JP3469772B2 - Magnetic detector - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic detection device. More specifically, the present invention relates to a magnetic detection device that detects an object to be detected based on a change in magnetic flux according to the magnetic permeability of the object to be detected.

[0002]

2. Description of the Related Art In recent years, in order to improve the recording density in magnetic recording, the S / N ratio of signals, and the reliability of signals against external magnetic fields, magnetic recording media such as magnetic cards have a high coercive force. There is a tendency. However, it is difficult to increase the coercive force of all the recording media used at one time, and recording media having different coercive forces will be used in a transient state or in the future in a mixed state. Therefore, the magnetic recording device is required to have compatibility so that recording media having different coercive forces can be handled.

In response to such diversification of coercive force of the recording medium, a magnetic recording apparatus has a magnetic head according to the coercive force of the recording medium in order to obtain maximum output and S / N ratio when recording on the recording medium. It is required to change the recording current of. Therefore, the magnetic recording apparatus must first identify the coercive force of the recording medium before recording on the recording medium.

By the way, for cassette tapes,
A marking for identifying coercive force (presence or absence of a hole formed in the case, position of the hole, etc.) is provided on the case or the like. Therefore, in a magnetic recording device that handles cassette tapes,
An appropriate recording current can be determined by identifying the coercive force of the cassette tape based on the marking when the medium is inserted. However, magnetic cards and the like are not provided with markings for recognizing the coercive force of the medium. Therefore, conventionally, the recording current value that maximizes the output is first found by repeatedly performing recording and reproduction with the recording current value corresponding to the coercive force that may be used first, and then the recording current The value is used to update the data. That is, when handling a recording medium such as a magnetic card that is not provided with a marking for identifying coercive force, the coercive force cannot be immediately identified from the magnetic layer of the recording medium, and recording and reproducing trials are repeated several times. The coercive force of the magnetic medium is determined.

[0005]

However, in the above-mentioned card reader that handles magnetic cards, the coercive force of the magnetic medium is determined by repeating the trial several times. It takes a long time. Therefore, there is a demand for the development of an apparatus capable of detecting the coercive force of a recording medium without repeating several trials.

On the other hand, even when a recording medium having a marking for identifying the coercive force is used, it is caused by the difference in the coercive force of the medium and the difference in the thickness of the protective film layer provided on the medium. The optimum recording current value is slightly different.
Therefore, when the coercive force is identified based on the marking, it is not possible to adjust even the subtle difference in the optimum recording current value, and even in this case, the coercive force of the recording medium can be adjusted by another means. It would be convenient if it could be detected quickly.

An object of the present invention is to provide a magnetic detection device capable of quickly detecting the coercive force of a recording medium.

[0008]

In order to achieve such an object, a magnetic detector according to a first aspect of the present invention has an exciting coil and a detecting coil in two main magnetic poles arranged side by side so as to have a void portion on at least one side. The magnetic sensor portion is wound to form a magnetic sensor portion, and the magnetic sensor portion is provided at the magnetic detection position so that the magnetic flux passing through one of the main magnetic poles of the main magnetic pole changes with respect to the other main magnetic pole. The change of the magnetic flux of the main magnetic pole is detected by the detection coil.

Therefore, the exciting coil generates magnetic flux in the two main magnetic poles. When the magnetic sensor unit is sufficiently separated from the object to be detected, the magnetic flux passing through the main magnetic poles does not leak to the object to be detected, and the magnetic flux passing through the main magnetic poles is balanced and no output is generated in the detection coil. On the other hand, when the object to be detected approaches the magnetic sensor unit, the magnetic flux passing through one of the main magnetic poles leaks to the object to be detected, and the balance of the magnetic flux passing through each of the main magnetic poles is lost, and an output is generated in the detection coil. The degree to which the balance of the magnetic flux that passes through each magnetic pole is disrupted depends on the magnitude of the magnetic permeability of the object to be detected, and there is a certain relationship between the magnetic permeability and the coercive force. Output will be obtained.

Further, the magnetic detection device according to the first aspect is 2
An excitation coil is wound around each of the two main magnetic poles, and the excitation coil is configured so that a closed loop magnetic flux flows through the main magnetic pole.

When the exciting coils are wound around the main magnetic poles in opposite directions, magnetic fluxes in opposite directions are generated in the respective main magnetic poles, and one closed loop magnetic flux is formed as a whole. Therefore, even when the object to be detected approaches the magnetic sensor unit, the amount of magnetic flux leaking from the closed loop passing through the two main magnetic poles to the object to be detected is small. That is, the magnetic flux leaking from one main magnetic pole side to the detected body side is not so large as to damage the data recorded on the detected body, and the soundness of the recorded data is maintained.

Further, the magnetic detection device according to claim 1 is 2
At least one end of each of the two main magnetic poles is formed with an auxiliary core portion that assists the formation of a magnetic path by the detected body.
Therefore, when the object to be detected approaches the magnetic sensor portion, a magnetic flux leaking from one main magnetic pole to the object to be detected through the auxiliary core portion is generated, and the balance of the magnetic flux passing through each main magnetic pole is lost.

According to a second aspect of the magnetic detection device,
A detection coil is wound around each of the two main magnetic poles, and a differential output is taken out from the detection coil. Therefore, in the state where the magnetic fluxes passing through the two main magnetic poles are balanced, there is no difference in the output of each detection coil. From this state, when the object to be detected approaches the magnetic sensor unit and the balance of the magnetic flux passing through each main magnetic pole is lost, a difference occurs in the output of each detection coil.

In the magnetic detector according to the third aspect of the present invention, the main magnetic pole and the auxiliary core portion are made of a high magnetic permeability magnetic material, and the two main magnetic poles are connected at the other end side by a connecting portion. The auxiliary core portions provided at both ends are formed so as to project to the opposite side to the connecting portion, and the space between the protruding auxiliary core portions is configured as a winding portion of the exciting coil or the detection coil.

Therefore, the two main magnetic poles, the connecting portion, and each auxiliary core portion have a substantially π-shape as a whole. And
When the magnetic flux passing through each main magnetic pole forms one closed loop as a whole, the magnetic flux is in the order of one main magnetic pole → gap part → the other main magnetic pole → coupling part → one main magnetic pole, or in the reverse order. Make a loop. Since the main magnetic poles and the auxiliary core portions are made of a magnetic material having high magnetic permeability, leakage of magnetic flux from the closed loop hardly occurs. By making the portion between the auxiliary core portions of each main magnetic pole a winding portion of the exciting coil or the detection coil, it becomes possible to wind each coil symmetrically with respect to both main magnetic poles. The magnetic flux passing through can be balanced.

Further, the main magnetic pole may be arranged so as to be parallel to the surface through which the object to be detected passes, as in the magnetic detection apparatus according to claim 4, and the object to be detected as described in claim 5. The main pole may be arranged so as to be perpendicular to the plane through which the body passes.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described below in detail based on the best mode shown in the drawings.

FIG. 1 shows a first embodiment of a magnetic detection device to which the present invention is applied. In this magnetic detection device, an excitation coil 3 and a detection coil 4 are wound around two main magnetic poles 2 arranged side by side so as to have a void portion 1 on at least one side to form a magnetic sensor unit 5 and a magnetic sensor unit 5 At a magnetic detection position of a magnetic recording device such as a card reader, a magnetic flux passing through one of the main magnetic poles 2 of the main magnetic pole 2 is changed by a detected body (for example, a magnetic layer such as a magnetic stripe of a magnetic medium such as a magnetic card). The detection coil 4 detects a change in the magnetic flux of one of the main magnetic poles 2. In the present embodiment, the void portion 1 is provided only on one end side of each main magnetic pole 2, and the other end side of each main magnetic pole 2 is connected by the connecting portion 8.

At least one end of each of the two main magnetic poles 2 has
An auxiliary core portion 7 is formed to assist the formation of a magnetic path by the detected body 6. In this embodiment, the auxiliary core portions 7 are formed at both ends of the two main magnetic poles 2. Each auxiliary core portion 7 is formed so as to project to the side opposite to the connecting portion 8. And
The main magnetic poles 2 and the auxiliary core portions 7 are integrally formed of a high magnetic permeability magnetic material, and the exciting coil 3 is provided between the auxiliary core portions 7.
And a winding portion 9 around which the detection coil 4 is wound.

The exciting coil 3 is wound around the winding portion 9 of each main magnetic pole 2. The exciting coils 3 are wound in mutually opposite directions, and the magnetic fluxes passing through the main magnetic poles 2 are directed in mutually opposite directions to generate a closed-loop magnetic flux Φ1 as a whole.

The lead wires 3a of the coils 3 and 4,
4a are arranged so as to have an equal positional relationship with each main magnetic pole 2 so that the magnetic fluxes passing through each main magnetic pole 2 are balanced. That is, so that the positional relationship of plane symmetry based on the virtual intermediate surfaces existing equidistant from each main magnetic pole 2, or FIG.
As shown in FIG. 12 , when it is considered that the main magnetic poles 2 are arranged equidistantly with the virtual intermediate axis L interposed therebetween, the main magnetic poles 2 are viewed from the direction of FIG. 12A (the direction of arrow A in FIG. Each coil 3, so as to have a point-symmetrical positional relationship based on the virtual intermediate axis L.
Four lead lines 3a and 4a are arranged. By arranging the lead wires 3a and 4a of the coils 3 and 4 in this way, the magnetic fluxes passing through the main magnetic poles 2 can be balanced. However, because of this positional relationship, each coil 3,
It is not necessary to arrange the four lead lines 3a, 4a, and the circuits connected to the coils 3, 4 may be electrically corrected to balance the magnetic fluxes passing through the main magnetic poles 2. Further, the exciting coil 3 is supplied with an exciting current to such an extent that the magnetic permeability of the object 6 to be detected can be detected in a region where the high magnetic permeability core members of the main magnetic poles 2 and the auxiliary core portions 7 are not magnetically saturated. Has been done.

This magnetic detection device is arranged so that each main magnetic pole 2 is parallel to the surface A through which the detected body 6 passes.

In the magnetic sensor section 5 of this magnetic detection device,
For example, the circuit shown in FIG. 2 is connected. Excitation coil 3
Is connected to, for example, an AC power supply 10 and generates a closed loop magnetic flux Φ1 through the two main magnetic poles 2. When the detected body 6 does not exist around the magnetic sensor unit 5 and the magnetic fluxes passing through the main magnetic poles 2 are equal, the magnetic fluxes passing through the main magnetic poles 2 are balanced and the output of the detection coil 4 does not change. When the detected body 6 approaches the magnetic sensor section 5 from this state, a magnetic flux Φ2 leaking from one main magnetic pole 2 toward the detected body 6 through each auxiliary core section 7 is generated, and passes through each main magnetic pole 2. The balance of magnetic flux is lost. Since the degree of leakage of the magnetic flux Φ2 changes depending on the magnetic permeability of the detected body 6, the output of the detection coil 4 changes according to the magnitude of the magnetic permeability. The output of the detection coil 4 is amplified by the amplifier circuit 11, then half-wave rectified by the detection circuit 12 and the peak hold circuit 13 and envelope detection is performed, and an output signal having a magnitude corresponding to the magnetic permeability of the detected object 6 is obtained. Become. In this case, the order of amplification and detection may be reversed. Since the magnetic permeability of the detected body 6 and the magnitude of the coercive force of the detected body 6 have a fixed relationship, it is necessary to confirm the output value of the detection coil 4 corresponding to the magnitude of the coercive force in advance. Thus, the coercive force of the detected body 6 can be identified based on the output of the detection coil 4.

That is, in this magnetic detection device, each exciting coil 3 is wound around a substantially π-type high magnetic permeability core member so that the magnetic flux Φ1 forms a closed loop, and the detection coil 4 is a differential type. It is wound. Therefore, when the detected body 6 approaches the magnetic sensor unit 5, most of the magnetic flux Φ1 becomes a closed loop, but the minimum magnetic flux Φ2 depending on the medium permeability of the detected body 6 acts on the detected body 6. . Therefore, a magnetic flux large enough to damage the recorded data does not act on the detected object 6, and the magnetic sensor unit 5 can be operated even on the data storage area of the detected object 6. That is, the detected object 6
Is, for example, the magnetic stripe 1 of the magnetic card 14 shown in FIG.
In the case of 5, the magnetic sensor portion 5 may be opposed to the empty area (guard band) 17 between the tracks 16 which is the storage area in the magnetic stripe 15, but it may be opposed to the track 16. . Therefore, the degree of freedom in installing the magnetic sensor unit 5 is improved, and the magnetic sensor unit 5 can be easily attached to a card reader or the like.

In this magnetic detection device, the magnetic sensor section 5 is provided at a magnetic detection position where it can face the object 6 to be detected. For example, as shown in FIG.
When it is applied to the card reader 18 that handles four, the magnetic sensor unit 5 is attached to the magnetic detection position 19 of the card insertion opening of the card reader 18, for example. By attaching the magnetic sensor unit 5 to the magnetic detection position 19 of the card insertion slot, the coercive force of the magnetic stripe 15 can be detected when the magnetic card 14 is inserted, and subsequent processing such as data update can be performed quickly. be able to.

The above-described embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the above description, the main magnetic poles 2 are arranged so as to be parallel to the surface A through which the detected body 6 passes.
As in the second embodiment of the magnetic detection device shown in FIG. 5, the main magnetic poles 2 may be arranged perpendicular to the surface A through which the detected body 6 passes. In this case, when the detected object 6 and the main magnetic poles 2 have the same positional relationship, the magnetic fluxes passing through the main magnetic poles 2 are balanced and the output of the detection coil 4 cannot be obtained.
As shown in the figure, the magnetic sensor unit 5 is installed at a position where the detected body 6 affects only the magnetic flux of the one main magnetic pole 2, that is, one main magnetic pole with respect to the path along which the detected body 6 relatively moves. Two
The magnetic sensor unit 5 is installed so that only the main magnetic poles 2 face each other when the detected body 6 approaches one of the main magnetic poles 2.
The balance of the magnetic flux passing through is lost. Alternatively,
Both main magnetic poles 2 with respect to the path along which the detected body 6 relatively moves
Even when the magnetic sensor units 5 are installed so as to face each other, at the stage where the relatively moving detection target 6 affects only the magnetic flux passing through one of the main magnetic poles 2, that is, both of the main magnetic poles 2. The magnetic permeability of the detected body 6 is detected in a state where the magnetic fluxes are not balanced. In this case, since the detected body 6 faces both the main magnetic poles 2 after the magnetic permeability is detected, most of the magnetic flux flowing through each main magnetic pole 2 passes through the detected body 6 at this time. Therefore, the magnetic permeability is detected by using a magnetic flux having a strength that does not impair the recorded data, or the magnetic sensor unit 5 is opposed to the empty area 17 of the magnetic stripe 15 of the magnetic card 14, for example. You can do it.

[0027]

[0028]

[0029]

Further, in the above description, one detection coil 4 is wound around the two main magnetic poles 2. However, as in the first reference example of the magnetic detection device shown in FIG. The detection coil 4 is wound around each of the two
More differential output may be taken out.

The second reference of the magnetic detection device shown in FIG.
As in the case of consideration, the detection coil 4 may be largely wound so as to include the two main magnetic poles 2.

Further, in the above description, one main magnetic pole 2
Although the detected body 6 acts only on the magnetic flux passing through, the detected body 6 may act on only the magnetic flux passing through the other main magnetic pole 2 instead of the one main magnetic pole 2. Of course.

[0033]

EXAMPLES The magnetic detection device shown in FIG. 1 was used to actually identify the coercive force of a magnetic card. As magnetic cards, three types of cards with the same coercive force as those actually used in transactions, specifically, coercive force of 300, 650
And 2750 (Oe) magnetic cards were used. For reference, we also confirmed the output when the magnetic card was not detected. The output of the magnetic sensor section 5 of the state in which no detecting magnetic card in FIG. 8, the output of the magnetic sensor section 5 when the coercivity detects magnetic card 300 (Oe) 9
FIG. 10 shows the output of the magnetic sensor unit 5 when a magnetic card having a coercive force of 650 (Oe) is detected .
FIG. 11 shows the output of the magnetic sensor unit 5 when a 0 (Oe) magnetic card is detected. 8 to 10
For, while the vertical scale is 50 mV,
In FIG. 11 , one scale on the vertical axis is 20 mV. As is clear from these results, it was confirmed that the output of the magnetic sensor unit 5 changes according to the coercive force of the magnetic card. That is, it was confirmed that the coercive force of the magnetic card can be identified based on the output of the magnetic sensor unit 5. Note that the driving is performed using the excitation current of the sine wave, but the driving current is not limited to the excitation current of the sine wave, and the driving may be performed using the excitation current of a rectangular wave, a triangular wave, or the like.

[0034]

As described above, in the magnetic detection device according to the first aspect, the magnetic sensor is formed by winding the exciting coil and the detecting coil around two main magnetic poles arranged side by side so as to have a gap on at least one side. And a magnetic sensor part is provided at a magnetic detection position so that the magnetic flux passing through one of the main magnetic poles of the main magnetic pole changes with respect to the other main magnetic pole at the magnetic detection position. The detection coil detects the change in the above condition. Therefore, when the object to be detected approaches the magnetic sensor unit, a signal corresponding to the magnetic permeability of the object to be detected is output from the detection coil. Since the relationship between the output value of the detection coil and the magnetic permeability of the detected object is constant, the magnetic permeability of the detected object can be identified based on the output of the detection coil. That is, the magnetic permeability of the object to be detected (recording medium) can be quickly detected. For example, when the present magnetic detection device is applied to a magnetic recording device such as a card reader that handles a recording medium that does not have a coercive force identification marking such as a magnetic card such as a credit card, the recording medium is inserted into the magnetic recording device at the same time. The coercive force can be identified. Therefore, the data can be immediately recorded with the optimum recording current value, and the recording can be updated in one processing, so that the processing time can be greatly reduced. Further, even when the present magnetic detection device is applied to a magnetic recording device that handles a recording medium having an identification marking in a case or the like, there are subtle differences such as a difference in coercive force of a medium and a difference in thickness of a protective film layer provided on the medium. Such a difference can be reflected in the recording current value, and the quality and reliability of data processing can be improved. Furthermore, since the main magnetic poles and the core member of the auxiliary core portion can be used in a region where magnetic saturation does not occur, it is possible to prevent destruction of data already recorded on the recording medium and to install the magnetic sensor portion. The degree of freedom of is improved.

Further, in the magnetic detection device according to claim 1 ,
An excitation coil is wound around each of the two main magnetic poles, and the excitation coil is configured so that a closed loop magnetic flux flows through the main magnetic pole. Therefore, most of the generated magnetic flux travels inside each main magnetic pole, and the detected object side Since only the minimum magnetic flux necessary for detecting the magnetic permeability acts on the recording medium, it is possible to prevent the recorded data that has already been recorded from being damaged and maintain the soundness of the data. Therefore, for example, it becomes possible to install the magnetic sensor unit at a position facing a portion other than the empty area such as the guard band of the magnetic stripe of the magnetic card, and the degree of freedom in installing the magnetic sensor unit can be further improved. I can.

Further, in the magnetic detection device according to claim 1 ,
Since at least one end of each of the two main magnetic poles is formed with an auxiliary core portion that assists the formation of a magnetic path by the object to be detected,
A magnetic flux for detecting the magnetic permeability of the detection body can be guided to the detection body side, and the detection sensitivity can be improved.

Further, as in the magnetic detection device according to claim 2, winding a detection coil on each of the two main poles, may be derived is a differential output from the detection coil,
Even in such a case, it is possible to quickly detect the magnetic permeability of the object to be detected, and it is possible to achieve the above-described respective effects.

According to the third aspect of the magnetic detector, the main magnetic pole and the auxiliary core portion are made of a high magnetic permeability magnetic material, and the other end sides of the two main magnetic poles are connected to each other by the connecting portion. Auxiliary core portions provided at both ends of may be formed so as to project to the side opposite to the connecting portion, and the space between the projecting auxiliary core portions may serve as the winding portion of the exciting coil or the detection coil. Also, it is possible to quickly detect the magnetic permeability of the object to be detected, and it is possible to achieve the above-described effects.

Furthermore, the magnetic pole may be arranged so as to be parallel to the plane through which the object to be detected as in the magnetic detection apparatus according to claim 4, and the magnetic detection apparatus according to claim 5 Thus, the main magnetic pole may be arranged so as to be perpendicular to the plane through which the object to be detected passes. In these cases as well, it is possible to quickly detect the magnetic permeability of the object to be detected, and it is possible to achieve the above-mentioned respective effects.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a magnetic detection device of the present invention.

FIG. 2 is a circuit diagram connected to a magnetic sensor unit of the magnetic detection device of the present invention.

FIG. 3 is a plan view showing a magnetic stripe of a magnetic card.

FIG. 4 is a perspective view showing a state in which the magnetic detection device of the present invention is attached to a card reader.

FIG. 5 is a schematic configuration diagram showing a second embodiment of the magnetic detection device of the invention.

FIG. 6 is a schematic configuration diagram showing a first reference example of a magnetic detection device of the present invention.

FIG. 7 is a schematic configuration diagram showing a second reference example of the magnetic detection device of the invention.

FIG. 8 is a diagram showing an example of the output signal of the magnetic sensor unit of the magnetic detection device of the present invention in a state in which nothing is detected.

FIG. 9 is a diagram showing an example of the output signal of the magnetic sensor unit of the magnetic detection device of the present invention, when a magnetic card having a coercive force of 300 (Oe) is detected.

FIG. 10 is a diagram showing an example of the output signal of the magnetic sensor unit of the magnetic detection device of the present invention, when a magnetic card having a coercive force of 650 (Oe) is detected.

FIG. 11 is a diagram showing an example of the output signal of the magnetic sensor unit of the magnetic detection device of the present invention, when a magnetic card having a coercive force of 2750 (Oe) is detected.

12A and 12B show arrangements of lead lines of an exciting coil and a detection coil, FIG. 12A is a view of a main magnetic pole seen from a direction along an imaginary intermediate axis, and FIG. 12B is a direction of a main magnetic pole orthogonal to the imaginary intermediate axis. It is the figure seen.

[Explanation of symbols]

1 void 2 main pole 3 Excitation coil 4 detection coil 5 Magnetic sensor section 6 Object to be detected 7 Auxiliary core part 8 connection 9 winding part 19 Magnetic detection position

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-213276 (JP, A) Actually open 2-60866 (JP, U) Actually open 55-172874 (JP, U) (58) Surveyed Field (Int.Cl. ⁷ , DB name) G11B 5/02

Claims (5)

(57) [Claims] 1. A magnetic sensor unit is constructed by winding an exciting coil and a detection coil around two main magnetic poles arranged side by side so as to have a gap on at least one side, and the magnetic sensor unit is placed at a magnetic detection position. with magnetic flux passing through one of the main pole of the main pole by the detection member is provided so as to change with respect to the other of the main pole, a change in the magnetic flux in one of the main magnetic pole above becomes as detected by the detection coil ,the above
An exciting coil is wound around each of the two main magnetic poles to
The coil is structured so that a closed loop magnetic flux flows through the main pole.
At least one end of the two main magnetic poles
Is an auxiliary core portion that assists the formation of a magnetic path by the object to be detected.
Magnetic detection device, characterized in that There are formed. Wherein said two winding a detection coil on each of the main magnetic pole, the detection configured characterized by comprising Claim 1 Symbol mounting magnetic sensing device to retrieve the differential output from the coil. 3. The main magnetic pole and the auxiliary core portion are made of a high-permeability magnetic material, the two main magnetic poles are connected at the other end side by a connecting portion, and the main magnetic pole and the auxiliary core portion are provided at both end portions of the main magnetic pole. auxiliary core portion is formed to protrude on the opposite side to the above connecting portions, claim 1 between the auxiliary core portion as described above protruding characterized by comprising configured to the winding portion of the exciting coil or the detection coil or 2. The magnetic detection device according to 2 . 4. The magnetic sensor apparatus according to claim 1 or et 3, characterized by being arranged in parallel to the main magnetic pole with respect to a plane passing through the said detection object. 5. A magnetic detection device according to claim 1 or et 3, characterized by being arranged such that the main magnetic pole perpendicular to the plane passing through the said detection object.