What is a Piston?

秦浪

2022/08/22

Piston is the "heart" of an automobile engine, which is subjected to alternating mechanical and thermal loads, and is one of the key components in the engine with the worst working conditions. The function of the piston is to withstand the gas pressure and transmit it to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also an integral part of the combustion chamber.

The engine is like the "heart" of the car, and the piston can be understood as the "hub" of the engine. In addition to being in a harsh working environment, it is also the busiest one in the engine, constantly going from bottom dead center to top. Dead point, reciprocating motion from top dead center to bottom dead center, suction, compression, workmanship, exhaust... The interior of the piston is hollowed out, more like a hat, and the round holes at both ends connect the piston The pin, the piston pin is connected to the small end of the connecting rod, and the large end of the connecting rod is connected to the crankshaft, which converts the reciprocating motion of the piston into the circular motion of the crankshaft.

The function of the piston is to withstand the gas pressure and transmit it to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also an integral part of the combustion chamber. Working conditions 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 3-5MPa, and the diesel engine is as high as 6-9MPa, which makes the piston produce 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.

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