Fixture and machining method for high-precision machining of a keyway-oriented crankshaft

Abstract

The present invention belongs to the technical field of machining, and relates to a fixture and a machining method for machining a keyway-oriented high-precision crankshaft. The method includes: 1) Assembling the A section of the keyway-oriented high-precision crankshaft into the crankshaft clamping hole of the eccentric sleeve; 2) Extending the orientation pin from the crankshaft clamping hole into the keyway-oriented high-precision crankshaft; 3) Installing the eccentric sleeve equipped with the orientation pin and the keyway-oriented high-precision crankshaft into the high-precision three-jaw inner hole of the CNC grinding machine; 4) Checking the runout of the outer circle of the B section of the keyway-oriented high-precision crankshaft; 5) Grinding the outer circle of the B section of the keyway-oriented high-precision crankshaft. The present invention provides a fixture and a machining method for machining a keyway-oriented high-precision crankshaft that can ensure product quality and improve machining efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining, and relates to a crankshaft machining process, in particular to a fixture and a machining method for machining a keyway-oriented high-precision crankshaft. Background Art

[0002] Crankshafts are generally divided into two categories: those without angular requirements and those with angular requirements. Among them, crankshafts with angular requirements are further divided into two types: those with the direction on the outer surface and those on the inner surface. A certain keyway-oriented high-precision crankshaft (structural schematic diagram as Figure 2 and Figure 3 ), its outer dimension is small, the eccentricity dimension requirement is strict, and the outer circle dimension accuracy is high (such as Figure 4 ), and it is impossible to complete the machining of the eccentric outer circle by using the center hole for positioning. Usually, special equipment is used to complete the machining of the eccentric outer circle of the part. Due to the high cost of the special equipment and the single type of machined parts, it causes waste of resources. In addition, when using a high-precision CNC external grinder to machine this type of part, a lever micrometer is required for single-piece alignment, resulting in low machining efficiency and unstable machining quality. Therefore, the machining of keyway-oriented high-precision crankshaft parts has become a difficult problem in machining. Summary of the Invention

[0003] In order to solve the above technical problems in the background art, the present invention provides a fixture and a machining method for machining a keyway-oriented high-precision crankshaft, which can ensure product quality and improve machining efficiency.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A fixture for machining a keyway-oriented high-precision crankshaft, the keyway-oriented high-precision crankshaft includes an A section, a B section and a C section connected in sequence, the axial direction of the B section is parallel to the axial direction of the A section and the axial direction of the C section respectively; the axial direction of the A section is coaxial with the axial direction of the C section; characterized in that: the fixture for machining a keyway-oriented high-precision crankshaft includes an eccentric sleeve, and a crankshaft clamping hole sleeved outside the A section is opened inside the eccentric sleeve; the axial direction of the crankshaft clamping hole is parallel to the axial direction of the eccentric sleeve; a through groove is opened along the axial direction of the eccentric sleeve on the side wall of the eccentric sleeve; the through groove communicates with the crankshaft clamping hole; the eccentric sleeve is a hollow columnar structure with a C-shaped cross section.

[0006] The above-mentioned fixture for machining a keyway-oriented high-precision crankshaft further includes an orientation pin clamped on the eccentric sleeve and extending into the inside of the A section of the keyway-oriented high-precision crankshaft from the crankshaft clamping hole.

[0007] The above-mentioned positioning pin includes an L1 section and an L2 section connected to the L1 section; the outer diameter of the L1 section is larger than that of the L2 section; the L1 section and the L2 section integrally form a T-shaped structure; the end face of the L1 section is clamped on the eccentric sleeve, and the L2 section extends into the interior of the machined crankshaft A section from the crankshaft clamping hole, and the structure of the L2 section matches the structure inside the keyway-equipped and orientation-high-precision crankshaft A section.

[0008] A keyway is provided on the end face of the above-mentioned eccentric sleeve, the structure of the keyway matches the structure of the L1 section, and the end face of the L1 section is placed in the keyway.

[0009] The above-mentioned keyway is arranged radially on the end face of the eccentric sleeve.

[0010] The distance between the axis where the above-mentioned crankshaft clamping hole is located and the axis where the eccentric sleeve is located is 2 ± 0.01 mm.

[0011] The parallelism between the axial direction of the above-mentioned keyway-equipped and orientation-high-precision crankshaft B section and the axial direction of the A section is not less than

[0012] A method for machining the outer circle of a keyway-equipped and orientation-high-precision crankshaft by using a fixture for machining a keyway-equipped and orientation-high-precision crankshaft as described above, characterized in that: the method includes the following steps:

[0013] 1) Assemble the A section of the keyway-equipped and orientation-high-precision crankshaft in the crankshaft clamping hole of the eccentric sleeve so that the two are in radial contact;

[0014] 2) Extend the positioning pin from the crankshaft clamping hole into the keyway-equipped and orientation-high-precision crankshaft, so that the L1 section of the positioning pin is clamped in the keyway on the end face of the eccentric sleeve, and the L2 section of the positioning pin is clamped in the A section structure of the keyway-equipped and orientation-high-precision crankshaft;

[0015] 3) Install the eccentric sleeve equipped with the positioning pin and the keyway-equipped and orientation-high-precision crankshaft into the high-precision three-jaw inner hole of the CNC grinding machine and clamp it tightly;

[0016] 4) Install a lever dial indicator on the machine tool, check that the runout of the outer circle of the keyway-equipped and orientation-high-precision crankshaft B section is not greater than 0.01 mm, and check that the runout of the end face at the joint between the A section and the B section of the keyway-equipped and orientation-high-precision crankshaft is not greater than 0.01 mm;

[0017] 5) Grind the outer circle of the keyway-equipped and orientation-high-precision crankshaft B section and grind the end face at the joint between the A section and the B section of the keyway-equipped and orientation-high-precision crankshaft.

[0018] A keyway-equipped and orientation-high-precision crankshaft formed based on the above-mentioned machining method.

[0019] The advantages of the present invention are:

[0020] The present invention provides a fixture and a processing method for high-precision crankshaft machining with keyway orientation. This process is to design a high-precision crankshaft tooling with rectangular groove orientation after finish milling the inner cavity, finish grinding, and achieving the drawing requirements for the outer circle. By converting the inner orientation to the outer orientation, the final grinding of the eccentric outer circle is solved. Using the process and the positioning and orientation tooling with simple structure provided by the present invention, the problem of single-piece alignment before machining the eccentric outer circle is eliminated, and efficient machining of a high-precision crankshaft with keyway orientation is realized, with stable and reliable machining quality. Among them, the eccentric sleeve is used to connect the machine tool spindle and the outer circle of the crankshaft, eliminating the eccentricity of the two outer circles of the crankshaft and solving the high-precision grinding of the size and axial dimension of the eccentric outer circle; the T-shaped orientation pin is used to determine the angular relationship between the reference A outer circle of the crankshaft and the eccentric outer circle, perform high-precision orientation on the part and the eccentric sleeve, and upgrade the original skilled operator's single-piece alignment on the machine tool with a micrometer to the self-orientation of the fixture, realizing the grinding of the eccentric circle, improving the machining efficiency, having the advantages of simple clamping, reliability, easy operation, stable machining quality of parts, meeting the requirements of the design drawing in terms of dimensions, and increasing the qualified rate of parts to 100%, and the machining efficiency is increased by 2 to 3 times. Description of the Drawings

[0021] Figure 1 is a flow diagram of the machining of a high-precision crankshaft with keyway orientation in the prior art;

[0022] Figure 2 is a three-dimensional model diagram of a certain crankshaft part;

[0023] Figure 3 is a three-dimensional model diagram of a certain crankshaft part (from another angle);

[0024] Figure 4 is a schematic diagram of the dimensional requirements and precision of a certain crankshaft part;

[0025] Figure 5 is a schematic diagram of the structure of the eccentric sleeve adopted by the present invention. Among them, (a) is a schematic diagram of the left side structure of the eccentric sleeve, and (b) is a schematic diagram of the A-A direction of (a);

[0026] Figure 6 is a schematic diagram of the structure of the T-shaped orientation pin adopted by the present invention. Among them, (a) is a schematic diagram of the right side structure of the T-shaped orientation pin, and (b) is a front view schematic diagram of the T-shaped orientation pin;

[0027] Figure 7 is an assembly model of a certain crankshaft part equipped with an eccentric sleeve and a T-shaped orientation pin;

[0028] Figure 8 is a schematic diagram of the structure of a certain crankshaft part equipped with an eccentric sleeve and a T-shaped orientation pin. Among them, (a) is a schematic diagram of the left side structure, and (b) is a schematic diagram of the A-A direction of (a).

[0029] Wherein:

[0030] 1 - High-precision keyway-oriented crankshaft; 2 - Eccentric sleeve; 3 - Orientation pin. Specific implementation mode

[0031] See Figure 7 and Figure 8 , the present invention provides a fixture for machining a high-precision keyway-oriented crankshaft. The high-precision keyway-oriented crankshaft 1 includes an A section, a B section, and a C section connected in sequence. The axial direction where the B section is located is parallel to the axial direction where the A section is located and the axial direction where the C section is located respectively; the axial direction where the A section is located is coaxial with the axial direction where the C section is located; the fixture for machining the high-precision keyway-oriented crankshaft includes an eccentric sleeve 2, and a crankshaft clamping hole sleeved outside the A section is provided inside the eccentric sleeve 2; the axial direction of the crankshaft clamping hole is parallel to the axial direction of the eccentric sleeve; a through groove is provided along the axial direction of the side wall of the eccentric sleeve; the through groove communicates with the crankshaft clamping hole; the eccentric sleeve is a hollow columnar structure with a C-shaped cross section (such as Figure 5 (a) and Figure 5 (b)).

[0032] Among them, see Figure 7 and Figure 6 , the fixture for machining the high-precision keyway-oriented crankshaft further includes an orientation pin 3 clamped on the eccentric sleeve and extending into the inside of the A section of the high-precision keyway-oriented crankshaft from the crankshaft clamping hole ( Figure 6 (a) and Figure 6 (b)). The orientation pin includes an L1 section and an L2 section connected to the L1 section ( Figure 6 (b)); the outer diameter of the L1 section is larger than the outer diameter of the L2 section; the L1 section and the L2 section form a T-shaped structure as a whole; the end face of the L1 section is clamped on the eccentric sleeve, and the L2 section extends into the inside of the A section of the machining crankshaft from the crankshaft clamping hole, and the structure of the L2 section matches the structure inside the A section of the high-precision keyway-oriented crankshaft.

[0033] In order to facilitate the more secure fixation of the orientation pin, a keyway is provided on the end face of the eccentric sleeve (such as Figure 5 (a)), and the structure of the keyway matches the structure of the L1 section, and the end face of the L1 section is placed in the keyway. The keyway is arranged on the end face of the eccentric sleeve along the radial direction of the eccentric sleeve. The distance between the axis where the keyway crankshaft clamping hole is located and the axis where the eccentric sleeve is located is 2 ± 0.01 mm. The parallelism between the axial direction where the B section of the high-precision keyway-oriented crankshaft is located and the axial direction where the A section is located is not less than

[0034] At the same time, the present invention also provides a method for machining the outer circle of a high-precision keyway-oriented crankshaft based on the fixture for machining a high-precision keyway-oriented crankshaft as described above. This method involves precision milling the inner cavity and precision grinding the outer circle to reach the drawing (the machining process is as Figure 1After the situation shown), the grinding of the outer circle of section B of the high-precision keyway-oriented crankshaft is carried out. The method includes the following steps:

[0035] 1) Assemble the A section of the high-precision keyway-oriented crankshaft (outer circle ) in the crankshaft clamping hole of the eccentric sleeve so that the two fit radially (closely fit the N surface of the crankshaft with the M surface of the eccentric sleeve);

[0036] 2) Extend the orientation pin from the crankshaft clamping hole into the high-precision keyway-oriented crankshaft, so that the L1 section of the orientation pin is clamped in the keyway on the end face of the eccentric sleeve, and the L2 section of the orientation pin is clamped in the A section structure of the high-precision keyway-oriented crankshaft, that is, the L1 section and the L2 section of the T-shaped orientation pin are flat respectively inserted into the wide keyway of the eccentric sleeve and the wide keyway of the crankshaft;

[0037] 3) Insert the eccentric sleeve equipped with the orientation pin and the high-precision keyway-oriented crankshaft into the high-precision three-jaw inner hole of the CNC grinding machine, and clamp and fasten it;

[0038] 4) Install a lever dial indicator on the machine tool, check that the runout of the outer circle of section B of the high-precision keyway-oriented crankshaft is not greater than 0.01 mm, and check that the runout of the end face at the joint between section A and section B of the high-precision keyway-oriented crankshaft is not greater than 0.01 mm;

[0039] 5) Grind the outer circle of section B of the high-precision keyway-oriented crankshaft, and grind the end face at the joint between section A and section B of the high-precision keyway-oriented crankshaft.

[0040] Among them, key element control and grinding parameters:

[0041] ① Eccentric circle Relative to the outer circle of A Parallelism of the axis

[0042] Control the cylindricity of the inner hole of the eccentric sleeve within 0.005 mm. By ensuring the clearance of 0.005 - 0.016 mm between the inner hole of the eccentric sleeve and the outer circle of part A to solve the parallelism of the axis of the eccentric circle relative to the outer circle of A Axis

[0043]

[0044] ② Eccentricity 2 ± 0.02 mm

[0045] Through the outer circle of the eccentric sleeve The eccentricity with the inner hole is indirectly ensured to be 2 ± 0.01 mm.

[0046] ③ Eccentric outer diameter size Axial dimensions 16 ± 0.02 mm and 0.5 ± 0.02 mm

[0047] By selecting appropriate grinding wheels and grinding parameters, the outer diameter and axial dimensions are ensured. The grinding parameters and grinding wheel specifications are shown in Table 1:

[0048] Table 1

[0049]

[0050]

[0051] In addition, the present invention also provides a keyway - equipped and directionally - accurate crankshaft formed based on the foregoing processing method.

[0052] For the processing of the keyway - equipped and directionally - accurate crankshaft, the simplified process flow diagram is as Figure 1 shown: In the process plan, after the inner cavity is finish - milled and the outer diameter is finish - ground to meet the drawing requirements, a high - precision crankshaft tooling with a rectangular groove for orientation is designed. By converting the inner orientation to the outer orientation, the final grinding of the eccentric outer diameter is solved. Using the Figure 1 shown process flow and a positioning and orientation tooling with a simple structure, the problem of single - piece alignment before the processing of the eccentric outer diameter is eliminated, and an efficient processing of the keyway - equipped and directionally - accurate crankshaft is realized, with stable and reliable processing quality. The positioning and orientation tooling consists of an eccentric sleeve ( Figure 5 shown) and a T - shaped orientation pin ( Figure 6 shown). The eccentric sleeve is used to connect the machine tool spindle and the outer diameter of the crankshaft, eliminating the eccentricity of the two outer diameters of the crankshaft by 2 ± 0.02 mm ( Figure 4 shown), and solving the high - precision grinding of the eccentric outer diameter size and the axial dimensions of 16 ± 0.02 mm and 0.5 ± 0.02 mm; the function of the T - shaped orientation pin is to determine the angular relationship between the reference A outer diameter of the crankshaft and the eccentric outer diameter ( Figure 4 shown), perform high - precision orientation on the part and the eccentric sleeve, and upgrade the single - piece alignment by the skilled operator on the machine tool with a micrometer to the self - orientation of the fixture, realizing the grinding of the eccentric circle and improving the processing efficiency. The positioning and orientation tooling has the following advantages: a. Simple, reliable, and easy - to - operate clamping; b. Stable part processing quality, and the dimensions meet the requirements of the design drawing; c. The qualified rate of parts is increased to 100%, and the processing efficiency is increased by 2 - 3 times.

Claims

1. A fixture for machining a keyway-oriented high-precision crankshaft. The keyway-oriented high-precision crankshaft includes an A section, a B section, and a C section connected in sequence. The axial direction of the B section is parallel to the axial direction of the A section and the axial direction of the C section respectively. The axial direction of the A section is coaxial with the axial direction of the C section. It is characterized in that: The fixture for machining a keyway - oriented high - precision crankshaft includes an eccentric sleeve. A crankshaft clamping hole sleeving outside the A section is provided inside the eccentric sleeve. The axial direction of the crankshaft clamping hole is parallel to the axial direction of the eccentric sleeve. A through - slot is provided along the axial direction of the side wall of the eccentric sleeve. The through - slot communicates with the crankshaft clamping hole. The eccentric sleeve is a hollow columnar structure with a C - shaped cross - section. The fixture for machining a keyway - oriented high - precision crankshaft further includes an orientation pin clamped on the eccentric sleeve and extending into the inside of the A section of the keyway - oriented high - precision crankshaft through the crankshaft clamping hole. The orientation pin includes an L1 section and an L2 section connected to the L1 section. The outer diameter of the L1 section is larger than that of the L2 section. The L1 section and the L2 section integrally form a T - shaped structure. The end face of the L1 section is clamped on the eccentric sleeve. The L2 section extends into the inside of the A section of the machined crankshaft through the crankshaft clamping hole, and the structure of the L2 section matches the structure inside the A section of the keyway - oriented high - precision crankshaft. A keyway is provided on the end face of the eccentric sleeve. The structure of the keyway matches the structure of the L1 section, and the end face of the L1 section is placed in the keyway. The keyway is arranged along the radial direction of the eccentric sleeve on the end face of the eccentric sleeve.

2. The fixture for high-precision machining of a crankshaft with keyway orientation according to claim 1, wherein: The distance between the axis where the crankshaft clamping hole is located and the axis where the eccentric sleeve is located is 2 ± 0.01 mm.

3. The fixture for machining the high-precision crankshaft with keyway orientation according to claim 2, wherein: The parallelism between the axial direction of the B section of the keyway - oriented high - precision crankshaft and the axial direction of the A section is not less than 0.02 mm.

4. A method for machining the outer circle of a high-precision crankshaft with keyway orientation based on the fixture for machining the high-precision crankshaft with keyway orientation as described in claim 3, characterized in that: The method includes the following steps: 1) Assemble the A section of the keyway - oriented high - precision crankshaft into the crankshaft clamping hole of the eccentric sleeve so that they are in radial contact. 2) Extend the orientation pin from the crankshaft clamping hole into the keyway - oriented high - precision crankshaft, so that the L1 section of the orientation pin is clamped in the keyway on the end face of the eccentric sleeve, and the L2 section of the orientation pin is clamped in the A - section structure of the keyway - oriented high - precision crankshaft. 3) Install the eccentric sleeve equipped with the orientation pin and the keyway - oriented high - precision crankshaft into the high - precision three - jaw inner hole of the CNC grinding machine and clamp it tightly. 4) Install a lever dial indicator on the machine tool, check that the run - out of the outer circle of the B section of the keyway - oriented high - precision crankshaft is not greater than 0.01 mm, and check that the run - out of the end face at the joint of the A section and the B section of the keyway - oriented high - precision crankshaft is not greater than 0.01 mm. 5) Grind the outer circle of the B section of the keyway - oriented high - precision crankshaft and grind the end face at the joint of the A section and the B section of the keyway - oriented high - precision crankshaft.

5. A keyway - oriented high - precision crankshaft formed based on the method as claimed in claim 4.

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