Engine pull cylinder refers to the obvious longitudinal mechanical scratches and scratches on the inner wall of the cylinder within the range of movement of the piston ring. In severe cases, fusion wear occurs, which causes difficulty in starting the engine or failure of self-extinguishing. Cylinder pulling is a major accident of the engine.
The root cause of the cylinder is that it is difficult to form an oil film between the inner wall of the cylinder, the piston ring and the piston, which results in poor lubrication and even dry friction. There are many specific reasons for this situation, which can be summed up in three aspects:
The reason for the cylinder liner
1. The roundness and cylindricity tolerances of the cylinder liner exceed the allowable range, which greatly reduces the sealing performance of the piston and the cylinder liner. The high-temperature gas in the cylinder moves downwards, destroys the oil film between the piston and the cylinder wall, and causes the cylinder to pull.
2. The cylinder liner is deformed during the assembly process. For example: the upper end surface of the cylinder liner is too protruding, and the cylinder liner is deformed after installing the cylinder head; the cylinder liner water blocking ring is too thick, and the cylinder liner is deformed after being pressed into the body, which will easily cause the cylinder to pull.
Reasons for use
The reason for the piston group
1. Piston ring clearance is too small. If the opening gap, side gap, or back gap of the piston ring is too small, the piston ring will be blocked by thermal expansion when the engine is working, and it will be tightly pressed against the cylinder wall, or the piston ring will break, and it will be easy to pull out the groove on the cylinder wall.
2. Piston pin leaped out. Because the piston pin circlip is not installed or falls off or breaks, the piston pin leaps out during the movement, it is easy to strain the inner wall of the cylinder, causing the cylinder to blow-by to the crankcase.
3. The clearance between the piston and the cylinder is too small or too large. If the material of the piston is poor, the manufacturing size error is too large, or the piston is deformed after the piston pin is assembled, the clearance between the piston and the cylinder is too small, the piston will be stuck after being heated and expanded, and the cylinder wall will be strained.
4. The piston ring is severely carbonized. Excessive carbon deposits cause the piston ring to stick or seize in the ring groove. At the same time, the carbon deposits are a hard abrasive that will grind into longitudinal grooves on the cylinder wall.
5. The piston is severely off-cylinder. Due to the bending and distortion of the connecting rod, the deviation of the parallelism and coaxiality of the connecting rod journal, main journal, and piston pin seat is too large, which causes the piston to be obviously biased, which will accelerate the wear of the piston ring, the piston and the cylinder wall, and destroy the oil film Formation.
1. The air filter is not sealed, which makes the filtering effect worse. The dust, sand and other impurities in the air are sucked into the cylinder to form abrasive wear. Tests have shown that if a few grams of dust is sucked in every day, the wear of the cylinder liner will increase by more than 10 times.
2. Poor running-in. For new or overhauled engines, there are many microscopic unevennesses on the surface of cylinder liners, pistons, piston rings and other parts, and it is difficult to form a lubricating oil film. If it is put into high-load operation immediately without running-in, it is easy to cause accidents such as cylinder pulling.
3. Always start at low temperature. When the engine is started at low temperature, the lubricating oil has high viscosity and poor fluidity, and it is difficult to form an effective oil film on the inner wall of the cylinder. According to tests conducted by the research department, when the diesel engine is operated under a load with a cooling water temperature of 30°C, the wear of cylinder liners and other parts is 5 to 7 times that of normal water temperature.
4. The engine is overheated. When the cooling system is poorly maintained or overloaded, the excessively high engine temperature not only reduces the mechanical strength of the parts, but also prevents the formation of a lubricating oil film on the inner wall of the cylinder. After the piston and other parts are heated and expanded, they are easy to get stuck in the cylinder liner. The result is often that the piston is partially melted and the inner wall of the cylinder liner is stretched, forcing the engine to stall.
In actual use, cylinder pulling is often the result of a combination of several factors. For example, if an engine that has not been run-in is started, it is immediately put into full-load operation, and it is prone to cylinder pulling accidents at this time.
Post time: Aug-31-2021