Overview
The engine body is the framework that constitutes the engine, serving as the foundation for the installation of various mechanisms and systems. It is equipped with all the main components and accessories of the engine, both inside and outside, and bears various loads. Therefore, the body must have sufficient strength and stiffness. The body assembly is mainly composed of parts such as cylinder block, cylinder sleeve, cylinder head, and cylinder gasket.
Cylinder block
The cylinder block and upper crankcase of a water-cooled engine are often cast together, known as the cylinder block - crankcase, also known as the cylinder block. The cylinder block is generally made of gray cast iron. The cylindrical cavity on the upper part of the cylinder block is called the cylinder, and the lower half is the crankcase that supports the crankshaft. The inner cavity is the space for the crankshaft to move. There are many reinforcing ribs, cooling water jackets, and lubricating oil channels cast inside the cylinder body.
The cylinder block should have sufficient strength and stiffness. According to the different positions of the cylinder block and the installation plane of the oil pan, the cylinder block is usually divided into the following three forms.
1. General cylinder block: Its characteristic is that the installation plane of the oil pan and the crankshaft rotation center are at the same height. The advantages of this type of cylinder block are small body height, light weight, compact structure, easy processing, and convenient disassembly and assembly of the crankshaft; But its disadvantage is poor stiffness and strength
2. Gantry cylinder block: Its characteristic is that the installation plane of the oil pan is lower than the rotation center of the crankshaft. Its advantages are good strength and stiffness, and it can withstand large mechanical loads; But its disadvantages are poor craftsmanship, bulky structure, and difficult processing.
3. Tunnel type cylinder block: This type of cylinder block has an integral main bearing hole for the crankshaft, using rolling bearings. The main bearing hole is larger, and the crankshaft is installed from the rear of the cylinder block. Its advantages are compact structure, good stiffness and strength, but its disadvantages are high machining accuracy requirements, poor processability, and inconvenient disassembly and assembly of crankshafts.
In order to ensure the normal operation of the inner surface of the cylinder at high temperatures, it is necessary to cool the cylinder and cylinder head appropriately. There are two cooling methods, one is water cooling and the other is air cooling. Cooling water jackets are processed around the cylinder and in the cylinder head of a water-cooled engine, and the cylinder block and cylinder head cooling water jackets are connected. The cooling water continuously circulates in the water jacket, taking away some of the heat and cooling the cylinder and cylinder head.
Crankcase
The lower part of the cylinder block where the crankshaft is installed is called the crankcase, which is divided into an upper crankcase and a lower crankcase. The upper crankcase is integrated with the cylinder block, while the lower crankcase is used to store lubricating oil and seal the upper crankcase, hence it is also known as the oil pan diagram. The oil pan is subjected to very little force and is generally made of thin steel plate stamping. Its shape depends on the overall layout of the engine and the capacity of the oil. The oil pan is equipped with a stable oil baffle to prevent excessive oil level fluctuations when the car is shaking. The bottom of the oil pan is also equipped with an oil drain plug, which is usually equipped with a permanent magnet to absorb metal shavings in the lubricating oil and reduce engine wear. A gasket is installed between the upper and lower crankcase joint surfaces to prevent lubricating oil leakage.
Cylinder head
The cylinder head is installed on top of the cylinder block, sealing the cylinder from the top and forming the combustion chamber. It often comes into contact with high-temperature and high-pressure gas, thus bearing significant thermal and mechanical loads. The cylinder head of a water-cooled engine is equipped with a cooling water jacket inside, and the cooling water hole on the lower end face of the cylinder head is connected to the cooling water hole on the cylinder block. Use circulating water to cool high-temperature parts such as the combustion chamber.