JP2000222704A - Magnetic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain detection sensitivity and precision even though an adverse effect of balance fluctuation caused by an external factor is received. SOLUTION: The detector is provided with a magnetic sensor core body 20, which has a magnetic gap section 1 on at least one side, an energizing coil 3, which is wound to generate a magnetic flux in the section 1 of the body 20, and a detection coil 4 which is wound to detect the change in the magnetic flux generated by the coil 3. The detection output changes in the range, which is larger than the amount of balance fluctuation caused by an external factor to the detection output with respect to a minimum level of the detection output of the coil 4. Thus, if the magnetic flux of one side of the section 1 is changed by a body 6 which is to be detected, the detection output varies in one direction only.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic detection device. More specifically, the present invention relates to a magnetic detection device that detects an object based on a change in magnetic flux according to the magnetic permeability of the object.

[0002]

2. Description of the Related Art A magnetic detection apparatus using a differential magnetic sensor measures a magnetism by detecting a coil current by utilizing a deviation of a magnetic balance when a detection medium which is a detection object approaches. . This detection device includes, for example,
As disclosed in Japanese Patent Application Laid-Open No. 2688, there is a device which does not have a balance adjustment function on the premise that the sensor output is minimized when there is no detection medium.

[0003] On the other hand, since the balance characteristics may differ from sensor to sensor due to manufacturing variations, Japanese Patent Application Laid-Open No.
As described in Japanese Patent Publication No. 506687 and the like, a device having a balance adjustment mechanism for obtaining detection accuracy has been proposed. In such a balance adjustment mechanism, the magnetic balance is adjusted so that the sensor output is minimized in the absence of the detection medium, and the absolute value of the sensor output is used as the detection amount.

In any of the above magnetic detecting devices, when no object to be detected is detected, the sensors are balanced and the sensor output is located at or near the minimum level M as shown in FIG. . When an object to be detected approaches this sensor, the balance is lost and a current flows to the detection circuit side, and a difference value is detected based on the current.

[0005]

However, the above-mentioned differential type magnetic detector has a characteristic that the balance fluctuates due to various external factors such as temperature characteristics and wear, and the balance actually fluctuates. If this occurs, there is a problem that a detection error occurs and the detection sensitivity / accuracy decreases. In particular,
As shown in FIG. 18, when the detected object is not detected and the minimum level M is included in the operation range of the sensor instead of the minimum level M, linearity is maintained in each sensor output before and during the medium detection. Because of this, a large detection error occurs and the detection sensitivity is reduced.

[0006] In order to prevent such a fluctuation in balance, it is necessary to periodically adjust the sensor balance. However, maintaining the performance of the sensor so that the sensor output characteristic at the time of non-detection is always kept at the minimum level M is troublesome and costly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic detector capable of maintaining detection sensitivity and accuracy even if the balance is affected by external factors.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a magnetic sensor core configured to have a magnetic gap on at least one side, and a magnetic gap of the magnetic sensor core. An exciting coil wound to generate a magnetic flux in the portion, and a detecting coil wound to detect a change in magnetic flux generated by the exciting coil, and a detection output from the detecting coil is minimized. The detection output with respect to the level is configured to change in a range larger than the amount of balance fluctuation due to an external factor with respect to the detection output, and the detection output is output when the magnetic flux on one side of the magnetic gap changes due to the detection target. Is changed in one direction.

In this case, a change area larger than the amount of balance fluctuation due to an external factor is provided so that the reference sensor output is sufficiently separated from the minimum level. Since the minimum level is not included in the operation range, high detection accuracy using linearity is maintained. In addition, even if the sensor balance is lost due to an external factor after the adjustment and the balance fluctuates, the minimum level is not included in the operating range of the sensor output. Therefore, after the adjustment, it is not necessary to readjust the sensor output at the time of non-detection to the minimum level. In addition, the life of the sensor can be determined from the magnitude of the balance fluctuation without readjustment.

Further, in detecting magnetism by using this device, detection can be performed based on the relative change amount of the sensor output read before and during the detection. In this case, even if the fluctuation due to the sensor balance collapse occurs after the adjustment, an error does not occur in the relative change amount itself before and after the detection, and the detected value is more accurate than when the absolute value is used.

According to a second aspect of the present invention, in the magnetic detection device of the first aspect, the minimum level of the detection output from the detection coil is smaller than the balance fluctuation amount due to an external factor with respect to the detection output. Give a large offset,
The detection output is set so as to increase or decrease in one direction when the detection output is changed by the detected object.

In this case, since the sensor output characteristic is offset in advance so that the reference sensor output is sufficiently separated from the minimum level, the minimum level is not included in the operating range from the sensor output before detection to the sensor output at the time of detection. High detection accuracy using linearity is maintained. In addition, even if the sensor balance is lost due to an external factor after the offset adjustment and the balance is changed, the minimum level is not included in the operating range of the sensor output, and therefore the influence of the balance loss is hardly caused. Therefore, after the offset adjustment, it is not necessary to readjust the sensor output at the time of non-detection to the minimum level. In addition, the life of the sensor can be determined from the magnitude of the balance fluctuation without readjustment.

According to a third aspect of the present invention, in the magnetic detection device according to the first or second aspect, the magnetic sensor core is formed in a substantially π shape, and the exciting coil and the detection coil are wound around the magnetic sensor core. The differential type sensor is formed by turning. Therefore, the object to be detected can be accurately detected by the substantially π-shaped magnetic sensor.

According to a fourth aspect of the present invention, in the magnetic detecting device of the first or second aspect, the magnetic sensor core is formed in a substantially E-shape, and the exciting coil and the detecting coil are wound around the magnetic sensor core. The differential type sensor is formed by turning. Therefore, the object to be detected can be accurately detected by the substantially E-shaped magnetic sensor.

Further, according to the invention described in claim 5, according to claim 2,
In the magnetic detection device according to any one of the above items, the offset amount given by the balance fluctuation amount due to an external factor of the sensor output may be any one of a variable resistor or a variable capacitor for adjusting the current flowing through the two coils or the phase thereof. The adjustment is made by one or both of the adjusting means. In this case, the offset amount can be easily adjusted by using the variable resistor alone or in combination with the variable capacitor.

Further, according to the invention described in claim 6, according to claim 5,
The adjusting means in the described magnetic detection device is provided on the detection circuit side. Therefore, the excitation-side circuit can be configured by a simple circuit composed of one system.

According to a seventh aspect of the present invention, in the magnetic detection device according to any one of the first to sixth aspects, a part or all of the magnetic sensor core body is housed in a mold. In this case, the surface of the object to be detected can be prevented from being damaged by storing the contact portion with the object to be detected in the mold.

Further, in the invention according to the eighth aspect, the object to be detected is a magnetic stripe of a magnetic card, and the coercive force can be quickly detected by the above-described magnetic detection device to enable accurate identification.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an example of an embodiment shown in the drawings.

FIG. 1 shows an embodiment of the magnetic detection device of the present invention. This magnetic detection device includes a magnetic sensor core 20 configured to have a magnetic gap 1 on at least one side, and an exciting coil wound to generate a magnetic flux in the magnetic gap 1 of the magnetic sensor core 20. A coil 3 and a detection coil 4 wound to detect a change in magnetic flux generated by the excitation coil 3, and a detection output P from the detection coil 4 is applied to one side of the magnetic gap 1. Is the object to be detected (hereinafter also referred to as “medium”) 6
The change of the detection output P changes in one direction (increases in one direction or decreases in one direction) when the change of the detection output P, and the change in the detection output P causes the balance fluctuation amount due to an external factor of the sensor output P. In order to avoid passing through the minimum level of the detection output, the output is changed with an output larger than the above-mentioned balance fluctuation amount.

As shown in FIG. 1, the magnetic sensor core body 20 is mainly composed of two symmetrical main poles 2 which are juxtaposed and connected by a connecting portion 8. Main pole 2 is 2
A magnetic sensor unit 5 capable of detecting magnetism is formed by winding the excitation coils 3 and 3 of the system and the detection coil 4 that is differentially connected in series. For example, the magnetic sensor unit 5 detects a magnetic flux passing through one of the main magnetic poles 2 at a magnetic detection position of a magnetic recording device such as a card reader 18 by a detection target (magnetic layer such as a magnetic stripe of a magnetic medium such as a magnetic card) 6. It is provided so as to change, and the change in the magnetic flux is detected by the detection coil 4. In the present embodiment, a gap 1 serving as a space between the two main magnetic poles 2 is provided only at one end of each main magnetic pole 2, and the other end of each main magnetic pole 2 is connected by a connecting portion 8 to connect the two main magnetic poles 2 to each other. The connecting portion 8 forms a U-shape.

Further, an auxiliary core 7 is formed at at least one end of the main magnetic pole 2 to assist the formation of a magnetic path by the object 6 to be detected. In the present embodiment, the auxiliary core portions 7 protruding from both ends of the two main magnetic poles 2 so as to face outward, respectively.
Is formed so that the magnetic sensor core body 20 has a substantially π shape as a whole. Each main pole 2 and each auxiliary core 7 are integrally formed of a high magnetic permeability magnetic material,
A portion of the main magnetic pole 2 between the two auxiliary core portions 7 is a winding portion 9 around which the exciting coil 3 and the detecting coil 4 are wound.

The exciting coils 3 are wound around the respective winding portions 9 in opposite directions, and the magnetic fluxes passing through the main magnetic poles 2 become opposite to each other to form a closed-loop magnetic flux Φ as a whole.
1 is generated. The exciting coil 3 is supplied with an exciting current sufficient to detect the magnetic permeability of the detection target 6 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. Have been.

The magnetic detecting device is arranged such that each main magnetic pole 2 is parallel to a plane A through which the object 6 passes.

The magnetic sensor unit 5 of the magnetic detection device includes:
For example, the circuit shown in FIG. 2 is connected. The exciting 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. The detected object 6 does not exist around the magnetic sensor unit 5 and each main magnetic pole 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 detection target 6 approaches the magnetic sensor unit 5 from this state, a magnetic flux Φ2 leaking from one main magnetic pole 2 to the detection target 6 through each auxiliary core unit 7 is generated, and each main magnetic pole 2 is generated. The balance of the passing magnetic flux is lost. Since the degree of leakage of the magnetic flux Φ2 changes depending on the magnetic permeability of the detection target 6, the output of the detection coil 4 changes according to the magnitude of the magnetic permeability. After the output of the detection coil 4 is amplified by the amplifier circuit 11, it is half-wave rectified by the detection circuit 12 and the peak hold circuit 13 and subjected to envelope detection, and an output signal having a magnitude corresponding to the magnetic permeability of the detection target 6. Becomes In this case, the order of amplification and detection may be reversed. Since there is a certain relationship between the magnetic permeability of the detection target 6 and the magnitude of the coercive force of the detection target 6, the output value of the detection coil 4 corresponding to the magnitude of the coercive force is checked in advance. Thus, the coercive force of the detection target 6 can be identified based on the output of the detection coil 4.

Further, in this embodiment, a circuit capable of adjusting the balance of the sensor is added to this circuit so that the sensor output characteristic can be adjusted in advance by modifying it. As shown in FIG. 11, this circuit is provided with adjusting means, specifically, two variable resistors 21 for level adjustment and two variable capacitors 22 for phase adjustment on the side of the drive circuit for sending the excitation signal. By doing so, the balance of the magnetic flux of the excitation side circuit is changed.

In this embodiment, the variable capacitor 22 or the like capable of adjusting the balance is used, and the output characteristic of the sensor which is normally adjusted to be at the minimum level M when there is no object to be detected is offset in advance. To give displacement. That is, as shown in FIG. 14, the reference sensor output P0, which is the output when the medium 6 is not present, is shifted in the right or left direction of the minimum level M, which is the result of the balance adjustment. It changes only in one direction, and the sensor output P is detected. For example, in the present embodiment, as shown in the figure, the output characteristic is shifted to the left side in the figure where the sensor balance is reduced, and is increased from the minimum level M to the left side so as to increase when there is a medium 6 compared to when there is no medium 6. Only the sensor output P is detected. Therefore, the reference sensor output P0 when the excitation is balanced in the state where the medium 6 is not present is the minimum level M
It is located on the left side. The output characteristics may be set such that the sensor balance is increased, and the sensor output is detected only in the area on the right side of the minimum level M. In this case, the sensor output is smaller when there is a detection medium than when there is no detection medium.

In this case, the offset amount of the output characteristic is such that the reference sensor output P0 still exceeds the minimum level M even if a balance fluctuation occurs due to a change in an external factor in the temperature characteristic or wear characteristic of the magnetic sensor unit 5. This is the amount that does not enter other areas. As a result, in FIG. 14, the reference sensor output P0 does not move to the right beyond the minimum level M even if a balance fluctuation occurs due to wear or the like. Therefore, when the offset is provided on the left side of the minimum level M, the balance fluctuation region is always positioned on the left side of the minimum level M so as not to straddle the minimum level M, and accurate output detection using linearity is performed. It can be carried out. When the offset is provided on the right side of the minimum level M, the sensor output changes in a region on the right side of the minimum level M.

Alternatively, it is possible to provide a case where the sensor balance is improved at the time of detection as compared with the case where the medium 6 is not present. In this case, for example, as shown in FIG. The output characteristics can be shifted by a large amount. That is, the output P when the medium 6 is detected by the detection coil 4 is configured to be smaller than when the medium 6 is not provided, and the offset is set so that the detected P1 does not pass through the minimum level M. Give and P
0 and P1 can also be set. In this case, medium 6
It is only necessary to secure an offset amount such that the sensor output P does not exceed the minimum level M when is detected, or when a balance fluctuation occurs due to a change in an external factor such as a wear characteristic. With this setting, the medium 6 can be detected based on a change that the sensor output becomes smaller than when the medium 6 is not provided.

In the case of the present embodiment in which the output characteristics are offset-adjusted in this manner, the sensor outputs P0 and P1 are read before and at the time of detection, respectively, and the medium 6 is determined based on the relative change (P1-P0). Has been detected. Therefore, as shown in FIG. 16, even if the fluctuation due to the sensor balance collapse occurs after the offset adjustment, no error occurs in the relative change amount (P1−P0) itself between before the detection and at the time of the detection, and when the absolute value is used. The detected value is more accurate.

When the offset of the sensor output characteristic is adjusted in advance, the offset may be offset to the left in the drawing as described above, or may be offset to the right of the minimum level M. In this case, the offset amount is such an amount that the sensor output P1 at the time of medium detection does not reach the left side beyond the minimum level M even if a balance fluctuation occurs.

Although an example of the detection circuit has been described in the above embodiment, the circuit applicable to the magnetic detection device is not particularly limited thereto. For example, a circuit in which a variable capacitor is omitted as shown in FIG. You may. That is, the variable capacitor 22 of the circuit shown in FIG. 11 is provided as means for adjusting the phase on the excitation side so that the reference sensor output P0 when the medium is not detected can be adjusted to the minimum level M. According to the magnetic detection device, it is not necessary to adjust the reference sensor output P0 to the minimum level M, so that it is not necessary to provide a variable capacitor capable of adjusting the phase.

Further, as shown in FIG. 13, it is also possible to employ a circuit provided with an adjusting means for adjusting the balance on the detection side. In this case, the magnetic sensor unit 5 shown in FIG.
3a is connected to the detection side and the extraction line 4a is connected to the excitation side, and the detection side is formed as a plurality of differential circuits, and the detection side is formed so as to perform detection based on the difference between outputs. . Further, in this circuit, a slip resistor 26 capable of adjusting the balance with only one unit is provided in parallel with two series fixed resistors 25 provided on the detection side,
The adjustment can be performed with only one operation.
Note that the circuits shown in FIGS. 11 to 13 include an amplifier circuit 11, a detection circuit 12, an A / D converter 2
3 and CPU 24, but this is an example,
These functions are substantially the same as those of the subsequent circuit shown in FIG.

Next, the operation of the magnetic detection device according to this embodiment will be described. In this magnetic detection device, each excitation coil 3 is wound around a substantially π-shaped high permeability core member so that the magnetic flux Φ1 forms a closed loop.
Are wound so as to be a differential type. For this reason, when the detection target 6 approaches the magnetic sensor unit 5, most of the magnetic flux Φ1 forms a closed loop, but the minimum magnetic flux Φ2 depending on the medium permeability of the detection target 6 acts on the detection target 6. . Therefore, a magnetic flux that is large enough to impair the recording data does not act on the detected object 6, and the magnetic sensor unit 5 can be operated even in the data storage area of the detected object 6. That is, when the detected object 6 is, for example, the magnetic stripe 15 of the magnetic card 14 shown in FIG. 3, the magnetic sensor 15 is provided in an empty area (guard band) 17 between the tracks 16 which is a storage area in the magnetic stripe 15. The section 5 may be opposed to the track 16 or may be opposed to the track 16. Therefore, the degree of freedom of installation of the magnetic sensor unit 5 is improved, and attachment to a card reader or the like becomes easy.

Moreover, in the magnetic detection device of the present embodiment,
Minimum level M when output of reference sensor output P0 is adjusted
The sensor output characteristics are offset in advance so as to be sufficiently away from the sensor, and the magnetic detection is performed based on the relative change between the pre-detection output P0 and the detection output P1. However, it is hardly affected, and thus high detection accuracy can be maintained. At the same time, the sensor output P becomes the minimum level M
, The sensitivity of the magnetic sensor unit 5 can be prevented from lowering. In addition, since it is not necessary to correct the sensor imbalance, once the offset is adjusted, there is no need to readjust until the sensor is replaced. Furthermore, when the deviation amount of the detection output with respect to the offset value becomes large, it can be determined that the sensor has reached the end of its life.

In this magnetic detection device, the magnetic sensor unit 5 is provided at a magnetic detection position where the magnetic sensor unit 5 can face the object 6 to be detected. For example, as shown in FIG. 4, when this magnetic detection device is applied to a card reader 18 that handles a magnetic card 14, the magnetic sensor unit 5 is attached to, for example, a magnetic detection position 19 at a card insertion slot of the card reader 18. 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 at the time when the magnetic card 14 is inserted, and the subsequent processing such as data update is quickly performed. be able to.

The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, the magnetic sensor core 20
Although the case where the excitation coil 3 and the detection coil 4 are connected to the circuits as shown in FIGS. 11 to 13 has been described,
What has been described here is a preferred example of a circuit with balance adjustment means, and it is needless to say that the invention is not limited to these and other circuits capable of offset adjustment may be employed.

Further, in the present embodiment, the magnetic detection device is substantially π
Although the case where the magnetic sensor core body 20 having a mold shape is applied has been described, the shape and form of the core body 20 are not particularly limited thereto, and can be variously modified. Therefore, another embodiment of the magnetic sensor core body 20 will be described below.

First, in the present embodiment, the main magnetic poles 2 are arranged so as to be parallel to the plane A through which the detection object 6 passes. However, in the second embodiment of the magnetic detection device shown in FIG. As described above, the main magnetic poles 2 may be arranged perpendicular to the plane A through which the detection target 6 passes. In this case, if the positional relationship between the detected object 6 and each of the main magnetic poles 2 is equal, the magnetic flux passing through each of the main magnetic poles 2 is balanced and the output of the detection coil 4 cannot be obtained. The magnetic sensor unit 5 is installed at a position where the magnetic field 6 affects only the magnetic flux of the one main magnetic pole 2, that is, the magnetic sensor unit 5 is arranged so that only the one main magnetic pole 2 is opposed to the path along which the detection target 6 relatively moves. The sensor unit 5 is provided so that when the detection target 6 approaches one of the main magnetic poles 2, the balance of the magnetic flux passing through each main magnetic pole 2 is lost. Alternatively, even when the magnetic sensor unit 5 is installed so that both the main magnetic poles 2 are opposed to the path along which the detection target 6 relatively moves, the detection target 6 that moves relatively does not have one main magnetic pole 2. The magnetic permeability of the detection target 6 is detected at a stage in which only the magnetic flux passing through the main body 2 is affected, that is, in a state where the magnetic fluxes of the two main magnetic poles 2 are not balanced. In this case, the detected object 6 faces both main magnetic poles 2 after the detection of the magnetic permeability. At this time, most of the magnetic flux flowing through each main magnetic pole 2 passes through the detected object 6. 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 made to face the empty area 17 of the magnetic stripe 15 of the magnetic card 14, for example. You can do it.

In the above description, the auxiliary cores 7 are formed at both ends of each main pole 2. However, the auxiliary cores 7 do not necessarily need to be formed at both ends, and one side of each main pole 2 is provided. The auxiliary core part 7 may be formed only in the auxiliary core part 7, or the auxiliary core part 7 may be omitted. For example, the auxiliary core unit 7 may be omitted as in the third embodiment of the magnetic detection device shown in FIG. 6 or the fourth embodiment of the magnetic detection device shown in FIG.

Further, in the above description, the exciting coils 3 of the respective main magnetic poles 2 are wound in opposite directions so that the direction of the magnetic flux passing through the respective main magnetic poles 2 is reversed to generate a magnetic flux Φ1 which forms a closed loop. However, as in the fifth embodiment of the magnetic detection device shown in FIG. 8, the exciting coil 3 of each main magnetic pole 2 is wound in the same direction, and the magnetic flux passing through each main magnetic pole 2 flows in one direction. You may make it become. In this case, as the detected object 6 approaches, almost all of the magnetic flux passing through the one main magnetic pole 2 becomes the magnetic flux Φ2 passing through the detected object 6, so that the magnetic flux having a strength that does not impair the recording data is used. The magnetic susceptibility may be detected or, for example, the magnetic sensor unit 5 may be opposed to the empty area 17 of the magnetic stripe 15 of the magnetic card 14.

In the above description, one detection coil 4 is wound around two main magnetic poles 2. However, as in the sixth embodiment of the magnetic detection device shown in FIG. Alternatively, the detection coil 4 may be wound around each of the detection coils 2 to extract a differential output from each detection coil 4.

In the above description, the detected object 6 acts only on the magnetic flux passing through one main magnetic pole 2. However, only the magnetic flux passing through the other main magnetic pole 2 is used instead of one main magnetic pole 2. It goes without saying that the detected object 6 may act on.

Further, as shown in FIG. 10, a magnetic sensor core body 20 formed in a substantially E-shape can be applied to a magnetic detection device. In the case of the seventh embodiment,
Three parallel winding portions 9 at the center and both sides at the tip of the magnetic sensor core body 20 are provided so as to face the detection target 6, and the exciting coil 3 is provided at the middle winding portion 9 and the two systems. Are wound around the winding portions 9 on both sides so as to form a differential type sensor so as to form a closed magnetic path in the sensor. Therefore,
A magnetic path as shown is formed around the magnetic sensor unit 5, and a differential output is obtained from a change in magnetic flux in this magnetic path. That is, when the detection object 6 approaches, the balance is lost by the magnetic flux Φ2 depending on the effective magnetic permeability of the magnetic path, and the detection coil 4
, The sensor output P is detected.

It should be noted that, of the magnetic sensor core body 20 of each of the above-described embodiments, one in which one of the excitation side and the detection side is a differential winding circuit of a plurality of systems has been described in the first embodiment. It is possible to adjust the offset of the output characteristics of the sensor by connecting to a circuit. For example, the circuit shown in FIG. 13 is connected to the substantially E-shaped magnetic sensor core body 20 shown in FIG. 10 to adjust the balance of the sensor output so as not to cause an error due to the deviation of the balance. it can. That is, an offset may be given to the minimum level M of the sensor output as shown in FIG. In the above-described embodiment, the detection side has two systems. However, the detection side and the excitation side may be interchanged, and the excitation side may have two systems.

Further, the magnetic sensor core body 20 of the present embodiment
When the detection target 6 is detected using the method, it is desirable that the surface of the detection target value 6 is not damaged as much as possible. For example, although not particularly shown in the present embodiment, housing a part or all of the magnetic sensor core body 20 in a mold is one of preferable means.

[0047]

As is apparent from the above description, according to the magnetic detection device of the first aspect, the reference sensor output is larger than the balance fluctuation amount due to external factors so as to be sufficiently separated from the minimum level. Since the change range of the range is provided, the minimum level is not included in the operation range from the sensor output before detection to the sensor output at the time of detection, and high detection accuracy using linearity is maintained. In addition, even if the sensor balance is lost due to an external factor after the adjustment and the balance fluctuates, the minimum level is not included in the operating range of the sensor output. Therefore, after the adjustment, it is not necessary to readjust the sensor output at the time of non-detection to the minimum level.

Further, in detecting magnetism using this device, it is possible to perform detection based on the relative change amount of the sensor output read before and during the detection. In this case, even if a change occurs due to the sensor balance collapse after the offset adjustment, an error does not occur in the relative change amount between before and during the detection, and the detected value is more accurate than when the absolute value is used.

According to the second aspect of the present invention, since the sensor output characteristic is offset in advance so that the reference sensor output is sufficiently separated from the minimum level,
Since the minimum level is not included in the operation range from the sensor output before detection to the sensor output at the time of detection, high detection accuracy using linearity is maintained. In addition, even if the sensor balance is lost due to an external factor after the offset adjustment and the balance is changed, the minimum level is not included in the operating range of the sensor output, and therefore the influence of the balance loss is hardly caused. Therefore,
After the offset adjustment, it is not necessary to readjust the sensor output at the time of non-detection to the minimum level.

According to the third aspect of the present invention, the object to be detected can be accurately detected by the substantially π-shaped magnetic sensor.

Further, according to the magnetic detecting device of the fourth aspect, the object to be detected can be accurately detected by the substantially E-shaped magnetic sensor.

According to the magnetic detecting device of the present invention, the offset amount is adjusted by the adjusting means including one or both of the variable resistor and the variable capacitor. Alternatively, it can be easily adjusted by a combination with a variable capacitor.

Further, according to the magnetic detection device of the sixth aspect, the adjusting means is provided on the detection circuit side, and the excitation side circuit can be constituted by a simple circuit of one system.

According to the magnetic detecting device of the present invention, since a part or the whole of the magnetic sensor core is housed in the mold, it is possible to prevent the surface of the detected object from being damaged.

Furthermore, according to the magnetic detecting device of the present invention, the magnetic card can be identified with high accuracy by quickly detecting its coercive force.

[Brief description of the drawings]

FIG. 1 is a diagram showing a substantially π-type sensor according to a first embodiment of a magnetic detection device of the present invention.

FIG. 2 is a diagram illustrating an example of a circuit diagram connected to a magnetic sensor unit of the magnetic detection device.

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

FIG. 4 is a perspective view showing a state where the magnetic detection device is attached to a card reader.

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

FIG. 6 is a schematic configuration diagram illustrating a third embodiment of the magnetic detection device.

FIG. 7 is a schematic configuration diagram showing a fourth embodiment of the magnetic detection device.

FIG. 8 is a schematic configuration diagram showing a fifth embodiment of the magnetic detection device.

FIG. 9 is a schematic configuration diagram showing a sixth embodiment of the magnetic detection device.

FIG. 10 is a schematic configuration diagram showing a seventh embodiment of the magnetic detection device.

FIG. 11 is a diagram illustrating an example of a circuit including an adjustment unit.

FIG. 12 is a diagram illustrating a modified example of a circuit including an adjusting unit.

FIG. 13 is a diagram illustrating an example of a circuit including an adjustment unit on the detection side.

FIG. 14 is a sensor balance-output diagram showing sensor output characteristics in the magnetic detection device of the present invention.

FIG. 15 is a sensor balance-output diagram showing another sensor output characteristic in the magnetic detection device of the present invention.

FIG. 16 is a sensor balance-output diagram showing a case where fluctuation due to sensor balance collapse occurs after offset adjustment.

FIG. 17 is a sensor balance-output diagram showing sensor output characteristics in a conventional magnetic detection device.

FIG. 18 is a sensor balance-output diagram showing sensor output characteristics in a conventional magnetic detection device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetic gap 2 main magnetic pole 3 excitation coil 4 detection coil 6 object to be detected 20 magnetic sensor core P detection output P0 reference sensor output

Claims (8)

[Claims] A magnetic sensor core configured to have a magnetic gap on at least one side; an exciting coil wound to generate a magnetic flux in the magnetic gap of the magnetic sensor core; A detection coil wound so as to detect a change in magnetic flux generated by the detection coil, wherein the detection output is balanced with the minimum level of the detection output from the detection coil by an external factor with respect to the detection output. The detection output is changed in one direction when the magnetic flux on one side of the magnetic gap is changed by the object to be detected. Magnetic detector. 2. When the detected output from the detection coil is given an offset larger than the amount of balance fluctuation due to an external factor with respect to the detected output, and the detected output is changed by an object to be detected. 2. The magnetic detection device according to claim 1, wherein the detection output is set to increase or decrease in one direction. 3. The differential sensor according to claim 1, wherein the magnetic sensor core body is formed in a substantially π shape, and the exciting coil and the detection coil are wound around the magnetic sensor core body. Item 3. The magnetic detection device according to item 1 or 2. 4. The magnetic sensor core body is formed in a substantially E-shape, and the excitation coil and the detection coil are wound around the magnetic sensor core body to form a differential sensor. Item 3. The magnetic detection device according to item 1 or 2. 5. An adjusting means comprising one or both of a variable resistor and a variable capacitor for adjusting a current flowing through two coils or a phase thereof, the offset amount being provided by an amount corresponding to a balance variation due to an external factor of the sensor output. The magnetic detection device according to claim 2, wherein the adjustment is performed by: 6. The magnetic detection device according to claim 5, wherein the adjustment means is provided on a detection circuit side. 7. The magnetic detection device according to claim 1, wherein a part or the whole of the magnetic sensor core body is housed in a mold. 8. The magnetic detection device according to claim 1, wherein the object to be detected is a magnetic stripe of a magnetic card.