Flexible gear with stable structure

Abstract

The invention discloses a flexible gear with a stable structure, and belongs to the technical field of harmonic reducers. The flexible gear comprises a tubular cylinder with a first end and a second end, and a wave generator enters the cylinder from the first end; the tooth part is arranged on the periphery of the cylinder body, the tooth part comprises a plurality of outer teeth, the outer teeth are evenly distributed in the circumferential direction of the cylinder body, each outer tooth is provided with a first transition inclined face, each first transition inclined face is provided with a low end and a high end, and the low end of each first transition inclined face is flush with the first end of the cylinder body. The technical problem that an existing flexible gear structure is low in stability is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic reducers, and particularly to a flexible gear with stable structure. Background Art

[0002] A harmonic reducer (HarmonicDrive) is a high-precision and high-rigidity mechanical transmission device, which is widely used in fields such as robots, aerospace, and precision instruments. Its core principle is to achieve power transmission by using elastic deformation, and it has the characteristics of compact structure, large transmission ratio, and small backlash.

[0003] It mainly consists of a wave generator, a flexible gear, and a rigid gear. When the wave generator rotates, it forces the flexible gear to undergo elliptical deformation. The teeth of the flexible gear and the rigid gear mesh at both ends of the major axis of the ellipse and disengage at the minor axis. For each revolution of the wave generator, the difference in the number of teeth between the flexible gear and the rigid gear causes the flexible gear to rotate in the opposite direction relative to the rigid gear by a certain angle.

[0004] Since the flexible gear is constantly undergoing irregular deformation under the drive of the wave generator, the stress distribution of the overall structure is uneven, resulting in the unstable structure of the flexible gear. Therefore, a flexible gear with stable structure is proposed. Summary of the Invention

[0005] The main purpose of the present invention is to provide a flexible gear with stable structure, aiming to improve the structural stability of the current flexible gear.

[0006] To achieve the above object, the flexible gear with stable structure proposed by the present invention includes: A cylinder body, the cylinder body is tubular and has a first end and a second end, and the wave generator enters the cylinder body from the first end; A tooth part, the tooth part is arranged on the outer periphery of the cylinder body, the tooth part includes a plurality of external teeth, the plurality of external teeth are evenly distributed along the circumferential direction of the cylinder body, the external teeth have a first transition inclined surface, the first transition inclined surface has a low end and a high end, and the low end of the first transition inclined surface is flush with the first end of the cylinder body.

[0007] Optionally, in an embodiment of the present invention, the external teeth further have a second transition inclined surface, the second transition inclined surface is located at the end of the external tooth close to the second end, and the inclination angle of the second transition inclined surface is smaller than that of the first transition inclined surface.

[0008] Optionally, in an embodiment of the present invention, the inclination angle of the first transition inclined surface is a, and the inclination angle of the second transition inclined surface is b, 40°≤a≤50°, 10°≤b≤20°.

[0009] Optionally, in an embodiment of the present invention, the first transition inclined surface is a planar inclined transition surface, and the second transition inclined surface is a curved surface inclined transition surface.

[0010] Optionally, in an embodiment of the present invention, the external teeth are circular teeth, the radius of the tooth top arc of the circular teeth is Ra, the height is h, and Ra=(0.2~0.3)h.

[0011] Optionally, in an embodiment of the present invention, the root arc radius of the circular tooth is Rf, and Rf=(0.4~0.6)h.

[0012] Optionally, in an embodiment of the present invention, a groove is provided between two adjacent external teeth, the groove extends a predetermined distance from the first end to the second end, and the length of the groove is greater than the length of the external teeth.

[0013] Optionally, in an embodiment of the present invention, the groove has a first groove section and a second groove section, the first groove section starts from the first end and is equal to the outer tooth in length, and the second groove section gradually tightens from the first end to the second end.

[0014] Optionally, in an embodiment of the present invention, the wall thickness of the cylinder gradually decreases from the first end to the second end.

[0015] Optionally, in one embodiment of the present invention, a connecting flange is further included, wherein the connecting flange is connected to the second end of the cylinder, and the connecting flange is provided with a plurality of connecting holes.

[0016] Compared with the prior art, the present invention can at least achieve the following beneficial effects. In this solution, the flexible wheel includes a cylinder and a tooth portion, wherein the cylinder is tubular and has a hollow structure inside for placing a wave generator. The two ends of the cylinder are respectively defined as a first end and a second end, and the first end is a port for the wave generator to enter. The outer periphery of the flexible wheel is provided with a tooth portion, and the tooth portion includes a plurality of external teeth, and the plurality of external teeth are evenly distributed on the outer periphery of the cylinder to mesh with the rigid wheel. A transition slope is provided at one end of the external tooth, specifically, at the end close to the first end of the cylinder.

[0017] During the operation of the flexible wheel, the transition bevel effectively disperses the stress concentration generated by the periodic elastic deformation of the flexible wheel with a smooth geometric transition. This delays the initiation of fatigue cracks and improves the structural stability. In addition, the transition bevel structure enhances the flexible wheel's ability to follow the deformation of the wave generator, which can avoid root fracture when subjected to large elastic deformation, and promotes the uniform distribution of lubricating oil to improve friction conditions. From a process perspective, the transition bevel design reduces the risk of cracking during heat treatment, and its stress release characteristics can also inhibit the extension of local cracks to the barrel. Ultimately, the coordinated improvement of the structural stability, durability and quietness of the harmonic reducer is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0019] Figure 1 Schematic diagram of the structure of the flexible gear with stable structure of the present invention; Figure 2 Side view schematic diagram of the external teeth in the flexible gear with stable structure of the present invention; Figure 3 Front view structure diagram of the external teeth in the flexible gear with stable structure of the present invention; Figure 4 Schematic diagram of the structure of the groove in the flexible gear with stable structure of the present invention.

[0020] Explanation of the reference numerals in the drawings: 100, cylinder body; 110, first end; 120, second end; 200, tooth part; 210, external teeth; 220, first transition inclined plane; 230, second transition inclined plane; 300, groove; 310, first groove section; 320, second groove section; 400, connecting flange; Ra, tooth tip arc radius; Rf, tooth root arc radius; h, tooth height; The realization, functional features and advantages of the purpose of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. Detailed implementation manners

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If this specific posture changes, the directional indications will also change accordingly.

[0023] In the present invention, unless otherwise clearly specified and defined, terms such as "connection" and "fixation" shall be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, such descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes Scenario A, or Scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] Referring to Figures 1 to 4 , the present invention provides a flexible gear with stable structure, including: A cylinder body 100, the cylinder body 100 is tubular and has a first end 110 and a second end 120, and the wave generator enters the cylinder body 100 from the first end 110; A tooth part 200, the tooth part 200 is arranged on the outer periphery of the cylinder body 100, the tooth part 200 includes a plurality of external teeth 210, the plurality of external teeth 210 are evenly distributed along the circumferential direction of the cylinder body 100, and the external teeth 210 have a first transition inclined surface 220, the first transition inclined surface 220 has a low end and a high end, and the low end of the first transition inclined surface 220 is flush with the first end 110 of the cylinder body 100.

[0026] In this solution, the flexible gear includes a cylinder body 100 and a tooth part 200. Among them, the cylinder body 100 is tubular and has a hollow structure inside for placing the wave generator. The two ends of the cylinder body 100 are respectively defined as a first end 110 and a second end 120, and the first end 110 is the port for the wave generator to enter. The tooth part 200 is arranged on the outer periphery of the cylinder body 100, and the tooth part 200 includes a plurality of external teeth 210, and the plurality of external teeth 210 are evenly distributed on the outer periphery of the cylinder body 100 and mesh with the rigid gear. At one end of the external teeth 210, specifically, at the end close to the first end 110 of the cylinder body 100, a transition inclined surface is provided.

[0027] During the operation of the flexible wheel, the transition bevel effectively disperses the stress concentration generated by the periodic elastic deformation of the flexible wheel with a smooth geometric transition. This delays the initiation of fatigue cracks and improves the structural stability. In addition, the transition bevel structure enhances the flexible wheel's ability to follow the deformation of the wave generator, which can avoid root fracture when subjected to large elastic deformation, and promotes the uniform distribution of lubricating oil to improve friction conditions. From a process perspective, the transition bevel design reduces the risk of cracking during heat treatment, and its stress release characteristics can also inhibit the expansion of local cracks to the cylinder 100. Ultimately, the coordinated improvement of the structural stability, durability and quietness of the harmonic reducer is achieved.

[0028] Reference Figure 2 and Figure 4 Furthermore, the outer tooth 210 is provided with two transition slopes, namely a first transition slope 220 and a second transition slope 230. Specifically, the first transition slope 220 is close to the first end 110 of the cylinder 100, and the lower end of the first transition slope 220 is flush with the first end 110 of the cylinder 100. The second transition slope 230 is located at the other end of the outer tooth 210, which is closer to the second end 120 of the cylinder 100 than the first transition slope 220, and the inclination angle of the second transition slope 230 is smaller than that of the first transition slope 220.

[0029] During the movement and deformation of the flexible wheel, under the action of the wave generator, the first end 110 of the cylinder 100 undergoes the maximum periodic elastic deformation. The first transition slope 220 is designed to have a larger inclination angle, which can significantly reduce the stress concentration phenomenon at the tooth root, disperse the bending stress and shear stress, and delay the initiation of fatigue cracks.

[0030] The second end 120 of the cylinder 100 is usually provided with a connecting flange 400 to form a cap-shaped flexible wheel, or to connect a driven device. Therefore, the deformation at the second transition slope 230 is relatively smaller. The second transition slope 230 is designed to have a smaller inclination angle, which can maintain the structural rigidity of the second end 120 of the cylinder 100 while ensuring a smooth transition of stress, and avoid a decrease in strength at this location due to a too rapid reduction in the tooth root thickness.

[0031] Specifically, refer to Figure 2 The inclination angle of the first transition slope 220 is a, and the angle of the second transition slope 230 is b, wherein 40°≤a≤50°, and 10°≤b≤20°.

[0032] The inclination angle of the first transition slope 220 is designed to be within the range of 40°~50°. The larger the inclination angle of the first transition slope 220 is, the structural strength of the cylinder 100 can be improved through the external teeth 210. Here, the external teeth 210 can be understood as reinforcing ribs on the outer periphery of the cylinder 100, which has the effect of improving the structural strength of the cylinder 100.

[0033] The inclination angle of the second transition inclined surface 230 is designed within the range of 10° to 20°. It can be understood that the dimensions spanned by the first transition inclined surface 220 and the second transition inclined surface 230 in the tooth thickness direction are the same, and the starting and ending points of the span are at the same height. Therefore, reducing the inclination angle of the second transition inclined surface 230 also extends the extension length of the second transition inclined surface 230. The second transition inclined surface 230 avoids the strength reduction caused by the too rapid change of the tooth thickness at this place through the gentle transition of the collective shape of the tooth root.

[0034] Furthermore, the first transition inclined surface 220 is a plane, and the second transition inclined surface 230 is a curved surface.

[0035] The plane transition surface can quickly disperse the concentrated stress generated by the large deformation at the first end 110 of the cylinder 100 through directional stress dispersion, including the combined bending stress and shear stress. In addition, the uniform gradient characteristic of the geometry of the plane can reduce the stress peak at the tooth root by about 15%.

[0036] The curved surface transition surface realizes the smooth transition of the stress field in the part close to the connecting flange 400 or the driven device through continuous and smooth curvature changes.

[0037] In addition to the above effects of optimizing the stress distribution, opening the transition inclined surface can also guide the flow of lubricating oil, facilitating the flow of the lubricating oil to the middle of the external teeth 210.

[0038] Refer to Figure 3 , furthermore, the external teeth 210 in this solution are circular teeth. Specifically, the relationship between the radius Ra of the tooth tip arc and the tooth height h satisfies Ra = (0.2 - 0.3)h.

[0039] First, the tooth profile of the external teeth 210 is optimized to circular teeth. Compared with the traditional tooth profile, circular teeth can avoid the edge effect and reduce the contact area during meshing with the rigid gear. The circular tooth tip provides a "soft contact" effect during the meshing entry and exit stages. Due to the geometric continuity of the arc, the movement path of the tooth surface contact point is smoother, avoiding the instantaneous impact load caused by the edge contact of the traditional tooth profile, thereby reducing vibration and noise. In addition, the elastic deformation of the flexspline under the action of the wave generator will cause the dynamic change of the relative position of the tooth surface. The symmetry and curvature adaptability of the circular tooth tip can better adapt to this dynamic offset and reduce the edge wear caused by meshing misalignment.

[0040] Furthermore, Ra = (0.2 - 0.3)h, and the tooth height h needs to be reasonably designed according to the modulus (m) and deformation of the flexspline. Generally speaking, h = (1.0 - 1.5)m.

[0041] According to Hertz contact theory, increasing Ra can reduce the contact stress and avoid pitting or wear on the tooth surface. However, if Ra is too large (close to h), the flattening of the tooth tip will cause the meshing area to expand outward, leading to edge contact or interference, which will instead increase the local stress. Therefore, Ra needs to strike a balance between reducing stress and avoiding geometric interference.

[0042] The periodic deformation of the flexspline under the action of the wave generator requires the tooth profile to adapt to the dynamic trajectory. The tooth height h is usually designed as h = (1.0~1.5)m (m is the module): too small h will result in insufficient meshing area, causing slipping or noise; too large h will increase the bending stress at the tooth root and accelerate fatigue failure. The arc radius of Ra = (0.2~0.3)h can effectively adapt to the deformation trajectory of the flexspline, avoiding the separation (backlash) or jamming (friction heating) of the tooth tip from the rigid spline. At the same time, it avoids the extreme cases of easy wear when Ra < 0.2h at the sharp tooth tip and easy interference when Ra > 0.3h at the flat tooth tip, ensuring the transmission smoothness and structural reliability.

[0043] Furthermore, during the parameter design process of the external teeth 210, Ra needs to be synchronously optimized in cooperation with the tooth root arc radius Rf to avoid stress concentration at the tooth root. Specifically, Rf = (0.4~0.6)h.

[0044] From a mechanical perspective, increasing Rf can reduce the stress concentration of the tooth root bending stress and delay the initiation of fatigue cracks. From the analysis of meshing characteristics, the progressive arc transition design of Rf and Ra (Rf / Ra ≈ 1.5~2.0) balances the distribution of the tooth tip contact stress and the tooth root bending stress, avoiding premature local failure. Tests show that the fatigue life can be extended by 30%~50%. In terms of dynamic adaptability, a larger Rf can improve the tooth root strain distribution during the periodic deformation of the flexspline, reduce the risk of local plastic deformation, and at the same time reduce meshing impact and noise, improving the transmission accuracy. In terms of manufacturing process, Rf = 0.4~0.6h is more easily achieved through precision machining (such as wire cutting), reducing tool wear and machining defects, enhancing the anti-overload ability, and reducing the risk of tooth breakage.

[0045] Refer to Figure 4 , furthermore, a groove 300 is provided between two external teeth 210. The starting point of the groove 300 is the same as that of the external teeth 210, but the groove 300 is longer than the external teeth 210 in length. That is, axially, the groove 300 protrudes a certain distance compared with the external teeth 210.

[0046] By opening the groove 300, the redundant material in the non-meshing area can be removed, which not only achieves the goal of lightweight, but also optimizes the mass distribution, thereby reducing the moment of inertia, allowing the harmonic reducer to respond quickly to instructions during frequent start-stop or high-speed reversing (such as industrial robot joints), and improving dynamic performance. At the same time, the structural characteristics of the groove 300 enhance the elastic deformation ability of the flexible wheel. Under the action of the wave generator, the flexible wheel needs to be elastically deformed periodically to achieve inter-tooth meshing transmission, and the groove 300 releases the local deformation space to make the stress distribution more uniform, avoiding the stress concentration problem caused by the sudden change of stiffness in the traditional design, not only improving the fatigue life, but also reducing the risk of work hardening caused by repeated deformation of the material, providing a guarantee for long-term stable operation. In addition, the axial extension design of the groove 300 forms a synergistic effect in terms of heat dissipation and lubrication: its increased surface area accelerates the dissipation of heat through air convection or the flow of lubricating media, preventing excessive temperature rise from causing material performance degradation; the groove 300 itself can also serve as a storage chamber and flow channel for lubricants, promoting oil film formation under high-speed or heavy-load conditions, and reducing dry friction and wear between tooth surfaces. This design also indirectly optimizes the smoothness of the transmission process. By reasonably regulating the contact area, the groove 300 reduces the sliding contact of unnecessary friction surfaces, and with the directional guidance of the lubricant, it effectively reduces vibration and noise, making it more advantageous in scenes with strict requirements for quietness, such as precision optical equipment.

[0047] Specifically, the groove 300 is formed by a first groove section 310 and a second groove section 320, wherein the first groove section 310 is an equal-width groove, which is the same length as the external tooth 210 and has external teeth 210 on both sides; the second groove section 320 protrudes from the external tooth 210, and gradually tightens along the direction from the first end 110 to the second end 120.

[0048] The equal-width groove section is axially the same length as the outer tooth 210. When the wave generator drives the flexible wheel to deform, its uniform width design allows the stress to be evenly diffused along the tooth root area, avoiding local stress mutations and reducing the risk of fatigue cracks. At the same time, the equal-width grooves form regular lubrication cavities that can store sufficient lubricating oil to provide continuous lubrication for tooth surface meshing and reduce dry friction losses.

[0049] The second groove section 320 gradually tightens from the end of the equal-width groove to the end of the flexible wheel, and realizes a gradient transition of stiffness through the tapered structure. While retaining the elastic deformation space brought by the axial extension, the tapered design reduces the excessive weakening of the end material, which not only prevents the instability problem caused by excessive flexibility of the flexible wheel end, but also optimizes the mass distribution, so that the moment of inertia is further concentrated in the meshing area, thereby improving the dynamic response capability of the equipment.

[0050] Furthermore, the flexspline proposed in this solution is a flexspline with variable wall thickness. In the direction from the first end 110 to the second end 120, the wall thickness of the cylinder 100 gradually decreases. Increasing the wall thickness in the meshing area can improve the local stiffness and load-bearing capacity, reduce the tooth surface uneven load caused by deformation, and extend the fatigue life; thinning in the non-meshing area reduces the overall weight, decreases the moment of inertia, and improves the dynamic response speed. This "demand-based distribution" wall thickness design makes the stress distribution more uniform, avoiding the stress concentration problem caused by sudden stiffness change in traditional constant wall thickness flexspline, and suppressing vibration and noise through mass distribution optimization. In addition, the variable wall thickness structure can accommodate the requirements of high load and lightweight, achieving a balance between high-strength transmission and energy-saving and efficient operation in scenarios such as aerospace and industrial robots.

[0051] In one embodiment, the flexspline proposed in this solution is a cap-shaped flexspline, and a connecting flange 400 is provided at the second end 120 of its cylinder 100 for connection with the driven device.

[0052] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A flexible pulley with a stable structure, characterized in that: include: A cylinder, wherein the cylinder is tubular and has a first end and a second end, and the wave generator enters the cylinder from the first end; A tooth portion, wherein the tooth portion is arranged on the outer periphery of the cylinder, and the tooth portion includes a plurality of external teeth, and the plurality of external teeth are evenly distributed along the circumference of the cylinder, and the external teeth have a first transition slope, and the first transition slope has a low end and a high end, and the low end of the first transition slope is flush with the first end of the cylinder.

2. The structurally stable flexible pulley according to claim 1, characterized in that: The outer tooth further has a second transition slope, which is located at the end of the outer tooth close to the second end, and the inclination angle of the second transition slope is smaller than that of the first transition slope.

3. The structurally stable flexible pulley according to claim 1, characterized in that: The inclination angle of the first transition slope is a, the inclination angle of the second transition slope is b, 40°≤a≤50°, 10°≤b≤20°.

4. The structurally stable flexible pulley according to claim 2, characterized in that: The first transition slope is a plane-inclined transition slope, and the second transition slope is a curved-inclined transition slope.

5. The structurally stable flexible pulley according to claim 1, characterized in that: The external teeth are circular teeth, the radius of the tooth top arc of the circular teeth is Ra, and the height is h, Ra=(0.2~0.3)h.

6. The structurally stable flexible wheel according to claim 5, characterized in that: The root arc radius of the circular tooth is Rf, and Rf=(0.4~0.6)h.

7. The structurally stable flexible pulley according to claim 1, characterized in that: A groove is defined between two adjacent outer teeth. The groove extends from the first end to the second end by a predetermined distance, and the length of the groove is greater than the length of the outer teeth.

8. The structurally stable flexible pulley according to claim 7, characterized in that: The groove has a first groove section and a second groove section. The first groove section starts from the first end and has the same length as the outer tooth. The second groove section gradually tightens from the first end to the second end.

9. The structurally stable flexible pulley according to claim 1, characterized in that: The wall thickness of the cylinder gradually decreases from the first end to the second end.

10. The structurally stable flexible pulley according to claim 1, characterized in that: It also includes a connecting flange, which is connected to the second end of the cylinder and has a plurality of connecting holes.

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