Planetary gear mechanism

Abstract

This invention provides a planetary gear assembly comprising a planetary gear, a carrier pin supporting the planetary gear, and a plurality of needle rollers. The plurality of needle rollers are positioned between the carrier pin and the planetary gear. The carrier pin has a grease holding portion. The grease holding portion holds a semi-solid grease for lubricating the needle rollers.

Description

Technical Field

[0001] This invention relates to planetary gear mechanisms. Background Technology

[0002] Conventional planetary gear mechanisms are known, which include a sun gear, multiple planetary gears arranged around the sun gear, and an internal gear surrounding the multiple planetary gears. A planetary gear mechanism is a device that, by inputting rotational motion to the sun gear, causes the planetary gears to rotate and revolve, and outputs the revolute motion of the planetary gears, thereby slowing down the rotational motion. Conventional planetary gear mechanisms are described, for example, in Japanese Patent Application Publication No. 2017-53461.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-53461

[0004] In the planetary gear assembly disclosed in Japanese Patent Application Publication No. 2017-53461, a needle roller bearing composed of multiple rollers is used in the bearing of the planetary gear. Furthermore, the same publication describes providing a grease retention groove on the inner circumferential surface of the planetary gear to lubricate the needle roller bearing.

[0005] The needle rollers used in needle roller bearings are internally tangent to the inner circumferential surface of the planetary gear and externally tangent to the carrier pin supporting the planetary gear. Therefore, the needle rollers experience stronger contact pressure with the externally tangent carrier pin compared to their internally tangent relationship with the planetary gear. However, in the construction disclosed in Japanese Patent Application Publication No. 2017-53461, grease is supplied to the needle roller bearing from the planetary gear side. Therefore, it is difficult to adequately lubricate the area between the needle rollers and the carrier pin, which generates strong contact pressure. Summary of the Invention

[0006] The purpose of this invention is to provide a technique for effectively lubricating the needle rollers and the gear carrier pins that generate strong contact pressure in a planetary gear assembly.

[0007] The present invention is a planetary gear device comprising: a sun gear that rotates about a central axis; planetary gears that mesh with the sun gear radially outward; and an annular internal gear that meshes with the planetary gears radially outward, wherein the planetary gears rotate on their own axis about a planetary axis parallel to the central axis while revolving around the central axis. The planetary gear device further comprises: a carrier pin extending along the planetary axis and supporting the planetary gears; a plurality of needle rollers located between the carrier pin and the planetary gears; and a carrier that rotates together with the carrier pin about the central axis, the carrier pin having a grease retention portion for retaining a semi-solid grease for lubricating the needle rollers.

[0008] According to the present invention, grease can be supplied to the needle rollers from the side of the planetary gear, rather than from the side of the wheel carrier pin. Therefore, the needle rollers and wheel carrier pin, which generate strong contact pressure, can be well lubricated. Attached Figure Description

[0009] Figure 1 This is a longitudinal sectional view of the planetary gear device according to the first embodiment.

[0010] Figure 2 This is a plan view of the sun gear, multiple planetary gears, and planetary support of the first embodiment as seen from the input side.

[0011] Figure 3 This is a partial longitudinal sectional view of the planetary gear device according to the first embodiment.

[0012] Figure 4 This is a partial longitudinal sectional view of the planetary gear device according to the second embodiment.

[0013] Figure 5 This is a partial longitudinal sectional view of a modified planetary gear assembly.

[0014] Label Explanation

[0015] 1: Planetary gear assembly; 10: Sun gear; 11: Input shaft; 12: External gear; 20: Planetary gear; 21: External gear; 22: Pin hole; 30: Planetary support; 31: Gear carrier; 32: Gear carrier pin; 33: Through hole; 34: Needle roller bearing; 35: Washer; 37: Bearing; 40: Internal gear; 41: Internal gear; 50: Housing; 60: Output shaft; 70: Needle roller; 71: First needle roller; 72: Second needle roller; 80: Grease holder; 81: First hole; 82: Second hole; 83: First groove; 84: Second groove; 91: Central axis; 92: Planetary axis; 811: First opening; 821: Second opening. Detailed Implementation

[0016] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In this application, the direction parallel to the central axis of the sun gear is referred to as the "axial direction," the direction perpendicular to the central axis is referred to as the "radial direction," and the direction along an arc centered on the central axis is referred to as the "circumferential direction." However, the aforementioned "parallel direction" also includes substantially parallel directions. Furthermore, the aforementioned "perpendicular direction" also includes substantially perpendicular directions.

[0017] Additionally, in the following explanation, Figure 1 The right side of the input is called the "input side". Figure 1 The left side of the symbol is called the "output side".

[0018] <1. First Embodiment>

[0019] <1-1. Overall Structure of Planetary Reducer>

[0020] Figure 1 This is a longitudinal sectional view of the planetary gear device 1 according to the first embodiment. The planetary gear device 1 is a device that reduces rotational motion from a motor input at a first rotational speed to a second rotational speed lower than the first speed and outputs it. The planetary gear device 1 is used, for example, in various industrial equipment such as industrial robots or packaging machines. However, the planetary gear device 1 can also be used in other devices such as robot joints, auxiliary kits, and unmanned transport trolleys.

[0021] like Figure 1 As shown, the planetary gear device 1 of this embodiment has a sun gear 10, a plurality of planetary gears 20, a planetary support 30, an internal gear 40, a housing 50, and an output shaft 60.

[0022] The sun gear 10 is a gear arranged along the central axis 91. The sun gear 10 is connected to a motor, which serves as the drive source, via an input shaft 11. The input shaft 11 is rotatably supported on the housing 50 via bearings (not shown). The input shaft 11 and the sun gear 10 rotate about the central axis 91 at a first rotational speed before deceleration, driven by a driving force input from the motor. A plurality of external teeth 12 are provided on the outer circumferential surface of the sun gear 10. These external teeth 12 are arranged at a certain angular interval about the central axis 91. Each external tooth 12 protrudes radially outward from the outer circumferential surface of the sun gear 10.

[0023] Planetary gear 20 is a gear located radially outside of sun gear 10. Figure 2 This is a plan view of the sun gear 10, multiple planetary gears 20, and planetary support 30 from the input side. However, in Figure 2 To avoid complicating the diagram, the teeth of each gear are omitted. For example... Figure 2 As shown, in this embodiment, three planetary gears 20 are arranged at equal intervals around the sun gear 10. However, the planetary gear device 1 may have one to two planetary gears 20, or four or more.

[0024] Each planetary gear 20 has a central pin hole 22. A carrier pin 32 (described later) and a needle roller bearing 34 are inserted into the pin hole 22. Each planetary gear 20 is supported by the carrier pin 32 and the needle roller bearing 34 so that it can rotate about a planetary axis 92 that is parallel to the central axis 91.

[0025] The planetary gear 20 has multiple external teeth 21 on its outer circumferential surface. These external teeth 21 are spaced at a certain angle around the planetary axis 92. Each external tooth 21 protrudes outward from the outer circumferential surface of the planetary gear 20. The external teeth 12 of the sun gear 10 mesh with the external teeth 21 of the planetary gear 20.

[0026] The planetary support 30 is a unit that supports multiple planetary gears 20. The planetary support 30 has a wheel carrier 31 and multiple wheel carrier pins 32. The wheel carrier 31 is coaxially arranged with the central axis 91. A bearing 37 is sandwiched between the inner circumferential surface of the housing 50 and the wheel carrier 31. The wheel carrier 31 is supported by the bearing 37 so that it can rotate about the central axis 91.

[0027] The wheel carrier 31 has multiple through holes 33. Each through hole 33 is a radially penetrating hole through the wheel carrier 31. The multiple through holes 33 are equally spaced about a central axis 91. Multiple wheel carrier pins 32 are arranged at circumferential intervals. Each wheel carrier pin 32 extends axially along a planetary axis 92 within a through hole 33. Both axial ends of the wheel carrier pins 32 are fixed to the wheel carrier 31. The wheel carrier pins 32 are fixed relative to the wheel carrier 31 by, for example, press-fitting.

[0028] Planetary gear 20 is disposed within the through hole 33 of the wheel carrier 31. Furthermore, planetary gear 20 is rotatably supported on the wheel carrier pin 32 via needle roller bearing 34. Therefore, planetary gear 20 can rotate about its own axis 92 while supported by the wheel carrier pin 32 and needle roller bearing 34. Additionally, planetary gear 20, together with the wheel carrier 31, wheel carrier pin 32, and needle roller bearing 34, can revolve around the central axis 91.

[0029] The internal gear 40 is a ring-shaped gear that meshes with the planetary gears 20 radially outside the planetary gears 20. The internal gear 40 is coaxially arranged with the central axis 91. The internal gear 40 has multiple internal teeth 41. The multiple internal teeth 41 are arranged at a certain angular interval with the central axis 91 as the center. Each internal tooth 41 protrudes radially inward from the inner circumferential surface of the internal gear 40. The external teeth 21 of the aforementioned planetary gears 20 mesh with the internal teeth 41 of the internal gear 40.

[0030] The outer casing 50 is a housing that internally houses the sun gear 10, the plurality of planetary gears 20, and the planetary support 30. The outer casing 50 has a generally cylindrical shape centered on the central axis 91. In this embodiment, the internal gear 40 and the outer casing 50 are formed as a single unit. However, the internal gear 40 and the outer casing 50 may also be separate components. The outer casing 50 is fixed to the frame of the device that is driven. Therefore, even when the planetary gear assembly 1 is driven, the outer casing 50 and the internal gear 40 remain stationary.

[0031] The output shaft 60 is a cylindrical component arranged along the central axis 91. The output shaft 60 rotates together with the wheel carrier 31 about the central axis 91. In this embodiment, the wheel carrier 31 and the output shaft 60 are formed as a single component. However, the wheel carrier 31 and the output shaft 60 may also be separate components.

[0032] When the sun gear 10 rotates at the first rotational speed, the planetary gear 20 rotates around its axis 92 by meshing with the sun gear 10. Additionally, the planetary gear 20 revolves around the sun gear 10 along the internal gear 40 by meshing with the internal gear 40. That is, the multiple planetary gears 20 rotate around their axes 92 and revolve around the central axis 91 simultaneously. At this time, the rotational speed of the planetary gear 20 around the central axis 91 is a second rotational speed, lower than the first rotational speed.

[0033] Furthermore, when the planetary gear 20 revolves at a second rotational speed, the multiple gear carrier pins 32, the gear carrier 31, and the output shaft 60 also rotate at a second rotational speed around the central axis 91. Therefore, the reduced rotational motion at the second rotational speed can be extracted from the output shaft 60.

[0034] <1-2. Regarding the retaining structure of lubricating grease>

[0035] Next, the grease retention structure in the planetary gear 20 described above will be explained. Figure 3 It is near planetary gear 20 ( Figure 1 A partial longitudinal sectional view of the planetary gear assembly 1 in region A).

[0036] like Figure 3 As shown, the needle roller bearing 34 is located between the wheel carrier pin 32 and the planetary gear 20. The needle roller bearing 34 has a plurality of needles 70. The needles 70 are cylindrical metal parts extending axially. The plurality of needles 70 are arranged in a ring around the planetary axis 91. When the planetary gear device 1 is driven, these plurality of needles 70 need to be adequately lubricated. Therefore, in this embodiment, grease is held in the grease holding portion 80 provided on the wheel carrier pin 32. The grease is a semi-solid oil.

[0037] The grease retention portion 80 is a hole extending from a first opening 811 provided on the outer peripheral surface of the wheel carrier pin 32 toward the interior of the wheel carrier pin 32. Specifically, the grease retention portion 80 has a first hole 81 and a second hole 82. The first hole 81 extends from the first opening 811 toward the planetary axis 92. The second hole 82 extends axially from the first hole 81 to a second opening 821 provided on the axial end face of the wheel carrier pin 32. That is, the first hole 81 and the second hole 82 form a generally L-shaped through hole. Grease is retained inside the first hole 81 and the second hole 82.

[0038] When the planetary gear unit 1 is driven, the grease held in the grease holder 80 is supplied to the plurality of needle rollers 70 through the first opening 811. The grease is supplied from the grease holder 80 to the needle rollers 70 by the centrifugal force accompanying the revolution of the wheel carrier pin 32 around the central axis 91, or by the negative pressure generated near the needle rollers 70 due to their rolling motion. Furthermore, the grease supplied to the needle rollers 70 expands circumferentially and axially with the rolling motion of the plurality of needle rollers 70. Thus, the plurality of needle rollers 70 are lubricated. As a result, the rotational motion of the planetary gear 20 around the wheel carrier pin 32 proceeds smoothly.

[0039] In this planetary gear assembly 1, a semi-solid grease is used instead of liquid oil. This allows the grease to be retained without flowing out of the grease holding section 80. Therefore, an oil seal is not required, thus reducing the number of components in the planetary gear assembly 1. Specifically, in the test method of JIS K 2220, a grease with a consistency of 340 or less is preferably used.

[0040] The needle roller 70 is internally tangent to the planetary gear 20. That is, the outer circumferential surface of the needle roller 70 contacts the inner circumferential surface of the planetary gear 20. Additionally, the needle roller 70 is externally tangent to the wheel carrier pin 32. That is, the outer circumferential surface of the needle roller 70 contacts the outer circumferential surface of the wheel carrier pin 32. The externally tangent portion generates a stronger contact pressure compared to the internally tangent portion. Therefore, when the planetary gear unit 1 is driven, a stronger contact pressure is generated between the needle roller 70 and the wheel carrier pin 32 than between the needle roller 70 and the planetary gear 20.

[0041] Therefore, in this planetary gear assembly 1, grease is supplied to the needle rollers 70 not from the planetary gears 20, but from the grease retaining portion 80 provided on the wheel carrier pin 32. In this way, the needle rollers 70 and the wheel carrier pin 32, which generate strong contact pressure, can be lubricated more effectively.

[0042] Furthermore, in this embodiment, no holes or grooves are formed on the outer peripheral surface of the wheel carrier pin 32, except for the first opening 811. Therefore, it is possible to ensure that the area on the outer peripheral surface of the wheel carrier pin 32 that can contact the needle roller 70 is large. Thus, it is possible to suppress the reduction of the supporting force of the wheel carrier pin 32 on the needle roller 70.

[0043] When the planetary gear assembly 1 is driven, the two end faces of the outer circumferential surface of the wheel carrier pin 32 relative to the central axis 91 (in) Figure 2The portion indicated by reference numeral 321 generates a particularly strong supporting force between itself and the needle rollers 70. That is, these two end faces 321 become particularly important support surfaces for supporting the multiple needle rollers 70. Therefore, the first opening 811 is preferably provided in a position on the outer peripheral surface of the wheel carrier pin 32 that avoids the aforementioned two end faces 321. In this way, it is possible to suppress the reduction of the supporting force on the aforementioned two end faces 321 of the wheel carrier pin 32.

[0044] In this embodiment, a first opening 811 is provided on the radially outer end face of the outer peripheral surface of the wheel carrier pin 32 relative to the central axis 91. Thus, when the planetary gear assembly 1 is driven, the centrifugal force generated by the revolution of the wheel carrier pin 32 around the central axis 91 allows grease to be supplied to the needle rollers 70 through the first opening 811. Therefore, the supply of grease from the grease holding portion 80 to the needle rollers 70 can be further facilitated.

[0045] like Figure 3 As shown, the plurality of needle rollers 70 in this embodiment includes a plurality of first needle rollers 71 and a plurality of second needle rollers 72. The plurality of first needle rollers 71 are arranged in a ring around the planetary axis 92. The plurality of second needle rollers 72 are also arranged in a ring around the planetary axis 92. In addition, the plurality of first needle rollers 71 and the plurality of second needle rollers 72 are adjacent to each other in the axial direction. In this way, if the needle rollers 70 are arranged in two rows, the tilting amount of each needle roller 70 relative to the axial direction can be suppressed. Therefore, poor lubrication caused by the tilting of the needle rollers 70 can be suppressed.

[0046] Furthermore, in this embodiment, the first opening 811 opens towards the boundary between the first needle roller 71 and the second needle roller 72. That is, the first opening 811 is provided on the portion of the outer peripheral surface of the wheel carrier pin 32 where the first needle roller 71 and the second needle roller 72 would not normally be in contact. In this way, the first opening 811 can be provided on the outer peripheral surface of the wheel carrier pin 32, and the reduction of the contact area between the first needle roller 71 and the second needle roller 72 and the wheel carrier pin 32 is minimized.

[0047] Furthermore, the grease holding portion 80 of this embodiment has not only a first hole 81, but also a second hole 82. Therefore, compared to the case where the grease holding portion 80 is only composed of a first hole 81, more grease can be held in the grease holding portion 80.

[0048] like Figure 3 As shown, the second hole 82 is inclined relative to the planetary axis 92. The radial position of the second hole 82 gradually moves radially outward as it approaches the first hole 81. Thus, the grease held in the second hole 82 moves towards the first hole 81 due to the centrifugal force accompanying the revolution of the wheel carrier pin 32 relative to the central axis 91. Therefore, when the planetary gear unit 1 is driven, grease can be supplied more effectively from the second hole 82 to the plurality of needle rollers 70 via the first hole 81.

[0049] The centrifugal force applied to the grease held in the first hole 81 and the second hole 82 varies depending on the drive speed of the planetary gear unit 1. Therefore, the amount of grease supplied from the grease holding section 80 to the needle roller 70 can be adjusted according to the drive speed of the planetary gear unit 1. Specifically, the amount of grease supplied can be reduced during low-speed driving and increased during high-speed driving. That is, as the necessity for lubricating the needle roller 70 increases, the supply of grease can be further promoted.

[0050] Furthermore, in this embodiment, the second hole 82 of the grease retention portion 80 extends to a second opening 821 provided on the end face of the wheel carrier pin 32 on the input side (axial side). Therefore, grease can be replenished into the second hole 82 through the second opening 821. In particular, as... Figures 1-3 As shown, the second hole 82 is exposed on the input side end face of the wheel carrier 31. Therefore, grease can be added to the second hole 82 through the second opening 821 without disassembling the wheel carrier 31, wheel carrier pin 32, needle roller bearing 34, and planetary gear 20. This reduces the burden on the user for grease replenishment.

[0051] Furthermore, in this embodiment, the output side (the other side of the axial direction) end face of the wheel carrier pin 32 is axially opposed to the bearing 37. The second opening 821 is not provided on the output side end face of the wheel carrier pin 32, but on the input side end face. Therefore, the wheel carrier 31 and the bearing 37 will not separate, and grease can be replenished to the second hole 82 through the second opening 821.

[0052] <2. Second Implementation>

[0053] Next, the second embodiment of the present invention will be described. Furthermore, the following description will focus on the differences from the first embodiment, and repeated descriptions of the parts identical to those in the first embodiment will be omitted. Figure 4 This is a partial longitudinal sectional view of the planetary gear device 1 according to the second embodiment.

[0054] The structure of the grease holding part 80 of the planetary gear device 1 in this embodiment differs from that in the first embodiment. For example... Figure 4 As shown, the grease holding part 80 in this embodiment is a groove provided on the outer peripheral surface of the wheel frame pin 32.

[0055] The grease holding portion 80 of this embodiment has a first groove 83 and a second groove 84. The first groove 83 is a spiral groove provided on the outer peripheral surface of the wheel carrier pin 32. The second groove 84 is an annular groove provided on the outer peripheral surface of the wheel carrier pin 32. The second groove 84 is located opposite the boundary portion of the first needle roller 71 and the second needle roller 72. The first groove 83 extends spirally from the second groove 84 towards both sides in the axial direction.

[0056] When forming the grease-retaining portion 80 on the outer peripheral surface of the wheel carrier pin 32, firstly, a second annular groove 84 is formed on the outer peripheral surface of the wheel carrier pin 32 by cutting. Then, starting from the second groove 84, a first spiral groove 83 is formed on both sides in the axial direction by cutting. This allows the first spiral groove 83 to be easily formed. Furthermore, by forming the first groove 83 in a spiral shape, the number of grooves can be reduced while providing grooves over a wider range on the outer peripheral surface of the wheel carrier pin 32.

[0057] Grease is retained inside the first groove 83 and the second groove 84. Therefore, when the planetary gear unit 1 is driven, grease is supplied to the needle roller 70 from the first groove 83 and the second groove 84. With the configuration of this embodiment, grease can be supplied to the needle roller 70 from a wider range of the outer peripheral surface of the wheel carrier pin 32 compared to the first embodiment. However, in this embodiment, since the first groove 83 and the second groove 84 are provided on the outer peripheral surface of the wheel carrier pin 32, the contact area between the wheel carrier pin 32 and the needle roller 70 is smaller. Therefore, from the viewpoint of ensuring the supporting force between the wheel carrier pin 32 and the needle roller 70, the configuration of the first embodiment is more preferable.

[0058] Furthermore, in this embodiment, the annular second groove 84 also faces the boundary between the first needle roller 71 and the second needle roller 72. That is, the second groove 84 is provided on the portion of the outer peripheral surface of the wheel carrier pin 32 where the first needle roller 71 and the second needle roller 72 would not normally be in contact. In this way, the second groove 84 can be provided, and the reduction of the contact area between the first needle roller 71 and the second needle roller 72 and the wheel carrier pin 32 is minimized.

[0059] In addition, such as Figure 4 As shown, the planetary gear assembly 1 has a pair of washers 35 on each planetary gear 20. One of the washers 35 is located between the input end (one axial end) of the first needle roller 71 and the gear carrier 31. The other of the washers 35 is located between the output end (the other axial end) of the second needle roller 72 and the gear carrier 31. Each washer 35 has an annular shape centered on the planetary axis 92. The hardness of the washer 35 is higher than that of the gear carrier 31.

[0060] By providing such a washer 35, direct sliding between the planetary gear 20 and the wheel carrier 31 can be prevented. In addition, wear on the wheel carrier 31 due to the pressing pressure from the needle roller 70 can be suppressed.

[0061] like Figure 4 As shown, in this embodiment, the spiral-shaped first groove 83 extends from a position in the same axial direction as one washer 35 to a position in the same axial direction as the other washer 35. Therefore, grease is provided not only to the needle roller 70 but also to the pair of washers 35. This further improves the sliding properties of the planetary gear 20, the washers 35, and the gear carrier 31.

[0062] <3. Variations>

[0063] The first and second embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above.

[0064] Figure 5 This is a partial longitudinal sectional view of a planetary gear assembly, a variation of the first embodiment. Figure 5 In this example, the grease holding portion 80 of the wheel carrier pin 32 has a first hole 81 and a pair of second holes 82. One of the pair of second holes 82 extends from the end of the first hole 81 toward the input side (axial side), similar to the first embodiment described above. The other of the pair of second holes 82 extends from the end of the first hole 81 toward the output side (axial side). Thus, by expanding the extent of the second holes 82, more grease can be held in the grease holding portion 80.

[0065] In the first embodiment, the second embodiment and the above-described embodiment Figure 5 In any of the variations, the grease holding portion 80 is provided at least within a range from the center of the planetary gear 20 along its axial direction to the end of the planetary gear 20 on the input side (axial side). In this way, by ensuring the axial range of the grease holding portion 80, a larger amount of grease can be retained in the grease holding portion 80.

[0066] However, the grease retention portion of the present invention does not necessarily need to be provided within such a range. For example, in the construction of the first embodiment, the second hole 82 may be omitted, and the grease retention portion 80 may be formed only by the first hole 81.

[0067] Furthermore, the shapes of the detailed parts of the planetary gear assembly may differ from those shown in the figures of this application. Additionally, the elements appearing in the above-described embodiments and variations may be selected selectively without causing contradictions.

[0068] Industrial availability

[0069] This invention can be used in planetary gear systems.

Claims

1. A planetary gear device, comprising: a sun gear that rotates about a central axis; and a ring gear that meshes with the planetary gear on a radially outer side of the planetary gear, wherein the planetary gear revolves around the central axis while rotating about a planetary axis that is parallel to the central axis, the planetary gear device further comprising: a carrier pin that extends along the planetary axis to support the planetary gear; a plurality of needles that are interposed between the carrier pin and the planetary gear; and a carrier that rotates about the central axis together with the carrier pin, the plurality of needles comprising: a plurality of first needles that are arranged in a ring shape about the planetary axis; and a plurality of second needles that are arranged in a ring shape about the planetary axis axially adjacent to the plurality of first needles, the carrier pin having a grease holding portion that holds grease in a semi-solid shape for lubricating the needles, the grease holding portion including: a first helical groove provided on an outer peripheral surface of the carrier pin; and a second ring-shaped groove provided on the outer peripheral surface of the carrier pin, the second groove facing the boundary portions of the first needles and the second needles, the first groove extending from the second groove to both axial sides, both end portions of the carrier pin in the axial direction being press-fitted into the carrier, the planetary gear device further comprising a pair of washers, one of the pair of washers being interposed between one end of the first needles in the axial direction and the carrier, the other of the pair of washers being interposed between the other end of the second needles in the axial direction and the carrier, the first groove extending from the same axial position as the one washer to the same axial position as the other washer.

2. A planetary gear device, comprising: a sun gear that rotates about a central axis; and a ring gear that meshes with the planetary gear on a radially outer side of the planetary gear, wherein the planetary gear revolves around the central axis while rotating about a planetary axis that is parallel to the central axis, the planetary gear device further comprising: a carrier pin that extends along the planetary axis to support the planetary gear; a plurality of needles that are interposed between the carrier pin and the planetary gear; and a carrier that rotates about the central axis together with the carrier pin, the carrier pin having a grease holding portion that holds grease in a semi-solid shape as a lubricating material for lubricating the needles, the grease holding portion having: a first hole that extends from a first opening provided on an outer peripheral surface of the carrier pin toward the planetary axis; and a second hole that extends from the first hole in the axial direction, the first hole being open on the outer peripheral surface of the carrier pin, one end of the second hole being connected to the first hole, and the other end of the second hole being exposed and open at the other end of the carrier pin, the second hole being an inclined hole with respect to the planetary axis. a planet gear meshing with the sun gear radially outside the sun gear; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a planet gear meshing with the sun gear radially outside the sun gear; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The radial position of the second hole gradually approaches the radially outer side as it approaches the first hole.

3. The planetary gear device according to claim 1 or 2, wherein The consistency of the grease based on the test method of JIS K 2220 is 340 or less.

4. The planetary gear device according to claim 1 or 2, wherein The grease holding portion is provided at least in a range from the axial center of the planetary gear to one end portion in the axial direction of the planetary gear.

5. The planetary gear device according to claim 2, wherein The first opening is located at a position other than both end surfaces in the circumferential direction with respect to the central axis in the outer peripheral surface of the carrier pin.

6. The planetary gear device according to claim 5, wherein The first opening is located at an end surface on the radially outer side with respect to the central axis in the outer peripheral surface of the carrier pin.

7. The planetary gear device according to claim 5, wherein The plurality of needle rollers have: A plurality of first needle rollers arranged in a circular ring shape with the planetary axis as the center; and A plurality of second needle rollers arranged in a circular ring shape with the planetary axis as the center, axially adjacent to the plurality of first needle rollers, The first opening opens toward a boundary portion of the first needle rollers and the second needle rollers.

8. The planetary gear device according to claim 2, wherein The second hole extends to a second opening provided at an end surface in the axial direction of the carrier pin.

9. The planetary gear device according to claim 1, wherein The gasket is in a circular ring shape.

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