KR20160122023A

KR20160122023A - Harmonic drive

Info

Publication number: KR20160122023A
Application number: KR1020150052040A
Authority: KR
Inventors: 전용준
Original assignee: (주)에이치아이티오토모티브
Priority date: 2015-04-13
Filing date: 2015-04-13
Publication date: 2016-10-21
Also published as: KR101697335B1

Abstract

It is a technical object of the present invention to provide a harmonic drive capable of reducing the manufacturing time and manufacturing cost by replacing the wave generator with a simple configuration and a simple configuration. To this end, the harmonic drive of the present invention includes: a center shaft on which an input shaft is mounted; Three or more circular members disposed to surround the central axis and rotated by the central axis; A flex spline which is made of a thin material which is elastically deformable so as to surround the three or more circular members so as to have three or more convex portions corresponding to the three or more circular members and to which the output shaft is mounted; And a circular spline of a rigid material having a circular hollow portion so that the three or more convex portions of the flex spline are inscribed and fixed relative to the flex spline.

Description

Harmonic drive {Harmonic drive}

The present invention relates to a harmonic drive.

In general, harmonic drives, which are one type of decelerators, are widely used in industrial robots, NC machine tools, semiconductor manufacturing apparatuses, and the like. They are compact and lightweight, have large transmission torque, can achieve a high reduction ratio and have very little backlash .

1 is a perspective view schematically showing a conventional harmonic drive.

A conventional harmonic drive 10 includes a wave generator 11, a flex spline 12, and a circular spline, as shown in FIG. (13).

The wave generator 11 is a type of ball bearing and includes an elliptic hub 11a on which an input shaft (not shown) is mounted, a hub 11a on which an outer shaft An outer race 11b and a plurality of balls 11c in rolling contact between the hub 11a and the outer race 11b.

The flex spline 12 is made of a thin material that can be deformed to elastically deform together with the outer race 11b in accordance with the rotation of the elliptical hub 11b surrounding the outer race 11b of the wave generator 11 A flexible flexure spline body 12a having a plurality of gear teeth T1 formed on the outer circumferential surface thereof and a diaphragm 12a having an output shaft (not shown) formed at the end of the flexure spline body 12a 12b.

The circular spline 13 is mounted on a housing (not shown) and has a circular hollow shape in the center so as to surround the flex spline 12. The circular spline 13 is made of a rigid material. The circular spline body 12a, A plurality of gear teeth T2 are formed on the inner circumferential surface thereof so as to be meshed with a plurality of gear teeth T1. Particularly, in order to obtain the reduction gear ratio, the number of gear teeth T2 of the circular spline 13 is made larger than the gear teeth T1 of the flex spline 12.

Hereinafter, with reference to FIG. 2, the conventional harmonic drive 10 constructed as described above performs the following operations.

FIG. 2 is a diagram sequentially illustrating a state in which the harmonic drive of FIG. 1 is driven.

2 (a), the flex spline 12 wrapping the wave generator 11 is deformed in the same elliptical shape as the wave generator 11, and the circular spline 13 and the gear teeth T1 (T2). At this time, the gears positioned in the major axis direction of the flex spline 12 engage with the gears of the circular spline 13, while the gears positioned in the minor axis direction of the flex spline 12 do not engage with the gears of the circular spline 13.

2 (b), the wave generator 11 is rotated 90 degrees clockwise by an input shaft (not shown) while the circular spline 13 is fixed by a housing (not shown) or the like, The flex spline 12 is elastically deformed and is continuously rotated in a state of being decelerated by a gear ratio in a counterclockwise direction while being meshed with the gear of the circular spline 13.

Thereafter, as shown in Fig. 2 (c), while the wave generator 11 is rotated 180 degrees in the clockwise direction, the flex spline 12 is moved by the distance of one gear in the counterclockwise direction. Of course, the moving distance may be set differently according to the gear ratio.

2 (d), while the wave generator 11 is rotated 360 degrees in the clockwise direction, the flex spline 12 is moved in the counterclockwise decelerated state by the gear ratio, (D) of FIG. 2 shows the shifted state of the two gears (see arrows).

Therefore, the output shaft (not shown) mounted on the flex spline 12 can be rotated counterclockwise by a gear ratio while the wave generator 11 is rotated in the clockwise direction by the input shaft (not shown).

However, in the conventional harmonic drive 10, since the wave generator included therein has a technical configuration including an elliptic hub, an outer race of an elastically deformable material, and a plurality of balls, There is a problem that many processes are required to be assembled. Particularly, it is difficult to make the hub into an elliptical shape because it is difficult to generalize the hub, and there is a problem that manufacturing time and manufacturing cost are increased due to manual work.

It is a technical object of the present invention to provide a harmonic drive capable of reducing manufacturing time and manufacturing cost by replacing a wave generator with a simple configuration and a simple shape.

In order to achieve the above object, a harmonic drive according to an embodiment of the present invention includes: a center shaft on which an input shaft is mounted; Three or more circular members disposed to surround the central axis and rotated by the central axis; A flex spline which is made of a thin material which is elastically deformable so as to surround the three or more circular members so as to have three or more convex portions corresponding to the three or more circular members and to which the output shaft is mounted; And a circular spline of a rigid material having a circular hollow portion so that the three or more convex portions of the flex spline are inscribed and fixed relative to the flex spline.

Each of the three or more circular members may be a ball or a roller.

The outer circumferential surface of the flex spline and the inner circumferential surface of the circular spline have a smooth shape and can contact with each other.

As another example, the outer circumferential surface of the flex spline and the inner circumferential surface of the circular spline each have a plurality of spline gears and can be engaged with each other.

The central axis includes a central axis body; A circular enlargement concentric with the central axis body and having a diameter larger than that of the central axis body; And a plurality of central axis gears formed on an outer peripheral surface of the enlarged portion, wherein each of the three or more circular members includes a circular member body, a circular member concentric with the circular member body, A shrinking portion; And a plurality of circular gear teeth formed on an outer circumferential surface of the reduced portion and engaged with the plurality of center shaft gears.

As another example, the central axis may include a central axis body; A circular enlargement concentric with the central axis body and having a diameter larger than that of the central axis body; And a plurality of central axis gears formed on an outer peripheral surface of the enlarged portion, wherein each of the three or more circular members includes a circular member body; A circular shrinking portion concentric with the circular member body and smaller than the diameter of the circular member body; And a plurality of circular gear teeth formed on an outer circumferential surface of the reduced portion and engaged with the plurality of center shaft gears.

A friction increasing member may be attached to the outer circumferential surface of the flex spline or the inner circumferential surface of the circular spline.

Deceleration can be achieved by the difference between the length of the inner circumference of the circular spline and the length of the outer circumference of the flex spline.

The harmonic drive includes: respective hinges for rotatably supporting the three or more circular members; And a support member for supporting the three hinges together so that the three or more circular members are spaced apart from each other.

As described above, the harmonic drive according to the embodiment of the present invention can have the following effects.

According to the embodiment of the present invention, the configuration of an existing wave generator including an elliptical hub, an outer race of an elastically deformable material, and a plurality of balls is completely changed to serve as a central shaft and three or more circular members Instead, it is possible to eliminate the outer race of the conventional wave generator and to simplify the construction thereof, and to eliminate the elliptic hub which is difficult to be machined, so that the manufacturing time and manufacturing cost can be reduced.

1 is a perspective view schematically showing a conventional harmonic drive.
FIG. 2 is a diagram sequentially illustrating a state in which the harmonic drive of FIG. 1 is driven.
3 is a schematic view of a harmonic drive according to a first embodiment of the present invention.
FIG. 4 is a diagram sequentially illustrating a state in which the harmonic drive of FIG. 3 is driven.
5 is a schematic view of a harmonic drive according to a second embodiment of the present invention.
6 is a schematic view of a harmonic drive according to a third embodiment of the present invention.
7 is a schematic view of a harmonic drive according to a fourth embodiment of the present invention.
8 is a schematic view of a harmonic drive according to a fifth embodiment of the present invention.
9 is a schematic view of a harmonic drive according to a sixth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

3 is a schematic view of a harmonic drive according to a first embodiment of the present invention.

3, the harmonic drive 200 according to the first embodiment of the present invention includes a central shaft 210, three or more circular members 220, a flex spline 230, Spline < / RTI > Hereinafter, each component will be described in detail with continued reference to Fig.

The center shaft 210 is surrounded by three or more circular members 220 and is placed at the center thereof. An input shaft (not shown) is mounted on the center shaft 210. For example, although not shown, the central axis 210 and the input shaft may be coupled by a key-keyway coupling method or the like.

The three or more circular members 220 are disposed so as to surround the center shaft 210 with the center shaft 210 therebetween and are rotated by the center shaft 210. For example, as shown in FIG. 3, each of the outer circumferential surfaces of the three or more circular members 220 has a smooth shape, and the outer circumferential surface of the central shaft 210 contacting the circumferential surfaces may also have a smooth shape. Accordingly, the three or more circular members 220 can be rotated by friction due to the contact with the outer circumferential surface of the central shaft 210, respectively. For reference, when three or more circular members 220 are in contact with each other while being rotated, they can continue to rotate while being moved in a direction away from each other by "tugging "

Further, the three or more circular members 220 may include first, second, third and fourth circular members A, B, C and D as shown in Fig. 3 . Of course, although not shown, it is natural that three or more circular members 220 may be three, or may be five or more. Further, each of the three or more circular members 220 may be a spherical ball or a cylindrical roller.

The flex spline 230 integrally surrounds three or more circular members 220 and is elastically deformed so as to have three or more convex portions in conformity with three or more circular members 220 that move inward along the rotation of the central axis 210. [ It is made of as thin material as possible and can have a cylindrical shape. An output shaft (not shown) may be mounted at the end of the flex spline 230. For example, as shown in FIG. 3, the outer circumferential surface of the flex spline 230 may have an overall smooth shape. Further, the flex spline 230 may be made of a metal such as iron or aluminum or a non-metallic material.

The circular spline 240 is mounted on a relatively fixed housing (not shown). The circular spline 240 surrounds the flex spline 230 and has a ring-like circular shape in a circular shape. The circular spline 240 is made of a rigid material. And may have a smooth inner peripheral surface in contact with the smooth outer circumferential surface of the flex spline 230. [ Therefore, the flex spline 230 can be moved along the inner circumferential surface of the circular spline 240 due to the friction due to the contact while being in contact with the inner circumferential surface of the circular spline 240. Particularly, the length of the inner circumference of the circular spline 240 (the length based on the rotational direction of the central axis 210) and the length of the outer circumference of the flex spline 230 (the length based on the rotational direction of the central axis 210) ], The deceleration can be performed. For example, the length of the inner circumference of the circular spline 240 may be shorter than the length of the outer circumference of the flex spline 230 to reduce the rotational speed of the output shaft (not shown) and increase the force. In addition, when friction is generated due to contact, a phenomenon of slipping occurs between the inner circumferential surface of the circular spline 240 and the outer circumference of the flex spline 230. This slipping phenomenon causes a reduction ratio to be inaccurate, A technique of mounting an encoder (not shown) on the flex spline 230 or the output shaft may be added in order to correct the final position of the output shaft to a desired position.

Hereinafter, the operation of the harmonic drive 200 according to the first embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a view showing a state in which the harmonic drive using the friction shown in FIG. 3 is driven.

First, as shown in Fig. 4 (a), by the four convex shapes of the first, second, third and fourth circular members A, B, C, B and D The outer circumferential surfaces of four convex portions of the smooth outer circumferential surface of the flex spline 230 are brought into contact with the smooth inner circumferential surface of the circular spline 240 while the flex spline 230 is similarly elastically deformed into four convex shapes. The smooth outer circumferential surface lying on the four convex portions of the flex spline 230 is in contact with the smooth inner circumferential surface of the circular spline 240 while the smooth outer circumferential surface lying on the remaining portion of the flex spline 230 is in contact with the inner circumferential surface of the circular spline 240 It does not come into contact with the smooth inner circumferential surface.

4 (b), the center shaft 210 is rotated clockwise by an input shaft (not shown) while the circular spline 240 is fixed by a housing (not shown) or the like The first, second, third, and fourth circular members A, B, C, and D are rotated in the counterclockwise direction while friction is applied to the inner circumferential surface of the flex spline 230 And moves in the clockwise direction along the inner circumferential surface of the flex spline 230. During this movement, the flex spline 230 is resiliently deformed so that the smooth outer circumferential surface, which is continuously placed on the four convex portions, is in contact with the smooth inner surface of the spline 240 and is decelerated in the counterclockwise direction . That is, as shown in FIG. 4, it can be seen that the position P of the flex spline 230 is moved by a predetermined amount counterclockwise.

Subsequently, as shown in Figs. 4C and 4D, while the central axis 210 is rotated in the clockwise direction between the two wheels 2R and 3R, The flex spline 230 is rotated in the counterclockwise direction and can be rotated in a decelerated state by the ratio of the length of the outer circumference of the flex spline 230 to the length of the inner circumference of the circular spline 240 (hereinafter referred to as the length ratio).

Therefore, while the center axis 210 is rotated in the clockwise direction by the input shaft (not shown) without using the conventional wave generator (11 in FIG. 1) having a complex configuration as well as an elliptical shape, The output shaft (not shown) mounted on the output shaft can be decelerated by the length ratio in the counterclockwise direction and rotated.

Hereinafter, a harmonic drive 300 according to a second embodiment of the present invention will be described with reference to FIG.

5 is a schematic view of a harmonic drive according to a second embodiment of the present invention.

5, the harmonic drive 300 according to the second embodiment of the present invention is the same as the first embodiment of the present invention except that the friction enhancing member 350 is additionally provided Hereinafter, the friction increasing member 350 will be described. The same constituent elements as those of the first embodiment of the present invention described above are denoted by the same reference numerals.

The friction enhancing member 350 may be attached to the inner circumferential surface of the circular spline 240 as shown in Fig. 5 or may be attached to the outer circumferential surface 231a of the flex spline 230 although not shown. Furthermore, a coating, fusing, adhesion, or the like may be used in a manner of being adhered. Therefore, the friction increasing member 350 increases the frictional force due to the contact between the inner circumferential surface of the circular spline 240 and the outer circumferential surface of the flex spline 230, so that the phenomenon of slipping therebetween can be minimized. Further, a technique of mounting an encoder (not shown) on the flex spline 230 or the output shaft in case the output shaft (not shown) can not be positioned at a desired position due to a skid phenomenon, So that the final position of the target position can be corrected.

Further, the frictional thickening member 350 may be made of a material for reducing the vibration together with the friction increase. Therefore, in addition to the technique of reducing the vibration by making the outer circumferential surface of the flex spline 230 and the inner circumferential surface of the circular spline 240 in contact with each other smooth, vibration can be further reduced through the material. For example, rubber or urethane may be used as the friction increasing member 350 which can also serve as vibration absorbing member.

Hereinafter, a harmonic drive 400 according to a third embodiment of the present invention will be described with reference to FIG.

6 is a schematic view of a harmonic drive according to a third embodiment of the present invention.

6, the harmonic drive 400 according to the third embodiment of the present invention has the same structure as that of the above-described present invention except for the inner circumferential surface shape of the flex spline 430 and the outer circumferential surface shape of the circular spline 440, The inner circumferential surface shape of the flex spline 430 and the circumferential surface shape of the circular spline 440 will be described below. The same constituent elements as those of the first embodiment of the present invention described above are denoted by the same reference numerals.

6, a plurality of spline gears 430a may be formed on the outer circumferential surface of the flex spline 430, and a plurality of spline gears 430 may be formed on the inner circumferential surface of the flexure spline 430 so as to correspond to the plurality of spline gears 430a. A plurality of spline gears 440a may be formed. That is, the flex spline 430 which entirely surrounds the first, second, third, and fourth circular members A, B, C, and D is elastically deformed to have four convex portions, The spline gear 430a placed on the spline 440 engages with the spline gear 440a of the circular spline 440. [ Thus, while the circular spline 440 is fixed by the housing (not shown) or the like, while the center shaft 210 is rotated 90 degrees clockwise by the input shaft (not shown), the flex spline 430 is rotated The spline gear 430a which is resiliently deformed by the first, second, third, and fourth circular members A, B, C, and D continues to be placed on the four convex portions, And is rotated in a state of being decelerated by a gear ratio counterclockwise while engaging with gear 440a.

Therefore, in the harmonic drive 400 according to the third embodiment of the present invention, when it is assumed that the encoder-related technology configuration is not applied to the first embodiment of the present invention, An accurate reduction ratio can be realized.

Hereinafter, a harmonic drive 500 according to a fourth embodiment of the present invention will be described with reference to FIG.

7 is a schematic view of a harmonic drive according to a fourth embodiment of the present invention.

7, the harmonic drive 500 according to the fourth embodiment of the present invention has a structure in which the rotational force transmitting structure between the three or more circular members 520 and the center shaft 510 is transmitted, The third embodiment will be described below with reference to a rotational force transmission structure between the three or more circular members 520 and the center shaft 510. [ The same constituent elements as those of the third embodiment of the present invention described above are denoted by the same reference numerals.

The center axis 510 may include a central axis body 511, a circular enlargement 512, and a plurality of center axis gears 513, as shown in FIG. The circular enlarged portion 512 is formed to be larger than the diameter of the central axis body 511 in a concentric manner with the central axis body 511, A plurality of central shaft gears 513 are formed at intervals on the outer peripheral surface of the enlarged portion 512.

7, each of the three or more circular members 520 may include a circular member body 521, a circular shrinkage portion 522, and a plurality of circular member gears 523 have. The circular member 521 is formed to be smaller than the diameter of the circular member body 521 and is concentric with the circular member body 521, A plurality of circular member gears 523 are formed on the outer peripheral surface of the reduced portion 522 and are engaged with a plurality of central shaft gears 523.

A plurality of circular member gear teeth 523 formed on the reduced portion 522 of each circular member 520 are formed on the enlarged portion 512 of the central shaft 510. In this embodiment, The power loss can be reduced as compared with the third embodiment of the present invention, which is rotated by the friction due to contact with the smooth surface as the center shaft gear 513 is rotated.

Hereinafter, a harmonic drive 600 according to a fifth embodiment of the present invention will be described with reference to FIG.

8 is a schematic view of a harmonic drive according to a fifth embodiment of the present invention.

8, the harmonic drive 600 according to the fifth embodiment of the present invention has a structure in which the rotational force transmission structure between the three or more circular members 620 and the center shaft 610, The third embodiment of the present invention will be described below with reference to a rotational force transfer structure between the three or more circular members 620 and the center shaft 610. [ The same constituent elements as those of the third embodiment of the present invention described above are denoted by the same reference numerals.

The central shaft 610 may include a central shaft body 611, a circular enlarged portion 612, and a plurality of central shaft gears 613, as shown in Fig. The central enlarged portion 612 is formed concentrically with the central axis body 611 and is formed to be larger than the diameter of the central axis body 611, A plurality of central shaft gears 613 are formed on the outer peripheral surface of the enlarged portion 612 at intervals.

8, each of the circular members A and B of the three or more circular members 620 includes a circular member body 621, a circular reduced portion 622, Of the ring gear 623. The circular reduced portion 622 is formed concentrically with the circular member body 621 and formed to be smaller than the diameter of the circular member body 621. The circular member body 621 is formed as a body of the circular members A and B, And a plurality of circular gear members 623 are formed on the outer peripheral surface of the reduced portion 622 and engage with the plurality of central shaft gears 623. For example, three or more circular members 620 may include first, second, third and fourth circular members A, B, C, D, and first and third circular members Each of which includes a circular member body 621, a circular shrinkage portion 622, and a plurality of circular member gears 623.

Therefore, according to the fifth embodiment of the present invention, a plurality of circular member gear teeth 623 formed on the reduced portion 622 of the circular members A and B are disposed on the enlarged portion 612 of the center shaft 610 The power loss can be reduced as compared with the third embodiment of the present invention, which is rotated by the friction due to contact with the smooth surface as it rotates in engagement with the plurality of center shaft gears 613 formed.

Hereinafter, a harmonic drive 700 according to a sixth embodiment of the present invention will be described with reference to FIG.

9 is a schematic view of a harmonic drive according to a sixth embodiment of the present invention.

The harmonic drive 700 according to the sixth embodiment of the present invention is similar to the harmonic drive 700 according to the first embodiment of the present invention except for the support unit 760 that supports three or more circular members, The following description will focus on the support unit 760. FIG. The same constituent elements as those of the first embodiment of the present invention described above are denoted by the same reference numerals.

The support unit 760 may include a plurality of hinges 761 and one support member 762, as shown in Fig. Each of the hinges 761 rotatably supports three or more circular members 220 and the supporting member 762 connects the hinges 761 to each other so that the three or more circular members 220 are spaced apart from each other .

Therefore, according to the sixth embodiment of the present invention, since the three or more circular members 220 are not brought into contact with each other by the support unit 760 during the rotation, the three or more circular members 220 are " The power loss can be reduced as compared with the first embodiment in which rotation is continued while being moved in a direction away from each other.

As described above, the harmonic drives 200, 300, 400, 500, 600, and 700 according to the embodiments of the present invention can have the following effects.

According to the embodiments of the present invention, it is possible to provide an existing wave including an elliptical hub (11a in Fig. 1), an outer race of elastically deformable material (11b in Fig. 1), and a plurality of balls The configuration of the generator (11 in FIG. 1) is completely changed to provide a technical configuration that replaces the role of the central shaft 210 (510) 610 and the three or more circular members 220, 520, 620 , The outer race (11b in Fig. 1) of the conventional wave generator (11 in Fig. 1) is removed, and the configuration of the hub is simplified, and the elliptic hub (11a in Fig. 1) Time and manufacturing costs can be reduced.

Further, the effects mentioned in the embodiments of the present invention may be present.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

200, 300, 400, 500, 600: harmonic drive
210, 510, 610: center axis
220, 520, 620: three or more circular members
230, 430: Flex spline 240; 440: Circular spline
430a: Spline gear of a flex spline
440a: Circular spline spline gear
350: friction increasing members 511 and 611: central shaft body
512, 612: Circular enlarged portions 513, 613: A plurality of central axis gears
521, 621: circular member body 522, 622:
523, 623: a plurality of circular member gears
760: support unit 761: a plurality of hinges
762: Support member

Claims

A central axis on which the input shaft is mounted;
Three or more circular members disposed to surround the central axis and rotated by the central axis;
A flex spline which is made of a thin material which is elastically deformable so as to surround the three or more circular members so as to have three or more convex portions corresponding to the three or more circular members and to which the output shaft is mounted; And
A circular spline of a rigid material having a circular hollow portion so that the three or more convex portions of the flex spline are inscribed and fixed relative to the flex spline,
Containing
Harmonic drive.

The method of claim 1,
Each of the three or more circular members
Ball or roller
Harmonic drive.

The method of claim 1,
The outer circumferential surface of the flex spline and the inner circumferential surface of the circular spline each have a smooth shape,
Harmonic drive.

The method of claim 1,
Wherein the outer peripheral surface of the flex spline and the inner peripheral surface of the circular spline each have a plurality of spline gears,
Harmonic drive.

The method of claim 1,
The central axis,
A central axis body;
A circular enlargement concentric with the central axis body and having a diameter larger than that of the central axis body; And
A plurality of center axis gears formed on an outer peripheral surface of the enlarged portion,
Lt; / RTI >
Wherein each of the three or more circular members comprises:
A circular member body;
A circular shrinking portion concentric with the circular member body and smaller than the diameter of the circular member body; And
And a plurality of circular member gears formed on an outer peripheral surface of the reduced portion and engaged with the plurality of central shaft gears
Containing
Harmonic drive.

The method of claim 1,
The central axis,
A central axis body;
A circular enlargement concentric with the central axis body and having a diameter larger than that of the central axis body; And
A plurality of center axis gears formed on an outer peripheral surface of the enlarged portion,
Lt; / RTI >
Wherein each of the three or more circular members has a circular member,
A circular member body;
A circular shrinking portion concentric with the circular member body and smaller than the diameter of the circular member body; And
And a plurality of circular member gears formed on an outer peripheral surface of the reduced portion and engaged with the plurality of central shaft gears
Containing
Harmonic drive.

4. The method of claim 3,
A friction increasing member is attached to an outer peripheral surface of the flex spline or an inner peripheral surface of the circular spline
Harmonic drive.

4. The method of claim 3,
The deceleration is performed by the difference between the length of the inner circumference of the circular spline and the length of the outer circumference of the flex spline
Harmonic drive.

The method of claim 1,
The harmonic drive
Each of the hinges rotatably supporting the three or more circular members;
A supporting member for supporting and connecting the respective hinges so that the three or more circular members are spaced apart from each other,
Containing
Harmonic drive.