Method for machining connecting rod pin hole and checking position degree of pin hole

Abstract

The invention provides a method for machining a connecting rod pin hole and checking the position degree of the pin hole, and belongs to the technical field of connecting rod machining. Machining of an upper rod cover and a lower rod cover: on a machining center, the upper rod cover is placed on a tool and is fixed after being limited by a side face a and an end face b of the upper rod cover, and a pin hole in the upper rod cover is machined with an alignment hole C in the tool as a zero point; the machined upper rod cover and the machined lower rod cover are assembled together after being positioned through a pin, the assembled connecting rod is placed on a tool and fixed after being limited through the side face a and the end face b, and the large-head hole is machined with the alignment hole C in the tool as the zero point; and connecting rod detection: placing the connecting rod on the tool, and measuring the position degree of the pin hole relative to the center of the large-head hole by taking the alignment hole C on the tool as a zero point and taking the alignment hole C as a reference. According to the method, processing and inspection are carried out by adopting a unified processing standard, and processed product data can be truly reflected, so that the technical requirements of product drawings are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of connecting rod processing, and particularly relates to a method for processing connecting rod pin holes and inspecting the position accuracy of the pin holes. Background Art

[0002] The connecting rod is one of the main force transmission parts of an internal combustion engine. Its main function is to transmit the explosion pressure acting on the top of the piston after gas combustion in the cylinder to the crankshaft, and convert the reciprocating linear motion of the piston into the rotational motion of the crankshaft, thereby outputting power. The connecting rod bears rapidly changing dynamic loads during operation, and the main part where the connecting rod is connected to the crankshaft is the big end hole. If the big end hole of the connecting rod is out of tolerance, after installing the bearing shell, the clearance between the connecting rod bearing shell and the connecting rod journal of the crankshaft will deviate, which directly affects the formation of the oil film between the big end bearing shell hole of the connecting rod and the crankshaft, resulting in the easy damage of the connecting rod bearing shell and the crankshaft journal during operation, seriously affecting the operating performance, noise, reliability and service life of the diesel engine.

[0003] The structure of a larger marine diesel engine connecting rod is shown in Figure 1 As shown, it consists of three parts: the rod body 3, the upper rod cover 1 and the lower rod cover 2. The hole formed after the upper rod cover 1 and the lower rod cover 2 are assembled is called the big end hole 8 of the connecting rod; generally, two pins 4 are used to position between the upper rod cover 1 and the lower rod cover 2, and then they are firmly connected by tightening with 4 or 2 bolts 5. Due to the importance of the big end hole, it is necessary to strictly control the position accuracy of the two pin holes 7 to ensure that the cylindricity of the hole meets the drawing requirements after each assembly of the upper rod cover and the lower rod cover. After investigation, according to the requirements of the current connecting rod drawings in production, some requirements are as high as 0.03, as shown in Figures 2-5 As shown.

[0004] Taking the processing and detection process method of the connecting rod pin hole of a certain model as an example to illustrate the existing processing method:

[0005] The processing steps adopted: After machining the side and end faces of the rod cover, the pin hole is machined with the side and end faces as the reference. The upper and lower rod covers are positioned by pins, and then fixed together by bolts and nuts. Then, the big end hole is machined with the side and end faces as the reference, and finish boring the hole using a vertical machining center / horizontal machining center. After completion of machining, loosen the bolts and nuts, separate the upper and lower rod covers for measurement.

[0006] The detection method adopted: The detection equipment is a coordinate measuring machine. By collecting 3 points in the big end hole (half circle), the center of the circle is simulated, and then the distance from the center of the circle to the center of the pin hole is measured with the center of the circle as the zero point, so as to obtain the position accuracy of the pin hole.

[0007] Defects existing in the prior art: 1. The measured position tolerance often exceeds the requirements of the drawing; 2. After finish boring, for the separated upper and lower rod covers, the semi - circle is not half of a perfect circle (due to deformation, only when the upper and lower rod covers are assembled together and under a certain pre - tightening force, the formed circle is a perfect circle); 3. The center of the circle obtained by the probe point collection of the coordinate measuring machine is not the real center of the circle, but a simulated center, which cannot reflect the real situation.

[0008] Based on the above - mentioned problems, there is an urgent need to propose a new method for processing connecting rod pin holes and inspecting the position tolerance of pin holes. Summary of the Invention

[0009] The technical problem solved by the present invention: Provide a method for processing connecting rod pin holes and inspecting the position tolerance of pin holes. The purpose of the present invention is to overcome the deficiencies of the prior art, use a unified machining reference for machining and inspection, and can truly reflect the product data after machining, so as to meet the technical requirements of the product drawing.

[0010] To achieve the above - mentioned purpose, the technical solution adopted by the present invention:

[0011] A method for processing connecting rod pin holes and inspecting the position tolerance of pin holes specifically includes the following steps:

[0012] Step 1): Machining of the upper and lower rod covers: On a machining center, place the upper rod cover on the fixture, fix it after being limited by the side a and end face b of the upper rod cover, and machine the pin hole on the upper rod cover with the alignment hole C on the fixture as the zero point;

[0013] The lower rod cover is machined in the same way as the upper rod cover;

[0014] Step 2): Finish boring of the large - end hole on the connecting rod: Assemble the upper and lower rod covers machined in Step 1) together after positioning with pins, place the assembled connecting rod on the fixture, fix it after being limited by the side a and end face b, and machine the large - end hole with the alignment hole C on the fixture as the zero point;

[0015] Step 3): Inspection of the connecting rod: Place the connecting rod machined in Step 2) on the fixture, use the alignment hole C on the fixture as the zero point, and take the alignment hole C as the reference to measure the position tolerance of the pin hole relative to the center of the large - end hole.

[0016] For further limitation of the above - mentioned solution, in the above - mentioned solution, the fixture is equipped with an alignment hole C, and the distance X between the limiting reference and the alignment hole C of the fixture used in different steps is fixed.

[0017] For further limitation of the above - mentioned solution, in Step 2), when the upper and lower rod covers are assembled, after being positioned with pins, they are fixed together with bolts and nuts.

[0018] For further limitation of the above solution, in the above steps 1) and 2), the upper rod cover or the combined connecting rod is fixed and clamped on the tooling by a pressing device.

[0019] For further limitation of the above solution, the pressing device includes a pressing plate which presses the workpiece, and the pressing plate is connected to the tooling through a stud-nut connection structure.

[0020] Advantages of the present invention compared with the prior art:

[0021] 1. For the processing and inspection of the pin holes and big end holes on the connecting rod, this solution uses a unified reference for processing and detection, which can truly reflect the product data after processing, so as to meet the technical requirements of the product drawing;

[0022] 2. This solution is equipped with alignment holes on the tooling. Between different processes, the distance between the limiting reference and the alignment holes of the used tooling is fixed. During measurement, the product is placed on the tooling and measured with the alignment holes on the tooling as the zero point. The reference is unified, making the processing and detection accurate and reliable;

[0023] 3. This solution has a novel design concept, simple structure, good versatility, and can be quickly promoted to solve similar problems. Brief Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the connecting rod structure in the present invention;

[0025] Figure 2 It is the front view of the upper rod cover structure in the present invention;

[0026] Figure 3 It is the top view of the upper rod cover structure in the present invention;

[0027] Figure 4 It is the front view of the lower rod cover structure in the present invention;

[0028] Figure 5 It is the top view of the lower rod cover structure in the present invention;

[0029] Figure 6 It is the front view of the alignment hole position when machining the pin hole on the upper rod cover in the present invention;

[0030] Figure 7 It is the top view of the alignment hole position when machining the pin hole on the upper rod cover in the present invention;

[0031] Figure 8 It is the schematic diagram of the alignment hole position when finely boring the big end hole in the present invention. Detailed Embodiments

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the 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] Please refer to Figures 1-8 , and detail the embodiments of the present invention.

[0034] Embodiment: A method for machining the connecting rod pin hole and inspecting the position degree of the pin hole, specifically including the following steps:

[0035] Step 1): Machining of the upper and lower rod caps: Refer to Figure 6 and 7 As shown, on the machining center, place the upper rod cap 1 on the tooling, limit it by the side surface a and the end surface b of the upper rod cap 1, and fix it with a pressing plate. Taking the alignment hole C on the tooling as the zero point, machine the pin hole 7 on the upper rod cap 1;

[0036] The lower rod cap 2 is machined by the same method as the upper rod cap 1;

[0037] Step 2): Precision boring of the large head hole on the connecting rod: Refer to Figure 8 As shown, position the upper rod cap 1 and the lower rod cap 2 machined in Step 1) with pins 4, and then fix them together with bolts 5 and nuts 6. Place the assembled connecting rod on the tooling, after limiting it by the side surface a and the end surface b, fix it with a pressing plate, and taking the alignment hole C on the tooling as the zero point, machine the large head hole 8;

[0038] Step 3): Connecting rod inspection: Place the connecting rod machined in Step 2) on the tooling, taking the alignment hole C on the tooling as the zero point and the alignment hole C as the reference, measure the position degree of the pin hole 7 relative to the center of the large head hole 8, and the obtained position degree truly reflects the data of the position degree relative to the center of the large head hole.

[0039] In the above, the tooling is equipped with an alignment hole C, and between different steps, for the tooling used, the distance X between the limiting reference and the alignment hole C remains fixed.

[0040] Specifically, the pressing device includes a pressing plate, the pressing plate presses the workpiece, and the pressing plate is connected to the tooling through a stud-nut connection structure.

[0041] This method is for the machining and inspection of the pin hole and the large head hole on the connecting rod. By adopting a unified reference, it can truly reflect the product data after machining, thus meeting the technical requirements of the product drawing; this method has novel ideas, simple structure, good versatility, and can be quickly promoted to solve similar problems.

[0042] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0043] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for machining a connecting rod pin hole and inspecting the position of the pin hole, characterized in that: The specific steps include: Step 1): Processing of the upper and lower rod covers: On a machining center, place the upper rod cover (1) on a tooling, and fix it after limiting the side surface a and end surface b of the upper rod cover (1), and process the pin hole (7) on the upper rod cover (1) with the alignment hole C on the tooling as the zero point; The lower rod cover (2) is processed in the same manner as the upper rod cover (1); Step 2): Fine boring of the large end hole on the connecting rod: the upper rod cover (1) and the lower rod cover (2) processed in step 1) are assembled together after positioning by the pin (4), the assembled connecting rod is placed on the tooling, fixed after limiting by the side surface a and the end surface b, and the large end hole (8) is processed with the alignment hole C on the tooling as the zero point; Step 3): Connecting rod inspection: Place the connecting rod processed in step 2) on the tooling, use the alignment hole C on the tooling as the zero point, and measure the position of the pin hole (7) relative to the center of the big head hole (8) with the alignment hole C as the reference.

2. The method for machining a connecting rod pin hole and inspecting the pin hole position according to claim 1, characterized in that: In the above scheme, the tooling is equipped with an alignment hole C. Between different steps, the distance X between the limit reference and the alignment hole C of the tooling used is fixed.

3. The method for machining a connecting rod pin hole and inspecting the pin hole position according to claim 1, characterized in that: In the above step 2), when the upper rod cover (1) and the lower rod cover (2) are assembled, they are positioned by the pin (4) and then fixed together by the bolts (5) and nuts (6).

4. The method for machining a connecting rod pin hole and inspecting the pin hole position according to claim 1, characterized in that: In the above steps 1) and 2), the upper rod cover (1) or the combined connecting rod is fixed and clamped on the tooling by a clamping device.

5. The method for machining a connecting rod pin hole and inspecting the pin hole position according to claim 4, characterized in that: The clamping device comprises a pressing plate, which presses the workpiece and is connected to the tooling via a stud nut connection structure.

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