Reducers and robots

Abstract

To provide a technology which can obtain higher reduction ratio.SOLUTION: A reduction gear comprises a planetary gear mechanism and a wave motion gear mechanism. The planetary gear mechanism has a planetary input shaft, a sun gear, a plurality of planetary gears, a carrier, a planetary-side inner tooth gear, and a planetary output shaft. The planetary output shaft is connected to the carrier or the planetary-side inner tooth gear, and rotatable at a first intermediate rotational speed with a first rotating shaft as a center. The wave motion gear mechanism has a wave motion input shaft, a cam, a flexible outer tooth gear, a stiff inner tooth gear, and a wave motion output shaft. The wave motion input shaft extends in a hollow cylindrical shape, and rotatable at a second intermediate rotational speed with a second rotating shaft as a center when the planetary output shaft is rotated. The wave motion output shaft is connected to the flexible outer tooth gear or the stiff inner tooth gear, and rotatable at an output rotational speed. The flexible outer tooth gear and the stiff inner tooth gear are engaged with each other, and relatively rotatable by a difference of tooth numbers. A part of the planetary output shaft and a part of the wave motion input shaft are superimposed on each other in a second radial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a reducer and a robot. [Background technology]

[0002] Conventionally, robots using a reducer are known. This type of reducer reduces the rotational motion of a motor and transmits it to the robot's arm. The arm rotates at a rotation speed reduced by the reducer (Patent Document 1). [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-085530 Summary of the Invention [Problem to be solved by the invention]

[0003] The hollow reducer (10) in the above publication is a planetary gear device including a crankshaft (11), a pinion (12) fitted around the crank portion (11a) of the crankshaft (11) and performing eccentric motion, and a case (13) having internal teeth on its inner circumferential surface that mesh with the external teeth of the pinion (12). A hollow circular tube (18) defines a hollow hole inside the hollow reducer (10). A center gear (20) is loosely fitted around the outer periphery of the hollow circular tube (18) and rotatably supported by bearings (19). Eight motors (21) are mounted equidistantly around the rotational axis of the center gear (20) on the outer periphery of the hollow reducer (10).

[0004] The rotation of each motor 21 is transmitted to the center gear 20 via the pinion 22, and the rotation of the center gear 20 rotates the crankshaft 11, generating crank motion, which in turn decelerates the rotation of the case 13 via the planetary motion of the pinion 12 fitted to the crankshaft 11. This decelerates the robot output member 32 attached to the case 13 of the hollow reducer 10. However, there is room for improvement in the positional relationship between the center gear 20 and each component in order to obtain a larger reduction ratio.

[0005] An object of the present invention is to provide a technique that can obtain a larger reduction ratio by devising the positional relationship of each part in a reducer. [Means for solving the problem]

[0006] The present invention provides a reducer that includes a planetary gear mechanism and a strain wave gear mechanism, and that is capable of reducing the rotation of a planetary input shaft that is an input part of the planetary gear mechanism and rotating a strain wave output shaft that is an output part of the strain wave gear mechanism. The planetary gear mechanism includes the planetary input shaft that is rotatable about a first rotation axis at an input rotation speed, a sun gear that is fixed to the planetary input shaft and has external teeth formed on its outer surface and is rotatable about the first rotation axis at the input rotation speed, a plurality of planetary gears that are arranged around the sun gear and have external teeth that mesh with the external teeth of the sun gear from the outside in a first radial direction about the first rotation axis and are rotatable as the sun gear rotates, a carrier to which a plurality of planet shafts that rotatably support each of the plurality of planetary gears are fixed, a planetary side internal gear that is annular and is centered on the first rotation axis and has internal teeth on its inner surface that mesh with the external teeth of the plurality of planetary gears from the outside in a first radial direction, and a carrier that is arranged along the first rotation axis and has internal teeth on its inner surface that mesh with the external teeth of the planetary gears from the outside in the first radial direction a planetary output shaft connected to one of the planetary side internal gears and rotatable about the first rotation shaft at a first intermediate rotation speed, and the wave gear mechanism includes a wave input shaft extending in a hollow cylindrical shape along the second rotation shaft and rotatable about the second rotation shaft at a second intermediate rotation speed as the planetary output shaft rotates, a cam rotatable together with the wave input shaft, a flexible external gear deformable in response to the rotation of the cam, and an annular rigid internal gear centered on the second rotation shaft. The planetary output shaft is arranged along the second rotation axis, connected to either the flexible external gear or the rigid internal gear, and is rotatable at an output rotational speed around the second rotation axis, and the flexible external gear and the rigid internal gear mesh with each other, and the flexible external gear and the rigid internal gear are rotatable relative to each other due to the difference in the number of teeth, and a portion of the planetary output shaft and a portion of the wave input shaft overlap in a second radial direction centered on the second rotation axis. [Effects of the Invention]

[0007] According to the present invention, the reduction ratio can be increased by arranging a planetary gear mechanism in the front stage and a strain wave gear mechanism in the rear stage in the reducer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of the robot. [Figure 2] FIG. 2 is a vertical cross-sectional view of the reducer. [Figure 3] FIG. 3 is a partial vertical cross-sectional view of the reducer. [Figure 4] FIG. 4 is a cross-sectional view of a sun gear, a plurality of planetary gears, a plurality of planetary shafts, and a planetary-side internal gear. [Figure 5] FIG. 5 is a cross-sectional view of the planetary transmission gear and the wave transmission gear. [Figure 6] FIG. 6 is a partial vertical cross-sectional view of the reducer. [Figure 7] FIG. 7 is a cross-sectional view that schematically shows a wave generator, a flexible external gear, and a rigid internal gear. [Figure 8] FIG. 8 is a vertical cross-sectional view of a motor and a reducer according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0010] 1. First Embodiment <1-1. About robots> FIG. 1 is a schematic diagram of a robot 100 equipped with a reducer 1 according to one embodiment. The robot 100 is a so-called industrial robot that performs tasks such as transporting, processing, and assembling parts in, for example, an industrial product manufacturing line. As shown in FIG. 1, the robot 100 has a reducer 1. In this embodiment, the robot 100 has a base frame 101, an arm 102, a motor 103, and the reducer 1.

[0011] The arm 102 is rotatably supported relative to the base frame 101. The motor 103 and the reducer 1 are incorporated into a joint between the base frame 101 and the arm 102. When a drive current is supplied to the motor 103, the motor 103 outputs rotational motion. The rotational motion output from the motor 103 is reduced by the reducer 1 and transmitted to the arm 102. As a result, the arm 102 rotates relative to the base frame 101 at the reduced speed. By including the reducer 1 in the robot 100, the reduction ratio can be increased by arranging the planetary gear mechanism 3 in the front stage of the reducer 1 and the strain wave gear mechanism 4 in the rear stage. Furthermore, by providing a hollow shaft structure for the input portion of the strain wave gear mechanism 4, the internal space can be effectively utilized. Furthermore, by arranging a portion of the planetary gear mechanism 3 and a portion of the strain wave gear mechanism 4 so that they overlap radially, the axial length of the reducer 1 including these can be reduced.

[0012] <1-2. Configuration of the reducer> Next, the overall structure of the reducer 1 will be described.

[0013] In the following, the direction parallel to the first rotation axis, which is the central axis of the motor and planetary gear mechanism described later, will be referred to as the "first axial direction," the direction perpendicular to the first rotation axis will be referred to as the "first radial direction," and the direction along the arc centered on the first rotation axis will be referred to as the "first circumferential direction." Furthermore, the direction parallel to the second rotation axis, which is the central axis of the strain wave gear mechanism described later, will be referred to as the "second axial direction," the direction perpendicular to the second rotation axis will be referred to as the "second radial direction," and the direction along the arc centered on the second rotation axis will be referred to as the "second circumferential direction."

[0014] 2, 3, 6, and 8, the direction of the central axes of the motor, planetary gear mechanism, and strain wave gear mechanism will be defined as the left-right direction, with the left side defined as the "one axial side" and the right side defined as the "other axial side," and the shapes and positional relationships of the various components will be described below. However, this definition of the left-right direction is not intended to limit the orientation of the reducer and robot according to the present invention during manufacture and use. Furthermore, in this application, the term "parallel direction" is not limited to being geometrically strictly parallel; it is sufficient that the directions are parallel to the extent that the effects of the invention are achieved. Furthermore, in this application, the term "orthogonal direction" is not limited to being geometrically strictly perpendicular; it is sufficient that the directions are orthogonal to the extent that the effects of the invention are achieved.

[0015] FIG. 2 is a vertical cross-sectional view of the reducer 1. The motor 103 is disposed along a central axis extending horizontally (left-right direction in FIG. 2). The central axis of the motor 103 and the first rotating shaft 91, which is the central axis of the reducer 1, coincide with each other. The motor 103 has a stationary part including a stator and a rotating part including a rotor. When a driving current is supplied to the stator, the rotating part including the rotor rotates around the first rotating shaft 91 at an input rotational speed N1, which is the rotational speed before reduction.

[0016] The reducer 1 reduces the speed of the rotational motion obtained from the motor 103 and transmits it to the arm 102. The reducer 1 includes a planetary gear mechanism 3 and a strain wave gear mechanism 4. The reducer 1 is capable of reducing the rotation of a planetary input shaft 31 (described later) which is the input part of the planetary gear mechanism 3, and rotating a wave output shaft 45 (described later) which is the output part of the strain wave gear mechanism 4. As described later, the planetary input shaft 31 is connected to a rotating part of the motor 103. The wave output shaft 45 is connected to the arm 102.

[0017] First, the configuration of the planetary gear mechanism 3 will be described. FIG. 3 is a partial vertical cross-sectional view of the planetary gear mechanism 3 and its vicinity in the reducer 1. As shown in FIGS. 2 and 3, the planetary gear mechanism 3 has a planetary input shaft 31, a sun gear 32, a plurality of planetary gears 33, a carrier 35, a planetary side internal gear 36, and a planetary output shaft 37. The planetary gear mechanism 3 also has a planetary side casing 7. In this embodiment, the planetary gear mechanism 3 has the planetary input shaft 31, the sun gear 32, a plurality of planetary gears 33 (three in this embodiment), a plurality of planetary shafts 34 (three in this embodiment), the carrier 35, the planetary side internal gear 36, the planetary output shaft 37, a planetary side transmission gear 38, a support bearing 396, and the planetary side casing 7.

[0018] The planetary side casing 7 is a member that houses the planetary input shaft 31, the sun gear 32, the multiple planetary gears 33, the multiple planetary shafts 34, the carrier 35, the planetary side internal gear 36, the planetary output shaft 37, the planetary side transmission gear 38, and the support bearing 396. However, the planetary side casing 7 only needs to house at least a portion of the multiple planetary gears 33. The planetary side casing 7 is fixed to the base frame 101 of the robot 100 so as to be immovable and imrotatable. The planetary side casing 7 has a planetary first casing cylindrical portion 71, a planetary second casing cylindrical portion 72, and a planetary casing top surface portion 73. That is, the planetary side casing 7 has the planetary casing top surface portion 73.

[0019] The planetary first casing cylindrical portion 71 and the planetary second casing cylindrical portion 72 are each a cylindrical member disposed approximately coaxially with the first rotating shaft 91. A coupling for connecting a rotating portion of the motor 103 and the planetary input shaft 31 is housed inside the planetary first casing cylindrical portion 71 in the first radial direction. The planetary first casing cylindrical portion 71 is located on the other axial side of the planetary second casing cylindrical portion 72 and the planetary casing top surface portion 73. In addition, a planetary casing flange portion 711 that extends outward in the first radial direction is formed near one axial end of the planetary first casing cylindrical portion 71.

[0020] The planetary second casing cylindrical portion 72 is adjacent to one axial side of the planetary first casing cylindrical portion 71. The planetary input shaft 31, the sun gear 32, the plurality of planet gears 33, the plurality of planet shafts 34, the carrier 35, and the planet side internal gear 36 are housed inside the planetary second casing cylindrical portion 72 in the first radial direction. The planetary second casing cylindrical portion 72 is fixed to the end portion of the planet casing flange portion 711 on the outer side in the first radial direction.

[0021] The planetary casing top surface portion 73 is adjacent to one axial side of the planetary second casing tubular portion 72. The planetary casing top surface portion 73 has a planetary third casing tubular portion 731 and an end surface portion 732. The planetary third casing tubular portion 731 is a portion that extends along the first rotation shaft 91. The planetary output shaft 37 and the planetary side transmission gear 38 are housed inside the planetary third casing tubular portion 731 in the first radial direction. The planetary third casing tubular portion 731 extends along the first rotation shaft 91 at the outermost part of the planetary side casing 7 in the first radial direction. In other words, the planetary third casing tubular portion 731 is located at the outer end of the planetary side casing 7 in the first radial direction. The planetary third casing tubular portion 731 is fixed to one axial end of the planetary second casing tubular portion 72 via a first connecting member 723. The end surface portion 732 expands in a plate shape in the first radial direction. The end surface portion 732 surrounds the planetary output shaft 37 and the planetary-side transmission gear 38 from one axial side. In other words, the planetary casing top surface portion 73 surrounds the planetary output shaft 37 from one axial side.

[0022] The planetary input shaft 31 is a member extending in a first axial direction around the first rotating shaft 91. The planetary input shaft 31 is fixed to a rotating portion of the motor 103 so as to be non-rotatable relative to the rotating portion. A bearing 391 is provided between the planetary input shaft 31 and the planetary first casing cylindrical portion 71 in the first radial direction. In this embodiment, a ball bearing is used for the bearing 391. An inner ring of the bearing 391 is fixed to an outer surface of the planetary input shaft 31. An outer ring of the bearing 391 is fixed to an inner surface of the planetary first casing cylindrical portion 71. As a result, the planetary input shaft 31, together with the rotating portion of the motor 103, is rotatably supported by the planet-side casing 7 including the planetary first casing cylindrical portion 71 via the bearing 391. The planetary input shaft 31 is rotatable around the first rotating shaft 91 at an input rotation speed N1.

[0023] The sun gear 32 is a gear disposed approximately coaxially with the first rotating shaft 91. The sun gear 32 is fixed around the planetary input shaft 31 so as to be unable to rotate relative to the planetary input shaft 31. In other words, the sun gear 32 is fixed to the planetary input shaft 31. As a result, when the motor 103 is driven, the planetary input shaft 31 and the sun gear 32 rotate around the first rotating shaft 91 at the input rotation speed N1. In other words, the sun gear 32 can rotate around the first rotating shaft 91 at the input rotation speed N1. However, the sun gear 32 and the planetary input shaft 31 may be a single member.

[0024] FIG. 4 is a cross-sectional view of the sun gear 32, the plurality of planetary gears 33, the plurality of planetary shafts 34, and the planetary-side internal gear 36, as seen from position AA in FIG. 2. To avoid complication of the drawing, hatching indicating cross sections has been omitted in FIG. 4. As shown in FIG. 4, the sun gear 32 has a plurality of external teeth 321 formed on its outer surface. That is, the sun gear 32 has external teeth 321 formed on its outer surface. Each of the external teeth 321 protrudes outward in the first radial direction. The external teeth 321 are arranged at a constant pitch along the first circumferential direction.

[0025] The planetary gears 33 are arranged around the sun gear 32. In this embodiment, as shown in FIG. 4, three planetary gears 33 are arranged at equal intervals around the sun gear 32. However, the number of planetary gears 33 included in the reducer 1 may be two, or four or more. The planetary gears 33 are arranged along the rotation axis 93. The rotation axis 93 is approximately parallel to the first rotation axis 91. The diameter of the planetary gears 33 is approximately constant along the rotation axis 93. Each planetary gear 33 has a plurality of external teeth 331 on its outer surface. That is, each of the plurality of planetary gears 33 has external teeth 331. Each of the plurality of external teeth 331 protrudes outward.

[0026] In this embodiment, the diameter of each planetary gear 33 is slightly larger than the diameter of the sun gear 32. Furthermore, the number of external teeth 331 of one planetary gear 33 is greater than the number of external teeth 321 of the sun gear 32. The external teeth 331 mesh with the external teeth 321 of the sun gear 32 from the outside in the first radial direction about the first rotation axis 91. As a result, when the sun gear 32 rotates about the first rotation axis 91, each planetary gear 33 receives power from the sun gear 32 and rotates about the rotation axis 93 in the direction opposite to the rotation direction of the sun gear 32. In other words, each of the multiple planetary gears 33 can rotate along with the rotation of the sun gear 32. Furthermore, each of the three planetary gears 33 has a through hole 330. Each through hole 330 penetrates the planetary gear 33 along the rotation axis 93.

[0027] The planetary shafts 34 are columnar members extending along the rotation axis 93. In this embodiment, three planetary shafts 34 are provided. Each planetary shaft 34 rotatably supports a planetary gear 33. That is, the multiple planetary shafts 34 rotatably support the multiple planetary gears 33, respectively. The planetary shafts 34 are inserted into the through holes 330 of the planetary gears 33 in the direction of the rotation axis 93. A bearing 392 is inserted between the planetary shafts 34 and the planetary gears 33. A needle bearing, for example, is used for the bearing 392. As a result, the planetary gears 33 are supported relative to the planetary shafts 34 so as to be rotatable about the rotation axis 93.

[0028] The carrier 35 has a first carrier portion 351, a second carrier portion 352, and a third carrier portion 353. The first carrier portion 351 extends columnarly along the first rotation axis 91 on one axial side of the carrier 35. The second carrier portion 352 extends radially outward from an end portion on the other axial side of the first carrier portion 351. The third carrier portion 353 extends further toward the other axial side from three locations in the first circumferential direction on the end face on the other axial side of the second carrier portion 352. The third carrier portion 353 extends in the first axial direction at a position that does not overlap the three planetary gears 33 and the three planetary shafts 34 in the first circumferential direction. The first carrier portion 351, the second carrier portion 352, and the third carrier portion 353 are a single member. The carrier 35 and the planetary output shaft 37 are also a single member. As a result, the carrier 35 and the planetary output shaft 37 are connected to each other so as to be non-rotatable relative to each other. However, the carrier 35 and the planetary output shaft 37 may be separate members as long as they are connected to each other so as to be non-rotatable relative to each other.

[0029] A bearing 393 is inserted between the first carrier part 351 and the planetary second casing cylindrical part 72 in the first radial direction. A ball bearing is used for the bearing 393. An inner ring of the bearing 393 is fixed to the outer surface of the first carrier part 351. An outer ring of the bearing 393 is fixed to the inner surface of the planetary second casing cylindrical part 72. A bearing 394 is inserted between the third carrier part 353 and the planetary second casing cylindrical part 72 in the first radial direction. A ball bearing is used for the bearing 394. An inner ring of the bearing 394 is fixed to the outer surface of the third carrier part 353. An outer ring of the bearing 394 is fixed to the inner surface of the planetary second casing cylindrical part 72. As a result, the carrier 35 and the planetary output shaft 37 are supported rotatably about the first rotary shaft 91 via the bearings 393 and 394 relative to the planetary side casing 7 including the planetary second casing cylindrical portion 72 .

[0030] The carrier 35 also has a plurality of through holes 350. In this embodiment, three through holes 350 are provided at intervals of approximately 120 degrees from one another in the circumferential direction around the first rotation axis 91. Each through hole 350 penetrates a portion of the second carrier part 352 on the outer side in the first radial direction along the first rotation axis 91. Each of the three planetary shafts 34 is inserted into one of the through holes 350. In this embodiment, each planetary shaft 34 is fixed to the carrier 35 through the through hole 350 by adhesive bonding, press fitting, or the like. That is, the three planetary shafts 34 are each fixed to the carrier 35. Each planetary shaft 34 is fixed to and supported by the carrier 35 so as not to rotate relative to the carrier 35. As a result, when the three planetary shafts 34 fixed to the carrier 35 and the planetary gears 33 supported by each planetary shaft 34 revolve in the first circumferential direction around the first rotating shaft 91, the carrier 35 and the planetary output shaft 37 rotate around the first rotating shaft 91.

[0031] The planetary side internal gear 36 is disposed approximately coaxially with the first rotation shaft 91. The planetary side internal gear 36 is annular and centered on the first rotation shaft 91. The planetary side internal gear 36 extends in an annular shape centered on the first rotation shaft 91, radially inside the planetary second casing cylindrical portion 72. The planetary side internal gear 36 is fixed to the inner surface of the planetary second casing cylindrical portion 72. That is, the planetary side internal gear 36 is fixed to the inner surface of the planetary side casing 7. As described above, in this embodiment, the planetary side internal gear 36 and the planetary side casing 7 are separate members. However, the planetary side internal gear 36 and the planetary side casing 7 may be a single member. This reduces the number of parts in the reducer 1, improving mass productivity.

[0032] Furthermore, a plurality of internal teeth 361 are formed on the inner surface of the planetary side internal gear 36. That is, the planetary side internal gear 36 has the internal teeth 361 on its inner surface. Each of the multiple internal teeth 361 protrudes inward in the first radial direction. The multiple internal teeth 361 are arranged at a constant pitch along the first circumferential direction. Each of the multiple internal teeth 361 meshes with the external teeth 331 of each of the three planetary gears 33 from the outside in the first radial direction. That is, the internal teeth 361 mesh with the external teeth 331 of the multiple planetary gears 33 from the outside in the first radial direction.

[0033] The planetary output shaft 37 is disposed along the first rotation shaft 91. The planetary output shaft 37 extends cylindrically along the first rotation shaft 91. As described above, the planetary output shaft 37 and the carrier 35 are a single member. That is, the planetary output shaft 37 is connected to the carrier 35. The planetary gear mechanism 3 of this embodiment is a so-called "planetary type" reduction mechanism. This allows the number of parts in the reducer 1 to be reduced, improving mass productivity.

[0034] When the motor 103 is driven, the planetary input shaft 31 and the sun gear 32 rotate together with the rotating portion of the motor 103 around the first rotation shaft 91 at an input rotation speed N1. Furthermore, the three planetary gears 33, which mesh with both the sun gear 32 and the planetary side internal gear 36, each rotate around a rotation shaft 93. Furthermore, while rotating around the rotation shaft 93, each of the three planetary gears 33 revolves together with the planetary shafts 34 around the first rotation shaft 91 at a first intermediate rotation speed N2 due to meshing with the planetary side internal gear 36. As a result, the carrier 35, to which the three planetary shafts 34 are fixed, rotates together with the planetary output shaft 37 around the first rotation shaft 91 at the decelerated first intermediate rotation speed N2. In other words, the planetary output shaft 37 can rotate around the first rotation shaft 91 at the first intermediate rotation speed N2.

[0035] As described above, the reducer 1 further includes the planetary transmission gear 38. The planetary transmission gear 38 is a cylindrical gear disposed approximately coaxially with the first rotating shaft 91. The planetary transmission gear 38 is fixed to the outer surface of the planetary output shaft 37 so as to be non-rotatable relative to the planetary output shaft 37. In other words, the planetary transmission gear 38 is fixed to the planetary output shaft 37. As a result, the planetary transmission gear 38 rotates together with the planetary output shaft 37 about the first rotating shaft 91 at the first intermediate rotation speed N2. In other words, the planetary transmission gear 38 can rotate about the first rotating shaft 91 at the first intermediate rotation speed N2. However, the planetary transmission gear 38 and the planetary output shaft 37 may be a single member.

[0036] FIG. 5 is a cross-sectional view of the planetary side transmission gear 38 and the wave side transmission gear 46, which will be described later, as viewed from the BB position in FIG. 2. To avoid complication of the drawing, hatching indicating cross sections has been omitted in FIG. 5. As shown in FIGS. 2 and 5, a plurality of external teeth 381 are formed on the outer surface of the planetary side transmission gear 38. That is, the planetary side transmission gear 38 has external teeth 381 formed on its outer surface. Each of the plurality of external teeth 381 protrudes outward in the first radial direction. The plurality of external teeth 381 are arranged at a constant pitch along the first circumferential direction.

[0037] Next, the configuration of the strain wave gear mechanism 4 will be described. Fig. 6 is a partial vertical cross-sectional view of the reducer 1 near the strain wave gear mechanism 4. As shown in Figs. 2 and 6, the second rotating shaft 92, which is the central axis of the strain wave gear mechanism 4, is spaced apart from the first rotating shaft 91 and is substantially parallel to the first rotating shaft 91. However, the first rotating shaft 91 and the second rotating shaft 92 may be in a twisted relationship. The strain wave gear mechanism 4 has a strain wave input shaft 41, a cam 421, a flexible external gear 43, a rigid internal gear 44, and a strain wave output shaft 45. The strain wave gear mechanism 4 also has a strain wave side casing 8. In this embodiment, the wave gear mechanism 4 has a wave input shaft 41, a wave generator 42, a flexible external gear 43, a rigid internal gear 44, a wave output shaft 45, an inner ring 151, an outer ring 152, a wave side transmission gear 46, and a wave side casing 8.

[0038] As described above, the reducer 1 further includes the wave-side transmission gear 46. The wave-side transmission gear 46 is a cylindrical gear disposed approximately coaxially with the second rotation shaft 92. In this embodiment, the wave-side transmission gear 46 and the wave input shaft 41 are a single member. Specifically, the wave-side transmission gear 46 is formed by a portion of the wave input shaft 41 in the second axial direction protruding outward in the second radial direction. Furthermore, the wave-side transmission gear 46 protrudes outward in the second radial direction from a portion of the wave input shaft 41 in the second axial direction over the entire circumference in the second circumferential direction. This reduces the number of parts in the reducer 1. However, the wave-side transmission gear 46 and the wave input shaft 41 may be separate members as long as they are connected so as not to rotate relative to each other. That is, the wave-side transmission gear 46 may be fixed to the wave input shaft 41 or may be a single member with the wave input shaft 41.

[0039] Furthermore, the wave-side transmission gear 46 does not have to protrude outward in the second radial direction from the wave input shaft 41. In other words, the outer diameter of the wave-side transmission gear 46 may be substantially the same as the outer diameter of the wave input shaft 41. This allows the wave-side transmission gear 46 and the wave input shaft 41 to be easily manufactured.

[0040] 5 and 6, a plurality of external teeth 461 are formed on the outer surface of the wave-side transmission gear 46. That is, the wave-side transmission gear 46 has external teeth 461 formed on its outer surface. Each of the external teeth 461 protrudes outward in the second radial direction. The external teeth 461 are arranged at a constant pitch along the second circumferential direction.

[0041] The wave-side transmission gear 46 is adjacent to the planetary-side transmission gear 38 in the second radial direction. The external teeth 461 of the wave-side transmission gear 46 mesh with the external teeth 381 of the planetary-side transmission gear 38, thereby receiving power. As a result, when the planetary-side transmission gear 38 rotates about the first rotation shaft 91 at the first intermediate rotation speed N2, the wave-side transmission gear 46 rotates about the second rotation shaft 92.

[0042] 5, in this embodiment, the diameter of the wave-side transmission gear 46 is sufficiently larger than the diameter of the planetary-side transmission gear 38. More specifically, as shown in FIGS. 2 and 6, a meshing position P1 between the external teeth 381 of the planetary-side transmission gear 38 and the external teeth 461 of the wave-side transmission gear 46 is closer to the first rotation shaft 91 than the outer surface of the planetary-side third casing cylindrical portion 731 of the planetary-side casing 7. That is, the meshing position P1 between the external teeth 381 of the planetary-side transmission gear 38 and the external teeth 461 of the wave-side transmission gear 46 is closer to the first rotation shaft 91 than the outer end of the planetary-side casing 7 in the first radial direction. Also, the meshing position P1 between the external teeth 381 of the planetary-side transmission gear 38 and the external teeth 461 of the wave-side transmission gear 46 is farther from the second rotation shaft 92 than the outer end of a cam 421, which will be described later, in the second radial direction. Furthermore, the number of teeth of the external teeth 461 of the wave side transmission gear 46 is larger than the number of teeth of the external teeth 381 of the planetary side transmission gear 38. As described above, in this embodiment, the outer diameter of the wave side transmission gear 46 is formed sufficiently large relative to the outer diameter of the planetary side transmission gear 38, and the number of teeth of the external teeth 461 of the wave side transmission gear 46 is made larger than the number of teeth of the external teeth 381 of the planetary side transmission gear 38, thereby making it possible to sufficiently reduce the first intermediate rotation speed N2 of the planetary side transmission gear 38 about the first rotation shaft 91. In other words, by increasing the outer diameter of the wave side transmission gear 46 relative to the outer diameter of the planetary side transmission gear 38, a higher reduction ratio can be obtained. As a result, when the planetary side transmission gear 38 rotates at the first intermediate rotation speed N2, the wave side transmission gear 46 rotates at a second intermediate rotation speed N3 that is sufficiently reduced in speed from the first intermediate rotation speed N2. That is, the wave-side transmission gear 46, together with the wave input shaft 41, is rotatable about the second rotation shaft 92 at the second intermediate rotation speed N3.

[0043] The wave side transmission gear 46 and the planetary side transmission gear 38 may be meshed with each other via a power transmission member such as another gear. Then, power may be transmitted from the planetary side transmission gear 38 to the wave side transmission gear 46 via the power transmission member such as another gear. In other words, the external teeth 461 of the wave side transmission gear 46 may be connected to the external teeth 381 of the planetary side transmission gear 38. This makes it possible to achieve a high reduction ratio by combining the planetary gear mechanism 3 and the wave gear mechanism 4.

[0044] The wave input shaft 41 extends in a hollow cylindrical shape along the second rotating shaft 92. As described above, the wave input shaft 41 and the wave side transmission gear 46 are unable to rotate relative to each other. Therefore, when the planetary output shaft 37 and the planetary side transmission gear 38 rotate about the first rotating shaft 91 at the first intermediate rotation speed N2, the wave input shaft 41 rotates together with the wave side transmission gear 46 about the second rotating shaft 92 at the second intermediate rotation speed N3. That is, the wave input shaft 41 can rotate about the second rotating shaft 92 at the second intermediate rotation speed N3 in conjunction with the rotation of the planetary output shaft 37. Furthermore, as described above, the wave input shaft 41 extends in a hollow cylindrical shape. This allows wiring and the like to be installed inside the wave input shaft 41 in the second radial direction. That is, in the wave gear mechanism 4, the internal space of the wave input shaft 41 (hollow shaft) can be effectively utilized.

[0045] The wave generator 42 is a mechanism for flexibly deforming the flexible external gear 43. The wave generator 42 has a cam 421 and a flexible bearing 422. The cam 421 and the flexible bearing 422 each extend in an annular shape centered on the second rotation shaft 92. FIG. 7 is a cross-sectional view schematically showing the wave generator 42, the flexible external gear 43, and the rigid internal gear 44 as seen from position CC in FIG. 2. To avoid complication of the drawing, hatching indicating cross sections has been omitted in FIG. 4.

[0046] In this embodiment, the cam 421 and the wave input shaft 41 are a single member. Specifically, the cam 421 is formed by a portion of the wave input shaft 41 in the second axial direction protruding outward in the second radial direction on one axial side of the wave-side transmission gear 46. The cam 421 also protrudes outward in the second radial direction from the portion of the wave input shaft 41 in the second axial direction over the entire circumference in the second circumferential direction. This prevents the cam 421 and the wave input shaft 41 from rotating relative to each other. As a result, when the wave input shaft 41 rotates about the second rotation shaft 92 at the second intermediate rotation speed N3, the cam 421 also rotates about the second rotation shaft 92 at the second intermediate rotation speed N3. In other words, the cam 421 can rotate together with the wave input shaft 41. However, the cam 421 and the wave input shaft 41 may be separate members as long as they are coupled together so as to prevent relative rotation.

[0047] As shown in Fig. 7, the cam 421 has an elliptical cam profile. That is, the outer surface of the cam 421 is elliptical when viewed in the second axial direction, and has an outer diameter that varies depending on the position in the second circumferential direction. The flexible bearing 422 is a bearing that can be flexibly deformed. The flexible bearing 422 is disposed between the outer surface of the cam 421 and the inner surface of a cylindrical portion 431 (described later) of the flexible external gear 43. The cam 421 and the cylindrical portion 431 can rotate at different rotational speeds.

[0048] As shown in Fig. 6, the flexible bearing 422 has an inner ring 96, a plurality of balls 97, and an elastically deformable outer ring 98. The inner ring 96 contacts the outer surface of the cam 421. The plurality of balls 97 are interposed between the inner ring 96 and the outer ring 98 and are arranged in the circumferential direction. The outer ring 98 elastically deforms (flexibly deforms) via the inner ring 96 and the balls 97 along the cam profile of the rotating cam 421. As such, a ball bearing is used for the flexible bearing 422 of this embodiment. However, instead of a ball bearing, another type of bearing such as a roller bearing may be used.

[0049] The flexible external gear 43 is a flexible, deformable annular gear. As will be described later, the flexible external gear 43 is fixed to the arm 102 of the robot 100 via a wave output shaft 45 and an outer ring 152. The flexible external gear 43 is provided along the second rotation shaft 92. The flexible external gear 43 has a cylindrical portion 431 and a flange portion 432.

[0050] The tubular portion 431 extends in a hollow tubular shape along the second rotation shaft 92. The tubular portion 431 is a flexible cylindrical portion that is bendable in the second radial direction. A plurality of external teeth 433 are formed on the outer surface of the tubular portion 431 near the other axial end. Each of the external teeth 433 protrudes outward in the second radial direction. The external teeth 433 are arranged at a constant pitch along the second circumferential direction. The outer ring 98 of the flexible bearing 422 comes into contact with the inner surface of the tubular portion 431. This allows the flexible external gear 43 to deform in response to the rotation of the cam 421.

[0051] The flange portion 432 extends outward in the second radial direction from one axial end of the cylindrical portion 431. The flange portion 432 extends in an annular shape centered on the second rotation shaft 92. By having the flange portion 432 extend outward in the second radial direction from the cylindrical portion 431 in this way, it is possible to prevent the flexible external gear 43 from interfering with the wave input shaft 41. Furthermore, by arranging the flange portion 432 in the space further outward in the second radial direction than the wave input shaft 41 in this way, it is possible to efficiently utilize this space.

[0052] Furthermore, the flange portion 432 is a flat plate-like portion that is less likely to bend than the cylindrical portion 431. Furthermore, as shown in Fig. 6, a boss portion 434 is formed at a position on the outer side of the flange portion 432 in the second radial direction. The boss portion 434 is a portion that is thick in the second axial direction. A plurality of through holes 430 are formed in the boss portion 434. Each of the plurality of through holes 430 penetrates the boss portion 434 in the second axial direction.

[0053] The rigid internal gear 44 is annular and centered on the second rotation shaft 92. In this embodiment, the rigid internal gear 44 extends in an annular shape centered on the second rotation shaft 92. The other axial end of the cylindrical portion 431 is disposed on the second radially inner side of the rigid internal gear 44. The rigid internal gear 44 has a much higher rigidity than the cylindrical portion 431. Therefore, the rigid internal gear 44 can be considered to be a substantially rigid body. As shown in FIGS. 6 and 7 , a plurality of internal teeth 441 are formed on the inner surface of the rigid internal gear 44. The plurality of internal teeth 441 are arranged at a constant pitch along the second circumferential direction. The number of teeth of the internal teeth 441 of the rigid internal gear 44 is slightly different from the number of teeth of the external teeth 433 of the flexible external gear 43.

[0054] The rigid internal gear 44 is also provided with a plurality of through holes 440. The plurality of through holes 440 are arranged at equal intervals in the circumferential direction around the second rotation shaft 92. Each through hole 440 passes through the rigid internal gear 44 in the second axial direction. The rigid internal gear 44 is also fixed to the end face portion 732 of the planetary side casing 7. As described above, the planetary side casing 7 is fixed immovably and imrotatably with respect to the base frame 101 of the robot 100 on which the reducer 1 is disposed. This restricts movement of the rigid internal gear 44 in the second circumferential direction, the second radial direction, and the second axial direction.

[0055] 2, in this embodiment, a fixed position P2 between the planetary casing top surface portion 73, including the end surface portion 732, and the rigid internal gear 44 is farther from the second rotation shaft 92 than a meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46. In addition, the fixed position P2 between the planetary casing top surface portion 73, including the end surface portion 732, and the rigid internal gear 44 is located on one axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46. That is, in this embodiment, the planetary casing top surface portion 73 and the rigid internal gear 44 are fixed farther from the second rotating shaft 92 than the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46, and on one axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46.

[0056] As described above, the outer ring 98 of the flexible bearing 422 comes into contact with the inner surface of the cylindrical portion 431 of the flexible external gear 43. Therefore, the cylindrical portion 431 is deformed into an elliptical shape that follows the outer surface of the cam 421. As a result, the external teeth 433 of the flexible external gear 43 mesh with the internal teeth 441 of the rigid internal gear 44 at two locations corresponding to both ends of the major axis of the ellipse. In other words, the flexible external gear 43 and the rigid internal gear 44 mesh with each other. However, at other positions in the circumferential direction, the external teeth 433 of the flexible external gear 43 do not mesh with the internal teeth 441 of the rigid internal gear 44.

[0057] When the wave input shaft 41 rotates together with the cam 421 around the second rotation axis 92 at the second intermediate rotation speed N3, the major axis of the ellipse of the flexible external gear 43 also rotates at the second intermediate rotation speed N3. As a result, the meshing position between the external teeth 433 and the internal teeth 441 also changes in the second circumferential direction at the second intermediate rotation speed N3. As described above, the number of teeth of the external teeth 433 of the flexible external gear 43 is slightly different from the number of teeth of the internal teeth 441 of the rigid internal gear 44. Due to this difference in the number of teeth, the meshing combination between the external teeth 433 and the internal teeth 441 changes slightly in the second circumferential direction with each rotation of the cam 421. Here, the rigid internal gear 44 is fixed to the base frame 101 of the robot 100 and does not rotate. As a result, the flexible external gear 43 rotates about the second rotation shaft 92 at an output rotation speed N4 that is slower than the second intermediate rotation speed N3, relative to the rigid internal gear 44 and the base frame 101. In other words, the flexible external gear 43 and the rigid internal gear 44 are rotatable relative to each other due to the difference in the number of teeth between them.

[0058] In this embodiment, the meshing position P3 between the flexible external gear 43 and the rigid internal gear 44 is farther from the second rotation shaft 92 than the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46. In this way, by increasing the outer diameter of the flexible external gear 43 and the inner diameter of the rigid internal gear 44, the relative rotation between the flexible external gear 43 and the rigid internal gear 44 can be stabilized.

[0059] The inner ring 151 is a member that expands in an annular shape centered on the second rotation shaft 92. Both the inner ring 151 and the outer ring 152 have high rigidity. The inner ring 151 is provided with a plurality of screw holes 153. The plurality of screw holes 153 are each formed from the end face of the inner ring 151 on the other axial side toward one axial side. The inner ring 151 is fixed to the rigid internal gear 44 by fastening a plurality of screws 154 that pass through a plurality of through holes 440 of the rigid internal gear 44, respectively, into the plurality of screw holes 153. In this way, the inner ring 151, together with the rigid internal gear 44, is fixed to the base frame 101 of the robot 100.

[0060] An outer ring 152 is disposed on the outside of the inner ring 151 in the second radial direction. The outer ring 152 is a member that expands in an annular shape centered on the second rotating shaft 92. The outer ring 152 is also part of the wave-side casing 8. The outer ring 152 has an inner diameter that is slightly larger than the outer diameter of the inner ring 151. As shown in FIG. 2 , the outer ring 152 is provided with a plurality of screw holes 155. The plurality of screw holes 155 are each formed from an end face on one axial side of the outer ring 152 toward the other axial side.

[0061] The outer ring 152 is rotatably connected to the inner ring 151 via a bearing 16. In this embodiment, a cross roller bearing is used as the bearing 16. The bearing 16 has multiple cylindrical rollers 161 between the outer surface of the inner ring 151 and the inner surface of the outer ring 152. The multiple cylindrical rollers 161 are arranged with their orientations alternating between an annular V-groove provided on the outer surface of the inner ring 151 and an annular V-groove provided on the inner surface of the outer ring 152. This allows the inner ring 151 and the outer ring 152 to be connected with high rigidity while allowing the outer ring 152 to rotate relative to the inner ring 151. Such cross roller bearings can achieve sufficient rigidity in the second axial direction and the second radial direction without being used in pairs like ball bearings. In other words, using a cross roller bearing can reduce the number of bearings (bearings) provided in the reducer 1. This reduces the weight of the bearing 16 and limits the axial dimension of the bearing 16.

[0062] The wave output shaft 45 is a member for extracting power after reduction in the reducer 1. The wave output shaft 45 is arranged along the second rotating shaft 92. In this embodiment, the wave output shaft 45 has a substantially circular ring shape centered on the second rotating shaft 92. The wave output shaft 45 has an inner extending portion 451, a radial extending portion 452, and an outer extending portion 453.

[0063] The inner extending portion 451 and the outer extending portion 453 are each cylindrical portions disposed approximately coaxially with the second rotation shaft 92. The inner extending portion 451 is located on one axial side of the radial extending portion 452 and the outer extending portion 453. A bearing 395 is provided between the inner extending portion 451 and the wave input shaft 41 in the second radial direction. A ball bearing is used as the bearing 395 in this embodiment. An inner ring of the bearing 395 is fixed to the outer surface of the wave input shaft 41. An outer ring of the bearing 395 is fixed to the inner surface of the inner extending portion 451. As a result, the wave output shaft 45 including the inner extending portion 451 is supported via the bearing 395 so as to be rotatable relative to the wave input shaft 41 around the second rotation shaft 92.

[0064] The radially extending portion 452 extends outward in the second radial direction from the other axial end of the inward extending portion 451. A plurality of through holes 450 are provided in the radially extending portion 452. Each through hole 450 penetrates the radially extending portion 452 in the second axial direction. The radially extending portion 452 is fixed to the flexible external gear 43 and the outer ring 152 by fastening a plurality of screws 156, which pass through each of the plurality of through holes 450 and each of the plurality of through holes 430 of the flexible external gear 43, into a plurality of screw holes 155 in the outer ring 152. In this way, the flange portion 432 of the flexible external gear 43 is fixed to the wave output shaft 45. As a result, the wave output shaft 45 , the flexible external gear 43 , and the outer ring 152 are supported via the bearing 395 so as to be rotatable relative to the wave input shaft 41 around the second rotation shaft 92 .

[0065] The outer extending portion 453 extends toward the other axial side from the second radially outer end of the radial extending portion 452. The outer extending portion 453 is also a part of the wave-side casing 8.

[0066] The wave side casing 8 is a member that houses the wave input shaft 41, the wave generator 42, the flexible external gear 43, the rigid internal gear 44, part of the wave output shaft 45, the inner ring 151, and the outer ring 152. However, it is sufficient that the wave side casing 8 houses at least part of the flexible external gear 43. The wave side casing 8 has the outer ring 152, the outer extension part 453, the wave casing cylindrical part 81, the first wave casing fixing part 82, and the second wave casing fixing part 83.

[0067] The outer extension portion 453 extends along the second rotation shaft 92 at the outermost portion in the second radial direction of the wave side casing 8. That is, the outer extension portion 453 is located at the outer end of the wave side casing 8 in the second radial direction. When viewed from the second rotation shaft 92, the outer surface of the outer extension portion 453 is farther from the second rotation shaft 92 than the first rotation shaft 91. That is, the outer end of the wave side casing 8 in the second radial direction is farther from the second rotation shaft 92 than the first rotation shaft 91. In this embodiment, by arranging the planetary gear mechanism 3 and the wave gear mechanism 4 close to each other in this manner, it is possible to reduce the space required for the entire reducer 1.

[0068] The wave casing cylindrical portion 81 extends along the second rotation axis 92. The wave casing cylindrical portion 81 is located between the first wave casing fixing portion 82 and the second wave casing fixing portion 83 in the second axial direction. The first wave casing fixing portion 82 extends outward in the second radial direction from one axial end of the wave casing cylindrical portion 81. One or more through holes 820 are provided in the first wave casing fixing portion 82. Each through hole 820 penetrates the first wave casing fixing portion 82 in the second axial direction. The wave-side casing 8 including the first wave casing fixing portion 82 is fixed to the rigid internal gear 44 and the inner ring 151 by fastening a screw 84 that passes through the through hole 820 and the through hole 440 of the rigid internal gear 44 to the threaded hole 153 of the inner ring 151.

[0069] As a result, the wave side casing 8 is fixed to the base frame 101 of the robot 100 together with the rigid internal gear 44 and the inner ring 151. However, the rigid internal gear 44 and the wave side casing 8 may be a single member. This reduces the number of parts in the reducer 1 and improves mass productivity.

[0070] The second wave casing fixing portion 83 extends radially inward from the other axial end of the wave casing cylindrical portion 81. A support bearing 396 is provided between the second wave casing fixing portion 83 and the wave input shaft 41 in the second radial direction. As described above, the support bearing 396 is also a component of the planetary gear mechanism 3. A ball bearing is used for the support bearing 396 in this embodiment. The inner ring of the support bearing 396 is fixed to the outer surface of the wave input shaft 41. The outer ring of the support bearing 396 is fixed to the inner surface of the second wave casing fixing portion 83 over a portion of the second circumferential direction. As a result, the wave input shaft 41 is supported via the support bearing 396 so as to be rotatable relative to the wave side casing 8 including the second wave casing fixing portion 83, the rigid internal gear 44, and the inner ring 151, about the second rotating shaft 92. The outer ring of the support bearing 396 is fixed at another part in the second circumferential direction to the planetary second casing cylindrical portion 72 via the second connecting member 724. In other words, the outer ring of the support bearing 396 is fixed to the planetary side casing 7.

[0071] As described above, the wave output shaft 45, together with the flexible external gear 43 and the outer ring 152, is supported via the bearing 395 so as to be rotatable relative to the wave input shaft 41 around the second rotation axis 92. The flexible external gear 43 is fixed to the arm 102 of the robot 100. This makes the wave output shaft 45, the flexible external gear 43, and the outer ring 152, and the arm 102 of the robot 100 rotatable around the second rotation axis 92 relative to the base frame 101 to which the rigid internal gear 44 is fixed. As a result, when the wave input shaft 41 rotates together with the cam 421 around the second rotation axis 92 at the second intermediate rotation speed N3, the wave output shaft 45, the flexible external gear 43, and the outer ring 152, and the arm 102 of the robot 100 rotate around the second rotation axis 92 at the output rotation speed N4.

[0072] 2 , in this embodiment, a fixed position P4 between the wave input shaft 41 and the inner ring of the support bearing 396 is closer to the second rotating shaft 92 than a meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46. Furthermore, the fixed position P4 between the wave input shaft 41 and the inner ring of the support bearing 396 is located on the other axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46. That is, in this embodiment, the wave input shaft 41 is closer to the second rotating shaft 92 than the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46, and is fixed to the inner ring of the support bearing 396 on the other axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46.

[0073] That is, in this embodiment, the planetary gear mechanism 3 and the wave gear mechanism 4 are fixed at the above-mentioned fixed position P2 on one axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46, and at the above-mentioned fixed position P4 on the other axial side. In this way, by fixing the planetary gear mechanism 3 and the wave gear mechanism 4 on one axial side and the other axial side of the meshing position P1 between the external teeth 381 of the planetary side transmission gear 38 and the external teeth 461 of the wave side transmission gear 46, the planetary gear mechanism 3 and the wave gear mechanism 4 can be fixed more firmly.

[0074] Furthermore, in this embodiment, the planetary gear mechanism 3 and the strain wave gear mechanism 4 are arranged closely to each other in the reducer 1 so that a portion of the planetary output shaft 37 of the planetary gear mechanism 3 in the first axial direction and a portion of the wave input shaft 41 of the strain wave gear mechanism 4 in the second axial direction overlap in the first radial direction and the second radial direction. That is, in this embodiment, a portion of the planetary output shaft 37 and a portion of the wave input shaft 41 overlap in the second radial direction about the second rotation shaft 92. By arranging a portion of the planetary gear mechanism 3 and a portion of the strain wave gear mechanism 4 so that they overlap in the radial direction in this way, the axial length of the reducer 1 including these can be reduced.

[0075] Furthermore, in this embodiment, in the reducer 1, the rotation of the rotating part of the motor 103 at an input rotation speed N1 is reduced in the planetary gear mechanism 3 in the upstream stage, and then further reduced in the strain wave gear mechanism 4 in the downstream stage. In this way, in this embodiment, by providing the strain wave gear mechanism 4 in the downstream stage, the reduction ratio can be increased.

[0076] 2. Second Embodiment Next, the configuration of a reducer 1B mounted on a robot according to a second embodiment of the present invention will be described. The following description will focus on differences from the reducer 1 of the first embodiment, and some overlapping descriptions of parts that are the same as those in the first embodiment will be omitted. Figure 8 is a vertical cross-sectional view of the reducer 1B according to the second embodiment.

[0077] The reducer 1B includes a planetary gear mechanism 3B and a strain wave gear mechanism 4B. The strain wave gear mechanism 4B of this embodiment has the same configuration as the strain wave gear mechanism 4 of the first embodiment.

[0078] 8, the planetary gear mechanism 3B has a planetary input shaft 31B, a sun gear 32B, a plurality of planetary gears 33B, a plurality of planetary shafts 34B, a carrier 35B, a planetary side internal gear 36B, a planetary output shaft 37B, a planetary side transmission gear 38B, a support bearing 396B, and a planetary side casing 7B. The planetary input shaft 31B, sun gear 32B, a plurality of planetary gears 33B, a plurality of planetary shafts 34B, planetary side transmission gear 38B, and support bearing 396B of this embodiment have the same configurations as the planetary input shaft 31, sun gear 32, a plurality of planetary gears 33, a plurality of planetary shafts 34, planetary side transmission gear 38, and support bearing 396 of the first embodiment, and therefore redundant description will be omitted.

[0079] Unlike the planetary side casing 7 of the first embodiment, the planetary side casing 7B of this embodiment does not have a portion corresponding to the planetary second casing cylindrical portion 72. The plurality of planetary gears 33B of this embodiment are arranged on the first radially inner side of the planetary casing top surface portion 73B. The carrier 35B of this embodiment is fixed to the planetary casing top surface portion 73B by screwing. That is, the carrier 35B is fixed to the planetary side casing 7B.

[0080] The planetary side internal gear 36B is disposed approximately coaxially with the first rotation shaft 91B. The internal teeth of the planetary side internal gear 36B mesh with the external teeth of the multiple planetary gears 33B from the outside in the first radial direction. The planetary output shaft 37B is a member extending cylindrically along the first rotation shaft 91B. In this embodiment, the planetary output shaft 37B and the planetary side internal gear 36B are a single member. That is, the planetary output shaft 37B is connected to the planetary side internal gear 36B. The planetary gear mechanism 3B of this embodiment is a so-called "star type." This structure makes it possible to reduce the axial length of the planetary gear mechanism 3B. That is, in the present invention, it is sufficient that the planetary output shaft 37B is connected to either the carrier 35B or the planetary side internal gear 36B.

[0081] Two bearings 397B are inserted between the carrier 35B and the planetary output shaft 37B in the first radial direction. The two bearings 397B are disposed adjacent to each other in the first axial direction. In this embodiment, a ball bearing is used for the bearing 397B. An inner ring of the bearing 397B is fixed to the outer surface of the carrier 35B. An outer ring of the bearing 397B is fixed to the inner surface of the planetary output shaft 37B. As a result, the planetary output shaft 37B and the planetary side internal gear 36B are supported rotatably about the first rotation shaft 91B relative to the carrier 35B and the planetary side casing 7B via the bearings 397B.

[0082] When the motor 103 is driven, the planetary input shaft 31B and the sun gear 32B rotate about the first rotation shaft 91B at an input rotation speed N1. Furthermore, the multiple planetary gears 33B, which mesh with both the sun gear 32B and the planetary side internal gear 36B, each rotate on their own axis. However, although the multiple planetary gears 33B are fixed to the carrier 35B via the planetary shaft 34B, the carrier 35B does not rotate because, as described above, it is fixed to the planetary side casing 7B. Therefore, the planetary side internal gear 36B, due to its meshing with the multiple planetary gears 33B, rotates together with the planetary output shaft 37B about the first rotation shaft 91B at a reduced first intermediate rotation speed N2.

[0083] <3. Modifications> Although the exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0084] In the above-described strain wave gear mechanism 4, the flexible external gear 43 is fixed to the wave output shaft 45 and the arm 102 of the robot 100, and the rigid internal gear 44 is fixed to the base frame 101 of the robot 100 so as to be immovable and unrotatable. However, the flexible external gear 43 may be fixed to the base frame 101 of the robot 100 so as to be immovable and unrotatable, and the rigid internal gear 44 may be fixed to the wave output shaft 45 and the arm 102 of the robot 100. Then, the rigid internal gear 44 may be rotated relative to the flexible external gear 43 by meshing the external teeth 433 of the flexible external gear 43 with the internal teeth 441 of the rigid internal gear 44. In other words, the wave output shaft 45 may be connected to either the flexible external gear 43 or the rigid internal gear 44, as long as it is rotatable about the second rotation shaft 92 at the output rotation speed N4.

[0085] The planetary gear mechanism used in the reducer may be a multi-stage type. In this case, for example, the planetary gear mechanism may include a front-stage planetary gear unit arranged in a front stage and a rear-stage planetary gear unit arranged in a rear stage relative to the front-stage planetary gear unit. The front-stage planetary gear unit may include a front-stage planetary input shaft that is the planetary input shaft of the above embodiment, a front-stage sun gear that is the sun gear of the above embodiment, multiple front-stage planetary gears that are the multiple planet gears of the above embodiment, a front-stage carrier that is the carrier of the above embodiment, a front-stage planetary side internal gear that is the planetary side internal gear of the above embodiment, and a front-stage planetary output shaft. The front-stage planetary output shaft may be an output shaft that is arranged along the first rotation axis, connected to the front-stage carrier, and rotatable about the first rotation axis.

[0086] The rear-stage planetary gear device may include a rear-stage planetary input shaft, a rear-stage sun gear, multiple rear-stage planetary gears, a rear-stage carrier, a rear-stage planetary-side internal gear, and a rear-stage planetary output shaft. The rear-stage planetary input shaft may be fixed to the front-stage planetary output shaft and rotatable about a first rotation axis. The rear-stage sun gear may be fixed to the rear-stage planetary input shaft, have external teeth formed on its outer surface, and be rotatable about the first rotation axis. The multiple rear-stage planetary gears may be arranged around the rear-stage sun gear, have external teeth that mesh with the external teeth of the rear-stage sun gear from outside in the first radial direction, and rotate with the rotation of the rear-stage sun gear. The rear-stage carrier may be fixed with multiple rear-stage planetary shafts that rotatably support the multiple rear-stage planetary gears. The rear planetary side internal gear may be annular about the first rotation axis and have internal teeth on its inner surface that mesh with the external teeth of the multiple rear planetary gears from the outside in the first radial direction. The rear planetary output shaft may be connected to the planetary output shaft of the above embodiment that is disposed along the first rotation axis, connected to the rear carrier, and rotatable about the first rotation axis at the first intermediate rotation speed N2. In this way, by using a multi-stage planetary gear mechanism, a higher reduction ratio can be obtained.

[0087] In the multi-stage planetary gear mechanism, the planetary output shaft and the rear-stage planetary output shaft of the above embodiment may be a single member. By making the planetary output shaft and the rear-stage planetary output shaft a single member, the number of parts can be reduced and mass productivity can be improved.

[0088] Furthermore, the detailed shapes of the reducer and the robot may differ from those shown in the drawings of the above-described embodiment. [Industrial Applicability]

[0089] The present application can be used in a reducer and a robot. [Explanation of symbols]

[0090] 1,1B reducer 3,3B Planetary gear mechanism 4,4B Strain Wave Gear Mechanism 7,7B Planetary side casing 8 Wave side casing 31,31B Planetary input shaft 32,32B Sun gear 33,33B Planetary gear 34,34B planetary shaft 35,35B Carrier 36,36B Planetary side internal gear 37,37B Planetary output shaft 38,38B Planetary transmission gear 41 Wave input shaft 42 Wave Generator 43 Flexible external gear 44 Rigid internal gear 45 Wave output shaft 46 Wave side transmission gear 73,73B Planetary casing top surface 91,91B First rotation axis 92 Second rotation axis 93 Rotation axis 100 robots 103 Motor 321 (sun gear) external teeth 331 (planetary gear) external teeth 361 (Planetary internal gear) 381 (Planetary transmission gear) outer teeth 396,396B Support bearing 421 Cam 431 (Flexible external gear) cylindrical part 432 (Flexible external gear) flange portion 433 (flexible external gear) external teeth 441 (of rigid internal gears) 461 (Wave side transmission gear) outer teeth P1 (Interlocking position between the outer teeth of the planetary transmission gear and the outer teeth of the wave transmission gear) P2 (fixing position between the top surface of the planetary casing and the rigid internal gear) P3 (Flexible external gear and rigid internal gear) meshing position P4 (fixed position between the wave input shaft and the inner ring of the support bearing)

Claims

1. A reducer comprising a planetary gear mechanism and a strain wave gear mechanism, capable of reducing the rotation of a planetary input shaft which is an input part of the planetary gear mechanism, and rotating a strain wave output shaft which is an output part of the strain wave gear mechanism, The planetary gear mechanism includes: the planetary input shaft rotatable about a first rotation shaft at an input rotation speed; a sun gear fixed to the planetary input shaft, having external teeth formed on an outer surface thereof, and rotatable about the first rotation axis at the input rotation speed; a plurality of planetary gears arranged around the sun gear, each having external teeth that mesh with the external teeth of the sun gear from the outside in a first radial direction about the first rotation axis, and capable of rotating in accordance with the rotation of the sun gear; a carrier to which a plurality of planetary shafts are fixed, each of which rotatably supports the plurality of planetary gears; a planetary side internal gear having an annular shape centered on the first rotation axis and internal teeth on an inner surface thereof that mesh with the external teeth of the plurality of planetary gears from the outside in a first radial direction; a planetary output shaft that is disposed along the first rotation shaft, that is connected to either the carrier or the planetary side internal gear, and that is rotatable about the first rotation shaft at a first intermediate rotation speed; and The strain wave gear mechanism comprises: a wave input shaft extending in a hollow cylindrical shape along the second rotation shaft and rotatable about the second rotation shaft at a second intermediate rotation speed in accordance with rotation of the planetary output shaft; a cam rotatable together with the wave input shaft; a flexible external gear that is deformable in response to rotation of the cam; an annular rigid internal gear centered on the second rotation axis; the wave output shaft, which is disposed along the second rotation axis, is connected to one of the flexible external gear and the rigid internal gear, and is rotatable around the second rotation axis at an output rotation speed; and the flexible external gear and the rigid internal gear mesh with each other, and the flexible external gear and the rigid internal gear are capable of relative rotation due to a difference in the number of teeth, a portion of the planetary output shaft and a portion of the wave input shaft overlap in a second radial direction centered on the second rotation axis, a planetary-side transmission gear fixed to the planetary output shaft or formed as a single member with the planetary output shaft, having external teeth formed on an outer surface thereof, and rotatable around the first rotation shaft at the first intermediate rotation speed; a wave-side transmission gear fixed to the wave input shaft or formed as a single member with the wave input shaft, having external teeth formed on an outer surface thereof, and rotatable around the second rotation shaft at the second intermediate rotation speed; and external teeth of the wave side transmission gear are connected to external teeth of the planetary side transmission gear, and the wave side transmission gear is rotatable together with the wave input shaft around the second rotation shaft at the second intermediate rotation speed, The planetary gear mechanism includes: a planetary-side casing that accommodates at least a portion of the planetary gears; and The planetary side casing includes: A planetary casing top surface portion that surrounds the planetary output shaft from one axial side and a speed reducer in which the planetary casing top surface portion and the rigid internal gear are fixed farther from the second rotation shaft than a meshing position between the external teeth of the planetary side transmission gear and the external teeth of the wave side transmission gear, and on one axial side of a meshing position between the external teeth of the planetary side transmission gear and the external teeth of the wave side transmission gear.

2. A reducer according to claim 1, the number of external teeth of the wave transmission gear is greater than the number of external teeth of the planetary transmission gear, a meshing position between the external teeth of the planetary-side transmission gear and the external teeth of the wave-side transmission gear is closer to the first rotation shaft than an outer end of the planetary-side casing in a first radial direction.

3. A reducer according to claim 2, The planetary side internal gear and the planetary side casing are a single member.

4. A reducer according to claim 1 or claim 2, the planetary side internal gear is fixed to an inner surface of the planetary side casing, The planetary output shaft is connected to the carrier.

5. A reducer according to claim 1 or claim 2, the carrier is fixed to the planetary side casing, The planetary output shaft is connected to the planetary side internal gear.

6. A reducer according to claim 1 or claim 2, the planetary gear mechanism includes a front-stage planetary gear device arranged in a front stage and a rear-stage planetary gear device arranged in a rear stage of the front-stage planetary gear device, The front planetary gear device is a front-stage planetary input shaft that is the planetary input shaft; a front sun gear that is the sun gear; a plurality of front planetary gears that are the plurality of planetary gears; a preceding stage carrier that is the carrier; a front stage planetary internal gear that is the planetary internal gear; a front-stage planetary output shaft that is an output shaft that is arranged along the first rotation shaft, is connected to the front-stage carrier, and is rotatable around the first rotation shaft; and The rear planetary gear device is a rear-stage planetary input shaft fixed to the front-stage planetary output shaft and rotatable about the first rotation shaft; a rear sun gear fixed to the rear planetary input shaft, having external teeth formed on an outer surface thereof, and rotatable about the first rotation axis; a plurality of rear-stage planetary gears arranged around the rear-stage sun gear, each having external teeth that mesh with the external teeth of the rear-stage sun gear from outside in a first radial direction, and rotating in accordance with the rotation of the rear-stage sun gear; a rear carrier to which a plurality of rear planetary shafts are fixed, the rear planetary gears being rotatably supported by the rear planetary gears; a rear-stage planetary-side internal gear that is annular about the first rotation axis and has internal teeth on an inner surface thereof that mesh with the external teeth of the plurality of rear-stage planetary gears from outside in a first radial direction; a rear-stage planetary output shaft disposed along the first rotation axis, connected to the rear-stage carrier, and connected to the planetary output shaft rotatable around the first rotation axis at the first intermediate rotation speed; A reducer having

7. A reducer according to claim 6, The planetary output shaft and the rear-stage planetary output shaft are a single member.

8. A reducer according to any one of claims 1 to 3, the number of external teeth of the wave transmission gear is greater than the number of external teeth of the planetary transmission gear, a meshing position between the external teeth of the planetary transmission gear and the external teeth of the wave transmission gear is farther from the second rotation shaft than an outer end of the cam in the second radial direction.

9. A reducer according to any one of claims 1 to 8, The strain wave gear mechanism comprises: a wave-side casing that accommodates at least a portion of the flexible external gear; and A reducer, wherein an outer end of the wave-side casing in the second radial direction is farther from the second rotation shaft than the first rotation shaft.

10. A reducer according to claim 9, The rigid internal gear and the wave side casing are a single member.

11. A reducer according to any one of claims 1 to 3, a meshing position between the flexible external gear and the rigid internal gear is farther from the second rotation shaft than a meshing position between the external teeth of the planetary side transmission gear and the external teeth of the wave side transmission gear.

12. A reducer according to claim 1, The planetary gear mechanism includes: A support bearing whose outer ring is fixed to the planetary-side casing and the wave input shaft is closer to the second rotation shaft than the meshing position between the external teeth of the planetary side transmission gear and the external teeth of the wave side transmission gear, and is fixed to the inner ring of the support bearing on the other axial side of the meshing position between the external teeth of the planetary side transmission gear and the external teeth of the wave side transmission gear.

13. A reducer according to any one of claims 1 to 3, The wave-side transmission gear and the wave input shaft are a single member.

14. A reducer according to any one of claims 1 to 3 and claim 13, The outer diameter of the wave-side transmission gear is approximately the same as the outer diameter of the wave input shaft.

15. A reducer according to any one of claims 1 to 14, The flexible external gear is a cylindrical portion extending in a hollow cylindrical shape along the second rotation axis; a flange portion extending from one axial end of the cylindrical portion toward the outside in a second radial direction; and The flange portion is fixed to the wave output shaft.

16. A robot having a reducer described in any one of claims 1 to 15.

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