Low-abrasion flexible gear

Abstract

The invention discloses a low-abrasion flexible gear, and belongs to the technical field of harmonic reducers. The flexible gear comprises a cylinder, the inner wall of the cylinder is provided with a rail groove, and a bearing of the wave generator moves along the rail groove; the tooth part is located on the outer circumferential wall of one end of the cylinder body, a plurality of outer teeth are formed on the tooth part, and the tooth part is meshed with a rigid gear; the connecting flange is located at the other end of the cylinder body and connected with the cylinder body, and a connecting hole is formed in the connecting flange. The technical problem that a current bearing has sliding friction on the inner wall of a flexible gear is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic reducers, and particularly to a low-wear flexspline. Background Art

[0002] A harmonic reducer is a high-precision transmission device based on the principle of elastic deformation, which realizes motion and torque transmission through the controllable deformation of a flexible element. Its core features are compact structure, large reduction ratio, and high transmission accuracy, and it is widely used in fields such as robotics, aerospace, and precision instruments.

[0003] During the operation of the harmonic reducer, the bearing of the wave generator moves inside the inner wall of the flexspline, deforming the flexspline into an oval shape. The teeth of the flexspline at the major axis engage with the teeth of the rigid gear, and the teeth of the flexspline at the minor axis disengage from the teeth of the rigid gear. During the movement of the bearing on the inner wall of the flexspline, a certain degree of sliding friction will occur, resulting in wear on the inner wall of the flexspline. Summary of the Invention

[0004] The main object of the present invention is to provide a low-wear flexspline, aiming to solve the technical problem of the existing sliding friction between the bearing and the inner wall of the flexspline.

[0005] To achieve the above object, the low-wear flexspline proposed by the present invention includes: A cylinder, the inner wall of the cylinder has a track groove, and the bearing of the wave generator moves along the track groove; A tooth part, which is located on the outer circumferential wall at one end of the cylinder and is formed with a plurality of external teeth, and the tooth part meshes with the rigid gear; A connecting flange, which is located at the other end of the cylinder and is connected to the cylinder, and the connecting flange is provided with connecting holes.

[0006] Optionally, in an embodiment of the present invention, the cylinder includes reinforcing ribs, at least two reinforcing ribs are provided, the two reinforcing ribs are respectively a first reinforcing rib and a second reinforcing rib, and the first reinforcing rib and the second reinforcing rib are arranged at intervals to form the track groove.

[0007] Optionally, in an embodiment of the present invention, the first reinforcing rib is a gradually thickening reinforcing rib, and in the direction from the tooth part to the connecting flange, the first reinforcing rib gradually thickens.

[0008] Optionally, in an embodiment of the present invention, the wall thickness of the cylinder is Tr, and the thickness of the thickest part of the reinforcing rib is Tw, 1.2 ≤ Tr / Tw ≤ 1.5.

[0009] Optionally, in an embodiment of the present invention, the cylinder body further includes a third reinforcing rib, which is located on the side of the second reinforcing rib away from the first reinforcing rib, and the second reinforcing rib and the third reinforcing rib form an oil storage groove.

[0010] Optionally, in an embodiment of the present invention, along the circumferential direction of the cylinder body, the cross-sections of the second reinforcing rib and the third reinforcing rib are isosceles trapezoids.

[0011] Optionally, in an embodiment of the present invention, the connection between the reinforcing rib and the cylinder body is a rounded corner.

[0012] Optionally, in an embodiment of the present invention, the track groove is provided on the inner wall of the cylinder body.

[0013] Optionally, in an embodiment of the present invention, the cross-section of the track groove along its circumferential direction is an isosceles trapezoid. The width of the groove opening of the track groove is W1, the width of the groove bottom is W2, and the thickness of the bearing is Tz. W2 = Tz, and 0.04 mm ≤ W1 - Tz ≤ 0.1 mm.

[0014] Optionally, in an embodiment of the present invention, an oil storage groove is provided at the bottom of the track groove.

[0015] Compared with the prior art, the present invention can at least achieve the following beneficial effects. A track groove is designed on the cylinder body of the flexspline to provide a movement track for the bearing of the wave generator. This track groove structure reduces the path deviation that may occur during the movement of the bearing by guiding the bearing to roll along a predetermined path, such as the movement offset along the axial direction of the cylinder body. Such movement offsets can cause sliding friction between the bearing and the inner wall of the cylinder body, resulting in wear. In addition, in addition to providing a movement path for the bearing, the track groove can also play a role in storing oil. The inside of the track groove can temporarily store oil to ensure that the bearing can be lubricated with a sufficient amount of lubricating oil during movement, ensuring the lubricity between the bearing and the inner wall of the cylinder body. A sufficient amount of lubricating fluid can reduce the wear of the inner wall of the cylinder body to a certain extent. In summary, this solution solves the technical problem of easy wear of the inner wall of the current flexspline by providing a track groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order 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 following drawings 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.

[0017] Figure 1 It is a schematic structural diagram of Embodiment 1 of a low-wear flexspline of the present invention; Figure 2Schematic diagram of Structure of Embodiment 2 of a Low-wear Flexspline according to the present invention; Figure 3 Cross-sectional view of Embodiment 2 of a Low-wear Flexspline according to the present invention; Figure 4 For Figure 3 Local enlarged view at A in Figure 5 For Figure 3 Local enlarged view at B in Figure 6 Schematic diagram of the structure of the track groove in a low-wear flexspline according to the present invention.

[0018] Explanation of the reference numerals in the drawings: 100, cylinder body; 110, track groove; 120, oil storage tank; 200, tooth part; 300, connecting flange; 410, first reinforcing rib; 420, second reinforcing rib; 430, third reinforcing rib; 440, oil storage groove; Tr, wall thickness of the cylinder body; Tw, thickness of the reinforcing rib; W1, width of the track groove opening; W2, width of the track groove bottom; The realization of the object of the present invention, functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed Embodiment

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] It should be noted that all 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 accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0021] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; 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 internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. 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 situations.

[0022] In addition, if there are descriptions such as "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one such feature. 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 the 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 it. 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.

[0023] Referring to Figure 1 and Figure 2 , the present invention provides a low-wear flexspline, comprising: A cylinder body 100, the inner wall of the cylinder body 100 has a track groove 110, and the bearing of the wave generator moves along the track groove 110; A tooth part 200, the tooth part 200 is located on the outer circumferential wall at one end of the cylinder body 100 and is formed with a plurality of external teeth, and the tooth part 200 meshes with the rigid gear; A connecting flange 300, the connecting flange 300 is located at the other end of the cylinder body 100 and is connected to the cylinder body 100, and the connecting flange 300 is provided with a connecting hole.

[0024] Designing a track groove 110 on the cylinder body 100 of the flexspline to provide a movement track for the bearing of the wave generator. This track groove 110 structure reduces the path deviation that will occur during the movement of the bearing by guiding the bearing to roll along a predetermined path, such as the movement offset along the axial direction of the cylinder body 100. Such movement offsets will cause sliding friction between the bearing and the inner wall of the cylinder body 100, resulting in wear. In addition, in addition to providing a movement path for the bearing, the track groove 110 can also play a role in storing oil. The inside of the track groove 110 can store oil temporarily to ensure that the bearing can be lubricated by a sufficient amount of lubricating oil during the movement, ensuring the lubricity between the bearing and the inner wall of the cylinder body 100. A sufficient amount of lubricating fluid can reduce the wear of the inner wall of the cylinder body 100 to a certain extent. In summary, this solution solves the technical problem of easy wear of the inner wall of the current flexspline by opening the track groove 110.

[0025] Embodiment 1 Referring to Figure 1 , in this embodiment, the track groove 110 can be directly opened on the inner wall of the cylinder body 100 to provide a movement path for the bearing.

[0026] In addition to achieving the above effects, since the structure of the track groove 110 is relatively simple in this embodiment, the processing difficulty is relatively low, and no other structures are added to the flexspline. Thus, the overall mass of the flexspline changes little. Specifically, processes such as micro-diameter milling or inner wall precision grinding can be selected to complete the processing of the track groove 110.

[0027] However, due to the certain depth of the track groove 110, it is preferred to select a flexspline with a relatively large wall thickness of the cylinder 100 for processing and opening. In addition, after directly opening the track groove 110, the wall thickness of the flexspline at the track groove 110 will be reduced, which will have a certain impact on the structural strength of the flexspline.

[0028] Embodiment 2 Refer to Figures 2 to 6 , considering that directly opening the track groove 110 will affect the structural strength of the flexspline, for this reason, another preferred embodiment is proposed. In this embodiment, two annular reinforcing ribs are provided on the inner wall of the cylinder 100. The two reinforcing ribs are arranged at intervals, and a track groove 110 for the movement of the bearing is formed between the reinforcing ribs.

[0029] The track groove 110 of this structure can be applied to a wider range, and it can be applied to thin-walled flexsplines, with relatively low requirements for the wall thickness of the flexspline.

[0030] The two reinforcing ribs restrict the movement trajectory of the bearing, and control the radial runout of the bearing within 0.05 mm. Similarly, this track groove 110 structure can also achieve the function of storing oil, improve the grease retention rate, ensure the lubricity of the bearing during operation, and reduce the possibility of wear between the bearing and the flexspline due to insufficient lubrication.

[0031] In addition, compared with Embodiment 1, the structural strength of the flexspline in Embodiment 2 is enhanced after setting the reinforcing ribs, which can avoid the problem of the decrease in the structural strength of the flexspline caused by opening the track groove 110 in Embodiment 1.

[0032] Specifically, the two reinforcing ribs are the first reinforcing rib 410 and the second reinforcing rib 420 respectively. Among them, the first reinforcing rib 410 is a gradually thickening structure. When installing the wave generator, the wave generator extends into the cylinder 100 from the thin end of the first reinforcing rib 410. Since the flexspline has a certain elasticity, as the wave generator gradually extends in, the tooth part 200 of the flexspline generates a certain circumferential expansion. When the wave generator completely enters the track groove 110, the tooth part 200 of the flexspline retracts, and the first reinforcing rib 410 and the second reinforcing rib 420 limit the wave generator, avoiding radial sliding or detachment of the wave generator during movement.

[0033] Strict motion path constraints synchronize the elliptical trajectory of the wave generator with the deformation height of the flexspline, reducing the meshing phase error between the flexspline and the rigid gear. This not only eliminates the risk of sudden backlash changes but also reduces the transmission backlash through the precise movement of the contact points on the flexspline tooth surface along the theoretical conjugate curve, laying a foundation for high-precision applications such as robot joints.

[0034] On this basis, the suppression of the radial degree of freedom significantly optimizes the tribological characteristics, reduces the slip rate of the flexspline tooth surface, effectively delays the initiation of microcracks, and extends the fatigue life.

[0035] Furthermore, this design forms a failure protection mechanism through closed-loop control of the motion path. It not only confines the maximum radial deformation of the flexspline within the elastic limit to avoid plastic collapse but also maintains the force-closed state during sudden overloads, improving the reliability of the system under extreme working conditions. Additionally, from an energy perspective, the transmission efficiency is increased by approximately 4% - 7%. This not only reduces frictional heat generation but also extends the service life of the lubricating medium through optimized thermal management.

[0036] Further, a third reinforcing rib 430 is also provided inside the cylinder body 100. The third reinforcing rib 430 and the second reinforcing rib 420 form an oil storage groove 440.

[0037] After adding the third reinforcing rib 430, in addition to the improvement in structural strength, the formed oil storage groove 440 can improve the lubricity of the flexspline. Before installing the wave generator, lubricating grease can be pre-filled in the oil storage groove 440. And when the flexspline deforms, the oil storage groove 440 deforms accordingly, pumping the lubricating oil to the wave generator through the deformation to ensure an adequate amount of lubricating oil between the wave generator and the inner wall of the flexspline.

[0038] Except for the first reinforcing rib 410, the second reinforcing rib 420 and the third reinforcing rib 430 have the same structure, and the cross-section is an isosceles trapezoid. The symmetric inclined plane design can form a bilinear stiffness transition zone, optimize the stress distribution, and guide the flow of the lubricating oil in the oil storage groove 440, facilitating the inflow and outflow of the lubricating oil.

[0039] In addition, the connection between the reinforcing rib and the inner wall of the cylinder body 100 is a rounded corner.

[0040] The rounded corner design weakens stress concentration through smooth transition, making the stress distribution under alternating load more uniform, thereby extending fatigue life. In addition, the rounded corner design also hinders the straight-line expansion of cracks along the connection through a continuous curvature structure, forcing the crack to change direction around the curvature, extending the critical expansion path, and improving the fracture toughness of the material. The rounded corner design avoids material accumulation or cutting residue at sharp corners, reduces casting shrinkage holes, cold shut defects and machining tool wear, while promoting the uniform release of residual stress during heat treatment and improving process stability. In addition, the rounded corner structure also optimizes fluid dynamics, reduces lubricant flow resistance, and increases the oil film coverage by about 10%, effectively ensuring lubrication stability under high-speed and heavy-load conditions.

[0041] Furthermore, in this embodiment, the wall thickness of the cylinder 100 is defined as Tr, the thicknesses of the thickest parts of the plurality of reinforcing ribs are the same, the thickness of the thickest part of the reinforcing ribs is Tw, and 1.2≤Tr / Tw≤1.5.

[0042] Since the elastic deformation of the flexspline is the core mechanism of the harmonic reducer transmission, the wave generator forces the flexspline to produce uniform elliptical deformation, so that the flexspline and the rigid wheel gradually engage in misalignment to achieve deceleration. However, since the reinforcing ribs are annular, the deformation amplitude of the flexspline will inevitably be limited after the reinforcement ribs are set. If the reinforcement ribs excessively enhance the local stiffness, it may cause uneven deformation of the flexspline (such as deformation only in the unreinforced area), destroying the elliptical deformation mode, and causing problems such as poor tooth contact and eccentric load wear.

[0043] Therefore, it is necessary to find a balance between increasing the stiffness of the reinforcing ribs and retaining the overall flexibility of the flexible wheel to ensure that the deformation amplitude is sufficient and controllable.

[0044] In order to prevent the reinforcing ribs from excessively weakening the deformation capacity of the flexible wheel, the lower limit of the ratio is controlled to be above 1.2; in order to ensure that the reinforcing ribs can produce a structural reinforcement effect on the flexible wheel, the upper limit of the ratio is controlled to be below 1.5. It should be noted that the ratios in the range of 1.2 to 1.5 are all selectable ratios. When the flexible wheel is used in high-precision scenarios such as surgical robots, a small ratio is considered to give priority to ensuring the uniformity of the deformation of the cylinder 100; when the flexible wheel is used in high-load scenarios such as heavy-loaded robotic arms, a large ratio is considered to focus on structural strength.

[0045] In addition to controlling the thickness ratio, performance can also be optimized through position adjustment and other methods. For example, by analyzing the sensitive areas of flexible wheel deformation, reinforcement ribs can be arranged in a targeted manner; the thickness ratio and geometric parameters can be optimized according to the target load and reduction ratio.

[0046] Below, a further structural optimization design applicable to both Embodiment 1 and Embodiment 2 is provided. Along the circumferential direction of the track groove 110 , the cross section of the track groove 110 is an isosceles trapezoid, wherein the small end of the isosceles trapezoid is connected to the inner wall of the cylinder 100 .

[0047] Specifically, the width of the notch of the track groove 110 is W1, the width of the bottom of the groove is W2, and the thickness of the bearing is Tz. W2 = Tz, and 0.04 mm ≤ W1 - Tz ≤ 0.1 mm.

[0048] First of all, the dimension matching design (W2 = Tz) enables the bottom of the groove to fit precisely with the bearing thickness, forming a clearance-free fit, controlling the concentricity error between the wave generator and the flexspline assembly within ±0.005 mm, and reducing the transmission backlash. At the same time, the notch width W1 is slightly larger than the bottom of the groove to form a micro-conical inlet, which not only simplifies the self-centering process of bearing assembly, but also allows the flexspline to generate a radial micro-displacement of 0.02 - 0.05 mm during elastic deformation, avoiding local stress overrun caused by interference fit and providing a controllable release space for the deformation of the flexspline under dynamic loads.

[0049] Furthermore, an oil storage groove 120 is opened at the bottom of the track groove 110. Specifically, the position where the oil storage groove 120 is opened corresponds to the corner of the bearing to lubricate the corner of the bearing.

[0050] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention. 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 low-wear flexible gear, characterized in that, include: A cylinder, wherein the inner wall of the cylinder has a track groove, and the bearing of the wave generator moves along the track groove; A tooth portion, the tooth portion is located on the outer circumferential wall of one end of the cylinder and is formed with a plurality of external teeth, and the tooth portion is meshed with the rigid wheel; A connecting flange is located at the other end of the cylinder and connected to the cylinder, and a connecting hole is provided on the connecting flange.

2. The low-wear flexspline according to claim 1, wherein The cylinder body includes reinforcing ribs, at least two of which are provided, the two reinforcing ribs are respectively a first reinforcing rib and a second reinforcing rib, the first reinforcing rib and the second reinforcing rib are arranged at intervals to form the track groove.

3. The low-wear flexspline according to claim 2, wherein The first reinforcing rib is a gradually thickening reinforcing rib, and the first reinforcing rib gradually thickens in a direction from the tooth portion to the connecting flange.

4. The low-wear flexspline according to claim 3, wherein The wall thickness of the cylinder is Tr, the thickness of the thickest part of the reinforcing rib is Tw, and 1.2≤Tr / Tw≤1.

5.

5. The low-wear flexspline according to claim 3, wherein The cylinder body further includes a third reinforcing rib, which is located on a side of the second reinforcing rib away from the first reinforcing rib, and the second reinforcing rib and the third reinforcing rib form an oil storage groove.

6. The low-wear flexspline according to claim 5, characterized in that, Along the circumference of the cylinder, the cross-sections of the second reinforcing rib and the third reinforcing rib are isosceles trapezoids.

7. The low-wear flexspline according to claim 2, wherein The connection between the reinforcing rib and the cylinder is rounded.

8. The low-wear flexspline according to claim 1, wherein, The track groove is formed on the inner wall of the cylinder.

9. The low-wear flexspline according to claim 2 or 8, characterized in that, The width of the track groove is W1, the width of the groove bottom is W2, the thickness of the bearing is Tz, W2=Tz, 0.04mm≤W1-Tz≤0.1mm.

10. The low-wear flexspline according to claim 9, wherein An oil storage tank is arranged at the bottom of the track tank.

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