Rotary actuator

Abstract

To provide a rotary actuator having a high degree of freedom in selecting an output shaft.SOLUTION: An rotary actuator (1) includes a wave generator (6) stored in a housing (5) for driving force to be transmitted from a motor (2) thereto, a flex spline (7) stored in the housing (5) for driving force to be transmitted from the wave generator (6) thereto, a first circular spline (8) fixed into the housing (5) and having internal teeth (8a) threaded to external teeth (7a) of the flex spline (7), a second circular spline (9) stored in the housing (5) and having internal teeth (9a) threaded to the external teeth (7a) of the flex spline (7), and an output shaft (10) stored in the housing (5) and having external teeth (10c) threaded to the internal teeth (9a) of the second circular spline (9).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to rotary actuators. [Background technology]

[0002] For example, the rotary actuator in Patent Document 1 uses a Harmonic Drive (registered trademark) as a reducer. This rotary actuator is configured so that the driving force of the motor is transmitted from a wave generator via a flexspline to a circular spline formed integrally with the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 024340 Summary of the Invention [Problem to be solved by the invention]

[0004] The present applicant has found the following problem: In the rotary actuator of Patent Document 1, the output shaft is integrally formed with the circular spline, so when changing the shape of the output shaft, it is necessary to recreate the output shaft and the circular spline, resulting in a problem of low flexibility in selecting the output shaft.

[0005] The present disclosure has been made in consideration of such problems, and realizes a rotary actuator with a high degree of freedom in selecting an output shaft. [Means for solving the problem]

[0006] A rotary actuator according to one aspect of the present disclosure includes: A motor; Housing and a wave generator rotatably accommodated within the housing and connected to the motor so as to transmit driving force; a flexspline that is rotatably accommodated inside the housing and covers an outer peripheral surface of the wave generator so as to be able to transmit a driving force from the wave generator; a first circular spline that is fixed to the housing while being accommodated inside the housing and has internal teeth that mesh with the external teeth of the flexspline; a second circular spline rotatably accommodated within the housing and having internal teeth that mesh with the external teeth of the flexspline; an output shaft rotatably accommodated within the housing and having external teeth that mesh with the internal teeth of the second circular spline; Equipped with.

[0007] In the above-described rotary actuator, it is preferable that the meshing rate between the internal teeth of the second circular spline and the external teeth of the output shaft is 100%.

[0008] In the above-described rotary actuator, it is preferable that the meshing ratio between the external teeth of the flexspline and the internal teeth of the second circular spline is 30%.

[0009] In the above-described rotary actuator, it is preferable that a portion of the internal teeth of the second circular spline that is threadedly engaged with the external teeth of the flexspline and a portion that is threadedly engaged with the external teeth of the output shaft are continuous.

[0010] In the above-described rotary actuator, the second circular spline preferably includes an insertion portion for inserting the output shaft into the second circular spline. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to realize a rotary actuator with a high degree of freedom in selecting an output shaft. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a partial cross-sectional view showing the configuration of a rotary actuator according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of part II in FIG. [Figure 3] FIG. 4 is a perspective view showing a second circular spline in the rotary actuator of the embodiment. [Figure 4] FIG. 2 is a perspective view showing an output shaft of the rotary actuator according to the embodiment. [Figure 5] 5A to 5C are diagrams for explaining a method of forming a second circular spline in the rotary actuator according to the embodiment. [Figure 6] 5A to 5C are diagrams illustrating a flow of assembling the second circular spline, the output shaft, and the second bearing in the rotary actuator of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Specific embodiments to which the present disclosure is applied will be described in detail below with reference to the drawings. However, the present disclosure is not limited to the following embodiments. For clarity of explanation, the following description and drawings have been simplified as appropriate. Here, for clarity of explanation, the following description will be made using a three-dimensional (XYZ) coordinate system.

[0014] Fig. 1 is a partial cross-sectional view showing the configuration of a rotary actuator of this embodiment. Fig. 2 is an enlarged view of part II in Fig. 1. Fig. 3 is a perspective view showing a second circular spline in the rotary actuator of this embodiment. Fig. 4 is a perspective view showing an output shaft in the rotary actuator of this embodiment.

[0015] 1, a rotary actuator 1 of this embodiment includes a motor 2 and a reducer 3. An output shaft 2a of the motor 2 extends in the Y-axis direction and protrudes from a housing 2b of the motor 2 toward the negative side of the Y-axis. The reducer 3 is connected to the output shaft 2a of the motor 2 so as to be able to transmit driving force.

[0016] As shown in FIG. 1, the reducer 3 includes a cover 4, a housing 5, a wave generator 6, a flexspline 7, a first circular spline 8, a second circular spline 9, and an output shaft 10, and constitutes a harmonic drive.

[0017] 1, the cover 4 is a cylindrical body with a bottom that extends in the Y-axis direction and has a through-hole 4b that passes through a bottom 4a located on the negative side of the Y-axis in the Y-axis direction. The motor 2 is fixed to the cover 4 with the negative side of the Y-axis of the motor 2 inserted inside the cover 4.

[0018] 1, the housing 5 is a cylindrical body with a bottom extending in the Y-axis direction, and has a bottom 5a located on the negative side of the Y-axis and a through-hole 5b passing through the bottom 5a in the Y-axis direction. A cover 4 is fixed to the end of the housing 5 on the positive side of the Y-axis.

[0019] The wave generator 6 is a wave generating device used in a general harmonic drive, and the outer periphery of the wave generator 6 is substantially elliptical. As shown in FIG. 1, the wave generator 6 is rotatably accommodated inside the housing 5.

[0020] 1, the output shaft 2a of the motor 2 is connected to the input shaft 6a of the wave generator 6 so as to be able to transmit driving force. At this time, the end of the input shaft 6a of the wave generator 6 on the Y-axis positive side is inserted into the through-hole 4b of the cover 4 and is supported by the cover 4 via a first bearing 11.

[0021] As shown in Fig. 1, the flexspline 7 is a flexible cylindrical body and extends in the Y-axis direction. As shown in Fig. 2, the flexspline 7 has external teeth 7a. The external teeth 7a extend, for example, in the Y-axis direction.

[0022] As shown in FIG. 1, the flexspline 7 is rotatably accommodated inside the housing 5, and covers the outer peripheral surface of the wave generator 6 so that the major diameter portion of the wave generator 6 comes into contact with the flexspline 7 and can transmit driving force from the wave generator 6.

[0023] The first circular spline 8 is a cylindrical body extending in the Y-axis direction, and has internal teeth 8a as shown in Fig. 2. The internal teeth 8a extend, for example, in the Y-axis direction. The first circular spline 8 is fixed to the housing 5 while being accommodated inside the housing 5 as shown in Fig. 1.

[0024] 2, the internal teeth 8a of the first circular spline 8 are threadedly engaged with the Y-axis positive side portion of the external teeth 7a of the flexspline 7. In this case, the number of teeth of the internal teeth 8a of the first circular spline 8 is greater than the number of teeth of the external teeth 7a of the flexspline 7.

[0025] 3, the second circular spline 9 is a cylinder extending in the Y-axis direction. That is, the end on the Y-axis + side and the end on the Y-axis - side of the second circular spline 9 are open. The second circular spline 9 has internal teeth 9a.

[0026] 3, the internal teeth 9a extend in the Y-axis direction, and the end of the internal teeth 9a on the +Y-axis side reaches the end of the second circular spline 9 on the +Y-axis side. The internal teeth 9a have the same shape and number of teeth as the internal teeth 8a of the first circular spline 8.

[0027] As shown in FIGS. 1 and 2, the second circular spline 9 is rotatably accommodated inside the housing 5, and the Y-axis positive side portions of the internal teeth 9a of the second circular spline 9 are threadedly engaged with the Y-axis negative side portions of the external teeth 7a of the flexspline 7.

[0028] 1, the second circular spline 9 is restricted from moving in the Y-axis direction by the first C-ring 12 fitted onto the inner peripheral surface of the housing 5 and the bottom 5a of the housing 5. Here, it is preferable that the meshing ratio between the external teeth 7a of the flexspline 7 and the internal teeth 9a of the second circular spline 9 is about 30%.

[0029] As shown in Fig. 4, the output shaft 10 includes a shaft body 10a and a flange portion 10b. The shaft body 10a is, for example, a substantially cylindrical body and extends in the Y-axis direction. The flange portion 10b protrudes radially outward from the end of the shaft body 10a on the +Y-axis side. The flange portion 10b is a substantially annular body and includes external teeth 10c.

[0030] As shown in FIG. 1, the output shaft 10 is rotatably accommodated inside the housing 5, and the external teeth 10c of the output shaft 10 are threadedly engaged with the Y-axis-side portion of the internal teeth 9a of the second circular spline 9.

[0031] At this time, as shown in FIG. 1, the output shaft 10 is pushed toward the + side of the Y axis by the spacer 14, with the flange portion 10b of the output shaft 10 sandwiched between the side surface of the wave generator 6 on the - side of the Y axis and the second C-ring 13 fitted into the inner surface of the second circular spline 9.

[0032] 1, the shaft body 10a of the output shaft 10 is inserted into the through-hole 5b of the housing 5 and is supported by the housing 5 via a second bearing 15. The second bearing 15 is sandwiched between a second C-ring 13 and a third C-ring 16 fitted onto the outer peripheral surface of the shaft body 10a of the output shaft 10 via a spacer 14, thereby restricting movement in the Y-axis direction.

[0033] As shown in FIG. 1, the output shaft 10 supports the input shaft 6a of the wave generator 6 via a third bearing 17, with the end of the input shaft 6a of the wave generator 6 on the negative Y-axis side inserted into a cutout portion 10d formed on the side surface of the output shaft 10 on the positive Y-axis side.

[0034] Here, it is preferable that the meshing ratio between the internal teeth 9a of the second circular spline 9 and the external teeth 10c of the output shaft 10 is approximately 100%. This allows the connection force (i.e., torque transmission) between the second circular spline 9 and the output shaft 10 to be three times or more the connection force between the flexspline 7 and the second circular spline 9.

[0035] In the rotary actuator 1 of this embodiment, when the driving force of the motor 2 is transmitted to the wave generator 6, the wave generator 6 rotates while receiving a reaction force from the first circular spline 8, and transmits the driving force to the output shaft 10 via the second circular spline 9. This causes the output shaft 10 to rotate.

[0036] Such a rotary actuator 1 is configured so that the internal teeth 9a of the second circular spline 9 and the external teeth 10c of the output shaft 10 are threadedly engaged with each other, thereby enabling the transmission of driving force from the second circular spline 9 to the output shaft 10.

[0037] Therefore, for example, when the second circular spline 9 and the output shaft 10 are fixed together by a fastening means or by welding, space is required to arrange the fastening means or to perform welding, but the rotary actuator 1 of the present embodiment does not require such space, and the rotary actuator 1 can be made smaller.

[0038] Moreover, the rotary actuator 1 of the present embodiment does not have a configuration in which the circular spline and the output shaft are integrally formed, as in the rotary actuator of Patent Document 1, so that, for example, when changing the shape of the shaft body 10a of the output shaft 10, it is sufficient to replace only the output shaft 10. Therefore, the rotary actuator 1 of the present embodiment has a higher degree of freedom in selecting the output shaft 10 than the rotary actuator of Patent Document 1.

[0039] Furthermore, in the rotary actuator 1 of this embodiment, the portion of the internal teeth 9a of the second circular spline 9 that threads with the external teeth 7a of the flexspline 7 and the portion of the internal teeth 9a of the second circular spline 9 that threads with the external teeth 10c of the output shaft 10 can be formed continuously.

[0040] Therefore, the internal teeth 9a can be formed more easily than when the internal teeth that threadably engage with the external teeth 7a of the flexspline 7 in the second circular spline 9 and the internal teeth that threadably engage with the external teeth 10c of the output shaft 10 in the second circular spline 9 are formed separately.

[0041] Moreover, as shown in Fig. 5, the second circular spline 9 can be easily formed by cutting the cylindrical member 18 to a predetermined length after forming the internal teeth 9a on the inner peripheral surface of the cylindrical member 18. In Fig. 5, the cutting position of the cylindrical member 18 is indicated by a two-dot chain line.

[0042] Here, a description will be given of the process for assembling the second circular spline 9, the output shaft 10, and the second bearing 15 in the rotary actuator 1 of this embodiment. Fig. 6 is a diagram showing the process for assembling the second circular spline, the output shaft, and the second bearing in the rotary actuator of this embodiment.

[0043] First, as shown in Fig. 6(a), the second C-ring 13 is fitted onto the inner peripheral surface of the second circular spline 9. Next, as shown in Fig. 6(b), the output shaft 10 is placed on, for example, a cylindrical first jig 20 having an outer diameter smaller than the outer diameter of the flange portion 10b of the output shaft 10.

[0044] Then, the shaft body 10a of the output shaft 10 is inserted into the second circular spline 9 so that the external teeth 10c of the output shaft 10 are threadedly engaged with the internal teeth 9a of the second circular spline 9, and the second circular spline 9 is placed on the flange portion 10b of the output shaft 10 via the second C-ring 13.

[0045] In this case, as described above, if the internal teeth 9a of the second circular spline 9 extend in the Y-axis direction and the end of the internal teeth 9a on the Y-axis + side reaches the end of the second circular spline 9 on the Y-axis + side, the open portion on the Y-axis + side of the second circular spline 9 can function as an insertion portion 9b for inserting the output shaft 10, and the output shaft 10 can be easily inserted into the second circular spline 9.

[0046] Next, as shown in Fig. 6(c), a spacer 14 is fitted between the second circular spline 9 and the shaft body 10a of the output shaft 10. Then, as shown in Fig. 6(d), the shaft body 10a of the output shaft 10 is inserted into the second bearing 15 using a second jig 21 having a cylindrical portion 21a with an inner diameter larger than the outer diameter of the shaft body 10a of the output shaft 10, and the second bearing 15 is brought into contact with the spacer 14.

[0047] Thereafter, as shown in FIG. 6(e), the third C-ring 16 is fitted onto the outer peripheral surface of the shaft body 10a of the output shaft 10, and the second bearing 15 is sandwiched between the second C-ring 13 and the third C-ring 16 via the spacer 14, thereby assembling the second circular spline 9, the output shaft 10, and the second bearing 15.

[0048] In this way, the second circular spline 9, the output shaft 10, and the second bearing 15 can be assembled without welding or press-fitting, and no excessive load is applied to the second circular spline 9 during assembly, ensuring tooth profile accuracy.

[0049] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0050] 1 Rotary Actuator 2 Motor, 2a Output shaft, 2b Housing 3 Reducer 4 cover, 4a bottom, 4b through hole 5 housing, 5a bottom, 5b through hole 6 wave generator, 6a input shaft 7 flexspline, 7a external teeth 8 first circular spline, 8a internal teeth 9 second circular spline, 9a internal tooth, 9b insert 10 output shaft, 10a shaft body, 10b flange portion, 10c external teeth, 10d notch portion 12 First C-ring 13 Second C-ring 14 spacer 16 Third C-ring 18 Cylindrical member 20 First jig 21 second jig, 21a cylindrical portion

Claims

1. A motor; Housing and a wave generator rotatably accommodated within the housing and connected to the motor so as to transmit driving force; a flexspline that is rotatably accommodated inside the housing and covers an outer peripheral surface of the wave generator so as to be able to transmit a driving force from the wave generator; a first circular spline that is fixed to the housing while being accommodated inside the housing, and that has internal teeth that are meshed with the external teeth of the flexspline; a second circular spline rotatably accommodated within the housing and having internal teeth that mesh with the external teeth of the flexspline; an output shaft rotatably accommodated within the housing and having external teeth that mesh with the internal teeth of the second circular spline; A rotary actuator comprising:

2. 2. The rotary actuator according to claim 1, wherein a meshing ratio between the internal teeth of the second circular spline and the external teeth of the output shaft is 100%.

3. 3. The rotary actuator according to claim 2, wherein a meshing ratio between the external teeth of the flexspline and the internal teeth of the second circular spline is 30%.

4. 4. The rotary actuator according to claim 1, wherein a portion of the internal teeth of the second circular spline that threadably engages with the external teeth of the flexspline and a portion of the output shaft that threadably engages with the external teeth of the output shaft are continuous.

5. The rotary actuator according to claim 4 , wherein the second circular spline includes an insertion portion for inserting the output shaft into the second circular spline.

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