gear arrangement

Abstract

The present application provides a gear device. The gear device of the embodiment is provided with a rotating member (13) having a cylindrical small-diameter portion (31) and a cylindrical large-diameter portion (32, 33) having a diameter dimension larger than that of the small-diameter portion (31). A recessed portion (40) recessed from an end surface (32a, 33a) of the large-diameter portion (32, 33) toward an axial direction of the rotating member (13) is formed in the rotating member (13). The recessed portion (40) has a curved inner surface (41) curved in a concave shape. The curved inner surface (41) is formed in connection with an outer peripheral surface (31a) of the small-diameter portion (31).

Description

Technical Field

[0001] This invention relates to a gear mechanism. Background Technology

[0002] Patent document 1 discloses a gear device that functions as a speed reduction device that outputs at a speed lower than the input speed.

[0003] The gear assembly of Patent Document 1 includes an external gear, an internal gear, a base plate portion (first gear carrier) disposed on one axial side of the external gear, and an end plate portion (second gear carrier) disposed on the other axial side of the external gear and connected to the base plate portion. A column portion extends integrally from the surface of the base plate portion opposite to the end plate portion to the end plate portion. In the base plate portion, the diameter of the column portion is smaller than the diameter of the main body portion. The gear carrier formed by connecting the base plate portion and the end plate portion via the column portion is an example of a rotating member that can be freely rotated relative to other components such as the housing.

[0004] Furthermore, the gear assembly in Patent Document 1 has a crankshaft including a journal and an eccentric portion. The axis of the journal is aligned with the rotation centerline of the crankshaft, while the axis of the eccentric portion is eccentric relative to the rotation centerline of the crankshaft. In the crankshaft, the diameter of the journal is smaller than the diameter of the eccentric portion. The crankshaft is another example of a rotating member mounted to rotate freely relative to the aforementioned gear carrier (base plate portion and end plate portion).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2023-086953 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, geared mechanisms require both miniaturization and high torque, a demand that is difficult to meet. To achieve high torque in geared mechanisms, rotating components (gear carrier, crankshaft) need to be enlarged to ensure their strength, thus hindering miniaturization. Conversely, miniaturization makes it difficult to ensure the strength of rotating components, thus making high torque difficult.

[0010] This invention provides a gear device that can achieve both miniaturization and high torque.

[0011] Solution for solving the problem

[0012] One aspect of the gear device of the present invention includes a rotating member having a columnar small-diameter portion and a columnar large-diameter portion with a diameter larger than that of the small-diameter portion. A recess is formed in the rotating member, which is recessed from the end face of the large-diameter portion toward the axial direction of the rotating member. The recess has a curved inner surface that is bent into a concave shape and is formed in connection with the outer peripheral surface of the small-diameter portion.

[0013] By forming the aforementioned recess at the boundary (corner) between the outer peripheral surface of the small-diameter portion and the end face of the large-diameter portion of the rotating member, stress concentration at the boundary between the small-diameter and large-diameter portions of the rotating member can be mitigated during gear operation. This ensures the strength of the rotating member without increasing its size. Therefore, it is possible to achieve both miniaturization and high torque in the gear mechanism.

[0014] In the above structure, the recess may also be recessed from the outer peripheral surface of the small diameter portion.

[0015] In the above structure, the first depth of the recess from the end face of the large diameter portion toward the axial direction may be greater than the second depth of the recess from the outer periphery of the small diameter portion toward the radial direction of the small diameter portion.

[0016] In the above structure, the first depth of the recess from the end face of the large diameter portion to the axial recess is less than the second depth of the recess from the outer periphery of the small diameter portion to the radial recess of the small diameter portion.

[0017] In the above structure, the gear device may also include a rolling bearing disposed on the outer peripheral surface of the small diameter portion. The inner ring of the rolling bearing, which fits into the outer peripheral surface of the small diameter portion, has an end face that faces the end face of the large diameter portion in the axial direction. The diameter of the small diameter portion with the rotation axis of the rotating member as the axis is defined as Ds. The radius of the outer periphery of the end face of the inner ring, which is formed as an annular shape with the rotation axis as the center, is defined as Roi. The radius of the outer periphery of the recess, which is formed as an annular shape with the rotation axis as the center, is defined as Ror. The ratio of (Roi-Ror) to (Roi-(Ds / 2)) is 30% or more.

[0018] In the above structure, the rotating member may also include a crankshaft having a journal portion, which is the small diameter portion, with the axis of rotation of the rotating member as its axis, and an eccentric portion, which is the large diameter portion, with its axis eccentric relative to the axis of rotation.

[0019] In the above structure, the rotating member may also include a gear carrier rotatably disposed radially inside the cylindrical housing. The gear carrier has: a base plate portion as the large-diameter portion; an end plate portion disposed opposite to the base plate portion in the axial direction; and a column portion as the small-diameter portion integrally formed on the base plate portion, extending from the base plate portion to the end plate portion and fixed to the end plate portion.

[0020] In the above structure, the base plate may have an insertion portion at a position radially away from the first rotation axis that serves as the rotation center of the gear carrier, into which a shaft member can be rotatably inserted, and when viewed from the axial direction, the insertion portion is located adjacent to the recess.

[0021] One aspect of the gear device of the present invention includes a rotating member having a columnar small-diameter portion and a columnar large-diameter portion located adjacent to the small-diameter portion and having a diameter larger than that of the small-diameter portion. The large-diameter portion has an end face facing the small-diameter portion in the axial direction of the rotating member. A recess is formed in the rotating member that is recessed from the outer peripheral surface of the small-diameter portion but not from the end face of the large-diameter portion. The recess has a curved inner surface that is bent into a concave shape and is formed in connection with the end face of the large-diameter portion.

[0022] By forming the aforementioned recess at the boundary (corner) between the outer peripheral surface of the small-diameter portion and the end face of the large-diameter portion of the rotating member, stress concentration at the boundary between the small-diameter and large-diameter portions of the rotating member can be mitigated during gear operation. This ensures the strength of the rotating member without increasing its size. Therefore, it is possible to achieve both miniaturization and high torque in the gear mechanism.

[0023] The effects of the invention

[0024] The aforementioned gear mechanism achieves both miniaturization and high torque. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view showing the deceleration device of the first embodiment.

[0026] Figure 2 It means Figure 1 A side view of the crankshaft of the speed reduction device, and a section of the crankshaft.

[0027] Figure 3 yes Figure 2 Enlarged view of the main parts.

[0028] Figure 4 This is a cross-sectional view showing the deceleration device according to the second embodiment.

[0029] Figure 5 Viewed from the end plate side Figure 4 A top view of the base plate and column portion of the gear carrier in the speed reduction device.

[0030] Figure 6 This is a cross-sectional view showing the main parts of the deceleration device according to the third embodiment.

[0031] Figure 7 It means Figure 6 A cross-sectional view of the main parts of the crankshaft in the speed reduction device.

[0032] Figure 8 This is a cross-sectional view showing the main parts of the deceleration device according to the fourth embodiment.

[0033] Figure 9 It means Figure 8 A cross-sectional view of the main part of the crankshaft of the speed reduction device.

[0034] Explanation of reference numerals in the attached figures

[0035] 1. 1A, 1C, 1D, Reduction gear (gear assembly); 2. Housing; 3A, Gear carrier (rotating component); 7A, Base plate (large diameter section); 7e, Crankshaft insertion hole (insertion section); 7Af, End face; 8. End plate section; 9A, Column section (small diameter section); 9Ab, Outer peripheral surface; 13. Crankshaft (rotating component); 13A, Crankshaft (shaft component); 18. Crankshaft bearing (rolling bearing); 21. Washer; 31. Journal (small diameter section); 31a, Outer peripheral surface; 32. First eccentric section (large diameter section); 32a, End face; 33. Second eccentric portion (large diameter portion); 33a, end face; 40, 40A, recess; 40o, outer periphery of recess 40; 41, 41A, curved inner surface; 81, inner ring of crankshaft bearing 18; 81a, end face of inner ring 81; A1, first axis of rotation; A2, second axis of rotation, central axis; d1, first depth of recess 40; d2, second depth of recess 40; Ds, diameter of journal 31; Roi, radius of outer periphery 81o of end face 81a; Ror, radius of outer periphery 40o of recess 40. Detailed Implementation

[0036] [First Implementation]

[0037] The following is for reference Figures 1-3 The first embodiment of the present invention will be described.

[0038] <Speed ​​Reduction Device>

[0039] like Figure 1As shown, a speed reduction device 1, as a type of gear mechanism, reduces the rotation of a drive source (rotary drive source) such as an electric motor (not shown) and outputs a speed reduction. The speed reduction device 1 is a so-called eccentric oscillating type speed reduction device. The speed reduction device 1 includes a cylindrical housing 2, a gear carrier 3 rotatably disposed radially inside the housing 2, and a speed reduction mechanism 4 connected to the gear carrier 3. The central axis of the housing 2 coincides with the rotation axis of the gear carrier 3.

[0040] In the following description, the common name for these central axes and axes of rotation is referred to as the first axis of rotation A1. Sometimes the direction parallel to the first axis of rotation A1 is simply referred to as the axial direction. Sometimes the direction of rotation of the gear carrier 3 is simply referred to as the circumferential direction. Sometimes the radial direction of the housing 2, orthogonal to both the axial and circumferential directions, is simply referred to as the radial direction.

[0041] <Shell>

[0042] An outer flange 2a extending radially outward is integrally formed on the outer peripheral surface of the housing 2. Multiple bolt holes 2b are formed in the outer flange 2a. These bolt holes 2b are spaced apart circumferentially. Bolts (not shown) are inserted into these bolt holes 2b, for example, to fasten the bolts to the arm of an industrial robot, thereby securing the reduction gear 1.

[0043] Multiple pin grooves 2c extending axially are formed on the inner circumferential surface 2d of the housing 2. The multiple pin grooves 2c are arranged at equal intervals in the circumferential direction. An internal toothed pin 5 is embedded in each pin groove 2c. The internal toothed pin 5 functions as internal teeth that mesh with the oscillating external gears 15 and 16 of the reduction mechanism 4, which will be described later.

[0044] <Gear Carrier>

[0045] The gear carrier 3 has a base plate portion 7 and an end plate portion 8, which are respectively formed into a generally circular shape when viewed from the axial direction and are arranged opposite each other in the axial direction. In addition, the gear carrier 3 has a column portion 9 integrally formed with the base plate portion 7 and extending from the base plate portion 7 to the end plate portion 8.

[0046] The substrate portion 7 is formed in the shape of a circular plate. The substrate portion 7 is supported on the housing 2 by means of a first main bearing 51. As a result, the substrate portion 7 can rotate relative to the housing 2 about the first rotation axis A1.

[0047] A sealing portion 24 is provided on the side opposite to the end plate portion 8, between the outer peripheral surface of the substrate portion 7 and the inner peripheral surface 2d of the housing 2, which is closer to the first main bearing 51. The sealing portion 24 is used to ensure the airtightness between the substrate portion 7 and the housing 2.

[0048] A substrate through-hole 7d is formed in the radial center of the substrate portion 7, extending axially through the substrate portion 7. A shaft bearing 17 is provided in the substrate through-hole 7d. The shaft bearing 17 is, for example, a tapered roller bearing.

[0049] A plurality of crankshaft insertion holes 7e, each penetrating the substrate portion 7 axially (e.g., three in this embodiment), are formed around the substrate through-hole 7d in the substrate portion 7. The plurality of crankshaft insertion holes 7e are arranged at equal intervals in the circumferential direction. A crankshaft bearing 18 is provided in each crankshaft insertion hole 7e. The crankshaft bearing 18 is, for example, a tapered roller bearing.

[0050] The pillar 9 extends from the end face 7f of the base plate 7 toward the end plate 8 to the end plate 8. Therefore, the pillar 9 is located adjacent to the base plate 7 in the axial direction. The size of the pillar 9, viewed from the axial direction, is sufficiently small compared to the base plate 7.

[0051] Although not shown in the figure, multiple pillars 9 are arranged at intervals in the circumferential direction (for example, three in this embodiment). Each pillar 9 is arranged between adjacent crankshaft insertion holes 7e in the circumferential direction. The multiple pillars 9 are arranged at equal intervals in the circumferential direction.

[0052] An internal thread 26 is formed on the top surface 9a of each column 9. Multiple (in) threads are formed on the same column 9. Figure 1 (Two internal threads are present in the middle) 26. Figure 1 In the middle, the two internally threaded portions 26 are arranged radially, but for example, they can also be arranged circumferentially. The internally threaded portions 26 are used to fix the column portion 9 to the end plate portion 8.

[0053] <Endplate Section>

[0054] The end plate portion 8 is formed in the shape of a circular plate. The end plate portion 8 is supported on the housing 2 by means of the second main bearing 52. Thus, the end plate portion 8 can rotate relative to the housing 2 about the first rotation axis A1.

[0055] An end plate through hole 8d is formed in the radial center of the end plate portion 8, extending axially through the end plate portion 8. The end plate through hole 8d and the substrate through hole 7d are arranged coaxially. A shaft bearing 17 is provided in the end plate through hole 8d in the same manner as in the substrate through hole 7d.

[0056] A plurality of crankshaft insertion holes 8e, each penetrating the end plate portion 8 axially, are formed around the end plate through hole 8d of the end plate portion 8. The crankshaft insertion holes 8e are arranged at equal intervals in the circumferential direction. Each crankshaft insertion hole 8e is coaxially arranged with the crankshaft insertion hole 7e of the base plate portion 7. That is, the central axis A2 of the crankshaft insertion holes 8e and 7e, which are axially opposite, is parallel to the first rotation axis A1. A crankshaft bearing 18 is provided in each crankshaft insertion hole 8e in the same manner as the crankshaft insertion hole 7e.

[0057] Bolt insertion holes 63 are formed at multiple locations on the end plate portion 8 that abut against the top surfaces 9a of the multiple column portions 9. The bolt insertion holes 63 are located axially connected to the internal threads 26 of the column portion 9 when the top surface 9a of the column portion 9 abuts against the end plate portion 8. There are multiple bolt insertion holes 63 corresponding to the same column portion 9 (in...). Figure 1 (There are two in the middle). The arrangement of the multiple bolt insertion holes 63 corresponding to the same column 9 corresponds to the arrangement of the multiple internal thread portions 26 in the column 9.

[0058] Insert the bolt 91 into the bolt insertion hole 63 from the side opposite to the base plate 7, and tighten the bolt 91 into the internal thread 26 of the pillar 9. Thus, the pillar 9 is fixed to the end plate 8, and the base plate 7, end plate 8, and pillar 9 are integrated. In this state, a space with a width equal to the height of the pillar 9 is formed between the base plate 7 and the end plate 8. The gear carrier 3, which integrates the base plate 7, end plate 8, and pillar 9, can rotate relative to the housing 2 about the first rotation axis A1.

[0059] <Speed ​​reduction mechanism>

[0060] The reduction mechanism 4 reduces the rotation of a rotary drive source (not shown) at a certain ratio, thereby causing the gear carrier 3 to rotate. The reduction mechanism 4 includes: an input shaft 11 connected to the rotation shaft of the rotary drive source; a transmission spur gear 12 meshing with the input shaft 11; a crankshaft 13 mounted on the transmission spur gear 12; and two oscillating external gears 15 and 16 (first oscillating external gear 15 and second oscillating external gear 16) disposed between the base plate portion 7 and the end plate portion 8.

[0061] The input shaft 11 has: a shaft body 11a extending axially; an input spur gear 11b located at a first axial end of the shaft body 11a; and a gear portion 11c located at a second axial end of the shaft body 11a.

[0062] The shaft body 11a is inserted into the substrate through-hole 7d of the substrate portion 7 and the end plate through-hole 8d of the end plate portion 8. The shaft body 11a is rotatably supported on the gear carrier 3 (substrate portion 7 and end plate portion 8) by means of shaft bearings 17. In this state, the first end and the second end of the shaft body 11a are located axially outside the gear carrier 3. In this embodiment, the shaft body 11a rotates relative to the gear carrier 3 about a first rotation axis A1. Alternatively, the rotation axis of the shaft body 11a may not be aligned with the first rotation axis A1.

[0063] The input spur gear 11b is generally circular when viewed axially and meshes with a gear (not shown) on the rotating shaft of the rotary drive source. Therefore, the input spur gear 11b rotates along with the gear of the rotary drive source. The diameter of the input spur gear 11b can, for example, be larger than the diameter of the gear of the rotary drive source. In this case, the rotational speed of the input spur gear 11b can be slower than the rotational speed of the gear of the rotary drive source.

[0064] The input spur gear 11b and the shaft body 11a are arranged coaxially and integrated. Therefore, the input spur gear 11b and the shaft body 11a rotate together about the first rotation axis A1.

[0065] The gear section 11c is a gear disposed coaxially with the shaft body 11a. Therefore, the gear section 11c rotates together with the shaft body 11a around the first rotation axis A1. In this embodiment, the gear section 11c is integrally formed with the shaft body 11a. The diameter of the gear section 11c is smaller than the diameter of the input spur gear 11b. In addition, the number of teeth of the gear section 11c is less than the number of teeth of the input spur gear 11b. The transmission spur gear 12, described later, meshes with the gear section 11c.

[0066] In the example shown, the input spur gear 11b is located axially on the side of the base plate portion 7. On the other hand, the gear portion 11c is located axially on the side of the end plate portion 8.

[0067] The transmission spur gear 12, when viewed axially, is approximately circular and meshes with the gear portion 11c of the input shaft 11. Therefore, the transmission spur gear 12 rotates as the input shaft 11 rotates. In this embodiment, the diameter of the transmission spur gear 12, viewed axially, is larger than the diameter of the gear portion 11c. Furthermore, the number of teeth on the transmission spur gear 12 is greater than the number of teeth on the gear portion 11c. Therefore, if the input shaft 11 is rotated while the gear portion 11c is engaged with the transmission spur gear 12, the rotational speed of the transmission spur gear 12 is slower than the rotational speed of the input shaft 11. That is, in the reduction gear 1 including the input shaft 11 and the transmission spur gear 12, the output rotational speed is lower than the input rotational speed.

[0068] The transmission spur gear 12 is mounted on the axial end of the crankshaft 13. In the example shown, the transmission spur gear 12 is mounted on the axial end of the crankshaft 13 located on the end plate portion 8 side (the journal 31 described later). Furthermore, the transmission spur gear 12 and the input shaft 11 meshing with it are located adjacent to the gear carrier 3 on the end plate portion 8 side.

[0069] Multiple transmission spur gears 12 are arranged at equal intervals around the input shaft 11 in the circumferential direction (for example, three in this embodiment).

[0070] The crankshaft 13 is inserted into the crankshaft insertion hole 7e of the base plate 7 and the crankshaft insertion hole 8e of the end plate 8. The crankshaft 13 is rotatably supported on the gear carrier 3 (base plate 7 and end plate 8) by means of each crankshaft bearing 18.

[0071] like Figure 1 , Figure 2 As shown, the crankshaft 13 has a journal 31 centered on the central axis A2, and a first eccentric portion 32 and a second eccentric portion 33 formed at the axial center of the journal 31. The two axial portions of the journal 31 are rotatably supported on the gear carrier 3 (base plate portion 7 and end plate portion 8) by means of crankshaft bearings 18.

[0072] like Figure 1 As shown, the crankshaft 13 (journal 31) and the transmission spur gear 12 are arranged coaxially and integrated. Thus, the crankshaft 13 and the transmission spur gear 12 rotate as a single unit around the central axis A2. Hereinafter, the central axis A2 will be referred to as the second axis of rotation A2 of the crankshaft 13.

[0073] like Figure 1 , Figure 2 As shown, the first eccentric portion 32 and the second eccentric portion 33 of the crankshaft 13 are eccentric relative to the second rotation axis A2. That is, the axes of the first eccentric portion 32 and the second eccentric portion 33 are eccentric relative to the second rotation axis A2. Therefore, the first eccentric portion 32 and the second eccentric portion 33 oscillate and rotate as the crankshaft 13 rotates. The first eccentric portion 32 and the second eccentric portion 33 are arranged axially adjacent between the two crankshaft bearings 18. In other words, the first eccentric portion 32 and the second eccentric portion 33 are arranged axially adjacent between the base plate portion 7 and the end plate portion 8. The first eccentric portion 32 and the second eccentric portion 33 are arranged with a 180° phase angle offset.

[0074] Washers 21 are respectively disposed on the end faces 32a and 33a of each eccentric portion 32 and 33 on the side near the journal 31. The washers 21 are formed into annular shapes centered on the central axis A2 of the journal 31. The inner circumferential end of the washer 21 is located at a position where the radial distance between it and the outer circumferential surface of the journal 31 decreases. The washers 21 protrude radially outward from the outer circumferential surface of each eccentric portion 32 and 33.

[0075] like Figure 1 As shown, the inner circumferential surfaces of roller bearings 19 are fitted into each of the eccentric portions 32 and 33. The roller bearings 19 are, for example, cylindrical roller bearings. The first oscillating external gear 15 and the second oscillating external gear 16 are rotatably supported on the crankshaft 13 by means of the roller bearings 19. The axial movement of these roller bearings 19 is restricted by washers 21 positioned axially on the outer sides of the two eccentric portions 32 and 33.

[0076] The first oscillating external gear 15 and the second oscillating external gear 16 are disposed in the space between the base plate portion 7 and the end plate portion 8. The first oscillating external gear 15 and the second oscillating external gear 16 overlap in the axial direction. A plurality of crankshaft insertion holes 15a and 16a are formed in the first oscillating external gear 15 and the second oscillating external gear 16, which pass through them in the axial direction. The outer peripheral surface of the roller bearing 19 is fitted into each crankshaft insertion hole 15a and 16a. Thus, when the first eccentric portion 32 and the second eccentric portion 33 are oscillating and rotating by the rotation of the crankshaft 13, the first oscillating external gear 15 and the second oscillating external gear 16 oscillate and rotate by means of the roller bearing 19.

[0077] The first oscillating external gear 15 and the second oscillating external gear 16 each have openings 15b and 16b to avoid interference with the column portion 9. Through holes 15c and 16c, which axially penetrate the first oscillating external gear 15 and the second oscillating external gear 16, are formed at their radial centers. The shaft body 11a of the input shaft 11 is inserted into these through holes 15c and 16c. The inner diameter of the through holes 15c and 16c is determined to avoid interference with the shaft body 11a.

[0078] External teeth 15d and 16d are formed on the outer periphery of the first oscillating external gear 15 and the outer periphery of the second oscillating external gear 16, respectively. The number of teeth of each external tooth 15d and 16d is slightly less than the number of internal tooth pins 5 of the housing 2 (for example, one less).

[0079] <crankshaft>

[0080] Next, the crankshaft 13 of the first embodiment will be further described.

[0081] Figure 1 , Figure 2 The crankshaft 13 shown is an example of a "rotating member" in this invention. The journal 31 in the crankshaft 13 is an example of a "columnar small-diameter portion" in this invention. In addition, the eccentric portions 32 and 33 (first eccentric portion 32 and second eccentric portion 33) are examples of a "columnar large-diameter portion" in this invention.

[0082] The diameters of the eccentric portions 32 and 33 are larger than the diameter of the journal 31. In other words, when the crankshaft 13 is viewed axially, the sizes of the eccentric portions 32 and 33 are larger than the size of the journal 31. Furthermore, when the crankshaft 13 is viewed axially, the journal 31 is located inside the eccentric portions 32 and 33. The eccentric portions 32 and 33 are located axially adjacent to the journal 31.

[0083] like Figure 2 , Figure 3As shown, the eccentric portions 32 and 33 have end faces 32a and 33a facing the journal 31 in the axial direction of the crankshaft 13. A recess 40 is formed in the crankshaft 13 that is recessed from the end faces 32a and 33a of the eccentric portions 32 and 33. In this embodiment, the recess 40 is also recessed from the outer peripheral surface 31a of the journal 31. The recess 40 is formed integrally in the circumferential direction of the journal 31. Figure 2 , Figure 3 In the design, only the portion forming the recess 40 in the crankshaft 13 is represented by a cross section orthogonal to the circumferential direction of the crankshaft 13.

[0084] like Figure 3 As shown, the recess 40 has a curved inner surface 41 that is bent into a concave shape. The curved inner surface 41 is formed as an arc with a constant radius of curvature in a section orthogonal to the circumference of the crankshaft 13.

[0085] The first depth d1 of the recess 40, which is recessed axially from the end faces 32a and 33a of the eccentric portions 32 and 33, is greater than the second depth d2 of the recess 40, which is recessed radially from the outer peripheral surface 31a of the journal 31 towards the journal 31.

[0086] <Operation of the deceleration device>

[0087] Next, the operation of the deceleration device 1 in the first embodiment will be explained.

[0088] exist Figure 1 In the reduction gear 1 shown, the rotation of the rotary drive source is transmitted from the input shaft 11 to each transmission spur gear 12 meshing with the gear section 11c of the input shaft 11. Each transmission spur gear 12 rotates about the second rotation axis A2. Here, since the number of teeth of the transmission spur gear 12 is greater than the number of teeth of the gear section 11c of the input shaft 11, the rotation of the transmission spur gear 12 is reduced relative to the rotation of the input shaft 11 (rotary drive source). When the rotation of the transmission spur gear 12 is transmitted to the crankshaft 13, the crankshaft 13 rotates about the second rotation axis A2.

[0089] Therefore, each of the oscillating external gears 15 and 16 oscillates and rotates. Here, the number of teeth on the external gears 15d and 16d is slightly less than the number of internal toothed pins 5 on the housing 2 side (for example, one less). Therefore, each of the oscillating external gears 15 and 16 rotates in a manner in which the meshing parts of each external tooth 15d and 16d relative to the internal toothed pins 5 (housing 2) are staggered in the circumferential direction. This rotation is decelerated relative to the rotation of the crankshaft 13.

[0090] As each of the oscillating external gears 15 and 16 rotates, each crankshaft 13 also rotates on its own axis about the second rotation axis A2 and revolves around the first rotation axis A1. Each crankshaft 13 is rotatably supported on the gear carrier 3 (base plate portion 7, end plate portion 8). Therefore, as each crankshaft 13 revolves, the gear carrier 3 rotates around the first rotation axis A1. As a result, the reduction device 1, for example, reduces the rotation of the rotary drive source and outputs it. Assuming that the gear carrier 3 is fixed to the arm of an industrial robot, the reduction device 1 can, for example, reduce the rotation of the rotary drive source and output it from the housing 2. In addition, assuming that the housing 2 is fixed to the arm of an industrial robot, the reduction device 1 can, for example, reduce the rotation of the rotary drive source and output it from the gear carrier 3.

[0091] In the reduction gear 1 of the first embodiment configured as described above, a recess 40 is formed in the crankshaft 13 (rotating member) that is recessed from the end faces 32a and 33a of the eccentric portions 32 and 33 (large diameter portions) toward the axial direction of the crankshaft 13. This recess 40 has a curved inner surface 41 that is bent into a concave shape. This curved inner surface 41 is formed in connection with the outer peripheral surface 31a of the journal 31 (small diameter portion). That is, the recess 40 is formed at the boundary portion (corner) between the outer peripheral surface 31a of the journal 31 and the end faces 32a and 33a of the eccentric portions 32 and 33.

[0092] Therefore, when the reduction gear 1 operates, it can alleviate stress concentration at the boundary between the journal 31 and the eccentric portions 32 and 33. For example, it can prevent breakage of the crankshaft 13 at this boundary. Thus, the strength of the crankshaft 13 can be ensured without increasing its size. Therefore, it is possible to achieve both miniaturization and high torque of the reduction gear 1.

[0093] Furthermore, in the deceleration device 1 of the first embodiment, the recess 40 is also recessed from the outer peripheral surface 31a of the journal 31. Therefore, the radius of curvature of the curved inner surface 41 of the recess 40 can be further increased without expanding the formation area of ​​the recess 40 at the end faces 32a and 33a of the eccentric portions 32 and 33. By increasing the radius of curvature of the curved inner surface 41, the strength of the crankshaft 13 at the boundary between the outer peripheral surface 31a of the journal 31 and the end faces 32a and 33a of the eccentric portions 32 and 33 can be further improved.

[0094] Furthermore, in the deceleration device 1 of the first embodiment, the first depth d1 of the recess 40 recessed axially from the end faces 32a, 33a of the eccentric portions 32, 33 is greater than the second depth d2 of the recess 40 recessed radially from the outer peripheral surface 31a of the journal 31 towards the journal 31. Therefore, it is possible to effectively suppress the decrease in the diameter of the journal 31 at the boundary between the journal 31 and the eccentric portions 32, 33 due to the formation of the recess 40, and it is possible to further increase the radius of curvature of the curved inner surface 41 of the recess 40. As a result, the strength of the crankshaft 13 at the boundary between the journal 31 and the eccentric portions 32, 33 can be further improved.

[0095] In the first embodiment, the first depth d1 of the recess 40 may, for example, be greater than or equal to the second depth d2 of the recess 40.

[0096] In the first embodiment, the recess 40 may be formed at least on the end faces 32a and 33a of the eccentric portions 32 and 33, or it may not be formed on the outer peripheral surface 31a of the journal 31. However, if the recess 40 is formed only on the end faces 32a and 33a of the eccentric portions 32 and 33, the curved inner surface 41 of the recess 40 may be formed in connection with the outer peripheral surface 31a of the journal 31.

[0097] [Second Implementation]

[0098] Next, the main references are... Figure 4 , Figure 5 The second embodiment of the present invention will be described focusing on its differences from the first embodiment. Furthermore, the same reference numerals are used to denote components common to the first embodiment, and their descriptions are omitted. The components of the second embodiment, which are common to the first embodiment, also include components that differ in shape and size from those of the first embodiment but have the same function.

[0099] Figure 4 The reduction mechanism 4A in the reduction device 1A of the second embodiment shown in the illustration does not have the input shaft 11 of the first embodiment (see reference). Figure 1 Except for this point, it is the same as the deceleration mechanism 4 of the first embodiment. Furthermore, the deceleration mechanism 4A of the second embodiment may, for example, include the same input shaft 11 as the first embodiment. The operation of the deceleration device 1A of the second embodiment is the same as that of the first embodiment.

[0100] Figure 4 The crankshaft 13A in the speed reduction device 1A of the second embodiment does not include the recess 40 of the crankshaft 13 in the first embodiment (see reference). Figure 1 , Figure 2 However, the crankshaft 13A of the second embodiment may, for example, include the same recess 40 as that of the first embodiment.

[0101] like Figure 4 , Figure 5 As shown, the gear carrier 3A in the reduction gear 1A of the second embodiment has the same base plate portion 7A, end plate portion 8, and column portion 9A as in the first embodiment. This gear carrier 3A is an example of a "rotating member" in this invention. The base plate portion 7A in the gear carrier 3A is an example of a "columnar large-diameter portion" in this invention. Furthermore, the column portion 9A is an example of a "columnar small-diameter portion" in this invention.

[0102] The diameter of the substrate portion 7A is larger than the diameter of the pillar portion 9A. In other words, as... Figure 5 As shown, when the gear carrier 3A is viewed axially from the gear carrier 3A, the size of the base plate portion 7A is larger than the size of the column portion 9A. Furthermore, when the gear carrier 3A is viewed axially, the column portion 9A is located inside the base plate portion 7A.

[0103] In this embodiment, the "diameter dimension" of the substrate portion 7A and the pillar portion 9A includes not only the diameter dimension of a pure circle viewed from the axial direction, but also the "dimension in a direction orthogonal to the axial direction" of any shape viewed from the axial direction. Figure 5 In the figure, the base plate portion 7A viewed from the axial direction is circular. On the other hand, the column portion 9A viewed from the axial direction is not circular, but is a triangle with rounded corners.

[0104] like Figure 4 , Figure 5 As shown, the base plate 7A has an end face 7Af facing the column portion 9A in the axial direction of the gear carrier 3A. A recess 40A is formed in the gear carrier 3A, recessed from the end face 7Af of the base plate 7A. The curved inner surface 41A of the recess 40A is formed in connection with the outer peripheral surface 9Ab of the column portion 9A. The recess 40A has a curved inner surface 41A that is curved into a concave shape. The curved inner surface 41A is formed as an arc with a constant radius of curvature in a section orthogonal to the circumferential direction of the column portion 9A. The recess 40A is not formed on the outer peripheral surface 9Ab of the column portion 9A. The recess 40A is formed in the circumferential integral part of the column portion 9A (especially referring to...). Figure 5 ).

[0105] The crankshaft insertion hole 7e (insertion portion) of the base plate 7A for inserting the crankshaft 13A (shaft member) is located radially away from the first rotation axis A1, which is the rotation center of the gear carrier 3A. Multiple crankshaft insertion holes 7e are arranged at equal intervals in the circumferential direction of the gear carrier 3A. Figure 5 (There are 3 in the middle). Additionally, the column portion 9A, like the crankshaft insertion hole 7e, is located radially away from the first rotation axis A1, which is the rotation center of the gear carrier 3A, and has multiple portions evenly spaced along the circumference of the gear carrier 3A (in... Figure 5(There are 3 in the middle). These crankshaft insertion holes 7e and column portions 9A are arranged alternately in the circumferential direction of the gear carrier 3A.

[0106] Furthermore, the recess 40A is formed around each column portion 9A when viewed axially. Therefore, when viewed axially, the crankshaft insertion hole 7e is located adjacent to the recess 40A in the circumferential direction of the gear carrier 3A. In other words, the recess 40A is located between the column portion 9A and the crankshaft insertion hole 7e.

[0107] The deceleration device 1A according to the second embodiment has the same effect as the first embodiment.

[0108] That is, in the reduction device 1A of the second embodiment, a recess 40A is formed in the gear carrier 3A (rotating member), which is recessed from the end face 7Af of the base plate portion 7A (large diameter portion) toward the gear carrier 3A in the axial direction. The recess 40A has a curved inner surface 41A that is bent into a concave shape. The curved inner surface 41A is formed in connection with the outer peripheral surface 9Ab of the column portion 9A (small diameter portion). That is, the recess 40A is formed at the boundary portion (corner) between the outer peripheral surface 9Ab of the column portion 9A and the end face 7Af of the base plate portion 7A.

[0109] Therefore, when the reduction gear 1A operates, stress concentration at the boundary between the column portion 9A and the base plate portion 7A can be mitigated. For example, damage to the gear carrier 3A at this boundary portion can be prevented. Thus, the strength of the gear carrier 3A (especially the integrally formed base plate portion 7A and column portion 9A) can be ensured without increasing the size of the gear carrier 3A. Therefore, both miniaturization and high torque of the reduction gear 1A can be achieved.

[0110] Furthermore, in the reduction gear 1A of the second embodiment, the crankshaft insertion hole 7e (insertion portion) of the gear carrier 3 into which the crankshaft 13 (shaft member) is rotatably inserted is located adjacent to the recess 40. Therefore, the remaining portion of the lubricant (e.g., oil, grease) between the crankshaft insertion hole 7e and the crankshaft 13 can be stored in the recess 40. That is, the recess 40, which helps to improve the strength of the gear carrier 3, can also function as a lubricant storage portion. Thus, compared to the case where the lubricant storage portion is formed independently relative to the recess 40, the shape of the gear carrier 3 can be simplified.

[0111] Furthermore, the remaining portion of the lubricant between the crankshaft insertion hole 7e and the crankshaft 13 is stored in the recess 40, thereby preventing the accumulation of excess lubricant between the crankshaft insertion hole 7e and the crankshaft 13. As a result, even if the rotational speed of the crankshaft 13 increases, the lubricant can be effectively prevented from scattering to the crankshaft 13 and the surrounding area of ​​the insertion part (e.g., the inner circumferential surface of the housing 2).

[0112] In the second embodiment, the crankshaft insertion hole 7e and the recess 40 need only be located adjacent to each other at least when viewed from the axial direction. Therefore, the crankshaft insertion hole 7e and the recess 40 are not limited to being adjacent in the circumferential direction of the gear carrier 3, but may also be adjacent in the radial direction of the gear carrier 3.

[0113] In the second embodiment, the recess 40 may, for example, be recessed from the outer peripheral surface 9Ab of the pillar portion 9 in the same manner as in the first embodiment. In this case, the first depth of the recess 40 recessed axially from the end face 7Af of the substrate portion 7 may, for example, be greater than the second depth of the recess 40 recessed radially from the outer peripheral surface 9Ab of the pillar portion 9 towards the pillar portion 9, just as in the first embodiment.

[0114] In the second embodiment, the rotation axis A2 of the crankshaft 13A (shaft member) may, for example, be located at a position that is not separated from the first rotation axis A1, that is, it may also be consistent with the first rotation axis A1.

[0115] [Third Implementation Method]

[0116] Next, the main references are... Figure 6 , Figure 7 The third embodiment of the present invention will be described focusing on its differences from the first embodiment. Furthermore, the same reference numerals are used to denote components common to the first embodiment, and their descriptions are omitted. The components of the third embodiment, which are common to the first embodiment, also include components that differ in shape and size from those of the first embodiment but have the same function.

[0117] In the reduction gear 1C of the third embodiment, the shape of the recess 40 formed on the crankshaft 13 differs from that of the first embodiment. The relationship between the components of the journal 31, the crankshaft bearing 18, and the recess 40 is also mentioned in the third embodiment. The other structures and operation of the reduction gear 1C in the third embodiment are the same as in the first embodiment.

[0118] like Figure 6 , Figure 7 As shown, the curved inner surface 41 of the recess 40 is formed as a circular arc with a constant radius of curvature Rcs in a section orthogonal to the circumference of the crankshaft 13, that is, a perfect circle. To ensure the strength of the crankshaft 13, the radius of curvature Rcs of the curved inner surface 41 needs to be set to a predetermined value or higher. For example, the radius of curvature Rcs of the curved inner surface 41 can be 10% or more of the diameter Ds of the journal 31 (small diameter portion) centered on the second axis of rotation A2 (the axis of rotation of the crankshaft 13).

[0119] In the third embodiment, the first depth d1 of the recess 40 recessed axially from the end faces 32a, 33a of the eccentric portions 32, 33 (large diameter portions) is less than or equal to the second depth d2 of the recess 40 recessed radially from the outer peripheral surface 31a of the journal 31 towards the journal 31. Figure 7 In the middle, the first depth d1 of the recess 40 is smaller than the second depth d2, but it can also be the same as the second depth d2.

[0120] like Figure 6 As shown, the crankshaft bearing 18 is a so-called tapered roller bearing. The crankshaft bearing 18 includes an inner ring 81, an outer ring 82 disposed radially outside the inner ring 81, a plurality of tapered rollers 83 (rolling elements) disposed between the outer ring 82 and the inner ring 81, and a retainer 84 for holding the plurality of tapered rollers 83.

[0121] The inner ring 81 is formed as an annular ring centered on the second axis of rotation A2. The inner ring 81 is formed as a triangle or trapezoid in a cross-section orthogonal to its circumference. The outer circumferential surface of the inner ring 81 includes an inner ring track surface 81b that contacts the tapered roller 83. The inner ring track surface 81b is inclined relative to the axial direction of the outer ring 82 and the inner ring 81. Specifically, the inner ring track surface 81b is inclined in such a way that the outer diameter of the inner ring 81 gradually decreases as it moves axially away from the eccentric portions 32 and 33. The inner ring 81 also has an end face 81a that is axially opposite to the end faces 32a and 33a of the eccentric portions 32 and 33.

[0122] The outer ring 82 is formed as an annulus centered on the second axis of rotation A2. The outer ring 82 is formed as a triangle or trapezoid in a cross-section orthogonal to its circumference. The inner circumferential surface of the outer ring 82 includes an outer ring track surface 82b that contacts the tapered roller 83. The outer ring track surface 82b is inclined relative to the axial direction of the outer ring 82 and the inner ring 81. Specifically, the outer ring track surface 82b is inclined in such a way that the inner diameter of the outer ring 82 gradually decreases as it moves axially away from the eccentric portions 32 and 33. The outer ring track surface 82b is radially opposite to the inner ring track surface 81b.

[0123] Multiple tapered rollers 83 are arranged circumferentially on the inner ring 81 and the outer ring 82. Each tapered roller 83 rotates about a second axis of rotation A2 while rolling on the outer ring raceway surface 82b and the inner ring raceway surface 81b. A cage 84 is located radially between the outer ring 82 and the inner ring 81. The cage 84 holds the multiple tapered rollers 83 so that the multiple tapered rollers 83 are arranged at equal intervals in the circumferential direction.

[0124] In each crankshaft bearing 18 respectively provided on the base plate portion 7 and the end plate portion 8, the outer ring 82 is fitted inside the crankshaft insertion holes 7e and 8e of the base plate portion 7 and the end plate portion 8, and the inner ring 81 is fitted outside the journal portion 31. The end face 81a of the inner ring 81 of the crankshaft bearing 18 abuts against the washer 21 which is overlapped on the end faces 32a and 33a of the eccentric portions 32 and 33. That is, the washer 21 is disposed between the end face 81a of the inner ring 81 and the end faces 32a and 33a of the eccentric portions 32 and 33. The end face 82a of the outer ring 82 of the crankshaft bearing 18 facing the side opposite to the end face 81a of the inner ring 81 in the axial direction abuts against the retaining ring 22 provided on the crankshaft insertion holes 7e and 8e of the base plate portion 7 and the end plate portion 8. The retaining ring 22 restricts the crankshaft bearing 18 from moving axially away from the end faces 32a and 33a of the eccentric portions 32 and 33. In addition, the retaining ring 22 also restricts the crankshaft 13 from moving outward from the base plate portion 7 side and the end plate portion 8 side toward the outside of the gear carrier 3.

[0125] Preload is applied to the crankshaft bearing 18 configured as described above. As a result, the crankshaft bearing 18 (especially the inner ring 81) is pressed against the end faces 32a and 33a of the eccentric portions 32 and 33 through the washer 21.

[0126] In this structure, the diameter of the journal 31 is set as Ds, the radius of the outer periphery 81o of the end face 81a of the inner ring 81 is set as Roi, and the radius of the outer periphery 40o of the annular recess 40 centered on the second rotation axis A2 is set as Ror. The ratio of (Roi-Ror) to (Roi-(Ds / 2)) is preferably a predetermined value or higher. In this embodiment, the ratio of (Roi-Ror) to (Roi-(Ds / 2)) is, for example, 30% or higher.

[0127] (Roi-(Ds / 2)) is the radial length in the axial direction of the portion of the end faces 32a and 33a of the eccentric portions 32 and 33 that includes the forming region of the recess 40, overlapping with the end face 81a of the inner ring 81. (Roi-Ror) is the radial length in the axial direction of the portion of the end faces 32a and 33a of the eccentric portions 32 and 33 that, excluding the forming region of the recess 40, overlap with the end face 81a of the inner ring 81. The ratio of (Roi-Ror) to (Roi-(Ds / 2)) is equivalent to the ratio of the area of ​​the washer 21 disposed between the end faces 32a and 33a of the eccentric portions 32 and 33 and the end face 81a of the inner ring 81, sandwiched between the end faces 32a and 33a of the eccentric portions 32 and 33 and the end face 81a of the inner ring 81.

[0128] The deceleration device 1C according to the third embodiment has the same effect as that of the first embodiment.

[0129] Furthermore, in the reduction gear 1C of the third embodiment, the first depth d1 of the recess 40 recessed axially from the end faces 32a and 33a of the eccentric portions 32 and 33 is less than the second depth d2 of the recess 40 recessed radially from the outer peripheral surface 31a of the journal 31 to the journal 31. That is, the first depth d1 of the recess 40 recessed axially from the end faces 32a and 33a of the eccentric portions 32 and 33 is small. Therefore, even if the crankshaft bearing 18 (especially the inner ring 81) is pressed against the end faces 32a and 33a of the eccentric portions 32 and 33 through the washer 21 by applying preload to the crankshaft bearing 18, deformation caused by the washer 21 being pressed into the inner side of the recess 40 can be effectively suppressed. Thus, preload loss of the crankshaft bearing 18 can be effectively suppressed. Furthermore, malfunctions of the reduction gear 1C due to preload loss of the crankshaft bearing 18 can be suppressed.

[0130] Furthermore, in the reduction gear 1C of the third embodiment, by making the first depth d1 of the recess 40 less than or equal to the second depth d2 of the recess 40, the strength of the crankshaft 13 can be ensured, and the preload loss of the crankshaft bearing 18 can be effectively suppressed. This point will be explained below.

[0131] To ensure the strength of the crankshaft 13, the radius of curvature Rcs of the curved inner surface 41 in the section orthogonal to the circumference of the crankshaft 13 needs to be set to a predetermined value or higher. That is, when considering ensuring the strength of the crankshaft 13, there exists a minimum value for the radius of curvature Rcs of the curved inner surface 41. Even if this radius of curvature Rcs is not set to a minimum value, or the size of the radius of curvature Rcs is not changed, it is possible to set the first depth d1 of the recess 40 to be less than or equal to the second depth d2. For example, as Figure 7 As shown, the curvature center Css of the curved inner surface 41 is axially directed away from the eccentric portions 32 and 33 (in... Figure 7 Move to the right (in the middle direction), or radially towards the journal 31 (in the middle direction). Figure 7 (Move downwards) This reduces the first depth d1 of the recess 40 and increases the second depth d2. Therefore, it is possible to effectively suppress the preload loss of the crankshaft bearing 18 while ensuring the strength of the crankshaft 13.

[0132] Furthermore, in the reduction gear 1C of the third embodiment, the ratio of (Roi-Ror) to (Roi-(Ds / 2)) is 30% or more. Therefore, it can be ensured that the area of ​​the washer 21 sandwiched between the crankshaft bearing 18 (particularly the end face 81a of the inner ring 81) and the end faces 32a and 33a of the eccentric portions 32 and 33 is sufficiently large. Thus, even when the crankshaft bearing 18 (particularly the inner ring 81) is pressed against the end faces 32a and 33a of the eccentric portions 32 and 33 through the washer 21 by applying preload to the crankshaft bearing 18, deformation caused by the washer 21 being pressed into the inner side of the recess 40 can be effectively suppressed. Therefore, preload loss of the crankshaft bearing 18 can be effectively suppressed.

[0133] Furthermore, as a structure prone to preload loss in the crankshaft bearing 18, consider a structure in which the washer 21 disposed on the end faces 32a and 33a of the eccentric portions 32 and 33 has a larger area overlapping the recess 40 axially, and a smaller area sandwiched between the crankshaft bearing 18 and the end faces 32a and 33a of the eccentric portions 32 and 33. In such a structure, the washer 21 is pressed towards the eccentric portions 32 and 33 by the crankshaft bearing 18 (especially the inner ring 81), thereby causing the inner circumferential portion of the washer 21 to enter the inner side of the recess 40 axially. Therefore, preload loss in the crankshaft bearing 18 is prone to occur.

[0134] [Fourth Implementation Method]

[0135] Next, the main references are... Figure 8 , Figure 9 The fourth embodiment of the present invention will be described focusing on its differences from the third embodiment. Furthermore, the same reference numerals are used to denote components common to the third embodiment, and their descriptions are omitted.

[0136] In the speed reduction device 1D of the fourth embodiment, the shape of the recess 40 formed on the crankshaft 13 differs from that of the third embodiment. The other structures of the speed reduction device 1D in the fourth embodiment are the same as those in the third embodiment.

[0137] like Figure 8 , Figure 9 As shown, the recess 40 is recessed from the outer peripheral surface 31a of the journal 31 (small diameter portion), and not from the end faces 32a and 33a of the eccentric portions 32 and 33 (large diameter portions). Therefore, only the second depth d2 of the recess 40 radially recessed from the outer peripheral surface 31a of the journal 31 to the journal 31 exists, and the first depth d1 of the recess 40 axially recessed from the end faces 32a and 33a of the eccentric portions 32 and 33 does not exist (refer to...). Figure 7 wait).

[0138] Figure 9The curved inner surface 41 of the illustrated recess 40, like in the third embodiment, is formed as a circular arc with a constant radius of curvature in a section orthogonal to the circumference of the crankshaft 13. The curved inner surface 41 is formed in connection with the end faces 32a and 33a of the eccentric portions 32 and 33.

[0139] exist Figure 9 In this design, the recess 40 is formed across both the outer peripheral surface 31a of the journal 31 and the end faces 32a and 33a of the eccentric portions 32 and 33. The portion of the curved inner surface 41 formed on the outer peripheral surface 31a of the journal 31 is recessed from the outer peripheral surface 31a of the journal 31. The portion of the curved inner surface 41 formed on the end faces 32a and 33a of the eccentric portions 32 and 33 extends axially from the end faces 32a and 33a of the eccentric portions 32 and 33 toward the journal 31. Alternatively, the curved inner surface 41 of the recess 40 may be formed only on the outer peripheral surface 31a of the journal 31.

[0140] exist Figure 9 In this configuration, there is no corner between the curved inner surface 41 of the recess 40 and the end faces 32a and 33a of the eccentric portions 32 and 33, and the curved inner surface 41 of the recess 40 is smoothly connected to the end faces 32a and 33a of the eccentric portions 32 and 33. Alternatively, there may be a corner between the curved inner surface 41 of the recess 40 and the end faces 32a and 33a of the eccentric portions 32 and 33.

[0141] In the speed reduction device 1D of the fourth embodiment, similarly to the third embodiment, the ratio of (Roi-Ror) to (Roi-(Ds / 2)) can be a predetermined value or higher (e.g., 30%) as a relationship between the diameter dimension Ds of the journal 31, the radius dimension Roi of the outer periphery 81o of the end face 81a of the inner ring 81, and the radius dimension Ror of the outer periphery 40o of the annular recess 40 centered on the second rotation axis A2.

[0142] The deceleration device 1D according to the fourth embodiment has the same effect as that of the third embodiment.

[0143] In the reduction gear 1D of the fourth embodiment, the recess 40 does not protrude from the end faces 32a and 33a of the eccentric portions 32 and 33. Therefore, the washer 21 disposed on the end faces 32a and 33a of the eccentric portions 32 and 33 does not overlap with the recess 40 in the axial direction. Thus, even if the crankshaft bearing 18 (especially the inner ring 81) is pressed against the end faces 32a and 33a of the eccentric portions 32 and 33 through the washer 21 by applying preload to the crankshaft bearing 18, it is possible to prevent the washer 21 from being pressed into the inside of the recess 40 and deformed. Therefore, preload loss of the crankshaft bearing 18 can be prevented.

[0144] Furthermore, in the reduction gear 1D of the fourth embodiment, similar to the third embodiment, it is possible to prevent preload loss of the crankshaft bearing 18 while ensuring the strength of the crankshaft 13.

[0145] This invention is not limited to the embodiments described above, but includes various modifications made to the embodiments described above without departing from the spirit of this invention.

[0146] In this invention, the crankshaft bearing 18 is not limited to tapered roller bearings; it can be any rolling bearing that has at least an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner and outer rings. Therefore, the crankshaft bearing 18 can also be, for example, a cylindrical roller bearing, a ball bearing, or the like.

[0147] In this invention, the curved inner surfaces 41 and 41A of the recesses 40 and 40A are not limited to circular arcs (circular arcs with constant radius of curvature) in a cross section orthogonal to the circumference of the rotating member (crankshaft 13 and gear carrier 3A), but can also be formed as elliptical arcs (circular arcs with varying radius of curvature).

[0148] This invention is not limited to speed reduction devices, but can be applied to any gear device having a rotating member having a columnar small-diameter portion and a columnar large-diameter portion with a diameter larger than the small-diameter portion.

[0149] In the embodiments disclosed in this specification, a component composed of multiple objects can be integrated into one object; conversely, a component composed of a single object can be divided into multiple objects. Whether integrated or not, it is acceptable as long as the configuration achieves the purpose of the invention.

Claims

1. A gear mechanism, wherein, The gear mechanism includes a rotating member having a cylindrical small-diameter portion and a cylindrical large-diameter portion located adjacent to the small-diameter portion and having a diameter larger than that of the small-diameter portion. The large-diameter portion has an end face facing the small-diameter portion side in the axial direction of the rotating member. The rotating member has a recess that is recessed from the end face of the large-diameter portion. The recess has a curved inner surface that is bent into a concave shape. The curved inner surface is formed in connection with the outer peripheral surface of the small diameter portion.

2. The gear device according to claim 1, wherein, The recess is also recessed from the outer peripheral surface of the small diameter portion.

3. The gear device according to claim 2, wherein, The first depth of the recess from the end face of the large diameter portion to the axial recess is greater than the second depth of the recess from the outer periphery of the small diameter portion to the radial recess of the small diameter portion.

4. The gear device according to claim 2, wherein, The first depth of the recess from the end face of the large diameter portion to the axial recess is below the second depth of the recess from the outer periphery of the small diameter portion to the radial recess of the small diameter portion.

5. The gear device according to any one of claims 1 to 4, wherein, The gear mechanism also includes a rolling bearing disposed on the outer circumferential surface of the small diameter portion. The inner ring of the rolling bearing, which fits into the outer circumferential surface of the small-diameter portion, has an end face that faces the end face of the large-diameter portion in the axial direction. Let Ds be the diameter of the small-diameter portion centered on the rotation axis of the rotating member, let Roi be the radius of the outer periphery of the end face of the inner ring formed as an annular shape centered on the rotation axis, and let Ror be the radius of the outer periphery of the recess formed as an annular shape centered on the rotation axis. The ratio of (Roi-Ror) to (Roi-(Ds / 2)) is over 30%.

6. The gear device according to any one of claims 1 to 4, wherein, The rotating component includes a crankshaft having a journal portion, which is the small diameter portion, with the axis of rotation of the rotating component as its axis, and an eccentric portion, which is the large diameter portion, with its axis eccentric relative to the axis of rotation.

7. The gear device according to any one of claims 1 to 3, wherein, The rotating member includes a gear carrier rotatably disposed radially inside the cylindrical housing. The gear carrier has: a base plate portion; an end plate portion disposed opposite to the base plate portion in the axial direction; and a column portion integrally formed on the base plate portion, extending from the base plate portion to the end plate portion and fixed to the end plate portion. The smaller diameter portion is the column portion. The large-diameter portion is the substrate portion.

8. The gear device according to claim 7, wherein, The base plate portion has an insertion portion into which the shaft member can be rotatably inserted. When viewed from the axial direction, the insertion portion is located adjacent to the recess.

9. A gear mechanism, wherein, The gear mechanism includes a rotating member having a cylindrical small-diameter portion and a cylindrical large-diameter portion located adjacent to the small-diameter portion and having a diameter larger than that of the small-diameter portion. The large-diameter portion has an end face facing the small-diameter portion side in the axial direction of the rotating member. The rotating member has a recess that is recessed from the outer peripheral surface of the small diameter portion but not from the end face of the large diameter portion. The recess has a curved inner surface that is bent into a concave shape. The curved inner surface is formed in connection with the end face of the large-diameter portion.

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