JP3283931B2 - Magnetic quality detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic substance detecting apparatus, and more particularly to a magnetic substance detecting apparatus for detecting magnetic properties of a magnetic substance contained in printing ink such as banknotes.

[0002]

2. Description of the Related Art In recent years, the progress of copying technology has been remarkable, and a problem has arisen that securities such as banknotes and checks are misused by copying.

[0003] Therefore, research for identifying such paper sheets is being rapidly promoted.

[0004] For example, two types of bills are distinguished by light and magnetism.

[0005] Among them, the magnetic discrimination utilizes the fact that magnetic ink is used for a banknote in some form, and detects the distribution of the magnetic ink to identify the banknote.

For example, conventionally, a magnetic field is applied to a banknote in advance using a magnet, and an intrinsic magnetic material, a magnetic pencil, a magnetic copy, or the like is used depending on the residual magnetic flux density after removing the magnetic field. There is a method of determining whether or not. However, in the method described above, since only the residual magnetic flux density is observed, the residual magnetic flux density becomes almost the same as that of the magnetic ink when it is lightly painted with a magnetic pencil or the like. There was a problem that identification was not possible.

In general, a measuring device for magnetic material can measure a residual magnetic flux density, a coercive force, etc., but an object to be measured must be kept stationary, and the measurement takes a certain amount of time. However, when it is desired to determine only whether or not the magnetic material has a specific magnetic property, the operation is complicated, and it is impossible to measure without a certain amount of mass. There was a problem that measurement was not possible.

In order to provide a method for easily detecting the magnetic quality of a magnetic material with a simple device, the present inventors have arranged a magnetic sensor for measuring a change in magnetic flux distribution and an upstream side of the magnetic sensor. A first magnet for applying a saturation magnetic field having a larger absolute value than the coercive force to the magnetic body to be detected, and a first magnet provided near the magnetic sensor and having a polarity opposite to that of the first magnet. A second magnet for applying a magnetic field having a value equal to the coercive force of the magnetic material to be detected, so that no output from the magnetic sensor is output when the target magnetic material passes. Has proposed a method for detecting whether or not the magnetic material has a desired magnetic property.

However, the saturation magnetic field strength of a bill is about 3
Since it is as large as about 000G and separated from the subject, a stronger magnet is needed to secure this value.
Since the bias magnetic field applied to the magnetic sensor for detection is strong, there is a problem that the sensitivity is lowered and a detailed magnetic pattern cannot be detected.

[0010]

As described above, since the conventional magnetic quality detecting device has low sensitivity, it can only detect the presence or absence of a magnetic pattern, that is, whether or not magnetic printing has been performed. There is a problem that details such as whether or not it is formed cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic quality detecting device capable of detecting a magnetic pattern and magnetic quality with high accuracy and high sensitivity.

[0012]

According to the present invention, in addition to the above-mentioned improved magnetic quality detecting apparatus, a magnetic field having a larger absolute value than its coercive force is applied to a magnetic substance to be detected. A third magnet dedicated to saturation magnetization is provided, and the first magnet provided near the magnetic sensor for measuring a change in magnetic flux distribution has a magnitude enough to apply a bias magnetic field having an optimum strength to the magnetic sensor. It is characterized by having a size.

That is, the apparatus of the present invention comprises a magnetic sensor for measuring a change in magnetic flux distribution, and a saturation sensor having an absolute value greater than its coercive force, which is disposed upstream of the magnetic sensor and which is to be detected. A third magnet dedicated to saturation magnetization for applying a magnetic field, a first magnet disposed near the magnetic sensor to apply a bias magnetic field having an optimal strength to the magnetic sensor, and a third magnet disposed near the magnetic sensor. And a second magnet for applying a magnetic field having a polarity opposite to that of the first magnet and equal to the coercive force of the magnetic material to be detected.

Here, in the case of bills, the first magnet is about 1000G.

[0015]

The coercive force Hc of the magnetic material is represented by Hc in the magnetic flux density-magnetic field strength (BH) curve as shown in FIG.
This is the intersection between the axis and the loop, and takes positive and negative values. At this time, that is, when the magnetic field strength H is Hc or -Hc, the magnetic flux density passing through the inside of the magnetic body is zero. When a magnetic material having a residual magnetic flux density of -Br enters a magnetic field of + Hc,
The absolute value of the residual magnetic flux density of the magnetic material decreases and becomes zero.

[0016] Even when the Br = 0 state moves on the differential type magnetoresistive element as shown in FIG. 17 (b), the magnetic field does not change and the differential output does not change.

Conversely, when the magnetic material of + Br enters the magnetic field of + Hc, the magnetic flux distribution is changed due to the residual magnetic flux density of Br ', and a change appears in the differential output.

The same applies to the case of a magnetic flux distribution of -Hc.

The present invention has been made in view of this point, and utilizes the fact that when the magnetic field strength H is Hc or -Hc, the magnetic flux density of the coercive force Hc passing through the inside of the magnetic material becomes zero. When the magnetic material passes, whether or not the magnetic material has a coercive force Hc is detected based on whether or not the magnetic flux density becomes zero, that is, whether or not the magnetic flux distribution changes.

According to the above configuration, it is possible to detect while scanning, and it is possible to easily and immediately determine whether or not the magnetic material has a specific magnetic property.

The magnetic body may be moved, or the detection device may be moved. In other words, the magnetic material may be moved relatively to the measuring device.

For example, when it is desired to detect the magnetic quality of a bill,
When the magnetic field strength at the detection position of the magnetic material is set to the magnitude of the coercive force of the magnetic ink of the banknote, the magnetic material having a coercive force other than the magnetic ink of the banknote passes through the magnetoresistive element because the residual magnetic flux density is not zero. A change is detected in the distribution of the magnetic flux, which is detected.

It should be noted that although a piece without magnetism is judged to be not a genuine bill, a bias magnetic field having an optimum strength for the magnetic sensor can be set for the magnetic pattern at the same time as the detection of the magnetic quality. Can be detected.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIGS. 1 (a) and 1 (b) are a schematic explanatory view and a sectional view of a main part of a bill discriminating apparatus according to an embodiment of the present invention.

This discriminating apparatus is, in addition to the above-described improved magnetic quality detecting apparatus, a third magnetic pole dedicated to saturation magnetization for applying a saturation magnetic field Hm having an absolute value larger than the coercive force to the magnetic substance to be detected. The first magnet 10 provided with the magnet 50 and disposed near the differential type magnetoresistive element 30 serving as a magnetic sensor for measuring a change in magnetic flux distribution includes the differential type magnetoresistive element 3.
It is characterized in that it is large enough to give a bias magnetic field having an optimum strength to zero.

A third magnet 50 dedicated to saturation magnetization installed on the most upstream side with respect to the traveling direction a of the banknote 1 and further arranged at predetermined intervals in the traveling direction a, and are sequentially detected. At the position where the magnetic material to be passed passes, the negative magnetic field -H
n, and a second magnet 20, which emits a positive magnetic field Hc, which is a magnetic field of the opposite polarity of the first magnet.
A differential type magnetoresistive element 30 disposed near the second magnet 20 and biased to a positive magnetic field Hc by the second magnet 20, and disposed near the first magnet 10; A magnetoresistive element array 60 biased to a negative magnetic field -Hn by the first magnet 10;
0 and the output of the magnetoresistive element array 60, a judging means 40 for judging whether it is a genuine bill or a magnetic copy.
It is composed of Note that the magnetoresistive element array 60
Has a plurality of differential type magnetoresistive elements arranged so that a magnetic pattern of a bill can be detected over a wide range.
Depending on the case, the magnetic pattern may be detected only by one instead of the array. As shown in FIG. 1 (b), the bill 1 is configured to travel on a top glass G of the main body of the detection device by a transfer means (not shown). Further, the first and second magnets are made of a top glass G
Support substrate 5 installed below and parallel to this
The magnetoresistive element array 60 and the differential type magnetoresistive element 30 are disposed on the front surface of the support substrate 50. The magnetoresistive element array 60 and the differential type magnetoresistive element 30 include a thin film magnetoresistive element array (not shown) and a thin film magnetoresistive element 32 disposed on the surface of an insulating substrate 31. Here, the positive magnetic field Hc by the second magnet 20 is set to the coercive force of the magnetic ink of the bill. The absolute value of the negative magnetic field -Hm is
It must be sufficiently larger than the absolute value of c. This thin film magnetoresistive element array may be constituted by bulk magnetoresistive elements.

Next, a method of recognizing bills using the bill recognizing device will be described.

The banknote 1 is caused to travel in the direction of the arrow a, and as shown in FIG. 2, first the magnetic material to be measured is negatively saturated by the third magnet at the position A, and then the first magnet is The magnetic pattern is detected by the magnetoresistive element array biased by, and the genuine bill or the magnetic copy is determined by the magnetoresistive element biased by the second magnet at the position C. Accordingly, the intensity of the generated magnetic field of each magnet and the arrangement of the magnetic field applied to the magnetic material from A to C are adjusted so that the magnetization state of the magnetic material changes along the saturation magnetization curve.

In this case, the differential magnetic resistance element 30 detects a magnetic field change when a magnetic material having a negative residual magnetic flux density -Br is passed through a magnetic field of + Hc by an applied magnetic field of -Hm. . Then, after a genuine bill having a magnetic pattern composed of a magnetic ink having a coercive force of + Hc is negatively saturated by the applied magnetic field, it passes through the magnetic field of -Hm and passes through the state of the residual magnetic flux density -Br to apply the magnetic field of + Hc. When passing through the inside, the residual magnetic flux density becomes 0 in this + Hc magnetic field, and the distribution of the applied magnetic field does not change, so that no change appears in the differential type magnetoresistive element. In the case of a magnetic material having a coercive force different from Hc, the residual magnetic flux density does not become 0 in the magnetic field of + Hc, and a change occurs in the distribution of the applied magnetic field. . FIG. 3 is a diagram showing the saturation magnetization curves of a genuine note and a counterfeit note. Therefore, in the case of a genuine note, the counter value is zero at the magnetic field Hc, whereas the counterfeit note has a magnetization of M.

Therefore, no change is detected in the differential type magnetoresistive element 30 as shown in FIG.
If it is the same as the genuine bill, it is determined that the genuine bill is genuine, and the next operation is performed. If a change is detected in the differential type magnetoresistive element as shown in FIG. It is determined that the bill is not genuine, and the transport direction of the bill is reversed to return the bill to the bill insertion slot.

As described above, according to the bill validator of the present invention, it is possible to detect a magnetic pattern and magnetic quality with good reproducibility without being affected by the residual magnetization state before detection. Further, since the discrimination is made based on the magnetic pattern and the magnetic quality, a high degree of authenticity determination can be performed. In addition, since each component is small, it is easy to reduce the size and thickness.

Further, the present invention can be applied not only to magnetic ink and magnetic toner of forms, but also to magnetic cards, magnetic plates and bars, and the like.

Embodiment 2 Next, a bill validator according to a second embodiment of the present invention will be described.

As shown in FIG. 5, this discriminating apparatus is the same as the magnetic discriminating apparatus shown in the first embodiment, and further includes one more magnetic discriminating apparatus.
A total of three sets (30a, 20a and 30b, 20b and 60, 10) are added to the set of the differential type magnetoresistive element and the bias magnet.
The number of measurement points on the magnetization curve of the magnetic material is increased, and the characteristic of the curve, that is, the unique characteristic such as squareness in addition to the coercive force is detected.
At this time, except for the holding power, the degree of change of the output signal is compared to see a pseudo squareness ratio.

The other parts are formed in the same manner as in the first embodiment. However, the magnetic pattern detecting means was installed on the downstream side.

FIG. 6 shows a saturation magnetization curve of the subject.
However, here, the magnetic pattern is detected at D.

The determination of the authenticity is made based on the presence or absence of magnetism, the authenticity of the coercive force, and the output voltage ratio corresponding to the magnetization.

Third Embodiment In the first embodiment, the magnetic pattern detecting means is provided on the upstream side of the differential type magnetoresistive element for detecting the magnetic quality. However, as shown in FIG. You may.

In this case, the saturation magnetization curve is as shown in FIG. 8, and the detection of the magnetic pattern is performed in a state where a positive magnetic field is applied.

It should be noted that the magnets used in these embodiments may be integrated as shown in FIGS. 9 to 12 without being divided individually. 9 and 10 are modifications of the first embodiment, and FIGS. 11 and 12 are modifications of the third embodiment.

Fourth Embodiment In the first embodiment, the polarities of the magnetic fields of the magnetic pattern detecting means 60 and the differential type magnetoresistive element 30 are reversed.
As shown in FIG. 13 and FIG.

Embodiment 5 Further, as shown in FIGS. 15 and 16, even if the detection of the magnetic pattern is performed under a positive magnetic field and the detection of the magnetic properties is performed on the minor loop, it is possible to perform the saturation magnetization once. Therefore, the reproducibility of detection is extremely good.

Further, the first and second bias magnets are used.
Although a permanent magnet was used for both magnets, the second magnet may be formed of an electromagnet, and when the magnetic body to be detected is changed, the strength of the bias magnetic field may be adjusted by changing the coil current.

Further, the yoke may be constituted by a first magnet and a yoke magnetized by the first magnet, and the yoke may be replaced as necessary.

Furthermore, although permanent magnets are used for both the first and second magnets, the bias magnetic field may be changed by attaching a position adjusting means to the second magnet and adjusting the height. Further, the first magnetic field is set to + Hm,
Can be detected in exactly the same manner even when the magnetic field of -Hc is applied in a direction opposite to that of the embodiment.

[0047]

As described above, according to the present invention, the magnet for magnetizing the saturation magnetic field is made independent,
Since an optimal magnetic field is separately provided for magnetic pattern detection, magnetic quality can be detected with good reproducibility,
It is possible to detect a magnetic pattern with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a bill validator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a hysteresis curve of a bill to be identified by the apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing saturation magnetization curves of genuine and counterfeit notes.

FIG. 4 is a diagram showing an output signal of a differential type magnetoresistive element.

FIG. 5 is a view showing a bill discriminating apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a saturation magnet curve in the bill validator according to the second embodiment of the present invention.

FIG. 7 is a view showing a bill validator according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a saturation magnet curve in the bill validator according to the third embodiment of the present invention.

FIG. 9 is a diagram showing a modification of the magnetic sensor of the bill validator of the present invention.

FIG. 10 is a diagram showing a modification of the magnetic sensor of the bill discriminating apparatus of the present invention.

FIG. 11 is a diagram showing a modification of the magnetic sensor of the bill validator of the present invention.

FIG. 12 is a diagram showing a modification of the magnetic sensor of the bill validator of the present invention.

FIG. 13 is a view showing a bill discriminating apparatus according to a third embodiment of the present invention.

FIG. 14 is a diagram showing a saturation magnet curve in the bill validator according to the third embodiment of the present invention.

FIG. 15 is a view showing a bill discriminating apparatus according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing a saturation magnet curve in the bill validator according to the fourth embodiment of the present invention.

FIG. 17 is a diagram illustrating the principle of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st magnet 20 2nd magnet 30 Differential type magnetoresistive element 40 Judgment means 50 Support substrate 60 Magnetoresistive element array

Claims (1)

(57) [Claims] A magnetic sensor configured to measure a change in magnetic flux distribution; a first magnet disposed upstream of the magnetic sensor and applying a predetermined bias magnetic field to a magnetic body to be detected; A magnetic pattern detecting means disposed near the first magnet to detect a magnetic pattern; and a magnetic pattern detecting means disposed near the magnetic sensor and having a polarity opposite to that of the first magnet and to be detected. A second magnet for applying a magnetic field having a value equal to the magnetic force and a saturation magnetic field which is disposed upstream of the magnetic pattern detecting means and has a larger absolute value than the coercive force is applied to the magnetic body to be detected. And a third magnet.