JP2017201284A - Angle sensor correction device and angle sensor - Google Patents

Abstract

An angular error including an error that does not cause a change in the magnitude of the sum of the square of a first detection signal and the square of a second detection signal is reduced.
An angle sensor correction device 3 includes a correction unit 33 that performs a first correction process on a first detection signal S1 and performs a second correction process on a second detection signal S2. ing. The first correction process is a process of generating the first post-correction detection signal S1c by combining the first detection signal S1 and the first correction value. The second correction process is a process for generating the second post-correction detection signal S2c by synthesizing the second detection signal S2 and the second correction value. The first correction value has a first amplitude and changes in the first period. The second correction value has a second amplitude and changes in the second period. The first and second amplitudes have the same value. The first and second periods have the same value of 1/3 or 1/5 of the period of each ideal component of the detection signals S1 and S2.
[Selection] Figure 4

Description

  The present invention relates to a correction device for correcting an error in an angle sensor that generates an angle detection value having a corresponding relationship with an angle to be detected, and an angle sensor including the correction device.

  In recent years, an angle sensor that generates an angle detection value having a corresponding relationship with an angle to be detected has been widely used in various applications such as detection of a rotational position of a steering wheel or a power steering motor in an automobile. An example of the angle sensor is a magnetic angle sensor. In a system in which a magnetic angle sensor is used, a magnetic field generator that generates a rotating magnetic field whose direction rotates in conjunction with the rotation or linear motion of an object is generally provided. The magnetic field generator is, for example, a magnet. The angle of the detection target in the magnetic angle sensor is, for example, an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction.

  The angle sensor has a detection signal generation unit that generates first and second detection signals that are 90 ° out of phase with each other, and generates an angle detection value by calculation using the first and second detection signals. It has been known. The detection signal generation unit includes a first detection circuit that outputs a first detection signal and a second detection circuit that outputs a second detection signal. Each of the first and second detection circuits includes at least one magnetic detection element. The magnetic sensing element includes, for example, 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 a nonmagnetic layer disposed between the magnetization fixed layer and the free layer A spin-valve magnetoresistive element (hereinafter also referred to as an MR element).

  In the case of a magnetic angle sensor, when the direction of the rotating magnetic field changes at a constant angular velocity and the angle of the detection target changes at a predetermined cycle, each waveform of the first and second detection signals is ideally And sinusoidal curves (including sine and cosine waveforms). However, the waveform of each detection signal may be distorted from a sine curve. In this case, the first detection signal includes a first ideal component that changes to draw an ideal sinusoid and an error component other than that, and the second signal draws an ideal sinusoid. The second ideal component that changes in this way and other error components are included. If the waveform of each detection signal is distorted, an error may occur in the angle detection value. Hereinafter, an error occurring in the detected angle value is referred to as an angle error.

  Patent Document 1 describes a technique for correcting a phase-shifted two-phase sinusoidal signal output from an encoder used for detecting an angle or the like. In this technique, an error from an ideal Lissajous waveform included in a Lissajous waveform formed by a two-phase sinusoidal signal is detected, and the two-phase sinusoidal signal is corrected based on this error. The two-phase sinusoidal signal in Patent Document 1 corresponds to the first and second detection signals described above. Further, the radius of the Lissajous waveform in Patent Document 1 corresponds to the square root of the square sum signal that is the sum of the square of the first detection signal and the square of the second detection signal.

JP 2006-112862 A

  The technique described in Patent Document 1 is a technique for correcting the first and second detection signals so that the variation in the magnitude of the square sum signal is small. Therefore, this technique can reduce an error that causes a variation in the magnitude of the square sum signal among the angular errors.

  However, the angle error may include an error that changes according to the angle of the detection target but does not cause a change in the magnitude of the square sum signal. Hereinafter, of the angle errors, an error that causes a change in the magnitude of the square sum signal is referred to as a first type error, and an error that changes according to the angle of the detection target but does not cause a change in the magnitude of the square sum signal Is called the second type error.

  In the magnetic angle sensor, the first type of error is, for example, that the free layer of the MR element has magnetic anisotropy in the magnetization direction of the magnetization fixed layer of the MR element, or the magnetization of the magnetization fixed layer of the MR element. It is caused by the direction changing due to the influence of a rotating magnetic field or the like.

  The second type of error is caused by an error that occurs in the same phase in the first detection signal and the second detection signal. More specifically, the second type of error is that the first detection signal and the second detection signal are different from the first ideal component and the second ideal component, respectively, according to the angle of the detection target. , Due to the difference in magnitude corresponding to the second type error.

  In the magnetic type angle sensor, the second type error is caused by, for example, magnetic anisotropy in the same direction in the free layer of the MR element of the first detection circuit and the free layer of the MR element of the second detection circuit. Or the positional relationship between the magnetic field generator and the detection signal generator is deviated.

  In the angle sensor, the angle error that occurs when correction is not performed includes at least one of a first type error and a second type error. When the angle error that occurs when correction is not performed includes only the second type error, the technique described in Patent Document 1 cannot reduce the angle error at all. Further, when the angle error that occurs when correction is not performed includes both the first type error and the second type error, the technique described in Patent Document 1 sufficiently reduces the angle error. I couldn't.

  The present invention has been made in view of such a problem, and an object of the present invention is to reduce the angle error even when the angle error generated when correction is not performed includes the second type error. An object of the present invention is to provide an angle sensor correction device and an angle sensor.

  A correction device for an angle sensor according to a first aspect of the present invention includes a first detection signal that generates a first detection signal and a second detection signal each having a corresponding relationship with an angle of a detection target, and a first detection signal. And an angle detection unit that generates an angle detection value having a correspondence relationship with the angle of the detection target based on the second detection signal. An angle sensor according to a first aspect of the present invention includes the detection signal generation unit, the angle detection unit, and a correction device according to the first aspect of the present invention.

  In the correction device according to the first aspect, when the angle of the detection target changes at a predetermined period, the first detection signal includes the first ideal component, the first third harmonic error component, and the first fifth signal. The second detection signal includes a second ideal component, a second third harmonic error component, and a second fifth harmonic error component. The first ideal component and the second ideal component change periodically so as to draw an ideal sinusoidal curve with different phases.

  The first third harmonic error component is an error component corresponding to the third harmonic with respect to the first ideal component. The first fifth harmonic error component is an error component corresponding to the fifth harmonic with respect to the first ideal component. The second third harmonic error component is an error component corresponding to the third harmonic with respect to the second ideal component. The second fifth harmonic error component is an error component corresponding to the fifth harmonic with respect to the second ideal component.

  The correction device according to the first aspect includes a correction unit that performs a first correction process on the first detection signal and performs a second correction process on the second detection signal. The first correction process is a process of generating a first post-correction detection signal used for generating an angle detection value by combining the first detection signal and the first correction value. The second correction process is a process of combining the second detection signal and the second correction value to generate a second post-correction detection signal used for generating the angle detection value.

  The first correction value is a value having a first amplitude and changing in the first period. The second correction value is a value having a second amplitude and changing in the second period. The first amplitude and the second amplitude are the same value. The first period and the second period have the same value of 1/3 or 1/5 of the predetermined period.

  In the correction device and the angle sensor according to the first aspect, the detection target angle may be an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction.

  In the correction device and the angle sensor according to the first aspect, the amplitude of the first third harmonic error component and the amplitude of the first fifth harmonic error component may be different from each other. The amplitude of the harmonic error component and the amplitude of the second fifth harmonic error component may be different from each other.

  In the correction device and the angle sensor according to the first aspect, the first and second amplitudes may be absolute values of the value F for defining the first and second correction values. In this case, the correction unit may generate the first and second correction values based on the value F, the first detection signal, and the second detection signal. The correction device according to the first aspect may further include a correction information holding unit that holds the value F.

  In the correction device and the angle sensor according to the first aspect, the phases of the first ideal component and the second ideal component may be 90 ° different from each other.

  The correction device according to the first aspect may further include a correction reference information holding unit and a correction information determination unit. The correction reference information holding unit holds information on the correspondence relationship between the parameter value and the value F obtained using the calculation using the first detection signal and the second detection signal. The correction information determination unit obtains a parameter value by using an operation using the first detection signal and the second detection signal, and refers to the information held by the correction reference information holding unit to obtain the calculated parameter value. A value F corresponding to is determined. In this case, the phases of the first ideal component and the second ideal component may be 90 ° different from each other, and the parameter value is the sum of the square of the first detection signal and the square of the second detection signal. It may be obtained from the fluctuation component.

  A correction device for an angle sensor according to a second aspect of the present invention includes a first detection signal having a correspondence relationship with an angle of a detection target, a detection signal generating unit for generating a second detection signal, and a first detection signal. And an angle detection unit that generates an angle detection value having a correspondence relationship with the angle of the detection target based on the second detection signal. An angle sensor according to a second aspect of the present invention includes the detection signal generation unit, the angle detection unit, and a correction device according to the second aspect of the present invention.

  In the correction device according to the second aspect, when the angle of the detection target changes at a predetermined cycle, the first detection signal includes the first ideal component, the first error component, the second error component, and the third error signal. The second detection signal includes a second ideal component, a fourth error component, a fifth error component, and a sixth error component. The first ideal component and the second ideal component change periodically so as to draw an ideal sinusoidal curve with different phases.

  The first error component and the second error component are both error components corresponding to the third harmonic with respect to the first ideal component. The third error component is an error component corresponding to the fifth harmonic with respect to the first ideal component. The fourth error component and the fifth error component are both error components corresponding to the third harmonic with respect to the second ideal component. The sixth error component is an error component corresponding to the fifth harmonic with respect to the second ideal component. The amplitude of the second error component and the amplitude of the third error component are equal to each other. The fifth error component and the sixth error component have the same amplitude.

  A correction apparatus according to a second aspect includes a front-stage correction unit that performs a first front-stage correction process and a second front-stage correction process, and a rear-stage correction unit that performs a first rear-stage correction process and a second rear-stage correction process. ing.

  The first pre-correction process is a process of correcting the first detection signal and generating a first post-correction detection signal in which the first error component is reduced compared to the first detection signal. The second upstream correction process is a process of correcting the second detection signal and generating a second post-correction detection signal in which the fourth error component is reduced as compared with the second detection signal.

  In the first post-stage correction process, the first post-correction detection signal and the first correction value are combined, and the second and third error components are reduced compared to the first post-correction detection signal. The first post-correction detection signal is generated. In the second post-stage correction process, the second post-correction detection signal and the second correction value are combined, and the fifth and sixth error components are reduced compared to the second pre-correction detection signal. The second post-correction detection signal is generated. The first post-correction detection signal and the second post-correction detection signal are used to generate an angle detection value.

  The first correction value is a value having a first amplitude and changing in the first period. The second correction value is a value having a second amplitude and changing in the second period. The first amplitude and the second amplitude are the same value. The first period and the second period have the same value of 1/3 or 1/5 of the predetermined period.

  In the correction device and the angle sensor according to the second aspect, the angle of the detection target may be an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction.

  In the correction device and the angle sensor according to the second aspect, the first and second amplitudes may be absolute values of the value F for defining the first and second correction values.

  In the correction device and the angle sensor according to the second aspect, the phases of the first ideal component and the second ideal component may be 90 ° different from each other.

  In the correction device and the angle sensor according to the second aspect, even if the initial phase of the second error component and the third error component are equal to α when the initial phase of the first error component is 0. The initial phase of the fifth error component and the sixth error component when the initial phase of the fourth error component is 0 may be a value α. In this case, the post-stage correction unit may generate the first and second correction values based on the value F, the value α, the first pre-stage post-correction detection signal, and the second pre-stage post-correction detection signal.

  The correction device according to the second aspect may further include a correction information holding unit that holds the value F and the value α.

  Alternatively, the correction device according to the second aspect may further include a correction reference information holding unit, a first correction information determination unit, and a second correction information determination unit. The correction reference information holding unit holds information on the correspondence relationship between the value of the parameter obtained using the calculation using the first detection signal and the second detection signal, the value F, and the value α. The first correction information determination unit obtains the value of the parameter using an operation using the first detection signal and the second detection signal. In this case, the upstream correction unit determines the contents of the first and second upstream correction processes based on the parameter values obtained by the first correction information determination unit. The second correction information determination unit determines the value F and the value α corresponding to the parameter values obtained by the first correction information determination unit with reference to the information held by the correction reference information holding unit. In this case, the phases of the first ideal component and the second ideal component may be 90 ° different from each other, and the parameter value is the sum of the square of the first detection signal and the square of the second detection signal. It may be obtained from the fluctuation component.

  According to the correction device and angle sensor of the first aspect of the present invention and the correction device and angle sensor of the second aspect of the present invention, the angle error that occurs when correction is not performed includes a second type error. In addition, the angle error can be reduced.

1 is a perspective view showing a schematic configuration of an angle sensor system including an angle sensor according to a first embodiment of the present 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 signal generation part of the angle sensor which concerns on the 1st Embodiment of this invention. It is a functional block diagram which shows the structure of the correction | amendment apparatus and angle detection part which concern on the 1st Embodiment of this invention. It is a perspective view which shows a part of one magnetic detection element in FIG. It is a wave form diagram which shows an example of the waveform of the 1st ideal component and error component of the 1st detection signal in the 1st Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the 2nd ideal component and error component of the 2nd detection signal in the 1st Embodiment of this invention. It is a flowchart which shows the correction information determination procedure in the 1st Embodiment of this invention. It is a flowchart which shows the angle detection procedure in the 1st Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the angle error of the angle detection value in the 1st Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the angle error of the angle detection value in the conventional correction method. It is a functional block diagram which shows the structure of the correction | amendment apparatus which concerns on the 2nd Embodiment of this invention, and an angle detection part. It is a wave form diagram which shows an example of the waveform of the square sum signal in the 2nd Embodiment of this invention. It is a flowchart which shows the angle detection procedure in the 2nd Embodiment of this invention. It is a functional block diagram which shows the structure of the correction | amendment apparatus and angle detection part which concern on the 3rd Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the error component of the 1st detection signal in the 3rd Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the error component of the 2nd detection signal in the 3rd Embodiment of this invention. It is a flowchart which shows the correction information determination procedure in the 3rd Embodiment of this invention. It is a flowchart which shows the angle detection procedure in the 3rd Embodiment of this invention. It is a wave form diagram which shows an example of the waveform of the angle error of the angle detection value after a pre-stage correction in the 3rd embodiment of the present invention. It is a functional block diagram which shows the structure of the correction | amendment apparatus and angle detection part which concern on the 4th Embodiment of this invention. It is a flowchart which shows the angle detection procedure in the 4th Embodiment of this invention.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a schematic configuration of an angle sensor system including an angle sensor according to a first embodiment of the present invention will be described with reference to FIG.

  The angle sensor 1 according to the present embodiment generates an angle detection value θs having a correspondence relationship with the angle θ of the detection target. The angle sensor 1 according to the present embodiment is particularly a magnetic angle sensor. As shown in FIG. 1, the angle sensor 1 according to the present embodiment detects a rotating magnetic field MF whose direction rotates. In this case, the angle θ of the detection target is an angle formed by the direction of the rotating magnetic field MF at the reference position with respect to the reference direction. The angle sensor system shown in FIG. 1 includes an angle sensor 1 and a columnar magnet 5 which is an example of a means for generating a 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. Thereby, the direction of the rotating magnetic field MF generated by the magnet 5 rotates around the rotation center C including the central axis of the cylinder.

  The reference position is located in a virtual plane (hereinafter referred to as a reference plane) parallel to one end face of the magnet 5. In this reference plane, the direction of the rotating magnetic field MF generated by the magnet 5 rotates around the reference position. The reference direction is located in the reference plane and intersects the reference position. 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 angle sensor 1 is disposed so as to face the one end surface of the magnet 5.

  In addition, the structure of the angle sensor system in this Embodiment is not restricted to the example shown in FIG. In the configuration of the angle sensor system in the present embodiment, the relative positional relationship between the means for generating the rotating magnetic field MF and the angle sensor 1 changes so that the direction of the rotating magnetic field MF at the reference position rotates when viewed from the angle sensor 1. Any configuration can be used. For example, in the magnet 5 and the angle sensor 1 arranged as shown in FIG. 1, the magnet 5 may be fixed and the angle sensor 1 may rotate, or the magnet 5 and the angle sensor 1 may rotate in opposite directions. Alternatively, the magnet 5 and the angle 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 angle 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 angle 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 angle 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 angle sensor 1 may be moved linearly in the direction in which the N and S poles of the magnetic scale are aligned.

  Also in the configuration of the various angle sensor systems described above, there is a reference plane having a predetermined positional relationship with the angle sensor 1, and the direction of the rotating magnetic field MF in this reference plane is the reference position when viewed from the angle sensor 1. Rotate around.

  The angle sensor 1 includes a detection signal generation unit 2 that generates a first detection signal and a second detection signal each having a corresponding relationship with the angle θ of the detection target. The detection signal generation unit 2 includes a first detection circuit 10 that generates a first detection signal and a second detection circuit 20 that generates a second detection signal. In FIG. 1, for ease of understanding, the first and second detection circuits 10 and 20 are depicted as separate bodies, but the first and second detection circuits 10 and 20 may be integrated. Good. In FIG. 1, the first and second detection circuits 10 and 20 are stacked in a direction parallel to the rotation center C, but the stacking order is not limited to the example shown in FIG. Each of the first and second detection circuits 10 and 20 includes at least one magnetic detection element that detects the rotating magnetic field MF.

  Here, with reference to FIG. 1 and FIG. 2, the definition of the direction and angle in this Embodiment is demonstrated. First, the direction parallel to the rotation center C shown in FIG. 1 and going from bottom to top in FIG. In FIG. 2, the Z direction is represented as a direction from the back to the front in FIG. 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.

  The reference position PR is a position where the angle sensor 1 detects the rotating magnetic field MF. The reference direction DR is the X direction. As described above, the angle θ of the detection target is an angle formed by the direction DM of the rotating magnetic field MF at the reference position PR with respect to the reference direction DR. 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.

  Next, the configuration of the detection signal generation unit 2 will be described in detail with reference to FIG. FIG. 3 is a circuit diagram showing a configuration of the detection signal generation unit 2. As described above, the detection signal generation unit 2 includes the first detection circuit 10 that generates the first detection signal S1 and the second detection circuit 20 that generates the second detection signal S2.

  When the direction DM of the rotating magnetic field MF rotates at a predetermined period, the detection target angle θ changes at a predetermined period T. In this case, both the first and second detection signals S1 and S2 periodically change with a signal period equal to the predetermined period T. The phase of the second detection signal S2 is different from the phase of the first detection signal S1. In the present embodiment, the phase of the second detection signal S2 is preferably different from the phase of the first detection signal S1 by an odd multiple of 1/4 of the signal period. However, the phase difference between the first detection signal S1 and the second detection signal S2 may be slightly deviated from an odd multiple of 1/4 of the signal period 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 detection signal S1 and the phase of the second detection signal S2 is the above-described preferable relationship.

  The first detection circuit 10 includes a Wheatstone bridge circuit 14 and a difference detector 15. The Wheatstone bridge circuit 14 includes a power supply port V1, a ground port G1, two output ports E11 and E12, a first pair of magnetic detection elements R11 and R12 connected in series, and a second connected in series. A pair of magnetic detection elements R13 and R14. 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 signal corresponding to the potential difference between the output ports E11 and E12 as the first detection signal S1.

  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 includes a power supply port V2, a ground port G2, two output ports E21 and E22, a first pair of magnetic detection elements R21 and R22 connected in series, and a second connected in series. A pair of magnetic detection elements R23 and R24. 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 signal corresponding to the potential difference between the output ports E21 and E22 as the second detection signal S2.

  In the present embodiment, each of the magnetic detection elements R11 to R14, R21 to R24 includes a plurality of magnetoresistance effect elements (MR elements) connected in series. Each of the plurality of MR elements is, for example, a spin valve type MR element. This spin-valve MR 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 fixed layer and a free layer. And a nonmagnetic layer disposed therebetween. The spin valve MR element may be a TMR element or a GMR element. 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 a spin-valve MR 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 the resistance value becomes the minimum value when this angle is 0 °. When the angle is 180 °, the resistance value becomes the maximum value. 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 plurality of MR elements included in the magnetic detection elements R11 and R14 is the Y direction, and the magnetization in the plurality of MR elements included in the magnetic detection elements R12 and R13. The direction of magnetization of the fixed layer is the -Y direction. In this case, the potential difference between the output ports E11 and E12 changes according to the intensity of the component in the Y direction of the rotating magnetic field MF. Accordingly, the first detection circuit 10 detects the intensity of the component in the Y direction of the rotating magnetic field MF, and generates a signal representing the intensity as the first detection signal S1. The intensity of the Y-direction component of the rotating magnetic field MF has a corresponding relationship with the angle θ of the detection target.

  In the second detection circuit 20, the magnetization direction of the magnetization fixed layer in the plurality of MR elements included in the magnetic detection elements R21 and R24 is the X direction, and the magnetization in the plurality of MR elements included in the magnetic detection elements R22 and R23. The direction of magnetization of the fixed layer is the −X direction. In this case, the potential difference between the output ports E21 and E22 changes according to the intensity of the component in the Y direction of the rotating magnetic field MF. Therefore, the second detection circuit 20 detects the intensity of the component in the X direction of the rotating magnetic field MF, and generates a signal representing the intensity as the second detection signal S2. The intensity of the component in the X direction of the rotating magnetic field MF has a corresponding relationship with the angle θ of the detection target.

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

  Here, an example of the configuration of the magnetic detection element will be described with reference to FIG. FIG. 5 is a perspective view showing a part of one magnetic detection element in the detection signal generator 2 shown in FIG. In this example, one magnetic detection element has a plurality of lower electrodes 62, a plurality of MR elements 50, and a plurality of upper electrodes 63. The plurality of lower electrodes 62 are arranged on a substrate (not shown). Each lower electrode 62 has an elongated shape. A gap is formed between two lower electrodes 62 adjacent to each other in the longitudinal direction of the lower electrode 62. As shown in FIG. 5, MR elements 50 are arranged on the upper surface of the lower electrode 62 in the vicinity of both ends in the longitudinal direction. The MR element 50 includes a free layer 51, a nonmagnetic layer 52, a magnetization fixed layer 53, and an antiferromagnetic layer 54, which are stacked in order from the lower electrode 62 side. The free layer 51 is electrically connected to the lower electrode 62. 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 63 are disposed on the plurality of MR elements 50. Each upper electrode 63 has an elongated shape, and is disposed on two lower electrodes 62 adjacent to each other in the longitudinal direction of the lower electrode 62 to electrically connect the antiferromagnetic layers 54 of the two adjacent MR elements 50. To do. With such a configuration, the magnetic detection element shown in FIG. 5 includes a plurality of MR elements 50 connected in series by a plurality of lower electrodes 62 and a plurality of upper electrodes 63. The arrangement of the layers 51 to 54 in the MR element 50 may be upside down from the arrangement shown in FIG.

  As described above, when the angle θ to be detected changes with the predetermined period T, the first and second detection signals S1 and S2 both change periodically with a signal period equal to the predetermined period T. To do. When the angle θ of the detection object changes at the predetermined period T, each of the first and second detection signals S1 and S2 includes an ideal sine curve (sine waveform and cosine waveform). ), And an error component other than the ideal component. Hereinafter, the ideal component of the first detection signal S1 is referred to as a first ideal component, and the ideal component of the second detection signal S2 is referred to as a second ideal component. The first and second ideal components have different phases and a predetermined phase relationship. Particularly in the present embodiment, the phases of the first ideal component and the second ideal component differ from each other by 90 °. In the following description, it is assumed that the levels of the first and second detection signals S1 and S2 are adjusted so that the center of change of their ideal components becomes zero. The error component will be described later.

  Next, with reference to FIG. 4, portions other than the detection signal generation unit 2 of the angle sensor 1 will be described. The angle sensor 1 includes a correction device 3 according to the present embodiment and an angle detection unit 4 in addition to the detection signal generation unit 2. FIG. 4 is a functional block diagram illustrating configurations of the correction device 3 and the angle detection unit 4. The correction device 3 and the angle detection unit 4 can be realized by, for example, an application specific integrated circuit (ASIC) or a microcomputer. The angle detection unit 4 generates an angle detection value θs having a correspondence relationship with the angle θ of the detection target based on the first detection signal S1 and the second detection signal S2.

  The correction device 3 includes analog-digital converters (hereinafter referred to as A / D converters) 31 and 32, a correction unit 33, and a correction information holding unit 34. In the correction device 3 and the angle detection unit 4, digital signals are used. The A / D converter 31 converts the first detection signal S1 into a digital signal. The A / D converter 32 converts the second detection signal S2 into a digital signal. The correction unit 33 performs a first correction process on the first detection signal S1 converted into a digital signal by the A / D converter 31, and also converts the first detection signal S1 converted into a digital signal by the A / D converter 32. A second correction process is performed on the second detection signal S2.

  The first correction process is a process of generating the first post-correction detection signal S1c by combining the first detection signal S1 and the first correction value. The first post-correction detection signal S1c is a signal in which an error component to be described later is reduced compared to the first detection signal S1. The first post-correction detection signal S1c is used for generation of the angle detection value θs by the angle detection unit 4. The first correction value is a value having a first amplitude and changing in the first period.

  The second correction process is a process for generating the second post-correction detection signal S2c by combining the second detection signal S2 and the second correction value. The second post-correction detection signal S2c is a signal in which an error component to be described later is reduced compared to the second detection signal S2. The second post-correction detection signal S2c is used for the generation of the angle detection value θs by the angle detection unit 4. The second correction value is a value having a second amplitude and changing in the second period. The first period and the second period have the same value of 1/3 or 1/5 of the predetermined period T.

  The first amplitude and the second amplitude are the same value. Particularly in the present embodiment, the first and second amplitudes are absolute values of the value F for defining the first and second correction values. The correction information holding unit 34 holds the value F. The correction unit 33 generates first and second correction values based on the value F, the first detection signal S1, and the second detection signal S2. A method for generating the first and second correction values will be described later.

  Next, error components of the first and second detection signals S1 and S2 will be described. Since each of the detection signals S1 and S2 includes an error component, an error may occur in the angle detection value θs. Hereinafter, an error that occurs in the detected angle value θs is referred to as an angle error. The angle error that occurs when correction is not performed includes the above-described first type error and second type error.

The main component of the first type error is caused by the same distortion of the waveform of the first detection signal S1 and the waveform of the second detection signal S2. The main component of the first type error changes with a period that is 1/4 of the predetermined period T. Hereinafter, the component of the angular error that changes at a quarter of the predetermined period T is referred to as an angular error quaternary component. It can be said that the first type of error includes an angular error quaternary component as a main component. Here, the first ideal component is sin θ, and the second ideal component is cos θ. When the angle error that occurs when correction is not performed includes only the first type error, the first detection signal S1 and the second detection signal S2 are expressed by the following equations (1) and (2), respectively. Can be represented. In Formulas (1) and (2), A ₁ is a real number. The angular error quaternary component of the first type error expressed in radians is −A ₁ sin4θ.

S1 = sin θ + A ₁ sin (3θ−180 °) (1)
S2 = cos θ + A ₁ cos 3θ (2)

The main component of the second type of error is caused by errors that occur in the same phase in the first detection signal S1 and the second detection signal S2. Further, the main component of the second type error changes in a cycle that is 1/4 of the predetermined cycle T. That is, the second type error includes an angular error quaternary component as a main component. When the angular error that occurs when correction is not performed includes only the second type error, the first detection signal S1 and the second detection signal S2 are expressed by the following equations (3) and (4), respectively. Can be represented. In formulas (3) and (4), A ₂ is a real number. The angular error quaternary component of the second type error expressed in radians is −A ₂ sin 4θ.

S1 = sin (θ−A ₂ sin4θ)
= Sin θ · cos (A ₂ sin 4θ) −cos θ · sin (A ₂ sin 4θ)
... (3)
S2 = cos (θ−A ₂ sin4θ)
= Cosθ · cos (A ₂ sin4θ) + sinθ · sin (A ₂ sin4θ)
(4)

By the way, when the angle x expressed in radians is sufficiently small, cosx and sinx can be approximated as 1 and x, respectively. In the present embodiment, the value of A ₂ is a small value that can approximate cos (A ₂ sin 4θ) and sin (A ₂ sin 4θ) to 1 and A ₂ sin 4θ, respectively. When this approximation is applied to the equations (3) and (4), the first detection signal S1 and the second detection signal S2 are represented by the following equations (5) and (6), respectively.

S1≈sin θ−cos θ · A ₂ sin 4θ
_{= Sinθ- (A 2/2)} {sin5θ-sin (-3θ)}
_{= Sinθ- (A 2/2)} sin3θ- (A 2/2) sin5θ ... (5)
S2≈cos θ + sin θ · A ₂ sin 4θ
_{= Cosθ- (A 2/2)} {cos5θ-cos (-3θ)}
_{= Cosθ + (A 2/2} ) cos3θ- (A 2/2) cos5θ ... (6)

  The angular error that occurs when correction is not performed includes at least one of a first type error and a second type error. Therefore, the first detection signal S1 and the second detection signal S2 can be expressed by the following equations (7) and (8), respectively.

S1 = sin θ + A ₁ sin (3θ−180 °)
_{- (A 2/2) sin3θ-} (A 2/2) sin5θ ... (7)
S2 = cos θ + A ₁ cos 3θ
_{+ (A 2/2) cos3θ-} (A 2/2) cos5θ ... (8)

Here, referred to as _{"A 1 sin (3θ-180} °)" the first error component of the formula _{(7), "- (A} 2/2) sin3θ" is called the second error component, "- the _(a 2/2) sin5θ "says third error components. Moreover, refers to _"A 1 _cos3θ" in the formula (8) and a fourth error _{component, "(A 2/2)} cos3θ" is called the fifth error _{components, "- (A 2/2} ) cos5θ" Is called the sixth error component.

  The first error component and the second error component are both error components corresponding to the third harmonic with respect to the first ideal component sin θ. The third error component is an error component corresponding to the fifth harmonic with respect to the first ideal component sin θ. The fourth error component and the fifth error component are both error components corresponding to the third harmonic with respect to the second ideal component cos θ. The sixth error component is an error component corresponding to the fifth harmonic with respect to the second ideal component cos θ. The amplitude of the second error component and the amplitude of the third error component are equal to each other. The fifth error component and the sixth error component have the same amplitude.

  The first error component and the fourth error component are both error components that cause the first type error. The second error component, the third error component, the fifth error component, and the sixth error component are all error components that cause the second type error. In the present embodiment, in each of the first and second detection signals S1 and S2, the phase difference between the error component causing the first type error and the error component causing the second type error is 0. It shall be a value close to ° or 0 °.

  FIG. 6 is a waveform diagram showing an example of waveforms of the first ideal component and the first to third error components of the first detection signal S1. FIG. 7 is a waveform diagram showing an example of waveforms of the second ideal component and the fourth to sixth error components of the second detection signal S2. 6 and 7, the horizontal axis indicates the angle θ to be detected, the left vertical axis indicates the ideal component, and the right vertical axis indicates the error component. In FIG. 6 and FIG. 7, normalization is performed so that the amplitudes of the first and second ideal components are 1. In FIG. 6, reference numerals 71, 72, 73, and 74 denote a first ideal component, a first error component, a second error component, and a third error component, respectively. In FIG. 7, reference numerals 75, 76, 77, and 78 denote a second ideal component, a fourth error component, a fifth error component, and a sixth error component, respectively. The waveforms shown in FIGS. 6 and 7 are created based on the equations (7) and (8).

  By the way, the first error component and the second error component in Expression (7) can be summarized as similar terms. Further, the fourth error component and the fifth error component in Expression (8) can also be summarized as similar terms. When formulas (7) and (8) are modified so that similar terms are combined, the following formulas (9) and (10) are obtained.

_{S1 = sinθ + (A 1 +} A 2/2) sin (3θ-180 °)
_{- (A 2/2) sin5θ} ... (9)
_{S2 = cosθ + (A 1 +} A 2/2) cos3θ
_{- (A 2/2) cos5θ} ... (10)

Here, referred to as _{"(A 1 + A 2/} 2) sin (3θ-180 °)" the first third harmonic error component of the formula _(9), - the "(A 2/2) sin5θ " This is referred to as a first fifth harmonic error component. _{Also, "(A 1 + A 2} /2) cos3θ" in the formula (10) is called the second third harmonic distortion _{component, "- (A 2/2} ) cos5θ" a second fifth harmonic of This is an error component. The first third harmonic error component is an error component corresponding to the third harmonic with respect to the first ideal component sin θ. The first fifth harmonic error component is an error component corresponding to the fifth harmonic with respect to the first ideal component sin θ. The second third harmonic error component is an error component corresponding to the third harmonic with respect to the second ideal component cos θ. The second fifth harmonic error component is an error component corresponding to the fifth harmonic with respect to the second ideal component cos θ.

  The correction device 3 according to the present embodiment can be applied when the angular error that occurs when correction is not performed includes a second type error. In this case, the first detection signal S1 includes a first ideal component, a first third harmonic error component, and a first fifth harmonic error component, and the second detection signal S2 includes the second detection signal S2 The ideal component, the second third harmonic error component, and the second fifth harmonic error component.

When the angle error that occurs when correction is not performed includes only the second type error, the amplitude of the first third harmonic error component and the amplitude of the first fifth harmonic error component are equal to each other, The amplitude of the second third harmonic error component and the amplitude of the second fifth harmonic error component are equal to each other. In Expressions (9) and (10), the case of A ₁ = 0 and A ₂ ≠ 0 corresponds to the above case.

When the angle error that occurs when correction is not performed includes both the first type error and the second type error, the amplitude of the first third harmonic error component and the first fifth harmonic error are included. The amplitudes of the error components are different from each other, and the amplitudes of the second third harmonic error component and the second fifth harmonic error component are different from each other. In equations (9) and (10), the case of A ₁ ≠ 0 and A ₂ ≠ 0 corresponds to the above case.

  Next, with reference to FIG. 4, FIG. 8, and FIG. 9, the operation of the correction device 3 and the angle detector 4 and the method of generating the detected angle value θs in the present embodiment will be described. The method for generating the angle detection value θs in the present embodiment includes a correction information determination procedure for determining correction information and an angle detection procedure for generating the angle detection value θs. FIG. 8 is a flowchart showing a correction information determination procedure. The correction information determination procedure is executed by the control unit (not shown) outside the angle sensor 1 before shipment or use of the angle sensor 1. FIG. 9 is a flowchart showing an angle detection procedure. The angle detection procedure is executed when the angle sensor 1 is used.

  First, the correction information determination procedure will be described. The correction information determination procedure is performed in a situation where the control unit can recognize the detection target angle θ. This situation is obtained, for example, when the angle θ is changed by a command from the control unit, or when the control unit can acquire information on the angle θ. Hereinafter, the angle θ recognized by the control unit is particularly referred to as a reference angle θr. As shown in FIG. 8, the correction information determination procedure includes a procedure S101 for obtaining an angular error quaternary component using the first and second detection signals S1 and S2 before correction, and a procedure S102 for determining correction information. Is included. In step S101, the first detection signal S1 converted into a digital signal by the A / D converter 31 and the second detection signal S2 converted into a digital signal by the A / D converter 32 may be used.

  In step S101, for example, an angle error for one cycle of the reference angle θr is calculated. Hereinafter, a method for calculating an angle error at an arbitrary reference angle θr will be described. First, based on the first and second detection signals S1 and S2 before correction, a value corresponding to the detected angle value θs when correction is not performed is calculated. Hereinafter, this value is referred to as an uncorrected angle detection value and is represented by the symbol θp. It is assumed that the phase difference between the uncorrected angle detection value θp and the reference angle θr is 0 ° or a value close to 0 °. The uncorrected angle detection value θp is calculated by the following equation (11). “Atan” represents an arc tangent.

  θp = atan (S1 / S2) (11)

  Within the range of θp between 0 ° and less than 360 °, the solution of θp in equation (11) has two values that differ by 180 °. However, it is possible to determine which of the two solutions of θp in Equation (11) is the true value of θp by the positive / negative combination of S1 and S2. In step S101, θp is determined within a range of 0 ° or more and less than 360 ° by determining the combination of the expression (11) and the positive / negative combination of S1 and S2.

  Next, the difference Ep between the uncorrected angle detection value θp and the reference angle θr is calculated by the following equation (12).

  Ep = θp−θr (12)

The difference Ep corresponds to an angle error that occurs when correction is not performed. Hereinafter, the difference Ep is referred to as an angle error of the uncorrected angle detection value θp. The angle error Ep includes an angular error quaternary component as a main component. The angular error quaternary component expressed in radians is expressed as -A ₃ sin4θ. A ₃ is a real number. In step S101, the angular error Ep waveforms obtained as described above, obtaining the _{A 3.} If A ₃ is obtained, the angular error quaternary component “−A ₃ sin 4θ” is specified. In this way, an angular error quaternary component is obtained. The waveform of the angle error Ep is shown in FIG. 10 described later.

In the present embodiment, the correction information is information of the value F described above. In step S102 for determining the correction information, the value F is determined based on the angle error quaternary component of the angle error Ep obtained in step S101. In the present embodiment, A ₃ is a value F. The value F is held by the correction information holding unit 34.

  Next, an angle detection procedure will be described. As shown in FIG. 9, the angle detection procedure includes a procedure S111 for performing a first correction process on the first detection signal S1 and performing a second correction process on the second detection signal S2. And a step S112 for generating the detected angle value θs.

  First, step S111 will be described. Step S111 is executed by the correction unit 33. In step S111, the correction unit 33 first refers to the correction information held by the correction information holding unit 34, that is, the value F. Next, first and second correction values C1 and C2 are generated based on the value F and the first detection signal S1.

  As described above, the first period of the first correction value C1 and the second period of the second correction value C2 are the same value of 1/3 or 1/5 of the predetermined period T. First, the case where the first period and the second period are the same value of 1/3 of the predetermined period T will be described. In this case, the first correction value C1 and the second correction value C2 are represented by the following equations (13) and (14), respectively.

C1 = −Fsin (3θp−180 °) (13)
C2 = −Fcos3θp (14)

  The correction unit 33 obtains the uncorrected angle detection value θp from the first and second detection signals S1 and S2 before correction using Expression (11), and substitutes this θp into Expressions (13) and (14). Thus, the first and second correction values C1 and C2 may be obtained.

  Alternatively, the correction unit 33 may obtain the first and second correction values C1 and C2 as follows without obtaining the uncorrected angle detection value θp. When Expressions (13) and (14) are modified, the following Expressions (15) and (16) are obtained.

C1 = −F (4 sin ³ θp− ³ sin θp) (15)
C2 = −F (4 cos ³ θp− ³ cos θp) (16)

  In the equations (15) and (16), sin θp and cos θp are values of the first detection signal S1 before correction and the second detection signal S2 before correction, respectively, normalized so that the amplitude becomes 1. Therefore, the first and second correction values C1 and C2 can be calculated using the value F, the value sin θp of the first detection signal S1, and the value cos θp of the second detection signal S2.

  Next, a case where the first period and the second period are the same value that is 1/5 of the predetermined period T will be described. In this case, the first correction value C1 and the second correction value C2 are represented by the following equations (17) and (18), respectively.

C1 = −Fsin (5θp−180 °) (17)
C2 = Fcos5θp (18)

  The correction unit 33 obtains the uncorrected angle detection value θp from the first and second detection signals S1 and S2 before correction using Expression (11), and substitutes this θp into Expressions (17) and (18). Thus, the first and second correction values C1 and C2 may be obtained.

  Alternatively, the correction unit 33 may obtain the first and second correction values C1 and C2 as follows without obtaining the uncorrected angle detection value θp. When the equations (17) and (18) are modified, the following equations (19) and (20) are obtained.

C1 = F (16 sin ⁵ θp−20 sin ³ θp + ⁵ sin θp) (19)
C2 = F (16 cos ⁵ θp−20 cos ³ θp + ⁵ cos θp) (20)

  Therefore, even when the first period and the second period are the same value that is 1/5 of the predetermined period T, the first and second correction values C1 and C2 have the value F and the first detection value. It can be calculated using the value sin θp of the signal S1 and the value cos θp of the second detection signal S2.

  In both cases where the first period and the second period have the same value of 1/3 of the predetermined period T and the same value of 1/5 of the predetermined period T, the value F is And the amplitude and phase of the second correction values C1 and C2.

  After generating the first and second correction values C1 and C2 as described above, the correction unit 33 performs a first correction process and a second correction process. In the first correction process, the first detection signal S1 and the first correction value C1 are combined to generate a first corrected detection signal S1c. In the second correction process, the second detection signal S2 and the second correction value C2 are combined to generate a second corrected detection signal S2c. The first corrected detection signal S1c and the second corrected detection signal S2c are represented by the following equations (21) and (22), respectively.

S1c = S1 + C1 (21)
S2c = S2 + C2 (22)

  The combination of C1 and C2 in formulas (21) and (22) may be a combination of C1 and C2 represented by formulas (13) and (14), or C1 represented by formulas (17) and (18). , C2 may be used.

  Next, the procedure S112 for generating the detected angle value θs will be described. Step S <b> 112 is executed by the angle detection unit 4. In step S112, the angle detection unit 4 calculates the angle detection value θs based on the first and second corrected detection signals S1c and S2c generated in step S111. Specifically, for example, the angle detection unit 4 calculates θs by the following equation (23).

  θs = atan (S1c / S2c) (23)

  Within the range of θs between 0 ° and less than 360 °, the solution of θs in Equation (23) has two values that differ by 180 °. However, it is possible to determine which of the two solutions of θs in Equation (23) is the true value of θs by the combination of S1c and S2c. The angle detection unit 4 obtains θs within a range of 0 ° or more and less than 360 ° based on the determination of Expression (23) and the positive / negative combination of S1c and S2c.

Here, the angle error Es of the detected angle value θs will be described. FIG. 10 is a waveform diagram showing an example of the waveform of the angle error Es of the detected angle value θs. In FIG. 10, the horizontal axis indicates the angle θ of the detection target equal to the reference angle θr, the left vertical axis indicates the angle error expressed in degrees (°), and the right vertical axis indicates the angle expressed in radians. Indicates an error. In FIG. 10, reference numeral 81 indicates the angle error Ep of the uncorrected angle detection value θp, and reference numeral 82 indicates the angle error Es of the angle detection value θs. In FIG. 10, the angle error Ep for one cycle of the uncorrected angle detection value θp is obtained. The angle error Ep for an arbitrary uncorrected angle detection value θp is calculated as follows in a situation where the reference angle θr corresponding to the angle θ is recognized. First, the uncorrected angle detection value θp was obtained using Equation (11). S1 and S2 represented by formulas (9) and (10) were used as S1 and S2 in formula (11), respectively. Note that A ₁ ≠ 0 and A ₂ ≠ 0. Next, the angle error Ep was calculated by the equation (12). The angle error Ep includes both the first type error and the second type error.

In FIG. 10, the angle error Es for one cycle of the detected angle value θs is obtained. The angle error Es at an arbitrary detected angle value θs is calculated as follows in a situation where the reference angle θr corresponding to the angle θ is recognized. First, the uncorrected angle detection value θp was obtained using the equation (11), and this θp was substituted into the equations (17) and (18) to obtain the first and second correction values C1 and C2. S1 and S2 represented by formulas (9) and (10) were used as S1 and S2 in formula (11), respectively. Note that A ₁ ≠ 0 and A ₂ ≠ 0. Next, the first and second post-correction detection signals S1c and S2c were obtained by the equations (21) and (22). Next, the detected angle value θs was calculated by the equation (23). Next, the angle error Es was calculated by the following equation (24) similar to the equation (12).

  Es = θs−θr (24)

  As shown in FIG. 10, it can be seen that the angle error Es of the detected angle value θs is sufficiently smaller than the angle error Ep of the uncorrected detected angle value θp. Thus, according to the present embodiment, even if the angle error that occurs when correction is not performed includes the second type error, the angle error Es of the detected angle value θs can be reduced. .

  Hereinafter, the effects of the correction device 3 according to the present embodiment will be described in more detail while comparing with the correction method described in Patent Document 1. Hereinafter, the correction method described in Patent Document 1 is referred to as a conventional correction method. The angular error that occurs when correction is not performed includes at least one of a first type error and a second type error. As described above, in the conventional correction method, when the angle error generated when correction is not performed includes the second type error, the angle error cannot be sufficiently reduced.

  FIG. 11 is a waveform diagram showing an example of an angle error waveform of an angle detection value in the conventional correction method. In FIG. 11, the horizontal axis indicates the angle θ of the detection target equal to the reference angle θr, the left vertical axis indicates the angle error expressed in degrees (°), and the right vertical axis indicates the angle expressed in radians. Indicates an error. In FIG. 11, reference numeral 83 indicates an angle error that occurs when correction is not performed, and reference numeral 84 indicates an angle error of the detected angle value in the conventional correction method. The angle error indicated by reference numeral 83 is the same as the angle error Ep indicated by reference numeral 81 in FIG.

  The angle error of the detected angle value in the conventional correction method was calculated as follows. First, the first and second detection signals S1, S2 were corrected by a conventional correction method. The conventional correction method is the same as the first and second previous correction processes described in the third embodiment. Next, S1c and S2c in equation (23) were changed to first and second detection signals S1 and S2 corrected by the conventional correction method, and angle detection values were calculated by equation (23). Next, the angle error was calculated by the equation (24) with the detected angle value as θs in the equation (24).

  As shown in FIG. 11, the angle error of the detected angle value in the conventional correction method is larger than the angle error Es of the detected angle value θs in the present embodiment indicated by reference numeral 82 in FIG. The angle error of the detected angle value in the conventional correction method is almost equal to the second type error. That is, the conventional correction method cannot reduce the second type error at all.

  On the other hand, according to the correction device 3 according to the present embodiment, as described above, even if the angle error Ep generated when correction is not performed includes the second type error, the detected angle value The angle error Es of θs can be sufficiently reduced.

  Further, according to the correction device 3 according to the present embodiment, even if the angle error that occurs when the correction is not performed includes both the first type error and the second type error, it can be easily performed. The angle error Es of the detected angle value θs can be sufficiently reduced. Hereinafter, this effect will be described in detail.

  When the first detection signal S1 and the second detection signal S2 are expressed by the equations (9) and (10), respectively, the first detection signal S1 and the second detection signal S2 are used to reduce the angle error. On the other hand, it is conceivable to perform the following correction process of the comparative example. In the correction process of the comparative example, with respect to the first detection signal S1, a correction value having the same amplitude as the first third harmonic error component and a phase different by 180 ° from the first third harmonic error component, The first fifth harmonic error component having the same amplitude as that of the first fifth harmonic error component is combined with a correction value that is 180 degrees out of phase. Further, in the correction process of the comparative example, the second detection signal S2 has a correction value that is the same amplitude as the second third harmonic error component and has a phase that is 180 ° different from the second third harmonic error component. Then, the second fifth harmonic error component having the same amplitude as that of the second fifth harmonic error component and a correction value different in phase by 180 ° are synthesized.

  However, the correction process of the comparative example has the following problems. First, in order to perform the correction process of the comparative example, the first third harmonic error component and the first fifth harmonic error component are extracted from the first detection signal S1, and from the second detection signal S2. It is necessary to extract the second third harmonic error component and the second fifth harmonic error component and analyze them. Further, the correction process of the comparative example is complicated.

  On the other hand, in the present embodiment, the angle error Es of the detected angle value θs can be reduced by an extremely simple process compared to the correction process of the comparative example. Specifically, in the present embodiment, the first detection signal S1 and the first correction value C1 are combined to generate the first post-correction detection signal S1c, and the second detection signal S2 and the second correction signal C1 are generated. Are combined with the correction value C2 to generate a second corrected detection signal S2c. The first correction value C1 is a value having a first amplitude and changing in the first period. The second correction value C2 is a value having a second amplitude and changing in the second period. The first amplitude and the second amplitude are the same value. The first period and the second period have the same value of 1/3 or 1/5 of the predetermined period T.

  In the present embodiment, even though the first detection signal S1 includes the first third harmonic error component and the first fifth harmonic error component, the first correction value C1 is It may be a value that changes in one first period. Similarly, although the second detection signal S2 includes the second third harmonic error component and the second fifth harmonic error component, the second correction value C2 is equal to one first correction value C2. It may be a value that changes in a period of 2. Moreover, the first amplitude and the second amplitude are the same value, and the first period and the second period are also the same value.

  As described above, according to the present embodiment, the angle error Es of the detected angle value θs can be obtained by a simple process even when the angle error that occurs when correction is not performed includes the second type error. Can be reduced.

  Further, according to the present embodiment, the angle error that occurs when correction is not performed includes only the second type error, and the angle error that occurs when correction is not performed is the first type error and the first type error. There is no need to change the contents of the first and second correction processes when both types of errors are included. That is, according to the present embodiment, the angular error that occurs when correction is not performed includes only the second type error, or the angular error that occurs when correction is not performed is the first type error and the first type error. The angle error Es of the detected angle value θs can be reduced without considering whether both of the two types of errors are included.

  Further, according to the present embodiment, when the angle error that occurs when correction is not performed includes both the first type error and the second type error, the first type error and the second type error Both types of errors can be reduced simultaneously.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. First, the configuration of the correction apparatus 3 according to the present embodiment will be described with reference to FIG. FIG. 12 is a functional block diagram illustrating configurations of the correction device 3 and the angle detection unit 4. The correction device 3 according to the present embodiment includes a correction reference information holding unit 35 and a correction information determination unit 36 instead of the correction information holding unit 34 in the first embodiment.

  The correction reference information holding unit 35 holds information on the correspondence relationship between the parameter value P and the value F obtained using the calculation using the first detection signal S1 and the second detection signal S2. The correction information determination unit 36 obtains the parameter value P by using the calculation using the first detection signal S1 and the second detection signal S2, and refers to the information held by the correction reference information holding unit 35. A value F corresponding to the obtained parameter value P is determined.

  Next, a method for generating the detected angle value θs in the present embodiment will be described. The method of generating the angle detection value θs in the present embodiment includes a correction reference information generation procedure for generating correction reference information and an angle detection procedure for generating the angle detection value θs.

  First, the correction reference information generation procedure will be described. The correction reference information generation procedure is executed before shipment of the angle sensor 1 by a control unit (not shown) outside the angle sensor 1. In addition, the correction reference information generation procedure is performed in a state where the control unit can recognize the detection target angle θ. In the corrected reference information generation procedure, information on the correspondence relationship between the parameter value P and the value F, which are obtained using the calculation using the first detection signal S1 and the second detection signal S2, is obtained. In the present embodiment, the value P of the parameter is obtained from the fluctuation component of the sum of the square of the first detection signal S1 and the square of the second detection signal S2. Hereinafter, the sum of the square of the first detection signal S1 and the square of the second detection signal S2 is referred to as a square sum signal. The parameter value P is related to the magnitude of the fluctuation component of the square sum signal.

  In the course of research by the inventors of the present application, it has been found that, in general, in a magnetic type angle sensor, the angle error changes according to the strength of the magnetic field to be detected. Hereinafter, the magnetic field to be detected is referred to as a target magnetic field. In addition, the fact that the angle error changes according to the strength of the target magnetic field is called the dependence of the angle error on the magnetic field strength. Further, in the course of research by the inventors of the present application, it has been found that the dependence of the angle error on the magnetic field strength is mainly due to the quaternary component of the angle error. It was also found that the first type error and the second type error including the angular error quaternary component as main components change according to the strength of the rotating magnetic field MF in the detection signal generation unit 2, respectively. . Hereinafter, the strength of the rotating magnetic field MF is referred to as applied magnetic field strength.

As described in the first embodiment, the value F is determined based on the quaternary component of the angle error Ep of the uncorrected angle detection value θp. Specifically, A ₃ corresponding to the magnitude of the angular error quaternary component of the angular error Ep is set as a value F. Therefore, the value F changes according to the applied magnetic field strength. In addition, the first type of error causes a variation in the magnitude of the square sum signal. Therefore, the parameter value P related to the magnitude of the fluctuation component of the square sum signal also changes according to the applied magnetic field strength. In the correction reference information generation procedure, the correspondence between the parameter value P and the value F when the applied magnetic field intensity is changed is examined.

  Here, a method for obtaining the correspondence between the parameter value P and the value F at an arbitrary applied magnetic field strength will be described. The square sum signal can be expressed by the following expression (25) using the first detection signal S1 and the second detection signal S2 expressed by expressions (1) and (2).

S1 ² + S2 ² = {sin θ + A ₁ sin (3θ−180 °)} ²
+ {Cos θ + A ₁ cos 3θ} ²
= Sin ² θ−2A ₁ sin θ · sin 3θ + A ₁ ² sin ² 3θ
+ Cos ² θ + 2A ₁ cos θ · cos 3θ + A ₁ ² cos ² 3θ
= 1 + A ₁ ² −A ₁ {cos (−2θ) −cos 4θ}
+ A ₁ {cos (−2θ) + cos4θ}
= 1 + A ₁ ² + 2A ₁ cos 4θ (25)

“2A ₁ cos 4θ” in the equation (25) is a fluctuation component of the square sum signal. The parameter value P is 2A ₁ related to the magnitude of the fluctuation component of the square sum signal. In the corrected reference information generation procedure, the waveform of the square sum signal for at least a quarter cycle of the reference angle θr corresponding to the angle θ is obtained. The waveform of the square sum signal is also the waveform of the fluctuation component of the square sum signal. In the correction reference information generation procedure, the parameter value P is obtained from the waveform of the square sum signal. FIG. 13 is a waveform diagram showing an example of the waveform of the square sum signal. In FIG. 13, the horizontal axis indicates the detection target angle θ equal to the reference angle θr, and the vertical axis indicates the square sum signal. The absolute value of the parameter value P can be obtained by dividing the value obtained by subtracting the minimum value from the maximum value of the square sum signal by two. The sign of the parameter value P is known from the waveform of the square sum signal.

  Further, the value F can be obtained by executing the correction information determination procedure described with reference to FIG. 8 in the first embodiment. As a result, the correspondence between the parameter value P and the value F at any applied magnetic field strength can be obtained.

  In the correction reference information generation procedure, the correspondence between the parameter value P and the value F is repeatedly obtained while changing the applied magnetic field strength. Thereby, information on the correspondence relationship between the parameter value P and the value F is generated. The correction reference information in the present embodiment is information on the correspondence between the parameter value P and the value F. The correction reference information is held by the correction reference information holding unit 35.

  Next, operations of the correction device 3 and the angle detection unit 4 and an angle detection procedure will be described with reference to FIGS. 12 and 14. FIG. 14 is a flowchart showing an angle detection procedure. The angle detection procedure is executed during a test operation when the angle sensor 1 is installed and when the angle sensor 1 is used. The test operation is executed by the control unit at the installation location of the angle sensor 1 prior to the actual use of the angle sensor 1. This test operation is performed in a situation where the control unit can recognize the angle θ to be detected, as in the correction reference information generation procedure. As shown in FIG. 14, the angle detection procedure includes steps S211, S212, S213, and S214.

  Step S211 is executed by the correction information determination unit 36. In step S211, the correction information determination unit 36 obtains the parameter value P using the first and second detection signals S1 and S2 before correction. The method for obtaining the parameter value P during the test operation is the same as the method for obtaining the parameter value P in the correction reference information generation procedure. When the angle sensor 1 is used, the angle detection value θs is generated by the angle detection unit 4 as described later. When the angle sensor 1 is used, the correction information determination unit 36 recognizes the angle detection value θs and generates a waveform of a square sum signal for at least ¼ period of the angle detection value θs before generating correction reference information. The parameter value P is obtained in the same manner as the parameter value P in the procedure.

  Step S212 is executed by the correction information determination unit 36. In step S212, the correction information determination unit 36 refers to the correction reference information held by the correction reference information holding unit 35, and determines correction information corresponding to the parameter value P, that is, the value F.

  Step S213 is executed by the correction unit 33. In step S213, the correction unit 33 refers to the correction information determined in step S212, that is, the value F, performs a first correction process on the first detection signal S1, and performs a correction on the second detection signal S2. Then, the second correction process is performed. The contents of the first and second correction processes are the same as those in step S111 (see FIG. 9) in the first embodiment. Thereby, the first and second corrected detection signals S1c and S2c are generated.

  Step S214 is executed by the angle detection unit 4. In step S214, the angle detection unit 4 generates an angle detection value θs. The calculation method of the detected angle value θs is the same as the procedure S112 (see FIG. 9) in the first embodiment.

  Steps S211 and S212 are always executed during the test operation. Thereafter, the procedures S211 and S212 may be set to be automatically executed with a time interval greater than or equal to a predetermined time, for example. Alternatively, steps S211 and S212 may be set to be executed at an arbitrary time according to a user's instruction or the like. The correction information determination unit 36 holds the last determined value F until the steps S211 and S212 are newly executed and the value F is updated. During the operation of the angle sensor 1, the correction unit 33 always executes step S <b> 213 using the value F held by the correction information determination unit 36.

  According to the present embodiment, even if the applied magnetic field strength changes, it is possible to execute an appropriate correction process according to the applied magnetic field strength and reduce the angle error Es of the detected angle value θs.

  In general, in a magnetic angle sensor, the angle error is not limited to the applied magnetic field strength, but can vary depending on the temperature. The correction device 3 according to the present embodiment can also be applied when the temperature changes. In this case, in the corrected reference information generation procedure, the correspondence between the parameter value P and the value F is repeatedly obtained while changing the temperature, and information on the correspondence between the parameter value P and the value F is generated. Thus, even if the temperature changes, it is possible to execute an appropriate correction process according to the temperature and reduce the angle error Es of the detected angle value θs.

  Other configurations, operations, and effects in the present embodiment are the same as those in the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. First, the first detection signal S1 and the second detection signal S2 in the present embodiment will be described. When the angle θ of the detection object changes at a predetermined period T, the first detection signal S1 includes a first ideal component, a first error component, a second error component, and a third error component, The second detection signal S2 includes a second ideal component, a fourth error component, a fifth error component, and a sixth error component. The definitions of the first and second ideal components and the first to sixth error components are as described in the first embodiment. Particularly in the present embodiment, the phases of the first ideal component and the second ideal component differ from each other by 90 °.

  Next, the configuration of the correction apparatus 3 according to the present embodiment will be described with reference to FIG. FIG. 15 is a functional block diagram illustrating configurations of the correction device 3 and the angle detection unit 4. The correction device 3 according to the present embodiment includes a front-stage correction unit 331 and a rear-stage correction unit 332 instead of the correction unit 33 in the first embodiment.

  The pre-stage correction unit 331 performs a first pre-stage correction process and a second pre-stage correction process. In the first pre-correction process, the first detection signal S1 converted into a digital signal by the A / D converter 31 is corrected, and the first error component is reduced compared to the first detection signal S1. This is a process for generating the first post-correction detection signal S1a. The second pre-correction processing corrects the second detection signal S2 converted into a digital signal by the A / D converter 32, and the fourth error component is reduced compared to the second detection signal S2. This is a process for generating the second post-correction detection signal S2a. Thus, the first and second pre-correction processes are processes for reducing the first and fourth error components that cause the first type of error.

  The post-stage correction unit 332 performs a first post-stage correction process and a second post-stage correction process. In the first post-stage correction process, the first post-correction detection signal S1a and the first correction value are combined, and the second and third error components are compared with the first post-post-correction detection signal S1a. This is a process for generating the reduced first post-correction detection signal S1b. In the second post-stage correction process, the second post-correction detection signal S2a and the second correction value are combined, and the fifth and sixth error components are compared to the second post-correction detection signal S2a. This is a process of generating a reduced second post-correction detection signal S2b. Thus, the first and second post-stage correction processes are processes for reducing the second, third, fifth, and sixth error components that cause the second type of error. The first post-correction detection signal S1b and the second post-correction detection signal S2b are used by the angle detection unit 4 to generate the detected angle value θs.

  The first correction value is a value having a first amplitude and changing in the first period. The second correction value is a value having a second amplitude and changing in the second period. The first amplitude and the second amplitude are the same value. Similar to the first embodiment, the first and second amplitudes are absolute values of the value F for defining the first and second correction values. The first period and the second period have the same value of 1/3 or 1/5 of the predetermined period T.

  Here, the first detection signal S1 and the second detection signal S2 in the present embodiment will be described in more detail. In the present embodiment, the initial phase of the second error component and the third error component when the initial phase of the first error component is 0 is the same value α. Further, the initial phase of the fifth error component and the sixth error component when the initial phase of the fourth error component is 0 is the value α. The value α is the phase difference between the first and fourth error components that cause the first type of error and the second, third, fifth, and sixth error components that cause the second type of error. Represents. In the present embodiment, the value α may be 0 or a value other than 0.

  The first detection signal S1 and the second detection signal S2 can be expressed by the following equations (26) and (27), respectively.

S1 = sin θ + A ₁ sin (3θ−180 °)
_{- (A 2/2) sin} (3θ + α)
_{- (A 2/2) sin} (5θ + α)
= Sin θ + A ₁ sin (3θ−180 °)
_{+ (A 2/2) sin} (3θ-180 ° + α)
_{- (A 2/2) sin} (5θ + α) ... (26)
S2 = cos θ + A ₁ cos 3θ
_{+ (A 2/2) cos} (3θ + α)
_{- (A 2/2) cos} (5θ + α) ... (27)

"Sin [theta" in the formula (26) represents a first ideal _{component, "A 1 sin (3θ-} 180 °)" represents the first error _{component, "(A 2/2)} sin (3θ-180 ° + α) "denotes the second error _{component," - (a 2/2} ) sin (5θ + α) " represents the third error components. Further, "cos [theta]" in the formula (27) represents a second ideal _components, "A 1 _cos3θ" represents the fourth error _{components, "(A 2/2)} cos (3θ + α)" is the fifth it represents the error _{component, "- (a 2/2} ) cos (5θ + α)" represents an error component of the sixth. When the value α is 0, the expressions (26) and (27) are substantially the same as the expressions (7) and (8) in the first embodiment, respectively.

  FIG. 16 is a waveform diagram showing an example of waveforms of first to third error components of the first detection signal S1. FIG. 17 is a waveform diagram showing an example of waveforms of the fourth to sixth error components of the second detection signal S2. 16 and 17, the horizontal axis indicates the angle θ of the detection target, and the vertical axis indicates the error component. FIGS. 16 and 17 show examples in which normalization is performed so that the amplitudes of the first and second ideal components are 1. FIG. In FIG. 16, reference numerals 91, 92, and 93 denote a first error component, a second error component, and a third error component, respectively. In FIG. 17, reference numerals 94, 95, and 96 indicate a fourth error component, a fifth error component, and a sixth error component, respectively. Each waveform shown in FIGS. 16 and 17 is created based on the equations (26) and (27).

  Similar to the first embodiment, the correction device 3 according to the present embodiment includes a correction information holding unit 34. The correction information holding unit 34 in the present embodiment holds the value F and the value α. The post-stage correction unit 332 generates first and second correction values based on the value F, the value α, the first pre-stage correction detection signal S1a, and the second pre-stage correction detection signal S2a. A method for generating the first and second correction values will be described later.

  Next, with reference to FIG. 15, FIG. 18, and FIG. 19, the operation of the correction device 3 and the angle detector 4 and the method of generating the detected angle value θs in the present embodiment will be described. The method for generating the detected angle value θs in the present embodiment includes a correction information determining procedure for determining the first and second correction information, and an angle detecting procedure for generating the detected angle value θs. FIG. 18 is a flowchart showing a correction information determination procedure. The correction information determination procedure is executed by the control unit (not shown) outside the angle sensor 1 before shipment or use of the angle sensor 1. FIG. 19 is a flowchart showing an angle detection procedure. The angle detection procedure is executed when the angle sensor 1 is used.

  First, the correction information determination procedure will be described. As in the first embodiment, the correction information determination procedure is performed in a situation where the control unit can recognize the angle θ of the detection target. As shown in FIG. 18, the correction information determination procedure includes steps S301, S302, S303, S304, and S305. In step S301, the parameter value P is obtained using the first and second detection signals S1 and S2 before correction. In step S302, first correction information is determined. In step S303, first and second previous correction processes are performed on the first and second detection signals S1 and S2 using the first correction information. In step S304, the amplitude and phase of the angular error quaternary component are obtained using the first and second pre-correction detection signals S1a and S2a. In step S305, second correction information is determined. The method for obtaining the parameter value P in step S301 is the same as the method for obtaining the parameter value P in the corrected reference information generation procedure described in the second embodiment.

In the present embodiment, the first correction information is information that defines the amplitude and phase of a correction value used to reduce the first and fourth error components that cause the first type of error. It is. As described in the second embodiment, the value P of the parameter is 2A _1. Further, the error components of the first and second detection signals S1 and S2 in the case where the angular error that occurs when correction is not performed include only the first type error, respectively, are “A ₁ sin (3θ−180). °) ”,“ A ₁ cos 3θ ”. In step S302 for determining the first correction information, the first correction information is determined based on the parameter value P obtained in step S301. In the present embodiment, P / 2 is the first correction information. The first correction information P / 2 is held by the correction information holding unit 34.

  In step S303, first and second previous correction processes are performed on the first and second detection signals S1 and S2 using the first correction information P / 2 determined in step S302. In the first pre-correction process, first, a correction value C1a used to reduce the first error component is generated based on the first correction information P / 2 and the first detection signal S1. Next, the first detection signal S1 and the correction value C1a are combined to generate the first post-correction detection signal S1a.

  In the second pre-correction process, first, a correction value C2a used to reduce the fourth error component is generated based on the first correction information P / 2 and the second detection signal S2. Next, the second detection signal S2 and the correction value C2a are combined to generate a second pre-correction detection signal S2a.

  In step S303, for example, correction values C1a and C2a and pre-correction detection signals S1a and S2a for one cycle of the reference angle θr corresponding to the angle θ are generated. Hereinafter, the correction values C1a and C2a and the pre-correction detection signals S1a and S2a at an arbitrary reference angle θr will be described. The correction value C1a and the correction value C2a are expressed by the following equations (28) and (29), respectively.

C1a = − (P / 2) sin (3θp−180 °) (28)
C2a = − (P / 2) cos3θp (29)

  Expressions (28) and (29) are obtained by replacing “F” in expressions (13) and (14) in the first embodiment with “P / 2”, respectively. Expressions (13) and (14) respectively indicate the first correction value C1 and the second correction value when the first period and the second period are the same value of 1/3 of the predetermined period T. C2 is represented. In step S303, the correction values C1a and C2a can be obtained by the same method as the generation method of the first and second correction values C1 and C2 in the above case.

  The first post-correction detection signal S1a and the second pre-correction detection signal S2a are represented by the following equations (30) and (31), respectively.

S1a = S1 + C1a (30)
S2a = S2 + C2a (31)

  In step S304, the first and second post-correction detection signals S1a and S2a generated in step S303 are used to determine the amplitude and phase of the angular error quaternary component. In step S304, for example, an angle error for one cycle of the reference angle θr corresponding to the angle θ is calculated. Hereinafter, a method for calculating an angle error at an arbitrary reference angle θr will be described. First, the pre-correction angle detection value θa is obtained based on the first and second pre-correction detection signals S1a and S2a. The phase difference between the post-correction detected angle value θa and the reference angle θr is assumed to be 0 ° or a value close to 0 °. The post-correction angle detection value θa is calculated by the following equation (32).

  θa = atan (S1a / S2a) (32)

  When θa is in the range of 0 ° or more and less than 360 °, the solution of θa in Equation (32) has two values that differ by 180 °. However, it is possible to determine which of the two solutions of θa in Equation (32) is the true value of θa by the positive / negative combination of S1a and S2a. In step S304, θa is determined within a range of 0 ° or more and less than 360 ° based on the determination of the positive / negative combination of equation (32) and S1a and S2a.

  Next, a difference Ea between the post-correction detected angle value θa and the reference angle θr is calculated by the following equation (33).

  Ea = θa−θr (33)

The difference Ea corresponds to an angle error when only the first and second pre-stage correction processes are performed as the correction process. Hereinafter, the difference Ea is referred to as an angle error of the post-correction detected angle value θa. The angle error Ea includes an angular error quaternary component as a main component. In step S304, the amplitude and phase of the angular error quaternary component of the angular error Ea are obtained from the angular error Ea obtained as described above. The amplitude and phase can be obtained from the waveform of the angle error Ea. FIG. 20 is a waveform diagram showing an example of the waveform of the angle error Ea. In FIG. 20, the horizontal axis indicates the angle θ of the detection target equal to the reference angle θr, the left vertical axis indicates the angle error expressed in degrees (°), and the right vertical axis indicates the angle expressed in radians. Indicates an error. The angular error quaternary component of the angular error Ea expressed in radians is expressed as -A ₄ sin (4θ + β). A ₄ and β are specified from the amplitude and phase of the angular error quaternary component of the angular error Ea.

In the present embodiment, the second correction information is information on the above-described value F and value α indicating the initial phases of the second, third, fifth and sixth error components. In step S305 for determining the second correction information, the value F and the value α are determined based on the amplitude and phase of the angular error quaternary component of the angular error Ea obtained in step S304. In this embodiment, the A ₄ to a value F, and the β value alpha. The value F and the value α are held by the correction information holding unit 34.

  Next, an angle detection procedure will be described. As shown in FIG. 19, the angle detection procedure includes steps S311, S312 and S313. In step S311, first and second previous correction processes are performed on the first and second detection signals S1 and S2 using the first correction information. In step S312, first and second post-stage correction processes are performed on the first and second post-stage post-correction detection signals S1a and S2a using the second correction information. In step S313, the detected angle value θs is generated.

  First, step S311 will be described in detail. Step S311 is executed by the upstream correction unit 331. In step S311, the upstream correction unit 331 first refers to the first correction information P / 2 held by the correction information holding unit 34. Next, the pre-correction unit 331 performs first and second pre-correction processes on the first and second detection signals S1 and S2 using the first correction information P / 2.

  In the first pre-correction process, first, a correction value C1a is generated based on the first correction information P / 2 and the first detection signal S1. Next, the first detection signal S1 and the correction value C1a are combined to generate the first post-correction detection signal S1a. The generation method of the correction value C1a and the first pre-correction detection signal S1a is the same as the procedure S303 (see FIG. 18) in the correction information determination procedure.

  In the second pre-stage correction process, first, a correction value C2a is generated based on the first correction information P / 2 and the second detection signal S2. Next, the second detection signal S2 and the correction value C2a are combined to generate a second pre-correction detection signal S2a. The generation method of the correction value C2a and the second pre-correction detection signal S2a is the same as the procedure S303 (see FIG. 18) in the correction information determination procedure.

  Next, step S312 will be described in detail. Step S312 is executed by the post-stage correction unit 332. In step S312, the post-stage correction unit 332 first refers to the second correction information held by the correction information holding unit 34, that is, the value F and the value α. The post-stage correction unit 332 then calculates the first and second correction values C1b and C2b based on the value F, the value α, the first post-stage correction detection signal S1a, and the second post-stage correction detection signal S2a. Generate.

  As described above, the first period of the first correction value C1b and the second period of the second correction value C2b are the same value of 1/3 or 1/5 of the predetermined period T. First, the case where the first period and the second period are the same value of 1/3 of the predetermined period T will be described. In this case, the first correction value C1b and the second correction value C2b are represented by the following equations (34) and (35), respectively.

C1b = −Fsin (3θa−180 ° + α) (34)
C2b = −Fcos (3θa + α) (35)

  The post-stage correction unit 332 obtains the post-stage post-correction angle detection value θa from the first and second pre-stage post-correction detection signals S1a and S2a before correction using the formula (32), and this θa is calculated using the formulas (34), ( 35), the first and second correction values C1b and C2b may be obtained.

  Alternatively, the post-stage correction unit 332 may obtain the first and second correction values C1b and C2b as follows without obtaining the pre-stage post-correction angle detection value θa. When Expressions (34) and (35) are modified, the following Expressions (36) and (37) are obtained.

C1b = F (sin3θa · cosα + cos3θa · sinα)
= -Fcos α (4 sin ³ θa- ³ sin θa)
+ Fsin α (4 cos ³ θa- ³ cos θa) (36)
C2b = −F (cos3θa · cosα−sin3θa · sinα)
= -Fcos α (4 cos ³ θa- ³ cos θa)
-Fsin α (4 sin ³ θa- ³ sin θa) (37)

  In the equations (36) and (37), sin θa and cos θa are the values of the first pre-correction detection signal S1a and the second pre-correction detection signal S2a that are normalized so that the amplitude is 1, respectively. Accordingly, the first and second correction values C1b and C2b include the value F, the value α, the value sin θa of the first pre-correction detection signal S1a, and the value cos θa of the second pre-correction detection signal S2a. Can be used to calculate.

  Next, a case where the first period and the second period are the same value that is 1/5 of the predetermined period T will be described. In this case, the first correction value C1b and the second correction value C2b are expressed by the following equations (38) and (39), respectively.

C1b = −Fsin (5θa−180 ° + α) (38)
C2b = Fcos (5θa + α) (39)

  The post-stage correction unit 332 obtains the post-stage post-correction angle detection value θa from the first and second pre-stage post-correction detection signals S1a and S2a before correction using the equation (32), and this θa is calculated using the equations (38), ( 39), the first and second correction values C1b and C2b may be obtained.

  Alternatively, the post-stage correction unit 332 may obtain the first and second correction values C1b and C2b as follows without obtaining the pre-stage post-correction angle detection value θa. When formulas (38) and (39) are modified, the following formulas (40) and (41) are obtained.

C1b = F (sin5θa · cosα + cos5θa · sinα)
= Fcos α (16 sin ⁵ θp−20 sin ³ θp + ⁵ sin θp)
+ Fsin α (16 cos ⁵ θp−20 cos ³ θp + ⁵ cos θp)
... (40)
C2b = F (cos5θa · cosα−sin5θa · sinα)
= Fcos α (16 cos ⁵ θp−20 cos ³ θp + ⁵ cos θp)
-Fsin α (16 sin ⁵ θp−20 sin ³ θp + ⁵ sin θp)
... (41)

  Therefore, even when the first period and the second period are the same value of 1/5 of the predetermined period T, the first and second correction values C1b and C2b are the value F, the value α, It can be calculated using the value sinθa of the first pre-correction detection signal S1a and the value cosθa of the second pre-correction detection signal S2a.

  After generating the first and second correction values C1b and C2b as described above, the post-stage correction unit 332 performs a first post-stage correction process and a second post-stage correction process. In the first post-stage correction process, the first post-stage correction detection signal S1a and the first correction value C1b are combined to generate the first post-stage correction detection signal S1b. In the second post-stage correction process, the second post-stage correction detection signal S2a and the second correction value C2b are combined to generate the second post-stage correction detection signal S2b. The first post-correction detection signal S1b and the second post-correction detection signal S2b are represented by the following equations (42) and (43), respectively.

S1b = S1a + C1b (42)
S2b = S2a + C2b (43)

  The combination of C1b and C2b in formulas (42) and (43) may be a combination of C1b and C2b represented by formulas (34) and (35), or C1b represented by formulas (38) and (39). , C2b.

  Next, step S313 will be described in detail. Step S <b> 313 is executed by the angle detection unit 4. In step S313, the angle detection unit 4 calculates the detected angle value θs based on the first and second post-correction detection signals S1b and S2b generated in step S312. Specifically, for example, the angle detection unit 4 calculates θs by the following equation (44).

  θs = atan (S1b / S2b) (44)

  When θs is in the range of 0 ° to less than 360 °, the solution of θs in Equation (44) has two values that differ by 180 °. However, it is possible to determine which of the two solutions of θs in Equation (44) is the true value of θs by the positive / negative combination of S1b and S2b. The angle detection unit 4 obtains θs within a range of 0 ° or more and less than 360 ° based on the determination of Expression (44) and the positive / negative combination of S1b and S2b.

  According to the present embodiment, even if the phase difference between the error component causing the first type error and the error component causing the second type error, that is, the value α is a value other than 0, the angle The angle error of the detected value θs can be reduced.

  Other configurations, operations, and effects in the present embodiment are the same as those in the first embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. First, the configuration of the correction apparatus 3 according to the present embodiment will be described with reference to FIG. FIG. 21 is a functional block diagram illustrating configurations of the correction device 3 and the angle detection unit 4. The correction device 3 according to the present embodiment replaces the correction information holding unit 34 in the third embodiment with a correction reference information holding unit 35, a first correction information determination unit 361, and a second correction information determination unit. 362.

  The correction reference information holding unit 35 holds information on the correspondence relationship between the parameter value P, the value F, and the value α obtained by using the calculation using the first detection signal S1 and the second detection signal S2. ing. The first correction information determination unit 361 obtains the parameter value P by using the calculation using the first detection signal S1 and the second detection signal S2. The method for obtaining the parameter value P is the same as the method for obtaining the parameter value P in the correction reference information generation procedure described in the second embodiment. In the present embodiment, the upstream correction unit 331 determines the contents of the first and second upstream correction processes based on the parameter value P obtained by the first correction information determination unit 361. The second correction information determination unit 362 refers to the information held by the correction reference information holding unit 35, and the value F and the value α corresponding to the parameter value P obtained by the first correction information determination unit 361. To decide.

  Next, a method for generating the detected angle value θs in the present embodiment will be described. The method of generating the angle detection value θs in the present embodiment includes a correction reference information generation procedure for generating correction reference information and an angle detection procedure for generating the angle detection value θs.

  First, the correction reference information generation procedure will be described. The correction reference information generation procedure is executed before shipment of the angle sensor 1 by a control unit (not shown) outside the angle sensor 1. In addition, the correction reference information generation procedure is performed in a state where the control unit can recognize the detection target angle θ. In the corrected reference information generation procedure, information on the correspondence relationship between the value P of the parameter, the value F, and the value α obtained using the calculation using the first detection signal S1 and the second detection signal S2 is obtained.

  As described in the second embodiment, the value F and the parameter value P vary depending on the applied magnetic field strength or temperature. In the correction reference information generation procedure, the correspondence between the parameter value P and the value F when the applied magnetic field strength or temperature is changed is examined. The method of obtaining the correspondence between the parameter value P and the value F is the same as in the second embodiment. In the present embodiment, the value α when the applied magnetic field strength or temperature is further changed is obtained. The value α can be obtained by executing the correction information determination procedure (see FIG. 18) in the third embodiment. Thereby, information on the correspondence relationship between the parameter value P, the value F, and the value α is obtained. The correction reference information in the present embodiment is information on the correspondence relationship between the parameter value P, the value F, and the value α. The correction reference information is held by the correction reference information holding unit 35.

  Next, operations of the correction device 3 and the angle detection unit 4 and an angle detection procedure will be described with reference to FIGS. 21 and 22. FIG. 22 is a flowchart showing an angle detection procedure. The angle detection procedure is executed during a test operation when the angle sensor 1 is installed and when the angle sensor 1 is used. The test operation is executed by the control unit at the installation location of the angle sensor 1 prior to the actual use of the angle sensor 1. This test operation is performed in a situation where the control unit can recognize the angle θ to be detected, as in the correction reference information generation procedure. As shown in FIG. 22, the angle detection procedure includes procedures S411, S412, S413, S414, S415, and S416.

  Step S411 is executed by the first correction information determination unit 361. In step S411, the first correction information determination unit 361 first obtains the parameter value P using the first and second detection signals S1 and S2 before correction. The method for obtaining the parameter value P during the test operation is the same as the method for obtaining the parameter value P in the correction reference information generation procedure. When the angle sensor 1 is used, the angle detection value θs is generated by the angle detection unit 4 as described later. When the angle sensor 1 is used, the first correction information determination unit 361 recognizes the angle detection value θs and corrects the waveform after obtaining a square sum signal waveform for at least ¼ period of the angle detection value θs. The parameter value P is obtained in the same manner as the parameter value P in the reference information generation procedure.

  Step S412 is executed by the first correction information determination unit 361. In step S412, the first correction information determination unit 361 determines first correction information. The first correction information is information that defines the amplitude and phase of a correction value used to reduce the first and fourth error components that cause the first type of error. In the present embodiment, the first correction information is determined based on the parameter value P obtained in step S411. In the present embodiment, P / 2 is the first correction information.

  Step S413 is executed by the second correction information determination unit 362. In step S413, the second correction information determination unit 362 refers to the correction reference information and determines second correction information corresponding to the parameter value P obtained in step S411, that is, the value F and the value α.

  Step S414 is executed by the upstream correction unit 331. In step S414, the pre-stage correction unit 331 uses the first correction information P / 2 determined in step S412 to perform the first and second pre-stage corrections on the first and second detection signals S1 and S2. Processing is performed to generate first and second post-correction detection signals S1a and S2a. The contents of the first and second preceding correction processes are the same as the contents of the first and second preceding correction processes in step S311 (see FIG. 19) in the third embodiment.

  Step S415 is executed by the post-stage correction unit 332. In step S415, the post-stage correction unit 332 uses the second correction information determined in step S413, that is, the value F and the value α, to generate the first and second pre-stage post-correction detection signals S1a, First and second post-stage correction processes are performed on S2a to generate first and second post-stage post-correction detection signals S1b and S2b. The contents of the first and second subsequent correction processes are the same as the contents of the first and second subsequent correction processes in step S312 (see FIG. 19) in the third embodiment.

  Step S416 is executed by the angle detection unit 4 to generate the detected angle value θs. In step S416, the angle detection unit 4 calculates the detected angle value θs based on the first and second post-correction detection signals S1b and S2b generated in step S415. The calculation method of the detected angle value θs is the same as step S313 (see FIG. 19) in the third embodiment.

  Steps S411, S412, and S413 are always executed during the test operation. Thereafter, the procedures S411, S412, and S413 may be set to be automatically executed with a time interval equal to or longer than a predetermined time, for example. Alternatively, steps S411, S412 and S413 may be set to be executed at an arbitrary time according to a user's instruction or the like.

  The first correction information determination unit 361 holds the first correction information determined last until the steps S411 and S412 are newly executed and the first correction information is updated. The pre-stage correction unit 331 always executes step S414 using the first correction information held by the first correction information determination unit 361 while the angle sensor 1 is operating.

  The second correction information determination unit 362 holds the second correction information determined last until the steps S411, S412, and S413 are newly executed and the second correction information is updated. The post-stage correction unit 332 always executes step S415 using the second correction information held by the second correction information determination unit 362 while the angle sensor 1 is operating.

  According to the present embodiment, even if the applied magnetic field strength or temperature changes, an appropriate correction process according to the applied magnetic field strength or temperature can be executed to reduce the angle error Es of the detected angle value θs. .

  Other configurations, operations, and effects in the present embodiment are the same as those in the second or third embodiment.

  In addition, this invention is not limited to the said embodiment, A various change is possible. For example, in the angle sensor of the present invention, in addition to the correction processing for reducing the first type error and the second type error by the correction device of the present invention, the first type error and the first type error that occur in the detected angle value. Other correction processes that reduce errors other than the type 2 error may also be performed. The other correction process is a process of generating a new angle detection value by changing the angle detection value corrected by the correction process for reducing the first type error and the second type error by a certain value. May be.

  The present invention can be applied not only to a magnetic angle sensor but also to all angle sensors including an optical angle sensor.

  DESCRIPTION OF SYMBOLS 1 ... Angle sensor, 2 ... Signal generation part, 3 ... Correction apparatus, 4 ... Angle detection part, 5 ... Magnet, 10 ... 1st detection circuit, 20 ... 2nd detection circuit, 14, 24 ... Bridge circuit, 31 32 ... A / D converter, 33 ... correction unit, 34 ... correction information holding unit, 35 ... correction reference information holding unit, 36 ... correction information determination unit, 331 ... previous correction unit, 332 ... back correction unit, 361 ... First correction information determination unit, 362... Second correction information determination unit.

In the second detection circuit 20, the magnetization direction of the magnetization fixed layer in the plurality of MR elements included in the magnetic detection elements R21 and R24 is the X direction, and the magnetization in the plurality of MR elements included in the magnetic detection elements R22 and R23. The direction of magnetization of the fixed layer is the −X direction. In this case, the potential difference between the output ports E21 and E22 changes according to the intensity of the component in the X direction of the rotating magnetic field MF. Therefore, the second detection circuit 20 detects the intensity of the component in the X direction of the rotating magnetic field MF, and generates a signal representing the intensity as the second detection signal S2. The intensity of the component in the X direction of the rotating magnetic field MF has a corresponding relationship with the angle θ of the detection target.

C1b = F (sin5θa · cosα + cos5θa · sinα)
= Fcos α (16 sin ⁵ θa −20 sin ³ θa +5 sin θa )
+ Fsin α (16 cos ⁵ θa −20 cos ³ θa +5 cos θa )
... (40)
C2b = F (cos5θa · cosα−sin5θa · sinα)
= Fcos α (16 cos ⁵ θa −20 cos ³ θa +5 cos θa )
−Fsin α (16 sin ⁵ θa −20 sin ³ θa +5 sin θa )
... (41)

Claims (21)

A detection signal generator for generating a first detection signal and a second detection signal, each of which has a corresponding relationship with an angle of the detection target; and the detection target based on the first detection signal and the second detection signal A correction device used for an angle sensor including an angle detection unit that generates an angle detection value having a correspondence relationship with an angle,
When the angle of the detection target changes at a predetermined cycle, the first detection signal includes a first ideal component, a first third harmonic error component, and a first fifth harmonic error component. The second detection signal includes a second ideal component, a second third harmonic error component, and a second fifth harmonic error component,
The first ideal component and the second ideal component periodically change so as to draw an ideal sinusoid with different phases.
The first third harmonic error component is an error component corresponding to a third harmonic with respect to the first ideal component,
The first fifth harmonic error component is an error component corresponding to a fifth harmonic with respect to the first ideal component,
The second third harmonic error component is an error component corresponding to a third harmonic with respect to the second ideal component,
The second fifth harmonic error component is an error component corresponding to the fifth harmonic with respect to the second ideal component,
The correction device includes:
A correction unit that performs a first correction process on the first detection signal and performs a second correction process on the second detection signal;
The first correction process is a process of generating a first post-correction detection signal used for generating the angle detection value by combining the first detection signal and a first correction value.
The second correction process is a process of combining the second detection signal and a second correction value to generate a second post-correction detection signal used for generating the angle detection value;
The first correction value is a value having a first amplitude and changing in a first period;
The second correction value is a value having a second amplitude and changing in a second period;
The first amplitude and the second amplitude are the same value,
The correction device for an angle sensor, wherein the first period and the second period have the same value of 1/3 or 1/5 of the predetermined period.   2. The angle sensor correction apparatus according to claim 1, wherein the angle of the detection target is an angle formed by a direction of the rotating magnetic field at the reference position with respect to the reference direction.   The amplitude of the first third harmonic error component and the amplitude of the first fifth harmonic error component are different from each other, and the amplitude of the second third harmonic error component and the second fifth harmonic are 3. The angle sensor correction device according to claim 1, wherein the amplitudes of the error components are different from each other.   4. The angle sensor according to claim 1, wherein the first and second amplitudes are absolute values of a value F for defining the first and second correction values. 5. Correction device.   The angle sensor according to claim 4, wherein the correction unit generates the first and second correction values based on the value F, the first detection signal, and the second detection signal. Correction device.   6. The angle sensor correction device according to claim 4, further comprising a correction information holding unit for holding the value F.   The angle sensor correction device according to claim 1, wherein phases of the first ideal component and the second ideal component differ from each other by 90 °. Furthermore, a correction reference information holding unit and a correction information determination unit are provided,
The correction reference information holding unit holds information on a correspondence relationship between a value of a parameter and the value F obtained using an operation using the first detection signal and the second detection signal,
The correction information determination unit obtains the value of the parameter using an operation using the first detection signal and the second detection signal, and refers to the information held by the correction reference information holding unit 6. The angle sensor correction device according to claim 4, wherein the value F corresponding to the obtained parameter value is determined.   9. The angle sensor correction device according to claim 8, wherein phases of the first ideal component and the second ideal component differ from each other by 90 degrees.   The angle sensor correction device according to claim 9, wherein the parameter value is obtained from a fluctuation component of a sum of a square of the first detection signal and a square of the second detection signal. A detection signal generator for generating a first detection signal and a second detection signal each having a corresponding relationship with the angle of the detection target;
An angle detection unit that generates an angle detection value having a corresponding relationship with the angle of the detection target based on the first detection signal and the second detection signal;
An angle sensor comprising the correction device according to claim 1. A detection signal generator for generating a first detection signal and a second detection signal, each of which has a corresponding relationship with an angle of the detection target; and the detection target based on the first detection signal and the second detection signal A correction device used for an angle sensor including an angle detection unit that generates an angle detection value having a correspondence relationship with an angle,
When the angle of the detection target changes in a predetermined cycle, the first detection signal includes a first ideal component, a first error component, a second error component, and a third error component, The second detection signal includes a second ideal component, a fourth error component, a fifth error component, and a sixth error component,
The first ideal component and the second ideal component periodically change so as to draw an ideal sinusoid with different phases.
The first error component and the second error component are both error components corresponding to the third harmonic with respect to the first ideal component,
The third error component is an error component corresponding to a fifth harmonic with respect to the first ideal component,
The fourth error component and the fifth error component are both error components corresponding to the third harmonic with respect to the second ideal component,
The sixth error component is an error component corresponding to a fifth harmonic with respect to the second ideal component,
The amplitude of the second error component and the amplitude of the third error component are equal to each other,
The amplitude of the fifth error component and the amplitude of the sixth error component are equal to each other,
The correction device includes:
A pre-stage correction unit that performs a first pre-stage correction process and a second pre-stage correction process;
A post-stage correction unit that performs a first post-stage correction process and a second post-stage correction process;
The first pre-correction processing corrects the first detection signal to generate a first post-correction detection signal in which the first error component is reduced compared to the first detection signal. Processing,
The second pre-correction processing corrects the second detection signal to generate a second post-correction detection signal with the fourth error component reduced compared to the second detection signal. Processing,
In the first post-stage correction process, the first post-correction detection signal and the first correction value are combined, and the second and third errors are compared with the first post-post-correction detection signal. A process of generating a first post-stage corrected detection signal with reduced components;
In the second post-stage correction process, the second post-correction detection signal and the second correction value are combined, and the fifth and sixth errors are compared with the second pre-correction detection signal. A process for generating a second post-correction detection signal with reduced components;
The first post-correction detection signal and the second post-correction detection signal are used to generate the angle detection value,
The first correction value is a value having a first amplitude and changing in a first period;
The second correction value is a value having a second amplitude and changing in a second period;
The first amplitude and the second amplitude are the same value,
The correction device for an angle sensor, wherein the first period and the second period have the same value of 1/3 or 1/5 of the predetermined period.   13. The angle sensor correction device according to claim 12, wherein the angle of the detection target is an angle formed by the direction of the rotating magnetic field at the reference position with respect to the reference direction.   14. The angle sensor correction apparatus according to claim 12, wherein the first and second amplitudes are absolute values of a value F for defining the first and second correction values.   The angle sensor correction device according to claim 12, wherein phases of the first ideal component and the second ideal component are different from each other by 90 °. The initial phase of the second error component and the third error component when the initial phase of the first error component is 0 is the same value α,
The initial phase of the fifth error component and the sixth error component when the initial phase of the fourth error component is 0 is the value α,
The post-stage correction unit generates the first and second correction values based on the value F, the value α, the first pre-stage post-correction detection signal, and the second pre-stage post-correction detection signal. The angle sensor correction device according to claim 14.   17. The angle sensor correction device according to claim 16, further comprising a correction information holding unit for holding the value F and the value α. Furthermore, a correction reference information holding unit, a first correction information determination unit, and a second correction information determination unit,
The correction reference information holding unit holds information on a correspondence relationship between a value of a parameter obtained using an operation using the first detection signal and the second detection signal, and the value F and the value α. And
The first correction information determination unit obtains a value of the parameter using an operation using the first detection signal and the second detection signal,
The pre-stage correction unit determines the contents of the first and second pre-stage correction processes based on the parameter values obtained by the first correction information determination unit,
The second correction information determination unit refers to the information held by the correction reference information holding unit, the value F corresponding to the value of the parameter obtained by the first correction information determination unit, and The angle sensor correction device according to claim 16, wherein the value α is determined.   19. The angle sensor correction device according to claim 18, wherein phases of the first ideal component and the second ideal component are different from each other by 90 degrees.   The angle sensor correction device according to claim 19, wherein the parameter value is obtained from a fluctuation component of a sum of a square of the first detection signal and a square of the second detection signal. A detection signal generator for generating a first detection signal and a second detection signal each having a corresponding relationship with the angle of the detection target;
An angle detection unit that generates an angle detection value having a corresponding relationship with the angle of the detection target based on the first detection signal and the second detection signal;
An angle sensor comprising the correction device according to claim 12.

Images