Water-cooled engine cylinder block and the upper crankcase often cast as one, called the cylinder block - crankcase, also known as the cylinder block. The cylinder block is generally cast with gray cast iron. The cylindrical cavity at the upper part of the cylinder block is called the cylinder. The lower half is the crankcase supporting the crankshaft, and the inner cavity is the space for crankshaft movement. In the cylinder body cast a lot of stiffeners, cooling water jacket and lubricating oil Road.
Cylinder block should have sufficient strength and stiffness, according to the cylinder block and the oil pan mounting plane of the different positions, usually the cylinder body is divided into the following three forms.
1, the general type cylinder block: It is characterized by the oil pan mounting surface and crankshaft rotation center at the same height. The advantages of this cylinder body is the body height, light weight, compact structure, easy processing, crankshaft disassembly easy; but its disadvantage is the poor rigidity and strength.
2, gantry cylinder block: It is characterized by oil pan installation plane below the crankshaft rotation center. Its advantage is strength and stiffness are good, can withstand greater mechanical load; but its disadvantage is less technology, the structure of heavy, more difficult to process.
3, the tunnel cylinder body: This form of cylinder body crankshaft main bearing hole for the whole, the use of rolling bearings, the main bearing hole larger crankshaft from the rear of the cylinder body into. Its advantages are compact structure, stiffness and strength, but the disadvantage is the high precision machining, poor workmanship, crankshaft disassembly inconvenient.
In order to be able to operate the inner surface of the cylinder at high temperatures, the cylinder and cylinder head must be properly cooled. There are two cooling methods, one is water-cooled, the other is air-cooled. The cooling water jacket is processed around the cylinder of the water-cooled engine and in the cylinder head, and the cylinder body and the cylinder head cooling water jacket are communicated with each other. The cooling water circulates continuously in the water jacket, takes away part of the heat, and cools the cylinder and the cylinder head.