JP2011095180A - Encoder and servomotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a rotary encoder. <P>SOLUTION: The encoder is so formed that the diameter of an optical wheel is be equal to the diameter of a magnetic wheel. The optical wheel is so arranged that the optical track formed at the optical wheel is positioned between the magnetic track formed at the magnetic wheel and a magnetic sensor, which detects the magnetic flux from the magnetic track. So, the optical wheel is miniaturized and the entire encoder unit 60 is miniaturized. Since the encoder unit 60 is miniaturized, a servomotor 10 equipped with the encoder unit 60 is miniaturized. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an encoder and a servo motor, and more particularly to an encoder for detecting the rotation of a rotating body and a servo motor including the encoder.

  The servo motor has a control method established and can generate torque relatively stably in a range from a low speed range to a high speed range. For this reason, it is often used for machine tools and industrial robots. In a system using a servo motor, it is common to detect the rotation of a rotating shaft using a rotary encoder and control the rotation angle and rotation speed of the rotating shaft based on the detected result.

  As a rotary encoder, an encoder that detects the rotation of a rotating body based on reflected light from a rotating code board or a change in magnetic flux of a rotating annular magnet is disclosed (for example, see Patent Document 1).

JP 2005-24283 A

  The rotary encoder described above requires both a magnetic wheel in which N poles and S poles are alternately formed around the rotation axis, and an optical wheel in which an optical pattern is formed around the rotation axis. For this reason, in this type of rotary encoder, as disclosed in Patent Document 1, for example, an optical wheel is generally arranged so as to surround a magnetic wheel.

  However, when the optical wheel is arranged so as to surround the magnetic wheel, or when the magnetic wheel is arranged so as to surround the optical wheel, the diameter of one wheel must be larger than the diameter of the other wheel. Absent. For this reason, it has been difficult for the conventional structure to meet the demand for downsizing of the apparatus.

  The present invention has been made under the circumstances described above, and it is an object of the present invention to reduce the size of a rotary encoder. It is another object of the present invention to reduce the size of a servo motor including a rotary encoder.

  In order to achieve the above object, an encoder according to the present invention is an encoder for detecting the rotation of a rotating body, and is N formed alternately along a first circle centered on the rotating shaft of the rotating body. A magnetic wheel having a magnetic track composed of a pole and an S pole, and a magnetic wheel that rotates together with the rotating body; and a magnet that detects a magnetic flux from the rotating magnetic wheel that is disposed away from the magnetic track in the direction of the rotation axis. A light having a detection means and an optical track formed along a second circle centered on the rotation axis, the optical wheel rotating with the rotating body, and irradiating light to the optical track of the rotating optical wheel And a light detection means for detecting reflected light reflected by the optical track, wherein the optical wheel is disposed between the magnetic track and the magnetic detection means.

  The optical track includes a plurality of first reflecting portions that reflect the light, and a plurality of first non-reflecting portions that absorb or scatter the light, which are alternately formed along the second circle. The light detecting means irradiates light onto the first pattern of the rotating optical wheel, receives reflected light that is intermittently reflected by the first reflecting portion, and reflects the reflected light. You may have the 1st optical sensor which outputs the signal according to the intensity | strength of light.

  The first optical sensor may output a first signal and a second signal whose phases are different from each other by a quarter of a period in which the first reflection units are arranged.

  The optical track has a second pattern formed of a second reflecting portion and a second non-reflecting portion formed along a third circle having the rotation axis as a center, and the light detection means rotates. A second optical unit configured to irradiate light onto the second pattern of the optical hole, receive reflected light periodically reflected by the second reflecting unit, and output a signal corresponding to the intensity of the reflected light; You may have a sensor.

  The magnetic wheel and the optical wheel may have the same size in a direction orthogonal to the rotation axis.

  The encoder of the present invention may further include a circuit board to which the magnetic detection means is fixed via a spacer.

  To achieve the above object, a servo motor according to the present invention includes a shaft, a rotor provided on the shaft, a stator that rotates the shaft together with the rotor by electromagnetic interaction between the rotor, An encoder of the present invention for detecting rotation of the shaft.

  The number of magnetic poles of the rotor may be equal to the number of magnetic poles of the magnetic track formed on the magnetic wheel.

  The N pole and S pole constituting the magnetic pole of the rotor and the N pole and S pole constituting the magnetic pole of the magnetic track may be arranged so that the phases around the shaft are the same.

  According to the invention, the optical wheel is arranged between the magnetic track of the magnetic wheel and the magnetic detection means. Thereby, an optical wheel can be made small. Therefore, it is possible to realize downsizing of the encoder and downsizing of the servo motor including the encoder.

It is a perspective view of the servomotor which concerns on one Embodiment of this invention. It is sectional drawing of a servomotor. It is a perspective view which shows a rotor, a shaft, and a wheel unit. It is a development perspective view of a wheel unit. It is a top view of an optical wheel. It is a figure which shows the cross section of a board | substrate with a shaft etc. It is a figure which shows an optical sensor with an optical wheel etc. It is a figure which shows a magnetic sensor with a magnetic wheel etc. (A) And (B) is a figure which shows the time change of A phase signal, B phase signal, and Z phase signal. It is a figure which shows the time change of CS signals 1-3.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a servo motor 10 according to the present embodiment. The servo motor 10 is a motor having a rotor having eight poles and a stator having nine poles. As shown in FIG. 1, the servo motor 10 includes a cylindrical shaft 20 whose longitudinal direction is the Y-axis direction, a motor unit 30 that rotates the shaft 20 around an axis parallel to the Y-axis, And an encoder unit 60 for detecting rotation.

  FIG. 2 is a diagram showing a ZY section of the servo motor 10. As can be seen with reference to FIGS. 2 and 1, the motor unit 30 includes a pair of bearings 33 </ b> A and 33 </ b> B that support the shaft 20 so as to be parallel to the Y axis, a rotor 34 fixed to the shaft 20, and It has a stator 32 arranged so as to surround the rotor 34 and a case 31 for accommodating the above-mentioned parts.

  The case 31 is a rectangular parallelepiped hollow member whose longitudinal direction is the Y-axis direction. Circular openings 31d penetrating in the Y-axis direction are formed on the −Y side and the + Y side of the case 31, respectively. The shaft 20 is rotatably supported by a pair of bearings 33A and 33B in a state where both end portions in the Y-axis direction protrude from the opening 31d to the outside.

  As shown in FIG. 1, cutout portions 31 a along the Y axis are formed at four corner portions formed by side surfaces around the axis parallel to the Y axis of the case 31. Further, an annular convex portion 31c protruding in the −Y direction so as to surround the opening 31d is formed on the surface of the case 31 on the −Y side, and through holes 31b reaching the cutout portions 31a are formed at the four corners. Each is formed. The case 31 is fixed to the body of a device to be driven such as a robot arm by, for example, a bolt or a screw inserted into the through hole 31b.

  FIG. 3 is a perspective view showing the rotor 34 together with the shaft 20 and the wheel unit 70. As shown in FIG. 3, the rotor 34 is a cylindrical member having a through hole through which the shaft 20 passes. The rotor 34 is magnetized so that four N poles and four S poles appear periodically and alternately along a circumference around the shaft 20. In the present embodiment, the colored portion is the north pole of the rotor 34. The rotor 34 is fixed to the shaft 20 inserted into the through hole.

  Returning to FIG. 2, the stator 32 is a cylindrical member whose longitudinal direction is the Y-axis direction. The stator 32 has nine poles facing the rotor 34 along a circumference centered on the shaft 20. In the present embodiment, the nine poles are divided into three groups, and the coils of the poles constituting each group are connected in series.

  The encoder unit 60 includes a wheel unit 70 fixed to the shaft 20, a substrate 62 disposed on the + Y side of the wheel unit 70, and a casing 61 that accommodates these.

  FIG. 4 is an exploded perspective view of the wheel unit 70. As shown in FIG. 4, the wheel unit 70 includes a base 71 and a magnetic wheel 75 and an optical wheel 77 that are fixed to the base 71.

  The base 71 includes a circular large-diameter portion 71b, a circular small-diameter portion 71c formed on the + Y side of the large-diameter portion 71b, a cylindrical cylindrical portion 71a protruding from the −Y side of the large-diameter portion 71b, It is comprised from the cyclic | annular annular convex part 71d which protrudes from the + Y side of the small diameter part 71c. Further, the base 71 is formed with a through hole 71e penetrating in the Y-axis direction.

  The magnetic wheel 75 is an annular member shaped so that the outer diameter is equal to the outer diameter of the large diameter portion 71b of the base 71 and the inner diameter is substantially equal to the outer diameter of the small diameter portion 71c. This magnetic wheel 75 is made of a magnetic material, and the surface on the + Y side is magnetized so that four N poles and four S poles appear periodically and alternately along the outer edge. Thus, the surface on the + Y side of the magnetic wheel 75 is a magnetic track in which N and S poles appear periodically and alternately along a circle C1 centered on the center of the magnetic wheel 75.

  The optical wheel 77 is a disk-shaped member having a thickness of 0.1 mm and made of a material mainly composed of nickel. The surface of the optical wheel 77 is processed so that the reflectance is 0.5 or more. FIG. 5 is a plan view of the optical wheel 77. As shown in FIG. 5, an opening 77 a having a diameter substantially equal to the outer diameter of the annular convex portion 71 d constituting the base 71 is formed in the central portion of the optical wheel 77. A plurality of fan-shaped marks M1 whose longitudinal direction is the radial direction of the circle C2 are formed at equal intervals along the circle C2 centered on the center of the optical wheel 77 on the surface on the −Y side of the optical wheel 77. Has been. In addition, one sector-shaped mark M2 is formed on the circumference of a circle C3 having a center in common with the circle C2 and having a radius larger than that of the circle C2.

  Each of the marks M1 and M2 has a lower reflectance than the surrounding area. For example, the reflectance is smaller than 0.5. The marks M1 and M2 form an optical track TR together with a region sandwiched between the marks M1. That is, the optical track TR includes an incremental pattern in which a portion having a low reflectance on which the mark M1 is formed and a portion having a high reflectance sandwiched between the marks M1 are alternately arranged along the circle C2, and an incremental pattern. And a mark M2 indicating the reference position.

  3 and 4, the base 71, the magnetic wheel 75, and the optical wheel 77 described above are fitted with the magnetic wheel 75 in the small diameter portion 71c of the base 71, and the optical wheel 77 in the annular convex portion 71d. Is integrated by fitting. At this time, almost the entire optical track TR is located on the + Y side of the magnetic wheel 75.

  The base 71 is positioned in such a manner that the phase of the magnetic wheel 75 around the north pole and south pole of the shaft 20 matches the phase of the rotor 34 around the north pole and south pole of the shaft 20. It is being fixed to the shaft 20 inserted in 71e.

  FIG. 6 is a view showing a cross section of the substrate 62 together with the shaft 20 and the like. The board | substrate 62 is a square plate-shaped member, and the circular opening 62a which the shaft 20 penetrates in the center part is formed. Two optical sensors PS1 and PS2 are mounted on the −Y side surface of the substrate 62, and three magnetic sensors MS1, MS2, and MS3 are mounted via spacers 62b.

  The substrate 62 is supported by a support member (not shown) such that the surface on which the optical sensors PS1 and PS2 and the magnetic sensors MS1 to MS3 are mounted faces the optical wheel 77. As a result, the optical sensors PS1 and PS2 face the optical track TR of the optical wheel 77, and the magnetic sensors MS1 to MS3 face the magnetic track of the magnetic wheel 75 via the optical track TR. Further, the gap between the optical wheel 77 and the magnetic sensors MS <b> 1 to MS <b> 3 is adjusted by a spacer 62 b made of the same material as the substrate 62, for example.

  FIG. 7 is a diagram showing the optical sensors PS1 and PS2 together with the optical wheel 77 and the like. As shown in FIG. 7, the optical sensor PS1 is disposed at a position corresponding to a point where a straight line L1 passing through the center of the optical wheel 77 and parallel to the X axis intersects with the circle C2. The optical sensor PS1 emits illumination light at a position on a circle C2 on the optical wheel 77. Then, the illumination light reflected by the optical wheel 77 is received, and two system voltage signals corresponding to the intensity of the received illumination light are output.

  The optical sensor PS2 is disposed at a position corresponding to a point where a straight line L2 passing through the center of the optical wheel 77 and parallel to the Z axis intersects with the circle C3. The optical sensor PS2 emits illumination light at a position on a circle C3 on the optical wheel 77. And the illumination light reflected by the optical wheel 77 is received, and one system voltage signal according to the intensity | strength of the received illumination light is output.

  For convenience of explanation, the two voltage signals output from the optical sensor PS1 are referred to as an A-phase signal and a B-phase signal, respectively. The voltage signal output from the optical sensor PS2 is a Z-phase signal.

  FIG. 8 is a diagram showing the magnetic sensors MS1 to MS3 together with the magnetic wheel 75 and the like. As shown in FIG. 8, the magnetic sensor MS1 is disposed at a position corresponding to a point where a straight line L3 passing through the center of the magnetic wheel 75 and parallel to the Z axis intersects with the circle C1. The magnetic sensor MS2 is disposed at a position corresponding to a point where a straight line L4 passing through the center of the magnetic wheel 75 and forming an angle of 30 degrees with the straight line L3 intersects with the circle C1. The magnetic sensor MS3 is disposed at a position corresponding to a point where a straight line L5 passing through the center of the magnetic wheel 75 and forming an angle of 30 degrees with the straight line L4 intersects with the circle C1. These magnetic sensors MS1 to MS3 are configured to include Hall elements, detect the magnetic flux from the magnetic wheel 75 through the optical wheel 77, and output a voltage signal corresponding to the detected magnetic flux.

  For convenience of explanation, voltage signals output from the magnetic sensors MS1, MS2, and MS3 are referred to as CS signal 1, CS signal 2, and CS signal 3, respectively.

  As can be seen from the above description, in this embodiment, the rotation of the shaft 20 includes the magnetic wheel 75, the optical wheel 77, the two optical sensors PS1, PS2, and the three magnetic sensors MS1, MS2, MS3. An encoder is configured to detect. The encoder is accommodated in a casing 61 attached to the case 31 of the motor unit 30.

  In the servo motor 10 configured as described above, when an AC voltage having a phase difference of 120 degrees is applied to each of the poles divided into three groups, for example, an electromagnetic wave between the stator 32 and the rotor 34 is generated. Due to the interaction, the shaft 20 rotates with the wheel unit 70.

  FIG. 9A shows a temporal relationship between the A-phase signal and the B-phase signal output from the optical sensor PS1 and the Z-phase signal output from the optical sensor PS2 when the shaft 20 rotates at a constant speed. It is a figure which shows a change. The rotation of the shaft 20 at this time is assumed to be normal rotation.

When the shaft 20 rotates forward at a constant speed, the illumination light emitted from the optical sensor PS1 is intermittently reflected by the optical track TR. The optical sensor PS1 outputs an A phase signal and a B phase signal corresponding to the intensity of illumination light that is intermittently reflected by the optical track TR. As shown in FIG. 9 (A), the value of the A-phase signal changes from a low level to a high level every time period T ₁ is passed. Furthermore, B-phase signal, to the A-phase signal, T _1/4 cycle delay is changed from a low level to a high level every time period T ₁ is passed.

The illumination light emitted from the optical sensor PS2 is scattered or absorbed when it enters the mark M2 of the optical track TR, and is reflected when it enters the other part. That is, the illumination light emitted from the optical sensor PS2 is scattered or absorbed by the mark M2 every time the shaft 20 rotates once. The optical sensor PS2 outputs a Z-phase signal corresponding to the intensity of the illumination light reflected on the optical track TR. As shown in FIG. 9 (A), the value of the Z phase signal, the shaft 20 is changed from the time required T ₂ each to the high level for one revolution at the low level.

This Z-phase signal is used to detect the reference angle of the shaft 20. For example, the rise of the Z-phase signal, by counting the number of times the A-phase signal and the B-phase signal changes, resolution 360 ° _/ a _{(T 2 / (T 1/} 4)), from the reference angle of the shaft 20 Can be detected.

  FIG. 9B shows the A-phase signal and B-phase signal output from the optical sensor PS1 and the optical sensor PS2 when the shaft 20 rotates (reverses) in the direction opposite to the normal rotation. It is a figure which shows the time change with a Z phase signal. As can be seen from FIGS. 9A and 9B, when the shaft 20 is rotating forward, the B-phase signal rises and the A-phase signal falls after the A-phase signal rises. Later, the B transmission signal falls. On the other hand, when the shaft 20 is rotating in reverse, the B phase signal rises after the A phase signal rises, and the B phase signal rises after the A phase signal falls. Therefore, it can be determined whether the shaft 20 is rotating forward or reversely from the timing pattern in which the A phase signal and the B phase signal change.

  FIG. 10 is a diagram illustrating temporal changes in the CS signal 1, the CS signal 2, and the CS signal 3 output from the magnetic sensors MS1 to MS3, respectively, when the shaft 20 is rotating forward at a constant speed. .

When the shaft 20 rotates in the forward direction, as can be seen with reference to FIG. 8, the N pole and the S pole of the magnetic wheel 75 alternately pass through the −Y side of each of the magnetic sensors MS1 to MS3. Each of the magnetic sensors MS1 to MS3 detects the magnetic flux from the N pole and the S pole passing alternately, the magnetic flux from the N pole as positive, and the magnetic flux from the S pole as negative, and the CS signal 1 corresponding to the detected magnetic flux Output ~ 3. As shown in FIG. 10, the CS signal 1 changes from a low level to a high level substantially every period T ₃ . Further, CS signals 2 and CS signal 3, to the CS signal 1, and delayed by _T 3/3 period or _2T 3/3 period, respectively, generally varies from period _{T 3} from the low level to the high level. Note that the period T ₃ is equivalent to a value obtained by dividing the time T ₂ by 4 (= 8 poles / 2).

  These CS signals 1 to 3 can be used to detect the relative positional relationship between each pole of the stator 32 and the magnetic pole of the rotor 34.

  As described above, in the present embodiment, the optical track TR formed on the optical wheel 77 is disposed between the magnetic track of the magnetic wheel 75 and the magnetic sensors MS1 to MS3. For this reason, the diameter of the optical wheel 77 can be reduced. Thereby, the whole encoder unit 60 can be reduced in size. Further, since the encoder unit 60 is reduced in size, the servo motor 10 can be reduced in size.

  In the encoder unit 60, each of the magnetic sensors MS <b> 1 to MS <b> 3 detects magnetism (magnetic flux) from the magnetic wheel 75 via the optical wheel 77. Therefore, in the present embodiment, the gap between the magnetic sensors MS1 to MS3 and the optical wheel 77 is adjusted by the spacer 62b provided on the substrate 62. Thereby, even if the magnetism from the magnetic wheel 75 attenuate | damps by presence of the optical wheel 77, magnetic sensor MS1-MS3 can detect a magnetic flux favorably.

  As mentioned above, although embodiment of this invention was described, this invention is not limited by the said embodiment.

  For example, in the present embodiment, the optical wheel 77 is formed with an optical track for outputting an A-phase signal and a B-phase signal, and the magnetic wheel 75 is formed with a magnetic track for outputting a CS signal. . Not limited to this, an optical track for outputting a CS signal may be formed on the optical wheel 77, and a magnetic track for outputting an A-phase signal and a B-phase signal may be formed on the magnetic wheel 75.

  In the present embodiment, the optical track TR of the optical wheel 77 includes a mark M2 for outputting a Z-phase signal. However, the present invention is not limited to this, and the optical track TR may have only an incremental pattern including the mark M1. Further, the mark M2 may be formed inside the incremental pattern.

  In the present embodiment, the spacer 62 b is made of a material equivalent to the material of the substrate 62. Not limited to this, the spacer 62b may have a mechanism for appropriately adjusting the gap between the optical wheel 77 and the magnetic sensors MS1 to MS3.

  In the present embodiment, the optical track TR of the optical wheel 77 is disposed between the magnetic track of the magnetic wheel 75 and the magnetic sensors MS1 to MS3. For this reason, the optical track TR overlaps the magnetic track in the Y-axis direction. At this time, the optical track TR may at least partially overlap the magnetic track, or may entirely overlap the magnetic track.

  In the present embodiment, the optical wheel 77 is a circular plate-like member made of a material whose main component is nickel and has a thickness of 0.1 mm. For example, the optical wheel 77 may be a member made of a stainless steel plate. The optical wheel 77 is preferably shaped as thin as possible. For example, a film made of a nonmagnetic material may be used as the optical wheel.

  In the present embodiment, as an example, the servo motor 10 is a servo motor having an 8-pole rotor 34 and a 9-pole stator 32. However, the number of poles of the rotor 34 and the stator 32 can be arbitrarily selected. The servo motor 10 may be a direct current motor instead of an alternating current motor.

  Moreover, in the said embodiment, magnetic sensor MS1-MS3 is comprised including the Hall element. Not only this but a magnetoresistive element may be used as magnetic sensors MS1-MS3.

  Further, the positions of the magnetic sensors MS1 to MS3 shown in FIG. 8 are an example, and the positions of the magnetic sensors MS1 to MS3 in the XZ plane are not necessarily on the circle C1. In short, the magnetic sensors MS <b> 1 to MS <b> 3 only need to be arranged at a position where the magnetic flux from the magnetic wheel 75 can be detected. For example, if the position in the center XZ plane overlaps the magnetic wheel 77. Good.

  In the above embodiment, the portions where the marks M1 and M2 are formed are portions that scatter or absorb the illumination light from the optical sensors PS1 and PS2. However, the optical wheel 77 may be formed so that the reflectance of the portion where the marks M1 and M2 are formed is high and the reflectance of the other portions is low.

  In the above embodiment, the magnetic wheel 75 is a member made of an annular magnetic material. For example, the magnetic wheel 75 may be formed by arranging a plurality of magnets along the circle C1 so that the N poles and the S poles are alternately positioned.

  Moreover, in the said embodiment, although the board | substrate 62 is shaped in square plate shape, this invention is not limited to this.

  Moreover, in the said embodiment, magnetic sensor MS1-MS3 is arrange | positioned in the position where the phase around the shaft 20 differs 30 degree | times at a time. Not only this but magnetic sensor MS1-MS3 may be arrange | positioned in the position from which a phase differs 60 degree | times at a time. Moreover, you may arrange | position in the position from which a phase differs 120 degree | times at a time. Further, the magnetic sensor MS2 is disposed at a position where the phase is 150 degrees different from the position where the magnetic sensor MS1 is disposed, and the magnetic sensor MS3 is disposed at a position where the phase is 60 degrees different from the position where the magnetic sensor MS2 is disposed. Also good.

  In the above embodiment, the optical sensors PS1 and PS2 are arranged at positions where the phases around the shaft are different by 90 degrees. Not only this but each of optical sensor PS1 and PS2 should just have the position regarding XZ surface on the circle C2 and the circle C3.

  Various embodiments and modifications of the present invention are possible without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention, and do not limit the scope of the present invention.

  The encoder of the present invention is suitable for detecting the rotation of the rotating body. Further, the servo motor of the present invention is suitable for rotating a driving object.

DESCRIPTION OF SYMBOLS 10 Servo motor 20 Shaft 30 Motor unit 31 Case 31a Notch 31b Through-hole 31c Protrusion 31d Open 32 Stator 33A, 33B Bearing 34 Rotor 60 Encoder unit 61 Casing 62 Substrate 62a Open 62b Spacer 70 Wheel unit 71 Base 71a Cylindrical part Large diameter portion 71c Small diameter portion 71d Annular convex portion 71e Through hole 75 Magnetic wheel 77 Optical wheel 77a Opening C1-C3 circle L1-L5 Straight line M1, M2 mark MS1-MS3 Magnetic sensor PS1, PS2 Optical sensor TR Optical track

Claims (9)

An encoder for detecting rotation of a rotating body,
A magnetic wheel having a magnetic track composed of N poles and S poles alternately formed along a first circle around the rotation axis of the rotating body, and rotating with the rotating body;
Magnetic detection means for detecting a magnetic flux from the magnetic wheel disposed and rotated away from the magnetic track in the rotation axis direction;
An optical wheel having an optical track formed along a second circle centered on the rotation axis and rotating together with the rotating body;
Light detection means for irradiating the optical track of the rotating optical wheel with light and detecting reflected light reflected by the optical track;
With
The optical wheel is an encoder disposed between the magnetic track and the magnetic detection means. The optical track includes a plurality of first reflecting portions that reflect the light, and a plurality of first non-reflecting portions that absorb or scatter the light, which are alternately formed along the second circle. Has one pattern,
The light detection means irradiates light onto the first pattern of the rotating optical wheel, receives reflected light that is intermittently reflected by the first reflecting portion, and corresponds to the intensity of the reflected light The encoder according to claim 1, further comprising a first optical sensor that outputs a signal.   3. The encoder according to claim 2, wherein the first optical sensor outputs a first signal and a second signal whose phases are different from each other by a quarter of a period in which the first reflection units are arranged. The optical track has a second pattern formed of a second reflecting portion and a second non-reflecting portion, which is formed along a third circle centered on the rotation axis.
The light detection means irradiates light onto the second pattern of the rotating optical hole, receives reflected light periodically reflected by the second reflecting portion, and according to the intensity of the reflected light The encoder according to claim 1, further comprising a second optical sensor that outputs a signal.   The encoder according to any one of claims 1 to 4, wherein the magnetic wheel and the optical wheel have the same size in a direction orthogonal to the rotation axis.   The encoder according to claim 1, further comprising a circuit board on which the magnetic detection unit is fixed via a spacer. A shaft,
A rotor provided on the shaft;
A stator that rotates the shaft together with the rotor by electromagnetic interaction with the rotor;
The encoder according to any one of claims 1 to 6, which detects rotation of the shaft;
Servo motor with   The servo motor according to claim 7, wherein the number of magnetic poles of the rotor is equal to the number of magnetic poles of the magnetic track formed on the magnetic wheel.   The N-pole and S-pole constituting the magnetic pole of the rotor and the N-pole and S-pole constituting the magnetic track magnetic pole are arranged so that the phases around the shaft are the same. Servo motor.

Images