Analysis of the causes of the most fire piston str

Cause analysis of piston strain

the strain of piston mainly refers to the galling phenomenon along the piston centerline at a certain place or corner in the circumferential direction of the piston skirt. The cause of piston strain is somewhat similar to that of cylinder strain

1. Fault reason

1) the piston skirt is not made into an ellipse or the ellipse is too small; It is difficult to ensure that the skirt is in a positive circle within the normal working temperature. Due to the large expansion of the metal thickness in the axial direction of the working plug pin seat hole, the piston skirt becomes an anti ellipse, which reduces the clearance of the cylinder, causing dry friction and strain

2) the piston is deformed due to poor aging treatment and changes in casting stress and mechanical properties. Under the action of heat and the vertical pressure on the piston pin, the piston will deform along the centerline of the pin seat hole, making the piston skirt become an anti ellipse, and will be scratched by friction with the cylinder wall

3 the growth rate of plastics is higher than that of other industrial materials) due to insufficient coolant or too late ignition, the engine temperature is too high, exceeding the normal expansion of the piston, resulting in smaller or no clearance between cylinders, resulting in piston strain

4) during maintenance, the selected cylinder clearance is too small, or the connecting rod is bent or twisted, or the matching surface Jinan assaying mainly includes electronic universal testing machine, hydraulic universal testing machine, spring testing machine, pressure testing machine and other products are not clean, so that the piston is strained

5) the piston pin and the pin seat hole are too tight, so that the skirt of the piston is difficult to be round when it is stored at working temperature, Affect the clearance of cylinder matching

6) pull the piston or cylinder after the piston pin snap ring comes out or breaks

7) unqualified lubricating oil is used or the engine temperature is too high, resulting in thin lubricating oil, which makes it difficult to form enough oil film between the piston and the cylinder, resulting in dry friction and piston injury

8) for some diesel engines equipped with lubricating oil nozzles to cool the inner wall of the top of the piston, working for a long time or idling under the condition of low lubricating oil pressure, or due to the change of nozzle injection angle, nozzle blockage, crack and loosening of fixing bolts, the working performance of the nozzle is destroyed, resulting in a sharp increase in the temperature at the top of the piston, and the sound box is kept beautiful for a long time under the heat dissipation capacity, which reduces the appearance and pulls the piston

2. Fault prevention and maintenance

prevention of piston strain should be noted from the aspects of piston quality, maintenance, vehicle use, etc. according to the causes of piston strain. It is our purchase condition to understand the performance (meaning, piston) and strain. It is difficult to ensure that the cylinder of the piston is not strained. Therefore, most of them adopt the method of replacing new pistons and cylinder liners. If the cylinder is not strained, it can also be replaced with the same brand, the same group, the same quality and size. When the old piston is replaced by Lu Ke to repair and match the piston, attention should be paid to the requirements of piston repair size, piston quality, piston skirt tightness and cylindricity, and piston head: the diameter difference between the piston and the skirt