Single pair tooth meshing double rigid wheel harmonic reducer

Abstract

The application provides a single-pair-tooth meshing double-rigid-wheel harmonic reducer, and relates to the technical field of reducers. The outer teeth of the flexible wheel comprise first outer teeth and second outer teeth, the inner teeth of the first rigid wheel are in same-tooth-number spline cooperation with the first outer teeth, and the inner teeth of the second rigid wheel are in two-tooth-difference meshing with the second outer teeth. The application can greatly reduce the backlash, improve the transmission precision, reduce the noise and vibration, and meet the use requirements in the high-precision field.

Description

Technical Field

[0001] The present invention relates to the technical field of reducers, and in particular to a double-rigid-wheel harmonic reducer with a single pair of teeth meshing. Background Art

[0002] Harmonic reducers feature high precision, compact size, and high torque capacity, making them widely used in industrial robotics. Traditional harmonic reducers feature a single rigid wheel structure with a cup-shaped or top-hat-shaped flexspline. The teeth are located in the barrel, and the bottom flange is typically used for torque output. There is a nearly 90° transition between the bottom flange and the straight-barrel teeth. To accommodate the flexible deformation of the flexspline, the wall thickness at this location is relatively thin, typically close to 0.3 mm. This is the weakest point in the harmonic reducer, making it prone to distortion when subjected to high or impact torque, leading to damage and significantly limiting its load capacity and impact resistance.

[0003] In conventional harmonic reducers with dual-rigid gears, the flexspline is annular and lacks the 90° bend found in conventional single-rigid gears. This improves the flexspline's load-bearing capacity and impact resistance. However, due to the meshing of two pairs of teeth, the tooth backlash in conventional harmonic reducers with dual-rigid gears is approximately twice that of a single-rigid gear harmonic reducer, making it difficult to achieve high tooth backlash accuracy. Furthermore, the noise and vibration generated by the additional pair of teeth are significantly greater than those of a single-rigid gear harmonic reducer, making these conventional dual-rigid gear harmonic reducers difficult to apply in high-precision applications. Summary of the Invention

[0004] The purpose of the present invention is to provide a double-rigid-wheel harmonic reducer with a single pair of teeth meshing, which can significantly reduce tooth clearance, improve transmission accuracy, reduce noise and vibration, and meet the use requirements in high-precision fields.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A double-rigid harmonic reducer with a single pair of teeth meshing comprises a wave generator, a flexspline, a first rigid wheel, and a second rigid wheel. The flexspline is arranged outside the wave generator, and the first and second rigid wheels are arranged outside the flexspline. The external teeth of the flexspline include a first external tooth and a second external tooth. The internal teeth of the first rigid wheel and the first external tooth are spline-matched with the same number of teeth, and the internal teeth of the second rigid wheel and the second external tooth are meshed with a two-tooth difference. A first bearing corresponding to the first rigid wheel and a second bearing corresponding to the second rigid wheel are provided between the wave generator and the flexspline. The position where the first bearing is installed on the wave generator is a true circle, and the position where the second bearing is installed is an elliptical cam.

[0007] By adopting the above technical solution, either rigid pulley 1 or rigid pulley 2 serves as the fixed end, while the other serves as the output end. The internal teeth of rigid pulley 2 mesh with the second external teeth of the flexspline by a two-tooth difference, following the same meshing principle as the rigid pulley and flexspline in a single rigid pulley harmonic reducer. The internal teeth of rigid pulley 1 and the first external teeth of the flexspline have the same number of teeth and engage with a spline. This spline fit replaces the 90° angled structure of the flexspline flange in a single rigid pulley harmonic reducer and the meshing engagement and disengagement of the same number of teeth between the rigid pulley and the flexspline in conventional dual rigid pulley harmonic reducers. This significantly reduces the clearance and improves the backlash accuracy, transmission accuracy, and torsional stiffness of the harmonic reducer. In addition, the spline combination of the same number of teeth on the rigid wheel and the flexible wheel changes the meshing of two pairs of teeth of the double rigid wheel harmonic reducer to only one pair of teeth. This not only avoids the noise and vibration caused by processing and assembly errors of the meshing of the same number of teeth, but also improves the stability of the operation of the double rigid wheel harmonic reducer, meets the use requirements in high-precision fields, and avoids the difficulty of tooth shape design caused by the meshing of the same number of teeth, thereby reducing the design difficulty.

[0008] Furthermore, the flexible spline is provided with a thin-walled connecting section between the first external teeth and the second external teeth, and the minimum thickness of the flexible spline at the thin-walled connecting section is 0.2 mm-1 mm.

[0009] By adopting the above technical solution, since the first outer tooth and the rigid wheel 1 are in a spline-locked state, and the second outer tooth and the rigid wheel 2 are in a two-tooth difference meshing state, the force difference between the first outer tooth position and the second outer tooth position on the flexible wheel is greater, and the deformation difference is greater. Therefore, a thin-walled connecting section is provided between the first outer tooth and the second outer tooth, which can generate a slight deformation when the harmonic reducer is running. On the one hand, it can be deformed in the process of the second outer tooth segment of the flexible wheel being stretched into an ellipse and continuously deformed periodically, providing sufficient elastic deformation space for the second outer tooth segment of the flexible wheel. On the other hand, it can play a buffering role in the middle part of the first outer tooth and the second outer tooth, reducing the mutual influence between the first outer tooth and the second outer tooth.

[0010] Furthermore, the first bearing is a flexible bearing or a deep groove ball bearing, the second bearing is a flexible bearing, and under normal conditions, the outer diameters of the first bearing and the second bearing are the same.

[0011] By adopting the above technical solution, Bearing 2 is a flexible bearing mounted outside the elliptical cam of the wave generator. The wave generator props Bearing 2 into an elliptical shape, which in turn props the corresponding second external tooth on the flexible wheel into an elliptical shape, enabling differential tooth number harmonic meshing with rigid wheel 2. The wave generator's corresponding position to Bearing 1 is a true circle, and Bearing 1 is also a true circle. Since Bearing 1 is not propped into an elliptical shape by the wave generator, Bearing 1 can be either a flexible bearing or a conventional deep groove ball bearing, providing flexibility in use. Under normal conditions, the outer diameters of Bearing 1 and Bearing 2 are the same, ensuring that the outer diameters of both ends are identical after the harmonic reducer is assembled.

[0012] Furthermore, the axial spline tooth width of the first external tooth and the axial thickness of the circular gear 1 are both smaller than the axial tooth width of the second external tooth meshing with the circular gear 2, and the axial spline tooth width of the first external tooth and the axial thickness of the circular gear 1 are not less than 2 mm.

[0013] By adopting the above technical solution, the first external tooth of the flexspline is splined with the first rigid wheel, achieving a certain degree of rigidity. The axial spline width of the first external tooth and the axial thickness of the first rigid wheel are both smaller than the axial width of the second external tooth meshing with the second rigid wheel. This minimizes the axial thickness of the harmonic reducer while ensuring rigidity, achieving a certain degree of miniaturization and lightweighting. Specifically, the axial spline width of the first external tooth and the axial thickness of the first rigid wheel are no less than 2mm, ensuring the stability and working performance of the spline fit between the first external tooth and the first rigid wheel.

[0014] Furthermore, the spline fit clearance between the first external tooth and the first gear is 0-1 arc minute.

[0015] By adopting the above technical solution, the spline fit clearance between the first external tooth and the rigid wheel 1 is as small as possible, or is zero, which is better than the ordinary spline fit accuracy, reduces the fit clearance, and improves the tooth gap accuracy and transmission accuracy of the harmonic reducer.

[0016] Furthermore, the axial thickness of the first and second rigid wheels is the same, and a gap of not less than 0.5 mm is provided between them.

[0017] By adopting the above technical solution, the axial thickness of the first and second rigid wheels is the same, and a gap of no less than 0.5 mm is provided between them. The thickness of the first rigid wheel is increased from the side of the first rigid wheel close to the second rigid wheel, thereby improving the rigidity of the first rigid wheel and reducing the axial width of the internal teeth of the first rigid wheel. Among them, a gap of no less than 0.5 mm must be left between the first and second rigid wheels to avoid interference between the first and second rigid wheels.

[0018] Furthermore, the axial tooth width of the inner teeth of the circular gear 1 is smaller than the axial tooth width of the second outer teeth meshing with the circular gear 2, and the axial tooth width of the inner teeth of the circular gear 1 is not less than 1 mm.

[0019] By adopting the above technical solution, after the axial thickness of the rigid wheel 1 is increased, the overall rigid wheel 1 is improved. Therefore, the axial tooth width of the inner teeth of the rigid wheel 1 can be designed to be smaller than the axial tooth width of the second outer teeth meshing with the rigid wheel 2 but not less than 1 mm, thereby reducing the design and processing requirements for the axial tooth width of the inner teeth of the rigid wheel 1 and ensuring the spline matching effect between the inner teeth of the rigid wheel 1 and the first outer teeth on the flexible wheel.

[0020] Furthermore, the inner hole of the flexible wheel is conical, the bearing one is a flexible bearing or a deep groove ball bearing, the bearing two is a flexible bearing, and the outer diameter of the bearing one is smaller than the outer diameter of the bearing two; the inner pitch circle of the rigid wheel one is smaller than the inner pitch circle of the rigid wheel two, and the inner diameter corresponding to the first external tooth position on the flexible wheel is smaller than the outer diameter corresponding to the second external tooth position; after the flexible wheel is inserted into the bearing two, the tooth axis of the second external tooth forms an inclination angle β with the inner tooth of the rigid wheel two.

[0021] By adopting the above technical solution, after the flexspline is inserted into the second bearing, the tooth axis of the second external tooth forms an inclination angle β with the internal tooth of the second rigid wheel, so that the gap between the second external tooth of the flexspline and the internal tooth of the second rigid wheel close to the outer end surface is reduced, that is, the meshing gap between the second external tooth of the flexspline and the internal tooth of the second rigid wheel is reduced, and the tooth gap can even be eliminated, thereby improving the tooth gap accuracy of the harmonic reducer, reducing noise and vibration, and further improving the stability of the operation of the harmonic reducer.

[0022] Furthermore, the spline fit between the rigid wheel 1 and the first external tooth is an involute spline fit or a rectangular spline fit.

[0023] By adopting the above technical solution, the spline fit is selected from either involute spline fit or rectangular spline fit. The involute spline has high manufacturing precision, high root strength of the spline teeth, small stress concentration, and is easy to center. It is suitable for connections with large loads, high centering accuracy requirements, and large sizes. The rectangular spline is easy to process, uses a small diameter for centering, and is easy to ensure centering accuracy. It is suitable for light load connections. The involute spline fit or rectangular spline fit can be selected according to the overall size of the harmonic reducer and the occasion of use. The selection is more flexible, effectively improving the scope of application of the present invention and ensuring the working effect.

[0024] Furthermore, the wave generator is provided with a groove or a rib located between the true circle and the elliptical cam.

[0025] By adopting the above technical solution, a groove or a rib is provided on the wave generator to separate the true circle and elliptical cams, which facilitates the processing of the wave generator and avoids interference or influence when processing the true circle and elliptical cams.

[0026] In summary, the present invention has the following beneficial effects:

[0027] 1. Compared with the traditional single-cup or top-hat type flexspline harmonic reducer, the flexspline of the present invention is annular in shape, replacing the 90° angle structure of the cup-shaped or top-hat type flexspline, which is easy to process. In addition, the torque output of the flexspline is achieved by spline-matching the internal teeth of the first flexspline with the first external teeth of the flexspline with the same number of teeth, replacing the torque output of the cup-shaped or top-hat type flexspline flange surface. This eliminates the possibility of failure at the thin-walled position of the flange surface and greatly enhances the impact resistance of the harmonic reducer.

[0028] 2. Compared with the conventional double-rigid-gear harmonic reducer, the spline fit of the inner teeth of the first rigid wheel and the first external teeth of the flexspline with the same number of teeth replaces the meshing mode, which greatly reduces the matching clearance between the first rigid wheel and the flexspline, and improves the tooth clearance accuracy, transmission accuracy and torsional stiffness of the double-rigid-gear harmonic reducer;

[0029] 3. In the present invention, the rigid wheel and the flexible wheel with the same number of teeth are splined, so that the double rigid wheel harmonic reducer is changed from two pairs of teeth meshing to only one pair of teeth meshing. This not only avoids the noise and vibration caused by processing and assembly errors of the same number of teeth meshing, improves the operation stability of the double rigid wheel harmonic reducer, but also avoids the difficulty of tooth profile design caused by the same number of teeth meshing, reducing the design difficulty.

[0030] 4. In the present invention, a thin-wall transition section is provided between the first and second outer teeth of the flexible spline. The thin-wall transition can provide sufficient flexibility for the periodic deformation of the ellipse on the second side of the rigid spline, provide sufficient elastic deformation space for the second outer tooth section of the flexible spline, and play a buffering role in the middle part of the first and second outer teeth, reducing the mutual influence between the first and second outer teeth, thereby reducing the vibration of the harmonic reducer;

[0031] 5. In the present invention, the second internal teeth of the rigid wheel with a differential number of teeth meshing with the axis of the second external teeth of the flexible wheel form an inclination angle, and the meshing gap becomes smaller on the side close to the outer end face of the reducer, and the tooth gap can even be eliminated, thereby improving the tooth gap accuracy of the reducer, while greatly reducing vibration and improving operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the overall structure of a double-rigid-gear harmonic reducer with a single pair of teeth meshing in Example 1;

[0033] Figure 2 Schematic diagram of the meshing of the second rigid wheel and the second external tooth of the flexspline in a double rigid wheel harmonic reducer with a single pair of teeth meshing in Example 1;

[0034] Figure 3 This is a schematic diagram of the meshing of the involute spline of the first rigid wheel and the second external tooth of the flexspline in a double rigid wheel harmonic reducer with a single pair of teeth meshing in Example 1;

[0035] Figure 4 This is a schematic diagram of the meshing of the rectangular spline of the first rigid wheel and the second external tooth of the flexspline in a double rigid wheel harmonic reducer with a single pair of teeth meshing in Example 1;

[0036] Figure 5 This is a schematic structural diagram of a medium wave generator of a double rigid wheel harmonic reducer with a single pair of teeth meshing in Example 1;

[0037] Figure 6 This is a partial structural diagram of a double-rigid-gear harmonic reducer with a single pair of teeth meshing in Example 1;

[0038] Figure 7 This is a schematic structural diagram of a double-rigid-gear harmonic reducer with a single pair of teeth meshing in Example 2;

[0039] Figure 8 This is a structural diagram of a double-gear harmonic reducer with a single pair of teeth meshing in Example 3.

[0040] In the figure, 1. wave generator; 11. true circle; 12. elliptical cam; 13. groove; 2. flexible spline; 21. first external tooth; 22. second external tooth; 23. thin-walled connecting section; 3. rigid wheel 1; 4. rigid wheel 2; 5. bearing 1; 6. bearing 2. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] Example 1:

[0043] A double-gear harmonic reducer with a single pair of teeth meshing, such as Figure 1 As shown, it includes a wave generator 1, bearing 1 5, bearing 2 6, flexspline 2, rigid pulley 1 3, and rigid pulley 2 4. Bearing 1 5 and bearing 2 6 are installed between wave generator 1 and flexspline 2, while rigid pulley 1 3 and rigid pulley 2 4 are installed outside flexspline 2, with rigid pulley 1 3 corresponding to bearing 1 5, and rigid pulley 2 4 corresponding to bearing 2 6. Either rigid pulley 1 3 or rigid pulley 2 4 serves as the fixed end, while the other serves as the output end. Its basic operating principle is the same as that of a double rigid pulley harmonic reducer in the prior art.

[0044] like Figure 1 and Figure 2 As shown, in this embodiment, the external teeth of the flexible spline 2 include two sections, the first external teeth 21 and the second external teeth 22. The internal teeth of the rigid spline 2 4 mesh with the second external teeth 22 of the flexible spline 2, and the internal teeth of the rigid spline 2 4 have two more teeth than the second external teeth 22 of the flexible spline 2. In other words, the rigid spline 2 4 and the flexible spline 2 mesh with a two-tooth difference. The meshing principle between the two is consistent with the meshing principle between the rigid spline and the flexible spline in a single rigid spline harmonic reducer. Figure 1 As shown, the inner teeth of the rigid wheel 3 mesh with the first outer teeth 21 of the flexible wheel 2, and the two have the same number of teeth and are spline-matched. Figure 3 and Figure 4 As shown, the spline fit between the internal teeth of the rigid wheel 3 and the first external teeth 21 can be either an involute spline fit or a rectangular spline fit, and the specific selection can be made according to the size of the reducer, the actual operating load, and other conditions.

[0045] like Figure 1As shown, the splined coupling of rigid wheel 3 and flexspline 2 replaces the 90° angle of the flexspline flange in a single rigid wheel harmonic reducer. Furthermore, the torque output of rigid wheel 3 is achieved through spline meshing with the same number of teeth, replacing the torque output of the cup-shaped or top-hat-shaped flexspline flange. This eliminates the possibility of failure at thin-walled locations on the flange surface and significantly enhances the harmonic reducer's impact resistance. Furthermore, the splined coupling of rigid wheel 3 and flexspline 2 replaces the meshing engagement of the rigid wheel and flexspline in conventional dual rigid wheel harmonic reducers, significantly reducing the clearance and improving the backlash accuracy, transmission accuracy, and torsional stiffness of the harmonic reducer. In addition, the spline matching of the same number of teeth of the rigid wheel 3 and the flexible wheel 2, and the meshing of the two teeth of the rigid wheel 2 4 and the flexible wheel 2 make the meshing of the two pairs of teeth of the double rigid wheel harmonic reducer be changed to only one pair of teeth. This not only avoids the noise and vibration caused by the processing and assembly errors of the meshing of the same number of teeth, but also improves the operation stability of the double rigid wheel harmonic reducer and avoids the difficulty of tooth shape design of the meshing of the same number of teeth.

[0046] like Figure 1 and Figure 5 As shown, in this embodiment, the section of the wave generator 1 where bearing 1 (5) is mounted is a true circle 11, while the section where bearing 2 (6) is mounted is an elliptical cam 12. Bearing 1 (5) can be either a flexible bearing or a conventional deep-groove ball bearing, while bearing 2 (6) is a flexible bearing. Thus, the elliptical cam 12 of the wave generator 1 props the thin-walled, flexible bearing 2 (6) into an elliptical shape, which in turn props the second external teeth 22 of the flexspline 2 into an elliptical shape, enabling differential harmonic meshing of the second external teeth 22 of the flexspline 2 with the internal teeth of the rigid wheel 2 (4). The corresponding sections of the wave generator 1 and the first external teeth 21 of the flexspline 2 are true circles 11, and bearing 1 (5) also has a corresponding true circle 11. Under normal conditions, the outer diameters of bearing 1 (5) and bearing 2 (6) are identical, ensuring that the two ends of the harmonic reducer are identical in size after assembly.

[0047] like Figure 6 As shown, the wave generator 1 is provided with a groove 13 or rib located between the true circle 11 and the elliptical cam 12. The groove 13 or rib separates the true circle 11 and the elliptical cam 12, facilitating the machining of the wave generator 1 and preventing interference or impact during machining of the true circle 11 and the elliptical cam 12. In this embodiment, the groove 13 is used to separate the true circle 11 and the elliptical cam 12.

[0048] like Figure 6As shown, a thin-walled connecting section 23 is provided on the flexspline 2 between the first outer teeth 21 and the second outer teeth 22, and the thickness of the thinnest part thereof is within the range of 0.2 mm to 1 mm, so as to ensure that the thin-walled connecting section 23 can produce a slight deformation during the operation of the harmonic reducer. On the one hand, the thin-walled connecting section 23 can be deformed in the process of the second outer teeth 22 of the flexspline 2 being supported into an ellipse and continuously deforming periodically, thereby providing sufficient elastic deformation space for the second outer teeth 22 of the flexspline 2. On the other hand, the thin-walled connecting section 23 can play a buffering role in the middle part of the first outer teeth 21 and the second outer teeth 22, thereby reducing the mutual influence between the first outer teeth 21 and the second outer teeth 22.

[0049] like Figure 6 As shown, in this embodiment, the axial spline width of the first external teeth 21 of the flexspline 2 and the axial thickness of the rigid wheel 3 are both smaller than the axial tooth width of the meshing second external teeth 22 and the internal teeth of the rigid wheel 4. However, their minimum tooth width and minimum axial thickness must be no less than 2 mm, and the spline clearance between the first external teeth 21 and the internal teeth of the rigid wheel 3 is between 0 and 1 arc minute. This minimizes the axial thickness of the harmonic reducer while ensuring the spline meshing stiffness between the internal teeth of the rigid wheel 3 and the first external teeth 21. At the same time, the spline clearance between the first external teeth 21 and the internal teeth of the rigid wheel 3 is minimized or zero, achieving better spline fit accuracy than conventional splines. This reduces the clearance and improves both the backlash and transmission accuracy of the harmonic reducer.

[0050] Example 2:

[0051] like Figure 6 and Figure 7 As shown, the difference between the single-pair meshing double-gear harmonic reducer of this embodiment and the one in the first embodiment is that, in this embodiment, the axial thickness of gear 1 3 and gear 2 4 is the same, and a gap of no less than 0.5 mm is provided between them. This prevents interference between gear 1 3 and gear 2 4 by increasing the thickness of gear 1 3 from the side closest to gear 2 4, thereby improving the rigidity of gear 1 3 and reducing the axial width of the internal teeth of gear 1 3. Furthermore, due to the increased axial thickness and enhanced overall rigidity of gear 1 3, the axial width of the internal teeth of gear 1 3 can be reduced accordingly, becoming smaller than the axial width of the meshing second external teeth 22 and gear 2 4, but should be no less than 1 mm, ensuring proper meshing and effective meshing of the internal teeth of gear 1 3 with the first external teeth 21.

[0052] Example 3:

[0053] like Figure 6 and Figure 8As shown, the difference between the single-pair meshing double-rigid harmonic reducer of this embodiment and the embodiment 1 is that, in this embodiment, the inner hole of the flexspline 2 is a tapered structure with a certain taper. Bearing 1 5 can also be a flexible bearing or a conventional deep groove ball bearing. Bearing 2 6 is a flexible bearing, but the outer diameter of bearing 1 5 is smaller than the outer diameter of bearing 2 6, ensuring that both bearing 1 5 and bearing 2 6 can fit within the inner hole of the flexspline 2. Specifically, the inner pitch circle of the flexspline 3 is smaller than the inner pitch circle of the flexspline 2 4, and the inner diameter of the position corresponding to the first outer tooth 21 on the flexspline 2 is smaller than the outer diameter of the position corresponding to the second outer tooth 22. Thus, after the flexspline 2 is inserted into the bearing 2 6, the tooth axis of the second outer tooth 22 forms an inclination angle β with the inner tooth of the flexspline 2 4. This reduces the gap between the second outer tooth 22 of the flexspline 2 and the inner tooth of the flexspline 2 4 near its outer end surface, and can even eliminate the backlash. This improves the backlash accuracy of the reducer, further reduces vibration, and improves the smoothness of the reducer's operation.

[0054] Working principle and usage of the present invention:

[0055] With either rigid wheel 1 3 or rigid wheel 2 4 serving as the fixed end and the other as the output end, the elliptical cam 12 of the wave generator 1 props the second external teeth 22 of the flexspline 2 into an elliptical shape via bearing 2 6, enabling the second external teeth 22 of the flexspline 2 to engage in harmonic meshing with the rigid wheel 2 4 with a differential number of teeth. The second external teeth 22 of the flexspline 2 are splined with the same number of teeth of rigid wheel 1 3, significantly enhancing the harmonic reducer's impact resistance. The single-pair tooth meshing significantly reduces clearance, improving the harmonic reducer's backlash accuracy, transmission accuracy, and torsional stiffness, while also reducing vibration and noise and improving the harmonic reducer's operational stability.

[0056] The foregoing description shows and describes preferred embodiments of the present invention. As previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A double-gear harmonic reducer with a single pair of teeth meshing, characterized by: The invention comprises a wave generator (1), a flexible wheel (2), a rigid wheel 1 (3), and a rigid wheel 2 (4), wherein the flexible wheel (2) is arranged outside the wave generator (1), and the rigid wheel 1 (3) and the rigid wheel 2 (4) are arranged outside the flexible wheel (2); the external teeth of the flexible wheel (2) include a first external tooth (21) and a second external tooth (22), the internal teeth of the rigid wheel 1 (3) and the first external tooth (21) are spline-matched with the same number of teeth, and the internal teeth of the rigid wheel 2 (4) and the second external tooth (22) are meshed with a two-tooth difference; a bearing 1 (5) corresponding to the rigid wheel 1 (3) and a bearing 2 (6) corresponding to the rigid wheel 2 (4) are provided between the wave generator (1) and the flexible wheel (2), and the position where the bearing 1 (5) is installed on the wave generator (1) is a true circle (11), and the position where the bearing 2 (6) is installed is an elliptical cam (12); The spline fit between the rigid wheel 1 (3) and the first external tooth (21) is an involute spline fit or a rectangular spline fit; The wave generator (1) is provided with a groove (13) or a rib located between the true circle (11) and the elliptical cam (12).

2. The double-gear harmonic reducer with single-pair tooth meshing according to claim 1, characterized in that: The flexible wheel (2) is provided with a thin-walled connecting section (23) located between the first outer teeth (21) and the second outer teeth (22), and the minimum thickness of the flexible wheel (2) at the thin-walled connecting section (23) is 0.2 mm to 1 mm.

3. The double-gear harmonic reducer with single-pair tooth meshing according to claim 2, characterized in that: The bearing 1 (5) is a flexible bearing or a deep groove ball bearing, the bearing 2 (6) is a flexible bearing, and under normal conditions, the outer diameters of the bearing 1 (5) and the bearing 2 (6) are the same.

4. The double-gear harmonic reducer with single-pair tooth meshing according to claim 3, characterized in that: The axial spline tooth width of the first external tooth (21) and the axial thickness of the rigid wheel one (3) are both smaller than the axial tooth width of the second external tooth (22) meshing with the rigid wheel two (4), and the axial spline tooth width of the first external tooth (21) and the axial thickness of the rigid wheel one (3) are not less than 2 mm.

5. The double-gear harmonic reducer with a single pair of teeth meshing according to claim 4, characterized in that: The spline fit clearance between the first external tooth (21) and the rigid wheel (3) is 0-1 arc minute.

6. A double-rigid-wheel harmonic reducer with a single pair of teeth meshing according to claim 1, 2 or 3, characterized in that: The axial thickness of the rigid wheel 1 (3) and the rigid wheel 2 (4) is the same, and a gap of not less than 0.5 mm is provided between them.

7. The double-rigid-gear harmonic reducer with a single pair of teeth meshing according to claim 6, characterized in that: The axial tooth width of the inner teeth of the rigid wheel 1 (3) is smaller than the axial tooth width of the second outer teeth (22) meshing with the rigid wheel 2 (4), and the axial tooth width of the inner teeth of the rigid wheel 1 (3) is not less than 1 mm.

8. A double-rigid-gear harmonic reducer with a single pair of teeth meshing according to claim 1 or 2, characterized in that: The inner hole of the flexible wheel (2) is conical, the bearing 1 (5) is a flexible bearing or a deep groove ball bearing, the bearing 2 (6) is a flexible bearing, and the outer diameter of the bearing 1 (5) is smaller than the outer diameter of the bearing 2 (6); the inner pitch circle of the rigid wheel 1 (3) is smaller than the inner pitch circle of the rigid wheel 2 (4), and the inner diameter of the position corresponding to the first outer tooth (21) on the flexible wheel (2) is smaller than the outer diameter of the position corresponding to the second outer tooth (22); after the flexible wheel (2) is inserted into the bearing 2 (6), the tooth axis of the second outer tooth (22) forms an inclination angle β with the inner tooth of the rigid wheel 2 (4).

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