JP2000056001A - Detecting method for nonmagnetic metal material by magnetoresistive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the features such as size, conductivity and scar of a nonmagnetic metal material with a simple circuit structure having good stability, reproducibility and S/N ratio. SOLUTION: When magnetizing means 3, 3' and a nonmagnetic metal material are relatively moved, an eddy current is generated on the nonmagnetic metal material. A slight magnetic field change by this eddy current is detected by means of magnetoresistive elements MR1, MR2, MR1', MR2'. The magnetoresistive elements MR1, MR2, MR1', MR2' are operated by a DC constant-voltage drive source, and the magnetizing means 3, 3' generate the DC magnetic field from permanent magnets or coils. The magnetic field generated by the eddy current has an inclination in the traveling direction of a detected object. The magnetoresistive elements MR1, MR2, MR1', MR2' and the magnetizing means 3, 3' are arranged on the surface and back face of the passage of the nonmagnetic metal material. The obtained signal is amplified and is signal- processed by a logical circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling the change of a magnetic field caused by an eddy current in the shape, thickness, weight,
The present invention relates to a method for detecting a property of a non-magnetic material by using a magnetoresistive element and a magnetizing means disposed near the resistive element, and paying attention to changes due to properties such as scratches, irregularities, conductivity, and resistance value.

[0002]

2. Description of the Related Art Conventionally, when detecting the size, unevenness, and the like of a non-magnetic metal material, a change in inductance of the pot-core inductor when the non-magnetic metal material approaches is detected using a pot-core inductor. Or by passing a non-magnetic metal material between the exciting coil and the receiving coil to detect using an electromagnetic shielding effect, or winding a coil around a ferrite core to change impedance in a high frequency range. It is detected by the so-called MI effect. That is,
What is also called a search coil or a flux gate is also a weak point of this kind of detecting means. However, since this type of magnetic sensor mainly includes a winding, it detects a disturbance magnetic field from any of the opening surface of the coil and any of the three axes, and thus has a problem in reproducibility and stability. Also, as already known, a magnetic sensor using a magnetoresistive element detects a magnetic material contained in ink such as banknotes, or detects a magnetic material as represented by a magnetic material gear. It has been disclosed and put into practical use as a means.

In addition, there is disclosed a magnetoresistive element in which a permanent magnet is disposed on the back surface of the magnetoresistive element or on an opposing surface in which an object to be detected is narrow because a low magnetic field sensitivity is low to apply a magnetic bias. . Furthermore, in order to improve the detection resolution,
There is also a sensor for detecting a magnetic material in which a magnet for magnetic bias is mounted on the back surface of the magnetoresistive element, and the magnetoresistive element and the magnetic yoke are arranged on the opposing surface which is narrowed via the object to be detected.

[0004]

However, in a method of detecting a non-magnetic metal material using a pot core, for example, in a well-known coin sorter, it is necessary to reduce the size of the pot core inductor when detecting minute irregularities. However, it is difficult to reduce the size of the device due to its constituent requirements, so that it is difficult to detect minute irregularities. When a coil is wound around a ferrite core and an attempt is made to detect the impedance by a change in impedance in a high-frequency region, the detection is not limited to an object to be originally detected due to the influence of leakage magnetic flux. Because the impedance changes, stability, reproducibility,
There was a problem in S / N. In addition, most of the above-described components have a problem that the driving circuit and the signal processing circuit are complicated due to the high frequency AC operation.

[0005]

When the magnetic field and the non-magnetic metal material move relatively, an eddy current is generated in the non-magnetic metal material. This minute magnetic field change is detected using a magnetoresistive element. The magnetoresistive element was operated by a DC constant voltage drive source, and the magnetic field generating means was a DC magnetic field from a permanent magnet, a coil, or the like.

Since the magnetic field generated by the eddy current has a gradient in the running direction of the object, the gradient of the magnetic field is reduced by at least two or more magnetoresistive elements and magnetizing means. It was arranged on the front and back surfaces of a magnetic metal material.

In some cases, the magnetic bias generating means of the magnetoresistive element responsive to the magnetic field change and the magnetic generating means for generating the eddy current are integrally formed.

Since the semiconductor magnetoresistive element has a large temperature coefficient, and the magnetic thin film element is vulnerable to a disturbance magnetic field change, two magnetoresistive elements are paired and arranged close to each other to form a voltage dividing circuit.

Further, a large number of magnetoresistive elements are arranged in a plane to form a bridge circuit, or a signal obtained from the element is taken out alone, and a planar overcurrent state obtained from the element is analyzed by a computer. In some cases, processing is performed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[0011]

FIG. 1 is a principle diagram for explaining the mechanism of eddy current generation. In the figure, 1 is a non-magnetic metal material already described, and the non-magnetic metal material is
Although they differ in electrical resistance and conductivity, they are generally electrical conductors. Now, the non-magnetic conductor 1 is driven by a roller 2 mechanically connected to a power source (not shown), moves in the direction of the arrow, and emits near the non-magnetic conductor 1 and the object to be detected. When the magnetic bodies 3 are arranged close to each other,
It is well known that eddy currents occur in this conductor. By the way, the eddy current generated in this way forms a short circuit in the same conductor, so that the eddy current also generates a magnetic field. In other words, it can be inferred that the magnetic field generated by the eddy current can be detected by installing the detection means 4 in the vicinity of or adjacent to the magnet. Furthermore, even if the strength of the magnetic field is constant, even if the moving speed of the nonmagnetic conductor 1 and the strength of the applied magnetic field are constant, the strength and the resistance of the nonmagnetic conductor and the object to be detected change. It is known as the magnetic damping effect often used in mechanical vibration phenomena, but there are few cases where it is quantitatively measured with high accuracy. As described above, in order to specify the material of the non-magnetic material by the magnetic sensor, first, the detected object is electrically conductive, a magnetic field is applied, and further, whether the detected object or the magnetizing means is used. Either requires three requirements of relative movement.

FIG. 2 shows an example of a basic configuration of a magnetic sensor for detecting a magnetic material in a banknote using a semiconductor magnetic sensor, which has been frequently used. In the figure, the housing of the magnetic sensor is indicated by a dashed line, and a magnet 22 is mounted in the housing on the back of the magnetoresistive elements MR1 and MR2 to apply a magnetic bias. Further, the respective magneto-resistive elements MR1 and MR2 are connected in series as shown in the drawing, and a so-called voltage dividing circuit is formed. Further, a DC power supply 24 is connected to the voltage dividing circuit. Now, as described above, when the magnetic body 23 moves in the direction of the arrow by connecting the magnetoresistive element and approaches the magnetoresistive element MR1, the magnetic flux of the magnetic bias magnet concentrates on the resistive element of MR1 and the magnetic bias magnetic field deviates from the magnetic bias magnetic field. And the resistance value of the magnetoresistive element MR1 increases. When the magnetic body moves further and approaches the magnetoresistive element MR2, the magnetic field applied to the element MR1 decreases,
At the same time, the magnetic field returns to a value close to the magnetic bias resistance, and the magnetic field of the magnetoresistive element MR2 increases, so that its resistance also increases. In this way, the change in the resistance value of the magnetoresistive element becomes a voltage change by the voltage dividing circuit, and is connected to the amplifier circuit 25 via the midpoint of the voltage dividing circuit and amplified.
The output voltage is sent to 6.

Further, in the magnetic sensor circuit shown in FIG. 2, in addition to the bias magnetic field from the magnetic bias magnet,
When a uniform magnetic field is simultaneously and uniformly applied to the elements MR1 and MR2 from the outside or the magnetic field is simultaneously changed, for example, if the longitudinal direction of the magnetoresistive element is arranged in a direction parallel to the running direction Then, even if the magnetic material approaches, the resistance values of both elements only increase relatively, and the output voltage of the voltage dividing circuit does not change. That is, an output signal cannot be obtained.

FIGS. 3, (a) and (b) show the relationship between the virtual eddy current and the magnetic field when a magnetic field is applied to the object and the object moves at a constant speed. It is a schematic diagram. (A) schematically shows the state of the eddy current of the nonmagnetic metal and the object to be detected, and (B) schematically shows the state of the eddy current near the magnetizing means and the state of the magnetic field generated by this eddy current. FIG. In FIG. 1A, a magnet 3 is arranged near the nonmagnetic metal conductor 1 with a gap,
If either the detection target 1 or the magnetizing means 3 moves in the direction shown by the solid arrow while maintaining the constant speed state, the conductor 1
Generates an eddy current i. The trajectory state of the eddy current is indicated by i in FIG. When the eddy current is examined in detail, as shown in the detailed view around the magnet in FIG. 2 (b), the eddy currents i1, i2, i3 at the center of the magnet flow in opposite directions to each other and are canceled. As a result, the flow of the eddy current strongly flows near the side in the running direction of the magnet, as indicated by the thick arrow in FIG. The magnetic field generated by this eddy current follows the right-handed screw rule so that the tip of the magnet repels the magnetic field of the magnetizing means in the opposite direction as shown by H '' In the part, the suction is performed in the same direction indicated by H '. That is, a strong magnetic field is generated near the edge of the magnet, and opposite magnetic fields are generated at the trailing edge and the leading edge as indicated by H ′ and H ″.

FIG. 4 shows only one quadrant of the magnetic field characteristics of the magnetoresistive element. The horizontal axis represents the magnetic field, and the vertical axis represents the resistance.
As described above, since the magnetic field sensitivity of the magnetoresistive element at a low magnetic field is low and the sensitivity at a high magnetic field is good, a magnetic bias Bb is applied to the magnetoresistive element.
The detection operation is performed by a magnetic field change centered on the resistance value Rb corresponding to this magnetic field. Therefore, in a magnetic field change caused by a magnetic material, a phenomenon in which the resistance value of the resistance element increases due to concentration of the magnetic field by the magnetic material approaching the magnetoresistive element is used. It changes only in the direction of Rb1. Further, the two elements constituting the voltage dividing circuit are juxtaposed with the object to be detected such that the longitudinal direction of the element is perpendicular to the traveling direction. From the relationship shown in FIG. 3, a magnetic field due to an eddy current is applied to the magnetic bias or is reduced on the contrary.
That is, the magnetic field resistance changes from Rb to Rb1 or Rb2. Based on such a hypothesis, if the magnetizing means is a square magnet, the magnetic field detection by eddy current is
Regardless of the orientation of the magnetoresistive element, it is also possible to arrange it at any one of the four edges. However, the magnetic field H ′ generated by the eddy current accompanying the movement in the plane direction and its opposite polarity,
The interval of H '' is expected to be narrower in the moving direction and wider in the perpendicular direction, and the optimal arrangement position of the element in the moving direction can be inferred to be from the edge of the magnet to the inside of the magnet. At the edge perpendicular to the direction, it is expected that the optimum value will be at a distance from the edge of the magnet. Therefore, in the method for detecting a non-magnetic metal material according to the present invention, it is required to determine the optimum arrangement position of the element based on the transfer speed of the detection object and the shape of the magnetic field generating means. However, unlike the magnetic material detection sensor, the shape of the magnetoresistive element is not limited to a square, and may be a circular element such as a regular square or a corbino element if the resolution and applied voltage allow. The resolution of this overcurrent detection method is
It also depends on the shape and area of the magnetizing means and the element.
Further, if the traveling direction is the same direction, in the detection by eddy current using only one magnetoresistive element, the resistance curve of Rb in the characteristic curve of FIG. It is determined whether the value changes to Rb1 or Rb2. In other words, if the required magnetic bias value is sufficiently obtained, the magnetoresistive element does not necessarily need to be arranged on the magnetic bias magnet, and is arranged near the magnet, and is located in a place where the magnetic field change due to the eddy current is most susceptible. It is preferable to arrange them.
As described in detail above, the method of detecting a non-magnetic metal material by the magneto-resistive element according to the present invention, which is currently frequently used, even though it looks like the same shape as the banknote identification magnetic sensor,
Its functional action is completely different.

[0016]

Embodiment 1 FIG. 5 shows a first embodiment of the present invention. Means of transportation, which is one element in the present invention,
The object to be detected is transported by the conveyor system described above, mounted on a rotating body, and a magnetizing means and a magnetoresistive element are arranged at the tip of a non-magnetic moving rod to reciprocate the surface of the object to be detected. There is a method of scanning the surface of the object to be detected, for example, but the figure shows an example particularly selected from the scanning methods. In the figure, the guide groove 52 of the detection target 1 is formed in the non-magnetic frame 51, and the two magnetoresistive elements MR1 and MR2 and the magnetizing means 3 have been described in detail at arbitrary positions of the guide groove 52. Arranged according to the content. The detection target 1 is moved in the direction of the arrow shown by the solid line by sliding down the guide groove and falling naturally, and contacts or slightly contacts the magnetizing means 3 and the magnetoresistive elements MR1 and MR2 arranged near the magnetizing means. By passing through the gap, a change in the magnetic field generated in the detection target 1 is detected. The properties of the non-magnetic metal material are determined by the output voltage obtained by amplifying the potential output by the magnetoresistive elements MR1 and MR2 and the pulse width thereof, as described later in detail. The frame 1 is installed in parallel with the direction of gravity, or installed with an inclination as shown.

An example of the result of detecting a non-magnetic metal material as the first embodiment will be described below. In the first embodiment, FIG.
As shown therein, two magneto-resistive elements MR1 and MR2 are connected in series, and a constant voltage of 5 V is applied to both ends thereof. The output voltage output from the connection point of the magnetoresistive element is set to a gain of 8
It is led to a 0 dB AC amplifier circuit and amplified. A permanent magnet as a magnetizing means is arranged on the back of the pair of magnetoresistive elements. Note that the pair of magnetoresistive elements and the permanent magnet were fixed.
As shown in FIG. 5, the non-magnetic metal material is moved along the guide groove 52 while sliding down along the guide groove 52 along the surface of the magnetoresistive element configured as described above. FIG. 6 shows the output voltage of the magnetoresistive element when three types of non-magnetic metal materials, namely, copper, aluminum, and brass having a thickness of 3 mm were moved. The horizontal axis in FIG. 6 is time, and the vertical magnetic axis is output voltage. It can be seen that the peak value of the output voltage becomes a unique value depending on the material in such a structure. In the present invention, this peak
The material values were determined by comparing the peak values using a well-known circuit process.

FIG. 7 shows data of a sample assuming a flaw of the object 1 to be detected. 3mm thick aluminum is used as the non-magnetic metal material, and the steps are 0.1mm and 0.3m
FIG. 7 shows the output voltage when each of them was moved to m, 0.5 mm, and 1.0 mm. The horizontal axis in FIG. 7 is time, and the vertical axis is
Output voltage. According to the knowledge obtained from this result, a difference occurs in the output voltage at the concave portion of the output waveform due to the difference in the depth of the step. By comparing the difference between the output voltages, the depth of the step can be detected. Here, aluminum was used as the object to be detected, and the level difference was detected.
Although not shown, the same result as described above was obtained for other non-magnetic metal materials, although the output voltage value was different.

FIG. 8 shows detection data of the hole diameter of one detected object. The perforated nonmagnetic metal material is moved by the apparatus shown in FIG. FIG. 8 shows the output voltage obtained when using brass having a thickness of 3 mm as the object to be detected and setting the hole diameters to φ2 mm, φ3 mm, φ4 mm, and φ5 mm, and moving each of them. 8, the horizontal axis represents time, and the vertical axis represents output voltage. As can be seen from this data, there is a difference in time at a portion corresponding to the hole diameter of the output waveform. The hole diameter was detected by comparing the difference between the times. A hole was detected in the center of the brass plate where the object was detected. The hole could be detected at any position in the plate, and other non-magnetic metal materials could be detected.

FIG. 9 shows an example of detecting a dimensional difference. The object to be detected is moved by the method shown in FIG. FIG. 9 shows the output voltage when each of the objects to be detected was made of brass, the dimensions in the movement direction were 15 mm, 20 mm, and 25 mm, and each was moved.
In FIG. 9, the horizontal axis represents time, and the vertical axis represents output voltage. This data
It can be seen that there is a difference in the time of the pulse width output from the data. By comparing the time difference, the size of the non-magnetic metal material in the moving direction was detected. This tendency is the same for other non-magnetic metal materials, although the output level is different.

Here, an example of detecting the thickness of the object to be detected will be described. The object to be detected is aluminum and the thickness is 2 mm, 3
mm, 4 mm, and 5 mm, and the output voltage when each was moved is shown in FIG. The horizontal axis in FIG. 10 is time, and the vertical axis is output voltage. By comparing the peak value of the output voltage with such a structure, the thickness of the non-magnetic metal material can be detected, but the output voltage value due to the material difference and the thickness difference may overlap. In such a case, the accuracy is further improved by combining with an auxiliary means such as a photosensor and checking the thickness in advance.

[0022]

[Embodiment 2] In the transfer method of the natural fall, the speed of the object 1 to be detected is braked or raised. This is due to the magnetic field due to the eddy current generated in the non-magnetic object to be detected, but the state differs depending on the weight and shape of the object and the shape of the magnetizing means. However, as already described in detail, the size of the magnetizing means used for eddy current detection must be small when the resolution is to be increased, and may be large in some cases. As described above, when the magnetizing means has various shapes, the detected object has various braking states and floating states. In the second embodiment, an auxiliary magnet for adjusting such a condition change is added. In the following, in FIG. 12, those having the same functions as those in FIG. 5 are given the same numbers, and new ones are given new numbers. In FIG. 12, a guide groove 52 of the detection target 1 is formed in the non-magnetic frame 51, and two magneto-resistive elements MR1 and MR2 and the magnetizing means 3 are arranged at arbitrary positions of the guide groove 52. However, in the second embodiment, an auxiliary magnet 31 is added to the magnetizing means 3. First, the detected object 1
Is inserted into a slot (not shown), the detected object 1 is transported in the direction of the solid line arrow by natural fall while sliding down the guide groove 52. However, when the frame body 51 is installed in a nearly vertical state, it is naturally possible to allow a margin for the dimensions of the guide groove and the object to be detected, or to throw the object 1 having a different size from the opening area of the groove. Therefore, the detection target 1 exhibits various sliding states such as not contacting the sliding bottom surface 12. Further, this state is doubled when the object to be detected approaches the magnetizing means 3, and a large variation occurs in the detection characteristics. In the second embodiment, at least one or more auxiliary magnets 32 are arranged between the magnetizing means 3 and the slot so as to allow the detection target 1 of various shapes to pass between the sliding surface 12 and the magnets. . In the second embodiment configured as described above, the input detection target slides down the guide groove while rattling. However, when approaching the auxiliary magnet 32, an eddy current is generated in the object to be detected and slides down while correcting the trajectory in the direction pressed against the slide-down surface 12. And when approaching the magnetizing means 3,
The magnetoresistive elements MR1 and MR2 arranged near the magnetizing means 3 while slightly rising from the orbit corrected by the auxiliary magnet while being corrected in accordance with the weight, electric resistance and conductivity of the detected object. In this case, a change in the magnetic field generated in the detection target 1 is detected while contacting or passing with a small gap to such an extent that no piezo noise is generated. The properties of the non-magnetic metal material are determined based on the output voltage and the pulse width after the potential corresponding to the change in the resistance value of the magnetoresistive elements MR1 and MR2 is amplified by the amplifier circuit as described in detail. As described in detail above, the present invention provides a method for detecting a non-magnetic metal material in which the property of the non-magnetic metal material can be determined based on a small magnetic field difference of an eddy current generated in the non-magnetic metal body.

[0023]

Third Embodiment FIG. 13 is a side sectional view of a third embodiment shown in FIG. In the third embodiment, an attempt is made to identify which surface has a scratch on the back or front surface. In FIG. 13, components having the same functions as those in FIG. 5 are assigned the same numbers, and new components are assigned new numbers. 13, a guide groove 52 of the detection target 1 is formed in the non-magnetic frame 51 in FIG.
A pair of magnetoresistive elements MR1 and MR2 and a pair of magnetoresistive elements MR are provided on the detection surface of the guide groove 52 at an arbitrary position.
1 'and MR2' are arranged independently on the surfaces of the magnetizing means 3 and 3 'so that the object 1 passes through the gaps between the respective magnetoresistive elements. Further, in the third embodiment, auxiliary magnets 32, 33 are added to the magnetizing means 3, 3 '.

First, when the detection target 1 is inserted into an input port (not shown), the detection target 1 is naturally dropped while sliding down the guide groove 52, and is transferred in the direction of the solid arrow.
The detection target 1 first reaches the auxiliary magnets 32 and 33, but when the surface magnetization of the magnets is configured to have the same polarity, the detection target 1 passes through a substantially central portion of the passage. Then, while maintaining that state, the magnetic resistance elements MR1 and MR2 mounted on the surfaces of the magnetizing means 3 and 3 'as shown in FIG.
1 ′ and MR2 ′, and if the 3 and 3 ′ magnetizing means are magnetized to the same polarity and are constituted by magnets of the same strength, the detection target 1 will be almost in the path. Pass through the center. If the auxiliary magnets and the magnetizing means shown in the figure are further composed of different poles, the detection target 1 is located near a detection unit by the magnetoresistive element MR1 or MR2, or
It passes close to the magnetoresistive elements MR1 'and MR2'. The magnetic poles of the assisted magnet and the magnetizing means may be provided such that the N pole is formed on the surface or the S pole is formed. The polarity is appropriately selected according to the surface condition of the detection target. In the third embodiment configured as described above, a change in resistance value is given to each magnetoresistive element in accordance with the content already described, as the detected object 1 passes through. The pair of magnetoresistive elements MR1, MR2 and MR1 ', MR2' independently constitute a voltage dividing circuit, and a potential corresponding to a change in the resistance value of the magnetoresistive element is extracted. Further, signals obtained by the respective magnetic field changes are guided to a signal processing circuit (not shown), and the shape and surface state are determined by determining the difference between the signals.

[0025]

According to the present invention, the non-magnetic metal material, shape,
Irregularities, plate thickness, etc. could be detected with high accuracy. In addition, the driving power supply for the magnetoresistive element can be simply configured, and not only does not require a complicated signal processing circuit, but also the means for transferring the detected object can be easily configured. In addition to being able to easily detect the material and shape of such coins and coins, miniaturization of coin sorters and the like has become possible. Furthermore, since the shape, unevenness, plate thickness, etc. of the non-magnetic material can be accurately detected, the method of detecting a non-magnetic metal material has an effect of detecting counterfeit coins.

[Brief description of the drawings]

FIG. 1 principle diagram

FIG. 2 is a basic configuration diagram of a magnetic sensor.

FIG. 3 (a) Schematic diagram of an eddy current of an object to be detected (b) Enlarged schematic diagram of an eddy current and a magnetic field

FIG. 4 shows a magnetic field characteristic and a magnetic bias value of a magnetoresistive element.

FIG. 5 is a bird's-eye view of the first embodiment.

FIG. 6 shows detection results of metal types according to the first embodiment.

FIG. 7 is a result of detecting a metal step according to the first embodiment.

FIG. 8 is a result of detecting a metal hole according to the first embodiment.

FIG. 9 shows a result of detecting a dimensional difference according to the first embodiment.

FIG. 10 shows a detection result of a thickness difference in the first embodiment.

FIG. 12 is a configuration diagram of a second embodiment.

FIG. 13 is a side cutaway view of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detected object 2 Drive roller 3, 3 'Magnetizing means 12 Slipping surface 21 Magnetic sensor 22 Magnet 23 Magnetic body 24 Power supply 25 Amplification circuit 26 Output terminal 32, 33 Auxiliary magnet 51 Frame 52 Guide groove B Magnetic field B1, B2 Micro magnetic field change point Bb Magnetic bias value i Locus of eddy current I, I 'Effective eddy current i1, i2, i3 Virtual eddy current H Magnetic field H', H '' Effective magnetic field due to eddy current MR1, MR2, MR1 ', MR2 'Magnetoresistance element R Resistance value Rb Magnetic resistance value at magnetic bias point Rb1 Resistance value due to small magnetic field change Rb2 Resistance value due to small magnetic field change N, S Magnetic pole φ Symbol of hole diameter

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[Procedure amendment]

[Submission date] December 10, 1998 (1998.12.
10)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Method for detecting non-magnetic metal material by using a magnetoresistive element

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling the change of a magnetic field caused by an eddy current in the shape, thickness, weight,
Focusing on changes due to properties such as scratches, irregularities, conductivity, and resistance, the change in the magnetic field is measured using a semiconductor magnetoresistive element or thin film.
Film magnetoresistive element and magnetizing means installed near it
Metal material whose properties are clarified by merging action
Method for the detection of charge.

[0002]

2. Description of the Related Art Conventionally, when detecting the size, unevenness, and the like of a non-magnetic metal material, a change in inductance of the pot-core inductor when the non-magnetic metal material approaches is detected using a pot-core inductor. Or by passing a non-magnetic metal material between the exciting coil and the receiving coil to detect using an electromagnetic shielding effect, or winding the coil around a ferrite core to change the impedance in a high frequency range, so-called It is detected by the MI effect. That is,
What is called etc. alias search coil and flux gay capital is also a brittle range of this type of detection means. However,
Since this type of magnetic sensor mainly includes windings, it detects a disturbance magnetic field from any of the opening surface of the coil and any of the three axes, and thus has a problem in reproducibility and stability. On the other hand,
As is well known in the art, a magnetic sensor using a magneto-resistive element detects a magnetic material contained in ink such as banknotes, and as represented by a magnetic material gear, as represented by a magnetic material gear, etc. It has been disclosed and put into practical use.

In addition, there is disclosed a magnetoresistive element in which a permanent magnet is disposed on the back surface of the magnetoresistive element or on an opposing surface in which an object to be detected is narrow because a low magnetic field sensitivity is low to apply a magnetic bias. . Furthermore, in order to improve the detection resolution,
There is also a magnetic body detection sensor in which a magnet for magnetic bias is mounted on the back surface of a magnetoresistive element, and a magnetoresistive element and a magnetic yoke are arranged on opposing surfaces that are narrowly interposed via a detection target.

[0004]

However, in a method of detecting a non-magnetic metal material using a pot core, for example, in a well-known coin sorter, it is necessary to reduce the size of the pot core inductor when detecting minute irregularities. However, it is difficult to reduce the size of the device due to its constituent requirements, so that it is difficult to detect minute irregularities. In addition, when a coil is wound around a ferrite core and an attempt is made to detect the impedance by a change in impedance in a high frequency region, the impedance is affected not only by an object to be originally detected due to the influence of leakage magnetic flux, but also by a material disposed around the object. Changes, so that stability, reproducibility,
There was a problem in S / N. And many of the foregoing for the AC operation at high frequencies, and a driving circuit, the signal processing circuit there is also complicated to become issues. In addition, different types
Many sensors with different shapes are arranged to distinguish coins
I had to do it.

[0005]

When the magnetic field and the non-magnetic metal material move relatively, an eddy current is generated in the non-magnetic metal material. This minute magnetic field change is detected using a magnetoresistive element. The magnetic resistance element was operated by a DC constant voltage drive source, and the magnetic field generating means was a DC magnetic field from a permanent magnet, a coil, or the like.

Since the magnetic field generated by the eddy current has a gradient in the running direction of the object, the gradient of the magnetic field is reduced by at least two or more magnetoresistive elements and magnetizing means. It was arranged on the front and back surfaces of a magnetic metal material.

In some cases, the magnetic bias generating means of the magnetoresistive element responsive to the magnetic field change and the magnetic generating means for generating the eddy current are integrally formed.

Since the semiconductor magnetoresistive element has a large temperature coefficient, and the magnetic thin film element is vulnerable to a disturbance magnetic field change, two magnetoresistive elements are paired and arranged close to each other to form a voltage dividing circuit.

Further, a large number of magnetoresistive elements are arranged in a plane to form a bridge circuit, or a signal obtained from the element is taken out independently, and a plane overcurrent state obtained from the element is analyzed by a computer. Sometimes.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[0011]

FIG. 1 is a principle diagram for explaining the mechanism of eddy current generation. In FIG. 1 , reference numeral 1 denotes a non-magnetic metal material which has already been described. The non-magnetic metal material is generally an electric conductor although there is a difference in electric resistance and electric conductivity. The non-magnetic conductor 1 is now driven by a roller 2 mechanically connected to a power source (not shown), moves in the direction of the arrow, and
It is well known that an eddy current is generated in this conductor when the magnetizing body 3 is arranged close to the object to be detected. By the way, the eddy current generated in this way forms a short circuit in the same conductor, so that the eddy current also generates a magnetic field. In other words, it can be inferred that the magnetic field generated by the eddy current can be detected by installing the detection means 4 in the vicinity of or adjacent to the magnet. Furthermore, even if the strength of the magnetic field is constant, even if the moving speed of the nonmagnetic conductor 1 and the strength of the applied magnetic field are constant, the strength and the resistance of the nonmagnetic conductor and the object to be detected change. It is known as the magnetic damping effect often used in mechanical vibration phenomena, but there are few cases where it is quantitatively measured with high accuracy.
As described above, in order to specify the material of the non-magnetic material by the magnetic sensor, first, the detected object is electrically conductive, a magnetic field is applied, and further, whether the detected object or the magnetizing means is used. Either requires three requirements of relative movement.

FIG. 2 shows an example of a basic configuration of a magnetic sensor for detecting a magnetic material in a banknote using a semiconductor magnetic sensor, which has been frequently used. In FIG. 2 , the housing of the magnetic sensor is indicated by a dashed line, and a magnet 22 includes magnetoresistive elements MR1 and MR2 in the housing.
And a magnetic bias is applied. The respective magneto-resistive elements MR1 and MR2 are connected in series as shown in the figure to form a so-called voltage dividing circuit. Further, a DC power supply 24 is connected to the voltage dividing circuit. Now, if the magnetic body 23 moves in the direction of the arrow by connecting the magnetoresistive element as described above and approaches the magnetoresistive element MR1,
The magnetic flux of the magnetic bias magnet concentrates on the resistance element of MR1 and becomes higher than the magnetic bias magnetic field.
The resistance value of R1 increases. This magnetic material moves further,
When approaching the magnetoresistive element MR2, the magnetic field applied to the element MR1 decreases and returns to a value close to the magnetic bias resistance value, and the magnetic field of the magnetoresistive element MR2 increases, so that its resistance value also increases. In this way, the change in the resistance value of the magnetoresistive element becomes a voltage change by the voltage dividing circuit, and is connected to the amplifying circuit 25 via the midpoint of the voltage dividing circuit and amplified, and then the output voltage is sent to the output terminal 26. I do.

Further, in the magnetic sensor circuit shown in FIG.
Is the bias magnetic field from the magnetic bias magnetof
In addition, a uniform magnetic field is simultaneously applied to the elements MR1 and MR2 from outside.
Or evenlySimultaneous magnetic field changesGiven to
When, for example, the longitudinal direction of the magnetoresistive element is the running direction
AgainstRight angleIf placed in the direction of
As the body approaches, the resistance of both elements will increase relatively
Therefore, the output voltage of the voltage dividing circuit does not change. That is, output
No signal can be obtained.

FIGS. 3, (a) and (b) show the relationship between the virtual eddy current and the magnetic field when a magnetic field is applied to the object and the object moves at a constant speed. It is a schematic diagram. (A) schematically shows the state of the eddy current of the nonmagnetic metal and the object to be detected, and (B) schematically shows the state of the eddy current near the magnetizing means and the state of the magnetic field generated by this eddy current. FIG. In FIG. 1A, a magnet 3 is arranged near the nonmagnetic metal conductor 1 with a gap,
If either the detection target 1 or the magnetizing means 3 moves in the direction shown by the solid arrow while maintaining the constant speed state, the conductor 1
Generates an eddy current i. The trajectory state of the eddy current is indicated by i in FIG. When this eddy current is examined in detail, as shown in a detailed view around the magnet in FIG. 2B, eddy currents i1, i2, i3 at the center of the magnet are shown.
Flows in opposite directions to cancel each other. As a result, the flow of the eddy current strongly flows near the side in the running direction of the magnet as indicated by I ′ and I ″ in FIG. The magnetic field generated by this eddy current follows the right-handed screw rule so that the tip of the magnet repels the magnetic field of the magnetizing means in the opposite direction as shown by H '' In the part, the suction is performed in the same direction indicated by H '. That is, a strong magnetic field is generated near the edge of the magnet, and opposite magnetic fields are generated at the trailing edge and the leading edge as indicated by H ′ and H ″.

FIG. 4 shows only one quadrant of the magnetic field characteristics of the magnetoresistive element. The horizontal axis represents the magnetic field, and the vertical axis represents the resistance.
As described above, since the magnetic field sensitivity of the magnetoresistive element at a low magnetic field is low and the sensitivity at a high magnetic field is good, a magnetic bias Bb is applied to the magnetoresistive element.
The detection operation is performed by a magnetic field change centered on the resistance value Rb corresponding to this magnetic field. Therefore, in a magnetic field change caused by a magnetic material, a phenomenon in which the resistance value of the resistance element increases due to concentration of the magnetic field by the magnetic material approaching the magnetoresistive element is used. It changes only in the direction of Rb1. Further, the two elements constituting the voltage dividing circuit are juxtaposed with the object to be detected so that the longitudinal direction of the element is parallel to the traveling direction. From the relationship shown in FIG. 3, a magnetic field due to an eddy current is applied to the magnetic bias or is reduced on the contrary.
That is, the magnetic field resistance changes from Rb to Rb1 or Rb2. Based on this hypothesis, if the magnetizing means is a square magnet, the magnetic field detection by the eddy current can be performed at any one of the four edges regardless of the direction of the magnetoresistive element. It is also possible. However, 'the vice versa <br/> polarity, H' the magnetic field H generated by the eddy currents with the movement in the plane direction spacing of the 'narrows in direction of movement, is expected to spread in a perpendicular direction, The optimal arrangement position of the element is
In the moving direction, it can be inferred that it is inside the magnet from the edge of the magnet, and it is expected that the edge in the direction perpendicular to the moving direction has an optimum value at a position away from the edge of the magnet. Therefore, in the method for detecting a non-magnetic metal material according to the present invention, it is required to determine the optimum arrangement position of the element based on the transfer speed of the detection object and the shape of the magnetic field generating means. However, unlike the magnetic body detection sensor, the shape of the magnetoresistive element without even that will be limited to rectangular and may be a circular element such as a positive square or Corbino element permitting resolution and applied voltage. The resolution of the eddy current detection method also depends on the shape and area of the magnetizing means and the element. Further, the traveling direction are the same direction, in the detection by a magneto-resistive element only eddy currents using only 1 element, by where the element is placed in the end of the magnet, the Rb in the characteristic curve of FIG resistance It is determined whether the value changes to Rb1 or Rb2. In other words, if the required magnetic bias value can be obtained sufficiently, the magnetoresistive element does not necessarily need to be arranged on the magnetic bias magnet, but is arranged near the magnet, and is located in a place most susceptible to a magnetic field change due to eddy current. It is preferable to arrange them. As described above in detail, the method of detecting a non-magnetic metal material using a magnetoresistive element according to the present invention has a functional effect even if the shape looks like the banknote identification magnetic sensor that is currently frequently used. It is completely different.

[0016]

Embodiment 1 FIG. 5 shows a first embodiment of the present invention. Means of transportation, which is one element in the present invention,
The object to be detected is transported by the conveyor system described above, mounted on a rotating body, and a magnetizing means and a magnetoresistive element are arranged at the tip of a non-magnetic moving rod to reciprocate the surface of the object to be detected. There is a method of scanning the surface of the object to be detected, and FIG. 5 shows an example particularly selected from the scanning methods. In FIG. 5 , the non-magnetic frame 51 includes the object 1 to be detected.
And the two magneto-resistive elements MR1 and MR2 and the magnetizing means 3 are arranged at arbitrary positions in the guide groove 52 in accordance with the contents already described in detail. Detected object 1
Is transported in the direction of the arrow shown by the solid line by natural fall through the guide groove, and passes through the magnetizing means 3 and the magnetoresistive elements MR1 and MR2 arranged near the magnetizing means with a small gap. Thus, a change in the magnetic field generated in the detection target 1 is detected. The properties of the non-magnetic metal material are determined based on the output voltage obtained by amplifying the potential output from the magnetoresistive elements MR1 and MR2 and the pulse width thereof, as described later in detail. The frame 1 is installed in parallel with the direction of gravity, or installed with an inclination as shown.

An example of the result of detecting a non-magnetic metal material as the first embodiment will be described below. In the first embodiment, FIG.
As shown in the figure, two magnetoresistive elements MR1 and MR2 are connected in series, and a constant voltage of 5 V is applied to both ends. The output voltage output from the connection point of the magnetoresistive element is guided to an AC amplifier circuit having a gain of 80 dB and amplified. A permanent magnet as a magnetizing means is arranged on the back of the pair of magnetoresistive elements. Note that the pair of magnetoresistive elements and the permanent magnet were fixed. As shown in FIG. 5, the non-magnetic metal material is moved along the guide groove 52 while sliding down along the guide groove 52 along the surface of the magnetoresistive element configured as described above. 3mm thick copper, aluminum, non-magnetic metal material
FIG. 6 shows the output voltage of the magnetoresistive element when three types of brass were moved. The horizontal axis in FIG. 6 is time, and the vertical axis is output voltage. It can be seen that with such a structure, the peak value of the output voltage becomes a unique value depending on the material. Pin of this in the present invention
It was determined for the material by comparison with the circuit processing the over click value.

FIG. 7 shows data of a sample assuming a flaw of the object 1 to be detected. 3mm thick aluminum is used as the non-magnetic metal material, and the steps are 0.1mm and 0.3m
FIG. 7 shows the output voltage when each of them was moved to m, 0.5 mm, and 1.0 mm. The horizontal axis in FIG. 7 is time, and the vertical axis is
Output voltage. According to the knowledge obtained from this result, a difference occurs in the output voltage at the concave portion of the output waveform due to the difference in the depth of the step. By comparing the difference between the output voltages, the depth of the step can be detected. Here, aluminum was used as the object to be detected, and the level difference was detected.
Figure is omitted, but the characteristics of the material in other non-magnetic metal material
Therefore, as a matter of course, the same result as described above was obtained although the output voltage value was different.

FIG. 8 shows detection data of the hole diameter of one detected object. The perforated nonmagnetic metal material is moved by the apparatus shown in FIG. FIG. 8 shows the output voltage obtained when using brass having a thickness of 3 mm as the object to be detected and setting the hole diameters to φ2 mm, φ3 mm, φ4 mm, and φ5 mm, and moving each of them. The horizontal axis in FIG. 8 is time, and the vertical axis is output voltage. As can be seen from this data, there is a difference in time in a portion corresponding to the hole diameter of the output waveform. The hole diameter was detected by comparing the difference between the times. And a hole formed in a substantially central portion of the brass plate body to be detected has been detected the hole that position may also Re Izu in the plate, also could be detected in other non-magnetic metal material .

FIG. 9 shows an example of detecting a dimensional difference. The object to be detected is moved by the method shown in FIG. FIG. 9 shows the output voltage when each of the objects to be detected was made of brass, the dimensions in the movement direction were 15 mm, 20 mm, and 25 mm, and each was moved.
In FIG. 9, the horizontal axis represents time, and the vertical axis represents output voltage. It can be seen that there is a difference in the time of the pulse width output from this data. By comparing the time difference, the size of the non-magnetic metal material in the moving direction was detected. This tendency is the same for other non-magnetic metal materials, although the output level is different.

Here, an example of detecting the thickness of the object to be detected will be described. The object to be detected is aluminum and the thickness is 2 mm, 3
mm, 4 mm, and 5 mm, and the output voltage when each was moved is shown in FIG. The horizontal axis in FIG. 10 is time, and the vertical axis is output voltage. By comparing the peak value of the output voltage with such a structure, the thickness of the nonmagnetic metal material can be detected, but the output voltage value due to the material difference and the thickness difference may overlap. In such a case, the accuracy is further improved by combining with an auxiliary means such as a photosensor and checking the thickness in advance.

[0022]

[Embodiment 2] In the transfer method of the natural fall, the object to be detected 1ofSpeed
Every time the brakes are applied or lifts up. This
This is due to the magnetic field due to the eddy current generated in the non-magnetic object.
Depends on the weight and shape of the object and the shape of the magnetizing means.RSo
Are different. However, as already detailed
In addition, the size of the magnetizing means used for eddy current detection increases the resolution.
You have to make it smaller,
Can be large. In this way, the magnetizing means
If the shape of the object becomes various, it will cause
The glue will be various. In the second embodiment,
Auxiliary magnet has been added to adjust for various conditions changes
Things. FIG.1Then, those with the same functions as those in FIG.
Numbers are numbered, new ones are numbered new. Figure
1In Example 2 shown in FIG.The detection target 1 is placed on the non-magnetic frame 51.
Guide groove 52, and any position of the guide groove 52
Two magneto-resistive elements MR1 and MR2,
The magnetic means 3 is arranged. In the second embodiment, the magnetic
An auxiliary magnet 31 was added in addition to the step 3. First, examine
When the exit 1 is inserted into an input port (not shown),
The detector 1 is naturally dropped while sliding down the guide groove 52.
It is transferred in the direction of the solid arrow. However, the frame 51
The guide groove and the test
Allow extra slack in the dimensions of the body, and the opening area and dimensions of the groove.
Since the detected object 1 having a different
The detection body 1 may or may not contact the sliding bottom surface 12.
It exhibits various sliding conditions. In addition, this state
When the body approaches the magnetizing means 3, it is doubled, and the detection characteristics become large.
Large variations occur. In the second embodiment, the magnetizing means 3
At least one auxiliary magnet 3 between the inlet and the slot
2 is an object to be detected having various shapes between the slide surface 12 and the magnet.
1 are arranged at intervals so that they can pass through. Configuration like this
In the second embodiment, the object to be detected is
It slides down along the guide groove as it comes. However,
When approaching the auxiliary magnet 32, an eddy current is applied to the detection target.
OccursIn addition, this current generates a magnetic field in the non-detecting body.
However, due to the action of the magnetic field, the non-detecting body 1Press on slide surface 12
Gliding down while correcting the trajectory in the disciplined direction. Soshi
Then, when approaching the magnetizing means 3,
From the corrected orbit, the weight and electrical resistance of the
Slightly lifted while being corrected according to conductivity
Ascending, the magnetic material arranged near the magnetizing means 3
To the extent that piezo noise does not occur in the resistance elements MR1 and MR2
Contact with or pass through with a small gap,
A change in a magnetic field generated in the detection target 1 is detected. Non-magnetic metal
The properties of the material are determined by the
1, the potential corresponding to the change in the resistance value of MR2 is amplified by an amplifier circuit.
After amplification, make a judgment based on the output voltage and pulse width.
You. As described in detail above, the present invention is applied to a non-magnetic metal body.
The characteristics of the non-magnetic metal material can be determined by the small magnetic field difference of the eddy current
It provides a method for detecting non-magnetic metal material
You.

[0023]

Embodiment 3 FIG. 1 is a side sectional view of the third embodiment.2Shown in
In the third embodiment, the back surface or the front surface has scratches on any surface.
It is to try to identify. FIG.2Then same as Fig.5
Those with one function are numbered the same, new ones are new
Numbered. FIG.1Figure 1 as well2Non-magnetic inside
A guide groove 52 of the detection target 1 is formed in the frame 51,
A pair of magnetoresistive elements is provided on the detection surface at any position of the
MR1 and MR2 and a pair of magnetoresistive elements MR1 ',
MR2 'is independently arranged on the surface of the magnetizing means 3, 3',
eachPair ofMagnetoresistive elementMR1, MR2 and MR
1 ', MR2'So that the object 1 passes through the gap
Done. Further, in the third embodiment, the magnetizing means 3,
3 'and auxiliary magnets 32 and 33 added.
is there.

First, when the detection target 1 is inserted into an input port (not shown), the detection target 1 is naturally dropped while sliding down the guide groove 52, and is transferred in the direction of the solid arrow.
The detection target 1 first reaches the auxiliary magnets 32 and 33, but when the surface magnetization of the magnets is configured to have the same polarity, the detection target 1 passes through a substantially central portion of the passage. Then, while maintaining that state, the magnetoresistive elements MR1 and MR2 mounted on the surfaces of the magnetizing means 3 and 3 'as shown in FIG.
R1 ', MR2' Sashikakari in between, this time if,
If the magnetizing means 3 and 3 'are magnetized to the same polarity and are constituted by magnets having the same strength, the detection target 1 passes through substantially the center of the passage. If the illustrated auxiliary magnet and the magnetizing means are further composed of different poles, the detected object 1
Passes through a portion close to the detection unit by the magnetoresistive element MR1 or MR2, or close to the magnetoresistive elements MR1 ′ and MR2 ′. The method of applying the magnetic poles of the assisted magnet and the magnetizing means is to form an N pole or an S pole,
Split or, but the surface state of the polarity of the detection object
Appropriately selected correspondingly. In the third embodiment configured as described above, a change in the resistance value is given to each of the magneto-resistive elements MR1 and MR2 in accordance with the contents already described , as the detected object 1 passes. A pair of magnetoresistive elements MR
1, MR2 and MR1 ', MR2' independently constitute a voltage dividing circuit, and a potential corresponding to a change in the resistance value of the magnetoresistive element is taken out.

FIG . 13 is a block diagram of the signal processing means.
Shown as ram. In FIG. 13, reference numerals 31 and 31 'denote magnetoresistance.
The element and magnetic bias magnet are built into the housing,
The behavior and motion of non-magnetic metal are
For converting correspondingly generated magnetic fields into electrical signals
A detection unit, and an electric signal detected by the detection unit 31 and obtained by each magnetic field change is amplified.
Guided to circuits 35 and 35 'for easy digital signal processing
The signal level is amplified up to the signal level performed at And this message
The signal is guided to the comparison unit 36, where addition or subtraction is performed.
To extract signals from the fingerprint area on the front and back, and extract only singular points
Time difference, which is a judgment factor set in advance,
A signal that is determined to be positive based on the voltage value, waveform shape, etc.
If it is incorrect, the signal is sent to the return signal processing unit 39. This
The discriminating unit 37 further subdivides the signal form of the comparing unit 36
Then, determine the characteristics of the non-detecting body 1 and create the discrimination signal.
However, the control signal circuit 38, 38 ', 38''... to 38 ⁿ
It has the function of sending out signals. Circuit configured in this way
In the block, if the coin is true or false, it is not shown
A desired operation such as sending a signal or sending a type signal to the sorting device is performed.

[002 6 ]

According to the present invention, the non-magnetic metal material, shape,
Irregularities, plate thickness, etc. could be detected with high accuracy. In addition, the driving power supply for the magnetoresistive element can be simply configured, and not only does not require a complicated signal processing circuit, but also the means for transferring the detected object can be easily configured. The material and shape of coins and coins can be easily detected, and the size of coin sorters and the like can be reduced. Furthermore, the shape, unevenness, plate thickness, etc. of the non-magnetic material can be detected with high accuracy , or different types, such as 1
Only one detection means for discriminating between 0 yen coins and 500 yen coins
This is a method for detecting a non-magnetic metal material having an effect that can be constituted by the following.

[Brief description of the drawings]

FIG. 1 principle diagram

FIG. 2 is a basic configuration diagram of a magnetic sensor.

FIG. 3 (a) Schematic diagram of an eddy current of a detection object (b) Enlarged schematic diagram of an eddy current and a magnetic field

FIG. 4 shows a magnetic field characteristic and a magnetic bias value of a magnetoresistive element.

FIG. 5 is a bird's-eye view of the first embodiment.

FIG. 6 shows detection results of metal types according to the first embodiment.

FIG. 7 is a result of detecting a metal step according to the first embodiment.

FIG. 8 is a result of detecting a metal hole according to the first embodiment.

FIG. 9 shows a result of detecting a dimensional difference according to the first embodiment.

FIG. 10 shows a detection result of a thickness difference in the first embodiment.

FIG. 11 is a configuration diagram of a second embodiment.

FIG. 12 is a side cutaway view of the third embodiment.

FIG. 13 is a block diagram illustrating an example of signal processing.

[Description of Signs] 1 Detected object 2 Drive roller 3, 3 ′ Magnetizing means 12 Slip surface 21 Magnetic sensor 22 Magnet 23 Magnetic body 24 Power supply 25 , 35, 35 ′ Amplifying circuit 26 Output terminals 31, 31 ′ Detecting section 32 , 33 Auxiliary magnet 36 Comparing unit 37 Discriminating unit 38, 38'38 ''... 38 ⁿ Control signal circuit 51 Frame 52 Guide groove B Magnetic field B1, B2 Micro magnetic field change point Bb Magnetic bias value i Eddy current locus I ', I " Effective eddy current i1, i2, i3 Virtual eddy current H Magnetic field H ', H" Effective magnetic field due to eddy current MR1, MR2, MR1', MR2 'Magnetoresistance element R Resistance value Rb Magnetoresistance value at magnetic bias point Rb1 Resistance value due to minute magnetic field change Rb2 Resistance value due to minute magnetic field change N, S Magnetic pole φ Symbol of hole diameter

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Added

[Correction contents]

FIG. 13

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Isao Iwasaki 1094 Nishitoshigumi Fujii Shigumi, Hanyu City, Saitama Prefecture F-term (reference) 2F063 AA16 AA41 AA43 BA30 BB02 BC06 BD17 CA08 GA52 2G017 AA01 AB01 AB05 AC04 AC09 AD04 AD05 AD42 AD55 AD61 BA02 BA15 2G053 AA22 AB19 AB21 BA15 BB03 BB10 BC03 BC20 CA03 CA06 DA10 DB02

Claims (4)

[Claims] At least one or more magnetoresistive elements installed near a magnetizing means and responsive to a cooperative magnetic field change, a DC power supply to be applied to the magnetoresistive element, and a non-magnetic material to be detected. It is made of a metal material, and detects a small magnetic field change due to eddy current generated in the nonmagnetic metal material by moving either the nonmagnetic metal material or the magnetoresistive element installed near the magnetizing means. A method for detecting a non-magnetic metal material using a magnetoresistive element, the method comprising: 2. A magnetoresistive element according to claim 1, wherein at least two or more magnetoresistive elements responsive to a magnetic field change and a magnetizing means are arranged on the front surface and the back surface of the non-magnetic metal material. For detecting non-magnetic metal materials by using 3. The device according to claim 1, wherein a magnetoresistive element responsive to a magnetic field change and a magnetizing means are integrally formed.
A method for detecting a non-magnetic metal material using the magnetoresistive element described in the above. 4. A magnetoresistive element responsive to a magnetic field change, wherein two elements are paired to constitute a voltage dividing circuit.
A method for detecting a nonmagnetic metal material using the magnetoresistance element according to claim 1.