Power transmissions, work machines, and bulldozers

Abstract

To enable downsizing of a power transmission device for a work machine.SOLUTION: Rotation centers of a first planetary gear mechanism 30 and a second planetary gear mechanism 40 are located on the same straight line. A first rotation transmission element 50 can rotate around a rotation center different from the rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. The first rotation transmission element 50 transmits rotation of a first ring gear 34 of the first planetary gear mechanism 30 to a second sun gear 41 of the second planetary gear mechanism 40. The second rotation transmission element 60 can rotate around a rotation center different from the rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. The second rotation transmission element 60 transmits rotation of a second ring gear 44 of the second planetary gear mechanism 40 to a first sun gear 31 of the first planetary gear mechanism 30.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a work machine power transmission device mounted on a work machine. [Background technology]

[0002] JP 2015-21594 A (Patent Document 1) discloses a power transmission device capable of transmitting driving torque while imparting a torque difference to left and right driving wheels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-21594 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the power transmission device described in the above document, a sun gear of a first planetary gear mechanism and a carrier of a second planetary gear mechanism are coupled to form a first coupling element, and a carrier of the first planetary gear mechanism and a sun gear of the second planetary gear mechanism are coupled to form a second coupling element. The first coupling element includes a hollow shaft, and the second coupling element is inserted therein. Because the shaft has a double structure, if the power transmission device described in the above document is applied to a bulldozer or the like that has a large passing torque, the device may become large in size.

[0005] The present disclosure proposes a power transmission device for a work machine that can suppress an increase in size of the device. [Means for solving the problem]

[0006] A work machine power transmission device according to an aspect of the present disclosure is mounted on a work machine. The work machine includes a vehicle body, and a first drive wheel and a second drive wheel. The first drive wheel and the second drive wheel are disposed on the left and right sides of the vehicle body, and are driven to rotate to move the vehicle body. The work machine power transmission device transmits a drive force to the first drive wheel and the second drive wheel. The work machine power transmission device includes a first drive motor that generates a rotational force, a second drive motor that generates a rotational force, a first output shaft that outputs a drive force to be transmitted to the first drive wheel, a second output shaft that outputs a drive force to be transmitted to the second drive wheel, a first planetary gear mechanism, and a second planetary gear mechanism. The first planetary gear mechanism has a plurality of rotating elements including a first input element to which the rotational force is input from the first drive motor, and a first output element connected to the first output shaft. The second planetary gear mechanism has a plurality of rotating elements including a second input element to which a rotational force is input from the second drive motor, and a second output element connected to the second output shaft. The first planetary gear mechanism and the second planetary gear mechanism have respective rotation centers on the same straight line. The power transmission device for a working machine further includes a first rotation transmission element and a second rotation transmission element. The first rotation transmission element is rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism. The first rotation transmission element transmits the rotation of one of the rotating elements of the first planetary gear mechanism to one of the rotating elements of the second planetary gear mechanism. The second rotation transmission element is rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism. The second rotation transmission element transmits the rotation of another one of the rotating elements of the second planetary gear mechanism to another one of the rotating elements of the first planetary gear mechanism.

[0007] A power transmission device for a work machine according to an aspect of the present disclosure is mounted on a work machine. The work machine includes a vehicle body, and a first drive wheel and a second drive wheel. The first drive wheel and the second drive wheel are disposed on the left and right sides of the vehicle body, and are driven to rotate to move the vehicle body. The power transmission device for a work machine transmits a drive force to the first drive wheel and the second drive wheel. The power transmission device for a work machine includes a first output shaft that outputs a drive force to be transmitted to the first drive wheel, a second output shaft that outputs a drive force to be transmitted to the second drive wheel, a first planetary gear mechanism, a second planetary gear mechanism, a first sun gear rotating shaft, and a second sun gear rotating shaft. The first planetary gear mechanism has a first sun gear, a first planetary carrier, and a first ring gear. The second planetary gear mechanism has a second sun gear, a second planetary carrier, and a second ring gear. The first sun gear rotating shaft and the second sun gear rotating shaft extend in the axial direction of rotation of the first planetary gear mechanism and the second planetary gear mechanism. The first sun gear rotating shaft rotates integrally with the first sun gear. The second sun gear rotating shaft rotates integrally with the second sun gear. The first output shaft, the first sun gear rotating shaft, the second sun gear rotating shaft, and the second output shaft are arranged side by side in the axial direction.

[0008] A power transmission device for a work machine according to an aspect of the present disclosure is mounted on a work machine and includes a first planetary gear mechanism, a first drive motor, a first output shaft, a second planetary gear mechanism, a second drive motor, a second output shaft, a first rotation transmission element, and a second rotation transmission element. The first planetary gear mechanism has a first sun gear, a first planetary gear, a first ring gear, and a first planetary carrier. The first drive motor generates a rotational force input to the first ring gear. The first output shaft is connected to the first planetary carrier. The second planetary gear mechanism has a second sun gear, a second planetary gear, a second ring gear, and a second planetary carrier. The second drive motor generates a rotational force input to the second ring gear. The second output shaft is connected to the second planetary carrier. The first rotation transmission element is rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism, and transmits the rotation of the first ring gear to the second sun gear. The second rotation transmission element is rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism, and transmits the rotation of the second ring gear to the first sun gear. Effect of the Invention

[0009] According to the present disclosure, it is possible to prevent an increase in size of a power transmission device for a work machine. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view of a bulldozer as an example of a work machine based on an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a power transmission system of a bulldozer. [Diagram 3] FIG. 1 is a skeleton diagram showing a power transmission device according to a first embodiment. [Figure 4] FIG. 11 is a skeleton diagram showing a power transmission device according to a second embodiment. [Diagram 5] FIG. 11 is a skeleton diagram showing a power transmission device according to a third embodiment. [Figure 6] FIG. 13 is a skeleton diagram showing a power transmission device according to a fourth embodiment. [Figure 7] FIG. 13 is a skeleton diagram showing a power transmission device according to a fifth embodiment. [Figure 8] FIG. 13 is a skeleton diagram showing a power transmission device according to a sixth embodiment. [Figure 9] FIG. 13 is a skeleton diagram showing a power transmission device according to a seventh embodiment. [Figure 10] FIG. 13 is a skeleton diagram showing a power transmission device according to an eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. It is also intended from the beginning that any configuration may be extracted from the embodiments and that they may be combined in any desired manner.

[0012] [First embodiment] First, the configuration of a bulldozer 1 will be described as an example of a work machine according to an embodiment. Fig. 1 is a perspective view of a bulldozer 1 as an example of a work machine according to an embodiment. The bulldozer 1 mainly includes a vehicle body 7, a blade 5, a ripper 6, and a traveling gear 4.

[0013] The blade 5 is attached to the vehicle body 7. The blade 5 is a working machine for performing work such as excavating and leveling the ground surface. The blade 5 is disposed at the front of the vehicle body 7. The ripper 6 is attached to the vehicle body 7. The ripper 6 is a working machine for penetrating and crushing hard materials such as rocks. The ripper 6 is disposed at the rear of the vehicle body 7.

[0014] The traveling gear 4 is provided on the left and right sides of the vehicle body 7. The traveling gear 4 is a track-type traveling gear having a pair of left and right tracks 3 separated in the left-right direction. The vehicle body 7 is disposed between the pair of left and right tracks 3. The left and right sprockets 2 drive the tracks 3 to cause the bulldozer 1 to travel. The tracks 3 and the sprockets 2 are disposed on the left and right sides of the vehicle body 7.

[0015] 2 is a schematic diagram showing the configuration of the power transmission system of the bulldozer 1. The engine 11 is the drive source of the bulldozer 1, and is, for example, a diesel engine. The engine 11 generates driving force for moving the vehicle body 7. The engine 11 generates driving force for operating the work implements (the blade 5, the ripper 6). The output of the engine 11 is controlled by adjusting the amount of fuel injected into the cylinder of the engine 11.

[0016] A power take-off (PTO) 12 distributes driving force from the engine 11 to a traveling system that drives the traveling device 4, a work implement pump 13, and a fan pump 14.

[0017] The work implement pump 13 is included in a hydraulic system that drives the work implement. The work implement pump 13 is a hydraulic pump. The work implement is driven by hydraulic oil discharged from the work implement pump 13. The fan pump 14 supplies hydraulic oil to a fan motor (not shown). The fan motor rotates a cooling fan (not shown).

[0018] The traveling system includes a generator 15 and a power transmission device 20. The generator 15 is driven by the driving force generated by the engine 11, and converts mechanical energy into electrical energy. The power transmission device 20 is provided on a power transmission path from the engine 11 to the sprockets 2L, 2R. The power transmission device 20 includes a first drive motor 21 and a second drive motor 22. The generator 15 is electrically connected to the first drive motor 21 and the second drive motor 22 via wiring 16.

[0019] The first drive motor 21 and the second drive motor 22 are electric motors. The first drive motor 21 and the second drive motor 22 are driven by electric power generated by the generator 15, and convert electric energy into mechanical energy. The bulldozer 1 is equipped with a diesel-electric type electric drive device in which the engine 11 drives the generator 15, and the first drive motor 21 and the second drive motor 22 are driven by the electric power generated by the generator 15 to travel.

[0020] Specifically, the first drive motor 21 and the second drive motor 22 generate a rotational force. The rotational force generated by the first drive motor 21 and the second drive motor 22 is transmitted to the sprockets 2L, 2R, which rotate and drive the sprockets 2L, 2R. The sprockets 2L, 2R are an example of drive wheels that are rotated and driven by the drive force generated by the engine 11 to move the vehicle body 7. The sprocket 2L is an example of a first drive wheel disposed on the left side of the vehicle body 7 (FIG. 1), and the sprocket 2R is an example of a second drive wheel disposed on the right side of the vehicle body 7.

[0021] In FIG. 2, a control unit (inverter, converter) is provided to control the power supplied from the generator 15 to the first drive motor 21 and the second drive motor 22, but this is omitted from the illustration.

[0022] Fig. 3 is a skeleton diagram showing the power transmission device 20 in the first embodiment. Note that the skeleton diagrams shown in Fig. 3 and the subsequent Figs. 4 to 10 are simplified diagrams showing power transmission paths from the first drive motor 21 and the second drive motor 22 to the sprockets 2L, 2R.

[0023] 3, the power transmission device 20 includes a first planetary gear mechanism 30. The first planetary gear mechanism 30 has a plurality of rotating elements. The plurality of rotating elements of the first planetary gear mechanism 30 includes a first sun gear 31, a first planetary gear 32, a first planetary carrier 33, and a first ring gear 34.

[0024] The first sun gear 31 is disposed at the center of the first planetary gear mechanism 30 and is configured to be rotatable. The first planetary gears 32 are disposed radially outside the first sun gear 31 and spaced apart in the circumferential direction. Each of the first planetary gears 32 is supported by a first planetary carrier 33. The first ring gear 34 is disposed radially outside the first planetary gear 32. The first ring gear 34 has inner peripheral teeth that mesh with the first planetary gear 32 and outer peripheral teeth that mesh with a first input gear 23 described below.

[0025] Each first planetary gear 32 meshes with the outer peripheral teeth of the first sun gear 31 and the inner peripheral teeth of the first ring gear 34 and is capable of rotating on its own axis. The first planetary carrier 33 is capable of rotating around the first sun gear 31. Each first planetary gear 32 is capable of revolving around the first sun gear 31 while being supported by the first planetary carrier 33. The first ring gear 34 is capable of rotating around the first planetary gear 32 and the first planetary carrier 33.

[0026] The rotation centers of the first sun gear 31 , first planetary carrier 33 and first ring gear 34 and the revolution axis of the first planetary gear 32 are on the same straight line, which serves as the rotation center of the first planetary gear mechanism 30 .

[0027] A first sun gear rotating shaft 35 is fixed to the first sun gear 31. The first sun gear rotating shaft 35 extends in the axial direction of rotation of the first planetary gear mechanism 30. The first sun gear rotating shaft 35 is disposed concentrically with the rotation center of the first planetary gear mechanism 30. The first sun gear rotating shaft 35 rotates integrally with the first sun gear 31.

[0028] The first sun gear rotating shaft 35 has one end fixed to the first sun gear 31 and the other end opposite to the one end. A first shaft end gear 36 is fixed to the other end of the first sun gear rotating shaft 35. The first shaft end gear 36 has the same rotation center as the first planetary gear mechanism 30. The first shaft end gear 36 and the first sun gear 31 are arranged on a straight line that forms the rotation center of the first planetary gear mechanism 30. The first shaft end gear 36 is connected to the first sun gear 31 via the first sun gear rotating shaft 35. The first shaft end gear 36 rotates integrally with the first sun gear 31. The first sun gear 31, the first sun gear rotating shaft 35, and the first shaft end gear 36 rotate integrally.

[0029] A first input gear 23 is fixed to the tip of the output shaft of the first drive motor 21. The first input gear 23 meshes with outer teeth of a first ring gear 34 of the first planetary gear mechanism 30. The rotational force generated by the first drive motor 21 is input to the first ring gear 34. In the first embodiment, among the multiple rotational elements of the first planetary gear mechanism 30, the first ring gear 34 corresponds to the first input element to which the rotational force is input from the first drive motor 21.

[0030] The power transmission device 20 includes a first output shaft 71. The first output shaft 71 is connected to the first planetary carrier 33 of the first planetary gear mechanism 30. The first output shaft 71 outputs a driving force transmitted to the sprocket 2L. The first output shaft 71 is connected to the left sprocket 2L via a left steering brake 73 and a left final reduction gear 81. The driving force transmitted from the first planetary gear mechanism 30 to the first output shaft 71 is transmitted to the sprocket 2L via the final reduction gear 81. The first planetary carrier 33 corresponds to a first output element connected to the first output shaft 71. In the first embodiment, the first sun gear 31 corresponds to a first intermediate element that is rotatable relative to the first ring gear 34 and the first planetary carrier 33.

[0031] The steering brake 73 is disposed between the first planetary gear mechanism 30 and the final reduction gear 81. The steering brake 73 brakes the rotation of the first output shaft 71. The steering brake 73 is, for example, a hydraulic brake that can be switched between a braking state and a non-braking state by hydraulic pressure. By placing the steering brake 73 in a braking state, the rotation of the first output shaft 71 is braked. As a result, the rotation of the final reduction gear 81 connected to the first output shaft 71 is reduced, and the rotation of the sprocket 2L is braked.

[0032] The first sun gear 31 and the first output shaft 71 are arranged side by side with a gap in the axial direction of rotation of the first planetary gear mechanism 30. The first sun gear rotation shaft 35 and the first output shaft 71 are arranged side by side with a gap in the axial direction of rotation of the first planetary gear mechanism 30. The first output shaft 71 constituting the first output element does not pass through the first sun gear 31.

[0033] There is no other shaft coaxially transmitting driving force on the outer periphery of first sun gear rotating shaft 35. There is no other shaft coaxially transmitting driving force on the outer periphery of first output shaft 71. There is no other shaft penetrating first sun gear rotating shaft 35. There is no other shaft penetrating first output shaft 71. In other words, the coaxial double structure as seen in Patent Document 1 does not exist on the side of first planetary gear mechanism 30 (the left half of FIG. 3).

[0034] The power transmission device 20 includes a second planetary gear mechanism 40. The second planetary gear mechanism 40 has a plurality of rotating elements. The plurality of rotating elements of the second planetary gear mechanism 40 includes a second sun gear 41, a second planetary gear 42, a second planetary carrier 43, and a second ring gear 44.

[0035] The second sun gear 41 is disposed at the center of the second planetary gear mechanism 40 and is configured to be rotatable. The second planetary gears 42 are disposed radially outside the second sun gear 41 at intervals in the circumferential direction. Each of the second planetary gears 42 is supported by a second planetary carrier 43. The second ring gear 44 is disposed radially outside the second planetary gear 42. The second ring gear 44 has inner peripheral teeth that mesh with the second planetary gear 42 and outer peripheral teeth that mesh with a second input gear 24 described later.

[0036] Each second planetary gear 42 meshes with the outer peripheral teeth of the second sun gear 41 and the inner peripheral teeth of the second ring gear 44 and is capable of rotating on its own axis. The second planetary carrier 43 is capable of rotating around the second sun gear 41. Each second planetary gear 42 is capable of revolving around the second sun gear 41 while being supported by the second planetary carrier 43. The second ring gear 44 is capable of rotating around the second planetary gear 42 and the second planetary carrier 43.

[0037] The rotation centers of the second sun gear 41, the second planetary carrier 43 and the second ring gear 44 and the revolution axis of the second planetary gear 42 are on the same straight line, which is the rotation center of the second planetary gear mechanism 40. The rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40 are on the same straight line.

[0038] A second sun gear rotating shaft 45 is fixed to the second sun gear 41. The second sun gear rotating shaft 45 extends in the axial direction of rotation of the second planetary gear mechanism 40. The second sun gear rotating shaft 45 is disposed concentrically with the rotation center of the second planetary gear mechanism 40. The second sun gear rotating shaft 45 rotates integrally with the second sun gear 41.

[0039] The second sun gear rotating shaft 45 has one end fixed to the second sun gear 41 and the other end opposite to the one end. A second shaft end gear 46 is fixed to the other end of the second sun gear rotating shaft 45. The second shaft end gear 46 has the same rotation center as the second planetary gear mechanism 40. The second shaft end gear 46 and the second sun gear 41 are arranged on a straight line that forms the rotation center of the second planetary gear mechanism 40. The second shaft end gear 46 is connected to the second sun gear 41 via the second sun gear rotating shaft 45. The second shaft end gear 46 rotates integrally with the second sun gear 41. The second sun gear 41, the second sun gear rotating shaft 45, and the second shaft end gear 46 rotate integrally.

[0040] A second input gear 24 is fixed to the tip of the output shaft of the second drive motor 22. The second input gear 24 meshes with outer teeth of a second ring gear 44 of the second planetary gear mechanism 40. The rotational force generated by the second drive motor 22 is input to the second ring gear 44. In the first embodiment, among the multiple rotational elements of the second planetary gear mechanism 40, the second ring gear 44 corresponds to the second input element to which the rotational force is input from the second drive motor 22.

[0041] The power transmission device 20 includes a second output shaft 72. The second output shaft 72 is connected to the second planetary carrier 43 of the second planetary gear mechanism 40. The second output shaft 72 outputs a driving force transmitted to the sprocket 2R. The second output shaft 72 is connected to the right sprocket 2R via a right steering brake 74 and a right final reduction gear 82. The driving force transmitted from the second planetary gear mechanism 40 to the second output shaft 72 is transmitted to the sprocket 2R via the final reduction gear 82. The second planetary carrier 43 corresponds to a second output element connected to the second output shaft 72. In the first embodiment, the second sun gear 41 corresponds to a second intermediate element that is rotatable relative to the second ring gear 44 and the second planetary carrier 43.

[0042] The steering brake 74 is disposed between the second planetary gear mechanism 40 and the final reduction gear 82. The steering brake 74 brakes the rotation of the second output shaft 72. The steering brake 74 is, for example, a hydraulic brake that can be switched between a braking state and a non-braking state by hydraulic pressure. By placing the steering brake 74 in a braking state, the rotation of the second output shaft 72 is braked. As a result, the rotation of the final reduction gear 82 connected to the second output shaft 72 is reduced, and the rotation of the sprocket 2R is braked. By making the rotation speeds of the left and right sprockets 2L, 2R different, the bulldozer 1 turns left and right. By driving only one of the left and right sprockets 2L, 2R to rotate and stopping the other, the bulldozer 1 makes a pivot turn.

[0043] The second sun gear 41 and the second output shaft 72 are arranged side by side with a gap in the axial direction of rotation of the second planetary gear mechanism 40. The second sun gear rotation shaft 45 and the second output shaft 72 are arranged side by side with a gap in the axial direction of rotation of the second planetary gear mechanism 40. The second output shaft 72 constituting the second output element does not pass through the second sun gear 41.

[0044] There is no other shaft coaxially transmitting driving force on the outer periphery of second sun gear rotating shaft 45. There is no other shaft coaxially transmitting driving force on the outer periphery of second output shaft 72. There is no other shaft penetrating second sun gear rotating shaft 45. There is no other shaft penetrating second output shaft 72. In other words, the coaxial double structure as seen in Patent Document 1 does not exist on the second planetary gear mechanism 40 side (the right half of FIG. 3 ).

[0045] The first output shaft 71, the first sun gear 31, the second sun gear 41, and the second output shaft 72 are arranged side by side at intervals in the axial direction of rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40 (the left-right direction in FIG. 3). The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side at intervals in the axial direction of rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0046] The power transmission device 20 further includes a first rotation transmission element 50. The first rotation transmission element 50 is configured to be rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. The first sun gear rotating shaft 35 is disposed concentrically with the rotation center of the first planetary gear mechanism 30, and the first rotation transmission element 50 is disposed away from the first sun gear rotating shaft 35 in the radial direction of the rotation of the first planetary gear mechanism 30. The first rotation transmission element 50 is disposed radially outside the first ring gear 34.

[0047] The first rotation transmission element 50 has a first shaft portion 51. The first shaft portion 51 extends in a direction parallel to the rotation axial direction of the first planetary gear mechanism 30. The first shaft portion 51 and the first sun gear rotation shaft 35 are arranged in parallel. The first shaft portion 51 and the first output shaft 71 are arranged in parallel.

[0048] The first rotation transmission element 50 has first connecting gears 52 and 53. The first connecting gear 52 is fixed to one end of a first shaft portion 51. The first connecting gear 53 is fixed to the other end of the first shaft portion 51. The first shaft portion 51 and the first connecting gears 52 and 53 rotate integrally.

[0049] The first connecting gear 52 meshes with the outer teeth of the first ring gear 34 of the first planetary gear mechanism 30. The first connecting gear 53 meshes with the second shaft end gear 46.

[0050] The rotational force generated by the first drive motor 21 is input to the first ring gear 34, causing the first ring gear 34 to rotate. The rotation of the first ring gear 34 is transmitted to the first connection gear 52. The first connection gear 53 rotates integrally with the first connection gear 52. The rotation of the first connection gear 53 is transmitted to the second shaft end gear 46. The second sun gear 41 rotates integrally with the second shaft end gear 46. The first rotation transmission element 50 transmits the rotation of the first ring gear 34 of the first planetary gear mechanism 30 to the second sun gear 41 of the second planetary gear mechanism 40 via the second shaft end gear 46. The first drive motor 21 is configured to be capable of transmitting a rotational force to the first ring gear 34 of the first planetary gear mechanism 30 and to be capable of transmitting a rotational force to the second sun gear 41 of the second planetary gear mechanism 40.

[0051] The power transmission device 20 further includes a second rotation transmission element 60. The second rotation transmission element 60 is configured to be rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. The second sun gear rotating shaft 45 is disposed concentrically with the rotation center of the second planetary gear mechanism 40, and the second rotation transmission element 60 is disposed away from the second sun gear rotating shaft 45 in the radial direction of the rotation of the second planetary gear mechanism 40. The second rotation transmission element 60 is disposed radially outside the second ring gear 44.

[0052] The second rotation transmission element 60 has a second shaft portion 61. The second shaft portion 61 extends in a direction parallel to the rotation axis direction of the second planetary gear mechanism 40. The second shaft portion 61 and the second sun gear rotation shaft 45 are arranged in parallel. The second shaft portion 61 and the second output shaft 72 are arranged in parallel.

[0053] The second rotation transmission element 60 has second connecting gears 62, 63. The second connecting gear 62 is fixed to one end of the second shaft portion 61. The second connecting gear 63 is fixed to the other end of the second shaft portion 61. The second shaft portion 61 and the second connecting gears 62, 63 rotate integrally.

[0054] The second connecting gear 62 meshes with the outer teeth of the second ring gear 44 of the second planetary gear mechanism 40. The second connecting gear 63 meshes with the first shaft end gear 36. In FIG. 3, a broken line is drawn between the second connecting gear 62 and the second ring gear 44, and a broken line is drawn between the second connecting gear 63 and the first shaft end gear 36, but in reality, the second connecting gear 62 directly meshes with the second ring gear 44, and the second connecting gear 63 directly meshes with the first shaft end gear 36. The second rotation transmission element 60 is actually disposed at a position different from the first rotation transmission element 50 in the circumferential direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40, so that the second connecting gear 62 can be directly meshed with the second ring gear 44, and the second connecting gear 63 can be directly meshed with the first shaft end gear 36.

[0055] The rotational force generated by the second drive motor 22 is input to the second ring gear 44, causing the second ring gear 44 to rotate. The rotation of the second ring gear 44 is transmitted to the second connection gear 62. The second connection gear 63 rotates integrally with the second connection gear 62. The rotation of the second connection gear 63 is transmitted to the first shaft end gear 36. The first sun gear 31 rotates integrally with the first shaft end gear 36. The second rotation transmission element 60 transmits the rotation of the second ring gear 44 of the second planetary gear mechanism 40 to the first sun gear 31 of the first planetary gear mechanism 30 via the first shaft end gear 36. The second drive motor 22 is configured to be capable of transmitting a rotational force to the second ring gear 44 of the second planetary gear mechanism 40 and to be capable of transmitting a rotational force to the first sun gear 31 of the first planetary gear mechanism 30.

[0056] Since the power transmission device 20 has the above-mentioned configuration, in the skeleton diagram shown in Figure 3, the first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and the second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically.

[0057] The power transmission device 20 described above includes the first planetary gear mechanism 30 and the second planetary gear mechanism 40 between the first drive motor 21, the second drive motor 22, and the left and right sprockets 2L, 2R. The rotating elements of the first planetary gear mechanism 30 other than the first planetary carrier 33 forming the first output element and the rotating elements of the second planetary gear mechanism 40 other than the second planetary carrier 43 forming the second output element are connected by the first rotation transmission element 50 and the second rotation transmission element 60. Specifically, the first rotation transmission element 50 connects the first ring gear 34 and the second sun gear 41, and the second rotation transmission element 60 connects the second ring gear 44 and the first sun gear 31. This realizes a four-element, two-degree-of-freedom differential mechanism.

[0058] When a difference is created between the torques output from the first drive motor 21 and the second drive motor 22, this torque difference is amplified by the differential mechanism and transmitted to the left and right drive wheels, sprockets 2L, 2R. In this way, the power transmission device 20 can increase the torque difference transmitted to the left and right sprockets 2L, 2R.

[0059] 3, the first and second transmission paths are symmetrical in structure, so that the components constituting the first and second transmission paths can be made common to each other. This allows the number of types of components to be reduced, thereby realizing cost reduction of the power transmission device 20.

[0060] The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71 is connected to the rotating elements of the first planetary gear mechanism 30 out of the first planetary gear mechanism 30 and the second planetary gear mechanism 40, and is not directly connected to the rotating elements of the second planetary gear mechanism 40. The second output shaft 72 is connected to the rotating elements of the second planetary gear mechanism 40 out of the first planetary gear mechanism 30 and the second planetary gear mechanism 40, and is not directly connected to the rotating elements of the first planetary gear mechanism 30.

[0061] The first output shaft 71, the first sun gear 31 of the first planetary gear mechanism 30, the second sun gear 41 of the second planetary gear mechanism 40, and the second output shaft 72 are arranged side by side in the axial direction of rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. The first output shaft 71, the first sun gear rotating shaft 35 connected to the first sun gear 31, the second sun gear rotating shaft 45 connected to the second sun gear 41, and the second output shaft 72 are arranged side by side in the axial direction of rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0062] In the power transmission path shown in the skeleton diagram of Fig. 3, the first output shaft 71 is disposed entirely closer to the sprocket 2L than the first planetary gear mechanism 30. The power transmission device 20 is structured such that the first output shaft 71 does not axially pass through the rotating elements of the first planetary gear mechanism 30. The first output shaft 71 and the rotating elements of the first planetary gear mechanism 30 do not form a coaxial double structure. The first output shaft 71 does not pass through the first sun gear 31.

[0063] In the power transmission path shown in the skeleton diagram of Fig. 3, the second output shaft 72 is disposed entirely closer to the sprocket 2R than the second planetary gear mechanism 40. The power transmission device 20 is structured such that the second output shaft 72 does not axially pass through the rotating elements of the second planetary gear mechanism 40. The second output shaft 72 and the rotating elements of the second planetary gear mechanism 40 do not form a coaxial double structure. The second output shaft 72 does not pass through the second sun gear 41.

[0064] 3, there is no other shaft coaxially transmitting driving force on the outer periphery of the first sun gear rotating shaft 35, the outer periphery of the first output shaft 71, the outer periphery of the second sun gear rotating shaft 45, or the outer periphery of the second output shaft 72. There is no other shaft penetrating the first sun gear rotating shaft 35, the first output shaft 71, the second sun gear rotating shaft 45, or the second output shaft 72. In other words, the coaxial double structure as seen in Patent Document 1 does not exist in the power transmission device 20 described above.

[0065] None of the first sun gear rotating shaft 35, the first output shaft 71, the second sun gear rotating shaft 45, and the second output shaft 72 constitutes a multiple shaft structure in which another shaft is inserted into the inner hole of a hollow shaft. The first sun gear rotating shaft 35, the first output shaft 71, the second sun gear rotating shaft 45, and the second output shaft 72 all have a single shaft structure, not a multiple shaft structure. Note that the fact that each of the first sun gear rotating shaft 35, the first output shaft 71, the second sun gear rotating shaft 45, and the second output shaft 72 has a single shaft structure does not exclude at least one shaft being a hollow shaft.

[0066] Therefore, the diameter of each shaft can be designed to be optimal according to the passing torque, and this makes it possible to prevent the entire device from becoming large, even in the power transmission device 20 used in a work machine such as a bulldozer 1 that needs to transmit a large torque.

[0067] [Second embodiment] Fig. 4 is a skeleton diagram showing a power transmission device 20 in the second embodiment. In the following description of the embodiments, the same configurations as those in the first embodiment will not be described, and the description will focus on the configurations specific to each embodiment that differ from the first embodiment. Note that in Figs. 4 to 10, the left and right sprockets 2L, 2R, the left and right steering brakes 73, 74, and the left and right final reduction gears 81, 82 are the same as those in the first embodiment, and therefore are not shown.

[0068] As shown in Fig. 4, the first input gear 23 and the first shaft end gear 36 mesh with each other. The first drive motor 21 generates a rotational force that is input to the first sun gear 31. The rotational force generated by the first drive motor 21 is input to the first sun gear 31 via the first shaft end gear 36. In the second embodiment, among the multiple rotating elements of the first planetary gear mechanism 30, the first sun gear 31 corresponds to the first input element to which the rotational force is input from the first drive motor 21. In the second embodiment, the first ring gear 34 corresponds to a first intermediate element that is rotatable relative to the first sun gear 31 and the first planetary carrier 33.

[0069] The second input gear 24 meshes with the second shaft end gear 46. The second drive motor 22 generates a rotational force that is input to the second sun gear 41. The rotational force generated by the second drive motor 22 is input to the second sun gear 41 via the second shaft end gear 46. In the second embodiment, among the multiple rotating elements of the second planetary gear mechanism 40, the second sun gear 41 corresponds to the second input element to which the rotational force is input from the second drive motor 22. In the second embodiment, the second ring gear 44 corresponds to a second intermediate element that is rotatable relative to the second sun gear 41 and the second planetary carrier 43.

[0070] The rotational force generated by the first drive motor 21 is input to the first shaft end gear 36. The first sun gear 31 rotates integrally with the first shaft end gear 36. The rotation of the first shaft end gear 36 is transmitted to the second connection gear 63. The second connection gear 62 rotates integrally with the second connection gear 63. The rotation of the second connection gear 62 is transmitted to the second ring gear 44. The second rotation transmission element 60 transmits the rotation of the first sun gear 31 of the first planetary gear mechanism 30 to the second ring gear 44 of the second planetary gear mechanism 40. The first drive motor 21 is configured to be capable of transmitting a rotational force to the first sun gear 31 of the first planetary gear mechanism 30 and to be capable of transmitting a rotational force to the second ring gear 44 of the second planetary gear mechanism 40.

[0071] The rotational force generated by the second drive motor 22 is input to the second shaft end gear 46. The second sun gear 41 rotates integrally with the second shaft end gear 46. The rotation of the second shaft end gear 46 is transmitted to the first connection gear 53. The first connection gear 52 rotates integrally with the first connection gear 53. The rotation of the first connection gear 52 is transmitted to the first ring gear 34. The first rotation transmission element 50 transmits the rotation of the second sun gear 41 of the second planetary gear mechanism 40 to the first ring gear 34 of the first planetary gear mechanism 30. The second drive motor 22 is configured to be capable of transmitting a rotational force to the second sun gear 41 of the second planetary gear mechanism 40 and to be capable of transmitting a rotational force to the first ring gear 34 of the first planetary gear mechanism 30.

[0072] In the power transmission device 20 of the second embodiment described above, the first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and the second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically in the skeleton diagram shown in Fig. 4. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by the first rotation transmission element 50 and the second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0073] Therefore, the power transmission device 20 of the second embodiment can also provide the same effects as those of the first embodiment.

[0074] [Third embodiment] FIG. 5 is a skeleton diagram showing a power transmission device 20 in a third embodiment. In the third embodiment, as shown in FIG. 5, an output shaft of the first drive motor 21 and a first shaft portion 51 of the first rotation transmission element 50 are integrally configured and can rotate together. A part of the output shaft of the first drive motor 21 may function as the first shaft portion 51. An output shaft of the second drive motor 22 and a second shaft portion 61 of the second rotation transmission element 60 are integrally configured and can rotate together. A part of the output shaft of the second drive motor 22 may function as the second shaft portion 61.

[0075] The rotational force generated by first drive motor 21 is input to first ring gear 34 and also to second shaft end gear 46. Second sun gear 41 rotates integrally with second shaft end gear 46. The rotational force generated by second drive motor 22 is input to second ring gear 44 and also to first shaft end gear 36. First sun gear 31 rotates integrally with first shaft end gear 36.

[0076] 5, in the power transmission device 20 of the third embodiment, a first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and a second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0077] Therefore, the power transmission device 20 of the third embodiment can also provide the same effects as those of the first embodiment.

[0078] [Fourth embodiment] 6 is a skeleton diagram showing a power transmission device 20 in a fourth embodiment. In the fourth embodiment, the output shaft of the first drive motor 21 extends to both the left and right sides from the first drive motor 21. The output shaft of the first drive motor 21 functions as a first shaft portion 51 of the first rotation transmission element 50. A first connecting gear 52 is fixed to one output shaft of the first drive motor 21. A first connecting gear 53 is fixed to the other output shaft of the first drive motor 21. The first connecting gears 52, 53 may be fixed to the tip of the output shaft of the first drive motor 21.

[0079] The output shaft of the second drive motor 22 extends to both the left and right sides from the second drive motor 22. The output shaft of the second drive motor 22 functions as a second shaft portion 61 of the second rotation transmission element 60. A second connecting gear 62 is fixed to one output shaft of the second drive motor 22. A second connecting gear 63 is fixed to the other output shaft of the second drive motor 22. The second connecting gears 62, 63 may be fixed to the tip of the output shaft of the second drive motor 22.

[0080] The rotational force generated by first drive motor 21 is input to first ring gear 34 and also to second shaft end gear 46. Second sun gear 41 rotates integrally with second shaft end gear 46. The rotational force generated by second drive motor 22 is input to second ring gear 44 and also to first shaft end gear 36. First sun gear 31 rotates integrally with first shaft end gear 36.

[0081] In the power transmission device 20 of the fourth embodiment, in the skeleton diagram shown in Fig. 6, a first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and a second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0082] Therefore, the power transmission device 20 of the fourth embodiment can also provide the same effects as those of the first embodiment.

[0083] [Fifth embodiment] 7 is a skeleton diagram showing a power transmission device 20 in the fifth embodiment. As shown in FIG. 7, the first input gear 23 and the first shaft end gear 36 are engaged with each other. The rotational force generated by the first drive motor 21 is input to the first sun gear 31 via the first shaft end gear 36. In the fifth embodiment, similarly to the second embodiment, the first sun gear 31 corresponds to the first input element to which the rotational force is input from the first drive motor 21. The first ring gear 34 corresponds to the first intermediate element that is rotatable relative to the first sun gear 31 and the first planetary carrier 33.

[0084] The second input gear 24 meshes with the second shaft end gear 46. The rotational force generated by the second drive motor 22 is input to the second sun gear 41 via the second shaft end gear 46. In the second embodiment, similarly to the second embodiment, the second sun gear 41 corresponds to the second input element to which the rotational force is input from the second drive motor 22. The second ring gear 44 corresponds to a second intermediate element that is rotatable relative to the second sun gear 41 and the second planetary carrier 43.

[0085] Of the multiple rotating elements of the first planetary gear mechanism 30, a first carrier gear 37 is connected to the first planetary carrier 33 which is a first output element. The first carrier gear 37 rotates integrally with the first planetary carrier 33. Of the multiple rotating elements of the second planetary gear mechanism 40, a second carrier gear 47 is connected to the second planetary carrier 43 which is a second output element. The second carrier gear 47 rotates integrally with the second planetary carrier 43.

[0086] The first connecting gear 52 of the first rotation transmission element 50 meshes with the first ring gear 34 of the first planetary gear mechanism 30. The first connecting gear 53 meshes with the second carrier gear 47. The first rotation transmission element 50 transmits rotation to the second planetary carrier 43, which is the second output element. The first rotation transmission element 50 synchronizes the rotation of the first ring gear 34 and the second planetary carrier 43.

[0087] The second connecting gear 62 of the second rotation transmission element 60 meshes with the second ring gear 44 of the second planetary gear mechanism 40. The second connecting gear 63 meshes with the first carrier gear 37. The second rotation transmission element 60 transmits rotation to the first planetary carrier 33, which is the first output element. The second rotation transmission element 60 synchronizes the rotation of the second ring gear 44 and the second planetary carrier 43.

[0088] 7, in the power transmission device 20 of the fifth embodiment, a first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and a second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0089] Therefore, the power transmission device 20 of the fifth embodiment can also provide the same effects as those of the first embodiment.

[0090] [Sixth embodiment] 8 is a skeleton diagram showing a power transmission device 20 in the sixth embodiment. As in the fifth embodiment, a first carrier gear 37 is connected to a first planetary carrier 33, which is a first output element, among a plurality of rotating elements of a first planetary gear mechanism 30. The first carrier gear 37 rotates integrally with the first planetary carrier 33. A second carrier gear 47 is connected to a second planetary carrier 43, which is a second output element, among a plurality of rotating elements of a second planetary gear mechanism 40. The second carrier gear 47 rotates integrally with the second planetary carrier 43.

[0091] As shown in Fig. 8, the output shaft of first drive motor 21 forms first sun gear rotating shaft 35. The rotational force generated by first drive motor 21 is input to first sun gear 31 without passing through a reduction mechanism. The output shaft of second drive motor 22 forms second sun gear rotating shaft 45. The rotational force generated by second drive motor 22 is input to second sun gear 41 without passing through a reduction mechanism.

[0092] As in the fifth embodiment, the first connecting gear 52 of the first rotation transmission element 50 meshes with the first ring gear 34 of the first planetary gear mechanism 30. The first connecting gear 53 meshes with the second carrier gear 47. The second connecting gear 62 of the second rotation transmission element 60 meshes with the second ring gear 44 of the second planetary gear mechanism 40. The second connecting gear 63 meshes with the first carrier gear 37.

[0093] In the power transmission device 20 of the sixth embodiment, in the skeleton diagram shown in Fig. 8, the first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and the second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by the first rotation transmission element 50 and the second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0094] Therefore, the power transmission device 20 of the sixth embodiment can also provide the same effects as those of the first embodiment.

[0095] [Seventh embodiment] 9 is a skeleton diagram showing a power transmission device 20 in the seventh embodiment. As in the fifth embodiment, a first carrier gear 37 is connected to a first planetary carrier 33, which is a first output element, among a plurality of rotating elements of a first planetary gear mechanism 30. The first carrier gear 37 rotates integrally with the first planetary carrier 33. A second carrier gear 47 is connected to a second planetary carrier 43, which is a second output element, among a plurality of rotating elements of a second planetary gear mechanism 40. The second carrier gear 47 rotates integrally with the second planetary carrier 43.

[0096] As shown in FIG. 9 , the first connecting gear 52 of the first rotation transmission element 50 meshes with the first carrier gear 37. The first connecting gear 53 meshes with the second shaft end gear 46. The first rotation transmission element 50 synchronizes the rotation of the first planetary carrier 33 and the second sun gear 41. The second connecting gear 62 of the second rotation transmission element 60 meshes with the second carrier gear 47. The second connecting gear 63 meshes with the first shaft end gear 36. The second rotation transmission element 60 synchronizes the rotation of the first sun gear 31 and the second planetary carrier 43.

[0097] 9, in the power transmission device 20 of the seventh embodiment, a first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and a second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0098] Therefore, the power transmission device 20 of the seventh embodiment can also provide the same effects as those of the first embodiment.

[0099] [Eighth embodiment] 10 is a skeleton diagram showing a power transmission device 20 in the eighth embodiment. As in the fourth embodiment, the output shaft of the first drive motor 21 extends to both the left and right sides from the first drive motor 21 and functions as a first shaft portion 51 of a first rotation transmission element 50. A first connecting gear 52 is fixed to one output shaft of the first drive motor 21. A first connecting gear 53 is fixed to the other output shaft of the first drive motor 21.

[0100] The output shaft of the second drive motor 22 extends to both the left and right sides from the second drive motor 22 and functions as a second shaft portion 61 of the second rotation transmission element 60. A second connecting gear 62 is fixed to one output shaft of the second drive motor 22. A second connecting gear 63 is fixed to the other output shaft of the second drive motor 22.

[0101] The power transmission device 20 of the eighth embodiment includes a first intervening member 91 and a second intervening member 92. The first connecting gear 52 of the first rotation transmission element 50 meshes with the first ring gear 34 of the first planetary gear mechanism 30 via the first intervening member 91. The rotational force generated by the first drive motor 21 is input to the first ring gear 34 via the first intervening member 91. The second connecting gear 62 of the second rotation transmission element 60 meshes with the second ring gear 44 of the second planetary gear mechanism 40 via the second intervening member 92. The rotational force generated by the second drive motor 22 is input to the second ring gear 44 via the second intervening member 92.

[0102] 10, in the power transmission device 20 of the eighth embodiment, a first transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2L and a second transmission path that transmits the rotational forces of the first drive motor 21 and the second drive motor 22 to the sprocket 2R are configured symmetrically. The rotating elements of the first planetary gear mechanism 30 and the rotating elements of the second planetary gear mechanism 40 are connected by a first rotation transmission element 50 and a second rotation transmission element 60. The first output shaft 71, the first sun gear rotating shaft 35, the second sun gear rotating shaft 45, and the second output shaft 72 are arranged side by side in the axial direction of the rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0103] Therefore, the power transmission device 20 of the eighth embodiment can also provide the same effects as those of the first embodiment.

[0104] The first rotation transmission element 50 and the second rotation transmission element 60 in the first to seventh embodiments are disposed radially outside the first planetary gear mechanism 30 and the second planetary gear mechanism 40. In contrast to this, the first rotation transmission element 50 and the second rotation transmission element 60 in the eighth embodiment are disposed radially inside the first ring gear 34 and disposed radially inside the second ring gear 44. The first rotation transmission element 50 and the second rotation transmission element 60 are disposed closer to the rotation centers of the first planetary gear mechanism 30 and the second planetary gear mechanism 40.

[0105] Therefore, according to the power transmission device 20 of the eighth embodiment, it is possible to achieve further miniaturization in the radial direction of rotation of the first planetary gear mechanism 30 and the second planetary gear mechanism 40. It is also possible to improve the degree of freedom in the arrangement of the first drive motor 21 and the second drive motor 22.

[0106] In the power transmission devices 20 of the first, third, fourth and seventh embodiments, intervening members similar to those in the eighth embodiment (intervening members 91, 92 in the eighth embodiment) may be provided between the first drive motor 21 and the first ring gear 34 and between the second drive motor 22 and the second ring gear 44. In the power transmission devices 20 of the second, fifth and sixth embodiments, intervening members may be provided between the first rotation transmission element 50 and the first ring gear 34 and between the second rotation transmission element 60 and the second ring gear 44.

[0107] In the above embodiment, an example has been described in which the engine 11 drives the generator 15, and the first drive motor 21 and the second drive motor 22 are driven by the electric power generated by the generator 15. The work machine may be equipped with a hydraulic pump instead of the generator 15, and the first drive motor 21 and the second drive motor 22 may be hydraulic motors. The hydraulic pump may be driven by the engine 11 to discharge pressurized oil, and the pressurized oil may be supplied to the first drive motor 21 and the second drive motor 22 to drive the first drive motor 21 and the second drive motor 22, causing the first drive motor 21 and the second drive motor 22 to generate rotational force.

[0108] In the above embodiment, the bulldozer 1 has been described as an example of a work machine, but the concept of the present disclosure can be applied to other types of work machines equipped with a tracked traveling device, such as a shovel, a crawler dump, etc. The concept of the present disclosure can also be applied to work machines equipped with a wheeled traveling device, such as a wheel loader, a motor grader, etc.

[0109] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0110] 1 Bulldozer, 2, 2L, 2R sprockets, 4 Travel gear, 7 Body, 11 Engine, 15 Generator, 16 Wiring, 20 Power transmission device, 21 First drive motor, 22 Second drive motor, 23 First input gear, 24 Second input gear, 30 First planetary gear mechanism, 31 First sun gear, 32 First planetary gear, 33 First planetary carrier, 34 First ring gear, 35 First sun gear rotating shaft, 36 First shaft end gear, 37 First carrier gear, 40 Second planetary gear mechanism, 41 Second sun gear, 42 Second planetary gear, 43 Second planetary carrier, 44 Second ring gear, 45 Second sun gear rotating shaft, 46 Second shaft end gear, 47 Second carrier gear, 50 First rotation transmission element, 51 First shaft portion, 52, 53 First connecting gear, 60 second rotation transmission element, 61 second shaft portion, 62, 63 second connecting gear portion, 71 first output shaft, 72 second output shaft, 73, 74 steering brake, 81, 82 final reduction gear, 91 first intermediate member, 92 second intermediate member.

Claims

1. A power transmission device that transmits driving force to a first drive wheel and a second drive wheel, a first drive motor that generates a rotational force; a second drive motor that generates a rotational force; a first output shaft that outputs a driving force to be transmitted to the first drive wheel; a second output shaft that outputs a driving force to be transmitted to the second drive wheel; a first planetary gear mechanism having a plurality of rotating elements including a first input element to which a rotational force is input from the first drive motor and a first output element connected to the first output shaft; a second planetary gear mechanism having a plurality of rotating elements including a second input element to which a rotational force is input from the second drive motor and a second output element connected to the second output shaft, the first output shaft, the second output shaft, the first planetary gear mechanism, and the second planetary gear mechanism have respective rotation centers that are on the same first straight line; a first sun gear rotation shaft of the first planetary gear mechanism, a second sun gear rotation shaft of the second planetary gear mechanism, the first output shaft, and the second output shaft have a single shaft structure, a power transmission device in which the rotation centers of the first drive motor and the second drive motor are both positioned offset from the first straight line.

2. A power transmission device, a first planetary gear mechanism having a first sun gear, a first planetary gear, a first ring gear, and a first planet carrier; a first drive motor that generates a rotational force that is input to the first ring gear; a first output shaft connected to the first planetary carrier; a second planetary gear mechanism having a second sun gear, a second planetary gear, a second ring gear, and a second planet carrier; a second drive motor that generates a rotational force that is input to the second ring gear; a second output shaft connected to the second planetary carrier; a first rotation transmission element that is rotatable about a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism and that transmits rotation of the first ring gear to the second sun gear; a second rotation transmission element that is rotatable around a rotation center different from the rotation centers of the first planetary gear mechanism and the second planetary gear mechanism and that transmits rotation of the second ring gear to the first sun gear.

3. 3. The power transmission device according to claim 1, wherein the first drive motor and the second drive motor are electric motors.

4. A power transmission device that transmits driving force to a first drive wheel and a second drive wheel, a first output shaft that outputs a driving force to be transmitted to the first drive wheel; a second output shaft that outputs a driving force to be transmitted to the second drive wheel; a first planetary gear mechanism having a first sun gear, a first planetary carrier, and a first ring gear; a second planetary gear mechanism having a second sun gear, a second planetary carrier, and a second ring gear; a first sun gear rotation shaft extending in the axial direction of rotation of the first planetary gear mechanism and the second planetary gear mechanism and rotating integrally with the first sun gear; a second sun gear rotation shaft extending in the axial direction and rotating integrally with the second sun gear, the first sun gear rotation shaft, the second sun gear rotation shaft, the first output shaft, and the second output shaft have rotation centers that are on the same first straight line; a power transmission device in which the first sun gear rotating shaft, the second sun gear rotating shaft, the first output shaft, and the second output shaft have a single-shaft structure and do not constitute part of a multiple-shaft structure.

5. A vehicle body, a first drive wheel disposed on the left side of the vehicle body and driven to rotate to propel the vehicle body; a second drive wheel disposed on the right side of the vehicle body and driven to rotate to cause the vehicle body to travel; The power transmission device according to claim 1, claim 2 or claim 4; A work machine comprising:

6. A vehicle body, a first drive wheel disposed on the left side of the vehicle body and driven to rotate to propel the vehicle body; a second drive wheel disposed on the right side of the vehicle body and driven to rotate to cause the vehicle body to travel; The power transmission device according to claim 1, claim 2 or claim 4; Equipped with a bulldozer.

Images