Aluminum piston forgings of internal combustion engines
The piston is a piece of reciprocating motion in the cylinder body of an automobile engine. The basic structure of the piston can be divided into the top, the head and the skirt. The top of the piston is the main part of the combustor, and its shape is related to the form of the chosen combustor. The gasoline engine mostly uses the flat top piston, which has the advantage of small heat absorption area. There are usually various pits on the top of diesel engine piston. The specific shape, location and size must be compatible with the requirements of diesel engine mixture formation and combustion.
The whole piston can be divided into 3 parts, the top of the piston, the head of the piston and the piston skirt.
The main function of the piston is to withstand the combustion pressure in the cylinder and pass it through the piston pin and connecting rods to the crankshaft. In addition, the piston also forms a combustion chamber with the cylinder head and cylinder wall.
aluminum forging piston | aluminum 4032 piston for internal combustion engines |
The piston crown is a part of the combustion chamber, so it is often made into different shapes. The top of the gasoline engine is mostly flat top or concave top, so that the combustion chamber is compact, the heat dissipation area is small, and the manufacturing process is simple. The crown piston is often used in a two stroke gasoline engine. The piston top of a diesel engine is often made into a variety of pits.
The piston head is the seat of the part above the piston pin, piston head of the piston ring, to prevent the high temperature and high pressure gas into the crankcase, and prevent oil from entering the combustion chamber; the top of the piston absorbed most of the heat also passed to the cylinder through the piston head, and then passed through the cooling medium.
The piston head is machined with several ring grooves in which the piston ring is installed. The number of piston rings depends on the requirements of the seal, which is related to the engine's speed and cylinder pressure. The ring number of the high speed engine is less than that of the low speed engine, and the ring number of the gasoline engine is less than that of the diesel engine. General gasoline engine with 2 air ring, 1 oil ring; diesel engine for 3 air ring, 1 oil ring; low speed diesel engine with 3~4 air ring. In order to reduce the friction loss, we should try to reduce the part height of the ring as far as possible. In the condition of ensuring the seal, the number of rings should be reduced.
All the parts below the piston ring groove are called piston skirts. The function of the piston is to guide the piston to reciprocate in the cylinder and to withstand the side pressure. When the engine is working, the piston will bend and deform because of the gas pressure in the cylinder. After the piston is heated, the expansion of the piston pin is larger than that of the other parts. In addition, the piston can also prodsuce extrusion deformation under the action of side pressure. The overall result of the above deformation makes the piston skirt section become an ellipse in the direction of the piston pin. 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 larger and lower.
Because the piston of the internal combustion engine works under high temperature and high load conditions, the requirement for the piston is relatively high, so it mainly talks about the classification of the piston of the internal combustion engine.
1. according to the use of fuel to divide, can be divided into gasoline engine piston, diesel engine piston, gas piston.
2. according to the material to make the piston, it can be divided into cast iron piston, steel piston, aluminum alloy piston and combined piston.
3. according to the process of manufacturing piston blank, it can be divided into gravity casting pistons, squeeze casting pistons and forging pistons.
4. according to the working condition of the piston, it can be divided into two types: non turbocharged piston and supercharged piston.
5. piston uses to points, can be divided into the car, truck, motorcycle piston piston piston, piston, piston, ship tank piston, piston and other tractor mowers.
1, it is necessary to have enough strength, stiffness, small mass and light weight to ensure the minimum inertia force.
2. Good thermal conductivity, high temperature resistance, high pressure and corrosion. It has sufficient heat dissipation capacity and small heating area.
3, there should be a small friction coefficient between the piston and the piston wall.
4. When the temperature changes, the size and shape change small, and the minimum gap between the cylinder wall and the cylinder wall is kept.
5. The coefficient of thermal expansion is small and the specific gravity is small, and it has better wear reduction and thermal strength.
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