Differential structure and assembling method thereof

Abstract

The invention belongs to the technical field of differential mechanisms, and provides a differential mechanism structure and an assembling method thereof.The differential mechanism structure comprises a main reduction gear, a differential shell, a planet shaft, a planet gear and a half axle gear; a plurality of planetary gears are installed in the differential shell along a first axis, meanwhile, a plurality of half axle gears are installed along a second axis perpendicular to the first axis, and the planetary gears are meshed with the half axle gears; in addition, the planet shaft is of a telescopic structure. By arranging the telescopic planet shaft, the telescopic planet shaft can be placed in the differential shell and then unfolded during installation, so that the installation direction of the telescopic planet shaft does not interfere with the main reduction gear; according to the assembling method, due to the fact that the telescopic planet shaft is adopted, the main reduction gear can be welded and ground at first, then parts in the differential shell are installed, the interior of the differential shell can be prevented from shaking, and foreign matter can be prevented from entering gaps of sub-parts in the differential shell during welding and gear grinding.

Description

Technical Field

[0001] The present invention belongs to the technical field of differentials, and particularly relates to a differential structure and an assembly method thereof. Background Art

[0002] With the development of new energy vehicle technology, there are increasing requirements for the weight and transmission efficiency of reducers. Compared with general bolt-connected differentials, welded differentials can eliminate the weight of the overlapping part of the differential flange and the main reduction gear web plate and bolts, and have obvious advantages in weight under the same applied torque. Their application in passenger car electric drive reducers is also becoming more and more extensive.

[0003] As Figure 1 shown, the existing welded differential includes a planetary shaft (denoted as A), a differential case (denoted as B), and a main reduction gear (denoted as C). Among them, the installation direction of the planetary shaft ( Figure 1 in the D direction in Figure 1 ) will interfere with the main reduction gear. Therefore, when assembling the differential in , it is necessary to first assemble the planetary shaft and the internal gear to the differential case, and then weld the main reduction gear and grind the teeth to avoid the interference between the planetary shaft and the main reduction gear during assembly. However, during tooth grinding, the sub-parts (such as the planetary shaft and the internal gear) shake inside the differential case, resulting in unstable tooth grinding. Moreover, foreign objects easily enter the gaps between the internal sub-parts during welding and tooth grinding and are difficult to clean, and the tooth grinding accuracy and the finished product cleanliness level are both poor. Summary of the Invention

[0004] In order to solve the problems in the background art, the present invention proposes a differential structure and an assembly method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A differential structure includes a main reduction gear, a differential case, a planetary shaft, a planetary gear, and a half shaft gear;

[0007] The main reduction gear is provided with a central hole for installing the differential case;

[0008] A plurality of the planetary gears are installed in the differential case and are arranged along a first axis;

[0009] A plurality of the half shaft gears are installed in the differential case and are arranged along a second axis;

[0010] The first axis is perpendicular to the second axis, and the second axis coincides with the rotation center line of the main reduction gear;

[0011] The planetary gear meshes with the half shaft gear;

[0012] The planetary shaft is of a telescopic structure, is installed in the differential case and is arranged along the first axis for rotatably cooperating with the planetary gear.

[0013] Preferably, the differential case is of a rotary body structure, and the rotation center line of the rotary body structure coincides with the second axis;

[0014] Along the first axis, first mating holes are formed in both end surfaces of the differential case, and each first mating hole is used for rotatably mounting a side gear.

[0015] Along the second axis, second mating holes are formed in both end surfaces of the differential case, and each second mating hole is used for detachably mounting a planetary shaft.

[0016] Between the second mating holes on both end surfaces of the differential case, an assembly window is further formed on the surface of the differential case.

[0017] The planetary shaft, the planetary gear and the side gear are placed into the differential case through the assembly window.

[0018] Preferably, the planetary shaft includes a shaft rod and a shaft sleeve;

[0019] The shaft rod is a stepped shaft, and the shaft sleeve is a hollow shaft;

[0020] The shaft rod is in sliding fit with the shaft sleeve;

[0021] One end of the shaft rod away from the shaft sleeve is detachably connected to the first second mating hole;

[0022] One end of the shaft sleeve away from the shaft rod is detachably connected to the second second mating hole.

[0023] Preferably, a pin shaft is detachably mounted in the second mating hole in the radial direction;

[0024] In the differential case, the pin shaft at one end passes through the shaft rod, and the pin at the other end passes through the shaft sleeve.

[0025] Preferably, first mating grooves are formed in both ends of the inner surface of the differential case along the second axis, and second mating grooves are formed along the first axis;

[0026] A second gasket is arranged in the first mating groove, and the second gasket contacts with one end of the side gear;

[0027] A first gasket is arranged in the second mating groove, and the first gasket contacts with one end of the planetary gear.

[0028] Preferably, the planetary shaft, the planetary gear and the first gasket satisfy:

[0029] a≥b+c+d;

[0030] Wherein, a is the distance between two intersection points, and the two intersection points are the intersection points of the contact lines between the two ends of the inner surface of the differential case and the outer circle of the planetary shaft; b is the minimum length of the planetary shaft after contraction; c is the width of the planetary gear; d is the thickness of the first gasket.

[0031] Preferably, the planetary shaft and the pin shaft satisfy:

[0032] f + g ≥ e + 5 mm;

[0033] Wherein, f represents the distance from the pin shaft at one end of the bushing to the other end of the bushing; g represents the distance from the pin shaft at one end of the shaft rod to the bushing; e represents the distance between the center lines of the two pin shafts.

[0034] An assembly method for assembling the above differential structure includes the following steps:

[0035] Weld the main reduction gear to the differential case and perform gear grinding;

[0036] Install the half shaft gear in the differential case and arrange it along the second axis;

[0037] Place the contracted planetary shaft in the differential case;

[0038] Install the first planetary gear at one end of the differential case and mesh it with the half shaft gear;

[0039] Install the second planetary gear at the other end of the differential case and mesh it with the half shaft gear;

[0040] Extend the planetary shaft and rotate it in cooperation with the two planetary gears;

[0041] Rotate the planetary shaft to make it coincide with the first axis;

[0042] Fix the planetary shaft on the differential case.

[0043] Preferably, rotating the planetary shaft to make it coincide with the first axis includes the following steps:

[0044] Rotate the planetary shaft in the horizontal plane where the first axis is located until the planetary shaft coincides with the first axis.

[0045] Preferably, fixing the planetary shaft on the differential case includes the following steps:

[0046] After the planetary shaft coincides with the first axis, continue to extend the planetary shaft to its maximum length so that both ends of the planetary shaft extend into the second mating holes on the surface of the differential case;

[0047] Insert the pin shaft radially along the second mating hole and make the pin shaft pass through the planetary shaft, thereby fixing the planetary shaft on the differential case.

[0048] The beneficial effects of the present invention:

[0049] 1. The present invention provides a telescopic planetary shaft. The telescopic planetary shaft can adjust its own length as needed. During installation, it can be first placed into the differential housing and then expanded. Therefore, its installation direction will not interfere with the main reduction gear, solving the drawback of the welding differential that when the position of the planetary shaft interferes with the main reduction gear, only the process of first assembling, then welding, and then grinding the teeth can be adopted, improving the grinding accuracy and the cleanliness of the assembly.

[0050] 2. The present invention provides an assembly window, enabling the planetary shaft to enter the differential housing after contraction through the assembly window, providing structural support for solving the interference with the main reducer.

[0051] 3. Due to the adoption of the telescopic planetary shaft in the assembly method of the present invention, the main reduction gear can be welded and ground first, and then the parts inside the differential housing can be installed. This method, on the one hand, avoids the problem of unstable grinding caused by the shaking inside the differential housing, and on the other hand, avoids the problem that foreign objects are likely to enter the gaps between the internal sub-parts during welding and grinding and are difficult to clean.

[0052] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0054] Figure 1 Shows a schematic diagram of the structure of an existing differential;

[0055] Figure 2 Shows a schematic diagram of the structure of a differential of the present invention;

[0056] Figure 3 Shows a full cross-sectional view of a differential of the present invention;

[0057] Figure 4 Shows a schematic diagram of the structure of the differential housing of the present invention;

[0058] Figure 5 Shows a cross-sectional view of the structure of the differential housing of the present invention;

[0059] Figure 6 Shows a schematic diagram of the structure of the planetary shaft of the present invention;

[0060] Figure 7 Shows a schematic structural diagram of the planetary gear and the first gasket of the present invention;

[0061] Figure 8 Shows a schematic structural diagram of the half shaft gear and the second gasket of the present invention;

[0062] Figure 9 Shows a dimensional relationship diagram of the planetary shaft after contraction in the differential case of the present invention;

[0063] Figure 10 Shows a dimensional relationship diagram of the planetary shaft after expansion in the differential case of the present invention;

[0064] Figure 11 Shows a flow chart of an assembly method of the present invention.

[0065] In the figure: 1, main reduction gear; 2, differential case; 201, first mating hole; 202, second mating hole; 203, assembly window; 204, first mating groove; 205, second mating groove; 3, planetary shaft; 301, shaft rod; 302, shaft sleeve; 4, planetary gear; 401, first gasket; 5, half shaft gear; 501, second gasket; 6, pin shaft. Detailed implementation manners

[0066] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0067] As Figure 2 shown, it is a differential structure, which includes a main reduction gear 1, a differential case 2, a planetary shaft 3, a planetary gear 4 and a half shaft gear 5. The main reduction gear 1 is provided with a central hole, and the differential case 2 is installed in the central hole. Parts such as the planetary shaft 3, the planetary gear 4 and the half shaft gear 5 can be installed inside the differential case 2.

[0068] As Figure 3 shown, it is a cross-sectional view of the differential structure in Figure 2 . Inside the differential case 2, two planetary gears 4 are installed in a relative state, and their setting direction is the first axis. At the same time, two opposite half shaft gears 5 are also installed inside the differential case 2, and their setting directions are along the second axis. It should be noted here that the first axis and the second axis are perpendicular to each other, and the second axis coincides with the rotation center line of the main reduction gear 1. In addition, the planetary gear 4 and the half shaft gear 5 are in a meshing state.

[0069] It should be noted that in Figure 2 and Figure 3 , the planetary shaft 3 is not yet fully installed. The planetary shaft 3 needs to be rotationally mated with the planetary gear 4 first, and then rotated until it coincides with and is fixed to the first axis before it can be fully installed. This can effectively solve the interference problem between the planetary shaft 3 and the main reduction gear 1. The following will be further described with reference to the accompanying drawings.

[0070] As Figure 4 shown, the differential case 2 is designed with a rotary body structure, and its rotary center line coincides with the second axis, ensuring high coaxiality and stability during power transmission.

[0071] Along the second axis, first mating holes 201 are respectively provided on the two end surfaces of the differential case 2. These two first mating holes 201 are specifically for rotatably installing a side gear 5, providing a precisely adapted installation basis for the smooth rotation of the side gear 5, ensuring that the side gear 5 can cooperate with the differential case 2 during operation and reducing unnecessary friction and loss.

[0072] Along the first axis, a second mating hole 202 is also provided on each of the two end surfaces of the differential case 2. These two second mating holes 202 are used for detachably installing the planetary shaft 3, enabling the planetary shaft 3 to be firmly installed on the differential case 2 and facilitating disassembly during maintenance or replacement, greatly improving the maintainability and practicality of the differential as a whole.

[0073] In addition, in the area between the second mating holes 202 on the two end surfaces of the differential case 2, an assembly window 203 is specially designed on the surface of the differential case 2. The opening of this assembly window 203 provides a convenient passage for the assembly and debugging of the internal components of the differential, facilitating technicians to precisely adjust and install the internal structure during the assembly process, and greatly improving the production assembly efficiency of the differential. For example, the planetary shaft 3, planetary gear 4, and side gear 5 are installed in the differential case 2 through the assembly window 203.

[0074] As Figure 5 shown, it is the internal structure diagram of the differential case 2. Among them, on the inner surface of the differential case 2 at the position corresponding to the first mating hole 201 (along the second axis), a first mating groove 204 is provided. Additionally, at the position corresponding to the second mating hole 202 (along the first axis), a second mating groove 205 is provided. Gaskets can be installed in both of these mating grooves. Specifically, a second gasket 501 is provided in the first mating groove 204, and the second gasket 501 contacts one end of the side gear 5; a first gasket 401 is provided in the second mating groove 205, and the first gasket 401 contacts one end of the planetary gear 4.

[0075] As Figure 6As shown, the planetary shaft 3 adopts a telescopic design and is installed in the differential case 2 along the first axis. Its main function is to form a rotational fit with the planetary gear 4 to ensure the smooth operation of the differential.

[0076] As an alternative, the planetary shaft 3 consists of two parts: a shaft rod 301 and a shaft sleeve 302. The shaft rod 301 is a stepped shaft, and this stepped structure can meet the assembly requirements of different parts and optimize the force distribution. The shaft sleeve 302 is designed as a hollow shaft, which reduces the overall weight while ensuring the structural strength. A sliding fit is adopted between the shaft rod 301 and the shaft sleeve 302, and this fit endows the planetary shaft 3 with the flexibility to expand and contract, enabling it to adjust its length as needed.

[0077] After installation, one end of the shaft rod 301 away from the shaft sleeve 302 is detachably connected to the first second mating hole 202 on the differential case 2. Similarly, one end of the shaft sleeve 302 away from the shaft rod 301 is detachably connected to the second second mating hole 202 on the differential case 2, ensuring the stability and maintainability of the installation of the planetary shaft 3 and the reliability of the entire differential structure during long-term use.

[0078] It should be noted that since the planetary shaft 3 is a telescopic structure, it can be placed into the differential case 2 through the assembly window 203 after contraction, without the need to be placed into the differential case 2 along the axial direction of the second mating hole 202. Moreover, after the planetary shaft 3 is placed into the differential case 2, its length can be adjusted as needed, and finally the planetary shaft 3 is installed in the second mating hole 202.

[0079] Combined Figure 4 As can be seen, in the second mating hole 202 of the differential case 2, a pin shaft 6 is detachably installed along the radial direction. Such a design has significant effects. One end of the pin shaft 6 precisely passes through the shaft rod 301, while the other end of the pin shaft 6 just passes through the shaft sleeve 302. Through this insertion connection of the pin shaft 6, the displacement of the shaft rod 301 and the shaft sleeve 302 in the radial direction can be effectively restricted, ensuring that the telescopic movement of the planetary shaft 3 is always maintained within a stable axial range, thereby guaranteeing the stability of the rotational fit between the planetary shaft 3 and the planetary gear 4 and enhancing the reliability and smoothness of the overall operation of the differential. At the same time, the detachably installed pin shaft 6 also brings great convenience to subsequent maintenance and repair work. When it is necessary to replace or debug components such as the planetary shaft 3, the pin shaft 6 can be easily removed to improve the maintenance efficiency.

[0080] As Figure 7 shown, the back of the planetary gear 4 is in contact with the first gasket 401, and the first gasket 401 is fitted with the second mating groove 205. As Figure 8 shown, the back of the half shaft gear 5 is in contact with the second gasket 501, and the second gasket 501 is fitted with the first mating groove 204.

[0081] As shown Figure 9 in Figure 9 , to prevent interference between parts, the planetary shaft 3, the planetary gear 4, and the first gasket 401 need to satisfy:

[0082] a ≥ b + c + d; (1)

[0083] In the formula, a is the distance between two intersection points, and the two intersection points are the intersection points of the contact lines between the two ends of the inner surface of the differential case 2 and the outer circle of the planetary shaft 3; b is the minimum length after the contraction of the planetary shaft 3; c is the width of the planetary gear 4; d is the thickness of the first gasket 401.

[0084] As shown Figure 10 in Figure 10 , to prevent interference between parts, the planetary shaft 3 and the pin shaft 6 need to satisfy:

[0085] f + g ≥ e + 5mm; (2)

[0086] In the formula, f represents the distance from the pin shaft 6 at one end of the sleeve 302 to the other end of the sleeve 302; g represents the distance from the pin shaft 6 at one end of the shaft rod 301 to the sleeve 302; e represents the distance between the center lines of the two pin shafts 6.

[0087] As shown Figure 11 in Figure 11 , a kind of assembly method is provided for assembling the above differential structure, including the following steps:

[0088] S1: Weld the main reduction gear 1 to the differential case 2 and perform gear grinding.

[0089] S2: Install the half shaft gear 5 in the differential case 2 and arrange it along the second axis; specifically, first put the half shaft gear 5 and the second gasket 501 etc. into the differential case 2 through the assembly window 203, and then install the two half shaft gears 5 and the second gasket 501 at the upper end and the lower end inside the differential case 2 respectively. At the same time, the half shaft gear 5 is rotationally matched with the first mating hole 201.

[0090] S3: Place the contracted planetary shaft 3 in the differential case 2;

[0091] S4: Install the first planetary gear 4 at one end of the differential case 2 and mesh it with the half shaft gear 5; specifically, first put the first planetary gear 4 and the first gasket 401 etc. into the differential case 2 through the assembly window 203, and then mesh the planetary gear 4 with the half shaft gear 5. In addition, to avoid interference of the planetary shaft 3, the planetary shaft 3 can be abutted against the other end of the differential case 2.

[0092] S5: Install the second planetary gear 4 at the other end of the differential case 2 and mesh it with the side gear 5. Specifically, first put the second planetary gear 4, the first gasket 401, etc. into the differential case 2 through the assembly window 203, and then mesh the planetary gear 4 with the side gear 5. In addition, to avoid interference of the planetary shaft 3, the planetary shaft 3 can be abutted against the end of the differential case 2 away from the second planetary gear 4.

[0093] S6: Stretch the planetary shaft 3 and make it rotatably cooperate with the two planetary gears 4. Specifically, the shaft rod 301 and the shaft sleeve 302 can be stretched to increase the length of the planetary shaft 3, so that both ends of the planetary shaft 3 rotatably cooperate with the two planetary gears 4.

[0094] S7: Rotate the planetary shaft 3 to make the planetary shaft 3 coincide with the first axis. For example, rotate the planetary shaft 3 and the planetary gear 4 together by 90° within the differential case 2 (rotate in the horizontal plane where the first axis is located) to align the planetary shaft 3 with the second mating hole 202 of the differential case 2. At this time, the planetary shaft 3 coincides with the first axis.

[0095] S8: Fix the planetary shaft 3 on the differential case 2. For example, after the planetary shaft 3 coincides with the first axis, continue to stretch the planetary shaft 3 to its maximum length so that both ends of the planetary shaft 3 extend into the second mating hole 202 on the surface of the differential case 2. Then, insert the pin shaft 6 radially along the second mating hole 202 and make the pin shaft 6 pass through the planetary shaft 3, thereby fixing the planetary shaft 3 on the differential case 2.

[0096] As an alternative, in S3 - S5, it can also be replaced with the following steps:

[0097] S3: Install the first planetary gear 4 at one end of the differential case 2 and mesh it with the side gear 5.

[0098] S4: Place the contracted planetary shaft 3 in the differential case 2 and make it rotatably cooperate with the first planetary gear 4.

[0099] S5: Install the second planetary gear 4 at the other end of the differential case 2 and mesh it with the side gear 5.

[0100] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A differential structure, characterized in that, It includes a main reduction gear (1), a differential case (2), a planetary shaft (3), a planetary gear (4) and a side gear (5); The main reduction gear (1) is provided with a central hole for installing the differential case (2); A plurality of the planetary gears (4) are installed in the differential case (2) and arranged along a first axis; A plurality of the side gears (5) are installed in the differential case (2) and arranged along a second axis; The first axis is perpendicular to the second axis, and the second axis coincides with the rotation center line of the main reduction gear (1); The planetary gear (4) meshes with the side gear (5); The planetary shaft (3) is of a telescopic structure, installed in the differential case (2) and arranged along the first axis for rotationally cooperating with the planetary gear (4).

2. The differential structure according to claim 1, characterized in that, The differential case (2) is of a rotary body structure, and the rotation center line of the rotary body structure coincides with the second axis; Along the first axis, first mating holes (201) are formed on both end surfaces of the differential case (2), and each first mating hole (201) is used for rotatably installing a side gear (5); Along the second axis, second mating holes (202) are formed on both end surfaces of the differential case (2), and each second mating hole (202) is used for detachably installing the planetary shaft (3); Between the second mating holes (202) on both end surfaces of the differential case (2), an assembly window (203) is further formed on the surface of the differential case (2); The planetary shaft (3), the planetary gear (4) and the side gear (5) are placed into the differential case (2) through the assembly window (203).

3. A differential structure according to claim 2, characterized in that, The planetary shaft (3) includes a shaft rod (301) and a shaft sleeve (302); The shaft rod (301) is a stepped shaft, and the shaft sleeve (302) is a hollow shaft; The shaft rod (301) is in sliding fit with the shaft sleeve (302); One end of the shaft rod (301) away from the shaft sleeve (302) is detachably connected to the first second mating hole (202); One end of the shaft sleeve (302) away from the shaft rod (301) is detachably connected to the second second mating hole (202).

4. A differential structure according to claim 3, characterized in that, A pin shaft (6) is detachably installed in the second mating hole (202) in the radial direction; In the differential case (2), the pin shaft (6) at one end passes through the shaft rod (301), and the pin (6) at the other end passes through the shaft sleeve (302).

5. A differential structure according to claim 3, characterized in that, First mating grooves (204) are formed on both ends of the inner surface of the differential case (2) along the second axis, and second mating grooves (205) are formed along the first axis; A second gasket (501) is arranged in the first mating groove (204), and the second gasket (501) contacts one end of the side gear (5); A first gasket (401) is arranged in the second mating groove (205), and the first gasket (401) contacts one end of the planetary gear (4).

6. The differential structure according to claim 5, characterized in that, The planetary shaft (3), the planetary gear (4) and the first gasket (401) satisfy: a≥b+c+d; Wherein, a is the distance between two intersection points, and the two intersection points are the intersection points of the contact lines between the two ends of the inner surface of the differential case (2) and the outer circle of the planetary shaft (3); b is the minimum length of the contracted planetary shaft (3); c is the width of the planetary gear (4); d is the thickness of the first gasket (401).

7. A differential structure according to claim 4, characterized in that, The planetary shaft (3) and the pin shaft (6) satisfy: f + g ≥ e + 5 mm; Wherein, f represents the distance from the pin shaft (6) at one end of the bushing (302) to the other end of the bushing (302); g represents the distance from the pin shaft (6) at one end of the shaft rod (301) to the bushing (302); e represents the distance between the center lines of the two pin shafts (6).

8. An assembly method for assembling a differential structure according to any one of claims 1-7, characterized in that It includes the following steps: Weld the main reduction gear (1) and the differential case (2), and perform gear grinding; Install the half shaft gear (5) in the differential case (2) and arrange it along the second axis; Place the contracted planetary shaft (3) in the differential case (2); Install the first planetary gear (4) at one end of the differential case (2) and mesh it with the half shaft gear (5); Install the second planetary gear (4) at the other end of the differential case (2) and mesh it with the half shaft gear (5); Stretch the planetary shaft (3) and rotatably cooperate with the two planetary gears (4); Rotate the planetary shaft (3) to make the planetary shaft (3) coincide with the first axis; Fix the planetary shaft (3) on the differential case (2).

9. An assembly method according to claim 8, characterized in that, Rotating the planetary shaft (3) to make the planetary shaft (3) coincide with the first axis includes the following steps: Rotate the planetary shaft (3) in the horizontal plane where the first axis is located until the planetary shaft (3) coincides with the first axis.

10. A method of assembly according to claim 8, characterized in that Fixing the planetary shaft (3) on the differential case (2) includes the following steps: After the planetary shaft (3) coincides with the first axis, continue to stretch the planetary shaft (3) to the maximum length so that both ends of the planetary shaft (3) extend into the second mating holes (202) on the surface of the differential case (2); Insert the pin shaft (6) radially along the second mating hole (202) and make the pin shaft (6) pass through the planetary shaft (3), thereby fixing the planetary shaft (3) on the differential case (2).

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