Backlash Elimination Device for Planetary Gear Train, Reducer and Robot Joint Based on Flexible Mechanism

Abstract

The present invention discloses a backlash elimination device for a planetary gear train, a reducer and a robot joint based on a flexible mechanism. The backlash elimination device includes an adjusting screw and a spring. The adjusting screw is threadedly connected to an integrated flexible planetary gear carrier. The integrated flexible planetary gear carrier has a moving platform, and a spring hole is provided on the moving platform. The spring is sleeved on the screw and installed in the spring hole. When the threaded connection depth between the adjusting screw and the integrated flexible planetary gear carrier reaches or exceeds a set depth, the adjusting screw can squeeze the spring, so that the moving platform generates elastic movement along the radial direction of the integrated flexible planetary gear carrier. This radial elastic movement can be converted into circumferential elastic rotation of the bearing hole of the planetary gear carrier around the center of the planetary gear carrier through an elastic connecting member. The planetary gear train backlash elimination device provided by the present invention has the advantages of integration, light weight, compact structure, simple and reliable principle, adjustable pre-tightening force, etc., and has a wide range of applications.

Description

Technical Field

[0001] The present invention relates to a planetary gear reducer, and more particularly to a backlash elimination device for a planetary gear train based on a flexible mechanism, a planetary gear reducer, and a collaborative robot joint, belonging to the technical field of planetary reducers. Background Art

[0002] The reducer is a core key component of a robot joint. Compared with the harmonic reducer used in traditional robot joints, the planetary gear reducer has the advantages of high stiffness, high efficiency, and good reverse transmission performance. Compared with the RV reducer, it has the advantages of small volume and light weight. By reasonably matching the teeth and optimizing the efficiency of the planetary gear train, a reducer with a large reduction ratio and high transmission efficiency suitable for robot joints can be obtained. However, due to the existence of tooth side clearance during gear meshing in traditional gear transmission, the transmission will enter the clearance dead zone during reverse rotation, greatly affecting its transmission accuracy. Therefore, the application of planetary gear reducers in precision transmission scenarios such as robot joints faces great difficulties.

[0003] There are many methods to eliminate tooth side clearance, such as using backlash elimination gears, variable tooth thickness gears, and dual-motor backlash elimination, etc. However, these methods are difficult to be implemented in planetary gear reducers. For example, CN110925409A adopts a combination of a fixed ring gear and a floating ring gear, and realizes backlash elimination by adjusting the relative angle of the two ring gears; CN105508585A uses a main and auxiliary planetary gear to achieve double-side meshing to eliminate clearance. In order to achieve backlash elimination, these methods add one or more redundant parts, thereby increasing the weight and moment of inertia of the reducer, which has an adverse effect on the dynamic performance of the reducer.

[0004] How to provide a backlash elimination mechanism that can eliminate the tooth side clearance of a planetary gear reducer and is lightweight and integrated is an urgent problem to be solved. Summary of the Invention

[0005] The main purpose of the present invention is to provide a backlash elimination device for a planetary gear train based on a flexible mechanism, a reducer, and a robot joint, so as to overcome the deficiencies of the prior art.

[0006] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include:

[0007] One aspect of an embodiment of the present invention provides a backlash elimination device for a planetary gear train based on a flexible mechanism, which includes an adjustment screw and a spring. The adjustment screw is threadedly connected to an integrated flexible planetary gear carrier. The integrated flexible planetary gear carrier has a moving platform, and a spring hole is provided on the moving platform. The spring is sleeved on the screw and installed in the spring hole. When the threaded connection depth between the adjustment screw and the integrated flexible planetary gear carrier reaches or exceeds a set depth, the adjustment screw can squeeze the spring, so that the moving platform elastically moves radially along the integrated flexible planetary gear carrier, and further makes the planetary gear shaft bearing holes in the integrated flexible planetary gear carrier elastically rotate circumferentially around the center of the integrated flexible planetary gear carrier.

[0008] In some embodiments, both the adjustment screw and the spring are arranged radially along the integrated flexible planetary gear carrier.

[0009] In some embodiments, one end of the spring is in close contact with the bottom surface of the spring hole, and the other end is in close contact with the nut of the adjustment screw.

[0010] In some embodiments, the integrated flexible planetary gear carrier includes a first annular member, a plurality of second annular members symmetrically arranged around the central annular member, and two moving platforms. The first annular member has a planetary gear carrier central shaft bearing hole, and the second annular member has a planetary gear shaft bearing hole. The two moving platforms are distributed on both sides of the integrated flexible planetary gear carrier, and any moving platform is arranged between two adjacent second annular members. The first annular member is connected to each second annular member through a first elastic connecting member, and the moving platform is connected to the adjacent second annular member through a second elastic connecting member.

[0011] In some embodiments, the first annular member, the second annular member, the moving platform, the first elastic connecting member, and the second elastic connecting member are all integrally provided.

[0012] In some embodiments, the number of the second annular members is an even number.

[0013] In some embodiments, two adjacent second annular members can rotate relative to each other in pairs around the center of the integrated flexible planetary gear carrier.

[0014] In some embodiments, the first elastic connecting member includes a flexible leaf spring, and the second elastic connecting member includes a first flexible hinge and a second flexible hinge connected in sequence.

[0015] Furthermore, the moving platform is connected to the adjacent second annular member through the first flexible hinge and the second flexible hinge in sequence.

[0016] In some embodiments, the radial stiffness of the backlash elimination device for the planetary gear train is:

[0017]

[0018] Among them, K 1 is the equivalent stiffness of the first flexible hinge in the radial direction of the integrated flexible planet gear carrier, K 2 is the equivalent stiffness of the second flexible hinge in the radial direction of the integrated flexible planet gear carrier, K 3 is the equivalent stiffness in the radial direction of the integrated flexible planet gear carrier when the second annular member rotates circumferentially through the first elastic connection member, K s is the stiffness of the spring.

[0019] Another aspect of the embodiments of the present invention provides a speed reducer, which includes:

[0020] A backlash elimination device for a planetary gear train based on a flexible mechanism; and

[0021] A sun gear and a plurality of planet gears arranged on the integrated flexible planet gear carrier, and the planet gears are kept meshed with the internal gear ring and the sun gear.

[0022] Another aspect of the embodiments of the present invention provides a robot joint, which includes the speed reducer described above.

[0023] Compared with the prior art, the technical solutions provided by the above embodiments of the present invention have at least the following beneficial effects:

[0024] (1) By designing an integrated flexible planet gear carrier, the bearing holes of the planet gear shafts can rotate relative to the center of the planet gear carrier without relying on additional redundant parts, and the backlash on both the forward and reverse sides can be eliminated in pairs;

[0025] (2) By arranging a pre-tightening force adjusting mechanism on the integrated flexible planet gear carrier, the pre-tightening force for eliminating the backlash of the planet gears can be adjusted to ensure the reliable operation of the backlash elimination device. Moreover, by adjusting the pre-tightening force, the threshold value for switching the backlash elimination state of the planet gears can be adjusted. When the load exceeds the threshold value, the follower planet gears will overcome the stiffness of the backlash elimination device under the torque acting on their own around the center of the planet gear carrier and return to the normal same-side meshing state;

[0026] (3) The provided backlash elimination device for a planetary gear train based on a flexible mechanism has the advantages of integration, light weight, compact structure, simple and reliable principle, adjustable pre-tightening force, and wide application range. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic diagram of the overall assembly structure of a backlash elimination device for a planetary gear train in an embodiment of the present invention;

[0029] Figure 2 It is a partial enlarged view of the threaded connection part of a planetary gear train backlash elimination device in an embodiment of the present invention ( Figure 1 the area shown as A in);

[0030] Figure 3 It is a three-dimensional view of an integrated flexible planetary gear carrier in an embodiment of the present invention;

[0031] Figure 4 It is the front view of an integrated flexible planetary gear carrier in an embodiment of the present invention;

[0032] Figure 5 It is a schematic diagram of a planetary gear train backlash elimination device working in an example gear train in an embodiment of the present invention;

[0033] Explanation of reference numerals: 10 - integrated flexible planetary gear carrier, 101 - first annular member, 102 - second annular member, 11 - flexible leaf spring, 12 - planetary gear shaft bearing hole, 13 - moving platform, 14 - first flexible hinge, 15 - second flexible hinge, 16 - planetary gear carrier central shaft bearing hole, 20 - adjusting screw, 21 - spring, 30 - internal gear ring, 31 - planetary gear shaft, 32 - bearing gland. Detailed implementation manners

[0034] The present invention will be more fully understood by the following detailed implementation manners which should be read in conjunction with the accompanying drawings. Specific embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the present invention, and the present invention can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching those skilled in the art to employ the present invention in any appropriate detailed embodiment in different ways.

[0035] Please refer to Figures 1-4, a backlash elimination device for a planetary gear train based on a flexible mechanism disclosed in an embodiment of the present invention includes an adjusting screw 20 and a spring 21. The adjusting screw 20 is threadedly connected to an integrated flexible planetary gear carrier 10. The integrated flexible planetary gear carrier 10 has a moving platform 13. A spring hole is provided on the moving platform 13. The spring 21 is sleeved on the screw 21 and installed in the spring hole. One end of the spring 21 is in close contact with the bottom surface of the spring hole, and the other end is in close contact with the nut of the adjusting screw 20. The adjusting screw 20 and the spring 21 are both arranged along the radial direction of the integrated flexible planetary gear carrier 10. The threaded connection depth between the adjusting screw 20 and the integrated flexible planetary gear carrier 10 can be directly adjusted by the adjusting screw 20.

[0036] Further, by adjusting the threaded connection depth between the adjusting screw 20 and the integrated flexible planetary gear carrier 10, the adjusting screw will squeeze the spring 21 to deform and transfer the pressure to the moving platform 13 of the planetary gear carrier 10, causing it to elastically move along the radial direction of the planetary gear carrier 10, and further causing the bearing holes of the planetary gear shafts in the integrated flexible planetary gear carrier to elastically rotate circumferentially around the center of the integrated flexible planetary gear carrier.

[0037] Further, the integrated flexible planetary gear carrier 10 includes a first annular member 101, a plurality of second annular members 102 symmetrically arranged around the central annular member, and two moving platforms 13. The first annular member has a bearing hole 16 for the central shaft of the planetary gear carrier. The second annular member has a bearing hole 12 for the planetary gear shaft. The two moving platforms 13 are distributed on both sides of the integrated flexible planetary gear carrier 10, and each moving platform 13 is arranged between two adjacent second annular members 102. The first annular member 101 and each second annular member 102 are connected by a first elastic connecting member. The moving platform 13 and the adjacent second annular member 102 are connected by a second elastic connecting member. Among them, the number of the second annular members 102 is an even number. The first elastic connecting member adopts a flexible leaf spring 11. The second elastic connecting member includes a first flexible hinge 14 and a second flexible hinge 15 connected in sequence, and the moving platform 13 is connected to the adjacent second annular member 102 through the first flexible hinge 14 and the second flexible hinge 15 in sequence.

[0038] Among them, the first annular member, the second annular member, the moving platform, the first elastic connecting member, and the second elastic connecting member are all integrally provided.

[0039] By adopting the above structural design, the integrated flexible planetary gear carrier 10 can convert the circumferential stiffness of each planetary gear shaft bearing hole 12 around the center of the planetary gear carrier 10 into the radial stiffness in the vertical direction of the moving platform 13 through the flexible hinges 14 and 15. At the same time, each planetary gear shaft bearing hole 12 can generate elastic rotation around the center of the planetary gear carrier 10 through the flexible leaf spring 11, and the moving platform 13 can generate elastic movement along the radial direction of the planetary gear carrier 10 through the flexible hinges 14 and 15.

[0040] Furthermore, the radial stiffness of the planetary gear train backlash eliminator is:

[0041]

[0042] where K 1 is the equivalent stiffness of the first flexible hinge 14 in the radial direction of the integrated flexible planetary gear carrier 10, K 2 is the equivalent stiffness of the second flexible hinge 15 in the radial direction of the integrated flexible planetary gear carrier 10, K 3 is the equivalent stiffness of the second annular member 102 in the radial direction of the integrated flexible planetary gear carrier 10 when it rotates circumferentially through the first elastic connector, and K s is the stiffness of the spring 21.

[0043] More intuitively, please refer to Figures 3-4 , the integrated flexible planetary gear carrier 10 can convert the elastic movement of the moving platform 13 in the radial direction into the circumferential elastic rotation of the planetary gear shaft bearing hole 12 around the center of the planetary gear carrier through the flexible leaf spring 11, the first flexible hinge 14 and the second flexible hinge 15, and maintain a certain restoring force during this process.

[0044] In this embodiment, the planetary gear train backlash eliminator described can be connected to the planetary gear shaft bearing (not shown in the figure) and the planetary carrier central shaft bearing (not shown in the figure) in a variety of planetary gear trains, so as to support the rotary motion of the planetary gear shaft (not shown in the figure). Figure 5The application of the backlash elimination device for the planetary gear train in an exemplary gear train is shown. The planetary gear train is a 3K planetary gear train, in which an even number of planetary gears are used, and the planet carrier is not a component that transmits torque in the transmission chain. The backlash elimination device for the planetary gear train adjusts the thread connection depth between it and the integrated flexible planet carrier 10 through the adjusting screw 20, and the extrusion spring 21 drives the moving platform 13 of the planet carrier to cause radial deformation of the planet carrier 10. The radial deformation of the planet carrier is converted into the rotation of the bearing hole 12 of the planetary gear shaft around the center of the planet carrier through a flexible mechanism, and this drives the adjacent two planetary gear shafts 31 to move in opposite directions. Furthermore, an adjacent pair of planetary gears will remain in a meshing state with the internal gear ring 30 and the sun gear (not shown in the figure) on the opposite sides. After the backlash elimination is completed, continue to adjust the thread connection depth between the adjusting screw 20 and the integrated flexible planet carrier 10 to further compress the spring 10. At this time, since the backlash has been eliminated, the planet carrier 10 will no longer undergo elastic deformation, and the deformation force of the spring 10 will be converted into a pre-tightening force applied on the meshing surface of the planetary gears to achieve the tight fit of the tooth surfaces, ensuring that there is always a planetary gear in a meshing state when the planetary gear train operates in both forward and reverse directions, that is, the backlash elimination of the planetary gears is achieved.

[0045] Therefore, by applying the backlash elimination device for the planetary gear train of this embodiment, a planetary gear reducer can be constructed. And the planetary gear reducer can be applied in multiple fields.

[0046] For example, in an application case, a planetary gear reducer incorporating the backlash elimination device for the planetary gear train can be used inside the transmission reduction mechanism of a collaborative robot joint to drive a collaborative robot with high human-machine interaction performance.

[0047] All aspects, embodiments, features and examples of the present invention should be considered illustrative in all respects and are not intended to limit the present invention, the scope of which is only defined by the claims. Without departing from the spirit and scope of the claimed present invention, those skilled in the art will appreciate other embodiments, modifications and uses.

[0048] In the present invention, the use of titles and chapters does not mean limiting the present invention; each chapter can be applied to any aspect, embodiment or feature of the present invention.

[0049] Unless otherwise specifically stated, the use of the terms "include (include, includes, including)", "have (have, has or having)" should generally be understood as open-ended and non-restrictive.

[0050] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and / or additions can be made without departing from the spirit and scope of the present invention and elements of the embodiments can be replaced with substantially equivalent ones. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the present invention. Therefore, it is not intended that the present invention be limited to the particular embodiments disclosed for carrying out the present invention, but rather that the present invention will include all embodiments falling within the scope of the appended claims. Further, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A backlash elimination device for a planetary gear train based on a flexible mechanism, characterized in that: The backlash elimination device includes an adjusting screw (20) and a spring (21). The adjusting screw (20) is threadedly connected to the integrated flexible planetary gear carrier (10). The integrated flexible planetary gear carrier (10) includes a first annular member, an even number of second annular members symmetrically arranged around the first annular member, and two moving platforms (13). Adjacent second annular members can rotate relative to each other in pairs around the center of the integrated flexible planetary gear carrier (10). The moving platform (13) is provided with a spring hole. The spring (21) is sleeved on the screw (21) and installed in the spring hole. When the threaded connection depth between the adjusting screw (20) and the integrated flexible planetary gear carrier (10) reaches or exceeds the set depth, the adjusting screw (20) can squeeze the spring (21), so that the moving platform (13) generates elastic movement along the radial direction of the integrated flexible planetary gear carrier (10), and further makes the planetary gear shaft bearing holes (12) in the integrated flexible planetary gear carrier (10) rotate elastically circumferentially around the center of the integrated flexible planetary gear carrier (10); The first annular member has a planetary gear carrier central shaft bearing hole (16), the second annular member has a planetary gear shaft bearing hole (12), the two moving platforms (13) are distributed on both sides of the integrated flexible planetary gear carrier (10), and any moving platform (13) is arranged between adjacent second annular members. The first annular member and each second annular member are connected by a first elastic connecting member, and the moving platform (13) and the adjacent second annular member are connected by a second elastic connecting member. The first annular member, the second annular member, the moving platform (13), the first elastic connecting member, and the second elastic connecting member are all integrally provided.

2. The backlash elimination device for a planetary gear train based on a flexible mechanism according to claim 1, characterized in that: The adjusting screw (20) and the spring (21) are both arranged along the radial direction of the integrated flexible planetary gear carrier (10).

3. The backlash elimination device for a planetary gear train based on a flexible mechanism according to claim 1, characterized in that: One end of the spring (21) is in close contact with the bottom surface of the spring hole, and the other end is in close contact with the nut of the adjusting screw (20).

4. The backlash elimination device for a planetary gear train based on a flexible mechanism according to any one of claims 1-3, characterized in that: The first elastic connecting member includes a flexible leaf spring (11), and the second elastic connecting member includes a first flexible hinge (14) and a second flexible hinge (15) connected in sequence.

5. The backlash elimination device for a planetary gear train based on a flexible mechanism according to claim 4, characterized in that The radial stiffness of the backlash elimination device for the planetary gear train is: Among them, K 1 is the equivalent stiffness of the first flexible hinge (14) in the radial direction of the integrated flexible planet gear carrier (10), K 2 is the equivalent stiffness of the second flexible hinge (15) in the radial direction of the integrated flexible planet gear carrier (10), K 3 is the equivalent stiffness in the radial direction of the integrated flexible planet gear carrier (10) when the second annular member rotates circumferentially through the first elastic connecting member, K s is the stiffness of the spring (21).

6. A speed reducer, characterized in that comprising: The backlash elimination device for a planetary gear train based on a flexible mechanism according to any one of claims 1-5; and A sun gear and a plurality of planetary gears arranged on the integrated flexible planetary gear carrier (10), and the planetary gears are kept meshed with the internal gear ring (30) and the sun gear.

7. A robot joint, characterized in that including the speed reducer according to claim 6.

Images