JP2011112438A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder for detecting an angle within one rotation of a motor by a magnetic sensor. <P>SOLUTION: The encoder includes: a magnet section (6) formed with a magnetic pattern, and rotated on a rotation axis (R); and a detection section (4) for detecting a magnetic field from the magnet section. The magnet section is provided so as to radially form the magnetic field between the inner circumference and the outer circumference, vary the direction of the magnetic field along the circumference in the rotation direction at least once, and includes a magnetic field varying section (9) for varying a magnetic force generated on the detection section side in the vicinity of a boundary (6d) at which at least the direction of the magnetic field is varied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an encoder.

  An encoder is known as a device that detects the number of rotations and rotation speed of a rotating body such as a rotating shaft of a motor (Patent Document 1). For example, the rotary encoder is used by being attached to a rotating shaft such as a motor. Further, as a specific configuration of the encoder, for example, a configuration for detecting the number of rotations using magnetism is known.

  The encoder having such a configuration rotates the magnet portion on which the magnetic pattern is formed integrally with the rotation shaft, and reads the change in the magnetic pattern of the magnet portion with a magnetic sensor, thereby determining the rotation speed of the rotation shaft of the motor and the like. It can be detected. As a specific configuration, for example, a configuration in which a rotating unit that rotates integrally with a rotating shaft is fixed to the rotating shaft and a magnet unit is held by the rotating unit is known.

JP-A-3-287014

  However, in a general encoder, a magnetic field generated by rotation of a magnet unit is detected as a rectangular wave signal by a detection unit such as a magnetic sensor. For this reason, there is a problem that the magnetic sensor may not be able to detect an angle within one rotation of a rotation shaft such as a motor.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an encoder that can detect an angle within one rotation of a motor by a detection unit that detects a magnetic field.

  In order to solve the above-described problems, the aspect of the present invention adopts the following configuration corresponding to FIGS. 1 to 5 shown in the embodiment. In addition, in order to explain the present invention in an easy-to-understand manner, the description will be made in association with the reference numerals of the drawings showing an embodiment, but the present invention is not limited to the embodiment.

  An encoder (EC) according to an aspect of the present invention includes a magnet unit (6) that is formed with a magnetic pattern and rotates about a rotation axis (R), and a detection unit (4) that detects a magnetic field generated by the magnet unit. The magnet portion is provided to form a magnetic field (M) in the radial direction between the inner peripheral side and the outer peripheral side, and to change the direction of the magnetic field at least once over one rotation in the rotation direction. A magnetic field changing unit (9) for changing the magnetic force generated on the detection unit side in the vicinity of the boundary (6d) where the direction of the magnetic field changes is provided.

  The encoder (EC) according to another aspect of the present invention is formed with a magnetic pattern and rotates about the rotation axis (R), and forms a radial magnetic field (M) between the inner peripheral side and the outer peripheral side, and rotates. A magnet unit (6) provided to change the direction of the magnetic field at least once over a round of direction, a detection unit (4) for detecting a magnetic field by the magnet unit, and detected by the detection unit Magnetic field changing means (9) for changing the magnetic field.

  According to the present invention, there is provided an encoder capable of detecting an angle within one rotation of a motor or the like by changing a magnetic field in a radial direction of a magnet unit by a magnetic field changing unit and detecting the change of the magnetic field by a detecting unit. Can do.

It is sectional drawing which shows schematic structure of the encoder which concerns on embodiment of this invention. It is a top view of the magnet part of the encoder shown in FIG. FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG. 2. FIG. 3 is a cross-sectional view taken along line B-B ′ of FIG. 2. It is a graph which shows the relationship between the rotation angle of the encoder shown in FIG. 1, and a magnetic field.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a configuration of an encoder EC according to this embodiment.
The encoder EC shown in FIG. 1 is a device that detects the rotation speed and rotation speed of a rotating body such as a motor MR. The encoder EC includes a detection unit D, a magnet unit 6, and a rotation unit 3, and is used in a state where the rotation unit 3 holding the magnet unit 6 is accommodated in the detection unit D.

  The rotating unit 3 is a portion that is fixed to the driving shaft 7 of the motor MR, which is a rotating body, by a bolt 8 or the like and rotates integrally with the driving shaft 7. The rotating unit 3 holds the magnet unit 6 facing the magnetic sensor 4 of the detecting unit D at a predetermined distance g. In a state in which the rotating unit 3 is fixed to the drive shaft 7, the disk surfaces 31 b and 31 c are perpendicular to the drive shaft 7, and the rotation axis R direction of the rotating unit 3 is the same as the extending direction of the drive shaft 7. The rotating part 3 has a disk part 31, a holding part 32, a hub 33, and a fitting part 34.

The disk part 31 is a part that is formed in a disk shape and forms the main body of the rotating part 3. The disk part 31 is provided with a through hole 31a in the center, and is fixed to the drive shaft 7 by a bolt 8 inserted through the through hole 31a.
The holding portion 32 is provided in a concave shape on the upper disc surface 31 b of the disc portion 31 in the drawing, and is provided in an annular groove shape around the through hole 31 a along the rotation direction of the rotating portion 3.

The hub 33 is a portion that is provided so as to protrude substantially vertically from a disk surface 31c on the lower side of the disk portion 31 in the drawing, and is connected to the drive shaft 7 of the motor MR. The hub 33 has a concave fitting portion 34 in the center portion in plan view.
The fitting portion 34 is formed in a bottomed cylindrical shape, and the end portion of the drive shaft 7 of the motor MR is fitted and fixed.

FIG. 2 is a plan view of the magnet unit 6 shown in FIG.
As shown in FIGS. 1 and 2, the magnet unit 6 is a permanent magnet formed in an annular shape along the rotation direction of the rotating unit 3. As the magnet portion 6, for example, a neodymium iron-based sintered magnet or the like is used. A predetermined magnetic pattern is formed on the magnet unit 6. As shown in FIG. 2, as the magnetic pattern of the magnet portion 6, for example, the magnetic poles N and S on the inner peripheral side are different from the magnetic poles N and S on the outer peripheral side. And magnetic patterns magnetized so that the magnetic poles N and S on the outer circumference and the magnetic poles N and S on the outer peripheral side are switched. Of course, other magnetic patterns may be formed.

  The magnet unit 6 is fixed to the rotating unit 3 and rotates around the rotation axis R in conjunction with the rotation of the rotating unit 3. With such a configuration, the magnet unit 6 forms a radial magnetic field between the magnetic poles N and S on the inner peripheral side and the magnetic poles N and S on the outer peripheral side, and changes the direction of the magnetic field over one rotation of the rotation direction. It is designed to change once.

  The detection unit D is a part that detects a magnetic field generated by the magnet unit 6. The detection unit D includes a housing 1, a substrate 5 that seals the housing 1, a bolt 2 that fixes the substrate 5 to the housing 1, and a magnetic sensor 4 provided on the substrate 5. The housing 1 is formed in a substantially cylindrical shape and is fixed to the motor MR. The housing 1 and the substrate 5 are provided independently of the rotating unit 3 and the drive shaft 7 so that the relative positions of the housing 1 and the substrate 5 and the motor MR do not change even when the drive shaft 7 rotates. It has become. The rotating part 3 and the magnet part 6 are accommodated in a state of being aligned so that their centers coincide with the center of the housing 1 when viewed in the axial direction of the drive shaft 7.

  A pair of magnetic sensors 4 are arranged at positions overlapping the magnet portion 6 when viewed in the axial direction of the drive shaft 7. Each magnetic sensor 4 is connected to a power supply unit and a control unit via a wiring (not shown) included in the substrate 5. The control unit performs processing for obtaining the rotational angle position, rotational speed, and rotational speed of the drive shaft 7 based on outputs from the magnetic sensors 4 and 4. Each magnetic sensor 4 has a bias magnet (not shown) and magnetoresistive elements 4a and 4b (see FIG. 3).

  The bias magnet is a magnet that forms a combined magnetic field with the magnetic field of the magnet unit 6. As a material constituting the bias magnet, for example, a rare earth magnet having a large magnetic force such as samarium / cobalt can be cited. The bias magnet is disposed at a position where it does not contact or adjoin the magnetoresistive elements 4a and 4b.

  The magnetoresistive elements 4a, 4b have two orthogonal repeating patterns formed by, for example, metal wiring. The magnetoresistive elements 4a and 4b are designed such that the electrical resistance decreases when the direction of the magnetic field is close to the direction perpendicular to the direction of the current flowing through the repetitive pattern. The magnetoresistive elements 4a and 4b convert the direction of the magnetic field into an electric signal by utilizing the decrease in the electric resistance. The magnetoresistive elements 4a and 4b are configured to detect a combined magnetic field generated by the magnetic field of the magnet unit 6 and the magnetic field of the bias magnet, and the detection result is transmitted to the control unit (not shown) as an electrical signal. It has become.

FIG. 3 is a cross-sectional view taken along line AA ′ of FIG. 4 is a cross-sectional view taken along the line BB ′ of FIG.
As shown in FIGS. 3 and 4, the magnetic sensor 4 includes a magnetoresistive element (parallel magnetic field detecting element) 4 a that detects a magnetic field M in a direction parallel to the upper surface (rotating surface) 6 a of the magnet unit 6, and a magnet unit 6. There are two types of magnetoresistive elements, namely, a magnetoresistive element (vertical magnetic field detecting element) 4b for detecting a magnetic field M in the direction of the rotation axis R perpendicular to the upper surface 6a.

  As shown in FIGS. 2 to 4, the magnet portion 6 is located at a position in the vicinity of the boundary 6 d where the magnetic poles N and S on the inner peripheral side and the magnetic poles N and S on the outer peripheral side are switched, and at a position away from the boundary 6 d. A magnetic field changing unit 9 for changing the magnetic force generated on the magnetic sensor 4 side of the detecting unit D is provided. The magnetic field changing unit 9 includes a magnetic field suppressing member 9a and a magnetic field increasing member 9b made of a magnetic material such as iron oxide, chromium oxide, cobalt, and ferrite.

The magnetic field suppressing member 9a suppresses the magnetic force generated by the magnet unit 6 on the magnetic sensor 4 side, and reduces the magnetic force generated on the magnetic sensor 4 side than when the magnetic field suppressing member 9a is not provided. (Surface facing the magnetic sensors 4, 4) 6a.
The magnetic field increasing member 9b has a lower surface (surface opposite to the magnetic sensors 4, 4) of the magnet unit 6 so that the magnetic force generated by the magnet unit 6 on the magnetic sensor 4 side is increased as compared with the case where the magnetic field increasing member 9b is not provided. ) 6b.

  As shown in FIGS. 2 and 3, the magnetic field suppressing member 9a is disposed on the boundary 6d where the magnetic poles N and S on the inner peripheral side of the magnet portion 6 and the magnetic poles N and S on the outer peripheral side are interchanged, and is lined with the boundary 6d. It is provided in a symmetrical fan shape. As shown in FIGS. 2 and 4, the magnetic field increasing member 9 b has a magnetic field M separated in the circumferential direction from the boundary 6 d where the magnetic poles N and S on the inner peripheral side of the magnet portion 6 and the magnetic poles N and S on the outer peripheral side are interchanged. It arrange | positions at the stationary part 6c from which a direction does not change, and is provided in the sector shape similar to the magnetic field suppression member 9a.

  As shown in FIGS. 3 and 4, the thickness Ta of the magnetic field suppressing member 9a in the direction of the rotation axis R is at the boundary 6d where the magnetic poles N and S on the inner peripheral side of the magnet portion 6 and the magnetic poles N and S on the outer peripheral side are interchanged. The maximum value is provided so as to gradually decrease as the distance from the boundary 6d increases. On the other hand, the thickness Tb of the magnetic field increasing member 9b provided on the lower surface 6b of the magnet portion 6 is maximized at a position 90 ° farthest from the boundary 6d in the circumferential direction, and gradually decreases as the boundary 6d is approached. ing. The thicknesses of the magnetic field suppressing member 9a and the magnetic field increasing member 9b are constant in the radial direction of the magnet portion 6.

FIG. 5 is a graph showing changes in the magnetic force measured by the magnetic sensor 4 when the magnet unit 6 is rotated once, with the horizontal axis representing the rotation angle of the magnet unit 6 and the vertical axis representing the magnetic force of the magnet unit 6.
The magnetic field changing unit 9 of the present embodiment is formed so as to change the magnetic field in one rotation by the magnet unit 6 in a sinusoidal manner, for example, by the following method.

  First, in a state in which the magnetic field changing unit 9 is not provided in the magnet unit 6, the magnet unit 6 is rotated once around the rotation axis R, and the magnetic sensor 4 measures a change in magnetic force when the magnet unit 6 makes one rotation. Here, as shown in FIG. 2, the magnet portion 6 is different from the magnetic poles N and S on the inner peripheral side and the magnetic poles N and S on the outer peripheral side, and the magnetic poles N and S on the inner peripheral side at 180 ° in the circumferential direction. It is provided so that the magnetic poles N and S on the outer peripheral side are interchanged.

  Therefore, a magnetic field in the radial direction is generated in the magnet portion 6 between the magnetic poles N and S on the inner peripheral side and the magnetic poles N and S on the outer peripheral side, and when the magnet portion 6 is rotated once, the magnetic poles N, The direction of the magnetic field is reversed at the boundary 6d where S and the outer magnetic poles N and S are interchanged. Then, the combined magnetic field of the magnetic field M of the magnet unit 6 and the magnetic field of the bias magnet changes by approximately 90 °. Therefore, when the boundary 6d of the magnet part 6 is arranged below the magnetic sensor 4 and the rotation is started with the state being 0 °, the magnetic sensor 4 generates a magnetic force every 180 ° as shown by a two-dot chain line in FIG. A rectangular wave signal S0 is detected in which the positive and negative signs are reversed.

  Next, a magnetic material for forming the magnetic field suppressing member 9a is disposed on the upper surface 6a of the magnet unit 6, the thickness of the magnetic material is changed, and the magnetic force detected by the magnetic sensor 4 is measured for each changed thickness. . By arranging a magnetic material on the upper surface 6a of the magnet portion 6, the magnetic force detected by the magnetic sensor 4 is reduced as compared with the case where there is no magnetic material. Further, when the thickness of the magnetic material is increased, the magnetic force detected by the magnetic sensor 4 is further reduced, and when the thickness is reduced, the magnetic force is approached when there is no magnetic material.

  Similarly, a magnetic material for forming the magnetic field increasing member 9b is arranged on the lower surface 6b of the magnet portion 6, the thickness of the magnetic material is changed, and the magnetic force detected by the magnetic sensor 4 is measured for each changed thickness. . By arranging a magnetic material on the lower surface 6b of the magnet portion 6, the magnetic force detected by the magnetic sensor 4 is increased as compared with the case where there is no magnetic material. Further, when the thickness of the magnetic material is increased, the magnetic force detected by the magnetic sensor 4 is further increased, and when the thickness is reduced, the magnetic force is approached when there is no magnetic material.

  Thereby, a relational expression between the thickness of the magnetic material when the magnetic material is disposed on the upper surface 6 a and the lower surface 6 b of the magnet portion 6 and the magnetic force detected by the magnetic sensor 4 is obtained. Based on the relational expression thus obtained, as shown in FIG. 5, the magnetic field suppressing member 9a and the magnetic field increasing member 9b are changed so that the rectangular wave signal S0 changes to a sine wave signal S1 indicated by a solid line. Adjust the position and thickness. As described above, the magnetic field changing unit 9 that changes the magnetic field in one rotation by the magnet unit 6 in a sine wave shape is obtained.

Next, the operation of the encoder EC configured as described above will be described.
When the drive shaft 7 of the motor MR rotates, the rotating portion 3 and the magnet portion 6 that are integrally attached to the drive shaft 7 rotate integrally with the drive shaft 7. Since the detection unit D fixed to the motor MR is not connected to the drive shaft 7, it remains stationary without rotating.

  When the magnet unit 6 rotates together with the rotation of the rotating unit 3, the combined magnetic field of the magnetic field M formed by the magnetic pattern of the magnet unit 6 and the magnetic field of the bias magnet changes periodically. The magnetoresistive element 4 a of each magnetic sensor 4 detects a combined magnetic field of the magnetic field M in a direction parallel to the upper surface 6 a of the magnet unit 6 and the magnetic field of the bias magnet. Further, the magnetoresistive element 4 b of each magnetic sensor 4 detects a combined magnetic field of the magnetic field M in a direction parallel to the rotation axis R of the magnet unit 6 and the magnetic field of the bias magnet.

  The synthesized magnetic field detected by the magnetic sensor 4 is transmitted as an electric signal to the control unit, and a sinusoidal signal S1 indicated by a solid line in FIG. 5 is obtained. The control unit calculates an angle, a rotation speed, and a rotation speed within one rotation of the motor based on the obtained sinusoidal signal S1.

  As described above, the encoder EC of the present embodiment includes the magnetic field changing unit 9 that changes the magnetic force on the magnetic sensor 4 side generated by the magnet unit 6, thereby changing the waveform of the signal S 0 detected by the magnetic sensor 4. Thus, the angle within one rotation of the motor MR can be detected. That is, the magnetic field changing unit 9 of the present embodiment is provided so as to change the magnetic field in one rotation by the magnet unit 6 in a sinusoidal shape. Therefore, the waveform of the signal S1 detected by the magnetic sensor 4 within one rotation of the motor MR can be changed to a sine wave, and the angle within one rotation of the motor MR can be calculated by the control unit.

  In addition, the magnetic field changing unit 9 of the present embodiment includes a magnetic field suppressing member 9 a formed of a magnetic material in the vicinity of the boundary 6 d of the upper surface 6 a of the magnet unit 6. Thereby, the change of the magnetic force in the vicinity of 180 °, 360 °,... Where the positive and negative of the rectangular wave signal S0 shown in FIG. 5 is reversed is moderated, and the signal S1 obtained by the magnetic sensor 4 is changed to a sine wave. You can get closer.

  Further, the thickness Ta of the magnetic field suppressing member 9a in the direction of the rotation axis R becomes maximum at the boundary 6d of the magnet portion 6, and gradually decreases as the distance from the boundary 6d increases. Thereby, the amount of suppression of magnetic force can be increased as it approaches the boundary 6d of the magnet portion 6, and the amount of suppression of magnetic force can be decreased as the distance from the boundary 6d increases. Therefore, it is possible to make the signal S1 obtained by the magnetic sensor 4 closer to a sine wave by making the slope of the portion where the positive and negative of the rectangular wave signal S0 shown in FIG.

  Further, the magnetic field changing unit 9 of the present embodiment includes a magnetic field increasing member 9b formed of a magnetic material in a stationary part 6c that is separated from the boundary 6d of the lower surface 6b of the magnet unit 6 in the circumferential direction and does not change the direction of the magnetic field. ing. As a result, as shown in FIG. 5, the magnetic force of the portion where the rectangular wave signal S0 has a constant value can be increased, and the signal S1 obtained by the magnetic sensor 4 can be made closer to a sine wave.

  Further, the thickness Tb of the magnetic field increasing member 9b in the direction of the rotation axis R is 90 ° and 270 ° when the position of the magnet portion 6 is the most distant from the boundary 6d, that is, the angular position of the boundary 6d is 0 °. And gradually decreases as the boundary 6d is approached. Accordingly, the magnetic force detected by the magnetic sensor 4 is maximized when the rotation angle shown in FIG. 5 is 90 °, and the magnetic force detected by the magnetic sensor 4 is minimized when the rotation angle is 270 °. Therefore, the signal obtained by the magnetic sensor 4 can be approximated to a sine wave.

  Further, the magnet portion 6 of the present embodiment is different from the magnetic poles N and S on the inner peripheral side and the magnetic poles N and S on the outer peripheral side, and the magnetic poles N and S on the inner peripheral side and the magnetic poles on the outer peripheral side at 180 ° in the circumferential direction. N and S are provided so as to be interchanged. Therefore, when the magnetic field changing unit 9 is not provided, a rectangular wave signal S0 shown in FIG. However, in combination with the magnetic field changing unit 9 described above, the magnetic sensor 4 can obtain a sinusoidal signal S1.

  In addition, the magnetic sensor 4 of the present embodiment detects a magnetic resistance element 4a that detects a magnetic field in a direction parallel to the upper surface 6a of the magnet unit 6 and a magnetic field in the direction of the rotation axis R that is perpendicular to the upper surface 6a of the magnet unit 6. And a magnetoresistive element 4b. As a result, both the magnetic field in the direction parallel to the upper surface 6a and the magnetic field in the direction of the rotation axis R can be detected by the magnetic sensor 4, and the sinusoidal signal S1 can be obtained from the magnetic field in each direction. Therefore, since the magnetic sensor 4 of the present embodiment can be duplicated, the reliability of the encoder EC can be improved.

In addition, even when one of the magnetoresistive elements 4a and 4b fails, the other can obtain a sinusoidal signal S1, and the controller calculates the angle within one rotation of the motor MR. Is possible. As a result, the reliability and safety of the encoder EC can be improved.
Moreover, since the magnetic sensor 4 is provided with a pair in the circumferential direction of the magnet unit 6, the A phase and the B phase are obtained by the respective magnetic sensors 4, and the rotation direction of the magnet unit 6 can be calculated by the control unit. Therefore, it is possible to detect the rotation direction and the multi-rotation amount of the drive shaft 7 of the motor MR.

  As described above, according to the encoder EC of the present embodiment, not only can the angle within one rotation of the motor MR be detected, but also the use of a magnetic field in two directions is possible. Thereby, the resolution, reliability, and safety of the encoder EC can be improved.

  Further, although the magnetic sensor 4 in the present embodiment detects the angle within one rotation of the motor MR, the rotation number of the motor MR may be detected. In this case, for example, the angle within one rotation of the motor MR is detected by an optical pattern (optical rotation code plate) provided in the rotating unit 3 and an optical sensor that reads the optical pattern.

  Further, as described above, the magnetic sensor 4 can detect a sinusoidal signal by using the magnetic field changing unit 9 which is a magnetic field changing means.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiment, and modifications can be made as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the number of magnetic sensors may be one instead of a pair. Further, the magnetoresistive element may be arranged corresponding to only a magnetic field in one direction. The magnetic sensor may be a Hall element.

4a magnetoresistive element (parallel magnetic field detecting element), 4b magnetoresistive element (vertical magnetic field detecting element), 6 magnet part, 6a upper surface (rotating surface), 6c stationary part, 6d boundary, 9 magnetic field changing part, 9a magnetic field suppressing member, 9b Magnetic field increasing member, D detector, EC encoder, M magnetic field, N, S magnetic pole, R rotation axis, Ta thickness, Tb thickness

Claims (10)

A magnet unit that is formed with a magnetic pattern and rotates about a rotation axis; and a detection unit that detects a magnetic field by the magnet unit;
The magnet portion is provided so as to form a radial magnetic field between an inner peripheral side and an outer peripheral side, and to change the direction of the magnetic field at least once over a rotation direction. An encoder comprising: a magnetic field changing unit that changes a magnetic force generated on the detection unit side in the vicinity of a boundary where the direction changes. The encoder according to claim 1, wherein
The encoder, wherein the magnetic field changing unit changes the magnetic field in one rotation by the magnet unit in a sine wave form. The encoder according to claim 1 or 2,
The magnetic field change unit is formed of a magnetic material, and is provided on a surface of the magnet unit facing the detection unit. The magnetic field change unit relatively generates the magnetic force generated on the detection unit side in the vicinity of the boundary where the direction of the magnetic field changes. An encoder characterized by comprising a magnetic field suppressing member that suppresses automatically. The encoder according to claim 3,
The encoder according to claim 1, wherein a thickness of the magnetic field suppressing member in the rotation axis direction is maximized at the boundary and gradually decreases as the distance from the boundary increases. The encoder according to any one of claims 1 to 4,
The encoder according to claim 1, wherein the magnetic field changing unit includes a magnetic field increasing member that relatively increases a magnetic force generated on the detection unit side in a stationary part where the direction of the magnetic field does not change. The encoder according to claim 5, wherein
The thickness of the magnetic field increasing member in the direction of the rotation axis is maximized at a position farthest from the boundary, and gradually decreases as the boundary is approached. The encoder according to any one of claims 1 to 6,
The magnet portion is provided such that the inner peripheral side magnetic pole and the outer peripheral side magnetic pole are different, and the inner peripheral side magnetic pole and the outer peripheral side magnetic pole are interchanged at 180 ° in the circumferential direction. Characteristic encoder. The encoder according to any one of claims 1 to 7,
The encoder includes a parallel magnetic field detection element that detects the magnetic field in a direction parallel to a rotation surface of the magnet unit. The encoder according to any one of claims 1 to 8,
The encoder includes a vertical magnetic field detecting element that detects the magnetic field in a direction perpendicular to a rotation surface of the magnet unit. A magnetic pattern is formed and rotates about the rotation axis, forms a magnetic field in the radial direction between the inner periphery side and the outer periphery side, and changes the direction of the magnetic field at least once over one rotation direction. A magnet portion provided in
A detection unit for detecting a magnetic field by the magnet unit;
An encoder comprising: magnetic field changing means for changing the magnetic field detected by the detection unit.

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