Actuator

Abstract

An actuator (1) equipped with a motor (5) and an encoder unit (40) includes: a first structure portion (19) that determines the relative angles between a plurality of coils (13) of a stator core (11) and a housing (12); a second structure portion (29) that determines the relative angles between the magnetic poles of a rotor core (12) and the fixed reference region (P) of a rotating disk (41) provided on a shaft (23); a third structure portion (39) that determines the relative angle between the shaft (23) and the rotating disk (41); and a fourth structure portion (48) that determines the relative angle between the housing (12) and a detection portion (42).

Description

[Technical Field]

[0001] The present disclosure relates to an actuator. [Background Art]

[0002] In an actuator including an encoder and a motor, for example a servo motor, it is necessary to attach the rotating disk of the encoder to the hollow shaft of the motor (see, for example, Japanese Patent Laid-Open No. 2017-203645). [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] Japanese Patent Laid-Open No. 2017-203645 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The positional relationship between the rotating disk and the hollow shaft determines the relative angle between the rotating disk and the rotor of the motor.

[0005] Furthermore, since the space between the stator housing and the stator core of the motor is generally a cylindrical interference fit by shrink fitting, the relative angle between the housing and each phase of the coils wound around the stator core is not fixed.

[0006] Furthermore, since the space between the hollow shaft and the rotor core of the motor rotor is also generally a cylindrical interference fit by shrink fitting, the relative angle between the fixing portion of the encoder's rotating disk provided on the hollow shaft of the rotor and the magnetic poles formed by the magnets mounted on the rotor core is also not fixed.

[0007] For these reasons, when attaching the rotating disk, it is not possible to adjust the angle of the motor coils and magnetic poles as viewed from the Z-phase (that is, the angle of the Z-phase when the coils and magnetic poles are aligned at predetermined positions).

[0008] Therefore, it is desirable to precisely adjust the Z-phase angle by using a method that determines the angle of the rotating disk by DC excitation. [Means for solving the problem]

[0009] According to a first aspect of the present disclosure, a stator comprises a housing and a stator core fixed within the housing and around which a plurality of coils are wound; further comprises a rotor positioned opposite the stator, the rotor comprising a rotor core forming a plurality of magnetic poles and a shaft coupled to the rotor core; further comprises an encoder unit, the encoder unit comprising a rotating disk connected to the shaft, a detection unit for detecting the rotation of the rotating disk, and a fixed part fixed to the housing; further comprises a first structural part for determining the relative angle between the plurality of coils of the stator core and the housing; a second structural part for determining the relative angle between the magnetic poles of the rotor core and a fixed reference part of the rotating disk provided on the shaft; a third structural part for determining the relative angle between the shaft and the rotating disk; and a fourth structural part for determining and adjusting the relative angle between the housing and the detection unit. The detection unit is positioned to face a plurality of radially extending slits formed on the rotating disk, excluding the center of the rotating disk. An actuator is provided.

[0010] The purposes, features, and advantages of this disclosure will become even clearer from the following description of embodiments related to the accompanying drawings. [Brief explanation of the drawing]

[0011] [Figure 1] This is an axial cross-sectional view of an actuator based on the first embodiment. [Figure 2A] This is a radial cross-sectional view of the housing. [Figure 2B] This is a radial cross-sectional view of the stator core. [Figure 3] This is a perspective view showing a hollow shaft and a rotating disk. [Figure 4] This is an axial cross-sectional view of the actuator to illustrate a modified example of the second structural component. [Figure 5] This is another axial cross-sectional view of the actuator shown in Figure 1. [Figure 6] This is an axial cross-sectional view of an actuator based on another embodiment. [Figure 7] This is a front view of the encoder mounting section. [Figure 8A] This is a partial axial cross-sectional view of an actuator based on another embodiment. [Figure 8B] Figure 7A is a radial cross-sectional view of the actuator shown. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below with reference to the attached drawings. Throughout all drawings, corresponding components are denoted by the same reference numerals. Figure 1 is an axial cross-sectional view of an actuator according to a first embodiment. The actuator 1 shown in Figure 1 mainly includes a motor 5 consisting of a stator 10 and a rotor 20, such as a servo motor, and an encoder 40 connected to the motor 5. The encoder 40, which includes a rotating disk 41, is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The encoder 40 may be an optical encoder or a magnetic encoder.

[0013] The stator 10 includes a stator core 11 located within a housing 12. The stator core 11 includes a plurality of coils 13 arranged around the central axis of the motor 5. The rotor 20 is rotatably positioned inside the stator core 11. The rotor 20 includes a rotor core 21 on which a plurality of magnets 22, such as permanent magnets, are arranged on its outer surface, and a hollow shaft 23 that rotates integrally with the rotor core 21 on the central axis of the motor 5. The hollow shaft 23 is rotatably positioned in the housing 12 via bearings 51, 52.

[0014] FIG. 2A is a radial cross-sectional view of the housing. As shown in FIG. 2A, a pair of key grooves 16 are formed on the inner circumferential surface of the housing 12. These key grooves 16 are formed at positions facing each other in the diametrical direction of the housing 12. It is preferable that the number of the key grooves 16 is one or more. Further, a plurality of key grooves 16 may be formed at non-equal intervals in the circumferential direction of the housing 12.

[0015] FIG. 2B is a radial cross-sectional view of the stator core. As shown in FIG. 2B, a plurality of coils 13 are fixed at equal intervals on the inner circumferential surface side of the stator core 11. A plurality of grooves 17 are formed on the outer circumferential surface of the stator core 11 at positions respectively corresponding to the central portions of the plurality of coils 13. Further, parallel keys 15 extending parallel to the axial direction of the hollow shaft 23 are respectively inserted into a pair of grooves 17 corresponding to the diametrical direction of the stator core 11. It is preferable that the number of the parallel keys 15 is one or more. In FIG. 2B, the parallel keys 15 are inserted into the pair of diametrically opposed grooves 17. However, the parallel key 15 may be inserted into another groove 17 located at a position corresponding to the key groove 16. Further, the groove 17 may be formed at a position different from the central portion of the coils 13, for example, at a position corresponding between two adjacent coils 13.

[0016] The positions of one or more key grooves 16 formed in the housing 12 are known in advance, and the positional relationship between the grooves 17 and the coils 13 is also known in advance. Therefore, by inserting one or more parallel keys 15 into the grooves 17 of the stator core so as to engage with such key grooves 16, the relative angle between the plurality of coils 13 of the stator core 11 and the housing 12 can be determined. Accordingly, the one or more parallel keys 15, the one or more key grooves 16, and the one or more grooves 17 function as a first structure 19 that determines the relative angle between the plurality of coils 13 of the stator core 11 and the housing 12. The same effect can also be obtained when the parallel key 15 and the groove 17 are integrated, and a part of the parallel key 15 protrudes from the groove 17 as a convex portion.

[0017] Generally, the rotor core 21 of the rotor 20 and the hollow shaft 23 are separate members, which are coupled to each other. However, in the first embodiment, as can be understood with reference to FIG. 1, the hollow shaft 23 and the rotor core 21 are integrally molded. That is, the hollow shaft 23 and the rotor core 21 are a single member.

[0018] Incidentally, FIG. 3 is a perspective view showing a hollow shaft and a rotary disk. As shown in FIG. 3, in order to accurately detect the Z-phase by the rotary disk 41, a fixing reference portion P for the rotary disk 41, for example, a mark, is formed on a part of the outer peripheral surface of the hollow shaft 23. Then, the rotary disk 41 is attached to the hollow shaft 23 such that the fixing reference portion P for the rotary disk and the Z-phase slit S pre-formed on the rotary disk 41 correspond to each other. Typically, the rotary disk 41 is attached to the hollow shaft 23 as described later such that the circumferential position of the fixing reference portion P for the rotary disk and the circumferential position of the Z-phase slit S coincide with each other.

[0019] As described above, since the hollow shaft 23 and the rotor core 21 are integrally molded, the relative angle between the magnetic pole of the rotor core 21 and the fixing reference portion P provided on the hollow shaft 23 is automatically and fixedly determined. Therefore, the integrally molded hollow shaft 23 and rotor core 21 serve as the second structural portion 29 that determines the positional relationship between the fixing reference portion P for the rotary disk of the hollow shaft 23 and the magnetic pole of the magnet 22 mounted on the rotor core 21.

[0020] FIG. 4 is an axial sectional view of an actuator for explaining a modified example of the second structural portion. In the actuator 1' shown in FIG. 4, the rotor core 21 and the hollow shaft 23 are separate members. One or more grooves (not shown) are formed on the inner peripheral surface of the rotor core 21 and the outer peripheral surface of the hollow shaft 23, respectively.

[0021] The rotor core 21 and the hollow shaft 23 are joined together by one or more parallel keys 26, which extend parallel to the axial direction of the hollow shaft 23, fitting into grooves in the rotor core 21 and grooves in the hollow shaft 23. The number and position of the parallel keys 26 are the same as those of the parallel keys 15 described above.

[0022] Since the rotor core 21 and the hollow shaft 23 are coupled to each other by these parallel keys 26 and grooves, the relative angle between the magnetic poles of the rotor core 21 and the fixed reference portion P provided on the hollow shaft 23 is fixed and automatically determined. Therefore, the grooves formed on the inner circumferential surface of the rotor core 21, the grooves formed on the outer circumferential surface of the hollow shaft 23, and the parallel keys 26 all function as the aforementioned second structural part 29. A similar effect can be obtained even if the parallel keys 26 and the corresponding grooves are integrated and a part of the parallel keys 26 protrudes from the groove as a convex portion.

[0023] As shown in Figure 1, the hollow shaft 23 includes an expanded portion 23A between the rotating disk 41 and the motor 5, whose thickness expands radially inward. The expanded portion 23A is formed at one end of the hollow shaft 23 on the encoder 40 side. Due to the presence of this expanded portion 23A, the inner diameter D1 of the hollow shaft 23 is larger than the inner diameter D2 of the expanded portion 23A. In one embodiment, (D1-D2) / D1 is preferably 0.1 to 0.2. The length and thickness of the expanded portion 23A in the axial direction of the hollow shaft 23 are made large enough to accommodate the rotating disk fixing portion 35, which will be described later.

[0024] In Figure 1, the rotating disk 41 of the encoder 40 is fixed to the end face of the expansion portion 23A by a rotating disk fixing portion 35. Typically, the rotating disk fixing portion 35 is a combination of a plurality of first screws 35 extending parallel to the axial direction of the hollow shaft 23 and a plurality of holes formed on the end face of the expansion portion 23A to correspond to the plurality of first screws 35. However, other forms of the rotating disk fixing portion 35 that can fix the rotating disk 41 to the expansion portion 23A may be used.

[0025] Therefore, in the first embodiment, the rotating disk 41 of the encoder 40 can be easily connected to the end face of the hollow shaft 23. The number of first screws 35 and the number of holes may be different, and the multiple first screws 35 do not have to be arranged at equal intervals in the circumferential direction of the hollow shaft 23.

[0026] Figure 5 is another axial cross-sectional view of the actuator shown in Figure 1. In Figure 5, at least one wire C, such as a cable or pipe supplying power, signals, or materials, penetrates the actuator 1 through the internal space of the hollow shaft 23. At least one wire C is fixed near both ends of the actuator 1 by fixing parts (not shown in Figures 1 and 5).

[0027] As can be seen from Figures 1 and 5, the thickness of the expanded portion 23A is sufficiently smaller than the inner diameter of the hollow shaft 23. Therefore, even if the expanded portion 23A is formed, there is no need to reduce the number of striatum C, and the slack of those striatum C can be maintained.

[0028] Strictly speaking, in Figures 1 and 5, the rotating disk 41 is fixed to the end face of the expanded portion 23A via a boss 25 by a plurality of first screws 35. Preferably, the boss 25 is attached to the rotating disk 41 with an adhesive or the like. Alternatively, the rotating disk 41 may be directly fixed to the end face of the expanded portion 23A. In this case, the rotating disk 41 of the encoder can be connected to the hollow shaft 23 even more easily. Here, it can be seen that the expanded portion 23A, the hole formed in the expanded portion 23A, and the first screws 35 serve as a third structural part 39 that determines the relative angle between the hollow shaft 23 and the rotating disk 41.

[0029] Incidentally, Figure 6 is an axial cross-sectional view of an actuator according to another embodiment. In the other embodiment, actuator 1a has an expansion portion 23B instead of the expansion portion 23A, which expands in thickness radially outward from the hollow shaft 23 between the rotating disk 41 and the motor 5. As shown in Figure 6, the inner diameter D1 of the hollow shaft 23 is equal to the inner diameter D2' of the expansion portion 23B. In other words, even if the expansion portion 23B is formed, the inner diameter of the hollow shaft 23 does not change throughout the hollow shaft 23. The rotating disk 41 of the encoder 40 is fixed to the end face of the expansion portion 23B by a plurality of first screws 35 that extend parallel to the axial direction of the hollow shaft 23.

[0030] In this case, since the inner diameter of the expanded portion 23B is equal to the inner diameter of the other portion of the hollow shaft 23, one or more linear bodies C can pass through the hollow shaft 23 with more clearance than in the embodiment shown in Figure 1. Also, as described above, the scope of this disclosure includes cases where the rotating disk 41 is directly fixed to the end face of the expanded portion 23B without the use of a boss 25. Furthermore, the scope of this disclosure also includes cases where both the expanded portion 23A and the expanded portion 23B are formed at one end of the hollow shaft 23.

[0031] Referring to Figure 1, the detection unit 42 provided on the substrate 49 of the encoder 40 detects the absolute position PA1 and the total number of rotations PB1 within one revolution of the hollow shaft 23 using a known method. The detected information is stored in memory (not shown), for example, volatile memory.

[0032] Figure 7 is a front view of the encoder mounting section. As can be seen from Figures 1 and 7, the substrate 49 of the encoder mounting section 43 of the encoder 40 has multiple elongated holes 46 formed therein. Each elongated hole 46 has a longer portion extending circumferentially around the hollow shaft 23 than the portion extending radially around the hollow shaft 23. Typical elongated holes 46 are oval or elliptical, but other shapes are also possible.

[0033] Multiple second screws 45 are then inserted into multiple elongated holes 46 in the substrate 49 and fixed to the housing 12. For this purpose, the housing 12 has holes formed for multiple second screws 45. Preferably, the second screws 45 extend parallel to the axial direction of the hollow shaft 23. Since the elongated holes 46 are not circular, after screwing in the second screws 45, the position of the encoder fixing part 43 can be finely adjusted in the circumferential direction within the range of the circumferential length of the elongated holes 46.

[0034] Since the detection unit 42 is in a predetermined position relative to the fixing part 43 of the encoder 40, the detection unit 42 can be positioned in a desired position relative to the housing 12. For this reason, the multiple second screws 45 and the elongated holes 46, as well as the holes in the housing 12, serve as a fourth structural part 48 that determines and adjusts the relative angle between the housing 12 and the detection unit 42. The fourth structural part 48 leaves room to adjust the position of the detection unit 42 in the rotational direction after the encoder 40 has been installed.

[0035] Figure 8A is an axial partial cross-sectional view of an actuator based on another embodiment, and Figure 8B is a radial cross-sectional view of the actuator shown in Figure 8A. In Figure 8A, the encoder 40 is omitted for the sake of simplicity. The housing 12 of the actuator 1b shown in Figure 8A has a plurality of through holes formed parallel to the axial direction of the hollow shaft 23. The stator core 11 has a flange 11a that extends radially outward from the hollow shaft 23 to the outer circumferential surface of the housing 12.

[0036] As shown in Figure 8A, the flange 11a is configured to engage with the notch in the housing 12. In other words, the flange 11a is sandwiched between the housing 12 from the axial upstream and downstream sides of the hollow shaft 23.

[0037] The flange 11a of the stator core 11 also has multiple through holes that correspond to the through holes in the housing 12. In other words, the multiple through holes in the flange 11a are each connected to the multiple through holes in the housing 12.

[0038] The tie rods TL are then positioned in the respective through-holes of the flange 11a. The length of the tie rods TL is longer than the length of the flange 11a in the axial direction of the hollow shaft 23, and shorter than the length of the housing 12 in the axial direction of the hollow shaft 23. Therefore, neither end of each tie rod TL reaches the ends of the housing 12 in the axial direction of the hollow shaft 23.

[0039] As can be seen from Figure 8B, the multiple tie rods TL are arranged at equal intervals in the circumferential direction of the hollow shaft 23. However, the multiple tie rods TL may be arranged at non-equal intervals in the circumferential direction of the hollow shaft 23.

[0040] Then, as shown in Figure 8A, multiple tie bolts TB are inserted into the aforementioned through holes from both ends of the housing 12 in the axial direction of the hollow shaft 23 and connected to each of the multiple tie rods TL. For this purpose, it is preferable that female threads are formed at both ends of each of the multiple tie rods TL. In this way, the multiple tie bolts TB and the multiple tie rods TL secure the housing 12 to the stator core 11.

[0041] Therefore, the relative angle between the coil 13 of the stator core 11 and the housing 12 is fixed. In other words, the flange 11a, tie rod TL, and tie bolt TB serve as the first structural component 19. Alternatively, the tie rod TL may be absent, and the tie bolt TB may be screwed into threads formed on the inner surface of the through-hole in the flange 11a and the through-hole in the housing 12.

[0042] Furthermore, in embodiments not shown, multiple tie rods TL may be used, each having male threads formed at both ends and being longer than the length of the housing 12 in the axial direction of the hollow shaft 23. In this case, since the male thread portions of the multiple tie rods TL protrude from both ends of the through hole, nuts are screwed onto the male thread portions instead of tie bolts TB.

[0043] Alternatively, in other embodiments not shown, multiple tie rods TL may be eliminated, and multiple bolts longer than the length of the housing 12 in the axial direction of the hollow shaft 23 may be used. These bolts are then screwed into the female threads pre-formed in the through holes of the flange 11a and the through holes of the housing 12.

[0044] In these embodiments not shown, the relative angle between the coil 13 of the stator core 11 and the housing 12 can be fixed, as described above. Therefore, the nuts and bolts described above also serve as the first structural part 19.

[0045] Thus, in this disclosure, the relative angle between the multiple coils 13 of the stator core 11 and the housing 12 is determined by the first structural part 19, the relative angle between the magnetic poles of the rotor core 21 and the fixed reference portion of the rotating disk 41 provided on the shaft 23 is determined by the second structural part 29, the relative angle between the shaft 23 and the rotating disk 41 is determined by the third structural part 39, and the relative angle between the housing 12 and the detection unit 42 is determined and adjustable by the fourth structural part 48. Therefore, the Z-phase angle of the encoder unit can be accurately adjusted.

[0046] The nature of this disclosure According to the first embodiment, an actuator is provided comprising a stator, the stator including a housing and a stator core fixed within the housing and around which a plurality of coils are wound; a rotor positioned facing the stator, the rotor including a rotor core forming a plurality of magnetic poles and a shaft coupled to the rotor core; an encoder unit, the encoder unit including a rotating disk connected to the shaft, a detection unit for detecting the rotation of the rotating disk, and a fixed part fixed to the housing; a first structural part for determining the relative angle between the plurality of coils of the stator core and the housing; a second structural part for determining the relative angle between the magnetic poles of the rotor core and a fixed reference part of the rotating disk provided on the shaft; a third structural part for determining the relative angle between the shaft and the rotating disk; and a fourth structural part for determining and adjusting the relative angle between the housing and the detection unit. According to a second embodiment, in the first embodiment, the third structural component includes a boss mounted on the rotating disk or a plurality of first screws that secure the rotating disk and the shaft, and a plurality of screw holes formed in the shaft that engage with the plurality of first screws. According to the third embodiment, in the first or second embodiment, the fourth structural component includes a plurality of elongated holes formed in the fixed portion of the encoder unit and a plurality of second screws inserted into each of the plurality of elongated holes. According to the fourth embodiment, in any of the first to third embodiments, the first structural component includes a plurality of keyways formed in the stator core and the housing, and a plurality of parallel keys that engage with each of the plurality of keyways. According to the fifth embodiment, in any of the first to third embodiments, the first structural component includes a plurality of keyways formed in one of the housing and the stator core, and a plurality of protrusions provided in the other of the housing and the stator core that engage with each of the plurality of keyways. According to the sixth aspect, in the first aspect, the first structural component includes a flange provided on the stator core and engaging with the housing, a plurality of through holes formed in the housing and the flange and communicating with each other, and a plurality of tie bolts screwed into the plurality of through holes. According to the seventh embodiment, in any of the first to sixth embodiments, the second structural component includes a plurality of keyways formed in the rotor core and the shaft, and a plurality of parallel keys that engage with each of the plurality of keyways. According to the eighth embodiment, in any of the first to sixth embodiments, the second structural component includes a plurality of keyways formed in one of the rotor core and the shaft, and a plurality of protrusions provided on the other of the rotor core and the shaft that engage with each of the plurality of keyways. According to the ninth embodiment, in any of the first to sixth embodiments, the rotor core and the shaft are integrally formed in the second structural part. According to the tenth embodiment, in any of the first to ninth embodiments, the encoder is an optical encoder or a magnetic encoder.

[0047] Effects of the configuration In the first embodiment, the Z-phase angle of the encoder unit can be precisely adjusted. In the second embodiment, the relative angle between the shaft and the rotating disk can be fixed. In the third embodiment, the relative angle between the housing and the detection unit is determined, and the relative angle is adjusted after the encoder is installed. In a fourth embodiment, the relative angles between the multiple coils of the stator core and the housing can be fixed. In a fifth embodiment, the relative angles between the multiple coils of the stator core and the housing can be fixed. In the sixth embodiment, the relative angles between the multiple coils of the stator core and the housing can be fixed. In the seventh embodiment, the angle between the magnetic poles of the rotor core and the shaft can be fixed. In the eighth embodiment, the angle between the magnetic poles of the rotor core and the shaft can be fixed. In the ninth embodiment, the second structural component can be easily constructed.

[0048] While embodiments of this disclosure have been described in detail, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, or partially deleted in various ways, without departing from the spirit of the invention or the idea and intent of the invention derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. Furthermore, combining some of the embodiments described above as appropriate is within the scope of this disclosure. [Explanation of symbols]

[0049] 1, 1a Actuator 5 Motors 10 staters 11 Stator Core 11a Flange 12 Housing 13 coils 15 Parallel Keys 19 First structure section 20 rotors 21 Rotor Core 22 Magnets 23 Hollow shaft 23A, 23B Extension section 25 Boss 26 Parallel Keys 29 Second structure part 30 Reducer 31 Slow tube 32 Output shaft 35 First Screw 39 Third structure 40 encoders 41 RPM disc 42 Detection unit 43 Encoder fixing part 46 long hole 48 Fourth structure 49 circuit boards 51, 52 Bearings 61, 62 Fixed part C. Striatum P fixed reference site SZ phase slit TL Tie Rod TB Tie Bolt

Claims

1. Equipped with a stator, The stator includes a housing and a stator core fixed within the housing and around which a plurality of coils are wound. moreover, The rotor is positioned facing the stator, The rotor includes a rotor core that forms multiple magnetic poles and a shaft coupled to the rotor core. moreover, It is equipped with an encoder unit, The encoder unit includes a rotating disk connected to the shaft, a detection unit for detecting the rotation of the rotating disk, and a fixing unit fixed to the housing. moreover, A first structural part that determines the relative angle between the plurality of coils of the stator core and the housing, A second structural part that determines the relative angle between the magnetic pole of the rotor core and the fixed reference portion of the rotating disk provided on the shaft, A third structural part that determines the relative angle between the shaft and the rotating disk, An actuator comprising: a fourth structural part for determining and adjusting the relative angle between the housing and the detection part, wherein the detection part is positioned to face a plurality of radially extending slits formed on the rotating disk, excluding the center of the rotating disk.

2. The actuator according to claim 1, wherein the third structural part includes a boss mounted on the rotating disk or a plurality of first screws that fix the rotating disk and the shaft, and a plurality of screw holes formed in the shaft that engage with the plurality of first screws.

3. The actuator according to claim 1 or 2, wherein the fourth structural part includes a plurality of elongated holes formed in the fixed part of the encoder unit and a plurality of second screws inserted into each of the plurality of elongated holes.

4. The actuator according to claim 1 or 2, wherein the first structural component includes a plurality of keyways formed in the stator core and the housing, and a plurality of parallel keys that engage with each of the plurality of keyways.

5. The actuator according to claim 1 or 2, wherein the first structural part includes a plurality of keyways formed in one of the housing and the stator core, and a plurality of protrusions provided in the other of the housing and the stator core that engage with each of the plurality of keyways.

6. The first structural part is, A flange provided on the stator core and engaging with the housing, A plurality of through holes formed in the housing and the flange and communicating with one another, The actuator according to claim 1, further comprising a plurality of tie bolts that are screwed into the plurality of through holes.

7. The actuator according to claim 1 or 2, wherein the second structural part includes a plurality of keyways formed in the rotor core and the shaft, and a plurality of parallel keys that engage with each of the plurality of keyways.

8. The actuator according to claim 1 or 2, wherein the second structural part includes a plurality of keyways formed in one of the rotor core and the shaft, and a plurality of protrusions provided on the other of the rotor core and the shaft that engage with each of the plurality of keyways.

9. The actuator according to claim 1 or 2, wherein in the second structural part, the rotor core and the shaft are integrally formed.

10. The actuator according to claim 1 or 2, wherein the encoder unit is an optical encoder.

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