A processing method for carburizing and quenching split gears for engines

Abstract

The present invention relates to a processing method for a carburized and quenched split-type gear for an engine, characterized in that: the split-type gear targeted is formed by splicing two semi-circular gears; the processing method includes the following steps: S1, forging a blank of a complete circle; S2, normalizing treatment; S3, cutting the blank of the complete circle into two semi-circular gear blanks; S4, respectively processing the two semi-circular gear blanks as follows: S4-1, surface processing; S4-2, machining the tooth part on the outer edge of the semi-circular gear blank by wire cutting; S4-3, carburizing and quenching treatment; S4-4, milling the mating surface of the semi-circular gear blank; S4-5, grinding the mating surface of the semi-circular gear blank; S5, splicing and assembling the two processed semi-circular gear blanks to form a whole blank; S6, grinding the inner circumferential surface of the whole blank; S7, grinding the tooth part of the whole blank.

Description

Technical Field

[0001] The present invention belongs to the technical field of carburized gear processing, and particularly relates to a processing method for a carburized and quenched split-type gear for an engine. Background Art

[0002] Conventional gears are mostly integral gears. When used in an engine, they are assembled onto a transmission shaft by a temperature difference method or a press-fitting method. Such gears can be in various forms such as spur gears or helical gears. However, because they are all integral gears, after a period of use, various problems will occur on the tooth surface of the gear, such as pitting, scuffing, and other damages of different degrees. After damage, replacement is required. When using conventional gears, all other parts (such as bearings, coupling sleeves, etc.) on the transmission shaft need to be disassembled. During the disassembly process, it is easy to cause damage to the transmission shaft, bearings, and gear parts, and after disassembly, these parts need to be repaired or remanufactured. This maintenance cycle is relatively long and the cost is high.

[0003] Therefore, split-type gears began to be used. A split-type gear is an assembled gear that divides the whole circle of the gear into a left semi-circular gear and a right semi-circular gear, which are assembled and fixed with fasteners.

[0004] For split gears, there are not only processing requirements for the teeth on the gear but also assembly accuracy requirements, so its processing method is very important. Currently, ordinary split gears are generally quenched and tempered gears with insufficient surface hardness. At the same time, due to the assembly form, the tooth accuracy of the gear is insufficient and it cannot be applied to high-precision transmission structures. Moreover, existing processing methods mostly first machine a whole-circle gear, then perform carburizing and quenching on the whole, and then cut it into two halves, and then process the mating surface. This is likely to cause uneven hardness of the carburized layer on the tooth surface, resulting in the service performance of the part not meeting that of a whole carburized and quenched gear. Summary of the Invention

[0005] The purpose of the present invention is to provide a processing method for a carburized and quenched split-type gear for an engine, which not only ensures good heat treatment performance of the finished gear but also ensures the accuracy of the gear teeth.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a processing method for a carburized and quenched split-type gear for an engine, where the split-type gear is composed of two semi-circular gears assembled together; the material of these two semi-circular gears is Cr-Ni-Mo steel;

[0007] The processing method includes the following steps:

[0008] S1, forge a whole-circle blank;

[0009] S2, perform normalizing treatment on the whole-circle blank;

[0010] S3. Cut the blank of the whole circle into two semi-circular gear blanks;

[0011] S4. Process the two semi-circular gear blanks respectively as follows:

[0012] S4-1. Machine the surface of the semi-circular gear blank with a machining center;

[0013] S4-2. Machine the tooth parts on the outer edges of the semi-circular gear blanks respectively by wire cutting, so that the centers of the tooth parts on the two semi-circular gear blanks have an eccentricity;

[0014] S4-3. Perform carburizing and quenching treatment on the semi-circular gear blank;

[0015] S4-4. Milling process the mating surfaces of the semi-circular gear blanks with a machining center;

[0016] S4-5. Grind the mating surfaces of the semi-circular gear blanks;

[0017] After the milling and grinding processes in steps S4-4 and S4-5, the above-mentioned eccentricity is removed, so that the centers of the tooth parts on the two semi-circular gear blanks can coincide;

[0018] S5. Assemble the two processed semi-circular gear blanks together, so that the centers of the tooth parts on the two semi-circular gear blanks truly coincide, forming the whole blank;

[0019] S6. Grind the inner circumferential surface of the whole blank;

[0020] S7. Grind the tooth parts of the whole blank to become the finished product.

[0021] In the above solution, in step S3, specifically, the blank of the whole circle is cut into two semi-circular gear blanks by wire cutting.

[0022] In the above solution, in step S4-1, specifically, the surface of the semi-circular gear blank is milled with a machining center.

[0023] In the above solution, between step S4-2 and step S4-3, there is also a step S4-2-1 to chamfer the tooth parts of the semi-circular gear blank. Further, in step S4-2-1, specifically, the tooth parts of the semi-circular gear blank are chamfered manually.

[0024] In the above solution, in step S4-2, first use CAD software to simulate the cutting tool for hobbing to obtain the target tooth part dimensions, and then when machining the tooth parts by wire cutting, according to the target tooth part dimensions and considering the deformation amount of gear carburizing heat treatment, reserve a tooth profile grinding allowance for each tooth profile.

[0025] In the above solution, in step S4-5, a tooling is used to fix and clamp the semi-circular gear blank with the tooth surface as the positioning reference.

[0026] The specific design features of the present invention are as follows:

[0027] 1. The processing method of the present invention is to perform carburizing and quenching heat treatment on the two semi-circular gear blanks respectively after cutting them into two semi-circular gear blanks, that is, "cut open before heat treatment", which makes the material more stable and eliminates the stress deformation problem after part cutting.

[0028] 2. The tooth part of the present invention is processed by wire cutting to form the tooth profile. The centers of the teeth on the two semi-circular gear blanks can be non-coincident, with an eccentricity, leaving enough machining allowance at the mating surface of the two semi-circular gear blanks. The existence of this machining allowance enables the milling of this mating surface in subsequent processing to correct the deformation caused by carburizing and quenching, so that the roundness of the two semi-circular gear blanks assembled into a complete circle meets the requirements, and the carburized layer on the tooth surface is not lost, ensuring the good carburizing and quenching performance of the finished product (hardness up to standard, carburized layer depth up to standard). It not only ensures the good heat treatment performance of the finished gear but also ensures the accuracy of the gear tooth part.

[0029] 3. The present invention grinds the mating surface of the two semi-circular gears to improve the mating accuracy.

[0030] 4. After the two semi-circular gears are assembled, the present invention grinds the inner circumferential surface of the whole blank. The inner circumferential surface of the whole blank is the installation surface during use, thus ensuring the gear accuracy and the accuracy of the inner hole circumferential scheme.

[0031] In summary, the half gear produced by the present invention has the following advantages: it has good carburizing and quenching performance (hardness up to standard, carburized layer depth up to standard), and also ensures the high precision of the gear tooth part. Brief Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the teeth processed on the outer edge of the semi-circular gear blank in step S4-2 of the embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the tooling used in step S4-5 of the embodiment of the present invention.

[0034] 1. Semi-circular gear blank; 2. Pitch circle cylindrical pin bar; 3. Tooling. Embodiment

[0035] The present invention will be further described below with reference to the drawings and embodiments: Embodiment

[0036] A processing method for carburizing and quenching split-type gears for engines. The split-type gears targeted are formed by splicing two semi-circular gears. The materials of these two semi-circular gears are Cr-Ni-Mo steel, specifically using a material with the grade 18CrNiMo7-6.

[0037] The processing method includes the following steps:

[0038] S1, forge a blank of a complete circle.

[0039] S2, normalize the blank of the complete circle.

[0040] S3, cut the blank of the complete circle into two semi-circular gear blanks. Preferably, it is cut by wire cutting. In practice, other methods such as sawing can also be used for cutting.

[0041] S4, process the two semi-circular gear blanks respectively as follows:

[0042] S4-1, mill the surface of the semi-circular gear blank with a machining center.

[0043] S4-2, use wire cutting on a wire cutting machine tool to machine the tooth part on the outer edge of the semi-circular gear blank, so that the centers of the tooth parts on the two semi-circular gear blanks have an eccentricity. Specifically, this step is: first, use CAD software for tool simulation of hobbing to obtain the target tooth part dimensions (such as the root fillet of the tooth), and then when machining the tooth part by wire cutting, according to the target tooth part dimensions, and considering the deformation amount of gear carburizing and heat treatment, reserve a tooth profile grinding allowance for each tooth profile. Finally, cut out the tooth part with this tooth profile grinding allowance, so that the cut tooth shape has the same root fillet as the hobbing process. The key elements of the tooth profile grinding allowance also ensure that there are no adverse factors such as steps after the subsequent gear grinding of the part, and at the same time do not reduce the tooth root strength of the part; also as Figure 1 designed, set the eccentricity of the centers of the tooth parts on the two semi-circular gear blanks as A (such as Figure 1 in one semi-circular gear blank, the center of the tooth part is O1, and in the other semi-circular gear blank, the center of the tooth part is O2, and the eccentricity between them is A). Specifically, A can be taken as 1.6 mm, that is, leave about 0.8 mm of allowance on the joint surface of each semi-circular gear blank. This allowance is to consider eliminating the deformation of the joint surface after carburizing and quenching, so that the actual center after processing coincides with the center of the tooth part.

[0044] S4-2-1, manually chamfer the tooth part of the semi-circular gear blank.

[0045] S4-3, perform carburizing and quenching treatment on the semi-circular gear blank.

[0046] S4-4, mill the joint surface of the semi-circular gear blank with a machining center.

[0047] S4-5. Grind the mating surface of the semi-circular gear blank using a surface grinding machine. In this step, use fixture 3 to fix and clamp the semi-circular gear blank 1 with the tooth surface as the positioning reference. Specifically, the surface to be ground (i.e., the mating surface) of the semi-circular gear blank 1 can be placed horizontally upward, and the lower tooth groove can be installed on two pitch circle cylindrical pin rods 2 with the same height on the left and right. The pitch circle cylindrical pin rods 2 are positioned in the tooth surface of the tooth groove. At the same time, through simulation calculation, control the distance between the pitch circle cylindrical pin rods 2 and the grinding surface (i.e., the mating surface) to control the grinding amount of the part, so as to ensure the distance from the tooth surface to the mating surface. For the specific fixture 3, please refer to Figure 2 ;

[0048] After the milling and grinding processes in steps S4-4 and S4-5, the above eccentricity is removed, so that the centers O1 and O2 of the teeth on the two semi-circular gear blanks can coincide.

[0049] S5. Assemble the two processed semi-circular gear blanks together so that the centers O1 and O2 of the teeth on the two semi-circular gear blanks truly coincide to form a whole blank. At this time, the inner hole of the whole blank is close to an ellipse.

[0050] S6. Grind the inner circumferential surface (i.e., the inner hole) of the whole blank using a vertical internal hole grinding machine to make it a perfect circle.

[0051] S7. Grind the teeth of the whole blank to form a finished product.

[0052] For the half gear processed by this embodiment, the part accuracy is controlled within national standard level 6, the tooth surface hardness can reach HRC58-63, and the carburized layer depth of the tooth surface is 2-2.5 mm. It not only has good carburizing and quenching performance (the hardness meets the standard and the carburized layer depth meets the standard), but also ensures the high precision of the gear teeth.

[0053] The above embodiments are only used to illustrate the technical concept and features of the present invention. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A processing method for a carburized and quenched split gear for an engine, characterized in that: The targeted half-type gear is formed by fitting together two semi-circular gears; the materials of these two semi-circular gears are Cr-Ni-Mo steel; The processing method includes the following steps: S1, forge a blank of a complete circle; S2, normalize the blank of the complete circle; S3, cut the blank of the complete circle into two semi-circular gear blanks; S4, perform the following processing on the two semi-circular gear blanks respectively: S4-1, machine the surface of the semi-circular gear blank with a machining center; S4-2, machine teeth on the outer edges of the semi-circular gear blanks respectively by wire cutting, so that the centers of the teeth on the two semi-circular gear blanks have an eccentricity; S4-3, perform carburizing and quenching treatment on the semi-circular gear blanks; S4-4, mill the mating surfaces of the semi-circular gear blanks with a machining center; S4-5, grind the mating surfaces of the semi-circular gear blanks; After the milling and grinding processes in steps S4-4 and S4-5, the above-mentioned eccentricity is removed, so that the centers of the teeth on the two semi-circular gear blanks can coincide; S5, fit and assemble the two processed semi-circular gear blanks together, so that the centers of the teeth on the two semi-circular gear blanks truly coincide, forming a whole blank; S6, grind the inner circumferential surface of the whole blank; S7, grind the teeth of the whole blank to become a finished product.

2. The processing method of the carburizing and quenching split gear for the engine according to claim 1, characterized in that: In step S3, specifically, the blank of the complete circle is cut into two semi-circular gear blanks by wire cutting.

3. The processing method of the carburizing and quenching split gear for the engine according to claim 1, characterized in that: In step S4-1, specifically, the surface of the semi-circular gear blank is milled with a machining center.

4. The machining method of the carburizing and quenching split gear for the engine according to claim 1, characterized in that: Between step S4-2 and step S4-3, there is also a step S4-2-1 to chamfer the teeth of the semi-circular gear blank.

5. The processing method of the carburized and quenched split gear for the engine according to claim 4, characterized in that: In step S4-2-1, specifically, the teeth of the semi-circular gear blank are chamfered manually.

6. The processing method of the carburizing and quenching split gear for the engine according to claim 1, wherein: In step S4-2, first use CAD software to simulate the cutting tool for hobbing to obtain the target tooth dimensions, and then when machining the teeth by wire cutting, according to the target tooth dimensions and considering the deformation amount of gear carburizing heat treatment, leave a tooth profile grinding allowance for each tooth profile.

7. The machining method of the carburizing and quenching split gear for the engine according to claim 1, characterized in that: In step S4-5, a tooling is used to fix and clamp the semi-circular gear blank with the tooth surface as the positioning reference.

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