CN217422054U - Reduction gear and robot - Google Patents

Abstract

The utility model provides a reduction gear and robot. The speed reducer has an input shaft, a preceding stage speed reduction mechanism, an intermediate rotating body, a flexible gear, and an internal gear. The input shaft rotates at 1 st rotational speed. The preceding stage deceleration mechanism decelerates the rotational motion at the 1 st rotational speed to a rotational motion at the 2 nd rotational speed lower than the 1 st rotational speed. The intermediate rotating body rotates at the 2 nd rotation speed. The intermediate rotating body contains a wave generator. The wave generator, the flexible gear and the internal gear reduce the 2 nd rotational speed to the 3 rd rotational speed lower than the 2 nd rotational speed. The intermediate rotating body is supported by the input shaft via a bearing.

Description

Reduction gear and robot

Technical Field

The utility model relates to a reduction gear and robot.

Background

Conventionally, in a production line of industrial products, an industrial robot that performs operations such as conveyance, processing, and assembly of parts is known. The industrial robot includes an arm, and a motor and a speed reducer for operating the arm. The motor and the reducer are mounted on a joint of the robot. The rotational motion output from the motor is decelerated by the decelerator and transmitted to the arm. Thereby, the arm rotates at a decelerated speed.

A speed reducer mounted on a robot is described in, for example, japanese laid-open patent publication No. 2020-076415.

The reduction gear described in japanese laid-open patent publication No. 2020-076415 is a so-called wave gear reduction gear. The wave gear reducer has an elliptical wave generator, a thin-walled flexible gear, and an internal gear. The wave generator rotates at a rotational speed output from the motor. The flexible gear is deformed into an elliptical shape by the wave generator, and is engaged with the internal gear at 2 positions corresponding to both ends of the major axis of the ellipse. The meshing position of the flexible gear and the internal gear moves in the circumferential direction in accordance with the rotation of the wave generator. Further, the flexible gear or the internal gear rotates at a reduced rotational speed due to the difference in the number of teeth between the flexible gear and the internal gear.

As described above, in the wave gear reducer, the flexible gear is meshed with the internal gear at 2 locations in the circumferential direction. Therefore, due to a minute misalignment of the wave generator with respect to the central axis or the like, vibration of a frequency corresponding to 2 times the rotational speed of the wave generator may be generated between the flexible gear and the internal gear. When the frequency of the vibration coincides with the natural frequency of the arm, a large vibration may be generated due to resonance. That is, when a rotational motion having a rotational speed equal to 1/2 times the natural frequency of the arm is input from the motor to the wave generator, the above-described resonance occurs.

In order to suppress such resonance, it is conceivable to shift the rotational speed of the wave generator from the rotational speed corresponding to 1/2 times the natural frequency of the arm. However, for this purpose, a mechanism for shifting the rotation speed of the wave generator needs to be added to the wave gear reducer. Thus, there is a problem that it is difficult to miniaturize the speed reducer.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a can make undulant generator rotate and easy miniaturized reduction gear with the rotational speed that is less than the rotational speed of input.

The utility model discloses an aspect 1 of illustrative embodiment is a reduction gear, its characterized in that, this reduction gear has: an input shaft that rotates at a1 st rotation speed around a central axis; a preceding stage speed reduction mechanism that reduces the rotational motion of the input shaft at the 1 st rotational speed to a rotational motion at a2 nd rotational speed lower than the 1 st rotational speed; an intermediate rotating body that rotates at the 2 nd rotation speed around the central axis, and that includes a wave generator; a flexible gear having a flexible cylindrical portion located radially outside the wave generator, and having a plurality of external teeth on an outer peripheral surface of the cylindrical portion; and an internal gear located radially outside the cylindrical portion, the internal gear having a plurality of internal teeth on an annular inner peripheral surface centered on the central axis, the internal teeth of the internal gear being different in number from the external teeth of the flexible gear, the external teeth of a part of the plurality of external teeth being pressed by the wave generator to mesh with the internal teeth, a meshing position of the internal teeth and the external teeth moving in a circumferential direction at the 2 nd rotational speed as the wave generator rotates, either the internal gear or the flexible gear rotating about the central axis at a 3 rd rotational speed lower than the 2 nd rotational speed due to a difference in the number of teeth between the internal teeth and the external teeth, and the intermediate rotating body being supported by the input shaft via a bearing.

The present invention according to an exemplary embodiment is a speed reducer according to claim 2, wherein, in the speed reducer according to claim 1, the preceding speed reduction mechanism includes: a sun gear that rotates together with the input shaft around the central axis line at the 1 st rotation speed; an internal gear located radially outside the sun gear and having an annular shape centered on the central axis; and a planetary gear that is meshed with the sun gear and the internal gear, and that rotates about a planetary axis parallel to the central axis, and the planetary gear and the intermediate rotating body rotate about the central axis and the 2 nd rotation speed as the planetary gear rotates.

The present invention provides a reduction gear according to claim 3 of an exemplary embodiment, wherein, in the reduction gear according to claim 1, at least a part of the preceding-stage reduction mechanism is located radially inside the cylindrical portion.

A reduction gear according to claim 4 of an exemplary embodiment of the present invention is characterized in that, in the reduction gear according to claim 2, at least a part of the preceding stage speed reduction mechanism is located radially inside the cylindrical portion.

A reduction gear according to an exemplary embodiment of the present invention according to claim 5 is characterized in that, in the reduction gear according to claim 3, the flexible gear further includes a diaphragm portion extending radially outward from an axial end of the cylindrical portion.

A reduction gear according to an exemplary embodiment of the present invention is the reduction gear according to claim 6, wherein the flexible gear further includes a diaphragm portion extending radially outward from an axial end of the cylindrical portion.

A reduction gear according to an exemplary embodiment of the present invention is the reduction gear according to any one of the aspects 1 to 6, wherein the preceding stage reduction mechanism and the wave generator are arranged at different axial positions, and the wave generator is arranged at the same radial position as a part of the preceding stage reduction mechanism.

The utility model discloses an aspect of exemplary embodiment is a robot in 8, it has: the speed reducer of any one of aspects 1 to 7; a motor that rotates the input shaft; and an arm that is operated by the speed reducer.

According to the utility model discloses, through setting up preceding stage reduction gears, make undulant generator rotate with the 2 nd rotational speed that is lower than the 1 st rotational speed of input. Thus, the period of the vibration generated by the meshing of the flexible gear and the internal gear can be shifted as compared with the case where there is no preceding-stage speed reduction mechanism. As a result, resonance can be suppressed when the reduction gear is used. Further, resonance can be suppressed when the robot having the reducer is driven.

Further, according to the present invention, the wave generator is not supported by the fixed portion via the bearing, but is supported by the input shaft via the bearing. Thus, the wave generator can be disposed at a position close to the input shaft. Therefore, the reduction in size of the speed reducer is easily achieved. In addition, in the robot having the speed reducer, the speed reducer can be miniaturized.

The above and other features, elements, steps, features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a schematic diagram of a robot.

Fig. 2 is a longitudinal sectional view of the reduction gear of embodiment 1.

Fig. 3 is a cross-sectional view of the pre-stage speed reduction mechanism (cross-sectional view taken along line a-a of fig. 2).

Fig. 4 is a cross-sectional view (a cross-sectional view taken along line B-B of fig. 2) of the rear stage speed reducing mechanism.

Fig. 5 is a longitudinal sectional view of the reduction gear of embodiment 2.

Detailed Description

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the drawings of the present application, hatching for showing the cross section is omitted except for a part in order to avoid complication of the drawings. In the present application, the "rotation speed" refers to the number of times the object rotates per unit time (rotation speed).

< 1. about robot >

Fig. 1 is a schematic diagram of a robot 100 mounted with a reducer 1 according to an embodiment. The robot 100 is a so-called industrial robot that performs operations such as conveyance, processing, and assembly of components in a production line of industrial products. As shown in fig. 1, the robot 100 includes a base frame 101, an arm 102, a motor 103, and a decelerator 1. As will be described later, the robot 100 includes a reducer 1, a motor 103 for rotating the input shaft 20, and an arm 102 operated by the reducer 1. This makes it possible to reduce the size of the robot 100 and suppress resonance when the robot 100 is driven.

The arm 102 is supported to be rotatable with respect to the base frame 101. The motor 103 and the speed reducer 1 are assembled to a joint portion between the base frame 101 and the arm 102. When a drive current is supplied to the motor 103, a rotational motion is output from the motor 103. The rotational motion output from the motor 103 is decelerated by the decelerator and transmitted to the arm 102. Thereby, the arm 102 rotates at a decelerated speed with respect to the base frame 101.

< 2. about decelerator

Next, a detailed structure of the speed reducer 1 will be described.

Hereinafter, a direction parallel to the central axis a1 of the speed reducer 1 is referred to as an "axial direction", a direction perpendicular to the central axis a1 is referred to as a "radial direction", and a direction along an arc centered on the central axis a1 is referred to as a "circumferential direction". However, the "parallel direction" also includes a substantially parallel direction. The "vertical direction" also includes a substantially vertical direction.

< 2-1 > embodiment 1

Fig. 2 is a longitudinal sectional view of the reduction gear 1 of embodiment 1. The speed reducer 1 is located on one axial side of the motor 103. As shown in fig. 2, the reduction gear 1 includes a fixed portion 10, an input shaft 20, a preceding-stage reduction mechanism 30, an intermediate rotation body 40, and a succeeding-stage reduction mechanism 50.

The fixing portion 10 is a portion fixed to the base frame 101. As shown in fig. 2, the fixing portion 10 includes a1 st fixing member 11 and a2 nd fixing member 12. The 1 st fixing member 11 and the 2 nd fixing member 12 are both annular members centered on the central axis a 1. The 1 st fixing element 11 and the 2 nd fixing element 12 are arranged in the axial direction. The 2 nd fixing member 12 is located on one axial side of the 1 st fixing member 11. The 1 st fixing member 11 and the 2 nd fixing member 12 are fixed to the base frame 101 by bolts together with a mounting portion 523 of the flexible gear 52 described later.

The input shaft 20 is a cylindrical member extending along the central axis a 1. The axial center of the input shaft 20 coincides with the central axis a1 of the reduction gear 1. The input shaft 20 is fixed to an output shaft of the motor 103. Therefore, when a drive current is supplied to the motor 103, the motor 103 rotates the input shaft 20 about the central axis a 1. Hereinafter, the rotation speed of the input shaft 20 about the central axis a1 is referred to as "1 st rotation speed". That is, the input shaft 20 rotates about the central axis a1 at the 1 st rotation speed.

The preceding stage speed reduction mechanism 30 is a mechanism that reduces the 1 st rotational speed rotational motion of the input shaft 20 to the 2 nd rotational speed lower than the 1 st rotational speed. Fig. 3 is a cross-sectional view of the pre-stage deceleration mechanism 30 (cross-sectional view taken along line a-a of fig. 2). The preceding stage speed reduction mechanism 30 is a so-called planetary speed reduction mechanism. As shown in fig. 2 and 3, the front stage speed reduction mechanism 30 has a sun gear 31, an internal gear 32, and a plurality of planetary gears 33.

The sun gear 31 is a gear that rotates together with the input shaft 20 at the 1 st rotation speed about the center axis a 1. In the present embodiment, the input shaft 20 and the sun gear 31 are one member. This reduces the number of parts of the speed reducer 1, compared to a case where the input shaft 20 and the sun gear 31 are separate members. However, the input shaft 20 and the sun gear 31 may be separate members. In this case, the input shaft 20 and the sun gear 31 may be fixed in a relatively non-rotatable state. The sun gear 31 has a plurality of external teeth 311 on the outer peripheral surface. The plurality of external teeth 311 are provided at a certain pitch in the circumferential direction. Each outer tooth 311 protrudes outward in the radial direction.

The internal gear 32 is an annular gear centered on the central axis a 1. The internal gear 32 is located radially outward of the sun gear 31. In the present embodiment, the 1 st fixing member 11 and the internal gear 32 are one member. Thus, the number of parts of the speed reducer 1 is reduced compared to the case where the 1 st fixing member 11 and the internal gear 32 are separate members. However, the 1 st fixing member 11 and the internal gear 32 may be different members. In this case, the 1 st fixing member 11 and the internal gear 32 may be fixed in a relatively non-rotatable state. The internal gear 32 has a plurality of internal teeth 321 on an inner peripheral surface. The plurality of internal teeth 321 are provided at a certain pitch in the circumferential direction. Each internal tooth 321 protrudes radially inward.

A plurality of planetary gears 33 are located between the sun gear 31 and the internal gear 32. As shown in fig. 3, the preceding stage speed reduction mechanism 30 of the present embodiment has 2 planetary gears 33. However, the number of the planetary gears 33 of the preceding stage speed reduction mechanism 30 may be 1, or 3 or more. Each planetary gear 33 is supported so as to be rotatable about a planetary axis a2 parallel to the central axis a 1. In addition, the planetary gear 33 has a plurality of external teeth 331. The external teeth 331 of the planetary gear 33 mesh with the external teeth 311 of the sun gear 31. The external teeth 331 of the planetary gear 33 also mesh with the internal teeth 321 of the internal gear 32. That is, the planetary gears 33 mesh with the sun gear 31 and the internal gear 32.

When the sun gear 31 rotates about the central axis a1 at the 1 st rotation speed, the planetary gear 33 rotates about the planetary axis a2 due to the meshing of the external teeth 311 of the sun gear 31 and the external teeth 331 of the planetary gear 33. Since the external teeth 331 of the planetary gear 33 also mesh with the internal teeth 321 of the internal gear 32, the planetary gear 33 revolves around the central axis a1 while rotating around the planetary axis a 2. At this time, the rotation speed of the planetary gear 33 centering on the central axis a1 becomes the 2 nd rotation speed lower than the 1 st rotation speed.

The intermediate rotating body 40 rotates at the 2 nd rotation speed about the central axis a1, and the intermediate rotating body 40 includes the wave generator 51. The intermediate rotor 40 is an annular member centered on the central axis a 1. The intermediate rotating body 40 is located on one axial side of the plurality of planetary gears 33. As shown in fig. 2, the intermediate rotating body 40 includes a wheel frame 41, a cylindrical portion 42, and a wave generator 51. The carrier 41, the cylindrical portion 42, and the wave generator 51 are arranged in this order from the other axial side toward the one axial side. In the present embodiment, the intermediate rotating body 40 is a single member including the wheel frame 41, the cylindrical portion 42, and the wave generator 51. However, the intermediate rotating body 40 may be formed of a plurality of members. In this case, the plurality of members may be fixed to each other in a state where they cannot rotate relative to each other.

The wheel carrier 41 is located on the other axial side of the intermediate rotating body 40. A plurality of carrier pins 44 are fixed to the other axial end surface of the carrier 41. Each carrier pin 44 extends axially along a planet axis a 2. The carrier pin 44 is inserted into a circular hole provided in the center of the planetary gear 33. Thereby, the planetary gear 33 is supported rotatably with respect to the carrier pin 44.

The cylindrical portion 42 extends from the carrier 41 toward one axial side. The cylindrical portion 42 is cylindrical about a central axis a 1. The outer diameter of the cylindrical portion 42 is smaller than the outer diameter of the carrier 41 and the outer diameter of the wave generator 51. Accordingly, the intermediate rotating body 40 can be reduced in weight as compared with the case where the outer diameter of the cylindrical portion 42 is the same as the outer diameter of the carrier 41 or the wave generator 51.

Between the input shaft 20 and the intermediate rotating body 40, 2 bearings 60 are interposed. The 2 bearings 60 are arranged in an axial direction. The intermediate rotating body 40 is supported by the input shaft 20 via 2 bearings 60. Therefore, the intermediate rotating body 40 can rotate about the central axis line a1 at a different rotation speed from the input shaft 20. The bearing 60 is, for example, a ball bearing. However, instead of the ball bearing, another type of bearing such as a slide bearing may be used.

As the planetary gear 33 rotates, the planetary gear 33 and the intermediate rotating body 40 rotate around the central axis a1 at the 2 nd rotation speed. More specifically, as described above, when the planetary gear 33 revolves around the central axis a1, the carrier pin 44 also rotates around the central axis a 1. Therefore, the plurality of planetary gears 33, the plurality of carrier pins 44, and the intermediate rotating body 40 rotate around the central axis a1 at the 2 nd rotation speed.

The subsequent reduction mechanism 50 is a mechanism that reduces the 2 nd rotation of the intermediate rotation body 40 to the 3 rd rotation lower than the 2 nd rotation. Fig. 4 is a cross-sectional view (a cross-sectional view taken along line B-B of fig. 2) of the rear stage speed reducing mechanism 50. Fig. 4 is a simplified illustration of the bearing 60 and a flexible bearing 53 described later. The rear stage speed reduction mechanism 50 is a so-called wave gear speed reduction mechanism. As shown in fig. 2 and 4, the rear stage speed reduction mechanism 50 has a wave generator 51, a flexible gear 52, a flexible bearing 53, and an internal gear 54.

The wave generator 51 is an element that imparts periodic flexural deformation to the flexible gear 52. The wave generator 51 of the present embodiment is a part of the intermediate rotating body 40 described above. However, the wave generator 51 may be a different member from the intermediate rotating body 40. In this case, the wave generator 51 may be fixed to the intermediate rotating body 40 in a state where relative rotation is not possible.

As shown in fig. 4, the wave generator 51 of the present embodiment is an elliptical cam. That is, the outer peripheral surface of the wave generator 51 has an elliptical shape centered on the central axis a 1. The wave generator 51 has a major axis and a minor axis. The outer diameter of the wave generator 51 centered on the central axis a1 is largest at the position of the major axis and smallest at the position of the minor axis. Therefore, the outer diameter of the wave generator 51 changes with a period of 180 degrees around the central axis a 1.

The flexible gear 52 is a thin-walled gear that can be deformed by bending. As shown in fig. 2, the flexible gear 52 includes a cylindrical portion 521, a diaphragm portion 522, and a mounting portion 523. The cylindrical portion 521 is located radially outward of the wave generator 51 and radially inward of the internal gear 54. The cylindrical portion 521 has a cylindrical shape extending in the axial direction. Further, the cylindrical portion 521 is thin and flexible. The flexible gear 52 has a plurality of external teeth 524 on the outer peripheral surface of the cylindrical portion 521. The plurality of external teeth 524 are provided at intervals in the circumferential direction. Each outer tooth 524 protrudes outward in the radial direction. That is, the flexible gear 52 has a flexible cylindrical portion 521 located radially outward of the wave generator 51, and the flexible gear 52 has a plurality of external teeth 524 on the outer peripheral surface of the cylindrical portion 521.

The diaphragm portion 522 is expanded radially outward from the other axial end of the cylindrical portion 521. That is, the flexible gear 52 further includes a diaphragm portion 522 that extends radially outward from an axial end of the cylindrical portion 521. The diaphragm portion 522 has a substantially circular plate shape centered on the central axis a 1. The mounting portion 523 is located radially outward of the diaphragm portion 522. The attachment portion 523 has an annular shape centered on the central axis a 1. The thickness of the attachment portion 523 in the axial direction is greater than the thickness of the diaphragm portion 522 in the axial direction and the thickness of the cylindrical portion 521 in the radial direction. The mounting portion 523 is sandwiched between the 1 st fixing member 11 and the 2 nd fixing member 12. The 1 st fixing member 11, the mounting portion 523, and the 2 nd fixing member 12 are fixed to each other by bolts 14. Therefore, the flexible gear 52 cannot rotate with respect to the fixed part 10.

The flexible bearing 53 is located radially outward of the wave generator 51 and radially inward of the cylindrical portion 521 of the flexible gear 52. The flexible gear 52 is non-rotatable by interposing the flexible bearing 53, and the wave generator 51 is rotatable about the central axis a 1. In addition, the flexible bearing 53 can be flexibly deformed by flexure. Therefore, the cylindrical portion 521 is deflected in the radial direction via the flexible bearing 53 by the rotation of the wave generator 51.

The internal gear 54 is located radially outward of the cylindrical portion 521. The ring gear 54 has an annular shape centered on the central axis a 1. The ring gear 54 has a plurality of internal teeth 541 on an annular inner peripheral surface centered on the central axis a 1. The plurality of internal teeth 541 are provided at a certain pitch in the circumferential direction. Each internal tooth 541 protrudes radially inward.

The reduction gear 1 of the present embodiment further includes a connection member 55. The connecting member 55 is located on the other axial side of the internal gear 54. The internal gear 54 and the connecting member 55 are fixed to each other by bolts 56. The connecting member 55 is located radially inward of the 2 nd fixing member 12. A plurality of rollers 70 arranged in alternating directions are interposed between the 2 nd fixing member 12 and the connecting member 55. That is, the 2 nd fixing member 12, the connecting member 55, and the plurality of rollers 70 constitute a cross roller bearing in which the 2 nd fixing member 12 is an outer ring and the connecting member 55 is an inner ring. The ring gear 54 is supported rotatably with respect to the fixed unit 10 via the cross roller bearing.

The flexible bearing 53 is deformed into an elliptical shape along the outer peripheral surface of the wave generator 51. Therefore, the cylindrical portion 521 of the flexible gear 52 is also deformed into an elliptical shape along the outer peripheral surface of the wave generator 51. As a result, at 2 locations corresponding to both ends of the major axis of the ellipse, the external teeth 524 of a part of the flexible gear 52 are pressed by the wave generator 51 via the flexible bearings 53, and thereby mesh with the internal teeth 541 of the internal gear 54. That is, some of the external teeth 524 are pressed by the wave generator 51 and mesh with the internal teeth 541. At other positions in the circumferential direction, the external teeth 524 are not meshed with the internal teeth 541.

When the wave generator 51 rotates at the 2 nd rotation speed, the major axis of the above ellipse of the flexible gear 52 also rotates at the 2 nd rotation speed. Then, the meshing position of the external teeth 524 and the internal teeth 541 also moves in the circumferential direction at the 2 nd rotation speed. The flexible gear 52 has a slightly different number of external teeth 524 from the internal teeth 541 of the internal gear 54. Due to the difference in the number of teeth, the meshing position of the external teeth 524 and the internal teeth 541 moves in the circumferential direction every 1 rotation of the wave generator 51. Therefore, as the wave generator 51 rotates, the meshing position of the internal teeth 541 and the external teeth 524 moves in the circumferential direction at the 2 nd rotation speed. As a result, the ring gear 54 rotates around the central axis a1 with respect to the flexible gear 52 at the 3 rd rotation speed lower than the 2 nd rotation speed. Further, any one of the internal gear 54 and the flexible gear 52 may rotate around the central axis a1 at the 3 rd rotation speed lower than the 2 nd rotation speed due to the difference in the number of teeth between the internal teeth 541 and the external teeth 524.

Further, the internal gear 54 is fixed to the arm 102. Accordingly, the arm 102 rotates together with the internal gear 54 at the 3 rd rotation speed.

As described above, the flexible gear 52 and the internal gear 54 are engaged at 2 locations corresponding to both ends of the long axis of the wave generator 51. Therefore, due to a slight misalignment or the like of the wave generator 51 with respect to the central axis a1, vibration due to the meshing of the flexible gear 52 and the internal gear 54 may be generated. The vibration has a frequency 2 times the rotation speed of the wave generator 51. When the frequency of the vibration matches the natural frequency of the arm 102, a large vibration may occur due to resonance. If the preceding stage speed reduction mechanism 30 is not provided as in the conventional art, the wave generator rotates at the rotational speed supplied from the motor to the input shaft. Therefore, when a rotational motion having a rotational speed 1/2 times the natural frequency of the arm is input from the motor to the input shaft, the above-described resonance occurs.

However, the reduction gear 1 of the present embodiment has a preceding stage reduction mechanism 30 on the input side of a succeeding stage reduction mechanism 50 as a wave gear reduction mechanism. Therefore, the wave generator 51 can be rotated at the 2 nd rotation speed lower than the input shaft 20. Thus, compared to the case where the preceding stage reduction mechanism 30 is not provided, the frequency of the vibration generated by the meshing of the flexible gear 52 and the internal gear 54 can be shifted. Therefore, even when a rotational motion with a rotational speed 1/2 times the natural frequency of the arm 102 is input from the motor 103 to the input shaft 20, resonance can be suppressed in the reduction gear 1 of the present embodiment.

The intermediate rotating body 40 is supported by the input shaft 20 via a bearing 60. That is, in the structure of the speed reducer 1 of the present embodiment, the intermediate rotating body 40 including the wave generator 51 is supported not by the fixed portion 10 via a bearing but by the input shaft 20 via a bearing 60. This enables the use of the small-diameter bearing 60. The wave generator 51 can be disposed at a position close to the input shaft 20. Therefore, the reduction gear 1 can be easily downsized.

Further, at least a part of the front stage deceleration mechanism 30 is located radially inward of the cylindrical portion 521. In the structure of the speed reducer 1 of the present embodiment, the pre-stage speed reduction mechanism 30 is located radially inward of the cylindrical portion 521 of the flexible gear 52. That is, the front stage speed reduction mechanism 30 is housed in a space radially inside the cylindrical portion 521 of the flexible gear 52. In this way, as compared with the case where the front stage speed reduction mechanism 30 is disposed at a position different from the flexible gear 52 in the axial direction, the dimension of the entire speed reducer 1 in the axial direction can be suppressed. Therefore, the reduction in size of the reduction gear 1 becomes easier.

Further, only a part of the pre-stage speed reduction mechanism 30 may be disposed radially inward of the cylindrical portion 521 of the flexible gear 52, and the other part of the pre-stage speed reduction mechanism 30 may be axially protruded from the flexible gear 52.

In the structure of the speed reducer 1 according to the present embodiment, the diaphragm portion 522 of the flexible gear 52 is not radially inwardly extended but radially outwardly extended from the other end portion in the axial direction of the cylindrical portion 521. Therefore, the pre-stage reduction mechanism 30 can be disposed radially inward of the flexible gear 52 without being restricted by the diaphragm portion 522. This makes it easier to reduce the size of the reduction gear 1.

Further, if the pre-stage reduction mechanism 30 and the wave generator 51 are arranged at the same position in the axial direction and the wave generator 51 is arranged radially outward of the pre-stage reduction mechanism 30, the size of the wave generator 51 in the radial direction increases. However, in the structure of the speed reducer 1 of the present embodiment, the pre-stage speed reduction mechanism 30 and the wave generator 51 are arranged at different positions in the axial direction. The wave generator 51 is disposed at the same radial position as a part of the front stage deceleration mechanism 30. Thereby, the radial dimension of the wave generator 51 is suppressed. Therefore, the entire reduction gear 1 can be reduced in size in the radial direction. In the present embodiment, the wave generator 51 is disposed at the same radial position as the planetary gear 33.

< 2-2 > embodiment 2

Fig. 5 is a longitudinal sectional view of the reduction gear 1 of embodiment 2. The speed reducer 1 is located on one axial side of the motor 103. As shown in fig. 5, the reduction gear 1 includes a fixed portion 10, an input shaft 20, a preceding-stage reduction mechanism 30, an intermediate rotating body 40, a succeeding-stage reduction mechanism 50, and an output member 80.

The fixing portion 10 is a portion fixed to the base frame 101. As shown in fig. 5, the fixing portion 10 includes a1 st fixing member 11, a2 nd fixing member 12, and a 3 rd fixing member 13. The 1 st fixing member 11, the 2 nd fixing member 12, and the 3 rd fixing member 13 are annular members centered on the central axis a 1. The 1 st fixing member 11, the 2 nd fixing member 12, and the 3 rd fixing member 13 are arranged in the axial direction. The 2 nd fixing member 12 is located on one axial side of the 1 st fixing member 11. The 3 rd fixing member 13 is located on one axial side of the 2 nd fixing member 12. The 1 st fixing member 11, the 2 nd fixing member 12, and the 3 rd fixing member 13 are fixed to the base frame 101 by bolts.

The input shaft 20 is a cylindrical member extending along the central axis a 1. The axial center of the input shaft 20 coincides with the central axis a1 of the reduction gear 1. The input shaft 20 is fixed to an output shaft of the motor 103. Therefore, when a drive current is supplied to the motor 103, the motor 103 rotates the input shaft 20 about the central axis a 1. Hereinafter, the rotation speed of the input shaft 20 about the central axis a1 is referred to as "1 st rotation speed".

The preceding stage deceleration mechanism 30 is a mechanism that decelerates the 1 st rotational speed rotational motion of the input shaft 20 to the 2 nd rotational speed lower than the 1 st rotational speed. The preceding stage speed reduction mechanism 30 is a so-called planetary speed reduction mechanism. As shown in fig. 5, the front stage speed reduction mechanism 30 has a sun gear 31, an internal gear 32, and a plurality of planetary gears 33.

The sun gear 31 is a gear that rotates together with the input shaft 20 around the central axis a1 at the 1 st rotation speed. In the present embodiment, the input shaft 20 and the sun gear 31 are one member. This reduces the number of components of the reduction gear 1, compared to a case where the input shaft 20 and the sun gear 31 are separate components. However, the input shaft 20 and the sun gear 31 may be separate members. In this case, the input shaft 20 and the sun gear 31 may be fixed in a relatively non-rotatable state. The sun gear 31 has a plurality of external teeth 311 on the outer peripheral surface. The plurality of external teeth 311 are provided at regular intervals in the circumferential direction. Each outer tooth 311 protrudes outward in the radial direction.

The internal gear 32 is an annular gear centered on the central axis a 1. The internal gear 32 is located radially outward of the sun gear 31. In the present embodiment, the internal gear 32 is fixed to the output member 80 described later, not to the fixed portion 10. The internal gear 32 has a plurality of internal teeth 321 on an inner peripheral surface. The plurality of internal teeth 321 are provided at a certain pitch in the circumferential direction. Each internal tooth 321 protrudes radially inward.

A plurality of planetary gears 33 are located between the sun gear 31 and the internal gear 32. Each planetary gear 33 is supported so as to be rotatable about a planetary axis a2 parallel to the central axis a 1. In addition, the planetary gear 33 has a plurality of external teeth 331. The external teeth 331 of the planetary gear 33 mesh with the external teeth 311 of the sun gear 31. The external teeth 331 of the planetary gear 33 also mesh with the internal teeth 321 of the internal gear 32.

When the sun gear 31 rotates about the central axis a1 at the 1 st rotation speed, the planetary gear 33 rotates about the planetary axis a2 due to the meshing of the external teeth 311 of the sun gear 31 and the external teeth 331 of the planetary gear 33. Since the external teeth 331 of the planetary gear 33 are also meshed with the internal teeth 321 of the internal gear 32, the planetary gear 33 revolves about the central axis a1 while rotating about the planetary axis a 2. At this time, the rotation speed of the planetary gear 33 centering on the central axis a1 becomes the 2 nd rotation speed lower than the 1 st rotation speed.

The intermediate rotor 40 is an annular member centered on the central axis a 1. The intermediate rotating body 40 is located on the other axial side of the plurality of planetary gears 33. As shown in fig. 5, the intermediate rotating body 40 includes a wheel frame 41 and a wave generator 51. The wave generator 51 is located on the other axial side of the wheel carrier 41. In the present embodiment, the intermediate rotating body 40 is a single member including the wheel frame 41 and the wave generator 51. However, the intermediate rotating body 40 may be formed of a plurality of members. In this case, the plurality of members may be fixed to each other in a state where they cannot rotate relative to each other.

The wheel carrier 41 is located on the axially outermost side of the intermediate rotating body 40. A plurality of carrier pins 44 are fixed to an axial end surface of the carrier 41. Each carrier pin 44 extends axially along a planet axis a 2. The carrier pin 44 is inserted into a circular hole provided in the center of the planetary gear 33. Thereby, the planetary gear 33 is supported rotatably with respect to the carrier pin 44.

2 bearings 60 are interposed between the input shaft 20 and the intermediate rotary body 40. The 2 bearings 60 are arranged in an axial direction. The intermediate rotating body 40 is supported by the input shaft 20 via 2 bearings 60. Therefore, the intermediate rotating body 40 can rotate about the central axis line a1 at a different rotation speed from the input shaft 20. The bearing 60 is, for example, a ball bearing. However, instead of the ball bearing, another type of bearing such as a slide bearing may be used.

As described above, when the planetary gear 33 revolves around the central axis a1, the carrier pin 44 also rotates around the central axis a 1. Therefore, the plurality of planetary gears 33, the plurality of carrier pins 44, and the intermediate rotating body 40 rotate around the central axis a1 at the 2 nd rotation speed.

The subsequent reduction mechanism 50 is a mechanism that reduces the 2 nd rotation speed of the intermediate rotation body 40 to the 3 rd rotation speed lower than the 2 nd rotation speed. The rear stage speed reduction mechanism 50 is a so-called wave gear speed reduction mechanism. As shown in fig. 2 and 4, the rear stage speed reduction mechanism 50 has a wave generator 51, a flexible gear 52, a flexible bearing 53, and an internal gear 54.

The wave generator 51 is an element that imparts periodic flexural deformation to the flexible gear 52. The wave generator 51 of the present embodiment is a part of the intermediate rotating body 40 described above. However, the wave generator 51 may be a different member from the intermediate rotating body 40. In this case, the wave generator 51 may be fixed to the intermediate rotating body 40 in a state in which relative rotation is not possible.

The wave generator 51 of the present embodiment is an elliptical cam. That is, the outer peripheral surface of the wave generator 51 has an elliptical shape centered on the central axis a 1. The wave generator 51 has a major axis and a minor axis. The outer diameter of the wave generator 51 centered on the central axis a1 is largest at the position of the major axis and smallest at the position of the minor axis. Therefore, the outer diameter of the wave generator 51 changes with a period of 180 degrees around the central axis a 1.

The flexible gear 52 is a thin-walled gear that can be deformed by bending. As shown in fig. 5, the flexible gear 52 includes a cylindrical portion 521, a diaphragm portion 522, and a mounting portion 523. The cylindrical portion 521 is located radially outward of the wave generator 51 and radially inward of the internal gear 54. The cylindrical portion 521 has a cylindrical shape extending in the axial direction. Further, the cylindrical portion 521 is thin and flexible. The flexible gear 52 has a plurality of external teeth 524 on the outer peripheral surface of the cylindrical portion 521. The plurality of external teeth 524 are provided at a certain pitch in the circumferential direction. Each outer tooth 524 protrudes outward in the radial direction.

The diaphragm portion 522 is expanded radially inward from the other axial end of the cylindrical portion 521. The diaphragm portion 522 has a substantially circular plate shape centered on the central axis a 1. The mounting portion 523 is located radially inward of the diaphragm portion 522. The attachment portion 523 has an annular shape centered on the central axis a 1. The thickness of the attachment portion 523 in the axial direction is greater than the thickness of the diaphragm portion 522 in the axial direction and the thickness of the cylindrical portion 521 in the radial direction. The mounting portion 523 is sandwiched between the internal gear 32 and the output member 80. The internal gear 32, the mounting portion 523, and the output member 80 are fixed to each other by bolts 56.

The flexible bearing 53 is located radially outward of the wave generator 51 and radially inward of the cylindrical portion 521 of the flexible gear 52. By interposing the flexible bearing 53, the flexible gear 52 can rotate around the central axis a1 at a different rotation speed from that of the wave generator 51. In addition, the flexible bearing 53 can flexibly flex. Therefore, the cylindrical portion 521 is deflected in the radial direction via the flexible bearing 53 by the rotation of the wave generator 51.

The internal gear 54 is located radially outward of the cylindrical portion 521. The ring gear 54 has an annular shape centered on the central axis a 1. The internal gear 54 is not rotatable with respect to the fixed portion 10. In the present embodiment, the 2 nd fixing member 12 and the internal gear 54 are one member. Thus, the number of parts of the speed reducer 1 is reduced as compared with the case where the 2 nd fixing member 12 and the internal gear 54 are different members. However, the 2 nd fixing member 12 and the internal gear 54 may be different members. In this case, the 2 nd fixing member 12 and the internal gear 54 may be fixed in a relatively non-rotatable state.

The internal gear 54 has a plurality of internal teeth 541 on an annular inner peripheral surface centered on the central axis a 1. The plurality of internal teeth 541 are provided at a certain pitch in the circumferential direction. Each internal tooth 541 protrudes radially inward.

The flexible bearing 53 is deformed into an elliptical shape along the outer peripheral surface of the wave generator 51. Therefore, the cylindrical portion 521 of the flexible gear 52 is also deformed into an elliptical shape along the outer peripheral surface of the wave generator 51. As a result, at 2 locations corresponding to both ends of the major axis of the ellipse, the external teeth 524 of a part of the flexible gear 52 are pressed by the wave generator 51 via the flexible bearing 53, and mesh with the internal teeth 541 of the internal gear 54. At other positions in the circumferential direction, the external teeth 524 are not meshed with the internal teeth 541.

When the wave generator 51 rotates at the 2 nd rotation speed, the major axis of the above ellipse of the flexible gear 52 also rotates at the 2 nd rotation speed. Then, the meshing position of the external teeth 524 and the internal teeth 541 also moves in the circumferential direction at the 2 nd rotation speed. The flexible gear 52 has a slightly different number of external teeth 524 from the internal teeth 541 of the internal gear 54. Due to the difference in the number of teeth, the meshing position of the external teeth 524 and the internal teeth 541 moves in the circumferential direction every 1 rotation of the wave generator 51. As a result, the flexible gear 52 rotates around the central axis a1 with respect to the ring gear 54 at the 3 rd rotation speed lower than the 2 nd rotation speed.

The output member 80 is an annular member centered on the central axis a 1. The output member 80 is located on one axial side of the compliant gear 52. In addition, the output member 80 is located radially inward of the 3 rd fixing member 13. A plurality of rollers 70 arranged in alternating directions are interposed between the 3 rd fixing member 13 and the output member 80. That is, the 3 rd fixing member 13, the output member 80, and the plurality of rollers 70 constitute a cross roller bearing in which the 3 rd fixing member 13 is an outer ring and the output member 80 is an inner ring. The output member 80 is supported rotatably with respect to the fixed unit 10 via the cross roller bearing.

As described above, the output member 80, the mounting portion 523 of the flexible gear 52, and the internal gear 32 are fixed to each other by the bolt 56. Therefore, when the flexible gear 52 rotates at the 3 rd rotation speed about the center axis a1, the internal gear 32 and the output member 80 also rotate at the 3 rd rotation speed about the center axis a 1.

Further, the output member 80 is fixed to the arm 102. Accordingly, the arm 102 rotates with the output member 80 at the 3 rd rotation speed.

As described above, the flexible gear 52 and the internal gear 54 are engaged at 2 locations corresponding to both ends of the long axis of the wave generator 51. Therefore, due to a slight misalignment or the like of the wave generator 51 with respect to the central axis a1, vibration due to the meshing of the flexible gear 52 and the internal gear 54 may be generated. The vibration has a frequency 2 times the rotation speed of the wave generator 51. When the frequency of the vibration matches the natural frequency of the arm 102, a large vibration may occur due to resonance. If the preceding stage speed reduction mechanism 30 is not provided as in the conventional art, the wave generator rotates at the rotational speed supplied from the motor to the input shaft. Therefore, if the preceding stage reduction mechanism 30 is not provided, the above-described resonance occurs when a rotational motion having a rotational speed 1/2 times the natural frequency of the arm is input from the motor to the input shaft.

However, the reduction gear 1 of the present embodiment has a preceding stage reduction mechanism 30 on the input side of a succeeding stage reduction mechanism 50 as a wave gear reduction mechanism. Therefore, the wave generator 51 can be rotated at the 2 nd rotation speed lower than the input shaft 20. Thus, compared to the case where the preceding stage reduction mechanism 30 is not provided, the frequency of the vibration generated by the meshing of the flexible gear 52 and the internal gear 54 can be shifted. Therefore, even when a rotational motion having a rotational speed 1/2 times the natural frequency of the arm 102 is input from the motor 103 to the input shaft 20, resonance can be suppressed in the reduction gear 1 of the present embodiment.

In the structure of the reduction gear 1 according to the present embodiment, the intermediate rotating body 40 including the wave generator 51 is supported by the input shaft 20 via the bearing 60, not by the fixed portion 10 via the bearing. This enables the use of the small-diameter bearing 60. The wave generator 51 can be disposed at a position close to the input shaft 20. Therefore, the reduction gear 1 can be easily downsized.

In the structure of the reduction gear 1 according to the present embodiment, the front stage speed reduction mechanism 30 is located radially inward of the cylindrical portion 521 of the flexible gear 52. That is, the front stage speed reduction mechanism 30 is housed in a space radially inside the cylindrical portion 521 of the flexible gear 52. In this way, as compared with the case where the front stage speed reduction mechanism 30 is disposed at a position different from the flexible gear 52 in the axial direction, the dimension of the entire speed reducer 1 in the axial direction can be suppressed. Therefore, the reduction in size of the reduction gear 1 becomes easier.

Further, only a part of the pre-stage speed reduction mechanism 30 may be disposed radially inward of the cylindrical portion 521 of the flexible gear 52, and the other part of the pre-stage speed reduction mechanism 30 may be axially extended from the flexible gear 52.

Further, if the pre-stage reduction mechanism 30 and the wave generator 51 are arranged at the same position in the axial direction and the wave generator 51 is arranged radially outward of the pre-stage reduction mechanism 30, the size of the wave generator 51 in the radial direction increases. However, in the structure of the speed reducer 1 of the present embodiment, the preceding stage speed reduction mechanism 30 and the wave generator 51 are arranged at different positions in the axial direction. The wave generator 51 is disposed at the same radial position as a part of the front stage speed reduction mechanism 30 (the internal gear 32 in the present embodiment). Thereby, the radial dimension of the wave generator 51 is suppressed. Therefore, the entire reduction gear 1 can be reduced in size in the radial direction.

< 3. modification example >

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

In the above embodiment, the wave generator 51 is an elliptical shaped cam. However, the wave generator 51 may be a cam of another shape. For example, the wave generator 51 may be a cam having a substantially triangular shape, and the cylindrical portion 521 of the flexible gear 52 may be pressed against the internal gear 54 at 3 positions in the circumferential direction. In this case, if the preceding stage reduction mechanism 30 is not provided, the above-described resonance occurs when a rotational motion having a rotational speed 1/3 times the natural frequency of the arm is input from the motor to the input shaft. However, the provision of the front-stage speed reduction mechanism 30 shifts the rotation speed of the wave generator, and thus resonance can be suppressed.

The wave generator 51 may be configured not to be a cam but to press the cylindrical portion 521 of the flexible gear 52 against the internal gear 54 by a plurality of rollers.

In the above embodiment, 2 bearings 60 are provided between the input shaft 20 and the intermediate rotating body 40. However, the number of the bearings 60 provided between the input shaft 20 and the intermediate rotating body 40 may be 1, or 3 or more.

In the above-described embodiment, the motor 103 and the speed reducer 1 are mounted on the joint between the base frame 101 and the arm 102 of the robot 100. However, the robot 100 may also be a multi-joint type having a plurality of arms. In this case, the motor 103 and the speed reducer 1 may be provided at a joint portion between the arms.

In the above-described embodiment, the reducer 1 mounted on the robot 100 is described. However, the speed reducer of the present invention may be mounted on a device other than a robot.

Further, the structure and shape of the detail of the speed reducer may be different from those shown in the drawings of the present application. In addition, each element appearing in the above-described embodiment or modification may be selected as appropriate within a range in which no contradiction occurs.

The present invention can be used for a speed reducer and a robot, for example.

Claims (8)

1. A speed reducer, comprising:

an input shaft that rotates at a1 st rotation speed around a central axis;

a preceding stage speed reduction mechanism that reduces the rotational motion of the input shaft at the 1 st rotational speed to a rotational motion at a2 nd rotational speed lower than the 1 st rotational speed;

an intermediate rotating body that rotates at the 2 nd rotation speed about the center axis, and that includes a wave generator;

a flexible gear having a flexible cylindrical portion located radially outside the wave generator, and having a plurality of external teeth on an outer peripheral surface of the cylindrical portion; and

an internal gear located radially outward of the cylindrical portion and having a plurality of internal teeth on an annular inner peripheral surface centered on the central axis,

the number of the inner teeth of the inner gear is different from the number of the outer teeth of the flexible gear,

the external teeth of a part of the plurality of external teeth mesh with the internal teeth by being pressed by the wave generator,

the meshing position of the internal teeth and the external teeth is moved in the circumferential direction at the 2 nd rotation speed with the rotation of the wave generator,

one of the internal gear and the flexible gear rotates around the central axis at a 3 rd rotation speed lower than the 2 nd rotation speed due to a difference in the number of teeth between the internal teeth and the external teeth,

it is characterized in that the preparation method is characterized in that,

the intermediate rotating body is supported by the input shaft via a bearing.

2. A decelerator according to claim 1,

the preceding stage speed reduction mechanism includes:

a sun gear that rotates together with the input shaft around the central axis line at the 1 st rotation speed;

an internal gear located radially outside the sun gear and having an annular shape centered on the central axis; and

a planetary gear that is meshed with the sun gear and the internal gear and rotates around a planetary axis parallel to the central axis,

as the planetary gear rotates, the planetary gear and the intermediate rotating body rotate around the central axis at the 2 nd rotation speed.

3. A decelerator according to claim 1,

at least a part of the pre-stage deceleration mechanism is located radially inside the cylindrical portion.

4. A decelerator according to claim 2,

at least a part of the pre-stage deceleration mechanism is located radially inside the cylindrical portion.

5. A decelerator according to claim 3,

the flexible gear further includes a diaphragm portion extending radially outward from an axial end of the cylindrical portion.

6. A decelerator according to claim 4,

the flexible gear further includes a diaphragm portion extending radially outward from an axial end of the cylindrical portion.

7. Decelerator according to any one of claims 1 to 6,

the pre-stage speed reduction mechanism and the wave generator are arranged at different positions in the axial direction,

the wave generator is disposed at the same radial position as a part of the pre-stage deceleration mechanism.

8. A robot is characterized in that a robot body is provided with a plurality of robots,

the robot having a decelerator according to any one of claims 1 to 7;

a motor that rotates the input shaft; and

and an arm that is operated by the speed reducer.

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