Tractor transmission system with HST and tractor

Abstract

The utility model relates to the technical field of tractors, in particular to a tractor transmission system with an HST and a tractor, an HST assembly is fixed on one side of a transfer case shell, a rear axle shell is fixedly connected with one side, far away from the HST assembly, of the transfer case shell, and the output end of a gearbox assembly is in transmission connection with an input shaft of the HST assembly. The HST assembly is provided with a first output shaft and a second output shaft, the first output shaft is in transmission connection with the input end of the wet clutch assembly, the output end of the wet clutch assembly is in transmission connection with the rear PTO assembly, and the rear PTO assembly is in transmission connection with the middle PTO assembly; the second output shaft is in transmission connection with the auxiliary speed change assembly, and the auxiliary speed change assembly is in transmission connection with the transfer case assembly. According to the utility model, stepless speed change can be realized, gears are few, clutches are avoided, user operation is convenient, and automatic control is easy to realize; the HST assembly is arranged outside the transfer case shell, so that the mounting space is saved; and various operation requirements are met.

Description

Technical Field

[0001] The utility model relates to the technical field of tractors, in particular to a tractor transmission system with HST and a tractor. Background Art

[0002] At present, farmland operations have an increasing demand for tractor power output forms, and different power output forms are used to match different work tools. Existing tractor transmission mechanisms are mostly complex mechanical shifting or power shifting, with many gears, requiring frequent clutching and braking, and are complicated to operate. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a tractor transmission system with HST and a tractor, which have simple structure and convenient operation.

[0004] The utility model solves the above technical problems with the following technical solutions: A tractor transmission system with HST, comprising a gearbox assembly, an HST assembly, a transfer case housing, a wet clutch assembly, a rear axle housing, a rear PTO assembly, a mid-mounted PTO assembly, an auxiliary transmission assembly and a transfer case assembly, wherein the HST assembly is fixed on one side of the transfer case housing, the rear axle housing is fixedly connected to a side of the transfer case housing away from the HST assembly, the transfer case assembly is installed in the transfer case housing, the wet clutch assembly, the rear PTO assembly, the mid-mounted PTO assembly, the auxiliary transmission assembly and the transfer case assembly The mid-mounted PTO assembly and the auxiliary transmission assembly are installed in the rear axle housing, the output end of the gearbox assembly is drivingly connected to the input shaft of the HST assembly, the HST assembly is provided with a first output shaft and a second output shaft, the first output shaft is drivingly connected to the input end of the wet clutch assembly, the output end of the wet clutch assembly is drivingly connected to the rear PTO assembly, the rear PTO assembly is drivingly connected to the mid-mounted PTO assembly; the second output shaft is drivingly connected to the auxiliary transmission assembly, the auxiliary transmission assembly is drivingly connected to the transfer case assembly.

[0005] The beneficial effects of the utility model are: it can realize stepless speed change, replacing the cumbersome frequent gear shifting, with fewer gears and no clutch, convenient for users to operate, easy to realize automatic control, and greatly simplifying the structure of the transmission system; the HST assembly is arranged outside the transfer case housing, saving installation space; and meeting various operating requirements.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows.

[0007] Furthermore, the gearbox assembly includes a gearbox housing, in which a speed change shaft is rotatably provided, the input end of the speed change shaft is fixedly connected to a torsional damper for installation on an engine flywheel, and the output end of the speed change shaft is coaxially fixedly connected to the input shaft of the HST assembly.

[0008] The beneficial effect of adopting the above further solution is that the transmission shaft is connected to the engine via a torsional vibration damper, which can effectively reduce the natural frequency of torsional vibration of the transmission system.

[0009] Furthermore, the input end of the speed change shaft is connected to the torsional damper via a spline, and the output end of the speed change shaft is connected to the input shaft of the HST assembly via a spline sleeve.

[0010] The beneficial effect of adopting the above further solution is that the arrangement of the spline and the spline sleeve can ensure the synchronization of the power transmission between the torsional vibration damper and the speed change shaft.

[0011] Furthermore, the rear PTO assembly includes a rear transmission shaft and a rear output shaft, the rear output shaft is rotatably mounted in the rear axle housing, one end of the rear transmission shaft is transmission-connected to the output end of the wet clutch assembly, and the rear transmission shaft and the rear output shaft are transmission-connected via a speed change gear set.

[0012] The beneficial effect of adopting the above further solution is that the rear output shaft can be used for external working tools, and the speed of the rear output shaft can be independently controlled through the speed change gear set, which has good versatility.

[0013] Furthermore, the speed gear set includes a first rear driving gear fixedly sleeved on the rear transmission shaft and a first rear passive gear rotatably sleeved on the rear output shaft, the first rear driving gear is meshed with the first rear passive gear, a rear speed change meshing sleeve is fixedly sleeved on the rear output shaft, and the rear speed change meshing sleeve is arranged in parallel with the first rear passive gear.

[0014] The beneficial effect of adopting the above further solution is that the arrangement of the rear speed change clutch sleeve can control the rotation of the rear output shaft as required.

[0015] Further, the mid-mounted PTO assembly includes a mid-mounted fixed shaft fixedly installed in the rear axle housing and a mid-mounted output shaft rotatably installed in the rear axle housing, the mid-mounted fixed shaft and the mid-mounted output shaft are arranged in parallel, a mid-mounted driving gear is rotatably sleeved on the mid-mounted fixed shaft, a second rear driving gear is also fixedly sleeved on the rear transmission shaft, a second rear driven gear is rotatably sleeved on the rear output shaft, the second rear driven gear is arranged on the side of the rear speed change meshing sleeve away from the first rear driven gear, the second rear driving gear is meshed with the second rear driven gear, the second rear driven gear is meshed with the mid-mounted driving gear, a mid-mounted driven gear is rotatably sleeved on the mid-mounted output shaft, the mid-mounted driven gear is meshed with the mid-mounted driving gear, a mid-mounted speed change meshing sleeve is fixedly sleeved on the mid-mounted output shaft, and the mid-mounted speed change meshing sleeve and the mid-mounted driven gear are arranged in parallel.

[0016] The beneficial effect of adopting the above further scheme is that the mid-mounted PTO assembly is transmission-connected to the rear PTO assembly, power is output through the mid-mounted output shaft, and the connection output for external working tools is increased to meet various working requirements.

[0017] Further, the auxiliary transmission assembly includes a first auxiliary transmission shaft and a second auxiliary transmission shaft rotatably mounted in the rear axle housing, the first auxiliary transmission shaft and the second auxiliary transmission shaft are arranged in parallel, and a low-speed driving gear, a middle-speed driving gear and a high-speed driving gear which rotate synchronously with the first auxiliary transmission shaft are sequentially arranged at intervals on the first auxiliary transmission shaft; a low-speed passive gear, a middle-speed passive gear and a high-speed passive gear are sequentially arranged at intervals on the second auxiliary transmission shaft, the low-speed passive gear meshes with the low-speed driving gear, the middle-speed passive gear meshes with the middle-speed driving gear, and the high-speed passive gear meshes with the high-speed driving gear; a first auxiliary transmission meshing sleeve is fixedly provided on the second auxiliary transmission shaft between the low-speed passive gear and the middle-speed passive gear, a second auxiliary transmission meshing sleeve is fixedly provided on the second auxiliary transmission shaft, and the second auxiliary transmission meshing sleeve is arranged next to the high-speed passive gear.

[0018] The beneficial effect of adopting the above further scheme is: achieving synchronous rotation of the low-speed passive gear, the middle-speed passive gear and the high-speed passive gear with the second auxiliary speed-change shaft respectively, thereby realizing high, middle and low gear control and meeting various operating requirements of the auxiliary speed-change transmission mechanism.

[0019] Further, the transfer case assembly includes a transfer case fixed shaft fixedly installed in the transfer case housing and a transfer case output shaft rotatably arranged in the transfer case housing, the transfer case fixed shaft and the transfer case output shaft are arranged in parallel, a transfer case driving gear is rotatably provided on the transfer case fixed shaft, a sub-speed transmission gear is fixedly provided on the second sub-speed change shaft, the sub-speed change transmission gear is meshed with the transfer case driving gear, a transfer case passive gear is rotatably provided on the transfer case output shaft, the transfer case passive gear is meshed with the transfer case driving gear, a transfer case speed change meshing sleeve is fixedly provided on the transfer case output shaft, and the transfer case speed change meshing sleeve and the transfer case passive gear are arranged in parallel.

[0020] The beneficial effect of adopting the above further solution is that the transfer case assembly is drivingly connected to the auxiliary transmission assembly, and power is output through the transfer case output shaft, which is used to connect to the front axle to output power and realize four-wheel drive.

[0021] Furthermore, the first output shaft is transmission-connected to the input end of the wet clutch assembly via a spline sleeve, and the second output shaft is transmission-connected to the input end of the auxiliary transmission assembly via a spline sleeve.

[0022] The beneficial effect of adopting the above further solution is: achieving transmission synchronization between the first output shaft and the wet clutch assembly and transmission synchronization between the second output shaft and the auxiliary transmission assembly.

[0023] The utility model solves the above technical problem and further provides a tractor, comprising the above tractor transmission system with HST.

[0024] The beneficial effects of adopting the above scheme are: it can realize stepless speed change, replacing the tedious frequent gear shifting, with fewer gears and no clutch, which is convenient for users to operate and easy to realize automatic control, thus greatly simplifying the structure of the transmission system; the HST assembly is arranged outside the transfer case housing, saving installation space; and meeting various operating requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the utility model;

[0026] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0027] 1. Gearbox assembly; 11. Gearbox housing; 12. Shift shaft; 13. Torsion damper; 2. Center PTO assembly; 21. Center fixed shaft; 22. Center output shaft; 23. Center driving gear; 24. Center passive gear; 25. Center speed change clutch sleeve; 3. HST assembly; 31. First output shaft; 32. Second output shaft; 4. Transfer case housing; 5. Wet clutch assembly; 6. Rear axle housing; 7. Rear PTO assembly; 71. Rear transmission shaft; 72. Rear output shaft; 73. First rear driving gear; 74. First rear passive gear; 75. Rear speed change clutch sleeve; 76. The second rear passive gear; 77, the second rear driving gear; 8, the transfer case assembly; 81, the transfer case fixed shaft; 82, the transfer case output shaft; 83, the transfer case driving gear; 84, the transfer case passive gear; 85, the transfer case speed gear engagement sleeve; 9, the auxiliary transmission assembly; 91, the first auxiliary transmission shaft; 92, the second auxiliary transmission shaft; 93, the low gear driving gear; 94, the middle gear driving gear; 95, the high gear driving gear; 96, the low gear passive gear; 97, the middle gear passive gear; 98, the high gear passive gear; 99, the first auxiliary transmission sleeve; 910, the second auxiliary transmission sleeve; 911, the auxiliary transmission gear. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0029] Embodiment 1

[0030] like Figure 1As shown, this embodiment includes a transmission assembly 1, an HST assembly 3, a transfer case housing 4, a wet clutch assembly 5, a rear axle housing 6, a rear PTO assembly 7, a mid-mounted PTO assembly 2, an auxiliary transmission assembly 9 and a transfer case assembly 8, wherein the HST assembly 3 is fixed on one side of the transfer case housing 4, the rear axle housing 6 is fixedly connected to a side of the transfer case housing 4 away from the HST assembly 3, the transfer case assembly 8 is installed in the transfer case housing 4, the wet clutch assembly 5, the rear PTO assembly 7, the mid-mounted PTO assembly 2 and the auxiliary transmission assembly 9 are installed in the rear axle housing 6, and the output end of the transmission assembly 1 is connected to the input shaft of the HST assembly 3. Transmission connection, the HST assembly 3 is provided with a first output shaft 31 and a second output shaft 32, the first output shaft 31 is transmission connected to the input end of the wet clutch assembly 5, the output end of the wet clutch assembly 5 is transmission connected to the rear PTO assembly 7, the rear PTO assembly 7 is transmission connected to the mid-mounted PTO assembly 2; the second output shaft 32 is transmission connected to the auxiliary transmission assembly 9, the auxiliary transmission assembly 9 is transmission connected to the transfer case assembly 8, in this embodiment, the first output shaft 31 is transmission connected to the input end of the wet clutch assembly 5 through a spline sleeve, and the second output shaft 32 is transmission connected to the input end of the auxiliary transmission assembly 9 through a spline sleeve.

[0031] In this embodiment, the gearbox assembly 1 includes a gearbox housing 11, in which a speed change shaft 12 is rotatably arranged, the input end of the speed change shaft 12 is fixedly connected to a torsion damper 13 for mounting on an engine flywheel, the output end of the speed change shaft 12 is fixedly connected to the input shaft of the HST assembly 3 coaxially, the input end of the speed change shaft 12 is connected to the torsion damper 13 via a spline, and the output end of the speed change shaft 12 is connected to the input shaft of the HST assembly 3 via a spline sleeve. Connecting the speed change shaft 12 to the engine via the torsion damper 13 can effectively reduce the torsional vibration natural frequency of the transmission system, and the arrangement of the spline and the spline sleeve can ensure the synchronization of power transmission between the torsion damper 13 and the speed change shaft 12.

[0032] In this embodiment, the rear PTO assembly 7 includes a rear transmission shaft 71 and a rear output shaft 72. The rear output shaft 72 is rotatably installed in the rear axle housing 6. One end of the rear transmission shaft 71 is transmission-connected to the output end of the wet clutch assembly 5. The rear transmission shaft 71 and the rear output shaft 72 are transmission-connected via a speed gear set. The rear output shaft 72 can be used for external working tools. The speed gear set can facilitate independent control of the rotation speed of the rear output shaft 72, and has good versatility.

[0033] Specifically, the speed gear set includes a first rear driving gear 73 and a second rear driving gear 77 fixedly sleeved on the rear transmission shaft 71, and a first rear passive gear 74 and a second rear passive gear 76 rotatably sleeved on the rear output shaft 72. The first rear driving gear 73 is meshed with the first rear passive gear 74, and the second rear driving gear 77 is meshed with the second rear passive gear 76. A rear speed change meshing sleeve 75 is fixedly sleeved on the rear output shaft 72. The rear speed change meshing sleeve 75 enables the first rear passive gear 74 to rotate synchronously with the rear output shaft 72. The rear speed change meshing sleeve 75 is arranged between the first rear passive gear 74 and the second rear passive gear 76. The arrangement of the rear speed change meshing sleeve 75 can control the rotation of the rear output shaft 72 as needed.

[0034] In this embodiment, the mid-mounted PTO assembly 2 includes a mid-mounted fixed shaft 21 fixedly mounted in the rear axle housing 6 and a mid-mounted output shaft 22 rotatably mounted in the rear axle housing 6. The mid-mounted fixed shaft 21 and the mid-mounted output shaft 22 are arranged in parallel. A mid-mounted driving gear 23 is rotatably sleeved on the mid-mounted fixed shaft 21. A second rear driving gear 77 is also fixedly sleeved on the rear transmission shaft 71. A second rear driven gear 76 is rotatably sleeved on the rear output shaft 72. The second rear driven gear 76 is arranged on the side of the rear speed change meshing sleeve 75 away from the first rear driven gear 74. The second rear driving gear 77 meshes with the second rear passive gear 76, and the second rear passive gear 76 meshes with the central driving gear 23. A central passive gear 24 is rotatably sleeved on the central output shaft 22, and the central passive gear 24 meshes with the central driving gear 23. A central speed change meshing sleeve 25 is fixedly sleeved on the central output shaft 22, and the central speed change meshing sleeve 25 is arranged in parallel with the central passive gear 24. The central PTO assembly 2 is transmission-connected with the rear PTO assembly 7, and power is output through the central output shaft 22, thereby increasing the connection output for external working tools to meet various working requirements.

[0035] Preferably, the auxiliary transmission assembly 9 includes a first auxiliary transmission shaft 91 and a second auxiliary transmission shaft 92 rotatably mounted in the rear axle housing 6. The first auxiliary transmission shaft 91 and the second auxiliary transmission shaft 92 are arranged in parallel. A low-speed driving gear 93, a middle-speed driving gear 94 and a high-speed driving gear 95 which rotate synchronously with the first auxiliary transmission shaft 91 are sequentially arranged on the first auxiliary transmission shaft 91; a low-speed passive gear 96, a middle-speed passive gear 97 and a high-speed passive gear 98 are sequentially arranged on the second auxiliary transmission shaft 92 to rotate. The low-speed passive gear 96 meshes with the low-speed driving gear 93, the middle-speed passive gear 97 meshes with the middle-speed driving gear 94, and the high-speed passive gear 98 meshes with the high-speed driving gear 95; a first secondary speed-changing meshing sleeve 99 is fixedly sleeved on the second secondary speed-changing shaft 92 between the low-speed passive gear 96 and the middle-speed passive gear 97, and a second secondary speed-changing meshing sleeve 910 is fixedly sleeved on the second secondary speed-changing shaft 92, and the second secondary speed-changing meshing sleeve 910 is arranged beside the high-speed passive gear 98. The low-speed passive gear 96, the middle-speed passive gear 97 and the high-speed passive gear 98 are respectively rotated synchronously with the second secondary speed-changing shaft 92, thereby realizing high, middle and low gear control, and meeting various operation requirements of the secondary speed-changing transmission mechanism.

[0036] Further preferably, the transfer case assembly 8 includes a transfer case fixed shaft 81 fixedly installed in the transfer case housing 4 and a transfer case output shaft 82 rotatably arranged in the transfer case housing 4, the transfer case fixed shaft 81 and the transfer case output shaft 82 are arranged in parallel, a transfer case driving gear 83 is rotatably sleeved on the transfer case fixed shaft 81, and a secondary speed change transmission gear 911 is fixedly sleeved on the second secondary speed change shaft 92, and the secondary speed change transmission gear 911 is rotatably sleeved on the transfer case driving gear 83. The transfer case output shaft 82 is provided with a transfer case driven gear 84, which is meshed with the transfer case driving gear 83. The transfer case output shaft 82 is provided with a transfer case speed change engagement sleeve 85, which is arranged in parallel with the transfer case driven gear 84. The transfer case assembly 8 is connected with the auxiliary transmission assembly 9 in driving connection, and power is output through the transfer case output shaft 82, which is used to connect with the front axle to output power, so as to realize four-wheel drive.

[0037] The engine power is output to the torsional damper 13, the torsional damper 13 drives the left input shaft of the HST assembly 3 to work, the left input shaft of the HST assembly 3 drives the first output shaft 31 and the second output shaft 32 on the right side to work, and the first output shaft 31 drives the wet clutch assembly 5, the rear PTO assembly 7, and the mid-mounted PTO assembly 2 to work in turn.

[0038] The second output shaft 32 drives the auxiliary transmission assembly 9, the transfer case assembly 8 and the entire vehicle to work.

[0039] Embodiment 2

[0040] This embodiment discloses a tractor, comprising the above-mentioned tractor transmission system with HST.

[0041] The utility model can realize stepless speed change, replacing the cumbersome frequent gear shifting; the open HST assembly 3 saves space; there is no need to frequently step on the clutch; various operating requirements can be met, and the wet clutch assembly 5 can realize electronic automatic control, which is easy to operate; it saves lubricating oil and reduces vehicle weight.

[0042] In the description of the present invention, it should be understood that the terms "center", "length", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "inside", "outside", "peripheral", "circumferential" and the like indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred system or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0043] In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0044] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tractor transmission system with HST, characterized in that: The invention comprises a gearbox assembly (1), an HST assembly (3), a transfer case housing (4), a wet clutch assembly (5), a rear axle housing (6), a rear PTO assembly (7), a mid-mounted PTO assembly (2), an auxiliary transmission assembly (9) and a transfer case assembly (8), wherein the HST assembly (3) is fixed on one side of the transfer case housing (4), the rear axle housing (6) is fixedly connected to a side of the transfer case housing (4) away from the HST assembly (3), the transfer case assembly (8) is installed in the transfer case housing (4), and the wet clutch assembly (5), the rear PTO assembly (7), the mid-mounted PTO assembly (2) and the auxiliary transmission assembly (9) are Installed in the rear axle housing (6), the output end of the gearbox assembly (1) is drivingly connected to the input shaft of the HST assembly (3), the HST assembly (3) is provided with a first output shaft (31) and a second output shaft (32), the first output shaft (31) is drivingly connected to the input end of the wet clutch assembly (5), the output end of the wet clutch assembly (5) is drivingly connected to the rear PTO assembly (7), the rear PTO assembly (7) is drivingly connected to the mid-mounted PTO assembly (2); the second output shaft (32) is drivingly connected to the auxiliary transmission assembly (9), the auxiliary transmission assembly (9) is drivingly connected to the transfer case assembly (8).

2. A tractor transmission system with HST according to claim 1, characterized in that: The gearbox assembly (1) comprises a gearbox housing (11), a speed change shaft (12) being rotatably arranged in the gearbox housing (11), an input end of the speed change shaft (12) being fixedly connected to a torsional vibration damper (13) mounted on an engine flywheel, and an output end of the speed change shaft (12) being coaxially fixedly connected to an input shaft of the HST assembly (3).

3. A tractor transmission system with HST according to claim 2, characterized in that: The input end of the speed change shaft (12) is connected to the torsion damper (13) via a spline, and the output end of the speed change shaft (12) is connected to the input shaft of the HST assembly (3) via a spline sleeve.

4. A tractor transmission system with HST according to claim 1, characterized in that: The rear PTO assembly (7) comprises a rear transmission shaft (71) and a rear output shaft (72), wherein the rear output shaft (72) is rotatably mounted in the rear axle housing (6), one end of the rear transmission shaft (71) is transmission-connected to the output end of the wet clutch assembly (5), and the rear transmission shaft (71) and the rear output shaft (72) are transmission-connected via a speed change gear set.

5. A tractor transmission system with HST according to claim 4, characterized in that: The speed change gear set comprises a first rear driving gear (73) fixedly sleeved on the rear transmission shaft (71) and a first rear passive gear (74) rotatably sleeved on the rear output shaft (72), the first rear driving gear (73) meshing with the first rear passive gear (74), a rear speed change meshing sleeve (75) fixedly sleeved on the rear output shaft (72), and the rear speed change meshing sleeve (75) and the first rear passive gear (74) being arranged in parallel.

6. A tractor transmission system with HST according to claim 5, characterized in that: The mid-mounted PTO assembly (2) comprises a mid-mounted fixed shaft (21) fixedly mounted in the rear axle housing (6) and a mid-mounted output shaft (22) rotatably mounted in the rear axle housing (6); the mid-mounted fixed shaft (21) and the mid-mounted output shaft (22) are arranged in parallel; a mid-mounted driving gear (23) is rotatably sleeved on the mid-mounted fixed shaft (21); a second rear driving gear (77) is also fixedly sleeved on the rear transmission shaft (71); a second rear driven gear (76) is rotatably sleeved on the rear output shaft (72); the second rear driven gear (76) is arranged on the rear variable speed drive shaft (71); The first rear driven gear (74) is provided with a speed engagement sleeve (75) at a side away from the first rear driven gear (74); the second rear driving gear (77) is meshed with the second rear driven gear (76); the second rear driven gear (76) is meshed with the middle driving gear (23); a middle driven gear (24) is rotatably sleeved on the middle output shaft (22); the middle driven gear (24) is meshed with the middle driving gear (23); a middle speed change engagement sleeve (25) is fixedly sleeved on the middle output shaft (22); the middle speed change engagement sleeve (25) and the middle driven gear (24) are arranged in parallel.

7. A tractor transmission system with HST according to any one of claims 1 to 6, characterized in that: The auxiliary transmission assembly (9) comprises a first auxiliary transmission shaft (91) and a second auxiliary transmission shaft (92) which are rotatably mounted in the rear axle housing (6); the first auxiliary transmission shaft (91) and the second auxiliary transmission shaft (92) are arranged in parallel; a low gear driving gear (93), a middle gear driving gear (94) and a high gear driving gear (95) which rotate synchronously with the first auxiliary transmission shaft (91) are sequentially arranged on the first auxiliary transmission shaft (91); a low gear driven gear (96), a middle gear driven gear (97) and a high gear driven gear (98) which rotate synchronously with the first auxiliary transmission shaft (91) are sequentially arranged on the second auxiliary transmission shaft (92); The low-gear driven gear (96) is meshed with the low-gear driving gear (93), the middle-gear driven gear (97) is meshed with the middle-gear driving gear (94), and the high-gear driven gear (98) is meshed with the high-gear driving gear (95); a first secondary speed-changing meshing sleeve (99) is fixedly sleeved on the second secondary speed-changing shaft (92) between the low-gear driven gear (96) and the middle-gear driven gear (97), a second secondary speed-changing meshing sleeve (910) is fixedly sleeved on the second secondary speed-changing shaft (92), and the second secondary speed-changing meshing sleeve (910) is arranged beside the high-gear driven gear (98).

8. A tractor transmission system with HST according to claim 7, characterized in that: The transfer case assembly (8) comprises a transfer case fixed shaft (81) fixedly mounted in the transfer case housing (4) and a transfer case output shaft (82) rotatably arranged in the transfer case housing (4), wherein the transfer case fixed shaft (81) and the transfer case output shaft (82) are arranged in parallel, a transfer case driving gear (83) is rotatably sleeved on the transfer case fixed shaft (81), and an auxiliary speed change transmission gear (93) is fixedly sleeved on the second auxiliary speed change shaft (92) (12). 11), the auxiliary speed change transmission gear (911) is meshed with the transfer case driving gear (83), the transfer case output shaft (82) is rotatably sleeved with a transfer case passive gear (84), the transfer case passive gear (84) is meshed with the transfer case driving gear (83), the transfer case output shaft (82) is fixedly sleeved with a transfer case speed change engagement sleeve (85), the transfer case speed change engagement sleeve (85) and the transfer case passive gear (84) are arranged in parallel.

9. A tractor transmission system with HST according to any one of claims 1 to 6, characterized in that: The first output shaft (31) is transmission-connected to the input end of the wet clutch assembly (5) via a spline sleeve, and the second output shaft (32) is transmission-connected to the input end of the auxiliary transmission assembly (9) via a spline sleeve.

10. A tractor, characterized in that: A tractor transmission system with a HST comprising the transmission system of any one of claims 1 to 9.

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