Actuator

Abstract

An actuator (1) comprises a motor (5) and an encoder unit (40). A hollow shaft (23) of the motor (5) includes, between a rotating disk (41) of the encoder unit (40) and the motor (5), an enlarged portion (23A, 23B) for enlarging the thickness thereof. The inner diameter of the hollow shaft (23) is larger than the inner diameter of the enlarged portion (23A, 23B). The rotating disk (41) is fixed to the enlarged portion by a rotating disk fixing portion (35).

Description

Actuator

[0001] The present disclosure relates to actuators.

[0002] In an actuator including a servomotor, various wires, such as cables for supplying power, signals, or materials, pass through the hollow shaft of the servomotor rotor and are held at both ends of the actuator. Similarly, in an actuator in which a reducer and a servomotor are connected, a low-speed tube extending from the output shaft of the reducer may pass through the hollow shaft of the servomotor rotor (see, for example, JP 2017-203645 A). In such cases, various wires pass through the low-speed tube and are held at both ends of the actuator. To reduce the risk of the wires breaking due to torsion, the wires are held with slack.

[0003] Japanese Patent Application Publication No. 2017-203645

[0004] In order to pass a large number of wires through the actuator, it is preferable that the inner diameter of the hollow shaft and / or the low-speed tube is large. However, since the thickness of the hollow shaft is small, it becomes difficult to screw the rotating disk of the encoder into the thickness of the hollow shaft.

[0005] Therefore, there is a need for an actuator that allows the rotary disk of the encoder to be easily connected to the end surface of the hollow shaft.

[0006] According to a first aspect of the present disclosure, there is provided an actuator comprising: a motor including a rotor with a hollow shaft; and an encoder unit with a rotating disk; wherein, between the rotating disk and the motor, the hollow shaft includes an extended portion whose thickness is extended, the inner diameter of the hollow shaft is larger than the inner diameter of the extended portion; and the rotating disk is fixed to the extended portion of the hollow shaft by a plurality of screws.

[0007] The objects, features, and advantages of the present disclosure will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0008] Fig. 2 is an axial sectional view of an actuator according to a first embodiment; Fig. 3 is a front view of an encoder fixing part; Fig. 4 is another axial sectional view of the actuator shown in Fig. 1; Fig. 5 is an axial sectional view of an actuator according to a second embodiment; Fig. 6 is an axial sectional view of an actuator according to a third embodiment; Fig. 7 is an axial sectional view of an actuator according to a fourth embodiment; Fig. 8 is an axial sectional view of an actuator according to an additional embodiment;

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Corresponding components are designated by common reference numerals throughout the drawings. FIG. 1 is an axial cross-sectional view of an actuator based on a first embodiment. The actuator 1 shown in FIG. 1 mainly includes a motor 5, such as a servo motor, consisting of a stator 10 and a rotor 20, 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.

[0010] The stator 10 includes a stator core 11 fixed in a housing 12 by a key 15. The stator core 11 includes a plurality of coils 13 arranged around the central axis of the motor 5.

[0011] The rotor 20 is rotatably disposed inside the stator core 11. The rotor 20 includes a rotor core 21 having a plurality of magnets 22, e.g., permanent magnets, disposed on the outer circumferential surface thereof, 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 disposed in the housing 12 via bearings 51 and 52.

[0012] 2 is a front view of the encoder fixing portion. As can be seen from FIGS. 1 and 2, the encoder fixing portion 43 of the encoder 40 is fastened to the housing 12 by a plurality of second screws 45 through elongated holes 46. A detection portion 42 provided on a substrate 49 of the encoder 40 detects the absolute position PA1 within one rotation of the hollow shaft 23 and the total number of rotations PB1 using a known method. The detected information is stored in a memory (not shown), for example, a volatile memory.

[0013] As shown in FIG. 1 , the hollow shaft 23 includes an expanded portion 23A between the rotary 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 large enough to accommodate the rotary disk fixing portion 35, which will be described later.

[0014] 1, the rotary disk 41 of the encoder 40 is fixed to the end surface of the extension portion 23A by a rotary disk fixing portion 35. Typically, the rotary 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 in the end surface of the extension portion 23A to correspond to the plurality of first screws 35. However, the rotary disk fixing portion 35 may have another form that can fix the rotary disk 41 to the extension portion 23A.

[0015] Therefore, in the first embodiment, the rotary disk 41 of the encoder 40 can be easily connected to the end surface of the hollow shaft 23. Note that the number of the first screws 35 and the number of the holes may be different, and the first screws 35 do not have to be arranged at equal intervals in the circumferential direction of the hollow shaft 23.

[0016] Figure 3 is another axial cross-sectional view of the actuator shown in Figure 1. In Figure 3, at least one wire C, such as a cable for supplying power, a signal, or a material, passes through the actuator 1 through the internal space of the hollow shaft 23. The at least one wire C is fixed near both ends of the actuator 1 by fixing portions (not shown in Figures 1 and 3).

[0017] As can be seen from Figures 1 and 3, the thickness of the expansion portion 23A is sufficiently smaller than the inner diameter of the hollow shaft 23, so even if the expansion portion 23A is formed, there is no need to reduce the number of filaments C, and the slack in these filaments C can be maintained.

[0018] 1 and 3, the rotary disk 41 is fixed to the end surface of the extension portion 23A via the boss 25 by a plurality of first screws 35. The boss 25 is preferably attached to the rotary disk 41 by adhesive or the like. Alternatively, the rotary disk 41 may be fixed directly to the end surface of the extension portion 23A. In this case, the rotary disk 41 of the encoder can be more easily connected to the hollow shaft 23.

[0019] FIG. 4 is an axial cross-sectional view of an actuator according to another embodiment. The actuator 1a according to this embodiment has, instead of the extended portion 23A, an extended portion 23B whose thickness extends radially outward of the hollow shaft 23 between the rotating disk 41 and the motor 5. As shown in FIG. 4 , the inner diameter D1 of the hollow shaft 23 is equal to the inner diameter D2' of the extended portion 23B. In other words, even with the extended portion 23B, the inner diameter of the hollow shaft 23 does not change throughout the entire hollow shaft 23. The rotating disk 41 of the encoder 40 is fixed to the end face of the extended portion 23B by a plurality of first screws 35 extending parallel to the axial direction of the hollow shaft 23.

[0020] In this case, since the inner diameter of the extended portion 23B is equal to the inner diameter of the other portions of the hollow shaft 23, it will be understood that one or more filaments C can be passed through the hollow shaft 23 with more leeway than in the embodiment shown in Fig. 1. Also, as described above, the scope of the present disclosure also includes a case in which the rotary disk 41 is fixed directly to the end face of the extended portion 23B without the boss 25. Furthermore, the scope of the present disclosure also includes a case in which both the extended portion 23A and the extended portion 23B are formed at one end of the hollow shaft 23.

[0021] Figure 5 is an axial cross-sectional view of an actuator based on a third embodiment. The actuator 1b shown in Figure 5 mainly includes a motor 5 (e.g., a servo motor) consisting of a stator 10 and a rotor 20, an encoder 40 connected to the motor 5, and a reducer 30 connected to the motor 5. Note that a separate encoder (not shown) may be connected to the reducer 30. The motor 5 and the encoder 40 are generally similar to those described above, and therefore will not be described again.

[0022] The low-speed pipe 31 connected to the output shaft 32 of the reducer 30 passes through the internal space of the hollow shaft 23 and extends toward the motor 5. The hollow shaft 23 and the low-speed pipe 31 of the reducer 30 are arranged coaxially with each other. As described above, the hollow shaft 23 of the rotor 20 has the expanded portion 23A. The low-speed pipe 31 of the reducer 30 has a step 33 immediately before the expanded portion 23A.

[0023] A portion of the low-speed pipe 31 located closer to the encoder 40 than the step 33 is bent to correspond to the expanded portion 23A. In other words, the inner diameter D3' of this portion of the low-speed pipe 31 is smaller than the inner diameter D3 of the low-speed pipe 31. As can be seen from Figure 5, the low-speed pipe 31 extends beyond the expanded portion 23A of the hollow shaft 23 to penetrate the encoder 40.

[0024] At least one filament C is fixed near both ends of the actuator 1 by fixing portions 61, 62. In Fig. 5, one fixing portion 61 is arranged inside the rotary disk 41 on the encoder 40 side, more specifically, in the internal space of the low-speed tube 31, and the other fixing portion 62 is arranged in the internal space of the hollow shaft 23 on the reducer 30 side.

[0025] These fixing portions 61, 62 serve to accurately center the at least one filament C within the hollow shaft 23 and / or the low-speed tube 31 and to prevent the bundle of filaments C from expanding excessively due to sagging. Furthermore, the fixing portions 61, 62 serve to prevent contact between the inner wall of the hollow shaft 23 and / or the low-speed tube 31 and the at least one filament C.

[0026] 5, the length of the step 33 in the radial direction of the hollow shaft 23 is sufficiently smaller than the outer diameter of the hollow shaft 23, so even if the expanded portion 23A and the step 33 are formed, there is no need to reduce the number of filaments C, and it is possible to maintain slack in the filaments C. Therefore, it can be seen that even when the actuator 1b is equipped with the reducer 30, substantially the same effect as described above can be obtained.

[0027] Fig. 6 is an axial cross-sectional view of an actuator according to a fourth embodiment. Similarly, an actuator 1c shown in Fig. 6 mainly includes a motor 5 (e.g., a servo motor) having a stator 10 and a rotor 20, an encoder 40 connected to the motor 5, and a reducer 30 connected to the motor 5.

[0028] In the fourth embodiment, the low-speed pipe 31 does not have a step 33, and the low-speed pipe 31 terminates just before the expanded portion 23A of the hollow shaft 23. With this configuration, in the fourth embodiment, there is no need to prepare a low-speed pipe 31 with a step 33, and it is also possible to further increase the thickness of the expanded portion 23A. Therefore, it can be seen that the rotary disk 41 can be easily fixed to the expanded portion 23A of the hollow shaft 23 by the multiple first screws 35.

[0029] Furthermore, in the fourth embodiment, a tube 50 is provided that extends at least partially from a position corresponding to the expanded portion 23A toward the rotary disk 41. The tube 50 at least partially penetrates inside the encoder 40. It is preferable that the tube 50 does not move relative to the fixed portion 61. Therefore, the tube 50 serves to prevent the at least one filament C from contacting the inner wall of the encoder 40 and the expanded portion 23A of the hollow shaft 23. This makes it possible to protect the encoder 40 and the like.

[0030] 6, the tubular member 50 may be attached to the encoder 40 via a flange 51 provided at one end of the tubular member 50. Alternatively, the outer peripheral surface of the tubular member 50 may be attached to the encoder 40. This makes it easy to attach the tubular member 50 to the encoder 40. It will be understood that in the fourth embodiment, even when the actuator 1c is equipped with a reducer 30, substantially the same effects as those described above can be obtained.

[0031] Figure 7 is an axial cross-sectional view of an actuator based on a further embodiment, and is a view generally similar to Figure 1. In the previously described embodiment, the multiple first screws 35 are arranged parallel to the axial direction of the hollow shaft 23. In contrast, in Figure 7, the multiple first screws 35 are arranged in the radial direction of the hollow shaft 23. Furthermore, multiple holes that extend in the radial direction of the hollow shaft 23 and correspond to the first screws 35 are formed on the outer circumferential surface of the expanded portion 23A.

[0032] In other words, the rotating disk fixing portion 35 in the additional embodiment is a combination of a plurality of first screws 35 extending radially relative to the axial direction of the hollow shaft 23 and a plurality of holes formed on the outer surface of the extension portion 23A to correspond to the plurality of first screws 35.

[0033] When using such a first screw 35 to fix the rotating disk 41 to the hollow shaft 23 via the boss 25, it can be seen that the first screw 35 can be brought close to the boss 25 from the radially outside of the hollow shaft 23, making it easier to fix the rotating disk 41.

[0034] 7 has a substantially L-shaped cross section, and the boss 25 includes a contact portion that contacts the outer peripheral surface of the expansion portion 23A. The first screws 35 engage with the expansion portion 23A via the contact portion of the boss 25. The boss 25 and the rotary disk 41 are fixed to each other with, for example, an adhesive.

[0035] Therefore, in an additional embodiment in which the plurality of first screws 35 are arranged radially on the hollow shaft 23, the boss 25 must include an abutment portion. In other words, in embodiments other than the additional embodiment shown in Figure 7, it is also possible to eliminate the boss 25 and directly connect the rotating disk 41 and the extension portion 23A.

[0036] In an additional embodiment, the boss 25 may include an abutting portion that abuts against the inner circumferential surface of the expanded portion 23A. In other words, the abutting portion of the boss 25 may be located inside the expanded portion 23A. Furthermore, some of the multiple first screws 35 may be arranged parallel to the axial direction of the hollow shaft 23, and the remaining first screws 35 may be arranged radially relative to the hollow shaft 23. Such cases are also within the scope of the present disclosure.

[0037] In either embodiment, the rotating disk 41 of the encoder 40 can be easily connected to the end face of the hollow shaft 23 without having to reduce the number of wires C and while maintaining slack in the wires C.

[0038] According to a first aspect of the present disclosure, there is provided an actuator comprising: a motor including a rotor with a hollow shaft; and an encoder unit with a rotating disk, wherein the hollow shaft includes an expanded portion between the rotating disk and the motor, the hollow shaft having an expanded portion whose thickness expands, the inner diameter of the hollow shaft being larger than the inner diameter of the expanded portion, and the rotating disk being fixed to the expanded portion of the hollow shaft by a rotating disk fixing portion. According to a second aspect, the actuator according to the first aspect further comprises a reducer coupled to the other end of the hollow shaft and a low-speed tube connected to an output shaft of the reducer, the low-speed tube extending inside the hollow shaft toward the encoder unit and terminating before the expanded portion. According to a third aspect, the actuator according to the first or second aspect further comprises a tube member extending at least partially from a position corresponding to the expanded portion toward the rotating disk. According to a fourth aspect, the rotary disk fixing portion of the first aspect further includes a reducer coupled to the other end of the hollow shaft and a low-speed tube connected to an output shaft of the reducer, the low-speed tube extending at least partially inside the hollow shaft toward the encoder unit, and the low-speed tube having a step corresponding to the expanded portion of the hollow shaft. According to a fifth aspect, in any of the first to fourth aspects, the rotary disk fixing portion is a plurality of screws extending parallel to the axial direction of the hollow shaft or extending in a radial direction of the hollow shaft.

[0039] Advantages of the Aspects In the first aspect, the rotary disk of the encoder can be easily connected to the end surface of the hollow shaft without having to reduce the number of wires and while maintaining slack in the wires. In the second aspect, it is not necessary to prepare a low-speed tube with a step, and the thickness of the extended portion can be increased. In the third aspect, at least one wire serves to prevent contact with the inner wall of the encoder and the extended portion of the hollow shaft. In the fourth aspect, the rotary disk of the encoder can be easily connected to the end surface of the hollow shaft even when the actuator is equipped with a reducer. In the fifth aspect, when the first screw extends in the radial direction of the hollow shaft, the fixing work of the rotary disk is facilitated. When the first screw extends parallel to the axial direction of the hollow shaft, the dimension of the extended portion can be minimized, and the fixing strength of the rotary disk can be increased.

[0040] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments. Furthermore, appropriate combinations of several of the above-described embodiments are within the scope of the present disclosure.

[0041] REFERENCE SIGNS LIST 1, 1a to 1c Actuator 5 Motor 10 Stator 11 Stator core 12 Housing 13 Coil 20 Rotor 21 Rotor core 22 Magnet 23 Hollow shaft 23A, 23B Expansion portion 25 Boss 30 Reducer 31 Low-speed tube 32 Output shaft 35 First screw (rotary disk fixing portion) 40 Encoder 41 Rotary disk 42 Detector 43 Encoder fixing portion 46 Slot 49 Board 51, 52 Bearings 61, 62 Fixing portion C Wire body

Claims

1. a motor including a rotor with a hollow shaft; an encoder unit having a rotating disk; Between the rotating disk and the motor, the hollow shaft includes an expansion portion whose thickness is expanded; The inner diameter of the hollow shaft is greater than the inner diameter of the expansion portion; The actuator, wherein the rotating disk is fixed to the extension portion of the hollow shaft by a rotating disk fixing portion.

2. a reducer coupled to the other end of the hollow shaft; a low speed pipe connected to the output shaft of the reducer; The actuator of claim 1 , wherein the low speed tube extends inside the hollow shaft toward the encoder unit and terminates short of the expanded portion.

3. 3. The actuator of claim 1, further comprising a tube extending at least partially from a location corresponding to the extension toward the rotating disk.

4. a reducer coupled to the other end of the hollow shaft; a low speed pipe connected to the output shaft of the reducer; the low speed tube extends at least partially within the hollow shaft toward the encoder unit; The actuator of claim 1 , wherein the low speed tube has a step corresponding to the expanded portion of the hollow shaft.

5. 3. The actuator according to claim 1, wherein the rotary disk fixing portion is a plurality of screws extending parallel to an axial direction of the hollow shaft or extending in a radial direction of the hollow shaft.