JP2007114032A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue detection of a rotation quantity of a rotor even when a trouble is generated in a rotation quantity detecting part. <P>SOLUTION: This encoder is attached with a transmission type disk 21 with a slit pattern formed in a rotary shaft 72, and a reflection type disk 31 formed with a reflection part pattern, and includes a transmission type rotation quantity detecting part 22 for detecting the rotation quantity of the rotary shaft 72, based on the slit pattern formed in the transmission type disk 21, and a reflection type rotation quantity detecting part 32 for detecting the rotation quantity of the rotary shaft 72 (i.e. by a system different from the transmission type rotation quantity detecting part 22), based on the reflection pattern formed in the reflection type disk 31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoder.

An encoder is often used for position detection of a control target in servo control of a robot device. The encoder is a sensor that converts a mechanical displacement amount into a digital amount and outputs it, and directly reads the position of a moving body that moves together with the object to be controlled by a position reading mechanism. A position reading mechanism using light is known, and a transmission type and a reflection type are mainly used. In addition, the position of the object to be rotated (rotating body) is optically read using a code plate for the moving body, and the amount of rotation of the controlled object (including the direction of rotation) is determined from the change in position of the moving body A rotary encoder that detects the rotation angle and the number of rotations is used (see, for example, the following patent document). used.
Japanese Patent Laid-Open No. 5-141988

  When the control object is a rotating body as described above, the encoder optically reads the amount of rotation of the code plate that moves with the rotating body and detects the amount of rotation of the rotating body. If a failure occurs in the position reading mechanism), it becomes impossible to continue the rotation amount detection of the rotating body.

  The present invention has been made in view of such problems, and provides an encoder having a configuration capable of continuing to detect the amount of rotation of a rotating body even when a failure occurs in the amount of rotation detection unit. It is an object.

  An encoder according to the present invention is a code plate that is attached to a rotating body and has a predetermined pattern formed thereon; a first detection unit that detects a rotation amount of the rotating body based on the predetermined pattern formed on the code plate; And a second detection unit that detects the amount of rotation of the rotating body by a method different from that of the first detection unit based on the predetermined pattern formed on the code plate.

  An encoder according to the present invention includes a first code plate that is mounted on a rotating body and has a first predetermined pattern formed thereon, and a second code plate that is mounted on the rotating body and has a second predetermined pattern formed thereon. Based on the first predetermined pattern formed on the first code plate, the first detection unit for detecting the rotation amount of the rotating body based on the first predetermined pattern formed on the first code plate, and the second predetermined pattern formed on the second code plate. And a second detection unit that detects the amount of rotation of the rotating body by a method different from that of the first detection unit. Here, it is preferable that the first code plate and the second code plate are separately mounted on the rotating body. The first detection unit is a transmission type detection unit that detects light transmitted through the first predetermined pattern formed on the first code plate, and the second detection unit is formed on the second code plate. It is preferable that the reflection type detection unit detects the light reflected by the second predetermined pattern. Further, the first predetermined pattern is a plurality of slits formed in the circumferential direction of the first code plate, and the second predetermined pattern is a plurality of reflecting portions formed in the circumferential direction of the second code plate. It is preferable. Moreover, it is preferable to have the magnet with which the rotary body was mounted | worn, and the magnetic detection part which detects the rotation speed of a rotary body based on the magnetism of a magnet.

  According to the encoder of the present invention, even when a failure occurs in one detection unit, it is possible to detect the amount of rotation of the rotating body based on detection information from the remaining detection units.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an encoder 10 according to the first embodiment of the present invention, and FIG. 2 shows a signal transmission system of a rotation amount detection system having the encoder 10. FIG. 3 shows an articulated robot (hereinafter simply referred to as a robot) RB to which the encoder 10 according to this embodiment is applied. In the first embodiment, the rotary encoder 10 is used as a sensor that detects the amount of rotation (a rotation angle and a rotation speed including the rotation direction) of the bidirectionally driven electric motor 70 that constitutes one joint portion of the robot RB. ing. The robot RB can be operated by a robot controller 81 (see FIGS. 2 and 3) of the robot controller 80. Therefore, the electric motor 70 is controlled by the robot controller 80. Since the mechanism relating to the operation control is well known and is not directly related to the configuration of the encoder 10 according to the present invention, the description thereof will be omitted.

  As shown in FIG. 1, the rotary encoder 10 includes a rotary shaft (rotary body) 72 driven by an output shaft 71 (see FIG. 3) of an electric motor 70. Side bearings 13) are rotatably supported. The rotary shaft 72 has its tip end directed upward in FIG. 1 in the housing 11, and a cylindrical cover member 14 that opens downward is attached to the housing 11 so as to cover the tip portion of the rotary shaft 72. . Here, if the rotary encoder 10 is a modular type configured integrally with the electric motor 70, the rotary shaft 72 may be the output shaft 71 itself of the electric motor 70.

  One transmission type disk 21 having a slit pattern (first predetermined pattern) composed of a plurality of (many) slits (not shown) arranged in parallel in the circumferential direction on the rotating shaft 72, and the transmission type A reflective disk 31 having a reflecting part pattern (second predetermined pattern) comprising a plurality of (many) reflecting parts attached to the lower side of the disk 21 and arranged in parallel in the circumferential direction on the surface (lower surface); Two upper and lower magnetic disks (first upper magnetic disk on the upper side) are provided so as to sandwich the transmissive disk 21 and the reflective disk 31 from above and below, and have permanent magnets arranged in a donut shape centering on the rotation shaft 72 on the surface. The disk 41 and the lower second magnetic disk 51) are fixed to the upper surface side of a horizontal portion 72 a formed on the upper portion of the rotary shaft 72 in a state where the disk 41 and the second magnetic disk 51) are integrally coupled by a plurality of screw members 16.

  A light emitting element holding portion 15 is provided at a side position of the rotation shaft 72 in the housing 11, and a first light emitting element (for example, a light emitting diode) 23 is placed on the light emitting element holding portion 15 with the light emitting direction facing upward. It is held in a posture extending in the vertical direction. A lens 24 is held at a position above the first light emitting element 23 in the light emitting element holding portion 15, and the first light emitting element 23 can irradiate the transmissive disc 21 with light through the lens 24. A first circuit board 61 (see also FIG. 3) connected to the robot controller 81 is provided at a position above the transmissive disk 21 so as to extend in a plane perpendicular to the rotation shaft 72. A first light receiving element (for example, a photodiode) 26 is provided at a position facing the first light emitting element 23 on the lower surface side of the substrate 61. A fixed slit 25 is provided between the transmissive disc 21 and the first light receiving element 26, and light emitted by the first light emitting element 23 passes through the lens 24, the transmissive disc 21 (its slit), and the fixed slit 25. The light is received by the first light receiving element 26, and the first light receiving element 26 outputs a voltage signal corresponding to the slit pattern of the transmissive disc 21. The voltage signal output from the first light receiving element 26 is amplified by the amplifier 27 and then converted into a digital signal by the processing circuit 28 to obtain the position of the transmissive disk 21. Based on this, the amount of rotation of the rotating shaft 72 (the rotation angle and the number of rotations including the rotation direction) is detected. Here, the first light emitting element 23, the lens 24, the fixed slit 25, the first light receiving element 26, the amplifier 27, and the processing circuit 28 constitute a transmissive rotation amount detection unit 22 that detects the rotation amount of the transmissive disk 21. The transmission type rotation amount detection mechanism 20 is configured by the transmission type disk 21 and the transmission type rotation amount detection unit 22 (see FIG. 2).

  A second circuit board 62 (see also FIG. 3) connected to the robot control unit 81 extends in a plane parallel to the first circuit board 61 at a position above the upper bearing 12 that supports the rotating shaft 72. (The rotary shaft 72 penetrates the second circuit board 62 in the vertical direction). A second light emitting element 33 and a second light receiving element 34 are provided on the upper surface side of the second circuit board 62, and the light emitted by the second light emitting element 33 is reflected by the reflective disk 31 and then received by the second light receiving element. Light is received by the element 34, and the second light receiving element 34 outputs a voltage signal corresponding to the reflection portion pattern of the reflection disk 31. The voltage signal output from the second light receiving element 34 is amplified by the amplifier 37 and then converted into a digital signal by the processing circuit 38 to obtain the position of the reflective disk 31. Based on this, the amount of rotation of the rotating shaft 72 (the rotation angle and the number of rotations including the rotation direction) is detected. Here, the second light emitting element 33, the second light receiving element 34, the amplifier 37, and the processing circuit 38 constitute a reflection type rotation amount detection unit 32 that detects the amount of rotation of the reflection type disk 31. The reflection-type rotation amount detection unit 32 is configured by the reflection-type rotation amount detection unit 32 (see FIG. 2).

  A first magnetic sensor 43 is provided at a position facing the first magnetic disk 41 on the lower surface side of the first circuit board 61. On the first magnetic disk 41, permanent magnets are arranged in a donut shape centered on the rotating shaft 72. The magnetism of the first magnetic disk 41 is detected by the first magnetic sensor 43, and the first magnetic sensor 43 is A voltage signal corresponding to the magnetism of the first magnetic disk 41 is output. The voltage signal output from the first magnetic sensor 43 is amplified by the amplifier 47, and then converted into a digital signal by the processing circuit 48, so that the rotational speed (including the rotation direction) of the first magnetic disk 41 (that is, the rotating shaft 72) is included. Rotation number) is detected. Here, the first magnetic sensor 43, the amplifier 47, and the processing circuit 48 constitute a first rotational speed detection unit (magnetic detection unit) 42 that detects the rotational speed of the first magnetic disk 41, and the first magnetic disk 41 and the first rotation speed detection unit 42 constitute a first rotation speed detection mechanism 40 (see FIG. 2).

  A second magnetic sensor 53 is provided at a position facing the second magnetic disk 51 on the upper surface side of the second circuit board 62. On the second magnetic disk 51, permanent magnets are arranged in a donut shape centered on the rotating shaft 72. The magnetism of the second magnetic disk 51 is detected by the second magnetic sensor 53, and the second magnetic sensor 53 is A voltage signal corresponding to the magnetism of the second magnetic disk 51 is output. The voltage signal output from the second magnetic sensor 53 is amplified by the amplifier 57, and then converted into a digital signal by the processing circuit 58, so that the rotational speed (including the rotation direction) of the second magnetic disk 51 (that is, the rotating shaft 72) is included. Rotation number) is detected. Here, the second magnetic sensor 53, the amplifier 57, and the processing circuit 58 constitute a second rotational speed detection unit (magnetic detection unit) 52 that detects the rotational speed of the second magnetic disk 51, and the second magnetic disk 51 and the second rotation speed detection unit 52 constitute a second rotation speed detection mechanism 50 (see FIG. 2).

  Information on the rotation amount of the rotary shaft 72 detected in the processing circuit 28 of the transmission type rotation amount detection mechanism 20 and information on the rotation amount of the rotation shaft 72 detected in the processing circuit 38 of the reflection type rotation amount detection mechanism 30 Are transmitted to the robot controller 81 of the robot controller 80 from the communication circuits 29 and 39 connected to the processing circuits 28 and 38, respectively, and used for servo control of the electric motor 70 performed by the robot controller 81. Further, information on the rotational speed of the rotary shaft 72 detected by the processing circuit 48 of the first rotational speed detection mechanism 40 and the rotational speed of the rotary shaft 72 detected by the processing circuit 58 of the second rotational speed detection mechanism 50. Is transmitted to the robot controller 81 of the robot controller 80 from the communication circuits 49 and 59 connected to the processing circuits 48 and 58, respectively, and when the rotating shaft 72 of the electric motor 70 rotates 360 ° or more, etc. It is used for verification of the position detection result of the rotating shaft 72 of the electric motor 70 performed by the transmission type rotation amount detection mechanism 20 and the reflection type rotation amount detection mechanism 30. Here, both the rotation amount information of the transmission type disc 21 detected by the transmission type rotation amount detection unit 22 and the rotation amount information of the reflection type disc 31 detected by the reflection type rotation amount detection unit 32 are both of the rotation axis 72. Both rotation amounts are phase-adjusted so that the rotation amount information is output with values that coincide with each other. For this reason, the signals received by the robot control unit 81 from both the rotation amount detection mechanisms 20 and 30 are the same as the rotation amount information of the rotation shaft 72.

  Here, when the robot controller 81 detects that one of the signals transmitted from the two rotation amount detection mechanisms 20 and 30 is abnormal, the robot control unit 81 outputs the abnormal signal to the rotation amount detection mechanism. It is determined that a failure has occurred, the signal is ignored, the position detection of the rotating shaft 72 is continued based on the remaining signals, and the electric motor 70 is controlled. The robot control unit 81 visually displays the rotation amount detection mechanism that has output an abnormal signal by the display device 82 such as a display provided in the robot controller 80, and notifies the operator of the occurrence of the abnormality. The case where the robot control unit 81 detects a signal abnormality is, for example, a case where a signal having a waveform or a magnitude (voltage value) that should not be clearly output is output.

  As described above, the rotary encoder 10 according to the first embodiment is mounted on the rotary shaft 72 and is mounted on the rotary shaft 72 in the same manner as the first code plate (transmission type disk 21) on which a predetermined slit pattern is formed. And a transmission type rotation amount detection unit 22 (transmission type detection) that detects the amount of rotation of the rotating shaft 72 based on the slit pattern in the first code plate. And a reflection type rotation amount detection unit 32 (reflection type detection) that detects the amount of rotation of the rotary shaft 72 based on the reflection part pattern on the second code plate (that is, in a different manner from the transmission type rotation amount detection unit 22) The rotation amount of the rotary shaft 72 can be detected based on the detection information from the remaining rotation amount detection unit even if a failure occurs in one rotation amount detection unit. Is possible . Moreover, not only a plurality of rotation amount detection units are provided, but also the transmission type rotation amount detection unit 22 and the reflection type rotation amount detection unit 32 have mutually different detection methods for the rotation amount of the corresponding disk (code plate). Since they are different, there is a low possibility that a plurality of rotation amount detection units will fail simultaneously due to the same cause, and the safety against the failure is very high. For this reason, the occurrence of an unsafe situation such as the robot RB running away due to an abnormality in the encoder 10 is prevented. In the first embodiment, the two rotation speed detection mechanisms (the first rotation speed detection mechanism 40 and the second rotation speed detection mechanism 50) are provided. However, the rotation speed detection mechanisms 40 and 50 have a rotation amount. Since it is used in an auxiliary manner to verify the detection results of the detection mechanisms 20 and 30, it may be configured to include only one of the both rotation speed detection mechanisms 40 and 50, or a second described later. As in the embodiment, the rotation speed detection unit itself may not be provided.

  In the encoder 10 according to the first embodiment, the rotation amount information of the disk (code plate) detected by each of the two rotation amount detection units 22 and 32, that is, the transmission type disc detected by the transmission type rotation amount detection unit 22. The rotation amount information 21 and the rotation amount information of the reflection type disc 31 detected by the reflection type rotation amount detection unit 32 are output as the position information of the rotation shaft 72 with the same value as each other. It is possible to execute the abnormality detection of the rotation amount detection unit to be performed by the device (the robot control unit 81 in this case) that receives the rotation amount information by a relatively simple program.

  Next, the rotary encoder 110 according to the second embodiment of the present invention will be described. FIG. 4 shows a rotary encoder 110 according to the second embodiment, and FIG. 5 shows a signal transmission system of a rotation amount detection system including the rotary encoder 110. The rotary encoder 110 according to the second embodiment has many parts in common with the rotary encoder 10 according to the first embodiment, and the same parts as those of the rotary encoder 10 according to the first embodiment are used in the description of the first embodiment. The same reference numerals are used and description thereof is omitted.

  In the rotary encoder 110 according to the second embodiment, one transmissive disk 121 and one reflective disk 131 are attached to a rotating shaft 172 having the same function as the rotating shaft 72 in the first embodiment. Here, the transmission type disc 121 is fixed to the rotary shaft 172 by the ring-shaped first disc holding member 112 in a state of being placed from above on the first horizontal portion 172a formed on the top of the rotary shaft 172. The reflective disk 131 is mounted on the rotating shaft 172 by the ring-shaped second disk pressing member 113 while being placed on the second horizontal part 172b formed above the first horizontal part 172a. It is fixed.

  Light from a first light emitting element (for example, a light emitting diode) 123 attached to the light emitting element holding unit 15 passes through the lens 24, the transmissive disk 121 (the slit) and the fixed slit 25, and the first light receiving element (for example, a photodiode). The first light receiving element 126 outputs a voltage signal corresponding to the slit pattern of the transmissive disc 121. The voltage signal output from the first light receiving element 126 is amplified by the amplifier 127 and then converted into a digital signal by the processing circuit 128 to obtain the position of the transmissive disc 121. Based on this, the amount of rotation of the rotating shaft 172 (the rotation angle and the rotation speed including the rotation direction) is detected. Here, the first light emitting element 123, the lens 24, the fixed slit 25, the first light receiving element 126, the amplifier 127, and the processing circuit 128 constitute a transmissive rotation amount detection unit 122 that detects the rotation amount of the transmissive disk 121. The transmission type rotation amount detection mechanism 120 is configured by the transmission type disk 121 and the transmission type rotation amount detection unit 122 (see FIG. 5).

  A circuit board 161 connected to the robot control unit 81 is provided above the transmission disk 121 so as to extend in a plane orthogonal to the rotation shaft 172, and faces the reflection disk 131 on the lower surface side of the circuit board 161. The second light emitting element 133 and the second light receiving element 134 are provided at the positions where the light is emitted, and the light emitted from the second light emitting element 133 is reflected by the reflective disk 131 and then received by the second light receiving element 134. The two light receiving elements 134 output a voltage signal corresponding to the reflection portion pattern of the reflective disk 131. The voltage signal output from the second light receiving element 134 is amplified by the amplifier 137 and then converted into a digital signal by the processing circuit 138 to obtain the position of the reflective disk 131. Based on this, the amount of rotation of the rotating shaft 172 (the rotation angle and the rotation speed including the rotation direction) is detected. Here, the second light emitting element 133, the second light receiving element 134, the amplifier 137, and the processing circuit 138 constitute a reflection type rotation amount detection unit 132 that detects the amount of rotation of the reflection type disk 131. The reflection-type rotation amount detection unit 132 includes the reflection-type rotation amount detection unit 132 (see FIG. 5).

  Information on the amount of rotation of the rotary shaft 172 detected by the processing circuits 128 and 138 is transmitted from the communication circuits 129 and 139 connected to the processing circuits 128 and 138 to the robot control unit 81 of the robot controller 80 to control the robot. It is used for servo control of the electric motor 70 performed by the unit 81. Here, both the rotation amount information of the transmission type disc 121 detected by the transmission type rotation amount detection unit 122 and the rotation amount information of the reflection type disc 131 detected by the reflection type rotation amount detection unit 132 are both of the rotation axis 172. Both rotation amounts are phase-adjusted so that the rotation amount information is output with values that coincide with each other. Further, when the robot control unit 81 detects that one of the signals transmitted from the two rotation amount detection mechanisms 120 and 130 is abnormal, the robot detection unit that has output the abnormal signal has failed. Therefore, the signal is ignored, the position detection of the rotating shaft 172 is continued based on the remaining signal, the electric motor 70 is controlled, and the robot controller 81 is connected to the robot controller 80. It is the same as in the case of the first embodiment that the rotation amount detection mechanism that has output an abnormal signal by the provided display device 82 is visually displayed to the operator.

  As described above, the rotary encoder 110 according to the second embodiment is mounted on the rotary shaft 172 and is also mounted on the rotary shaft 172 and the first code plate (transmission type disk 121) formed with a predetermined slit pattern. And a transmission type rotation amount detection unit 122 (transmission type detection) that detects the amount of rotation of the rotary shaft 172 based on the slit pattern in the first code plate. And a reflection type rotation amount detection unit 132 (reflection type detection) that detects the amount of rotation of the rotation shaft 172 based on the reflection part pattern on the second code plate (that is, in a different manner from the transmission type rotation amount detection unit 122). The same effect as that of the rotary encoder 10 according to the first embodiment can be obtained. Further, in the rotary encoder 110 according to the second embodiment, the plurality of code plates (the transmission type disc 121 and the reflection type disc 131) are not integrated as in the case of the first embodiment, but are separately provided on the rotary shaft 172. In the case where one code plate slips (idles) with respect to the rotation shaft 172 and the position of the rotation shaft 172 cannot be detected by the rotation amount detection unit corresponding to the code plate. Even in this case (in this case, the output from the rotation amount detection unit on the slipped side is abnormal, but the output abnormality is detected by the robot control unit 81), the other code plate that has not slipped It is possible to detect the position of the rotating shaft 172 based on detection information from the corresponding rotation amount detection unit.

  The preferred embodiments of the present invention have been described so far, but the scope of the present invention is not limited to those shown in the above-described embodiments. For example, in the above-described embodiment, the encoder according to the present invention is installed for detecting the rotation amount (rotation angle and rotation speed including the rotation direction) of the bidirectionally driven electric motor. The electric motor is not necessarily a bidirectional drive type, and may be a unidirectional drive type electric motor. Further, the electric motor is not necessarily required. Moreover, although the case where this invention was applied to the rotary encoder which detects the rotation amount of a control object (rotating body) was shown in the above-mentioned embodiment, this invention is a linear encoder which detects the linear movement position of a control object. It is also possible to apply to.

  In the above-described embodiment, the first code plate (transmission type disk on which the slit pattern is formed) on which the first predetermined pattern is formed on the rotating body (rotating shaft) and the second predetermined pattern on which the second predetermined pattern is formed. 2 code plates (reflective disk on which a reflection part pattern is formed) are mounted, and these two predetermined patterns are different from each other by two rotation amount detection units (transmission type rotation amount detection unit and reflection type rotation amount detection unit). It was configured to detect the amount of rotation of the rotating body by detecting with the method, but the rotating body is mounted with one code plate on which two predetermined patterns (for example, a slit pattern and a reflecting portion pattern) are formed, and two rotations are performed. A configuration may be adopted in which the two predetermined patterns are detected by different methods by the amount detection unit to detect the amount of rotation of the rotating body. Further, in the above-described embodiment, the predetermined pattern formed on the code plate was a slit pattern or a reflection portion pattern, but if the rotation amount of the control target (rotating body) can be obtained from the position of the code plate, Other patterns may be used.

It is sectional drawing of the rotary encoder which concerns on 1st Embodiment of this invention. It is a block diagram which shows the signal transmission system of the rotation amount detection system comprised by having the rotary encoder which concerns on 1st Embodiment. 1 is a perspective view of an articulated robot to which an encoder according to a first embodiment is applied. It is sectional drawing of the rotary encoder which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the signal transmission system of the rotation amount detection system comprised by having the rotary encoder which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rotary encoder 20 Transmission type rotation amount detection mechanism 21 Transmission type disk 22 Transmission type rotation amount detection part 30 Reflection type rotation amount detection mechanism 31 Reflection type disk 32 Reflection type rotation amount detection part 72 Rotating shaft

Claims (6)

A sign plate mounted on a rotating body and having a predetermined pattern formed thereon;
A first detector for detecting a rotation amount of the rotating body based on the predetermined pattern formed on the code plate;
An encoder comprising: a second detection unit that detects a rotation amount of the rotating body by a method different from that of the first detection unit based on the predetermined pattern formed on the code plate. A first code plate mounted on a rotating body and having a first predetermined pattern formed thereon;
A second code plate mounted on the rotating body and having a second predetermined pattern formed thereon;
A first detector that detects a rotation amount of the rotating body based on the first predetermined pattern formed on the first code plate;
A second detection unit configured to detect the amount of rotation of the rotating body by a method different from that of the first detection unit based on the second predetermined pattern formed on the second code plate; Encoder. The encoder according to claim 2, wherein the first code plate and the second code plate are separately mounted on the rotating body. The first detection unit is a transmission type detection unit that detects light transmitted through the first predetermined pattern formed on the first code plate,
The said 2nd detection part is a reflection type detection part which detects the light reflected by the said 2nd predetermined pattern formed in the said 2nd code | symbol plate, The Claim 2 or Claim 3 characterized by the above-mentioned. Encoder. The first predetermined pattern is a plurality of slits formed in a circumferential direction of the first code plate,
The encoder according to any one of claims 2 to 4, wherein the second predetermined pattern is a plurality of reflecting portions formed in a circumferential direction of the second code plate. A magnet mounted on the rotating body;
The encoder according to claim 1, further comprising: a magnetic detection unit that detects the number of rotations of the rotating body based on magnetism of the magnet.

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