automotive piston engine is the “heart”, subjected to mechanical and thermal loads alternating, is one of the key components of the engine operating condition is the worst. Function of the piston is subjected to a gas pressure, and driven by a piston rod to pass pin crankshaft rotation, the top part of the piston or combustion chamber.
1. Introduction piston
is like a car engine is the “heart”, and a piston engine can be understood as a “hub”, in addition to living in harsh working environments, it is a busiest engine, performed continuously from the bottom dead point to the top dead center from the top dead point to the lower dead center of reciprocation, intake, compression, work, exhaust piston inside …… design is hollowed out, like a hat, circular connecting both ends of the piston pin, connecting rod small end the piston pin, connecting rod is connected to the crankshaft of the reciprocating motion of the piston into the circular motion of the crankshaft.
2. The operating principle of the piston
is a function of the piston to withstand the gas pressure, and driven by a piston rod to pass pin crankshaft rotation, the top part of the piston or combustion chamber. Working conditions of the piston at high temperatures, high pressure, high speed, poor lubrication conditions. Hot gas in direct contact with the piston, the instantaneous temperature of up to 2500K or more, and therefore, severe heat, and cooling conditions is very poor, so that when the piston working temperature is high, up to the top 600 ~ 700K, and the temperature distribution is not uniform; top of the piston to withstand large gas pressure, in particular, the maximum pressure power stroke, gasoline up to 3 ~ 5MPa, diesel up to 6 ~ 9MPa, which makes an impact piston, and a pressure receiving side effect; the piston in the cylinder at high speed (8 ~ 12m / s) to reciprocate, and the speed is constantly changing, which had a great inertia force by the piston significant additional load. Piston working in such harsh conditions, will produce distortion and accelerated wear, but also have additional loads and thermal stress, while the chemical etching action by the gas.
3. The structure of the piston
The piston is generally cylindrical body, and according to the requirements of different operating conditions of the engine, there are various configuration of the piston itself, this generally small things into the piston head and the piston skirt portion of the pin holder three.
refers to the top of the head portion of the piston ring groove. Depends entirely on the requirements of the piston to the top of the combustion chamber, or near the top of using flattened flattened piston design facilitates reducing the contact area with the high temperature gas, so that uniform stress distribution. Most flat-top piston using gasoline, some engines (e.g., direct injection diesel engine and a new cylinder injection gasoline engine) required to mixture formation, combustion efficiency, the deflagration as to minimize the required piston top having more complex shapes , with a certain depth of the pit as a part of the combustion chamber. The groove of the piston ring groove is referred to for mounting piston rings. The role of the piston ring is sealed to prevent leakage and prevent the oil from entering the combustion chamber.
refers to a portion of the skirt portion of the piston, its role is to keep the piston reciprocating motion in the vertical attitude, that is, the guide portion of the piston.
The shape of the piston skirt very particular, especially as a light passenger car type, the designer from the structure and performance of the engine, often in the brains of the piston skirt, to minimize the engine compact and smooth operation.
support pin boss portion is connected to the piston through a piston pin and the connecting rod, located above the piston skirt. High-speed engine piston pin boss is unique in that the piston pin bore is not necessarily the center line in the same plane, may be shifted a little to one side, namely the side during the power stroke of the piston in contact with the cylinder wall offset so when the piston top dead center to the direction of extent of conversion percussion piston of the cylinder wall will decrease, thereby reducing engine noise.