SHOP SENSOR SYSTEM

Abstract

Angle sensor system (100), comprising: a magnetic field generator (5) for generating a detection target magnetic field, wherein the detection target magnetic field is a magnetic field to be detected and is referenced to an angle to be detected; and an angle sensor (1) for detecting the target magnetic field and for generating an angle detection value which corresponds to the angle to be detected, characterized in that the angle sensor (1) has: a first magnetic sensor (10) for detecting a first applied magnetic field, comprising the target magnetic field for detection, at a first detection position and for generating first detection information corresponding to the angle to be detected; a second magnetic sensor (20) for detecting a second applied magnetic field, comprising the target magnetic field, at a second detection position and for generating second detection information corresponding to the angle to be detected; and a processor (30) for generating the angle detection value by performing arithmetic processing using the first detection information and the second detection information; the direction of the target magnetic field changes at both the first and second detection positions according to the angle to be detected; the detection target magnetic field has a first strength at the first detection position and a second strength at the second detection position, wherein the ratio of the second strength to the first strength is 1.65 or more, the magnetic field generator (5) has a magnetic structure (206) which is made of a magnetic material, wherein the magnetic structure (206) has a magnetization in a direction perpendicular to an axis of rotation and when the magnetic structure (206) is rotated about the axis of rotation, rotates itself about the axis of rotation, the first detection position and the second detection position are located on the same side of the magnetic structure (206) in a direction parallel to the axis of rotation and are spaced at different distances from the axis of rotation, the magnetic structure (206) has a first section (261) and a second section (262) which are coupled together, wherein the second section (262) is located between the first section (261) and the first and second detection positions in the direction parallel to the axis of rotation, the second section (262) has a cavity (262h) through which the axis of rotation passes, whereas the first section (261) has no cavity through which the axis of rotation passes, the first section (261) has a section (261A) of soft magnetic material, which is formed from a soft magnetic material, and a section (261B) of hard magnetic material, which is formed from a hard magnetic material, The section (261B) made of hard magnetic material has a receiving section (261Ba) through which the axis of rotation passes, and the section (261A) made of soft magnetic material is received in the receiving section (261Ba).

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The present invention relates to an angle sensor system for generating an angle detection value which corresponds to an angle to be detected. 2. State of the art

[0002] In recent years, angle sensors have been widely used in various applications, such as detecting the rotational position of a steering wheel or a power steering motor in an automobile. Angle sensors generate an angle measurement value, which corresponds to the angle being measured. Examples of angle sensors include magnetic angle sensors. An angle sensor system that uses a magnetic angle sensor is typically equipped with a magnetic field generator to create a detectable magnetic field, the direction of which changes in response to the rotation or linear movement of an object. Hereinafter, the detectable magnetic field is referred to as the target magnetic field. The magnetic field generator is, for example, a magnet.The angle to be detected by the magnetic angle sensor corresponds to an angle formed by the direction of the detection target magnetic field at a reference position in relation to a reference direction.

[0003] Known magnetic angle sensors include one disclosed in DE 10 2012 100 194 A1, DE 10 2017 122 475 A1 and DE 10 2018 101 909 A1, which has a plurality of detection circuits for generating a plurality of detection signals of different phases and generates an angle detection value by performing arithmetic operations using the plurality of detection signals. Each of the plurality of detection circuits detects a target magnetic field. Each of the plurality of detection circuits has at least one magnetic detection element.

[0004] In some magnetic angle sensors, as described in DE 10 2017 122 475 A1 and DE 10 2018 101 909 A1, each detection circuit can be subject not only to a target magnetic field but also to a magnetic interference field that is not the target magnetic field. Examples of magnetic interference fields include the Earth's magnetic field and stray magnetic fields from a motor. When subjected to such a magnetic interference field, each detection circuit detects a composite magnetic field consisting of the target magnetic field and the magnetic interference field. If the target magnetic field and the magnetic interference field are oriented in different directions, errors occur in the angle measurement value. These errors in the angle measurement value are referred to below as the angle error.

[0005] DE 10 2017 122 475 A1 and DE 10 2018 101 909 A1 describe a technology for detecting the composite magnetic field consisting of the target magnetic field and the magnetic interference field at a multitude of detection positions and use the detection information to generate an angular detection value in which an error caused by the magnetic interference field is reduced. The target magnetic field has different strengths at the multitude of detection positions.

[0006] According to the technology described in DE 10 2017 122 475 A1 and DE 10 2018 101 909 A1, using the detection information from two magnetic sensors arranged at two different positions enables the generation of an angle detection value in which an error caused by the magnetic interference field is reduced. However, research carried out by the inventor of the present invention has shown that the effect varies depending on the design of the two magnetic sensors.

[0007] US 6 479 987 B1 and US 2014 / 0 015 384 A1 each disclose an angle sensor system known in the prior art. US 2010 / 0 176 804 A1 discloses an angle sensor with a ring magnet suitable for mounting on a rotatable shaft. BRIEF SUMMARY OF THE INVENTION

[0008] One object of the present invention is to provide an angle detection system which effectively reduces an angular error caused by a magnetic interference field by using two magnetic sensors.

[0009] An angle sensor system according to the present invention comprises a magnetic field generator and an angle sensor. The magnetic field generator produces a target magnetic field, which is a magnetic field to be detected and is referenced to a specific angle.

[0010] The angle sensor detects the target magnetic field and generates an angle detection value that corresponds to the angle to be detected.

[0011] The angle sensor comprises a first magnetic sensor, a second magnetic sensor, and a processor. The first magnetic sensor detects a first applied magnetic field at a detection position, possessing the target magnetic field, and generates initial detection information corresponding to the angle to be measured. The second magnetic sensor detects a second applied magnetic field at a second detection position, also possessing the target magnetic field, and generates further detection information corresponding to the angle to be measured. The processor generates the angle measurement value by performing arithmetic processing using the first and second detection information.

[0012] At both the first and second detection positions, the direction of the target magnetic field changes according to the angle being detected. The target magnetic field has a first strength at the first detection position and a second strength at the second detection position, and the ratio of the first strength to the second strength is 1.65 or greater.

[0013] In the angle sensor system of the present invention, the ratio of the first strength to the second strength can be 4 or less.

[0014] In the angle sensor system of the present invention, a rotating field angle can correspond to the angle to be detected, and the angle detection value can correspond to the rotating field angle. The rotating field angle is an angle formed by the direction of the detection target magnetic field at a reference position with respect to a reference direction on a reference plane. In such a case, the first detection information can correspond to an angle formed by the direction of a first applied field component with respect to the reference direction, wherein the first applied field component is a component of the first applied magnetic field that lies parallel to the reference plane, and the second detection information can correspond to an angle formed by the direction of a second applied field component with respect to the reference direction, wherein the second applied field component is a component of the second applied magnetic field that lies parallel to the reference plane.

[0015] The initial acquisition information can include a first acquisition value, corresponding to the cosine of the angle formed by the direction of the first applied field component with respect to the reference direction, and a second acquisition value, corresponding to the sine of the angle formed by the direction of the first applied field component with respect to the reference direction. The second acquisition information can include a third acquisition value, corresponding to the cosine of the angle formed by the direction of the second applied field component with respect to the reference direction, and a fourth acquisition value, corresponding to the sine of the angle formed by the direction of the second applied field component with respect to the reference direction.

[0016] The first and second recording positions can be located on the reference plane.

[0017] In the angle sensor system of the present invention, the magnetic field generator comprises a magnetic structure formed from a magnetic material, wherein the magnetic structure is magnetized in a direction perpendicular to an axis of rotation and rotates about the axis of rotation. The first detection position and the second detection position are located on the same side of the magnetic structure in a direction parallel to the axis of rotation and are spaced at different distances from the axis of rotation. The magnetic structure comprises a first section and a second section, which are coupled to each other. The second section is located between the first section and the first and second detection positions in the direction parallel to the axis of rotation.The second section has a cavity through which the axis of rotation passes, whereas the first section has no cavity through which the axis of rotation passes.

[0018] The first section can be shaped like a circular plate. The second section has an outer circumference and an inner circumference, each of which can be circular in any cross-section of the second section perpendicular to the axis of rotation.

[0019] If the magnetic structure has a first section and a second section, the entire magnetic structure can be made of a hard magnetic material. According to a first aspect, the first section has a section of soft magnetic material and a section of hard magnetic material. The hard magnetic section has a receiving section through which the axis of rotation passes, and the soft magnetic section is received within this receiving section.

[0020] If the magnetic structure has a first section and a second section, when viewed in the direction parallel to the axis of rotation, the first detection position can be placed to intersect the cavity of the second section, and the second detection position can be placed to intersect the second section but not the cavity.

[0021] According to the present invention, the ratio between the strength of the target magnetic field at the second detection position and the strength of the target magnetic field at the first detection position is 1.65 or more. This makes it possible to effectively reduce the angular error caused by the magnetic interference field.

[0022] Other and further tasks, features and advantages of the present invention will become fully apparent from the following description. BRIEF SUMMARY OF THE DRAWINGS Fig. Figure 1 is a perspective view to illustrate a schematic design of an angle sensor system according to a first embodiment of the invention. Fig. Figure 2 is an explanatory diagram to illustrate the definitions of directions and angles used in the first embodiment of the invention. Fig. Figure 3 is a perspective exploded view of a magnetic structure of the first embodiment of the invention. Fig. Figure 4 is a cross-sectional view of the magnetic structure of the first embodiment of the invention. Fig. Figure 5 is a functional block diagram to illustrate the design of an angle sensor according to the first embodiment of the invention. Fig. Figure 6 is a circuit diagram illustrating an embodiment example of a first detection value generator of the first embodiment of the invention. Fig. Figure 7 is a circuit diagram illustrating an embodiment example of a second detection value generator of the first embodiment of the invention. Fig. Figure 8 is a perspective view of part of a magnetic detection element in Fig. 4 and Fig. 5. Fig. Figure 9 is an explanatory diagram for the schematic illustration of a relationship between both the first and the second applied field component and a magnetic interference field in the first embodiment of the invention. Fig. Figure 10 is a waveform diagram illustrating an example of waveforms of angular errors obtained through an initial simulation. Fig. Figure 11 is a characteristic curve diagram to illustrate the results of a second simulation. Fig. Figure 12 is a characteristic curve diagram to illustrate the results of a third simulation. Fig. Figure 13 is a characteristic curve diagram to illustrate the results of a fourth simulation. Fig. Figure 14 is a characteristic curve diagram to illustrate the results of the fourth simulation. Fig. 15 is a characteristic curve diagram to illustrate a characteristic curve which is derived from the in Fig. 13 and Fig. The results shown in the 14 images are as follows. Fig. Figure 16 is a characteristic curve diagram to illustrate a characteristic curve which is derived from the values ​​in Fig. 13 and Fig. The results shown in the 14 images are as follows. Fig. Figure 17 is a characteristic curve diagram to illustrate the results of a fifth simulation. Fig. Figure 18 is a characteristic curve diagram to illustrate the results of a sixth simulation. Fig. Figure 19 is a perspective exploded view of a magnetic structure of a second embodiment of the invention. Fig. Figure 20 is a cross-sectional view of the magnetic structure of the second embodiment of the invention. Fig. Figure 21 is a characteristic curve diagram to illustrate the results of a seventh simulation. Fig. Figure 22 is a perspective exploded view of a magnetic structure of a third embodiment of the invention. Fig. Figure 23 is a cross-sectional view of the magnetic structure of the third embodiment of the invention. Fig. Figure 24 is a characteristic curve diagram to illustrate the results of an eighth simulation. DETAILED DESCRIPTION OF THE PREFERRED EXECUTIONS [First embodiment]

[0023] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, we will refer to Fig. Reference is made to a schematic configuration of an angle sensor system according to a first embodiment of the invention. The angle sensor system 100 according to the first embodiment comprises an angle sensor 1 according to the first embodiment and a magnetic field generator 5. The angle sensor 1 is, in particular, a magnetic angle sensor.

[0024] The magnetic field generator 5 generates a target magnetic field for detection, wherein the target magnetic field is a magnetic field to be detected and is referenced to a detection angle. The magnetic field generator 5 has a magnetic structure 6, which is formed from a magnetic material. In the present embodiment, the magnetic structure 6 is formed entirely from a hard magnetic material. The magnetic structure 6 is magnetized in a direction perpendicular to a rotation axis C and rotates about the rotation axis C. The shape of the magnetic structure 6 is described in detail elsewhere.

[0025] In the following, the angle to be detected is referred to as the detection target angle and is denoted by the symbol θ. The detection target angle θ in the present embodiment is an angle corresponding to the rotational position of the magnetic structure 6.

[0026] The angle sensor 1 is set up to detect the target magnetic field and generate an angle detection value θs which corresponds to the target detection angle θ.

[0027] In the following, an angle formed by the direction of the detection target magnetic field at a reference position with respect to a reference direction DR on a reference plane P is referred to as the rotating field angle and denoted by the symbol θM. The rotating field angle θM corresponds to the detection target angle θ. The rotating field angle θM is identical to the detection target angle θ if the magnet 5 generates an ideal rotating magnetic field. In the present embodiment, the assumption is that the rotating field angle θM is identical to the detection target angle θ.

[0028] The reference plane P is an imaginary plane, which, for example, lies perpendicular to the axis of rotation C. The reference position lies on the reference plane P. On the reference plane P, the direction of the detection target magnetic field generated by the magnetic structure 6 rotates around the reference position. The reference direction DR lies on the plane P and intersects the reference direction. In the following description, the direction of the detection target magnetic field at the reference position refers to a direction on the reference plane P. Fig. Figure 1 shows that the distance between the magnetic structure 6 and the reference plane P is excessively large.

[0029] The angle detection value θs corresponds to the rotation field angle θM. As mentioned above, the rotation field angle θM corresponds to the detection target angle θ. The angle detection value θs therefore corresponds to the detection target angle θ.

[0030] The angle sensor 1 comprises a first magnetic sensor 10 and a second magnetic sensor 20. The first magnetic sensor 10 detects a first applied magnetic field MF1 at a first detection position P1. The first applied magnetic field MF1 has the target detection magnetic field. The second magnetic sensor 20 detects a second applied magnetic field MF2 at a second detection position P2. The second applied magnetic field MF2 has the target detection magnetic field.

[0031] The first and second detection positions P1 and P2 are located on the same side of the magnetic structure 6 in a direction parallel to the axis of rotation C. In the present embodiment, both the first and second detection positions P1 and P2 lie on the reference plane P. The first and second detection positions P1 and P2 are spaced at different distances from the axis of rotation C. In the present embodiment, the first and second detection positions P1 and P2 are defined such that they are spaced at different distances from the intersection of the reference plane P and the axis of rotation C. In the Fig. In the example shown in Figure 1, the first detection position P1 is the intersection of the reference plane P and the axis of rotation C, and the second detection position P2 is spaced away from the axis of rotation C. Possible positional relationships between the first and second detection positions P1, P2, and the magnetic structure 6 are not shown in Figure 1. Fig. The example shown is limited. For example, the first and second detection positions P1 and P2 can be two positions located at different distances from the magnetic structure 6.

[0032] In the following, the target magnetic field at the first detection position P1 is referred to as the first partial magnetic field MFa, and the target magnetic field at the second detection position P2 is referred to as the second partial magnetic field MFb. The directions of the first and second partial magnetic fields MFa and MFb change according to the target angle θ and the rotation angle θM. The directions of the first and second partial magnetic fields MFa and MFb are parallel or nearly parallel to the reference plane P. Since the first and second detection positions P1 and P2 differ from each other, the first and second partial magnetic fields MFa and MFb differ in their strengths.

[0033] Angle sensor 1 may be subject not only to the target magnetic field but also to a magnetic interference field Mex, which is not the target magnetic field. The direction and strength of the magnetic interference field Mex at the second detection position are the same as the direction and strength of the magnetic interference field Mex at the first detection position P1. The magnetic interference field Mex can be a magnetic field whose direction and strength are temporarily constant, a magnetic field whose direction and strength vary in a regular manner, or a magnetic field whose direction and strength vary randomly.

[0034] When the magnetic interference field Mex is applied to the angle sensor 1, the first applied magnetic field MF1 is a composite magnetic field consisting of the first partial magnetic field MFa and the magnetic interference field Mex, and the second applied magnetic field MF2 is a composite magnetic field consisting of the second partial magnetic field MFb and the magnetic interference field Mex.

[0035] Definitions of directions and angles used in the present embodiment are now given with reference to Fig. 1 and Fig. 2 described. First, the Z-direction is defined as the one in Fig. 1 shown parallel to the axis of rotation C as well as in Fig. 1. A direction running from bottom to top is defined. Fig. Figure 2 illustrates the Z-direction as the direction outside the plane of the drawing. The X and Y directions are defined as two directions orthogonal to each other and perpendicular to the Z-direction. Fig. Figure 2 illustrates the X direction as the right direction and the Y direction as the upward direction. Furthermore, the -X direction denotes the direction opposite to the X direction and the -Y direction denotes the direction opposite to the Y direction.

[0036] The rotation field angle θM is expressed with respect to the reference direction DR. In the present embodiment, the reference direction DR is the X-direction. Furthermore, in the present embodiment, the reference position is the intersection of the reference plane P and the axis of rotation C.

[0037] A component of the first applied magnetic field MF1 lying parallel to the reference plane P is called the first applied field component MF1c, and a component of the second applied magnetic field MF2 lying parallel to the reference plane P is called the second applied field component MF2c.

[0038] The prerequisite is that the directions of the first and second applied field components MF1c and MF2c both point counterclockwise in Fig. Turn 2. As in Fig. In Figure 2, θ1 represents an angle formed by the direction of the first applied field component MF1c with respect to the reference direction DR, and θ2 represents an angle formed by the direction of the second applied field component MF2c with respect to the reference direction DR. The angles θ1 and θ2 are expressed as positive values ​​when viewed counterclockwise from the reference direction DR and as negative values ​​when viewed clockwise from the reference direction DR.

[0039] The main component of the first applied magnetic field MF1 is the first partial magnetic field MFa. The main component of the second applied magnetic field MF2 is the second partial magnetic field MFb. The following description assumes that the directions of the first and second partial magnetic fields MFa and MFb are identical to the direction of the target magnetic field at the reference position. In this case, the respective angles formed by the first and second partial magnetic fields MFa and MFb with respect to the reference direction DR are equal to the rotational field angle θM. The positive and negative signs of these angles are defined in the same way as those of angles θ1 and θ2.

[0040] Fig. Figure 1 illustrates an example where the reference position and the first detection position P1 are identical. Provided that the relationships described above between the first and second partial magnetic fields MFa and MFb and the detection target magnetic field at the reference position are satisfied, the reference position can differ from the intersection of the reference plane P and the axis of rotation C.

[0041] Now, the focus will shift to... Fig. 3 and Fig. 4 Reference is made to describe the shape of the magnetic structure 6 in detail. Fig. Figure 3 is a perspective exploded view of the magnet structure 6. Fig. Figure 4 is a cross-sectional view of the magnetic structure 6. The magnetic structure 6 has a first end surface 6a and a second end surface 6b, which are opposite each other in a direction parallel to the axis of rotation C. The second end surface 6b faces the reference plane P. In the present embodiment, both the first end surface 6a and the second end surface 6b are perpendicular to the axis of rotation C.

[0042] The magnetic structure 6 has a first section 61 and a second section 62, which are coupled to each other. In Fig. In Figure 3, the first section 61 and the second section 62 are shown separately. Fig. In section 4, the boundary between the first section 61 and the second section 62 is represented by dotted lines. The first section 61 has the first end surface 6a. The second section 62 has the second end surface 6b.

[0043] As in Fig. As shown in Figure 4, the second section 62 is located in a direction parallel to the axis of rotation C between the first section 61 and the first and second detection positions P1 and P2. As shown in Fig. 3 and Fig. As shown in Figure 4, the second section 62 has a cavity 62h through which the axis of rotation C passes, whereas the first section 61 has no cavity through which the axis of rotation C passes.

[0044] In the present embodiment, the second section 62 is shaped as follows. The second section 62 has an outer circumference and an inner circumference, each of which, in any cross-section of the second section 62 perpendicular to the axis of rotation C, has a circular shape centered on the axis of rotation C. The diameter of the outer circumference of the second section 62 in the aforementioned cross-section is hereinafter referred to as the outer diameter of the second section 62 and is denoted by the symbol D. The diameter of the inner circumference of the second section 62 in the aforementioned cross-section is referred to as the inner diameter of the second section 62 and is denoted by the symbol d. In the present embodiment, both the outer diameter D and the inner diameter d of the second section 62 are constant regardless of the distance from the second end face 6b.A dimension of the second section 62 in a direction parallel to the axis of rotation C is referred to as the thickness of the second section 62 and is denoted by the symbol T2.

[0045] In the present embodiment, the first section 61 is shaped like a circular plate whose central axis lies on the axis of rotation C. The diameter of an outer circumference of the first section 61 in any cross-section of the first section 61 perpendicular to the axis of rotation C is referred to as the outer diameter of the first section 61. In the present embodiment, the outer diameter of the first section 61 is constant regardless of the distance to the first end surface 6a. A dimension of the first section 61 in a direction parallel to the axis of rotation C is referred to as the thickness of the first section 61 and is denoted by the symbol T1.

[0046] At the in Fig. In the 4 illustrated and unclaimed comparative example, when viewed in a direction parallel to the axis of rotation C, the first detection position P1 is placed to intersect the cavity 62h of the second section 62, and the second detection position P2 is placed to intersect the second section 62, but not the cavity 62h. When viewed in a direction parallel to the axis of rotation C, both the first and second detection positions P1 and P2 are placed to intersect the cavity 62h of the second section 62.

[0047] Now, the focus will shift to... Fig. 5 Reference is made to describe in detail the design of the angle sensor 1. Fig. Figure 5 is a functional circuit diagram illustrating the design of the angle sensor 1. As mentioned above, the angle sensor 1 comprises the first and second magnetic sensors 10 and 20. The first magnetic sensor 10 generates initial detection information corresponding to the target detection angle θ. This initial detection information corresponds to the angle θ1, which is formed by the direction of the first applied field component MF1c with respect to the reference direction DR. The second magnetic sensor 20 generates secondary detection information corresponding to the target detection angle θ. This secondary detection information corresponds to the angle θ2, which is formed by the direction of the second applied field component MF2c with respect to the reference direction DR.

[0048] The initial data collection includes a first data value S1, which corresponds to the cosine of the angle θ1, and a second data value S2, which corresponds to the sine of the angle θ1. The first data value S1 can correspond to the strength of a component in the X-direction of the first applied field component MF1c. The second data value S2 can correspond to the strength of a component in the Y-direction of the first applied field component MF1c.

[0049] The second set of acquisition data includes a third acquisition value S3, which corresponds to the cosine of the angle θ2, and a fourth acquisition value S4, which corresponds to the sine of the angle θ2. The third acquisition value S3 can correspond to the strength of a component in the X-direction of the second applied field component MF2c. The fourth acquisition value S4 can correspond to the strength of a component in the Y-direction of the second applied field component MF2c.

[0050] The first magnetic sensor 10 has a first acquisition value generator 11 for generating the first acquisition value S1 and a second acquisition value generator 12 for generating the second acquisition value S2. The second magnetic sensor 20 has a third acquisition value generator 21 for generating the third acquisition value S3 and a fourth acquisition value generator 22 for generating the fourth acquisition value S4.

[0051] Each of the first to fourth acquisition value generators 11, 12, 21, and 22 has at least one magnetic sensing element. The at least one magnetic sensing element can include at least one magnetoresistive element. The magnetoresistive element can be a giant magnetoresistive element (GMR element), a tunnel magnetoresistive element (TMR element), or an anisotropic magnetoresistive element (AMR element). The at least one magnetic sensing element can also include at least one element that is not a magnetoresistive element and is configured to detect a magnetic field, such as a Hall effect sensor.

[0052] Since the direction of the target magnetic field rotates at a specific time interval T, the rotation angle θM varies according to the predetermined time interval T. In this case, all of the first through fourth detection values, S1 to S4, vary regularly according to the time interval T. The first detection value S1 and the third detection value S3 have the same phase. The second detection value S2 and the fourth detection value S4 have the same phase. The phase of the second detection value S2 differs from the phase of the first detection value S1 by an odd multiple of 1 / 4 of the time interval T. The phase of the fourth detection value S4 differs from the phase of the third detection value S3 by an odd multiple of 1 / 4 of the time interval T. Due to the manufacturing accuracy of the magnetic detection elements or other factors, the phase ratios may differ slightly from those described above.

[0053] The angle sensor 1 further comprises a processor 30. The processor 30 generates the angle measurement value θs by performing arithmetic processing using the first and second measurement information. The processor 30 can be implemented, for example, by an application-specific integrated circuit (ASIC) or a microcomputer.

[0054] In the present embodiment, the processor 30 comprises analog-to-digital converters (hereinafter referred to as "A / D converters") 31, 32, 33, and 34, a first initial angle calculation section 35, a second initial angle calculation section 36, an arithmetic processor 37, and a memory area 38. The A / D converters 31 and 32 each convert the first and second acquisition values ​​S1 and S2 into digital form. The first initial angle calculation section 35 determines a first initial angle acquisition value θ1s, which is an acquisition value of the angle θ1, by performing arithmetic processing using the first and second acquisition values ​​S1 and S2, which have been converted into digital form by the A / D converters 31 and 32.

[0055] The A / D converters 33 and 34 convert the third and fourth acquisition values ​​S3 and S4, respectively, into digital form. The second initial angle calculation section 36 determines a second initial angle acquisition value θ2s, which is an acquisition value of the angle θ2, by performing arithmetic processing using the third and fourth acquisition values ​​S3 and S4, which have been converted into digital form by the A / D converters 33 and 34.

[0056] The arithmetic processor 37 calculates the angle detection value θs using θ1s and θ2s. The procedures for calculating θ1s, θ2s and θs, as well as the function of the memory area 38, are described elsewhere.

[0057] The design of the first to fourth data acquisition generators 11, 12, 21 and 22 will now be described. Fig. Figure 6 illustrates a specific embodiment of the first detection value generator 11. In this example, the first detection value generator 11 comprises a Wheatstone bridge circuit 17 and a differential detector 18. The Wheatstone bridge circuit 17 has four magnetic detection elements R11, R12, R13, and R14, a power supply terminal V1, a ground terminal G1, and two output terminals E11 and E12. Magnetic detection element R11 is provided between the power supply terminal V1 and the output terminal E11. Magnetic detection element R12 is provided between the output terminal E11 and the ground terminal G1. Magnetic detection element R13 is provided between the power supply terminal V1 and the output terminal E12. Magnetic detection element R14 is provided between the output terminal E12 and the ground terminal G1.A supply voltage of a predetermined magnitude is applied to the power supply terminal V1. The ground terminal G1 is connected to ground.

[0058] The third data acquisition generator 21 has the same design as the first data acquisition generator 11. Therefore, in the following description, components of the third data acquisition generator 21 are identified by the same reference symbols used for the components of the first data acquisition generator 11.

[0059] Fig. Figure 7 illustrates a specific embodiment of the second acquisition value generator 12. In this example, the second acquisition value generator 12 comprises a Wheatstone bridge circuit 27 and a differential detector 28. The Wheatstone bridge circuit 27 has four magnetic sensing elements R21, R22, R23, and R24, a power supply terminal V2, a ground terminal G2, and two output terminals E21 and E22. Magnetic sensing element R21 is provided between the power supply terminal V2 and the output terminal E21. Magnetic sensing element R22 is provided between the output terminal E21 and the ground terminal G2. Magnetic sensing element R23 is provided between the power supply terminal V2 and the output terminal E22. Magnetic sensing element R24 is provided between the output terminal E22 and the ground terminal G2.A supply voltage of a specified value is applied to the power supply terminal V2. The ground terminal G2 is connected to ground.

[0060] The fourth data acquisition generator 22 has the same design as the second data acquisition generator 12. Therefore, in the following description, components of the fourth data acquisition generator 22 are identified with the same reference symbols used for the components of the second data acquisition generator 12.

[0061] In the present embodiment, each of the magnetic sensing elements R11 to R14 and R21 to R24 comprises a plurality of magnetoresistive elements (MR elements) connected in series. Each of the plurality of MR elements is, for example, a spin-valve MR element. The spin-valve MR element comprises a pinned magnetization layer with a pinned magnetization direction, a free layer which is a magnetic layer whose magnetization direction changes according to the direction of the sensing target magnetic field, and a non-magnetic layer located between the pinned magnetization layer and the free layer. The spin-valve MR element can be a TMR element or a GMR element. In the TMR element, the non-magnetic layer is a tunnel barrier layer. In the GMR element, the non-magnetic layer is a non-magnetic conductive layer.The resistance of the spin-valve MR element changes according to the angle formed by the magnetization direction of the free layer relative to the magnetization direction of the pinned magnetization layer. The resistance of the spin-valve MR element is at its minimum value when the aforementioned angle is 0° and at its maximum value when the aforementioned angle is 180°. Fig. 6 and Fig. 7. The filled arrows indicate the magnetization directions of the pinned magnetization layers of the MR elements, and the empty arrows indicate the magnetization directions of the free layers of the MR elements.

[0062] In the first detection value generator 11, the pinned magnetization layers of the MR elements in magnetic detection elements R11 and R14 are magnetized in the X direction, and the pinned magnetization layers of the MR elements in magnetic detection elements R12 and R13 are magnetized in the -X direction. In this case, the potential difference between the output terminals E11 and E12 changes according to the cosine of the angle θ1. The differential detector 18 outputs a signal corresponding to the potential difference between the output terminals E11 and E12 as the first detection value S1. The first detection value S1 thus corresponds to the cosine of the angle θ1.

[0063] In the second detection value generator 12, the pinned magnetization layers of the MR elements in magnetic detection elements R21 and R24 are magnetized in the Y-direction, and the pinned magnetization layers of the MR elements in magnetic detection elements R22 and R23 are magnetized in the -Y-direction. In this case, the potential difference between the output terminals E21 and E22 changes according to the sine of the angle θ1. The differential detector 28 outputs a signal corresponding to the potential difference between the output terminals E21 and E22 as the second detection value S2. The second detection value S2 thus corresponds to the sine of the angle θ1.

[0064] In the third acquisition value generator 21, the potential difference between the output terminals E11 and E12 changes according to the cosine of the angle θ2. The differential detector 18 outputs a signal corresponding to the potential difference between the output terminals E11 and E12 as the third acquisition value S3. The third acquisition value S3 thus corresponds to the cosine of the angle θ2.

[0065] In the fourth acquisition value generator 22, the potential difference between the output terminals E21 and E22 changes according to the sine of the angle θ2. The differential detector 28 outputs a signal corresponding to the potential difference between the output terminals E21 and E22 as the fourth acquisition value S4. The fourth acquisition value S4 thus corresponds to the sine of the angle θ2.

[0066] With regard to the manufacturing accuracy of the MR elements and other factors, the magnetization directions of the pinned magnetization layers of the multitude of MR elements in the detection value generators 11, 12, 21 and 22 may differ slightly from the directions described above.

[0067] An example design of the magnetic detection elements will now be presented with reference to Fig. 8 described. Fig. Figure 8 is a perspective view of part of a magnetic detection element in the Fig. 6 and Fig. The 7 shown acquisition value generators 11 and 12. In this example, the magnetic sensing element has a plurality of lower electrodes 65, a plurality of MR elements 50, and a plurality of upper electrodes 66. The lower electrodes 65 are arranged on a substrate (not shown). The lower electrodes 65 each have an elongated, slender shape. Every pair of lower electrodes 65 that are adjacent to each other in the longitudinal direction of the lower electrodes 65 has a gap between them. As in Fig. Figure 8 shows MR elements 50 arranged on the surface of the lower electrode 65 at positions near longitudinally opposite ends. Each MR element 50 has a free layer 51, a non-magnetic layer 52, a pinned magnetizing layer 53, and an antiferromagnetic layer 54, stacked in this order from the nearest to the furthest position from the lower electrode 65. The free layer 51 is electrically connected to the lower electrode 65. The antiferromagnetic layer 54 is formed from an antiferromagnetic material and is in an exchange coupling with the pinned magnetizing layer 53 to pin the magnetization direction of the pinned magnetizing layer 53. The upper electrodes 66 are arranged above the MR elements 50.Each upper electrode 66 has an elongated, slender shape and establishes an electrical connection between the respective antiferromagnetic layers 54 of two adjacent MR elements 50, which are arranged on two lower electrodes 65 that are adjacent in the longitudinal direction of the lower electrodes 65. In such a configuration, the MR elements 50 are in the Fig. The magnetic detection element shown in Figure 8 is connected in series by the upper and lower electrodes 66 and 65.

[0068] It is understood that layers 51 to 54 of the MR elements 50 can be stacked in the order reversed to that in Fig. 8. Furthermore, the MR element 50 can be configured without the antiferromagnetic layer 54. The configuration can, for example, be such that the antiferromagnetic layer 54 and the pinned magnetizing layer 53 can be replaced by a pinned magnetizing layer of an artificial antiferromagnetic structure, which has two ferromagnetic layers and a non-magnetic metal layer arranged between the two ferromagnetic layers.

[0069] Next, a procedure for calculating the first and second initial angle detection values ​​θ1 and θ2 is described. The first initial angle calculation section 35 of the processor 30 calculates θ1s by performing an initial arithmetic operation, which includes, for example, the equation (1) mentioned below. θ1s=atan(S2 / S1)

[0070] It should be noted that "atan" stands for an arcanth.

[0071] For θ1s in the range from 0° to less than 360°, equation (1) yields two solutions of θ1s that differ in value by 180°. Which of the two solutions of θ1s in equation (1) is the actual value of θ1s can be determined according to the combination of the signs of S1 and S2. The first initial angle calculation section 35 determines θ1s in the range from 0° to less than 360° according to equation (1) and the determination based on the combination of the signs of S1 and S2.

[0072] The second initial angle calculation section 36 of the processor 30 calculates θ2s by performing a second arithmetic processing operation, which includes, for example, the equation (2) mentioned below. θ2s=atan(S4 / S3)

[0073] For θ2s in the range from 0° to less than 360°, equation (2) yields two solutions of θ2s that differ in value by 180°. Which of the two solutions of θ2s in equation (1) is the actual value of θ2s can be determined according to the combination of the signs of S3 and S4. The second initial angle calculation section 36 determines θ2s in the range from 0° to less than 360° according to equation (2) and the determination based on the combination of the signs of S1 and S2.

[0074] The first arithmetic processing step can include an arithmetic processing step to reduce an error of θ1s, which is calculated according to equation (1). Similarly, the second arithmetic processing step can include an arithmetic processing step to reduce an error of θ2s, which is calculated according to equation (2).

[0075] Next, a procedure for calculating the angle detection value θs is described. First, the relationship between the angles θ1, θ2, and the rotating field angle θM is described. If no magnetic interference field Mex is present, the angle θ1 is equal to the rotating field angle θM. If a magnetic interference field Mex is present, the direction of the first applied field component MF1c can deviate from that of the first partial magnetic field MFa, so that the angle θ1 can be different from the value of the rotating field angle θM. A difference between the angle θ1 and the rotating field angle θM is referred to below as the angular error of the angle θ1. The angular error of the angle θ1 is caused by the magnetic interference field Mex.

[0076] If no magnetic interference field Mex is present, the angle θ2 is equal to the rotating field angle θM. If a magnetic interference field Mex is present, the direction of the second applied field component MF2c can deviate from that of the second partial magnetic field MFb, so that the angle θ2 becomes different from the value of the rotating field angle θM. A difference between the angle θ2 and the rotating field angle θM is referred to below as the angular error of the angle θ2. The angular error of the angle θ2 is caused by the magnetic interference field Mex.

[0077] The magnetic interference field Mex will now be discussed separately with regard to its first to third components. A first component of the magnetic interference field Mex is a component in a direction parallel to the reference plane P and orthogonal to the directions of the first and second partial magnetic fields MFa and MFb. A second component of the magnetic interference field Mex is a component in a direction parallel to the directions of the first and second partial magnetic fields MFa and MFb. A third component of the magnetic interference field Mex is a component in a direction perpendicular to the reference plane P. Fig. Figure 9 is an explanatory diagram schematically illustrating the relationship between both the first and second applied field components MF1c and MF2c and the magnetic interference field Mex. Fig. In Figure 9, the arrows Mex1 denote the first component of the magnetic interference field Mex. The magnitude of the first component Mex1 is given in Fig. 9 is depicted as excessively large. As in Fig. Figure 9 shows that the directions of the first and second applied field components MF1c and MF2c deviate from the directions of the first and second partial magnetic fields MFa and MFb due to the effect of the first component Mex1.

[0078] In the present embodiment, it is a prerequisite that the strength of the magnetic interference field Mex is sufficiently lower than the strengths of the first and second partial magnetic fields MFa and MFb such that the second component of the magnetic interference field Mex has an insignificant effect on the directional deviations of the first and second applied field components MF1c and MF2c. Furthermore, the third component of the magnetic interference field Mex does not affect the directions of the first and second applied field components MF1c and MF2c. Fig. Figure 9 shows the first applied field component MF1c as a composite magnetic field from the first partial magnetic field MFa and the first component Mex1 of the magnetic disturbance field Mex, and the second applied field component MF2c is shown as a composite magnetic field from the second partial magnetic field Mfb and the first component Mex1 of the magnetic disturbance field Mex.

[0079] As in Fig. As shown in Figure 9, a deviation in the direction of the first applied field component MF1c from the direction of the first partial magnetic field MFa causes the angle θ1 to exhibit an angular error. The angular error θ1 is atan(Bex / B 1), where B1 represents the strength of the first partial magnetic field MFa and Bex represents the strength of the first component Mex1 of the magnetic disturbance field Mex.

[0080] As in Fig. As shown in Figure 9, a deviation in the direction of the second applied field component MF2c from the direction of the second partial magnetic field MFb causes the angle θ2 to exhibit an angular error. The angular error θ2 is atan(Bex / B2), where B2 represents the strength of the second partial magnetic field MFb.

[0081] The angle θ1 can be expressed using the rotation field angle θM and the angular error of angle θ1. The angle θ2 can be expressed using the rotation field angle θM and the angular error of angle θ2. Specifically, the angles θ1 and θ2 can each be expressed in equations (3) and (4) mentioned below. θ1=θM−atan(Bex / B1) θ2=θM−atan(Bex / B2)

[0082] If x is sufficiently small, atan(x) can be expressed approximately as AT*x. AT is a constant value, for which 56,57 is an example. In the present embodiment, atan(Bex / B1) can be expressed approximately as AT*(Bex / B1) and atan(Bex / B2) can be expressed approximately as AT*(Bex / B2) because the strength Bex of the first component Mex1 of the magnetic disturbance field Mex is sufficiently smaller than the strengths B1 and B2 of the first and second partial magnetic fields MFa and MFb, respectively. Applying the approximation of equation (3) and rearranging the equation allows Bex to be expressed in equation (5) below. Bex=−B1∗(θ1−θM) / AT

[0083] Applying the approximation described above to equation (4) to rearrange the equation and further to substitute equation (5) into the rearranged equation leads to the equation (6) mentioned below. θ2=θM+B1∗(θ1−θM) / B2

[0084] Rearranging equation (6) makes it possible to express the rotation field angle θM in the equation (7) mentioned below. θM={θ2−(B1 / B2)∗θ1} / {1−(B1 / B2)}

[0085] In the present embodiment, the ratio of the strength of the target magnetic field at the second detection position P2 to the strength of the target magnetic field at the first detection position P1 is an important parameter related to the angular error of the angular detection value θs. The aforementioned ratio is the same as the ratio B2 / B1, i.e., the ratio of the strength B2 of the second partial magnetic field MFb to the strength B1 of the first partial magnetic field MFa. A ratio B1 / B2, which is the reciprocal of the ratio B2 / B1, is here designated by the symbol B12. The values ​​of the ratios B2 / B1 and B12 vary depending on the positional relationship between the first and second detection positions P1 and P2.

[0086] Next, the method by which the arithmetic processor 37 calculates the angle detection value θs is described in detail. In the present embodiment, the arithmetic processor 37 performs arithmetic processing using θ1s and θ2s, which are the detection values ​​of the angles θ1 and θ2, and the ratio B12 mentioned above. More precisely, the arithmetic processor 37 performs arithmetic processing, which is expressed in the equation (8) mentioned below, in order to generate the angle detection value θs. θs=(θ2s−B12∗θ1s) / (1−B12)

[0087] Equation (8) results from replacing θM, θ1, θ2 and B1 / B2 from equation (7) with θs, θ1s, θ2s and B12 respectively.

[0088] Memory area 38 stores the ratio B12. The arithmetic processor 37 calculates the angle detection value θs according to equation (8) using: θ1s, which is calculated from the first initial angle calculation section 35; θ2s, which is calculated from the second initial angle calculation section 36; and the ratio B12 stored in memory area 38.

[0089] θ1s is calculated using the first and second acquisition values ​​S1 and S2. θ2s is calculated using the third and fourth acquisition values ​​S3 and S4. Therefore, the arithmetic processing expressed in equation (8) is an arithmetic processing using the first to fourth acquisition values ​​S1 to S4 and is also an arithmetic processing using the first and second acquisition information.

[0090] The ratio B12 can be determined by measuring the strengths B1 and B2 of the first and second partial magnetic fields MFa and MFb. The measurement of strengths B1 and B2 is performed by a control unit (not shown) located outside the angle sensor 1 before delivery or use of the angle sensor 1. The measurement of strengths B1 and B2 can also be performed using the first and second magnetic sensors 10 and 20, or other magnetic sensors.

[0091] According to the present embodiment, performing the arithmetic processing using both the first and second acquisition information enables the generation of the angle acquisition value θs, which, compared to generating the angle acquisition value θs based solely on either the first or the second acquisition information, contains a lower angular error caused by the magnetic interference field Mex. The reason for this is explained in detail below.

[0092] As can be seen from equation (3), the angle θs varies depending on the angular error “atan(Bex / B1)” caused by the magnetic interference field Mex. As can be seen from equation (4), the angle θ2 varies depending on the angular error “atan(Bex / B2)” caused by the magnetic interference field Mex.

[0093] In the present embodiment, the strength B1 of the first partial magnetic field MFa and the strength B2 of the second partial magnetic field MFb differ from each other. Consequently, a difference arises between the values ​​of the angular errors of angles θ1 and θ2, depending on the magnetic interference field Mex. The rotating field angle θM, expressed in equation (7), is guided by this property. In the present embodiment, the angle detection value θs is generated by performing arithmetic processing using the first detection information and the second detection information, more precisely, the arithmetic processing expressed in equation (8).

[0094] θ1 and θ2, which are respectively the acquisition values ​​of angles θ1 and θ2, correspond to an angle acquisition value generated based solely on either the first or the second acquisition information. Since angles θ1 and θ2 contain angular errors caused by the magnetic interference field Mex, as described above, θ1s and θ2s also contain similar errors. On the other hand, the angle acquisition value θs generated by performing the arithmetic processing expressed in equation (8) theoretically contains no angular error caused by the magnetic interference field Mex, since the rotating field angle θM contains no angular error caused by the magnetic interference field. The present embodiment thus enables the generation of the angle acquisition value θs with a reduced angular error caused by the magnetic interference field compared to angles θ1s and θ2s.

[0095] The effects of the present embodiment are now described with reference to the results of a first simulation. In the first simulation, a first model of the angle sensor system 100 was used to determine the respective angular errors θ1s, θ2s, and θs when θ1s, θ2s, and θs were determined in the presence of a magnetic disturbance field Mex with constant direction and strength.

[0096] The magnetic structure 6 of the first model has the following configuration. The first section 61 has an outer diameter of 6 mm. The first section 61 has a thickness T1 of 2 mm (see Fig. 4). The second section 62 has an outer diameter D of 6 mm (see Fig. 4). The second section 62 has an inner diameter d of 2 mm (see Fig. 4). The second section 62 has a thickness T2 of 1 mm (see Fig. 4) The residual magnetic flux density corresponding to the magnetization of the magnetic structure 6 is 0.615 T.

[0097] The positional relationships between the magnetic structure 6, the axis of rotation C, the reference plane P, the first detection position P1, and the second detection position P2 in the first model are as follows. The second end face 6b of the magnetic structure 6 is 0.5 mm away from the reference plane P. Both the first and second detection positions P1 and P2 lie on the reference plane P. The first detection position P1 is an intersection of the reference plane P and the axis of rotation C. The second detection position P2 is 2.4 mm away from the axis of rotation C. In the first simulation, the magnetic flux density, corresponding to the strength of the magnetic interference field Mex, is 5 mT.

[0098] Fig. Figure 10 is a waveform diagram illustrating an example of angular errors of θ1s, θ2s, and θs obtained through the first simulation. Fig. Reference numeral 10 represents the horizontal axis, the target angle θ, and the vertical axis represents the angular error. Reference numeral 71 represents the angular error of θ1s. Reference numeral 72 represents the angular error of θ2s. Reference numeral 73 represents the angular error of θs. As in Fig. Figure 10 shows that the angular error of θs is much smaller than the angular errors of both θ1s and θ2s. The angular errors of θ1s and θ2s are mainly caused by the magnetic interference field Mex. The results of the first simulation indicate that the present embodiment enables the generation of an angular detection value θs in which a reduction of the angular error caused by the magnetic interference field Mex is achieved.

[0099] Next, a second simulation is described. In the second simulation, a second model of the angle sensor system 100 was used to determine a relationship between the ratio B2 / B1, i.e., the ratio of the strength B2 of the second partial magnetic field MFb to the strength B1 of the first partial magnetic field MFa, and the angular error of the angle detection value θs. Hereinafter, unless otherwise specified, an angular error refers to a maximum value of angular errors that cause the detection target angle θ to vary over a range of 360°. The second model is the same as the first model except that the distance from the axis of rotation C to the second detection position P2 is 1.9 mm. In the second simulation, the ratio B2 / B1 was varied by varying the strength B1 of the first partial magnetic field MFa, while keeping the strength B2 of the second partial magnetic field MFb constant.The other conditions of the second simulation were the same as those of the first simulation.

[0100] Fig. Figure 11 is a characteristic curve diagram illustrating the relationship between the ratio B2 / B1 and the angular error of the angle measurement value θ, which was obtained through the second simulation. Fig. Figure 11 represents the horizontal axis B2 / B1, and the vertical axis represents the angular error. As in Fig. Figure 11 shows that the angular error in the B2B1 range increases by up to 2.5 as B2 / B1 approaches 1. In the B2B1 range of at least 2.5, the angular error hardly changes with the change in B2 / B1.

[0101] One reason for the angular error increasing as B2 / B1 approaches 1 in the B2 / B1 range of up to 2.5 is considered as follows. The angular detection value θs determined in the present embodiment corresponds to an angle formed by the direction of a difference vector between the vector representing the second applied field component MF2c and a vector representing the first applied field component MF1c, which in Fig. Figure 9 is shown in relation to the reference direction DR. As B2 / B1 approaches 1, the magnitude of the aforementioned difference vector decreases, and consequently the signal-to-noise ratio of the angle detection value θs decreases to increase the angular error.

[0102] The angular error is preferably 1.5° or less. Fig. Figure 11 shows that the angular error can be reduced to 1.5° or less by setting B2 / B1 to 1.65 or more. Therefore, B2 / B1 is preferably 1.65 or more. To further reduce the angular error, B2 / B1 is more preferably 2 or more, or even more preferably 2.5 or more.

[0103] The angular error of θ1s, corresponding to the angular error of angle θ1, is denoted by the symbol AE1. The angular error of θ2s, corresponding to the angular error of angle θ2, is denoted by the symbol AE2. The angular error AE1 can be expressed approximately as AT*(Bex / B1). The angular error AE2 can be expressed approximately as AT*(Bex / B2). AE1 / AE2 is thus approximately equal to B2 / B1. Therefore, if B2 / B1 is preferably 1.65 or more, then AE1 / AE2 is preferably 1.65 or more.

[0104] An example of the requirements a typical angle sensor must meet is that the angular error must be less than or equal to a predetermined value when the magnetic flux density, corresponding to the strength of the target magnetic field in the absence of a magnetic interference field, falls within a specific range. This predetermined range, for example, extends from 20 mT to 80 mT. The requirement that the angular error be less than or equal to a predetermined value when the magnetic flux density is within the range of 20 mT to 80 mT in the absence of a magnetic interference field is referred to below as the standard error requirement.

[0105] In the present embodiment, it can be assumed that the first magnetic sensor 10, the A / D converters 31 and 32, and the first initial angle calculation section 35 form a single angle sensor. In this context, a section of the angle sensor 1, which is formed from the first magnetic sensor 10, the A / D converters 31 and 32, and the first initial angle calculation section 35, is referred to as the first angle sensor section. Likewise, it can be assumed that the second magnetic sensor 20, the A / D converters 33 and 34, and the second initial angle calculation section 36 form another single angle sensor. In this context, a further section of the angle sensor 1, which is formed from the second magnetic sensor 20, the A / D converters 33 and 34, and the second initial angle calculation section 36, is referred to as the second angle sensor section.

[0106] The prerequisite is that the first and second angle sensor sections meet the normal error requirement. In this case, the first initial angle detection value θ1s, in the absence of the magnetic interference field Mex, is at or below the predetermined value defined by the normal error requirement if the magnetic flux density corresponding to the strength B1 of the first partial magnetic field MFa is in the range of 20 mT to 80 mT. Similarly, in the absence of the magnetic interference field Mex, the second initial angle detection value θ2 is at or below the predetermined value defined by the normal error requirement if the magnetic flux density corresponding to the strength B2 of the second partial magnetic field MFb is in the range of 20 mT to 80 mT.

[0107] In the present embodiment, both the magnetic flux density corresponding to the strength B1 of the first partial magnetic field MFa and the magnetic flux density corresponding to the strength B2 of the second partial magnetic field Mfb are preferably in the range of 20 mT to 80 mT. To meet such a requirement, B2 / B1 must be 4 or less. Therefore, B2 / B1 is preferably 4 or less.

[0108] As can be seen from the foregoing, a preferred requirement for B2 and B1 in the present embodiment is that both the magnetic flux density according to B1 and the magnetic flux density according to B2 are in the range of 20 mT to 80 mT and B2 / B1 is 1.65 or more and not more than 4.

[0109] Next, a third simulation is described. In the third simulation, a third model of the angle sensor system 100 was used to vary T1 / T2, i.e., the ratio of the thickness T1 (see Fig. 4) of the first section 61 to the thickness T2 (see Fig. 4) of the second section 62, to investigate a distribution of magnetic flux densities on an imaginary straight line on the reference plane P, wherein the imaginary straight line passes through the intersection of the reference plane P and the axis of rotation C. The intersection of the reference plane P and the axis of rotation C is hereafter referred to as the starting point. Any point on the aforementioned imaginary straight line is referred to as a measurement point. The position of the measurement point is expressed as the distance from the starting point to the measurement point. The magnetic flux density at a measurement point corresponds to the strength of the detection target magnetic field at the measurement point. The third model is the same as the first model except that the thickness T1 of the first section 61 of the magnetic structure 6 is a variable value.In the third simulation, the ratio T1 / T2 was varied by changing the thickness T1 of the first section 61 to 0.9 mm, 1 mm, 2 mm, and 3 mm, whereas the thickness T2 of the second section 62 was fixed at 1 mm. The other conditions of the third simulation were the same as those of the first simulation.

[0110] Fig. Figure 12 is a characteristic curve diagram illustrating the relationship between the T1 / T2 ratio and the magnetic flux density, which was obtained through the third simulation. Fig. Figure 12 shows that the horizontal axis represents the position of the measurement point and the vertical axis represents the magnetic flux density. Fig. Figure 12 shows the curve marked by reference numeral 81, which represents the magnetic flux density in the case where T1 / T2 = 0.9. The curve marked by reference numeral 82 shows the magnetic flux density in the case where T1 / T2 = 1. The curve marked by reference numeral 83 shows the magnetic flux density in the case where T1 / T2 = 2. The curve marked by reference numeral 84 shows the magnetic flux density in the case where T1 / T2 = 3. As in Fig. As shown in Figure 12, the magnetic flux density at any point on the above-mentioned imaginary straight line increases according to the increase of T1 / T2.

[0111] As described above, the preferred requirement for B2 / B1 in the present embodiment is that both the magnetic flux density corresponding to B1 and the magnetic flux density corresponding to B2 are in the range of 20 mT to 80 mT, and that B2 / B1 is 1.65 or more and not more than 4. Since T1 / T2 falls within the range used in the third simulation, it is possible, regardless of the value of T1 / T2, to arrange the first and second magnetic sensors 10 and 20 such that the above requirement is met and the first and second detection positions P1 and P2 lie on the reference plane. In particular, if T1 / T2 is 1 or more, it is possible to arrange the first magnetic sensor 10 such that the first detection position P1 coincides with the starting point. This facilitates the positioning of the first magnetic sensor 10. Therefore, T1 / T2 is preferably 1 or more.

[0112] If T1 / T2 (reference numeral 81) is 0.9, the first magnetic sensor 10 can, for example, be arranged such that the first detection position P1 coincides with a point (which is not the starting point) on the reference plane P at which the magnetic flux density reaches or exceeds 20 mT. This makes it possible to arrange the first and second magnetic sensors 10 and 20 on the reference plane P such that the above requirement is met and the first and second detection positions P1 and P2 lie on the reference plane P.

[0113] Next, a fourth simulation is described. In the fourth simulation, a fourth model of the angle sensor system 100 was used to vary d / D, i.e., the ratio of the inner diameter d (see Fig. 4) of the second section 62 to the outer diameter D (see Fig. 4) to investigate a distribution of magnetic flux densities along the aforementioned imaginary straight line of the second section 62. The fourth model is the same as the first model except that the inner diameter d of the second section 62 of the magnetic structure 6 is a variable value. In the fourth simulation, the ratio d / D was varied by incrementally increasing the inner diameter d of the second section 62 by 0.2 mm in the range from 1 to 5.2 mm, with the outer diameter D of the second section 62 being fixed at 6 mm. The other conditions of the fourth simulation were the same as those of the first simulation.

[0114] The Fig. 13 and Fig. Figure 14 are characteristic curve diagrams illustrating the relationship between the d / D ratio and the magnetic flux density, which were obtained through the fourth simulation. In the Fig. 13 and Fig. Figure 14 shows that the horizontal axis represents the position of the measurement point and the vertical axis represents the magnetic flux density. The in Fig. The 13 plotted curves show the magnetic flux densities when d / D is in the range of 0.17 to 0.50. The in Fig. The 14 plotted curves show the magnetic flux densities when d / D is in the range of 0.53 to 0.87. In the Fig. 13 and Fig. 14 only some of the curves are marked by reference symbols.

[0115] In Fig. Figure 13 shows the curve marked by reference numeral 91, which represents the magnetic flux density in the case where d / D = 0.17. The curve marked by reference numeral 92 shows the magnetic flux density in the case where d / D = 0.33. The curve marked by reference numeral 93 shows the magnetic flux density in the case where d / D = 0.50. As in Fig. Figure 13 shows that the magnetic flux density at a measurement point varies depending on d / D. For example, in the d / D range from 0.17 to 0.50, the magnetic flux density at the measurement point at the 1 mm position decreases as d / D increases.

[0116] In Fig. Figure 14 shows the curve marked by reference numeral 94, which represents the magnetic flux density in the case where d / D = 0.53. The curve marked by reference numeral 95 shows the magnetic flux density in the case where d / D = 0.70. The curve marked by reference numeral 96 shows the magnetic flux density in the case where d / D = 0.87. As in Fig. Figure 14 shows that the magnetic flux density at a measurement point varies depending on d / D. For example, the magnetic flux density decreases in the d / D range from 0.53 to 0.87 at the measurement point at the 2 mm position as d / D increases.

[0117] Now, for each value of d / D, a measurement point at which the magnetic flux density reaches a minimum value Bmin and a measurement point at which the magnetic flux density reaches a maximum value Bmax are considered. The measurement point at which the magnetic flux density reaches a minimum value Bmin is referred to below as the minimum flux density point. The measurement point at which the magnetic flux density reaches a maximum value Bmax is referred to below as the maximum flux density point. As in the Fig. 13 and Fig. As shown in 14, the minimum flux density point is not limited to the starting point.

[0118] The minimum flux density point is a potential first detection position P1. However, the first detection position P1 does not necessarily have to coincide with the minimum flux density point. If Bmin is 20 mT or more, the first detection position P1 can be selected such that the magnetic flux density corresponding to B is 120 mT or more. Thus, Bmin is preferably 20 mT or more.

[0119] On the other hand, the requirement is that B2 / B1 is 1.65 or more. In this case, if Bmin exceeds 80 / 1.65, i.e., 48.5 mT, there is no longer a measurement point that could be a potential second detection position P2, i.e., where the magnetic flux density corresponding to B2 is 80 mT or less. Therefore, Bmin is preferably 48.5 mT or less.

[0120] To set B2 / B1 to 1.65 or more, Bmax / Bmin must be 1.65 mT or less.

[0121] In view of this, a preferred requirement for the magnetic structure 6 in the present embodiment is the generation of a detection target magnetic field such that on the reference plane P Bmin is 20 mT or more and not more than 48.5 mT and Bmax / Bmin is 1.65 or more.

[0122] Fig. Figure 15 is a characteristic curve diagram illustrating a relationship between d / D and Bmin, which is derived from the values ​​in Fig. 13 and Fig. The results shown in the 14 images are as follows. Fig. Figure 15 represents the horizontal axis d / D and the vertical axis represents Bmin. Fig. 15. Dashed lines are drawn at positions where Bmin is 20 mT and where Bmin is 48.5 mT. From Fig. 15 shows that Bmin falls in the range of 20 mT to 48.5 mT when d / D is in the range of 0.23 to 0.8.

[0123] Fig. Figure 16 is a characteristic curve diagram illustrating the relationship between d / D and Bmax / Bmin, which is derived from the values ​​in Fig. 13 and Fig. The results shown in the 14 images are as follows. Fig. Figure 16 represents the horizontal axis d / D and the vertical axis represents Bmax / Bmin. Bmax / Bmin is 1.65 or more when d / D is in Fig. The area shown in section 16 is located there.

[0124] The in the Fig. 15 and Fig. The 16 results presented suggest that a preferred range of d / D is from 0.23 to 0.8.

[0125] Next, a fifth simulation is described. In the fifth simulation, a distribution of magnetic flux densities along the aforementioned imaginary straight line was investigated using a fifth model of the angle sensor system 100. Instead of the magnetic structure 6, the fifth model has a magnetic structure consisting only of the first section 61 of the magnetic structure.

[0126] The magnetic structure of the fifth model has a first end face and a second end face, which are opposite each other in a direction parallel to the axis of rotation C. The second end face faces the reference plane P. The distance between the second end face of the magnetic structure of the fifth model and the reference plane P is 0.5 mm. The magnetic structure of the fifth model is magnetized in a direction perpendicular to the axis of rotation C. The residual magnetic flux density corresponding to the magnetization of the magnetic structure of the fifth model is 0.615 T.

[0127] The definitions of the outer diameter and thickness of the magnet structure of the fifth model are the same as those of the outer diameter and thickness T1 of the first section 61. Hereinafter, the thickness of the magnet structure of the fifth model is denoted by the symbol T3. In the fifth simulation, the thickness T3 of the magnet structure of the fifth model was varied to be 1 mm, 2 mm, and 3 mm, with the outer diameter fixed at 6 mm.

[0128] Fig. Figure 17 is a characteristic curve diagram illustrating the relationship between the thickness T3 and the magnetic flux density, which was obtained through the fifth simulation. Fig. In Figure 17, the horizontal axis represents the position of the measurement point, and the vertical axis represents the magnetic flux density. Fig. Figure 17 shows the curve marked by reference numeral 111, which represents the magnetic flux density in the case where the thickness T3 is 1 mm. The curve marked by reference numeral 112 shows the magnetic flux density in the case where the thickness T3 is 2 mm. The curve marked by reference numeral 113 shows the magnetic flux density in the case where the thickness T3 is 3 mm. As in Fig. As shown in 17, the magnetic flux density at the same measuring point increases according to the increase in thickness T3.

[0129] As from Fig. As can be seen from Figure 17, it is not possible to arrange the first and second magnetic sensors 10 and 20 in such a way that the preferred requirement for B1 and B2 mentioned above is met and the first and second detection positions P1 and P2 lie on the reference plane P when the magnetic structure of the fifth model is used. However, the preferred requirement for B1 and B2 mentioned above can be met, for example, by arranging the first and second magnetic sensors 10 and 20 at different distances from the magnetic structure of the fifth model. For example, the angle sensor system can be configured such that the first magnetic sensor 10 is located further away from the magnetic structure of the fifth model than the second magnetic sensor 20 in order to meet the preferred requirement for B1 and B2 mentioned above.

[0130] However, when the magnetic structure of the fifth model is used, the first and second magnetic sensors 10 and 20 cannot be arranged on the same plane. This increases the dimensions of the angle sensor system 100 in a direction parallel to the axis of rotation C. Conversely, when the magnetic structure 6, comprising the first section 61 and the second section 62, is used, the first and second magnetic sensors 10 and 20 can be arranged on the same plane. This allows the dimensions of the angle sensor system 100 to be reduced in a direction parallel to the axis of rotation C.

[0131] Next, a sixth simulation is described. In the sixth simulation, a distribution of magnetic flux densities along the aforementioned imaginary straight line was investigated using a sixth model of the angle sensor system 100. Instead of the magnet structure 6, the sixth model has a magnet structure consisting solely of the second section 62 of the magnet structure 6.

[0132] The magnetic structure of the sixth model has a first end face and a second end face, which are opposite each other in a direction parallel to the axis of rotation C. The second end face faces the reference plane P. The distance between the second end face of the magnetic structure of the sixth model and the reference plane P is 0.5 mm. The magnetic structure of the sixth model is magnetized in a direction perpendicular to the axis of rotation C. The residual magnetic flux density corresponding to the magnetization of the magnetic structure of the sixth model is 0.615 T.

[0133] The definitions of the outer diameter, inner diameter, and thickness of the magnetic structure of the sixth model are the same as those of the outer diameter D, inner diameter d, and thickness T2 of Section 62, Part 2. Hereinafter, the thickness of the magnetic structure of the sixth model is denoted by the symbol T4. In the sixth simulation, the thickness T4 of the magnetic structure of the sixth model was varied to be 1 mm, 2 mm, 3 mm, and 4 mm, with the outer diameter set to 6 mm and the inner diameter to 2 mm.

[0134] Fig. Figure 18 is a characteristic curve diagram illustrating the relationship between the thickness T4 and the magnetic flux density, which was obtained through the sixth simulation. Fig. In Figure 18, the horizontal axis represents the position of the measurement point, and the vertical axis represents the magnetic flux density. Fig. Figure 18 shows the curve marked by reference numeral 121, which represents the magnetic flux density in the case where the thickness T4 is 1 mm. The curve marked by reference numeral 122 shows the magnetic flux density in the case where the thickness T4 is 2 mm. The curve marked by reference numeral 123 shows the magnetic flux density in the case where the thickness T4 is 3 mm. The curve marked by reference numeral 124 shows the magnetic flux density in the case where the thickness T4 is 4 mm. As in Fig. Figure 18 shows that the magnetic flux density at the same measuring point increases according to the increase in thickness T4, except at and near the starting point.

[0135] As from Fig. As can be seen in Figure 18, it is possible to arrange the first and second magnetic sensors 10 and 20 such that the above-mentioned preferred requirement for B1 and B2 is met and the first and second positions lie on the reference plane P when the magnetic structure of the sixth model is used. If the thickness T4 is 4 mm, the first magnetic sensor 10 can, for example, be arranged such that the first detection position P1 coincides with the starting point. If the thickness T4 is 1 mm, 2 mm, or 3 mm, the above-mentioned preferred requirement can, for example, be met by arranging the first magnetic sensor 10 such that the first detection position P1 coincides with a point (which is not the starting point) on the reference plane P at which the magnetic flux density falls within the range of 20 mT to 48.5 mT.

[0136] As from the Fig. 12 and Fig. As can be seen from Figure 18, a comparison between the magnetic structure 6 of the third model and the magnetic structure of the sixth model at the same thickness shows that the magnetic structure 6 of the third model provides a higher magnetic flux density at and near the starting point. Thus, it is evident that the magnetic structure 6 of the third model can have a smaller thickness than the magnetic structure of the sixth model if a comparison is made by setting the first detection positions P1 at or near the starting point and setting B1 to the same value. The dimension of the angle sensor system 100 in a direction parallel to the axis of rotation C can therefore be reduced by using the magnetic structure 6, comprising the first section 61 and the second section 62, compared to the case of using the magnetic structure of the sixth model. [Second embodiment]

[0137] A second embodiment of the present invention will now be described with reference to the Fig. 19 and Fig. 20 described. Fig. Figure 19 is a perspective exploded view of a magnetic structure of the second embodiment. Fig. Figure 20 is a cross-sectional view of the magnetic structure of the second embodiment. In the second embodiment, the magnetic field generator 5 has a magnetic structure 106 instead of the magnetic structure 6 of the first embodiment. The magnetic structure 6 is made entirely of a hard magnetic material. The magnetic structure 106 is magnetized in a direction perpendicular to the axis of rotation C and rotates about the axis of rotation C.

[0138] The magnetic structure 106 has a first end surface 106a and a second end surface 106b, which are opposite each other in a direction parallel to the axis of rotation C. The second end surface 106b faces the reference plane P. In the present embodiment, both the first end surface 106a and the second end surface 106b are perpendicular to the axis of rotation C.

[0139] The magnetic structure 106 has a first section 161 and a second section 162, which are coupled to each other. In Fig. In section 19, the first section (161) and the second section (162) are shown separately. Fig. In Figure 20, the boundary between the first section 161 and the second section 162 is represented by a dotted line. The first section 161 has the first end surface 106a. The second section 162 has the second end surface 106b. The first and second sections 161 and 162 are arranged in the same way as the first and second sections 61 and 62 of the magnetic structure 6 of the first embodiment.

[0140] As in the Fig. 19 and Fig. As shown in Figure 20, the second section 162 has a cavity 162h through which the axis of rotation C passes, whereas the first section 161 has no cavity through which the axis of rotation C passes.

[0141] In the present embodiment, the second section 162 is shaped as follows. The second section 162 has an outer circumference and an inner circumference, each of which, in any cross-section of the second section 162 perpendicular to the axis of rotation C, has a circular shape centered on the axis of rotation C. The diameter of the outer circumference of the second section 162 in the above-mentioned cross-section is hereinafter referred to as the outer diameter of the second section 162. The diameter of the inner circumference of the second section 162 in the above-mentioned cross-section is referred to as the inner diameter of the second section 162. In the present embodiment, the outer diameter D of the second section 162 is constant regardless of the distance from the second end face 106b.

[0142] The inner diameter of the second section 162 is longest at the second end face 106b and decreases with increasing distance from the second end face 106b. In particular, in the present embodiment, the cavity has the shape of a hemisphere centered at the intersection of an imaginary plane, comprising the second end face 106b, and the axis of rotation C. The radius of this hemisphere is hereinafter referred to as the radius of the cavity 162h and denoted by the symbol r. A dimension of the second section 162 in a direction parallel to the axis of rotation C is referred to as the thickness of the second section 106b.

[0143] The first section 161 has a shape similar to that of the first section 61 of the first embodiment. The diameter of the outer circumference of the first section 161 in any cross-section of the first section 161 perpendicular to the axis of rotation C is referred to as the outer diameter of the first section 161. A dimension of the first section 161 in a direction parallel to the axis of rotation C is referred to as the thickness of the first section 161.

[0144] Next, a seventh simulation is described. In the seventh simulation, a seventh model of the angle sensor system 100 according to the present embodiment was used. The design of the magnetic structure 106 of the seventh model and the positional relationships between the magnetic structure 106 and the reference plane are as follows. The first section 161 and the second section 162 have an outer diameter of 6 mm. The residual magnetic flux density corresponding to the magnetization of the magnetic structure 106 is 0.615 T. The distance between the second end face 106b of the magnetic structure 106 and the reference plane P is 0.5 mm.

[0145] In the seventh simulation, a distribution of magnetic flux densities along an imaginary straight line lying on the reference plane P and passing through the starting point was investigated for both the first and second cases, which are described below. In the first case, the thickness of the first section 161 was set to 2 mm, and both the thickness of the second section 162 and the radius r of the cavity 162h were set to 1 mm. In the second case, both the thickness of the first section 161 and the thickness of the second section 162, as well as the radius r of the cavity 162h, were set to 1.5 mm.

[0146] Fig. Figure 21 is a characteristic curve diagram illustrating the magnetic flux densities, obtained through the seventh simulation. Fig. Figure 21 shows that the horizontal axis represents the position of the measurement point and the vertical axis represents the magnetic flux density. Fig. Figure 21 shows the magnetic flux density in the first case, indicated by reference numeral 131. The curve indicated by reference numeral 132 shows the magnetic flux density in the second case.

[0147] A preferred requirement for the magnetic structure 106 is the same as that for the magnetic structure 6 of the first embodiment. As in Fig. As shown in Figure 21, the first case (reference numeral 131) does not meet the preferred requirement for the magnetic structure 106, whereas the second case (reference numeral 132) does meet the preferred requirement for the magnetic structure 106.

[0148] The preferred requirement for B1 and B2 in the present embodiment is the same as in the first embodiment. As can be seen from Fig. As can be seen in Figure 21, the second case (reference numeral 132) allows the first and second magnetic sensors 10 and 20 to be arranged such that the preferred requirement for B1 and B2 is met and the first and second detection positions P1 and P2 lie on the reference plane P. Furthermore, in the second case (reference numeral 132), it is possible to arrange the first magnetic sensor 10 such that the first detection position P1 coincides with the starting point.

[0149] In the first case (reference numeral 131), the preferred requirement for B1 and B2 can be met, for example, by arranging the first and second magnetic sensors 10 at different distances from the magnetic structure 106. For example, the angle sensor system can be configured such that the first magnetic sensor 10 is arranged at a greater distance from the magnetic structure 106 than the second magnetic sensor 20, thus meeting the preferred requirement for B1 and B2.

[0150] The design, function and effects of the present embodiment are otherwise the same as those of the first embodiment. [Third embodiment]

[0151] A third embodiment of the present invention will now be described with reference to the Fig. 22 and Fig. 23 described. Fig. Figure 22 is a perspective exploded view of a magnetic structure of the third embodiment. Fig. Figure 23 is a cross-sectional view of the magnetic structure of the third embodiment. In the third embodiment, the magnetic field generator 5 has a magnetic structure 206, which is made of a magnetic material, instead of the magnetic structure 6 of the first embodiment. The magnetic structure 206 has a magnetization in a direction perpendicular to the axis of rotation C and rotates about the axis of rotation C.

[0152] The magnetic structure 206 has a first end surface 206a and a second end surface 206b, which are opposite each other in a direction parallel to the axis of rotation C. The second end surface 206b faces the reference plane P. In the present embodiment, both the first end surface 206a and the second end surface 206b are perpendicular to the axis of rotation C.

[0153] The magnetic structure 206 has a first section 261 and a second section 262, which are coupled to each other. In Fig. In section 22, the first section 261 and the second section 262 are shown separately. Fig. Figure 23 shows the boundary between the first section 261 and the second section 262 as a dotted line. The first section 261 has the first end surface 206a. The second section 262 has the second end surface 206b. The first and second sections 261 and 262 are arranged in the same way as the first and second sections 61 and 62 of the magnet structure 6 of the first embodiment.

[0154] As in the Fig. 22 and Fig. As shown in Figure 23, the second section 262 has a cavity 262h through which the axis of rotation C passes, whereas the first section 261 has no cavity through which the axis of rotation C passes.

[0155] The second section 262 has the same shape as the second section 62 of the first embodiment. The diameter of the outer circumference of the second section 262 in any cross-section of the second section 262 perpendicular to the axis of rotation C is hereinafter referred to as the outer diameter of the second section 262. The diameter of the inner circumference of the second section 262 in the aforementioned cross-section is referred to as the inner diameter of the second section 262. A dimension of the second section 262 in a direction parallel to the axis of rotation C is referred to as the thickness of the second section 262.

[0156] The first section 261 refers to a section 261A made of soft magnetic material, and a section 261B made of hard magnetic material. An example of the soft magnetic material is Fe. The section 261B made of hard magnetic material has a receiving section 261Ba through which the axis of rotation C passes. The section 261A made of soft magnetic material is received within the receiving section 261Ba.

[0157] In the present embodiment, the section 261B made of hard magnetic material is shaped as follows. The section 261B made of hard magnetic material has an outer circumference and an inner circumference, each of which, in any cross-section of the section 261B made of hard magnetic material perpendicular to the axis of rotation C, has a circular shape centered on the axis of rotation C. The diameter of the outer circumference of the section 261B made of hard magnetic material in the above-mentioned cross-section is hereinafter referred to as the outer diameter of the section 261B made of hard magnetic material. The diameter of the inner circumference of the section 261B made of hard magnetic material in the above-mentioned cross-section is referred to as the inner diameter of the section 261B made of hard magnetic material.In the present embodiment, both the outer diameter and the inner diameter of the section 261B made of hard magnetic material are constant, independent of the distance from the second end face 206b. A dimension of the section 261B made of hard magnetic material in a direction parallel to the axis of rotation C is referred to as the thickness of the section 261B made of hard magnetic material.

[0158] In the present embodiment, the section 261A made of soft magnetic material has a cylindrical shape whose central axis lies on the axis of rotation C. The diameter of an outer circumference of the section 261A made of soft magnetic material in any cross-section of the section 261A made of soft magnetic material perpendicular to the axis of rotation C is hereinafter referred to as the outer diameter of the section 261A made of soft magnetic material. In the present embodiment, the outer diameter of the section 261A made of soft magnetic material is constant regardless of the distance from the first end face 206a and is equal to the inner diameter of the section 261B made of hard magnetic material. A dimension of the section 261A made of soft magnetic material in a direction parallel to the axis of rotation C is referred to as the thickness of the section 261A made of soft magnetic material.

[0159] Section 261A, made of soft magnetic material, can be part of a shaft that rotates around the axis of rotation C. In such a case, a magnetic structure formed from section 261B, made of hard magnetic material, and the second section 262 can be formed using a hard magnetic material, and the part of the shaft can be inserted into the receiving section 261Ba to construct a magnetic structure 206 integrated into the shaft.

[0160] Next, an eighth simulation is described. In the eighth simulation, an eighth model of the angle sensor system 100 according to the present embodiment was used. The configuration of the magnetic structure 206 of the eighth model and the positional relationships between the magnetic structure 206 and the reference plane P are as follows. Section 261B made of hard magnetic material and the second section 262 have an outer diameter of 6 mm. The inner diameter of section 261B made of hard magnetic material, the outer diameter of section 261A made of soft magnetic material, and the inner diameter of the second section 262 are 2 mm. The second section 262 has a thickness of 1 mm. The residual magnetic flux density corresponding to the magnetization of the magnetic structure 206 is 0.615 T. The distance between the second end face 206b of the magnetic structure 206 and the reference plane P is 0.5 mm.

[0161] In the eighth simulation, the distribution of magnetic flux densities along an imaginary straight line lying on the reference plane P and passing through the starting point was investigated for the third, fourth, and fifth cases, which are described below. In the third case, the thickness of both section 261B (made of hard magnetic material) and section 261A (made of soft magnetic material) was set to 1 mm. In the fourth case, both the thickness of section 261B (made of hard magnetic material) and section 261A (made of soft magnetic material) were set to 2 mm. In the fifth case, both the thickness of section 261B (made of hard magnetic material) and section 261A (made of soft magnetic material) were set to 3 mm.

[0162] Fig. Figure 24 is a characteristic curve diagram illustrating the magnetic flux densities, obtained through the eighth simulation. Fig. Figure 24 shows that the horizontal axis represents the position of the measurement point and the vertical axis represents the magnetic flux density. Fig. Figure 24 shows the magnetic flux density in the third case, indicated by reference numeral 141. The curve indicated by reference numeral 142 shows the magnetic flux density in the fourth case. The curve indicated by reference numeral 143 shows the magnetic flux density in the fifth case.

[0163] A preferred requirement for the magnetic structure 206 is the same as that for the magnetic structure 6 of the first embodiment. As in Fig. As shown in Figure 24, the third case (reference numeral 14) does not meet the preferred requirement for the magnetic structure 206, whereas the fourth case (reference numeral 142) and the fifth case (reference numeral 143) meet the preferred requirement for the magnetic structure 206.

[0164] The preferred requirement for B1 and B2 in the present embodiment is the same as in the first embodiment. As can be seen from Fig.As can be seen from reference 24, all of the third to fifth cases (reference numeral 132) allow the first and second magnetic sensors 10 and 20 to be arranged such that the preferred requirement for B1 and B2 is met and the first and second detection positions P1 and P2 lie on the reference plane P. In particular, in the fourth case (reference numeral 142) and the fifth case (reference numeral 143), it is possible to arrange the first magnetic sensor 10 such that the first detection position P1 coincides with the starting point. In the third case (reference numeral 141), the preferred requirement for B1 and B2 can be met, for example, by arranging the first magnetic sensor 10 such that the first detection position P1 coincides with a point (which is not the starting point) on the reference plane P at which the magnetic flux density falls within the range of 20 mT to 48.5 mT.

[0165] The design, function and effects of the present embodiment are otherwise the same as those of the first embodiment.

[0166] The present invention is not limited to the preceding embodiments and various modifications can be made to it. For example, possible configurations of the magnetic structure are not limited to the examples illustrated in the preceding embodiments. The magnetic structure is preferably designed such that the preferred requirement for the magnetic structure 6 described in relation to the first embodiment is met. However, even if the magnetic structure does not meet the preferred requirement, the angle sensor system can sometimes be configured to meet the preferred requirement for B1 and B2 as described in relation to the preceding embodiments.

[0167] Specific operations in the arithmetic processing for generating the angle measurement value θs are not limited to those described in relation to the first embodiment. Assuming, for example, that the first measurement value S1 corresponds to the thickness of a component in the X-direction of the first applied field component MF1c, the second measurement value S2 corresponds to the thickness of a component in the Y-direction of the first applied field component MF1c, the third measurement value S3 corresponds to the thickness of a component in the X-direction of the second applied field component MF2c, and the measurement value S4 corresponds to the thickness of a component in the Y-direction of the second applied field component MF2c, the angle measurement value θs can be generated by performing the following operations. First, S3-S1 is determined as Sa, and S4-S2 is determined as Sb. Then, atan(Sb / Sa) is determined as θs.

[0168] Naturally, numerous modifications and variations are possible with regard to the aforementioned provisions. It is therefore understood that the invention, within the scope of the attached claims and equivalents thereof, can be implemented in other embodiments which are not the foregoing most preferred embodiments.

Claims

Angle sensor system (100), comprising: a magnetic field generator (5) for generating a target magnetic field, wherein the target magnetic field is a magnetic field to be detected and is referenced to an angle to be detected; and an angle sensor (1) for detecting the target magnetic field and for generating an angle detection value corresponding to the angle to be detected, characterized in that the angle sensor (1) comprises: a first magnetic sensor (10) for detecting a first applied magnetic field, comprising the target magnetic field, at a first detection position and for generating first detection information corresponding to the angle to be detected; a second magnetic sensor (20) for detecting a second applied magnetic field, comprising the target magnetic field, at a second detection position and for generating second detection information.which correspond to the angle to be detected; and a processor (30) for generating the angle detection value by performing arithmetic processing using the first detection information and the second detection information; the direction of the detection target magnetic field changes at both the first and second detection positions according to the angle to be detected; the detection target magnetic field has a first strength at the first detection position and a second strength at the second detection position, wherein the ratio of the second strength to the first strength is 1.65 or more; the magnetic field generator (5) has a magnetic structure (206) formed from a magnetic material, wherein the magnetic structure (206) has a magnetization in a direction perpendicular to an axis of rotation and, when the magnetic structure (206) is rotated about the axis of rotation, rotates itself about the axis of rotation;the first detection position and the second detection position are located on the same side of the magnetic structure (206) in a direction parallel to the axis of rotation and are spaced at different distances from the axis of rotation; the magnetic structure (206) has a first section (261) and a second section (262) which are coupled to each other, wherein the second section (262) is located between the first section (261) and the first and second detection positions in a direction parallel to the axis of rotation; the second section (262) has a cavity (262h) through which the axis of rotation passes, whereas the first section (261) has no cavity through which the axis of rotation passes; the first section (261) has a section (261A) made of soft magnetic material and a section (261B) made of hard magnetic material.which is formed from a hard magnetic material, the section (261B) made of hard magnetic material has a receiving section (261Ba) through which the axis of rotation passes, and the section (261A) made of soft magnetic material is received in the receiving section (261Ba). Angle sensor system (100), comprising: a magnetic field generator (5) for generating a target magnetic field, wherein the target magnetic field is a magnetic field to be detected and is referenced to an angle to be detected; and an angle sensor (1) for detecting the target magnetic field and for generating an angle detection value corresponding to the angle to be detected, characterized in that the angle sensor (1) comprises: a first magnetic sensor (10) for detecting a first applied magnetic field, comprising the target magnetic field, at a first detection position and for generating first detection information corresponding to the angle to be detected; a second magnetic sensor (20) for detecting a second applied magnetic field, comprising the target magnetic field, at a second detection position and for generating second detection information corresponding to the angle to be detected;and a processor (30) for generating the angle detection value by performing arithmetic processing using the first detection information and the second detection information; the direction of the detection target magnetic field changes at both the first and second detection positions according to the angle to be detected; the detection target magnetic field has a first strength at the first detection position and a second strength at the second detection position, wherein the ratio of the second strength to the first strength is 1.65 or more; the magnetic field generator (5) has a magnetic structure (6; 106; 206) formed from a magnetic material, wherein the magnetic structure (6; 106; 206) has a magnetization in a direction perpendicular to a rotation axis and upon rotation of the magnetic structure (6; 106;206) about the axis of rotation rotates itself about the axis of rotation, the first detection position and the second detection position are located on the same side of the magnetic structure (6; 106; 206) in a direction parallel to the axis of rotation and are spaced at different distances from the axis of rotation, the magnetic structure (6; 106; 206) has a first section (61; 161; 261) and a second section (62; 162; 262) which are coupled to each other, the second section (62; 162; 262) being located between the first section (61; 161; 261) and the first and second detection positions in the direction parallel to the axis of rotation, the second section (62; 162; 262) has a cavity (62h, 162h; 262h) through which the axis of rotation passes, whereas the first section (61; 161;261) has no cavity through which the axis of rotation passes; when viewed in a direction parallel to the axis of rotation, both the first detection position (P1) and the second detection position (P2) are placed to overlap the cavity (62h; 162h; 262h) of the second section (62; 162; 262). Angle sensor system (100) according to claim 2, wherein the magnetic structure (6; 106) is formed in its entirety from a hard magnetic material. Angle sensor system (100) according to claim 2, wherein the first section (261) has a section (261A) made of soft magnetic material, which is formed from a soft magnetic material, and a section (261B) made of hard magnetic material, which is formed from a hard magnetic material, the section (261B) made of hard magnetic material having a receiving section (261Ba) through which the axis of rotation passes, and the section (261A) made of soft magnetic material is received in the receiving section (261Ba). Angle sensor system (100) according to one of claims 1 to 4, wherein the ratio of the second strength to the first strength is 4 or less. Angle sensor system (100) according to one of claims 1 to 5, wherein a rotating field angle corresponds to the angle to be detected, wherein the rotating field angle is an angle formed by the direction of the detection target magnetic field at a reference position with respect to a reference direction on a reference plane, and the angle detection value corresponds to the rotating field angle. Angle sensor system (100) according to claim 6, wherein the first angle detection information corresponds to an angle which forms a direction of a first applied field component with respect to the reference direction, wherein the first applied field component is a component of the first applied magnetic field which is parallel to the reference plane, and the second detection information corresponds to an angle which forms a direction of a second applied field component with respect to the reference direction, wherein the second applied field component is a component of the second applied magnetic field which is parallel to the reference plane. Angle sensor system (100) according to claim 7, wherein the first detection information comprises a first detection value corresponding to a cosine of the angle forming the direction of the first applied field component with respect to the reference direction, and a second detection value corresponding to a sine of the angle forming the direction of the first applied field component with respect to the reference direction, and the second detection information comprises a third detection value corresponding to a cosine of the angle forming the direction of the second applied field component with respect to the reference direction, and a fourth detection value corresponding to a sine of the angle forming the direction of the second applied field component with respect to the reference direction. Angle sensor system (100) according to one of claims 6 to 8, wherein the first detection position and the second detection position are in the reference plane. Angle sensor system (100) according to one of claims 1 to 9, wherein the first section (61; 161; 261) is shaped as a circular plate, and the second section (62; 162; 262) has an outer circumference and an inner circumference, each of which has a circular shape in any cross-section of the second section (62; 162; 262) perpendicular to the axis of rotation. Angle sensor system (100) according to claim 1, wherein, when viewed in the direction parallel to the axis of rotation, the first detection position is placed to overlap the cavity (262h) of the second section (262), and the second detection position is placed to overlap the second section (262) but not the cavity (262h).

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