A planetary gear and a planetary gear reducer

Abstract

This application discloses a planetary gear and a planetary gear reducer. The planetary gear has a preset thin-walled structure. This structure is configured to, when the planetary gear is assembled into the planetary gear reducer, cause radial elastic deformation of the planetary gear under an assembly preload, thereby applying a preset pressure value to the first and second meshing portions to offset the side clearances reserved in the first and second meshing portions respectively. The first meshing portion is the meshing part between the planetary gear and the internal gear ring of the planetary gear reducer, and the second meshing portion is the meshing part between the planetary gear and the sun gear of the planetary gear reducer. This technical solution, through its preset thin-walled structure, can simultaneously eliminate the side clearances at two key meshing portions, effectively reducing or eliminating the backlash of the planetary gear reducer, thereby significantly improving the transmission accuracy, repeatability, and transmission performance of the planetary gear reducer.

Description

Technical Field

[0001] This application relates to the field of transmission technology, and in particular to a planetary gear and a planetary gear reducer. Background Technology

[0002] A planetary gear reducer is a precision mechanical device that uses planetary gear trains to transmit power. A planetary gear reducer typically consists of an internal gear ring, two or more planetary gears, a sun gear, a planet carrier, and planetary gear support shafts. Due to its advantages such as small size, high load capacity, high transmission accuracy and efficiency, impact resistance, and high reliability, planetary gear reducers have been widely used in many demanding fields, including industrial automation, new energy vehicles, aerospace, robotics, and heavy machinery.

[0003] In the manufacturing process of planetary gear reducers, due to machining and assembly errors in components such as the internal gear ring, planetary gears, sun gear, and planetary carrier, small backlashes (i.e., clearances) are designed to exist between the teeth of the internal gear ring and planetary gears (i.e., the meshing part between the internal gear ring and planetary gears), and between the teeth of the planetary gears and sun gears (i.e., the meshing part between the planetary gears and sun gears). These clearances cause a small free-spinning angle when the output shaft of the planetary gear reducer rotates; this angle is called backlash. In practical use, it has been found that if this backlash is too large, it will reduce the transmission accuracy and repeatability of the planetary gear reducer. Furthermore, in applications requiring constant forward and reverse rotation, such as industrial robots, large backlashes can cause impacts, resulting in additional mechanical noise and vibration. Long-term operation will also accelerate wear and shorten its service life. Therefore, how to effectively reduce or even eliminate the backlash of planetary gear reducers has become an important design issue.

[0004] In related technologies, existing planetary gear reducers have many backlash elimination designs. For example, Japanese Patent [2000-179629] proposes a design that utilizes the elastic deformation of a thin-walled internal gear ring to absorb installation errors of various parts and gear machining errors, thereby eliminating backlash. Another example is Chinese Patent [CN113757349B], which proposes a modified planetary carrier that uses adjusting bolts or elastic elements to press the planetary gears radially against the meshing internal gear ring, thus eliminating backlash. However, in practical use, it has been found that while the former method, through the deformation of the thin-walled internal gear ring, can eliminate the backlash at the meshing part between the planetary gear and the internal gear ring, it cannot reduce or eliminate the backlash at the meshing part between the planetary gear and the sun gear. Similarly, the latter method, which expands the planetary carrier by adjusting bolts, can only eliminate the backlash at the meshing part between the planetary gear and the internal gear ring, but not the backlash at the meshing part between the planetary gear and the sun gear. It is evident that existing backlash elimination design schemes for planetary gear reducers cannot effectively reduce or eliminate backlash, resulting in low transmission accuracy and poor repeatability of existing planetary gear reducers. Summary of the Invention

[0005] The purpose of this application is to provide a planetary gear and a planetary gear reducer, which aims to improve the problem that existing planetary gear reducer backlash elimination design schemes cannot effectively reduce and eliminate backlash, resulting in low transmission accuracy and poor repeatability of existing planetary gear reducers.

[0006] To achieve this objective, this application provides a planetary gear having a preset thin-walled structure. This preset thin-walled structure is configured to, when the planetary gear is assembled into the planetary gear reducer, cause radial elastic deformation of the planetary gear under the action of an assembly preload, thereby applying a preset pressure value to the first meshing portion and the second meshing portion to respectively offset the side clearance reserved in the first meshing portion and the second meshing portion. The first meshing portion is the meshing part between the planetary gear and the internal gear ring of the planetary gear reducer, and the second meshing portion is the meshing part between the planetary gear and the sun gear of the planetary gear reducer.

[0007] Optionally, in some embodiments of this application, the preset thin-walled structure satisfies the condition: h / r≤0.3, where h is the tooth root wall thickness of the planetary gear and r is the radius of the center circle of the tooth root wall thickness of the planetary gear.

[0008] Optionally, in some embodiments of this application, the planetary gear is made of a gear material with a preset elastic modulus, so that the planetary gear has a preset thin-walled structure.

[0009] Optionally, in some embodiments of this application, the preset elastic modulus is less than or equal to 210 GPa.

[0010] Optionally, in some embodiments of this application, the gear material is any one of resin material, metal alloy material, composite material, and amorphous alloy material.

[0011] Optionally, in some embodiments of this application, the planetary gear has an annular inner groove recessed on at least one side surface, and the annular inner groove is located between the cylindrical portion of the planetary gear and the bearing seat portion of the planetary gear.

[0012] Optionally, in some embodiments of this application, the cylindrical portion of the planetary gear and the bearing seat portion of the planetary gear are connected by the bottom of the annular inner groove, and the bottom of the annular inner groove is configured as a curved structure that can cause the planetary gear to undergo radial deformation.

[0013] Optionally, in some embodiments of this application, the planetary gear is further modified along the tooth length direction by a preset modification angle, and the shape of the tooth modification corresponds to the size relationship between the groove depth of the annular inner groove and the tooth width of the planetary gear.

[0014] Optionally, in some embodiments of this application, the preset shaping angle is 0° to 2°.

[0015] Furthermore, to achieve this objective, this application embodiment also provides a planetary gear reducer, which includes an internal gear ring, a sun gear, and at least two planetary gears of any one of the above. The sun gear and each of the planetary gears are rotatably disposed in the internal gear ring, and each of the planetary gears is meshed with the sun gear and the internal gear ring.

[0016] The planetary gear and planetary gear reducer provided in this application embodiment, through the above-described structural configuration, employ a pre-designed thin-walled structure for the planetary gear, enabling controlled radial elastic deformation after assembly. This simultaneously applies a preload of a preset pressure value to the first meshing part (the meshing part between the planetary gear and the internal gear ring) and the second meshing part (the meshing part between the planetary gear and the sun gear). The pressure generated by this preload effectively offsets the side clearances left by machining and assembly errors between the planetary gear and the internal gear ring, and between the planetary gear and the sun gear, ensuring that the two meshing parts are in a tight fit from the initial state. Consequently, when the planetary gear reducer equipped with this planetary gear rotates the output shaft, the slight freewheeling angle caused by the backlash is significantly reduced, i.e., the backlash is effectively reduced or eliminated. Therefore, compared to existing methods that only target backlash elimination at a single meshing part or rely on deformation of other components, this technical solution achieves simultaneous elimination of backlash in both the first and second meshing parts through structural optimization of the planetary gear itself (i.e., setting a pre-designed thin wall that easily generates radial elastic deformation). This significantly improves the transmission performance of the planetary gear reducer equipped with this planetary gear, reduces backlash and impact during forward and reverse switching, and thus effectively improves the transmission accuracy and repeatability of the planetary gear reducer equipped with this planetary gear. Simultaneously, since the preload is controllable and achieved through the radial elastic deformation of the planetary gear itself, there is no need to introduce additional adjusting bolts or elastic elements. The structure is more compact and reliable, avoiding the problem of increased unilateral wear caused by deformation of the thin-walled inner gear ring or expansion of the planetary carrier. This achieves a more balanced and controllable load distribution, ensuring both backlash elimination and the durability and reliability of the planetary gear, helping to reduce vibration and noise and extend the service life of the planetary gear. It is evident that this technical solution, which can effectively improve the existing design schemes for eliminating backlash in planetary gear reducers, cannot effectively reduce or eliminate backlash in planetary gear reducers, resulting in low transmission accuracy and poor repeatability of existing planetary gear reducers. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0019] Figure 1 This is a schematic diagram of the structure of the planetary gear reducer according to an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the structure of a planetary gear according to an embodiment of this application.

[0021] Figure 3 This is a front view structural diagram of the planetary gear in an embodiment of this application.

[0022] Figure 4 for Figure 3 The diagram shows the first cross-sectional view of the planetary gear along section line AA.

[0023] Figure 5 for Figure 3 The diagram shows a second cross-sectional view of the planetary gear along section line AA.

[0024] Figure 6 for Figure 3 The diagram shows a third cross-sectional view of the planetary gear along section line AA.

[0025] Figure 7 for Figure 3 The diagram shows the fourth cross-sectional structure of the planetary gear along section line AA.

[0026] Figure 8 for Figure 3 The diagram shows the fifth cross-sectional view of the planetary gear along section line AA.

[0027] Figure 9 for Figure 3 The diagram shows the sixth cross-sectional view of the planetary gear along section line AA.

[0028] Figure label:

[0029] 1. Planetary gear reducer; 10. Planetary gear; 11. Annular inner groove; 111. Groove bottom; 12. Cylindrical section; 13. Bearing housing section; 14. Tooth section; 20. Internal gear ring; 30. Sun gear. Detailed Implementation

[0030] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0032] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] Please see Figures 1 to 9 As shown, in one embodiment, this application provides a planetary gear 10 with a preset thin-walled structure. This preset thin-walled structure is configured such that, when the planetary gear 10 is assembled into the planetary gear reducer 1, radial elastic deformation is caused by the assembly preload force, thereby applying a preset pressure value to the first meshing portion and the second meshing portion to respectively offset the side clearance reserved in the first and second meshing portions. The first meshing portion is the meshing part between the planetary gear 10 and the internal gear ring 20 of the planetary gear reducer 1, and the second meshing portion is the meshing part between the planetary gear 10 and the sun gear 30 of the planetary gear reducer 1.

[0034] It should be noted that the planetary gear 10 in this embodiment is mainly used in a planetary gear reducer 1. The planetary gear reducer 1 typically consists of an internal gear ring 20, two or more planetary gears 10, a sun gear 30, a planet carrier, and a gear support shaft. It utilizes a planetary gear system formed by the meshing of each planetary gear 10 with the sun gear 30 and the internal gear ring 20 to achieve power transmission, making it widely applicable in high-requirement fields such as industrial automation, new energy vehicles, aerospace, robotics, and heavy machinery. The aforementioned pre-set thin-walled structure specifically refers to the adjustment of the tooth root wall thickness of the planetary gear 10 (i.e., the radial thickness of the cylindrical portion 12 of the planetary gear 10) and the center circle formed by the portion of the tooth root wall thickness of the planetary gear 10 (i.e., half the radial thickness of the cylindrical portion 12 of the planetary gear 10). Figure 3 The ratio between the radii of the circles represented by the dashed lines shown in the diagram forms a thin-walled structure that possesses a certain degree of elasticity in the radial direction. This thin-walled structure is precisely calculated and optimized to produce controllable and uniform radial elastic deformation under assembly loads, thereby synchronously applying a preload with a preset pressure value to the two meshing parts of the planetary gear 10 and the internal gear ring 20, and the planetary gear 10 and the sun gear 30. The core of this design lies in transforming the planetary gear 10 itself into an active backlash-eliminating elastic element, acting directly on both sides of the meshing parts, achieving complete elimination of backlash through structural innovation.

[0035] Furthermore, the aforementioned preset pressure value is not directly set, but indirectly achieved through precise design of the stiffness (wall thickness, material, shape) and assembly interference of the preset thin-walled structure. The goal is to generate a radial preload, which is typically set numerically to 3% to 15% of the meshing force required for the rated output torque of the transmission system (i.e., planetary gear reducer 1). This is because if the preset pressure value is much smaller than the working load (e.g., <3%), it is easily "cancelled" under high loads or impacts, resulting in unstable backlash elimination. Conversely, if the preset pressure value is close to the working load (e.g., >15%), it means that the gears are subjected to near-full-load contact stress even under no-load or light-load conditions, which is extremely uneconomical and harmful. This application sets the preset pressure value in the range of 3% to 15%, which provides a safe and reliable backlash elimination margin without significantly increasing losses and wear, sufficient to compensate for manufacturing errors, thermal expansion, and absorb minor impacts.

[0036] In this way, the planetary gear 10 of this embodiment, through the above-described structural configuration and its pre-designed thin-walled structure, can generate controlled radial elastic deformation after being assembled into the planetary gear reducer 1. This simultaneously applies a preload of a preset pressure value to the first meshing part (the meshing part between the planetary gear 10 and the internal gear ring 20) and the second meshing part (the meshing part between the planetary gear 10 and the sun gear 30). The pressure generated by this preload can effectively offset the side clearances left by machining and assembly errors between the planetary gear 10 and the internal gear ring 20, and between the planetary gear 10 and the sun gear 30, so that the two meshing parts are in a tight fit in the initial state. As a result, when the planetary gear reducer 1 equipped with this planetary gear 10 rotates the output shaft, the small free spin angle caused by the backlash is significantly reduced, that is, the backlash is effectively reduced or eliminated. Thus, compared to existing methods that only target backlash elimination at a single meshing part or rely on deformation of other parts, this technical solution, through structural optimization of the planetary gear 10 itself (i.e., setting a pre-designed thin-walled structure that easily generates radial elastic deformation), achieves simultaneous elimination of the backlash of the first and second meshing parts. This significantly improves the transmission performance of the planetary gear reducer 1 equipped with the planetary gear 10, reduces idle travel and impact during forward and reverse switching, and effectively improves the transmission accuracy and repeatability of the planetary gear reducer 1 equipped with the planetary gear 10. Simultaneously, since the preload is controllable and achieved through the radial elastic deformation of the planetary gear 10 itself, there is no need to introduce additional adjusting bolts or elastic elements, resulting in a more compact and reliable structure. This avoids the problem of increased unilateral wear caused by deformation of the thin-walled internal gear ring 20 or expansion of the planetary carrier, achieving a more balanced and controllable load distribution. This ensures both backlash elimination effect and durability and reliability of the planetary gear 10, helping to reduce vibration and noise and extend the service life of the planetary gear 10.

[0037] In some examples, such as Figure 2 and Figure 3As shown, the aforementioned pre-designed thin-walled structure satisfies the condition: h / r ≤ 0.3, where h is the tooth root wall thickness of planetary gear 10 and r is the radius of the center circle of the tooth root wall thickness of planetary gear 10. Thus, by limiting the ratio of the tooth root wall thickness to the center circle radius of the tooth root wall thickness (h / r ≤ 0.3) through the above proportional condition, a clear quantitative design criterion is provided for the pre-designed thin-walled structure of planetary gear 10. This ensures that planetary gear 10 possesses sufficient flexibility and radial elastic deformation capacity, enabling it to generate precise and controllable radial deformation under assembly preload without plastic deformation or excessive stress, thereby effectively eliminating backlash in the two meshing parts. Furthermore, this proportional design optimizes the elastic performance of planetary gear 10 while ensuring its overall load-bearing strength, making the backlash elimination effect controllable and durable, and preventing excessive rigidity from affecting assembly adaptability or exacerbating wear. This allows planetary gear 10 to achieve the best balance between backlash elimination function and long-term operational reliability.

[0038] In some examples, such as Figure 2 and Figure 3 As shown, the planetary gear 10 is made of a gear material with a preset elastic modulus, giving it a preset thin-walled structure. Thus, by selecting a gear material with a specific elastic modulus, the core purpose is to provide a matching mechanical performance basis for the preset thin-walled structure. Through the coordinated design of the material's elastic modulus and the stiffness of the thin-walled structure, it can be ensured that when preloaded, the planetary gear 10 can generate sufficient radial elastic deformation to effectively eliminate backlash on both sides, while precisely controlling the deformation stress level to avoid insufficient deformation due to excessive material hardness or plastic deformation and early fatigue due to excessive softness. This material-level optimization fundamentally guarantees the reliability, durability, and performance consistency of the backlash-eliminating structure.

[0039] In some examples, such as Figure 2 and Figure 3 As shown, the preset elastic modulus is less than or equal to 210 GPa. Thus, limiting the preset elastic modulus to no more than 210 GPa aims to provide moderate material flexibility for the thin-walled structure, ensuring that the radial deformation required to eliminate the backlash of the first and second meshing parts can be obtained under controllable assembly forces or deformations. Simultaneously, it helps to control deformation stress within a low range, improving the fatigue life and operational reliability of the gears while ensuring the backlash elimination function.

[0040] In some examples, such as Figure 2 and Figure 3As shown, the gear materials mentioned above can be any one of resin materials, metal alloy materials, composite materials, or amorphous alloy materials. Thus, by setting the range of selectable gear materials to resin materials, metal alloy materials, composite materials, and amorphous alloy materials, flexible material selection freedom is provided to meet different application scenarios with varying loads, precision requirements, and costs. This design allows for better comprehensive performance optimization, such as weight reduction, vibration reduction, noise reduction, or corrosion resistance, by selecting materials with lower elastic modulus than traditional fully hardened steel or with superior specific strength, while ensuring the pre-defined elastic function of the thin-walled structure. For example, high-performance resin materials or composite materials can be used in lightweight robots with high dynamic response, while special alloys can be selected in heavy-duty industrial scenarios, thereby significantly expanding the application areas and performance boundaries of the reducer while ensuring effective backlash elimination.

[0041] It should be noted that when resin is specifically chosen as the gear material in this example, its elastic modulus (typically in the range of 1-10 GPa) is naturally much lower than the upper limit of 210 GPa. This makes it an ideal choice for achieving the low stiffness and high elastic deformation capacity of the pre-designed thin-walled structure. Therefore, the design focus is not on deliberately reducing the elastic modulus, but on precisely matching the elastic modulus of the resin with the geometric parameters of the thin wall (such as the h / r ratio) to ensure stable and sufficient meshing surface clamping force under a given pre-compression deformation. At the same time, material modification (such as fiber reinforcement) or structural optimization is needed to compensate for the shortcomings of resin in terms of strength and wear resistance to ensure the dimensional stability and durability of the gear under load.

[0042] When a metallic alloy is used as the gear material in this example, its elastic modulus can be adjusted to no higher than 210 GPa through specific heat treatment processes or by selecting an alloy system with inherently low elastic modulus (such as some titanium alloys, magnesium alloys, or steel that has undergone special annealing). This approach retains the high strength and high wear resistance of metallic materials while providing the planetary gear 10 with the appropriate elasticity required for its thin-walled structure, ensuring that it can effectively eliminate the backlash of the first and second meshing parts through controlled deformation. Simultaneously, precise structural design and process control are necessary to balance the low elastic modulus of the material with the fatigue strength required for gear load bearing, achieving a balance between backlash elimination performance and long-term reliability.

[0043] When a composite material is specifically selected for the gear material in this example, the overall equivalent elastic modulus can be actively controlled and ensured not to exceed 210 GPa by precisely designing the ratio of its reinforcing phase (such as fiber type, orientation, and content) to the matrix phase. This customizable material design capability allows for the significant improvement of the material's specific strength and fatigue resistance through fiber reinforcement while meeting the low stiffness requirements of thin-walled structures, effectively overcoming the contradiction between elasticity and strength in traditional homogeneous materials. Preferably, the composite material can be carbon fiber reinforced polymer (CFRP) or glass fiber reinforced polymer (GFRP). By adjusting the fiber type, content, and layup direction, the overall elastic modulus of these materials can be precisely designed within the required range, while possessing high specific strength, excellent fatigue resistance, and damping characteristics, effectively meeting the comprehensive requirements of lightweight, low backlash, and high dynamic response for the precision planetary gear 10. In addition, specially designed metal matrix composites (such as SiC particle-reinforced aluminum matrix composites) can also be used as a high-performance option, providing higher thermal conductivity and load-bearing capacity while maintaining a moderate elastic modulus.

[0044] When amorphous alloys are specifically chosen as the gear material in this example, thanks to their unique disordered atomic structure, the elastic modulus of most amorphous alloys (such as zirconium-based and iron-based amorphous materials) is already in the range of 70-150 GPa, naturally meeting the requirement of not exceeding 210 GPa. This allows the thin-walled structure of the planetary gear 10 to directly utilize its excellent mechanical properties of high elastic limit (up to about 2%) and high hardness. While generating large radial elastic deformation to eliminate the backlash of the first and second meshing parts, it also possesses wear resistance and fatigue strength far exceeding that of traditional steel, perfectly balancing the requirements of low elastic modulus backlash elimination and ultimate load-bearing capacity. Therefore, using amorphous alloy materials is an ideal material solution for achieving high performance, long service life, and backlash elimination in the planetary gear 10 of high-end precision reducers.

[0045] In some examples, such as Figure 2 and Figure 3 As shown, the planetary gear 10 has an annular inner groove 11 recessed on at least one side surface, and the annular inner groove 11 is located between the cylindrical portion 12 and the bearing housing portion 13 of the planetary gear 10. Thus, by providing the annular inner groove 11 between the cylindrical portion 12 and the bearing housing portion 13 of the planetary gear 10, the local radial stiffness of this transition region can be significantly reduced. This allows the planetary gear 10 to generate a larger controllable radial deformation under the same assembly or load conditions, more effectively pressing its meshing surfaces with both sides of the internal gear ring 20 and the sun gear 30 simultaneously to eliminate backlash. At the same time, the geometric parameters of the annular inner groove 11 (such as depth and width) provide key design variables for precisely controlling the overall elastic characteristics and stress distribution of the gear, achieving an optimized balance between backlash elimination performance and structural strength.

[0046] In some examples, such as Figure 2 , Figure 4 , Figure 8 and Figure 9 As shown, the cylindrical portion 12 of the planetary gear 10 and the bearing housing portion 13 of the planetary gear 10 are connected by the bottom 111 of the annular inner groove 11, and the bottom 111 of the annular inner groove 11 is configured as a curved structure that can cause radial deformation of the planetary gear 10. Thus, by designing the bottom 111 of the annular inner groove 11 as a specific curved structure, the connection between the cylindrical portion 12 and the bearing housing portion 13 of the planetary gear 10 can be constructed as a low-stiffness, high-flexibility elastic hinge. This not only further guides and amplifies the radial deformation required for the meshing rim of the planetary gear 10, making the preload on both sides more significant and uniform. Furthermore, this design, while improving the radial deformation capability for reliable backlash elimination, also significantly enhances the elasticity and fatigue life of the gear, ensuring the long-term stability of the backlash elimination effect.

[0047] It should be noted that the curved structure in this example can specifically be... Figure 8 The V-shaped structure shown or Figure 9 The zigzag structure shown can also be other bending structures that give it specific elastic deformation capabilities, including but not limited to wave-shaped structures, U-shaped structures, sine wave structures, etc.

[0048] In some examples, such as Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, the planetary gear 10 also undergoes tooth profile modification along its tooth length direction, with a preset modification angle for its tooth portion 14. The shape of this tooth profile modification corresponds to the size relationship between the groove depth of the annular inner groove 11 (i.e., the length shown as L in the figure) and the tooth width of the planetary gear 10 (i.e., the length shown as B in the figure). Thus, by performing a preset tooth profile modification on the tooth portion 14 of the planetary gear 10 that matches the radial elastic deformation of the thin wall, it can be ensured that when the planetary gear 10 undergoes radial preload deformation, its tooth surface can still achieve uniform contact with the tooth surfaces of the inner gear ring 20 and the sun gear 30 across the entire tooth length, avoiding stress concentration or uneven loading caused by load concentration at the tooth ends due to deformation. Furthermore, this collaborative design effectively eliminates meshing backlash while further optimizing the tooth surface contact state, improving transmission smoothness, load uniformity, and service life. Meanwhile, based on the relative size relationship between the groove depth of the annular inner groove 11 and the tooth width of the planetary gear 10, the design of different tooth profiles is matched, and it is also ensured that the radial elastic deformation behavior and tooth surface contact form of the planetary gear 10 can be optimally adapted under different size specifications.

[0049] It should be noted that the shape of the tooth profile modification in this example corresponds to the size relationship between the groove depth of the annular inner groove 11 (i.e., the length shown as L in the figure) and the tooth width of the planetary gear 10 (i.e., the length shown as B in the figure). Specifically, when L < B, corresponding to the case where the axial dimension of the planetary gear 10 is small, the shape of its tooth profile modification can be either a bevel surface where both the tooth part 14 and the tooth bottom are inclined along one side in the axial direction, as shown in Figure 4 or a curved convex surface where both the tooth part 14 and the tooth bottom are radially protruded in the middle in the axial direction, as shown in Figure 5 or a curved concave surface where both the tooth part 14 and the tooth bottom are radially recessed in the middle in the axial direction, as shown in Figure 6 . When L > B, corresponding to the case where the axial dimension of the planetary gear 10 is large, the shape of its tooth profile modification is mainly a bevel surface where both the tooth part 14 and the tooth bottom are inclined along one side in the axial direction, as shown in Figure 7 . Thus, when the axial dimension is small (L < B), diverse modification options (bevel surface, convex surface, concave surface) are provided to flexibly adapt to different load distributions and compensation requirements. When the axial dimension is large (L > B), bevel surface (or conical surface) modification is mainly adopted to effectively compensate for the non-uniform deformation or inclination that may occur when the long tooth width structure is under preloading. This targeted design enables the backlash-preventing pre-pressure to be transmitted more evenly and stably to the entire meshing tooth surface, achieving high-precision and high-reliability transmission effects for various size specifications.

[0050] In some examples, as shown in Figure 4 , Figure 5 , Figure 6 and Figure 7 , the preset modification angle is 0° to 2°. Thus, by precisely limiting the preset modification angle of the tooth profile modification within the range of 0° to 2°, while ensuring sufficient compensation for the tooth profile offloading caused by the radial elastic deformation and installation error of the planetary gear 10, the effective contact area of the tooth surface can be maintained to the greatest extent. This small angle is sufficient to optimize the load distribution, avoid stress concentration at the tooth ends, and will not cause uneven contact problems during the meshing process of the tooth part 14 due to excessive modification amount. In this way, the transmission smoothness and durability can be effectively improved while ensuring the efficiency and reliability of the backlash-preventing structure.

[0051] In one embodiment, this application also provides a planetary gear reducer 1, which includes an internal gear ring 20, a sun gear 30, and at least two planetary gears 10. The sun gear 30 and each planetary gear 10 are rotatably disposed in the internal gear ring 20, and each planetary gear 10 is meshed with the sun gear 30 and the internal gear ring 20. Thus, since the planetary gear reducer 1 of this application embodiment can be equipped with the planetary gears 10 described in the above embodiment, the backlash of the planetary gear reducer 1 can be effectively reduced or eliminated, thereby significantly improving the transmission accuracy, repeatability, and transmission performance of the planetary gear reducer 1.

[0052] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application.

Claims

1. A planetary gear, used in a planetary gear reducer, characterized in that, The planetary gear has a preset thin-walled structure. The preset thin-walled structure is configured to apply a preset pressure value to the first meshing part and the second meshing part respectively by causing the planetary gear to undergo radial elastic deformation under the action of the assembly preload force when the planetary gear is assembled in the planetary gear reducer, so as to offset the side clearance reserved in the first meshing part and the second meshing part respectively. The first meshing part is the meshing part between the planetary gear and the internal gear ring of the planetary gear reducer; the second meshing part is the meshing part between the planetary gear and the sun gear of the planetary gear reducer; the preset pressure value is 3% to 15% of the meshing force required for the rated output torque of the planetary gear reducer; the preset thin-walled structure meets the condition: h / r ≤ 0.3, where h is the tooth root wall thickness of the planetary gear and r is the radius of the center circle of the tooth root wall thickness of the planetary gear; The planetary gear has an annular inner groove recessed on at least one side surface, and the annular inner groove is located between the cylindrical part of the planetary gear and the bearing seat part of the planetary gear. The planetary gear is further modified along its tooth length by a preset modification angle, and the shape of the tooth modification corresponds to the size relationship between the groove depth of the annular inner groove and the tooth width of the planetary gear.

2. The planetary gear according to claim 1, characterized in that, The planetary gear is made of a gear material with a preset elastic modulus, so that the planetary gear has a preset thin-walled structure.

3. The planetary gear according to claim 2, characterized in that, The preset elastic modulus is less than or equal to 210 GPa.

4. The planetary gear according to claim 2, characterized in that, The gear material can be any one of resin material, metal alloy material, composite material, or amorphous alloy material.

5. The planetary gear according to claim 1, characterized in that, The cylindrical portion of the planetary gear is connected to the bearing housing portion of the planetary gear through the bottom of the annular inner groove, and the bottom of the annular inner groove is configured as a curved structure that can cause the planetary gear to undergo radial deformation.

6. The planetary gear according to claim 1, characterized in that, The preset shaping angle is 0° to 2°.

7. A planetary gear reducer, characterized in that, The planetary gear reducer includes an internal gear ring, a sun gear, and at least two planetary gears as described in any one of claims 1-6. The sun gear and each of the planetary gears are rotatably disposed in the internal gear ring, and each of the planetary gears is meshed with the sun gear and the internal gear ring.

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