You just need to understand that.
Engines are really complicated and people without mechanical background should give up soon. But if you cut the engine into "upper half" and "lower half", it might be simpler. The "upper seat" parts mainly provide oil and gas as a fuel source, while the "lower seat" is to convert fuel into power for output to the gearbox, as long as the two concepts are mastered, the functions of these main parts are not difficult to imagine.
Camshaft
The cam on the shaft is responsible for driving the valve switch, so that the intake and exhaust journey can run smoothly. Because modern engines are equipped with DOHC with overhead double camshafts, the eggshell surface of the cam can be used to drive the opening of various valve rods. This direct compression method becomes "direct" with simple structure and high efficiency. Another kind of "rocker-arm" valve structure, if the speed is too high, will not work well because of too much inertia force, and has gradually withdrawn from the mainstream.
Valve mechanism
Including valve seat, valve spring, valve rod and so on. Simply speaking, the rotation motion of camshaft is converted into linear motion to control the opening and closing of intake and exhaust valves. Interestingly, the camshaft controls the opening of the valve, while the closing depends on the elastic force of the valve spring, which is tightly closed on the valve seat. If the elastic force is too small, it will continue to return to vibration at high speed, resulting in leakage. Therefore, different spring pitches are used to prevent the occurrence of return shocks.
Timing gear
The rotation of the camshaft is driven by the crankshaft. There are timing gear discs and TIMING CHAINs on the camshaft and crankshaft, and the timing gear discs are marked to align the compression dead point of the first cylinder piston. Why do we have to be punctual? Because the crankshaft of a four-stroke engine rotates twice and the camshaft rotates only once, the speed ratio of the crankshaft to the camshaft is 2:1. Therefore, when the belt or chain is changed, the two will be in sync.
Gasoline engine ignition oil and gas power generation of important parts, the original plant is usually nickel-manganese alloy as the electrode, if need more durable, will use platinum, iridium and other precious metals to build, according to the engine performance and use environment, the model of Mars plug is also different. A high-voltage IGNITION COIL is connected above the spark plug, which releases arc when the discharge passes through the gap at the bottom of the spark plug, thereby igniting saturated oil and forming a strong explosive force.
Piston + connecting rod
When oil and gas are ignited and exploded, the piston and connecting rod will be pushed to produce mechanical thrust. Because it has to withstand high pressure and heat, the material and accuracy requirements of piston are very strict. It must have the characteristics of lightweight, low friction, fast heat dissipation and so on. There are usually three layers of PISTON RINGs on the periphery to prevent air leakage and lubrication of the cylinder wall, but to prevent the aluminum alloy piston from being blocked by thermal expansion, so the piston skirt at the bottom is often designed as an ellipse. The connecting rod transmits the thrust of the piston to the crankshaft, which must bear a great impact. Most of the cross sections are designed as "Gong", and even the connecting rod ends in different positions are designed according to the characteristics of the engine.
crankshaft
The function of crankshaft is to convert the reciprocating motion of piston into rotary motion, and output power to gearbox through flywheel or torsion converter. In order to reduce excessive vibration and noise, there will be a counterweight design on the crankshaft to improve the balance inertia force. The balance axle at both ends of the crankshaft rotates with the crankshaft and also reduces vibration. According to the number and configuration of cylinders, the length of crankshaft, the angle of spacing and the ignition sequence are also determined. The more cylinders the engine has, the bigger the angle of ignition overlap is, the smoother the operation will be. For example, V8 engine, the idle speed can be designed very low.
Oil pan
It is used to store engine oil. There are partitions inside to prevent oil from shaking and foaming. The oil pan is connected to the lower half of the cylinder, and a rubber GASKET is clamped in the middle to prevent oil leakage. Some oil pans are made of steel and plastic, which are attached to the inner side to absorb the vibration of the engine.
Fuel injection system
The liquid gasoline is pumped through the gasoline pump to the fuel rail of the engine. The liquid oil is atomized by the nozzle and injected into the intake port to mix with air to form oil and gas (the other is direct injection in the cylinder). In order to mix with air more evenly, there are several holes in the nozzle of each cylinder for multi-point injection.
Starting motor
Electricity is needed to start the engine instantaneously. Batteries supply electricity to the starter motor. The pinion is started to rotate the flywheel. The piston connecting rod of the engine acts first, and then the explosive power supplied by the FUEL INJECTOR and the Mars plug is used to make the engine work.
Flywheel
Connect the back end of the crankshaft, because it is heavy, the inertia force generated by rotation can be used to suppress the piston's speed of return, so that the engine's power can be output smoothly. In other words, the flywheel can store part of the kinetic energy for the engine's four-stroke use. (Volleyball has torsion converter, no flywheel required)