JP3971091B2 - Magnetic detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic material detection device that detects a small amount of magnetic material contained in a printing ink used for printing a paper sheet such as a printed material in a non-contact manner.
[0002]
[Prior art]
For example, a method for identifying a paper sheet by detecting a magnetic material contained in a printing ink used for printing the paper sheet is widely known. Conventionally, in order to detect the magnetic substance contained in the printing ink used for printing this paper sheet, a primary coil is wound around the center of the S-shaped core, and two openings are set at a minute gap. A differential coil type transformer system, in which a secondary coil is wound around each of the section sides, a paper sheet is passed through one opening, and the difference between the induced voltages of the two secondary coils is output, There is a method in which a minute gap is provided in a part of the provided annular core, and a change in impedance of the annular core is detected when passing through the gap.
[0003]
Further, as a method for detecting the magnetic body in a non-contact state, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-141058, two U-shaped cores face each other with a predetermined gap. In addition, there is a method of detecting a change in impedance when a magnetic material passes through the gap by winding a coil around each core and connecting the coils in series.
[0004]
Further, for example, as disclosed in Japanese Patent Laid-Open No. 9-236642, a pair of J-shaped cores in which a coil is wound around each of the open ends, the long open ends of each core, and the short open ends are predetermined. There is a method of detecting a magnetic material passing through the gap by detecting a difference in impedance between the coils 1 and 2 in which the coils at the open ends are connected in series with the gaps facing each other.
[0005]
[Problems to be solved by the invention]
However, in the differential coil type transformer method and the annular core impedance method, the detection signal becomes maximum when the magnetic material passes while contacting the gap between the cores, and when the distance between the core and the magnetic material increases, the signal suddenly increases. To decrease. Therefore, when the magnetic body passes while swinging, the detection signal also fluctuates accordingly. Also, if the distance of the magnetic material is more than the gap between the cores, the detection signal becomes almost zero.
[0006]
In this way, it is easy to be affected by the gap between the core and the magnetic material, and when a paper sheet is conveyed at high speed, the vibration of the paper sheet becomes intense, making it difficult to obtain a stable detection signal. It is.
[0007]
In the non-contact detection method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-141058, a detection signal is obtained when there is a magnetic substance in one or both of the opposed parts of the U-shaped core. However, if the amount of magnetic material is uniform, the detection signal when there is a magnetic material on both of the opposing parts will be twice as large as when it is only on one side of the opposing part. It was difficult. Further, since the detection signal can be obtained regardless of whether the magnetic body is in the facing portion, the location cannot be specified. Furthermore, since the magnetic permeability of the core changes due to a change in ambient temperature, the detection signal is likely to change.
[0008]
In addition, in the magnetic body detection device disclosed in the above-mentioned JP-A-9-236642, the manufacturing process of the J-shaped core is complicated, and a special process is required for the fixing method of the J-shaped core. There were problems such as increased production costs.
[0009]
Therefore, in the present invention, even if the distance between the core and the magnetic material changes, the detection signal hardly fluctuates, a detection signal proportional to the amount of the magnetic material can be obtained, the location can be specified, and the temperature can be changed. Another object of the present invention is to provide a magnetic body detection device that is stable and easy to manufacture.
[0010]
[Means for Solving the Problems]
The magnetic body detection device of the present invention includes a pair of identical, straight plate-like cores that face each other with a predetermined gap through which each detected object passes , and the pair of A first coil formed by connecting each coil wound around each opposite end of the core in series and each end opposite to the opposite ends of the pair of cores, respectively. The second coil formed by connecting the mounted coils in series and the ends opposite to the opposing ends of the pair of cores, respectively , A pair of magnetic covers formed of a magnetic material whose interval is set to be larger than a gap between opposite ends of the pair of cores, a detection signal from the first coil, and the second coil And a processing circuit for processing a detection signal from.
In addition, the magnetic body detection device of the present invention includes a pair of identical and straight cores having a plate-like shape opposite to each other with a predetermined gap through which each detected object passes. A first coil formed by serially connecting coils wound at opposite ends of the pair of cores and ends opposite to the opposite ends of the pair of cores. A detection unit group having a second coil formed by connecting each coil wound in series with each other, and a line connecting opposite ends of each core is a passage direction of the detected object A plurality of detection units arranged in a straight line in a direction perpendicular to each other, and surrounding each end side opposite to the opposite ends of each pair of cores of this detection unit group, opposite each other It is formed of a magnetic material in which the interval between the portions to be formed is set larger than the gap between the opposite ends of the pair of cores A pair of magnetic cover which is, and a processing circuit for processing a detection signal from the detection signal and the second coil from each first coil of the sensing portion group.
[0011]
The pair of cores are preferably formed by stacking amorphous foils. The gap between the core and the magnetic cover is set to be larger than the gap between the opposing ends of the pair of cores, the surfaces of the opposing ends of the pair of cores and the magnetic cover The gap between the opening ends of the pair of cores is set to be larger than the gap between the opposing ends of the pair of cores, and the pair of plate-like cores has a longitudinal width passing through the object to be detected. It is preferable to dispose them so as to be parallel to the direction orthogonal to the direction.
[0012]
In addition, a plurality of detection units configured as described above are arranged in a straight line in a direction perpendicular to the passing direction of the detection object to form a magnetic substance detection device. In this case, the interval between the cores of the plurality of detection units is set to be larger than the gap between the opposing ends of the pair of cores , and the pair of straight and straight shapes in the plate shape. The core is preferably arranged so that its longitudinal width is parallel to a direction orthogonal to the direction of passage of the detected object.
[0013]
According to the present invention configured as described above, each end of the pair of cores is opposed to each other, and the coils provided at the respective ends opposite to the opposed portions are connected in series. The fluctuation of the impedance value of the coil due to the position of the magnetic material is small, and non-contact detection is possible.
[0014]
In addition, the gap between the pair of cores facing each other outputs a detection signal in response to the magnetic material, but each end on the opposite side is far away from the magnetic material, and thus hardly senses. Therefore, by detecting the impedance difference between the coils, fluctuation due to temperature is canceled out, and a signal proportional to the amount of the magnetic material can be obtained.
[0015]
In addition, since the core shape is simple, the core can be easily manufactured, can be incorporated into the apparatus, and the manufacturing cost can be reduced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
First, the first embodiment will be described.
[0018]
FIG. 1 schematically illustrates the configuration of a magnetic material detection device according to the first embodiment that detects a small amount of magnetic material contained in a printing ink used for printing a paper sheet such as a printed material in a non-contact manner. It is shown in In FIG. 1, reference numeral 1 denotes a detection unit, which includes a pair of plate-like cores 2 and 3, coils 4 a and 4 b, coils 5 a and 5 b, and magnetic covers 6 and 7. Reference numeral 8 denotes paper sheets such as printed matter (for example, securities) printed with printing ink containing magnetic powder, and is conveyed in the direction of arrow E in the figure.
[0019]
The cores 2 and 3 are formed, for example, by laminating amorphous foils, and are disposed to face each other with a predetermined gap G through which the paper sheets 8 pass through one end. In this case, the cores 2 and 3 are arranged so that the width b (see FIG. 2) in the longitudinal direction thereof is parallel to a direction orthogonal to the passing direction E of the paper sheet 8.
[0020]
Coils 4a and 4b are wound around the facing portions of the cores 2 and 3, respectively, and coils 5a and 5b are wound on the opposite side of the facing portions, respectively. And the coil 4a, 4b of an opposing part is connected in series, the 1st coil 100 is comprised, and the coil 5a, 5b on the opposite side to an opposing part is connected in series, and the 2nd coil 200 is comprised. .
[0021]
The magnetic covers 6 and 7 are made of a magnetic material, and are provided so as to surround at least the portions of the coils 5a and 5b opposite to the opposing portions of the cores 2 and 3, thereby It has become unaffected.
[0022]
The lines of magnetic force generated in the coils 4a and 4b when the first coil 100 is energized are aligned with, for example, the direction of the arrow A in the gap G where the cores 2 and 3 face each other. Similarly, in the second coil 200, the coil 5a is aligned with the directions indicated by the arrows B1 and B2 and the coil 5b is indicated in the directions indicated by the arrows C1 and C2, and the first coil 100 and the second coil 200 are energized. The arrow A, the arrow C1, the magnetic cover 7 through the illustrated arrow D1, the magnetic cover 6 through the arrow B1, the arrow B1, the arrow A1, the arrow C2, the magnetic cover 7, the illustrated arrow D2, and the magnetic cover 6 through. An annular magnetic path through which the magnetic lines of force pass through the path indicated by the arrow B2 is formed.
[0023]
When the paper sheet 8 printed with magnetic ink containing magnetic powder or the like is inserted into the opposed gap G between the cores 2 and 3, the distribution of the magnetic lines of force in the gap G changes, and therefore the first coil 100 and the first coil 100 The impedance of the second coil 200 changes. However, since the gap between the magnetic paths of the magnetic lines D1 and D2 is wider than the facing part of the cores 2 and 3, the leakage of the magnetic flux is large, the amount of the magnetic lines D1 and D2 of the annular magnetic flux decreases, and the magnetic lines of force caused by the paper sheet 8 And the impedance change of the second coil 200 is also small. Accordingly, the magnetic powder in the printing ink of the paper sheet 8 is detected by the first coil 100 at a portion in the gap G between the facing portions 2 a and 3 a of the cores 2 and 3.
[0024]
If the paper sheet 8 moves in the direction of the arrow E, the magnetic ink distributed in the moving direction of the paper sheet 8 is the first in accordance with the change in the magnetic ink amount in the gap G between the opposed portions 2a and 3a. It can be detected as a change in impedance of the coil 100.
[0025]
On the other hand, when the ambient temperature of the detection unit 1 changes, the magnetic permeability of the core 2 and the core 3 changes, and the impedances of the first coil 100 and the second coil 200 change. Since the ambient temperatures of the first coil 100 and the second coil 200 are substantially the same, the increase / decrease in the impedance change due to the temperature change is the same. Therefore, if the difference in impedance between the first coil 100 and the second coil 200 is taken, the change in impedance due to temperature is eliminated, and only the change in impedance due to the magnetic material can be taken out.
[0026]
Next, the influence of the position variation of the paper sheet 8 in the gap G between the facing portions 2a and 3a of the cores 2 and 3 will be described. When the paper sheet 8 is in the middle of the gap G, the amount of change in the impedance of the coil 4a and the coil 4b is the same, but when the paper sheet 8 approaches the facing portion 2a of the core 2, the impedance of the coil 4a is The impedance increases and the impedance of the coil 4b decreases. Further, when the paper sheet 8 approaches the facing portion 3a of the core 3, the impedance of the coil 4b increases and the impedance of the coil 4a decreases.
[0027]
However, since the first coil 100 has the coil 4a and the coil 4b connected in series, the increase and decrease in the impedance of the two coils 4a and 4b cancel each other, and as a result, the change becomes small. Therefore, even if the paper sheet 8 swings in the gap G between the opposed portions 2a and 3a of the cores 2 and 3, the influence on the detection signal is small.
[0028]
The configuration and operation of the detection unit 1 have been described above. Even if the directions A, D1, D2 and B1, B2, and C1, C2 of the magnetic force lines in the magnetic path are opposite, the magnetic force lines A, D1, The effect of the present invention is maintained even when both or one of the magnetic lines of force B1, B2 and C1, C2 are opposite to the direction of D2.
[0029]
The cores 2 and 3 can be made of a magnetic material other than the amorphous foil. However, by using a material having a high magnetic permeability such as an amorphous foil, the spread of the lines of magnetic force can be reduced. The gap G between 2a and 3a can be made large.
[0030]
The gap w between the cores 2 and 3 and the magnetic covers 6 and 7 is set to be equal to or larger than the gap G between the core facing portions 2a and 3a, and the facing portions 2a and 3a of the cores 2 and 3 and the magnetic covers 6 and 7 are set. The distance p between the end portions of the upper and lower magnetic covers 6 and 7 is equal to or larger than the gap G between the core facing portions 2a and 3a. G or more is preferable in order not to disturb the detection sensitivity of the magnetic substance in the gap G between the core facing portions 2a and 3a.
[0031]
FIG. 2 shows the outer shape of the cores 2 and 3 in detail. The horizontal width (longitudinal width) b of the cores 2 and 3 is set to be at least twice as large as the thickness (width in the short direction) t, and in a direction perpendicular to the moving direction E of the paper sheet 8. A certain width is provided, and the thickness t is reduced to reduce the thickness of the lines of magnetic force, so that the change in the moving direction distribution of the magnetic material can be accurately detected.
[0032]
The coils 4a and 4b are wound at positions close to the core facing portions 2a and 3a, so that fluctuations in the magnetic field lines in the gap G between the core facing portions 2a and 3a can be detected with high sensitivity. Yes. The gap between the core facing portions 2a and 3a and the core release portions 2b and 3b, that is, the length L of the cores 2 and 3 is preferably equal to or larger than the gap G because the influence of the core release portions 2b and 3b can be reduced.
[0033]
FIG. 3 schematically shows a signal processing circuit of the detection unit 1 shown in FIG. In FIG. 3, reference numeral 13 denotes a bridge circuit including the first coil 100 and the second coil 200 of the detection unit 1, R1 and R2 are side resistances for configuring the bridge circuit 13, and VR1 and VR2 are bridge circuits 13. This is a variable resistor for adjusting the balance. Reference numeral 14 denotes an oscillation circuit that generates a signal for energizing the bridge circuit 13. 15 is a differential amplifier that differentially amplifies the output of the bridge circuit 13, 16 is a phase synchronous detection circuit, 17 is a phase setting circuit, and 18 is a low-pass filter circuit.
[0034]
In the bridge circuit 13, the variable resistors VR1 and VR2 are adjusted so that the amplitude of the output waveform of the differential amplifier 15 is as small as possible. When the impedance of the first coil 100 changes, the output waveform and amplitude of the differential amplifier 15 change. The phase synchronous detection circuit 16 detects and rectifies the output signal of the differential amplifier 15 under the phase set by the phase setting circuit 17.
[0035]
The phase setting circuit 17 sends a signal shifted by a phase set with respect to the input waveform of the oscillation circuit 14 to the phase synchronous detection circuit 16. Set so that the detected and rectified output signal is maximized when placed. In this phase setting, a noise component signal that is harmful to the detection signal may be minimized.
[0036]
The low-pass filter circuit 18 removes high-frequency components from the signal detected and rectified by the phase-locked detection circuit 16 and outputs a detection signal. The filter circuit 18 may have a function of changing the voltage level of the output signal.
[0037]
FIG. 4 schematically shows another embodiment of the signal processing circuit of the detection unit 1 shown in FIG. In FIG. 4, reference numeral 19 denotes a bridge circuit including the first coil 100 and the second coil 200 of the detection unit 1 as constituent elements, R1 and R2 are side resistors for configuring the bridge circuit 19, and VR1 and VR2 are bridge circuits 19. This is a variable resistor for adjusting the balance. 20 is a rectangular wave oscillation circuit that generates a rectangular wave, 21 is a differential amplifier that differentially amplifies the output of the bridge circuit 19, 22 and 23 are sample hold circuits, 24 is a frequency reduction circuit, 25 is a differential amplifier, and 26 is This is a low-pass filter circuit.
[0038]
The frequency reduction circuit 24 reduces the output waveform of the rectangular wave oscillation circuit 20 to a rectangular wave having a frequency of 1/100, for example, and energizes the bridge circuit 19 with the reduced rectangular wave. In the bridge circuit 19, the variable resistors VR1 and VR2 are adjusted so that the amplitude of the output waveform of the differential amplifier 21 is in an optimal state.
[0039]
The frequency reduction circuit 24 is configured by, for example, a decimal counter circuit, and uses a function of generating a reduced waveform and outputting a pulse count result, and performs phase setting by the pulse count number, which corresponds to the set phase. The sampling pulse is output to the sample-and-hold circuits 22 and 23 at the timing.
[0040]
The output waveform on the positive side of the differential amplifier 21 is sampled by the sample hold circuit 22 and the sampled voltage is held until the next sampling pulse. Sampling of the output waveform on the negative side of the differential amplifier 21 is performed by the sample hold circuit 23, and the sampled voltage is similarly held.
[0041]
The differential amplifier 25 calculates the difference between the positive and negative sample voltages obtained from the sample hold circuits 22 and 23, removes the common bias voltage component, and removes the high frequency component by the low-pass filter circuit 26. Then, a detection signal is output. The filter circuit 26 may have a function of changing the voltage level of the output signal.
[0042]
Next, a second embodiment will be described.
[0043]
FIG. 5 schematically shows the configuration of the magnetic body detection device according to the second embodiment. The magnetic body detection apparatus according to the second embodiment is configured so that the width of the paper sheet 8 is such that the lines connecting the opposing ends of the cores of the detection unit 1 shown in FIG. A plurality (5 in this example) are arranged in parallel in the direction, and the same parts as those in the first embodiment described above are denoted by the same reference numerals and redundant description is omitted.
[0044]
In FIG. 5, reference numerals 9 and 10 denote support members that sandwich and support the cores 2 and 3, and are made of a non-magnetic material. The interval s between the cores 2 and 3 of each detection unit 1 is preferably equal to or greater than the facing portion gap G of the cores 2 and 3 in order to reduce interference between adjacent detection units 1.
[0045]
FIG. 6 schematically shows a cross section taken along the arrow JJ in FIG. In FIG. 6, the support tools 9 and 10 are provided with recesses 9a, 9b, 10a and 10b, respectively, and the portions of the coils 4a, 4b, 5a and 5b are accommodated in the recesses 9a, 9b, 10a and 10b. The cores 2 and 3 are sandwiched and supported in the state. In addition, you may fix by filling resin etc. in the clearance gap between the recessed parts 9a, 9b, 10a, 10b and the cores 2 and 3 of the support tools 9 and 10.
[0046]
According to the second embodiment, detection can be performed over almost the entire surface of the paper sheet 8 in the width direction (direction perpendicular to the transport direction), and the detection location can be specified.
[0047]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
[0048]
For example, in the detection unit 1 shown in FIG. 1, excitation coils are respectively provided in the cores 2 and 3, connected to each other in series, the excitation coils connected in series are energized, and the first coil 100 and the first coil 100 are connected to each other. By obtaining a difference in the output of the two coils 200 with a differential amplifier, or by differentially connecting the first coil 100 and the second coil 200 and performing phase-locked detection as a difference in induced voltage, the same effect can be obtained. can get.
[0049]
【The invention's effect】
As described above in detail, according to the present invention, even if the distance between the core and the magnetic material changes, the detection signal hardly fluctuates, a detection signal proportional to the amount of the magnetic material can be obtained, and the location can be specified. It is possible to provide a magnetic body detection device that is stable against temperature changes and easy to manufacture.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing a configuration of a magnetic body detection device according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing an outer shape of a core.
FIG. 3 is a configuration diagram schematically illustrating a signal processing circuit of a detection unit.
FIG. 4 is a configuration diagram schematically illustrating another embodiment of a signal processing circuit of a detection unit.
FIG. 5 is a front view schematically showing a part of the configuration of a magnetic body detection device according to a second embodiment of the present invention.
6 is a cross-sectional view schematically showing a cross section taken along an arrow JJ in FIG. 5;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Detection part 2, 3 ... Core 4a, 4b, 5a, 5b ... Coil 100 ... 1st coil 200 ... 2nd coil 6, 7 ... Magnetic cover 8 ... Paper sheet (printed matter) )
13, 19 ... Bridge circuit 14 ... Oscillator circuits 15, 21, 25 ... Differential amplifier 16 ... Phase synchronous detector circuit 17 ... Phase setting circuit 18, 26 ... Filter circuit 20 ... Rectangular wave oscillator circuit 22 , 23... Sample hold circuit 24... Frequency reduction circuit

Claims (7)

A pair of identical and straight cores in the shape of a plate opposed to each other with a predetermined gap through which each detected object passes;
A first coil formed by connecting in series each of the coils wound around the opposing ends of the pair of cores;
A second coil formed by connecting in series each coil wound on each end opposite to the opposite ends of the pair of cores;
Each of the ends of the pair of cores opposite to the opposite ends of the pair of cores is surrounded , and the interval between the opposing portions of the pair of cores is larger than the gap between the opposing ends of the pair of cores. A pair of magnetic covers formed of a magnetic material set to a large size ;
A processing circuit for processing the detection signal from the first coil and the detection signal from the second coil;
A magnetic substance detection device comprising:   The magnetic body detection device according to claim 1, wherein the pair of cores is formed by stacking amorphous foils.   The magnetic body detection device according to claim 1, wherein an interval between the core and the magnetic cover is set larger than a gap between opposite ends of the pair of cores.   The gap between the opposed end surfaces of the pair of cores and the opening end of the magnetic cover is set to be larger than the gap between the opposed ends of the pair of cores. The magnetic substance detection apparatus according to claim 1. A pair of identical and straight cores that are opposed to each other with a predetermined gap through which to-be-detected objects pass, and the opposite ends of the pair of cores. A first coil formed by connecting each wound coil in series and each coil wound at each end of the pair of cores opposite to the opposite ends are connected in series. A plurality of detectors each having a second coil formed in a straight line in a direction perpendicular to the passing direction of the object to be detected. Group,
Each of the pair of cores of the detection unit group surrounds the opposite end portions of the pair of cores, and the interval between the mutually facing portions is the opposite end portion of the pair of cores. A pair of magnetic covers formed of a magnetic material set larger than the gap between them,
A processing circuit for processing a detection signal from each first coil and a detection signal from each second coil of the detection unit group;
Magnetic material detecting apparatus characterized by comprising a. The magnetic body detection device according to claim 5, wherein an interval between the cores of the detection unit group is set larger than a gap between opposite ends of the pair of cores. The pair of straight cores having the same plate shape are arranged such that the longitudinal width thereof is parallel to a direction perpendicular to the passing direction of the detected object. The magnetic substance detection apparatus of Claim 1 or Claim 5.

Images