A transmission system for a tractor and a method of operation thereof

Abstract

The application discloses a tractor transmission system and a working method thereof, and solves the problem that the PTO output end speed cannot be positively correlated with the vehicle speed in the prior art, and has the beneficial effect that the PTO output end speed can be selected to be correlated with the engine speed or the output vehicle speed, and the specific scheme is as follows: a tractor transmission system comprises a first shaft and a second shaft, the first shaft is directly connected with an engine, the second shaft is an output shaft of a continuously variable transmission, a first synchronizer is arranged at a first shaft output end, the first synchronizer is fixedly connected with a third shaft, the other side of a second synchronizer is provided with a fourth shaft, the second synchronizer is fixedly connected with the fourth shaft, a first gear pair is arranged between the second shaft and the third shaft, a first gear in the first gear pair is sleeved on the third shaft and can rotate relative to the third shaft, a second gear in the first gear pair is fixedly connected with the second shaft, a second gear pair is arranged between the third shaft and the fourth shaft, a fourth gear in the second gear pair is sleeved on the fourth shaft and can rotate relative to the fourth shaft.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tractor technology, in particular to a transmission system for tractors and a working method thereof. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] A power take-off (PTO) is generally designed at the rear end of the rear axle of a tractor, which is used to provide power for agricultural equipment such as rotary cultivators, balers, seeders, etc. In general, 1-3 PTO gears are provided at the rear end of the rear axle of the tractor, the PTO input shaft is directly connected to the engine, each gear has a fixed transmission ratio relationship with the engine speed, and the driver or user adjusts the PTO output speed by selecting different gears, so that the PTO speed of the tractor is directly related to the engine speed.

[0004] For some special agricultural conditions, the PTO speed directly affects the agronomic characteristics, such as seeding, fertilizing, etc. The PTO speed directly affects the seeding amount and fertilizing concentration. At this time, the PTO speed needs to change in real time according to the vehicle speed, otherwise, it will cause uneven seeding amount or fertilizing concentration, affecting the agronomic characteristics. The inventor found that the PTO speed of the tractor in the prior art has no fixed transmission ratio relationship with the vehicle speed, and in actual operation, the vehicle speed of the tractor will often fluctuate due to load changes, and the PTO speed cannot change in real time with the vehicle speed, which cannot meet the special working condition requirements and easily affects the operation of the tractor. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a transmission system for tractors, which can stably maintain the engine speed, so that the tractor has multiple working modes, and the PTO output speed is positively related to the vehicle speed in some working modes.

[0006] In order to achieve the above-mentioned purpose, the present application is realized by the following technical solutions:

[0007] A tractor transmission system, comprising a first shaft and a second shaft, the first shaft is directly connected with an engine, the second shaft is an output shaft of a continuously variable transmission, a first synchronizer is arranged at an output end of the first shaft, the first synchronizer is fixedly connected with a third shaft, a second synchronizer is arranged at an output end of the second shaft, the second synchronizer is fixedly connected with a fourth shaft, a first gear pair is arranged between the second shaft and the third shaft, a first gear of the first gear pair is sleeved on the third shaft and can rotate relative to the third shaft, a second gear of the first gear pair is fixedly connected with the second shaft, a second gear pair is arranged between the fourth shaft and the third shaft, a third gear of the second gear pair is sleeved on the third shaft and can rotate relative to the third shaft, the first gear and the third gear can synchronously rotate, a fourth gear of the second gear pair is sleeved on the fourth shaft and can rotate relative to the fourth shaft, the first synchronizer can be combined with the first shaft or the first gear or kept in neutral state, the second synchronizer can be combined with the second gear or the fourth gear or kept in neutral state;

[0008] An output end of the third shaft is provided with a PTO clutch, the PTO clutch is connected with a fifth shaft, an output end of the fifth shaft is connected with a PTO output end through a transmission assembly.

[0009] The tractor transmission system as described above, the third shaft supports the first gear and the third gear through the first rotating bearing, so that the first gear and the third gear can synchronously rotate relative to the third shaft.

[0010] The fourth shaft supports the fourth gear through the second rotating bearing, so that the fourth gear can rotate relative to the fourth shaft.

[0011] The tractor transmission system as described above, the third shaft supports a first transition gear through the first rotating bearing, the first transition gear, the first gear and the third gear are fixedly connected through the first rotating bearing, the first transition gear is located on one side of the first synchronizer, the first synchronizer can be combined with the first transition gear, when the first synchronizer is combined with the first transition gear, the first synchronizer, the first gear and the third gear can synchronously rotate.

[0012] The fourth shaft supports a fourth transition gear through the second rotating bearing, so that the fourth transition gear and the fourth gear are fixedly connected, the fourth transition gear is located on one side of the second synchronizer, the second synchronizer can be combined with the fourth transition gear, when the second synchronizer is combined with the fourth transition gear, the second synchronizer and the fourth gear can synchronously rotate.

[0013] The second shaft is fixedly connected with the second transition gear and the second gear, the second transition gear is located on one side of the second synchronizer, the second synchronizer can be combined with the second transition gear to realize synchronous rotation of the second synchronizer, the second shaft and the second gear; and the output end of the first shaft is provided with a third transition gear, and the first synchronizer is combined with the first shaft through the third transition gear.

[0014] The fourth shaft is connected with the rear axle structure through a transmission assembly, and the fourth shaft is connected with the front axle structure through the transmission assembly.

[0015] The transmission assembly comprises a fifth gear fixedly connected with the fourth shaft, the fifth gear is engaged with a sixth gear, and the sixth gear is connected with the front axle structure through a sixth shaft.

[0016] In order to realize that the PTO output end has multiple gears, the fifth shaft is provided with a third synchronizer, the third synchronizer is fixedly connected with the fifth shaft, the fifth shaft is provided with a seventh gear on one side of the third synchronizer, the seventh gear is in synchronous rotation with a fifth transition gear, the seventh gear is rotatable relative to the fifth shaft, the seventh gear is engaged with an eighth gear, and the eighth gear is connected with the PTO output end through a seventh shaft.

[0017] The fifth shaft is provided with a ninth gear on the other side of the third synchronizer, the ninth gear is in synchronous rotation with a sixth transition gear, the ninth gear is rotatable relative to the fifth shaft, the ninth gear is engaged with a tenth gear, and the tenth gear is connected with the PTO output end through the seventh shaft.

[0018] In a second aspect, the application further provides a working method of the transmission system for a tractor, comprising the following contents.

[0019] The first PTO mode: in this mode, the first synchronizer is combined with the first shaft, at this time, a part of engine input power is transmitted to the second shaft through the continuously variable transmission, the second synchronizer can select high and low gears, the second synchronizer is directly combined with the second shaft in the low gear, and a part of engine input power is directly transmitted to the front axle structure and the rear axle structure through the second shaft-second synchronizer-fourth shaft, the second synchronizer is combined with the fourth gear in the high gear, and a part of engine input power is transmitted to the front axle structure and the rear axle structure through the second shaft-first gear pair-second gear pair-second synchronizer-fourth shaft.

[0020] The working method of the transmission system for the tractor as described above, in the first PTO mode, another part of the power and the speed of the engine is transmitted to the PTO clutch and the third synchronizer via the first synchronizer and the third shaft, the third synchronizer can select different PTO gears, and is transmitted to the PTO output end through the third synchronizer-seventh gear-eighth gear or is transmitted to the PTO output end through the third synchronizer-ninth gear-tenth gear.

[0021] The working method of the transmission system for the tractor as described above, further includes the following contents:

[0022] The ground speed PTO mode: the first synchronizer is combined with the first gear, at this time, the engine input power is transmitted to the second synchronizer through the continuously variable transmission, the second synchronizer can select high and low gears, the second synchronizer is directly combined with the second shaft in the low gear, and a part of the engine input power is directly transmitted to the front axle and the rear axle structure through the second shaft-second synchronizer-fourth shaft; another part of the engine input power and the speed is transmitted to the output end through the first gear pair-first synchronizer-third shaft-PTO clutch;

[0023] The second synchronizer is combined with the fourth gear in the high gear, a part of the engine input power is transmitted to the front axle and the rear axle structure through the second shaft-first gear pair-second gear pair-second synchronizer-fourth shaft, and another part of the engine input power is transmitted to the PTO output end through the second shaft-first gear pair-first synchronizer-third shaft-PTO clutch.

[0024] The working method of the transmission system for the tractor as described above, further includes the following contents:

[0025] The PTO reverse mode: the second shaft is in the reverse state through the continuously variable transmission, at the same time, the second synchronizer is in the intermediate neutral position, the first synchronizer is combined with the first gear, the engine input power and the speed are transmitted to the PTO output end through the second shaft-first gear pair-first synchronizer-third shaft-PTO clutch, at this time, the speed of the PTO output end is reversely rotated.

[0026] The working method of the transmission system for the tractor as described above, further includes the following contents:

[0027] The PTO neutral mode: in this mode, the first synchronizer is in the intermediate neutral position, and there is no power and speed output at the PTO output, so that the useless work such as PTO dragging power can be reduced to the maximum extent, which helps to improve the overall transmission efficiency of the transmission system.

[0028] The beneficial effects of the above-mentioned application are as follows:

[0029] 1) In the present application, the PTO output speed can be selected to be related to the engine speed or related to the output vehicle speed, which is suitable for stable PTO speed working conditions such as rotary tillage, and is also suitable for ground speed PTO working conditions such as seeding, thereby meeting various agricultural needs, improving agricultural effects, and increasing the working condition adaptability of the power assembly and the tractor.

[0030] 2) In the first PTO mode, part of the engine power is directly output to the PTO shaft through the first shaft, and the other part is output to the front axle and the rear axle through the continuously variable transmission. Through the continuously variable transmission, the tractor speed and the engine speed have no fixed transmission ratio relationship. When working in this mode, the vehicle speed changes in real time with the load size, while the engine speed is relatively stable, and then the PTO output speed is relatively stable, which is suitable for agricultural working conditions such as rotary tillage and harrowing.

[0031] 3) In the ground speed PTO mode, part of the engine power is output to the PTO shaft through the first synchronizer, and the other part is output to the front axle and the rear axle through the second synchronizer. At this time, the PTO output speed is positively related to the vehicle speed, that is, the PTO speed changes in real time with the vehicle speed, which is suitable for agricultural working conditions such as seeding and pesticide spraying.

[0032] 4) In the PTO reverse mode, the reverse speed generated by the continuously variable transmission is output to the PTO shaft through the second shaft-first synchronizer, so as to realize the reverse rotation of the PTO shaft, which is suitable for agricultural machinery reverse cleaning weeds and other working conditions.

[0033] 5) In the PTO neutral mode, no power and speed is transmitted to the PTO, which can minimize the useless work such as PTO drag power and PTO stirring oil, and is helpful to improve the overall transmission efficiency of the transmission system.

[0034] 6) In the present application, the third synchronizer is arranged on the fifth shaft, and the two sides of the third synchronizer can be combined with corresponding gear transmission parts, so that the PTO output end can have different output speeds. BRIEF DESCRIPTION OF DRAWINGS

[0035] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and the explanation thereof, explain the present application, and do not constitute an improper limitation of the present application.

[0036] Figure 1 is a schematic diagram of a tractor transmission system according to one or more embodiments of the present application Figure One .

[0037] Figure 2 is a schematic diagram of a tractor transmission system according to one or more embodiments of the present application Figure Two .

[0038] In the drawings: the mutual spacing or dimensions are exaggerated for showing the positions of the parts, and the schematic diagrams are only for illustration.

[0039] Wherein: S1. first axis, S2. second axis, S3. third axis, S4. fourth axis, S5. fifth axis, S6. sixth axis, S7. seventh axis;

[0040] SY1. first synchronizer, SY2. second synchronizer, SY3. third synchronizer;

[0041] Z1. first gear, Z2. second gear, Z3. third gear, Z4. fourth gear, Z5. fifth gear, Z6. sixth gear, Z7. seventh gear, Z8. eighth gear, Z9. ninth gear, Z10. tenth gear, Z11. eleventh gear, Z12. twelfth gear;

[0042] G1. first transition gear, G2. second transition gear, G3. third transition gear, G4. fourth transition gear, G5. fifth transition gear, G6. sixth transition gear, G7. seventh transition gear. DETAILED DESCRIPTION

[0043] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0044] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0045] As introduced in the background, the problem that the PTO output speed is not positively correlated with the vehicle speed cannot be solved in the prior art. In order to solve the above technical problem, the present application provides a transmission system for a tractor.

[0046] Example one

[0047] In a typical embodiment of the present application, reference is made to Figure 1As shown, a tractor transmission system comprises a first shaft S1 and a second shaft S2, the first shaft is directly connected with an engine, the second shaft S2 is an output shaft of a continuously variable transmission, a first synchronizer SY1 is arranged at an output end of the first shaft, the first synchronizer is fixedly connected with a third shaft S3, a second synchronizer SY2 is arranged at an output end of the second shaft, the second synchronizer is fixedly connected with a fourth shaft S4, a first gear pair is arranged between the second shaft and the third shaft, a first gear Z1 of the first gear pair is sleeved on the third shaft and can rotate relative to the third shaft, a second gear Z2 of the first gear pair is fixedly connected with the second shaft S2, a second gear pair is arranged between the third shaft and the fourth shaft, a fourth gear Z4 of the second gear pair is sleeved on the fourth shaft and can rotate relative to the fourth shaft, a third gear Z3 of the second gear pair is fixedly connected with the first gear and can rotate relative to the third shaft, the first synchronizer SY1 can be combined with or kept in neutral with the first shaft S1 or the first gear Z1, the second synchronizer SY2 can be combined with or kept in neutral with the second gear Z2 or the fourth gear Z4, the fourth shaft is connected with a rear axle structure and a front axle structure respectively;

[0048] An output end of the third shaft is provided with a PTO clutch CPTO, the PTO clutch is connected with a fifth shaft S5, an output end of the fifth shaft is connected with a PTO output end through a transmission assembly.

[0049] Need to be explained is that the third shaft supports the first gear and the third gear through a first rotating bearing, so that the first gear and the third gear can synchronously rotate relative to the third shaft; the first transition gear is fixedly connected with the first gear through the first rotating bearing, the first transition gear is located on one side of the first synchronizer, the first synchronizer can be combined with the first transition gear, and the combination of the first synchronizer and the first gear can be realized when the first synchronizer is combined with the first transition gear.

[0050] Moreover, the fourth shaft supports the fourth gear Z4 through a second rotating bearing, so that the fourth gear can rotate relative to the fourth shaft, the fourth transition gear is fixedly connected with the fourth gear, the fourth transition gear is located on one side of the second synchronizer, the second synchronizer can be combined with the fourth transition gear, and the combination of the second synchronizer and the fourth gear can be realized; moreover, a third transition gear G3 is arranged at an output end of the first shaft, the first synchronizer is combined with the first shaft through the third transition gear, a second transition gear G2 is arranged at an output end of the second shaft, the second synchronizer is combined with the second shaft through the second transition gear.

[0051] It is easy to understand that the output end of the fourth shaft is connected with the rear axle structure on one hand; on the other hand, the fourth shaft is connected with the front axle structure through the transmission assembly;

[0052] The transmission assembly includes a fifth gear Z5 fixed to the fourth shaft, the fifth gear is located on one side of the fourth gear, the fifth gear is engaged with a sixth gear Z6, and the sixth gear is connected with the front axle structure through a sixth shaft S6. Of course, in other examples, the fourth shaft can also be connected with the front axle structure through other transmission assemblies.

[0053] In order to realize that the PTO output end has multiple gears, the fifth shaft is provided with a third synchronizer SY3, the fifth shaft is provided with a seventh gear Z7 on one side of the third synchronizer, the seventh gear is rotatable relative to the fifth shaft S5, the seventh gear Z7 is engaged with an eighth gear Z8, and the eighth gear Z8 is connected with the PTO output end; the fifth shaft is provided with a ninth gear Z9 on the other side of the third synchronizer, the ninth gear is rotatable relative to the fifth shaft, the ninth gear is engaged with a tenth gear Z10, and the tenth gear is connected with the PTO output end.

[0054] Specifically, the fifth shaft supports the seventh gear and the fifth transition gear through a third rotating bearing, the third synchronizer can be combined with the fifth transition gear G5 to realize the combination with the seventh gear; the fifth shaft supports the ninth gear and the sixth transition gear G6 through a fourth rotating bearing, the third synchronizer can be combined with the sixth transition gear to realize the combination with the ninth gear; in addition, the eighth gear and the tenth gear are fixed to the seventh shaft S7, and the output end of the seventh shaft is the PTO output end.

[0055] It should be noted that the first rotating bearing, the second rotating bearing, the third rotating bearing and the fourth rotating bearing are existing rolling bearings, and of course, they can also be other structural members.

[0056] Among them, the continuously variable transmission, the first synchronizer, the second synchronizer, the third synchronizer and the PTO clutch are existing structural members.

[0057] It can be understood that the second synchronizer has multiple gears, which means that the second synchronizer is combined with the second gear on one side in high gear, and is combined with the fourth gear on the other side in low gear; the third synchronizer also has multiple gears, and the third synchronizer can be combined with the seventh gear on one side or the ninth gear on the other side.

[0058] In other examples, in order to realize that the PTO output end has a third gear, as shown in Figure 2 The seventh shaft S7 is provided with a fourth synchronizer SY4, specifically, the fifth shaft is provided with an eleventh gear Z11, the eleventh gear is engaged with a twelfth gear, the seventh shaft supports a seventh transition gear and the twelfth gear through a rotating bearing, the fourth synchronizer is fixedly connected with the seventh shaft, and the fourth synchronizer can be combined with the seventh transition gear, so as to realize the output of different PTO output end transmission ratios.

[0059] The transmission system provided by the embodiment can realize that the rotation speed of the PTO output end is related to the rotation speed of the engine or the output vehicle speed, meets the ground speed PTO working condition requirement and the agricultural requirement of the tractor seeding, improves the agricultural effect, and increases the working condition adaptability of the power assembly and the tractor.

[0060] Embodiment two

[0061] The embodiment discloses a working method of a transmission system for a tractor, and comprises the following contents.

[0062] The first PTO mode is a traditional PTO mode: in this mode, the first synchronizer SY1 is combined with the first shaft S1. At this time, part of the engine input power is transmitted to the second shaft SY2 through the continuously variable transmission, the second synchronizer can select high and low gears, and the second synchronizer is directly combined with the second shaft S2 when the second synchronizer is in the low gear, part of the engine input power is directly transmitted to the front axle structure and the rear axle structure through the second shaft S2-second synchronizer SY2-fourth shaft S4, and the second synchronizer is combined with the fourth gear when the second synchronizer is in the high gear, and part of the engine input power is transmitted to the front axle structure and the rear axle structure through the second shaft S2-first gear pair Z2-Z1-second gear pair Z3-Z4-second synchronizer SY2-fourth shaft S4.

[0063] In the first PTO mode, another part of the engine power and the rotation speed is transmitted to the PTO clutch CPTO and the third synchronizer SY3 through the first synchronizer SY1 and the third shaft, the third synchronizer SY3 can select different PTO gears, and is transmitted to the PTO output end through the third synchronizer SY3-seventh gear Z7-eighth gear Z8 or transmitted to the PTO output end through the third synchronizer SY3-ninth gear Z9-tenth gear Z10. In this mode, the rotation speed of the PTO output end is positively related to the rotation speed of the engine and is irrelevant to the vehicle speed (the rotation speed of the front axle and the rear axle determines the vehicle speed).

[0064] The ground speed PTO mode (in this mode, the rotation speed of the PTO output end is positively related to the walking vehicle speed of the tractor): in this mode, the first synchronizer SY1 is combined with the first gear Z1. At this time, the engine input power is transmitted to the second synchronizer SY2 through the continuously variable transmission, the second synchronizer can select high and low gears, and the second synchronizer is directly combined with the second shaft S2 when the second synchronizer is in the low gear, part of the engine input power is directly transmitted to the front axle and the rear axle structure through the second shaft S2-second synchronizer SY2-fourth shaft S4; another part of the engine input power and the rotation speed is transmitted to the third synchronizer SY3 through the second gear Z2-first gear Z1-first synchronizer SY1-third shaft S3-PTO clutch CPTO.

[0065] The second synchronizer SY2 is combined with the fourth gear Z4 in the high gear, and a part of the engine input power is transmitted to the front axle and rear axle structure via the second shaft S2-the first gear pair Z2-Z1-the second gear pair Z3-Z4-the second synchronizer SY2-the fourth shaft S4, and another part of the engine input power is transmitted CPTO to the third synchronizer SY3 via the second shaft S2-the first gear pair Z2-Z1-the first synchronizer SY1-the third shaft S3-the PTO clutch.

[0066] The third synchronizer SY3 can select different PTO gears, and is transmitted to the PTO output via the third synchronizer SY3-the seventh gear Z7-the eighth gear Z8 or is transmitted to the PTO output via the third synchronizer SY3-the ninth gear Z9-the tenth gear Z10. In this mode, the PTO rotation speed is irrelevant to the engine rotation speed, and is related to the vehicle speed (the front axle and rear axle rotation speed), and the transmission ratio can be calculated by the gear number ratio, which is not described here again.

[0067] The PTO reverse mode: in the above ground speed PTO mode, the second shaft S2 is in the reverse state (because the second shaft is the output shaft of the continuously variable transmission) by the continuously variable transmission, and at the same time, the second synchronizer SY2 is in the intermediate neutral position, the first synchronizer SY1 is combined with the first gear Z1, and the engine input power and rotation speed are transmitted to the third synchronizer SY3 via the second shaft S2-the second gear Z2-the first gear Z1-the first synchronizer SY1-the third shaft S3-the PTO clutch CPTO, at this time, the PTO output end is reversely rotated. In this mode, the PTO output end is reversed, which can be used for special working conditions such as reversing agricultural implements, for example, a baler can clear the jammed weeds by reversing.

[0068] The PTO neutral mode: in this mode, the first synchronizer SY1 is in the intermediate neutral position, and the PTO has no power and rotation speed output. In this mode, the PTO drag power and other useless work can be reduced to the maximum extent, which helps to improve the overall transmission efficiency of the transmission system.

[0069] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A power transmission system for a tractor, characterized by, The first shaft is directly connected with the engine, and the second shaft is an output shaft of the continuously variable transmission. The output end of the third shaft is provided with a PTO clutch, the PTO clutch is connected with a fifth shaft, and the output end of the fifth shaft is connected with a PTO output end through a transmission assembly.

2. A transmission system for a tractor as claimed in claim 1, characterised in that, The third shaft supports the first gear and the third gear through a first rotating bearing. The fourth shaft supports the fourth gear through a second rotating bearing.

3. A tractor drive system according to claim 2, characterised in that, The third shaft supports a first transition gear through the first rotating bearing, the first transition gear is located on one side of the first synchronizer, and the first synchronizer can be combined with the first transition gear. The fourth shaft supports a fourth transition gear through the second rotating bearing, the fourth transition gear is located on one side of the second synchronizer, and the second synchronizer can be combined with the fourth transition gear.

4. A transmission system for a tractor as claimed in claim 1, characterized in that, The output end of the fourth shaft is connected with a rear axle structure, and the fourth shaft is connected with a front axle structure through a transmission assembly. The transmission assembly comprises a fifth gear fixed to the fourth shaft, the fifth gear is located on one side of the fourth gear, the fifth gear is engaged with a sixth gear, and the sixth gear is connected with the front axle structure through a sixth shaft.

5. The transmission system for a tractor as claimed in claim 1 wherein, The fifth shaft is provided with a third synchronizer, the third synchronizer is fixed to the fifth shaft, the fifth shaft is located on one side of the third synchronizer and provided with a seventh gear, the seventh gear is synchronously rotated with the fifth transition gear, the seventh gear is rotatable relative to the fifth shaft, the seventh gear is engaged with an eighth gear, and the eighth gear is connected with the PTO output end through a seventh shaft. The fifth shaft is located on the other side of the third synchronizer and provided with a ninth gear, the ninth gear is synchronously rotated with the sixth transition gear, the ninth gear is rotatable relative to the fifth shaft, the ninth gear is engaged with a tenth gear, and the tenth gear is connected with the PTO output end through the seventh shaft.

6. A method of operating a transmission system for a tractor according to any one of claims 1-5, characterized in that, The following contents are included: The first PTO mode: in this mode, the first synchronizer is combined with the first shaft, at this time, a part of the engine input power is transmitted to the second shaft through the continuously variable transmission, the second synchronizer can select high and low gears, when the second synchronizer is in the low gear, it is directly combined with the second shaft, a part of the engine input power is directly transmitted to the front axle structure and the rear axle structure through the second shaft-second synchronizer-fourth shaft, when the second synchronizer is in the high gear, the second synchronizer is combined with the fourth gear, a part of the engine input power is transmitted to the front axle structure and the rear axle structure through the second shaft-first gear pair-second gear pair-second synchronizer-fourth shaft.

7. A method of operating a transmission system for a tractor as claimed in claim 6, characterised in that, In the first PTO mode, another part of the engine power and the speed is transmitted to the PTO clutch and the third synchronizer through the first synchronizer and the third shaft, the third synchronizer can select different PTO gears, and is transmitted to the PTO output end through the third synchronizer-seventh gear-eighth gear or the third synchronizer-ninth gear-tenth gear.

8. A method of operating a transmission system for a tractor as claimed in claim 6, characterized in that, Further comprising the following contents: The ground speed PTO mode: the first synchronizer is combined with the first gear, at this time, the engine input power is transmitted to the second synchronizer through the continuously variable transmission, the second synchronizer can select high and low gears, when the second synchronizer is in the low gear, it is directly combined with the second shaft, a part of the engine input power is directly transmitted to the front axle and the rear axle structure through the second shaft-second synchronizer-fourth shaft; another part of the engine input power and the speed is transmitted to the output end through the first gear pair-first synchronizer-third shaft-PTO clutch; When the second synchronizer is in the high gear, it is combined with the fourth gear, a part of the engine input power is transmitted to the front axle and the rear axle structure through the second shaft-first gear pair-second gear pair-second synchronizer-fourth shaft, another part of the engine input power is transmitted to the PTO output end through the second shaft-first gear pair-first synchronizer-third shaft-PTO clutch.

9. A method of operating a transmission system for a tractor as claimed in claim 8, characterised in that, Further comprising the following contents: The PTO reverse mode: through the continuously variable transmission, the second shaft is in the reverse state of reverse rotation, at the same time, the second synchronizer is in the intermediate neutral position, the first synchronizer is combined with the first gear, the engine input power and the speed are transmitted to the PTO output end through the second shaft-first gear pair-first synchronizer-third shaft-PTO clutch, at this time, the speed of the PTO output end is reversely rotated.

10. The method of claim 6, wherein, Further comprising the following contents: The PTO neutral mode: in this mode, the first synchronizer is in the intermediate neutral position, and there is no power and speed output at the PTO output.

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