Tractor gearbox with creeper gear

By designing a tractor gearbox with crawling gear, the problem that the prior art cannot meet the requirements of low-speed travel operation is solved, and the wider application of tractors and higher flexibility in low-speed operation is achieved.

CN222992048UActive Publication Date: 2025-06-17GEOMETRY HEAVY IND (SHANDONG) CO LTD
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Patent Information

Application Number
CN202422023768.2
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-08-20
Publication Date
2025-06-17
Estimated Expiration
2034-08-20

AI Technical Summary

Technical Problem

The existing tractor gearbox cannot meet the requirements of some agricultural machinery that require lower speed travel.

Method used

A tractor gearbox with crawler gear is designed, including a bridge box and a transmission box. The transmission box has eight gears, and components such as crawler sliding gear, reverse passive gear and reverse internal meshing sleeve are introduced into the bridge box to achieve lower speed driving.

Benefits of technology

It realizes the wider application of tractors during low-speed operation, meets the requirements for use of low-speed agricultural machinery, expands the scope of use of tractors, and can perform intensive farming, fine sowing and other operations.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model discloses a tractor gearbox with creeper gears, which comprises a gap bridge box and a transmission box, the gap bridge box is provided with two forward gears and a reverse gear, and the transmission box is provided with eight gears; the gap bridge box is provided with a front driving input shaft, a gap bridge box input shaft front section shaft, a gap bridge box input shaft rear section shaft and an idler shaft; the front section shaft of the gap bridge box input shaft is provided with a gap bridge box input gear and a front section shaft spline; a creeper gear sliding gear, a reverse gear driven gear and a reverse gear meshing sleeve are arranged on the rear section shaft of the input shaft of the gap bridge box; the creeper gear sliding gear, the reverse gear driven gear and the reverse gear meshing sleeve are respectively connected with the rear section shaft of the input shaft of the gap bridge box through splines; the front driving input shaft is provided with a creeper gear triple gear, the creeper gear triple gear comprises a triple first gear, a triple second gear and a reversing driving gear, and the triple first gear is meshed with the gap bridge box input gear. The gearbox is additionally provided with a creeper gear, so that the tractor has a lower speed, and the requirements of low-speed operation agricultural implements are met.
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Description

Technical Field

[0001] The utility model relates to the technical field of tractors, and specifically to a tractor gearbox with a creep gear. Background Art

[0002] The gearbox used in tractors usually has eight forward gears and eight reverse gears, which can better meet the usage requirements of the tractor for walking and driving various agricultural implements. With the rapid development of the degree of agricultural mechanization and the continuous increase in the types of agricultural implements, the requirement for the adjustment range of the tractor speed is getting larger and larger. For some equipment that requires operation at a lower speed, the existing gearbox cannot meet the requirements. Content of the Utility Model

[0003] Aiming at the above deficiencies, the technical problem to be solved by the utility model is: to provide a tractor gearbox with a creep gear, and the tractor equipped with this gearbox can travel at a lower speed to meet the usage requirements of low-speed agricultural implements.

[0004] To solve the above technical problems, the technical solution of the utility model is as follows:

[0005] A tractor gearbox with a creep gear includes a cross-over box and a transmission box. The transmission box has eight gears; the cross-over box is rotatably installed with a front drive input shaft, a front section shaft of the cross-over box input shaft that is coaxial and hollow, and a rear section shaft of the cross-over box input shaft. The front section shaft of the cross-over box input shaft and the rear section shaft of the cross-over box input shaft are coaxially and loosely sleeved on the front end shaft of the clutch; the front section shaft of the cross-over box input shaft is provided with a cross-over box input gear and a spline on the front section shaft; the rear section shaft of the cross-over box input shaft is provided with a creep gear sliding gear, a reverse gear driven gear, a reverse gear internal engaging sleeve, and a reverse gear external engaging sleeve. The creep gear sliding gear, the reverse gear driven gear, and the reverse gear internal engaging sleeve are respectively spline-connected to the rear section shaft of the cross-over box input shaft, and the reverse gear external engaging sleeve is spline-connected to the reverse gear internal engaging sleeve; the reverse gear driven gear is provided with a reverse gear spline. The creep gear sliding gear can be spline-connected to the spline on the front section shaft, and the reverse gear external engaging sleeve can be spline-connected to the reverse gear spline; the front drive input shaft is provided with a creep gear triple gear, and the creep gear triple gear includes a triple first gear, a triple second gear, and a reverse drive gear. The triple first gear meshes with the cross-over box input gear; the cross-over box is also provided with an idler shaft, and an idler gear meshing with the reverse drive gear is arranged on the idler shaft.

[0006] Preferably, the transmission case includes a rotationally mounted input shaft of the transmission case, an output shaft of the transmission case, and a hollow spline shaft; the input shaft of the transmission case is coaxially connected to the rear-section shaft of the input shaft of the intermediate housing through a spline sleeve. The input shaft of the transmission case is provided with an input gear of the transmission case, a second-gear driving gear, a third-gear driving gear, an internal engagement sleeve for the third and fourth gears, and an external engagement sleeve for the third and fourth gears. The third-gear driving gear is provided with a third-gear spline. The internal engagement sleeve for the third and fourth gears is spline-connected to the input shaft of the transmission case. The external engagement sleeve for the third and fourth gears is spline-connected to the internal engagement sleeve for the third and fourth gears. An auxiliary transmission double gear for the fourth gear is provided on the front-end shaft of the clutch. The auxiliary transmission double gear for the fourth gear is fixed with a fourth-gear spline. The external engagement sleeve for the third and fourth gears is selectively connected to the third-gear spline and the fourth-gear spline. The double gear includes a first double gear and a second double gear. The spline shaft is sleeved on the output shaft of the transmission case. The spline shaft is provided with a first-gear driven gear, a main transmission internal engagement sleeve, a main transmission external engagement sleeve, a second-gear driven gear, a third-gear driven gear, and a fourth-gear driven gear. The first-gear driven gear meshes with the input gear of the transmission case. The main transmission internal engagement sleeve is spline-connected to the spline shaft. The main transmission external engagement sleeve is spline-connected to the main transmission internal engagement sleeve. The second-gear driven gear meshes with the second-gear driving gear. The third-gear driven gear meshes with the third-gear driving gear. The fourth-gear driven gear meshes with the first double gear. The first-gear driven gear is provided with a first-gear spline. The second-gear driven gear is provided with a second-gear spline. The main transmission external engagement sleeve is selectively connected to the first-gear spline or the second-gear spline. The output shaft of the transmission case is provided with a high-low gear internal engagement sleeve, a high-low gear external engagement sleeve, a low-gear driven gear, and a bevel gear. The high-low gear internal engagement sleeve is spline-connected to the output shaft of the transmission case. The high-low gear external engagement sleeve is spline-connected to the high-low gear internal engagement sleeve. The low-gear driven gear meshes with the second double gear. The spline shaft is provided with a high-gear spline. The low-gear driven gear is provided with a low-gear spline. The high-low gear external engagement sleeve is selectively connected to the high-gear spline or the low-gear spline.

[0007] Preferably, a reverse gear support is mounted on the intermediate housing, and the idle gear shaft is mounted on the reverse gear support.

[0008] Preferably, the input shaft of the transmission case is coaxially connected to the rear-section shaft of the input shaft of the intermediate housing through a spline sleeve.

[0009] After adopting the above technical solution, the beneficial effects of the present utility model are as follows:

[0010] The present utility model not only has a normal gear H and a reverse gear R, but also adds a creep gear L, achieving a lower speed, meeting the use requirements of low-speed operation agricultural implements. The tractor can be matched with more agricultural implements and can perform precision tillage, precision seeding operations, etc. The application range of the tractor is wider. Description of the Drawings

[0011] Figure 1 is a schematic cross-sectional structure diagram of a tractor gearbox with a crawler gear in an embodiment of the utility model tractor;

[0012] Figure 2 is Figure 1 an enlarged structure diagram of the overpass box in;

[0013] Figure 3 is Figure 2 a schematic cross-sectional structure diagram in the C-C direction in;

[0014] Figure 4 is Figure 1 an enlarged structure diagram of the transmission box in;

[0015] In the figure: A, overpass box

[0016] 1. Front shaft of the overpass box input shaft; 11. Input gear of the overpass box; 12. Spline of the front shaft; 2. Rear shaft of the overpass box input shaft; 21. Crawler gear sliding gear; 22. Reverse passive gear; 221. Reverse spline; 23. Reverse internal meshing sleeve; 24. Reverse external meshing sleeve; 3. Front shaft of the clutch; 31. IV-speed auxiliary transmission double gear; 311. First gear of the double gear; 312. Second gear of the double gear; 313. IV-speed spline; 4. Front drive input shaft; 41. Crawler gear triple gear; 411. First gear of the triple gear; 412. Second gear of the triple gear; 413. Reverse driving gear; 5. Idler shaft; 51. Reverse idler; 52. Reverse support;

[0017] B, transmission box

[0018] 6. Input shaft of the transmission box; 61. Input gear of the transmission box; 62. Second-gear driving gear; 63. Third-gear driving gear; 631. Third-gear spline; 64. Third-IV internal meshing sleeve; 65. Third-IV external meshing sleeve; 7. Output shaft of the transmission box; 71. High-low gear internal meshing sleeve; 72. High-low gear external meshing sleeve; 73. Low-gear driven gear; 731. Low-gear spline; 74. Bevel gear; 8. Spline shaft; 81. First-gear driven gear; 811. First-gear spline; 82. Main transmission internal meshing sleeve; 83. Main transmission external meshing sleeve; 84. Second-gear driven gear; 841. Second-gear spline; 85. Third-gear driven gear; 86. Fourth-gear driven gear; 87. High-gear spline; 9. Spline sleeve. Detailed implementation manners

[0019] In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0020] Such asFigure 1 As shown in the figure, a tractor transmission with a crawler gear includes a cross-over box A and a transmission box B, and the transmission box B has eight gears;

[0021] As Figure 2 shown in the figure, the cross-over box A is rotatably installed with a front drive input shaft 4, a front section shaft 1 of the cross-over box input shaft coaxial and hollow, and a rear section shaft 2 of the cross-over box input shaft. The front section shaft 1 of the cross-over box input shaft and the rear section shaft 2 of the cross-over box input shaft are coaxially and loosely sleeved on the front end shaft 3 of the clutch;

[0022] The front section shaft 1 of the cross-over box input shaft is provided with a cross-over box input gear 11 and a spline on the front section shaft 12;

[0023] The rear section shaft 2 of the cross-over box input shaft is provided with a crawler gear sliding gear 21, a reverse gear driven gear 22, a reverse gear internal engagement sleeve 23 and a reverse gear external engagement sleeve 24. The crawler gear sliding gear 21, the reverse gear driven gear 22 and the reverse gear internal engagement sleeve 23 are respectively spline-connected to the rear section shaft 2 of the cross-over box input shaft, and the reverse gear external engagement sleeve 24 is spline-connected to the reverse gear internal engagement sleeve 23;

[0024] The reverse gear driven gear 22 is provided with a reverse gear spline 221. The crawler gear sliding gear 21 can be connected to the spline on the front section shaft 12, and the reverse gear external engagement sleeve 24 can be connected to the reverse gear spline 221;

[0025] The front drive input shaft 4 is provided with a crawler gear triple gear 41. The crawler gear triple gear 41 includes a triple first gear 411, a triple second gear 412 and a reverse drive gear 413. The triple first gear 411 meshes with the cross-over box input gear 11;

[0026] As Figure 3 shown in the figure, the cross-over box is further provided with an idle gear shaft 5. The idle gear shaft 5 is installed on a reverse gear support 52, and the idle gear shaft 5 is provided with a reverse idle gear 51 that meshes with the reverse drive gear 413.

[0027] The transmission route of the cross-over box is:

[0028] Crawler gear L

[0029] Engine - Clutch - Front section shaft 1 of the cross-over box input shaft - Cross-over box input gear 11 - Triple first gear 411 - Triple second gear 412 - Crawler gear sliding gear 21 - Rear section shaft 2 of the cross-over box input shaft - Transmission box;

[0030] Normal gear H (forward gear)

[0031] The crawler gear sliding gear 21 is connected to the spline on the front section shaft 12;

[0032] Engine - Clutch - Front section shaft 1 of the cross-over box input shaft - Spline on the front section shaft 12 - Crawler gear sliding gear 21 - Rear section shaft 2 of the cross-over box input shaft - Transmission box;

[0033] Reverse gear R

[0034] The reverse external engagement sleeve 24 is connected to the reverse spline 221;

[0035] The front section of the input shaft of the engine - clutch - overpass box 1 - the input gear 11 of the overpass box - the first gear 411 of the triple - gear - the driving gear 413 for reverse - the idler gear 51 - the driven gear 22 for reverse - the reverse spline 221 - the reverse external engagement sleeve 24 - the reverse internal engagement sleeve 23 - the rear section of the input shaft of the overpass box 2 - the transmission box.

[0036] The utility model not only has the normal gear H and the reverse gear R, but also adds the creep gear L, achieving a lower speed, meeting the usage requirements of low - speed operation agricultural implements. The tractor can be matched with more agricultural implements and can perform precision tillage, precision seeding operations, etc. The application range of the tractor is wider.

[0037] As Figure 4 shown, the transmission box B includes a transmission - box input shaft 6 rotatably installed, a transmission - box output shaft 7, and a hollow spline shaft 8;

[0038] The transmission - box input shaft 6 is coaxially connected to the rear section of the input shaft of the overpass box 2 through a spline sleeve 9. The transmission - box input shaft 6 is provided with a transmission - box input gear 61, a second - gear driving gear 62, a third - gear driving gear 63, a third - fourth - gear internal engagement sleeve 64, and a third - fourth - gear external engagement sleeve 65. The third - gear driving gear 63 is provided with a third - gear spline 631. The third - fourth - gear internal engagement sleeve 64 is spline - connected to the transmission - box input shaft 6, and the third - fourth - gear external engagement sleeve 65 is spline - connected to the third - fourth - gear internal engagement sleeve 64;

[0039] A fourth - gear auxiliary - speed double - gear 31 is provided on the front - end shaft 3 of the clutch. The fourth - gear auxiliary - speed double - gear 31 includes a double - gear first gear 311 and a double - gear second gear 312. The fourth - gear auxiliary - speed double - gear 31 is fixed with a fourth - gear spline 313. The third - fourth - gear external engagement sleeve 65 is selectively connected to the third - gear spline 631 and the fourth - gear spline 313;

[0040] The spline shaft 8 is sleeved on the transmission - box output shaft 8. The spline shaft 8 is provided with a first - gear driven gear 81, a main - speed internal engagement sleeve 82, a main - speed external engagement sleeve 83, a second - gear driven gear 84, a third - gear driven gear 85, and a fourth - gear driven gear 86. The first - gear driven gear 81 meshes with the transmission - box input gear 61. The main - speed internal engagement sleeve 82 is spline - connected to the spline shaft 8. The main - speed external engagement sleeve 83 is spline - connected to the main - speed internal engagement sleeve 82. The second - gear driven gear 84 meshes with the second - gear driving gear 62. The third - gear driven gear 85 meshes with the third - gear driving gear 63. The fourth - gear driven gear 86 meshes with the double - gear first gear 311;

[0041] The first-gear driven gear 81 is provided with a first-gear spline 811, the second-gear driven gear 84 is provided with a second-gear spline 841, and the main transmission external engagement sleeve 83 is selectively connected to the first-gear spline 811 or the second-gear spline 841;

[0042] The transmission case output shaft 7 is provided with a high-low gear internal engagement sleeve 71, a high-low gear external engagement sleeve 72, a low-gear driven gear 73, and a bevel gear 74. The high-low gear internal engagement sleeve 71 is spline-connected to the transmission case output shaft 7, the high-low gear external engagement sleeve 72 is spline-connected to the high-low gear internal engagement sleeve 71, the low-gear driven gear 73 meshes with the double-connected second gear 312, and the low-gear driven gear 73 is rotatably mounted on the transmission case output shaft 7;

[0043] The spline shaft 8 is provided with a high-gear spline 87, the low-gear driven gear 73 is provided with a stop gear spline 731, and the high-low gear external engagement sleeve 72 is selectively connected to the high-gear spline 87 or the stop gear spline 731.

[0044] The transmission route of the transmission case is as follows:

[0045] B1. Low first gear

[0046] The main transmission external engagement sleeve 83 is connected to the first-gear spline 811, and the high-low gear external engagement sleeve 72 is connected to the stop gear spline 731;

[0047] The rear section of the input shaft of the overpass box - spline sleeve 9 - input shaft 6 of the transmission case - input gear 61 of the transmission case - first-gear driven gear 81 - first-gear spline 811 - main transmission external engagement sleeve 83 - main transmission internal engagement sleeve 82 - spline shaft 8 - fourth-gear driven gear 86 - double-connected first gear 311 - double-connected second gear 312 - low-gear driven gear 73 - stop gear spline 731 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - transmission case output shaft 7 - bevel gear 74 (the input gear 61 of the transmission case is the first-gear driving gear);

[0048] B2. Low second gear

[0049] The main transmission external engagement sleeve 83 is connected to the second-gear spline 841, and the high-low gear external engagement sleeve 72 is connected to the stop gear spline 731;

[0050] The rear section of the input shaft of the overpass box - spline sleeve 9 - input shaft 6 of the transmission case - second-gear driving gear 62 - second-gear driven gear 84 - second-gear spline 841 - main transmission external engagement sleeve 83 - main transmission internal engagement sleeve 82 - spline shaft 8 - fourth-gear driven gear 86 - double-connected first gear 311 - double-connected second gear 312 - low-gear driven gear 73 - stop gear spline 731 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - transmission case output shaft 7 - bevel gear 74;

[0051] B3. Low third gear

[0052] The third-fourth gear external engagement sleeve 65 is connected to the third gear spline 631, and the high-low gear external engagement sleeve 72 is connected to the reverse gear spline 731;

[0053] The rear section of the input shaft of the transfer case 2 - spline sleeve 9 - input shaft of the transmission case 6 - third-fourth gear internal engagement sleeve 64 - third-fourth gear external engagement sleeve 65 - third gear spline 631 - third gear driving gear 63 - third gear driven gear 85 - spline shaft 8 - fourth gear driven gear 86 - double gear first gear 311 - double gear second gear 312 - low gear driven gear 73 - reverse gear spline 731 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - output shaft of the transmission case 7 - bevel gear 74;

[0054] B4, low fourth gear

[0055] The third-fourth gear external engagement sleeve 65 is connected to the fourth gear spline 313, and the high-low gear external engagement sleeve 72 is connected to the reverse gear spline 731;

[0056] The rear section of the input shaft of the transfer case 2 - spline sleeve 9 - input shaft of the transmission case 6 - third-fourth gear internal engagement sleeve 64 - third-fourth gear external engagement sleeve 65 - fourth gear spline 313 - double gear first gear 311 - double gear second gear 312 - low gear driven gear 73 - reverse gear spline 731 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - output shaft of the transmission case 7 - bevel gear 74;

[0057] B5, high first gear

[0058] The main transmission external engagement sleeve 83 is connected to the first gear spline 811, and the high-low gear external engagement sleeve 72 is connected to the high gear spline 87;

[0059] The rear section of the input shaft of the transfer case 2 - spline sleeve 9 - input shaft of the transmission case 6 - input gear of the transmission case 61 - first gear driven gear 81 - first gear spline 811 - main transmission external engagement sleeve 83 - main transmission internal engagement sleeve 82 - spline shaft 8 - high gear spline 87 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - output shaft of the transmission case 7 - bevel gear 74;

[0060] B6, high second gear

[0061] The main transmission external engagement sleeve 83 is connected to the second gear spline 841, and the high-low gear external engagement sleeve 72 is connected to the high gear spline 87;

[0062] The rear section of the input shaft of the transfer case 2 - spline sleeve 9 - input shaft of the transmission case 6 - second gear driving gear 62 - second gear driven gear 84 - second gear spline 841 - main transmission external engagement sleeve 83 - main transmission internal engagement sleeve 82 - spline shaft 8 - high gear spline 87 - high-low gear external engagement sleeve 72 - high-low gear internal engagement sleeve 71 - output shaft of the transmission case 7 - bevel gear 74;

[0063] B7, high third gear

[0064] The third - fourth gear external engagement sleeve 65 is connected to the third - gear spline 631, and the high - low gear external engagement sleeve 72 is connected to the high - gear spline 87;

[0065] The rear - section shaft 2 of the input shaft of the transfer case - spline sleeve 9 - input shaft 6 of the transmission case - third - fourth gear internal engagement sleeve 64 - third - fourth gear external engagement sleeve 65 - third - gear spline 631 - third - gear driving gear 63 - third - gear driven gear 85 - spline shaft 8 - high - gear spline 87 - high - low gear external engagement sleeve 72 - high - low gear internal engagement sleeve 71 - output shaft 7 of the transmission case - bevel gear 74;

[0066] B8 high fourth gear

[0067] The third - fourth gear external engagement sleeve 65 is connected to the fourth - gear spline 313, and the high - low gear external engagement sleeve 72 is connected to the high - gear spline 87;

[0068] The rear - section shaft 2 of the input shaft of the transfer case - spline sleeve 9 - input shaft 6 of the transmission case - third - fourth gear internal engagement sleeve 64 - third - fourth gear external engagement sleeve 65 - fourth - gear spline 313 - double - joint first gear 311 - fourth - gear driven gear 86 - spline shaft 8 - high - gear spline 87 - high - low gear external engagement sleeve 72 - high - low gear internal engagement sleeve 71 - output shaft 7 of the transmission case - bevel gear 74;

[0069] Among the high - low gears B1 - B8, the bevel gear 74 is drivingly connected to the differential, the differential then drives the half - shafts on the left and right sides, and the half - shafts drive the driving wheels to realize the walking of the tractor.

[0070] When the tractor operates in the creep gear, the creep gear L + high - low gears B1 - B8 form eight creep - gear positions to meet the requirements of precise operation of agricultural implements; when the tractor moves forward, the normal gear H + high - low gears B1 - B8 form eight normal gear positions to meet the requirements of the tractor moving forward; when the tractor reverses, the reverse gear R + high - low gears B1 - B8 form eight reverse gear positions to meet the requirements of the tractor reversing.

[0071] The above are examples of the best implementation modes of the present utility model. Those parts not described in detail are common general knowledge of those skilled in the art. The protection scope of the present utility model is subject to the content of the claims, and any equivalent transformation based on the technical inspiration of the present utility model is also within the protection scope of the present utility model.

Claims

1. A tractor gearbox with a creeper gear, comprising a bridge box and a transmission box, wherein the transmission box has eight gears, and is characterized in that: The said bridge box is rotatably mounted with a front drive input shaft and a coaxial and hollow bridge box input shaft front section shaft and bridge box input shaft rear section shaft, and the said bridge box input shaft front section shaft and the said bridge box input shaft rear section shaft are coaxially sleeved on the front end shaft of the clutch; The front section of the input shaft of the axle box is provided with an input gear of the axle box and a front section of the shaft spline; The rear section of the input shaft of the axle box is provided with a crawler gear, a reverse gear driven gear, a reverse gear inner gear sleeve and a reverse gear outer gear sleeve. The crawler gear, the reverse gear driven gear and the reverse gear inner gear sleeve are respectively spline-connected with the rear section of the input shaft of the axle box, and the reverse gear outer gear sleeve is spline-connected with the reverse gear inner gear sleeve. The reverse gear driven gear is provided with a reverse gear spline, the creeper gear sliding gear can be connected with the front shaft spline, and the reverse gear outer gear sleeve can be connected with the reverse gear spline; The front drive input shaft is provided with a crawler gear triple gear, the crawler gear triple gear comprises a triple first gear, a triple second gear and a reverse driving gear, the triple first gear is meshed with the bridge box input gear; The bridge box is also provided with an idler shaft, and the idler shaft is provided with a reversing idler gear meshing with the reversing driving gear.

2. The tractor gearbox with a crawler gear as claimed in claim 1, characterized in that: The transmission box comprises a rotatably mounted transmission box input shaft, a transmission box output shaft and a hollow spline shaft; The transmission box input shaft is coaxially connected with the rear section shaft of the bridge box input shaft through a spline sleeve, and the transmission box input shaft is provided with a transmission box input gear, a II gear driving gear, a III gear driving gear, a III-IV gear internal gear sleeve and a III-IV gear external gear sleeve, the III gear driving gear is provided with a III gear spline, the III-IV gear internal gear sleeve is spline-connected with the transmission box input shaft, and the III-IV gear external gear sleeve is spline-connected with the III-IV gear internal gear sleeve; The front end shaft of the clutch is provided with a Ⅳ-speed auxiliary transmission double gear, the Ⅳ-speed auxiliary transmission double gear is fixed with a Ⅳ-speed spline, the Ⅲ-Ⅳ-speed outer gear sleeve is selectively connected with the Ⅲ-speed spline and the Ⅳ-speed spline, and the double gear includes a double first gear and a double second gear; The spline shaft is sleeved on the output shaft of the transmission box, and the spline shaft is provided with a driven gear of gear Ⅰ, a main speed internal gear sleeve, a main speed external gear sleeve, a driven gear of gear Ⅱ, a driven gear of gear Ⅲ and a driven gear of gear Ⅳ. The driven gear of gear Ⅰ is meshed with the input gear of the transmission box, the main speed internal gear sleeve is spline-connected with the spline shaft, the main speed external gear sleeve is spline-connected with the main speed internal gear sleeve, the driven gear of gear Ⅱ is meshed with the driving gear of gear Ⅱ, the driven gear of gear Ⅲ is meshed with the driving gear of gear Ⅲ, and the driven gear of gear Ⅳ is meshed with the first double gear; The I-speed driven gear is provided with an I-speed spline, the II-speed driven gear is provided with a II-speed spline, and the main transmission outer gear sleeve is selectively connected to the I-speed spline or the II-speed spline; The transmission box output shaft is provided with a high-low gear internal gear sleeve, a high-low gear external gear sleeve, a low-speed driven gear and a bevel gear, the high-low gear internal gear sleeve is spline-connected with the transmission box output shaft, the high-low gear external gear sleeve is spline-connected with the high-low gear internal gear sleeve, and the low-speed driven gear is meshed with the duplex second gear; The spline shaft is provided with a high-speed spline, the low-speed driven gear is provided with a resisting spline, and the high-speed and low-speed external engagement sleeves are selectively connected with the high-speed spline or the resisting spline.

3. The tractor gearbox with a crawler gear as claimed in claim 1, characterized in that: A reverse gear support is installed on the bridge box, and the idler shaft is installed on the reverse gear support.

4. The tractor gearbox with a crawler gear as claimed in claim 2, characterized in that: The transmission box input shaft is coaxially connected with the rear section shaft of the bridge box input shaft through a spline sleeve.