Rotation sensor

Abstract

Provided is a rotation sensor with which it is possible to improve detection accuracy of a rotation angle. A rotation sensor (1) comprises a rotor (2), a stator (3), and a soft magnetic element (23). The rotor (2) is attached to a rotation object (rotary shaft (4)) and rotates integrally with the rotation object. The rotor (2) has a plurality of electrically conductive parts (22). The electrically conductive parts (22) are disposed along the rotational direction of the rotor (2). The stator (3) has a substrate, an excitation coil, and a detection coil. The substrate faces the rotor (2). The excitation coil is disposed annularly on the substrate so as to lie along the outer edge of the rotor (2) in a plan view along one direction, and generates a magnetic field. The detection coil is disposed at the inner side of the excitation coil on the substrate, and detects a change in the magnetic field. The soft magnetic element (23) has portions that are positioned between the electrically conductive parts (22) in a plan view along said one direction.

Description

Rotational sensor

[0001] This disclosure generally relates to rotational sensors. More particularly, this disclosure relates to rotational sensors that detect the rotational angle of a rotating object.

[0002] Patent Document 1 describes a rotational sensor that detects the rotational angle of a rotating object. The rotational sensor described in Patent Document 1 includes a rotor and a stator. The rotor has conductivity and is attached to the rotating object and rotates integrally with the rotating object. The stator faces the rotor in one direction. The rotor has a plurality of conductive portions and a portion with a different thickness. The plurality of conductive portions are arranged side by side along the rotation direction of the rotor. The portion with a different thickness has a thickness in one direction that is relatively different from other parts of the rotor. In the rotor, a plurality of gaps are provided so that the plurality of conductive portions are separated from each other. The stator has a substrate, an excitation coil, a detection coil, and a detection electrode portion. The substrate has a facing surface that faces the rotor. The excitation coil is annularly arranged on the facing surface of the substrate so as to follow the outer edge of the rotor in a plan view from one direction and generates a magnetic field. The detection coil is arranged inside the excitation coil on the facing surface of the substrate and detects changes in the magnetic field. The detection electrode portion is arranged on the facing surface of the substrate so as to overlap a part of the rotation locus of the portion with a different thickness when the rotor rotates in a plan view from one direction, and detects the capacitance generated between the rotor and the stator.

[0003] International Publication No. 2023 / 149063

[0004] The rotational sensor with the above configuration is also called an inductive sensor. Inductive sensors are generally said to have higher detection accuracy of the rotational angle than rotational sensors using magnetoresistive elements and Hall elements, but there is a requirement to further improve the detection accuracy of the rotational angle of the rotor.

[0005] An object of the present disclosure is to provide a rotational sensor capable of improving the detection accuracy of the rotational angle of the rotor.

[0006] A rotation sensor according to one aspect of the present disclosure detects the rotation angle of an object to be rotated. The rotation sensor comprises a rotor, a stator, and a soft magnetic material. The rotor is attached to the object to be rotated and rotates integrally with the object. The stator faces the rotor in one direction. The rotor has a plurality of conductive parts arranged along the direction of rotation of the rotor. The stator has a substrate, an excitation coil, and a detection coil. The substrate faces the rotor. The excitation coil is arranged in a ring on the substrate along the outer edge of the rotor in a plan view from one direction and generates a magnetic field. The detection coil is located inside the excitation coil on the substrate and detects changes in the magnetic field. The detection coil includes a proximity portion close to the excitation coil and a distance portion further from the excitation coil than the proximity portion. The soft magnetic material has portions located between the plurality of conductive parts in a plan view from one direction.

[0007] The rotation sensor of this disclosure makes it possible to improve the accuracy of detecting the rotation angle of the rotor.

[0008] Figure 1 is a perspective view showing the external appearance of a rotation sensor according to Embodiment 1. Figure 2 is a front view of the main part of the rotation sensor according to Embodiment 1. Figure 3 is a perspective view showing the rotor of the rotation sensor according to Embodiment 1. Figure 4 is a plan view showing the rotor of the rotation sensor according to Embodiment 1. Figure 5 is a plan view of the substrate used in the rotation sensor according to Embodiment 1. Figure 6 is a plan view showing the excitation coil and detection coil arranged on opposite sides of the same substrate. Figure 7 is a plan view showing the excitation coil and detection coil arranged on the opposite side of the same substrate. Figure 8 is a schematic plan view showing the same excitation coil and detection coil. Figure 9 is a first explanatory diagram of the induced current flowing through the detection coil. Figure 10 is a second explanatory diagram of the induced current flowing through the detection coil. Figure 11 is a graph showing the change in output voltage with respect to the thickness of the soft magnetic material. Figure 12 is a graph showing the change in output voltage with respect to the coverage rate of the detection coil covered by the soft magnetic material. Figure 13 is a front view of the rotor of the rotation sensor according to Embodiment 2. Figure 14 is a perspective view of the rotor of the rotation sensor according to Embodiment 2. Figure 15 is a perspective view of the rotor of a rotary sensor according to Modification 1. Figure 16 is a perspective view of the rotor of a rotary sensor according to Modification 2. Figure 17 is a front view of the main part of a rotary sensor according to Modification 3. Figure 18 is a plan view of the excitation coil and detection coil of a rotary sensor according to Modification 4.

[0009] The rotation sensor according to the embodiment will be described in detail below with reference to the drawings. However, the figures described in the following embodiments are schematic diagrams, and the dimensional ratios of the size of each component do not necessarily reflect the actual dimensional ratios. Furthermore, the configuration described in the following embodiments is merely one example of the disclosure. The disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the disclosure can be achieved.

[0010] (Embodiment 1) Hereinafter, the rotation sensor 1 according to Embodiment 1 will be described with reference to the drawings.

[0011] (1) Overview Figure 1 is a perspective view showing the external appearance of the rotation sensor 1 according to Embodiment 1. The rotation sensor 1 according to Embodiment 1 is a sensor for detecting the rotation angle of a rotation shaft 4, as shown in Figure 1. The rotation shaft 4 is the "object to be rotated" as referred to in this disclosure. The rotation shaft 4 is, for example, the rotation shaft of an electric motor mounted on an electric vehicle (including two-wheeled vehicles), a hybrid vehicle (including two-wheeled vehicles), or industrial equipment (for example, a robot arm). The rotation sensor 1 is, for example, an inductive sensor. That is, the rotation sensor 1 can detect the rotation angle of the rotor 2 relative to the stator 3, which will be described later, by detecting the change in the magnetic field due to eddy currents accompanying the rotation of the rotor 2, which will be described later.

[0012] Conventionally, sensors used to detect the rotation angle of a rotating shaft 4 include magnetoresistive sensors (MR sensors) and Hall element sensors. However, while these sensors can detect the rotation angle of a rotating shaft 4 at a rotation speed of several thousand rpm, they may not be able to detect the rotation speed of a rotating shaft 4 at a rotation speed exceeding 10,000 rpm. On the other hand, an inductive sensor like the rotation sensor 1 can detect the rotation speed of a rotating shaft 4 even at a rotation speed exceeding 10,000 rpm.

[0013] The rotation sensor 1 according to Embodiment 1 employs the following configuration in order to accurately detect the rotation angle of the rotor 2 relative to the stator 3.

[0014] In other words, as shown in Figure 1, the rotation sensor 1 comprises a rotor 2, a stator 3, and a soft magnetic material 23. The rotor 2 is attached to the rotation shaft 4 and rotates integrally with the rotation shaft 4. Figure 2 is a front view of the main part of the rotation sensor 1 according to Embodiment 1. As shown in Figure 2, the stator 3 faces the rotor 2 in one direction D1. That is, one direction D1 is the direction in which the rotor 2 and the stator 3 face each other, for example, the up and down direction.

[0015] The rotor 2 has a plurality of conductive parts 22 (four in this embodiment). The plurality of conductive parts 22 are arranged along the rotation direction D2 of the rotor (see Figure 4, etc., described later). The soft magnetic material 23 has a portion located between the plurality of conductive parts 22 when viewed from one direction D1 in a plan view.

[0016] The stator 3 includes a substrate 31, an excitation coil 32 for generating a magnetic field, and a detection coil 33 for detecting changes in the magnetic field (see Figure 5, etc., described later). The substrate 31 faces the rotor 2 (see Figure 2). The excitation coil 32 is arranged in an annular shape on the substrate 31 so as to follow the outer edge 20 of the rotor 2 in a plan view from one direction D1 (see Figure 5, etc.). The detection coil 33 is arranged inside the excitation coil 32 on the substrate 31. The detection coil 33 includes a proximity portion 336 that is close to the excitation coil 32 and a distance portion 337 that is further from the excitation coil 32 than the proximity portion 336 (see Figure 8, etc., described later).

[0017] In the rotation sensor 1 with the above configuration, the following effects occur during use. First, when the excitation coil 32 is energized, a magnetic field is generated by the excitation coil 32 near the detection coil 33. When a magnetic field is generated near the detection coil 33, an induced voltage is generated in the detection coil 33 due to electromagnetic induction, and an induced current flows. The proximity portion 336 of the detection coil 33, which is closer to the excitation coil 32, receives a larger magnetic flux from the excitation coil 32 than the distance portion 337, so the induced voltage is larger. In contrast, the distance portion 337 of the detection coil 33, which is further from the excitation coil 32 than the proximity portion 336, receives a smaller magnetic flux from the excitation coil 32 than the proximity portion 336, so the induced voltage is smaller. As shown in Figure 9, which will be described later, if there is no conductive portion 22 on the rotor 2, the induced currents flowing through the proximity portion 336 and the distance portion 337 of the detection coil 33 are balanced, and no potential difference (hereinafter also referred to as the output voltage of the detection coil 33) occurs in the detection coil 33.

[0018] On the other hand, as shown in Figure 10, which will be described later, if a conductive part 22 is present on the rotor 2, eddy currents are generated in the conductive part 22 due to the magnetic field generated from the excitation coil 32. The magnetic field generated by the eddy currents is generated in a direction that cancels out the magnetic field generated from the excitation coil 32. Therefore, in the part of the detection coil 33 that overlaps with the conductive part 22, the magnetic flux from the excitation coil 32 becomes smaller, and the induced voltage decreases. As a result, the induced currents flowing through the nearby part 336 and the far part 337 of the detection coil 33 become unbalanced, and an output voltage of the detection coil 33 is generated (see Figure 10). By detecting the output voltage of the detection coil 33, the rotation angle of the rotor 2 can be detected.

[0019] If the output voltage of the detection coil 33 is low, the detection accuracy of the rotation angle of the rotor 2 will be low. In the rotation sensor 1 of Embodiment 1, since the soft magnetic material 23 is located between a plurality of conductive parts 22, it is possible to increase the magnetic flux from the excitation coil 32 in the portion of the detection coil 33 that does not overlap with the conductive parts 22. This makes it possible to increase the output voltage of the detection coil 33. Therefore, the rotation sensor 1 of this embodiment can improve the detection accuracy of the rotation angle.

[0020] In Figures 1 and 2 and subsequent drawings, an XYZ Cartesian coordinate system is appropriately established, with the Z-axis being the direction parallel to the rotation axis 4, the X-axis being the direction from the rotation axis 4 toward the circuit block, and the Y-axis being the direction perpendicular to the X and Z axes. Here, referring to Figure 2, the direction from the rotation axis 4 toward the circuit block 35 is defined as the positive direction of the X-axis, and the direction from the stator 3 toward the rotor 2 is defined as the positive direction of the Z-axis.

[0021] (2) Details Below, the details of the rotation sensor 1 according to Embodiment 1 will be described in detail with reference to Figures 1 to 12.

[0022] Figure 3 is a perspective view showing the rotor 2 of the rotation sensor 1 according to Embodiment 1. Figure 4 is a plan view showing the rotor 2 of the rotation sensor 1 according to Embodiment 1. Figure 5 is a plan view of the substrate 31 used in the rotation sensor 1 according to Embodiment 1. Figure 6 is a plan view showing the excitation coil 32 and detection coil 33 arranged on the opposing surface 301 of the substrate 31. Figure 7 is a plan view showing the excitation coil 32 and detection coil 33 arranged on the opposite surface 304 of the substrate 31. In Figure 5, dot hatching is applied to the rotor 2 to make it easier to distinguish between the rotor 2 and the stator 3. In other words, the dot hatching in Figure 5 does not show a cross-section of the rotor 2. Also, in Figure 5, the excitation coil 32 and detection coil 33 are shown by solid lines on the opposing surface 301 of the substrate 31, but as will be described later, the excitation coil 32 and detection coil 33 are arranged on the opposing surface 301 and the opposite surface 304 of the substrate 31, respectively. In other words, the excitation coil 32 shown in Figure 5 is a composite of the first excitation coil pattern portion 32A on the opposing surface 301 of the substrate 31 (see Figure 6) and the second excitation coil pattern portion 32B on the opposite surface 304 (see Figure 7). Similarly, the detection coil 33 shown in Figure 5 is a composite of the first detection coil pattern portion 33A on the opposing surface 301 of the substrate 31 (see Figure 6) and the second detection coil pattern portion 33B on the opposite surface 304 (see Figure 7). In the detection coil 33 shown in Figure 5, the parts that appear to intersect are located on different layers, and the intersecting parts are not electrically connected.

[0023] As described above, the rotation sensor 1 according to this embodiment is a sensor for detecting the rotation angle of a rotating shaft 4. As described above, the rotating shaft 4 is, for example, the rotating shaft of an electric motor. As shown in Figure 1 and the like, the rotation sensor 1 comprises a rotor 2 (target), a stator 3, and a soft magnetic body 23.

[0024] (2-1) Rotor The rotor 2 is made of a conductor (a material having electrical conductivity), such as a steel plate, and is attached to the rotating shaft 4 and rotates together with the rotating shaft 4.

[0025] As shown in Figures 3 and 4, the rotor 2 comprises a rotor body 21, a plurality of conductive parts 22 (four in the illustrated example), and a soft magnetic material 23.

[0026] As shown in Figure 4, the rotor body 21 is annular in plan view from one direction D1. One direction D1 is the direction in which the rotor 2 and the stator 3 face each other (see Figure 2). In other words, one direction D1 is the direction along the rotation axis 4. The rotor body 21 has a through hole 211. The through hole 211 penetrates the rotor body 21 in the thickness direction of the rotor body 21 (the direction perpendicular to the plane of the paper in Figure 4). The rotation axis 4 is inserted through the through hole 211 of the rotor body 21, and the rotation axis 4 is fitted into the through hole 211 of the rotor body 21, thereby attaching the rotation axis 4 to the center of the rotor body 21. The rotation axis 4 is circular in plan view from one direction D1.

[0027] Multiple conductive parts 22 are arranged at equal intervals along the outer edge of the rotor body 21 (see Figure 4). That is, the multiple conductive parts 22 are arranged along the rotation direction D2 of the rotor 2. Each conductive part 22 protrudes outward from the outer edge of the rotor body 21. In this embodiment, the rotor 2 has four conductive parts 22, and two adjacent conductive parts 22 are offset by 90 degrees from each other in the rotation direction D2 of the rotor 2. In other words, the multiple conductive parts 22 extend radially from the rotation center RC1 of the rotor 2. That is, the four conductive parts 22 extend radially from the rotation center RC1 of the rotor 2 and are provided at equal intervals in the circumferential direction of the rotor body 21.

[0028] Each of the multiple conductive parts 22 is fan-shaped when viewed from a planar direction D1. The material of the conductive parts 22 is a non-magnetic conductor such as stainless steel. On the central side of the rotor 2, multiple gaps 24 are provided so that the multiple conductive parts 22 are separated from each other. That is, on the central side of the rotor 2, the multiple conductive parts 22 and the multiple gaps 24 are arranged alternately along the rotation direction D2 of the rotor 2. In this embodiment, the rotor body 21 and the multiple conductive parts 22 are integrated, but they may be separate as long as they are electrically connected.

[0029] The rotation center RC1 of the rotor 2 is the center of rotation of the rotor 2, and as shown in Figure 4, it is the center of the through hole 211. The radial direction centered on the rotation center RC1 of the rotor 2 is called the "radial direction D3". The rotor body 21 is positioned inside the detection coil 33, that is, closer to the rotation center RC1, and the conductive part 22 is positioned opposite the detection coil 33 (see Figure 5).

[0030] In Figures 4 and 5, "P1" is the reference position (origin position) of the rotor 2 relative to the stator 3, where the rotation angle (mechanical angle) of the rotor 2 relative to the stator 3 is 0 degrees or 360 degrees. Also in Figures 4 and 5, "P2" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 90 degrees. Also in Figures 4 and 5, "P3" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 180 degrees. Also in Figures 4 and 5, "P4" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 270 degrees.

[0031] (2-2) The soft magnetic rotating sensor 1 is equipped with a soft magnetic material 23. More specifically, on the outside of the rotor 2, a plurality of soft magnetic materials 23 are provided such that a plurality of conductive parts 22 are spaced apart from each other (see Figures 3 and 4, etc.). That is, on the outside of the rotor 2, a plurality of conductive parts 22 and a plurality of soft magnetic materials 23 are arranged alternately along the rotation direction D2 of the rotor 2. The plurality of soft magnetic materials 23 are arranged at equal intervals along the outer edges 221 of the plurality of conductive parts 22 (see Figure 4).

[0032] The soft magnetic material 23 includes multiple (four in the figure) components. More specifically, as shown in Figure 3, the soft magnetic material 23 includes a first component 231, a second component 232, a third component 233, and a fourth component 234. Hereinafter, the first component 231, the second component 232, the third component 233, and the fourth component 234 of the soft magnetic material 23 may be collectively referred to simply as "multiple soft magnetic materials 23." Also, any one of the first component 231, the second component 232, the third component 233, and the fourth component 234 of the soft magnetic material 23 may be referred to simply as "soft magnetic material 23." Each of the multiple soft magnetic materials 23 is positioned between two adjacent conductive parts 22 of the multiple conductive parts 22 in the rotational direction of the rotor 2.

[0033] Here, a soft magnetic material is a material that is easily magnetized by an external magnetic field, but quickly returns to a state of no magnetization or low magnetization when the external magnetic field is removed; in other words, a material with low coercivity. In this embodiment, the soft magnetic material 23 has an electrical conductivity of 1 × 10⁻⁶ ４ Materials with a density of (1 / Ωm) or less are used. The material of the soft magnetic material 23 is, for example, Ni-Zn ferrite, Mn-Zn ferrite, or powdered magnetic core.

[0034] Each of the multiple soft magnetic materials 23 is fan-shaped when viewed from a plane in one direction D1. In other words, the shape of the soft magnetic material 23 located between two adjacent conductive parts 22 is fan-shaped when viewed from a plane in one direction D1. Both sides of the soft magnetic material 23 located between two adjacent conductive parts 22 in the rotation direction D2 of the rotor 2 are joined to the two opposing sides of the rotor 2 of the two adjacent conductive parts 22 in the rotation direction D2 of the rotor 2. In other words, the soft magnetic material 23 is integrally constructed with the rotor 2 (multiple conductive parts 22).

[0035] When the thickness of the soft magnetic material 23 is denoted as dth, the thickness of the soft magnetic material 23 is set as shown in equation (1).

[0036]

[0037] ds is the skin depth. The skin depth ds of a soft magnetic material is expressed by the following formula.

[0038]

[0039] π: pi, f: frequency of alternating current (Hz), μ: permeability of soft magnetic material (H / m), σ: conductivity of soft magnetic material (S / m).

[0040] Thus, the thickness dth of the soft magnetic material 23 is set to a value of four times or less the skin depth ds. In other words, the upper limit of the thickness dth of the soft magnetic material 23 is four times the skin depth ds.

[0041] The lower limit value of the thickness dth of the soft magnetic material 23 will be described. FIG. 11 is a graph showing the change in the output voltage with respect to the thickness of the soft magnetic material 23. The graph in FIG. 11 is the result of simulating the increase rate of the output voltage of the detection coil 33 with respect to the thickness dth of the soft magnetic material 23. The horizontal axis of the graph indicates the thickness dth of the soft magnetic material 23 with respect to the skin depth ds. The vertical axis of the graph indicates the increase rate of the output voltage of the detection coil 33 when the rotor 2 has the soft magnetic material 23 with respect to the case where the rotor 2 does not have the soft magnetic material 23. As simulation conditions, the relative permeability was set to 1000 and the conductivity was set to 1×10 ５ (1 / Ωm). From the simulation results, the preferred range of the thickness dth of the soft magnetic material 23 is as follows. The thickness dth of the soft magnetic material 23 with respect to the skin depth ds of the soft magnetic material 23 is preferably in the range from 0.2 times to 4 times. Also, the thickness dth of the soft magnetic material 23 with respect to the skin depth ds of the soft magnetic material 23 is more preferably in the range from 0.5 times to 2 times.

[0042] (2 - 3) Stator The stator 3 faces the rotor 2 attached to the rotating shaft 4 in one direction D1. As shown in FIG. 5, the stator 3 has a substrate 31, an excitation coil 32, and a detection coil 33.

[0043] The substrate 31 is, for example, a printed wiring board made of glass epoxy resin. The substrate 31 has opposing surfaces 301 and 304 that are located on opposite sides of each other in one direction D1 (see FIG. 2). The opposing surface 301 of the substrate 31 faces the rotor 2 in one direction D1. The opposing surface 301 of the substrate 31 corresponds to the "first surface of the substrate" in the present disclosure, and the opposing surface 304 of the substrate 31 corresponds to the "second surface of the substrate" in the present disclosure.

[0044] As shown in FIG. 5, the substrate 31 includes a first substrate portion 31A and a second substrate portion 31B.

[0045] The first substrate portion 31A is circular in plan view from one direction D1 and is the portion where the excitation coil 32 and the detection coil 33 are formed. A part of the excitation coil 32 and the detection coil 33 is arranged on the opposing surface 301 of the first substrate portion 31A, and the remaining part of the excitation coil 32 and the detection coil 33 described later is arranged on the opposing surface 304.

[0046] The second substrate portion 31B is rectangular in shape when viewed from a plan view from one direction D1, and a circuit block 35 is mounted on the opposing surface 301. The circuit block 35 is a group of electronic circuits for detecting the rotation angle of the rotor 2 relative to the stator 3, and may include one or more electronic components. One or more electronic components may constitute an electronic circuit such as an oscillator, amplifier, AD converter, or microcontroller. The first substrate portion 31A and the second substrate portion 31B are integrated. As shown in Figure 5, the substrate 31 has a through hole 319 that penetrates in the thickness direction of the substrate 31. The through hole 319 is a hole for inserting the rotating shaft 4, and the opening diameter of the through hole 319 is larger than the diameter of the rotating shaft 4. The substrate 31 is positioned such that the center of the through hole 319 of the substrate 31 coincides with the rotation center RC1 of the rotor 2. In this embodiment, the stator 3 further has a housing portion 300 for housing the substrate 31 (see Figure 1).

[0047] (2-3-1) Excitation Coil The excitation coil 32 generates an alternating current that intersects with the detection coil 33 along one direction D1 when an alternating current output from the circuit block 35 (more specifically, the oscillator, etc.) flows through it. In Figure 5, the one direction D1 is parallel to the Z-axis. The frequency of the alternating current output from the oscillator is, for example, 1 MHz to 10 MHz. More specifically, the excitation coil 32 includes a first excitation coil pattern section 32A and a second excitation coil pattern section 32B. The first excitation coil pattern section 32A is located on the opposite surface 301 of the first substrate section 31A (see Figure 6). The second excitation coil pattern section 32B is located on the opposite surface 304 of the first substrate section 31A (see Figure 7). In other words, the excitation coil 32 is located on the opposite surface 301 and the opposite surface 304 of the substrate 31, respectively. The excitation coil 32 shown in Figure 5 is formed by interlayer connection between the first excitation coil pattern portion 32A on the opposing surface 301 of the first substrate portion 31A and the second excitation coil pattern portion 32B on the opposite surface 304 of the first substrate portion 31A.

[0048] (2-3-2) Detection Coil The detection coil 33 detects changes in the alternating magnetic field generated by the excitation coil 32 and outputs it to the circuit block 35 (more specifically, the amplifier) ​​(see Figure 5). The detection coil 33 includes a first detection coil 331 and a second detection coil 332. The first detection coil 331 and the second detection coil 332 have sinusoidal patterns that extend in the rotation direction D2 of the rotor 2, and are arranged so that the phase of their outputs is shifted by π / 2 relative to each other in the rotation direction D2 of the rotor 2. As a result, the first detection coil 331 and the second detection coil 332 output output voltage signals whose amplitude changes with different phases of π / 2. That is, one is an output voltage signal corresponding to a sinusoidal signal, and the other is an output voltage signal corresponding to a cosine wave signal.

[0049] More specifically, the detection coil 33 includes a first detection coil pattern section 33A and a second detection coil pattern section 33B. The first detection coil pattern section 33A is located on the opposing surface 301 of the first substrate section 31A (see Figure 6). The first detection coil pattern section 33A includes a portion corresponding to the first detection coil 331 and a portion corresponding to the second detection coil 332. The second detection coil pattern section 33B is located on the opposite surface 304 of the first substrate section 31A (see Figure 7). The second detection coil pattern section 33B includes a portion corresponding to the first detection coil 331 and a portion corresponding to the second detection coil 332. In other words, the first detection coil 331 and the second detection coil 332 are located on the opposing surface 301 and the opposite surface 304 of the substrate 31, respectively. The first detection coil 331 and the second detection coil 332 are formed by interlayer connection between the first detection coil pattern portion 33A (see Figure 6) on the opposing surface 301 of the substrate 31 and the second detection coil pattern portion 33B (see Figure 7) on the opposite surface 304.

[0050] (2-3-3) The coil pattern on the first surface, Figure 6, is a plan view showing the opposing surface (first surface) 301 of the substrate 31. As shown in Figure 6, the first excitation coil pattern portion 32A of the excitation coil 32 and the first detection coil pattern portion 33A of the detection coil 33 are arranged on the opposing surface 301 of the substrate 31. The parts indicated by multiple white circles on the opposing surface 301 in Figure 6 correspond to vias for electrical connection with the opposite surface 304.

[0051] The first excitation coil pattern portion 32A of the excitation coil 32 is arranged in an annular shape on the opposing surface 301 of the substrate 31 (see Figure 6). More specifically, the first excitation coil pattern portion 32A of the excitation coil 32 is arranged in an annular shape on the opposing surface 301 of the substrate 31 so as to follow the outer edge 20 of the rotor 2 in a plan view from one direction D1. Here, the "outer edge 20 of the rotor 2" is the circumference including the arc-shaped outer edge 221 of each of the plurality of conductive portions 22 along the rotation direction D2 of the rotor 2, as shown in Figure 4. The first excitation coil pattern portion 32A is arranged concentrically and spirally so as to overlap in the radial direction D3 of the substrate 31.

[0052] The first end (outer side) of the first excitation coil pattern portion 32A is electrically connected via vias to the second excitation coil pattern portion 32B of the excitation coil 32, which is located on the opposite side 304 of the substrate 31 (see Figure 6). This forms the excitation coil 32 shown in Figure 5.

[0053] The first detection coil pattern portion 33A of the detection coil 33 is located inside the first excitation coil pattern portion 32A of the excitation coil 32 on the opposing surface 301 of the substrate 31 (see Figure 6). More specifically, the first detection coil pattern portion 33A is located inside the first excitation coil pattern portion 32A on the opposing surface 301 of the substrate 31. The first detection coil pattern portion 33A is arranged in a wave-like manner to form a spiral. The first detection coil pattern portion 33A is arranged in the rotational direction D2. The first detection coil pattern portion 33A includes a part of the first detection coil 331 and a part of the second detection coil 332. The first detection coil pattern portion 33A is electrically connected by vias to the second detection coil pattern portion 33B of the detection coil 33 formed on the opposite surface 304 of the substrate 31. This forms the first detection coil 331 and the second detection coil 332 shown in Figure 5.

[0054] (2-3-4) The coil pattern on the second surface, Figure 7, is a plan view showing the opposite surface (second surface) 304 of the substrate 31. As shown in Figure 7, the second excitation coil pattern portion 32B of the excitation coil 32 and the second detection coil pattern portion 33B of the detection coil 33 are arranged on the opposite surface 304 of the substrate 31. Note that the parts indicated by multiple white circles on the opposite surface 304 in Figure 7 correspond to vias for electrical connection with other layers.

[0055] The second excitation coil pattern portion 32B of the excitation coil 32 is arranged in an annular shape on the opposite surface 304 of the substrate 31 (see Figure 7). More specifically, the second excitation coil pattern portion 32B is arranged in an annular shape on the opposing surface 301 of the substrate 31 so as to follow the outer edge 20 of the rotor 2 when viewed from one direction D1 in plan view. The second excitation coil pattern portion 32B is arranged concentrically and spirally so as to overlap in the radial direction D3 of the substrate 31.

[0056] The first end (outer side) of the second excitation coil pattern portion 32B is electrically connected via vias to the first excitation coil pattern portion 32A of the excitation coil 32 formed on the opposing surface 301 of the substrate 31. This forms the excitation coil 32 shown in Figure 5.

[0057] The second detection coil pattern portion 33B of the detection coil 33 is located inside the second excitation coil pattern portion 32B of the excitation coil 32 on the opposite side 304 of the substrate 31 (see Figure 7). More specifically, the second detection coil pattern portion 33B is located inside the second excitation coil pattern portion 32B on the opposite side 304 of the substrate 31. The second detection coil pattern portion 33B is arranged in a wave-like pattern that swirls around. The second detection coil pattern portion 33B of the detection coil 33 includes the remainder of the first detection coil 331 excluding a portion of it, and the remainder of the second detection coil 332 excluding a portion of it. The second detection coil pattern portion 33B is electrically connected by vias to the first detection coil pattern portion 33A of the detection coil 33 located on the opposing side 301 of the substrate 31. This forms the first detection coil 331 and the second detection coil 332 shown in Figure 5.

[0058] (2-3-5) Proximity and Remote Sections Figure 8 is a schematic plan view showing the configuration of the excitation coil 32 and the detection coil 33. In Figure 8, for convenience, the substrate 31 is omitted, and the outer excitation coil 32 and the inner detection coil 33 are shown as annular rings with the same center. Also in Figure 8, the rotor 2 is shown by a dashed line. The centers of the annular rings of the excitation coil 32 and the detection coil 33 coincide with the rotation center RC1 of the rotor 2.

[0059] The excitation coil 32 is arranged in an annular shape along the outer edge 20 of the rotor 2 when viewed from one direction D1 in a plan view. The detection coil 33 is also arranged in an annular shape along the inside of the excitation coil 32 when viewed from one direction D1 in a plan view. In Figure 8, the radial widths of the excitation coil 32 and the detection coil 33 correspond to the radial widths of the excitation coil 32 and the detection coil 33 shown in Figures 5 to 7, and the radial width of the inner detection coil 33 is larger than the radial width of the outer excitation coil 32.

[0060] The detection coil 33 includes a proximity portion 336 that is close to the excitation coil 32 and a distance portion 337 that is further from the excitation coil 32 than the proximity portion 336. In this embodiment, the boundary between the proximity portion 336 and the distance portion 337 is defined by a circle C1 midway between the outer edge 334 and the inner edge 335 in the radial direction of the detection coil 33. That is, the proximity portion 336 is the outer half of the annular region of the detection coil 33 in the radial direction, and the distance portion 337 is the inner half of the annular region of the detection coil 33 in the radial direction.

[0061] The proximity portion 336 is positioned to overlap with the soft magnetic material 23 in one direction D1. More specifically, the proximity portion 336 located between two adjacent conductive portions 22 is fan-shaped in a plan view from one direction D1, and the soft magnetic material 23 located between two adjacent conductive portions 22 is also fan-shaped in a plan view from one direction D1. The soft magnetic material 23 located between adjacent conductive portions 22 covers the entire area of ​​the proximity portion 336 located between the adjacent conductive portions 22 in one direction D1. The proximity portion 336 of the detection coil 33 is closer to the excitation coil 32 than the remote portion 337, and therefore the magnetic flux from the excitation coil 32 is greater in the proximity portion 336 than in the remote portion 337. By positioning the proximity portion 336 of the detection coil 33 to overlap with the soft magnetic material 23 in one direction, it becomes possible to further increase the magnetic flux from the excitation coil 32 in the proximity portion 336 of the detection coil 33. This makes it possible to further increase the induced voltage (output voltage) of the detection coil 33. As a result, it becomes possible to detect the rotation angle of rotor 2 with greater accuracy.

[0062] A portion of the remote portion 337 is positioned so as not to overlap with the soft magnetic material in one direction D1. More specifically, the remote portion 337 located between adjacent conductive portions 22 is fan-shaped in a plan view from one direction D1. The soft magnetic material 23 located between adjacent conductive portions 22 covers a portion (more specifically, about half) of the remote portion 337 located between adjacent conductive portions 22 in one direction D1. Since the remote portion 337 of the detection coil 33 is further from the excitation coil 32 than the proximity portion 336, the magnetic flux from the excitation coil 32 is smaller than that from the proximity portion 336. By positioning a portion of the remote portion 337 of the detection coil 33 so as not to overlap with the soft magnetic material 23 in one direction D1, it becomes easier to overlap the proximity portion 336, which has a large magnetic flux from the excitation coil 32, with the soft magnetic material 23. This makes it easier to increase the magnetic flux from the excitation coil 32 in the detection coil 33.

[0063] Here, we define the percentage to which the soft magnetic material 23 covers the detection coil 33. Hereafter, this percentage will be referred to as the "coverage rate of the soft magnetic material" or simply the "coverage rate". The coverage rate of the soft magnetic material 23 is based on the outer edge of the soft magnetic material 23. Therefore, if the coverage rate of the soft magnetic material 23 is 0%, it means that the soft magnetic material 23 does not cover the detection coil 33. However, in this case, it does not mean that the soft magnetic material 23 does not exist, but rather that the soft magnetic material 23 exists and covers part or all of the excitation coil 32.

[0064] Figure 12 is a graph showing the change in the output voltage of the detection coil 33 with respect to the coverage of the soft magnetic material 23. The horizontal axis of the graph represents the coverage of the soft magnetic material 23. The vertical axis of the graph represents the rate of increase in the output voltage of the detection coil 33 when the soft magnetic material 23 is present compared to when the soft magnetic material 23 is not present.

[0065] Point A in the graph represents the case where the coverage of the soft magnetic material 23 is 50%, and the output voltage of the detection coil 33 increases by nearly 50%. A 50% coverage of the soft magnetic material 23 means that the soft magnetic material 23 covers only the proximity portion 336. In other words, a 50% coverage of the soft magnetic material 23 means that the proximity portion 336 is positioned to overlap with the soft magnetic material 23 in one direction D1, and the distance portion 337 is positioned not to overlap with the soft magnetic material 23 in one direction D1. By positioning only the proximity portion 336 of the detection coil 33 to overlap with the soft magnetic material 23 in one direction D1, it becomes possible to further increase the magnetic flux from the excitation coil 32 at the proximity portion 336 of the detection coil 33. This makes it possible to further increase the output voltage of the detection coil 33.

[0066] Point B in the graph represents the case where the coverage of the soft magnetic material 23 is approximately 80%, and even here, the output voltage of the detection coil 33 increases by nearly 50%. When the coverage of the soft magnetic material 23 is approximately 80%, as shown in Figure 8, the soft magnetic material 23 located between adjacent conductive parts 22 covers the entire area of ​​the proximity portion 336 located between adjacent conductive parts 22 in one direction D1. Furthermore, the soft magnetic material 23 located between adjacent conductive parts 22 covers approximately half of the distance portion 337 located between adjacent conductive parts 22 in one direction D1. In this case as well, since the proximity portion 336 of the detection coil 33 is positioned to overlap with the soft magnetic material 23 in one direction D1, it becomes possible to further increase the magnetic flux from the excitation coil 32 in the proximity portion 336 of the detection coil 33. This makes it possible to further increase the output voltage of the detection coil 33.

[0067] Furthermore, even when the coverage rate of the soft magnetic material 23 is 0%, the output voltage of the detection coil 33 increases by nearly 20%. When the coverage rate of the soft magnetic material 23 is 0%, the soft magnetic material 23 does not cover the detection coil 33, but the soft magnetic material 23 covers part or all of the excitation coil 32. Even with this configuration, it is possible to increase the magnetic flux from the excitation coil 32 in the detection coil 33.

[0068] (2-4) Principle of detecting rotation angle Next, the principle of detecting the rotation angle by the rotation sensor 1 will be explained using Figures 8 to 10. For convenience, this explanation will use one detection coil 33.

[0069] When an alternating current flows through the excitation coil 32 shown in Figure 8, a magnetic field is generated in the vicinity of the detection coil 33 by the excitation coil 32. When a magnetic field is generated in the vicinity of the detection coil 33, an induced voltage is generated in the detection coil 33 due to electromagnetic induction, and an induced current flows. The proximity portion 336 of the detection coil 33, which is close to the excitation coil 32, has a large magnetic flux from the excitation coil 32, so the induced voltage is large. In contrast, the remote portion 337 of the detection coil 33, which is further from the excitation coil 32 than the proximity portion 336, has a small magnetic flux from the excitation coil 32, so the induced voltage is small.

[0070] Figure 9 is an explanatory diagram illustrating the induced current flowing through the detection coil 33 when there is no conductive part 22 on the rotor 2. For convenience, only the first detection coil 331 of the detection coil 33 is shown in Figure 9. As described above, the first detection coil 331 is formed by interlayer connection of the first detection coil pattern portion 33A (see Figure 6) on the opposing surface 301 of the substrate 31 and the second detection coil pattern portion 33B (see Figure 7) on the opposite surface 304. As shown in Figure 9, the first detection coil 331 has a sinusoidal first pattern portion extending in the circumferential direction of the detection coil 33 and a second pattern portion with an inverse phase shape of the first pattern, and the first pattern portion and the second pattern portion are connected in series. The current arrows in the figure indicate the induced current flowing through the first detection coil 331. The thickness of the arrows indicates the magnitude of the induced current. A thicker arrow indicates a larger induced current, and a thinner arrow indicates a smaller induced current. Here, the proximity portion 336 and the distance portion 337 (see Figure 8) can also be defined for the first detection coil 331 (see "(2-3-5) Proximity and Distance Portions"). In Figure 9, a virtual circle (not shown) formed by connecting multiple points (seven in Figure 9) where the first pattern and the second pattern of the first detection coil 331 intersect corresponds to the boundary between the proximity portion 336 and the distance portion 337 in the detection coil 33 shown in Figure 8 (C1 in Figure 8). In other words, the part of the first detection coil 331 outside the virtual circle corresponds to the proximity portion 336, and the part of the first detection coil 331 inside the virtual circle corresponds to the distance portion 337. As shown in Figure 9, if there is no conductive portion 22 on the rotor 2, the induced currents flowing through the proximity portion 336 and the distance portion 337 of the first detection coil 331 are balanced, and the total current flowing is zero, so no potential difference is generated in the detection coil 33. In other words, the output voltage of the detection coil 33 is zero.

[0071] Figure 10 is an explanatory diagram illustrating the induced current flowing through the detection coil 33 when the rotor 2 has conductive parts 22. In Figure 10, as in Figure 9, only the first detection coil 331 of the detection coil 33 is shown, and the soft magnetic material 23 is located between the multiple conductive parts 22 of the rotor 2. As mentioned above, the coverage of the soft magnetic material 23 is approximately 75%. In other words, the soft magnetic material 23 located between adjacent conductive parts 22 covers the entire area of ​​the proximity portion 336 of the first detection coil 331 located between adjacent conductive parts 22 in one direction D1, and approximately half of the distance portion 337 of the first detection coil 331.

[0072] When a conductive portion 22 is present on the rotor 2, eddy currents are generated in the conductive portion 22 due to the magnetic field generated from the excitation coil 32. The magnetic field generated by the eddy currents is generated in a direction that cancels out the magnetic field generated from the excitation coil 32. Therefore, the magnetic flux from the excitation coil 32 becomes smaller in the portion of the detection coil 33 that overlaps with the conductive portion 22 compared to the portion that does not overlap with the conductive portion 22, and the induced voltage decreases.

[0073] When the rotation angle of the rotor 2 relative to the stator 3 is 45 degrees or 90 degrees, the induced currents flowing through the proximity 336 and the distance 337 of the first detection coil 331 are balanced, and the overall current flowing is zero, so no potential difference is generated in the detection coil 33. In other words, the output voltage of the detection coil 33 is zero.

[0074] In contrast, when the rotation angle of the rotor 2 relative to the stator 3 is at the position shown in Figure 10 (a position between 45 and 90 degrees), the induced currents flowing through the proximity 336 and distance 337 of the detection coil 33 become unbalanced. As a result, a potential difference is generated in the detection coil 33, and an output voltage is generated in the detection coil 33.

[0075] The rotation angle of the rotor 2 can be detected by detecting the output voltage of the detection coil 33 as the rotor rotates. If the output voltage of the detection coil 33 is small, the accuracy of detecting the rotation angle of the rotor 2 will be low.

[0076] In the rotation sensor 1 of Embodiment 1, since the soft magnetic material 23 is positioned between the multiple conductive parts 22, it becomes possible to increase the magnetic flux from the excitation coil 32 in the portion of the detection coil 33 that does not overlap with the conductive parts 22. This makes it possible to increase the output voltage of the detection coil 33. Therefore, the rotation sensor 1 of Embodiment 1 can improve the accuracy of rotation angle detection.

[0077] (2-5) Method for detecting the rotation angle Next, an example of a method for detecting the rotation angle using the rotation sensor 1 will be described.

[0078] The rotation sensor 1 includes a circuit block 35 for detecting the rotation angle of the rotor 2 relative to the stator 3 (see Figure 5). The circuit block 35 includes electronic circuits such as an oscillator for outputting alternating current to an excitation coil 32, a differential amplifier for amplifying the induced voltage generated by the detection coil 33, an AD converter for converting the voltage signal (analog signal) amplified by the differential amplifier into a digital signal, and a microcontroller for calculating the rotation angle through digital processing.

[0079] First, in circuit block 35 (more specifically, the oscillator and waveform shaping circuit, etc.), a sinusoidal alternating current as represented by equation (1-1) is generated and output to the excitation coil 32.

[0080]

[0081] As a result, an alternating magnetic field is generated from the excitation coil 32 in the first detection coil 331 and the second detection coil 332. The alternating magnetic flux from the excitation coil 32 passes through the first detection coil 331 and the second detection coil 332 along one direction D1. The alternating magnetic field from the excitation coil 32 fluctuates in strength depending on the presence or absence of the conductive part 22 in the rotation direction D2 of the conductive part 22 of the rotor 2.

[0082] The first detection coil 331 and the second detection coil 332 have a sinusoidal pattern extending in the rotation direction D2 of the rotor 2, and are arranged so that the phase of their outputs is shifted by π / 2 relative to each other in the rotation direction D2 of the rotor 2 (conductive part 22). As a result, the first detection coil 331 and the second detection coil 332 output output voltage signals whose amplitude changes with different phases of π / 2. In other words, due to the alternating magnetic field from the excitation coil 32, the first detection coil 331 and the second detection coil 332 generate a first output voltage signal V1 corresponding to a sinusoidal signal and a second output voltage signal V2 corresponding to a cosine wave signal, respectively, with respect to the rotation angle of the rotor 2 (conductive part 22), through electromagnetic induction.

[0083]

[0084]

[0085] In equations (1-2) and (1-3), θ represents the rotation angle of the rotor 2, and A represents the amplitude of the output voltage signal. In Embodiment 1, as shown in Figure 8, the soft magnetic material 23 is arranged between two adjacent conductive parts 22, 22 in the rotation direction D2 of the rotor 2, so that the magnetic flux from the excitation coil 32 can be increased in the portion of the first detection coil 331 and the second detection coil 332 that does not overlap with the conductive parts 22. This makes it possible to increase the amplitude A of the first output voltage signal V1 and the second output voltage signal V2.

[0086] Digital signal processing is performed in circuit block 35 (more specifically, the AD converter, microcontroller, etc.). More specifically, from equations (1-2) and (1-3), the signal is converted to the digital signal VD1 shown in equation (1-4) and the digital signal VD2 shown in equation (1-5) at the timing of cos(ωt) = 1, and the rotation angle θ of the rotor 2 is calculated. This improves the detection accuracy of the rotation angle θ of the rotor 2. In equations (1-4) and (1-5), B is the amplitude of the digital signals VD1 and VD2.

[0087]

[0088]

[0089] (3) Effects As shown in Figures 3 and 4, in the rotation sensor 1 of Embodiment 1, the soft magnetic material 23 is positioned between the multiple conductive parts 22 in a plan view from one direction D1, so that the magnetic flux from the excitation coil 32 can be increased in the portion of the detection coil 33 that does not overlap with the conductive parts 22. This makes it possible to increase the output voltage of the detection coil 33. As a result, the detection accuracy of the rotation angle of the rotor 2 can be improved.

[0090] Furthermore, as shown in Figure 3, in the first embodiment of the rotation sensor 1, the soft magnetic material 23 is positioned between two adjacent conductive parts 22 in the rotation direction D2 of the rotor 2, which allows the thickness of the rotor 2 in one direction D1 to be reduced. This makes it possible to miniaturize the rotation sensor 1.

[0091] Furthermore, in the rotation sensor 1 of Embodiment 1, the proximity portion 336 of the detection coil 33 is closer to the excitation coil 32 than the remote portion 337, and therefore the magnetic flux from the excitation coil 32 is greater at the proximity portion 336 than at the remote portion 337. As shown in Figure 8, by positioning the proximity portion 336 of the detection coil 33 to overlap with the soft magnetic material 23 in one direction D1, it becomes possible to further increase the magnetic flux from the excitation coil 32 at the proximity portion 336 of the detection coil 33. This makes it possible to further increase the induced voltage of the detection coil 33. As a result, it becomes possible to detect the rotation angle of the rotor 2 with greater accuracy.

[0092] Furthermore, in the rotation sensor 1 of Embodiment 1, the remote portion 337 of the detection coil 33 is further from the excitation coil 32 than the proximity portion 336, so the magnetic flux from the excitation coil 32 is smaller than that from the proximity portion 336. In one direction D1, by positioning a part of the remote portion 337 of the detection coil 33 in a position that does not overlap with the soft magnetic material 23, it becomes easier to overlap the proximity portion 336, which has a large magnetic flux from the excitation coil 32, with the soft magnetic material 23. This makes it easier to increase the magnetic flux from the excitation coil 32 in the detection coil 33.

[0093] Furthermore, in the rotation sensor 1 of Embodiment 1, the conductivity of the soft magnetic material 23 is 1 × 10 ４It is less than or equal to / Ωm. When the conductivity of the soft magnetic material 23 is high, eddy currents are more likely to be generated in the soft magnetic material 23. Due to these eddy currents, magnetic flux is generated in the soft magnetic material 23 in a direction that cancels out the magnetic flux from the excitation coil. As a result, the effect of increasing magnetic flux by the soft magnetic material 23 is reduced. Therefore, in Embodiment 1, by reducing the conductivity of the soft magnetic material 23, the eddy currents generated in the soft magnetic material 23 are reduced, and the effect of increasing magnetic flux by the soft magnetic material 23 can be made more pronounced. This makes it possible to increase the induced voltage of the detection coil 33. As a result, the rotation angle of the rotor 2 can be detected with greater accuracy.

[0094] Furthermore, in the rotation sensor 1 of Embodiment 1, the thickness of the soft magnetic material 23 is four times or less the skin depth. When the thickness of the soft magnetic material 23 increases, the eddy currents generated in the soft magnetic material 23 tend to increase. As a result, the effect of increasing magnetic flux by the soft magnetic material 23 is reduced. By keeping the thickness of the soft magnetic material 23 below a certain level, the eddy currents generated in the soft magnetic material 23 can be reduced, and the effect of increasing magnetic flux by the soft magnetic material 23 can be made more pronounced. This makes it possible to increase the induced voltage of the detection coil 33. As a result, the rotation angle of the rotor 2 can be detected with greater accuracy.

[0095] (Embodiment 2) Next, the rotor 2A of the rotation sensor 1A according to Embodiment 2 will be described with reference to Figures 13 and 14. Components similar to those in Embodiment 1 described above are denoted by the same reference numerals and their description is omitted. Figure 13 is a front view of the rotor 2A of the rotation sensor 1A according to Embodiment 2. Figure 14 is a perspective view of the rotor 2A. For convenience, only the rotor 2A is shown in Figures 13 and 14.

[0096] In the rotor 2 of Embodiment 1 described above, as shown in Figure 3, the soft magnetic material 23 is composed of multiple (four in Figure 3) members. In contrast, the rotor 2A of Embodiment 2 differs from Embodiment 1 in that, as shown in Figures 13 and 14, the soft magnetic material 23A is annular, and the annular soft magnetic material 23A is positioned on the opposite side of the stator 3 from the multiple conductive parts 22.

[0097] In other words, in the rotation sensor 1A of Embodiment 2, a plurality of conductive parts 22 are arranged between the soft magnetic body 23A and the stator 3. More specifically, the lower surface of the annular soft magnetic body 23A is attached to the upper surface of each of the plurality of conductive parts 22, and the annular soft magnetic body 23A rotates together with the plurality of conductive parts 22. The soft magnetic body 23A may be directly attached to the conductive parts 22, or it may be attached indirectly via an insulating member (for example, a donut-shaped flat plate member). A known method can be used for joining the annular soft magnetic body 23A and the conductive parts 22.

[0098] In Embodiment 2, in addition to the effects of Embodiment 1, it becomes possible to construct the soft magnetic material 23A from a single component. This makes it easier to assemble the rotation sensor 1A.

[0099] The annular soft magnetic material 23A may be separated from the rotor 2 (multiple conductive parts 22). In other words, the annular soft magnetic material 23A does not have to be integrally configured with the rotor 2 (multiple conductive parts 22).

[0100] (4) Modifications Each of the above embodiments is merely one of many embodiments of the present disclosure. The above embodiments can be modified in various ways depending on the design, etc., as long as the objectives of the present disclosure are achieved. Modifications of the above embodiments are listed below. The modifications described below can be combined and applied as appropriate.

[0101] (4-1) Modification 1 In the above embodiment, the shape of the soft magnetic material 23 located between the multiple conductive parts 22 in a plan view from one direction D1 is fan-shaped (see Figure 3, etc.), but slits may be formed in the soft magnetic material 23 located between the multiple conductive parts 22.

[0102] Figure 15 is a perspective view of the rotor 2B of the rotary sensor 1B according to Modification 1. For convenience, only the rotor 2B is shown in Figure 15. As shown in Figure 15, the soft magnetic material 23B has a slit 235 formed in the portion located between the plurality of conductive parts 22.

[0103] Soft magnetic materials have the property that eddy currents tend to increase when their conductivity is high or when their thickness is high. When eddy currents become large in the soft magnetic material 23, they cancel out the magnetic flux from the excitation coil 32. Therefore, in the modified example 1, by forming a slit 235 in the soft magnetic material 23B located between the multiple conductive parts 22, the eddy current path in the soft magnetic material 23B is blocked, and the generated eddy currents can be reduced. As a result, the magnetic flux from the excitation coil 32 can be increased, and the induced voltage of the detection coil 33 can be increased. As a result, the rotation angle of the rotor 2B can be detected with greater accuracy.

[0104] Furthermore, as shown in Figure 15, the slit 235 is formed along the radial direction D3 of the rotor 2B. Eddy currents have the property of flowing in a vortex inside a soft magnetic material due to a change in magnetic flux inside the soft magnetic material. By forming the slit 235 along the radial direction D3 of the rotor 2B in the soft magnetic material 23B, it becomes easier to block the eddy current path in the soft magnetic material 23B.

[0105] Furthermore, as shown in Figure 15, the slit 235 is formed extending from the outer edge of the soft magnetic material 23B toward the center of the rotor 2B. In Figure 15, the slit 235 extends from the outer edge of the soft magnetic material 23B to the middle of the soft magnetic material 23B in the radial direction D3. Since the outer edge of the soft magnetic material 23B is along the outer edge 20 of the rotor 2, it is close to the excitation coil 32, and the magnetic flux from the excitation coil 32 is large. By forming the slit 235 from the outer edge of the soft magnetic material 23B toward the center of the rotor 2B, the eddy current path is more easily blocked.

[0106] In Figure 15, the slit 235 penetrates through the soft magnetic material 23B in the thickness direction, but it may also be an irregularity provided in the thickness direction of the soft magnetic material 23B.

[0107] (4-2) Modification 2 In Modification 1, as shown in Figure 15, the slit 235 extends from the outer edge of the soft magnetic material 23B to the middle of the soft magnetic material 23B in the radial direction D3. However, the slit 235 may extend from the outer edge to the inner edge of the soft magnetic material 23B.

[0108] Figure 16 is a perspective view of the rotor 2C of the rotary sensor 1C according to Modification 2. For convenience, only the rotor 2C is shown in Figure 16. As shown in Figure 16, in the rotor 2C of Modification 2, the soft magnetic material 23C has a slit 235A that extends from the outer edge to the inner edge of the soft magnetic material 23C along the radial direction D3 of the soft magnetic material 23C. In other words, the soft magnetic material 23C is divided in the rotation direction D2 of the rotor 2C. In Figure 16, the gap between the divided soft magnetic material 23C is shown as transparent, but the soft magnetic material 23C is formed on an insulating and non-magnetic substrate (not shown).

[0109] Furthermore, as shown in Figure 16, the slit 235A is formed extending from the outer edge of the soft magnetic material 23C toward the center of the rotor 2C. In Figure 16, the slit 235A extends from the outer edge of the soft magnetic material 23C to the inner edge of the soft magnetic material 23C.

[0110] (4-3) Modification 3 In the above embodiment, as shown in Figure 2, the rotor 2 including the soft magnetic material 23 is arranged facing the opposing surface 301 of the substrate 31 in one direction D1, but two rotors 2 including the soft magnetic material 23 may be arranged facing each other on both sides of the substrate 31.

[0111] Figure 17 is a front view of the main part of the rotary sensor 1D according to the third modification. As shown in Figure 17, the rotor 2D has a first rotor 2E and a second rotor 2F. The first rotor 2E includes a plurality of first conductive parts 22E which are a plurality of conductive parts 22 and a first soft magnetic material 23E which is a soft magnetic material 23. The second rotor 2F includes a plurality of second conductive parts 22F which are different from the plurality of first conductive parts 22E and a second soft magnetic material 23F which is different from the first soft magnetic material 23E. The stator 3 is arranged between the first rotor 2E and the second rotor 2F in one direction D1. The first rotor 2E faces the opposing surface 301 of the substrate 31, and the second rotor 2F faces the opposite surface 304 of the substrate 31.

[0112] In the rotation sensor 1D of the modified example 3, the first soft magnetic material 23E of the first rotor 2E, which is positioned facing the opposing surface 301 of the substrate 31, and the second soft magnetic material 23F of the second rotor 2F, which is positioned facing the opposite surface 304, make it possible to double the magnetic flux from the excitation coil 32 in the detection coil 33 compared to the rotation sensor 1 of the embodiment 1. This makes it possible to increase the induced voltage of the detection coil 33. As a result, the rotation angle of the rotor 2D can be detected with greater accuracy.

[0113] (4-4) Modification 4 In the above embodiment, the external shape of the excitation coil 32 and the detection coil 33 was circular when viewed from one direction D1, but they may be formed in a substantially semi-circular or fan shape.

[0114] Figure 18 is a plan view showing an example of the excitation coil 32C and detection coil 33C of the rotation sensor 1E according to Modification 4. For convenience, the substrate 31 is omitted in Figure 18, and only the excitation coil 32C and detection coil 33C are shown. As shown in Figure 18, the outer shape of the excitation coil 32C and detection coil 33C is formed in a substantially semi-circular arc shape when viewed from one direction D1. This reduces the area required for the excitation coil 32C and detection coil 33C on the substrate 31. The freed-up space on the substrate 31 makes it possible to arrange a circuit block 35 as shown in Figure 5. Therefore, according to the rotation sensor 1E of Modification 4, the area of ​​the substrate 31 can be effectively utilized, and the entire rotation sensor 1E can be miniaturized.

[0115] In Figure 18, the detection coil 33C includes a first detection coil 331C, a second detection coil 332C, and a third detection coil 333C. In Figure 18, the first detection coil 331C, the second detection coil 332C, and the third detection coil 333C are arranged to output three-phase AC voltages with electrical angles shifted by 2 / 3π each, by changing the arrangement phase of the sinusoidal conductor patterns. In the above embodiment of the rotation sensor 1, the detection coil 33 included a first detection coil 331 and a second detection coil 332, but as in Modification 4, the rotation angle may be detected based on the output voltages output from the three detection coils.

[0116] (4-5) Other Modifications In the above embodiment, the material of the soft magnetic material 23 was Ni-Zn ferrite, Mn-Zn ferrite, or compacted magnetic core, but the conductivity was 1 × 10 ４ Even soft magnetic materials with a magnetic resistance exceeding (1 / Ωm) can achieve a certain effect. Examples of such soft magnetic materials include: iron, silicon steel sheets (an alloy of iron and silicon), electromagnetic stainless steel (an alloy of iron and chromium), permalloy (an alloy of iron and nickel), Sendust (an alloy of iron, silicon, and aluminum), and amorphous magnetic materials formed from the above four alloys in an amorphous state.

[0117] (Summary) Based on the embodiments described above, the following embodiments are disclosed.

[0118] The first embodiment of the rotation sensor (1) detects the rotation angle of the object to be rotated (4). The rotation sensor (1) comprises a rotor (2), a stator (3), and a soft magnetic material (23). The rotor (2) is attached to the object to be rotated (4) and rotates integrally with the object to be rotated (4). The stator (3) faces the rotor (2) in one direction (D1). The rotor (2) has a plurality of conductive parts (22) arranged along the rotation direction (D2) of the rotor (2). The stator (3) comprises a substrate (31), an excitation coil (32) that generates a magnetic field, and a detection coil (33) that detects changes in the magnetic field. The substrate (31) faces the rotor (2). The excitation coil (32) is arranged in a ring on the substrate (31) along the outer edge (20) of the rotor (2) in a plan view from one direction (D1), and generates a magnetic field. The detection coil (33) is positioned inside the excitation coil (32) on the substrate (31) and detects changes in the magnetic field. The detection coil (33) includes a proximity portion (336) that is close to the excitation coil (32) and a distance portion (337) that is further from the excitation coil (32) than the proximity portion (336). The soft magnetic material (23) has a portion that is located between a plurality of conductive portions (22) in a plan view from one direction (D1).

[0119] According to this embodiment, when a magnetic field is generated by the excitation coil (32) near the detection coil (33), an induced voltage is generated in the detection coil (33) by electromagnetic induction. Since the soft magnetic material (23) of the rotor (2) has a portion located between a plurality of conductive parts (22) when viewed from one direction (D1) in a plan view, it becomes possible to increase the magnetic flux from the excitation coil (32) in the portion of the detection coil (33) that does not overlap with the conductive parts (22). This makes it possible to increase the induced voltage of the detection coil (33). As a result, the detection accuracy of the rotation angle of the rotor (2) can be improved.

[0120] In the second embodiment of the rotation sensor (1), the soft magnetic material (23) includes a plurality of members (231, 232, 233, 234). Each of the plurality of members (231, 232, 233, 234) is positioned between two adjacent conductive parts (22) of a plurality of conductive parts (22) in the rotation direction (D2) of the rotor (2).

[0121] According to this embodiment, each of the multiple soft magnetic material (23) members (231, 232, 233, 234) is arranged between two adjacent conductive parts (22) in the rotation direction (D2) of the rotor (2), so the thickness of the rotor (2) in one direction (D1) can be reduced. This makes it possible to miniaturize the rotation sensor (1).

[0122] In the third embodiment of the rotation sensor (1A), the soft magnetic material (23A) is annular in the first embodiment. The soft magnetic material (23A) is positioned on the opposite side of the stator (3) from the plurality of conductive parts (22).

[0123] According to this embodiment, the soft magnetic material (23A) can be configured as a single component. This makes it easier to assemble the rotation sensor (1A).

[0124] In the fourth embodiment of the rotation sensor (1, 1A), in any one of the first to third embodiments, the proximity portion (336) is positioned to overlap with the soft magnetic material (23) in one direction (D1).

[0125] The proximity portion (336) of the detection coil (33) is closer to the excitation coil (32) than the distance portion (337), and therefore the magnetic flux from the excitation coil (32) is greater at the proximity portion (336) than at the distance portion (337). According to this embodiment, by positioning the proximity portion (336) of the detection coil (33) to overlap with the soft magnetic material (23) in one direction (D1), it becomes possible to further increase the magnetic flux from the excitation coil (32) at the proximity portion (336) of the detection coil (33). This makes it possible to further increase the induced voltage of the detection coil (33). As a result, it becomes possible to detect the rotation angle of the rotor (2) with greater accuracy.

[0126] In the fifth embodiment of the rotation sensor (1, 1A), the remote portion (337) is positioned so as not to overlap with the soft magnetic material (23) in one direction (D1).

[0127] Since the remote portion (337) of the detection coil (33) is further from the excitation coil (32) than the nearby portion (336), the magnetic flux from the excitation coil (32) is smaller at the remote portion (337) than at the nearby portion (336). In this embodiment, by positioning the remote portion (337) of the detection coil (33) in a position that does not overlap with the soft magnetic material (23) in one direction (D1), it becomes possible to overlap only the nearby portion (336), where the magnetic flux from the excitation coil (32) is large, with the soft magnetic material (23). This makes it easier to increase the magnetic flux from the excitation coil (32) in the detection coil (33).

[0128] The sixth embodiment of the rotation sensor (1, 1A) is such that in any one of the first to fifth embodiments, the soft magnetic material (23) has an conductivity of 1 × 10 ４ It is less than or equal to / Ωm.

[0129] If the conductivity of the soft magnetic material (23) is high, eddy currents are more likely to be generated in the soft magnetic material (23). Due to these eddy currents, a magnetic flux is generated in the soft magnetic material (23) in a direction that cancels out the magnetic flux from the excitation coil (32). As a result, the effect of increasing magnetic flux by the soft magnetic material (23) is reduced. According to this embodiment, by reducing the conductivity of the soft magnetic material (23), the eddy currents generated in the soft magnetic material (23) can be reduced, and the effect of increasing magnetic flux by the soft magnetic material (23) can be made more pronounced. This makes it possible to increase the induced voltage of the detection coil (33). As a result, the rotation angle of the rotor (2) can be detected with greater accuracy.

[0130] In the seventh embodiment of the rotation sensor (1, 1A), in any one of the first to fifth embodiments, the soft magnetic material (23) has a thickness of four times or less the skin depth.

[0131] As the thickness of the soft magnetic material (23) increases, the eddy currents generated in the soft magnetic material (23) tend to increase. As a result, the effect of increasing magnetic flux by the soft magnetic material (23) is reduced. By keeping the thickness of the soft magnetic material (23) below a certain level, the eddy currents generated in the soft magnetic material (23) can be reduced, and the effect of increasing magnetic flux by the soft magnetic material (23) can be made more pronounced. This makes it possible to increase the induced voltage of the detection coil (33). As a result, the rotation angle of the rotor (2) can be detected with greater accuracy.

[0132] The rotation sensor (1B, 1C) of the eighth embodiment, in any one of the first to seventh embodiments, has a soft magnetic material (23B, 23C) having slits (235, 235A) formed in the portion located between the plurality of conductive parts (22).

[0133] When the conductivity of the soft magnetic material (23) is high, or when the thickness of the soft magnetic material (23) is high, the eddy currents generated in the soft magnetic material (23) tend to be large. In this embodiment, by forming slits (235, 235A) in the soft magnetic material (23B, 23C) located between the multiple conductive parts (22), the eddy current path in the soft magnetic material (23B, 23C) can be blocked, and the generated eddy currents can be reduced. As a result, the magnetic flux from the excitation coil (32) can be increased, and the induced voltage of the detection coil (33) can be increased. As a result, the rotation angle of the rotor (2B, 2C) can be detected with greater accuracy.

[0134] In the ninth embodiment of the rotation sensor (1B, 1C), the outer edge (20) of the rotor (2B, 2C) is circular in a plan view from one direction (D1), as in the eighth embodiment. The outer edge of the soft magnetic material (23B, 23C) is along the outer edge (20) of the rotor (2B, 2C). The slits (235, 235A) are formed along the radial direction (D3) of the rotor (2B, 2C) and extending from the outer edge of the soft magnetic material (23B, 23C) toward the center of the rotor (2B, 2C).

[0135] According to this embodiment, by forming the slits (235, 235A) in the soft magnetic material (23B, 23C) along the radial direction (D3) of the rotor (2B, 2C), it becomes easier to block the eddy current paths that may be generated in the soft magnetic material (23B, 23C). Also, since the outer edge of the soft magnetic material (23B, 23C) is along the outer edge (20) of the rotor (2B, 2C), it is close to the excitation coil (32) and the magnetic flux is large. By forming the slits (235, 235A) from the outer edge of the soft magnetic material (23B, 23C) toward the center of the rotor (2B, 2C), it becomes easier to block the eddy current paths. As a result, the eddy currents generated in the soft magnetic material (23B, 23C) can be reduced.

[0136] The rotation sensor (1D) of the tenth embodiment, in any one of the first to ninth embodiments, has a rotor (2D) comprising a first rotor (2E) and a second rotor (2F). The first rotor (2E) includes a plurality of first conductive parts (22E) which are a plurality of conductive parts (22) and a first soft magnetic material (23E) which is a soft magnetic material (23). The second rotor (2F) includes a plurality of second conductive parts (22F) which are different from the plurality of first conductive parts (22E) and a second soft magnetic material (23F) which is different from the first soft magnetic material (23E). The stator (3) is positioned between the first rotor (2E) and the second rotor (2F) in one direction. The substrate (31) has a first surface (301) and a second surface (304) which are located opposite to each other in one direction (D1). The first rotor (2E) faces the first surface (301) of the substrate (31). The second rotor (2F) faces the second surface (304) of the substrate (31).

[0137] In this embodiment, a first rotor (2E) containing a first soft magnetic material (23E) and a second rotor (2F) containing a second soft magnetic material (23F) are arranged facing each other on both sides (301, 304) of the substrate (31). This makes it possible to double the magnetic flux from the excitation coil (32) in the detection coil (33) compared to a configuration in which a single rotor (2) containing a soft magnetic material (23) is arranged. This makes it possible to increase the induced voltage of the detection coil (33). As a result, the rotation angle of the rotor (2) can be detected with greater accuracy.

[0138] In the eleventh embodiment of the rotation sensor (1, 1A to 1D), in any one of the first to tenth embodiments, the soft magnetic material (23, 23A to 23F) is integrally configured with the rotor (2, 2A to 2F).

[0139] The configurations relating to the second to eleventh aspects are not essential to the rotation sensor (1) and can be omitted as appropriate.

[0140] The rotation sensor of this disclosure can improve the accuracy of detecting the rotation angle of a rotor. Therefore, by using the rotation sensor of this disclosure, the rotation angle of the rotor can be obtained with high accuracy. Thus, the rotation sensor of this disclosure is industrially useful.

[0141] 1, 1A-1E Rotation sensor 2, 2A-2D Rotor 2E First rotor 2F Second rotor 3 Stator 4 Rotation axis (object to be rotated) 20, 221, 334 Outer edge 22 Conductive part 22E First conductive part 22F Second conductive part 23, 23A-23C Soft magnetic material 23E First soft magnetic material 23F Second soft magnetic material 24 Gap 31 Substrate 32, 32C Excitation coil 33, 33C Detection coil 231 First member 232 Second member 233 Third member 234 Fourth member 235, 235A Slit 301 Opposing surface 304 Opposite surface 331, 331C First detection coil 332, 332C Second detection coil 333C Third detection coil 336 Proximity part 337 Remote section D1 Unidirectional D2 Rotational direction D3 Radial direction RC1 Center of rotation

Claims

1. A rotation sensor for detecting the rotation angle of a rotating object, comprising: a rotor attached to the rotating object and rotating integrally with the rotating object; a stator facing the rotor in one direction; and a soft magnetic material, wherein the rotor has a plurality of conductive parts arranged along the rotation direction of the rotor; the stator has a substrate facing the rotor; an excitation coil arranged in a ring on the substrate along the outer edge of the rotor in a plan view from the one direction and generating a magnetic field; and a detection coil arranged inside the excitation coil on the substrate and detecting changes in the magnetic field, wherein the detection coil includes a proximity portion close to the excitation coil and a distance portion further from the excitation coil than the proximity portion; and the soft magnetic material has a portion located between the plurality of conductive parts in a plan view from the one direction.

2. The rotation sensor according to claim 1, wherein the soft magnetic material comprises a plurality of members, each of which is positioned between two adjacent conductive parts of the plurality in the rotation direction of the rotor.

3. The rotation sensor according to claim 1, wherein the soft magnetic material is annular in shape, and the soft magnetic material is positioned on the opposite side of the stator from the plurality of conductive parts.

4. The proximity portion is positioned to overlap with the soft magnetic material in one direction, the rotation sensor according to any one of claims 1 to 3.

5. The rotation sensor according to claim 4, wherein the remote portion is positioned so as not to overlap with the soft magnetic material in one direction.

6. The soft magnetic material has an electrical conductivity of 1 × 10⁻⁶ ４ A rotation sensor according to any one of claims 1 to 3, wherein the resistance is less than or equal to / Ωm.

7. The rotation sensor according to any one of claims 1 to 3, wherein the soft magnetic material has a thickness of four times or less the depth of the surface.

8. The rotation sensor according to any one of claims 1 to 3, wherein the soft magnetic material has a slit formed in a portion located between the plurality of conductive parts.

9. The rotation sensor according to claim 8, wherein the outer edge of the rotor is circular in a plan view from one direction, the outer edge of the soft magnetic material is along the outer edge of the rotor, and the slit is formed along the radial direction of the rotor and from the outer edge of the soft magnetic material toward the center of the rotor.

10. The rotor comprises a first rotor including a plurality of first conductive parts which are a plurality of conductive parts and a first soft magnetic material which is a soft magnetic material, and a second rotor including a plurality of second conductive parts which are different from the plurality of first conductive parts and a second soft magnetic material which is different from the first soft magnetic material, the stator is disposed between the first rotor and the second rotor in the one direction, the substrate has a first surface and a second surface which are opposite to each other in the one direction, the first rotor faces the first surface of the substrate, and the second rotor faces the second surface of the substrate, the rotation sensor according to any one of claims 1 to 3.

11. The rotation sensor according to claim 1, wherein the soft magnetic material is integrally configured with the rotor.

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