The piston works under the conditions of high temperature, high pressure, high speed and poor lubrication. The piston is in direct contact with the high-temperature gas, and the instantaneous temperature can reach more than 2500K. Therefore, the heating is serious and the heat dissipation conditions are very poor, so the temperature of the piston is very high during operation, the top is as high as 600-700K, and the temperature distribution is very uneven; the top of the piston is subjected to The gas pressure is very large, especially the working stroke pressure is the largest. The gasoline engine is as high as 3 to 5 MPa, and the diesel engine is as high as 6 to 9 MPa, which makes the piston impact and bear the effect of side pressure; the piston moves at a high speed in the cylinder (8 ~12m/s) reciprocating motion, and the speed is constantly changing, which produces a large inertial force, which makes the piston subject to a large additional load. When the piston works under such harsh conditions, it will deform and accelerate the wear, and it will also generate additional load and thermal stress, and at the same time, it will be chemically corroded by the gas.
Piston inspection is mainly the measurement of skirt diameter, piston ring groove height and piston pin seat hole size:
① The selection of the piston should be determined according to the repair size of the cylinder. Usually, the enlarged size value is marked on the top of the piston;
② In the same series of fish feeders, the structure of the pistons is not necessarily the same. Therefore, when purchasing pistons, the corresponding types of pistons must be selected according to the type of engine. On the same engine, the same brand, the same group or Pistons with the same product code; the same model must use pistons with the same product code to ensure that the difference in diameter and quality of the piston does not exceed the range specified by the original factory. Otherwise, it will cause the engine to burn badly, work rough, and reduce economy and power. . Therefore, when selecting pistons, the corresponding type of piston must be selected according to the type of engine.
