Encoder, servo motor and servo system

Abstract

The invention provides an encoder, a servo motor and a servo system. The encoder (7) is provided with: a hub section (17) that is rotatable about a rotational axis (Ax); a disc (19) which is fixed to the hub part (17) and on which an annular scale (S) is formed; an optical module (25) that is disposed so as to face the disc (19) and detects the scale (S); a magnet (33) that is disposed closer to the load side than the disk (19) in the direction of the rotational axis (Ax) and that is fixed to the hub section (17); and a trigger signal generator (31) that detects the magnetism of the magnet (33), the trigger signal generator (31) being disposed on the load-opposite side of the disk (19) in the direction of the rotation axis (Ax).

Description

Technical Field

[0001] The disclosed embodiments relate to encoders, servo motors, and servo systems. Background Art

[0002] Patent document 1 describes an encoder device comprising: a position detection system including a detection unit that detects position information of a moving unit; an electric signal generating unit that generates an electric signal through movement of the moving unit; and a battery that supplies at least a portion of the power consumed by the position detection system based on the electric signal generated by the electric signal generating unit.

[0003] Patent Document 1: International Publication No. 2017 / 126338

[0004] Further miniaturization of encoder devices is desired. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an encoder, a servo motor, and a servo system that can be reduced in size.

[0006] In order to solve the above-mentioned problems, according to one aspect of the present invention, an encoder is applied, which comprises: a rotating body capable of rotating around a rotation axis; a disk fixed to the rotating body and forming an annular scale; an optical module arranged to be opposite to the disk and detect the scale; a first magnet arranged at a position closer to one side than the disk in the direction of the rotation axis and fixed to the rotating body; and a first magnetic detection unit arranged at a position closer to the other side than the disk in the direction of the rotation axis and detecting the magnetism of the first magnet.

[0007] According to another aspect of the present invention, a servo motor is applied, which includes: a motor in which a rotor rotates relative to a stator; and the above-mentioned encoder, which detects at least one of the position, speed, and acceleration of the rotor.

[0008] In addition, according to another aspect of the present invention, a servo system is applied, which comprises: a motor in which a rotor rotates relative to a stator; the above-mentioned encoder, which detects at least one of the position, speed, and acceleration of the rotor; and a control device, which controls the motor based on the detection result of the encoder.

[0009] According to the encoder and the like of the present invention, miniaturization can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is an explanatory diagram showing an example of the overall configuration of a servo system.

[0011] Figure 2 is an example of the overall structure of the encoder, equivalent to Figure 3 Cross-sectional view of section II-II.

[0012] Figure 3 This is a plan view of an example of the overall structure of the encoder as viewed from the substrate side.

[0013] Figure 4 This is a plan view of the hub viewed from the substrate side, showing an example of the arrangement structure of the magnets.

[0014] Figure 5 is equivalent to Figure 4 A cross-sectional view of the hub portion of section VV.

[0015] Figure 6 This is a plan view for explaining an example of the flow of magnetic flux generated by a magnet.

[0016] Figure 7 This is a side view for explaining an example of the flow of magnetic flux generated by a magnet.

[0017] Figure 8 This is a plan view of a substrate showing an example of the positional relationship between a magnetic detection unit and a magnet, and the positional relationship between a trigger signal generator and a magnet.

[0018] Fig. 9 This is a block diagram showing an example of the functional structure of a processing module.

[0019] Fig.10 This is an explanatory diagram showing an example of the angular position of the magnet when a trigger signal is generated when the disk is rotating forward.

[0020] Fig.11 This is an explanatory diagram showing an example of the angular position of the magnet when a trigger signal is generated when the disk is reversed.

[0021] Fig.12 It is an explanatory diagram showing an example of the waveforms of the trigger signal, the A-phase multi-rotation signal, and the B-phase multi-rotation signal when the hysteresis of the phase angle of the trigger signal is large.

[0022] Fig.13 It is an explanatory diagram showing an example of the waveforms of the trigger signal, the A-phase multi-rotation signal, and the B-phase multi-rotation signal when the hysteresis of the phase angle of the trigger signal is small.

[0023] Fig.14 This is a plan view of the hub viewed from the substrate side, showing an example of the arrangement structure of the magnets in a modified example in which the gaps between the magnets are filled with a non-magnetic material.

[0024] Fig.15This is a plan view for explaining an example of the flow of magnetic flux generated by a magnet in a modified example in which a hub portion is formed of a non-magnetic material and the magnet is magnetized in the circumferential direction.

[0025] Fig.16 This is a side view for explaining an example of the flow of magnetic flux generated by a magnet in a modified example in which a hub portion is formed of a non-magnetic material and the magnet is magnetized in the circumferential direction.

[0026] Description of symbols

[0027] 1 Servo system

[0028] 3 Servo motors

[0029] 5. Control Device

[0030] 7. Encoder

[0031] 9 Motor

[0032] 17 hub (rotating body)

[0033] 17a Inner circumference

[0034] 17b Periphery

[0035] 17c Magnet storage part

[0036] 19 plates

[0037] 21 substrate

[0038] 25 optical modules

[0039] 27 Magnetic detection unit (second magnetic detection unit)

[0040] 29 magnet (second magnet)

[0041] 31 trigger signal generator (first magnetic detection unit)

[0042] 33 magnet (first magnet)

[0043] 33N1 magnet

[0044] 33N2 magnet

[0045] 33S1 magnet

[0046] 33S2 magnet

[0047] 35 Battery

[0048] 37 Connectors

[0049] 43 Processing Module

[0050] 45 Cable

[0051] 61 magnet (second magnet)

[0052] 63 magnet (first magnet)

[0053] Ap1 angular position

[0054] Ap2 angular position

[0055] Ax Rotation Axis

[0056] D1 outer diameter

[0057] D2 inner diameter

[0058] G Clearance

[0059] S scale DETAILED DESCRIPTION

[0060] Hereinafter, embodiments will be described with reference to the drawings.

[0061] <1. Overall structure of servo system>

[0062] Reference Figure 1 , an example of the overall structure of the servo system of the implementation method is described. Figure 1 This is an explanatory diagram showing an example of the overall configuration of a servo system.

[0063] like Figure 1 As shown, the servo system 1 has a servo motor 3 and a control device 5. The servo motor 3 has an encoder 7 and a motor 9.

[0064] The motor 9 is, for example, a rotary motor in which a rotor (not shown) rotates relative to a stator (not shown). The motor 9 rotates a shaft 11 fixed to the rotor around a rotation axis Ax. The motor 9 is sometimes referred to as a servo motor alone, but in the embodiment, the structure including the motor 9 and the encoder 7 is referred to as a servo motor 3.

[0065] The encoder 7 is connected to the load side ( Figure 1 The load opposite side ( Figure 1 However, the encoder 7 may be connected to the load side of the motor 9. The encoder 7 detects at least one of the angular position information indicating the angular position of the shaft 11 (rotor) of the motor 9 within one rotation and the multi-rotation information indicating the rotation speed, and outputs position data based on the information. The encoder 7 may also detect at least one of the rotation speed or the rotation acceleration based on or instead of the angular position of the shaft 11.

[0066] The control device 5 controls the current or voltage applied to the motor 9 based on the position data output from the encoder 7, thereby controlling the rotation of the motor 9. The current or voltage applied to the motor 9 is an example of a control signal. The control device 5 controls the motor 9 to achieve the position, speed, torque, etc. indicated by the upper control signal output from the upper control device.

[0067] <2. Overall structure of the encoder>

[0068] Reference Figure 2 and Figure 3 , an example of the overall structure of encoder 7 is described. Figure 2 is an example of the overall structure of the encoder 7. Figure 3 Cross-sectional view of section II-II. Figure 3 This is a top view of an example of the overall structure of the encoder 7 as viewed from the substrate side. Figure 2 The illustration of the cable 45 and the like is appropriately omitted.

[0069] like Figure 2 As shown, the servo motor 3 has an encoder 7 and a motor 9. The motor 9 has a shaft 11, a bearing 13 and a housing 15. The bearing 13 is fixed to the housing 15, and supports the shaft 11 so that it can rotate around the rotation axis Ax. The motor 9 may also have a braking device (not shown in the figure). The braking device is, for example, arranged between the motor 9 and the encoder 7. In addition, the braking device may also be arranged on the load side of the motor 9. The braking device may also be, for example, an electromagnetic brake of an excitation working type that works by energizing the brake coil, or a non-excitation working type that works when the power to the brake coil is interrupted.

[0070] in addition, Figure 2 The lower side in the direction of the rotation axis Ax and Figure 3 The inner side of the paper in the direction of the central rotation axis Ax corresponds to the aforementioned load side. Figure 2 The upper side in the direction of the rotation axis Ax and Figure 3 The front side of the paper in the direction of the rotation axis Ax is equivalent to the aforementioned opposite side of the load. The load side is an example of one side in the direction of the rotation axis Ax, and the opposite side of the load is an example of the other side in the direction of the rotation axis Ax. In addition, hereinafter, the direction of the rotation axis Ax is appropriately referred to as the axial direction, the radial direction centered on the rotation axis Ax is referred to as the radial direction, and the circumferential direction around the rotation axis Ax is referred to as the circumferential direction.

[0071] like Figure 2 and Figure 3 As shown, the encoder 7 has a hub 17 , a disk 19 , a substrate 21 , a substrate support member 23 , an optical module 25 , a magnetic detection unit 27 , a magnet 29 , a trigger signal generator 31 , a magnet 33 , a battery 35 , a connector 37 , and an encoder cover 39 .

[0072] The hub 17 (an example of a rotating body) is fixed to the opposite side of the shaft 11 ( Figure 2 The hub 17 is an end portion of the shaft 11 (upper side) and rotates around the rotation axis Ax together with the shaft 11. In addition, the hub 17 may not be fixed to the shaft 11 itself, but may be fixed to, for example, a small-diameter encoder shaft connected to the shaft 11. The hub 17 is a supporting member that supports the disk 19, the magnet 29, and the magnet 33. The hub 17 is made of a magnetic material and is formed to cover the load side of the magnet 29 and the magnet 33. The magnetic material is not particularly limited as long as it is a magnetic material, and may be, for example, ferritic or martensitic stainless steel (SUS416, etc.), iron, etc. The bolt 40 is made of a non-magnetic material.

[0073] The disk 19 is fixed to the surface of the hub 17 on the opposite side of the load, and rotates around the rotation axis Ax together with the shaft 11. The disk 19 is made of non-magnetic material and is an annular component with a circular through hole formed in the center. As an example, the disk 19 can also be made into a complete rotating body shape formed by rotating a predetermined cross-sectional shape around the rotation axis Ax. In this case, the dimensional accuracy is improved and the disk can be manufactured inexpensively. In addition, the disk 19 can also be set as a disc-shaped component without a through hole. The disk 19 is supported by the hub 17 in a manner covering the opposite side of the load of the magnet 33. The non-magnetic material is not particularly limited as long as it is a non-magnetic material, for example, austenitic stainless steel (SUS304, etc.), aluminum, glass, etc. An annular scale S is formed on the surface of the disk 19 on the opposite side of the load. The scale S has a plurality of slits (not shown) arranged in an annular shape along the circumferential direction around the rotation axis Ax. The slits are formed on the surface of the disk 19 and are for the light source 41 (see below) from the optical module 25. Fig. 9 ) is an area where light emitted from the disk 19 is reflected or the like. The scale S includes, for example, a scale SA having an absolute pattern and a scale SI having an incremental pattern. In addition, as long as the absolute position of the disk 19 can be detected with high precision, the number of scales S formed on the disk 19 may be a single scale or more than three scales.

[0074] The substrate 21 is a printed circuit board formed by mounting printed wiring (not shown) and a plurality of circuit components on a board made of insulating material. The substrate 21 is arranged on the opposite side of the disk 19 to the load. Figure 3As shown, the substrate 21 is roughly disk-shaped. Through holes 21a for inserting fixing screws (not shown) are formed at multiple locations (for example, three locations) on the outer peripheral side in the radial direction of the substrate 21. The substrate 21 is fixed to the substrate support member 23 by fastening the fixing screws to the threaded holes of the substrate support member 23 through the through holes 21a. Alternatively, the substrate 21 is fastened to the threaded holes of the housing 15 by passing the fixing screws through the through holes 21a and the through holes of the substrate support member 23, thereby being fixed to the housing 15 together with the substrate support member 23. In addition, the substrate 21 is not limited to a single substrate, and may also be composed of multiple substrates.

[0075] The substrate support member 23 is, for example, a cylindrical member, which accommodates the hub 17 and the disk 19 and the like inside, and supports the substrate 21 to be substantially parallel to the disk 19. A threaded hole or a through hole is formed at a position of the substrate support member 23 corresponding to the through hole 21a of the substrate 21. The substrate support member 23 is fixed to the end portion of the housing 15 of the motor 9 on the opposite side of the load. In addition, the substrate support member 23 may be, for example, a plurality of cylindrical members.

[0076] The optical module 25 is arranged on the opposite side of the disk 19 to the load side of the disk 19 so as to face the disk 19. For example, the optical module 25 is arranged on the surface of the substrate 21 facing the disk 19, that is, on the surface of the load side of the substrate 21. Figure 3 As shown in FIG. 1 , the optical module 25 is arranged to face the scales SA and SI of the disk 19. The optical module 25 detects the scales SA and SI to detect the angular position information indicating the angular position within one rotation of the disk 19. The structure of the optical module 25 is not particularly limited as long as it can detect the angular position information optically. For example, as described later Fig. 9 As shown, the optical module 25 may also include a light source 41 and light receiving arrays PA and PI on the surface opposite to the disk 19. The light receiving array PA receives light reflected by the scale SA of the disk 19 and outputs an absolute signal. The light receiving array PI receives light reflected by the scale SI of the disk 19 and outputs an incremental signal. The optical module 25 is a so-called reflective optical module in which the light source 41 and the light receiving arrays PA and PI are arranged on the same side (e.g., the opposite side to the load) relative to the disk 19.

[0077] The magnetic detection unit 27 (an example of a second magnetic detection unit) detects the multi-rotation information indicating the rotation speed of the disk 19 by detecting the magnetism of the magnet 29. The magnetic detection unit 27 is, for example, arranged on the surface of the substrate 21 opposite to the disk 19, that is, the surface on the load side of the substrate 21. The magnetic detection unit 27 is arranged, for example, on the rotation axis Ax in a manner opposite to the magnet 29. The structure of the magnetic detection unit 27 is not particularly limited as long as it can detect the multi-rotation information of the disk 19 magnetically. For example, as the magnetic detection unit 27, a magnetoresistive element such as an MR element, a GMR element, a TMR element, a Hall element, a magnetoresistive element, etc. can also be used. The magnetic detection unit 27 can also be composed of a single element that can output a two-phase multi-rotation signal with a specified phase difference (for example, 90 degrees). In addition, it can also be composed of a plurality of elements that are configured to output a multi-rotation signal of one phase at an angle that becomes a specified phase difference.

[0078] The magnet 29 (an example of a second magnet) is fixed to the surface of the hub 17 that is opposite to the magnetic detection portion 27, that is, the surface on the opposite side of the hub 17 from the load. The magnet 29 is, for example, arranged on the rotation axis Ax. In addition, "arranged on the rotation axis Ax" includes not only the case where a part of the magnet 29 is located on the rotation axis Ax, but also includes the case where the rotation axis Ax passes through the hollow portion of the magnet 29, for example, when the magnet 29 is annular. The structure of the magnet 29 is not particularly limited as long as the direction of the magnetic flux detected by the magnetic detection portion 27 is reversed every time the disk 19 rotates approximately 180 degrees. For example, as described later Figure 4 As shown, the magnet 29 may be magnetized to form N poles and S poles in the diameter direction of the disk 19. Figure 4 In the figure, the portion of the magnet 29 whose magnetic pole is the N pole on the opposite side of the load is illustrated as 29N, and the portion of the magnetic pole on the opposite side of the load is illustrated as 29S. The magnet 29 is formed into a ring shape, for example. In addition, the magnet 29 can also be formed into a disk shape, for example, or the magnet 29 can be set as two magnets, for example, the N pole and the S pole. The magnetic detection unit 27 detects the direction of the magnetic flux of the magnet 29, and outputs a multi-rotation signal that changes by one cycle when the disk 19 rotates one circle as two A-phase signals and B-phase signals whose phases differ by 90 degrees from each other.

[0079] The trigger signal generator 31 (an example of the first magnetic detection unit) detects the magnetism of the magnet 33, and based on the detection of the magnetism of the magnet 33, generates a trigger signal (an example of the first electrical signal) that triggers the supply of power from the battery 35 to the magnetic detection unit 27. Figure 2As shown, the trigger signal generator 31 is arranged at a position on the opposite side of the load from the disk 19. The trigger signal generator 31 is arranged, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the surface of the substrate 21 opposite to the load. The trigger signal generator 31 detects the magnetism of the magnet 33 that has passed through the disk 19 and the substrate 21. The structure of the trigger signal generator 31 is not particularly limited as long as it can periodically generate a trigger signal through the rotation of the disk 19. For example, the trigger signal generator 31 can also be configured as a magnetic element 31a (see below) that generates a large Barkhausen effect. Figure 7 ) and coil 31b (see below) Figure 7 ). The "large Barkhausen effect" refers to the phenomenon that the magnetization direction of the magnetic element 31a is suddenly reversed when the strength of the external magnetic field applied exceeds a certain strength, which is also called a large Barkhausen jump. When this structure is adopted, the trigger signal generator 31 outputs a trigger signal such as a pulse signal from the coil 31b when the large Barkhausen effect occurs. When viewed from the axial side opposite to the load, the trigger signal generator 31 is configured so that at least a portion of it is located on the rotation trajectory of the magnet 33 (see the following description). Figure 8 ).

[0080] The magnet 33 (an example of the first magnet) is arranged at a position closer to the load side than the disk 19 and is fixed to the hub 17. The magnet 33 is fixed, for example, to the surface of the hub 17 that is opposite to the trigger signal generator 31, that is, the surface of the hub 17 on the opposite side of the load. The structure of the magnet 33 is not particularly limited as long as the magnetic field of the magnetic element 31a given to the trigger signal generator 31 is periodically reversed by the rotation of the disk 19. For example, as described later Figure 4 As shown, the four magnets 33N1, 33S1, 33N2, and 33S2 may be arranged at intervals of approximately 90 degrees in the circumferential direction in a manner that the magnetic poles are alternately different. Figure 4 In the figure, the magnets 33 whose magnetic poles on the opposite side of the load are N poles are shown as 33N1 and 33N2, and the magnets 33 whose magnetic poles on the opposite side of the load are S poles are shown as 33S1 and 33S2. The trigger signal generator 31 generates four trigger signals through the four magnets 33N1, 33S1, 33N2, and 33S2 every time the disk 19 rotates once. In addition, the number of magnets 33 is not limited to four, and can also be an even number other than four.

[0081] When no external power is supplied to the encoder 7, the battery 35 supplies power to the magnetic detection unit 27 (an example of a circuit of at least a part of the substrate). In addition to the magnetic detection unit 27, power may be supplied to other circuits of the substrate 21. The battery 35 does not supply power directly to the magnetic detection unit 27, but rather supplies power to the processing module 43 (see below). Fig. 9) supplies power. That is, the battery 35 is a supply source for supplying power to the magnetic detection unit 27 without supplying external power to the encoder 7. The battery 35 may also be a secondary battery that can be used repeatedly by being charged. The battery 35 may be, for example, a fully solid battery having a solid electrolyte. The battery 35 is, for example, arranged on the surface of the substrate 21 opposite to the disk 19, that is, the surface of the substrate 21 opposite to the load. The battery 35 is, for example, electrically connected and mechanically fixed to the substrate 21 by solder.

[0082] When external power is supplied to the encoder 7, the processing module 43 generates the position data of the disk 19 based on the angular position information and the multi-rotation information. When external power is not supplied to the encoder 7, the processing module 43 controls the switching of supplying or stopping the power from the battery 35 to the magnetic detection unit 27. The processing module 43 is, for example, arranged on the surface of the substrate 21 opposite to the disk 19, that is, the surface of the substrate 21 opposite to the load (at Figure 2 and Figure 3 (not shown in the figure). In addition, the processing module 43 may be arranged on the surface of the load side of the substrate 21. The structure of the processing module 43 is not particularly limited, and for example, it may be configured as a processor having a plurality of circuit elements such as a CPU and a memory.

[0083] The connector 37 is disposed, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the surface of the substrate 21 opposite to the load side. The connector 37 is connected to a cable 45, and the encoder 7 outputs the generated position data to the outside via the cable 45. The cable 45 is, for example, a wire. Figure 3 As shown, the cable 45 is routed through the space between the trigger signal generator 31 and the battery 35. The cable 45 is routed, for example, in a manner that passes through the rotation axis Ax. The trigger signal generator 31 and the battery 35 are configured to form a routing space for the cable 45 between each other. For example, the trigger signal generator 31 is configured on one side of the rotation axis Ax, and the battery 35 is configured on the other side of the rotation axis Ax. Alternatively, at least one of the trigger signal generator 31 and the battery 35 is configured to be substantially parallel to the routing direction of the cable 45. Figure 3 In the illustrated example, for example, the trigger signal generator 31 is arranged substantially parallel to the wiring direction of the cable 45 .

[0084] The encoder cover 39 accommodates the components of the encoder 7. The encoder cover 39 is fixed to the end of the housing 15 of the motor 9 on the opposite side of the load. The encoder cover 39 has an external connector (not shown). One end of the cable 45 is connected to the connector 37 of the substrate 21, and the other end is connected to the external connector of the encoder cover 39.

[0085] The structure of the encoder 7 described above is an example and is not limited to the above content. For example, the hub 17 can also be made of a non-magnetic material and formed so as not to cover the load side of the magnet 33. In this case, for example, the magnet 33 can be arranged on the surface of the load side of the hub 17 or the radially outer side. In addition, the disk 19 can also be made of a magnetic material and formed so as not to cover the load opposite side of the magnet 33. In this case, for example, the magnet 33 can also be fixed to the hub 17 in a manner that is located on the outer peripheral side of the outer diameter of the disk 19. In addition, the magnetic detection unit 27 can also be arranged on the surface of the substrate 21 on the opposite side of the load, and the trigger signal generator 31, the battery 35, etc. can also be arranged on the surface of the load side of the substrate 21.

[0086] <3. Structure of the magnet>

[0087] Reference Figures 4 to 8 , an example of the structure of the magnets 29 and 33 is described. Figure 4 FIG. 2 is a plan view showing an example of the arrangement structure of the magnets 29 and 33, when the hub 17 is viewed from the substrate 21 side. Figure 5 is equivalent to Figure 4 A cross-sectional view of the hub 17 at section VV, Figure 6 2 is a plan view for explaining an example of the flow of magnetic flux generated by the magnets 29 and 33. Figure 7 is a side view for explaining an example of the flow of magnetic flux generated by the magnets 29 and 33. Figure 8 2 is a plan view of the substrate 21 showing an example of the positional relationship between the magnetic detection unit 27 and the magnet 29 and the positional relationship between the trigger signal generator 31 and the magnet 33. Figure 4 The disk 19 is omitted in the figure. Figure 8 The illustration of the connector 37, the cable 45, etc. is appropriately omitted.

[0088] like Figure 4 and Figure 5As shown, the hub 17 supports the magnets 33 and 29 respectively in such a manner that the magnet 33 is arranged at a position on the outer peripheral side of the magnet 29 in the radial direction. As an example, the hub 17 has an inner peripheral portion 17a located on the inner peripheral side in the radial direction, and an outer peripheral portion 17b located on the outer peripheral side of the inner peripheral portion 17a in the radial direction and thinner in the axial direction than the inner peripheral portion 17a. The hub 17 is formed in such a manner that the surfaces of the inner peripheral portion 17a and the outer peripheral portion 17b on the load side are coplanar, and a step is formed between the inner peripheral portion 17a and the outer peripheral portion 17b on the surface on the opposite side of the load. The disk 19 is arranged on the opposite side of the load of the inner peripheral portion 17a, and the magnet 33 is arranged on the opposite side of the load of the outer peripheral portion 17b. The disk 19 is fixed to the surface of the inner peripheral portion 17a on the opposite side of the load by, for example, an adhesive, and the magnet 33 is fixed to the surface of the outer peripheral portion 17b on the opposite side of the load by, for example, an adhesive. The side surface of the inner circumference side of the magnet 33 is in contact with or close to the step of the hub 17. The surface of the inner circumference 17a of the hub 17 on the opposite side of the load protrudes toward the opposite side of the load than the surface of the magnet 33 disposed on the outer circumference 17b on the opposite side of the load. The disk 19 protrudes toward the outer circumference side in the radial direction than the inner circumference 17a. According to the above structure, Figure 5 As shown, in the axial direction, a gap G is formed between the disk 19 and the magnet 33. In addition, the outer diameter D1 of the inner peripheral portion 17a in the radial direction is smaller than the inner diameter D2 of the scale S of the disk 19 in the radial direction.

[0089] According to the above structure, the hub 17 supports the disk 19 in a manner that the disk 19 covers the load side of the magnet 33 like the back yoke and the disk 19 covers the load-opposite side of the magnet 33. That is, the hub 17 does not cover the load-opposite side of the magnet 33 like the back yoke, in other words, the hub itself does not cover the load side of the outer peripheral portion (including the portion where the scale S is formed) of the disk 19, but supports the disk 19 by the inner peripheral portion 17a in a manner that the surface on the load-opposite side of the magnet 33 faces the surface on the load side of the disk 19. Specifically, the outer diameter of the inner peripheral portion 17a of the hub 17 is smaller than the outer diameter of the outer peripheral portion 17b, and the inner peripheral portion 17a is formed to be longer than the outer peripheral portion 17b in the axial direction. The magnet 33 is arranged to abut against the axial step between the outer peripheral portion 17b and the inner peripheral portion 17a, and the disk 19 is supported by the inner peripheral portion 17a in a manner that the magnet 33 is covered. Alternatively, a component made of a material that easily transmits magnetic flux (non-magnetic material, etc.) may be sandwiched in the gap G between the surface of the magnet 33 on the opposite side of the load and the surface of the disk 19 on the load side. Alternatively, the surface of the magnet 33 on the opposite side of the load may be brought into contact with the surface of the disk 19 on the load side.

[0090] The magnet 33 is configured to alternately switch the N pole and the S pole every 90 degrees in the circumferential direction. Figure 4As shown, the magnet 33 has a plurality of (for example, four) magnets, which have magnetic poles in the axial direction by being magnetized in the axial direction respectively, and are arranged with gaps between each other along the circumferential direction in a manner that the magnetic poles of adjacent magnets are different from each other. The plurality of magnets have two magnets 33N1 and 33N2 whose opposite side of the load is magnetized to the N pole and whose load side is magnetized to the S pole, and two magnets 33S1 and 33S2 whose opposite side of the load is magnetized to the S pole and whose load side is magnetized to the N pole, totaling four magnets. These magnets 33N1, 33S1, 33N2, and 33S2 are arranged so that the magnetic poles on the opposite side of the load are alternately switched to the N pole and the S pole every 90 degrees in the circumferential direction. The plurality of magnets 33N1, 33S1, 33N2, and 33S2 possessed by the magnet 33 each have an arc shape. In addition, the magnet 33 may be formed into a shape other than an arc shape, such as a quadrilateral such as a circle, an ellipse, a square or a rectangle, or a polygon other than a quadrilateral. Furthermore, the plurality of magnets 33N1, 33S1, 33N2, and 33S2 of the magnet 33 may be arranged without gaps, or the magnet 33 may be formed into a single ring-shaped magnet magnetized along the axial direction in such a way that the magnetic pole on the opposite side of the load is alternately switched to the N pole and the S pole every 90 degrees.

[0091] The magnet 29 is configured to alternately switch the N pole and the S pole every 180 degrees in the circumferential direction. Figure 4 As shown, the magnet 29 is an annular magnet, which is magnetized in the axial direction and is configured such that the magnetic pole on the opposite side of the load is alternately switched between the N pole and the S pole every 180 degrees in the circumferential direction. The magnet 29 has a magnetic pole 29N in which the side opposite to the load is magnetized to the N pole and the load side is magnetized to the S pole, and a magnetic pole 29S in which the side opposite to the load is magnetized to the S pole and the load side is magnetized to the N pole. In addition, the magnet 29 may be configured to have a shape other than an annular shape, such as a circular plate, a quadrilateral such as a square or a rectangle, or a polygon other than a quadrilateral. In addition, the magnet 29 may be configured to have two magnets, such as an N pole and an S pole. As Figure 4 and Figure 5 As shown, the hub 17 has a magnet receiving portion 17c, and the magnet receiving portion 17c has a wall portion protruding toward the magnetic detection portion 27 side (opposite to the load side) along the outer peripheral shape of the magnet 29. The magnet 29 is received in the magnet receiving portion 17c in a manner that is engaged with the wall portion, and is fixed to the bottom and wall portion of the magnet receiving portion 17c by, for example, an adhesive. The magnet receiving portion 17c is disposed at a position that is closer to the radial inside of the inner peripheral portion 17a. A circular through hole 19a corresponding to the magnet receiving portion 17c is formed in the center portion of the disk 19, and the through hole 19a abuts against the wall portion of the magnet receiving portion 17c, whereby the disk 19 is positioned. The axial height of the wall portion of the magnet receiving portion 17c is not particularly limited, but is preferably 0.1 mm in diameter. Figure 5 In the example shown, the wall portion is lower than the magnet 29. Alternatively, the wall portion may be equal to the magnet 29 or higher in height.

[0092] like Figure 4 As shown, at least one of the magnets 33N1, 33S1, 33N2, 33S2 and the magnet 29 constituting the magnet 33 is arranged so that the angular position Ap1 of the boundary between the magnetic pole 29N and the magnetic pole 29S in the magnet 29 is offset by approximately 45 degrees from the angular position Ap2 of the center of any magnet 33N1, 33S1, 33N2, 33S2 in the circumferential direction. In addition, the angular difference between the angular position Ap1 and the angular position Ap2 is not limited to 45 degrees, as long as it is an angle greater than 0 degrees (preferably close to 45 degrees).

[0093] like Figure 6 and Figure 7 As shown, the magnetic flux Mf1 of the magnet 29 is an arc-shaped magnetic flux that comes out from the magnetic pole 29N on the radial inner side opposite to the load side of the hub 17, passes through the magnetic detection part 27, and enters the magnetic pole 29S. The magnetic flux Mf1 is a magnetic flux with a specified width that extends from the vicinity of the center of the magnetic pole 29N toward the vicinity of the center of the magnetic pole 29S. In addition, the magnetic flux can also be called a magnetic field, a magnetic field, or a magnetic field. Due to the synergistic effect of the magnet 29 being magnetized in the axial direction and the hub 17 made of magnetic material serving as a back yoke, the intensity of the magnetic flux Mf1 is increased, and the magnetic flux passing through the magnetic detection part 27 can be increased. In addition, the wall portion of the magnet storage portion 17c can be used to suppress the magnetic flux Mf1 from diffusing radially outward and concentrate it on the side of the magnetic detection part 27, thereby reducing the magnetic interference with the magnet 33 on the outer peripheral side.

[0094] The magnetic flux Mf2 of the magnet 33 is a total of four magnetic fluxes, including two arc-shaped magnetic fluxes that come out of the magnet 33N1 and enter the magnet 33S1 or the magnet 33S2 on the radially outer side opposite to the load side of the hub 17, and two arc-shaped magnetic fluxes that come out of the magnet 33N2 and enter the magnet 33S1 or the magnet 33S2. The magnetic flux Mf2 is a magnetic flux with a predetermined width that goes from the vicinity of the center of the magnet 33N1 toward the vicinity of the center of the magnet 33S1 or the magnet 33S2, and from the vicinity of the center of the magnet 33N2 toward the vicinity of the center of the magnet 33S1 or the magnet 33S2. Due to the rotation of the hub 17, any magnetic flux Mf2 passes through the trigger signal generator 31, generating a large Barkhausen effect that reverses the magnetization direction of the magnetic element 31a. The magnets 33N1, 33S1, 33N2, and 33S2 are magnetized in the axial direction, and the outer peripheral portion 17b of the hub 17 made of a magnetic material serves as a synergistic effect to increase the intensity of the magnetic flux Mf2, thereby increasing the amount of magnetic flux passing through the trigger signal generator 31. In addition, by arranging the magnets 33N1, 33S1, 33N2, and 33S2 with gaps between them, the arc shape of the magnetic flux Mf2 formed between the magnets can be increased and easily reach the trigger signal generator 31.

[0095] The arrangement of the magnetic detector 27 and the trigger signal generator 31 is optimized in accordance with the magnetic flux Mf1 of the magnet 29 and the magnetic flux Mf2 of the magnet 33. Figure 8 As shown, the magnetic detection unit 27 is arranged on the surface of the load side of the substrate 21 on the rotation axis Ax in a manner opposite to the magnet 29 and located approximately at the center of the magnetic flux Mf1. The trigger signal generator 31 is arranged on the surface of the substrate 21 on the opposite side of the load in a manner radially located approximately at the center of the magnetic flux Mf2. Specifically, the center of the trigger signal generator 31 is arranged to be located slightly radially inward of the rotation trajectory of the magnets 33N1, 33S1, 33N2, and 33S2. In addition, the circumferential installation angle of the magnetic detection unit 27 and the magnet 29 is set based on the phase angle of the trigger signal generated by the trigger signal generator 31 and the phase angle of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb generated by the processing module 43, taking into account the hysteresis of the phase angle of the trigger signal. This content will be described later.

[0096] <4. Functional structure of processing module>

[0097] Reference Fig. 9 , an example of the functional structure of the processing module 43 is described. Fig. 9 It is a block diagram showing an example of the functional structure of the processing module 43.

[0098] The processing module 43 generates the position data of the disk 19 based on both the angular position information and the multi-rotation information when external power is supplied to the encoder 7, and generates the multi-rotation amount of the disk 19 based on the multi-rotation information detected by the magnetic detection unit 27 using the power supplied from the battery 35 when external power is not supplied to the encoder 7. An example of a functional structure for realizing such functions of the processing module 43 is described below.

[0099] like Fig. 9 As shown, the processing module 43 includes an angle position signal generating unit 47 , an A-phase multi-rotation signal generating unit 49 , a B-phase multi-rotation signal generating unit 51 , a counter 53 , a position data generating unit 55 and a recording unit 57 .

[0100] The angular position signal generating unit 47 determines the absolute position within one rotation of the disk 19 based on the output of the light receiving array PA. The method for determining the absolute position is not particularly limited. For example, it is also possible that the multiple light receiving elements of the light receiving array PA process the light receiving or non-light receiving one by one as a bit based on whether the scale SA with an absolute pattern is detected, and output a multi-bit absolute signal. In this case, the angular position signal generating unit 47 decodes the absolute position of the bit pattern encrypted (encoded) as a serial bit pattern based on the absolute signal to determine the absolute position.

[0101] The angular position signal generating unit 47 determines the relative position within one rotation of the disk 19 based on the output of the light receiving array PI. For example, the plurality of light receiving elements of the light receiving array PI may output incremental signals based on the detection results of the scale SI having an incremental pattern. In this case, the angular position signal generating unit 47 determines the position within one pitch of the incremental pattern based on the incremental signal.

[0102] The angular position signal generating unit 47 generates an angular position signal As indicating a high-precision angular position within one rotation of the disk 19 by superimposing a position within one pitch determined by the incremental signal on an absolute position determined by the absolute signal.

[0103] The A-phase multi-rotation signal generating unit 49 converts the A-phase signal from the magnetic detection unit 27 into a rectangular wave signal to generate an A-phase multi-rotation signal Ma (an example of a second electrical signal. See the following). Fig.12 and Fig.13 ). As described above, the direction of the magnetic flux of the magnet 29 is reversed within a rotation angle range of approximately 180 degrees, and therefore, the duty cycle of the A-phase multi-rotation signal Ma is 50%, and each rotation of the disk 19 becomes a pulse signal. The A-phase multi-rotation signal generating unit 49 is, for example, a comparator. In addition, the "second electrical signal generated by the second magnetic detection unit" includes the A-phase multi-rotation signal Ma, which is a pulse signal generated by binarizing the A-phase signal output from the magnetic detection unit 27 as an analog signal by the A-phase multi-rotation signal generating unit 49.

[0104] The B-phase multi-rotation signal generating unit 51 converts the B-phase signal from the magnetic detection unit 27 into a rectangular wave signal to generate a B-phase multi-rotation signal Mb (an example of a second electrical signal. See the following). Fig.12 and Fig.13 ). The B-phase multi-rotation signal Mb has a duty cycle of 50% similar to the A-phase multi-rotation signal Ma, and becomes a pulse signal every time the disk 19 rotates one circle. The B-phase multi-rotation signal Mb is 90 degrees out of phase with the A-phase multi-rotation signal Ma. The B-phase multi-rotation signal generating unit 51 is, for example, a comparator. In addition, the "second electrical signal generated by the second magnetic detection unit" includes the B-phase multi-rotation signal Mb, which is a pulse signal generated by binarizing the B-phase signal output from the magnetic detection unit 27 as an analog signal by the B-phase multi-rotation signal generating unit 51.

[0105] The counter 53 performs a counting operation to count the multi-rotation amount indicating the rotation speed of the disk 19 based on the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb, and generates a multi-rotation signal Rn. The counter 53 outputs the multi-rotation signal Rn as a result of the counting operation to the position data generating unit 55.

[0106] When external power is supplied to the encoder 7, the processing module 43 enters the active mode. In the active mode based on external power, the processing module 43 supplies power to the magnetic detection unit 27. The position data generation unit 55 synthesizes the angle position signal As and the multi-rotation signal Rn to generate position data, and outputs it to the control device 5. When external power is not supplied to the encoder 7, the processing module 43 switches to the sleep mode. In the sleep mode, the processing module 43 stops the power supply to the magnetic detection unit 27. In the sleep mode, the processing module 43 stops various calculation processes including the generation of position data, but it does not become a completely stopped state, and the start-up state is maintained by the power supplied from the battery 35.

[0107] As described above, the trigger signal generator 31 generates a trigger signal by the rotation of the disk 19. When the processing module 43 receives a trigger signal from the trigger signal generator 31 in the sleep mode, it returns to the active mode by the power supplied from the battery 35. In the active mode based on the battery 35, the processing module 43 supplies power to the magnetic detection unit 27 and obtains the A-phase signal and the B-phase signal from the magnetic detection unit 27. The counter 53 receives the A-phase multi-rotation signal Ma from the A-phase multi-rotation signal generating unit 49 and the B-phase multi-rotation signal Mb from the B-phase multi-rotation signal generating unit 51, and performs counting operation processing. The counter 53 records the multi-rotation signal Rn as a result of the counting operation processing in the recording unit 57. After obtaining the A-phase signal and the B-phase signal from the magnetic detection unit 27, the processing module 43 stops the power supply from the battery 35 to the magnetic detection unit 27. For example, the power supply to the magnetic detection unit 27 may be stopped before the counting operation processing starts.

[0108] The recording unit 57 records the multi-rotation signal Rn from the counter 53. The recording unit 57 is not particularly limited as long as it is a non-volatile memory that can read and write data and can also maintain the recorded content when power is not supplied. For example, a ferroelectric memory or the like can be used as the recording unit 57. The recording unit 57 is built into the processing module 43. In addition, the recording unit 57 can also be provided outside the processing module 43.

[0109] When the encoder 7 is restored from a state in which external power is not supplied to the encoder 7, the position data generating unit 55 reads the multi-rotation signal Rn recorded in the recording unit 57, and synthesizes it with the angle position signal As output from the angle position signal generating unit 47 to generate an initial value of the position data. Thereafter, the processing module 43 performs a normal position data generating process when the encoder 7 is supplied with external power.

[0110] The processing in the above-mentioned angular position signal generating unit 47, A-phase multi-rotation signal generating unit 49, B-phase multi-rotation signal generating unit 51, counter 53, position data generating unit 55, recording unit 57, etc. is not limited to the example of sharing of these processing. For example, it can be processed by a smaller number of processing units (for example, one processing unit), or it can be processed by a more subdivided processing unit. The processing module 43 can also be a part that only supplies power to the magnetic detection unit 27 installed by an actual device, and the functions of the other above-mentioned processing units are installed by a program executed by a CPU (not shown). Part or all of the functions of each processing unit can also be installed by an actual device such as an ASIC, FPGA or other circuits.

[0111] <5. Magnetic Detection Unit and Magnet Installation Angle Based on the Phase Angle of the Trigger Signal and the Multi-rotation Signal>

[0112] In the encoder 7 of the embodiment, the hysteresis of the phase angle of the trigger signal is taken into consideration to set the circumferential installation angle of the magnetic detection unit 27 and the magnet 29 based on the phase angle of the trigger signal generated by the trigger signal generator 31 and the phase angle of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb generated by the processing module 43. Figure 10 to Figure 13 , and explain its details. Fig.10 1 is an explanatory diagram showing an example of the angular position of the magnet 33 when the trigger signal is generated when the disk 19 rotates forward. Fig.11 This is an explanatory diagram showing an example of the angular position of the magnet 33 when the trigger signal is generated when the disk 19 is reversed. Fig.12 It is an explanatory diagram showing an example of the waveforms of the trigger signal, the A-phase multi-rotation signal Ma, and the B-phase multi-rotation signal Mb when the hysteresis of the phase angle of the trigger signal is large. Fig.13 1 is an explanatory diagram showing an example of the waveforms of the trigger signal, the A-phase multi-rotation signal Ma, and the B-phase multi-rotation signal Mb when the hysteresis of the phase angle of the trigger signal is small. Fig.10 and Fig.11 The magnet 29 and the like are omitted in the figure. In addition, when viewed from the opposite side of the load in the axial direction, for example, the case where the magnet 33 (hub 17, disk 19) rotates in the clockwise direction (an example of the first direction) is referred to as positive rotation, and the case where the magnet 33 rotates in the counterclockwise direction (an example of the second direction) is referred to as reverse rotation. In addition, for example, the circumferential center position of the gap between the magnet 33N1 and the magnet 33S2 (at Fig.10 as well as Fig.11 The case where the magnet 33N1 (shown by a black circle) is located at the origin OP as a predetermined reference angle is taken as a reference, and the rotation angle (phase angle) of the circumferential center position of the gap between the magnet 33N1 and the magnet 33S2 in the forward direction relative to the origin OP is set to θ.

[0113] For the trigger signal generator 31, when the center position between the N pole and the S pole comes to the bottom of the trigger signal generator 31, the magnetic field reaches the maximum value. When the hub 17 rotates 45 degrees and the center position of the magnetic pole of the N pole or the S pole comes to the bottom of the trigger signal generator 31, the magnetic field becomes zero. When the angle is slightly ahead of this point and the magnetic field applied to the trigger signal generator 31 in the opposite direction exceeds a certain intensity, a trigger signal is generated. In an embodiment, the trigger signal generator 31 generates a trigger signal at a predetermined first phase angle based on the magnetic field detected by the magnet 33 when the hub 17 rotates forward. As an example, for example, in Fig.10 and Fig.12 In the example shown, when the magnet 33 rotates forward, the trigger signal generator 31 generates a trigger signal at each timing when θ becomes 50 degrees, 140 degrees, 230 degrees, and 320 degrees (an example of the first phase angle). In addition, when the magnet 33 rotates reversely, the trigger signal generator 31 generates a trigger signal at a second phase angle based on the detected magnetism of the magnet 33. As an example, for example, Fig.11 and Fig.12 In the example shown, when the magnet 33 is reversed, the trigger signal generator 31 generates a trigger signal at each timing when θ becomes 310 degrees, 220 degrees, 130 degrees, and 40 degrees (an example of the second phase angle). Figure 10 to Figure 12 In the example shown, in forward rotation, a trigger signal is generated when the center position between the N pole and the S pole becomes a phase angle of -40 degrees relative to the origin OP, and in reverse rotation, a trigger signal is generated when the center position between the N pole and the S pole becomes a phase angle of +40 degrees relative to the origin OP. That is, Figure 10 to Figure 12 This corresponds to a case where the phase angle hysteresis of the trigger signal is ±40 degrees.

[0114] The phases of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb are 90 degrees different from each other, and the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb are pulse-shaped signals that switch high and low at a third phase angle. Fig.12 In the example shown, the A-phase multi-rotation signal Ma switches between high and low when the phase angle is 0 degrees and 180 degrees (an example of the third phase angle), and the B-phase multi-rotation signal Mb switches between high and low when the phase angle is 90 degrees and 270 degrees (an example of the third phase angle). At least one of the magnet 29 and the magnetic detection unit 27 is configured by adjusting the circumferential installation angle in such a manner that the third phase angle has a phase difference of more than a specified angle relative to the first phase angle and the second phase angle. The reason for setting the phase difference of more than a specified angle is as follows.

[0115] After the processing module 43 receives the trigger signal and transfers from the sleep mode to the active mode, a slight time delay actually occurs before the counter 53 reads the A-phase multi-rotation signal Ma from the A-phase multi-rotation signal generating unit 49 and the B-phase multi-rotation signal Mb from the B-phase multi-rotation signal generating unit 51. Sometimes the rotation angle advances within the time delay, and the values ​​of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb at the moment the trigger signal is generated and the values ​​of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb at the moment the counter 53 reads change. The possibility of value changes occurring at a high rotation speed becomes higher. Therefore, it is desirable to set a phase difference of more than a specified angle between the timing (the first phase angle and the second phase angle) of the generation of the trigger signal and the timing (the third phase angle) of the high and low switching of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb, so as to avoid unstable detection caused by reading near the timing of the high and low switching. For example, the above-mentioned time delay at the highest rotation speed of the motor as the most stringent condition can also be considered to determine the phase difference of more than a specified angle. Specifically, at the highest rotation speed (for example, a rotation speed of 6000 revolutions per minute), it takes about 0.5 milliseconds from the generation of the trigger until the counter 53 completes the reading of the values ​​of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb, which is about 20 degrees if converted into an angle. Therefore, "above a predetermined angle" is preferably above 20 degrees, and more preferably above 30 degrees.

[0116] exist Fig.12 In the example shown, the installation angle of at least one of the magnet 29 and the magnetic detection unit 27 is adjusted and configured in such a manner that the third phase angle (0 degrees, 90 degrees, 180 degrees, 270 degrees) has a phase difference (40 degrees in this example) of a predetermined angle or more relative to the first phase angle (50 degrees, 140 degrees, 230 degrees, 320 degrees) and the second phase angle (40 degrees, 130 degrees, 220 degrees, 310 degrees). Ideally, the installation angle of at least one of the magnet 29 and the magnetic detection unit 27 is adjusted so that the third phase angle (0 degrees, 90 degrees, 180 degrees, 270 degrees) is located between the first phase angle and the second phase angle (320 degrees and 40 degrees, 50 degrees and 130 degrees, 140 degrees and 220 degrees, 230 degrees and 310 degrees) corresponding to each other.

[0117] Fig.12 The shaded portion of is an example of the timing at which the counter 53 of the processing module 43 reads the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb. Fig.12In the example shown, during forward rotation, after a trigger signal is generated at a timing of θ of 50 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 50 degrees to 90 degrees. Similarly, after a trigger signal is generated at a timing of θ of 140 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 140 degrees to 180 degrees. After a trigger signal is generated at a timing of θ of 230 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 230 degrees to 270 degrees. After a trigger signal is generated at a timing of θ of 320 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 320 degrees to 0 degrees (360 degrees). On the other hand, during reversal, after a trigger signal is generated at a timing when θ is 310 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 310 degrees to 270 degrees. Similarly, after a trigger signal is generated at a timing when θ is 220 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 220 degrees to 180 degrees. After a trigger signal is generated at a timing when θ is 130 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 130 degrees to 90 degrees. After a trigger signal is generated at a timing when θ is 40 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 40 degrees to 0 degrees. By reading the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb within the above-mentioned phase angle range by counter 53, unstable detection caused by reading near the timing of high and low switching can be avoided, and the multi-rotation amount of the disk 19 can be stably counted.

[0118] In addition, in the above description, the case where the hysteresis of the phase angle of the trigger signal is relatively large (±40 degrees) is described, but depending on the device structure, the case where the hysteresis is small is also considered. Fig.13 In the example shown, when the magnet 33 rotates forward, the trigger signal generator 31 generates a trigger signal at each timing when θ becomes 80 degrees, 170 degrees, 260 degrees, and 350 degrees (an example of the first phase angle). In addition, when the magnet 33 rotates reversely, the trigger signal generator 31 generates a trigger signal at each timing when θ becomes 280 degrees, 190 degrees, 100 degrees, and 10 degrees (an example of the second phase angle). Fig.13 In the example shown, in forward rotation, a trigger signal is generated when the center position between the N pole and the S pole becomes a phase angle of -10 degrees relative to the origin OP, and in reverse rotation, a trigger signal is generated when the center position between the N pole and the S pole becomes a phase angle of +10 degrees relative to the origin OP. That is, Fig.13 This corresponds to a case where the phase angle hysteresis of the trigger signal is ±10 degrees.

[0119] exist Fig.13 In the example shown, the A-phase multi-rotation signal Ma switches between high and low when the phase angle is, for example, 135 degrees and 315 degrees (an example of the third phase angle), and the B-phase multi-rotation signal Mb switches between high and low when the phase angle is, for example, 45 degrees and 225 degrees (an example of the third phase angle). Based on the above reasons, at least one of the magnet 29 and the magnetic detection unit 27 is configured to adjust the circumferential installation angle in such a way that the third phase angle has a phase difference of more than a specified angle relative to the first phase angle and the second phase angle. Fig.13 In the example shown, the mounting angle of at least one of the magnet 29 and the magnetic detection unit 27 is adjusted and arranged so that the third phase angle (45 degrees, 135 degrees, 225 degrees, 315 degrees) has a phase difference of a predetermined angle or more (35 degrees in this example) with respect to the first phase angle (80 degrees, 170 degrees, 260 degrees, 350 degrees) and the second phase angle (10 degrees, 100 degrees, 190 degrees, 280 degrees), respectively. Ideally, the mounting angle of at least one of the magnet 29 and the magnetic detection unit 27 is preferably adjusted so that the third phase angle (45 degrees, 135 degrees, 225 degrees, 315 degrees) is located between the first phase angle and the second phase angle (350 degrees and 100 degrees, 80 degrees and 190 degrees, 170 degrees and 280 degrees, 260 degrees and 10 degrees) corresponding to each other.

[0120] Fig.13 The shaded portion of is an example of the timing at which the counter 53 of the processing module 43 reads the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb. Fig.13In the example shown, during forward rotation, after a trigger signal is generated at a timing of 80 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 80 degrees to 135 degrees. Similarly, after a trigger signal is generated at a timing of 170 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 170 degrees to 225 degrees. After a trigger signal is generated at a timing of 260 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 260 degrees to 315 degrees. After a trigger signal is generated at a timing of 350 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 350 degrees to 45 degrees. On the other hand, during reversal, after a trigger signal is generated at a timing when θ is 280 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 280 degrees to 225 degrees. Similarly, after a trigger signal is generated at a timing when θ is 190 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 190 degrees to 135 degrees. After a trigger signal is generated at a timing when θ is 100 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in a range of θ of, for example, 100 degrees to 45 degrees. After a trigger signal is generated at a timing when θ is 10 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in a range of θ of, for example, 10 degrees to 315 degrees. By reading the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb within the above-mentioned phase angle range by counter 53, unstable detection caused by reading near the timing of high and low switching can be avoided, and the multi-rotation amount of the disk 19 can be stably counted.

[0121] In addition, the above waveform is an example, and the phase angle hysteresis of the trigger signal may be an angle other than the above, and the timing for reading the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb may be outside the above range.

[0122] <6. Effects of Implementation Methods>

[0123] As described above, in the encoder 7 of the embodiment, the disk 19 and the magnet 33 are fixed to the rotatable hub 17, and rotate around the rotation axis Ax together with the hub 17. The magnet 33 is arranged at a position closer to the load side than the disk 19 in the axial direction. The trigger signal generator 31 that detects the magnetism of the magnet 33 is arranged at a position closer to the load side than the disk 19 in the axial direction. According to the encoder 7 of the embodiment, the axial dimension of the encoder 7 can be miniaturized compared to the case where both the magnet 33 and the trigger signal generator 31 are arranged on either the load side or the load opposite side in the axial direction with respect to the disk 19.

[0124] In the embodiment, the hub 17 may be made of a magnetic material, and the hub 17 may be formed to cover the load side of the magnet 33. In this case, the hub 17 can function as a back yoke to increase the strength of the magnetic field generated from the magnet 33 on the trigger signal generator 31 side. In addition, the hub 17 can function as a magnetic shield to block leakage magnetic flux from the motor and brake device arranged on the load side of the encoder 7, thereby preventing the trigger signal generator 31 and the magnetic detection unit 27 from reducing the magnetic detection accuracy. In addition, it is also possible to prevent the leakage magnetic flux from affecting the electronic components mounted on the substrate 21 such as the optical module 25.

[0125] In the embodiment, the disk 19 may be made of a non-magnetic material, the hub 17 may support the disk 19 in a manner that the disk 19 covers the load-opposite side of the magnet 33, and the trigger signal generator 31 may detect the magnetism of the magnet 33 that has passed through the disk 19. In this case, since the disk 19 is made of a non-magnetic material, the magnetism of the magnet 33 can be passed through the disk 19 and detected by the trigger signal generator 31. Thus, compared with the case where the magnet 33 and the trigger signal generator 31 are arranged radially outside the disk 19, the radial dimension of the encoder 7 can be miniaturized.

[0126] In the embodiment, the encoder 7 may also have a gap G formed in the axial direction between the disk 19 and the magnet 33. Assuming that the disk 19 is in contact with the magnet 33, the distance between the scale S of the disk 19 and the optical module 25 may change with the rotation of the disk 19 due to the unevenness of the surface of the magnet 33 or the influence of the adhesive between the disk 19 and the magnet 33. According to the encoder 7 of the embodiment, by providing the gap G between the disk 19 and the magnet 33, the distance between the scale S of the disk 19 and the optical module 25 can be prevented from changing due to the above reasons, and the detection accuracy of the scale S by the optical module 25 can be ensured.

[0127] In the embodiment, the hub 17 may include an inner peripheral portion 17a located on the inner peripheral side in the radial direction, and an outer peripheral portion 17b located on the outer peripheral side in the radial direction of the inner peripheral portion 17a and having an axial thickness thinner than the inner peripheral portion 17a. Alternatively, the disk 19 may be arranged on the opposite side of the load of the inner peripheral portion 17a, and the magnet 33 may be arranged on the opposite side of the load of the outer peripheral portion 17b. In this case, the disk 19 may be arranged on the opposite side of the load of the magnet 33 with a simple structure. In addition, the magnet 33 may be positioned using a step between the inner peripheral portion 17a and the outer peripheral portion 17b.

[0128] In an embodiment, the surface of the inner circumference 17a of the hub 17 on the opposite side of the load may protrude toward the opposite side of the load than the surface of the magnet 33 disposed on the outer circumference 17b, and the disk 19 may protrude toward the outer circumference than the inner circumference 17a in the radial direction. In this case, a structure having a gap between the disk 19 and the magnet 33 can be realized with a simple structure.

[0129] In the embodiment, the outer diameter D1 of the inner circumference 17a in the radial direction may be smaller than the inner diameter D2 of the scale S in the radial direction. According to the encoder 7 of the embodiment, the fixing area of ​​the disk 19 fixed to the inner circumference 17a of the hub 17 can be set to an area closer to the inner circumference than the scale S. Therefore, the influence of the adhesive bonding the disk 19 and the inner circumference 17a can be eliminated, and thus the detection accuracy of the scale S by the optical module 25 can be ensured. In particular, in the case where the gap G is formed between the disk 19 and the magnet 33, the gap G can be used to prevent the change of the distance between the scale S and the optical module 25 caused by the unevenness of the surface of the magnet 33, and the influence of the adhesive can be eliminated, so that the detection accuracy can be greatly improved.

[0130] In the embodiment, the magnet 33 may also include a plurality of magnets 33N1, 33S1, 33N2, and 33S2, each of which has a magnetic pole in the axial direction and is arranged with gaps between each other in the circumferential direction in a manner that the magnetic poles of adjacent magnets are different. In this case, compared with a case where no gap is formed between the magnets, the arched shape of the magnetic flux Mf2 formed between the magnets can be increased and easily reach the trigger signal generator 31. Therefore, the degree of freedom of configuration of the trigger signal generator 31 is improved, and the design becomes easy.

[0131] In the embodiment, the plurality of magnets 33N1, 33S1, 33N2, and 33S2 of the magnet 33 may each have an arc shape. In this case, by configuring the magnet 33 in an arc shape and arranging the magnets 33 with gaps therebetween, more magnetic flux can reach the trigger signal generator 31 by utilizing the synergistic effect of the two.

[0132] In the embodiment, the encoder 7 may include: a magnet 29 fixed to the hub 17 at a position on the rotation axis Ax; and a magnetic detection unit 27 arranged to face the magnet 29 and detect the magnetism of the magnet 29, and the hub 17 may support the magnet 33 in a manner that the magnet 33 is arranged radially at a position closer to the outer circumference than the magnet 29. In this case, the magnetic circuit of the magnet 33 can be separated from the magnetic circuit of the magnet 29 in the radial direction to suppress magnetic interference.

[0133] In an embodiment, the hub 17 may be made of a magnetic material, or may have a magnet housing portion 17c for housing the magnet 29, wherein the magnet housing portion 17c has a wall portion protruding toward the magnetic detection portion 27 along the outer peripheral shape of the magnet 29. In this case, by using the wall portion of the magnet housing portion 17c to fit the magnet 29, the magnet 29 can be easily positioned and can be firmly fixed. In addition, the magnetic flux of the magnet 29 can easily reach the magnetic detection portion 27 through the wall portion, thereby improving the degree of freedom of configuration of the magnetic detection portion 27 and making the design easier. Furthermore, the magnetic field of the magnet 29 can be suppressed from expanding toward the outer peripheral side through the wall portion, thereby further reducing the magnetic interference with the magnet 33 on the outer peripheral side.

[0134] In an embodiment, the magnet 33 may be configured such that the N pole and the S pole are switched alternately every 90 degrees in the circumferential direction around the rotation axis Ax, and the magnet 29 may be configured such that the N pole and the S pole are switched alternately every 180 degrees in the circumferential direction. The magnet 33 or the magnet 29 may be configured such that the angular position Ap1 of the boundary between the N pole and the S pole in the magnet 29 is offset by approximately 45 degrees from the angular position Ap2 of the center of any pole of the magnet 33 in the circumferential direction.

[0135] Assume that in the case of a configuration structure in which the angular position Ap1 of the boundary between the N pole and the S pole of the magnet 29 is consistent with or close to the angular position Ap2 of the center of any magnetic pole of the magnet 33 in the circumferential direction, one of the N pole and the S pole of the magnet 29 is opposed to the magnet 33 of the same pole, and the other is opposed to the magnet 33 of the opposite pole. In this case, a repulsive force acts on the portion where the same poles of the magnet 33 and the magnet 29 are opposed, and an attractive force acts on the portion where the opposite poles are opposed, which may cause magnetic interference. According to the encoder 7 of the embodiment, by configuring the configuration structure in which the angular position Ap1 of the boundary between the N pole and the S pole of the magnet 29 is offset by approximately 45 degrees from the angular position Ap2 of the center of any magnetic pole of the magnet 33 in the circumferential direction, the repulsive force and attractive force acting between the magnet 33 and the magnet 29 can be reduced, and magnetic interference can be reduced.

[0136] In an embodiment, the encoder 7 may include: a magnet 29 fixed to the hub 17 at a position on the rotation axis Ax; and a magnetic detection unit 27, which is configured to be opposite to the magnet 29 and detect the magnetism of the magnet 29. The trigger signal generator 31 may also generate a trigger signal at a first phase angle based on the magnetism detected by the magnet 33 when the hub 17 rotates forward, and generate a trigger signal at a second phase angle based on the magnetism detected by the magnet 33 when the hub 17 rotates reversely. The magnet 29 and the magnetic detection unit 27 may also be configured so that the magnetic detection unit 27 (specifically, the A-phase multi-rotation signal generating unit 49 and the B-phase multi-rotation signal generating unit 51 of the processing module 43) generates a pulsed A-phase multi-rotation signal Ma and a B-phase multi-rotation signal Mb, and the pulsed A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb switch high and low at a third phase angle having a phase difference greater than a specified angle relative to the first phase angle and the second phase angle, respectively. In this case, when the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb are obtained based on the trigger signal, it is possible to avoid unstable signals caused by being obtained near the timing of high and low switching of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb, and the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb can be obtained in a stable state.

[0137] In the embodiment, the encoder 7 may also include a battery 35 that supplies power to the magnetic detection unit 27 without supplying external power, and the trigger signal generator 31 may also generate a trigger signal that triggers the supply of power from the battery 35 to the magnetic detection unit 27 based on the detection of the magnetism of the magnet 33. In this case, it is not necessary to provide a battery outside the encoder, and an encoder that does not require maintenance such as replacement of an external battery can be realized.

[0138] In the embodiment, the encoder 7 may include: a substrate 21, on which the trigger signal generator 31 is arranged on the surface of the substrate 21 on the opposite side of the load; a battery 35, which is arranged on the surface of the substrate 21 on the opposite side of the load and supplies power to at least a part of the circuit of the substrate 21 without supplying external power to the encoder 7; a connector 37, which is arranged on the surface of the substrate 21 on the opposite side of the load; and a cable 45, which is connected to the connector 37 and is wired through the space between the trigger signal generator 31 and the battery 35. In this case, by wiring the cable 45 through the space between the trigger signal generator 31 and the battery 35, the space between the trigger signal generator 31 and the battery 35, which has a relatively high height among the circuit components arranged on the substrate 21, can be effectively utilized, and the encoder 7 can be made compact. In addition, the cable length of the cable 45 can be shortened.

[0139] <7. Modifications>

[0140] In addition, the disclosed embodiment is not limited to the above, and various modifications can be made without departing from the gist and technical concept. Such modified examples are described below.

[0141] (7-1. When the gaps between magnets are filled with non-magnetic materials)

[0142] In the embodiment, the plurality of magnets 33N1, 33S1, 33N2, and 33S2 of the magnet 33 are arranged with gaps between them in the circumferential direction, but the arrangement of the magnets 33N1, 33S1, 33N2, and 33S2 is not limited to the above. Fig.14 As shown, the spacers 59 may be filled so as to fill the gaps between the magnets 33N1, 33S1, 33N2, and 33S2. The spacers 59 are made of a non-magnetic material.

[0143] According to this modification, compared with a case where gaps are provided between magnets 33N1 , 33S1 , 33N2 , and 33S2 , the weight balance of hub 17 in the circumferential direction can be improved by spacer 59 , and shaft swing and vibration can be less likely to occur when hub 17 rotates.

[0144] (7-2. When the hub is made of non-magnetic material and the magnet is magnetized in the circumferential direction)

[0145] In the embodiment, the hub 17 is made of a magnetic material, and the magnets 29 and 33 are magnetized in the axial direction to have magnetic poles in the axial direction. However, the magnetization direction of the magnets 29 and 33 is not limited to the axial direction. Fig.15 as well as Fig.16 As shown, a structure may be adopted in which the hub 17 is made of a non-magnetic material and the magnets 61 and 63 are magnetized in the circumferential direction so as to have magnetic poles in the circumferential direction. Fig.15 61 and 63 are plan views for explaining an example of the flow of magnetic flux generated by the magnets 61 and 63. Fig.16 This is a side view for explaining an example of the flow of magnetic flux generated by the magnets 61 and 63 .

[0146] like Fig.15 and Fig.16As shown, the magnet 61 is configured to be magnetized in the circumferential direction, and the magnetic pole is alternately switched to the N pole and the S pole every 180 degrees in the circumferential direction. The magnet 61 has a magnetic pole 61N magnetized to the N pole and a magnetic pole 61S magnetized to the S pole. The magnetic flux Mf3 of the magnet 61 is an arc-shaped magnetic flux that comes out from the magnetic pole 61N on the radial inner side of the opposite load side of the hub 17 and passes through the magnetic detection part 27 and enters the magnetic pole 61S. The magnetic flux Mf3 is a magnetic flux with a specified width from the vicinity of the center of the magnetic pole 61N toward the vicinity of the center of the magnetic pole 61S. When the magnet 61 is magnetized in the circumferential direction, if the hub 17 is composed of a magnetic material, the arch shape of the magnetic flux Mf3 becomes smaller due to the short circuit of the magnetic circuit, but by forming the hub 17 with a non-magnetic material, the arch shape of the magnetic flux Mf3 can be enlarged, and the magnetic flux Mf3 can be easily reached by the magnetic detection part 27.

[0147] like Fig.15 and Fig.16 As shown, the magnet 63 has a plurality of (for example, four) magnets, which are magnetized in the circumferential direction and have magnetic poles at both ends of the circumferential direction, and are arranged with gaps between each other along the circumferential direction in such a way that the magnetic poles of adjacent magnets face opposite directions. The plurality of magnets have two magnets 63A and 63C magnetized to N poles on one side of the circumferential direction and S poles on the other side of the circumferential direction, and two magnets 63B and 63D magnetized to S poles on one side of the circumferential direction and N poles on the other side of the circumferential direction, totaling four magnets. The plurality of magnets 63A, 63B, 63C, and 63D of the magnet 63 each have an arc shape.

[0148] The magnetic flux Mf4 of the magnet 63 is four arc-shaped magnetic fluxes that come out of the N pole and enter the S pole in each magnet 63A, 63B, 63C, and 63D on the radially outer side of the opposite load side of the hub 17. Each magnetic flux Mf4 is a magnetic flux with a predetermined width that extends from the vicinity of the end of the N pole side of each magnet 63A, 63B, 63C, and 63D toward the vicinity of the end of the S pole side. By the rotation of the hub 17, any magnetic flux Mf4 passes through the trigger signal generator 31, generating a large Barkhausen effect that reverses the magnetization direction of the magnetic element 31a. In the case of magnetizing the magnet 63 in the circumferential direction, if the hub 17 is made of a magnetic material, the arc shape of the magnetic flux Mf4 becomes smaller due to the short circuit of the magnetic circuit, but by making the hub 17 of a non-magnetic material, the arc shape of the magnetic flux Mf4 can be enlarged, and the magnetic flux Mf4 can easily reach the trigger signal generator 31.

[0149] Also in this modification, the magnetism of the magnet 61 can be detected satisfactorily by the magnetism detector 27 , and the magnetism of the magnet 63 can be detected satisfactorily by the trigger signal generator 31 .

[0150] (7-3. Others)

[0151] In the embodiment, the case where the encoder 7 has a battery 35 is described, but according to the situation, the various effects described in the above embodiment can be exerted even without the battery 35. Therefore, according to the desired effect, the case where the encoder 7 does not have the battery 35 is of course included in the scope of rights. Furthermore, in the embodiment, the case where the encoder 7 detects the multi-rotation amount when there is no power supply is described, but similarly, according to the situation, even the encoder that does not detect the multi-rotation amount when there is no power supply can exert the various effects described in the above embodiment. Therefore, according to the desired effect, the case where the encoder 7 does not detect the multi-rotation amount when there is no power supply is of course included in the scope of rights. In addition, as an example of the encoder 7 without a battery 35, for example, the case where power is supplied from a battery outside the encoder, the case where a plurality of trigger signal generators 31 are provided and the signals are recorded and the multi-rotation amount is calculated according to the signal, the case where the signal generated by the trigger signal generator 31 is used as power to drive the magnetic detection unit 27, etc., can be cited, but it is not limited to these examples.

[0152] In the embodiment, the case where the optical module 25 is a reflective optical module is described, but the optical module 25 may also be a transmissive optical module. In this case, for example, the light source 41 and the light receiving arrays PA and PI may be arranged on opposite sides of the disk 19, and the slits of the scales SA and SI in the disk 19 may be formed as transmissive slits (e.g., holes).

[0153] In the embodiment, a case where one incremental pattern is provided on the disk 19 is described, but a plurality of incremental patterns with different pitches may be provided on the disk 19. In this case, a higher-resolution angular position signal can be generated based on a plurality of incremental signals with different resolutions.

[0154] The problems to be solved by the implementation methods and the effects of the implementation methods are not limited to the above contents. That is, according to the implementation methods, problems not recorded in the above contents can also be solved, or effects not recorded in the above contents can be achieved. In addition, sometimes only part of the recorded problems can be solved, or only part of the recorded effects can be achieved.

[0155] In addition, in the above description, when there are descriptions of "perpendicular", "parallel", "plane", etc., these descriptions are not strictly defined. That is, these "perpendicular", "parallel", "plane" allow for tolerances and errors in design and manufacturing, and mean "substantially perpendicular", "substantially parallel", and "substantially plane".

[0156] In addition, in the above description, when there are descriptions of "same", "identical", "equal", "different" and the like in terms of external dimensions, sizes, shapes, positions, etc., such descriptions are not strictly defined. That is, these "same", "identical", "equal", "different" allow for tolerances and errors in design and manufacturing, and mean "substantially the same", "substantially the same", "substantially equal", "substantially different".

[0157] In addition to the above, the above-mentioned embodiments and the methods of each modified example may be used in combination as appropriate. In addition, although not illustrated one by one, the above-mentioned embodiments and each modified example may be implemented with various changes without departing from the gist thereof.

Claims

1. An encoder, comprising: A rotating body, which can rotate around an axis of rotation; a disk fixed to the rotating body and formed with an annular scale; an optical module, which is arranged to be opposite to the disk and detect the scale; A first magnet, which is arranged at a position closer to one side than the disk in the direction of the rotation axis and is fixed to the rotating body; as well as The first magnetism detection unit is disposed on the other side of the disk in the direction of the rotation axis, and detects magnetism of the first magnet.

2. The encoder according to claim 1, wherein The rotating body is made of a magnetic material and is formed to cover the one side of the first magnet.

3. The encoder according to claim 2, wherein: The disk is made of non-magnetic material, The rotating body supports the disk in such a manner that the disk covers the other side of the first magnet, The first magnetism detection unit detects magnetism of the first magnet that has passed through the disk.

4. The encoder according to claim 3, wherein: The encoder has a gap formed between the disk and the first magnet in the direction of the rotation axis.

5. The encoder according to claim 3, wherein: The rotating body has: an inner peripheral portion located on the inner peripheral side of the radial direction centered on the rotation axis; as well as The outer peripheral portion is located on the outer peripheral side of the radial direction relative to the inner peripheral portion, and has a thickness in the direction of the rotation axis that is thinner than that of the inner peripheral portion. The disk is arranged on the other side of the inner peripheral portion, The first magnet is disposed on the other side of the outer peripheral portion.

6. The encoder according to claim 5, wherein: The surface of the other side of the inner peripheral portion of the rotating body protrudes toward the other side more than the surface of the other side of the first magnet disposed on the outer peripheral portion. The disk protrudes toward the outer peripheral side from the inner peripheral portion in the radial direction.

7. The encoder according to claim 5 or 6, wherein: An outer diameter of the inner peripheral portion in the radial direction is smaller than an inner diameter of the scale in the radial direction.

8. The encoder according to claim 2, wherein: The first magnet includes a plurality of magnets each having a magnetic pole in the rotation axis direction and arranged with gaps therebetween in a circumferential direction around the rotation axis so that adjacent magnets have different magnetic poles.

9. The encoder according to claim 8, wherein: The plurality of magnets included in the first magnet each have an arc shape.

10. The encoder according to claim 1, wherein: The encoder also has: a second magnet fixed to the rotating body at a position on the rotating axis; as well as a second magnetism detection unit disposed opposite to the second magnet and detecting magnetism of the second magnet; The rotating body supports the first magnet so that the first magnet is arranged on the outer peripheral side of the second magnet in the radial direction around the rotation axis.

11. The encoder according to claim 10, wherein: The rotating body is made of a magnetic material and has a magnet housing portion that houses the second magnet. The magnet housing portion includes a wall portion that protrudes toward the second magnetism detecting portion along an outer peripheral shape of the second magnet.

12. The encoder according to claim 10, wherein: The first magnet is configured to alternately switch between an N pole and an S pole every 90 degrees in a circumferential direction around the rotation axis. The second magnet is configured to alternately switch between the N pole and the S pole every 180 degrees in the circumferential direction. The first magnet or the second magnet is arranged so that the angular position of the boundary between the N pole and the S pole of the second magnet is shifted by approximately 45 degrees from the angular position of the center of any magnetic pole of the first magnet in the circumferential direction.

13. The encoder according to claim 1, wherein: The encoder also has: a second magnet fixed to the rotating body at a position on the rotating axis; as well as a second magnetism detection unit disposed opposite to the second magnet and detecting magnetism of the second magnet; The first magnetic detection unit generates a first electrical signal based on a first phase angle of the magnetism of the first magnet when the rotating body rotates in a first direction, and generates the first electrical signal based on a second phase angle of the magnetism of the first magnet when the rotating body rotates in a second direction opposite to the first direction. The second magnet and the second magnetic detector are configured so that the second magnetic detector generates a pulse-shaped second electrical signal that switches between high and low at a third phase angle having a phase difference of a predetermined angle or more with respect to each of the first phase angle and the second phase angle.

14. The encoder according to claim 13, wherein: The encoder further includes a battery, and when external power is not supplied to the encoder, the battery supplies power to the second magnetic detection unit. The first magnetism detector generates the first electrical signal that triggers supply of the power of the battery to the second magnetism detector based on detection of the magnetism of the first magnetic body.

15. The encoder according to claim 1, wherein: The encoder also has: a substrate, wherein the first magnetic detection unit is arranged on the surface of the other side of the substrate; a battery disposed on the surface of the other side of the substrate and supplying power to at least a portion of the circuit of the substrate without supplying external power to the encoder; a connector disposed on the surface of the other side of the substrate; as well as A cable is connected to the connector and is routed through a space between the first magnetism detector and the battery.

16. A servo motor, comprising: a motor in which a rotor rotates relative to a stator; and The encoder according to claim 1 detects at least one of the position, speed, and acceleration of the rotor.

17. A servo system comprising: a motor in which a rotor rotates relative to a stator; The encoder according to claim 1, which detects at least one of the position, speed, and acceleration of the rotor; and A control device controls the motor based on the detection result of the encoder.

Images