Sun gear clamping device and clamping method for reducing heat treatment deformation of internal spline

Abstract

The invention discloses a sun gear clamping device for reducing heat treatment deformation of an internal spline and a clamping method. The sun gear clamping device comprises a bearing chassis; the carburizing, quenching and tempering clamps are arranged in multiple layers and are stacked on the bearing base plate in parallel, vertical columns are vertically arranged on the upper surfaces of the carburizing, quenching and tempering clamps, and the vertical columns are distributed in a matrix shape; the stand column is sleeved with the compensation core rod with a gap, the compensation core rod is sleeved with the sun gear with a gap, an annular groove is formed in the outer side face of the compensation core rod, the width of the annular groove is 1 / 3 of the thickness of the sun gear arranged on the annular groove in a sleeved mode, and the annular groove corresponds to the middle position of the sun gear arranged on the annular groove in a sleeved mode. In the heat treatment process, the problem that in the heat treatment production process of an existing thin-wall hollow circular ring structure sun gear with outer teeth and inner splines, the deformation reject ratio of the inner splines is high is solved through the method matched with the device.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment, and particularly to a sun gear clamping device and a clamping method for reducing the heat treatment deformation of internal splines. Background Art

[0002] The sun gear, as a core component of the planetary gear transmission system, plays a crucial role. It is not only the power output wheel in the system but also realizes efficient power transmission through the combination of its central shaft and multiple gears. Structurally, the sun gear usually has more teeth than other gears to ensure the stability and efficiency of transmission. Its working principle is based on the precise meshing between gears, and it completes the power output and conversion by actively driving other gears, such as planetary gears. When it comes to applications, the sun gear can be found in almost all fields requiring precise transmission. Whether it is the power transmission of vehicles, the propulsion system of ships, the complex mechanical structures of spacecraft, or even the automatic control of generators, wind turbines, and industrial machinery, the sun gear plays an irreplaceable role with its unique transmission performance and wide adaptability.

[0003] The specifications of sun gears are very diverse. Among them, the ring structure with thin walls, hollow, and both external teeth and internal splines is a commonly used sun gear structure in electric vehicles. The wall thickness of this kind of sun gear is usually only 4 - 5 mm, and the ratio of the wall thickness to the outer diameter reaches more than 11:1. The module of the internal spline is relatively small (m n <1 mm). When the sun gear with the above structure is processed by carburizing and quenching in a conventional method, the scatter difference of its deformation amount is usually high, resulting in difficulties in the quality control of the sun gear (the defective rate is generally greater than 20%). At this time, it is only possible to ensure the smooth progress of subsequent processing by increasing the machining allowance of the sun gear. However, increasing the machining allowance will not only increase the cutting workload during the machining of the sun gear, reduce the machining efficiency, and increase the machining cost. At the same time, the increased thickness will also affect the carburizing and quenching effects of the sun gear, resulting in an increase in the uncertainty factors of the quality of the sun gear after processing. Therefore, it is very necessary to develop a method that can stably reduce the heat treatment deformation of the sun gear with the above structure. Summary of the Invention

[0004] The purpose of the present invention is to provide a sun gear clamping device and a clamping method for reducing the heat treatment deformation of internal splines, so as to reduce the deformation amount of the sun gear after heat treatment through the improvement of the clamping device and the clamping method.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A sun gear clamping device for reducing the heat treatment deformation of internal splines, comprising

[0007] A load-bearing chassis;

[0008] Carburizing, quenching and tempering fixture. The carburizing, quenching and tempering fixture is provided with multiple layers and is stacked parallelly on a load-bearing chassis. The upper surface of the carburizing, quenching and tempering fixture has vertical columns, and the columns are distributed in a matrix.

[0009] Compensation mandrel, sleeved on the column with a gap. The sun gear is sleeved on the compensation mandrel with a gap. An annular groove is provided on the outer side surface of the compensation mandrel. The width of the annular groove is 1 / 3 of the thickness of the sun gear sleeved thereon, and the annular groove corresponds to the middle position of the sun gear sleeved thereon.

[0010] Preferably, the outer diameters of both ends of the compensation mandrel are 1.2 - 1.5 mm smaller than the inner spline diameter of the sun gear.

[0011] Preferably, the outer diameters of both ends of the compensation mandrel are 1.0 mm larger than the outer diameter of the middle annular groove of the compensation mandrel.

[0012] Preferably, the height of the compensation mandrel is 0.5 - 1.0 mm higher than the sun gear sleeved thereon.

[0013] Preferably, the carburizing, quenching and tempering fixture includes a support plate. The support plate is in a grid shape, and the columns are vertically arranged at the grid nodes of the support plate.

[0014] Preferably, the cross-section of the column is in a triangular star shape, and the outer diameter of the column is 1 - 1.5 mm smaller than the inner diameter of the compensation mandrel.

[0015] A method for clamping a sun gear to reduce heat treatment deformation of internal splines, including:

[0016] Step 1: According to the specifications of the sun gear to be processed, select a layer of carburizing, quenching and tempering fixture with a suitable column spacing, and horizontally install the carburizing, quenching and tempering fixture on the load-bearing chassis.

[0017] Step 2: Vertically sleeve the compensation mandrel onto the corresponding column on the carburizing, quenching and tempering fixture.

[0018] Step 3: Sleeve the sun gear onto the compensation mandrel. When one layer is filled, it should be noted that after the sun gear is sleeved onto the sun gear compensation mandrel, it is necessary to ensure that the annular groove in the middle of the sun gear compensation mandrel is in the middle position of the sun gear.

[0019] Step 4: Stack and load the second layer of the carburizing, quenching and tempering fixture onto the first layer that has been filled with workpieces.

[0020] Step 5: Repeat Step 2 - Step 4 until the stacking height reaches the height suitable for the heat treatment furnace to maximize the utilization of the equipment during each heat treatment.

[0021] Preferably, in the step 1, the selected carburizing, quenching and tempering fixture is based on the principle that after the sun gear is sleeved on the compensation mandrel, the gap between two adjacent sun gear workpieces is not less than 12 mm, and there is a height difference of not less than 20 mm between the sun gear and the support plate of the upper carburizing, quenching and tempering fixture.

[0022] Preferably, in the step 5, when clamping the sun gear, after clamping every two layers of sun gears, one layer of the carburizing, quenching and tempering fixture is left unclamped to ensure that the upper and lower parts of every two layers of sun gears are vacant layers.

[0023] Beneficial effects:

[0024] 1. The present invention preferably designs a tooling fixture and a compensation mandrel for carburizing, quenching and tempering of the sun gear. Without changing the original carburizing and quenching process parameters, in addition to meeting the technical requirements of the drawing for hardness, case depth and metallographic structure, it effectively reduces the thermal deformation of the thin-walled sun gear, reduces the deformation amount and scatter of the external teeth and internal splines, cancels the machining process of the internal splines after heat treatment, and ensures the size and precision of the internal splines;

[0025] 2. After the tooling fixture and the compensation mandrel for carburizing, quenching and tempering of the special sun gear preferably designed by the present invention are put into production, the defective rate of thermal deformation is reduced from more than 20% to less than 0.4%.

[0026] 3. The tooling fixture and the compensation mandrel for carburizing, quenching and tempering of the special sun gear preferably designed by the present invention have a simple and reasonable structure, which is convenient for operators to assemble, disassemble and load, and maintains a high clamping efficiency. Description of the drawings

[0027] Figure 1 is a structural schematic diagram of the present invention;

[0028] Figure 2 is the load-bearing chassis in the present invention;

[0029] Figure 3 is the test data table of Example 1 in the present invention;

[0030] Figure 4 is a sectional view of the compensation mandrel in the present invention.

[0031] Reference numerals: 1. Load-bearing chassis 2. Carburizing, quenching and tempering fixture 21. Support plate 22. Column 3. Compensation mandrel 31. Annular groove 4. Sun gear. Detailed implementation manners

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. 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.

[0033] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] Embodiment 1

[0036] This embodiment discloses a sun gear clamping device for reducing the heat treatment deformation of internal splines, so as to overcome the problem of high defective rate of internal spline deformation existing in the heat treatment production of a sun gear with a thin-walled, hollow, and ring structure with external teeth and internal splines at the same time.

[0037] Specifically, as Figures 1 to 4 shown, it includes a load-bearing chassis 1. The load-bearing chassis used in this embodiment is a general model for continuous furnaces, with a specification of 600x600x50 mm, so as to ensure that this clamping device has wide adaptability.

[0038] As Figure 1 shown, multiple layers of carburizing, quenching, and tempering fixtures 2 are stacked on the load-bearing chassis 1, and the sun gears 4 to be heat-treated can be clamped on each layer of carburizing, quenching, and tempering fixtures. It should be noted that according to the thickness of the sun gear to be processed, the specific height of the carburizing, quenching, and tempering fixture 2 also needs to be adaptively changed, that is, there can be multiple selectable specifications for the carburizing, quenching, and tempering fixture, so as to ensure that after the sun gear is clamped on each layer of carburizing, quenching, and tempering fixture, there is still enough space for the atmosphere during carburizing and the quenching oil to fully contact with the sun gear.

[0039] It should be noted that in this embodiment, the selection principle of the carburizing, quenching and tempering fixture 2 is that while making the height of the stacked carburizing, quenching and tempering fixtures as close as possible to the effective processing height of the heat treatment equipment, it is ensured that after the sun gear is clamped on the carburizing, quenching and tempering fixture 2, the distance between the upper end surface of the sun gear and the bottom surface of the upper stacked carburizing, quenching and tempering fixture is not less than 20 mm, so as to ensure that during carburizing and quenching, the atmosphere during carburizing and the quenching liquid can smoothly pass through the location where the sun gear is located. Specifically, taking this embodiment as an example, if the overall height of the carburizing, quenching and tempering fixture in this solution is about 63 mm and the effective processing height of the heat treatment equipment is about 600 mm, then after the carburizing, quenching and tempering fixtures are stacked in 7 layers, the maximum height of the effective processing interval during the heat treatment process will be reached. Under this stacking number, the carburizing and heat treatment effects of each layer of sun gears clamped on the carburizing, quenching and tempering fixtures are uniform and stable, so as to ensure the unity of the sun gear quality in the same batch.

[0040] As Figure 3 shown, the carburizing, quenching and tempering fixture 2 in this solution specifically includes a support plate 21 and a number of upright columns 22 uniformly arrayed on the support plate 21. The upright columns 22 provided on the support plate 21 extend vertically so as to be able to serve as support columns when stacking the carburizing, quenching and tempering fixtures to support the upper carburizing, quenching and tempering fixture 2.

[0041] At the same time, as Figure 3 shown, this solution also includes a number of compensation mandrels 3 sleeved on the upright columns 22 in one-to-one correspondence. Through this compensation mandrel, the problem of excessive deformation of the internal spline of the existing sun gear during the heat treatment process is improved.

[0042] Specifically, the compensation mandrel 3 in this solution has an axially through middle to form a tubular structure that can be sleeved on the upright column. At the same time, a circular groove 31 surrounding the outer surface of the compensation mandrel is also opened on the outer surface of the compensation mandrel. This circular groove is located in the middle of the compensation mandrel to ensure that after the sun gear is sleeved on the compensation mandrel, the circular groove is aligned with the middle position of the sun gear. Preferably, in this solution, the width of the circular groove on the compensation mandrel is 1 / 3 of the thickness of the sun gear.

[0043] It should be noted that the reason why the structure of the compensation mandrel is set to a dumbbell shape with an annular groove in the middle in this solution is mainly that if a traditional cylindrical guide post is used to sleeve and clamp the sun gear, during the carburizing and quenching processes, the smoothness of the carburizing atmosphere and quenching oil entering the internal spline through the gap between the guide post and the internal spline is different. Especially after entering the middle position, its flow rate will be lower than that at both ends. At this time, the temperature changes in the two end regions and the middle region of the internal spline of the sun gear will be asynchronous, and there will also be certain differences in the thermal deformation amounts of each region of the internal spline (mainly the difference between the two end regions and the middle region). Then, the middle part of the internal spline of the sun gear will undergo inward / outward radial bulging deformation, that is, there are large differences in the thermal deformation amounts of the middle part of the internal spline. As a result, after heat treatment of the sun gear clamped by the traditional cylindrical guide post, its two ends are also forced to undergo follow-up structural changes. Finally, reflected in the detection values, the end runout values and M values measured after heat treatment of the sun gear using the traditional clamping device and clamping method deviate greatly from the design requirements, the qualified rate of heat treatment of the sun gear is generally low, the subsequent processing cost of the sun gear is high, and the uncertainty of the product increases.

[0044] However, in this solution, by opening an annular groove on the outer surface of the compensation mandrel, the gap between the compensation mandrel and the middle position of the internal spline of the sun gear is increased, and the problem that the temperature change caused by the low flow efficiency of the carburizing atmosphere and quenching oil at this position cannot be synchronized with both ends is effectively solved. After heat treatment of the sun gear, the deformation amount of its morphological structure can naturally be reduced accordingly, thus effectively improving the qualified rate of the sun gear.

[0045] Preferably, in this solution, to ensure that the carburizing atmosphere and the quenching liquid during quenching can flow smoothly through the surface of the internal spline of the sun gear and be in full contact with the surface of the internal spline of the sun gear. The outer diameters of the two ends with larger diameters of the compensation mandrel are 1.2 - 1.5 mm smaller than the inner diameter of the internal spline of the sun gear.

[0046] It should be noted that under the above values, both the carburizing atmosphere and the quenching oil can pass through the surface of the internal spline of the sun gear at an appropriate rate to ensure the optimal treatment of carburizing and quenching.

[0047] It should be noted that as a further optimization, the outer diameters at both ends of the compensation mandrel 3 are 1.0 mm larger than the outer diameter of the middle annular groove 31 of the compensation mandrel 3. That is, the annular groove is radially contracted inward by 1.0 mm based on the outer diameter values at both ends of the compensation mandrel. At this time, the gap between the annular groove 31 and the inner diameter of the sun gear is between 1.1 and 1.25 on one side. It should be noted that through production verification, this gap value is the range value that can best maintain the synchronization of the temperature change speed between the two ends and the middle part of the internal spline of the sun gear under the structure of this solution. That is, at this gap value, the two end parts and the middle part of the internal spline of the sun gear can maintain synchronous temperature rise and fall, and the quenching and carburizing effects are not affected.

[0048] It should be noted that there are chamfers at the ports of the internal splines at both ends of the sun gear. To ensure that the compensation mandrel can completely cover the internal spline, the length of the compensation mandrel in this solution is set to be 0.5 - 1 mm greater than the thickness of the sun gear sleeved outside the compensation mandrel.

[0049] The carburizing, quenching and tempering fixture 2 in this solution is mainly composed of a support plate 21 and columns 22 arrayed on the support plate. Among them, to facilitate the entry of the atmosphere during carburizing and quenching oil from the lower port of the sun gear during the heat treatment process, the support plate 21 is set in a grid shape, and the columns 22 are arranged at the grid nodes of the support plate. Preferably, it can be set in a honeycomb structure. Under this structure, the stability and physical properties of the carburizing, quenching and tempering fixture can be effectively guaranteed, and the grid structure can also effectively reduce the overall weight of the clamping device in this solution, achieving the purpose of weight reduction and energy saving.

[0050] In addition, it should also be noted that during the heat treatment process, to ensure that the temperature of the compensation mandrel inserted inside the sun gear can be consistent with the surrounding environment to avoid unnecessary disturbance to the temperature of the sun gear, the cross-section of the column in this solution is in a triangular structure. That is, after the compensation mandrel is sleeved on the column, there is a channel for the entry of quenching oil and the atmosphere during carburizing between the column and the inner control of the compensation mandrel. Through this structure in this solution, rapid heat exchange between the internal part and the outside of the compensation mandrel is achieved, ensuring the consistency of the temperature of the compensation mandrel and the external environment, and avoiding disturbance to the temperature of the sun gear during the heat treatment process (mainly to avoid that because the compensation mandrel is wrapped by the sun gear, if there is no heat exchange channel between the compensation mandrel and the outside, it is difficult to achieve rapid synchronization with the external environment temperature. At this time, it will lead to inconsistent internal and external temperatures of the sun gear, and then cause inconsistent internal and external thermal deformations of the sun gear, and the sun gear will be distorted in shape).

[0051] It should also be noted that to facilitate the sleeving of the compensation mandrel onto the column and its subsequent removal from the column, there is a dimensional difference in the range of 1 - 1.5 mm between the outer diameter of the column 22 and the inner diameter of the compensation mandrel 3.

[0052] In addition, this embodiment also discloses a method for clamping a sun gear using the sun gear clamping device in the above embodiment, which specifically includes the following steps:

[0053] Step 1: According to the specifications of the sun gear to be processed, select a carburizing, quenching and tempering fixture with an appropriate column spacing, and horizontally install the carburizing, quenching and tempering fixture on the load-bearing chassis. Specifically, the selected carburizing, quenching and tempering fixture needs to ensure that when the sun gear is clamped onto the carburizing, quenching and tempering fixture in this solution, the gap between adjacent sun gears is not less than 12 mm, so as to ensure that the workpieces will not collide with each other and facilitate the smooth flow of the atmosphere during carburizing and the uniform and orderly flow of the quenching liquid during quenching. At the same time, ensure that when the sun gear is clamped onto the carburizing, quenching and tempering fixture, there is a height difference of not less than 20 mm between the upper end face of the sun gear and the bottom surface of the carburizing, quenching and tempering fixture above it, so as to ensure that the upper and lower layer workpieces will not be damaged and facilitate the smooth flow of the atmosphere during carburizing and the uniform and orderly flow of the quenching liquid during quenching.

[0054] Step 2: Vertically sleeved the compensation mandrel onto the corresponding column on the carburizing, quenching and tempering fixture;

[0055] Step 3: Sleeve the sun gear onto the compensation mandrel and fill one layer. It should be noted that after the sun gear is sleeved onto the sun gear compensation mandrel, it is necessary to ensure that the annular groove in the middle of the sun gear compensation mandrel is in the middle position of the sun gear;

[0056] Step 4: Stack and load the second layer of the carburizing, quenching and tempering fixture onto the first layer that has been filled with workpieces;

[0057] Step 5: Repeat Step 2 to Step 4 until the stacking height reaches the height adapted to the heat treatment furnace to maximize the utilization of the equipment during each heat treatment.

[0058] In addition, it should be noted that in Step 5, that is, when stacking the sun gears layer by layer, the following arrangement can also be made. Specifically, when clamping the sun gears, leave one layer empty every two layers of clamping to ensure that the upper and lower parts of every two layers of sun gears are empty. Through the above arrangement, it is convenient for the smooth flow of the atmosphere during carburizing (to make the carburized layer of the whole batch of products uniform) and the uniform and orderly flow of the quenching liquid during quenching (to make the quenched hardened layer and the deformation amount of the whole batch of products uniform).

[0059] Using the process of this embodiment, the surface hardness of the product reaches more than 700 HV1, the core hardness reaches 340 - 400 HV1, and the hardened layer (550 HV1) reaches 0.4 - 0.7 mm. The single-furnace output reaches 588 pieces, the deformation of the internal spline is stably within 0.03 mm, and the qualified rate of the heat treatment process of the sun gears produced in large quantities reaches more than 99.6%. For specific data, refer to Table 21 and Table 2-2.

[0060] Control Example

[0061] In this solution, the clamping device for the sun gear is different from that in Embodiment 1 in that the support plate in the carburizing, quenching and tempering fixture 2 is non-grid-shaped, and the guide post for clamping the sun gear is only of a cylindrical structure. The method for clamping the sun gear is as follows:

[0062] Step 1: According to the specifications of the sun gear to be processed, select a layer of fixture with an appropriate column spacing, and horizontally install the fixture on the load-bearing chassis;

[0063] Step 2: Put the sun gear on the guide posts of the fixture and fill one layer;

[0064] Step 3: Stack and load the second layer of the fixture on the first layer that is already full of workpieces;

[0065] Step 4: Repeat Steps 2 to 3 until the stacking height reaches the height suitable for the heat treatment furnace to maximize the utilization of the equipment during each heat treatment.

[0066] The actual data of the sun gear after heat treatment by the above structure and method can be referred to Table 1-1 and Table 1-2.

[0067] It should be noted that from the comparison of the detection data in Table 1-1, Table 1-2, Table 2-1 and Table 2-2, it can be seen that the yield rate of the sun gear is significantly improved by using the clamping device and the clamping method disclosed in this solution.

[0068] Table 1-1

[0069]

[0070] Table 1-2

[0071]

[0072] Table 2-1

[0073]

[0074] Table 2-2

[0075]

[0076] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sun gear clamping device for reducing the deformation of internal splines during heat treatment, characterized in that: include load-bearing chassis (1); A carburizing, quenching and tempering fixture (2), wherein the carburizing, quenching and tempering fixture (2) is provided with multiple layers and is stacked in parallel on a load-bearing chassis (1), and the upper surface of the carburizing, quenching and tempering fixture (2) has vertically arranged columns (22), and the columns (22) are distributed in a matrix shape; A compensation core rod (3) is sleeved on the column (22) with a gap, and a sun gear is sleeved on the compensation core rod (3) with a gap. An annular groove (31) is provided on the outer surface of the compensation core rod (3), and the width of the annular groove (31) is 1 / 3 of the thickness of the sun gear sleeved thereon, and the annular groove (31) corresponds to the middle position of the sun gear sleeved thereon.

2. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 1, characterized in that: The outer diameters of both ends of the compensating core rod (3) are 1.2 to 1.5 mm smaller than the diameter of the inner spline of the sun gear.

3. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 2, characterized in that: The outer diameters of both ends of the compensating core rod (3) are 1.0 mm larger than the outer diameter of the annular groove (31) in the middle of the compensating core rod (3).

4. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 3, characterized in that: The height of the compensating core rod (3) is 0.5 to 1.0 mm higher than the sun gear sleeved thereon.

5. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 4, characterized in that: The carburizing, quenching and tempering fixture (2) comprises a support plate (21), the support plate (21) is in a grid shape, and the columns (22) are vertically arranged on the grid nodes of the support plate (21).

6. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 5, characterized in that: The cross section of the column (22) is in the shape of a triangular star, and the outer diameter of the column (22) is 1 to 1.5 mm smaller than the inner diameter of the compensation core rod (3).

7. A sun gear clamping method using the sun gear clamping device according to any one of claims 1 to 6, characterized in that: include: Step 1: According to the specifications of the sun gear to be processed, select a carburizing, quenching and tempering fixture with a suitable column spacing, and install the carburizing, quenching and tempering fixture horizontally on the load-bearing chassis; Step 2: Vertically fit the compensating mandrel onto the corresponding column on the carburizing, quenching and tempering fixture; Step 3: Put the sun gear onto the compensation core rod and fill it with one layer. It should be noted that after the sun gear is put onto the sun gear supplementary core rod, it is necessary to ensure that the annular groove in the middle of the sun gear supplementary core rod is in the middle position of the sun gear; Step 4: Load the second layer of the carburizing, quenching and tempering fixture onto the first layer filled with workpieces; Step 5: Repeat steps 2 to 4 until the stacking height reaches a height that matches the heat treatment furnace to maximize equipment utilization during each heat treatment.

8. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 7, characterized in that: In step 1, the adapted carburizing, quenching and tempering fixture is selected based on the principle of ensuring that after the sun gear sleeve is mounted on the compensating core rod, the gap between two adjacent sun gear workpieces is not less than 12 mm, and at the same time, there is a height difference of not less than 20 mm between the sun gear and the support plate of the upper carburizing, quenching and tempering fixture.

9. A sun gear clamping device for reducing heat treatment deformation of internal splines as claimed in claim 8, characterized in that: In step 5, when clamping the sun gear, after clamping two layers of sun gear, a layer of carburizing, quenching and tempering fixture is left empty and no sun gear is clamped, so as to ensure that the upper and lower parts of every two layers of sun gear are empty layers.

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