FIG. 11) is also stable. Thus, the sensitivity of the AMR element 10 can be increased to increase the output.

  Similarly, when the bias magnetic field range B is used, in FIG. 9, for example, when the thickness of the AMR element 10 is 0.3 mm (Z = 0.3 mm), the AMR element 10 is set to x = 6.2 mm to 9.8 mm. The magnetic field applied to the bill 5 from FIG. 10 is Bz = about 130 mT to 170 mT, and the output when the AMR element 10 and the bill 5 are separated from the bias magnetic field range A is somewhat. Although it falls, it is possible to detect the magnetic pattern of the banknote 5 with high sensitivity with a very loose assembly position accuracy of Δ3 mm or more.

  Thus, since the strong magnetic field of a space | interval direction (Z-axis direction) is applied to a banknote, even if the AMR element and the banknote are spaced apart, the magnetic pattern of a banknote is detected with sufficient sensitivity. Further, since the bias magnetic field strength in the transport direction (X-axis direction) applied to the resistance patterns 102a and 102b of the AMR element 10 has a small change at the position in the X-axis direction, the assembly accuracy is improved. Further, by reducing the thickness of the AMR element 10, even if the magnetic field strength of the magnet 6 is increased in order to improve the output or the sensitivity of the AMR element 10 is increased, a stable output can be obtained in multiple channels. Further, since the magnet 6 and the magnetic carrier 8 are arranged to face each other, a stable magnetic path is formed, and the magnetic pattern of the detected object 5 is stably detected without being affected by the external magnetic body.

  Although the resistor patterns 102a and 102b of the AMR element 10 have a rectangular shape, as shown in FIG. 12, they may have a meander shape in which the long sides extend in the reading width direction (Y-axis direction). In this case, the resistance values of the resistor patterns 102a and 102b increase from the rectangular shape to a high resistance value, so that the detection sensitivity of the magnetic field change of the AMR element 10 is improved and the detection sensitivity of the magnetic sensor device is increased.

  The arrangement of the resistor patterns 102a and 102b of the AMR element 10 may be a vertical arrangement as shown in FIG. Even in this arrangement, a meander shape may be used as shown in FIG.

  Further, in order to improve the magnetic field uniformity on both side surfaces in the transport direction, the magnet 6 is provided with a pair of magnet yokes 7. However, the magnet yoke 7 may not be provided.

  Further, the magnetic poles of the magnet 6 are arranged as the S pole N pole in order along the conveying direction of the detected object 5, but may be arranged as the N pole S pole.

  In the first embodiment, an AMR element is used as the magnetoresistive effect element 10, but a giant magnetoresistive effect (GMR) element or a tunnel magnetoresistive effect (TMR) element may be used.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIG. In Embodiment 1 (FIG. 1) of the present invention, the magnet 6 is arranged so as to have the S pole and the N pole along the conveyance direction of the detected object 5, but in Embodiment 2 of the present invention, One magnetic pole (N pole in FIG. 15) is arranged along the transport direction. In FIG. 15, the same components as those of FIG.

  Also in FIG. 15, since a magnetic field in the Z direction is formed between the magnet 6 and the magnetic carrier, the same effects as those of the first embodiment of the present invention can be obtained.

DESCRIPTION OF SYMBOLS 1 Case 2 Hollow part 3 1st slit part 4 2nd slit part 5 Detected object (banknote)
6 Magnet 7 Yoke 8 Magnetic Carrier 9 Substrate 9a Hole in Substrate 10 Anisotropic Magnetoresistance Effect Element (AMR Element)
101a to 101c AMR element electrodes 102a to 102c Resistor pattern 11 Transmission line 111a to 111c Transmission line electrode 112a to 112c Transmission line external pad 12 Metal wire (electrical connection means)
15 Processing Circuit 17 Magnetic Field Line 31 Electric Shield Plate 71 Cable

Claims (5)

A magnet that faces one surface of the object to be detected and has different magnetic poles alternately along the transport direction of the object to be detected;
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. A magnetic sensor device comprising: a magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value. A magnet facing one surface of the object to be detected and having a magnetic pole having a predetermined length along the transport direction of the object to be detected;
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. A magnetic sensor device comprising: a magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value. A housing,
An elongated first slit portion for inserting an object to be detected over a reading width on one side wall of the housing;
A second slit portion for discharging the detected object disposed in parallel with the first slit portion on the other side wall of the casing facing the first slit portion;
A hollow portion connected to the first slit portion and the second slit portion, and the object to be detected is conveyed from the first slit portion to the second slit portion;
A magnet provided on the housing, facing one surface of the object to be detected, and having different magnetic poles alternately along the transport direction;
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. A magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value;
A substrate for outputting the resistance value change from the output terminal of the magnetoresistive element to the outside from the connection pad;
A magnetic sensor device comprising electrical connection means for electrically connecting the connection pad of the substrate and the output terminal of the magnetoresistive element. A housing,
An elongated first slit portion for inserting an object to be detected over a reading width on one side wall of the housing;
A second slit portion for discharging the detected object disposed in parallel with the first slit portion on the other side wall of the casing facing the first slit portion;
A hollow portion connected to the first slit portion and the second slit portion, and the object to be detected is conveyed from the first slit portion to the second slit portion;
A magnet provided on the housing, facing one surface of the object to be detected, and having a magnetic pole having a predetermined length along a conveying direction;
A magnetic body that faces the other surface of the object to be detected and is arranged to face the magnet along the transport direction and generates a crossing magnetic field that is formed between the magnet and intersects the object to be detected; ,
On the side of the magnetic body facing the object to be detected, a plurality of arrays are placed in a direction orthogonal to the transport direction, have an output terminal, and are transported in the cross magnetic field. A magnetoresistive element having a magnetosensitive effect in the transport direction for outputting a change in the transport direction component of the magnetic field due to a magnetic component as a change in resistance value;
A substrate for outputting the resistance value change from the output terminal of the magnetoresistive element to the outside from the connection pad;
A magnetic sensor device comprising electrical connection means for electrically connecting the connection pad of the substrate and the output terminal of the magnetoresistive element. 4. The magnetic sensor device according to claim 1, wherein the magnet is provided with a pair of yokes formed of a magnetic body on both side surfaces orthogonal to the transport direction. 5.

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