Harmonic reducer and cam wave generator and cam thereof

Abstract

The embodiment of the invention discloses a cam applied to a harmonic reducer, the harmonic reducer is provided with a flexible gear, a rigid gear and a cam wave generator, the cam wave generator comprises a cam, and the cam is provided with a long shaft and a short shaft. The profile of the cam is constructed in a way that the length of a vertical line of a tangent line of any point on the profile and an original point of the profile is a multi-term Fourier expansion function about an included angle between the vertical line and the long axis; wherein the sum value of the Fourier expansion coefficients of the multiple Fourier expansion functions is related to the meshing deformation coefficient and the flexible gear modulus, and under the condition that the Fourier expansion coefficients of the multiple Fourier expansion functions meet constraint conditions, the maximum curvature difference of the cam profile is made to be as small as the target degree; wherein the constraint conditions include that the corresponding curvature difference of the cam at the stress separation angle is maximum, the curvature difference of the cam at the short axis is minimum, and the angle range of the stress separation angle is 0-55 degrees.

Description

Technical Field

[0001] The present application relates to the field of reducers, and in particular, to a harmonic reducer and a cam wave generator and a cam thereof. Background Art

[0002] The harmonic reducer is a precision reducer used in the joints of industrial robots. It is usually composed of three major components: a flexible wheel, a rigid wheel, and a wave generator. The cam wave generator is used to rotate to cause the flexible wheel to produce periodic wave deformation, forcing the flexible wheel and the rigid wheel to mesh with each other with a small tooth difference, thereby realizing the transmission of motion and power. In the cam profile design of the harmonic reducer, common profiles include elliptical, cosine and other curve forms.

[0003] The inventors of the present application have discovered in actual production research that the flexible wheel of the harmonic reducer has a technical problem of being prone to failure and fracture. Summary of the invention

[0004] The embodiments of the present application provide a harmonic reducer and a cam wave generator and a cam thereof, so as to at least solve or alleviate the technical problem that the flexible wheel of the harmonic reducer is prone to failure and fracture.

[0005] According to a first aspect of an embodiment of the present application, a cam applied to a harmonic reducer is provided. The harmonic reducer has a flexible wheel, a rigid wheel and a cam wave generator. The cam wave generator includes a cam. The cam has a major axis and a minor axis.

[0006] The profile of the cam is constructed such that the length of a perpendicular line between the origin of the profile and a tangent line at any point on the profile is a multinomial Fourier expansion function with respect to the angle between the perpendicular line and the major axis;

[0007] The sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is related to the meshing deformation coefficient and the flexspline modulus, and the Fourier expansion coefficients of the multiple Fourier expansion functions make the maximum curvature difference of the cam profile as small as a target level while satisfying the constraint conditions;

[0008] The constraint conditions include: the curvature difference of the cam at the stress separation angle is the largest, and the curvature difference at the short axis is the smallest, and the angle range of the stress separation angle is 0 to 55°.

[0009] In combination with the first aspect, in an optional implementation manner of the embodiment of the present application, the sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is equal to the product of the meshing deformation coefficient and the flexspline modulus.

[0010] In combination with the first aspect, in an optional implementation of the embodiment of the present application, the value range of the meshing deformation coefficient is 1<γ<5, and γ represents the meshing deformation coefficient.

[0011] In combination with the first aspect, in an optional implementation method of the embodiment of the present application, the constraint condition also includes: the difference between the maximum curvature difference and the minimum curvature difference of the neutral layer curve of the flexible wheel is less than a set value, and the set value is a function of the meshing deformation coefficient, the flexible wheel module and the equivalent circle radius of the flexible wheel.

[0012] In combination with the first aspect, in an optional implementation of the embodiment of the present application, the set value satisfies:

[0013] Wherein, y represents the set value, q is a constant, γ represents the meshing deformation coefficient, m represents the flexspline modulus, and r f represents the equivalent circular radius of the flexible wheel.

[0014] In combination with the first aspect, in an optional implementation method of the embodiment of the present application, the constraint condition also includes: the value range of the stress separation coefficient ξ of the cam satisfies: 1<ξ<5, wherein the stress separation coefficient refers to the ratio of the maximum curvature difference corresponding to the stress separation angle to the curvature difference of the major axis.

[0015] In combination with the first aspect, in an optional implementation manner of the embodiment of the present application, the multi-layer Fourier expansion function satisfies the following form:

[0016]

[0017] Among them, the P c represents the length of the vertical line, the r c represents the equivalent circle radius of the cam, φ represents the angle between the radius vector and the major axis, a n represents the Fourier expansion coefficients of the multi-item Fourier expansion function, 2≤n≤7, or n=3.

[0018] In combination with the first aspect, in an optional implementation of the embodiment of the present application, the following optimization model is used to optimize the multinomial Fourier expansion function to obtain the a n Values:

[0019]

[0020] Wherein, γ is the meshing deformation coefficient, m is the flexspline modulus, α is the stress separation angle, which represents the angle between the corresponding point at the maximum curvature difference and the major axis, ξ is the stress separation coefficient, which represents the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis, q is a constant, Δk represents the curvature difference, minf(x)=min(Δk max ) indicates that the optimization objective of the optimization model is to maximize the curvature difference Δk max Minimum.

[0021] In combination with the first aspect, in an optional implementation of the embodiment of the present application, the Fourier expansion coefficients of the multiple Fourier expansion functions make the maximum curvature difference of the cam profile as small as a target degree under the condition of satisfying the constraint condition, which means:

[0022] The corresponding maximum curvature difference value Δk obtained in the process of optimizing the multi-layer Fourier expansion function for a set number of times using the optimization model max The minimum expansion coefficient makes the maximum curvature difference of the cam profile as small as the target level.

[0023] In a second aspect, an embodiment of the present application provides a cam wave generator applied to a harmonic reducer, wherein the cam wave generator comprises the cam of the first aspect of the embodiment of the present application and a flexible bearing cooperating with the cam.

[0024] In a third aspect, an embodiment of the present application provides a harmonic reducer, which includes a flexible wheel, a rigid wheel and the cam wave generator of the second aspect of the embodiment of the present application.

[0025] By adopting the embodiments of the present application, it is possible to at least solve or alleviate the technical problem that the flexible wheel of the harmonic reducer is prone to failure and fracture. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of a profile of a cam applied to a harmonic reducer according to an embodiment of the present application;

[0027] Figure 2 It is a schematic diagram comparing the bending stress of a flexible wheel with a cam profile provided in an embodiment of the present application and a conventional curved profile. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0029] It should be understood that the "plurality" mentioned in this article refers to two or more. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second" and so on are used to distinguish between the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that the words "first", "second" and so on do not limit the quantity and execution order, and the words "first", "second" and so on do not limit certain different

[0030] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

[0031] The harmonic reducer is mainly composed of three basic components: a rigid wheel, a flexwheel and a wave generator. Among them, the rigid wheel is a rigid internal gear, usually with more gear teeth. The flexwheel is a thin-walled external gear that is easily deformed and has fewer gear teeth than the rigid wheel. The wave generator is a component that makes the flexwheel produce controllable elastic deformation.

[0032] The cam wave generator usually consists of an elliptical cam and a thin-walled flexible bearing. The cam is the core part of the wave generator, and its elliptical shape enables periodic radial deformation force to be generated during rotation. The flexible bearing is installed on the outside of the cam. On the one hand, it plays a supporting and positioning role, and on the other hand, it can produce corresponding deformation with the rotation of the cam to adapt to the deformation requirements of the flexible wheel. When the wave generator rotates, due to the elliptical shape of the cam, the radial distance between its contact point with the flexible wheel at different rotation angles is constantly changing. In the direction of the major axis, the wave generator will push the flexible wheel outward, causing local radial deformation of the flexible wheel; in the direction of the minor axis, the flexible wheel will shrink relatively. This periodic deformation propagates on the flexible wheel like a wave, thereby realizing the staggered tooth movement between the flexible wheel and the rigid wheel.

[0033] The flexspline is a thin-walled cylindrical structure with gear teeth machined on its outer surface. The wall thickness of the flexspline is usually very thin, which makes it have good elastic deformation ability. The gear teeth of the flexspline need to have high precision to ensure good cooperation with the rigid wheel and wave generator.

[0034] Under the action of the wave generator, the flexspline undergoes periodic elastic deformation. The deformation of the flexspline enables its teeth to mesh and disengage with the teeth of the rigid wheel in sequence. Since the number of teeth of the flexspline is less than that of the rigid wheel, when the wave generator rotates one circle, the flexspline will produce a certain amount of staggered tooth movement relative to the rigid wheel, thereby achieving the deceleration function. For example, if the rigid wheel has 200 teeth and the flexspline has 198 teeth, when the wave generator rotates one circle, the flexspline will rotate in the opposite direction by an angle of 2 teeth relative to the rigid wheel, thereby achieving a deceleration effect with a reduction ratio of 100:1 (200÷2=100). At the same time, the flexspline needs to withstand a certain torque and alternating stress during operation, so there are high requirements for its material strength, elastic modulus and fatigue performance.

[0035] The inventors of the present application have found in their research that actual working conditions have proven that after the traditional elliptical and cosine curve profile cams are assembled into the flexible wheel, the bending stress at the long axis of the flexible wheel is relatively large, and the position of the bending stress at the long axis coincides with the meshing stress at the long axis, further increasing the comprehensive stress at the long axis, which is the main reason for the failure and fracture of the flexible wheel. Therefore, the embodiments of the present application propose a design that can alleviate the technical problem of the failure and fracture of the flexible wheel. In addition, in at least one embodiment of the present application, a new cam profile curve is proposed that can reduce the bending stress amplitude of the flexible wheel rim after assembly and separate the bending stress at the long axis from the meshing stress, so as to increase the life of the flexible wheel.

[0036] Figure 1 It is a schematic diagram of a cam profile applied to a harmonic reducer according to an embodiment of the present application. In this embodiment, the features related to the cam profile in the relevant embodiments of the present application are uniformly explained. It should be understood by those skilled in the art that the explanation of these features here does not mean that the following embodiments must also include the limitations related to these features.

[0037] like Figure 1 As shown, the cam is elliptical in shape as a whole, with a major axis and a minor axis. The parameters related to the cam profile 10 mainly include the cam profile equivalent circle 09, the cam equivalent circle radius 8 (i.e., the radius of the equivalent circle 09), any point 11 on the cam (represented as point A), the tangent 12 through any point on the cam, the distance 13 from the origin to the tangent (i.e., the vector radius of the cam support function), the vector radius 14 of the cam profile, the angle 15 between the cam vector radius and the major axis (or angle θ), and the angle 16 between the support function vector radius and the major axis (equal to the angle φ in the figure).

[0038] Reference Figure 1 In one embodiment of the application, the profile of the cam is constructed as follows: the length of a perpendicular line between the origin of the profile and a tangent line at any point on the profile is a multinomial Fourier expansion function of the angle between the perpendicular line and the major axis.

[0039] In other words, the radius vector 13 of the cam support function can be constructed as a multi-factor Fourier expansion function about the angle φ between the cam radius vector 13 and the long axis of the cam. The sum of the Fourier expansion coefficients of the multi-factor Fourier expansion function is related to the meshing deformation coefficient and the flexwheel modulus, and the Fourier expansion coefficients of the multi-factor Fourier expansion function make the maximum curvature difference of the cam profile as small as the target level under the condition of satisfying the constraint conditions. The constraint conditions include: the curvature difference corresponding to the stress separation angle of the cam is the largest, and the curvature difference at the short axis is the smallest, and the angle range of the stress separation angle is 0 to 55°. The size of the meshing deformation coefficient can control the meshing depth of the rigid wheel and the flexwheel and the deformation of the flexwheel, and is proportional.

[0040] In this embodiment, the target degree is quantifiable information, for example, the maximum curvature difference is as small as a set value, or reaches a minimum under certain conditions, which will be described in more detail below.

[0041] By adopting the method provided in this embodiment, the sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is associated with the meshing deformation coefficient and the flexspline modulus, and the curvature difference corresponding to the stress separation angle of the cam and the curvature difference at the short axis are constrained, and the angle range of the stress separation angle is limited to 0 to 55°, so that the multiple Fourier expansion functions with Fourier expansion coefficients that meet these conditions are used as the support functions of the cam, and a new cam profile is provided that can reduce the bending stress amplitude of the flexspline rim after assembly and achieve the separation of the bending stress at the long axis from the meshing stress. This profile is conducive to alleviating the problem or risk of failure or fracture of the flexspline caused by traditional cams.

[0042] Optionally, in one implementation of this embodiment, the sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is equal to the product of the meshing deformation coefficient and the flex spline modulus. The Fourier expansion coefficients here refer to the Fourier expansion coefficients corresponding to the harmonic components, and do not include the coefficients corresponding to the DC components. The coefficients corresponding to the DC components (i.e., constants) are given. By associating the sum of the Fourier expansion coefficients with the product of the meshing deformation coefficient and the flex spline modulus, it is helpful to solve the Fourier expansion coefficients that meet the purpose of the invention of this application under constraints.

[0043] Exemplarily, the meshing deformation coefficient has a value range of 1<γ<5, where γ represents the meshing deformation coefficient.

[0044] Optionally, in an implementation of the present embodiment, in order to further solve the problem of failure and fracture of the flexible pulley, the constraint condition also includes: the difference between the maximum curvature difference and the minimum curvature difference of the neutral layer curve of the flexible pulley is less than a set value, and the set value is a function of the meshing deformation coefficient, the flexible pulley modulus and the equivalent circle radius of the flexible pulley.

[0045] By adopting this implementation method, by making the difference between the maximum curvature difference and the minimum curvature difference based on the flexspline neutral layer curve smaller than a set value, it is beneficial to further obtain the Fourier expansion coefficient that meets the purpose of the invention of this application, and then obtain the profile of the cam.

[0046] In this implementation, the set value can satisfy Wherein, y represents the set value, q is a constant (for example, q∈[5,8], for example, q=6, or q=6.5), γ represents the meshing deformation coefficient, m represents the flexspline modulus, and r f represents the equivalent circular radius of the flexible wheel.

[0047] Optionally, in an implementation of this embodiment, the constraint condition may further include: the range of values ​​of the stress separation coefficient ξ of the cam satisfies: 1<ξ<5, wherein the stress separation coefficient refers to the ratio of the maximum curvature difference corresponding to the stress separation angle to the curvature difference of the major axis. By adopting this implementation, by constraining the stress separation coefficient ξ, it is beneficial to further obtain the Fourier expansion coefficient that meets the purpose of the invention of this application, and then obtain the profile of the cam.

[0048] Optionally, in an implementation of this embodiment, the multi-term Fourier expansion function satisfies the following form:

[0049] Among them, P c represents the length of the vertical line (or the radius vector of the cam support function), and r c represents the equivalent circle radius of the cam, φ represents the angle between the vertical line and the major axis, a n represents the Fourier expansion coefficient of the multi-term Fourier expansion function, 2≤n≤7, or n=3. Wherein, n=3 means that the multi-term Fourier expansion function is a 4-term Fourier expansion, wherein the Fourier expansion coefficients corresponding to the harmonic components are a1, a2, and a3 respectively, wherein the coefficient corresponding to the DC component is r c . r c The value of is the set value. In this implementation, r c Used to control the size of the cam profile and optimize the model to obtain a n , is used to control the shape of the cam profile.

[0050] Compared with the traditional profile, the cam profile that satisfies the multi-functional Fourier expansion function of this form associates the cam profile parameters with the bending stress of the flexspline rim, which can optimize the bending stress amplitude of the flexspline rim and separate the bending stress and meshing stress at the major axis. It also has the characteristics of simple profile design ideas, simple equation form, and easy profile processing.

[0051] Further, in this implementation, the following optimization model can be used to optimize the multinomial Fourier expansion function to obtain the a n Values:

[0052]

[0053] Wherein, γ is the meshing deformation coefficient, m is the flexspline modulus, α is the stress separation angle, which represents the angle between the corresponding point at the maximum curvature difference and the major axis, ξ is the stress separation coefficient, which represents the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis, Δk represents the curvature difference, minf(x)=min(Δk max ) indicates that the optimization objective of the optimization model is to maximize the curvature difference Δk max minimum, q is a constant.

[0054] Exemplarily, γ∈(0,5), for example, γ∈(1.2,4.5), or γ=2.6 or 3. ξ∈(0,5), for example, ξ∈(1.5,4.3), or ξ=2 or 3. α∈(0,55°), for example, α∈(5°,50°), or α∈(13.5°,40.5°), for example, α=20°, 30° or 35.5°.

[0055] By using the optimization model provided by this implementation, the maximum curvature difference Δk obtained in the optimization process of the set number of times that meets the above constraints can be obtained. max The cam profile of the flex spline is based on the multiple Fourier expansion functions, and the cam profile can achieve the beneficial effect of optimizing the comprehensive bending stress amplitude of the flex spline rim after being assembled with the flex spline, and can also achieve the separation of the flex spline rim bending stress and the tooth meshing stress at the long axis position. This design can significantly reduce the risk of flex spline failure and extend the service life of the entire harmonic reducer.

[0056] Specifically, please refer to Figure 2 The schematic diagram of the bending stress comparison of the flexspline of the cam profile provided by the present embodiment and the conventional curve profile is shown. Among them, 17 represents the conventional cam profile curve (ellipse), 18 represents the cam profile curve provided by the present embodiment (four-term Fourier expansion), 19 represents the stress difference between the long axis and the short axis in the conventional cam profile design (i.e., the flexspline bending stress amplitude), 20 represents the stress difference between the long axis and the short axis in the cam profile provided by the present embodiment, and 21 represents the flexspline bending stress amplitude in the cam profile provided by the present embodiment. It can be clearly seen from the comparison that the cam profile provided by the present embodiment has a lower flexspline bending stress amplitude than the conventional cam profile.

[0057] The above optimization model is further explained as follows. Among them, ① means: the sum of the Fourier expansion coefficients is set to γm; ② means: the curvature difference corresponding to α is set to be the largest; ③ means: the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis is set to ξ; ④ means: the curvature difference Δk at the minor axis is the minimum point, that is, the second-order derivative of Δk at φ = 0.5π should be greater than 0; ⑤ means: the difference between the maximum curvature difference and the minimum curvature difference of the neutral layer curve of the flexible wheel is less than

[0058] The following is an in-depth study and analysis of the reasons why the cam profile provided in the embodiment of the present application has the beneficial effects mentioned above.

[0059] like Figure 1 As shown, the equivalent circle radius of the cam is 08, which is denoted as r c In this design, an n+1-term Fourier expansion equation is used as the support function of the cam profile, and the support function radius vector 13 is recorded as P c :

[0060]

[0061] This function represents the set of perpendicular lines from the origin to the tangent line of any point on the cam profile curve, where a n represents the Fourier expansion coefficient, and the angle 16 between the support function radius vector and the major axis is recorded as angle φ.

[0062] In traditional cam profile design, it is considered that the flexspline neutral layer profile support function is an equidistant curve of the cam profile support function. f It can be expressed as:

[0063]

[0064] In the formula, r f is the equivalent circle radius of the neutral layer of the flexible wheel, r f =r c +t+δ, t is the thickness of the flexible bearing without clearance, δ is half of the wall thickness of the flexwheel rim. c is the equivalent circle radius of the cam, given r c The value of r can be determined f The value of .

[0065] The curvature radius ρ of the neutral layer of the flexible wheel can be expressed as:

[0066] ρ=P f +P″ f =r f -λ f

[0067] Among them, P fis the support function of the neutral layer profile of the flexspline, P″ f P f The second derivative of the variable φ,

[0068] After the flexspline and the wave generator are assembled, the neutral layer is approximately elliptical. The circumferential stress caused by the deformation of the flexspline can be calculated using the following formula:

[0069] σ=EδΔk

[0070] E is the elastic modulus of the flexspline material, δ is half of the flexspline rim wall thickness, and Δk is the change in neutral line curvature before and after the flexspline is deformed (the curvature is equal to the derivative of the radius of curvature, the curvature difference is equal to the change in curvature before and after the flexspline is deformed, and Δk is the curvature after the flexspline is deformed minus the curvature before deformation).

[0071] It can be seen that the circumferential bending stress of the flexspline rim is determined by the curvature difference, so the minimum curvature difference is taken as the design goal and the Fourier expansion coefficient is used as the design variable. The following optimization model can be constructed, and the 4-term cosine Fourier expansion function is used as the support function.

[0072] Cam profile optimization model:

[0073]

[0074] Among them, γ is the meshing deformation coefficient, and its value range is ∈(0, 5), ξ is the stress separation coefficient, and its value range is ∈(1, 5), m is the flexspline modulus, α is the stress separation angle, that is, the angle between the corresponding point at the design maximum curvature difference and the major axis, and its value range is (0, 55°), and q is a constant. Model optimization goal: Minimize the bending stress of the flexspline rim, that is, minimize the maximum curvature difference of the flexspline neutral layer. Explanation of constraints: ①: Set the sum of the Fourier expansion coefficients to γm; ②: Set the curvature difference corresponding to α to be the largest (that is, when the α value is given, the change in the neutral line curvature of the flexspline before and after deformation corresponding to α is the largest); ③: Set the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis to ξ; ④: The curvature difference Δk at the minor axis is the minimum point, that is, the second-order derivative of Δk at φ=0.5π should be greater than 0; ⑤: The difference between the maximum curvature difference and the minimum curvature difference of the flexspline neutral layer curve is less than

[0075] In one specific implementation, r c Take 22.17mm, ξ as 1.1, α as 20°, m as 0.3175mm, γ as 1.7268, δ as 0.4445mm, t as 6.532mm, and the cam profile support function is optimized by the model. The result is:

[0076]

[0077] a1=0.000577293583799118;

[0078] a2=-2.49349456612113*10-5;

[0079] a3=-4.14095027658642*10-6;

[0080] Naturally, by r f =r c +t+δ, the support function of the neutral layer of the flexible wheel can be obtained as:

[0081]

[0082] a1=0.000577293583799118;

[0083] a2=-2.49349456612113*10-5;

[0084] a3=-4.14095027658642*10-6;

[0085] Comparison of bending stress of the flexspline rim of the optimized cam profile and the elliptical cam Figure 2 As shown in the figure, it can be seen that the maximum bending stress of the designed cam profile curve 18 is at the angle α on both sides of the major axis (0°), which realizes the separation of the flexible wheel bending stress and the tooth meshing stress at the major axis. The bending stress amplitude 21 in the cam profile of this design is also smaller than the flexible wheel bending stress amplitude 19 in the traditional cam profile design, which can effectively increase the service life of the flexible wheel and extend the service life of the whole machine.

[0086] The embodiment of the present application also provides a cam wave generator for use in a harmonic reducer, and the cam wave generator includes a cam provided in the embodiment of the present application and a flexible bearing that cooperates with the cam. The cam cooperates with the inner ring of the flexible bearing. After the two are assembled, the flexible bearing is forced to deform into a shape similar to the cam profile as the cam profile is deformed. The cam rotates, and the inner ring of the flexible bearing fits the cam and rotates with it. The outer ring of the flexible bearing fits the inner hole of the flexible wheel and rotates with it. The ball of the flexible bearing is designed to reduce friction. Since the cam is an irregular structure similar to an ellipse, its rotation will change the shape of the flexible wheel, causing the teeth of the long axis part to mesh with the rigid wheel, and the teeth of the short axis part to disengage from the teeth of the rigid wheel. There is a small tooth difference between the rigid wheel and the flexible wheel. When the wave generator rotates one circle, the flexible wheel will rotate relative to the rigid wheel by 1 times the tooth difference.

[0087] An embodiment of the present application also provides a harmonic reducer, which includes a flexible wheel, a rigid wheel and the above-mentioned cam wave generator.

[0088] In one embodiment of the present application, a segmented cam can be used to achieve separate design and optimization of the long shaft segment and the short shaft segment, and then the connection between the two cam segments can be smoothed. The advantage is that the overall cam profile can achieve the optimal bending stress of the flexible wheel rim. The disadvantage is that the model is cumbersome to implement, and the segmented cam profile will increase the difficulty of processing.

[0089] The sequence of serial numbers or introduction of the embodiments of the present application is for description only and does not represent the superiority or inferiority of the embodiments.

[0090] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0091] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0092] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0093] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access, or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a digital versatile disc (DVD)), or a semiconductor medium (e.g., a solid state disk (SSD)). It is worth noting that the computer-readable storage medium mentioned in the embodiment of the present application may be a non-volatile storage medium, in other words, a non-transient storage medium.

[0094] It should be noted that the information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data for analysis, stored data, displayed data, etc.) and signals involved in the embodiments of this application are all authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of the relevant countries and regions. For example, the scene data of the current frame in the three-dimensional virtual scene, the device information of the client, and the scene interaction information involved in the embodiments of this application are all obtained with full authorization.

[0095] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A cam for a harmonic reducer, the harmonic reducer having a flexible wheel, a rigid wheel and a cam wave generator, the cam wave generator comprising a cam, the cam having a major axis and a minor axis, characterized in that: The profile of the cam is constructed such that the length of a perpendicular line between the origin of the profile and a tangent line at any point on the profile is a multinomial Fourier expansion function with respect to the angle between the perpendicular line and the major axis; The sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is related to the meshing deformation coefficient and the flexspline modulus, and the Fourier expansion coefficients of the multiple Fourier expansion functions make the maximum curvature difference of the cam profile as small as a target level while satisfying the constraint conditions; The constraint conditions include: the curvature difference of the cam at the stress separation angle is the largest, and the curvature difference at the short axis is the smallest, and the angle range of the stress separation angle is 0 to 55°.

2. The cam according to claim 1, characterized in that: The sum of the Fourier expansion coefficients of the multiple Fourier expansion functions is equal to the product of the meshing deformation coefficient and the flexspline modulus.

3. The cam according to claim 2, characterized in that: The meshing deformation coefficient has a value range of 1<γ<5, where γ represents the meshing deformation coefficient.

4. The cam according to claim 1, characterized in that: The constraint condition also includes: the difference between the maximum curvature difference and the minimum curvature difference of the neutral layer curve of the flexspline is less than a set value, and the set value is a function of the meshing deformation coefficient, the flexspline module and the equivalent circle radius of the flexspline.

5. The cam according to claim 4, characterized in that: The set value satisfies: Wherein, y represents the set value, q is a constant, γ represents the meshing deformation coefficient, m represents the flexspline modulus, and r f represents the equivalent circular radius of the flexible wheel.

6. The cam according to claim 1, characterized in that: The constraint condition also includes: the value range of the stress separation coefficient ξ of the cam satisfies: 1<ξ<5, wherein the stress separation coefficient refers to the ratio of the maximum curvature difference corresponding to the stress separation angle to the curvature difference of the major axis.

7. The cam according to claim 1, characterized in that: The multinomial Fourier expansion function satisfies the following form: Among them, the P c represents the length of the vertical line, the P c represents the equivalent circle radius of the cam, φ represents the angle between the vertical line and the major axis, a n represents the Fourier expansion coefficients of the multi-item Fourier expansion function, 2≤n≤7, or n=3.

8. The cam according to claim 7, characterized in that: The following optimization model is used to optimize the multinomial Fourier expansion function to obtain the a n Values: Wherein, γ is the meshing deformation coefficient, m is the flexspline modulus, α is the stress separation angle, which represents the angle between the corresponding point at the maximum curvature difference and the major axis, ξ is the stress separation coefficient, which represents the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis, q is a constant, Δk represents the curvature difference, minf(x)=min(Δk max ) indicates that the optimization objective of the optimization model is to maximize the curvature difference Δk max Minimum.

9. The cam according to claim 7, characterized in that: The Fourier expansion coefficients of the multiple Fourier expansion functions make the maximum curvature difference of the cam profile as small as a target level under the condition of satisfying the constraint conditions, including: The corresponding maximum curvature difference value Δk obtained in the process of optimizing the multi-layer Fourier expansion function for a set number of times using the optimization model max The minimum expansion coefficient makes the maximum curvature difference of the cam profile as small as the target level.

10. A cam wave generator applied to a harmonic reducer, characterized in that: The cam wave generator comprises the cam as described in claims 1 to 9 and a flexible bearing cooperating with the cam.

11. A harmonic reducer, characterized in that: The harmonic reducer includes a flex spline, a rigid spline and the cam wave generator as claimed in claim 10.

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