Cam and Harmonic Reducer

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 an application number of 202211066353.2 and a title of "Cam for Harmonic Speed Reducer and Harmonic Speed Reducer", which was filed on August 29, 2022, and hereby incorporates all of its content 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 engage with a rigid wheel to transmit 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 reasonably 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 the deformation of the flexible wheel under actual load mode. 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 of time, reducing the service life 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 for a harmonic speed reducer and a harmonic speed reducer designed based on the deformation theory of a flexible wheel in an actual load mode are proposed.

Means for Solving the Problems

[0006] According to one aspect, the present application provides a cam for a harmonic reducer. The cam includes a cam body, and the outer contour line of the cam body 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 to jointly form the outer contour line of the cam body, and the meshing region contour curves and the non-meshing region contour curves are tangent at the intersection points.

[0007] Each of the meshing region contour curves includes a first curve and a second curve. The first curve is connected to the second curve and is tangent 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 the present application, the plurality of first curves are uniformly distributed on the outer contour of the cam body, and the plurality of second curves are uniformly distributed on the outer contour of the cam body.

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

[0011] In one embodiment of the present application, the outer contour line is arranged in a polar coordinate system. The intersection point of the first curve and the second curve of one meshing region is arranged on the OX initial line, and the rotation center of the cam body coincides with the polar coordinate origin o.

[0012] TIFF2025518389000002.tif46160

[0013] TIFF2025518389000003.tif45161

[0014] TIFF2025518389000004.tif39161

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

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

[0017] TIFF2025518389000005.tif58161

[0018] TIFF2025518389000006.tif40161

[0019] According to another aspect, the present application provides a harmonic reducer including a rigid wheel, a flexible wheel, and a cam according to any one of the above embodiments, wherein the flexible wheel is fitted on the outer peripheral surface of the cam, and the rigid wheel is fitted on the outer peripheral surface of the flexible wheel.

Advantages of the Invention

[0020] In the present application, at the vertex of the meshing region contour curve of the cam, the outer contour curve of the meshing region is divided into a first curve and a second curve, such that the first section of the first curve protrudes more and the second section of the second curve protrudes more. By doing so, when the cam rotates in the direction of the first curve, the harmonic reducer becomes more accurate. When the cam rotates in the direction of the second curve, the harmonic reducer can withstand a greater load force and receive the force more stably.

Brief Description of the Drawings

[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 their descriptions of the present application are for interpreting the present application and do not constitute an undue limitation to the present application.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0022] To enable 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. However, it is obvious that the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor should belong to the protection scope of the present application.

[0023] It should be noted that terms such as "first", "second", etc. in the description, claims and the above drawings of this application are not necessarily used to describe a specific order or priority, but are for distinguishing similar objects. "The first section of the first curve" and "the second section of the first curve" do not refer to two points at both ends of the first curve, but refer to the regions of two opposing sections of the first curve, that is, "the first section of the first curve" and "the second section of the first curve" respectively refer to two different curves of the first curve that jointly constitute the first curve. Similarly, "the first section of the second curve" and "the second section of the second curve" do not refer to two points at both ends of the second curve, but refer to the regions of two opposing sections of the second curve, that is, "the first section of the second curve" and "the second section of the second curve" respectively refer to two different curves of the two sections of the second curve that jointly constitute the second curve. The specific lengths of the first curve and the second curve are determined by the curve equation and the angular variable. It should be understood that the data used in this way is exchangeable when appropriate so that the embodiments of this application described herein can be implemented in the order except those illustrated or described herein. Furthermore, the terms "comprising" and "having", and their variants are intended to cover non-exclusive inclusion.

[0024] This application relates to a speed reducer, and particularly to a cam for a harmonic speed reducer and a harmonic speed reducer. 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 to transmit motion and power. In the transmission process, the wear of the harmonic speed reducer wave generator and gears is a major factor causing the accuracy attenuation of the speed reducer. Since the cam profile has the most influence on the meshing situation between the wave generator and the wheel teeth, it is the key 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 the deformation of the flexible wheel under actual load mode. The performance of the harmonic speed reducer during actual operation is worse compared with the no-load performance, and significant wear occurs after a certain period of time, reducing the service life of the harmonic speed reducer.

[0025] In view of the above problems, a cam for a harmonic reducer and a harmonic reducer designed based on the deformation theory of a flexible wheel in an actual load mode are proposed.

[0026] The present application is introduced by taking a harmonic reducer as an example. As shown in FIGS. 1-4 and FIG. 7, the harmonic reducer includes a rigid wheel 2, a flexible wheel 3, and a cam. The flexible wheel 3 is fitted on the outer peripheral surface of the cam, and the rigid wheel 2 is fitted on the outer peripheral surface of the flexible wheel 3. The cam of the harmonic reducer includes a cam body 1, and the meshing region and the non-meshing region are alternately distributed on the outer peripheral surface of the cam body 1. The 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 curve and the non-meshing region contour curve are alternately connected so as to jointly form the outer contour line of the cam body 1. The meshing region contour curve and the non-meshing region contour curve are tangent at the intersection. 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. 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, a part of the flexible wheel 3 and the rigid wheel 2 corresponding to the second curve 20 mesh as the main support region, and a part of the flexible wheel 3 and the rigid wheel 2 corresponding to the first curve 10 mesh as the secondary region. The meshing of the flexible wheel 3 and the rigid wheel 2 in the main load region is not affected by the second curve 20. Under the action of the outer peripheral surface where the first curve 10 is located, the gap between the flexible wheel 3 and the rigid wheel 2 in the secondary load region becomes smaller, and the meshing between the flexible wheel 3 and the rigid wheel 2 becomes more accurate.When the cam rotates towards one side of the second curve 20, a part of the flexible wheel 3 corresponding to the first curve 10 and the rigid wheel 2 mesh as the main support area, and a part of the flexible wheel 3 corresponding to the second curve 20 and the rigid wheel 2 mesh as the secondary support area. The meshing of the flexible wheel 3 and the rigid wheel 2 in the main load area is not affected by the circumferential surface where the first curve 10 is located. Under the action of the outer circumferential surface where the second curve 20 is located, the number of teeth meshing between the flexible wheel 3 and the rigid wheel 2 increases, the maximum load at which the flexible wheel 3 and the rigid wheel 2 mesh increases, and the load capacity of the harmonic reducer increases.

[0027] As shown in FIG. 5, it is a comparative schematic diagram of the first curve 10 and the second curve 20 in the meshing area of the cam contour. 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, at least two meshing areas and two non-meshing areas are provided on the cam body 1. The contour of each meshing area of the cam body 1 includes the first curve 10 and the second curve 20. A plurality of the first curves 10 are uniformly distributed on the contour of the cam body 1, and a plurality of the second curves 20 are uniformly distributed on the contour of the cam body 1. FIG. 1 is a schematic diagram of the double-wave cam of the embodiment of the present application. As shown in FIG. 1, two meshing areas and two non-meshing areas are provided on the cam body 1. The two meshing areas are symmetrically distributed with respect to the rotation center of the cam, and the two non-meshing areas are symmetrically distributed with respect to the rotation center of the cam. By being provided in this way, the force received by the flexible wheel 3 and the rigid wheel 2 can be balanced, the operation of the harmonic reducer can be made more stable, and thereby unnecessary vibration and noise can be reduced.

[0029] TIFF2025518389000007.tif154161

[0030] TIFF2025518389000008.tif61161

[0031] FIG. 2 is a schematic diagram of a triple-wave cam according to an embodiment of the present application. As shown in FIG. 2, in some embodiments, there are three meshing regions and three non-meshing regions. The meshing regions and the non-meshing regions are alternately distributed on the outer peripheral surface of the cam body 1. The adjacent first curve 10 and the non-meshing region contour curve are the same curve. The cam is also called a triple-wave cam. The difference in the number of teeth between the flexible wheel 3 and the rigid wheel 2 caused by the triple-wave cam is an integer multiple of 3, and the difference in the number of teeth between the flexible wheel 3 and the rigid wheel 2 caused by the double-wave cam is an integer multiple of 2. The meshing accuracy between the flexible wheel 3 and the rigid wheel 2 is higher due to the triple-wave cam. The non-meshing region contour curve and the first curve 10 are the same curve, and the processing difficulty can be effectively reduced on the premise of ensuring normal operation.

[0032] TIFF2025518389000009.tif105161

[0033] As can be seen from the test, as shown in FIG. 6, the radial displacement w of the flexible wheel 3 transmitted by the cam wave generator t and the load F on the wheel teeth of the flexible wheel 3 t are test curves. Each of the curves L1, L2, and L3 is the change situation of the radial displacement w of the flexible wheel 3 under torques of 0, 400, and 800 Nm t . 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 region of the flexible wheel 3 protrudes more outward, and the protruding part moves away from the contact position between the main load region and the secondary load region. Based on this feature, the outer contour line of the cam is redesigned to improve the load capacity. Each of the curves L4, L5, and L6 is the load F on the wheel teeth of the flexible wheel 3 under torques of 0, 400, and 800 Nm tThis is a change. As 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 that bears 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 meshing teeth between the flexible wheel 3 and the rigid wheel 2 increases, and the load capacity of the harmonic reducer is effectively improved.

[0034] For cams with more peaks, as long as the improvement conforms to the principle, when the cam rotates in one direction, the meshing clearance between the flexible wheel and the rigid wheel becomes smaller, and the accuracy of the harmonic reducer becomes higher. When the cam rotates in another direction, the number of meshing teeth between the flexible wheel and the rigid wheel increases, achieving an increase in the maximum load that the harmonic reducer can bear. All these improvements are within the protection scope of this application.

[0035] This application has the following remarkable advantages.

[0036] In this application, at the apex of the meshing area contour curve of the cam, the meshing area contour curve is divided into a first curve and a second curve, such that the first section of the first curve protrudes more than the first section of the second curve, and the second section of the second curve protrudes more than the first section of the first curve. By doing so, when the cam rotates in the direction of the first curve, the operation of the harmonic reducer becomes more accurate; when the cam rotates in the direction of the second curve, the operation of the harmonic reducer can withstand a greater load force and receive the force more stably.

[0037] As described above, the exemplary embodiments of the present disclosure have been specifically shown and described. It should be understood that the present disclosure is not limited to the detailed structures, setting forms, or implementation forms described herein. Rather, the intention of the present disclosure is to encompass various modifications and equivalent settings included in the spirit and scope of the appended patent claims.

Description of Reference Numerals

[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 outer contour line of the cam body includes a plurality of meshing region contour curves and a plurality of non-meshing region contour curves, and the meshing region contour curves and the non-meshing region contour curves are alternately connected to jointly form the outer contour line of the cam body, and the meshing region contour curves and the non-meshing region contour curves are tangent to each other at the intersection points. 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 the second curve at the connection point. 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 beyond the first section of the second curve, and the second section of the second curve protrudes outward beyond the second section of the first curve. A cam for a harmonic reducer, characterized in that.

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

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

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

5. The outer contour line is arranged in a polar coordinate system, the intersection point of the first curve and the second curve of one of the meshing regions is arranged on the OX starting line, and the rotation center of the cam body is overlapped with the polar coordinate origin o. The equation of the second curve is as follows.

6. The outer contour line is arranged in a polar coordinate system, the intersection point of the first curve and the second curve of one of the meshing regions is arranged on the OX starting line, and the rotation center of the cam body is overlapped with the polar coordinate origin o. The equation of the outer contour curve of the non-meshing region is as follows.

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

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

9. The rotation center of the cam body is overlapped with the origin o of the polar coordinate system, and the intersection point of the first curve and the second curve of one meshing region is arranged on the OX initial line. 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 overlapped with the origin o of the polar coordinate system, and the intersection point of the first curve and the second curve of one meshing region is arranged on the OX initial line. The equation of the second curve is as follows.

11. It includes a rigid wheel, a flexible wheel, and the cam according to any one of claims 1 to 10. The flexible wheel is fitted on the outer peripheral surface of the cam, and the rigid wheel is fitted on the outer peripheral surface of the flexible wheel. A harmonic reducer, characterized in that.

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