JP2004206316A - Magnetic detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise stability and reliability of a magnetic detection device by preventing a detection error, damage of a medium, etc. due to adhesion of iron powder in circumference environment in a conventional magnetic detection device which identifies the medium by detecting magnetic fields H1 and H2 generated by remnant magnetism with which a magnetic ink is charged by impressing a polarization magnetic field produced on a medium in a prestage of a carrier path of the medium which is printed with a magnetic ink and carried to a relative movement direction Y through a magnetic detection element 16 in a poststage on the carrier path. <P>SOLUTION: A permanent magnet which forms a magnetizing magnetic field is changed to an electromagnet 120 for magnetization, and the permanent magnet used for a conventional magnetic detection device is changed into an electromagnet 128 for bias in order to provide a biased magnetic field Hb to a magnetic detection element 16. Only when a medium arrival on a carrier path is detected by a means (not shown in the figure) to detect the arrival of a medium, the electromagnets 120, 128 are energized. Even if the iron powder is adhered to a magnetic pole face of the electromagnet 120 for polarization, it can be removed when the medium 10 is not passing. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention magnetizes a medium holding a magnetic material, such as a banknote or a magnetic card printed with magnetic ink, and detects a residual magnetic field generated by the residual magnetism of the magnetic material to detect the magnetic characteristics of the medium. And a magnetic detection device that reads a magnetic pattern and identifies a medium.
In the drawings, the same reference numerals indicate the same or corresponding parts.
[0002]
[Prior art]
For example, a magnetic sensor shown in FIGS. 4 and 5 is disclosed as a magnetic sensor used in this type of conventional magnetic detection device (see Patent Document 1).
Here, FIG. 4 is a perspective view showing a configuration of a magnetic sensor 34 in which a later-described magnetized body 20 and a magnetic detection element 16 are integrally housed in the same holder 32, and FIG. 5 is a magnetic pole surface (FIG. 4) of the magnetized body 20 of FIG. FIG. 2 is a top view showing a relative positional relationship between a hatched square) and a magnetic detection element 16 and a print medium (hereinafter, also simply referred to as a medium) 10 such as a banknote printed with magnetic ink.
[0003]
FIG. 6 is a side view of the portion of the magnetized body 20 of FIG. 5 viewed from the relative movement direction (indicated by a bidirectional arrow) Y between the magnetic sensor 34 and the medium 10. It is the figure added separately.
4 to 6, the magnetized body 20 applies a magnetizing magnetic field to the band-shaped magnetized portion 14 on the medium 10 when the magnetic sensor 34 and the medium 10 move relative to each other in the relative movement direction Y. Accordingly, the magnetic ink has a role of magnetizing the magnetic ink applied in the magnetized portion 14 on the surface of the medium 10 prior to its detection.
The magnetism detecting element 16 has a role of detecting the magnetic fields H1 and H2 generated by the residual magnetism of the magnetic ink in the magnetized portion 14 due to the magnetization. At this time, it is necessary to prevent the strong magnetizing magnetic field of the magnetized body 20 from interfering with the weak magnetic field to be detected by the magnetic detecting element 16.
[0004]
In the magnetic sensor 34 of FIG. 4, the quadrangular prism-shaped magnet 12 having the S pole on the medium detection surface Sd side is provided perpendicular to the medium detection surface Sd which is the lower end surface of the holder 32 of the magnetic sensor 34, A soft magnetic material 18 such as permalloy or ferrite having a U-shape and having a rectangular cross section is combined so as to straddle a magnetic pole (N pole in this example) on the opposite side of the medium detection surface Sd of the magnet 12. A magnetized body 20 having a substantially E-shape as a whole is formed inside.
Then, the magnetic pole faces as three rectangular end faces on the E-shaped open side of the magnetized body 20 (that is, one magnetic pole face (S pole) of the magnet 12 and two magnetic pole faces of the soft magnetic material 18) (N pole)) on the medium detection surface Sd, in contact with or close to the surface of the medium 10 in parallel, and in such a manner that the three magnetic pole surfaces are arranged in a direction perpendicular to the relative movement direction Y. 20 are arranged.
[0005]
With the configuration of the magnetized body 20, the magnetic flux from the magnet 12 is concentrated in a direction connecting the magnetic pole surfaces as the E-shaped open side end surfaces (in other words, a direction orthogonal to the relative movement direction Y). The magnetic field component from the magnetic detection element 12 to the magnetic detection element 16 can be extremely reduced, and the magnetic field component along the magnetic ink detection surface (surface) of the medium 10 is strengthened by the magnetization of the medium 10 so that the magnetized portion after the magnetization is formed. The effect of increasing the magnetic fields H1 and H2 from 14 is also obtained.
As shown in FIG. 6, in this example, the magnet 12 has an S pole, the soft magnetic material 18 has an N pole on the magnetic pole surface (three open end faces of the E-shape) of the magnetized body 20, and the N pole has an S pole. Is applied to the medium 10 to magnetize the magnetic ink. Therefore, the magnetic ink side of the magnetized body 20 near the N pole is magnetized to the S pole, and the magnetic ink side of the magnetized body 20 near the S pole is magnetized to the N pole. Is done. As a result, the residual magnetism of the magnetic ink after being magnetized produces a magnetic field in the directions indicated by arrows H1 and H2 shown in FIG.
[0006]
When it is necessary to further suppress the magnetic field propagation from the magnetized body 20 to the magnetic detection element 16, for example, as shown in FIG. 4, a screen-shaped magnetic shield member 22 made of permalloy or amorphous is used. 16 between.
The magnetic detection element 16 as a magnetic impedance element is composed of two magnetic detection elements formed on a non-magnetic substrate 24 made of glass, ceramic or the like in a zigzag linear pattern made of a magnetic thin film of high permeability such as amorphous or permalloy. In this example, the cities 16A and 18B are electrically connected in series.
Here, the serpentine linear pattern of the magnetic detection units 16A and 16B is a magnetic pattern as a connection point between the center of the magnetized magnetic pole surface, which is the end surface on the medium detection surface Sd side of the magnet 12, and the magnetic detection units 16A and 16B. The magnetic detectors 16A and 16B are configured to be substantially symmetrical with respect to a straight line L connecting the middle point of the detecting element 16 and thus to have substantially the same characteristics.
[0007]
The magnet 12 and the magnetic detection element 16 are arranged so that the direction of the straight line L coincides with the relative movement direction Y, so that the sensitivities of the magnetic detection units 16A and 16B to the magnetic field of the magnetized unit 14 can be made substantially equal. It is configured.
Then, the length in the longitudinal direction (that is, the direction orthogonal to the mutual movement direction Y) of the winding portions of the magnetic detection units 16A and 16B is selected according to the required detection width of the detection target portion, and the number of times of the winding is determined according to the resolution. And the line width and spacing of the pattern are selected.
The serpentine portions of the magnetic detection units 16A and 16B are held so as to be parallel to the detection surface Sd of the medium 10 at intervals of a few millimeters. Then, the magnetic detection units 16A and 16B are further arranged so that the longitudinal direction of each of the zigzag portions that become the magnetic field detection direction is in the same direction and is orthogonal to the relative movement direction Y in a plane parallel to the surface of the medium 10. It is configured so that they are arranged side by side along the magnetic field detection direction.
[0008]
The bias magnet 28 installed near and above the magnetic detection element 16 generates a bias magnetic field Hb (see FIG. 5), and sets the magnetic detection element 16 to a sensitive operating point. Thereby, the sensitivities of the magnetic detection units 16A and 16B to the magnetic field of the magnetized unit 14 are made substantially equal.
That is, in a state where the magnetic detection element 16 is biased by the magnetic field Hb and no other magnetic field (hereinafter referred to as an external magnetic field) superimposed on the bias magnetic field Hb exists, the impedances of the magnetic detection units 16A and 16B are substantially equal and minute. The impedance is configured to linearly change with an almost equal gradient with respect to an external magnetic field.
[0009]
It should be noted that the magnetic detectors 16A, 16B are connected through terminals 30 connected to both ends and the midpoint of the series connection of the magnetic detectors 16A, 16B, respectively. The detection signal of 16B is drawn out on the side opposite to the medium detection surface Sd.
With such a configuration, at the time of magnetic ink detection, the magnetic sensor 34 is relatively moved with respect to the medium 10 in the relative movement direction Y, and the medium 10 is magnetized by the magnetized body 20 as described above. Then, an external magnetic field generated according to the amount of the magnetic ink in the magnetized portion is differentially detected by the magnetic detection units 16A and 16B of the magnetic detection element 16.
[0010]
That is, at this time, since the external magnetic fields H1 and H2 due to the residual magnetism of the magnetic ink are superimposed on the bias magnetic field Hb, the magnetic detection unit 16A receives the magnetic field of (Hb−H1), and the magnetic detection unit 16B generates the magnetic field of (Hb + H2). receive.
Accordingly, when the impedance of the bias magnetic field Hb alone and no external magnetic field is used as a reference, the impedance of the magnetic detection unit 16A changes (decreases in this example) in proportion to (−H1), and The impedance of 16B changes (increases in this example) by an amount proportional to (+ H2).
Therefore, when one end (for example, the magnetic detection unit 16A side) of the series connection of the magnetic detection units 16A and 16B is grounded and a predetermined voltage is applied to the other end, the voltage at the midpoint of the series connection does not have an external magnetic field. The voltage changes in proportion to the external magnetic field (H1 + H2) with respect to the voltage in the case (referred to as a reference voltage).
[0011]
Using this principle, in practice, for example, a voltage applied to the series connection is a high-frequency voltage, and a voltage (comparison voltage Vref) indicating a base line in a waveform of a detection output (Vs) of a voltage at a middle point of the series connection is set. From the detection output Vs via a peak hold circuit (or a minimum hold circuit) from the portion corresponding to the reference voltage in the absence of an external magnetic field, and further compare via a DC differential amplifier circuit. A voltage proportional to the external magnetic field (H1 + H2), that is, a magnetic field corresponding to the amount of magnetic ink printed on the medium 10, is detected by a method of extracting a difference voltage between the voltage Vref and the detection output Vs.
[0012]
In the configuration of the magnetic sensor 34 described above, the disturbance magnetic field affects both the magnetic detection units 16A and 16B in the form of a change in the bias magnetic field Hb, but the external magnetic field extracted from the midpoint of the series connection of the magnetic detection units 16A and 16B. The voltage component proportional to the magnetic field (H1 + H2) hardly changes, and the influence of the minute disturbance magnetic field is canceled.
The above-described method of detecting the external magnetic field (H1 + H2) is a so-called differential detection method in which a difference between voltages across the magnetic detection units 16A and 16B is obtained in principle. As a method of performing such differential detection, for example, a middle point of the series connection of the magnetic detection units 16A and 16B is separately grounded, and a high-frequency current equal to the respective magnetic detection units 16A and 16B is applied from both ends of the series connection. There is also a method in which the voltage generated at the magnetic detection units 16A and 16B at this time is detected, and the detected voltages are DC-differentially amplified.
[0013]
Next, as a magnetic detecting device using a magnetic sensor, for example, a magnetic detecting device shown in FIG. 7 has been disclosed (see Patent Document 2).
In FIG. 7, a medium 10 is a medium using a magnetic material that generates a residual magnetic field when magnetized, such as a banknote or a check printed with magnetic ink. It is transported in the Y direction by the transport means.
On the upper surface side of the medium 10, a magnet 41 constituted by a permanent magnet as a magnetizing means for magnetizing the magnetized surface of the medium 10 is attached to face, and the direction of the magnetic pole of the magnet 41 is orthogonal to the transport direction Y. It is set in the width direction.
[0014]
A magnetic sensor 43 as a magnetic detecting means is disposed at an upper portion of the magnetizing means at a stage subsequent to the conveying direction Y with respect to the magnet 41, and a touch roller 45 urged by a spring 44 is in contact with the magnetic sensor 43.
The above-mentioned magnetic sensor 43 is constituted by a magnetic impedance element having directivity in sensitivity, and the direction of the sensitivity is set in the width direction orthogonal to the transport direction Y.
In the magnetic detection device shown in FIG. 7, the medium 10 is conveyed and magnetized by the magnet 41, and the magnetized residual magnetic field is detected by the magnetic sensor 43.
[0015]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-105847 (FIGS. 1 and 4)
[Patent Document 2]
JP-A-11-96430 (FIG. 3)
[0016]
[Problems to be solved by the invention]
In the above-mentioned conventional example, since the magnetized magnet has a magnetic force of 1K gauss or more, in an actual environment, a detection error occurs due to the suction of iron powder, or the medium may be scratched by the attached iron powder or the like. Problems arise.
Further, the magnetism of the magnet has a large variation due to temperature and changes over time, so that the reliability of the sensor output of the entire magnetism detection device is low.
Therefore, an object of the present invention is to provide a magnetic detection device which (1) has excellent environmental resistance and (2) can stably and accurately detect the amount of magnetic ink even with disturbance factors.
[0017]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the magnetic detection device according to claim 1 is
Magnetizing means for applying a magnetizing magnetic field (Hx, -Hx) to a paper sheet or thin plate-like medium (such as the print medium 10) for conveying the medium at a front stage on a conveying path for conveying the medium, Magnetic detection means (including a magnetic detection circuit 108) for detecting magnetic fields (H1, H2) generated by residual magnetism of the magnetic material on the medium by the application at the subsequent stage on the transport path, and magnetic detection for identifying the medium In the device,
The magnetizing means includes means for detecting the arrival of the medium (the entrance sensor 101, the medium entrance detecting means 106, etc.) and energizing based on the arrival detection (via the magnetizing coil / bias coil driving means 107, etc.). And a magnetizing electromagnet (120) that generates the magnetizing magnetic field in a direction perpendicular to the medium transport direction (relative movement direction Y).
[0018]
The magnetic detecting device according to claim 2 is the magnetic detecting device according to claim 1,
The magnetic detecting means includes a thin-film magnetic impedance element (magnetic detecting element 16) formed on a substrate made of a non-magnetic material (non-magnetic substrate 24), and a bias magnetic field for applying a bias magnetic field (Hb) to the thin-film magnetic impedance element. Generating means.
The magnetic detecting device according to claim 3 is the magnetic detecting device according to claim 2,
The bias magnetic field generating means includes a biasing electromagnet (128) having a magnetic core (soft magnetic body 127) for generating the bias magnetic field and a bias excitation coil (bias coil 126) for exciting the magnetic core by energization. ).
[0019]
According to a fourth aspect of the present invention, there is provided the magnetic detection device according to the third aspect.
The biasing electromagnet is energized based on the detection of the means for detecting the arrival of the medium (via the magnetizing coil / bias coil driving means 107 or the like).
The magnetic detection device according to claim 5 is the magnetic detection device according to claim 3 or 4,
At least the magnetizing electromagnet constituting the magnetizing means and the thin-film magnetic impedance element and the biasing electromagnet constituting the magnetic detecting means are integrated in the same housing (holder 32).
[0020]
The effect of the present invention is to magnetize the magnetic ink used for printing the medium or to change the permanent magnet used in the conventional magnetic detection device to an electromagnet to apply a bias magnetic field to the magnetic detection element, and to change the medium to an electromagnet. Detects intrusion and energizes these electromagnets to eliminate the effects of iron powder in the surrounding environment, reduce detection errors, and improve the stability and reliability of the magnetic detection device. It is.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration of a magnetic detection device as one embodiment of the present invention, and FIG. 2 shows one embodiment of a configuration of a magnetic sensor 103 of the magnetic detection device.
In FIG. 1, a medium 10 inserted into an insertion slot 102 is a paper leaf or a thin plate that holds a magnetic material, such as a banknote or a check printed with magnetic ink, that generates a residual magnetic field upon magnetization on the surface or inside. The sheet is conveyed in the Y direction by conveyance means (not shown) such as a conveyance roller and a conveyance belt.
An entry sensor 101 for detecting the entry of the medium 10 is provided on the upper surface side of the medium 10. The entry sensor 101 is an optical sensor such as a reflection type photointerrupter that can detect the medium 10 in a non-contact manner.
[0022]
The entry sensor 101 is disposed on the front side with respect to the transport direction Y of the medium 10, and the magnetic sensor 103 as a magnetic detection unit is disposed on the upper surface side on the rear side of the transport direction Y.
A medium entry detecting unit 106 is connected to the entry sensor 101, and a magnetizing coil / bias coil driving unit 107 is connected to the magnetizing coil terminal 140 and the bias coil terminal 141 (see FIG. 2) of the magnetic sensor 103. A magnetic detection circuit 108 is connected to each of the terminals 30 (see FIG. 2) of the magnetic detection element 16 of the sensor 103.
[0023]
The basic configuration of the magnetic sensor 103 in FIG. 2 is basically the same as the conventional magnetic sensor 34 described in FIG. 4, but the magnetized body is used as the magnetizing electromagnet 120 and the bias magnet is used as the biasing electromagnet 128. The changed points are different.
In the embodiment shown in FIG. 2, the magnetizing electromagnet 120 has a magnetizing coil 112 attached to the center leg of the three quadrangular prism-shaped legs of the soft magnetic material 118 having a quadrangular cross section and an E-shape as a whole. Is wound.
The magnetic pole surfaces as open end surfaces of the three quadrangular prism-shaped legs are parallel to the surface of the medium 10 in the same manner as the magnetic pole surface of the magnetized body 20 in FIG. 4 (the hatched portion in FIG. 5). They are arranged so as to be in contact with or close to each other and to be arranged in a direction perpendicular to the relative movement direction Y.
[0024]
The bias electromagnet 128 is configured by winding a bias coil 126 around a quadrangular prism-shaped soft magnetic body 127. The bias magnetic field Hb similar to that shown in FIG. 5 is generated above the magnetic detection element 16 like the bias magnet 28 shown in FIG. 4, and the magnetic detection element 16 is set to a sensitive operating point.
Next, the operation of the magnetic detection device of FIG. 1 will be described.
When the medium 10 inserted into the insertion port 102 is conveyed by a conveying unit (not shown) and passes below the entry sensor 101, the medium entry detection unit 106 detects the arrival of the medium 10 from the output signal of the entry sensor 101. The signal indicating this arrival is transmitted to the magnetizing coil / bias coil driving means 107.
[0025]
As a result, the magnetizing coil / bias coil driving means 107 energizes the magnetizing coil 112 and the bias coil 126 in the magnetic sensor 103 via the terminals 140 and 141, respectively, and attaches the magnetizing electromagnet 120 and the bias electromagnet 128. Drive.
Thereafter, the medium 10 reaches the magnetic sensor 103, but is first magnetized by the magnetizing electromagnet 120 in the directions of the magnetizing magnetic fields Hx and -Hx shown in FIG. When the medium 10 is further conveyed and reaches the magnetic detection element 16, the magnetic detection element 16 is affected by magnetic fields (the above-described external magnetic fields) H1 and H2 which are generated by the residual magnetism of the medium 10 and are superimposed on the bias magnetic field Hb. , The impedance changes.
[0026]
Here, the magnetic detection circuit 108 detects the residual voltage of the medium 10 from the signal voltage obtained by the magnetic detection elements 16A and 16B through the terminal 30 of the magnetic detection element 16 of the magnetic sensor 103, as in the case of the magnetic sensor 34 of FIG. A value proportional to the sum (H1 + H2) of the external magnetic fields H1 and H2 generated by magnetism is differentially detected. In this manner, the disturbance magnetic field is canceled, and the magnetic field corresponding to the amount of the magnetic ink printed on the medium 10 is accurately detected.
According to the present embodiment, the magnetizing magnetic field is generated only when the medium 10 is conveyed. Therefore, even if the iron powder adheres to the magnetic pole surface of the magnetizing electromagnet 120 in an environment where iron powder or the like exists, for example, Can be eliminated. That is, even if iron powder or the like adheres, it can be removed when the medium 10 does not pass through, so that the magnetic pattern on the medium can be detected stably with high reliability without damaging the medium.
[0027]
FIG. 3 shows another embodiment of the magnetizing electromagnet 120. In FIG. 3, magnetizing coils 112a and 112b are wound around two portions connecting three legs of an E-shaped soft magnetic body 118, respectively, to form a magnetizing electromagnet 120.
In the case of the configuration of FIG. 3, it is possible to control the amounts of magnetization in the directions of the magnetization magnetic fields Hx and −Hx with respect to the medium 10 by the currents applied to the coils 112a and 112b, respectively. Can be corrected, and the magnetic pattern on the medium can be accurately detected.
In FIG. 2, a means for measuring the ambient temperature, such as a thermistor or a thermocouple, is added, and the current to the magnetizing coil 112 of the magnetizing electromagnet 120 or the bias coil 126 of the biasing electromagnet 128 is changed to the temperature. By performing the correction and control, the magnetic field generated by each of the electromagnets 120 and 128 can be stabilized regardless of the temperature.
[0028]
In the configuration of the magnetic sensor 103 of FIG. 2, the magnetizing electromagnet 120 is integrated in the same holder 32 as the magnetism detecting element 16 and the biasing electromagnet 128. There is a characteristic that is hardly affected by
[0029]
【The invention's effect】
According to the present invention, a permanent magnet used in a conventional magnetic detecting device is magnetized to magnetize magnetic ink used for printing on a medium or to apply a bias magnetic field to a magnetic detecting element to an electromagnet. A means is provided to detect the intrusion and energize these electromagnets, eliminating the effects of iron powder etc. in the surrounding environment, reducing detection errors, and providing excellent stability and reliability. A magnetic detection device can be configured.
Furthermore, the coil current of the electromagnet can be controlled so as to compensate for the aging and temperature change of the electromagnet and the like, so that the stability of the magnetic detection device can be improved, and The effect of (1) can improve the magnetic discrimination ability of the magnetic detection device.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a magnetic detection device as one embodiment of the present invention. FIG. 2 is a configuration diagram of one embodiment of a magnetic sensor of FIG. 1. FIG. 3 is another embodiment of the magnetizing electromagnet of FIG. FIG. 4 is a conventional configuration diagram corresponding to FIG. 2; FIG. 5 is a diagram showing an arrangement relationship between a magnetized body of FIG. 4 and a magnetic sensing element; FIG. FIG. 7 is a diagram showing a configuration example of a conventional magnetism detection device.
10 Print media (medium)
16 Magnetic Detecting Elements 16A, 16B Magnetic Detecting Unit 22 Magnetic Shielding Member 24 Nonmagnetic Substrate 30 Terminal 32 Holder 101 Entry Sensor 102 Insertion Slot 103 Magnetic Sensor 106 Medium Entry Detection Means 107 Magnetizing Coil / Bias Coil Driving Means 108 Magnetic Detection Circuit 112 , 112a, 112b Magnetizing coil 118 Soft magnet 120 Magnetizing magnet 126 Bias coil 127 Soft magnet 128 Magnet for bias 140 Magnetizing coil terminal 141 Bias coil terminal Y Transport direction, relative movement direction Hx, -Hx Magnetizing magnetic field Hb Bias magnetic field H1, H2 Magnetic field generated by remanence of medium (external magnetic field, residual magnetic field)

Claims (5)

Magnetizing means for applying a magnetizing magnetic field to the medium at a front stage on a transport path for transporting a sheet-like or sheet-like medium holding a magnetic material, remnant magnetism of the magnetic material on the medium by applying the magnetizing magnetic field Magnetic detection means for detecting the magnetic field generated by the subsequent stage on the transport path, the magnetic detection device for identifying the medium,
The magnetizing means includes means for detecting the arrival of the medium, and a magnetizing electromagnet which is energized based on the arrival detection and generates the magnetizing magnetic field in a direction orthogonal to the transport direction of the medium. A magnetic detection device. The magnetic detection device according to claim 1,
A magnetic detecting apparatus, wherein the magnetic detecting means includes a thin-film magnetic impedance element formed on a substrate made of a non-magnetic material, and a bias magnetic field generating means for applying a bias magnetic field to the thin-film magnetic impedance element. The magnetic detection device according to claim 2,
A magnetic detection device, wherein the bias magnetic field generating means includes a bias electromagnet having a magnetic core for generating the bias magnetic field, and a bias excitation coil for exciting the magnetic core when energized. The magnetic detection device according to claim 3,
The magnetic detecting device according to claim 1, wherein the biasing electromagnet is energized based on detection of a unit that detects the arrival of the medium. The magnetic detection device according to claim 3, wherein
At least a magnetizing electromagnet constituting the magnetizing means, and a thin-film magnetic impedance element and a biasing electromagnet constituting the magnetic detecting means are integrated in the same housing. .

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