Rotation sensor and sensor board

Abstract

The present disclosure addresses the problem of easily detecting an absolute angle of a rotor with respect to a stator. Multiple conductive parts (22) are arranged along a rotational direction (DR1) of a rotor (2). A different-thickness part (24) has a relatively different thick in one direction. The rotor (2) is provided with multiple gaps (23) such that the multiple conductive parts (22) are separated from each other. An excitation coil (32) is annularly disposed on a facing surface (310) of the substrate (31). Detection coils (33) are disposed on the inner side of the excitation coil (32) on the facing surface (310) of the substrate (31). A detection electrode part (34) is disposed on the facing surface (310) of the substrate (31) so as to partially overlap with a rotation track (RT1) of the different-thickness part (24) in a plan view from the one direction when the rotor (2) is rotating and detects a capacitance generated between the detection electrode part and the rotor (2).

Description

Technical Field

[0001] The present disclosure generally relates to a rotation sensor and a sensor substrate, and more particularly, to a rotation sensor for detecting the rotation angle of a rotating object and a sensor substrate used for the rotation sensor.

Background Art

[0002] Patent Document 1 describes a position sensor including a sensor stator and a sensor rotor facing the sensor stator. The sensor stator has a detection coil and an excitation coil disposed on the inner circumference of the detection coil. The sensor rotor has two magnetic field shielding portions and two magnetic field non-shielding portions. The two magnetic field shielding portions and the two magnetic field non-shielding portions are alternately arranged along the rotation direction of the sensor rotor.

[0003] In the position sensor described in Patent Document 1, in a state where a magnetic field is generated by the excitation coil, the position of the sensor rotor with respect to the sensor stator can be detected by detecting a change in the magnetic field due to eddy current accompanying the rotation of the sensor rotor with the detection coil.

[0004] In the position sensor (rotation sensor) described in Patent Document 1, two magnetic field shielding portions (gaps) and two magnetic field non-shielding portions (conductive portions) are alternately arranged along the rotation direction of the sensor rotor (rotor), and a plurality of cycles of magnetic field changes occur when the sensor rotor makes one rotation. Therefore, it is impossible to determine which cycle the output signal from the detection coil corresponds to, and it has been difficult to detect the absolute angle of the sensor rotor with respect to the sensor stator (stator).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The object of this disclosure is to provide a rotation sensor and a sensor substrate capable of easily detecting the absolute angle of the rotor relative to the stator.

[0007] A rotation sensor according to one aspect of the present disclosure is a rotation sensor for detecting the rotation angle of an object to be rotated. The rotation sensor comprises a rotor and a stator. The rotor is conductive and 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 and parts of different thicknesses. The plurality of conductive parts are arranged along the rotation direction of the rotor. The parts of different thicknesses have relatively different thicknesses in the one direction. The rotor is provided with a plurality of gaps such that the plurality of conductive parts are separated from each other. The stator comprises a substrate, an excitation coil, a detection coil, and a detection electrode part. The substrate has a surface facing the rotor. The excitation coil is arranged in an annular manner on the surface facing the substrate so as to be along the outer edge of the rotor in a plan view from the one direction, and generates a magnetic field. The detection coil is arranged inside the excitation coil on the surface facing the substrate, and detects changes in the magnetic field. The detection electrode portion is positioned on the opposing surface of the substrate so as to overlap with a portion of the rotational trajectory of the different-thickness portion when the rotor is rotating, in a plan view from one direction, and detects the capacitance generated between it and the rotor.

[0008] A sensor substrate according to one aspect of this disclosure is used as the substrate of the rotation sensor. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view showing the usage state of the rotation sensor according to Embodiment 1. [Figure 2] Figure 2 is a plan view of the rotor surface of the same rotation sensor as shown above. [Figure 3] Figure 3 is a plan view of the rotor used in the same rotation sensor. [Figure 4]Figure 4 is a plan view of the stator used in the same rotation sensor. [Figure 5] Figure 5 is a cross-sectional view of the substrate used in the rotation sensor described above. [Figure 6] Figure 6 is a conceptual diagram showing an example of the connection of the detection coil used in the rotation sensor described above. [Figure 7] Figure 7 is a circuit block diagram of the same rotation sensor. [Figure 8] Figure 8A is a graph showing the change in the detection signal of the same rotation sensor. Figure 8B is a graph showing the change in the capacitance of the same rotation sensor. [Figure 9] Figure 9 is a cross-sectional view showing the usage state of the rotation sensor according to Modification 1 of Embodiment 1. [Figure 10] Figure 10 is a cross-sectional view showing the usage state of a rotation sensor according to a modified example 2 of Embodiment 1. [Figure 11] Figure 11 is a plan view of the rotation sensor according to Embodiment 2. [Figure 12] Figure 12A is a graph showing the change in the detection signal of the same rotation sensor. Figure 12B is a graph showing the change in the capacitance of the same rotation sensor. [Figure 13] Figure 13 is a plan view of a rotation sensor according to a modified example 1 of Embodiment 2. [Figure 14] Figure 14A is a graph showing the change in the detection signal of the same rotation sensor. Figure 14B is a graph showing the change in the capacitance of the same rotation sensor. [Figure 15] Figure 15 is a perspective view of a case used in a rotation sensor according to a modified example 2 of Embodiment 2. [Figure 16] Figure 16 is a plan view of a rotation sensor according to a modified example 3 of Embodiment 2. [Figure 17] Figure 17 is a plan view of the rotation sensor according to Embodiment 3. [Figure 18] Figure 18 is a plan view of a rotation sensor according to a modified example 1 of Embodiment 3. [Figure 19] Figure 19 is a plan view of a rotation sensor according to a modified example 2 of Embodiment 3.

Best Mode for Carrying Out the Invention

[0010] Hereinafter, the rotary sensor and the sensor substrate according to Embodiments 1 to 3 will be described with reference to the drawings. Each of the drawings described in the following Embodiments 1 to 3 is a schematic diagram, and the ratio of the size and thickness of each component does not necessarily reflect the actual dimensional ratio. Further, the configurations described in the following Embodiments 1 to 3 are merely examples of the present disclosure. The present disclosure is not limited to the following Embodiments 1 to 3, and various modifications can be made according to the design and the like as long as the effects of the present disclosure can be achieved.

[0011] (Embodiment 1) Hereinafter, the rotary sensor 1 and the sensor substrate 10 according to Embodiment 1 will be described with reference to FIGS. 1 to 10.

[0012] (1) Overview First, the overview of the rotary sensor 1 and the sensor substrate 10 according to Embodiment 1 will be described with reference to FIGS. 1 and 2.

[0013] As shown in FIG. 1, the rotary sensor 1 according to Embodiment 1 is a sensor for detecting the rotation angle of a rotation object 4. The rotation object 4 is, for example, the rotation axis (hereinafter, also referred to as "rotation axis 4") of an electric motor (motor) mounted on an electric vehicle (including two-wheelers), a hybrid vehicle (including two-wheelers), or industrial equipment (for example, a robot arm). The rotary sensor 1 is, for example, an inductive sensor. That is, in the rotary sensor 1, the rotation angle of the rotor 2 with respect to the stator 3 described later can be detected by detecting the change in the magnetic field due to the eddy current accompanying the rotation of the rotor 2 described later.

[0014] Here, examples of sensors for detecting the rotation angle of the rotating object 4 include sensors using magnetoresistive elements (MR sensors) and sensors using Hall elements. However, while these sensors can detect the rotation angle of a rotating object 4 with a rotation speed of several thousand rpm, they may not be able to detect the rotation speed of a rotating object 4 with a rotation speed exceeding 10,000 rpm. On the other hand, inductive sensors such as rotation sensor 1 can detect the rotation speed of a rotating object 4 even if its rotation speed exceeds 10,000 rpm.

[0015] By the way, the rotation sensor 1 according to Embodiment 1 employs the following configuration for the purpose of detecting the absolute angle of the rotor 2 relative to the stator 3.

[0016] In other words, as shown in Figures 1 and 2, the rotation sensor 1 comprises a rotor 2 and a stator 3. The rotor 2 is conductive and 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 and parts of different thicknesses 24. The plurality of conductive parts 22 are arranged along the rotation direction DR1 of the rotor 2. The parts of different thicknesses 24 have a relatively different thickness in one direction D1 compared to the plurality of conductive parts 22. In the rotation sensor 1, a plurality of gaps 23 are provided so that the plurality of conductive parts 22 are separated from each other. The stator 3 comprises a substrate 31, an excitation coil 32, a detection coil 33, and a detection electrode part 34. The substrate 31 has a facing surface 310 that faces the rotor 2. The excitation coil 32 is arranged in a ring shape on the opposing surface 310 of the substrate 31 so as to follow the outer edge 20 of the rotor 2 when viewed from one direction D1, and generates a magnetic field. A portion of the excitation coil 32 is open in the circumferential direction, and both ends are connected to the oscillator 352 described later. The detection coil 33 is arranged inside the excitation coil 32 on the opposing surface 310 of the substrate 31, and detects the change in the magnetic field. The detection electrode 34 is arranged on the opposing surface 310 of the substrate 31 so as to overlap a portion of the rotation trajectory RT1 of the thickness difference portion 24 when the rotor 2 rotates when viewed from one direction D1, and detects the capacitance C1 generated between it and the rotor 2.

[0017] Furthermore, the sensor substrate 10 is used as the substrate 31 of the rotation sensor 1 described above.

[0018] In such a rotation sensor 1 and sensor substrate 10, the capacitance C1 generated between the rotor 2 and the detection electrode 34 can be detected by the detection electrode 34. Since the value of capacitance C1 detected by the detection electrode 34 changes depending on the rotational position of the rotor 2 relative to the stator 3, it is possible to detect the reference position OP1 of the rotor 2 relative to the stator 3 from the value of capacitance C1 detected by the detection electrode 34. As a result, the absolute angle of the rotor 2 relative to the stator 3 can be easily detected.

[0019] (2) Details Next, the details of the rotation sensor 1 and sensor substrate 10 according to Embodiment 1 will be described with reference to Figures 1 to 7. In Figure 2, dot hatching is applied to the rotor 2 to make it easier to distinguish between the rotor 2 and the stator 3, and the rotor 2 in Figure 2 is not a cross-section. Also, in Figures 2, 4, and 6, the first detection coil 331 is shown with a solid line and the second detection coil 332 is shown with a dashed line to make it easier to distinguish between the first detection coil 331 and the second detection coil 332.

[0020] As described above, the rotation sensor 1 according to Embodiment 1 is a sensor for detecting the rotation angle of a rotating object 4. As described above, the rotating object 4 is, for example, the rotating shaft 4 of an electric motor. As shown in Figures 1 and 2, the rotation sensor 1 comprises a rotor 2 (target) and a stator 3.

[0021] (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 object to be rotated 4 and rotates together with the object to be rotated 4. As shown in Figures 2 and 3, the rotor 2 has a rotor body 21, a plurality of (four in the illustrated example) conductive parts 22, and parts of different thicknesses 24.

[0022] 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, as shown in Figure 1. In other words, one direction D1 is the direction along the axis of rotation 4 as the object to be rotated 4 (the up and down direction in Figure 1). 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 3) at the center of the rotor body 21. The through hole 211 is circular in plan view from one direction D1.

[0023] The multiple conductive parts 22 are arranged at equal intervals along the outer edge of the rotor body 21. That is, the multiple conductive parts 22 are arranged along the rotational direction DR1 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 rotational direction DR1 of the rotor 2. In other words, the multiple conductive parts 22 extend radially from the rotational center RC1 of the rotor 2.

[0024] Each of the multiple conductive parts 22 is fan-shaped when viewed from a planar direction D1. The rotor 2 is provided with multiple gaps 23 such that the multiple conductive parts 22 are separated from each other. That is, in the rotor 2, the multiple conductive parts 22 and the multiple gaps 23 are arranged alternately along the rotational direction DR1 of the rotor 2. In this embodiment, the shape of each of the multiple conductive parts 22 and the shape of each of the multiple gaps 23 are substantially the same when viewed from a planar direction D1, but they may be different. Also, 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.

[0025] The portion with different thickness 24 is provided on the rotor body 21, and its thickness in one direction D1 is relatively different from that of the plurality of conductive parts 22. More specifically, as shown in Figure 3, the portion with different thickness 24 is provided in a first region R1 and a second region R2 of the rotor body 21. The first region R1 is the region between one of the plurality of conductive parts 22 and the rotation center RC1 of the rotor 2. The second region R2 is the region between one of the plurality of gaps 23 and the rotation center RC1 of the rotor 2. The rotation center RC1 of the rotor 2 is the center when the rotor 2 rotates, and as shown in Figures 2 and 3, it is the center of the through hole 211. The portion with different thickness 24 is arc-shaped when viewed from one direction D1. More specifically, the portion with different thickness 24 is arc-shaped with a length of 1 / 4 of the circumference. In this embodiment, the portion with different thickness 24 is a through hole 212 that penetrates the rotor 2 in one direction D1. In this disclosure, "different thickness portion" refers to a portion whose thickness in the direction in which the rotor and stator face each other differs from that of other portions (for example, the rest of the rotor body), and includes through holes.

[0026] The rotor 2 configured in this way is attached to the rotating shaft 4 with the rotating shaft 4 inserted through the through hole 211 of the rotor body 21. In Figures 2 and 3, "P1 (OP1)" is the reference position (origin position) of the rotor 2 relative to the stator 3, where the rotation angle (machine angle) of the rotor 2 relative to the stator 3 is 0 degrees or 360 degrees. Also in Figures 2 and 3, "P2" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 90 degrees. Also in Figures 2 and 3, "P3" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 180 degrees. Also in Figures 2 and 3, "P4" is the position where the rotation angle of the rotor 2 relative to the stator 3 is 270 degrees.

[0027] (2.2) Stator The stator 3 faces the rotor 2, which is attached to the object to be rotated 4, in one direction D1. As shown in Figures 2 and 4, the stator 3 includes a substrate 31, an excitation coil 32, a detection coil 33, and a detection electrode section 34.

[0028] The substrate 31 is, for example, a printed circuit board made of glass epoxy resin. As shown in Figures 2 and 4, the substrate 31 includes a first substrate portion 31A and a second substrate portion 31B. The first substrate portion 31A is circular in shape when viewed from one direction D1, and the excitation coil 32, detection coil 33, and detection electrode portion 34 described later are formed on it. The second substrate portion 31B is rectangular in shape when viewed from one direction D1, and the circuit block 35 described later is mounted on it. As shown in Figure 4, the first substrate portion 31A and the second substrate portion 31B are integrated. As shown in Figures 1 and 4, the substrate 31 has through holes 319 that penetrate in the thickness direction of the substrate 31. The through holes 319 are holes for inserting the rotating shaft 4, and the opening diameter of the through holes 319 is larger than the diameter of the rotating shaft 4 (see Figure 1). In this embodiment, the first substrate portion 31A and the second substrate portion 31B are integrated, but they may be separate as long as they are electrically connected.

[0029] As shown in Figure 5, the substrate 31 has a plurality (two in the illustrated example) of prepregs 311, 312 and a core 313. The plurality of prepregs 311, 312 are located on both sides of the core 313 in one direction D1. On the surface of the prepreg 311 opposite to the core 313, a pattern portion 315 forms the first portion 33A (see Figure 6) of the excitation coil 32 and the detection coil 33. On the surface of the core 313 on the prepreg 311 side, a pattern portion 315 forms the second portion 33B (see Figure 6) of the detection coil 33.

[0030] The first portion 33A of the detection coil 33 includes a part of the first detection coil 331 described later (the first portion 33A of the first detection coil 331) and a part of the second detection coil 332 described later (the first portion 33A of the second detection coil 332). The second portion 33B of the detection coil 33 includes the remainder of the first detection coil 331 excluding the portion included in the first portion 33A of the detection coil 33 (the second portion 33B of the first detection coil 331), and the remainder of the second detection coil 332 excluding the portion included in the first portion 33A of the detection coil 33 (the second portion 33B of the second detection coil 332).

[0031] Specifically, as shown in Figure 6, the first portion 33A of the detection coil 33 is formed on the surface of the prepreg 311 of the substrate 31, and the second portion 33B of the detection coil 33 is formed on the surface of the core 313 of the substrate 31. Furthermore, the first portion 33A of the detection coil 33 formed on the surface of the prepreg 311 and the second portion 33B of the detection coil 33 formed on the surface of the core 313 are electrically connected by vias 314 (see Figure 5). Note that the pattern portion 315 formed on the surface of the core 313 on the prepreg 312 side, and the pattern portion 315 formed on the surface of the prepreg 312 opposite to the core 313 side, are, for example, wiring that connects each electronic component constituting the circuit block 35.

[0032] The excitation coil 32 (transmitting coil) is arranged in an annular shape on the opposing surface 310 of the substrate 31. The opposing surface 310 is the surface facing the rotor 2 in one direction D1 (the direction in which the rotor 2 and stator 3 face each other). That is, the substrate 31 has an opposing surface 310 that faces the rotor 2. More specifically, the excitation coil 32 is arranged in an annular shape on the opposing surface 310 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 parts 22 along the rotation direction DR1 of the rotor 2, as shown in Figures 2 and 3. The excitation coil 32 generates an alternating current that penetrates the excitation coil 32 along one direction D1 when an alternating current output from the oscillator 352 (see Figure 7), which will be described later, flows through it. Here, the frequency of the AC current output from oscillator 352 is, for example, 1 MHz to 10 MHz.

[0033] The detection coil 33 (receiving coil) is positioned inside the excitation coil 32 on the opposing surface 310 of the substrate 31. The detection coil 33 detects changes in the alternating magnetic field generated by the excitation coil 32. As shown in Figure 4, 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 are offset by 45 degrees from each other in the rotation direction DR1 of the rotor 2. As a result, the first detection coil 331 detects a first voltage signal corresponding to a first sine wave signal corresponding to the rotation angle of the rotor 2 relative to the stator 3. The second detection coil 332 detects a second voltage signal corresponding to a first cosine wave signal corresponding to the rotation angle of the rotor 2 relative to the stator 3.

[0034] The detection electrode section 34 is positioned on the opposing surface 310 of the substrate 31. More specifically, as shown in Figure 2, the detection electrode section 34 is positioned on the opposing surface 310 of the substrate 31 such that, in a plan view from one direction D1 (a direction perpendicular to the plane of the paper in Figure 2), it overlaps with a portion of the rotation trajectory RT1 of the uneven thickness section 24 when the rotor 2 is rotating. The detection electrode section 34 is, for example, an arc shape with a length of 1 / 4 of the circumference. When the rotor 2 is positioned at a reference position OP1 relative to the stator 3 (as shown in Figure 2), the detection electrode section 34 overlaps with the uneven thickness section 24 in a plan view from one direction D1. That is, the detection electrode section 34 is the same size as the uneven thickness section 24. The detection electrode section 34 detects the capacitance C1 (see Figure 1) generated between the stator 3 and the opposing surface 210 of the rotor 2 facing it. Furthermore, if the portion with different thickness 24 is a through hole 212, when the portion with different thickness 24 and the detection electrode portion 34 overlap in a plan view from one direction D1, no capacitance C1 is generated between the portion with different thickness 24 and the detection electrode portion 34, so the capacitance is effectively 0.

[0035] (2.3) Circuit Configuration Next, the circuit configuration of the rotation sensor 1 will be explained with reference to Figure 7.

[0036] As shown in Figure 7, the rotation sensor 1 comprises an analog front-end circuit 351, an oscillator 352, a CV converter 353, a plurality of (two in the illustrated example) buffers 354, 356, a plurality of (two in the illustrated example) inverters 355, 357, a phase shifter 358, and a microcontroller 359. The analog front-end circuit 351, oscillator 352, CV converter 353, plurality of buffers 354, 356, plurality of inverters 355, 357, phase shifter 358, and microcontroller 359 are composed of a circuit block 35 (see Figure 2) containing a plurality of electronic components.

[0037] The analog front-end circuit 351 receives a first voltage signal from the first detection coil 331 and a second voltage signal from the second detection coil 332, demodulates the first voltage signal into a first sine wave signal, and demodulates the second voltage signal into a first cosine wave signal. The analog front-end circuit 351 also adjusts the gain of the first sine wave signal and the first cosine wave signal, respectively.

[0038] The oscillator 352 outputs an alternating current of, for example, 1 to 10 MHz to the excitation coil 32. A capacitor 333 is connected between the ends of the excitation coil 32. When the alternating current from the oscillator 352 flows through the excitation coil 32, it generates an alternating magnetic field that passes through the excitation coil 32 along one direction D1.

[0039] The CV converter 353 is electrically connected to the detection electrode unit 34 and outputs an alternating current to the detection electrode unit 34. The CV converter 353 converts the change in capacitance C1 generated between the rotor 2 and the detection electrode unit 34 into a voltage change, and further converts the voltage change into a digital signal. The CV converter 353 outputs the above digital signal to the microcontroller 359. Here, the frequency of the alternating current from the oscillator 352 to the excitation coil 32 is 1 to 10 MHz, as described above. For this reason, it is preferable that the frequency of the alternating current from the CV converter 353 to the detection electrode unit 34 is less than 1 MHz or greater than 10 MHz. This makes it possible to suppress the effect of the alternating magnetic field on the capacitance C1. It is even more preferable that the frequency of the alternating current from the CV converter 353 to the detection electrode unit 34 be less than 1 MHz, and as an example, it is good to have a frequency of about 100 kHz.

[0040] Buffer 354 outputs the first sine wave signal from the analog front-end circuit 351. Inverter 355 outputs the second sine wave signal, which is obtained by inverting the phase of the first sine wave signal from the analog front-end circuit 351. Buffer 356 outputs the first cosine wave signal from the analog front-end circuit 351. Inverter 357 outputs the second cosine wave signal, which is obtained by inverting the phase of the first cosine wave signal from the analog front-end circuit 351.

[0041] The phase shifter 358 detects the phase of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal, which are input through a plurality of buffers 354, 356 and a plurality of inverters 355, 357.

[0042] The microcontroller 359 has memory. The microcontroller 359 performs the origin correction and angle detection described later by executing a program stored in memory. In origin correction, the microcontroller 359 corrects the reference position OP1 (origin position) of the rotor 2 based on the digital signal from the CV converter 353. In angle detection, the microcontroller 359 detects (calculates) the rotation angle (absolute angle) of the rotor 2 based on the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal. Origin correction and angle detection will be explained in the section "(3) Origin Correction and Angle Detection" below.

[0043] (3) Origin correction and angle detection Next, the origin correction and angle detection performed by the microcontroller 359 will be explained with reference to Figures 8A and 8B.

[0044] Figure 8A is a graph showing the change in the detection signal of the rotation sensor 1 according to Embodiment 1. In the rotation sensor 1, the first sine wave signal detected by the first detection coil 331 contains a sine wave for four periods when the rotor 2 rotates once, as shown by the solid line a1 in Figure 8A. In addition, in the rotation sensor 1, the first cosine wave signal detected by the second detection coil 332 contains a sine wave for four periods when the rotor 2 rotates once, as shown by the dashed line a2 in Figure 8A. In Figure 8A, the dashed line a3 shows the change in the rotation angle (mechanical angle) of the rotor 2 corresponding to the first cosine wave signal, and the dashed line a4 shows the change in the rotation angle of the rotor 2 corresponding to the first sine wave signal.

[0045] Figure 8B is a graph showing the change in capacitance C1 of the rotation sensor 1 according to Embodiment 1. In the rotation sensor 1, capacitance C1 changes as shown by the solid line a5 in Figure 8B. More specifically, capacitance C1 is minimum when the rotation angle of the rotor 2 is 0 degrees or 360 degrees. Furthermore, capacitance C1 increases linearly in the range of 0 degrees to 90 degrees for the rotation angle of the rotor 2, remains constant in the range of 90 degrees to 270 degrees, and decreases linearly in the range of 270 degrees to 360 degrees.

[0046] (3.1) Origin Correction As described above, the microcontroller 359 receives a digital signal corresponding to the capacitance C1 generated between the rotor 2 and the detection electrode unit 34. As shown in Figure 8B, the capacitance C1 is minimized when the rotation angle (mechanical angle) of the rotor 2 is 0 degrees, that is, when the rotor 2 is in the reference position OP1. Therefore, the microcontroller 359 corrects the rotation angle of the rotor 2 to 0 degrees, that is, to the reference position OP1 of the rotor 2, where the capacitance C1 is minimized.

[0047] (3.2) Angle detection As described above, the microcontroller 359 receives the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal. Therefore, the microcontroller 359 detects the rotation angle (absolute angle) of the rotor 2 based on the phases of the first sine wave signal, the second sine wave signal, the first cosine wave signal, and the second cosine wave signal.

[0048] (4) Effects In the rotation sensor 1 and sensor substrate 10 according to Embodiment 1, the capacitance C1 generated between the rotor 2 and the detection electrode 34 can be detected by the detection electrode 34. Therefore, the reference position (origin position) OP1 of the rotor 2 relative to the stator 3 can be detected from the value of capacitance C1 detected by the detection electrode 34. As a result, the absolute angle of the rotor 2 relative to the stator 3 can be easily detected. Furthermore, in the rotation sensor 1 and sensor substrate 10 according to Embodiment 1, it is also possible to detect that the rotation sensor 1 is operating from the change in capacitance C1.

[0049] In the rotation sensor 1 according to Embodiment 1, the different thickness portion 24 is provided in the first region R1 and the second region R2. Therefore, compared to the case where the different thickness portion 24 is provided in the conductive portion 22, it is possible to improve the rotational stability of the rotor 2. In addition, compared to the case where the different thickness portion 24 is provided in only one of the first region R1 and the second region R2, the change in capacitance C1 is larger, and as a result, it becomes easier to detect the absolute angle of the rotor 2 with respect to the stator 3.

[0050] In the rotation sensor 1 according to Embodiment 1, the detection electrode portion 34 overlaps with the portion with different thickness 24 when viewed from a plan view from one direction D1, with respect to the stator 3, while the rotor 2 is positioned at the reference position OP1. Therefore, it is possible to set the position where the capacitance C1 is minimized as the reference position OP1.

[0051] In the rotation sensor 1 according to Embodiment 1, the portion with different thicknesses 24 is a through hole 212 that penetrates the rotor 2 in one direction D1. Therefore, it is possible to easily form the portion with different thicknesses 24.

[0052] (5) Variant Embodiment 1 is just one of many embodiments of this disclosure. Embodiment 1 can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0053] (5.1) Variation 1 In Embodiment 1, the portion with different thickness 24 is a through hole 212 that penetrates the rotor body 21, but the portion with different thickness 24 may be a recess 213 provided on the opposing surface 210 of the rotor 2, as shown in Figure 9. The opposing surface 210 of the rotor 2 is the surface that faces the stator 3 in one direction D1, as shown in Figure 9. That is, in the rotation sensor 1 according to Modification 1, the portion with different thickness 24 is a recess 213 provided on the opposing surface 210 of the rotor 2 that faces the stator 3. In short, the portion with different thickness 24 only needs to have a relatively different thickness in one direction D1 with respect to the plurality of conductive portions 22, and may be a recess 213.

[0054] In the rotation sensor 1 according to Modification 1, it is possible to detect the reference position OP1 of the rotor 2 relative to the stator 3 from the capacitance C1 value detected by the detection electrode 34, and as a result, it becomes possible to easily detect the absolute angle of the rotor 2 relative to the stator 3. Furthermore, in the rotation sensor 1 according to Modification 1, it is also possible to easily form the different thickness portion 24.

[0055] (5.2) Variation 2 In Embodiment 1, the portion with different thickness 24 is a through hole 212 that penetrates the rotor body 21, but the portion with different thickness 24 may also be a protrusion 214 provided on the opposing surface 210 of the rotor 2, as shown in Figure 10. The opposing surface 210 of the rotor 2 is the surface that faces the stator 3 in one direction D1, as shown in Figure 10. That is, in the rotation sensor 1 according to Modification 2, the portion with different thickness 24 is a protrusion 214 provided on the opposing surface 210 of the rotor 2 that faces the stator 3. In short, the portion with different thickness 24 only needs to have a relatively different thickness in one direction D1 with respect to the plurality of conductive portions 22, and may also be a protrusion 214.

[0056] In the rotation sensor 1 according to the modified example 2, it is possible to detect the reference position OP1 of the rotor 2 relative to the stator 3 from the capacitance C1 value detected by the detection electrode unit 34, and as a result, it becomes possible to easily detect the absolute angle of the rotor 2 relative to the stator 3.

[0057] (5.3) Other variations In Embodiment 1, the portion with a different thickness 24 is provided on the rotor body 21, but the portion with a different thickness 24 may be provided on, for example, one of the multiple conductive portions 22.

[0058] In Embodiment 1, the rotor 2 has four conductive parts 22, but the rotor 2 may have, for example, two, three, or five or more conductive parts 22.

[0059] The shape of the detection coil 33 (first detection coil 331 and second detection coil 332) is just an example, and is not limited to the shape shown in Figure 4, as long as it is a shape capable of detecting sinusoidal and cosine wave signals.

[0060] (Embodiment 2) The rotation sensor 1A according to Embodiment 2 will be described with reference to Figures 11 to 16. The rotation sensor 1A according to Embodiment 2 differs from the rotation sensor 1 according to Embodiment 1 in that the detection electrode section 34A includes a first electrode section 341, a second electrode section 342, and a third electrode section 343. In the rotation sensor 1A according to Embodiment 2, components similar to those in the rotation sensor 1 according to Embodiment 1 are denoted by the same reference numerals and their description is omitted.

[0061] (1) Composition The rotation sensor 1A according to Embodiment 2 comprises a rotor 2 and a stator 3A, as shown in Figure 11. The rotor 2 has a rotor body 21 (see Figure 3), a plurality of conductive parts 22 (see Figure 3), and parts of different thicknesses 24 (see Figure 3).

[0062] As shown in Figure 11, the stator 3A includes a substrate 31, an excitation coil 32, a detection coil 33, and a detection electrode section 34A.

[0063] The detection electrode section 34A includes a first electrode section 341, a second electrode section 342, and a third electrode section 343. The first electrode section 341 overlaps with the portion with different thicknesses 24 of the rotor 2 (see Figure 3) in a plan view from one direction D1 when the rotor 2 rotates 90 degrees clockwise in Figure 11, from a first state where the rotor 2 is positioned at a reference position OP1 relative to the stator 3A, to a second state (where the rotor 2 has rotated 90 degrees clockwise from the reference position OP1). The second electrode section 342 overlaps with the portion with different thicknesses 24 of the rotor 2 (see Figure 3) in a plan view from one direction D1 when the rotor 2 rotates 90 degrees clockwise in Figure 11, from the second state to a third state (where the rotor 2 has rotated 180 degrees from the reference position OP1). The third electrode portion 343 overlaps with the portion of the rotor 2 with different thicknesses 24 (see Figure 3) in a plan view from one direction D1 when the rotor 2 rotates 90 degrees clockwise from the third state to the fourth state (the rotor 2 rotates 270 degrees from the reference position OP1) as shown in Figure 11. The first electrode portion 341, the second electrode portion 342, and the third electrode portion 343 are integrally connected along the rotation direction DR1 of the rotor 2, as shown in Figure 11.

[0064] In the rotation sensor 1A according to Embodiment 2, the first sine wave signal detected by the first detection coil 331 changes as shown by the solid line a1 in Figure 12A, and the first cosine wave signal detected by the second detection coil 332 changes as shown by the dashed line a2 in Figure 12A. Note that the dashed line a3 in Figure 12A is the rotation angle (mechanical angle) of the rotor 2 corresponding to the first cosine wave signal, and the dashed line a4 in Figure 12A is the rotation angle of the rotor 2 corresponding to the first sine wave signal.

[0065] In the rotation sensor 1A according to Embodiment 2, the capacitance C1 detected by the detection electrode 34A changes as shown by the solid line a5 in Figure 12B. More specifically, the capacitance C1 is maximum when the rotation angle (mechanical angle) of the rotor 2 is 0 degrees or 360 degrees. Furthermore, the capacitance C1 decreases linearly in the range of 0 degrees to 90 degrees, remains constant in the range of 90 degrees to 270 degrees, and increases linearly in the range of 270 degrees to 360 degrees.

[0066] Therefore, in the rotation sensor 1A according to Embodiment 2, it is possible to correct the position where the capacitance C1 is maximum to the reference position OP1 (origin position). As a result, it becomes possible to easily detect the absolute angle of the rotor 2 with respect to the stator 3A. Furthermore, in the rotation sensor 1A according to Embodiment 2, it is also possible to detect that the rotation sensor 1A is operating from the change in capacitance C1.

[0067] (2) Variant The following lists some modifications of Embodiment 2. The modifications described below can be combined and applied as appropriate.

[0068] (2.1) Variation 1 In Embodiment 2, the widths of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343 are the same in the direction perpendicular to the rotation direction DR1 of the rotor 2 (hereinafter referred to as the "orthogonal direction") (see Figure 11). In contrast, the widths of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343 in the above orthogonal direction may be different from each other, as shown in Figure 13. The rotation sensor 1B according to Modification 1 will be described below with reference to Figures 13, 14A, and 14B.

[0069] In the rotation sensor 1B according to modified example 1, the detection electrode section 34B includes a first electrode section 341, a second electrode section 342, and a third electrode section 343. The first electrode section 341, the second electrode section 342, and the third electrode section 343 are integrally aligned along the rotation direction DR1 of the rotor 2.

[0070] In the rotation sensor 1B according to Modification 1, as shown in Figure 13, the width W11 of the first electrode portion 341 in the orthogonal direction is smaller than the width W12 of the second electrode portion 342 in the orthogonal direction. Also, in the rotation sensor 1B according to Modification 1, the width W12 of the second electrode portion 342 in the orthogonal direction is smaller than the width W13 of the third electrode portion 343 in the orthogonal direction. In other words, in the rotation sensor 1B according to Modification 1, the widths W11 of the first electrode portion 341, W12 of the second electrode portion 342, and W13 of the third electrode portion 343 are larger in the order of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343. In short, the widths W11 of the first electrode portion 341, W12 of the second electrode portion 342, and W13 of the third electrode portion 343 change in steps.

[0071] In the rotation sensor 1B according to Modification 1, the first sine wave signal detected by the first detection coil 331 changes as shown by the solid line a1 in Figure 14A, and the first cosine wave signal detected by the second detection coil 332 changes as shown by the dashed line a2 in Figure 14A.

[0072] In the rotation sensor 1B according to Modification 1, the capacitance C1 detected by the detection electrode section 34B changes as shown by the solid line a5 in Figure 14B. More specifically, the capacitance C1 is maximum when the rotor 2 is in the reference position OP1 (when the rotation angle of the rotor 2 is 0 degrees or 360 degrees), as the entire detection electrode section 34B overlaps with the rotor 2. Furthermore, the capacitance C1 decreases linearly in the range of the rotor 2's rotation angle from 0 degrees to 270 degrees, and increases linearly in the range of 270 degrees to 360 degrees.

[0073] Therefore, in the rotation sensor 1B according to Modification 1, it is possible to correct the position where the capacitance C1 is maximum to the reference position OP1 (origin position). As a result, it becomes possible to easily detect the absolute angle of the rotor 2 with respect to the stator 3B. Furthermore, in the rotation sensor 1B according to Modification 1, it is also possible to detect that the rotation sensor 1B is operating from the change in capacitance C1. Moreover, in the rotation sensor 1B according to Modification 1, the rate of change of capacitance C1 differs depending on whether the rotor 2 rotates clockwise or counterclockwise. For this reason, it is also possible to detect the rotation direction DR1 of the rotor 2 from the rate of change of capacitance C1.

[0074] The widths W11 of the first electrode portion 341, W12 of the second electrode portion 342, and W13 of the third electrode portion 343 may be progressively smaller in the order of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343.

[0075] (2.2) Modification 2 The rotation sensor according to Modification 2 differs from the rotation sensor 1A according to Embodiment 2 in that it further includes a case 36. The rotation sensor according to Modification 2 will be described below with reference to Figure 15. In the rotation sensor according to Modification 2, components similar to those in the rotation sensor 1A according to Embodiment 2 are denoted by the same reference numerals and their description is omitted.

[0076] The rotation sensor according to Modification 2 further comprises a case 36, as shown in Figure 15. The case 36 is formed in a cylindrical shape with one side (the bottom side in Figure 15) open, for example, from ABS (Acrylonitrile-Butadiene-Styrene) resin or PBT (Poly Butylene Terephthalate) resin. The case 36 has a bottom wall 36A and a peripheral wall 36B. The bottom wall 36A is annular in plan view from one direction D1 and has a circular through hole 360 ​​in the center. With the rotation sensor 1A attached to the rotation shaft 4, the rotation shaft 4 is inserted through the through hole 360. The peripheral wall 36B is formed along the outer edge of the bottom wall 36A and extends around the entire circumference of the bottom wall 36A. The peripheral wall 36B protrudes along the thickness direction (one direction D1) of the bottom wall 36A.

[0077] Furthermore, a projection 36C is provided on one surface of the bottom wall 36A (the lower surface in Figure 13). The projection 36C includes a first portion 361, a second portion 362, and a third portion 363. The thickness T11 of the first portion 361 is smaller (thinner) than the thickness T12 of the second portion 362. Also, the thickness T12 of the second portion 362 is smaller (thinner) than the thickness T13 of the third portion 363. That is, in one direction D1, the thicknesses T11 of the first portion 361, T12 of the second portion 362, and T13 of the third portion 363 are larger (thicker) in the order of the first portion 361, the second portion 362, and the third portion 363. In short, the thickness T11 of the first part 361, the thickness T12 of the second part 362, and the thickness T13 of the third part 363 increase in a stepwise manner in the order of the thickness T11 of the first part 361, the thickness T12 of the second part 362, and the thickness T13 of the third part 363. Here, the thickness T11 of the first part 361 is the amount of the first part 361 protruding from the lower surface of the bottom wall 36A. The thickness T12 of the second part 362 is the amount of the second part 362 protruding from the lower surface of the bottom wall 36A. The thickness T13 of the third part 363 is the amount of the third part 363 protruding from the lower surface of the bottom wall 36A.

[0078] When the rotor 2 is attached to the rotating shaft 4, the case 36 has its entire bottom wall 36A and part of its peripheral wall 36B positioned between the rotor 2 and the stator 3A in one direction D1, and accommodates at least the substrate 31. When the rotor 2 is attached to the rotating shaft 4, the first portion 361 of the protrusion 36C overlaps with the first electrode portion 341 of the detection electrode portion 34A of the stator 3A in a plan view from one direction D1. Also when the rotor 2 is attached to the rotating shaft 4, the second portion 362 of the protrusion 36C overlaps with the second electrode portion 342 of the detection electrode portion 34A of the stator 3A in a plan view from one direction D1. Furthermore, when the rotor 2 is attached to the rotating shaft 4, the third portion 363 of the protrusion 36C overlaps with the third electrode portion 343 of the detection electrode portion 34A of the stator 3A in a plan view from one direction D1.

[0079] In the rotation sensor according to Modified Example 2, in one direction D1, the first portion 361 overlaps with the first electrode portion 341, the second portion 362 overlaps with the second electrode portion 342, and the third portion 363 overlaps with the third electrode portion 343. Therefore, the distance between the rotor 2 and the first electrode portion 341, the distance between the rotor 2 and the second electrode portion 342, and the distance between the rotor 2 and the third electrode portion 343 are different. As a result, similar to the rotation sensor 1A according to Embodiment 2, the rate of change of capacitance C1 differs depending on whether the rotor 2 rotates clockwise or counterclockwise. Therefore, the rotation sensor according to Modified Example 2 makes it possible to detect the reference position OP1 of the rotor 2 relative to the stator 3A, as well as the rotation direction of the rotor 2.

[0080] Furthermore, the thickness T11 of the first part 361, the thickness T12 of the second part 362, and the thickness T13 of the third part 363 may decrease in the order of the first part 361, the second part 362, and the third part 363. Also, the thickness T11 of the first part 361, the thickness T12 of the second part 362, and the thickness T13 of the third part 363 may increase or decrease continuously (gradually) in the order of the first part 361, the second part 362, and the third part 363.

[0081] (2.3) Modification 3 In the rotation sensor 1B according to Modification 1, the widths W11 of the first electrode section 341, W12 of the second electrode section 342, and W13 of the third electrode section 343, which constitute the detection electrode section 34B, change in steps (see Figure 13). In contrast, the widths of the first electrode section 341, the second electrode section 342, and the third electrode section 343 may be changed continuously (gradually). The rotation sensor 1C according to Modification 3 will be described below with reference to Figure 16.

[0082] The rotation sensor 1C according to the modified example 3 comprises a rotor 2 and a stator 3C, as shown in Figure 16. The rotor 2 has a rotor body 21 (see Figure 3), a plurality of conductive parts 22 (see Figure 3), and parts of different thicknesses 24 (see Figure 3). The stator 3C has a substrate 31, an excitation coil 32, a detection coil 33, and a detection electrode part 34C.

[0083] The detection electrode section 34C includes a first electrode section 341, a second electrode section 342, and a third electrode section 343. In the rotation sensor 1C according to the modified example 3, as shown in Figure 16, the widths of the first electrode section 341, the second electrode section 342, and the third electrode section 343 increase in the order of the first electrode section 341, the second electrode section 342, and the third electrode section 343.

[0084] In the rotation sensor 1C according to Modification 3, similar to the rotation sensor 1B according to Modification 1, the capacitance C1 is maximum when the rotor 2 is at the reference position OP1 (when the rotation angle of the rotor 2 is 0 degrees or 360 degrees), as the entire detection electrode section 34C overlaps with the rotor 2. Therefore, with the rotation sensor 1C according to Modification 3, it is possible to correct the position where the capacitance C1 is maximum to the reference position OP1, and as a result, it becomes possible to easily detect the absolute angle of the rotor 2 with respect to the stator 3C. Furthermore, with the rotation sensor 1C according to Modification 3, it is also possible to detect that the rotation sensor 1C is operating from the change in capacitance C1. Moreover, with the rotation sensor 1C according to Modification 3, since the rate of change of capacitance C1 differs depending on whether the rotor 2 rotates clockwise or counterclockwise, it is also possible to detect the rotation direction DR1 of the rotor 2 from the rate of change of capacitance C1.

[0085] The widths of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343 may decrease continuously in the order of the first electrode portion 341, the second electrode portion 342, and the third electrode portion 343.

[0086] Furthermore, the various configurations described in Embodiment 2 can be appropriately combined with the various configurations (including modified versions) described in Embodiment 1.

[0087] (Embodiment 3) The rotation sensor 1D according to Embodiment 3 will be described with reference to Figure 17. The rotation sensor 1D according to Embodiment 3 differs from the rotation sensor 1 according to Embodiment 1 in that the difference in thickness portion 24A includes a first difference in thickness portion 241, a second difference in thickness portion 242, and a third difference in thickness portion 243. In the rotation sensor 1D according to Embodiment 3, components that are the same as those in the rotation sensor 1 according to Embodiment 1 are denoted by the same reference numerals and their description is omitted.

[0088] (1) Composition The rotation sensor 1D according to Embodiment 3 comprises a rotor 2A and a stator 3. The rotor 2A has a rotor body 21, a plurality of conductive parts 22, and a part of different thickness 24A. The stator 3 has a substrate 31 (see Figure 4), an excitation coil 32 (see Figure 4), a detection coil 33 (see Figure 4), and a detection electrode part 34 (see Figure 4).

[0089] As shown in Figure 17, the different thickness portion 24A includes a first different thickness portion 241, a second different thickness portion 242, and a third different thickness portion 243. The first different thickness portion 241 overlaps with the detection electrode portion 34 in a plan view from one direction D1 when the rotor 2 rotates 90 degrees counterclockwise in Figure 17, from the first state where the rotor 2A is positioned at a reference position OP1 relative to the stator 3, to the second state. The second different thickness portion 242 overlaps with the detection electrode portion 34 in a plan view from one direction D1 when the rotor 2 rotates 90 degrees counterclockwise in Figure 17, from the second state, to the third state. The third different thickness portion 243 overlaps with the detection electrode portion 34 in a plan view from one direction D1 when the rotor 2 rotates 90 degrees counterclockwise in Figure 17, from the third state, to the fourth state. The first different thickness section 241, the second different thickness section 242, and the third different thickness section 243 are integrally connected along the rotational direction DR1 of the rotor 2.

[0090] In the rotation sensor 1D according to Embodiment 3, when the rotor 2A is located at the reference position OP1 (when the rotation angle of the rotor 2A is 0 degrees or 360 degrees), the rotor 2A and the detection electrode 34 overlap in one direction D1, and the capacitance C1 detected by the detection electrode 34 is at its maximum. Therefore, it is possible to detect the reference position OP1 of the rotor 2A relative to the stator 3 from the value of capacitance C1, and as a result, it is possible to easily detect the absolute angle of the rotor 2A relative to the stator 3. Furthermore, in the rotation sensor 1D according to Embodiment 3, it is also possible to detect that the rotation sensor 1D is operating from the change in capacitance C1.

[0091] (2) Variant The following lists some modifications of Embodiment 3. The modifications described below can be combined and applied as appropriate.

[0092] (2.1) Variation 1 In Embodiment 3, the widths of the first, second, and third thickness portions 241, 242, and 343 are the same in the direction perpendicular to the rotation direction DR1 of the rotor 2 (hereinafter referred to as the "orthogonal direction") (see Figure 17). In contrast, the widths of the first, second, and third thickness portions 241, 242, and 343 in the orthogonal direction may be different from each other, as shown in Figure 18. The rotation sensor 1E according to Modification 1 will now be described with reference to Figure 18.

[0093] In the rotation sensor 1E according to modified example 1, the different thickness portion 24B includes a first different thickness portion 241, a second different thickness portion 242, and a third different thickness portion 243. The first different thickness portion 241, the second different thickness portion 242, and the third different thickness portion 243 are integrally connected along the rotation direction DR1 of the rotor 2.

[0094] In the rotation sensor 1E according to Modification 1, as shown in Figure 18, the width W21 of the first different thickness portion 241 in the orthogonal direction is smaller than the width W22 of the second different thickness portion 242 in the orthogonal direction. Also, in the rotation sensor 1E according to Modification 1, the width W22 of the second different thickness portion 242 in the orthogonal direction is smaller than the width W23 of the third different thickness portion 243 in the orthogonal direction. In other words, in the rotation sensor 1E according to Modification 1, the widths W21 of the first different thickness portion 241, W22 of the second different thickness portion 242, and W23 of the third different thickness portion 243 are larger in the order of the first different thickness portion 241, the second different thickness portion 242, and the third different thickness portion 243. In short, the widths W21 of the first different thickness portion 241, W22 of the second different thickness portion 242, and W23 of the third different thickness portion 243 change in steps.

[0095] In the rotation sensor 1E according to Modification 1, similar to the rotation sensor 1D according to Embodiment 3, when the rotor 2B is located at the reference position OP1 (when the rotation angle of the rotor 2B is 0 degrees or 360 degrees), the rotor 2B and the detection electrode 34 overlap in one direction D1, and the capacitance C1 detected by the detection electrode 34 is at its maximum. Therefore, it is possible to detect the reference position OP1 of the rotor 2B relative to the stator 3 from the value of capacitance C1, and as a result, it is possible to easily detect the absolute angle of the rotor 2B relative to the stator 3. Furthermore, in the rotation sensor 1E according to Modification 1, it is also possible to detect that the rotation sensor 1D is operating from the change in capacitance C1. Moreover, in the rotation sensor 1E according to Modification 1, it is also possible to detect the rotation direction DR1 of the rotor 2B from the rate of change of capacitance C1.

[0096] The widths W21 of the first different thickness section 241, W22 of the second different thickness section 242, and W23 of the third different thickness section 243 may decrease in a gradual manner in the order of the first different thickness section 241, the second different thickness section 242, and the third different thickness section 243.

[0097] (2.2) Modification 2 In the rotation sensor 1E according to Modification 1, the widths W21 of the first thickness portion 241, W22 of the second thickness portion 242, and W23 of the third thickness portion 243, which constitute the thickness portion 24B, change in steps (see Figure 18). In contrast, the widths of the first thickness portion 241, the second thickness portion 242, and the third thickness portion 243 may be changed continuously. The rotation sensor 1F according to Modification 2 will be described below with reference to Figure 19.

[0098] The rotation sensor 1F according to the modified example 2 comprises a rotor 2C and a stator 3, as shown in Figure 19. The rotor 2C has a rotor body 21, a plurality of conductive parts 22, and a part of different thickness 24C. The stator 3 has a substrate 31 (see Figure 4), an excitation coil 32 (see Figure 4), a detection coil 33 (see Figure 4), and a detection electrode part 34 (see Figure 4).

[0099] The different thickness portion 24C includes a first different thickness portion 241, a second different thickness portion 242, and a third different thickness portion 243. In the rotation sensor 1F according to the modified example 2, as shown in Figure 19, the widths of the first different thickness portion 241, the second different thickness portion 242, and the third different thickness portion 243 increase in the order of the first different thickness portion 241, the second different thickness portion 242, and the third different thickness portion 243.

[0100] In the rotation sensor 1F according to Modification 2, similar to the rotation sensor 1E according to Modification 1, when the rotor 2C is located at the reference position OP1 (when the rotation angle of the rotor 2C is 0 degrees or 360 degrees), the rotor 2C and the detection electrode 34 overlap in one direction D1, and the capacitance C1 detected by the detection electrode 34 is at its maximum. As a result, it is possible to detect the reference position OP1 of the rotor 2C relative to the stator 3 from the value of capacitance C1, and as a result, it is possible to easily detect the absolute angle of the rotor 2C relative to the stator 3. Furthermore, in the rotation sensor 1F according to Modification 2, it is also possible to detect that the rotation sensor 1F is operating from the change in capacitance C1. Moreover, in the rotation sensor 1F according to Modification 2, it is also possible to detect the rotation direction DR1 of the rotor 2C from the rate of change of capacitance C1.

[0101] Furthermore, the widths of the first, second, and third thickness portions 241, 242, and 243 may decrease sequentially in that order.

[0102] Furthermore, the various configurations described in Embodiment 3 can be appropriately combined with the various configurations (including modified versions) described in Embodiments 1 and 2.

[0103] (Aspect) This specification discloses the following aspects:

[0104] The first embodiment of the rotation sensor (1; 1A~1F) is a rotation sensor (1) that detects the rotation angle of an object to be rotated (4). The rotation sensor (1) comprises a rotor (2; 2A~2C) and a stator (3; 3A~3C). The rotor (2; 2A~2C) is conductive and is attached to the object to be rotated (4) and rotates integrally with the object to be rotated (4). The stator (3; 3A~3C) faces the rotor (2; 2A~2C) in one direction (D1). The rotor (2; 2A~2C) has a plurality of conductive parts (22) and parts of different thicknesses (24; 24A~24C). The plurality of conductive parts (22) are arranged along the rotation direction (DR1) of the rotor (2; 2A~2C). The sections with different thicknesses (24; 24A~24C) have relatively different thicknesses in one direction (D1). In the rotor (2; 2A~2C), multiple gaps (23) are provided so that multiple conductive parts (22) are separated from each other. The stator (3; 3A~3C) has a substrate (31), an excitation coil (32), a detection coil (33), and detection electrode sections (34; 34A~34C). The substrate (31) has a facing surface (310) that faces the rotor (2; 2A~2C). The excitation coil (32) is arranged in a ring on the facing surface (310) of the substrate (31) so as to follow the outer edge (20) of the rotor (2; 2A~2C) 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 opposing surface (310) of the substrate (31) and detects the change in the magnetic field. The detection electrode section (34; 34A~34C) is positioned on the opposing surface (310) of the substrate (31) so as to overlap with a part of the rotation trajectory (RT1) of the different thickness section (24; 24A~24C) when the rotor (2; 2A~2C) rotates, when viewed from one direction (D1), and detects the capacitance (C1) generated between it and the rotor (2; 2A~2C).

[0105] According to this embodiment, the absolute angle of the rotor (2; 2A~2C) relative to the stator (3; 3A~3C) can be easily detected based on the change in capacitance (C1) detected by the detection electrode section (34; 34A~34C).

[0106] In the second embodiment of the rotation sensor (1; 1A~1F), in the first embodiment, each of the plurality of conductive parts (22) is fan-shaped when viewed from one direction (D1) in plan view.

[0107] According to this embodiment, the absolute angle of the rotor (2; 2A~2C) relative to the stator (3; 3A~3C) can be easily detected based on the change in capacitance (C1) detected by the detection electrode section (34; 34A~34C).

[0108] In the third embodiment of the rotation sensor (1; 1A to 1F), in the first or second embodiment, the different thickness portions (24; 24A to 24C) are provided in at least one of the regions (R1) between one of the plurality of conductive portions (22) and the rotation center (RC1) of the rotor (2), and the region (R2) between one of the plurality of gaps (23) and the rotation center (RC1) of the rotor (2).

[0109] According to this embodiment, it is possible to improve the rotational stability of the rotor (2;2A~2C) compared to the case in which a portion of different thickness is provided in the conductive portion.

[0110] In the rotation sensor (1; 1A~1F) according to the fourth embodiment, in the third embodiment, the different thickness portions (24; 24A~24C) are provided in the region (R1) between the conductive portion (22) of 1 and the rotation center (RC1) of the rotor (2), and in the region (R2) between the gap (23) of 1 and the rotation center (RC1) of the rotor (2).

[0111] According to this embodiment, the change in capacitance (C1) becomes larger, and as a result, it becomes easier to detect the absolute angle of the rotor (2; 2A~2C) relative to the stator (3; 3A~3C).

[0112] In the fifth embodiment of the rotation sensor (1), in the fourth embodiment, the detection electrode portion (34) overlaps with the portion of different thickness (24) in a plan view from one direction (D1) when the rotor (2) is positioned at a reference position (OP1) relative to the stator (3).

[0113] According to this embodiment, it is possible to correct the reference position (OP1) to the position where the capacitance (C1) is minimized.

[0114] In the sixth embodiment of the rotation sensor (1A to 1C), in the fourth embodiment, the detection electrode section (34A to 34C) includes a first electrode section (341), a second electrode section (342), and a third electrode section (343). The first electrode section (341) overlaps with the portion of different thickness (24) in a plan view from one direction (D1) when the rotor (2) moves from a first state in which the rotor (2) is positioned at a reference position (OP1) relative to the stator (3A to 3C) to a second state in which the rotor (2) has rotated 90 degrees. The second electrode section (342) overlaps with the portion of different thickness (24) in a plan view from one direction (D1) when the rotor (2) moves from the second state to a third state in which the rotor (2) has rotated 90 degrees. The third electrode portion (343) overlaps with the portion of different thickness (24) in a plan view from one direction (D1) when the rotor (2) rotates 90 degrees from the third state to the fourth state. The first electrode portion (341), the second electrode portion (342), and the third electrode portion (343) are integrally connected along the rotation direction (DR1) of the rotor (2).

[0115] According to this embodiment, it is possible to correct the position where the capacitance (C1) is maximum to the reference position (OP1).

[0116] In the seventh embodiment of the rotation sensor (1B;1C), in the sixth embodiment, the widths (W11, W12, W13) of the first electrode portion (341), the second electrode portion (342), and the third electrode portion (343) are larger or smaller in the order of the first electrode portion (341), the second electrode portion (342), and the third electrode portion (343).

[0117] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0118] In the rotation sensor (1B) according to the eighth embodiment, as in the seventh embodiment, the widths (W11, W12, W13) of the first electrode portion (341), the second electrode portion (342), and the third electrode portion (343) are changed in steps.

[0119] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0120] In the rotation sensor (1C) according to the ninth embodiment, the widths of the first electrode portion (341), the second electrode portion (342), and the third electrode portion (343) change continuously, as in the seventh embodiment.

[0121] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0122] In the rotation sensor (1D~1F) according to the tenth embodiment, in the fifth embodiment, the different thickness portion (24A~24C) includes a first different thickness portion (241), a second different thickness portion (242), and a third different thickness portion (243). The first different thickness portion (241) overlaps with the detection electrode portion (34) in a plan view from one direction (D1) when the rotor (2A~2C) rotates 90 degrees from the first state in which the rotor (2A~2C) is positioned at a reference position (OP1) relative to the stator (3) to the second state. The second different thickness portion (242) overlaps with the detection electrode portion (34) in a plan view from one direction (D1) when the rotor (2A~2C) rotates 90 degrees from the second state to the third state. The third thickness difference portion (243) overlaps with the detection electrode portion (34) in a plan view from one direction (D1) when the rotor (2A~2C) rotates 90 degrees from the third state to the fourth state. The first thickness difference portion (241), the second thickness difference portion (242), and the third thickness difference portion (243) are integrated along the rotation direction (DR1) of the rotor (2A~2C).

[0123] According to this embodiment, it becomes possible to detect the absolute angle of the rotor (2A~2C) relative to the stator (3), and whether the object to be rotated (4) is rotating.

[0124] In the rotation sensor (1E, 1F) according to the 11th embodiment, in the 10th embodiment, the widths (W21, W22, W23) of the first different thickness portion (241), the second different thickness portion (242), and the third different thickness portion (243) are larger or smaller in the order of the first different thickness portion (241), the second different thickness portion (242), and the third different thickness portion (243).

[0125] According to this embodiment, the rotation direction (DR1) of the rotor (2B, 2C) can be detected by the rate of change of capacitance (C1).

[0126] In the rotation sensor (1E) according to the twelfth embodiment, in the eleventh embodiment, the widths (W21, W22, W23) of the first different thickness portion (241), the second different thickness portion (242), and the third different thickness portion (243) change in steps.

[0127] According to this embodiment, the rotation direction (DR1) of the rotor (2B) can be detected by the rate of change of capacitance (C1).

[0128] In the rotation sensor (1F) according to the 13th embodiment, the widths of the first different thickness portion (241), the second different thickness portion (242), and the third different thickness portion (243) change continuously, as in the 11th embodiment.

[0129] According to this embodiment, the rotation direction (DR1) of the rotor (2C) can be detected by the rate of change of capacitance (C1).

[0130] The rotation sensor (1A) according to the 14th embodiment further comprises a case (36) in the sixth embodiment. The case (36) is made of resin and a portion of it is positioned between the rotor (2) and the stator (3A) in one direction (D1) and houses at least a substrate (31). The case (36) has a first part (361), a second part (362), and a third part (363). The first part (361) overlaps with the first electrode part (341) in a plan view from one direction (D1). The second part (362) overlaps with the second electrode part (342) in a plan view from one direction (D1). The third part (363) overlaps with the third electrode part (343) in a plan view from one direction (D1). In one direction (D1), the thicknesses (T11, T12, T13) of the first part (361), the second part (362), and the third part (363) are larger or smaller in the order of the first part (361), the second part (362), and the third part (363).

[0131] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0132] In the rotation sensor (1A) according to the 15th embodiment, in the 14th embodiment, the thicknesses (T11, T12, T13) of the first part (361), the second part (362), and the third part (363) change in steps.

[0133] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0134] In the rotation sensor (1A) according to the 16th embodiment, the thickness of each of the first part (361), the second part (362), and the third part (363) changes continuously, as in the 14th embodiment.

[0135] According to this embodiment, the rotation direction (DR1) of the rotor (2) can be detected by the rate of change of capacitance (C1).

[0136] In the rotation sensor (1) according to the 17th embodiment, in any one of the 1st to 16th embodiments, the portion of different thickness (24) is a recess (213) provided on the opposing surface (210) of the rotor (2) that faces the stator (3).

[0137] According to this embodiment, it becomes possible to easily form a portion of different thickness (24).

[0138] In the rotation sensor (1) according to the 18th embodiment, in any one of the 1st to 16th embodiments, the portion of different thickness (24) is a through hole (212) that penetrates the rotor (2) in one direction (D1).

[0139] According to this embodiment, it becomes possible to easily form a portion of different thickness (24).

[0140] The sensor substrate (10) according to the 19th embodiment is used as the substrate (31) of any one of the rotation sensors (1) according to the 1st to 18th embodiments.

[0141] According to this embodiment, it is possible to detect the absolute angle of the rotor (2) relative to the stator (3) based on the change in capacitance (C1) detected by the detection electrode unit (34).

[0142] The configurations relating to the second to eighteenth aspects are not essential for the rotation sensor (1; 1A to 1F) and can be omitted as appropriate. [Explanation of Symbols]

[0143] 1,1A~1F Rotation Sensor 2,2A~2C Rotor 3,3A~3C stator 4. Rotating Objects 10 Sensor board 20 Outer edge 22 Conductive part 23 Gap 24,24A~24C Different thickness part 31 circuit boards 32 Excitation coil 33 detection coil 34, 34A~34C Detection electrode section 36 cases 210 Opposing surface 212 Through hole 213 Recess 241 First Different Thickness Section 242 Second Uneven Section 243 Third Different Thickness Section 310 Opposing surface 341 1st electrode part 342 2nd electrode part 343 Third electrode section 361 Part 1 362 Part 2 363 Part 3 C1 Capacitance D1 One direction DR1 Rotation direction OP1 Reference position R1 1st area (area) R2 2nd area (area) RC1 Rotation Center RT1 Rotation Trajectory Thickness T11, T12, T13 W11, W12, W13, W21, W22, W23 width

Claims

1. A rotation sensor for detecting the rotation angle of a rotating object, A rotor that is electrically conductive, is attached to the object to be rotated, and rotates integrally with the object to be rotated, A stator facing the rotor in one direction, The rotor is, Multiple conductive parts arranged along the rotational direction of the rotor, It has a portion with different thicknesses, where the thickness in one direction is relatively different. Multiple gaps are provided so that the multiple conductive parts are separated from each other. The stator is, A substrate having a surface facing the rotor, An excitation coil that generates a magnetic field is arranged in an annular shape on the opposing surface of the substrate so as to be along the outer edge of the rotor in a plan view from the aforementioned one direction, A detection coil is positioned on the opposing surface of the substrate, inside the excitation coil, and detects the change in the magnetic field. The substrate is positioned on the opposing surface such that, in a plan view from one direction, it overlaps with a portion of the rotation trajectory of the portion of the different thickness when the rotor is rotating, and has a detection electrode portion for detecting capacitance generated between it and the rotor. Rotation sensor.

2. Each of the plurality of conductive parts is fan-shaped when viewed from one direction in plan. The rotation sensor according to claim 1.

3. The portion of varying thickness is provided in at least one of the regions between one of the plurality of conductive portions and the rotation center of the rotor, and the region between one of the plurality of gaps and the rotation center of the rotor. The rotation sensor according to claim 1.

4. The portions of different thicknesses are provided in the region between the conductive portion of the first and the rotation center of the rotor, and in the region between the gap of the first and the rotation center of the rotor. The rotation sensor according to claim 3.

5. The detection electrode portion overlaps with the portion of different thickness in a plan view from one direction when the rotor is positioned at a reference position relative to the stator. The rotation sensor according to claim 4.

6. The detection electrode section is When the rotor moves from a first state, where it is positioned relative to the stator, to a second state, where it has rotated 90 degrees, the first electrode portion overlaps with the portion of different thickness in a plan view from one direction, When the rotor rotates 90 degrees from the second state to the third state, the second electrode portion overlaps with the portion of different thickness in a plan view from one direction, When the rotor rotates 90 degrees from the third state to the fourth state, it includes a third electrode portion that overlaps with the portion of different thickness in a plan view from one direction, The first electrode portion, the second electrode portion, and the third electrode portion are integrally connected along the rotational direction of the rotor. The rotation sensor according to claim 4.

7. The widths of the first electrode portion, the second electrode portion, and the third electrode portion are larger or smaller in the order of the first electrode portion, the second electrode portion, and the third electrode portion. The rotation sensor according to claim 6.

8. The width of each of the first electrode portion, the second electrode portion, and the third electrode portion changes in steps. The rotation sensor according to claim 7.

9. The width of each of the first electrode portion, the second electrode portion, and the third electrode portion changes continuously. The rotation sensor according to claim 7.

10. The aforementioned portion of different thickness is When the rotor moves from a first state in which it is positioned relative to the stator to a second state in which it has rotated 90 degrees, the first different-thickness portion overlaps with the detection electrode portion in a plan view from one direction, When the rotor rotates 90 degrees from the second state to the third state, the second thickness portion overlaps with the detection electrode portion in a plan view from one direction, When the rotor rotates 90 degrees from the third state to the fourth state, it includes a third different-thickness portion that overlaps with the detection electrode portion in a plan view from one direction, The first, second, and third thickness portions are integrally connected along the rotational direction of the rotor. The rotation sensor according to claim 5.

11. The widths of the first, second, and third different thickness portions are larger or smaller in the order of the first, second, and third different thickness portions, respectively. The rotation sensor according to claim 10.

12. The width of each of the first, second, and third different thickness portions changes in steps. The rotation sensor according to claim 11.

13. The width of each of the first, second, and third different thickness portions changes continuously. The rotation sensor according to claim 11.

14. In the aforementioned one direction, a portion is positioned between the rotor and the stator, and further comprises a resin case that houses at least the substrate, The aforementioned case is, The first portion overlaps with the first electrode portion in a plan view from the aforementioned one direction, The second portion overlaps with the second electrode portion in a plan view from the aforementioned one direction, It has a third portion that overlaps with the third electrode portion in a plan view from the aforementioned one direction, The thickness of each of the first, second, and third parts in the aforementioned one direction is larger or smaller in the order of the first part, second part, and third part. The rotation sensor according to claim 6.

15. The thickness of each of the first, second, and third parts changes in stages. The rotation sensor according to claim 14.

16. The thickness of each of the first, second, and third parts changes continuously. The rotation sensor according to claim 14.

17. The aforementioned difference in thickness is a recess provided on the opposing surface of the rotor that faces the stator. The rotation sensor according to claim 1.

18. The aforementioned difference in thickness is a through hole that penetrates the rotor in the aforementioned one direction. The rotation sensor according to claim 1.

19. The substrate used in the rotation sensor according to any one of claims 1 to 18, Sensor board.

Images