WHAT IS CAR PISTON?
The piston is a reciprocating motion in the cylinder body of a car engine.
The basic structure of the piston can be divided into top, head and skirt.
The top of the piston is the main part of the combustor, and its shape is related to the form of combustion chamber.
The advantage of gasoline engine is that it absorbs hot area.
The piston tops of diesel engines often have various pits, and their specific shape, location and size must be adapted to the combustion requirements of diesel engines.
1.structure of car piston
The piston top, piston head and piston skirt can be divided into three parts.
The main function of the piston is to bear the combustion pressure in the cylinder and pass the force through the piston pin and connecting rod to the crankshaft.
In addition, the piston is also composed of cylinder cover and cylinder wall to form the combustion chamber.
Piston crown is part of the combustion chamber, and therefore often made into different shapes, gasoline engine piston at most using flat or concave head, so that the combustion chamber structure is compact, the cooling area is small, simple manufacturing process.
The convex piston is often used for two - stroke gasoline engines.
The piston top of a diesel engine is often made into various pits.
The piston head is part of the piston pin seat. Piston ring is installed in the piston head to prevent high temperature and high pressure gas from entering the crankcase, while preventing the oil from running into the combustion chamber.
Most of the heat absorbed at the top of the piston also passes through the head of the piston to the cylinder, passing through the cooling medium.
The piston head process has several ring grooves with piston rings. The number of piston rings depends on the seal requirement. It is related to the engine speed and cylinder pressure.
High speed engine has fewer rings than low-speed engines, and gasoline engines have fewer rings than diesel engines.
General gasoline engine USES 2 air rings and 1 oil ring;
The diesel engine is 3 gas ring and 1 oil ring;
Low speed diesel engine USES 3 ~ 4 air rings.
In order to reduce the friction loss, it is necessary to minimize the height of the ring and strive to reduce the ring number in the condition of sealing.
All the parts below the piston ring are known as the piston skirt.
The function is to guide the piston to reciprocate in the cylinder and bear the lateral pressure.
When the engine is working, the piston can bend and deform because of the pressure of the gas in the cylinder. After the piston is heated, the piston pin has more metal, so its expansion is greater than that of other parts.
In addition, the piston can be extruded under lateral pressure.
The combined results of the above deformation make the section of the piston skirt become the ellipse of the shaft in the piston.
In addition, due to the uneven distribution of the temperature and mass of the piston along the axis, the thermal expansion of each section is small.