Work machine and transfer device

Abstract

This transfer device comprises an input shaft, a planetary gear mechanism, a driving gear, a driven gear, an output shaft, a first shaft bearing, a second shaft bearing, a first boss bearing, a second boss bearing, and a transfer case. The input shaft has a first axial end and a second axial end. The driving gear has a first boss end and a second boss end. The transfer case includes a first shaft support part, a second shaft support part, a first boss support part, and a second boss support part. The first shaft support part supports the input shaft via the first shaft bearing. The second shaft support part supports the input shaft via the second shaft bearing. The first boss support part supports the driving gear via the first boss bearing. The second boss support part supports the driving gear via the second boss bearing.

Description

Work machine and transfer device

[0001] The present disclosure relates to a work machine and a transfer device.

[0002] Some work machines are equipped with a transfer device (see, for example, Patent Document 1). The transfer device transmits driving force from the powertrain to an axle. Some transfer devices are equipped with an input shaft, a planetary gear mechanism, a drive gear, a driven gear, and an output shaft. The input shaft is connected to the drive gear via the planetary gear mechanism. The drive gear meshes with the driven gear. The driven gear is connected to the output shaft. The driving force from the powertrain is transmitted from the input shaft to the output shaft via the planetary gear mechanism, drive gear, and driven gear.

[0003] Patent No. 5113949

[0004] In some transfer devices described above, the end of the input shaft is supported by the drive gear via a planetary gear mechanism. In such transfer devices, if the drive gear is deflected due to a reaction force from the driven gear, the center position of the input shaft may shift, resulting in misalignment. An object of the present disclosure is to reduce misalignment of the input shaft in a transfer device.

[0005] A work machine according to one aspect of the present disclosure includes a powertrain, an axle, and a transfer device. The transfer device includes an input shaft, a planetary gear mechanism, a drive gear, a driven gear, an output shaft, a first shaft bearing, a second shaft bearing, a first boss bearing, a second boss bearing, and a transfer case. The input shaft includes a first shaft end and a second shaft end. The second shaft end is located opposite the first shaft end in the axial direction of the input shaft. The input shaft is connected to the powertrain. The planetary gear mechanism is arranged coaxially with the input shaft. The planetary gear mechanism is connected to the input shaft. The drive gear includes a first boss end and a second boss end. The second boss end is located opposite the first boss end in the axial direction. The drive gear is arranged coaxially with the input shaft. The drive gear is rotatable relative to the input shaft. The drive gear is connected to the planetary gear mechanism. The driven gear meshes with the drive gear. The output shaft is arranged coaxially with the driven gear. The output shaft is connected to the driven gear. The output shaft is connected to the axle. The first shaft bearing is attached to the first shaft end. The second shaft bearing is attached to the second shaft end. The first boss bearing is attached to the first boss end. The second boss bearing is attached to the second boss end. The transfer case houses the input shaft, the planetary gear mechanism, the drive gear, the driven gear, and the output shaft. The transfer case includes a first shaft support portion, a second shaft support portion, a first boss support portion, and a second boss support portion. The first shaft support portion supports the input shaft via the first shaft bearing. The second shaft support portion supports the input shaft via the second shaft bearing. The first boss support portion supports the drive gear via the first boss bearing. The second boss support portion supports the drive gear via the second boss bearing.

[0006] A transfer device according to another aspect of the present disclosure includes an input shaft, a planetary gear mechanism, a drive gear, a driven gear, an output shaft, a first shaft bearing, a second shaft bearing, a first boss bearing, a second boss bearing, and a transfer case. The input shaft includes a first shaft end and a second shaft end. The second shaft end is located opposite the first shaft end in the axial direction of the input shaft. The planetary gear mechanism is arranged coaxially with the input shaft. The planetary gear mechanism is connected to the input shaft. The drive gear includes a first boss end and a second boss end. The second boss end is located opposite the first boss end in the axial direction. The drive gear is arranged coaxially with the input shaft. The drive gear is rotatable relative to the input shaft. The drive gear is connected to the planetary gear mechanism. The driven gear meshes with the drive gear. The output shaft is arranged coaxially with the driven gear. The output shaft is connected to the driven gear. The first shaft bearing is attached to the first shaft end. The second shaft bearing is attached to the second shaft end. The first boss bearing is attached to the first boss end. The second boss bearing is attached to the second boss end. The transfer case houses the input shaft, the planetary gear mechanism, the drive gear, the driven gear, and the output shaft. The transfer case includes a first shaft support portion, a second shaft support portion, a first boss support portion, and a second boss support portion. The first shaft support portion supports the input shaft via the first shaft bearing. The second shaft support portion supports the input shaft via the second shaft bearing. The first boss support portion supports the drive gear via the first boss bearing. The second boss support portion supports the drive gear via the second boss bearing.

[0007] According to the present disclosure, in a transfer device, both shaft ends of an input shaft are supported by a transfer case via bearings, and both boss ends of a drive gear are supported by a transfer case via bearings, thereby suppressing misalignment of the input shaft.

[0008] Fig. 4 is a side view of a work machine according to an embodiment. Fig. 5 is a block diagram showing the configuration of a drive system of a work machine. Fig. 6 is a front view of a transfer device. Fig. 7 is a sectional view taken along line IV-IV of the transfer device in Fig. 3. Fig. 8 is a sectional view taken along line V-V of the transfer device in Fig. 3. Fig. 9 is an enlarged sectional view showing the configuration inside a first case portion. Fig. 10 is an enlarged sectional view showing the configuration inside a second case portion.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a side view of a work machine 1 according to an embodiment of the present disclosure. The work machine 1 according to this embodiment is a wheel loader. As shown in Fig. 1, the work machine 1 includes a vehicle body 2, a work implement 3, and a traveling device 4.

[0010] The vehicle body 2 includes a cab 5. The work implement 3 is operably connected to the vehicle body 2. The work implement 3 includes, for example, a bucket 6. The work implement 3 is used for work such as excavation. The travelling device 4 is attached to the vehicle body 2. The travelling device 4 causes the work machine 1 to travel. The travelling device 4 includes front wheels 7 and rear wheels 8. The front wheels 7 and rear wheels 8 are rotatably supported by the vehicle body 2. Note that, of the left and right front wheels 7, only the left one is shown in the drawings. Of the left and right rear wheels 8, only the left one is shown in the drawings.

[0011] Figure 2 is a block diagram showing the configuration of the drive system of the work machine 1. As shown in Figures 1 and 2, the work machine 1 includes a powertrain 11, a transfer device 12, a drive shaft 13, a front axle 14, and a rear axle 15. The powertrain 11 includes a drive source 16 and a transmission 17. The drive source 16 includes, for example, an engine. Alternatively, the drive source 16 may include an electric motor. The transmission 17 transmits driving force from the drive source 16 to the transfer device 12.

[0012] The transmission 17 is, for example, a hydrostatic transmission (HST). The transmission 17 includes a hydraulic pump 20, a first travel motor 21, and a second travel motor 22. The hydraulic pump 20 is connected to the drive source 16. The hydraulic pump 20 discharges hydraulic oil when driven by the drive source 16. The hydraulic pump 20 supplies hydraulic oil to the first travel motor 21 and the second travel motor 22 via a hydraulic circuit 23. The first travel motor 21 and the second travel motor 22 are hydraulic motors. The first travel motor 21 and the second travel motor 22 are driven by the hydraulic oil from the hydraulic pump 20. The first travel motor 21 includes a first motor shaft 24. The second travel motor 22 includes a second motor shaft 25. The first motor shaft 24 and the second motor shaft 25 are connected to the transfer device 12.

[0013] The transfer device 12 transmits driving force from the powertrain 11 to the front axle 14 and the rear axle 15 via the drive shaft 13. The transfer device 12 will be described in detail later. The drive shaft 13 is connected to the transfer device 12. The drive shaft 13 extends in the front-to-rear direction of the work machine 1. The drive shaft 13 includes a front drive shaft 131 and a rear drive shaft 132. The front drive shaft 131 is connected to the front axle 14. The rear drive shaft 132 is connected to the rear axle 15.

[0014] The front axle 14 is connected to the front wheels 7. The driving force from the powertrain 11 is transmitted to the front wheels 7 via the transfer device 12, the front drive shaft 131, and the front axle 14, causing the front wheels 7 to rotate. The rear axle 15 is connected to the rear wheels 8. The driving force from the powertrain 11 is transmitted to the rear wheels 8 via the transfer device 12, the rear drive shaft 132, and the rear axle 15, causing the rear wheels 8 to rotate.

[0015] Fig. 3 is a front view of the transfer device 12. Fig. 4 is a cross-sectional view of the transfer device 12 taken along line IV-IV in Fig. 3. Fig. 5 is a cross-sectional view of the transfer device 12 taken along line V-V in Fig. 3. As shown in Figs. 2 to 5, the transfer device 12 includes an input shaft 30, a planetary gear mechanism 31, a clutch 32, a first drive gear 33, a second drive gear 34, a driven gear 35, an output shaft 36, and a transfer case 37.

[0016] The input shaft 30, planetary gear mechanism 31, and first drive gear 33 are arranged coaxially. In the following description, the axial direction refers to a direction parallel to the central axis A1 of the input shaft 30, as shown in FIG. 4 . The input shaft 30 extends in the front-to-rear direction of the work machine 1. The input shaft 30 is connected to the first motor shaft 24. The input shaft 30 is rotationally driven by the first traveling motor 21.

[0017] The planetary gear mechanism 31 includes a sun gear 40, planetary gears 41, a carrier 42, and a ring gear 43. The sun gear 40 is connected to the input shaft 30. The sun gear 40 rotates integrally with the input shaft 30. The planetary gears 41 mesh with the sun gear 40. The planetary gears 41 rotate around the sun gear 40 as the sun gear 40 rotates. The planetary gears 41 rotate around their own axes as the sun gear 40 rotates. Note that only some of the multiple planetary gears 41 are shown in the drawings.

[0018] The carrier 42 is connected to the planetary gear 41. The carrier 42 is rotatable around the input shaft 30. The carrier 42 rotates integrally with the planetary gear 41. The ring gear 43 meshes with the planetary gear 41. The ring gear 43 rotates around the input shaft 30 in conjunction with the rotation of the planetary gear 41.

[0019] The clutch 32 is connected to the ring gear 43 and the transfer case 37. The clutch 32 switches between connecting and disconnecting the ring gear 43 and the transfer case 37. The clutch 32 includes a plurality of clutch plates 38. Some of the plurality of clutch plates 38 are connected to the ring gear 43, and the other clutch plates 38 are connected to the transfer case 37.

[0020] The clutch 32 is in an engaged state when the clutch plates 38 connected to the ring gear 43 come into contact with the clutch plates 38 connected to the transfer case 37. The clutch 32 is in a disengaged state when the clutch plates 38 connected to the ring gear 43 separate from the clutch plates 38 connected to the transfer case 37. When the clutch 32 is in an engaged state, it connects the ring gear 43 to the transfer case 37. When the clutch 32 is in a disengaged state, it disconnects the ring gear 43 from the transfer case 37.

[0021] The first drive gear 33 is connected to the carrier 42. The first drive gear 33 is rotatable relative to the input shaft 30. The first drive gear 33 rotates integrally with the carrier 42. When the clutch 32 is engaged, the rotation of the input shaft 30 is transmitted to the first drive gear 33 via the sun gear 40, the planetary gears 41, and the carrier 42. When the clutch 32 is disengaged, the first drive gear 33 is able to rotate freely relative to the input shaft 30. The second drive gear 34 is disposed eccentrically relative to the input shaft 30. The second drive gear 34 is connected to the second motor shaft 25. The second drive gear 34 is rotationally driven by the second travel motor 22. Although the second drive gear 34 is directly connected to the second motor shaft 25, it may also be connected to the second motor shaft 25 via an input shaft separate from the second motor shaft 25, similar to the first drive gear 33.

[0022] The driven gear 35 is disposed eccentrically with respect to the input shaft 30. The driven gear 35 is disposed eccentrically with respect to the second drive gear 34. The driven gear 35 meshes with the first drive gear 33 and the second drive gear 34. The output shaft 36 is disposed coaxially with the driven gear 35. The output shaft 36 extends parallel to the input shaft 30. The output shaft 36 is connected to the driven gear 35. The output shaft 36 rotates integrally with the driven gear 35. The output shaft 36 is connected to the front axle 14 and the rear axle 15 via the drive shaft 13.

[0023] The above-mentioned clutch 32 is used to switch between dual-motor running and single-motor running. For example, when the vehicle speed is lower than a predetermined switching threshold, the clutch 32 is engaged. As a result, the rotation of the first travel motor 21 and the rotation of the second travel motor 22 are transmitted to the output shaft 36, and the work machine 1 runs in dual-motor running using the first travel motor 21 and the second travel motor 22. When the vehicle speed is higher than the predetermined switching threshold, the clutch 32 is disengaged. As a result, the input shaft 30 rotates freely relative to the first drive gear 33, and the work machine 1 runs in single-motor running using the second travel motor 22.

[0024] 3 to 5, the transfer case 37 includes a first case portion 44, a second case portion 45, and a third case portion 46. The first case portion 44 houses the input shaft 30, the planetary gear mechanism 31, and the first drive gear 33. The second case portion 45 houses the driven gear 35 and the output shaft 36. The third case portion 46 houses the second drive gear 34.

[0025] As shown in FIG. 4 , the first case portion 44 includes a first front wall portion 47. The first front wall portion 47 is provided on the front surface of the first case portion 44. The first traveling motor 21 is attached to the first front wall portion 47. The second case portion 45 includes a second front wall portion 48. The second front wall portion 48 is provided on the front surface of the second case portion 45. The output shaft 36 protrudes from the second front wall portion 48. The third case portion 46 includes a third front wall portion 49. The third front wall portion 49 is provided on the front surface of the third case portion 46. The second traveling motor 22 is attached to the third front wall portion 49.

[0026] Figure 6 is an enlarged cross-sectional view showing the configuration inside the first case portion 44. As shown in Figure 6, the input shaft 30 extends in the axial direction, passing through the first drive gear 33 and the planetary gear mechanism 31. The input shaft 30 includes a first shaft end portion 51 and a second shaft end portion 52. The first shaft end portion 51 is connected to the first motor shaft 24. The second shaft end portion 52 is located opposite the first shaft end portion 51 in the axial direction.

[0027] The transfer device 12 includes a first shaft bearing 53 and a second shaft bearing 54. The first shaft bearing 53 is attached to the first shaft end 51. The second shaft bearing 54 is attached to the second shaft end 52. The transfer case 37 rotatably supports the input shaft 30 via the first shaft bearing 53 and the second shaft bearing 54.

[0028] More specifically, a first shaft support portion 55 is provided on the first front wall portion 47. The first shaft support portion 55 rotatably supports the input shaft 30 via a first shaft bearing 53. The first case portion 44 also includes a first rear wall portion 56. The first rear wall portion 56 is provided on the rear surface of the first case portion 44. A second shaft support portion 57 is provided on the first rear wall portion 56. The second shaft support portion 57 protrudes from the first rear wall portion 56 in the axial direction. The second shaft support portion 57 rotatably supports the input shaft 30 via a second shaft bearing 54.

[0029] The first drive gear 33 includes a first gear portion 60, a first boss end portion 61, and a second boss end portion 62. The first gear portion 60 meshes with the driven gear 35. The first boss end portion 61 protrudes from the first gear portion 60 toward the first shaft end portion 51 of the input shaft 30. The second boss end portion 62 is located opposite the first boss end portion 61 in the axial direction. The second boss end portion 62 protrudes from the first gear portion 60 toward the second shaft end portion 52.

[0030] The transfer device 12 includes a first boss bearing 63 and a second boss bearing 64. The first boss bearing 63 is attached to the first boss end portion 61. The second boss bearing 64 is attached to the second boss end portion 62. The transfer case 37 rotatably supports the first drive gear 33 via the first boss bearing 63 and the second boss bearing 64.

[0031] Specifically, the transfer case 37 includes a first wall portion 65 and a second wall portion 66. The first wall portion 65 extends from the inner surface of the transfer case 37. The first wall portion 65 is disposed between the first front wall portion 47 and the first drive gear 33. The first wall portion 65 is provided with a first boss support portion 67. The first boss support portion 67 rotatably supports the first drive gear 33 via a first boss bearing 63.

[0032] The second wall portion 66 extends from the inner surface of the transfer case 37. The second wall portion 66 is disposed between the first drive gear 33 and the planetary gear mechanism 31. A second boss support portion 68 is provided on the second wall portion 66. The second boss support portion 68 rotatably supports the first drive gear 33 via the second boss bearing 64.

[0033] The transfer device 12 includes a carrier bearing 58 and a ring gear bearing 59. The carrier bearing 58 is disposed between the sun gear 40 and the ring gear bearing 59 in the axial direction. The carrier bearing 58 is connected to the carrier 42. The input shaft 30 rotatably supports the carrier 42 via the carrier bearing 58. The ring gear bearing 59 is disposed between the carrier bearing 58 and the second shaft bearing 54 in the axial direction. The ring gear bearing 59 is connected to the ring gear 43. The input shaft 30 rotatably supports the ring gear 43 via the ring gear bearing 59.

[0034] The first drive gear 33 and the planetary gear mechanism 31 are disposed axially between the first shaft bearing 53 and the second shaft bearing 54. The first drive gear 33, the first boss bearing 63, and the second boss bearing 64 are disposed axially between the first shaft bearing 53 and the planetary gear mechanism 31. The planetary gear mechanism 31 is disposed axially between the first drive gear 33 and the second shaft bearing 54. The clutch 32 is disposed on the outer circumferential side of the second shaft support portion 57.

[0035] 7 is an enlarged cross-sectional view showing the configuration inside the second case portion 45. As shown in FIG. 7, the output shaft 36 extends axially through the driven gear 35. The transfer device 12 includes a third shaft bearing 71 and a fourth shaft bearing 72. The transfer case 37 rotatably supports the output shaft 36 via the third shaft bearing 71 and the fourth shaft bearing 72.

[0036] More specifically, a third shaft support portion 73 is provided on the second front wall portion 48. The third shaft support portion 73 rotatably supports the output shaft 36 via a third shaft bearing 71. The second case portion 45 includes a second rear wall portion 74. The second rear wall portion 74 is provided on the rear surface of the second case portion 45. A fourth shaft support portion 75 is provided on the second rear wall portion 74. The fourth shaft support portion 75 protrudes from the second rear wall portion 74 in the axial direction. The fourth shaft support portion 75 rotatably supports the output shaft 36 via a fourth shaft bearing 72.

[0037] The transfer device 12 includes a brake device 76. The brake device 76 is disposed axially between the third shaft bearing 71 and the driven gear 35. The brake device 76 includes a plurality of brake discs 77. Some of the plurality of brake discs 77 are connected to the transfer case 37, and the other brake discs 77 are connected to the output shaft 36. The output shaft 36 is braked when the brake disc 77 connected to the transfer case 37 comes into contact with the brake disc 77 connected to the output shaft 36.

[0038] As shown in FIG. 5 , the second drive gear 34 includes a second gear portion 81, a third boss portion 82, and a fourth boss portion 83. The transfer device 12 includes a third boss bearing 84 and a fourth boss bearing 85. The third front wall portion 49 includes a third boss support portion 86. The third boss support portion 86 rotatably supports the third boss portion 82 via the third boss bearing 84. The third case portion 46 includes a third rear wall portion 87. The third rear wall portion 87 includes a fourth boss support portion 88. The fourth boss support portion 88 rotatably supports the fourth boss portion 83 via the fourth boss bearing 85.

[0039] In the transfer device 12 of the work machine 1 according to the present embodiment described above, both shaft ends 51, 52 of the input shaft 30 are supported by the transfer case 37 via bearings 53, 54, respectively. Also, both boss ends 61, 62 of the first drive gear 33 are supported by the transfer case 37 via bearings 63, 64, respectively. This reduces misalignment of the input shaft 30. Furthermore, the arrangement of the input shaft 30, first drive gear 33, planetary gear mechanism 31, and bearings 53, 54, 63, 64 as described above allows the transfer device 12 to be made more compact.

[0040] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0041] The work machine 1 is not limited to a wheel loader, and may be other machines such as a bulldozer, motor grader, or excavator. The configuration of the work machine 1 is not limited to that of the above embodiment, and may be modified. For example, the transmission 17 is not limited to an HST, and may be another transmission such as an HMT (Hydro Mechanical Transmission). Alternatively, the transmission 17 may be a combination of a generator and an electric motor. The number of travel motors is not limited to two, and may be one.

[0042] The configuration of the transfer device 12 is not limited to that of the above embodiment and may be modified. For example, the second drive gear 34 may be omitted. The location of the clutch 32 may be changed. Alternatively, the clutch 32 may be omitted.

[0043] According to the present disclosure, misalignment of the input shaft in the transfer device is reduced.

[0044] 1: Work machine, 11: Power train, 12: Transfer device, 14: Front axle, 15: Rear axle, 30: Input shaft, 31: Planetary gear mechanism, 32: Clutch, 33: First drive gear, 35: Driven gear, 36: Output shaft, 37: Transfer case, 40: Sun gear, 41: Planetary gear, 42: Carrier, 43: Ring gear, 47: First front wall portion, 51: First shaft end portion, 52: Second shaft end portion, 53: First shaft bearing, 54: Second shaft bearing, 55: First shaft support portion, 56: First rear wall portion, 57: Second shaft support portion, 61: First boss end portion, 62: Second boss end portion, 63: First boss bearing, 64: Second boss bearing, 65: First wall portion, 66: Second wall portion, 67: First boss support portion, 68: Second boss support portion

Claims

1. A powertrain; an axle; and a transfer device, wherein the transfer device comprises: an input shaft connected to the powertrain, the input shaft including a first shaft end and a second shaft end located opposite the first shaft end in the axial direction of the input shaft; a planetary gear mechanism arranged coaxially with the input shaft and connected to the input shaft; a drive gear including a first boss end and a second boss end located opposite the first boss end in the axial direction, arranged coaxially with the input shaft, rotatable relative to the input shaft, and connected to the planetary gear mechanism; a driven gear that meshes with the drive gear; an output shaft arranged coaxially with the driven gear, connected to the driven gear, and connected to the axle; a first shaft bearing attached to the first shaft end; a second shaft bearing attached to the second shaft end; a first boss bearing attached to the first boss end; and a second boss bearing attached to the second boss end. a transfer case that houses the input shaft, the planetary gear mechanism, the drive gear, the driven gear, and the output shaft, and includes a first shaft support portion that supports the input shaft via the first shaft bearing, a second shaft support portion that supports the input shaft via the second shaft bearing, a first boss support portion that supports the drive gear via the first boss bearing, and a second boss support portion that supports the drive gear via the second boss bearing.

2. A work machine according to claim 1, wherein the input shaft extends in the axial direction through the drive gear, and the drive gear is disposed between the first shaft bearing and the planetary gear mechanism in the axial direction.

3. A work machine according to claim 2, wherein the first boss bearing and the second boss bearing are disposed between the first shaft bearing and the planetary gear mechanism in the axial direction.

4. A work machine according to claim 1, wherein the input shaft extends in the axial direction through the drive gear and the planetary gear mechanism, and the drive gear and the planetary gear mechanism are disposed between the first shaft bearing and the second shaft bearing in the axial direction.

5. A work machine according to claim 1, wherein the transfer case includes a first wall portion extending from an inner surface of the transfer case, and the first boss support portion is provided on the first wall portion.

6. A work machine according to claim 5, wherein the transfer case includes a second wall portion extending from an inner surface of the transfer case, and the second boss support portion is provided on the second wall portion.

7. A work machine as described in claim 1, wherein the transfer case includes a front wall portion provided on the front surface of the transfer case and a rear wall portion provided on the rear surface of the transfer case, the first shaft support portion being provided on the front wall portion, and the second shaft support portion being provided on the rear wall portion.

8. A work machine according to claim 1, wherein the planetary gear mechanism includes: a sun gear connected to the input shaft and rotating integrally with the input shaft; planetary gears meshing with the sun gear; and a carrier connected to the planetary gears, rotating together with the planetary gears around the input shaft, and connected to the drive gear.

9. A work machine according to claim 8, wherein the planetary gear mechanism further includes a ring gear that meshes with the planetary gear, and further includes a clutch that is connected to the ring gear and the transfer case, the clutch being disposed on the outer circumferential side of the second shaft support portion.

10. An input shaft including a first shaft end and a second shaft end, the second shaft end being located opposite the first shaft end in the axial direction of the input shaft; a planetary gear mechanism arranged coaxially with the input shaft and connected to the input shaft; a drive gear including a first boss end and a second boss end located opposite the first boss end in the axial direction, arranged coaxially with the input shaft, rotatable relative to the input shaft and connected to the planetary gear mechanism; a driven gear meshing with the drive gear; an output shaft arranged coaxially with the driven gear and connected to the driven gear; a first shaft bearing attached to the first shaft end; a second shaft bearing attached to the second shaft end; a first boss bearing attached to the first boss end; and a second boss bearing attached to the second boss end. a transfer case that houses the input shaft, the planetary gear mechanism, the drive gear, the driven gear, and the output shaft, and includes a first shaft support portion that supports the input shaft via the first shaft bearing, a second shaft support portion that supports the input shaft via the second shaft bearing, a first boss support portion that supports the drive gear via the first boss bearing, and a second boss support portion that supports the drive gear via the second boss bearing.

11. The transfer device according to claim 10, wherein the input shaft extends in the axial direction through the drive gear, and the drive gear is disposed between the first shaft bearing and the planetary gear mechanism in the axial direction.

12. A transfer device according to claim 11, wherein the first boss bearing and the second boss bearing are disposed between the first shaft bearing and the planetary gear mechanism in the axial direction.

13. A transfer device according to claim 10, wherein the input shaft extends in the axial direction through the drive gear and the planetary gear mechanism, and the drive gear and the planetary gear mechanism are disposed between the first shaft bearing and the second shaft bearing in the axial direction.

14. The transfer apparatus of claim 10, wherein the transfer case includes a first wall portion extending from an inner surface of the transfer case, and the first boss support portion is provided on the first wall portion.

15. The transfer apparatus of claim 14, wherein the transfer case includes a second wall portion extending from an inner surface of the transfer case, and the second boss support portion is provided on the second wall portion.

16. A transfer device as described in claim 10, wherein the transfer case includes a front wall portion provided on the front surface of the transfer case and a rear wall portion provided on the rear surface of the transfer case, the first shaft support portion being provided on the front wall portion, and the second shaft support portion being provided on the rear wall portion.

17. A transfer device according to claim 10, wherein the planetary gear mechanism includes: a sun gear connected to the input shaft and rotating integrally with the input shaft; planetary gears meshing with the sun gear; and a carrier connected to the planetary gears, rotating together with the planetary gears around the input shaft, and connected to the drive gear.

18. A transfer device according to claim 17, wherein the planetary gear mechanism further includes a ring gear that meshes with the planetary gear, and further includes a clutch that is connected between the ring gear and the transfer case, the clutch being disposed on the outer circumferential side of the second shaft support portion.

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