阅读说明：本技术 减速器 (Speed reducer ) 是由 井上仁 冈村晖久夫 于 2018-06-28 设计创作，主要内容包括：该减速器具有输入旋转体、输出旋转体以及壳体。输入旋转体包含输入轴、臂部以及辊。输出旋转体包含可动冕状齿轮和输出轴。壳体包含固定冕状齿轮。可动冕状齿轮和固定冕状齿轮相对于中心轴线垂直或者倾斜地扩展。而且,可动冕状齿轮与固定冕状齿轮具有彼此对置的侧面齿。辊与可动冕状齿轮的周向的一部分接触。可动冕状齿轮与固定冕状齿轮通过从辊受到的按压而局部啮合。而且,伴随着输入旋转体的旋转,可动冕状齿轮与固定冕状齿轮的啮合位置以中心轴线为中心,以输入转速沿周向变化。而且,通过可动冕状齿轮与固定冕状齿轮的齿数之差,可动冕状齿轮相对于固定冕状齿轮以输出转速旋转。(The speed reducer includes an input rotating body, an output rotating body, and a housing. The input rotating body includes an input shaft, an arm portion, and a roller. The output rotating body includes a movable crown gear and an output shaft. The housing contains a fixed crown gear. The movable ring gear and the fixed ring gear are extended perpendicularly or obliquely with respect to the central axis. The movable ring gear and the fixed ring gear have side teeth facing each other. The roller is in contact with a part of the circumferential direction of the movable crown gear. The movable crown gear and the fixed crown gear are partially engaged by the pressing force received from the roller. As the input rotating body rotates, the meshing position between the movable ring gear and the fixed ring gear changes in the circumferential direction around the central axis at the input rotation speed. The movable ring gear rotates at an output rotational speed with respect to the fixed ring gear by a difference in the number of teeth between the movable ring gear and the fixed ring gear.)

1. A speed reducer that converts a rotational motion of an input rotational speed into a rotational motion of an output rotational speed lower than the input rotational speed, wherein,

the speed reducer is provided with:

an input rotating body that rotates around a central axis at the input rotational speed;

an output rotating body that rotates around the central axis at the output rotational speed; and

a housing that supports the input rotating body and the output rotating body,

the input rotator includes:

an input shaft;

an arm portion extending radially outward from the input shaft; and

a roller that rotates around a rotation shaft supported by the arm,

the output rotating body includes:

a movable ring gear that is flexible and extends perpendicularly or obliquely to the center axis, and that has a plurality of first side teeth arranged in a circular ring shape around the center axis; and

an output shaft extending from a center of the movable crown gear along the center axis,

the casing contains fixed crown gear, and this fixed crown gear for the central axis is perpendicular or expand aslope, has and uses the central axis is a plurality of second side teeth of ring form range as the center,

the number of teeth of the first side teeth of the movable crown gear is different from the number of teeth of the second side teeth of the fixed crown gear,

a part of the circumferential direction of the movable crown gear is in contact with the roller, and the fixed crown gear and the movable crown gear are partially engaged with each other by the pressing force applied from the roller,

the meshing position between the movable ring gear and the fixed ring gear changes in the circumferential direction around the central axis with the rotation of the input rotating body,

by the difference between the numbers of teeth of the first side face teeth and the second side face teeth, the movable crown gear rotates at the output rotation speed relative to the fixed crown gear.

2. A decelerator according to claim 1 wherein,

the movable crown gear is extended in a conical shape with the center axis as a center.

3. A decelerator according to claim 1 or 2 wherein,

the rotation axis of the roller extends in a direction perpendicular to a circumferential direction with respect to the center axis.

4. A decelerator according to claim 3 wherein,

a first virtual line obtained by extending the rotation axis of the roller radially inward and a second virtual line obtained by extending a contact portion of the outer circumferential surface of the roller, which is in contact with the movable crown gear, radially inward intersect on the central axis.

5. A decelerator according to any one of claims 1 to 4 wherein,

the input rotary body has a plurality of the rollers,

the plurality of rollers are arranged at equal intervals in the circumferential direction around the central axis.

6. A decelerator according to claim 5 wherein,

the input rotary body has two of the rollers,

the two rollers are disposed at an interval of 180 ° around the central axis.

7. A decelerator according to any one of claims 1 to 6 wherein,

at a position where the movable crown gear is engaged with the fixed crown gear,

a gap exists circumferentially between the first side tooth and the second side tooth.

8. A decelerator according to any one of claims 1 to 7 wherein,

the outer diameter of the roller around the rotation shaft is 1/10 times or more and 1/2 times or less of the outer diameter of the movable crown gear around the central axis.

9. A decelerator according to any one of claims 1 to 8 wherein,

at least one of the movable crown gear and the fixed crown gear is made of resin.

10. A decelerator according to claim 9 wherein,

at least the movable crown gear is made of resin.

11. A decelerator according to any one of claims 1 to 10 wherein,

the output rotating body is a member including the movable crown gear and the output shaft.

Technical Field

The present invention relates to a speed reducer.

Background

In recent years, development of a small robot that performs work in cooperation with a human has been actively performed. Such a robot requires extremely delicate movements. Therefore, a demand for a small and inexpensive speed reducer to be incorporated into a joint portion of a robot has increased. A conventional speed reducer is described in, for example, japanese patent application laid-open publication No. 2011-002084.

The reduction gear of jp 2011-one 002084 has a ring-shaped rigid gear 9 and a ring-shaped flexible gear 5. The annular flexible gear 5 is deformed in a wave shape by the annular flexible gear rotating mechanism 2 via the bearing 3 having flexibility. Thereby, only a part of the annular flexible gear 5 is meshed with the annular rigid gear 9.

Patent document 1: japanese patent laid-open publication No. 2011-002084

Disclosure of Invention

Problems to be solved by the invention

As described above, in the structure of japanese patent application laid-open publication No. 2011-002084, the bearing 3 having flexibility is disposed between the ring flexible gear 5 and the ring flexible gear rotating mechanism 2. Therefore, in the structure of japanese patent application laid-open No. 2011-002084, the manufacturing cost increases due to the expensive bearing 3, and the number of parts increases, so that the reduction gear is difficult to be miniaturized. Moreover, the deformed bearing may also become a main cause of noise.

The invention aims to provide a structure which can restrain the number of parts of a speed reducer and is easy to miniaturize the speed reducer.

Means for solving the problems

An exemplary embodiment of the present application is a speed reducer that converts a rotational motion at an input rotational speed to a rotational motion at an output rotational speed lower than the input rotational speed, the speed reducer including: an input rotating body that rotates around a central axis at the input rotational speed; an output rotating body that rotates around the central axis at the output rotational speed; and a housing that supports the input rotating body and the output rotating body, the input rotating body including: an input shaft; an arm portion extending radially outward from the input shaft; and a roller that rotates around a rotation shaft supported by the arm portion, the output rotating body including: a movable ring gear that is flexible and extends perpendicularly or obliquely to the center axis, and that has a plurality of first side teeth arranged in a circular ring shape around the center axis; and output shaft, its follow movable crown gear's central authorities follow the central axis extends, the casing contains fixed crown gear, this fixed crown gear for the central axis is expanded perpendicularly or sloping, has and uses the central axis is a plurality of second side teeth that the ring was arranged for the center, movable crown gear's the number of teeth of first side tooth with fixed crown gear's the number of teeth of second side tooth is different, a part of movable crown gear's circumference with the roller contact, through the follow the pressure that the roller received, fixed crown gear with movable crown gear local meshing, is accompanied with the rotation of input rotator, movable crown gear with fixed crown gear's meshing position uses the central axis is the center, with input rotational speed changes along circumference, through first side tooth with the difference in the number of teeth of second side tooth, the movable ring gear rotates at the output rotational speed relative to the ring gear.

Effects of the invention

According to an exemplary embodiment of the present application, by bringing the roller into contact with the movable ring gear, a part of the circumferential direction of the movable ring gear can be deformed in the axial direction without interposing a bearing having flexibility. Therefore, the number of parts of the speed reducer is suppressed, and the speed reducer can be easily downsized.

Drawings

Fig. 1 is a longitudinal sectional view of the speed reducer.

Fig. 2 is a longitudinal sectional view of the speed reducer.

Fig. 3 is a cross-sectional view of the speed reducer.

Fig. 4 is a cross-sectional view of the housing.

Fig. 5 is a partial longitudinal sectional view of the speed reducer.

Fig. 6 is a longitudinal sectional view of a reducer according to a modification.

Detailed Description

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present application, a direction parallel to the central axis of the input rotor and the output rotor is referred to as an "axial direction", a direction perpendicular to the central axis is referred to as a "radial direction", and a direction along an arc centered on the central axis is referred to as a "circumferential direction". The "parallel direction" also includes a substantially parallel direction. The "vertical direction" also includes a substantially vertical direction. Hereinafter, the input rotary member side is referred to as "input side" and the output rotary member side is referred to as "output side" in the axial direction.

< 1. Structure of speed reducer

Fig. 1 and 2 are longitudinal sectional views of a reduction gear 1 according to an embodiment of the present invention. Fig. 3 is a cross-sectional view of the speed reducer 1. In addition, fig. 1 shows a cross section of the speed reducer 1 as viewed from a-a position in fig. 3. Fig. 2 shows a section of the reducer 1 viewed from the B-B position in fig. 3. Fig. 3 shows a section of the reducer 1 from the position C-C in fig. 1 and 2.

The speed reducer 1 is a device that converts a rotational motion at an input rotational speed obtained from an external motor into a rotational motion at an output rotational speed lower than the input rotational speed. The speed reducer 1 is assembled to, for example, a joint portion of a small robot that performs work in cooperation with a human. The speed reducer of the present invention may be used in auxiliary equipment, such as a suit, a wheelchair, and an automated guided vehicle.

As shown in fig. 1, the reduction gear 1 of the present embodiment includes an input shaft 10, two arm portions 20, two rollers 30, a movable ring gear 40, an output shaft 50, and a housing 60. The input shaft 10, the two arm portions 20, and the two rollers 30 constitute an input rotary body 81 that rotates around the central axis 9 at an input rotation speed. The movable ring gear 40 and the output shaft 50 constitute an output rotary body 82 that rotates around the central axis 9 at an output rotation speed.

The input shaft 10 is a columnar member extending along the center axis 9. The input shaft 10 is inserted into an input hole 610, which will be described later, of the housing 60. The input shaft 10 is rotatably supported by the housing 60 via a bearing 11. The bearing 11 is, for example, a ball bearing. The input-side end of the input shaft 10 is connected to an external motor directly or via another power transmission mechanism. When the motor is driven, the input shaft 10 rotates at an input rotation speed around the central axis 9. The end portion on the output side of the input shaft 10 is located inside the housing 60. The output-side end of the input shaft 10 may be connected to the output shaft 50 via a bearing.

The two arm portions 20 are members extending radially outward from the input shaft 10. The radially inner end of each arm portion 20 is fixed to the input shaft 10 by, for example, screw fastening. When the motor is driven, the arm portion 20 also rotates around the central axis 9 together with the input shaft 10 at the input rotation speed. In the present embodiment, rod-shaped arm portions 20 extending in the radial direction are provided around the input shaft 10 at intervals of 180 °. The shape, number, and circumferential position of the arm portions 20 may be different from those of the present embodiment. Further, the arm portions 20 may be connected in the circumferential direction.

The two rollers 30 are rotating bodies held at the radially outer ends of the arm portions 20. The rotation shaft 31 of the roller 30 is supported by the arm 20 in a posture inclined with respect to the axial direction and the radial direction and perpendicular to the circumferential direction. The roller 30 is rotatably attached to the rotating shaft 31. The roller 30 has a conical outer peripheral surface 32 centered on a rotation shaft 31. The outer peripheral surface 32 of the roller 30 is enlarged in diameter as it is spaced radially outward from the input shaft 10. When the motor is driven, the roller 30 also rotates around the central axis 9 at the input rotation speed together with the input shaft 10 and the arm 20.

The movable ring gear 40 is a flexible gear that can rotate about the center axis 9. The movable crown gear 40 is located on the output side of the two rollers 30. As shown in fig. 1 and 2, the movable crown gear 40 has a thin plate-like flexible disk portion 41 and a plurality of first side teeth 42. The flexible disk portion 41 expands radially outward from the input-side end of the output shaft 50. The flexible disk portion 41 of the present embodiment extends conically around the center axis 9. Moreover, the flexible disk portion 41 is elastically deformable in the axial direction. The first side teeth 42 axially project from the flexible disk 41 toward the output side (the fixed ring gear 70 side). The plurality of first side teeth 42 are arranged in a circular ring shape around the central axis 9. Further, the plurality of first side teeth 42 are arranged at regular intervals in the circumferential direction. When a part of the flexible circular plate portion 41 in the circumferential direction is elastically deformed in the axial direction, the position of the first side teeth 42 located in the part in the circumferential direction also moves in the axial direction.

In the present embodiment, the flexible disk portion 41 of the movable ring gear 40 spreads obliquely with respect to the center axis 9. However, the flexible disk portion 41 may also extend perpendicularly with respect to the center axis 9.

The output shaft 50 extends along the center axis 9 from the center of the movable ring gear 40 toward the output side. The output shaft 50 has a cylindrical outer peripheral surface. The output shaft 50 is inserted into an output hole 620 of the housing 60, which will be described later. Thereby, the output shaft 50 is supported rotatably with respect to the housing 60. When the movable ring gear 40 rotates about the center axis 9, the output shaft 50 also rotates about the center axis 9. In the present embodiment, the movable ring gear 40 and the output shaft 50 are one member. However, the movable ring gear 40 and the output shaft 50 may be prepared as separate members and fixed to each other.

The housing 60 is a box body that supports the input rotary body 81 and the output rotary body 82. The housing 60 has an input side wall portion 61, an output side wall portion 62, and a peripheral wall portion 63. The input side wall portion 61 extends substantially perpendicularly to the central axis 9 at a position closer to the input side than the two arm portions 20. The input side wall portion 61 is provided at the center thereof with an input hole 610 for passing the input shaft 10 therethrough. The output side wall portion 62 extends substantially perpendicularly to the center axis 9 on the output side of the movable ring gear 40. The output side wall portion 62 is provided at the center thereof with an output hole 620 for passing the output shaft 50 therethrough. The peripheral wall portion 63 extends cylindrically in the axial direction between the outer peripheral portion of the input-side wall portion 61 and the outer peripheral portion of the output-side wall portion 62. The peripheral wall portion 63 is located radially outward of the two arm portions 20, the two rollers 30, and the movable ring gear 40.

In the present embodiment, the output side wall portion 62 and the peripheral wall portion 63 are formed as one member. The input-side wall portion 61 of the separate member is fixed to a cup-shaped member including the output-side wall portion 62 and the peripheral wall portion 63. However, the input-side wall portion 61 and the peripheral wall portion 63 may be formed as one member, and the output-side wall portion 62 may be a separate member. Further, the input side wall portion 61, the output side wall portion 62, and the peripheral wall portion 63 may all be separate members.

Fig. 4 is a cross-sectional view of the housing 60 as viewed from the position C-C in fig. 1 and 2. As shown in fig. 1, 2 and 4, the output side wall portion 62 of the housing 60 includes a fixed crown gear 70. The fixed ring gear 70 has a fixed disc portion 71 and a plurality of second side teeth 72. The fixed disk portion 71 may be expanded perpendicularly to the center axis 9 or may be expanded obliquely to the center axis 9. The flexibility of the fixed disc portion 71 is much smaller than that of the flexible disc portion 41. Therefore, the fixed disc portion 71 can be regarded as a rigid body substantially free from flexibility. The second side teeth 72 axially project from the fixed disk portion 71 toward the input side (the movable ring gear 40 side). The plurality of second side teeth 72 are arranged in a circular ring shape centering on the central axis 9. Also, the plurality of second side teeth 72 are arranged at regular intervals in the circumferential direction.

Fig. 5 is a partial longitudinal sectional view of the speed reducer 1. As shown by the solid line in fig. 5, the roller 30 is in contact with a part of the circumferential direction of the input-side surface of the flexible disk portion 41 of the movable crown gear 40. Thereby, some of the first side teeth 42 are displaced to the output side by the pressing force from the roller 30. As a result, the movable ring gear 40 and the fixed ring gear 70 are engaged with each other at the position on the output side of each of the two rollers 30. As shown by the two-dot chain line in fig. 5, the movable ring gear 40 and the fixed ring gear 70 do not mesh with each other at other positions in the circumferential direction. In this way, the first plurality of side teeth 42 and the second plurality of side teeth 72 mesh with each other only at specific portions of the circumferential direction.

When the reduction gear 1 is used, the input shaft 10 rotates around the central axis 9 at an input rotation speed. Thus, the two arm portions 20 and the two rollers 30 also rotate together with the input shaft 10 around the central axis 9 at the input rotation speed. The two rollers 30 rotate around the rotation shaft 31 and revolve around the center axis 9 by frictional force with the movable ring gear 40.

When the two rollers 30 revolve, the shape of the movable crown gear 40 changes accordingly. That is, the portions of the first side teeth 42 that are displaced to the output side rotate following the revolution of the roller 30. Therefore, the portion of the plurality of first side teeth 42 that meshes with the second side teeth 72 of the fixed ring gear 70 varies circumferentially around the central axis 9 with respect to the input rotational speed.

The number of first side teeth 42 of the movable ring gear 40 is slightly different from the number of second side teeth 72 of the fixed ring gear 70. Due to the difference in the number of teeth, the first side teeth 42 of the movable ring gear 40 that mesh with the second side teeth 72 at the same position of the fixed ring gear 70 are shifted in position every revolution of the roller 30. Thereby, the movable ring gear 40 rotates slowly about the center axis 9 with respect to the fixed ring gear 70. As a result, the output shaft 50 rotates slowly together with the movable ring gear 40. The rotation speed of the output shaft 50 at this time is an output rotation speed lower than the input rotation speed.

As described above, in the reduction gear 1, the roller 30 is brought into contact with the movable ring gear 40, whereby a part of the circumferential direction of the movable ring gear 40 is deformed in the axial direction. The roller 30 can smoothly move with respect to the movable ring gear 40 by rotating. Therefore, it is not necessary to separately interpose a bearing having flexibility between the roller 30 and the movable ring gear 40. This makes it possible to reduce the size of the reduction gear 1 while suppressing the number of parts of the reduction gear 1.

In the present embodiment, the arm 20 is present only at the same circumferential position as the roller 30, and the arm is not present at the other circumferential positions. Therefore, there is no concern that a portion of the movable ring gear 40, which is shifted to the output side by a small amount, may contact the arm portion 20. For example, at a position 90 ° away from the roller 30 about the center axis 9, there is no fear that the movable crown gear 40 comes into contact with the arm portion 20. This enables reduction in size of the reduction gear 1. Moreover, noise generated when the reduction gear 1 is driven can be suppressed.

In the present embodiment, the posture of the roller 30 is inclined with respect to the central axis 9. Specifically, the rotary shaft 31 of the roller 30 is inclined with respect to the axial direction and the radial direction, and extends in a direction perpendicular to the circumferential direction. In this way, the circumferential speed difference in the radial direction of the portion of the outer peripheral surface 32 of the roller 30 that contacts the movable ring gear 40 coincides with the circumferential speed difference in the radial direction with respect to the center axis 9. Thereby, the slip between the roller 30 and the movable ring gear 40 is suppressed. As a result, energy loss in the reduction gear 1 can be reduced.

Here, as shown in fig. 5, a virtual line obtained by extending the rotation shaft 31 of the roller 30 radially inward is referred to as a "first virtual line V1". A virtual line obtained by extending the contact portion of the outer circumferential surface 32 of the roller 30 with the movable ring gear 40 radially inward is referred to as a "second virtual line V2". In the present embodiment, the first virtual line V1 and the second virtual line V2 intersect on the central axis 9. Thus, the slippage between the roller 30 and the movable crown gear 40 is further suppressed. As a result, the energy loss in the reduction gear 1 can be further reduced.

In the present embodiment, the two rollers 30 are disposed around the center axis 9 at an interval of 180 °. Thus, by arranging the plurality of rollers 30 at equal intervals in the circumferential direction, the vibration of the center of gravity during the operation of the reduction gear 1 can be suppressed. The number of the rollers 30 included in the reduction gear 1 may be three or more.

As shown in fig. 5, the axial distance between the outer peripheral surface 32 of the roller 30 and the input-side surface of the fixed disc portion 71 is d 1. The total axial dimension of the flexible disk portion 41 and the first side teeth 42 is d 2. In this embodiment, distance d1 is greater than dimension d 2. In this way, a circumferential gap (backlash) between the first side teeth 42 and the second side teeth 72 can be secured at a position where the movable ring gear 40 and the fixed ring gear 70 mesh with each other. This enables the plurality of first side teeth 42 to smoothly mesh with the plurality of second side teeth 72. As a result, noise during operation of the reduction gear 1 can be further suppressed.

When the outer diameter of the roller 30 around the rotation shaft 31 is too small, the number of teeth of the first side teeth 42 and the second side teeth 72 becomes small. Therefore, the engagement of the first side teeth 42 with the second side teeth 72 is unstable. On the other hand, if the outer diameter of the roller 30 around the rotation shaft 31 is too large, the reduction gear 1 is difficult to be downsized. Therefore, the roller 30 preferably has an appropriate outer diameter. The outer diameter of the roller 30 around the rotation shaft 31 is preferably 1/10 times or more and 1/2 times or less the outer diameter of the movable ring gear 40 around the center axis 9.

The material of each component constituting the speed reducer 1 is, for example, metal such as iron. However, a part or all of the components may be made of resin. When resin is used, the reduction gear 1 can be made lighter than when metal is used. For example, at least one of the movable ring gear 40 and the fixed ring gear 70 may be made of resin. The side teeth of these crown gears 40, 70 project in the axial direction. Therefore, the crown gears 40 and 70 can be easily manufactured by injection molding using a mold combined in the axial direction. In particular, if the movable ring gear 40 is made of resin, the flexibility of the flexible disk portion 41 is easily obtained.

< 2. modification example >

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

Fig. 6 is a longitudinal sectional view of a reducer 1A according to a modification. In the example of fig. 6, a hollow shaft 80A is provided in the center of the reduction gear 1A. The hollow shaft 80A is a cylindrical member and is disposed along the central axis 9A. A bearing 12A is interposed between the inner peripheral surface of the input shaft 10A and the outer peripheral surface of the hollow shaft 80A. Therefore, the input shaft 10A and the hollow shaft 80A can rotate relative to each other about the central axis 9A. The bearing 12A uses, for example, a slide bearing. The hollow shaft 80A is fixed to the output shaft 50A by a screw 51A. Therefore, the hollow shaft 80A rotates together with the output shaft 50A around the central axis 9A at the output rotation speed.

The arm 20A, the roller 30A, the movable ring gear 40A, the casing 60A, and the fixed ring gear 70A have the same configurations as those of the above-described embodiment. The reduction gear 1A transmits power only at a position radially outward of the input shaft 10A and the output shaft 50A. Therefore, as in the example of fig. 6, the hollow shaft 80A can be disposed radially inward of the input shaft 10A and the output shaft 50A. In this way, the space radially inside the hollow shaft 80A can be effectively utilized. For example, it is possible to pass the support shaft 90A for supporting the speed reducer through the inside of the hollow shaft 80. Alternatively, the electric wiring of the device on which the reduction gear 1A is mounted may be passed through the inside of the hollow shaft 80A.

In particular, in the example of fig. 6, the hollow shaft 80A is fixed to the output shaft 50A, not the input shaft 10A. Thus, the rotation speed of the hollow shaft 80A becomes the output rotation speed lower than the input rotation speed. Therefore, the rotation speed of the hollow shaft 80A can be suppressed. This makes it easier to use the space inside the hollow shaft 80A in the radial direction.

The shape of the detail portion of the speed reducer may be different from the shape shown in the respective drawings of the present application. Further, the respective elements appearing in the above-described embodiment or modification may be appropriately combined within a range not to contradict each other.

The present application claims priority based on japanese patent application No. 2017-134057 as a japanese application filed 7/2017, and cites the entire contents of the description in the japanese application.

Industrial applicability

The present invention can be used for a speed reducer.

Description of the reference symbols

1. 1A: a speed reducer; 9. 9A: a central axis; 10. 10A: an input shaft; 11: a bearing; 12A: a bearing; 20. 20A: an arm portion; 30. 30A: a roller; 31: a rotating shaft; 32: an outer peripheral surface; 40. 40A: a movable crown gear; 41: a flexible circular plate portion; 42: a first side tooth; 50. 50A: an output shaft; 60. 60A: a housing; 61: an input side wall portion; 62: an output side wall portion; 63: a peripheral wall portion; 70. 70A: a fixed crown gear; 71: a fixed circular plate portion; 72: a second side tooth; 80A: a hollow shaft; 81: an input rotating body; 82: an output rotating body; 610: an input aperture; 620: an output aperture; v1: a first imaginary line; v2: a second imaginary line.