Flexible gear, design method of flexible gear, harmonic reducer and industrial robot

Abstract

The invention relates to the technical field of harmonic reducers, and discloses a flexible gear, a design method of the flexible gear, the harmonic reducer and an industrial robot, the flexible gear comprises a cylinder, a tooth part, a cylinder part, a bending part, a diaphragm part and a flange part are sequentially arranged in the axial direction of the cylinder, the joint of the diaphragm part and the flange part is a transition area, and on the axial section cutting plane of the cylinder, the bending part is arranged on the flange part. The side wall contour line, deviating from the tooth part, of the transition area is a spline curve. A tooth part is arranged at one end of the cylinder, a flange part is arranged at the other end of the cylinder, and torque of the wave generator can be transmitted to the flange part through the flexible gear so that the torque can be output through the flange part. The contour line of the transition area between the diaphragm part and the flange part is arranged to be the spline curve instead of two sections of arc lines, so that stress concentration can be reduced, the deformation bearing capacity of the flexible gear is improved, the risk of tearing failure of the flexible gear due to deformation is reduced, the fatigue strength of the flexible gear is improved, the service life of the flexible gear is prolonged, and therefore the reliability of the harmonic reducer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic reducers, and in particular to a flexspline, a flexspline design method, a harmonic reducer and an industrial robot. Background Art

[0002] The harmonic reducer drives the flexwheel to deform through a wave generator so that the flexwheel meshes with the rigid wheel, thereby realizing the transmission of motion. Due to the inherent characteristics of harmonic gears, the meshing area between the flexwheel and the rigid wheel is large, making its load-bearing capacity higher. When the harmonic reducer is running, the deformation of the flexwheel transmits the torque to the flange of the flexwheel, and stress concentration is easily formed in the transition area between the flange and the diaphragm, causing damage to the flexwheel in this area. The contour line of the transition zone usually includes two arc lines. The continuity of the connection between the two arc lines is difficult to handle. An unreasonable design is likely to cause greater stress concentration, resulting in a short service life of the flexwheel and affecting the stability of the use of the harmonic reducer. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a flexible wheel, which can improve the service life and reliability through reasonable wall thickness design.

[0004] The present invention also provides a design method for the flexible pulley.

[0005] The present invention also provides a harmonic reducer having the above-mentioned flexible wheel and an industrial robot using the harmonic reducer.

[0006] According to the first aspect of the present invention, the flexible wheel comprises a cylinder, and a tooth portion, a cylinder portion, a bending portion, a diaphragm portion and a flange portion are sequentially arranged along the axial direction of the cylinder, and the connection between the diaphragm portion and the flange portion is a transition zone. On the axial cross-sectional plane of the cylinder, the side wall contour line of the transition zone away from the tooth portion is a spline curve.

[0007] According to the first aspect of the present invention, the flexible wheel has at least the following beneficial effects: a tooth portion is provided at one end of the cylinder, and a flange portion is provided at the other end of the cylinder, and the torque of the wave generator can be transmitted to the flange portion through the flexible wheel, so as to output the torque through the flange portion. Along the axial direction of the cylinder, the tooth portion, the cylinder portion, the bending portion, the diaphragm portion and the flange portion are connected in sequence, and the contour line of the transition zone between the diaphragm portion and the flange portion is set as a spline curve instead of two arcs, which can reduce stress concentration, improve the deformation bearing capacity of the flexible wheel, reduce the risk of tearing failure of the flexible wheel due to deformation, improve the fatigue strength of the flexible wheel, and extend the service life of the flexible wheel, thereby improving the reliability of the harmonic reducer.

[0008] According to some embodiments of the first aspect of the present invention,

[0009] The two endpoints P of the spline curve 0, P 3 The coordinates of (X 0 , Y 0 )、(X 3 , Y 3 ), the spline curve has a first control point P 1 and the second control point P 2 , the first control point P 1 The coordinates of (X 1 , Y 1 ), the second control point P 2 The coordinates of (X 2 , Y 2 ), the coordinates (X, Y) of any point on the spline curve satisfy:

[0010] X=(1-t) 3 X 0 +3t(1-t) 2 X 1 +3t 2 (1-t)X 2 +t 3 X 3 ,

[0011] Y=(1-t) 3 Y 0 +3t(1-t) 2 Y 1 +3t 2 (1-t)Y 2 +t 3 Y 3 ,

[0012] Where t∈[0,1], and satisfies:

[0013] X 1 =t 1 X 0 +(1-t 1 )X 3 , Y 1 =t 2 Y 0 +(1-t 2 )Y 3 , X 2 =t 3 X 0 +(1-t 3 )X 3 , Y 2 =t 4 Y 0 +(1-t 4 )Y 3 , t 1 0.05 to 0.16, t 20.85 to 0.96, t 3 0.06 to 0.15, t 4 It is 0.68 to 0.82.

[0014] According to some embodiments of the first aspect of the present invention, t 1 0.09 to 0.12, t 2 0.92 to 0.96, t 3 0.08 to 0.13, t 4 It is 0.72 to 0.79.

[0015] According to some embodiments of the first aspect of the present invention, the P 0 The slope is B 0 , the P 1 The slope is B 1 , the P 2 The slope is B 2 , the P 3 The slope is B 3 , the slope of any point on the spline curve is B t ,satisfy:

[0016] B t =(1-t) 3 B 0 +3t(1-t) 2 B 1 +3t 2 (1-t)B 2 +t 3 B 3 , where t∈[0,1].

[0017] According to some embodiments of the first aspect of the present invention, the P 0 The slope of is 0.

[0018] According to some embodiments of the first aspect of the present invention, the P 3 The slope is -tan(84.58).

[0019] According to some embodiments of the first aspect of the present invention, the spline curve is tangent to a side wall contour line of the diaphragm.

[0020] According to some embodiments of the first aspect of the present invention, the spline curve is tangent to a side wall contour line of the flange portion.

[0021] The design method of the flexible spline according to the second aspect of the present invention is applied to the flexible spline of the first aspect, and comprises the following steps: calculating the coordinates of the two endpoints of the spline curve;

[0022] Setting a plurality of control points, wherein the control points are set with a plurality of sets of coordinates;

[0023] Generate a plurality of said spline curves by using the spline curve theory;

[0024] The spline curve with the minimum stress is calculated through simulation.

[0025] According to some embodiments of the second aspect of the present invention, in the step of calculating the spline curve with the minimum stress through simulation, mechanical simulation calculation is performed through finite element software under the same working conditions.

[0026] According to the third aspect of the present invention, the harmonic reducer comprises a rigid wheel, a wave generator and the flexible wheel described in the first aspect, wherein the rigid wheel is sleeved on the outside of the flexible wheel, the rigid wheel is provided with internal teeth matching the tooth portion, the flexible wheel is sleeved on the outside of the wave generator, and the wave generator abuts against the inner wall of the tooth portion.

[0027] The industrial robot according to the fourth aspect of the present invention comprises the harmonic reducer according to the third aspect of the present invention. By adopting the harmonic reducer according to the third aspect of the present invention, the harmonic reducer has high reliability and stability in use, so that the movement of the industrial robot is smooth, the maintenance frequency of the industrial robot is reduced, the use cost is reduced, and the reliability of the industrial robot is improved.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0030] Figure 1 A cross-sectional view of a flexible wheel according to some embodiments of the first aspect of the present invention;

[0031] Figure 2 are cross-sectional views of flexible wheels according to other embodiments of the first aspect of the present invention;

[0032] Figure 3 for Figure 1 A partial enlarged view of point A in the middle;

[0033] Figure 4 A cross-sectional view of a harmonic reducer according to an embodiment of the third aspect of the present invention;

[0034] Figure 5 A schematic diagram of a spline curve Figure 1 ;

[0035] Figure 6 A schematic diagram of a spline curve Figure 2 ;

[0036] Figure 7 A schematic diagram of a spline curve Figure 3 ;

[0037] Figure 8 A flow chart of the design method of a flexible pulley.

[0038] The figures are as follows:

[0039] Cylinder 100, tooth portion 110, cylinder portion 120, bending portion 130, diaphragm portion 140, flange portion 150, transition zone 160, spline curve 161;

[0040] Ganglun 200;

[0041] Wave generator 300. DETAILED DESCRIPTION

[0042] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0043] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0044] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0045] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0046] A harmonic gear reducer is a reducer consisting of a fixed rigid wheel, a flexible wheel, and a wave generator that causes the flexible wheel to deform radially. The flexible wheel is sleeved on the outside of the wave generator, and the rigid wheel is sleeved on the outside of the flexible wheel. The wave generator drives the flexible wheel to deform radially and rotate, causing the flexible wheel to generate a controllable elastic deformation wave, causing the teeth of the rigid wheel and the flexible wheel to be relatively staggered to transmit power and motion. Due to the inherent characteristics of the harmonic reducer, the meshing area of ​​the flexible wheel and the rigid wheel is larger, making its load-bearing capacity relatively high. Therefore, harmonic reducers are widely used in electronics, aerospace, industrial robots and other fields.

[0047] The application scenarios of harmonic reducers tend to be small equipment. At present, harmonic reducers are developing towards high speed, high rigidity, long life and other aspects. At the same time, the test on flexible wheels and flexible bearings is more stringent. In order to facilitate manufacturing, the inner wall of the existing flexible wheel is straight, so that the wall thickness of the flexible wheel is uniform. When the harmonic reducer is running, the flexible wheel needs to withstand the alternating stress applied by the wave generator and the meshing torque applied by the rigid wheel. However, the high-load torque will cause the flexible wheel to deform, and the flexible wheel with uniform wall thickness has poor ability to absorb deformation, which can easily lead to the flexible wheel breaking and failure due to repeated deformation, especially in the transition zone where the flange and the diaphragm are connected. Stress concentration is prone to tearing and other failure problems, thereby reducing the service life and reliability of the harmonic reducer. At present, the contour line design of the transition zone is usually two arc lines, and the continuous transition at the connection of the two arc lines is difficult to handle. The unreasonable design is easy to cause large stress concentration, resulting in a short service life of the flexible wheel and affecting the stability of the use of the harmonic reducer.

[0048] In order to solve the above technical problems, the present invention proposes a flexible wheel and a design method for a flexible wheel applied to a harmonic reducer, which can improve the ability of the flexible wheel to withstand deformation, reduce stress concentration, and extend the service life of the flexible wheel, thereby improving the reliability of the harmonic reducer.

[0049] The following is a description with reference to the accompanying drawings:

[0050] Reference Figures 1 to 3 A flexible wheel according to a first aspect of the present invention is applied to a harmonic reducer. The main body of the flexible wheel is a cylinder 100. Figure 4 As shown, one end of the cylinder 100 is open and the outer wall is provided with a tooth portion 110 so that the cylinder 100 can be mounted on the wave generator 300 of the harmonic reducer. The other end of the cylinder 100 is provided with a flange portion 150, which is the output end of the harmonic reducer and is used to connect other devices to transmit motion and torque to other devices.

[0051] Along the axial direction of the cylinder 100, the cylinder 100 includes a tooth portion 110, a cylinder portion 120, a bent portion 130, a diaphragm 140 and a flange portion 150 which are connected in sequence. The tooth portion 110 is a portion of the cylinder 100 provided with external teeth. One end of the cylinder 120 is connected to the tooth portion 110, and the other end is connected to the bent portion 130. The bent portion 130 is turned from the axial direction of the cylinder 100 to the radial direction of the cylinder 100. The diaphragm 140 is a radial structure connected to the bent portion 130. The flange portion 150 is used to connect the load and is roughly distributed along the radial direction of the cylinder 100. It can be understood that, as Figure 1 As shown, the flange portion 150 may extend radially outwardly from the cylinder 100, as shown in FIG. Figure 2 As shown, the flange portion 150 may also extend radially inwardly of the cylinder 100. The flange portion 150 is provided with a plurality of mounting holes along the circumferential direction to cooperate with the connection of other equipment. Therefore, the thickness of the flange portion 150 is usually relatively large (along the axial direction of the cylinder 100). The connection between the flange portion 150 and the diaphragm 140 is a transition zone 160. Since the thickness difference between the flange portion 150 and the diaphragm 140 is relatively large, stress concentration is easily formed in the transition zone 160. During the operation of the harmonic reducer, the flexible wheel may be torn, thereby affecting the stability of the harmonic reducer.

[0052] Therefore, the contour line of the transition zone 160 is designed as a spline curve 161. On the axial section of the cylinder 100, the spline curve 161 is the contour line of the side wall of the transition zone 160 away from the tooth portion 110. The side walls of the flange portion 150 and the diaphragm portion 140 facing the tooth portion 110 are usually flush. The function of the spline curve 161 is to serve as a transition between the flange portion 150 and the diaphragm portion 140. The spline curve 161 extends simultaneously in the axial and radial directions of the cylinder 100. The side wall of the transition zone 160 uses the spline curve 161 as a contour line, which helps to form a smooth curved surface, reduce stress concentration, and reduce the risk of flexible wheel tearing failure.

[0053] It can be understood that spline curves are smooth curves that pass through a series of given points. Initially, spline curves were obtained with the help of physical splines. The lofter fixed the elastic thin wooden strips (or plexiglass strips) with a weight at the given type value points that the curve should pass through. The curve drawn by the natural bending of the spline is the spline curve. The spline curve not only passes through each ordered type value point, but also has continuous first-order and second-order derivatives at each type value point, that is, the curve has the characteristics of continuity and uniform curvature change. Therefore, the side wall contour line of the transition zone 160 is designed as a spline curve 161 to form a smooth transition surface. The spline curve 161 replaces the contour line of the two arc lines, eliminating the continuity problem at the connection between the two arc lines, which is conducive to simplifying the design of the flexible wheel and improving the durability of the flexible wheel.

[0054] Reference Figure 4One end of the cylinder 100 of the flexible wheel is open and can be connected to the wave generator 300. The other end of the cylinder 100 is a flange 150. The load can be connected to the flexible wheel through the flange 150. The load is driven to move by the flexible wheel, and the movement and torque are transmitted by the flexible wheel. During the operation of the harmonic reducer, the flexible wheel must repeatedly withstand deformation and torsion. By designing the side wall contour line of the transition zone 160 as a spline curve 161, the connection between the diaphragm 140 and the flange 150 is smoothly transitioned, which can reduce stress concentration, improve the deformation bearing capacity of the flexible wheel, reduce the risk of fracture and failure of the flexible wheel due to deformation, and improve the fatigue strength of the flexible wheel. The connection between the diaphragm 140 and the flange 150 can withstand greater stress and torsional force, which is beneficial to prolonging the service life of the flexible wheel, thereby improving the reliability of the harmonic reducer.

[0055] It should be noted that, refer to Figure 4 The wave generator 300 is arranged at the opening of the cylinder 100, and the steel wheel 200 is mounted on the outside of the cylinder 100. The rigid wheel 200 and the flexible wheel have teeth with the same modulus, but different numbers of teeth. Usually, the number of teeth of the flexible wheel is two less than that of the rigid wheel 200. The difference in the number of teeth of the harmonic drive represents the deformation wave number of the flexible wheel. In the free state (without the wave generator 300), the rigid wheel 200 and the flexible wheel are in a concentric position, and the gaps between the teeth of the rigid wheel 200 and the flexible wheel are uniform. The wave generator 300 is usually elliptical, and the wave generator 300 undergoes radial deformation to become an ellipse. On the long axis of the ellipse, the steel wheel 200 is meshed with part of the teeth 110 of the flexible wheel, and on the short axis, a radial gap is formed. The wave generator 300 drives the flexible wheel to rotate. During the rotation of the generator, the shape of the flexible wheel is always close to the above shape. Among them, due to the differential tooth meshing torque generated when the rigid wheel 200 and the flexible wheel are meshed, the flexible wheel is bent and deformed. Since the flange portion 150 is connected to the load and serves as the output end, the stress at the connection between the flange portion 150 and the diaphragm portion 140 is relatively large, and fatigue or even tearing and failure may occur easily. Therefore, by designing the shape of the flexible wheel, the side wall contour line of the transition zone 160 is designed as a spline curve 161 to form a smooth transition surface. The spline curve 161 replaces the contour lines of the two arc lines, thereby eliminating the continuity problem at the connection between the two arc lines, which is conducive to simplifying the design of the flexible wheel and improving the durability of the flexible wheel.

[0056] In some embodiments, the spline curve 161 adopts a third-order equation, and the two end points P of the spline curve 161 are 0 , P 3 The coordinates of (X 0 , Y 0 )、(X 3 , Y 3 ), the spline curve 161 has a first control point P 1 and the second control point P 2, the first control point P 1 The coordinates of (X 1 , Y 1 ), the second control point P 2 The coordinates of (X 2 , Y 2 ), the coordinates (X, Y) of any point on the spline curve 161 satisfy:

[0057] X=(1-t) 2 X 0 +3t(1-t) 2 X 1 +3t 2 (1-t)X 2 +t 3 X 3 ,

[0058] Y=(1-t) 3 Y 0 +3t(1-t) 2 Y 1 +3t 2 (1-t)Y 2 +t 3 Y 3 ,

[0059] Where t∈[0,1], the value of t ranges from 0 to 1, corresponding to an endpoint P of the spline curve 161 0 To another endpoint P 3 , P 0 and P 3 The two control points P are calculated based on the shapes of the diaphragm 140 and the flange 150 of the flexible wheel. 1 and P 2 , and obtain the third-order equation of the spline curve 161.

[0060] It should be understood that the first control point P 1 and the second control point P 2 For controlling the shape of the spline curve 161, the first control point P 1 and the second control point P 2 It is not necessarily a point on the spline curve 161 .

[0061] Reference Figure 5 The coordinates of the two endpoints of the spline curve 161 are P0(1.131, 20) and P 3 (0.761, 20.547), the coordinates of the two control points are P 1 (1.1, 20) and P2 (0.8, 20.136), the shape of the spline curve 161 is as follows Figure 5 shown; reference Figure 6The coordinates of the two endpoints of the spline curve 161 are P0(1.131, 20) and P 3 (0.761, 20.547), the coordinates of the two control points are P 1 (0.9, 20) and P2 (0.8, 20.136), the shape of the spline curve 161 is as follows Figure 6 shown; reference Figure 7 The coordinates of the two endpoints of the spline curve 161 are P0(1.131, 20) and P 3 (0.761, 20.547), the coordinates of the two control points are P 1 (0.8, 20.05) and P2(0.8, 20.547), the shape of the spline curve 161 is as follows Figure 7 As shown. By setting two control points P 1 and P 2 The coordinates of the spline curve 161 can be used to control the shape of the spline curve 161, and then mechanical simulation is performed through finite element software to calculate the spline curve 161 with the minimum stress. Figure 7 As shown in the spline curve 161 , the maximum stress value is reduced by about 9.3%, which effectively reduces the stress concentration of the flexible wheel.

[0062] It can be understood that the first control point P 1 and the second control point P 2 The coordinates of X are limited to: 1 =t 1 X 0 +(1-t 1 )X 3 , Y 1 =t 2 Y 0 +(1-t 2 )Y 3 , X 2 =t 3 X 0 +(1-t 3 )X 3 , Y 2 =t 4 Y 0 +(1-t 4 )Y 3 , where t 1 The value range is 0.05 to 0.16, t 2 The value range is 0.85 to 0.96, t 3 The value range is 0.06 to 0.15, t 4 The value range is 0.68 to 0.82.

[0063] In some embodiments, t 1The value range is 0.09 to 0.12, t 2 The value range is 0.92 to 0.96, t 3 The value range is 0.08 to 0.13, t 4 The value range of is 0.72 to 0.79, which has a better technical effect and the stress in the transition zone 160 is lower.

[0064] It can be understood that in the spline curve 161, the slope of P0 is B 0 , B 0 By P 0 and P 1 The coordinates of P are limited. Similarly, 1 The slope is B 1 , P 2 The slope is B 2 , P 3 The slope is B 3 , the slope of any point on the spline curve 161 is B t , B t The third-order equation is also used for calculation, and the calculation formula is:

[0065] B t =(1-t) 3 B 0 +3t(1-t) 2 B 1 +3t 2 (1-t)B 2 +t 3 B 3 ,

[0066] Where t∈[0,1], the value of t ranges from 0 to 1, corresponding to the spline curve 161 from one end point P0 to another end point P 3 .

[0067] In some embodiments, the slope of P0 is set to 0, P 3 The slope of the 0 and P 3 The slope of the spline curve 161 is controlled to control the shape of the spline curve 161, so that the spline curve 161 is close to the contour line of the diaphragm 140 and the contour line of the flange 150, which is conducive to smooth transition and reduces stress concentration. It can be understood that the flexible wheel can be designed so that the two ends of the spline curve 161 are tangent to the side wall contour lines of the diaphragm 140 and the flange 150, so that the connection position of the transition zone 160 and the diaphragm 140 and the flange 150 is smoothly transitioned, which helps to reduce stress concentration and improve the reliability and durability of the flexible wheel.

[0068] Reference Figure 1 and Figure 2It can be understood that the bending portion 130 is the connection portion between the cylinder 120 and the diaphragm 140, and realizes reversal. The bending portion 130 is usually designed to be a circular arc surface transition. Therefore, the side contour lines of the bending portion 130 are all circular arc lines. The cylinder 120, the diaphragm 140 and the bending portion 130 are connected by a smooth curved surface, which reduces stress concentration and is beneficial to improving the reliability of the flexible wheel.

[0069] The embodiment of the second aspect of the present invention provides a design method for a flexible pulley, which is applied to the flexible pulley of the embodiment of the first aspect, referring to Figure 8 , including the following steps:

[0070] S100: Calculate the coordinates of the two endpoints of the spline curve 161;

[0071] S200: Setting multiple control points, where multiple sets of coordinates are set for the control points;

[0072] S300: Generate multiple spline curves 161 using spline curve theory;

[0073] S400: Calculate the spline curve 161 with the minimum stress through simulation.

[0074] According to the flexible wheel design method of the embodiment of the present invention, the flexible wheel is designed with a contour line according to the spline curve 161 with the minimum stress, which can effectively reduce the maximum stress in the transition zone, is beneficial to improving the stress concentration of the flexible wheel, improves the deformation bearing capacity of the flexible wheel, reduces the risk of the flexible wheel breaking and failing due to deformation, improves the fatigue strength of the flexible wheel, and is beneficial to extending the service life of the flexible wheel, thereby improving the reliability of the harmonic reducer.

[0075] It is understandable that, in the step of calculating the spline curve 161 with the minimum stress through simulation, mechanical simulation can be performed through finite element software under the same working conditions to calculate the spline curve 161 with the minimum stress.

[0076] It is understandable that in the step of setting multiple control points, two control points can be selected, three control points can be selected, or four or more control points can be selected. Two control points can be selected to control the shape of the spline curve 161 to meet the requirements of the simulation calculation stress, and the amount of calculation can be reduced, thereby reducing the manufacturing cost of the flexible wheel. The two control points are matched with the two endpoints to design the spline curve 161, so that the connection between the diaphragm 140 and the flange 150 has a smooth transition, reduces the concentration of stress, improves the bearing capacity of the flexible wheel deformation, reduces the risk of the flexible wheel breaking and failing due to deformation, and improves the fatigue strength of the flexible wheel. The connection between the diaphragm 140 and the flange 150 can withstand greater stress and torsional force, which is conducive to extending the service life of the flexible wheel, thereby improving the reliability of the harmonic reducer. In addition, the more control points are selected, the more accurate the fitting of the spline curve 161 is, and the corresponding calculation is more complicated and time-consuming.

[0077] The following is an explanation using two control points as an example.

[0078] In some embodiments, the spline curve 161 adopts a third-order equation, and the two endpoints of the spline curve 161 are set as P 0 (X 0 , Y 0 ) and P 3 (X 3 , Y 3 ), the two control points are the first control point P 1 (X 1 , Y 1 ) and the second control point P 2 (X 2 , Y 2 ), the coordinates (X, Y) of any point on the spline curve 161 satisfy:

[0079] X=(1-t) 3 X 0 +3t(1-t) 2 X 1 +3t 2 (1-t)X 2 +t 3 X 3 ,

[0080] Y=(1-t) 3 Y 0 +3t(1-t) 2 Y 1 +3t 2 (1-t)Y 2 +t 3 Y 3 ,

[0081] Where t∈[0,1], the value of t ranges from 0 to 1, corresponding to an endpoint P of the spline curve 161 0 To another endpoint P 3 , P 0 and P 3 The two control points P are calculated based on the shapes of the diaphragm 140 and the flange 150 of the flexible wheel. 1 and P 2 The coordinates of the spline curve 161 are obtained to obtain the third-order equation of the spline curve 161, and then the spline curve 161 with the minimum stress is calculated through simulation.

[0082] It can be understood that the first control point P 1 (X 1 , Y 1 ) and the second control point P 2 (X 2 , Y2 ) is used to control the shape of the spline curve 161.

[0083] It can be understood that the first control point P1 and the second control point P 2 The coordinates can be: X 1 =t 1 X 0 +(1-t 1 )X 3 , Y 1 =t 2 Y 0 +(1-t 2 )Y 3 , X 2 =t 3 X 0 +(1-t 3 )X 3 , Y 2 =t 4 Y 0 +(1-t 4 )Y 3 , where t 1 The value range is 0.05 to 0.16, t 2 The value range is 0.85 to 0.96, t 3 The value range is 0.06 to 0.15, t 4 The value range is 0.68 to 0.82.

[0084] It can be understood that in the spline curve 161, P 0 The slope is B 0 , B 0 By P 0 and P 1 The coordinates of P are limited. Similarly, 1 The slope is B 1 , P 2 The slope is B 2 , P 3 The slope is B 3 , the slope of any point on the spline curve 161 is B t , B t The third-order equation is also used for calculation, and the calculation formula is:

[0085] B t =(1-t) 3 B 0 +3t(1-t) 2 B 1 +3t 2 (1-t)B 2 +t 3 B 3 ,

[0086] Wherein t∈[0, 1], the value of t ranges from 0 to 1, corresponding to one endpoint P0 to another endpoint P3 of the spline curve 161.

[0087] Reference Figure 4 The harmonic reducer provided in the third embodiment of the present invention comprises a rigid wheel 200, a wave generator 300 and a flexwheel of the first embodiment, the rigid wheel 200 is mounted on the outside of the flexwheel, the rigid wheel is provided with internal teeth, the tooth portion 110 of the flexwheel is provided with external teeth, the flexwheel is mounted on the outside of the wave generator 300, and the wave generator 300 abuts against the inner wall of the tooth portion 110. The internal teeth of the rigid wheel 200 and the external teeth of the flexwheel are gear teeth with the same module, but different numbers of teeth, usually the number of teeth of the flexwheel is 2 less than the number of teeth of the rigid wheel 200, the difference in the number of teeth of the harmonic drive represents the deformation wave number of the flexwheel, in the free state (without the wave generator 300), the rigid wheel 200 and the flexwheel are in a concentric position, and the gaps between the teeth of the rigid wheel 200 and the flexwheel are uniform. The wave generator 300 is usually elliptical, and the wave generator 300 undergoes radial deformation to become an ellipse. On the long axis of the ellipse, the steel wheel 200 is meshed with part of the teeth 110 of the flexible wheel, and a radial gap is formed on the short axis. The wave generator 300 drives the flexible wheel to rotate, and during the rotation of the generator, the shape of the flexible wheel is always close to the above shape. Among them, due to the differential tooth meshing torque generated when the rigid wheel 200 and the flexible wheel are meshed, the flexible wheel is bent and deformed.

[0088] like Figure 4 As shown, the main body of the flexible wheel is a cylinder 100. Along the axial direction of the cylinder 100, the cylinder 100 includes a tooth portion 110, a cylinder portion 120, a bending portion 130, a diaphragm 140 and a flange portion 150 which are connected in sequence. The tooth portion 110 is a part of the cylinder 100 provided with external teeth. One end of the cylinder 120 is connected to the tooth portion 110, and the other end is connected to the bending portion 130. The bending portion 130 is turned from the axial direction of the cylinder 100 to the radial direction of the cylinder 100. The diaphragm 140 is a radial structure connected to the bending portion 130. The flange portion 150 is used to connect the load and is roughly distributed along the radial direction of the cylinder 100. The flange portion 150 is provided with a plurality of mounting holes along the circumferential direction to cooperate with the connection with other equipment. Therefore, the thickness of the flange portion 150 is usually relatively large (along the axial direction of the cylinder 100). The connection between the flange portion 150 and the diaphragm portion 140 is a transition zone 160. Since the thickness difference between the flange portion 150 and the diaphragm portion 140 is relatively large, stress concentration is easily formed in the transition zone 160. During the operation of the harmonic reducer, the flexible wheel may be torn, thereby affecting the stability of the harmonic reducer.

[0089] Therefore, the contour line of the transition zone 160 is designed as a spline curve 161. On the axial section of the cylinder 100, the spline curve 161 is the contour line of the side wall of the transition zone 160 away from the tooth portion 110. The side walls of the flange portion 150 and the diaphragm portion 140 facing the tooth portion 110 are usually flush. The function of the spline curve 161 is to serve as a transition between the flange portion 150 and the diaphragm portion 140. The spline curve 161 extends simultaneously in the axial and radial directions of the cylinder 100. The side wall of the transition zone 160 uses the spline curve 161 as a contour line, which helps to form a smooth curved surface, reduce stress concentration, and reduce the risk of flexible wheel tearing failure.

[0090] The industrial robot of the fourth embodiment of the present invention includes the harmonic reducer of the third embodiment. The industrial robot may be a handling robot, a welding robot, an assembly robot, a processing robot, a spraying robot, a cleaning robot, a collaborative robot, etc. The harmonic reducer of the third embodiment of the present invention is applied to the industrial robot. The harmonic reducer adopts the flexible wheel of the first embodiment. The contour line of the transition zone 160 of the flexible wheel is designed as a spline curve 161, which helps to form a smooth transition surface, reduce stress concentration, reduce the risk of flexible wheel tearing failure, improve the reliability of the harmonic reducer, and facilitate the long-term stable operation of the industrial robot.

[0091] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. Flexspline, characterized in that: include: The cylinder body is provided with a tooth portion, a cylinder portion, a bending portion, a diaphragm portion and a flange portion in sequence along the axial direction of the cylinder body. The connection between the diaphragm portion and the flange portion is a transition zone. On the axial cross-sectional surface of the cylinder body, the side wall contour line of the transition zone away from the tooth portion is a spline curve.

2. The flexible wheel according to claim 1, characterized in that: The coordinates of the two endpoints P0 and P3 of the spline curve are (X0, Y0) and (X3, Y3). The spline curve has a first control point P1 and a second control point P2. The coordinates of the first control point P1 are (X1, Y1), and the coordinates of the second control point P2 are (X2, Y2). The coordinates (X, Y) of any point on the spline curve satisfy: X=(1-t) 3 X0+3t(1-t) 2 X1+3t 2 (1-t)X2+t 3 X3, Y=(1-t) 3 Y0+3t(1-t) 2 Y1+3t 2 (1-t)Y2+t 3 Y3, Where t∈[0,1], and satisfies: X1=t1X0+(1-t1)X3, Y1=t2Y0+(1-t2)Y3, X2=t3X0+(1-t3)X3, Y2=t4Y0+(1-t4)Y3, t1 is 0.05 to 0.16, t2 is 0.85 to 0.96, t3 is 0.06 to 0.15, and t4 is 0.68 to 0.

82.

3. The flexible wheel according to claim 2, characterized in that: t1 is 0.08 to 0.12, t2 is 0.92 to 0.96, t3 is 0.08 to 0.13, and t4 is 0.72 to 0.

79.

4. The flexible wheel according to claim 2, characterized in that: The slope of P0 is B0, the slope of P1 is B1, the slope of P2 is B2, the slope of P3 is B3, and the slope of any point on the spline curve is B t ,satisfy: B t =(1-t) 3 B0+3t(1-t) 2 B1+3t 2 (1-t)B2+t 3 B3, where t∈[0, 1].

5. The flexible wheel according to claim 4, characterized in that: The slope of P0 is 0.

6. The flexible wheel according to claim 5, characterized in that: The slope of P3 is -tan(84.58).

7. The flexible wheel according to claim 1, characterized in that: The spline curve is tangent to a sidewall contour line of the diaphragm.

8. The flexible wheel according to claim 1 or 7, characterized in that: The spline curve is tangent to a side wall contour line of the flange portion.

9. A method for designing a flexible spline, applied to a flexible spline according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: calculating the coordinates of the two endpoints of the spline curve; Setting a plurality of control points, wherein the control points are set with a plurality of sets of coordinates; Generate a plurality of said spline curves by using the spline curve theory; The spline curve with the minimum stress is calculated through simulation.

10. The design method of the flexible pulley according to claim 9, characterized in that: In the step of calculating the spline curve with the minimum stress through simulation, mechanical simulation calculation is performed through finite element software under the same working conditions.

11. Harmonic reducer, characterized in that: It comprises a rigid wheel, a wave generator and a flexible wheel as claimed in any one of claims 1 to 8, wherein the rigid wheel is sleeved on the outside of the flexible wheel, the rigid wheel is provided with internal teeth matching the tooth portion, the flexible wheel is sleeved on the outside of the wave generator, and the wave generator abuts against the inner wall of the tooth portion.

12. An industrial robot, characterized in that Comprising the harmonic reducer as claimed in claim 11.

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