Planetary gear reduction mechanism

Abstract

To provide a planetary gear reduction mechanism which can perform stable movement.SOLUTION: A fifth ball bearing BB5 for rotatably supporting a rotating shaft 31 is arranged at one side of a pinion gear 30 in an axial direction of the rotating shaft 31, and a sixth ball bearing BB6 for rotatably supporting the rotating shaft 31 is arranged at the other side of the pinion gear 30 in the axial direction of the rotating shaft 31. A bearing fixing part 65c for immovably supporting the fifth ball bearing BB5 in the axial direction of the rotating shaft 31, and a shaft guide part 66c for movably supporting the sixth ball bearing BB6 in the axial direction of the rotating shaft 31 are arranged at a carrier 60. The fifth and sixth ball bearings BB5, BB6 cannot approach each other with respect to the axial direction of the rotating shaft 31, and a wobble adjustment member 68 for pressing the sixth ball bearing BB6 to a side at which the fifth ball bearing BB5 is arranged is arranged at a female screw part 66d.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a planetary gear reduction mechanism having a plurality of gears. [Background technology]

[0002] For example, Patent Document 1 describes a planetary reduction device in which front and rear planetary reduction mechanisms, each consisting of a sun gear, planetary gears, a planet carrier, and an internal gear, are stacked in the axial direction. This reduces the rotational speed of the sun gear of the front planetary reduction gear, and a high-torque rotational force is output from the planet carrier of the rear planetary reduction gear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 014647 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, a pressure mechanism is provided on the rear-stage planetary carrier, and the pressure mechanism is arranged between the rear-stage planetary carrier and the front-stage planetary carrier with which the rear-stage sun gear is integrally provided, so that the pressure mechanism is pushed against the rear-stage planetary carrier. This allows the rear-stage sun gear and the rear-stage planetary gear to mesh with each other while restricting movement in the axial direction. However, since pressure is not applied to the front-stage sun gear by the pressure mechanism, there is a problem that the front-stage sun gear rattles in the axial direction or experiences rotational wobble, resulting in unstable operation.

[0005] An object of the present invention is to provide a planetary gear reduction mechanism capable of stable operation. [Means for solving the problem]

[0006] In one aspect of the present invention, a planetary gear reduction mechanism includes a sun gear provided on a rotating shaft, an internal gear arranged radially outside the sun gear, planetary gears arranged between the sun gear and the internal gear, and a planetary carrier that rotatably supports the planetary gears, the planetary gear reduction mechanism having a first bearing provided on one side of the sun gear in the axial direction of the rotating shaft and rotatably supporting the rotating shaft, a second bearing provided on the other side of the sun gear in the axial direction of the rotating shaft and rotatably supporting the rotating shaft, a first bearing support portion provided on the planetary carrier and supporting the first bearing so as to be immovable in the axial direction of the rotating shaft, and a second bearing support portion provided on the planetary carrier and supporting the second bearing so as to be movably in the axial direction of the rotating shaft, the first bearing and the second bearing are provided so as not to be able to approach each other in the axial direction of the rotating shaft, and the second bearing support portion is provided with a pressing member that presses the second bearing toward the side on which the first bearing is provided. Effect of the Invention

[0007] According to the present invention, a planetary gear reduction mechanism capable of stable operation can be realized. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view of the planetary gear reduction mechanism as viewed from the output side. [Diagram 2] FIG. 2 is a perspective view of the planetary gear reduction mechanism as viewed from the input side. [Diagram 3] 2 is a cross-sectional view showing the internal structure of the planetary gear reduction mechanism of FIG. 1. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of the backlash adjustment mechanism. [Diagram 5] FIG. 11 is an enlarged cross-sectional view of a portion of a fifth ball bearing. [Figure 6] FIG. 2 is a perspective view showing a pinion gear alone. [Figure 7] FIG. 2 is a perspective view showing an internal gear alone. [Figure 8] FIG. 2 is a perspective view showing three helical gears. [Figure 9]FIG. 2 is a perspective view showing the carrier alone. [Figure 10] FIG. [Figure 11] 11 is a perspective view showing an assembly procedure of the carrier assembly. FIG. [Figure 12] 11 is a perspective view showing a procedure for assembling the internal gear to the carrier assembly. FIG. [Figure 13] 10A to 10C are perspective views showing a procedure for assembling a housing body and a ring member. [Figure 14] 11 is a perspective view showing an assembly procedure of the pinion gear and the backlash adjustment mechanism. FIG. [Figure 15] This is a diagram comparing gear transmission efficiency [%]. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] Figure 1 is an oblique view of the planetary gear reduction mechanism seen from the output side, Figure 2 is an oblique view of the planetary gear reduction mechanism seen from the input side, Figure 3 is a cross-sectional view showing the internal structure of the planetary gear reduction mechanism of Figure 1, Figure 4 is an enlarged cross-sectional view of the backlash adjustment mechanism, Figure 5 is an enlarged cross-sectional view of the fifth ball bearing, Figure 6 is an oblique view of the pinion gear alone, Figure 7 is an oblique view of the internal gear alone, Figure 8 is an oblique view of three helical gears, Figure 9 is an oblique view of the carrier alone, and Figure 10 is an exploded oblique view of the backlash adjustment mechanism.

[0011] [Outline of planetary gear reduction mechanism] 1 to 5 is used, for example, to drive the joints of a robot. An electric motor (not shown), which is a drive source, is provided on the input side (lower side in the figures) of the planetary gear reduction mechanism 10 in a power-transmittable manner, and a drive mechanism (not shown), which is an object to be driven, of the robot is provided on the output side (upper side in the figures) of the planetary gear reduction mechanism 10 in a power-transmittable manner.

[0012] Specifically, the rotating shaft 31 of the planetary gear reduction mechanism 10 is rotated by an electric motor, and the carrier 60 of the planetary gear reduction mechanism 10 drives the drive mechanism of the robot. The planetary gear reduction mechanism 10 then reduces the speed of rotation of the rotating shaft 31 to increase the torque, and outputs the increased torque from the carrier 60.

[0013] As a result, the planetary gear reduction mechanism 10 can transmit a large drive torque to the drive mechanism of the robot even if the drive source is a small electric motor, which makes it possible to reduce the size of the electric motor and, in turn, to easily install it inside the arm of a robot or the like, which has a small installation space.

[0014] The planetary gear reduction mechanism 10 according to the present embodiment is not limited to use in driving the joints of a robot, but can also be applied to small-sized in-vehicle drive systems, such as power sliding door devices and power window devices mounted on vehicles such as automobiles.

[0015] [housing] The planetary gear reduction mechanism 10 includes a housing 20 that forms the outer shell of the planetary gear reduction mechanism 10. The housing 20 includes a housing body 21 formed in a substantially cylindrical shape, and a ring member 22 that is attached to one axial side (the lower side in the figure) of the housing body 21 and formed in an annular shape. Both the housing body 21 and the ring member 22 are made of aluminum, which reduces the overall weight of the planetary gear reduction mechanism 10.

[0016] The housing body 21 includes a cylindrical portion 21a extending in the axial direction of the planetary gear reduction mechanism 10, and a total of eight first flange portions 21b integrally provided on one axial side of the cylindrical portion 21a and protruding radially outward from the cylindrical portion 21a. Each of the eight first flange portions 21b is provided with an insertion hole 21c through which a fixing bolt (not shown) is inserted.

[0017] On the other hand, an annular second flange portion 21d is integrally provided on the other axial side (upper side in the figure) of the cylindrical portion 21a so as to protrude radially inward of the cylindrical portion 21a. An outer race of the first ball bearing BB1 is attached to the radially inner side of the second flange portion 21d. The one axial side (lower side in the figure) of the second flange portion 21d supports the other axial side (upper side in the figure) of the internal gear 40.

[0018] In this manner, the second flange portion 21d of the housing body 21 has the function of supporting both the first ball bearing BB1 and the internal gear 40.

[0019] Here, the first ball bearing BB1 rotatably supports the other axial side (upper side in the figure) of the carrier 60, and specifically, the inner race of the first ball bearing BB1 is mounted on the outer periphery of the output side cylindrical portion 66 (see Figure 9) that forms the carrier 60.

[0020] Further, a plurality of screw holes 21e are provided on the other axial side (upper side in the figure) of the second flange portion 21d. Fixing screws (not shown) for fixing the planetary gear reduction mechanism 10 to an internal fixing portion (not shown) of a robot arm or the like are screwed into these screw holes 21e.

[0021] The ring member 22 includes an annular main body 22a. A total of eight third flange portions 22b are integrally provided on the annular main body 22a so as to protrude radially outward. These third flange portions 22b are provided corresponding to the first flange portions 21b of the housing main body 21. Each of the third flange portions 22b is provided with a female threaded hole 22c into which a fixing bolt (not shown) is screwed.

[0022] In addition, in the axial direction of the housing 20, a total of eight fourth flange portions 42 provided on the internal gear 40 are sandwiched between the first flange portion 21b and the third flange portion 22b that form the housing 20. As a result, the reducer SD is accommodated and fixed inside the housing 20 by inserting a fixing bolt (not shown) into the insertion hole 21c of the first flange portion 21b and the insertion hole 42a of the fourth flange portion 42 and screwing it into the female threaded hole 22c of the third flange portion 22b.

[0023] In addition, an outer ring of the second ball bearing BB2 is attached to the radially inner side of the ring member 22. That is, the ring member 22 has a function of supporting the second ball bearing BB2 and fixing the internal gear 40 inside the housing 20.

[0024] Here, the second ball bearing BB2 rotatably supports one axial side of the carrier 60 (the lower side in the figure), and specifically, the inner ring of the second ball bearing BB2 is mounted on the outer periphery of the input side cylindrical portion 65 (see Figure 9) that forms the carrier 60.

[0025] Furthermore, a total of four positioning protrusions P (see FIG. 13) are integrally provided on the other axial side (upper side in the figure) of the ring member 22. These positioning protrusions P protrude toward the internal gear 40 in the axial direction of the ring member 22 and engage with engaging recesses (not shown) of the internal gear 40. This makes it easy to position the ring member 22 with respect to the internal gear 40 (improving assembly).

[0026] The first and second ball bearings BB1, BB2 supporting both axial ends of the carrier 60 are ball bearings of the same size and specifications. The first and second ball bearings BB1, BB2 are the largest ball bearings among all the ball bearings provided in the planetary gear reduction mechanism 10.

[0027] [Outline of the reducer] 3 to 9, the planetary gear reduction mechanism 10 has a plurality of gears. Specifically, the reducer SD accommodated inside the housing 20 includes one pinion gear 30, one internal gear 40, a total of three planetary gears 50, and a carrier 60 that holds these planetary gears 50. In other words, the reducer SD is a planetary reducer.

[0028] [Pinion gear] 3 to 6, the pinion gear 30 is provided integrally with the other axial side (upper side in the figures) of the rotating shaft 31. An output shaft (not shown) of an electric motor, which is a drive source, is connected to one axial side (lower side in the figures) of the rotating shaft 31 in a power-transmitting manner. As a result, the pinion gear 30 rotates in a predetermined rotational direction at a predetermined rotational speed as the electric motor is driven to rotate.

[0029] The pinion gear 30 corresponds to the sun gear in this invention.

[0030] Helical teeth 32 are integrally formed on the outer periphery of the pinion gear 30. The axial length of the pinion gear 30 (helical teeth 32) is slightly longer than the axial length of the planetary gear 50. This allows the helical teeth 32 to mesh reliably with the planetary gear 50.

[0031] The helical tooth 32 corresponds to one tooth in the present invention.

[0032] The helical teeth 32 are connected in a helical shape in the axial direction of the rotating shaft 31, and the pinion gear 30 is provided with only one helical tooth 32. In other words, the pinion gear 30 has one tooth. The cross-sectional shape of the helical tooth 32 is substantially semicircular, and the helical tooth 32 enters (meshews with) a meshing recess 51a of the planetary gear 50 (see FIG. 8).

[0033] In this way, by setting the number of teeth of the pinion gear 30 to "1", the gear transmission efficiency [%] is increased and a large reduction ratio is obtained despite the small size. Therefore, it is possible to realize a reduction in size and power consumption of the electric motor that is the driving source.

[0034] [Internal gear] 3 and 7, the internal gear 40 is fixed to the radially inner side of the cylindrical portion 21a that forms the housing main body 21. Specifically, the internal gear 40 is sandwiched between the housing main body 21 and the ring member 22 in the axial direction of the planetary gear reduction mechanism 10. The internal gear 40 includes a cylindrical main body 41 formed in a substantially cylindrical shape, and a total of eight fourth flange portions 42 that protrude radially outward from the cylindrical main body 41 on one axial side of the cylindrical main body 41.

[0035] The cylindrical body 41 is disposed radially outward of the pinion gear 30, and a gear forming portion 43 is provided radially inward of the cylindrical body 41. A plurality of internal teeth 43a having a substantially semicircular cross section is integrally provided on the gear forming portion 43 of the cylindrical body 41, similar to the helical teeth 32 of the pinion gear 30. Here, the plurality of internal teeth 43a are inclined at a predetermined angle with respect to the axial direction of the cylindrical body 41, and thus can mesh with a meshing recess 51a (see FIG. 8) of the planetary gear 50.

[0036] The internal gear 40 corresponds to the internal gear in this invention.

[0037] Further, the fourth flange portion 42 provided on the internal gear 40 is provided corresponding to the first flange portion 21b of the housing body 21 and the third flange portion 22b of the ring member 22. Each of the eight fourth flange portions 42 is provided with an insertion hole 42a through which a fixing bolt (not shown) is inserted.

[0038] As a result, the fourth flange portion 42 is sandwiched between the first flange portion 21b and the third flange portion 22b, and thus the internal gear 40 is firmly fixed without any rattling in both the axial and circumferential directions of the housing 20.

[0039] [Planetary Gear] 3 and 8, a total of three planetary gears 50 are disposed between the pinion gear 30 and the internal gear 40 in the radial direction of the planetary gear reduction mechanism 10. The planetary gears 50 are disposed at equal intervals (120 degree intervals) in the circumferential direction of the pinion gear 30 and the internal gear 40, and are meshed with both the pinion gear 30 and the internal gear 40.

[0040] The planetary gear 50 corresponds to the planetary gear of the present invention.

[0041] The planetary gear 50 is formed in a generally cylindrical shape, and on its radially outer side is provided a gear forming portion 51. A plurality of meshing recesses 51a are provided in the gear forming portion 51 of the planetary gear 50 so as to be aligned in the circumferential direction. These meshing recesses 51a are inclined at a predetermined angle with respect to the axial direction of the planetary gear 50, so that the helical teeth 32 of the pinion gear 30 and the internal teeth 43a of the internal gear 40 can enter and mesh with the inside of the meshing recesses 51a.

[0042] Here, the planetary gear 50 has a meshing recess 51a inclined with respect to the axial direction of the planetary gear 50, and can also be called a helical gear.

[0043] Therefore, each planetary gear 50 rolls between the pinion gear 30 rotated by an electric motor (not shown) and the internal gear 40 fixed to the housing 20. The meshing recess 51a of the planetary gear 50 is recessed so that its cross-sectional shape is approximately semicircular.

[0044] A third ball bearing BB3 and a fourth ball bearing BB4 are provided on the radially inner side of the planetary gear 50. Specifically, the third ball bearing BB3 is disposed on one axial side (lower side in the figure) of the planetary gear 50, and the fourth ball bearing BB4 is disposed on the other axial side (upper side in the figure) of the planetary gear 50. The outer rings of the third and fourth ball bearings BB3, BB4 are attached to the radially inner side of the planetary gear 50.

[0045] The third ball bearing BB3 and the fourth ball bearing BB4 provided on both axial sides of the planetary gear 50 respectively support the planetary gear 50 so as to be free to rotate, and correspond to the ball bearings in the present invention.

[0046] The third and fourth ball bearings BB3 and BB4 are ball bearings of the same size and specifications. The third and fourth ball bearings BB3 and BB4 are smaller than the first and second ball bearings BB1 and BB2 that rotatably support the carrier 60.

[0047] Each of the three planetary gears 50 is rotatably supported by a support shaft 52. Specifically, when assembling the carrier assembly CA (see FIG. 12), the support shaft 52 is inserted into inner rings of third and fourth ball bearings BB3 and BB attached to the planetary gears 50. Both axial ends of the support shaft 52 are fixed to first and second support shaft fixing holes 64a and 64b provided in the carrier 60, respectively.

[0048] A first washer WS1 is provided on one axial side (lower side in the figure) of the third ball bearing BB3 and the other axial side (upper side in the figure) of the fourth ball bearing BB4. This allows planetary gear 50, on which the third and fourth ball bearings BB3 and BB4 are mounted, to rotate smoothly without rattling relative to carrier 60 and support shaft 52.

[0049] [Career] 3 and 9, the carrier 60 is formed into a generally cylindrical shape by cutting an aluminum material or the like. The carrier 60 has a cylindrical main body 61, and the cylindrical main body 61 is provided with a total of three gear support parts 62. Each gear support part 62 has a function of supporting the planetary gear 50 so as to be freely rotatable.

[0050] Here, the carrier 60 rotatably supports a total of three planetary gears 50, and corresponds to the planetary carrier of the present invention.

[0051] The gear support portions 62 are provided at equal intervals (at 120 degree intervals) in the circumferential direction of the cylindrical main body portion 61, and include communication holes 62a that communicate between the radially inner side and the radially outer side of the cylindrical main body portion 61. The communication hole 62a is formed in a substantially square shape when the carrier 60 is viewed from the side. The planetary gear 50 is rotatably housed in the communication hole 62a via a small gap.

[0052] Among the components constituting the planetary gear reduction mechanism 10, the carrier 60 is one of the components that requires particularly high machining precision in order to rotate the planetary gear 50 smoothly without rattling.

[0053] Further, first and second pedestals 63a, 63b supporting both axial sides of the planetary gear 50 are provided on both sides of the communication hole 62a in the axial direction of the carrier 60. Specifically, the first pedestal 63a is disposed on one axial side of the carrier 60 (the lower side in the figure), and the second pedestal 63b is disposed on the other axial side of the carrier 60 (the upper side in the figure).

[0054] The first and second seats 63a, 63b are in contact with first washers WS1 provided on both axial sides of the planetary gear 50. This allows the planetary gear 50 to rotate smoothly in the axial direction of the carrier 60 without rattling.

[0055] An input side cylindrical portion 65 having a smaller diameter than the cylindrical main body portion 61 is provided on one axial side of the carrier 60. An insertion hole 65a through which the rotating shaft 31 (pinion gear 30) is inserted is provided on the radially inner side of the input side cylindrical portion 65, and a fifth ball bearing BB5 that rotatably supports the rotating shaft 31 is fixed to the insertion hole 65a.

[0056] 5, the insertion hole 65a is provided with a stepped bearing fixing portion 65c. The fifth ball bearing BB5 includes an inner ring IR5 and an outer ring OR5. The outer ring OR5 of the fifth ball bearing BB5 is supported by the bearing fixing portion 65c of the insertion hole 65a.

[0057] In contrast, the inner ring IR5 of the fifth ball bearing BB5 is fixed by press fitting to approximately the center (near the pinion gear 30) of the rotating shaft 31 in the axial direction. That is, the fifth ball bearing BB5 is immovable relative to the rotating shaft 31 on both one axial side and the other axial side of the rotating shaft 31.

[0058] 3 and 5, one axial side of the input side cylindrical portion 65 is covered with a cover member 67 formed in a substantially annular shape. The cover member 67 presses the outer ring OR5 of the fifth ball bearing BB5 to prevent the fifth ball bearing BB5 from falling off from the input side cylindrical portion 65. In other words, the cover member 67 prevents the rotating shaft 31 to which the fifth ball bearing BB5 is fixed from falling off from the carrier 60.

[0059] Here, the bearing fixing portion 65c cooperates with the cover member 67 to support the fifth ball bearing BB5 so as to be immovable in the axial direction of the rotating shaft 31, and corresponds to the first bearing support portion in the present invention.

[0060] A total of three screw insertion holes 67a (see FIGS. 2 and 14) are provided in the cover member 67, and a total of three screw holes 65b are provided on one axial side of the input side cylindrical portion 65. Fixing screws (not shown) for fixing the cover member 67 to the input side cylindrical portion 65 are screwed into the total of three screw holes 65b.

[0061] The fifth ball bearing BB5 is provided on one side (the lower side in the figure) of the pinion gear 30 in the axial direction of the rotating shaft 31, and corresponds to the first bearing in the present invention. The inner ring IR5 of the fifth ball bearing BB5 corresponds to the first inner ring in the present invention, and the outer ring OR5 of the fifth ball bearing BB5 corresponds to the first outer ring in the present invention.

[0062] In addition, an inner ring of a second ball bearing BB2 is mounted on the radial outside of the input side cylindrical portion 65, and the inner ring of the second ball bearing BB2 is abutted from one axial side against a first step portion ST1 (see Figure 9) between the cylindrical main body portion 61 and the input side cylindrical portion 65.

[0063] Furthermore, a first support shaft fixing hole 64a is provided at a location where the first seat 63a of the input side cylindrical portion 65 is provided so as to extend in the axial direction of the carrier 60. Three first support shaft fixing holes 64a are provided corresponding to the first seats 63a and are arranged at equal intervals (120 degree intervals) in the circumferential direction of the cylindrical main body portion 61. The first support shaft fixing hole 64a penetrates both the first seat 63a and the input side cylindrical portion 65, and one axial side (lower side in the figure) of the support shaft 52 that rotatably supports the planetary gear 50 is attached to the first support shaft fixing hole 64a.

[0064] Further, an output side cylindrical portion 66 having the same diameter as the input side cylindrical portion 65 is provided on the other axial side of the carrier 60. A bearing support portion 66a is provided on the radially inner side of the output side cylindrical portion 66 so as to penetrate the output side cylindrical portion 66. As shown in Fig. 4, the bearing support portion 66a has a bearing guide portion 66c and a female thread portion 66d, and the bearing guide portion 66c is arranged on one axial side (lower side in the figure) of the bearing support portion 66a, and the female thread portion 66d is arranged on the other axial side (upper side in the figure) of the bearing support portion 66a.

[0065] A sixth ball bearing BB6 that rotatably supports the other axial side of the rotating shaft 31 is attached to the bearing guide portion 66c, and the sixth ball bearing BB6 is movable in the axial direction relative to the bearing guide portion 66c. In other words, the bearing guide portion 66c of the bearing support portion 66a supports the sixth ball bearing BB6 movably in the axial direction of the rotating shaft 31.

[0066] The bearing guide portion 66c forming the bearing support portion 66a corresponds to the second bearing support portion in this invention.

[0067] Furthermore, a backlash adjustment member 68 that adjusts (removes) backlash in the axial direction of the rotating shaft 31 relative to the carrier 60 is provided on the female thread portion 66d of the bearing support portion 66a. Specifically, the backlash adjustment member 68 is screwed into the female thread portion 66d. In this manner, a backlash adjustment mechanism BA that removes backlash of the rotating shaft 31 is attached to the carrier 60.

[0068] The female thread portion 66d that forms the bearing support portion 66a also corresponds to the second bearing support portion in the present invention.

[0069] Further, at a location of the output side cylindrical portion 66 where the second seat 63b is provided, a second support shaft fixing hole 64b is provided so as to extend in the axial direction of the carrier 60. Three second support shaft fixing holes 64b are provided corresponding to the second seat 63b, and are disposed at equal intervals (120 degree intervals) in the circumferential direction of the cylindrical main body portion 61. The second support shaft fixing hole 64b penetrates both the second seat 63b and the output side cylindrical portion 66, and the other axial side (upper side in the figure) of the support shaft 52 that rotatably supports the planetary gear 50 is attached to the second support shaft fixing hole 64b.

[0070] Here, the support shaft 52 is inserted into the first support shaft fixing hole 64a without any rattling, and is fixed into the second support shaft fixing hole 64b by press fitting. This reduces the insertion load of the support shaft 52 into the first and second support shaft fixing holes 64a, 64b when assembling the carrier assembly CA (see FIG. 13), improving the ease of assembly.

[0071] 9, a plurality of female threaded holes 66b are provided on the other axial side (upper side in the figure) of the output side cylindrical portion 66. These female threaded holes 66b extend in the axial direction of the carrier 60. Fixing screws (not shown) for fixing a driving mechanism (not shown) of a robot, which is an object to be driven, are screwed into the female threaded holes 66b.

[0072] Furthermore, an inner ring of a first ball bearing BB1 is attached to the radial outside of the output side cylindrical portion 66, and the inner ring of the first ball bearing BB1 abuts from the other axial side against a second step portion ST2 (see FIG. 9) between the cylindrical main body portion 61 and the output side cylindrical portion 66. Specifically, a third washer WS3 (see FIG. 13) is provided between the inner ring of the first ball bearing BB1 and the second step portion ST2, and the inner ring of the first ball bearing BB1 abuts against the second step portion ST2 via the third washer WS3.

[0073] [Backlash adjustment mechanism] As shown in FIGS. 3, 4 and 10, the play adjustment mechanism BA provided in the output side cylindrical portion 66 has a second washer WS2, a sixth ball bearing BB6 and a play adjustment member 68.

[0074] The sixth ball bearing BB6 includes an inner ring IR6 and an outer ring OR6. The outer ring OR6 of the sixth ball bearing BB6 is mounted on a bearing guide portion 66c that forms the bearing support portion 66a. This allows the sixth ball bearing BB6 to move in the axial direction relative to the bearing support portion 66a.

[0075] On the other hand, the inner ring IR6 of the sixth ball bearing BB6 is mounted on a bearing mounting portion 31a provided on the other axial side (upper side in FIG. 4) of the rotating shaft 31. Here, as shown in FIG. 6, the bearing mounting portion 31a is formed in a cylindrical shape with a smaller diameter than the main body of the rotating shaft 31, and a support step 31b is provided between the bearing mounting portion 31a and the pinion gear 30.

[0076] One axial side of the inner ring IR6 is abutted against the support step 31b from the other axial side via the second washer WS2. That is, one axial side of the inner ring IR6 is supported by the support step 31b via the second washer WS2. This makes the sixth ball bearing BB6 immovable toward one axial side of the rotating shaft 31 with respect to the rotating shaft 31.

[0077] In this manner, the fifth ball bearing BB5 and the sixth ball bearing BB6 are provided so as not to be able to approach each other in the axial direction of the rotating shaft 31.

[0078] The support step 31b corresponds to the step portion in this invention.

[0079] In addition, the second washer WS2 has a function of eliminating rattle between the inner ring IR6 of the sixth ball bearing BB6 and the pinion gear 30, thereby allowing the pinion gear 30 (rotary shaft 31) to rotate smoothly.

[0080] Here, an angular ball bearing is used for the sixth ball bearing BB6. As a result, the sixth ball bearing BB6 presses the rotating shaft 31 to one axial side (the lower side in the figure) while receiving axial force from the backlash adjustment member 68. This prevents the rotating shaft 31 from wobbling relative to the carrier 60. Therefore, the pinion gear 30 and the planetary gear 50 are properly meshed, improving the transmission efficiency [%] of these gears. This improves quietness during operation of the planetary gear reduction mechanism 10.

[0081] The sixth ball bearing BB6 is provided on the other side (upper side in the figure) of the pinion gear 30 in the axial direction of the rotating shaft 31, and corresponds to the second bearing in the present invention. The inner ring IR6 of the sixth ball bearing BB6 corresponds to the second inner ring in the present invention, and the outer ring OR6 of the sixth ball bearing BB6 corresponds to the second outer ring in the present invention.

[0082] Here, the play adjustment member 68 comprises an adjustment main body portion 68a formed in a substantially disk shape, and a cylindrical pressing portion 68b integrally formed on one axial side (the sixth ball bearing BB6 side) of the adjustment main body portion 68a.

[0083] Then, by rotating the adjustment main body 68a clockwise (in the direction of arrow A10) relative to the female threaded hole 66b, the backlash adjustment member 68 moves to one axial side (the lower side in FIG. 4). As a result, the pressing portion 68b in contact with the outer ring OR6 of the sixth ball bearing BB6 presses the outer ring OR6 toward the one axial side. On the other hand, by rotating the adjustment main body 68a counterclockwise (the opposite direction to the direction of arrow A10) relative to the female threaded hole 66b, the backlash adjustment member 68 moves to the other axial side (the upper side in FIG. 4).

[0084] In this way, the other axial side of the outer ring OR6 of the sixth ball bearing BB6 is supported by the pressing portion 68b of the backlash adjustment member 68. Note that the backlash adjustment member 68 is provided on the female thread portion 66d of the bearing support portion 66a, and presses the sixth ball bearing BB6 towards the side where the fifth ball bearing BB5 is provided, and corresponds to the pressing member in this invention.

[0085] [Assembly Instructions] Next, a procedure for assembling the planetary gear reduction mechanism 10 formed as above will be described in detail with reference to FIGS.

[0086] Figure 11 is an oblique view showing the assembly procedure for the carrier assy, ​​Figure 12 is an oblique view showing the assembly procedure for the internal gear to the carrier assy, ​​Figure 13 is an oblique view showing the assembly procedure for the housing body and ring member, Figure 14 is an oblique view showing the assembly procedure for the pinion gear and backlash adjustment mechanism, and Figure 15 is a diagram comparing the gear transmission efficiency [%].

[0087] [Assembling the carrier assembly] As shown in Fig. 11, first, the carrier assembly CA is assembled. Specifically, a carrier 60 manufactured through a separate manufacturing process, a total of three planetary gears 50, and a total of three support shafts 52 are prepared. Note that, for ease of viewing, Fig. 11 shows one each of the planetary gears 50 and the support shafts 52.

[0088] Next, as shown by arrow A1 in Fig. 8, the planetary gear 50 is brought into contact with the communication hole 62a from the radially outer side of the carrier 60. At this time, the third and fourth ball bearings BB3 and BB4 (see Fig. 3) are mounted in advance on the radially inner side of the planetary gear 50. Also, first washers WS1 are mounted on the third and fourth ball bearings BB3 and BB4 (see Fig. 3).

[0089] Thereafter, the planetary gear 50 is inserted into the communication hole 62a, and the support shaft 52 is brought to face the other axial side of the carrier 60, as shown by the arrow A2 in Fig. 11. At this time, the input side cylindrical portion 65 of the carrier 60 is disposed on one axial side (lower side in the figure), and the output side cylindrical portion 66 of the carrier 60 is disposed on the other axial side (upper side in the figure).

[0090] Then, the support shaft 52 is inserted into the second support shaft fixing hole 64b and the first support shaft fixing hole 64a in this order. Note that the support shaft 52 is inserted into the first support shaft fixing hole 64a, and the support shaft 52 is press-fit into the second support shaft fixing hole 64b. Therefore, the insertion load of the support shaft 52 is not so large, and the carrier assembly CA can be easily assembled.

[0091] Thereafter, the above-described attachment operation of the planetary gear 50 to the communication hole 62a is carried out twice in succession, thereby completing the assembly operation of the carrier assembly CA (see FIG. 12).

[0092] [Installing the internal gear to the carrier assembly] Next, as shown in FIG. 12, an internal gear 40 manufactured through a separate manufacturing process is prepared, and the internal gear 40 is attached to the assembled carrier assembly CA.

[0093] Specifically, the internal gear 40 is brought to face the other axial side of the carrier assembly CA, i.e., the output side cylindrical portion 66 side (upper side in the figure), as indicated by the arrow A3 in the figure. At this time, the fourth flange portion 42 side in the axial direction of the internal gear 40 faces the carrier assembly CA.

[0094] The internal gear 40 is then disposed so as to cover the radially outer side of the carrier assembly CA. At this time, the planetary gear 50 of the carrier assembly CA is capable of smoothly rotating relative to the carrier 60. Therefore, the internal teeth 43a of the internal gear 40 and the meshing recesses 51a of the planetary gear 50 mesh smoothly with each other.

[0095] This completes the assembly work of the internal gear 40 to the carrier assembly CA.

[0096] [Assembly of housing body and ring components] 13, the housing body 21, the ring member 22, and the third washer WS3, which are manufactured through a separate manufacturing process, are prepared. Note that the first ball bearing BB1 is attached to the housing body 21 in advance, and the second ball bearing BB2 is attached to the ring member 22 in advance.

[0097] Thereafter, as shown by arrow A4 in the figure, a third washer WS3 is attached to the output side cylindrical portion 66 of the carrier 60. Next, as shown by arrow A5 in the figure, the housing body 21 is attached so as to cover the radially outer side of the internal gear 40. At this time, the first flange portion 21b side of the housing body 21 in the axial direction faces the internal gear 40.

[0098] Thereafter, as shown by arrow A6 in the figure, the ring member 22 (the second ball bearing BB2) is attached to the input side cylindrical portion 65 of the carrier 60. At this time, the side of the ring member 22 on which the positioning protrusion P is provided faces the internal gear 40. Then, while the second ball bearing BB2 is being attached to the input side cylindrical portion 65, the positioning protrusion P of the ring member 22 is engaged with an engagement recess (not shown) of the internal gear 40.

[0099] Then, a fixing bolt (not shown) is inserted through the insertion hole 21c of the first flange portion 21b and the insertion hole 42a of the fourth flange portion 42, and the fixing bolt is screwed into the female threaded hole 22c of the third flange portion 22b. This causes the reducer SD to be accommodated inside the housing 20, and the assembly of the housing main body 21 and the ring member 22 is completed.

[0100] [Installation of pinion gear and backlash adjustment mechanism] 14, a rotating shaft 31 having a pinion gear 30 manufactured through a separate manufacturing process, and a cover member 67 are prepared. A fifth ball bearing BB5 is fixed in advance to the rotating shaft 31. A second washer WS2, a sixth ball bearing BB6, and a play adjustment member 68 which form the play adjustment mechanism BA are also prepared.

[0101] Thereafter, as indicated by arrow A7 in the figure, the pinion gear 30 is brought into contact with the input side cylindrical portion 65 (see FIG. 3) of the carrier 60. Then, the pinion gear 30 is inserted between a total of three planetary gears 50 (see FIG. 6). At this time, the planetary gears 50 are able to rotate smoothly relative to the carrier 60. Therefore, while each planetary gear 50 rotates, the helical teeth 32 of the pinion gear 30 and the meshing recesses 51a (see FIG. 8) of the planetary gears 50 mesh smoothly with each other.

[0102] Then, the outer ring OR5 of the fifth ball bearing BB5 is attached to the bearing fixing portion 65c (see FIG. 5) of the insertion hole 65a. Furthermore, as shown by the arrow A8 in FIG. 14, the cover member 67 is fixed to the input side cylindrical portion 65 (see FIG. 3). At this time, a total of three fixing screws (not shown) are inserted into the screw insertion holes 67a of the cover member 67 and screwed into the screw holes 65b (see FIG. 3) of the input side cylindrical portion 65.

[0103] As a result, the outer ring OR5 of the fifth ball bearing BB5 is fixed to the bearing fixing portion 65c, and the rotating shaft 31 (pinion gear 30) is prevented from coming off the carrier 60.

[0104] Next, as shown by the arrow A9 in the figure, the second washer WS2 is placed in the bearing support portion 66a of the output side cylindrical portion 66, and the second washer WS2 is placed on the support step 31b of the rotating shaft 31. Following this, the sixth ball bearing BB6 is placed in the bearing support portion 66a of the output side cylindrical portion 66, and the inner ring IR6 is attached to the bearing mounting portion 31a of the rotating shaft 31. Then, the backlash adjustment member 68 is screwed into the female thread portion 66d of the bearing support portion 66a.

[0105] As a result, one axial side (the fifth ball bearing BB5 side) of the inner ring IR6 of the sixth ball bearing BB6 is supported by the support step 31b via the second washer WS2. Also, the other axial side (the backlash adjustment member 68 side) of the outer ring OR6 of the sixth ball bearing BB6 is supported by the pressing portion 68b of the backlash adjustment member 68.

[0106] Thereafter, as shown by arrow A10 in Fig. 4 and Fig. 14, the play adjustment member 68 is rotated clockwise with a predetermined tightening torque. Then, the play adjustment member 68 moves to one axial side (toward the rotating shaft 31), and the sixth ball bearing BB6 also moves to one axial side. Specifically, the outer ring OR6 is pressed to one axial side by the pressing portion 68b. As a result, the outer ring OR6 moves in the direction of arrow M1 in Fig. 4.

[0107] As the outer ring OR6 moves in the direction of the arrow M1, the inner ring IR6 of the sixth ball bearing BB6 also moves in the same direction as the outer ring OR6, that is, in the direction of the arrow M2 (see FIG. 4). During this time, the rattle of the sixth ball bearing BB6 is absorbed (removed).

[0108] Then, the inner ring IR6 presses the support step 31b to one side in the axial direction via the second washer WS2, so that the rotating shaft 31 is also pressed to one side in the axial direction, as shown by the arrow M2 in Fig. 5. At this time, any rattle in the axial direction of the rotating shaft 31 between the inner ring IR6, the second washer WS2, and the pinion gear 30 is also removed.

[0109] Thereafter, the inner ring IR5 of the fifth ball bearing BB5 fixed to the rotating shaft 31 is moved axially to one side as indicated by an arrow M3 in FIG. 5 in association with the movement of the rotating shaft 31 axially to one side.

[0110] As the inner ring IR5 moves in the direction of the arrow M3, the outer ring OR5 of the fifth ball bearing BB5 also moves in the direction of the arrow M4 (see FIG. 5), which is the same direction as the inner ring IR5. Then, the outer ring OR5 abuts against the cover member 67 from the other axial side. During this time, any rattle of the fifth ball bearing BB5 is absorbed (removed).

[0111] In this way, by turning the backlash adjustment member 68 clockwise with a predetermined tightening torque, the backlash of the fifth and sixth ball bearings BB5 and BB6 is eliminated, and the backlash of the fifth ball bearing BB5 relative to the bearing fixing portion 65c of the outer ring OR5 is also eliminated. Therefore, the rotating shaft 31 does not wobble in the axial direction relative to the carrier 60.

[0112] However, if the tightening torque of the backlash adjustment member 68 is too large, it will increase the rotational resistance of the fifth and sixth ball bearings BB5, BB6. Therefore, the tightening torque of the backlash adjustment member 68 should not exceed the allowable axial force of the fifth and sixth ball bearings BB5, BB6.

[0113] This completes the assembly of the pinion gear 30 and the backlash adjustment mechanism BA, and removes the axial backlash of the rotating shaft 31 relative to the carrier 60 (planetary gear reduction mechanism 10). Thus, the assembly of the planetary gear reduction mechanism 10 is finally completed.

[0114] The transmission efficiency [%] of the pinion gear 30 and the planetary gear 50 for the rotational drive of the rotating shaft 31 in the forward and reverse directions was as shown in the graph of FIG. 15. That is, when the rotating shaft 31 wobbles in the axial direction, that is, in the "comparative example" with wobble, a relatively large difference occurred in the transmission efficiency [%] between the clockwise direction (dashed arrow CW) and the counterclockwise direction (solid arrow CCW). This means that the output characteristics of the planetary gear reduction mechanism 10 change relatively greatly depending on the rotational direction of the rotating shaft 31. This can cause problems such as the mechanism being unsuitable for driving the joints of a robot, which requires precise drive control.

[0115] In contrast, when the rotating shaft 31 does not wobble in the axial direction, that is, in the case of the "present embodiment" where there is no wobble, the transmission efficiency [%] in the clockwise direction (dashed arrow CW) and the counterclockwise direction (solid arrow CCW) are closer to each other than in the "comparative example". Specifically, the difference in transmission efficiency [%] can be reduced to approximately half or less compared to the "comparative example". This prevents the output characteristics of the planetary gear reduction mechanism 10 from changing significantly depending on the rotation direction of the rotating shaft 31, enabling stable operation. Therefore, it can be fully adapted to the joint drive of a robot, which requires precise drive control.

[0116] Furthermore, in the planetary gear reduction mechanism 10, as described above, only one helical tooth 32 is provided on the pinion gear 30, and the cross-sectional shape of the helical tooth 32 is substantially semicircular. Therefore, when the planetary gear reduction mechanism 10 is in operation, each planetary gear 50 tries to move away from the pinion gear 30 with a relatively strong force. In other words, the pinion gear 30 is prone to rotational wobble.

[0117] In contrast, in the planetary gear reduction mechanism 10, as described above, the pinion gear 30 is supported by the fifth and sixth ball bearings BB5 and BB6, which have relatively high rigidity, and this effectively suppresses rotational wobble of the pinion gear 30. Therefore, the planetary gear reduction mechanism 10 is capable of stable operation even when a relatively large load (large torque) is applied.

[0118] As described above in detail, the planetary gear reduction mechanism 10 of this embodiment has the fifth ball bearing BB5, which is provided on one side of the pinion gear 30 in the axial direction of the rotating shaft 31 and rotatably supports the rotating shaft 31, the sixth ball bearing BB6, which is provided on the other side of the pinion gear 30 in the axial direction of the rotating shaft 31 and rotatably supports the rotating shaft 31, a bearing fixing portion 65c, which is provided on the carrier 60 and supports the fifth ball bearing BB5 so as to be immovable in the axial direction of the rotating shaft 31, and a bearing guide portion 66c, which is provided on the carrier 60 and supports the sixth ball bearing BB6 so as to be movable in the axial direction of the rotating shaft 31, and the fifth ball bearing BB5 and the sixth ball bearing BB6 are provided so as not to be able to approach each other in the axial direction of the rotating shaft 31, and the female thread portion 66d is provided with a backlash adjustment member 68 that presses the sixth ball bearing BB6 towards the side where the fifth ball bearing BB5 is provided.

[0119] As a result, by adjusting the backlash adjustment member 68, it is possible to eliminate backlash in the fifth and sixth ball bearings BB5 and BB6, and also to eliminate backlash of the fifth ball bearing BB5 relative to the bearing fixing portion 65c. This prevents the rotating shaft 31 from backlashing in the axial direction relative to the carrier 60, thereby optimizing the gear transmission efficiency [%]. This makes it possible to realize a planetary gear reduction mechanism 10 that is capable of stable operation.

[0120] Furthermore, according to the planetary gear reduction mechanism 10 of the present embodiment, the fifth ball bearing BB5 has an inner ring IR5 and an outer ring OR5, the inner ring IR5 is fixed to the rotating shaft 31, and the outer ring OR5 is supported by the bearing fixing portion 65c.

[0121] As a result, by simply adjusting the play adjustment member 68 and applying an axial force to the rotating shaft 31, play in the axial direction of the fifth ball bearing BB5 can be removed.

[0122] Furthermore, according to the planetary gear reduction mechanism 10 of this embodiment, the sixth ball bearing BB6 has an inner ring IR6 and an outer ring OR6, and one axial side of the inner ring IR6 is supported by a support step 31b provided on the rotating shaft 31, and the other axial side of the outer ring OR2 is supported by the pressing portion 68b of the play adjustment member 68.

[0123] As a result, by simply adjusting the backlash adjustment member 68 and applying an axial force to the outer ring OR2, backlash in the axial direction of the sixth ball bearing BB6 can be removed.

[0124] Furthermore, according to the planetary gear reduction mechanism 10 of this embodiment, the backlash adjustment member 68 is screwed to the female thread portion 66d of the bearing support portion 66a.

[0125] As a result, by simply controlling the amount of screwing of the play adjustment member 68 (controlling the tightening torque), the play of the fifth and sixth ball bearings BB5, BB6 and the play of the fifth ball bearing BB5 relative to the bearing fixing portion 65c can be easily eliminated (improved workability).

[0126] Furthermore, according to the planetary gear reduction mechanism 10 of the present embodiment, both axial ends of the planetary gear 50 are supported by the third and fourth ball bearings BB3 and BB4, respectively.

[0127] This effectively reduces rattling of the planetary gear 50 relative to the carrier 60. This also optimizes the gear transmission efficiency [%], thereby achieving a planetary gear reduction mechanism 10 that can operate more stably.

[0128] Furthermore, according to the planetary gear reduction mechanism 10 of this embodiment, the pinion gear 30 has only the helical teeth 32 that are connected in a spiral shape in the axial direction of the rotating shaft 31 .

[0129] This increases the gear transmission efficiency [%] and allows a large reduction ratio to be obtained despite the small size, which in turn allows the electric motor, which is the driving source, to be made smaller and consume less power.

[0130] Furthermore, according to the planetary gear reduction mechanism 10 of this embodiment, by adjusting the backlash adjustment member 68, it is possible to absorb the dimensional error of the parts that differs from product to product, and optimize the gear transmission efficiency [%] for each product. Therefore, it is possible to simplify parts management and eliminate work such as reassembly. Therefore, it is possible to save manufacturing energy for manufacturing the planetary gear reduction mechanism 10, and in particular, it is possible to achieve Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all) and Goal 13 (Take urgent action to combat climate change and its impacts) in the Sustainable Development Goals (SDGs) established by the United Nations.

[0131] The present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications are possible without departing from the gist of the present invention. For example, in the above-mentioned embodiment, the first and second ball bearings BB1 and BB2 are provided between the housing 20 and the carrier 60, but the present invention is not limited to this, and instead of the first and second ball bearings BB1 and BB2, bearings also called bushes or metals can be used (cost reduction).

[0132] In the above embodiment, a total of three planetary gears 50 are provided, but the present invention is not limited to this, and four or more planetary gears 50 may be provided. If there are two planetary gears 50 (an even number), they will be arranged 180 degrees apart, making it difficult to maintain the pinion gears 30 in a well-balanced manner. This leads to increased operating noise and a decrease in transmission efficiency [%]. On the other hand, if there are five or more planetary gears 50, the assembly process will be difficult and the size will increase. Therefore, when used for applications such as those in the above embodiment, it is desirable to have three planetary gears 50 (an odd number).

[0133] Furthermore, the above-mentioned procedure for assembling the planetary gear reduction mechanism 10 is merely one example among many possible procedures, and it goes without saying that other procedures can also be used for assembly. For example, "assembly of the pinion gear 30 and the backlash adjustment mechanism BA" shown in Fig. 14 can be performed prior to "assembly of the housing body 21 and the ring member 22" shown in Fig. 13.

[0134] Furthermore, the material, shape, size, number, installation location, etc. of each component in the above-described embodiment may be arbitrary as long as it achieves the present invention, and is not limited to the above-described embodiment. [Explanation of symbols]

[0135] 10: planetary gear reduction mechanism, 20: housing, 21: housing body, 21a: cylindrical portion, 21b: first flange portion, 21c: insertion hole, 21d: second flange portion, 21e: screw hole, 22: ring member, 22a: annular body, 22b: third flange portion, 22c: female screw hole, 30: pinion gear (sun gear), 31: rotating shaft, 31a: bearing mounting portion, 31b: support step (step portion), 32: helical tooth (one tooth), 40: internal gear (internal Gear), 41: Cylindrical main body, 42: Fourth flange portion, 42a: Through hole, 43: Gear forming portion, 43a: Internal teeth, 50: Planetary gear, 51: Gear forming portion, 51a: Meshing recess, 52: Support shaft, 60: Carrier (planetary carrier), 61: Cylindrical main body portion, 62: Gear support portion, 62a: Through hole, 63a: First base, 63b: Second base, 64a: First support shaft fixing hole, 64b: Second support shaft fixing hole, 65: Input side cylindrical portion, 65a: Through hole, 65b: Screw hole, 65c: bearing fixing part (first bearing support part), 66: output side cylindrical part, 66a: bearing support part, 66b: female thread hole, 66c: bearing guide part (second bearing support part), 66d: female thread part (second bearing support part), 67: cover member, 67a: screw insertion hole, 68: backlash adjustment member (pressing member), 68a: adjustment main body part, 68b: pressing part, BA: backlash adjustment mechanism, BB1: first ball bearing, BB2: second ball bearing, BB3: third ball bearing (ball bearing), BB4: 4th ball bearing (ball bearing), BB5: 5th ball bearing (1st bearing), BB6: 6th ball bearing (2nd bearing), CA: Carrier assembly, IR5: Inner ring (1st inner ring), IR6: Inner ring (2nd inner ring), OR5: Outer ring (1st outer ring), OR6: Outer ring (2nd outer ring), P: Positioning protrusion, SD: Reducer, ST1: 1st step, ST2: 2nd step, WS1: 1st washer, WS2: 2nd washer, WS3: 3rd washer

Claims

1. A sun gear provided on the rotating shaft; an internal gear disposed radially outside the sun gear; a planetary gear disposed between the sun gear and the internal gear; a planetary carrier that rotatably supports the planetary gear; A planetary gear reduction mechanism comprising: a first bearing provided on one side of the sun gear in an axial direction of the rotation shaft and configured to rotatably support the rotation shaft; a second bearing provided on the other side of the sun gear in the axial direction of the rotation shaft and configured to rotatably support the rotation shaft; a first bearing support portion provided on the planetary carrier and configured to support the first bearing so as to be immovable in an axial direction of the rotating shaft; a second bearing support portion provided on the planetary carrier and configured to support the second bearing movably in the axial direction of the rotation shaft; having the first bearing and the second bearing are provided so as not to be able to approach each other in the axial direction of the rotating shaft, The second bearing support portion is provided with a pressing member that presses the second bearing toward a side where the first bearing is provided. Planetary gear reduction mechanism.

2. 2. The planetary gear reduction mechanism according to claim 1, the first bearing includes a first inner ring and a first outer ring; The first inner ring is fixed to the rotating shaft, The first outer ring is supported by the first bearing support portion. Planetary gear reduction mechanism.

3. 2. The planetary gear reduction mechanism according to claim 1, the second bearing includes a second inner ring and a second outer ring; One axial side of the second inner ring is supported by a step portion provided on the rotating shaft, The other axial side of the second outer ring is supported by the pressing member. Planetary gear reduction mechanism.

4. The pressing member is screw-connected to the second bearing support portion.

2. The planetary gear reduction mechanism according to claim 1.

5. 2. The planetary gear reduction mechanism according to claim 1, Both axial ends of the planetary gear are supported by ball bearings, Planetary gear reduction mechanism.

6. The sun gear has only one tooth spirally arranged in the axial direction of the rotation shaft.

2. The planetary gear reduction mechanism according to claim 1.

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