Low-speed-ratio harmonic speed reduction device of industrial robot and design method

Abstract

The invention relates to the technical field of precision speed reducers, in particular to a low-speed-ratio harmonic speed reducer of an industrial robot and a design method. Comprising a camshaft, a flexible bearing, a flexible gear, a roller pin and an inner gear, the flexible bearing is mounted on the elliptical cam shaft; an inner hole of the flexible gear is matched with an outer ring of the flexible bearing; the outer tooth surface of the flexible gear is in contact with each roller pin, and the roller pins are uniformly distributed in the semicircular tooth grooves of the inner gear; according to the structure that the bearing inner ring of the main bearing is fixedly connected with the flexible gear and the bearing outer ring is fixedly connected with the inner gear and the design method of the low-speed-ratio harmonic speed reduction device, the low-speed-ratio harmonic speed reduction device is stable in harmonic transmission process, high in transmission precision, high in transmission efficiency, small in size and low in cost. And miniaturization is facilitated, the deformation of the flexible gear is effectively reduced, design parameters can be rapidly adjusted according to different application scenes and requirements, and the adaptability and the flexibility of the harmonic speed reduction device are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of precision reducers, and in particular to a low-speed ratio harmonic reduction device for an industrial robot and a design method thereof. Background Art

[0002] Precision reducers are a core component in the fields of industrial robots, service robots, precision turntable equipment, machine tool equipment, measurement and testing equipment, and intelligent transmission control. In these fields, reducers are required to be small, light, highly rigid, overload-resistant, stable and smooth, with small clearance, small angular transmission error, and good acceleration performance.

[0003] The reducers in the prior art are especially used in scenarios such as robot arms, joint motion efficiency, and AGV transporters. The reducers with ordinary structures are large in size, heavy in weight, low in work efficiency, poor in positioning accuracy, unstable in transmission process, too low in transmission accuracy, and too large in size. Compared with the reducers with ordinary structures in the prior art, the low-speed ratio harmonic reduction device has the characteristics of compact structure, light weight and high acceleration performance.

[0004] However, the low-speed ratio harmonic reduction device in the existing technology cannot achieve a low speed ratio due to the excessive deformation of the flexible wheel. The speed ratio of the existing harmonic reducer products should remain above 30 speed ratios. It is impossible to effectively reduce the deformation of the flexible wheel while taking into account the advantages of high transmission accuracy, high transmission efficiency, small size, and miniaturization. Summary of the invention

[0005] The purpose of the present invention is to provide a low-speed ratio harmonic reduction device and a design method for an industrial robot in view of the defects existing in the prior art, so as to achieve a smooth harmonic transmission process of the low-speed ratio harmonic reduction device, high transmission accuracy, high transmission efficiency, and small size, which is conducive to miniaturization and effectively reduces the deformation of the flexible wheel. The design parameters can be quickly adjusted according to different application scenarios and requirements, thereby further improving the adaptability and flexibility of the harmonic reduction device.

[0006] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is: a low-speed ratio harmonic reduction device for an industrial robot, comprising a camshaft, a flexible bearing, a flexible wheel, a needle roller and an internal gear;

[0007] The flexible bearing is mounted on the elliptical camshaft;

[0008] The inner hole of the flexible wheel cooperates with the outer ring of the flexible bearing;

[0009] The outer tooth surface of the flex spline is in contact with each of the needle rollers, and the needle rollers are evenly distributed in the semicircular tooth grooves of the internal gear;

[0010] The inner ring of the main bearing is fixedly connected to the flexible gear, and the outer ring of the bearing is fixedly connected to the internal gear.

[0011] Furthermore, the camshaft is installed in the inner ring of the flexible bearing and is supported to deform the flexible bearing.

[0012] Furthermore, the circumference of the needle rollers is evenly distributed in the semicircular tooth grooves of the internal gear;

[0013] The semicircular tooth groove of the internal gear is provided with a retaining ring, and the inner diameter of the retaining ring is larger than the distribution circle diameter of the needle roller plus one quarter of the needle roller radius.

[0014] Further, the flexible wheel is a cup-shaped or cap-shaped structure, a through hole is provided at the bottom of the flexible wheel, a central through hole corresponding to the through hole is provided at the bottom of the inner ring of the bearing, a plurality of inner ring threaded holes are provided at the inner ring of the bearing, and the through hole is fixedly connected to the central through hole by screws;

[0015] The outer ring of the inner gear is provided with a plurality of inner gear threaded holes, and the outer ring of the bearing is provided with corresponding outer ring through holes. The inner gear threaded holes and the outer ring through holes are fixedly connected by screws, and the main bearing is a cross roller bearing.

[0016] Furthermore, after fixing the internal gear and the needle roller, the flexible wheel moves relative to the internal gear in a fixed pattern, and the movement pattern is determined by the mechanism and transmission ratio of the reducer. The gear tooth shape of the flexible wheel is composed of continuous and smooth arc teeth formed by several arc segments, forming a smooth tooth profile curve.

[0017] A design method for a low-speed ratio harmonic reduction device for an industrial robot.

[0018] Determine the outer ring radius R2 of the flexible bearing;

[0019] Determine the wall thickness p at the root of the flexspline teeth;

[0020] Determine the flex spline tooth root circle radius R5;

[0021] Determine the deformation amount E and tooth height e of the flexspline;

[0022] Determine the flex spline tooth top circle radius R6;

[0023] Determine the tip circle radius R8 of the internal gear pin teeth;

[0024] Determine the radius R7 of the pin tooth distribution circle of the internal gear;

[0025] Determine the arc radius R9 of the AB segment of the flex spline tooth shape, R9=R4+Δ, and the optimal Δ=0-0.02 mm;

[0026] Determine the arc tooth radius R12 of the middle BC segment of the flexible wheel;

[0027] Determine the arc radius R10 of the CD segment of the flex spline tooth top.

[0028] The included angle between the half-side tooth profile angle DO1 of the flexspline tooth profile and O1A is determined to be α=360° / Z2 / 2.

[0029] Furthermore, the design parameters of the arc-shaped tooth profile of the flexible wheel are:

[0030] The radius R7 of the reference circle where the needle roller center is distributed on the needle gear housing;

[0031] The number of needle rollers Z1 and the number of flex spline teeth Z2 are 2 less than the number of needle rollers;

[0032] The radius R4 of the needle roller;

[0033] The deformation amount E of the flexspline and the wall thickness p at the root of the flexspline teeth;

[0034] The outer ring radius R2 of the flexible bearing and the inner ring radius R3 of the flexible bearing, and the tooth height are half of the deformation amount of the flexible wheel E / 2.

[0035] Furthermore, the full tooth shape of the arc-shaped tooth of the flexspline is obtained by mirroring the half-side tooth shape with the x-axis as the quasi-mirror; with the center O1 of the flexspline as the coordinate origin, the outer tooth shape of the flexspline forms a conjugate relationship with the needle roller, and the half-side tooth shape design experience and empirical formula of the arc-shaped tooth of the flexspline are composed of the following three smooth arcs:

[0036] The arc radius of the tooth profile line of the AB segment of the flex spline is: the radius of the needle tooth plus the adjustment amount, that is, R4+Δ,

[0037] The center coordinates of the arc of the tooth profile line of the AB segment of the flexspline tooth profile are: (R7, 0),

[0038] The arc radius of the tooth line of the middle BC section of the flexible wheel is: R12,

[0039] The center coordinates of the arc of the tooth line of the middle BC segment of the flexible wheel are: (x, y),

[0040] The (x, y) coordinates are determined by the following formula:

[0041] The tooth profile is represented by a rectangular coordinate system with O as the center:

[0042]

[0043] The tooth profile is represented by a rectangular coordinate system with O1 as the center:

[0044] The (x1, y1) coordinates are determined by the following formula:

[0045]

[0046] After the flexible wheel is deformed, the direction of the long axis includes the wall thickness p at the root of the flexible wheel teeth and the thickness of the flexible bearing, and the long semi-axis length b of the inherent elliptical cam is R7-R9-(R2-R3).

[0047] Further, the length a of the minor axis of the elliptical cam is calculated according to the length b of the major axis of the elliptical cam and the circumference 2*π*R3 of the elliptical cam;

[0048] The deformation amount E of the flexible wheel is equal to the difference between the major axis length of the flexible wheel and the base circle diameter of the deformed flexible wheel, R7 is equal to the distribution circle radius of the needle roller, Z1 is the number of the needle roller, Z1≤2*π*R7 / (2.2*R9), and Z1 is rounded off to an integer.

[0049] Furthermore, the specific size of the elliptical cam is determined by the inner ring diameter R3 of the thin-walled bearing, the outer ring diameter R2 of the thin-walled bearing and the thickness p at the root of the flex spline. The major semi-axis length b parameter of the elliptical cam is calculated by the following formula:

[0050] b=R7-R9-p-(R2-R3)

[0051] The circumference of the elliptical cam is 2*π*R3, and the short semi-axis length a of the flexible wheel elliptical cam is calculated according to the circumference of the flexible wheel elliptical cam and the long semi-axis length b of the flexible wheel elliptical cam.

[0052] The invention comprises a camshaft, a flexible bearing, a flexible wheel, a needle roller and an internal gear; the flexible bearing is installed on the elliptical camshaft; the inner ring of the flexible wheel cooperates with the outer ring of the flexible bearing; the outer tooth surface of the flexible wheel contacts each of the needle rollers, and the needle rollers are evenly distributed in the semicircular tooth grooves of the internal gear; the inner ring of the main bearing is fixedly connected to the flexible wheel, the outer ring of the bearing is fixedly connected to the internal gear, and the design method of the low-speed ratio harmonic reduction device achieves a low-speed ratio harmonic reduction device with a smooth harmonic transmission process, high transmission accuracy, high transmission efficiency and small size, which is conducive to miniaturization, effectively reduces the deformation of the flexible wheel, and can quickly adjust the design parameters according to different application scenarios and requirements, further improving the adaptability and flexibility of the harmonic reduction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 It is a schematic diagram of the harmonic drive structure principle;

[0055] Figure 2 It is a schematic diagram of an internal gear;

[0056] Figure 3 It is a cross-sectional view of the flexible wheel structure;

[0057] Figure 4 It is a pressure ring diagram;

[0058] Figure 5 It is an elliptical cam diagram;

[0059] Figure 6 It is a hollow axis diagram;

[0060] Figure 7 It is a rolling pin diagram;

[0061] Figure 8 It is a diagram of a crossed roller bearing;

[0062] Fig. 9 This is the tooth profile diagram before the change;

[0063] Fig.10 It is a tooth profile diagram;

[0064] Fig.11 It is a meshing diagram.

[0065] Reference numerals:

[0066] 1. Internal gear, 2. Bearing outer ring, 8. Bearing inner ring, 5. First sealing ring, 9. First fastening screw, 10. Pressing ring, 11. Second fastening screw, 12. Hollow shaft, 15. Second sealing ring, 16. Elliptical cam, 17. Top screw, 18. Flexible bearing, 19. Flexible wheel, 20 Needle roller, 21 Retaining ring, 22. Motor shaft. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present invention will be described clearly and completely below 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, rather than all the embodiments.

[0068] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by “center”, “up”, “down”, “left”, “right”, “vertical”, “horizontal”, “inside” and “outside”, etc., 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, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0069] A low speed ratio harmonic reduction device for an industrial robot, such as Figure 1 , 2 , 3, comprising a camshaft 16, a flexible bearing 18, a flexible wheel 19, a needle roller 20 and an internal gear 1;

[0070] The flexible bearing 18 is mounted on the elliptical camshaft 16;

[0071] The inner ring of the flexible wheel 19 cooperates with the outer ring of the flexible bearing 18;

[0072] The outer tooth surface of the flexible wheel 19 contacts each of the needle rollers 20, and the needle rollers 20 are evenly distributed in the semicircular tooth grooves of the internal gear 1;

[0073] The inner ring 8 of the main bearing is fixedly connected to the flexible spline 19 , and the outer ring 2 of the bearing is fixedly connected to the internal gear 1 .

[0074] Specifically, by installing the flexible bearing 18 on the elliptical camshaft 16, the flexible deformation ability of the flexible wheel 19 in the radial direction is realized, and the elliptical shape of the camshaft 16 is effectively used to guide and control the deformation of the flexible wheel 19, so as to realize the control of the small deformation of the flexible wheel and the appropriate meshing force of the needle roller 20. The needle roller 20 is evenly distributed in the semicircular tooth groove of the internal gear 1 and keeps in contact with the outer tooth surface of the flexible wheel 19, which not only improves the stability and accuracy of the transmission, but also disperses the load by increasing the contact area, reduces wear and noise. The inner ring 8 of the main bearing is fixedly connected to the flexible wheel 19, and the outer ring 2 of the bearing is fixedly connected to the internal gear 1. This double fixed structure The structure enhances the rigidity and stability of the entire transmission system, which is conducive to achieving high-precision transmission control. Compared with the traditional planetary reducer and belt combination transmission system, the overall structure of this solution is more compact and lighter, which is conducive to reducing the overall size and weight of the equipment and improving space utilization. Through the precise matching of the flexible bearing 18, the camshaft 16 and the needle roller 20 with the internal gear 1, the device can achieve high-precision transmission control and meet the application scenarios with high requirements for transmission accuracy. In addition, since the number and complexity of transmission components are reduced, the failure rate of the device is relatively low, the maintenance cost is also reduced accordingly, and the reliability and service life of the equipment are improved.

[0075] As a preferred embodiment of the above, Figure 1 , 5 As shown, the camshaft 16 is installed in the inner ring of the flexible bearing 18 and is supported to deform the flexible bearing 18;

[0076] The camshaft 16 and the inner ring of the flexible bearing 18 are tightly matched to form a wave generator.

[0077] Specifically, the camshaft 16 is specially designed and installed in the inner ring of the flexible bearing 18. Its unique shape supports and causes the flexible bearing 18 to deform accordingly. The camshaft 16 and the inner ring of the flexible bearing 18 are tightly matched to form a wave generator. When the camshaft 16 rotates, its non-circular cross section drives the flexible bearing 18 to deform periodically, and this deformation is then transmitted to the flexible wheel 19 that matches the outer ring of the flexible bearing 18. After being affected by this periodic deformation, the flexible wheel 19 will have relative movement between its outer tooth surface and the needle rollers 20 evenly distributed in the semicircular tooth grooves of the inner gear 1. At the same time, the needle rollers 20 rotate in the semicircular tooth grooves of the inner gear 1, so that the outer tooth surface of the flexible wheel 19 and the needle rollers 20 form rolling contact, reducing the wear of the outer tooth surface of the flexible wheel 19 and extending the service life; thereby achieving a deceleration effect, the accuracy of the entire transmission system is significantly improved, and it helps to maintain the stability of the entire transmission system.

[0078] As a preferred embodiment of the above, Figure 1 , 7 As shown, the needle rollers 20 are evenly distributed in the semicircular tooth grooves of the internal gear 1;

[0079] The semicircular tooth groove of the internal gear 1 is provided with a retaining ring 21, and the inner diameter of the retaining ring 21 is larger than the distribution circle diameter of the needle roller 20 plus one quarter of the needle roller radius.

[0080] Specifically, the needle rollers 20 are designed to be evenly distributed in the semicircular tooth grooves of the internal gear 1. This distribution ensures that the needle rollers can be in uniform contact with the outer tooth surface of the flexible wheel 19, thereby improving the stability and accuracy of the transmission. At the same time, the gaps between the needle rollers are also reasonably distributed to avoid wear or damage caused by local overload. A retaining ring 21 is also provided in the semicircular tooth grooves of the internal gear 1. The inner diameter of the retaining ring 21 is carefully designed to be larger than the distribution circle diameter of the needle rollers 20 plus one-quarter of the needle roller radius. The retaining ring 21 provides a physical barrier for the needle rollers 20 to prevent them from falling out of the semicircular tooth grooves when rotating at high speed or being impacted, thereby ensuring the continuity and reliability of the transmission. The existence of the retaining ring 21 helps to reduce the gap between the needle rollers and the semicircular tooth grooves, thereby reducing the noise and vibration caused by the excessive gap. By limiting the range of motion of the needle rollers, the retaining ring 21 helps to maintain the contact stability between the needle rollers and the flexible wheel 19, thereby improving the accuracy and stability of the transmission.

[0081] As a preferred embodiment of the above, Figure 1 , 3 As shown, the flexible wheel 19 is a cup-shaped or cap-shaped structure, a through hole is provided at the bottom of the flexible wheel 19, a central through hole corresponding to the through hole is provided at the bottom of the bearing inner ring 8, and a plurality of inner ring threaded holes are provided on the bearing inner ring 8, and the through hole is fixedly connected with the central through hole by screws;

[0082] The outer ring of the inner gear 1 is provided with a plurality of inner gear threaded holes, and the outer ring 2 of the bearing is provided with corresponding outer ring through holes. The inner gear threaded holes and the outer ring through holes are fixedly connected by screws, and the main bearing is a cross roller bearing.

[0083] Specifically, the flexible wheel 19 is designed as a cup-shaped or cap-shaped structure to withstand certain axial and radial forces, and is convenient for assembly with other components. A central through hole corresponding to the flexible wheel through hole is also provided at the bottom of the inner ring 8 of the bearing. The screws are passed through the two through holes and fixed to achieve a firm connection between the flexible wheel and the inner ring of the bearing. The outer ring 2 of the bearing is provided with a corresponding outer ring through hole. The screws are passed through the threaded holes of the inner gear and the through holes of the outer ring and fastened to achieve the connection between the inner gear and the outer ring of the bearing, ensuring the precise positioning and stable operation of the inner gear on the outer ring of the bearing. The main bearing uses a cross roller bearing. The cross roller bearing is a high-precision, high-load bearing, suitable for complex working conditions that need to withstand radial force, axial force and overturning moment at the same time. Its structural feature is that the rollers are arranged crosswise on the raceway, which can effectively disperse the load, improve rigidity and reduce friction, thereby extending the service life of the bearing.

[0084] As a preferred embodiment of the above, Figure 1 , 9 As shown in Figures 10, after the internal gear 1 and the needle roller 20 are fixed, the flexible wheel 19 moves relative to the internal gear 1 in a fixed pattern. The movement pattern is determined by the mechanism and transmission ratio of the reducer. The gear tooth shape of the flexible wheel 19 is composed of continuous and smooth arc teeth composed of several arc segments, forming a smooth tooth profile curve.

[0085] Specifically, the gear tooth profile of the flexible wheel 19 adopts a special design, that is, a continuous and smooth arc-shaped tooth is formed by several arc segments, so that the tooth profile curve becomes a smooth tooth profile curve, which is conducive to reducing the impact and vibration during the gear meshing process and improving the stability and accuracy of the transmission. The design of the arc-shaped tooth also takes into account the stress conditions during the gear meshing process and has a certain flexibility to adapt to deformation. At the same time, the design of the arc-shaped tooth also helps to disperse the contact stress of the tooth surface and extend the service life of the gear, so that the harmonic reduction device can achieve high-efficiency deceleration while maintaining high transmission accuracy and stability.

[0086] Specifically, a first sealing ring 5 and a second sealing ring 15 are provided for oil sealing to prevent oil leakage, a first fastening screw 9 and a second fastening screw 11 are used to fasten the hollow shaft 12, and a top screw 17 is used to fasten the motor shaft 22 and the cam 16 as a whole.

[0087] A design method for a low-speed ratio harmonic reduction device for an industrial robot, such as Fig. 9 As shown, the outer ring radius R2 of the flexible bearing 18 is determined;

[0088] Determine the wall thickness p at the tooth root of the flexible wheel 19;

[0089] Determine the tooth root circle radius R5 of the flexible spline 19;

[0090] Determine the deformation amount E and tooth height e of the flexible wheel 19;

[0091] Determine the radius R6 of the tooth top circle of the flexible wheel 19;

[0092] Determine the radius R8 of the tip circle of the pinion teeth of the internal gear 1;

[0093] Determine the radius R7 of the pinion tooth distribution circle of the internal gear 1;

[0094] Determine the arc radius R9 of the tooth profile AB segment of the flexible wheel 19, R9=R4+Δ, and the optimal Δ=0-0.02 mm;

[0095] Determine the arc tooth radius R12 of the middle BC segment of the flexible wheel 19;

[0096] Determine the arc radius R10 of the CD segment of the tooth top of the flexible wheel 19.

[0097] The included angle between the half-side tooth profile angle DO1 of the flexspline tooth profile and O1A is determined to be α=360° / Z2 / 2.

[0098] Specifically, by using several arc segments to form continuous and smooth arc teeth, a continuous closed tooth profile curve is formed, which not only reduces the impact and vibration during the gear meshing process, but also improves the smoothness and accuracy of the transmission. The flexible wheel tooth shape is subdivided into AB segment, BC segment and CD segment, and the arc radius of each segment is determined respectively, so that the tooth shape is more flexible and can be accurately adjusted according to different transmission requirements to achieve the best transmission effect. The outer ring radius of the flexible bearing is accurately calculated according to the assembly relationship of the camshaft, the deformation requirements of the flexible wheel and the size limit of the entire reduction device to ensure the normal operation of the wave generator and the effective deformation of the flexible wheel. By comprehensively considering factors such as material strength, deformation, and stress distribution, it is ensured that the flexible wheel can work stably and reliably within the design life. And because of the use of continuous smooth arc teeth and accurately calculated geometric parameters, the harmonic reduction device can achieve high-precision transmission and meet the occasions with high requirements for transmission accuracy. The segmented arc design and the continuous closed tooth profile curve reduce the impact and vibration during the gear meshing process, making the transmission process smoother. By accurately calculating parameters such as the tooth root wall thickness p, it is ensured that the flexible wheel has sufficient strength reserve when bearing load to avoid fatigue fracture and other situations. Because the transmission process is smooth and the impact is small, the wear between the gears is effectively controlled, thereby extending the service life of the harmonic reduction device, where R6 can be equal to R10.

[0099] As a preferred embodiment of the above, Fig. 9 , 10 As shown, the design parameters of the arc-shaped tooth profile of the flexible wheel 19 are:

[0100] The radius R7 of the reference circle on which the center of the needle roller 20 is distributed on the needle gear housing;

[0101] The number Z1 of the needle rollers 20 and the number Z2 of the teeth of the flexible wheel 19 are two less than the number of the needle rollers 20;

[0102] The radius R4 of the needle roller 20;

[0103] The deformation E of the flexible spline 19 and the wall thickness p at the tooth root of the flexible spline 19;

[0104] The outer ring radius R2 of the flexible bearing 18 and the inner ring radius R3 of the flexible bearing 18 have a tooth height that is half the deformation amount of the flexible wheel 19 E / 2.

[0105] Specifically, the number Z1 of needle rollers 20 is two more than the number Z2 of teeth of the flexible wheel 19. This design not only ensures that each flexible wheel tooth can be effectively supported by at least one needle roller during the transmission process, but also provides additional stability and fault tolerance through the redundant needle rollers, reduces vibration and noise during the transmission process, and improves the smoothness and reliability of the transmission. The tooth height is designed to be half (E / 2) of the deformation amount E of the flexible wheel 19. The precise matching ensures that the tooth shape can maintain the appropriate meshing depth and contact area during the deformation of the flexible wheel, thereby optimizing the transmission efficiency and load-bearing capacity. At the same time, it also reduces the tooth shape distortion and transmission error caused by excessive deformation. The selection of the outer ring radius R2 and the inner ring radius R3 of the flexible bearing 18 not only considers the assembly relationship with the camshaft, but also fully considers the deformation requirements of the flexible wheel 19 and the compactness of the overall structure, ensuring that the wave generator can work smoothly while reducing energy loss and friction wear.

[0106] As a preferred embodiment of the above, Fig. 9 , 10 As shown, the full tooth shape of the arc-shaped teeth of the flexible wheel 19 is obtained by mirroring the half-side tooth shape with the x-axis as the standard;

[0107] Taking the center O1 of the flexible spline 19 as the coordinate origin, the half-side tooth profile design experience and empirical formula of the arc-shaped tooth of the flexible spline 19, the outer tooth profile of the flexible spline 19 forms a conjugate relationship with the needle roller 20, and is composed of the following three smooth arcs:

[0108] The arc radius of the tooth profile line of the AB segment of the flexible wheel 19 is: the radius of the needle tooth plus the adjustment amount, that is, R4+Δ,

[0109] The center coordinates of the arc of the tooth profile line of the AB segment of the flexible wheel 19 are: R7, 0,

[0110] The arc radius of the tooth profile line of the middle BC section of the flexible wheel 19 is: R12,

[0111] The center coordinates of the arc of the tooth line of the middle BC section of the flexible wheel 19 are: x, y,

[0112] The x,y coordinates are determined by the following formula:

[0113] The tooth profile is represented by a rectangular coordinate system with O as the center:

[0114]

[0115] The tooth profile is represented by a rectangular coordinate system with O1 as the center:

[0116] The x1, y1 coordinates are determined by the following formula:

[0117]

[0118] After the deformation, the long axis direction of the flexible wheel 19 includes the wall thickness p at the tooth root of the flexible wheel 19 and the thickness of the flexible bearing, and the long semi-axis length b of the inherent elliptical cam is R7-R9-R2-R3.

[0119] Specifically, the full tooth profile is obtained by mirroring half of the tooth profile with the x-axis as the quasi-mirror, which not only simplifies the design process, but also ensures the symmetry and consistency of the tooth profile on the left and right sides. This symmetry helps to reduce the unbalanced force and vibration during the transmission process and improve the smoothness of the transmission. The arc tooth profile of the flexible wheel 19 is divided into multiple arcs such as the AB segment and the BC segment for design, and each arc has a different radius and center coordinate. This segmented design makes the tooth profile more flexible and can better adapt to the deformation requirements of the flexible wheel during the transmission process. At the same time, the precise calculation and optimization of each arc ensures the continuity and stability of the tooth profile during the deformation process. The arc radius of the AB segment tooth profile is designed to be the needle tooth radius plus the adjustment amount R4+Δ, taking into account the gap and contact pressure between the needle roller and the flexible wheel teeth. The transmission performance and wear are optimized by adjusting the amount Δ. The arc radius R12 of the BC segment tooth profile is determined according to the specific transmission requirements and the deformation characteristics of the flexible wheel. The determination of the center coordinates also uses an accurate calculation formula to ensure that the tooth profile can maintain the correct position and shape during the deformation process. During the design process, The wall thickness p at the root of the tooth in the direction of the long axis after the flexible wheel is deformed, the thickness of the flexible bearing, and the long semi-axis length b of the elliptical cam are particularly considered. The determination of these parameters not only considers the strength and stiffness requirements of the flexible wheel, but also considers the compactness and transmission efficiency of the overall structure. By accurately calculating these parameters, the stability and reliability of the harmonic reduction device during the transmission process are ensured. The mirror-symmetrical full tooth design and the tooth profile composed of segmented arcs work together to improve the stability of the transmission, reduce the unbalanced force and vibration during the transmission process, and make the transmission more stable and reliable. The experience-based radius and center coordinate determination method ensures the continuity and stability of the tooth profile during the transmission process. At the same time, by adjusting the parameters such as the gap and contact pressure between the needle roller and the flexible wheel teeth, the transmission performance and wear can be further optimized. The tooth profile design method composed of segmented arcs and the precise calculation formula make the design process more accurate and efficient. Designers can adjust the design parameters according to specific transmission requirements and working environment requirements to achieve the best design effect. This design method allows designers to adjust the design parameters according to different application scenarios and requirements. Whether it is changes in transmission ratio, load-bearing capacity or working environment requirements, they can be adapted by adjusting the design parameters. This makes the harmonic reduction device more adaptable and flexible.

[0120] As a preferred embodiment of the above, Fig. 9 As shown, the length a of the minor axis of the elliptical cam is calculated based on the length b of the major axis of the elliptical cam and the circumference 2*π*R3 of the elliptical cam.

[0121] The deformation amount E of the flexible wheel 19 is equal to the difference between the major axis length of the flexible wheel 19 and the base circle diameter of the deformed flexible wheel 19, R7 is equal to the distribution circle radius of the needle roller 20, and Z1 is the number of the needle roller 20.

[0122] Specifically, the short semi-axis length a of the elliptical cam is accurately calculated by the given long semi-axis length b of the elliptical cam and the circumference of the elliptical cam, i.e., 2*π*R3, where R3 is the radius of the inner ring of the flexible bearing, which can be regarded as the average distance from a focus of the ellipse to any point on the ellipse, making full use of the geometric characteristics of the ellipse to ensure the accuracy and reliability of the design parameters. The deformation E of the flexible wheel 19 is directly defined as the difference between the long axis length of the flexible wheel after deformation and the base circle diameter when not deformed. It intuitively reflects the deformation degree of the flexible wheel in the transmission process, provides an important reference basis for the design, and establishes a direct connection between the design parameters, which is convenient for overall optimization. In the design, the distribution circle radius R7 of the needle roller 20 is set to a fixed value. This setting simplifies the design process and ensures the uniform distribution of the needle roller on the flexible wheel teeth. At the same time, it also makes the contact relationship between the needle roller and the flexible wheel teeth more stable and reliable, thereby ensuring the accuracy of the short semi-axis length a of the elliptical cam based on the accurate calculation of the geometric characteristics of the ellipse, thereby improving the design accuracy of the entire harmonic reduction device. This high-precision design helps to reduce errors and vibrations in the transmission process, improve the smoothness and reliability of the transmission, and simplifies the design process due to the fixed radius R7 of the needle roller distribution circle, reduces design variables and calculation complexity, allowing more focus on the optimization and adjustment of key parameters, thereby improving design efficiency and accuracy.

[0123] As a preferred embodiment of the above, Fig. 9 As shown, the specific size of the elliptical cam is determined by the inner ring diameter R3 of the thin-walled bearing, the outer ring diameter R2 of the thin-walled bearing and the thickness p of the flexible wheel 19 at the root of the tooth. The major semi-axis length b parameter of the elliptical cam is calculated by the following formula:

[0124] b=R7-R9-p-(R2-R3)

[0125] The circumference of the elliptical cam is 2*π*R3, and the short semi-axis length a of the elliptical cam of the flexible wheel 19 is calculated according to the circumference of the elliptical cam of the flexible wheel 19 and the long semi-axis length b of the elliptical cam of the flexible wheel 19.

[0126] Specifically, a dimension chain is cleverly constructed through the inner ring diameter R3, outer ring diameter R2 of the thin-walled bearing and the thickness p at the root of the flexible wheel 19 to determine the key dimension of the elliptical cam - the major semi-axis length b. This dimension chain construction method not only takes into account the assembly relationship between the various components, but also makes full use of the existing design parameters, reduces additional measurement and calculation work, and calculates the minor semi-axis length a by applying the geometric characteristics of the ellipse when the circumference of the elliptical cam (and the major semi-axis length b) is known. This calculation method makes full use of the basic properties of the ellipse to ensure the accuracy and reliability of the calculation results. By constructing a dimension chain and using existing design parameters, the designer can determine the key dimensions of the elliptical cam more quickly, thereby improving the design efficiency. At the same time, this design method also reduces the accumulation of errors caused by repeated measurements and calculations.

[0127] During operation, when the camshaft 16 is installed in the flexible bearing 18, and the flexible bearing 18 is installed in the flexible wheel 19, the flexible wheel 19 is forced to produce elastic deformation and present an elliptical shape, so that the tooth root of the flexible wheel 19 at the long axis is embedded in the needle roller 20, forming a state in which the two areas of the tooth root are meshed, while the tooth top of the flexible wheel 19 at the short axis is disengaged from the needle roller 20. When the camshaft 16 rotates continuously, the flexible wheel 19 is forced to continuously deform, and the contact position between the flexible wheel 19 and the needle roller 20 is constantly changing, resulting in the so-called staggered tooth motion, thereby realizing motion transmission.

[0128] Furthermore, we assume that the internal gear 1 is fixed, and when the camshaft 16 rotates one circle, the flexible wheel 19 rotates two teeth positions in the opposite direction relative to the internal gear 1. Therefore, when the internal gear is fixed and the flexible wheel rotates, the reduction ratio is equal to half the number of teeth of the flexible wheel 19.

[0129] The main bearing in the present invention can be a deep groove ball bearing, a needle roller bearing, etc.

[0130] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A low speed ratio harmonic reduction device for an industrial robot, characterized in that: It comprises a camshaft (16), a flexible bearing (18), a flexible wheel (19), a needle roller (20) and an internal gear (1); The flexible bearing (18) is mounted on the elliptical camshaft (16); The inner hole of the flexible wheel (19) and the outer ring of the flexible bearing (18) cooperate with each other; The outer tooth surface of the flexible wheel (19) is in contact with the needle roller (20), and the needle roller (20) is evenly distributed in the semicircular tooth groove of the internal gear (1); The inner ring (8) of the main bearing is fixedly connected to the flexible wheel (19), and the outer ring (2) of the bearing is fixedly connected to the internal gear (1).

2. The low speed ratio harmonic reduction device for an industrial robot according to claim 1, characterized in that: The camshaft (16) is mounted in the inner ring of the flexible bearing (18) and is supported to deform the flexible bearing (18); The camshaft (16) and the inner ring of the flexible bearing (18) are tightly matched to form a wave generator.

3. The low speed ratio harmonic reduction device for an industrial robot according to claim 2, characterized in that: The circumference of the needle rollers (20) is evenly distributed in the semicircular tooth grooves of the internal gear (1); The semicircular tooth groove of the internal gear (1) is provided with a retaining ring (21), and the inner diameter of the retaining ring (21) is larger than the distribution circle diameter of the needle roller (20) plus one quarter of the needle roller radius.

4. The low speed ratio harmonic reduction device for an industrial robot according to claim 3, characterized in that: The flexible wheel (19) is a cup-shaped or cap-shaped structure, a through hole is provided at the bottom of the flexible wheel (19), a central through hole corresponding to the through hole is provided at the bottom of the bearing inner ring (8), a plurality of inner ring threaded holes are provided on the bearing inner ring (8), and the through hole is fixedly connected to the central through hole by screws; The outer ring of the inner gear (1) is provided with a plurality of inner gear threaded holes, and the outer ring (2) of the bearing is provided with corresponding outer ring through holes. The inner gear threaded holes and the outer ring through holes are fixedly connected by screws, and the main bearing is a cross roller bearing.

5. The low speed ratio harmonic reduction device for an industrial robot according to claim 4, characterized in that: After the internal gear (1) and the needle roller (20) are fixed, the flexible wheel (19) moves relative to the internal gear (1) in a fixed pattern. The movement pattern is determined by the mechanism and transmission ratio of the reducer. The gear tooth shape of the flexible wheel (19) is composed of a number of arcs forming continuous and smooth arc teeth, forming a smooth tooth profile curve.

6. A design method for a low-speed ratio harmonic reduction device for an industrial robot, characterized in that ； Determine the outer ring radius R2 of the flexible bearing (18); Determine the wall thickness p of the flexspline (19) at the tooth root; Determining the tooth root circle radius R5 of the flexible wheel (19); Determining the deformation amount E and the tooth height e of the flexspline (19); Determine the tooth top circle radius R6 of the flexible wheel (19); Determine the radius R8 of the pinion tooth tip circle of the internal gear (1); Determine the radius R7 of the pinion tooth distribution circle of the internal gear (1); Determine the arc radius R9 of the tooth profile AB segment of the flexible wheel (19), R9=R4+Δ, Δ=0-0.02 mm; Determine the arc tooth radius R12 of the middle BC segment of the flexible wheel (19); Determine the circular arc radius R10 of the CD segment of the tooth top of the flexible wheel (19); The included angle between the tooth profile half-side angle DO1 and O1A of the flexible wheel (19) is determined to be α=360° / Z2 / 2.

7. The design method of a low-speed ratio harmonic reduction device for an industrial robot according to claim 6, characterized in that: The design parameters of the arc-shaped tooth profile of the flexible wheel (19) are: The radius R7 of the reference circle on which the center of the needle roller (20) is distributed on the needle gear housing; The number Z1 of the needle rollers (20) and the number Z2 of the teeth of the flexible wheel (19) are two less than the number of the needle rollers (20); The radius R4 of the needle roller (20); The deformation amount E of the flexspline (19) and the wall thickness p of the flexspline (19) at the tooth root; The outer ring radius R2 of the flexible bearing (18) and the inner ring radius R3 of the flexible bearing (18) have a tooth height that is half the deformation amount E / 2 of the flexible wheel (19).

8. The design method of a low-speed ratio harmonic reduction device for an industrial robot according to claim 7, characterized in that: The full tooth shape of the arc-shaped teeth of the flexible wheel (19) is obtained by mirroring the half-side tooth shape with the x-axis as the reference; Taking the center O1 of the flexible wheel (19) as the coordinate origin, the outer tooth shape of the flexible wheel (19) forms a conjugate relationship with the needle roller (20), and the half-side tooth shape design experience and empirical formula of the arc-shaped tooth of the flexible wheel (19) are composed of the following three smooth arcs: The arc radius of the tooth profile line of the tooth profile AB section of the flexible wheel (19) is: the radius of the needle tooth plus the adjustment amount, that is, R4+Δ, The center coordinates of the circular arc of the tooth profile line of the tooth profile AB segment of the flexible wheel (19) are: (R7, 0), The arc radius of the tooth profile line of the middle BC section of the flexible wheel (19) is: R12, The center coordinates of the arc of the tooth profile line of the middle BC section of the flexible wheel (19) are: (x, y), The (x, y) coordinates are determined by the following formula: The tooth profile is represented by a rectangular coordinate system with O as the center: The tooth profile is represented by a rectangular coordinate system with O1 as the center: The (x1, y1) coordinates are determined by the following formula: After the deformation, the long axis direction of the flexible wheel (19) includes the wall thickness p at the tooth root of the flexible wheel (19), the thickness of the flexible bearing, and the long semi-axis length b of the inherent elliptical cam = R7-R9-(R2-R3).

9. The design method of a low-speed ratio harmonic reduction device for an industrial robot according to claim 8, characterized in that: Calculate the length a of the minor axis of the elliptical cam according to the length b of the major axis of the elliptical cam and the circumference 2*π*R3 of the elliptical cam; The deformation amount E of the flexible wheel (19) is equal to the difference between the major axis length of the flexible wheel (19) and the base circle diameter of the deformed flexible wheel (19), R7 is equal to the distribution circle radius of the needle roller (20), Z1 is the number of the needle roller (20), Z1≤2*π*R7 / (2.2*R9), and Z1 is rounded off to an integer.

10. The design method of a low-speed ratio harmonic reduction device for an industrial robot according to claim 9, characterized in that: The specific size of the elliptical cam is determined by the inner ring diameter R3 of the thin-walled bearing, the outer ring diameter R2 of the thin-walled bearing and the thickness p of the flex spline (19) at the tooth root. The major semi-axis length b parameter of the elliptical cam is calculated by the following formula: b=R7-R9-p-(R2-R3) The circumference of the elliptical cam is 2*π*R3, and the short semi-axis length a of the elliptical cam of the flexible wheel (19) is calculated based on the circumference of the elliptical cam of the flexible wheel (19) and the long semi-axis length b of the elliptical cam of the flexible wheel (19).

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