Reduction gear

Abstract

To provide a long-life reduction gear by securing smooth movement of an oscillation gear by preventing interference of an outside corner part of the oscillation gear with an inside corner part of an outer ring so as to prevent a scratch from being made by contact between the outer ring and the oscillation gear, when the oscillation gear is oscillation-rotated in association with rotation of a crankshaft.SOLUTION: Rolling bearings 10A and 10B for rotatably supporting an inside member 30 with respect to an outside member 20 comprise: outer rings 11A and 11B that are internally fitted to the outside member 20; inner rings 12A and 12B that are externally fitted to the inside member 30; and a plurality of rolling elements 13A and 13B that are rollably arranged between the outer rings 11A and 11B and the inner rings 12A and 12B. The outer rings 11A and 11B have overlapping parts that overlap oscillation gears 50A and 50B even when eccentric parts 43 and 44 are positioned on the innermost diameter side in an axial view.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an eccentric oscillating type reducer. [Background technology]

[0002] In industrial robots, machine tools, etc., reducers are used to reduce the rotation speed of a rotary drive source such as a motor. In rotating equipment such as a reducer, an outer member is connected to the outer periphery of an inner member via a bearing so as to be capable of relative rotation.

[0003] Patent Document 1 discloses an eccentric oscillating gear device that reduces the rotation speed at a predetermined reduction ratio between two mating members. The eccentric oscillating gear device of Patent Document 1 includes an outer cylinder fixed to one mating member, and a carrier disposed within the outer cylinder and fixed to the other mating member, and the carrier rotates relative to the outer cylinder due to the oscillating rotation of an oscillating gear attached to an eccentric portion of a crankshaft.

[0004] For example, in a conventional eccentric oscillating type reducer, as shown in Figures 5 and 6, an inner member 111 is rotatably supported relative to an outer member 112 by a roller bearing 100. The roller bearing 100 comprises an inner ring 101 fitted onto the outside of the inner member 111, an outer ring 102 fitted onto the inside of the outer member 112, a plurality of rollers 103 disposed between the inner ring 101 and the outer ring 102 so as to be able to roll, and a cage 104 which holds the plurality of rollers 103 so as to be able to rotate.

[0005] An oscillating gear 120 that is oscillatingly rotated by the crankshaft of the reducer is disposed on one axial side (the left side in the figure) of the outer ring 102. A side surface 120a of the oscillating gear 120 on the roller bearing 100 side and a side surface 102a of the outer ring 102 on the oscillating gear 120 side are substantially on the same plane. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-122582 A Summary of the Invention [Problem to be solved by the invention]

[0007] In a conventional reducer, as shown in FIG. 5, when the crankshaft rotates and the oscillating gear 120 is positioned at the top dead center of the oscillating rotation, that is, when the outer diameter surface 120b of the oscillating gear 120 is positioned on the inner diameter side relative to the inner diameter surface 102b of the outer ring 102, the outer corner 120c of the oscillating gear 120 is spaced apart from the inner corner 102c of the outer ring 102.

[0008] 6, when the crankshaft further rotates and the oscillating gear 120 reaches the bottom dead center of the oscillating rotation, the outer diameter surface 120b of the oscillating gear 120 is positioned on the outer diameter side of the inner diameter surface 102b of the outer ring 102. In other words, the side surface 120a of the oscillating gear 120 and the side surface 102a of the outer ring 102 are partially overlapped with each other when viewed in the axial direction.

[0009] When the state shown in Fig. 5, in which the outer diameter surface 120b of the oscillating gear 120 is located on the inner diameter side of the inner diameter surface 102b of the outer ring 102, transitions to the state shown in Fig. 6, in which the outer diameter surface 120b of the oscillating gear 120 is located on the outer diameter side of the inner diameter surface 102b of the outer ring 102, or conversely, when transitions from the state shown in Fig. 6 to the state shown in Fig. 5, there is a risk that the outer corner 120c of the oscillating gear 120 and the inner corner 102c of the outer ring 102 will interfere with each other, causing damage to both corners 102c, 120c. Such damage is undesirable because it hinders the smooth movement of the oscillating gear 120 and adversely affects the life of the reducer.

[0010] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a reducer with a long life by preventing the outer corner of the oscillating gear from interfering with the inner corner of the outer ring when the oscillating gear rotates in accordance with the rotation of the crankshaft, thereby preventing contact scratches on the outer ring and the oscillating gear, and ensuring smooth movement of the oscillating gear. [Means for solving the problem]

[0011] Therefore, the above object of the present invention is achieved by the following configuration [1] of a reducer. [1] An outer member having an inner diameter surface on which a plurality of pin grooves in which internal tooth pins are rotatably held are formed at regular intervals in the circumferential direction; an oscillating gear having external teeth on an outer diameter surface thereof, the external teeth being capable of meshing with the internal tooth pins, formed at regular intervals in the circumferential direction, the oscillating gear being fitted to an eccentric portion of the crankshaft and oscillatingly rotating in association with the rotation of the crankshaft; an inner member disposed axially to the side of the oscillating gear and rotatably supporting the crankshaft; a rolling bearing that rotatably supports the inner member relative to the outer member; A reducer comprising: the rolling bearing comprises an inner ring fitted onto the inside of the inner member, an outer ring fitted onto the inside of the outer member, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be able to roll freely; the outer ring has an overlapping portion that overlaps with the oscillating gear even when the eccentric portion is positioned at the innermost radial side when viewed in the axial direction, reducer. Effect of the Invention

[0012] According to the reducer of the present invention, the oscillating gear and the outer ring are maintained in a radially overlapping state at any eccentric position of the oscillating gear, so that the outer corners of the oscillating gear do not interfere with the inner corners of the outer ring, thereby preventing contact damage between the outer ring and the oscillating gear and allowing the oscillating gear to move smoothly. Also, the life of the reducer can be extended. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of a main portion of a reducer according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged view of a portion surrounded by a two-dot chain line A shown in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] FIG. 3 is an enlarged view of a modified example, equivalent to FIG. [Diagram 5]FIG. 11 is a cross-sectional view of a main portion of a conventional reducer, illustrating the positional relationship between a rocking gear located at the top dead center and a roller bearing. [Figure 6] FIG. 11 is a cross-sectional view of a main portion of a conventional reducer, illustrating the positional relationship between a rocking gear located at the bottom dead center and a roller bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a reducer 1 according to an embodiment of the present invention will be described with reference to Figs. 1 to 3. Fig. 1 is a cross-sectional view of a main part of the reducer according to this embodiment. Fig. 2 is an enlarged view of a part surrounded by a two-dot chain line A shown in Fig. 1. Fig. 3 is a cross-sectional view taken along the line III-III in Fig. 1. Note that in Fig. 1, only a lower part with respect to the axis O is shown, whereas in Fig. 3, not only a lower part with respect to the axis O but also an upper part is shown. That is, Fig. 3 is a cross-sectional view of the entire reducer 1 as seen from the axial direction. The reducer 1 of this embodiment is an eccentric oscillating gear transmission having an epitrochoid gear on the external teeth and a pin gear on the internal teeth, which is applied to, for example, a joint part of a robot arm, etc.

[0015] As shown in Figures 1 and 3, the reducer 1 comprises an outer member 20 as a case, an inner member 30 rotatably supported on the outer member 20, a plurality of (e.g., three) crankshafts 40 rotatably supported on the inner member 30, a first oscillating gear 50A and a second oscillating gear 50B rotatably attached to the plurality of crankshafts 40, a first tapered roller bearing 10A and a second tapered roller bearing 10B which are rolling bearings interposed between the outer member 20 and the inner member 30, a first needle bearing 60A and a second needle bearing 60B interposed between the inner member 30 and the crankshaft 40, a third needle bearing 60C interposed between the first eccentric portion 43 of the crankshaft 40 and the first oscillating gear 50A, and a fourth needle bearing 60D interposed between the second eccentric portion 44 of the crankshaft 40 and the second oscillating gear 50B.

[0016] The reducer 1 is an eccentric oscillating gear transmission in which an input shaft (not shown) is rotated relative to the outer member 20, and the outer member 20 and the inner member 30 are rotated relatively around an axis O to obtain an output rotation that is reduced from the input rotation of the input shaft. In the following description, the direction along the axis O is referred to as the axial direction (axial direction), the direction perpendicular to the axis O and extending radially from the axis O is referred to as the radial direction, and the direction rotating around the axis O is referred to as the circumferential direction. In the following description, the term "inner side in the axial direction" refers to the axial center side of the outer member 20, and the term "outer side in the axial direction" refers to the opposite side to the axial center of the outer member 20.

[0017] The outer member 20 is formed in a cylindrical shape centered on the axis O. A plurality of pin grooves 21 are formed in the inner peripheral surface of the outer member 20 at equal intervals in the circumferential direction in the axial middle portion, and a cylindrical internal tooth pin 25 is rotatably held in each pin groove 21.

[0018] A carrier 4 arranged coaxially with the outer member 20 is housed within the outer member 20. The carrier 4 rotates relatively to the outer member 20 about the same axis. The carrier 4 is arranged on the inner diameter side of the outer member 20, and in this state, is supported by a pair of bearings (not shown) spaced apart from each other in the axial direction so as to be rotatable relative to the outer member 20.

[0019] The carrier 4 has a plurality of shaft portions 4a (three in the illustrated example) extending in the axial direction. The shaft portions 4a are inserted into shaft portion insertion holes 55 of the first oscillating gear 50A and the second oscillating gear 50B with some play. The shaft portion insertion holes 55 are provided at equal intervals in the circumferential direction around the axis O in the first oscillating gear 50A and the second oscillating gear 50B. In addition, the first oscillating gear 50A and the second oscillating gear 50B are provided with eccentric portion insertion portions 56, into which the first eccentric portion 43 and the second eccentric portion 44 are inserted, at equal intervals in the circumferential direction around the axis O. The shaft portion insertion holes 55 and the eccentric portion insertion portions 56 are provided alternately in the circumferential direction.

[0020] Furthermore, on the inner diameter side of the outer member 20, a first outer ring retaining portion 22 and a second outer ring retaining portion 23 are formed adjacent to the pin groove 21 in the axial direction on either side of the pin groove 21. The first outer ring retaining portion 22 and the second outer ring retaining portion 23 are formed into a generally L-shaped cross section facing outward in the axial direction. The first outer ring retaining portion 22 retains the outer ring 11A of the first tapered roller bearing 10A, and the second outer ring retaining portion 23 retains the outer ring 11B of the second tapered roller bearing 10B.

[0021] Furthermore, a seal retaining portion 24 is provided axially adjacent to the second outer ring retaining portion 23 on the axially outer side of the second outer ring retaining portion 23. The inner diameter of the seal retaining portion 24 is larger than the inner diameter of the second outer ring retaining portion 23, and is in contact with the outer periphery of the oil seal 2.

[0022] The inner member 30 functions as an output shaft to which a driven part that receives the output rotation of the reduction gear 1 is attached. The inner member 30 is formed into a cylindrical shape centered on the axis O as a whole, and is disposed on the inner peripheral side of the outer member 20, protruding from both sides in the axial direction.

[0023] The inner member 30 is formed so as to be separable in the axial direction into a substantially disk-shaped first inner member 31 and a second inner member 32 including a plurality of support pillars (not shown) protruding axially inward from a base portion 32a. The first inner member 31 is integrally fastened to the second inner member 32 by bolts via the plurality of support pillars.

[0024] The first inner member 31 is rotatably supported by the outer member 20 via a first tapered roller bearing 10A, and the second inner member 32 is rotatably supported by the outer member 20 via a second tapered roller bearing 10B.

[0025] The inner ring 12A of the first tapered roller bearing 10A is held by a first inner ring retaining portion 34 having a substantially L-shaped cross section, which is formed on the outer peripheral surface of the first inner member 31 opposite the first outer ring retaining portion 22. The inner ring 12B of the second tapered roller bearing 10B is held by a second inner ring retaining portion 35 having a substantially L-shaped cross section, which is formed on the outer peripheral surface of the second inner member 32 opposite the second outer ring retaining portion 23. Also, the inner peripheral portion of the oil seal 2 is attached in contact with a seal retaining portion 36 formed on the outer peripheral surface of the base 32a opposite the seal retaining portion 24 of the outer member 20.

[0026] The first inner member 31 and the second inner member 32 have circular shaft holes 37, the number of which corresponds to the number of the crankshafts 40, into which the crankshafts 40 are inserted.

[0027] The crankshafts 40 are arranged at equal intervals in the circumferential direction on the inner circumferential side of the outer member 20. Each crankshaft 40 has a first journal portion 41 and a second journal portion 42 arranged at an interval in the axial direction. The first journal portion 41 and the second journal portion 42 are formed coaxially. The first journal portion 41 is rotatably supported in the shaft hole 37 of the first inner member 31 via a first needle bearing 60A, and the second journal portion 42 is rotatably supported in the shaft hole 37 of the second inner member 32 via a second needle bearing 60B.

[0028] Further, the crankshafts 40 have a first eccentric portion 43 and a second eccentric portion 44 disposed between the first journal portion 41 and the second journal portion 42. The first eccentric portion 43 and the second eccentric portion 44 are eccentric by the same eccentric amount ε with respect to the common axis O1 of the first journal portion 41 and the second journal portion 42. The first eccentric portion 43 and the second eccentric portion 44 have a phase difference from each other of a predetermined angle (180° in this embodiment).

[0029] A first oscillating gear 50A is rotatably fitted to the first eccentric portion 43 via a third needle bearing 60C, and a second oscillating gear 50B is rotatably fitted to the second eccentric portion 44 via a fourth needle bearing 60D.

[0030] The first oscillating gear 50A and the second oscillating gear 50B are disposed between the first inner member 31 and the second inner member 32. The first oscillating gear 50A and the second oscillating gear 50B are formed in a disk shape having an outer diameter smaller than the inner diameter of the outer member 20, and are oscillatingly rotatable relative to the inner member 30 and rotatable about a common axis O1 in synchronization with the inner member 30.

[0031] The first oscillating gear 50A and the second oscillating gear 50B have a plurality of external teeth 51 formed over the entire circumference of their outer circumferential surfaces. The plurality of external teeth 51 are, for example, epitrochoid gears, and are set to at least one less than the number of the internal tooth pins 25 provided on the outer member 20, and are capable of meshing with the internal tooth pins 25.

[0032] When each crankshaft 40 rotates and the first eccentric portion 43 rotates eccentrically, the first oscillating gear 50A oscillates and rotates about the axis O while meshing with some of the internal pins 25 in conjunction with the eccentric rotation of the first eccentric portion 43. When each crankshaft 40 rotates and the second eccentric portion 44 rotates eccentrically, the second oscillating gear 50B oscillates and rotates about the axis O while meshing with some of the internal pins 25 in conjunction with the eccentric rotation of the second eccentric portion 44.

[0033] Therefore, the multiple crankshafts 40 supported by the first oscillating gear 50A and the second oscillating gear 50B revolve around the axis O, and the inner member 30 supporting the multiple crankshafts 40 rotates around the axis O.

[0034] Although not shown, each of the first oscillating gear 50A and the second oscillating gear 50B has the same number of escape holes as the plurality of support pillars of the second inner member 32. A plurality of support pillars are inserted into each escape hole one by one. Each escape hole is formed with an inner diameter sufficiently large relative to the support pillars so that each support pillar does not interfere with the oscillating rotation of the first oscillating gear 50A and the second oscillating gear 50B.

[0035] As shown in Fig. 2, the first tapered roller bearing 10A comprises an outer ring 11A, an inner ring 12A, a plurality of tapered rollers 13A, and a cage 14A. The second tapered roller bearing 10B has a similar configuration to the first tapered roller bearing 10A, except that the mounting direction to the outer member 20 and the inner member 30 is reversed, so only the first tapered roller bearing 10A will be described below, and a description of the second tapered roller bearing 10B will be omitted. Also, rolling bearings such as angular contact ball bearings may be used instead of the first tapered roller bearing 10A and the second tapered roller bearing 10B.

[0036] The outer ring 11A is formed in an annular shape centered on the axis O. The outer ring 11A has an outer peripheral surface 11b extending in the axial direction with a constant outer diameter, a side surface 11c facing inward in the axial direction, an outer ring raceway surface 11d inclined with respect to the axis O, an inner peripheral surface 11e extending in the axial direction with a constant inner diameter, and an annular protrusion 11f protruding inward from the end of the inner peripheral surface 11e on the oscillating gear 50A side (axially inner side).

[0037] The outer ring 11A is fitted and fixed to the first outer ring holding portion 22 of the outer member 20 with the side surface 11c, i.e., the annular protrusion 11f, facing the oscillating gear 50A side. The side surface 11c of the outer ring 11A and a side surface 52A of the oscillating gear 50A on the outer ring 11A side (axially outer side) are substantially on the same plane.

[0038] The inner ring 12A is formed in an annular shape coaxial with the outer ring 11A. The inner ring 12A has an inner circumferential surface 12b extending with a constant inner diameter, an end face 12c facing outward in the axial direction, an inner ring rolling surface 12d inclined with respect to the axis O, and an end face 12e facing inward in the axial direction. The inner ring 12A is fitted and fixed to a first inner ring holding portion 34 of the first inner member 31.

[0039] The multiple tapered rollers 13A are arranged to roll freely between the outer ring 11A and the inner ring 12A, and revolve around the axis O while rolling on the outer ring raceway surface 11d of the outer ring 11A and on the inner ring rolling surface 12d of the inner ring 12A.

[0040] The retainer 14A is disposed between the outer ring 11A and the inner ring 12A, and rotatably holds a plurality of tapered rollers 13A accommodated in a plurality of pockets.

[0041] The inner diameter d of the annular protrusion 11f of the outer ring 11A is set smaller than the outer diameter D of the circle centered on the axis O passing through the point closest to the axis O on the outer peripheral surface 53A of the oscillating gear 50A (d < D). In other words, in the axial view, regardless of the eccentric phase of the first eccentric portion 43 (oscillating gear 50A), at least a radially partial portion of the annular protrusion 11f always overlaps a part of the side surface 52A of the oscillating gear 50A. Thus, the inner diameter d of the annular protrusion 11f is set smaller than the outer diameter D of the oscillating gear 50A when the first eccentric portion 43 is located closest to the inner diameter side. Therefore, it can be said that the outer ring 11A has an overlapping portion that overlaps the oscillating gear 50A even when the first eccentric portion 43 (oscillating gear 50A) is located closest to the inner diameter side when viewed in the axial direction.

[0042] Therefore, even when the first oscillating gear 50A oscillates and rotates due to the eccentric rotation of the first eccentric portion 43, the state where the first oscillating gear 50A and the outer ring 11A overlap in the radial direction is maintained. Thus, there is no possibility of interference between the outer corner portion 54A of the first oscillating gear 50A and the inner corner portion 11g of the annular protrusion 11f of the outer ring 11A, damage to both corner portions 54A, 11g can be prevented, smooth movement of the first oscillating gear 50A can be ensured, and the life of the speed reducer 1 can be extended.

[0043] Also, the distance L1 between the axially outer end face 11h of the annular protrusion 11f and the axially inner end face 12e of the inner ring 12A is set larger than the axial thickness L2 of the annular protrusion 11f (L1 > L2). Therefore, there is no possibility of contact between the outer ring 11A and the retainer 14A, and smooth rotation of the first tapered roller bearing 10A can be ensured. Furthermore, the cross-section of the retainer 14A can be enlarged, and the rigidity of the retainer 14A is improved.

[0044] (Modification example) FIG. 3 is an enlarged view of a first tapered roller bearing according to a modification example of the present invention. First tapered roller bearing 10A of this modification does not have an inner peripheral surface 11e (see FIG. 2), and differs from first tapered roller bearing 10A of the embodiment in that an annular protrusion 11f protruding inwardly is formed on the end of outer ring raceway surface 11d on the first oscillating gear 50A side (axially inner side). Other configurations and effects are similar to those of first tapered roller bearing 10A of the embodiment, so description will be omitted.

[0045] The present invention is not limited to the above-described embodiment and modified examples, and can be modified, improved, etc., as appropriate. For example, in the above-described embodiment, a tapered roller bearing is used as an example of the rolling bearing, but the present invention is not limited to a tapered roller bearing, and can be applied to other types of rolling bearings, such as ball bearings.

[0046] As described above, the present specification discloses the following: (1) an outer member having an inner diameter surface on which a plurality of pin grooves, in which internal tooth pins are rotatably held, are formed at regular intervals in the circumferential direction; an oscillating gear having external teeth on an outer diameter surface thereof, the external teeth being capable of meshing with the internal tooth pins, formed at regular intervals in the circumferential direction, the oscillating gear being fitted to an eccentric portion of the crankshaft and oscillatingly rotating in association with the rotation of the crankshaft; an inner member disposed axially to the side of the oscillating gear and rotatably supporting the crankshaft; a rolling bearing that rotatably supports the inner member relative to the outer member; A reducer comprising: the rolling bearing comprises an inner ring fitted onto the inside of the inner member, an outer ring fitted onto the inside of the outer member, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be able to roll freely; the outer ring has an overlapping portion that overlaps with the oscillating gear even when the eccentric portion is positioned at the innermost radial side when viewed in the axial direction, reducer.

[0047] According to this configuration, the oscillating gear and the outer ring are maintained in a state of being radially overlapped at any eccentric position of the oscillating gear, so that the outer corners of the oscillating gear do not interfere with the inner corners of the outer ring, thereby preventing contact damage between the outer ring and the oscillating gear and allowing the oscillating gear to move smoothly, thereby extending the life of the reducer.

[0048] (2) The outer ring has an annular protrusion formed on a side surface of the outer ring facing the oscillating gear, the annular protrusion protruding radially inward, an inner diameter of the annular protrusion portion is smaller than an outer diameter of the oscillating gear when the eccentric portion is located at the innermost side; The reducer according to (1).

[0049] According to this configuration, the oscillating gear and the annular protrusion of the outer ring are maintained in a radially overlapping state at any eccentric position of the oscillating gear, so that the outer corner of the oscillating gear does not interfere with the inner corner of the outer ring, thereby preventing contact damage between the outer ring and the oscillating gear and allowing the oscillating gear to move smoothly, thereby extending the life of the reducer.

[0050] (3) A distance L1 between an axially outer end face of the annular protrusion and an axially inner end face of the inner ring is greater than an axial thickness L2 of the annular protrusion. (2) The reducer according to the present invention.

[0051] According to this configuration, there is no risk of contact between the outer ring and the cage, and smooth rotation of the tapered roller bearing is ensured. Furthermore, the cross section of the cage can be made larger, improving the rigidity of the cage. [Explanation of symbols]

[0052] 1 Reducer 10A No. 1 tapered roller bearing (rolling bearing) 10B No. 2 tapered roller bearing (rolling bearing) 11A, 11B Outer ring 11f Circular protrusion 12A, 12B Inner ring 13A, 13B Rolling elements 14A, 14B retainer 20 Outer member 21 Pin groove 25 Internal tooth pin 30 Inner member 40 Crankshaft 43 1st eccentric part (eccentric part) 44 2nd eccentric part (eccentric part) 50A 1st oscillating gear (oscillating gear) 50B Second oscillating gear (oscillating gear) 51 Outer teeth D: Outer diameter of the oscillating gear when the eccentric part is located at the innermost side d Inner diameter of annular protrusion L1 Distance between the axially outer end face of the annular protrusion and the axially inner end face of the inner ring L2 Axial thickness of the annular protrusion

Claims

1. an outer member having an inner diameter surface on which a plurality of pin grooves, in which internal tooth pins are rotatably held, are formed at regular intervals in a circumferential direction; an oscillating gear having external teeth on an outer diameter surface thereof, the external teeth being capable of meshing with the internal tooth pins, formed at regular intervals in the circumferential direction, the oscillating gear being fitted to an eccentric portion of the crankshaft and oscillatingly rotating in association with the rotation of the crankshaft; an inner member disposed axially to the side of the oscillating gear and rotatably supporting the crankshaft; a rolling bearing that rotatably supports the inner member relative to the outer member; A reducer comprising: the rolling bearing comprises an inner ring fitted onto the inside of the inner member, an outer ring fitted onto the inside of the outer member, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be able to roll freely; the outer ring has an overlapping portion that overlaps with the oscillating gear even when the eccentric portion is positioned at the innermost radial side when viewed in the axial direction, reducer.

2. The outer ring has an annular protrusion formed on a side surface of the outer ring facing the oscillating gear, the annular protrusion protruding radially inward, an inner diameter of the annular protrusion portion is smaller than an outer diameter of the oscillating gear when the eccentric portion is located at the innermost side; The reducer according to claim 1 .

3. a distance L1 between an axially outer end face of the annular protrusion and an axially inner end face of the inner ring is greater than an axial thickness L2 of the annular protrusion; The reducer according to claim 2 .

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