Piston ring is one of the precision parts of diesel engine, and its working conditions are bad. If the diesel engine is used and maintained improperly, and the method of assembling the piston ring is incorrect, abnormal wear of the piston ring will result. Here is a brief introduction to the characteristics and reasons of abnormal wear of the piston ring:

1. Fatigue damage

1) Features. The upper and lower working surfaces of the piston ring are severely scratched and worn seriously, and the color of the piston ring is dim; the contact surface of the first piston ring and the cylinder is severely worn, and the outer working surface of the piston ring of most cylinders has small scratches along the cylinder axis. ; There are a lot of sludge and paint film on the back of the gas ring and around the oil return hole of the oil ring groove.

2) Reasons. The direct cause of the fatigue damage of the piston ring is the operation mode and improper maintenance of the engine during the running-in period. The main influencing factors are: the diesel engine works at high speed and heavy load for a long time during the running-in operation period, or suddenly turns off when the car is hot; the hose connecting the air filter to the intake pipe is short-circuited, causing dust to enter the cylinder; The type of lubricating oil injected does not meet the specified requirements, and the pollution is serious; the quality of the fuel injection of the injector is poor or the quality of the selected fuel is poor, the diesel engine works at low temperature for a long time; the fuel supply advance angle is inaccurate, etc.

2. Fracture

1) Features. The first piston ring is broken and the piston ring groove is damaged; there are corrugated pull marks on the outer working surface of the piston ring and the upper part of the cylinder; the piston skirt and the upper part of the cylinder are melted and worn; fractures often occur on both sides of the opening. Point area.

2) Reasons. The direct cause of piston ring fracture is improper use or maintenance of the engine. The main influencing factors are: the diesel engine works under overheating for a long time, causing the piston ring to jam; the viscosity of the lubricating oil used is too large; the selection of the piston ring is not reasonable or the installation method is incorrect, which causes the stress concentration of the piston ring; the piston and the cylinder The matching clearance of the diesel engine is too small; the diesel engine has been working under deflagration conditions for a long time.

3. Sticky ring

1) Features. There are a lot of sludge, carbon deposits and colloidal deposits on the piston ring and piston ring groove; the outer working surface of the piston ring presents a polished luster, and there are deep longitudinal scratches; the elasticity of the piston ring is weak.

2) Reasons. The direct cause of the sticking ring is that the piston ring is bonded by sludge and carbon deposits, and the piston ring and cylinder are deformed. The main influencing factors are: severe thermal deformation of the piston ring and cylinder, too small backlash and backlash of the piston ring, making the ring stuck in the ring groove and unable to move; the diesel engine is overheated or long-term overloaded, which causes the lubricating oil to produce high-temperature colloid; Poor quality of lubricating oil; poor fuel injection quality of the fuel injector; poor work of the crankcase ventilation device, causing excessive negative pressure or poor cylinder air tightness, causing oil to run up; unreasonable selection of cylinder liners or improper press-fitting methods Deformation and so on.

4. Partial wear

1) Features. The upper and lower end faces of the piston ring and the ring groove have small wear, unilateral or uneven wear on the circumferential surface; there are longitudinal scratches on the outer working surface of the piston ring due to adhesive wear; there is blow-by on the piston ring and the top of the piston trace.

2) Reasons. The direct cause of the biased wear of the piston ring is due to the incorrect position of the piston in the cylinder. The main influencing factors are: insufficient running-in operation of the new engine or diesel engine after overhaul; thermal deformation of the cylinder liner and incorrect position after the cylinder is fitted into the cylinder block; bending or twisting of the connecting rod; excessive crankshaft axial clearance, etc.


5. Scratches on the working surface

1) Features. There are longitudinal grooves on one side of the piston ring or on the circumferential working surface; metal peeling or large-area scratches on the contact surface; working surface scratches and sticking rings often occur at the same time.

2) Reasons. The direct cause of piston ring scratches is due to the destruction of the lubricating oil film between the piston ring and the cylinder. The main influencing factors are: the matching clearance between the piston and the cylinder is too small; the method of assembling the piston ring is improper or the ring mouth is compressed or stretched at will during the assembly to cause deformation; the method of assembling the cylinder liner or tightening the cylinder head is incorrect, causing the cylinder liner to deform; Long-term operation of the diesel engine under high temperature conditions causes the lubricating oil film to break; insufficient lubricating oil or serious pollution, etc.