JP2001092915A - Magntic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic detector capable of exactly detecting a magnetic change by removing the influence of a disturbance noise concerning the magnetic detector for detecting the magnetic change of an object to be detected such as magnetic recording medium like magnetic card or paper money printed in magnetic ink. SOLUTION: By arranging magnetic sensors 2 and 4 while deviating them just for a prescribed distance in the moving direction of an object 6 to be detected, the magnetic change on the object 6 to be detected can be detected with a prescribed time difference. On the other hand, since the disturbance noise is almost simultaneously transmitted to the magnetic sensors 2 and 4, by differentially amplifying output signals from the magnetic sensors 2 and 4, the disturbance noise is canceled and only a signal based on the magnetic change of the object 6 to be detected can be extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reading device for reading information recorded on a magnetic recording medium such as a magnetic card or a banknote printed with magnetic ink or the like. The present invention relates to a magnetic detection device that detects a magnetic change of a magnetic field.

[0002]

2. Description of the Related Art Conventionally, a magnetic card in which various kinds of information are magnetically recorded in accordance with the purpose of use or application is used. Banknotes and the like printed with magnetic ink so that authenticity can be determined are used. In order to read information magnetically recorded on these magnetic cards and bills, Japanese Patent Application Laid-Open No. H10-34040 is used.
No. 5, JP-A-10-334300, or the like is used. For example, JP-A-10
An information reading device disclosed in Japanese Patent No. 340405 is intended to prevent a sensor unit of a magnetic detection device and a magnetic card from coming into contact with each other at the time of reading information, thereby preventing both contact surfaces from being worn. Therefore, a magnetic inductance type magnetic sensor capable of measuring a weak magnetic field and having high sensitivity is arranged in non-contact with the magnetic stripe portion of the magnetic card. The magnetic inductance type magnetic sensor outputs a signal proportional to the strength of the external magnetic field by using a change in inductance due to the external magnetic field.

[0003]

SUMMARY OF THE INVENTION Magnetic cards and bills are
The information is inserted from the insertion opening of the information reading device, transported by an internal transport system, and passed through a magnetic sensor to detect information. Therefore, the magnetic sensor detects a signal on which disturbance noise such as mechanical vibration noise or electromagnetic noise generated from the transport motor or the transport path is superimposed.

By the way, a magnetic change in a magnetic stripe portion of a magnetic card or a magnetic ink of a banknote is extremely weak. In order to detect the magnetic change in a non-contact manner and obtain an output of a level which can be determined, an amplification circuit is provided. It becomes necessary to amplify the detection signal. This is not limited to the magnetic inductance type magnetic sensor, and is the same when an MR (magnetic resistance element) sensor, a differential transformer sensor, or the like is used.

However, when the detection signal is amplified, the disturbance noise component is also amplified, so that it is difficult to extract only the signal based on the magnetic change, and there is a problem that the magnetic change cannot be detected accurately.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic detector capable of accurately detecting a magnetic change by removing the influence of disturbance noise.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic detecting device provided with a magnetic sensor for detecting a magnetic change on a moving object to be detected, wherein at least two of the magnetic sensors are connected to the object to be detected. This is achieved by a magnetic detection device characterized in that the magnetic detection device is arranged to be shifted by a predetermined distance in the moving direction.

By disposing the two magnetic sensors by a predetermined distance in the moving direction of the detected object,
The two magnetic sensors detect a magnetic change on the detected object with a predetermined time difference. On the other hand, disturbance noise is transmitted to the two magnetic sensors almost simultaneously. Therefore, by differentially amplifying the output signals from the two magnetic sensors, disturbance noise can be canceled and only signals based on the magnetic change of the detected object can be extracted.

In the above-described magnetic detection device of the present invention, the predetermined distance is shorter than a width of a magnetic detection surface of the magnetic sensor in a moving direction of the detected object.
Preferably, the predetermined distance is substantially １ ／ to ／ of a width of the magnetic detection surface in a moving direction of the detected object. Although the function and effect of the present invention occur when the predetermined distance is other than 0, the predetermined distance is approximately ほ ぼ of the width of the magnetic sensor in the moving direction of the detected object, and the output signals of the two magnetic sensors are The differential amplification output is maximized, and the SN ratio can be improved. For this reason, it is practically preferable to use 1/2 and 3/4 including both sides.

Further, in the above-described magnetic detection device of the present invention, the two magnetic sensors are arranged so that the magnetic detection surfaces face each other with a moving path of the moving object to be detected interposed therebetween. And By arranging the magnetic detection surfaces of the two magnetic sensors to face each other so as to sandwich the moving object to be detected, the arrangement position of the two magnetic sensors in the moving direction of the object to be detected can be changed. The degree can be increased. Further, by causing the magnetic detection surfaces of the two magnetic sensors to face the detected object, even if the detected object is displaced in the normal direction of the magnetic recording surface during movement, the detected object Since the two magnetic sensors are arranged on both sides of the magnetic recording surface of
At least one of the magnetic sensors can reliably capture the magnetic change of the detected object.

In the magnetic detection device according to the present invention, the magnetic sensor detects a magnetic change on the detected object in a non-contact manner. Since the magnetic change can be detected in a non-contact manner, wear of the magnetic sensor and the surface of the detected object can be prevented.

[0012] In the magnetic detection device of the present invention, each output signal of at least two magnetic sensors is differentially amplified and output as a signal based on a magnetic change. As described above, according to the present invention, an extremely small magnetic change can be detected in a non-contact manner. Further, a non-contact type magnetic detection device that is resistant to disturbance noise can be realized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic detector according to an embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the magnetic detection device according to the present embodiment will be described with reference to FIG. FIG. 1A shows a side surface in the vicinity of a magnetic sensor arrangement region of the present magnetic detection device, and FIG. 1B shows the same plane. In FIG. 1, two magnetic sensors 2 and 4 for detecting a magnetic change on a moving detection target object (for example, a banknote printed with magnetic ink) 6 are shifted by a predetermined distance in the moving direction of the detection target object 6. It is arranged. In this example, the magnetic sensor 2 is arranged to detect a magnetic change of the detected object 6 before the magnetic sensor 4. In addition, the two magnetic sensors 2 and 4 move the detected object 6.
Are arranged so that the magnetic detection surfaces face each other. As is clear from FIG. 1B, the two magnetic sensors 2 and 4 have the same circular magnetic detection surface having a diameter (width) d. In this example, the two magnetic sensors 2 and 4 have the same shape. Reference numeral 4 is arranged at a position shifted by d / 2 in the moving direction of the detected object 6. Also, as shown in FIG.
Are arranged with a predetermined gap so as to detect a magnetic change on the detected object 6 in a non-contact manner even if the surface of the detected object 6 has irregularities or the detected object 6 is slightly bent. ing.

Since the magnetic detection surfaces of the magnetic sensors 2 and 4 are opposed to each other with the moving path of the detected object 6 interposed therebetween, even if the magnetic sensors 2 and 4 are moved in the moving direction of the detected object 6, 2, 4 do not interfere with each other. Therefore, the distance between the magnetic sensors 2 and 4 in the moving direction of the detected object 6 is d / 2.
Adjustments to make it shorter or longer can easily be made. Also, even if the detected object 6 bends while moving and the magnetic recording surface is displaced in the normal direction, the magnetic detection surfaces of the magnetic sensors 2 and 4 are arranged to face the front and back surfaces of the detected object 6, respectively. Therefore, at least one of the magnetic sensors 2 and 4 can reliably detect a magnetic change of the detected object 6.

The object to be detected 6 is a magnetic card on which various information is magnetically recorded according to the purpose of use or the purpose of use, a bill printed with magnetic ink so that the authenticity can be determined, or the like. The magnetic card is obtained by applying a magnetic substance to a base material and changing the magnetization direction at a predetermined density to perform magnetic recording. The magnetization direction of a magnetic card or a banknote with magnetism may be parallel or perpendicular to the moving direction of the card or the banknote, and may be horizontal or vertical on the surface of the card or the banknote. You may. Further, the information may be recorded by changing the thickness of the magnetic body in the moving direction. The detected object 6 is inserted from an insertion opening (not shown), is conveyed by a conveyance system (not shown), and passes through a gap between the magnetic sensors 2 and 4.

Next, a schematic configuration of the magnetic sensors 2 and 4 will be described with reference to FIG. FIG. 2 shows a magnetic sensor using a differential transformer. Drive coil L1, reference coil L
2, and the detection coil L3 are wound around the core. When the driving coil L1 is driven at a high frequency, the output V0 becomes V0 =
(V2-V3). The output voltages of the reference coil L2 and the detection coil L3 at the reference level for detecting the magnetic change are V20 and V30, respectively, and are adjusted so that V30 = V20. Thus, the output V0 = V20− with respect to the output change ΔV3 of the detection coil L3 due to the magnetic change.
(V30 + ΔV3) = − ΔV3, and the magnetic change ΔV
3 is directly obtained as the output V0.

Next, processing of output signals from the magnetic sensors 2 and 4 will be described with reference to FIG. FIG. 3 is a block diagram showing a processing circuit for the output signals V01 and V02 from the magnetic sensors 2 and 4. As shown in FIG. 3, output signals V01 and V02 from the magnetic sensors 2 and 4 are input to a differential amplifier 8. From the differential amplifier 8, the difference V01 between the two signals is obtained.
A signal VS obtained by amplifying −V02 is output. The output signal VS from the differential amplifier 8 is input to the comparison circuit 10 and compared with the reference signal VR generated by the reference signal generation circuit 12. The comparison result is displayed or printed out from a predetermined output device (not shown).

Next, the operation of the magnetic sensor according to the present embodiment will be described with reference to FIGS. 4 and 5 in addition to FIGS. First, two magnetic sensors 2 that are shifted by a distance d / 2 in the traveling direction of the detected object 6 and face each other with a predetermined gap,
When the detected object 6 that has been inserted from an insertion opening (not shown) and conveyed by a conveyance system (not shown) moves between the magnetic sensors 2 and 4, the magnetic sensors 2 and 4 generate a magnetic field on the surface of the detected object 6. A change is detected. The magnetic sensor 2 includes the detected object 6
From the front side, and outputs an output signal V01 to the differential amplifier 8. The magnetic sensor 4 detects a magnetic change from the back side of the detected object 6 and outputs an output signal V
02 to the differential amplifier 8.

FIG. 4A shows an output signal V01 of the magnetic sensor 2 input to the differential amplifier 8. FIG. 4
(B) shows an output signal V02 of the magnetic sensor 4 input to the differential amplifier 8. FIG. 4C shows an output signal VS from the differential amplifier 8. In each of the figures, the horizontal axis represents time, and the vertical axis represents signal level.

At time t1, disturbance noise n due to, for example, mechanical vibrations generated from the transport system is generated by the magnetic sensors 2, 4
The noise component n1 is superimposed on the output signal V01 of the magnetic sensor 2 while the noise component n2 is superimposed on the output signal V02 of the magnetic sensor 4. Magnetic sensor 2,
4 is separated by a predetermined distance (d / 2 in the present embodiment) in the moving direction of the detected object 6, but as long as it can be considered that the transmission path of the noise from the noise source is almost the same, these noise components n1, n2 has almost the same signal level at the same time. Therefore, as shown in FIG. 4C, these components are canceled by the differential amplifier 8 and the output signal V from which the noise component has been removed.
S can be obtained.

At times t2 and t3, the signal components S1 and S3 based on the magnetic change on the detected object 6 are
Is detected by the magnetic sensor 4 as signal components S2 and S4 with a delay of time to. The time delay to is determined by the moving speed of the detected object 6 and the distance between the magnetic sensors 2 and 4 in the moving direction of the detected object 6.

These signals are input to the differential amplifier 8, and the output signal VS = S1-S2 (or VS = S3-
S4) is obtained. At time t2 or t3, time t1
Even if the disturbance noise n is transmitted to the magnetic sensors 2 and 4 in the same manner as described above, they can be canceled out by the differential amplifier 8 and the output signal VS from which the noise component has been removed can be obtained as described above.

The signal component S1 (or S3) of the magnetic sensor 2 and the signal component S2 (or S4) of the magnetic sensor 4
For example, when the magnetic change on the detected object 6 is substantially the same level on the front surface and the back surface, and when the detected object 6 passes through substantially the center of the gap between the magnetic sensors 2 and 4, the substantially same level is obtained. Is obtained as the signal strength of However, when it is sufficient to determine whether the detected object 6 is a magnetic card or a bill printed with magnetic ink,
Output signal VS of high SN ratio from which disturbance noise components have been removed
, The signal components S1 and S2 (or S3
And S4) need not be detected at the same signal level.

The signal VS output from the differential amplifier 8 is input to a comparison circuit 10 and compared with a reference signal VR generated by a reference signal generation circuit 12. When it is only necessary to determine whether or not the detected object 6 is a card or paper coated with a magnetic substance, a predetermined constant voltage level as a threshold may be output to the comparison circuit 10 as a reference signal VR. A special magnetic pattern recorded on a magnetic card or bill is output signal V
In the case where the signal is obtained from S, the signal corresponding to the magnetic pattern may be output to the comparison circuit 10 as the reference signal VR. For example, if it is determined that the detected object 6 is a magnetic card or a bill based on the comparison result in the comparison circuit 10, the process proceeds to a step of further transporting the detected object 6 and reading out the magnetic recording information, and If it is determined that the object 6 is not a magnetic card or a bill, a message to that effect is displayed on the display device, and the operation shifts to an operation of ejecting the detected object 6, thereby ending a series of processes for magnetic detection.

Next, the adjustment of the distance between the magnetic sensors 2 and 4 arranged in the moving direction of the detected object 6 will be described with reference to FIG. The graph shown in FIG. 5 shows the maximum output level of the output signal VS from the differential amplifier 8, and the horizontal axis represents the distance l between the centers of the two magnetic sensors 2, 4 in the moving direction of the detected object 6. The vertical axis represents the signal level (voltage: V). In addition, a schematic diagram showing the positional relationship between the magnetic sensors 2 and 4 is shown at the lower left of the graph. As shown by the solid line in the schematic diagram, when the distance l between the centers of the magnetic sensors 2 and 4 is zero and there is no deviation between the two, the output signal VS from the differential amplifier 8 is detected based on a magnetic change together with disturbance noise. Since the signal also cancels out, it becomes zero. Further, as shown by the wavy line 2 'in the figure, when the magnetic sensor 2 relatively moves and the center distance l with the magnetic sensor 4 is d or more, that is, when the magnetic detection surfaces of both do not overlap, each magnetic sensor 2 Since the detection signals based on the magnetic changes of the sensors 2 and 4 are output from the differential amplifier 8 independently of each other, the signal VS has the maximum signal level for one magnetic sensor. And the distance l
The maximum voltage level increases almost monotonically in the range of 0 <l <d / 2, and decreases almost monotonously in the range of d / 2 <l <d.
Therefore, the magnetic sensors 2 and 4 are set to 1 = d / 2 and a value close thereto.
By setting the distance between the centers of the above, it is possible to further improve the SN ratio.

However, as the distance l increases, the correlation of the disturbance noise transmitted to the magnetic sensors 2 and 4 decreases, so if the first purpose is to reduce the disturbance noise,
It is necessary to approach 1 = 0. However, if the signal level is too close, the signal level will be small. In practice, the distance l between the centers of the two magnetic sensors 2 and 4 in the moving direction of the detected object 6 is in the range of d / 4 <l <3d / 4. In addition, the transfer function of disturbance noise at the position of the magnetic sensors 2 and 4, the distance from the detected object 6 to the magnetic sensors 2 and 4, the recording density of the detected object 6, the sensor sensitivity, and the like are considered. To determine the optimal position.

Here, the diameter d of the magnetic detection surfaces of the magnetic sensors 2 and 4 according to the present embodiment will be described with reference to FIG. FIG. 6 shows a partial cross section obtained by cutting the center of the magnetic detection surface in a direction perpendicular to the detection surface. As shown in FIG. 6, a coil bobbin 22 is housed inside the housing 20.
The coil bobbin 22 has three concave portions formed around the cylindrical tube, and is arranged so that the central axis of the cylinder faces up and down in the figure. On the coil bobbin 22, a coil L3 is wound in a lower concave portion in the figure, a coil L1 is wound in a next stage, and a coil L2 is wound in an upper stage. The bottom surface 24 of the coil bobbin 22 is a magnetic detection surface. Therefore, in the present embodiment, the diameter d of the magnetic detection surfaces of the magnetic sensors 2 and 4 is equal to the diameter of the bottom surface 24 of the coil bobbin 2. In the present embodiment, since the magnetic detection surfaces of the sensors are circular, the width of the magnetic detection surfaces of the two magnetic sensors 2 and 4 is defined using the diameter d. When the detection surface has a rectangular shape or the like, the maximum length of the magnetic detection surface in the moving direction of the detected object 6 corresponds to the width d of the magnetic detection surface.

As described above, according to the present embodiment, the magnetic sensors 2 and 4 are displaced from each other by a predetermined distance in the moving direction of the detected object 6, so that the magnetic sensor 2 The change can be detected with a predetermined time difference. On the other hand, since the disturbance noise is transmitted to the magnetic sensors 2 and 4 almost simultaneously, the output signal from the magnetic sensors 2 and 4 is differentially amplified, thereby canceling the disturbance noise and causing the magnetic change of the detection target object 6 to change. It is possible to extract only signals based on the above.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above embodiment, a magnetic sensor using a differential transformer is used as the magnetic sensors 2 and 4, but the present invention is not limited to this, and other magnetic sensors,
For example, an MR sensor, a magnetic inductance type magnetic sensor, or the like can be used. Here, for example, the width d of the magnetic detection surface in the case of the MR sensor is defined as follows. FIG. 7 shows a partial cross section of the MR sensor cut in a direction perpendicular to the magnetic detection surface and parallel to the moving direction. FIG.
As shown in FIG. 7, an MR element section 34 is mounted on a support section 32 in the housing 30. MR for support 32
A permanent magnet 36 is fixed to the opposite side of the element section 34. In the MR element section 34, an MR element 38 and an MR element 40 are arranged side by side at a predetermined interval along the moving direction of the detected object 6. The exposed surface 42 where the MR element 38 and the MR element 40 are exposed serves as a magnetic detection surface. Therefore, MR
The width of the magnetic detection surface of the sensor is the width d of the exposed surface 42 of the MR element section 34 in the moving direction.

In the above-described embodiment, the two magnetic sensors 2, 4 are sandwiched so as to sandwich the moving object 6 to be detected.
However, the present invention is not limited to this. The magnetic sensors 2 and 4 are arranged in parallel so that the two magnetic detection surfaces face one of the front surface and the back surface of the detection target 6. May be. However, in this case, the magnetic sensors 2, 4
The degree of freedom to shorten the arrangement distance is reduced depending on the size of.

In the above embodiment, the two magnetic sensors 2 and 4 are arranged parallel to the moving direction of the detected object 6, but the present invention is not limited to this, and the magnetic sensors 2 and 4 are shifted in the moving direction of the detected object 6. At the same time, it can be shifted in a direction orthogonal to the moving direction.

[0032]

As described above, according to the present invention, an extremely small magnetic change can be detected in a non-contact manner. Further, it is possible to realize a non-contact type magnetic detector that is resistant to disturbance noise. Therefore, the present invention can be suitably used for an information reading device such as a magnetic card reader and a bill discriminating device that handles a magnetic recording medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration near a magnetic sensor arrangement region of a magnetic detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a magnetic sensor of the magnetic detection device according to one embodiment of the present invention.

FIG. 3 is a block diagram showing a circuit for processing an output signal from a magnetic sensor of the magnetic detection device according to one embodiment of the present invention.

FIG. 4 is a diagram showing an operation of the differential amplifier 8 of the magnetic detection device according to one embodiment of the present invention.

FIG. 5 shows a second embodiment of the magnetic detection device according to the embodiment of the present invention.
It is a figure showing arrangement relation of two magnetic sensors.

FIG. 6 is a diagram illustrating a width d of a magnetic detection surface of the magnetic detection device according to one embodiment of the present invention.

FIG. 7 is a diagram illustrating a width d of a magnetic detection surface of the MR sensor.

[Explanation of symbols]

 2, 4 Magnetic sensor 6 Detected object 8 Differential amplifier 10 Comparison circuit 12 Reference signal generation circuit 20, 30 Housing 22 Coil bobbin 24, 42 Magnetic detection surface 36 Permanent magnet 38, 40 MR element 42 MR element part

Continued on the front page F term (reference) 2G017 AA01 AB01 AD04 AD51 AD54 BA05 BA18 3E041 AA02 AA03 AA10 BA09 BB07 5B072 CC27 DD05 FF00 HH20 5D091 AA11 AA20 BB06 FF20 HH08

Claims (6)

[Claims] 1. A magnetic detecting device comprising a magnetic sensor for detecting a magnetic change on a moving object to be detected, wherein at least two magnetic sensors are shifted by a predetermined distance in a moving direction of the object to be detected. A magnetic detection device characterized by being arranged. 2. The magnetic detection device according to claim 1, wherein the predetermined distance is shorter than a width of a magnetic detection surface of the magnetic sensor in a moving direction of the detected object. 3. The magnetic detection device according to claim 2, wherein the predetermined distance is approximately １ ／ to 3 times a width of the magnetic detection surface.
/ 4. 4. The magnetic detection device according to claim 1, wherein the two magnetic sensors are arranged so that the magnetic detection surface sandwiches a moving path of the moving object to be detected. A magnetic detection device, which is arranged to face each other. 5. The magnetic detection device according to claim 1, wherein the magnetic sensor detects a magnetic change on the detected object in a non-contact manner. Detection device. 6. The magnetic detection device according to claim 1, wherein each output signal of the magnetic sensor is differentially amplified and output as a signal based on a magnetic change. Characteristic magnetic detection device.