Magnetic sensor, electrical control device, correction method, and method for manufacturing a magnetic sensor

Abstract

To provide a magnetic sensor whose output signal has good linearity regardless of the direction of an applied external magnetic field, an electric control device using the same, a method of correcting the output signal of the magnetic sensor, and a method of manufacturing the magnetic sensor.SOLUTION: A magnetic sensor includes a magnetic detection unit that outputs a signal by applying a magnetic field and a signal correction unit that corrects a signal output from the magnetic detection unit. The magnetic detection unit includes a magnetoresistive element having a predetermined sensitivity axis. The signal correction unit corrects the signal using a correction value capable of reducing distortion error included in the signal when the magnetic field in a cross direction crossing the sensitivity axis is applied to the magnetoresistive element, and generates a corrected signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic sensor, an electrical control device using the same, a method for correcting the output signal of a magnetic sensor, and a method for manufacturing a magnetic sensor. [Background technology]

[0002] In recent years, position detection devices for detecting the position, amount of movement (amount of change), and orientation of moving objects due to linear movement have been used in various applications. Position detection devices known to include a magnetic sensor unit that outputs a signal based on an applied magnetic field are common. Examples of magnetic sensor units include a laminate having a free layer and a magnetized fixed layer, and containing a magnetoresistive element (MR element) whose resistance changes in accordance with the change in the easy axis direction of the magnetization of the free layer in response to an external magnetic field.

[0003] Some magnetoresistive elements in the above-mentioned magnetic sensor section have a sensitivity axis parallel to the magnetization direction of the magnetized fixed layer. When an external magnetic field is applied to the magnetoresistive element in a direction along this sensitivity axis, a signal corresponding to the magnetic field strength of the external magnetic field is output. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-117184 [Overview of the project] [Problems that the invention aims to solve]

[0005] Depending on the operating environment of the above-mentioned position detection device, an external magnetic field that intersects the sensitivity axis at an angle (hereinafter sometimes referred to as an "oblique magnetic field") may be applied to the magnetoresistive element. In this case, the distortion caused by higher-order harmonic components, such as the third-order harmonic component, included in the signal output from the magnetic sensor unit becomes large. As a result, there is a problem in that the linearity of the output signal from the magnetic sensor unit deteriorates when an oblique magnetic field is applied to the magnetoresistive element.

[0006] In view of the above problems, the present invention aims to provide a magnetic sensor with good linearity of the output signal regardless of the direction of the applied external magnetic field, an electrical control device using the same, a method for correcting the output signal of a magnetic sensor, and a method for manufacturing a magnetic sensor. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a magnetic sensor comprising a magnetic detection unit that outputs a signal when a magnetic field is applied, and a signal correction unit that corrects the signal output from the magnetic detection unit, wherein the magnetic detection unit includes a magnetoresistive element having a predetermined sensitivity axis, and the signal correction unit corrects the signal using a correction value that can reduce the distortion error contained in the signal output from the magnetic detection unit when the magnetic field in an intersecting direction that is tilted and intersecting with respect to the sensitivity axis is applied to the magnetoresistive element, thereby generating a corrected signal.

[0008] In the magnetic sensor described above, the magnetic detection unit may include a magnetoresistive element having the sensitivity axis on the first axis. The magnetoresistive element may also include a first magnetoresistive element and a second magnetoresistive element, wherein the sensitivity axis of the first magnetoresistive element is parallel to the first axis, the sensitivity axis of the second magnetoresistive element is parallel to the second axis, the first axis and the second axis are orthogonal to each other, and the direction of intersection may be a direction that intersects both the first axis and the second axis at an inclination.

[0009] In the magnetic sensor described above, the signal correction unit may add the inverse distortion of the distortion error as the correction value to the signal, or it may correct the signal using the following formula (1) to generate the corrected signal. V'=V+V 3 ×a ···(1) In the above formula (1), V represents "the signal output from the magnetic detection unit", V' represents "the correction signal", and a represents "the correction coefficient".

[0010] The present invention provides an electrical control device characterized by comprising the above-mentioned magnetic sensor. The present invention provides a method for correcting a signal output from a magnetic detection unit, which includes a magnetoresistive element having a predetermined sensitivity axis and a magnetic detection unit that outputs a signal when a magnetic field is applied to the magnetoresistive element, the method comprising the steps of: acquiring the signal output from the magnetic detection unit; and correcting the signal acquired in the first step so as to reduce the distortion error included in the signal when a magnetic field in a crossing direction intersecting the sensitivity axis is applied to the magnetoresistive element.

[0011] The present invention provides a method for manufacturing a magnetic sensor comprising a magnetoresistive element having a predetermined sensitivity axis, a magnetic detection unit that outputs a signal when a magnetic field is applied to the magnetoresistive element, and a signal correction unit that corrects the signal output from the magnetic detection unit, the method comprising the steps of: applying a test magnetic field to the magnetic detection unit in a direction intersecting the sensitivity axis of the magnetoresistive element; and determining a correction value that can reduce the distortion error included in the test signal based on the test signal output from the magnetic detection unit in response to the application of the test magnetic field. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a magnetic sensor with good linearity of the output signal regardless of the direction of the applied external magnetic field, an electrical control device using the same, a method for correcting the output signal of a magnetic sensor, and a method for manufacturing a magnetic sensor.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a magnetic sensor according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a circuit diagram showing a schematic configuration of a magnetic detection unit in an embodiment of the present invention. [Figure 2B] FIG. 2B is a circuit diagram showing a schematic configuration of another aspect of the magnetic detection unit in an embodiment of the present invention. [Figure 3] FIG. 3 is a perspective view showing a schematic configuration of a magnetoresistive element in an embodiment of the present invention. [Figure 4] FIG. 4 is a block diagram showing a schematic configuration of another aspect of the magnetic sensor according to an embodiment of the present invention. [Figure 5] FIG. 5 is a graph showing the results of Test Example 1. [Figure 6] FIG. 6 is a graph showing the results of Test Example 2. [Figure 7] FIG. 7 is a graph showing the results of Test Example 3. [Figure 8] FIG. 8 is a graph showing the results of Test Example 3.

Embodiments for Carrying Out the Invention

[0014] The magnetic sensor according to the embodiment of the present invention will be described with reference to the drawings. In this embodiment, a current sensor as a magnetic sensor will be described as an example, but the magnetic sensor according to this embodiment is not limited to a current sensor.

[0015] In describing this embodiment, the terms "first axis and second axis" are defined in some drawings as needed. Here, the first axis is parallel to the sensitivity axis of the magnetoresistive element. The second axis is perpendicular to the first axis. In this specification and drawings, the first axis may be referred to as the "X axis" and the second axis as the "Y axis". In this specification, "orthogonal" is a concept that includes not only two line segments, axes, directions, etc. intersecting at a perfect 90° angle, but also being nearly orthogonal, that is, intersecting with a slight deviation from 90° (intersection angle within the range of 90° ± 5°), and "parallel" is a concept that includes not only two line segments, axes, directions, etc., being perfectly parallel, but also being nearly parallel (intersection angle within the range of 5° or less).

[0016] As shown in Figure 1, the magnetic sensor 1 according to this embodiment includes a magnetic detection unit 2 that outputs a signal S when a magnetic field is applied, and a signal processing unit 3 that processes the signal S output from the magnetic detection unit 2. The magnetic sensor 1 according to this embodiment may be formed as a single chip with the magnetic detection unit 2 and the signal processing unit 3 integrally (monolithically), or it may be formed as a single chip with the magnetic detection unit 2 and the signal processing unit 3 resin-encapsulated, or it may be formed as a single chip with the magnetic detection unit 2 and the signal processing unit 3 resin-encapsulated separately and independently.

[0017] As shown in Figures 2A and 2B, the magnetic detection unit 2 may include, for example, multiple element sections 20 (e.g., first to fourth element sections 21 to 24), or it may include only one element section 20. If multiple element sections 20 are included, the magnetic detection unit 2 may be configured as a Wheatstone bridge circuit C made up of the multiple element sections 20 (a full bridge circuit made up of the first to fourth element sections 21 to 24 (see Figure 2A) or a half bridge circuit made up of the first element section 21 and the second element section 22 (see Figure 2B)). The Wheatstone bridge circuit C shown in Figure 2A includes a power port V, a ground port G, two output ports E1 and E2, and the first to fourth element sections 21 to 24. One end of the first element section 21 and the fourth element section 24 are connected to the power port V. The other end of the first element section 21 is connected to one end of the second element section 22 and to output port E1. The other end of the fourth element section 24 is connected to one end of the third element section 23 and to the output port E2. The other ends of the second element section 22 and the third element section 23 are connected to the ground port G. A predetermined power supply voltage is applied to the power supply port V, and the ground port G is connected to ground.

[0018] In this embodiment, as shown in Figure 3, the element section 20 includes a plurality of magnetoresistive elements 40 connected in series. Each of the plurality of magnetoresistive elements 40 is, for example, a spin valve type magnetoresistive element. In this embodiment, the element section 20 has a plurality of magnetoresistive elements 40 that are substantially oval-shaped in plan view, connected via a first lead electrode 51 and a second lead electrode 52 (see Figure 3).

[0019] The spin valve type magnetoresistive element 40 includes an antiferromagnetic layer 41, a magnetization-fixed layer 42, a non-magnetic layer 43, and a free layer 44, which are stacked in order from the substrate side (not shown). In the embodiment shown in Figure 3, the free layer 44 is electrically connected to the first lead electrode 51, and the antiferromagnetic layer 41 is electrically connected to the second lead electrode 52. The antiferromagnetic layer 41 is made of an antiferromagnetic material and plays a role in fixing the direction of magnetization of the magnetization-fixed layer 42 by creating exchange coupling with the magnetization-fixed layer 42. The magnetoresistive element 40 may also have a configuration in which the free layer 44, non-magnetic layer 43, magnetization-fixed layer 42, and antiferromagnetic layer 41 are stacked in order from the substrate side. Furthermore, the antiferromagnetic layer 41 may be omitted by making the magnetization fixed layer 42 a so-called self-pinned fixed layer (Synthetic Ferri Pinned layer, SFP layer) with a stacked ferri structure of a ferromagnetic layer / non-magnetic intermediate layer / ferromagnetic layer, and the two ferromagnetic layers antiferromagnetically coupled. In the embodiment shown in Figure 3, the magnetoresistive element 40 may include a cap layer located between the free layer 44 and the first lead electrode 51, or it may include a base layer located between the antiferromagnetic layer 41 and the second lead electrode 52. The spin valve type magnetoresistive element 40 may be a TMR element or a GMR element. In a TMR element, the non-magnetic layer 43 is a tunnel barrier layer. In a GMR element, the non-magnetic layer 43 is a non-magnetic conductive layer. In the spin valve type magnetoresistive element 40, the resistance value changes according to the angle that the magnetization direction of the free layer 44 makes with respect to the magnetization direction of the magnetized fixed layer 42. The resistance value is at its minimum when this angle is 0° and at its maximum when it is 180°.

[0020] In this embodiment, the magnetization direction of the magnetization fixed layer 42 of the magnetoresistive element 40 is fixed in a direction parallel to the X-axis. In the embodiment shown in Figure 2A, the magnetization direction of the magnetization fixed layer 42 of the magnetoresistive element 40 of the first element section 21 and the third element section 23 is the "+X direction", and the magnetization direction of the magnetization fixed layer 42 of the magnetoresistive element 40 of the second element section 22 and the fourth element section 24 is the "-X direction". In Figure 2A, the magnetization direction of the magnetization fixed layer 42 of the magnetoresistive element 40 of the first to fourth element sections 21 to 24 is indicated by arrows. The magnetization direction of the magnetization fixed layer 42 of the magnetoresistive element 40 of the first to fourth element sections 21 to 24 is parallel to the minor axis direction or minor side direction of the magnetoresistive element 40, which is approximately oval or rectangular in shape in a plan view. In other words, the sensitivity axis of the magnetoresistive elements 40 of the first to fourth element sections 21 to 24 is parallel to the X-axis.

[0021] In this embodiment, the magnetization direction of the free layer 44 of the magnetoresistive element 40 in its initial state (when no magnetic field to be detected by the magnetic detection unit 2 is applied) is parallel to the Y axis. In the embodiment shown in Figure 2A, the easy magnetization axis direction of the free layer 44 of the magnetoresistive element 40 in the first element section 21 and the fourth element section 24 is the "-Y direction", and the easy magnetization axis direction of the free layer 44 of the magnetoresistive element 40 in the second element section 22 and the third element section 23 is the "+Y direction". In this embodiment, the easy magnetization axis direction of the free layer 44 of the magnetoresistive element 40 in the first to fourth element sections 21 to 24 is parallel to the major axis direction of the substantially oval-shaped magnetoresistive element 40 in a plan view. Note that the easy magnetization axis direction of the free layer 44 of the magnetoresistive element 40 in the first to fourth element sections 21 to 24 may all be either the "+Y direction" or the "-Y direction". If the shape of the magnetoresistive element 40 in plan view is elongated in the direction parallel to the Y direction in plan view, for example, an oval shape or an oblong shape, the easy magnetization axis direction of the free layer 44 tends to be "+Y direction" or "-Y direction" due to shape magnetic anisotropy. However, instead of relying on shape magnetic anisotropy, or in addition to it, a bias magnetic field generating unit (not shown) such as a hard magnet may be provided, and a bias magnetic field applied to the free layer 44 may be made to have the easy magnetization axis direction of the free layer 44 be "+Y direction" or "-Y direction".

[0022] In the magnetic detection unit 2, as a magnetic field is applied to each of the magnetoresistive elements 40 of the first to fourth element units 21 to 24, the potential difference between the output ports E1 and E2 changes, and a difference detector (not shown) outputs a signal S corresponding to the potential difference between the output ports E1 and E2 to the signal processing unit 3 as a signal representing the magnetic field strength.

[0023] The signal processing unit 3 only needs to include an A / D (analog-to-digital) conversion unit 31 that converts the analog signal output from the magnetic detection unit 2 into a digital signal, and an arithmetic unit 32 that performs arithmetic processing on the digital signal converted by the A / D conversion unit 31.

[0024] The signal S (analog signal) output from the magnetic detection unit 2 is converted into a digital signal by the A / D conversion unit 31, and this digital signal is input to the calculation unit 32. The calculation unit 32 performs correction processing to correct the digital signal converted from the analog signal by the A / D conversion unit 31 to generate a corrected signal, or performs calculation processing based on this corrected signal. This calculation unit 32 is composed of, for example, a microcomputer, an ASIC (Application Specific Integrated Circuit), etc. In this embodiment, the calculation unit 32 or the signal processing unit 3 including the calculation unit 32 constitutes the signal correction unit.

[0025] In the magnetic sensor 1 having the above configuration, when a magnetic field parallel to the sensitivity axis (X-axis) of the magnetoresistive element 40 of the magnetic detection unit 2 is applied to the magnetoresistive element 40, the signal S output from the magnetic detection unit 2 substantially does not contain distortion errors due to higher-order harmonic components such as third-order harmonic components. "Substantially does not contain distortion errors" means that even if the signal S contains distortion errors, it is permissible to include distortion errors to the extent that they do not cause errors in the physical quantities or directions determined based on the signal S. On the other hand, when a magnetic field that is inclined to intersect the sensitivity axis (X-axis) of the magnetoresistive element 40 (intersecting at an angle greater than 0° and less than 90° with respect to the X-axis) and parallel to the XY plane (oblique magnetic field) is applied, the signal S output from the magnetic detection unit 2 contains distortion errors due to higher-order harmonic components such as third-order harmonic components. The distortion errors included in this signal S are of a degree that causes unacceptable errors in the physical quantities or directions determined based on the signal S. Furthermore, the magnitude of the distortion error included in signal S depends on the angle at which the oblique magnetic field intersects the sensitivity axis (X-axis). Therefore, when the oblique magnetic field is applied to the magnetoresistive element 40, the output signal from the magnetic sensor 1 changes depending on the angle of the oblique magnetic field with respect to the sensitivity axis (X-axis), and there is a risk that the linearity of the output signal from the magnetic sensor 1 will deteriorate.

[0026] In the magnetic sensor 1 according to this embodiment, even when the oblique magnetic field is applied to the magnetoresistive element 40, the signal S output from the magnetic detection unit 2 is corrected by the calculation unit 32 of the signal processing unit 3, and a corrected signal S' is output. Therefore, the linearity of the output signal from the magnetic sensor 1 can be improved.

[0027] The signal correction process in the calculation unit 32 will now be explained. The calculation unit 32 corrects the signal S output from the magnetic detection unit 2 using a predetermined correction value and generates a corrected signal S'.

[0028] The above correction value is a magnetic field that intersects the sensitivity axis (X-axis) of the magnetoresistive element 40 at an angle greater than 0° and less than 90° with respect to the X-axis, and is a correction value that can reduce the distortion error included in the signal S when a magnetic field parallel to the XY plane (oblique magnetic field) is applied to the magnetoresistive element 40. Specifically, the calculation unit 32 may, for example, correct the signal S using the following formula (1) to generate a corrected signal S'. V'=V+V 3 ×a ···(1) In the above formula (1), V represents the signal S output from the magnetic detection unit 2, V' represents the correction signal S', and a represents the correction coefficient (correction value).

[0029] When an oblique magnetic field intersects the sensitivity axis (X-axis) of the magnetoresistive element 40 at 45°, the distortion error included in the signal S output from the magnetic detection unit 2 reaches its maximum value. Therefore, it is preferable that "a", which represents the correction coefficient in the above formula (1), be set to a value that can reduce the distortion error included in the signal S by half when an oblique magnetic field intersecting the sensitivity axis (X-axis) of the magnetoresistive element 40 is applied to the magnetoresistive element 40. That is, the signal S is corrected by adding inverse distortion due to the third harmonic component so that the distortion error included in the signal S when a magnetic field parallel to the sensitivity axis (X-axis) is applied to the magnetoresistive element 40 is the same as the distortion error included in the signal S when a magnetic field intersecting the sensitivity axis (X-axis) at 45° is applied to the magnetoresistive element 40, and a corrected signal S' is generated. By setting a correction coefficient (correction value) that can reduce the distortion error in the signal S by half when an oblique magnetic field intersecting at 45° is applied to the magnetoresistive element 40, and generating a corrected signal S' using the above formula (1), the distortion error in the signal S can be stabilized regardless of the angle at which the magnetic field applied to the magnetoresistive element 40 intersects with respect to the sensitivity axis (X axis) of the magnetoresistive element 40. Therefore, the linearity of the output signal from the magnetic sensor 1 can be improved regardless of the angle of the magnetic field applied to the magnetoresistive element 40 with respect to the sensitivity axis (X axis). When correcting the signal S by adding inverse distortion due to the third harmonic component, it is desirable that the distortion error in the signal S when a magnetic field parallel to the sensitivity axis (X axis) is applied to the magnetoresistive element 40 be the same as the distortion error in the signal S when a magnetic field intersecting the sensitivity axis (X axis) at 45° is applied to the magnetoresistive element 40. However, the signal S may be corrected by adding inverse distortion due to the third harmonic component so as to reduce the distortion error in the signal S when a magnetic field intersecting the sensitivity axis (X axis) at 45° is applied to the magnetoresistive element 40.

[0030] The magnetic sensor 1 according to this embodiment may include a magnetic detection unit 2, which includes a first magnetic detection unit 2A and a second magnetic detection unit 2B, and a signal processing unit 3, as shown in Figure 4. The first magnetic detection unit 2A may have a first magnetoresistive element 40 whose sensitivity axis is parallel to the X axis, and the second magnetic detection unit 2B may have a second magnetoresistive element 40 whose sensitivity axis is parallel to the Y axis. The first magnetic detection unit 2A is for detecting a magnetic field parallel to the X axis, and the second magnetic detection unit 2B is for detecting a magnetic field parallel to the Y axis. However, if a magnetic field that is tilted and intersects both the X axis and the Y axis is applied to the magnetoresistive elements 40 of the first magnetic detection unit 2A and the second magnetic detection unit 2B, the distortion errors included in the signals S output from the first magnetic detection unit 2A and the second magnetic detection unit 2B will be superimposed, which may further worsen the linearity of the output signal from the magnetic sensor 1. In this embodiment, the magnetic sensor 1 corrects the signal S using a correction value that can reduce the distortion error contained in the signal S output from the first magnetic detection unit 2A and the second magnetic detection unit 2B when an oblique magnetic field is applied, and generates a corrected signal S'. Therefore, the linearity of the output signal from the magnetic sensor 1 can be improved regardless of the angle of the magnetic field applied to the magnetoresistive element 40 with respect to the sensitivity axis.

[0031] The magnetic sensor 1 according to this embodiment can be manufactured, for example, as follows. First, a first lead electrode 51, a second lead electrode 52, and a magnetoresistive element 40 are formed on the substrate. When forming the magnetoresistive element 40, the magnetization of the magnetization fixing layer 42 is fixed in a direction parallel to the minor axis direction of the magnetoresistive element 40, which is approximately oval-shaped in a plan view.

[0032] Next, a test magnetic field intersecting the sensitivity axis of the magnetoresistive element 40 (the magnetization direction of the magnetization fixed layer 42) at a 45° angle is applied to the magnetoresistive element 40, and a test signal output from the magnetic detection unit 2 in response to the application of the test magnetic field is acquired. This test signal contains distortion errors due to third-harmonic components associated with the application of the oblique magnetic field. Therefore, a correction coefficient (correction value) that can reduce this distortion error by half is determined. Then, a signal processing unit 3 is created that stores the correction coefficient (correction value) obtained in this way. This allows the magnetic sensor 1 according to this embodiment to be manufactured.

[0033] The magnetic sensor 1 according to this embodiment may be provided in an electrical control device. Examples of electrical control devices in this embodiment include a magnetic field strength sensor, a Gauss meter, an electronic compass, and a linear encoder. As described above, the magnetic sensor 1 in this embodiment can output a signal with good linearity regardless of the angle of the magnetic field applied to the magnetoresistive element 40 with respect to the sensitivity axis. Therefore, the magnetic sensor 1 according to this embodiment is particularly useful as a sensor for detecting direction in an electronic compass used in an environment where a 360° magnetic field may be applied in the XY plane.

[0034] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. Furthermore, the dimensions and layouts of each element disclosed in the embodiments are illustrative and not limiting. [Examples]

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the examples described below.

[0036] [Test Example 1] In a magnetic sensor 1 having the configuration shown in Figure 1, which includes a magnetic detection unit 2 (see Figure 2A) containing a magnetoresistive element 40 (see Figure 3), the signal S output from the magnetic detection unit 2 when a magnetic field parallel to the sensitivity axis (X-axis) of the magnetoresistive element 40 is applied was determined by simulation. The results are shown in Figure 5. In the graph shown in Figure 5, the horizontal axis represents the standardized magnetic field strength applied to the magnetoresistive element 40, and the vertical axis represents the output of the magnetoresistive element 40 (Vout) and the distortion error due to the third harmonic component (Delta). As a result, the signal S did not contain the distortion error due to the third harmonic component (Delta=0) and showed good linearity (see Figure 5).

[0037] [Test Example 2] In the magnetic sensor 1 of Test Example 1, the signal S output from the magnetic detection unit 2 was determined by simulation when a magnetic field intersecting the sensitivity axis (X-axis) of the magnetoresistive element 40 at a 45° angle was applied. The results are shown in Figure 6. In the graph shown in Figure 6, the horizontal axis represents the standardized magnetic field strength applied to the magnetoresistive element 40, and the vertical axis represents the output (Vout) of the magnetoresistive element 40 and the distortion error due to the third harmonic component (Delta). As a result, the signal S included distortion error due to the third harmonic component, and its linearity deteriorated compared to the signal S obtained in Test Example 1 (see Figure 6).

[0038] [Test Example 3] A correction coefficient (correction value) capable of reducing the distortion error contained in the signal S obtained in Test Example 2 by half was determined, and the corrected signal S' was obtained by correcting the signal S obtained in Test Example 1 using the above formula (1). Similarly, the corrected signal S' was obtained by correcting the signal S obtained in Test Example 2. The results are shown in Figures 7 and 8. In the graphs shown in Figures 7 and 8, the horizontal axis is the standardized magnetic field strength applied to the magnetoresistive element 40, and the vertical axis is the output (Vout) and the distortion error (Delta) due to the third harmonic component of the magnetoresistive element 40.

[0039] As a result, the corrected signal S’ obtained by correcting the signal S obtained in Test Example 1 included distortion errors due to the third harmonic component, and the corrected signal S’ obtained by correcting the signal S obtained in Test Example 2 included distortion errors due to the third harmonic component (see Fig. 7). However, the corrected signal S’ obtained by correcting the signal S obtained in Test Example 2 showed better linearity than the signal S obtained in Test Example 2 (see Fig. 8).

[0040] The maximum value MAX of the distortion error Er1 included in the signal S obtained in Test Example 1 Er1 (=0) and the maximum value MAX of the distortion error Er2 included in the signal S obtained in Test Example 2 Er2 The difference (MAX Er1 -MAX Er2 ) and the absolute value ABS, and the maximum value MAX of the distortion error Er1’ included in the corrected signal S’ obtained by correcting the signal S obtained in Test Example 1 Er1’ and the maximum value MAX of the distortion error Er2’ included in the corrected signal S’ obtained by correcting the signal S obtained in Test Example 2 Er2’ The difference (MAX Er1’ -MAX Er2’ ) and the absolute value ABS’ were obtained and compared. As a result, the absolute value ABS’ was 0.003% of the absolute value ABS. From this result, it was found that by correcting the signal S output from the magnetic detection unit 2 when an oblique magnetic field, preferably an oblique magnetic field inclined at 45° with respect to the sensitivity axis (X axis) and intersecting, was applied to the magnetoresistive element 40, using a correction value (correction coefficient a) capable of reducing the distortion error included in the signal S, regardless of the angle of the magnetic field applied to the magnetoresistive element 40 with respect to the sensitivity axis, the linearity of the output signal from the magnetic sensor 1 can be improved well.

Description of symbols

[0041] 1... Magnetic sensor 2... Magnetic detection unit 2A... First magnetic detection unit 2B... Second magnetic detection unit 21... First element unit 22... Second element unit 23... Third element unit 24... Fourth element unit 3... Signal processing unit 32...Arithmetic section 40…Magnetoresistive element 42...Magnetization fixed layer 44…free layer

Claims

1. A magnetic detection unit that outputs a signal when a magnetic field is applied, The system includes a signal correction unit that corrects the signal output from the magnetic detection unit, The magnetic detection unit includes a magnetoresistive element having a predetermined sensitivity axis, The signal correction unit, When the magnetic field in the intersecting direction, which is tilted and intersects the sensitivity axis and is in a direction different from the sensitivity axis, is applied to the magnetoresistive element, the distortion error included in the signal output from the magnetic detection unit is shown to be at its maximum value. A reverse distortion is calculated as a correction value that can reduce the maximum value of the distortion error included in the signal output from the magnetic detection unit by half when the magnetic field is applied to the magnetoresistive element from the intersecting direction, which is at an angle to the sensitivity axis and is in a direction different from the sensitivity axis. The method is characterized by generating a corrected signal by correcting the signal output from the magnetic detection unit by adding the correction value of the inverse distortion to the signal, including the case when the magnetic field in a direction parallel to the sensitivity axis is applied to the magnetoresistive element. Magnetic sensor.

2. The magnetic field in the aforementioned intersecting direction intersects the direction of the sensitivity axis at an angle greater than 0° and less than 90°. The magnetic sensor according to claim 1.

3. The magnetic detection unit is characterized by including the magnetoresistive element having the sensitivity axis on the first axis. The magnetic sensor according to claim 1.

4. The magnetoresistive element includes a first magnetoresistive element and a second magnetoresistive element. The sensitivity axis of the first magnetoresistive element is parallel to the first axis, The sensitivity axis of the second magnetoresistive element is parallel to the second axis, The first axis and the second axis are orthogonal to each other, The aforementioned intersection direction is characterized by being an inclined direction that intersects both the first axis and the second axis. The magnetic sensor according to claim 1.

5. The signal correction unit is characterized by correcting the signal according to the following formula (1) to generate the corrected signal. A magnetic sensor according to any one of claims 1 to 4. V'=V+V ３ ×a ・・・(1) In the above formula (1), V represents "the signal output from the magnetic detection unit", V' represents "the correction signal", and a represents "the correction coefficient".

6. The aforementioned strain error is characterized by repeatedly increasing and decreasing alternately in response to changes in the strength of the magnetic field. A magnetic sensor according to any one of claims 1 to 5.

7. The correction coefficient a is a coefficient such that the distortion error included in the signal output from the magnetic detection unit when the magnetic field applied to the magnetoresistive element in a direction parallel to the sensitivity axis is equal to the distortion error included in the signal output from the magnetic detection unit when the magnetic field applied to the magnetoresistive element from the intersecting direction where the distortion error is maximum. The magnetic sensor according to claim 5.

8. The direction of intersection in which the distortion error shows its maximum value is 45° with respect to the sensitivity axis. The magnetic sensor according to claim 1.

9. A magnetic sensor as described in any one of claims 1 to 8, Electrical control device.

10. A magnetic sensor comprising a magnetoresistive element having a predetermined sensitivity axis and a magnetic detection unit that outputs a signal when a magnetic field is applied to the magnetoresistive element, wherein the method for correcting the signal output from the magnetic detection unit is as follows: A step of acquiring the signal output from the magnetic detection unit, The process of calculating a correction value for the signal obtained in the above step, which is an inverse distortion that can reduce by half the maximum value of the distortion error included in the signal output from the magnetic detection unit when the magnetic field in the intersecting direction, which is in a direction different from the sensitivity axis and intersects the sensitivity axis, is applied to the magnetoresistive element, and the distortion error included in the signal is at its maximum value when the magnetic field in the intersecting direction is applied to the magnetoresistive element from the intersecting direction, and the distortion error included in the signal is at its maximum value when the magnetic field in the intersecting direction is applied to the magnetoresistive element, The process includes generating a corrected signal by correcting the signal output from the magnetic detection unit by adding the correction value of the inverse distortion to the signal, including the case when the magnetic field in a direction parallel to the sensitivity axis is applied to the magnetoresistive element, Features including, Correction method.

11. A method for manufacturing a magnetic sensor comprising a magnetoresistive element having a predetermined sensitivity axis, a magnetic detection unit that outputs a signal when a magnetic field is applied to the magnetoresistive element, and a signal correction unit that corrects the signal output from the magnetic detection unit, A step of applying a test magnetic field to the magnetic detection unit that intersects the sensitivity axis of the magnetoresistive element and is in a direction different from the sensitivity axis, A step of calculating a correction value for inverse strain that can reduce the maximum value of the strain error included in the signal output from the magnetic detection unit by half when the magnetic field is applied to the magnetoresistive element from the crossing direction in which the strain error included in the test signal shows its maximum value, based on the test signal output from the magnetic detection unit in response to the application of the test magnetic field, The process of creating a signal correction unit that stores the correction value of the inverse distortion for adding to the signal output from the magnetic detection unit to correct the signal, including the case when the magnetic field in a direction parallel to the sensitivity axis is applied to the magnetoresistive element, Features including, A method for manufacturing magnetic sensors.

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