Double-rigid-wheel harmonic speed reducer with flexible bearing without inner ring and outer ring

Abstract

The utility model relates to the technical field of harmonic speed reducers, in particular to a double-rigid-wheel harmonic speed reducer with a flexible bearing without an inner ring and an outer ring, which comprises a wave generator, a flexible wheel, a novel flexible bearing, a first rigid wheel, a connecting bearing and a second rigid wheel, the novel flexible bearing comprises a novel outer ring, a novel inner ring and a plurality of rolling bodies, and the flexible wheel is the novel outer ring. The inner surface of the flexible gear is provided with a roller path, the outer surface of the flexible gear is provided with teeth, the wave generator serves as a novel inner ring, the outer surface of the wave generator is provided with a roller path and is of an annular oval structure, at most two rows of rolling bodies are arranged in parallel in the axial direction of the wave generator, and an isolation body is further arranged between every two adjacent rolling bodies in the same row. An inner ring, an outer ring and a retainer of the flexible bearing are reduced, the purposes of reducing the outer diameter of the speed reducer and enabling the structure to be compact are achieved, and meanwhile the failure problem caused by damage of parts is avoided.

Description

Technical Field

[0001] This utility model relates to the field of harmonic reducer technology, specifically to a double rigid wheel harmonic reducer with flexible bearings without inner and outer rings. Background Technology

[0002] Harmonic reducers are flexible reducers that rely on the deformation of flex wheels for transmission. They are mainly composed of a wave generator, a flex wheel, a flexible bearing, and a rigid wheel. When the wave generator rotates inside the flex wheel, it forces the flex wheel to produce continuous elastic deformation. At this time, the continuous rotation of the wave generator causes the flex wheel teeth to continuously change their original meshing state, thereby forming a toothed motion and changing the high-speed input rotation into a low-speed output rotation, thus achieving the purpose of deceleration.

[0003] In existing technologies, cam-type wave generators are common, meaning their outer contour is elliptical rather than circular during transmission. This forces the inner ring of the flexible bearing mounted on the wave generator to become elliptical, leading to issues such as bearing inner ring deformation under pressure, inconsistent interference fit between the bearing inner ring and the wave generator, different contact states between the needle rollers and raceways, and inability to achieve ideal contact during use. Furthermore, the needle rollers and cage within the bearing are constantly in a state of wear and deformation. Under high loads and high-speed rotation, the cage also withstands significant impacts and vibrations, making it highly susceptible to burn-out and breakage. In addition to rotational motion, the flexible wheel and flexible bearing also undergo bending deformation during operation, and high-pair alternating contact stresses are generated between the rolling elements and raceways inside the flexible bearing. Therefore, the motion and stress conditions between the flexible wheel and flexible bearing are quite unique and complex, making them prone to damage and with weak impact resistance. Existing conventional harmonic reducers typically have an efficiency of around 60%, which is low and requires improvement. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is to overcome the defects of flexible bearings in the prior art, thereby providing a double rigid wheel harmonic reducer with flexible bearings without inner and outer rings.

[0005] The above-mentioned technical objective of this utility model is achieved through the following technical solution:

[0006] A dual-rigid-wheel harmonic reducer with a flexible bearing without inner and outer rings includes a wave generator, a flexible wheel, a novel flexible bearing, a first rigid wheel, a connecting bearing, and a second rigid wheel. The first rigid wheel and the second rigid wheel are both mounted on the outside of the flexible wheel. The external teeth of the flexible wheel mesh with the internal teeth of the first rigid wheel and the internal teeth of the second rigid wheel, respectively. A connecting bearing is provided between the first rigid wheel and the second rigid wheel.

[0007] The novel flexible bearing is disposed between the wave generator and the flexible wheel. The novel flexible bearing includes a novel outer ring, a novel inner ring, and a plurality of rolling elements. The novel outer ring is a flexible wheel with raceways on its inner surface and teeth on its outer surface. The wave generator and the novel inner ring are integral components. The outer surface of the wave generator has raceways and has an annular elliptical structure. The rolling elements are arranged in at most two rows along the axial direction of the wave generator. The rolling elements are arranged in a circumferential array along the wave generator. An isolator is also provided between two adjacent rolling elements in the same row.

[0008] By adopting the above technical solution, the outer diameter of the reducer is reduced and the structure is made more compact by reducing the inner and outer rings and cage of the flexible bearing. This eliminates the assembly gap between the wave generator and the inner ring of the flexible bearing, and between the flexible wheel and the outer ring of the flexible bearing, while also avoiding failure problems caused by component damage.

[0009] Furthermore, the rolling elements are arranged in two rows along the axis of the wave generator. The rolling elements are two rows of steel balls or two rows of needle rollers arranged in parallel. The outer surface of the wave generator is provided with corresponding raceways or grooves for the two rows of rolling elements.

[0010] By adopting the above technical solution, the original two flexible bearings are transformed into a single new flexible bearing containing two rows of rolling elements, which greatly improves the impact resistance and anti-lateral swaying ability of the new flexible bearing. At the same time, the single new flexible bearing is easy to install.

[0011] Furthermore, the rolling elements are arranged in a row along the axis of the wave generator. The rolling elements are needle rollers. A receiving ring extends from one end of the wave generator, and a retaining ring is engaged at the other end of the wave generator. The rolling elements are disposed between the receiving ring and the retaining ring.

[0012] By adopting the above technical solution, the installation of the inner and outer rings and the cage of the flexible bearing is eliminated, thus providing a larger selection space for the diameter of the rolling elements. This increases the diameter and number of single-row rolling elements, thereby greatly improving the load capacity of the new flexible bearing. In other words, a single row of rolling elements can achieve the effect of the original single flexible bearing double-row needle roller bearing or double flexible bearing.

[0013] Furthermore, the isolator is a middle spacer block, which is disposed between two adjacent rolling elements and does not contact the inner surface of the flexure or the outer surface of the wave generator on either side. The two ends of the middle spacer block that contact the rolling elements are concave arc surfaces. The axial length of the middle spacer block is not less than half of the axial length of the rolling elements and is not greater than the axial length of the rolling elements.

[0014] By adopting the above technical solution, the intermediate spacer block can appropriately reduce the distance between rolling elements through the contact of the concave arc surface with gaps, thereby increasing the number of bearing rollers and better conforming to the outer contour of the wave generator, achieving the purpose of improving the bearing load capacity and reducing the deformation of the bearing inner ring. It can also improve the load and life of the new flexible bearing and has good reliability.

[0015] Furthermore, the isolator is an intermediate needle roller, the length and shape of which are the same as the length and shape of the rolling element and the diameter of the intermediate needle roller is smaller than the diameter of the rolling element. The intermediate needle roller is tangent to the outer circle of the two adjacent rolling elements and the outer surface of the wave generator, respectively.

[0016] By adopting the above technical solution, there is no problem of damage and burning caused by sliding friction, wear and high-speed operation between the ordinary bearing cage and rolling elements. The intermediate needle roller and the rolling elements have rolling friction, which can reduce the coefficient of friction and thus improve efficiency.

[0017] Furthermore, the isolator and the wave generator are integral components. The wave generator has several grooves corresponding to the rolling element, and the rolling element is disposed in the grooves. The depth of the groove is not less than one-third of the diameter of the rolling element, and the depth of the groove is not greater than the diameter of the rolling element minus 0.1 mm.

[0018] By adopting the above technical solution, the isolator is combined with the wave generator and a groove is opened on it to form the raceway and limiting structure of the rolling element. There is no need to set up a separate cage, and the space between the flexible wheel and the wave generator is reduced, making it easier to fill the groove with lubricating grease. Correspondingly, the diameter of the flexible wheel and the external connecting bearing is also reduced, thereby reducing the outer diameter of the entire reducer.

[0019] Furthermore, the raceway of the wave generator is provided with an oil groove, and the rolling element contacts the outer top surface of the oil groove. The oil groove is a plurality of rings arranged in an array along the axial direction of the wave generator and spaced apart, or a continuous spiral with an axial length equal to the axial length of the wave generator.

[0020] By adopting the above technical solution, the oil groove is set to reduce the contact area between the rolling element and the wave generator, thereby reducing friction and improving efficiency. The oil groove can store lubricating grease for easy lubrication.

[0021] Furthermore, the first rigid wheel and the second rigid wheel serve as the inner and outer rings of the connecting bearing, respectively, and the connecting bearing is one of a cross roller bearing, a four-point contact ball bearing, or a double-row deep groove ball bearing.

[0022] By adopting the above technical solution, a connecting bearing is set between the first and second rigid wheels, connecting them into an integrated structure. This makes the overall structure operate more smoothly, reduces the starting torque, and is easier to manufacture, thus lowering production costs. Crossed roller bearings have a high load-bearing capacity, especially strong bending moment capacity, and are usually made with negative clearance, resulting in high rotational accuracy, but they are generally not suitable for high speeds. Double-row deep groove ball bearings can withstand radial and bidirectional axial loads, and can be used at higher speeds compared to crossed roller bearings, but their load-bearing capacity is relatively weaker. Four-point contact ball bearings can also withstand radial and bidirectional axial loads, but their load-bearing capacity is also relatively weaker than that of crossed roller bearings. The type of connecting bearing can be selected according to the actual application requirements of the reducer to achieve optimal performance.

[0023] In summary, the technical solution of this utility model has the following advantages:

[0024] 1. The dual rigid wheel harmonic reducer with flexible bearings without inner and outer rings provided by this utility model breaks away from the conventional thinking of a three-part structure consisting of a flexible wheel, a flexible bearing, and a wave generator. It integrates the functions of the flexible wheel and the outer ring of the flexible bearing, and the wave generator and the inner ring of the flexible bearing into a single unit. Furthermore, it uses an isolator to replace the bearing cage, optimizes the connecting bearing between the two rigid wheels, substantially improves the operating accuracy and service life of the flexible wheel and the wave generator, simplifies the structure of the harmonic reducer, effectively reduces the size and weight of the dual rigid wheel structure, and reduces the overall radial diameter through the integration of components, making the structure of the harmonic reducer more compact.

[0025] 2. The dual rigid wheel harmonic reducer with flexible bearings without inner and outer rings provided by this utility model features a cage-free design for the novel flexible bearings, which effectively avoids bearing failure caused by cage damage. The rolling elements directly contact the flexible wheel and the wave generator, simplifying manufacturing costs and improving the fit between the rolling elements and the outer contour of the wave generator. This ensures that the rolling elements are in an ideal contact state, reduces the alternating contact stress of the high pair caused by transmission, and improves the operating accuracy and service life of the components. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a cross-sectional view of the prior art;

[0028] Figure 2This is a cross-sectional view of a novel flexible bearing provided in one embodiment of the present invention, wherein the outer ring is a flexible wheel and the rolling elements are arranged in a double row.

[0029] Figure 3 The novel flexible bearing provided in one embodiment of this utility model has a novel outer ring that is a flexible wheel, a novel inner ring that is a wave generator, and a double-row cross-sectional view of the rolling elements.

[0030] Figure 4 This is a cross-sectional view of a flexible bearing without inner and outer rings, double-row rolling elements of balls, and a wave generator with grooves provided in one embodiment of the present invention.

[0031] Figure 5 This is a cross-sectional view of a flexible bearing without inner and outer rings, double-row rolling elements made of needle rollers, and a wave generator with grooves, provided in one embodiment of the present invention.

[0032] Figure 6 This is a cross-sectional view of a single-row rolling element, consisting of needle rollers, and an isolator, consisting of a middle spacer, provided in one embodiment of the present invention.

[0033] Figure 7 This is a cross-sectional view of a single-row rolling element with a needle roller and an isolator with an intermediate needle roller, provided in one embodiment of the present invention.

[0034] Figure 8 This is a cross-sectional view of a single-row rolling element provided in one embodiment of the present invention, which is an integral part of a needle roller, an isolator, and a wave generator;

[0035] Figure 9 This is a structural diagram of one embodiment of the present invention, in which the single-row rolling element is a needle roller and the connecting bearing is a cross roller bearing;

[0036] Figure 10 This is a structural diagram of one embodiment of the present invention, in which the single-row rolling element is a needle roller and the connecting bearing is a four-point contact ball bearing.

[0037] Figure 11 This is a structural diagram of one embodiment of the present invention, in which the single-row rolling element is a needle roller and the connecting bearing is a double-row deep groove ball bearing.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1. Wave generator; 11. Groove; 12. Oil groove; 13. Receiving ring; 14. Retaining ring; 2. Flexible wheel; 3. Flexible bearing; 3. New type of flexible bearing; 4. Rolling element; 5. Isolator; 51. Intermediate spacer block; 52. Intermediate needle roller; 6. First rigid wheel; 7. Connecting bearing; 8. Second rigid wheel. Detailed Implementation

[0040] 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 for explaining the present invention and are not intended to limit the present invention.

[0041] A dual rigid wheel harmonic reducer with flexible bearings without inner and outer rings, such as Figure 1 As shown, the device includes a wave generator 1, a flexible wheel 2, two flexible bearings 03, a first rigid wheel 6, a connecting bearing 7, and a second rigid wheel 8. The two flexible bearings are arranged side-by-side along the axial direction of the wave generator 1 and are sleeved on the outside of the wave generator 1. The flexible wheel 2 is sleeved on the two flexible bearings 03. The first rigid wheel 6 and the second rigid wheel 8 are both sleeved on the flexible wheel 2. The external teeth of the flexible wheel 2 mesh with the internal teeth of the first rigid wheel 6 and the second rigid wheel 8, respectively. A connecting bearing 7 is provided between the first rigid wheel 6 and the second rigid wheel 8. The working principle of the dual rigid wheel harmonic reducer in this application is the same as that of the dual rigid wheel harmonic reducer in the prior art, and will not be described in detail.

[0042] like Figure 2 As shown, a new type of flexible bearing 3 replaces the original two flexible bearings 03. The new flexible bearing 3 is positioned between the wave generator 1 and the flexure 2. The new flexible bearing 3 includes a new outer ring, a new inner ring, and several rolling elements 4. In this embodiment, the new outer ring is the flexure 2. The inner surface of the flexure 2 has raceways for the rolling elements 4 to roll, and the outer surface of the flexure 2 has teeth that mesh with the first rigid wheel 6 and the second rigid wheel 8. The thickness of the integrated flexible bearing 03 outer ring and the flexure 2 is less than the total thickness of the flexible bearing 03 outer ring and the flexure 2 when they are separate. Therefore, when the reducer is working, the force required for metal deformation can be reduced, thereby improving efficiency. The rolling elements 4 are arranged in two rows and are balls.

[0043] Furthermore, such as Figure 3 and Figure 4 As shown, the wave generator 1 and the novel inner ring are integral components. The wave generator 1 has an annular elliptical structure, and the rolling elements 4 are arranged in two rows along the axial direction of the wave generator 1. The rolling elements 4 are also arranged in a circumferential array along the wave generator 1. The outer surface of the wave generator 1 has raceways for the rolling elements 4 to roll, or two grooves can be directly formed on the wave generator 1. By using the novel flexible bearing 3 to reduce the inner and outer rings of the flexible bearing, the outer diameter of the reducer is reduced and the structure is made more compact, eliminating the assembly gaps between the wave generator 1 and the inner ring of the flexible bearing, and between the flexible wheel 2 and the outer ring of the flexible bearing. The overall efficiency of the dual rigid wheel harmonic reducer with a flexible bearing without inner and outer rings and without a cage in this application is improved compared to the prior art, and can be increased to over 85%.

[0044] like Figure 4 or Figure 5 The rolling elements 4 are arranged in two rows along the axis of the wave generator 1. The rolling elements 4 are two rows of steel balls or two rows of needle rollers arranged in parallel. The outer surface of the wave generator 1 is provided with corresponding raceways or grooves for the two rows of rolling elements 4.

[0045] like Figure 9 and Figure 6 As shown, the double-row rolling elements 4 can be combined into one row. A row of rolling elements 4 is arranged along the axis of the wave generator 1, and the rolling elements 4 are needle rollers. To limit the axial movement of the rolling elements 4, a receiving ring 13 extends outward from one end of the wave generator 1. The receiving ring 13 is integrally formed with the wave generator, and a retaining ring 14 is externally engaged at the other end of the wave generator 1. The rolling elements 4 are positioned between the receiving ring 13 and the retaining ring 14, thereby axially limiting the rolling elements 4. To minimize the radial dimension of the reducer and avoid affecting its performance, the bearing cage is omitted, and instead, an isolator 5 is used to isolate and limit the rolling elements 4.

[0046] The raceway of the wave generator 1 is provided with an oil groove 12. The rolling element 4 contacts the outer top surface of the oil groove 12. The oil groove 12 consists of multiple rings arranged in an array along the axial direction of the wave generator 1 and spaced apart. Alternatively, the groove can be a continuous spiral with an axial length equal to that of the wave generator 1. In the spiral shape, the top threads need to be widened and thickened to fit the rolling element 4. The oil groove 12 reduces the contact area between the rolling element 4 and the wave generator 1, thereby reducing friction and improving efficiency. The oil groove 12 can store lubricating grease for easy lubrication.

[0047] The isolator 5 is a spacer block 51, which is positioned between two adjacent rolling elements 4 and does not contact the inner surface of the flexible wheel 2 or the outer surface of the wave generator 1 on its inner and outer sides. The two ends of the spacer block 51 that contact the rolling elements 4 are concave arc surfaces that adapt to the outer surface of the rolling elements 4. The length of the spacer block 51 has a range; when it is at its longest, it is the same length as the rolling elements 4, and when it is at its shortest, it is not less than half the length of the rolling elements 4. The spacer block 51, through the contact of its concave arc surfaces with gaps, can appropriately reduce the distance between the rolling elements 4, thereby increasing the number of bearing rollers and better conforming to the outer contour of the wave generator 1, thus improving the bearing's load-bearing capacity and reducing the deformation of the bearing's inner ring.

[0048] like Figure 9 and Figure 7 As shown, the isolator 5 is an intermediate needle roller 52. The length and shape of the intermediate needle roller 52 are the same as those of the rolling element 4, but the diameter of the intermediate needle roller 52 is smaller than that of the rolling element 4. The intermediate needle roller 52 is tangent to the outer circles of the two adjacent rolling elements 4 and the outer surface of the wave generator 1. This further reduces the volume of the isolator 5 and avoids the damage and burning problems caused by sliding friction, wear, and high-speed operation between the ordinary bearing cage, ordinary block, and rolling element 4. The intermediate needle roller 52 and the rolling element 4 have rolling friction, which can also reduce the coefficient of friction and thus improve efficiency.

[0049] like Figure 8As shown, the isolator 5 and the wave generator 1 are integral components. The isolator 5 and the wave generator 1 are combined, and a groove 11 is formed on it. The groove 11 is set corresponding to the rolling element 4 and its length is consistent with the length of the rolling element 4. The rolling element 4 is accommodated in the groove 11. The groove 11 forms the raceway and limiting structure of the rolling element 4. The depth of the groove 11 is limited according to the diameter of the rolling element 4. When the depth of the groove 11 is minimum, it is not less than one-third of the diameter of the rolling element 4. When the depth of the groove 11 is maximum, it is not greater than the diameter of the rolling element 4 minus 0.1mm. That is, when the rolling element 4 is accommodated in the groove 11, there is only a 0.1mm gap between the inner wall of the flexible wheel 2 and the outer surface of the wave generator 1. This greatly reduces the space between the flexible wheel 2 and the wave generator 1, and also makes it convenient to fill the groove 11 with lubricating grease. In addition, it also reduces the diameter of the flexible wheel 2 and the external connecting bearing 7, thereby reducing the outer diameter of the entire reducer.

[0050] To ensure smooth operation of the reducer and reduce the overall starting torque, such as Figure 7 , Figure 8 and Figure 9 As shown, the first rigid wheel 6 and the second rigid wheel 8 serve as the inner and outer rings of the connecting bearing 7, respectively. The connecting bearing 7 is one of a cross roller bearing, a four-point contact ball bearing, or a double-row deep groove ball bearing. The type of connecting bearing 7 can be selected according to the actual application requirements of the reducer to achieve optimal performance.

[0051] like Figure 7 As shown, connecting bearing 7 is a cross-roller bearing, suitable for applications requiring high bending moment capacity, negative clearance, and high rotational accuracy; it is not suitable for high-speed applications. Figure 8 As shown, connecting bearing 7 is a four-point contact ball bearing, used to withstand radial and bidirectional axial loads in a lightweight, ultra-thin structure. Figure 9 As shown, the connecting bearing 7 is a double-row deep groove ball bearing, which can be used in scenarios with higher speeds and lower load requirements.

[0052] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A dual-rigid-wheel harmonic reducer with flexible bearings without inner and outer rings, characterized in that, It includes a wave generator (1), a flexible wheel (2), a new type of flexible bearing (3), a first rigid wheel (6), a connecting bearing (7), and a second rigid wheel (8). The first rigid wheel (6) and the second rigid wheel (8) are both fitted outside the flexible wheel (2). The external teeth of the flexible wheel (2) mesh with the internal teeth of the first rigid wheel (6) and the internal teeth of the second rigid wheel (8). A connecting bearing (7) is provided between the first rigid wheel (6) and the second rigid wheel (8). The novel flexible bearing (3) is disposed between the wave generator (1) and the flexure (2). The novel flexible bearing (3) includes a novel outer ring, a novel inner ring and several rolling elements (4). The novel outer ring is the flexure (2). The inner surface of the flexure (2) has a raceway and the outer surface has teeth. The wave generator (1) and the novel inner ring are integral components. The outer surface of the wave generator (1) has a raceway and is an annular elliptical structure. The rolling elements (4) are arranged in at most two rows along the axial direction of the wave generator (1). The rolling elements (4) are arranged in a circumferential array along the wave generator (1). An isolator (5) is also provided between two adjacent rolling elements (4) in the same row.

2. The dual rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 1, characterized in that, The rolling elements (4) are arranged in two rows along the axis of the wave generator (1). The rolling elements (4) are two rows of steel balls or two rows of rollers arranged in parallel. The outer surface of the wave generator (1) is provided with corresponding raceways or grooves for the two rows of rolling elements (4).

3. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 1, characterized in that, The rolling elements (4) are arranged in a row along the axis of the wave generator (1). The rolling elements (4) are needle rollers. A receiving ring (13) extends from one end of the wave generator (1), and a retaining ring (14) is snapped onto the other end of the wave generator (1). The rolling elements (4) are arranged between the receiving ring (13) and the retaining ring (14).

4. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 3, characterized in that, The isolator (5) is a middle spacer (51). The middle spacer (51) is disposed between two adjacent rolling bodies (4) and does not contact the inner surface of the flexible wheel (2) and the outer surface of the wave generator (1) on both sides. The two ends of the middle spacer (51) that contact the rolling body (4) are concave arc surfaces. The axial length of the middle spacer (51) is not less than half of the axial length of the rolling body (4) and the axial length of the middle spacer (51) is not greater than the axial length of the rolling body (4).

5. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 3, characterized in that, The isolator (5) is an intermediate needle roller (52). The length and shape of the intermediate needle roller (52) are the same as the length and shape of the rolling body (4), and the diameter of the intermediate needle roller (52) is smaller than the diameter of the rolling body (4). The intermediate needle roller (52) is tangent to the outer circle of the two adjacent rolling bodies (4) and the outer surface of the wave generator (1).

6. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 3, characterized in that, The isolator (5) and the wave generator (1) are integral components. The wave generator (1) has several grooves (11) corresponding to the rolling body (4). The rolling body (4) is set in the grooves (11). The depth of the grooves (11) is not less than one-third of the diameter of the rolling body (4), and the depth of the grooves (11) is not greater than the diameter of the rolling body (4) minus 0.1 mm.

7. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 4 or 5, characterized in that, The raceway of the wave generator (1) is provided with an oil groove (12), and the rolling body (4) is in contact with the outer top surface of the oil groove (12). The oil groove (12) is a plurality of rings arranged in an array along the axial direction of the wave generator (1) and spaced apart, or a continuous spiral with an axial length equal to the axial length of the wave generator (1).

8. A double rigid wheel harmonic reducer with flexible bearings without inner and outer rings according to claim 1, characterized in that, The first rigid wheel (6) and the second rigid wheel (8) serve as the inner and outer rings of the connecting bearing (7), respectively. The connecting bearing (7) is one of a cross roller bearing, a four-point contact ball bearing, or a double-row deep groove ball bearing.

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