Main drive train of a wind turbine and method of assembling the same

Abstract

The application discloses a main transmission system of a wind turbine generator and an assembling method thereof, the main transmission system comprising a transition flange and a gearbox, the transition flange comprising an upper wind side flange structure connected with an impeller and a lower wind side flange structure connected with an input end of the gearbox, an output end of the gearbox being connected with a generator, the gearbox comprising a box body, a primary planetary gear train structure and a main bearing, the primary planetary gear train structure and the main bearing being arranged in the box body, an outer ring of the main bearing being connected with the box body, an inner ring of the main bearing being connected with an upper wind side of a planet carrier of the primary planetary gear train structure, and the main bearing being a three-row cylindrical roller bearing. The main bearing is built in the gearbox, the main shaft of the traditional wind turbine generator is cancelled, the axial dimension of the main transmission system of the wind turbine generator is small, the structure is more compact, and the weight is lighter; meanwhile, the influence of the deformation of the main shaft of the high-power wind turbine generator on the tooth shape meshing of the gearbox is solved, and the carrying capacity and the service life of the gearbox are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a main transmission system of a wind turbine generator set and an assembly method thereof. Background Art

[0002] As the capacity of wind turbines continues to grow, the diameter of wind turbine rotors is increasing. Long blades and tall towers have become the mainstream due to their favorable economics. As blades grow longer and unit power increases, the loads on wind turbine main bearings are increasing, and the requirements are becoming increasingly demanding. Furthermore, as the most critical components of the wind turbine drive train, the main bearings and gearboxes of wind turbines are subject to extremely high reliability requirements. Conventional wind turbine main drive system designs for main bearings and gearboxes are increasingly unable to meet the requirements for high-power unit designs. Designing a new, reliable, and high-load-bearing main drive system is crucial for the design and application of high-power wind turbines.

[0003] To meet the main bearing and gearbox transmission system requirements of long-bladed, high-power wind turbines, several key solutions are currently available. The first utilizes a conventional wind turbine gearbox, matching the main shaft with two single-row tapered main bearings and a primary ring gear with a support bearing. This solution is costly, places high demands on the design and operating clearances of the single-row tapered bearings, and is difficult to install. Bearing life is significantly affected by the operating environment and cannot be guaranteed. The second approach utilizes a compact design, with two single-row tapered main bearings supporting the main shaft. The main shaft and gearbox are directly and rigidly connected. The front end of the compact primary planetary carrier is devoid of a support bearing, and the primary ring gear is connected to the main bearing housing. This approach is less expensive than the first, but the main bearing issues remain. Furthermore, due to the long main shaft and bearing stiffness, deformation of the integrated primary planetary carrier results in unbalanced loading of the planetary gears. This requires compensating for tooth surface meshing deviations caused by overall system deformation by gear reshaping or deformation of the planetary gear flexpins. However, this approach is currently immature, presents significant challenges in gear system design and manufacturing, and carries significant technical risks. The third solution is to integrate the main bearing and main shaft of the wind turbine with the gearbox, and the front end bearing of the gearbox planetary frame adopts a large cone angle double row tapered bearing. This solution is currently used in semi-direct drive wind turbines, and the large cone angle double row tapered bearing in this solution also has high requirements for clearance design. At the same time, it is limited by the load capacity and size limitations of the large cone angle double row tapered bearing, and has not been used in high-power units.

[0004] In summary, existing high-power wind turbine main drive systems suffer from insufficient load-bearing capacity of the first-stage planetary carrier bearings in the gearbox, high operational risks, and poor gear precision and adaptability. Therefore, a new wind turbine main drive system is urgently needed that offers high load-bearing capacity and reliability, ensuring both safe and economical operation of high-power wind turbines. Summary of the Invention

[0005] The Summary of the Invention introduces a series of simplified concepts that will be further described in the Detailed Description of the Invention. The Summary of the Invention is not intended to limit the key features and essential features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0006] In order to at least partially solve the above problems, according to a first aspect of the present invention, a main transmission system of a wind turbine is provided, wherein the main transmission system includes a transition flange and a gearbox, the transition flange includes an upwind flange structure connected to the impeller and a downwind flange structure connected to the input end of the gearbox, the output end of the gearbox is connected to the generator, the gearbox includes a housing, a first-stage planetary gear structure and a main bearing, the first-stage planetary gear structure and the main bearing are both arranged in the housing, the outer ring of the main bearing is connected to the housing, the inner ring of the main bearing is connected to the upwind side of the planetary carrier of the first-stage planetary gear structure, and the main bearing is a three-row cylindrical roller bearing.

[0007] Optionally, the transition flange includes a tapered section that gradually decreases from the upwind side to the downwind side, so that the radial dimension of the downwind side flange structure is smaller than the radial dimension of the upwind side flange structure.

[0008] Optionally, the upwind side of the planetary carrier of the first-stage planetary gear system structure is provided with a first step portion matching the inner ring of the main bearing, the end face of the first step portion is provided with a first threaded hole extending in the axial direction, the inner ring of the main bearing is provided with a first through hole extending along the axial direction, and the leeward flange structure of the transition flange is provided with a fourth through hole extending along the axial direction, the first threaded hole, the first through hole and the fourth through hole match, so that the transition flange and the inner ring of the main bearing are jointly connected to the planetary carrier of the first-stage planetary gear system through high-strength bolts.

[0009] Optionally, the main bearing and the gears inside the gearbox share oil lubrication, and the gearbox is provided with a forced lubrication oil circuit, which is connected to the lubrication oil channel of the main bearing.

[0010] Optionally, the gearbox further includes a sealing end plate, and the sealing end plate and the outer ring of the main bearing are connected to the box body through high-strength bolts.

[0011] Optionally, the sealing end plate includes a first sealing assembly and a second sealing assembly, the first sealing assembly is engaged with the outer peripheral surface of the transition flange, and the second sealing assembly is engaged with the upwind side of the box body.

[0012] Optionally, the transition flange includes a tapered section that gradually decreases from the upwind side to the leeward side and a straight section whose size remains unchanged in the axial direction, and the first sealing assembly is engaged with the outer circumferential surface of the straight section.

[0013] Optionally, the housing, the planet carrier of the first-stage planetary gear system structure, the transition flange and the sealing end plate together form an independent sealed cavity of the gearbox, and the main bearing is located in the independent sealed cavity.

[0014] Optionally, the box is provided with a connecting arm connected to a main frame of the wind turbine generator set, and the axial position of the main bearing is adjacent to or at least partially overlaps with the axial position of the connecting arm.

[0015] The present invention also provides an assembly method of the main transmission system, comprising:

[0016] The main bearing is placed on the first step portion of the planetary carrier from the upwind side of the planetary carrier of the primary planetary gear train structure, so that the downwind end surface of the outer ring of the main bearing abuts against the end surface of the second step portion of the gear box, and the downwind end surface of the inner ring of the main bearing abuts against the end surface of the first step portion of the planetary carrier, the first through hole of the inner ring of the main bearing is aligned with the first threaded hole of the planetary carrier, the second through hole of the outer ring of the main bearing is aligned with the second threaded hole of the gear box, and the lubricating oil passage of the main bearing is aligned with the forced lubricating oil passage of the gear box to maintain communication;

[0017] Connect the sealing end plate and the outer ring of the main bearing to the housing through high-strength bolts so that the second sealing assembly of the sealing end plate is tightly engaged with the upwind side of the housing;

[0018] Insert the transition flange into the annular sealing end plate until the leeward end surface of the transition flange abuts against the upwind end surface of the inner ring of the main bearing, the fourth through hole of the transition flange aligns with the first through hole of the inner ring of the main bearing, and the first sealing assembly of the sealing end plate tightly engages with the outer circumferential surface of the corresponding position of the transition flange;

[0019] The transition flange and the inner ring of the main bearing are connected to the planet carrier of the first-stage planetary gear structure by high-strength bolts.

[0020] The present invention integrates the main bearing into the gearbox, and the main bearing is also used as the support bearing of the planetary carrier of the first-level planetary gear system structure, eliminating the main shaft of the traditional wind turbine set. The inner ring of the three-row cylindrical roller bearing serves as the main shaft. The integrated gearbox integrates the unit main shaft, the unit main bearing and the main gearbox into one, so that the axial dimension of the main transmission system of the wind turbine set is small, the structure is more compact and the weight is lighter; at the same time, it solves the influence of the deformation of the main shaft of the high-power wind turbine set on the gear box tooth meshing, and improves the load-bearing capacity and life of the gearbox. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following drawings of the present invention are hereby incorporated into the present invention for understanding the present invention. The drawings show embodiments of the present invention and their descriptions, and are used to explain the device and principle of the present invention. In the drawings,

[0022] Figure 1 This is a schematic diagram of the assembly of the main transmission system in a wind turbine generator system according to an embodiment of the present invention;

[0023] Figure 2 This is a structural diagram of the main transmission system of a wind turbine generator set according to an embodiment of the present invention;

[0024] Figure 3 A partially enlarged structural diagram of a main transmission system of a wind turbine generator set according to an embodiment of the present invention;

[0025] Figure 4 A partially enlarged structural diagram of a main transmission system of a wind turbine generator set according to an embodiment of the present invention;

[0026] Figure 5 A partially enlarged structural diagram of a main transmission system of a wind turbine generator set according to an embodiment of the present invention;

[0027] Figure 6 This is a partially enlarged structural diagram of the main transmission system of a wind turbine generator set according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0029] To provide a thorough understanding of the present invention, a detailed structure will be provided in the following description to illustrate the present invention. Obviously, the practice of the present invention is not limited to the specific details familiar to those skilled in the art. Preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other embodiments and should not be construed as being limited to the embodiments set forth herein.

[0030] It should be understood that the purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. The singular forms "a", "an" and "said / the" are also intended to include the plural forms, unless the context clearly indicates otherwise. When the terms "comprise" and / or "include" are used in this specification, they indicate the presence of the features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof. The terms "upper", "lower", "front", "back", "left", "right" and similar expressions used in the present invention are for illustrative purposes only and are not limiting.

[0031] Ordinal numbers such as "first" and "second" cited in the present invention are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term "first component" itself does not imply the existence of a "second component", and the term "second component" itself does not imply the existence of a "first component".

[0032] Hereinafter, specific embodiments of the present invention will be described in more detail with reference to the accompanying drawings. These drawings illustrate representative embodiments of the present invention and do not limit the present invention.

[0033] The present invention provides a main transmission system of a wind turbine generator set and a wind turbine generator set, such as Figure 1-6 As shown, the main transmission system includes a transition flange 1 and a gearbox 2, wherein the transition flange 1 includes an upwind flange structure 11 connected to the impeller 3 and a downwind flange structure 12 connected to the input end of the gearbox 2, the output end of the gearbox 2 is connected to the generator 4, and the gearbox 2 includes a housing 21, a primary planetary gear structure and a main bearing 22, the primary planetary gear structure and the main bearing 22 are both arranged in the housing 21, the outer ring 221 of the main bearing 22 is connected to the housing 1, and the inner ring 222 of the main bearing 22 is connected to the upwind side of the planet carrier 23 of the primary planetary gear structure, and the main bearing 22 is a three-row cylindrical roller bearing.

[0034] The main bearing 22 is the main bearing of the main transmission system of the wind turbine set, and carries the rotating parts of the main transmission system of the set including the impeller 3 and the transition flange 1. The present invention integrates the main bearing 22 into the gearbox 2. The main bearing 22 also serves as the support bearing of the planetary carrier 23 of the first-level planetary gear structure, eliminating the main shaft of the traditional wind turbine set. The inner ring of the three-row cylindrical roller bearing serves as the main shaft. The integrated gearbox integrates the main shaft of the set, the main bearing of the set and the main gearbox into one, and at the same time solves the influence of the deformation of the main shaft of the high-power wind turbine set on the gearbox tooth meshing, thereby improving the load-bearing capacity and life of the gearbox; three-row cylindrical roller bearings are used as the main bearings, of which two rows of rolling elements arranged radially mainly bear axial forces, and the other row of rolling elements arranged axially mainly bear radial forces. The three-row cylindrical roller bearings can greatly improve the load-bearing capacity of the main bearings; and due to the characteristics of the three-row cylindrical roller bearings, there is no need to consider the installation clearance of the three-row cylindrical roller bearings when assembling the main bearings, so the installation is more convenient and the reliability is higher.

[0035] According to an embodiment of the present invention, Figure 2-4 As shown, the transition flange 1 includes a tapered section 13 that tapers from the upwind side to the leeward side, making the radial dimension of the leeward flange structure 12 smaller than the radial dimension of the upwind flange structure 11. This arrangement reduces the size of the main bearing and other gearbox components located on the leeward side of the transition flange, thereby reducing the weight of the entire main transmission system.

[0036] According to an embodiment of the present invention, Figure 2 As shown, the gearbox 2 also includes a single-row cylindrical roller bearing 24. The outer ring of the single-row cylindrical roller bearing 24 is connected to the housing 21, and the inner ring of the single-row cylindrical roller bearing 24 is connected to the leeward side of the planet carrier 23 of the primary planetary gear structure. The main bearing 22 and the single-row cylindrical roller bearing 24 together serve as support bearings for the planet carrier 23 of the primary planetary gear structure.

[0037] According to an embodiment of the present invention, the main bearing 22 and the gears inside the gearbox share oil lubrication. The main bearing 22 adopts forced lubrication, such as Figure 3 and Figure 6 As shown, the gearbox 2 is equipped with a forced lubrication oil circuit 25, which communicates with the lubrication oil passage 223 of the main bearing 22. The lubrication oil passage 223 can be located in the outer ring 221 of the main bearing 22, allowing lubricating oil to reach the rolling elements of the main bearing 22 via the forced lubrication oil circuit 25 and the lubrication oil passage 223. Preferably, the forced lubrication oil circuit 25 is partially located external to the housing 21, facilitating installation and maintenance and simplifying the processing of the housing 21. The main bearing and the gears within the gearbox share oil lubrication, eliminating the need for a separate lubrication system and facilitating operation and maintenance. Forced lubrication ensures effective lubrication of the main bearing.

[0038] According to an embodiment of the present invention, Figure 5 and Figure 6 As shown, the planet carrier 23 of the primary planetary gear system is provided with a first step 231 on the upwind side. A first threaded hole 232 extending axially is formed on the end surface 231-1 of the first step 231. The inner ring 222 of the main bearing 22 is provided with a first through hole extending along the axial direction. The leeward flange structure 12 of the transition flange 1 is provided with a fourth through hole 121 extending along the axial direction. The first threaded hole 232, the first through hole, and the fourth through hole 121 match, so that the transition flange 1 and the inner ring 222 of the main bearing 22 are jointly connected to the planet carrier 23 of the primary planetary gear system via high-strength bolts 5. Preferably, the outer circumferential surface 231-2 of the first step 231 is clearance-fitted with the inner circumferential surface of the inner ring 222 of the main bearing 22.

[0039] According to an embodiment of the present invention, Figure 2 、 Figure 3 and Figure 6 As shown, the gearbox 2 further includes a sealing end plate 26, which is connected to the housing 21 together with the outer ring 221 of the main bearing 22 via high-strength bolts 6. Preferably, the housing 21 is provided with a second step portion 211, and a second threaded hole 212 extending in the axial direction is formed on the end surface 211-1 of the second step portion 211. The outer ring 221 of the main bearing 22 is provided with a second through hole extending along the axial direction, and the sealing end plate 26 is provided with a third through hole 261 extending along the axial direction. The second through hole, the third through hole 261, and the second threaded hole 212 match, so that the sealing end plate 26 and the outer ring 221 of the main bearing 22 are connected to the housing 1 via high-strength bolts 6.

[0040] According to a preferred embodiment of the present invention, Figure 3As shown, the sealing end plate 26 includes a first sealing assembly 262 and a second sealing assembly 263. The first sealing assembly 262 engages with the outer circumferential surface of the transition flange 1, and the second sealing assembly 263 engages with the upwind side of the housing 21. Specifically, a third step portion is provided on the leeward side of the sealing end plate 26 to match the upwind end surface and inner circumference of the housing 21. Annular sealing members are provided on the end surface and outer circumference of the third step portion facing the housing 21, respectively. These two annular sealing members constitute the second sealing assembly 263 of the sealing end plate 26. Furthermore, two annular sealing members are provided on the inner circumference of the sealing end plate 26 to engage with the outer circumferential surface of the transition flange 1. These two annular sealing members constitute the first sealing assembly 262 of the sealing end plate 26. By setting a first sealing assembly 262 consisting of two annular seals between the sealing end plate 26 and the transition flange 1, the sealing effect of the connection between the sealing end plate 26 and the transition flange 1 is enhanced; and by setting a second sealing assembly 263 consisting of two annular seals respectively located on different joint surfaces between the sealing end plate 26 and the box body 21, the sealing effect of the connection between the sealing end plate 26 and the box body 21 is enhanced.

[0041] According to an embodiment of the present invention, the transition flange 1 further includes a straight section 14 connected to the tapered section 13. The straight section 14 maintains a constant axial dimension, and the first sealing assembly 262 engages with the outer circumferential surface of the straight section 14. By configuring the portion of the transition flange 1 that fits within the sealing end plate 26 to be cylindrical, the sealing end plate 26 and the first sealing assembly 262 to be correspondingly annular, thereby facilitating processing and ensuring a good sealing effect.

[0042] When assembling the gearbox, the main bearing 22 is placed on the first step 231 of the planet carrier 23 from the upwind side of the planet carrier 23 of the first-stage planetary gear structure, so that the downwind end face 221-1 of the outer ring 221 of the main bearing 22 abuts against the end face 211-1 of the second step 211 of the housing 21, and at the same time, the downwind end face 222-1 of the inner ring 222 of the main bearing 22 abuts against the end face 231-1 of the first step 231 of the planet carrier 23, the first through hole of the inner ring 222 of the main bearing 22 is aligned with the first threaded hole 232 of the planet carrier 23, the second through hole of the outer ring 221 of the main bearing 22 is aligned with the second threaded hole 212 of the housing 21, and the lubricating oil passage 23 of the main bearing 2 is aligned with the forced lubricating oil passage 5 of the gearbox to maintain communication. ; The sealing end plate 26 and the outer ring 221 of the main bearing 22 are connected to the casing 21 by high-strength bolts 6, so that the second sealing component 263 of the sealing end plate 26 is tightly engaged with the upwind side of the casing 21; then the transition flange 1 is inserted into the annular sealing end plate 26 until the end face 122 of the leeward side flange structure 12 of the transition flange 1 abuts against the upwind side end face 222-2 of the inner ring 222 of the main bearing 22, the fourth through hole 121 of the transition flange 1 is aligned with the first through hole of the inner ring 222 of the main bearing 22, and the first sealing component 262 of the sealing end plate 26 is tightly engaged with the outer peripheral surface of the straight section 14 of the transition flange 1; the transition flange 1 and the inner ring 222 of the main bearing 22 are connected to the planet carrier 23 of the primary planetary gear structure by high-strength bolts 5.

[0043] According to an embodiment of the present invention, the upwind end face 233 of the planet carrier 23 of the first-stage planetary gear system serves as the front face of the gearbox. A first step 231 for accommodating the main bearing 22 is defined from this upwind end face 233. This allows the main bearing 22 to be directly inserted into the planet carrier 23 from the upwind side, facilitating installation. Furthermore, on the upwind side of the main bearing 22, the outer ring 221 and inner ring 222 are connected to the sealing end plate 26 and the transition flange 1, respectively. The first sealing assembly 262 of the sealing end plate 26 tightly engages the transition flange 1, while the second sealing assembly 263 of the sealing end plate 26 tightly engages the housing 21. As a result, the housing 21, the planet carrier 23 of the first-stage planetary gear system, the transition flange 1, and the sealing end plate 26 collectively form an independent sealed cavity within the gearbox, in which the main bearing 22 is located. This independent sealed cavity provides a common oil lubrication environment for the main bearing and the gears within the gearbox.

[0044] According to an embodiment of the present invention, the housing 21 of the gearbox 2 is provided with a connecting arm 213 connected to the main frame of the wind turbine. The axial position of the main bearing 22 is adjacent to, or at least partially overlaps with, the axial position of the connecting arm 213. The main bearing 22 supports rotating components of the wind turbine, including the impeller 3 and the transition flange 1, and is subject to high torsional torque. Therefore, the axial position of the main bearing 22 is arranged to be close to the axial position of the connecting arm 213 to ensure balanced force on the gearbox.

[0045] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the field of the invention. The terms used herein are only for describing specific implementation purposes and are not intended to limit the invention. Terms such as "part" and "component" appearing herein may refer to either a single part or a combination of multiple parts. Terms such as "installation" and "setting" appearing herein may refer to either a component being directly attached to another component or a component being attached to another component through an intermediate component. Features described herein in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise specified.

[0046] The present invention has been described through the above embodiments, but it should be understood that the above embodiments are for illustrative and illustrative purposes only and are not intended to limit the present invention to the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the above embodiments and that various variations and modifications may be made based on the teachings of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A main transmission system of a wind turbine generator set, characterized in that: The main transmission system includes a transition flange and a gearbox. The transition flange includes an upwind flange structure connected to the impeller and a downwind flange structure connected to the input end of the gearbox. The output end of the gearbox is connected to the generator. The gearbox includes a housing, a primary planetary gear structure, and a main bearing. The primary planetary gear structure and the main bearing are both disposed within the housing. The outer ring of the main bearing is connected to the housing, and the inner ring of the main bearing is connected to the upwind side of the planet carrier of the primary planetary gear structure. The main bearing is a three-row cylindrical roller bearing. The planet carrier of the first-stage planetary gear system is provided with a first step portion on the upwind side thereof, which matches the inner ring of the main bearing; a first threaded hole extending in the axial direction is provided on the end surface of the first step portion; a first through hole extending along the axial direction is provided on the inner ring of the main bearing; a fourth through hole extending along the axial direction is provided on the leeward flange structure of the transition flange; the first threaded hole, the first through hole, and the fourth through hole match each other, so that the transition flange and the inner ring of the main bearing are connected to the planet carrier of the first-stage planetary gear system via high-strength bolts; The main bearing and the gears inside the gear box share oil lubrication. The gear box is provided with a forced lubrication oil circuit, and the forced lubrication oil circuit is communicated with the lubrication oil channel of the main bearing.

2. The main transmission system according to claim 1, characterized in that: The transition flange includes a tapered section that gradually decreases from the upwind side to the downwind side, so that the radial dimension of the downwind side flange structure is smaller than the radial dimension of the upwind side flange structure.

3. The main transmission system according to claim 1, characterized in that: The gearbox further comprises a sealing end plate, wherein the sealing end plate and the outer ring of the main bearing are connected to the box body via high-strength bolts.

4. The main transmission system according to claim 3, characterized in that: The sealing end plate includes a first sealing assembly and a second sealing assembly. The first sealing assembly is engaged with the outer peripheral surface of the transition flange, and the second sealing assembly is engaged with the upwind side of the box body.

5. The main transmission system according to claim 4, characterized in that: The transition flange includes a tapered section that gradually decreases from the upwind side to the leeward side and a straight section whose size remains unchanged in the axial direction, and the first sealing assembly is engaged with the outer circumferential surface of the straight section.

6. The main transmission system according to claim 3, characterized in that: The housing, the planet carrier of the first-stage planetary gear system structure, the transition flange and the sealing end plate together form an independent sealing cavity of the gear box, and the main bearing is located in the independent sealing cavity.

7. The main transmission system according to any one of claims 1 to 6, characterized in that: The box body is provided with a connecting arm connected to the main frame of the wind turbine generator set, and the axial position of the main bearing is adjacent to or at least partially overlaps with the axial position of the connecting arm.

8. A method for assembling a main transmission system according to any one of claims 1 to 7, characterized in that: The method comprises: The main bearing is placed on the first step portion of the planetary carrier from the upwind side of the planetary carrier of the primary planetary gear train structure, so that the downwind end surface of the outer ring of the main bearing abuts against the end surface of the second step portion of the gearbox, and the downwind end surface of the inner ring of the main bearing abuts against the end surface of the first step portion of the planetary carrier, the first through hole of the inner ring of the main bearing is aligned with the first threaded hole of the planetary carrier, the second through hole of the outer ring of the main bearing is aligned with the second threaded hole of the gearbox, and the lubricating oil passage of the main bearing is aligned with the forced lubricating oil passage of the gearbox to maintain communication; Connect the sealing end plate and the outer ring of the main bearing to the casing through high-strength bolts, so that the second sealing assembly of the sealing end plate is tightly engaged with the upwind side of the casing; Insert the transition flange into the annular sealing end plate until the leeward end surface of the transition flange abuts against the upwind end surface of the inner ring of the main bearing, the fourth through hole of the transition flange aligns with the first through hole of the inner ring of the main bearing, and the first sealing assembly of the sealing end plate tightly engages with the outer circumferential surface of the corresponding position of the transition flange; The transition flange and the inner ring of the main bearing are connected to the planet carrier of the first-stage planetary gear structure by high-strength bolts.

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