JP5254924B2 - Rotation angle detector - Google Patents

Description

  The present invention relates to a rotation angle detection device that magnetically detects the rotation angle of a rotating body to be detected.

  2. Description of the Related Art Conventionally, a rotation angle detection device is known that includes a magnetic detection body that rotates in conjunction with a detection target, and a magnetic sensor that performs alternating transmission and reception on the outer peripheral surface of the magnetic detection body. For example, in the rotation angle detection device disclosed in Patent Document 1, the shape of the outer peripheral edge of the magnetic detector is configured so that the length from the center to the outer peripheral surface gradually increases in the rotation direction. The change of the alternating magnetic field according to the rotation position is detected by a magnetic sensor, and the rotation angle of the magnetic detector is detected by this detection to detect the rotation angle of the detection target.

JP 2002-310609 A

  However, in the rotation angle detection device described in Patent Document 1, a magnetic detector having a non-circular outer peripheral edge is used. Therefore, the outer peripheral surface of the magnetic detector is not circular, and magnetic detection is performed. The amount of eccentricity of the body tended to be large. This leads to deterioration of the rotation balance, and causes various problems such as a burden on the shaft supporting the magnetic detector, an increase in vibration, and a decrease in detection accuracy due to vibration.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a rotation angle detection device that can reduce the amount of eccentricity of the magnetic detector and reduce defects during rotation. is there.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 includes a magnetic detector that rotates in conjunction with a detection target, and a magnetic sensor that transmits and receives an alternating magnetic field to the outer peripheral surface of the magnetic detector, and the magnetic detector The rotation angle detection device detects a rotation angle of the magnetic detection body by detecting a change in the alternating magnetic field according to the rotation position of the magnetic detection sensor, and detects a rotation angle of the magnetic detection body by the detection. The magnetic detector has a disk shape, and a radially inner portion is provided with a nonmagnetic portion that gradually changes the length of the magnetic portion from the outer peripheral surface in the rotational direction, and the length of the magnetic portion in the rotational direction. The gist of the invention is that the change in the alternating magnetic field based on the change in height is detected by the magnetic sensor, and the absolute angle of the magnetic detector is detected by the detection.

  In the present invention, the magnetic detector has a disk shape, and the radially inner portion is provided with a non-magnetic portion that gradually changes the length of the magnetic portion from the outer peripheral surface in the rotational direction. The change in the alternating magnetic field based on the change in the length of the part is detected by the magnetic sensor, and the absolute angle of the magnetic detector is detected by the detection. For this reason, in a magnetic detection body, an outer peripheral surface can be comprised circularly and it becomes possible to set it as a structure with small eccentricity. Thereby, it leads to the improvement of the rotation balance of a magnetic detection body, etc., and reduction of the malfunction at the time of rotation by providing a rotation angle detection apparatus is attained.

  According to a second aspect of the present invention, in the rotation angle detecting device according to the first aspect, a plurality of concave portions and convex portions are alternately arranged at equal angular intervals on the outer peripheral surface of the magnetic detector, and the magnetic sensor Detects a change in an alternating magnetic field corresponding to the uneven portion of the magnetic detector, counts the number of passages of the uneven portion by the detection, and detects a relative angle of the magnetic detector based on the count This is the gist.

  In the present invention, a plurality of concave and convex portions are alternately formed at equal angular intervals on the outer peripheral surface of the magnetic detector, and a change in the alternating magnetic field corresponding to the concave and convex portions of the magnetic detector is detected by the magnetic sensor. Then, the number of passages of the concavo-convex portions is counted by the detection, and the relative angle of the magnetic detector is detected. Therefore, in addition to the detection of the absolute angle described above, the rotation angle of the magnetic detector (detection target) can be detected in a short time by combining this easy angle detection of the relative angle by counting.

  According to a third aspect of the present invention, in the rotation angle detecting device according to the second aspect of the present invention, one magnetic sensor is provided, and the magnetic sensor has an alternating magnetic field having a low frequency from the outer peripheral surface of the magnetic detector. An absolute angle of the magnetic detector is detected based on a change in the alternating magnetic field according to a change in the length of the magnetic part up to the non-magnetic part, and the magnetic detector is detected with an alternating magnetic field having a high frequency in the same magnetic sensor. The gist of the invention is that the relative angle of the magnetic detection body is detected based on the change of the alternating magnetic field according to the uneven portion provided on the outer peripheral surface.

  In the present invention, the absolute angle of the magnetic detector based on the change of the alternating magnetic field according to the change in the length of the magnetic part up to the non-magnetic part of the magnetic detector by the exchange of the alternating magnetic field having a low frequency with one magnetic sensor. Is detected, and the relative angle of the magnetic detector is detected based on the change of the alternating magnetic field corresponding to the concave and convex portions of the magnetic detector by the exchange of an alternating magnetic field having a high frequency. For this reason, by changing the frequency of the alternating magnetic field, the absolute angle and the relative angle of the magnetic detector (detection target) can be detected by one magnetic sensor, which can contribute to downsizing of the apparatus.

  ADVANTAGE OF THE INVENTION According to this invention, in a rotation angle detection apparatus, the rotation angle detection apparatus which can suppress the fall of the detection accuracy of the rotation angle of a magnetic detection body can be provided.

(A) Sectional drawing of the brushless motor which mounts a rotation angle detection apparatus, (b) The block diagram of a rotation angle detection apparatus, (c) The block diagram of a magnetic sensor. (A) A graph showing the relationship between the frequency of the magnetic sensor and the length of the magnetic part from the outer peripheral surface of the magnetic detector to the groove, (b) the rotation angle of the magnetic detector and the magnetism from the outer peripheral surface of the magnetic detector to the groove. The graph which shows the relationship with the length of a part.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of a brushless motor equipped with a rotation angle detection device, and FIG. 1B is a configuration diagram of the rotation angle detection device.

  As shown in FIG. 1A, the motor 1 includes a stator 3 that is fixed to the inner peripheral surface of the cylindrical portion 2 a of the housing 2, and a rotor 4 that is rotatably accommodated inside the stator 3. ing. A rotating shaft 5 provided in the rotor 4 is rotatably supported by a pair of bearings 6 a and 6 b provided in the housing 2.

  Further, the motor 1 is provided with a rotation angle detection device 10 for detecting the rotation angle of the rotor 4 through the rotation shaft 5. Incidentally, the rotation angle of the rotor 4 is detected by detecting the position of a magnet (not shown) provided in the rotor 4 and generating a rotating magnetic field corresponding to that position in the stator 3. This is done to generate a drive current to be supplied (not shown).

  As shown in FIG. 1B, such a rotation angle detection device 10 includes a substantially disk-shaped magnetic detection body 11 and one magnetic sensor 12. A circular shaft fitting hole 11 a is formed at the center of the magnetic detection body 11, and the rotation shaft 5 is fitted into the shaft fitting hole 11 a so that the magnetic detection body 11 is integrated with the rotation shaft 5. Mounted to rotate. A spiral groove 11b is formed on the radially inner side of the magnetic detector 11 from a predetermined reference angular position (reference line L1) as viewed in the axial direction. The groove portion 11b is a spiral and has a uniform width extending from the substantially intermediate portion in the radial direction of the magnetic detector 11 to the radially outer portion as it advances in the clockwise direction (R direction) from the reference line L1, and extending again to the reference line L1. Is formed.

  That is, as the length d of the magnetic part 11d from the outer peripheral surface 11c facing the magnetic sensor 12 from the reference line L1 in the clockwise direction (R direction), the outer side in the radial direction than the groove 11b of the magnetic detection body 11 is opposed. The structure becomes gradually smaller. Accordingly, as shown in FIG. 2B, when the reference angle position (reference line L1) is set to the rotation angle 0 ° of the magnetic detector 11, the length d of the magnetic portion 11d on the outer peripheral side of the magnetic detector 11 is rotated. As the angle θ increases, the angle θ decreases (in this case, decreases linearly) and repeats at a cycle of 360 °.

  Further, on the outer peripheral surface 11c of the magnetic detector 11, a plurality of concave portions 11e having the same shape and a plurality of convex portions 11f having the same shape are alternately formed at equal angular intervals. The concave portions 11e and the convex portions 11f are provided at an angular pitch corresponding to the detected rotation angle.

  As shown in FIG. 1C, the magnetic sensor 12 includes an excitation coil 12 a and a measurement coil 12 b, and exchanges an alternating magnetic field with respect to the outer peripheral surface 11 c of the magnetic detector 11. Specifically, the exciting coil 12a applies an alternating magnetic field to the outer peripheral surface 11c of the magnetic detector 11 based on the supply of AC power, and generates an eddy current in the magnetic detector 11. On the other hand, the measurement coil 12b detects an alternating magnetic field that changes depending on the shape of the magnetic part of the magnetic detector 11, and outputs an alternating signal generated in the alternating magnetic field according to the change in the shape of the magnetic detector 11.

  In this case, when the frequency of the alternating magnetic field is increased, the magnetic lines of force act near the surface of the outer peripheral surface 11c of the magnetic detector 11, and when the frequency of the alternating magnetic field is decreased, the magnetic lines of force penetrate from the outer peripheral surface 11c of the magnetic detector 11 into the inside. Using this property, detection is performed by switching the frequency of this alternating magnetic field.

  That is, when the frequency of the alternating magnetic field, that is, the predetermined frequency on the higher AC power side that excites the exciting coil 12a is used, the alternating magnetic field affected by the concave portion 11e and the convex portion 11f provided on the outer peripheral surface 11c of the magnetic detector 11 is used. Acts on the measuring coil 12b, and an AC signal based on this alternating magnetic field is generated in the measuring coil 12b. On the other hand, if the frequency of the alternating magnetic field, that is, the predetermined frequency on the lower side of the AC power for exciting the exciting coil 12a is used, it is affected by the length d of the magnetic portion 11d from the outer peripheral surface 11c of the magnetic detector 11 to the groove 11b. The alternating magnetic field acts on the measuring coil 12b, and an AC signal based on the alternating magnetic field is generated in the measuring coil 12b.

  The excitation coil 12a and the measurement coil 12b of the magnetic sensor 12 are electrically connected to the control device 13, and the control device 13 performs magnetic control from the drive control of the excitation coil 12a and the AC signal generated by the measurement coil 12b. Detection of the rotation angle of the detection body 11, that is, the rotor 4, is performed.

  In detecting the rotation angle θ of the magnetic detector 11 (rotor 4), the control device 13 first generates an alternating magnetic field having a predetermined frequency on the lower side by the magnetic sensor 12, and the magnetic portion 11d on the outer peripheral side of the magnetic detector 11 is used. The absolute angle θ1 is detected from the length d. In this case, as shown in FIG. 2A, the frequency f of the AC signal generated in the measuring coil 12b is correlated with the length d of the magnetic portion 11d on the outer peripheral side of the magnetic detector 11, and the length d The frequency f of the AC signal becomes higher as the value becomes smaller. The control device 13 detects the length d of the magnetic portion 11d based on the frequency f of the AC signal from the magnetic sensor 12 from the correlation shown in FIG. 2A, and from the correlation shown in FIG. Based on the detected length d of the magnetic part 11d, the absolute angle θ1 of the rotation angle θ of the magnetic detector 11 is detected.

  Next, the alternating magnetic field generated by the magnetic sensor 12 is switched to an alternating magnetic field of a predetermined frequency on the higher side, and the relative angle θ2 is detected from the detection of the concave portion 11e and the convex portion 11f provided on the outer peripheral surface 11c of the magnetic detector 11. In this case, although not shown, the AC signal generated in the measuring coil 12b has a higher signal level on the convex portion 11f side than the concave portion 11e. The control device 13 counts based on the periodic level change of the AC signal, that is, counts for each of the convex portion 11f and the concave portion 11e, so that the magnetic detector 11 from the angular position where the absolute angle θ1 is detected first. The relative angle θ2 is detected. That is, the control device 13 detects the rotation angle θ (absolute angle) of the magnetic detector 11 by combining the relative angle detection by counting and the previous absolute angle detection.

  Then, the control device 13 detects the rotation angle position of the rotor 4 based on the rotation angle θ of the magnetic detector 11 thus detected, and determines the energization timing of the coils of the stator 3 based on the detected rotation angle position. The rotation control of the motor 1 is performed.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) In this embodiment, the magnetic detector 11 has a disk shape, and is provided with a groove portion 11b that gradually changes the length d of the magnetic portion 11d from the outer peripheral surface 11c in the rotational direction on the radially inner portion. . And the change of the alternating magnetic field based on the change of the length d of the magnetic part 11d in the rotation direction is detected by the magnetic sensor 12, and the absolute angle θ1 of the magnetic detector 11 is detected by the detection. For this reason, in the magnetic detection body 11, the outer peripheral surface 11c can be comprised circularly, and it becomes possible to set it as a structure with small eccentricity. Thereby, it leads to the improvement of the rotation balance of the magnetic detection body 11, etc., and the malfunction at the time of rotation by providing the rotation angle detection apparatus 10 can be reduced.

  (2) In this embodiment, a plurality of concave portions 11e and convex portions 11f are alternately formed at equiangular intervals on the outer peripheral surface 11c of the magnetic detector 11, and the magnetic sensor 12 uses the concave portions 11e and 11f of the magnetic detector 11 to A change in the alternating magnetic field corresponding to the convex portion 11f is detected. Then, the number of passages of the concave portion 11e and the convex portion 11f is counted by the detection, and the relative angle θ2 of the magnetic detector 11 is detected. Therefore, in addition to the detection of the absolute angle θ1, the rotation angle of the magnetic detector 11 (detection target) can be detected in a short time by combining easy detection of the relative angle θ2 by counting.

  (3) In the present embodiment, the change in the alternating magnetic field according to the change in the length d of the magnetic part 11d up to the groove 11b of the magnetic detector 11 by the transmission / reception of the alternating magnetic field having a low frequency by one magnetic sensor 12. The absolute angle θ1 of the magnetic detection body 11 based on the magnetic detection body 11 is detected, and relative to the magnetic detection body 11 based on the change of the alternating magnetic field according to the concave portion 11e and the convex portion 11f of the magnetic detection body 11 by transmission / reception of an alternating magnetic field having a high frequency. The angle θ2 is detected. For this reason, by changing the frequency of the alternating magnetic field, the single magnetic sensor 12 can detect the absolute angle θ1 and the relative angle θ2 of the magnetic detector (detection target), which can contribute to downsizing of the apparatus.

(4) In this embodiment, since the nonmagnetic part of the magnetic detection body 11 is comprised by the groove part 11b, formation of a nonmagnetic part can be performed easily.
(5) In this embodiment, since the nonmagnetic part of the magnetic detector 11 is constituted by the spiral groove 11b, it can be easily formed and the rotation balance of the magnetic detector 11 can be further improved.

  (6) In the present embodiment, the magnetic sensor 12 includes an excitation coil 12a and a measurement coil 12b, and an alternating magnetic field of the excitation coil 12a of the magnetic sensor 12 is applied to the magnetic detector 11, and the influence of the magnetic detector 11 is affected. The rotation angle θ of the magnetic detector 11 can be detected by detecting the alternating magnetic field received by the measuring coil 12b. Thereby, the magnetic sensor 12 can be configured in a small size.

  (7) In this embodiment, the absolute angle θ1 is first detected by the magnetic sensor 12, and then the rotation angle θ (absolute) of the magnetic detector 11 is detected based on the detection of the relative angle θ2 from the detected absolute angle θ1. Corner). In this case, detection of the absolute angle θ1 by the magnetic sensor 12 requires some calculation, but detection of the relative angle θ2 only counts. Therefore, as compared with the case where the absolute angle θ1 is always detected by the magnetic sensor 12, the calculation load can be reduced in the configuration of the present embodiment, and the rotation angle θ of the magnetic detector 11 can be detected in a shorter time. .

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
In the above embodiment, the magnetic detector 11 is combined with detection of the absolute angle θ1 using the groove 11b (magnetic portion 11d) of the magnetic detector 11 and detection of the relative angle θ2 using the concave portion 11e and the convex portion 11f. However, for example, the concave portion 11e and the convex portion 11f may be omitted, and only the absolute angle θ1 using the groove portion 11b may be detected.

  In the above embodiment, the shape (configuration) of the groove 11b of the magnetic detection body 11 is as shown in FIG. 1B, but is not limited thereto, and may be changed as appropriate. For example, the groove part 11b does not need to have a uniform width. Moreover, although the nonmagnetic part was comprised in the groove part 11b (space), you may comprise a nonmagnetic part using a nonmagnetic material separately.

  In the above embodiment, the single sensor 12 detects the absolute angle θ1 and the relative angle θ2 of the magnetic detector 11 and detects the rotation angle θ of the magnetic detector 11. However, two or more sensors are used. It is good also as a structure which detects rotation angle (theta) of the magnetic detection body 11 using.

  In the above embodiment, the rotation angle detection device 10 is mounted on the brushless motor 1, but the rotation angle detection device 10 may be mounted on another rotation device to detect the rotation angle of the rotation device.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(A) The rotation angle detection device according to any one of claims 1 to 3, wherein the nonmagnetic portion of the magnetic detector is configured by a groove portion.

In the present invention, since the nonmagnetic portion of the magnetic detector is constituted by the groove portion, the nonmagnetic portion can be easily formed.
(B) In the rotation angle detection device according to (a) above, the groove is formed in a spiral shape so as to gradually change the length of the magnetic portion from the outer peripheral surface in the radial direction on the radially inner portion of the magnetic detector. A rotation angle detecting device characterized in that it is configured as described above.

In this invention, since the nonmagnetic part of the magnetic detector is constituted by a spiral groove, it is easy to form and the rotation balance of the magnetic detector can be further improved.
(C) The rotation angle detection device according to any one of claims 1 to 3 and (a) and (b), wherein the magnetic sensor is configured using an excitation coil and a measurement coil. A rotation angle detection device.

  In this invention, the magnetic sensor has an exciting coil and a measuring coil, the alternating magnetic field of the exciting coil of the magnetic sensor is applied to the magnetic detector, and the alternating magnetic field affected by the magnetic detector is detected by the measuring coil. Thus, the rotation angle of the magnetic detector can be detected. As a result, the magnetic sensor can be made compact.

  (2) In the rotation angle detection device according to claim 2 or 3, the magnetic sensor detects the absolute angle first by the magnetic sensor and then detects the relative angle from the detected absolute angle. A rotation angle detection device that detects the absolute angle of the rotation angle.

  In the present invention, the absolute angle is first detected by the magnetic sensor, and then the rotation angle (absolute angle) of the magnetic detector is detected based on the detection of the relative angle from the detected absolute angle. Compared with the case where an absolute angle is detected by a sensor, the calculation load can be reduced, and the rotation angle of the magnetic detector can be detected in a shorter time.

  DESCRIPTION OF SYMBOLS 10 ... Rotation angle detection apparatus, 11 ... Magnetic detection body, 11b ... Groove part (nonmagnetic part), 11c ... Outer peripheral surface, 11d ... Magnetic part, 11e ... Concave part, 11f ... Convex part, 12 ... Magnetic sensor, d ... Length , F: frequency, θ: rotation angle (rotation angle), θ1: absolute angle, θ2: relative angle.

Claims (3)

A magnetic detection body that rotates in conjunction with the detection target; and a magnetic sensor that transmits and receives an alternating magnetic field to the outer peripheral surface of the magnetic detection body, the alternating magnetic field corresponding to the rotational position of the magnetic detection body. A rotation angle detection device that detects a change in the magnetic sensor, detects a rotation angle of the magnetic detection body by the detection, and detects a rotation angle of the detection target;
The magnetic detector has a disk shape, and a radially inner portion includes a non-magnetic portion that gradually changes the length of the magnetic portion from the outer peripheral surface in the rotational direction, and the length change of the magnetic portion in the rotational direction. A rotation angle detecting device, wherein a change in the alternating magnetic field based on the magnetic sensor is detected by the magnetic sensor, and an absolute angle of the magnetic detector is detected by the detection. The rotation angle detection device according to claim 1,
On the outer peripheral surface of the magnetic detector, a plurality of concave portions and convex portions are alternately formed at equiangular intervals,
The magnetic sensor detects a change in an alternating magnetic field corresponding to the uneven portion of the magnetic detector, counts the number of passages of the uneven portion by the detection, and detects a relative angle of the magnetic detector based on the count A rotation angle detection device characterized by that. In the rotation angle detection device according to claim 2,
One magnetic sensor is provided, and in this one magnetic sensor, the alternating magnetic field changes according to the length change of the magnetic part from the outer peripheral surface of the magnetic detector to the non-magnetic part with an alternating magnetic field having a low frequency. Based on the detection of the absolute angle of the magnetic detector,
In the same magnetic sensor, the relative angle of the magnetic detector is detected based on the change of the alternating magnetic field according to the uneven portion provided on the outer peripheral surface of the magnetic detector with an alternating magnetic field having a high frequency. A rotation angle detection device.

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