Harmonic reducer

Abstract

The invention belongs to the technical field of speed reducers, and particularly relates to a harmonic speed reducer. The harmonic reducer comprises a wave generator, a flexible gear and rigid gears, the flexible gear is arranged on the circumferential outer side of the wave generator in a sleeving mode, the wave generator enables the whole flexible gear to deform, the rigid gears comprise the outer rigid gear and the inner rigid gear, the outer rigid gear is arranged on the circumferential outer side of the flexible gear in a sleeving mode, and the outer rigid gear and the inner rigid gear are meshed through a gear ring; the number of teeth of the inner gear ring of the outer rigid gear is larger than that of teeth of the outer gear ring of the flexible gear. An inner gear ring is arranged on the inner wall of the end, deviating from the wave generator, of the flexible gear, the inner rigid gear is located on the inner side of the flexible gear and meshed with the inner gear ring of the flexible gear, the number of teeth of the inner gear ring of the flexible gear is larger than that of teeth of an outer gear ring of the inner rigid gear, and the flexible gear drives the inner rigid gear to rotate. The invention has the advantage of ensuring high output torque after reducing the reduction ratio.

Description

Technical Field

[0001] This invention belongs to the field of speed reducer technology, and particularly relates to a harmonic speed reducer. Background Technology

[0002] Harmonic reducers are mainly used in industrial robots. Some industrial robots require harmonic reducers with higher output speeds and larger rated output torques. Conventional harmonic reducers are limited by the maximum speed of the servo motor. To increase the output speed of a harmonic reducer, the reduction ratio of the reducer needs to be appropriately reduced.

[0003] However, reducing the reduction ratio of a harmonic reducer will decrease its rated output torque. One reason is that a smaller reduction ratio decreases the number of teeth on the flexure and rigid gears, and also reduces the number of meshing tooth pairs, leading to a drop in rated output torque. Another reason is that a harmonic reducer mainly consists of a wave generator, a flexure, and a rigid gear. The wave generator is elliptical, and the flexure deforms after being fitted onto it. The rigid gear is fitted outside the flexure and meshes with it via gears. Typically, a portion of the bending stress on the flexure tooth root of a harmonic reducer originates from the stress introduced by the deformation caused by the cam after the wave generator (the flexible bearing and cam are assembled as a single unit). This stress increases with the increase in cam deformation. In conventional harmonic reducers, the cam deformation is determined by the reduction ratio; the smaller the reduction ratio, the greater the required cam deformation, resulting in greater bending stress after the flexure is assembled, leading to a decrease in rated output torque and consequently, a lower rated output torque for the harmonic reducer. Summary of the Invention

[0004] The purpose of this invention is to provide a harmonic reducer with a low reduction ratio and high output rated torque.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a harmonic reducer, comprising a wave generator, a flexible wheel, and a rigid wheel. The flexible wheel is sleeved on the circumferential outer side of the wave generator, and the wave generator causes the flexible wheel to deform as a whole. The rigid wheel comprises an outer rigid wheel and an inner rigid wheel. The outer rigid wheel is sleeved on the circumferential outer side of the flexible wheel, and the two are meshed by a gear ring. The number of teeth on the inner gear ring of the outer rigid wheel is greater than the number of teeth on the outer gear ring of the flexible wheel. The flexible wheel has an inner gear ring on its inner wall at one end away from the wave generator. The inner rigid wheel is located inside the flexible wheel and meshes with the inner gear ring of the flexible wheel. The number of teeth on the inner gear ring of the flexible wheel is greater than the number of teeth on the outer gear ring of the inner rigid wheel. The flexible wheel drives the inner rigid wheel to rotate.

[0006] During operation, the output shaft of the servo motor connects to the wave generator, driving the wave generator to rotate. Because the wave generator is elliptical, the flex wheel deforms entirely when it engages with the outer gear ring. Both the outer and inner gear rings of the flex wheel deform. As the wave generator rotates, the flex wheel rotates in the opposite direction to the outer rigid wheel. This rotation drives the inner rigid wheel to rotate in the same direction as the flex wheel, and the inner rigid wheel rotates in the same direction relative to the flex wheel. A flange is connected to the inner rigid wheel, which then outputs force.

[0007] The inner rigid wheel will not deform but can rotate circumferentially, while the outer rigid wheel cannot deform or rotate circumferentially.

[0008] In this scheme, if the number of teeth on the inner gear ring of the outer rigid wheel is 'a' and the number of teeth on the outer gear ring of the flexible wheel is 'b', then for one rotation of the wave generator, the flexible wheel will rotate (ab) teeth relative to the outer rigid wheel in the opposite direction of the wave generator's rotation, typically 2 teeth. If the number of teeth on the outer gear ring of the inner rigid wheel is 'c' and the number of teeth on the inner gear ring of the flexible wheel is 'b', then for one rotation of the wave generator, the inner rigid wheel will rotate (bc) teeth relative to the flexible wheel in the opposite direction of the wave generator's rotation, typically 2 teeth. Finally, for one rotation of the wave generator, the inner rigid wheel will rotate (ab) + (bc) = (ac) teeth relative to the outer rigid wheel in the opposite direction of the wave generator's rotation, typically 4 teeth. At this point, the final reduction ratio is a:(ac), typically a:4.

[0009] In this scheme, the reduction ratio is reduced without changing the deformation of the cam, so the bending stress of the flexure will not increase, and the rated output torque of the harmonic reducer will not be reduced in terms of the deformation of the cam.

[0010] Meanwhile, the flexure of the harmonic reducer is elliptical, consisting of a long shaft and a short shaft. The long shaft protrudes outward and engages with the outer rigid wheel, while the short shaft is recessed inward and does not engage with the outer rigid wheel. Therefore, the effective contact teeth between the flexure and the outer rigid wheel are approximately 15%. Ordinary harmonic reducers require fewer teeth on the external gear to achieve a lower reduction ratio, which reduces the number of effective contact teeth and consequently lowers the rated output torque. However, this design achieves a lower reduction ratio without reducing the number of teeth on the external gear; simultaneously, because the number of teeth on the external gear remains unchanged, the number of effective contact teeth remains constant, thus ensuring a higher rated output torque for the harmonic reducer.

[0011] In summary, this solution provides a harmonic reducer with a low reduction ratio and high rated output torque.

[0012] Preferably, the flexible wheel includes a flexible wheel body, which is arranged with a constant diameter along its own axial direction. An external gear ring of the flexible wheel is provided on the outer wall of one end of the flexible wheel body, and an internal gear ring of the flexible wheel is provided on the inner wall of the other end of the flexible wheel body.

[0013] The flexible gear body has equal diameters in all parts, which makes the deformation at both ends of the axial direction the same and facilitates the deformation of the flexible gear. At the same time, compared with conventional harmonic reducers, the flexible gear in a conventional harmonic reducer needs to deform at one end but not at the other. Therefore, in order to facilitate the deformation of the flexible gear, the axial length of the flexible gear needs to be made longer, otherwise the flexible gear is difficult to deform. However, in this solution, both ends of the flexible gear need to deform, so the flexible gear in this solution can be made shorter in the axial direction compared with conventional flexible gears, thereby reducing the overall volume of the harmonic reducer.

[0014] Preferably, the wave generator includes a cam for receiving the output torque of the driver and a flexible bearing sleeved on the outside of the cam; a stepped structure is formed between one axial end of the internal gear ring of the flexible wheel and the inner wall of the flexible wheel body, the stepped structure being used to limit the axial position of the flexible bearing; when the flexible wheel is engaged with the wave generator, one axial end of the flexible wheel bearing is in contact with one axial end of the internal gear ring of the flexible wheel.

[0015] A stepped structure is directly formed between the axial end of the internal gear ring of the flexure and the flexure body. This stepped structure can restrict the axial position of the flexible bearing, so there is no need to set an additional structure on the inner wall of the flexure to restrict the flexible bearing. The structure is more compact, reducing the axial length of the entire flexure, thereby further reducing the volume of the entire harmonic reducer.

[0016] Preferably, the number of teeth on the inner gear ring of the outer rigid wheel is two more than the number of teeth on the outer gear ring of the flexible wheel.

[0017] Having two more teeth on the internal gear ring of the rigid outer wheel than on the external gear ring of the flexible wheel is more in line with conventional design range.

[0018] Preferably, the number of teeth on the internal gear ring of the flexible wheel is two more than the number of teeth on the external gear ring of the internal rigid wheel.

[0019] Having two more teeth on the internal gear ring of the flexible gear than the external gear ring of the internal rigid gear is more in line with conventional design range.

[0020] Preferably, the number of teeth on the inner gear ring of the flexible wheel is the same as the number of teeth on the outer gear ring, and each tooth on the inner gear ring of the flexible wheel corresponds one-to-one with each tooth on the outer gear ring in the axial direction.

[0021] The number of teeth on the inner gear ring of the flexure is the same as the number of teeth on the outer gear ring, so that each tooth on the inner gear ring and the outer gear ring can correspond one-to-one, and the outer teeth and the inner teeth are not separated. This allows each tooth on the inner gear ring and the outer gear ring to deform in the same direction when the two ends of the flexure are deformed, which is beneficial to the deformation of the entire flexure.

[0022] Preferably, the number of flexible bearings is two, and the two flexible bearings are spaced apart along the axial direction.

[0023] By setting two flexible bearings, the radial force can be better supported, and the contact area between the bearing and the flexible wheel can be increased, thus ensuring that the flexible wheel can deform as a whole after it is fitted onto the wave generator.

[0024] Preferably, the inner rigid wheel has an axially open mating groove at the center of its end face, and the end face of the inner rigid wheel has a plurality of fixing holes for fixing to the flange.

[0025] The mating groove facilitates mating with the flange, and the fixing hole enables fixation with the flange.

[0026] The harmonic reducer of the present invention has the advantages of low reduction ratio and high output torque. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention.

[0028] Figure 2 This is an exploded view of the present invention.

[0029] Figure 3 This is an axonometric sectional view of the present invention.

[0030] Figure 4 This is an axonometric sectional view of the present invention.

[0031] Figure 5 This is a cross-sectional view of the present invention.

[0032] Figure 6 This is a magnified view of the flexible wheel.

[0033] Figure 7 for Figure 5 Enlarged view of point A.

[0034] Figure 8 This is a partially enlarged view of the front view of the flexible wheel.

[0035] Figure 9 This is a schematic diagram of the structure between the outer rigid wheel and the flexible wheel.

[0036] Figure 10 This is a schematic diagram of the structure between the inner rigid wheel and the flexible wheel.

[0037] Reference numerals: 1. Outer rigid wheel; 2. Inner rigid wheel; 21. Fixing hole; 22. Mating groove; 3. Flexible wheel; 31. Flexible wheel body; 32. External gear ring of the flexible wheel; 33. Internal gear ring of the flexible wheel; 34. Stepped structure; 4. Wave generator; 5. Flexible bearing; 6. Cam. Detailed Implementation

[0038] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0039] like Figures 1 to 6 As shown, this embodiment discloses a harmonic reducer, including an outer rigid wheel 1, an inner rigid wheel 2, a flexible wheel 3, and a wave generator 4. The wave generator 4 is elliptical and consists of a cam 6 and two flexible bearings 5 ​​sleeved on the outer periphery of the cam 6. The flexible wheel 3 is sleeved on the outer side of the flexible bearings 5 ​​with a transition fit between them, and the flexible wheel 3 is elliptical under the action of the wave generator 4. The flexible wheel 3 includes a flexible wheel body 31, which is a regular cylindrical shape and has a uniform diameter throughout its axial direction. An outer gear ring 32 of the flexible wheel body 31 is provided on the outer wall of one end of the flexible wheel body 31 located from the wave generator 4, and an inner gear ring 33 of the flexible wheel is provided on the inner wall of the flexible wheel body 31 located away from the wave generator 4. The cam 6 has a keyway at its center for connection with the output shaft of a servo motor.

[0040] The wave generator 4 causes the flexible wheel 3 to deform into an elliptical shape. An outer rigid wheel 1 is fitted on the circumferential outer wall of one end of the wave generator 4. The outer rigid wheel 1 is fixed and cannot be deformed. The outer rigid wheel 1 and the flexible wheel 3 are meshed by teeth. The number of teeth on the inner gear ring of the outer rigid wheel 1 is 164, and the number of teeth on the outer gear ring of the flexible wheel 3 is 162.

[0041] The inner rigid wheel 2 cannot deform. It is used to connect to the flange and output torque. The inner rigid wheel 2 is located at one end of the flexible wheel 3, away from the wave generator 4. The inner rigid wheel 2 and the internal gear ring of the flexible wheel 3 mesh with each other. The inner rigid wheel 2 has 160 external teeth, and the flexible wheel 3 has 162 internal teeth. The inner rigid wheel 2 has an axially open mating groove 22 at its center, which is used for positioning and mating with the flange. Several fixing holes 21 are provided on the end face of the inner rigid wheel 2 for fixing to the flange.

[0042] like Figures 5 to 8 As shown, each tooth of the outer gear ring 32 of the flexure corresponds one-to-one with each tooth of the inner gear ring 33 of the flexure in the axial direction, and they are not separated. A stepped structure 34 is formed between one axial end of the inner gear ring 33 of the flexure and the inner wall of the flexure body 31. The flexible bearing 5 on the left side contacts the stepped structure 34 (contacts one axial end of the inner gear ring 33 of the flexure). The two flexible bearings 5 ​​are spaced apart along the axial direction.

[0043] The number of teeth on the inner gear ring of the outer rigid wheel 1 is two more than the number of teeth on the outer gear ring of the flexible wheel. Therefore, the reduction ratio between the outer rigid wheel 1 and the flexible wheel 3 is calculated as 164 / (164-162), which is 82:1. If the wave generator 4 rotates clockwise relative to the outer rigid wheel 1, the flexible wheel 3 will rotate counterclockwise relative to the outer rigid wheel 1 by two teeth. The flexible wheel 3 will drive the inner rigid wheel 2 to rotate counterclockwise relative to the outer rigid wheel 1. The inner rigid wheel 2 will rotate two more teeth than the flexible wheel 3, so the inner rigid wheel 2 will rotate four teeth (2+2) counterclockwise relative to the outer rigid wheel 1. Therefore, the reduction ratio is calculated as 164 / 4, which is 41:1. That is, this scheme reduces the reduction ratio but does not change the number of teeth on the outer rigid wheel 1 and the flexible wheel 3, nor the deformation of the cam 6.

[0044] like Figure 9 and Figure 10 As shown, the flexible wheel 3 deforms as a whole under the action of the wave generator and becomes elliptical. Figure 9 and Figure 10 This diagram shows the meshing of the outer rigid wheel 1 and the inner rigid wheel 2 with the flexible wheel 3 at the same time. Point B represents the long axis portion of the flexible wheel 3, and point C represents the short axis portion. The long axis portion of the outer gear ring 32 of the flexible wheel protrudes outward and engages with the outer rigid wheel 1, while the short axis portion of the outer gear ring 32 is recessed inward and does not engage with the outer rigid wheel 1. At the same time, the long axis portion of the inner gear ring 33 of the flexible wheel protrudes outward and does not engage with the outer rigid wheel 1, while the short axis portion of the inner gear ring 33 is recessed inward and engages with the outer rigid wheel 1.

Claims

1. A harmonic reducer comprising a wave generator, a flexspline, a rigid spline, the flexspline being sleeved on the circumferential outside of the wave generator, characterized in that: The wave generator makes the flexible gear whole deformed, the rigid gear includes an outer rigid gear and an inner rigid gear, the outer rigid gear is sleeved on the circumferential outside of the flexible gear and is engaged through a gear ring, the number of teeth of the inner gear ring of the outer rigid gear is more than the number of teeth of the outer gear ring of the flexible gear; the flexible gear is provided with an inner gear ring on the inner wall of one end deviated from the wave generator, the inner rigid gear is located on the inner side of the flexible gear and is engaged with the inner gear ring of the flexible gear, the number of teeth of the inner gear ring of the flexible gear is more than the number of teeth of the outer gear ring of the inner rigid gear, and the flexible gear drives the inner rigid gear to rotate.

2. The harmonic reducer of claim 1, wherein: The flexible gear includes a flexible gear body, the flexible gear body is provided with an outer gear ring of the flexible gear on the outer wall of one end in the axial direction of the flexible gear body, and the flexible gear body is provided with an inner gear ring of the flexible gear on the inner wall of the other end.

3. The harmonic reducer of claim 2, wherein: The wave generator includes a cam for receiving the output torque of the driver and a flexible bearing sleeved on the outside of the cam; a step structure is formed between the axial one end of the inner gear ring of the flexible gear and the inner wall of the flexible gear body, the step structure is used for limiting the axial position of the flexible bearing, and when the flexible gear is matched with the wave generator, the axial one end of the flexible gear bearing is in contact with the axial one end of the inner gear ring of the flexible gear.

4. The harmonic reducer of claim 1, wherein: The number of teeth of the inner gear ring of the outer rigid gear is more than the number of teeth of the outer gear ring of the flexible gear by 2.

5. The harmonic reducer of claim 1, wherein: The number of teeth of the inner gear ring of the flexible gear is more than the number of teeth of the outer gear ring of the inner rigid gear by 2.

6. The harmonic reducer of claim 1 or 2 or 3, wherein: The number of teeth of the inner gear ring of the flexible gear is the same as the number of teeth of the outer gear ring, and each tooth of the inner gear ring of the flexible gear corresponds to each tooth of the outer gear ring in the axial direction.

7. The harmonic reducer of claim 3, wherein: The number of the flexible bearings is two, and the two flexible bearings are spaced apart in the axial direction.

8. The harmonic reducer of claim 1 or 2 or 3, wherein: An axial opening matching groove is arranged at the center of the end face of the inner rigid gear, and a plurality of fixing holes for fixing the flange are arranged on the end face of the inner rigid gear.

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