Double-layer welded planet carrier and manufacturing method thereof

Abstract

The invention discloses a double-layer welded planet carrier and a manufacturing method thereof. The planet carrier comprises a planet carrier front plate, a stepped shaft, an end plate and a planet carrier rear plate, front plate stepped shaft holes are formed in the circumference of the planet carrier front plate, the stepped shaft comprises a first small-diameter shaft section, a large-diameter shaft section and a second small-diameter shaft section, rear plate stepped shaft holes are formed in the circumference of the planet carrier rear plate, the front plate stepped shaft holes correspond to the rear plate stepped shaft holes in a one-to-one mode, and the first small-diameter shaft section is in interference fit with the front plate stepped shaft holes. The second small-diameter shaft section is in interference fit with the rear plate stepped shaft hole, the peripheral face of the first small-diameter shaft section is welded to the hole wall of the end, away from the first shaft shoulder, of the front plate stepped shaft hole, and the peripheral face of the second small-diameter shaft section is welded to the hole wall of the end, away from the second shaft shoulder, of the rear plate stepped shaft hole. Therefore, the bearing capacity of the double-layer planet carrier is high.

Description

Technical Field

[0001] The present invention relates to a planetary carrier and a manufacturing method thereof, and belongs to the field of planetary gear transmission devices, in particular to a double-layer welded planetary carrier and a manufacturing method thereof. Background Art

[0002] In mechanical transmission systems, the planetary carrier is the core load-bearing component of the planetary reducer. Its structural strength and manufacturing precision directly affect the reducer's service life and transmission efficiency. For heavy-duty planetary reducers, a double-layer planetary carrier is often used to improve load-bearing capacity. Currently, traditional double-layer planetary carriers rely mainly on casting or forging processes. The casting process is formed through a mold. During this process, the molten metal cools and shrinks, resulting in shrinkage holes, which leads to poor load-bearing capacity of the double-layer planetary carrier. The forging process is formed through forging, but uneven metal flow can lead to inconsistent structural properties of the planetary carrier, resulting in internal defects and similarly poor load-bearing capacity.

[0003] Chinese patent application No. 201720024936.7, filed on January 10, 2017, discloses a novel double-walled integral planetary carrier, comprising a circular panel, a sun gear mounting hole provided at the center of the circular panel, a circular annular recessed groove provided around the sun gear mounting hole, fan-shaped spokes provided on the outer side of the circular annular recessed groove, and planet gear mounting holes provided within the fan-shaped spokes. The lower end of the circular panel is connected to a bottom panel via a connecting block, and the bottom panel is connected to a bottom cover via bolts. The bottom cover is provided with a stabilizing shaft. Although the patent increases the stability of the equipment through the double-walled integral design, it still has the following disadvantages: The double-layer planetary carriers of this design are fixed by a movable connection, which cannot provide sufficient rigidity and stability, resulting in poor load-bearing capacity of the double-layer planetary carriers.

[0004] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of this patent application, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects and problems of the poor load-bearing capacity of the double-layer planetary carrier in the prior art, and to provide a double-layer welded planetary carrier with higher load-bearing capacity and a manufacturing method thereof.

[0006] To achieve the above objectives, the technical solution of the present invention is: a double-layer welded planet carrier and a manufacturing method thereof, wherein the double-layer welded planet carrier comprises a planet carrier front plate, a stepped shaft, an end plate, and a planet carrier rear plate; One side of the planet carrier front plate is uniformly provided with internal splines along the circumference, the other side of the planet carrier front plate is provided with a right central inner hole, and a plurality of through-going front plate stepped shaft holes are provided on the circumference of the planet carrier front plate; The stepped shaft includes a first small-diameter shaft segment, a large-diameter shaft segment, and a second small-diameter shaft segment connected in sequence, wherein the diameter and length of the first small-diameter shaft segment and the second small-diameter shaft segment are the same, and the diameters of the first small-diameter shaft segment and the second small-diameter shaft segment are smaller than the diameter of the large-diameter shaft segment; the portion where the first small-diameter shaft segment and the large-diameter shaft segment are connected is a first shaft shoulder, and the portion where the second small-diameter shaft segment and the large-diameter shaft segment are connected is a second shaft shoulder; A through rear plate center hole is provided at the center of the planet carrier rear plate, and a plurality of through rear plate stepped shaft holes are provided on the circumference of the planet carrier rear plate; The front plate stepped shaft hole corresponds to the rear plate stepped shaft hole one by one, the first small diameter shaft section is interference fit with the front plate stepped shaft hole, and the second small diameter shaft section is interference fit with the rear plate stepped shaft hole; the first shaft shoulder is tightly fitted with one side of the planetary carrier front plate, and the second shaft shoulder is tightly fitted with one side of the planetary carrier rear plate; the lengths of the first small diameter shaft section and the second small diameter shaft section are respectively greater than the thickness of the corresponding planetary carrier front plate and planetary carrier rear plate at the circumference, the outer circumferential surface of the first small diameter shaft section is welded to the hole wall of the front plate stepped shaft hole away from the first shaft shoulder, and the outer circumferential surface of the second small diameter shaft section is welded to the hole wall of the rear plate stepped shaft hole away from the second shaft shoulder; the end plate is interference fit with the right center inner hole; a number of through planetary gear pin shaft mounting holes are opened at corresponding positions on the circumference of the planetary carrier front plate and the planetary carrier rear plate.

[0007] The hole wall of the front plate stepped shaft hole away from the first shaft shoulder is a front inclined hole wall, and the front straight hole wall is connected to the front inclined hole wall; the hole wall of the rear plate stepped shaft hole away from the second shaft shoulder is a rear inclined hole wall, and the rear straight hole wall is connected to the rear inclined hole wall; The angle between the front inclined hole wall and the outer peripheral surface of the first small-diameter shaft segment is the front welding chamfer, and the angle between the rear inclined hole wall and the outer peripheral surface of the second small-diameter shaft segment is the rear welding chamfer.

[0008] In the radial direction perpendicular to the axis of the stepped shaft, the maximum distance between the front inclined hole wall and the outer peripheral surface of the first small-diameter shaft segment, and the maximum distance between the rear inclined hole wall and the outer peripheral surface of the second small-diameter shaft segment are both the welding width L0; The axial length L3 of the weld on the outer circumference of the first small-diameter shaft segment and the axial length L4 of the weld on the outer circumference of the second small-diameter shaft segment are both greater than or equal to twice the welding width L0.

[0009] The minimum distance L1 between the front straight hole wall of the front plate stepped shaft hole and the outer edge of the planetary carrier front plate is not less than 4 times the welding width L0; the minimum distance L2 between the rear straight hole wall of the rear plate stepped shaft hole and the outer edge of the planetary carrier rear plate is not less than 4 times the welding width L0.

[0010] The interference fit between the first small-diameter shaft segment and the stepped shaft hole of the front plate is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the stepped shaft hole of the front plate; the interference fit between the second small-diameter shaft segment and the stepped shaft hole of the rear plate is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the stepped shaft hole of the rear plate; The straight section of the front plate stepped shaft hole is a cylindrical hole section corresponding to the front straight hole wall; the straight section of the rear plate stepped shaft hole is a cylindrical hole section corresponding to the rear straight hole wall.

[0011] The manufacturing method comprises the following steps: Step 1: First, heat treat the raw materials of the planetary carrier front plate and the planetary carrier rear plate, and then perform precision lathing on the heat-treated raw materials to obtain the planetary carrier front plate with a right center inner hole and the planetary carrier rear plate with a rear plate center hole. The right center inner hole is the same size as the rear plate center hole. Step 2: First, perform a centering operation on the right central inner hole and the rear plate central hole to align the corresponding end faces of the planetary carrier front plate and the planetary carrier rear plate to form a pre-assembled component. Then, a plurality of through pin holes are machined on the circumference of the pre-assembled component, and positioning is performed using interference pins corresponding to the pin holes to obtain a positioned assembly. Then, a plurality of through inner holes are machined on the circumferential surface of the positioned assembly to the same number as the planetary gears. Step 3: First, split the assembled parts after positioning into the planetary carrier front plate and the planetary carrier rear plate, and then process the internal spline along the circumference of the left inner side of the planetary carrier front plate; Step 4: First, strengthen the raw material of the stepped shaft, and then perform precision turning on the strengthened raw material of the stepped shaft to obtain a stepped shaft that meets the design requirements; Step 5: Install the two ends of the stepped shaft into the through inner holes of the planet carrier front plate and the planet carrier rear plate by cold assembly, so that the two ends of the stepped shaft extend out of the end surfaces of the planet carrier front plate and the planet carrier rear plate respectively; Step 6: Weld the outer circumference of one end of the stepped shaft to the hole wall of the through hole of the planet carrier front plate, and the outer circumference of the other end of the stepped shaft to the hole wall of the through hole of the planet carrier rear plate respectively; Step 7: Evenly distributed planetary gear pin mounting holes are machined on the circumferential surfaces of the planetary carrier front plate and the planetary carrier rear plate welded together as above, and then the end plate is interference fit into the right center inner hole of the planetary carrier front plate to complete the double-layer welded planetary carrier manufacturing.

[0012] In the second step, processing the through inner holes on the circumferential surface of the assembly after positioning to be the same number as the planetary gears means: processing a number of through inner holes on the circumferential surface of the assembly after positioning according to the number of planetary gears, wherein the through inner holes located on the front plate of the planetary carrier are the front plate stepped shaft holes, and the through inner holes located on the rear plate of the planetary carrier are the rear plate stepped shaft holes; processing the hole wall of the front plate stepped shaft hole away from the mating surface of the two plates to be the front inclined hole wall, and processing the hole wall of the rear plate stepped shaft hole away from the mating surface of the two plates to be the rear inclined hole wall.

[0013] In the fourth step, the strengthening treatment of the stepped shaft raw material refers to: performing a tempering or quenching operation on the stepped shaft raw material; In the fourth step, obtaining a stepped shaft that meets the design requirements means: through precision turning, the two ends of the stepped shaft are respectively processed into a first small-diameter shaft section and a second small-diameter shaft section, and the middle part of the stepped shaft is processed into a large-diameter shaft section, the connection between the large-diameter shaft section and the first small-diameter shaft section is processed into a first shaft shoulder, and the connection between the large-diameter shaft section and the second small-diameter shaft section is processed into a second shaft shoulder; the diameter and length of the first small-diameter shaft section and the second small-diameter shaft section are the same, the outer circle size accuracy of the first small-diameter shaft section and the second small-diameter shaft section is higher than h6, and the coaxiality form and position tolerance grade of the first small-diameter shaft section and the second small-diameter shaft section is not less than grade 6; the diameter of the large-diameter shaft section is larger than the diameters of the first small-diameter shaft section and the second small-diameter shaft section, and the axial length of the large-diameter shaft section is consistent; the interference of the first small-diameter shaft section and the second small-diameter shaft section with the front plate stepped shaft hole and the rear plate stepped shaft hole is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the front plate stepped shaft hole and the rear plate stepped shaft hole.

[0014] In the sixth step, the outer peripheral surface of one end of the stepped shaft and the hole wall of the through-hole of the front plate of the planetary carrier, and the outer peripheral surface of the other end of the stepped shaft and the hole wall of the through-hole of the rear plate of the planetary carrier respectively refer to: using laser welding to weld the outer peripheral surface of the first small-diameter shaft segment in the stepped shaft and the front inclined hole wall of the stepped shaft hole of the front plate, and using laser welding to weld the outer peripheral surface of the second small-diameter shaft segment in the stepped shaft and the rear inclined hole wall of the stepped shaft hole of the rear plate.

[0015] In the second step, the centering operation in the right central inner hole and the rear plate central hole is as follows: installing a positioning ring in the right central inner hole and the rear plate central hole for centering, wherein the positioning ring is L-shaped; In the second step, positioning by using an interference pin corresponding to the pin hole refers to: passing the interference pin corresponding to the pin hole through the pin hole for positioning.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The first and second smaller diameter shaft sections are connected to each other to form a first shoulder, and the second smaller diameter shaft section is connected to the first and second smaller diameter shaft sections to form a second shoulder. The planetary carrier rear plate is provided with a rear plate stepped shaft hole, and the front plate stepped shaft hole corresponds to the rear plate stepped shaft hole one by one. When in use, the planetary carrier front plate first receives external input power to drive the stepped shaft with interference fit to rotate, and the stepped shaft then drives the planetary carrier rear plate to rotate synchronously to realize power transmission. During the power transmission process, the radial force generated by the operation of the planetary gear is borne by the large diameter shaft section in the middle of the stepped shaft. Its larger diameter forms a stable support base, effectively disperses the radial force by expanding the force-bearing area, avoids local stress concentration, thereby improving the radial bearing capacity, and the planetary gear The axial force generated by the operation is carried by the stepped matching structure of the first shaft shoulder and the planetary carrier front plate, and the second shaft shoulder and the planetary carrier rear plate. This structure constrains the axial displacement by mechanical limit, ensuring the stable transmission of the axial load. At the same time, the first small diameter shaft section at both ends of the stepped shaft and the front plate stepped shaft hole, and the second small diameter shaft section and the rear plate stepped shaft hole adopt interference fit and are supplemented by welding process, forming a double constraint mechanism. The interference fit ensures that there is no relative displacement between the shaft and the hole under static and dynamic loads. The welding process further strengthens the connection stiffness, so that the planetary carrier front plate, the planetary carrier rear plate and the stepped shaft form a rigid whole, significantly improving the structural rigidity to withstand higher loads. In addition, during the manufacturing process, the center centering and interference pin positioning process are used to complete the precise processing of the front plate stepped shaft hole and the rear plate stepped shaft hole in one processing, ensuring the dimensional accuracy and coaxiality of the hole system, reducing the eccentric load problem caused by assembly error, and further optimizing the bearing performance of the planetary carrier from the perspective of structural accuracy. Therefore, the bearing capacity of the present invention is relatively high.

[0017] 2. In a double-layer welded planetary carrier and its manufacturing method of the present invention, a centering operation is first performed on the right central inner hole and the rear plate central hole, so that the corresponding end faces of the planetary carrier front plate and the planetary carrier rear plate are fitted together to form a pre-assembled part, and then a plurality of through pin holes are machined on the circumference of the pre-assembled part, and positioning is performed by interference pins corresponding to the pin holes to obtain a positioned assembled part, and then a through inner hole is machined on the circumferential surface of the positioned assembled part; when in use, a centering operation is performed on the right central inner hole and the rear plate central hole by a positioning ring, so that the line The corresponding end faces of the star carrier front plate and the planet carrier rear plate are tightly fitted and the central axes are strictly aligned, ensuring that the relative positions of the two in the radial and axial directions are fixed and unchanged, and a unified reference coordinate system is established for subsequent processing. On this basis, the pin holes are processed and the interference pins are used for positioning, which further locks the relative positions of the planet carrier front plate and the planet carrier rear plate in the circumferential direction, avoids the rotation deviation of the two plates in the circumferential direction, and forms a stable positioning constraint. Then, when the through-holes (i.e. the stepped shaft holes of the front plate and the stepped shaft holes of the rear plate) are processed on the circumferential surface of the assembly after positioning, due to the planet The relative positions of the carrier front plate and the planetary carrier rear plate are rigidly fixed through the aforementioned positioning process. The through-holes can be machined simultaneously based on the same datum, directly ensuring that the axes of the corresponding holes on the front and rear plates are completely coaxial and that the dimensions and shape of the through-holes are consistent. Finally, after the stepped shaft is welded to the carrier front and rear plates to form the integral structure, the planetary pin mounting holes are machined. Because the two plates have been welded together into a rigid entity, and the initial positioning and machining steps have ensured basic accuracy, the mounting holes can be positioned and formed directly in a single step using the welded assembly as a datum. This ensures the circumferential distribution accuracy (such as equal division and concentricity) of all planetary pin mounting holes, as well as the dimensional accuracy of the planetary pin mounting holes themselves. This avoids the error accumulation caused by structural deformation or changes in the positioning datum in traditional step-by-step machining, thereby improving the accuracy of the double-layer planetary carrier. This high-precision double-layer planetary carrier ensures precise fit between components, evenly distributes loads, and reduces stress concentration and assembly errors, maximizing the coordinated load-bearing capacity of each component and thereby improving the overall load-bearing capacity. Therefore, the present invention not only has a higher load-bearing capacity but also has a higher precision.

[0018] 3. In a double-layer welded planetary carrier and a manufacturing method thereof of the present invention, the angle between the front bevel hole wall and the outer peripheral surface of the first small-diameter shaft segment is the front welding chamfer, and the angle between the rear bevel hole wall and the outer peripheral surface of the second small-diameter shaft segment is the rear welding chamfer. In the radial direction perpendicular to the axis of the stepped shaft, the maximum distances between the front bevel hole wall and the outer peripheral surface of the first small-diameter shaft segment and between the rear bevel hole wall and the outer peripheral surface of the second small-diameter shaft segment are both the welding width L0. The axial length L3 of the weld on the outer peripheral surface of the first small-diameter shaft segment and the axial length L4 of the weld on the outer peripheral surface of the second small-diameter shaft segment are both greater than or equal to 2 times the welding width L0. When used, the presence of the front welding chamfer and the rear welding chamfer is conducive to maintaining stable burning of the welding arc, promoting full fusion of the welding material and the base material, and can effectively avoid common welding defects such as lack of fusion and pores, thereby ensuring a strong connection. The wider weld width L0 enables the width of the weld to effectively disperse stress and reduce stress concentration. Compared with traditional planetary carriers, the present invention has higher connection reliability when subjected to complex radial forces, axial forces, dynamic and impact loads. The axial lengths L3 and L4 welded on the outer circumference of the first and second small-diameter shaft segments are both greater than or equal to twice the weld width L0. In addition, these two small-diameter shaft segments are partially welded on the outer circumferences of the front and rear plate ends of the planetary carrier, further increasing the contact area between the weld area and the parent material, making the connection tighter and more conducive to the transmission of torque and force, and effectively avoiding the occurrence of desoldering or loosening. These welding parameters cooperate with each other to evenly distribute the forces borne by the planetary carrier during operation in the weld area, ensuring the strength of the connection and thereby improving the stability of the double-layer planetary carrier. Therefore, the present invention not only has high precision but also good stability.

[0019] 4. In a double-layer welded planetary carrier and its manufacturing method, the stepped shaft raw material is first strengthened and then fine-turned. In application, during the manufacturing process, the planetary carrier front plate, planetary carrier rear plate, and stepped shaft are all independent components. Because the stepped shaft must withstand the main radial and axial forces generated by the operation of the planetary gears, strengthening the stepped shaft raw material and then fine-turning it can improve the strength and toughness of the stepped shaft, reduce bending deformation under high loads, and enhance impact resistance, thereby ensuring the accurate motion trajectory of the planetary gears and the overall stability of the planetary carrier. The independent structural design of each component makes the manufacturing process highly flexible. The stepped shaft, a key load-bearing component, can be strengthened separately, while non-critical components such as the planetary carrier front plate and rear plate are made of conventional materials and the processing process is simplified, eliminating the need for overall material upgrades or complex processes. This differentiated processing method not only meets the high performance requirements of the stepped shaft, but also avoids the cost waste caused by overall strengthening in traditional solutions. In addition, strengthening and fine-turning are both conventional mechanical manufacturing processes, with simple and easy implementation, effectively reducing processing costs. Therefore, the present invention not only has good stability, but also has a simple processing process and low processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the cross-sectional structure of the planet carrier in the present invention.

[0021] Figure 2 It is a left side view of the planet carrier in the present invention.

[0022] Figure 3 It is a structural schematic diagram of the planet carrier front plate and the planet carrier rear plate in the present invention.

[0023] Figure 4 It is a structural schematic diagram of the stepped shaft in the present invention.

[0024] Figure 5 It is a structural schematic diagram of the preassembled parts in the present invention.

[0025] Figure 6 It is a left side view of the assembled part after positioning in the present invention.

[0026] Figure 7 It is a schematic cross-sectional view of the assembled component after positioning with a through inner hole processed in the present invention.

[0027] Figure 8 It is a left view of the assembled part after positioning with a through inner hole processed in the present invention.

[0028] Figure 9 It is a schematic diagram of the cross-sectional structure after the first small-diameter shaft segment and the planetary carrier front plate are welded in the present invention.

[0029] Figure 10 It is a schematic diagram of the cross-sectional structure after the second small-diameter shaft segment and the planetary carrier rear plate are welded in the present invention.

[0030] In the figure: planetary carrier front plate 1, internal spline 11, right center inner hole 12, front plate stepped shaft hole 13, front inclined hole wall 131, front straight hole wall 132, front welding chamfer 133, pre-assembled part 14, positioned rear assembly part 15, stepped shaft 2, first small diameter shaft section 21, large diameter shaft section 22, second small diameter shaft section 23, first shaft shoulder 24, second shaft shoulder 25, end plate 3, planetary carrier rear plate 4, rear plate center hole 41, rear plate stepped shaft hole 42, rear inclined hole wall 421, rear straight hole wall 422, rear welding chamfer 423, locating ring 5, interference pin 6, pin hole 61, planetary gear pin shaft mounting hole 62. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] See also Figure 1 — Figure 10A double-layer welded planetary carrier and a manufacturing method thereof, wherein the double-layer welded planetary carrier comprises a planetary carrier front plate 1, a stepped shaft 2, an end plate 3, and a planetary carrier rear plate 4; One side of the planetary carrier front plate 1 is uniformly provided with internal splines 11 along the circumference, the other side of the planetary carrier front plate 1 is provided with a right central inner hole 12, and a plurality of through-going front plate stepped shaft holes 13 are provided on the circumference of the planetary carrier front plate 1; The stepped shaft 2 includes a first small-diameter shaft section 21, a large-diameter shaft section 22, and a second small-diameter shaft section 23, which are connected in sequence. The diameter and length of the first small-diameter shaft section 21 and the second small-diameter shaft section 23 are the same, and the diameters of the first small-diameter shaft section 21 and the second small-diameter shaft section 23 are smaller than the diameter of the large-diameter shaft section 22. The connection between the first small-diameter shaft section 21 and the large-diameter shaft section 22 is a first shaft shoulder 24, and the connection between the second small-diameter shaft section 23 and the large-diameter shaft section 22 is a second shaft shoulder 25. A through rear plate center hole 41 is formed in the center of the planet carrier rear plate 4, and a plurality of through rear plate stepped shaft holes 42 are formed on the circumference of the planet carrier rear plate 4; The front plate stepped shaft hole 13 corresponds to the rear plate stepped shaft hole 42 one by one, the first small diameter shaft section 21 is interference fit with the front plate stepped shaft hole 13, and the second small diameter shaft section 23 is interference fit with the rear plate stepped shaft hole 42; the first shaft shoulder 24 is tightly fitted with one side of the planetary carrier front plate 1, and the second shaft shoulder 25 is tightly fitted with one side of the planetary carrier rear plate 4; the lengths of the first small diameter shaft section 21 and the second small diameter shaft section 23 are respectively greater than the thickness of the corresponding planetary carrier front plate 1 and planetary carrier rear plate 4 at the circumference, the outer circumferential surface of the first small diameter shaft section 21 is welded to the hole wall of the front plate stepped shaft hole 13 away from the first shaft shoulder 24, and the outer circumferential surface of the second small diameter shaft section 23 is welded to the hole wall of the rear plate stepped shaft hole 42 away from the second shaft shoulder 25; the end plate 3 is interference fit with the right center inner hole 12; a number of through planetary gear pin shaft mounting holes 62 are opened at corresponding positions on the circumference of the planetary carrier front plate 1 and the planetary carrier rear plate 4.

[0033] The hole wall of the front plate stepped shaft hole 13 at the end away from the first shaft shoulder 24 is a front inclined hole wall 131, and the front straight hole wall 132 is connected to the front inclined hole wall 131; the hole wall of the rear plate stepped shaft hole 42 at the end away from the second shaft shoulder 25 is a rear inclined hole wall 421, and the rear straight hole wall 422 is connected to the rear inclined hole wall 421; The angle between the front inclined hole wall 131 and the outer peripheral surface of the first small-diameter shaft segment 21 is the front welding chamfer 133 , and the angle between the rear inclined hole wall 421 and the outer peripheral surface of the second small-diameter shaft segment 23 is the rear welding chamfer 423 .

[0034] In the radial direction perpendicular to the axis of the stepped shaft 2, the maximum distance between the front bevel hole wall 131 and the outer peripheral surface of the first small-diameter shaft segment 21, and the maximum distance between the rear bevel hole wall 421 and the outer peripheral surface of the second small-diameter shaft segment 23 are both the welding width L0; The axial length L3 of the weld on the outer circumference of the first small-diameter shaft segment 21 and the axial length L4 of the weld on the outer circumference of the second small-diameter shaft segment 23 are both greater than or equal to twice the welding width L0.

[0035] The minimum distance L1 between the front straight hole wall 132 of the front plate stepped shaft hole 13 and the outer edge of the planetary carrier front plate 1 is not less than 4 times the welding width L0; the minimum distance L2 between the rear straight hole wall 422 of the rear plate stepped shaft hole 42 and the outer edge of the planetary carrier rear plate 4 is not less than 4 times the welding width L0.

[0036] The interference fit between the first small-diameter shaft segment 21 and the front plate stepped shaft hole 13 is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the front plate stepped shaft hole 13; the interference fit between the second small-diameter shaft segment 23 and the rear plate stepped shaft hole 42 is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the rear plate stepped shaft hole 42; The straight section of the front plate stepped shaft hole 13 is a cylindrical hole section corresponding to the front straight hole wall 132 ; the straight section of the rear plate stepped shaft hole 42 is a cylindrical hole section corresponding to the rear straight hole wall 422 .

[0037] The manufacturing method comprises the following steps: Step 1: First, heat treat the raw materials of the planetary carrier front plate 1 and the planetary carrier rear plate 4, and then fine-turn the heat-treated raw materials to obtain the planetary carrier front plate 1 with a right central inner hole 12 and the planetary carrier rear plate 4 with a rear plate central hole 41. The right central inner hole 12 and the rear plate central hole 41 have the same size. Step 2: First, perform a centering operation on the right central inner hole 12 and the rear plate central hole 41 to align the corresponding end faces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 to form a pre-assembled component 14. Then, a plurality of through pin holes 61 are machined on the circumference of the pre-assembled component 14, and the pre-assembled component 14 is positioned using interference pins 6 corresponding to the pin holes 61 to obtain a positioned assembly 15. Then, a plurality of through inner holes are machined on the circumference of the positioned assembly 15, the same number as the planetary gears. Step 3: First, the assembled part 15 after positioning is split into the planetary carrier front plate 1 and the planetary carrier rear plate 4, and then the internal spline 11 is processed along the circumference of the left inner side of the planetary carrier front plate 1; Step 4: First, the raw material of the stepped shaft 2 is strengthened, and then the stepped shaft 2 raw material after strengthening is fine-turned to obtain the stepped shaft 2 that meets the design requirements; Step 5: Install the two ends of the stepped shaft 2 into the through inner holes of the planetary carrier front plate 1 and the planetary carrier rear plate 4 by cold assembly, so that the two ends of the stepped shaft 2 extend out of the end surfaces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 respectively; Step 6: Weld the outer circumference of one end of the stepped shaft 2 to the hole wall of the through hole of the planet carrier front plate 1, and the outer circumference of the other end of the stepped shaft 2 to the hole wall of the through hole of the planet carrier rear plate 4 respectively; Step 7: Evenly distributed planetary gear pin mounting holes 62 are machined on the circumferential surface of the planetary carrier front plate 1 and the planetary carrier rear plate 4 welded together as above, and then the end plate 3 is interference fit into the right center inner hole 12 of the planetary carrier front plate 1 to complete the double-layer welded planetary carrier manufacturing.

[0038] In the second step, processing the through inner holes on the circumferential surface of the rear-positioned assembly 15 in the same number as the planetary gears means: processing a number of through inner holes on the circumferential surface of the rear-positioned assembly 15 in accordance with the number of the planetary gears, wherein the through inner hole located on the front plate 1 of the planetary carrier is the front plate stepped shaft hole 13, and the through inner hole located on the rear plate 4 of the planetary carrier is the rear plate stepped shaft hole 42; processing the hole wall of the front plate stepped shaft hole 13 away from the mating surface of the two plates into a front inclined hole wall 131, and processing the hole wall of the rear plate stepped shaft hole 42 away from the mating surface of the two plates into a rear inclined hole wall 421.

[0039] In the fourth step, the strengthening treatment of the raw material of the stepped shaft 2 refers to: performing a tempering or quenching operation on the raw material of the stepped shaft 2; In the fourth step, obtaining the stepped shaft 2 that meets the design requirements means: processing the two ends of the stepped shaft 2 into the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 respectively through fine turning, processing the middle part of the stepped shaft 2 into the large-diameter shaft segment 22, processing the connection between the large-diameter shaft segment 22 and the first small-diameter shaft segment 21 into the first shaft shoulder 24, and processing the connection between the large-diameter shaft segment 22 and the second small-diameter shaft segment 23 into the second shaft shoulder 25; the diameter and length of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are the same, and the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are the same. The outer circle dimension accuracy of the two small-diameter shaft segments 23 is higher than h6, and the coaxiality form and position tolerance grade of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 is not less than grade 6; the diameter of the large-diameter shaft segment 22 is larger than the diameters of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23, and the axial length of the large-diameter shaft segment 22 is consistent; the interference fit of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 with the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 is not less than R7 / h6 and is larger than the maximum deformation of the straight section of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42.

[0040] In the sixth step, the outer peripheral surface of one end of the stepped shaft 2 and the hole wall of the through-hole of the planetary carrier front plate 1, and the outer peripheral surface of the other end of the stepped shaft 2 and the hole wall of the through-hole of the planetary carrier rear plate 4 respectively refer to: using laser welding to weld the outer peripheral surface of the first small-diameter shaft segment 21 in the stepped shaft 2 to the front inclined hole wall 131 of the front plate stepped shaft hole 13, and using laser welding to weld the outer peripheral surface of the second small-diameter shaft segment 23 in the stepped shaft 2 to the rear inclined hole wall 421 of the rear plate stepped shaft hole 42.

[0041] In the second step, the centering operation in the right central inner hole 12 and the rear plate central hole 41 is to install the positioning ring 5 in the right central inner hole 12 and the rear plate central hole 41 for centering, and the positioning ring 5 is L-shaped; In the second step, positioning by using the interference pin 6 corresponding to the pin hole 61 refers to: passing the interference pin 6 corresponding to the pin hole 61 through the pin hole 61 for positioning.

[0042] The supplementary description of the present invention is as follows: In the present invention, the welding width L0 is preferably 1 / 15 of the diameter of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 and is not less than 5 mm.

[0043] In the sixth step of the present invention, the welding is preferably performed by a welding method that generates less heat.

[0044] Example 1: See also Figure 1 — Figure 10A double-layer welded planetary carrier and a manufacturing method thereof, the double-layer welded planetary carrier comprises a planetary carrier front plate 1, a stepped shaft 2, an end plate 3, and a planetary carrier rear plate 4; one side of the planetary carrier front plate 1 is uniformly distributed with internal splines 11 along the circumference, the other side of the planetary carrier front plate 1 is provided with a right center inner hole 12, and a plurality of through front plate stepped shaft holes 13 are provided on the circumference of the planetary carrier front plate 1; the stepped shaft 2 comprises a first small diameter shaft segment 21, a large diameter shaft segment 22, a second small diameter shaft segment 23 connected in sequence 3, the diameter and length of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are the same, and the diameters of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are smaller than the diameter of the large-diameter shaft segment 22; the connection point between the first small-diameter shaft segment 21 and the large-diameter shaft segment 22 is the first shaft shoulder 24, and the connection point between the second small-diameter shaft segment 23 and the large-diameter shaft segment 22 is the second shaft shoulder 25; a through rear plate center hole 41 is opened in the center of the planetary carrier rear plate 4, and the circumference of the planetary carrier rear plate 4 is A plurality of through rear plate stepped shaft holes 42 are opened on the upper surface; the front plate stepped shaft hole 13 corresponds to the rear plate stepped shaft hole 42 one by one, the first small diameter shaft section 21 is interference fit with the front plate stepped shaft hole 13, and the second small diameter shaft section 23 is interference fit with the rear plate stepped shaft hole 42; the first shaft shoulder 24 is tightly fitted with one side of the planetary carrier front plate 1, and the second shaft shoulder 25 is tightly fitted with one side of the planetary carrier rear plate 4; the lengths of the first small diameter shaft section 21 and the second small diameter shaft section 23 are respectively greater than the corresponding According to the thickness of the planetary carrier front plate 1 and the planetary carrier rear plate 4 at the circumference, the outer circumference of the first small-diameter shaft segment 21 is welded to the hole wall of the front plate stepped shaft hole 13 away from the first shaft shoulder 24, and the outer circumference of the second small-diameter shaft segment 23 is welded to the hole wall of the rear plate stepped shaft hole 42 away from the second shaft shoulder 25; the end plate 3 is interference fit with the right center inner hole 12; a number of through planetary gear pin shaft mounting holes 62 are opened at corresponding positions on the circumference of the planetary carrier front plate 1 and the planetary carrier rear plate 4.

[0045] When in use, the planetary carrier front plate 1 is rigidly connected to the external power source (such as the input shaft) through the internal spline 11 to transmit the input torque to the stepped shaft 2. The first small-diameter shaft section 21 at both ends of the stepped shaft 2 and the front plate stepped shaft hole 13, and the second small-diameter shaft section 23 and the rear plate stepped shaft hole 41 are interference fit. At the same time, the first shaft shoulder 24 and the second shaft shoulder 25 are tightly fitted with the planetary carrier front plate 1 and the planetary carrier rear plate 4 respectively to form axial positioning. The interference fit prevents radial displacement and the shoulder positioning limits axial movement, ensuring that the stepped shaft 2 and the planetary carrier front plate 1 and the planetary carrier rear plate 4 are in a state of tight contact. There is no relative motion, and a rigid force transmission path is constructed. During the power transmission process, the radial force generated by the operation of the planetary gear is borne by the large-diameter shaft section 22 in the middle of the stepped shaft 2, whose diameter is larger than the small-diameter shaft sections at both ends. By expanding the support cross-sectional area, the radial load is effectively dispersed, reducing local stress concentration. The axial force generated by the operation of the planetary gear is transmitted through the fitting surface between the first shaft shoulder 24 and the planetary carrier front plate 1, and the second shaft shoulder 25 and the planetary carrier rear plate 4. The mechanical limit of the first shaft shoulder 24 and the second shaft shoulder 25 is used to constrain the axial displacement of the stepped shaft, effectively avoiding the bending deformation and movement of the shaft body. In addition, the first shaft shoulder 24 and the second shaft shoulder 25 are used to constrain the axial displacement of the stepped shaft, effectively avoiding the bending deformation and movement of the shaft body. The lengths of the first and second small-diameter shaft segments 21 and 23 are both greater than the thickness of the circumference of the planetary frame front plate 1 and the planetary frame rear plate 4. The outer circumferences of the first and second small-diameter shaft segments 21 and 23 extending out of the end faces of the planetary frame front plate 1 and the planetary frame rear plate 4 are welded to the hole wall to form an annular weld surrounding the shaft segment. In addition, the outer circumferences of the first and second small-diameter shaft segments 21 and 23 extending out of the end faces of the planetary frame front and rear plates are also partially welded. This welding structure expands the contact area between the shaft and the hole, effectively disperses the stress concentration under dynamic load, improves the impact resistance of the connection part, and avoids The traditional interference fit structure is prevented from desoldering or loosening under high-frequency vibration; the end plate 3 is interference fit with the right center inner hole 12, which meets the axial limit requirement of the sun gear and ensures the coaxiality of the entire assembly during rotation. The planetary gear pin shaft mounting holes 62 are evenly distributed around the circumference, so that the running trajectory of the planetary gear is accurate after installation; the present invention uses the dual constraints of interference fit and shaft shoulder positioning, the reasonable distribution of force flow formed by the diameter difference between the shaft shoulder and the stepped shaft, and the strengthening of the connection area by welding the extended end of the shaft segment, so that the double-layer welded planetary carrier is more efficient and stable during power transmission, and the overall load-bearing capacity is significantly improved.

[0046] Example 2: The basic content is the same as Example 1, except that: the hole wall of the front plate stepped shaft hole 13 away from the first shaft shoulder 24 is a front bevel hole wall 131, and the front straight hole wall 132 is connected to the front bevel hole wall 131; the hole wall of the rear plate stepped shaft hole 42 away from the second shaft shoulder 25 is a rear bevel hole wall 421, and the rear straight hole wall 422 is connected to the rear bevel hole wall 421; the angle between the front bevel hole wall 131 and the outer peripheral surface of the first small-diameter shaft segment 21 is a front welding chamfer 133, and the angle between the rear bevel hole wall 421 and the outer peripheral surface of the second small-diameter shaft segment 23 is a rear welding chamfer 423.

[0047] When used, the front bevel hole wall 131 is a bevel machined at the end of the front plate stepped shaft hole 13 away from the first shaft shoulder 24, and the rear bevel hole wall 421 is a bevel machined at the end of the rear plate stepped shaft hole 42 away from the second shaft shoulder 25. These bevels constitute the groove structure required for welding. During the welding process, the groove structure can enable the welding rod or welding wire to penetrate into the connection between the shaft and the hole wall, ensuring that the welding arc energy effectively acts on the base material, allowing the welding material and the base material to fully fuse, thereby forming a firm and reliable weld; the front welding chamfer 133 is a bevel between the front bevel hole wall 131 and the first small diameter hole 42. The angle between the outer peripheral surfaces of the shaft section 21, the rear welding chamfer 423 is the angle between the rear inclined hole wall 421 and the outer peripheral surface of the second small-diameter shaft section 23; on this basis, it is preferred that the angles of the front welding chamfer 133 and the rear welding chamfer 423 are both 30°-40°. The reason for selecting this angle range is: if the angle is less than 30°, the groove is narrow, and it is difficult for the welding rod to penetrate into the bottom, which may easily cause problems such as unfused weld root and difficulty in slag discharge. If the angle is greater than 40°, the amount of welding material and the heat-affected zone will increase, which may cause changes in the properties of the parent material and generate greater welding stress.

[0048] Example 3: The basic content is the same as Example 1, except that: in the radial direction perpendicular to the axis of the stepped shaft 2, the maximum distance between the front bevel hole wall 131 and the outer peripheral surface of the first small-diameter shaft segment 21, and the maximum distance between the rear bevel hole wall 421 and the outer peripheral surface of the second small-diameter shaft segment 23 are both the welding width L0; the axial length L3 welded on the outer peripheral surface of the first small-diameter shaft segment 21 and the axial length L4 welded on the outer peripheral surface of the second small-diameter shaft segment 23 are both greater than or equal to 2 times the welding width L0.

[0049] When applied, the welding width L0 and the axial lengths L3 and L4 of the welding have a greater impact on the quality of the weld. The combination of the two can expand the cross-sectional area of ​​the weld to disperse the load, reduce stress concentration and enhance the shaft-hole connection strength. They are key parameters to ensure that the planetary carrier can stably transmit power under complex loads and avoid weld failure. On this basis, it is preferred that the welding width L0 is respectively greater than 1 / 10 of the diameter of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 and not less than 5 mm. This is because a wider weld can effectively disperse stress and avoid stress concentration, thereby ensuring that the weld has sufficient strength and stability. It also effectively avoids the problem of insufficient load-bearing capacity caused by the small welding width L0, which makes the fusion welding area too small; the axial length L3 welded on the outer peripheral surface of the first small-diameter shaft segment 21 and the axial length L4 welded on the outer peripheral surface of the second small-diameter shaft segment 23 are both greater than or equal to 2 times the welding width L0, which can further increase the contact area between the welding area and the parent material. At the same time, the outer peripheral surfaces of the front and rear plate end faces of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are also partially welded, making the connection tighter, better able to transmit torque and force, and effectively avoiding the occurrence of desoldering or loosening.

[0050] Example 4: The basic content is the same as that of Example 1, except that: the minimum distance L1 between the front straight hole wall 132 of the front plate stepped shaft hole 13 and the outer edge of the planetary carrier front plate 1 is not less than 4 times the welding width L0; the minimum distance L2 between the rear straight hole wall 422 of the rear plate stepped shaft hole 42 and the outer edge of the planetary carrier rear plate 4 is not less than 4 times the welding width L0.

[0051] During application, the minimum distance (L1, L2) between the straight hole wall of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 and the outer edge of the planetary carrier plate is set to be no less than 4 times the welding width L0. By controlling the material thickness of the front plate stepped shaft hole 13, the rear plate stepped shaft hole 42 and the edge of the plate, sufficient rigid support is ensured around the welding area. In the field of mechanical engineering, the distance between the hole edge and the outer edge of the part directly affects the local stiffness and stress distribution. If the distance is too small (less than 4 times the welding width L0), the material thickness near the welding area is insufficient, and stress concentration is easily caused by weak edge stiffness under dynamic load, causing hole wall deformation or plate edge cracking. When L1 and L2 are ≥ 4 times the welding width L0, the load borne by the weld joint can be evenly distributed to the entire plate through a sufficiently thick base material, avoiding a sudden change in stiffness caused by the edges being too close, and ensuring that the double-layer welded planetary carrier maintains a reliable rigid connection during power transmission.

[0052] Example 5: The basic content is the same as Example 1, except that: the interference between the first small-diameter shaft segment 21 and the front plate stepped shaft hole 13 is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the front plate stepped shaft hole 13, and the interference between the second small-diameter shaft segment 23 and the rear plate stepped shaft hole 42 is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the rear plate stepped shaft hole 42; the straight section of the front plate stepped shaft hole 13 is a cylindrical hole segment corresponding to the front straight hole wall 132; the straight section of the rear plate stepped shaft hole 42 is a cylindrical hole segment corresponding to the rear straight hole wall 422.

[0053] When used, the interference fit between the first small-diameter shaft section 21 and the front plate stepped shaft hole 13, and between the second small-diameter shaft section 23 and the rear plate stepped shaft hole 42 is selected to be no less than R7 / h6 and greater than the maximum deformation of the corresponding straight section of the hole, which can ensure that the stepped shaft 2 and the front and rear plates always maintain a rigid connection state without relative displacement under dynamic load; the R7 / h6 interference fit is a medium interference fit, which can form sufficient contact pressure on the contact surface between the shaft and the hole to resist the torque and radial force transmitted through the stepped shaft when the planetary gear is running, and effectively avoid the traditional clearance fit or low interference fit. The micro-wear and loosening problems caused by this can be solved while taking into account the processing economy; and the interference is greater than the maximum deformation of the straight section of the hole, which is based on the elastic deformation characteristics of the planetary carrier when it is subjected to alternating loads: when the cylindrical hole sections corresponding to the front straight hole wall 132 and the rear straight hole wall 422 produce elastic expansion and deformation due to stress, if the interference is insufficient, once the deformation exceeds the interference, a gap will appear between the shaft and the hole, resulting in failure of the fit; so the interference must cover the maximum deformation of the hole under extreme working conditions to ensure that the contact pressure continues to exist and maintain the connection stiffness.

[0054] Example 6: The basic content is the same as that of Example 1, except that the manufacturing method includes the following steps: Step 1: First, heat treat the raw materials of the planetary carrier front plate 1 and the planetary carrier rear plate 4, and then fine-turn the heat-treated raw materials to obtain the planetary carrier front plate 1 with a right central inner hole 12 and the planetary carrier rear plate 4 with a rear plate central hole 41. The right central inner hole 12 and the rear plate central hole 41 have the same size. Step 2: First, perform a centering operation on the right central inner hole 12 and the rear plate central hole 41 to align the corresponding end faces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 to form a pre-assembled component 14. Then, a plurality of through pin holes 61 are machined on the circumference of the pre-assembled component 14, and the pre-assembled component 14 is positioned using interference pins 6 corresponding to the pin holes 61 to obtain a positioned assembly 15. Then, a plurality of through inner holes are machined on the circumference of the positioned assembly 15, the same number as the planetary gears. Step 3: First, the assembled part 15 after positioning is split into the planetary carrier front plate 1 and the planetary carrier rear plate 4, and then the internal spline 11 is processed along the circumference of the left inner side of the planetary carrier front plate 1; Step 4: First, the raw material of the stepped shaft 2 is strengthened, and then the stepped shaft 2 raw material after strengthening is fine-turned to obtain the stepped shaft 2 that meets the design requirements; Step 5: Install the two ends of the stepped shaft 2 into the through inner holes of the planetary carrier front plate 1 and the planetary carrier rear plate 4 by cold assembly, so that the two ends of the stepped shaft 2 extend out of the end surfaces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 respectively; Step 6: Weld the outer circumference of one end of the stepped shaft 2 to the hole wall of the through hole of the planet carrier front plate 1, and the outer circumference of the other end of the stepped shaft 2 to the hole wall of the through hole of the planet carrier rear plate 4 respectively; Step 7: Evenly distributed planetary gear pin mounting holes 62 are machined on the circumferential surface of the planetary carrier front plate 1 and the planetary carrier rear plate 4 welded together as above, and then the end plate 3 is interference fit into the right center inner hole 12 of the planetary carrier front plate 1 to complete the double-layer welded planetary carrier manufacturing.

[0055] Example 7: The basic content is the same as Example 1, except that: in the first step, obtaining the planetary carrier front plate 1 with the right center inner hole 12 and the planetary carrier rear plate 4 with the rear plate center hole 41 means: the planetary carrier front plate 1 and the planetary carrier rear plate 4 are obtained by precision turning, and the shapes and sizes of the planetary carrier front plate 1 and the planetary carrier rear plate 4 meet the design requirements, the planetary carrier front plate 1 is processed with the right center inner hole 12, and the planetary carrier rear plate 4 is processed with the rear plate center hole 41.

[0056] During application, the planetary carrier front plate 1 and the planetary carrier rear plate 4 are precision-turned to ensure that their external dimensions meet the design requirements, providing an accurate reference structure for subsequent assembly; during the precision turning process, a right-side center inner hole 12 is machined on one side of the planetary carrier front plate 1, and a through rear plate center hole 41 is machined in the center of the planetary carrier rear plate 4. The precision turning process ensures the thickness uniformity and flatness of the front and rear plates, avoids assembly stress caused by external shape deviation, ensures the axial limit accuracy of the sun gear after the end plate 3 is installed, and at the same time, ensures the coaxiality of the entire planetary carrier assembly, laying a solid foundation for stable power transmission.

[0057] Example 8: The basic content is the same as Example 1, except that: in the second step, the through inner holes processed on the circumferential surface of the positioned rear assembly 15 are the same number as the planetary gears, which means that: on the circumferential surface of the positioned rear assembly 15, a number of through inner holes are processed according to the number of planetary gears, wherein the through inner hole located on the planetary carrier front plate 1 is the front plate stepped shaft hole 13, and the through inner hole located on the planetary carrier rear plate 4 is the rear plate stepped shaft hole 42; the hole wall of the front plate stepped shaft hole 13 away from the mating surface of the two plates is processed into a front inclined hole wall 131, and the hole wall of the rear plate stepped shaft hole 42 away from the mating surface of the two plates is processed into a rear inclined hole wall 421.

[0058] When in use, first accurately position and assemble the planetary carrier front plate 1 and the planetary carrier rear plate 4 to ensure that the axes of the two coincide and the hole position references are consistent to form a positioned assembly part 15; then, on the circumferential surface of the positioned assembly part 15, through-holes are machined according to the number of planetary gears, of which the front plate stepped shaft hole 13 is located on the planetary carrier front plate 1, and the rear plate stepped shaft hole 42 is located on the planetary carrier rear plate 4; when machining the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42, the axially connected inner holes are machined at one time. The cylindrical hole wall is further processed into an inclined surface at one end of the planetary carrier front plate 1 and the planetary carrier rear plate 4 away from the fitting end surface of the front and rear plates. Among them, the inclined surface wall of the front plate stepped shaft hole 13 is the front inclined surface wall 131, and the inclined surface wall of the rear plate stepped shaft hole 42 is the rear inclined surface wall 421. The cylindrical parts connected to the front inclined surface wall 131 and the rear inclined surface wall 421 are the front straight surface wall 132 and the rear straight surface wall 422; the inclined surfaces of the front inclined surface wall 131 and the rear inclined surface wall 421 are designed to be The design can provide a groove for the subsequent welding operation of the stepped shaft 2, so that the welding rod or welding wire can penetrate better and ensure the welding quality; on the other hand, it can ensure that the weld formed after welding has high strength and uniform stress distribution, thereby enhancing the reliability of the planetary carrier when bearing dynamic loads; since the hole walls of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 are synchronously processed and formed, and the positioning of the assembly 15 after positioning is accurate, the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 are both good in dimensional accuracy and coaxiality; on this basis, it is preferred that the angles between the front bevel hole wall 131 and the rear bevel hole wall 421 and the straight line where the axis of the planetary carrier front plate 1 and the planetary carrier rear plate 4 are located are all controlled at 30°-40°. This is because if the angle is less than 30°, the groove is narrow and it is difficult for the welding rod to penetrate the bottom, which can easily cause problems such as unfused weld root and difficulty in slag discharge. If the angle is greater than 40°, the amount of welding material used and the heat-affected zone will increase, which may cause changes in the properties of the parent material and generate greater welding stress.

[0059] Example 9: The basic content is the same as that of Example 1, except that: in the fourth step, obtaining the stepped shaft 2 that meets the design requirements means that the two ends of the stepped shaft 2 are respectively processed into a first small-diameter shaft segment 21 and a second small-diameter shaft segment 23 by fine turning, and the middle part of the stepped shaft 2 is processed into a large-diameter shaft segment 22, and the connection between the large-diameter shaft segment 22 and the first small-diameter shaft segment 21 is processed into a first shaft shoulder 24, and the connection between the large-diameter shaft segment 22 and the second small-diameter shaft segment 23 is processed into a second shaft shoulder 25; the diameter and length of the first small-diameter shaft segment 21 and the second small-diameter shaft segment 23 are the same, and the first The outer circle dimension accuracy of the small diameter shaft segment 21 and the second small diameter shaft segment 23 is higher than h6, and the coaxiality form and position tolerance grade of the first small diameter shaft segment 21 and the second small diameter shaft segment 23 is not less than grade 6; the diameter of the large diameter shaft segment 22 is larger than the diameters of the first small diameter shaft segment 21 and the second small diameter shaft segment 23, and the axial length of the large diameter shaft segment 22 is consistent; the interference fit of the first small diameter shaft segment 21 and the second small diameter shaft segment 23 with the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42 is not less than R7 / h6 and is larger than the maximum deformation of the straight section of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42.

[0060] When used, the stepped shaft 2 is designed to have a structure of small-diameter shaft sections at both ends (the first small-diameter shaft section 21 and the second small-diameter shaft section 23) and a large-diameter shaft section 22 in the middle. This is mainly because: the small-diameter shaft sections at both ends are respectively interference-fitted with the stepped shaft holes (the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42) of the planetary carrier front plate 1 and the planetary carrier rear plate 4, thereby achieving precise radial positioning and preliminary axial constraint; the diameter of the large-diameter shaft section 22 in the middle is larger than that of the two ends, which can effectively increase the main radial load transmitted during the operation of the planetary gear and reduce the bending deformation of the middle part of the shaft body; and the connection between the large-diameter shaft section 22 and the small-diameter shaft section The first shoulder 24 and the second shoulder 25 are in close contact with the planetary carrier front plate 1 and the planetary carrier rear plate 4 respectively, forming a clear axial positioning reference, bearing the axial load and limiting the axial movement of the stepped shaft 2, so that the load is evenly transmitted to the front and rear plates through the shoulders, avoiding stress concentration; this stepped structure reasonably distributes the axial and radial loads through the shoulder positioning and cross-sectional size changes, which not only meets the assembly accuracy requirements of the interference fit, but also enhances the load-bearing capacity of the middle part of the shaft body, and cooperates with the groove welding structure of the front and rear plates to form a stable force flow transmission path, ensuring the reliable operation of the planetary carrier.

[0061] Example 10: The basic content is the same as Example 1, except that: in the sixth step, the outer peripheral surface of one end of the above-mentioned stepped shaft 2 and the hole wall of the through-hole of the planetary carrier front plate 1, and the outer peripheral surface of the other end of the above-mentioned stepped shaft 2 and the hole wall of the through-hole of the planetary carrier rear plate 4 respectively refer to: using laser welding to weld the outer peripheral surface of the first small-diameter shaft segment 21 in the above-mentioned stepped shaft 2 to the front inclined hole wall 131 of the front plate stepped shaft hole 13, and using laser welding to weld the outer peripheral surface of the second small-diameter shaft segment 23 in the above-mentioned stepped shaft 2 to the rear inclined hole wall 421 of the rear plate stepped shaft hole 42.

[0062] During application, laser welding is used to weld the stepped shaft 2. This welding method generates little heat, can effectively reduce thermal deformation during welding, and ensure welding accuracy and structural stability. The specific welding parts include the outer circumference of the first small-diameter shaft segment 21 and the front bevel hole wall 131 of the front plate stepped shaft hole 13, and the outer circumference of the second small-diameter shaft segment 23 and the rear bevel hole wall 421 of the rear plate stepped shaft hole 42. At the same time, the outer circumference of the first small-diameter shaft segment 21 extending out of the end face of the planetary carrier front plate 1 and the outer circumference of the second small-diameter shaft segment 23 extending out of the end face of the planetary carrier rear plate 4 are also partially welded. The groove design of the front bevel hole wall 131 and the rear bevel hole wall 421, combined with the high energy density characteristics of laser welding, makes the weld deep and uniform, which not only ensures the welding quality, but also makes the weld strength high and the stress distribution uniform, significantly enhancing the reliability of the planetary carrier when bearing dynamic loads. The partial welding of the protruding end surface further improves the connection stability, effectively avoids the failure of the fit, and gives full play to the advantages of high efficiency and precision of laser welding, making the manufacturing process simple, efficient and with high yield.

[0063] Example 11: The basic content is the same as Example 1, except that: in the second step, the centering operation in the above-mentioned right side center inner hole 12 and the rear plate center hole 41 refers to: installing the positioning ring 5 in the above-mentioned right side center inner hole 12 and the rear plate center hole 41 for centering, and the positioning ring 5 is L-shaped; in the second step, positioning through the interference pin 6 corresponding to the pin hole 61 refers to: passing the interference pin 6 corresponding to the pin hole 61 through the pin hole 61 for positioning.

[0064] When in use, the L-shaped positioning ring 5 is inserted into the right center inner hole 12 and the rear plate center hole 41, and its vertical section cooperates with the hole wall of the right center inner hole 12 and the rear plate center hole 41 to achieve radial centering, and the horizontal section fits the end faces of the front and rear plates to achieve axial positioning, so that the center axes of the planetary frame front plate 1 and the rear plate 4 are strictly aligned and the end faces are tightly fitted, thereby constructing a unified reference coordinate system; on this basis, the pin hole 61 is machined, and the interference pin 6 is used to pass through the pin hole 61 for positioning, further locking the relative positions of the planetary frame front plate 1 and the planetary frame rear plate 4 in the circumferential direction, avoiding the circumferential rotational deviation of the two plates, and forming a stable positioning constraint; then, when the through inner hole (i.e., the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42) is machined on the circumferential surface of the rear assembly 15, since the relative positions of the planetary frame front plate 1 and the planetary frame rear plate 4 have been positioned by the above-mentioned positioning process Strictly fixed, the through inner holes can be processed synchronously based on the same reference, which directly ensures that the axes of the corresponding through inner holes on the front and rear plates are completely coaxial, and the size and shape accuracy of the through inner holes are consistent. Finally, after the stepped shaft 2 is welded with the planetary frame front plate 1 and the planetary frame rear plate 4 to form an integral structure, the planetary gear pin shaft mounting hole 62 is processed. Since the planetary frame front plate 1 and the planetary frame rear plate 4 have been welded into a rigid whole, and the preliminary positioning and processing steps have ensured the basic accuracy, the mounting hole can be directly based on the welded assembly as the reference, and positioned and formed in one time, ensuring the distribution accuracy of all planetary gear pin shaft mounting holes 62 on the circumference (such as equal division and concentricity) and the dimensional accuracy of the planetary gear pin shaft mounting hole 62 itself, avoiding the error accumulation caused by structural deformation or positioning reference changes in traditional step-by-step processing, thereby improving the accuracy of the double-layer planetary frame.

[0065] Example 12: The basic content is the same as that of Example 1, except that: in the fourth step, the strengthening treatment of the raw material of the stepped shaft 2 refers to: tempering or quenching operation on the raw material of the stepped shaft 2.

[0066] During application, since the stepped shaft 2 needs to bear the main radial force and axial force generated by the operation of the planetary gear, the stepped shaft raw material is subjected to strengthening treatments such as tempering or quenching operations, and then fine turning is performed. This can improve the strength and toughness of the stepped shaft, reduce bending deformation under high load, and enhance impact resistance, thereby ensuring the accuracy of the planetary gear movement trajectory and the overall stability of the planetary carrier.

[0067] Example 13: The basic content is the same as Example 6, except that: if the planetary gear pin shaft mounting hole 62 is consistent with the size of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42, then in the second step, after the through inner hole is processed, the planetary gear pin shaft mounting hole 62 is directly processed.

[0068] During application, if the size requirements of the planetary gear pin shaft mounting hole 62 are consistent with those of the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42, the through inner hole (i.e., the front plate stepped shaft hole 13 and the rear plate stepped shaft hole 42) and the planetary gear pin shaft mounting hole 62 are processed simultaneously, and there is no need to process the planetary gear pin shaft mounting hole 62 after welding. This can simplify the processing flow, save steps and reduce costs while ensuring good dimensional accuracy and coaxiality.

[0069] Example 14: The basic content is the same as Example 1, except that: in the fifth step, making the two ends of the stepped shaft 2 extend out of the end faces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 respectively means: making the first small-diameter shaft segment 21 extend out of the end face of the planetary carrier front plate 1 by a certain length, and the second small-diameter shaft segment 23 extend out of the end face of the planetary carrier rear plate 4 by a certain length.

[0070] During application, the two ends of the stepped shaft 2 are respectively extended out of the end faces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 by a certain length in order to ensure the processing of the chamfers and the welding structure requirements of the stepped shaft 2; partial welding is performed on the length extending out of the end faces of the planetary carrier front plate 1 and the planetary carrier rear plate 4 to form an inverted triangle structure, increase the area of ​​the weld, improve the weld strength, and ensure that the stepped shaft 2 is firmly connected to the planetary carrier front plate 1 and the planetary carrier rear plate 4.

[0071] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A double-layer welded planet carrier, characterized in that: The double-layer welded planetary frame comprises a planetary frame front plate (1), a stepped shaft (2), an end plate (3), and a planetary frame rear plate (4); One side of the planetary frame front plate (1) is uniformly provided with internal splines (11) along the circumference, the other side of the planetary frame front plate (1) is provided with a right central inner hole (12), and a plurality of through-going front plate stepped shaft holes (13) are provided on the circumference of the planetary frame front plate (1); The stepped shaft (2) comprises a first small-diameter shaft section (21), a large-diameter shaft section (22), and a second small-diameter shaft section (23) connected in sequence, wherein the diameter and length of the first small-diameter shaft section (21) and the second small-diameter shaft section (23) are the same, and the diameters of the first small-diameter shaft section (21) and the second small-diameter shaft section (23) are smaller than the diameter of the large-diameter shaft section (22); the portion where the first small-diameter shaft section (21) and the large-diameter shaft section (22) are connected is a first shaft shoulder (24), and the portion where the second small-diameter shaft section (23) and the large-diameter shaft section (22) are connected is a second shaft shoulder (25); A through rear plate center hole (41) is provided at the center of the planetary frame rear plate (4), and a plurality of through rear plate stepped shaft holes (42) are provided on the circumference of the planetary frame rear plate (4); The front plate stepped shaft hole (13) corresponds to the rear plate stepped shaft hole (42) in a one-to-one manner; the first small-diameter shaft section (21) is interference-fitted with the front plate stepped shaft hole (13); the second small-diameter shaft section (23) is interference-fitted with the rear plate stepped shaft hole (42); the first shaft shoulder (24) is tightly fitted with one side of the planetary frame front plate (1); the second shaft shoulder (25) is tightly fitted with one side of the planetary frame rear plate (4); the lengths of the first small-diameter shaft section (21) and the second small-diameter shaft section (23) are respectively greater than the lengths of the corresponding planetary frame front plate (1) and the second small-diameter shaft section (23). The thickness of the planetary frame rear plate (4) at the circumference is such that the outer circumference of the first small-diameter shaft section (21) is welded to the hole wall of the front plate stepped shaft hole (13) away from the first shaft shoulder (24), and the outer circumference of the second small-diameter shaft section (23) is welded to the hole wall of the rear plate stepped shaft hole (42) away from the second shaft shoulder (25); the end plate (3) is interference-fitted with the right center inner hole (12); and a plurality of through planetary gear pin mounting holes (62) are provided at corresponding positions on the circumference of the planetary frame front plate (1) and the planetary frame rear plate (4).

2. The double-layer welded planet carrier according to claim 1, characterized in that: The hole wall of the front plate stepped shaft hole (13) at one end away from the first shaft shoulder (24) is a front inclined hole wall (131), and the hole wall connected to the front inclined hole wall (131) is a front straight hole wall (132); the hole wall of the rear plate stepped shaft hole (42) at one end away from the second shaft shoulder (25) is a rear inclined hole wall (421), and the hole wall connected to the rear inclined hole wall (421) is a rear straight hole wall (422); The included angle between the front inclined hole wall (131) and the outer peripheral surface of the first small-diameter shaft segment (21) is the front welding chamfer (133), and the included angle between the rear inclined hole wall (421) and the outer peripheral surface of the second small-diameter shaft segment (23) is the rear welding chamfer (423).

3. The double-layer welded planet carrier according to claim 2, characterized in that: In a radial direction perpendicular to the axis of the stepped shaft (2), the maximum distance between the front inclined hole wall (131) and the outer peripheral surface of the first small-diameter shaft segment (21), and the maximum distance between the rear inclined hole wall (421) and the outer peripheral surface of the second small-diameter shaft segment (23) are both the welding width L0; The axial length L3 welded on the outer circumference of the first small-diameter shaft segment (21) and the axial length L4 welded on the outer circumference of the second small-diameter shaft segment (23) are both greater than or equal to twice the welding width L0.

4. The double-layer welded planet carrier according to claim 3, characterized in that: The minimum distance L1 between the front straight hole wall (132) of the front plate stepped shaft hole (13) and the outer edge of the planetary frame front plate (1) is not less than 4 times the welding width L0; and the minimum distance L2 between the rear straight hole wall (422) of the rear plate stepped shaft hole (42) and the outer edge of the planetary frame rear plate (4) is not less than 4 times the welding width L0.

5. The double-layer welded planet carrier according to claim 2, characterized in that: The interference between the first small-diameter shaft segment (21) and the front plate stepped shaft hole (13) is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the front plate stepped shaft hole (13); the interference between the second small-diameter shaft segment (23) and the rear plate stepped shaft hole (42) is not less than R7 / h6 and is greater than the maximum deformation of the straight section of the rear plate stepped shaft hole (42); The straight section of the front plate stepped shaft hole (13) is a cylindrical hole section corresponding to the front straight hole wall (132); the straight section of the rear plate stepped shaft hole (42) is a cylindrical hole section corresponding to the rear straight hole wall (422).

6. A method for manufacturing a double-layer welded planet carrier according to claim 1, characterized in that: The manufacturing method comprises the following steps: The first step is to heat-treat the raw materials of the planetary carrier front plate (1) and the planetary carrier rear plate (4), and then perform precision lathing on the raw materials after the heat treatment to obtain the planetary carrier front plate (1) having a right side central inner hole (12) and the planetary carrier rear plate (4) having a rear plate central hole (41), wherein the right side central inner hole (12) and the rear plate central hole (41) have the same size; Step 2: First, a centering operation is performed in the above-mentioned right central inner hole (12) and the rear plate central hole (41), so that the corresponding end faces of the planetary frame front plate (1) and the planetary frame rear plate (4) are fitted together to form a pre-assembled part (14), and then a plurality of through pin holes (61) are machined on the circumference of the pre-assembled part (14), and positioning is performed by interference pins (6) corresponding to the pin holes (61) to obtain a positioned assembled part (15); and then, a number of through inner holes equal to the number of planetary gears are machined on the circumferential surface of the positioned assembled part (15); Step 3: First, the assembled part (15) after positioning is split into the planetary carrier front plate (1) and the planetary carrier rear plate (4), and then an internal spline (11) is machined along the circumference of the left inner portion of the planetary carrier front plate (1); Step 4: First, the raw material of the stepped shaft (2) is subjected to a strengthening treatment, and then the raw material of the stepped shaft (2) after the strengthening treatment is subjected to a precision lathe processing to obtain a stepped shaft (2) that meets the design requirements; Step 5: Install the two ends of the stepped shaft (2) into the through inner holes of the planetary frame front plate (1) and the planetary frame rear plate (4) by cold assembly, so that the two ends of the stepped shaft (2) extend out of the end faces of the planetary frame front plate (1) and the planetary frame rear plate (4) respectively; Step 6: Weld the outer circumference of one end of the stepped shaft (2) to the hole wall of the through hole of the planetary frame front plate (1), and the outer circumference of the other end of the stepped shaft (2) to the hole wall of the through hole of the planetary frame rear plate (4); Step 7: Evenly distributed planetary gear pin mounting holes (62) are machined on the circumferential surfaces of the planetary carrier front plate (1) and the planetary carrier rear plate (4) welded together, and then the end plate (3) is interference-fitted into the right center inner hole (12) of the planetary carrier front plate (1) to complete the double-layer welded planetary carrier manufacturing.

7. The method for manufacturing a double-layer welded planet carrier according to claim 6, characterized in that: In the second step, the through inner holes having the same number as the planetary gears are machined on the circumferential surface of the rear-positioned assembly (15) refer to: machining a plurality of through inner holes on the circumferential surface of the rear-positioned assembly (15) according to the number of the planetary gears, wherein the through inner holes located on the front plate (1) of the planetary frame are the front plate stepped shaft holes (13), and the through inner holes located on the rear plate (4) of the planetary frame are the rear plate stepped shaft holes (42); machining the hole wall of the front plate stepped shaft hole (13) away from the mating surface of the two plates into a front inclined hole wall (131), and machining the hole wall of the rear plate stepped shaft hole (42) away from the mating surface of the two plates into a rear inclined hole wall (421).

8. The method for manufacturing a double-layer welded planet carrier according to claim 7, characterized in that: In the fourth step, the strengthening treatment of the raw material of the stepped shaft (2) refers to: performing a tempering or quenching operation on the raw material of the stepped shaft (2); In the fourth step, obtaining the stepped shaft (2) that meets the design requirements means: processing the two ends of the stepped shaft (2) into a first small-diameter shaft section (21) and a second small-diameter shaft section (23) by precision turning, processing the middle of the stepped shaft (2) into a large-diameter shaft section (22), processing the connection between the large-diameter shaft section (22) and the first small-diameter shaft section (21) into a first shaft shoulder (24), and processing the connection between the large-diameter shaft section (22) and the second small-diameter shaft section (23) into a second shaft shoulder (25); the first small-diameter shaft section (21) and the second small-diameter shaft section (23) have the same diameter and length, and the first small-diameter shaft section (21) The outer circle dimension accuracy of the second small-diameter shaft segment (23) is higher than h6, and the coaxiality form and position tolerance grade of the first small-diameter shaft segment (21) and the second small-diameter shaft segment (23) is not less than grade 6; the diameter of the large-diameter shaft segment (22) is larger than the diameters of the first small-diameter shaft segment (21) and the second small-diameter shaft segment (23), and the axial length of the large-diameter shaft segment (22) is consistent; the interference of the first small-diameter shaft segment (21) and the second small-diameter shaft segment (23) with the front plate stepped shaft hole (13) and the rear plate stepped shaft hole (42) is not less than R7 / h6 and is larger than the maximum deformation of the straight section of the front plate stepped shaft hole (13) and the rear plate stepped shaft hole (42).

9. The method for manufacturing a double-layer welded planet carrier according to claim 8, characterized in that: In the sixth step, the outer peripheral surface of one end of the stepped shaft (2) and the hole wall of the through hole of the planetary frame front plate (1), and the outer peripheral surface of the other end of the stepped shaft (2) and the hole wall of the through hole of the planetary frame rear plate (4) respectively refer to: using laser welding to weld the outer peripheral surface of the first small-diameter shaft section (21) in the stepped shaft (2) to the front inclined hole wall (131) of the front plate stepped shaft hole (13), and using laser welding to weld the outer peripheral surface of the second small-diameter shaft section (23) in the stepped shaft (2) to the rear inclined hole wall (421) of the rear plate stepped shaft hole (42).

10. The method for manufacturing a double-layer welded planet carrier according to claim 6, characterized in that: In the second step, the centering operation in the right central inner hole (12) and the rear plate central hole (41) refers to: installing a positioning ring (5) in the right central inner hole (12) and the rear plate central hole (41) for centering, wherein the positioning ring (5) is L-shaped; In the second step, positioning by using the interference pin (6) corresponding to the pin hole (61) refers to positioning by passing the interference pin (6) corresponding to the pin hole (61) through the pin hole (61).

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