Crank structure of large-displacement split crankshaft

Abstract

The crank structure comprises a fan-shaped large outer circle, a crank hole is formed in the large outer circle, a shaft neck part rod body and a taper rod body are arranged in the center of the end face of the large outer circle, the outer diameter of the taper rod body is smaller than that of the shaft neck part rod body, and a semicircular key groove is formed in the outer wall of the taper rod body. An inner threaded hole is formed in the center of the taper rod body. The hardness of the inner wall of the crank hole is HRC50-HRC60. And the depth of a carburized layer on the inner wall of the crank hole is 0.5-3mm. The cylindricity of the shaft neck part rod body does not exceed 0.005, and the waviness generated by grinding does not exceed 0.0015. The roughness of the shaft neck shaft body does not exceed Rz0.8, and the average value of the measured metal rates of the four 0.25 mm length regions is greater than 97%. According to the crank structure of the large-displacement split type crankshaft, the problem that a large-displacement engine above 300cc needs to be matched with the crankshaft journal and the bearing bush is solved, so that the problem of rotation failure is solved, and the product quality is improved.

Description

Technical Field

[0001] The utility model relates to a crank of a crankshaft, and more precisely, to a crank structure of a large-displacement split crankshaft. Background Art

[0002] The crankshaft connecting rod assembly is a key component on a motorcycle engine, used to convert the linear reciprocating motion of a piston into the rotational motion of a crankshaft. During the high-speed operation of components such as the engine crankshaft connecting rod assembly, the crank plays a very crucial role. The crank is subjected to the combined action of the centrifugal force of the rotating mass, the periodically changing gas pressure, and the reciprocating inertia force, causing the crank to bear bending force and torsional load. To ensure the continuous and reliable operation of the engine, it is required that the crank has sufficient stiffness and strength, good lubrication on each working surface, can withstand impact alternating loads, and has good wear resistance. For existing large-displacement split crankshafts, the requirements for increasing the wear resistance of the crank hole, the roughness, waviness, and metal rate of the crankshaft journal have increased significantly. The existing processing technology cannot meet the requirements of the crankshaft journal and the crank hole, thus affecting the performance of the cooperation between the crank hole, the needle roller bearing, and the crank pin, as well as the performance of the cooperation between the crankshaft journal and the bearing bush. In severe cases, rotational failure may occur, and improvement is needed. Summary of the Utility Model

[0003] Based on this, in view of the above technical problems, it is necessary to provide a crank structure of a large-displacement split crankshaft.

[0004] To solve the above technical problems, the utility model adopts the following technical solutions:

[0005] A crank structure of a large-displacement split crankshaft, characterized in that the crank structure of the large-displacement split crankshaft includes a fan-shaped large outer circle, a crank hole is provided on the large outer circle, a shaft neck rod body and a tapered rod body are provided at the center of the end face of the large outer circle, the outer diameter of the tapered rod body is smaller than that of the shaft neck rod body, a semi-circular keyway is provided on the outer wall of the tapered rod body, and an internal threaded hole is provided at the center of the tapered rod body.

[0006] As a preferred embodiment of the utility model, the hardness of the inner wall of the crank hole is HRC50 - HRC60.

[0007] As a preferred embodiment of the utility model, the carburized layer depth of the inner wall of the crank hole is 0.5 mm - 3 mm.

[0008] As a preferred embodiment of the utility model, the cylindricity of the shaft neck rod body does not exceed 0.005, and the waviness generated by grinding does not exceed 0.0015.

[0009] As a preferred embodiment of the present utility model, the roughness of the rod body of the shaft neck does not exceed Rz0.8, and the average value of the metal ratio measured in four 0.25 mm length regions is greater than 97%.

[0010] As a preferred embodiment of the present utility model, the crank structure of the large-displacement split crankshaft is made of 40Cr.

[0011] Compared with the prior art, the present utility model has the following beneficial effects:

[0012] The present utility model provides a crank structure of a large-displacement split crankshaft. The finishing process sequence of the crank of the large-displacement split crankshaft is: forming grinding of the rod body → precision grinding of the shaft neck → precision boring of the crank hole and turning of the small plane → deburring and polishing of the shaft neck. Among them, through the process method of forming grinding → precision grinding → polishing three times at the shaft neck, it is ensured that the cylindricity of the rod body of the shaft neck does not exceed 0.005 mm, the waviness generated by grinding does not exceed 0.0015 mm, the roughness does not exceed Rz0.8, and the average value of the metal ratio measured in four 0.25 mm length regions is greater than 97%. Thus, the problem of the need for the crankshaft neck to cooperate with the bearing bush in large-displacement engines above 300 cc is satisfied, the problem of rotational failure is solved, and the product quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the solutions in the present utility model, the following will briefly introduce the drawings required for use in the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] Figure 1 is a three-dimensional structural schematic diagram of the crank structure of the large-displacement split crankshaft of the present utility model;

[0015] Figure 2 is Figure 1 a cross-sectional structural schematic diagram of the crank structure of the large-displacement split crankshaft in;

[0016] The reference numerals in the drawings are explained as follows: 1, large outer circle; 2, crank hole; 3, rod body of shaft neck; 4, tapered rod body; 5, semi-circular keyway; 6, internal threaded hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to enable those skilled in the art to better understand the solutions of the present utility model, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the drawings in the embodiments of the present utility model.

[0018] As shown in Figure 1 and Figure 2As shown, the crank structure of the large-displacement split crankshaft includes a large outer circle 1 in the shape of a sector. A crank hole 2 is provided on the large outer circle 1. At the center of the end face of the large outer circle 1, there is a shaft neck rod body 3 and a tapered rod body 4. The outer diameter of the tapered rod body 4 is smaller than that of the shaft neck rod body 3. A semi-circular keyway 5 is provided on the outer wall of the tapered rod body 4, and an internal threaded hole 6 is provided at the center of the tapered rod body 4.

[0019] It should be noted that the hardness of the inner wall of the crank hole 2 is HRC50 - HRC60.

[0020] The carburized layer depth of the inner wall of the crank hole 2 is 0.5 mm - 3 mm.

[0021] In addition, the cylindricity of the shaft neck rod body 3 does not exceed 0.005, and the waviness generated by grinding does not exceed 0.0015.

[0022] In addition, the roughness of the shaft neck rod body 3 does not exceed Rz0.8, and the average value of the metal ratio measured in 4 regions with a length of 0.25 mm is greater than 97%.

[0023] The processing technology of the crank of the large-displacement split crankshaft includes rough machining, semi-finishing machining, and finishing machining. Among them, the rough machining sequence is blank forging → external processing → quenching and shot peening treatment. The crank structure of the large-displacement split crankshaft is forged with 40Cr material, and the hot die forging process is used during forging.

[0024] The semi-finishing sequence of the crank of the large-displacement split crankshaft is drilling the center hole, drilling the threaded hole → CNC turning forming → drilling and boring the crank hole → milling the keyway → high-frequency quenching. Among them, high-frequency quenching includes simultaneously performing high-frequency quenching on the crank hole 2, the shaft neck rod body 3, and the tapered rod body 4. After quenching, the hardness of the crank hole 2 is HRC50 - HRC60, and the carburized layer depth is 0.5 - 3 mm, thereby improving the wear resistance of the crank hole and reducing the risk of failure due to excessive wear between the crank hole and the crank pin during the operation of the large-displacement engine.

[0025] The finishing process sequence of the crank of the large-displacement split crankshaft is forming and grinding the rod body → precision grinding the journal → precision boring the crank hole, turning the small plane → deburring and polishing the journal. Among them, through the process method of forming grinding → precision grinding → polishing the journal 3 times, it is ensured that the cylindricity of the shaft neck rod body 3 does not exceed 0.005 mm, the waviness generated by grinding does not exceed 0.0015 mm, the roughness does not exceed Rz0.8, and the average value of the metal ratio measured in 4 regions with a length of 0.25 mm is greater than 97%. Thus, it meets the problem of the need for the crank journal to cooperate with the bearing bush in large-displacement engines above 300 cc, thereby solving the problem of rotational failure and improving the product quality.

[0026] Obviously, the embodiments described above are only a part of the embodiments of this application, rather than all embodiments. The preferred embodiments of this application are shown in the drawings, but they do not limit the patent scope of this application.

Claims

1. A crank structure of a large-displacement split crankshaft, characterized in that, The crank structure of the large-displacement split crankshaft described above includes a fan-shaped large outer circle (1), on which a crank hole (2) is provided. At the center of the end face of the large outer circle (1), there are a shaft neck rod body (3) and a tapered rod body (4). The outer diameter of the tapered rod body (4) is smaller than that of the shaft neck rod body (3). A semi-circular keyway (5) is provided on the outer wall of the tapered rod body (4), and an internal threaded hole (6) is provided at the center of the tapered rod body (4).

2. The crank structure of the large-displacement split crankshaft according to claim 1, characterized in that, The hardness of the inner wall of the crank hole (2) is HRC50 - HRC60.

3. The crank structure of the large-displacement split crankshaft according to claim 1, characterized in that, The carburized layer depth of the inner wall of the crank hole (2) is 0.5 mm - 3 mm.

4. The crank structure of the large-displacement split crankshaft according to claim 1, characterized in that, The cylindricity of the shaft neck rod body (3) does not exceed 0.005, and the waviness generated by grinding does not exceed 0.0015.

5. The crank structure of the large-displacement split crankshaft according to claim 1, characterized in that, The roughness of the shaft neck rod body (3) does not exceed Rz0.8, and the average value of the metal ratio measured in four 0.25 mm length regions is greater than 97%.

6. The crank structure of the large-displacement split crankshaft according to claim 1, characterized in that, The crank structure of the large-displacement split crankshaft is made of 40Cr.

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