A double-stage planetary gear differential driving based slip-ring-free variable-pitch propeller hub mechanism

Abstract

The application discloses a double-stage planetary gear differential driving slip-ring-free variable-pitch hub mechanism, which comprises a main transmission shaft serving as a driving input end; a first-stage planetary gear train composed of a first sun gear, a first planetary carrier and a first ring gear; a static end driving assembly comprising a stepping motor and a worm installed on a static structure of a machine body; a second-stage planetary gear train composed of a second sun gear, a second planetary carrier and a second ring gear; a second bevel gear coaxially fixedly connected with the second sun gear; and at least one pitch executing unit comprising a blade root and an executing bevel gear. The application eliminates the problems of poor electrical contact, serious wear and tear and electromagnetic interference of a conventional slip ring in a high-speed rotation and severe vibration environment, greatly improves the long-term working reliability and the adaptability to harsh working conditions of a rotorcraft power system, and significantly reduces the maintenance cost of the system.

Description

Technical Field

[0001] This invention relates to the field of rotorcraft transmission system technology, specifically to a slip-ring-free variable collective pitch rotor hub mechanism based on two-stage planetary gear differential drive. Background Technology

[0002] Rotorcraft (such as helicopters, tiltrotor aircraft and multi-rotor drones) mainly rely on changing the pitch angle of the rotor blades to adjust lift and control flight attitude. Among them, precise control of collective pitch is one of the core technologies of rotor power system.

[0003] Traditional rotor pitch control designs typically employ swashplate mechanisms. However, swashplates are complex, have numerous components, and are bulky, increasing the overall weight of the rotor system and leading to higher aerodynamic drag and maintenance costs. With the development of fly-by-wire and distributed electric drive technologies, some modern rotor designs tend to directly install servo motors inside the rotating rotor hub to achieve independent pitch control. However, this approach has a fatal flaw: because the rotor hub is constantly rotating at high speed, it is necessary to rely on rotating contact electrical interfaces such as conductive slip rings (collector rings) to transmit power and control signals from the stationary fuselage to the rotating rotor hub.

[0004] Under the long-term high-speed rotation, strong vibration, and harsh conditions of rotor systems, conductive slip rings are prone to mechanical wear, contact resistance fluctuations, and even arc oxidation. This not only leads to control signal distortion or interruption, significantly reducing the safety and reliability of the aircraft, but also has a limited service life, requiring frequent disassembly and maintenance. Furthermore, in certain special scenarios with extremely high electromagnetic compatibility requirements or extremely limited structural space, the size and electromagnetic interference issues of traditional slip rings and swashplates become technical bottlenecks restricting the improvement of system performance.

[0005] Therefore, how to break free from the dependence on traditional swashplates and conductive slip rings, and design a compact, highly reliable mechanism that can achieve precise collective pitch adjustment of the blades in a rotating coordinate system through mechanical or power input at the stationary end, is a technical problem that urgently needs to be solved in the field of rotor drive. Summary of the Invention

[0006] The present invention proposes a slip-ring-free variable collective pitch propeller hub mechanism based on a two-stage planetary gear differential drive, which can at least solve one of the technical problems in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A slip-ring-free variable collective pitch propeller hub mechanism based on a two-stage planetary gear differential drive includes: The main drive shaft serves as the main power input end. A first bevel gear is fixedly connected to the front end of the main drive shaft, and a first sun gear is also fixedly connected to the main drive shaft. The first-stage planetary gear system consists of a first sun gear, a first-stage planetary gear, a first planet carrier, and a first gear ring. The outer side of the first gear ring is integrally formed and fixedly connected to a worm gear, forming a gear ring worm gear. The stationary end drive assembly includes a stepper motor and a worm gear mounted on the stationary structure of the machine body. The worm gear meshes with the gear ring worm wheel, and the output shaft of the stepper motor is connected to the worm gear drive. The second-stage planetary gear system consists of a second sun gear, a second-stage planetary gear, a second planetary carrier, and a second ring gear. The second planetary carrier is fixedly connected to the first planetary carrier to form a shared planetary carrier, and the second ring gear is fixed to the stationary structure of the fuselage. The second bevel gear is coaxially and fixedly connected to the second sun gear, and its axis coincides with that of the first bevel gear and their end faces are arranged opposite each other. At least one pitch actuator unit includes a blade root, a rotor rod, and an actuator bevel gear. The actuator bevel gear is fixedly connected to the pitch shaft at the blade root and simultaneously meshes with the inner tooth surfaces of the first bevel gear and the second bevel gear. The stepper motor drives the worm to rotate to change the speed of the gear ring worm wheel. After differential compensation by the two-stage planetary gear system, a speed difference is generated between the first bevel gear and the second bevel gear. The speed difference drives the actuating bevel gear to rotate around the blade axis to adjust the blade collective pitch angle. The average speed of the first bevel gear and the second bevel gear determines the revolution speed of the blade around the main drive shaft axis.

[0008] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive described in this invention, wherein: the gear parameters of the first-stage planetary gear system and the second-stage planetary gear system satisfy the speed compensation matching relationship: when the gear ring worm gear is stationary, the output speed of the second sun gear is exactly equal to the input speed of the first sun gear, so that the first bevel gear and the second bevel gear rotate synchronously.

[0009] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on dual-stage planetary gear differential drive described in this invention, the worm gear and worm wheel mechanism has a reverse self-locking characteristic, and its lead angle is smaller than the equivalent friction angle between the meshing gear teeth. When the stepper motor loses power or stops outputting, the worm automatically locks the worm wheel to keep the propeller collective pitch angle unchanged.

[0010] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive described in this invention, the common planetary carrier is an integral hollow structure that runs through the first-stage planetary gear system and the second-stage planetary gear system. The main drive shaft passes through the central through hole of the common planetary carrier and is supported by a rolling bearing with the common planetary carrier.

[0011] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive described in this invention, the second sun gear is fixedly connected to the second bevel gear through a secondary output shaft. The secondary output shaft is a hollow shaft, sleeved on the outside of the main drive shaft, and supported by at least two rolling bearings between it and the main drive shaft.

[0012] As a preferred embodiment of the slip-ring-free variable collective pitch rotor hub mechanism based on two-stage planetary gear differential drive described in this invention, the number of the actuating bevel gears is equal to the number of blades and is evenly distributed along the circumference of the main drive shaft, and the apex of the pitch cone of all the actuating bevel gears is located on the axis of the main drive shaft; the rotor tie rod provides centripetal force to the actuating bevel gears and is radially fixed to the rotor disk, and has a built-in rotor tie rod bearing, which fixes it axially to the main drive shaft and allows it to rotate freely.

[0013] As a preferred embodiment of the slip-ring-free variable collective pitch hub mechanism based on two-stage planetary gear differential drive described in this invention, the stepper motor is a closed-loop stepper motor with an absolute encoder. By precisely controlling the angular displacement and angular velocity of the stepper motor, the digital precise adjustment of the blade collective pitch angle and the continuous control of the variable pitch rate are realized.

[0014] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on dual-stage planetary gear differential drive described in this invention, the first bevel gear, the second bevel gear, and the actuating bevel gear are all zero-degree spiral bevel gears, and the three have the same module and pressure angle to ensure the smoothness of meshing transmission and load-bearing capacity.

[0015] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive described in this invention, wherein: a flange is provided on the outer side of the second gear ring, which is fixedly connected to the static support structure of the fuselage by bolts, and rolling bearings are provided between the second gear ring and the common planetary carrier, and between the gear ring worm gear and the static support structure of the fuselage.

[0016] As a preferred embodiment of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive described in this invention, wherein: the first-stage planetary gear has a built-in first bearing, so that the first-stage planetary gear is axially fixed on the common planetary carrier and can rotate freely; the second-stage planetary gear has a built-in second bearing, so that the second-stage planetary gear is axially fixed on the common planetary carrier and can rotate freely.

[0017] The beneficial effects of this invention are: This invention cleverly introduces a series-connected two-stage planetary gear system and a differential transmission system to transmit stepper motor control commands from the stationary reference frame to the high-speed rotating rotor hub in a purely mechanical power distribution and compensation manner. This eliminates the problems of poor electrical contact, severe wear, and electromagnetic interference that traditional slip rings are prone to in high-speed rotation and severe vibration environments. This greatly improves the long-term reliability and adaptability to harsh working conditions of the rotorcraft's power system, while significantly reducing the system's later maintenance costs. This invention achieves dynamic decoupling between variable collective pitch and rotor speed through mechanical coupling. The angular velocity of collective pitch change directly and uniquely depends on the speed difference between the first and second bevel gears, while the overall rotor rotation speed is determined by the average speed of the two gears. The two operate independently, resulting in clear control logic and high adjustment precision. More importantly, utilizing the inherent reverse self-locking physical characteristics of the worm gear, the worm can firmly lock the worm wheel during normal flight while maintaining a fixed collective pitch, or in the event of a sudden power failure of the stepper motor or a control system malfunction. Combined with the same-speed restoration compensation effect of the second-stage planetary gear system, the system automatically locks and maintains the current collective pitch angle, providing highly reliable low-level mechanical failure protection redundancy for the rotor transmission system. This effectively prevents flight accidents caused by sudden pitch changes due to power failure at the control end. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive of the present invention.

[0019] Figure 2 This is a schematic diagram of the core transmission component of the slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1-First sun gear, 2-Second sun gear, 3-Main drive shaft, 4-Second bevel gear, 5-First bevel gear, 6-First bearing, 7-First stage planetary gear, 8-Ring gear worm gear, 9-Worm, 10-Second ring gear, 11-Second bearing, 12-Rotor rod bearing, 13-Rotor rod, 14-Secondary output shaft, 15-Actuating bevel gear, 16-Common planetary carrier, 17-Second stage planetary gear. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0022] like Figures 1-2 As shown, the present invention provides a slip-ring-free variable collective pitch hub mechanism based on a two-stage planetary gear differential drive, which mainly includes four parts: a power input and distribution system, a two-stage planetary differential compensation system, a stationary end drive system, and a pitch actuator.

[0023] Power input and distribution system: The core component of the power input and distribution system is the main drive shaft 3, whose lower end is connected to the output shaft of the aircraft's main reducer to receive the main power from the engine. The upper end (front end) of the main drive shaft 3 is fixedly connected to a first bevel gear 5 via a spline or interference fit, with the tooth surface of the first bevel gear 5 facing downwards. A first sun gear 1 is fixedly connected to the middle of the main drive shaft 3, rotating coaxially with the main drive shaft 3, serving as the power input end of the first-stage planetary gear system.

[0024] Two-stage planetary differential compensation system: The two-stage planetary differential compensation system consists of a first-stage planetary gear train and a second-stage planetary gear train arranged coaxially in series, both sharing a common planetary carrier 16 with an integrated hollow structure.

[0025] The first-stage planetary gear system includes a first sun gear 1, multiple first planet gears evenly distributed on a common planet carrier 16, and a ring gear and worm gear 8. The first planet gears are mounted on the common planet carrier 16 via pins and mesh with the inner tooth surfaces of the first sun gear 1 and the ring gear and worm gear 8. The outer side of the ring gear and worm gear 8 is integrally formed with worm gear teeth, forming an integrated component that combines the functions of a ring gear and a worm gear.

[0026] The second-stage planetary gear system includes a second sun gear 2, multiple second planet gears evenly distributed on a common planet carrier 16, and a second ring gear 10. The second planet gears are mounted on the upper end of the common planet carrier 16 via pins and mesh with the inner tooth surfaces of the second sun gear 2 and the second ring gear 10. The outer side of the second ring gear 10 is provided with a flange and is fixed to the static support structure of the machine body by bolts, thus maintaining a stationary state.

[0027] A shared planetary carrier 16 runs through the two-stage planetary gear system, and the main drive shaft 3 passes through the central through-hole of the shared planetary carrier 16. The two are supported by two deep groove ball bearings to ensure smooth relative rotation. A hollow secondary output shaft 14 is fixedly connected to the upper end of the second sun gear 2 via a spline. The secondary output shaft 14 is sleeved on the upper outer side of the main drive shaft 3, and a second bevel gear 4 is fixedly connected to its upper end. The tooth surfaces of the second bevel gear 4 are arranged upwards, coinciding with the axis of the first bevel gear 5 and with their end faces opposite each other, forming an annular meshing space between them.

[0028] To achieve precise speed compensation, the gear parameters of the two-stage planetary gear system are strictly matched. When the ring gear worm gear 8 is stationary, the first-stage planetary gear system reduces the input speed of the first sun gear and transmits it to the common planet carrier. The second-stage planetary gear system then increases the speed of the common planet carrier, making the output speed of the second sun gear exactly equal to the input speed of the first sun gear, thereby causing the second bevel gear 4 and the first bevel gear 5 to rotate synchronously.

[0029] Stationary drive system: The stationary drive system includes a stepper motor and a worm gear 9, both mounted on the stationary structure of the machine body. The stepper motor is a closed-loop stepper motor with an absolute encoder, and its output shaft is connected to the worm gear 9 via a coupling. The axis of the worm gear 9 is arranged perpendicularly to the axis of the main drive shaft 3 and meshes with the outer worm gear teeth of the gear ring worm gear 8.

[0030] In this embodiment, the worm 9 is a single-start worm, whose lead angle is smaller than the equivalent friction angle between the meshing gear teeth, thus possessing reliable reverse self-locking characteristics. When the stepper motor loses power or stops outputting, the worm 9 cannot be driven to rotate by the gear ring worm wheel 8, thereby firmly locking the gear ring worm wheel 8 in its current position.

[0031] Pitch actuator: The number of pitch actuators is equal to the number of blades. In this embodiment, three blades are used, corresponding to three pitch actuator units evenly distributed around the main drive shaft 3. Each pitch actuator unit includes a blade root and an actuator bevel gear 15. The actuator bevel gear 15 is fixed to the pitch-changing shaft at the blade root, and the pitch-changing shaft is supported on the blade hub housing by bearings. The actuator bevel gear 15 meshes with the inner tooth surfaces of the first bevel gear 5 and the second bevel gear 4 simultaneously, and the apex of its pitch cone is located on the axis of the main drive shaft 3.

[0032] The first bevel gear 5, the second bevel gear 4, and the actuating bevel gear 15 all use zero-degree spiral bevel gears with the same module and pressure angle to ensure smooth meshing transmission and high load-bearing capacity.

[0033] Working principle: Steady-state condition (collective pitch unchanged): When the aircraft maintains a fixed collective pitch, the stepper motor is locked, and the worm gear 9 remains stationary. Due to the reverse self-locking characteristic of the worm gear mechanism, the ring gear 8 also remains stationary. At this time, the main drive shaft 3 drives the first sun gear 1 and the first bevel gear 5 to rotate at the same speed.

[0034] The first sun gear 1 drives the first planet gear to rotate, which in turn drives the common planet carrier 16 to rotate. The common planet carrier 16 drives the second planet gear to rotate. Since the second ring gear 10 is fixed, the second sun gear 2 rotates under the drive of the second planet gear. Because the parameters of the two-stage planetary gear system are precisely matched, the rotational speeds of the second sun gear 2 and the second bevel gear 4 are exactly equal to the rotational speeds of the first sun gear 1 and the first bevel gear 5.

[0035] At this time, the first bevel gear 5 and the second bevel gear 4 rotate synchronously with no speed difference between them. The actuating bevel gear 15 does not rotate on its own axis but revolves around the main drive shaft 3 along with the two bevel gears, while the collective pitch angle of the blades remains unchanged. The revolution speed of the blades is the same as the rotation speed of the main drive shaft 3.

[0036] Variable pitch operation (collective pitch adjustment): When it is necessary to adjust the collective pitch of the propeller blades, the flight control system sends a control command to the stepper motor, which drives the worm 9 to rotate at a certain angular velocity, thereby driving the gear ring worm wheel 8 to rotate at a corresponding angular velocity.

[0037] The rotation of the ring gear worm gear 8 disrupts the original speed balance of the first-stage planetary gear system, causing a change in the speed of the common planetary carrier 16. This change in the speed of the common planetary carrier 16 is transmitted through the second-stage planetary gear system, causing the speeds of the second sun gear 2 and the second bevel gear 4 to deviate from the speed of the first bevel gear 5, thus creating a speed difference between the first bevel gear 5 and the second bevel gear 4.

[0038] The speed difference drives the actuator bevel gear 15 to rotate around the blade axis. The rotation of the actuator bevel gear 15 directly drives the blade to rotate around the pitch axis, thereby changing the collective pitch angle of the blade. By precisely controlling the angular displacement and rotation direction of the stepper motor, precise adjustment of the blade collective pitch angle and pitch change operation in the positive and negative directions can be achieved.

[0039] During the pitch adjustment process, the revolution speed of the blades is determined by the average speed of the first bevel gear 5 and the second bevel gear 4. Since the speed of the stepper motor is much lower than the speed of the main drive shaft 3, the change in the revolution speed of the blades is extremely small and can be ignored, thus achieving effective decoupling between the pitch adjustment and the rotor speed.

[0040] Failure protection conditions: When the stepper motor experiences a sudden power outage or a control system malfunction, it loses its output torque. The worm 9, due to the reverse self-locking characteristic of the worm gear mechanism, cannot be driven to rotate by the gear ring worm wheel 8, and the gear ring worm wheel 8 is immediately locked in its current position. At this time, the two-stage planetary gear system returns to its steady-state transmission relationship, the first bevel gear 5 and the second bevel gear 4 rotate synchronously again, the actuating bevel gear 15 stops rotating, and the propeller collective pitch angle remains at its pre-failure state, thus preventing flight accidents caused by sudden changes in propeller pitch.

[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0042] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A slip-ring-free variable collective pitch propeller hub mechanism based on a two-stage planetary gear differential drive, characterized in that, include: The main drive shaft (3) serves as the main power input end. The front end of the main drive shaft (3) is fixedly connected to a first bevel gear (5), and the main drive shaft (3) is also fixedly connected to a first sun gear (1). The first-stage planetary gear system consists of a first sun gear (1), a first-stage planetary gear (7), a first planet carrier, and a first gear ring. The outer side of the first gear ring is integrally formed and fixedly connected to a worm gear, forming a gear ring worm gear (8). The stationary end drive assembly includes a stepper motor and a worm (9) mounted on the stationary structure of the machine body. The worm (9) meshes with the gear ring worm wheel (8), and the output shaft of the stepper motor is connected to the worm (9) in a transmission manner. The second-stage planetary gear system consists of a second sun gear (2), a second-stage planetary gear (17), a second planetary carrier, and a second gear ring (10). The second planetary carrier is fixedly connected to the first planetary carrier to form a shared planetary carrier (16). The second gear ring (10) is fixed to the static structure of the fuselage. The second bevel gear (4) is coaxially fixedly connected to the second sun gear (2), and its axis coincides with that of the first bevel gear (5), with their end faces facing each other. At least one pitch actuator unit includes a blade root, a rotor rod (13) and an actuator bevel gear (15), wherein the actuator bevel gear (15) is fixedly connected to the pitch shaft of the blade root and simultaneously meshes with the inner tooth surfaces of the first bevel gear (5) and the second bevel gear (4); The stepper motor drives the worm (9) to rotate to change the speed of the gear ring worm wheel (8). After differential compensation by the two-stage planetary gear system, a speed difference is generated between the first bevel gear (5) and the second bevel gear (4). The speed difference drives the execution bevel gear (15) to rotate around the blade axis to adjust the blade collective pitch angle. The average speed of the first bevel gear (5) and the second bevel gear (4) determines the revolution speed of the blade around the axis of the main drive shaft (3).

2. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The gear parameters of the first-stage planetary gear system and the second-stage planetary gear system satisfy the speed compensation matching relationship: when the gear ring worm gear (8) is stationary, the output speed of the second sun gear (2) is exactly equal to the input speed of the first sun gear (1), so that the first bevel gear (5) and the second bevel gear (4) rotate synchronously.

3. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The worm gear mechanism composed of the worm (9) and the toothed worm wheel (8) has a reverse self-locking characteristic. Its lead angle is smaller than the equivalent friction angle between the meshing teeth. When the stepper motor loses power or stops outputting, the worm (9) automatically locks the toothed worm wheel (8) to keep the blade collective pitch angle unchanged.

4. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The shared planetary carrier (16) is an integral hollow structure that runs through the first-stage planetary gear system and the second-stage planetary gear system. The main drive shaft (3) passes through the central through hole of the shared planetary carrier (16) and is supported by a rolling bearing.

5. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The second sun gear (2) is fixedly connected to the second bevel gear (4) via the auxiliary output shaft (14). The auxiliary output shaft (14) is a hollow shaft, sleeved on the outside of the main drive shaft (3), and supported by at least two rolling bearings between it and the main drive shaft (3).

6. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The number of the actuating bevel gears (15) is equal to the number of blades, and they are evenly distributed along the circumference of the main drive shaft (3). The apex of the pitch cone of all the actuating bevel gears (15) is located on the axis of the main drive shaft (3). The rotor rod (13) provides centripetal force to the actuating bevel gears (15) and is radially fixed to the rotor disk. It has a built-in rotor rod bearing (12) to fix it axially to the main drive shaft (3) and allow it to rotate freely.

7. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The stepper motor is a closed-loop stepper motor with an absolute encoder. By precisely controlling the angular displacement and angular velocity of the stepper motor, the digital precision adjustment of the blade collective pitch angle and the continuous control of the pitch rate are realized.

8. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The first bevel gear (5), the second bevel gear (4) and the actuating bevel gear (15) are all zero-degree spiral bevel gears, and the three have the same module and pressure angle to ensure the smoothness of meshing transmission and load-bearing capacity.

9. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The second gear ring (10) has a flange on its outer side, which is fixedly connected to the static support structure of the fuselage by bolts. Rolling bearings are provided between the second gear ring (10) and the common planetary carrier (16), and between the gear ring worm gear (8) and the static support structure of the fuselage.

10. The slip-ring-free variable collective pitch propeller hub mechanism based on two-stage planetary gear differential drive according to claim 1, characterized in that: The first-stage planetary gear (7) has a first bearing (6) built in, so that the first-stage planetary gear (7) is axially fixed on the common planetary carrier (16) and can rotate freely; the second-stage planetary gear (17) has a second bearing (11) built in, so that the second-stage planetary gear (17) is axially fixed on the common planetary carrier (16) and can rotate freely.

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