Encoder, servo motor, servo system

Abstract

To provide an encoder, a servo motor, and a servo system that can be miniaturized.SOLUTION: An encoder 7 has: a hub 17 that is rotatable around a rotation axis Ax; a disk 19 that is fixed to the hub 17 and is formed with a ring-like scale S; an optical module 25 that is arranged to face the disk 19 and detects the scale S; magnets 33 that are arranged closer to a load side than the disk 19 in the direction of the rotation axis Ax and fixed to the hub 17; and a trigger signal generator 31 that is arranged closer to an anti-load side than the disk 19 in the direction of the rotation axis Ax and detects the magnetism of the magnets 33.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosed embodiments relate to an encoder, a servo motor, and a servo system.

Background Art

[0002] Patent Document 1 describes an encoder device including a position detection system including a detection unit that detects position information of a moving part, an electric signal generation unit that generates an electric signal by the movement of the moving part, and a battery that supplies at least part of the power consumed by the position detection system in response to the electric signal generated by the electric signal generation unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an encoder device, further miniaturization is desired.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide an encoder, a servo motor, and a servo system that can be miniaturized.

Means for Solving the Problems

[0006] In order to solve the above problems, according to one aspect of the present invention, there is provided a rotator rotatable around a rotation axis, a disk fixed to the rotator and having a ring-shaped scale formed thereon, an optical module disposed to face the disk for detecting the scale, a first magnet disposed on one side in the direction of the rotation axis with respect to the disk and fixed to the rotator, and a first magnetic detection unit disposed on the other side in the direction of the rotation axis with respect to the disk for detecting the magnetism of the first magnet, to which an encoder is applied.

[0007] Further, according to another aspect of the present invention, there is provided a servo motor including a motor in which a rotor rotates with respect to a stator, and the above-described encoder for detecting at least one of the position, speed, and acceleration of the rotor.

[0008] Further, according to another aspect of the present invention, there is provided a servo system including a motor in which a rotor rotates with respect to a stator, the above-described encoder for detecting at least one of the position, speed, and acceleration of the rotor, and a control device for controlling the motor based on the detection result of the encoder.

Advantages of the Invention

[0009] According to the encoder and the like of the present invention, miniaturization can be achieved.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described with reference to the drawings.

[0012] <1. Overall Configuration of Servo System> While referring to FIG. 1, an example of the overall configuration of a servo system according to an embodiment will be described. FIG. 1 is an explanatory diagram showing an example of the overall configuration of the servo system.

[0013] As shown in FIG. 1, the servo system 1 includes a servo motor 3 and a control device 5. The servo motor 3 includes an encoder 7 and a motor 9.

[0014] The motor 9 is, for example, a rotary motor in which a rotor (not shown) rotates with respect to a stator (not shown). The motor 9 rotates a shaft 11 fixed to the rotor around the rotation axis Ax. In some cases, the motor 9 alone may be referred to as a servo motor, but in the embodiment, the configuration including the motor 9 and the encoder 7 is referred to as the servo motor 3.

[0015] The encoder 7 is connected, for example, to the anti-load side (the right side in FIG. 1) opposite to the load side (the left side in FIG. 1) which is the side where the rotational force of the motor 9 is output. However, the encoder 7 may be connected to the load side of the motor 9. The encoder 7 detects at least one of angle position information representing the angular position within one rotation of the shaft 11 (rotor) of the motor 9 and multi-rotation information representing the number of rotations, and outputs position data based on such information. The encoder 7 may detect at least one of the rotational speed or rotational acceleration in addition to or instead of the angular position of the shaft 11.

[0016] The control device 5 controls the current, voltage, etc. applied to the motor 9 based on the position data output from the encoder 7, and controls the rotation of the motor 9. The current, voltage, etc. applied to the motor 9 are an example of a control signal. The control device 5 controls the motor 9 so as to realize the position, speed, torque, etc. represented by the upper control signal output from the upper control device.

[0017] <2. Overall Configuration of Encoder> With reference to FIGS. 2 and 3, an example of the overall configuration of the encoder 7 will be described. FIG. 2 is a cross-sectional view corresponding to the II-II cross-section of FIG. 3 showing an example of the overall configuration of the encoder 7. FIG. 3 is a top view of an example of the overall configuration of the encoder 7 as viewed from the substrate side. Note that in FIG. 2, illustration of the cable 45 and the like is appropriately omitted.

[0018] As shown in FIG. 2, 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 rotatably supports the shaft 11 around the rotation axis Ax. The motor 9 may have a brake device (not shown). The brake device is disposed, for example, between the motor 9 and the encoder 7. Note that the brake device may be disposed on the load side of the motor 9. The brake device may be, for example, an electromagnetic brake of an excitation operation type that operates by energizing a brake coil, or a non-excitation operation type that operates when the energization of the brake coil is interrupted.

[0019] Note that the lower side in the direction of the rotation axis Ax in FIG. 2 and the back side of the paper in the direction of the rotation axis Ax in FIG. 3 correspond to the aforementioned load side, and the upper side in the direction of the rotation axis Ax in FIG. 2 and the front side of the paper in the direction of the rotation axis Ax in FIG. 3 correspond to the aforementioned anti-load side. The load side is an example of one side in the direction of the rotation axis Ax, and the anti-load side is an example of the other side in the direction of the rotation axis Ax. Also, hereinafter, the direction of the rotation axis Ax will be appropriately referred to as the axial direction, the radial direction centered on the rotation axis Ax will be referred to as the radial direction, and the circumferential direction around the rotation axis Ax will be referred to as the circumferential direction.

[0020] As shown in FIGS. 2 and 3, 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.

[0021] The hub 17 (an example of a rotating body) is fixed to the end of the non-load side (the upper side in FIG. 2) of the shaft 11 by bolts 40, and rotates around the rotation axis Ax together with the shaft 11. Note that the hub 17 may be fixed not to the shaft 11 itself but, for example, to a small-diameter encoder shaft connected to the shaft 11. The hub 17 is a support 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 so as to cover the load side of the magnet 29 and the magnet 33. The magnetic material is not particularly limited as long as it has magnetism, and examples thereof include ferrite-based or martensitic stainless steels (such as SUS416), iron, and the like. The bolt 40 is made of a non-magnetic material.

[0022] The disk 19 is fixed to the surface of the non-load side of the hub 17 and rotates around the rotation axis Ax together with the shaft 11. The disk 19 is made of a non-magnetic material and is an annular member having a circular through-hole formed in the central portion. As an example, the disk 19 may have a perfect 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 at low cost. Note that the disk 19 may be a disk-shaped member having no through-hole. The disk 19 is supported by the hub 17 so as to cover the non-load side of the magnet 33. The non-magnetic material is not particularly limited as long as it has no magnetism, and examples thereof include austenitic stainless steels (such as SUS304), aluminum, glass, and the like. A ring-shaped scale S is formed on the surface of the non-load side of the disk 19. The scale S has a plurality of slits (not shown) arranged in a ring shape along the circumferential direction around the rotation axis Ax. The slit is a region formed on the surface of the disk 19 and that acts on the light emitted from the light source 41 (see FIG. 9 described later) of the optical module 25, such as reflection. The scale S has, for example, a scale SA having an absolute pattern and a scale SI having an incremental pattern. Note that the number of scales S formed on the disk 19 may be single or three or more as long as the absolute position of the disk 19 can be detected with high accuracy.

[0023] The substrate 21 is a printed circuit board in which printed wiring (not shown) and a plurality of circuit components are mounted on a board made of an insulating material. The substrate 21 is arranged to face the disk 19 on the anti-load side of the disk 19. As shown in FIG. 3, the substrate 21 is substantially disk-shaped. Through holes 21a for inserting fixing screws (not shown) are formed at a plurality of 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 fixing screws through the through holes 21a to the screw holes of the substrate support member 23. Alternatively, the substrate 21 is fixed to the housing 15 together with the substrate support member 23 by fastening fixing screws through the through holes 21a and the through holes of the substrate support member 23 to the screw holes of the housing 15. Note that the substrate 21 is not limited to a single substrate and may be composed of a plurality of substrates.

[0024] The substrate support member 23 is, for example, a cylindrical member that houses the hub 17, the disk 19, etc. inside and supports the substrate 21 substantially parallel to the disk 19. Screw holes or through holes are formed in the substrate support member 23 at positions corresponding to the through holes 21a of the substrate 21. The substrate support member 23 is fixed to the end portion on the anti-load side of the housing 15 of the motor 9. Note that the substrate support member 23 may be, for example, a plurality of columnar members.

[0025] The optical module 25 is arranged to face the disk 19 on the anti-load side of the disk 19. The optical module 25 is arranged, for example, on the surface of the substrate 21 facing the disk 19, that is, on the load side surface of the substrate 21. As shown in FIG. 3, the optical module 25 is arranged to face the scales SA, SI of the disk 19. By detecting the scales SA, SI, the optical module 25 detects angle position information representing the angle position within one rotation of the disk 19. The configuration of the optical module 25 is not particularly limited as long as it can optically detect the angle position information. For example, as shown in FIG. 9 to be described later, the optical module 25 may have a light source 41 and light receiving arrays PA, PI on the surface facing the disk 19. The light receiving array PA receives the light reflected by the scale SA of the disk 19 and outputs an absolute signal. The light receiving array PI receives the light reflected by the scale SI of the disk 19 and outputs an incremental signal. The optical module 25 is a so-called reflection type optical module in which the light source 41 and the light receiving arrays PA, PI are arranged on the same side (for example, the anti-load side) with respect to the disk 19.

[0026] The magnetic detection unit 27 (an example of the second magnetic detection unit) detects the magnetic rotation information representing the number of rotations of the disk 19 by detecting the magnetism of the magnet 29. The magnetic detection unit 27 is arranged, for example, on the surface of the substrate 21 facing the disk 19, that is, on the load side surface of the substrate 21. The magnetic detection unit 27 is arranged, for example, on the rotation axis Ax so as to face the magnet 29. The configuration of the magnetic detection unit 27 is not particularly limited as long as it can magnetically detect the multi-rotation information of the disk 19. For example, as the magnetic detection unit 27, a magnetoresistive element such as an MR element, a GMR element, or a TMR element, a Hall element, a magnetic impedance element, etc. may be used. The magnetic detection unit 27 may be composed of, for example, a single element capable of outputting two-phase multi-rotation signals having a predetermined phase difference (for example, 90 degrees). Also, a configuration may be adopted in which a plurality of elements each outputting a one-phase multi-rotation signal are arranged at an angle such that a predetermined phase difference is obtained.

[0027] The magnet 29 (an example of the second magnet) is fixed to the surface facing the magnetic detection unit 27 of the hub 17, that is, the surface on the anti-load side of the hub 17. The magnet 29 is arranged, for example, on the rotation axis Ax. Note that the expression "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 the case where the rotation axis Ax passes through the hollow portion of the magnet 29 when the magnet 29 is ring-shaped. The configuration of the magnet 29 is not particularly limited as long as the direction of the magnetic flux detected by the magnetic detection unit 27 is reversed every time the disk 19 rotates approximately 180 degrees. For example, as shown in FIG. 4 described later, the magnet 29 may be magnetized so that the N pole and the S pole are formed in the diameter direction of the disk 19. In FIG. 4, the portion of the magnet 29 where the anti-load side magnetic pole is the N pole is shown as 29N, and the portion where the anti-load side magnetic pole is the S pole is shown as 29S. The magnet 29 is formed in a ring shape, for example. Note that the magnet 29 may be formed in a disk shape, for example, or the magnet 29 may be composed of two magnets, an N pole and an S pole, for example. The magnetic detection unit 27 detects the direction of the magnetic flux of the magnet 29 and outputs a multi-rotation signal that changes periodically once when the disk 19 makes one rotation as two A-phase signals and B-phase signals whose phases are different by 90 degrees from each other.

[0028] The trigger signal generator 31 (an example of the first magnetic detection unit) detects the magnetism of the magnet 33 and generates a trigger signal (an example of the first electrical signal), which serves as a trigger to supply the power of the battery 35 to the magnetic detection unit 27 based on the detection of the magnetism of the magnet 33. As shown in FIG. 2, the trigger signal generator 31 is disposed on the anti-load side with respect to the disk 19. The trigger signal generator 31 is disposed, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the anti-load side surface of the substrate 21. The trigger signal generator 31 detects the magnetism of the magnet 33 that has passed through the disk 19 and the substrate 21. The configuration of the trigger signal generator 31 is not particularly limited as long as it can periodically generate a trigger signal by the rotation of the disk 19. For example, the trigger signal generator 31 may have a configuration including a magnetic element 31a (see FIG. 7 described later) that produces the giant Barkhausen effect and a coil 31b (see FIG. 7 described later). The "giant Barkhausen effect" is a phenomenon in which the magnetization direction of the magnetic element 31a suddenly reverses when the intensity of the applied external magnetic field exceeds a certain intensity, and is also called a giant Barkhausen jump. In this case, when the giant Barkhausen effect occurs, the trigger signal generator 31 outputs a trigger signal, for example, a pulse signal, from the coil 31b. The trigger signal generator 31 is arranged such that at least a part thereof is located on the rotation locus of the magnet 33 when viewed from the anti-load side in the axial direction (see FIG. 8 described later).

[0029] The magnet 33 (an example of the first magnet) is disposed on the load side with respect to the disk 19 and fixed to the hub 17. The magnet 33 is fixed, for example, to the surface of the hub 17 facing the trigger signal generator 31, that is, the surface on the side opposite to the load side of the hub 17. The configuration of the magnet 33 is not particularly limited as long as the magnetic field applied to the magnetic element 31a of the trigger signal generator 31 is periodically reversed by the rotation of the disk 19. For example, as shown in FIG. 4 described later, a configuration in which four magnets 33N1, 33S1, 33N2, and 33S2 are arranged at substantially 90-degree intervals in the circumferential direction so that the magnetic poles are alternately different may be adopted. In FIG. 4, the magnets 33 with the N pole on the side opposite to the load side are illustrated as 33N1 and 33N2, and the magnets 33 with the S pole on the side opposite to the load side are illustrated as 33S1 and 33S2. The trigger signal generator 31 generates four trigger signals each time the disk 19 makes one rotation by the four magnets 33N1, 33S1, 33N2, and 33S2. Note that the number of the magnets 33 is not limited to four, and may be an even number other than four.

[0030] The battery 35 supplies power to the magnetic detection unit 27 (an example of at least a part of the circuit on the substrate) when external power is not supplied to the encoder 7. In addition to the magnetic detection unit 27, power may be supplied to other circuits on the substrate 21. The battery 35 does not directly supply power to the magnetic detection unit 27, but supplies power via the processing module 43 (see FIG. 9 described later). That is, the battery 35 is a power supply source for supplying power to the magnetic detection unit 27 when external power is not supplied to the encoder 7. The battery 35 may be a secondary battery that can be repeatedly used by charging. The battery 35 may be, for example, an all-solid-state battery having a solid electrolyte. The battery 35 is disposed, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the surface on the side opposite to the load side of the substrate 21. The battery 35 is electrically connected and mechanically fixed to the substrate 21 by, for example, solder.

[0031] When external power is supplied to the encoder 7, the processing module 43 generates position data of the disk 19 based on the angular position information and the multi-rotation information. When no external power is supplied to the encoder 7, the processing module 43 controls the switching of the power supply or stop from the battery 35 to the magnetic detection unit 27. The processing module 43 is disposed, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the anti-load side surface of the substrate 21 (not shown in FIGS. 2 and 3). Note that the processing module 43 may be disposed on the load side surface of the substrate 21. The configuration 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.

[0032] The connector 37 is disposed, for example, on the surface of the substrate 21 opposite to the disk 19, that is, on the anti-load side surface of the substrate 21. A cable 45 is connected to the connector 37, and the encoder 7 outputs the generated position data externally via the cable 45. The cable 45 is, for example, a lead wire. As shown in FIG. 3, the cable 45 is wired through the space between the trigger signal generator 31 and the battery 35. The cable 45 is wired, for example, so as to pass on the rotation axis Ax. The trigger signal generator 31 and the battery 35 are arranged such that a wiring space for the cable 45 is formed between them. For example, the trigger signal generator 31 is disposed on one side of the rotation axis Ax, and the battery 35 is disposed on the other side of the rotation axis Ax. At least one of the trigger signal generator 31 and the battery 35 may be arranged to be substantially parallel to the wiring direction of the cable 45. In the example shown in FIG. 3, for example, the trigger signal generator 31 is arranged to be substantially parallel to the wiring direction of the cable 45.

[0033] The encoder cover 39 houses each component of the encoder 7 described above. The encoder cover 39 is fixed to the anti-load side end of the housing 15 of the motor 9. 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.

[0034] The configuration of the encoder 7 described above is an example and is not limited to the above description. For example, the hub 17 may be made of a non-magnetic material and formed so as not to cover the load side of the magnet 33. In that case, for example, the magnet 33 may be disposed on the surface of the load side of the hub 17 or on the side surface in the radial direction outside. Also, the disk 19 may be made of a magnetic material and formed so as not to cover the anti-load side of the magnet 33. In that case, for example, the magnet 33 may be fixed to the hub 17 so as to be located on the outer peripheral side rather than the outer diameter of the disk 19. Further, the magnetic detection unit 27 may be disposed on the surface of the anti-load side of the substrate 21, or the trigger signal generator 31, the battery 35, etc. may be disposed on the surface of the load side of the substrate 21.

[0035] <3. Configuration of Magnet> With reference to FIGS. 4 to 8, an example of the configuration of the magnets 29 and 33 will be described. FIG. 4 is a plan view of the hub 17 as seen from the substrate 21 side, showing an example of the arrangement configuration of the magnets 29 and 33. FIG. 5 is a cross-sectional view of the hub 17 corresponding to the V-V cross-section of FIG. 4. FIG. 6 is a plan view for explaining an example of the flow of magnetic flux by the magnets 29 and 33. FIG. 7 is a side view for explaining an example of the flow of magnetic flux by the magnets 29 and 33. FIG. 8 is a plan view of the substrate 21 showing an example of the positional relationship between the magnetic detection unit 27, the magnet 29, the trigger signal generator 31, and the magnet 33. Note that the illustration of the disk 19 is omitted in FIG. 4, and the illustrations of the connector 37, the cable 45, etc. are appropriately omitted in FIG. 8.

[0036] As shown in FIGS. 4 and 5, the hub 17 supports the magnets 33 and 29 such that the magnet 33 is arranged 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 in the radial direction with a thickness in the axial direction thinner than that of the inner peripheral portion 17a. The hub 17 is formed such that the load-side surfaces of the inner peripheral portion 17a and the outer peripheral portion 17b are flush, and a step is formed between the inner peripheral portion 17a and the outer peripheral portion 17b on the non-load-side surface. The disk 19 is arranged on the non-load side of the inner peripheral portion 17a, and the magnet 33 is arranged on the non-load side of the outer peripheral portion 17b. The disk 19 is fixed to the non-load-side surface of the inner peripheral portion 17a by, for example, an adhesive, and the magnet 33 is fixed to the non-load-side surface of the outer peripheral portion 17b by, for example, an adhesive. The inner peripheral side surface of the magnet 33 abuts or is close to the step of the hub 17. The hub 17 has the non-load-side surface of the inner peripheral portion 17a protruding on the non-load side more than the non-load-side surface of the magnet 33 arranged on the outer peripheral portion 17b. The disk 19 protrudes on the outer peripheral side of the inner peripheral portion 17a in the radial direction. With the above configuration, as shown in FIG. 5, a gap G is formed between the disk 19 and the magnet 33 in the axial direction. Also, 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.

[0037] With the above configuration, the hub 17 covers the load side of the magnet 33 like a back yoke and supports the disk 19 so that the disk 19 covers the non-load side of the magnet 33. That is, the hub 17 does not cover the non-load side of the magnet 33 like a back yoke. In other words, the hub itself does not cover the load side of the outer peripheral portion of the disk 19 (including the portion where the scale S is formed), and the disk 19 is supported by the inner peripheral portion 17a so that the non-load side surface of the magnet 33 faces the load side surface of the disk 19. Specifically, the hub 17 has an outer diameter of the inner peripheral portion 17a smaller than the outer diameter of the outer peripheral portion 17b, the inner peripheral portion 17a is formed longer in the axial direction than the outer peripheral portion 17b, the magnet 33 is arranged so as to abut on 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 so as to cover the magnet 33. Note that a component (such as a non-magnetic body) made of a material through which magnetic flux easily passes may be sandwiched in the gap G between the non-load side surface of the magnet 33 and the load side surface of the disk 19. Also, the non-load side surface of the magnet 33 and the load side surface of the disk 19 may be brought into contact with each other.

[0038] The magnet 33 is configured such that the N pole and the S pole alternate every 90 degrees in the circumferential direction. As an example, as shown in FIG. 4, the magnet 33 has magnetic poles in the axial direction by being magnetized in the axial direction, and a plurality (for example, four) of magnets are arranged with gaps between them along the circumferential direction such that the magnetic poles of adjacent magnets are different. The plurality of magnets include two magnets 33N1 and 33N2 with the anti-load side magnetized as the N pole and the load side magnetized as the S pole, and two magnets 33S1 and 33S2 with the anti-load side magnetized as the S pole and the load side magnetized as the N pole, for a total of four magnets. These magnets 33N1, 33S1, 33N2, and 33S2 are arranged such that the magnetic poles on the anti-load side alternate between the N pole and the S pole every 90 degrees in the circumferential direction. The plurality of magnets 33N1, 33S1, 33N2, and 33S2 that the magnet 33 has each have an arc shape. Note that the magnet 33 may have a shape other than an arc shape, such as a circular shape, an elliptical shape, a quadrilateral such as a square or a rectangle, a polygon other than a quadrilateral, etc. Also, the plurality of magnets 33N1, 33S1, 33N2, and 33S2 that the magnet 33 has may be arranged without gaps, or the magnet 33 may be a single ring-shaped magnet magnetized in the axial direction such that the magnetic poles on the anti-load side alternate between the N pole and the S pole every 90 degrees.

[0039] The magnet 29 is configured such that the N pole and the S pole alternate every 180 degrees in the circumferential direction. As an example, as shown in FIG. 4, the magnet 29 is a ring-shaped magnet that is magnetized in the axial direction and is configured such that the poles on the anti-load side alternate between the N pole and the S pole every 180 degrees in the circumferential direction. The magnet 29 has a magnet 29N magnetized with the anti-load side being the N pole and the load side being the S pole, and a magnet 29S magnetized with the anti-load side being the S pole and the load side being the N pole. Note that the magnet 29 may have a shape other than a ring shape, such as a disk shape, a quadrangle such as a square or a rectangle, a polygon other than a quadrangle, etc. Also, the magnet 29 may be, for example, two magnets of the N pole and the S pole. As shown in FIGS. 4 and 5, the hub 17 has a magnet housing portion 17c provided with a wall portion protruding toward the magnetic detection portion 27 side (anti-load side) along the outer peripheral shape of the magnet 29. The magnet 29 is housed in the magnet housing portion 17c so as to fit into the wall portion, and is fixed to the bottom portion and the wall portion of the magnet housing portion 17c by, for example, an adhesive. The magnet housing portion 17c is provided further radially inward of the inner peripheral portion 17a. A circular through-hole 19a corresponding to the magnet housing portion 17c is formed in the central portion of the disk 19, and the disk 19 is positioned by the through-hole 19a abutting against the wall portion of the magnet housing portion 17c. The axial height of the wall portion of the magnet housing portion 17c is not particularly limited, but in the example shown in FIG. 5, it is lower than the magnet 29. Note that the height of the wall portion may be equal to or higher than the magnet 29.

[0040] As shown in FIG. 4, at least one of the magnets 33N1, 33S1, 33N2, 33S2 constituting the magnet 33 and the magnet 29 is arranged with the circumferential angle adjusted such that the angular position Ap1 of the boundary between the magnet 29N and the magnet 29S in the magnet 29 is shifted by approximately 45 degrees from the angular position Ap2 at the center in the circumferential direction of any of the magnets 33N1, 33S1, 33N2, 33S2 of the magnet 33. Note that the angular difference between the angular position Ap1 and the angular position Ap2 is not limited to 45 degrees, and may be any angle greater than 0 degrees (although an angle closer to 45 degrees is preferable).

[0041] As shown in FIGS. 6 and 7, the magnetic flux Mf1 of the magnet 29 is an arc-shaped magnetic flux that exits from the magnetic pole 29N, passes through the magnetic detection unit 27, and enters the magnetic pole 29S on the radially inner side of the anti-load side of the hub 17. The magnetic flux Mf1 is a magnetic flux having a predetermined width that extends from the vicinity of the center of the magnetic pole 29N to the vicinity of the center of the magnetic pole 29S. Note that the magnetic flux can also be referred to as magnetism, 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 a magnetic material serving as a back yoke, the intensity of the magnetic flux Mf1 is increased, and the amount of magnetic flux passing through the magnetic detection unit 27 can be increased. Further, the wall portion of the magnet housing portion 17c can suppress the diffusion of the magnetic flux Mf1 to the outside in the radial direction and concentrate it toward the magnetic detection unit 27, so that magnetic interference with the magnet 33 on the outer peripheral side can be reduced.

[0042] The magnetic flux Mf2 of the magnet 33 is composed of a total of four arc-shaped magnetic fluxes that exit from the magnet 33N1 and enter the magnet 33S1 or the magnet 33S2, and two arc-shaped magnetic fluxes that exit from the magnet 33N2 and enter the magnet 33S1 or the magnet 33S2, on the radially outer side of the anti-load side of the hub 17. The magnetic flux Mf2 is a magnetic flux having a predetermined width that extends from the vicinity of the center of the magnet 33N1 to the vicinity of the center of the magnet 33S1 or the magnet 33S2 and from the vicinity of the center of the magnet 33N2 to the vicinity of the center of the magnet 33S1 or the magnet 33S2. When the hub 17 rotates, any one of the magnetic fluxes Mf2 passes through the trigger signal generator 31, generating the giant Barkhausen effect that reverses the magnetization direction of the magnetic element 31a. Due to the synergistic effect of the magnets 33N1, 33S1, 33N2, and 33S2 being magnetized in the axial direction and the outer peripheral portion 17b of the hub 17 made of a magnetic material serving as a back yoke, the intensity of the magnetic flux Mf2 is increased, and the amount of magnetic flux passing through the trigger signal generator 31 can be increased. Further, since the magnets 33N1, 33S1, 33N2, and 33S2 are arranged with gaps between them, the arch shape of the magnetic flux Mf2 formed between the magnets can be enlarged to facilitate reaching the trigger signal generator 31.

[0043] In correspondence with the magnetic fluxes Mf1 of the magnet 29 and Mf2 of the magnet 33, the arrangements of the magnetic detection unit 27 and the trigger signal generator 31 are optimized. As an example, as shown in FIG. 8, the magnetic detection unit 27 is arranged on the rotation axis Ax so as to face the magnet 29 and be positioned at substantially the center of the magnetic flux Mf1 on the surface of the substrate 21 on the load side. The trigger signal generator 31 is arranged on the surface of the substrate 21 on the anti-load side so as to be positioned at substantially the center of the magnetic flux Mf2 in the radial direction. Specifically, the center of the trigger signal generator 31 is arranged so as to be slightly radially inside the rotation locus of the magnets 33N1, 33S1, 33N2, 33S2. Note that the circumferential mounting angles of the magnetic detection unit 27 and the magnet 29 are set based on the phase angle of the trigger signal generated by the trigger signal generator 31 and the phase angles 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 will be described later.

[0044] <4. Functional Configuration of the Processing Module> With reference to FIG. 9, an example of the functional configuration of the processing module 43 will be described. FIG. 9 is a block diagram showing an example of the functional configuration of the processing module 43.

[0045] When external power is supplied to the encoder 7, the processing module 43 generates position data of the disk 19 based on both the angular position information and the multi-rotation information. When external power is not supplied to the encoder 7, the processing module 43 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. An example of the functional configuration for realizing such a function of the processing module 43 will be described.

[0046] As shown in FIG. 9, the processing module 43 includes an angular position signal generation unit 47, an A-phase multi-rotation signal generation unit 49, a B-phase multi-rotation signal generation unit 51, a counter 53, a position data generation unit 55, and a recording unit 57.

[0047] The angular position signal generation unit 47 identifies the absolute position within one rotation of the disk 19 based on the output of the light receiving array PA. The method for identifying the absolute position is not particularly limited. For example, each of the plurality of light receiving elements of the light receiving array PA may treat each reception or non-reception as a bit based on the detection of the scale SA having an absolute pattern, and output an absolute signal of multiple bits. In this case, the angular position signal generation unit 47 decodes the absolute position encrypted (coded) into a serial bit pattern based on the absolute signal, and identifies the absolute position.

[0048] The angular position signal generation unit 47 identifies the relative position within one rotation of the disk 19 based on the output of the light receiving array PI. For example, each of the plurality of light receiving elements of the light receiving array PI may output an incremental signal based on the detection result of the scale SI having an incremental pattern. In this case, the angular position signal generation unit 47 identifies the position within one pitch of the incremental pattern based on the incremental signal.

[0049] The angular position signal generation unit 47 generates an angular position signal As representing a high-precision angular position within one rotation of the disk 19 by superimposing the position within one pitch identified based on the incremental signal on the absolute position identified based on the absolute signal.

[0050] The A-phase multi-rotation signal generation 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 the second electrical signal. Refer to FIGS. 12 and 13 described later). As described above, since the direction of the magnetic flux of the magnet 29 is inverted every rotation angle range of approximately 180 degrees, the A-phase multi-rotation signal Ma becomes a signal with a duty ratio of 50% and one pulse per rotation of the disk 19. The A-phase multi-rotation signal generation unit 49 is, for example, a comparator. Note that 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, which is an analog signal output from the magnetic detection unit 27, by the A-phase multi-rotation signal generation unit 49.

[0051] The B-phase multi-rotation signal generation 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 the second electrical signal. Refer to FIGS. 12 and 13 described later). The B-phase multi-rotation signal Mb, similar to the A-phase multi-rotation signal Ma, has a duty ratio of 50% and becomes a signal with 1 pulse per rotation of the disk 19. The B-phase multi-rotation signal Mb has a phase difference of 90 degrees from the A-phase multi-rotation signal Ma. The B-phase multi-rotation signal generation unit 51 is, for example, a comparator. Note that 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, which is an analog signal output from the magnetic detection unit 27, by the B-phase multi-rotation signal generation unit 51.

[0052] The counter 53 executes a count arithmetic process for counting the multi-rotation amount representing 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, which is the result of the count arithmetic process, to the position data generation unit 55.

[0053] When external power is supplied to the encoder 7, the processing module 43 enters the active mode. In the active mode by external power, the processing module 43 supplies power to the magnetic detection unit 27. The position data generation unit 55 synthesizes the angular position signal As and the multi-rotation signal Rn to generate position data and outputs it to the control device 5. When no external power is supplied to the encoder 7, the processing module 43 switches to the sleep mode. In the sleep mode, the processing module 43 stops supplying power to the magnetic detection unit 27. In the sleep mode, the processing module 43 stops various arithmetic processes including the generation of position data, but does not enter a complete stop state, and the startup state is maintained by the power supplied from the battery 35.

[0054] 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 from the sleep mode by the power supplied from the battery 35 and enters the active mode. In the active mode by the battery 35, the processing module 43 supplies power to the magnetic detection unit 27 and acquires an A-phase signal and a 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 generation unit 49 and the B-phase multi-rotation signal Mb from the B-phase multi-rotation signal generation unit 51, and executes a count arithmetic process. The counter 53 records the multi-rotation signal Rn, which is the result of the count arithmetic process, in the recording unit 57. After acquiring the A-phase signal and the B-phase signal from the magnetic detection unit 27, the processing module 43 stops supplying power 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 start of the count arithmetic process.

[0055] 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 capable of reading and writing data and retaining the recorded content even when not energized. For example, a ferroelectric memory or the like may be used as the recording unit 57. The recording unit 57 is built into the processing module 43. Note that the recording unit 57 may be installed outside the processing module 43.

[0056] When the encoder 7 returns from a state where no external power is supplied to a state where external power is supplied, the position data generation unit 55 reads out the multi-rotation signal Rn recorded in the recording unit 57 and synthesizes it with the angular position signal As output from the angular position signal generation unit 47 to generate an initial value of the position data. Thereafter, the processing module 43 executes a normal position data generation process when external power is supplied to the encoder 7.

[0057] The processing and the like in the above-described angular position signal generation unit 47, A-phase multi-rotation signal generation unit 49, B-phase multi-rotation signal generation unit 51, counter 53, position data generation unit 55, recording unit 57, etc. are not limited to the examples of the division of these processes. For example, the processing may be performed by an even smaller number of processing units (for example, one processing unit), or may be performed by further subdivided processing units. The processing module 43 is implemented by an actual device only for the part that supplies power to the magnetic detection unit 27, and the functions of the other above-described processing units may be implemented by a program executed by a CPU (not shown). Part or all of the functions of each processing unit may be implemented by an actual device such as an ASIC, FPGA, or other electric circuit.

[0058] <5. Magnetic Detection Unit and Mounting Angle of Magnet Based on Trigger Signal and Phase Angle of Multi-Rotation Signal> In the encoder 7 of the embodiment, the circumferential mounting angles of the magnetic detection unit 27 and the magnet 29 are set based on the phase angle of the trigger signal generated by the trigger signal generator 31 and the phase angles 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 detailed content will be described with reference to FIGS. 10 to 13. FIG. 10 is an explanatory diagram showing an example of the angular position of the magnet 33 at the time of trigger signal generation when the disk 19 rotates forward. FIG. 11 is an explanatory diagram showing an example of the angular position of the magnet 33 at the time of trigger signal generation when the disk 19 rotates in reverse. FIG. 12 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 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. Note that the illustration of the magnet 29 and the like is omitted in FIGS. 10 and 11. Also, when viewed from the anti-load side in the axial direction, for example, when the magnet 33 (hub 17, disk 19) rotates in the clockwise direction (an example of the first direction), it is defined as forward rotation, and when the magnet 33 rotates in the counterclockwise direction (an example of the second direction), it is defined as reverse rotation. Further, for example, when the circumferential center position of the gap between the magnet 33N1 and the magnet 33S2 (illustrated as a black circle in FIGS. 10 and 11) is located at the origin OP which is a predetermined reference angle, the rotation angle (phase angle) in the forward rotation direction with respect to the origin OP of the circumferential center position of the gap between the magnet 33N1 and the magnet 33S2 is set as θ.

[0059] The trigger signal generator 31 generates a trigger signal when the magnetic field reaches its maximum value when the center position between the N pole and the S pole comes directly below the trigger signal generator 31, and when the hub 17 rotates 45 degrees and the center position of the magnetic pole of the N pole or the S pole comes directly below the trigger signal generator 31, the magnetic field becomes zero. When the intensity of the magnetic field in the opposite direction applied to the trigger signal generator 31 exceeds a certain level after that, a trigger signal is generated. In the embodiment, when the hub 17 rotates forward, the trigger signal generator 31 generates a trigger signal at a predetermined first phase angle based on the detection of the magnetism of the magnet 33. As an example, in the examples shown in FIGS. 10 and 12, when the magnet 33 rotates forward, the trigger signal generator 31 generates a trigger signal at each timing when θ is 50 degrees, 140 degrees, 230 degrees, and 320 degrees (an example of the first phase angle). Also, when the magnet 33 rotates in reverse, the trigger signal generator 31 generates a trigger signal at a second phase angle based on the detection of the magnetism of the magnet 33. As an example, in the examples shown in FIGS. 11 and 12, when the magnet 33 rotates in reverse, the trigger signal generator 31 generates a trigger signal at each timing when θ is 310 degrees, 220 degrees, 130 degrees, and 40 degrees (an example of the second phase angle). In the examples shown in FIGS. 10 to 12, in the forward rotation, a trigger signal is generated at the timing when the center position between the N pole and the S pole has a phase angle of -40 degrees with respect to the origin OP, and in the reverse rotation, a trigger signal is generated at the timing when the center position between the N pole and the S pole has a phase angle of +40 degrees with respect to the origin OP. That is, FIGS. 10 to 12 correspond to the case where the hysteresis of the phase angle of the trigger signal is ±40 degrees.

[0060] The A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb have a 90-degree phase difference from each other, and each is a pulsed signal in which high and low states are switched at the third phase angle. As an example, for instance, in the example shown in FIG. 12, the A-phase multi-rotation signal Ma switches between high and low at phase angles of 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 at phase angles of 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 arranged with its circumferential mounting angle adjusted so that the third phase angle has a phase difference of a predetermined angle or more with respect to each of the first phase angle and the second phase angle. The reason for providing a phase difference of a predetermined angle or more is as follows.

[0061] After the processing module 43 receives the trigger signal and shifts from the sleep mode to the active mode, there is a slight time delay until the counter 53 actually reads the A-phase multi-rotation signal Ma from the A-phase multi-rotation signal generation unit 49 and the B-phase multi-rotation signal Mb from the B-phase multi-rotation signal generation unit 51. During this time delay, the rotation angle advances, and the values of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb at the time when the trigger signal is generated may change from the values of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb when the counter 53 reads them. The fluctuation of the values is more likely to occur when the rotation speed is high. Therefore, it is desirable to provide a phase difference of a predetermined angle or more between the timing of the trigger signal generation (the first phase angle and the second phase angle) and the timing at which the high and low states of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb are switched (the third phase angle) to avoid unstable detection by reading near the timing of the high and low state switching. For example, considering the above-mentioned time delay at the maximum rotation speed of the motor, which is the most severe condition, the phase difference of a predetermined angle or more may be determined. Specifically, at the maximum rotation speed (for example, a rotation speed of 6000 revolutions per minute), it takes approximately 0.5 milliseconds from the trigger generation until the counter 53 completes reading the values of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb, and when converted to an angle, it is about 20 degrees. Therefore, it is preferable that "a predetermined angle or more" is 20 degrees or more. It is more desirable if it can be made 30 degrees or more.

[0062] In the example shown in FIG. 12, 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 (0 degrees, 90 degrees, 180 degrees, 270 degrees) has a phase difference (40 degrees in this example) of a predetermined angle or more with respect to each of 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, it is desirable that the mounting 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 in the middle of the corresponding first phase angle and second phase angle (320 degrees and 40 degrees, 50 degrees and 130 degrees, 140 degrees and 220 degrees, 230 degrees and 310 degrees).

[0063] The hatched portion in Fig. 12 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. In the example shown in Fig. 12, after the trigger signal is generated at the timing when θ is 50 degrees during forward rotation, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in the range where θ is, for example, from 50 degrees to 90 degrees. Similarly, after the trigger signal is generated at the timing when θ is 140 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in the range where θ is, for example, from 140 degrees to 180 degrees. After the trigger signal is generated at the timing when θ is 230 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in the range where θ is, for example, from 230 degrees to 270 degrees. After the trigger signal is generated at the timing when θ is 320 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in the range where θ is, for example, from 320 degrees to 0 degrees (360 degrees). On the other hand, during reverse rotation, after the trigger signal is generated at the 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 the range where θ is, for example, from 310 degrees to 270 degrees. Similarly, after the trigger signal is generated at the 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 the range where θ is, for example, from 220 degrees to 180 degrees. After the trigger signal is generated at the 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 the range where θ is, for example, from 130 degrees to 90 degrees. After the trigger signal is generated at the 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 the range where θ is, for example, from 40 degrees to 0 degrees. By having the counter 53 read the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb within the above phase angle range, it is possible to avoid unstable detection due to reading near the timing when high and low switch, and the multi-rotation amount of the disk 19 can be stably counted.

[0064] In the above description, the case where the hysteresis of the phase angle of the trigger signal is relatively large (±40 degrees) has been explained. However, depending on the device configuration, a case where the hysteresis is small may also be considered. As an example, for instance, in the example shown in FIG. 13, when the magnet 33 rotates forward, the trigger signal generator 31 generates a trigger signal at each timing when θ is 80 degrees, 170 degrees, 260 degrees, 350 degrees (an example of the first phase angle), for example. Further, when the magnet 33 rotates reversely, the trigger signal generator 31 generates a trigger signal at each timing when θ is 280 degrees, 190 degrees, 100 degrees, 10 degrees (an example of the second phase angle), for example. In the example shown in FIG. 13, in the forward rotation, the trigger signal is generated at the timing when the central position between the N pole and the S pole has a phase angle of -10 degrees with respect to the origin OP, and in the reverse rotation, the trigger signal is generated at the timing when the central position between the N pole and the S pole has a phase angle of +10 degrees with respect to the origin OP. That is, FIG. 13 corresponds to the case where the hysteresis of the phase angle of the trigger signal is ±10 degrees.

[0065] In the example shown in FIG. 13, for the A-phase multi-rotation signal Ma, for example, the high and low levels are switched at phase angles of 135 degrees and 315 degrees (an example of the third phase angle), and for the B-phase multi-rotation signal Mb, for example, the high and low levels are switched at phase angles of 45 degrees and 225 degrees (an example of the third phase angle). For the reasons described above, at least one of the magnet 29 and the magnetic detection unit 27 is arranged with its circumferential mounting angle adjusted so that the third phase angle has a phase difference of a predetermined angle or more with respect to each of the first phase angle and the second phase angle. In the example shown in FIG. 13, the mounting angles of at least one of the magnet 29 and the magnetic detection unit 27 are adjusted and arranged so that the third phase angle (45 degrees, 135 degrees, 225 degrees, 315 degrees) has a phase difference (35 degrees in this example) of a predetermined angle or more with respect to each of 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). Ideally, it is desirable that the mounting angles of at least one of the magnet 29 and the magnetic detection unit 27 be adjusted so that the third phase angle (45 degrees, 135 degrees, 225 degrees, 315 degrees) is positioned in the middle of the corresponding first phase angle and second phase angle (350 degrees and 100 degrees, 80 degrees and 190 degrees, 170 degrees and 280 degrees, 260 degrees and 10 degrees).

[0066] The hatched portion in FIG. 13 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. In the example shown in FIG. 13, after the trigger signal is generated at the timing when θ is 80 degrees during forward rotation, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (high) are read in the range where θ is, for example, 80 degrees to 135 degrees. Similarly, after the trigger signal is generated at the timing when θ is 170 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (high) are read in the range where θ is, for example, 170 degrees to 225 degrees. After the trigger signal is generated at the timing when θ is 260 degrees, the A-phase multi-rotation signal Ma (low) and the B-phase multi-rotation signal Mb (low) are read in the range where θ is, for example, 260 degrees to 315 degrees. After the trigger signal is generated at the timing when θ is 350 degrees, the A-phase multi-rotation signal Ma (high) and the B-phase multi-rotation signal Mb (low) are read in the range where θ is, for example, 350 degrees to 45 degrees. On the other hand, during reverse rotation, after the trigger signal is generated at the 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 the range where θ is, for example, 280 degrees to 225 degrees. Similarly, after the trigger signal is generated at the 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 the range where θ is, for example, 190 degrees to 135 degrees. After the trigger signal is generated at the 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 the range where θ is, for example, 100 degrees to 45 degrees. After the trigger signal is generated at the 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 the range where θ is, for example, 10 degrees to 315 degrees. By having the counter 53 read the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb within the above phase angle range, it is possible to avoid unstable detection due to reading near the timing when high and low switch, and it is possible to stably count the multi-rotation amount of the disk 19.

[0067] Note that the above waveforms are just examples. The hysteresis of the phase angle of the trigger signal may be at angles other than those described above, and the timing for reading the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb may also be outside the above range.

[0068] <6. Effects of the Embodiment> 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 on the load side in the axial direction with respect to the disk 19. The trigger signal generator 31 that detects the magnetism of the magnet 33 is arranged on the anti-load side in the axial direction with respect to the disk 19. According to the encoder 7 of the embodiment, the axial dimension of the encoder 7 can be reduced compared to the case where both the magnet 33 and the trigger signal generator 31 are arranged on either the load side or the anti-load side in the axial direction with respect to the disk 19.

[0069] 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 intensity of the magnetic field generated from the magnet 33 toward the trigger signal generator 31 side. Also, the hub 17 can function as a magnetic shield to block the leakage magnetic flux from the motor or brake device arranged on the load side of the encoder 7, preventing a decrease in the magnetic detection accuracy by the trigger signal generator 31 and the magnetic detection unit 27. Also, it can be prevented that the leakage magnetic flux affects the electronic components mounted on the substrate 21 such as the optical module 25.

[0070] In an embodiment, the disk 19 may be made of a non-magnetic material, the hub 17 may support the disk 19 such that the disk 19 covers the anti-load 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 transmitted through the disk 19 and detected by the trigger signal generator 31. Thereby, compared with the case where the magnet 33 and the trigger signal generator 31 are arranged on the outer side in the radial direction of the disk 19, the radial dimension of the encoder 7 can be reduced.

[0071] In an embodiment, the encoder 7 may have a gap G formed between the disk 19 and the magnet 33 in the axial direction. If the disk 19 and the magnet 33 are in contact, due to the unevenness of the surface of the magnet 33 and the influence of the adhesive interposed between the disk 19 and the magnet 33, the distance between the scale S of the disk 19 and the optical module 25 may vary as the disk 19 rotates. According to the encoder 7 of the embodiment, by providing the gap G between the disk 19 and the magnet 33, it is possible to prevent the distance between the scale S of the disk 19 and the optical module 25 from varying due to the above reasons, and ensure the detection accuracy of the scale S by the optical module 25.

[0072] In an embodiment, the hub 17 may have 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 with respect to the inner peripheral portion 17a and having a thickness in the axial direction thinner than that of the inner peripheral portion 17a. The disk 19 may be disposed on the anti-load side of the inner peripheral portion 17a, and the magnet 33 may be disposed on the anti-load side of the outer peripheral portion 17b. In this case, a configuration in which the disk 19 is disposed on the anti-load side of the magnet 33 with a simple structure can be realized. Also, the magnet 33 can be positioned using the step between the inner peripheral portion 17a and the outer peripheral portion 17b.

[0073] In an embodiment, the hub 17 may protrude toward the non-load side such that the surface of the inner peripheral portion 17a on the non-load side protrudes more toward the non-load side than the surface of the magnet 33 disposed on the outer peripheral portion 17b on the non-load side, and the disk 19 may protrude to the outer peripheral side of the inner peripheral portion 17a in the radial direction. In this case, a configuration having a gap between the disk 19 and the magnet 33 can be realized with a simple structure.

[0074] In an embodiment, the outer diameter D1 of the inner peripheral portion 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 region of the disk 19 fixed to the inner peripheral portion 17a of the hub 17 can be set to a region on the inner peripheral side of the scale S. Therefore, the influence of the adhesive for bonding the disk 19 and the inner peripheral portion 17a can be eliminated, and the detection accuracy of the scale S by the optical module 25 can be ensured. In particular, when a gap G is formed between the disk 19 and the magnet 33, the influence of the adhesive can be eliminated while preventing the variation in the distance between the scale S and the optical module 25 due to the unevenness of the surface of the magnet 33 in the gap G, so that the detection accuracy can be greatly improved.

[0075] In an embodiment, the magnet 33 may have a plurality of magnets 33N1, 33S1, 33N2, 33S2 each having a magnetic pole in the axial direction and arranged with a gap therebetween along the circumferential direction such that the magnetic poles of adjacent ones are different. In this case, compared with the case where no gap is formed between the magnets, the arch shape of the magnetic flux Mf2 formed between the magnets can be enlarged to facilitate reaching the trigger signal generator 31. Therefore, the degree of freedom in the arrangement of the trigger signal generator 31 is improved, and the design becomes easier.

[0076] In an embodiment, the plurality of magnets 33N1, 33S1, 33N2, 33S2 of the magnet 33 may each have an arc shape. In this case, by forming the magnet 33 into an arc shape and arranging it with a gap, more magnetic flux can reach the trigger signal generator 31 due to the synergistic effect of the two.

[0077] In an embodiment, the encoder 7 may include a magnet 29 fixed to the hub 17 at a position on the rotation axis center Ax, and a magnetic detection unit 27 arranged to face the magnet 29 and detect the magnetism of the magnet 29. The hub 17 may support a magnet 33 such that the magnet 33 is arranged on the outer peripheral side of the magnet 29 in the radial direction. In this case, the magnetic paths of the magnet 33 and the magnet 29 can be separated in the radial direction to suppress magnetic interference.

[0078] In an embodiment, the hub 17 may be made of a magnetic material and may have a magnet housing portion 17c that includes a wall portion protruding toward the magnetic detection unit 27 along the outer peripheral shape of the magnet 29 and houses the magnet 29. In this case, by fitting the magnet 29 with the wall portion of the magnet housing portion 17c, the magnet 29 can be easily positioned and firmly fixed. In addition, since the magnetic flux of the magnet 29 can be easily transmitted to the magnetic detection unit 27 by the wall portion, the degree of freedom in arranging the magnetic detection unit 27 is improved and the design becomes easier. Furthermore, since the wall portion can suppress the expansion of the magnetic field of the magnet 29 to the outer peripheral side, the magnetic interference with the magnet 33 on the outer peripheral side can be further reduced.

[0079] In an embodiment, the magnet 33 may be configured such that the N pole and the S pole alternate every 90 degrees in the circumferential direction around the rotation axis center Ax, and the magnet 29 may be configured such that the N pole and the S pole alternate every 180 degrees in the circumferential direction. The magnet 33 or the magnet 29 may be arranged such that the angular position Ap1 of the boundary between the N pole and the S pole in the magnet 29 is shifted by approximately 45 degrees from the angular position Ap2 at the center in the circumferential direction of any magnetic pole of the magnet 33.

[0080] If the angular position Ap1 of the boundary between the N pole and the S pole of the magnet 29 coincides with or is near the angular position Ap2 of the center in the circumferential direction of any magnetic pole of the magnet 33, one of the N pole and the S pole of the magnet 29 faces the magnet 33 of the same pole, and the other faces the magnet 33 of the opposite pole. In this case, a repulsive force acts at the location where the same poles face each other between the magnet 33 and the magnet 29, and an attractive force acts at the location where the opposite poles face each other, which may cause magnetic interference. According to the encoder 7 of the embodiment, by setting the angular position Ap1 of the boundary between the N pole and the S pole of the magnet 29 to be offset by approximately 45 degrees from the angular position Ap2 of the center in the circumferential direction of any magnetic pole of the magnet 33, the repulsive force and the attractive force acting between the magnet 33 and the magnet 29 can be reduced, and magnetic interference can be reduced.

[0081] 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. The trigger signal generator 31 may generate a trigger signal at a first phase angle based on the detection of the magnetism of the magnet 33 when the hub 17 rotates forward, and generate a trigger signal at a second phase angle based on the detection of the magnetism of the magnet 33 when the hub 17 rotates backward. The magnet 29 and the magnetic detection unit 27 may be arranged such that the magnetic detection unit 27 (specifically, the A-phase multi-rotation signal generation unit 49 and the B-phase multi-rotation signal generation unit 51 of the processing module 43) generates a pulsed A-phase multi-rotation signal Ma and a B-phase multi-rotation signal Mb whose high and low levels are switched 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. In this case, when acquiring the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb based on the trigger signal, it is possible to avoid obtaining an unstable signal by acquiring them near the timing when the high and low levels of the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb are switched, and the A-phase multi-rotation signal Ma and the B-phase multi-rotation signal Mb can be acquired in a stable state.

[0082] In an embodiment, the encoder 7 may have a battery 35 that supplies power to the magnetic detection unit 27 when no external power is supplied. The trigger signal generator 31 may generate a trigger signal that serves as a trigger to supply the power of 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 install a battery outside the encoder, and an encoder that does not require maintenance of external battery replacement can be realized.

[0083] In an embodiment, the encoder 7 includes a substrate 21 on the surface of which the trigger signal generator 31 is disposed on the anti-load side, a battery 35 that is disposed on the surface of the substrate 21 on the anti-load side and supplies power to at least a part of the circuits of the substrate 21 when no external power is supplied to the encoder 7, a connector 37 that is disposed on the surface of the substrate 21 on the anti-load side, and a cable 45 that is connected to the connector 37 and is routed through the space between the trigger signal generator 31 and the battery 35. In this case, by routing the cable 45 through the space between the trigger signal generator 31 and the battery 35, the space between the trigger signal generator 31, which is relatively tall among the circuit components disposed on the substrate 21, and the battery 35 can be effectively utilized, and the encoder 7 can be made more compact. Also, the cable length of the cable 45 can be shortened.

[0084] <7. Modification Example> Note that the disclosed embodiments are not limited to the above, and various modifications are possible without departing from the spirit and technical idea thereof. Hereinafter, such modification examples will be described.

[0085] (7-1. Case of Filling the Gap between Magnets with a Non-Magnetic Material) In the embodiment, the plurality of magnets 33N1, 33S1, 33N2, and 33S2 of the magnet 33 are arranged with gaps therebetween along the circumferential direction, but the arrangement form of the magnets 33N1, 33S1, 33N2, and 33S2 is not limited to the above. For example, as shown in FIG. 14, a spacer 59 may be filled so as to fill the mutual gaps of the magnets 33N1, 33S1, 33N2, and 33S2. The spacer 59 is made of a non-magnetic material.

[0086] According to this modification example, compared with the case where gaps are provided between the magnets 33N1, 33S1, 33N2, and 33S2, the spacer 59 can improve the weight balance in the circumferential direction of the hub 17, and it is possible to make it difficult for shaft runout, vibration, etc. to occur when the hub 17 rotates.

[0087] (7-2. When the hub is made of a non-magnetic material and the magnets are magnetized in the circumferential direction) 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 directions of the magnets 29 and 33 are not limited to the axial direction. For example, as shown in FIGS. 15 and 16, the hub 17 may be made of a non-magnetic material, and the magnets 61 and 63 may be magnetized in the circumferential direction to have magnetic poles in the circumferential direction. FIG. 15 is a plan view for explaining an example of the magnetic flux flow by the magnets 61 and 63, and FIG. 16 is a side view for explaining an example of the magnetic flux flow by the magnets 61 and 63.

[0088] As shown in FIGS. 15 and 16, the magnet 61 is magnetized in the circumferential direction, and the magnetic poles are configured to alternately switch between N poles and S poles 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 exits from the magnetic pole 61N and passes through the magnetic detection unit 27 and enters the magnetic pole 61S on the radially inner side of the anti-load side of the hub 17. The magnetic flux Mf3 is a magnetic flux having a predetermined width that travels from the vicinity of the center of the magnetic pole 61N to 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 made of a magnetic material, the arch shape of the magnetic flux Mf3 becomes smaller due to the short circuit of the magnetic path. However, by making the hub 17 of a non-magnetic material, the arch shape of the magnetic flux Mf3 can be enlarged, and the magnetic flux Mf3 can be made to reach the magnetic detection unit 27 more easily.

[0089] As shown in FIGS. 15 and 16, the magnet 63 has magnetic poles at both circumferential ends by being magnetized in the circumferential direction, and a plurality (for example, four) of magnets are arranged with gaps between them along the circumferential direction so that the directions of the magnetic poles of adjacent magnets are opposite to each other. The plurality of magnets include a total of four magnets, namely, two magnets 63A and 63C magnetized with the N pole on one circumferential side and the S pole on the other circumferential side, and two magnets 63B and 63D magnetized with the S pole on one circumferential side and the N pole on the other circumferential side. The plurality of magnets 63A, 63B, 63C, and 63D included in the magnet 63 each have an arc shape.

[0090] The magnetic flux Mf4 of the magnet 63 is four arc-shaped magnetic fluxes that emerge from the N pole and enter the S pole in each of the magnets 63A, 63B, 63C, and 63D on the radially outer side of the anti-load side of the hub 17. Each magnetic flux Mf4 is a magnetic flux having a predetermined width that extends from the vicinity of the end on the N pole side to the vicinity of the end on the S pole side of each magnet 63A, 63B, 63C, and 63D. When the hub 17 rotates, any one of the magnetic fluxes Mf4 passes through the trigger signal generator 31, generating the giant Barkhausen effect that reverses the magnetization direction of the magnetic element 31a. When the magnet 63 is magnetized in the circumferential direction, if the hub 17 is made of a magnetic material, the arch shape of the magnetic flux Mf4 becomes smaller due to the short circuit of the magnetic path. However, by configuring the hub 17 with a non-magnetic material, the arch shape of the magnetic flux Mf4 can be enlarged, making it easier for the magnetic flux Mf4 to reach the trigger signal generator 31.

[0091] Also in this modified example, the magnetic detection unit 27 can detect the magnetism of the magnet 61 well, and the trigger signal generator 31 can detect the magnetism of the magnet 63 well.

[0092] (7-3. Others) In the embodiment, the case where the encoder 7 has the battery 35 has been described. However, various effects described in the above embodiment may be exhibited even without the battery 35 in some cases. Therefore, depending on the desired effects, it goes without saying that the case where the encoder 7 does not have the battery 35 is also included in the scope of rights. Further, in the embodiment, the case of detecting the multi-rotation amount when there is no power supply to the encoder 7 has been described. Similarly, various effects described in the above embodiment may be exhibited even by an encoder that does not detect the multi-rotation amount when there is no power supply in some cases. Therefore, depending on the desired effects, it goes without saying that the case where the multi-rotation amount is not detected when there is no power supply to the encoder 7 is also included in the scope of rights. Note that examples of the encoder 7 not having the battery 35 include, for example, the case where power is supplied from a battery outside the encoder, the case of having a plurality of trigger signal generators 31 and recording those signals and calculating the multi-rotation amount from those signals, the case of driving the magnetic detection unit 27 etc. using the signal generated by the trigger signal generator 31 as power, etc., but are not limited to these examples.

[0093] In the embodiment, the case where the optical module 25 is a reflection type optical module has been described. However, the optical module 25 may be a transmission type optical module. In this case, for example, the light source 41 and the light receiving arrays PA, PI may be arranged on opposite sides with the disk 19 interposed therebetween, and each slit of the scales SA, SI on the disk 19 may be formed as a transmission slit (for example, a hole).

[0094] In the embodiment, the case of providing one type of incremental pattern on the disk 19 has been described. However, a plurality of types of incremental patterns with different pitches may be provided on the disk 19. In this case, it becomes possible to generate a higher resolution angular position signal based on a plurality of incremental signals with different resolutions.

[0095] The problems to be solved by the embodiments and the effects of the embodiments are not limited to the above-described content. That is, depending on the embodiments, it is also possible to solve problems not described above or to achieve effects not described above, and it is also possible to solve only some of the described problems or to achieve only some of the described effects.

[0096] In addition, in the above description, when there are descriptions such as "vertical", "parallel", and "plane", such descriptions do not have a strict meaning. That is, these "vertical", "parallel", and "plane" mean "substantially vertical", "substantially parallel", and "substantially plane" with allowances for design and manufacturing tolerances and errors.

[0097] Also, in the above description, when there are descriptions such as "identical", "the same", "equal", and "different" regarding external dimensions, sizes, shapes, positions, etc., such descriptions do not have a strict meaning. That is, these "identical", "the same", "equal", and "different" mean "substantially identical", "substantially the same", "substantially equal", and "substantially different" with allowances for design and manufacturing tolerances and errors.

[0098] In addition to what has been already described above, the methods according to the above embodiments and each modification may be appropriately combined and used. Other than not listing them one by one, the above embodiments and each modification may be implemented with various changes within the scope not departing from the gist thereof.

Description of Reference Numerals

[0099] 1 Servo System 3 Servo Motor 5 Control Device 7 Encoder 9 Motor 17 Hub (Rotating Body) 17a Inner Peripheral Portion 17b Outer Peripheral Portion 17c Magnet Accommodation Portion 19 Disk 21 Substrate 25 Optical Module 27 Magnetic detection unit (second magnetic detection unit) 29 Magnet (second magnet) 31 Trigger signal generator (first magnetic detection unit) 33 Magnet (first magnet) 33N1 Magnet 33N2 Magnet 33S1 Magnet 33S2 Magnet 35 Battery 37 Connector 43 Processing module 45 Cable 61 Magnet (second magnet) 63 Magnet (first magnet) Ap1 Angular position Ap2 Angular position Ax Axis of rotation D1 Outer diameter D2 Inner diameter G Gap S Scale

Claims

1. A rotating body rotatable around a rotation axis, a disk fixed to the rotating body and having a ring-shaped scale formed thereon, an optical module arranged to face the disk and detecting the scale, a first magnet arranged on one side in the direction of the rotation axis from the disk and fixed to the rotating body, a first magnetic detection unit arranged on the other side in the direction of the rotation axis from the disk and detecting the magnetism of the first magnet, characterized by comprising: The disk is made of a non-magnetic material, The rotating body supports the disk so that the disk covers the other side of the first magnet, The first magnetic detection unit detects the magnetism of the first magnet that has passed through the disk, has a gap formed between the disk and the first magnet in the direction of the rotation axis, The first magnet has a plurality of magnets arranged along the circumferential direction around the rotation axis, each having magnetic poles in the direction of the rotation axis and the magnetic poles of adjacent ones being different from each other, The plurality of magnets each have an arc shape along the circumferential direction and are arranged with gaps between them, The first magnetic detection unit is an encoder arranged such that the center of the first magnetic detection unit is located inside the rotation locus of the plurality of magnets due to the rotation of the rotating body in the radial direction centered on the rotation axis.

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

3. The rotating body has an inner peripheral portion located on the inner peripheral side in the radial direction, and an outer peripheral portion located on the outer peripheral side in the radial direction from the inner peripheral portion and having a thickness in the direction of the rotation axis 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 arranged on the other side of the outer peripheral portion, The encoder according to claim 2.

4. The rotating body has a surface on the other side of the inner peripheral portion protruding further to the other side than the surface on the other side of the first magnet arranged on the outer peripheral portion, The disk protrudes to the outer peripheral side more than the inner peripheral portion in the radial direction, The encoder according to claim 3.

5. The outer diameter of the inner peripheral portion in the radial direction is smaller than the inner diameter of the scale in the radial direction, The encoder according to claim 3 or 4.

6. a second magnet fixed to the rotating body at a position on the rotation axis A second magnetic detection unit that is disposed to face the second magnet and detects the magnetism of the second magnet. The rotating body Supports the first magnet such that the first magnet is disposed on the outer peripheral side of the second magnet in the radial direction. The encoder according to claim 1.

7. A rotating body rotatable around a rotation axis, A disk fixed to the rotating body and having a ring-shaped scale formed thereon, An optical module disposed to face the disk and detecting the scale, A first magnet disposed on one side of the disk in the direction of the rotation axis and fixed to the rotating body, A first magnetic detection unit disposed on the other side of the disk in the direction of the rotation axis and detecting the magnetism of the first magnet, A second magnet fixed to the rotating body at a position on the rotation axis, A second magnetic detection unit disposed to face the second magnet and detecting the magnetism of the second magnet. The rotating body Supports the first magnet such that the first magnet is disposed on the outer peripheral side of the second magnet in the radial direction centered on the rotation axis. The first magnet Is configured such that the N pole and the S pole alternate every 90 degrees in the circumferential direction around the rotation axis. The second magnet Is configured such that the N pole and the S pole alternate every 180 degrees in the circumferential direction. The first magnet or the second magnet Is disposed such 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 in the circumferential direction of any one of the magnetic poles of the first magnet. Encoder.

8. A rotating body rotatable around a rotation axis, A disk fixed to the rotating body and having a ring-shaped scale formed thereon, An optical module disposed to face the disk and detecting the scale, A first magnet disposed on one side of the disk in the direction of the rotation axis and fixed to the rotating body, A first magnetic detection unit disposed on the other side of the disk in the direction of the rotation axis and detecting the magnetism of the first magnet, A second magnet fixed to the rotating body at a position on the rotation axis, A second magnetic detection unit disposed to face the second magnet and detecting the magnetism of the second magnet. The first magnetic detection unit When the rotating body rotates in the first direction, a first electrical signal is generated at a first phase angle based on the detection of the magnetism of the first magnet. When the rotating body rotates in a second direction opposite to the first direction, the first electrical signal is generated at a second phase angle based on the detection of the magnetism of the first magnet. The second magnet and the second magnetic detection unit are arranged such that the second magnetic detection unit generates a pulsed second electrical signal in which high and low are switched 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. Encoder.

9. When no external power is supplied to the encoder, it further has a battery that supplies power to the second magnetic detection unit. The first magnetic detection unit generates the first electrical signal that serves as a trigger for supplying the power of the battery to the second magnetic detection unit based on the detection of the magnetism of the first magnet. The encoder according to claim 8.

10. A rotating body rotatable around a rotation axis, a disk fixed to the rotating body and having a ring-shaped scale formed thereon, an optical module arranged to face the disk and detecting the scale, a first magnet arranged on one side in the direction of the rotation axis with respect to the disk and fixed to the rotating body, a first magnetic detection unit arranged on the other side in the direction of the rotation axis with respect to the disk and detecting the magnetism of the first magnet, a substrate on which the first magnetic detection unit is arranged on the other surface, a battery arranged on the other surface of the substrate and supplying power to at least a part of the circuit of the substrate when no external power is supplied, a connector arranged on the other surface of the substrate, a cable connected to the connector and wired through the space between the first magnetic detection unit and the battery, An encoder having.

11. A motor in which a rotor rotates with respect to a stator, the encoder according to claim 1 for detecting at least one of the position, speed, and acceleration of the rotor, A servo motor having.

12. A motor in which a rotor rotates with respect to a stator, the encoder according to claim 1 for detecting at least one of the position, speed, and acceleration of the rotor, a control device for controlling the motor based on the detection result of the encoder, A servo system having.

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