Heavy duty speed reducer

Abstract

The utility model relates to the technical field of speed reducer discloses a heavy load speed reducer, including the gear reduction gearbox, primary planetary reduction gearbox and secondary planetary reduction gearbox of connection installation together, the inside of gear reduction gearbox is provided with gear reduction group, the inside of primary planetary reduction gearbox is provided with primary planetary reduction group, the inside of secondary planetary reduction gearbox is provided with secondary planetary reduction group, the input end rotation of gear reduction gearbox is installed with input shaft, the output end rotation of secondary planetary reduction gearbox is installed with output cylinder, and input shaft links with output cylinder through gear reduction group, primary planetary reduction group, secondary planetary reduction group, and the first planetary reduction group and secondary planetary reduction group are connected through the butt -joint structure between. The utility model discloses through two stage offset compensation measures, can effectively compensate the vibration and running deviation on the working machine main shaft, guarantees the reliability of torque transmission, reduces the vibration on heavy load speed reducer, the abrasion between parts and noise.

Description

Technical Field

[0001] This utility model relates to the field of speed reducer technology, specifically a heavy-duty speed reducer. Background Technology

[0002] Existing heavy-duty speed reducers often employ a combination of one gear reducer and two planetary gear reducers to achieve speed reduction and torque increase, thereby providing sufficient operating power for heavy-duty working machines (such as plate feeders).

[0003] To ensure the reliability of torque transmission between the heavy-duty reducer and the working machine, the output end of the heavy-duty reducer must be hollow and cylindrical, connected to the main shaft of the working machine through a shrink sleeve, relying on friction to transmit torque, axial force, and load. Therefore, vibration on the main shaft of the working machine and offset error during the operation of the main shaft will be transmitted to the heavy-duty reducer, causing the components inside the heavy-duty reducer, especially the two planetary gear sets, to be prone to uneven loading or even offset, resulting in aggravated vibration transmission, increased noise, and severe tooth surface wear under heavy-duty conditions.

[0004] In summary, to solve the above problems, a heavy-duty speed reducer is proposed. Utility Model Content

[0005] The purpose of this invention is to provide a heavy-duty speed reducer with two-stage offset compensation measures, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: A heavy-duty speed reducer includes a gear reducer, a first-stage planetary reducer, and a second-stage planetary reducer connected and mounted together. The gear reducer contains a gear reduction assembly, the first-stage planetary reducer contains a first-stage planetary reducer assembly, and the second-stage planetary reducer contains a second-stage planetary reducer assembly. An input shaft is rotatably mounted at the input end of the gear reducer, and an output cylinder is rotatably mounted at the output end of the second-stage planetary reducer. The input shaft is connected to the output cylinder via the gear reduction assembly, the first-stage planetary reducer assembly, and the second-stage planetary reducer assembly. The first-stage and second-stage planetary reducer assemblies are connected by a mating structure. The mating structure includes an internal spline, a limiting block, and a drum-shaped external spline. The output end of the first-stage planetary reducer assembly has a fixedly mounted internal spline, which is internally fitted with a drum-shaped external spline. A stepped hole is centrally located at the output end of the first-stage planetary reducer assembly, and a limiting block is installed within the stepped hole by a snap ring. The limiting block abuts against the input end of the first-stage planetary reducer assembly and the drum-shaped external spline.

[0007] Specifically, the gear reduction assembly includes a second driven spur gear and a second driving gear meshing together, a driven bevel gear and a driving bevel gear meshing together, and a first driving gear and a first driven spur gear meshing together; a first rotating shaft, a second rotating shaft, and a third rotating shaft are rotatably mounted inside the gear reduction box; a driving bevel gear is integrally formed at one end of the input shaft that extends into the gear reduction box; the driven bevel gear and the first driving gear are fixedly mounted on the first rotating shaft; the second driving gear and the first driven spur gear are fixedly mounted on the second rotating shaft; and the second driven spur gear is fixedly mounted on the third rotating shaft.

[0008] Specifically, the first-stage planetary gearbox includes a flange and an internal gear ring. There are two flanges, which are symmetrically arranged at both ends of the internal gear ring. The flanges and the internal gear ring are assembled into a whole by connecting them with screws.

[0009] Specifically, the first-stage planetary reduction gear assembly includes a first planet carrier, a first sun gear, and first planet gears. The first planet carrier is located inside the internal gear ring. The first sun gear is integrally formed on the end of the third rotating shaft and is located inside the first planet carrier. Fourth rotating shafts are uniformly fixedly installed on the circumference of the first planet carrier. Each of the fourth rotating shafts is rotatably mounted with a first planet gear. The first planet gears are meshed between the internal gear ring and the first sun gear, and the end face of the first sun gear abuts against the limiting block.

[0010] Specifically, the second-stage planetary reduction gearbox includes an annular internal toothed belt, a second planetary carrier, a second sun gear, and second planetary gears. The annular internal toothed belt is integrally formed inside the second-stage planetary reduction gearbox. The second planetary carrier is located inside the annular internal toothed belt. A centering hole is provided at the center of the second planetary carrier. A centering shaft is inserted into the centering hole by clearance fit. The second sun gear is fixedly installed on the centering shaft. The drum-shaped toothed external spline is integrally formed with the second sun gear. Fifth rotating shafts are evenly fixedly installed on the circumference of the second planetary carrier. Each of the fifth rotating shafts is rotatably mounted with a second planetary gear. The second planetary gears are meshed between the annular internal toothed belt and the second sun gear.

[0011] Specifically, the limiting block includes a stepped shaft body, a through hole, and a cross-shaped groove. The stepped shaft body is a three-stage stepped shaft with a large diameter in the middle and small diameters at both ends. A through hole is coaxially opened at the center of the stepped shaft body, and a cross-shaped groove is opened at both ends of the stepped shaft body.

[0012] Compared with the prior art, the beneficial effects of this utility model are: One end of the centering shaft is inserted into the centering hole through clearance fit, which allows the integrated drum-shaped external spline and the second sun gear to have adaptive movement space, achieving first-level offset compensation in the radial and / or axial directions between the output cylinder and the internal spline. The position of the first planetary carrier is determined by the radial support of multiple first planetary gears and the axial support of the limiting block, so that the first planetary carrier has the function of floating load distribution, realizing adaptive clearance adjustment, and forming a two-level offset compensation between the drum-shaped tooth external spline and the first sun gear. The two-stage offset compensation measures described above can effectively compensate for vibration and running deviation on the spindle of the machine tool, ensuring the reliability of torque transmission and reducing vibration, wear between parts, and noise in the heavy-duty reducer, thereby improving the stability and service life of the torque transmission of the heavy-duty reducer. Attached Figure Description

[0013] Figure 1 This is a top view schematic cross-sectional view of the structure of this utility model; Figure 2 This is a top view schematic cross-sectional view of the internal structure of the gear reducer in this utility model; Figure 3 This is a top view schematic cross-sectional view of the internal structure of the first-stage planetary gearbox in this utility model; Figure 4 This is a top view schematic cross-sectional view of the internal structure of the two-stage planetary gearbox in this utility model; Figure 5 This is an enlarged view of the structure of the limiting block in this utility model.

[0014] In the diagram: 1. Second-stage planetary gearbox; 2. Connecting structure; 21. Internal spline; 22. Drum-shaped external spline; 23. Limiting block; 231. Stepped shaft body; 232. Through hole; 233. Cross-shaped groove; 3. First-stage planetary gearbox; 31. Flange; 32. Internal gear ring; 4. Gear reducer; 5. Gear reducer assembly; 51. Second driven spur gear; 52. Second driving gear; 53. Driven bevel gear; 54. Driving bevel gear; 55. First driving gear; 56. First driven spur gear; 6. Input shaft; 7. First-stage planetary reducer assembly; 71. First planet carrier; 72. First sun gear; 73. First planet gear; 8. Second-stage planetary reducer assembly; 81. Annular internal gear belt; 82. Second planet carrier; 83. Second sun gear; 84. Second planet gear; 9. Output cylinder. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] Example content: Please see Figure 1 , Figure 2 , Figure 3 This invention provides a heavy-duty speed reducer, comprising a gear reducer 4, a first-stage planetary reducer 3, and a second-stage planetary reducer 1 bolted together, which facilitates assembly and provides an installation base for subsequent components.

[0017] The gear reducer 4 has a gear reduction group 5 inside, the first-stage planetary reducer 3 has a first-stage planetary reducer group 7 inside, and the second-stage planetary reducer 1 has a second-stage planetary reducer group 8 inside. The input end of the gear reducer 4 (i.e., the front side of the gear reducer 4) is rotatably mounted with an input shaft 6, and the output end of the second-stage planetary reducer 1 (i.e., the right side of the second-stage planetary reducer 1) is rotatably mounted with an output cylinder 9. The input shaft 6 is connected to the output cylinder 9 via the gear reduction group 5, the first-stage planetary reducer group 7, and the second-stage planetary reducer group 8.

[0018] The gear reduction group 5 works with the input shaft 6 to perform initial deceleration and direction conversion. The first-stage planetary reduction group 7 and the second-stage planetary reduction group 8 achieve torque amplification through planetary gear transmission. The three-stage transmission path ensures continuous power transmission under heavy load conditions. The overall structure is compact and the load-bearing capacity is significantly improved.

[0019] The inner circumference of the output cylinder 9 is sloped and connected to the main shaft of the working machine (such as a plate feeder) through a shrink sleeve. It has no coupling or keyway, good concentricity, large torque transmission, and is suitable for heavy-duty working conditions.

[0020] The first-stage planetary deceleration group 7 and the second-stage planetary deceleration group 8 are connected by a docking structure 2.

[0021] Please see Figure 3 The structure of docking structure 2: The docking structure 2 includes an internal spline 21, a limiting block 23, and a drum-shaped external spline 22. The output end of the first-stage planetary reducer 7 is fixedly installed with the internal spline 21, and the drum-shaped external spline 22 is internally meshed with the internal spline 21. A stepped hole is centrally opened at the output end of the first-stage planetary reducer 7, and the limiting block 23 is installed in the stepped hole by means of a snap ring. The limiting block 23 abuts against the input end of the first-stage planetary reducer 7 and the drum-shaped external spline 22.

[0022] The meshing of the internal spline 21 and the external spline 22 with the drum-shaped teeth not only achieves torque transmission, but the design of the drum-shaped teeth can also compensate for axial and / or radial transmission deviations, preventing vibration and offset errors on the working machine from being transmitted to the first-stage planetary reduction group 7 via the second-stage planetary reduction group 8, thus ensuring the smooth operation of the reducer.

[0023] Here, "and / or" means three cases: axial, radial, and axial and radial.

[0024] Please see Figure 2The structure of gear reduction group 5: The gear reduction assembly 5 includes a second driven spur gear 51 and a second driving gear 52 meshing together, wherein the diameter of the second driven spur gear 51 is larger than that of the second driving gear 52; a driven bevel gear 53 and a driving bevel gear 54 meshing together, wherein the diameter of the driven bevel gear 53 is larger than that of the driving bevel gear 54; and a first driving gear 55 and a first driven spur gear 56 meshing together, wherein the diameter of the first driven spur gear 56 is larger than that of the first driving gear 55.

[0025] The gear reducer 4 has a first shaft, a second shaft, and a third shaft rotatably mounted inside it via multiple pairs of tapered roller bearings, giving the first shaft, second shaft, and third shaft sufficient load-bearing capacity. The input shaft 6 extends into the gear reducer 4 and has an integrally formed drive bevel gear 54. The first shaft is fixedly mounted with a driven bevel gear 53 and a first drive gear 55. The second shaft is fixedly mounted with a second drive gear 52 and a first driven spur gear 56. The third shaft is fixedly mounted with a second driven spur gear 51.

[0026] The meshing of the driving bevel gear 54 and the driven bevel gear 53 enables the change of the power input direction of the external variable frequency motor (90° steering) and completes the first deceleration. The meshing of the first driving gear 55 and the first driven spur gear 56 performs the second deceleration. The meshing of the second driving gear 52 and the second driven spur gear 51 completes the third deceleration, and finally transmits the torque to the first-stage planetary reduction gear 7.

[0027] Please see Figure 3 The structure of the first-stage planetary gearbox 3: The first-stage planetary gearbox 3 includes a flange 31 and an internal gear ring 32. There are two flanges 31, which are symmetrically arranged at both ends of the internal gear ring 32. The flanges 31 and the internal gear ring 32 are connected by screws to form a whole. The spliced ​​form of the first-stage planetary gearbox 3 reduces the difficulty of manufacturing, facilitates assembly, and is easy to disassemble and maintain.

[0028] Please see Figure 3 The structure of the first-stage planetary deceleration group 7: The first-stage planetary reduction gear 7 includes a first planet carrier 71, a first sun gear 72, and a first planet gear 73. The first planet carrier 71 is located inside the internal gear ring 32. The first sun gear 72 is integrally formed on the end of the third rotating shaft and is located inside the first planet carrier 71. A fourth rotating shaft is uniformly fixedly installed on the circumference of the first planet carrier 71. The first planet gear 73 is rotatably installed on each of the fourth rotating shafts. The first planet gear 73 is meshed between the internal gear ring 32 and the first sun gear 72. The end face of the first sun gear 72 abuts against the limiting block 23.

[0029] The first planetary carrier 71 has a slot on its circumferential side to avoid the first planetary gear 73. The first planetary gear 73 consists of three evenly distributed circumferentially to achieve uniform load distribution. The first sun gear 72 serves as the input end. By moving the first planetary gear 73 along the internal gear ring 32, deceleration can be achieved. The right side of the first planetary carrier 71 serves as the output end to output torque.

[0030] The position of the first planetary carrier 71 is determined by the radial support of multiple first planetary gears 73 and the axial support of the limiting block 23, so that the first planetary carrier 71 also has a certain adaptive activity space and the ability to float and distribute load, which is used to compensate for transmission deviation and ensure that the power torque on the first sun gear 72 can be stably transmitted to the drum-shaped tooth external spline 22.

[0031] Please see Figure 4 The structure of the second-stage planetary deceleration group 8: The second-stage planetary reduction gear 8 includes an annular internal toothed belt 81, a second planetary carrier 82, a second sun gear 83, and a second planetary gear 84. The annular internal toothed belt 81 is integrally formed inside the second-stage planetary reduction gearbox 1. The second planetary carrier 82 is located inside the annular internal toothed belt 81. A centering hole is provided at the center of the second planetary carrier 82. A centering shaft is inserted into the centering hole by clearance fit. The second sun gear 83 is fixedly installed on the centering shaft. The drum-shaped toothed external spline 22 is integrally formed with the second sun gear 83.

[0032] The second planetary carrier 82 has three evenly distributed second planetary gears 84, which are rotatably mounted on the circumference of the second planetary carrier 82. The second planetary gears 84 are meshed between the annular internal toothed belt 81 and the second sun gear 83. The second planetary gears 84 are three evenly distributed on the circumference to achieve uniform load distribution. The second sun gear 83 serves as the input end. By moving the second planetary gears 84 along the annular internal toothed belt 81, speed reduction can be achieved. The right side of the second planetary carrier 82 serves as the output end, transmitting torque to the output cylinder 9.

[0033] The centering shaft is installed in the centering hole by means of clearance fit, so that the integrated drum-shaped external spline 22 and the second sun gear 83 have an adaptive range of movement. When the second planetary carrier 82 has axial and / or radial transmission deviation due to vibration on the output cylinder 9, the way the centering hole is connected to the second planetary carrier 82 can reduce the range of movement of the drum-shaped external spline 22 with the second planetary carrier 82, and avoid the transmission of vibration and offset errors to the first planetary carrier 71.

[0034] Please see Figure 5 The structure of limit block 23: The limiting block 23 includes a stepped shaft body 231, a through hole 232 and a cross-shaped groove 233. The stepped shaft body 231 is a three-stage stepped shaft with a large diameter in the middle and small diameters at both ends. A through hole 232 is coaxially opened at the center of the stepped shaft body 231, and a cross-shaped groove 233 is opened at both ends of the stepped shaft body 231.

[0035] An annular groove for engaging the retaining ring is provided in the stepped hole. After the retaining ring is installed, the stepped shaft in the middle of the limiting block 23 can be engaged in the stepped hole, so that the limiting block 23 is limited between the first sun gear 72 and the drum-shaped external spline 22. At the same time, it can determine the axial position of the first planetary carrier 71. Furthermore, the contact between the limiting block 23 and the drum-shaped external spline 22 can prevent the centering shaft from disengaging from the centering hole. With a certain amount of room for movement, the torque transmission of the two-stage planetary reduction gear can be ensured, and tooth surface wear caused by uneven loading can also be avoided.

[0036] Among them, the through hole 232 and the cross-shaped groove 233 serve as lubrication channels to ensure that the components have sufficient lubrication protection when they move relative to each other, thereby reducing wear between the components.

[0037] The working principle of this embodiment: During use, the interior of this heavy-duty reducer is filled with lubricating oil, and the input shaft 6 of the heavy-duty reducer is connected to the output shaft of the frequency converter motor. The output cylinder 9 of the heavy-duty reducer is connected to the main shaft of the working machine through a shrink sleeve.

[0038] Torque transmission process in gear reducer 4: The power of the variable frequency motor is input into the gear reduction group 5 through the input shaft 6. The driving bevel gear 54 meshes with the driven bevel gear 53 to achieve a 90° turn and complete the first deceleration. The first driving gear 55 meshes with the first driven spur gear 56 to perform the second deceleration. The second driving gear 52 meshes with the second driven spur gear 51 to complete the third deceleration. The torque is then transmitted to the first-stage planetary reduction group 7.

[0039] Torque transmission process in the first-stage planetary gearbox 3: In the first-stage planetary reduction gear 7, the first sun gear 72 serves as the input end, and the first planet gear 73 travels along the internal gear ring 32 to achieve deceleration. The first planet carrier 71 serves as the output end, transmitting torque to the docking structure 2. In the docking structure 2, the internal spline 21 meshes with the external spline 22 of the drum-shaped tooth to transmit torque. The drum-shaped tooth design can compensate for the axial and / or radial deviation caused by the second sun gear 83 side, and can also prevent the vibration and offset error on the working machine side from being further transmitted to the first planet carrier 71, ensuring the reliability of torque transmission.

[0040] Meanwhile, the limiting block 23 is fixed in the stepped hole by a snap ring, axially supported between the first sun gear 72 and the drum-shaped external spline 22, and defines the position of the first planetary carrier 71. The cross-shaped groove 233 and the through hole 232 form a lubrication channel, which facilitates the lubricating oil to enter the gap between the first planetary carrier 71 and the first sun gear 72, and between the first planetary carrier 71 and the drum-shaped external spline 22, thereby reducing the wear of the parts.

[0041] Compared to the traditional method, the first planetary carrier 71 does not rely on a pair of bearings for rotational support. Instead, its position is determined by the radial limitation of multiple first planetary gears 73 and the axial limitation of the limiting block 23, giving the first planetary carrier 71 a certain amount of room to move and the ability to offset compensation and floating load sharing during operation.

[0042] Torque transmission process in the second-stage planetary gearbox 1: In the second-stage planetary reduction gear 8, the drum-shaped external spline 22 is integrally formed with the second sun gear 83. The second sun gear 83 drives the second planet gear 84 to move along the annular internal tooth belt 81 to achieve deceleration. The second planet carrier 82 outputs torque to the output cylinder 9, which ultimately provides running power to the working machine.

[0043] Among them, the second sun gear 83 on the central axis also has a certain amount of room for movement, and works together with the drum-shaped tooth external spline 22 to perform offset compensation.

[0044] It achieves functions such as high load-bearing capacity, continuous power transmission, and offset compensation, with a compact overall structure that is suitable for heavy-duty working conditions.

[0045] Implementation parameters of heavy-duty speed reducer: Rated speed of input shaft 6: 750-1500 r / min; The torque of output cylinder 9 is 80,000 N·m; Commonly used nominal speed ratios: i = 270 / 310 / 350 / 390 / 440 / 490 / 610.

[0046] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0047] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A heavy-duty speed reducer, comprising a gear reducer (4), a first-stage planetary reducer (3), and a second-stage planetary reducer (1) connected and mounted together, characterized in that: The gear reducer (4) is equipped with a gear reducer assembly (5), the first-stage planetary reducer (3) is equipped with a first-stage planetary reducer assembly (7), and the second-stage planetary reducer (1) is equipped with a second-stage planetary reducer assembly (8). The input end of the gear reducer (4) is rotatably mounted with an input shaft (6), and the output end of the second-stage planetary reducer (1) is rotatably mounted with an output cylinder (9). The input shaft (6) is connected to the output cylinder (9) via the gear reducer assembly (5), the first-stage planetary reducer assembly (7), and the second-stage planetary reducer assembly (8). The first-stage planetary reducer assembly (7) and the second-stage planetary reducer assembly (8) are connected by a docking structure (2). The docking structure (2) includes an internal spline (21), a limiting block (23), and a drum-shaped external spline (22). The output end of the first-stage planetary reducer (7) is fixedly installed with an internal spline (21). The internal spline (21) is internally meshed with a drum-shaped external spline (22). The output end of the first-stage planetary reducer (7) has a stepped hole in the center. The limiting block (23) is installed in the stepped hole by means of a snap ring. The limiting block (23) abuts against the input end of the first-stage planetary reducer (7) and the drum-shaped external spline (22).

2. The heavy-duty speed reducer according to claim 1, characterized in that: The gear reduction group (5) includes a second driven spur gear (51) and a second driving gear (52) meshing together, a driven bevel gear (53) and a driving bevel gear (54) meshing together, and a first driving gear (55) and a first driven spur gear (56) meshing together. The gear reducer (4) is rotatably mounted with a first shaft, a second shaft and a third shaft. The input shaft (6) extends into the gear reducer (4) and is integrally formed with a driving bevel gear (54). The first shaft is fixedly mounted with a driven bevel gear (53) and a first driving gear (55). The second shaft is fixedly mounted with a second driving gear (52) and a first driven spur gear (56). The third shaft is fixedly mounted with a second driven spur gear (51).

3. A heavy-duty speed reducer according to claim 2, characterized in that: The first-stage planetary gearbox (3) includes a flange (31) and an internal gear ring (32). There are two flanges (31) and they are symmetrically arranged at both ends of the internal gear ring (32). The flanges (31) and the internal gear ring (32) are assembled into a whole by connecting them with screws.

4. A heavy-duty speed reducer according to claim 3, characterized in that: The first-stage planetary reduction gear (7) includes a first planet carrier (71), a first sun gear (72) and a first planet gear (73). The first planet carrier (71) is located inside the internal gear ring (32). The first sun gear (72) is integrally formed on the end of the third rotating shaft and is located inside the first planet carrier (71). The first planetary carrier (71) has a fourth rotating shaft evenly fixed on its circumference. The fourth rotating shaft is rotatably mounted with a first planetary gear (73). The first planetary gear (73) is meshed between the internal gear ring (32) and the first sun gear (72). The end face of the first sun gear (72) abuts against the limiting block (23).

5. A heavy-duty speed reducer according to claim 4, characterized in that: The second-stage planetary reduction gear (8) includes an annular internal toothed belt (81), a second planetary carrier (82), a second sun gear (83), and a second planetary gear (84). The annular internal toothed belt (81) is integrally formed inside the second-stage planetary reduction gearbox (1). The second planetary carrier (82) is located inside the annular internal toothed belt (81). A centering hole is provided at the center of the second planetary carrier (82). A centering shaft is inserted into the centering hole by clearance fit. The second sun gear (83) is fixedly installed on the centering shaft. The drum-shaped toothed external spline (22) is integrally formed with the second sun gear (83). The second planetary carrier (82) has a fifth rotating shaft evenly fixedly installed on its circumference. The fifth rotating shaft is rotatably mounted with a second planetary gear (84). The second planetary gear (84) is meshed between the annular inner toothed belt (81) and the second sun gear (83).

6. A heavy-duty speed reducer according to claim 1, characterized in that: The limiting block (23) includes a stepped shaft body (231), a through hole (232) and a cross-shaped groove (233). The stepped shaft body (231) is a three-stage stepped shaft with a large diameter in the middle and small diameters at both ends. A through hole (232) is coaxially opened at the center of the stepped shaft body (231), and a cross-shaped groove (233) is opened at both ends of the stepped shaft body (231).

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