4.2.3 Piston
The piston looks like an inverted cup, usually cast from an aluminum alloy. The piston is installed in the cylinder with a very small clearance (usually hundredths of a millimeter). The piston is sealed with piston rings in order to prevent the gases that are created during fuel combustion from breaking into the crankcase of the engine block through this gap. Usually, two compression rings are installed (they perceive the main load when the piston moves) and one oil-scraper ring (it consists of several elements), which is necessary for removing engine oil from the cylinder walls. The piston, pivotally, that is, via the pin, is connected to the upper head of the connecting rod. And the connecting rod, in turn, is pivotally connected to the crankshaft. If joined together, these elements are called the connecting rod and piston group. And the connecting rod and piston group, which is connected to the crankshaft, creates the movable elements of the crank gear (further, speaking about this mechanism, we will mean precisely these elements). Thanks to the connecting rod, the upward and downward movement of the piston is converted into a rotational movement of the crankshaft.
Note
Dear reader, you may think that you missed a whole section, because in figure 4.1, both the stud and the upper connecting rod head are missing, but this is not so: the above description is provided for a general idea of the internal combustion engine, but the structure of each of the elements is discussed in detail in section 4.7 "Cylinder Block and Crank Gear".
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