JP2015014549A - Rotation angle detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the miniaturization of a device, and to reduce the influence of a noise.SOLUTION: The rotation angle detection device includes: a distance detection part 6 arranged in a non-contact state at the opposite position of the inner peripheral surface (distance detected surface 4) of a rotary body 2 or a passive member 3 for detecting a distance between itself and the distance detected surface 4 which continuously changes in accordance with the rotation of the rotary body 2; and an angle specification part 7 for specifying the absolute rotation angle of the rotary body 2 on the basis of the distance detected by the distance detection part 6. The distance detection part 6 includes a plurality of detection coils 9 for detecting the distance between itself and the distance detected surface 4 as the change of inductance. The angle specification part 7 for specifying the absolute rotation angle of the rotary body 2 on the basis of the inductance change of the detection coils 9 is configured to specify the absolute rotation angle of the rotary body 2 on the basis of the phase shifts of AC excitation waves generated in accordance with the inductance change of the detection coils 9 while AC-exciting the detection coils 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, Arranged in a non-contact state at a position facing the inner peripheral surface of the rotating body or the inner peripheral surface of a passive member that rotates according to the rotation of the rotating body, and the inner surface of the rotating body or the inner surface of the passive member A distance detection unit that detects a distance to the peripheral surface, and an inner peripheral surface of the rotating body or an inner peripheral surface of the passive member, and the distance to the distance detecting unit is continuously set according to the rotation of the rotating body. A distance detection surface to be changed to an angle, and an angle specifying unit for specifying an absolute rotation angle of the rotating body based on a detection distance by the distance detection unit, wherein the distance detection surface is an eddy current in a magnetic field. The distance detecting unit is configured to generate the A detection coil that detects a distance from the exit surface as a change in inductance is provided, and the angle specifying unit detects an inductance change of the plurality of detection coils arranged at a predetermined interval in a rotation direction of the distance detection surface. In order to specify the absolute rotation angle of the rotating body based on the AC coil, the detection coil is AC-excited and connected to an AC excitation circuit that causes a phase shift in the AC excitation wave according to an inductance change of the detection coil. An absolute rotation angle of the rotating body is specified based on a phase shift of the AC excitation wave.
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.

According to the first aspect of the present invention, since the detection coil is arranged at a position opposite to the distance detection surface formed on the inner peripheral surface of the rotating body or the passive member and the distance fluctuation with the distance detection surface is detected, the rotation body Compared with the case where a detection coil is arranged on the outer peripheral side of a passive member (such as a rotor), not only can the apparatus be miniaturized, but also 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.

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 sectional drawing of a distance detection part. 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.

  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, It is arrange | positioned in the non-contact state in the position facing the internal peripheral surface of the body 2, or the internal peripheral surface of the passive member 3 rotated according to rotation of the rotary body 2, and with the internal peripheral surface of the rotary body 2 or the passive member 3. A distance detection surface 6 that detects the distance, and a distance detection surface that is formed on the inner peripheral surface of the rotating body 2 or the passive member 3 and continuously changes the distance from the distance detecting portion 6 according to the rotation of the rotating body 2. 4, an angle specifying unit 7 that specifies an absolute rotation angle of the rotating body 2 based on a detection distance by the distance detection unit 6, and an AC excitation circuit 8 to be described later.

  For example, in the rotation angle detection device 1 of the present embodiment, the cylindrical passive member 3 is integrally attached to the end surface of the rotating body 2 formed of the rotation shaft in an eccentric state, and the inner peripheral surface of the passive member 3 is covered by a distance. A distance detection unit 6 is arranged in a non-contact state at a position opposite to the detection surface 4. In this way, the distance between the distance detector 6 and the distance detection surface 4 can be continuously changed according to the rotation of the rotating body 2.

  The distance detection surface 4 is formed of a conductor that generates an eddy current in a magnetic field. For example, in the present embodiment, when the distance detection 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 distance detection surface 4 may be a conductor. For example, a plate-like conductor member is attached to the distance detection surface 4 or a thin film made of a conductor is formed on the distance detection surface 4 by plating or vapor deposition.

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 arranged in a non-contact state at a position opposed to the distance detection surface 4, and is a distance from the distance detection surface 4 that continuously changes according to the rotation of the rotating body 2. The distance detection unit 6 of the present embodiment includes a detection coil 9 that detects a distance from the distance detection surface 4 as a change in inductance, and a core 10 around which the detection coil 9 is wound. It is prepared for.

  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 distance detection surface 4, a U-shape (冂) is generated in order to generate a magnetic field having a specific direction on the distance detection surface 4. The U-shaped core 10 is used, and the U-shaped core 10 is arranged in a direction orthogonal to the rotation direction of the distance detection surface 4. In this way, since the width of the magnetic field generated by the distance detection unit 6 (the rotation direction of the distance detection surface 4) can be reduced, the distance detection accuracy of each distance detection unit 6 can be increased.

  The rotation angle detection device 1 includes a plurality of distance detection units 6 arranged at a predetermined interval in the rotation direction of the distance detection surface 4. For example, the rotation angle detection device 1 of the present embodiment includes three distance detection units 6 that are arranged along the circumference centered on the rotation axis of the passive member 3 and at equal intervals of 120 °.

FIG. 3 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.
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 facing the distance detection surface 4, the distance between each distance detection unit 6 and the distance detection surface 4 is continuous. Fluctuates. For example, when the three distance detectors 6 are arranged along the circumference centered on the rotational axis of the passive member 3 and at equal intervals of 120 ° as in the present embodiment, each distance The distance between the detection unit 6 and the distance detection 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 detection unit 6 and the distance detection surface 4 is 0.1 mm, the maximum distance is 0.6 mm, and the distance variation width is 0.5 mm. If the reach distance of the magnetic flux is adjusted based on the number of windings, the size of the core 10, and the like, the distance between the distance detection unit 6 and the distance-exposed surface 4 can be changed in a wide range.

4A and 4B are diagrams showing an AC excitation circuit of the rotation angle detection device according to the embodiment of the present invention. FIG. 4A is a circuit diagram showing an oscillation circuit, and FIG. 4B 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. 4A shows an AC excitation circuit 8 composed of an oscillation circuit, and by disposing a 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. 4B 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 a predetermined interval in the rotation direction of the distance detection 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. 5 and 6. 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. 5 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. 6 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 vibration wave generated by the AC excitation circuit 8 causes a phase shift in accordance with the inductance change of the detection coil 9 (change in the distance to the distance detection surface 4). Therefore, in the distance detection process, this phase shift is temporally changed. Accumulate and 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 above, the magnetic rotation angle detection device 1 detects the absolute rotation angle of the rotating body 2, and includes the inner peripheral surface of the rotating body 2 or the rotating body 2. A distance detection unit 6 that is arranged in a non-contact state at a position facing the inner peripheral surface of the passive member 3 that rotates according to the rotation, and detects the distance from the inner peripheral surface of the rotating body 2 or the inner peripheral surface of the passive member 3. A distance detection surface 4 that is formed on the inner peripheral surface of the rotating body 2 or the inner peripheral surface of the passive member 3 and that continuously changes the distance from the distance detecting unit 6 according to the rotation of the rotating body 2; And an angle specifying unit 7 for specifying an absolute rotation angle of the rotating body 2 based on a detection distance by the detection unit 6, and the distance detection surface 4 is made of a conductor that generates an eddy current in a magnetic field, and detects the distance The unit 6 includes a detection coil 9 that detects the distance to the distance detection surface 4 as a change in inductance. 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 a predetermined interval in the rotation direction of the distance detection surface 4. The detection coil 9 is AC-excited and connected to an AC excitation circuit 8 for generating a phase shift in the AC excitation wave in accordance with the inductance change of the detection coil 9, and based on the phase shift of the AC excitation wave, the rotating body 2 Therefore, the problem to be solved by the present invention can be solved.

  That is, since the detection coil 9 is arranged at a position opposite to the distance detection surface 4 formed on the inner peripheral surface of the rotator 2 or the passive member 3 and the distance variation with the distance detection surface 4 is detected, Compared with the case where the detection coil 9 is arranged on the outer peripheral side of the passive member 3, not only can the apparatus be miniaturized, but also the degree of freedom of installation can be increased.

  In addition, absolute rotation of the rotating body 2 is performed based on the phase shift of the AC excitation wave in accordance with the change in inductance of the detection coil 9 while AC excitation of the detection coil 9 without separating the excitation coil and the detection coil. Since the phase modulation method for specifying the 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.

  Further, the angle specifying unit 7 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. The detection accuracy and stability can be improved compared to the case where the absolute rotation angle of the rotating body 2 is specified based on the above.

  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 distance detection surface and the distance detection unit, the fluctuation range of the distance, and the like can be arbitrarily changed according to the use situation.

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

Claims (2)

A magnetic rotation angle detection device for detecting an absolute rotation angle of a rotating body,
Arranged in a non-contact state at a position facing the inner peripheral surface of the rotating body or the inner peripheral surface of a passive member that rotates according to the rotation of the rotating body, and the inner surface of the rotating body or the inner surface of the passive member A distance detector for detecting the distance to the peripheral surface;
A distance detection surface that is formed on the inner peripheral surface of the rotating body or the inner peripheral surface of the passive member, and continuously changes the distance to the distance detection unit 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 distance detection 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 distance detection 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 a predetermined interval in the rotation direction of the distance detection 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.

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