Ultra-thin robot rotary joint with non-metallic planetary reduction
By using a non-metallic NGWNII-type planetary gear mechanism and a specific material combination, the contradiction between torque density and compactness in robot rotary joints has been resolved, achieving an ultra-thin, compact, and high torque density robot rotary joint design that meets the requirements of high precision and large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NAT INST OF INTELLIGENT ROBOTICS SHENYANG CO LTD
- Filing Date
- 2025-09-19
- Publication Date
- 2026-07-21
AI Technical Summary
Existing robot rotary joints struggle to balance torque density and compactness. Mainstream harmonic reducers and RV reducers each have their shortcomings, resulting in failure to meet high torque requirements and excessive size or insufficient precision.
It adopts a non-metallic NGWNII type planetary gear mechanism, combined with carbon fiber reinforced polyetheretherketone composite material and aluminum alloy, and is designed with a radial concentric layout. It eliminates the traditional planet carrier and uses four-point contact thin-walled bearings and multi-planet gear assembly to achieve compactness and high torque density.
It achieves an ultra-thin design for robot rotary joints, with an axial length of less than 50mm, improved torque density, compact overall structure, low cost, long life, suitable for mass production, and meets high precision requirements.
Smart Images
Figure CN224533363U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of robot rotary joint technology, specifically a non-metallic planetary deceleration ultrathin robot rotary joint. Background Technology
[0002] Currently, humanoid robot rotary joints are caught in an irreconcilable contradiction between "torque density" and "compactness." Mainstream harmonic reducers are limited by the fatigue strength of the flexible gears, with a torque density of ≤25Nm / kg, which cannot meet the load requirements of ≥35Nm / kg for humanoid joints. Although RV reducers can increase torque, their axial dimensions exceed the standard, making them unsuitable for joint cavities in some cases. Traditional two-stage planetary reducers are forced to adopt a double sun gear series structure, with a traditional planet carrier in the middle to transmit power. This results in excessive axial length and thermal deformation of the integral internal gear ring exceeding 0.1mm at a temperature rise of 60℃, expanding the meshing backlash to 3-5 arc-min, far exceeding the motion control requirements (≤1.5 arc-min).
[0003] Existing improvement solutions, such as harmonic planetary cascade and micro RV, have all failed due to material limitations or machining precision, leaving the industry in a stalemate where "high torque inevitably leads to increased volume, and compact design inevitably sacrifices precision." Utility Model Content
[0004] To address the aforementioned problems, the purpose of this invention is to provide an ultra-thin robotic rotary joint with non-metallic planetary deceleration.
[0005] The objective of this utility model is achieved through the following technical solution:
[0006] A non-metallic planetary deceleration ultrathin robot rotary joint includes a fixed housing, an external rotor motor, a sun gear, a planetary gear assembly, an internal gear ring mounting ring A, an internal gear ring A, an internal gear ring mounting ring B, an internal gear ring B, and an output flange.
[0007] One side of the fixed housing is designated as the inner side. A stator mounting portion protrudes from the center of the inner side of the fixed housing. The stator end of the outer rotor motor is mounted on the outer side of the stator mounting portion of the fixed housing. The sun gear is mounted on the outer rotor end of the outer rotor motor. A gear surface C is formed on the outer circumferential surface of the sun gear.
[0008] The internal gear ring mounting ring A is fixed to the inner side of the fixed housing, and the internal gear ring mounting ring A is located outside the sun gear. The internal gear ring A is mounted inside the internal gear ring mounting ring A and is also located outside the sun gear. A gear surface A is formed on the inner circumferential surface of the internal gear ring A.
[0009] The planetary gear assembly is located in the space between the sun gear and the internal gear ring A. The internal gear ring B is located outside the planetary gear assembly. A gear surface B is formed on the inner circumferential surface of the internal gear ring B. The planetary gear assembly meshes with the gear surface C of the sun gear, the gear surface A of the internal gear ring A, and the gear surface B of the internal gear ring B, respectively.
[0010] The internal gear ring mounting ring B is mounted on the outside of the internal gear ring B, and the output flange is mounted on the internal gear ring mounting ring B; the axes of the fixed housing, the external rotor motor, the sun gear, the planetary gear assembly, the internal gear ring mounting ring A, the internal gear ring A, the internal gear ring mounting ring B, the internal gear ring B, and the output flange are all collinear, wherein the sun gear, the planetary gear assembly, the internal gear ring A, and the internal gear ring B constitute an NGWNII type planetary gear mechanism;
[0011] The sun gear, the internal gear ring A, the internal gear ring B, and each of the planetary gears are all made of carbon fiber reinforced polyetheretherketone composite material.
[0012] A bearing mounting step A is formed on the inner side of the fixed housing, and a bearing mounting surface A is formed on the outer circumferential surface of the sun gear at a location corresponding to the bearing mounting step A of the fixed housing. A bearing A is provided between the bearing mounting surface A of the sun gear and the bearing mounting step A of the fixed housing.
[0013] The bearing A is a four-point contact thin-walled bearing.
[0014] A bearing mounting step B is formed on the output flange, and a bearing mounting surface B is formed on the outer circumferential surface of the sun gear at a location corresponding to the bearing mounting step B of the output flange. A bearing B is provided between the bearing mounting surface B of the sun gear and the bearing mounting step B of the output flange.
[0015] The bearing B is a four-point contact thin-walled bearing.
[0016] An outer bearing clamping ring is installed at the outer peripheral edge of the internal gear ring mounting ring B. The integral formed by the internal gear ring mounting ring B and the outer bearing clamping ring is formed with a bearing locking groove A. The integral formed by the internal gear ring mounting ring A and the fixed housing is formed with a bearing locking groove B on its outer peripheral position. The setting position of the bearing locking groove B corresponds to the setting position of the bearing locking groove A, and the bearing locking groove B and the bearing locking groove A are locked together with a bearing C.
[0017] The bearing C is a four-point contact thin-walled bearing.
[0018] The inner circumferential surface of the internal gear ring mounting ring A is provided with a plurality of snap-fit grooves A, and the outer circumferential surface of the internal gear ring A is provided with circumferential keys A at positions corresponding to each snap-fit groove A on the internal gear ring mounting ring A, and each circumferential key A is snapped into the corresponding snap-fit groove A.
[0019] The inner circumferential surface of the internal gear ring mounting ring B is provided with a plurality of snap-fit grooves B, and the outer circumferential surface of the internal gear ring B is provided with circumferential keys B at positions corresponding to each snap-fit groove B on the internal gear ring mounting ring B, and each circumferential key B is snapped into the corresponding snap-fit groove B.
[0020] The planetary gear assembly includes an annular planetary gear cage, planetary gear shafts, washers, planetary gears, and retaining rings. Two corresponding annular planetary gear cages are provided. A plurality of planetary gear shafts are evenly spaced axially between the two annular planetary gear cages. Each planetary gear shaft has two ends passing through a corresponding annular planetary gear cage and is provided with a retaining ring for axial positioning. Two identical planetary gears and a washer are fitted onto each planetary gear shaft between the two annular planetary gear cages. The washer on each planetary gear shaft is used to separate the two planetary gears on that planetary gear shaft.
[0021] Each planetary gear has a gear surface D formed on its outer peripheral surface. The gear surface D of each planetary gear directly meshes with the gear surface C of the sun gear. The gear surface D of each planetary gear also directly meshes with the gear surface A of the corresponding internal gear ring A or the gear surface B of the corresponding internal gear ring B. The axis of each planetary gear shaft, the axis of each planetary gear, and the axis of each gasket are all parallel to the axis of the fixed housing.
[0022] The annular planetary gear cage and each planetary gear shaft are made of POM material, while the fixed housing and output flange are die-cast from aluminum alloy material.
[0023] The advantages and positive effects of this utility model are as follows:
[0024] 1. This utility model, through the setting of the NGWNII type planetary gear mechanism, forms a radial concentric layout, which effectively reduces the transmission chain length, shortens the axial space, increases the torque density, can achieve a larger reduction ratio, improves the uniformity of output torque, increases the total meshing length between the sun gear and planet gear assembly while reducing the single tooth load, and can make the overall axial length of the robot's rotary joint less than 50mm, achieving an ultra-thin level.
[0025] 2. This utility model eliminates the traditional planetary carrier design, maximizes space utilization, has a compact overall structure, low manufacturing cost, and long service life. It is suitable for mass production and humanoid robot applications, can improve processing speed, simplify assembly and maintenance, and optimize design flexibility. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the disassembled structure of this utility model;
[0027] Figure 2 This is a cross-sectional structural diagram of the present invention;
[0028] Figure 3 for Figure 2 Enlarged view of point A.
[0029] In the diagram: 1 is the fixed housing, 101 is the stator mounting part, 2 is the external rotor motor, 3 is the sun gear, 4 is the internal gear ring mounting ring A, 401 is the snap-fit groove A, 5 is the internal gear ring A, 501 is the circumferential key A, 6 is the internal gear ring mounting ring B, 601 is the snap-fit groove B, 7 is the internal gear ring B, 701 is the circumferential key B, 8 is the output flange, 9 is the bearing A, 10 is the bearing B, 11 is the bearing C, 12 is the external bearing clamping ring, 13 is the annular planetary gear cage, 14 is the planetary gear shaft, and 15 is the planetary gear. Detailed Implementation
[0030] The following is in conjunction with the appendix Figure 1-3 The present invention will be described in further detail.
[0031] A non-metallic planetary deceleration ultrathin robotic rotary joint, such as Figure 1-3 As shown, this embodiment includes a fixed housing 1, an external rotor motor 2, a sun gear 3, a planetary gear assembly, an internal gear ring mounting ring A 4, an internal gear ring A 5, an internal gear ring mounting ring B 6, an internal gear ring B 7, and an output flange 8.
[0032] One side of the fixed housing 1 is designated as the inner side. A stator mounting portion 101 protrudes from the center of the inner side of the fixed housing 1. The stator end of the outer rotor motor 2 is mounted to the outer side of the stator mounting portion 101 of the fixed housing 1 by screws. The sun gear 3 is mounted on the outer rotor end of the outer rotor motor 2, and a gear surface C is formed on the outer circumferential surface of the sun gear 3. In this embodiment, the outer rotor motor 2 is a commercially available product. A product with a hollow stator end can be used, and the stator mounting portion 101 can also be hollow, making it easier to install the entire joint. The outer rotor motor 2 is controlled by an external controller. In this embodiment, the outer rotor end of the outer rotor motor 2 and the sun gear 3 are connected by an interference fit and a high-strength adhesive to ensure no relative rotation.
[0033] The internal gear ring mounting ring A4 is fixed to the inner side of the fixed housing 1, and the internal gear ring mounting ring A4 is located outside the sun gear 3. The internal gear ring A5 is mounted inside the internal gear ring mounting ring A4 and is also located outside the sun gear 3. A gear surface A is formed on the inner circumferential surface of the internal gear ring A5.
[0034] The planetary gear assembly is located in the space between the sun gear 3 and the internal gear ring A 5. The internal gear ring B 7 is located outside the planetary gear assembly. A gear surface B is formed on the inner circumferential surface of the internal gear ring B 7. The planetary gear assembly meshes with the gear surface C of the sun gear 3, the gear surface A of the internal gear ring A 5, and the gear surface B of the internal gear ring B 7, respectively.
[0035] An internal gear ring mounting ring B6 is mounted on the outside of an internal gear ring B7, and an output flange 8 is mounted on the internal gear ring mounting ring B6 with screws. The axes of the fixed housing 1, the external rotor motor 2, the sun gear 3, the planetary gear assembly, the internal gear ring mounting ring A4, the internal gear ring A5, the internal gear ring mounting ring B6, the internal gear ring B7, and the output flange 8 are all collinear. The sun gear 3, planetary gear assembly, internal gear ring A5, and internal gear ring B7 constitute an NGWNII type planetary gear mechanism. The fixed housing 1 and the output flange 8 are each provided with several connection holes for connecting to external structures. The output flange 8 directly reuses and outputs the revolution power transmitted by the planetary gear assembly, replacing the output function of the traditional planetary carrier in existing technologies.
[0036] Specifically, such as Figure 2As shown, in this embodiment, a bearing mounting step A is formed on the inner side of the fixed housing 1. A bearing mounting surface A is also formed on the outer peripheral surface of the sun gear 3 at a location corresponding to the bearing mounting step A of the fixed housing 1. A bearing A 9 is provided between the bearing mounting surface A of the sun gear 3 and the bearing mounting step A of the fixed housing 1. In this embodiment, a bearing mounting step B is formed on the output flange 8. A bearing mounting surface B is also formed on the outer peripheral surface of the sun gear 3 at a location corresponding to the bearing mounting step B of the output flange 8. A bearing B10 is provided between the bearing mounting surface B of the sun gear 3 and the bearing mounting step B of the output flange 8. In this embodiment, an outer bearing clamping ring 12 is installed on the outer periphery of the inner gear ring mounting ring B6 by screws. The inner gear ring mounting ring B6 and the outer bearing clamping ring 12 are fixedly connected to form a bearing locking groove A. The inner gear ring mounting ring A4 and the fixed housing 1 are fixedly connected to form a bearing locking groove B on their outer periphery. The position of bearing locking groove B corresponds to the position of bearing locking groove A, and bearing C11 is locked between bearing locking groove B and bearing locking groove A. The specific fit of the bearing mounting step A, bearing mounting surface A, bearing mounting step B, bearing mounting surface B, bearing locking groove A, and bearing locking groove B can be arbitrarily adjusted according to requirements. In this embodiment, bearings A9, B10, and C11 are all four-point contact thin-walled bearings with ceramic rolling elements to simultaneously bear axial and radial loads, maintain concentricity, stabilize rotational accuracy, reduce vibration and noise, further compress axial space, and reduce the overall joint size. The use of ceramic rolling elements reduces friction and improves accuracy. The use of four-point contact thin-walled bearings reduces the width compared to crossed roller bearings, further compressing the axial space and shortening the total joint length by 2% compared to the original design. Each bearing can simultaneously bear bidirectional axial and radial loads through a single set of bearings with a contact angle of 40°. While achieving thin-walled design, it ensures radial stiffness ≥170N / μm and axial stiffness ≥120N / μm, meeting the requirements for supporting composite loads.
[0037] Specifically, such as Figure 1 and Figure 3As shown, in this embodiment, the inner circumferential surface of the internal gear ring mounting ring A4 has several snap-fit grooves A401. The outer circumferential surface of the internal gear ring A5 has circumferential keys A501 protruding at positions corresponding to the snap-fit grooves A401 on the internal gear ring mounting ring A4. Each circumferential key A501 snaps into its corresponding snap-fit groove A401, facilitating the installation, positioning, and power transfer between the internal gear ring mounting ring A4 and the internal gear ring A5. The internal gear ring mounting ring A4 and the internal gear ring A5 can be further bonded and fixed together using a high-strength adhesive. The inner circumferential surface of the internal gear ring mounting ring B6 has several snap-fit grooves B601. The outer circumferential surface of the internal gear ring B7 has circumferential keys B701 protruding at positions corresponding to the snap-fit grooves B601 on the internal gear ring mounting ring B6. Each circumferential key B701 is snapped into the corresponding snap-fit groove B601, which facilitates the installation, positioning and power transfer between the internal gear ring mounting ring B6 and the internal gear ring B7.
[0038] Specifically, such as Figure 1 and Figure 2 As shown, in this embodiment, the planetary gear assembly includes annular planetary gear cages 13, planetary gear shafts 14, gaskets, planetary gears 15, and retaining rings. Two corresponding annular planetary gear cages 13 are provided. A plurality of planetary gear shafts 14 are evenly spaced axially between the two annular planetary gear cages 13. Each planetary gear shaft 14 has two ends passing through a corresponding annular planetary gear cage 13 and is provided with a retaining ring for axial positioning. Two identical planetary gears 15 and a gasket are respectively fitted onto each planetary gear shaft 14 and located between the two annular planetary gear cages 13. The gasket on each planetary gear shaft 14 is used to separate the two planetary gears 15 on that planetary gear shaft 14.
[0039] Each planetary gear 15 has a gear surface D formed on its outer peripheral surface. The gear surface D of each planetary gear 15 directly meshes with the gear surface C of the sun gear 3. The gear surface D of each planetary gear 15 also directly meshes with the gear surface A of the corresponding internal gear ring A 5 or the gear surface B of the internal gear ring B 7. The axis of each planetary gear shaft 14, the axis of each planetary gear 15, and the axis of each washer are all parallel to the axis of the fixed housing 1.
[0040] Specifically, in this embodiment, the sun gear 3, internal gear ring A 5, internal gear ring B 7, and each planet gear 15 can be manufactured using carbon fiber reinforced polyetheretherketone (CF / PEEK) composite material. This effectively ensures strength and can adaptively compensate for gear machining errors, ensuring uniform load distribution among the planet gears and eliminating stress concentration points through floating. In this embodiment, the annular planet gear cage 13 and each planet gear shaft 14 are made of POM material. The fixed housing 1 and the output flange 8 are made of aluminum alloy material, such as 6061-T6 die-casting, and the surface can be hard anodized with an oxide layer thickness of 5-8 μm to further improve wear resistance and corrosion resistance. The aluminum alloy material ensures that even with an ultra-thin structure of 8 mm thickness, it can still withstand an output torque of 200 N·m. The tensile modulus of the CF / PEEK composite material (30-40% carbon fiber content) can reach 30-40 GPa, while the tensile modulus of the aluminum alloy shell (6061-T6) is 69 GPa. Through the precise positioning of the annular planetary gear cage 13, the load-sharing effect of the multiple planetary gears 15, and the rigid support of the four-point contact thin-walled bearing, the overall torsional stiffness is ≥360 N·m / arcmin, meeting the high-precision positioning requirements of the robot. In this embodiment, the overall axial length of the robot's rotary joint can be less than 50 mm, achieving an ultra-thin level, while the typical thickness of existing similar products is 80 mm-150 mm, effectively reducing the overall size.
[0041] In a specific embodiment, the specific parameters of each component are as follows.
[0042] The sun gear 3 has 52 teeth on its gear face C, a module m of 1.5 mm, a pressure angle α of 20°, and a tooth width of 21.4 mm. The sun gear 3 itself is injection molded from 30% carbon fiber reinforced PEEK and then precision ground, achieving a tooth surface roughness Ra ≤ 0.4 μm and a flatness at the connection with the rotor ≤ 0.01 mm, providing a stable power input foundation for the reuse of multiple planetary gears.
[0043] The internal gear ring A5 has 78 teeth on gear face A, a module m of 1.5 mm, and a pressure angle α of 20°. Internal gear ring A5 is a fixed constraint component used in conjunction with the planetary gear assembly, providing a fixed track for the revolution of each planetary gear 15. It is made of 30% carbon fiber reinforced PEEK material through injection molding and machining. The internal teeth are precision ground with a tooth direction tolerance ≤0.008 mm / 100 mm to ensure meshing rigidity.
[0044] The internal gear ring B 7 has 88 teeth on gear face B (Z4 = 88), a module (m = 1.5 mm), and a pressure angle (α = 20°). The internal gear ring B 7 is also made of 30% carbon fiber reinforced PEEK material.
[0045] Each planetary gear 15 has 17 teeth on its gear face D (Z3 = 17), a module (m = 1.5 mm), a pressure angle (α = 20°), and a tooth width of 8 mm. Each planetary gear 15 is made of 30% carbon fiber reinforced PEEK material, hot-pressed and then polished to achieve a surface roughness Ra ≤ 0.4 μm. The reuse design of this planetary gear assembly, which simultaneously undertakes the meshing transmission tasks with the sun gear 3, internal gear ring A5, and internal gear ring B7, is key to achieving a compact structure. By significantly displacing the gear face A of the internal gear ring A5, planetary gear reuse is achieved, along with a radially concentric layout, reducing the transmission chain length, shortening the axial space, and increasing the torque density.
[0046] The annular planetary gear cage 13 is specifically injection molded from glass fiber reinforced POM (containing 25% glass fiber). The annular planetary gear cage 13 has 9-10 mounting holes machined to mate with the planetary gear shafts 14. The hole tolerance grade is IT5, the hole system position tolerance is ≤0.008mm, and the surface roughness Ra=0.8μm. The annular planetary gear cage 13, by eliminating the traditional planetary carrier, precisely constrains the revolution trajectory of each planetary gear 15, ensuring correct meshing clearance with the sun gear 3, internal gear ring A 5, and internal gear ring B 7, without undertaking torque transmission, significantly simplifying the structure and reducing weight. All planetary gear shafts 14 are made of POM material, the retaining rings are made of carbon fiber reinforced PEEK, and the shims are 1mm thick. The mating clearance between the planetary gear shafts 14 and the corresponding mounting holes on the annular planetary gear cage 13 is controlled within 0.01-0.015mm. Considering the differences in thermal expansion characteristics of CF / PEEK, POM and aluminum alloy, the rotational flexibility and structural stability are ensured through reasonable clearance design. The multi-planetary gear reuse form of this utility model is reflected here by the planetary gear 15 on each planetary gear shaft 14 participating in two sets of meshing transmissions at the same time, which shortens the axial dimension by 40% compared with the traditional structure.
[0047] After the external rotor motor 2 is powered on and starts to operate, the stator end of the external rotor motor 2 is fixed on the fixed housing 1. The external rotor end drives the sun gear 3 to rotate synchronously. The sun gear 3 drives each planet gear 15 to rotate. Each planet gear 15 revolves around the fixed internal gear ring A 5 under the constraint of the annular planet gear cage 13 (replacing the traditional planet carrier). Since the traditional planet carrier is eliminated, the revolution motion is converted into low-speed rotation through the meshing of each planet gear 15 with the internal gear ring B 7, and then transmitted to the robot joint rotation component through the output flange 8.
[0048] Based on the kinematic relationship of the double internal gear ring meshing (internal gear ring A5 fixed + internal gear ring B7 output), the reduction ratio formula is: i=(Z2×Z4) / [Z2×(Z4-Z1)-Z1×(Z2-Z1)]. Substituting the aforementioned tooth number parameters, the reduction ratio is approximately 22. This reduction ratio is achieved by the coupling relationship between the output of internal gear ring B7 and the multiple planetary gears 15, which cannot be achieved with the same number of teeth using the output structure of the traditional planetary carrier, demonstrating the superiority of the design combination. Completely eliminating the torque transmission function of the traditional planetary carrier eliminates the structural redundancy caused by the dual requirements of "positioning + torque transmission," allowing the axial length to be shortened by 20%. Using suitable materials can reduce the weight by 15-20%, while avoiding the impact of planetary carrier deformation on meshing accuracy and reducing costs.
[0049] This invention enables a four-way synergy, forming a closed-loop system of "redundancy elimination (elimination of the traditional planetary carrier), precise positioning (setting of the annular planetary gear cage 13), high-efficiency output (setting of the internal gear ring B 7 and output flange 8), and load-sharing compactness (setting of the planetary gear assembly)." Combined with the support of a four-point contact thin-walled bearing, it achieves a comprehensive breakthrough in core indicators such as stiffness, weight, size, and efficiency compared to traditional structures, ensuring high stiffness and ultra-thin characteristics. In this specific embodiment, the overall axial length of the rotary joint can be controlled within 42mm, which is approximately 30% shorter than the traditional structure. The use of lightweight materials contributes to excellent weight reduction.
Claims
1. A non-metallic planetary deceleration ultrathin robot rotary joint, characterized in that: Includes a fixed housing (1), an external rotor motor (2), a sun gear (3), a planetary gear assembly, an internal gear ring mounting ring A (4), an internal gear ring A (5), an internal gear ring mounting ring B (6), an internal gear ring B (7), and an output flange (8); One side of the fixed housing (1) is the inner side, and a stator mounting part (101) is protruding from the middle of the inner side of the fixed housing (1). The stator end of the inner side of the external rotor motor (2) is mounted on the outer side of the stator mounting part (101) of the fixed housing (1). The sun gear (3) is mounted on the outer rotor end of the external rotor motor (2). A gear surface C is formed on the outer peripheral surface of the sun gear (3). The internal gear ring mounting ring A (4) is fixed to the inner side of the fixed housing (1), and the internal gear ring mounting ring A (4) is located on the outer side of the sun gear (3). The internal gear ring A (5) is mounted on the inner side of the internal gear ring mounting ring A (4) and is located on the outer side of the sun gear (3). A gear surface A is formed on the inner circumferential surface of the internal gear ring A (5). The planetary gear assembly is located in the space between the sun gear (3) and the internal gear ring A (5). The internal gear ring B (7) is located outside the planetary gear assembly. A gear surface B is formed on the inner circumferential surface of the internal gear ring B (7). The planetary gear assembly meshes with the gear surface C of the sun gear (3), the gear surface A of the internal gear ring A (5), and the gear surface B of the internal gear ring B (7), respectively. The internal gear ring mounting ring B (6) is mounted on the outside of the internal gear ring B (7), and the output flange (8) is mounted on the internal gear ring mounting ring B (6); the axis of the fixed housing (1), the axis of the external rotor motor (2), the axis of the sun gear (3), the axis of the planetary gear assembly, the axis of the internal gear ring mounting ring A (4), the axis of the internal gear ring A (5), the axis of the internal gear ring mounting ring B (6), the axis of the internal gear ring B (7), and the axis of the output flange (8) are all collinear, wherein the sun gear (3), the planetary gear assembly, the internal gear ring A (5), and the internal gear ring B (7) constitute an NGWNII type planetary gear mechanism; The sun gear (3), the internal gear ring A (5), the internal gear ring B (7), and each of the planetary gears (15) are all made of carbon fiber reinforced polyether ether ketone composite material.
2. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 1, characterized in that: A bearing mounting step A is formed on the inner side of the fixed housing (1), and a bearing mounting surface A is formed on the outer peripheral surface of the sun gear (3) at a position corresponding to the bearing mounting step A of the fixed housing (1). A bearing A (9) is provided between the bearing mounting surface A of the sun gear (3) and the bearing mounting step A of the fixed housing (1).
3. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 2, characterized in that: The bearing A(9) is a four-point contact thin-walled bearing.
4. The ultra-thin robot rotary joint with non-metallic planetary deceleration according to claim 1, characterized in that: A bearing mounting step B is formed on the output flange (8), and a bearing mounting surface B is formed on the outer circumferential surface of the sun gear (3) at a location corresponding to the bearing mounting step B of the output flange (8). A bearing B (10) is provided between the bearing mounting surface B of the sun gear (3) and the bearing mounting step B of the output flange (8).
5. The ultra-thin robot rotary joint with non-metallic planetary deceleration according to claim 4, characterized in that: The bearing B(10) is a four-point contact thin-walled bearing.
6. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 1, characterized in that: An outer bearing clamping ring (12) is installed at the outer peripheral edge of the inner gear ring mounting ring B (6). The inner gear ring mounting ring B (6) and the outer bearing clamping ring (12) are fixedly connected to form a bearing locking groove A. The inner gear ring mounting ring A (4) and the fixed housing (1) are fixedly connected to form a bearing locking groove B at the outer peripheral position. The setting position of the bearing locking groove B corresponds to the setting position of the bearing locking groove A. The bearing locking groove B and the bearing locking groove A are locked together by a bearing C (11).
7. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 6, characterized in that: The bearing C(11) is a four-point contact thin-walled bearing.
8. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 1, characterized in that: The inner circumferential surface of the internal gear ring mounting ring A (4) is provided with a plurality of snap-fit grooves A (401). The outer circumferential surface of the internal gear ring A (5) is provided with circumferential keys A (501) at positions corresponding to each snap-fit groove A (401) on the internal gear ring mounting ring A (4). Each circumferential key A (501) is snapped into the corresponding snap-fit groove A (401). The inner circumferential surface of the internal gear ring mounting ring B (6) is provided with a plurality of snap-fit grooves B (601). The outer circumferential surface of the internal gear ring B (7) is provided with circumferential keys B (701) at positions corresponding to the snap-fit grooves B (601) on the internal gear ring mounting ring B (6). Each circumferential key B (701) is snapped into the corresponding snap-fit groove B (601).
9. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 1, characterized in that: The planetary gear assembly includes an annular planetary gear cage (13), planetary gear shafts (14), gaskets, planetary gears (15), and retaining rings. The annular planetary gear cages (13) are provided in two corresponding positions. A plurality of planetary gear shafts (14) are evenly inserted between the two annular planetary gear cages (13) along the axial direction. Each planetary gear shaft (14) has its two ends passing through a corresponding annular planetary gear cage (13) and is provided with a retaining ring for axial positioning. Each planetary gear shaft (14) is provided with two identical planetary gears (15) and a gasket between the two annular planetary gear cages (13). The gasket on each planetary gear shaft (14) is used to separate the two planetary gears (15) on the planetary gear shaft (14). Each of the planetary gears (15) has a gear surface D formed on its outer peripheral surface. The gear surface D of each planetary gear (15) directly meshes with the gear surface C of the sun gear (3). The gear surface D of each planetary gear (15) also directly meshes with the gear surface A of the corresponding internal gear ring A (5) or the gear surface B of the internal gear ring B (7). The axis of each planetary gear shaft (14), the axis of each planetary gear (15), and the axis of each gasket are all parallel to the axis of the fixed housing (1).
10. The ultrathin robot rotary joint with non-metallic planetary deceleration according to claim 9, characterized in that: The annular planetary gear cage (13) and each planetary gear shaft (14) are made of POM material, and the fixed housing (1) and output flange (8) are die-cast from aluminum alloy material.