JP2013167562A - Magnetic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a quantity of magnetism of a magnetic substance as well as a detection of the magnetic substance.SOLUTION: A magnetic detector for detecting a magnetic substance moving in a bias magnetic field on the basis of a change in a magnetic field comprises: a magnet unit for generating a bias magnetic field; and an anisotropic magnetoresistance element arranged at a prescribed arrangement position. The anisotropic magnetoresistance element is arranged in such a direction that the direction of the magnetic substance moving in the bias magnetic field at the upper part of the magnetic unit, matches with the magnetosensitive direction of the anisotropic magnetoresistance element, and such a position that a magnetic flux density of the bias magnetic field of a magnetosensitive-direction component of the anisotropic magnetoresistance element approximates to 0 (zero).

Description

  The present invention relates to a magnetic detection device for detecting a magnetic material, and more particularly to a magnetic detection device capable of detecting the amount of magnetism of a magnetic material.

  Conventionally, a magnetic detection device for detecting a magnetic material has been used in various fields. For example, in a paper sheet processing apparatus, a magnetic detection device is used to identify the authenticity and type of the paper sheet. Some paper sheets are printed using magnetic ink so that the authenticity and type can be identified, and some include a magnetic thread. A paper sheet can be identified by measuring the magnetic properties of such a paper sheet using a magnetic detection device.

  For example, Patent Document 1 discloses a magnetic sensor used in a magnetic detection device. This magnetic sensor is composed of two rows and four anisotropic magnetoresistive elements (AMR). A bias magnetic field is applied by a permanent magnet, and a change in the magnetic field generated when the magnetic material passes through the bias magnetic field is detected by the magnetic sensor. Thereby, a magnetic body can be detected.

  In a line-type magnetic detection device using a plurality of magnetic sensors, a plurality of magnets for generating a magnetic field are arranged and used in a line shape. Then, above these magnets, a plurality of magnetic sensors are arranged so that the column direction of the anisotropic magnetoresistive elements arranged in two rows matches the arrangement direction of the magnets. In the magnetic sensor, when the magnet array is viewed from the side, the arrangement positions of all anisotropic magnetoresistive elements do not coincide with the positions where the magnetic field strength is 0 (zero), the minimum value, and the maximum value. The arrangement position is set in When the magnet rows are viewed from the row direction, the center lines between the two anisotropic magnetoresistive elements and the center lines between the magnet rows are arranged so as to coincide with each other. That is, the anisotropic magnetoresistive element is disposed so as to be symmetric with respect to the center line between the two magnet rows. Similarly, when the number of magnet rows is one, the anisotropic magnetoresistive elements are arranged so as to be symmetrical with respect to the center line of this magnet row.

US Patent Application Publication No. 2011/0148408

  However, according to the above-described prior art, it is possible to detect a magnetic body that passes a bias magnetic field by a magnetic sensor, but there is a problem that the amount of magnetism of the magnetic body cannot be measured.

  In a magnetic sensor using a plurality of anisotropic magnetoresistive elements, a bridge circuit is usually formed by a plurality of anisotropic magnetoresistive elements, and a change in the magnetic field is detected based on a change in the midpoint voltage. However, when a magnetic material is detected, the resistance value of each anisotropic magnetoresistive element varies depending on the magnetic field strength of the bias magnetic field at the position where the anisotropic magnetoresistive element is disposed. When the anisotropic magnetoresistive elements are arranged in two rows and the midpoint voltage between the rows is measured, if the magnetic field strength changes, the relationship between the voltage values output from the anisotropic magnetoresistive devices in each row changes. Therefore, the voltage waveform output as the midpoint voltage also changes in a complicated manner.

  The arrangement position of the anisotropic magnetoresistive element with respect to the magnet that generates the bias magnetic field is fixed by design, but includes variations due to manufacturing errors. In addition, since there are variations in the magnetic force of the magnet that generates the bias magnetic field and variations in the arrangement position of the magnet, the magnetic field strength at the arrangement position of the anisotropic magnetoresistive element may vary.

  As a result, even if the same magnetic material passes, the output voltage waveform differs depending on the magnetic sensor, and it can be detected that the magnetic material has passed based on the change in the voltage waveform, but it has passed based on the voltage waveform. It is difficult to measure the magnetic quantity of a magnetic material.

  To solve this, the magnetic field strength at the arrangement position of the anisotropic magnetoresistive elements arranged in two rows may be made constant, but it is difficult to make the magnetic forces of the permanent magnets that generate the bias magnetic field uniform. It is also difficult to correct the voltage waveform output from the magnetic sensor in consideration of the magnetic field strength, or to change the arrangement position of the anisotropic magnetoresistive element according to the magnetic field strength.

  The present invention has been made to solve the above-described problems caused by the prior art, and an object thereof is to provide a magnetic detection device capable of measuring the magnetic quantity of the magnetic material in addition to the detection of the magnetic material. To do.

  In order to solve the above-described problems and achieve the object, the present invention provides a magnetic detection device for detecting a magnetic body moving in a bias magnetic field based on a change in the magnetic field, and generating the bias magnetic field. And the direction in which the magnetic body moves in the bias magnetic field above the magnet unit and the magnetic sensitive direction coincide with each other, and the magnetic flux density of the magnetic sensitive direction component of the bias magnetic field is in the vicinity of 0 (zero). And an anisotropic magnetoresistive element for detecting a change in the magnetic field due to the passage of the magnetic material.

  Moreover, the present invention is characterized in that, in the above invention, the plurality of anisotropic magnetoresistive elements are arranged in a line in an array.

  Moreover, the present invention is characterized in that, in the above-mentioned invention, the magnet unit is formed by two or more rows of magnets arranged side by side in the magnetosensitive direction with magnetic poles having the same polarity facing upward.

  Further, the present invention is characterized in that, in the above invention, the magnet unit is formed by a row of magnets and a yoke for controlling a magnetic field distribution by the magnets.

  Further, according to the present invention, in the above invention, a half-bridge circuit is formed by connecting the anisotropic magnetoresistive element in series with a fixed resistor and applying a voltage, and based on the change in the midpoint voltage, the magnetic It is characterized by detecting the body.

  According to the present invention, the magnetic sensing direction of the anisotropic magnetoresistive element is matched to the moving direction of the magnetic substance to be detected, and the element of the bias magnetic field in the magnetic substance moving direction is close to 0 (zero). The magnetic material can be accurately detected without being affected by variations in the magnetic field intensity of the bias magnetic field, and the magnetic quantity of the magnetic material can be measured.

  In addition, according to the present invention, magnetic characteristics of a paper sheet or the like can be measured by arranging the anisotropic magnetoresistive elements in an array of one row.

  Further, according to the present invention, the direction and density of the magnetic flux at the measurement position can be measured by configuring the magnet unit that generates the bias magnetic field with, for example, two or more rows of magnets arranged with the north pole facing upward. An anisotropic magnetoresistive element can be arranged so as to be in an advantageous state.

  In the present invention, the yoke is used when the magnet units for generating the bias magnetic field are arranged in a row. Thus, the anisotropic magnetoresistive element can be arranged so that the direction and density of the magnetic flux at the measurement position are in an advantageous state for measurement.

  Further, according to the present invention, it is possible to measure the magnetic quantity of the magnetic material by forming a half bridge circuit using an anisotropic magnetoresistive element and a fixed resistance and measuring a change in the bias magnetic field.

FIG. 1 is a diagram showing a schematic configuration of a magnetic detection device according to the present invention. FIG. 2 is a diagram illustrating a configuration of the magnetic sensor according to the present embodiment and a configuration of a measurement circuit using the magnetic sensor. FIG. 3 is a diagram schematically showing a voltage waveform of the output voltage of the magnetic sensor according to the present embodiment. FIG. 4 is a diagram illustrating an example of a magnetic detection device having a different configuration of the magnetic sensor. FIG. 5 is a diagram illustrating a configuration of the magnetic sensor illustrated in FIG. 4 and a configuration of a measurement circuit using the magnetic sensor. FIG. 6 is a diagram showing an analysis surface of the bias magnetic field according to the present embodiment. FIG. 7 is a diagram showing a vector distribution of the bias magnetic field according to the present embodiment. FIG. 8 is a view showing the intensity distribution of the magnetic flux density of the bias magnetic field according to the present embodiment. FIG. 9 is a diagram showing the arrangement positions of the bias magnetic field magnet and the magnetic sensor according to the present embodiment. FIG. 10 is a diagram showing a plurality of analysis planes for analyzing the bias magnetic field according to the present embodiment. FIG. 11 is a diagram in which intensity distributions of magnetic flux densities of bias magnetic fields on a plurality of analysis surfaces are superimposed. FIG. 12 is a diagram illustrating an example of a magnetic detection device having a different configuration of the bias magnetic field magnet. FIG. 13 is a diagram illustrating an analysis example of the bias magnetic field of the magnetic detection device illustrated in FIG. 12. FIG. 14 is a diagram showing the arrangement positions of the bias magnetic field magnet and the magnetic sensor shown in FIG. FIG. 15 is a diagram illustrating an example of the present magnetic detection device that generates a bias magnetic field using a magnet and a yoke. FIG. 16 is a diagram illustrating an analysis example of the bias magnetic field of the magnetic detection device illustrated in FIG. 15. FIG. 17 is a diagram showing the arrangement positions of the bias magnetic field magnet and the magnetic sensor shown in FIG. FIG. 18 is a diagram showing a schematic configuration of a conventional magnetic detection device. FIG. 19 is a diagram illustrating a configuration of a conventional magnetic sensor and a configuration of a sensor circuit using the magnetic sensor. FIG. 20 is a diagram schematically showing the cause of variation in the voltage waveform of the output voltage of the conventional magnetic sensor. FIG. 21 is a diagram showing the cause of variation in sensor sensitivity of a conventional magnetic sensor.

  Hereinafter, a magnetic detection device according to the present invention will be described in detail with reference to the accompanying drawings. In order to clarify the features of the magnetic detection device according to the present embodiment, as a related technique, after describing a conventional magnetic detection device, the magnetic detection device according to the present embodiment will be described. In the following description, devices and components according to the present embodiment are denoted by reference numerals smaller than 200, and devices and components according to the related technology are denoted by reference numerals 200 or more to distinguish them. Yes.

  First, as a technique related to the present embodiment, a conventionally used magnetic detection device will be described with reference to FIGS. FIG. 18 is a diagram illustrating an example of a magnetic detection device 201 that has been conventionally used. 18A is a diagram of the magnetic detection device 201 viewed from the front (X-axis negative direction), and FIG. 18B is a diagram viewed from above (Z-axis positive direction). ) Is a view seen from the side (Y-axis positive direction).

  The magnetic detection device 201 includes a magnetic sensor 210 including anisotropic magnetoresistive elements 211 and 212 which are magnetosensitive elements, and magnets 221 and 222 for generating a bias magnetic field used for detection of a magnetic material by the magnetic sensor 210. And a mounting substrate 230 for mounting the magnetic sensor 210. The magnetic sensor 210 has a magnetic sensing direction of the anisotropic magnetoresistive elements 211 and 212 in the Y direction so as to detect a change in the bias magnetic field when the magnetic material passes in the Y axis direction above (Z axis positive direction). It arrange | positions so that it may become an axial direction.

  In the magnetic detection device 201, a plurality of magnets 221 and 222 are arranged in an array with the X-axis direction as the column direction, forming two rows of magnet rows. Similarly, a plurality of magnetic sensors 210 are arranged in an array in a row with the X-axis direction as the column direction. One mounting substrate 230 is disposed on the upper surface (Z-axis positive direction) side of the plurality of magnets 221 and 222 disposed in two rows, and the magnetic sensor 210 is disposed on the upper surface side of the mounting substrate 230. At this time, the magnetic sensor 210 is assembled so that the center line 220 between the two rows of anisotropic magnetoresistive elements 211 and 212 and the center line 220 between the two rows of magnets 221 and 222 coincide. That is, the anisotropic magnetoresistive elements 211 and 212 are arranged at positions symmetrical with respect to the center line 220 of the two magnet rows.

  FIG. 19 is a diagram illustrating an internal configuration of the magnetic sensor 210. As shown in FIG. 19A, in the magnetic sensor 210, two anisotropic magnetoresistive elements 211 and 212 arranged so as to be aligned in the Y-axis direction have the terminals 213a to 213c as shown in FIG. It is connected. Each magnetic sensor 210 forms a half-bridge circuit as shown in FIG. A voltage (+ V) is applied to the terminal 213a, the terminal 213c is grounded (GND), and the midpoint voltage of the anisotropic magnetoresistive elements 211 and 212 when the magnetic material is detected is set as the output voltage (Vout). Measure with Note that these circuits are formed using the mounting substrate 230 or provided outside the magnetic sensor 210 or the magnetic detection device 201.

  FIG. 20 is a diagram illustrating a measurement example of the output voltage (Vout) from the magnetic sensor 210. In FIG. 20, the vertical axis in the upper and middle diagrams shows the resistance value of the magnetoresistive element, and the vertical axis in the lower diagram shows the voltage value. The horizontal axis shows time in any figure. The magnetic sensor 210 is arranged such that the center line 220 between the two rows of anisotropic magnetoresistive elements 211 and 212 and the center line 220 between the two rows of magnets 221 and 222 coincide. The arrangement position is set so that the intensity of the bias magnetic field applied to the anisotropic magnetoresistive elements 211 and 212 is equal. When the magnetic material passes above the magnetic sensor 210 in the positive Y-axis direction shown in FIG. 18, the resistance value Rc of one anisotropic magnetoresistive element 211 changes as shown in the upper part of FIG. When the moving magnetic material passes over the other anisotropic magnetoresistive element 212, the resistance value Rd of the anisotropic magnetoresistive element 212 changes as shown in the middle part of FIG. At this time, each resistance value changes in the same way, but this change appears with a shift of the distance between the two elements. As a result, at the midpoint of the anisotropic magnetoresistive elements 211 and 212, the output voltage Vout is measured as the difference between the resistance values of Rc and Rd as shown in the lower part of FIG.

  However, due to an assembly error of the magnetic sensor 210, an assembly error of the magnets 221 and 222, a variation in the magnetic force of the magnets 221 and 222, etc., a difference occurs in the intensity of the bias magnetic field at the positions where the anisotropic magnetoresistive elements 211 and 212 are arranged. Thus, there is a difference in sensor sensitivity between the anisotropic magnetoresistive elements 211 and 212.

  FIG. 21 is a diagram showing an example of the sensitivity of a barber pole type anisotropic magnetoresistive element, with the horizontal axis representing the magnetic field strength and the vertical axis representing the output voltage of the anisotropic magnetoresistive element. If the magnetic field strength (position in the left-right direction on FIG. 21) at the positions where the anisotropic magnetoresistive elements 211 and 212 are different, for example, as shown in FIG. 21, the same magnetic material passes and the magnetic field strength becomes ΔHy. Even when it changes, the sensitivity Δrc of the anisotropic magnetoresistive element 211 becomes smaller than the sensitivity Δrd of the anisotropic magnetoresistive element 212. For this reason, even when the same magnetic body from which the measurement result shown in FIG. 20A is obtained passes through the same position, the resistance value Rc of the anisotropic magnetoresistive element 211 is shown in FIG. Shows a value lower than the resistance value Rd of the anisotropic magnetoresistive element 212. As a result, the measured output voltage Vout shows a different detection waveform as shown in FIGS. 20A and 20B even though the same magnetic material has passed.

  In addition, when the resistance value of the anisotropic magnetoresistive element 211 is larger than the resistance value of the anisotropic magnetoresistive element 212 due to the relationship of the magnetic field strength at the positions where the anisotropic magnetoresistive elements 211 and 212 are arranged, FIG. As shown in FIG. 20C, an output voltage Vout different from those shown in FIGS.

  As described above, in the magnetic detection device 201 shown in FIGS. 18 and 19, if the magnetic field strengths at the positions where the anisotropic magnetoresistive elements 211 and 212 are different due to assembly errors and variations in magnet magnetic force, the same magnetic material is used. Even when the signal is detected, the detection waveform of the output voltage Vout changes as shown in FIGS. For this reason, although the passage of the magnetic material can be detected based on the change in the detection waveform of the output voltage Vout, the relationship between the voltage value of the output voltage Vout and the magnetic amount of the magnetic material cannot be specified, and the magnetic amount Cannot be measured.

  Next, the magnetic detection device 1 according to this embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of the magnetic detection device 1. 1A is a diagram of the magnetic detection device 1 viewed from the front (X-axis negative direction), and FIG. 1B is a diagram viewed from above (Z-axis positive direction). ) Is a view seen from the side (Y-axis positive direction). The magnetic detection device 1 includes a magnetic sensor 10 including an anisotropic magnetoresistive element 11 that is a magnetosensitive element, and magnets 21 and 22 for generating a bias magnetic field used for magnetic substance detection and magnetic quantity measurement by the magnetic sensor 10. And a mounting substrate 30 for mounting the magnetic sensor 10. In the magnetic sensor 10, the anisotropic magnetic resistance element 11 has a magnetic sensitive direction in the Y-axis direction so as to detect a change in the bias magnetic field when the magnetic material passes in the Y-axis direction above (Z-axis positive direction). It is arranged to become. The signal output from the magnetic sensor 10 is processed by a signal processing board provided separately in the magnetic detection device 1.

  In the magnetic detection device 1, a plurality of magnets 21 and 22 are arranged in an array with the X-axis direction as a column direction to form two magnet rows. Similarly, a plurality of magnetic sensors 10 are arranged in an array in a row with the X-axis direction as the column direction. One mounting board 30 is arranged on the upper surface (Z-axis positive direction) side of the plurality of magnets 21 and 22 arranged in two rows, and the magnetic sensor 10 is arranged on the upper surface side of the mounting board 30. At this time, the magnetic sensor 10 is assembled such that the position of the anisotropic magnetoresistive element 11 is on the center line 20 between the two rows of magnets 21 and 22.

  As described above, in the magnetic detection device 1 according to the present embodiment, the magnetic sensor 10 has only one anisotropic magnetoresistive element 11 that is a magnetosensitive element, and the position of the anisotropic magnetoresistive element 11 is 2. The point which arrange | positions the magnetic sensor 10 so that it may be on a center line between the magnet rows of a row | line | column differs from the conventional magnetic detection apparatus 201. FIG. To be precise, the arrangement position of the anisotropic magnetoresistive element 11 is determined based on the magnetic field distribution of the bias magnetic field, and details thereof will be described later.

  FIG. 2 is a diagram illustrating an internal configuration of the magnetic sensor 10. As shown in FIG. 2A, in the magnetic sensor 10, one anisotropic magnetoresistive element 11 is disposed at the approximate center in the Y-axis direction and is connected to the terminals 13a and 13b. The terminals 13 a and 13 b of the magnetic sensor 10 are connected so as to form a half-bridge circuit shown in FIG. 2B by using the fixed resistor 12 included in the mounting substrate 30. Specifically, a voltage (+ V) is applied to the terminal 13 a and the terminal 13 b is connected to one end of the fixed resistor 12 provided on the mounting substrate 30. The other end of the fixed resistor 12 is grounded (GND), and the half-point voltage of the half bridge composed of the anisotropic magnetoresistive element 11 and the fixed resistor 12 when the magnetic material is detected is output as the output voltage (Vout). Measure at 13b.

  As described above, in the magnetic detection device 1 according to the present embodiment, the fixed resistor 12 that is a magnetosensitive element is used, and this is connected in series with the anisotropic magnetoresistive element 11 that is a magnetosensitive element. It differs from the conventional magnetic detector 201 in that a circuit is formed.

  FIG. 3 is a diagram illustrating a measurement example of the output voltage (Vout) from the magnetic sensor 10. In FIG. 3, the vertical axis in the upper and middle diagrams shows the resistance value of the magnetoresistive element, and the vertical axis in the lower diagram shows the voltage value. The horizontal axis shows time in all the figures. When the magnetic material passes above the anisotropic magnetoresistive element 11 in the positive direction of the Y axis shown in FIG. 1, the resistance value Ra of the anisotropic magnetoresistive element 11 depends on the amount of magnetism of the magnetic material. 3 Changes as shown in the upper part. On the other hand, the resistance value Rb of the fixed resistor 12 is constant and not affected by the magnetic material as shown in the middle part of FIG. As a result, at the midpoint between Ra and Rb, the output voltage Vout is measured as the difference between the resistance values of Ra and Rb as shown in the lower part of FIG.

  Even when the intensity of the bias magnetic field is deviated from the design value due to the displacement (assembly error) of the arrangement position of the anisotropic magnetoresistive element 11 and the magnetic force variation of the magnet, the resistance value Ra of the anisotropic magnetoresistive element 11 changes. The resistance value Rb of the fixed resistor 12 does not change. For this reason, although the output voltage Vout changes due to the change in the bias magnetic field intensity, the detection waveform of the output voltage Vout does not change in a complicated manner unlike the conventional magnetic detection device 201 shown in FIG.

  Thus, since the magnetic detection apparatus 1 according to the present embodiment includes only one anisotropic magnetoresistive element 11 that is a magnetosensitive element, even when there is an assembly error, a variation in the magnetic force of the magnet, or the like, The resistance value of the anisotropic magnetoresistive element 11 only changes. Only the value of the output voltage Vout changes, and the detected waveform is not affected. Further, this voltage change can be easily adjusted by, for example, gain adjustment by software processing. For this reason, it is possible to adjust the gain of the amplifier of the output voltage Vout to obtain the output voltage Vout corresponding to the magnetic quantity of the magnetic material. That is, the magnetic detection device 1 according to the present embodiment can not only detect the magnetic material but also measure the magnetic amount of the detected magnetic material. Thus, the magnetic detection device 1 has a function of performing gain adjustment. This gain adjusting means can also be used as means for correcting variation in sensitivity between channels when the magnetic sensor 10 is arrayed.

  Note that the magnetic detection device 1 according to the present embodiment is not limited to a mode in which the fixed resistor 12 used as a magnetosensitive element is provided on the mounting substrate 30 as shown in FIGS. 1 and 2. For example, the magnetic sensor may include a fixed resistor. A configuration when the magnetic sensor includes a fixed resistor will be described with reference to FIGS.

  FIG. 4 is a diagram showing a different aspect of the magnetic detection device 1. As described above, the magnetic detection device 1 may be configured to use the magnetic sensor 110 including both the anisotropic magnetoresistive element 111 that is a magnetosensitive element and the fixed resistor 112 that is a magnetosensitive element. Also in this case, the magnetic sensor 110 is arranged so that the position of the anisotropic magnetoresistive element 111 is on the center line 20 between the two rows of magnets 21 and 22, and a measurement circuit as shown in FIG. May be configured.

  FIG. 5 is a diagram showing an internal configuration of the magnetic sensor 110 shown in FIG. As shown in FIG. 5A, the anisotropic magnetoresistive element 111 and the fixed resistor 112 are connected inside the magnetic sensor 110 to form a half-bridge circuit as shown in FIG. 5B. Thereby, as in the case of the magnetic sensor 10 shown in FIGS. 1 and 2, the resistance value changes due to the passage of the magnetic material, and the output voltage Vout can be measured as shown in FIG.

  Next, details of the method for setting the arrangement position of the magnetosensitive element in the magnetic detection device 1 will be described. FIG. 6 is a schematic diagram showing an analysis surface 40 for analyzing the magnetic field distribution in order to determine the arrangement position of the anisotropic magnetoresistive element 11. The analysis surface 40 is set to include a position where the magnetic body 300 passes above the anisotropic magnetoresistive element 11 and the magnets (21 and 22). In FIG. 6, the arrangement positions of the conventional anisotropic magnetoresistive elements 211 and 212 are indicated by broken lines for comparison with the conventional magnetic detection device 201.

  The anisotropic magnetoresistive element 11 is arranged so that the magnetosensitive direction coincides with the Y-axis direction. And the detection of the magnetic body 300 which passes the upper direction in the Y-axis direction, and the measurement of a magnetic quantity are performed. In the magnetic detection device 1, the anisotropic magnetoresistive element 11 is disposed on the center line 20 above the two rows of magnets 21 and 22 (in the positive Z-axis direction). It is set based on the magnetic field distribution of the bias magnetic field.

  Specifically, in order to accurately measure the change in the bias magnetic field in the Y-axis direction, the anisotropic magnetoresistive element 11 that is a magnetosensitive element is used so that the direction of the YZ component vector of the bias magnetic field is substantially parallel to the Z-axis. It is preferable to arrange at a position, in other words, at a position where the magnetic field strength in the Y-axis direction is near 0 (zero).

  FIG. 7 is a diagram showing the YZ component vector of the bias magnetic field. As shown in FIG. 6, this distribution chart shows a vector distribution in the analysis surface 40 set above the magnets 21 and 22. FIG. 7 shows the arrangement position 51 of the anisotropic magnetoresistive element 11 of the magnetic detection device 1 according to the present embodiment and the arrangement positions 251 and 252 of the anisotropic magnetoresistive elements 211 and 212 of the conventional apparatus. .

  As described above, in the conventional device, the two anisotropic magnetoresistive elements 211 and 212 are arranged at the positions 251 and 252 in which the direction of the magnetic field vector has an angle with respect to the Z axis. On the other hand, in the magnetic detection apparatus 1 according to the present embodiment, the anisotropic magnetoresistive element 11 is disposed at a position 51 where the direction of the magnetic field vector is substantially parallel to the Z axis.

  FIG. 8 is a diagram showing the intensity distribution of the magnetic flux density in the Y-axis direction. In consideration of the assembly error, the positions 251 and 252 where the anisotropic magnetoresistive elements 211 and 212 of the conventional device are arranged can take any position within the rectangular regions 261 and 262 shown in FIG. 8, for example. It will be. In the conventional apparatus, since the two anisotropic magnetoresistive elements 211 and 212 are set to be arranged at the positions 251 and 252 where the distribution of the magnetic flux density is dense, the arrangement positions in the rectangular regions 261 and 262 are If they are different, the magnetic field strength changes greatly. As a result, the sensitivity of the anisotropic magnetoresistive elements 211 and 212 and the output voltage Vout of the magnetic sensor 210 vary as shown in FIGS.

  On the other hand, in the magnetic detection device 1 according to the present embodiment, the anisotropic magnetoresistive element 11 is arranged at a position 51 where the magnetic flux density is near 0 (zero). For this reason, even when the arrangement position 51 changes in the rectangular area 61 in consideration of the assembly error similar to the conventional apparatus, the influence due to the change in the magnetic flux density is small. Further, even when the magnetic force of the magnets 21 and 22 is changed, the influence of the change in the magnetic flux density is also small.

  In this way, the anisotropic magnetoresistive element 11 whose magnetic sensing direction is the Y-axis direction is applied to a position where the direction of the magnetic field vector in the YZ plane is substantially parallel to the Z-axis direction, that is, the magnetic field strength in the Y-axis direction is 0 By disposing at the position 51 in the vicinity of (zero), it is possible to suppress the effects of assembly errors and variations in the magnetic force of the magnets 21 and 22. For this reason, it is possible to detect a magnetic body moving in the Y-axis direction and measure the amount of magnetic force. Specifically, it is preferable that the magnetic field strength in the magnetosensitive direction in which the anisotropic magnetoresistive element 11 is disposed is ± 1 mT or less.

  FIG. 9 is a diagram showing an example of the distribution of the bias magnetic field by the two rows of magnets 21 and 22 and the arrangement position 51 of the anisotropic magnetoresistive element 11 with respect to the magnets 21 and 22. When the arrangement position 51 of the anisotropic magnetoresistive element 11 is determined in consideration of the bias magnetic field, the positions of the magnetic sensor 10 and the magnets 21 and 22 are determined in order to arrange the anisotropic magnetoresistive element 11 at this position 51. Adjusted. The position of the magnetic sensor 10 is adjusted by the mounting substrate 30 between the magnets 21 and 22, but if the position cannot be adjusted only by the mounting substrate 30, a spacer may be provided on the lower surface of the mounting substrate 30, or the mounting substrate The position is adjusted by changing the plate thickness of 30.

  In addition, the arrangement position 51 of the anisotropic magnetoresistive element 11 is not limited to an aspect set in consideration of the magnetic field distribution on one analysis plane, but in an aspect set in consideration of the magnetic field distribution on a plurality of analysis planes. It does not matter. For example, as shown in FIG. 10, a plurality of analysis surfaces 41a to 41c are set at positions where the anisotropic magnetoresistive element 11 is arranged, and the anisotropic magnetism is taken into consideration in consideration of the analysis results on these setting surfaces. The arrangement position of the resistance element 11 is determined. Specifically, as shown in FIG. 11, the magnetic flux density distribution in the Y-axis direction on the plurality of analysis surfaces 41a to 41c is synthesized, and from this result, the position where the magnetic flux density is near 0 (zero) is anisotropic. The position 51 of the magnetoresistive element 11 is assumed.

  Moreover, although the case where the magnetic detection apparatus 1 generate | occur | produces a bias magnetic field using the magnets 21 and 22 of 2 rows was shown, this embodiment is not limited to this. For example, as a magnet unit that generates a bias magnetic field, in addition to an aspect using two rows of magnets, three or more rows of magnets may be used, or one row of magnets and a yoke may be used. Absent.

  Specifically, as shown in FIG. 12, three rows of magnets 21 to 23 may be used. Even in this case, the arrangement position 51 of the anisotropic magnetoresistive element 11 is set in consideration of the magnetic flux density distribution in the Y-axis direction as shown in FIG. And the anisotropic magnetoresistive element 11 should just be arrange | positioned so that the positional relationship of the anisotropic magnetoresistive element 11 and the magnets 21-23 may become the relationship shown in FIG.

  Further, as shown in FIG. 15, a row of magnets 25 and a yoke 70 having a concave shape when viewed from the X-axis direction may be used. Even in this case, the arrangement position 51 of the anisotropic magnetoresistive element 11 is set in consideration of the magnetic flux density distribution in the Y-axis direction as shown in FIG. Then, the anisotropic magnetoresistive element 11 may be arranged so that the positional relationship between the anisotropic magnetoresistive element 11 and the magnet 25 and the yoke 70 becomes the relationship shown in FIG. 13 and 16 are set in consideration of the same assembly error, but the anisotropic magnetoresistive element 11 can be arranged in FIG. This area is wider than in FIG. That is, as shown in FIG. 15, when the magnet 25 and the yoke 70 are used, the range in which the anisotropic magnetoresistive element 11 can be disposed is widened.

  As described above, according to the present embodiment, one anisotropic magnetoresistive element 11 that is a magnetosensitive element used in the magnetic sensor 10 is used, and the magnetic sensitive direction of the anisotropic magnetoresistive element 11 is detected. By matching the moving direction of the target magnetic body and setting the position of the anisotropic magnetoresistive element 11 at a position where the magnetic flux density in the magnetosensitive direction is near 0 (zero), it is possible to detect the passing magnetic body. In addition, the amount of magnetism of the magnetic material can be measured. Since the anisotropic magnetoresistive element 11 is disposed at a position that is not easily affected by the change of the bias magnetic field, accurate measurement can be performed even when the disposed position of the anisotropic magnetoresistive element 11 is shifted due to an assembly error. It becomes possible.

  In addition, since it is possible to accurately detect the position and magnetic quantity of the magnetic material, for example, when characters and symbols are formed on the paper using a magnetic material such as magnetic ink, These characters and symbols can be recognized.

  As described above, the present invention is a useful technique for detecting a magnetic material and detecting the magnetic quantity of the magnetic material.

1,201 Magnetic detection device 10, 110, 210 Magnetic sensor 11, 111, 211, 212 Anisotropic magnetoresistive element 12, 112 Fixed resistance 21-25, 221, 222 Magnet 30, 230 Mounting substrate 70 Yoke 300 Magnetic body

Claims (5)

A magnetic detection device for detecting a magnetic body moving in a bias magnetic field based on a change in the magnetic field,
A magnet unit for generating the bias magnetic field;
Position where the direction in which the magnetic body moves in the bias magnetic field above the magnet unit coincides with the magnetic sensitive direction, and the magnetic flux density of the magnetic sensitive direction component of the bias magnetic field is near 0 (zero). And an anisotropic magnetoresistive element for detecting a change in the magnetic field due to the passage of the magnetic body.   The magnetic detection device according to claim 1, wherein the plurality of anisotropic magnetoresistive elements are arranged in a line in an array.   3. The magnetic detection device according to claim 1, wherein the magnet unit is formed by two or more rows of magnets arranged with the same polarity magnetic poles facing upward in the magnetic sensing direction. 4.   The magnetic detection device according to claim 1, wherein the magnet unit is formed by a row of magnets and a yoke for controlling a magnetic field distribution by the magnets.   A half-bridge circuit is formed by applying a voltage by connecting the anisotropic magnetoresistive element in series with a fixed resistor, and detecting the magnetic body based on a change in a midpoint voltage thereof. Item 5. The magnetic detection device according to any one of Items 1 to 4.

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