Motor oil is a lubricant in various types of internal combustion engines. These include motor vehicles or Road Vehicles - the typical light automobiles (including cars, SUVs, minivans, pick-up trucks). Heavy automobiles would include Busses, Trucks and HGVs. Other vehicles, include motorcycles and mopeds, quad-bikes or ATVs, go-karts, snowmobiles, boats (fixed engine installations and outboards), ride-on lawn mowers, large agricultural and construction equipment, trains and airplanes. In engines there are parts which move very closely against each other at high speeds, often for prolonged periods of time. Such motion causes friction, absorbing otherwise useful power produced by the motor and converting the energy to useless heat. Friction also wears away the contacting surfaces of those parts, which could lead to lower efficiency and degradation of the motor. This increases fuel consumption.
Lubricating oil makes a separating film between surfaces of parts moving next to each other so as to minimize direct contact between them decreasing friction, wear, and production of excessive heat, thus protecting the engine. Motor oil also carries away heat from moving parts, which is important because materials tend to become softer and less abrasion-resistant at high temperatures. Some engines have an additional oil cooler.
In petrol (gasoline) engines, the top compression ring can expose the motor oil to temperatures of 320 °F / 160 °C . In diesel engines the top ring can expose the oil to temperatures over 600 °F / 315 °C. Motor oils with the higher viscosity indexes tend to thin less at these higher temperatures.
Coating metal parts with oil also keeps them from being exposed to oxygen, which inhibits their oxidation at elevated operating temperatures (basically preventing them from rusting) Corrosion inhibitors may also be added to the motor oil. Many motor oils also have detergent additives to help keep the engine clean and minimize oil sludge buildup.
Rubbing of metal engine parts inevitably produces some microscopic metallic particles from the wearing of the surfaces. Sludge also accumulates in the engine. Such particles could circulate in the oil and grind against the moving parts, causing erosion and wear. Because particles inevitably build up in the oil, it is typically circulated through an oil filter to remove harmful particles. An oil pump, a vane or gear pump powered by the vehicle engine, pumps the oil throughout the engine, including the oil filter. Oil filters can be a full flow or bypass type.
In the crankcase of a vehicle engine, motor oil lubricates rotating or sliding surfaces between the crankshaft journals bearings (main bearings and big-end bearings), and rods connecting the pistons to the crankshaft. The oil collects in an oil pan, or sump at the bottom of the crankcase. In some small engines such as lawn mower engines, dippers on the bottoms of connecting rods dip into the oil at the bottom and splash it around the crankcase as needed to lubricate parts inside. In modern vehicle engines, the oil pump takes oil from the oil pan and sends it through the oil filter into oil galleries, from which the oil lubricates the main bearings holding the crankshaft up at the main journals and camshaft bearings operating the valves. In typical modern vehicles, oil pressure-fed from the oil galleries to the main bearings enters holes in the main journals of the crankshaft. From these holes in the main journals, the oil moves through passageways inside the crankshaft to exit holes in the rod journals to lubricate the rod bearings and connecting rods. Some simpler designs relied on these rapidly moving parts to splash and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders. However, in modern designs, there are also passageways through the rods which carry oil from the rod bearings to the rod-piston connections and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders. This oil film also serves as a seal between the piston rings and cylinder walls to separate the combustion chamber in the cylinder head from the crankcase. The oil then drips back down into the oil pan. To see these details on a crankshaft, see "How Car Engines Work" at HowStuffWorks or "Types of Lubricating Systems" at Integrated Publishing.
Lubricating oil makes a separating film between surfaces of parts moving next to each other so as to minimize direct contact between them decreasing friction, wear, and production of excessive heat, thus protecting the engine. Motor oil also carries away heat from moving parts, which is important because materials tend to become softer and less abrasion-resistant at high temperatures. Some engines have an additional oil cooler.
In petrol (gasoline) engines, the top compression ring can expose the motor oil to temperatures of 320 °F / 160 °C . In diesel engines the top ring can expose the oil to temperatures over 600 °F / 315 °C. Motor oils with the higher viscosity indexes tend to thin less at these higher temperatures.
Coating metal parts with oil also keeps them from being exposed to oxygen, which inhibits their oxidation at elevated operating temperatures (basically preventing them from rusting) Corrosion inhibitors may also be added to the motor oil. Many motor oils also have detergent additives to help keep the engine clean and minimize oil sludge buildup.
Rubbing of metal engine parts inevitably produces some microscopic metallic particles from the wearing of the surfaces. Sludge also accumulates in the engine. Such particles could circulate in the oil and grind against the moving parts, causing erosion and wear. Because particles inevitably build up in the oil, it is typically circulated through an oil filter to remove harmful particles. An oil pump, a vane or gear pump powered by the vehicle engine, pumps the oil throughout the engine, including the oil filter. Oil filters can be a full flow or bypass type.
In the crankcase of a vehicle engine, motor oil lubricates rotating or sliding surfaces between the crankshaft journals bearings (main bearings and big-end bearings), and rods connecting the pistons to the crankshaft. The oil collects in an oil pan, or sump at the bottom of the crankcase. In some small engines such as lawn mower engines, dippers on the bottoms of connecting rods dip into the oil at the bottom and splash it around the crankcase as needed to lubricate parts inside. In modern vehicle engines, the oil pump takes oil from the oil pan and sends it through the oil filter into oil galleries, from which the oil lubricates the main bearings holding the crankshaft up at the main journals and camshaft bearings operating the valves. In typical modern vehicles, oil pressure-fed from the oil galleries to the main bearings enters holes in the main journals of the crankshaft. From these holes in the main journals, the oil moves through passageways inside the crankshaft to exit holes in the rod journals to lubricate the rod bearings and connecting rods. Some simpler designs relied on these rapidly moving parts to splash and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders. However, in modern designs, there are also passageways through the rods which carry oil from the rod bearings to the rod-piston connections and lubricate the contacting surfaces between the piston rings and interior surfaces of the cylinders. This oil film also serves as a seal between the piston rings and cylinder walls to separate the combustion chamber in the cylinder head from the crankcase. The oil then drips back down into the oil pan. To see these details on a crankshaft, see "How Car Engines Work" at HowStuffWorks or "Types of Lubricating Systems" at Integrated Publishing.
No comments:
Post a Comment