JP2009282866A - Apparatus for detecting magnetic characteristic of paper sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the magnetic characteristic of paper sheets by means of a simple circuit arrangement. <P>SOLUTION: This apparatus for detecting the magnetic characteristic of paper has: a detection head 2 for detecting the magnetic characteristic of a bill S as a change in the resistance value of a magnetic resistance element R; an oscillating circuit 3 which causes a phase shift in an oscillating wave according to the change in the resistance value of the magnetic resistance element R; and a detection circuit 4 for detecting the phase shift of the oscillating wave. The detection circuit 4 performs an oscillating wave counting process for counting the number of oscillating waves output from the oscillating circuit 3 and determining whether the number of times of counting has reached a predetermined number N, and measures the phase shifts of the accumulated oscillating waves, based on the time required for the oscillating wave counting process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper sheet magnetic property detection device that detects magnetic properties of paper sheets such as banknotes, securities, documents, and postal items.

2. Description of the Related Art Paper magnetic property detection devices that detect magnetic properties (such as the density and type of magnetic ink, the presence or absence and type of metal threads) of a paper sheet are known. There are various detection methods for this kind of paper sheet magnetic property detection device. In particular, the magnetic property of the paper sheet is detected by a magnetic detection element such as a magnetoresistive element while magnetizing the paper sheet. A method for detecting the magnetic characteristics of a paper sheet with a magnetic head without magnetizing or magnetizing the paper sheet is widely used.
Japanese Patent No. 4024964

  However, in the above conventional paper sheet magnetic property detection device, a slight resistance value change generated in the magnetoresistive element and a small inductance change generated in the detection coil of the magnetic head are amplified in multiple stages by an amplifier. It was difficult to detect with high accuracy.

In view of the above situation, the paper sheet magnetic property detection device of the present invention created for the purpose of solving these problems is a paper sheet magnetic property detection device for detecting the magnetic property of a paper sheet. A magnetic detection element whose detection value changes according to the magnetic characteristics of the paper sheet, an oscillation circuit which causes a phase shift in the oscillation wave when the detection value of the magnetic detection element changes, And a detection circuit that detects a phase shift of the oscillation wave, the detection circuit counts a plurality of oscillation waves output from the oscillation circuit, and determines whether or not the count number has reached a predetermined number N A count process is performed, and a phase shift of the accumulated oscillation wave is detected based on the time required for the oscillation wave count process. In this way, the magnetic characteristics of the paper sheet can be detected with high accuracy. In other words, in the oscillation wave output from the oscillation circuit as described above, the magnetic characteristics of the paper sheets clearly appear as phase shift, and the phase shift in the oscillation wave is accumulated by the number of oscillation waves. Therefore, the magnetic characteristics of the paper sheet can be detected with high accuracy based on the accumulated phase shift. In addition, the number of oscillation waves output from the oscillation circuit is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time required for the oscillation wave count process Since the phase shift of the accumulated oscillation wave is measured, the phase shift component of the oscillation wave can be measured with high accuracy using an inexpensive digital circuit. In addition, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit, high-resolution detection can be performed while optimizing the reference frequency of the oscillation circuit according to the detection target.
The magnetic detection element is a magnetoresistive element whose resistance value changes according to the magnetic characteristics of the paper sheet. In this way, it is possible to detect the magnetic characteristics of the paper sheet with high accuracy using an inexpensive magnetoresistive element.
The detection circuit detects a magnetic characteristic in the reference region of the paper sheet, and stores a reference value storage means for storing the detected value as a reference value; and a magnetic characteristic in the detection target region of the paper sheet. It comprises magnetic characteristic detection means for detecting, and difference detection means for obtaining a difference between a detection value of a detection target region and a reference value. In this way, the temperature error included in the detected value can be eliminated, so that the detection accuracy can be further improved.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a paper sheet magnetic property detection apparatus according to an embodiment of the present invention. A paper sheet magnetic property detection device 1 shown in this figure is for detecting the magnetic property of a bill S, and includes a detection head 2, an oscillation circuit 3, and a detection circuit 4. .

  The detection head 2 includes a magnetic detection element whose detection value changes according to the magnetic characteristics of the banknote S as the surface of the banknote S is relatively scanned. For example, a permanent magnet (not shown) for magnetizing the banknote S and a magnetoresistive element (MR element) R whose resistance value changes according to the magnetic characteristics of the banknote S are configured. The magnetic detection element is not limited to the magnetoresistive element R, and other magnetic detection elements (Hall element, MI element, etc.) may be used.

  The oscillation circuit 3 is configured such that a phase shift occurs in the oscillation wave in accordance with a change in the resistance value of the magnetoresistive element R. For example, if the magnetoresistive element R is arranged in the feedback circuit 3a of the Schmitt oscillation circuit, the oscillation circuit 3 in which a phase shift occurs in the oscillation wave in accordance with a change in the resistance value of the magnetoresistive element R can be configured.

  The Schmitt oscillation circuit is an oscillation circuit that uses the hysteresis characteristics of the Schmitt trigger circuit included in the Schmitt inverter INV. The Schmitt inverter INV, the capacitor C connected to the input side of the Schmitt inverter INV, and the output of the Schmitt inverter INV The feedback circuit 3a is fed back to the input side of the Schmitt inverter INV and a resistance element interposed in the feedback circuit 3a is provided.

In the Schmitt oscillation circuit in the initial state, since no charge is accumulated in the capacitor C, the voltage across the capacitor C is 0V. At this time, the Schmitt inverter INV has an output H level (5 V) because the input side voltage Vin is equal to or lower than _VL . When the output side voltage Vout of the Schmitt inverter INV is 5V, a current flows to the input side of the Schmitt inverter INV via the feedback circuit 3a, so that charges are gradually accumulated in the capacitor C, and the voltage at both ends thereof increases. When the input side voltage Vin of the Schmitt inverter INV reaches _VH , the output of the Schmitt inverter INV is switched to the L level (0 V). When the output side voltage Vout of the Schmitt inverter INV becomes 0V, the capacitor C is discharged, and the input side voltage Vin of the Schmitt inverter INV gradually decreases. When the input voltage Vin of the Schmitt inverter INV drops to _VL , the output of the Schmitt inverter INV is switched to the H level.

By repeating the above operation, a rectangular wave having a predetermined frequency is obtained from the output side of the Schmitt inverter INV. The Schmidt oscillation circuit of the oscillation frequency f (= 1 / T) is determined by the energy storage time period _{T H} discharge period _{T L,} the electric storage period _{T H} and the discharging period _{T L} is determined by the constants of the capacitor C and a resistor element. Therefore, if the magnetoresistive element R is arranged in the feedback circuit 3a as a resistance element, a phase shift can be generated in the oscillation wave of the Schmitt oscillation circuit in accordance with the change in the resistance value of the magnetoresistive element R.

  Of course, the oscillation circuit of the present invention is not limited to the Schmitt oscillation circuit. If the oscillation circuit generates a phase shift in the oscillation wave according to the change in the detection value of the magnetic detection element, the CR oscillation circuit and the LC oscillation are possible. A circuit, a crystal oscillation circuit, or the like may be used.

  The detection circuit 4 is configured using, for example, a one-chip microcomputer with a built-in CPU, ROM, RAM, I / O, and the like, and performs phase shift measurement processing described later according to a program written in the ROM.

  The detection circuit 4 is configured to accumulate and measure the phase shift of the oscillation wave when detecting the magnetic characteristic of the banknote S based on the phase shift of the oscillation wave oscillated from the oscillation circuit 3. Specifically, the number of oscillation waves output from the oscillation circuit 3 is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N, which is necessary for the oscillation wave count process. Based on the measured time, the phase shift of the accumulated oscillation wave is measured.

  According to such a detection method, measurement is performed after accumulating the phase shift of the oscillating wave. Therefore, even in a synchronous detection circuit having a complicated circuit configuration or an inexpensive digital circuit having no high-speed counter, the magnetic force of the bill S It is possible to detect the phase shift of the oscillating wave according to the characteristic with high accuracy. In addition, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit 3, high-resolution detection can be performed while optimizing the reference frequency of the oscillation circuit 3 according to the detection target. it can.

  The detection circuit 4 detects a magnetic characteristic in the reference area of the banknote S, and detects a magnetic characteristic in the reference value storage means for storing the detected value as a reference value and the detection target area of the banknote S. It is preferable to include magnetic characteristic detection means and difference detection means for obtaining a difference between the detection value of the detection target region and the reference value. In this way, the temperature error included in the detected value can be eliminated, so that the detection accuracy can be further improved.

  Moreover, it is preferable that the detection circuit 4 includes a count number changing unit that changes the count number N of the oscillation wave in one oscillation wave count process. If it does in this way, the count number N can be changed according to use conditions, and a measurement precision and response performance can be adjusted. For example, in a situation where measurement accuracy is given priority, the count number N in one detection process can be increased, and in a situation where response performance is given priority, the count number N in one detection process can be reduced. Note that the change of the count number N may be executed by internal determination of the detection circuit 4 or may be executed based on an externally set number change signal.

  Next, the phase shift accumulation action of the oscillation wave in the present invention will be described with reference to FIGS.

  FIG. 2 is an explanatory diagram showing the phase shift accumulation action of the oscillation wave (enlarged detection waveform start end), and FIG. 3 is an explanatory view showing the phase shift accumulation action of the oscillation wave (enlargement of the detection waveform end section). The waveforms shown in these figures are output waveforms of the oscillation circuit 3 in one detection process, and the number of oscillation waves output from the oscillation circuit 3 is counted, and whether the count number has reached a predetermined number N or not. The oscillation wave count process is performed, and when measuring the phase shift of the accumulated oscillation wave based on the time required for the oscillation wave count process, the oscillation wave count N in the oscillation wave count process is set to 100. The upper waveform indicates a case where the banknote S is not in contact with the detection head 2, and the lower waveform is a case where the magnetic ink portion or the metal thread portion of the banknote S contacts the detection head 2. It shows the case. As is clear from these figures, since the phase shift is not accumulated so much at the beginning of the detected waveform, that is, at the stage where the number N of oscillation waves in the oscillation wave count processing is small, the difference is not clear ( It can be seen that when the count number N increases, the phase shift of the oscillation wave is accumulated and the difference becomes clear, so that the phase shift can be easily measured (see FIG. 3).

  Next, a specific detection processing procedure of the detection circuit 4 will be described with reference to FIGS.

  4 is a flowchart showing an overall processing procedure of the detection circuit, FIG. 5 is a flowchart showing a count number setting processing procedure of the detection circuit, and FIG. 6 is a flowchart showing a magnetic characteristic detection processing procedure of the detection circuit. As shown in FIG. 4, the detection circuit 4 determines the input of the detection start signal while executing a count number changing process (S1) described later (S2), and if the determination result is YES, the reference area signal Is input (S3). When the determination result is YES, a magnetic property detection process (S4) described later is executed to detect the magnetic property of the reference area in the banknote S, and the detected value is stored as a reference value (S5). : Reference value storage means). Next, input of the detection target area signal is determined (S6), and when the determination result is YES, magnetic characteristic detection processing (S7: magnetic characteristic detection means) is executed to detect the magnetic field of the detection target area in the banknote S. In addition to detecting a characteristic, the difference between the detected value and the reference value is calculated and output as a signal in a predetermined format (S8: difference detecting means). And the magnetic characteristic detection (S7, S8) of the detection target area in the banknote S is repeated until the detection target area signal is turned off (S9).

  As shown in FIG. 5, the count number changing process is a process of changing the oscillation wave count number N in accordance with a count number changing signal input from a host controller or the like (S11) (S12). As shown in FIG. 6, the magnetic characteristic detection process includes a counter clear process (S21), an oscillation wave count process (S22, S23), and a measurement time reading process (S24). The counter clear process is a process for clearing the oscillation wave counter and the time measurement counter (S21). The oscillation wave count process is a process for counting the number of oscillation waves output from the oscillation circuit 3 (S22) and determining whether the count number has reached a predetermined number N (S23). The SK right fixed time reading process is a process of reading the time measurement counter value at the timing when the count number of the oscillating wave becomes N (S24).

  According to the present embodiment configured as described above, the paper sheet magnetic property detection device 1 detects the magnetic property of a paper sheet such as the banknote S, according to the magnetic characteristic of the paper sheet. A magnetic detection element (magnetoresistance element R) whose detected value changes, an oscillation circuit 3 for generating a phase shift in the oscillation wave in response to a change in the detection value of the magnetic detection element, and a phase shift of the oscillation wave are detected The detection circuit 4 counts a plurality of oscillation waves output from the oscillation circuit 3 and performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N. Since the phase shift of the accumulated oscillating wave is detected based on the time required for the oscillating wave counting process, the magnetic characteristics of the paper sheet can be detected with high accuracy. That is, in the oscillation wave output from the oscillation circuit 3 as described above, the magnetic characteristics of the paper sheets clearly appear as phase shifts, and the phase shift in the oscillation wave is equal to the number of oscillation waves. Since it is accumulated, the magnetic characteristics of the paper sheet can be detected with high accuracy based on the accumulated phase shift. Further, the number of oscillation waves output from the oscillation circuit 3 is counted, an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N, and the time required for the oscillation wave count process is determined. Basically, since the phase shift of the accumulated oscillation wave is measured, the phase shift component of the oscillation wave can be measured with high accuracy using an inexpensive digital circuit. In addition, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit 3, high-resolution detection can be performed while optimizing the reference frequency of the oscillation circuit 3 according to the detection target. it can.

  In addition, since the magnetic detection element of the present embodiment is the magnetoresistive element R whose resistance value changes according to the magnetic characteristics of the paper sheet, the magnetism of the paper sheet is obtained using the inexpensive magnetoresistive element R. Characteristic can be detected with high accuracy.

  Further, the detection circuit 4 of the present embodiment detects a magnetic characteristic in the reference region of the paper sheet and stores a reference value storage unit that stores the detected value as a reference value, and magnetically detects in the detection target region of the paper sheet. Magnetic characteristic detecting means for detecting a characteristic and a difference detecting means for obtaining a difference between the detected value of the detection target region and the reference value, thereby eliminating a temperature error included in the detected value and further improving the detection accuracy. Can be improved.

It is a block diagram which shows the structure of the paper sheet magnetic property detection apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the phase shift accumulation effect | action (enlarged detection waveform start end part) of an oscillation wave. It is explanatory drawing which shows the phase shift accumulation effect | action (an enlarged detection waveform termination | terminus part) of an oscillation wave. It is a flowchart which shows the whole detection process procedure of a detection circuit. It is a flowchart which shows the count number setting process sequence of a detection circuit. It is a flowchart which shows the magnetic characteristic detection processing procedure of a detection circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper sheet magnetic property detection apparatus 2 Detection head 3 Oscillation circuit 4 Detection circuit R Magnetoresistance element S Banknote

Claims (3)

A paper sheet magnetic property detection device for detecting a magnetic property of a paper sheet,
A magnetic detection element whose detection value changes according to the magnetic characteristics of the paper sheet;
An oscillation circuit that causes a phase shift in the oscillation wave in response to a change in the detection value of the magnetic detection element;
A detection circuit for detecting a phase shift of the oscillation wave,
The detection circuit
A plurality of oscillating waves output from the oscillating circuit are counted, an oscillating wave counting process is performed to determine whether or not the count number has reached a predetermined number N, and based on the time required for the oscillating wave counting process, A paper sheet magnetic property detection device for detecting a phase shift of accumulated oscillation waves.   2. The paper sheet magnetic property detection apparatus according to claim 1, wherein the magnetic detection element is a magnetoresistive element whose resistance value changes in accordance with a magnetic property of the paper sheet. The detection circuit includes:
A reference value storage means for detecting a magnetic characteristic in a reference region of the paper sheet and storing the detected value as a reference value;
Magnetic property detection means for detecting magnetic properties in the detection target region of the paper sheet;
The paper sheet magnetic property detection device according to claim 1, further comprising difference detection means for obtaining a difference between the detection value of the detection target region and the reference value.

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