CN109538702B

CN109538702B - Speed variator

Info

Publication number: CN109538702B
Application number: CN201810906737.8A
Authority: CN
Inventors: 竹本心路; 徐文德
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2017-09-22
Filing date: 2018-08-10
Publication date: 2022-07-08
Anticipated expiration: 2038-08-10
Also published as: JP2019056443A; CN109538702A; JP7047301B2

Abstract

The invention provides a transmission. The first rotating part of the eccentric oscillating type transmission rotates around the central axis. The eccentric body rotates together with the first rotating part, and the distance from the central axis to the outer peripheral surface of the eccentric body differs depending on the position in the circumferential direction and is arranged at different positions in the axial direction. The bearing is arranged on the outer peripheral surface of each of the eccentric bodies. The external gear is provided on the outer peripheral surface of each of the plurality of bearings. The internal gear is cylindrical in shape surrounding the central axis in the circumferential direction, and is disposed radially outward of the plurality of external gears. The carrier pin is inserted into a through hole of each of the plurality of external gears, the through hole being provided at a position that coincides in the axial direction. The second rotating part is fixed with a wheel carrier pin and rotates around the central axis. The number of teeth of the plurality of external gears is different from the number of teeth of the internal gear. The outer teeth of each of the plurality of outer gears, which are farthest from the central axis, mesh with the inner gear. The meshing positions of the internal gear and each of the plurality of external gears are not equal in the circumferential direction.

Description

Speed variator

Technical Field

The present invention relates to transmissions.

Background

Japanese laid-open publication 2014-16019 describes an eccentric oscillation deceleration mechanism. The reduction mechanism of this publication is included in a motor torque transmission device that transmits a motor torque of an electric motor to a pair of rear wheels in a four-wheel drive vehicle. The reduction mechanism includes an internal gear and an external gear disposed inside the internal gear. The outer gear is engaged with the inner gear while being oscillated along an inner surface of the inner gear. Such an eccentric oscillating type reduction mechanism is small in size and can achieve a high reduction ratio.

In recent years, there has been an increasing demand for small robots that work in cooperation with humans. Further, it is proposed to use an actuator combining the eccentric oscillation type speed reducer and the motor as a joint of a small robot. However, smooth operation is required for such a small robot. Also, such a small robot has a performance (backdriveability) of being easily transmitted to the input side in a case where an external force is applied to the output side. By improving the reverse drivability, when an impact is applied to the output side, the actuator or an application to which the actuator is attached is easily prevented from being damaged. Therefore, improvement in reverse driving performance is required.

Disclosure of Invention

The invention aims to provide a structure capable of improving reverse driving performance by using a plurality of external gears in a transmission.

An exemplary embodiment of the present invention is an eccentric oscillating type transmission. The transmission includes a first rotating portion, a plurality of eccentric bodies, a plurality of bearings, a plurality of external gears, an internal gear, a carrier pin, and a second rotating portion. The first rotating portion rotates around a central axis. The eccentric body rotates together with the first rotating part, and the distance from the central axis to the outer peripheral surface of the eccentric body differs depending on the position in the circumferential direction and is arranged at different positions in the axial direction. The bearing is provided on the outer peripheral surface of each of the plurality of eccentric bodies. The external gear is provided on an outer peripheral surface of each of the plurality of bearings. The internal gear is cylindrical in shape surrounding the central axis in the circumferential direction, and is disposed radially outward of the plurality of external gears. The carrier pin is inserted into a through hole provided at a position where the plurality of external gears overlap each other in the axial direction. The second rotating portion is fixed with the wheel carrier pin and rotates around the central axis. The number of teeth of the plurality of outer gears is different from the number of teeth of the inner gear. The outer teeth of each of the plurality of outer gears, which are farthest from the central axis, mesh with the inner gear. The meshing positions of the internal gear and the plurality of external gears are not uniform in the circumferential direction.

According to the exemplary embodiment of the present invention, it is possible to reduce a peak of the reverse driving torque of the transmission.

The above and other features, elements, steps, features and advantages of the present invention will be more clearly understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings.

Drawings

Fig. 1 is a longitudinal sectional view of a transmission of the embodiment.

Fig. 2 is an exploded perspective view of the transmission.

Fig. 3 is a cross-sectional view taken along line III-III of fig. 1.

Fig. 4 is a diagram for explaining a positional relationship between the central axis of the first eccentric body and the central axis of the second eccentric body.

Fig. 5 is a graph showing a simulation result of measuring the reverse driving torque.

Detailed Description

Hereinafter, exemplary embodiments 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 transmission 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". In the present application, the shape and positional relationship of the respective portions will be described with the axial direction as the vertical direction and the first carrier member side of the second rotating portion as the upper side with respect to the first rotating portion. However, the definition of the up-down direction does not limit the direction of the transmission according to the present application when used. The "parallel direction" also includes a substantially parallel direction. The "vertical direction" also includes a substantially vertical direction.

< 1. integral Structure of Transmission

Fig. 1 is a longitudinal sectional view of a transmission 1 of the present embodiment. Fig. 2 is an exploded perspective view of the transmission 1. Fig. 3 is a cross-sectional view taken along line III-III of fig. 1. In fig. 3, hatching is omitted to avoid complication of the drawing.

The transmission 1 is a gear reducer that converts a rotational motion at a first rotational speed (input rotational speed) into a rotational motion at a second rotational speed (output rotational speed) lower than the first rotational speed. The transmission 1 is used for joints of a small robot such as a service robot working in cooperation with a human. However, the transmission having the same structure may be used for other applications such as a large industrial robot, a machine tool, an X-Y table, a material cutting device, a conveyor line, a rotary table, and a roll. The transmission 1 is an eccentric oscillating type transmission.

The transmission 1 includes a first rotating portion 10, first and second

eccentric bodies

21 and 22, first and second

external gears

31 and 32, a frame 40, a plurality of carrier pins 50, and a second rotating portion 60. That is, the transmission 1 includes a plurality of eccentric bodies and a plurality of external gears. The plurality of external gears include a first external gear 31 and a second external gear 32.

The first rotating portion 10 is a columnar member extending vertically along the central axis 9. As schematically shown in fig. 1, the first rotating portion 10 is connected to a motor as a driving source directly or via another power transmission mechanism. When the motor is driven, the first rotating portion 10 rotates around the central axis 9 at a first rotation speed by power obtained from the motor. That is, in the present embodiment, the first rotating portion 10 is an input portion.

The first eccentric body 21 is fixed to the outer peripheral surface of the first rotating portion 10. The first eccentric body 21 rotates together with the first rotating portion 10. The first rotating portion 10 and the first eccentric body 21 may be a single component or may be separate components. As shown in fig. 3, the first eccentric body 21 has a circular outer peripheral surface when viewed in the axial direction. The central axis 91 of the first eccentric body 21 is located at a position offset from the central axis 9. Therefore, the distance from the center axis 9 to the outer peripheral surface of the first eccentric body 21 differs depending on the position in the circumferential direction.

The second eccentric body 22 is fixed to the outer peripheral surface of the first rotating portion 10. The second eccentric body 22 is located at a position different from the first eccentric body 21 in the axial direction. The second eccentric body 22 rotates together with the first rotating part 10. The first rotating portion 10 and the second eccentric body 22 may be a single component or may be separate components. Like the first eccentric body 21, the second eccentric body 22 has a circular outer peripheral surface when viewed in the axial direction. The central axis 92 of the second eccentric body 22 is located at a position offset from the central axis 9. That is, each of the plurality of eccentric bodies has a perfect circle shape when viewed from the axial direction, and the center of the perfect circle is located at a position deviated from the central axis 9. Thus, the distance from the center axis 9 to the outer peripheral surface of the second eccentric body 22 differs depending on the position in the circumferential direction. That is, the plurality of eccentric bodies rotate together with the first rotating portion 10, and the distance from the center axis 9 to the outer peripheral surface differs depending on the position in the circumferential direction.

Fig. 4 is a diagram for explaining a positional relationship between the central axis 91 of the first eccentric body 21 and the central axis 92 of the second eccentric body 22. The central axis 91 and the central axis 92 are located on the same circle centered on the central axis 9 and at different positions as viewed from the axial direction. The plurality of eccentric bodies are respectively arranged at different positions in the axial direction. That is, the distance between the central axis 9 and the central axis 91 is the same as the distance between the central axis 9 and the central axis 92. The central axis 91 and the central axis 92 are not equally present in the circumferential direction. Here, "unequal" means that the angular intervals around the central axis 9 are not constant. As in the present embodiment, when the number of eccentric bodies is two, an angle R1 from the center axis 91 to the center axis 92 centering on the center axis 9 in the clockwise direction is different from an angle R2 from the center axis 92 to the center axis 91 centering on the center axis 9. In the present embodiment, the center axis 92 is offset by 144 ° in the clockwise direction from the center axis 91 with the center axis 9 as the center. That is, the angle R1 of fig. 4 is 144 °.

When the first rotating portion 10 rotates about the central axis 9, the first eccentric body 21 and the second eccentric body 22 rotate about the central axis 9. At this time, the central axis 91 of the first eccentric body 21 and the central axis 92 of the second eccentric body 22 also rotate about the central axis 9.

The first external gear 31 is disposed radially outward of the first eccentric body 21. A first bearing 71 is present between the first eccentric body 21 and the first external gear 31. The first bearing 71 is, for example, a ball bearing. The first external gear 31 is supported by the first bearing 71 so as to be rotatable about the center axis 91. As shown in fig. 3, a plurality of external teeth 311 are provided on the outer peripheral portion of the first external gear 31. Each external tooth 311 protrudes radially outward. The first external gear 31 has a plurality of (10 in the example of fig. 3) through holes 312. Each through hole 312 penetrates the first external gear 31 in the axial direction. The plurality of through holes 312 are arranged at equal angular intervals in the circumferential direction around the center axis 91.

The second external gear 32 is disposed radially outward of the second eccentric body 22. A second bearing 72 is present between the second eccentric body 22 and the second external gear 32. That is, the transmission 1 includes a plurality of bearings. The plurality of bearings are provided on the outer peripheral surfaces of the plurality of eccentric bodies, respectively. The plurality of external gears are provided on the outer peripheral surfaces of the plurality of bearings, respectively. The second bearing 72 is, for example, a ball bearing. The second external gear 32 is supported by the second bearing 72 so as to be rotatable about the central axis 92. The second external gear 32 is provided with a plurality of external teeth 321 on the outer peripheral portion, similarly to the first external gear 31. The second external gear 32 is provided with a plurality of through holes 322 that penetrate in the axial direction. The plurality of through holes 322 are arranged at equal angular intervals in the circumferential direction around the central axis 92. The diameter of the through-hole 312 is the same as the diameter of the through-hole 322. A part of each through hole 322 axially overlaps each through hole 312 of the first external gear 31. A plurality of through holes are provided in each of the plurality of external gears in the circumferential direction.

The frame 40 is a cylindrical member that circumferentially surrounds the center axis 9 and extends in the axial direction. The frame 40 is disposed around the radial outside of the first external gear 31 and the second external gear 32. As shown in fig. 3, a plurality of internal teeth 41 are provided on the inner peripheral surface of the frame 40. The plurality of internal teeth 41 protrude radially inward from the inner peripheral surface of the frame 40. In the present embodiment, the internal gear including the internal teeth 41 is a part of the frame 40. That is, the transmission 1 includes an internal gear. The internal gear is cylindrical and circumferentially surrounds the central axis 9. The inner gear is disposed radially outward of the plurality of outer gears. However, the internal gear may be a separate member from the frame 40. In the case where the internal teeth 41 and the frame 40 are made of the same member as in the present embodiment, there is no need to provide an internal gear having the internal teeth 41 separately from the frame 40, and therefore the transmission 1 can be easily downsized.

A part of each of the plurality of external teeth 311 of the first external gear 31 and the plurality of external teeth 321 of the second external gear 32 meshes with a part of the plurality of internal teeth 41 of the frame 40. Specifically, the outer teeth 311 of the first external gear 31 located at the farthest position from the central axis 9 mesh with the inner teeth 41. And, the external teeth 321 of the second external gear 32 located at the farthest position from the central axis 9 mesh with the internal teeth 41. That is, the outer teeth of each of the plurality of outer gears, which are farthest from the central axis 9, mesh with the inner gear. Hereinafter, the meshing position of the external teeth 311 and the internal teeth 41 of the first external gear 31 is referred to as a meshing position a1 (see fig. 3). The meshing position between the external teeth 321 and the internal teeth 41 of the second external gear 32 is referred to as a meshing position a2 (see fig. 3).

The positional relationship between the engagement position a1 and the engagement position a2 is not uniform in the circumferential direction, as is the positional relationship between the central axis 91 and the central axis 92. That is, the meshing positions of the internal gear and the plurality of external gears are not uniform in the circumferential direction. As described above, the central axis 92 of the second eccentric body 22 is offset by 144 ° in the clockwise direction from the central axis 91 of the first eccentric body 21 around the central axis 9. Thus, the engagement position a1 is offset from the engagement position a2 by 144 ° in the circumferential direction centered on the central axis 9. That is, the meshing position a1 of the internal gear and the first external gear 31 and the meshing position a2 of the internal gear and the second external gear 32 are offset by 144 ° in the circumferential direction around the central axis 9.

As described above, the first external gear 31 and the second external gear 32 are identical in structure except for the meshing position with the internal teeth 41. Therefore, in the following description, only the first external gear 31 will be described.

When the first rotating portion 10 rotates about the central axis 9, the first external gear 31 revolves around the central axis 9 together with the central axis 91. Then, a part of the plurality of external teeth 311 of the first external gear 31 meshes with the internal teeth 41 of the frame 40, and the first external gear 31 rotates. Here, the number of the internal teeth 41 of the frame 40 is larger than the number of the external teeth 311 of the first external gear 31. Therefore, the position of the external teeth 311 that mesh with the internal teeth 41 at the same position of the frame 40 is shifted every revolution of the first external gear 31. Thereby, the first external gear 31 rotates in the direction opposite to the rotation direction of the first rotating portion 10 at the second rotation speed lower than the first rotation speed. Therefore, the position of the through hole 312 of the first external gear 31 also rotates at the second rotation speed. When the transmission 1 is operated, the first external gear 31 performs a rotational motion combining revolution and rotation. The number of teeth of the plurality of external gears is different from the number of teeth of the internal gear.

When the number of the external teeth 311 of the first external gear 31 is N and the number of the internal teeth 41 of the frame 40 is M, the reduction ratio P of the transmission 1 is (first rotation speed)/(second rotation speed) N/(M-N). In the example of fig. 3, N is 29 and M is 30, so the reduction ratio in this example is P is 29. That is, the second rotation speed is 1/29, which is the first rotation speed. However, the number N of the outer teeth 311 and the number M of the inner teeth 41 may have other values.

In the present embodiment, the plurality of internal teeth 41 are provided as a part of the frame 40 as a single member. Therefore, it is not necessary to provide an internal gear having the internal teeth 41 separately from the frame 40, and therefore, the transmission 1 can be easily downsized.

The carrier pin 50 is a cylindrical member extending in the axial direction. The plurality of wheel carrier pins 50 are arranged annularly at equal angular intervals in the circumferential direction around the center axis 9. In this example, as shown in fig. 3, the transmission 1 has 10 carrier pins 50. Therefore, the plurality of carrier pins 50 are arranged at equal angular intervals of 36 ° (360 °/10) in the circumferential direction around the central axis 9. The aforementioned angular difference 144 ° between the engagement position a1 and the engagement position a2 is a multiple of the equal angle 36 ° at which the plurality of wheel carrier pins 50 are arranged. That is, the angular difference between the meshing positions of the internal gear and the plurality of external gears around the central axis 9 is a multiple of the equal angle at which the plurality of carrier pins 50 are arranged. The engagement positions a1 and a2 are located at positions that are shifted by an equal angle of 36 ° from a state where the engagement positions a1 and a2 are circumferentially equalized. That is, the meshing positions of the internal gear and the plurality of external gears are located at positions that are shifted by an equal angle from a state in which the meshing positions of the internal gear and the plurality of external gears are made equal in the circumferential direction.

The carrier pins 50 are inserted into the through holes 312 of the first external gear 31 and the through holes 322 of the second external gear 32, which are axially overlapped with each other. That is, the carrier pin 50 is inserted into each of the through holes provided at the positions where the plurality of external gears overlap in the axial direction. Thereby, the plurality of carrier pins 50 are pressed by the first external gear 31 and the second external gear 32, and rotate around the central axis 9 at the same second rotation speed as the first external gear 31 and the second external gear 32.

The second rotating portion 60 includes an annular first carrier member 61 and an annular second carrier member 62. The first carrier member 61 is disposed axially above the first external gear 31. A bearing 73 is present between the first rotating part 10 and the first carrier member 61. Further, a bearing 74 is present between the first wheel carrier member 61 and the frame 40.

The second carrier member 62 is disposed axially below the second external gear 32. A bearing 75 is present between the first rotating part 10 and the second wheel carrier member 62. Also, a bearing 76 is present between the second wheel carrier member 62 and the frame 40. For example, ball bearings are used as the

bearings

73 and 75. The

bearings

74 and 76 are sliding bearings made of resin such as polyoxymethylene, for example.

The axial upper end of each wheel carrier pin 50 is fixed to the first wheel carrier member 61. The lower end in the axial direction of each wheel carrier pin 50 is fixed to the second wheel carrier member 62. That is, the carrier pin 50 is fixed to the second rotating portion 60. Further, a fixing method of fixing the wheel frame pins 50 to the first wheel frame member 61 and the second wheel frame member 62 is, for example, a press-fitting method. Therefore, when the plurality of carrier pins 50 rotate at the second rotational speed about the central axis 9, the first carrier member 61 and the second carrier member 62 also rotate at the second rotational speed about the central axis 9. That is, the second rotating portion 60 rotates at the second rotation speed around the central axis 9.

The second rotating portion 60 is connected to a member to be driven directly or via another power transmission mechanism. That is, in the present embodiment, the second rotating portion 60 is an output portion.

< 2. simulation example >

In the transmission 1 configured as described above, the engagement position a1 and the engagement position a2 are not uniformly present in the circumferential direction around the central axis 9. With this configuration, Backdrivability (Backdrivability) of the transmission 1 is improved.

The following shows simulation results of measuring the reverse drive torque by creating a model equivalent to that of the transmission 1 described above in simulation software. Fig. 5 is a graph showing a simulation result of measuring the reverse driving torque.

The reverse driving torque is a magnitude of resistance when the second rotating portion 60 serving as an output portion is rotated by an external force. When the reverse drive torque is small, the rotation resistance of the second rotating portion 60 is small, and the rotation loss is small. Namely, the reverse drivability is improved.

The waveform (a) of fig. 5 is a simulation result when the engagement position a1 and the engagement position a2 are arranged at equal intervals of an angle of 180 ° in the circumferential direction around the central axis 9. The waveform (B) of fig. 5 is a simulation result of the transmission 1 having the above-described structure in which the engagement position a1 and the engagement position a2 are made circumferentially unequal. In the waveform (a) and the waveform (B), conditions other than the positional relationship between the engagement position a1 and the engagement position a2 are the same.

As is clear from a comparison of the waveform (a) and the waveform (B), when the engagement position a1 and the engagement position a2 are made to be unequal about the central axis 9, the peak of the reverse drive torque of the transmission 1 is small.

The waveform (C) of fig. 5 is a simulation result of the transmission 1 in which three external gears are provided and the meshing positions of the three external gears and the internal gears are distributed at unequal intervals in the circumferential direction around the central axis 9. As is clear from a comparison of the waveform (B) and the waveform (C), when the number of external gears is three, the peak of the reverse drive torque of the transmission 1 is smaller than that in the case where the number of external gears is two.

As described above, the meshing positions of the external teeth and the internal teeth of the plurality of external gears are unevenly distributed in the circumferential direction around the center axis 9, and thereby the reverse drivability of the transmission 1 can be improved.

The transmission 1 is not limited to the above configuration. For example, the engagement position a1 and the engagement position a2 are offset by 144 ° about the central axis 9, but the angle is not limited thereto. The number of external teeth of the external gear and the number of internal teeth of the internal gear can be appropriately changed.

Although the embodiments of the present invention have been described above, the elements described in the above embodiments and modifications may be appropriately combined within a range where no contradiction occurs.

The present invention can be used for a transmission, for example.

Claims

1. A transmission, comprising:

a first rotating part which rotates around a central axis;

a plurality of eccentric bodies that rotate together with the first rotating portion, the distance from the central axis to the outer peripheral surface of the eccentric body varying depending on the position in the circumferential direction, and the eccentric bodies being arranged at different positions in the axial direction;

a plurality of bearings provided on outer peripheral surfaces of the plurality of eccentric bodies, respectively;

a plurality of external gears provided on the outer peripheral surfaces of the plurality of bearings, respectively;

an internal gear that is cylindrical in shape surrounding the central axis in the circumferential direction and is disposed radially outward of the plurality of external gears;

a plurality of carrier pins extending in the axial direction and inserted into through holes provided at positions overlapping in the axial direction of each of the plurality of external gears; and

a second rotating part to which the wheel carrier pin is fixed and which rotates around the central axis,

the transmission is characterized in that it is provided with,

the transmission is an eccentric oscillating type transmission,

the number of teeth of the plurality of outer gears is different from the number of teeth of the inner gear,

the outer teeth of each of the plurality of outer gears farthest from the central axis mesh with the inner gear,

the respective meshing positions of the internal gear and the plurality of external gears are not uniform in the circumferential direction,

a plurality of the through holes are provided in a circumferential direction in each of the plurality of outer gears,

a plurality of the wheel carrier pins are respectively inserted into each of the plurality of through holes,

the plurality of wheel carrier pins are arranged at equal angular intervals in the circumferential direction around the central axis,

an angular difference between the meshing positions of the internal gear and the external gears, which is centered on the central axis, is a multiple of the equal angle.

2. The transmission of claim 1,

when viewed axially, the plurality of eccentric bodies are respectively in a perfect circle shape, and the center of the perfect circle is located at a position deviated from the central axis.

3. The transmission of claim 1,

the respective meshing positions of the internal gear and the plurality of external gears are located at positions deviated from a state where the respective meshing positions of the internal gear and the plurality of external gears are equalized in the circumferential direction by the equal angle.

4. The transmission of claim 1 or 2,

the plurality of external gears includes a first external gear and a second external gear,

the meshing position of the internal gear and the first external gear and the meshing position of the internal gear and the second external gear are deviated from each other by 144 ° in the circumferential direction around the central axis.

5. The transmission of claim 1 or 2,

the first rotating part is an input part that rotates at a first rotational speed by power obtained from a motor,

the second rotating portion is an output portion that rotates at a second rotational speed lower than the first rotational speed.