EP4689449A1

EP4689449A1 - Planet gear mechanism

Info

Publication number: EP4689449A1
Application number: EP24730828.1A
Authority: EP
Inventors: Pixiang Lan
Original assignee: Timken Co
Current assignee: Timken Co
Priority date: 2023-06-29
Filing date: 2024-05-06
Publication date: 2026-02-11
Also published as: WO2025006061A1; CN121368691A

Abstract

A planet gear mechanism (112) includes a shaft pin (108), a bearing sleeve (114), thrust bearings (116A), and a planet gear (104). The shaft pin (108) includes a radially extending oil supply passage (122A), an axially extending oil reservoir (124), radially extending oil delivery passages (130), and a leak hole (126). The oil reservoir (124) is in fluid communication with the oil supply passage (122A), the oil delivery passages (130) are in fluid communication with the oil reservoir (124), and the leak hole (126) is in fluid communication with the oil reservoir (124). The bearing sleeve (114) includes openings (134) and a trough (136) in fluid communication with the openings (134). Each of the openings (134) is aligned with a corresponding oil delivery passage (130). The thrust bearings (116A) and the planet gear (104) are disposed about the shaft pin (108). The planet gear (104) is also disposed between the thrust bearings (116A).

Description

PLANET GEAR MECHANISM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63/511,003, filed June 29, 2023, the entire contents of which are incorporated by reference herein.

BACKGROUND

[0002] Wind power turbines commonly utilize planetary gear mechanisms. To gain higher power density and reduce production and maintenance costs, manufacturers of the bearings in the planetary gear mechanisms of wind power turbines are moving away from roller element bearings and toward journal and thrust bearings.

[0003] Further, oil supply is crucial for journal bearings. There is a possibility, however, that the main oil supply system (e g., the oil pump) can malfunction during the 20+ years of service life of the wind turbine. Once the main oil supply system is off, the wind turbine needs to urgently stop rotation to avoid damaging the internal components. Due to inertia, however, the turbine cannot stop immediately and instead will continue to run for some time. During this emergency stop window without a main oil supply, it can be crucial to have at least a minimum oil supply to protect components such as the journal bearings from severe wear and damage.

SUMMARY

[0004] In one aspect, embodiments disclosed herein relate to a planet gear mechanism including a shaft pin, a bearing sleeve, thrust bearings, and a planet gear. The shaft pin includes a radially extending oil supply passage, an axially extending oil reservoir, radially extending oil delivery passages, and a leak hole. The oil reservoir is in fluid communication with the oil supply passage, the oil delivery passages are in fluid communication with the oil reservoir, and the leak hole is in fluid communication with the oil reservoir. The bearing sleeve includes openings and a trough in fluid communication with the openings. Each of the openings is aligned with a corresponding oil delivery passage. The thrust bearings and the planet gear are disposed about the shaft pin. The planet gear is also disposed between the thrust bearings. [0005] In another aspect, embodiments disclosed herein relate to a planet gear mechanism including a shaft pin, a bearing sleeve, thrust bearings, and a planet gear. The shaft pin includes a first end, a second end, a central longitudinal axis, an oil supply passage, an oil reservoir, oil delivery passages, and a leak hole. The second end is opposite the first end. The central longitudinal axis extends through both the first end and the second end. The oil supply passage is located nearer to the second end than to the first end and extends in a direction transverse to the central longitudinal axis. The oil reservoir extends along the central longitudinal axis and is in fluid communication with the oil supply passage. Each oil delivery passage extends in a direction transverse to the central longitudinal axis and is in fluid communication with the oil reservoir. The bearing sleeve includes a trough and openings. The trough includes a planar surface. The openings extend through the planar surface of the trough in a direction transverse to the central longitudinal axis. Each opening is in fluid communication with a corresponding oil delivery passage. The planet gear is disposed about the bearing sleeve and is sized to allow oil from the trough to pass between the planet gear and the bearing sleeve. The thrust bearings are disposed about the shaft pin with the bearing sleeve and the planet gear between the thrust bearings. Each thrust bearing is positioned relative to the planet gear to allow oil to pass between the thrust bearing and the planet gear.

[0006] In another aspect, embodiments disclosed herein relate to a planet gear mechanism including a shaft pin, a bearing layer, and a planet gear. The shaft pin includes a first end, a second end, a central longitudinal axis, an oil reservoir, a plurality of oil delivery passages, and a leak hole. The second end is opposite the first end. The central longitudinal axis extends through the first and second ends. The oil supply passage is defined in the shaft pin at a location nearer to the second end than to the first end. The oil supply passage extends in a direction transverse to the central longitudinal axis. The oil reservoir is defined in the shaft pin. The oil reservoir extends along the central longitudinal axis and is in fluid communication with the oil supply passage. The plurality of oil delivery passages is defined in the shaft pin. Each oil delivery passage extends in a direction transverse to the central longitudinal axis. Each oil delivery passage is in fluid communication with the oil reservoir. The leak hole is defined in the first end of the shaft pin. The leak hole is in fluid communication with the oil reservoir. The bearing layer is deposited on the shaft pin. The bearing layer at least partially defines a trough. The trough is in fluid communication with the oil delivery passages. The planet gear is disposed about the bearing layer.

[0007] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates a front cross-sectional elevation view of a planetary gear box including a plurality of planet gear mechanisms surrounding a sun gear mechanism, according to embodiments disclosed herein.

[0009] FIG. 2 illustrates a side cross-sectional elevation view of a single planet gear mechanism of the planetary gear box of FIG. 1 during normal operation.

[0010] FIG. 3 illustrates a side cross-sectional elevation view of the single planet gear mechanism of FIG. 2 during a system shutdown.

[0011] FIG. 4 illustrates a perspective view of a bearing sleeve of the planet gear mechanism of FIG. 2.

[0012] FIG. 5 illustrates the performance of the planet gear mechanism of FIG. 2 in the form of a line graph plotting speed versus the maximum pressure of the oil.

[0013] FIG. 6 illustrates the performance of the planet gear mechanism of FIG. 2 in the form of a line graph plotting speed versus the minimum film thickness of the oil.

[0014] FIG. 7 illustrates the performance of the planet gear mechanism of FIG. 2 in the form of a line graph plotting speed versus an oil temperature rise.

[0015] FIG. 8 illustrates a side cross-sectional elevation view of a shaft pin and bearing sleeve of the single planet gear mechanism of FIG. 2.

[0016] FIG. 9 illustrates a side cross-sectional elevation view of a shaft pin and layer of material of a single planet gear mechanism, according to embodiments disclosed herein. [0017] FIG. 10 illustrates a perspective view of the shaft pin and layer of material of FIG. 9.

DETAILED DESCRIPTION

[0018] Before any embodiments are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

[0019] With reference to FIG. 1, a planetary gear box 100 includes a sun gear 102. A plurality of planet gears 104 engage the sun gear 102 and travel about the sun gear 102. The planet gears 104 are each mounted to a carrier 106 by corresponding shaft pins 108. The planet gears 104 also engage a ring gear 110 that surrounds them.

[0020] Turning now to FIG. 2, an embodiment of a planet gear mechanism 112 is shown. The planet gear mechanism 112 includes a planet gear 104, a shaft pin 108, a bearing sleeve 114, and a pair of thrust bearings 116a, 116b.

[0021] The shaft pin 108 is illustrated as a generally cylindrical pin. The shaft pin 108 includes a first end 118 and a second end 120. The second end 120 is opposite the first end 118. A central longitudinal axis Al extends through both the first end 118 and the second end 120.

[0022] An oil supply passage 122a, 122b is defined in the shaft pin 108 at a location nearer to the second end 120 than to the first end 118. In some embodiments, the oil supply passage 122a is defined in the shaft pin 108 generally adjacent the second end 120. The oil supply passage includes a first oil supply passage portion (e.g., a radially extending oil supply passage) 122a that extends in a direction transverse to the central longitudinal axis Al. In some embodiments, the first oil supply passage portion 122a extends in a radial direction, which is perpendicular to the central longitudinal axis Al. The oil supply passage further includes a second oil supply passage portion (e.g., an axially extending oil supply passage) 122b that extends in a direction along the central longitudinal axis Al. In some embodiments, the second oil supply passage portion 122b extends in a direction parallel to the central longitudinal axis Al, and further embodiments include the second oil supply passage portion 122b extending in a direction that is colinear with the central longitudinal axis Al (e.g., the second oil supply passage portion 122b may be defined along the centroid of the cylindrical shaft pin 108). A main oil supply system including a pump may supply oil to the first oil supply passage portion 122a, which in turn supplies the oil to the second oil supply passage portion 122b.

[0023] The planet gear mechanism 112 further includes an oil reservoir 124 defined in the shaft pin 108. The oil reservoir 124 extends along the central longitudinal axis Al (e.g., axially parallel to and/or colinear with the central longitudinal axis Al). The oil reservoir 124 receives oil from the second oil supply passage portion 122b and, in the illustrated embodiment, has a larger diameter than the second oil supply passage portion 122b. In some embodiments, the oil reservoir 124 is a cylindrical bore defined in the shaft pin 108. Such embodiments may further include the second oil supply passage portion 122b formed as a cylindrical bore. A method of manufacturing the shaft pin 108 may include drilling into the first end 118 of the shaft pin 108 to form the second oil supply passage portion 122b and the oil reservoir 124. The oil reservoir 124 may extend along a majority of the length of the shaft pin 108. In some embodiments, the planet gear mechanism 112 does not include a second oil supply passage portion 122b. Instead, the oil reservoir 124 receives oil from the first oil supply passage portion 122a. The oil reservoir 124, for instance, may meet the first oil supply passage portion 122a at a right angle.

[0024] The shaft pin 108 further includes a leak hole 126 defined in the shaft pin 108. In some embodiments, the opening in the first end 118 of the shaft pin 108 after drilling the second oil supply passage portion 122b and the oil reservoir 124 is covered with a plate or plug 128 disposed in or on the first end 118 of the shaft pin 108. The plate 128 may include the leak hole 126 defined therein, or the leak hole 126 may be defined at a location where the plate 128 meets the rest of the shaft pin 108 at the first end 118. The leak hole 126 is in fluid communication with the oil reservoir 124 such that excess oil in the oil reservoir 124 may escape through the leak hole 126 to eventually join an oil bath of the planetary gear box 100. In the illustrated embodiment, the leak hole 126 is off-center in the first end 118 of the shaft pin 108. Stated another way, the leak hole 126 extends in the direction of the central longitudinal axis Al at a distance therefrom (e.g., parallel to the central longitudinal axis Al). The diameter and length of the leak hole 126 can be chosen to minimally impact the pressure of the oil delivered through the planet gear mechanism 112. In some embodiments, the leak hole 126 has a diameter that is less than a third of the diameter of the oil reservoir 124. Some embodiments include the leak hole 126 having a diameter that is less than a fifth of the diameter of the oil reservoir 124.

[0025] The shaft pin 108 also includes at least two oil delivery passages 130 defined therein. Each oil delivery passage 130 extends in a direction transverse to the central longitudinal axis Al (e.g., radially perpendicular to the central longitudinal axis Al) and is in fluid communication with the oil reservoir 124. In the illustrated embodiment, the two oil delivery passages 130 extend parallel to each other.

[0026] As best shown in FIG. 4, the planet gear mechanism 112 further includes a bearing sleeve 114. The bearing sleeve 114 may be coupled to the shaft pin 108 in any appropriate manner (e g., press fit, keyed together, fastened together, or the like). In some embodiments, the bearing sleeve 114 may be 5 millimeters to 15 millimeters thick. In other embodiments, the bearing sleeve 114 may be less than 20 millimeters thick. The bearing sleeve 114 is disposed about the shaft pin 108 (as shown in FIG. 2). At least two openings 134 are defined in the bearing sleeve 114 through the thickness of the bearing sleeve 114. Each opening 134 is aligned with a corresponding one of the oil delivery passages 130 such that each opening 134 receives oil from the corresponding oil delivery passage 130. When the bearing sleeve 114 is disposed about the shaft pin 108 (FIG. 2), the openings 134 extend in a direction transverse to the central longitudinal axis Al (e.g., radially perpendicular to the central longitudinal axis Al).

[0027] The bearing sleeve 114 further includes a trough 136 defined therein. In the illustrated embodiment, the trough 136 is formed as a truncated portion of the otherwise cylindrical (or circular in cross-section) outer surface of the annular bearing sleeve 114. In some embodiments, the trough 136 includes a rectangular planar surface that is milled into the bearing sleeve 114. The openings 134 extend through this planar surface of the trough 136 such that the trough 136 receives oil from the openings 134. In the illustrated embodiment, the trough 136 has a length that is shorter than the length of the bearing sleeve 114 in a direction parallel to the central longitudinal axis Al.

[0028] The bearing sleeve 114 also includes first and second channels 138a, 138b defined therein. The channels 138a, 138b extend in a direction of the central longitudinal axis Al (e.g., parallel to the central longitudinal axis Al) from the trough 136 to a respective end of the bearing sleeve 114. In the illustrated embodiment, the channels 138a, 138b are also milled into the otherwise cylindrical (or circular in cross-section) outer surface of the annular bearing sleeve 114. The channels 138a, 138b are narrower than a width of the trough 136 and receive oil from the trough 136.

[0029] As shown in FIG. 2, the planet gear mechanism 112 further comprises a planet gear 104 disposed about the bearing sleeve 114. The planet gear 104 is sized such that oil is allowed to pass between the planet gear 104 and the bearing sleeve 114, thereby lubricating the interface for operation of the planetary gear box 100.

[0030] The planet gear 104 is buttressed on either side by first and second thrust bearings 116a, 116b. Each thrust bearing 116a, 116b is disposed about the shaft pin 108. In the illustrated embodiment, the bearing sleeve 114 is shorter along the central longitudinal axis Al than the planet gear 104 between the thrust bearings 116a, 116b. This arrangement, along with the channels 138a, 138b defined in the bearing sleeve 114, allows for oil to lubricate the interface between the planet gear 104 and the thrust bearings 116a, 116b in addition to the interface between the planet gear 104 and the bearing sleeve 114. The thrust bearings 116a, 116b, therefore, are positioned relative to the planet gear 104 such that oil is allowed to pass therebetween. The first channel 138a extends from the trough 136 toward the first thrust bearing 116a, and the second channel 138b extends from the trough 136 toward the second thrust bearing 116b.

[0031] In some embodiments, such as the illustrated embodiment, a common plane (such as the plane of the cross-sectional view in FIG. 2) intersects the central longitudinal axis Al, the first oil supply passage portion 122a, the second oil supply passage portion 122b, the oil reservoir 124, the leak hole 126, the oil delivery passages 130, the openings 134, the trough 136, and the channels 138a, 138b.

[0032] With reference to FIG. 2, under normal working conditions, the oil is supplied through an oil path originating at an oil pump, through the carrier 106, and into the shaft pin 108 via the first oil supply passage portion 122a. The oil then travels through the second oil supply passage portion 122b and into the oil reservoir 124. From the oil reservoir 124, the oil takes one of two paths to return to the oil bath in the planetary gear box 100. A first path is to exit the oil reservoir 124 via the leak hole 126. While the amount of oil exiting the leak hole 126 is relatively small compared to the other oil pathways, this path prevents over-pressurization of the system during normal working conditions and provides benefits during a shutdown condition (described in more detail below). The second path is through one or more of the oil delivery passages 130 and into the trough 136. The oil then travels along the interface between the bearing sleeve 114 and the planet gear 104 to eventually work toward one of the thrust bearings 116a, 116b, or the oil travels through one of the channels 138a, 138b toward the respective thrust bearing 116a, 116b. Once the oil reaches the thrust bearings 116a, 116b, it travels radially outwardly between the respective thrust bearing 116a, 116b and the planet gear 104 to then exit the planet gear mechanism 112 and join the oil bath in the planetary gear box 100.

[0033] The size and arrangement of the oil delivery passages 130, the openings 134, and the trough 136 allow for higher load carrying capacity and higher oil film thickness than previous designs. A potential drawback when increasing these metrics is a higher oil film temperature, especially at high relative speeds between the components being lubricated by the oil. Considering the high load and low sliding speed conditions for the planetary gear box 100 of a wind turbine, the higher load carrying capacity and higher oil film thickness is preferable. Performance metrics of the illustrated embodiment are represented in the line graphs plotting the rotational speed (RPMs) versus the maximum oil pressure (FIG. 5), the rotational speed versus the minimum oil film thickness (FIG. 6), and the rotational speed versus the increase in oil temperature (FIG. 7).

[0034] Turning now to FIG. 3, during an oil delivery system malfunction or other emergency shutdown condition, the present planet gear mechanism 112 is able to supply oil from the oil reservoir 124 by centrifugal force due to the movement of the planet gear mechanism 112. The diameter, depth, and location (such as near the boundary of the oil reservoir 124 diameter and opposite to the direction of the centrifugal force) of the leak hole 126 in the illustrated embodiment can allow air to pass through the leak hole 126 during this emergency shutdown condition when no (or very little) new oil is being supplied to the oil supply passage 122a, 122b. This air pathway helps prevent a vacuum condition inside the oil reservoir 124 and allows oil to continue to escape through the oil delivery passages 130 to lubricate the planet gear 104 and the thrust bearings 1 16a, 116b as shown by the arrows representing oil flow.

[0035] In some embodiments, instead of the bearing sleeve 114 discussed above being placed onto the shaft pin 108, a layer of material is directly applied to the shaft pin 108. As shown in FIG. 8, the bearing sleeve 114 described above has a greater thickness than might be necessary in some embodiments for wear protection of the shaft pin 108. This greater thickness may be necessary in some embodiments for the structural integrity of the bearing sleeve 114.

[0036] With reference to FIG. 9, however, a thinner layer of material 140 (compared to the bearing sleeve 114) is possible by depositing a coating of the material 140 directly onto the outer surface of the shaft pin 108. In some embodiments, the layer of material 140 may be 0.02 millimeters to 3 millimeters thick. In other embodiments, the layer of material 140 may be less than 5 millimeters thick. The layer of material 140 is deposited generally uniformly around the shaft pin 108 according to known material deposition techniques (e.g., chemical plating, electroplating, sputtering, or the like). In some embodiments, the layer of material 140 includes an appropriately wear-resistant material (e.g., copper alloy, high wear resistance polymer, or the like). The embodiment shown in FIG. 9 and 10 may be similar to the embodiment of FIGS. 2, 3, and 8, but the layer of material 140 replaces the bearing sleeve 114. The layer of material 140 may similarly include at least one of the opening, trough 136, and first and second channels 138a, 138b. To form these features, a manufacturer may mask off sections of the shaft pin 108 to prevent deposition of the layer of material 140 in the appropriate locations. In some embodiments, a manufacturer may remove some of all of the layer of material 140 in the appropriate locations to produce these features by, for instance, sanding, grinding, chemically dissolving, laser etching, or the like.

[0037] The embodiment shown in FIG. 10 includes the layer of material 140 removed or missing in locations corresponding to the trough 136 and first and second channels 138a, 138b. Stated another way, the layer of material 140 nearly completely surrounds the shaft pin 108 but is interrupted by the trough 136 and first and second channels 138a, 138b such that the layer of material 140 does not fully encircle the shaft pin 108 due to these features. The trough 136 and first and second channels 138a, 138b, therefore, may be said to be bordered by the layer of material 140. The floor of each of the trough 136 and first and second channels 138a, 138b may be formed by the curved outer surface of the shaft pin 108. In some embodiments, portions of the shaft pin 108 may be removed to form a flat floor of one or more of the trough 136 and first and second channels 138a, 138b. In such embodiments, the primary way of excluding the layer of material 140 for these features may be to mill the layer of material 140 away during the process of milling the shaft pin 108.

[0038] Various features and advantages of the invention are set forth in the following claims.

Claims

CLAIMS What is claimed is:

1. A planet gear mechanism comprising: a shaft pin including a radially extending oil supply passage defined in the shaft pin, an axially extending oil reservoir defined in the shaft pin, the oil reservoir in fluid communication with the oil supply passage, a plurality of radially extending oil delivery passages defined in the shaft pin, each oil delivery passage in fluid communication with the oil reservoir, and a leak hole defined in the shaft pin, the leak hole in fluid communication with the oil reservoir; a bearing sleeve disposed about the shaft pin, the bearing sleeve including a plurality of openings defined in the bearing sleeve, each opening aligned with a corresponding one of the oil delivery passages, and a trough defined in the bearing sleeve, the trough in fluid communication with the openings; first and second thrust bearings disposed about the shaft pin; and a planet gear disposed about the bearing sleeve and between the first and second thrust bearings.

2. The planet gear mechanism of claim 1, wherein the leak hole is defined in a longitudinal end of the shaft pin.

3. The planet gear mechanism of claim 2, wherein the leak hole is off-center in the longitudinal end of the shaft pin.

4. The planet gear mechanism of claim 1, further comprising an axially extending oil supply passage defined in the shaft pin, the axially extending oil supply passage in fluid communication with the radially extending oil supply passage.

5. The planet gear mechanism of claim 1, wherein the radially extending oil supply passage and the plurality of radially extending oil delivery passages all lie in a common plane.

6. The planet gear mechanism of claim 1, wherein a length of the trough is shorter than a length of the bearing sleeve.

7. The planet gear mechanism of claim 6, wherein the trough is rectangular.

8. The planet gear mechanism of claim 1, wherein the trough is formed as a truncated portion of an otherwise circular perimeter of the bearing sleeve.

9. A planet gear mechanism comprising: a shaft pin including a first end, a second end opposite the first end, a central longitudinal axis extending through the first end and the second end, an oil supply passage defined in the shaft pin at a location nearer to the second end than to the first end, the oil supply passage extending in a direction transverse to the central longitudinal axis, an oil reservoir defined in the shaft pin, the oil reservoir extending along the central longitudinal axis and in fluid communication with the oil supply passage, a plurality of oil delivery passages defined in the shaft pin, each oil delivery passage extending in a direction transverse to the central longitudinal axis, each oil delivery passage in fluid communication with the oil reservoir, and a leak hole defined in the first end, the leak hole in fluid communication with the oil reservoir; a bearing sleeve disposed about the shaft pin, the bearing sleeve including a trough defined in the bearing sleeve, the through including a planar surface, a plurality of openings defined in the bearing sleeve and extending through the planar surface in a direction transverse to the central longitudinal axis, each opening in fluid communication with a corresponding one of the oil delivery passages; a planet gear disposed about the bearing sleeve, the planet gear sized to allow oil from the trough to pass between the planet gear and the bearing sleeve; and first and second thrust bearings disposed about the shaft pin, the bearing sleeve and the planet gear disposed between the first and second thrust bearings, each of the first and second thrust bearings positioned relative to the planet gear to allow oil to pass therebetween.

10. The planet gear mechanism of claim 9, wherein the shaft pin is cylindrical.

11. The planet gear mechanism of claim 9, wherein the bearing sleeve further includes first and second channels defined therein, each of the first and second channels extending from the trough to a respective end of the bearing sleeve, the first channel extending toward the first thrust bearing and the second channel extending toward the second thrust bearing.

12. The planet gear mechanism of claim 11, wherein the bearing sleeve includes a cylindrical outer surface interrupted by the trough, the first channel, and the second channel.

13. The planet gear mechanism of claim 9, wherein the shaft pin includes a plug disposed in the first end, the plug covering the oil reservoir.

14. The planet gear mechanism of claim 13, wherein the leak hole is defined in the plug of the shaft pin.

15. The planet gear mechanism of claim 9, wherein the oil reservoir is a cylindrical bore defined in the shaft pin, and the oil reservoir extends colinearly with the central longitudinal axis of the shaft pin.

16. The planet gear mechanism of claim 9, wherein a plane intersects the central longitudinal axis, the oil supply passage, the oil reservoir, the delivery passages, the leak hole, the trough, and the openings.

17. The planet gear mechanism of claim 9, wherein the bearing sleeve is shorter along the central longitudinal axis than the planet gear.

18. The planet gear mechanism of claim 9, wherein each of the oil supply passage and the oil delivery passages extend in a direction perpendicular to the central longitudinal axis.

19. The planet gear mechanism of claim 9, wherein the planar surface of the trough is rectangular, and a length of the trough extends in a direction parallel to the central longitudinal axis.

20. The planet gear mechanism of claim 9, wherein the oil supply passage includes a first oil supply passage portion extending in the direction transverse to the central longitudinal axis and a second oil supply passage portion extending from the first oil supply passage portion to the oil reservoir in a direction along the central longitudinal axis.

21. A planet gear mechanism comprising: a shaft pin including a first end, a second end opposite the first end, a central longitudinal axis extending through the first end and the second end, an oil supply passage defined in the shaft pin at a location nearer to the second end than to the first end, the oil supply passage extending in a direction transverse to the central longitudinal axis, an oil reservoir defined in the shaft pin, the oil reservoir extending along the central longitudinal axis and in fluid communication with the oil supply passage, a plurality of oil delivery passages defined in the shaft pin, each oil delivery passage extending in a direction transverse to the central longitudinal axis, each oil delivery passage in fluid communication with the oil reservoir, and a leak hole defined in the first end, the leak hole in fluid communication with the oil reservoir; a bearing layer deposited on the shaft pin, the bearing layer at least partially defining a trough, the trough in fluid communication with the oil delivery passages; and a planet gear disposed about the bearing layer.

22. The planet gear mechanism of claim 21, wherein the trough is bordered by the bearing layer.

23. The planet gear mechanism of claim 22, wherein the trough extends radially through the bearing layer.

24. The planet gear mechanism of claim 21, wherein the bearing layer at least partially defines first and second channels extending from the trough to a respective end of the bearing layer.