Improvement of the processing technology of air compressor crankshaft in modern commercial industry. Zhou Chaoming Ningbo Zhenhai Railway Locomotive Equipment Manufacturing Co., Ltd., Ningbo Ningbo 315200, Zhejiang, is an ideal crankshaft processing technology.

There are two basic types of compressor crankshafts, the crankshaft and the crankshaft. The crankshaft structure, together with the motor shaft, generally has only two main bearings, which are less sensitive to bearing deflection and facilitate crankshaft mounting. However, the compressor of the crankshaft can only be used in a horizontal type, which makes the machine bulky and has a large foundation. The 2.4 air compressor made by our company adopts a crankshaft to arrange the connecting rod piston structure in a symmetrical manner, so that the compressor is compact and light in weight. However, there have been many questions in the early processing of the crankshaft. In order to solve these problems, we have taken a series of improvement measures.

1 main question, 2.4 air compressor crankshaft structure using forged blank, material is 40. The main process is rough forging rough end of the rough end plane and two crank heat treatment quenching and finishing car two spindle end fine milling turn corner car Car oil pump eccentric borehole crank high frequency quenching train oil pump eccentric grinding spindle grinding and turning keyway.

However, in the processing, the next few questions were found. The oil pump journal eccentric grinding spindle has a complicated tooling and the machining accuracy is not high. The hardness of the two curved surfaces is low, and the crank is easy to break. The user finds that the connecting rod is bitten and finally Check the crankshaft for cracks at the inclined oil holes at the crank.

2 Reason analysis and process improvement Because the lubrication of the 2.4 air compressor crankshaft is mainly through the plunger pump installed at the end of the crankshaft, and the plunger pump works by the rotation of the crankshaft to the crankshaft and the connecting rod mounted on the crankshaft and The connecting rod is lubricated, so the crankshaft is designed to be eccentric at the end. However, when starting the manufacturing process, only the tooling is used to ensure the machining accuracy of the part, but during the processing, it is found that since the centers of the two ends are not on the same line, The car cranking, eccentricity and grinding process have to design and make the mold, and because it is a different fixture, the installation process, taking into account the installation error, the center will definitely be biased, so it is decided to increase the length to 40 in the eccentricity. The 50-step process is designed to ensure that the machining process can be installed and machined in the same hole. This not only reduces the number of fixtures in the process, but also the dimensional accuracy of the parts. Can be well guaranteed.

The crank is a key part of the crankshaft movement, and the piston is connected to the crank and wear resistance. Therefore, in the process, the high-frequency quenching of the crank and the pump journal is arranged, and the hardness value is only 14550. However, after processing, the hardness value is lower than the design requirement, and then the crankshaft just heat-treated is measured. It was found that the hardness value was basically between 4548, which met the design requirements. The reason for chasing the original is that the design process is too large before the high-frequency quenching of the crank and the pump journal, resulting in a low hardness value after the parts are ground. Under the premise of not changing the heat treatment process, it is also necessary to ensure sufficient initiality of the core at the crankshaft of the crankshaft. Therefore, the rough grinding process is added before the high frequency quenching.

That is, the rough grinding turns to 0.4 ± 0.03, and the fine grinding allowance of 0.4, after the processing according to this process, the hardness of the parts meets the design requirements.

After using the crankshaft fittings provided by our factory in the initial stage, the user performs magnetic particle testing on the crankshaft after the operation year. It is found that cracks appear at different points in the crank joint, which seriously affects the service life of the product and has certain safety hazards. Our company analyzes the questions asked by the customer layer by layer and finds that the excessive rounding of the crank can be too small, because during the crankshaft movement, the stress concentration phenomenon is most likely to occur here, and the information from the customer feedback is also the same. The place where the crack appears most, the reason is that the excessive rounding of the team's turn in the production process may be too small, according to the reference formula provided by the Mechanical Industry Press piston compression design = 0.05, 0.06, The diameter of the turn, the company used the overfilling method. However, in order not to weaken the strength of the crank, the company considered the excessive rounding to the original design value of 0.5. After the customer used it, it reflected well.

The oil hole on the crankshaft is generally in the form of a slanted oil hole or a right angle oil hole depending on the shape of the crankshaft and the manner of oil supply. The diameter of the oil hole is about 0.

050.06 times, but should not be less than 3mm. The oil hole should be inverted at the journal surface. It should be inverted and polished. The radius of the round hole is about half of the diameter of the oil hole to improve the oil hole except the crank. The remaining oil hole ends are sealed with a 018 screw plug and then sealed.

However, during the secondary use process, the connecting rod and the crankshaft are killed, and the magnetic powder is detected on the crankshaft after the joint. It is found that there is a crack in the end face of the inclined oil hole at the crank, and the crack may be generated after the analysis, and the belt is in the movement of the connecting rod. This phenomenon occurs when the connecting rod is inserted. Our company later found that after drilling the inclined hole, the end and the crank turn produced a thin edge, and the analysis produced in each processing step was caused by the extremely rapid cooling after the high-frequency quenching of the crank. . In order to prevent the similar situation from happening again, the company took a series of measures, but the effect was very small. There were more or less cracks on the edge of the inclined hole. Finally decided to insert a length of not less than 8 in several oil holes of the crank, and the copper rod with the hole interference is not less than 5, the copper rod is knocked into the oil hole before the high frequency quenching, and the end surface is smoothed after being knocked in, The crank is subjected to high frequency quenching for rejection. According to this processing technology, the subsequent batches of the crankshaft were inspected and analyzed, and no similar situation occurred. The question was finally solved.

3 Conclusion After the transformation of the above process, the company's recent, 2.4 air compressor crankshaft finished product qualification rate has increased significantly, after the customer's use, it reflects very well.

Piston compressor design. Beijing Mechanical Industry Press, 1981.

2 mechanical engineering manual. Fan. Air blower. compressor. Beijing. Mechanical industry

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