JP2015001375A - Rotation angle detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detection device which miniaturizes the device and reduce an influence of a noise.SOLUTION: A magnetic type rotation angle detection device 1 for detecting an absolute rotation angle of a rotating body 2 includes: distance detection units 6 arranged at opposing positions on an inclined plane 4 of the rotating body 2 or a passive member 3 in a non-contact state, for detecting a distance to the inclined plane 4 which continuously changes according to a rotation of the rotating body 2; and an angle specifying unit 7 for specifying the absolute rotation angle of the rotating body 2 based on the detected distance by the distance detection units 6. The distance detection unit 6 each includes a detection coil 9 for detecting a distance to the inclined plane 4 as a change in inductance. The angle specifying unit 7 specifies the absolute rotation angle of the rotating body 2 based on a phase shift of an AC-exciting wave generated in response to the inductance change of the detection coil 9 while AC-exciting the detection coil 9 when the absolute rotation angle of the rotating body 2 is specified based on the inductance change of the detection coil 9.

Description

  The present invention relates to a magnetic rotation angle detection device that detects an absolute rotation angle of a rotating body.

  As an absolute rotation angle detection device that detects an absolute rotation angle of a rotating body, a magnetic rotation angle detection device that does not use a permanent magnet or a magnetic sensor (such as a Hall element or an MR element) is known (for example, , See Patent Document 1). Since such a rotation angle detection device can be used even in an environment where iron powder or the like may enter, it is widely used for in-vehicle applications that require high environmental resistance.

  For example, a magnetic rotation angle detection device disclosed in Patent Document 1 is a variable reluctance type resolver (VR type resolver), and includes a non-circular rotor provided on a rotary shaft and a stator surrounding the outer periphery of the rotor. The stator is wound with a plurality of coils for detecting distance fluctuations accompanying the rotation of the rotor. According to such a rotation angle detection device, a two-phase angle detection signal corresponding to the rotation angle of the rotor can be obtained in the same manner as in a conventional resolver, so that an existing R / D converter (dedicated IC) is used. Thus, the rotation angle of the rotation axis can be specified.

JP2013-53890A

  However, in the rotation angle detection device of Patent Document 1, since it is necessary to dispose the stator so as to surround the rotor, there is a problem that the device is not only large, but is also subject to installation restrictions. Further, since the rotation angle detection device of Patent Document 1 is an amplitude modulation method that changes the amplitude of a detection signal in accordance with a variation in the distance from the rotor, it is easily affected by noise, and in a noisy environment, such as a magnetic shield. There is a problem that a separate measure is required and the apparatus is further increased in size.

The present invention was created for the purpose of solving these problems in view of the above circumstances, and is a magnetic rotation angle detection device that detects the absolute rotation angle of a rotating body, An inclined surface that is formed on one end surface of the rotating body or one end surface of a passive member that rotates in accordance with the rotation of the rotating body and is inclined at a predetermined angle with respect to an orthogonal plane of the rotation axis, and an opposite position of the inclined surface A distance detecting unit that is arranged in a non-contact state and detects a distance from the inclined surface that continuously changes according to the rotation of the rotating body, and an absolute value of the rotating body based on a detection distance by the distance detecting unit An angle specifying unit for specifying a specific rotation angle, wherein the inclined surface is made of a conductor that generates an eddy current in a magnetic field, and the distance detecting unit detects a distance from the inclined surface as a change in inductance. Comprising a detection coil, The degree specifying unit determines the absolute rotation angle of the rotating body based on the inductance change of the plurality of detection coils arranged at predetermined intervals in the rotation direction of the inclined surface. Is connected to an AC excitation circuit that causes a phase shift in the AC excitation wave in accordance with a change in inductance of the detection coil, and the absolute rotation of the rotating body is based on the phase shift in the AC excitation wave. It is characterized by specifying an angle.
In addition, the angle specifying unit accumulates a phase shift of the AC excitation wave with time, and specifies an absolute rotation angle of the rotating body based on the accumulated phase shift.
The distance detection unit includes a core around which the detection coil is wound and generates a loop-shaped magnetic field toward the inclined surface in response to alternating current excitation of the detection coil. It has a pot core shape that generates a magnetic field having no specific directionality.
The distance detection unit includes a core around which the detection coil is wound and generates a loop-shaped magnetic field toward the inclined surface in response to alternating current excitation of the detection coil. It has a U-shape that generates a magnetic field having a specific directionality, and is arranged along the radial direction of the inclined surface.
In addition, a plurality of cores along the radial direction of the inclined surface are integrated.

According to the first aspect of the present invention, since the detection coil is arranged at a position opposite to the inclined surface formed on the one end surface of the rotating body or the passive member to detect the variation in distance from the inclined surface, the rotating body or the passive member (rotor And the like, the apparatus can be downsized and the degree of freedom of installation can be increased. Moreover, the absolute rotation angle of the rotating body is specified based on the phase shift of the AC excitation wave according to the change in inductance of the detection coil while AC exciting the detection coil without separating the excitation coil and the detection coil. Since the phase modulation method is applied, the influence of noise can be reduced as compared with the amplitude modulation method that specifies the absolute rotation angle of the rotating body based on the amplitude change of the detection signal.
According to the second aspect of the present invention, the phase shift of the AC excitation wave is accumulated in terms of time, and the absolute rotation angle of the rotating body is specified based on the accumulated phase shift. As compared with the case where the absolute rotation angle of the rotating body is specified based on the above, the detection accuracy and stability can be improved.
According to the invention of claim 3, since the core that generates the loop-shaped magnetic field toward the inclined surface has a pot core shape that generates a magnetic field having no specific directionality on the inclined surface, the influence of the external magnetic field Can be reduced and the environmental resistance can be improved.
According to the invention of claim 4, the core that generates a loop-shaped magnetic field toward the inclined surface is formed into a U-shape that generates a magnetic field having a specific direction on the inclined surface, and is arranged in the radial direction of the inclined surface. Since it arrange | positions along, it can narrow the width | variety (rotation direction of an inclined surface) of the magnetic field which a distance detection part produces | generates, As a result, it becomes possible to raise the distance detection precision of each distance detection part.
According to the invention of claim 5, the same effect as that of claim 4 can be obtained, but a plurality of distance detectors can be arranged in a compact manner, and the rotation angle detector can be miniaturized.

It is a block diagram which shows the structure of the rotation angle detection apparatus which concerns on embodiment of this invention. It is a figure which shows the distance detection part of the rotation angle detection apparatus which concerns on embodiment of this invention, (a) is a front view of a distance detection part, (b) is XX sectional drawing of a distance detection part. It is a side view which shows the detection principle of the rotation angle detection apparatus which concerns on embodiment of this invention. It is a graph which shows the relationship between the rotation angle of the rotation angle detection apparatus which concerns on embodiment of this invention, and distance fluctuation | variation. It is a figure which shows the alternating current excitation circuit of the rotation angle detection apparatus which concerns on embodiment of this invention, (a) is a circuit diagram which shows an oscillation circuit, (b) is a circuit diagram which shows a resonance circuit. It is a flowchart which shows the rotation angle detection process sequence of the rotation angle detection apparatus which concerns on embodiment of this invention. It is a flowchart which shows the distance detection process sequence of the rotation angle detection apparatus which concerns on embodiment of this invention. It is a figure which shows the distance detection part of the rotation angle detection apparatus which concerns on 2nd Embodiment of this invention, (a) is a front view of a distance detection part, (b) is YY sectional drawing of a distance detection part. It is a figure which shows the distance detection part of the rotation angle detection apparatus which concerns on 3rd Embodiment of this invention, (a) is a front view of a distance detection part, (b) is ZZ sectional drawing of a distance detection part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a rotation angle detection device according to an embodiment of the present invention.
As shown in this figure, a rotation angle detection device 1 according to an embodiment of the present invention is an absolute type magnetic encoder that detects the absolute rotation angle of a rotating body 2 without using a permanent magnet, An inclined surface 4 formed on one end surface of the body 2 or one end surface of the passive member 3 that rotates in accordance with the rotation of the rotating body 2, and a detection module 5 that is disposed in a non-contact state at a position facing the inclined surface 4. And is configured. For example, in the rotation angle detection device 1 of the present embodiment, the passive member 3 including the inclined surface 4 that is inclined by a predetermined angle θ with respect to the orthogonal surface of the rotation axis is integrated with the end of the rotating body 2 (rotation shaft). The detection module 5 is disposed in a non-contact state at a position facing the inclined surface 4 of the passive member 3.

  The inclined surface 4 is formed of a conductor that generates an eddy current in a magnetic field. For example, in the present embodiment, when the inclined surface 4 is formed on the passive member 3, the entire passive member 3 is formed of aluminum as a conductor. If the rotating body 2 or the passive member 3 is not a conductor, only the surface portion of the inclined surface 4 may be a conductor. For example, a plate-like conductor member is attached to the inclined surface 4 or a thin film made of a conductor is formed on the inclined surface 4 by plating or vapor deposition.

  The detection module 5 of the present embodiment integrally includes a distance detection unit 6, an angle specification unit 7, and an AC excitation circuit 8. For example, if the distance detecting unit 6 is mounted on one surface of the substrate facing the inclined surface 4 and the angle specifying unit 7 and the AC excitation circuit 8 are mounted on the other surface of the substrate, the distance detecting unit 6, the angle specifying unit 7 and the AC A detection module 5 is integrally provided with the excitation circuit 8.

2A and 2B are diagrams illustrating a distance detection unit of the rotation angle detection device according to the embodiment of the present invention, in which FIG. 2A is a front view of the distance detection unit, and FIG. 2B is an XX sectional view of the distance detection unit. is there.
As shown in this figure, the distance detection unit 6 is disposed in a non-contact state at a position facing the inclined surface 4 and detects a distance from the inclined surface 4 that continuously changes according to the rotation of the rotating body 2. In this embodiment, the distance detection unit 6 includes a detection coil 9 that detects a distance from the inclined surface 4 as a change in inductance, and a core 10 around which the detection coil 9 is wound.

  The core 10 is a member for forming a desired magnetic path, and is formed using a magnetic material such as ferrite or permalloy. For example, in the present embodiment, when a loop-shaped magnetic field (magnetic flux) is generated toward the inclined surface 4, a magnetic field that does not have a specific direction on the inclined surface 4 is used in order to reduce magnetic flux leakage as much as possible. The so-called pot core-shaped core 10 to be generated is used.

  The detection module 5 includes a plurality of distance detection units 6 arranged at a predetermined interval in the rotation direction of the inclined surface 4. For example, the detection module 5 of the present embodiment includes three distance detectors 6 arranged along a circumference centered on the rotation axis of the inclined surface 4 and arranged at equal intervals of 120 °. Incidentally, in this embodiment, the distance detection part 6 is formed using the pot core of diameter 5.6mm, and this is positioned and hold | maintained by the three fitting holes 11a formed in the holder member 11 of diameter 20mm.

FIG. 3 is a side view showing the detection principle of the rotation angle detection device according to the embodiment of the present invention, and FIG. 4 is a graph showing the relationship between the rotation angle and the distance variation of the rotation angle detection device according to the embodiment of the present invention. It is.
As shown in FIG. 3, when the rotating body 2 is rotated in a state where a plurality of distance detection units 6 are arranged in a non-contact state at a position opposite to the inclined surface 4, the distance between each distance detection unit 6 and the inclined surface 4 is set. The distance varies continuously. For example, when the three distance detectors 6 are arranged along the circumference centered on the rotation axis of the inclined surface 4 and arranged at equal intervals of 120 ° as in the present embodiment, each distance The distance between the detection unit 6 and the inclined surface 4 varies as a three-phase waveform shown in FIG. The rotation angle detection device 1 of the present invention magnetically detects such a variation in distance and specifies the absolute rotation angle of the rotating body 2 based on the detected distance. Incidentally, in this embodiment, the minimum distance between the distance detector 6 and the inclined surface 4 is 0.1 mm, the maximum distance is 0.6 mm, and the distance fluctuation width is 0.5 mm. If the reach distance of the magnetic flux is adjusted based on the size of the core 10 or the like, the distance between the distance detector 6 and the inclined surface 4 can be changed in a wide range.

5A and 5B are diagrams showing an AC excitation circuit of the rotation angle detection device according to the embodiment of the present invention. FIG. 5A is a circuit diagram showing an oscillation circuit, and FIG. 5B is a circuit diagram showing a resonance circuit.
As shown in this figure, the AC excitation circuit 8 is configured to cause a phase shift in an AC excitation wave according to a change in inductance of the detection coil 9 while exciting the detection coil 9 with AC. For example, FIG. 5A shows an AC excitation circuit 8 composed of an oscillation circuit, and by arranging the detection coil 9 in a feedback circuit of an oscillation circuit (eg, a Schmitt oscillation circuit) that oscillates at a predetermined frequency. Then, a phase shift is generated in the oscillation wave according to the inductance change of the detection coil 9. FIG. 5B shows an AC excitation circuit 8 composed of a resonance circuit. A predetermined number of drive pulses are input to a resonance circuit (for example, a series resonance circuit) in which a detection coil 9 and a capacitor C are connected. While the detection coil 9 is AC-excited by the resonance operation (damped vibration) after this, a phase shift is generated in the damped vibration wave according to the inductance change of the detection coil 9.

  The angle specifying unit 7 specifies the absolute rotation angle of the rotating body 2 based on the inductance change of the plurality of detection coils 9 arranged at predetermined intervals in the rotation direction of the inclined surface 4. For example, the angle specifying unit 7 of the present embodiment is configured by a microcomputer (microcontroller), and the AC excitation wave output from the AC excitation circuit 8 is processed by a process based on a program or table data written in the microcomputer. A phase shift is detected, and an absolute rotation angle of the rotating body 2 is specified based on the phase shift.

  It is preferable that the angle specifying unit 7 accumulates the phase shift of the AC excitation wave with respect to time and specifies the absolute rotation angle of the rotating body 2 based on the accumulated phase shift. The reason is that even a minute phase shift can be detected with high accuracy by accumulating the minute change over time. For example, the accumulated phase shift can be detected based on the time until the count reaches a predetermined number or the count within the predetermined time by counting the number of alternating excitation waves.

  Next, a specific processing procedure of the angle specifying unit 7 will be described with reference to FIGS. 6 and 7. However, a processing procedure when a resonance circuit is used as the AC excitation circuit 8 is shown, and a processing procedure when an oscillation circuit is used as the AC excitation circuit 8 is omitted.

FIG. 6 is a flowchart showing a rotation angle detection processing procedure of the rotation angle detection device according to the embodiment of the present invention.
As shown in this figure, in the rotation angle detection process by the angle specifying unit 7, the first distance detection process S <b> 1 for detecting a phase shift according to the inductance change of the first detection coil 9 and the second detection coil 9. A second distance detection process S2 for detecting a phase shift according to an inductance change, a third distance detection process S3 for detecting a phase shift according to an inductance change of the third detection coil 9, and these processes (S1 to S3) A rotation angle specifying process S4 for specifying the absolute rotation angle of the rotating body 2 based on the distance detected in (1), and a signal output process S5 for outputting the specified rotation angle as a rotation angle detection signal of a predetermined form, By repeating these processes (S1 to S5), a rotation angle detection signal is output at a predetermined response speed.

FIG. 7 is a flowchart showing a distance detection processing procedure of the rotation angle detection device according to the embodiment of the present invention.
As shown in this figure, in the first to third distance detection processing (S1 to S3), first, after clearing the wave number counter and the time measurement counter (S11), a drive pulse is applied to the corresponding AC excitation circuit 8. Output (S12). When a drive pulse is output to the AC excitation circuit 8, a damped vibration wave is generated by the resonance action of the AC excitation circuit 8 and is input to the angle specifying unit 7. The damped oscillatory wave generated by the AC excitation circuit 8 causes a phase shift according to the inductance change of the detection coil 9 (change in the distance to the inclined surface 4). Therefore, in the distance detection process, this phase shift is accumulated over time. To detect. That is, after outputting a drive pulse to the AC excitation circuit 8 (S12), the number of damped vibration waves is counted (S13), and if it is determined that the count reaches a preset number (S14). Then, a time measurement counter value is acquired and used as a distance detection value (S15).

  The first to third distance detection processes (S1 to S3) can be executed simultaneously or sequentially in a predetermined order. When the first to third distance detection processes (S1 to S3) are performed simultaneously, there is no deviation in the timing of each distance detection process, which is advantageous in terms of detection accuracy and response speed. It is necessary to consider the magnetic mutual interference between the six. On the other hand, when the first to third distance detection processes (S1 to S3) are sequentially executed, there is a slight deviation in the timing of each distance detection process, so that the detection accuracy and response speed may be reduced compared to the former. However, since there is no need to consider the magnetic mutual interference between the distance detectors 6, the latter may be superior in detecting the rotation angle of a rotating body that rotates at a relatively low speed.

  Although detailed illustration of the processing procedure is omitted, in the rotation angle specifying process S4, the distance detection values of the first to third distance detection processes (S1 to S3) are acquired, and the rotator 2 is based on these distance detection values. Specify the absolute rotation angle. For example, the absolute rotation angle of the rotating body 2 can be specified by a calculation process using an inverse trigonometric function or a reference process of a look-up table written in advance, and the specified rotation angle is determined by the signal output process S5. It is converted into an output signal in a predetermined form and output as a rotation angle detection signal.

The distance detection values of the first to third distance detection processes (S1 to S3) include a detection component that changes according to the distance and a constant bias component regardless of the distance. In the specific process, it is preferable to perform the arithmetic process and the table reference process after removing the bias component. For example, in the present embodiment in which three-phase distance detection values are obtained, it is assumed that the sum of the three-phase detection components is “0”, and the bias component is removed using the following equation.
Bias component = (sum of distance detection values for three phases) / 3
Detection component of first distance detection value = first distance detection value−bias component Detection component of second distance detection value = second distance detection value−bias component Detection component of third distance detection value = third distance detection value−bias component

  According to the present embodiment configured as described, a magnetic rotation angle detection device 1 that detects an absolute rotation angle of the rotator 2, the one end surface of the rotator 2, or the rotation of the rotator 2. Is formed on one end surface of the passive member 3 that rotates in response to the inclined surface 4 and is inclined at a predetermined angle with respect to the orthogonal surface of the rotation axis, and is disposed in a non-contact state at a position opposite the inclined surface 4. A distance detection unit 6 that detects a distance from the inclined surface 4 that continuously changes according to the rotation of the angle detector, and an angle specification unit that specifies an absolute rotation angle of the rotating body 2 based on the detection distance by the distance detection unit 6 7, the inclined surface 4 is made of a conductor that generates an eddy current in a magnetic field, and the distance detection unit 6 includes a detection coil 9 that detects the distance from the inclined surface 4 as a change in inductance, and includes an angle specifying unit. 7 are arranged at predetermined intervals in the rotation direction of the inclined surface 4. In specifying the absolute rotation angle of the rotating body 2 based on the inductance change of the plurality of detection coils 9, the detection coil 9 is AC-excited, and the phase shift is caused to the AC excitation wave according to the inductance change of the detection coil 9. Since the absolute rotation angle of the rotating body 2 is specified based on the phase shift of the AC exciting wave, the inclined surface 4 is provided on one end surface of the rotating body 2 or the passive member 3. It is possible to specify the entire rotation angle of the rotator 2 by simply forming and disposing the distance detection unit 6 in a non-contact state at the opposite position. As a result, the rotator 2 and the passive member 3 Compared with the case where the detection coil 9 is arranged on the outer peripheral side, not only the apparatus can be miniaturized, but also the degree of freedom of installation can be increased.

  In addition, while the excitation coil and the detection coil 9 are not separated, the absolute value of the rotating body 2 is determined based on the phase shift of the AC excitation wave according to the inductance change of the detection coil 9 while the excitation excitation of the detection coil 9 is performed. Since the phase modulation method for specifying the rotation angle is applied, the influence of noise can be reduced compared to the amplitude modulation method for specifying the absolute rotation angle of the rotating body 2 based on the amplitude change of the detection signal.

  In addition, the angle specifying unit 7 of the present embodiment accumulates the phase shift of the AC excitation wave with time, and specifies the absolute rotation angle of the rotating body 2 based on the accumulated phase shift. As compared with the case where the absolute rotation angle of the rotating body 2 is specified based on the phase shift, the detection accuracy and stability can be improved.

  Further, the distance detection unit 6 of the present embodiment includes a core 10 around which a detection coil 9 is wound, and generates a loop-shaped magnetic field toward the inclined surface 4 in response to AC excitation of the detection coil 9. Since the core 10 has a pot core shape that generates a magnetic field having no specific direction on the inclined surface 4, the influence of the external magnetic field can be reduced and the environmental resistance can be improved.

  Next, a rotation angle detection device according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 8 is a diagram illustrating a distance detection unit of a rotation angle detection device according to the second embodiment of the present invention, where (a) is a front view of the distance detection unit, and (b) is a YY cross section of the distance detection unit. FIG.
As shown in this figure, in the rotation angle detection device of the second embodiment, the shape and arrangement of the core 10 constituting the distance detection unit 6 are different from those of the embodiment. Specifically, a U-shaped core 10 that generates a magnetic field having a specific direction on the inclined surface 4 is used, and the U-shaped core 10 is disposed in the radial direction of the inclined surface 4. It is arranged along. In this way, since the width of the magnetic field generated by the distance detection unit 6 (the rotation direction of the inclined surface 4) can be reduced, the distance detection accuracy of each distance detection unit 6 can be increased.

  Next, a rotation angle detection device according to a third embodiment of the present invention will be described with reference to FIG.

FIG. 9 is a diagram illustrating a distance detection unit of a rotation angle detection device according to a third embodiment of the present invention, where (a) is a front view of the distance detection unit, and (b) is a ZZ cross section of the distance detection unit. FIG.
As shown in this figure, the rotation angle detection device of the third embodiment is different from the above embodiment in that it includes a core 10 having a shape in which three U-shaped cores are integrated. Specifically, one leg portion of the U-shaped core is made common, and the common leg portion is positioned on the center line of the inclined surface 4. According to such a core 10, the same effect as that of the second embodiment can be obtained, but a plurality (three) of distance detectors 6 can be arranged in a compact manner, and the rotation angle detector can be downsized. It becomes. In addition, when integrating the core 10 of the some distance detection part 6, it is necessary to perform the 1st-3rd distance detection process (S1-S3) mentioned above sequentially, shifting timing.

  Although the present invention has been described with reference to the embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, the number of distance detection units, the size of the core, the distance between the inclined surface and the distance detection unit, the fluctuation range of the distance, and the like can be arbitrarily changed according to the use situation.

  Moreover, in the said embodiment, although an inclined surface is comprised by one plane and the distance change of 1 period is produced by one rotation, an inclined surface is comprised by the combination of several planes, and it is several periods by 1 rotation. A change in distance may be generated. Further, the inclined surface is not limited to a flat surface, but may be a curved surface.

DESCRIPTION OF SYMBOLS 1 Rotation angle detection apparatus 2 Rotating body 3 Passive member 4 Inclined surface 5 Detection module 6 Distance detection part 7 Angle specification part 8 AC excitation circuit 9 Detection coil 10 Core 11 Holder member

Claims (5)

A magnetic rotation angle detection device for detecting an absolute rotation angle of a rotating body,
An inclined surface that is formed on one end surface of the rotating body or one end surface of a passive member that rotates according to the rotation of the rotating body, and is inclined at a predetermined angle with respect to an orthogonal plane of the rotation axis;
A distance detection unit that is arranged in a non-contact state at a position opposite to the inclined surface and detects a distance from the inclined surface that continuously changes according to the rotation of the rotating body;
An angle specifying unit that specifies an absolute rotation angle of the rotating body based on a detection distance by the distance detection unit;
The inclined surface is made of a conductor that generates an eddy current in a magnetic field,
The distance detection unit includes a detection coil that detects a distance from the inclined surface as a change in inductance,
The angle specifying unit includes:
In specifying the absolute rotation angle of the rotating body based on the inductance change of the plurality of detection coils arranged at predetermined intervals in the rotation direction of the inclined surface,
While the detection coil is AC-excited, the detection coil is connected to an AC excitation circuit that causes a phase shift in an AC excitation wave according to an inductance change of the detection coil.
A rotation angle detection device that identifies an absolute rotation angle of the rotating body based on a phase shift of the AC excitation wave.   The angle specifying unit accumulates a phase shift of the AC excitation wave with time, and specifies an absolute rotation angle of the rotating body based on the accumulated phase shift. The rotation angle detection device described.   The distance detection unit includes a core around which the detection coil is wound, and generates a loop-shaped magnetic field toward the inclined surface in response to alternating current excitation of the detection coil. The rotation angle detection device according to claim 1, wherein the rotation angle detection device has a pot core shape that generates a magnetic field having no directionality.   The distance detection unit includes a core around which the detection coil is wound, and generates a loop-shaped magnetic field toward the inclined surface in response to alternating current excitation of the detection coil. The rotation angle detection device according to claim 1, wherein the rotation angle detection device has a U shape that generates a magnetic field having directionality and is arranged along a radial direction of the inclined surface.   The rotation angle detection device according to claim 4, wherein a plurality of cores along the radial direction of the inclined surface are integrated.

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