JP2013217767A - Magnetic sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic sensor device having a small gradient of a magnetic field distribution in magnetosensitive direction of a magnetoresistance effect element and a large area in which the magnetoresistance effect element can be installed.SOLUTION: There is provided a magnetic sensor device which comprises: a magnet disposed on one surface in the conveying direction of an object to be detected; a first yoke joined to a side surface orthogonal to the conveying direction of the object to be detected in one magnetic pole of the magnet; a second yoke joined to a side surface orthogonal to the conveying direction of the object to be detected in the other magnetic pole of the magnet; a magnetic plate which faces the magnet on the other surface in the conveying direction of the object to be detected and provided apart from the object to be detected; and a magnetoresistance effect element provided apart from the object to be detected between the magnetic plate and the object to be detected, wherein the magnetoresistance effect element is disposed outside the magnet from a joining surface between the magnet, and the first yoke and an end part of the magnetic plate in a direction where the magnetoresistance effect element is disposed extends outside the first yoke.

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.

Japanese Patent Laid-Open No. 2008-145379 (refer to Patent Document 1) discloses that a magnetic field amount of a bias magnetic field of a ferromagnetic thin film magnetoresistive element simultaneously applied with a magnetic field for detection by a permanent magnet is a magnetic flux amount equal to or less than a saturation magnetic field. Thus, a magnetic sensor arranged by adjusting the position of a permanent magnet is disclosed.

JP 2008-145379 A

  However, the magnetic sensor described in Patent Document 1 does not disclose a specific arrangement method of the permanent magnets such that the bias magnetic field strength in the magnetic sensing direction of the ferromagnetic thin film magnetoresistive element is equal to or less than the saturation magnetic field. . Further, the ferromagnetic thin film magnetoresistive element is disposed in a region where the change in the magnetic field strength in the magnetosensitive direction is large, and there is a problem that the range in which the optimum bias magnetic field can be obtained is narrow and adjustment is difficult.

  The present invention has been made to solve the above-described problems, and provides a magnetic sensor device in which the gradient of the magnetic field distribution in the magnetosensitive direction of the magnetoresistive effect element is small and the area where the magnetoresistive effect element can be installed is large. obtain.

A magnetic sensor device according to the present invention includes a conveyance path through which an object to be detected is conveyed,
On one surface of the transport path in the transport direction of the detected object, magnets that are alternately arranged with different magnetic poles separated from the detected object in the transport direction of the detected object,
A first yoke joined to a side surface perpendicular to the conveying direction of the object to be detected in one magnetic pole of the magnet;
A second yoke joined to a side surface perpendicular to the conveying direction of the object to be detected in the other magnetic pole of the magnet;
A magnetic plate provided on the other surface of the transport path in the transport direction of the detected object, facing the magnet and spaced apart from the detected object;
Between the magnetic body plate and the detected object, a magnetoresistive effect element provided apart from the detected object,
This magnetoresistive effect element is disposed outside the magnet from the joint surface between the magnet and the first yoke,
In the magnetic plate, an end portion in a direction in which the magnetoresistive effect element is arranged extends to the outside of the first yoke.

  According to the present invention, since the magnetic carrier is extended outward from the magnetic field generating means composed of the magnet and the yoke, the change in the magnetic field distribution in the conveyance direction of the detected object is reduced, and the magnetoresistive element is installed. There is an effect that the possible area is increased and the degree of freedom of the installation position of the magnetoresistive effect element is increased.

It is sectional drawing seen from the conveyance direction of the to-be-detected body (detected object) 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 a figure which shows arrangement | positioning of the components which comprise the magnetic circuit regarding Embodiment 1 of this invention. It is a figure which shows distribution of the magnetic force line in the structure of FIG. It is a figure which shows the relationship between the magnetic flux density applied to a magnetoresistive effect element, and the resistance value of a magnetoresistive effect element. It is a figure which shows distribution of Bx in the case of arrangement | positioning of FIG. It is a figure which shows arrangement | positioning of the components which comprise the magnetic circuit regarding Embodiment 2 of this invention. FIG. 8 is a magnetic field line distribution diagram in the case of the arrangement of FIG. 7. It is a figure which shows distribution of Bx in the case of arrangement | positioning of FIG.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of the magnetic sensor device according to the first embodiment of the present invention as viewed from the conveyance direction of the detected object (detected object). FIG. 2 is a cross-sectional view of the magnetic sensor device according to Embodiment 1 of the present invention as viewed 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 having S poles and N poles along the carrying direction in which a pair of yokes 7 (7a, 7b) for improving magnetic field uniformity is arranged on one side of the carrying direction in the hollow portion 2 on both sides in the carrying direction 6 is installed in the housing 1 at a distance from the banknote 5, and the magnetic carrier 8 is installed in the housing 1 at a distance from the banknote 5 on the opposite surface. The magnetic carrier 8 extends outward from the yokes 7a and 7b along the transport direction.

  A non-magnetic carrier 15 and a substrate 9 made of a resin such as glass epoxy are provided on the surface of the magnetic carrier 8 on the conveyance path side so as to be separated from the banknote 5, and the non-magnetic carrier 15 has a magnetoresistive effect element. 10 is implemented. The magnetoresistive element 10 has 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.

  The operation of the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing the arrangement of the parts constituting the magnetic circuit according to the first embodiment of the present invention. FIG. 3 shows only the components necessary for explaining the operation in FIG. Yes. The magnetoresistive element 10 is separated from the magnetic carrier 8 by the thickness of the non-magnetic carrier 15, and this thickness is about 0.4 mm, for example.

  FIG. 4 shows the distribution of the lines of magnetic force in the configuration of FIG. Magnetic field lines are distributed in the magnetic carrier 8 densely from the yokes 7a and 7b. A broken line 6 indicates a position 0.4 mm away from the magnetic carrier 8, and the magnetoresistive element 10 is installed on the broken line 30 at a position outside the magnet 6 relative to the joint between the yoke 7 a and the magnet 6. The

  The magnetoresistive effect element 10 is disposed on the broken line 30 at a position outside the magnet 6 relative to the joint between the yoke 7 a and the magnet 6, and is in a magnetic field formed by the magnet 6, the yokes 7 a and 7 b, and the magnetic carrier 8. Is placed in. Here, when the ink containing the magnetic material applied to the object to be detected such as the banknote 5 passes through this magnetic field, the magnetic field distribution changes, and the magnetic field applied to the magnetoresistive element changes. It can be electrically detected as a change in

  FIG. 5 is a diagram showing the relationship between the magnetic flux density applied to the magnetoresistive effect element 10 and the resistance value of the magnetoresistive effect element 10. In FIG. 5, the magnetoresistive effect element 10 changes its resistance value when the magnetic flux density is increased or decreased from the state where the magnetic flux density is 0, and when reaching a magnetic flux density of a certain value or less, the resistance value becomes almost constant. This state is called saturation. When the change in magnetic flux density to be measured using the magnetoresistive element is small with respect to the magnitude of the magnetic flux density at which the magnetoresistive element reaches a saturation state, for example, the magnitude indicated by the one-dot chain line 40 in FIG. If the direct current magnetic flux density is given, the change in resistance due to the change in magnetic flux density to be measured becomes large, and a large electric signal can be obtained. The magnetic flux density indicated by the alternate long and short dash line 40 is called a bias magnetic field.

  As can be seen from the magnetic field distribution shown in FIG. 4, the magnetic field lines 20 are perpendicularly incident on the magnetic carrier 8, so that the magnetoresistive effect element 10 located slightly away from the magnetic carrier 8 has a magnetic flux. The x-axis direction component of density (hereinafter referred to as Bx) is very small. Since the Bx bias magnetic field required for the magnetoresistive effect element 10 is small, an appropriate Bx bias magnetic field can be obtained by installing the magnetoresistive effect element 10 at a location about 0.4 mm from the magnetic carrier 8. The bias magnetic field to be applied to the magnetoresistive effect element 10 is appropriately an absolute value of, for example, about 2 ± 0.5 mT.

  6 is a diagram showing the distribution of Bx on the broken line 30 in FIG. 4. In FIG. 3, A = 10 mm, P = 2.3 mm, B = 19 mm, Q = 1 mm, C = 3.2 mm, G = The distribution of Bx is 4.9 mm. In FIG. 6, the horizontal axis is the distance where the left end of the magnetic carrier 8 is x = 0, 50 is a curve indicating the Bx distribution, 51 is a range indicating −2 ± 0.5 mT, and 52 is the magnetoresistive element 10. The possible areas are shown.

  In FIG. 6, in the Bx distribution curve, in the vicinity of a location where Bx = −2 mT, the gradient of Bx is small, and the installable range of the magnetoresistive effect element 10 is about 0.5 mm.

Thus, by extending the length of the magnetic carrier 8 in the x direction from the yoke 7 (7a), the gradient of Bx is reduced, and the degree of freedom of the installation position of the magnetoresistive effect element 10 is increased. There is.
Note that the arrangement of the N pole and the S pole may be opposite to that shown in FIGS.

Embodiment 2. FIG.
Next, the second embodiment will be described with reference to FIG. FIG. 7 is a diagram showing the arrangement of components constituting the magnetic circuit according to the second embodiment of the present invention. The components in FIG. 7 are the same as those in the first embodiment, but the magnetic carrier 8 The yoke 7a side extends outward from the yoke 7a, but the yoke 7b side is shorter to the magnet 6 side than the yoke 7b, so that the magnetic body The left and right center 60 of the carrier 3 and the left and right center 61 of the magnet 6 are not aligned.

  FIG. 8 shows the distribution of the lines of magnetic force in such a case. The Bx distribution at a position 0.4 mm away from the iron plate (indicated by a broken line 62) is as shown in FIG. FIG. 9 shows the distribution of Bx when C = 3.2 mm and D = 2.8 mm in FIG. In FIG. 9, the horizontal axis is the distance where the left end of the magnetic carrier 8 is x = 0, 50 is a curve indicating the Bx distribution, 51 is a range indicating −2 ± 0.5 mT, and 52 is the magnetoresistive element 10. The possible areas are shown.

FIG. 9 shows that the gradient of the magnetic flux density can be reduced also in the second embodiment of the present invention. As a result, there is an effect that the gradient of Bx is reduced and the degree of freedom of the installation position of the magnetoresistive effect element 10 is increased.
Furthermore, since the magnetic carrier 8 such as an iron plate to be used can be made small, it contributes to downsizing and cost reduction.

DESCRIPTION OF SYMBOLS 1 Case 2 Hollow part 3 1st slit part 4 2nd slit part 5 Detected object (banknote)
6 Magnet 7, 7a, 7b Yoke 8 Magnetic carrier 9 Substrate 10 Anisotropic magnetoresistive element 11 Metal wire (electrical connection means)
DESCRIPTION OF SYMBOLS 12 Processing circuit 13 Electric shielding board 14 Cable 15 Nonmagnetic carrier 20 Magnetic field line 30 Broken line 40 Dotted line 50 Curve 51 which shows Bx distribution 52 Range which shows -2 +/- 0.5mT 52 Area | region which can install a magnetoresistive element 60 Center of an iron plate 61 Center of permanent magnet 62 Broken line

Claims (1)

A conveyance path through which the object to be detected is conveyed;
On one surface of the transport path in the transport direction of the detected object, magnets that are alternately arranged with different magnetic poles separated from the detected object in the transport direction of the detected object,
A first yoke joined to a side surface perpendicular to the conveying direction of the object to be detected in one magnetic pole of the magnet;
A second yoke joined to a side surface perpendicular to the conveying direction of the object to be detected in the other magnetic pole of the magnet;
A magnetic plate provided on the other surface of the transport path in the transport direction of the detected object, facing the magnet and spaced apart from the detected object;
Between the magnetic body plate and the detected object, a magnetoresistive effect element provided apart from the detected object,
This magnetoresistive effect element is disposed outside the magnet from the joint surface between the magnet and the first yoke,
The magnetic plate is a magnetic sensor device in which an end portion in a direction in which the magnetoresistive effect element is arranged extends to the outside of the first yoke.

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