A harmonic reducer using an external wave generator

Abstract

This invention relates to the field of harmonic reducer technology, specifically to a harmonic reducer using an external wave generator, comprising: an external wave generator including an internal cam body and a flexible wheel bearing, the flexible wheel bearing being embedded in the internal cam body and rotated by the internal cam body; a flexible wheel, one end of which is embedded in the inner ring of the flexible bearing and circumferentially driven by the flexible bearing; and a rigid wheel, the rigid wheel being embedded in the inner ring of one end of the flexible wheel, and the external teeth on the outer ring of the rigid wheel meshing with the internal teeth on the long axis of the inner ring of the flexible wheel for circumferential transmission, thereby reducing speed, increasing torque, and transmitting work outward. This invention significantly increases the hollow through-hole diameter of the harmonic reducer without changing the pitch circle size and module of the harmonic teeth.

Description

Technical Field

[0001] This invention relates to the field of harmonic reducers, and more particularly to a harmonic reducer using an external wave generator. Background Technology

[0002] Harmonic reducers, as precision transmission devices, are widely used in high-precision motion control fields such as industrial robots, aerospace, and precision instruments due to their advantages such as high transmission ratio, compact structure, high transmission accuracy, and low backlash. Their basic working principle utilizes the elastic deformation of a flexible wheel to transmit motion and power. The core components typically include a rigid wheel, a flexible wheel, and a wave generator that causes controllable elastic deformation of the flexible wheel.

[0003] The wave generator is a key component of a harmonic reducer, its function being to generate excitation that causes the flexspline to deform periodically. Currently, common wave generators mainly employ an "internal" structure, where the wave generator is placed inside the flexspline. Through mechanical structures such as cams, ball bearings, or a four-axis ellipse, a radial force is applied to the flexspline from the inside out, forcing the center of the flexspline to undergo elliptical deformation, thus meshing with the rigid gear teeth. However, this type of traditional internal wave generator has gradually revealed some inherent limitations in practical applications: Firstly, in certain special fields, such as when the output speed requirement is not high, the torque is moderate, and the precision is high, but the harmonic reducer needs to reserve an extra-large aperture in the middle to pass through the cable or pipe, the conventional internal wave generator harmonic reducer is limited by the hollow aperture, which forces the selection of a very large harmonic base model, resulting in a large torque margin, and at the same time, the whole machine is very large and heavy.

[0004] Secondly, regarding structural layout and space constraints, the internal wave generator requires space within the flexspline, necessitating a sufficiently large inner diameter to accommodate the generator components. This limits further miniaturization and lightweight design of the harmonic reducer's axial dimensions, particularly in applications requiring ultra-thin, compact structures (such as small robotic arm joints and precision optical adjustment mechanisms). Furthermore, the complex internal structure increases the difficulty and cost of overall assembly. Furthermore, in terms of heat dissipation and lubrication, since the wave generator is built into the flexible wheel, the frictional heat it generates is not easily dissipated, which may lead to a high internal temperature rise, affecting the performance of the lubricant and accelerating the aging of components. At the same time, the limited internal space also poses a challenge to the design of a long-lasting and uniform lubrication system.

[0005] Therefore, existing harmonic reducer technology, especially the mainstream built-in wave generator structure, is facing increasing structural constraints and performance bottlenecks as the trend towards higher power density, better heat dissipation, and more compact axial dimensions emerges. There is an urgent need for a new wave generator structure that can effectively improve the aforementioned problems while maintaining the core advantages of harmonic drives, thereby broadening the application scope of harmonic reducers in high-end equipment and enhancing their overall performance. Summary of the Invention

[0006] To address the technical problems existing in the prior art, embodiments of the present invention provide a harmonic reducer using an external wave generator. The technical solution is as follows: A harmonic reducer using an external wave generator, comprising: An external wave generator includes an internal cam body and a flexible wheel bearing, wherein the flexible wheel bearing is embedded in the internal cam body and is driven to rotate by the internal cam body. A flexible wheel, one end of which is embedded in the inner ring of the flexible bearing so as to be circumferentially driven by the flexible bearing; A rigid wheel is fitted into the inner ring of one end of the flexible wheel, and the external teeth on the outer ring of the rigid wheel mesh with the internal teeth on the long axis of the inner ring of the flexible wheel for circumferential transmission, so as to reduce speed, increase torque and transmit work outward.

[0007] Preferably, the inner ring wall of the inner cam body is in the shape of a cam with long and short axes, for mounting the flexure bearing.

[0008] Preferably, the external cam body is provided with a first mounting hole, which is used for mechanical transmission connection with the power device.

[0009] Preferably, the outer ring of the flexible bearing is pressed into the inner ring of the inner cam body, so that it is squeezed into an elliptical shape with major and minor axes by the inner ring of the inner cam body. The inner ring of the elliptical flexible bearing is used to transmit power to the flexible wheel.

[0010] Preferably, the inner ring of the inner cam body is fitted with a retaining ring to axially limit the flexible bearing.

[0011] Preferably, after one end of the flexible wheel is embedded in the inner ring of the flexible bearing, it is compressed into an elliptical shape by the long and short shaft inner ring structure of the flexible bearing for circumferential transmission with the rigid wheel.

[0012] Preferably, the rigid wheel is provided with a second mounting hole, which is used to connect with an external mechanical structure for transmission, thereby transmitting power outward.

[0013] Preferably, the power unit is arranged in the space outside the flexible wheel to improve the overall integration.

[0014] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: (1) The harmonic reducer using an external wave generator in this invention greatly improves the hollow through-hole diameter of the harmonic reducer without changing the pitch circle size and module of the harmonic teeth. (2) The harmonic reducer using an external wave generator in this invention greatly enriches the application scenarios of the harmonic reducer through excellent structural design without changing the performance of the harmonic gear; from another perspective, under the same hollow hole usage conditions, this design occupies less space, weighs less, and has lower cost. (3) The present invention uses an external wave generator for the harmonic reducer. This design extends the input end of the harmonic reducer from a closed and limited space to an open space, which greatly facilitates the design of the harmonic reduction module. For example, the motor rotor can be directly arranged outside the external wave generator, so that the motor output end and the input end of the harmonic reducer are integrated into one component, which can achieve more extreme space utilization; (4) The harmonic reducer of the present invention uses an external wave generator. The internal cavity of the flexible wheel can be designed as a flow channel for air or cooling medium, or directly form convection with the external environment, so that the heat generated in the meshing area and deformation area can be dissipated more efficiently, and the problem of internal heat accumulation in traditional structures can be completely solved. Attached Figure Description

[0015] Figure 1 This is the front-end main view of the present invention; Figure 2 This is the main backend view of the present invention; Figure 3 This is a schematic diagram of the front-end three-dimensional structure of the present invention; Figure 4 For the present invention Figure 1 Schematic diagram of the three-dimensional structure in the AA direction section; Figure 5 For the present invention Figure 4 A magnified view of part B in the image.

[0016] In the diagram: 1-flexible wheel, 2-rigid wheel, 3-internal cam body, 4-flexible wheel bearing, 5-circlip. Detailed Implementation

[0017] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0018] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0019] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0020] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0021] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0022] according to Figures 1-5 As shown, a harmonic reducer using an external wave generator includes an external wave generator, a flexible wheel, and a rigid wheel. The external wave generator is driven by a power component. The flexible wheel is fitted into the external wave generator and is driven to rotate by the external wave generator. The rigid wheel is fitted into the flexible wheel and is driven by the flexible wheel to reduce speed, increase torque, and transmit work outward.

[0023] The external wave generator includes an internal cam body and a flexible wheel bearing. The flexible wheel bearing is embedded in the internal cam body and is driven to rotate by the internal cam body. The internal cam body is generally annular, and the inner ring wall of the internal cam body has a cam shape (elliptical shape) with its major and minor axes, for mounting the flexible wheel bearing. Furthermore, the external cam body is provided with a first mounting hole for mechanically engaging and transmitting power with the power component.

[0024] The outer ring of the flexible bearing is pressed into the inner ring of the inner cam body, so that it is compressed by the inner ring of the inner cam body into an elliptical shape with major and minor axes. The elliptical inner ring of the flexible bearing is used to drive the flexure wheel, so as to form an external wave generator. Furthermore, the inner ring of the inner cam body is fitted with a retaining spring to limit the axial movement of the flexible bearing.

[0025] One end of the flexible wheel is embedded within the inner ring of the flexible bearing, and the elliptical structure of the major and minor axes of the flexible bearing compresses the flexible wheel into an elliptical shape. Furthermore, internal teeth are provided on the inner wall of one end of the flexible wheel for transmitting power to the rigid wheel. The rigid wheel is embedded in the inner ring of one end of the flexible wheel, and the external teeth on the outer ring of the rigid wheel mesh with the internal teeth on the major axis of the flexible wheel. The number of internal teeth on the flexible wheel is greater than the number of external teeth on the rigid wheel.

[0026] Furthermore, the rigid wheel is provided with a second mounting hole, which is used for mechanical connection with an external structure to perform external transmission work.

[0027] When the power component drives the external wave generator to rotate, the internal teeth have more teeth than the external teeth, causing the flexible wheel and rigid wheel to engage and disengage continuously, thus forming a staggered tooth motion and producing a deceleration effect.

[0028] Since the above structural design does not change the pitch circle diameter and module of the tooth profile, the performance of the tooth will not change significantly. However, it greatly expands the hollow through-hole diameter of the harmonic reducer, which brings good economic and usage benefits with little change in overall processing difficulty and process.

[0029] Meanwhile, the above structural design also allows the power components (such as motors) to be conveniently arranged in the space outside the flexible wheel, which is exactly in the same space as the input component of the reducer, the external wave generator, bringing greater optimization possibilities to the highly integrated harmonic reduction module.

[0030] It should be noted that currently, all harmonic reducers used in the market are internal wave generator harmonic reducers, meaning the wave generator is encased in a flexspline. The outer surface of the wave generator is machined into a cam shape with long and short axes. After the inner ring of the flexspline bearing is mounted on the outer surface of the cam, the shape of the cam compresses the outer ring of the flexspline bearing into an "elliptical" shape with long and short axes, thus forming an internal wave generator. This internal wave generator is then installed inside the flexspline, forcing the outer teeth of the flexspline to mesh with the inner teeth of the rigid wheel at the convex point. If the wave generator is driven by a motor to rotate continuously, since the rigid wheel has more teeth than the flexspline, the flexspline and rigid wheel undergo continuous tooth engagement and disengagement, resulting in a staggered tooth motion and a speed reduction effect. However, the through-hole diameter of the internal wave generator harmonic reducer is significantly reduced because the radial wall thickness of the flexspline bearing, the cam forming, and the radial wall thickness required to ensure its strength must be subtracted. In certain special application scenarios, the output torque and accuracy of harmonic reducers with small base sizes can meet the application requirements. However, the required hollow aperture is much larger than that of the internal wave generator harmonic reducer of this model. In this case, a harmonic reducer with a larger base size is often selected to prioritize meeting the aperture requirement. However, this results in a large torque margin, and the increased base size of the harmonic reducer significantly increases the overall size and weight of the machine.

[0031] To meet existing requirements, we designed a harmonic reducer using an external wave generator. Compared to conventional internal wave generator harmonic reducers, this external wave generator moves the wave generator from inside the flex wheel cavity to outside it. Simultaneously, the flex wheel teeth are changed from external to internal, as are the rigid wheel teeth. The wave generator itself is changed from an external cam to an internal cam. Through rotational motion outside the flex wheel cavity, the internal teeth of the flex wheel are forced to mesh with the external teeth of the rigid wheel, resulting in a "tooth-shifting motion," thus achieving speed reduction. Because the wave generator is moved outside the flex wheel, the through-diameter of the flex wheel cavity, after deducting the necessary radial thickness of the rigid wheel, is much larger than that of an internal wave generator. This design also allows the drive motor to be placed outside the reducer, making it suitable for applications with short, large-diameter bores.

[0032] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A harmonic reducer using an external wave generator, characterized in that, include: An external wave generator includes an internal cam body and a flexible wheel bearing, wherein the flexible wheel bearing is embedded in the internal cam body and is driven to rotate by the internal cam body. A flexible wheel, one end of which is embedded in the inner ring of the flexible bearing so as to be circumferentially driven by the flexible bearing; A rigid wheel is fitted into the inner ring of one end of the flexible wheel, and the external teeth on the outer ring of the rigid wheel mesh with the internal teeth on the long axis of the inner ring of the flexible wheel for circumferential transmission, so as to reduce speed, increase torque and transmit work outward.

2. The harmonic reducer using an external wave generator according to claim 1, characterized in that, The inner ring wall of the internal cam body is shaped like a cam with long and short axes, and is used to mount the flexible wheel bearing.

3. The harmonic reducer using an external wave generator according to claim 1 or 2, characterized in that, The external cam body is provided with a first mounting hole, which is used for mechanical transmission connection with the power device.

4. The harmonic reducer using an external wave generator according to claim 1 or 2, characterized in that, The outer ring of the flexible bearing is pressed into the inner ring of the inner cam body, so that it is squeezed into an elliptical shape with major and minor axes by the inner ring of the inner cam body. The inner ring of the elliptical flexible bearing is used to transmit power to the flexible wheel.

5. The harmonic reducer using an external wave generator according to claim 1 or 2, characterized in that, The inner ring of the inner cam body is fitted with a retaining ring to limit the axial movement of the flexible bearing.

6. The harmonic reducer using an external wave generator according to claim 1 or 2, characterized in that, After one end of the flexible wheel is embedded in the inner ring of the flexible bearing, it is compressed into an elliptical shape by the long and short shaft inner ring structure of the flexible bearing, and is used for circumferential transmission with the rigid wheel.

7. The harmonic reducer using an external wave generator according to claim 1 or 2, characterized in that, The rigid wheel is provided with a second mounting hole, which is used to connect with an external mechanical structure for transmission, thereby transmitting power outward.

8. The harmonic reducer using an external wave generator according to claim 3, characterized in that, The power unit is arranged in the space outside the flexible wheel, which improves the overall integration.

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