Cams and harmonic reducers

Abstract

A cam and a harmonic reducer, wherein the cam includes a cam body (1), an outer contour line of the cam body (1) includes a plurality of meshing region contour curves and a plurality of non-meshing region contour curves, the meshing region contour curves and the non-meshing region contour curves are alternately connected so as to jointly form the outer contour line of the cam body, the meshing region contour curves and the non-meshing region contour curves are tangent at the intersection points, each meshing region contour curve includes a first curve (10) and a second curve (20), the first curve (10) is connected to the second curve (20) and is tangent at the connection point, a first section (101) of the first curve protrudes outside a first section (201) of the second curve, and a second section (202) of the second curve protrudes outside a second section (102) of the first curve.

Description

Technical Field

[0001] This application belongs to the technical field of speed reducers, and particularly relates to cams and harmonic speed reducers.

[0002] [Cross-reference to Related Applications] This application claims the priority of a Chinese patent application with the application number 202211066353.2 and the title "Cam and Harmonic Speed Reducer for Harmonic Speed Reducer" filed on August 29, 2022, and hereby incorporates all of its contents by reference.

Background Art

[0003] A harmonic speed reducer is a transmission device that uses a wave generator to generate controllable elastic deformation in a flexible wheel to mesh with a rigid wheel for transmitting motion and power. During use, the wear of the harmonic speed reducer wave generator and gears is a major factor leading to the accuracy attenuation of the speed reducer. Since the cam profile has the greatest influence on the meshing situation between the wave generator and the wheel teeth, it is crucial to rationally design the cam profile of the wave generator. The conventional cam profile design is based on the deformation of the flexible wheel under no-load conditions rather than under actual load modes. The performance of the harmonic speed reducer during actual operation is worse compared to the no-load performance, and significant wear occurs after a certain period, reducing the lifespan of the harmonic speed reducer.

[0004] Currently, no effective solution has been proposed for the above problems.

Summary of the Invention

Problems to be Solved by the Invention

[0005] A cam and a harmonic speed reducer for a harmonic speed reducer designed based on the deformation theory of the flexible wheel in the actual load mode are proposed.

Means for Solving the Problems

[0006] In one embodiment, the present application provides a cam for a harmonic reducer, the cam including a cam body, the outline of the cam body including a plurality of meshing region contour curves and a plurality of non-meshing region contour curves, the meshing region contour curves and the non-meshing region contour curves are alternately connected so as to jointly constitute the outline of the cam body, and the meshing region contour curves and the non-meshing region contour curves are tangent at their intersections.

[0007] Each of the meshing region contour curves includes a first curve and a second curve, and the first curve is connected to the second curve and is tangent to it at the connection point.

[0008] The end of the first curve connected to the second curve is the first section of the first curve, and the other end is the second section of the first curve; the end of the second curve connected to the first curve is the first section of the second curve, and the other end is the second section of the second curve; the first section of the first curve protrudes outward more than the first section of the second curve, and the second section of the second curve protrudes outward more than the second section of the first curve.

[0009] In one embodiment of this application, the plurality of first curves are uniformly distributed on the outer casing of the cam body, and the plurality of second curves are uniformly distributed on the outer casing of the cam body.

[0010] In one embodiment of this application, there are two meshing regions which are distributed symmetrically with respect to the center, and there are two non-meshing regions which are distributed symmetrically with respect to the rotation center of the cam.

[0011] In one embodiment of this application, the outline is arranged in polar coordinates, the intersection of the first curve and the second curve of one of the meshing regions is placed on the OX starting line, and the rotation center of the cam body is aligned with the polar coordinate origin o.

[0012] TIFF0007861167000001.tif46160

[0013] TIFF0007861167000002.tif45161

[0014] TIFF0007861167000003.tif39161

[0015] In one embodiment of this application, there are three meshing regions and three non-meshing regions, and the meshing regions and non-meshing regions are alternately distributed on the outer circumferential surface of the cam body.

[0016] In one embodiment of this application, the adjacent first curve and the non-meshing region contour curve are the same curve.

[0017] TIFF0007861167000004.tif58161

[0018] TIFF0007861167000005.tif40161

[0019] In another embodiment, the present application further provides a harmonic reducer comprising a rigid wheel, a flexible wheel, and a cam as described in any one embodiment above, wherein the flexible wheel is fitted onto the outer circumferential surface of the cam, and the rigid wheel is fitted onto the outer circumferential surface of the flexible wheel. [Effects of the Invention]

[0020] In this application, the outer contour curve of the meshing region of the cam is divided into a first curve and a second curve at the apex of the meshing region contour curve, so that the first section of the first curve protrudes more and the second section of the second curve protrudes more. This makes the harmonic reducer more accurate when the cam rotates in the direction of the first curve. When the cam rotates in the direction of the second curve, the harmonic reducer can withstand a larger load force and receive the force more stably. [Brief explanation of the drawing]

[0021] The drawings described herein are provided for a better understanding of the present application, form a part of the present application, and the schematic examples and descriptions thereof are for interpreting the present application and do not constitute an undue limitation on the present application. [Figure 1] It is a schematic diagram of a double-wave cam according to an embodiment of the present application. [Figure 2] It is a schematic diagram of a triple-wave cam according to an embodiment of the present application. [Figure 3] It is a schematic diagram of the interrelationship among the double-wave cam, the flexible wheel, and the rigid wheel according to an embodiment of the present application. [Figure 4] It is a schematic diagram of the interrelationship between the double-wave cam and the rigid wheel according to an embodiment of the present application. [Figure 5] It is a schematic comparison diagram of the first curve and the second curve of the meshing region of the cam according to an embodiment of the present application. [Figure 6] It is a curve diagram of the radial displacement of the flexible wheel and the load on the wheel teeth of the flexible wheel according to an embodiment of the present application. [Figure 7] It is a schematic cross-sectional view of a harmonic reducer according to an embodiment of the present application.

Modes for Carrying Out the Invention

[0022] For those skilled in the art to better understand the aspects of the present application, the following will clearly and completely describe the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. It is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0023] It should be explained that the terms "first," "second," etc., used in the specification, claims, and drawings of this application are not necessary to describe a specific order or priority, but are used to distinguish similar objects. "First section of the first curve" and "second section of the first curve" refer to the regions of two opposing sections of the first curve, not the two points at both ends of the first curve; that is, "first section of the first curve" and "second section of the first curve" refer to the two distinct curves of the first curve that jointly constitute the first curve. Similarly, "first section of the second curve" and "second section of the second curve" refer to the regions of two opposing sections of the second curve, not the two points at both ends of the second curve; that is, "first section of the second curve" and "second section of the second curve" refer to the two distinct curves of the two sections of the second curve that jointly constitute the second curve. The specific lengths of the first and second curves are determined by the equations of the curves and the angular variables. It should be understood that the data used herein is interchangeable where appropriate so that the embodiments of this application described herein can be carried out in any order other than those illustrated or described herein. Furthermore, the terms “includes” and “has,” and their variations, are intended to cover non-exclusive inclusion.

[0024] This application relates to speed reducers, and more particularly to cams for harmonic speed reducers and harmonic speed reducers. A harmonic speed reducer is a transmission device that uses a wave generator to generate controllable elastic deformation in a flexible wheel to mesh with a rigid wheel and transmit motion and power. During the transmission process, wear of the harmonic speed reducer wave generator and gears is a major factor in the precision damping of the speed reducer, and the cam profile has the greatest influence on the meshing condition between the wave generator and the wheel teeth, so rationally designing the cam profile of the wave generator is key. Conventional cam profile designs are based on the deformation of the flexible wheel under no-load conditions rather than the deformation of the flexible wheel under actual load conditions, and the performance of the harmonic speed reducer in actual operation is worse than that under no-load conditions, and significant wear occurs after a certain period of time, reducing the lifespan of the harmonic speed reducer.

[0025] To address the above problem, we propose a cam and a harmonic reducer designed based on the deformation theory of flexible wheels in actual load modes.

[0026] This application will introduce a harmonic speed reducer as an example. As shown in Figures 1-4 and 7, the harmonic speed reducer includes a rigid wheel 2, a flexible wheel 3, and a cam. The flexible wheel 3 is fitted onto the outer circumferential surface of the cam, and the rigid wheel 2 is fitted onto the outer circumferential surface of the flexible wheel 3. The cam of the harmonic speed reducer includes a cam body 1, with meshing and non-meshing regions alternately distributed on the outer circumferential surface of the cam body 1. The outline of the cam body 1 includes a plurality of meshing region contour curves and a plurality of non-meshing region contour curves. The meshing region contour curves and non-meshing region contour curves are alternately connected so as to jointly constitute the outline of the cam body 1. The meshing region contour curves and non-meshing region contour curves are tangent at their intersections. Each occlusal region contour curve includes a first curve 10 and a second curve 20. The first curve 10 is connected to and adjacent to the second curve 20 at the connection point. The end of the first curve 10 connected to the second curve 20 is the first section 101 of the first curve, and the other end is the second section 102 of the first curve. The end of the second curve 20 connected to the first curve 10 is the first section 201 of the second curve, and the other end is the second section 202 of the second curve. The first section 101 of the first curve protrudes outward more than the first section 201 of the second curve, and the second section 202 of the second curve protrudes outward more than the second section 102 of the first curve. When the cam rotates toward one side of the first curve 10, some of the flexible wheel 3 and rigid wheel 2 corresponding to the second curve 20 mesh as the main support region, and some of the flexible wheel 3 and rigid wheel 2 corresponding to the first curve 10 mesh as the secondary region. The meshing of the flexible wheel 3 and rigid wheel 2 in the main load region is not affected by the second curve 20, and under the action of the outer surface on which the first curve 10 is located, the gap between the flexible wheel 3 and rigid wheel 2 in the secondary load region becomes smaller, resulting in more precise meshing of the flexible wheel 3 and rigid wheel 2.When the cam rotates toward one side of the second curve 20, some of the flexible wheel 3 and rigid wheel 2 corresponding to the first curve 10 mesh as the main support area, and some of the flexible wheel 3 and rigid wheel 2 corresponding to the second curve 20 mesh as the secondary support area. The meshing of the flexible wheel 3 and rigid wheel 2 in the main load area is not affected by the circumferential surface on which the first curve 10 is located, and under the action of the circumferential surface on which the second curve 20 is located, the number of teeth that mesh between the flexible wheel 3 and rigid wheel 2 increases, the maximum load on which the flexible wheel 3 and rigid wheel 2 mesh increases, and the load capacity of the harmonic reducer increases.

[0027] As shown in Figure 5, this is a schematic comparison of the first curve 10 and the second curve 20 in the meshing region of the cam outer casing. After folding the first curve 10 and the second curve 20 in half, the first section 101 of the first curve protrudes outward more than the first section 201 of the second curve, and the second section 202 of the second curve protrudes outward more than the second section 102 of the first curve.

[0028] In some embodiments, the cam body 1 is provided with at least two meshing regions and two non-meshing regions. The outline of each meshing region of the cam body 1 includes a first curve 10 and a second curve 20. Multiple first curves 10 are uniformly distributed on the outline of the cam body 1, and multiple second curves 20 are uniformly distributed on the outline of the cam body 1. Figure 1 is a schematic diagram of a double corrugated cam according to an embodiment of the present invention, and as shown in Figure 1, the cam body 1 is provided with two meshing regions and two non-meshing regions. The two meshing regions are distributed symmetrically with respect to the rotation center of the cam, and the two non-meshing regions are distributed symmetrically with respect to the rotation center of the cam. This arrangement balances the forces received by the flexible wheel 3 and the rigid wheel 2, making the operation of the harmonic reducer more stable and thereby reducing unwanted vibrations and noise.

[0029] TIFF0007861167000006.tif154161

[0030] TIFF0007861167000007.tif61161

[0031] Figure 2 is a schematic diagram of a triple-wave cam according to an embodiment of this application. As shown in Figure 2, in some embodiments, there are three meshing regions and three non-meshing regions. The meshing regions and non-meshing regions are alternately distributed on the outer circumferential surface of the cam body 1. The adjacent first curve 10 and the non-meshing region contour curve are identical curves. This cam is also called a triple-wave cam. With a triple-wave cam, the difference in the number of teeth between the flexible wheel 3 and the rigid wheel 2 is an integer multiple of 3, and with a double-wave cam, the difference in the number of teeth between the flexible wheel 3 and the rigid wheel 2 is an integer multiple of 2. The meshing accuracy between the flexible wheel 3 and the rigid wheel 2 is higher with a triple-wave cam. The non-meshing region contour curve and the first curve 10 are identical curves, and the difficulty of machining can be effectively reduced while ensuring normal operation.

[0032] TIFF0007861167000008.tif105161

[0033] As can be seen from the test, as shown in Figure 6, the radial displacement w of the flexible wheel 3 to which the cam wave generator is transmitted. t and load F on the wheel teeth of the flexible wheel 3 t These are the test curves, where curves L1, L2, and L3 represent the radial displacement w of the flexible wheel 3 under torques of 0, 400, and 800 Nm, respectively. t This describes the changes in the flexible wheel. As the load on the wheel teeth of the flexible wheel 3 gradually increases, the radial deformation of the flexible wheel 3 also increases, and the main load area of ​​the flexible wheel 3 protrudes further outward, with the protruding portion moving away from the contact point between the main load area and the secondary load area. Based on this characteristic, the outer contour of the cam is redesigned to improve the load capacity. Curves L4, L5, and L6 represent the load F on the wheel teeth of the flexible wheel 3 under torques of 0, 400, and 800 Nm, respectively. tAs the load on the flexible wheel 3 gradually increases, the load on the wheel teeth of the flexible wheel 3 increases, and the position of the wheel teeth of the flexible wheel 3 receiving the maximum load moves away from the contact point with the main load area. Based on the characteristics of the flexible wheel 3, the number of teeth that mesh with the flexible wheel 3 and the rigid wheel 2 increases, effectively improving the load capacity of the harmonic reducer.

[0034] For cams with more peaks, if the improvements are consistent with the principle, rotation of the cam in one direction reduces the meshing gap between the flexible wheel and the rigid wheel, increasing the accuracy of the harmonic reducer, and rotation of the cam in another direction increases the number of teeth that mesh between the flexible wheel and the rigid wheel, achieving an increase in the maximum load that the harmonic reducer can withstand. All of these improvements are within the scope of protection of this application.

[0035] This application has the following notable advantages:

[0036] In this application, the meshing region contour curve of the cam is divided into a first curve and a second curve at the apex of the meshing region contour curve, with the first section of the first curve protruding more than the first section of the second curve, and the second section of the second curve protruding more than the first section of the first curve. As a result, when the cam rotates in the direction of the first curve, the operation of the harmonic reducer becomes more precise, and when the cam rotates in the direction of the second curve, the harmonic reducer can withstand a larger load force and receive the force more stably.

[0037] The above has provided specific examples and descriptions of exemplary embodiments of this disclosure. It should be understood that this disclosure is not limited to the detailed structures, configurations, or implementations described herein. Rather, the intent of this disclosure is to encompass various modifications and equivalent configurations that fall within the spirit and scope of the appended claims. [Explanation of Symbols]

[0038] 1: Cam body, 2: Rigid wheel, 3: Flexible wheel, 10: First curve, 20: Second curve, 101: First section of the first curve, 102: Second section of the first curve, 201: First section of the second curve, 202: Second section of the second curve.

Claims

1. A cam for a harmonic reducer, comprising a cam body, wherein the outline of the cam body comprises a plurality of meshing region contour curves and a plurality of non-meshing region contour curves, the meshing region contour curves and the non-meshing region contour curves are alternately connected so as to jointly constitute the outline of the cam body, and the meshing region contour curves and the non-meshing region contour curves are tangent at their intersections. Each of the aforementioned meshing region contour curves includes a first curve and a second curve, the first curve is connected to the second curve and is tangent to it at the connection point. A cam for a harmonic reducer, characterized in that the end of the first curve connected to the second curve is the first section of the first curve, and the other end is the second section of the first curve; the end of the second curve connected to the first curve is the first section of the second curve, and the other end is the second section of the second curve; the first section of the first curve protrudes outward more than the first section of the second curve; and the second section of the second curve protrudes outward more than the second section of the first curve.

2. The cam according to claim 1, characterized in that a plurality of the first curves are uniformly distributed on the outer casing of the cam body, and a plurality of the second curves are uniformly distributed on the outer casing of the cam body.

3. The cam according to claim 2, characterized in that there are two meshing regions and they are distributed symmetrically with respect to the rotation center of the cam, and there are two non-meshing regions and they are distributed symmetrically with respect to the rotation center of the cam.

4. The outline is placed in a polar coordinate system, the intersection point of the first curve and the second curve of one of the meshing regions is placed on the OX starting line, and the rotation center of the cam body is aligned with the polar coordinate origin o. The equation of the first curve is as follows: ρ is the polar coordinate radius, r is the base circle radius, and ω ０ and ω １ The cam according to claim 3, wherein is a deformation coefficient, ξ is a contour adjustment parameter such that -3 < ξ < -1, and φ is an angular variable such that 0 ≤ φ ≤ 2π / 9 and π ≤ φ ≤ 11π / 9.

5. The outline is placed in polar coordinates, the intersection point of the first curve and the second curve in one of the meshing regions is placed on the initial line OX, the rotation center of the cam body is aligned with the polar coordinate origin o, and the equation of the second curve is as follows:

6. The outline is placed in polar coordinates, the intersection point of the first and second curves in one of the meshing regions is placed on the initial line OX, and the rotation center of the cam body coincides with the polar coordinate origin o. The equation of the outline curve of the non-meshing region is as follows:

7. The cam according to claim 2, characterized in that there are three meshing regions and three non-meshing regions, and the meshing regions and non-meshing regions are alternately distributed on the outer circumferential surface of the cam body.

8. The cam according to claim 7, characterized in that the adjacent first curve and the non-meshing region contour curve are the same curve.

9. The rotation center of the cam body is aligned with the origin o of the polar coordinate system, and the intersection point of the first curve and the second curve in one meshing region is placed on the starting line OX. The curve equations of the adjacent first curve and the non-meshing region contour curve are as follows:

10. The rotation center of the cam body is aligned with the origin o of the polar coordinate system, and the intersection point of the first curve and the second curve in one meshing region is placed on the starting line OX. The equation of the second curve is as follows:

11. A harmonic reducer comprising a rigid wheel, a flexible wheel, and a cam according to any one of claims 1 to 10, wherein the flexible wheel is fitted onto the outer circumferential surface of the cam, and the rigid wheel is fitted onto the outer circumferential surface of the flexible wheel.

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