The main German brands Mercedes-Benz, Audi, BMW, Porsche and Volkswagen basically have the latest in-cylinder direct injection technology, and the most common one is Volkswagen's FSI. The working principle is the same, but Mercedes-Benz and BMW have different names.
American cars: Buick, Chevrolet, Cadillac and Ford under GM also have direct injection technology; Chrysler, JEEP, the models currently on sale have no direct injection engine, but the 300C has variable cylinder function.
Other European cars: Peugeot Citroen, Fiat, etc., are basically similar to Japanese cars.
Engine basic structure
The engine block is the skeleton of the engine and the installation foundation of various mechanisms and systems of the engine.
It is equipped with all main parts inside and outside the engine and bears various loads. Therefore, the car body must have sufficient strength and rigidity. Engine cylinder block is mainly composed of cylinder block, cylinder liner, cylinder head and cylinder gasket.
cylinder block
The cylinder block and upper crankcase of water-cooled engine are usually cast as a whole.
Known as the cylinder block-crankcase, it can also be called the cylinder block. The cylinder block is usually made of gray cast iron. The cylindrical cavity in the upper part of the cylinder block is called the cylinder, the lower part is the crankcase supporting the crankshaft, and its inner cavity is the space for the crankshaft to move. Many reinforcing ribs, cooling water jackets and lubricating oil passages are cast in the cylinder block.
The cylinder block should have sufficient strength and rigidity. According to the different installation plane positions of the cylinder block and the oil pan, the cylinder block is usually divided into the following three forms.
1. General cylinder block: characterized in that the installation plane of oil pan is at the same height as the rotation center of crankshaft. The advantages of this cylinder block are small height, light weight, compact structure, convenient processing and convenient disassembly and assembly of crankshaft; But its disadvantages are poor rigidity and strength.
2. Gantry cylinder block: characterized in that the installation plane of oil pan is lower than the rotation center of crankshaft.
Its advantages are good strength and rigidity, and it can bear large mechanical load. But its disadvantages are poor manufacturability, heavy structure and difficult processing.
3. Tunnel cylinder block: The main bearing hole of the crankshaft of this type of cylinder block is integral with rolling bearings, and the main bearing hole is larger, and the crankshaft is loaded from the back of the cylinder block. Its advantages are compact structure, good rigidity and strength, but its disadvantages are high machining accuracy, poor manufacturability and inconvenient disassembly and assembly of crankshaft.
In order to make the inner surface of the cylinder work normally at high temperature, it is necessary to properly cool the cylinder and cylinder head. There are two cooling methods, one is water cooling and the other is air cooling. Cooling water jackets are processed around the cylinder and cylinder head of water-cooled engine, and the cylinder block and cylinder head are communicated with each other. The cooling water continuously circulates in the water jacket, taking away some heat and cooling the cylinder and cylinder head.
crank case
The lower part of the cylinder used to install the crankshaft is called crankcase, which is divided into upper crankcase and lower crankcase. The upper crankcase is integrated with the cylinder block, and the lower crankcase is used to store lubricating oil and seal the upper crankcase, so it is also called oil pan diagram. The oil pan bears little force and is generally stamped from thin steel plate. Its shape depends on the overall layout of the engine and the oil capacity. An oil stabilizing baffle is installed in the oil pan to prevent the oil level from fluctuating too much when the car bumps. There is also an oil drain plug at the bottom of the oil pan. A permanent magnet is usually installed on the oil drain plug to absorb the metal chips in the lubricating oil and reduce the wear of the engine. The gasket is installed between the joint surfaces of the upper crankcase and the lower crankcase to prevent the lubricating oil from leaking.
cylinder head
The cylinder head is installed on the cylinder block to seal the cylinder from the upper part to form a combustion chamber.
It is often in contact with high temperature and high pressure gas, so it bears great thermal load and mechanical load. A cooling water jacket is arranged in the cylinder head of the water-cooled engine, and the cooling water hole at the lower end face of the cylinder head is communicated with the cooling water hole of the cylinder block. Circulating water is used to cool high-temperature components such as combustion chambers.
The cylinder head is also equipped with intake and exhaust valve seats, valve guide holes for installing intake and exhaust valves, and intake and exhaust passages. The cylinder head of gasoline engine has holes for installing spark plugs, and the cylinder head of diesel engine has holes for installing fuel injectors. There are also camshaft bearing holes on the cylinder head of overhead camshaft engines for installing camshafts.
Generally, the cylinder head is made of gray cast iron or alloy cast iron, and the aluminum alloy has good thermal conductivity, which is conducive to improving the compression ratio, so the use of aluminum alloy cylinder heads is increasing in recent years.
The cylinder head is an integral part of the combustion chamber, and the shape of the combustion chamber has a great influence on the work of the engine. Because of the different combustion modes of gasoline engine and diesel engine, the parts of cylinder head that make up the combustion chamber are also very different. The combustion chamber of gasoline engine is mainly on the cylinder head, and the combustion chamber of diesel engine is mainly in the pit at the top of piston. Only the combustion chamber of gasoline engine is introduced here, and the combustion chamber of diesel engine is introduced in the diesel supply system.
Three common types of combustion chambers in gasoline engines.