Blank (small crankshaft for forging, large crankshaft for nodular cast iron), forging is to burn the barred through the multi-channel forging die, forging into a multi-turn plane, in the red and hot state of the last process to turn each nut to the corresponding Angle.
1) car positioning, find the center of the main deck on the ordinary lathe and locate the two ends of the car.
2) owner’s journal.
3) the automobile link journal is on the special lathe, the tool frame follows the link journal neck while rotating and feeding the knife, and at one time the car has two connecting rod journals with the same Angle; (trial production or non-mass production is to make an eccentric fixture on a regular lathe plate and use the connecting rod journal as the center of rotation).
4) drilling an oil channel hole, a crankshaft from the main neck to the turning arm to the inner part of the shaft of the connecting rod, is the special equipment for deep hole drilling.
5) high-frequency quenching, quenching the spindle neck, and connecting rod journal to improve the surface hardness.
6) grind the spindle neck.
7) grinding rod journal, is a very precise special crankshaft grinder, that will be automatically measured and grinding, the accuracy is controlled by 0.01 mm;
8) another machining (flywheel connection key slot, back oil groove, thread, etc.)
The main cause of crankshaft fracture
1) the long-term use of oil has deteriorated due to improper selection of oil, or not paying attention to the cleaning and replacement of; Severe overload and super hang, resulting in a long-term overload of the engine and the occurrence of the burning drain accident. The engine burns watts and the crankshaft is badly worn. The engine crankshaft is used to change and repair, that is, buying a new crankshaft installed, will damage the crankshaft to the factory for repair backup. Some users in the vehicle after the problem of crankshaft wear, out of cost and time consideration, find some small factories in the local repair and processing, serious wear crankshaft for surfacing, processing, overall heat treatment after grinding processing. Repair means and process problems, the connection Angle of crankpin and spindle neck and crank arm changes, resulting in local stress concentrated; The crankshaft is precision no. 45 steel die forging, and surfacing welding makes the metal fabric of the curved vehicle change. The above is the main cause of crankshaft fracture.
2) after the engine is repaired, the loading vehicle does not pass through the rundown period, that is, the overload overhang, the engine long-term overload operation, so that the crankshaft load exceeds the allowable limit.
3) surfacing welding was used in the repair of the crankshaft, which damaged the power balance of the crankshaft, and did not make a balance check.
4) due to the poor road condition, the vehicle is seriously overloaded and overrun, and the engine is often at the critical speed of torsional vibration, the shock absorber fails, and the crankshaft torsional vibration fatigue is broken.
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The grinding of the crankshaft journal is carried out on the basis of crankshaft correction. In addition to the accuracy and roughness of the crankshaft surface, the grinding of the crankshaft must meet the technical requirements of shape tolerance: when grinding the crankshaft, it must ensure the of each axis line of the spindle neck and connecting rod journal and the parallel between the two axis lines, and limit the crank radius error. And ensure the accuracy of the Angle between the shaft neck of the connecting rod. The grinding of the crankshaft is usually performed on a special crankshaft grinder.
Grinding of connecting rod journal
Due to the uneven wear of connecting rod journal, two grinding methods are generated: the eccentric grinding method and the concentric grinding method. The concentric grinding method is to maintain the axis position of the connecting rod neck after grinding, that is, the crank radius and distribution Angle are unchanged. When the crankshaft of the diesel engine is grinding, the concentric method is often used to keep the crank radius unchanged, the compression ratio of the diesel engine remains unchanged, but the grinding volume is large each time. At present, during the service life of the car, the number of overhauls decreases, and the concentric method can ensure that the engine performance remains unchanged.
Eccentric grinding is used to locate the grinding according to the worn rod journal surface, and the centerline position and crank radius of the journal has changed. Generally, the radius of the crankshaft after grinding is greater than the radius of the original crank, which increases the compression ratio, and the variation of each cylinder is not uniform, and at the same time, the mass center of the crankshaft is not on the center of the crankshaft spindle neck, causing the crankshaft imbalance, resulting in the additional dynamic load during operation. Therefore, in the grinding of connecting rod journal, the increase of crank radius should be minimized, and the error of the axial line of the same connecting rod journal is not greater than + 0.10mm, so as to ensure the balance in crankshaft operation.