Rotation angle detection device and rotation angle detection method

Abstract

The present application provides a rotation angle detection device and a rotation angle detection method, which can simplify the structure. The rotation angle detection device comprises: a first gear, which rotates integrally with a rotating member; a second gear, which meshes with the first gear and rotates at a different speed from the first gear; a first angle sensor, which detects the rotation angle of the first gear; a second angle sensor, which detects the rotation angle of the second gear; and a control unit, which calculates the rotation angle of the rotating member from a reference position based on the detection results of the first angle sensor and the second angle sensor. The control unit calculates an integer value of the electrical rotation number of the first angle sensor or the second angle sensor from the reference position based on the detection result of the first angle sensor and the detection result of the second angle sensor, and calculates the rotation angle of the rotating member from the reference position based on any one of the detection result of the first angle sensor and the detection result of the second angle sensor and the above integer value.

Description

Technical Field

[0001] This invention relates to a rotation angle detection device and a method for detecting rotation angle. Background Technology

[0002] Patent Document 1 discloses a rotation angle detection device, for example, for detecting the rotation angle of a car's steering wheel. The rotation angle detection device of Patent Document 1 includes: a first gear that rotates integrally with the steering wheel; a second gear that meshes with the first gear and has a different number of teeth than the first gear; a third gear that meshes with the second gear and has a different number of teeth than both the first and second gears; a first detection unit that outputs a signal corresponding to the rotation angle of the second gear; and a second detection unit that outputs a signal corresponding to the rotation angle of the third gear. Furthermore, the rotation angle detection device of Patent Document 1 combines the output information of the first and second detection units to calculate the steering rotation angle.

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2010-96518

[0005] However, from the viewpoint of simplifying the structure, there is room for improvement in the rotation angle detection device described in Patent Document 1. Summary of the Invention

[0006] The present invention was made in view of the above circumstances, and its object is to provide a rotation angle detection device and a rotation angle detection method that can simplify the structure.

[0007] In addition, to achieve the above objective, the present invention provides a rotation angle detection device for detecting the rotation angle of a rotating component from a reference position, comprising: a first gear and a second gear that rotate at different speeds as the rotating component rotates; a first angle sensor that detects the rotation angle of the first gear; a second angle sensor that detects the rotation angle of the second gear; and a control unit that calculates the rotation angle of the rotating component from the reference position based on the detection results of the first angle sensor and the second angle sensor, wherein the control unit calculates an integer value of the number of electrical rotations of the first angle sensor or the second angle sensor from the reference position based on the detection results of the first angle sensor and the second angle sensor, and calculates the rotation angle of the rotating component from the reference position based on either the detection results of the first angle sensor or the second angle sensor and the integer value.

[0008] Additionally, a method for detecting rotation angle is provided, which detects the rotation angle of a rotating component from a reference position. Based on the detection results of the rotation angles of a first gear and a second gear that rotate at different speeds accompanying the rotation of the rotating component, an integer value of the number of electrical rotations of a first angle sensor that detects the rotation angle of the first gear from the reference position or a second angle sensor that detects the rotation angle of the second gear is calculated. Based on either the detection results of the rotation angles of the first gear and the second gear and the integer value, the rotation angle of the rotating component from the reference position is calculated.

[0009] The effects of this invention are as follows.

[0010] According to the present invention, a rotation angle detection device and a rotation angle detection method that can simplify the structure can be provided. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a vehicle equipped with the electric power steering system with a rotation angle detection device as described in the first embodiment.

[0012] Figure 2 This is a perspective view of the rotation angle detection device and the upper shaft in the first embodiment.

[0013] Figure 3 This is an exploded perspective view of the rotation angle detection device in the first embodiment.

[0014] Figure 4 This is a bottom view of the first gear, second gear, first target, second target, substrate, and control unit in the first embodiment.

[0015] Figure 5 This is a bottom view of the substrate, first transmitting coil, first receiving coil, second transmitting coil, second receiving coil, and control unit in the first embodiment.

[0016] Figure 6 This is a schematic cross-sectional view of the substrate in the first embodiment.

[0017] Figure 7 It is Figure 5 An enlarged view of the periphery of the first transmitting coil and the first receiving coil.

[0018] Figure 8 It shows Figure 7 The second layer (back pattern).

[0019] Figure 9 It is Figure 5 An enlarged view of the periphery of the second transmitting coil and the second receiving coil.

[0020] Figure 10 It shows Figure 9 The second layer (back pattern).

[0021] Figure 11 This is a circuit diagram of the transmitting coil circuit in the first embodiment.

[0022] Figure 12 This represents the electrical angle of the first inductive sensor in the first embodiment and the input voltage V. input A graph showing the relationship between the first output voltage V1 and the second output voltage V2.

[0023] Figure 13 It is a graph showing the relationship between the absolute rotation angle θ, the first detection angle ψ, and the second detection angle φ in the first embodiment.

[0024] Figure 14 It is a graph showing the relationship between the absolute rotation angle θ in the first embodiment and the phase difference resulting from subtracting the second detection angle φ from the first detection angle ψ.

[0025] Figure 15 It is a graph showing the relationship between the absolute rotation angle θ and the normalized phase difference δ in the first embodiment.

[0026] Figure 16 The dashed line represents the normalized phase difference δ and the absolute angle φ of the second target in the first embodiment. s The relationship is represented by a solid line based on the absolute angle φ. s A graph showing the integer values ​​of the electrical rotation count of the second inductive sensor.

[0027] Figure 17 It is a graph showing the relationship between the true value and the calculated value of the absolute rotation angle θ in the first embodiment.

[0028] Figure 18 This is a flowchart illustrating an example of the calculation process performed by the control unit in the first embodiment to determine the absolute rotation angle θ.

[0029] Figure 19 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device according to the second embodiment.

[0030] Figure 20 (a) to (d) are explanatory diagrams showing the structure and operation of the first angle sensor in the second embodiment, with the first and second gears omitted.

[0031] Figure 21This is an explanatory diagram showing an example of the circuit structure of the first fixed electrode according to the second embodiment. The circuit structure is used by the control unit to detect the capacitance between the first fixed electrode and the rotating electrode.

[0032] Figure 22 (a) and (b) indicate that... Figure 20 (a) shows the rotation position of the rotating electrode as a reference position with a rotation angle of 0°, and the curve of the change in capacitance between the rotating electrode and the first and second fixed electrodes when the rotating electrode rotates 360° from the reference position.

[0033] Figure 23 (a) is a schematic diagram showing the overlap between the rotating electrode and the first fixed electrode and the second fixed electrode when the rotation angle of the rotating electrode is less than 90°. (b) is a schematic diagram showing the overlap between the rotating electrode and the first fixed electrode and the second fixed electrode when the rotation angle of the rotating electrode is greater than 90°.

[0034] Figure 24 This is a structural diagram showing a modified example of the shapes of the first fixed electrode and the second fixed electrode in the second embodiment.

[0035] Figure 25 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device according to the third embodiment.

[0036] Figure 26 (a) is a structural diagram showing a rotating electrode mounted on the substrate side of the second gear in the third embodiment, and (b) is a structural diagram showing a first fixed electrode and a second fixed electrode provided on the substrate.

[0037] Figure 27 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device according to the fourth embodiment.

[0038] Figure 28 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device according to the fifth embodiment.

[0039] Figure 29 (a) is a structural diagram showing the guide plate mounted on the substrate side of the first gear and the guide plate mounted on the substrate side of the second gear. (b) is a top view showing the electromagnetic coil provided on the substrate and the electromagnetic coil.

[0040] In the figure: 1, 1A~1D—rotation angle detection device; 101, 101A, 101C, 101D—first angle sensor; 102, 102A, 102B, 102D—second angle sensor; 121—upper shaft (rotating component); 21, 23—first gear; 22, 24—second gear; 31—first target; 32—second target; 4, 6A~6D—substrate; 402—arc-shaped recess; 41—first transmitting coil; 42—first receiving coil; 43—second transmitting coil; 44—second receiving coil; 90, 90A~90D—control unit. Detailed Implementation

[0041] [First Implementation Method]

[0042] Reference Figures 1 to 18 The first embodiment of the present invention will be described. Furthermore, the embodiments described below are specific examples of preferred embodiments for carrying out the present invention, and also illustrate various technically preferred aspects; however, the scope of the present invention is not limited to these specific embodiments.

[0043] (Electric power steering system 10)

[0044] Figure 1 This is a schematic diagram of a vehicle equipped with an electric power steering system 10 having a rotation angle detection device 1 of this type.

[0045] This method relates to a rotation angle detection device 1 for detecting the rotation angle of a rotating component from a reference position. In this embodiment, an example is shown where the rotation angle detection device 1 is mounted on an electric power steering device 10, but the application of the rotation angle detection device 1 is not limited to this.

[0046] like Figure 1 As shown, the electric power steering system 10 includes: a steering wheel 11; a steering shaft 12 connected to the steering wheel 11; a rotation angle detection device 1 that detects the rotation angle, i.e., the steering angle, of the upper shaft 121 of the steering shaft 12 (described later); a torque sensor 13 that detects the steering torque applied to the steering wheel 11; a rack shaft 14; left and right tie rods 15, which are respectively connected to the two ends of the rack shaft 14 in a swingable manner; an electric motor 16 for power assistance; a reduction mechanism 17 that reduces the rotation of the output rotation shaft 161 of the electric motor 16 and transmits it to the steering shaft 12; and a steering control device 18 that controls the electric motor 16.

[0047] The steering shaft 12 has a torsion bar 120 that is torsion-torsional by steering torque, an upper shaft 121 located on the side of the steering wheel 11 opposite to the torsion bar 120, and a lower shaft 122 located on the side of the rack shaft 14 opposite to the torsion bar 120. The steering wheel 11 is mounted on the end of the upper shaft 121 opposite to the torsion bar 120. A pinion tooth 122a is provided on the end of the lower shaft 122 opposite to the torsion bar 120, which meshes with the rack tooth 141 provided on the rack shaft 14. The torque sensor 13 detects the steering torque based on the torsion angle of the torsion bar 120. If the steering shaft 12 rotates, the rack shaft 14 moves forward and backward in the vehicle width direction, causing the left and right steering wheels, i.e., the front wheels 19, to turn.

[0048] The reduction mechanism 17 has a worm gear 171 fixed to the output shaft 161 of the electric motor 16 and a worm wheel 172 fixed to the lower shaft 122 and meshing with the worm gear 171. The output torque of the electric motor 16 is amplified by the reduction mechanism 17 and transmitted to the lower shaft 122, becoming an auxiliary torque to assist the driver in steering the steering wheel 11. An absolute encoder 162 is provided in the electric motor 16 for detecting the rotation angle of the output shaft 161.

[0049] The steering control device 18 controls the electric motor 16 by imparting an auxiliary torque to the steering shaft 12 corresponding to the steering angle and steering torque, based on information about the steering angle obtained from the rotation angle detection device 1, the steering torque obtained from the torque sensor 13, and the rotation angle of the output rotation shaft 161 obtained from the encoder 162 of the electric motor 16. The steering control device 18 is, for example, composed of an ECU (Electronic Control Unit).

[0050] (Rotation angle detection device 1)

[0051] The rotation angle detection device 1 uses the rotational position of the upper shaft 121 when the steering wheel 11 is in the neutral position as a reference position, and detects the rotation angle from the reference position of the upper shaft 121. That is, in this embodiment, the rotating component that the rotation angle detection device 1 detects is the upper shaft 121. The upper shaft 121 rotates more than 360° from the reference position to one side and to the other side respectively.

[0052] Figure 2 This is a perspective view of the rotation angle detection device 1 and the upper shaft 121. Figure 3 This is an exploded perspective view of the rotation angle detection device 1. Furthermore, in Figure 3 The diagrams of the first transmitting coil, the first receiving coil, the second transmitting coil, and the second receiving coil are omitted. Figure 4 This is a bottom view of the first gear 21, the second gear 22, the first target 31, the second target 32, the base plate 4, and the control unit 90. Figure 4In the diagram, the shaded area indicated by symbol R1 represents the formation area of ​​the first transmitting coil and the first receiving coil, and the shaded area indicated by symbol R2 represents the formation area of ​​the second transmitting coil and the second receiving coil. Figure 5 This is a bottom view of the substrate 4, the first transmitting coil 41, the first receiving coil 42, the second transmitting coil 43, the second receiving coil 44, and the control unit 90. The control unit 90 is, for example, composed of a Micro Controller Unit (MCU).

[0053] like Figures 3 to 5 As shown, the rotation angle detection device 1 includes a first gear 21, a second gear 22, a first target 31, a second target 32, a substrate 4, a first transmitting coil 41, a first receiving coil 42, a second transmitting coil 43, a second receiving coil 44, a control unit 90, a housing 51, and a cover 52. The first gear 21 rotates integrally with the upper shaft 121, which is a rotating component. The second gear 22 meshes with the first gear 21 and rotates at a different speed than the first gear 21. The first target 31 is made of a conductor and rotates integrally with the first gear 21. The second target 32 ​​is made of a conductor and rotates integrally with the second gear 22. The substrate 4 is arranged opposite to both the first target 31 and the second target 32.

[0054] A first transmitting coil 41 is formed on the substrate 4, generating an alternating magnetic field to induce eddy currents in the first target 31. A first receiving coil 42 is formed on the substrate 4 and is electromagnetically coupled to the first transmitting coil 41. A second transmitting coil 43 is formed on the substrate 4, generating an alternating magnetic field to induce eddy currents in the second target 32. A second receiving coil 44 is formed on the substrate 4 and is electromagnetically coupled to the second transmitting coil 43. The control unit 90 controls the energizing state of the first transmitting coil 41 and the second transmitting coil 43, and processes the output signals from the first receiving coil 42 and the second receiving coil 44. The housing 51 and the cover 52 house the components of the rotation angle detection device 1.

[0055] Next, the details of the rotation angle detection device 1 will be explained.

[0056] The first gear 21 is made of a non-magnetic resin with electrical insulation properties. The first gear 21 is a spur gear. The first gear 21 has a cylindrical portion 211 and a main body portion 212 extending outward from the cylindrical portion 211. Engaging protrusions 211a protruding inward are formed on the cylindrical portion 211. Figure 2 As shown, the engaging protrusion 211a engages with the groove 121a formed axially in the upper shaft 121, thereby causing the first gear 21 to rotate integrally with the upper shaft 121. Furthermore, in this embodiment, when referred to simply as "axial," it refers to the direction in which the rotation axis of the upper shaft 121 extends. Figure 3As shown, one end of the cylindrical portion 211 is rotatably fitted into the fitting recess 511b of the housing 51 (described later). The other end of the cylindrical portion 211 is rotatably inserted into the opening 521a of the cover 52 (described later).

[0057] like Figure 3 and Figure 4 As shown, the main body 212 has a plurality of teeth 212a on its outer periphery. In this embodiment, as an example, the first gear 21 has 58 teeth. The plurality of teeth 212a of the main body 212 mesh with the second gear 22.

[0058] The second gear 22 is made of a non-magnetic resin with electrical insulation properties. The second gear 22 is a spur gear that rotates passively in response to the rotation of the first gear 21. The diameter of the second gear 22 is smaller than the diameter of the first gear 21. The second gear 22 has a circular plate portion 221 and an annular protrusion 222 that protrudes axially from the circular plate portion 221 to one side.

[0059] The circular plate portion 221 has a plurality of teeth 221a on its outer periphery that mesh with the first gear 21. The second gear 22 has fewer teeth than the first gear 21, and therefore, the rotational speed of the second gear 22 is faster than that of the first gear 21. In this embodiment, as an example, the second gear 22 has 24 teeth. The annular protrusion 222 can be rotatably inserted into the annular groove 511c formed in the housing 51.

[0060] like Figure 3 as well as Figure 4 As shown, the first target 31 rotates integrally with the upper shaft 121 and the first gear 21. In this embodiment, the first gear 21 is formed by molding the first target 31, so that the first target 31 and the first gear 21 are integrally formed.

[0061] The first target 31 is made of a conductor such as metal. The first target 31 is annular in shape, with alternating protrusions 311 and recesses 312 formed along its outer periphery. The number of protrusions 311 is the same as the number of recesses 312. In this embodiment, the first target 31 has five protrusions 311. The protrusions 311 are areas through which magnetic flux from an alternating magnetic field generated by energizing the first transmitting coil 41 passes, and are areas where eddy currents are generated by varying the density of the passing magnetic flux over time. These eddy currents are generated in a manner that generates magnetic flux in the direction that cancels out the alternating magnetic field. The dimensions of the circumferential protrusions 311 and the recesses 312 are the same. However, this is not a limitation; the dimensions of the circumferential protrusions 311 and the recesses 312 may also be different. For example, when the first target 31 and the first receiving coil 42 are located relatively far apart, it is preferable that the dimensions of the circumferential protrusions 311 are smaller than the dimensions of the recesses 312. When the first target 31 and the first receiving coil 42 are at a relatively far distance, the magnetic field emitted from the first target 31 extends and propagates to the first receiving coil 42. Therefore, the range of the first receiving coil 42 affected by the magnetic field from the first target 31 expands, but the strength of the output signal of the first receiving coil 42 is maximum when the aforementioned range is half the length of the first receiving coil 42. Therefore, the strength of the output signal of the first receiving coil 42 decreases. Considering the above, when the first target 31 and the first receiving coil 42 are at a relatively far distance, it is preferable that the size of the circumferential protrusion 311 is smaller than the size of the recess 312.

[0062] The second target 32 ​​rotates integrally with the second gear 22. In this embodiment, the second gear 22 is formed by molding the second target 5, so that the second target 5 and the second gear 22 are integrally formed.

[0063] The second target 32 ​​is made of a conductor such as metal. Alternatively, the second target 32 ​​can also be formed on a printed circuit board using copper foil or the like. The second target 32 ​​is in the shape of an annular plate, with alternating protrusions 321 and recesses 322 formed along its outer periphery in the circumferential direction. The number of protrusions 321 is the same as the number of recesses 322. In this embodiment, the second target 32 ​​has two protrusions 321. The protrusions 321 are the portions through which magnetic flux of the alternating magnetic field generated by energizing the second transmitting coil 43 passes, and are portions through which eddy currents are generated by changing the density of the passing magnetic flux over time. These eddy currents are generated in a manner that generates magnetic flux in the direction that cancels the alternating magnetic field. The dimensions of the circumferential protrusions 321 and the recesses 322 are the same. Furthermore, similar to the first target 31, the dimensions of the circumferential protrusions 321 and the recesses 322 can also be different.

[0064] Furthermore, the number of protrusions 311 of the first target 31 and the number of protrusions 321 of the second target 32 ​​are not limited to the numbers mentioned above. For example, the diameter and number of teeth of the first gear 21 can be varied according to the diameter of the rotating component of the object being measured for rotation angle, but the appropriate number of protrusions 311 of the first target 31 and the number of protrusions 321 of the second target 32 ​​can be appropriately selected based on these variations. The substrate 4 is arranged in a manner that faces the protrusions 311 of the first target 31 and the protrusions 321 of the second target 32.

[0065] Substrate 4 is a printed circuit board arranged in an orientation where the normal direction is the axial direction. For example... Figure 3 As shown, a plurality of positioning holes 401 are formed on the substrate 4, and pins 514 formed on the housing 51 or pins 521b formed on the cover 52 are inserted into the positioning holes 401. In addition, the substrate 4 is fixed to the housing 51 and the cover 52 and is configured non-rotatingly relative to the vehicle body.

[0066] An arc-shaped recess 402 is formed on the substrate 4. The arc-shaped recess 402 has an arc shape centered on the central axis of the upper shaft 121, with one side of the substrate 4 cut into it. The arc-shaped recess 402 is arranged along the outer peripheral surface of the cylindrical portion 211 of the first gear 21. The center point of the arc-shaped recess 402 coincides with the center of the cylindrical portion 211. The arc-shaped recess 402 is arranged along the outer peripheral surface of the upper shaft 121 via the first gear 21. The substrate 4 is arranged on the side of the upper shaft 121 without penetrating it. That is, the substrate 4 does not have a closed through hole that allows the upper shaft 121 to pass through.

[0067] Although the illustration is omitted, various electronic components such as capacitors are mounted on the substrate 4. In addition, the substrate 4 has: a first transmitting coil 41 and a first receiving coil 42, which are formed in the axial direction opposite to the protrusion 311 of the first target 31; and a second transmitting coil 43 and a second receiving coil 44, which are formed in the axial direction opposite to the protrusion 321 of the second target 32.

[0068] The first transmitting coil 41, the first receiving coil 42, and the second receiving coil 44 are respectively formed on both sides of the substrate 4. That is, in this embodiment, the substrate 4 is a double-layer substrate (i.e., a double-sided substrate). Figure 6 This is a schematic cross-sectional view of substrate 4. (For example...) Figure 6 As shown, the wiring layers 403 (i.e., the first transmitting coil, the first receiving coil, the second transmitting coil, and the second receiving coil) formed on each layer of the substrate 4 are electrically connected via vias 404.

[0069] The first transmitting coil 41 and the first receiving coil 42, together with the first target 31, constitute a first inductive sensor 101 as a first angle sensor for detecting the rotation angle of the first gear 21 relative to the substrate 4. When viewed from the axial direction, the first transmitting coil 41 and the first receiving coil 42 are formed in an arc-shaped region R1 along the arc-shaped recess 402 (see reference). Figure 4 As will be described in detail later, when viewed from the axial direction, the first transmitting coil 41 is wound in an arc-shaped frame, and the first receiving coil 42 is formed in such a way that it is housed inside the first transmitting coil 41. The area from the outer edge of the first transmitting coil 41 to the inner side is region R1.

[0070] Figure 7 It is Figure 5 Enlarged view of the periphery of the first transmitting coil 41 and the first receiving coil 42. Figure 8 It shows Figure 7 The second layer (back pattern). Additionally, in Figure 8 In the diagram, the outline of substrate 4 is indicated by a double-dotted line. The first transmitting coil 41 is formed by winding multiple turns in an arc-shaped frame. One end of the first transmitting coil 41 is electrically connected to the lead-out portion 4a of the control unit 90, and the other end is electrically connected to the connecting portion 4k that connects the first transmitting coil 41 and the second transmitting coil 43. The outermost portion of the first transmitting coil 41 is electrically connected to the connecting portion 4k.

[0071] The first receiving coil 42 is formed inside the first transmitting coil 41 when viewed from the axial direction. In other words, the first transmitting coil 41 is formed in a manner that surrounds the first receiving coil 42. The first receiving coil 42 includes a first sine wave coil 421 and a first cosine wave coil 422.

[0072] The shape of the first sine wave coil 421 is designed to output a voltage signal along the beat frequency waveform of a sine wave based on the rotation of the upper shaft 121 (described later). For example, the first sine wave coil 421 is formed along an imaginary sine wave that curves circumferentially with one end of the first sine wave coil 421 as the phase axis. The first sine wave coil 421 has a generally chain-like shape, forming multiple closed loops, such that a sine wave is superimposed with a wave after the sine wave is reversed vertically. The two ends of the first sine wave coil 421 are electrically connected to the leads 4b and 4c. The leads 4b and 4c are electrically connected to the control unit 90.

[0073] The shape of the first cosine wave coil 422 is designed to output a voltage signal along the beat frequency waveform of a cosine wave according to the rotation of the upper shaft 121. For example, the first cosine wave coil 422 is formed along an imaginary cosine wave that curves circumferentially with one end of the first cosine wave coil 422 as the phase axis. The first cosine wave coil 422 has a generally chain-like shape formed by overlapping a cosine wave and a wave after the cosine wave is reversed vertically, forming multiple closed loops. The two ends of the first cosine wave coil 422 are electrically connected to the leads 4d and 4e. The leads 4d and 4e are electrically connected to the control unit 90.

[0074] The second transmitting coil 43 and the second receiving coil 44, together with the second target 32, constitute a second inductive sensor 102 as a second angle sensor for detecting the rotation angle of the second gear 22 relative to the substrate 4. Figure 4 as well as Figure 5 As shown, the second transmitting coil 43 and the second receiving coil 44, when viewed from the axial direction, are located on the side opposite to the upper axis 121 relative to region R1, and are formed in an annular region R2. When viewed from the axial direction, the second transmitting coil 43 is wound into an annular shape, and the second receiving coil 44 is formed in such a way that it is housed inside the second transmitting coil 43. Region R2 is the area from the outer edge of the second transmitting coil 43 to its inner edge, as detailed later.

[0075] Figure 9 It is Figure 5 Enlarged view of the periphery of the second transmitting coil 43 and the second receiving coil 44. Figure 10 It shows Figure 9 The second layer (back pattern). Additionally, in Figure 10 In the diagram, the outline of substrate 4 is indicated by a double-dotted line. The second transmitting coil 43 is formed by winding multiple turns in a circular shape. One end of the second transmitting coil 43 is electrically connected to the connecting portion 4k, and the other end is electrically connected to the lead-out portion 4f connected to the control unit 90. The outermost periphery of the second transmitting coil 43 is electrically connected to the connecting portion 4k. The first transmitting coil 41 and the second transmitting coil 43 are electrically connected in series via the connecting portion 4k. The lead-out portion 4f has: a first portion 4fa, formed at a position overlapping the connecting portion 4k in the axial direction; a second portion 4fb, formed along the first transmitting coil 41 from the outer periphery; and a third portion 4fc, extending radially outward from the second portion 4fb towards the upper axis 121, and the third portion 4fc is electrically connected to the control unit 8.

[0076] The second receiving coil 44 is formed inside the second transmitting coil 43 when viewed from the axial direction. In other words, the second transmitting coil 43 is formed in a manner that surrounds the second receiving coil 44. The second receiving coil 44 includes a second sine wave coil 441 and a second cosine wave coil 442.

[0077] The shape of the second sine wave coil 441 is designed to output a voltage signal along the beat frequency waveform of a sine wave based on the rotation of the upper shaft 121. For example, the second sine wave coil 441 is formed along a virtual sine wave drawn in a circular shape with a predetermined position in the circumference of the second sine wave coil 441 as the phase axis. The second sine wave coil 441 has a generally chain-like shape in which the sine wave is superimposed with the wave after the sine wave is reversed vertically, forming multiple closed loops. The two ends of the second sine wave coil 441 are electrically connected to the leads 4g and 4h. The leads 4g and 4h are electrically connected to the control unit 90.

[0078] The shape of the second cosine wave coil 442 is designed to output a voltage signal along the beat frequency waveform of a cosine wave according to the rotation of the upper shaft 121. For example, the second cosine wave coil 442 is formed along an imaginary cosine wave that is circularly curved with a predetermined position in the circumference of the second cosine wave coil 442 as the phase axis. The second cosine wave coil 442 has a generally chain shape formed by overlapping a cosine wave and a wave after the cosine wave is reversed vertically, forming multiple closed loops. The two ends of the second cosine wave coil 442 are electrically connected to the leads 4i and 4j. The leads 4i and 4j are electrically connected to the control unit 90. In addition, the wiring from each lead 4a to 4j to the control unit 90 is omitted in the illustration. In addition, the shapes of the first transmitting coil 41 and the first receiving coil 42 constituting the first inductive sensor 101 can also adopt, for example, the coil shapes of a known inductive sensor. The same applies to the second inductive sensor 102.

[0079] In this embodiment, the second inductive sensor 102 can detect angles with higher accuracy than the first inductive sensor 101. That is, the detection accuracy of the rotation angle of the second gear 22 by the second inductive sensor 102 is higher than the detection accuracy of the angle of the first gear 21 by the first inductive sensor 101. Here, higher detection accuracy means, for example, a smaller angle error. Next, the case where the second inductive sensor 102 can detect rotation angles with even higher accuracy will be described in more detail.

[0080] First, as described above, the first inductive sensor 101 has a first transmitting coil 41 and a first receiving coil 42 formed only within a portion of the circumferential direction. Therefore, for example, if the first target 31 is assembled at an angle relative to an imaginary plane orthogonal to the axial direction, the gap between the first transmitting coil 41, the first receiving coil 42, and the opposing protrusion 311 varies depending on the protrusion 311. Consequently, the strength of the output signal generated by the first receiving coil 42 can easily decrease the accuracy of the first inductive sensor 101. On the other hand, as described above, the second inductive sensor 102 has a second transmitting coil 43 and a second receiving coil 44 formed throughout the entire circumference. Therefore, for example, when the second target 32 ​​is assembled at an angle relative to an imaginary plane orthogonal to the axial direction, even if the axial gap between a specific protrusion 321 and the second transmitting coil 43 and the second receiving coil 44 decreases, the axial gap between the protrusion 321 on the opposite side and the second transmitting coil 43 and the second receiving coil 44 increases. Therefore, the overall impact on the voltage output from the second receiving coil 44 is small. Thus, in this embodiment, the second inductive sensor 102 can detect angles with higher accuracy than the first inductive sensor 101. Furthermore, compared to the first inductive sensor 101, the second inductive sensor 102 is less susceptible to horizontal positional offsets between the target (i.e., the first target 31 or the second target 32) and the receiving coil (i.e., the first receiving coil 42 or the second receiving coil 44). Moreover, regarding the formation of the coil pattern, the case where it is formed in a ring shape as in the second inductive sensor 102 is less prone to error compared to the case where it is formed in a ring shape as in the first inductive sensor 101. Therefore, compared with the first inductive sensor 101, the second inductive sensor 102 can detect angles more accurately.

[0081] The control unit 90 may include, for example, a control area containing a processor and a RAM (Random Access Memory) that serves as the processing area when the processor operates, or a ROM (Read Only Memory). The control unit 90 is composed of an IC (Integrated Circuit) such as a MCU (Micro Controller Unit). Furthermore, at least a portion of the functions of the control unit 90 may also be implemented by, for example, a steering control device 18.

[0082] The control unit 90 controls the energization of the first transmitting coil 41 and the second transmitting coil 43, and processes the output signals of the first receiving coil 42 and the second receiving coil 44 (e.g., AD conversion). Details of the processing performed by the control unit 90 will be described later.

[0083] like Figure 3As shown, the housing 51 has a bottom wall portion 511, a side wall portion 512 erected from the periphery of the bottom wall portion 511, a dividing wall 513 erected from the bottom wall portion 511 and dividing the space inside the housing 51, a pin 514 for positioning the substrate 4, a connector portion 515 for electrical connection to a connected object, and a fixing portion 516 for fixing to a mounting object.

[0084] The bottom wall portion 511 is formed along a plane orthogonal to the axial direction. An insertion hole 511a is formed in the bottom wall portion 511 for the upper shaft 121 to pass through. Around the insertion hole 511a in the bottom wall portion 511, an annular fitting recess 511b is formed at one end of the cylindrical portion 211 that can rotatably engage with the first gear 21. Additionally, an annular groove 511c is formed in the bottom wall portion 511 for rotatably engaging with the annular protrusion 222 of the second gear 22.

[0085] The side wall portion 512 has an opening portion 512a at the end opposite to the bottom wall portion 511.

[0086] A dividing wall 513 is erected from the bottom wall portion 511. A portion of the dividing wall 513 is formed along the first gear 21 and the second gear 22, dividing the arrangement space of the first gear 21 and the second gear 22. In addition, a substrate 4 is placed on the side of the dividing wall 513 opposite to the bottom wall portion 511.

[0087] Pin 514 is erected from the dividing wall 513 toward the side opposite to the bottom wall 511. Pin 514 is inserted into the positioning hole 401 of the substrate 4.

[0088] The connector of the connection object connected to the rotation angle detection device 1 is engaged with the connector part 515. The connector part 515 is formed by further molding a core (not shown) formed by molding a plurality of connector terminals 515a. The plurality of connector terminals 515a are respectively inserted into a plurality of through holes 405 formed on the substrate 4 and electrically connected to the control part 90 mounted on the substrate 4.

[0089] The fixing part 516 is formed to extend outward from the bottom wall part 511 and has a bolt insertion hole 516a for inserting a bolt for fixing.

[0090] The cover 52 closes the opening 512a of the side wall portion 512. The cover 52 has a top wall portion 521 opposite to the bottom wall portion 511 of the housing 51 and a plurality of flexible pieces 522 erected from the periphery of the top wall portion 521 toward the housing 51.

[0091] An opening 521a is formed in the top wall portion 521 for inserting one end of the cylindrical portion 211 of the first gear 21. Additionally, an upper shaft 121 is inserted into the opening 521a. A pin 521b for inserting a positioning hole 401 into the substrate 4 is vertically provided in the bottom wall portion 511.

[0092] Multiple flexible sheets 522 are engaged with the housing 51 via snap-fit ​​mechanisms. Thus, the cover 52 is fixed to the housing 51.

[0093] (Transmitting coil circuit)

[0094] Figure 11 This is the circuit diagram of the transmitting coil circuit. (Refer to...) Figure 11 The transmission coil circuit from the control unit 90 to the first transmission coil 41 and the second transmission coil 43 will be described.

[0095] The control unit 90 outputs an AC voltage of a predetermined frequency. The waveform of the voltage output by the control unit 90 to the transmitting coil circuit is described later. Figure 12 As shown, for example, is a sine wave. The transmitting coil circuit has a series connection between a first transmitting coil 41 and a second transmitting coil 43. Furthermore, two capacitors 45 are connected in series on both sides of the series connection, and the connection between the two capacitors is grounded. Thus, the transmitting coil circuit is configured as an LC oscillating circuit, specifically a Colpitts oscillating circuit.

[0096] In the transmitting coil circuit, the first transmitting coil 41 and the second transmitting coil 43 are connected in series rather than in parallel. As a result, the combined inductance of the transmitting coil circuit increases, and consequently, the Q value (Quality Factor) rises, making it easier to selectively allow only specific frequencies to pass through.

[0097] (Rotation angle detection method)

[0098] Next, the method for calculating the absolute rotation angle θ of the upper shaft 121 using the rotation angle detection device 1 of this method will be explained. The absolute rotation angle θ of the upper shaft 121 refers to the rotation angle of the upper shaft 121 when the steering wheel 11 is in the neutral position is set to 0°, the rotation angle of the upper shaft 121 when the steering wheel 11 is rotated to the left to make contact is set to the negative maximum value, and the rotation angle of the upper shaft 121 when the steering wheel 11 is rotated to the right to make contact is set to the positive maximum value.

[0099] Figure 12 This represents the electrical angle of the first inductive sensor 101 relative to the input voltage V. input A graph showing the relationship between the first output voltage V1 and the second output voltage V2. Figure 12 In the three graphs shown, the horizontal axis is set to the same scale for each other. Input voltage V inputIt is a sinusoidal voltage applied to the first transmitting coil 41 and the second transmitting coil 43. The first output voltage V1 is the voltage induced in the first sinusoidal coil 421 or the second sinusoidal coil 441. The second output voltage V2 is the voltage induced in the first cosine coil 422 or the second cosine coil 442.

[0100] When detecting the rotation angle of the upper shaft 121, firstly, the control unit 90 applies a sinusoidal voltage of a predetermined frequency to the first transmitting coil 41 and the second transmitting coil 43. As a result, an alternating magnetic field is formed around the first transmitting coil 41 and the second transmitting coil 43 respectively.

[0101] The first output voltage V1 generated by electromagnetic induction in the first sine wave coil 421 changes with time through the alternating magnetic field generated by the first transmitting coil 41, and the second output voltage V2 generated by electromagnetic induction in the first cosine wave coil 422 changes with time.

[0102] Here, when the protrusion 311 of the first target 31 is opposite to the first transmitting coil 41, eddy currents are generated in the protrusion 311, and magnetic flux is formed that cancels out the direction of the magnetic flux generated by energizing the first transmitting coil 41. Therefore, the magnetic flux generated by energizing the first transmitting coil 41 and passing through the closed loop portions of the first sine wave coil 421 and the first cosine wave coil 422, passing through the portion opposite to the protrusion 311, is canceled out by the magnetic flux in the opposite direction generated by the eddy currents.

[0103] Furthermore, the first target 31 has alternating protrusions 311 and concave portions 312 formed in the circumferential direction. Therefore, as the first target 31 rotates, the area of ​​the protrusions 311 opposite to the closed-loop portions of the first sine wave coil 421 and the first cosine wave coil 422 changes periodically, thereby causing the first output voltage V1 and the second output voltage V2 to change periodically, respectively. Figure 12 As shown, in this method, the waveform of the voltage generated by the first sine wave coil 421 as the first target 31 rotates becomes the beat frequency waveform of the sine wave, and the waveform of the voltage generated by the first cosine wave coil 422 as the first target 31 rotates becomes the beat frequency waveform of the cosine wave.

[0104] Then, the control unit 90 generates a first demodulated voltage obtained by demodulating the output signal from the first sine wave coil 421. The waveform of the first demodulated voltage relative to the rotation angle of the upper shaft 121 is as follows: Figure 12 The dashed line L1 indicates a sinusoidal wave shape. Additionally, the control unit 90 generates a second demodulated voltage obtained by demodulating the output signal from the first cosine wave coil 422. The waveform of the second demodulated voltage relative to the rotation angle of the upper shaft 121 is as follows... Figure 12 The dashed line L2 indicates a cosine wave shape.

[0105] Furthermore, the control unit 90 uses the atan2 function to calculate the first detection angle ψ (electrical angle), which is the detection value of the rotation angle of the first target 31, based on the first demodulation voltage and the second demodulation voltage. Similarly, the detection value of the rotation angle of the second target 32, i.e., the second detection angle φ (electrical angle), is calculated.

[0106] Figure 13 This is a graph showing the relationship between the absolute rotation angle θ and the first detection angle ψ and the second detection angle φ. Figure 13 In the diagram, the first detection angle ψ is represented by a dashed line, and the second detection angle φ is represented by a solid line. Figure 13 The horizontal axis of the graph shown is the absolute rotation angle θ of the upper axis 121, and the vertical axis is the first detection angle ψ or the second detection angle φ.

[0107] Here, the first target 31 maintains the same posture for each fifth of a rotation (i.e., 72°) within the range where the protrusions 311 and concave portions 312 are formed. Therefore, the first detection angle ψ changes periodically with a cycle of one fifth of a rotation (i.e., 72°) of the first target 31. That is, during one rotation of the first target 31, the first detection angle ψ (i.e., the electrical angle) changes for 5 cycles. Therefore, the speed transfer ratio j from the upper shaft 121 to the first inductive sensor 101 (i.e., the rotational speed of the upper shaft 121 ÷ the rotational speed of the first inductive sensor 101) is considered to be 0.20 (i.e., 1 / 5).

[0108] Furthermore, the second target 32 ​​maintains the same posture for each half-turn (i.e., 180°) of rotation within the area where the protrusion 321 and concave portion 322 are formed. Therefore, the second detection angle φ changes periodically with each half-turn (i.e., 180°) of rotation of the second target 32 ​​as one cycle. That is, the second detection angle φ (i.e., the electrical angle) changes for two cycles during one rotation of the second target 32. Also, the gear ratio of the second gear 22 relative to the first gear 21 is 24 / 58. Therefore, the speed transfer ratio i from the upper shaft 121 to the second inductive sensor 102 is considered to be 24 / (58×2)≈0.21.

[0109] Furthermore, when rotating the steering wheel 11 from the position of contacting the left to the position of contacting the right, such as Figure 13 As shown, the first detection angle ψ and the second detection angle φ change with different periods. Therefore, the absolute rotation angle θ cannot be obtained from either the first detection angle ψ or the second detection angle φ alone.

[0110] Because the speed transmission ratio j is different from the speed transmission ratio i, if the steering wheel 11 rotates from the neutral position to the left or right, the first detection angle ψ and the second detection angle φ gradually deviate and the difference increases. In this embodiment, the absolute rotation angle θ is calculated using the difference between the first detection angle ψ and the second detection angle φ.

[0111] like Figure 13 As shown, when the first detection angle ψ and the second detection angle φ are both set to 0° when the absolute rotation angle θ is 0°, the difference between the first detection angle ψ and the second detection angle φ gradually increases as the absolute value of the absolute rotation angle θ increases.

[0112] Figure 14 This is a graph showing the relationship between the absolute rotation angle θ and the phase difference (resulting from the first detection angle ψ minus the second detection angle φ). When the steering wheel 11 rotates from the neutral position to the left or right, the speed transmission ratio i from the upper shaft 121 to the second inductive sensor 102 is smaller than the speed transmission ratio j from the upper shaft 121 to the first inductive sensor 101. Therefore, the second detection angle φ crosses zero before the first detection angle ψ, and then the first detection angle ψ crosses zero. During the period from the zero crossing of the second detection angle φ to the zero crossing of the first detection angle ψ, the absolute value of the difference between the first detection angle ψ and the second detection angle φ is temporarily greater than 180°. Here, zero crossing refers to a temporary large change in the detection angle from around 0° to around 360°.

[0113] Figure 15 This is a graph showing the phase difference after performing a phase difference calculation: if the second detection angle φ crosses zero before the first detection angle ψ and the phase difference is greater than 180°, then 360° is subtracted from the phase difference; if the phase difference is less than -180°, then 360° is added to the phase difference. This calculation is referred to as normalization, and the phase difference after normalization is called the normalized phase difference δ. By implementing normalization, as... Figure 15 As shown, the curve representing the normalized phase difference δ becomes a straight line. Figure 15 In the curve graph, single-dotted lines are used to represent the -180° and +180° of the vertical axis, respectively.

[0114] In this embodiment, Figure 15 The normalized phase difference δ shown in the graph is within the range of -180° to +180°, meaning that the absolute rotation angle θ can be accurately calculated when the steering wheel 11 is rotated from the left-hand contact position to the right-hand contact position without the first detection angle ψ and the second detection angle φ deviating by more than one cycle. This will be described later.

[0115] In this embodiment, the integer value of the number of electrical rotations of the first inductive sensor 101 or the second inductive sensor 102 (in this embodiment, the second inductive sensor 102) from the reference position is calculated based on the first detection angle ψ and the second detection angle φ. The absolute rotation angle θ is then calculated based on the calculated integer value and the second detection angle φ. By using only the first detection angle ψ in the calculation of the integer value of the number of electrical rotations of the second inductive sensor 102, the adverse effect of the detection error of the first detection angle ψ on the final detection accuracy of the absolute rotation angle θ can be suppressed. For example, in this embodiment, the electrical angle of the first inductive sensor 101 changes for five cycles per revolution of the first gear 21, therefore the number of electrical rotations of the first inductive sensor 101 is five times the number of mechanical rotations of the first gear 21. Similarly, the electrical angle of the second inductive sensor 102 changes for two cycles per revolution of the second gear 22, therefore the number of electrical rotations of the second inductive sensor 102 is twice the number of mechanical rotations of the second gear 22.

[0116] In this embodiment, the integer value of the number of electrical rotations of the second inductive sensor 102 is calculated based on the normalized phase difference δ described above. Next, reference will be made to... Figure 16 This describes a method for calculating the integer value of the number of electrical rotations of the second inductive sensor 102.

[0117] Figure 16 The dashed line represents the absolute angle φ between the normalized phase difference δ and the second target 32. s The relationship is represented by a solid line based on the absolute angle φ. s A graph showing the integer values ​​of the electrical rotation count of the second inductive sensor 102. The absolute angle φ of the second target 32. s The speed transfer ratio j from the upper shaft 121 to the first inductive sensor 101, the speed transfer ratio i from the upper shaft 121 to the second inductive sensor 102, and the normalized phase difference δ are expressed as follows (1). Absolute angle φ s This is equivalent to the absolute angle of the second detection angle φ.

[0118] [Formula 1]

[0119]

[0120] When the integer value of the number of electrical rotations of the second inductive sensor 102 is set as R, R is obtained by the following equations (2) and (3).

[0121] [Equation 2]

[0122]

[0123] [Formula 3]

[0124]

[0125] Figure 17 It is a graph representing the absolute rotation angle θ obtained by the following formula (4) based on the integer value R of the electrical rotation number of the second inductive sensor 102 and the second detection angle. Figure 17 The horizontal axis of the graph shows the true value of the absolute rotation angle θ of the upper axis 121, and the vertical axis shows the calculated value of the absolute rotation angle θ obtained by the control unit 90.

[0126] [Formula 4]

[0127]

[0128] As shown in equation (4), the first detection angle ψ is not included in the formula used to calculate the absolute rotation angle θ. Therefore, when the integer value R of the electrical rotation number of the second inductive sensor 102 is accurately obtained, as shown in equation (4), Figure 17 As shown in the curve, the absolute rotation angle θ can be obtained accurately without being affected by the detection error ε. ψ The influence of this. Furthermore, the rotation angle detection method is just one example and can be modified in various ways. For example, the position of the first inductive sensor 101 or the second inductive sensor 102 relative to the origin of the upper shaft 121, the direction of rotation, the direction of increase of the phase difference, etc., can vary depending on the structure of the rotation angle detection device 1, but can be addressed by appropriately changing the coefficients of the above calculation formula.

[0129] (Detection error ε) ψ and detection error ε φ (First condition)

[0130] If the detection error of the first detection angle ψ is ε ψ And the detection error ε of the second detection angle φ φ If the angle is too large, then within the range (i.e., locked to locked) that the rotation angle detection device 1 should detect the absolute rotation angle θ, if the first detection angle ψ and the second detection angle φ deviate by more than one cycle, the absolute rotation angle θ cannot be accurately calculated. That is, in order to accurately calculate the absolute rotation angle θ, even considering the individual errors of the first detection angle ψ and the second detection angle φ, within the range where the absolute rotation angle θ should be detected, Figure 8 The curve showing the normalized phase difference δ also needs to converge to the range of -180° to +180°. A necessary condition for this is the detection error ε. ψ and detection error ε φ The permitted range is explained.

[0131] Using the speed transfer ratio j from the upper shaft 121 to the first inductive sensor 101 and the speed transfer ratio i from the upper shaft 121 to the second inductive sensor 102, the change in normalized phase difference δ when the second gear 22 rotates one revolution with the rotation of the upper shaft 121 is obtained by the following equation (5).

[0132] [Formula 5]

[0133]

[0134] Furthermore, the variation range Δ′ of the phase difference of the entire detection range of the absolute rotation angle θ of the rotation angle detection device 1 is obtained by the following equation (6). In addition, in the following equation (6), when the size of the range of the absolute rotation angle θ to be detected (i.e., locked to locked, for example 1800°) is set to F, R... max It is the integer obtained by rounding down the decimal point of the value obtained by F / (i×360).

[0135] [Formula 6]

[0136]

[0137] In order to accurately calculate the absolute rotation angle θ, the normalized phase difference δ varies with the rotation of the upper axis 121, and its variation range must satisfy the following equation (7).

[0138] [Formula 7]

[0139]

[0140] Therefore, Δ′ needs to be greater than 0 and less than 360 as in equation (8) below, in other words, equation (9) below needs to be satisfied.

[0141] [Formula 8]

[0142]

[0143] [Formula 9]

[0144]

[0145] However, the range of variation of the normalized phase difference δ depends on the detection error ε of the first detection angle ψ. ψ And the detection error ε of the second detection angle φ φ However, this changes, therefore, if the detection error ε is taken into account... ψ and detection error ε φ Then equation (8) is as shown in equation (10) below.

[0146] [Formula 10]

[0147]

[0148] If equation (10) is transformed, then the detection error ε is taken as... ψ and detection error ε φ The absolute value of should satisfy the following condition, which is given by equation (11).

[0149] [Equation 11]

[0150]

[0151] Equation (11) can also be rewritten as Equation (12) below.

[0152] [Equation 12]

[0153]

[0154] In equation (12), z i It is the ratio of the number of teeth of the second gear 22 to the number of teeth of the first gear 21. j It refers to the number of protrusions 311 on the first target 31. P i It refers to the number of protrusions 321 on the second target 32.

[0155] (Detection error ε) ψ and detection error ε φ (Second condition)

[0156] Here, the normalized phase difference δ is calculated based on the first detection angle ψ and the second detection angle φ. Therefore, the normalized phase difference δ includes the detection error ε of the first detection angle ψ. ψ However, if the detection error ε of the first detection angle ψ... ψ And the detection error ε of the second detection angle φ φ Within a range that does not affect the integer value R of the number of electrical rotations of the second inductive sensor 102 obtained by equations (2) and (3) above, the integer value R can be accurately determined. The permissible detection error ε from this perspective... ψ and detection error ε φ The conditions will be explained.

[0157] To accurately determine the integer value R of the electrical rotation number of the second inductive sensor 102, the absolute angle φ s The difference between the second detection angle φ and the detection angle ε will not be affected by the detection error ε. ψ and ε φ The influence of this can cause a change of more than 180° from the error-free true value. That is, if φ s The value of -φ (true value) is affected by the detection error ε. ψ and ε φ The effect changes to (φ) sIf -φ)′, then the following equation (13) needs to be satisfied.

[0158] [Equation 13]

[0159]

[0160] Here, based on the above equation (1) and δ≡ψ N -φ N The following equations (14) and (15) hold true.

[0161] [Formula 14]

[0162]

[0163] [Formula 15]

[0164]

[0165] Then, from equation (14) and equation (15), we obtain equation (16).

[0166] [Formula 16]

[0167]

[0168] If we substitute equation (16) into equation (13), we get the following equation (17).

[0169] [Equation 17]

[0170]

[0171] Here, the detection error ε φ and detection error ε φ It can take either a positive or a negative value, so the left side of equation (17) under the maximum condition is as shown in equation (18) below.

[0172] [Formula 18]

[0173]

[0174] If we transform the above equation (18), we obtain the following equation (19). Equation (19) is the detection error ε used to accurately calculate the integer value R of the electrical rotation number of the second inductive sensor 102. ψ and detection error ε φ The necessary condition, that is, the allowable range of error.

[0175] [Formula 19]

[0176]

[0177] (Flowchart of the processing in control unit 8)

[0178] Figure 18 This is a flowchart illustrating an example of the sequence of calculations performed by the control unit 8 to determine the absolute rotation angle θ.

[0179] In step S1, the control unit 90 receives voltage signals from the first sine wave coil 421, the first cosine wave coil 422, the second sine wave coil 441, and the second cosine wave coil 442, respectively. Next, in step S2, as described above, a first detection angle ψ is calculated based on the voltage signals from the first sine wave coil 421 and the first cosine wave coil 422, and a second detection angle φ is calculated based on the voltage signals from the second sine wave coil 441 and the second cosine wave coil 442, respectively.

[0180] Next, in step S3, the control unit 90 calculates the phase difference by subtracting the second detection angle φ from the first detection angle ψ.

[0181] Next, in step S4, the control unit 90 determines whether the phase difference calculated in step S3 is 180° or more. If the phase difference is 180° or more, then in step S5, the value obtained by subtracting 360° from the phase difference is used as the normalized phase difference δ.

[0182] Next, in step S6, the control unit 90 determines whether the phase difference calculated in step S3 is less than or equal to -180°. If the phase difference is less than or equal to -180°, then in step S7, the value obtained by adding 360° to the phase difference is set as the normalized phase difference δ. Alternatively, if the phase difference calculated in step S3 is greater than -180° and less than 180°, then in step S8, the phase difference calculated in step S3 is set as the normalized phase difference δ. Steps S4 to S8 are phase difference normalization processes.

[0183] Next, in step S9, the control unit 90 calculates the absolute angle φ using equation (1). s .

[0184] Next, in step S10, the control unit 8 calculates the integer value R of the electrical rotation number of the second inductive sensor 102 by performing the operation of formula (2) or (3).

[0185] Next, in step S11, the control unit 8 calculates the absolute rotation angle θ using equation (4). The calculated absolute rotation angle θ is sent to the steering control device 18 as the detection result of the steering angle (see reference). Figure 1 ).

[0186] (The function and effects of the first implementation method)

[0187] The rotation angle detection device 1 of this method includes: a first gear 21 that rotates integrally with a rotating component; a second gear 22 that meshes with the first gear 21; a first target 31 that rotates integrally with the first gear 21; a second target 32 ​​that rotates integrally with the second gear 22; a first transmitting coil 41 that generates an alternating magnetic field for inducing eddy currents in the first target 31; a first receiving coil 42 that is electromagnetically coupled to the first transmitting coil 41; a second transmitting coil 43 that generates an alternating magnetic field for inducing eddy currents in the second target 32; and a second receiving coil 44 that is electromagnetically coupled to the second transmitting coil 43. Therefore, the structure of the rotation angle detection device 1 can be simplified.

[0188] Furthermore, the first transmitting coil 41 and the first receiving coil 42 are formed on a portion of the circumference of the first gear 21, while the second transmitting coil 43 and the second receiving coil 44 are formed over the entire circumference of the second gear 22. Therefore, the formation area of ​​the first transmitting coil 41 and the first receiving coil 42 is prevented from becoming too large, achieving miniaturization. Moreover, in the second inductive sensor 102, by forming the second transmitting coil 43 and the second receiving coil 44 over the entire circumference of the second gear 22, the accuracy of angle detection is improved.

[0189] Furthermore, an arc-shaped recess 402 is formed on the substrate 4 along the outer peripheral surface of the rotating member. Therefore, compared to forming a hole in the substrate 4 for inserting the upper shaft 121, which is the rotating member, the structure of the substrate 4 can be simplified, and it is not necessary to insert the upper shaft 121 into the substrate 4, thus improving assemblability.

[0190] Furthermore, the first transmitting coil 41 and the second transmitting coil 43 are connected in series. As a result, the combined inductance of the transmitting coil circuit increases, and consequently, the Q value rises, making it easier to selectively allow only specific frequencies to pass through.

[0191] Furthermore, the first transmitting coil 41 is formed to surround the first receiving coil 42, and the second transmitting coil 43 is formed to surround the second receiving coil 44. The first transmitting coil 41 and the second transmitting coil 43 are interconnected at their outermost peripheries. Therefore, the connection structure between the first transmitting coil 41 and the second transmitting coil 43 is easily simplified.

[0192] Furthermore, the control unit 90 calculates the integer value of the number of electrical rotations of the first inductive sensor 101 or the second inductive sensor 102 from the reference position based on the output results of the first receiving coil 42 and the second receiving coil 44, and calculates the rotation angle of the rotating component from the reference position based on the integer value of either the output result of the first receiving coil 42 or the output result of the second receiving coil 44. Therefore, the detection accuracy of the absolute rotation angle θ of the upper shaft 121 can be easily improved.

[0193] Furthermore, the control unit 90 calculates the integer value of the number of electrical rotations of the second inductive sensor 102 from the reference position based on the output results of the first receiving coil 42 and the second receiving coil 44, and calculates the rotation angle of the rotating component from the reference position based on the output results and integer value of the second receiving coil 44. Thus, by using the more accurate second inductive sensor 102 to calculate the final detected value of the absolute rotation angle θ of the upper shaft 121, the detection accuracy of the absolute rotation angle θ of the upper shaft 121 is further improved.

[0194] As described above, this method provides a rotation angle detection device that simplifies the structure.

[0195] [Other Implementation Methods]

[0196] Next, other embodiments that modify the structure of the rotation angle detection device will be described. In the following description of the embodiments, for components that are the same as those described in the first embodiment, the same reference numerals as those used in the first embodiment will be used, and repeated descriptions will be omitted.

[0197] [Second Implementation]

[0198] Figure 19 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device 1A of this embodiment. Figure 19 (a) indicates the rotation angle detection device 1A observed along the rotation axis O of the upper shaft 121. Figure 19 (b) indicates the rotation angle detection device 1A as viewed from a direction perpendicular to the rotation axis O of the upper shaft 121.

[0199] As a main component, the rotation angle detection device 1A includes: a base plate 6A; a first gear 23 and a second gear 24 that rotate at different speeds in conjunction with the rotation of the upper shaft 121; a first angle sensor 101A that detects the rotation angle of the first gear 23 relative to the base plate 6A; a second angle sensor 102A that detects the rotation angle of the second gear 24 relative to the base plate 6A; a control unit 90A that calculates the rotation angle of the upper shaft 121 based on the detection results of the first angle sensor 101A and the second angle sensor 102A; and a housing 53 that houses them.

[0200] The base plate 6A is fixed to the housing 53 and is configured non-rotatingly relative to the vehicle body. The first gear 23 rotates integrally with the upper shaft 121. The second gear 24 meshes with the first gear 23 and rotates at a faster speed than the first gear 23. The control unit 90A is mounted on the base plate 6A and sends the detection result of the rotation angle to the steering control device 18. Furthermore, in Figure 19In (a), the wiring patterns such as signal lines and power lines formed on the substrate 6A are omitted.

[0201] The first gear 23, the second gear 24, and the housing 53 are made of insulating resin, which is non-magnetic and non-conductive. A through hole 230 is formed in the center of the first gear 23, through which an upper shaft 121 is inserted. The first gear 23 is fixed to the upper shaft 121, for example, by adhesive bonding. The second gear 24 integrally has a flat gear portion 241 and a shaft-shaped support shaft 242, which is rotatably supported on the housing 53. The diameter of the second gear 24 is smaller than that of the first gear 23, and it rotates consequently as the first gear 23 rotates. The number of teeth of the second gear 24 is less than that of the first gear 23, and the number of teeth of the first gear 23 is a non-integer multiple of the number of teeth of the second gear 24. In this embodiment, the first gear 23 has 50 teeth, and the second gear 24 has 22 teeth.

[0202] The second angle sensor 102A has a permanent magnet 81 fixed to the center of the second gear 24 and facing the substrate 6A, and a magnetic field detection element 82 mounted on the substrate 6A. The permanent magnet 81 and the magnetic field detection element 82 face each other with a small air gap between them. The permanent magnet 81 is a bipolar magnet with one N pole 811 and one S pole 812, which are arranged in the diametrical direction of the second gear 24. The magnetic field detection element 82 is preferably an element with higher sensitivity than a Hall element, such as a GMR (Giant Magneto Resistive effect) sensor, an AMR (Anisotropic Magneto Resistive) sensor, or a TMR (Tunneling Magneto Resistive) sensor.

[0203] A signal indicating the detection result of the magnetic field detection element 82 is transmitted to the control unit 90A. The control unit 90A can detect the angle of the magnetic field detection element 82 relative to the substrate 6A, i.e., the rotation angle of the second gear 24, based on the signal from the magnetic field detection element 82. That is, the second angle sensor 102A is a magnetic angle sensor that detects the rotation angle of the second gear 24 by using the magnetic field detection element 82 to detect the direction of the magnetic field of the permanent magnet 81 that rotates together with the second gear 24, which is the object of rotation angle detection.

[0204] The second angle sensor 102A has a higher resolution for detecting the rotation angle of the second gear 24 than the first angle sensor 101A for detecting the rotation angle of the first gear 23. It also has higher accuracy and smaller angle detection error than the first angle sensor 101A. In other words, in this embodiment, the second angle sensor 102A has higher accuracy in detecting the rotation angle of the second gear 24 than the first angle sensor 101A has in detecting the rotation angle of the first gear 23.

[0205] Figure 20 (a) to (d) are explanatory diagrams showing the structure and operation of the first angle sensor 101A, omitting the illustrations of the first gear 23 and the second gear 24. The first angle sensor 101A has a rotating electrode 71 that rotates integrally with the upper shaft 121 and the first gear 23, a first fixed electrode 61 and a second fixed electrode 62 disposed opposite to the rotating electrode 71. The rotating electrode 71 is made of a non-magnetic conductive material, such as aluminum or an aluminum alloy. One surface of the substrate 6A is disposed opposite to the rotating electrode 71. A through hole 600 is formed in the substrate 6A for the upper shaft 121 to pass through.

[0206] The rotating electrode 71 is generally flat, with a through hole 710 formed in the center. An upper shaft 121 is inserted through the through hole 710. The rotating electrode 71 is fixed to the upper shaft 121, for example, by welding. Alternatively, the rotating electrode 71 can be fixed to the first gear 21 by, for example, adhesive bonding. Furthermore, the rotating electrode 71 and the first gear 23 can be integrally embedded and formed, or the rotating electrode 71 can be made of conductive resin and integrally formed in a two-color manner with the non-conductive resin constituting the first gear 23.

[0207] The rotating electrode 71 integrally has an annular portion 711 surrounding the upper shaft 121 and two protrusions 712 extending radially outward from the annular portion 711. The two protrusions 712 are positioned at points symmetrical about the axis of rotation O of the upper shaft 121. Each protrusion 712 is fan-shaped with a central angle of 90° centered on the axis of rotation O of the upper shaft 121, and the portion between the two protrusions 712 forms a fan-shaped cutout 713.

[0208] The first fixed electrode 61 and the second fixed electrode 62 are formed as wiring patterns on the surface of the substrate 6A on the side of the rotating electrode 71. The first fixed electrode 61 and the second fixed electrode 62 are formed as arcs extending circumferentially about the rotation axis of the upper shaft 121, and their width in the radial direction perpendicular to the rotation axis O of the upper shaft 121 varies depending on their circumferential position. In addition, the first fixed electrode 61 and the second fixed electrode 62 are formed with an arc angle of 90° centered on the rotation axis O of the upper shaft 121.

[0209] The first fixed electrode 61 is composed of an inner portion 611 and an outer portion 612 that radially sandwich the second fixed electrode 62, and the inner portion 611 and the outer portion 612 are electrically connected at one end of the first fixed electrode 61. The radial width of the inner portion 611 and the outer portion 612 gradually narrows from one end of the first fixed electrode 61 toward the other end. The radial width of the second fixed electrode 62 gradually widens from one end of the first fixed electrode 61 toward the other end.

[0210] If the upper shaft 121 rotates together with the rotating electrode 71, the opposing areas of the first fixed electrode 61 and the second fixed electrode 62 opposite the protrusion 712 of the rotating electrode 71 change according to the rotational position of the upper shaft 121. Figure 20 In (a) to (c), the first fixed electrode 61 and the second fixed electrode 62, which are opposite to the protrusion 712 of the rotating electrode 71, are indicated by dashed lines. The protrusion 712 of the rotating electrode 71 is opposite to the first fixed electrode 61 and the second fixed electrode 62 through a tiny air gap, forming a capacitance between the first fixed electrode 61 and the second fixed electrode 62.

[0211] That is, in this embodiment, the first angle sensor 101A is a capacitive angle sensor that detects the rotation angle of the first gear 23 by means of the capacitance between the rotating electrode 71, the first fixed electrode 61, and the second fixed electrode 62. The protrusion 712 functions as a capacitance forming part in the rotating electrode 71.

[0212] exist Figure 20 In (a) to (d), it indicates that the rotating electrode 71 and the upper shaft 121 rotate together in the direction of arrow D (clockwise) by 45° each time. Figure 20 In the state shown in (a), half of the length of the first fixed electrode 61 and the second fixed electrode 62 in the circumferential direction is not opposite to the protrusion 712 of the rotating electrode 71, but is located in the portion corresponding to the cutout 713 of the rotating electrode 71. Figure 20 As shown in (b), when the rotating electrode 71 is from Figure 20 When rotated 45° as shown in (a), the first fixed electrode 61 and the second fixed electrode 62 are aligned with the protrusion 712 of the rotating electrode 71. When rotated further by 45°, as... Figure 20 As shown in (c), in Figure 20 In the state shown in (a), the portion of the rotating electrode 71 that is not opposite to the protrusion 712 is opposite to the protrusion 712 of the rotating electrode 71. Figure 20 (d) indicates that the rotating electrode 71 is from Figure 20(c) shows a state that is further rotated by 45°. In this state, the entire first fixed electrode 61 and the second fixed electrode 62 are not opposite to the protrusion 712 of the rotating electrode 71, but are located at the portion corresponding to the cutout 713 of the rotating electrode 71.

[0213] Thus, the first angle sensor 101A rotates the electrode 71 to change the opposing area of ​​the first fixed electrode 61 and the second fixed electrode 62 according to the rotational position of the upper shaft 121. The control unit 90A can detect the change in capacitance between the rotating electrode 71 and the first fixed electrode 61, and the change in capacitance between the rotating electrode 71 and the second fixed electrode 62 caused by the change in the opposing area. In addition, in this embodiment, the rotating electrode 71 has two protrusions 712, so during one rotation of the upper shaft 121, the capacitance change between the rotating electrode 71 of the first angle sensor 101A and each of the first fixed electrode 61 and the second fixed electrode 62 is equal to two cycles. That is, the electrical angle change of the first gear 23 detected by the first angle sensor 101A during one rotation of the upper shaft 121 is equal to two cycles. Furthermore, the electrical angle of the second gear 24 detected by the second angle sensor 102A is the same as the mechanical angle of the second gear 24.

[0214] Figure 21 This is an explanatory diagram showing an example of the circuit structure of the control unit 90A for detecting the capacitance between the first fixed electrode 61 and the rotating electrode 71. Figure 21 The circuit structure shown mimics the circuit structure of a touch sensor that detects the contact of a human finger. The second fixed electrode 62 is also configured to... Figure 21 The circuit shown is the same circuit.

[0215] The control unit 90A outputs a pulse-shaped signal from the output terminal 901. A resistor 91 and a capacitor 92 are connected in series between the output terminal 901 and the ground potential. A first fixed electrode 61 is connected at node 93 between the resistor 91 and the capacitor 92. The potential of node 93 is input to the gate element 94, and the output signal of the gate element 94 is input to the input terminal 902 of the control unit 90A. The rotating electrode 71 is electrically grounded via the upper shaft 121. In this circuit structure, if the area opposite the first fixed electrode 61 of the protrusion 712 of the rotating electrode 71 increases, the capacitance between the rotating electrode 71 and the first fixed electrode 61 increases, and the response time from the rise of the pulse signal output from the control unit 90A to the rise of the output signal of the gate element 94 increases.

[0216] The control unit 90A detects the capacitance between the rotating electrode 71 and the first fixed electrode 61 based on the difference in response time. That is, since the capacitance between the rotating electrode 71 and the first fixed electrode 61 changes with the rotation of the upper shaft 121, the control unit 90A uses this capacitance value as the detection result of the first angle sensor 101A to calculate the rotation angle of the upper shaft 121. In other words, the control unit 90A calculates the rotation angle from the reference position of the upper shaft 121 based on the capacitance between the rotating electrode 71 and the first fixed electrode 61. Furthermore, as an example, the resistor 91, capacitor 92, and gate element 94 are mounted on the substrate 6A, but some or all of these circuit components can also be integrated into the control unit 90A. Alternatively, the capacitor 92 can be omitted, except... Figure 21 In addition to the circuit components shown, additional circuit components such as resistors and capacitors can also be added.

[0217] Figure 22 (a) and (b) indicate that... Figure 20 (a) The rotational position of the rotating electrode 71 shown is used as a reference position with a rotation angle of 0°. The rotating electrode 71 rotates from this reference position towards... Figure 20 (a) to (d) are graphs showing the change in capacitance between the rotating electrode 71 and the first fixed electrode 61 and the second fixed electrode 62 when the electrode rotates 360° in the direction of arrow D. Figure 21 As shown in (a) and (b), in this embodiment, the capacitance change between the rotating electrode 71 and the first fixed electrode 61 and the second fixed electrode 62 occurs for two cycles during one rotation of the upper shaft 121. Therefore, in this embodiment, the speed transfer ratio from the upper shaft 121 to the first angle sensor 101A can be considered as 0.50, and the speed transfer ratio from the upper shaft 121 to the second angle sensor 102A can be considered as 0.44 (=22 / 50). Furthermore, the absolute rotation angle θ of the upper shaft 121 can be calculated using the same calculation method as that described with reference to equations (1) to (4) in the first embodiment.

[0218] Here, the method for calculating the rotation angle of the rotating electrode 71 of the first angle sensor 101A will be explained. Here, [the following is a more detailed explanation of the calculation method]. Figure 22 The calculation method for the rotation angle of the rotating electrode 71 in one cycle from 0° to 180° in (a) and (b) is explained, but the rotation angle of the rotating electrode 71 in the range of 180° to 360° can also be calculated in the same way.

[0219] In this calculation method, the rotation angle of the rotating electrode 71 is calculated in two ranges: the rotation angle of the rotating electrode 71 is 0° to 90°, i.e., the area of ​​the rotating electrode 71 overlapping with the first fixed electrode 61 is larger than the area of ​​the rotating electrode 71 overlapping with the second fixed electrode 62; and the rotation angle of the rotating electrode 71 is 90° to 180°, i.e., the area of ​​the rotating electrode 71 overlapping with the second fixed electrode 62 is larger than the area of ​​the rotating electrode 71 overlapping with the first fixed electrode 61.

[0220] Figure 23 (a) is a schematic diagram showing the overlapping state of the rotating electrode 71 with the first fixed electrode 61 and the second fixed electrode 62 when the rotation angle of the rotating electrode 71 is less than 90°. Figure 23 (b) is a schematic diagram illustrating the overlap between the rotating electrode 71, the first fixed electrode 61, and the second fixed electrode 62 when the rotation angle of the rotating electrode 71 is 90° or more. When the area of ​​overlap between the rotating electrode 71 and the first fixed electrode 61 is set as A, and the area of ​​overlap between the rotating electrode 71 and the second fixed electrode 62 is set as B, whether the rotation angle of the rotating electrode 71 is less than 90° or more can be determined by whether the value obtained from the following formula (20) is less than 0.5 or more.

[0221] [Formula 20]

[0222]

[0223] Hereinafter, the area where the rotating electrode 71 overlaps with the first fixed electrode 61 is defined as the first opposing area A, and the area where the rotating electrode 71 overlaps with the second fixed electrode 62 is defined as the second opposing area B. The first opposing area A can be determined by the capacitance between the rotating electrode 71 and the first fixed electrode 61. The second opposing area B can be determined by the capacitance between the rotating electrode 71 and the second fixed electrode 62.

[0224] (The case where the rotation angle of the rotating electrode 71 is less than 90°)

[0225] like Figure 23 As shown in (a), when the maximum width of the first fixed electrode 61 and the second fixed electrode 62 is set to h, and the rotation angle of the rotating electrode 71 is set to x (°), the first opposing area A is represented by the following formula (21), and the second opposing area B is represented by the following formula (22).

[0226] [Equation 21]

[0227]

[0228] [Equation 22]

[0229]

[0230] In addition, the sum of the maximum area of ​​the overlapping area of ​​the rotating electrode 71 with the first fixed electrode 61 and the second fixed electrode 62, that is, the sum of the maximum value of the first opposing area A and the maximum value of the second opposing area B, is 90h. Therefore, the value obtained by dividing the total opposing area obtained by adding the first opposing area A and the second opposing area B by 90h is expressed by the following equation (23) through equation (21) and equation (22).

[0231] [Equation 23]

[0232]

[0233] Therefore, x can be obtained by the following equation (24).

[0234] [Equation 24]

[0235]

[0236] (When the rotation angle of the rotating electrode 71 is 90° or more)

[0237] like Figure 23 As shown in (b), when the maximum width of the first fixed electrode 61 and the second fixed electrode 62 is set to h, and the rotation angle of the rotating electrode 71 is set to x (°), the first opposing area A is represented by the following formula (25), and the second opposing area B is represented by the following formula (26).

[0238] [Equation 25]

[0239]

[0240] [Equation 26]

[0241]

[0242] In addition, the sum of the maximum area of ​​the overlapping area of ​​the rotating electrode 71 with the first fixed electrode 61 and the second fixed electrode 62, that is, the sum of the maximum value of the first opposing area A and the maximum value of the second opposing area B, is 90h. Therefore, according to equations (25) and (26), the value obtained by dividing the total opposing area obtained by adding the first opposing area A and the second opposing area B by 90h is represented by the following equation (27).

[0243] [Equation 27]

[0244]

[0245] Therefore, x can be obtained by the following equation (28).

[0246] [Equation 28]

[0247]

[0248] In addition, the first fixed electrode 61 and the second fixed electrode 62 can also be as follows: Figure 24 To deform the shape as shown. Figure 20 The diagram shows a first fixed electrode 61 consisting of an inner portion 611 and an outer portion 612 that radially sandwich a second fixed electrode 62. However,... Figure 24 In the example shown, the first fixed electrode 61 is formed radially inward of the second fixed electrode 62. Even with the first fixed electrode 61 and the second fixed electrode 62 formed in this way, the rotation angle of the rotating electrode 71 can be calculated in the same manner as described above.

[0249] [Third Implementation Method]

[0250] Figure 25 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device 1B according to the third embodiment. In the second embodiment, the second angle sensor 102A was described as magnetic, but in the third embodiment, the rotation angle detection device 1B has a capacitive second angle sensor 102B. The second angle sensor 102B has a rotating electrode 72 mounted on the side of the substrate 6B in the second gear 24, a first fixed electrode 63 and a second fixed electrode 64 provided as a wiring pattern on the substrate 6B.

[0251] Figure 26 (a) is a structural diagram showing the rotating electrode 72 mounted on the surface of the substrate 6B side of the second gear 24. Figure 26 (b) is a structural diagram showing the first fixed electrode 63 and the second fixed electrode 64 disposed on the substrate 6B. The rotating electrode 72 is composed of a semi-circular fan-shaped conductor and is electrically grounded through a grounding wire (not shown). The first fixed electrode 63 is composed of an inner portion 631 and an outer portion 632 that radially sandwich the second fixed electrode 64, and the inner portion 631 and the outer portion 632 are connected at one end of the first fixed electrode 63. The radial width of the inner portion 631 and the outer portion 632 gradually narrows from one end of the first fixed electrode 63 toward the other end. The radial width of the second fixed electrode 64 gradually widens from one end to the other end.

[0252] The control unit 90B of the rotation angle detection device 1B communicates with... Figure 21The circuit shown is the same as the one used in the previous embodiment. It can detect the capacitance between the rotating electrode 72 and the first fixed electrode 63, and the capacitance between the rotating electrode 72 and the second fixed electrode 64. Based on these capacitances, it can determine the rotation angles of the first gear 23 and the second gear 24 relative to the substrate 6B. That is, the control unit 90B can use the magnitude of the capacitance between the rotating electrode 72 and the second fixed electrode 64 as the detection result of the second angle sensor 101B, and detect the rotation angle of the upper shaft 121 based on the rotation angles of the first gear 23 and the second gear 24, in the same manner as in the first embodiment.

[0253] It should be noted that, in the third embodiment, as an example, similar to the first and second embodiments, the detection accuracy of the rotation angle of the second gear 24 by the second angle sensor 102B is higher than the detection accuracy of the rotation angle of the first gear 23 by the first angle sensor 101A. Based on the detection results of the first angle sensor 101A and the second angle sensor 102B, an integer value of the number of electrical rotations of the second angle sensor 102B is calculated. Based on this integer value and the detection result of the second angle sensor 102B, the rotation angle of the upper shaft 121 from the reference position is calculated. However, when the detection accuracy of the rotation angle of the first gear 23 by the first angle sensor 101A is higher than the detection accuracy of the rotation angle of the second gear 24 by the second angle sensor 102B, an integer value of the number of electrical rotations of the first angle sensor 101A is calculated based on the detection results of the first angle sensor 101A and the second angle sensor 102B. Based on this integer value and the detection result of the first angle sensor 101A, the rotation angle from the reference position of the upper shaft 121 is calculated. The same applies to the fourth to sixth embodiments described below.

[0254] (Fourth Implementation)

[0255] Figure 27 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device 1C according to the fourth embodiment. In the second embodiment, the case where the first angle sensor 101A is capacitive was described, but in the fourth embodiment, the rotation angle detection device 1C has a magnetic first angle sensor 101C. The first angle sensor 101C has a rotating magnet 83 mounted on the side of the substrate 6C of the first gear 23 and a magnetic field detection element 84 mounted on the substrate 6C. The rotating magnet 83 and the magnetic field detection element 84 are positioned opposite each other with a small air gap between them. The rotating magnet 83 is a quadrupole magnet having two N poles and one S pole. The magnetic field detection element 84 is, for example, a GMR sensor, an AMR sensor, or a TMR sensor.

[0256] A signal indicating the detection result of the magnetic field detection element 84 is sent to the control unit 90C. The control unit 90C can detect the angle of the rotating magnet 83 relative to the substrate 6C, i.e., the rotation angle of the first gear 23, based on the signal from the magnetic field detection element 84. Furthermore, it can detect the rotation angle of the upper shaft 121 based on the rotation angle of the first gear 23, similar to the first embodiment.

[0257] [Fifth Implementation Method]

[0258] Figure 28 (a) and (b) are structural diagrams showing the structure of the rotation angle detection device 1D according to the fifth embodiment. In the fifth embodiment, the rotation angle detection device 1D has an inductive first angle sensor 101D and a second angle sensor 102D. The first angle sensor 101D has a guide plate 73 that rotates integrally with the first gear 23 and an electromagnetic coil 65 disposed at a position opposite to the guide plate 73. The second angle sensor 102D has a guide plate 74 that rotates integrally with the second gear 24 and an electromagnetic coil 66 disposed at a position opposite to the guide plate 74.

[0259] Figure 29 (a) is a structural diagram showing the guide plate 73 mounted on the side of the substrate 6D of the first gear 23 and the guide plate 74 mounted on the side of the substrate 6D of the second gear 24. Figure 29 (b) is a top view showing the electromagnetic coils 65 and 66 disposed on the substrate 6D. The guide plates 73 and 74 are made of conductive metals such as aluminum and are electrically grounded. The electromagnetic coils 65 and 66 are formed as a wiring pattern of the substrate 6D.

[0260] The guide plate 73 of the first angle sensor 101D integrally has an annular portion 731 surrounding the upper shaft 121 and two protrusions 732 arranged to extend radially outward from the annular portion 731. The two protrusions 732 are positioned at a point symmetrical about the rotation axis O of the upper shaft 121. Each protrusion 732 is fan-shaped with a central angle of 90° centered on the rotation axis O of the upper shaft 121.

[0261] The electromagnetic coil 65 of the first angle sensor 101D is formed within a range of 90° centered on the rotation axis O of the upper shaft 121. When the guide plate 73 rotates together with the upper shaft 121, the inductance of the electromagnetic coil 65 changes according to the area of ​​the protrusion 732 of the guide plate 73 opposite to the electromagnetic coil 65. The control unit 90D of the rotation angle detection device 1D can determine the rotation angle of the first gear 23 relative to the substrate 6D based on the change in inductance.

[0262] The guide plate 74 of the second angle sensor 102D is a semi-circular sector surrounding the center of the second gear 24. The electromagnetic coil 66 of the second angle sensor 102D is formed within a 180° range around the rotation center of the second gear 24. When the guide plate 74 rotates together with the upper shaft 121, the inductance of the electromagnetic coil 66 changes according to the opposing area of ​​the guide plate 74 and the electromagnetic coil 66. The control unit 90D can determine the rotation angle of the second gear 24 relative to the base plate 6D based on this change in inductance.

[0263] According to this fifth embodiment, the rotation angle of the upper shaft 121 can also be detected in the same way as in the first embodiment, based on the rotation angles of the first gear 23 and the second gear 24 detected by the first angle sensor 101D and the second angle sensor 102D.

[0264] [Sixth Implementation Method]

[0265] In the sixth embodiment, Figure 1 The worm gear 172 of the reduction mechanism 17 shown is used as the first gear for detecting the rotation angle of the upper shaft 121, and the encoder 162 of the electric motor 16 is used as the first angle sensor. The rotation angle of the worm gear 172 can be calculated by multiplying the rotation angle detected by the encoder 162 by the reciprocal of the reduction ratio of the reduction mechanism 17. However, since the worm gear 172 is mounted on the lower shaft 122, the rotation angle calculated by the encoder 162 becomes a value that deviates from the torsion angle of the torsion bar 120 relative to the rotation angle of the upper shaft 121. As the second angle sensor, a sensor with any structure from the first to fifth embodiments can be used.

[0266] According to this sixth embodiment, by detecting the rotation angle of the upper shaft 121 in the same way as in the first embodiment, low cost can be achieved, and the rotation angle of the upper shaft 121 can be detected with high precision.

[0267] (Summary of implementation methods)

[0268] Next, the technical ideas grasped from the embodiments described above will be described by reference to symbols and the like in the embodiments. However, the symbols and the like in the following description are not limited to specifically representing the constituent elements in the scope of the technical solution as components of the embodiments.

[0269] [1] A rotation angle detection device 1, 1A-1D, which detects the rotation angle of a rotating component 121 from a reference position, comprises: first gears 21, 23 and second gears 22, 24, which rotate at different speeds as the rotating component 121 rotates; first angle sensors 101, 101A, 101C, 101D, which detect the rotation angles of the first gears 21, 23; second angle sensors 102, 102A, 102B, 102D, which detect the rotation angles of the second gears 22, 24; and control units 90, 90A-90D, which calculate the rotation angle of the rotating component 121 based on the detection results of the first angle sensors 101, 101A, 101C, 101D and the detection results of the second angle sensors 102, 102A, 102B, 102D. The control units 90, 90A to 90D calculate the integer value of the number of electrical rotations of the first angle sensors 101, 101A, 101C, 101D or the second angle sensors 102, 102A, 102B, 102D from the reference position, based on the detection results of the first angle sensors 101, 101A, 101C, 101D or the second angle sensors 102, 102A, 102B, 102D. Based on any one of the detection results of the first angle sensors 101, 101A, 101C, 101D and the second angle sensors 102, 102A, 102B, 102D, and the integer value, they calculate the rotation angle of the rotating component 121 from the reference position.

[0270] [2] According to the rotation angle detection device 1, 1A to 1D described in [1], the control unit 90, 90A to 90D calculates the rotation angle of the rotating component 121 from the reference position based on the detection results of the first angle sensor 101, 101A, 101C, 101D and the second angle sensor 102, 102A, 102B, 102D with high rotation angle detection accuracy and the integer value.

[0271] [3] According to the rotation angle detection device 1A described in [2], the high-precision sensor is a magnetic angle sensor that detects the rotation angle by detecting the direction of the magnetic field of the rotating magnet 81.

[0272] [4] According to any one of [1] to [3], the rotation angle detection device 1, 1A to 1D, wherein the detection error of the first angle sensor 101, 101A, 101C, 101D is set as ε ψ Let the detection error of the second angle sensors 102, 102A, 102B, and 102D be ε. φLet j be the speed transmission ratio from the rotating component 121 relative to the electrical angle of the first gears 21 and 23 whose rotation angle is detected by the first angle sensors 101, 101A, 101C, and 101D, and i be the speed transmission ratio from the rotating component 121 relative to the electrical angle of the second gears 22 and 24 whose rotation angle is detected by the second angle sensors 102, 102A, 102B, and 102 ... integer obtained by rounding up the decimal part of the quotient obtained by dividing the range of rotation angles of the rotating component 121 to be calculated by the control units 90, 90A to 90D by (i × 360), and R be the integer obtained by rounding up the decimal part of the quotient. max At that time, ε ψ and ε φ The permissible range is represented by the following two formulas.

[0273]

[0274] [5] A method for detecting rotation angle, wherein the rotation angle of a rotating component 121 from a reference position is detected, and based on the detection results of the rotation angles of a first gear 21, 23 and a second gear 22, 24 rotating at different speeds accompanying the rotation of the rotating component 121, the method calculates an integer value of the number of electrical rotations of a first angle sensor 101, 101A, 101C, 101D that detects the rotation angle of the first gear 21, 23 from the reference position or a second angle sensor 102, 102A, 102B, 102D that detects the rotation angle of the second gear 22, 24, and the integer value, the method calculates the rotation angle of the rotating component 121 from the reference position based on any one of the detection results of the rotation angles of the first gear 21, 23 and the second gear 22, 24 and the integer value.

[0275] [6] According to the rotation angle detection method described in [5], based on the detection results of the rotation angles of the first gears 21 and 23 and the detection results of the rotation angles of the second gears 22 and 24, the detection result with high detection accuracy of the rotation angle and the integer value, the rotation angle of the rotating component 121 from the reference position is calculated.

[0276] [7] According to the rotation angle detection method described in [5] or [6], the difference between the rotation angle of the first gear 21 and the second gear 23 and the rotation angle of the second gear 22 and the second gear 24, i.e., the phase difference, is calculated. If the calculated phase difference is greater than 180°, the phase difference is normalized by subtracting 360°. If the calculated phase difference is less than -180°, the phase difference is normalized by adding 360° to obtain the normalized phase difference. Based on the normalized phase difference, the integer value of the number of electrical rotations of the first angle sensor 101, 101A, 101C, 101D or the second angle sensor 102, 102A, 102B, 102D is calculated.

[0277] [8] According to the rotation angle detection method described in [7], the difference between the value obtained by multiplying the coefficient corresponding to the speed transmission ratio from the rotating component 121 to the first gear 21, 23 and the second gear 22, 24 by the normalized phase difference and the rotation angle of the second gear 22, 24 is calculated, and the integer value of the number of electrical rotations of the first angle sensor 101, 101A, 101C, 101D or the second angle sensor 102, 102A, 102B, 102D is calculated based on the difference.

[0278] [9] A rotation angle detection device 1, for detecting the rotation angle of a rotating component 121 from a reference position, comprises: a first gear 21 that rotates integrally with the rotating component 121; a second gear 22 that meshes with the first gear 21 and rotates at a different speed than the first gear 21; a first target 31 that is made of a conductor and rotates integrally with the first gear 21; a second target 32 ​​that is made of a conductor and rotates integrally with the second gear 22; a substrate 4 that is arranged opposite to both the first target 31 and the second target 32; a first transmitting coil 41 formed on the substrate 4 that generates an alternating magnetic field for inducing eddy currents in the first target 31; a first receiving coil 42 formed on the substrate 4 and electromagnetically coupled to the first transmitting coil 41; a second transmitting coil 43 formed on the substrate 4 that generates an alternating magnetic field for inducing eddy currents in the second target 32; and a second receiving coil 44 formed on the substrate 4 and electromagnetically coupled to the second transmitting coil 43.

[0279]

[10] According to the rotation angle detection device 1 described in [9], the first transmitting coil 41 and the first receiving coil 42 are formed on a portion of the circumference of the first gear 21, and the second transmitting coil 43 and the second receiving coil 44 are formed over the entire circumference of the second gear 22.

[0280]

[11] According to the rotation angle detection device 1 described in

[10] , an arc-shaped recess 402 along the outer peripheral surface of the rotating component 121 is formed on the substrate 4.

[0281]

[12] In the rotation angle detection device 1 according to any one of [9] to

[11] , the first transmitting coil 41 and the second transmitting coil 43 are connected in series.

[0282]

[13] According to the rotation angle detection device 1 described in

[12] , the first transmitting coil 41 is formed in a manner that surrounds the first receiving coil 42, and the second transmitting coil 43 is formed in a manner that surrounds the second receiving coil 44. The first transmitting coil 41 and the second transmitting coil 43 are connected to each other at the outermost periphery of the first transmitting coil 41 and the outermost periphery of the second transmitting coil 43.

[0283]

[14] The rotation angle detection device 1 according to [9] further includes a control unit 90, which calculates the rotation angle of the rotating component 121 from the reference position based on the output results of the first receiving coil 42 and the second receiving coil 44. When the angle sensor composed of the first target 31, the first transmitting coil 41 and the first receiving coil 42 is set as the first inductive sensor 101, and the angle sensor composed of the second target 32, the second transmitting coil 43 and the second receiving coil 44 is set as the second inductive sensor 102, the control unit 90 calculates the integer value of the number of electrical rotations of the first inductive sensor 101 or the second inductive sensor 102 from the reference position based on the output results of the first receiving coil 42 and the second receiving coil 44, and calculates the rotation angle of the rotating component 121 from the reference position based on either the output result of the first receiving coil 42 or the output result of the second receiving coil 44 and the integer value.

[0284]

[15] The rotation angle detection device 1 according to

[10] or

[11] further includes a control unit 90, which calculates the rotation angle of the rotating component 121 from the reference position based on the output result of the first receiving coil 42 and the output result of the second receiving coil 44. When the angle sensor composed of the first target 31, the first transmitting coil 41 and the first receiving coil 42 is set as the first inductive sensor 101 and the angle sensor composed of the second target 32, the second transmitting coil 43 and the second receiving coil 44 is set as the second inductive sensor 102, the control unit 90 calculates the integer value of the number of electrical rotations of the second inductive sensor 102 from the reference position based on the output result of the first receiving coil 42 and the output result of the second receiving coil 44, and calculates the rotation angle of the rotating component 121 from the reference position based on the output result of the second receiving coil 44 and the integer value.

[0285]

[16] A rotation angle detection device 1A, 1B, for detecting the rotation angle of a rotating component 121 from a reference position, comprises: a first gear 23 and a second gear 24, which rotate at different speeds as the rotating component 121 rotates; a first angle sensor 101A, which detects the rotation angle of the first gear 23; second angle sensors 102A, 102B, which detect the rotation angle of the second gear 24; and control units 90A, 90B, which, based on the detection result of the first angle sensor 101A and the second angle... Based on the detection results of the angle sensors 102A and 102B, the rotation angle of the rotating component 121 from the reference position is calculated. The first angle sensor 101A has a rotating electrode 71 that rotates integrally with the first gear 23 and a fixed electrode 61 that is disposed opposite to the rotating electrode 71. Due to the rotation of the rotating component 121, the capacitance between the rotating electrode 71 and the fixed electrode 61 changes. Based on the magnitude of the capacitance, the control units 90A and 90B calculate the rotation angle of the rotating component 121 from the reference position.

[0286]

[17] According to the rotation angle detection device 1A described in

[16] , the second angle sensor 102A is a magnetic angle sensor that detects the rotation angle by detecting the direction of the magnetic field of the rotating magnet 81.

[0287] (Postscript)

[0288] The embodiments of the present invention have been described above, but these embodiments do not limit the scope of the invention. Furthermore, it should be noted that the combinations of features described in the embodiments are not necessarily all necessary means to solve the problems of the invention. Additionally, the present invention can be implemented with appropriate modifications without departing from its spirit.

Claims

1. A rotation angle detection device for detecting the rotation angle of a rotating component from a reference position, characterized in that, have: The first gear and the second gear rotate at different speeds as the rotating component rotates. A first angle sensor detects the rotation angle of the first gear; The second angle sensor detects the rotation angle of the second gear; as well as The control unit calculates the rotation angle of the rotating component from the reference position based on the detection results of the first angle sensor and the detection results of the second angle sensor. The control unit calculates an integer value of the number of electrical rotations of the first angle sensor or the second angle sensor from the reference position based on the detection results of the first angle sensor and the second angle sensor. Based on either the detection results of the first angle sensor or the second angle sensor and the integer value, the control unit calculates the rotation angle of the rotating component from the reference position.

2. The rotation angle detection device according to claim 1, characterized in that, The control unit calculates the rotation angle of the rotating component from the reference position based on the detection results of the first angle sensor and the second angle sensor with high rotation angle detection accuracy, and the integer value.

3. The rotation angle detection device according to claim 2, characterized in that, The high-precision sensor is a magnetic angle sensor that detects the rotation angle by detecting the direction of the magnetic field of the rotating magnet.

4. The rotation angle detection device according to any one of claims 1 to 3, characterized in that, Let the detection error of the first angle sensor be ε ψ Let the detection error of the second angle sensor be ε. φ The speed transmission ratio from the rotating component to the electrical angle of the first gear relative to the rotation angle detected by the first angle sensor is set as j; the speed transmission ratio from the rotating component to the electrical angle of the second gear relative to the rotation angle detected by the second angle sensor is set as i; and the integer obtained by rounding down the decimal part of the quotient obtained by dividing the size of the angle range of the rotation angle of the rotating component to be calculated by the control unit by (i×360) is set as R. max At that time, ε ψ and ε φ The permissible range is expressed by the following two formulas: 。 5. A method for detecting rotation angle, wherein the rotation angle of a rotating component from a reference position is detected, characterized in that, Based on the detection results of the rotation angles of the first gear and the second gear, which rotate at different speeds accompanying the rotation of the rotating component, the integer value of the number of electrical rotations of the first angle sensor that detects the rotation angle of the first gear from the reference position or the second angle sensor that detects the rotation angle of the second gear is calculated. Based on either the detection result of the rotation angle of the first gear or the detection result of the rotation angle of the second gear and the integer value, the rotation angle of the rotating component from the reference position is calculated.

6. The method for detecting rotation angle according to claim 5, characterized in that, Based on the detection results of the rotation angle of the first gear and the rotation angle of the second gear, the detection result with higher detection accuracy of the rotation angle, and the integer value, the rotation angle of the rotating component from the reference position is calculated.

7. The method for detecting rotation angle according to claim 5 or 6, characterized in that, The phase difference is calculated by measuring the difference between the rotation angle of the first gear and the rotation angle of the second gear. A normalization process is performed to calculate the normalized phase difference. If the calculated phase difference is greater than 180°, 360° is subtracted from the phase difference; if the calculated phase difference is less than -180°, 360° is added to the phase difference. The integer value of the number of electrical rotations of the first angle sensor or the second angle sensor is calculated based on the normalized phase difference.

8. The method for detecting rotation angle according to claim 7, characterized in that, The difference between the normalized phase difference multiplied by a coefficient corresponding to the speed transmission ratio from the rotating component to the first gear and the second gear and the rotation angle of the second gear is calculated, and an integer value of the electrical rotation number of the first angle sensor or the second angle sensor is calculated based on this difference.

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