JP4507585B2 - Drive circuit for paper sheet identification sensor and paper sheet identification device - Google Patents

Description

  The present invention relates to a drive circuit for driving a sensor for identifying paper sheets, and particularly to reducing mutual interference when a plurality of such sensors are arranged and driven simultaneously.

  Conventionally, the presence or absence, amount, and pattern of magnetic ink (printing ink containing magnetic substances) embedded in paper sheets such as banknotes and checks are detected by a magnetic sensor. There is a magnetic banknote identification sensor for identifying the type. Various proposals have been made to improve the identification accuracy of the magnetic banknote identification sensor (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  The invention disclosed in Patent Document 1 is provided with two magnetic heads, a differential magnetic head and a residual magnetic detection type magnetic head, and obtains a ratio between the maximum magnetic flux density and the residual magnetic flux density of the magnetic ink, and the value of this ratio And the set value are compared, it is possible to reliably identify the type of magnetic ink of the paper sheet.

  The invention disclosed in Patent Document 2 improves identification performance by sharing only one amplifier circuit while providing a plurality of magnetic heads, and at the same time simplifies the circuit configuration to achieve uniform quality. That's it.

  The invention disclosed in Patent Document 3 uses at least two magnetic sensors that read magnetic information recorded on a paper-like medium, and generates false magnetic information by the interaction of read signal amplification circuits connected to the respective magnetic sensors. Even if is inputted, it does not respond, and only true magnetic information can be reliably discriminated.

  As described above, the above-described conventional technology improves the identification accuracy of the magnetic banknote identification sensor by providing a plurality of magnetic heads. Moreover, it is preferable to provide multiple magnetic heads also from a viewpoint of speeding up a banknote identification process.

Japanese Examined Patent Publication No. 4-52518 JP 58-24984 A JP 59-75386

  However, as described above, when a plurality of magnetic sensors (magnetic heads) are provided and driven from the viewpoint of improving identification accuracy or speeding up processing, magnetic mutual interference occurs between the respective magnetic sensors. There is a risk of lowering the identification accuracy.

  In addition, in order to further increase the resolution of paper sheet identification, it is necessary to provide a large number of magnetic sensors. As a result, the interval between adjacent magnetic sensors becomes narrow, which increases the mutual interference described above. Will do.

  The present invention has been made in view of these points, and the object thereof is to suppress the occurrence of magnetic mutual interference between the magnetic sensors even when a plurality of magnetic sensors are provided. An object of the present invention is to provide a driving circuit for a possible paper sheet identification sensor.

  In order to solve the problems as described above, the present invention provides a sensor driving circuit having two or more paper sheet identification sensors arranged adjacent to each other and an AC signal from a power supply circuit to the paper sheet identification sensor. A sensor driving means for supplying an excitation signal and a sensor switching means for switching on and off the paper sheet identification sensor are provided for each paper sheet identification sensor, and in addition, a power source supplied to the paper sheet identification sensor A switching control means for sending a control signal for controlling the supply timing of the AC signal from the circuit to the sensor switching means is provided.

  More specifically, the present invention provides the following.

(1) In order to detect a magnetic substance printed on the surface of a paper sheet as an electromagnetic signal, a plurality of paper sheet identification sensors arranged adjacent to each other in a direction substantially perpendicular to the transport direction of the paper sheet a sensor driving circuit comprising: a sensor drive means for supplying an alternating current signal to the paper sheet recognition sensor from the power supply circuit, before switching SL paper sheet recognition sensor switch means, the performing of the paper sheet recognition sensor A plurality of paper sheet identifications which are provided for each sensor and which simultaneously drive among the plurality of paper sheet identification sensors by controlling the supply timing of an AC signal from a power supply circuit supplied to the paper sheet identification sensor. A sensor comprising a switching control means for controlling the sensor and for sending a control signal to the sensor switching means for controlling at least not to simultaneously drive adjacent paper sheet identification sensors. Driving circuit.

  According to the present invention, in order to detect a magnetic substance printed on the surface of a paper sheet such as a check or banknote as an electromagnetic signal (electrical signal or magnetic signal), A sensor driving circuit having two or more paper sheet identification sensors arranged adjacent to each other in a substantially orthogonal direction receives an AC signal (high frequency signal) from a power circuit such as an AC power supply device to the paper sheet identification sensor. A sensor driving means for supplying and a sensor switching means for switching the paper sheet identification sensor electrically / electronically or mechanically are provided for each paper sheet identification sensor, and further to the paper sheet identification sensor. Since it is provided with a switching control means for controlling the supply timing (including the supply pattern) of the AC signal from the supplied power supply circuit and sending the control signal to the sensor switching means such as an electric signal or an optical signal. The presence of the switching control means, the AC signal from the power supply circuit can be controlled timing (supply pattern) supplied to the paper sheet recognition sensor.

  For example, the switching control means can perform control so that adjacent paper sheet identification sensors are not turned on, or can perform control to turn on every second paper sheet identification sensor, and consequently magnetic fields adjacent to each other. It is possible to suppress the occurrence of mutual interference between the sensors and prevent the identification accuracy from being lowered. In addition, when the supply timing of the AC signal from the power supply circuit supplied to the paper sheet identification sensor is patterned and stored in advance and the control by the switching control means is performed based on the stored contents, the magnetic sensor By setting the supply pattern so that no mutual interference occurs, it is possible to prevent the identification accuracy from being lowered.

  Moreover, since only one power supply circuit for supplying an AC signal to a plurality of paper sheet identification sensors is sufficient, the circuit manufacturing cost can be reduced, and the circuit size can be reduced to reduce the size of the entire paper sheet identification apparatus. In addition, power consumption can be reduced.

  Here, “detect as an electromagnetic signal” means that a magnetic signal is detected using a magnetic interaction (for example, impedance change) with a magnetic substance printed on the surface of a paper sheet, and is detected. After converting to an electrical signal by electromagnetic induction or the like, the electrical signal is detected as a sensor output.

  In addition, as a “paper sheet identification sensor”, a separately excited type sensor comprising a coil that is excited by an AC signal supplied from a power supply circuit and a coil that is detected as an electromagnetic signal as separate coils, and an impedance change There are two methods: a self-excited sensor in which a coil that is excited by an AC signal supplied from a power supply circuit and a coil that is detected as an electromagnetic signal are formed of the same coil is provided. However, the present invention is not intended to be limited to any one of the methods. By adopting a self-excited sensor, the excitation function and the detection function can be achieved with a single coil, which in turn can contribute to the reduction of the arrangement space and the cost reduction of the entire paper sheet identification apparatus. .

  As the “sensor driving means”, a transistor having a current amplification function can be employed. As a result, the AC signal from the power supply circuit input to the sensor driving means can be reduced, and as a result, power saving can be achieved.

  In addition, as a “sensor switching means”, not only a contactless switching means that electronically turns on / off a signal (current) using the action of a semiconductor element / electronic element based on an electrical input signal, but also an electrical Various contact types, such as contact type switching means that opens and closes mechanical contacts based on typical input signals to turn signals (currents) on and off, and hybrid type switching means that combines both contactless and contact types However, the present invention is not intended to be limited to any one of these. When contactless switching means that electronically turns on and off signals using the function of semiconductor elements is adopted, high-speed processing is possible, such as when multiple sheets of paper are identified at a time. When required, good switching (response) characteristics can be obtained.

  Furthermore, as described above, the “switching control means” sends a control signal for controlling the supply timing of the AC signal from the power supply circuit supplied to the paper sheet identification sensor to the sensor switching means. In this case, an electrical input signal is supplied to the sensor switching means. However, the present invention is not intended to limit the switching control means to supply an electrical input signal. For example, when a photoelectric switch is adopted as the sensor switching means, an optical signal is supplied.

  (2) The sensor driving circuit, wherein the switching control means sends a control signal to the sensor switching means so that magnetic interference does not occur between the two or more paper sheet identification sensors.

  According to the present invention, the switching control means described above sends a control signal to the sensor switching means so that no magnetic interference occurs between two or more paper sheet identification sensors. It is possible to prevent a decrease in identification accuracy due to magnetic mutual interference between the identification sensors.

  (3) A paper sheet identification device including an identification circuit for identifying a paper sheet based on the electromagnetic signal detected by the sensor driving circuit according to (1) or (2).

  According to the present invention, since the paper sheet identification device includes an identification circuit that identifies paper sheets such as banknotes based on the electromagnetic signal detected by the sensor drive circuit described above, a plurality of paper sheets By suppressing the occurrence of mutual interference between identification sensors (magnetic sensors), it is possible to prevent a decrease in identification accuracy.

  It is possible to connect not only one identification circuit to the entire sensor driving circuit but also one identification circuit, that is, the number of identification circuits equal to the number of paper sheet identification sensors. is there. As a result, since the signal of only the selected paper sheet identification sensor can be picked up and the paper sheet can be identified, the mutual interference between the plurality of paper sheet identification sensors is suppressed and the paper sheet is accurately detected. Identification can be made.

  As described above, the position detection device according to the present invention is a sensor that switches the paper sheet identification sensor with the control signal that controls the supply timing of the AC signal supplied to the paper sheet identification sensor by the sensor driving means. Even if a plurality of paper sheet identification sensors are provided since they are sent to the switching means, for example, the occurrence of magnetic mutual interference between the sensors can be avoided by avoiding the simultaneous operation of adjacent paper sheet identification sensors. As a result, the accuracy of the paper sheet identification device can be prevented from being lowered. In addition, since only one power supply circuit that supplies an AC signal to a plurality of paper sheet identification sensors is sufficient, it is possible to contribute to cost reduction in circuit manufacture, circuit size reduction, and power consumption reduction.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Circuit configuration]
FIG. 1 is a circuit diagram showing a circuit configuration of a drive circuit 1 and its peripheral circuits of a paper sheet identification sensor according to an embodiment of the present invention.

In FIG. 1, a drive circuit 1 for a paper sheet identification sensor includes separately excited magnetic heads S _{1 to} S ₄ as an example of a paper sheet and a paper sheet identification sensor, and transistors Tr _{1 to} Tr as an example of a sensor driving unit. _4, a base resistance _R 1 to R ₄ of the transistor _Tr 1 to Tr _4, a switching transistor SWTr ₁ ~SWTr ₄ as an example of a sensor switching means, the switching timing control unit 11 as an example of a switching control means, the I have. An AC power supply 2 as an example of a power supply circuit is connected to the drive side of the drive circuit 1, and a sensor signal processing circuit 3 as an example of an identification circuit (single or plural) is connected to the detection side of the drive circuit 1. Has been.

The four separately-excited magnetic heads S _{1 to} S ₄ are arranged adjacent to each other in this order in a direction substantially orthogonal to the sheet transport direction. However, “adjacent” here includes not only that the _four separately-excited magnetic heads S _{1 to} S ₄ are in contact with each other but also that they are arranged at regular intervals. Although the sensor drive circuit 1 in the case of four separately excited magnetic heads is shown here, the present invention is not limited to four separately excited magnetic heads, and is used for, for example, a general identification sensor. There may be 12 or 24. The transistors Tr _{1 to} Tr ₄ and the switching transistors SWTr _{1 to} SWTr ₄ may be either NPN transistors or PNP transistors. Furthermore, these transistors may be field effect transistors such as junction FETs or MOSFETs, or analog switches of general-purpose logic ICs depending on circumstances.

In FIG. 1, an AC power source 2 provided on the drive side of the drive circuit 1 is connected to a drive end (base end) of a transistor Tr ₁ via a base resistor R ₁ and is connected to a transistor via a base resistor R _2. The drive end (base end) of Tr _2, the drive end (base end) of transistor Tr ₃ via base resistor R _3, and the drive end (base end) of transistor Tr ₄ via base resistor R ₄ are also respectively provided. It is connected.

The emitter terminal of the transistor Tr ₁ is connected to the exciting coil of the separately excited magnetic head S _1, the collector terminal of the transistor Tr ₁ is connected to the collector terminal of the switching transistor SWTr _1. Similarly, the emitter terminal of the transistor Tr ₂ is connected to the exciting coil of the separately excited magnetic head S _2, the collector terminal of the transistor Tr ₂ is connected to the collector terminal of the switching transistor SWTr _2. The emitter terminal of the transistor Tr ₃ is connected to the exciting coil of the separately excited magnetic head S _3, the collector terminal of the transistor Tr ₃ is connected to the collector terminal of the switching transistor SWTr _3. The emitter terminal of the transistor Tr ₄ is connected to the exciting coil of the separately excited magnetic head S _4, the collector terminal of the transistor Tr ₄ is connected to the collector terminal of the switching transistor SWTr _4. Note that the emitter of the transistor Tr ₁ to Tr _4, but separately excited magnetic head S ₁ to S ₄ are directly connected, for example, a fixed resistor may be interposed as an emitter resistance.

The emitter terminal of the switching transistor SWTr _{1 ~SWTr 4,} a switching transistor SWTr power supply for supplying a collector current to _{1 ~SWTr 4} are respectively connected, the drive end of the switching transistor SWTr _{1 ~SWTr 4} (base end) Is connected to the switching timing control unit 11. Note that the present invention is not intended to limit the circuit arrangement of the switching transistors SWTr _{1 to} SWTr _{4 to} the circuit arrangement shown in FIG. 1, but is connected to the base terminals and emitter terminals of the transistors Tr _{1 to} Tr ₄ . Changes can be made without departing from the purpose of avoiding magnetic interference.

Here, the switching timing control unit 11 is out two signal lines, one signal line is branched to the base end of the switching transistors SWTr ₁ and SWTr _3, the other signal line, a switching transistor Branching to the base ends of SWTr ₂ and SWTr ₄ . In such a circuit configuration, by transmitting a control signal to only one of the two signal lines, the separately excited magnetic head S ₁ , the separately excited magnetic head S ₂ , and the separately excited magnetic head disposed adjacent to each other. Control can be performed such that S ₂ and the separately excited magnetic head S ₃ , and the separately excited magnetic head S ₃ and the separately excited magnetic head S ₄ are not driven simultaneously. That is, it is possible to perform control so that adjacent separately excited magnetic heads are not driven simultaneously.

The switching timing control unit 11 transmits a control signal to two signal lines as described above, and includes, for example, a CPU core, a high-frequency clock circuit, and primary and secondary caches. It can be embodied by a microprocessor. In the present invention, the type of the implementation circuit (device) of the switching timing control unit 11 is not limited. In the present embodiment, the switching timing control unit 11 sends the control signal via one of the two signal lines. However, the present invention is not limited to this. A signal line is provided for each of the magnetic heads S _{1 to} S ₄ (four signal lines are provided), and relay control is performed in the switching timing control unit 11 so that control signals are not sent simultaneously to two adjacent signal lines. You may make it the structure which does.

The detection coils of the separately excited magnetic heads S _{1 to} S ₄ are connected to a sensor signal processing circuit 3 provided on the detection side of the drive circuit 1. The sensor signal processing circuit 3 includes a half-wave rectification or full-wave rectification circuit, a low-pass filter, and an operational amplifier. The sensor signal processing circuit 3 amplifies an electromagnetic signal from a separately-excited magnetic head or paper sheets based on the electromagnetic signal. Various signal processing related to the identification of the image is performed, but detailed description thereof is omitted here.

[Basic circuit operation]
FIG. 2 is a plan view showing a state in which paper sheets (thousand-yen bills) are identified by the paper sheet identification device incorporating the drive circuit 1 according to the embodiment of the present invention.

In FIG. 2, a plurality of separately excited magnetic heads including a unit 21 in which the drive circuit 1 according to the embodiment of the present invention is incorporated and separately excited magnetic heads S _{1 to} S ₄ installed in the unit 21 ( 12), a thousand-yen bill 22 to be identified, a magnetic ink 23 embedded in the thousand-yen bill, and a conveyance path 24 for conveying the thousand-yen bill to the right. The separately excited magnetic heads S _{1 to} S ₄ are arranged adjacent to each other in a direction perpendicular to the direction in which the thousand yen bill is conveyed. The separately excited magnetic heads other than the separately excited magnetic heads S _{1 to} S ₄ are connected to a drive circuit similar to the drive circuit 1 shown in the circuit diagram of FIG.

  In FIG. 2, first, when the thousand yen bill 22 is inserted from the left (FIG. 2A), the thousand yen bill 22 is moved rightward by a conveyance belt (not shown) provided in the conveyance path 24. Be transported.

When the thousand-yen bill 22 is conveyed directly below (near) the unit 21 (FIG. 2B), the separately-excited magnetic heads S _{1 to} S ₄ detect the magnetic ink 23 as an electromagnetic signal. More specifically, in the circuit diagram of FIG. 1, the transistors Tr _{1 to} Tr ₄ to which an AC signal is supplied from the AC power source 2 are used to excite collector currents (AC currents) of the separately excited magnetic heads S _{1 to} S ₄ . Supply to coil. When the magnetic ink 23 comes near the air gap portion of the separately excited magnetic heads S _{1 to} S ₄ , a change (disturbance) occurs in the amount of magnetic flux (magnetic signal) that passes through the air gap portion and the core portion. Thus, the change is output as an electric signal to the detection coils of the separately excited magnetic heads S _{1 to} S ₄ .

At this time, as described above, the switching timing control unit 11 uses the two signal lines to control the switching transistors SWTr ₁ and SWTr ₃ and the switching transistors SWTr ₂ and SWTr ₄ separately. Since the (driving signal) is transmitted, the collector currents of the transistors Tr ₁ and Tr ₃ (excitation currents of the separately excited magnetic heads S ₁ and S ₃ ) and the collector currents of the transistors Tr ₂ and Tr ₄ (the separately excited type magnetic head S) are transmitted. ₄ and the S ₄ excitation current), so that is separately on-off controlled. Therefore, adjacent separately-excited magnetic heads (externally-excited magnetic heads S ₁ and S ₂ , separately-excited magnetic heads S ₂ and S ₃ , and separately-excited magnetic heads S ₃ and S ₄ ) are not driven simultaneously but adjacent to each other. Magnetic mutual interference between separately excited magnetic heads can be prevented.

  The switching timing control unit 11 switches control signals for two signal lines at high speed. For example, in the case of the switching timing control unit 11 having a clock frequency of 1 MHz, the control signal is switched at intervals of about 5 μs. Therefore, according to the switching timing control unit 11, the magnetic ink 23 of the thousand yen bill 22 can be detected with high resolution.

<Modification>
[Circuit configuration]
FIG. 3 is a circuit diagram showing a circuit configuration of the drive circuit 1 and its peripheral circuits of the paper sheet identification sensor according to another embodiment of the present invention. The same elements as those shown in the circuit diagram of FIG.

In FIG. 3, the drive circuit 1 of the paper sheet identification sensor includes impedance changes of self-excited magnetic heads S _{5 to} S ₈ and self-excited magnetic heads S _{5 to} S ₈ as an example of the paper sheet and paper sheet identification sensor. a sensor resistor _R 5 to R ₈ to capture, the transistor _Tr 1 to Tr ₄ as an example of a sensor drive means, a base resistor _R 1 to R ₄ of the transistor _Tr 1 to Tr _4, switching as an example of a sensor switching means Transistors SWTr _{1 to} SWTr ₄ and a switching timing control unit 11 as an example of switching control means are provided. As in FIG. 1, the drive side of the drive circuit 1 has an AC power supply 2 as an example of a power supply circuit, and the detection side of the drive circuit 1 has a sensor signal as an example of an identification circuit (single or plural). A processing circuit 3 is connected.

  Here, the difference between the circuit diagram of FIG. 3 and the circuit diagram of FIG. 1 is the difference between whether the magnetic head is separately excited or self-excited. Therefore, the description of the same points as in the circuit diagram of FIG. 1 is omitted.

  FIG. 4 is an explanatory diagram for explaining the difference between the separately excited magnetic head and the self-excited magnetic head. FIG. 4A shows a separately-excited magnetic head, and FIG. 4B shows a self-excited magnetic head. Since the functions and operations of the separately excited magnetic head shown in FIG. 4A are as described above, description thereof is omitted.

  In FIG. 4B, the self-excited magnetic head has a coil excited by an AC signal supplied from a power supply circuit and a coil to be detected as an electromagnetic signal, and one end of the coil is grounded. The other end of the coil is connected to an AC power source via a sensor resistor for capturing a change in impedance. The output is taken out from the connection point between the coil and the sensor resistance.

  First, the self-excited magnetic head is excited by an alternating current supplied from an alternating current power source. When the magnetic substance (magnetic ink) comes near the lower part of the coil, the eddy current flowing through the core portion is disturbed, and the coil impedance change (change in the current flowing through the coil) is detected by the sensor resistance. And an electrical signal is output from the connection point of the sensor resistance.

  The circuit diagram of FIG. 3 uses four self-excited magnetic heads and four sensor resistors as described above, and detects a magnetic substance (magnetic ink) printed on the surface of a paper sheet as an electromagnetic signal. This is the same as the circuit diagram of FIG.

[Basic circuit operation]
The basic circuit operation of the circuit shown in FIG. 3 is the same as the basic operation of the circuit shown in FIG. That is, the transistors Tr _{1 to} Tr ₄ to which an AC signal is supplied from the AC power supply 2 pass collector currents (AC currents) through the sensor resistors R _{5 to} R ₈ and excite coils of the self-excited magnetic heads S _{5 to} S ₈ . To supply. When the thousand yen note 22 (see FIG. 2) comes down near the self-excited magnetic head _S 5 to S _8, the connection point of the self-excited magnetic head _S 5 to S ₈ and the sensor resistor _R 5 to R ₈ An electrical signal is output. At this time, the switching timing control unit 11 transmits a control signal to the switching transistors SWTr _{1 to} SWTr _{4 so} that adjacent self-excited magnetic heads are not driven simultaneously. Thereby, magnetic mutual interference between adjacent self-excited magnetic heads can be prevented. Further, since the paper sheets can be identified by one coil having the excitation function and the detection function, the arrangement space can be reduced and the cost of the entire paper sheet identification apparatus can be reduced.

  FIG. 5 is an explanatory diagram of an embodiment of the present invention. More specifically, it is an experimental result that, by not driving adjacent magnetic heads at the same time, the influence (toggle output) due to magnetic mutual interference between these magnetic heads is removed.

  5A, in the embodiment of the present invention, a printing unit 53 (magnetic ink as shown in FIG. 2) is used for a sensor 51 (corresponding to the unit 21 as shown in FIG. 2) having three magnetic heads (ch1 to ch3). The measurement medium 52 (corresponding to the thousand-yen bill 22 in FIG. 2) such as copy paper is conveyed so that the arrangement direction of the three magnetic heads and the printing unit 53 are orthogonal to each other. The air gap between the sensor 51 and the conveyance path 24 is zero. That is, the measurement medium 52 is conveyed while being in sliding contact with the sensor 51.

  First, a case where three magnetic heads (ch1 to ch3) are driven simultaneously will be described. When the printing unit 53 of the measurement medium 52 passes below the sensor 51, the output of the waveform shown in FIG. 5B is output in the identification circuits (ch1 to ch3) corresponding to the three magnetic heads (ch1 to ch3). can get. In FIG. 5B, the horizontal axis indicates displacement [mm], and the vertical axis indicates output [V]. The top waveform shows a composite waveform of the second ch1 waveform from the top, the third ch2 waveform from the top, and the bottom ch3 waveform.

  According to FIG. 5B, it can be seen that the outline of the waveforms of ch1 to ch3 is concave, and the output timing is shifted depending on the transport distance of the measurement medium 52. That is, when the measurement medium 52 is displaced in the range of 7 [mm] to 14 [mm], the ch3 waveform is output, and the measurement medium 52 is in the range of 15 [mm] to 22 [mm]. When it is displaced, the waveform of ch2 is output, and when the measurement medium 52 is displaced in the range of 23 [mm] to 30 [mm], the waveform of ch1 is output. In each of the waveforms of ch1 to ch3, the peak value is taken at both the timing when the measurement medium 52 approaches the magnetic head and the moment when the measurement medium 52 moves away from the magnetic head. This is because the amount of magnetic flux is the largest at the corner of the magnetic head and the sensitivity is the highest.

Here, the waveform of 3ch, and appears pointed output Tg ₁ immediately to the right of the right peak value, the waveform of 2ch, kurtosis and immediate left of the left peak value, and just to the right of the right peak value, the Outputs Tg ₂ and Tg ₃ appear, and in the waveform of 1ch, a toggari output Tg ₄ appears immediately to the left of the left peak value. This is nothing but the influence of mutual interference between the magnetic heads.

  Next, the case where the magnetic heads (ch1 to ch3) are driven separately will be described (FIGS. 5C to 5E). When only the magnetic head ch1 is driven, an output waveform as shown in FIG. 5C is obtained, and when only the magnetic head ch2 is driven, an output waveform as shown in FIG. 5D is obtained. When only the magnetic head ch3 is driven, an output waveform as shown in FIG. 5 (e) is obtained. According to FIGS. 5C to 5E, when each of the magnetic heads ch1 to ch3 is driven as a single unit, there is no influence (toggle output) due to magnetic mutual interference between the magnetic heads. I understand that.

Finally, the case where the magnetic head ch1 and the magnetic head ch3 are driven simultaneously will be described (FIG. 5 (f)). When the magnetic head ch1 and the magnetic head ch3 are driven simultaneously, an output waveform as shown in FIG. 5 (f) is obtained. According to FIG. 5 (f), it can be seen that the toggari outputs Tg ₁ and Tg ₄ that appeared in FIG. 5 (b) have been removed. More specifically, it can be seen that the toggari outputs Tg ₁ and Tg ₄ appearing in FIG. 5B are about 1/5.

  Therefore, in the embodiment shown in FIG. 5A, the effect of magnetic mutual interference between the magnetic heads is achieved by performing control so that adjacent magnetic heads (ch1 and ch2, ch2 and ch3) are not driven simultaneously. (Togari output) is removed, and as a result, it is possible to prevent the identification accuracy from being lowered.

  A drive circuit for a paper sheet identification sensor according to the present invention includes: a sensor switching unit that switches on / off the paper sheet identification sensor based on the supply timing of an AC signal from a power supply circuit supplied to the paper sheet identification sensor; The switching control unit transmits a control signal to the sensor switching unit, and is useful as a component capable of suppressing the occurrence of magnetic mutual interference between the paper sheet identification sensors.

It is a circuit diagram which shows the circuit structure of the drive circuit of the paper sheet identification sensor which concerns on embodiment of this invention, and its peripheral circuit. It is a top view which shows a mode that paper sheets (thousand-yen bill) are identified by the paper sheet identification device incorporating the drive circuit which concerns on embodiment of this invention. It is a circuit diagram which shows the circuit structure of the drive circuit of the paper identification sensor which concerns on other embodiment of this invention, and its peripheral circuit. It is explanatory drawing for demonstrating the difference between a separately excited type magnetic head and a self-excited type magnetic head. It is explanatory drawing about the Example of this invention.

Explanation of symbols

1 driving circuit 2 supply circuit 3 sensor signal processing circuit 11 switching timing controller S ₁ to S ₄ separately excited magnetic head S ₅ to S ₈ self-excited magnetic head Tr ₁ to Tr ₄ transistor SWTr ₁ ~SWTr ₄ switching transistors R ₁ ~ R ₄ base resistance R _{5 to} R ₈ sensor resistance

Claims (3)

Sensor drive having a plurality of paper sheet identification sensors arranged adjacent to each other in a direction substantially orthogonal to the paper sheet transport direction in order to detect the magnetic substance printed on the surface of the paper sheet as an electromagnetic signal A circuit,
Sensor driving means for supplying an AC signal from the power supply circuit to the paper sheet identification sensor, and sensor switching means for switching the paper sheet identification sensor, are provided for each of the paper sheet identification sensors,
Controlling the supply timing of the AC signal from the power supply circuit supplied to the paper sheet identification sensor, and controlling a plurality of paper sheet identification sensors that are driven simultaneously among the plurality of paper sheet identification sensors, A sensor drive circuit comprising switching control means for sending a control signal for controlling not to simultaneously drive at least adjacent paper sheet identification sensors to the sensor switching means.   2. The sensor drive circuit according to claim 1, wherein the switching control means sends a control signal to the sensor switching means so that no magnetic interference occurs between the two or more paper sheet identification sensors. A paper sheet identification apparatus comprising an identification circuit for identifying a paper sheet based on an electromagnetic signal detected by the sensor drive circuit according to claim 1.

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