Harmonic reducer, cam wave generator and cam

Abstract

An embodiment of the present application discloses a cam applied to a harmonic reducer, wherein the harmonic reducer has a flexible spline, a rigid spline and a cam wave generator, wherein the cam wave generator includes a cam, wherein the cam has a major axis and a minor axis, and 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 of any point on the profile is a multinomial Fourier expansion function with respect to the angle between the perpendicular line and the major axis; wherein the sum of the Fourier expansion coefficients of the multinomial Fourier expansion function is related to the meshing deformation coefficient and the flexible spline modulus, and the Fourier expansion coefficients of the multinomial Fourier expansion function make the maximum curvature difference of the cam profile as small as a target degree while satisfying the constraint conditions; wherein 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 minor axis is the smallest, and the angle range of the stress separation angle is 0 to 55°.

Description

Technical Field

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

[0002] Harmonic reducers are precision speed reducers used in industrial robot joints. They typically consist of three main components: a flexspline, a rigid pulley, and a wave generator. The cam wave generator's rotation causes the flexspline to deform periodically, forcing the flexspline and rigid pulley to engage with each other with a small tooth difference, thereby achieving motion and power transmission. Common cam profile designs for harmonic reducers include elliptical and cosine curves.

[0003] The inventors of the present application have discovered in actual production research that the flexible pulley 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 for a harmonic reducer is provided. The harmonic reducer comprises a flex spline, a rigid spline, and a cam wave generator. The cam wave generator comprises a cam having 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 corresponding to the stress separation angle is the largest, and the curvature difference at the minor axis is the smallest, and the angle range of the stress separation angle is 0 to 55 degrees.

[0009] In combination with the first aspect, in an optional implementation 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 of an 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 pulley is less than a set value, and the set value is a function of the meshing deformation coefficient, the flexible pulley module and the equivalent circle radius of the flexible pulley.

[0012] In conjunction 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, r f represents the equivalent circle radius of the flexible spline.

[0014] In combination with the first aspect, in an optional implementation of an 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 conjunction with the first aspect, in an optional implementation of the embodiment of the present application, the multinomial 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-term 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 Value:

[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 point corresponding to 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 conjunction 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, while satisfying the constraint conditions, make the maximum curvature difference of the cam profile as small as a target degree, which means:

[0022] The corresponding maximum curvature difference Δk obtained during the optimization process of the multi-level Fourier expansion function for a set number of times using the optimization model max The minimum expansion coefficient is the one that reduces the maximum curvature difference of the cam profile to 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 includes 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 flex spline, a rigid spline, 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 the profile of a cam applied to a harmonic reducer according to an embodiment of the present application;

[0027] Figure 2 3 is a schematic diagram comparing the bending stress of a flexible pulley 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 invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in 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 this application.

[0029] It should be understood that the “plurality” mentioned herein refers to two or more than two. 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 merely 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 a clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as “first” and “second” are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art can understand that words such as “first” and “second” do not limit the quantity and execution order, and words such as “first” and “second” do not limit certain different

[0030] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion. 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 expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or apparatus.

[0031] A harmonic reducer consists of three basic components: a rigid wheel, a flexspline, and a wave generator. The rigid wheel is a rigid internal gear, typically with a large number of teeth. The flexspline is a thin-walled external gear that is easily deformed and has fewer teeth than the rigid wheel. The wave generator is the component that causes the flexspline to produce controllable elastic deformation.

[0032] A cam wave generator typically consists of an elliptical cam and a thin-walled flexible bearing. The cam is the core component of the wave generator, and its elliptical shape enables it to generate periodic radial deformation forces during rotation. The flexible bearing is mounted on the outside of the cam. It provides support and positioning while also deforming as the cam rotates to accommodate the deformation requirements of the flexspline. As the wave generator rotates, the elliptical shape of the cam causes the radial distance between its contact point and the flexspline to vary at different rotation angles. Along the major axis, the wave generator pushes the flexspline outward, causing localized radial deformation; along the minor axis, the flexspline contracts. This periodic deformation propagates through the flexspline like a wave, achieving staggered tooth motion between the flexspline and the rigid wheel.

[0033] A flexspline is a thin-walled cylindrical structure with teeth machined onto its outer surface. The flexspline's walls are typically thin, giving it excellent elastic deformation capabilities. The flexspline's teeth require high precision to ensure a good fit 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 engage and disengage with the teeth of the rigid wheel in sequence. Since the flexspline has fewer teeth than 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 a 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 amount of torque and alternating stress during operation, so there are high requirements for its material strength, elastic modulus, and fatigue performance.

[0035] The inventors of this application discovered in their research that actual working conditions have proven that when a conventional elliptical or cosine-curve cam is assembled into a flexible pulley, the bending stress at the long axis of the flexible pulley is relatively large, and the stress coincides with the meshing stress at the long axis, further increasing the combined stress at the long axis. This is the main reason for the failure and fracture of the flexible pulley. Therefore, the embodiments of this application propose a design that can alleviate the technical problem of flexible pulley failure and fracture. Furthermore, in at least one embodiment of this application, a new cam profile curve is proposed that can both reduce the bending stress amplitude of the flexible pulley rim after assembly and separate the bending stress at the long axis from the meshing stress, thereby increasing the life of the flexible pulley.

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

[0037] like Figure 1 As shown, the cam is elliptical in shape, with a major axis and a minor axis. Parameters associated with the cam profile 10 primarily include the cam profile equivalent circle 09, the cam equivalent circle radius 8 (i.e., the radius of the equivalent circle 09), an arbitrary point on the cam 11 (denoted as point A), a tangent line 12 passing through an arbitrary point on the cam, the distance 13 from the origin to the tangent line (i.e., the radius vector of the cam support function), the cam profile radius 14, the angle 15 between the cam radius vector and the major axis (or angle θ), and the angle 16 between the support function radius vector 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 the perpendicular line between the origin of the profile and the tangent line of any point on the profile is a multinomial Fourier expansion function with respect to 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 multinomial Fourier expansion function with respect to the angle φ between the cam radius vector 13 and the major axis of the cam. The sum of the Fourier expansion coefficients of the multinomial Fourier expansion function is related to the meshing deformation coefficient and the flexspline modulus, and the Fourier expansion coefficients of the multinomial Fourier expansion function minimize the maximum curvature difference of the cam profile to a target level while 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 minor 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 flexspline and the deformation of the flexspline, and is in direct proportion.

[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 minor axis are constrained, and the angle range of the stress separation angle is limited to 0 to 55 degrees, so that the multiple Fourier expansion functions with Fourier expansion coefficients that meet these conditions are used as the support function of the cam, and a new cam profile is provided that can reduce the bending stress amplitude of the flexspline rim after assembly and realize the separation of the bending stress at the major 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 flexspline 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 flexspline modulus, it is beneficial to solve the Fourier expansion coefficients that meet the purpose of the invention of this application under constraints.

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

[0044] Optionally, in one implementation of this 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 module 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 the 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, r f represents the equivalent circle radius of the flexible spline.

[0047] Optionally, in one implementation of this embodiment, the constraint condition may further include: the stress separation coefficient ξ of the cam satisfies the range of 1 < ξ < 5, where 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. This implementation, by constraining the stress separation coefficient ξ, facilitates obtaining Fourier expansion coefficients that meet the objectives of the present invention, thereby determining the cam profile.

[0048] Optionally, in an implementation of this embodiment, the multinomial 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 polynomial Fourier expansion function, 2≤n≤7, or n=3. Wherein, n=3 means that the polynomial 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-factor 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 long axis. It also has the characteristics of simple profile design ideas, simple equation form, and easy profile processing.

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

[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 point corresponding to 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] Illustratively, 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, it is possible to obtain the maximum curvature difference Δk that meets the above constraints and is obtained during the optimization process of a set number of times. max The multiple Fourier expansion coefficients are the smallest (i.e., the "minimum under certain conditions" mentioned above) (i.e., satisfying the condition of "making the maximum curvature difference of the cam profile as small as the target degree"), so that the cam profile based on the multiple Fourier expansion functions can achieve the beneficial effect of optimizing the comprehensive bending stress amplitude of the flexspline rim after the cam profile is assembled with the flexspline, and can also achieve the separation of the flexspline rim bending stress and the tooth meshing stress at the long axis position. This design can significantly reduce the risk of flexspline failure and extend the service life of the entire harmonic reducer.

[0056] Specifically, please refer to Figure 2 The following is a schematic diagram comparing the bending stress of a flexspline with a cam profile provided by this embodiment and a conventional curved profile. 17 represents the conventional cam profile curve (ellipse), 18 represents the cam profile curve provided by this embodiment (four-term Fourier expansion), 19 represents the stress difference between the major and minor axes in the conventional cam profile design (i.e., the flexspline bending stress amplitude), 20 represents the stress difference between the major and minor axes in the cam profile provided by this embodiment, and 21 represents the flexspline bending stress amplitude in the cam profile provided by this embodiment. The comparison clearly shows that the cam profile provided by this embodiment has a lower flexspline bending stress amplitude than the conventional cam profile.

[0057] The above optimization model is further explained as follows. ① indicates that the sum of the Fourier expansion coefficients is set to γm; ② indicates that the curvature difference corresponding to α is set to the maximum; ③ indicates that the ratio of the maximum curvature difference corresponding to α to the curvature difference of the major axis is set to ξ; ④ indicates that 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 indicates that the difference between the maximum curvature difference and the minimum curvature difference of the flexspline neutral layer curve 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 and is recorded 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 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. Therefore, the flexspline neutral layer profile support function P f It can be expressed as:

[0063]

[0064] Where r f is the equivalent circle radius of the neutral layer of the flexspline, 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 flexible wheel rim. c is the equivalent circle radius of the cam, by giving r c The value of r can be determined f value.

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

[0066] ρ=P f +P″ f =r f -λ f

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

[0068] After the flexspline and wave generator are assembled, the neutral layer is approximately elliptical. The circumferential stress generated 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 deformation (the curvature is equal to the derivative of the curvature radius, the curvature difference is equal to the change in curvature before and after the flexspline deformation, and Δk is the curvature after the flexspline deformation 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. Therefore, with the minimum curvature difference as the design goal and the Fourier expansion coefficient as the design variable, the following optimization model can be constructed, using the four-term cosine Fourier expansion function 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 the 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 Taking 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, the cam profile support function is optimized through the model, and 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 spline 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 flexible wheel rim of the optimized cam profile and the elliptical cam Figure 2 As shown in the figure, the maximum bending stress of the designed cam profile curve 18 occurs at angles α on either side of the major axis (0°), achieving separation of the flexspline bending stress and the tooth meshing stress at the major axis. The bending stress amplitude 21 in this designed cam profile is also smaller than the flexspline bending stress amplitude 19 in the traditional cam profile design, effectively extending the service life of the flexspline and the overall machine life.

[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 the 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 formed. When the cam rotates, 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, it will change the shape of the flexible wheel as it rotates, causing the teeth of its 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 with a tooth difference of 1 times relative to the rigid wheel.

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

[0088] In one embodiment of this application, a segmented cam can be used to achieve separate design and optimization of the long and short shaft segments, with the connection between the two cam segments then smoothed. This has the advantage of optimizing the overall cam profile for the bending stress of the flexspline rim. However, its disadvantages are the cumbersome modeling and the increased difficulty of machining due to the segmented cam profile.

[0089] The sequence of the serial numbers or introduction of the embodiments of this 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 exemplary. For example, the division of the units can be a logical function division. In actual implementation, there may be other division methods, such as 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 separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across 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, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0093] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented 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, all or part of the processes or functions described in the embodiments of the present application are generated. 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 one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, or 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 embodiments 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 used 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 client's device information, 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 embodiment 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 comprising a flexible spline, a rigid spline, and a cam wave generator, the cam wave generator comprising a 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 corresponding to the stress separation angle is the largest, and the curvature difference at the minor axis is the smallest, and the angle range of the stress separation angle is 0-55°.

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 value range of the meshing deformation coefficient is 1< <5, represents the meshing deformation coefficient.

4. The cam according to claim 1, wherein: The constraint condition also includes: the difference between the maximum curvature difference and the minimum curvature difference of the flexspline neutral layer curve 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: y= ,in, y Indicates the set value, is a constant, represents the meshing deformation coefficient, represents the flexspline modulus, represents the equivalent circle radius of the flexible spline.

6. The cam according to claim 1, wherein: The constraint conditions also include: the stress separation coefficient of the cam The value range of satisfies: 1< <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 represents the length of the vertical line, represents the equivalent circle radius of the cam, represents the angle between the vertical line and the major axis, represents the Fourier expansion coefficients of the multinomial Fourier expansion function, 2≤ ≤7.

8. The cam according to claim 1, wherein: The multinomial Fourier expansion function satisfies the following form: Among them, the represents the length of the vertical line, represents the equivalent circle radius of the cam, represents the angle between the vertical line and the major axis, represents the Fourier expansion coefficients of the multinomial Fourier expansion function, =3.

9. The cam according to claim 7 or 8, characterized in that: The following optimization model is used to optimize the multinomial Fourier expansion function to obtain the Value: in, is the meshing deformation coefficient, expressed as is the flexspline modulus, is the stress separation angle, which represents the angle between the corresponding point at the maximum curvature difference and the major axis, is the stress separation coefficient, which indicates the The ratio of the corresponding maximum curvature difference to the curvature difference of the major axis, is a constant, represents the curvature difference, It means that the optimization purpose of the optimization model is to maximize the curvature difference Minimum.

10. The cam according to claim 9, 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 while satisfying the constraint conditions, including: The corresponding maximum curvature difference value obtained during the optimization process of the multi-item Fourier expansion function for a set number of times using the optimization model The minimum expansion coefficient is the one that reduces the maximum curvature difference of the cam profile to the target level.

11. A cam wave generator used in a harmonic reducer, characterized in that: The cam wave generator includes the cam according to any one of claims 1 to 10 and a flexible bearing cooperating with the cam.

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

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