Engine pulling cylinder refers to the obvious longitudinal mechanical scratches and scratches on the inner wall of the cylinder within the movement range of the piston ring. In severe cases, fused wear occurs, which causes difficulty in starting the engine or self-extinguishing. Cylinder pulling is a major failure in engine failure.
The fundamental reason for pulling the cylinder is that it is difficult to form an oil film between the inner wall of the cylinder and the piston ring and piston, thus causing poor lubrication and even dry friction. There are many specific reasons for this situation. Master Du summarized it in three ways:
The reason for the piston group
1. The piston ring clearance is too small. If the opening clearance, side clearance or back clearance of the piston ring is too small, the piston ring will be stuck due to thermal expansion when the engine is working, and it will be pressed tightly against the cylinder wall, or the piston ring will break, and it is easy to pull out the groove on the cylinder wall.
2. The piston pin popped out. Because the piston pin retainer is not installed or falls off or breaks, the piston pin escapes during the movement, and it is easy to damage the inner wall of the cylinder, causing the cylinder to blow air to the crankcase.
3. The clearance of the piston is too small or too large. If the piston material is poor, the manufacturing size error is too large, or the piston is deformed after the piston pin is assembled, resulting in a too small gap between the piston and the cylinder, the piston is stuck after being heated and expanded, and then the cylinder wall is injured.
4. The piston ring is heavily carbonized. Too much carbon deposit causes the piston ring to stick or bite in the ring groove. At the same time, the carbon deposit is a hard abrasive that will be ground into a longitudinal groove on the cylinder wall.
5. The piston is severely deviated from the cylinder. Due to the bending and twisting of the connecting rod, the parallelism and coaxiality deviation of the connecting rod journal, main journal, and piston pin seat are too large, causing the piston to deviate significantly from the cylinder, which will accelerate the wear of the piston ring, piston and cylinder wall, destroying the oil film Formation.
Reasons for cylinder liner
1. The roundness and cylindricity tolerance of the cylinder liner exceeds the allowable range, which greatly reduces the sealability of the piston and the cylinder liner.
2. The cylinder liner is deformed during assembly. For example: the amount of protrusion on the upper end surface of the cylinder liner is too large, and the cylinder liner is deformed after the cylinder head is installed; the water blocking ring of the cylinder liner is too thick, and the cylinder liner is deformed after being pressed into the body, which is likely to cause cylinder pulling.
Reasons for use
1. Whether the size of the cylinder liner used during assembly is not compatible with the cylinder block and the piston.
2. The air filter is not sealed, which makes the filtering effect worse. Dust, sand and other impurities in the air are sucked into the cylinder, resulting in abrasive wear. Tests have shown that if a few grams of dust are sucked in each day, the wear of the cylinder liner will increase by more than 10 times.
3. Poor run-in. New or overhauled engines have many microscopic irregularities on the surface of cylinder liners, pistons and piston rings, and lubricant films are more difficult to form. If the heavy load is put into operation immediately without running-in, it may easily cause accidents such as cylinder pulling.
4. Frequent low temperature start. When the engine starts at a 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 the research of the research department, when the diesel engine is operated under load with a cooling water temperature of less than 30 ° C, the wear of the cylinder liner and other mechanical parts is 5 to 7 times that of the normal water temperature.
5. The engine is overheated. When the cooling system is poorly maintained or overloaded, the excessively high machine temperature not only reduces the mechanical strength of the parts, but also prevents the formation of a lubricant film on the inner wall of the cylinder. After the piston and other parts are heated and expanded, they are easily stuck in the cylinder liner. The consequence is often that the piston is partially melted and the inner wall of the cylinder liner is damaged, forcing the engine to shut down.
In actual use, the pulling cylinder is often the result of several factors. For example, an engine that has not been run-in is put into full-load operation immediately after it is started. At this time, a cylinder pulling accident is likely to occur.
