Harmonic reduction gear

Abstract

The present application discloses a harmonic reduction device, which includes a wave generator, a flexspline, a first rigid gear and a second rigid gear. The wave generator can be driven to rotate about the central axis. The periphery of the flexspline has a plurality of first external tooth-like structures, separation grooves and a plurality of second external tooth-like structures. The first rigid gear includes a plurality of first internal tooth-like structures for meshing with the plurality of first external tooth-like structures. The second rigid gear includes a plurality of second internal tooth-like structures for meshing with the plurality of second external tooth-like structures. The included angle between the first intersection line of the first top surface and the cross-section of each first internal tooth-like structure and the first horizontal line is between 0.1 and 5 degrees. The distance between the first intersection line and the central axis in the cross-section gradually decreases from the inner side to the outer side of the first rigid gear. The normal line of the cross-section is perpendicular to the central axis, and the central axis passes through the cross-section.

Description

Technical Field

[0001] The present application relates to a speed reduction device, in particular to a harmonic speed reduction device with two rigid wheels. Background Art

[0002] Please refer to Figure 1 , which shows a partial cross-sectional schematic view of a known double rigid wheel harmonic speed reduction device. After the flexible gear F of the known double rigid wheel harmonic speed reduction device is installed on the periphery of the wave generator WG, the outer toothed structure F1 of the flexible gear F will be deformed, and interference will occur between the deformed outer toothed structure F1 and the inner toothed structures R11 and R21 respectively possessed by the two rigid wheels R1 and R2 (i.e., Figure 1 the circled part A in Summary of the Invention

[0003] The present application discloses a harmonic speed reduction device, which is mainly used to improve the problems of poor meshing efficiency and low service life existing in the known double rigid wheel harmonic speed reduction device.

[0004] One embodiment of the present application discloses a harmonic reduction device, which includes: a wave generator for connecting to a driving unit, the wave generator can be driven by the driving unit and rotate around a central axis; a flexible gear connected to the periphery of the wave generator, the periphery of the flexible gear has a plurality of first external tooth-like structures, a plurality of second external tooth-like structures and a separation groove, and the separation groove is located between each first external tooth-like structure and each second external tooth-like structure; two rigid gears, respectively defined as a first rigid gear and a second rigid gear, the first rigid gear includes a plurality of first internal tooth-like structures, the second rigid gear includes a plurality of second internal tooth-like structures, the plurality of first internal tooth-like structures are used to mesh with the plurality of first external tooth-like structures, and the plurality of second internal tooth-like structures are used to mesh with the plurality of second external tooth-like structures; the number of the plurality of first internal tooth-like structures included in the first rigid gear is the same as the number of the plurality of first external tooth-like structures included in the flexible gear, and the number of the plurality of second internal tooth-like structures included in the second rigid gear is greater than the number of the plurality of second external tooth-like structures included in the flexible gear; the two opposite sides of the first rigid gear are respectively defined as an inner side and an outer side, the two opposite sides of the second rigid gear are respectively defined as an inner side and an outer side, the first rigid gear and the second rigid gear are arranged adjacent to each other, and the inner side of the first rigid gear and the inner side of the second rigid gear are arranged facing each other; each of the first internal tooth-like structures of the first rigid gear includes a first top surface and four first connecting surfaces, and the four first connecting surfaces are connected to the four side lines of the first top surface; a first intersection line between each first top surface and a cross-section and a first included angle between a first horizontal line parallel to the central axis are between 0.1 and 5 degrees, and in the cross-section, the linear distance between the first intersection line and the central axis gradually decreases from the inner side of the first rigid gear to the outer side of the first rigid gear, the normal direction of the cross-section is perpendicular to the central axis, and the central axis passes through the cross-section.

[0005] Optionally, the maximum radial dimension of the flexible gear deformed by the wave generator is defined as a flexible gear major axis, and the minimum radial dimension of the flexible gear deformed by the wave generator is defined as a flexible gear minor axis; wherein, the flexible gear major axis is defined as C L , the flexible gear minor axis is defined as C S , the width of a first tooth surface of each first internal tooth-like structure is defined as L1, the first included angle is defined as θ1, and C L 、C S 、L1、θ1 satisfy the relationship of θ1 = C1 * tan -1 ((C L - C S ) / (4 * L1)), where 0.08 ≤ C1 ≤ 0.45.

[0006] Optionally, each second internal tooth-shaped structure of the second rigid gear includes a second top surface and four second connecting surfaces, and the four second connecting surfaces are connected to the four side lines of the second top surface; a second intersection line between each second top surface and the cross-section forms a second included angle with a second horizontal line parallel to the central axis, and the second included angle is between 0.1 and 5 degrees. In the cross-section, the linear distance between the second intersection line and the central axis gradually decreases from the inner side to the outer side of the second rigid gear.

[0007] Optionally, the maximum radial dimension at which the flexible gear is deformed by the wave generator is defined as a flexible gear major axis, and the minimum radial dimension at which the flexible gear is deformed by the wave generator is defined as a flexible gear minor axis; wherein, the flexible gear major axis is defined as C L , and the flexible gear minor axis is defined as C S , the tooth face width of each second internal tooth-shaped structure is defined as L2, the second included angle is defined as θ2, and C L , C S , L2, and θ2 satisfy the relationship of θ2 = C2 * tan -1 ((C L - C S ) / (4 * L2)), where 0.08 ≤ C2 ≤ 0.45.

[0008] Optionally, the flexible gear is defined with an annular body, each first external tooth-shaped structure is formed on the periphery of the annular body, each second external tooth-shaped structure is formed on the periphery of the annular body, and a separation groove is formed between the multiple first external tooth-shaped structures and the multiple second external tooth-shaped structures.

[0009] Optionally, the addendum circle diameter of the first external tooth-shaped structure is defined as D a1 , the dedendum circle diameter of the first external tooth-shaped structure is defined as D f1 , the addendum circle diameter of the second external tooth-shaped structure is defined as D a2 , the dedendum circle diameter of the second external tooth-shaped structure is defined as D f2 , and the width of the separation groove is defined as W G ; wherein, when D f1 < D f2 , D f1 , D a2 , and W G satisfy the following relationship:

[0010] 3.5 ≤ R ≤ 20.8; wherein, when D f1 > D f2 ,

[0011] D a1 , Df2 and W G conforms to the following relational expression:

[0012] 3.5 ≤ R ≤ 20.8;

[0013] Among them, the flexspline is defined to have a first annular portion, a second annular portion and a connecting annular portion. One side of the first annular portion is connected to the connecting annular portion, and the other side of the connecting annular portion is connected to the second annular portion. A plurality of first external tooth-like structures are formed on the periphery of the first annular portion, and a plurality of second external tooth-like structures are formed on the periphery of the second annular portion. The periphery of the connecting annular portion, the plurality of first external tooth-like structures and the plurality of second external tooth-like structures together form a partition groove; among them, the thickness of the first annular portion is defined as t1, the thickness of the second annular portion is defined as t2, the thickness of the connecting annular portion is defined as t3, and the inner diameter of the flexspline is defined as D b ; where t1 = (D f1 - D b ) / 2, t2 = (D f2 - D b ) / 2; when t1 < t2, then t1 ≤ t3 ≤ t2; when t1 > t2, t2 ≤ t3 ≤ t1.

[0014] Optionally, each of the first external tooth-like structures and each of the second external tooth-like structures have the same shape.

[0015] Optionally, each of the first external tooth-like structures and each of the second external tooth-like structures have different shapes, and each of the first external tooth-like structures or each of the second external tooth-like structures is a straight tooth structure.

[0016] In summary, through the design of the first angle, the second angle and the partition groove, the harmonic reduction device of the present application can effectively improve the meshing efficiency between the first external tooth-like structure of the flexspline and the first internal tooth-like structure of the first rigid gear, and the meshing efficiency between the second external tooth-like structure of the flexspline and the second internal tooth-like structure of the second rigid gear, thereby improving the service life of the harmonic reduction device.

[0017] To further understand the features and technical content of the present application, please refer to the following detailed description and drawings of the present application. However, these descriptions and drawings are only used to illustrate the present application and do not impose any limitation on the protection scope of the present application. Brief Description of the Drawings

[0018] Figure 1 It is a partial cross-sectional schematic view of a known double rigid gear harmonic reduction device.

[0019] Figure 2 It is a schematic view of the harmonic reduction device of the present application.

[0020] Figure 3Schematic cross-sectional view of the harmonic reduction gear of the present application.

[0021] Figure 4 Exploded schematic view of the harmonic reduction gear of the present application.

[0022] Figure 5 Along Figure 2 Schematic cross-sectional view taken along section line V-V.

[0023] Figure 6 Is Figure 5 Partial enlarged schematic view of.

[0024] Figure 7 Partial cross-sectional schematic view of the first rigid gear and the second rigid gear of the harmonic reduction gear of the present application.

[0025] Figure 8 Partial cross-sectional schematic view of the first rigid gear of the harmonic reduction gear of the present application.

[0026] Figure 9 Partial cross-sectional schematic view of the second rigid gear of the harmonic reduction gear of the present application.

[0027] Figure 10 Partial cross-sectional schematic view of the flexspline of the harmonic reduction gear of the present application.

[0028] Figure 11 Schematic views of the flexspline of the harmonic reduction gear of the present application before and after deformation.

[0029] Figure 12 Partial cross-sectional schematic view of the flexspline of the harmonic reduction gear of the present application.

[0030] Figure 13 Cross-sectional schematic view of the flexspline of the harmonic reduction gear of the present application. Detailed Description of the Invention

[0031] In the following description, if a specific figure is referred to or as shown in a specific figure, it is only used to emphasize that in the subsequent description, most of the relevant content mentioned appears in that specific figure, but does not limit that only the specific figure can be referred to in the subsequent description.

[0032] Please refer to Figures 2 to 6 together. The harmonic reduction gear 100 of the present application includes a wave generator 1, a flexspline 2, and two rigid gears. The flexspline 2 is disposed around the wave generator 1, and the two rigid gears are disposed around the flexspline 2. For the convenience of description, in the following description, the two rigid gears are respectively defined as a first rigid gear 3 and a second rigid gear 4, and the multiple internal toothed structures respectively included in the first rigid gear 3 and the second rigid gear 4 are respectively defined as a first internal toothed structure 31 and a second internal toothed structure 41.

[0033] The wave generator (Wave Generator) 1 is used to connect to a driving unit (such as the rotating shaft of a motor, the rotor of a motor, etc.). The wave generator 1 can be driven by the driving unit and rotate around a central axis CP.

[0034] The flexspline 2 is connected to the periphery of the wave generator 1. The flexspline 2 defines an annular body 2A. Each first external tooth-like structure 21 is formed on the periphery of the annular body 2A. Each second external tooth-like structure 22 is formed on the periphery of the annular body 2A. A separation groove 2B is formed between the plurality of first external tooth-like structures 21 and the plurality of second external tooth-like structures 22.

[0035] In one embodiment, the shape of each first external tooth-like structure 21 can be exactly the same as the shape of each second external tooth-like structure 22, and the number of all first external tooth-like structures 21 included in the flexspline 2 and the number of all second external tooth-like structures 22 included in the flexspline 2 can be exactly the same, but this is not a limitation. In different embodiments, the shape of each first external tooth-like structure 21 can also be different from the shape of each second external tooth-like structure 22. For example, the plurality of first external tooth-like structures 21 can be straight tooth designs, while the plurality of second external tooth-like structures 22 can be non-straight tooth designs.

[0036] The first rigid gear 3 includes a plurality of first internal tooth-like structures 31. The plurality of first internal tooth-like structures 31 included in the first rigid gear 3 are used to mesh with the plurality of first external tooth-like structures 21 of the flexspline 2. The second rigid gear 4 includes a plurality of second internal tooth-like structures 41. The plurality of second internal tooth-like structures 41 included in the second rigid gear 4 are used to mesh with the plurality of second external tooth-like structures 22 of the flexspline 2. In practical applications, the second rigid gear 4 can be connected to an external output member. For example, the second rigid gear 4 can be directly or indirectly connected to components such as wheels and arms.

[0037] The first rigid gear 3 and the second rigid gear 4 are arranged adjacent to each other. The two opposite sides of the first rigid gear 3 are respectively defined as an inner side 3A and an outer side 3B. The two opposite sides of the second rigid gear 4 are respectively defined as an inner side 4A and an outer side 4B. And the inner side 3A of the first rigid gear 3 is arranged facing the inner side 4A of the second rigid gear 4.

[0038] As described above, in one specific application, the number of the plurality of first external tooth-like structures 21 included in the flexspline 2 can be the same as the number of the plurality of second external tooth-like structures 22 included in the flexspline 2. And the number of the plurality of first internal tooth-like structures 31 included in the first rigid gear 3 can be the same as the number of the plurality of first external tooth-like structures 21 of the flexspline 2. And the number of the plurality of second internal tooth-like structures 41 included in the second rigid gear 4 is greater than the number of the plurality of second external tooth-like structures 22 included in the flexspline 2.

[0039] Continuing from the above, when the driving unit drives the wave generator 1 to actuate, the wave generator 1 will drive the flexible gear 2 to flexibly deform repeatedly. A part of the multiple first external tooth-like structures 21 of the flexible gear 2 will mesh with a part of the multiple first internal tooth-like structures 31 of the first rigid gear 3. Since the number of the first internal tooth-like structures 31 included in the first rigid gear 3 is the same as the number of the first external tooth-like structures 21 included in the flexible gear 2, when the flexible gear 2 flexibly deforms repeatedly, the flexible gear 2 will not rotate relative to the first rigid gear 3. Instead, a part of the second external tooth-like structures 22 of the repeatedly flexibly deformed flexible gear 2 will mesh with a part of the second internal tooth-like structures 41 of the second rigid gear 4. Since the number of the second external tooth-like structures 22 included in the flexible gear 2 is different from the number of the second internal tooth-like structures 41 of the second rigid gear 4, the second rigid gear 4 will be driven by the repeatedly flexibly deformed flexible gear 2 to rotate. In this way, the high-speed power input by the driving unit will be output by the second rigid gear 4 at a relatively low speed.

[0040] Please refer to Figures 4 to 8 together. Each of the first internal tooth-like structures 31 of the first rigid gear 3 includes a top surface 311 and four connecting surfaces 312. The four connecting surfaces 312 are connected to the four side lines of the top surface 311. An intersection line 3111 between each top surface 311 and a cross-section S forms a first included angle θ1 with a first horizontal line H1 parallel to the central axis CP, and the first included angle θ1 is between 0.1 and 5 degrees. And in the cross-section S, the straight-line distance between the intersection line 3111 and the central axis CP gradually decreases from the inner side 3A to the outer side 3B. Among them, a normal direction N of the cross-section S is perpendicular to the central axis CP, and the central axis CP passes through the cross-section S.

[0041] Similarly, each of the second internal tooth-like structures 41 of the second rigid gear 4 includes a top surface 411 and four connecting surfaces 412. The four connecting surfaces 412 are connected to the four side lines of the top surface 411. An intersection line 4111 between each top surface 411 and the cross-section S forms a second included angle θ2 with a second horizontal line H2 parallel to the central axis CP, and the second included angle θ2 is between 0.1 and 5 degrees. And in the cross-section S, the straight-line distance D2 between the intersection line 4111 and the central axis CP gradually decreases from the inner side 4A to the outer side 4B.

[0042] As described above, through the designs of the first included angle θ1, the second included angle θ2, the separating groove 2B, etc., the flexible gear 2 can be axially positioned, and the meshing efficiency between the flexible gear 2 and the two rigid gears and the load-bearing capacity of the harmonic reduction device 100 can be effectively improved. Moreover, the overall service life of the harmonic reduction device 100 can be further extended.

[0043] Such as Figure 1 , Figure 2 , Figure 4 and Figure 5As shown, in the known harmonic speed reducer Q, the periphery of the flexible gear F does not have the separation groove 2B of the flexible gear 2 of the present application. When the known flexible gear F is installed on the periphery of the wave generator WG, the external tooth structure F1 of the flexible gear F will undergo relatively obvious deformation. Moreover, after the two rigid gears R1 and R2 are combined with the flexible gear F, since the external tooth structure F1 of the flexible gear F has been deformed, the flexible gear F is prone to axial displacement. For this reason, the meshing efficiency of the internal tooth structures R11 and R21 of the two rigid gears R1 and R2 with the external tooth structure F1 of the flexible gear F will be poor, and furthermore, it may lead to a decrease in the overall service life of the harmonic speed reducer Q.

[0044] In addition, due to the relatively obvious deformation of the external tooth structure F1 of the known flexible gear F in the known harmonic speed reducer Q, during the operation of the known harmonic speed reducer Q, the flexible gear F is prone to the problem of left - right shaking. On the contrary, in the harmonic speed reducer 100 of the present application, by providing the flexible gear 2 with a separation groove 2B, a first included angle θ1 (as Figure 8 shown) and a second included angle θ2 (as Figure 9 shown), etc., during the operation of the harmonic speed reducer 100, the flexible gear 2 is relatively not prone to the problem of left - right shaking.

[0045] Please refer to Figures 7 to 12 together. In a preferred embodiment, the maximum radial dimension by which the flexible gear 2 is deformed by the wave generator is defined as a flexible gear major axis, and the minimum radial dimension by which the flexible gear 2 is deformed by the wave generator is defined as a flexible gear minor axis; assuming the flexible gear major axis is defined as C L , and the flexible gear minor axis is defined as C S , the width of a first tooth surface of each first internal tooth structure 31 is defined as L1, the first included angle is defined as θ1, the width of a second tooth surface of each second internal tooth structure 41 is defined as L2, and the second included angle is defined as θ2. Then C L , C S , L1, and θ1 satisfy the relation θ1 = C1 * tan -1 ((C L - C S ) / (4 * L1)), where 0.08 ≤ C1 ≤ 0.45; C L , C S , L2, and θ2 satisfy the relation θ2 = C2 * tan -1 ((C L - C S ) / (4 * L2)), where 0.08 ≤ C2 ≤ 0.45. In this way, the flexible gear 2, the first rigid gear 3, and the second rigid gear 4 can achieve relatively better meshing efficiency.

[0046] Please refer to Figures 7 to 13, in a preferred embodiment, the annular body 2A of the flexible gear 2 may be defined with a first annular portion 2A1, a second annular portion 2A2, and a connecting annular portion 2A3. One side of the first annular portion 2A1 is connected to the connecting annular portion 2A3, and the other side of the connecting annular portion 2A3 is connected to the second annular portion 2A2. A plurality of first external tooth-like structures 21 are formed on the periphery of the first annular portion 2A1, and a plurality of second external tooth-like structures 22 are formed on the periphery of the second annular portion 2A2. The periphery of the connecting annular portion 2A3, the plurality of first external tooth-like structures 21, and the plurality of second external tooth-like structures 22 together form a separation groove 2B. The addendum circle diameter of the first external tooth-like structure 21 is defined as D a1 , the dedendum circle diameter of the first external tooth-like structure 21 is defined as D f1 , the addendum circle diameter of the second external tooth-like structure 22 is defined as D a2 , the dedendum circle diameter of the second external tooth-like structure 22 is defined as D f2 , the width of the separation groove 2B is defined as W G ; wherein, when D f1 < D f2 , D f1 , D a2 , W G comply with the following relationship:

[0047] 3.5 ≤ R ≤ 20.8;

[0048] wherein, when D f1 > D f2 , D f2 , D a1 , W G comply with the following relationship:

[0049] 3.5 ≤ R ≤ 20.8;

[0050] wherein, the thickness of the first annular portion 2A1 is defined as t1, the thickness of the second annular portion 2A2 is defined as t2, the thickness of the connecting annular portion 2A3 is defined as t3, and the inner diameter of the flexible gear 2 is defined as D b ; wherein, t1 = (D f1 - D b ) / 2, t2 = (D f2 - D b ) / 2; when t1 < t2, then t1 ≤ t3 ≤ t2; when t1 > t2, t2 ≤ t3 ≤ t1.

[0051] As described above, through the above design, the flexspline 2, the first rigid spline 3 and the second rigid spline 4 can achieve relatively better meshing efficiency.

[0052] In summary, through the design of the first angle, the second angle and the separation groove, the harmonic reduction device of the present application can effectively improve the meshing efficiency between the first external tooth-like structure of the flexspline and the first internal tooth-like structure of the first rigid spline, and the meshing efficiency between the second external tooth-like structure of the flexspline and the second internal tooth-like structure of the second rigid spline, thereby improving the service life of the harmonic reduction device. In addition, by making the first angle, the second angle and the flexspline conform to the above relational expressions, the meshing efficiency between the flexspline and the first rigid spline, and the meshing efficiency between the flexspline and the second rigid spline can be further improved.

[0053] The above is only the preferred feasible embodiment of the present application, and does not limit the patent scope of the present application. Therefore, all equivalent technical changes made by using the content of the specification and drawings of the present application are included in the protection scope of the present application.

Claims

1. A harmonic reduction device, characterized in that, The harmonic speed reducer device includes: A wave generator for connecting to a driving unit, which can be driven by the driving unit and rotate about a central axis; A flexible gear connected to the periphery of the wave generator. The periphery of the flexible gear has a plurality of first external tooth-like structures, a plurality of second external tooth-like structures, and a separation groove located between each first external tooth-like structure and each second external tooth-like structure; the number of all the first external tooth-like structures included in the flexible gear and the number of all the second external tooth-like structures included in the flexible gear are exactly the same; Two rigid gears, respectively defined as a first rigid gear and a second rigid gear. The first rigid gear includes a plurality of first internal tooth-like structures, and the second rigid gear includes a plurality of second internal tooth-like structures. A plurality of the first internal tooth-like structures are used to mesh with a plurality of the first external tooth-like structures, and a plurality of the second internal tooth-like structures are used to mesh with a plurality of the second external tooth-like structures; The number of the plurality of the first inner tooth-shaped structures included in the first rigid gear is the same as the number of the plurality of the first outer tooth-shaped structures included in the flexible gear, and the number of the plurality of the second inner tooth-shaped structures included in the second rigid gear is greater than the number of the plurality of the second outer tooth-shaped structures included in the flexible gear; two opposite sides of the first rigid gear are respectively defined as an inner side and an outer side, two opposite sides of the second rigid gear are respectively defined as an inner side and an outer side, the first rigid gear and the second rigid gear are arranged adjacent to each other, and the inner side of the first rigid gear and the inner side of the second rigid gear are arranged facing each other; each of the first inner tooth-shaped structures of the first rigid gear includes a first top surface and four first connecting surfaces, and the four first connecting surfaces are connected to the four side lines of the first top surface; a first intersection line of each of the first top surfaces and a cross section and a first horizontal line parallel to the central axis has a first included angle θ1 between 0.1 and 5 degrees, and in the cross section, a linear distance between the first intersection line and the central axis gradually decreases from the inner side of the first rigid gear to the outer side of the first rigid gear, a normal direction of the cross section is perpendicular to the central axis, and the central axis passes through the cross section; a maximum radial dimension of the flexible gear deformed by the wave generator is defined as a flexible gear major axis, and a minimum radial dimension of the flexible gear deformed by the wave generator is defined as a flexible gear minor axis; wherein, the flexible gear major axis is defined as C L , the flexible gear minor axis is defined as C S , a first tooth surface width of each of the first inner tooth-shaped structures is defined as L1, the first included angle is defined as θ1, and C L , C S , L1, and θ1 satisfy the relationship of θ1 = C1 * tan -1 ((C L - C S ) / (4 * L1)), where 0.08≤C1≤0.45。 2. The harmonic reduction gear according to claim 1, characterized in that, Each of the second internal tooth-like structures of the second rigid gear includes a second top surface and four second connecting surfaces, and the four second connecting surfaces are connected to the four side lines of the second top surface; a second intersection line between each second top surface and the cross section and a second horizontal line parallel to the central axis has a second included angle between 0.1 and 5 degrees, and in the cross section, the straight-line distance between the second intersection line and the central axis gradually decreases from the inner side to the outer side of the second rigid gear.

3. The harmonic reduction gear according to claim 2, characterized in that, The maximum radial dimension at which the flexspline is deformed by the wave generator is defined as a major axis of the flexspline, and the minimum radial dimension at which the flexspline is deformed by the wave generator is defined as a minor axis of the flexspline; wherein, the major axis of the flexspline is defined as C L , the minor axis of the flexspline is defined as C S , the width of a second tooth surface of each of the second internal tooth-shaped structures is defined as L2, the second included angle is defined as θ2, and C L , C S , L2, and θ2 satisfy the relation θ2 = C2 * tan -1 ((C L - C S ) / (4 * L2)), where 0.08 ≤ C2 ≤ 0.

45.

4. The harmonic reduction gear device according to claim 1, characterized in that The flexible gear defines an annular body. Each of the first external tooth-like structures is formed on the periphery of the annular body, each of the second external tooth-like structures is formed on the periphery of the annular body, and the separation groove is formed between the plurality of first external tooth-like structures and the plurality of second external tooth-like structures.

5. The harmonic reduction gear according to claim 4, characterized in that, The pitch diameter of the first external toothed structure is defined as D a1 , the root diameter of the first external toothed structure is defined as D f1 , the pitch diameter of the second external toothed structure is defined as D a2 , the root diameter of the second external toothed structure is defined as D f2 , the width of the separation groove is defined as W G ; Among them, at D f1 <D f2 When, D f1 、D a2 、W G Meet the following relational expressions: Among them, at D f1 > D f2 When, D a1 , D f2 , W G Satisfy the following relational expressions: Wherein, the flexspline is defined with a first annular portion, a second annular portion and a connecting annular portion. One side of the first annular portion is connected to the connecting annular portion, and the other side of the connecting annular portion is connected to the second annular portion. A plurality of the first external tooth-like structures are formed on the periphery of the first annular portion, and a plurality of the second external tooth-like structures are formed on the periphery of the second annular portion. The periphery of the connecting annular portion, the plurality of the first external tooth-like structures and the plurality of the second external tooth-like structures together form the separation groove. Wherein, the thickness of the first annular portion is defined as t1, the thickness of the second annular portion is defined as t2, the thickness of the connecting annular portion is defined as t3, and the inner diameter of the flexspline is defined as D b ; wherein, t1 = (D f1 - D b ) / 2, t2 = (D f2 - D b ) / 2; when t1 < t2, then t1 ≤ t3 ≤ t2; when t1 > t2, t2 ≤ t3 ≤ t1.

6. The harmonic reduction gear according to claim 1, characterized in that, Each of the first external tooth-like structures and each of the second external tooth-like structures have the same shape.

7. The harmonic reduction gear according to claim 1, wherein Each of the first external tooth-like structures and each of the second external tooth-like structures have different shapes, and each of the first external tooth-like structures or each of the second external tooth-like structures is a straight-tooth structure.

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