Intake, induction or suction: The intake valves are open as a result of the cam lobe pressing down on the valve stem.
The air or air-fuel mixture is called the charge in any case. Compression: In this stroke, both valves are closed and the piston moves upward reducing the combustion chamber volume which reaches its minimum when the piston is at TDC.
The piston performs work on the charge as it is being compressed; as a result its pressure, temperature and density increase; an approximation to this behavior is provided by the ideal gas law.
Just before the piston reaches TDC, ignition begins.In the case of a SI engine, the spark plug receives a high voltage pulse that generates the spark which gives it its name and ignites the charge.
For naturally aspirated engines a small part of the combustion gases may remain in the cylinder during normal operation because the piston does not close the combustion chamber completely; these gases dissolve in the next charge.
At the end of this stroke, the exhaust valve closes, the intake valve opens, and the sequence repeats in the next cycle.The intake valve may open before the exhaust valve closes to allow better scavenging. Źródło: https://en.wikipedia.org/wiki/Internal_combustion_engine
Lubrication Diagram of an engine using pressurized lubrication Wikimedia Commons has media related to Internal combustion piston engine lubrication systems. Surfaces in contact and relative motion to other surfaces require lubrication to reduce wear, noise and increase efficiency by reducing the power wasting in overcoming friction, or to make the mechanism work at all.
At the very least, an engine requires lubrication in the following parts: Between pistons and cylinders Small bearings Big end bearings Main bearings Valve gear (The following elements may not be present): Tappets Rocker arms Pushrods Timing chain or gears.
Toothed belts do not require lubrication. Źródło: https://en.wikipedia.org/wiki/Internal_combustion_engine
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