Cam for harmonic reducer and harmonic reducer

Abstract

The present invention relates to a reducer, in particular to a cam for a harmonic reducer and a harmonic reducer; the cam includes a cam body, the outer contour line of the cam body includes a plurality of meshing area contour curves and a plurality of non-meshing area contour curves; the meshing area contour curves and the non-meshing area contour curves are alternately connected to form the outer contour line of the cam body; the meshing area contour curves and the non-meshing area contour curves are tangent at the intersection; each meshing area contour curve includes a first curve and a second curve, and the first curve and the second curve are tangently connected; one end of the first curve connected to the second curve is the first curve A end, and the other end is the first curve B end; one end of the second curve connected to the first curve is the second curve A end, and the other end is the second curve B end; the first curve A end is more outwardly protruding than the second curve A end, and the second curve B end is more outwardly protruding than the first curve B end.

Description

Technical Field

[0001] The present invention relates to a reducer, and in particular to a cam for a harmonic reducer and the harmonic reducer. Background Art

[0002] A harmonic reducer is a transmission device that uses a wave generator to cause a flexible wheel to produce controllable elastic deformation and mesh with a rigid wheel to transmit motion and power. During the transmission process, wear of the harmonic reducer's wave generator and gears is the main factor causing the reducer's accuracy to decrease, and the cam profile has the greatest impact on the meshing condition of the wave generator and the gear teeth. Therefore, reasonable design of the wave generator's cam profile is the key point. Traditional 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 conditions. As a result, the performance of the harmonic reducer in actual operation is worse than its no-load performance, and it will produce relatively large wear after a period of time, reducing the life of the harmonic reducer.

[0003] To address the above issues, no effective solutions have been proposed so far. Summary of the Invention

[0004] A cam for a harmonic reducer and a harmonic reducer are proposed based on the deformation theory of a flexible wheel under actual load conditions.

[0005] In one aspect, a cam of a harmonic reducer comprises a cam body, wherein an outer contour line of the cam body comprises a plurality of meshing area contour curves and a plurality of non-meshing area contour curves; the meshing area contour curves and the non-meshing area contour curves are alternately connected to form the outer contour line of the cam body; the meshing area contour curves and the non-meshing area contour curves are tangent at the intersection;

[0006] Each meshing area contour curve includes a first curve and a second curve, wherein the first curve and the second curve are connected and tangent to each other at the connection point;

[0007] One end of the first curve connected to the second curve is end A of the first curve, and the other end is end B of the first curve; one end of the second curve connected to the first curve is end A of the second curve, and the other end is end B of the second curve; end A of the first curve is more protruding outward than end A of the second curve, and end B of the second curve is more protruding outward than end B of the first curve.

[0008] Preferably, a plurality of the first curves are evenly distributed on the outer contour of the cam body, and a plurality of the second curves are evenly distributed on the outer contour of the cam body.

[0009] Preferably, there are two meshing areas and they are symmetrically distributed about the center, and there are two non-meshing areas and they are symmetrically distributed about the rotation center of the cam.

[0010] Preferably, the outer contour line is placed in a polar coordinate system, wherein the intersection of the first curve and the second curve of one of the meshing areas is placed on the X-axis, and the rotation center of the cam body coincides with the polar coordinate origin o;

[0011] The equation of the first curve is:

[0012] ρ is the polar coordinate radius; r is the base circle radius; ω0 and ω1 are deformation coefficients; ξ is the profile adjustment parameter, -3<ξ<-1; φ is the angle variable, 0≤φ≤2π / 9, π≤φ≤11π / 9.

[0013] Preferably, the equation of the second curve is:

[0014] ρ=r+ω0×cos2φ-ω1×cos4φ;

[0015] ρ is the polar coordinate radius, r is the base circle radius, ω0 and ω1 are the deformation coefficients, φ is the angle variable,

[0016] Preferably, the equation of the non-meshing area profile curve is:

[0017] ρ=r+ω0×cos2φ;

[0018] Among them, ρ is the polar coordinate radius, r is the base circle radius, ω0 is the deformation coefficient, φ is the angle variable,

[0019] Preferably, there are three meshing areas and three non-meshing areas; the meshing areas and the non-meshing areas are alternately distributed on the outer contour of the cam body.

[0020] Preferably, the adjacent first curve and the non-meshing area contour curve are the same curve.

[0021] Preferably, the rotation center of the cam body is coincident with the origin o of the polar coordinate system, and the intersection of the first curve and the second curve in one meshing area is placed on the X-axis;

[0022] Curve equations of the adjacent first curve and the non-meshing area contour curve:

[0023] ρ=r0+ω0×cos3φ; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 is the deformation coefficient, and φ is the angle variable.

[0024] Preferably, the equation of the second curve is:

[0025] ρ=r0+ω0×cos3φ+ω1×3×sin4φ-ω1×4×sin4φ^3; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 and ω1 are the deformation coefficients, and φ is the angle variable.

[0026] On the other hand, the present invention also provides a harmonic reducer, including a rigid wheel, a flexspline and a cam for a harmonic reducer; the flexspline is sleeved on the outer contour surface of the cam, and the rigid wheel is sleeved on the outer peripheral surface of the flexspline.

[0027] The present invention divides the meshing area profile curve of the cam into a first curve and a second curve at the vertex of the meshing area profile curve, and makes the end A of the first curve more protruding and the end B of the second curve more protruding; when the cam rotates in the direction of the first curve, the harmonic reducer is more precise; when the cam rotates in the direction of the second curve, the harmonic reducer can withstand a greater load-bearing force and is more stable in force. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of a double-wave cam according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a three-wave cam according to an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the relationship between the double-wave cam, the flexible spline and the rigid spline according to an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the relationship between the double-wave cam and the rigid wheel in an embodiment of the present invention;

[0032] Figure 5 Schematic diagram comparing the first curve and the second curve of the meshing area of ​​the cam according to an embodiment of the present invention;

[0033] Figure 6 Graph showing radial displacement of the flexspline and load on the flexspline teeth according to an embodiment of the present invention;

[0034] Figure 7 It is a cross-sectional schematic diagram of a harmonic reducer according to an embodiment of the present invention.

[0035] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] In the accompanying drawings: 1-cam body; 2-rigid wheel; 3-flexible wheel; 10-first curve; 20-second curve; 101-end A of the first curve; 102-end B of the first curve; 201-end A of the second curve; 202-end B of the second curve. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first," "second," and the like in the specification, claims, and accompanying drawings of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. "End A of the first curve" and "end B of the first curve" refer to two opposite regions of the first curve, rather than two points at either end of the first curve. That is, "end A of the first curve" and "end B of the first curve" refer to two different segments of the first curve, which together constitute the first curve. Similarly, "end A of the second curve" and "end B of the second curve" refer to two opposite regions of the second curve, rather than two points at either end of the second curve. That is, "end A of the second curve" and "end B of the second curve" refer to two different segments of the second curve, which together constitute the second curve. The specific lengths of the first and second curves are determined by the equations of the curves and the angle variables. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0039] The present invention relates to a reducer, and in particular to a cam for a harmonic reducer and a harmonic reducer. A harmonic reducer is a transmission device that uses a wave generator to make a flexible wheel produce controllable elastic deformation to mesh with a rigid wheel, thereby transmitting motion and power. During the transmission process, wear of the wave generator and gears of the harmonic reducer is the main factor causing the reduction in reducer accuracy, and the cam profile has the greatest influence on the meshing condition of the wave generator and the gear teeth. Therefore, reasonable design of the wave generator cam profile is the key point. Traditional cam profile design is based on the deformation of the flexible wheel under no-load conditions, rather than based on the deformation of the flexible wheel under actual load conditions, which makes the performance of the harmonic reducer in actual operation worse than the no-load performance, and will produce relatively large wear after a period of time, reducing the service life of the harmonic reducer.

[0040] In view of the above problems, a cam for a harmonic reducer and a harmonic reducer are proposed, which are designed based on the deformation theory of the flexspline under actual load conditions.

[0041] The present invention is introduced by taking a harmonic reducer as an example. Figure 1-7 As shown, a harmonic reducer includes a rigid wheel 2, a flexible wheel 3 and a cam; the flexible wheel 3 is sleeved on the outer contour surface of the cam, and the rigid wheel 2 is sleeved on the outer peripheral surface of the flexible wheel 3. The cam of the harmonic reducer includes a cam body 1, and the outer contour line of the cam body 1 includes a plurality of meshing area contour curves and a plurality of non-meshing area contour curves; the meshing area contour curves and the non-meshing area contour curves are alternately connected to form the outer contour line of the cam body 1; the meshing area contour curves and the non-meshing area contour curves are tangent at the intersection; each meshing area contour curve includes a first curve 10 and a second curve 20, and the first curve 10 and the second curve 20 are connected and tangent at the connection; one end of the first curve 10 connected to the second curve 20 is the first curve A end 101, and the other end is the first curve B end 102; one end of the second curve 20 connected to the first curve 10 is the second curve A end 201, and the other end is the second curve B end 202; as shown Figure 6 As shown, the first curve A end 101 is more convex outward than the second curve A end 201 , and the second curve B end 202 is more convex outward than the first curve B end 102 . When the cam rotates toward the side of the first curve 10, the part of the flexible spline 3 and the rigid wheel 2 corresponding to the second curve 20 meshes as the main load-bearing area, and the part of the flexible spline 3 and the rigid wheel 2 corresponding to the first curve 10 meshes as the secondary load-bearing area. The meshing of the flexible spline 3 and the rigid wheel 2 in the main load-bearing area is not affected by the second curve 20. Under the action of the first curve 10, the gap between the flexible spline 3 and the rigid wheel 2 in the secondary load-bearing area is smaller, and the matching between the flexible spline 3 and the rigid wheel 2 is more precise; when the cam rotates toward the side of the second curve 20, the part of the flexible spline 3 and the rigid wheel 2 corresponding to the first curve 10 meshes as the main load-bearing area, and the part of the flexible spline 3 and the rigid wheel 2 corresponding to the second curve 20 meshes as the secondary load-bearing area. The meshing of the flexible spline 3 and the rigid wheel 2 in the main load-bearing area is not affected by the first curve 10. Under the action of the second curve 20, the number of meshing teeth of the flexible spline 3 and the rigid wheel 2 increases, the maximum load of the matching of the flexible spline 3 and the rigid wheel 2 increases, and the load capacity of the harmonic reducer increases.

[0042] like Figure 5 As shown, a schematic diagram comparing the first curve 10 and the second curve 20 of the meshing area of ​​the cam outer profile shows that after the first curve 10 and the second curve 20 are folded and overlapped, the end A 101 of the first curve is more convex outward than the end A 201 of the second curve, and the end B 202 of the second curve is more convex outward than the end B 102 of the first curve;

[0043] Preferably, Figure 1-2As shown, multiple first curves 10 and multiple second curves 20 are evenly distributed on the outer contour of the cam body 1. Two first curves 10 are evenly distributed about the center of the meshing area, and two second curves 20 are evenly distributed about the center of the cam. The even and symmetrical distribution around the center of the cam ensures more balanced forces on the flexspline 3 and the rigid wheel 2, resulting in smoother operation of the harmonic reducer and reduced unnecessary vibration and noise.

[0044] Preferably, Figure 1 As shown, the outer contour line is placed in a polar coordinate system, wherein the intersection of the first curve 10 and the second curve 20 of a meshing area is placed on the X-axis, and the rotation center of the cam body 1 coincides with the polar coordinate origin o; the equation of the first curve 10 is: ρ is the polar coordinate radius; r is the base circle radius; ω0 and ω1 are deformation coefficients; ξ is the profile adjustment parameter, -3<ξ<-1; φ is the angle variable, 0≤φ≤2π / 9, π≤φ≤11π / 9; the curve equation of the second curve 20 is: ρ=r+ω0×cos2φ-ω1×cos4φ; ρ is the polar coordinate radius, r is the base circle radius, ω0 and ω1 are deformation coefficients, φ is the angle variable, According to the above formula, the first curve 10 can reduce the gap between the flexspline 3 and the rigid wheel 2 when the cam squeezes the flexible wheel 3, while preventing the flexspline 3 from deforming too much, which may increase the friction between the flexspline 3 and the cam and reduce the service life; according to the above formula, the second curve 20 can increase the number of meshing teeth between the flexspline 3 and the rigid wheel 2 when the cam squeezes the flexible wheel 3, while preventing the flexspline 3 from deforming too much, which may increase the friction between the flexspline 3 and the cam and reduce the service life.

[0045] Preferably, Figure 1 As shown, the equation of the non-meshing area contour curve is: ρ = r + ω0 × cos2φ; where ρ is the polar coordinate radius, r is the base circle radius, ω0 is the deformation coefficient, and φ is the angle variable. The above formula allows for a smooth transition between the meshing area and the non-meshing area of ​​the cam, thereby ensuring the rigidity and structural strength of the cam itself while preventing the non-meshing area from contacting the flexible spline 3 and thus avoiding unnecessary friction.

[0046] Preferably, Figure 2 As shown, there are three meshing zones and three non-meshing zones, alternating across the outer contour of the cam body 1. Adjacent first curves 10 and the contours of the non-meshing zones are identical. This cam, also known as a three-wave cam, creates a tooth difference between the flexspline 3 and the rigid wheel 2 that is an integer multiple of three, while a double-wave cam creates a tooth difference between the flexspline 3 and the rigid wheel 2 that is an integer multiple of two. The three-wave cam achieves higher precision in the fit between the flexspline 3 and the rigid wheel 2. The identical non-meshing zones and first curve 10 effectively reduce machining complexity while ensuring proper operation.

[0047] Preferably, Figure 2 As shown, the rotation center of the cam body 1 is coincident with the origin o of the polar coordinate system, and the intersection of the first curve 10 and the second curve 20 of one meshing area is placed on the X-axis; the curve equation of the adjacent first curve 10 and the contour curve of the non-meshing area is:

[0048] ρ=r0+ω0×cos3φ; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 is the deformation coefficient, and φ is the angle variable; the equation of the second curve 20 is: ρ = r0 + ω0 × cos3φ + ω1 × 3 × sin4φ - ω1 × 4 × sin4φ^3; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 and ω1 are the deformation coefficients, and φ is the angle variable. Through the above formula, the load-bearing capacity and transmission accuracy of the three-wave cam are greatly improved.

[0049] According to the test, it can be known that Figure 5-6 The figure shows the test curves of the radial displacement w of the flexspline 3 and the load Ft on the flexspline 3 teeth driven by the cam wave generator. Curves L1, L2, and L3 respectively show the changes in the radial displacement w of the flexspline 3 under torques of 0, 400, and 800 Nm. As the load on the flexspline 3 teeth gradually increases, the radial deformation of the flexspline 3 also increases. At the same time, the main load-bearing area of ​​the flexspline 3 protrudes outward, and the protruding part is further away from the intersection of the main load-bearing area and the secondary load-bearing area. Based on this characteristic, the outer contour of the cam is redesigned to improve the load-bearing capacity. Curves L4, L5, and L6 respectively show the changes in the load Ft on the flexspline 3 teeth under torques of 0, 400, and 800 Nm. As the load on the flexspline 3 gradually increases, the load on the flexspline 3 teeth increases accordingly, and the position of the flexspline 3 teeth subjected to the maximum load is further away from the intersection of the main load-bearing area and the secondary load-bearing area. Based on this characteristic of the flexspline 3, the number of meshing between the flexspline 3 and the rigid wheel 2 is increased, effectively improving the load-bearing capacity of the harmonic reducer.

[0050] For cams with more peaks, as long as the improvements conform to the principle: the cam rotates in one direction to reduce the meshing gap between the flexible wheel and the rigid wheel, thereby achieving higher accuracy of the harmonic reducer; the cam rotates in the other direction to increase the number of meshing between the flexible wheel and the rigid wheel, thereby increasing the maximum load that the harmonic reducer can withstand; all are within the scope of protection of the present invention.

[0051] The present invention has the following significant advantages:

[0052] The present invention divides the meshing area profile curve of the cam into a first curve and a second curve at the vertex of the meshing area profile curve, and makes the end A of the first curve more protruding than the end A of the second curve, and the end B of the second curve more protruding than the end A of the first curve; when the cam rotates in the direction of the first curve, the operation of the harmonic reducer is more precise; when the cam rotates in the direction of the second curve, the operation of the harmonic reducer can withstand a greater load-bearing force and is more stable.

[0053] The exemplary embodiments of the present disclosure are specifically shown and described above. It should be understood that the present disclosure is not limited to the detailed structures, configurations or implementations described herein; on the contrary, the present disclosure is intended to cover various modifications and equivalent configurations included within the spirit and scope of the appended claims.

Claims

1. A cam for a harmonic reducer, characterized in that: The cam body comprises a cam body, the cam body comprises a plurality of meshing areas and a plurality of non-meshing areas, the outer contour line of the cam body comprises a plurality of meshing area contour curves and a plurality of non-meshing area contour curves; the meshing area contour curves and the non-meshing area contour curves are alternately connected to form the outer contour line of the cam body; the meshing area contour curves and the non-meshing area contour curves are tangent at the intersection; Each meshing area contour curve includes a first curve and a second curve, wherein the first curve and the second curve are connected and tangent to each other at the connection point; One end of the first curve connected to the second curve is end A of the first curve, and the other end is end B of the first curve; one end of the second curve connected to the first curve is end A of the second curve, and the other end is end B of the second curve; end A of the first curve is more protruding outward than end A of the second curve, and end B of the second curve is more protruding outward than end B of the first curve.

2. The cam for a harmonic reducer according to claim 1, characterized in that: A plurality of the first curves are evenly distributed on the outer contour of the cam body, and a plurality of the second curves are evenly distributed on the outer contour of the cam body.

3. The cam for a harmonic reducer according to claim 2, characterized in that: There are two meshing areas and they are symmetrically distributed about the center, and there are two non-meshing areas and they are symmetrically distributed about the rotation center of the cam.

4. The cam for a harmonic reducer according to claim 3, characterized in that: Placing the outer contour line in a polar coordinate system, wherein the intersection of the first curve and the second curve of one meshing area is placed on the X-axis, and the rotation center of the cam body coincides with the polar coordinate origin o; The equation of the first curve is: ρ is the polar coordinate radius; r is the base circle radius; ω0 and ω1 are deformation coefficients; ξ is the profile adjustment parameter, -3<ξ<-1; φ is the angle variable, 0≤φ≤2π / 9, π≤φ≤11π / 9.

5. The cam for a harmonic reducer according to claim 4, characterized in that: The equation of the curve of the second curve is: ρ=r+ω0×cos2φ-ω1×cos4φ; ρ is the polar coordinate radius, r is the base circle radius, ω0 and ω1 are the deformation coefficients, φ is the angle variable, 6. The cam for a harmonic reducer according to claim 5, characterized in that: The equation of the non-meshing area profile curve is: ρ=r+ω0×cos2φ; Among them, ρ is the polar coordinate radius, r is the base circle radius, ω0 is the deformation coefficient, φ is the angle variable, 7. The cam for a harmonic reducer according to claim 2, characterized in that: There are three meshing areas and three non-meshing areas; the meshing areas and the non-meshing areas are alternately distributed on the outer contour of the cam body.

8. The cam for a harmonic reducer according to claim 7, characterized in that: The adjacent first curve and the non-meshing area contour curve are the same curve.

9. The cam for a harmonic reducer according to claim 8, characterized in that: The rotation center of the cam body is aligned with the origin o of the polar coordinate system, and the intersection of the first curve and the second curve in one meshing area is placed on the X-axis; Curve equations of the adjacent first curve and the non-meshing area contour curve: ρ=r0+ω0×cos3φ; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 is the deformation coefficient, and φ is the angle variable.

10. The cam for a harmonic reducer according to claim 9, characterized in that: The equation of the curve of the second curve is: ρ=r0+ω0×cos3φ+ω1×3×sin4φ-ω1×4×sin4φ^3; ρ is the polar coordinate radius, r0 is the base circle radius, ω0 and ω1 are the deformation coefficients, and φ is the angle variable.

11. A harmonic reducer, characterized in that: The invention comprises a rigid wheel, a flexspline and a cam for a harmonic reducer according to claim 6 or 10; the flexspline is sleeved on the outer contour surface of the cam, and the rigid wheel sleeve is sleeved on the outer peripheral surface of the flexspline.

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