Double-transmission device for crawler tractor

Abstract

The invention provides a double-transmission device for a caterpillar tractor. The device comprises a power main shaft, the end of the power main shaft is in transmission connection with a power output shaft, a mechanical transmission gear is coaxially fixed to the power output shaft, the power output shaft is coaxially connected with the input end of a driving hydraulic motor, a driven main shaft is arranged on one side of the power output shaft, and a mechanical driven gear is axially and rotationally connected to the driven main shaft. A mechanical gear ring is formed on one side of the mechanical driven gear, a hydraulic driven gear is rotationally connected to the end of the driven main shaft, a hydraulic gear ring is formed on one side of the hydraulic driven gear, the mechanical driven gear ring and the hydraulic driven gear ring are fixed to the driven main shaft, the mechanical gear ring rotates through a mechanical shifting fork set, and the hydraulic gear ring rotates through a hydraulic shifting fork set. And an output gear is coaxially fixed on the driven main shaft. The device has the advantages of high transmission efficiency and traction force of mechanical transmission and flexible control of hydraulic transmission at the same time, and has a wider application range and a wider operation scene.

Description

Technical Field

[0001] The invention belongs to the technical field of crawler vehicle transmission, and in particular relates to a double transmission device for a crawler tractor. Background Art

[0002] In paddy field farming, traditional crawler agricultural machinery and transport vehicles are responsible for harvesting and transporting crops.

[0003] Crawler tractors are mainly used for compound agricultural operations such as rotary tillage and plowing in paddy and dry fields. Their crawler walking mechanism can effectively avoid damage to the soil protective layer during paddy field operations. Limited by the fact that the crawler chassis needs to rely on trailer transportation for transfer, it is currently mainly used in paddy field farming scenes, and the main operation is completed by crawler tractors and crawler rotary tillers. Traditional crawler tractors use a mechanical transmission system with the advantages of high transmission efficiency and low energy consumption. Its mechanical step-by-step speed regulation mode can provide large traction output, especially suitable for large-load agricultural machinery such as plowing; but it has shortcomings such as high operating intensity and complex shifting process. The special gearbox for paddy field rotary tillage adopts hydraulic stepless speed regulation HST technology. Although it has the advantage of convenient operation, it is limited by the inherent characteristics of low hydraulic transmission efficiency and is difficult to adapt to the operation needs of large traction agricultural implements. Summary of the invention

[0004] The purpose of the present invention is to provide a dual transmission device for a crawler tractor, which effectively integrates mechanical stepped speed regulation and hydraulic stepless speed regulation modes, retains the high efficiency characteristics of mechanical transmission, and integrates the control advantages of hydraulic stepless speed regulation.

[0005] The object of the present invention is achieved in that:

[0006] A dual transmission device for a crawler tractor comprises a power main shaft input by a power source, the end of the power main shaft is connected to a power output shaft through a meshing bevel gear set, a mechanical transmission gear is coaxially fixed on the power output shaft, the end of the power output shaft is coaxially connected to the input end of a driving hydraulic motor, a parallel driven main shaft is arranged on one side of the power output shaft, a mechanical driven gear meshing with the mechanical transmission gear is axially rotatably connected on the driven main shaft, a coaxial mechanical gear ring is formed on one side of the mechanical driven gear, the end of the driven main shaft is rotatably connected to a hydraulic driven gear meshing with the output end gear of the driving hydraulic motor, and a coaxial hydraulic gear ring is formed on one side of the hydraulic driven gear, a mechanical driven gear ring and a hydraulic driven gear ring are fixed on the driven main shaft, the mechanical gear ring is engaged by a mechanical fork set and drives the mechanical driven gear ring to rotate, the hydraulic gear ring is engaged by a hydraulic fork set and drives the hydraulic driven gear ring to rotate, and an output gear is coaxially fixed on the driven main shaft.

[0007] The present invention is further configured as follows: the mechanical transmission gear includes a forward gear and a reverse gear fixed on the power output shaft, a parallel idler shaft is provided on one side of the power output shaft, and an idler gear meshing with the reverse gear is coaxially fixed on the idler shaft, the mechanical driven gear includes a forward driven gear and a reverse driven gear rotatably connected to the driven main shaft, the forward driven gear meshes with the forward gear, and the reverse driven gear meshes with the idler gear, the mechanical ring gear includes a forward ring gear on one side of the forward driven gear and a reverse ring gear on one side of the reverse driven gear, and the forward ring gear and the reverse ring gear are arranged opposite to each other, the mechanical driven ring gear is located between the forward ring gear and the reverse ring gear, and the mechanical fork group can selectively engage the forward ring gear with the mechanical driven ring gear, or engage the reverse ring gear with the mechanical driven ring gear, or engage the mechanical driven ring gear alone.

[0008] The present invention is further configured as follows: the hydraulic fork group includes a hydraulic fork shaft, a hydraulic fork is slidably arranged on the hydraulic fork shaft, and the end of the hydraulic fork is adapted to be equipped with a hydraulic engagement sleeve sleeved on the hydraulic driven gear ring; the mechanical fork group includes a mechanical fork shaft, a mechanical fork is slidably arranged on the mechanical fork shaft, and the end of the mechanical fork is adapted to be equipped with a mechanical engagement sleeve sleeved on the mechanical driven gear ring, the hydraulic fork shaft and the mechanical fork shaft are parallel to each other, a slidable shift block is provided on the hydraulic fork shaft to drive the hydraulic fork to move, and the shift block is simultaneously slidably arranged on the mechanical fork shaft and drives the mechanical fork to move axially along the mechanical fork shaft.

[0009] The present invention is further configured such that the output gear includes a plurality of gears of different sizes which are axially fixed on the driven main shaft; one side of the output gear drives the traveling intermediate wheel through a meshing reduction gear set; both sides of the traveling intermediate wheel are transmission-connected with a left planetary gear set and a right planetary gear set; the outer sides of the left planetary gear set and the right planetary gear set are respectively meshed-connected with a left output shaft and a right output shaft; and driving wheels are fixed to the ends of the left output shaft and the right output shaft.

[0010] The present invention is further configured as follows: a steering driving wheel is fixed on the power main shaft, a parallel steering shaft is arranged above the power main shaft, an end of the steering shaft is meshed and connected with the steering driving wheel, the other end of the steering shaft is connected to the input end of the steering hydraulic motor through a steering gear set, and the output end of the steering hydraulic motor synchronously drives two sets of parallel steering temporary shafts, the ends of the two steering temporary shafts are meshed and connected through gears and rotate synchronously in opposite directions, a left steering gear meshed with the left planetary gear set is coaxially fixed on one steering temporary shaft, and a right steering gear meshed with the right planetary gear set is coaxially fixed on the other steering temporary shaft.

[0011] The present invention is further configured as follows: the reduction gear group includes a parallel reduction shaft one, a reduction shaft two and a reduction shaft three, the reduction shaft one is rotatably connected with a plurality of single-shaft reduction gears meshing with the output gear, and the single-shaft reduction gears are switched by a shift fork; the reduction shaft three is rotatably connected with a plurality of three-shaft reduction gears, and the three-shaft reduction gears are switched by a shift fork, and a driving intermediate wheel meshing with the traveling intermediate wheel is axially fixed on the reduction shaft three; a plurality of linkage gears for linkage between the single-shaft reduction gear and the three-shaft reduction gear are coaxially fixed on the reduction shaft two.

[0012] The present invention is further configured such that the left planetary gear set and the right planetary gear set have the same mirror image structure and both include a plurality of planetary gears and a sun gear.

[0013] Compared with the prior art, the present invention has the following outstanding and beneficial technical effects:

[0014] 1. The dual transmission device for crawler tractors provided by the present invention changes the output mode of the output gear on the driven main shaft through the control switching of the mechanical fork group and the hydraulic fork group, thereby achieving the advantages of large traction force and high transmission efficiency of mechanical transmission; at the same time, it can adopt the hydraulic motor to achieve stepless speed regulation and perform more precise operations, which is convenient for more farming operations.

[0015] 2. The mechanical transmission gear further provided by the present invention includes forward and reverse, and the forward gear and the reverse gear cooperate with the idler shaft to realize the forward and reverse control of the mechanical transmission, without the need for an additional reversing mechanism, thereby reducing the manufacturing cost; the forward gear ring and the reverse gear ring are arranged opposite to each other, and cooperate with the central mechanical driven gear ring, so that the fork group only needs a single axial movement to complete the forward and reverse switching, and the operation response is faster; the three controls of the mechanical fork group can quickly cut off the mechanical transmission path, which is convenient for rapid switching with the hydraulic transmission mode.

[0016] 3. In the present invention, the hydraulic and mechanical fork groups adopt a parallel axis layout, and realize linkage control through a common shift block to ensure the synchronization of switching between the two transmission modes and avoid misoperation. The hydraulic engagement sleeve and the mechanical engagement sleeve adopt a sleeve structure to improve the centering of the gear ring when engaging and reduce the impact wear of the gear.

[0017] 4. The present invention further adopts multi-size output gears in conjunction with a reduction gear set to achieve multi-stage speed change, thereby expanding the speed and torque adaptation range of the tractor, such as low-speed high-torque farming / high-speed low-torque transportation.

[0018] 5. The present invention further uses a steering hydraulic motor to drive a reversely rotating temporary steering shaft through a gear set, directly inputting differential torque to a planetary gear set, thereby achieving precise crawler differential steering control. Meanwhile, the reverse rotation can achieve a large-angle U-turn operation, thereby enhancing the control and application range of the crawler tractor.

[0019] 6. The present invention adopts a multi-gear gear set, which cooperates with a fork to achieve different speed ratio combinations, ensuring the linkage of power transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural view of a part of the present invention Figure 1 ;

[0021] Figure 2 is a schematic structural view of a part of the present invention Figure 2 ;

[0022] Figure 3 is a schematic structural view of a part of this utility, thank you Figure 3

[0023] Figure 4 is a schematic structural view of the present invention;

[0024] Figure 5 is a schematic structural view of the present invention;

[0025] Figure 6 is a schematic structural view of the reduction gear set of the present invention;

[0026] Reference Signs:

[0027] 1 - Power main shaft; 10 - Steering driving wheel; 11 - Steering shaft; 12 - Steering gear set; 13 - Steering hydraulic motor; 14 - Steering temporary shaft; 140 - Left steering gear; 141 - Right steering gear;

[0028] 2 - Power output shaft; 20 - Idler shaft; 200 - Idler gear

[0029] 3 - Mechanical transmission gear; 30 - Forward gear; 31 - Reverse gear;

[0030] 4 - Driving hydraulic motor;

[0031] 5 - Driven main shaft; 50 - Mechanical driven gear; 500 - Mechanical gear ring; 501 - Forward driven gear; 502 - Reverse driven gear; 503 - Forward gear ring; 504 - Reverse gear ring; 51 - Hydraulic driven gear; 510 - Hydraulic gear ring; 52 - Mechanical driven gear ring; 53 - Hydraulic driven gear ring; 54 - Output gear;

[0032] 6 - Mechanical fork group; 60 - Mechanical fork shaft; 61 - Mechanical fork; 62 - Mechanical engaging sleeve;

[0033] 7 - Hydraulic fork group; 70 - Hydraulic fork shaft; 71 - Hydraulic fork; 72 - Hydraulic engaging sleeve; 73 - Fork block;

[0034] 8 - Reduction gear set; 80 - First reduction shaft; 800 - First shaft reduction gear; 81 - Second reduction shaft; 810 - Linkage gear; 82 - Third reduction shaft; 820 - Third shaft reduction gear; 83 - Driving idler wheel;

[0035] 9 - Traveling idler wheel; 90 - Left planetary gear set; 91 - Right planetary gear set; 92 - Left output shaft; 93 - Right output shaft; 94 - Driving wheel. Specific embodiments

[0036] The present invention will be further described below with specific embodiments in conjunction with the accompanying drawings. See Figure 1 — Figure 6 :

[0037] A dual - drive device for a crawler tractor, comprising a power main shaft 1 input by a power source. The end of the power main shaft 1 is drivingly connected to a power output shaft 2 through an engaged bevel gear set. A mechanical transmission gear 3 is coaxially fixed on the power output shaft 2. The end of the power output shaft 2 is coaxially connected to the input end of a driving hydraulic motor 4. A driven main shaft 5 parallel to one side of the power output shaft 2 is provided. A mechanical driven gear 50 meshing with the mechanical transmission gear 3 is axially rotatably connected on the driven main shaft 5. A coaxial mechanical gear ring 500 is formed on one side of the mechanical driven gear 50. The end of the driven main shaft 5 is rotatably connected to a hydraulic driven gear 51 meshing with the output end gear of the driving hydraulic motor 4. And a coaxial hydraulic gear ring 510 is formed on one side of the hydraulic driven gear 51. A mechanical driven gear ring 52 and a hydraulic driven gear ring 53 are fixed on the driven main shaft 5. The mechanical gear ring 500 is engaged and driven by a mechanical fork group 6 to drive the mechanical driven gear ring 52 to rotate. The hydraulic gear ring 510 is engaged and driven by a hydraulic fork group 7 to drive the hydraulic driven gear ring 53 to rotate. An output gear 54 is coaxially fixed on the driven main shaft 5.

[0038] During the use of the above - mentioned dual - drive device, the following two power output methods are adopted:

[0039] As Figures 1-3 shown, one is to output in a mechanical manner. The hydraulic fork group drives to disengage the hydraulic gear ring 510 from the hydraulic driven gear ring 53. And the mechanical fork group 6 drives to engage and rotate the mechanical gear ring 500 with the mechanical driven gear ring 52. At this time, the driven main shaft rotates, driving the output gear 54 to rotate. The main power output comes from mechanical transmission, providing stronger traction and greatly improving the transmission efficiency.

[0040] Another way is to use the method of engaging the hydraulic gear ring 510 with the hydraulic driven gear ring 53; the shift forks in the mechanical shift fork group 6 do not engage with the mechanical gear ring 500, that is, the mechanical transmission gear 3 drives the mechanical driven gear 50, making it idle on the driven main shaft 5 and unable to drive the rotation of the driven main shaft 5. At this time, since the hydraulic gear ring 510 engages with the hydraulic driven gear ring 53 through the hydraulic shift fork group 7, that is, all power outputs are output in the output mode of the driving hydraulic motor 4, the rotation of the driven main shaft 5 is the stepless output of the driving hydraulic motor. Although the traction force will decrease to some extent, there will be a significant improvement in accuracy, making it suitable for more agricultural operations.

[0041] It is worth mentioning that the driving hydraulic motor 4 is a kind of hydrostatic motor. Its input end is the power support, and its output can provide forward rotation and reverse rotation of the output end, and at the same time, the output speed can be effectively adjusted.

[0042] Preferably, the mechanical transmission gear 3 includes a forward gear 30 and a reverse gear 31 fixed on the power output shaft 2. A parallel idler shaft 20 is arranged on one side of the power output shaft 2, and an idler 200 meshing with the reverse gear 31 is coaxially fixed on the idler shaft 20. The mechanical driven gear 50 includes a forward driven gear 501 and a reverse driven gear 502 rotatably connected to the driven main shaft 5. The forward driven gear 501 meshes with the forward gear 30, and the reverse driven gear 502 meshes with the idler 200. The mechanical gear ring 500 includes a forward gear ring 503 on one side of the forward driven gear 501 and a reverse gear ring 504 on one side of the reverse driven gear 502, and the forward gear ring 503 and the reverse gear ring 504 are arranged facing each other. The mechanical driven gear ring 52 is located between the forward gear ring 503 and the reverse gear ring 504. The mechanical shift fork group 6 can selectively engage the forward gear ring 503 with the mechanical driven gear ring 52, or engage the reverse gear ring 504 with the mechanical driven gear ring 52, or engage the mechanical driven gear ring 52 alone.

[0043] In the above structure, the mechanical transmission gear 3 includes the forward gear 30 and the reverse gear 31. Among them, the reverse gear 31 realizes the rotation in the direction through the idler 200 on the idler shaft 20, so as to provide the reverse rotation of the driven main shaft 5, and the tractor realizes reverse. At the same time, the mechanical shift fork group has three states of moving left, moving right or remaining in the middle, so as to realize three working forms of forward, backward and switching the power of the driving hydraulic motor in mechanical transmission. And the operation of moving the shift fork is relatively convenient.

[0044] Preferably, the hydraulic fork group 7 includes a hydraulic fork shaft 70, on which a hydraulic fork 71 is slidably provided, and the end of the hydraulic fork 71 is adapted to be equipped with a hydraulic engagement sleeve 72 sleeved on the hydraulic driven gear ring 53; the mechanical fork group 6 includes a mechanical fork shaft 60, on which a mechanical fork 61 is slidably provided, and the end of the mechanical fork 61 is adapted to be equipped with a mechanical engagement sleeve 62 sleeved on the mechanical driven gear ring 52, the hydraulic fork shaft 70 and the mechanical fork shaft 60 are parallel to each other, a slidable shift block 73 is provided on the hydraulic fork shaft 70 to drive the hydraulic fork 71 to move, and the shift block 73 is simultaneously slidably provided on the mechanical fork shaft 60, and drives the mechanical fork 61 to move axially along the mechanical fork shaft 60.

[0045] In the above structure, the hydraulic and mechanical fork shafts are arranged in parallel, and linkage control is achieved through a common shift block. The shift block slides left or right to achieve different working states of the shift forks on both sides, enhancing the synchronization of switching.

[0046] Preferably, the output gear 54 includes a plurality of gears of different sizes which are axially fixed on the driven main shaft 5. One side of the output gear 54 drives the traveling intermediate wheel 9 through a meshing reduction gear set 8. The two sides of the traveling intermediate wheel 9 are transmission-connected with a left planetary gear set 90 and a right planetary gear set 91. The outer sides of the left planetary gear set 90 and the right planetary gear set 91 are respectively meshed and connected with a left output shaft 92 and a right output shaft 93, and the ends of the left output shaft 92 and the right output shaft 93 are fixed with driving wheels 94.

[0047] In the above structure, the output gear 54 provides gears of different sizes, thereby providing different differential effects, so as to adapt to operations of various speeds and torque ranges, such as low-speed high-torque farming / high-speed low-torque transportation.

[0048] Preferably, a steering driving wheel 10 is fixed on the power main shaft 1, and a parallel steering shaft 11 is arranged above the power main shaft 1. The end of the steering shaft 11 is meshed and connected with the steering driving wheel 10, and the other end of the steering shaft 11 is connected to the input end of the steering hydraulic motor 13 through the steering gear set 12. The output end of the steering hydraulic motor 13 synchronously drives two sets of parallel steering temporary shafts 14. The ends of the two steering temporary shafts 14 are meshed and connected through gears and rotate synchronously in opposite directions. A left steering gear 140 meshed with the left planetary gear set 90 is coaxially fixed on one steering temporary shaft, and a right steering gear 141 meshed with the right planetary gear set 91 is coaxially fixed on the other steering temporary shaft.

[0049] In the above structure, the power spindle 1 distributes a certain amount of power to provide power to the steering hydraulic motor 13, so that the steering hydraulic motor provides power to the two groups of steering temporary shafts 14. The two groups of steering temporary shafts rotate synchronously and in opposite directions, realizing different steering of the two planetary gear sets, and thus realizing a large-angle turning operation. In addition, when the power spindle provides power to the steering hydraulic motor 13, a set of fork device is added to select whether to provide power to the steering hydraulic motor 13.

[0050] Preferably, the reduction gear set 8 includes a reduction first shaft 80, a reduction second shaft 81 and a reduction third shaft 82 that are parallel to each other. A plurality of first shaft reduction gears 800 meshing with the output gear 54 are rotatably connected to the reduction first shaft 80, and the first shaft reduction gears 800 are switched by a fork; A plurality of third shaft reduction gears 820 are rotatably connected to the reduction third shaft 82, and the third shaft reduction gears 820 are switched by a fork, and a driving intermediate gear 83 meshing with the traveling intermediate wheel 9 is fixed axially on the reduction third shaft 82; A plurality of linkage gears 810 for linking the first shaft reduction gears 800 and the third shaft reduction gears 820 are coaxially fixed on the reduction second shaft 81.

[0051] As Figure 6 shown, in the above structure, the reduction gear set 8, in cooperation with the fork, realizes different speed ratio combinations to ensure the linkage of power transmission.

[0052] In the implementation process, no matter what the final speed ratio is, the power is output to the traveling intermediate wheel 9. The traveling intermediate wheel 9 then outputs the two planetary gear sets on both sides to drive the rotation of the left and right output shafts, and further drives the rotation of the drive wheels 94.

[0053] The above embodiments are only the preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A dual transmission device for a crawler tractor, comprising a power main shaft (1) input by a power source, the end of the power main shaft (1) being connected to a power output shaft (2) through a meshing bevel gear set, characterized in that: A mechanical transmission gear (3) is coaxially fixed on the power output shaft (2), and the end of the power output shaft (2) is coaxially connected to the input end of the driving hydraulic motor (4). A parallel driven main shaft (5) is provided on one side of the power output shaft (2), and a mechanical driven gear (50) meshing with the mechanical transmission gear (3) is axially rotatably connected to the driven main shaft (5), and a coaxial mechanical gear ring (500) is formed on one side of the mechanical driven gear (50), and the end of the driven main shaft (5) is rotatably connected to the output end of the driving hydraulic motor (4). A hydraulic driven gear (51) is meshed with gears, and a coaxial hydraulic gear ring (510) is formed on one side of the hydraulic driven gear (51); a mechanical driven gear ring (52) and a hydraulic driven gear ring (53) are fixed on the driven main shaft (5); the mechanical gear ring (500) is engaged with and drives the mechanical driven gear ring (52) to rotate through a mechanical fork group (6); the hydraulic gear ring (510) is engaged with and drives the hydraulic driven gear ring (53) to rotate through a hydraulic fork group (7); and an output gear (54) is coaxially fixed on the driven main shaft (5).

2. A dual transmission device for a crawler tractor according to claim 1, characterized in that: The mechanical transmission gear (3) comprises a forward gear (30) and a reverse gear (31) fixed on a power output shaft (2); a parallel idler shaft (20) is provided on one side of the power output shaft (2); an idler wheel (200) meshing with the reverse gear (31) is coaxially fixed on the idler shaft (20); the mechanical driven gear (50) comprises a forward driven gear (501) and a reverse driven gear (502) rotatably connected to the driven main shaft (5); the forward driven gear (501) meshes with the forward gear (30), and the reverse driven gear (502) meshes with the idler wheel (200). The mechanical gear ring (500) comprises a forward gear ring (503) on one side of the forward driven gear (501) and a backward gear ring (504) on one side of the backward driven gear (502), and the forward gear ring (503) and the backward gear ring (504) are arranged opposite to each other, and the mechanical driven gear ring (52) is located between the forward gear ring (503) and the backward gear ring (504). The mechanical shift fork assembly (6) can selectively engage the forward gear ring (503) with the mechanical driven gear ring (52), or engage the backward gear ring (504) with the mechanical driven gear ring (52), or engage the mechanical driven gear ring (52) alone.

3. A dual transmission device for a crawler tractor according to claim 1 or 2, characterized in that: The hydraulic fork assembly (7) comprises a hydraulic fork shaft (70), on which a hydraulic fork (71) is slidably arranged, and the end of the hydraulic fork (71) is adapted to be equipped with a hydraulic engagement sleeve (72) sleeved on the hydraulic driven gear ring (53); the mechanical fork assembly (6) comprises a mechanical fork shaft (60), on which a mechanical fork (61) is slidably arranged, and the end of the mechanical fork (61) is adapted to be equipped with a mechanical engagement sleeve (62) sleeved on the mechanical driven gear ring (52), the hydraulic fork shaft (70) and the mechanical fork shaft (60) are parallel to each other, a slidable shift block (73) is provided on the hydraulic fork shaft (70) to drive the hydraulic fork (71) to move, and the shift block (73) is slidably arranged on the mechanical fork shaft (60) at the same time, and drives the mechanical fork (61) to move axially along the mechanical fork shaft (60).

4. A dual transmission device for a crawler tractor according to claim 1, characterized in that: The output gear (54) comprises a plurality of gears of different sizes axially fixed on the driven main shaft (5); one side of the output gear (54) drives the travel intermediate wheel (9) through a meshing reduction gear set (8); the two sides of the travel intermediate wheel (9) are transmission-connected with a left planetary gear set (90) and a right planetary gear set (91); the outer sides of the left planetary gear set (90) and the right planetary gear set (91) are meshedly connected with a left output shaft (92) and a right output shaft (93), respectively; and the ends of the left output shaft (92) and the right output shaft (93) are both fixed with driving wheels (94).

5. A dual transmission device for a crawler tractor according to claim 4, characterized in that: A steering driving wheel (10) is fixed on the power main shaft (1), and a parallel steering shaft (11) is arranged above the power main shaft (1). The end of the steering shaft (11) is meshedly connected with the steering driving wheel (10), and the other end of the steering shaft (11) is connected to the input end of a steering hydraulic motor (13) through a steering gear set (12). The output end of the steering hydraulic motor (13) synchronously drives two sets of parallel steering temporary shafts (14). The ends of the two steering temporary shafts (14) are meshedly connected through gears and rotate synchronously in opposite directions. A left steering gear (140) meshed with the left planetary gear set (90) is coaxially fixed on one of the steering temporary shafts, and a right steering gear (141) meshed with the right planetary gear set (91) is coaxially fixed on the other steering temporary shaft.

6. A dual transmission device for a crawler tractor according to claim 4, characterized in that: The reduction gear set (8) comprises a parallel first reduction shaft (80), a second reduction shaft (81) and a third reduction shaft (82); the first reduction shaft (80) is rotatably connected to a plurality of first reduction gears (800) meshing with the output gear (54), and the first reduction gears (800) are switched by a shift fork; the third reduction shaft (82) is rotatably connected to a plurality of third reduction gears (820), and the third reduction gears (820) are switched by a shift fork; and a driving intermediate wheel (83) meshing with the travel intermediate wheel (9) is axially fixed to the third reduction shaft (82); and a plurality of linkage gears (810) for linkage between the first reduction gear (800) and the third reduction gear (820) are coaxially fixed to the second reduction shaft (81).

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