Pin retaining mechanism and reducer

Abstract

The present invention provides a pin holding mechanism and a reducer. The pin holding mechanism comprises: a pin; and a holding member having a pin groove formed on its inner or outer periphery for holding the pin, and a fall-off prevention unit provided on at least one edge of the pin groove for preventing the pin from falling off.

Description

Technical Field

[0001] The invention relates to a pin holding mechanism and a speed reducer. Background Art

[0002] Rotating equipment such as industrial robots and machine tools uses a speed reducer to reduce the speed of a rotational drive source (see, for example, Patent Document 1).

[0003] The reducer described in Patent Document 1 comprises: an outer cylinder that also serves as a housing; a gear carrier that is rotatably supported within the outer cylinder; a plurality of crankshafts that are rotatably supported on the outer peripheral edge of the gear carrier; two swing gears that rotate in response to the rotation of the eccentric portions of the plurality of crankshafts; a plurality of internal tooth pins that are arranged in an area within the outer cylinder that is opposite to the outer peripheral surfaces of the two swing gears; and an input rotating body that inputs rotational power to the plurality of crankshafts. In this reducer, the input rotating body is connected to a rotational drive source such as a motor, and the gear carrier serves as an output rotating body coupled to a rotated body such as a turntable. In addition, two eccentric portions are provided on each crankshaft to cause the two swing gears to rotate in different phases (for example, a phase that is 180° offset).

[0004] In the area of ​​the inner circumference of the outer cylinder that is opposite to the outer circumference of the two swinging gears, a plurality of pin grooves extending in the axial direction are formed at predetermined intervals in the circumferential direction. The aforementioned plurality of internal tooth pins are rotatably arranged in each pin groove. External teeth having a smaller number of teeth than the number of pin grooves (the number of internal tooth pins) are formed on each outer circumference of the two swinging gears. If the two swinging gears rotate together with the eccentric portion of the crankshaft, during one rotation, each external tooth engages with the internal tooth pin while receiving a reaction force from the internal tooth pin, and rotates (rotates) in a direction opposite to the rotation direction by a predetermined pitch. At this time, the rotation (rotation) of the two swinging gears is transmitted to the gear carrier via the plurality of crankshafts. As a result, the rotation transmitted from the input rotating body to the crankshaft and the swinging gear is decelerated at a predetermined reduction ratio and output to the gear carrier.

[0005] Furthermore, the internally toothed pins disposed within the pin grooves of the outer cylinder are formed to span the axial length of the external teeth of both oscillation gears. In other words, approximately half of the axial area of ​​each internally toothed pin meshes with the external teeth of one oscillation gear, and approximately the remaining half of the axial area meshes with the external teeth of the other oscillation gear.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5798882 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The reducer described in Patent Document 1 varies the meshing depth between the external teeth and the internal pins depending on the rotational position of the oscillating gear. This leads to a point where a portion of the internal pin is no longer pressed by the external teeth, depending on the rotational position. At this point, a portion of the internal pin is removed from the pin groove, potentially tilting toward the oscillating gear. Furthermore, if the internal pin tilts toward the oscillating gear, the axial end of the internal pin will strongly collide with the external teeth of the oscillating gear, potentially damaging the external teeth.

[0011] In particular, in a speed reducer such as that described in Patent Document 1, where an internally toothed pin meshes with the external teeth of one oscillating gear and the external teeth of another oscillating gear, the internally toothed pin is simultaneously subjected to pressing forces of varying magnitude and direction from the external teeth of the two oscillating gears, which rotate in different phases. Consequently, as the two oscillating gears rotate, the internally toothed pin tends to tilt significantly, causing the axial end of the internally toothed pin to be strongly pressed against the external teeth of the oscillating gears.

[0012] Patent Document 1 also describes the application of a drum-like finishing process to the ends of the internal pins and external teeth. This drum-like finishing process can prevent the axial ends of the internal pins from strongly colliding with the external teeth of the swing gear when the internal pins are tilted. However, drum-like finishing increases the internal pin's displacement relative to the pin groove and the tilt angle during operation, potentially leading to unstable reducer operation.

[0013] The present invention provides a pin holding mechanism and a speed reducer capable of suppressing unstable behavior of a pin in a pin groove.

[0014] Solutions for solving problems

[0015] A pin holding mechanism according to a first aspect of the present invention comprises: a pin; and a holding member having a pin groove formed on an inner or outer periphery thereof, the pin groove holding the pin, and a fall-off preventing means for preventing the pin from falling off at least one edge of the pin groove.

[0016] According to the above configuration, the pin is prevented from falling out of the pin groove by the fall-off preventing means at the edge of the pin groove.

[0017] In the first aspect of the present invention, the pin may be an internally toothed pin, and the holding member may be a housing.

[0018] In the first aspect of the present invention, the pin may be an externally toothed pin, and the holding member may be a housing.

[0019] A second aspect of the present invention provides a speed reducer comprising an internally toothed pin and a housing having a pin groove formed on its inner periphery for holding the internally toothed pin, and a fall-off prevention unit for preventing the internally toothed pin from falling off at least one edge of the pin groove.

[0020] According to the above configuration, the pin is prevented from falling out of the pin groove by the fall-off preventing means at the edge of the pin groove.

[0021] In the second aspect of the present invention, the inner wall of the pin groove and the inner wall of the fall-off prevention unit may be formed in an arc shape to cover more than half of the circular cross section of the internal tooth pin in a direction perpendicular to the axial direction.

[0022] In this case, the inner tooth pin is covered with more than half of the outer circumference by the inner wall of the pin groove and the inner wall of the fall-off prevention unit, thereby allowing the inner tooth pin to rotate in the pin groove and more reliably preventing the inner tooth pin from falling out of the pin groove.

[0023] In the second aspect of the present invention, the fall-off prevention means may include a protrusion directed radially inward of the housing and formed integrally with the housing.

[0024] In the second aspect of the present invention, the fall-off prevention unit may be formed of a member independent of the housing.

[0025] Alternatively, the reducer of the above-mentioned second technical solution of the present invention includes a plurality of swing gears, each of which has external teeth with a smaller number of teeth than the number of grooves of the pin groove. The plurality of swing gears are arranged axially on the inner side of the housing and rotate while meshing with the internal tooth pins. The internal tooth pins are arranged in the pin grooves in a manner that independently meshes with the external teeth of each of the swing gears.

[0026] In this case, when the external teeth of one oscillating gear apply pressure to the internal pin, the pressure applied to that pin is prevented from affecting the other oscillating gears. This eliminates unnecessary frictional resistance during the rotation of the multiple oscillating gears, improving the power transmission efficiency of the reducer and suppressing heat generation due to frictional heat. Furthermore, in this case, since the internal pins do not engage across the external teeth of multiple oscillating gears, they are easily separated from the pin slots during the rotation of the oscillating gears. However, since the edges of each pin slot are provided with a fall-out prevention mechanism, this prevents the internal pins from falling out of the slots.

[0027] The reducer of the third technical solution of the present invention comprises: a housing having a plurality of pin grooves extending in the axial direction on the inner circumference; internal tooth pins, which are respectively arranged in the plurality of pin grooves; a plurality of swinging gears having external teeth with a smaller number of teeth than the number of grooves of the pin grooves, and the plurality of swinging gears are arranged axially on the inner side of the housing, and rotate while meshing with the internal tooth pins in accordance with the input rotation; and a fall-off prevention unit, which protrudes from the edge of each of the pin grooves toward the radial inner side of the housing, and is used to prevent each of the internal tooth pins from falling off, and a plurality of the internal tooth pins are arranged in each of the pin grooves in a manner that independently meshes with the external teeth of each of the swinging gears.

[0028] Effects of the Invention

[0029] The pin holding mechanism and the speed reducer described above can prevent the pin from falling out of the pin groove by utilizing the fall-off preventing means at the edge of the pin groove, thereby suppressing unstable behavior of the pin in the pin groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a longitudinal sectional view of the speed reducer according to the embodiment of the present invention.

[0031] Figure 2 The reducer of the embodiment of the present invention is Figure 1 A cross-sectional view obtained by enlarging a part of the image.

[0032] Figure 3 The reducer of the embodiment of the present invention Figure 2 III-direction view.

[0033] Description of Reference Numerals

[0034] 10. Reducer; 17. Outer cylinder (holding member, housing); 19A. 1st swing gear (swing gear); 19B. 2nd swing gear (swing gear); 19Aa, 19Ba, external teeth; 20A, 20B, internal tooth pins (pins); 60. Pin groove; 62. Holding protrusion (protrusion, fall-off prevention unit). DETAILED DESCRIPTION

[0035] Next, embodiments of the present invention will be described with reference to the drawings.

[0036] Figure 1 is a longitudinal sectional view of the speed reducer 10 according to this embodiment. Figure 2 It will Figure 1 A cross-sectional view showing a partially enlarged portion.

[0037] The speed reducer 10 is connected to a rotational drive source such as an electric motor (not shown) on the input side and to a rotated body (not shown) on the output side.

[0038] The reducer 10 includes: a fixed component not shown in the figure, which is installed on the equipment used; a first gear rack module 15A and a second gear rack module 15B, which are integrated with the fixed component; an outer cylinder 17 (retaining member, shell), which is rotatably supported on the outer peripheral side of the first gear rack module 15A and the second gear rack module 15B by means of a bearing 16; a plurality of (for example, three) crankshafts 18, which are rotatably supported on the first gear rack module 15A and the second gear rack module 15B; and a first swinging gear 19A and a second swinging gear 19B, which rotate together with the two eccentric parts 18a and 18b of each crankshaft 18.

[0039] The first gear rack module 15A in the form of a perforated circular plate is stacked on the fixed assembly, and the first gear rack module 15A is fixed to the fixed assembly as a whole by bolts or the like. Figure 1 The second gear rack module 15B is fixed to the lower surface of the gear rack module 15B by bolt fastening or the like. The second gear rack module 15B has a base plate portion 15Ba in the shape of an open circular plate and a plurality of pillar portions (not shown) extending from the end face of the base plate portion 15Ba toward the direction of the first gear rack module 15A. The end face of the pillar portion of the second gear rack module 15B is in contact with the end face of the first gear rack module 15A, and each pillar portion is fixed to the first gear rack module 15A. An axial gap is ensured between the base plate portion 15Ba of the second gear rack module 15B and the first gear rack module 15A. The first swing gear 19A and the second swing gear 19B are arranged in the gap.

[0040] Furthermore, the first swing gear 19A and the second swing gear 19B are provided with escape holes (not shown) through which the support columns of the second gear rack module 15B pass. The escape holes are formed to have an inner diameter sufficiently large relative to the support columns so that the support columns do not hinder the rotation of the first swing gear 19A and the second swing gear 19B.

[0041] The outer cylinder 17 is arranged across the outer circumferential surface of the first gear rack module 15A and the outer circumferential surface of the base plate portion 15Ba of the second gear rack module 15B. The two axial end portions of the outer cylinder 17 are rotatably supported on the base plate portions 15Ba of the first gear rack module 15A and the second gear rack module 15B by means of bearings 16. In addition, a plurality of pin grooves 60 extending parallel to the rotation center axis c1 of the outer cylinder 17 (extending in the axial direction) are formed on the inner circumferential surface of the axial central region of the outer cylinder 17 (the region opposite to the outer circumferential surface of the first swing gear 19A and the second swing gear 19B). The plurality of pin grooves 60 are arranged on the inner circumferential surface of the outer cylinder 17 at predetermined intervals in the circumferential direction. In each pin groove 60, a pair of substantially cylindrical internal tooth pins 20A, 20B (pins) are rotatably accommodated in the pair of internal tooth pins 20A, 20B. The end edges of both sides of each of the internal gear pins 20A and 20B in the axial direction are crowned.

[0042] The first and second oscillating gears 19A and 19B are arranged axially side by side on the inner side of the outer cylinder 17. The outer diameters of the first and second oscillating gears 19A and 19B are slightly smaller than the inner diameter of the outer cylinder 17. External teeth 19Aa and 19Ba are formed on the outer circumferences of the first and second oscillating gears 19A and 19B, respectively. These external teeth 19Aa and 19Ba mesh with and contact a plurality of internally toothed pins 20A and 20B arranged on the inner circumference of the outer cylinder 17. The number of external teeth 19Aa and 19Ba formed on the outer circumferences of the first and second oscillating gears 19A and 19B is set to be slightly less (for example, one less) than the number of pin grooves 60 formed in the outer cylinder 17 (the number of internally toothed pins 20A and 20B, respectively).

[0043] Furthermore, the internally toothed pin 20A on one side of the pin groove 60 located on the outer cylinder 17 side is formed to have an axial length approximately equal to the thickness (axial length) of the first swing gear 19A. The internally toothed pin 20B on the other side is formed to have an axial length approximately equal to the thickness (axial length) of the second swing gear 19B. The pair of internally toothed pins 20A and 20B, housed in the same pin groove 60, independently mesh with the external teeth 19Aa and 19Ba of the first and second swing gears 19A and 19B, respectively.

[0044] Multiple crankshafts 18 are arranged on the same circumference centered on the rotational axis c1 of the first gear rack module 15A and the second gear rack module 15B. Each crankshaft 18 is rotatably supported by the first gear rack module 15A and the second gear rack module 15B via a bearing 22. The eccentric portions 18a and 18b of each crankshaft 18 respectively penetrate the first swing gear 19A and the second swing gear 19B. Each eccentric portion 18a and 18b rotatably engages with a support hole 21 formed in the first swing gear 19A and the second swing gear 19B via an eccentric portion bearing 23.

[0045] In addition, the two eccentric portions 18a and 18b of each crankshaft 18 are eccentric in a manner that the phases are offset by 180° from each other around the axis of the crankshaft 18. In addition, in the present embodiment, the gear rack is composed of a first gear rack module 15A and a second gear rack module 15B. The first gear rack module 15A and the second gear rack module 15B are fixed relative to the first swing gear 19A and the second swing gear 19B in the rotation direction of the first swing gear 19A and the second swing gear 19B by means of a plurality of crankshafts 18. In the case of the present embodiment, the first gear rack module 15A and the second gear rack module 15B are integrated with the fixing component, so the first gear rack module 15A and the second gear rack module 15B do not rotate, and the first swing gear 19A and the second swing gear 19B do not rotate.

[0046] When the multiple crankshafts 18 are rotated in one direction by an external force, the eccentric portions 18a and 18b of the crankshafts 18 rotate in the same direction at a predetermined radius, and the first and second oscillating gears 19A and 19B rotate in the same direction at the same radius. At this time, the external teeth 19Aa and 19Ba of the first and second oscillating gears 19A and 19B, respectively, mesh with the multiple internal tooth pins 20A and 20B retained on the inner circumference of the outer cylinder 17.

[0047] In the speed reducer 10 of this embodiment, the number of external teeth 19Aa and 19Ba on the first and second oscillating gears 19A and 19B, respectively, is set slightly smaller than the number of internal tooth pins 20A and 20B on the outer cylinder 17. Therefore, during one rotation of the first and second oscillating gears 19A and 19B, the outer cylinder 17 is rotated by a predetermined pitch in the same direction as the rotation. As a result, the rotation of the crankshaft 18 is significantly reduced and transmitted to the outer cylinder 17. Furthermore, in this embodiment, the eccentric portions 18a and 18b of each crankshaft 18 are eccentrically offset 180° from each other about the axis, resulting in a 180° rotational phase shift between the first and second oscillating gears 19A and 19B.

[0048] At the end of the outer cylinder 17 on the side opposite to the fixed component ( Figure 1The output plate 26 is installed at the lower end of the second gear rack module 15B. The output plate 26 covers the end of the second gear rack module 15B in a non-contact state. Figure 1 The output plate 26 is provided with a cylindrical portion 27 that extends through the inner periphery of the second gear carrier module 15B, the second swing gear 19B, the first swing gear 19A, and the first gear carrier module 15A in a non-contact manner.

[0049] The first gear carrier module 15A rotatably supports a central gear 30 via a bearing 35B. The central gear 30 rotates in response to rotation from a rotation drive source (not shown). External teeth 30 a are formed on the outer periphery of the central gear 30 .

[0050] In addition, the end portion (upper end portion) of each crankshaft 18 passes through the first gear frame module 15A in the axial direction. A crankshaft gear 31 is installed at the end portion of each crankshaft 18 that passes through the first gear frame module 15A. The tooth surface 31a of each crankshaft gear 31 meshes with the outer teeth 30a of the central gear 30. If the power of the rotational drive source is input to the central gear 30, the rotation of the central gear 30 is transmitted to each crankshaft 18 via the crankshaft gear 31. In this way, when each crankshaft 18 rotates, the first swing gear 19A and the second swing gear 19B rotate as described above, and the rotation after being decelerated at the set reduction ratio is transmitted to the rotated body via the outer cylinder 17 and the output plate 26.

[0051] Figure 3 yes Figure 2 The reducer 10 is shown in the III direction.

[0052] like Figure 3 As shown, each pin groove 60 on the inner circumference of the outer cylinder 17 is formed in a roughly arc-like shape, enabling sliding contact with the outer circumference of the corresponding internally toothed pin 20A, 20B. Retaining protrusions 62 are formed on the left and right edges of each pin groove 60 in a direction perpendicular to the longitudinal (axial) direction (the width direction of each pin groove 60), projecting radially inward from the edge of the outer cylinder 17. These retaining protrusions 62, along with the pin groove 60, rotatably retain the corresponding internally toothed pin 20A, 20B. The pin groove 60 and its left and right retaining protrusions 62 are formed to continuously arcuately cover an area A (more than half of the outer circumference of the circular cross-section) of the corresponding internally toothed pin 20A, 20B in a direction perpendicular to the axial direction. The protruding ends 62a of the retaining protrusions 62, radially inward of the outer cylinder 17, are curved to avoid collision with the edges between the internally toothed pins 20A, 20B.

[0053] In the present embodiment, the holding projections 62 are continuously formed over substantially the entire region in the longitudinal direction of each pin groove 60. However, the holding projections 62 may be formed only on a portion of each pin groove 60 in the longitudinal direction.

[0054] In this embodiment, the pin retaining mechanism comprises internally toothed pins 20A and 20B (pins) and an outer cylinder 17 (housing) that retains these pins 20A and 20B via pin grooves 60 on its inner circumference. Furthermore, retaining protrusions 62 formed on the edges of the pin grooves 60 on the outer cylinder 17 serve as fall-off prevention means to prevent the internally toothed pins 20A and 20B from falling out.

[0055] As described above, the reducer 10 of this embodiment has retaining protrusions 62 formed on the left and right side edges of each pin groove 60 of the outer cylinder 17. The retaining protrusions 62 rotatably retain the corresponding internal gear pins 20A and 20B. Therefore, when the first swing gear 19A and the second swing gear 19B rotate, Figure 3 As shown, even if the first swing gear 19A and the second swing gear 19B are significantly separated from the inner circumferential surface of the outer cylinder 17, the retaining protrusion 62 can be used to limit the displacement of the internal tooth pins 20A and 20B from the pin groove 60. Therefore, it is possible to suppress the internal tooth pins 20A and 20B from being displaced or tilted in the direction of the first swing gear 19A and the second swing gear 19B. Therefore, when the reducer 10 of this embodiment is adopted, the axial ends of the internal tooth pins 20A and 20B can be prevented from strongly colliding with the external teeth 19Aa and 19Ba of the first swing gear 19A and the second swing gear 19B, thereby damaging the external teeth 19Aa and 19Ba. In addition, the movement of the internal tooth pins 20A and 20B can be reduced, thereby stabilizing the operation of the reducer 10.

[0056] Furthermore, the pin retaining mechanism employed in the reducer 10 of this embodiment includes a retaining projection 62 as a means for preventing the internal gear pins 20A and 20B from falling out of the pin groove 60 of the outer cylinder 17, which serves as a retaining member. Thus, when the pin retaining mechanism of this embodiment is employed, the internal gear pins 20A and 20B are prevented from falling out of the pin groove 60, thereby suppressing unstable movement of the internal gear pins 20A and 20B within the pin groove 60.

[0057] In addition, in the speed reducer 10 of this embodiment, the internal gear pins 20A and 20B are restricted from being disengaged from the pin grooves 60 by the retaining protrusions 62. Figure 3As shown, when the first and second oscillating gears 19A and 19B are significantly separated from the inner circumference of the outer cylinder 17, some of the internal gear pins 20A and 20B come out of contact with the external teeth 19Aa and 19Ba of the first and second oscillating gears 19A and 19B. At this point, some of the internal gear pins 20A and 20B stop rolling, suppressing the heat generated by rolling friction. Therefore, this configuration can suppress the heat generated during the operation of the speed reducer 10.

[0058] In particular, in the reducer 10 of this embodiment, the pin groove 60 and the retaining projection 62 protruding from the side edge of the pin groove 60 are formed so as to cover an area A of at least half of the circular cross-section of the internal gear pins 20A and 20B in a direction perpendicular to the axial direction. Therefore, while allowing rotation of the internal gear pins 20A and 20B, the retaining projection 62 can reliably restrict displacement of the internal gear pins 20A and 20B toward the first and second oscillating gears 19A and 19B.

[0059] Furthermore, in the reducer 10 of this embodiment, a pair of internally toothed pins 20A and 20B are arranged in each pin groove 60 of the outer cylinder 17 so as to independently mesh with the external teeth 19Aa and 19Ba of the first and second oscillating gears 19A and 19B, respectively. Therefore, when the external teeth of one of the first and second oscillating gears 19A and 19B press against the internally toothed pins, the pressing force applied to the internally toothed pins is prevented from acting on the external teeth of the other. This prevents the generation of unnecessary frictional resistance during operation of the reducer 10, and reduces the possibility of heating of the reducer 10 due to frictional heat.

[0060] Furthermore, when the inner tooth pins 20A and 20B are not engaged across the outer teeth 19Aa of the first swing gear 19A and the outer teeth 19Ba of the second swing gear 19B, the inner tooth pins 20A and 20B are easily separated from the outer teeth 19Aa and 19Ba. However, in the case of this embodiment, the displacement of each inner tooth pin 20A and 20B in the falling direction can be reliably limited by the retaining protrusion 62.

[0061] In addition, the present invention is not limited to the above-mentioned embodiment, and various design changes can be made without departing from the scope of the present invention.

[0062] For example, in the above-mentioned embodiment, the gear rack (the first gear rack module 15A and the second gear rack module 15B) is fixed and the outer cylinder 17 rotates as the output rotating body, but it can also be set to a structure in which the outer cylinder 17 is fixed and the gear rack (the first gear rack module 15A and the second gear rack module 15B) rotates as the output rotating body.

[0063] In the above embodiment, two oscillation gears (first oscillation gear 19A and second oscillation gear 19B) are provided that mesh with the internal tooth pins 20A and 20B of the outer cylinder 17 while rotating. However, the number of oscillation gears is not limited to two and can be arbitrary.

[0064] In the pin holding mechanism and reduction gear of the above-described embodiment, internally toothed pins 20A and 20B are held on the inner circumference of outer cylinder 17, serving as a holding member (housing), and external teeth 19Aa and 19Ba of first and second swing gears 19A and 19B, respectively, are meshed with the internally toothed pins 20A and 20B. However, a pin groove may be formed on the outer circumference of the holding member (housing), the externally toothed pins (pins) being held in the groove, and a swing gear having internal teeth may be rotatably disposed on the outer circumference of the holding member, with the internal teeth of the swing gear meshing with the externally toothed pins.

[0065] Furthermore, in the above-described embodiment, the retaining projection 62 (projection) serving as the fall-off preventing means is formed integrally with the edge of the pin groove 60. However, a separate fall-off preventing means (a fall-off preventing means formed of a member independent of the outer cylinder 17) having the function of preventing the pin from falling out of the pin groove 60 may be attached to the edge of the pin groove 60. Furthermore, in the above-described embodiment, the retaining projection 62 constituting the fall-off preventing means is disposed on the left and right edges of the pin groove 60. However, the fall-off preventing means may be disposed only on the edge of one side of the pin groove.

Claims

1. A reducer, wherein: The reducer has: a housing having a plurality of pin grooves extending in the axial direction on an inner circumference thereof; Internal tooth pins, which are respectively configured in the plurality of pin slots; a plurality of oscillating gears having external teeth having a smaller number of teeth than the number of grooves in the pin groove, the plurality of oscillating gears being arranged axially inside the housing and rotating while meshing with the corresponding internally toothed pins in the pin groove in response to input rotation; and A retaining protrusion protrudes from an edge of each pin groove in a direction perpendicular to its longitudinal direction toward the radial inner side of the housing, and a protruding end of the retaining protrusion on the radial inner side of the housing is formed into a curved shape in a manner away from the outer peripheral surface of the internal tooth pin, and the retaining protrusion is used to prevent each internal tooth pin from falling off. A plurality of the internally toothed pins are arranged in each of the pin grooves so as to independently mesh with the external teeth of each of the swing gears, and the holding protrusions are continuously formed over substantially the entire region in the longitudinal direction of each of the pin grooves.

2. The reducer according to claim 1, wherein: The holding protrusion holds the internal tooth pin in a non-contact state with the external teeth of the oscillation gear when the oscillation gear is largely separated from the inner peripheral surface of the housing.

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