Large-ratio low-gap nw planetary joint module

Abstract

The large-speed-ratio low-gap NW planetary joint module of the application adds multiple groups of transition planetary gears which are sequentially engaged from inside to outside between the second planetary gear and the second inner gear ring, the innermost group of transition planetary gears is in one-to-one engagement with the second planetary gear, the outermost group of transition planetary gears is in engagement with the second inner gear ring, the pitch circle radius of the second inner gear ring is no longer constrained by the first center distance, the center distance is decoupled, the second inner gear ring can be expanded to the mold shell, the speed ratio is effectively improved under the constraint of the same size of the module shell, the compactness of the joint module is improved, the demand of the robot joint drive for large speed ratio is met, the power density of the joint module is improved, the "rigid-soft-soft" step-by-step transmission and self-adaptive load sharing structure is formed, the low-gap engagement between the engaged gears after gear wear is maintained through the radial floating of the flexible shaft, the influence of gear wear on control accuracy is effectively reduced, and the control accuracy of the planetary transmission structure in the use process is ensured.

Description

Technical Field

[0001] This invention relates to a high speed ratio, low clearance NW planetary joint module, belonging to the field of joint module technology. Background Technology

[0002] Planetary gear reducers have become a core component in fields such as robot joint drives due to their numerous advantages. The humanoid robot industry is entering a new stage of standardized and accelerated development. The performance of joint modules has a significant impact on humanoid robots. Currently, commonly used NW-type planetary gear transmission structures (such as...) Figure 7 As shown, the first-stage sun gear is the input, the first-stage planetary gear meshes with the first-stage sun gear, the second-stage planetary gear meshes with the second-stage internal gear ring, the first and second-stage planetary gears form a double gear, the second-stage internal gear ring is fixed, and the planetary carrier is the output. Due to its large speed ratio and compact structure, it is widely used in electric vehicles and industrial reducers. Its speed ratio formula is i=K1*K2+1, where K1 refers to the pitch circle ratio between the first-stage planetary gear and the sun gear, and K2 refers to the pitch circle ratio between the second-stage internal gear ring and the second-stage planetary gear. In the existing NW planetary gear set structure, the secondary planetary gears directly mesh with the secondary internal gear ring, which means that the center distance a1 (center distance between the primary sun gear and the primary planetary gears) and the center distance a2 (center distance between the secondary planetary gears and the secondary internal gear ring) must be equal, a phenomenon known as center distance coupling. This makes it extremely difficult to increase the speed ratio when the size of the module housing is fixed, due to the limited radial dimensions of the housing. If an attempt is made to increase the speed ratio by increasing K1 (i.e., increasing the pitch circle ratio between the primary planetary gears and the primary sun gear), the primary planetary gears are difficult to increase due to the constraint of the radial dimensions of the housing, and the diameter of the primary sun gear can only be reduced. When the diameter of the primary sun gear decreases, in order to achieve meshing, the primary planetary gears need to move inward to approach the primary sun gear, thus reducing the center distance of the primary gear set. The secondary planetary gears are coaxial with the primary planetary gears and will move inward synchronously with the primary planetary gears, which forces the pitch circle of the secondary internal gear ring to decrease, thereby compressing the space for increasing K2 (the pitch circle ratio between the secondary internal gear ring and the secondary planetary gears). According to the speed ratio formula, it is difficult to guarantee the increase of the speed ratio when K1 increases and K2 decreases. This "center-distance coupling" effect creates a sharp contradiction between the speed ratio increase and the outer diameter envelope of the housing, making it difficult to achieve a larger speed ratio within a limited radial space. To improve the speed ratio, some existing solutions employ a reduction gear meshing outside the secondary internal gear ring of the NW, such as CN118912171A, which discloses a precision transmission device for a robot joint with a large transmission ratio. This device has a first variable-thickness gear fixedly connected to the planetary carrier assembly, a fixed gear meshing on the first variable-thickness gear, and a second variable-thickness gear meshing between the fixed gear and the output gear of the gear ring. By changing the tooth ratio between the output gear of the gear ring and the second variable-thickness gear, different transmission ratios can be obtained, achieving a wider transmission ratio coverage. The disadvantage of this solution is that it increases the spatial volume of the joint module, reduces structural compactness, and contributes little to improving power density. Summary of the Invention

[0003] The high-ratio, low-backlash NW planetary joint module provided by this invention effectively increases the speed ratio under the constraint of a module shell of the same size, improves the structural compactness of the joint module, meets the high speed ratio requirement of robot joint drive, increases the power density of the joint module, and forms a "rigid-flexible-flexible" step-by-step transmission and adaptive load-sharing structure. By radially floating the flexible shaft, it maintains low-backlash meshing between meshing gears after gear wear, effectively reducing the impact of gear wear on control accuracy and ensuring the control accuracy of the planetary transmission structure during use.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-ratio, low-backlash NW planetary joint module includes a motor, a primary sun gear connected to the motor, primary planet gears meshing with the primary sun gear, a secondary planet gear fixed coaxially with the primary planet gears and having an outer diameter smaller than the primary planet gears, a planet carrier assembling the primary and secondary planet gears, and a secondary internal gear ring fixed to the module housing. Its distinguishing feature is that multiple sets of transition planet gears are arranged between the secondary planet gears and the secondary internal gear ring. The number of transition planet gears in each set is equal to the number of secondary planet gears. The multiple sets of transition planet gears mesh sequentially from the inside to the outside. The innermost set of transition planet gears meshes one-to-one with the secondary planet gears, and the outermost set of transition planet gears meshes with the secondary internal gear ring.

[0005] Preferably, the multiple sets of transition planetary gears consist of an inner transition planetary gear set and an outer transition planetary gear set located outside the inner transition planetary gear set. The inner transition planetary gear set consists of inner transition planetary gears that mesh one-to-one with the secondary planetary gears, and the outer transition planetary gear set consists of outer transition planetary gears that mesh one-to-one with the inner transition planetary gears. The outer transition planetary gears mesh with the secondary internal gear ring, and both the inner and outer transition planetary gears are evenly spaced along the circumference in the secondary internal gear ring.

[0006] Preferably, the outer diameters of the inner and outer transition planetary gears are both larger than the outer diameter of the second-stage planetary gear and smaller than the outer diameter of the first-stage planetary gear. The second-stage planetary gear, the inner transition planetary gear meshing with the second-stage planetary gear, and the outer transition planetary gear meshing with the inner transition planetary gear are arranged in a triangular pattern.

[0007] Preferably, the secondary planetary gear is supported by a rigid shaft fixed within the planet carrier, and both the inner and outer transition planetary gears are supported by flexible shafts that can float radially within the planet carrier.

[0008] Preferably, the planet carrier is provided with a rigid shaft for assembling the first-stage planetary gear and the second-stage planetary gear, an inner flexible shaft for assembling the inner transition planetary gear, and an outer flexible shaft for assembling the outer transition planetary gear. Both ends of the rigid shaft are fixed to the planet carrier, one end of the inner flexible shaft is fixed to the planet carrier, and the other end is a free end suspended in the air. One end of the outer flexible shaft is fixed to the planet carrier, and the other end is a free end suspended in the air.

[0009] Preferably, the planetary carrier includes a first disk, a second disk coaxially aligned with the first disk, and a connecting column connecting the first disk and the second disk. The connecting column is evenly spaced along the outer circumference of the first disk. The first-stage planetary gear, the second-stage planetary gear, the inner transition planetary gear, and the outer transition planetary gear are all disposed in the planetary carrier. The first-stage planetary gear is located on the side where the first disk is located, and the second-stage planetary gear is located on the side where the second disk is located. The two ends of the rigid shaft are fixed to the first disk and the second disk, respectively. The inner flexible shaft and the outer flexible shaft are fixed to the second disk, and are separated from the first disk and do not contact it.

[0010] Preferably, both the inner flexible shaft and the outer flexible shaft include a pin and a bushing fitted on the pin and capable of swinging on the pin. One end of the pin is fixed to the second disk, and the other end is a free end that is suspended. The inner transition planetary gear is assembled on the bushing of the inner flexible shaft through a needle roller bearing, and the outer transition planetary gear is assembled on the bushing of the outer flexible shaft through a needle roller bearing.

[0011] Preferably, the pin consists of an interference section with a free end and a fixed section fixed to the second disk. The diameter of the interference section is larger than the diameter of the fixed section. The bushing is interference-fitted with the interference section and clearance-fitted with the fixed section, and is separated from the second disk and does not contact it.

[0012] Preferably, the secondary internal gear ring is integrally formed with the module housing, and the outer diameter of the secondary internal gear ring is equal to the outer diameter of the module housing.

[0013] The beneficial effects of the invention are: The high-ratio, low-backlash NW planetary joint module of this invention adds multiple sets of transition planetary gears that mesh sequentially from the inside to the outside between the secondary planetary gears and the secondary internal gear ring. The innermost set of transition planetary gears meshes one-to-one with the secondary planetary gears, while the outermost set of transition planetary gears meshes with the secondary internal gear ring. The secondary internal gear ring does not directly mesh with the secondary planetary gears. This solves the limitation that the center distances of the primary and secondary planetary gears in the NW planetary set must be equal. The pitch circle radius of the secondary internal gear ring is no longer constrained by the center distance of the primary gear ring, achieving center distance decoupling. This allows the secondary internal gear ring to extend to the mold shell, fully utilizing the radial space of the mold shell. In terms of space, multiple sets of transition planetary gears are added between the secondary planetary gears and the secondary internal gear ring. With the primary center distance a1 and the pitch circle ratio K1 between the primary planetary gears and the primary sun gear remaining unchanged, the pitch circle ratio K2 between the secondary internal gear ring and the secondary planetary gears is effectively increased. Meanwhile, the transmission path of the primary planetary gear input and the planet carrier output remains unchanged. The speed ratio formula of the NW planetary joint module is still i=k1×k2+1. This achieves an effective increase in speed ratio under the constraint of the module shell of the same size, improves the structural compactness of the joint module, meets the robot joint drive's requirement for a large speed ratio, and increases the power density of the joint module.

[0014] The second-stage planetary gears are rigidly supported by shafts within the planet carrier, ensuring high rigidity for the meshing of the first-stage planetary gears and the first-stage sun gear, which are coaxially fixed with the second-stage planetary gears. This guarantees basic transmission accuracy. Furthermore, to address rigid interference and off-center loading issues caused by the addition of transition planetary gears, accumulated chain drive errors, and phase errors in multiple sets of double-gear couplings, both the inner and outer transition planetary gears are supported by flexible shafts. This allows both the inner and outer transition planetary gears to radially float within the planet carrier with the movement of the flexible shafts, enabling fine-tuning of their positions. When a second-stage planetary gear becomes overloaded due to premature contact with its corresponding inner transition planetary gear caused by a phase error, the flexibility of the flexible shaft... The deformation creates radial floating, which drives the inner transition planetary gear to fine-tune its position and absorb phase errors. This allows the load to be flexibly distributed to other meshing gear sets (the second-stage planetary gear, the corresponding inner transition planetary gear, and the corresponding outer transition planetary gear form a meshing gear set). This effectively solves the problems of rigid interference and off-center loading, enabling the transition planetary gear to have precise compliance in the tangential direction of the meshing force. This forms a "rigid-flexible-flexible" step-by-step transmission and adaptive load-sharing structure. The radial floating of the flexible shaft maintains low-clearance meshing between meshing gears after gear wear, effectively reducing the impact of gear wear on control accuracy and ensuring the control accuracy of the planetary transmission structure during use. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the high speed ratio, low clearance NW planetary joint module of the present invention.

[0016] Figure 2 This is a half-section view of a high-speed-ratio, low-gap NW planetary joint module.

[0017] Figure 3 for Figure 1 A magnified view of a portion of the image.

[0018] Figure 4 This is a schematic diagram of the secondary planetary gear, inner transition planetary gear, and outer transition planetary gear in the planet carrier.

[0019] Figure 5 This is a schematic diagram of the meshing of the second planetary gear, the inner transition planetary gear, the outer transition planetary gear, and the second-stage internal gear ring.

[0020] Figure 6 This is a schematic diagram of the transmission principle of a high-ratio, low-backlash NW planetary joint module.

[0021] Figure 7 The NW-type planetary gear transmission structure is used in the joint module in the prior art. Detailed Implementation

[0022] The following is combined Figures 1-6 The embodiments of the present invention will be described in detail below.

[0023] A high-ratio, low-backlash NW planetary joint module includes a motor 1, a primary sun gear 2 connected to the motor 1, a primary planetary gear 3 meshing with the primary sun gear 2, a secondary planetary gear 4 coaxially fixed with the primary planetary gear 3 and having an outer diameter smaller than the primary planetary gear 3, a planet carrier 5 assembling the primary planetary gear 3 and the secondary planetary gear 4, and a secondary internal gear ring 7 fixed to the module housing 6. The module is characterized by: multiple sets of transition planetary gears 8 arranged between the secondary planetary gear 4 and the secondary internal gear ring 7, with the number of transition planetary gears in each set equal to the number of secondary planetary gears 4. The multiple sets of transition planetary gears mesh sequentially from the inside to the outside, with the innermost set of transition planetary gears meshing one-to-one with the secondary planetary gear 4, and the outermost set of transition planetary gears meshing with the secondary internal gear ring 7.

[0024] The high-ratio, low-backlash NW planetary joint module described above adds multiple sets of transition planetary gears 8 between the secondary planetary gears 4 and the secondary internal gear ring 7, meshing sequentially from the inside out. The innermost set of transition planetary gears 8 meshes one-to-one with the secondary planetary gears 4, while the outermost set meshes with the secondary internal gear ring 7. The secondary internal gear ring 7 does not directly mesh with the secondary planetary gears 4, thus resolving the constraint that the center distances of the primary and secondary planetary gears in the NW planetary set must be equal. The pitch circle radius of the secondary internal gear ring 7 is no longer constrained by the center distance of the primary gear, achieving center distance decoupling. This allows the secondary internal gear ring 7 to extend to the mold shell, fully utilizing the space of the mold shell. In the radial space, multiple sets of transition planetary gears 8 are added between the secondary planetary gear 4 and the secondary internal gear ring 7. With the primary center distance a1 and the pitch circle ratio K1 of the primary planetary gear 3 and the primary sun gear 2 remaining unchanged, the pitch circle ratio K2 of the secondary internal gear ring 7 and the secondary planetary gear 4 is effectively increased. Meanwhile, the transmission path of the primary sun gear input and the planetary carrier output remains unchanged. The speed ratio formula of the NW planetary joint module is still i=k1×k2+1. This achieves an effective increase in speed ratio under the constraint of the module shell of the same size, improves the structural compactness of the joint module, meets the robot joint drive's requirement for a large speed ratio, and increases the power density of the joint module.

[0025] Among them, the multiple sets of transition planetary gears 8 are composed of an inner transition planetary gear set and an outer transition planetary gear set located outside the inner transition planetary gear set. The inner transition planetary gear set is composed of inner transition planetary gears 81 that mesh with the secondary planetary gears 4 in a one-to-one correspondence. The outer transition planetary gear set is composed of outer transition planetary gears 82 that mesh with the inner transition planetary gears 81 in a one-to-one correspondence. The outer transition planetary gears 82 mesh with the secondary internal gear ring 7. The inner transition planetary gears 81 and the outer transition planetary gears 82 are evenly spaced along the circumference in the secondary internal gear ring. As shown in the figure, the secondary planetary gear 4 is coaxially fixed with the primary planetary gear 3. There are three secondary planetary gears 4. Each secondary planetary gear 4 meshes with an inner transition planetary gear 81, and each inner transition planetary gear 81 meshes with an outer transition planetary gear 82. The outer transition planetary gears 82 all mesh with the secondary internal gear ring 7. The primary sun gear 2 is driven by a motor, which drives the primary planetary gear 3 to rotate. The secondary planetary gears 4 rotate synchronously with the primary planetary gear 3, which drives the inner transition planetary gears 81 to rotate. The inner transition planetary gears 81 drive the outer transition planetary gears 82 to rotate. The outer transition planetary gears 82 rotate within the secondary internal gear ring 7, which is fixed to the module housing 6, thereby driving the planet carrier 5 to rotate and realizing the power output. The secondary internal gear ring 7 and the secondary planetary gear 4 do not mesh directly. Instead, the radial space in the mold housing is used to expand the secondary internal gear ring 7 to be equal to the outer diameter of the mold housing. Two sets of transition planetary gears are added between the secondary planetary gear 4 and the secondary internal gear ring 7. The increase in the outer diameter of the secondary internal gear ring 7 can effectively increase the pitch circle ratio K2 between the secondary internal gear ring 7 and the secondary planetary gear 4, thereby increasing the speed ratio of the NW planetary joint module. Without increasing the radial dimension of the module housing, the speed ratio is improved by setting two sets of inner and outer transition planetary gears between the secondary internal gear ring 7 and the secondary planetary gear 4. The speed ratio is improved without reducing the structural compactness of the NW planetary joint module, thereby improving the power density of the joint module. As can be seen from the attached diagram, the three primary planetary gears 3 are evenly spaced and meshed on the outer circumference of the primary sun gear 2. Each secondary planetary gear 4 is meshed with an inner transition planetary gear 81, and each inner transition planetary gear 81 is meshed with an outer transition planetary gear 82. The primary sun gear 2 and the secondary internal gear ring 7 are coaxially aligned. Therefore, the inner transition planetary gears 81 and the outer transition planetary gears 82 are evenly spaced along the circumference in the secondary internal gear ring, ensuring the reliability of power transmission from the primary sun gear 2 through the primary planetary gears 3, the secondary planetary gears 4, the inner transition planetary gears 81, and the outer transition planetary gears 82 to the planet carrier 5.

[0026] The outer diameters of the inner transition planetary gear 81 and the outer transition planetary gear 82 are both greater than the outer diameter of the second-stage planetary gear 4 and smaller than the outer diameter of the first-stage planetary gear 3. The second-stage planetary gear 4, the inner transition planetary gear 81 meshing with the second-stage planetary gear 4, and the outer transition planetary gear 82 meshing with the inner transition planetary gear 81 are arranged in a triangular pattern. As shown in the figure, the secondary planetary gear 4, the inner transition planetary gear 81 corresponding to the secondary planetary gear 4, and the outer transition planetary gear 82 corresponding to the inner transition planetary gear 81 mesh sequentially. The outer transition planetary gear 82 and the secondary planetary gear 4 mesh on both sides of the inner transition planetary gear 81. The centers of the secondary planetary gear 4, the inner transition planetary gear 81, and the outer transition planetary gear 82 are not aligned sequentially, but are distributed in a triangle. This distribution can make full use of the radial space between the secondary planetary gear 4 and the secondary internal gear ring 7. Thus, without increasing the outer diameter of the module housing 6, two sets of inner and outer transition planetary gears can be added between the secondary planetary gear 4 and the secondary internal gear ring 7. The outer diameter of the secondary planetary gear 4 remains unchanged, and the outer diameter of the secondary internal gear ring 7 is extended to be equal to the outer diameter of the mold housing to increase the pitch circle ratio K2 between the secondary internal gear ring 7 and the secondary planetary gear 4, thereby achieving an effective increase in the speed ratio under the same outer diameter constraint.

[0027] The secondary planetary gear 4 is supported by a rigid shaft fixed within the planet carrier 5, while the inner transition planetary gear 81 and outer transition planetary gear 82 are both supported by flexible shafts that can float radially within the planet carrier 5. The rigid shaft support within the planet carrier 5 ensures high rigidity for the meshing of the primary planetary gear 3 and the primary sun gear 2, guaranteeing basic transmission accuracy. Furthermore, to address rigid interference and off-center loading issues caused by the addition of transition planetary gears, accumulated chain drive errors, and phase errors of multiple sets of double gears, both the inner and outer transition planetary gears 81 and 82 are supported by flexible shafts. This allows both gears to float radially within the planet carrier 5 with the movement of the flexible shafts, enabling fine-tuning of their positions. When a secondary planetary gear 4 becomes overloaded due to premature contact with the corresponding inner transition planetary gear 81 caused by a phase error, the flexible shafts can provide additional support. The flexible deformation of the flexible shaft creates radial floating, which drives the inner transition planetary gear 81 to fine-tune its position and absorb phase errors. This allows the load to be flexibly distributed to other meshing gear sets (the second-stage planetary gear 4, the corresponding inner transition planetary gear 81, and the corresponding outer transition planetary gear 82 form a meshing gear set). This effectively solves the problems of rigid interference and off-center loading, enabling the transition planetary gears to have precise compliance in the tangential direction of the meshing force. This forms a "rigid-flexible-flexible" step-by-step transmission and adaptive load-sharing structure. The radial floating of the flexible shaft maintains low-clearance meshing between meshing gears after gear wear, effectively reducing the impact of gear wear on control accuracy and ensuring the control accuracy of the planetary transmission structure during use.

[0028] The planetary carrier 5 is provided with a rigid shaft 51 for assembling the first-stage planetary gear 3 and the second-stage planetary gear 4, an inner flexible shaft 52 for assembling the inner transition planetary gear 81, and an outer flexible shaft 53 for assembling the outer transition planetary gear 82. Both ends of the rigid shaft 51 are fixed to the planetary carrier 5. One end of the inner flexible shaft 52 is fixed to the planetary carrier 5, and the other end is a free end that is suspended in the air. One end of the outer flexible shaft 53 is fixed to the planetary carrier 5, and the other end is a free end that is suspended in the air. The inner flexible shaft 52 provides flexible support for the inner transition planetary gear 81, and the outer flexible shaft 53 provides flexible support for the outer transition planetary gear 82. Both the inner and outer flexible shafts are fixed at one end and suspended at the other. When the corresponding gears on the inner and outer flexible shafts are overloaded, the load will be transferred to the flexible shaft, forming radial floating of the flexible shaft. The inner transition planetary gear 81 meshes with the second-stage planetary gear 4 and the outer transition planetary gear 82 at the same time, and the outer transition planetary gear meshes with the fixed second-stage internal gear ring 7, forming a "rigid-flexible-flexible" step-by-step transmission and adaptive load-sharing structure. Through the cooperation of the inner and outer flexible shafts, the transmission structure can automatically adapt to manufacturing errors and phase errors of the double planetary gears. The rigid shaft ensures the basic rigidity of force transmission, while the flexible shaft acts as an "error compensator," enabling multiple sets of meshing gears (the second-stage planetary gear 4, the corresponding inner transition planetary gear 81, and the corresponding outer transition planetary gear 82 form a set of meshing gears) to evenly distribute the load, significantly reducing vibration and noise, and improving life and reliability.

[0029] The planetary carrier 5 includes a first disk 9, a second disk 10 coaxially aligned with the first disk 9, and a connecting post 11 connecting the first disk 9 and the second disk 10. The connecting post 11 is evenly spaced along the outer circumference of the first disk. A first-stage planetary gear 3, a second-stage planetary gear 4, an inner transition planetary gear 81, and an outer transition planetary gear 82 are all housed within the planetary carrier 5. The first-stage planetary gear 3 is located closer to the first disk 9, and the second-stage planetary gear 4 is located closer to the second disk 10. A rigid shaft 51 is fixed at both ends to the first disk 9 and the second disk 10, respectively. An inner flexible shaft 52 and an outer flexible shaft 52 are fixed to the second disk 10 and are separated from the first disk 9, not in contact with it. The first and second-stage planetary gears, as well as the inner and outer transition planetary gears, are all housed within the planetary carrier 5, resulting in a compact structure that fully utilizes the radial space of the module housing without increasing the outer diameter of the module housing. The planetary carrier 5 is formed by connecting disk 1 9, disk 2 10 and connecting column 11. The secondary planetary gear 4, inner transition planetary gear 81 and outer transition planetary gear 82 are all installed in the planetary carrier 5. The two ends of the rigid shaft 51 are fixed to disk 1 and disk 2 respectively. One end of the inner and outer flexible shafts 52 is fixed to disk 2 10, and the other end is a suspended free end that does not contact disk 1 9, ensuring that the inner and outer flexible shafts will form an adaptive radial floating within the planetary carrier 5 due to the increase of load.

[0030] The inner flexible shaft 52 and the outer flexible shaft 53 both include a pin 11 and a bushing 12 that is fitted on the pin 11 and can swing on the pin 11. One end of the pin 11 is fixed to the disk 10, and the other end is a free end that is suspended. The inner transition planetary gear 81 is assembled on the bushing 12 of the inner flexible shaft 52 through a needle roller bearing, and the outer transition planetary gear 82 is assembled on the bushing 12 of the outer flexible shaft 53 through a needle roller bearing. As shown in the figure, one end of the pin 11 is fixed to the disk 10, and the other end is a free end that is suspended. When the load on the transition planetary gear on the bushing 12 increases, the radial force causes the bushing 12 to swing on the pin 11 and transmits the load to the pin 11. This causes the pin 11 to elastically deform with the swing of the bushing 12, forming a radial float. This fine-tunes the position of the transition planetary gear on the bushing 12, so that the meshing gears maintain a low clearance meshing during operation. Both the inner flexible shaft 52 and the outer flexible shaft 53 will form an adaptive radial float with the change of load, adjusting the uneven load caused by different tolerances of the meshing gear sets, so that each meshing gear set bears a uniform load.

[0031] The pin 11 consists of an interference section 111 with a free end and a fixed section 112 fixed to the second disk 10. The diameter of the interference section 111 is larger than the diameter of the fixed section 112. The bushing 12 is interference-fitted with the interference section 111 and clearance-fitted with the fixed section 112, and is separated from the second disk 10 and does not contact it. The interference section 111 is used to assemble the bushing 12. The fixed section 112 is fixed to the second disk 10 and clearance-fitted with the bushing 12, allowing the bushing 12 to swing on the pin 11. One end of the pin 11 is fixed, and the other end is free. The fixed section 112 has a smaller diameter, which allows it to swing radially with changes in radial load during the bearing process. This enables the inner and outer flexible shafts to float radially, allowing the inner and outer transition planetary gears to adaptively adjust their positions according to changes in load. This adjusts the uneven load caused by different tolerances in each meshing gear set, achieving uniform load distribution in each meshing gear set.

[0032] The secondary internal gear ring 7 is integrally formed with the module housing 6, and the outer diameter of the secondary internal gear ring 7 is equal to the outer diameter of the module housing 6. By extending the outer diameter of the secondary internal gear ring 7 to be equal to the outer diameter of the mold housing, the radial space of the mold housing 6 is fully utilized. Multiple sets of transition planetary gears 8 are added between the secondary planetary gear 4 and the secondary internal gear ring 7 to effectively increase the pitch ratio K2 between the secondary internal gear ring 7 and the secondary planetary gear 4. This achieves an effective increase in the speed ratio under the constraint of the module housing of the same size, improves the structural compactness of the joint module, meets the requirements of robot joint drive for a high speed ratio, and increases the power density of the joint module.

[0033] The technical solutions of the embodiments of the present invention have been fully described above with reference to the accompanying drawings. It should be noted that the described embodiments are only a part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A high-ratio, low-backlash NW planetary joint module, comprising a motor, a primary sun gear connected to the motor, primary planetary gears meshing with the primary sun gear, a secondary planetary gear coaxially fixed with the primary planetary gears and having an outer diameter smaller than the primary planetary gears, a planet carrier assembling the primary and secondary planetary gears, and a secondary internal gear ring fixed to the module housing, characterized in that: Multiple sets of transition planetary gears are set between the secondary planetary gears and the secondary internal gear ring. The number of transition planetary gears in each set is equal to the number of secondary planetary gears. The multiple sets of transition planetary gears mesh sequentially from the inside to the outside. The innermost set of transition planetary gears meshes with the secondary planetary gears one by one, and the outermost set of transition planetary gears meshes with the secondary internal gear ring.

2. The high speed ratio, low clearance NW planetary joint module according to claim 1, characterized in that: The multiple sets of transition planetary gears consist of an inner transition planetary gear set and an outer transition planetary gear set located outside the inner transition planetary gear set. The inner transition planetary gear set consists of inner transition planetary gears that mesh one-to-one with the secondary planetary gears, and the outer transition planetary gear set consists of outer transition planetary gears that mesh one-to-one with the inner transition planetary gears. The outer transition planetary gears mesh with the secondary internal gear ring. Both the inner and outer transition planetary gears are evenly spaced along the circumference in the secondary internal gear ring.

3. The high speed ratio, low clearance NW planetary joint module according to claim 2, characterized in that: The outer diameters of the inner and outer transition planetary gears are both greater than the outer diameter of the second-stage planetary gear and smaller than the outer diameter of the first-stage planetary gear. The second-stage planetary gear, the inner transition planetary gear meshing with the second-stage planetary gear, and the outer transition planetary gear meshing with the inner transition planetary gear are arranged in a triangular pattern.

4. The high speed ratio, low clearance NW planetary joint module according to claim 1, characterized in that: The secondary planetary gears are supported by rigid shafts fixed within the planet carrier, while the inner and outer transition planetary gears are both supported by flexible shafts that can float radially within the planet carrier.

5. The high speed ratio, low clearance NW planetary joint module according to claim 4, characterized in that: The planetary carrier is provided with a rigid shaft for assembling the first-stage planetary gear and the second-stage planetary gear, an inner flexible shaft for assembling the inner transition planetary gear, and an outer flexible shaft for assembling the outer transition planetary gear. Both ends of the rigid shaft are fixed to the planetary carrier. One end of the inner flexible shaft is fixed to the planetary carrier, and the other end is a free end that is suspended in the air. One end of the outer flexible shaft is fixed to the planetary carrier, and the other end is a free end that is suspended in the air.

6. The high speed ratio, low backlash NW planetary joint module according to claim 5, characterized in that: The planetary carrier includes a first disk, a second disk coaxially aligned with the first disk, and a connecting column connecting the first disk and the second disk. The connecting column is evenly spaced along the outer circumference of the first disk. The first-stage planetary gear, the second-stage planetary gear, the inner transition planetary gear, and the outer transition planetary gear are all disposed in the planetary carrier. The first-stage planetary gear is located on the side where the first disk is located, and the second-stage planetary gear is located on the side where the second disk is located. The two ends of the rigid shaft are fixed to the first disk and the second disk, respectively. The inner flexible shaft and the outer flexible shaft are fixed to the second disk, and are separated from the first disk and do not contact it.

7. The high speed ratio, low backlash NW planetary joint module according to claim 6, characterized in that: Both the inner and outer flexible shafts include a pin and a bushing fitted on the pin and capable of swinging on the pin. One end of the pin is fixed to the second disk, and the other end is a free end that is suspended. The inner transition planetary gear is assembled on the bushing of the inner flexible shaft through a needle roller bearing, and the outer transition planetary gear is assembled on the bushing of the outer flexible shaft through a needle roller bearing.

8. The high speed ratio, low backlash NW planetary joint module according to claim 7, characterized in that: The pin consists of an interference section with a free end and a fixed section fixed to the second disk. The diameter of the interference section is larger than the diameter of the fixed section. The bushing is interference-fitted with the interference section and clearance-fitted with the fixed section, and is separated from the second disk and does not contact it.

9. The high speed ratio, low backlash NW planetary joint module according to claim 1, characterized in that: The secondary internal gear ring is integrally formed with the module housing, and the outer diameter of the secondary internal gear ring is equal to the outer diameter of the module housing.

Images