Wave generator, harmonic speed reducer and industrial robot

Abstract

The invention discloses a wave generator, a harmonic speed reducer and an industrial robot, and relates to the technical field of speed reducers, the wave generator comprises a cam and a flexible bearing, the flexible bearing is arranged on the peripheral wall of the cam, and a first rolling body of the flexible bearing is arranged between an inner ring and an outer ring, so that the inner ring and the outer ring can rotate relatively. An inner ring of the flexible bearing is provided with an inner ring track surface, and an outer ring is provided with an outer ring track surface. When the Re / De and the ratio of the Re / De are too small, although the bearing capacity of the wave generator can be increased, the friction resistance is increased, and the starting torque is increased. When the Re / De and the ratio of the Re / De are too large, although the starting torque can be reduced, the bearing capacity of the wave generator can be reduced. Therefore, the Re / De and the Re / De ratio range are reasonably designed, the bearing capacity of the wave generator can be improved, and meanwhile it is ensured that the starting torque is not too large.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of speed reducer, in particular to a wave generator, a harmonic speed reducer and an industrial robot. BACKGROUND

[0002] In the related art, the harmonic speed reducer includes a wave generator, a flexspline and a rigid gear, the flexspline is sleeved on the wave generator, and the outer tooth part of the flexspline and the inner tooth part of the rigid gear are engaged. The wave generator includes a cam and a flexible bearing, the cam is embedded in the inner hole of the flexible bearing, and the flexible bearing is deformed. Since the flexible bearing needs to be deformed flexibly, the carrying capacity is low, and it is difficult to adapt to occasions with high carrying capacity. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a wave generator capable of improving the carrying capacity of the flexible bearing.

[0004] The present application also provides a harmonic speed reducer with the above wave generator and an industrial robot thereof.

[0005] According to the wave generator of the first aspect of the present application, the wave generator is installed in the inner hole of the flexspline, and includes: a cam; a flexible bearing installed on the outer peripheral wall of the cam, the flexible bearing including an inner ring, an outer ring and first rolling bodies, the first rolling bodies being arranged between the inner ring and the outer ring; wherein the maximum cross-sectional diameter of the first rolling bodies is De, the inner ring is provided with an inner ring raceway surface with a curvature radius Rei, and the outer ring is provided with an outer ring raceway surface with a curvature radius Reo, and the following conditions are met: 0.505*De≤Rei≤0.515*De; 0.511*De≤Reo≤0.523*De.

[0006] According to the wave generator of the present application, at least the following beneficial effects are achieved: By arranging the flexible bearing to be installed on the outer peripheral wall of the cam, and arranging the first rolling bodies of the flexible bearing to be between the inner ring and the outer ring, the inner ring and the outer ring can rotate relative to each other. The inner ring of the flexible bearing has an inner ring raceway surface, and the outer ring has an outer ring raceway surface. When the ratio of Rei / De and Rei / De is too small, although the carrying capacity of the wave generator can be increased, the frictional resistance will increase, i.e. the starting torque will increase. When the ratio of Rei / De and Rei / De is too large, although the starting torque can be reduced, the carrying capacity of the wave generator will be reduced. Therefore, by reasonably designing the range of the ratio of Rei / De and Rei / De, the carrying capacity of the wave generator can be improved while ensuring that the starting torque is not too large.

[0007] According to some embodiments of the present invention, the radius of curvature Rei of the inner track surface and the radius of curvature Reo of the outer track surface satisfy: Rei < Reo.

[0008] According to some embodiments of the present invention, the outer peripheral wall of the cam is provided with at least two inwardly recessed circumferential grooves. When projected along the axis of the cam, the projection of the outer peripheral wall of the cam is elliptical, and the at least two circumferential grooves are respectively arranged on both sides of the major axis of the ellipse.

[0009] According to some embodiments of the present invention, at least two of the circumferential grooves are arranged symmetrically along the long axis.

[0010] According to some embodiments of the present invention, on a cross section passing through one of the circumferential grooves, the line connecting the midpoint of the bottom of the circumferential groove and the center of the cam is a first reference line, and the angle between the first reference line and the major axis is βw0, satisfying: 15°≤βw0≤30°.

[0011] According to some embodiments of the present invention, on the cross section passing through the circumferential groove, the maximum angle between the two endpoints of the circumferential groove along the circumference of the cam and the center of the cam is βw1, satisfying: βw0≤βw1≤1.6*βw0.

[0012] According to some embodiments of the present invention, the maximum cross-sectional diameter of the first rolling element is De, and on the cross-section passing through one of the circumferential grooves, the line connecting the midpoint of the bottom of the circumferential groove and the center of the cam is a first reference line. On the cross-section passing through the first reference line, the maximum depth of the circumferential groove is Tw, satisfying: 0.002*De≤Tw≤0.005*De.

[0013] According to some embodiments of the present invention, on a cross section passing through one of the circumferential grooves, the line connecting the midpoint of the bottom of the circumferential groove and the center of the cam is a first reference line. On a cross section passing through the first reference line, the bottom of the circumferential groove is an arc with a radius of Rw, and the maximum width of the inner ring is Bei, satisfying: 0.5*Bei≤Rw≤0.8*Bei.

[0014] According to some embodiments of the present invention, the flexible wheel includes a cylindrical portion and a flange portion, wherein the minimum distance between the end wall of the cylindrical portion away from the flange portion and the flange portion is Lf, the maximum width of the inner ring is Bei, and the maximum width of the outer ring is Beo, satisfying: 0.2*Lf≤Bei≤0.35*Lf; and / or, 0.2*Lf≤Beo≤0.35*Lf.

[0015] According to some embodiments of the present invention, the inner diameter of the flexible wheel is Df, the minimum wall thickness of the inner ring is Tei, and the minimum wall thickness of the outer ring is Teo, satisfying: 0.015*Df≤Tei≤0.03*Df; and / or, 0.015*Df≤Teo≤0.03*Df.

[0016] The harmonic reducer according to a second aspect of the present invention includes the wave generator described in the above embodiments.

[0017] The harmonic reducer according to embodiments of the present invention has at least the following beneficial effects: By employing the wave generator of the first aspect embodiment, the wave generator is mounted on the outer peripheral wall of the cam using a flexible bearing. The first rolling element of the flexible bearing is located between the inner and outer rings, allowing the inner and outer rings to rotate relative to each other. The inner ring of the flexible bearing has an inner ring track surface, and the outer ring has an outer ring track surface. When the Rei / De ratio is too small, although the load-bearing capacity of the wave generator can be increased, it will lead to an increase in frictional resistance, i.e., an increase in starting torque. When the Rei / De ratio is too large, although the starting torque can be reduced, the load-bearing capacity of the wave generator will be reduced. Therefore, by reasonably designing the Rei / De ratio range, the load-bearing capacity of the wave generator can be improved while ensuring that the starting torque is not too large.

[0018] An industrial robot according to a third aspect of the present invention includes the harmonic reducer described in the above embodiments.

[0019] The industrial robot according to embodiments of the present invention has at least the following beneficial effects: By employing the harmonic reducer of the second aspect embodiment, the wave generator of the harmonic reducer is mounted on the outer peripheral wall of the cam using a flexible bearing. The first rolling element of the flexible bearing is located between the inner and outer rings, allowing the inner and outer rings to rotate relative to each other. The inner ring of the flexible bearing has an inner ring track surface, and the outer ring has an outer ring track surface. When the Rei / De ratio is too small, although it can increase the load-bearing capacity of the wave generator, it will lead to an increase in frictional resistance, i.e., an increase in starting torque. When the Rei / De ratio is too large, although it can reduce the starting torque, it will lead to a decrease in the load-bearing capacity of the wave generator. Therefore, by reasonably designing the Rei / De ratio range, the load-bearing capacity of the wave generator can be improved while ensuring that the starting torque is not too large.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a cross-sectional schematic diagram of a harmonic reducer according to an embodiment of the present invention; Figure 2 This is a partial structural cross-sectional view of a wave generator according to an embodiment of the present invention; Figure 3 This is a partial structural cross-sectional view of a flexible bearing according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a cam according to an embodiment of the present invention; Figure 5 This is a cross-sectional view of the cam portion structure according to an embodiment of the present invention; Figure 6 This is a partial structural cross-sectional view of a wave generator according to an embodiment of the present invention; Figure 7 This is a partial structural cross-sectional view of a flexible wheel and a rigid wheel according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of the inner bearing ring according to an embodiment of the present invention; Figure 9 This is a cross-sectional view of the outer bearing ring according to an embodiment of the present invention; Figure 10 This is a graph showing the relationship between different values ​​of Rei / De, starting torque, and rated dynamic load according to an embodiment of the present invention. Figure 11 This is a graph showing the relationship between different values ​​of βw0 and the maximum load of the ball bearings in one embodiment of the present invention. Figure 12 This is a graph showing the relationship between different values ​​of βw1 / βw0 and the maximum load of the ball bearings in one embodiment of the present invention. Figure 13 This is a graph showing the relationship between different values ​​of Tw / De and the maximum load of the ball bearings according to an embodiment of the present invention. Figure 14 This is a graph showing the relationship between different values ​​of Rw / Bei and the maximum load of the ball bearings according to an embodiment of the present invention. Figure 15 This is a comparison curve of ball load on a cam according to an embodiment of the present invention and on cams in related technologies.

[0022] Icon labels: Harmonic reducer 1000; Wave generator 100; Cam 110; Circumferential groove 111; Flexible bearing 120; Inner ring 121; Inner ring track surface 1211; Outer ring 122; Outer ring track surface 1221; First rolling element 123; Cage 124; Flexible wheel 200; cylindrical part 210; external toothed part 211; diaphragm part 220; flange part 230; inner hole 240; Rigid wheel 300; internal gear 310; Bearing assembly 400; first oil storage space 410; second oil storage space 420; inner bearing ring 430; first raceway 431; second raceway 432; outer bearing ring 440; third raceway 441; fourth raceway 442; first oil seal 450; second oil seal 460; second rolling element 470; third rolling element 480. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0025] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0026] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0027] Reference Figure 1 and Figure 2As shown, a wave generator 100 according to an embodiment of the present invention is applied to a harmonic reducer 1000. The wave generator 100 includes a cam 110 and a flexible bearing 120. The cam 110 is used for drive connection with the output shaft of a motor. The flexible bearing 120 is annular and mounted on the outer peripheral wall of the cam 110. The flexible bearing 120 includes an inner ring 121, an outer ring 122, a cage 124, and a plurality of first rolling elements 123. The outer ring 122 is sleeved on the outside of the inner ring 121 and spaced apart from the inner ring 121. The outer ring 122 has an outer ring track surface 1221 on the side facing the inner ring 121, and the outer ring track surface 1221 is recessed towards the outside of the outer ring 122. The inner ring 121 has an inner ring track surface 1211 on the side facing the outer ring 122, and the inner ring track surface 1211 is recessed towards the inside of the inner ring 121. The first rolling elements 123 can be balls, rollers, etc. A plurality of first rolling elements 123 are disposed between the inner ring track surface 1211 and the outer ring track surface 1221. A cage 124 is disposed between the inner ring 121 and the outer ring 122 and connected to the plurality of first rolling elements 123. The cage 124 is used to restrict the first rolling elements 123 from disengaging from the inner ring track surface 1211 and the outer ring track surface 1221.

[0028] Reference Figure 2 and Figure 3 As shown, both the inner track surface 1211 and the outer track surface 1221 are curved surfaces, such as circular or elliptical surfaces. The radius of curvature of the inner track surface 1211 is Rei, and the radius of curvature of the outer track surface 1221 is Reo. The maximum cross-section of the first rolling element 123 is circular with a diameter of De, satisfying: 0.505*De≤Rei≤0.515*De, 0.511*De≤Reo≤0.523*De. For example, the value of Rei can be 0.505*De, 0.507*De, 0.508*De, 0.512*De, or 0.515*De; the value of Reo can be 0.511*De, 0.513*De, 0.516*De, 0.52*De, or 0.523*De. It should be noted that the above formula is equivalent to 0.505≤Rei / De≤0.515 and 0.511≤Reo / De≤0.523. When the maximum cross-section of the first rolling element 123 is not circular, the diameter of the smallest circumscribed circle of the maximum cross-section of the first rolling element 123 is used as De.

[0029] Reference Figure 10 As shown, Figure 10 The horizontal axis represents the range of Rei / De values, the vertical axis on the left represents the starting torque, and the vertical axis on the right represents the rated dynamic load. Figure 10The two curves in the diagram generally maintain a downward trend because, with De constant, when Rei / De is less than 0.505, the radius of curvature of the inner raceway 1211 is smaller, resulting in a larger bending amplitude of the inner raceway 1211 and an increased contact area with the first rolling element 123. While this increases the rated dynamic load, i.e., the load-bearing capacity, it also increases the frictional resistance of the first rolling element 123 during movement, leading to an increase in starting torque. When Rei / De is greater than 0.515, the radius of curvature of the inner raceway 1211 is larger, resulting in a smaller bending amplitude of the inner raceway 1211 and a smaller contact area with the first rolling element 123. While this reduces the starting torque, it leads to a decrease in load-bearing capacity. Therefore, to balance the relationship between load-bearing capacity and starting torque, the value of Rei / De is set between 0.505 and 0.515 to improve load-bearing capacity while ensuring that the starting torque of the harmonic reducer 1000 is not too high.

[0030] When Reo / De is greater than 0.511, the radius of curvature of the outer ring track surface 1221 is small, resulting in a larger bending amplitude of the outer ring track surface 1221 and an increased contact area with the first rolling element 123, leading to increased friction and thus increased starting torque. When Reo / De is greater than 0.523, the radius of curvature of the outer ring track surface 1221 is large, resulting in a smaller bending amplitude of the outer ring track surface 1221 and a smaller contact area with the first rolling element 123, making it difficult to effectively restrict the position of the first rolling element 123. Therefore, in order to reduce the starting torque while effectively restricting the position of the first rolling element 123, the value of Reo / De is set between 0.511 and 0.523 to reduce the starting torque and effectively prevent the first rolling element 123 from disengaging from the inner ring track surface 1211 and the outer ring track surface 1221.

[0031] Reference Figure 1 and Figure 2As shown, another embodiment of the wave generator 100 of the present invention is applied to a harmonic reducer 1000. The wave generator 100 includes a cam 110 and a flexible bearing 120. The cam 110 is used for drive connection with the output shaft of a motor. The flexible bearing 120 is annular and mounted on the outer peripheral wall of the cam 110. The flexible bearing 120 includes an inner ring 121, an outer ring 122, a cage 124, and a plurality of first rolling elements 123. The outer ring 122 is sleeved on the outside of the inner ring 121 and spaced apart from the inner ring 121. The outer ring 122 has an outer ring track surface 1221 on the side facing the inner ring 121, and the outer ring track surface 1221 is recessed towards the outside of the outer ring 122. The inner ring 121 has an inner ring track surface 1211 on the side facing the outer ring 122, and the inner ring track surface 1211 is recessed towards the inside of the inner ring 121. The first rolling elements 123 can be balls, rollers, etc. A plurality of first rolling elements 123 are disposed between the inner ring track surface 1211 and the outer ring track surface 1221. A cage 124 is disposed between the inner ring 121 and the outer ring 122 and connected to the plurality of first rolling elements 123. The cage 124 is used to prevent the first rolling elements 123 from disengaging from the inner ring track surface 1211 and the outer ring track surface 1221. (Refer to...) Figure 3 As shown, both the inner track surface 1211 and the outer track surface 1221 are curved surfaces, such as circular arc surfaces or elliptical surfaces. The radius of curvature of the inner track surface 1211 is Rei, and the radius of curvature of the outer track surface 1221 is Reo, satisfying: Rei < Reo.

[0032] Understandably, since the inner ring track surface 1211 is the load-bearing surface, when the radius of curvature Rei of the inner ring track surface 1211 is smaller than the radius of curvature Reo of the outer ring track surface 1221, meaning the bending amplitude of the inner ring track surface 1211 is greater than that of the outer ring track surface 1221, the contact area between the first rolling element 123 and the inner ring track surface 1211 is larger, which can effectively distribute the load and improve the load-bearing capacity of the flexible bearing 120. The outer ring track surface 1221 is usually not a load-bearing surface; therefore, the radius of curvature Reo of the outer ring track surface 1221 is designed to be larger than the radius of curvature Rei of the inner ring track surface 1211. This aims to reduce the contact area between the first rolling element 123 and the outer ring track surface 1221, thereby reducing friction and improving the situation of excessive starting torque in the harmonic reducer 1000, thus increasing the service life of the flexible bearing 120.

[0033] Reference Figure 4As shown, in an embodiment of the present invention, the outer peripheral wall of the cam 110 is provided with at least two inwardly recessed circumferential grooves 111, which extend circumferentially along the cam 110. Along a direction perpendicular to the rotation axis of the cam 110, the projection of the outer peripheral wall of the cam 110 is elliptical, and the at least two circumferential grooves 111 are respectively arranged on both sides of the major axis S1 of the ellipse. For example, when there are two circumferential grooves 111, the two grooves 111 are located on both sides of the major axis S1 of the ellipse; when there are three circumferential grooves 111, two are located on one side of the major axis S1 of the ellipse, and the other groove 111 is located on the other side of the major axis S1 of the ellipse.

[0034] It is understandable that, such as Figure 5 and Figure 6 As shown, since the cam 110 is mainly loaded near its long axis S1, by adopting a scheme of setting circumferential grooves 111 on both sides of the long axis S1 of the cam 110, when the inner ring 121 of the flexible bearing 120 is subjected to greater pressure, a part of the structure of the inner ring 121 is squeezed into the circumferential grooves 111, causing the inner ring track surface 1211 to bend and the radius of curvature Rei of the inner ring track surface 1211 to further decrease, thereby increasing the contact area with the first rolling element 123, increasing the rated dynamic load, and thus increasing the load-bearing capacity of the flexible bearing 120 and improving the performance of the harmonic reducer 1000. Since the inner ring 121 is only squeezed into the circumferential grooves 111 when subjected to greater pressure, the harmonic reducer 1000 can reduce the situation where the inner ring track surface 1211 always maintains a large contact area with the first rolling element 123 during normal operation, thereby reducing the starting torque of the harmonic reducer 1000 and extending the service life of the flexible bearing 120.

[0035] Reference Figure 4 As shown, in an embodiment of the present invention, at least two circumferential grooves 111 are symmetrically arranged along the major axis S1. For example, four circumferential grooves 111 are provided, which are symmetrically arranged along the major axis S1 and also symmetrically arranged along the minor axis S2. That is, a circumferential groove 111 is provided on each side of one end near the major axis S1; similarly, a circumferential groove 111 is provided on each side of the other end near the major axis S1. By adopting the symmetrical distribution of the circumferential grooves 111 along the major axis S1 and also symmetrically distributed along the minor axis S2, the flexible bearing 120 can operate more smoothly, reducing adverse effects such as slippage and vibration of the flexible bearing 120, and improving the load-bearing capacity of the harmonic reducer 1000 with minimal increase in starting torque.

[0036] Reference Figure 4As shown in the embodiment of the present invention, on the cross-section passing through one of the circumferential grooves 111, the line connecting the midpoint of the bottom of the circumferential groove 111 and the center of the cam 110 is the first reference line S3. The angle between the first reference line S3 and the major axis S1 is βw0, satisfying: 15°≤βw0≤30°. For example, the value of βw0 can be 15°, 18°, 20°, 25°, or 30°. It should be noted that the cross-section "passing through one of the circumferential grooves 111" is perpendicular to the rotation axis of the cam 110, and this cross-section is the maximum cross-section, that is, the cross-section passing through the midpoint of the circumferential groove 111 along the axial direction. The center of the cam 110 is the intersection of the major axis S1 and the minor axis S2.

[0037] Reference Figure 11 As shown, Figure 11 The horizontal axis represents the range of values ​​for βw0, and the vertical axis represents the maximum load of the first rolling element 123 (taking the ball as an example). Figure 11 The curve first decreases and then increases because: when βw0 is less than 15°, the circumferential groove 111 is closer to the top of the long axis S1. Since the pressure on the cam 110 at the top of the long axis S1 is usually the greatest, when the circumferential groove 111 is closer to or located at the end of the long axis S1 of the cam 110, the long axis S1 of the cam 110 will shorten, reducing the number of meshing teeth between the flexible wheel 200 and the rigid wheel 300, resulting in increased impact and vibration. The flexible bearing 120 needs to withstand greater pressure, thus increasing the maximum load on the first rolling element 123. When βw0 is greater than 30°, the circumferential groove 111 is closer to the short axis S2. Since the cam 110 basically does not bear pressure at the short axis S2, the inner ring 121 is difficult to deform at the circumferential groove 111, thus failing to distribute the load, and therefore the maximum load on the ball increases.

[0038] Therefore, by rationally designing the position of the circumferential groove 111, i.e., βw0 within the range of 15° to 30°, the deformation of the inner ring 121 is used to increase the contact area with the first rolling element 123, disperse the load on the first rolling element 123, reduce the maximum load on the first rolling element 123, thereby increasing the load-bearing capacity of the flexible bearing 120.

[0039] Reference Figure 4As shown in the embodiment of the present invention, on the cross-section passing through the circumferential groove 111, the maximum angle between the two endpoints of the circumferential groove 111 along the circumferential direction of the cam 110 and the center of the cam 110 is βw1, satisfying: βw0≤βw1≤1.6*βw0. It should be noted that the above formula is equivalent to 1≤βw1 / βw0≤1.6, for example, the ratio of βw1 / βw0 is 1, 1.2, 1.4, 1.6, etc. The cross-section in "cross-section passing through the circumferential groove 111" is perpendicular to the rotation axis of the cam 110, and this cross-section is the maximum cross-section, that is, the cross-section passing through the midpoint of the circumferential groove 111 along the axial direction. The two endpoints of the circumferential groove 111 along the circumferential direction of the cam 110 are the two endpoints that are furthest apart along the circumferential direction of the circumferential groove 111. In other embodiments below, when referring to "cross-section passing through the circumferential groove 111", please refer to this embodiment for explanation; to avoid repetition, it will not be repeated hereafter.

[0040] Reference Figure 12 As shown, Figure 12 The horizontal axis represents the range of values ​​for βw1 / βw0, and the vertical axis represents the maximum load of the first rolling element 123 (taking a ball as an example). Figure 12 The curve first decreases and then increases because, with βw0 constant, when βw1 / βw0 is less than 1, the groove width of the circumferential groove 111 is small, making it difficult for the inner ring 121 to deform within the groove. Therefore, the contact area between the inner ring track surface 1211 and the first rolling element 123 cannot be increased, and the load cannot be effectively distributed, resulting in an increase in the maximum load on the first rolling element 123. When βw1 / βw0 is greater than 1.6, the length of the circumferential groove 111 is longer, and it will be closer to or located at the end of the long axis S1. The long axis S1 of the cam 110 will shorten, reducing the number of meshing teeth between the flexible wheel 200 and the rigid wheel 300, leading to increased impact and vibration. The flexible bearing 120 needs to withstand greater pressure, thus increasing the maximum load on the first rolling element 123.

[0041] Therefore, by rationally designing the opening width of the circumferential groove 111, i.e. βw1 / βw0 within the range of 1 to 1.6, when the load increases, the deformation of the inner ring 121 is used to increase the contact area with the first rolling element 123, disperse the load on the first rolling element 123, reduce the maximum load on the first rolling element 123, and thus increase the load-bearing capacity of the flexible bearing 120.

[0042] Reference Figure 4 and Figure 5As shown, in an embodiment of the present invention, on the cross-section passing through the first reference line S3, the maximum depth of the circumferential groove 111 is Tw, satisfying: 0.002*De≤Tw≤0.005*De, which is equivalent to 0.002≤Tw / De≤0.005. For example, the value of Tw / De can be 0.002, 0.003, 0.004, or 0.005. (Refer to...) Figure 13 It can be seen that, Figure 13 The horizontal axis represents the range of Tw / De values, and the vertical axis represents the maximum load of the first rolling element 123 (taking a ball as an example). Figure 13 The curve in the image first decreases and then increases because: With De remaining constant, when Tw / De is less than 0.002, meaning the depth of the circumferential groove 111 is shallow, the inner ring 121 cannot undergo suitable deformation within the circumferential groove 111. Therefore, the contact area between the inner ring track surface 1211 and the first rolling element 123 cannot be increased, and the load cannot be effectively distributed, resulting in an increase in the maximum load on the first rolling element 123. When Tw / De is greater than 0.005, the depth of the circumferential groove 111 is deep, and the inner ring 121 cannot abut against the bottom wall of the circumferential groove 111 when subjected to greater pressure. That is, the inner ring 121 is in a suspended state at the circumferential groove 111, meaning it cannot be supported by the bottom wall of the circumferential groove 111, and the load cannot be distributed, leading to an increase in the maximum load on the first rolling element 123.

[0043] Therefore, by reasonably designing the Tw / De ratio to be within the range of 0.002 to 0.005, the deformation of the inner ring 121 can be used to increase the contact area with the first rolling element 123, disperse the load on the first rolling element 123, reduce the maximum load on the first rolling element 123, and thus increase the load-bearing capacity of the flexible bearing 120.

[0044] Reference Figure 5 As shown, in an embodiment of the present invention, on the cross-section passing through the first reference line S3, the bottom of the circumferential groove 111 is an arc with a radius of Rw, referring to... Figure 3 As shown, the maximum axial width of the inner ring 121 is Bei, satisfying: 0.5*Bei≤Rw≤0.8*Bei, which is equivalent to 0.5≤Rw / Bei≤0.8. For example, the value of Rw / Bei can be 0.5, 0.6, 0.7, or 0.8. (Refer to...) Figure 14 As shown, Figure 14 The horizontal axis represents the range of values ​​for Rw / Bei, and the vertical axis represents the maximum load of the first rolling element 123 (taking a ball as an example). Figure 14 The curve in the image first decreases and then increases because: With Bei remaining constant, when Rw / Bei is less than 0.5, meaning the bottom radius of the circumferential groove 111 is small, the axial width of the circumferential groove 111 decreases. This makes it difficult for the inner ring 121 to undergo suitable deformation within the circumferential groove 111, thus failing to increase the contact area between the inner ring track surface 1211 and the first rolling element 123, and failing to effectively distribute the load, resulting in an increase in the maximum load on the first rolling element 123. When Rw / Bei is greater than 0.8, the axial width of the circumferential groove 111 is too large, making it difficult for the inner ring track surface 1211 to bend at both ends axially, failing to effectively increase the contact area between the inner ring track surface 1211 and the first rolling element 123, leading to an increase in the maximum load on the first rolling element 123.

[0045] Therefore, by reasonably designing the Rw / Be ratio to be in the range of 0.5 to 0.8, the deformation of the inner ring 121 can be effectively utilized to increase the contact area with the first rolling element 123, disperse the load on the first rolling element 123, reduce the maximum load on the first rolling element 123, and thus increase the load-bearing capacity of the flexible bearing 120.

[0046] Reference Figure 15 As shown in the embodiments of the present invention, Figure 15 The horizontal axis represents the angle between each ball and the major axis S1 of the cam 110 ellipse, and the vertical axis represents the ball load. Figure 15 The curves with triangular symbols represent the scheme of this embodiment, namely 15°≤βw0≤30°, βw0≤βw1≤1.6*βw0, 0.002*De≤Tw≤0.005*De, and 0.5*Bei≤Rw≤0.8*Bei. The curves with dot symbols represent the schemes in related technologies. When using twice the rated torque, it can be seen from the figure that the scheme of this embodiment can reduce the load on the balls, thus improving the load-bearing capacity of the harmonic reducer 1000.

[0047] Reference Figure 1 As shown, in an embodiment of the present invention, the harmonic reducer 1000 includes a flexible wheel 200, a rigid wheel 300, and a support bearing. The rigid wheel 300 is annular and has an internal toothed portion 310 on its inner sidewall. The flexible wheel 200 includes a cylindrical portion 210, a diaphragm portion 220, and a flange portion 230. The cylindrical portion 210 is cylindrical, and an external toothed portion 211 that mates with the internal toothed portion 310 is provided on the outer sidewall of one end of the cylindrical portion 210. The diaphragm portion 220 is connected to the end of the cylindrical portion 210 away from the external toothed portion 211 and extends along the outer side of the cylindrical portion 210. Extending along the outer side of the cylindrical portion 210 means extending in a direction away from the rotation axis of the harmonic reducer 1000. The flange portion 230 is annular, and its inner sidewall is connected to the outer periphery of the diaphragm portion 220. The wave generator 100 is installed in the inner hole 240 of the flexible wheel 200.

[0048] Reference Figure 3 andFigure 7 As shown, in an embodiment of the present invention, the minimum distance between the end wall of the cylindrical portion 210 away from the flange portion 230 and the flange portion 230 is Lf, the maximum width of the inner ring 121 is Bei, and the maximum width of the outer ring 122 is Beo, satisfying: 0.2*Lf≤Bei≤0.35*Lf; 0.2*Lf≤Beo≤0.35*Lf. The above formula is equivalent to 0.2≤Bei / Lf≤0.35; 0.2≤Beo / Lf≤0.35. For example, the ratio of Bei / Lf can be 0.2, 0.23, 0.26, 0.3, 0.33, 0.35; the ratio of Beo / Lf can be 0.2, 0.23, 0.26, 0.3, 0.33, 0.35, and Beo / Lf can be equal to Bei / Lf. It should be noted that the maximum width of the inner ring 121 refers to the width of the inner ring 121 along the axial direction of the cam 110, and the maximum width of the outer ring 122 refers to the width of the outer ring 122 along the axial direction of the cam 110.

[0049] With Lf constant, when both Bei / Lf and Beo / Lf are less than 0.2, the widths of the inner ring 121 and outer ring 122 are small, resulting in large deformation and high processing difficulty, leading to reduced reliability and low production efficiency of the flexible bearing 120. When both Bei / Lf and Beo / Lf are greater than 0.35, the widths of the inner ring 121 and outer ring 122 are large, occupying more space and affecting the structural compactness of the flexible bearing 120. Therefore, by rationally designing the values ​​of Bei / Lf and Beo / Lf to be between 0.2 and 0.35, the reliability of the flexible bearing 120 can be improved, the processing difficulty of the inner ring 121 and outer ring 122 can be reduced, production efficiency can be increased, and the structural compactness of the flexible bearing 120 can be guaranteed.

[0050] Reference Figure 1 and Figure 3As shown, in this embodiment of the invention, the inner diameter 240 of the flexible wheel 200 is Df (based on the inner diameter 240 when the wave generator 100 is not installed), the minimum wall thickness of the inner ring 121 is Tei, and the minimum wall thickness of the outer ring 122 is Teo, satisfying: 0.015*Df≤Tei≤0.03*Df, 0.015*Df≤Teo≤0.03*Df. The above formula is equivalent to 0.015≤Tei / Df≤0.03, 0.015≤Teo / Df≤0.03. For example, the value of Tei / Df can be 0.015, 0.02, 0.025, 0.028, 0.03, and the value of Teo / Df can be 0.015, 0.02, 0.025, 0.028, 0.03. Furthermore, Tei / Df can be equal to Teo / Df. With Df remaining constant, when Tei / Df is less than 0.015 and Teo / Df is less than 0.015, the inner ring 121 and outer ring 122 are relatively thin, making manufacturing difficult, resulting in low strength and a high risk of breakage, thus reducing the reliability of the flexible bearing 120. When Tei / Df is greater than 0.03 and Teo / Df is greater than 0.03, the inner ring 121 and outer ring 122 are relatively thick, which is not conducive to the filling of the first rolling element 123, making filling difficult or impossible.

[0051] Therefore, by reasonably designing the Tei / Df ratio to be within the range of 0.015 to 0.03 and the Teo / Df ratio to be within the range of 0.015 to 0.03, the thickness of the inner ring 121 and the outer ring 122 can be made appropriate, reducing manufacturing difficulty, increasing the strength of the inner ring 121 and the outer ring 122, reducing the risk of breakage, improving the stability and reliability of the flexible bearing 120, and at the same time facilitating the installation of the first rolling element 123 and improving assembly efficiency.

[0052] Reference Figure 1As shown, a harmonic reducer 1000 according to an embodiment of the present invention is applied to the rotating joint of an industrial robot, which may be a welding robot, a handling robot, a painting robot, a processing robot, or an assembly robot, etc. The harmonic reducer 1000 uses the wave generator 100 of the above embodiment. A flexible bearing 120 is mounted on the outer peripheral wall of a cam 110. The first rolling element 123 of the flexible bearing 120 is located between the inner ring 121 and the outer ring 122, thus allowing the inner ring 121 and the outer ring 122 to rotate relative to each other. The inner ring 121 of the flexible bearing 120 has an inner ring track surface 1211, and the outer ring 122 has an outer ring track surface 1221. Since the inner ring track surface 1211 is the load-bearing surface, its radius of curvature Rei is smaller than that of the outer ring track surface 1221. This means the curvature of the inner ring track surface 1211 is greater than that of the outer ring track surface 1221, resulting in a larger contact area between the first rolling element 123 and the inner ring track surface 1211. This effectively distributes the load and improves the load-bearing capacity of the flexible bearing 120. The outer ring track surface 1221 is typically not a load-bearing surface. Therefore, its radius of curvature Reo is designed to be larger than that of the inner ring track surface 1211. This reduces the contact area between the first rolling element 123 and the outer ring track surface 1221, thereby reducing friction and mitigating excessive starting torque, ultimately extending the service life of the flexible bearing 120.

[0053] Reference Figure 1 As shown in the embodiment of the present invention, the harmonic reducer 1000 further includes a bearing assembly 400, a first oil seal 450, and a second oil seal 460. The bearing assembly 400 is used to support the rigid wheel 300 and the flexible wheel 200 so that they can rotate relative to each other. The bearing assembly 400 is arranged around the outer side of the cylindrical portion 210, and a first oil storage space 410 is formed between the bearing assembly 400, the cylindrical portion 210, and the diaphragm portion 220. The bearing assembly 400 includes an inner bearing ring 430 and an outer bearing ring 440. The inner bearing ring 430 is fixedly connected to the rigid wheel 300, and the outer bearing ring 440 is arranged around the outer side of the inner bearing ring 430 and fixedly connected to the flange portion 230. Next, a second oil storage space 420 is formed between the outer bearing ring 440 and the inner bearing ring 430. The outer bearing ring 440 and the inner bearing ring 430 are provided with a first gap on the side of the second oil storage space 420 near the first oil storage space 410. The outer bearing ring 440 and the rigid wheel 300 are provided with a second gap on the side of the second oil storage space 420 away from the first oil storage space 410. A first oil seal 450 is installed in the first gap to prevent the exchange of lubricant between the first oil storage space 410 and the second oil storage space 420. A second oil seal 460 is installed in the second gap to prevent the lubricant in the second oil storage space 420 from overflowing outward.

[0054] It is understandable that the first oil seal 450 is installed in the first gap, and the first oil seal 450 is used to prevent the exchange of lubricant in the first oil storage space 410 and the second oil storage space 420. The second oil seal 460 is installed in the second gap, and the second oil seal 460 is used to prevent the lubricant in the second oil storage space 420 from overflowing to the outside of the harmonic reducer 1000. The second oil seal 460 is generally a conventional skeleton oil seal.

[0055] Because foreign matter such as iron powder and abrasive particles are easily generated when the external gear 211 and the internal gear 310 mesh, these iron powder and abrasive particles will mix into the lubricant and contaminate it. The contaminated lubricant has little effect on the flexible bearing 120, the internal gear 310 and the external gear 211, but it has a greater impact on components such as the bearing assembly 400 that are subjected to large contact stress. Therefore, the first oil seal 450 can prevent the lubricant containing iron powder and abrasive particles in the first oil storage space 410 from entering the second oil storage space 420, effectively preventing abnormal damage to the bearing assembly 400 and thus preventing premature failure, thereby extending the service life of the harmonic reducer 1000.

[0056] Under the combined action of the first oil seal 450 and the second oil seal 460, the second oil storage space 420 forms a sealed cavity, which is isolated from the first oil storage space 410. Therefore, the first oil storage space 410 and the second oil storage space 420 can use different lubricants. In particular, the lubricant of the bearing device 400 can be reasonably selected according to the performance and working conditions of the harmonic reducer 1000, thereby improving the lubrication effect in the bearing device 400 and thus improving the overall performance of the harmonic reducer 1000.

[0057] Furthermore, under the sealing effect of the first oil seal 450, the lubricant in the first oil storage space 410 cannot enter the second oil storage space 420, so that the grease in the harmonic reducer 1000 cannot leak from the outer peripheral wall of the wheel 300, thereby improving the sealing performance of the harmonic reducer 1000.

[0058] Reference Figure 1 , Figure 8 and Figure 9 As shown, in an embodiment of the present invention, the inner bearing ring 430 is provided with a first raceway 431 and a second raceway 432 at two ends opposite to the rotation axis of the wave generator 100, respectively. The first raceway 431 and the second raceway 432 are annular and spaced apart. The outer bearing ring 440 is provided with a third raceway 441 located outside the first raceway 431 and opposite to the first raceway 431, and a fourth raceway 442 located outside the second raceway 432 and opposite to the second raceway 432. A plurality of second rolling elements 470 are installed in the first annular space formed between the first raceway 431 and the third raceway 441, and a plurality of third rolling elements 480 are installed in the second annular space formed between the second raceway 432 and the fourth raceway 442.

[0059] Understandably, the second rolling element 470 and the third rolling element 480 can be ball bearings, employing a double-row angular contact ball bearing design. This eliminates the need for a filling port when assembling the first rolling element 123 and the second rolling element 470, thus simplifying assembly and improving efficiency. Simultaneously, it enhances the load-bearing capacity and vibration performance of the harmonic reducer 1000 while maintaining its compact structure, such as improving overturning moment and overturning moment stiffness.

[0060] Since the harmonic reducer 1000 of this invention adopts all the technical solutions of the wave generator 100 of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0061] This invention discloses an industrial robot according to one embodiment. The industrial robot can be a welding robot, a handling robot, a painting robot, a processing robot, or an assembly robot. The industrial robot employs the harmonic reducer 1000 described in the above embodiment. A flexible bearing 120 is mounted on the outer peripheral wall of the cam 110. The first rolling element 123 of the flexible bearing 120 is located between the inner ring 121 and the outer ring 122, allowing the inner ring 121 and the outer ring 122 to rotate relative to each other. The inner ring 121 of the flexible bearing 120 has an inner ring track surface 1211, and the outer ring 122 has an outer ring track surface 1221. When the Rei / De ratio is too small, although it can increase the load-bearing capacity of the wave generator 100, it will lead to an increase in frictional resistance, i.e., an increase in starting torque. When the Rei / De ratio is too large, although it can reduce the starting torque, it will lead to a decrease in the load-bearing capacity of the wave generator 100. Therefore, by reasonably designing the Rei / De and Rei / De ratio range, the load-bearing capacity of the wave generator 100 can be improved while ensuring that the starting torque is not too large.

[0062] The industrial robot of this invention adopts all the technical solutions of the harmonic reducer 1000 of the above embodiments, and therefore has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0063] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A wave generator mounted in the bore of a flexible gearwheel, characterised in that, The cam comprises: a flexible bearing mounted on an outer peripheral wall of the cam, the flexible bearing comprising an inner ring, an outer ring and first rolling elements arranged between the inner ring and the outer ring; wherein a maximum cross-sectional diameter of the first rolling elements is De, the inner ring is provided with an inner ring raceway surface having a radius of curvature Rei, the outer ring is provided with an outer ring raceway surface having a radius of curvature Reo, and the following conditions are satisfied: 0.505*De≤Rei≤0.515*De; and 0.511*De≤Reo≤0.523*De. The radius of curvature Rei of the inner ring raceway surface and the radius of curvature Reo of the outer ring raceway surface satisfy Rei<Reo.

2. The wave generator of claim 1, wherein: The outer peripheral wall of the cam is provided with at least two inwardly recessed circumferential grooves, and a projection of the outer peripheral wall of the cam along an axis of the cam is elliptical, and the at least two circumferential grooves are arranged on both sides of a major axis of the ellipse, respectively.

3. The wave generator of claim 1, wherein: The at least two circumferential grooves are symmetrically arranged along the major axis.

4. The wave generator of claim 3, wherein: In a cross section passing through one of the circumferential grooves, a line connecting a midpoint of a groove bottom of the circumferential groove and a center of the cam is a first reference line, and an included angle between the first reference line and the major axis is βw0, and the following condition is satisfied:

5. A wave generator according to claim 3 or 4, characterised in that: 15°≤βw0≤30°.

6. The wave generator of claim 5, wherein: In the cross section passing through the circumferential groove, two end points of the circumferential groove along a circumference of the cam correspond to a maximum angle of the center of the cam, and the maximum angle is βw1, and the following condition is satisfied:

7. The wave generator of claim 3, wherein: βw0≤βw1≤1.6*βw0.

8. A wave generator according to claim 3 or 7, characterised in that: The maximum cross-sectional diameter of the first rolling elements is De, in the cross section passing through one of the circumferential grooves, a line connecting a midpoint of a groove bottom of the circumferential groove and a center of the cam is a first reference line, and in a cross section passing through the first reference line, a maximum depth of the circumferential groove is Tw, and the following condition is satisfied:

9. The wave generator of claim 1, wherein: 0.002*De≤Tw≤0.005*De. In the cross section passing through one of the circumferential grooves, a line connecting a midpoint of a groove bottom of the circumferential groove and a center of the cam is a first reference line, and in a cross section passing through the first reference line, the groove bottom of the circumferential groove is a circular arc with a radius Rw, a maximum width of the inner ring is Bei, and the following condition is satisfied: 0.5*Bei≤Rw≤0.8*Bei.

10. The wave generator of claim 1, wherein: The flexible gear comprises a cylindrical portion and a flange portion, a minimum distance between an end wall of the cylindrical portion away from the flange portion and the flange portion is Lf, a maximum width of the inner ring is Bei, and a maximum width of the outer ring is Beo, and the following conditions are satisfied: 0.2*Lf≤Bei≤0.35*Lf; and / or 0.2*Lf≤Beo≤0.35*Lf.

11. A harmonic reducer characterized by: A bore diameter of the flexible gear is Df, a minimum wall thickness of the inner ring is Tei, and a minimum wall thickness of the outer ring is Teo, and the following conditions are satisfied:

12. Industrial robot, characterized by 0.015*Df≤Tei≤0.03*Df; and / or 0.015*Df≤Teo≤0.03*Df. The wave generator comprises any one of claims 1 to 10. The harmonic reducer comprises claim 11.

Images