JP2014035204A - Rotation magnetic field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce errors caused by generation of magnetic anisotropy in a magnetic detection element.SOLUTION: A rotation magnetic field sensor 1 comprises: detection circuits 10, 20, and 30 for generating signals S1, S2, and S3 respectively; and arithmetic circuits 61 and 62. The detection circuit 10 comprises a first MR element, and the detection circuit 30 comprises a third MR element. The detection circuit 20 includes a second MR element set with first magnetic anisotropy that is not set in the first and third MR elements. The first arithmetic circuit 61 obtains correction information for correcting errors, generated in detection values θs, and caused by second magnetic anisotropy generated in the first MR element. The first arithmetic circuit obtains correction information for correcting errors, generated in detection values, and caused by the second magnetic anisotropy generated in the first MR element. Then, detection information is obtained based on two different signals of one of first signals generated by the detection circuit 10 and second signals generated by the detection circuit 20. The arithmetic circuit 62 calculates the detection values θs with the signals S1 and S3 and the correction information.

Description

  The present invention relates to a rotating magnetic field sensor that detects an angle formed by the direction of a rotating magnetic field with respect to a reference direction.

  In recent years, a rotating magnetic field sensor has been used to detect the rotational position of an object in various applications such as detection of the opening of a throttle valve of an automobile, detection of the rotational position of a steering of an automobile, and detection of the rotational position of an automobile wiper. Is widely used. The rotating magnetic field sensor is used not only when detecting the rotational position of the object, but also when detecting a linear displacement of the object. In a system using a rotating magnetic field sensor, generally, means (for example, a magnet) that generates a rotating magnetic field whose direction rotates in conjunction with the rotation or linear motion of an object is provided. The rotating magnetic field sensor detects an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction using a magnetic detection element. As a result, the rotational position and linear displacement of the object are detected.

  As a sensor that can be used as a rotating magnetic field sensor, a magnetoresistive effect element (hereinafter also referred to as an MR element) that is a magnetoresistive effect type magnetic sensing element using a magnetoresistive effect is used as a magnetic sensing element. It has been known. Patent Documents 1 to 4 describe a sensor using a spin valve MR element as a magnetic detection element. A spin-valve MR element has a fixed magnetization layer whose magnetization direction is fixed, a free layer whose magnetization direction changes according to the direction of the rotating magnetic field, and a nonmagnetic layer disposed between the fixed magnetization layer and the free layer. And have a layer.

JP-T-2002-525609 JP 2008-268219 A JP 2009-36770 A JP 2010-32484 A

  In a rotating magnetic field sensor using a spin-valve MR element as a magnetic detection element, as described in Patent Document 4, an error may occur in the detection angle due to variations in magnetic characteristics of the MR element. Patent Document 4 describes a technique for reducing detection angle errors caused by manufacturing variations of MR elements. In other words, this technique is a technique for reducing an error in detection angle when a rotating magnetic field sensor is completed.

  The detection angle error that can occur in the rotating magnetic field sensor includes an error that occurs after the rotating magnetic field sensor is installed, in addition to the error that is present when the product is completed as described above. One of the causes of the detection angle error appearing after the installation of the rotating magnetic field sensor is that an induced magnetic anisotropy is acquired in the free layer of the MR element. Such induced magnetic anisotropy of the free layer occurs, for example, when the temperature of the MR element drops from a high temperature while an external magnetic field in a specific direction is applied to the MR element. Such a situation may occur, for example, when the rotating magnetic field sensor is installed in an automobile and the rotating magnetic field sensor and the rotating magnetic field sensor are in a specific positional relationship when the automobile is not operating. More specifically, the above situation may occur when a rotating magnetic field sensor is used to detect the position of an object that stops at a fixed position when not in operation, such as a car wiper.

  A rotating magnetic field sensor is required to reduce an error in a detection angle that occurs due to induced magnetic anisotropy generated after installation. Up to this point, in a rotating magnetic field sensor using a spin valve type MR element as a magnetic detecting element, there is a problem in the case where induced magnetic anisotropy is acquired in the free layer of the MR element after the rotating magnetic field sensor is installed. I have explained the point. However, this problem applies in general to cases where some magnetic anisotropy occurs in the magnetic detection element in a magnetic field detection element including a magnetic detection element, particularly a magnetoresistive effect type magnetic detection element.

  The present invention has been made in view of such problems, and an object thereof is a rotating magnetic field sensor including a magnetic detection element, particularly a magnetoresistive effect type magnetic detection element, and magnetic anisotropy is generated in the magnetic detection element. An object of the present invention is to provide a rotating magnetic field sensor that can reduce an error in a detected value.

  The rotating field sensor of the present invention generates a detection value having a correspondence relationship with the angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction. The direction of the rotating magnetic field at the reference position rotates as viewed from the rotating magnetic field sensor. The rotating field sensor of the present invention includes a first detection circuit, a second detection circuit, a first arithmetic circuit, and a second arithmetic circuit.

  The first detection circuit includes a first magnetic detection element, and generates a first signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction. The second detection circuit includes a second magnetic detection element, and generates a second signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction. The first magnetic anisotropy is present in at least one of the first and second magnetic sensing elements so that variations of the first signal and the second signal due to the first magnetic anisotropy are different from each other. Is set.

  The first arithmetic circuit obtains correction information for correcting an error generated in the detection value due to the second magnetic anisotropy generated in the first magnetic detection element. The first arithmetic circuit obtains correction information for correcting an error occurring in the detection value due to the second magnetic anisotropy generated in the first magnetic detection element. Correction information is obtained based on two different signals, one of the first signal generated by the second detection circuit and the second signal generated by the second detection circuit 20. The second arithmetic circuit calculates a corrected detection value using the first signal and the correction information.

The rotating field sensor of the present invention is further set to at least one of two different angles and at least one of the first and second magnetic detection elements obtained by at least one trigonometric function value and an inverse function of the trigonometric function value. A setting unit configured to output an angular variation term based on the first magnetic anisotropy, and the first arithmetic circuit inputs the first and second signals and the value of the trigonometric function; A signal acquisition unit that outputs two different signals obtained when one of the two signals is equal to a trigonometric value, and two different angles and angular variation terms from the other two other signals are input. In addition, a rotating magnetic field sensor having a correction information calculation unit for obtaining correction information may be used.

In the rotating field sensor of the present invention, the first signal and the second signal are different from each other in the direction of the length of the perpendicular to the first straight line connecting the points where the first signal and the second signal have the same value. Smax1, Smax2 (where Smax1> Smax2), the first maximum value and the second maximum value of the one signal having the maximum length of the perpendicular of each of the other signals having one as an argument. ), The range of values that can be taken by one of the signals may be a rotating magnetic field sensor having a value between Smax2 and Smax1.

The rotating field sensor of the present invention may be a rotating field sensor having at least one trigonometric function value.

The rotating field sensor of the present invention may be a rotating field sensor in which the first signal and the second signal output a sine wave output or a cosine wave output.

  In the rotating field sensor of the present invention, the first magnetic anisotropy may be set in at least the second magnetic detection element of the first and second magnetic detection elements. In this case, the second magnetic detection element includes a magnetic layer whose magnetization direction changes according to the direction of the rotating magnetic field, and the first magnetic anisotropy is set by the shape magnetic anisotropy of the magnetic layer. May be. The second magnetic detection element is disposed between the magnetization fixed layer whose magnetization direction is fixed, the free layer whose magnetization direction changes according to the direction of the rotating magnetic field, and between the magnetization fixed layer and the free layer. You may have a nonmagnetic layer. In this case, the first magnetic anisotropy may be set by the shape magnetic anisotropy of the free layer. The easy axis direction of the free layer may not be parallel to or orthogonal to the magnetization direction of the magnetization fixed layer.

  In the rotating field sensor of the present invention, when the angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction is θ and the correction information is A and α, the first signal is θ−Asin {2 It may be expressed by a trigonometric function with (θ−α)} as a variable.

  The rotating field sensor of the present invention may further include a third detection circuit. The third detection circuit includes a third magnetic detection element, and generates a third signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction. The phase of the third signal is different from the phase of the first signal. In this case, the second arithmetic circuit may calculate the corrected detection value using the third signal in addition to the first signal and the correction information.

  According to the present invention, it is possible to reduce an error that occurs in a detection value due to magnetic anisotropy in a magnetic detection element.

1 is a perspective view showing a schematic configuration of a rotating field sensor according to a first embodiment of the invention. It is explanatory drawing which shows the definition of the direction and angle in the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the rotating field sensor which concerns on the 1st Embodiment of this invention. FIG. 4 is a block diagram showing a configuration of a first arithmetic circuit shown in FIG. 3. It is a perspective view which shows a part of 1st and 3rd MR element in the 1st Embodiment of this invention. It is a perspective view which shows a part of 2nd MR element in the 1st Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the 1st signal in the 1st Embodiment of this invention, and the waveform of a 2nd signal. It is a Lissajous figure showing an example of the relation between the 1st signal in the 1st embodiment of the present invention, and the 2nd signal. It is a block diagram which shows the structure of the 2nd arithmetic circuit which concerns on embodiment of this invention. It is a block diagram which shows the structure of another 2nd arithmetic circuit which concerns on embodiment of this invention. It is a block diagram which shows the structure of another 2nd arithmetic circuit which concerns on embodiment of this invention. It is an example of correction | amendment of this Embodiment. It is a comparison of errors before and after implementation correction of the present embodiment. It is a comparison of errors before and after implementation correction of the present embodiment. It is a comparison of errors before and after implementation correction of the present embodiment.

[Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a schematic configuration of the rotating field sensor according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a schematic configuration of a rotating field sensor according to the present embodiment. FIG. 2 is an explanatory diagram showing definitions of directions and angles in the present embodiment.

  As shown in FIG. 1, the rotating field sensor 1 according to the present embodiment detects a rotating field MF. Here, the reference plane, the reference position, and the reference direction are assumed as follows. The reference plane is a virtual plane having a predetermined positional relationship with the rotating magnetic field sensor 1. The reference position is located in the reference plane. The reference direction is located in the reference plane and intersects the reference position. The direction of the rotating magnetic field MF at the reference position and located in the reference plane rotates around the reference position when viewed from the rotating magnetic field sensor 1. In the following description, the direction of the rotating magnetic field MF at the reference position refers to the direction located in the reference plane. The rotating field sensor 1 generates a detection value having a correspondence relationship with an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction.

  FIG. 1 shows a cylindrical magnet 5 as an example of means for generating the rotating magnetic field MF. The magnet 5 has an N pole and an S pole that are arranged symmetrically about a virtual plane including the central axis of the cylinder. The magnet 5 rotates around the central axis of the cylinder. The magnet 5 has two end surfaces located at both ends in the central axis direction of the cylinder. The rotating field sensor 1 is disposed so as to face one end surface of the magnet 5. In the present embodiment, the reference plane is, for example, a plane parallel to one end face of the magnet 5. The reference position is, for example, a position where the rotating magnetic field sensor 1 detects the rotating magnetic field MF. The reference position may be a position where the rotation center C including the center axis of the cylinder and the reference plane intersect. In this case, when the magnet 5 rotates, the direction of the rotating magnetic field MF at the reference position rotates around the reference position as viewed from the rotating magnetic field sensor 1.

  The configuration of the means for generating the rotating magnetic field MF and the rotating magnetic field sensor 1 is not limited to the example shown in FIG. The means for generating the rotating magnetic field MF and the rotating magnetic field sensor 1 are configured so that the rotating magnetic field sensor MF and the rotating magnetic field sensor 1 are relative to each other so that the direction of the rotating magnetic field MF at the reference position rotates when viewed from the rotating magnetic field sensor 1. It is sufficient if the positional relationship changes. For example, in the magnet 5 and the rotating field sensor 1 arranged as shown in FIG. 1, the magnet 5 may be fixed and the rotating field sensor 1 may rotate, or the magnet 5 and the rotating field sensor 1 may be in opposite directions. The magnet 5 and the rotating magnetic field sensor 1 may rotate at different angular velocities in the same direction.

  Further, instead of the magnet 5, a magnet in which one or more sets of N poles and S poles are alternately arranged in a ring shape may be used, and the rotating field sensor 1 may be disposed in the vicinity of the outer periphery of the magnet. In this case, at least one of the magnet and the rotating magnetic field sensor 1 may be rotated.

  Further, instead of the magnet 5, a magnetic scale in which a plurality of sets of N poles and S poles are alternately arranged in a straight line may be used, and the rotating field sensor 1 may be disposed in the vicinity of the outer periphery of the magnetic scale. In this case, at least one of the magnetic scale and the rotating magnetic field sensor 1 may be moved linearly in the direction in which the N and S poles of the magnetic scale are aligned. This example will be described in detail later as a second embodiment.

  The reference plane, reference position, and reference direction can also be assumed in the configuration of the rotating magnetic field sensor 1 and the means for generating the various rotating magnetic fields MF described above.

  The rotating magnetic field sensor 1 includes a first detection circuit 10, a second detection circuit 20, and a third detection circuit 30. The first detection circuit 10 includes a first magnetic detection element. The second detection circuit 20 includes a second magnetic detection element. The third detection circuit 30 includes a third magnetic detection element. In FIG. 1, for ease of understanding, the first to third detection circuits 10, 20, and 30 are drawn separately, but the first to third detection circuits 10, 20, and 30 are integrated. May be. In FIG. 1, the first to third detection circuits 10, 20, and 30 are stacked in a direction parallel to the rotation center C, but the stacking order is not limited to the example shown in FIG.

  The first detection circuit 10 generates a first signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction. The second detection circuit 20 generates a second signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction. The third detection circuit 30 generates a third signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction.

  In the present embodiment, the positions of the detection circuits 10, 20, and 30 in the space do not exactly match. Similarly, the positions of the first to third magnetic detection elements included in the detection circuits 10, 20, and 30 in the space do not exactly match. However, the difference between the positions of the detection circuits 10, 20, and 30 in the space is sufficiently small compared to the size of the region in which the direction of the rotating magnetic field MF is the same in space. Therefore, the direction of the rotating magnetic field MF at each position of the detection circuits 10, 20, and 30 is substantially the same. Therefore, by setting an arbitrary position in the detection circuits 10, 20, and 30 as the reference position, the detection circuits 10, 20, and 30 each have an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction. A first signal, a second signal, and a third signal having a correspondence relationship can be generated.

  The first to third signals having a corresponding relationship with the angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction may indicate the detected value of the angle, and are linked to the angle. It may be a value that changes. As will be described in detail later, in the present embodiment, each of the first to third signals is a signal indicating a value that changes in conjunction with the angle, and specifically, the rotating magnetic field MF at the reference position. Is a signal indicating the intensity of the component in a predetermined direction.

  Similarly to the first to third signals, a detected value having a correspondence relationship with the angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction may also indicate the value of the detected angle. It may be a value that changes in conjunction with the angle. As will be described in detail later, in the present embodiment, the detected value indicates the detected value of the angle.

  Here, with reference to FIG. 2, the definition of the direction and angle in this Embodiment is demonstrated. First, a direction parallel to the rotation center C shown in FIG. 1 and directed from one end face of the magnet 5 toward the rotating magnetic field sensor 1 is defined as a Z direction. Next, two directions perpendicular to the Z direction and orthogonal to each other are defined as an X direction and a Y direction. In FIG. 2, the X direction is represented as a direction toward the right side, and the Y direction is represented as a direction toward the upper side. In addition, a direction opposite to the X direction is defined as -X direction, and a direction opposite to the Y direction is defined as -Y direction.

  Here, the reference position PR is a position where the rotating magnetic field sensor 1 detects the rotating magnetic field MF. The reference direction DR is the X direction. The angle formed by the direction DM of the rotating magnetic field MF at the reference position PR with respect to the reference direction DR is represented by the symbol θ. The direction DM of the rotating magnetic field MF is assumed to rotate counterclockwise in FIG. The angle θ is represented by a positive value when viewed counterclockwise from the reference direction DR, and is represented by a negative value when viewed clockwise from the reference direction DR.

  The first and second detection circuits 10 and 20 detect the component in the first direction D1 of the rotating magnetic field MF at the reference position PR. The third detection circuit 30 detects a component in the second direction D2 of the rotating magnetic field MF at the reference position PR. In the present embodiment, the first direction D1 is a direction rotated 90 ° counterclockwise from the reference direction DR (X direction) and coincides with the Y direction. The second direction D2 coincides with the reference direction DR and the X direction.

  In the present embodiment, at least one of the first and second magnetic detection elements is provided with the first signal so that the variation of the first signal and the second signal caused by the first magnetic anisotropy is different from each other. The magnetic anisotropy is set. The fluctuation caused by the first magnetic anisotropy in the first signal and the second signal is that the first magnetic anisotropy is set in at least one of the first and second magnetic detection elements. Thus, the first and second magnetic detection elements are compared with the case where the first magnetic anisotropy is not set, and the fluctuations that occur in the first signal and the second signal.

  The first magnetic anisotropy may be set in at least the second magnetic detection element of the first and second magnetic detection elements. In the present embodiment, in particular, the first magnetic anisotropy is not set in the first and third magnetic detection elements, but the first magnetic anisotropy is set in the second magnetic detection element. Yes. In this case, fluctuations due to the first magnetic anisotropy do not occur in the first and third signals, but fluctuations due to the first magnetic anisotropy occur in the second signal. As a result, the variations of the first signal and the second signal due to the first magnetic anisotropy are different from each other.

  In the present embodiment, the first magnetic anisotropy is set by the shape magnetic anisotropy of the magnetic layer included in the second magnetic detection element. In FIG. 2, reference numerals 11, 21, and 31 represent planar shapes (shapes viewed from above) of the magnetic layers included in the first magnetic detection element, the second magnetic detection element, and the third magnetic detection element, respectively. ing. As shown in FIG. 2, in the present embodiment, for example, the planar shape of the magnetic layer of the first and third magnetic detection elements is circular, and the planar shape of the magnetic layer of the second magnetic detection element is elliptical. Thus, the first magnetic anisotropy due to the shape anisotropy that is not set in the first and third magnetic detection elements is set in the second magnetic detection element.

  In FIG. 2, the broken line with the symbol DA1 is the easy axis direction of magnetization due to the first magnetic anisotropy set in the second magnetic detection element, that is, the planar shape of the magnetic layer of the second magnetic detection element. It represents the long axis direction of the ellipse. Here, an angle formed by the direction DA1 with respect to the reference direction DR when viewed in the counterclockwise direction from the reference direction DR is represented by a symbol β. The angle β is 0 ° or more and less than 180 °.

  In the first to third magnetic detection elements, a second magnetic anisotropy different from the first magnetic anisotropy occurs, for example, in an acquired manner. The second magnetic anisotropy is, for example, due to induced magnetic anisotropy. The second magnetic anisotropy is, for example, that the temperature of the first to third magnetic sensing elements decreases from a high temperature while an external magnetic field in a specific direction is applied to the first to third magnetic sensing elements. Occurs in some cases. In FIG. 2, the broken line with the symbol DA2 represents the easy axis direction of magnetization due to the second magnetic anisotropy. Here, the angle formed by the direction DA2 with respect to the reference direction DR when viewed counterclockwise from the reference direction DR is represented by the symbol α. The angle α is not less than 0 ° and less than 180 °.

  Next, the configuration of the rotating magnetic field sensor 1 will be described in detail with reference to FIG. FIG. 3 is a circuit diagram showing a configuration of the rotating magnetic field sensor 1. The first detection circuit 10 generates a first signal S1 having a correspondence relationship with the angle θ. The second detection circuit 20 generates a second signal S2 having a correspondence relationship with the angle θ. The third detection circuit 30 generates a third signal S3 having a correspondence relationship with the angle θ. The first and second signals S1 and S2 are signals corresponding to the intensity of the component in the first direction D1 of the rotating magnetic field MF at the reference position PR. The third signal S3 is a signal corresponding to the intensity of the component in the second direction D2 of the rotating magnetic field MF at the reference position PR.

  The first to third signals S1 to S3 change periodically with the same signal period T. In a state where the second magnetic anisotropy is not generated in the first and third magnetic detection elements, the waveforms of the first and third signals S1 and S3 are ideally sinusoidal (Sine). Waveform and cosine waveform). When the second magnetic anisotropy occurs in the first and third magnetic detection elements, the waveforms of the first and third signals S1 and S3 are distorted from sinusoidal curves.

  The waveform of the second signal S2 is distorted from a sine curve due to at least the first magnetic anisotropy. When the second magnetic anisotropy occurs in the second magnetic detection element, the waveform of the second signal S2 is distorted from the sine curve due to the first and second magnetic anisotropies.

  The phase of the third signal S3 is different from the phase of the first signal S1. In the present embodiment, the phase of the third signal S3 is preferably different from the phase of the first signal S1 by an odd multiple of 1/4 of the signal period T. However, the phase difference between the first signal S1 and the third signal S3 may be slightly deviated from an odd multiple of 1/4 of the signal period T from the viewpoint of the accuracy of manufacturing the magnetic detection element. In the following description, it is assumed that the relationship between the phase of the first signal S1 and the phase of the third signal S3 is the above-described preferable relationship.

  The first detection circuit 10 has an output terminal that outputs the first signal S1. The second detection circuit 20 has an output terminal that outputs the second signal S2. The third detection circuit 30 has an output terminal that outputs a third signal S3. As shown in FIG. 3, the rotating field sensor 1 further includes a first arithmetic circuit 61 and a second arithmetic circuit 62. Each of the first and second arithmetic circuits 61 and 62 has two input ends and one output end. The two input terminals of the first arithmetic circuit 61 are connected to the output terminals of the first and second detection circuits 10 and 20, respectively. The two input terminals of the second arithmetic circuit 62 are connected to the output terminals of the third detection circuit 30 and the first arithmetic circuit 61, respectively.

  The second arithmetic circuit 62 calculates a detection value θs having a correspondence relationship with the angle θ. In the present embodiment, the detected value θs is the value of the angle θ detected by the rotating magnetic field sensor 1. The first and second arithmetic circuits 61 and 62 can be realized by a single microcomputer, for example. The operation of the first and second arithmetic circuits 61 and 62 and the calculation method of the detected value θs will be described in detail later.

  The first detection circuit 10 includes a Wheatstone bridge circuit 14 and a difference detector 15. The Wheatstone bridge circuit 14 is connected in series with a power supply port V1, a ground port G1, two output ports E11 and E12, and a first pair of magnetic detection elements R11 and R12 connected in series. A second pair of magnetic detection elements R13 and R14 is included. One end of each of the magnetic detection elements R11 and R13 is connected to the power supply port V1. The other end of the magnetic detection element R11 is connected to one end of the magnetic detection element R12 and the output port E11. The other end of the magnetic detection element R13 is connected to one end of the magnetic detection element R14 and the output port E12. The other ends of the magnetic detection elements R12 and R14 are connected to the ground port G1. A power supply voltage having a predetermined magnitude is applied to the power supply port V1. The ground port G1 is connected to the ground. The difference detector 15 outputs a first signal S1, which is a signal corresponding to the potential difference between the output ports E11 and E12, to the first arithmetic circuit 61.

  The circuit configuration of the second detection circuit 20 is the same as that of the first detection circuit 10. That is, the second detection circuit 20 includes a Wheatstone bridge circuit 24 and a difference detector 25. The Wheatstone bridge circuit 24 is connected in series with the power supply port V2, the ground port G2, the two output ports E21 and E22, and the first pair of magnetic detection elements R21 and R22 connected in series. A second pair of magnetic detection elements R23 and R24 is included. One end of each of the magnetic detection elements R21 and R23 is connected to the power supply port V2. The other end of the magnetic detection element R21 is connected to one end of the magnetic detection element R22 and the output port E21. The other end of the magnetic detection element R23 is connected to one end of the magnetic detection element R24 and the output port E22. The other ends of the magnetic detection elements R22 and R24 are connected to the ground port G2. A power supply voltage having a predetermined magnitude is applied to the power supply port V2. The ground port G2 is connected to the ground. The difference detector 25 outputs a second signal S2 that is a signal corresponding to the potential difference between the output ports E21 and E22 to the first arithmetic circuit 61.

  The circuit configuration of the third detection circuit 30 is the same as that of the first detection circuit 10. That is, the third detection circuit 30 includes a Wheatstone bridge circuit 34 and a difference detector 35. The Wheatstone bridge circuit 34 is connected in series with the power supply port V3, the ground port G3, the two output ports E31 and E32, and the first pair of magnetic detection elements R31 and R32 connected in series. And a second pair of magnetic detection elements R33 and R34. One end of each of the magnetic detection elements R31 and R33 is connected to the power supply port V3. The other end of the magnetic detection element R31 is connected to one end of the magnetic detection element R32 and the output port E31. The other end of the magnetic detection element R33 is connected to one end of the magnetic detection element R34 and the output port E32. The other ends of the magnetic detection elements R32 and R34 are connected to the ground port G3. A power supply voltage having a predetermined magnitude is applied to the power supply port V3. The ground port G3 is connected to the ground. The difference detector 35 outputs a third signal S3, which is a signal corresponding to the potential difference between the output ports E31 and E32, to the second arithmetic circuit 62.

  In the present embodiment, as all the magnetic detection elements included in the Wheatstone bridge circuit (hereinafter referred to as a bridge circuit) 14, 24, 34, MR elements that are magnetoresistive effect type magnetic detection elements, in particular, spin-valve type elements. An MR element is used. The spin valve MR element may be a TMR element or a GMR element. The TMR element or GMR element includes a magnetization fixed layer whose magnetization direction is fixed, a free layer that is a magnetic layer whose magnetization direction changes according to the direction DM of the rotating magnetic field MF, and a magnetization layer between the magnetization fixed layer and the free layer. And a nonmagnetic layer disposed thereon. In the TMR element, the nonmagnetic layer is a tunnel barrier layer. In the GMR element, the nonmagnetic layer is a nonmagnetic conductive layer. In the TMR element or the GMR element, the resistance value changes according to the angle formed by the magnetization direction of the free layer with respect to the magnetization direction of the magnetization fixed layer, and when this angle is 0 °, the resistance value becomes the minimum value. When the angle is 180 °, the resistance value becomes the maximum value. In the following description, the magnetic detection elements included in the bridge circuits 14, 24, and 34 are referred to as MR elements. The first to third magnetic detection elements are referred to as first to third MR elements. In FIG. 3, a solid arrow indicates the magnetization direction of the magnetization fixed layer in the MR element, and a white arrow indicates the magnetization direction of the free layer in the MR element.

  In the first detection circuit 10, the magnetization direction of the magnetization fixed layer in the MR elements R11 and R14 is parallel to the first direction D1 (Y direction), and the magnetization of the magnetization fixed layer in the MR elements R12 and R13. This direction is opposite to the magnetization direction of the magnetization fixed layer in the MR elements R11 and R14. In FIG. 2, the arrow denoted by reference numeral DP1 represents the magnetization direction of the magnetization fixed layer in the MR elements R11 and R14. In this case, the potential difference between the output ports E11 and E12 changes according to the intensity of the component in the first direction D1 (Y direction) of the rotating magnetic field MF. Accordingly, the first detection circuit 10 detects the intensity of the component in the first direction D1 of the rotating magnetic field MF and outputs the first signal S1 representing the intensity.

  In the second detection circuit 20, the magnetization direction of the magnetization fixed layer in the MR elements R21 and R24 is a direction parallel to the first direction D1 (Y direction), and the magnetization of the magnetization fixed layer in the MR elements R22 and R23. This direction is opposite to the magnetization direction of the magnetization fixed layer in the MR elements R21 and R24. In FIG. 2, the arrow denoted by reference numeral DP2 represents the magnetization direction of the magnetization fixed layer in the MR elements R21 and R24. In this case, the potential difference between the output ports E21 and E22 changes according to the intensity of the component in the first direction D1 (Y direction) of the rotating magnetic field MF. Therefore, the second detection circuit 20 detects the intensity of the component in the first direction D1 of the rotating magnetic field MF, and outputs a second signal S2 representing the intensity.

  In the third detection circuit 30, the magnetization direction of the magnetization fixed layer in the MR elements R31 and R34 is a direction parallel to the second direction D2 (X direction), and the magnetization of the magnetization fixed layer in the MR elements R32 and R33. This direction is opposite to the magnetization direction of the magnetization fixed layer in the MR elements R31 and R34. In FIG. 2, the arrow with the symbol DP3 represents the direction of magnetization of the magnetization fixed layer in the MR elements R31 and R34. In this case, the potential difference between the output ports E31 and E32 changes according to the intensity of the component in the second direction D2 (X direction) of the rotating magnetic field MF. Therefore, the third detection circuit 30 detects the intensity of the component in the second direction D2 of the rotating magnetic field MF, and outputs a third signal S3 representing the intensity.

  Note that the magnetization direction of the magnetization fixed layer in the plurality of MR elements in the detection circuits 10, 20, and 30 may be slightly deviated from the above-mentioned direction from the viewpoint of the accuracy of manufacturing the MR element.

  Next, an example of the configuration of the MR element and the first magnetic anisotropy will be described with reference to FIG. 2, FIG. 5, and FIG. FIG. 5 is a perspective view showing a part of the first and third MR elements. In this example, the first and third MR elements have a plurality of lower electrodes, a plurality of MR films, and a plurality of upper electrodes. The plurality of lower electrodes 42 are disposed on a substrate (not shown). Each lower electrode 42 has an elongated shape. A gap is formed between two lower electrodes 42 adjacent to each other in the longitudinal direction of the lower electrode 42. As shown in FIG. 5, MR films 50 are disposed on the upper surface of the lower electrode 42 in the vicinity of both ends in the longitudinal direction.

  The MR film 50 includes a free layer 51, a nonmagnetic layer 52, a magnetization fixed layer 53, and an antiferromagnetic layer 54 that are sequentially stacked from the lower electrode 42 side. In the example shown in FIG. 5, the MR film 50 has a cylindrical shape. In this case, the planar shape of the free layer 51 is circular. The free layer 51 is electrically connected to the lower electrode 42. The antiferromagnetic layer 54 is made of an antiferromagnetic material and causes exchange coupling with the magnetization fixed layer 53 to fix the magnetization direction of the magnetization fixed layer 53. The plurality of upper electrodes 43 are disposed on the plurality of MR films 50. Each upper electrode 43 has an elongated shape and is disposed on two lower electrodes 42 adjacent to each other in the longitudinal direction of the lower electrode 42 to electrically connect the antiferromagnetic layers 54 of the two adjacent MR films 50 to each other. To do. With such a configuration, the MR element shown in FIG. 5 has a plurality of MR films 50 connected in series by a plurality of lower electrodes 42 and a plurality of upper electrodes 43. The arrangement of the layers 51 to 54 in the MR film 50 may be upside down from the arrangement shown in FIG.

  FIG. 6 is a perspective view showing a part of the second MR element. The configuration of the second MR element is basically the same as that of the first and third MR elements. However, in the second MR element, the shape of the MR film 50 is different from the shape of the MR film 50 in the first and third MR elements. In the example shown in FIG. 6, the MR film 50 has an elliptic cylinder shape. In this case, the planar shape of the free layer 51 is elliptical.

  As described above, in the present embodiment, the planar shape of the free layer 51 of the first and third MR elements is circular, and the planar shape of the free layer 51 of the second MR element is elliptical. First magnetic anisotropy due to shape anisotropy, which is not set in the first and third MR elements, is set in the second MR element.

  In the second MR element, the major axis direction of the ellipse that is the planar shape of the free layer 51 is the easy axis direction of magnetization of the free layer 51. The easy axis direction of the free layer 51 coincides with the easy axis direction DA1 due to the first magnetic anisotropy shown in FIG. In the second MR element, it is preferable that the easy axis direction of the free layer 51 is not parallel to or orthogonal to the magnetization direction of the magnetization fixed layer 53 (first direction D1).

  The shape of the MR film 50 is not limited to the examples shown in FIGS. For example, the MR film 50 in the first and third MR elements may have a prismatic shape with a square top surface, and the MR film 50 in the second MR element has a prismatic shape with a rectangular top surface. You may do it.

  Next, the waveforms of the first and third signals S1 and S3 will be described. In the example shown in FIG. 3, in the state where the second magnetic anisotropy is not generated in the first and third MR elements, ideally, the magnetization direction of the magnetization fixed layer of the third MR element is It is orthogonal to the magnetization direction of the magnetization fixed layer of the first MR element. In this case, ideally, the waveform of the first signal S1 is a sine waveform depending on the angle θ, and the waveform of the third signal S3 is a cosine waveform depending on the angle θ. Become. In this case, the phase of the third signal S3 differs from the phase of the first signal S1 by ¼ of the signal period T, that is, π / 2 (90 °).

  When the angle θ is larger than 0 ° and smaller than 180 °, the first signal S1 is a positive value, and when the angle θ is larger than 180 ° and smaller than 360 °, the first signal S1 is Negative value. Further, when the angle θ is not less than 0 ° and less than 90 °, and when it is greater than 270 ° and less than or equal to 360 °, the third signal S3 is a positive value, and the angle θ is greater than 90 ° and greater than 270 °. When small, the third signal S3 is a negative value.

  As described above, in the present embodiment, in the state where the second magnetic anisotropy is not generated in the first and third MR elements, the waveforms of the first and third signals S1 and S3 are ideal. Is a sinusoidal curve. However, when the second magnetic anisotropy is acquired in the first and third MR elements, the waveforms of the first and third signals S1 and S3 are distorted from sinusoidal curves. The second magnetic anisotropy generated in the first and third MR elements is due to the induced magnetic anisotropy generated in the free layer 51 of the MR element. The induced magnetic anisotropy of the free layer 51 occurs, for example, when the temperature of the MR element falls from a high temperature while an external magnetic field in a specific direction is applied to the MR element.

  The first and third signals S1 and S3 whose waveforms are distorted by the second magnetic anisotropy are approximately represented by a trigonometric function using a variable including an angular variation term based on the second magnetic anisotropy. be able to. Specifically, the first and third signals S1 and S3 can be approximately expressed by the following equations (1) and (2).

S1 = sin [θ-Asin {2 (θ-α)}] (1)
S3 = cos [θ-Asin {2 (θ−α)}] (2)

  In the above formulas (1) and (2), Asin {2 (θ−α)} is an angular variation term based on the second magnetic anisotropy. In this angular variation term, A represents amplitude (maximum value of angular variation), and α represents a phase difference with respect to θ. Note that α in this angular variation term is the same as α shown in FIG. The period of this angular variation term is ½ of the signal period T, that is, π (180 °).

  Next, the waveform of the second signal S2 will be described. In the example shown in FIG. 3, the magnetization direction of the magnetization fixed layer of the second MR element coincides with the magnetization direction of the magnetization fixed layer of the first MR element. In this case, the waveform of the second signal S2 is similar to the waveform of the first signal S1. However, since the second MR element has the first magnetic anisotropy that is not set in the first MR element, the first MR anisotropy causes the first MR anisotropy. The waveform of the second signal S2 is slightly different from the waveform of the first signal S1. In this way, the variations caused by the first magnetic anisotropy in the first signal S1 and the second signal S2 are different from each other.

  When the second magnetic anisotropy is acquired in the second MR element, the waveform of the second signal S2 is distorted from the sine curve due to the first and second magnetic anisotropies. The second signal S2 distorted due to the first and second magnetic anisotropies is approximately an angle variation term based on the first magnetic anisotropy and an angle based on the second magnetic anisotropy. It can be expressed by a trigonometric function using a variable including a fluctuation term. Specifically, the second signal S2 can be approximately expressed by the following equation (3).

  S2 = sin [[theta] -Asin {2 ([theta]-[alpha])}-Bsin {2 ([theta]-[beta])}] (3)

  In the above formula (3), B sin {2 (θ−β)} is an angular variation term based on the first magnetic anisotropy. In this angular variation term, B represents amplitude (maximum value of angular variation), and β represents a phase difference with respect to θ. Note that β in this angular variation term is the same as β shown in FIG. The period of this angular variation term is ½ of the signal period T, that is, π (180 °). Since the first magnetic anisotropy can be set arbitrarily, the values of B and β can also be set arbitrarily.

  FIG. 7 shows an example of the waveform of the first signal S1 and the waveform of the second signal S2. In FIG. 7, the horizontal axis indicates the angle θ, and the vertical axis indicates the magnitudes (voltages) of the first and second signals S1 and S2. The waveform denoted by reference numeral 71 represents the waveform of the first signal S1, and the waveform denoted by reference numeral 72 represents the waveform of the second signal S2. Each waveform shown in FIG. 7 is created by simulation using equations (1) and (3). In this simulation, A in equations (1) and (3) is 5 °, α in equations (1) and (3) is 0 °, B in equation (3) is 10 °, and in equation (3) β was 45 °. As shown in FIG. 7, the waveform of the second signal S2 is slightly different from the waveform of the first signal S1.

  Next, the first arithmetic circuit 61 will be described. The first arithmetic circuit 61 obtains correction information for correcting an error that occurs in the detected value θs due to the second magnetic anisotropy. FIG. 4 is a block diagram illustrating an example of the configuration of the first arithmetic circuit 61. In this example, the first arithmetic circuit 61 includes a signal acquisition unit 61A, a correction information calculation unit 61B, and a setting unit 61C. Here, the signal obtaining unit 61A obtains one signal having a predetermined value and the other signal obtained at the same time among the first signal S1 and the second signal S2 that change with time. To do. The setting unit 61C includes at least two different angles (θa, θb) obtained by inverse functions of trigonometric function values (S1a, S2a) and trigonometric function values and angles based on the first magnetic anisotropy. B and β in the fluctuation term are set. When the signal acquisition unit 61A uses a pair of the first signal S1 and the second signal S2 obtained at the same time as a signal pair, the signal acquisition unit 61A From the transition, the second signal S2a when the output of the first signal S1 is equal to the value S1a of at least one or more trigonometric functions set in the setting unit 61C (obtained at the same time) is acquired. Similarly, the second signal S2b when the output of the first signal S1 is equal to the value S1b of at least one or more trigonometric functions set in the setting unit 61C (obtained at the same time) is acquired. The correction information calculation unit 61B uses two different angles (θa, θb) preset in the setting unit 61C, B and β set arbitrarily, and the second signals S2a and S2b acquired by the signal acquisition unit 61A. To calculate correction information A and α. The predetermined range may be 360 °, or may be a range of less than 360 ° as long as correction information can be obtained from the manner of transition of signal pairs described later. Alternatively, it may be a plurality of different ranges of less than 360 °, or a plurality of different angles. In the following description, the predetermined range is 360 °.

  (A), (b), and (c) of FIG. 8 show three examples of changes in signal pairs. 8A, 8B, and 8C, the horizontal axis indicates the magnitude (voltage) of the first signal S1, and the vertical axis indicates the magnitude (voltage) of the second signal S2. Yes. The three Lissajous curves shown in (a), (b), and (c) of FIG. 8 are created by simulation using equations (1) and (3). In this simulation, α in equations (1) and (3) was 0 °, B in equation (3) was 10 °, and β in equation (3) was 45 °. (A), (b), and (c) of FIG. 8 show Lissajous curves when A in Formulas (1) and (3) is 0 °, 5 °, and 10 °, respectively.

  As shown in FIG. 8, the transition state of the signal pair (the shape of the Lissajous curve) varies depending on the second magnetic anisotropy aspect. Therefore, it is possible to obtain information on the second magnetic anisotropy from the transition state of the signal pair (the shape of the Lissajous curve). This information is correction information for correcting an error that occurs in the detected value θs due to the second magnetic anisotropy. More specifically, the second aspect of magnetic anisotropy is determined by the combination of the values of A and α in the equations (1) and (3). Hereinafter, the combination of the values of A and α is expressed as (A, α). In the present embodiment, it is possible to specify (A, α) based on two different second signals obtained from the transition state of the signal pair (the shape of the Lissajous curve). α) is the correction information.

  With the exception of the following exceptions, if (A, α) is different, the transition of the signal pair (the shape of the Lissajous curve) is different. The exceptions are when β is 90 ° and 0 °, that is, in the second MR element, the magnetization easy axis direction DA1 of the free layer 51 is relative to the magnetization direction (first direction D1) of the magnetization fixed layer 53. Parallel and orthogonal. In these cases, on the premise that A is equal, when α = γ (γ is larger than 0 ° and smaller than 90 °) and when α = 180 ° −γ, how signal pairs change (Lissajous curve shape) becomes equal. Therefore, in the second MR element, it is preferable that the easy axis direction DA1 of the free layer 51 is not parallel to or orthogonal to the magnetization direction (first direction D1) of the magnetization fixed layer 53.

Here, the magnetoresistive elements are designed so that the maximum value and the minimum value of the first signal S1 and the second signal S2 are equal. A saturation magnetic field is applied to each magnetoresistive element that outputs the first signal S1 and the second signal S2, and each magnetoresistive element that forms a bridge circuit in the direction of the same saturation magnetic field. The fixed direction of the magnetization fixed layer is designed to be the same direction. Since the magnetoresistive element is designed in this way, the angles in the reference plane having the fixed direction of each magnetization fixed layer with respect to the same saturation magnetic field as the reference direction can be regarded as equivalent. Further, since the maximum value and the minimum value of the first signal S1 and the second signal S2 are designed to be equal, the handling of the signal is easy.

The acquisition of the second signals S2a and S2b in the signal acquisition unit 61A will be specifically described with reference to (b) of FIG.

(B) in FIG. 8 is created by simulation using equations (1) and (3). In this simulation, Lissajous curves when α in equations (1) and (3) is 0 °, A is 5 °, B in equation (3) is 10 °, and β in equation (3) is 45 °. Is shown.

The setting unit 61C has at least one trigonometric function value when the correction information A = 0 and α = 0, for example, S1a = S2a = 0.5, and an inverse trigonometric function, for example, an inverse sine function of Expression (1). Output two different angles obtained by (i.e., θa = 30 °, θb = 150 °), and B and β in the angular variation term based on the first magnetic anisotropy, for example, B = 10 °, β = 45 ° To do. The setting unit 61C has at least one trigonometric function value (S1a, S2a), two different angles (θa, θb) obtained by an inverse sine function, and B in the angle variation term based on the first magnetic anisotropy. And β may be stored in a memory in advance or may be calculated at any time.

For example, the signal acquisition unit 61A outputs the second signal S2a obtained at the same time when the output of the first signal S1 is S1 = S1a = 0.5. Similarly, the second signal S2b different from S2a obtained at the same time when the output of the first signal S1 is S1 = S1b = 0.5 is output. S1a and S1b are output from the setting unit 61C.

Next, the calculation of the correction information (A, α) will be specifically described using equations (1) and (3).

Based on S2a and S2b obtained by the signal acquisition unit 61A and B and β in the angle variation term based on the first magnetic anisotropy set in the setting unit 61C, the correction information calculation unit 61B calculates correction information (A , Α). “Arcsin” represents an arc sine.
When θa = 30 °, the expression (1) is as follows.
From the inverse trigonometric function of 0.5 = sin [θ-Asin {2 (θ-α)}],
θ−Asin {2 (θ−α)} = 30 ° (4)
Moreover, it becomes the following by substituting Formula (4) for Formula (3).
S2a = sin [30 ° −Bsin {2 (θ−β)}] (5)
Here, when equation (5) is solved for θ,
30 ° -Bsin {2 (θ-β)} = arcsin (S2a)
From the inverse trigonometric (sine) function of Bsin {2 (θ−β)} = 30 ° -arcsin (S2a),
2 (θ−β) = arcsin [{30 ° -arcsin (S2a)} / B]
θ = (1/2) · arcsin [{30 ° -arcsin (S2a)} / B] + β (6)
Here, the equation (6) is a constant derived from B, β, and S2a set in the setting unit 61C. When θ = θac (constant) is set, the following equation is obtained from the equation (4).
θac−Asin {2 (θac−α)} = 30 ° (7)
Similarly, the following equation is derived at θb = 150 °.
θbc−Asin {2 (θbc−α)} = 150 ° (8)
In addition,
θbc = (1/2) · arcsin [{150 ° -arcsin (S2b)} / B] + β
... (9)
Therefore, the correction information A and α can be obtained from the equations (7) and (8). As described above, the correction information (A, α) can be obtained based on the two different second signals S2a and S2b. It is also possible to perform the same calculation based on the signals of two different first signals S1a and S1b. In this case, two different angles may be obtained from the value of the inverse sine function for the first signal S1. For the sake of explanation, the first signal S1 is shown on the horizontal axis and the second signal S2 is shown on the vertical axis. Even so, it is possible to calculate the correction information (A, α). Accordingly, correction information can be obtained based on two different signals of one of the first signal S1 and the second signal S2.

In the present embodiment, the correction information (A, α) is obtained for two different angles 30 ° and 150 ° obtained by the inverse function of the trigonometric function value. Any angle can be selected within a range of less than 360 °. Further, at least one or more trigonometric functions may not have the same value.

When at least one trigonometric function value is the same, that is, when it is one value, the voltage detected by the signal acquisition unit is one, so that the actual circuit scale can be reduced. In addition, if the angle is different from the maximum and minimum of the first signal and the second signal, the detection error of the signal acquisition unit can be reduced, so that more accurate correction information can be obtained. It becomes.

In order to obtain the correction information (A, α), it is necessary to acquire a signal obtained in the process in which the direction DM of the rotating magnetic field MF rotates within a predetermined range by the signal acquisition unit 61A. In addition, the signal acquisition unit 61A acquires a signal at a predetermined time interval or more and when the rotating magnetic field sensor 1 is operating and the direction DM of the rotating magnetic field MF rotates more than a predetermined range. It may be set as follows. Alternatively, the signal acquisition unit 61A may be set so as to acquire a signal when an instruction from the user is given. Further, the signal acquisition unit 61A may be set to store the transition of the signal pair in a memory or the like and select and acquire the second signal.

  In the first arithmetic circuit 61, a new signal is acquired by the signal acquisition unit 61 </ b> A, new correction information (A, α) is obtained accordingly, and the correction information (A, α) to be output is updated.

Further, at least one trigonometric function value (S1a, S2a) output from the setting unit 61C, two different angles (θa, θb) obtained by an inverse sine function, and an angle variation term based on the first magnetic anisotropy. B and β may be given to the calculation unit 61 via a communication interface or the like.

Further, instead of the second magnetoresistive element, first magnetic anisotropy may be set in the first magnetoresistive element. Even in this case, the corresponding angle variation term is output from the setting unit, and the handling of the correction information calculation unit 61B in the mathematical expression does not change.

Further, as is apparent from FIG. 8, when magnetic anisotropy exists in the free layer of the magnetoresistive element that outputs the first signal S1 and the second signal S2, the first signal whose offset voltage is zero. The Lissajous curve using S1 and the second signal S2 is away from an ideal curve (straight line) in the vicinity where each signal becomes zero. That is, two different values of the other one of the first signal S1 and the second signal S2 for one of the first signal S1 and the second signal S2 that are the same in the vicinity are the other values. Since the difference between two different signals with respect to one signal is larger than that of the other signal, a calculation error can be further reduced. Therefore, the continuous first first signal S1 and second signal S2 are different in the direction of the length of the perpendicular to the first straight line connecting the points where the first signal S1 and the second signal S2 have the same value. Smax1 and Smax2 (where Smax1> Smax2) are the first maximum value and the second maximum value of one of the signals having the maximum length of the other perpendicular to each other. In this case, the range of values that one signal can take is preferably Smax2 or more and Smax1 or less. The above relationship is satisfied even when the DC offset signals Voff1 and Voff2 are applied to the respective signals. When an AC offset is applied, the above relationship is satisfied by subtracting the AC offset. This configuration can be easily realized by using an existing integrated circuit or the like.

  Next, the operation of the second arithmetic circuit 62 and the calculation method of the detection value θs will be described with reference to FIG. As shown in FIG. 3, the first arithmetic circuit 62 receives the first and third signals S1, S3 and the correction information (A, α). The second arithmetic circuit 62 calculates the corrected detection value θs using the first signal S1, the third signal S3, and the correction information (A, α).

  Here, an example of a method for calculating the detection value θs will be described. In this example, the second arithmetic circuit 62 first substitutes the correction information (A, α) obtained by the first arithmetic circuit 61 into the equations (1) and (2). Next, in Expressions (1) and (2), a table showing a correspondence relationship between the angle θ and the calculated values of the first and third signals S1 and S3 by changing the angle θ at a predetermined angular interval. create. Table 1 shows a table showing the correspondence between the angle θ and the calculated value of the first signal S1. Similar to this table, a table indicating the correspondence between the angle θ and the calculated value of the third signal S3 is also created.

In Table 1, θ ₀ , θ ₁ ,..., Θ _m are permutations of values of the angle θ selected with a predetermined angular interval within a range of 0 ° to less than 360 °. _{S1 0, S1 1, ···,} S1 m , respectively, ₀ theta in the formula (1), theta _1, · · ·, represents a calculated value of the first signal S1 obtained by substituting theta _m ing. Here, an arbitrary value in the permutation θ ₀ , θ ₁ ,..., Θ _m is expressed as θ _n, and the calculated value of the first signal S 1 obtained by substituting θ _n into Equation (1) is This is expressed as S1 _n .

Next, the second arithmetic circuit 62 uses the table shown in Table 1 to search for the calculated value S1 _n closest to the first signal S1 input to the second arithmetic circuit 62. Specifically, the second arithmetic circuit 62 searches for a calculated value S1 _n that minimizes the square of the difference from the first signal S1. The second arithmetic circuit 62 sets the angle θ _n corresponding to the calculated value S1 _n obtained by this search as the first candidate for the detected value θs.

  When the angle θ is in the range of 0 ° or more and less than 360 °, the first signal S1 has the same value at two different θs except when the first signal S1 has a maximum value or a minimum value. Therefore, in the above method, in most cases, two first candidates of the detected value θs are obtained for one value of the first signal S1.

Similarly, the second arithmetic circuit 62 uses the table indicating the correspondence relationship between the angle θ and the calculated value of the third signal S3 to obtain the third signal S3 input to the second arithmetic circuit 62. The nearest calculated value S3 _n is searched, and the angle θ _n corresponding to the calculated value S3 _n obtained by this search is set as the second candidate of the detected value θs. Also in this case, in most cases, two second candidates of the detected value θs are obtained for one value of the third signal S3.

One of the two first candidates and one of the two second candidates should match or be very close. When there is a matching first candidate and a second candidate, the second arithmetic circuit 62 sets the matching first and second candidates as the corrected detection value θs. The second arithmetic circuit 62 does not have the matching first candidate and the second candidate, but when there are the first candidate and the second candidate that are very close, for example, among them, the calculated value Of the squares of the difference between S1 _n and the first signal S1 and the squares of the difference between the calculated value S3 _n and the third signal S3, the candidate corresponding to the smaller value S1 _n or S3 _n Is the corrected detection value θs.

  As described above, in the rotating magnetic field sensor 1 according to the present embodiment, the first arithmetic circuit 61 is based on the transition state of the signal pair obtained in the process in which the direction DM of the rotating magnetic field MF rotates within a predetermined range. Then, the correction information (A, α) is obtained, and the second calculation circuit 62 calculates the corrected detection value θs using the first signal S1, the third signal S3, and the correction information (A, α). calculate. As a result, according to the present embodiment, even when the second magnetic anisotropy is acquired in the first MR element and the third MR element, the second magnetic anisotropy is caused. It is possible to reduce an error that occurs in the detected value θs.

In the present embodiment, the second arithmetic circuit 62 calculates the corrected detection value θs using the first signal S1, the third signal S3, and the correction information (A, α). May be. FIG. 129 is a block diagram illustrating an example of the configuration of the second arithmetic circuit 62. In this example, the second calculation circuit 62 includes a correction amount calculation unit 62A, a correction signal calculation unit 62B, and a detection value calculation unit 62C.

The second arithmetic circuit 62 receives the first signal S1, the third signal S3, and the correction information (A, α), and equalizes the primary signals of the first signal S1 and the third signal S3. And a correction amount calculation unit 62A that outputs a first correction amount S1e and a third correction amount S3e as third-order harmonic components, a first signal S1, a third signal S3, and a first correction amount S1e. And the third correction amount S3e, the first correction amount S1e is subtracted from the first signal S1, and the third correction amount S3e is subtracted from the third signal S3. The correction signal calculation unit 62B that outputs the correction signal S1n and the third correction signal S3n, and the detection value calculation that inputs the first correction signal S1n and the third correction signal S3n and calculates the corrected detection value θs 62C. This will be described below.

…（１０）

…（１１） In the present embodiment, first, the correction information (A, α) obtained by the first arithmetic circuit 61, the first signal S1, and the third signal S3 are the correction amount arithmetic unit included in the second arithmetic circuit 62. 62A is input. The correction amount calculation unit 62A approximately calculates the correction amount S1e of the first signal S1 and the correction amount S3e of the third signal S3 expressed by the following equations (10) and (11).

(10)

... (11)

Here, expressions (10) and (11) will be described. For example, the waveforms of the first signal S1 and the third signal S3 can be expressed by the equations (1) and (2) due to magnetic anisotropy generated in the free layer of the magnetoresistive element. In contrast to the ideal waveform (sine waveform) indicated by reference numeral 71 in FIG. 7, the waveform indicated by reference numeral 72 is a distorted waveform. Here, A in the equations (1) and (2) is an odd order obtained by Fourier expansion of sin {2 (θ−α)} in the first signal and the third signal when the value can be regarded as minute. In the higher harmonic components, the fifth and subsequent harmonic components of A · sin {2 (θ−α)} are minimized. When induced magnetic anisotropy is acquired in the free layer, even-order harmonic components are not generated, so that only odd-orders need to be handled. Here, the range of A is approximately 2 ° or less.

Here, the difference between the ideal waveform (sinusoidal waveform) and the waveforms of the first signal S1 and the third signal S3 can be said to be a component that generates an error in the detected value. This is the amount to be corrected of the third signal S3. It is known that when the range of A in the equation can be regarded as small, this difference can be approximated to an equalized first-order component and third-order harmonic component. Equal differentiation refers to equal signal amplitude. Thus, the correction amount calculation unit 62A can approximately express the correction amount S1e of the first signal S1 and the correction amount S3e of the third signal S3 using the equations (10) and (11). It is possible to calculate without using a complicated arithmetic unit.

…（１４）

…（１５）

ここで、補正情報Ａが小さい場合、式（１６）および（１７）の近似が成り立つ。

ｃｏｓ［Ａｓｉｎ｛２（θ−α）｝］≒１ …（１６）
ｓｉｎ［Ａｓｉｎ｛２（θ−α）｝］≒（Ａ・π／１８０）・ｓｉｎ｛２（θ−α）｝
…（１７）

この式（１６）、（１７）を式（１４）、（１５）に代入し、三角関数の積和の公式より展開すると、以下の式（１８）、（１９）となる。

…（１８）

…（１９）
この式（１８）、（１９）は、第１の信号Ｓ１および第３の信号Ｓ３の補正すべき量が、Ａ／２倍された一倍角および三倍角と等価であることを示している。つまりＡ値が小さい場合は、５次以降の高調波成分は極小になり、Ａ／２倍に等分化された一次成分および、３次高調波成分に近似するとこができる。式（１０）及び（１１）は、上記式（１８）および（１９）を、三角関数の加法定理および三倍角の公式を用いて展開したものである。 The details of the amounts to be corrected of the first signal S1 and the third signal S3 described above will be described. As described above, the components caused by the magnetic anisotropy that is acquired are the equations (1) and (2) of the first and third signals S1 and S3, and sin θ that is an ideal waveform (sine waveform). And cos θ, and can be expressed by equations (12) and (13). This is the amount to be corrected of the first signal S1 and the third signal S3.

S1e = sin [θ-Asin {2 (θ−α)}] − sin θ (12)
S3e = cos [θ-Asin {2 (θ−α)}] − cos θ (13)

These equations (12) and (13) can be converted into equations (14) and (15), respectively, by the addition theorem of trigonometric functions.

... (14)

... (15)

Here, when the correction information A is small, approximations of equations (16) and (17) hold.

cos [Asin {2 (θ−α)}] ≈1 (16)
sin [Asin {2 (θ−α)}] ≈ (A · π / 180) · sin {2 (θ−α)}
... (17)

Substituting these formulas (16) and (17) into formulas (14) and (15) and expanding them from the product-sum formula of trigonometric functions, the following formulas (18) and (19) are obtained.

... (18)

... (19)
These equations (18) and (19) indicate that the amounts to be corrected of the first signal S1 and the third signal S3 are equivalent to the A / 2-folded single angle and triple angle. That is, when the A value is small, the harmonic components after the fifth order are minimized, and can be approximated to the primary component and the third harmonic component that are equally divided by A / 2 times. Expressions (10) and (11) are obtained by expanding the above expressions (18) and (19) using the trigonometric addition theorem and the triple angle formula.

  In the correction signal calculation unit 62A, a numerical table for α is prepared as means for obtaining cos (2α) and sin (2α) in the equations (10) and (11) from the correction information (A, α). In addition, it may be obtained from this table. Further, the correction signal calculation unit 62A may have a calculation unit having a CORDIC algorithm, and cos (2α) and sin (2α) may be obtained using this calculation unit.

Next, the second calculation circuit 62 calculates the corrected first signal S1 _n and the corrected third signal S3 _n in the correction signal calculation unit 62B. First, the first signal S1, the third signal S3, the correction amount S1e of the first signal S1, and the correction amount S3e of the third signal S3 are input to the correction signal calculation unit 62B. Next, in Expressions (20) and (21), the corrected first signal S1 _n is calculated by subtracting the correction amount S1e from the first signal S1, and the correction amount S3e is calculated from the third signal S3. Is corrected to calculate the corrected third signal S3 _n .

S1 _n = S1-S1 _e (20)
S3 _n = S3-S3 _e (21)

Next, the second calculation circuit 62 is corrected by the detected value calculation unit 62C from the corrected first signal S1 _n and the corrected third signal S3 _n by the following equation (22). The detection value θs is calculated. “Arctan” represents an arc tangent.

θs = arctan (S1 _n / S3 _n ) (22)

If the correction information A is 1 °, the error of the detected value θs is ± 1 °, but the error of the detected value θs corrected in the present embodiment is ± 0.02 ° or less.

In the range where the angle θs is not less than 0 ° and less than 360 °, the solution of θs in the equation (22) has two values different by 180 °. However, it is possible to determine which of the two solutions of θs in Equation (22) is the true value of θs by the combination of S1 _n and S3 _n . That is, when S1 _n is a positive value, θs is larger than 0 ° and smaller than 180 °. When S1 _n is a negative value, θs is greater than 180 ° and smaller than 360 °. When S3 _n is a positive value, θs is in the range of 0 ° to less than 90 ° and greater than 270 ° to 360 °. When S3 _n is a negative value, θs is greater than 90 ° and smaller than 270 °. θs can be obtained by the determination of the expression (22) and the positive / negative combination of S1 _n and S3 _n described above. The above-described method for calculating the first signal corrected in the second arithmetic circuit 62 is completed only by the arithmetic processing by the mathematical formula as described above, so that the calculation time is shortened, and a memory for storing a table or the like. Is also unnecessary.

The correction is performed using the sin inverse function equation (23) using the corrected first signal S1 _n or the cos inverse function equation (24) using the corrected third signal S3 _n. The detected value θs may be calculated. In this case, two candidates for the detected value θs are obtained, but can be specified as the true detected value θs based on the positive / negative relationship between the signal S1 _n and the signal S3 _n . Note that “arcsin” in the following equation (23) represents an arc sine, and “arccos” in the following equation (24) represents an arc cosine.

θs = arcsin (S1 _n ) (23)
θs = arccos (S3 _n ) (24)

In the present embodiment, the second arithmetic circuit 62 obtains a provisional detection value θo from the first signal S1, or the first signal S1 and the third signal S3, and obtains the provisional detection value θo and The correction value θc may be obtained from the correction information (A, α), and the detection value θs may be calculated from the provisional detection value θo and the correction value θc. FIG. 10 is a block diagram illustrating an example of the configuration of another second arithmetic circuit 63. This will be described with reference to FIG. The second arithmetic circuit 63 receives the first signal S1, or the first signal S1 and the third signal S3, and outputs a provisional detection value θo, and a provisional detection value. A correction value calculation unit 63B that inputs θo and correction information (A, α), outputs a correction value θc for correcting the provisional detection value θo, and inputs and adds the correction value θc and the provisional detection value θo, and adds And an adding unit 63C that calculates the added value as the detected value θs. This will be described below.

  The detection value calculation unit 63A included in the second calculation circuit 63 receives the first signal S1, or the first signal S1 and the third signal S3, and calculates a provisional detection value θo. Here, the provisional detection value θo is obtained from the first signal S1 or the inverse trigonometric function of the first signal S1 and the third signal S3 as shown in the following formulas (25) and (26). It is done.

θo = arcsin (S1) (25)
θo = arctan (S1 / S3) (26)

  The correction value calculator 63B receives the provisional detection value θo and the correction information (A, α), and calculates the correction value θc (initial correction value θc0, initial correction value θc0 + additional correction value θc1). Details will be described later.

  The adding unit 63C adds the provisional detection value θo and the correction value θc to calculate the detection value θs.

  Note that within the range where the provisional detection value θo is not less than 0 ° and less than 360 °, the solutions of θo in the equations (25) and (26) have two values different by 180 °. However, it is possible to determine which of the two solutions of θo in Equation (25) is the true value of θo by the combination of S1 and S3. That is, when S1 is a positive value, θo is larger than 0 ° and smaller than 180 °. When S1 is a negative value, θo is larger than 180 ° and smaller than 360 °. When S3 is a positive value, θo is in the range of 0 ° to less than 90 ° and greater than 270 ° to 360 °. When S3 is a negative value, θo is greater than 90 ° and smaller than 270 °. θo can be obtained by determining the expression (26) and the positive / negative combination of S1 and S3.

In the correction value calculation unit 63B, the initial correction value θc0 and the additional correction value θc1 are calculated. The correction value θc is output as the initial correction value θc0 or the sum of the initial correction value θc0 and the additional correction value θc1. Here, the additional correction value θc1 is an approximate term for correcting the error of the initial correction value θc0 and is not used alone.

The provisional detection value θo calculated by the detection value calculation unit 63A is based on the actual first signal S1 and third signal S3 itself as shown in the equations (25) and (26). Since the angle variation term (A, α) based on the second magnetic anisotropy shown in the equations 1) and (2) is included, the angle variation term Asin2 (θ−α) is subtracted from the accurate detected value θ. (27). Accordingly, the accurate detection value θ can be obtained by adding the angle variation term Asin2 (θ−α) to the calculated provisional detection value θo (28).

θo = θ−Asin {2 (θ−α)} (27)
θ = θo−Asin {2 (θ−α)} (28)

The angle variation term Asin {2 (θ−α)} in the equation (27) corresponds to the error of the provisional detection value θo, and is a sine of two cycles of amplitude A ° and phase α ° between 0 ° and 360 °. Become a wave. Considering the correction information (A, α), α can take the entire range from 0 ° to 360 °. However, since A is practically about several degrees, the error fluctuation range is about ± several degrees at the maximum. It becomes. Accordingly, the provisional detection value θo is a two-cycle sine wave with an amplitude of ± several degrees around the accurate detection value θ.

As shown in the equation (28), the accurate θ can be obtained by adding the angle variation term Asin {2 (θ−α)} to the provisional detection value θo, and this includes the exact θ to be obtained. It is not possible to calculate directly. Therefore, assuming that θ in the angle variation term Asin {2 (θ−α)} is replaced with the provisional detection value θo, the difference Δ (θ → θo) at that time is calculated to obtain equation (31). It is done.

…(２９)
第１項に加法定理を適用すると、

…(３０)
となり、

…(３１)

... (29)
Applying the additive theorem to the first term,

... (30)
And

... (31)

Since A is practically about several degrees, it can be treated as a small angle in the arc degree method, and the approximation of equation (32) holds.

…(３２)
ここでは、Ａ［ｄｅｇ］＝ πＡ／１８０［ｒａｄ］を適用している。

... (32)
Here, A [deg] = πA / 180 [rad] is applied.

  When the approximation of equation (32) is applied to equation (31), the difference Δ (θ → θo) is simplified to equation (33). Further, the equation (34) is obtained by modifying this.

…(３３)

…(３４)

... (33)

... (34)

  Considering a case where a temporary detection value θo is used instead of θ in the angle variation term Asin2 (θ−α) of equation (28), and substituting equation (13-5) into equation (28), Equation (35) including an error generated in the second term when Asin2 (θo−α) is added to the provisional detection value θo is obtained.

…(３５)

... (35)

The second term of the equations (28) and (35) becomes an accurate difference from θ, that is, an error term, and the maximum value corresponds to the amplitude of each sine wave. For example, A, the maximum? Pa ^2/180 in (35) in (28). This means that become? Pa ^2/180 cases, the error from A using the provisional detected value θo instead of theta in (28) the angle variation term Asin2 (θ-α) of the formula. That is, in the range of A> πA ^2/180 is satisfied, (28) the angle variation term Asin2 a theta of (theta-alpha) by replacing the temporary detection values .theta.o, it is possible to reduce the error.

…(３６)

... (36)

Since the actual A is about several degrees and is within the range of (36), the second term of the equation (35) is smaller than the second term of the equation (28). That is, correction can be made by replacing θ in the angle variation term Asin2 (θ−α) of the equation (28) with the provisional detection value θo. As described above, the initial correction value θc0 of the correction term to be added to the temporary detection value θo is defined as the initial correction value by replacing θ of the angle variation term Asin2 (θ−α) with the temporary detection value θo. it can.

…(３７)

... (37)

Further, (35) second term of the equation, since the error from the exact θ in the case of calculating the .theta.o + .theta.c1 obtained by adding the provisional detected value .theta.o the expression (37), the second term (? Pa ^2/180) By adding sin (4 (θ−α)), further error reduction is possible. However, this term also contains the exact θ that we want to find and cannot be directly calculated. Therefore, when the difference Δ1 (θ → θo) is calculated when θ in this term is replaced with the provisional detection value θo, equation (40) is obtained.

…(３８)
第１項に加法定理を適用すると、

…(３９)
となり、

…(４０)

... (38)
Applying the additive theorem to the first term,

... (39)
And

... (40)

Since A is practically about several degrees, it can be treated as a small angle in the arc degree method, and the approximation of (41) holds.

…(４１)
ここでは、Ａ［ｄｅｇ］＝ πＡ／１８０［ｒａｄ］を適用している。

... (41)
Here, A [deg] = πA / 180 [rad] is applied.

  When the approximation of (19) is applied to the equation (18-3), the difference Δ1 (θo−θ) is simplified to the equation (42).

…(４２)

... (42)

Here, the second term of the equation (35) and the maximum value of the equation (18-4) correspond to the amplitudes of the respective trigonometric functions. For example, the? Pa ^2/180, in (18-4) Formula (π / ⁹⁰⁾ 2 ^{A 3} in (35). Namely, (35) second term of the equation (? Pa ^2/180) sin the case of using a temporary detection value θo instead of theta in (4 (theta-alpha)), from ^{πA 2/180 (π / 90} ) It means to become ² a ^3. That is, in the range where ^{πA 2/180> (π /} 90) 2 A 3 is satisfied, (35) second term of the equation ^{(πA 2/180) sin (} 4 (θ-α)) provisionally in place of theta in It is possible to reduce the error by replacing with the detected value θo. However, since only the amplitude is compared here, it is stricter than the actual correction range.

…(４３)

... (43)

Since the actual A is in the range of (43), it is possible to reduce the error by replacing ^{(πA 2/180) sin (} 4 (θ-α)) of the provisional detected value θo instead of theta. As described above, the additional correction value θc1 can be defined by the equation (21) as a correction term to be added after the initial correction value θc0 is added to the provisional detection value θo.

…(４４)

... (44)

Here, either one of the following is applied to the correction value θc calculated by the correction value calculator 62B depending on the required accuracy.

θc = θc ₀ (45)
θc = θc ₀ + θc ₁ (46)

  FIG. 12 shows an example of detection value correction using correction information (A = 5 ° α = 45 °). The two-cycle error due to the angle variation term is reduced to a small four-cycle error by correction of (45). It turns out that it is almost invisible by further correction by addition. FIGS. 13 to 15 compare actual correction effects according to equations (45) and (46) when the value of the correction information A is shaken. If A is within 30 °, the correction is sufficiently performed. It shows that it is possible. In addition, the maximum value of the amplitude fluctuation value A at which the detected value error is 0.1 degrees or less is about 2.3 ° when the equation (45) is used, and is about 5.5 ° when the equation (46) is used. This means that a practical value of A is sufficiently effective. From the above, it is possible to select which correction formula is used in a trade-off such as arithmetic processing capability, circuit mounting scale, and required accuracy.

  Expressions (37) and (44) give similar results even if they are modified using the properties of trigonometric functions, theorems, and the like. For example, equation (37) is transformed as follows using a double-square formula.

…(４７)

... (47)

  As another configuration of the second arithmetic circuit, the arithmetic circuit 64 in FIG. 11 can be used. The calculation circuit 64 includes a detection calculation unit 64A, a correction value calculation unit 64B, and an addition unit 64C, and uses the first signal S1, the third signal S3, and the correction information (A, α) to detect the detected value. θs is calculated. The difference from FIG. 9 is that the third signal S3 is input to the correction value calculator 64B. This will be described below.

  When the expressions (1) and (2) are expressed by the provisional detection angle θo, the expressions (48) and (49) are obtained.

S1 = sin θo (48)
S3 = cos θo (49)

…(５０)

…(５１)

…(５２) Here, when a double angle formula is applied to the trigonometric function part of the equations (37) and (44), equations (50) to (52) are obtained.

... (50)

... (51)

... (52)

When equation (50) is applied to equation (37), initial correction value θc0 is expressed by equation (53) using S1, S3 and correction information (A, α).

…(５３)

... (53)

Further, when the formulas (51) and (52) are applied to the formula (53), the additional correction value θc1 is expressed by the formula (57) using S1 and S3, the correction information (A, α), and the initial correction value θc0. .

…(５４)
ここで、

…(５５)
と変形し、初期補正値θｃ０で置き換えると、

…(５６)
(５１)式を適用すると、

…(５７)

... (54)
here,

... (55)
And is replaced by the initial correction value θc0,

... (56)
Applying equation (51),

... (57)

  In the equations (53) and (57), the correction value θc is calculated by the four arithmetic operations using the signal values S1, S2, etc. without performing the trigonometric function operation except for the calculation of sin2α and cos2α after the correction information is acquired. It is possible. Further, the correction effect in this case is equivalent to that obtained when the equations (37) and (44) are used.

Accordingly, the equation (37) or (53) can be used to calculate the initial correction value θc0, and the equation (44) or (57) can be used to calculate the additional correction value θc1, and the processing capacity, circuit implementation scale, and necessary Select by trade-off such as accuracy. Therefore, as the correction value θc, the sum of the expressions (37) and (57) and the sum of the expressions (44) and (53) can be used.

Since S1 and S3 are sine and cosine having the same arguments, equation (58) is established.

S1 ² + S3 ² = 1 (58)

  Therefore, the initial correction value θc0 and the additional correction value θc1 are not always the expressions (53) and (57). For example, equation (53) can be replaced with equation (59) using equation (58), but the correction effect is equivalent to equation (53).

…(５９)

… (59)

  In the present embodiment, the second detection circuit 20 may be configured to detect a component in the second direction D2 of the rotating magnetic field MF, similarly to the third detection circuit 30. In this case, the transition (Lissajous curve) of the signal pair acquired by the signal acquisition unit 61A is close to a circle. In this case as well, in principle, if (A, α) is different, the transition mode of the signal pair (the shape of the Lissajous curve) is different.

  In the present embodiment, the first and second detection circuits 10 and 20 are configured to detect the component of the rotating magnetic field MF in the second direction D2, and the third detecting circuit 30 is configured to detect the rotating magnetic field MF. You may be comprised so that the component of the 1st direction D1 may be detected. In this case, the transition (Lissajous curve) of the signal pair acquired by the signal acquisition unit 61A is similar to the transition (Lissajous curve) of the signal pair already described in the present embodiment.

  In the present embodiment, when high measurement accuracy is required, the first and second signals S1 and S2 are normalized, and the normalized signals S1 and S2 are subjected to the first calculation. You may make it input to the circuit 61. FIG. In this normalization process, the signals S1 and S2 before normalization are converted into signals S1 and S1 after normalization by linear calculation so that the maximum values and the minimum values of the signals S1 and S2 after normalization are equal to each other. This is a process of converting to S2.

  The rotating magnetic field sensor 1 is used for detecting an angle within an angle range smaller than a predetermined range (for example, 360 °) in which the direction DM of the rotating magnetic field MF needs to rotate in order to obtain the correction information (A, α). It may be used for In this case, the actual angle may be detected after the correction information (A, α) is obtained by rotating the direction DM of the rotating magnetic field MF by a predetermined range or more.

In the present embodiment, instead of the third detection circuit 30, a determination circuit that performs only positive / negative determination of the component in the second direction D2 of the rotating magnetic field MF at the reference position PR may be provided. This discrimination circuit can be realized by, for example, a magnetic detection element having sensitivity in the second direction D2 and a circuit that binarizes the detection output of the magnetic detection element using a predetermined threshold value. . As the magnetic detection element having sensitivity in the second direction D2, for example, a TMR element or GMR element in which the magnetization direction of the magnetization fixed layer is set in a direction parallel to the second direction D2, or the second direction D2 It is possible to use a Hall element set so as to have sensitivity. In this case, the second arithmetic circuit 62 detects based on the first candidate of the detected value θs corresponding to the calculated value S1 _n obtained by the above-described search and the positive / negative discrimination result obtained by the discrimination circuit. The value θs is determined. As described above, in most cases, two first candidates of the detected value θs are obtained for one value of the first signal S1. When one of the two candidates is greater than 0 ° and less than 90 °, the other of the two candidates is greater than 90 ° and less than 180 °. Also, when one of the two candidates is greater than 180 ° and less than 270 °, the other of the two candidates is greater than 270 ° and less than 360 °. On the other hand, when the angle θ is 0 ° or more and less than 90 ° and within a range greater than 270 ° and 360 ° or less, the component in the second direction D2 is a positive value, and θs is greater than 90 ° and 270. When it is smaller than °, the component in the second direction D2 is a negative value. Therefore, using the discrimination result of the discrimination circuit, one of the two first candidates of the detection value θs can be specified as the true detection value θs.

  When the rotating magnetic field sensor 1 is used for an application in which the angle θ is in the range of 90 ° to 270 ° or in the range of 0 ° to 90 ° and 270 ° to less than 360 °, the third The detection circuit 30 may be omitted. That is, in this case, since only one first candidate for the detected value θs is obtained, this candidate can be used as the detected value θs.

  In addition, this invention is not limited to said each embodiment, A various change is possible. For example, the magnetic detection element in the present invention is not limited to a spin valve type MR element (GMR element, TMR element), and may be any element that can have magnetic anisotropy in some form. For example, an AMR (anisotropic magnetoresistive effect) element may be used as the magnetic detection element. The first and third magnetic anisotropies are not limited to shape magnetic anisotropy, and may be set by crystal magnetic anisotropy or stress magnetic anisotropy.

Further, the present invention is not applied only to the above embodiment, that is, the case where the rotating magnetic field sensor and the columnar magnet are arranged in parallel, but the case where the rotating magnetic field sensor is inclined with respect to the magnet. Even applicable. In this case, the reference plane is also inclined according to the inclination of the rotating magnetic field sensor, and the reference direction and the reference position are also inclined according to the inclination of the rotating magnetic field sensor. That is, the rotating magnetic field sensor, the reference plane, the reference direction, and the reference position can be integrated. Further, for example, the present invention can be applied even when a plurality of NS magnets such as linear sensors are arranged on a straight line and the rotation sensor moves in parallel with the NS magnet arrangement direction. In this case, the rotation angle of the rotating magnetic field sensor changes according to the linear movement amount of the rotating magnetic field sensor. For example, the rotating magnetic field sensor is arranged so that the NS magnet arrangement direction is perpendicular to the lamination direction of the film forming the rotating magnetic field sensor and the moving direction of the rotating magnetic field sensor is included in the reference plane integrated with the rotating magnetic field sensor. If it arrange | positions, the free layer of a magnetoresistive element will rotate according to the magnetic field which NS magnet generate | occur | produces. Therefore, the rotation angle of the rotating magnetic field sensor corresponds to the linear movement amount of the rotating magnetic field sensor. Thus, the present invention is not limited to angle detection of a rotating body, but can be applied to a rotating magnetic field sensor that performs magnetic field detection based on various amounts of relative movement.

DESCRIPTION OF SYMBOLS 1 ... Rotary magnetic field sensor, 10 ... 1st detection circuit, 20 ... 2nd detection circuit, 30 ... 3rd detection circuit, 14, 24, 34 ... Wheatstone bridge circuit, 61 ... 1st arithmetic circuit, 61A ... Signal acquisition unit, 61B ... correction information calculation unit, 61C ... set value, 62 ... second calculation circuit, 62A ... correction amount calculation unit, 62B ... correction signal calculation unit, 62C ... detection value calculation unit, 63 ... second Arithmetic circuit, 63A ... detected value calculating unit, 63B ... correction value calculating unit, 63C ... adding unit, 64 ... second calculating circuit, 64A ... detected value calculating unit, 64B ... correction value calculating unit, 64C ... adding unit.

Claims (11)

A rotating field sensor that generates a detection value having a correspondence relationship with an angle formed by a direction of a rotating magnetic field at a reference position with respect to the reference direction, wherein the direction of the rotating magnetic field at the reference position is viewed from the rotating field sensor. Is rotating,
A first detection circuit that includes a first magnetic detection element and generates a first signal having a correspondence relationship with an angle formed by a direction of the rotating magnetic field at the reference position with respect to the reference direction;
A second detection circuit that includes a second magnetic detection element and generates a second signal having a correspondence relationship with an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction;
A first arithmetic circuit;
A second arithmetic circuit,
At least one of the first and second magnetic detection elements is arranged so that the first signal anisotropy and the second signal have different variations caused by the first magnetic anisotropy. Magnetic anisotropy is set,
The first arithmetic circuit obtains correction information for correcting an error generated in the detection value due to second magnetic anisotropy generated in the first magnetic detection element, Obtaining the correction information based on two different signals of one of the first signal and the second signal;
The rotating magnetic field sensor, wherein the second arithmetic circuit calculates the corrected detection value using the first signal and the correction information. The rotating magnetic field sensor is further set to at least one of two different angles obtained by at least one trigonometric function value and an inverse function of the trigonometric function value and the first and second magnetic sensing elements. A setting unit that outputs an angular variation term based on the first magnetic anisotropy;
The first arithmetic circuit receives the first and second signals and the value of the trigonometric function, and is obtained when one of the first and second signals is equal to the value of the trigonometric function. A signal acquisition unit that outputs the other two different signals, a correction information calculation unit that inputs the two different other signals, the two different angles, and the angle variation term, and obtains the correction information. The rotating magnetic field sensor according to claim 1, comprising: Of the continuous first signal and second signal, the first signal and the second signal are different from each other in the direction of the length of the perpendicular to the first straight line connecting the points where the first signal and the second signal have the same value. Smax1 and Smax2 (where Smax1> Smax2) are set as the first maximum value and the second maximum value of the one signal that maximizes the length of the perpendicular of each of the two other signals having one as an argument. The rotating magnetic field sensor according to claim 1, wherein a range of values that can be taken by the one signal is Smax2 or more and Smax1 or less. The rotating field sensor according to claim 2, wherein the value of the at least one trigonometric function is one. 5. The rotating field sensor according to claim 1, wherein the first signal and the second signal output a sine wave output or a cosine wave output. 6.   6. The rotating field sensor according to claim 1, wherein the first magnetic anisotropy is set in at least a second magnetic detection element of the first and second magnetic detection elements. . The second magnetic detection element includes a magnetic layer whose direction of magnetization changes according to the direction of the rotating magnetic field,
The rotating magnetic field sensor according to claim 6, wherein the first magnetic anisotropy is set by a shape magnetic anisotropy of the magnetic layer. The second magnetic detection element is disposed between a magnetization fixed layer whose magnetization direction is fixed, a free layer whose magnetization direction changes according to the direction of the rotating magnetic field, and the magnetization fixed layer and the free layer. A non-magnetic layer,
The rotating magnetic field sensor according to claim 6, wherein the first magnetic anisotropy is set by a shape magnetic anisotropy of the free layer.   9. The rotating field sensor according to claim 8, wherein the easy axis direction of magnetization of the free layer is not parallel to or orthogonal to the magnetization direction of the magnetization fixed layer.   When the angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction is θ and the correction information is A and α, the first signal is θ−Asin {2 (θ−α). The rotating magnetic field sensor according to claim 1, wherein the rotating magnetic field sensor is represented by a trigonometric function having a variable as a variable. The rotating magnetic field sensor further includes a third detection circuit,
The third detection circuit includes a third magnetic detection element, and generates a third signal having a correspondence relationship with an angle formed by a direction of the rotating magnetic field at the reference position with respect to the reference direction,
The phase of the third signal is different from the phase of the first signal,
11. The second arithmetic circuit calculates the corrected detection value using the third signal in addition to the first signal and the correction information. A rotating magnetic field sensor according to claim 1.

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