Actuator

Abstract

This actuator includes: a motor having a hollow motor shaft; a speed reducer having an output shaft; a hollow pipe connected to the output shaft and extending toward the motor side through the motor shaft; a hollow spacer member provided at an end of the hollow pipe; and a support part disposed between the inner peripheral surface of the actuator and the outer peripheral surface of the spacer member and rotatably supporting the spacer member.

Description

Actuator

[0001] The present disclosure relates to actuators.

[0002] The actuator may include a servo motor, a reducer, and an encoder, all connected to one another. The actuator disclosed in JP 2020-205742 A has a motor shaft formed as a hollow shaft, and a hollow tube connected to the output shaft of the reducer extends through the inside of the motor shaft toward the motor. A support (referred to as "holding portion 922" in JP 2020-205742 A) is provided between the end of the hollow tube and the encoder, rotatably supporting the end of the hollow tube.

[0003] Japanese Patent Publication No. 2020-205742

[0004] The outer circumferential surface of the distal end of the hollow tube and the inner circumferential surface of the inner ring of the support part must be joined together, but it is not easy to accurately join the outer circumferential surface of the distal end of the hollow tube to the inner circumferential surface of the inner ring of the support part.

[0005] Therefore, it is desirable to have an actuator in which the distal end of a hollow tube can be easily and accurately attached to the support of the actuator.

[0006] According to a first aspect of the present disclosure, there is provided an actuator comprising: a motor having a hollow motor shaft; a reducer connected to the motor and having an output shaft; a hollow tube connected to the output shaft of the reducer and extending through the motor shaft toward the motor; a hollow spacer member provided at the end of the hollow tube; and a support portion disposed between an inner circumferential surface of the actuator and an outer circumferential surface of the spacer member, which rotatably supports the spacer member.

[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] 7A is an axial cross-sectional view of an actuator in a typical embodiment; FIG. 7B is a perspective view of the end of a hollow tube in one embodiment; FIG. 7C is a perspective view of a spacer member; FIG. 7D is a perspective view of a hollow tube, a spacer member, and a bearing; FIG. 7E is a cross-sectional view of a hollow tube, a spacer member, and a bearing in the axial direction of the hollow tube; FIG. 7F is a partial axial cross-sectional view of an actuator in the prior art; FIG. 7G is a perspective view of a spacer member in another example; FIG. 7H is an axial cross-sectional view of an actuator in another embodiment; FIG. 7I is an axial cross-sectional view of an actuator in yet another embodiment; FIG. 7J is a perspective view of a hollow tube, a spacer member, and a bearing in a modified example; FIG. 7I is a perspective view of the end of the hollow tube shown in FIG. 7A; FIG. 7I is an exploded perspective view of the spacer member shown in FIG. 7A.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings, in which corresponding components are designated by common reference numerals throughout the drawings.

[0010] 1 is an axial cross-sectional view of an actuator according to a typical embodiment, which is incorporated into a machine having a shaft, such as a robot or machine tool.

[0011] The actuator 5a mainly includes a motor 10, such as a servo motor, consisting of a stator 11 and a rotor 12, an electromagnetic brake B connected to the motor 10, a reducer 20 connected to the motor shaft 13 of the motor 10, a force sensor S coupled to the reducer, and an encoder E.

[0012] In the present application, it is defined that the reducer 20 is disposed in front of the motor 10, and the motor 10 is disposed behind the reducer 20. In addition, in principle, the "radial direction" in the present application means the radial direction of the actuator 5a, etc., and the "axial direction" means the axial direction of the actuator 5a, etc.

[0013] The motor 10 includes a rotor 12 that rotates integrally with a motor shaft 13, and a stator 11 that is disposed to surround the rotor 12. The tip of the output shaft 23 of the reducer 20 is connected to a link 2 (not shown) via a force sensor S. Therefore, the actuator 5 controls the positioning of the link 2 (not shown) by rotating it relative to the actuator 5 within a predetermined operating range. The reduction ratio of the reducer 20 is, for example, 1:50.

[0014] The motor shaft 13 is, for example, a hollow shaft, and has a primary encoder 15 equipped with a rotary disk 15A attached to its rear end. The primary encoder 15 is, for example, an absolute encoder, and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detector 15B, which uses a known method to detect the absolute position within one rotation of the motor shaft 13 and the total number of rotations of the motor shaft 13. The detected information is stored in a memory, for example, a volatile memory or a nonvolatile memory, of the detector 15B.

[0015] A hollow tube 23a is coupled to the output shaft 23 of the reducer 20, and this hollow tube 23a extends toward the motor 10 through the hollow motor shaft 13. A secondary encoder 25 equipped with a rotary disk 25A is attached near the rear end of the hollow tube 23a. The output shaft 23 of the reducer 20 and the hollow tube 23a may be integrally formed. In other words, the hollow tube 23a may be a part of the output shaft 23.

[0016] The secondary encoder 25 is, for example, an absolute encoder, and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detector 25B, which uses a known method to detect the absolute position within one rotation of the output shaft 23 and the total number of rotations. The detected information is stored in a memory, such as a volatile memory or a non-volatile memory, of the detector 25B. The primary encoder 15 and secondary encoder 25 may be collectively referred to as an encoder E.

[0017] The force sensor S is composed of a torque sensor or the like that detects the force acting around the axis of the actuator 5a. The force sensor S preferably has a spring portion (not shown) that exhibits spring properties. When a force acts around the axis of the actuator 5a, the spring portion deforms, and the force acting around the axis can be detected through the amount of deformation of the spring portion. The force sensor S may be a strain gauge type, a capacitance type, a magnetic type, an optical encoder type, or the like.

[0018] As shown in the figure, the force sensor S, reducer 20, motor 10, electromagnetic brake B, and encoder E, which are coaxially connected to one another, preferably have a hollow structure. Furthermore, the hollow portions of the force sensor S, reducer 20, motor 10, electromagnetic brake B, and encoder E preferably have a common inner diameter. This allows for smooth placement of the hollow tube 23a. Hereinafter, the internal spaces of the force sensor S, reducer 20, motor 10, electromagnetic brake B, and encoder E may be collectively referred to as the hollow portion 22. Furthermore, at least one filament L, such as a signal line, a current supply line, or an air tube, is assumed to pass through the hollow tube 23a.

[0019] As shown in Fig. 1, a circular first support member 18 extending in the radial direction is attached to the rear end of the motor shaft 13. The first support member 18 is provided with an annular protrusion 18a, which preferably engages with the rear end of the motor shaft 13. A radially outer portion of the first support member 18 extends in the axial direction of the motor shaft 13 so as to be spaced away from the motor 10. An annular rotating disk 15A for the primary encoder 15 is provided on the rear end surface of the portion extending in the axial direction. In other words, the rotating disk 15A is supported by a portion of the first support member 18.

[0020] Furthermore, a flange 10b is provided at the rear end of the housing 10a of the actuator 5a. A cylindrical extension member 41 is attached to the flange 10b. The rear end surface of the extension member 41 extends radially inward. Furthermore, a support portion 29 that rotatably supports a spacer member 50 (described later) is provided on the inner circumferential surface of the portion extending radially inward. In other words, the support portion 29 rotatably supports the hollow tube 23a via the spacer member 50.

[0021] A typical example of the support portion 29 is a bearing 29. The support portion 29 may be another structure capable of rotatably supporting the hollow tube 23a and the spacer member 50, such as a protrusion having a shape generally corresponding to the outer circumferential surface of the spacer member 50. In the following, the description will be continued assuming that the support portion 29 is a bearing 29.

[0022] The second support member 28 extends from near the rear end of the actuator 5a toward the reducer 20, and the tip of the portion extending toward the reducer 20 extends radially outward. An annular rotating disk 25A for the secondary encoder 25 is provided on the rear end surface of the portion extending radially outward. In other words, the rotating disk 25A is supported by a portion of the second support member 28. A substrate 42 including the detection units 15B and 25B is attached to the inner circumferential surface of the extension member 41. The inner diameter of the second support member 28 is approximately equal to the outer diameter of the hollow tube 23a, and therefore the second support member 28 rotates integrally with the hollow tube 23a. For this purpose, the inner circumferential surface of the second support member 28 and the outer circumferential surface of the hollow tube 23a may be provided with concave and convex portions that can engage with each other.

[0023] With this configuration, the rotating disk 15A of the primary encoder 15 and the rotating disk 25A of the secondary encoder 25 are arranged concentrically with a predetermined gap between them. Note that the rotating disk 15A and the rotating disk 25A may be arranged concentrically with other configurations, and such configurations are also included in the scope of the present disclosure.

[0024] 1, the rear end of the hollow tube 23a does not reach the bearing 29. A spacer member 50 is disposed between the rear end of the hollow tube 23a and the bearing 29. The spacer member 50 serves to connect the hollow tube 23a and the bearing 29. The spacer member 50 is hollow, and at least one filament L passes through the hollow tube 23a and the spacer member 50.

[0025] FIG. 2A is a perspective view of the distal end of a hollow tube in one embodiment. As shown in FIG. 2A, at least one protrusion 61 extending in the longitudinal direction of hollow tube 23a is formed at the rear end of hollow tube 23a. The at least one protrusion 61 may be formed by cutting out a portion of the distal end of hollow tube 23a. Alternatively, at least one protrusion 61 may be attached to the distal end of hollow tube 23a. When multiple protrusions 61 are formed, these protrusions 61 are preferably formed at equal intervals around the circumference of the hollow tube. Furthermore, it is preferable that the protrusions 61 do not extend radially toward the interior space of hollow tube 23a, so that the filament L (see FIG. 4A) does not interfere with the protrusions 61.

[0026] 2B is a perspective view of the spacer member. The hollow spacer member 50 has a first portion 51 to be engaged with the hollow tube 23a and a second portion 52 to be engaged with the bearing 29. The second portion 52 is located rearward of the first portion 51 and is arranged coaxially with the first portion 51. A flange 53 extending radially outward is provided between the first portion 51 and the second portion 52. The spacer member 50, including the first portion 51, the second portion 52, and the flange 53, is preferably formed integrally. The wall thicknesses of the first portion 51 and the second portion 52 are generally equal. The spacer member 50 is preferably made of, for example, metal.

[0027] 2B, the inner and outer diameters of the first portion 51 are smaller than the inner and outer diameters of the second portion 52. This is because, as can be seen from FIG. 1, the inner and outer diameters of the hollow tube 23a to which the first portion 51 is connected are smaller than the inner and outer diameters of the bearing 29 to which the second portion 52 is connected. In other words, the outer diameters of the first portion 51 and the second portion 52 are determined according to the dimensions of the corresponding hollow tube 23a and bearing 29.

[0028] As can be seen in FIG. 2B , at least one receiving portion 62 is formed on the first portion 51 side of the flange 53. The receiving portion 62 has a size suitable for receiving and engaging the protrusion 61. In FIG. 2B , the first portion 51 has a thick portion 63 provided circumferentially adjacent to the flange 53. The receiving portion 62 may be formed by partially cutting out this thick portion 63. Alternatively, the receiving portion 62 may be formed by partially adding a member corresponding to the thick portion 63 to the outer circumferential surface of the first portion 51. When multiple receiving portions 62 are formed, these receiving portions 62 are preferably formed at equal intervals in the circumferential direction of the first portion 51. Note that the protrusions 61 and receiving portions 62 may have other configurations.

[0029] 3A is a perspective view of the hollow tube, the spacer member, and the bearing. In FIG. 3A, the spacer member 50 is engaged with the hollow tube 23a and the bearing 29. As shown in FIG. 3A, the protrusion 61 and the receiving portion 62 are engaged with each other, so that the spacer member 50 and the hollow tube 23a do not rotate relative to each other in the circumferential direction.

[0030] 3B is a cross-sectional view of the hollow tube, spacer member, and bearing taken along the axial direction of the hollow tube. As shown in FIG. 3B, bearing 29 has an outer ring 29a, an inner ring 29b, and a plurality of balls 29c disposed between outer ring 29a and inner ring 29b. The outer peripheral surface of first portion 51 of spacer member 50 engages with the inner peripheral surface of hollow tube 23a. Similarly, the outer peripheral surface of second portion 52 engages with the inner peripheral surface of inner ring 29b.

[0031] In other words, the first and second portions 51, 52 of the spacer member 50 are sized to engage, preferably with a tight fit, with the hollow tube 23a and the inner ring 29b, respectively. As previously mentioned, the spacer member 50 can be made of metal, so the size of the spacer member 50 can be relatively freely determined according to the needs of the user of the actuator 5a.

[0032] FIG. 4B is a partial axial cross-sectional view of a conventional actuator. Similar components in FIG. 4B are designated by similar reference numerals. To precisely couple the outer circumferential surface of the other end of hollow tube 23a' to the inner circumferential surface of the inner ring of bearing 29', it is preferable to tightly fit the other end of hollow tube 23a' onto the inner circumferential surface of the inner ring of bearing 29'. However, bearing 29' in the conventional art and bearing 29 in the present disclosure are standard products manufactured by bearing manufacturers and have dimensions that vary in increments of 5 millimeters. Therefore, the dimensions of the bearing cannot be freely changed. Therefore, the dimensions of hollow tube 23a' must be changed. However, hollow tube 23a' in the conventional art and hollow tube 23a in the present disclosure are typically made of resin, making it difficult to precisely machine the hollow tube to within a few millimeters.

[0033] In contrast, the present disclosure employs a spacer member 50 whose dimensions can be freely determined. Therefore, by creating a spacer member 50 with an appropriate dimension, the end of the hollow tube 23a can be easily and accurately attached to the bearing 29 of the actuator 5a via the spacer member 50. In other words, the spacer member 50, which has a first portion 51 and a second portion 52 with different diameters, serves as a radial spacer between the hollow tube 23a and the bearing 29.

[0034] 3B, the front surface of the flange 53 abuts against the end of the hollow tube 23a, and the rear surface of the flange 53 abuts against the front side of the inner ring 29b. In other words, the thickness of the flange 53 is approximately equal to the distance between the end of the hollow tube 23a and the front side of the bearing 29. Therefore, the flange 53 serves to properly position the rear end of the hollow tube 23a and the front end of the bearing 29, and the spacer member 50 including the flange 53 serves as an axial spacer between the hollow tube 23a and the bearing 29.

[0035] 4A is a partial axial cross-sectional view of the actuator. In FIG. 4A, a wire body fixing portion 71 is attached to the rear end of the actuator 5a, for example, the rear end of the encoder E. For example, the wire body fixing portion 71 is a substantially L-shaped member having two extending portions 61a and 61b that are perpendicular to each other. One extending portion 61a is attached to the rear end of the actuator 5a, and the other extending portion 61b extends from the rear end side of the actuator 5a into the spacer member 50.

[0036] At least one filament L is attached to the other extension 61b by a mounting member 72, for example, a cable tie. The filament L passes through the inside of the hollow tube 23a and penetrates the actuator 5a. Although not shown in the drawings, a similar filament fixing portion 71 may also be provided at the front end of the actuator 5a.

[0037] As can be seen from FIG. 4A, the other extension 61b generally terminates at the second portion 52 of the spacer member 50, and the other extension 61b does not extend very far into the first portion 51 of the spacer member 50.

[0038] Therefore, the other extension 61b of the filament fixing portion 71 and the related member 72 are generally disposed within the second portion 52 of the spacer member 50. The inner diameter D1 of the second portion 52 is larger than the inner diameter D0 of the hollow tube 23a. In other words, since the other extension 61b is disposed within the second portion 52, which has ample space, the present disclosure provides greater freedom in arranging the other extension 61b, and also allows a greater number of filaments L to be attached to the other extension 61b.

[0039] Referring again to Figure 4B, the distal end of hollow tube 23a' extends to the rear end of actuator 5'. In this case, since spacer member 50 is not provided, bearing 29' shown in Figure 4B is positioned radially inward of bearing 29 shown in Figure 4A.

[0040] In Fig. 4B, the inner diameter of the location where the other extension 61b of the filament fixing portion 71 and related components are disposed is equal to the inner diameter D0 of the hollow tube 23a. Therefore, compared to Fig. 4A, there is less space available for disposing the other extension 61b. Therefore, in the prior art, the degree of freedom in disposing the other extension 61b is limited, and it is also difficult to attach a large number of filaments L to the other extension 61b.

[0041] In contrast, in the configuration shown in Figure 4A described above, the other extension of the filament fixing portion 71 and related members can be arranged with a high degree of freedom in the space determined by the inner diameter of the second portion 52, which is larger than the space determined by the inner diameter of the hollow tube 23a.

[0042] Fig. 5 is a perspective view of a spacer member in another embodiment. The spacer member 50a shown in Fig. 5 is engaged with a hollow tube 23b having a larger diameter than the hollow tube 23a and a bearing 29 similar to that described above.

[0043] The spacer member 50a has a first portion 51a to be engaged with the hollow tube 23b and a second portion 52a that is disposed coaxially with the first portion 51a and to be engaged with the bearing 29. A flange 53a is provided between the first portion 51a and the second portion 52a. The spacer member 50a, including the first portion 51a, the second portion 52a, and the flange 53a, is preferably formed integrally. The spacer member 50a is preferably made of metal. The spacer member 50a also has a hollow structure similar to that described above.

[0044] 5, because hollow tube 23b is larger than hollow tube 23a, the inner and outer diameters of first portion 51a of spacer member 50a are larger than the inner and outer diameters of second portion 52a. When using such a spacer member 50a, substantially the same effects as those described above can be obtained. Furthermore, when second portion 52a is smaller than first portion 51a, a bearing 29 with a smaller diameter can be used, resulting in reduced weight and manufacturing costs for the actuator.

[0045] Fig. 6A is an axial cross-sectional view of an actuator according to another embodiment. The actuator 5b shown in Fig. 6A mainly includes a motor 10 consisting of a stator 11 and a rotor 12, a reducer 20 connected to the motor 10, and an encoder E. In other words, the actuator 5b does not include a force sensor S or an electromagnetic brake B. The extension member 41 is attached to the stator 11. In this case, it will be apparent that the actuator 5b can be made even smaller.

[0046] Fig. 6B is an axial cross-sectional view of an actuator according to yet another embodiment. The actuator 5c shown in Fig. 6B mainly includes a motor 10 consisting of a stator 11 and a rotor 12, and a reducer 20 connected to the motor 10. In other words, the actuator 5c does not include a force sensor S, an electromagnetic brake B, or an encoder E. The motor shaft 13 is rotatably attached to the extension member 41 by another bearing. In such a case, it will be apparent that the actuator 5c can be made even more compact. A configuration in which the actuator 5a does not include at least one of the force sensor S, the electromagnetic brake B, and the encoder E is also within the scope of the present disclosure.

[0047] Furthermore, the scope of the present disclosure also includes hollow tube 23a that does not have protrusion 61 and spacer member 50 (see FIG. 1 ) that does not have receiving portion 62. Similarly, the scope of the present disclosure also includes spacer member 50 that does not have flange 53. Furthermore, the scope of the present disclosure also includes spacer member 50 in which the inner diameter and outer diameter of first portion 51 are equal to the inner diameter and outer diameter of second portion 52, respectively.

[0048] Fig. 7A is a perspective view of a hollow tube, a spacer member, and a bearing in a modified example. Furthermore, Figs. 7B and 7C are a perspective view of the end of the hollow tube and an exploded perspective view of the spacer member shown in Fig. 7A, respectively. The spacer member 50b shown in Fig. 7A is composed of a first portion 51b and a second portion 52b. As can be seen from Fig. 7C, the first portion 51b and the second portion 52b can be separate components. The first portion 51b and the second portion 52b are preferably composed of the same material, for example, metal.

[0049] The outer diameter of the first portion 51b is the same as the outer diameter of the first portion 51, and the outer diameter of the rear end of the second portion 52b is the same as the outer diameter of the second portion 52. The outer diameter of the front end of the second portion 52b is the same as the outer diameter of the first portion 51b. As described above, the inner diameters of the first portion 51b and the second portion 52b may be different from each other or may be equal to each other.

[0050] As shown in Figure 7B, a pair of protrusions 61a extending in the longitudinal direction of the hollow tube 23a is formed at the rear end of the hollow tube 23a. The pair of protrusions 61a preferably face each other in the diametrical direction. Each of the pair of protrusions 61a preferably has a predetermined length in the circumferential direction.

[0051] As shown on the left side of Figure 7C, a pair of receiving portions 62a having dimensions suitable for receiving and engaging the pair of protrusions 61a are formed at the front end of the annular first portion 51b. The pair of receiving portions 62a are preferably diametrically opposed to each other. Furthermore, a pair of receiving portions 62b having dimensions suitable for receiving and engaging the pair of protrusions 61b (described below) are formed at the rear end of the first portion 51b. The pair of receiving portions 62b are preferably diametrically opposed to each other.

[0052] Furthermore, as can be seen from Fig. 7C, the positions of the pair of receiving portions 62a in the circumferential direction of the first portion 51b are preferably different from the positions of the pair of receiving portions 62b in the circumferential direction. In Fig. 7C, the positions of the pair of receiving portions 62a are different from the positions of the pair of receiving portions 62b by about 90 degrees.

[0053] As shown on the right side of Fig. 7C, a pair of protrusions 61b extending in the longitudinal direction of the annular second portion 52b is formed at the front end of the second portion 52b. Each of the pair of protrusions 61b preferably has a predetermined length in the circumferential direction. As described above, the pair of protrusions 61b can be received in a pair of receiving portions 62b.

[0054] With this configuration, when hollow tube 23a and first portion 51b are assembled in the axial direction, pair of protrusions 61a and pair of receiving portions 62a engage with each other, preventing hollow tube 23a and first portion 51b from moving relative to each other in the circumferential direction. Similarly, when first portion 51b and second portion 52b are assembled in the axial direction, pair of receiving portions 62b and pair of protrusions 62a engage with each other, preventing first portion 51b and second portion 52b from moving relative to each other in the circumferential direction.

[0055] Therefore, the first portion 51b and the second portion 52b cooperate with the end of the hollow tube 23a to function as an Oldham coupling. In other words, the end of the hollow tube 23a and the second portion 52b correspond to the hub of the Oldham coupling, and the first portion 51b functions as an insert for the Oldham coupling.

[0056] In this case, the same effect as described above can be obtained. Furthermore, in this case, since the first portion 51 b and the second portion 52 b are separate members, it will be understood that these members can be easily manufactured. Note that cases in which multiple pairs of protrusions and receiving portions are formed are also within the scope of the present disclosure.

[0057] An advantage of at least one of the embodiments described above is that the distal end of the hollow tube can be easily and accurately attached to the support of the actuator.

[0058] 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.

[0059] The following supplementary notes are further disclosed regarding the above embodiments and variations. (Supplementary Note 1) An actuator comprising: a motor having a hollow motor shaft; a reducer connected to the motor and having an output shaft; a hollow tube connected to the output shaft of the reducer and extending toward the motor through the motor shaft; a hollow spacer member provided at an end of the hollow tube; and a support portion disposed between an inner circumferential surface of the actuator and an outer circumferential surface of the spacer member, the support portion rotatably supporting the spacer member. (Supplementary Note 2) The actuator according to claim 1, further comprising: an encoder that detects at least one of the position of the motor shaft of the motor and the position of the output shaft of the reducer, the support portion being disposed between the inner circumferential surface of the encoder and the outer circumferential surface of the spacer member. (Supplementary Note 3) The actuator according to claim 1, wherein the outer circumferential surface of one end of the spacer member is generally flush with the inner circumferential surface of the hollow tube, and the outer circumferential surface of the other end of the spacer member is generally flush with the inner circumferential surface of the support portion. (Supplementary Note 4) The actuator according to claim 3, wherein the end of the hollow tube is provided with at least one protrusion extending in the longitudinal direction of the hollow tube, and the one end of the spacer member is formed with a receiving portion that engages with the at least one protrusion. (Supplementary Note 5) The actuator according to claim 1, wherein the support portion is a bearing. (Supplementary Note 6) The actuator according to Supplementary Note 1, wherein the spacer member includes an Oldham coupling.

[0060] DESCRIPTION OF SYMBOLS 5a to 5c Actuator 10 Motor 10a Housing 10b Flange 11 Stator 12 Rotor 13 Motor shaft 15 Primary encoder 15A Rotating disk 15B Detection section 18 First support member 18a Projection 20 Reducer 23 Output section 23a, 23b Hollow tube 25A Rotating disk 25B Detection section 28 Second support member 29 Bearing 41 Extension member 42 Substrate 50, 50a Spacer member 51, 51a First portion 52, 52a Second portion 53, 53a Flange 61 Projection 62 Receiving portion 71 Wire body fixing portion 72 Mounting member B Electromagnetic brake E Encoder L Wire body S Force sensor

Claims

1. An actuator comprising: a motor having a hollow motor shaft; a reducer connected to the motor and having an output shaft; a hollow tube connected to the output shaft of the reducer and extending through the motor shaft toward the motor; a hollow spacer member provided at the end of the hollow tube; and a support portion disposed between the inner circumferential surface of the actuator and the outer circumferential surface of the spacer member, for rotatably supporting the spacer member.

2. An actuator according to claim 1, further comprising an encoder that detects at least one of the position of the motor shaft of the motor and the position of the output shaft of the reducer, and the support portion is disposed between the inner peripheral surface of the encoder and the outer peripheral surface of the spacer member.

3. An actuator according to claim 1, wherein the outer peripheral surface of one end of said spacer member is approximately equal to the inner peripheral surface of said hollow tube, and the outer peripheral surface of the other end of said spacer member is approximately equal to the inner peripheral surface of said support portion.

4. The actuator according to claim 3, wherein the end of the hollow tube is provided with at least one protrusion extending in the longitudinal direction of the hollow tube, and the one end of the spacer member is formed with a receiving portion that engages with the at least one protrusion.

5. The actuator of claim 1, wherein the support is a bearing.

6. The actuator of claim 1, wherein the spacer member comprises an Oldham coupling.

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