The cause of the fracture of the diesel engine crankshaft
The crankshaft suddenly breaks during the operation of the diesel engine, causing the engine to stop running and causing a malfunction. So what are the reasons for the fracture of the diesel engine crankshaft? Today, Xiaobian talks about the cause of the fracture of the diesel engine crankshaft and hopes to help everyone. The reasons for the fracture of the diesel engine crankshaft are described below.
Crankshaft spindle neck offset
The axis of the crankshaft spindle is offset, which destroys the dynamic balance of the crankshaft assembly. When the diesel engine runs at high speed, it generates a strong inertial force, which causes the crankshaft to break.
The rounded corners of the crankshaft journal are too small
When grinding the crankshaft, the grinder fails to properly control the shaft fillet of the crankshaft. In addition to the rough machining of the arc surface, the radius of the fillet is too small, so that the crankshaft works with a large stress concentration at the rounded corner and shortens the crankshaft. Fatigue life.
Flywheel loose
If the flywheel bolt is loose, the crankshaft assembly loses its original dynamic balance. When the diesel engine is running, it will shake and generate a large inertia force, which will cause the crankshaft to fatigue and easily break at the end.
The cold ratio of the crankshaft is too large
Long-term use of the crankshaft, especially after the occurrence of burning or smashing, will cause large bending, should be removed for cold pressure correction. Since the plastic deformation of the metal inside the crankshaft during calibration will generate a large additional stress, thereby reducing the strength of the crankshaft. If the cold gauge is too large, the crankshaft may be damaged or cracked. This crankshaft will be broken shortly after installation.
Poor quality of the crankshaft itself
Buying a crankshaft is not cheap, you must buy it from regular channels. It should be carefully checked before installation, and if there is any problem, it will be replaced or returned in time. In addition, when the engine is overhauled, the crankshaft should be subjected to magnetic flaw detection or oil immersion inspection. If the journal surface has radial or extended axial cracks to the shoulder fillet, the crankshaft can no longer be used.
Crankshaft assembly clearance is too large
If the clearance between the crankshaft journal and the bearing bush is too large, the crankshaft will impact the bearing after the diesel engine is running, but the alloy will fall off and the shaft will be hung, and the crankshaft will be easily damaged.
Main shaft of different bearings
When the crankshaft is assembled, if the center line of each main shaft of the cylinder is different, the engine will be prone to burn accident after the diesel engine is working, and the crankshaft will break under the strong influence of the alternating stress.
Poor crankshaft lubrication
If the oil pump is seriously worn, the lubricating oil channel is dirty and the circulation is not smooth, the oil supply will be insufficient and the oil pressure will drop, resulting in the formation of a normal lubricating oil film between the crankshaft and the bearing bush, thus causing dry friction and causing the burning of the shaft. Breaking the crankshaft and other major accidents.
Premature oil supply time or uneven oil volume
If the oil supply time of the fuel injection pump is too early, the piston will not burn to the top dead center and will cause the diesel engine to knock and cause the crankshaft to be subjected to the alternating stress. If the oil supply amount of each cylinder is not uniform, the crankshafts will be unevenly stressed due to the inconsistency of the explosions of the cylinders, and the tires will be fatigued and cracked prematurely.
Improper operation causes crankshaft fracture
If the throttle is too large or too small, the brakes are frequent or the engine is overloaded for a long time, the crankshaft will be damaged by excessive torque or impact load. In addition, when a diesel engine has an accident such as a flying car, a smashing cylinder, and a top valve, it is also easy to break the crankshaft.
The above is about the reasons for the fracture of the diesel engine crankshaft. I hope that everyone can understand the cause of the fracture of the diesel engine crankshaft and help everyone to repair the crankshaft of the diesel engine.