Planetary reducer for joint

Abstract

The invention relates to a planetary reducer for a joint, belongs to the technical field of transmission machinery, and solves the problems that a planetary reducer in the prior art is large in overall weight and low in torque density. The planetary gear train comprises two stages of planetary gear trains, the first-stage planetary gear train comprises four first-stage planetary gears, and the second-stage planetary gear train comprises five second-stage planetary gears; the first-stage sun gear serves as a power input part, the output end of the first-stage planet carrier is coaxially and fixedly connected with the second-stage sun gear, and the second-stage planet carrier serves as a final output component of the speed reducer. The multi-planet differential design of the first-stage four planet gears and the second-stage five planet gears is adopted, the weight of the whole machine is reduced, and the torque density can be increased by about 15%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transmission machinery, and in particular to a joint planetary reducer. BACKGROUND

[0002] With the rapid development of robot technology, more stringent requirements are put forward for the performance indicators of planetary reducers, especially torque density, running stability, and service life. However, the existing planetary reducer technology mainly has the following problems and shortcomings:

[0003] (1) Small torque density

[0004] Traditional planetary reducers, especially high-load models, use steel for key components such as planetary carriers, gears, and housings. Although the all-steel structure has strong strength, it has a large density, resulting in a heavy overall machine. Under the given external dimensions (volume constraint), it is difficult to significantly increase the output torque by simply adding material or size, i.e., it is difficult to improve the torque density.

[0005] (2) Uneven load distribution

[0006] In multi-planet (usually ≥4) planetary transmission, due to the combined effects of gear manufacturing errors (deviations in pitch, tooth shape, tooth direction, etc.), planetary pin hole position errors, bearing clearances, and part deformation under load, it is difficult to ensure that all planet gears evenly bear the load during transmission. This can cause some planet gears and their tooth surfaces to bear local overload far exceeding the average value, while other planet gears may be underloaded, making the actual load-carrying capacity of the reducer much lower than the design value under theoretical uniform load, and accelerating local wear and shortening the service life.

[0007] (3) Conflict between torsional stiffness and weight

[0008] In order to achieve lightweight, if the planetary carrier and other components are simply lightened (such as using lightweight materials but not fully optimizing the structure), it is easy to cause large elastic deformation (increased deflection) of the carrier when it bears torque. This deformation will change the actual meshing posture of the planet gears, leading to deterioration of the gear meshing line load distribution (such as increased eccentric load and edge effect), which not only affects the transmission accuracy, but also may exacerbate vibration, noise, and wear. SUMMARY

[0009] In view of the above analysis, the present application aims to provide a joint planetary reducer to solve the problem of large overall weight and low torque density of the existing planetary reducer (especially the traditional structure using a steel carrier) due to material and design limitations.

[0010] The application provides a joint planetary reducer, comprising two-stage planetary systems, wherein the first-stage planetary system comprises a first-stage sun wheel, a first-stage planet carrier and four first-stage planet wheels, and the second-stage planetary system comprises a second-stage sun wheel, a second-stage planet carrier and five second-stage planet wheels; the first-stage sun wheel is a power input element, the output end of the first-stage planet carrier is fixedly connected with the second-stage sun wheel in a coaxial manner, and the second-stage planet carrier is a final output component of the reducer.

[0011] Further, the first-stage planetary system further comprises a first-stage ring gear fixedly connected with the shell of the joint planetary reducer.

[0012] Further, the first-stage sun wheel is connected with the input shaft through a spline or interference fit.

[0013] Further, the first-stage planet wheel is connected with the first-stage planet carrier through a first-stage needle bearing and a first-stage planet wheel shaft.

[0014] Further, the second-stage planetary system further comprises a second-stage ring gear fixedly connected with the shell of the joint planetary reducer.

[0015] Further, the second-stage planet wheel is connected with the second-stage planet carrier through a second-stage needle bearing and a second-stage planet wheel shaft.

[0016] Further, the first-stage sun wheel, the first-stage planet wheel, the first-stage ring gear, the second-stage sun wheel, the second-stage planet wheel and the second-stage ring gear are all made of steel; the first-stage planet carrier and the second-stage planet carrier are made of an aviation aluminum alloy.

[0017] Further, the first-stage planet carrier and the second-stage planet carrier are both of an integral hollow box type structure.

[0018] Further, the second-stage planet carrier comprises a second-stage front end face flange, a second-stage rear end face flange and a second-stage force bearing column, and the second-stage force bearing column is located between the second-stage front end face flange and the second-stage rear end face flange.

[0019] Further, the diameter of the second-stage front end face flange is smaller than that of the second-stage rear end face flange.

[0020] Compared with the prior art, the application can at least realize one of the following beneficial effects:

[0021] (1) The present application adopts a multi-planet differential design of first stage 4 planetary gears and second stage 5 planetary gears, the first stage adopts a smaller number of planetary gears (4), mainly undertakes the primary speed reduction task, and plays a certain role in inertia buffering, and adapts to a higher input rotating speed; the second stage adopts a larger number of planetary gears (for example, 5), effectively disperses the load acting on the tooth surface and the planetary gear bearing by increasing the number of teeth participating in meshing at the same time, reduces the local contact stress, and the torque density can be increased by about 15%, and the total carrying capacity is improved.

[0022] (2) The planet carrier of the present application adopts 7075-T6 high-strength aluminum alloy, and the structure of the planet carrier is optimized, adopts a hollow box structure, greatly reduces the weight of the planet carrier, and ensures sufficient stiffness and strength. The mass reduction of the planet carrier as the core rotating part directly reduces the rotational inertia of the entire speed reducer.

[0023] (3) The first and second stage planet carriers of the present application are composed of front and rear two end flanges with different diameters, and a plurality of first and second force columns uniformly distributed along the circumference connecting the two flanges. Compared with the rib plate structure of the same mass, this structure has higher torsional resistance. This makes the overall torsional deformation when bearing large torque be suppressed to the minimum, ensuring the accuracy and stability of the relative position of the first and second stage planetary gears.

[0024] In the present application, the above-mentioned technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification or will be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained through the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0026] Figure 1 is a cross-sectional view of the joint planetary reducer;

[0027] Figure 2 is a three-dimensional structure diagram of the joint planetary reducer;

[0028] Figure 3 is an exploded view of the joint planetary reducer;

[0029] Figure 4 is a second stage front end flange structure diagram of the second stage planet carrier of the joint planetary reducer, wherein (a) is a three-dimensional view, and (b) is a cross-sectional view;

[0030] Figure 5 Fig. 2 is a schematic diagram of the flange structure of the rear end face of the secondary planetary carrier of the articulated planetary reducer, wherein (a) is a three-dimensional view, and (b) is a sectional view;

[0031] Figure 6 Fig. 3 is a schematic diagram of the overall structure of the secondary planetary carrier of the articulated planetary reducer, wherein (a) is a three-dimensional view, and (b) is a sectional view;

[0032] Figure 7 Fig. 4 is a schematic diagram of the gear composite modification scheme in Example 2;

[0033] Figure 8 Fig. 5 is a schematic diagram of the finite element analysis results of the planetary carrier of the articulated planetary reducer, wherein (b) is a partial enlarged schematic diagram of (a).

[0034] Reference signs:

[0035] 1 - primary sun gear; 2 - primary planet gear; 3 - primary ring gear; 4 - primary needle bearing; 5 - primary planetary carrier; 51 - primary front end face flange; 52 - primary rear end face flange; 53 - primary load-bearing column; 6 - secondary sun gear; 7 - secondary planet gear; 8 - secondary ring gear; 9 - secondary needle bearing; 10 - secondary planetary carrier; 101 - secondary front end face flange; 102 - secondary rear end face flange; 103 - secondary load-bearing column; 11 - first bearing; 12 - second bearing; 13 - third bearing. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which form a part of this application. The accompanying drawings and the embodiments together illustrate the principles of the present application, but do not limit the scope of the present application.

[0037] Example 1

[0038] One specific embodiment of the present application, as shown in Figure 1 , Figure 2 , Figure 3 discloses an articulated planetary reducer comprising two-stage planetary systems, wherein the primary planetary system comprises four primary planet gears 2, and the secondary planetary system comprises five secondary planet gears 7; the primary sun gear 1 serves as a power input member, the output end of the primary planetary carrier 5 is coaxially and fixedly connected with the secondary sun gear 6, and the secondary planetary carrier 10 serves as the final output member of the reducer.

[0039] According to the technical scheme of the embodiment, the first stage adopts a small number of planetary gears (for example, 4) and mainly undertakes the primary speed reduction task and plays a certain inertia buffering role, and is suitable for a higher input rotating speed; the second stage adopts a larger number of planetary gears (for example, 5), and realizes multi-tooth bearing by increasing the number of teeth participating in meshing at the same time, so as to further amplify the torque on the basis of the first stage speed reduction and improve the total bearing capacity.

[0040] The first stage (4 planetary gears) is a high-speed and high-efficiency preprocessing stage, is directly connected with a high-speed input source (such as a servo motor), and can realize optimal high-speed adaptability and efficiency. Compared with more planetary gears, 4 first-stage planetary gears 2 can effectively reduce the rotational inertia, reduce the centrifugal force and lubrication loss during high-speed operation, thereby improving the transmission efficiency, reducing the temperature rise, and providing an optimized speed-reduced and stable input for the second stage.

[0041] The second stage (5 planetary gears) is a torque amplification stage based on a high-rigidity frame. In the traditional technology, it is considered almost impossible to realize reliable uniform loading of 5 second-stage planetary gears 7 on a lightweight carrier. The second-stage planetary carrier 10 structure of the present application realizes reliable uniform loading of 5 second-stage planetary gears 7.

[0042] The first-stage planetary system further includes a first-stage ring gear 3, which is fixedly connected with the outer shell. The first-stage sun gear 1 is a power input member, which is usually connected with an input shaft (such as a motor shaft) through a spline or interference fit.

[0043] The first-stage planetary gears 2 are connected with the first-stage planetary carrier 5 through first-stage needle bearings 4 and first-stage planetary gear shafts, and are uniformly distributed between the first-stage sun gear 1 and the first-stage ring gear 3. In the embodiment, 4 first-stage planetary gears 2 are adopted. Each first-stage planetary gear 2 is installed on a planetary gear shaft through a needle bearing 4, and the planetary gear shaft is fixed to the first-stage planetary carrier 5. The first-stage planetary carrier 5 is used to bear the first-stage planetary gears 2 and their bearings. The output end of the first-stage planetary carrier 5 is coaxially and rigidly connected with the second-stage sun gear 6 or formed as an integral structure.

[0044] The input end of the second-stage sun gear 6 in the second-stage planetary system is connected with the first-stage planetary carrier 5 to receive the motion and torque from the first-stage planetary system.

[0045] The second-stage planetary system further includes a second-stage ring gear 8, which is fixedly connected with the outer shell. The second-stage planetary gears 7 are connected with the second-stage planetary carrier 10 through second-stage needle bearings 9 and second-stage planetary gear shafts. In the embodiment, 5 second-stage planetary gears 7 are adopted, which are uniformly distributed between the second-stage sun gear 6 and the second-stage ring gear 8. Each second-stage planetary gear 7 is installed on a planetary gear shaft through a needle bearing 9, and the planetary gear shaft is fixed to the second-stage planetary carrier 10. The second-stage planetary carrier 10 is used to bear the second-stage planetary gears 7 and their bearings, and serves as the final output component of the reducer.

[0046] The first sun gear 1, the first planet gear 2, the first ring gear 3, the second sun gear 6, the second planet gear 7 and the second ring gear 8 are all made of steel, preferably high-quality steel such as 20CrMnMo, which is subjected to precise heat treatment to obtain high tooth surface hardness and good core toughness, thereby ensuring high wear resistance and contact fatigue strength.

[0047] The first planet carrier 5 and the second planet carrier 10 are made of aerospace aluminum alloy, preferably 7075-T6 aluminum alloy. The blank is subjected to precise forging or high-quality bar machining to ensure material performance. The topological optimization design scheme described above is used for precise numerical control machining to form a lightweight and high-stiffness structure. After machining, a coating is applied to improve surface hardness, wear resistance and corrosion resistance.

[0048] The planet pin is preferably made of 52100 chromium steel, which is subjected to overall heat treatment and precise grinding to ensure its strength, hardness and fitting accuracy. The load path of the joint planetary reducer provided in the embodiment is as follows: power is input to the first sun gear 1, transmitted to the first ring gear 3 (fixed to the housing) and the first planet carrier 5 through the first planet gear 2. The first planet carrier 5 drives the second sun gear 6 to rotate, which in turn transmits power to the second ring gear 8 (fixed to the housing) and the second planet carrier 10 through the second planet gear 7. Finally, the second planet carrier 10 outputs torque.

[0049] The first planet carrier 5 and the second planet carrier 10 are both hollow box structures.

[0050] As shown in Figure 4 , Figure 5 , Figure 6 The second planet carrier 10 includes a second front end face flange 101, a second rear end face flange 102 and a second load-bearing column 103, which is located between the second front end face flange 101 and the second rear end face flange 102. The diameter of the second front end face flange 101 is smaller than that of the second rear end face flange 102. This arrangement makes the overall structure easy to assemble and meets the requirement of a small assembly space for the joint. Figure 8 The length of the second load-bearing column 103 between the two flanges is determined according to the results of finite element analysis to ensure that the stress concentration at the root of the load-bearing column is minimized under normal working conditions, as shown in

[0051] There are multiple second load-bearing columns 103, which are evenly distributed along the circumference of the second planet carrier 10. There are preferably five second load-bearing columns 103. The cross section of the second load-bearing column 103 is approximately an isosceles triangle, in which the base coincides with the outer circumference of the second front end face flange 101 and is an outwardly convex arc; the top is directed toward the center of the second front end face flange 101, and the two waists of the triangle are inwardly concave arcs. A second planet gear 7 is arranged between adjacent two load-bearing columns.

[0052] The cross section of the secondary force bearing column 103 is designed according to the principle of not interfering with the operation of the secondary planetary gear 7 and maximizing the area, i.e. the arc of the two sides of the approximate isosceles triangle, the center of the circle and the radius are set to meet the motion of the secondary planetary gear 7 while maximizing the cross section area. This setting can maximize the volume of the secondary force bearing column 103 to improve the torsional and bending resistance of the structure. The secondary planetary carrier 10 of the embodiment can minimize the relative torsional angle of the two end faces when subjected to the rated torque by adopting the secondary force bearing column 103 with this structure, which ensures that the secondary planetary carrier 10 has high overall rigidity when transmitting large torque, and inhibits the positional misalignment of the planetary gears caused by torsional deformation from the source.

[0053] Further, since the planetary pin holes are arranged in the secondary front end face flange 101 and the secondary rear end face flange 102, the relative torsional angle of the secondary front end face flange 101 and the secondary rear end face flange 102 is minimized, so that the radial displacement and axial tilt deformation of all planetary pin holes are relatively small under the rated torque. In addition, the scheme of the embodiment can meet the requirements of minimizing the mass, avoiding the working area of the first-order natural frequency, keeping the maximum stress below the material fatigue allowable stress, and meeting the manufacturing constraints of CNC machining process.

[0054] In the preferred scheme, the secondary force bearing column 103 is divided into a front half and a rear half, the front half is integrally formed with the secondary front end face flange 101, and the rear half is integrally formed with the secondary rear end face flange 102. The cross-sectional shape and distribution position of the front half and the rear half are completely consistent. The end face of the front half is provided with a positioning protrusion, and the end face of the rear half is provided with a positioning through hole matched with the positioning protrusion, which is a stepped hole. The middle part of the positioning protrusion is provided with a threaded hole. During assembly, the positioning protrusion is inserted into the positioning through hole and abuts against the stepped surface. The screw is inserted into the positioning through hole from the other side of the secondary front end face flange 101 and then into the threaded hole in the positioning protrusion, realizing the fixed connection between the secondary front end face flange 101 and the secondary rear end face flange 102.

[0055] This setting of the secondary force bearing column 103 into two parts and integrally forming the two parts with one end face flange makes the secondary planetary carrier 10 as a whole similar to "digging away" most of the non-bearing material between the two planetary gears from a solid cylindrical body, forming a larger space, and the remaining part naturally constitutes the bearing column with this cross section. It is different from the scheme of "adding" stiffeners on a flat plate. Compared with the ribbed plate structure of the same mass, the overall hollow box type structure has higher torsional resistance. This makes the overall torsional deformation of the structure inhibited to the minimum when subjected to large torque, ensuring the accuracy and stability of the relative position of the secondary planetary gears 7.

[0056] Further, the height d of the front half of the secondary load-bearing column 103 is in the range of 2mm≤d≤8mm. By setting the height in this way, the assembly difficulty can be reduced while ensuring the overall torsion resistance.

[0057] The primary planet carrier 5 has a structure similar to the secondary planet carrier 10, and reference is made to Figure 3 The primary planet carrier 5 includes a primary front end face flange 51, a primary rear end face flange 52, and primary load-bearing columns 53 located between the primary front end face flange 51 and the primary rear end face flange 52. The diameter of the primary front end face flange 51 is less than or equal to the diameter of the primary rear end face flange 52. The primary planet carrier 5 is provided with primary planet gears 2 between two adjacent primary load-bearing columns 53.

[0058] The primary rear end face flange 52 and the secondary sun gear 6 are in an integrated structure. The integrated structure has better strength and stronger torque transmission capability, which can effectively reduce the axial gear and improve the safety and reliability.

[0059] Further, reference is made to Figure 1 The joint planetary reducer of the embodiment further includes a first bearing 11, a second bearing 12, and a third bearing 13. The first bearing 11 is axially arranged at the left end of the primary sun gear 1 and radially located between the primary sun gear 1 and the primary rear end face flange 52. The second bearing 12 is axially arranged at the left end of the secondary sun gear 6 and radially located between the secondary sun gear 6 and the secondary rear end face flange 102. The third bearing 13 is axially arranged at the left end of the primary planet carrier 5 and radially located outside the primary planet carrier 5. The above-mentioned three bearing support forms can improve the motion stability of the joint planetary reducer and shorten the overall axial size.

[0060] The specific working principle of the embodiment is as follows: the power is transmitted from the input end (such as the motor shaft) to the primary sun gear 1, the primary sun gear 1 drives the primary planet gears 2 to make planetary motion in the primary ring gear 3, and the revolution motion of the primary planet gears 2 is output through the primary planet carrier 5. The primary planet carrier 5 is coaxially rigidly connected or integrally designed with the secondary sun gear 6, and transmits the motion and torque to the second stage. The secondary sun gear 6 drives the second stage planet gears 7 to make planetary motion in the secondary ring gear 8, and the revolution motion of the second stage planet gears 7 is output through the secondary planet carrier 10, and finally the power is output externally through the output shaft.

[0061] Compared with existing technologies, the planetary reducer for joints provided in this embodiment, with its extreme torsional stiffness / weight ratio, ensures that the relative positions of the five planetary gears remain highly stable even when subjected to enormous torque. This reducer achieves rated output torque with a 15% increase in torque density, despite its compact size and lightweight design. Compared to traditional all-steel planetary reducers of the same specifications, this represents a significant improvement in torque density and weight reduction, validating the effectiveness and superiority of the present invention.

[0062] Example 2

[0063] This embodiment 2 relates to a planetary reducer for joints. Based on embodiment 1, for a gear system with multiple planetary gears (≥5 gears), the tooth profile and tooth direction of the second planetary gear 7 are modified according to the actual load and deformation.

[0064] Among them, see Figure 7 Tooth profile modification includes progressive edge trimming at the tooth tip and root. The amount of trimming is determined based on the meshing impact speed and tooth pitch deviation; preferably, the trimming amount is 3-5 micrometers. Tooth profile modification can smooth the entry and exit of the gear pair, reducing meshing impact noise; it also increases the tolerance for circumferential positional errors of the second planetary gear 7, ensuring smooth meshing even if the installation position of a second planetary gear 7 is slightly ahead or behind, without rigid impact, thereby achieving load sharing of the second planetary gear 7.

[0065] Simulation calculations show that by modifying the tooth profile, the load distribution among the five second planetary gears 7 can be made more uniform, improving the effective contact area of ​​the tooth surface, the overlap ratio and the smoothness of meshing, and making the load unevenness coefficient Kγ among the second planetary gears 7 ≤ 1.1.

[0066] Because the planetary carrier of this invention has an "integral hollow box structure" with extremely high torsional stiffness, its main deformation mode under load is a small and uniform overall tilt, rather than complex, nonlinear local bending. This deformation behavior is highly stable and predictable. Therefore, tooth profile modification can be achieved by superimposing tooth profile drum-shaped modification and tooth profile helix angle compensating modification.

[0067] Among them, tooth-direction drum-shaped modification refers to modification in the tooth width direction, with a modification amount of 3-5 micrometers, used to address general, unavoidable assembly errors and bearing clearance. Tooth-direction helix angle compensation modification refers to machining a helix angle compensation amount of opposite direction and equal size on the gear based on the average tilt angle of the planetary pin holes generated by the "integral hollow box structure" planetary carrier under rated torque, obtained from finite element analysis.

[0068] In this embodiment 2, all gears are subjected to a precision manufacturing process including rough machining, heat treatment and high-precision grinding. In the gear finishing stage, the gears are machined according to the composite modification scheme described above (including tooth direction and tooth profile modification). The high-precision gear detection equipment is used to ensure the accurate implementation of the modification parameters to achieve the expected load uniform distribution effect, as shown in Figure 8

[0069] The composite modification scheme of the gears in this embodiment, combined with the "monolithic hollow box structure" design in embodiment 1, through the composite modification of the gears, the gears in embodiment 2 and the rotating frame achieve dynamic compensation, which improves the problems of uneven load distribution of multiple planetary gears and local stress concentration caused by manufacturing, assembly errors and load deformation. The composite gear modification method can compensate for the sudden change of engagement stiffness and tooth bending deformation, reduce the meshing impact noise, transmission error, meshing impact and tooth tip / root interference, and compensate for the partial load to make the load distribution more uniform. By improving the contact spot pattern, the edge contact, stress concentration and load capacity reduction problems in the gear meshing process are solved. Finally, under the rated torque, the "micro-deformed rotating frame" and the "micro-compensated gear" are combined to form an ideal meshing close to zero error, so that the five planetary gears 7 can share the load and maximize their load-carrying potential.

[0070] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.​

Claims

1. A planetary reducer for joints, characterized in that, It includes a two-level planetary system. The first-level planetary system includes a first-level sun gear, a first-level planetary carrier, and four first-level planetary gears. The second-level planetary system includes a second-level sun gear, a second-level planetary carrier, and five second-level planetary gears. The first-level sun gear serves as the power input component. The output end of the first-level planetary carrier is coaxially and fixedly connected to the second-level sun gear. The second-level planetary carrier serves as the final output component of the reducer.

2. The planetary reducer for joints according to claim 1, characterized in that, The first-stage planetary system also includes a first-stage gear ring, which is fixedly connected to the outer shell of the joint planetary reducer.

3. The planetary reducer for joints according to claim 2, characterized in that, The primary sun gear is connected to the input shaft via a spline or interference fit.

4. The planetary reducer for joints according to claim 2 or 3, characterized in that, The first-stage planetary gears are connected to the first-stage planetary carrier via a first-stage needle roller bearing and a first-stage planetary gear shaft.

5. The planetary reducer for joints according to claim 1, characterized in that, The secondary planetary system also includes a secondary gear ring, which is fixedly connected to the outer shell of the joint planetary reducer.

6. The planetary reducer for joints according to claim 5, characterized in that, The secondary planetary gear is connected to the secondary planetary carrier via a secondary needle roller bearing and a secondary planetary gear shaft.

7. The planetary reducer for joints according to claim 1, characterized in that, The first-stage sun gear, first-stage planet gear, first-stage ring gear, second-stage sun gear, second-stage planet gear, and second-stage ring gear are all made of steel; the first-stage planet carrier and the second-stage planet carrier are made of aerospace aluminum alloy.

8. The planetary reducer for joints according to claim 7, characterized in that, Both the primary planetary carrier and the secondary planetary carrier are integral hollow box-shaped structures.

9. The planetary reducer for joints according to claim 8, characterized in that, The secondary planetary carrier includes a secondary front face flange, a secondary rear face flange, and a secondary load-bearing column, with the secondary load-bearing column located between the secondary front face flange and the secondary rear face flange.

10. The planetary reducer for joints according to claim 9, characterized in that, The diameter of the secondary front flange is smaller than the diameter of the secondary rear flange.

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