Motor drive assembly for work machine, and work machine

Abstract

This motor drive assembly includes a motor, a first planetary gear mechanism, a central shaft, a second planetary gear mechanism, a third planetary gear mechanism, and a housing. The motor includes a motor shaft. The motor shaft, the first planetary gear mechanism, the central shaft, the second planetary gear mechanism, and the third planetary gear mechanism are arranged coaxially with each other. The first planetary gear mechanism is disposed on the outer side of the motor in the axial direction of the motor drive assembly. The third planetary gear mechanism is disposed on the inner side of the second planetary gear mechanism in the axial direction. The housing accommodates the second planetary gear mechanism and a third gear mechanism.

Description

Motor Drive Assembly for Working Machine and Working Machine

[0001] The present disclosure relates to a motor drive assembly for a working machine and a working machine.

[0002] The motor drive assembly for a working machine includes a motor assembly and a final drive assembly. The final drive assembly is connected to the motor assembly. For example, the motor drive assembly of Patent Document 1 includes a brake and a planetary gear mechanism. The brake is connected to the motor assembly. The planetary gear mechanism is connected to a sprocket. The rotation from the motor assembly is transmitted to the planetary gear mechanism via the brake, decelerated, and then transmitted to the sprocket.

[0003] U.S. Patent No. 12,084,132

[0004] In the motor drive assembly, miniaturization and obtaining a large reduction ratio are desired. The object of the present disclosure is to miniaturize the motor drive assembly for a working machine and obtain a large reduction ratio.

[0005] A motor drive assembly for a work machine according to one aspect of the present disclosure includes a motor, a first planetary gear mechanism, a central shaft, a second planetary gear mechanism, a third planetary gear mechanism, and a housing. The motor includes a motor shaft. The first planetary gear mechanism is arranged coaxially with the motor shaft. The first planetary gear mechanism is located outside the motor in the axial direction of the motor drive assembly. The first planetary gear mechanism includes a first sun gear, a first planetary gear, and a first carrier. The first sun gear is fixed to the motor shaft. The first planetary gear meshes with the first sun gear. The first carrier is connected to the first planetary gear. The central shaft is arranged coaxially with the first planetary gear mechanism. The central shaft is fixed to the first carrier. The central shaft extends in the axial direction. The second planetary gear mechanism is arranged coaxially with the central shaft. The second planetary gear mechanism includes a second sun gear, a second planetary gear, a second ring gear, and a second carrier. The second sun gear is fixed to the central axis. The second planetary gear meshes with the second sun gear. The second ring gear meshes with the second planetary gear. The second carrier is connected to the second planetary gear. The third planetary gear mechanism is located inside the second planetary gear mechanism in the axial direction. The third planetary gear mechanism is located coaxially with the central axis. The third planetary gear mechanism includes a third sun gear, a third planetary gear, and a third ring gear. The third sun gear is fixed to the second carrier. The third planetary gear meshes with the third sun gear. The third ring gear meshes with the third planetary gear. The housing houses the second planetary gear mechanism and the third gear mechanism. The second ring gear and the third ring gear are fixed to the housing.

[0006] Other aspects of the present disclosure of work machines include a vehicle body and a running gear. The running gear supports the vehicle body. The running gear includes the motor drive assembly described above.

[0007] According to this disclosure, the motor drive assembly for industrial machinery can be miniaturized while achieving a large reduction ratio.

[0008] This is a perspective view of a work machine according to an embodiment. This is a block diagram showing the configuration of the work machine. This is a cross-sectional view of a motor drive assembly. This is a skeleton diagram of a motor drive assembly. This is an enlarged cross-sectional view of a motor drive assembly. This is a cross-sectional view of a motor drive assembly showing the area filled with lubricating oil.

[0009] The following description of the working machine according to the embodiment will be made with reference to the drawings. Figure 1 is a perspective view of the working machine 1 according to the embodiment. Figure 2 is a block diagram showing the configuration of the working machine 1. The working machine 1 according to this embodiment is a bulldozer. As shown in Figure 1, the working machine 1 comprises a body 2, a working machine 3, and left and right traveling devices 4 and 5. The body 2 includes a driver's cab 6 and a power room 7. The power room 7 is located in front of the driver's cab 6. The working machine 3 is operably supported relative to the body 2. The working machine 3 includes a blade 8.

[0010] The left and right running gears 4 and 5 support the vehicle body 2. The left running gear 4 includes a track 11, a motor drive assembly 12, and a track frame 13. The track frame 13 supports the track 11 via several road wheels (not shown) and idlers. The track 11 is wound around the motor drive assembly 12. The motor drive assembly 12 is attached to the track frame 13. The axis Ax1 of the motor drive assembly 12 extends in the left-right direction of the work machine 1. In the following description, the direction parallel to axis Ax1 is defined as the axial direction.

[0011] As shown in Figure 2, the motor drive assembly 12 includes a motor assembly 21 and a final drive assembly 22. The motor assembly 21 is connected to the final drive assembly 22. In this embodiment, the motor assembly 21 is an electric motor. The final drive assembly 22 is located outside the motor assembly 21 in the axial direction.

[0012] The final drive assembly 22 includes a fixed case 23, a final drive housing 24, and a sprocket 25. The final drive assembly 22 is located coaxially with the motor assembly 21. As will be described in detail later, the final drive housing 24 is located coaxially with the fixed case 23. The final drive housing 24 is rotatably supported by the fixed case 23. The sprocket 25 is fixed to the final drive housing 24. The track 11 is wound around the sprocket 25. The motor assembly 21 is attached to the fixed case 23.

[0013] The right-side running gear 5 includes the track 14 shown in Figure 1, the track frame 15 shown in Figure 2, and the motor drive assembly 16. The motor drive assembly 16 includes the motor assembly 17 and the final drive assembly 18. The track 14, track frame 15, and motor drive assembly 16 of the right-side running gear 5 have the same configuration as the track 11, track frame 13, and motor drive assembly 12 of the left-side running gear 4 described above. The configuration of running gear 5 is the same as that of running gear 4, and therefore its description is omitted.

[0014] As shown in Figure 2, the work machine 1 includes an engine 31, a generator 32, a PTO 33, a lubrication pump 34, a scavenging pump 35, an oil tank 36, and an oil cooler 37. The engine 31 drives the generator 32. The generator 32 generates electricity when driven by the engine 31. The electricity generated by the generator 32 is supplied to the motor assemblies 21 and 17 of the travel devices 4 and 5 via an inverter / converter (not shown). This drives the motor assemblies 21 and 17, which in turn move the work machine 1.

[0015] The PTO 33 distributes the driving force of the engine 31 to the lubrication pump 34 and the scavenging pump 35. The lubrication pump 34 is driven by the driving force of the engine 31 and discharges lubricating oil. The lubricating oil is supplied from the oil tank 36 through the lubrication pump 34 and the oil cooler 37 to the motor drive assemblies 12 and 16. The scavenging pump 35 is driven by the driving force of the engine 31 and draws lubricating oil from the motor drive assemblies 12 and 16. The lubricating oil returns from the motor drive assemblies 12 and 16 through the scavenging pump 35 to the oil tank 36.

[0016] Next, the motor drive assembly 12 will be described. Figure 3 is a cross-sectional view of the motor drive assembly 12. Figure 4 is a skeleton view of the motor drive assembly 12. As shown in Figures 3 and 4, the motor assembly 21 is arranged coaxially with the final drive assembly 22 and the fixed case 23.

[0017] As shown in Figure 3, the motor assembly 21 includes a motor 40 and a motor case 41. The motor case 41 is fixed to the fixed case 23. The motor 40 includes a stator 42, a rotor 43, and a motor shaft 44. The stator 42 and rotor 43 are located inside the motor case 41. The stator 42 is fixed to the inner surface of the motor case 41. The motor shaft 44 is fixed to the rotor 43. The rotor 43 is rotatable relative to the stator 42. The motor shaft 44 and rotor 43 are rotatably supported by the motor case 41. The motor shaft 44 is located coaxially with the fixed case 23. The motor shaft 44 extends in the axial direction. The motor shaft 44 protrudes outward from the motor case 41 in the axial direction.

[0018] As shown in Figures 3 and 4, the final drive assembly 22 includes a central shaft 45, a high-speed rotation mechanism 46, and a low-speed rotation mechanism 47. The central shaft 45 is coaxially positioned with respect to the fixed case 23. The central shaft 45 extends in the axial direction. The central shaft 45 is rotatably supported by the fixed case 23 via bearings 48 and 49.

[0019] The high-speed rotation mechanism 46 rotates at a higher speed than the low-speed rotation mechanism 47. The high-speed rotation mechanism 46 is connected to the motor shaft 44. The high-speed rotation mechanism 46 reduces the rotation of the motor shaft 44 and transmits it to the low-speed rotation mechanism 47. The low-speed rotation mechanism 47 rotates at a lower speed than the high-speed rotation mechanism 46. The low-speed rotation mechanism 47 is connected to the final drive housing 24. The low-speed rotation mechanism 47 reduces the rotation of the high-speed rotation mechanism 46 and transmits it to the final drive housing 24. The high-speed rotation mechanism 46 includes a first planetary gear mechanism 51 and a brake 52. The low-speed rotation mechanism 47 includes a second planetary gear mechanism 53 and a third planetary gear mechanism 54.

[0020] The first planetary gear mechanism 51 is arranged coaxially with the central shaft 45. The first planetary gear mechanism 51 is located outside the motor assembly 21 in the axial direction. The first planetary gear mechanism 51 is connected to the motor shaft 44. The first planetary gear mechanism 51 is located between the motor assembly 21 and the brake 52 in the axial direction. The first planetary gear mechanism 51 includes a first sun gear 55, a first planetary gear 56, a first ring gear 57, and a first carrier 58.

[0021] The first sun gear 55 is fixed to the motor shaft 44. The first sun gear 55 rotates integrally with the motor shaft 44. The first planetary gear 56 meshes with the first sun gear 55. The first planetary gear 56 is capable of revolving around the first sun gear 55. The first planetary gear 56 is supported by the first carrier 58 so that it can rotate on its own axis. The first ring gear 57 meshes with the first planetary gear 56. The first ring gear 57 is connected to the fixed case 23. The first ring gear 57 is fixed to the fixed case 23 so that it cannot rotate. The first carrier 58 rotates around the first sun gear 55 along with the revolving of the first planetary gear 56. The first carrier 58 is fixed to the central shaft 45. The central shaft 45 rotates integrally with the first carrier 58.

[0022] The brake 52 is located outside the first planetary gear mechanism 51 in the axial direction. The brake 52 is connected to the first carrier 58 of the first planetary gear mechanism 51 via the central shaft 45. The brake 52 brakes the rotation of the central shaft 45, thereby braking the sprocket 25. Figure 5 is an enlarged cross-sectional view of the motor drive assembly 12. As shown in Figure 5, the brake 52 includes a brake hub 59, a plurality of brake discs 60, 61, a piston 62, and a biasing member 63. The brake hub 59 is fixed to the central shaft 45. The brake hub 59 rotates integrally with the central shaft 45.

[0023] The multiple brake discs 60, 61 include a rotor disc 60 and a stator disc 61. The rotor disc 60 is connected to the brake hub 59 so as to be non-rotatable and axially movable relative to the brake hub 59. The rotor disc 60 rotates integrally with the brake hub 59. The stator disc 61 is positioned axially opposite to the rotor disc 60. The stator disc 61 is supported by a fixed case 23 so as to be axially movable.

[0024] The piston 62 is positioned axially opposite the brake discs 60 and 61. The piston 62 is supported by a fixed case 23 so as to be movable in the axial direction. The biasing member 63 is, for example, a coil spring. Alternatively, the biasing member 63 may be another type of spring, such as a leaf spring. The biasing member 63 biases the piston 62 in a direction that presses against the brake discs 60 and 61.

[0025] The fixed case 23 includes a hydraulic chamber 64. When hydraulic fluid is supplied to the hydraulic chamber 64, the piston 62 is driven. When hydraulic fluid is not supplied to the hydraulic chamber 64, the piston 62 presses against the brake discs 60 and 61 by the biasing force of the biasing member 63. As a result, the rotor disc 60 and the stator disc 61 engage with each other, and the brake 52 brakes the central shaft 45. When hydraulic fluid is supplied to the hydraulic chamber 64, the piston 62 moves away from the brake discs 60 and 61 against the biasing force of the biasing member 63. Also, a spring (not shown) is placed between the stator discs 61 that biases them in a direction that pulls them apart from each other. As a result, the rotor disc 60 and the stator disc 61 separate from each other, and the brake 52 releases the central shaft 45. In other words, the brake 52 is a negative-type brake in which the braking state is released by the supply of hydraulic fluid.

[0026] As shown in Figure 3, the second planetary gear mechanism 53 is arranged coaxially with the central shaft 45. The second planetary gear mechanism 53 is connected to the first planetary gear mechanism 51 via the central shaft 45. The second planetary gear mechanism 53 is located outside the brake 52 in the axial direction. The second planetary gear mechanism 53 includes a second sun gear 65, a second planetary gear 66, a second ring gear 67, and a second carrier 68.

[0027] The second sun gear 65 is fixed to the central axis 45. The second sun gear 65 rotates integrally with the central axis 45. The second planetary gear 66 meshes with the second sun gear 65. The second planetary gear 66 is capable of revolving around the second sun gear 65. The second planetary gear 66 is supported by the second carrier 68 so that it can rotate on its own axis. The second ring gear 67 meshes with the second planetary gear 66. The second ring gear 67 is fixed to the final drive housing 24. The second ring gear 67 rotates together with the final drive housing 24. The second carrier 68 rotates around the second sun gear 65 along with the revolving second planetary gear 66.

[0028] The third planetary gear mechanism 54 is arranged coaxially with the central axis 45. The third planetary gear mechanism 54 is connected to the second planetary gear mechanism 53. In the axial direction, the third planetary gear mechanism 54 is located outside the brake 52. In the axial direction, the third planetary gear mechanism 54 is located inside the second planetary gear mechanism 53. The third planetary gear mechanism 54 includes a third sun gear 69, a third planetary gear 70, and a third ring gear 71.

[0029] The third sun gear 69 is positioned on the outer circumference of the central axis 45. The third sun gear 69 includes a hole 72, which extends axially through the third sun gear 69. The central axis 45 extends through the hole 72 of the third sun gear 69. The third sun gear 69 is rotatable relative to the central axis 45. The third sun gear 69 is fixed to the second carrier 68 of the second planetary gear mechanism 53. The third sun gear 69 rotates together with the second carrier 68.

[0030] The third planetary gear 70 meshes with the third sun gear 69. The third planetary gear 70 is supported by the fixed case 23 so as to be able to rotate on its own axis but not be able to revolve around the third sun gear 69. The third ring gear 71 meshes with the third planetary gear 70. The third ring gear 71 is fixed to the final drive housing 24. The third ring gear 71 rotates together with the final drive housing 24.

[0031] In the final drive assembly 22 described above, the first planetary gear mechanism 51 reduces the rotation of the motor shaft 44 and transmits it to the central shaft 45. The second planetary gear mechanism 53 and the third planetary gear mechanism 54 reduce the rotation of the central shaft 45 and transmit it to the final drive housing 24. In detail, the rotation of the motor shaft 44 is transmitted to the central shaft 45 in the first planetary gear mechanism 51 via the first sun gear 55, the first planetary gear 56, and the first carrier 58.

[0032] The rotation of the central shaft 45 is transmitted to the final drive housing 24 via the second sun gear 65, second planetary gear 66, and second ring gear 67 in the second planetary gear mechanism 53. The revolution of the second planetary gear 66 causes the second carrier 68 to rotate, and the rotation of the second carrier 68 is transmitted to the final drive housing 24 via the third sun gear 69, third planetary gear 70, and third ring gear 71 in the third planetary gear mechanism 54. As a result, the sprocket 25 rotates together with the final drive housing 24.

[0033] As shown in Figure 3, the fixed case 23 includes a fixed case housing 73 and a partition wall 74. The fixed case housing 73 includes a cylindrical portion 75 and a flange portion 76. The flange portion 76 protrudes radially outward from the cylindrical portion 75. The cylindrical portion 75 extends in the axial direction. The cylindrical portion 75 supports the final drive housing 24 via bearings 77 and 78.

[0034] As shown in Figure 5, the fixed case housing 73 has a first internal space S1, a first opening 79, and a second opening 80. The first planetary gear mechanism 51 and the brake 52 are located within the first internal space S1. The first opening 79 and the second opening 80 communicate with the first internal space S1. The first opening 79 opens inward in the axial direction. The second opening 80 opens outward in the axial direction. The central shaft 45 extends through the second opening 80.

[0035] The partition wall 74 is located within the first internal space S1 between the first planetary gear mechanism 51 and the brake 52. The partition wall 74 is a separate component from the fixed case housing 73. The first internal space S1 includes a first region A1 and a second region A2. The partition wall 74 divides the first internal space S1 into the first region A1 and the second region A2. The first planetary gear mechanism 51 is located in the first region A1. The brake 52 is located in the second region A2.

[0036] The partition wall 74 includes a first wall portion 81, a second wall portion 82, and a third wall portion 83. The first wall portion 81 is located radially outward of the first planetary gear mechanism 51. The first wall portion 81 is attached to the first opening 79 of the fixed case housing 73. The first ring gear 57 described above is provided on the inner circumference of the first wall portion 81. The second wall portion 82 extends radially inward from the first wall portion 81, passing between the first planetary gear mechanism 51 and the brake 52. The third wall portion 83 extends axially from the second wall portion 82 toward the brake 52. The third wall portion 83 supports the central shaft 45 via a bearing 49.

[0037] As shown in Figure 3, the final drive housing 24 has a second internal space S2. The cylindrical portion 75 of the fixed case housing 73 is located within the second internal space S2. The second planetary gear mechanism 53 and the third planetary gear mechanism 54 are located within the second internal space S2. The fixed case housing 73 separates the first internal space S1 and the second internal space S2.

[0038] As shown in Figure 5, oil seals 84 and 85 are installed in the second opening 80 of the fixed case housing 73. The oil seals 84 and 85 are positioned between the second opening 80 and the central axis 45. The oil seals 84 and 85 are positioned between the first internal space S1 and the second internal space S2. The oil seals 84 and 85 seal the space between the first internal space S1 and the second internal space S2.

[0039] As shown in Figure 3, floating seals 86 and 87 are positioned between the flange portion 76 of the fixed case housing 73 and the final drive housing 24. The floating seals 86 and 87 seal the second internal space S2 from the external space of the final drive assembly 22.

[0040] Next, the lubrication of the motor drive assembly 12 will be described. As shown in Figure 5, the fixed case 23 includes a lubrication oil passage 88 and a scavenging oil passage 89. The lubrication oil passage 88 is an oil passage for supplying lubricating oil to the first internal space S1. The lubricating oil from the lubrication pump 34 described above is supplied to the lubrication oil passage 88. The scavenging oil passage 89 is an oil passage for suctioning lubricating oil from the first internal space S1. The lubricating oil in the first internal space S1 is suctioned through the scavenging oil passage 89 by the scavenging pump 35 described above. The first planetary gear mechanism 51 and the brake 52, which are located in the first internal space S1, are lubricated in a dry sump system (forced lubrication system) by the lubricating oil supplied through the lubrication oil passage 88.

[0041] More specifically, the lubrication oil passage 88 extends through the first wall portion 81, the second wall portion 82, and the third wall portion 83. The lubrication oil passage 88 includes the first lubrication oil passage 90, the second lubrication oil passage 91, and the third lubrication oil passage 92. The first lubrication oil passage 90 extends axially through the first wall portion 81. The second lubrication oil passage 91 extends radially through the second wall portion 82. The third lubrication oil passage 92 extends axially through the third wall portion 83. The third lubrication oil passage 92 communicates with the second region A2.

[0042] The partition wall 74 includes a restrictor 93. The restrictor 93 is provided in the second wall portion 82. The restrictor 93 communicates with the lubrication oil passage 88 and the first region A1. The lubrication oil passage 88 communicates with the first region A1 via the restrictor 93. Lubricating oil from the lubrication pump 34 is supplied to the second region A2 through the first lubrication oil passage 90, the second lubrication oil passage 91, and the third lubrication oil passage 92. This lubricates the brake 52.

[0043] Lubricating oil from the lubrication pump 34 is supplied to the first region A1 through the first lubricating oil passage 90, the second lubricating oil passage 91, and the throttle 93. This lubricates the first planetary gear mechanism 51. In addition, by supplying lubricating oil to the first planetary gear mechanism 51 via the throttle 93, the supply of an excessive amount of lubricant to the first planetary gear mechanism 51 is suppressed. This reduces the agitation loss of the lubricating oil in the first planetary gear mechanism 51.

[0044] The scavenging oil passage 89 extends through the first wall portion 81 and the second wall portion 82. The scavenging oil passage 89 includes a first scavenging oil passage 94 and a second scavenging oil passage 95. The first scavenging oil passage 94 extends in the axial direction through the first wall portion 81. The second scavenging oil passage 95 extends in the radial direction through the second wall portion 82. The second scavenging oil passage 95 communicates with the second region A2. The lubricating oil supplied to the first internal space S1 through the lubricating oil passage 88 is returned to the oil tank 36 through the scavenging oil passage 89. As described above, the first planetary gear mechanism 51 and the brake 52 are lubricated by a dry sump system (forced lubrication system) using the lubricating pump 34 and the scavenging pump 35.

[0045] The second internal space S2 is sealed from the outside of the final drive housing 24 by the oil seals 84, 85 and the floating seals 86, 87. As shown in FIG. 6, lubricating oil 98 is enclosed in the second internal space S2. In FIG. 6, the hatched area indicates the lubricating oil filled in the second internal space S2. For ease of understanding, in FIG. 6, the hatching of other components is omitted. The lubricating oil from the lubricating pump 34 described above is not supplied to the second internal space S2. The second planetary gear mechanism 53 and the third planetary gear mechanism 54 arranged in the second internal space S2 are lubricated by an oil bath of the lubricating oil in the second internal space S2.

[0046] In the motor drive assembly 12 according to the present embodiment described above, a simple single-stage planetary gear mechanism by the first planetary gear mechanism 51 and a compound planetary gear mechanism by the second planetary gear mechanism 53 and the third planetary gear mechanism 54 are combined. Thereby, the motor drive assembly 12 is miniaturized and a large reduction ratio can be obtained.

[0047] As described above, an embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.

[0048] The work machine 1 may be not only a bulldozer but also other machines such as an excavator, a wheel loader, a grader, or a dump truck. The configurations of the traveling devices 4 and 5 are not limited to those of the above-described embodiment and may be changed. For example, the traveling devices 4 and 5 may include tires instead of crawlers.

[0049] The structure of the motor assembly 21 or the final drive assembly 22 is not limited to that of the above-described embodiment and may be changed. For example, the arrangement of the lubricating oil passage 88 and the scavenging oil passage 89 may be changed. Alternatively, the inside of the fixed case 23 may be lubricated by an oil bath, similarly to the inside of the final drive housing 24. In that case, the lubricating oil passage 88 and the scavenging oil passage 89 may be omitted.

[0050] According to the present disclosure, it is possible to miniaturize the motor drive assembly for a work machine and obtain a large reduction ratio.

[0051] 1: Work machine, 2: Vehicle body, 4, 5: Traveling devices, 12: Motor drive assembly, 23: Fixed case, 24: Final drive housing, 25: Sprocket, 40: Motor, 44: Motor shaft, 45: Central shaft, 51: First planetary gear mechanism, 52: Brake, 53: Second planetary gear mechanism, 54: Third planetary gear mechanism, 55: First sun gear, 56: First planetary gear, 57: First ring gear, 58: First carrier, 65: Second sun gear, 66: Second planetary gear, 67: Second ring gear, 68: Second carrier, 69: Third sun gear, 70: Third planetary gear, 71: Third ring gear

Claims

1. A motor drive assembly for a work machine, comprising: a motor including a motor shaft; a first planetary gear mechanism including a first sun gear fixed to the motor shaft, a first planetary gear meshing with the first sun gear, and a first carrier connected to the first planetary gear, arranged coaxially with the motor shaft and located outside the motor in the axial direction of the motor drive assembly; a central shaft arranged coaxially with the first planetary gear mechanism, fixed to the first carrier and extending in the axial direction; a second planetary gear mechanism including a second sun gear fixed to the central shaft, a second planetary gear meshing with the second sun gear, a second ring gear meshing with the second planetary gear, and a second carrier connected to the second planetary gear, arranged coaxially with the central shaft; A motor drive assembly comprising: a third sun gear fixed to the second carrier; a third planetary gear meshing with the third sun gear; and a third ring gear meshing with the third planetary gear; a third planetary gear mechanism coaxially arranged with the central axis and positioned inside the second planetary gear mechanism in the axial direction; and a housing that houses the second planetary gear mechanism and the third gear mechanism, and to which the second ring gear and the third ring gear are fixed.

2. The motor drive assembly according to claim 1, further comprising a fixed case that rotatably supports the housing, wherein the first planetary gear mechanism includes a first ring gear that meshes with the first planetary gear, and the first ring gear is fixed to the fixed case.

3. The motor drive assembly according to claim 2, wherein the first planetary gear mechanism is disposed within the fixed case.

4. The motor drive assembly according to claim 1, further comprising a brake arranged coaxially with the central axis, located outside the first planetary gear mechanism in the axial direction, and connected to the central axis, wherein the second planetary gear mechanism and the third planetary gear mechanism are located outside the brake in the axial direction.

5. The motor drive assembly according to claim 4, further comprising a fixed case that rotatably supports the housing, wherein the first planetary gear mechanism and the brake are disposed within the fixed case.

6. A work machine comprising a vehicle body and a running device supporting the vehicle body, wherein the running device includes a motor drive assembly according to any one of claims 1 to 5.

Images