A double-pulley simple-harmonic wave reducer

Abstract

The application discloses a double-flexspline simple-harmonic reducer, which comprises a shell assembly and an output wheel; the shell assembly is internally provided with a first wave generator and a second wave generator; the outer rings of the first wave generator and the second wave generator are respectively provided with a first flexspline and a second flexspline; the shell assembly comprises an upper shell, a lower shell and a cover; the upper shell, the lower shell and the cover are sequentially arranged from top to bottom to form a cylindrical cavity with a closed bottom; the two wave generators driven by an input shaft have a fixed phase difference, the two flexsplines have a dislocation meshing movement, the transmission precision is significantly improved by using the error averaging effect, the continuous rotation of the input end is converted into the high-precision limited-angle swing of the output end, and the high-performance requirement of the small-angle joint of the humanoid robot is perfectly met.

Description

Technical Field

[0001] This invention relates to the field of speed reducers, specifically a dual-flexible-wheel simple harmonic speed reducer. Background Technology

[0002] With the continuous advancement of robotics technology, especially in applications such as collaborative robots and humanoid robots, the performance requirements for harmonic reducers are becoming increasingly stringent. They not only need to have characteristics such as high transmission accuracy and large transmission ratio, but also require higher standards in terms of low friction and quiet operation. Existing robot harmonic reducer bearings typically utilize the elastic deformation of flexible components to achieve large transmission ratio and high-precision transmission, thereby achieving the goal of using a flexible outer ring to adapt to deformation requirements, using rolling elements to reduce friction, and using a rigid inner ring to transmit power.

[0003] For example, our company's earlier patent application, publication number CN119435674A, discloses a wave reducer for robot joints, including a roller cross bearing; a flexible wheel is installed on the inner ring of the roller cross bearing, a rigid wheel is installed on the outer side of the flexible wheel, a lubrication mechanism is installed on the rigid wheel near the inner wall of the flexible wheel, a wave generator is installed inside the flexible wheel, and the lubrication mechanism includes a retaining ring, a through hole and a lubrication layer, and a retaining ring is installed on the rigid wheel near the inner wall of the flexible wheel.

[0004] The aforementioned patent utilizes a combination of a fixed ring, a through hole, and a lubrication layer. Lubricating oil inside the fixed ring is delivered to the lubrication layer through the through hole. When the flex wheel rotates, the lubricating oil adsorbed on the lubrication layer is directly applied to the outer surface of the flex wheel. The lubricating oil gradually penetrates between the flex wheel and the rigid wheel, providing lubrication at the transmission point between the outer surface of the flex wheel and the inner wall of the rigid wheel. This reduces wear caused by insufficient lubrication in the reducer, lowers the internal temperature of the reducer, and thus does not affect the reducer's operation. However, the disadvantage of this patent is that the transmission accuracy of traditional single-flex wheel harmonic reducers is limited by the manufacturing precision limit of a single flex wheel. Since all errors accumulate from a single transmission chain and cannot be offset by the structure itself, further improvements in accuracy require extremely costly ultra-precision machining, exhibiting a significant "ceiling" effect.

[0005] Therefore, it is necessary to improve such a structure to overcome the above-mentioned defects. Summary of the Invention

[0006] The purpose of this invention is to provide a dual flexible wheel harmonic reducer to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A dual-flexible-wheel harmonic reducer includes a housing assembly and an output wheel. The housing assembly houses a first wave generator and a second wave generator. The outer rings of the first and second wave generators are respectively equipped with a first flexible wheel and a second flexible wheel. The housing assembly includes an upper housing, a lower housing, and a cover. The upper housing, lower housing, and cover are arranged sequentially from top to bottom to form a bottom-closed cylindrical cavity. The top of the inner ring of the upper housing is equipped with a first rigid wheel, and the bottom of the inner ring of the lower housing is equipped with a second rigid wheel, wherein the first flexible wheel meshes with the first rigid wheel, and the second flexible wheel meshes with the second rigid wheel. The output wheel is sleeved on the reducer's input shaft, and the upper and lower ends of the output wheel are respectively fixedly mounted with the first and second flexible wheels.

[0008] Furthermore, there is a phase difference between the first wave generator and the second wave generator, that is, at the same moment, there is an angle θ between the meshing point α of the first flexible wheel and the first rigid wheel, the meshing point β of the second flexible wheel and the second rigid wheel.

[0009] The value of θ is 60° ± 5°.

[0010] Furthermore, the upper shell, lower shell, and cover are fixedly connected by a first fixing screw; specifically, the edge of the upper shell has a countersunk hole adapted to the first fixing screw; the edge of the lower shell has a countersunk hole for the first fixing screw to pass through; the edge of the upper shell has a countersunk hole adapted to the first fixing screw; and the edge of the cover has a threaded hole adapted to the first fixing screw.

[0011] Furthermore, both the first wave generator and the second wave generator are fixedly mounted on the input shaft of the reducer. The bottom of the input shaft of the reducer is rotatably connected to the bottom of the cover through a tapered roller bearing. An upper cam mounting seat is fixedly mounted on the upper section of the input shaft of the reducer; a lower cam mounting seat is fixedly mounted on the lower section of the input shaft of the reducer; and the first wave generator and the second wave generator are fixedly mounted on the upper cam mounting seat and the lower cam mounting seat, respectively.

[0012] Furthermore, the first wave generator includes a first flexible bearing and a first cam; the first flexible bearing and the first cam are located inside the first flexible wheel, and after the first wave generator is embedded in the first flexible wheel, it opens the teeth on the upper outer wall of the first flexible wheel, and the teeth of the first flexible wheel mesh with the teeth of the first rigid wheel.

[0013] Furthermore, the second wave generator includes a second flexible bearing and a second cam; the second flexible bearing and the second cam are located inside the second flexible wheel, and after the second wave generator is embedded in the second flexible wheel, it opens the teeth on the upper outer wall of the second flexible wheel, and the teeth of the second flexible wheel mesh with the teeth of the second rigid wheel.

[0014] Furthermore, an output arm extends horizontally outward from the outer side of the output wheel, and an arc-shaped clearance groove is provided at the connection between the upper and lower housings to allow the output arm to swing.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention drives two wave generators with a fixed phase difference through an input shaft, causing the two flexible wheels to produce misaligned meshing motion. It significantly improves transmission accuracy by utilizing the error averaging effect. Furthermore, through the cooperation of the output arm and the clearance groove, the continuous rotation at the input end is converted into high-precision finite-angle oscillation at the output end, perfectly meeting the high-performance requirements of small-angle joints in humanoid robots. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a dual-flexible-wheel simple harmonic reducer.

[0017] Figure 2 This is a front view of a dual-flexible-wheel simple harmonic reducer.

[0018] Figure 3 This is a side view of a dual-flexible-wheel simple harmonic reducer.

[0019] Figure 4 This is a top view of a dual-flexible-wheel simple harmonic reducer.

[0020] Figure 5 for Figure 3 Sectional view at point AA. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] Please see Figure 1-5 A dual flexible wheel simple harmonic reducer includes a housing assembly 1 and an output wheel 7; The housing assembly 1 is provided with a first wave generator 2 and a second wave generator 3 inside; and the outer rings of the first wave generator 2 and the second wave generator 3 are respectively provided with a first flexible wheel 4 and a second flexible wheel 5. The housing assembly 1 includes an upper housing 101, a lower housing 102, and a cover 103; the upper housing 101, lower housing 102, and cover 103 are arranged sequentially from top to bottom to form a cylindrical cavity with a closed bottom; the upper housing 101, lower housing 102, and cover 103 are fixedly connected by a first fixing screw 104; specifically, the edge of the upper housing 101 has a countersunk hole adapted to the first fixing screw 104; the edge of the lower housing 102 has a countersunk hole for the first fixing screw 104 to pass through; the edge of the upper housing 101 has a countersunk hole adapted to the first fixing screw 104; the edge of the cover 103 has a threaded hole adapted to the first fixing screw 104. Meanwhile, the top of the inner ring of the upper housing 101 is provided with a first rigid wheel 105, and the bottom of the inner ring of the lower housing 102 is provided with a second rigid wheel 106, wherein the first flexible wheel 4 meshes with the first rigid wheel 105, and the second flexible wheel 5 meshes with the second rigid wheel 106. The first wave generator 2 and the second wave generator 3 are both fixedly mounted on the input shaft 6 of the reducer. The bottom of the input shaft 6 of the reducer is rotatably connected to the bottom of the cover 103 through a tapered roller bearing 601. An upper cam mounting seat 602 is fixedly mounted on the upper section of the input shaft 6 of the reducer; a lower cam mounting seat 603 is fixedly mounted on the lower section of the input shaft 6 of the reducer. The first wave generator 2 and the second wave generator 3 are respectively fixedly installed on the upper cam mounting base 602 and the lower cam mounting base 603; The first wave generator 2 includes a first flexible bearing 201 and a first cam 202; the first flexible bearing 201 and the first cam 202 are located inside the first flexible wheel 4. After the first wave generator 2 is embedded in the first flexible wheel 4, it opens the teeth on the upper outer wall of the first flexible wheel 4, and the teeth of the first flexible wheel 4 mesh with the teeth of the first rigid wheel 105. The second wave generator 2 includes a second flexible bearing 301 and a second cam 302; the second flexible bearing 301 and the second cam 302 are located inside the second flexible wheel 5. After the second wave generator 2 is embedded in the second flexible wheel 4, it opens the teeth on the upper outer wall of the second flexible wheel 5, and the teeth of the second flexible wheel 5 mesh with the teeth of the second rigid wheel 106. Meanwhile, the output wheel 7 is sleeved on the input shaft 6 of the reducer. In this scheme, the output wheels 7 do not directly contact the input shaft 6 of the reducer. At the same time, the upper and lower ends of the output wheel 7 are respectively fixedly installed with the first flexible wheel 4 and the second flexible wheel 5. Traditional reducers require the output end to rotate continuously and more than 360°. However, considering that the rotation angle of some robot joints is very small, especially in modern humanoid robots which are designed to simulate the human body, the angle range is usually even smaller. For example, the pitch / swing angle of the ankle joint (corresponding to the human ankle) is usually ±30°-±45°. Therefore, in this solution, an output arm 701 is also provided on the outer side of the output wheel 7, and an arc-shaped clearance groove 107 for the output arm 701 to swing is provided at the connection between the upper housing 101 and the lower housing 102. There is a phase difference between the first wave generator 2 and the second wave generator 3. That is, at the same moment, the meshing point α between the first flexible wheel 4 and the first rigid wheel, and the meshing point β between the second flexible wheel 5 and the second rigid wheel, have an included angle θ between them. In this scheme, the θ is 60°±5°. Since there will inevitably be a small tooth pitch error (some teeth have large gaps and some have small gaps) during the machining of the teeth of the flexible wheel and the steel wheel, when there is a phase difference of 30°–90° between the two flexible wheels, when the "largest error tooth" of the first flexible wheel 4 enters the mesh, the "smallest error tooth" of the second flexible wheel 5 also enters the mesh. The two flexible wheels drive the output arm to move together, which can maximize the averaging of errors and improve the transmission accuracy. It's also important to note that we don't need to know precisely which tooth has the "maximum error" and which has the "minimum error." What we rely on is that while the pitch error of the flexspline is fixed, its distribution on the circumference is pseudo-random; when you rotate the second flexspline by 60°±5°, its error waveform shifts relative to the first flexspline; as the wave generator continues to rotate, the error waveforms of the two flexsplines are staggered on the time axis; when one flexspline is at its "error peak," the other flexspline is likely at its "error trough" or "error neutral zone."

[0023] The principle is similar to the fact that two sets of sine waves cancel each other out after being superimposed. Ideally, the two sets of sine waves would completely cancel each other out after being superimposed. However, in actual production, the probability of obtaining two sets of perfectly symmetrical flex wheels is extremely low. Therefore, we set the included angle θ to 60°±5°, which can reduce the error to a certain extent and make the assembly and processing less difficult.

[0024] Meanwhile, during assembly, the installation angle of the second wave generator 3 can be manually fine-tuned by ±5° to adjust the engagement point β of the second flexible wheel 5, thereby making the two error curves "aligned in opposite directions" in time, resulting in smaller and more uniform output errors. Furthermore, in this solution, by adjusting the installation angle of the second flexible wheel at a large angle, an assembly method with smaller transmission errors can be obtained with a limited number of adjustments.

[0025] When this solution is put into use, the external servo motor is located on the top of the housing. The output shaft of the servo motor drives the input shaft of the reducer to rotate. The upper cam mounting seat and the lower cam mounting seat fixed on the input shaft of the reducer rotate synchronously, thereby driving the first wave generator and the second wave generator to start rotating at the same speed and phase. The elliptical cams of the first and second wave generators are respectively embedded in the thin-walled inner holes of the first and second flexible wheels. The rotation of the cams forces the two flexible wheels to undergo periodic elastic deformation from their original circular shape, being "stretched" into an elliptical shape; The deformed flexible wheel has its external teeth meshing with the internal teeth of the first and second rigid wheels fixed on the housing. Since the rigid wheels are stationary, according to the principle of harmonic drive, the flexible wheel will produce a small deceleration rotation opposite to the rotation direction of the wave generator under the reaction force of the meshing.

[0026] Meanwhile, since the flexible wheel and the steel wheel only mesh in a certain area in this solution, after wear causes a decrease in accuracy, the two sets of flexible wheels can be installed by disassembling the flexible wheel and rotating them to change different meshing areas, thereby restoring accuracy.

[0027] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connect" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A dual-flexible-wheel harmonic reducer, comprising a housing assembly and an output wheel; characterized in that, The housing assembly contains a first wave generator and a second wave generator; the outer rings of the first wave generator and the second wave generator are respectively provided with a first flexible wheel and a second flexible wheel; the housing assembly includes an upper housing, a lower housing, and a cover; the upper housing, the lower housing, and the cover are arranged sequentially from top to bottom to form a cylindrical cavity with a closed bottom; the top of the inner ring of the upper housing is provided with a first rigid wheel, and the bottom of the inner ring of the lower housing is provided with a second rigid wheel, wherein the first flexible wheel meshes with the first rigid wheel, and the second flexible wheel meshes with the second rigid wheel; the output wheel is sleeved on the input shaft of the reducer, and the upper and lower ends of the output wheel are respectively fixedly installed with the first flexible wheel and the second flexible wheel.

2. The dual flexible wheel harmonic reducer according to claim 1, characterized in that, The first wave generator and the second wave generator have a phase difference, that is, at the same time, there is an angle θ between the meshing point α of the first flexible wheel and the first rigid wheel, the meshing point β of the second flexible wheel and the second rigid wheel.

3. The dual flexible wheel harmonic reducer according to claim 2, characterized in that, The value of θ is 60° ± 5°.

4. The dual flexible wheel harmonic reducer according to claim 1, characterized in that, The upper shell, lower shell, and cover are fixedly connected by a first fixing screw; specifically, the edge of the upper shell has a countersunk hole adapted to the first fixing screw; the edge of the lower shell has a countersunk hole for the first fixing screw to pass through; the edge of the upper shell has a countersunk hole adapted to the first fixing screw; and the edge of the cover has a threaded hole adapted to the first fixing screw.

5. A dual-flexible gear harmonic reducer according to claim 1, characterized in that, The first wave generator and the second wave generator are both fixedly mounted on the input shaft of the reducer. The bottom of the input shaft of the reducer is rotatably connected to the bottom of the cover through a tapered roller bearing. An upper cam mounting seat is fixedly mounted on the upper section of the input shaft of the reducer; a lower cam mounting seat is fixedly mounted on the lower section of the input shaft of the reducer; the first wave generator and the second wave generator are respectively fixedly mounted on the upper cam mounting seat and the lower cam mounting seat.

6. A dual-flexible gear harmonic reducer according to claim 5, characterized in that, The first wave generator includes a first flexible bearing and a first cam; the first flexible bearing and the first cam are located inside the first flexible wheel. After the first wave generator is embedded in the first flexible wheel, it opens the teeth on the upper outer wall of the first flexible wheel, and the teeth of the first flexible wheel mesh with the teeth of the first rigid wheel.

7. A dual-flexible gear harmonic reducer according to claim 6, characterized in that, The second wave generator includes a second flexible bearing and a second cam; the second flexible bearing and the second cam are located inside the second flexible wheel. After the second wave generator is embedded in the second flexible wheel, it opens the teeth on the upper outer wall of the second flexible wheel, and the teeth of the second flexible wheel mesh with the teeth of the second rigid wheel.

8. A dual-flexible gear harmonic reducer according to any one of claims 1-7, characterized in that, An output arm extends horizontally outward from the outer side of the output wheel, and an arc-shaped clearance groove is provided at the connection between the upper and lower housings to allow the output arm to swing.

Images