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Role of lubrication in Automobile

The document discusses lubrication systems in engines, emphasizing their importance for reducing wear and tear on moving parts, absorbing shocks, cooling, and keeping engine components clean. It details different lubrication methods, including splash and pressurized systems, along with their advantages and disadvantages, and addresses troubleshooting issues related to lubrication failures. The conclusion highlights the necessity of proper lubrication maintenance for optimal engine performance and longevity.

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INTRODUCTION Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each other, by interposing a substance called lubricant between the surfaces to carry or to help carry the load between the opposing surfaces. Lubrication system is one of the most important ones in the engine. The engine cannot run smoothly for more than a few minutes without lubricating oil. The engine lubrication system distributes oil to the moving parts i.e. rotating and sliding parts to reduce friction between surfaces and save the engine from excessive wear and tear.
Objectives of lubricating system:  It is used to reduce the friction between the mating parts and reduce the wear and tear.  It is used to absorb shocks between bearings and other parts of the engine .  It is used as a cooling medium for removing heat.  It is used to keep the engine parts clean i.e. it prevents deposition of carbon produced when combustion is incomplete.  It forms a good seal between piston ring and cylinder walls.
LUBRICATION SYSTEM SOME EXAMPLES OF ITS USES
Used in Automatic transmission torque convertor Lubricants known as hydraulic fluid are used as the working fluid in hydrostatic power transmission. Hydraulic fluids comprise a large portion of all lubricants produced in the world. Used in Pistons and shafts. Lubricants will occupy the clearance between moving parts through the capillary force, thus sealing the clearance. This effect can be used to seal pistons and shafts. Used in Automotive oil - cooled turbocharger. Turbochargers get red hot during operation and the oil coolant survives only at high flow rate. Non-flowing lubricants such as greases and pastes contribute by reducing the generation of heat in the first place.
PROPERTIES OF LUBRICATING OIL Lubricating oil should be highly viscous. Should have high viscosity index. Should have high flash and fire point. Should have low pour point. It should be highly corrosion resistive. Lubricant must resist oxidation or it should oxidize at very high temperature.
TYPES OF LUBRICANT
SAE Number • Society of Automotive Engineers (SAE) uses various numbers to grade the lubricating oil according to the viscosity index of the oil. • Viscosity index is a measure of the change in viscosity at varying temperature. • For normal use SAE20, SAE30, SAE40 are used.
PARTS OF LUBRICATING SYSTEM : It is the lowest part of the crank chamber which provides a covering for the crankshaft and contains oil in it. It is made of steel pressings and also by aluminium or cast iron. It contains drain plug at its lowest part to drain out the oil. : It is located inside the crankcase . It’s function is to supply oil under pressure to various engine parts to be lubricated. Various types of oil pumps are Gear pump, Rotor pump, Plunger pump etc.
: In oil filters, micro-porous paper filters are used to screen out particles and remove harmful materials. Oil filters are of Two Types Full Flow: All the oil goes to the system through filter. Bypass: Part of oil goes from sump to filter, part goes to engine for lubrication.
They are used to cool the lubricating oil in heavy duty engines . Oil coolers are just like a simple heat exchanger. Oil is cooled either by cold water from the radiator or by the air stream. Water type coolers are commonly used. : It is used to indicate the oil pressure in the engine. It can be a light or a gauge.
: The level of the oil in the crankcase is checked by dip stick. To check the oil level, the long stick is dipped into the crankcase and taken out. Some engines equipped with an electrical level indicator. : Relief valve must be incorporated to prevent the building up of excessively high oil pressures during high-speed or cold-weather operation.
: water tends to mix with the lubricating oil in the crankcase and form sludge. The oil is also diluted by liquid gasoline that seeps down past the piston rings and enters the crankcase. So, crankcase ventilation is used.  Some other parts include etc.
METHODS OF LUBRICATION TWO-STROKE AND FOUR- STROKE LUBRICATION SYSTEMS
FOR FOUR STROKE ENGINES  Four-stroke engines are lubricated by oil held in an oil sump. The oil is distributed through the engine by  Splash lubrication  Pressurized lubrication pump system These systems may be used alone or together.
SPLASH LUBRICATION SYSTEM The crankshaft is kept immersed in crankcase which is full of lubricating oil. When the crankshaft rotates, the oil is splashed in different directions and the engine parts are lubricated. Arrangement is provided through a system of specially drilled holes and galleries to take the oil to crankpin ,connecting rod bearings ,main bearings and camshaft bearings. The oil after lubricating different parts drains back to the sump. Oil level in the troughs is maintained by means of an oil pump which takes the oil from the sump through a filter or strainer. The splash lubrication system is mostly used for one-cylinder stationary engines.
Fig-: Splash lubrication system
PRESSURIZED LUBRICATION SYSTEM The lubricating oil under pressure is circulated through drilled passages and oil lines to various engine parts which require lubrication. Pressurized lubrication system can be classified into two categories-: Wet Sump System  Dry Sump System
WET SUMP SYSTEM  In the wet sump ,the pump that supplies oil is either submerged in the oil or is slightly placed above the oil level  The system is used in small automobile level.  The oil contained in the oil sump is then drawn by gear pump through a strainer and after filtration is delivered to the oil distributor at a pressure ranging from 1.5 to 4 bar . It is then delivered to various engine parts .  One pipe supplies oil to the main bearings of the camshaft through the holes drilled in the crank shaft and crank pin bearings. The flow of oil is from the main bearings to the crank arms and then to the crank pin bearings  The connecting rod has a hole drilled in its central position. The oil from the crankpin is forced under pressure through this hole and it reaches the gudgeon pin bearing. The oil from the gudgeon pin bearing and the hole in the connecting rod is made to splash to the cylinder walls
 The piston gets lubricated from the oil which is thrown from the ends of the big end bearings.  The pipes from the distributor take the oil under pressure to the timing gears , and to the rocker arms of an overhead valve engine.  After proper lubrication of these units , the oil returns to the oil sump.  The system is provided with a pressure gauge that confirms that the oil is being delivered to all parts. Fig-: Wet sump lubrication system
DRY SUMP SYSTEM  In dry sump system the pump is outside the sump and it forces oil into a small reservoir from where it is delivered to the main gallery by another pump.  The oil reservoir is usually placed behind the radiator and thus takes advantage of the air blast for cooling the lubricating oil.  Dry sump system is generally used in large stationary and marine engines. Fig-: Dry sump lubrication system
FOR TWO STROKE ENGINES  Two-stroke engines collect some oil beneath the crankshaft; however, two- stroke engines employ a total-loss lubrication system that combines oil and fuel to provide both energy and engine lubrication. It is also called petroil lubrication system.  The oil and fuel are combined in the cylinder’s intake tract and lubricate critical components such as the crankshaft, connecting rods and cylinder walls.
PETROIL/MIST LUBRICATION SYSTEM  The lubrication of two stroke engines fitted with motor cycles and scooters is accomplished by mixing 3 to 6% 0f lubricating oil with petrol.  The gasoline from the oil and fuel mixture, induced through the carburettor, vaporises and the oil in the form of mist passes into the cylinder with crankcase.  The main and connecting rod bearings get lubricated by the oil that impinges on the crankcase walls.  The lubrication of the piston , piston rings and the cylinder is done by the rest of the oil that passes into the cylinder during the charging and scavenging operations.
ADVANTAGES ADVANTAGES OF SPLASH LUBRICATION  It works for a wider range of speeds Visual verification of oil level is possible Can be used for light duty and slow speed engines ADVANTAGES OF PRESSURIZED LUBRICATION It is more technically advanced than splash lubrication. Lubricant reach every components used in the engine due to application of pressure. This system has added longevity and reliability. There is positive introduction of oil to bearings. Cooling effect caused by large quantities of oil which can be circulated through the bearings.
ADVANTAGES OF PETROIL LUBRICATION SYSTEM This system is simple, low cost and maintenance free because it does not require any oil pump, filter, etc.
DISADVANTAGES DISADVANTAGES OF PETROIL LUBRICATION The proportion of oil and fuel mixture used in this system should be proper. If this proportion is less, the danger of oil starvation causes damage to the engine. If the proportion is more, the engine gives dark smoke and excessive carbon deposits on the cylinder head. During combustion in the engine, some lubricating oil is also burnt and it causes heavy exhaust and forms deposits on the piston crown, exhaust port and exhaust system. Since the lubricating oil comes in contact with acidic vapours produced during the combustion, it gets contaminated and may result in the corrosion of the bearings surface. When the vehicle is moving downhill, the throttle is almost closed, and the engine suffers lack of lubrication as supply of fuel is less. It is a very serious drawback of this system.
DISADVANTAGE OF PRESSURIZED LUBRICATION There is no control over the supply of lubricating oil to the engine. In normal operating conditions, the two-stroke engines are always over-oiled. Thus consumption of oil is also more. This system requires thorough mixing of oil and fuel prior to admission into the engine. It requires either separate mixing or use of some additives.  Pressurized lubrication system requires regular oil changes . So consumption of oil is high. DISADVANTAGES OF SPLASH LUBRICATION SYSTEM Due to the presence of scoop at the end of piston, it does not serves the proper lubrication throughout the engine cylinder. The lubricant just spills on the piston parts. Wear and tear of the components takes place is more compared to other systems.
Troubleshooting of lubricating system:  External oil leakage out of the engine, internal leakage of oil into the combustion chamber which may occur if the piston ring gets worn out. Worn oil pump, broken or cracked oil lines, obstructions in the oil lines, thin or diluted oil i.e. low viscosity oil, weak or broken pressure relief valve spring, worn connecting rod or main bearings due to which pump cannot provide enough oil volume, low oil level. Pressure relief valve struck open , high oil viscosity i.e. excessively thick oil or use of oil additive that increase viscosity, defective block casting or debris in passage. Sometimes the oil pressure indicator or gauge may show some faulty setting. The indicator light may say on or flicker. The wire going to ECU may have short circuited
CONCLUSION Oil is the life blood of an engine keeping engine property lubricated and reducing friction, heat buildup and wear. This means that good engine lubrication maintenance will help engine to run better and to last longer. Following recommendations can be concluded:  Oil specified by the vehicle manufacturer in owner’s manual should be used.  Proper storage is necessary for the lubricant because storage conditions affect the life of oil. It should not be exposed to extreme temperature changes as well as moisture which reduces shelf life of lubricant.  Performance of lubricant put into the engine should be monitored.  Genuine engine oil should be used and engine oil myths should be dispelled.
REFERENCES  Automobile engineering by DS Kumar.  https://www.techtransfer.com/blog/lubrication-properties/  http://constructionmanuals.tpub.com/14264/css/Lubricating-System- Maintenance-245.htm  https://wiki.anton-paar.com/in-en/sae-viscosity-grades/
Role of lubrication in Automobile