JP4953666B2 - Magnetic sensor device and identification device - Google Patents

Description

  The present invention relates to a magnetic sensor device including a bulk type magnetic sensor element in which a coil is wound around a core, and an identification device using the magnetic sensor device.

  Since a bulk type magnetic sensor device in which a coil is wound around a core can output an analog signal proportional to the amount of magnetism (permeability), it is printed on a bill with magnetic ink in an identification device such as a bill. It is used to detect patterns and identify the authenticity and type of banknotes (see, for example, Patent Document 1).

In such a magnetic sensor device, since the sensor signal output from the coil of the magnetic sensor element is an AC signal as shown in FIG. 7, it is first necessary to detect a pattern printed on a bill or the like. A detection method is often used in which an AC signal is rectified by a full-wave rectifier circuit and then smoothed and converted to a DC signal.
JP 2004-318541 A

  However, since the signal processing speed is low in the detection method, it is difficult to process the sensor signals output from each magnetic sensor element in time series when the multi-channel is formed using a plurality of magnetic sensor elements.

  In view of the above problems, an object of the present invention is to provide a magnetic sensor device and an identification device that can improve the processing speed as compared with the detection method.

In order to solve the above problems, in the present invention, a magnetic sensor having a plurality of magnetic sensor elements each having a coil wound around a core and a signal processing circuit that processes sensor signals output from the plurality of magnetic sensor elements. In the apparatus, the signal processing circuit holds a peak value of the sensor signal by a capacitor and outputs it, and a switching command signal for outputting the sensor signal from the plurality of magnetic sensor elements to the peak hold circuit. And a switch circuit that switches in time series based on the above, and for the peak hold circuit, the capacitor is discharged by a discharge command signal synchronized with the switch command signal to reset the peak value. It is characterized by having a discharge circuit that performs the above.

  In the present invention, since the peak hold value of the sensor signal is used, the signal processing speed can be improved. In addition, since the signal processing speed is high, when a plurality of magnetic sensor elements are used, it is easy to process the sensor signals of the plurality of magnetic sensor elements in a time series with a common signal processing circuit. Can be simplified.

In the present invention, the magnetic sensor element is preferably a differential magnetic sensor element that outputs a differential between the first coil and the second coil used as the coil as the sensor signal. If comprised in this way, since it does not receive to the influence of environmental changes, such as temperature, a detection with high precision can be performed. In this case, the first coil is an exciting coil,
The second coil is a differential detection coil, and the signal processing circuit includes a second switch circuit that switches excitation to the plurality of magnetic sensor elements in time series based on the switching command signal. The configuration that is provided can be adopted.

  In the identification device using the magnetic sensor device according to the present invention, the plurality of magnetic sensor elements output the sensor signal corresponding to a print pattern of the magnetic material printed on the surface of the medium, and output from the peak hold circuit. Based on the output signal, at least one of authenticity and type of the medium is identified.

  In the present invention, since the peak hold value of the sensor signal is used, the signal processing speed can be improved. In addition, since the signal processing speed is high, when a plurality of magnetic sensor elements are used, it is easy to process the sensor signals of the plurality of magnetic sensor elements in a time series with a common signal processing circuit. Can be simplified.

  With reference to the drawings, a paper sheet identification device using a magnetic sensor device to which the present invention is applied will be described.

(overall structure)
FIGS. 1A and 1B are a configuration diagram showing a main configuration of a paper sheet identification device (magnetic sensor device) to which the present invention is applied, and a self-excited magnetism used in the paper sheet identification device. It is explanatory drawing of a sensor element.

  In FIG. 1A, a paper sheet identification device 1 is a magnetic sensor device for detecting a pattern formed on a paper surface of a paper sheet 2, such as a banknote or a check, and identifying its authenticity and type. . That is, a printed pattern 21 is formed on the paper sheet 2 by a magnetic material such as magnetic ink. By detecting the printed pattern 21, the authenticity and type of the paper sheet 2 are identified.

  The paper sheet identification device 1 includes a transport mechanism (not shown) that transports the paper sheet 2 along the transport path 3, a magnetic sensor element 100 disposed in the middle of the transport path 3, and the magnetic sensor element 100. An excitation circuit (not shown in FIG. 1 (a)) for supplying an alternating excitation current, a signal processing circuit (not shown in FIG. 1 (a)) for processing the output from the magnetic sensor element 100, etc. It has.

  Further, in the paper sheet identification device 1 of the present embodiment, a plurality of magnetic sensor elements 100 are arranged with a predetermined gap in the width direction of the transport path 3 (the direction intersecting the transport direction of the paper sheet 2). It is a multi-channel type, and the magnetic sensor element 100 detects a pattern of a portion passing through the upper position of the transported paper sheet 2 in time series. Note that the conveyance direction of the paper sheet 2 is indicated by an arrow W.

  As shown in FIG. 1B, the magnetic sensor element 100 is self-excited, and includes a core body 11 having a sensor surface 110 having an opening in the groove 16 and an excitation coil for pattern detection disposed in the groove 16. 12. More specifically, the core body 11 includes a horizontal portion 111 and a total of six vertical plate portions 112 extending from the center, one end, and the other end toward the transport path and the opposite side. , 113, 114, 115, 116, 117, and the sensor surface 110 is constituted by the upper end surfaces of the vertical plate portions 112, 113, 114. For this reason, in the core body 11, a groove portion 16 opened at the sensor surface 110 is formed between the vertical plate portions 112 and 113, and between the vertical plate portions 112 and 114. An excitation coil 12 (first coil) for pattern detection composed of a voice coil wound around a winding bobbin (not shown) is disposed so as to wind the portion 112.

  The core body 11 is also formed with a groove portion 17 that opens on the opposite side of the sensor surface 110 between the vertical plate portions 115 and 116 and between the vertical plate portions 115 and 117. In order to wind the vertical plate portion 115, a differential detection coil 15 (second coil) comprising a voice coil wound around a winding bobbin (not shown) is disposed. The grooves 16 and 17 may be filled with resin after the excitation coil 12 and the differential detection coil 15 are mounted.

  Here, since the magnetic sensor element 100 is a differential type, the excitation coil 12 for pattern detection and the coil 15 for differential detection are connected in series, and an excitation current is supplied to both ends thereof. A sensor signal is output from a connection point between the pattern detection excitation coil 12 and the differential detection coil 15.

  In such a sensor signal, while the area where the print pattern 21 is formed on the paper sheet 2 passes under the magnetic sensor element 100, the magnetic permeability is increased by the print pattern 21, so that the output is increased. After the region where 21 is formed passes, the output decreases. As shown in FIG. 1A, when a hologram pattern such as aluminum is formed on the paper sheet 2, in a period in which the region where the hologram pattern is formed passes below the magnetic sensor element 100. Since an eddy current is generated in the hologram pattern, the output is further reduced. Therefore, if the sensor signal output from each magnetic sensor element 100 is converted into a DC signal and the signal pattern obtained from this DC signal is collated in the signal processing circuit described later, the authenticity and type of the sheet 2 Can be identified.

(Configuration of signal processing circuit)
2A and 2B are configuration diagrams of a main part of a signal processing circuit used in the paper sheet identification device 1 of the present embodiment, and explanatory diagrams showing signal waveforms at each stage of the signal processing circuit. is there. 3 and 4 are a configuration diagram of the entire drive circuit used in the paper sheet identification apparatus 1 of the present embodiment and a circuit diagram of a signal processing circuit. FIG. 5 is a waveform diagram of signals used in the signal processing circuit used in the paper sheet identification apparatus according to the present invention. In FIG. 4, the illustration of the amplifier circuit shown in FIG. 3 is omitted.

  In this embodiment, when performing signal detection using the differential type magnetic sensor element 100, the paper sheet identification device 1 performs excitation for pattern detection of each magnetic sensor element 100 as shown in FIG. An oscillator 41 and an excitation circuit 40 for supplying an excitation current to the coil 12 and the differential detection coil 15, and a signal processing circuit 5 common to the plurality of magnetic sensor elements 100 are provided.

  In this embodiment, the signal processing circuit 5 includes a peak hold circuit 51 that detects and outputs the peak value of the sensor signal output from the magnetic sensor element 100, as shown in FIGS. 2 (a) and 2 (b). Yes.

Further, since the paper sheet identification apparatus 1 of the present embodiment is a multi-channel type in which a plurality of magnetic sensor elements 100 are formed, the clock signal generation circuit 50 is used in the paper sheet identification apparatus 1 as shown in FIG. A logic circuit 54 that switches between channels ch1 to ch16 each having a magnetic sensor element 100 is used based on a clock signal output from the first analog switch circuit according to a switching command signal. (Second switch circuit) 56 is controlled to control excitation from the excitation circuit 40 to the magnetic sensor elements 100 corresponding to the channels ch1 to ch16. Further, the logic circuit 54 controls the second analog switch circuit 57 by the switching command signal, and controls the signal output from the magnetic sensor element 100 corresponding to each channel ch1 to ch16 to the signal processing circuit 5. Therefore, the magnetic sensor elements 100 corresponding to the channels ch1 to ch16 are sequentially excited in time series from the excitation circuit 40 under the control of the logic circuit 54, and output sensor signals to the signal processing circuit 5. In addition, the logic circuit 54 resets the signal processing circuit 5 by a discharge command signal every time the channels ch1 to ch16 that input signals to the signal processing circuit 5 are switched. As described above, the signal processing circuit 5 includes the analog switch circuits 56 and 57 for processing the sensor signals output from the plurality of magnetic sensor elements 100 in time series, and the logic circuit 54 includes the magnetic sensor elements. It functions as a switching command means for switching the output of the sensor signal from 100 to the peak hold circuit 51.

  More specifically, such a signal processing circuit 5 detects and outputs an amplification circuit 58 that amplifies the differential output from the magnetic sensor element 100 and a peak value of the output signal amplified by the amplification circuit 58. And an adjustment circuit 59 that performs offset adjustment and gain adjustment on the output from the peak hold circuit 51 based on the offset correction command signal and the gain correction command signal. The analog output that is output from the peak hold circuit 51 that has been output is subjected to predetermined digital signal processing and used for pattern matching.

  Among these circuits, as shown in FIG. 4, the peak hold circuit 51 includes diodes D1, D2, D6, a capacitor C1, an operational amplifier X2, and the like. From the magnetic sensor element 100 of the channel selected by the switching command signal, The peak value of the output sensor signal is held by the capacitor C1. A discharge circuit 510 is formed for the peak hold circuit 51. The discharge circuit 510 causes the capacitor C1 to discharge by turning on and off the transistor Q2 by a discharge command signal synchronized with the switching command signal. , Reset the peak value of the previously selected channel.

  In the signal processing circuit 5 configured as described above, after the discharge command signal having the waveform S0 shown in FIG. 5 is output to the discharge circuit 510, the sensor signal indicated by the waveform S1 in FIG. Is output. At that time, the peak value held by the peak hold circuit 51 changes as shown by the waveform S2 and is output as an analog signal. Thus, the sensor signal attenuates after the amplitude increases, but in this embodiment, the peak value held by the peak hold circuit 51 is output as an analog signal.

(Main effects of this form)
As described above, in the paper sheet identification apparatus 1 of this embodiment, the signal processing circuit 5 includes the peak hold circuit 51 that detects and outputs the peak value of the sensor signal output from the magnetic sensor element 100. Therefore, the signal processing speed can be improved as compared with the detection method.

  In addition, since the paper sheet identification apparatus 1 of this embodiment can improve the signal processing speed, the conveyance speed of the paper sheet 2, that is, the identification processing speed for the paper sheet 2 can be improved. In addition, since the paper sheet identification device 1 of this embodiment has a high signal processing speed, the outputs of the plurality of magnetic sensor elements 100 can be processed in time series by the common signal processing circuit 5, and the configuration of the signal processing circuit 5 is simplified. Can be

[Other embodiments]
The above embodiment is an example in which the present invention is applied to the paper sheet identification apparatus 1, but it is used as a position sensor that detects the position of the magnetic material by using the gap characteristics between the magnetic sensor element 100 and the medium. In some cases, the present invention may be applied.

  In the above embodiment, the case where the self-excited magnetic sensor element 100 is used has been described as an example. However, the present invention may be applied to the case where the separately excited magnetic sensor element 100 is used.

  Furthermore, in the above embodiment, the case where the differential magnetic sensor element 100 is used has been described as an example. However, the present invention is applied to the case where a magnetic sensor element in which one coil is wound around a core is used. Also good. As a magnetic sensor element in this case, as shown in FIG. 6A, in the T-shaped core body 11 in which one vertical plate portion 112 extends from the horizontal plate portion 111, the coil 12 is connected to the vertical plate portion 112. In the E-shaped core body 11 in which the three vertical plate portions 112, 113, 114 extend from the horizontal plate portion 111 to one side as shown in FIG. Various types of magnetic sensor elements 100 can be used, such as a coil in which the coil 12 of the vertical plate 112 is wound.

(A), (b) is the block diagram which shows the principal part structure of the paper sheet identification device to which this invention is applied, and explanatory drawing of the self-excitation type magnetic sensor element used for this paper sheet identification device. . (A), (b) is the block diagram of the principal part of the signal processing circuit used for the paper sheet identification device based on this invention, and explanatory drawing which shows the signal waveform in each step of this signal processing circuit. It is a block diagram of the whole drive circuit used for the paper sheet identification device based on this invention. It is a circuit diagram of the signal processing circuit used for the paper sheet identification device according to the present invention. It is a wave form chart of a signal used with a signal processing circuit used for a paper sheet discernment device concerning the present invention. It is explanatory drawing of another magnetic sensor element which can be used with the paper sheet identification device which concerns on this invention. It is explanatory drawing of the conventional signal processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper sheet identification apparatus 2 Paper sheet 5 Signal processing circuit 11 Core body 12 Excitation coil 15 for pattern detection Coil 51 for differential detection Peak hold circuit 100 Magnetic sensor element

Claims (4)

In a magnetic sensor device having a plurality of magnetic sensor elements each having a coil wound around a core, and a signal processing circuit that processes sensor signals output from the plurality of magnetic sensor elements.
The signal processing circuit holds a peak value of the sensor signal by a capacitor and outputs the peak signal, and outputs the sensor signal from the plurality of magnetic sensor elements to the peak hold circuit based on a switching command signal. A discharge circuit that resets the peak value by causing the capacitor to discharge in response to a discharge command signal synchronized with the switch command signal. A magnetic sensor device comprising:   2. The magnetic sensor according to claim 1, wherein the magnetic sensor element is a differential magnetic sensor element that outputs a differential between the first coil and the second coil used as the coil as the sensor signal. apparatus. In claim 2,
The first coil is an exciting coil;
The second coil is a differential detection coil,
The signal processing circuit includes a second switch circuit that switches excitation of the plurality of magnetic sensor elements in time series based on the switching command signal. In the identification device using the magnetic sensor device defined in any one of claims 1 to 3,
The plurality of magnetic sensor elements output the sensor signal corresponding to a print pattern of a magnetic material printed on the surface of the medium,
An identification apparatus for identifying at least one of authenticity and type of the medium based on an output signal from the peak hold circuit.

Images