Planetary gear inner hole carburizing and quenching process

Abstract

The present application relates to the technical field of machining, and discloses a planet wheel inner hole carburizing and quenching process, which comprises the following steps: inner hole processing, i.e. processing a stepped inner hole in a planet wheel blank, wherein the inner hole comprises two bearing tracks and a middle hole connected between the two bearing tracks, the inner diameter of the two bearing tracks gradually increases from the end close to the middle hole to the opening end, and the inner diameter of the middle hole is smaller than the minimum inner diameter of the two bearing tracks; and performing overall carburizing and quenching on the inner wall surface of the inner hole. The planet wheel inner hole carburizing and quenching process effectively compensates for the local abnormal expansion caused by the difference in quenching stress between the two ends and the middle part of the inner hole in the tooth width direction. Meanwhile, the overall carburizing and quenching of the inner wall surface of the inner hole suppresses the local abnormal expansion phenomenon caused by the stress mutation in the high-carbon area at the two ends and the low-carbon area in the middle part of the inner hole due to the difference in chemical composition during the quenching process. The present application also discloses a planet wheel, which also has the above technical effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical processing, more particularly, to a planet wheel inner hole carburizing and quenching process. BACKGROUND

[0002] The planetary transmission mechanism in the wind power gear box is widely used in the wind power gear box due to the advantages of large transmission ratio, compact structure, power split and the like. The planet wheel is an important component of the planetary transmission mechanism in the wind power gear box. The planet wheel and bearing outer ring integration technology of the main speed-up gear box of the wind turbine is a landmark progress in the design technology of the gear box of the wind turbine in recent years. The integration technology brings great difficulty to the manufacturing technology. The planet wheel is used as the bearing outer ring, and the inner hole of the planet wheel is required to have high hardness and wear resistance required by the bearing. Therefore, the planet gear heat treatment realizes the best cooperation of the ideal carbon concentration distribution of carburizing, the high hardness gradient of quenching and the small distortion deformation control, so as to ensure the high hardness of the inner hole of the processed product.

[0003] The conventional surface hardening mode of the planet wheel of the wind power gear box is carburizing and quenching, and the gear is ground into a finished product. Due to the irregular wind force and strong wind impact variable load effect of the wind field, the planet wheel accounts for a large proportion in the gear failure of the gear box, and is also a gear part with more actual damage. Through the analysis of the manufacturing process, the inevitable deformation of the planet wheel caused by the heat treatment process is relatively large, which can cause the grinding allowance to change, resulting in uneven depth and hardness of the inner hole hardening layer. Excessive deformation can even cause insufficient inner hole hardness and hardening layer depth, reduce the reliability in use, affect the contact fatigue life of the part, reduce the life cycle of the wind power gear box, increase the processing time of the subsequent process, and increase the manufacturing cost. In the production and processing process, the inner hole is often expanded to a large extent, which exceeds the finished product size and causes waste.

[0004] In summary, how to effectively solve the problem of large deformation of the planet wheel inner hole carburizing and quenching affecting the product quality is a problem to be solved by the technical personnel in the field at present. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a planet wheel inner hole carburizing and quenching process and planet wheel, which can effectively solve the problem of large deformation of the planet wheel inner hole carburizing and quenching affecting the product quality.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] A planet wheel inner hole carburizing and quenching process, comprising:

[0008] The inner hole is processed in the planetary gear blank, and the inner hole includes two bearing tracks and a middle hole connected between the two bearing tracks, the inner diameters of the two bearing tracks gradually increase from the end close to the middle hole to the open end, and the inner diameter of the middle hole is smaller than the minimum inner diameters of the two bearing tracks;

[0009] The inner wall surface of the inner hole is carburized and quenched as a whole.

[0010] Optionally, in the planetary gear inner hole carburizing and quenching process, the inner circumferential surfaces of the two bearing tracks are conical surfaces.

[0011] Optionally, in the planetary gear inner hole carburizing and quenching process, the inner wall surface of the inner hole is carburized and quenched as a whole, and specifically includes:

[0012] The inner wall surface of the inner hole is carburized and quenched as a whole, and the gaskets are arranged on the upper and lower end surfaces of the planetary gear.

[0013] Optionally, in the planetary gear inner hole carburizing and quenching process, the thickness of each gasket is not greater than 50 mm.

[0014] Optionally, in the planetary gear inner hole carburizing and quenching process, before the inner hole is processed, the process further includes:

[0015] The circumferential surfaces of the two bearing tracks of the planetary gear inner hole with the circumferential surfaces of the two bearing tracks being cylindrical surfaces are simulated to be carburized and quenched, and the deformation amounts of the two bearing tracks are obtained.

[0016] According to the deformation amounts, the inner diameter changes of the two bearing tracks from the end close to the middle hole to the open end are determined.

[0017] The inner hole is processed according to the determined inner diameter changes.

[0018] Optionally, in the planetary gear inner hole carburizing and quenching process, before the inner hole is processed, the process further includes:

[0019] The circumferential surfaces of the two bearing tracks of the planetary gear inner hole with the circumferential surfaces of the two bearing tracks being cylindrical surfaces are simulated to be carburized and quenched, and the deformation amounts of the two bearing tracks are obtained.

[0020] According to the deformation amounts, the inner diameter changes of the two bearing tracks from the end close to the middle hole to the open end are determined.

[0021] The inner hole is processed according to the determined inner diameter changes.

[0022] The planet wheel inner hole carburizing and quenching process provided by the application is used to process the bearing track of the inner hole to gradually increase the inner diameter from the end close to the middle hole to the opening end, the inner diameter of the middle part is small and the inner diameters of the two ends are large, so that the local abnormal expansion caused by the difference in quenching stress between the two ends and the middle part of the inner hole in the tooth width direction is effectively compensated, the reverse deformation effect is achieved, and the deformation of the saddle-shaped structure formed by the bearing track and the middle hole of the planet wheel obtained after carburizing and quenching is not obvious. Meanwhile, the inner wall surface of the inner hole is subjected to overall carburizing and quenching, compared with the traditional local carburizing and quenching, the chemical composition of the inner hole surface is unified, and the local abnormal expansion phenomenon caused by the stress mutation of the high-carbon two ends and the low-carbon middle part of the inner hole in the quenching process is inhibited. In summary, the planet wheel inner hole carburizing and quenching process provided by the application effectively solves the planet wheel carburizing and quenching deformation control problem and improves the product quality.

[0023] In order to achieve the above-mentioned purpose, the application further provides a planet wheel which is processed by using any one of the planet wheel inner hole carburizing and quenching processes described above. Since the planet wheel inner hole carburizing and quenching process described above has the technical effects described above, the planet wheel prepared by using the planet wheel inner hole carburizing and quenching process should also have corresponding technical effects. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 It is a structural schematic diagram of a target planet wheel product;

[0026] Figure 2 It is a schematic diagram of the deformation of a planet wheel blank after carburizing and quenching;

[0027] Figure 3 It is a simulation diagram of the stress distribution of a planet wheel blank after carburizing and quenching;

[0028] Figure 4 It is a flowchart of the planet wheel inner hole carburizing and quenching process of one specific embodiment of the application;

[0029] Figure 5 It is a schematic diagram of the inner hole structure.

[0030] The marks in the drawings are as follows:

[0031] Bearing track 100, middle hole 200, protrusion 300. DETAILED DESCRIPTION

[0032] The planetary gear inner hole carburizing and quenching process and the planetary gear disclosed by the embodiments of the present application can optimize the planetary gear carburizing and quenching deformation control and improve the product quality.

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0034] The planetary gear inner hole carburizing and quenching process provided by the present application is suitable for the carburizing and quenching treatment of the inner hole of a planetary gear. Figure 1 As shown in the figure, the outer circumferential surface is provided with teeth, the middle inner hole includes bearing tracks 100 at both ends and a middle hole 200 connected between the two bearing tracks 100, the part of the planetary gear corresponding to the bearing track 100 is used as a bearing outer ring, the inner diameter of the middle hole 200 is smaller than the inner diameter of the two bearing tracks 100, so that a protrusion 300 is formed between the two bearing tracks 100, that is, a saddle-shaped structure is formed in the overall height direction of the planetary gear. The two bearing tracks 100 are respectively used as the action surface of the bearing outer ring for cooperation with the bearing inner ring, so that they have higher requirements on properties such as wear resistance and hardness. The conventional inner hole carburizing and quenching treatment is mostly local carburizing and quenching, that is, the tooth surface and the inner wall surface of the two bearing tracks 100 of the planetary gear are subjected to carburizing and quenching, and the wall surface of the middle hole 200 is not subjected to carburizing and quenching. Therefore, the wall surface of the middle hole 200 is coated with a non-carburizing surface paint for protection during the carburizing and quenching treatment.

[0035] After the above carburizing and quenching treatment is performed on the blank with the same shape as the target planetary gear product, the deformation of the part is large. As shown in the figure, Figure 2 , Figure 2 After the tooth part and the two bearing tracks 100 of a certain type of wind turbine gearbox two-stage planetary gear are subjected to carburizing and quenching (with a single-side allowance of 1 mm in the inner hole), the deformation schematic diagram is shown by the dashed line, and the shape after the carburizing and quenching is shown by the solid line. As can be seen, after the carburizing and quenching of the part, the surface of the root part of the protrusion 300 is abnormally expanded, which is about 0.5-1 mm larger than the hole at both ends, causing the product to be unable to be machined. Through simulation of the carburizing and quenching, as shown in the figure, Figure 3 , the stress distribution is consistent with the actual deformation trend.

[0036] The research finds that the causes of the above deformation mainly include the following two points. On the one hand, the core and the surface carburized layer are two corresponding stress acting aspects. The surface high-carbon austenite is obviously contracted in the temperature range from about 830 degrees of quenching temperature to Ms point. At this time, the core is transformed from low-carbon austenite to ferrite or low-carbon bainite and martensite, and the volume increases, so a larger internal stress is generated between the two. Therefore, the two bearing tracks 100 are subjected to a deformation process of first contraction and then expansion during carburizing and quenching. The raised portion 300 is not protected by high-carbon austenite, and the deformation process during carburizing and quenching cooling is all expansion. Therefore, the inner hole near the root of the raised portion 300 expands greatly. On the other hand, the deformation caused by the stress of the part after quenching is basically regular, the end face is reduced, the sharp corner is raised, and the surface is concave.

[0037] Therefore, based on the research on the above deformation causes, the present application improves the carburizing and quenching process of the inner hole of the planetary gear to reduce the influence of the carburizing and quenching of the inner hole of the planetary gear on the size of the part. In the following embodiments, this is mainly explained.

[0038] In some embodiments, referring to Figure 4 , the present application provides a carburizing and quenching process for the inner hole of a planetary gear, which comprises the following steps:

[0039] S1: inner hole processing, machining a stepped inner hole in the planetary gear blank, and the inner hole comprises two bearing tracks and a middle hole connected between the two bearing tracks, the diameter of the middle hole is smaller than the diameter of the two bearing tracks, and the inner diameter of the two bearing tracks gradually increases from the end close to the middle hole to the opening end, as shown in Figure 5 , the partial cross-sectional structure of the planetary gear is shown, which mainly embodies the shape of the inner hole; Figure 5

[0040] S2: the inner wall surface of the inner hole is carburized and quenched as a whole.

[0041] That is, before carburizing and quenching, the shape of the two bearing tracks is changed by processing the inner hole. During carburizing and quenching, the local carburizing is optimized to whole carburizing. The surface high-carbon austenite is obviously contracted in the temperature range from about 830 degrees of quenching temperature to Ms point during quenching and cooling; the core is transformed from low-carbon austenite to ferrite or low-carbon bainite and martensite, and the volume increases. Therefore, after adopting whole carburizing, the stress of each part of the inner hole surface tends to be consistent in macroscopic view. Therefore, the abnormal expansion of the inner hole near the root of the raised portion is reduced.

[0042] In addition, the organizational stress during carburizing and quenching is inevitable, so the inner hole is processed to gradually increase the inner diameter of the two bearing tracks from the end close to the middle hole to the opening end before carburizing, so as to offset the size deformation caused by the organizational stress during carburizing and quenching.

[0043] ​In summary, the planetary gear inner hole carburizing and quenching process provided by the present application processes the bearing track of the inner hole to gradually increase in inner diameter from the end close to the middle hole to the open end before carburizing and quenching, the middle inner diameter is small and the end inner diameter is large, effectively compensating for the local abnormal expansion caused by the difference in quenching stress between the two ends and the middle of the inner hole in the tooth width direction, and playing a reverse deformation effect, so that the obtained planetary gear after carburizing and quenching has no obvious deformation of the saddle-shaped structure formed by the bearing track and the middle hole. Through effective control of the saddle shape, the quality control problem of the planetary gear inner hole carburizing and quenching deformation is ensured. At the same time, the inner wall surface of the inner hole is uniformly carburized and quenched, compared with the traditional local carburizing and quenching, the chemical composition of the inner hole surface is unified, and the local abnormal expansion phenomenon caused by the stress mutation of the high-carbon two ends and the low-carbon middle part in the quenching process is inhibited. The planetary gear inner hole carburizing and quenching process provided by the present application effectively solves the planetary gear carburizing and quenching deformation control problem and improves the product quality.

[0044] In some embodiments, the inner circumferential surface of the two bearing tracks is a conical surface. In this way, the deformation caused by carburizing and quenching can be better offset, thereby reducing the deformation amount of the part and improving the product quality. In other embodiments, the inner circumferential surface of the two bearing tracks can also be an arc surface or other shape with smooth inner diameter transition.

[0045] In some embodiments, the inner wall surface of the inner hole is uniformly carburized and quenched, specifically including: disposing a gasket on the upper and lower end surfaces of the planetary gear and uniformly carburizing and quenching the inner wall surface of the inner hole. By adding a gasket to the upper and lower end surfaces of the part, the quenching effect of the two ends is reduced, thereby reducing the volume change difference caused by the stress of the two ends and the middle. Specifically, the thickness of each gasket is not greater than 50 mm.

[0046] In some embodiments, the inner hole processing further includes:

[0047] The inner hole of the planetary gear with the circumferential surface of the two bearing tracks being a cylindrical surface is simulated to perform carburizing and quenching on the circumferential surface of the two bearing tracks, and the deformation amount of the two bearing tracks is obtained;

[0048] According to the deformation amount, the inner diameter change of the two bearing tracks from the end close to the middle hole to the open end is determined;

[0049] Then, the inner hole is processed according to the determined inner diameter change. That is, during subsequent inner hole processing, the inner diameter of the two bearing tracks gradually increases from the end close to the middle hole to the open end and satisfies the above inner diameter change. By simulating to predict the deformation caused by carburizing and quenching, the inner diameter change of the two bearing tracks is set accordingly, which can better offset the size difference deformation caused by the organizational stress during carburizing and quenching, thereby improving the product quality.

[0050] In some embodiments, the inner hole processing further includes:

[0051] The inner hole of the planet wheel with the two bearing tracks of the cylindrical surface is carburized and quenched, and the deformation of the two bearing tracks is obtained;

[0052] According to the deformation, the inner diameter of the two bearing tracks from the end close to the middle hole to the opening end is determined to change;

[0053] According to the determined inner diameter change, the inner hole is processed. That is, when the subsequent inner hole is processed, the inner diameter of the two bearing tracks from the end close to the middle hole to the opening end is gradually increased and meets the above-mentioned inner diameter change. Through the test method, the deformation caused by carburizing and quenching is obtained, and the inner diameter change of the two bearing tracks is set accordingly, which can better offset the size deformation caused by the organizational stress during carburizing and quenching, thereby improving the product quality.

[0054] Based on the planet wheel inner hole carburizing and quenching process provided in the above-mentioned embodiments, the present application also provides a planet wheel, which is processed by any one of the planet wheel inner hole carburizing and quenching processes in the above-mentioned embodiments. Since the planet wheel is processed by the planet wheel inner hole carburizing and quenching process in the above-mentioned embodiments, the beneficial effects of the planet wheel are referred to the above-mentioned embodiments.

[0055] In some embodiments, the inner hole of the planet wheel includes bearing tracks for assembling bearing inner rings and a middle hole connected between the two bearing tracks, and the inner wall surface of the inner hole has a carburized and quenched layer.

[0056] In the present specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between each embodiment can be referred to each other.

[0057] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for carburizing and quenching the inner bore of a planetary gear, characterized in that, include: Internal machining involves machining stepped internal holes in a planetary gear blank. The internal holes include two bearing tracks and a central hole connecting the two bearing tracks. The inner diameter of the two bearing tracks gradually increases from the end near the central hole to the open end, and the inner diameter of the central hole is smaller than the minimum inner diameter of the two bearing tracks. The entire inner wall surface of the inner hole is subjected to carburizing and quenching.

2. The carburizing and quenching process for the inner bore of the planetary gear according to claim 1, characterized in that, The inner circumferential surfaces of the two bearing tracks are conical.

3. The carburizing and quenching process for the inner bore of the planetary gear according to claim 1, characterized in that, The inner wall surface of the inner hole is subjected to carburizing and quenching, specifically including: Washers are installed on the upper and lower end faces of the planetary gear, and the inner wall of the inner hole is carburized and quenched as a whole.

4. The carburizing and quenching process for the inner bore of the planetary gear according to claim 3, characterized in that, The thickness of each gasket shall not exceed 50mm.

5. The carburizing and quenching process for the inner bore of a planetary gear according to any one of claims 1-4, characterized in that, The process before machining the inner hole also includes: Using the inner holes of the planetary gears with cylindrical circumferential surfaces of the two bearing tracks, the circumferential surfaces of the two bearing tracks are simulated for carburizing and quenching, and the deformation of the two bearing tracks is obtained. The inner diameter of the two bearing tracks changes from the end closest to the central hole to the open end, based on the amount of deformation. The inner hole is machined according to the determined inner diameter variation.

6. The carburizing and quenching process for the inner bore of a planetary gear according to any one of claims 1-4, characterized in that, The process before machining the inner hole also includes: Using the inner holes of the planetary gears with cylindrical circumferential surfaces of the two bearing tracks, carburizing and quenching are performed on the circumferential surfaces of the two bearing tracks to obtain the deformation of the two bearing tracks. The inner diameter of the two bearing tracks changes from the end closest to the central hole to the open end, based on the amount of deformation. The inner hole is machined according to the determined inner diameter variation.

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