High-torque tightening tool and method for helicopter inner rotor shaft nut

Abstract

The invention belongs to the technical field of aviation assembly, and discloses a high-torque tightening tool and method for a nut of an inner rotor shaft of a helicopter, and the tool comprises a quick-change disc assembly, a high-torque tightening assembly and an inner rotor shaft flexible assembly. The quick-change disc assembly is used for being connected with an external executing mechanism and achieving quick change. The high-torque tightening assembly achieves accurate tightening of a nut through a servo motor, a hollow speed reducer and a dynamic torque sensor. The inner rotor shaft flexible assembly penetrates through the hollow speed reducer and is used for being connected with an inner rotor shaft spline to provide counter torque. The core lies in that the tightening torque and the counter torque are transmitted together and fixed in the same hollow speed reducer mounting base to offset each other, so that torque internal circulation is formed, and the requirement for a supporting structure is greatly lowered. Through the coaxial integrated design, synchronous alignment of rotation stopping of the inner rotor shaft and nut tightening is achieved, the centering operation is simplified, the assembling efficiency and precision are improved, and the flexible buffering and modular quick-changing capacity is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aviation assembly, and particularly relates to a large torque tightening tool and method for a helicopter inner rotor shaft nut. BACKGROUND

[0002] After installing a bearing of a helicopter main speed reducer inner rotor shaft, a nut needs to be installed to ensure that the bearing will not fall out. According to the installation process requirements, when tightening the nut, a certain torque needs to be controlled. A conventional scheme usually designs a clamping tool for the inner rotor shaft at the lower part and a nut tightening tool at the upper part. This scheme has the following disadvantages: the upper and lower tools need very high concentricity, and adjustment is difficult; when tightening the nut with a large torque, a huge reaction force needs to be borne by an external support structure, which leads to very high requirements for the strength and rigidity of the support structure, increases the complexity and cost of the tool, and reduces the assembly efficiency. SUMMARY

[0003] The present application aims to provide a large torque tightening tool and method for a helicopter inner rotor shaft nut to solve the above technical problems.

[0004] To solve the above technical problems, the specific technical scheme of the large torque tightening tool and method for the helicopter inner rotor shaft nut of the present application is as follows: A large torque tightening tool for a helicopter inner rotor shaft nut comprises a quick-change disc assembly, a large torque tightening assembly and an inner rotor shaft flexible assembly. The quick-change disc assembly is used to suspend and connect the entire tool to an external device. The quick-change disc assembly and the large torque tightening assembly are connected through a zero-position locator. The large torque tightening assembly and the inner rotor shaft flexible assembly are fixed on a hollow speed reducer mounting seat of the large torque tightening assembly and share the same axis. The tightening torque of the large torque tightening assembly and the counter torque of the inner rotor shaft flexible assembly are transmitted to the hollow speed reducer mounting seat and offset each other.

[0005] Further, the quick-change disc assembly comprises a tool docking quick-change disc, a quick-change welding frame one, a zero-position locator female head and a tightening assembly quick-change disc. The tool docking quick-change disc is fixedly installed above the quick-change welding frame one. The zero-position locator female head and the tightening assembly quick-change disc are fixed on one side of the quick-change welding frame one. The tool docking quick-change disc is used to be connected with an external actuating mechanism. The zero-position locator female head is connected with the zero-position locator male head of the large torque tightening assembly. The tightening assembly quick-change disc realizes the connection and quick-change function with the large torque tightening assembly. The tool docking quick-change disc and the tightening assembly quick-change disc are integrated with an electrical interface and an air interface.

[0006] Further, the large torque tightening assembly comprises a quick-change welding frame two, a tightening assembly quick-change disc, a zero point locator male head, a hollow speed reducer, an inner rotor shaft nut tool, a hollow speed reducer mounting seat, a large torque dynamic torque sensor and a servo motor, the hollow speed reducer is installed on the hollow speed reducer mounting seat, the output end of the hollow speed reducer is installed with the inner rotor shaft nut tool, the output of the servo motor is connected with the input end of the hollow speed reducer through the large torque dynamic torque sensor, the quick-change welding frame two is fixedly installed above the hollow speed reducer mounting seat, the tightening assembly quick-change disc and the zero point locator male head are fixedly installed on one side of the quick-change welding frame two, the zero point locator male head is connected with the zero point locator female head of the quick-change disc assembly, so that the accurate positioning of the large torque tightening assembly and the quick-change disc assembly is realized, the tightening assembly quick-change disc female head is connected with the tightening assembly quick-change disc male head of the quick-change disc assembly, so that the connection and quick change of the large torque tightening assembly 2 and the quick-change disc assembly 1 are realized, and the inner rotor shaft nut tool is fixedly installed below the hollow speed reducer mounting seat.

[0007] Further, the inner rotor shaft flexible assembly is installed on the hollow speed reducer mounting seat together with the hollow speed reducer through the hollow part of the hollow speed reducer.

[0008] Further, the inner rotor shaft flexible assembly comprises an assembly fixing shaft and an inner rotor shaft rotation-stopping tool, the upper end of the fixing shaft is fixedly installed on the hollow speed reducer mounting seat and coaxial with the hollow speed reducer, and the lower end of the fixing shaft is fixedly connected with the inner rotor shaft rotation-stopping tool, and the lower end of the inner rotor shaft rotation-stopping tool is provided with a involute spline.

[0009] Further, the inner rotor shaft flexible assembly further comprises an axle end cover, an assembly upper plate, a connecting shaft, a guide sleeve and a spring, the assembly upper plate is coaxially sleeved on the fixing shaft, the assembly upper plate and the inner rotor shaft rotation-stopping tool are connected through a plurality of connecting shafts, the upper end of the connecting shaft is limited by the axle end cover, a plurality of springs are sleeved on the plurality of connecting shafts, the upper end of the spring is provided with a guide sleeve, and the guide sleeve is sleeved on the connecting shaft and fixedly connected with the assembly upper plate.

[0010] Further, the inner rotor shaft flexible assembly penetrates through the hollow speed reducer, so that the inner rotor shaft rotation-stopping tool and the inner rotor shaft nut tool can be synchronously aligned.

[0011] The application also discloses a tightening method of a helicopter inner rotor shaft nut. The tool is installed to an external executing mechanism through a quick-change disc assembly. The inner rotor shaft rotation-stopping tool of the inner rotor shaft flexible assembly is connected with the spline of the inner rotor shaft. Adjust the tooling angle, so that the inner rotor shaft nut tooling of the large torque tightening assembly is connected with the bayonet of the nut; Start the servo motor, and tighten the nut through closed-loop torque control; During the tightening process, the spring of the inner rotor shaft flexible assembly absorbs the axial displacement, and the tightening torque and the counter torque are mutually offset in the hollow speed reducer mounting seat.

[0012] The large torque tightening tooling and method for the inner rotor shaft nut of a helicopter have the following advantages: 1. The torque is internally circulated and self-balanced, greatly reducing the dependence on external support: the large torque tightening assembly and the inner rotor shaft flexible assembly are creatively integrated in the same hollow speed reducer mounting seat. During the tightening process, the tightening torque is transmitted to the mounting seat through the hollow speed reducer, and the counter torque is also transmitted to the same mounting seat through the inner rotor shaft flexible assembly. The two torques form a couple inside the mounting seat and are mutually offset, fundamentally solving the problem that the huge counterforce needs to be borne by the external support structure in the traditional scheme. This greatly reduces the strength and rigidity requirements of the external execution mechanism such as robots and trusses, simplifies the overall tooling system, and significantly reduces the manufacturing cost.

[0013] 2. The concentricity accuracy and assembly efficiency are significantly improved: by designing the inner rotor shaft flexible assembly to penetrate the hollow speed reducer, the inner rotor shaft stop tooling and the inner rotor shaft nut tooling are inherently highly concentric. In actual operation, only the central inner rotor shaft stop tooling needs to be aligned with the spline of the inner rotor shaft, and the outer nut tooling will automatically synchronize and align with the nut, achieving "one-time alignment and double positioning", completely avoiding the complex process of repeatedly adjusting the concentricity of the traditional upper and lower toolings, simplifying the operation steps, and improving the assembly efficiency by more than 50%.

[0014] 3. High-precision torque control capability, ensuring assembly quality: a servo motor is used in combination with a large torque dynamic torque sensor to form a high-precision torque closed-loop control system. This system can monitor and control the tightening torque in real time and accurately, ensuring that each tightening strictly meets the process specification requirements, effectively avoiding the quality risks of overtightening or undertightening, and ensuring the reliability and safety of the connection of the key components of the helicopter main reducer from the process equipment level.

[0015] 4. Built-in flexible buffer mechanism, adapting to dynamic assembly process: A flexible buffer structure composed of a spring and a guide sleeve is designed in the inner rotor shaft flexible assembly. The structure can effectively absorb the axial displacement generated during the nut tightening process, thereby ensuring that the spline connection between the inner rotor shaft nut tooling and the nut, and the spline connection between the inner rotor shaft rotation stopping tooling and the inner rotor shaft, always maintains good contact and stress state, preventing jamming, wear or accidental disengagement caused by rigid contact, and improving the stability and reliability of the tooling working process.

[0016] 5. Modular and quick-change design, greatly improving production line flexibility: The entire tooling is combined with the zero position locator through the quick-change disc assembly, realizing quick positioning, connection and replacement with external actuators. The integrated electrical and pneumatic interfaces of the quick-change disc realize instant power and signal connection. This modular design allows a production line to quickly deploy different toolings to adapt to different bearing nut tightening tasks of different models or torque requirements, greatly improving the flexibility and equipment utilization of the production line, meeting the modern aviation production characteristics of multiple varieties and small batches.

[0017] 6. Simplified rotor shaft fixing method, more convenient operation: By using a small modulus and large number of involute splines as the connection method of the inner rotor shaft rotation stopping tooling, the operator only needs to insert the spline and rotate a small angle to complete the cooperation, which can withstand a large reverse torque. This method eliminates the complex and bulky external clamping tooling in traditional schemes, making the operation more convenient and efficient, further improving the assembly efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The overall structure diagram of the tooling described in the present application; Figure 2 The structure diagram of the quick-change disc assembly of the present application; Figure 3 The structure diagram of the large torque tightening assembly of the present application; Figure 4 The structure diagram of the inner rotor shaft flexible assembly of the present application; Figure 5 The structure diagram of the tooling cross-section of the present application; The markings in the diagram are as follows: 1. Quick-change disc assembly; 2. High-torque tightening assembly; 3. Inner rotor shaft flexible assembly; 4. Tooling docking quick-change disc; 5. Quick-change welding bracket one; 6. Zero-point positioner female head; 7. Tightening assembly quick-change disc; 8. Quick-change welding bracket two; 9. Tightening assembly quick-change disc; 10. Zero-point positioner male head; 11. Hollow reducer; 12. Inner rotor shaft nut tooling; 13. Hollow reducer mounting base; 14. High-torque dynamic torque sensor; 15. Servo motor; 16. Assembly fixing shaft; 17. Shaft end cover; 18. Assembly upper plate; 19. Connecting shaft; 20. Guide sleeve; 21. Spring; 22. Inner rotor shaft anti-rotation tooling. Detailed Implementation

[0019] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, provides a high-torque tightening fixture and method for a helicopter internal rotor shaft nut.

[0020] like Figure 1 As shown, a high-torque tightening fixture for a helicopter internal rotor shaft nut according to the present invention includes a quick-change disc assembly 1, a high-torque tightening assembly 2, and an internal rotor shaft flexible assembly 3. The quick-change disc assembly 1 is used to suspend and connect the entire fixture to external equipment. The quick-change disc assembly 1 and the high-torque tightening assembly 2 are connected by a zero-point positioner. The high-torque tightening assembly 2 and the internal rotor shaft flexible assembly 3 are both fixed on the hollow reducer mounting base 13 of the high-torque tightening assembly 2 and share the same axis.

[0021] like Figure 2 As shown, the quick-change tray assembly 1 includes a tooling docking quick-change tray 4, a quick-change welding frame 5, a zero-point locator female head 6, and a tightening component quick-change tray male head 7. The tooling docking quick-change tray 4 is fixedly mounted above the quick-change welding frame 5, while the zero-point locator female head 6 and the tightening component quick-change tray male head 7 are fixed to one side of the quick-change welding frame 5. The tooling docking quick-change tray 4 is used to connect with external robots or gantry actuators, fulfilling the connection and quick-change function of high-torque tightening tooling. The zero-point locator female head 6 mates with the zero-point locator male head 10 of the high-torque tightening component 2, achieving precise positioning of the quick-change tray assembly 1 and the high-torque tightening component 2. The tightening component quick-change tray male head 7 enables connection and quick-change with the high-torque tightening component 2. The tooling quick-change disc 4 and the tightening assembly quick-change disc male connector 7 integrate electrical and pneumatic interfaces. The electrical interface provides power and communication for the components in the high-torque tightening assembly 2; the pneumatic interface supplies air to the zero-point positioner and meets the air supply needs of subsequent product expansion. The quick-change disc assembly 1 enables rapid and precise positioning and connection of the entire tooling with external actuators (via the zero-point positioner), and provides power, communication, and pneumatic power (through the quick-change disc), thereby enabling rapid tooling replacement and deployment on the production line, improving assembly flexibility and efficiency. The quick-change function of the quick-change disc can achieve the tightening process of bearing nuts with different requirements.

[0022] As Figure 3 shown, the high torque tightening assembly 2 includes a quick-change welding frame two 8, a tightening assembly quick-change disc female head 9, a zero position locator male head 10, a hollow speed reducer 11, an inner rotor shaft nut tool 12, a hollow speed reducer mounting seat 13, a high torque dynamic torque sensor 14 and a servo motor 15. The hollow speed reducer 11 is installed on the hollow speed reducer mounting seat 13, the output end of the hollow speed reducer 11 is installed with the inner rotor shaft nut tool 12, the inner rotor shaft nut tool 12 is connected with the nut through the spline, and the nut is tightened through the rotation of the hollow speed reducer 11. The output of the servo motor 15 is connected with the input end of the hollow speed reducer 11 through the high torque dynamic torque sensor 14, the quick-change welding frame two 8 is fixedly installed above the hollow speed reducer mounting seat 13, the tightening assembly quick-change disc female head 9 and the zero position locator male head 10 are fixedly installed on one side of the quick-change welding frame two 8, the zero position locator male head 10 is connected with the zero position locator female head 6 of the quick-change disc assembly 1, and the precise positioning of the high torque tightening assembly 2 and the quick-change disc assembly 1 is realized. The tightening assembly quick-change disc female head 9 is connected with the tightening assembly quick-change disc male head 7 of the quick-change disc assembly 1, and the connection and quick change of the high torque tightening assembly 2 and the quick-change disc assembly 1 are realized. The inner rotor shaft nut tool 12 is fixedly installed below the hollow speed reducer mounting seat 13. The whole high torque tightening assembly 2 takes the hollow speed reducer mounting seat 13 as the structural basis, the servo motor 15 provides the tightening power, the hollow speed reducer 11 increases the output torque, the high torque dynamic torque sensor 14 detects the tightening torque in real time and feeds back the signal to the control system, and the servo motor 15 constitutes a high-precision torque closed-loop control to ensure the accuracy of the tightening torque.

[0023] As Figure 4As shown, the inner rotor shaft flexible assembly 3 is installed on the hollow speed reducer mounting seat 13 together with the hollow speed reducer 11 through the hollow part of the hollow speed reducer 11, the inner rotor shaft flexible assembly 3 penetrates the hollow speed reducer 11 of the large torque tightening assembly 2, so that the inner rotor shaft rotation stopping tool 22 and the inner rotor shaft nut tool 12 can be synchronously aligned, which can ensure that the inner rotor shaft flexible assembly 3 and the large torque tightening assembly 2 have high concentricity, so that when the actual operation is tightened, the center inner rotor shaft rotation stopping tool 22 is aligned, and the outer side inner rotor shaft nut tool 12 is aligned together, which simplifies the operation steps. Specifically, the inner rotor shaft flexible assembly 3 includes an assembly fixed shaft 16, a shaft end cover 17, an assembly upper plate 18, a connecting shaft 19, a guide sleeve 20, a spring 21 and an inner rotor shaft rotation stopping tool 22. The upper end of the fixed shaft 16 is fixedly installed on the hollow speed reducer mounting seat 13 and is coaxial with the hollow speed reducer 11, and the lower end of the fixed shaft 16 is fixedly connected with the inner rotor shaft rotation stopping tool 22. The lower end of the inner rotor shaft rotation stopping tool 22 has an involute spline, and the inner rotor shaft rotation stopping tool 22 is connected with the inner rotor shaft through the spline. When connected, the inner rotor shaft needs to rotate slightly to adapt to the inner rotor shaft rotation stopping tool 22, and after being installed together, the spline can bear large torque without the need for additional clamping support equipment. In order to adapt to the displacement in the vertical direction when the nut is tightened, the inner rotor shaft flexible assembly 3 is designed to have a flexible part. Specifically, the assembly upper plate 18 is coaxially sleeved on the fixed shaft 16 and above the inner rotor shaft rotation stopping tool 22, the assembly upper plate 18 is connected with the inner rotor shaft rotation stopping tool 22 through four connecting shafts 19, the upper end of the connecting shaft 19 is limited by the shaft end cover 17, and the lower end has a precision hole fixed with the inner rotor shaft rotation stopping tool 22, four springs 21 are sleeved on the four connecting shafts 19, the upper end of the spring 21 is provided with a guide sleeve 20, the guide sleeve 20 is sleeved on the connecting shaft 19 and is fixedly connected with the assembly upper plate 18, and the guide sleeve 20 provides a circumferential guide function for the connecting shaft 19. During rotation, the height of the nut will change as the nut is tightened, at which time the spring 21 in the inner rotor shaft flexible assembly 3 can absorb this displacement, so as to ensure that the spline of the inner rotor shaft nut tool 12 and the bayonet of the nut always have good contact. At the same time, the elasticity of the spring 21 can ensure that the spline of the inner rotor shaft rotation stopping tool 22 and the inner rotor shaft always have good connection and will not be accidentally detached.

[0024] The torque for tightening the nut is transmitted to the mounting seat 13 through the hollow speed reducer 11, and the counter torque is also transmitted to the same mounting seat 13 through the inner rotor shaft flexible assembly 3. The two torques form a force couple inside the mounting seat and cancel each other out, which greatly reduces the requirements for the strength and rigidity of the external support structure.

[0025] The present application is used as a tool in a production line, which needs to use other actuators (such as a truss, a robot, etc.), and the tool is installed on the actuator through the quick-change disc assembly 1, the zero-point locator female head 6 and the zero-point locator male head 10 are used to realize the zero-point positioning and quick-change connection of the large-torque tightening assembly 2, and the tool-to-tool quick-change disc 4 and the tightening assembly quick-change disc male head 7 provide the power supply, gas supply and communication functions.

[0026] As shown in Figure 5 After the whole tool is installed in place, the locking nut is manually sleeved and rotated for several turns to preliminarily connect the locking nut with the inner rotor shaft, and then the inner rotor shaft flexible assembly 3 is manually placed on the inner rotor shaft to be matched with the spline position. Since the inner rotor shaft rotation-stopping tool 22 has a gradually opened spline with a small modulus and a large number of teeth, only a relatively small angle needs to be rotated during the butt joint to make the spline shaft matched with the spline sleeve. After the completion of the matching of the rotor shaft and the tool, the angle between the tool and the nut is further adjusted, so that the inner rotor shaft nut tool 12 can be exactly clamped into the locking nut gap.

[0027] After the installation is completed, the servo motor 15 can be started, the servo motor 15 outputs power to the inner rotor shaft nut tool 12 through the large-torque dynamic torque sensor 14, and finally realizes the tightening of the nut. During the process, the servo motor 15 outputs torque, which is further fed back by the large-torque dynamic torque sensor 14 to realize closed-loop control, thereby achieving high precision.

[0028] During the rotation, the height of the nut will change to a certain extent, at which time the spring 21 in the inner rotor shaft flexible assembly 3 can absorb this part of displacement, thereby ensuring that the spline of the shaft and the gap of the nut are always in good contact. Further, the clamping torque is transmitted to the hollow speed reducer mounting seat 13 through the hollow speed reducer 11, and the counter torque on the rotor shaft spline is transmitted to the hollow speed reducer mounting seat 13 through the fixed shaft 16 and the connecting shaft 19. Such a design can make the tightening torque and the counter torque cancel each other out in the mounting seat, without affecting the external structure.

[0029] It can be understood that the present application is described through some embodiments, and those skilled in the art know that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, these features and embodiments can be modified to adapt to specific conditions and materials under the guidance of the present application without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope of protection of the present application.

Claims

1. A high torque tightening tool for a main rotor shaft nut in a helicopter, characterized in that, Including quick change disc assembly (1), large torque tightening assembly (2) and inner rotor shaft flexible assembly (3), the quick change disc assembly (1) is used to hang and connect the whole tool to external equipment, the quick change disc assembly (1) and large torque tightening assembly (2) are connected by zero positioner, the large torque tightening assembly (2) and inner rotor shaft flexible assembly (3) are fixed on the hollow speed reducer mounting seat (13) of large torque tightening assembly (2) and share the same axis, the tightening torque of large torque tightening assembly (2) and the counter torque of inner rotor shaft flexible assembly (3) are transmitted to hollow speed reducer mounting seat (13) and offset each other.

2. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 1, characterized in that, The quick change disc assembly (1) includes tool butt joint quick change disc (4), quick change welding frame one (5), zero positioner female head (6) and tightening assembly quick change disc (7), the tool butt joint quick change disc (4) is fixedly installed above quick change welding frame one (5), the zero positioner female head (6) and tightening assembly quick change disc (7) are fixed on one side of quick change welding frame one (5), the tool butt joint quick change disc (4) is used to be connected with external robot or truss etc. Executive mechanism, meet the connection and quick change function of large torque tightening tool, the zero positioner female head (6) is connected with the zero positioner male head (10) of large torque tightening assembly (2), the precise positioning of quick change disc assembly (1) and large torque tightening assembly (2) is realized, the tightening assembly quick change disc (7) realizes the connection and quick change function of large torque tightening assembly (2), the tool butt joint quick change disc (4) and tightening assembly quick change disc (7) are integrated with electrical interface, gas interface, the electrical interface is used for power supply communication of components in large torque tightening assembly (2); The gas interface is used for zero positioner gas supply and subsequent expansion product gas supply demand.

3. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 2, characterized in that, The large torque tightening assembly (2) comprises a quick-change welding frame two (8), a tightening assembly quick-change disc (9), a zero-position locator male head (10), a hollow speed reducer (11), an inner rotor shaft nut tooling (12), a hollow speed reducer mounting seat (13), a large torque dynamic torque sensor (14), and a servo motor (15). The hollow speed reducer (11) is installed on the hollow speed reducer mounting seat (13). The output end of the hollow speed reducer (11) is installed with the inner rotor shaft nut tooling (12). The inner rotor shaft nut tooling (12) is connected with the nut through the spline. The nut is tightened through the rotation of the hollow speed reducer (11). The output of the servo motor (15) is connected with the input end of the hollow speed reducer (11) through the large torque dynamic torque sensor (14). The quick-change welding frame two (8) is fixedly installed above the hollow speed reducer mounting seat (13). The tightening assembly quick-change disc (9) and the zero-position locator male head (10) are fixedly installed on one side of the quick-change welding frame two (8). The zero-position locator male head (10) is connected with the zero-position locator female head (6) of the quick-change disc assembly (1) in a matched mode, so as to realize the accurate positioning of the large torque tightening assembly (2) and the quick-change disc assembly (1). The tightening assembly quick-change disc female head (9) is connected with the tightening assembly quick-change disc male head (7) of the quick-change disc assembly (1) in a matched mode, so as to realize the connection and quick change of the large torque tightening assembly (2) and the quick-change disc assembly (1). The inner rotor shaft nut tooling (12) is fixedly installed below the hollow speed reducer mounting seat (13). The zero-position locator male head (10) and the zero-position locator female head (6) of the quick-change disc assembly (1) are butted.

4. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 3, characterized in that, The inner rotor shaft flexible assembly (3) is installed on the hollow speed reducer mounting seat (13) together with the hollow speed reducer (11) through the hollow part of the hollow speed reducer (11).

5. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 3, characterized in that, The inner rotor shaft flexible assembly (3) comprises an assembly fixing shaft (16) and an inner rotor shaft rotation-stopping tooling (22). The upper end of the fixing shaft (16) is fixedly installed on the hollow speed reducer mounting seat (13) and is coaxial with the hollow speed reducer (11). The lower end of the fixing shaft (16) is fixedly connected with the inner rotor shaft rotation-stopping tooling (22). The lower end of the inner rotor shaft rotation-stopping tooling (22) is provided with a involute spline. The inner rotor shaft rotation-stopping tooling (22) is connected with the inner rotor shaft through the spline.

6. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 5, characterized in that, The inner rotor shaft flexible assembly (3) further comprises a shaft end cover (17), an assembly upper plate (18), connecting shafts (19), a guide sleeve (20) and springs (21), the assembly upper plate (18) is coaxially sleeved on the fixed shaft (16) above the inner rotor shaft rotation-stopping tool (22), the assembly upper plate (18) and the inner rotor shaft rotation-stopping tool (22) are connected by the connecting shafts (19), the upper end of the connecting shaft (19) is limited by the shaft end cover (17), the lower end has a precision hole fixed with the inner rotor shaft rotation-stopping tool (22), the springs (21) are sleeved on the connecting shafts (19), the upper end of the spring (21) is provided with the guide sleeve (20), the guide sleeve (20) is sleeved on the connecting shaft (19) and is fixedly connected with the assembly upper plate (18), and the circumferential guiding effect of the connecting shaft (19) is provided.

7. A high torque tightening tool for helicopter internal rotor shaft nuts according to claim 5, characterized in that, The inner rotor shaft flexible assembly (3) penetrates the hollow speed reducer (11) of the large torque tightening assembly (2), so that the inner rotor shaft rotation-stopping tool (22) and the inner rotor shaft nut tool (12) can be synchronously aligned.

8. A method of tightening the shaft nut of a rotor of a helicopter using a tool as claimed in any one of claims 1 to 7, characterized in that, The method comprises the following steps: The tool is installed to an external actuating mechanism through a quick-change disc assembly (1); The inner rotor shaft rotation-stopping tool (22) of the inner rotor shaft flexible assembly (3) is connected with the spline of the inner rotor shaft; The tool angle is adjusted, so that the inner rotor shaft nut tool (12) of the large torque tightening assembly (2) is connected with the bayonet of the nut; The servo motor (15) is started, and the nut is tightened through closed-loop torque control. During the tightening process, the springs (21) of the inner rotor shaft flexible assembly (3) absorb axial displacement, and the tightening torque and the counter torque are mutually offset in the hollow speed reducer mounting seat (13).

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