Rotation angle detection device

Abstract

The present application provides a rotation angle detection device capable of inhibiting a structure from becoming complicated when being redundant. The rotation angle detection device detects a rotation angle of a rotating member from a reference position. The rotation angle detection device includes: a target that rotates in conjunction with rotation of the rotating member; a main transmitting coil (71M, 73M) that generates an alternating magnetic field for generating eddy current in the target; a main receiving coil (72M, 74M) that is electromagnetically coupled to the main transmitting coil (71M, 73M); a backup transmitting coil (71B, 73B) that is disposed on one side of the main transmitting coil (71M, 73M) in an axial direction of the rotating member and generates an alternating magnetic field for generating eddy current in the target; and a backup receiving coil (72B, 74B) that is electromagnetically coupled to the backup transmitting coil (71B, 73B).

Description

Technical Field

[0001] This invention relates to a rotation angle detection device. Background Technology

[0002] Patent Document 1 discloses, for example, a rotation angle detection device for detecting the steering angle of a vehicle's steering wheel. The rotation angle detection device described in Patent Document 1 includes a main gear mounted on a shaft component that rotates in conjunction with the steering wheel, a secondary gear meshing with the main gear, an inductive sensor that outputs a signal corresponding to the rotation angle of the main gear, and a magnetic sensor that outputs a signal corresponding to the rotation angle of the secondary gear.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2024-43178 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the rotation angle detection device described in Patent Document 1, the redundancy of the sensor unit (inductive sensor and magnetic sensor in the case of Patent Document 1) was studied. In this case, it is considered to provide multiple main gears, multiple secondary gears, multiple inductive sensors and multiple magnetic sensors respectively, but in this case, the structure becomes complicated.

[0008] The present invention was made in view of the above circumstances, and its object is to provide a rotation angle detection device that can suppress the structural complexity during redundancy.

[0009] Solution for solving the problem

[0010] To achieve the above objectives, the present invention provides a rotation angle detection device for detecting the rotation angle of a rotating component from a reference position. The device comprises: a target that rotates along with the rotating component; a main transmitting coil that generates an alternating magnetic field to induce eddy currents in the target; a main receiving coil electromagnetically coupled to the main transmitting coil; a backup transmitting coil disposed on one side of the main transmitting coil along the axial direction of the rotating component, generating an alternating magnetic field to induce eddy currents in the target; and a backup receiving coil electromagnetically coupled to the backup transmitting coil.

[0011] The effects of the invention are as follows.

[0012] According to the present invention, a rotation angle detection device is provided that can suppress the structural complexity caused by redundancy. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a vehicle equipped with an electric power steering system having a rotation angle detection device, as described in the first embodiment.

[0014] Figure 2 This is a perspective view of the rotation angle detection device and the upper shaft in the first embodiment.

[0015] Figure 3 This is an exploded perspective view of the rotation angle detection device in the first embodiment.

[0016] Figure 4 This is a bottom view of the first gear, second gear, first target, second target, multilayer substrate, and control unit in the first embodiment.

[0017] Figure 5 This is a bottom view showing the multilayer substrate, pattern, and mounting components together in the first embodiment.

[0018] Figure 6 This is an exploded perspective view showing the first main transmitting coil, the first main receiving coil, the second main transmitting coil, the second main receiving coil, the main control unit, the first backup transmitting coil, the first backup receiving coil, the second backup transmitting coil, the second backup receiving coil, and the backup control unit in the first embodiment.

[0019] Figure 7 This is a schematic cross-sectional view of the multilayer substrate in the first embodiment.

[0020] Figure 8 This diagram illustrates the first main transmitting coil and the first main receiving coil formed on the first layer of a multilayer substrate in the first embodiment, or the first backup transmitting coil and the first backup receiving coil formed on the third layer of a multilayer substrate.

[0021] Figure 9 This diagram illustrates the first main transmitting coil and the first main receiving coil formed on the second layer of a multilayer substrate in the first embodiment, or the first backup transmitting coil and the first backup receiving coil formed on the fourth layer of a multilayer substrate.

[0022] Figure 10 This diagram illustrates the second main transmitting coil and the second main receiving coil formed on the first layer of the multilayer substrate in the first embodiment, or the second backup transmitting coil and the second backup receiving coil formed on the third layer of the multilayer substrate.

[0023] Figure 11 This diagram illustrates the second main receiving coil formed on the second layer of the multilayer substrate in the first embodiment, or the second backup receiving coil formed on the fourth layer of the multilayer substrate.

[0024] Figure 12This is a circuit diagram of the transmitting coil circuit in the first embodiment.

[0025] Figure 13 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.

[0026] Figure 14 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.

[0027] Figure 15 It is a graph showing the relationship between the absolute rotation angle θ in the first embodiment and the phase difference obtained by subtracting the second detection angle φ from the first detection angle ψ.

[0028] Figure 16 It is a graph showing the relationship between the absolute rotation angle θ and the standardized phase difference δ in the first embodiment.

[0029] Figure 17 In the first embodiment, the standardized phase difference δ and the absolute angle φ between the second target are represented by dashed lines. 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.

[0030] Figure 18 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.

[0031] Figure 19 This is a flowchart illustrating an example of the calculation process performed by the main control unit and the backup control unit in the first embodiment to determine the absolute rotation angle θ.

[0032] Figure 20 This is a bottom view showing the multilayer substrate, pattern, and mounting components in the second embodiment.

[0033] Figure 21 This is a circuit diagram of the transmitting coil circuit in the second embodiment.

[0034] Symbol Explanation

[0035] 1—Rotation angle detection device; 103—Main supplementary coil; 104—Backup supplementary coil; 121—Upper shaft (rotating component); 4—First target; 5—Second target; 6—Multilayer substrate; 71B—First backup transmitting coil; 71M—First main transmitting coil; 72B—First backup receiving coil; 72M—First main receiving coil; 73B—Second backup transmitting coil; 73M—Second main transmitting coil; 74B—Second backup receiving coil; 74M—Second main receiving coil. Detailed Implementation

[0036] [First Implementation Method]

[0037] Reference Figures 1 to 19 The first embodiment of the present invention will be described. Furthermore, the embodiments described below are shown as preferred examples in terms of carrying out the present invention, and various technically preferred aspects are also specifically illustrated, but the scope of the present invention is not limited to these specific methods.

[0038] (Electric power steering system 10)

[0039] 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, as described in this method.

[0040] This invention relates to a rotation angle detection device 1 for detecting the rotation angle of a rotating component from a reference position. In this invention, an example is shown where the rotation angle detection device 1 is mounted on an electric power steering system 10, but the application of the rotation angle detection device 1 is not limited to this.

[0041] 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 for detecting the rotation angle of the upper shaft 121 of the steering shaft 12, i.e., the steering angle, a torque sensor 13 for detecting the steering torque applied to the steering wheel 11, a rack shaft 14, left and right steering tie rods 15 that are oscillatingly connected to the two ends of the rack shaft 14, an electric motor 16 for power assistance, a reduction mechanism 17 for reducing the rotation of the output shaft 161 of the electric motor 16 and transmitting it to the steering shaft 12, and a steering control device 18 for controlling the electric motor 16.

[0042] The steering shaft 12 has a torsion bar 120 that twists due to 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. When the steering shaft 12 rotates, the rack shaft 14 moves forward and backward in the vehicle width direction, causing the front wheels 19, which serve as the left and right steering wheels, to turn.

[0043] The reduction mechanism 17 has a worm 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 171. The output torque of the electric motor 16 is amplified by the reduction mechanism 17 and transmitted to the lower shaft 12, becoming an auxiliary torque to assist the driver in steering the steering wheel 11. An absolute encoder 162 for detecting the rotation angle of the output shaft 161 is provided in the electric motor 16.

[0044] The steering control device 18 controls the electric motor 16 based on information about the steering angle obtained from the rotation angle detection device 1, information about the steering torque obtained from the torque sensor 13, and information about the rotation angle of the output rotation shaft 161 obtained from the encoder 162 of the electric motor 16, so as to apply an auxiliary torque to the steering shaft 12 corresponding to the steering angle and steering torque. The steering control device 18 is, for example, composed of an ECU (Electronic Control Unit).

[0045] (Rotation angle detection device 1)

[0046] 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 of the upper shaft 121 from the reference position. That is, in this method, 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.

[0047] 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, Figure 3 The diagram omits the structures other than the main control unit 8M and the backup control unit 8B formed on the multilayer substrate 6. Figure 4 This is a bottom view omitting the rotation angle detection device for the housing and cover. Furthermore, Figure 4In the diagram, the shaded area indicated by symbol R1 represents the formation area of ​​the first main transmitting coil 71M, the first main receiving coil 72M, the first backup transmitting coil 71B, and the first backup receiving coil 72B, and the shaded area indicated by symbol R2 represents the formation area of ​​the second main transmitting coil 73M, the second main receiving coil 74M, the second backup transmitting coil 73B, and the second backup receiving coil 74B. Figure 5 This is a bottom view showing the multilayer substrate 6 together with the pattern and mounting components. Figure 6 This is an exploded perspective view showing the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, the second main receiving coil 74M, the main control unit 8M, the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, the second backup receiving coil 74B, and the backup control unit 8B. Figure 7 This is a schematic cross-sectional view of the multilayer substrate 6. Figure 8 This diagram shows the first main transmitting coil 71M and the first main receiving coil 72M formed on the first layer of the multilayer substrate 6, or the first backup transmitting coil 71B and the first backup receiving coil 72B formed on the third layer of the multilayer substrate 6. Furthermore, Figure 8 In the diagram, dashed lines represent the first main transmitting coil 71M and the first main receiving coil 72M formed on the second layer of the multilayer substrate 6, or the first backup transmitting coil 71B and the first backup receiving coil 72B formed on the fourth layer of the multilayer substrate 6. The first to fourth layers refer to the layers counted starting from the side of the first gear 2 and the second gear 3. Figure 9 This diagram shows the first main transmitting coil 71M and the first main receiving coil 72M formed on the second layer of the multilayer substrate 6, or the first backup transmitting coil 71B and the first backup receiving coil 72B formed on the fourth layer of the multilayer substrate 6. Figure 10 This diagram shows the second main transmitting coil 73M and the second main receiving coil 74M formed on the first layer of the multilayer substrate 6, or the second backup transmitting coil 73B and the second backup receiving coil 74B formed on the third layer of the multilayer substrate 6. Furthermore, Figure 10 In the diagram, the second main receiving coil 74M formed on the second layer of the multilayer substrate 6 or the second backup receiving coil 74B formed on the fourth layer of the multilayer substrate 6 is indicated by dashed lines. Figure 11 This diagram shows the second main receiving coil 74M formed on the second layer of the multilayer substrate 6, or the second backup receiving coil 74B formed on the second layer of the multilayer substrate 6. Furthermore, Figures 8 to 11 In the diagram, the outline of the multilayer substrate 6 is represented by a double-dotted line.

[0048] The rotation angle detection device 1 includes a first gear 2, a second gear 3, a first target 4, a second target 5, a multilayer substrate 6, a first main transmitting coil 71M, a first main receiving coil 72M, a first backup transmitting coil 71B, a first backup receiving coil 72B, a second main transmitting coil 73M, a second main receiving coil 74M, a second backup transmitting coil 73B, a second backup receiving coil 74B, a main control unit 8M, a backup control unit 8B, a housing 91, and a cover 92.

[0049] like Figures 2 to 4 As shown, the first gear 2 rotates integrally with the upper shaft 121, which is a rotating component. The second gear 3 meshes with the first gear 2 and rotates at a different speed than the first gear 2. The first target 4 is made of a conductor and rotates integrally with the first gear 2. The second target 5 is made of a conductor and rotates integrally with the second gear 3. The multilayer substrate 6 is configured to face both the first target 4 and the second target 5.

[0050] like Figure 5 , Figure 6 , Figures 8 to 11 As shown, a first main transmitting coil 71M, a first main receiving coil 72M, a first backup transmitting coil 71B, a first backup receiving coil 72B, a second main transmitting coil 73M, a second main receiving coil 74M, a second backup transmitting coil 73B, and a second backup receiving coil 74B are formed on a multilayer substrate 6, and a main control unit 8M and a backup control unit 8B are mounted thereon.

[0051] The first main transmitting coil 71M generates an alternating magnetic field to induce eddy currents in the first target 4. The first main receiving coil 72M is electromagnetically coupled to the first main transmitting coil 71M. The first backup transmitting coil 71B is disposed on one side of the first main transmitting coil 71M in the axial direction and generates an alternating magnetic field to induce eddy currents in the first target 4. The first backup receiving coil 72B is electromagnetically coupled to the first backup transmitting coil 71B.

[0052] The second main transmitting coil 73M generates an alternating magnetic field to induce eddy currents in the second target 5. The second main receiving coil 74M is electromagnetically coupled to the second main transmitting coil 73M. The second backup transmitting coil 73B is disposed on one side of the second main transmitting coil 73M in the axial direction and generates an alternating magnetic field to induce eddy currents in the second target 5. The second backup receiving coil 74B is electromagnetically coupled to the second backup transmitting coil 73B. The main control unit 8M controls the energizing state of the first main transmitting coil 71M and the second main transmitting coil 73M, and processes the output signals from the first main receiving coil 72M and the second main receiving coil 74M. The backup control unit 8B controls the energizing state of the first backup transmitting coil 71B and the second backup transmitting coil 73B, and processes the output signals from the first backup receiving coil 72B and the second backup receiving coil 74B. The housing 91 and the cover 92 house the components of the rotation angle detection device 1.

[0053] Next, the detailed structure of the rotation angle detection device 1 will be described.

[0054] The first gear 2 is made of a non-magnetic resin with electrical insulation properties. The first gear 2 is a spur gear. The first gear 2 has a cylindrical portion 21 and a main body portion 22 extending outward from the cylindrical portion 21. Engaging protrusions 211 protruding inward are formed on the cylindrical portion 21. (Example:) Figure 2 As shown, the engaging protrusion 211 engages with the axially formed groove 121a in the upper shaft 121, thereby allowing the first gear 2 to rotate integrally with the upper shaft 121. Furthermore, in this embodiment, when referred to only as "axial," it means the direction in which the rotation axis of the upper shaft 121 extends. Figure 3 As shown, one end of the cylindrical portion 21 can be rotatably engaged with the following fitting recess 911b of the housing 91. The other end of the cylindrical portion 21 can be rotatably inserted into the following opening 921a of the cover 92.

[0055] like Figure 3 and Figure 4 As shown, the main body 22 has a plurality of teeth 221 on its outer periphery. In this embodiment, as an example, the first gear 2 has 58 teeth. The plurality of teeth 221 of the main body 22 mesh with the second gear 3.

[0056] The second gear 3 is made of a non-magnetic resin with electrical insulation properties. The second gear 3 is a spur gear that rotates passively in response to the rotation of the first gear 2. The diameter of the second gear 3 is smaller than that of the first gear 2. The second gear 3 has a circular plate portion 31 and an annular protrusion 32 protruding axially from the circular plate portion 31 to one side.

[0057] The circular plate portion 31 has a plurality of teeth 311 on its outer periphery that mesh with the first gear 2. The second gear 3 has fewer teeth than the first gear 2, thereby the second gear 3 rotates faster than the first gear 2. In this embodiment, as an example, the second gear 3 has 24 teeth. The annular protrusion 32 can be rotatably inserted into the annular groove 911c formed in the housing 91.

[0058] like Figure 3 and Figure 4 As shown, the first target 4 rotates integrally with the upper shaft 121 and the first gear 2. In this configuration, the first gear 2 is formed by molding the first target 4, and the first target 4 and the first gear 2 are formed integrally.

[0059] The first target 4 is made of a conductor such as metal. The first target 4 is in the shape of an annular plate, with alternating protrusions 41 and recesses 42 formed on its outer periphery in the circumferential direction. The number of protrusions 41 is the same as the number of recesses 42. In this embodiment, the first target 4 has five protrusions 41. The protrusions 41 are the portions through which the magnetic flux of the alternating magnetic field generated by energizing the first main transmitting coil 71M or the first backup transmitting coil 71B passes, and are the portions where eddy currents are generated due to the time-varying density of the passing magnetic flux. 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 41 and the recesses 42 are the same. However, this is not a limitation; the dimensions of the circumferential protrusions 41 and the recesses 42 may also be different. For example, when the first target 4 is located relatively far from the first main receiving coil 72M and the first backup receiving coil 72B, it is preferable that the dimensions of the circumferential protrusions 41 are smaller than the dimensions of the recesses 42. When the first target 4 is located relatively far from the first main receiving coil 72M and the first backup receiving coil 72B, the magnetic field emitted from the first target 4 extends and propagates to the first main receiving coil 72M and the first backup receiving coil 72B. Therefore, the range of the magnetic influence on the first main receiving coil 72M and the first backup receiving coil 72B from the first target 4 expands. However, the strength of the output signal of the first main receiving coil 72M and the first backup receiving coil 72B reaches its maximum when the aforementioned range is half the length of each of the first main receiving coil 72M and the first backup receiving coil 72B. Consequently, the strength of the output signal of the first main receiving coil 72M and the first backup receiving coil 72B decreases. Considering the above, when the first target 4 is located relatively far from the first main receiving coil 72M and the first backup receiving coil 72B, it is preferable to make the size of the circumferentially convex portion 41 smaller than the size of the concave portion 42.

[0060] The second target 5 and the second gear 3 rotate integrally. In this configuration, the second gear 3 is formed by molding the second target 5, and the second target 5 and the second gear 3 are formed integrally.

[0061] The second target 5 is made of a conductor such as metal. Alternatively, the second target 5 can be formed on a printed circuit board using copper foil or the like. The second target 5 is in the shape of an annular plate, with alternating protrusions 51 and recesses 52 formed on its outer periphery in the circumferential direction. The number of protrusions 51 is the same as the number of recesses 52. In this embodiment, the second target 5 has two protrusions 51. The protrusions 51 are the portions through which the magnetic flux of the alternating magnetic field generated by energizing the second main transmitting coil 73M or the second backup transmitting coil 73B passes, and are portions where eddy currents are generated due to the time-varying density of the passing magnetic flux. 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 51 and the recesses 52 are the same. Furthermore, similar to the first target 4, the dimensions of the circumferential protrusions 51 and the recesses 52 can also be different.

[0062] Furthermore, the number of protrusions 41 of the first target 4 and the number of protrusions 51 of the second target 5 are not limited to the aforementioned numbers. For example, the diameter and number of teeth of the first gear 2 can be varied according to the diameter of the rotating component of the rotation angle detection object, thereby allowing for the appropriate selection of the number of protrusions 41 of the first target 4 and the number of protrusions 51 of the second target 5. The multilayer substrate 6 is arranged in a manner that faces the protrusions 41 of the first target 4 and the protrusions 51 of the second target 5.

[0063] The multilayer substrate 6 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 61 are formed on the multilayer substrate 6, and pins 914 formed on the housing 91 or pins 921b formed on the cover 92 are inserted into the positioning holes 61. Furthermore, the multilayer substrate 6 is fixed to the housing 91 and the cover 92 and is configured without rotating relative to the vehicle body.

[0064] An arc-shaped recess 62 is formed on the multilayer substrate 6. The arc-shaped recess 62 has one side of the multilayer substrate 6 cut into an arc shape centered on the central axis of the upper shaft 121. The arc-shaped recess 62 is disposed along the outer peripheral surface of the cylindrical portion 21 of the first gear 2. The center point of the arc-shaped recess 62 coincides with the center of the cylindrical portion 21. The arc-shaped recess 62 is disposed along the outer peripheral surface of the upper shaft 121 via the first gear 2. The multilayer substrate 6 is disposed on the side of the upper shaft 121 in a manner that does not penetrate through the upper shaft 121. That is, the multilayer substrate 6 is not a component having a closed through hole that allows the upper shaft 121 to pass through. Various electronic devices such as a main control unit 8M, a backup control unit 8B, and capacitors are mounted on both sides of the multilayer substrate 6.

[0065] like Figure 7As shown, in this embodiment, the multilayer substrate 6 is a multilayer substrate having four wiring layers. The multilayer substrate 6 has a core layer 64, core wiring layers 65 patterned on two main surfaces of the core layer 64, prepreg layers 66 disposed on both main surfaces of the core layer 64, an outermost wiring layer 67 patterned on the surface of the prepreg layer 66 opposite to the core layer 64, and microvias 68 electrically connecting the core wiring layers 65 and the outermost wiring layer 67. The core layer 64 can be made of a known insulating material, such as impregnating glass fiber with epoxy resin and then curing it. The prepreg layer 66 is electrically insulating and bonded to the core layer 64. The microvias 68 electrically connect adjacent wiring layers (i.e., the core wiring layer 65 and the outermost wiring layer 67), for example, by plating copper on the inner walls of tiny holes formed by laser. The core wiring layer 65 and the outermost wiring layer 67 formed on the side of the first gear 2 and the second gear 3 constitute the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, and the second main receiving coil 74M. Furthermore, the core wiring layer 65 and the outermost wiring layer 67 formed on the side of the core layer 64 opposite to the first gear 2 and the second gear 3 constitute the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, and the second backup receiving coil 74B.

[0066] The first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, and the second backup receiving coil 74B perform the same functions as the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, and the second main receiving coil 74M, and are configured for redundancy. For example, in the rotation angle detection device 1 that detects the rotation angle of the upper shaft 121 as described in this embodiment, redundancy is sometimes required as a specification, regardless of the ease of failure.

[0067] The first main transmitting coil 71M and the first main receiving coil 72M together with the first target 4 constitute an inductive sensor. Furthermore, the first backup transmitting coil 71B and the first backup receiving coil 72B together with the first target 4 constitute an inductive sensor. Hereinafter, these inductive sensors with the first target 4 will also be referred to as "first inductive sensor 101". When viewed axially, the first main transmitting coil 71M, the first main receiving coil 72M, the first backup transmitting coil 71B, and the first backup receiving coil 72B are formed in the arc-shaped region R1 along the arc-shaped recess 62 (see reference). Figure 4When viewed axially, the first main transmitting coil 71M and the first backup transmitting coil 71B are wound in an arc-shaped frame. The first main receiving coil 72M and the first backup receiving coil 72B are formed and housed inside the first main transmitting coil 71M and the first backup transmitting coil 71B. The area from the outer edge of the first main transmitting coil 71M and the first backup transmitting coil 71B to the inner edge is region R1, which will be described in detail below. Region R1 is axially opposite to the protrusion 41 of the first target 4.

[0068] like Figure 8 and Figure 9 As shown, the first backup transmitting coil 71B has the same shape as the first main transmitting coil 71M, is positioned on the side of the first main transmitting coil 71M opposite to the first target 4, and is positioned axially overlapping with the first main transmitting coil 71M. The first backup receiving coil 72B has the same shape as the first main receiving coil 72M, is positioned on the side of the first main receiving coil 72M opposite to the first target 4, and is positioned axially overlapping with the first main receiving coil 72M. In the following description, without specifically distinguishing between the first main transmitting coil 71M and the first backup transmitting coil 71B (i.e., both are identical), it is simply referred to as "first transmitting coil 71". Furthermore, without specifically distinguishing between the first main receiving coil 72M and the first backup receiving coil 72B, it is simply referred to as "first receiving coil 72". Moreover, when describing the relationship between the first transmitting coil 71 and the first receiving coil 72, unless otherwise specified, it refers to the relationship between the first main transmitting coil 71M and the first main receiving coil 72M, or the relationship between the first backup transmitting coil 71B and the first backup receiving coil 72B.

[0069] The first transmitting coil 71 is formed by winding it multiple times in an arc frame shape. One end of the first transmitting coil 71 is electrically connected to the lead-out portion 7a, which is electrically connected to the main control unit 8M or the backup control unit 8B, and the other end is electrically connected to the connecting portion 7k, which electrically connects the first transmitting coil 71 to the second main transmitting coil 73M or the second backup transmitting coil 73B. The outermost part of the first transmitting coil 71 is electrically connected to the connecting portion 7k.

[0070] The first receiving coil 72 is formed inside the first transmitting coil 71 when viewed from the axial direction. In other words, the first transmitting coil 71 is formed to surround the first receiving coil 72. The first receiving coil 72 includes a first sine wave coil 721 and a first cosine wave coil 722.

[0071] The shape of the first sine wave coil 721 was studied so that a voltage signal (described below) along the beat waveform of a sine wave could be output based on the rotation of the upper shaft 121. For example, the first sine wave coil 721 is formed along an imaginary sine wave drawn in a manner that bends circumferentially with one end of the first sine wave coil 721 as the phase axis. The first sine wave coil 721 is in a generally chain-like shape that overlaps the sine wave with a wave after the sine wave is reversed vertically, forming multiple closed loops. The two ends of the first sine wave coil 721 are electrically connected to the leads 7b and 7c. The leads 7b and 7c are electrically connected to the main control unit 8M or the backup control unit 8B.

[0072] The shape of the first cosine wave coil 722 was studied so that a voltage signal along the beat frequency waveform of the cosine wave could be output according to the rotation of the upper shaft 121. For example, the first cosine wave coil 722 is formed along an imaginary cosine wave drawn in a manner that bends circumferentially with one end of the first cosine wave coil 722 as the phase axis. The first cosine wave coil 722 is in a roughly chain-like shape that overlaps the cosine wave with the wave after the cosine wave is reversed vertically, forming multiple closed loops. The two ends of the first cosine wave coil 722 are electrically connected to the leads 7d and 7e. The leads 7d and 7e are electrically connected to the main control unit 8M or the backup control unit 8B.

[0073] The second main transmitting coil 73M and the second main receiving coil 74M together constitute an inductive sensor with the second target 5. Furthermore, the second backup transmitting coil 73B and the second backup receiving coil 74B together constitute an inductive sensor with the second target 5. Hereinafter, these inductive sensors with the second target 5 will also be referred to as "second inductive sensor 102". When viewed axially, the second main transmitting coil 73M, the second main receiving coil 74M, the second backup transmitting coil 73B, and the second backup receiving coil 74B are located relative to region R1 (refer to...). Figure 4 On the opposite side of the upper axis 121, a ring-shaped region R2 is formed (see reference). Figure 4 When viewed axially, the second main transmitting coil 73M and the second backup transmitting coil 73B are each wound in a circular shape. The second main receiving coil 74M and the second backup receiving coil 74B are formed and housed inside the second main transmitting coil 73M and the second backup transmitting coil 73B. The area from the outer edge of the second main transmitting coil 73M and the second backup transmitting coil 73B to the inner edge is region R2, which will be described in detail below. Region R2 is axially opposed to the protrusion 51 of the second target 5.

[0074] like Figure 10 and Figure 11As shown, the second backup transmitting coil 73B has the same shape as the second main transmitting coil 73M, is positioned on the side of the second main transmitting coil 73M opposite to the second target 5, and is positioned to overlap with the second main transmitting coil 73M axially. The second backup receiving coil 74B has the same shape as the second main receiving coil 74M, is positioned on the side of the second main receiving coil 74M opposite to the second target 5, and is positioned to overlap with the second main receiving coil 74M axially. In the following description, without specifically distinguishing between the second main transmitting coil 73M and the second backup transmitting coil 73B, it will simply be referred to as "second transmitting coil 73". And without specifically distinguishing between the second main receiving coil 74M and the second backup receiving coil 74B, it will simply be referred to as "second receiving coil 74". Furthermore, when describing the relationship between the first transmitting coil 71, the first receiving coil 72, the second transmitting coil 73, and the second receiving coil 74, unless otherwise specified, it refers to the relationship between the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, and the second main receiving coil 74M, or the relationship between the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, and the second backup receiving coil 74B. Moreover, compared to the first inductive sensor 101, the second inductive sensor 102 is less susceptible to the influence of horizontal positional offset between the target (i.e., the first target 4 or the second target 5) and the receiving coil (i.e., the first receiving coil 72 or the second receiving coil 74). Furthermore, regarding the formation of the coil pattern, compared to the arc-shaped pattern of the first inductive sensor 101, the annular pattern of the second inductive sensor 102 is less prone to errors. Therefore, it can be said that, compared with the first inductive sensor 101, the second inductive sensor 102 can perform angle detection with high precision.

[0075] The second transmitting coil 73 is formed by winding it multiple times in a circular shape. One end of the second transmitting coil 73 is electrically connected to the connecting portion 7k, and the other end is electrically connected to the lead-out portion 7f, which is connected to the main control unit 8M or the backup control unit 8B. The outermost part of the second transmitting coil 73 is electrically connected to the connecting portion 7k. The first transmitting coil 71 and the second transmitting coil 73 are electrically connected in series via the connecting portion 7k. The lead-out portion 7f has a first portion 7fa formed at a position that overlaps with the connecting portion 7k in the axial direction, a second portion 7fb formed from the outer peripheral side along the first transmitting coil 71, and a third portion 7fc extending radially outward from the second portion 7fb toward the upper shaft 121. The third portion 7fc is electrically connected to the main control unit 8M or the backup control unit 8B.

[0076] The second receiving coil 74 is formed inside the second transmitting coil 73 when viewed from the axial direction. In other words, the second transmitting coil 73 is formed to surround the second receiving coil 74. The second receiving coil 74 includes a second sine wave coil 741 and a second cosine wave coil 742.

[0077] The shape of the second sine wave coil 741 was studied so that a voltage signal along the beat frequency waveform of a sine wave could be output according to the rotation of the upper shaft 121. For example, the second sine wave coil 741 is formed along an imaginary sine wave that is curved in a circular shape with a predetermined position in the circumference of the second sine wave coil 741 as the phase axis. The second sine wave coil 741 is in a roughly chain-like shape that overlaps the sine wave with the wave after the sine wave is reversed, forming multiple closed loops. The two ends of the second sine wave coil 741 are electrically connected to the leads 7g and 7h. The leads 7g and 7h are electrically connected to the main control unit 8M or the backup control unit 8B.

[0078] The shape of the second cosine wave coil 742 was studied so that a voltage signal along the beat frequency waveform of the cosine wave could be output according to the rotation of the upper shaft 121. For example, the second cosine wave coil 742 is formed along an imaginary cosine wave that is curved in a circular shape with a predetermined position in the circumference of the second cosine wave coil 742 as the phase axis. The second cosine wave coil 742 is formed in a generally chain-like shape with the cosine wave superimposed on the wave after the cosine wave is reversed, forming multiple closed loops. The two ends of the second cosine wave coil 742 are electrically connected to the leads 7i and 7j. The leads 7i and 7j are electrically connected to the main control unit 8M or the backup control unit 8B. In addition, a portion of the wiring from the leads 7a to 7j to the main control unit 8M or the backup control unit 8B is omitted from the illustration. Furthermore, the shapes of the first transmitting coil 71 and the first receiving coil 72 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 approach, the second inductive sensor 102 can detect angles with higher accuracy compared to the first inductive sensor 101. This will be explained below. First, as described above, the first transmitting coil 71 and the first receiving coil 72 of the first inductive sensor 101 are formed only within a portion of the circumferential direction. Therefore, for example, if the first target 4 is assembled at an angle relative to an imaginary plane orthogonal to the axial direction, the gap between the first transmitting coil 71, the first receiving coil 72, and the opposing protrusion 41 varies depending on the protrusion 41 opposite to the first transmitting coil 71 and the first receiving coil 72. Therefore, the strength of the output signal generated by the first receiving coil 72 can easily reduce the accuracy of the first inductive sensor 101. On the other hand, as described above, the second transmitting coil 73 and the second receiving coil 74 of the second inductive sensor 102 are formed throughout the entire circumference. Therefore, for example, when the second target 5 is assembled at an angle relative to an imaginary plane orthogonal to the axial direction, even if the axial gap between the specific protrusion 51 and the second transmitting coil 73 and the second receiving coil 74 becomes smaller, the overall impact on the voltage output from the second receiving coil 74 is smaller because the axial gap between the protrusion 51 on the opposite side and the second transmitting coil 73 and the second receiving coil 74 becomes larger. Therefore, in this embodiment, the second inductive sensor 102 can perform angle detection with higher accuracy compared to the first inductive sensor 101.

[0080] The main control unit 8M and the backup control unit 8B, for example, have a control area and a ROM (Read Only Memory) that include a processor and a computing area for the processor during operation. The main control unit 8M and the backup control unit 8B are composed of an IC (Integrated Circuit) such as a Micro Controller Unit (MCU). Furthermore, at least a portion of the functions of each of the main control unit 8M and the backup control unit 8B can also be implemented, for example, by a steering control device 18. The main control unit 8M is mounted on the main surface of the multilayer substrate 6 on the side of the first target 4 and the second target 5, and the backup control unit 8B is mounted on the main surface on the opposite side. The main control unit 8M and the backup control unit 8B are arranged in a position where they overlap each other axially.

[0081] The main control unit 8M controls the energization of the first main transmitting coil 71M and the second main transmitting coil 73M, and processes the output signals of the first main receiving coil 72M and the second main receiving coil 74M (e.g., AD conversion). The backup control unit 8B controls the energization of the first backup transmitting coil 71B and the second backup transmitting coil 73B, and processes the output signals of the first backup receiving coil 72B and the second backup receiving coil 74B (e.g., AD conversion). The backup control unit 8B performs the same functions as the main control unit 8M, and is set up for redundancy purposes. In the following description, without specifically distinguishing between the main control unit 8M and the backup control unit 8B, they are simply referred to as "control unit 8". Furthermore, when describing the relationship between the control unit 8 and the first transmitting coil 71, the first receiving coil 72, the second transmitting coil 73, and the second receiving coil 74, unless otherwise specified, it refers to the relationship between the main control unit 8M and the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, and the second main receiving coil 74M, or the relationship between the backup control unit 8B and the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, and the second backup receiving coil 74B. The details of the processing performed by the control unit 8 will be explained below.

[0082] like Figure 3 As shown, the housing 91 has a bottom wall portion 911, a side wall portion 912 erected from the periphery of the bottom wall portion 911, a dividing wall 913 erected from the bottom wall portion 911 and dividing the space inside the housing 91, a pin 914 for positioning the multilayer substrate 6, a connector portion 915 for electrical connection with a connected object, and a fixing portion 916 for fixing to a mounting object.

[0083] The bottom wall portion 911 is formed in a plane direction orthogonal to the axial direction. An insertion hole 911a is formed in the bottom wall portion 911 for inserting the upper shaft 121. Around the insertion hole 911a in the bottom wall portion 911, an annular fitting recess 911b is formed to rotatably engage one end of the cylindrical portion 21 of the first gear 2. Furthermore, an annular groove 911c is formed in the bottom wall portion 911 to rotatably engage the annular protrusion 32 of the second gear 3.

[0084] The side wall portion 912 has an opening 912a at the end opposite to the bottom wall portion 911.

[0085] A dividing wall 913 is erected from the bottom wall portion 911. A portion of the dividing wall 913 is formed along the first gear 2 and the second gear 3, dividing the arrangement space of the first gear 2 and the second gear 3. Furthermore, a multilayer substrate 6 is placed on the surface of the dividing wall 913 opposite to the bottom wall portion 911.

[0086] Pin 914 is erected from the dividing wall 913 toward the side opposite to the bottom wall 911. Pin 914 is inserted into the positioning hole 61 of the multilayer substrate 6.

[0087] A connector that is fitted to and connected to the rotation angle detection device 1 is connected to the connector section 915. The connector section 915 is formed by molding a core (not shown) that is formed by molding multiple connector terminals 915a. The multiple connector terminals 915a are respectively inserted into multiple through holes 63 formed on the multilayer substrate 6 and electrically connected to the control section 8 mounted on the multilayer substrate 6.

[0088] The fixing part 916 is formed to extend outward from the bottom wall part 911 and has a bolt insertion hole 916a for inserting a bolt for fixing.

[0089] The cover 92 seals the opening 912a of the side wall portion 912. The cover 92 has a top wall portion 921 opposite to the bottom wall portion 911 of the housing 91 and a plurality of flexible tabs 922 erected from the periphery of the top wall portion 921 toward the housing 91.

[0090] An opening 921a is formed at one end of the cylindrical portion 21 into which the first gear 2 is inserted. An upper shaft 121 is inserted into the opening 921a. A pin 921b for inserting a positioning hole 61 into the multilayer substrate 6 is erected on the bottom wall portion 911.

[0091] Multiple flexible sheets 922 are engaged with the housing 91 by snap-fit ​​mechanisms. Thus, the cover 92 is fixed relative to the housing 91.

[0092] (Transmitting coil circuit)

[0093] Figure 12 This is the circuit diagram of the transmitting coil circuit. (Refer to...) Figure 12 The transmission coil circuit from the control unit 8 to the first transmission coil 71 and the second transmission coil 73 will be described.

[0094] The control unit 8 outputs an AC voltage of a predetermined frequency. As follows: Figure 13 As shown, the voltage waveform output by the control unit 8 to the transmitting coil circuit is, for example, a sine wave. The transmitting coil circuit has a series connection between a first transmitting coil 71 and a second transmitting coil 73. Furthermore, two capacitors 75 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 Kolpithecus oscillating circuit.

[0095] In the transmitting coil circuit, the first transmitting coil 71 and the second transmitting coil 73 are connected in series rather than in parallel. As a result, the combined inductance of the transmitting coil circuit increases, and the Q value (Quality Factor) rises accordingly, making it easier to selectively transmit only a specific frequency.

[0096] (Rotation angle detection method)

[0097] 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 under the following conditions: 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 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 is set to the positive maximum value.

[0098] Figure 13 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 13 In the three graphs shown, the horizontal axis is set to the same scale for all of them. Input voltage V input The voltage is a sinusoidal voltage applied to the first transmitting coil 71 and the second transmitting coil 73. The first output voltage V1 is the voltage induced in the first sine wave coil 721 or the second sine wave coil 741. The second output voltage V2 is the voltage induced in the first cosine wave coil 722 or the second cosine wave coil 742.

[0099] When detecting the rotation angle of the upper shaft 121, the control unit 8 first applies a sinusoidal voltage of a predetermined frequency to the first transmitting coil 71 and the second transmitting coil 73. As a result, an alternating magnetic field is formed around the first transmitting coil 71 and the second transmitting coil 73 respectively.

[0100] The alternating magnetic field generated by the first transmitting coil 71 causes the first output voltage V1 generated by the first sine wave coil 721 to change with time through electromagnetic induction, and the second output voltage V2 generated by the first cosine wave coil 722 to change with time through electromagnetic induction.

[0101] Here, when the protrusion 41 of the first target 4 is opposite to the first transmitting coil 71, eddy currents are generated in the protrusion 41, and magnetic flux is formed that cancels out the magnetic flux generated by energizing the first transmitting coil 71 in the opposite direction. Therefore, in the magnetic flux generated by energizing the first transmitting coil 71 and passing through the closed loop portions of the first sine wave coil 721 and the first cosine wave coil 722, the magnetic flux passing through the portion opposite to the protrusion 41 is canceled out by the magnetic flux in the opposite direction generated by the eddy currents.

[0102] Furthermore, since the first target 4 has alternating protrusions 41 and concave portions 42 in the circumferential direction, as the first target 4 rotates, the area of ​​the protrusions 41 opposite to the closed loop portions of the first sine wave coil 721 and the first cosine wave coil 722 changes periodically, thereby causing the first output voltage V1 and the second output voltage V2 to change periodically, respectively. Figure 13 As shown, in this method, the waveform of the voltage generated by the first sine wave coil 721 along with the rotation of the first target 4 is a beat frequency waveform of a sine wave, and the waveform of the voltage generated by the first cosine wave coil 722 along with the rotation of the first target 4 is a beat frequency waveform of a cosine wave.

[0103] Furthermore, the control unit 8 generates a first demodulated voltage after demodulating the output signal from the first sine wave coil 721. The waveform of the first demodulated voltage relative to the rotation angle of the upper shaft 121 is shown in... Figure 13 The waveform, as shown by the dashed line L1, becomes a sine wave shape. Furthermore, the control unit 8 generates a second demodulated voltage, which is the output signal demodulated from the first cosine wave coil 722. The waveform of the second demodulated voltage relative to the rotation angle of the upper shaft 121 is... Figure 13 As shown by the dashed line L2, the shape is a cosine wave.

[0104] Furthermore, the control unit 8 uses the atan2 function to calculate the detected value of the rotation angle of the first target 4, i.e., the first detection angle ψ (electric angle), based on the first demodulation voltage and the second demodulation voltage. Similarly, it calculates the detected value of the rotation angle of the second target 5, i.e., the second detection angle φ (electric angle).

[0105] Figure 14 It 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 14 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 14 The horizontal axis of the graph shown represents the absolute rotation angle θ of the upper axis 121, and the vertical axis represents either the first detection angle ψ or the second detection angle φ.

[0106] Here, the first target 4 rotates to form the area of ​​the protrusion 41 and concave 42 by one-fifth (i.e., 72°) of a circle, thus achieving the same posture. Therefore, the first detection angle ψ changes periodically with the range of the first target 4 rotating by one-fifth of a circle (i.e., 72° rotation) as a cycle. That is, during the period when the first target 4 rotates once, the first detection angle ψ (i.e., electrical angle) changes for five 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).

[0107] Furthermore, the second target 5 rotates to form the area of ​​the protrusion 51 and concave 52 by half a revolution (i.e., 180°) to achieve the same posture. Therefore, the second detection angle φ changes periodically with the range of the second target 5 rotating by half a revolution (i.e., 180° rotation) as a cycle. That is, during the period of one revolution of the second target 5, the second detection angle φ (i.e., electrical angle) changes for two cycles. Moreover, the gear ratio of the second gear 3 relative to the first gear 2 is 24 / 58. Therefore, the speed transmission ratio i from the upper shaft 121 to the second inductive sensor 102 is considered to be 24 / (58×2)≈0.21.

[0108] Furthermore, when the steering wheel 11 is rotated from the position where it is against the steering wheel in the left direction to the position where it is against the steering wheel in the right direction, as Figure 14 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 by using only one of the results of the first detection angle ψ and the second detection angle φ.

[0109] Because the speed transmission ratio j is different from the speed transmission ratio i, when 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 shift and the difference increases. In this method, the difference between the first detection angle ψ and the second detection angle φ is used to calculate the absolute rotation angle θ.

[0110] like Figure 14 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.

[0111] Figure 15This 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 (Zero-Cross) before the first detection angle ψ. During the period between the second detection angle φ crossing zero and the first detection angle ψ crossing zero, the absolute value of the difference between the first detection angle ψ and the second detection angle φ is temporarily greater than 180°. Here, crossing zero refers to the following situation: from near 0° to near 360°, the detection angle temporarily changes significantly.

[0112] Figure 16 This is a graph showing the phase difference after performing the following operations: subtracting 360° from the phase difference when the second detection angle φ crosses zero before the first detection angle ψ, and adding 360° to the phase difference when the phase difference is below -180°. This operation will be referred to as standardization, and the phase difference after standardization will be called the standardized phase difference δ. Through standardization, as... Figure 16 As shown, the curve representing the standardized phase difference δ becomes a straight line. Figure 16 In the curve graph, the lines representing -180° and +180° on the vertical axis are shown by single-dot dashed lines respectively.

[0113] In this method, Figure 16 The standardized phase difference δ shown in the curve falls within the range of -180° to +180°, meaning that when the steering wheel 11 is rotated from the left-hand stop position to the right-hand stop position, the first detection angle ψ and the second detection angle φ will not deviate from the range of more than one cycle, thus enabling accurate calculation of the absolute rotation angle θ. This will be explained below.

[0114] In this method, the integer value of the number of electrical rotations of the first inductive sensor 101 or the second inductive sensor 102 (in this method, 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 the first detection angle ψ only for calculating the integer value of the number of electrical rotations of the second inductive sensor 102, the adverse effects 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 method, since the electrical angle of the first inductive sensor 101 changes for five cycles every time the first gear 2 rotates once, the number of electrical rotations of the first inductive sensor 101 is five times the number of mechanical rotations of the first gear 2. Furthermore, since the electrical angle of the second inductive sensor 102 changes for two cycles every time the second gear 3 rotates once, the number of electrical rotations of the second inductive sensor 102 is twice the number of mechanical rotations of the second gear 3.

[0115] In this embodiment, the integer value of the number of electrical rotations of the second inductive sensor 102 is calculated based on the standardized phase difference δ described above. Next, referring to... Figure 17 The method for calculating the integer value of the electrical rotation number of the second inductive sensor 102 is explained.

[0116] Figure 17 The dashed line represents the absolute angle φ between the standardized phase difference δ and the second target 5. 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 5. 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.

[0117] Formula 1

[0118]

[0119] When the integer value of the electrical rotation number of the second inductive sensor 102 is set as R, R is obtained by the following equations (2) and (3).

[0120] Formula 2

[0121]

[0122] Formula 3

[0123]

[0124] Figure 18 It is a graph representing the absolute rotation angle θ calculated 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 φ. Figure 18 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 8.

[0125] Formula 4

[0126]

[0127] As shown in equation (4), the formula for calculating the absolute rotation angle θ does not include the first detection angle ψ. Therefore, if the integer value R of the electrical rotation number of the second inductive sensor 102 is accurately calculated, it will not be affected by the detection error ε. ψ The impact, can be as Figure 18 The absolute rotation angle θ is accurately calculated as shown in the curve. Furthermore, the rotation angle detection method is just one example and can be varied. For instance, 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, and the direction of increase in phase difference can be varied depending on the structure of the rotation angle detection device 1, but can be adjusted by appropriately changing the coefficients of the aforementioned formula.

[0128] (Detection error ε) ψ and detection error ε φ (First condition)

[0129] When the detection error of the first detection angle ψ is ε ψ and the detection error ε of the second detection angle φ φ When the absolute rotation angle θ is large, within the range (i.e., lock-to-lock) that the rotation angle detection device 1 should detect, the first detection angle ψ and the second detection angle φ deviate from each other by more than one cycle, making it impossible to accurately calculate the absolute rotation angle θ. In other words, to accurately calculate the absolute rotation angle θ, even if the errors of the first detection angle ψ and the second detection angle φ are included, within the range that the absolute rotation angle θ should be detected, Figure 9 The curve showing the standardized phase difference δ also needs to be included in the range of -180° to +180°. This requires a necessary condition, namely the detection error ε. ψ and detection error ε φ The permitted range is explained.

[0130] The change Δ of the standardized phase difference δ when the second gear 3 rotates one revolution along with the rotation of the upper shaft 121 is obtained by 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 and by the following equation (5).

[0131] Formula 5

[0132]

[0133] Furthermore, the variation range Δ´ of the phase difference of the overall 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), R... max It is the integer obtained by rounding down the decimal point of the value obtained by F / (i×360) when the size of the range of absolute rotation angles θ to be detected (i.e., lock-to-lock, for example 1800°) is set to F.

[0134] Formula 6

[0135]

[0136] 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).

[0137] Formula 7

[0138]

[0139] Therefore, as shown in equation (8) below, Δ´ needs to be greater than 0 and less than 360, in other words, it needs to satisfy equation (9) below.

[0140] Formula 8

[0141]

[0142] Formula 9

[0143]

[0144] The variation range of the standardized phase difference δ is based 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 varies, therefore, when considering the detection error ε ψ and detection error ε φ When, equation (8) becomes equation (10).

[0145] Formula 10

[0146]

[0147] When equation (10) is transformed, the detection error ε is used. ψ and detection error ε φ The absolute value of must satisfy the following condition, which is given by equation (11).

[0148] Formula 11

[0149]

[0150] Equation (11) can also be rewritten as shown in Equation (12) below.

[0151] Formula 12

[0152]

[0153] In equation (12), z i It is the ratio of the number of teeth on the second gear 3 to the number of teeth on the first gear 2. P j It refers to the number of protrusions 41 in the first target 4. i It is the number of protrusions 51 of the second target 5.

[0154] (Detection error ε) ψ and detection error ε φ (Second condition)

[0155] Here, since the standardized phase difference δ is calculated based on the first detection angle ψ and the second detection angle φ, the standardized phase difference δ includes the detection error ε of the first detection angle ψ. ψ However, as long as 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 electrical rotation number of the second inductive sensor 102 obtained through equations (2) and (3) above, the integer value R can be accurately determined. From this perspective, the allowable detection error ε... ψ and detection error ε φ The conditions will be explained.

[0156] 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 should not be affected by the detection error ε. ψ and ε φ The influence of φ causes a change of more than 180° from the true value without error. That is, when φ s The value of φ (true value) is affected by the detection error ε. ψ and ε φ The effect changes to (φ) s When -φ)´, the following equation (13) needs to be satisfied.

[0157] Formula 13

[0158]

[0159] Here, according to the above equation (1) and δ≡ψ N -φ N The following equations (14) and (15) hold true.

[0160] Formula 14

[0161]

[0162] Formula 15

[0163]

[0164] Moreover, equation (16) is obtained from equations (14) and (15).

[0165] Formula 16

[0166]

[0167] When equation (16) is substituted into equation (13), the following equation (17) is obtained.

[0168] Formula 17

[0169]

[0170] Here, due to the detection error ε ψ and detection error ε φ It can take either positive or negative values, so the left side of equation (17) becomes equation (18) under the maximum condition.

[0171] Formula 18

[0172]

[0173] When equation (18) is transformed, equation (19) is obtained. Equation (19) is the detection error ε, which is used to accurately determine the integer value R of the electrical rotation number of the second inductive sensor 102. ψ and detection error ε φ The necessary condition, namely the allowable range of error.

[0174] Formula 19

[0175]

[0176] (Flowchart of the processing in control unit 8)

[0177] Figure 19This is a flowchart illustrating an example of the calculation process performed by the control unit 8 to solve for the absolute rotation angle θ.

[0178] In step S1, the control unit 8 receives voltage signals from the first sine wave coil 721, the first cosine wave coil 722, the second sine wave coil 741, and the second cosine wave coil 742, 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 721 and the first cosine wave coil 722, and a second detection angle φ is calculated based on the voltage signals from the second sine wave coil 741 and the second cosine wave coil 742, respectively.

[0179] Next, in step S3, the control unit 8 calculates the phase difference by subtracting the second detection angle φ from the first detection angle ψ.

[0180] Next, in step S4, the control unit 8 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 standardized phase difference δ.

[0181] Next, in step S6, the control unit 8 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 phase difference is added to 360° to obtain the standardized phase difference δ. Furthermore, if the phase difference calculated in step S3 is greater than -180° but less than 180°, then in step S8, the phase difference calculated in step S3 is used as the standardized phase difference δ. The processing in steps S4 to S8 is the phase difference standardization process.

[0182] Next, in step S9, the control unit 8 calculates the absolute angle φ using equation (1). s .

[0183] 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 formula (3).

[0184] 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 ).

[0185] In this method, there are a main control unit 8M and a backup control unit 8B, both of which perform the above-described processing. Here, for example, if it is assumed that the main control unit 8M and the backup control unit 8B are functioning normally, the information of the absolute rotation angle θ calculated by the main control unit 8M and the backup control unit 8B is used as the steering angle detection result and sent to the steering control device 18 (see reference 8M). Figure 1 On the other hand, for example, if a malfunction is detected by the system on the main control unit 8M side (e.g., an abnormal output voltage value from the first main receiving coil 72M or the second main receiving coil 74M), the information of the absolute rotation angle θ calculated by the backup control unit 8B is sent to the steering control device 18 (see reference 8M) as the detection result of the steering angle. Figure 1 ).

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

[0187] The rotation angle detection device 1 of this embodiment includes a target (i.e., a first target 4 or a second target 5) that rotates with the rotation of the rotating component (i.e., the upper shaft 121), a main transmitting coil (i.e., a first main transmitting coil 71M or a second main transmitting coil 73M) that generates an alternating magnetic field for inducing eddy currents in the target, and a main receiving coil (i.e., a first main receiving coil 72M or a second main receiving coil 74M) that is electromagnetically coupled to the main transmitting coil. Furthermore, the rotation angle detection device 1 of this embodiment includes a backup transmitting coil (i.e., a first backup transmitting coil 71B or a second backup transmitting coil 73B) disposed on one side of the main transmitting coil in the axial direction and generating an alternating magnetic field for inducing eddy currents in the target, and a backup receiving coil (i.e., a first backup receiving coil 72B or a second backup receiving coil 74B) that is electromagnetically coupled to the backup transmitting coil. Therefore, redundancy can be achieved using a common target, thus suppressing structural complexity during redundancy (e.g., the addition of gears or targets).

[0188] Furthermore, the main transmitting coil and the backup transmitting coil have the same shape, and the main receiving coil and the backup receiving coil have the same shape. Therefore, the structure of the rotation angle detection device 1 can be further simplified.

[0189] Furthermore, the main transmitting coil and the main receiving coil are formed on different wiring layers in the multilayer substrate 6, as are the backup transmitting coil and the backup receiving coil. Thus, by forming the main transmitting coil and the main receiving coil, as well as the backup transmitting coil and the backup receiving coil, on a common multilayer substrate 6, the increase in the number of components can be suppressed. Furthermore, the deviation between the output of the main receiving coil and the output of the backup receiving coil can be suppressed. For example, a comparison and study were conducted on the case where the main transmitting coil and the main receiving coil, as well as the backup transmitting coil and the backup receiving coil, are formed on two different substrates. In this case, there is a concern that the output of the main receiving coil and the backup receiving coil may differ from the output of the backup receiving coil if the positions of the main receiving coil and the backup receiving coil deviate in a plane direction orthogonal to the axial direction due to assembly errors of the two substrates. On the other hand, in this embodiment, such a concern is suppressed.

[0190] As described above, according to this method, a rotation angle detection device capable of suppressing the structural complexity during redundancy can be provided.

[0191] [Second Implementation]

[0192] Reference Figure 20 and Figure 21 The second embodiment of the present invention will be described. Figure 20 This is a bottom view showing the multilayer substrate 6 together with the pattern and mounting components in this embodiment. Figure 21 This is the circuit diagram of the transmitting coil circuit in this method.

[0193] like Figure 21 As shown, compared with the first embodiment, this method also includes a main supplementary coil 103 connected in series with the first main transmitting coil 71M and the second main transmitting coil 73M, and a backup supplementary coil 104 connected in series with the first backup transmitting coil 71B and the second backup transmitting coil 73B.

[0194] like Figure 20 As shown, the main additional coil 103 and the backup additional coil 104 are respectively patterned in the wiring layers of the multilayer substrate 6 in a spiral shape when viewed from the axial direction. The main additional coil 103 is formed in the first layer of the multilayer substrate 6, and the backup additional coil 104 is formed in the third layer of the multilayer substrate 6. Alternatively, the main additional coil 103 may be formed throughout the first and second layers of the multilayer substrate 6, and the backup additional coil 104 may be formed throughout the third and fourth layers, etc., and thus formed throughout multiple layers.

[0195] When viewed from the axial direction, the main additional coil 103 and the backup additional coil 104 are formed at different positions. In this configuration, when viewed from the axial direction, the main additional coil 103 and the backup additional coil 104 are arranged in the side direction (short side direction in this configuration) of the multilayer substrate 6.

[0196] Furthermore, the main supplementary coil 103 and the backup supplementary coil 104 are formed in a region on the long side of the multilayer substrate 6 that differs from the formation range of the first transmitting coil 71, the first receiving coil 72, the second transmitting coil 73, and the second receiving coil 74. This suppresses the influence of the magnetic field generated by energizing the main supplementary coil 103 and the backup supplementary coil 104 on the first receiving coil 72 and the second receiving coil 74.

[0197] The other structures of this method are the same as those of the first embodiment.

[0198] Furthermore, in the embodiments following the second embodiment, unless otherwise specified, the same symbols as those used in the described embodiments represent the same constituent elements as those in the described embodiments.

[0199] (The function and effects of the second embodiment)

[0200] The rotation angle detection device 1 of this method also includes a main auxiliary coil 103 and a backup auxiliary coil 104. Therefore, the inductance of the transmitting coil circuit increases, and the Q value increases. This makes it easier to selectively allow only specific frequencies to pass through.

[0201] Furthermore, when viewed from the axial direction, the main additional coil 103 and the backup additional coil 104 are each formed in a spiral shape and are formed at different positions. Therefore, electromagnetic coupling between the main additional coil 103 and the backup additional coil 104 can be suppressed, and thus the Q value can be easily increased further.

[0202] In addition, this method has the same function and effect as the first embodiment.

[0203] [Variation Example]

[0204] Next, examples of modifications that can be taken for the first and second embodiments will be described.

[0205] In the first and second embodiments, examples are shown where the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, the second main receiving coil 74M, the main control unit 8M, the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, the second backup receiving coil 74B, and the backup control unit 8B are concentrated on a single multilayer substrate 6, but this is not a limitation. For example, the first main transmitting coil 71M, the first main receiving coil 72M, the second main transmitting coil 73M, the second main receiving coil 74M, and the main control unit 8M may be formed on the first substrate, while the first backup transmitting coil 71B, the first backup receiving coil 72B, the second backup transmitting coil 73B, the second backup receiving coil 74B, and the backup control unit 8B may be formed on the second substrate.

[0206] Furthermore, in the first and second embodiments, examples are shown of combining the outputs of two inductive sensors (i.e., the first inductive sensor 101 and the second inductive sensor 102) to detect the rotation angle of the rotating component, but this is not a limitation; at least one inductive sensor may be used. For example, the outputs of an inductive sensor and a magnetic sensor may also be combined to detect the rotation angle of the rotating component.

[0207] Furthermore, in the second embodiment, the main additional coil 103 and the backup additional coil 104 are respectively formed in a spiral pattern on the multilayer substrate 6, but this is not a limitation. For example, the main additional coil 103 and the backup additional coil 104 may also be chip inductors. In this case, it is easier to suppress the enlargement of the multilayer substrate 6.

[0208] (Summary of implementation methods)

[0209] Next, the technical ideas learned from the embodiments described above will be described by reference to symbols and the like. It should be noted that the symbols and the like used in the following description do not limit the constituent elements in the claims to the components specifically shown in the embodiments.

[0210] [1] A rotation angle detection device 1 detects the rotation angle of a rotating component 121 from a reference position, comprising: targets 4 and 5 that rotate with the rotation of the rotating component 121; main transmitting coils 71M and 73M that generate an alternating magnetic field for generating eddy currents in the targets 4 and 5; main receiving coils 72M and 74M that are electromagnetically coupled to the main transmitting coils 71M and 73M; backup transmitting coils 71B and 73B that are disposed on one side of the main transmitting coils 71M and 73M in the axial direction of the rotating component 121 and generate an alternating magnetic field for generating eddy currents in the targets 4 and 5; and backup receiving coils 72B and 74B that are electromagnetically coupled to the backup transmitting coils 71B and 73B.

[0211] [2] According to the rotation angle detection device 1 described in [1], the main transmitting coils 71M and 73M and the backup transmitting coils 71B and 73B have the same shape, and the main receiving coils 72M and 74M and the backup receiving coils 72B and 74B have the same shape.

[0212] [3] The rotation angle detection device 1 according to [1] or [2] further comprises a multilayer substrate 6 having the main transmitting coils 71M, 73M, the main receiving coils 72M, 74M, the backup transmitting coils 71B, 73B and the backup receiving coils 72B, 74B formed thereon, wherein the main transmitting coils 71M, 73M and the main receiving coils 72M, 74M and the backup transmitting coils 71B, 73B and the backup receiving coils 72B, 74B are formed in different wiring layers in the multilayer substrate 6.

[0213] [4] The rotation angle detection device 1 according to any one of [1] to [3] further comprises: a main supplementary coil 103 connected in series with the main transmitting coils 71M and 73M; and a backup supplementary coil 104 connected in series with the backup transmitting coils 71B and 73B.

[0214] [5] According to the rotation angle detection device 1 described in [4], when viewed from the axial direction, the main additional coil 103 and the backup additional coil 104 are respectively formed in a spiral shape and are formed at different positions.

[0215] (Postscript)

[0216] The embodiments of the present invention have been described above, but these embodiments do not limit the invention as described in the claims. Furthermore, it should be noted that the combination of all the features described in the embodiments is not necessarily necessary for solving the problems of the invention. Moreover, 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 target rotates along with the aforementioned rotating component; The main transmitting coil generates an alternating magnetic field to induce eddy currents in the aforementioned target; The main receiving coil is electromagnetically coupled to the aforementioned main transmitting coil; A backup transmitting coil, disposed axially on one side of the main transmitting coil of the aforementioned rotating component, generates an alternating magnetic field for inducing eddy currents in the aforementioned target; and A backup receiving coil is electromagnetically coupled to the aforementioned backup transmitting coil.

2. The rotation angle detection device according to claim 1, characterized in that, The main transmitting coil and the backup transmitting coil described above have the same shape. The main receiving coil and the backup receiving coil described above have the same shape.

3. The rotation angle detection device according to claim 1 or 2, characterized in that, It also comprises a multilayer substrate having the aforementioned main transmitting coil, main receiving coil, backup transmitting coil, and backup receiving coil. The main transmitting coil and the main receiving coil are formed in different wiring layers in the multilayer substrate as well as the backup transmitting coil and the backup receiving coil.

4. The rotation angle detection device according to claim 1 or 2, characterized in that, It also has: A main supplementary coil, which is connected in series with the aforementioned main transmitting coil; and A backup additional coil is connected in series with the aforementioned backup transmitting coil.

5. The rotation angle detection device according to claim 4, characterized in that, When viewed from the aforementioned axial direction, the aforementioned main additional coil and the aforementioned backup additional coil are respectively formed in a spiral shape and are formed in different positions.

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