Rotation detection device

Abstract

A rotation detection device is provided that uses both an induction detection section and a magnetic detection section and has a structure that is advantageous for reducing the size in the radial direction. [Solution] A rotation detection device (100) includes a rotor (1) that rotates around a rotation axis (3), a stator (2) that faces the rotor (1) with a gap (7) therebetween, an induction detection unit (5), and a magnetic detection unit (6). The induction detection unit (5) includes a conductor (10) to be detected that is held by the rotor (1), a receiving coil (20) that is arranged in an annular region (30) centered on the rotation axis (3), and an excitation coil (40). The magnetic detection unit (6) includes a magnet (M) to be detected that is arranged on the opposite side of the stator (2) from the conductor (10) to the stator (1) so that at least a portion of the magnet overlaps with the annular region (30), and magnetic sensors (61, 62) that are arranged on the opposite side of the rotor (1) from the receiving coil (20) and the excitation coil (40) and that are held by the stator (2) so that at least a portion of the magnet overlaps with the annular region (30).

Description

[Technical Field]

[0001] The present invention relates to a rotation detection device including an induction detection unit and a magnetic detection unit. [Background technology]

[0002] Patent Document 1 discloses an inductive rotation detector. This inductive rotation detector has a configuration in which an excitation coil and a detection coil are formed by conductor patterns on a printed wiring board, and a conductive screen to be detected moves along a track facing the detection coil. The detection coil is formed in a figure-eight shape with two loops arranged along the track, and each of the two loops forms two coils with one turn each wound in a different direction. The excitation coil is arranged to surround the detection coil.

[0003] When an alternating current is passed through the excitation coil, an alternating magnetic field is generated, which induces electromotive forces in opposite directions in the two loops (coils) of the detection coil, causing eddy currents to flow in the conductive screen. When neither of the two loops is faced with a conductive screen, the electromotive forces of the two loops are balanced, and the output of the detection coil is zero. On the other hand, since the eddy currents flowing through the conductive screen act in a direction that weakens the alternating magnetic field generated by the excitation coil, when a conductive screen faces the detection coil, an imbalance occurs in the electromotive forces of the two loops depending on the relative positions of the conductive screen and the detection coil. This makes it possible to obtain an output from the detection coil that corresponds to the position of the conductive screen.

[0004] Patent Documents 2 and 3 disclose rotation detection devices that have an inductive detector and a magnetic detector. Using two detectors with different detection methods in combination provides the benefit of ensuring redundancy. Also, by differentiating the detection cycles of the two detectors, the detection cycle can be extended through appropriate signal processing. This allows for highly accurate measurement of absolute angles and multi-rotation absolute angles.

[0005] Patent Document 2 discloses a sensor device including a stator and a rotor facing each other. An antenna is formed in a circular zone by conductor tracks on a printed circuit board constituting the stator, and a magnetoresistive element or a Hall sensor is disposed in a central zone separated inward from the antenna. Meanwhile, the rotor includes a shaft, a magnet attached to the axial end of the shaft, and a modulator disposed around the magnet and fixed to the shaft. The magnet faces the magnetoresistive element or the Hall sensor, and the modulator faces the antenna. Thus, the antenna and the modulator constitute a first rotation angle sensor, and the magnetoresistive element or the Hall sensor and the magnet constitute a second rotation angle sensor.

[0006] Patent Document 3 discloses a rotary encoder including an inductive detector based on the inductive measurement principle and a magnetic detector using a magnet. The rotary encoder has a stator and a rotor that can rotate relative to each other around an axis. The stator has a ring-shaped scanning circuit board, and the rotor has a code plate facing the scanning circuit board. In one example, the scanning circuit board has an excitation land pattern that forms an excitation winding and two receiver land patterns, one inner and one outer, that form two receiver windings, respectively. The code plate has inner and outer scale tracks that correspond to the two receiver land patterns. This forms the inductive detector. The magnetic detector includes a pulse wire attached to the stator and a magnet fixed to the outer edge of the rotor. The pulse wire generates a pulse voltage when the magnet approaches. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 61-15101 [Patent Document 2] Special Publication No. 2022-512249 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-203259 Summary of the Invention [Problem to be solved by the invention]

[0008] The structure of Patent Document 2 cannot be applied to double-shaft or hollow rotation detection devices because the magnet is located at the axial end of the rotor shaft. Also, when viewed in the axial direction along the rotation axis of the rotor, the detection area (annular zone) of the first rotation angle sensor and the detection area (central zone) of the second rotation angle sensor must be separated radially to prevent mutual interference, making it difficult to reduce the size in the radial direction.

[0009] The structure of Patent Document 3 does not have a magnet or angle detector located on the rotation axis, so it can also be applied to double-axis and hollow rotation detection devices. However, since the detection areas of the inductive detection unit and the magnetic detection unit are separated in the radial direction, it is difficult to reduce the size in the radial direction.

[0010] One embodiment of the present invention provides a rotation detection device that uses both an induction detection unit and a magnetic detection unit and has a structure that is advantageous for reducing the size in the radial direction. [Means for solving the problem]

[0011] An embodiment of the present invention provides a rotation detection device having the following features.

[0012] 1. A first support that rotates around a rotation axis; a second support body facing the first support body across a gap in an axial direction parallel to the rotation axis; an induction detection unit that detects rotation information about the first support about the rotation axis; a magnetic detection unit that detects rotation information about the first support body around the rotation axis, The induction detection unit a detection target conductor held by the first support; a receiving coil held by the second support in an arrangement facing the target conductor in the axial direction, and arranged in an annular region centered on the rotation axis when viewed in the axial direction; an excitation coil held by the second support and generating a magnetic field for inducing a voltage in the receiving coil; The magnetic detection unit a magnet to be detected that is disposed on the opposite side of the conductor to be detected from the second support body in the axial direction, and that is held by the first support body and that is disposed so that at least a portion of the magnet overlaps with the annular region when viewed in the axial direction; a magnetic sensor that is disposed on the opposite side of the first support in the axial direction with respect to the receiving coil and the exciting coil, and that is held by the second support so as to overlap at least a portion of the annular region when viewed in the axial direction, and that detects a magnetic field generated by the magnet to be detected; Rotation detection device.

[0013] The induction detection unit, magnetic detection unit, conductor to be detected, magnet to be detected, magnetic sensor, excitation coil, and receiving coil may each be provided singly or in plural.

[0014] 2. The rotation detection device according to item 1, wherein the conductor to be detected includes a screen-shaped conductor.

[0015] 3. The rotation detection device according to item 1 or 2, wherein the magnet to be detected has a ring shape with its center on the rotation axis line and is magnetized in the axial direction.

[0016] 4. A rotation detection device according to item 1 or 2, wherein the magnet to be detected includes a plurality of individual magnets magnetized in the axial direction and arranged along a circumference having a center on the rotation axis.

[0017] 5. A rotation detection device as described in item 4, wherein the plurality of individual magnets are held by the first support in an arrangement that completely overlaps the screen-shaped conductor when viewed in the axial direction.

[0018] 6. A rotation detection device as described in item 1, wherein the conductor to be detected is formed in a ring shape along a circumference having a center on the rotation axis, and is an annular coil pattern with a periodic uneven pattern having radial unevenness with respect to the circumference.

[0019] 7. A rotation detection device according to item 6, wherein the magnet to be detected has a ring shape with its center on the rotation axis line and is magnetized in the axial direction.

[0020] 8. A rotation detection device according to item 6, wherein the magnet to be detected includes a plurality of individual magnets magnetized in the axial direction and arranged along a circumference having a center on the rotation axis.

[0021] 9. A rotation detector according to item 8, wherein the circumferential center position of each of the individual magnets is aligned (matches) with the circumferential position of the midpoint between the circumferentially adjacent recesses and protrusions of the concave-convex pattern.

[0022] 10. A rotation detection device described in item 8 or 9, wherein the circumferential width (angular width: length on the same circumference) of each individual magnet is a natural number multiple of the periodic width (angular width: length on the same circumference) of the concave-convex pattern of the annular coil pattern.

[0023] 11. A plurality of the individual magnets are arranged at equal intervals along the circumference of a circle having a center on the axis of rotation; 11. The rotation detector according to any one of items 8 to 10, wherein the number of periods of the concave-convex pattern of the annular coil pattern around the rotation axis is an odd number.

[0024] 12. The annular coil pattern is an inner circumferential annular coil pattern; Item 9. The rotation detector according to item 8, further comprising an outer circumferential annular coil pattern disposed radially outward of the inner circumferential annular coil pattern.

[0025] 13. The circumferential center position of each of the individual magnets is aligned (matched) with the circumferential position of the midpoint between the recessed and protruding portions adjacent in the circumferential direction of the concave-convex pattern of one of the inner annular coil pattern and the outer annular coil pattern, Item 13. The rotation detection device according to item 12, wherein the circumferential width (angular width: length on the same circumference) of each of the individual magnets is a natural number multiple of the periodic width (angular width: length on the same circumference) of the other of the inner annular coil pattern and the outer annular coil pattern.

[0026] 14. An even number of the individual magnets are equally spaced along the circumference of a circle having a center on the axis of rotation; the circumferential center position of each of the individual magnets is aligned (matched) with the circumferential position of the midpoint of the recess and protrusion that are adjacent in the circumferential direction of one of the concave and convex patterns of the inner annular coil pattern and the outer annular coil pattern, Item 13. The rotation detector according to item 12, wherein the number of periods around the rotation axis of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern is an odd number.

[0027] 15. An even number of the individual magnets are equally spaced along the circumference of a circle having a center on the axis of rotation; the circumferential center position of each of the individual magnets is aligned (matched) with the circumferential position of the midpoint of the recess and protrusion that are adjacent in the circumferential direction of one of the concave and convex patterns of the inner annular coil pattern and the outer annular coil pattern, the circumferential width (angular width: length on the same circumference) of each individual magnet is a natural number multiple of the periodic width (angular width: length on the same circumference) of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern, Item 13. The rotation detector according to item 12, wherein the number of periods around the rotation axis of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern is an odd number.

[0028] 14. The rotation detection device according to any one of items 1 to 13, wherein the magnetic sensor includes a Hall element or a magnetic resistance element.

[0029] 15. The magnetic sensor includes a power generation sensor; Item 14. The rotation detection device according to any one of items 1 to 13, wherein the power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire.

[0030] 16. The magnetic sensor includes a first magnetic sensor including a power generation sensor and a second magnetic sensor including a Hall element or a magnetic resistance element; 14. The rotation detector according to any one of items 1 to 13, wherein the power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire.

[0031] 17. A rotation detection device according to item 15 or 16, wherein the power generation sensor is arranged on a circumference having a center on the rotation axis with the magnetic wire oriented parallel to a tangent to the circumference.

[0032] 18. The rotation detection device according to any one of items 1 to 17, which detects an absolute angle.

[0033] 19. The rotation detection device according to any one of items 1 to 18, which detects a multiple rotation absolute angle. [Effects of the Invention]

[0034] According to the present invention, it is possible to provide a rotation detection device having a structure that is advantageous for reducing the size in the radial direction while using both an induction detection section and a magnetic detection section. [Brief explanation of the drawings]

[0035] [Figure 1A] FIG. 1A is an exploded perspective view illustrating an example of the configuration of a rotation detection device according to an embodiment of the present invention. [Figure 1B] FIG. 1B is an exploded perspective view showing the configuration of FIG. 1A from diagonally below. [Figure 2] FIG. 2 is a cross-sectional view of the rotation detection device. [Figure 3A] FIG. 3A is a plan view of the stator. [Figure 3B] FIG. 3B is a bottom view of the stator. [Figure 4A-4B] 4A and 4B are diagrams for explaining an example of the configuration of a receiving coil. [Figure 5] FIG. 5 shows an example of the arrangement of a screen-shaped conductor, which is an example of a conductor to be detected, and a magnet to be detected. [Figure 6] FIG. 6 shows an example of the arrangement of a screen-shaped conductor, which is an example of a conductor to be detected, and a magnet to be detected. [Figure 7] FIG. 7 shows an example of the arrangement of a screen-shaped conductor, which is an example of a conductor to be detected, and a magnet to be detected. [Figure 8] FIG. 8 shows an example of the configuration of a circular coil pattern, which is another example of a conductor to be detected. [Figure 9] FIG. 9 shows an example of the arrangement of the annular coil pattern and the magnet to be detected. [Figure 10] FIG. 10 shows an example of the arrangement of the annular coil pattern and the magnet to be detected. [Figure 11] FIG. 11 shows an example of the arrangement of the annular coil pattern and the magnet to be detected. [Figure 12] FIG. 12 is a block diagram showing the electrical configuration of the rotation detection device. [Figure 13] FIG. 13 is a cross-sectional view illustrating the configuration of a rotation detector according to another embodiment of the present invention. [Figure 14A] 14A is a bottom view of a stator provided in the rotation detection device of FIG. 13. FIG. [Figure 14B] 14B is a plan view of a rotor provided in the rotation detection device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0037] 1A and 1B are exploded perspective views illustrating an example of the configuration of a rotation detection device according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view thereof. Fig. 1A is an exploded perspective view of the configuration of Fig. 2 as seen obliquely from above, and Fig. 1B is an exploded perspective view of the configuration of Fig. 2 as seen obliquely from below. In this case, up and down are based on the position shown in Fig. 2 and are unrelated to up and down in actual use.

[0038] The rotation detection device 100 includes a rotor 1 as a first support that rotates around a rotation axis 3, and a stator 2 as a second support that faces the rotor 1 across a gap 7 in an axial direction A that is parallel to the rotation axis 3, and is equipped with an induction detection unit 5 and a magnetic detection unit 6. Both the induction detection unit 5 and the magnetic detection unit 6 detect rotation information about the rotor 1 around the rotation axis 3.

[0039] In this example, the rotor 1 is coupled to a rotating shaft 4 that rotates about a rotation axis 3, and rotates together with the rotating shaft 4. The rotor 1 is made of, for example, a printed circuit board. The stator 2 is installed in a non-rotating state. The stator 2 is made of, for example, a printed circuit board. The stator 2 has an opening 2c through which the rotating shaft 4 is inserted. The rotor 1 and the stator 2 are parallel to a plane perpendicular to the rotation axis 3 and face each other parallel to each other with a gap 7 in the axial direction A. The rotor 1 and the stator 2 are arranged closely to each other, and the distance between the gap 7 in the axial direction A is, for example, 0.5 mm.

[0040] The printed wiring boards constituting the rotor 1 and the stator 2 may be multilayer printed wiring boards in which multiple (e.g., four) wiring layers are stacked. Each wiring layer is typically composed of a copper foil pattern, with an insulating layer interposed between one wiring layer and another. The thickness of the copper foil is, for example, approximately 20 μm. For example, a first wiring layer is arranged on one of the two main surfaces of the printed wiring board, a second wiring layer is arranged with a 0.2 mm insulating layer sandwiched between them, a third wiring layer is arranged with a 1.2 mm insulating layer sandwiched between them, and a fourth wiring layer is arranged with a further 0.2 mm insulating layer sandwiched between them. The fourth wiring layer is arranged on the other of the two main surfaces of the printed wiring board. Of course, the two printed wiring boards constituting the rotor 1 and the stator 2 do not need to have the same structure.

[0041] The rotor 1 holds a conductor 10 to be detected. More specifically, the conductor 10 to be detected is formed on a wiring layer (first wiring layer) on a main surface 1a of a printed wiring board that constitutes the rotor 1, the main surface 1a facing the stator 2. The rotor 1 also holds a magnet M to be detected. More specifically, the magnet M to be detected is fixed to a main surface 1b of the printed wiring board that constitutes the rotor 1, the main surface 1b being on the opposite side to the stator 2. The magnet M to be detected is magnetized (magnetized), for example, in an axial direction A that is parallel to the rotation axis 3.

[0042] In the illustrated example, the detection target magnet M is a plurality of (specifically, two) individual magnets M1, M2, ... arranged at intervals (typically equal intervals) on a circumference 150 centered on the rotation axis 3. The plurality of magnets are fixed to the rotor 1 so that magnetic poles of different polarities are arranged alternately in the circumferential direction. That is, in the illustrated example, the two individual magnets M1, M2 arranged at a phase of 180 degrees around the rotation axis 3 have their magnetic pole directions determined so that their magnetic poles of different polarities face the stator 2. When the rotor 1 rotates around the rotation axis 3, the detection target magnet M (individual magnets M1, M2, ...) moves through a circumferential orbit along the circumference 151. The individual magnets M1, M2, ... may be neodymium magnets, and their surfaces may be nickel-plated.

[0043] 3A is a plan view of the stator 2 seen from the opposite side of the rotor 1 along the rotation axis 3, and FIG. 3B is a bottom view of the stator 2 seen from the rotor 1 side along the rotation axis 3. FIG.

[0044] The stator 2 holds magnetic sensors 61 and 62 that detect the magnetic field generated by the target magnet M. The magnetic detection unit 6 includes the magnetic sensors 61 and 62 and the target magnet M. In this embodiment, the stator 2 holds the first magnetic sensor 61 and the second magnetic sensor 62.

[0045] The first magnetic sensor 61 is, for example, a power generating sensor. The power generating sensor includes a magnetic wire FE that exhibits the large Barkhausen effect and a winding SP wound around the magnetic wire FE. The magnetic wire FE is also called a pulse wire or a Wiegand wire, and the power generating sensor is also called a Wiegand sensor. The power generating sensor generates a pulse voltage from the winding SP when the magnetization direction of the magnetic wire FE is reversed due to a change in the magnetic field. The power generating sensor constituting the first magnetic sensor 61 is arranged on a circumference 151 having a center on the rotation axis 3, with the axial direction of the magnetic wire FE oriented parallel to a tangent to the circumference (more specifically, at the tangent point).

[0046] Typically, the circumference 151 overlaps with the circumferential orbit (circumference 150) of the magnet M to be detected when viewed in the axial direction A. Therefore, the circumferential orbit (circumference 150) of the magnet M to be detected faces the first magnetic sensor 61 (power generation sensor) in the axial direction A at the position closest to the first magnetic sensor 61 (power generation sensor). When the magnet M to be detected passes along the circumferential orbit (circumference 150), the large Barkhausen effect occurs, causing the first magnetic sensor 61 to generate a pulse voltage.

[0047] The second magnetic sensor 62 may be, for example, a Hall element or a magnetic resistance element. The second magnetic sensor 62 is also disposed so as to face the circumferential orbit (circumference 150) of the detection target magnet M in the axial direction A.

[0048] The first magnetic sensor 61 and the second magnetic sensor 62 may be mounted, for example, on the main surface 2a of the printed wiring board constituting the stator 2 opposite the rotor 1, and joined to a first wiring layer formed on this main surface 2a.

[0049] The stator 2 further includes a signal processing circuit 8 that processes signals for the induction detection unit 5 and the magnetic detection unit 6. More specifically, the signal processing circuit 8 is mounted on a main surface 2a of the printed wiring board constituting the stator 2 opposite to the rotor 1, i.e., on the main surface 2a on which the first magnetic sensor 61 and the second magnetic sensor 62 are mounted. The signal processing circuit 8 is, for example, joined to and electrically connected to the first wiring layer of the printed wiring board.

[0050] A receiving coil 20 is held on the stator 2 so as to face the conductor 10 to be detected which is held by the rotor 1. More specifically, the receiving coil 20 is formed by a fourth wiring layer formed on the main surface 2b of the printed wiring board constituting the stator 2 which faces the rotor 1, and a third wiring layer which is the wiring layer adjacent to the fourth wiring layer. The receiving coil 20 is arranged in an annular region 30 (a circular annular region in this example; see FIG. 3A) centered on the rotation axis 3 when viewed in the axial direction A.

[0051] The stator 2 also holds an excitation coil 40 that generates a magnetic field for inducing a voltage in the receiving coil 20. In this example, the excitation coil 40 is arranged in a ring shape (in this example, a circular ring shape) so as to surround the receiving coil 20. The excitation coil 40 is formed by a wiring layer of a printed wiring board that forms the stator 2. The wiring layer that forms the excitation coil 40 may include the same wiring layer as the receiving coil 20, or may include a different wiring layer.

[0052] By passing an alternating current through the excitation coil 40, an alternating magnetic field is generated in the axial direction A in the space surrounded by the excitation coil 40. This alternating magnetic field induces a voltage in the receiving coil 20. The alternating magnetic field is affected by the conductor 10 to be detected formed on the rotor 1. As a result, the voltage induced in the receiving coil 20 changes.

[0053] The induction detection unit 5 includes a conductor 10 to be detected, a receiving coil 20, and an exciting coil 40. The gap 7 between the rotor 1 and the stator 2 is, for example, 0.5 mm, in which case the distance between the conductor 10 to be detected and the receiving coil 20 is approximately 0.5 mm. If the thickness of the printed wiring board that makes up the rotor 1 is 1.6 mm, the distance from the receiving coil 20 to the magnet M to be detected is approximately 2.1 mm.

[0054] The magnet to be detected M that constitutes the magnetic detection unit 6 is held by the rotor 1 and arranged so that, when viewed in the axial direction A, it at least partially, and in this embodiment, entirely, overlaps the annular region 30 in which the receiving coil 20 is arranged. Therefore, when the magnet to be detected M rotates together with the rotor 1, when viewed in the axial direction A, the magnet to be detected M rotates around the rotation axis 3 within the annular region 30 in which the receiving coil 20 is arranged. Furthermore, the first magnetic sensor 61 and the second magnetic sensor 62 are held by the stator 2 and arranged so that, when viewed in the axial direction A, it at least partially, and in this embodiment, entirely overlaps the annular region 30 in which the receiving coil 20 is arranged.

[0055] In this way, the detection area of ​​the induction detection unit 5 and the detection area of ​​the magnetic detection unit 6 overlap in the axial direction A, so that the size of the rotation detection device 100, particularly the size in the radial direction, can be reduced.

[0056] 4A and 4B are diagrams illustrating an example configuration of the receiver coil 20. The receiver coil 20 is configured with copper foil patterns that form the third and fourth wiring layers of the multilayer printed wiring board that forms the stator 2. In this embodiment, the receiver coil 20 includes an A-phase receiver coil 20A and a B-phase receiver coil 20B that are shifted by a quarter period around the rotation axis 3.

[0057] The A-phase receiver coil 20A shown in FIG. 4A includes a first coil portion 23 (shown by a solid line) formed in the fourth wiring layer, and a second coil portion 24 (shown by a dashed line) formed in the third wiring layer.

[0058] First coil portion 23 makes one revolution from start point 25 along one circumferential direction around rotation axis 3 (clockwise in FIG. 4A ), and has a periodic waveform pattern in which recesses and protrusions repeatedly appear so that the distance from rotation axis 3 changes over four periods. First coil portion 23 is connected to one end of second coil portion 24 of the third wiring layer at turn-back point 26 near start point 25. Second coil portion 24 makes one revolution from turn-back point 26 along the other circumferential direction around rotation axis 3 (counterclockwise in FIG. 4A ), and has a periodic waveform pattern in which recesses and protrusions repeatedly appear so that the distance from rotation axis 3 changes over four periods, and terminates at end point 27 near start point 25.

[0059] The waveform patterns of the first coil portion 23 and the second coil portion 24 are shifted by half a period around the rotation axis 3, so that the concave / convex portions of the first coil portion 23 and the convex / concave portions of the second coil portion 24 are positioned at angular positions that match each other. As a result, the loops formed by the concave / convex portions of the first coil portion 23 and the convex / concave portions of the second coil portion 24 each constitute one turn of a coil portion 28, resulting in a total of eight coil portions 28. These eight coil portions 28 are coils with different winding directions that are alternately arranged in order along the circumferential direction. Therefore, the A-phase receiver coil 20A has a configuration in which eight coil portions 28 with different winding directions that are alternately connected in series.

[0060] The B-phase receiver coil 20B shown in Fig. 4B has a substantially similar configuration, and the same reference numerals as those in Fig. 4A are used for the components in Fig. 4B. However, as explained above, the A-phase coil and the B-phase coil are arranged with a 1 / 4 period offset around the axis of rotation 3.

[0061] When the rotor 1 rotates around the rotation axis 3, the relative positions of the conductor 10 to be detected on the rotor 1 and the receiving coil 20 on the stator 2 change, and the voltage induced in the receiving coil 20 changes accordingly. Therefore, information about the rotational position of the rotor 1 can be obtained based on the voltage induced in the receiving coil 20. Furthermore, when the rotor 1 rotates around the rotation axis 3, the relative positions of the magnet M to be detected held on the rotor 1 and the magnetic sensors 61, 62 held on the stator 2 change, and the magnetic fields detected by the magnetic sensors 61, 62 change accordingly. Therefore, information about the rotational position of the rotor 1 can be obtained based on the output signals of the magnetic sensors 61, 62.

[0062] As shown in FIG. 12 , the signal processing circuit 8 includes a first signal processing unit 81 (induction detection processing unit) that performs signal processing related to the induction detection unit 5 and a second signal processing unit 82 (magnetic detection processing unit) that performs signal processing related to the magnetic detection unit 6. The first signal processing unit 81 performs a first rotational position calculation process that calculates first rotational position information representing the rotational position of the rotor 1 by supplying an AC current to the excitation coil 40 and detecting and processing the voltage induced in the receiving coil 20. The second signal processing unit 82 performs a second rotational position calculation process that calculates second rotational position information representing the rotational position of the rotor 1 based on output signals from the magnetic sensors 61 and 62. The signal processing circuit 8 further includes a calculation processing unit 83 that uses one or both of the first rotational position information and the second rotational position information to determine and output rotational position information representing the rotational position of the rotor 1. For example, the first rotational position information may be precise angle information representing a precise (high-resolution) rotation angle within one rotation of the rotor 1 around the rotation axis 3. The second rotational position information may also be rotation number information that indicates the number of rotations of the rotor 1 around the rotation axis 3. In this case, the arithmetic processing unit 83 may use the induction detection unit 5 as a precision angle detector and utilize the magnetic detection unit 6 for period discrimination to expand the detection range of the induction detection unit 5 to obtain the angle information.

[0063] Next, we will consider the mutual influence of the induction detection unit 5 and the magnetic detection unit 6, particularly the influence caused by their detection areas overlapping in the axial direction A. First, we will explain the influence on the magnetic detection unit 6, and then we will explain the influence on the induction detection unit 5.

[0064] The magnetic detection unit 6 includes a magnet M to be detected and magnetic sensors 61 and 62, with a printed wiring board constituting the rotor 1 and a printed wiring board constituting the stator 2 interposed between them. The printed wiring board is constructed by alternately laminating insulating layers made of glass epoxy resin, phenolic resin, or the like and wiring layers made of copper foil patterns, or the like. Both the insulating layers and the wiring layers are made of non-magnetic materials and do not affect the magnetic field. Therefore, the rotor 1 and the stator 2 do not affect the magnetic detection unit 6.

[0065] An alternating magnetic field is generated by passing an alternating current through the excitation coil 40 of the induction detection unit 5. However, since the generated alternating magnetic field is weaker than the magnetic field generated by the target magnet M of the magnetic detection unit 6, it has almost no effect on the detection by the magnetic detection unit 6. Furthermore, while the excitation frequency of the excitation coil 40 of the induction detection unit 5 is a high frequency of, for example, about 3 MHz, the signal frequency detected by the magnetic detection unit 6 is a low frequency of less than 1 kHz. Therefore, if necessary, the influence of the high-frequency alternating magnetic field generated by the excitation coil 40 can be eliminated by separating and removing the high-frequency components using a low-pass filter or the like.

[0066] Furthermore, as described above, when the induction detection unit 5 is used as a high-precision angle detector and the magnetic detection unit 6 is used for period discrimination to expand the detection range of the induction detection unit 5, the detection precision of the magnetic detection unit 6 does not affect the precision of the final rotational position information. Therefore, the fact that the magnetic detection unit 6 is slightly affected by the induction detection unit 5 does not actually pose a problem.

[0067] In this way, the influence on the magnetic detection unit 6 caused by the detection areas of the induction detection unit 5 and the magnetic detection unit 6 overlapping in the axial direction A is hardly a problem.

[0068] Meanwhile, induction detection unit 5 detects the voltage induced by changes in the magnetic field. More specifically, it extracts and detects from the output signal of receiving coil 20 the component that changes with the excitation frequency (carrier frequency) when exciting coil 40. As mentioned above, the excitation frequency is a high frequency of about 3 MHz, whereas the magnetic field generated by magnet M, the object of detection, of magnetic detection unit 6 does not change when rotor 1 is stopped, and is a low frequency of less than 1 kHz even when rotor 1 is rotating. Therefore, there is no influence of the magnetic field generated by magnet M, the object of detection, of magnetic detection unit 6.

[0069] Furthermore, both the excitation coil 40 and the receiving coil 20 of the induction detection unit 5 are coreless air-core coils. When a magnetic material is used for the core of a coil, characteristics may change due to magnetic saturation of the magnetic material caused by an external magnetic field, but in this embodiment, such characteristics do not change. From this perspective, too, there is no effect on the induction detection unit 5 from the target magnet M to be detected.

[0070] If the magnet M to be detected is a conductor, eddy currents will be induced by the alternating magnetic field generated by the excitation coil 40, and these eddy currents will weaken the magnetic field that interlinks with the receiving coil 20, which may affect detection by the induction detection unit 5. For example, neodymium magnets are conductors, and the nickel plated on their surfaces is also a conductor. Therefore, if the magnet M to be detected is a conductor, some ingenuity may be required to reduce this effect.

[0071] 5 to 7 show examples of the arrangement of the magnet M to be detected when the conductor 10 to be detected is composed of a screen-shaped conductor S. The screen-shaped conductor S is a conductor that spreads out in a planar shape. When the rotor 1 is viewed in the axial direction A, the area where the screen-shaped conductor S is arranged constitutes a conductor portion, and the area where the screen-shaped conductor S is not arranged constitutes a non-conductor portion. The screen-shaped conductor S is formed on the rotor 1 in a pattern in which the ratio of conductor portions to non-conductor portions that overlap with each of the multiple coil portions 28 (eight coil portions 28 in the example of FIGS. 4A and 4B) of the receiving coil 20 changes periodically as the rotor 1 rotates around the rotation axis 3.

[0072] In the examples of Figures 5 to 7, multiple screen-shaped conductors S (four in this example) are arranged at intervals (equally spaced in this example) around the rotation axis 3. In this example, the shapes of the multiple screen-shaped conductors S are substantially congruent and are sectors with a portion cut out near the central angle. The central angle of the sector is approximately 45 degrees, and adjacent screen-shaped conductors S are spaced at an angular interval of approximately 45 degrees around the rotation axis 3. The multiple screen-shaped conductors S are arranged so as to be rotationally symmetric (four-fold symmetry in the example shown) around the rotation axis 3.

[0073] 5 and 7, the magnet M to be detected is a plurality of (two in this example) individual magnets M1, M2, ..., and in the example of FIG. 6, it is a single ring magnet Mr that is ring-shaped (specifically, annular) and centered on the rotation axis 3. The ring magnet Mr is magnetized (magnetized) in the axial direction A, and is a multi-pole magnetized magnet (for example, a four-pole magnetized magnet) that is magnetized so that north and south poles are alternately arranged in the circumferential direction along the circumference 150 when viewed from the axial direction A. When the rotor 1 rotates around the rotation axis 3, the magnetic poles of the ring magnet Mr move on a circular orbit along the circumference 150.

[0074] 5 and 6, the magnet M to be detected is held in the rotor 1 in a position where a portion of the magnet M protrudes from the screen-shaped conductor S when viewed in the axial direction A. The example in FIG. 7 shows an arrangement in which the entire magnet M to be detected overlaps with the screen-shaped conductor S.

[0075] The alternating magnetic field generated by the excitation coil 40 induces eddy currents in the screen-like conductor S. These eddy currents generate a magnetic field in a direction that weakens the alternating magnetic field, thereby weakening the voltage induced in the opposing coil portion 28 of the receiving coil 20 (see FIGS. 4A and 4B).

[0076] When the target magnet M is a conductor, eddy currents are similarly induced on the surface of the target magnet M facing the receiving coil 20, and the magnetic field generated by these eddy currents weakens the voltage induced in the coil portion 28 of the opposing receiving coil 20.

[0077] The screen-shaped conductor S, which is the detection target of the induction detection unit 5, and the conductor of the detection target magnet M, which is not the detection target of the induction detection unit 5, function in a similar manner, so it is difficult to use signal processing to remove noise components caused by eddy currents on the surface of the detection target magnet M. Although the detection target magnet M is farther from the receiving coil 20 than the screen-shaped conductor S, it may affect the voltage induced in the receiving coil 20, and therefore may affect the accuracy of rotation detection by the induction detection unit 5.

[0078] Magnetic force is inversely proportional to the square of the distance. The distance between the receiving coil 20 and the conductor 10 to be detected is approximately equal to the distance between the rotor 1 and the stator 2, for example, about 0.5 mm. Adding to this the thickness of the printed wiring board that makes up the rotor 1, for example, 1.6 mm, the distance between the receiving coil 20 and the surface of the magnet M to be detected is, for example, about 2.1 mm. The influence of eddy currents flowing on the surface of the magnet M to be detected, which is located relatively far from the receiving coil 20, is smaller than the influence of eddy currents flowing in the screen-shaped conductor S, which is located relatively close to the receiving coil 20.

[0079] Therefore, in the structure of this embodiment, even if there is some decrease in accuracy due to the influence of eddy currents on the surface of the magnet M to be detected, the induction detection unit 5 can detect the position of the screen-shaped conductor S with sufficient accuracy.

[0080] The effect can be further reduced by increasing the thickness of the printed wiring board that constitutes the rotor 1 and further moving the target magnet M. However, since the distance between the magnetic sensors 61, 62 and the target magnet M becomes longer, it is preferable to consider the trade-off with the detection accuracy of the magnetic detection unit 6.

[0081] Among the arrangement examples shown in FIGS. 5, 6 and 7, the arrangements shown in FIGS. 6 and 7 are relatively preferable.

[0082] In the arrangement examples of Figures 5 and 6, the target magnet M partially overlaps the screen-shaped conductor S, and a portion of the target magnet M faces the receiving coil 20 without the screen-shaped conductor S in between. In the arrangement example of Figure 6, the magnetic field caused by eddy currents induced on the surface of the ring magnet Mr slightly reduces the voltage induced in the receiving coil 20, but since the effect is uniform over the entire circumference around the rotation axis 3, it does not result in a decrease in detection accuracy. On the other hand, in the arrangement example of Figure 5, the effect of the target magnet M is not uniform over the entire circumference, which is disadvantageous compared to the arrangement example of Figure 6. The ring magnet Mr is also effective when the target conductor 10 is configured with a ring-shaped coil pattern C (see Figure 8), which will be described later.

[0083] In the arrangement example of FIG. 7, the entire magnet M to be detected overlaps the screen-shaped conductor S, and as viewed from the receiving coil 20, the entire magnet M to be detected is located behind the screen-shaped conductor S. The shielding effect of the screen-shaped conductor S shields the magnetic field induced by the excitation coil 40, significantly reducing the magnetic flux reaching the magnet M to be detected, and accordingly reducing the eddy currents induced on the surface of the magnet M to be detected. In addition, the magnetic field generated by the eddy currents on the surface of the magnet M to be detected is also shielded by the screen-shaped conductor S, making it difficult for it to reach the receiving coil 20. Therefore, the impact of the magnet M to be detected on the detection accuracy of the induction detection unit 5 can be reduced.

[0084] FIG. 8 shows an example of a circular coil pattern C, which is another example of the conductor 10 to be detected.

[0085] The annular coil pattern C is formed in a ring shape along a circumference 13 whose center is on the rotation axis 3, and is a periodic uneven pattern having radial unevenness with respect to the circumference 13. The annular coil pattern C is an endless pattern made up of a linear conductor pattern. In other words, the annular coil pattern C is a linear conductor pattern whose distance from the rotation axis 3 changes periodically depending on the circumferential position.

[0086] The annular coil pattern C is configured by alternately arranging convex portions 11 that protrude radially (away from the rotation axis 3) and concave portions 12 that are recessed radially (toward the rotation axis 3) in the circumferential direction around the rotation axis 3. In the example of FIG. 8, the annular coil pattern C has a plurality of (specifically, four) convex portions 11 and a plurality of (specifically, four) concave portions 12, and is formed to be rotationally symmetric (four-fold symmetric in the illustrated example) around the rotation axis 3. In this example, the four convex portions 11 and the four concave portions 12 are each formed in an angular range of 45 degrees around the rotation axis 3.

[0087] The annular coil pattern C has four outer arc portions 16 formed along an outer circumference 14 having a center on the rotation axis 3, four inner arc portions 17 formed along an inner circumference 15 having a center on the rotation axis 3, and eight straight portions 18 formed to connect the ends of the outer arc portions 16 to the inner arc portions 17. In the illustrated example, the straight portions 18 extend along the radial direction, but may be inclined relative to the radial direction. The outer arc portion 16 and the two straight portions 18 connected to both ends thereof form a convex portion 11, and the inner arc portion 17 and the two straight portions 18 connected to both ends thereof form a concave portion 12.

[0088] When an induced current i (FIG. 8 shows an induced current flowing clockwise around the rotation axis 3) flows in the annular coil pattern C due to the alternating magnetic field generated by the excitation coil 40, this induced current i generates a magnetic field B in the convex portions 11 and the concave portions 12 in a direction parallel to the rotation axis 3. The direction of the magnetic field B is opposite in the convex portions 11 and the concave portions 12 (one direction and the other direction parallel to the rotation axis 3), and the convex portions 11 and the concave portions 12 form a positive magnetic flux region B+ and a negative magnetic flux region B-. The relationship between the convex portions 11 and the concave portions 12 and the positive and negative magnetic flux regions B+, B- reverses depending on the direction of the induced current i. Therefore, one of the convex portions 11 and the concave portions 12 strengthens the magnetic field generated by the excitation coil 40, and the other of them weakens the magnetic field generated by the excitation coil 40.

[0089] As the annular coil pattern C rotates around the rotation axis 3 together with the rotor 1, the opposing area ratio between the positive magnetic flux region B+ and the negative magnetic flux region B- for each coil portion 28 of the receiving coil 20 (see Figures 4A and 4B) changes, and accordingly, a voltage corresponding to the rotational position of the rotor 1 is induced in the receiving coil 20.

[0090] The annular coil pattern C, whose shape changes periodically with the distance from the axis of rotation 3 depending on the circumferential position around the axis of rotation 3, has an inner region and an outer region with respect to the circumference 13. The change in distance from the axis of rotation 3 may be gradual. However, a pattern in which the two distances (the distance to the outer arc portion 16 and the distance to the inner arc portion 17) change sharply, as shown in Figure 8, can increase the change in area of ​​the positive magnetic flux region B+ and the negative magnetic flux region B- that face the coil portion 28 of the receiver coil 20 (see Figures 4A and 4B), thereby increasing the signal voltage.

[0091] While the screen-shaped conductor S prevents magnetic flux changes due to eddy currents and acts only in a direction that reduces the voltage induced in the receiving coil 20, the annular coil pattern C generates magnetic flux in both positive and negative directions, which can act on the receiving coil 20. This allows the signal voltage output from the receiving coil 20 to be increased, thereby relatively reducing the influence of the magnet M to be detected. Therefore, by using the annular coil pattern C as the conductor 10 to be detected, the influence of the magnet M to be detected can be reduced compared to when the screen-shaped conductor S is used.

[0092] 9 to 11 show examples of arrangements of the magnet M to be detected when the conductor 10 to be detected is configured with an annular coil pattern C. In all of the examples of arrangements, when viewed from the axial direction A, the magnet M to be detected is entirely arranged within the annular region in which the annular coil pattern C is formed (the annular region defined by the outer circumference 14 and the inner circumference 15 in FIG. 8).

[0093] 9, the magnet M to be detected includes a plurality of individual magnets M1, M2, ... (two in this example) that are arranged at intervals in the circumferential direction around the rotation axis 3. In this example, the individual magnets M1, M2, ... are cylindrical (columnar) magnets, and the magnetization direction (magnetization direction) is parallel to the rotation axis 3.

[0094] When viewed in the axial direction A, each individual magnet M1, M2, ... has a shape that is line-symmetrical with respect to a radius extending from the rotation axis 3 so as to pass through the circumferential center position. The circumferential center position 161 of each individual magnet M1, M2, ... is aligned (coincides) with the circumferential position of the midpoint (the midpoint of the straight portion 18) between the circumferentially adjacent convex portions 11 and concave portions 12 of the concave-convex pattern of the annular coil pattern C. In other words, the center position of the transition point of the annular coil's distance from the rotation axis 3 is aligned (coincides) with the circumferential center position 161 of the magnet M to be detected. As a result, each individual magnet M1, M2, ... is arranged so that the positive magnetic flux region and the negative magnetic flux region face each other (overlap) with equal areas, regardless of the circumferential width. Therefore, the individual magnets M1, M2, ... equally affect the positive magnetic flux and the negative magnetic flux, and therefore have little effect on the detection accuracy of the induction detection unit 5.

[0095] 10, the magnet M to be detected includes a plurality of individual magnets M1, M2, ... (two in this example) arranged at intervals in the circumferential direction around the rotation axis 3. In this example, the individual magnets M1, M2, ... are arc-shaped with their center on the rotation axis 3. The multiple individual magnets M1, M2, ... are arranged along a circumference 150 whose center is on the rotation axis 3, and are arc-shaped along the circumference 150. When viewed in the axial direction A, the circumferences 13 and 150 may substantially overlap each other.

[0096] When viewed in the axial direction A, each individual magnet M1, M2, ... has a shape that is line-symmetrical with respect to a radius extending from the rotation axis 3 so as to pass through the circumferential center position 162. The circumferential width 163 (angular width or length on the circumference 13,150) of each individual magnet M1, M2, ... is a natural number multiple of the periodic width 164 (angular width or length on the circumference 13,150) of the concave-convex pattern of the annular coil pattern C.

[0097] In the illustrated example, the circumferential width 163 of the individual magnets M1, M2, ... is one time the periodic width 164 of the concave-convex pattern of the annular coil pattern C. However, for example, the circumferential width 163 of the individual magnets M1, M2, ... may remain the same, and the number of periods within one rotation of the concave-convex pattern of the annular coil pattern C may be doubled, tripled, ..., etc., so that the circumferential width 163 of the individual magnets M1, M2, ... is two, three, ..., etc. times the periodic width 164 of the concave-convex pattern. With this arrangement, the individual magnets M1, M2, ... face (overlap) the positive magnetic flux region and the negative magnetic flux region with equal areas, regardless of their circumferential arrangement. Therefore, they affect the positive magnetic flux and the negative magnetic flux equally, and therefore have little effect on the detection accuracy of the induction detection unit 5.

[0098] 11, the magnet M to be detected includes an even number (two in the illustrated example) of individual magnets M1, M2, ... arranged at equal intervals along a circumference 150 having a center on the rotation axis 3. The periodic number of the concave-convex pattern of the annular coil pattern C (the number of periods within one rotation) is an odd number (three in the illustrated example).

[0099] In this case, the two individual magnets M1, M2, which are arranged on opposite sides of the rotation axis 3 (positions with a phase difference of 180 degrees), are arranged in opposite phase relative to the concave-convex pattern of the annular coil pattern C. Therefore, the area facing the positive magnetic flux region and the area facing the negative magnetic flux region are equal across the multiple individual magnets M1, M2, .... Therefore, the individual magnets M1, M2, ... affect the positive magnetic flux and the negative magnetic flux equally, and therefore have little effect on the detection accuracy of the induction detection unit 5.

[0100] As described above, the arrangement in which the ring magnet Mr (see FIG. 6) is combined with the annular coil pattern C also has little effect on the detection accuracy of the induction detection unit 5.

[0101] Figures 13, 14A, and 14B are diagrams for explaining the configuration of a rotation detector 101 according to another embodiment of the present invention, with Figure 13 being a cross-sectional view similar to Figure 2, Figure 14A being a bottom view of stator 2, and Figure 14B being a plan view of rotor 1. In Figures 13, 14A, and 14B, parts corresponding to those shown in Figures 1 to 3B are designated by the same reference numerals. Figures 4A to 12 will also be referenced as necessary.

[0102] This rotation detection device 101 includes a rotor 1 as a first support that rotates about a rotation axis 3, and a stator 2 as a second support that faces the rotor 1 across a gap 7 in an axial direction A that is parallel to the rotation axis 3, and is equipped with an induction detection unit 5 and a magnetic detection unit 6. Both the induction detection unit 5 and the magnetic detection unit 6 detect rotation information about the rotor 1 about the rotation axis 3. In this embodiment, the induction detection unit 5 is a precision absolute angle detector that detects a precise absolute angle within one rotation of the rotor 1 about the rotation axis 3. The magnetic detection unit 6 is a multi-rotation detector that detects multi-rotation information corresponding to the number of rotations of the rotor 1 about the rotation axis 3.

[0103] The stator 2 is configured with a printed wiring board, more specifically, a four-layer printed wiring board. A first magnetic sensor 61 and a second magnetic sensor 62 are mounted on the surface of the printed wiring board that configures the stator 2 opposite the rotor 1, and detect the magnetic field generated by the target magnet M. The first magnetic sensor 61 is, for example, a power generation sensor. The second magnetic sensor 62 is, for example, a Hall element or a magnetic resistance element, and detects the magnetic field in the axial direction A parallel to the rotation axis 3. The first magnetic sensor 61 (power generation sensor) and the second magnetic sensor 62 are joined (for example, soldered) to a copper foil pattern that configures the first wiring layer located on the opposite side of the printed wiring board that configures the stator 2 from the rotor 1. The configuration and arrangement of the first magnetic sensor 61 and the second magnetic sensor 62 are the same as those in the above-described embodiment.

[0104] The stator 2 further includes a signal processing circuit 8 that processes signals for the induction detection unit 5 and the magnetic detection unit 6. More specifically, the signal processing circuit 8 is mounted on a main surface 2a of the printed wiring board constituting the stator 2 opposite to the rotor 1, i.e., on the main surface 2a on which the first magnetic sensor 61 and the second magnetic sensor 62 are mounted. The signal processing circuit 8 is, for example, joined to and electrically connected to the first wiring layer of the printed wiring board.

[0105] An excitation coil 40 is formed on the printed wiring board that constitutes the stator 2. Specifically, the excitation coil 40 is formed by a copper foil pattern on the wiring layer on the surface of the printed wiring board that faces the rotor 1, i.e., the fourth wiring layer. As shown in FIG. 14A , the excitation coil 40 has an outer circumference excitation coil 41 and an inner circumference excitation coil 42 that are concentric and centered on the rotation axis 3, and are connected in series in opposite directions, and an AC voltage is applied to both ends 43, 44 of the series circuit of the outer circumference excitation coil 41 and the inner circumference excitation coil 42. In the illustrated example, the outer circumference excitation coil 41 and the inner circumference excitation coil 42 are each a one-turn coil, but the number of turns may be multiple.

[0106] When a clockwise (right-handed) current flows through the outer-circumference excitation coil 41 on the paper surface of Fig. 14A, a counterclockwise (left-handed) current flows through the inner-circumference excitation coil 42, and a magnetic flux is generated in the annular region sandwiched between the two coils toward the back of the paper surface of Fig. 14A. When a counterclockwise (left-handed) current flows through the outer-circumference excitation coil 41 on the paper surface of Fig. 14A, a clockwise (right-handed) current flows through the inner-circumference excitation coil 42, and a magnetic flux is generated in the annular region sandwiched between the two coils toward the front of the paper surface of Fig. 14A.

[0107] Two sets of receiver coils, namely, outer receiver coil 21 and inner receiver coil 22, are arranged in an annular region sandwiched between outer excitation coil 41 and inner excitation coil 42. The outer receiver coil 21 and inner receiver coil 22 are formed in two concentric annular regions, namely, outer receiver coil region 31 and inner receiver coil region 32, which are centered on rotation axis 3. The outer receiver coil 21 and inner receiver coil 22 are formed by a fourth wiring layer (copper foil pattern) formed on main surface 2b facing rotor 1 of the printed wiring board constituting stator 2, and a third wiring layer (copper foil pattern) which is the wiring layer adjacent to this fourth wiring layer.

[0108] The outer receiving coil 21 and the inner receiving coil 22 are each configured with a pair of an A-phase receiving coil and a B-phase receiving coil, similar to the receiving coil 20 in Figures 4A and 4B. However, the number of periods differs from the examples in Figures 4A and 4B; for example, the outer receiving coil 21 is configured with a waveform pattern that changes 16 periods per revolution, and the inner receiving coil 22 is configured with a waveform pattern that changes 15 periods per revolution.

[0109] The printed wiring board constituting the rotor 1 holds a conductor 10 to be detected on its main surface 1a facing the stator 2, and a magnet M to be detected on its main surface 1b opposite the stator 2. The conductor 10 to be detected is composed of annular coil patterns C1 and C2. More specifically, two annular coil patterns, namely, an outer annular coil pattern C1 and an inner annular coil pattern C2, are arranged concentrically with their centers on the axis of rotation 3. These two annular coil patterns C1 and C2 are composed of a wiring layer (copper foil pattern) formed on the surface of the printed wiring board facing the rotor 1. Because no coil patterns are provided on the side of the rotor 1 opposite the stator 2, a single-sided printed wiring board will suffice as the printed wiring board constituting the rotor 1, although a multilayer printed wiring board or a double-sided printed wiring board may also be used.

[0110] The outer annular coil pattern C1 is arranged to overlap the outer receiver coil area 31, i.e., the outer receiver coil 21, when viewed in the axial direction A. Similarly, the inner annular coil pattern C2 is arranged to overlap the inner receiver coil area 32, i.e., the inner receiver coil 22, when viewed in the axial direction A.

[0111] The annular coil patterns C1 and C2 are configured with linear conductor patterns of a waveform (in this example, a rectangular waveform) in which the distance from the rotation axis 3 changes periodically depending on the circumferential position, as in the case of Fig. 8. However, the number of periods differs from the example of Fig. 8; for example, the outer annular coil pattern C1 is configured with a waveform (rectangular waveform) pattern that changes 16 periods per revolution, and the inner annular coil pattern C2 is configured with a waveform (rectangular waveform) pattern that changes 15 periods per revolution.

[0112] In this embodiment, the detection target magnet M is individual magnets M1, M2, ... in a sector shape (more precisely, a sector shape with a portion near the central angle removed, i.e., an arc shape). The magnetization direction of the individual magnets M1, M2, ... is parallel to the rotation axis 3. A plurality of (more specifically, four) individual magnets M1, M2, M3, M4 are arranged at intervals in the circumferential direction around the rotation axis 3. That is, the four individual magnets M1, M2, M3, M4 are arranged at angular intervals of 90 degrees around the rotation axis 3, in other words, at equal intervals on a circumference 150 having a center on the rotation axis 3. The four individual magnets M1, M2, M3, M4 are fixed to the rotor 1 such that the magnetic poles facing the stator 2 are arranged in a circumferential direction such that N poles and S poles alternate. As a result, an alternating magnetic field with two periods is generated per rotation, and this alternating magnetic field is detected by the first magnetic sensor 61 and the second magnetic sensor 62.

[0113] The first magnetic sensor 61 and the second magnetic sensor 62 are fixed to the stator 2 at positions opposite in the axial direction A to the circumferential orbit (orbit along the circumference 150) along which the individual magnets M1, M2, ... pass when the rotor 1 rotates around the rotation axis 3.

[0114] The individual magnets M1, M2, ... are arranged so as to overlap the annular region 30, that is, the annular outer receiver coil region 31 and inner receiver coil region 32, respectively, when viewed in the axial direction A. In other words, when viewed in the axial direction A, the individual magnets M1, M2, ... overlap both the outer receiver coil region 31 and the inner receiver coil region 32. Therefore, when viewed in the axial direction A, the individual magnets M1, M2, ... are arranged so as to overlap the outer annular coil pattern C1 and the inner annular coil pattern C2.

[0115] The individual magnets M1, M2, . . . are arranged in the same manner as in FIG. 9 relative to the outer circumferential annular coil pattern C1, and are arranged in the same manner as in FIG. 10 relative to the inner circumferential annular coil pattern C2.

[0116] That is, the multiple individual magnets M1, M2, ... are arranged along a circumference whose center is on the rotation axis 3. When viewed in the axial direction A, each individual magnet M1, M2, ... has a shape that is line-symmetrical with respect to a radius extending from the rotation axis 3 so as to pass through the circumferential center position. The circumferential center position 161 of the individual magnets M1, M2, ... coincides with the circumferential position of the radius switching position of the outer annular coil pattern C1. Therefore, when viewed in the axial direction A, the areas of the individual magnets M1, M2, ... that overlap with the positive magnetic flux region of the outer annular coil pattern C1 are equal to the areas of the areas that overlap with the negative magnetic flux region. Therefore, the individual magnets M1, M2, ... equally affect the positive magnetic flux and the negative magnetic flux, and therefore have little impact on the detection accuracy based on the output signal of the outer peripheral receiving coil 21.

[0117] On the other hand, the circumferential width 163 of the individual magnets M1, M2, ... is a natural number multiple of the periodic width 164 of the concave-convex pattern of the inner annular coil pattern C2, and in the illustrated example, is equal to the periodic width 164 of the concave-convex pattern of the inner annular coil pattern C2. Therefore, the individual magnets M1, M2, ... face the positive magnetic flux region and the negative magnetic flux region of the inner annular coil pattern C2 with an area equal to that of the positive magnetic flux region and the negative magnetic flux region, regardless of their circumferential position. As a result, the individual magnets M1, M2, ... affect the positive magnetic flux and the negative magnetic flux equally, and therefore have little effect on the detection accuracy based on the output signal of the inner receiving coil 22.

[0118] In the illustrated example, the number of individual magnets M1, M2, ... is four, which is an even number, and the periodicity of the inner annular coil pattern C2 is 15, which is an odd number, resulting in the same arrangement as in FIG. 11. Therefore, the two individual magnets M1, M3 and M2, M4 located on opposite sides of the rotation axis 3 (positions with a phase difference of 180 degrees) are in opposite phase with respect to the inner annular coil pattern C2. Therefore, the total area of ​​all the individual magnets M1, M2, ... facing the positive magnetic flux region is equal to the total area of ​​all the individual magnets M1, M2, ... facing the negative magnetic flux region. Therefore, the multiple individual magnets M1, M2, ... equally affect the positive and negative magnetic flux, resulting in little impact on the detection accuracy based on the output signal of the inner receiving coil 22.

[0119] The individual magnets M1, M2, ... may be arranged relative to the outer circumferential annular coil pattern C1 in the same manner as in Fig. 10, and may be arranged relative to the inner circumferential annular coil pattern C2 in the same manner as in Fig. 9. In this case, the individual magnets M1, M2, ... may be arranged relative to the outer circumferential annular coil pattern C1 in the same manner as in Fig. 11.

[0120] When the rotor 1 rotates around the rotation axis 3, an angle signal with 16 periods per rotation is obtained from the outer receiving coil 21, and an angle signal with 15 periods per rotation is obtained from the inner receiving coil 22. Then, by appropriately processing the angle signals with 16 periods / rotation and the angle signals with 15 periods / rotation in the first signal processing unit 81 (induction detection processing unit) of the signal processing circuit 8, absolute angle information for one period / rotation can be obtained.

[0121] The power generation sensor constituting the first magnetic sensor 61 is disposed on the circumference 151 (more specifically, at the tangent point) with the axial length direction of the magnetic wire FE oriented parallel to a tangent line on the circumference 151 centered on the rotation axis 3. When the rotor 1 rotates around the rotation axis 3, the detection target magnet M moves along a circumferential orbit (orbit along the circumference 150) around the rotation axis 3. The circumferential orbit faces the first magnetic sensor 61 (power generation sensor) in the axial direction A at a position closest to the first magnetic sensor 61 (power generation sensor). When the individual magnets M1, M2, ... pass near the first magnetic sensor 61 along the circumferential orbit, the large Barkhausen effect occurs, causing the first magnetic sensor 61 to generate a pulse voltage. As the four individual magnets M1, M2, M3, and M4 rotate along the circumferential orbit, four pulse voltages are generated per rotation, for example.

[0122] When the rotor 1 rotates in the clockwise direction, a positive pulse voltage is generated when the N pole passes near the first magnetic sensor 61, and a negative pulse voltage is generated when the S pole passes near the first magnetic sensor 61. On the other hand, when the rotor 1 rotates in the counterclockwise direction, a negative pulse voltage is generated when the N pole passes near the first magnetic sensor 61, and a positive pulse voltage is generated when the S pole passes near the first magnetic sensor 61.

[0123] The second magnetic sensor 62 determines the polarity of a magnetic pole passing near the first magnetic sensor 61 (the polarity of the magnetic pole facing the first magnetic sensor 61) when the first magnetic sensor 61 generates a pulse voltage. Since the arrangement of the magnetic poles of the four individual magnets M1, M2, M3, and M4 is known in advance, if the second magnetic sensor 62 is positioned so that it faces the magnetic pole of one of the four individual magnets M1, M2, M3, and M4 when one individual magnet M1, M2, ... faces the first magnetic sensor 61, the polarity of the magnetic pole passing near the first magnetic sensor 61 can be determined. In the illustrated example, the second magnetic sensor 62 is positioned 180 degrees out of phase with the first magnetic sensor 61, and therefore the second magnetic sensor 62 detects a magnetic pole of the same polarity as the magnetic pole located near the first magnetic sensor 61.

[0124] As shown in FIG. 12, the signal processing circuit 8 includes a first signal processing unit 81 (induction detection processing unit) that performs signal processing related to the induction detection unit 5, and a second signal processing unit 82 (magnetic detection processing unit) that performs signal processing related to the magnetic detection unit 6. The first signal processing unit 81 performs a first rotational position calculation process to calculate first rotational position information representing the rotational position of the rotor 1 by supplying an AC current to the excitation coil 40 and detecting and processing the voltage induced in the receiving coils 21 and 22. The second signal processing unit 82 performs a second rotational position calculation process to calculate second rotational position information representing the rotational position of the rotor 1 based on the output signals of the magnetic sensors 61 and 62. The first rotational position information is precise absolute angle information within one rotation, i.e., one-rotation absolute angle information. The second rotational position information is multiple-rotation information corresponding to the number of rotations of the rotor 1 around the rotation axis 3, i.e., rotation number information. The signal processing circuit 8 further includes a calculation processing unit 83 that integrates the first rotational position information and the second rotational position information to calculate multi-rotation absolute angle information. In this way, the rotation detection device 101 of this embodiment constitutes an absolute angle detection device, more specifically, a multi-rotation absolute angle detection device.

[0125] For example, the second signal processing unit 82 (magnetic detection processing unit) of the signal processing circuit 8 determines the rotation direction of the rotor 1 based on the polarity of the pulse voltage generated by the first magnetic sensor 61 (power generation sensor) and the output signal of the second magnetic sensor 62 (Hall element or the like). Then, based on the result of the rotation direction determination, the amount of rotation is counted each time the first magnetic sensor 61 generates a pulse voltage. The count value is updated each time a pulse voltage is generated and stored in a non-volatile memory (not shown) provided in the second signal processing unit 82.

[0126] The second magnetic sensor 62 (Hall element) and the second signal processing unit 82 (magnetic detection processing unit) can operate using power supplied from an external power supply, and can also operate using power from the pulse voltage generated by the first magnetic sensor 61 (power generation sensor). Therefore, the counting operation based on the pulse voltage of the first magnetic sensor 61 continues even when the external power supply is cut off, and the updated count value is stored in non-volatile memory while the energy of the pulse voltage remains. In other words, the detection of rotation information by the magnetic detection unit 6 (multi-rotation detection unit) continues even when the power supply is cut off.

[0127] The first signal processing unit 81 (induction detection processing unit) and arithmetic processing unit 83 of the signal processing circuit 8 can detect rotation information only when external power is supplied. Therefore, when external power is supplied, the first signal processing unit 81 detects a precise absolute angle within one rotation based on the output signals of the two receiving coils 21, 22. This one-rotation precise absolute angle and the count value of the magnetic detection unit 6 (multi-rotation detection unit) are integrated by the arithmetic processing unit 83, thereby making it possible to determine a precise absolute angle over multiple rotations.

[0128] As described above, this embodiment provides an absolute angle detection device, more specifically a multi-rotation absolute angle detection device, that includes the induction detection unit 5 and the magnetic detection unit 6. When viewed from the axial direction A, the detection areas of the induction detection unit 5 and the magnetic detection unit 6 overlap and are shared. This allows for miniaturization, particularly in the radial direction, without compromising detection accuracy.

[0129] Although the embodiment of the present invention has been described above, the present invention can also be embodied in other forms.

[0130] For example, in the above-described embodiment, an example of a pattern in which the facing relationship between the screen-shaped conductor S constituting the conductor to be detected and the receiving coils 20, 21, and 22 changes multiple times per rotation (see FIGS. 5, 6, and 7), but a pattern in which the facing relationship changes once per rotation may also be used. For example, a single sector-shaped screen-shaped conductor spanning an angular range of 180 degrees around the rotation axis 3 may be used as the conductor to be detected 10, or a single circular or elliptical screen-shaped conductor disposed eccentrically with respect to the rotation axis 3 may be used as the conductor to be detected 10. In other words, the screen-shaped conductor S may have any pattern designed so that the facing area of ​​the conductor portion / non-conductor portion with respect to the coil portions 28 of the receiving coils 20, 21, and 22 changes periodically with the rotation of the rotor.

[0131] 13 and other embodiments show an example in which the outer circumferential annular coil pattern C1 and the inner circumferential annular coil pattern C2 are used as the conductor to be detected 10, but one or both of these may be replaced with a screen-like conductor. Furthermore, the conductor to be detected 10 may be configured by arranging three or more annular coil patterns or screen-like conductors in a concentric pattern centered on the rotation axis 3.

[0132] In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0133] 1: Rotor 2: Stator 3: Rotation axis 5: Induction detection unit 6: Magnetic detection unit 7 :Void 8: Signal processing circuit 10: Conductor to be detected 11: Convex part 12: Recess 20: Receiving coil 21: Peripheral receiving coil 22: Inner receiving coil 30: Annular region 31: Outer receiving coil area 32: Inner receiving coil area 40: Excitation coil 61: First magnetic sensor 62: Second magnetic sensor 100: Rotation detection device 101: Rotation detection device 161: Circumferential center position 162: Circumferential center position 163: Circumferential width 164: Period width A: Axial direction C: Circular coil pattern C1: Outer ring coil pattern C2: Inner circular coil pattern FE: Magnetic wire M: Magnet to be detected M1,M2,… :Individual magnet Mr: Ring Magnet S: Screen conductor SP: Winding

Claims

1. a first support that rotates about a rotation axis; a second support member facing the first support member across a gap in an axial direction parallel to the rotation axis; an induction detection unit that detects rotation information about the first support about the rotation axis; a magnetic detection unit that detects rotation information about the first support body about the rotation axis, The induction detection unit a detection target conductor held by the first support; a receiving coil held by the second support in an arrangement facing the target conductor in the axial direction, and arranged in an annular region centered on the rotation axis when viewed in the axial direction; an excitation coil held by the second support and generating a magnetic field for inducing a voltage in the receiving coil; The magnetic detection unit a magnet to be detected that is disposed on the opposite side of the conductor to be detected from the second support body in the axial direction, and that is held by the first support body and that is disposed so that at least a portion of the magnet overlaps with the annular region when viewed in the axial direction; a magnetic sensor that is disposed on the opposite side of the first support in the axial direction with respect to the receiving coil and the exciting coil, that is disposed so as to overlap at least a portion of the annular region when viewed in the axial direction, and that is held by the second support, and that detects a magnetic field generated by the magnet to be detected; Rotation detection device.

2. The rotation detector according to claim 1 , wherein the conductor to be detected includes a screen-shaped conductor.

3. 3. The rotation detection device according to claim 2, wherein the magnet to be detected has a ring shape with a center on the rotation axis line and is magnetized in the axial direction.

4. 3. The rotation detection device according to claim 2, wherein the magnet to be detected includes a plurality of individual magnets magnetized in the axial direction and arranged along a circumference having a center on the rotation axis.

5. 5. The rotation detection device according to claim 4, wherein the plurality of individual magnets are held by the first support in an arrangement in which the individual magnets entirely overlap the screen-shaped conductor when viewed in the axial direction.

6. 2. The rotation detection device according to claim 1, wherein the conductor to be detected is an annular coil pattern formed in a ring shape along a circumference having a center on the rotation axis, and having a periodic uneven pattern with unevenness in the radial direction relative to the circumference.

7. 7. The rotation detector according to claim 6, wherein the magnet to be detected has a ring shape with a center on the rotation axis line and is magnetized in the axial direction.

8. 7. The rotation detection device according to claim 6, wherein the magnet to be detected includes a plurality of individual magnets magnetized in the axial direction and arranged along a circumference having a center on the rotation axis.

9. 9. The rotation detector according to claim 8, wherein a circumferential center position of each of the individual magnets is aligned with a circumferential position of a midpoint between a recess and a protrusion that are adjacent in the circumferential direction of the uneven pattern.

10. 9. The rotation detection device according to claim 8, wherein the circumferential width of each of the individual magnets is a natural number multiple of the periodic width of the concave-convex pattern of the annular coil pattern.

11. an even number of the individual magnets are arranged at equal intervals along the circumference of a circle having a center on the axis of rotation; 9. The rotation detector according to claim 8, wherein the number of periods of the concave and convex patterns of the annular coil pattern around the rotation axis is an odd number.

12. The annular coil pattern is an inner circumferential annular coil pattern; The rotation detection device according to claim 8 , further comprising: an outer circumferential annular coil pattern disposed radially outward of the inner circumferential annular coil pattern.

13. a circumferential center position of each of the individual magnets is aligned with a circumferential position of a midpoint between a recess and a protrusion that are adjacent in the circumferential direction of one of the concave-convex patterns of the inner annular coil pattern and the outer annular coil pattern, 13. The rotation detection device according to claim 12, wherein the circumferential width of each of the individual magnets is a natural number multiple of the periodic width of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern.

14. an even number of the individual magnets are arranged at equal intervals along the circumference of a circle having a center on the axis of rotation; a circumferential center position of each of the individual magnets is aligned with a circumferential position of a midpoint between a recess and a protrusion that are adjacent in the circumferential direction of one of the concave-convex patterns of the inner annular coil pattern and the outer annular coil pattern, 13. The rotation detector according to claim 12, wherein the number of periods around the rotation axis of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern is an odd number.

15. an even number of the individual magnets are arranged at equal intervals along the circumference of a circle having a center on the axis of rotation; a circumferential center position of each of the individual magnets is aligned with a circumferential position of a midpoint between a recess and a protrusion that are adjacent in the circumferential direction of one of the concave-convex patterns of the inner annular coil pattern and the outer annular coil pattern, a circumferential width of each of the individual magnets is a natural number multiple of a periodic width of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern, 13. The rotation detector according to claim 12, wherein the number of periods around the rotation axis of the concave-convex pattern of the other of the inner annular coil pattern and the outer annular coil pattern is an odd number.

16. The rotation detection device according to any one of claims 1 to 13, wherein the magnetic sensor includes a Hall element or a magnetoresistive element.

17. the magnetic sensor includes a power generation sensor; 14. The rotation detection device according to claim 1, wherein the power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire.

18. the magnetic sensors include a first magnetic sensor including a power generation sensor and a second magnetic sensor including a Hall element or a magnetoresistive element; 14. The rotation detection device according to claim 1, wherein the power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire.

19. The rotation detection device according to claim 15 , wherein the power generation sensor is arranged on a circumference having a center on the rotation axis with the magnetic wire oriented parallel to a tangent to the circumference.

20. The rotation detection device according to any one of claims 1 to 13, which detects an absolute angle.

21. The rotation detection device according to any one of claims 1 to 13, which detects a multiple rotation absolute angle.

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