A machining method for a yaw gearbox output structure of a wind turbine

Abstract

This invention relates to the field of yaw gearboxes, specifically to a machining method for the output structure of a yaw gearbox for a wind turbine generator. The method includes: opening at least two inner raceways on the outer peripheral wall of a planetary carrier blank; radially opening mounting holes on each inner raceway; and performing heat treatment. A ring-shaped body is prepared; a sampling raceway is machined along the outer peripheral wall of the ring-shaped body; a plug for sealing the mounting holes is machined radially along the sampling raceway and then heat-treated. The plugs are installed into the mounting holes of the planetary carrier blank; limiting holes are opened along the axial direction of the planetary carrier; locating pins are inserted into the limiting holes for fixation; the planetary carrier blank with the plugs is then machined to specified dimensions to obtain the finished planetary carrier and plugs; the planetary carrier and the output housing are assembled as a whole; ball bearings are installed into the raceways; the plugs are used to seal the mounting holes and the locating pins are inserted; finally, the gearbox output shaft is pressed into the inner hole of the planetary carrier. By implementing this method, the machining accuracy of the yaw gearbox output structure can be improved.

Description

Technical Field

[0001] This invention relates to the field of yaw gearboxes, and more specifically to a machining method for the output structure of a yaw gearbox for a wind turbine generator. Background Technology

[0002] The yaw gearbox is an important component of a wind turbine generator set. The yaw gearbox is vertically mounted, and from top to bottom, it consists of an input assembly, a planetary assembly (usually four stages), and an output assembly. Existing yaw gearboxes have a large total height of the final stage planetary assembly and the output assembly, and the output positioning structure is not compact and has a large weight. This increases the rotational inertia of the yaw system, thereby increasing energy consumption during equipment start-up and shutdown, affecting the overall efficiency of the wind power generation system. At the same time, under frequent yaw operations, the high energy consumption will directly affect the power generation cost and economic benefits of the wind turbine generator set.

[0003] To address the aforementioned shortcomings, the applicant developed and applied for a yaw gearbox, such as the one published under CN217713572U. This technical solution greatly improved the overall height and weight of the yaw gearbox. During subsequent analysis and research, the applicant discovered that the above structure had even more room for improvement. Therefore, the applicant subsequently developed a lightweight, small-volume yaw gearbox output shaft structure, such as the one applied under 2024225454534, as well as a compact yaw gearbox output structure as applied for in this application, making the structure of the yaw gearbox simpler, smaller, and lighter.

[0004] While the two structures mentioned above offer significant structural advantages, their multi-raceway design presents considerable challenges in manufacturing. Current technologies often employ a modular assembly method for the raceways, which, while facilitating assembly, reduces structural rigidity and stability. In contrast, patent application CN 115614380 A discloses a monolithic assembly method. This method involves first creating axial holes, filling holes, and limiting holes in the inner ring of the bearing. Then, a pin is inserted into the filling hole and machined. After machining, the pin is removed for ball bearing filling. However, this approach is not suitable for this solution. Specifically, because the planetary carrier wall is thin, there is no space to create axial holes. Even if axial holes were created, it would affect the load-bearing capacity of the planetary carrier and thus the service life of the yaw gearbox. On the other hand, since this solution is used in the field of wind power generation, it is necessary to ensure the precise assembly of each component. Otherwise, it will greatly affect the operation between the components, leading to problems such as insensitive operation or accelerated wear of the equipment, resulting in increased maintenance costs in the later stages. The aforementioned document only discloses how to assemble the components, and it is impossible to manufacture a high-precision yaw gearbox output structure according to this assembly method.

[0005] Therefore, a high-precision machining method is needed for the output structure of the yaw gearbox of a wind turbine. Summary of the Invention

[0006] The present invention aims to provide a machining method for the output structure of a yaw gearbox in a wind turbine generator, so as to improve the machining accuracy of the output structure of the yaw gearbox.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a processing method for the output structure of a yaw gearbox of a wind turbine generator, comprising the following steps:

[0008] Planetary carrier blank processing: At least two inner raceways are opened on the outer peripheral wall of the planetary carrier blank, and mounting holes are opened radially on each inner raceway. The mounting holes are connected to the inner hole of the planetary carrier. The mounting holes on adjacent inner raceways are staggered and heat-treated.

[0009] Blocking body processing: Prepare an annular body, process a sampling raceway along the outer peripheral wall of the annular body, the radius of which is not less than the radius of the inner raceway, process the blocking body for blocking the mounting hole radially along the sampling raceway, and perform batch heat treatment on the blocking body.

[0010] Assembly machining: Install the plug into each mounting hole of the planetary carrier blank, so that the sampling raceway of the plug and the inner raceway are on the same pitch circle radius. A limiting hole is opened along the axial direction of the planetary carrier. The limiting hole passes through the plug. The positioning pin is inserted into the limiting hole for fixation. Then, the planetary carrier blank with the plug is machined according to the specified dimensions to obtain the finished planetary carrier and the plug. The finished plug is then removed.

[0011] Output box machining: An outer raceway that matches the inner raceway of the planetary carrier is opened on the inner peripheral wall of the output box blank, and heat treatment is performed. After heat treatment, it is machined into a finished product.

[0012] Assembly: Assemble the planetary carrier and output housing into one piece, so that the inner raceway and the outer raceway form a closed raceway. Insert the balls into the raceway through the respective mounting holes. After installation, seal each mounting hole with a plug and insert a locating pin to fix the plug. Finally, press the gearbox output shaft into the inner hole of the planetary carrier.

[0013] Preferably, as an improvement, in the planetary carrier blank machining step, the inner and outer radii, raceway radius, and mounting holes of the planetary carrier blank are all left with the same machining allowance q. After the mounting hole is heat-treated, the mounting hole is machined into a standard mounting hole according to the specified inner diameter.

[0014] Preferably, as an improvement, in the block body processing step, when processing the block body from the annular body, a processing allowance q needs to be left in the circumferential direction of the block body. After heat treatment, the block body is processed into a standard block body according to the specified diameter.

[0015] Preferably, as an improvement, in the plugging body processing step, the inner radius of the annular body is not less than the inner radius of the planetary carrier blank, and the outer radius of the annular body is not greater than the outer radius of the planetary carrier blank.

[0016] Preferably, as an improvement, in the blockage body processing step, the differences between the inner radius of the annular body and the inner radius of the planetary carrier blank, the differences between the outer radius of the annular body and the outer radius of the planetary carrier blank, and the differences between the sampling raceway radius and the raceway radius are all between 0 and q / 5.

[0017] Preferably, as an improvement, before pressing the gearbox output shaft into the planetary carrier bore, the sealing ring is first installed into the groove of the gasket, then the planetary carrier is inverted, and the gasket is placed into the planetary carrier bore and fits against the spline end face.

[0018] Preferably, as an improvement, the sealing ring is installed on the shoulder of the output gear shaft, the output gear shaft is then pressed into the inverted planetary carrier, and finally a nut is installed to axially lock the output gear shaft and the planetary carrier.

[0019] Preferably, as an improvement, there are two raceways, and the ball in the lower raceway is larger than the ball in the upper raceway.

[0020] Preferably, as an improvement, the ratio of the size of the upper rolling ball to the diameter of the lower rolling ball is 0.7-0.9.

[0021] The principle and advantages of this scheme are:

[0022] 1. High assembly precision: In the early stages of processing this yaw gearbox, the applicant installed the plug and locating pin into the planetary carrier mounting holes and limit holes respectively for uniform heat treatment. This method has high processing efficiency, but occasionally some gearboxes will have low precision. After disassembling and analyzing the faulty gearboxes, it was found that the problems mainly occurred in two places. First, there was a height difference between the raceway of the plug and the raceway of the planetary carrier, which caused the ball to jam when running. Second, there was slight deformation of varying degrees at the locating pin and the limit hole (including the limit hole of the plug and the planetary carrier), which caused the locating pin to not be positioned in the designated position of the limit hole, resulting in the plug being loose.

[0023] To address the aforementioned issues, this solution incorporates allowances in both the planetary carrier and the toroidal body. First, the planetary carrier is machined with internal raceways and allowance-filled mounting holes, followed by heat treatment. After heat treatment, the allowance-filled mounting holes are machined to a standard diameter. Then, a toroidal body matching the inner and outer diameters of the lower end of the planetary carrier is selected, and a sampling raceway is machined along this raceway. A plug with allowances is then extracted and batch-processed. This ensures uniform surface heating and controllable deformation of all components during heat treatment. Furthermore, the shape and size of the plug, machined in this way, match the height of the mounting holes, eliminating the need for additional processing. The two components are then assembled, and locating holes are drilled simultaneously. These locating holes, drilled when the plug and planetary carrier are in their optimal mating positions, ensure accurate overlap and facilitate rapid and precise positioning during subsequent assembly. A locating pin secures the plug within the mounting hole. Finally, during finishing, the mating planetary carrier and plug are simultaneously ground away to remove excess material. This method ensures the precision of each component, and then the high-precision components are assembled to achieve high overall assembly precision of the yaw gearbox.

[0024] 2. Stable machining: Due to the close proximity of the two adjacent raceways (only 3-6mm), radial drilling in the same vertical position would easily damage the retaining arm between them during machining, leading to the scrapping of the entire planetary carrier. Therefore, this solution avoids interference during drilling of adjacent mounting holes, preventing scrap. Furthermore, the staggered arrangement of the two mounting holes ensures even stress distribution on the planetary carrier and the entire gearbox during operation.

[0025] 3. In the processing of the plugs, an annular body with an inner radius greater than or equal to the inner radius of the planetary carrier blank and an outer radius less than or equal to the outer radius of the planetary carrier blank is selected. A sampling raceway is first machined on the outer peripheral wall of the annular body. Finally, multiple plugs are machined radially along the sampling raceway. The plugs are then subjected to batch heat treatment. The plugs processed in this way have two advantages. First, their two end faces are machined in one go and are highly matched with the raceway surface and inner hole surface of the planetary carrier, respectively. This is beneficial for the accurate and rapid installation of the plugs into the mounting holes during subsequent assembly and drilling. At the same time, it is possible to quickly observe or judge whether the two end faces of the plugs are inside the mounting holes by sight or by hand, so as to quickly determine whether the plugs are installed accurately and make timely adjustments, thereby effectively ensuring the high precision of each component after assembly and drilling. Second, this method allows for the batch production of plugs, effectively improving production efficiency.

[0026] 4. In this solution, the machining of the limiting hole is performed after the plug, inner raceway, and mounting hole have all been machined. That is, the limiting hole is machined after the plug is fitted into the mounting hole. The effect of this design is that when the plug is precisely fitted into the mounting hole, the planetary carrier and the plug are drilled simultaneously. In the subsequent actual assembly, it is only necessary to insert the plug with the limiting hole into the mounting hole, and to roughly align the limiting hole of the plug with the limiting hole of the planetary carrier. Then, when the locating pin is inserted, the installation position of the plug can be automatically and quickly adjusted so that the two end faces of the plug are matched with the inner wall of the planetary carrier and the curved surface of the raceway. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the output structure of a compact yaw gearbox according to the present invention.

[0028] Figure 2 A partial schematic diagram of the machining of the planetary carrier blank.

[0029] Figure 3 This is a schematic diagram of the upper plug body processing.

[0030] Figure 4 This is a schematic diagram of the machining process for the lower plug body.

[0031] Figure 5 This is a schematic diagram of the assembly and processing.

[0032] Figure 6 This is a magnified view of the inner raceway of the planetary carrier and the sampling raceway of the upper blockage.

[0033] Figure 7 This is a magnified view of a portion of the sampling raceway between the planetary carrier and the lower plug. Detailed Implementation

[0034] The following detailed description illustrates the specific implementation method:

[0035] The reference numerals in the accompanying drawings include: planetary carrier 1, output gear shaft 2, output housing 3, inner hole 4, axial limiting groove 5, fixing unit 6, limiting nut 7, upper ball bearing 8, lower ball bearing 9, upper oil seal 10, lower oil seal 11, gasket 12, O-ring 13, upper plug 14, lower plug 15, limiting hole 16, locating pin 17, mounting hole 18, sampling raceway 19.

[0036] A compact yaw gearbox output structure, as shown in the attached figure. Figure 1The diagram shows a planetary carrier 1, an output housing 3, and an output gear shaft 2. The planetary carrier 1 and the output housing 3 each integrate inner and outer raceways, forming two raceways. The balls in the lower raceway are larger than those in the upper raceway, with a diameter ratio of 0.7-0.9 between the upper and lower balls. Within this ratio range, the upper and lower balls experience more uniform force and better load-bearing capacity. The output gear shaft 2 is housed within the planetary carrier 1, and a limiting unit and a fixing unit 6 are provided between them from top to bottom to fix the output gear shaft 2 axially and radially, respectively. The fixing unit 6 is a spline structure, including splines on the planetary carrier 1. The limiting unit includes an axial limiting groove 5 formed at the top of the planetary carrier and the output gear shaft 2, with a limiting nut 7 threaded into the groove.

[0037] A method for fabricating the output structure of a yaw gearbox for a wind turbine is as follows: This embodiment takes the fabrication of two raceways, with the lower raceway radius being larger than the upper raceway radius, as an example, and includes the following steps:

[0038] Planetary carrier 1 blank machining: such as Figure 2 As shown, a ring-shaped planetary carrier 1 blank is prepared. The inner radius of the lower end of the planetary carrier 1 blank is d, and the outer radius is D. Two inner raceways are opened on the outer peripheral wall of the planetary carrier 1 blank. The radius of the upper inner raceway is r, and the radius of the lower inner raceway is R. A mounting hole 18 is opened radially on each inner raceway. Each mounting hole 18 is connected to the inner hole 4 of the planetary carrier 1. The upper and lower mounting holes 18 are staggered. As a preferred embodiment, the two mounting holes 18 are symmetrically arranged along the axis of the planetary carrier 1. The inner and outer radii of the planetary carrier 1, the radii of the two inner raceways, and the mounting holes all have the same allowance q, which is 0.3mm-0.7mm. In this embodiment, it can be 0.5mm. By setting this allowance, after the planetary carrier 1 has been heat-treated and is precisely matched with the heat-treated plug, the two are then simultaneously precision-machined to remove the allowance, thereby ensuring that the plug and the planetary carrier 1 are precisely integrated and the outer contour remains on the same curved surface. Then, the planetary carrier 1 blank with inner raceway and mounting hole 18 is heat treated. After the heat treatment is completed, the mounting hole is machined into a standard mounting hole according to the specified inner diameter.

[0039] Block body processing:

[0040] 1. Processing of the upper plug body 14: such as Figure 3As shown, a ring-shaped body is prepared. The difference between the inner and outer radii of this ring-shaped body and the inner and outer radii of the planetary carrier 1 is ±q / 5, specifically ±0.1mm. This ensures that the wall thickness of the ring-shaped body is basically consistent with that of the planetary carrier 1, and the removed plug body is basically consistent with the mounting hole 18, facilitating subsequent processing. In this embodiment, to achieve better results, the inner radius of the ring-shaped body is selected as d1, and the outer radius is D1. The inner radius d1 of the ring-shaped body is greater than or equal to the inner radius d of the planetary carrier 1 blank, and the greater amount does not exceed 0.1mm. The outer radius D1 of the ring-shaped body is less than or equal to the outer radius D of the planetary carrier 1 blank, and the less than 0.1mm. In this way, during subsequent assembly and finishing, on the one hand, it is possible to quickly and intuitively determine whether the two ends of the plug body protrude beyond the two end faces of the planetary carrier 1 through visual observation and touch, while controlling the error to q / 5, i.e., 0.1mm. As long as the two end faces of the plug body do not protrude beyond the two end faces of the planetary carrier 1, the high-precision fit after the two are combined and processed can be ensured. On the other hand, the cutting tool is smoother during processing and less prone to vibration, resulting in higher surface finishing accuracy. A sampling raceway 19 is machined along the circumferential wall of the annular body. The radius of the sampling raceway 19 is r1, where r1 is greater than or equal to the radius r of the upper inner raceway, but the difference is not more than 0.1 mm, in order to avoid tool vibration when machining this area. Several upper plugs 14 are machined radially along the sampling raceway 19 for transition fitting into the mounting holes 18 of the upper inner raceway. The upper plugs 14 have a radial allowance q, which is 0.3 mm to 0.7 mm. In this embodiment, it can be 0.5 mm. Then, the several upper plugs 14 are subjected to batch heat treatment. After heat treatment, they are machined into standard plugs according to the specified diameter of the upper plugs.

[0041] 2. Processing of the lower plug body 15: (e.g.) Figure 4 As shown, an annular body is prepared. The difference between the inner and outer radii of the annular body and the inner and outer radii of the planetary carrier 1 is ±q / 5, specifically ±0.1mm. In this embodiment, the inner radius of the annular body is d2, and the outer radius is D2. The inner radius d2 of the annular body is ≥ the inner radius d of the planetary carrier 1 blank, and the greater amount does not exceed 0.1mm. The outer radius D2 of the annular body is ≤ the outer radius D of the planetary carrier 1 blank, and the lesser amount does not exceed 0.1mm. A sampling raceway 19 is machined along the circumferential wall of the annular body. The radius of the sampling raceway 19 is r2, and r2 is ≥ the radius R of the lower inner raceway, and the greater amount does not exceed 0.1mm. Several lower plugs 15 are machined radially along the sampling raceway 19 for transition fitting in the mounting holes 18 of the lower inner raceway. The lower plugs 15 have a radial allowance q, which is 0.3mm-0.7mm, specifically 0.5mm. Then, the several lower plugs 15 are subjected to batch heat treatment. After heat treatment, they are machined into standard plugs according to the specified diameter of the lower plugs.

[0042] Combined processing: such as Figure 5As shown, the heat-treated upper and lower plugs 15 are installed into the mounting holes 18 of the upper and lower inner raceways, respectively. After installation, it is first determined whether the sampling raceway of the plug and the inner raceway are on the same pitch circle radius, that is, whether the two end faces of the plug are flush with the inner and outer surfaces of the planetary carrier blank. Since the two end faces of the plug are initially formed in the previous step, the accuracy of the installation angle of the plug is particularly important in this step. If the plug is rotated 10° from the normal angle during installation, it will cause the sampling raceway and the inner raceway on the planetary carrier to be misaligned. At the same time, the plug and the inner wall of the planetary carrier will also be uneven. When assembling the output gear shaft, the plug will be squeezed to move along the outer raceway, which will cause the sampling raceway to protrude from the inner raceway, causing the ball located or moved to that location to get stuck or rotate unevenly. Therefore, before drilling the limiting hole, this solution requires determining the installation angle of the plug. The method is to slide your hand along the end face of the plug around its length to feel if the plug protrudes beyond the planetary carrier's end face. If the protrusion is significant, the installation angle needs adjustment; if it's minor, no additional processing is needed, and it can be resolved directly in the finishing (removing excess material) step below. Current practice shows that the installation angle deviation of the plug is not significant and can generally be resolved through the finishing step. This is another important purpose of setting allowances during the machining of each component in this solution. Then, a limiting hole 16 is drilled along the axial direction of the planetary carrier 1. This limiting hole 16 is tapered and penetrates the plug. A positioning pin 17 is inserted into the limiting hole 16 to fix the plug. The positioning pin 17 is a tapered pin. Finally, the outline of the planetary carrier 1 blank with the plug is finished to the specified dimensions, such as... Figures 5-7 As shown, the planetary carrier 1 blank is machined along the dotted outline. After machining, the finished planetary carrier 1 and the finished plug are obtained, and the plug is removed.

[0043] Output box 3 machining: Two outer raceways that match the inner raceway of planetary carrier 1 are opened on the inner peripheral wall of the output box 3 blank. The outer raceways have a machining allowance q. After heat treatment of the output box 3 blank, the outer raceways are precision machined to the specified dimensions to obtain the finished output box 3.

[0044] Assembly: First, install the upper oil seal 10 on the output housing, then invert the output housing 3 and install the lower oil seal 11 onto the output housing 3. Lift the planetary carrier and insert it into the output housing 3, ensuring the inner and outer raceways correspond to form the upper and lower raceways. Keeping the planetary carrier stationary, insert the upper ball 8 and lower ball 9 into the mounting holes 18 of the upper and lower raceways, respectively. After installation, fit the plug into each mounting hole 18, ensuring the plug roughly aligns with the limiting hole 16 on the planetary carrier 1. Release the lifting device at this point (this can also be done after installing the upper or lower ball). Then, drive the locating pin into the limiting hole to secure the plug. Insert the O-ring 13 into the groove of the gasket 12, then place the gasket 12 containing the O-ring 13 into the inner hole 4 of the planetary carrier 1, ensuring it fits against the spline end face.

[0045] Install another O-ring 13 onto the shoulder of the output gear shaft 2, then press the output gear shaft 2 into the inverted planetary carrier 1 along the spline of the planetary carrier, and finally install the limit nut 7 into the axial limit groove 5 between the output gear shaft 2 and the planetary carrier 1, and tighten the limit nut 7 on the output gear shaft 2 for axial locking.

[0046] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method of machining a yaw gearbox output structure for a wind turbine generator, characterized by: Includes the following steps: Planetary carrier blank processing: At least two inner raceways are opened on the outer peripheral wall of the planetary carrier blank, and mounting holes are opened radially on each inner raceway. The mounting holes are connected to the inner hole of the planetary carrier blank. The mounting holes on adjacent inner raceways are staggered and heat-treated. Blocking body processing: Prepare an annular body, process a sampling raceway along the outer peripheral wall of the annular body, the radius of which is not less than the radius of the inner raceway, process the blocking body for blocking the mounting hole radially along the sampling raceway, and perform batch heat treatment on the blocking body. Assembly machining: Install the plug into each mounting hole of the planetary carrier blank, so that the sampling raceway of the plug and the inner raceway are on the same pitch circle radius. Make a limiting hole along the axial direction of the planetary carrier blank. The limiting hole passes through the plug. Insert the positioning pin into the limiting hole for fixation. Then process the planetary carrier blank with the plug according to the specified dimensions to obtain the finished planetary carrier and the plug. Remove the finished plug. Output box machining: An outer raceway that matches the inner raceway of the planetary carrier is opened on the inner peripheral wall of the output box blank, and heat treatment is performed. After heat treatment, it is machined into a finished product. Assembly: Assemble the planetary carrier and output housing into one piece, so that the inner raceway and the outer raceway form a closed raceway. Insert the balls into the raceway through the respective mounting holes. After installation, seal each mounting hole with a plug and insert a locating pin to fix the plug. Finally, press the gearbox output shaft into the inner hole of the planetary carrier.

2. A machining method for a yaw gearbox output structure of a wind turbine generator according to claim 1, characterized in that: In the planetary carrier blank machining process, the inner and outer radii, raceway radii, and mounting holes of the planetary carrier blank all have the same machining allowance q. After the mounting holes are heat-treated, they are machined into standard mounting holes according to the specified inner diameter.

3. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 2, characterized in that: In the block body processing steps, when processing the block body from the annular body, a processing allowance q needs to be left in the circumferential direction of the block body. After heat treatment, the block body is processed into a standard block body according to the specified diameter.

4. The processing method for the output structure of a yaw gearbox for a wind turbine generator according to claim 3, characterized in that: During the plugging process, the inner radius of the annular body is not less than the inner radius of the planetary carrier blank, and the outer radius of the annular body is not greater than the outer radius of the planetary carrier blank.

5. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 4, characterized in that: In the blockage body processing steps, the differences between the inner radius of the annular body and the inner radius of the planetary carrier blank, the differences between the outer radius of the annular body and the outer radius of the planetary carrier blank, and the differences between the sampling raceway radius and the raceway radius are all between 0 and q / 5.

6. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 5, characterized in that: Before pressing the gearbox output shaft into the planetary carrier bore, first install the sealing ring into the groove of the gasket, then invert the planetary carrier, place the gasket into the planetary carrier bore and make it fit against the spline end face.

7. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 6, characterized in that: Install the sealing ring onto the shoulder of the output gear shaft, then press the output gear shaft into the inverted planetary carrier, and finally install the limit nut to axially lock the output gear shaft and the planetary carrier.

8. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 7, characterized in that: There are two raceways, and the ball size in the lower raceway is larger than that in the upper raceway.

9. A method of machining an output structure for a yaw gearbox of a wind turbine generator according to claim 8, characterized in that: The diameter ratio of the upper rolling ball to the lower rolling ball is 0.7-0.9.

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